MPP power cable protection pipe containing rare earth anti-aging system and preparation method thereof

Abstract

The application belongs to the field of polymer materials and power engineering protection technology, and particularly relates to a MPP power cable protection pipe containing a rare earth anti-aging system and a preparation method thereof. The protection pipe is composed of rare earth coordination modified polypropylene, N,N'-bis(2-hydroxyethyl)adipamide, antioxidant 1010, light stabilizer 622, hindered amine light stabilizer 944, lubricant and ultraviolet absorption agent. Rare earth ions and polypropylene grafted maleic anhydride form a stable coordination structure, and organic small molecules enhance the interface combination through hydrogen bonds of hydroxyl and amide groups, so that the molecular chain is stably connected at multiple points. The application significantly improves the thermal oxidation resistance, ultraviolet aging resistance and thermal deformation performance of the material, and the prepared cable protection pipe has excellent mechanical strength, heat resistance and long-term weather resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials and power engineering protection, and particularly relates to a MPP power cable protection pipe containing a rare earth anti-aging system and a preparation method thereof. BACKGROUND

[0002] At present, modified polypropylene (MPP) power cable protection pipes are widely used in the underground laying of urban power cables, communication optical cables and power transmission lines, and have the advantages of light weight, high strength, convenient construction and high pressure resistance. However, in the long-term operation process, the cable protection pipe is often in a high-temperature, current-induced, humid-heat, ultraviolet radiation and oxidation environment, and the traditional MPP material is prone to molecular chain rupture, oxidation aging and mechanical property decay, resulting in pipe brittleness, deformation or insulation performance degradation, thereby affecting the safe operation of the power system.

[0003] In the prior art, in order to improve the anti-aging performance of the MPP material, methods such as adding hindered phenolic antioxidants, ultraviolet absorbers and hindered amine light stabilizers are usually used, but these small molecule anti-aging agents have problems such as strong thermal volatility, high migration and insufficient long-term stability, which are difficult to meet the long-term use requirements in high-temperature and high-ultraviolet environments. In addition, the conventional anti-aging system has limited improvement on the polarity of the polypropylene matrix, resulting in poor dispersibility of the additives and insufficient interfacial compatibility, which affects the overall performance of the material.

[0004] Rare earth elements can significantly improve the thermal stability and anti-aging performance of polymers through complexation, coordination or free radical capture due to their unique 4f orbital electron structure. However, current rare earth modification technology is mainly applied in polyolefin films, optical materials and catalysis fields, and there is little research on its application in MPP cable protection pipe systems. Moreover, the existing reports are mostly simple physical blending, and the dispersion of rare earth ions is poor, which makes it difficult to form stable combination with the polypropylene main chain, resulting in short-term modification effect.

[0005] Therefore, it is urgent to develop a new MPP anti-aging system that combines the stable structure of rare earth coordination and the interface regulation function of organic small molecules, so that the rare earth ions can be stably distributed in the polypropylene chain segment and form a synergistic effect with the organic small molecules, thereby improving the anti-aging ability and structural stability of the material from the molecular level, and achieving the requirements of high heat resistance, long service life and high safety use of the power cable protection pipe. SUMMARY

[0006] In order to overcome the technical problems of the MPP power cable protection pipe in the prior art, i.e., easy aging, short service life and insufficient thermal stability in high temperature, ultraviolet and oxidation environment, the present application provides a MPP power cable protection pipe containing a rare earth anti-aging system and a preparation method thereof, and the thermal oxidation stability and long-term weather resistance of the material are improved from the molecular level by constructing a synergistic system of a rare earth coordination structure and a reactive organic small molecule.

[0007] The object of the present application can be achieved by the following technical solutions.

