Weather-resistant flame-retardant mpp power tube material and preparation method thereof

Abstract

This invention discloses a weather-resistant and flame-retardant MPP power pipe material and its preparation method, belonging to the field of power pipe material preparation technology. It is used to solve the technical problem that the flame-retardant and weather-resistant properties of existing MPP power pipe materials need to be further improved. This invention uses phosphine-nitrogen flame-retardant oligomers as the main flame-retardant component, polysiloxane-shell phytate cerium hybrid clusters as synergistic functional components, and flame-retardant and toughening auxiliary masterbatch, and is compounded with polypropylene, high-density polyethylene and other components to obtain a special material for MPP power pipes. Furthermore, by constructing a phosphorus-nitrogen synergistic flame-retardant structure, a core-shell hybrid interface structure and a compatible toughening transition system, the stable dispersion and interface coordination of each functional component in the matrix are achieved, taking into account the flame retardancy, mechanical support, heat resistance and aging stability of the material.

Description

Technical Field

[0001] This invention relates to the field of power pipe materials technology, specifically to a weather-resistant and flame-retardant MPP power pipe material and its preparation method. Background Technology

[0002] Currently, MPP power pipes typically use polypropylene as the main resin, and according to the usage requirements, high-density polyethylene, flame retardants, toughening agents, antioxidants, lubricants, and inorganic additives are added to prepare special materials, which are then extruded to obtain pipes. The relevant modification methods mainly include the introduction of phosphorus-based flame retardants, nitrogen-based flame retardants, metal salt additives, siloxane modifying components, and elastomer toughening components to adjust the flame retardancy, processing fluidity, mechanical properties, and long-term stability of the material. For polyolefin materials used in power pipes, existing technologies usually achieve a balance of comprehensive performance through multi-component compounding.

[0003] Currently, flame retardant components are mostly low-molecular-weight flame retardants or inorganic flame retardant fillers directly added to the polyolefin matrix. These components often have insufficient interfacial compatibility and limited dispersion stability with non-polar resins such as polypropylene. They are prone to local enrichment or weak interphase bonding during melt processing. This not only affects the effective function of the flame retardant components in the material, but also has an adverse effect on tensile strength, ring stiffness and resistance to heat deformation, making it difficult to achieve a balance between flame retardancy and mechanical support in the material.

[0004] Furthermore, traditional MPP power pipe materials often lack hierarchical synergistic design among different functional components, making it difficult to form a stable interfacial transition relationship between the flame-retardant system, toughening system, and inorganic functional phase. Consequently, under conditions of heat, light, and long-term service, the structure is prone to insufficient retention. Specifically, the material tends to migrate and precipitate functional components during processing and use, and its performance degrades rapidly after aging. Moreover, there is still room for improvement in terms of heat resistance, dimensional stability, and long-term reliability, making it difficult to meet the comprehensive performance requirements of MPP power pipes. Summary of the Invention

[0005] The purpose of this invention is to provide a weather-resistant and flame-retardant MPP power pipe material and its preparation method, in order to solve the technical problem that the flame-retardant and weather-resistant properties of existing MPP power pipe materials need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a weather-resistant and flame-retardant MPP power pipe material, comprising the following raw material composition by weight: 52-58 parts polypropylene, 11-13 parts high-density polyethylene, 13-16 parts phosphine nitrogen flame-retardant oligomer, 13-17 parts flame-retardant toughening auxiliary masterbatch and 3-5 parts polysiloxane shell cerium phytate hybrid cluster.

[0007] The preparation method of the phosphonium-nitrogen flame-retardant oligomer is as follows: the bridged phosphonium-nitrogen flame-retardant intermediate, acetone and N-methylpyrrolidone are added to the reaction vessel and stirred. After mixing evenly, the reaction vessel is cooled to 0-5℃, cyanuric chloride is added and stirred for 40-60 min, then piperazine is added and stirred for another 40-60 min. Subsequently, the temperature is raised to 35-45℃ and stirred for another 40-60 min. Then, the temperature is raised to 70-75℃ and stirred for 2-3 h. The phosphonium-nitrogen flame-retardant oligomer is obtained after post-treatment.

[0008] The mechanism for preparing bridged phosphine-nitrogen flame retardant intermediates is as follows:

[0009]

[0010] Furthermore, in the preparation of the phosphonium-nitrogen flame-retardant oligomer, the ratio of the bridged phosphonium-nitrogen flame-retardant intermediate, acetone, N-methylpyrrolidone, cyanuric chloride, and piperazine is 50-60g:150mL:60mL:8-10g:4-5g. The post-treatment includes: after the reaction is completed, the reaction vessel is cooled to room temperature, the reaction liquid is filtered, the filter cake is collected, washed, and dried to obtain the phosphonium-nitrogen flame-retardant oligomer.

[0011] Furthermore, the bridged phosphine-nitrogen flame retardant intermediate is prepared by the following method:

[0012] A1. Add terephthalaldehyde, anhydrous ethanol and o-xylene to a reaction vessel and stir. After mixing evenly, add p-phenylenediamine and heat the reaction vessel to 75-85℃. Keep it heated and stir for 1-2 hours. Then continue to heat to 135-140℃ and keep it heated and stir for 3-4 hours. Post-treatment yields phosphine nitrogen flame retardant precursor.

[0013] A2. Add the phosphonium flame retardant precursor and N-methylpyrrolidone to a reaction vessel and stir. After mixing evenly, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Then heat the reaction vessel to 115-120℃ and stir for 5-7 hours. Post-processing yields the bridged phosphonium flame retardant intermediate.

[0014] The mechanism for preparing bridged phosphine-nitrogen flame retardant intermediates is as follows:

[0015]

[0016] In the formula: ; .

[0017] Further, in step A1, the ratio of terephthalaldehyde, anhydrous ethanol, o-xylene, and p-phenylenediamine is 30-36g:250mL:120mL:27-32g. The post-treatment includes: after the reaction is completed, the reaction solution is poured into twice the amount of acetone to precipitate the precipitate. After the precipitation is complete, the filter cake is collected by filtration, washed, and dried to obtain the phosphine nitrogen flame retardant precursor.

