High-strength anti-aging MPP pipe and preparation method thereof

Abstract

The invention discloses a high-strength anti-aging MPP pipe and a preparation method thereof. The high-strength anti-aging MPP pipe is prepared from the following raw materials in percentage by weight: 53-59% of irregular polypropylene, 12-17% of syndiotactic polypropylene, 7-11% of an ethylene-vinyl alcohol copolymer, 4-8% of ethylene propylene diene monomer, 2.5-5% of polypropylene grafted maleic anhydride, 2-4% of dioctyl adipate, 6-10% of functional particles, 0.5-1% of an antioxidant and 0.2-0.5% of an ultraviolet light absorber. The functional particles are composite modified particles of nano calcium carbonate, nano silicon dioxide, nano zinc oxide, nano titanium dioxide and a hindered amine light stabilizer. The impact resistance of the MPP pipe at a low temperature and the aging resistance of the MPP pipe in a photo-thermal environment can be improved, so that the strength and the lasting stability of the MPP pipe are improved, and the MPP pipe has excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to a high-strength, aging-resistant MPP pipe and its preparation method, belonging to the field of polypropylene material technology. Background Technology

[0002] Polypropylene spiral corrugated pipe is a type of pipe made primarily of polypropylene (PP). It boasts advantages such as low density, easy processing, convenient construction, and low cost, and also exhibits good insulation and resistance to chemical corrosion, making it widely applicable in power, telecommunications, and municipal engineering fields. However, due to the structural characteristics of polypropylene molecules, the pipe is prone to brittle fracture at low temperatures, causing a sharp drop in its impact strength. Furthermore, the pipe is sensitive to ultraviolet radiation and heat-oxidation; long-term outdoor exposure can lead to photo-oxidative degradation of its molecular chains, resulting in surface chalking, discoloration, and a decline in mechanical properties. This ultimately affects the strength of the polypropylene pipe, reducing its mechanical properties and significantly shortening its service life. Summary of the Invention

[0003] To address at least one problem in the existing technology, the present invention provides a high-strength, aging-resistant MPP pipe and its preparation method, which can improve the impact resistance of MPP pipe at low temperatures and its aging resistance in photothermal and oxygen environments, thereby improving the strength and long-term stability of MPP pipe and exhibiting excellent mechanical properties.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a high-strength, aging-resistant MPP pipe, prepared from raw materials comprising the following weight percentages: random polypropylene 53-59%, syndiotactic polypropylene 12-17%, ethylene-vinyl alcohol copolymer 7-11%, ethylene propylene diene monomer (EPDM) rubber 4-8%, polypropylene grafted with maleic anhydride 2.5-5%, dioctyl adipate 2-4%, functional particles 6-10%, antioxidant 0.5-1%, and ultraviolet absorber 0.2-0.5%; Furthermore, the functional particles are composite modified particles of nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide, and hindered amine light stabilizer HALS.

[0005] Preferably, in the functional particles, the weight ratio of the nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide and hindered amine light stabilizer is 2~3:4~6:3~4:1~2:2~3.

[0006] Preferably, the preparation process of the functional particles is as follows: Step 1: Mix nano calcium carbonate, nano silica, nano zinc oxide, nano titanium dioxide and hindered amine light stabilizer evenly to form a mixed powder; Step 2: Dissolve the silane coupling agent in anhydrous ethanol at a volume ratio of 1:5~6, and add glacial acetic acid to adjust the pH to 4~5. Stir at room temperature for 30~40 minutes to form a transparent silanol solution. Step 3: While stirring at 300-400 rpm, add the transparent silanol solution dropwise to the mixed powder. After the addition is complete, continue stirring for 15-25 minutes to ensure that the silane coupling agent fully contacts the surface of the mixed solid material. Control the amount of silane coupling agent to be 1-3% of the weight of the mixed powder. Centrifuge to precipitate, vacuum dry, and pulverize to obtain functional particles.

[0007] Preferably, the silane coupling agent is one or more of silane coupling agent KH-550, silane coupling agent KH-560, or silane coupling agent KH-570.

[0008] Preferably, the hindered amine light stabilizer is one of light stabilizer 770, light stabilizer 292, light stabilizer 622 or light stabilizer 944.

[0009] Preferably, the particle size of the nano-calcium carbonate is 80~100nm.

[0010] Preferably, the particle size of the nano-silica is 20~50nm.

[0011] Preferably, the particle size of the nano zinc oxide is 20~60nm.

[0012] Preferably, the particle size of the nano-titanium dioxide is 50~80nm.

