Wear and corrosion resistant modified polyethylene special pipe and method of making same

Abstract

The application discloses wear-resistant and corrosion-resistant modified polyethylene special pipe and a preparation method thereof, and relates to the technical field of high polymer materials.The application comprises the following raw materials in mass parts: 360-440 parts of high-density polyethylene, 100-120 parts of ethylene-1-octene copolymer, 15-20 parts of modified nanotube, 20-25 parts of composite flame retardant, 8-10 parts of cold-resistant toughening agent, 0.2-0.4 parts of antioxidant 1010, and 0.2-0.4 parts of antioxidant 168.The modified nanotube is a multi-walled carbon nanotube, which is pretreated by nitric acid aqueous solution, then is compounded with tetrabutyl titanate and aluminum nitrate nonahydrate, then is heated to 800 DEG C under a nitrogen atmosphere, is treated by a mixed gas of methane, nitrogen and ammonia for 2-3 hours at 800 DEG C, and finally is cooled under a nitrogen atmosphere to obtain the modified nanotube; and the introduction of the composite flame retardant and the like effectively improves the impact resistance, wear resistance, flame resistance and corrosion resistance of the polyethylene pipe.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to wear-resistant and corrosion-resistant modified polyethylene special pipes and their preparation methods. Background Technology

[0002] Polyethylene is a highly crystalline, non-polar thermoplastic resin with strong chemical stability, excellent low-temperature resistance, easy processing and molding, and moderate cost. It also possesses good toughness and fatigue resistance. Therefore, it is widely used in packaging, building materials, chemicals, agriculture, and many other fields, encompassing film products, injection molded parts, pipes and fittings, and cable sheaths. Among these, polyethylene pipes are particularly widely used in water supply and drainage, gas transmission, agricultural irrigation, and industrial fluid transportation due to their non-toxic and odorless nature, excellent aging resistance, low fluid resistance, and convenient installation.

[0003] However, polyethylene pipes still have the following performance shortcomings in practical applications: First, they have poor wear resistance. When used to transport media containing mud, sand, particles, etc., the pipe wall is easily worn thinner, which may lead to leakage and shorten service life after long-term use. Second, they lack flame retardancy. Polyethylene is a flammable material, and pipes without flame retardant modification are easily combusted in high-temperature or open-flame environments, releasing harmful gases, making them unsuitable for high-temperature, flammable, and explosive scenarios. Third, their corrosion resistance is limited. Although they can withstand most acid and alkali media, long-term contact can easily cause corrosion to the pipes. Therefore, the wear resistance, flame retardancy, and corrosion resistance of existing polyethylene pipes still need to be improved. Summary of the Invention

[0004] The purpose of this invention is to provide wear-resistant and corrosion-resistant modified polyethylene special pipes and their preparation method, thereby solving the following technical problems:

[0005] Existing polyethylene pipes still suffer from poor wear resistance, flame retardancy, and corrosion resistance.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] Wear-resistant and corrosion-resistant modified polyethylene special pipes, comprising the following raw materials by weight: 360-440 parts high-density polyethylene, 100-120 parts ethylene-1-octene copolymer, 15-20 parts modified nanotubes, 20-25 parts composite flame retardant, 8-10 parts cold-resistant toughening agent, 0.2-0.4 parts antioxidant 1010, and 0.2-0.4 parts antioxidant 168;

[0008] The modified nanotubes are multi-walled carbon nanotubes that are first pretreated with nitric acid aqueous solution, then combined with tetrabutyl titanate and aluminum nitrate nonahydrate, then heated to 800℃ in a nitrogen atmosphere and treated with a mixture of methane, nitrogen and ammonia at 800℃ for 2-3 hours, and finally cooled in a nitrogen atmosphere to obtain the modified nanotubes.

[0009] The composite flame retardant is prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde, p-toluenesulfonic acid, cyanuric chloride, γ-aminopropyltriethoxysilane, glycidyl methacrylate, hydroquinone, and trimethylchlorosilane.

[0010] Preferably, the modified nanotubes are prepared by the following method:

[0011] A1: Under a nitrogen atmosphere, multi-walled carbon nanotubes were added to an aqueous nitric acid solution and stirred at 60°C for 4-6 hours. After centrifugation, washing, and drying, pretreated nanotubes were obtained.