[0018] Further, in step A2, the ratio of the phosphine-nitrogen flame retardant precursor, N-methylpyrrolidone, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 45-55g:200mL:27-32g. The post-treatment includes: after the reaction is completed, the reaction solution is poured into twice the amount of acetone to precipitate the precipitate. After the precipitation is complete, the filter cake is collected by filtration, washed, and dried to obtain the bridged phosphine-nitrogen flame retardant intermediate.

[0019] Furthermore, the preparation method of the flame-retardant and toughening auxiliary masterbatch is as follows: polypropylene grafted with maleic anhydride, polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, zinc borate, antioxidant 1010, antioxidant 168 and calcium stearate are added to a high-speed mixer and mixed evenly. Then, the mixture is added to a twin-screw extruder and melt-extruded and granulated at 170-190°C. The post-treatment yields the flame-retardant and toughening auxiliary masterbatch.

[0020] Furthermore, in the process of preparing the flame-retardant and toughening auxiliary masterbatch, the ratio of polypropylene grafted with maleic anhydride, polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, zinc borate, antioxidant 1010, antioxidant 168 and calcium stearate is 24-27g:10-15g:8-15g:0.5g:0.5g:0.3g. The post-processing includes: the extrudate is cooled in a cooling water tank and then pelletized and dried to obtain flame-retardant and toughening auxiliary masterbatch with a diameter of 2-3mm and a particle length of 2-4mm.

[0021] Furthermore, the polysiloxane-shell cerium phytate hybrid cluster is prepared by the following method:

[0022] B1. Add the acid solution and deionized water to the reaction vessel and stir. After mixing evenly, add cerium nitrate hexahydrate and adjust the pH of the reaction system to 3.8-4.2 with ammonium hydroxide. Then heat the reaction vessel to 55-65℃ and keep it at that temperature for 3-4 hours. The post-treatment yields cerium phytate coordination polymer clusters.

[0023] B2. Add cerium phytate coordination polymer clusters, anhydrous ethanol, deionized water and ammonium hydroxide to a reaction vessel and stir. After mixing evenly, add γ-glycidoxypropyltrimethoxysilane. Then heat the reaction vessel to 50-55℃ and stir for 4-5 hours. Post-treatment yields polysiloxane-shell cerium phytate hybrid clusters.

[0024] Further, in step B1, the ratio of acid solution, deionized water, ammonium hydroxide and cerium nitrate hexahydrate is 60-75 mL: 270 mL: 8-10 g, wherein the acid solution is a 50 wt% phytic acid aqueous solution, and the post-treatment includes: after the reaction is completed, the reaction vessel is cooled to room temperature, the reaction liquid is filtered and the filter cake is collected, washed and dried to obtain cerium phytate coordination polymer clusters;

[0025] In step B2, the ratio of the cerium phytate coordination polymer cluster, anhydrous ethanol, deionized water, ammonium hydroxide, and γ-glycidyl etheroxypropyltrimethoxysilane is 25g:100mL:25-30mL:4-6mL:6-9mL. The post-processing includes: after the reaction is completed, the reaction vessel is cooled to room temperature, the reaction liquid is filtered, the filter cake is collected, washed and dried to obtain polysiloxane-shell cerium phytate hybrid clusters.

[0026] The present invention also discloses a method for preparing a weather-resistant and flame-retardant MPP power pipe material, comprising the following steps:

[0027] S1. Phosphorus nitrogen flame retardant oligomer, polysiloxane shell phytate cerium hybrid cluster and flame retardant toughening auxiliary masterbatch are added to a high-speed mixer and mixed evenly. Then, the mixture is added to the first twin-screw extruder and melt-extruded into granules at 170-185℃. After post-treatment, flame retardant and weather-resistant pre-granules are obtained.

[0028] S2. Polypropylene, high-density polyethylene and flame-retardant and weather-resistant pre-granules are added to a high-speed mixer and mixed evenly. Then, the mixture is added to a second twin-screw extruder and melt-extruded into granules at 180-205℃. After post-treatment, MPP power pipe special material is obtained.

[0029] Furthermore, in step S1, the post-processing includes: the extrudate is cooled in a cooling water tank, then granulated and dried to obtain flame-retardant and weather-resistant pre-granules with a diameter of 2-4 mm and a particle length of 2-5 mm.

[0030] Furthermore, in step S2, the post-processing includes: the extrudate is cooled in a cooling water tank, then granulated and dried to obtain MPP power pipe special material with a diameter of 3-4 mm and a particle length of 3-5 mm.

[0031] The present invention has the following beneficial effects:

[0032] 1. The flame-retardant and toughening auxiliary masterbatch prepared by this invention, after entering the polypropylene / high-density polyethylene matrix, preferentially exhibits its regulating effect on the interface between the continuous and dispersed phases of the system. This makes the distribution of phosphine-nitrogen flame-retardant oligomers and polysiloxane-shell cerium phytate hybrid clusters in the matrix more balanced, avoiding the adverse effects of local aggregation of functional components on the continuity of stress. On this basis, the rigid structure of the phosphine-nitrogen flame-retardant oligomers can be stably embedded in the matrix, and the inorganic characteristics of the polysiloxane-shell cerium phytate hybrid clusters can also participate in load transfer more smoothly. This results in the material exhibiting better stress dispersion and deformation coordination during tensile testing. The resulting composite system not only helps to improve the tensile strength of the special material, but also makes the circumferential support of the pipe after molding more stable, and less prone to local instability under external pressure.

[0033] 2. The phosphine-nitrogen flame-retardant oligomers prepared in this invention are primarily the core contributing components to the flame-retardant performance of the system. Their introduction results in a higher tendency for char formation and a lower level of flammability under heating conditions, and an improved oxygen index. Furthermore, the use of polysiloxane shell cerium phytate hybrid clusters in conjunction with these oligomers makes it easier for the material surface to form a stable and continuous protective barrier under heat and light conditions, thereby mitigating the adverse effects of external oxygen, heat, and ultraviolet factors on the polyolefin matrix. The flame-retardant toughening auxiliary masterbatch improves the compatibility and dispersion of the above two types of functional components in the matrix, reducing the performance degradation caused by weak phase interfaces. This ensures that the improvement in flame retardancy does not come at the expense of mechanical retention after aging. While maintaining a high oxygen index, the material can still maintain a relatively ideal tensile strength retention rate after aging.