[0013] Preferably, in the modified functional nanoparticles, the nano-calcium carbonate, nano-silica, and hindered amine light stabilizer are formed into composite particles in which the hindered amine light stabilizer is loaded onto nano-calcium carbonate / nano-silica.

[0014] Preferably, the hindered amine light stabilizer is loaded onto nano-calcium carbonate / nano-silica composite particles, and the preparation method is as follows: Step ①: Add nano-calcium carbonate with a particle size of 80~100nm to deionized water and mix. Sonicate at 350~450W for 60~90min until uniformly dispersed to form a 10~15wt% uniform nano-calcium carbonate suspension. Dissolve sodium silicate in deionized water to form a 40~45wt% sodium silicate solution. Dissolve hindered amine light stabilizer in anhydrous ethanol to form an ethanol solution containing hindered amine light stabilizer. Step ②: Under stirring conditions of 1500~2000 rpm, add the nano calcium carbonate suspension to the sodium silicate solution, first sonicate at 500~600W for 30~40 min, and then stir at 1500~2000 rpm for 2~3 h to obtain the reaction system. Step 3: Place the above reaction system in a water bath at 70-80℃, and under stirring at 2500-3000 rpm, add dilute sulfuric acid solution dropwise, and slowly add ethanol solution containing hindered amine light stabilizer. After the addition is complete, age for 4-5 hours, centrifuge to precipitate, wash, and then vacuum dry. Control the weight ratio of nano-calcium carbonate, nano-silica and hindered amine light stabilizer HALS to be 2-3:4-6:2-3 to obtain composite particles of hindered amine light stabilizer loaded on nano-calcium carbonate / nano-silica.

[0015] Preferably, the nano zinc oxide is nano zinc oxide with its surface coated and modified with alumina.

[0016] Preferably, the nano-titanium dioxide is nano-titanium dioxide with a surface coated and modified with bismuth oxide.

[0017] Preferably, the nano-zinc oxide with an alumina-coated surface is prepared by the following method: 1) Dissolve aluminum isopropoxide in anhydrous ethanol, slowly add deionized water, wherein the molar ratio of water to aluminum isopropoxide is 3:1, adjust the pH to 3~4, heat to 35~40℃ and stir for 2~4h to form a transparent sol, and control the aluminum source concentration to 0.075~0.15mol / L to obtain alumina sol; 2) First, add 15-40 nm nano zinc oxide to alumina sol and mix, controlling the molar ratio of nano zinc oxide to alumina to be 1:0.2-0.4. Then, sonicate at 400-500W for 60-90 min to disperse evenly. Adjust the pH of the sol to 5-6, stir at 500-800 rpm for 6-8 h, and then vacuum dry to form a dry gel. 3) Grind the dry gel into powder, pre-treat it at 300~350℃ for 2~3h, and then calcine it at 550~580℃ for 2~4h at a rate of 2~5℃ / min to form a coating structure with a particle size of 20~60nm, thus obtaining nano zinc oxide with a surface coated and modified with alumina, i.e., nano zinc oxide with a particle size of 20~60nm.

[0018] Preferably, the nano-titanium dioxide with a surface coated with bismuth oxide is prepared by the following method: (1) Bismuth nitrate is dissolved in 1~2 mol / L dilute nitric acid to form a 0.05~0.1 mol / L bismuth salt solution. Nano-titanium dioxide with a particle size of 20~50 nm is added to deionized water and mixed. The mixture is ultrasonically treated at 350~450 W for 60~90 min. After uniform dispersion, a uniform nano-titanium dioxide suspension is formed. (2) Under stirring conditions of 400~600 rpm, bismuth salt solution was added dropwise to nano-titanium dioxide suspension, pH was adjusted to 6~7, and the mixture was heated to 60~70℃ and stirred for 2~4 h. The molar ratio of nano-titanium dioxide to bismuth oxide was controlled to be 1:0.2~0.4 to obtain the reaction solution. (3) Heat the reaction solution at 140~160℃ for 8~10h to promote the oxidation of bismuth compound to bismuth oxide. Centrifuge, precipitate, wash, and then vacuum dry to form a coating structure with a particle size of 50~80nm, and obtain nano titanium dioxide with a surface coated and modified by bismuth oxide, i.e. nano titanium dioxide with a particle size of 50~80nm.

[0019] Preferably, the antioxidant is a combination of antioxidant 1010 or antioxidant 3114 and antioxidant 168.

[0020] Preferably, antioxidant 168 accounts for 20-25% of the total antioxidant mass.

[0021] Preferably, the ultraviolet absorber is at least one of benzotriazole, benzophenone, or triazine.

[0022] Preferably, the ultraviolet absorber is benzotriazole UV-P, benzophenone UV-9, triazine UV-1164, etc.