[0008] A MPP power cable protection pipe containing a rare earth anti-aging system, the protection pipe comprises the following raw materials by weight: 70-85 parts of rare earth coordination modified polypropylene; 10-20 parts of N,N'-bis(2-hydroxyethyl)adipamide; 0.2-0.6 parts of antioxidant 1010; 0.3-0.8 parts of light stabilizer 6220; 0.2-0.5 parts of hindered amine light stabilizer 944; 0.5-1.5 parts of lubricant; 0.2-0.5 parts of dispersing aid; and 0.2-0.8 parts of ultraviolet absorbing agent; wherein the rare earth coordination modified polypropylene is a rare earth coordination polypropylene material formed by a coordination reaction between polypropylene grafted maleic anhydride, rare earth nitrate and acetylacetone ligand in a solution; the N,N'-bis(2-hydroxyethyl)adipamide is a reactive organic small molecule not used in the field of MPP cable pipes, which can form hydrogen bonds and polar interactions with polypropylene molecular chains, thereby enhancing the interfacial bonding force and improving the anti-aging performance.

[0009] Optionally, the rare earth coordination modified polypropylene comprises the following raw materials by weight: 90-110 parts of polypropylene grafted maleic anhydride; 10-20 parts of acetylacetone; 3-8 parts of rare earth nitrate; 120-180 parts of anhydrous ethanol; and 10-30 parts of deionized water.

[0010] Optionally, the preparation method of the rare earth coordination modified polypropylene comprises the following steps:

[0011] (1) polypropylene grafted maleic anhydride is added to a reaction kettle, anhydrous ethanol is added, and a uniformly dispersed system is formed under the condition of heating and stirring;

[0012] (2) adding acetylacetone into the dispersion system, and continuing to stir to make the acetylacetone fully contact with the grafting sites of the maleic anhydride;

[0013] (3) slowly adding an ethanol solution of a rare earth nitrate, and maintaining a constant temperature to form a coordination structure between the rare earth ions and the acetylacetone and maleic anhydride groups;

[0014] (4) after the reaction is completed, standing and cooling, centrifugal separation, and washing with anhydrous ethanol to remove unreacted substances and impurities, to obtain a solid;

[0015] (5) drying the obtained solid under vacuum to obtain the rare earth coordination modified polypropylene.

[0016] Optionally, the reaction conditions of step (1) are a temperature of 70-80℃, a stirring speed of 200-300 r / min, and a time of 30-40 min; and the reaction conditions of step (2) are stirring at a constant temperature of 70-80℃ for 10-20 min.

[0017] Optionally, the reaction conditions of step (3) are a dropping speed of 1-2 ml / min, a reaction time of 2-4 h, and a pH of 6-7.

[0018] Optionally, the drying conditions of step (5) are a temperature of 60℃, a vacuum degree of -0.08 MPa, and a drying time of 8-10 h.

[0019] Optionally, the lubricant is a mixture of calcium stearate and polyethylene wax at a mass ratio of 1:1-1.5; the dispersing agent is a mixture of γ-aminopropyl triethoxysilane and ethanol at a mass ratio of 1:4-6; and the ultraviolet absorption agent is a mixture of 2-(2'-hydroxy-5'-tert-butyl phenyl) benzotriazole and o-hydroxybenzoyl aniline at a mass ratio of 1:0.8-1.2.

[0020] Optionally, a preparation method of a MPP power cable protection pipe containing a rare earth anti-aging system comprises the following steps:

[0021] S1, sequentially adding rare earth coordination modified polypropylene, N,N'-bis (2-hydroxyethyl) adipamide, antioxidant 1010, light stabilizer 622, hindered amine light stabilizer 944, lubricant, dispersing agent, and ultraviolet absorption agent into a mixing device, and stirring and mixing to form a uniform material;

[0022] S2, feeding the uniform material into a twin-screw extruder to perform melt blending, to obtain a modified MPP composite material;

[0023] S3, extruding the modified MPP composite material into a pipe through an extrusion molding machine, and performing cooling, shaping, and cutting, to obtain a MPP power cable protection pipe containing a rare earth anti-aging system.

[0024] Optionally, the reaction condition of step S1 is stirring at room temperature for 10-20 minutes, and the stirring speed is 200-300 r / min.

[0025] Optionally, the reaction condition of step S2 is an extrusion temperature of 180-220 DEG C and a screw rotation speed of 80-120 r / min, and the molding condition of step S3 is a cooling water temperature of 20-30 DEG C and a setting time of 5-10 minutes.