[0012] A2: Add tetrabutyl titanate to anhydrous ethanol and stir for 5-7 min, then add acetic acid and continue stirring for 10 min, then add aluminum nitrate nonahydrate and stir for 10-15 min, then add deionized water and stir for 30-50 min, age for 2 h, then add pretreated nanotubes and ultrasonically disperse for 1-2 h, evaporate the solvent by rotary evaporation, grind and sieve, then heat to 800℃ under a nitrogen atmosphere, and finally keep warm at 800℃ under a mixed atmosphere of methane, nitrogen and ammonia for 2-3 h, and cool under a nitrogen atmosphere to obtain modified nanotubes.

[0013] Preferably, the ratio of the nitric acid aqueous solution and multi-walled carbon nanotubes in A1 is 1900-2000 mL: 20 g;

[0014] The mass fraction of the nitric acid aqueous solution described in A1 is 10%-12%.

[0015] Preferably, the ratio of anhydrous ethanol, tetrabutyl titanate, acetic acid, aluminum nitrate nonahydrate, deionized water, and pretreated nanotubes in A2 is 400-420 mL: 8 g: 8 mL: 6 g: 8 mL: 20 g;

[0016] The volume ratio of methane, nitrogen, and ammonia in the mixture described in A2 is 10:70-80:10-20, and the total flow rate of the mixture is 200 sccm.

[0017] Preferably, the preparation method of the composite flame retardant is as follows:

[0018] B1: Under a nitrogen atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and p-hydroxybenzaldehyde were added to toluene and stirred for 30-40 min. Then p-toluenesulfonic acid was added and refluxed at 110 °C for 4-6 h. After cooling, toluene was removed by rotary evaporation under reduced pressure. Then it was added to deionized water at 5-15 °C and stirred for 30-40 min. After filtration, washing and drying, the intermediate was obtained.

[0019] B2: Under a nitrogen atmosphere, add the intermediate, cyanuric chloride, and triethylamine to acetonitrile and stir at 0-5℃ for 2 hours, then stir at 45℃ for 2 hours. Then add γ-aminopropyltriethoxysilane and triethylamine at 25℃ and stir at 65℃ for 6 hours. After filtration and rotary evaporation, add the filtrate dropwise to petroleum ether, stir for 20-30 minutes, filter, and dry to obtain the modified intermediate.

[0020] B3: Under a nitrogen atmosphere, add the modified intermediate and glycidyl methacrylate to toluene and stir for 20-30 min. Then add hydroquinone, triethylamine, and trimethylchlorosilane and reflux at 90°C under a nitrogen atmosphere for 10-12 h. After cooling, wash and then dry the organic phase with anhydrous magnesium sulfate. After filtration and rotary evaporation to remove toluene, dry to obtain the composite flame retardant.

[0021] Preferably, the ratio of toluene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde, p-toluenesulfonic acid, and deionized water in B1 is 150 mL: 21.6 g: 18.4 g: 0.5 g: 200-300 mL.

[0022] Preferably, the ratio of acetonitrile, intermediate, cyanuric chloride, triethylamine, γ-aminopropyltriethoxysilane, triethylamine, and petroleum ether in B2 is 200mL: 28-30g: 18.4g: 3g: 22.2g: 3g: 500mL.

[0023] Preferably, the ratio of toluene, modified intermediate, glycidyl methacrylate, hydroquinone, triethylamine, and trimethylchlorosilane in B3 is 75-80 mL: 25 g: 5.75 g: 0.05 g: 0.15 g: 0.25 g.

[0024] A method for preparing wear-resistant and corrosion-resistant modified polyethylene special pipes includes the following steps:

[0025] Ethylene-1-octene copolymer, modified nanotubes, composite flame retardant, cold-resistant toughening agent, antioxidant 1010, and antioxidant 168 are mixed and dry-mixed at 50-60℃ for 8-10 minutes. Then, the mixture is melt-extruded, water-cooled, pelletized, and mixed with high-density polyethylene at 90℃ for 5-7 minutes. After cooling, it is melt-extruded again and then hot-pressed to obtain wear-resistant and corrosion-resistant modified polyethylene special pipes.

[0026] Preferably, the hot pressing treatment is as follows: the extrudate is placed in a pipe mold at 185°C, preheated for 3 minutes, hot-pressed at 5-10 MPa pressure for 10-12 minutes, then cooled to 50°C at 5-10 MPa pressure and demolded, sized at room temperature for 30-50 minutes, then vacuum heat-treated at 100°C for 2-3 hours, and finally treated at 80°C for 1 hour.