[0023] This invention also provides a method for preparing high-strength, aging-resistant MPP pipes, comprising the following steps: S1. Random polypropylene, syndiotactic polypropylene, ethylene-vinyl alcohol copolymer, EPDM rubber, polypropylene grafted with maleic anhydride, dioctyl adipate, functional particles, antioxidants and ultraviolet absorbers are placed in a high-speed mixer and mixed to form a mixture. S2. Place the mixture in a twin-screw extruder for melt extrusion. Control the temperature of the twin-screw extruder to be 220~230℃ and the screw speed to be 180~200rpm. After melt extrusion, cut and granulate the mixture and dry it at 35~40℃ for 40~45min to obtain a high-strength, aging-resistant modified polypropylene material. S3. The modified polypropylene material is fed into a pipe forming machine for extrusion and shaping to obtain the required high-strength and aging-resistant MPP pipe.

[0024] The beneficial effects of this invention are as follows: 1. This invention provides MPP pipes, which are modified by blending random polypropylene, syndiotactic polypropylene, ethylene-vinyl alcohol copolymer, EPDM rubber, polypropylene grafted with maleic anhydride, dioctyl adipate, antioxidants, and ultraviolet absorbers. This not only effectively improves the flexibility and mechanical strength of the MPP pipes at low temperatures and enhances their low-temperature impact resistance, but also ensures that they have certain resistance to light, heat, and oxidation, and improves their aging resistance, making them high-performance polypropylene materials. 2. This invention further modifies the material by adding functional particles. These functional particles have good interfacial bonding with the polypropylene system. At the same time, nano-calcium carbonate and nano-silica synergistically enhance its low-temperature resistance and cold resistance. Nano-silica, nano-zinc oxide, and nano-titanium dioxide synergistically further enhance its low-temperature resistance and cold resistance. Further enhancing the resistance to light, heat, and oxidation, nano-silica, nano-zinc oxide, and nano-titanium dioxide, in synergy with hindered amine light stabilizers, further improve photothermal stability. This multi-layered synergistic effect not only enables the polypropylene system to maintain good high elasticity at low temperatures and further improves low-temperature impact resistance, but also increases the ultraviolet reflection sites of the polypropylene system, thereby improving the photothermal and oxidation resistance of MPP pipes. 3. The functional particles of this invention, by using nano-zinc oxide with alumina coating, nano-titanium dioxide with bismuth oxide coating, and / or hindered amine light stabilizers loaded onto nano-calcium carbonate / nano-silica, can greatly prevent photothermal oxidative degradation, discoloration, and pulverization of the MPP pipe molecular chains, further improving the stability, aging resistance, and mechanical properties of the MPP pipe. Detailed Implementation

[0025] The following is a clear and complete description of the technical solutions in the implementation of this invention. The described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents, instruments, and components used that do not specify the manufacturer are all conventional products that can be purchased commercially.

[0026] Preliminary Example 1 The specific steps for preparing a nano-zinc oxide, namely nano-zinc oxide with an alumina-coated surface, are as follows: 1) Dissolve aluminum isopropoxide in anhydrous ethanol, slowly add deionized water, wherein the molar ratio of water to aluminum isopropoxide is 3:1, adjust the pH to 3~4, heat to 35~40℃ and stir for 2~4h to form a transparent sol, and control the aluminum source concentration to 0.1mol / L to obtain alumina sol. 2) First, add 15-40nm nano zinc oxide to alumina sol and mix, controlling the molar ratio of nano zinc oxide to alumina to be 1:0.3. Then, sonicate at 450W for 70min to disperse evenly. Adjust the pH of the sol to 5-6 and stir at 750rpm for 6-8h to fully coat the nano zinc oxide particles with alumina sol. Then, vacuum dry to form a dry gel. 3) Grind the dry gel into powder, pretreat it at 320℃ for 2-3 hours, and then calcine it at 560℃ for 2-4 hours at a rate of 2-5℃ / min to form a coating structure with a particle size of 20-60nm, thus obtaining nano zinc oxide with a surface coated and modified with alumina, i.e., nano zinc oxide with a particle size of 20-60nm.