[0026] The present application has the following beneficial effects:

[0027] The present application realizes the substantial innovation of anti-aging mechanism in the MPP power cable protection pipe system through the introduction of rare earth ion coordination modification mechanism and the cooperative structure design of reactive organic small molecules. The rare earth ions form a stable ternary coordination structure with acetylacetone and polypropylene grafted maleic anhydride, and a “main chain-rare earth-ligand” type molecular network is constructed, so that the rare earth atoms are uniformly distributed in the polypropylene matrix in a coordination state. This chemical combination structure significantly improves the stability of the rare earth ions in a high-temperature and oxidizing environment, can continuously capture free radicals and block chain oxidation reactions, thereby effectively delaying the thermal oxidation aging process of polypropylene and avoiding the problems of easy migration and easy failure of traditional small molecule antioxidants.

[0028] The present application uses N,N'-bis(2-hydroxyethyl)adipamide which has not been applied in the MPP system as a reactive organic small molecule, and uses the multi-point hydrogen bond effect formed by the terminal hydroxyl group and the amide group to establish a flexible network structure between molecules, which significantly improves the polar interaction and interface bonding performance of the polypropylene segment. The small molecule can form a reversible hydrogen bond reconstruction network during the heating process, giving the material the characteristics of self-regulating energy release, improving the structural stability and toughness of the pipe material under thermal stress and mechanical stress.

[0029] The synergistic effect between the rare earth coordination structure and the organic small molecule network enables the system to form a stable barrier layer with energy absorption and free radical passivation functions in a high-temperature and strong ultraviolet environment. After 120 DEG C x 500 h accelerated aging test, the tensile strength retention rate of the material is still more than 90%, the oxidation induction time is more than doubled compared with the traditional system, and there is no cracking or powdering phenomenon on the surface.

[0030] In summary, through the innovative combination of rare earth coordination and molecular level interface regulation, the present application realizes the structural stabilization and anti-aging performance breakthrough of the MPP cable protection pipe under long-term high temperature and strong light conditions, and has significant creativity and engineering application value. BRIEF DESCRIPTION OF DRAWINGS

[0031] The present application will be further described below in conjunction with the drawings.

[0032] Figure 1The infrared spectrum contrast chart of polypropylene and rare earth coordination modified polypropylene;

[0033] Figure 2 The oxidation induction time result contrast chart of different ratio samples;

[0034] Figure 3 The tensile strength retention rate result contrast chart of different ratio samples;

[0035] Figure 4 The thermal deformation and Vicat softening temperature test result contrast chart of different ratio samples. DETAILED DESCRIPTION

[0036] The application will be further described below in conjunction with specific examples, but the application is not limited to the following examples, and equivalent adjustments made without departing from the spirit and essence of the application shall be deemed to fall within the protection scope of the application.

[0037] Example 1:

[0038] The purpose of the present example is to verify the basic improvement effect of the rare earth coordination modified polypropylene system on the anti-aging performance of the cable protection pipe under the condition of lower rare earth content and organic small molecule addition amount, and to evaluate the initial thermal stability and processing performance of the system.

[0039] S1, take 90 parts of polypropylene grafted maleic anhydride into a reaction kettle, add 120 parts of anhydrous ethanol, stir at 70-80℃ for 30-40 minutes to form a uniform dispersion system; add 10 parts of acetylacetone to the system, continue to stir under constant temperature conditions for 10-20 minutes; slowly add 3 parts of rare earth nitrate ethanol solution, the dropwise adding speed is controlled at 1ml per minute, react for 2 hours, the system pH is maintained at 6-7; after the reaction is completed, naturally cool to room temperature, centrifugal separation and washing with anhydrous ethanol for 3 times, vacuum drying to constant weight, to obtain the rare earth coordination modified polypropylene;

[0040] S2, add 70 parts of rare earth coordination modified polypropylene, 10 parts of N,N'-bis(2-hydroxyethyl)adipamide, 0.2 parts of antioxidant 1010, 0.3 parts of light stabilizer 622, 0.2 parts of hindered amine light stabilizer 944, 0.5 parts of lubricant, 0.2 parts of dispersing aid, and 0.2 parts of ultraviolet absorbing agent into a high-speed mixer in sequence, stir at room temperature for 15 minutes to prepare a uniform mixture;

[0041] S3, send the mixture into a double screw extruder, control the temperature interval at 180-190℃, the screw rotation speed is 80r / minute, after extruding and granulating, pass through an extrusion molding machine to form a pipe, the water bath temperature is 25℃, the setting time is 8 minutes, to obtain a MPP power cable protection pipe with uniform gloss and smooth surface.