[0027] The beneficial effects of this invention are:

[0028] This invention provides wear-resistant and corrosion-resistant modified polyethylene special pipes and their preparation methods. This invention simultaneously improves the impact resistance, wear resistance, flame retardancy and corrosion resistance of polyethylene pipes through the following methods.

[0029] (1) In the modified nanotubes of the present invention, the one-dimensional nanostructure of the acidified multi-walled carbon nanotube is a high-modulus, high-toughness carbon material. When it is impacted in the matrix, it will produce bridging and pull-out effects: when the crack extends to the multi-walled carbon nanotube, it needs to overcome the interfacial bonding force between it and the matrix in order to continue to extend. In the process, it absorbs a large amount of impact energy, which directly slows down the crack propagation. The aluminum-titanium composite oxide shell improves the interfacial compatibility between the multi-walled carbon nanotube and the matrix. The anhydride group of the toughening agent (maleic anhydride grafted ethylene-octene copolymer) can interact strongly with the hydroxyl groups on the surface of the aluminum-titanium oxide shell. At the same time, its polyolefin segments are well compatible with the polyethylene matrix, which significantly improves the interfacial compatibility and bonding strength between the multi-walled carbon nanotube and the matrix, greatly reduces interfacial defects and voids, thereby achieving more efficient stress transfer and alleviating stress concentration. The inorganic aluminum-titanium composite oxide is a rigid phase that is dispersed in the flexible polyethylene matrix to form a micro-stress zone. When impacted, it will induce the matrix to produce silver crazes and shear bands, further consuming the impact energy. During the friction process, the high-hardness aluminum-titanium oxide shell acts as the main load-bearing phase, preferentially bearing and dispersing wear stress, thereby reducing direct wear and plastic deformation of the polyethylene soft matrix. The high modulus of multi-walled carbon nanotubes forms nano-reinforcement on the polyethylene matrix, improving the overall deformation resistance of the matrix and reducing the shedding of surface material during the wear process. The core-shell structure is tightly bonded to the matrix interface, preventing filler shedding and the formation of secondary abrasive particles, further optimizing wear resistance. The aluminum-titanium composite oxide can catalyze the carbonization reaction of the polyethylene matrix, making the carbon layer formed at high temperatures more dense. The one-dimensional structure of multi-walled carbon nanotubes forms a rigid carbon skeleton in the carbon layer, improving the mechanical strength and thermal stability of the carbon layer, preventing the carbon layer from cracking and falling off at high temperatures, thus effectively blocking the transfer of heat and oxygen and reducing the release of combustible gases. The treatment with a methane-nitrogen-ammonia mixed gas at 800℃ introduces a nitrogen-doped structure on the surface of the carbon nanotubes, enhancing the thermal stability of the multi-walled carbon nanotubes themselves and their mechanical strength as a carbon layer skeleton. Simultaneously, the nitrogen source component in the composite flame retardant decomposes to produce non-combustible gases such as nitrogen and ammonia in the early stage of combustion, which can dilute the concentration of oxygen and combustible gases and exert a gas-phase flame retardant effect. The modified nanotubes and the composite flame retardant work synergistically to enhance the flame retardant effect from the aspects of improving the quality of the char layer and assisting in gas-phase dilution. The oxide char formation catalysis of the modified nanotubes and the char layer skeleton function of the carbon tubes complement the phosphorus-based condensed phase flame retardant, nitrogen-based gas-phase flame retardant and silicon-based oxygen-barrier char formation of the composite flame retardant, which greatly improves the overall char layer quality and flame retardant synergistic efficiency.Aluminum-titanium composite oxides exhibit extremely stable chemical properties in dilute acids and alkalis, showing almost no dissolution or reaction upon immersion. Multi-walled carbon nanotubes are inherently resistant to acids and alkalis, and the 800℃ heat treatment partially carbonizes the oxygen-containing functional groups introduced by acidification, further enhancing surface stability and resulting in no significant acid-alkali reaction. Polyethylene itself is resistant to acids and alkalis, but pure high-density polyethylene contains intercrystalline voids and amorphous regions, allowing dilute acid and alkali media to slowly penetrate along these tiny voids, causing slight swelling of the matrix. Modified nanotubes dispersed in the matrix, due to their one-dimensional core-shell structure, can overlap or tightly arrange themselves to form a barrier that effectively blocks or extends the penetration path. This inorganic phase barrier significantly increases the tortuosity of acid and alkali media diffusion, reducing their effective contact area and penetration rate with the polyethylene matrix. The modified nanotubes are tightly bonded to the matrix interface, with no obvious interfacial voids, preventing the accumulation and penetration of acid and alkali media at the interface and eliminating the core cause of interfacial corrosion.