[0027] Preliminary Example 2 The specific steps for preparing nano-titanium dioxide, specifically nano-titanium dioxide with a surface coated with bismuth oxide, are as follows: (1) Bismuth nitrate was dissolved in 1.5 mol / L dilute nitric acid to form a 0.08 mol / L bismuth salt solution. Nano-titanium dioxide with a particle size of 20~50 nm was added to deionized water and mixed. The mixture was ultrasonically treated at 400 W for 80 min. After being dispersed evenly, a uniform nano-titanium dioxide suspension was formed. (2) Under stirring at 500 rpm, bismuth salt solution was added dropwise to nano-titanium dioxide suspension, pH was adjusted to 6-7, and the mixture was heated to 60-70℃ and stirred for 2-4 h to allow bismuth ions to combine with hydroxyl groups on the surface of titanium dioxide to form a bismuth compound adsorption layer. The molar ratio of nano-titanium dioxide to bismuth oxide was controlled to be 1:0.25 to obtain the reaction solution. (3) Heat the reaction solution at 150°C for 8-10 hours to promote the oxidation of bismuth compound to bismuth oxide. Centrifuge, precipitate, wash, and then vacuum dry to form a coating structure with a particle size of 50-80 nm, and obtain nano titanium dioxide with a surface coated and modified by bismuth oxide, i.e. nano titanium dioxide with a particle size of 50-80 nm.

[0028] Preliminary Example 3 The specific steps for preparing a functional particle are as follows: Step 1: Mix nano-calcium carbonate with a particle size of 80-100nm, nano-silica with a particle size of 20-50nm, nano-zinc oxide with a particle size of 20-60nm, nano-titanium dioxide with a particle size of 50-80nm, and light stabilizer 770 evenly, with the weight ratio of nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide, and light stabilizer 770 being 2:5:4:1:2.5 to form a mixed powder; Step 2: Dissolve silane coupling agent KH-550 in anhydrous ethanol at a volume ratio of 1:5, add glacial acetic acid to adjust the pH to 4-5, stir at room temperature for 30 minutes to form a transparent silanol solution. Step 3: While stirring at 350 rpm, add the transparent silanol solution dropwise to the mixed powder over 10-20 minutes. After the addition is complete, continue stirring for 20 minutes to ensure that the silane coupling agent KH-550 fully contacts the surface of the mixed solids. Control the amount of silane coupling agent KH-550 to be 1.5% of the weight of the mixed powder. Centrifuge to precipitate, vacuum dry, and pulverize to obtain functional particles.

[0029] Preliminary Example 4 The specific steps for preparing a functional particle are as follows: Step 1: Mix nano-calcium carbonate (80-100nm), nano-silica (20-50nm), nano-zinc oxide (20-60nm), nano-titanium dioxide (50-80nm), and light stabilizer 292 evenly, with the weight ratio of nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide, and hindered amine light stabilizer being 3:4:3.5:2:2, to form a mixed powder; Step 2: Dissolve silane coupling agent KH-560 in anhydrous ethanol at a volume ratio of 1:6, and add glacial acetic acid to adjust the pH to 4-5. Stir at room temperature for 35 minutes to form a transparent silanol solution. Step 3: While stirring at 300 rpm, add the transparent silanol solution dropwise to the mixed powder over 10-20 minutes. After the addition is complete, continue stirring for 25 minutes to ensure that the silane coupling agent KH-560 fully contacts the surface of the mixed solids. Control the amount of silane coupling agent KH-560 to be 2% of the weight of the mixed powder. Centrifuge to precipitate, vacuum dry, and pulverize to obtain functional particles.

[0030] Preliminary Example 5 The specific steps for preparing a functional particle are as follows: Step 1: Mix nano-calcium carbonate with a particle size of 80-100nm, nano-silica with a particle size of 20-50nm, nano-zinc oxide with a particle size of 20-60nm, nano-titanium dioxide with a particle size of 50-80nm, and light stabilizer 622 evenly, and form a mixed powder with a weight ratio of nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide and hindered amine light stabilizer of 2.5:6:3:1.5:3. Step 2: Dissolve silane coupling agent KH-570 in anhydrous ethanol at a volume ratio of 1:5.5, add glacial acetic acid to adjust the pH to 4-5, stir at room temperature for 40 minutes to form a transparent silanol solution. Step 3: While stirring at 400 rpm, add the transparent silanol solution dropwise to the mixed powder over 10-20 minutes. After the addition is complete, continue stirring for 15-25 minutes to ensure that the silane coupling agent KH-570 fully contacts the surface of the mixed solids. Control the amount of silane coupling agent KH-570 to be 2.5% of the weight of the mixed powder. Centrifuge to precipitate, vacuum dry, and pulverize to obtain functional particles.

[0031] Preliminary Example 6 Prepare a functional particle that differs from Preliminary Example 3 in that the nano zinc oxide of Preliminary Example 1 is replaced by nano zinc oxide with alumina coating on its surface.