[0034] 3. The polysiloxane-shell cerium phytate hybrid cluster prepared in this invention significantly improves the thermal stability of the material. On the one hand, it improves the thermal stability distribution of the functional phase in the polyolefin matrix, and on the other hand, it enhances the material's ability to inhibit chain segment relaxation and structural softening during heating. At the same time, when the phosphine-nitrogen flame-retardant oligomer coexists with the hybrid cluster, it can maintain the structural integrity of the system at higher temperatures and slow down the decrease in the continuous phase load-bearing capacity under thermal action. The flame-retardant and toughening auxiliary masterbatch, through its interfacial stabilizing effect, ensures that the two types of functional components maintain a good synergistic state after processing and molding. As a result, the Vicat softening temperature of the material is higher, and this thermal improvement can be transferred to the pipe end, allowing it to maintain good ring stiffness and dimensional stability under heating conditions. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a SEM image of the polysiloxane-shell cerium phytate hybrid cluster prepared in Example 6 of the present invention. Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In this application, the polypropylene used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P816226; the high-density polyethylene used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number H790495; the polypropylene grafted with maleic anhydride used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P922016; the antioxidant 1010 used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P750268; the antioxidant 168 used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number T822863; the calcium stearate used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number C805417; and the polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene used was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P742032.

[0039] Example 1

[0040] This embodiment provides a method for preparing phosphine-nitrogen flame-retardant oligomers, including the following steps:

[0041] Step I: Preparation of Phosphorus Nitrogen Flame Retardant Precursors

[0042] Weigh out 30.0 g of terephthalaldehyde, 250.0 mL of anhydrous ethanol and 120.0 mL of o-xylene and add them to the reaction vessel. Stir and mix well. Then add 27.0 g of p-phenylenediamine. Heat the reaction vessel to 75°C and stir for 1 h. Then continue to heat to 135°C and stir for 3 h. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the phosphine nitrogen flame retardant precursor.

[0043] Step II: Preparation of bridged phosphine-nitrogen flame retardant intermediates

[0044] Weigh 45.0g of phosphine-nitrogen flame retardant precursor and 200.0mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix thoroughly. Then add 27.0g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Heat the reaction vessel to 115℃ and stir for 5 hours. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the bridged phosphine-nitrogen flame retardant intermediate.

[0045] Step III: Preparation of Phosphine Nitrogen Flame Retardant Oligomers

[0046] Weigh out 50.0 g of bridged phosphine-nitrogen flame retardant intermediate, 150.0 mL of acetone and 60.0 mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix evenly. Then cool the reaction vessel to 0°C, add 8.0 g of cyanuric chloride and keep it warm and stirred for 40 min. Then add 4.0 g of piperazine and keep it warm and stirred for another 40 min. Then raise the temperature to 35°C and keep it warm and stirred for another 40 min. Then raise the temperature to 70°C and keep it warm and stirred for 2 h. After the reaction is complete, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain phosphine-nitrogen flame retardant oligomer.

[0047] The reaction principle for preparing phosphine nitrogen flame retardant oligomers is as follows:

[0048] The aldehyde group in the terephthalaldehyde molecule undergoes a condensation reaction with the amino group in the p-phenylenediamine molecule to form a Schiff base structure containing an imine bond, thereby constructing the basic framework of the phosphine nitrogen flame retardant precursor. Subsequently, the phosphine hydrogen group in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes an addition reaction with the aforementioned imine bond structure to form a bridged phosphine nitrogen flame retardant intermediate. Further, the active chlorine atom in the cyanuric chloride molecule can undergo a stepwise nucleophilic substitution reaction, allowing the bridged phosphine nitrogen flame retardant intermediate and the piperazine molecule to be linked to the triazine ring structure, thereby introducing the phosphorus-containing structure, the nitrogen-containing structure, and the triazine ring unit into the same molecular system, ultimately forming a phosphine nitrogen flame retardant oligomer with a certain degree of oligomerization. In this process, the product molecular structure mainly contains imine bonds, PC bonds, P=O bonds, triazine rings, and amine bridged structures.

[0049] The mechanism of action of phosphine-nitrogen flame-retardant oligomers in MPP power pipe special materials is as follows:

[0050] In this process, the structures obtained in steps I to III do not have isolated effects on the MPP power pipe material, but rather, through a progressive approach of precursor skeleton establishment, bridging synergistic enhancement, and oligomer level adaptation, they jointly determine the final state and mode of action of the flame retardant component in the polyolefin system. In this process, the aromatic-nitrogen-containing rigid framework formed in step I provides the basic structural stability, char formation tendency, and polar site source for the final flame-retardant component. Step II further introduces phosphorus-containing bridging units, enabling the flame-retardant component to possess both phosphorus-nitrogen synergistic characteristics and enhancing its ability to regulate condensed phases under heating conditions and its interfacial coordination with the matrix / other functional phases. Step III constructs a multi-unit synergistic structure with a certain degree of oligomerization, making it easier for the flame-retardant component to maintain dispersion stability and reduce migration and precipitation tendencies during melt blending. It also balances flame-retardant response and structural retention during material service. Thus, the aforementioned three-layer structure source is transferred to the MPP power pipe special material system via the final-state phosphine-nitrogen flame-retardant oligomer, which can synergistically affect the material's flame retardancy, mechanical support, heat deformation resistance, and performance retention after aging. This is further reflected in the overall performance of the prepared MPP power pipe, such as ring stiffness and Vicat softening temperature.

[0051] Example 2

[0052] This embodiment provides a method for preparing phosphine-nitrogen flame-retardant oligomers, including the following steps:

[0053] Step I: Preparation of Phosphorus Nitrogen Flame Retardant Precursors

[0054] Weigh out 36.0 g of terephthalaldehyde, 250.0 mL of anhydrous ethanol and 120.0 mL of o-xylene and add them to the reaction vessel. Stir and mix well. Then add 32.0 g of p-phenylenediamine. Heat the reaction vessel to 85 °C and keep it at that temperature for 2 h. Then continue to heat to 140 °C and keep it at that temperature for 4 h. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the phosphine nitrogen flame retardant precursor.

[0055] Step II: Preparation of bridged phosphine-nitrogen flame retardant intermediates

[0056] Weigh 55.0g of phosphine-nitrogen flame retardant precursor and 200.0mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix thoroughly. Then add 32.0g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Heat the reaction vessel to 120℃ and stir for 7 hours. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the bridged phosphine-nitrogen flame retardant intermediate.