[0030] (2) In the composite flame retardant of this invention, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide decomposes at high temperatures to produce free radicals such as PO· and HPO·, which can quickly capture active free radicals that initiate chain reactions during combustion, cut off the combustion chain, and achieve gas-phase flame retardancy; at the same time, phosphorus oxide acts as a carbonization promoter, catalyzing the dehydration and carbonization of the polyethylene matrix to form a dense carbon layer, isolating oxygen, heat and combustible gases, achieving condensed-phase flame retardancy, and the carbon layer can inhibit the molten dripping of polyethylene, further improving flame retardancy; the composite flame retardant contains - The Si-O-Si- structure forms a silica ceramic layer at high temperature, which is deposited on the surface of the carbon layer catalyzed by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. This compensates for the shrinkage and cracking defects of the carbon layer at high temperature, enhances the thermal stability and density of the carbon layer, and significantly improves the efficiency of condensed phase flame retardancy. The carbon skeleton of the modified carbon nanotubes provides carbonization nuclei for the carbonization of the matrix, promoting the uniform formation of the carbon layer. At the same time, the high aspect ratio of the carbon nanotubes forms a network structure in the matrix, which interweaves with the silica ceramic layer and the carbon layer, further improving the integrity of the flame retardant barrier. In the composite flame retardant of this invention, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide decomposes at high temperatures to generate free radicals such as PO· and HPO·, which can rapidly capture active free radicals that initiate chain reactions during combustion, cutting off the combustion chain and achieving gas-phase flame retardancy. Simultaneously, the phosphorus oxide acts as a carbonization catalyst, catalyzing the dehydration and carbonization of the polyethylene matrix to form a dense carbon layer, isolating oxygen, heat, and combustible gases, achieving condensed-phase flame retardancy. Furthermore, the carbon layer can inhibit the molten dripping of polyethylene, further enhancing flame retardancy. In the composite... The -Si-O-Si- structure in the flame retardant forms a silica ceramic layer at high temperature, which is deposited on the surface of the carbon layer formed by phosphorus-based components. This compensates for the shrinkage and cracking defects of the carbon layer at high temperature, enhances the thermal stability and density of the carbon layer, and significantly improves the flame retardant efficiency of the condensed phase. The multi-walled carbon nanotubes of the modified nanotubes provide a one-dimensional rigid skeleton for the carbon layer, promote the uniform formation of the carbon layer and avoid collapse. The network structure formed by its high aspect ratio in the matrix intertwines with the silica ceramic layer and the carbon layer, further improving the integrity and stability of the flame retardant barrier.The composite flame retardant exhibits excellent chemical stability in its -Si-O-Si-, aromatic, and phosphorus heterocycles, showing no chemical reaction with 1 mol / L strong acids or bases. Furthermore, during preparation, all active groups such as hydroxyl, amino, and cyano groups, which are prone to acid and base reactions, have participated in covalent reactions, leaving no free active groups. Therefore, it demonstrates excellent chemical stability and is unlikely to hydrolyze or dissolve under the stated acid or base conditions. The -Si-O-Si- structure in the flame retardant forms continuous siloxane microdomains in the matrix. The high bond energy and strong chemical inertness of the Si-O bonds effectively shield against the penetration of acid and base media, preventing contact between the media and the matrix interior and reducing swelling. This reduces mass loss; the composite flame retardant combines with the hydroxyl groups of the modified nanotube surface aluminum-titanium composite oxide through silane groups, and is bridged by the polar groups of the toughening agent, forming good compatibility and interaction with the polyethylene matrix; it promotes tight composite between components, reduces microscopic defects generated during phase separation and melt processing, thereby improving the overall density of the matrix and reducing the erosion of the matrix by the medium from the root; the aluminum-titanium composite oxide coated on the surface of the modified nanotube forms an inorganic shielding layer, which intertwines with the siloxane shielding layer of the composite flame retardant to construct an organic-inorganic dual shielding network, further improving the acid and alkali corrosion resistance.

[0031] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention:

[0034] The cold-resistant toughening agent was purchased from Dongguan Shenghao Plastic Raw Materials Co., Ltd., item number: 5541254; the ethylene-1-octene copolymer was purchased from Dongguan Zhangmutou Keruida Plastic Business Department, brand number: 8440; and the high-density polyethylene was purchased from Shanghai Pengyue New Materials Co., Ltd., brand number: HYA-600.