[0032] Preliminary Example 7 A functional particle was prepared, which differed from Preliminary Example 3 in that the nano-titanium dioxide of Preliminary Example 2 was replaced by nano-titanium dioxide with a surface coated with bismuth oxide.

[0033] Preliminary Example 8 Prepare a functional particle that differs from Preliminary Example 3 in that: light stabilizer 770 is loaded onto nano-calcium carbonate / nano-silica composite particles instead of nano-calcium carbonate with a particle size of 80~100nm, nano-silica with a particle size of 20~50nm and light stabilizer 770. Preparation method of light stabilizer 770 supported on nano-calcium carbonate / nano-silica composite particles: ① Add nano-calcium carbonate with a particle size of 80~100nm to deionized water and mix. Sonicate at 400W for 90min to disperse evenly, forming a 15wt% uniform nano-calcium carbonate suspension; dissolve sodium silicate in deionized water to form a 40wt% sodium silicate solution; dissolve light stabilizer 770 in anhydrous ethanol to form an ethanol solution containing light stabilizer 770. ② Under stirring conditions of 1800 rpm, the nano calcium carbonate suspension was added to the sodium silicate solution, and the mixture was first sonicated at 550 W for 35 min, and then stirred at 1800 rpm for 2-3 h to obtain the reaction system. ③ Place the above reaction system in a water bath at 70~80℃, add dilute sulfuric acid solution dropwise under stirring at 2800rpm, and slowly add ethanol solution containing light stabilizer 770. After the addition is complete, age for 4~5h, centrifuge to precipitate, wash, and then vacuum dry. Control the weight ratio of nano calcium carbonate, nano silica and hindered amine light stabilizer HALS to be 2:5:2.5 to obtain composite particles of light stabilizer 770 loaded on nano calcium carbonate / nano silica. The mass ratio of light stabilizer 770 loaded on nano-calcium carbonate / nano-silica composite particles to nano-zinc oxide with a particle size of 20~60nm and nano-titanium dioxide with a particle size of 50~80nm is 9.5:4:1.

[0034] Preliminary Example 9 A functional particle was prepared, which differed from Preliminary Example 3 in that: the nano zinc oxide of Preliminary Example 1 was replaced by nano zinc oxide with alumina coating; and the nano titanium dioxide of Preliminary Example 2 was replaced by nano titanium dioxide with bismuth oxide coating.

[0035] Preliminary Example 10 A functional particle was prepared, differing from Preliminary Example 3 in that: nano zinc oxide modified with alumina coating on the surface of nano zinc oxide in Preliminary Example 1 replaced nano zinc oxide; nano titanium dioxide modified with bismuth oxide coating on the surface of nano titanium dioxide in Preliminary Example 2 replaced nano titanium dioxide; and composite particles of nano calcium carbonate / nano silica loaded with light stabilizer 770 replaced nano calcium carbonate with a particle size of 80~100nm, nano silica with a particle size of 20~50nm, and light stabilizer 770, and the preparation of composite particles of nano calcium carbonate / nano silica loaded with light stabilizer 770 was the same as in Preliminary Example 7.

[0036] Example 1 A high-strength, aging-resistant MPP pipe and its preparation method, comprising the following steps: S1. Weigh the raw materials according to the following weight percentages: 55% random polypropylene, 17% syndiotactic polypropylene, 9% ethylene-vinyl alcohol copolymer, 5% EPDM rubber, 5% polypropylene grafted maleic anhydride, 3% dioctyl adipate, 5% functional particles from Example 3, 0.64% antioxidant 1010, 0.16% antioxidant 168, and 0.2% benzotriazole UV-P. Then, place all raw materials in a high-speed mixer and mix them to form a mixture. S2. Place the mixture in a twin-screw extruder for melt extrusion. Control the temperature of the twin-screw extruder to 220℃ and the screw speed to 180~200rpm. After melt extrusion, cut and granulate the mixture and dry it at 35~40℃ for 40~45min to obtain a high-strength, aging-resistant modified polypropylene material. S3. The modified polypropylene material is fed into the pipe forming machine for extrusion and shaping. The die temperature is 210℃, the cooling water tank temperature is 10℃, and the traction speed is 2m / min to obtain a high-strength and aging-resistant MPP pipe with a diameter of 110mm and a wall thickness of 2.5mm.