[0042] Example 2:

[0043] The purpose of the present embodiment is to investigate the structural uniformity, thermal stability and comprehensive mechanical properties under the synergistic conditions of medium proportion of rare earth coordination modification and small organic molecules, so as to evaluate the optimal performance balance interval.

[0044] S1, 100 parts of polypropylene grafted maleic anhydride were added into a reaction kettle, 150 parts of anhydrous ethanol were added, and stirring was carried out at 75°C for 35 minutes to form a dispersion system; 15 parts of acetylacetone were added, and constant temperature stirring was continued for 15 minutes; 5 parts of rare earth nitrate ethanol solution was slowly added dropwise, the dropwise adding speed was controlled at 1.5 ml per minute, the reaction was carried out for 3 hours, and the pH of the system was adjusted to 6.5; after the reaction was completed, it was cooled and separated by centrifugation, and washed with anhydrous ethanol for 3 times, and dried at 60°C under vacuum for 9 hours to obtain a rare earth coordination modified polypropylene; Figure 1 The infrared spectrum shows that the rare earth coordination modified polypropylene sample appears new absorption peaks at 1620, 1210, 930 and 480 cm⁻¹, which correspond to rare earth–O=C coordination bond, C–O–M coordination structure, rare earth–O bond and rare earth–O–C bridge bond respectively, indicating that the rare earth ions form a stable coordination network with acetylacetone and maleic anhydride groups; at the same time, the C=O peak intensity at 1720 cm⁻¹ is enhanced and slightly red shifted, indicating that the carbonyl group participates in the coordination reaction, and the C–H and C–O characteristic peaks of the polypropylene main chain remain unchanged, verifying that the rare earth coordination modification is successfully realized and does not damage the matrix structure;

[0045] S2, 78 parts of rare earth coordination modified polypropylene, 15 parts of N,N'-bis(2-hydroxyethyl)adipamide, 100.4 parts of antioxidant 1010, 20.5 parts of light stabilizer 622, 40.3 parts of hindered amine light stabilizer 944, 1.0 parts of lubricant, 0.3 parts of dispersing aid, and 0.5 parts of ultraviolet absorbing agent were mixed at room temperature for 15 minutes to obtain a uniform material;

[0046] S3, the mixed material was put into a double screw extruder, the temperature interval was controlled at 190-205°C, and the screw rotation speed was 100 r / min for melt blending; after extrusion granulation, it was sent into a molding equipment, and was shaped at a water bath temperature of 25°C for 7 minutes to obtain a MPP power cable protection pipe with excellent mechanical properties and uniform color.

[0047] Example 3:

[0048] The purpose of the present embodiment is to verify the extreme improvement effect of the high rare earth content and high proportion of organic small molecule complex system on the antioxidant and ultraviolet aging resistance, and to investigate the structural stability and durability in high temperature environment.

[0049] S1, take polypropylene grafted maleic anhydride 110 parts into the reaction kettle, add anhydrous ethanol 180 parts, stir at 80℃ for 40 minutes to form a stable dispersion system; add acetylacetone 20 parts, keep constant temperature stirring for 20 minutes; slowly add rare earth nitrate 8 parts of ethanol solution, the dropwise adding speed is controlled at 2 milliliters per minute, react for 4 hours, the system pH is maintained at 6.5-7; after reaction, cool to room temperature, centrifugal separation and washing 4 times, vacuum drying for 10 hours, to get the rare earth coordination modified polypropylene;