[0035] Example 1: A method for preparing a wear-resistant and corrosion-resistant modified polyethylene special pipe is as follows:

[0036] S1: Under a nitrogen atmosphere, 20 g of multi-walled carbon nanotubes (diameter 10-20 nm, length 10-30 μm) were added to 1900 mL of 10% nitric acid solution and stirred at 60 °C for 4 h. After centrifugation, the precipitate was washed with deionized water until the pH of the filtrate was 7. Then, the precipitate was vacuum dried at 80 °C for 12 h to obtain pretreated nanotubes.

[0037] S2: Add 8g tetrabutyl titanate to 400mL anhydrous ethanol and stir for 5min. Then add 8mL acetic acid and continue stirring for 10min. Next, add 6g aluminum nitrate nonahydrate and stir for 10min. Then add 8mL deionized water at 0.1mL / min and stir for 30min. After aging for 2h, add 20g pretreated nanotubes and ultrasonically disperse for 1h. After the solvent is evaporated by rotary evaporation at 60℃, grind and pass through a 100-mesh sieve. Then, heat to 800℃ at 5℃ / min under a nitrogen atmosphere. Finally, keep warm at 800℃ under a mixed atmosphere of methane, nitrogen and ammonia (methane, nitrogen and ammonia volume ratio of 10:70:20, total flow rate of 200sccm) for 2h. After cooling under a nitrogen atmosphere, the modified nanotubes are obtained.

[0038] S3: Under a nitrogen atmosphere, 21.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 18.4 g of p-hydroxybenzaldehyde were added to 150 mL of toluene and stirred for 30 min. Then, 0.5 g of p-toluenesulfonic acid was added and refluxed at 110 °C for 4 h. After cooling, toluene was removed by rotary evaporation under reduced pressure. Then, it was added to 200 mL of deionized water at 5 °C and stirred for 30 min. The mixture was filtered and washed three times with deionized water at 5 °C. Finally, it was dried under vacuum at 60 °C for 6 h to obtain the intermediate.

[0039] S4: Under a nitrogen atmosphere, 28g of intermediate, 18.4g of cyanuric chloride, and 3g of triethylamine were added to 200mL of acetonitrile and stirred at 0℃ for 2h, then stirred at 45℃ for 2h. Then, 22.2g of γ-aminopropyltriethoxysilane and 3g of triethylamine were added at 25℃ and stirred at 65℃ for 6h. The mixture was filtered and the filtrate was rotary evaporated to 50mL. The filtrate was then added dropwise to 500mL of petroleum ether stirred at 400r / min. After stirring for 20min, the mixture was filtered under vacuum. Finally, the filter cake was vacuum dried at 50℃ for 8h to obtain the modified intermediate.

[0040] S5: Under a nitrogen atmosphere, 25g of modified intermediate and 5.75g of glycidyl methacrylate were added to 75mL of toluene and stirred for 20min. Then, 0.05g of hydroquinone, 0.15g of triethylamine and 0.25g of trimethylchlorosilane were added and refluxed at 90℃ under a nitrogen atmosphere for 10h. After cooling, the mixture was washed once with 5% dilute hydrochloric acid and then twice with saturated sodium chloride aqueous solution. The organic phase was then dried with anhydrous magnesium sulfate for 4h. After filtration and rotary evaporation to remove toluene, the mixture was vacuum dried at 60℃ for 12h to obtain the composite flame retardant.

[0041] S6: Mix 100g of ethylene-1-octene copolymer, 15g of modified nanotubes, 20g of composite flame retardant, 8g of cold-resistant toughening agent, 0.2g of antioxidant 1010, and 0.2g of antioxidant 168, and dry mix at 1000r / min for 8min at 50℃. Then, melt extrude the mixture in a twin-screw extruder at a temperature of 170℃ in zone 1, 180℃ in zone 2, 190-195℃ in zone 3, 190℃ in zone 4, and 195℃ at the die head, with a screw speed of 250r / min. After water cooling and pelletizing, mix the extrudate with 360g of high-density polyethylene and heat at 90℃. The mixture was mixed at 800 r / min for 5 min, cooled to room temperature, and then fed into a twin-screw extruder for melt extrusion at a zone temperature of 170℃, a zone temperature of 180℃, a zone temperature of 190℃, a die head temperature of 190℃, and a screw speed of 200 r / min. The extrudate was then placed in a pipe die at 185℃, preheated for 3 min, and hot-pressed at 5 MPa for 10 min. It was then cooled to 50℃ at 5 MPa and demolded. After sizing at room temperature for 30 min, it was vacuum heat-treated at 100℃ for 2 h, and finally treated at 80℃ for 1 h to obtain wear-resistant and corrosion-resistant modified polyethylene special pipe.