[0057] Step III: Preparation of Phosphine Nitrogen Flame Retardant Oligomers

[0058] Weigh out 60.0 g of bridged phosphine-nitrogen flame retardant intermediate, 150.0 mL of acetone and 60.0 mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix evenly. Then cool the reaction vessel to 5°C, add 10.0 g of cyanuric chloride and keep it warm and stirred for 60 min. Then add 5.0 g of piperazine and keep it warm and stirred for another 60 min. Then raise the temperature to 45°C and keep it warm and stirred for another 60 min. Then raise the temperature to 75°C and keep it warm and stirred for 3 h. After the reaction is complete, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain phosphine-nitrogen flame retardant oligomer.

[0059] Example 3

[0060] This embodiment provides a method for preparing phosphine-nitrogen flame-retardant oligomers, including the following steps:

[0061] Step I: Preparation of Phosphorus Nitrogen Flame Retardant Precursors

[0062] Weigh out 33.0 g of terephthalaldehyde, 250.0 mL of anhydrous ethanol and 120.0 mL of o-xylene and add them to the reaction vessel. Stir and mix well. Then add 29.5 g of p-phenylenediamine. Heat the reaction vessel to 80 °C and stir for 2 h. Then continue to heat to 138 °C and stir for 4 h. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the phosphine nitrogen flame retardant precursor.

[0063] Step II: Preparation of bridged phosphine-nitrogen flame retardant intermediates

[0064] Weigh 50.0g of phosphine-nitrogen flame retardant precursor and 200.0mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix thoroughly. Then add 29.5g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Heat the reaction vessel to 118℃ and stir for 6 hours. After the reaction is complete, pour the reaction solution into twice the amount of acetone to precipitate. After precipitation is complete, filter and collect the filter cake. Wash and dry to obtain the bridged phosphine-nitrogen flame retardant intermediate.

[0065] Step III: Preparation of Phosphine Nitrogen Flame Retardant Oligomers

[0066] Weigh out 55.0 g of bridged phosphine-nitrogen flame retardant intermediate, 150.0 mL of acetone and 60.0 mL of N-methylpyrrolidone and add them to the reaction vessel. Stir and mix evenly. Then cool the reaction vessel to 3°C, add 9.0 g of cyanuric chloride and keep it warm and stirred for 50 min. Then add 4.5 g of piperazine and keep it warm and stirred for another 50 min. Then raise the temperature to 40°C and keep it warm and stirred for another 50 min. Then raise the temperature to 73°C and keep it warm and stirred for 3 h. After the reaction is complete, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain phosphine-nitrogen flame retardant oligomer.

[0067] Example 4

[0068] This embodiment provides a method for preparing polysiloxane-shell cerium phytate hybrid clusters, including the following steps:

[0069] Step ①: Preparation of cerium phytate coordination polymer clusters

[0070] Weigh out 60.0 mL of 50 wt% phytic acid aqueous solution and 270.0 mL of deionized water and add them to the reaction vessel. Stir and mix well. Then add 8.0 g of cerium nitrate hexahydrate and adjust the pH of the reaction system to 3.8 with ammonium hydroxide. Then heat the reaction vessel to 55 °C and keep it at that temperature for 3 h with stirring. After the reaction is completed, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain cerium phytate coordination polymer clusters.

[0071] Step 2: Preparation of polysiloxane-shelled cerium phytate hybrid clusters

[0072] Weigh out 25.0 g of cerium phytate coordination polymer cluster, 100.0 mL of anhydrous ethanol, 25.0 mL of deionized water and 4.0 mL of ammonium hydroxide and add them to the reaction vessel. Stir and mix well. Then add 6.0 mL of γ-glycidoxypropyltrimethoxysilane. Heat the reaction vessel to 50 °C and stir for 4 h. After the reaction is completed, let the reaction vessel cool to room temperature. Filter the reaction liquid, collect the filter cake, wash and dry it to obtain polysiloxane-shell cerium phytate hybrid cluster.

[0073] The reaction principle for preparing polysiloxane-shell cerium phytate hybrid clusters is as follows:

[0074] Phytic acid molecules contain multiple phosphate sites. Under weakly acidic conditions, partially deprotonated phosphate oxygen atoms can coordinate with cerium ions at multiple sites, thereby forming aggregated coordination polymer clusters with cerium ions as nodes and phytic acid molecules as ligands through coordination linkage. After further introducing γ-glycidoxypropyltrimethoxysilane, its trimethoxysilane group undergoes hydrolysis in a water / ethanol system and under alkaline conditions to generate silanol, which further condenses to form a polysiloxane network. At the same time, the generated silanol groups can condense or combine with the oxygen-containing groups on the surface of the cerium phytate coordination polymer cluster, causing the polysiloxane structure to be deposited and coated on the surface of the coordination polymer cluster, ultimately forming a polysiloxane-shell cerium phytate hybrid cluster.

[0075] The mechanism of action of polysiloxane-shell cerium phytate hybrid clusters in MPP power pipe special materials is as follows:

[0076] In this process, the structures obtained in steps ① and ② do not remain at the isolated levels of inorganic filling or surface modification for MPP power pipe materials. Instead, they work in a progressive manner—"coordination aggregation core formation - organosilicon shell interface extension"—to jointly determine the dispersion state, interfacial behavior, and service response of the hybrid functional phase in the polyolefin system. Specifically, the cerium phytate coordination polymer clusters formed in step ① provide the system with functional cores containing phosphorus, rare earth elements, and multi-site oxygen-containing structures, enabling this component to possess certain thermal response capabilities, polar interaction basis, and inorganic framework support characteristics within the material. Step ② further constructs a polysiloxane shell on its surface. The two-layer structure transforms the hybrid clusters from simple coordinated aggregated particles into core-shell functional phases with organic-interface transition capabilities. This makes it more conducive to maintaining dispersion stability during melt blending, improving interfacial coordination with the matrix and other flame-retardant components, and reducing local agglomeration and interfacial debonding tendency. Thus, after the above two-layer structure is transferred to the MPP power pipe special material system through the polysiloxane shell cerium phytate hybrid clusters, it can jointly affect the material's thermal stability, flame retardant synergy, mechanical support, and structural retention ability under aging conditions. This is further reflected in the comprehensive performance of MPP power pipes, such as ring stiffness, Vicat softening temperature, and long-term service stability.