[0037] Example 2 A high-strength, aging-resistant MPP pipe and its preparation method, comprising the following steps: S1. Weigh the raw materials according to the following weight percentages: random polypropylene 53%, syndiotactic polypropylene 12.7%, ethylene-vinyl alcohol copolymer 11%, EPDM rubber 8%, polypropylene grafted with maleic anhydride 2.5%, dioctyl adipate 2%, preparative Example 4 functional particles 10%, antioxidant 1010 0.4%, antioxidant 168 0.1%, and benzophenone-based UV-9 0.3%. Then, place all raw materials in a high-speed mixer and mix them to form a mixture. S2. Place the mixture in a twin-screw extruder for melt extrusion. Control the temperature of the twin-screw extruder to 230℃ and the screw speed to 190rpm. After melt extrusion, cut and granulate the mixture and dry it at 35~40℃ for 40~45min to obtain a high-strength, aging-resistant modified polypropylene material. S3. The modified polypropylene material is fed into the pipe forming machine for extrusion and shaping. The die temperature is 210℃, the cooling water tank temperature is 10℃, and the traction speed is 2m / min to obtain a high-strength and aging-resistant MPP pipe with a diameter of 110mm and a wall thickness of 2.5mm.

[0038] Example 3 A high-strength, aging-resistant MPP pipe and its preparation method, comprising the following steps: S1. Weigh the raw materials according to the following weight percentages: random polypropylene 59%, syndiotactic polypropylene 12%, ethylene-vinyl alcohol copolymer 7%, EPDM rubber 4%, polypropylene grafted maleic anhydride 4%, dioctyl adipate 4%, preparative Example 5 functional particles 8.5%, antioxidant 3114 0.75%, antioxidant 168 0.25%, and triazine-based UV-1164 0.5%. Then, place all raw materials in a high-speed mixer and mix them to form a mixture. S2. Place the mixture in a twin-screw extruder for melt extrusion. Control the temperature of the twin-screw extruder to 225℃ and the screw speed to 200rpm. After melt extrusion, cut and granulate the mixture and dry it at 35~40℃ for 40~45min to obtain a high-strength, aging-resistant modified polypropylene material. S3. The modified polypropylene material is fed into the pipe forming machine for extrusion and shaping. The die temperature is 210℃, the cooling water tank temperature is 10℃, and the traction speed is 2m / min to obtain a high-strength and aging-resistant MPP pipe with a diameter of 110mm and a wall thickness of 2.5mm.

[0039] Example 4 A high-strength, aging-resistant MPP pipe and its preparation method are different from Example 1 in that the functional particles of Preparatory Example 6 are replaced with the functional particles of Preparatory Example 3.

[0040] Example 5 A high-strength, aging-resistant MPP pipe and its preparation method are different from Example 1 in that the functional particles of Preliminary Example 7 are replaced with the functional particles of Preliminary Example 3.

[0041] Example 6 A high-strength, aging-resistant MPP pipe and its preparation method are different from Example 1 in that the functional particles of Preparatory Example 8 are replaced with the functional particles of Preparatory Example 3.

[0042] Example 7 A high-strength, aging-resistant MPP pipe and its preparation method are different from Example 1 in that the functional particles of Preparatory Example 9 are replaced with the functional particles of Preparatory Example 3.

[0043] Example 8 A high-strength, aging-resistant MPP pipe and its preparation method are different from Example 1 in that the functional particles of Preliminary Example 10 are replaced with the functional particles of Preliminary Example 3.

[0044] Comparative Example 1 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that: random polypropylene 72% and syndiotactic polypropylene 0%.

[0045] Comparative Example 2 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that: random polypropylene 64% and ethylene-vinyl alcohol copolymer 0%.

[0046] Comparative Example 3 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that: 60% random polypropylene and 0% EPDM rubber.

[0047] Comparative Example 4 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that: random polypropylene 58% and dioctyl adipate 0%.

[0048] Comparative Example 5 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that: 60% random polypropylene and 0% functional particles from Preliminary Example 3.

[0049] Comparative Example 6 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that the functional particles do not contain nano-calcium carbonate, and the weight ratio of nano-silica, nano-zinc oxide, nano-titanium dioxide and light stabilizer 770 is 5:4:1:2.5.

[0050] Comparative Example 7 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that the functional particles do not contain nano-silica, and the weight ratio of nano-calcium carbonate, nano-zinc oxide, nano-titanium dioxide and light stabilizer 770 is 2:4:1:2.5.

[0051] Comparative Example 8 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that the functional particles do not contain nano zinc oxide, and the weight ratio of nano calcium carbonate, nano silicon dioxide, nano titanium dioxide and light stabilizer 770 is 2:5:1:2.5.

[0052] Comparative Example 9 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that the functional particles do not contain nano-titanium dioxide, and the weight ratio of nano-calcium carbonate, nano-silica, nano-zinc oxide and light stabilizer 770 is 2:5:4:2.5.