[0042] Example 2: A method for preparing a wear-resistant and corrosion-resistant modified polyethylene special pipe is as follows:

[0043] S1: Under a nitrogen atmosphere, 20 g of multi-walled carbon nanotubes (diameter 10-20 nm, length 10-30 μm) were added to 1950 mL of 11% nitric acid solution and stirred at 60 °C for 5 h. After centrifugation, the precipitate was washed with deionized water until the pH of the filtrate was 7. Then, the precipitate was vacuum dried at 80 °C for 14 h to obtain pretreated nanotubes.

[0044] S2: Add 8g tetrabutyl titanate to 410mL anhydrous ethanol and stir for 6min. Then add 8mL acetic acid and continue stirring for 10min. Next, add 6g aluminum nitrate nonahydrate and stir for 13min. Then add 8mL deionized water at 0.1mL / min and stir for 40min. After aging for 2h, add 20g pretreated nanotubes and ultrasonically disperse for 1.5h. After the solvent is evaporated by rotary evaporation at 60℃, grind and pass through a 100-mesh sieve. Then, heat to 800℃ at 7℃ / min under a nitrogen atmosphere. Finally, keep warm at 800℃ under a mixed atmosphere of methane, nitrogen and ammonia (methane, nitrogen and ammonia volume ratio of 10:75:15, total flow rate of 200sccm) for 2.5h. After cooling under a nitrogen atmosphere, the modified nanotubes are obtained.

[0045] S3: Under a nitrogen atmosphere, 21.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 18.4 g of p-hydroxybenzaldehyde were added to 150 mL of toluene and stirred for 35 min. Then, 0.5 g of p-toluenesulfonic acid was added and refluxed at 110 °C for 5 h. After cooling, toluene was removed by rotary evaporation under reduced pressure. Then, it was added to 250 mL of deionized water at 10 °C and stirred for 35 min. The mixture was filtered and washed four times with deionized water at 10 °C. Finally, it was dried under vacuum at 60 °C for 7 h to obtain the intermediate.

[0046] S4: Under a nitrogen atmosphere, 29 g of intermediate, 18.4 g of cyanuric chloride, and 3 g of triethylamine were added to 200 mL of acetonitrile and stirred at 3 °C for 2 h, then stirred at 45 °C for 2 h. Then, 22.2 g of γ-aminopropyltriethoxysilane and 3 g of triethylamine were added at 25 °C and stirred at 65 °C for 6 h. The mixture was filtered and the filtrate was rotary evaporated to 50 mL. The filtrate was then added dropwise to 500 mL of petroleum ether stirred at 500 r / min. After stirring for 25 min, the mixture was filtered under vacuum. Finally, the filter cake was vacuum dried at 50 °C for 9 h to obtain the modified intermediate.

[0047] S5: Under a nitrogen atmosphere, 25g of modified intermediate and 5.75g of glycidyl methacrylate were added to 78mL of toluene and stirred for 25min. Then, 0.05g of hydroquinone, 0.15g of triethylamine and 0.25g of trimethylchlorosilane were added and refluxed at 90℃ under a nitrogen atmosphere for 11h. After cooling, the mixture was washed once with 5% dilute hydrochloric acid and then twice with saturated sodium chloride aqueous solution. The organic phase was then dried with anhydrous magnesium sulfate for 5h, filtered, and rotary evaporated to remove toluene. The mixture was then vacuum dried at 60℃ for 13h to obtain the composite flame retardant.

[0048] S6: Mix 110g of ethylene-1-octene copolymer, 18g of modified nanotubes, 23g of composite flame retardant, 9g of cold-resistant toughening agent, 0.3g of antioxidant 1010, and 0.3g of antioxidant 168, and dry mix at 55℃ and 1000r / min for 9min. Then, melt extrude the mixture in a twin-screw extruder at zone 1 (173℃), zone 2 (183℃), zone 3 (193℃), zone 4 (193℃), die head temperature (195-200℃), and screw speed (265r / min). After water cooling and pelletizing, mix the extrudate with 400g of high-density polyethylene and mix at 90℃. The mixture was mixed at 900 r / min for 6 min, cooled to room temperature, and then fed into a twin-screw extruder for melt extrusion at a zone temperature of 173℃, a zone temperature of 183℃, a zone temperature of 193℃, a die head temperature of 193℃, and a screw speed of 210 r / min. The extrudate was then placed in a pipe die at 185℃, preheated for 3 min, and hot-pressed at 8 MPa for 11 min. It was then cooled to 50℃ at 8 MPa and demolded. After sizing at room temperature for 40 min, it was vacuum heat-treated at 100℃ for 2.5 h, and finally treated at 80℃ for 1 h to obtain wear-resistant and corrosion-resistant modified polyethylene special pipe.