[0077] Example 5

[0078] This embodiment provides a method for preparing polysiloxane-shell cerium phytate hybrid clusters, including the following steps:

[0079] Step ①: Preparation of cerium phytate coordination polymer clusters

[0080] Weigh out 75.0 mL of 50 wt% phytic acid aqueous solution and 270.0 mL of deionized water and add them to the reaction vessel. Stir and mix well. Then add 10.0 g of cerium nitrate hexahydrate and adjust the pH of the reaction system to 4.2 with ammonium hydroxide. Then heat the reaction vessel to 65 °C and keep it at that temperature for 4 h with stirring. After the reaction is completed, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain cerium phytate coordination polymer clusters.

[0081] Step 2: Preparation of polysiloxane-shelled cerium phytate hybrid clusters

[0082] Weigh out 25.0 g of cerium phytate coordination polymer cluster, 100.0 mL of anhydrous ethanol, 30.0 mL of deionized water and 6.0 mL of ammonium hydroxide and add them to the reaction vessel. Stir and mix well. Then add 9.0 mL of γ-glycidoxypropyltrimethoxysilane. Heat the reaction vessel to 55 °C and stir for 5 h. After the reaction is completed, let the reaction vessel cool to room temperature. Filter the reaction liquid, collect the filter cake, wash and dry it to obtain polysiloxane-shell cerium phytate hybrid cluster.

[0083] Example 6

[0084] This embodiment provides a method for preparing polysiloxane-shell cerium phytate hybrid clusters, including the following steps:

[0085] Step ①: Preparation of cerium phytate coordination polymer clusters

[0086] Weigh out 67.5 mL of 50 wt% phytic acid aqueous solution and 270.0 mL of deionized water and add them to the reaction vessel. Stir and mix well. Then add 9.0 g of cerium nitrate hexahydrate and adjust the pH of the reaction system to 4.0 with ammonium hydroxide. Then heat the reaction vessel to 60 °C and keep it at that temperature for 4 h with stirring. After the reaction is completed, let the reaction vessel cool to room temperature, filter the reaction liquid, collect the filter cake, wash and dry it to obtain cerium phytate coordination polymer clusters.

[0087] Step 2: Preparation of polysiloxane-shelled cerium phytate hybrid clusters

[0088] Weigh out 25.0 g of cerium phytate coordination polymer cluster, 100.0 mL of anhydrous ethanol, 27.5 mL of deionized water and 5.0 mL of ammonium hydroxide and add them to the reaction vessel. Stir and mix well. Then add 7.5 mL of γ-glycidoxypropyltrimethoxysilane. Heat the reaction vessel to 53 °C and stir for 5 h. After the reaction is completed, let the reaction vessel cool to room temperature. Filter the reaction liquid, collect the filter cake, wash and dry it to obtain polysiloxane-shell cerium phytate hybrid cluster.

[0089] Example 7

[0090] This embodiment provides a method for preparing weather-resistant and flame-retardant MPP power pipe material, including the following steps:

[0091] Step 1: Preparation of flame-retardant and toughening auxiliary masterbatch

[0092] Weigh out 24.0g of polypropylene grafted maleic anhydride, 10.0g of polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, 8.0g of zinc borate, 0.5g of antioxidant 1010, 0.5g of antioxidant 168 and 0.3g of calcium stearate and add them to a high-speed mixer and mix evenly. Then add them to a twin-screw extruder and melt extrude and granulate at 170℃. After cooling in a cooling water tank, the extrudate is granulated and dried to obtain flame-retardant toughening auxiliary masterbatch with a diameter of 2mm and a particle length of 2mm.

[0093] The reaction principle for preparing flame-retardant and toughening auxiliary masterbatch is as follows:

[0094] The main chain of polypropylene grafted with maleic anhydride has a polyolefin structure. The anhydride groups in the side groups give it a certain polarity. Under melt shear conditions, it can physically entangle with polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene segments and interact with the oxygen-containing sites on the surface of zinc borate particles, thus forming a composite system with organic polymer as the continuous phase and inorganic components dispersed in it. During the twin-screw extrusion process, each component completes melting, dispersion and interfacial rearrangement under heat and shear. Zinc borate is uniformly dispersed in the polymer matrix. At the same time, antioxidants 1010 and 168 are used to stabilize the polymer system during processing, while calcium stearate plays a role in regulating the lubrication and dispersion state of the system. This results in a flame-retardant and toughening auxiliary masterbatch with a relatively uniform composition.

[0095] The mechanism of action of flame-retardant and toughening auxiliary masterbatch in MPP power pipe special material is as follows:

[0096] The flame-retardant and toughening auxiliary masterbatch obtained in this process has an effect on MPP power pipe special materials that is not limited to the pre-mixing of toughening components, inorganic additives, and processing stabilizing components. Instead, it pre-determines the existence form and interfacial relationship of the auxiliary functional phase in the polyolefin system through a composite approach of "compatibility continuous phase construction - toughening phase embedding - inorganic additive stable dispersion". Among them, polypropylene grafted with maleic anhydride provides a main chain structure similar to the polyolefin matrix and a certain polar bonding ability, so that the auxiliary masterbatch can take into account both continuous phase embedding and heterogeneous component coordination in the subsequent blending process. Polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene imparts a certain stress to the system. The auxiliary masterbatch serves as a buffer and toughness modifier, with zinc borate embedded as an inorganic functional component to provide auxiliary support for the stable response of the material under thermal and combustion effects. Antioxidant 1010, antioxidant 168, and calcium stearate further enhance the thermo-oxidative stability, flow regulation, and dispersion uniformity of the auxiliary masterbatch during processing. Thus, after the above structure is transferred to the MPP power pipe special material system via the flame-retardant and toughening auxiliary masterbatch, it helps to improve the dispersion stability and interphase adhesion coordination of each functional component during the melt blending process, reduce stress concentration and performance fluctuations caused by interface mismatch, and support the tensile strength, ring stiffness, post-aging performance retention, and overall comprehensive performance of the material.

[0097] Step 2: Preparation of raw materials

[0098] Weigh out the following components by weight: 52 parts polypropylene, 11 parts high-density polyethylene, 13 parts phosphine-nitrogen flame-retardant oligomer prepared in Example 1, 13 parts flame-retardant toughening auxiliary masterbatch, and 3 parts polysiloxane-shell cerium phytate hybrid cluster prepared in Example 4, for later use.