[0053] Comparative Example 10 A high-strength, aging-resistant MPP pipe and its preparation method differ from Example 1 in that the functional particles do not contain light stabilizer 770, and the weight ratio of nano-calcium carbonate, nano-silica, nano-zinc oxide and nano-titanium dioxide is 2:5:4:1.

[0054] The pipes of Examples 1-8 and Comparative Examples 1-10 were tested. Tensile strength (MPa) and elongation at break (%) were determined according to GB / T 8804.3-2003. Low-temperature impact strength: Following GB / T 14152-2001, the pipe was kept at -40℃ for 6 hours, then a 2.5kg d90 hammer was used to freely impact the side of the pipe from a certain height. After the impact, the pipe first cracked and broke. The maximum drop height (m) was measured, and the impact strength (MPa) was calculated. Photothermal-oxidative aging resistance: Following GB / T16422.3-2022, standard samples were tested using a UV-B 313nm lamp under the conditions of 65℃ / 8h illumination + 55℃ / 4h condensation cycle for 2500 hours. The tensile strength retention rate (%) and the breaking strength retention rate (%) were tested, and the performance results are shown in Table 1.

[0055] Table 1 Performance

[0056] As shown in Table 1 above, the present invention overcomes the problems of poor impact resistance at low temperatures and poor aging resistance in photothermal and oxygen environments of existing polypropylene pipes. The present invention effectively improves the low-temperature impact resistance and photothermal and oxygen aging resistance of MPP pipes, thereby improving the strength and long-term stability of MPP pipes and exhibiting excellent mechanical properties.

[0057] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-strength, aging-resistant MPP pipe, characterized in that, It is prepared from raw materials comprising the following weight percentages: random polypropylene 53-59%, syndiotactic polypropylene 12-17%, ethylene-vinyl alcohol copolymer 7-11%, ethylene propylene diene monomer (EPDM) rubber 4-8%, polypropylene grafted with maleic anhydride 2.5-5%, dioctyl adipate 2-4%, functional particles 6-10%, antioxidant 0.5-1%, and ultraviolet absorber 0.2-0.5%. Furthermore, the functional particles are composite modified particles consisting of nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide, and hindered amine light stabilizers.

2. The high-strength, aging-resistant MPP pipe according to claim 1, characterized in that, The preparation process of functional particles is as follows: Step 1: Mix nano calcium carbonate, nano silica, nano zinc oxide, nano titanium dioxide and hindered amine light stabilizer evenly to form a mixed powder; Step 2: Dissolve the silane coupling agent in anhydrous ethanol at a volume ratio of 1:5~6, and add glacial acetic acid to adjust the pH to 4~5. Stir at room temperature for 30~40 minutes to form a transparent silanol solution. Step 3: While stirring at 300-400 rpm, add the transparent silanol solution dropwise to the mixed powder. After the addition is complete, continue stirring for 15-25 minutes. Control the amount of silane coupling agent to be 1-3% of the weight of the mixed powder. Centrifuge to precipitate, vacuum dry, and pulverize to obtain functional particles.

3. A high-strength, aging-resistant MPP pipe according to claim 1 or 2, characterized in that, In the functional particles, the weight ratio of the nano-calcium carbonate, nano-silica, nano-zinc oxide, nano-titanium dioxide and hindered amine light stabilizer is 2~3:4~6:3~4:1~2:2~3.

4. A high-strength, aging-resistant MPP pipe according to claim 1 or 2, characterized in that, In the functional particles, the nano-calcium carbonate, nano-silica and the hindered amine light stabilizer are formed into a composite particle in which the hindered amine light stabilizer is loaded onto nano-calcium carbonate / nano-silica. The nano zinc oxide is nano zinc oxide with a surface coated and modified with aluminum oxide; The nano-titanium dioxide is nano-titanium dioxide with a surface coated and modified with bismuth oxide.

5. The high-strength, aging-resistant MPP pipe according to claim 4, characterized in that, The hindered amine light stabilizer is loaded onto nano-calcium carbonate / nano-silica composite particles, and the preparation method is as follows: Step ①: Add nano-calcium carbonate with a particle size of 80~100nm to deionized water and mix. Sonicate at 350~450W for 60~90min until uniformly dispersed to form a 10~15wt% uniform nano-calcium carbonate suspension. Dissolve sodium silicate in deionized water to form a 40~45wt% sodium silicate solution. Dissolve hindered amine light stabilizer in anhydrous ethanol to form an ethanol solution containing HALS. Step ②: Under stirring conditions of 1500~2000 rpm, add the nano calcium carbonate suspension to the sodium silicate solution, first sonicate at 500~600W for 30~40 min, and then stir at 1500~2000 rpm for 2~3 h to obtain the reaction system. Step 3: Place the above reaction system in a water bath at 70~80℃, and add dilute sulfuric acid solution dropwise under stirring at 2500~3000rpm. Then slowly add ethanol solution containing HALS. After the addition is complete, age for 4~5 hours, centrifuge to precipitate, wash, and then vacuum dry. Control the weight ratio of nano-calcium carbonate, nano-silica and hindered amine light stabilizer HALS to be 2~3:4~6:2~3 to obtain composite particles of hindered amine light stabilizer loaded on nano-calcium carbonate / nano-silica.