[0049] Example 3: A method for preparing a wear-resistant and corrosion-resistant modified polyethylene special pipe is as follows:

[0050] S1: Under a nitrogen atmosphere, 20 g of multi-walled carbon nanotubes (diameter 10-20 nm, length 10-30 μm) were added to 2000 mL of 12% nitric acid solution and stirred at 60 °C for 6 h. After centrifugation, the precipitate was washed with deionized water until the pH of the filtrate was 7. Then, the precipitate was vacuum dried at 80 °C for 16 h to obtain pretreated nanotubes.

[0051] S2: Add 8g tetrabutyl titanate to 420mL anhydrous ethanol and stir for 7min. Then add 8mL acetic acid and continue stirring for 10min. Next, add 6g aluminum nitrate nonahydrate and stir for 15min. Then add 8mL deionized water at 0.1mL / min and stir for 50min. After aging for 2h, add 20g pretreated nanotubes and ultrasonically disperse for 2h. After the solvent is evaporated by rotary evaporation at 60℃, grind and pass through a 100-mesh sieve. Then, heat to 800℃ at 10℃ / min under a nitrogen atmosphere. Finally, keep warm at 800℃ under a mixed atmosphere of methane, nitrogen and ammonia (methane, nitrogen and ammonia volume ratio of 10:80:10, total flow rate of 200sccm) for 3h. After cooling under a nitrogen atmosphere, the modified nanotubes are obtained.

[0052] S3: Under a nitrogen atmosphere, 21.6 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 18.4 g of p-hydroxybenzaldehyde were added to 150 mL of toluene and stirred for 40 min. Then, 0.5 g of p-toluenesulfonic acid was added and refluxed at 110 °C for 6 h. After cooling, toluene was removed by rotary evaporation under reduced pressure. Then, it was added to 300 mL of deionized water at 15 °C and stirred for 40 min. The mixture was filtered and washed 5 times with deionized water at 15 °C. Finally, it was dried under vacuum at 60 °C for 8 h to obtain the intermediate.

[0053] S4: Under a nitrogen atmosphere, 30g of intermediate, 18.4g of cyanuric chloride, and 3g of triethylamine were added to 200mL of acetonitrile and stirred at 5℃ for 2h, then stirred at 45℃ for 2h. Then, 22.2g of γ-aminopropyltriethoxysilane and 3g of triethylamine were added at 25℃ and stirred at 65℃ for 6h. The mixture was filtered and the filtrate was rotary evaporated to 50mL. The filtrate was then added dropwise to 500mL of petroleum ether stirred at 600r / min. After stirring for 30min, the mixture was filtered. Finally, the filter cake was vacuum dried at 50℃ for 10h to obtain the modified intermediate.

[0054] S5: Under a nitrogen atmosphere, 25g of modified intermediate and 5.75g of glycidyl methacrylate were added to 80mL of toluene and stirred for 30min. Then, 0.05g of hydroquinone, 0.15g of triethylamine and 0.25g of trimethylchlorosilane were added and refluxed at 90℃ under a nitrogen atmosphere for 12h. After cooling, the mixture was washed once with 5% dilute hydrochloric acid and then three times with saturated sodium chloride aqueous solution. The organic phase was then dried with anhydrous magnesium sulfate for 6h. After filtration and rotary evaporation to remove toluene, the mixture was vacuum dried at 60℃ for 14h to obtain the composite flame retardant.