[0050] S2, take rare earth coordination modified polypropylene 85 parts, N,N'-bis (2-hydroxyethyl) adipamide 20 parts, antioxidant 1010 0.6 parts, light stabilizer 622 0.8 parts, hindered amine light stabilizer 944 0.5 parts, lubricant 1.5 parts, dispersion aid 0.5 parts, ultraviolet absorption agent 0.8 parts into the mixing equipment, stir at room temperature for 20 minutes, to get the uniform mixture;

[0051] S3, put the material into the twin screw extruder, control the temperature interval at 200-220℃, screw rotation speed 120r / minute for melt blending; after granulation, extrude into pipe in the extrusion molding machine, water bath cooling temperature 28℃ for 5 minutes, get the MPP power cable protection pipe with high gloss and excellent heat resistance.

[0052] Comparative example 1:

[0053] The purpose of this comparative example is to verify the change of thermal stability and structural uniformity of the material when the system contains only rare earth coordination modified polypropylene without reactive organic small molecules, to compare the importance of synergistic effect.

[0054] S1, take polypropylene grafted maleic anhydride 100 parts into the reaction kettle, add anhydrous ethanol 150 parts, stir at 75℃ for 35 minutes to form a dispersion system; add acetylacetone 15 parts, keep constant temperature continue stirring for 15 minutes; slowly add rare earth nitrate 5 parts of ethanol solution, the dropwise adding speed is controlled at 1.5 milliliters per minute, react for 3 hours, the system pH is adjusted to 6.5; after reaction, cool, centrifugal separation and washing 3 times with anhydrous ethanol, vacuum drying at 60℃ for 9 hours, to get the rare earth coordination modified polypropylene;

[0055] S2, take rare earth coordination modified polypropylene 93 parts, antioxidant 1010 0.4 parts, light stabilizer 622 0.5 parts, hindered amine light stabilizer 944 0.3 parts, lubricant 1.0 parts, dispersion aid 0.3 parts, ultraviolet absorption agent 0.5 parts, mix at room temperature for 15 minutes, to get the uniform material;

[0056] S3, the mixture is put into a twin-screw extruder, the temperature interval is controlled at 190-205℃, and the screw rotation speed is 100r / min for melt blending; after extrusion granulation, it is sent into a molding equipment, and is shaped at a water bath temperature of 25℃ for 7 minutes to obtain MPP power cable protection pipe with smooth surface.

[0057] Comparative Example 2

[0058] The purpose of the present comparative example is to verify the influence degree on the anti-aging performance and thermal oxidative stability of the material when the system only contains reactive organic small molecules without rare earth coordination structure, and to analyze the necessity of the rare earth coordination network.

[0059] S1, polypropylene grafted maleic anhydride 100 parts is added into a mixing kettle, anhydrous ethanol 150 parts is added, and stirring is performed for 35 minutes to form a uniform system; without adding acetylacetone and rare earth nitrate, drying is directly performed until the solvent is completely volatilized to obtain a polypropylene grafted substrate;

[0060] S2, polypropylene grafted maleic anhydride 78 parts, N,N'-bis(2-hydroxyethyl)adipamide 15 parts, antioxidant 101 0.4 parts, light stabilizer 622 0.5 parts, hindered amine light stabilizer 944 0.3 parts, lubricant 1.0 part, dispersing aid 0.3 parts, and anti-ultraviolet absorbing agent 0.5 parts are mixed at room temperature for 15 minutes to obtain a uniform material;

[0061] S3, the mixture is put into a twin-screw extruder, the temperature interval is controlled at 190-205℃, and the screw rotation speed is 100r / min for melt blending; after extrusion granulation, it is sent into a molding equipment, and is shaped at a water bath temperature of 25℃ for 7 minutes to obtain MPP power cable protection pipe with smooth surface.

[0062] Comparative Example 3

[0063] The purpose of the present comparative example is to serve as a blank control system for comparing the comprehensive synergistic effect of the anti-aging structure design of the present application, and analyzing the overall contribution of the synergistic effect of rare earth and organic small molecules.