6. The high-strength, aging-resistant MPP pipe according to claim 4, characterized in that, The nano-zinc oxide with an alumina-coated surface is prepared by the following method: 1) Dissolve aluminum isopropoxide in anhydrous ethanol, slowly add deionized water, wherein the molar ratio of water to aluminum isopropoxide is 3:1, adjust the pH to 3~4, heat to 35~40℃ and stir for 2~4h to form a transparent sol, and control the aluminum source concentration to 0.075~0.15mol / L to obtain alumina sol; 2) First, add 15-40 nm nano zinc oxide to alumina sol and mix, controlling the molar ratio of nano zinc oxide to alumina to be 1:0.2-0.

4. Then, sonicate at 400-500W for 60-90 min to disperse evenly. Adjust the pH of the sol to 5-6, stir at 500-800 rpm for 6-8 h, and then vacuum dry to form a dry gel. 3) Grind the dry gel into powder, pre-treat it at 300~350℃ for 2~3h, and then calcine it at 550~580℃ for 2~4h at a rate of 2~5℃ / min to form a coating structure with a particle size of 20~60nm, thus obtaining nano zinc oxide with a surface coated and modified with alumina, i.e., nano zinc oxide with a particle size of 20~60nm.

7. The high-strength, aging-resistant MPP pipe according to claim 4, characterized in that, The nano-titanium dioxide with a surface coated and modified with bismuth oxide is prepared by the following method: (1) Bismuth nitrate is dissolved in 1~2 mol / L dilute nitric acid to form a 0.05~0.1 mol / L bismuth salt solution. Nano-titanium dioxide with a particle size of 20~50 nm is added to deionized water and mixed. The mixture is ultrasonically treated at 350~450 W for 60~90 min. After uniform dispersion, a uniform nano-titanium dioxide suspension is formed. (2) Under stirring conditions of 400~600 rpm, bismuth salt solution was added dropwise to nano-titanium dioxide suspension, pH was adjusted to 6~7, and the mixture was heated to 60~70℃ and stirred for 2~4 h. The molar ratio of nano-titanium dioxide to bismuth oxide was controlled to be 1:0.2~0.4 to obtain the reaction solution. (3) Heat the reaction solution at 140~160℃ for 8~10h to promote the oxidation of bismuth compound to bismuth oxide. Centrifuge, precipitate, wash, and then vacuum dry to form a coating structure with a particle size of 50~80nm, and obtain nano titanium dioxide with a surface coated and modified by bismuth oxide, i.e. nano titanium dioxide with a particle size of 50~80nm.

8. A high-strength, aging-resistant MPP pipe according to claim 2, characterized in that, The silane coupling agent is one or more of silane coupling agent KH-550, silane coupling agent KH-560, or silane coupling agent KH-570.

9. A high-strength, aging-resistant MPP pipe according to claim 1, characterized in that, The hindered amine light stabilizer is one of light stabilizer 770, light stabilizer 292, light stabilizer 622 or light stabilizer 944; the antioxidant is one of antioxidant 1010 or antioxidant 3114 combined with antioxidant 168; the ultraviolet absorber is at least one of benzotriazole, benzophenone or triazine.

10. A method for preparing a high-strength, aging-resistant MPP pipe as described in claim 1, characterized in that, Includes the following steps: S1. Random polypropylene, syndiotactic polypropylene, ethylene-vinyl alcohol copolymer, EPDM rubber, polypropylene grafted with maleic anhydride, dioctyl adipate, functional particles, antioxidants and ultraviolet absorbers are placed in a high-speed mixer and mixed to form a mixture. S2. Place the mixture in a twin-screw extruder for melt extrusion. Control the temperature of the twin-screw extruder to be 220~230℃ and the screw speed to be 180~200rpm. After melt extrusion, cut and granulate the mixture and dry it at 35~40℃ for 40~45min to obtain a high-strength, aging-resistant modified polypropylene material. S3. The modified polypropylene material is fed into a pipe forming machine for extrusion and shaping to obtain the required high-strength and aging-resistant MPP pipe.

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