[0099] Step 3: Preparation of flame-retardant and weather-resistant pre-granules

[0100] Phosphorus nitrogen flame-retardant oligomers, polysiloxane shell phytate cerium hybrid clusters, and flame-retardant toughening auxiliary masterbatch were added to a high-speed mixer and mixed evenly. Then, the mixture was fed into a first twin-screw extruder and melt-extruded into granules at 170°C. The extrudate was cooled in a cooling water tank and then granulated and dried to obtain flame-retardant and weather-resistant pre-granules with a diameter of 2 mm and a particle length of 2 mm.

[0101] Step 4: Preparation of MPP power pipe special material

[0102] Polypropylene, high-density polyethylene, and flame-retardant and weather-resistant pre-granules are added to a high-speed mixer and mixed evenly. Then, the mixture is fed into a second twin-screw extruder and melt-extruded into granules at 180°C. The extrudate is cooled in a cooling water tank, then granulated and dried to obtain MPP power pipe special material with a diameter of 3mm and a particle length of 3mm.

[0103] The reaction principle for preparing flame-retardant and toughening auxiliary masterbatch is as follows:

[0104] Polypropylene and high-density polyethylene form a continuous phase dominated by polyolefin segments in the molten state. Phosphine nitrogen flame retardant oligomers, polysiloxane shell cerium phytate hybrid clusters, and flame retardant toughening auxiliary masterbatches are dispersed and embedded in this continuous phase under heat and shear. Among them, the anhydride groups contained in the polypropylene grafted with maleic anhydride in the flame retardant toughening auxiliary masterbatch can form strong interfacial interactions with the phosphine nitrogen structure, the oxygen-containing groups on the surface of the cerium phytate coordination structure, and the polysiloxane shell, thereby enhancing the interfacial bonding between the components. Polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene participates in the physical entanglement and phase regulation between polyolefin segments. Zinc borate and polysiloxane shell cerium phytate hybrid clusters exist in the form of dispersed phases, ultimately forming a multi-component molten composite system composed of a polyolefin matrix and phosphorus-, nitrogen-, silicon-, and cerium-containing structures.

[0105] Example 8

[0106] This embodiment provides a method for preparing weather-resistant and flame-retardant MPP power pipe material, including the following steps:

[0107] Step 1: Preparation of flame-retardant and toughening auxiliary masterbatch

[0108] Weigh out 27.0g of polypropylene grafted maleic anhydride, 15.0g of polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, 15.0g of zinc borate, 0.5g of antioxidant 1010, 0.5g of antioxidant 168 and 0.3g of calcium stearate and add them to a high-speed mixer and mix evenly. Then add them to a twin-screw extruder and melt extrude and granulate at 190℃. After cooling in a cooling water tank, the extrudate is granulated and dried to obtain flame-retardant toughening auxiliary masterbatch with a diameter of 3mm and a particle length of 4mm.

[0109] Step 2: Preparation of raw materials

[0110] Weigh out the following components by weight: 58 parts polypropylene, 13 parts high-density polyethylene, 16 parts phosphine-nitrogen flame-retardant oligomer prepared in Example 2, 17 parts flame-retardant toughening auxiliary masterbatch, and 5 parts polysiloxane-shell cerium phytate hybrid cluster prepared in Example 5, and set aside for later use.

[0111] Step 3: Preparation of flame-retardant and weather-resistant pre-granules

[0112] Phosphine nitrogen flame retardant oligomers, polysiloxane shell phytate cerium hybrid clusters, and flame retardant toughening auxiliary masterbatch were added to a high-speed mixer and mixed evenly. Then, the mixture was fed into a first twin-screw extruder and melt-extruded into granules at 185°C. The extrudate was cooled in a cooling water tank and then granulated and dried to obtain flame retardant and weather-resistant pre-granules with a diameter of 4 mm and a particle length of 5 mm.

[0113] Step 4: Preparation of MPP power pipe special material

[0114] Polypropylene, high-density polyethylene, and flame-retardant and weather-resistant pre-granules are added to a high-speed mixer and mixed evenly. Then, the mixture is fed into a second twin-screw extruder and melt-extruded into granules at 205°C. The extrudate is cooled in a cooling water tank and then granulated and dried to obtain MPP power pipe special material with a diameter of 4 mm and a particle length of 5 mm.

[0115] Example 9

[0116] This embodiment provides a method for preparing weather-resistant and flame-retardant MPP power pipe material, including the following steps:

[0117] Step 1: Preparation of flame-retardant and toughening auxiliary masterbatch

[0118] Weigh out 25.5g of polypropylene grafted maleic anhydride, 12.5g of polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, 11.5g of zinc borate, 0.5g of antioxidant 1010, 0.5g of antioxidant 168 and 0.3g of calcium stearate and add them to a high-speed mixer and mix evenly. Then add them to a twin-screw extruder and melt extrude and granulate at 180℃. After cooling in a cooling water tank, the extrudate is granulated and dried to obtain flame-retardant toughening auxiliary masterbatch with a diameter of 3mm and a particle length of 3mm.

[0119] Step 2: Preparation of raw materials

[0120] Weigh out the following components by weight: 55 parts polypropylene, 12 parts high-density polyethylene, 15 parts phosphine-nitrogen flame-retardant oligomer prepared in Example 3, 15 parts flame-retardant toughening auxiliary masterbatch, and 4 parts polysiloxane-shell cerium phytate hybrid cluster prepared in Example 6, and set aside for later use.

[0121] Step 3: Preparation of flame-retardant and weather-resistant pre-granules

[0122] Phosphine nitrogen flame retardant oligomers, polysiloxane shell phytate cerium hybrid clusters, and flame retardant toughening auxiliary masterbatch were added to a high-speed mixer and mixed evenly. Then, the mixture was fed into a first twin-screw extruder and melt-extruded into granules at 178°C. The extrudate was cooled in a cooling water tank and then granulated and dried to obtain flame retardant and weather-resistant pre-granules with a diameter of 3 mm and a particle length of 4 mm.