[0064] S1, polypropylene grafted maleic anhydride 100 parts is added into a mixing kettle, anhydrous ethanol 150 parts is added, and stirring is performed for 35 minutes to form a uniform system; without adding acetylacetone, rare earth nitrate or organic small molecules, drying is directly performed until the solvent is completely volatilized to obtain a polypropylene grafted material;

[0065] S2, polypropylene grafted maleic anhydride 93 parts, antioxidant 101 0.4 parts, light stabilizer 622 0.5 parts, hindered amine light stabilizer 944 0.3 parts, lubricant 1.0 part, dispersing aid 0.3 parts, and anti-ultraviolet absorbing agent 0.5 parts are mixed at room temperature for 15 minutes to obtain a uniform material;

[0066] S3, the mixture is put into a twin-screw extruder, the temperature interval is controlled at 190-205℃, the screw rotation speed is 100 r / min for melt blending; after extrusion granulation, it is sent into a molding equipment, and is shaped at a water bath temperature of 25℃ for 7 minutes to obtain the ordinary MPP power cable protection pipe.

[0067] Performance test:

[0068] 1. Thermal oxidative stability test:

[0069] The oxidative induction time test is carried out according to GB / T19466.6-2009 Differential Scanning Calorimetry of Polymers. The samples of Examples 1-3 and Comparative Examples 1-3 are cut into about 5 mg particles, and are tested at an oxygen flow rate of 50 mL / min and a temperature of 200℃. The time of occurrence of the exothermic peak of oxidation is recorded. Each group of samples is tested repeatedly for 3 times to take the average value, which is used to evaluate the inhibiting effect of the rare earth coordination structure and the organic small molecule system on the thermal oxidative degradation of polypropylene.

[0070] 2. UV aging acceleration test:

[0071] The test is carried out according to GB / T16422.2-2014 Laboratory Light Source Exposure Test Method for Plastics. The samples of Examples 1-3 and Comparative Examples 1-3 are placed in a xenon arc lamp aging box, and are irradiated at an irradiation intensity of 0.55 W / m², a temperature of 63℃, and a humidity of 50%. The cycle of light exposure for 8 hours and condensation for 4 hours is repeated for a total of 500 hours. After aging, the tensile strength retention rate and the surface color change value are measured, which are used to evaluate the anti-UV aging performance of the rare earth coordination structure and the organic small molecule system.

[0072] 3. Mechanical property test:

[0073] The tensile and bending property tests are carried out according to GB / T1040.2-2006 and GB / T9341-2008 standards. The standard sample of 80 mm x 10 mm x 4 mm is prepared, and is balanced in an environment of 23℃ and a relative humidity of 50% for 24 hours. Then, the tensile and bending tests are carried out at a rate of 50 mm / min and 2 mm / min, respectively. The tensile strength, bending modulus and elongation at break are measured, which are used to evaluate the influence of different systems on the mechanical properties of the material.

[0074] 4. Heat distortion and Vicat softening temperature test:

[0075] The heat distortion temperature and Vicat softening temperature of the sample are measured according to GB / T1634.2-2004 and GB / T1633-2000 standards. The sample bar of 10 mm x 10 mm x 4 mm is prepared, and is tested under the conditions of a load of 1.8 MPa and a temperature rising rate of 120℃ / h. The test is used to evaluate the influence of the rare earth coordination structure and the organic small molecule system on the heat resistance and dimensional stability of the material.

[0076] Table 1. Results of thermal oxidation stability test:

[0077] Sample No. Oxidation induction time (min) Relative increase rate (%) Example 1 29.5 +46.0 Example 2 34.8 +68.0 Example 3 31.2 +54.0 Comparative Example 1 22.1 +10.0 Comparative Example 2 20.5 +2.0 Comparative Example 3 20.1 0

[0078] Table 2. Results of accelerated UV aging test:

[0079] Sample No. Tensile strength retention rate (%) Surface color change ΔE Light aging grade (0~5) Example 1 85.2 1.6 4 Example 2 91.8 1.1 5 Example 3 88.5 1.4 4 Comparative Example 1 75.3 2.2 3 Comparative Example 2 70.8 2.7 2 Comparative Example 3 68.1 3.0 2

[0080] Table 3. Mechanical property test results:

[0081] Sample No. Tensile strength (MPa) Flexural modulus (MPa) Elongation at break (%) Example 1 41.5 1650 132 Example 2 45.8 1755 145 Example 3 44.1 1720 138 Comparative Example 1 38.9 1600 120 Comparative Example 2 36.7 1550 115 Comparative Example 3 35.8 1525 110

[0082] Table 4. Test results of heat distortion and Vicat softening temperature:

[0083] Sample No. Heat distortion temperature (°C) Vicat softening temperature (°C) Example 1 132 138 Example 2 138 144 Example 3 136 141 Comparative Example 1 127 134 Comparative Example 2 125 132 Comparative Example 3 123 130

[0084] As can be seen from Table 1, Figure 2 The oxidation induction times of samples 1-3 in Examples 1-3 were significantly higher than those in the comparative examples, with Example 2 reaching 34.8 min, the highest among all samples. This indicates that the rare earth coordination modification and organic small molecule synergistic system can effectively delay the thermal oxidation process of polypropylene. Through the stable coordination between rare earth ions and maleic anhydride groups, combined with the hydrogen-bonded auxiliary structure of N,N'-bis(2-hydroxyethyl)hexamethylenediamide, the system's resistance to thermal oxidation is significantly improved. In contrast, the comparative examples, which do not contain rare earth elements or organic small molecules, show a significantly faster thermal oxidation degradation rate due to the lack of a stable energy level barrier.

[0085] As can be seen from the UV aging accelerated test results in Table 2, Figure 3 The tensile strength retention rates of Examples 1-3 were all above 85%, significantly higher than those of the comparative samples, with Example 2 reaching 91.8%. Simultaneously, Example 2 exhibited the lowest surface color change ΔE, at only 1.1. This indicates that the rare-earth coordination centers can absorb some high-energy ultraviolet radiation, while the polar interaction between the organic small molecules and the light stabilizer further reduces the photoinduced degradation rate, achieving a dual anti-aging mechanism. This system also demonstrates significant effects on the capture and energy transfer of photoinduced free radicals.

[0086] As shown in Table 3, the sample from the example exhibits significantly better tensile strength, flexural modulus, and elongation at break than the comparative sample. Example 2 demonstrates the best performance, with a tensile strength of 45.8 MPa and a flexural modulus of 1755 MPa. Rare earth ions form multi-point coordination bonds between polypropylene chains, which helps improve rigidity. Meanwhile, small organic molecules enhance compatibility through hydrogen bonding between polar segments and the main chain, enabling the system to possess both high strength and toughness.

[0087] As can be seen from the test results of heat deformation and Vicat softening temperature in Table 4, Figure 4The heat distortion temperature and the Vicat softening temperature of the sample of the middle embodiment are higher than those of the comparative example, wherein the heat distortion temperature of the middle embodiment 2 is 138°C, and the Vicat softening temperature is 144°C. The result shows that the rare earth coordination network structure improves the thermal stability and the spatial orientation arrangement capability of the polypropylene segment, reduces the segment movement in a high temperature environment, and the synergistic effect of the organic small molecule further improves the interface combination and enhances the heat distortion resistance of the system.

[0088] In summary, the middle embodiment 2 performs best in the four indexes of thermal oxidation stability, ultraviolet aging resistance, mechanical property and heat resistance, which shows that there is a significant synergistic enhancement effect between the rare earth coordination modification and the reactive organic small molecule, and the long-term use reliability and environmental weather resistance of the MPP power cable protection pipe can be significantly improved without reducing the processing property.

Claims

1. An MPP power cable protection pipe containing a rare earth anti-aging system, characterized in that, The protective tube comprises the following raw materials in parts by weight: 70-85 parts of rare earth coordination-modified polypropylene; 10-20 parts of N,N'-bis(2-hydroxyethyl)hexamethylenediamide; 0.2-0.6 parts of antioxidant 1010; 0.3-0.8 parts of light stabilizer 622; 0.2-0.5 parts of hindered amine light stabilizer 944; 0.5-1.5 parts of lubricant; 0.2-0.5 parts of dispersant; and 0.2-0.8 parts of UV absorber. The rare earth coordination-modified polypropylene is a rare earth coordination polypropylene material formed by grafting maleic anhydride with rare earth nitrates and acetylacetone ligands onto polypropylene in solution via a coordination reaction.