[0123] Step 4: Preparation of MPP power pipe special material

[0124] Polypropylene, high-density polyethylene, and flame-retardant and weather-resistant pre-granules are added to a high-speed mixer and mixed evenly. Then, the mixture is fed into a second twin-screw extruder and melt-extruded into granules at 193°C. The extrudate is cooled in a cooling water tank, then granulated and dried to obtain MPP power pipe special material with a diameter of 4 mm and a particle length of 4 mm.

[0125] Comparative Example 1

[0126] The difference between this comparative example and Example 9 is that step III is omitted in the preparation process of the phosphine-nitrogen flame-retardant oligomer used in step two.

[0127] Comparative Example 2

[0128] The difference between this comparative example and Example 9 is that step ② is omitted in the preparation process of the polysiloxane-shell cerium phytate hybrid cluster used in step 2.

[0129] Comparative Example 3

[0130] The difference between this comparative example and Example 9 is that in step one, polypropylene of equal mass is used instead of polypropylene grafted with maleic anhydride.

[0131] Performance testing:

[0132] The oxygen index of the MPP power pipe materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test".

[0133] The tensile strength of the MPP power pipe materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 2406.2-2009 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics".

[0134] The MPP power pipe materials prepared in Examples 7-9 and Comparative Examples 1-3 were aged according to standard GB / T 16422.2-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp" and then the tensile strength was determined according to standard GB / T2406.2-2009, and the tensile strength retention rate was calculated.

[0135] The MPP power pipe materials obtained in Examples 7-9 and Comparative Examples 1-3 were dried at 80°C for 2 hours. After drying, they were cooled to 45°C and added to the hopper of a φ75 / 33 single-screw extruder for extrusion molding. The temperatures of zones one, two, three, and four of the barrel were set to 170°C, 178°C, 185°C, and 190°C, respectively. The connecting neck temperature was set to 193°C. The temperatures of zone one and zone two of the die head were set to 193°C and 191°C, respectively. The die temperature was set to 188°C. The melt temperature was controlled at 190°C. The screw speed was controlled at 38 rpm. The melt pressure was controlled at 12 MPa. a; After the extruded melt is extruded through the die, it enters the sizing system. The inner diameter of the sizing sleeve is set to 110.2 mm. The vacuum degree of the first vacuum chamber is set to -0.032 MPa and the water temperature is set to 22℃. The vacuum degree of the second vacuum chamber is set to -0.022 MPa and the water temperature is set to 26℃. The temperature of the subsequent spray cooling water is set to 28℃. The internal blowing support air pressure is set to 0.010 MPa. The traction speed is set to 0.60 m / min. The length of the cooling and shaping section is set to 9 m. The final cutting length is set to 6000 mm, and an MPP power pipe with specifications of DS110×8×6000 mm is obtained.

[0136] The ring stiffness of the MPP power pipes prepared from the MPP power pipe materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 9647-2015 "Determination of ring stiffness of thermoplastic pipes".

[0137] The Vicat softening temperature of MPP power pipes prepared from the MPP power pipe materials prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 1633-2000 "Determination of Vicat softening temperature (VST) of thermoplastic plastics". The specific data are shown in Table 1.

[0138] Table 1 - Performance Test Data for Each Sample

[0139]

[0140] Data Analysis:

[0141] Comparative analysis of the data in Table 1 reveals that the MPP power pipe material prepared in this invention has an oxygen index of 29.6%, a tensile strength of 27.9 MPa, and a tensile strength retention rate of 85.7% after xenon arc lamp aging. Furthermore, the MPP power pipe prepared using this material exhibits a ring stiffness of 35.9 kN·m. 2 Furthermore, the Vicat softening temperature is 153.2℃, and all data are superior to the comparative example, indicating that:

[0142] In Comparative Example 1, the flame-retardant component did not further form a relatively complete oligomerization bridging structure, resulting in insufficient multi-point connection relationships at the molecular scale after it entered the polyolefin system. It was difficult to establish a relatively stable embedded state with the matrix and the phytate cerium hybrid cluster of the polysiloxane shell under the adjustment of the flame-retardant and toughening auxiliary masterbatch. As a result, the distribution continuity and interface coordination between functional phases were affected during the pre-granulation preparation and subsequent melt extrusion process. Local areas were more prone to phase separation, stress transmission interruption and uneven thermal response. The above changes further weakened the integration of the internal structure of the material, making the multi-component relationship that could originally support each other under the action of heat, stress and environment tend to loosen. Ultimately, the overall composite state of the sample could not maintain the coordination level in the example.

[0143] In Comparative Example 2, the coordination polymer clusters did not have a further silicone shell layer, resulting in a lack of necessary interfacial transition layer between the inorganic functional phase and the continuous polyolefin phase. During high-speed mixing and twin-screw melt shearing, the matching between the particle surface state and the overall rheological environment of the system decreased. As a result, the dispersion uniformity and interfacial coating integrity of the functional components in the matrix were affected, and structural abrupt change points were more likely to form in local areas. Furthermore, the synergistic network established by the phosphine nitrogen flame retardant oligomer and the flame retardant toughening auxiliary masterbatch was difficult to extend to the surrounding inorganic phase. As the material was subjected to external conditions such as heat, oxygen, and light, the original continuous shielding relationship and interphase support relationship within the system were weakened, making it difficult to maintain the overall stability of the sample under long-term use conditions.

[0144] In Comparative Example 3, the auxiliary masterbatch did not form an effective polar interface connection structure, resulting in insufficient compatibility between the phosphine-nitrogen flame-retardant oligomer, the polysiloxane shell cerium phytate hybrid cluster, and the polypropylene / high-density polyethylene matrix. In the pre-granulation stage, the above deficiencies were first manifested in the difficulty of obtaining a stable and balanced pre-dispersion state of the functional components. In the final mixing and extrusion stage, they were further manifested in discontinuous phase interface bonding, insufficient local adhesion, and decreased microstructure uniformity. Since the interface layer failed to effectively undertake the transition and coordination between components, the system was more prone to local defect expansion and synergistic response imbalance during heating, stress, and long-term service. This weakened the overall structural relationship that originally depended on the joint maintenance of multiple components, ultimately leading to a significant decline in the composite performance of the sample.