2. The MPP power cable protection pipe containing a rare earth anti-aging system according to claim 1, characterized in that, The rare earth coordination modified polypropylene comprises the following raw materials in parts by weight: 90-110 parts of polypropylene grafted with maleic anhydride; 10-20 parts of acetylacetone; 3-8 parts of rare earth nitrate; 120-180 parts of anhydrous ethanol; and 10-30 parts of deionized water.

3. An MPP power cable protection pipe containing a rare earth anti-aging system according to any one of claims 1 or 2, characterized in that, The preparation method of the rare earth coordination modified polypropylene includes the following steps: (1) Add polypropylene grafted with maleic anhydride to the reactor, add anhydrous ethanol, and form a uniform dispersion system under heating and stirring conditions. (2) Add acetylacetone to the dispersion system and continue stirring; (3) Slowly add an ethanol solution of rare earth nitrates and maintain the reaction under constant temperature conditions to form a coordination structure between rare earth ions and acetylacetone and maleic anhydride groups; (4) After the reaction is complete, allow the mixture to stand and cool, then centrifuge and wash with anhydrous ethanol to obtain a solid. (5) The obtained solid was dried under vacuum to obtain rare earth coordination modified polypropylene.

4. The MPP power cable protection pipe containing a rare earth anti-aging system according to claim 3, characterized in that, The reaction conditions for step (1) are a temperature of 70-80℃, a stirring speed of 200-300 r / min, and a time of 30-40 minutes; the reaction conditions for step (2) are stirring at a constant temperature of 70-80℃ for 10-20 minutes.

5. The MPP power cable protection pipe containing a rare earth anti-aging system according to claim 3, characterized in that, The reaction conditions for step (3) are: a dropping rate of 1-2 mL per minute, a reaction time of 2-4 hours, and a system pH of 6-7.

6. The MPP power cable protection pipe containing a rare earth anti-aging system according to claim 3, characterized in that, The drying conditions for step (5) are: temperature 60°C, vacuum degree −0.08 MPa, and drying time 8 to 10 hours.

7. The MPP power cable protection pipe containing a rare earth anti-aging system according to claim 1, characterized in that, The lubricant is a mixture of calcium stearate and polyethylene wax in a mass ratio of 1:1 to 1.5; the dispersing agent is a mixture of γ-aminopropyltriethoxysilane and ethanol in a mass ratio of 1:4 to 6; and the UV absorber is a mixture of 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole and o-hydroxybenzoylaniline in a mass ratio of 1:0.8 to 1.

2.

8. A method for preparing an MPP power cable protection pipe, wherein the MPP power cable protection pipe comprises a rare earth anti-aging system, and is prepared specifically according to the description of any one of claims 1 to 7, characterized in that, Includes the following steps: S1, rare earth coordination modified polypropylene, N,N'-bis(2-hydroxyethyl)hexamethylenediamide, antioxidant 1010, light stabilizer 622, hindered amine light stabilizer 944, lubricant, dispersant and UV absorber are added to the mixing equipment in sequence and stirred to form a uniform material. S2, the uniform material is fed into a twin-screw extruder for melt blending to obtain the modified MPP composite material; S3, the modified MPP composite material is extruded into a tube by an extrusion molding machine, and after cooling, shaping and cutting, an MPP power cable protection tube containing a rare earth anti-aging system is obtained.

9. The method for preparing an MPP power cable protection pipe containing a rare earth anti-aging system according to claim 8, characterized in that, The reaction conditions for step S1 are stirring at room temperature for 10 to 20 minutes at a stirring speed of 200 to 300 r / min.

10. The method for preparing an MPP power cable protection pipe containing a rare earth anti-aging system according to claim 8, characterized in that, The reaction conditions for step S2 are an extrusion temperature of 180–220°C and a screw speed of 80–120 r / min; the molding conditions for step S3 are a cooling water temperature of 20–30°C and a setting time of 5–10 minutes.

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