[0145] In conclusion, this application does not revolve around the parallel superposition of a single flame-retardant component, a single inorganic component, or a single compatibility additive. Instead, it utilizes a hierarchical coordination among the phosphine-nitrogen flame-retardant oligomer structure, the polysiloxane shell phytate cerium hybrid structure, and the auxiliary masterbatch containing compatibility units. This allows each functional phase to sequentially complete pre-dispersion, interfacial transition, and continuous phase embedding during the pre-granulation and final mixing extrusion stages. Consequently, if any structural link is omitted or replaced, the transfer relationship formed by molecular-level connections, particle-level coating, and phase interface coordination within the system is no longer complete. During melt processing, the rheological matching, dispersion stability, and interphase adhesion state of each component change accordingly, and this is further transmitted to the overall response mode of the material under thermal, mechanical, and environmental influences. Thus, the relevant performance characterization is not isolated and dependent on a single component, but rather reflects the systematic result formed under the combined action of specific material configuration and processing path.

[0146] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A weather resistant flame retardant MPP electrical power pipe material, characterized in that, The raw material composition includes the following parts by weight: 52-58 parts polypropylene, 11-13 parts high-density polyethylene, 13-16 parts phosphine nitrogen flame retardant oligomer, 13-17 parts flame retardant toughening auxiliary masterbatch and 3-5 parts polysiloxane shell cerium phytate hybrid cluster. The preparation method of the phosphonium-nitrogen flame-retardant oligomer is as follows: the bridged phosphonium-nitrogen flame-retardant intermediate, acetone and N-methylpyrrolidone are added to the reaction vessel and stirred. After mixing evenly, the reaction vessel is cooled to 0-5℃, cyanuric chloride is added and stirred for 40-60 min, then piperazine is added and stirred for another 40-60 min. Then the temperature is raised to 35-45℃ and stirred for another 40-60 min. Then the temperature is raised to 70-75℃ and stirred for 2-3 h. The phosphonium-nitrogen flame-retardant oligomer is obtained after post-treatment. The bridged phosphine-nitrogen flame retardant intermediate was prepared by the following method: A1. Add terephthalaldehyde, anhydrous ethanol and o-xylene to a reaction vessel and stir. After mixing evenly, add p-phenylenediamine and heat the reaction vessel to 75-85℃. Keep it heated and stir for 1-2 hours. Then continue to heat to 135-140℃ and keep it heated and stir for 3-4 hours. Post-treatment yields phosphine nitrogen flame retardant precursor. A2. Add the phosphonium flame retardant precursor and N-methylpyrrolidone to the reaction vessel and stir. After mixing evenly, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Then heat the reaction vessel to 115-120℃ and stir for 5-7 hours. After post-treatment, the bridged phosphonium flame retardant intermediate is obtained. The polysiloxane-shell cerium phytate hybrid cluster was prepared by the following method: B1. Add the acid solution and deionized water to the reaction vessel and stir. After mixing evenly, add cerium nitrate hexahydrate and adjust the pH of the reaction system to 3.8-4.2 with ammonium hydroxide. Then heat the reaction vessel to 55-65℃ and keep it at that temperature for 3-4 hours. The post-treatment yields cerium phytate coordination polymer clusters. B2. Add cerium phytate coordination polymer clusters, anhydrous ethanol, deionized water and ammonium hydroxide to a reaction vessel and stir. After mixing evenly, add γ-glycidoxypropyltrimethoxysilane. Then heat the reaction vessel to 50-55℃ and stir for 4-5 hours. Post-treatment yields polysiloxane-shell cerium phytate hybrid clusters.

2. The weather-resistant and flame-retardant MPP power pipe material according to claim 1, characterized in that, In the preparation of phosphonium-nitrogen flame-retardant oligomers, the ratio of the bridged phosphonium-nitrogen flame-retardant intermediate, acetone, N-methylpyrrolidone, cyanuric chloride and piperazine is 50-60g:150mL:60mL:8-10g:4-5g.

3. The weather-resistant and flame-retardant MPP power pipe material according to claim 1, characterized in that, In step A1, the ratio of terephthalaldehyde, anhydrous ethanol, o-xylene, and p-phenylenediamine is 30-36g:250mL:120mL:27-32g; in step A2, the ratio of the phosphonium flame retardant precursor, N-methylpyrrolidone, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 45-55g:200mL:27-32g.

4. The weather-resistant and flame-retardant MPP power pipe material according to claim 1, characterized in that, The preparation method of the flame-retardant and toughening auxiliary masterbatch is as follows: polypropylene grafted with maleic anhydride, polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, zinc borate, antioxidant 1010, antioxidant 168 and calcium stearate are added to a high-speed mixer and mixed evenly. Then, the mixture is added to a twin-screw extruder and melt-extruded and granulated at 170-190℃. The post-treatment yields the flame-retardant and toughening auxiliary masterbatch.

5. The weather-resistant and flame-retardant MPP power pipe material according to claim 4, characterized in that, In the process of preparing the flame-retardant and toughening auxiliary masterbatch, the ratio of polypropylene grafted with maleic anhydride, polystyrene-block-poly(ethylene-ran-butene)-block-polystyrene, zinc borate, antioxidant 1010, antioxidant 168 and calcium stearate is 24-27g:10-15g:8-15g:0.5g:0.5g:0.3g.

6. The weather-resistant and flame-retardant MPP power pipe material according to claim 1, characterized in that, In step B1, the ratio of the acid solution, deionized water, ammonium hydroxide, and cerium nitrate hexahydrate is 60-75 mL: 270 mL: 8-10 g, wherein the acid solution is a 50 wt% phytic acid aqueous solution; in step B2, the ratio of the cerium phytate coordination polymer cluster, anhydrous ethanol, deionized water, ammonium hydroxide, and γ-glycidoxypropyltrimethoxysilane is 25 g: 100 mL: 25-30 mL: 4-6 mL: 6-9 mL.

7. A method for preparing a weather-resistant and flame-retardant MPP power pipe material as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Phosphorus nitrogen flame retardant oligomer, polysiloxane shell phytate cerium hybrid cluster and flame retardant toughening auxiliary masterbatch are added to a high-speed mixer and mixed evenly. Then, the mixture is added to the first twin-screw extruder and melt-extruded into granules at 170-185℃. After post-treatment, flame retardant and weather-resistant pre-granules are obtained. S2. Polypropylene, high-density polyethylene and flame-retardant and weather-resistant pre-granules are added to a high-speed mixer and mixed evenly. Then, the mixture is added to a second twin-screw extruder and melt-extruded into granules at 180-205℃. After post-treatment, MPP power pipe special material is obtained.

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