[0055] S6: Mix 120g of ethylene-1-octene copolymer, 20g of modified nanotubes, 25g of composite flame retardant, 10g of cold-resistant toughening agent, 0.4g of antioxidant 1010, and 0.4g of antioxidant 168, and dry mix at 1000r / min for 10min at 60℃. Then, melt extrude the mixture in a twin-screw extruder at zone 1 (175℃), zone 2 (185℃), zone 3 (195℃), zone 4 (195℃), die head temperature (200℃), and screw speed (280r / min). After water cooling and pelletizing, mix the extrudate with 440g of high-density polyethylene and dry mix at 90℃. Mix at 1000 r / min for 7 min, cool to room temperature, and then feed into a twin-screw extruder for melt extrusion at a zone temperature of 175℃, a zone temperature of 185℃, a zone temperature of 195℃, a die head temperature of 195℃, and a screw speed of 220 r / min. Then, place the extrudate in a pipe die at 185℃, preheat for 3 min, and hot press at 10 MPa for 12 min. Subsequently, cool to 50℃ at 10 MPa and demold, sizing at room temperature for 50 min, and then vacuum heat treat at 100℃ for 3 h. Finally, treat at 80℃ for 1 h to obtain wear-resistant and corrosion-resistant modified polyethylene special pipe.

[0056] Comparative Example 1:

[0057] Compared with Example 1, this comparative example only replaces the "modified nanotubes" added in the preparation process of S6 with "pretreated nanotubes". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, wear-resistant and corrosion-resistant modified polyethylene special pipes are obtained.

[0058] Comparative Example 2:

[0059] This comparative example differs from Example 1 only in that the "modified nanotubes" were not added during the preparation process of S6. All other steps and parameters are the same, and will not be repeated here. The final product is a wear-resistant and corrosion-resistant modified polyethylene special pipe.

[0060] Comparative Example 3:

[0061] Compared with Example 1, this comparative example only omits the addition of "composite flame retardant" in the preparation process of S6. All other steps and parameters are the same, and will not be repeated here. The final product is a wear-resistant and corrosion-resistant modified polyethylene special pipe.

[0062] Performance testing:

[0063] Impact resistance testing:

[0064] Referring to GB / T 1843-2008 standard, the wear-resistant and corrosion-resistant modified polyethylene special pipes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were used to make notched 80mm×10mm×3.2mm specimens (notch depth 2mm), and the impact strength (kJ / m²) at an impact velocity of 200cm / s and an impact energy of 1J was measured. 2 The measurement results are shown in Table 1.

[0065] Abrasion resistance testing:

[0066] Referring to GB / T 3960-2016 standard, the wear-resistant and corrosion-resistant modified polyethylene special pipes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were made into specimens with dimensions of 30mm×7mm×6mm, and the wear mass (mg) after 1000 revolutions at 100 rpm under a 5N load was measured. The test results are shown in Table 1.

[0067] Flame retardancy testing:

[0068] Referring to GB / T 2408-2021 standard, the wear-resistant and corrosion-resistant modified polyethylene special pipes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were made into specimens with a thickness of 3.2 mm and the vertical combustion flame retardancy rating (grade) was determined. The test results are shown in Table 1.

[0069] Corrosion resistance testing:

[0070] Referring to GB / T 11547-2008 standard, the wear-resistant and corrosion-resistant modified polyethylene special pipes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were made into 50mm×50mm×3mm specimens, and the mass loss rate (%) after immersion in 1mol / L hydrochloric acid solution (acid solution) and 1mol / L sodium hydroxide solution (alkali solution) for 120 days was determined. The test results are shown in Table 1.

[0071] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-3

[0072] ;

[0073] Data Analysis:

[0074] As can be seen from Table 1, the wear-resistant and corrosion-resistant modified polyethylene special pipe prepared in the embodiments of the present invention has excellent impact resistance, wear resistance, flame retardancy and corrosion resistance.

[0075] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A wear-resistant and corrosion-resistant modified polyethylene special pipe, characterized in that, The raw materials include the following parts by weight: 360-440 parts of high-density polyethylene, 100-120 parts of ethylene-1-octene copolymer, 15-20 parts of modified nanotubes, 20-25 parts of composite flame retardant, 8-10 parts of cold-resistant toughening agent, 0.2-0.4 parts of antioxidant 1010, and 0.2-0.4 parts of antioxidant 168; The modified nanotubes are multi-walled carbon nanotubes that are first pretreated with nitric acid aqueous solution, then combined with tetrabutyl titanate and aluminum nitrate nonahydrate, then heated to 800℃ in a nitrogen atmosphere and treated with a mixture of methane, nitrogen and ammonia at 800℃ for 2-3 hours, and finally cooled in a nitrogen atmosphere to obtain the modified nanotubes. The composite flame retardant is prepared from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde, p-toluenesulfonic acid, cyanuric chloride, γ-aminopropyltriethoxysilane, glycidyl methacrylate, hydroquinone, and trimethylchlorosilane. The preparation method of the composite flame retardant is as follows: B1: Under a nitrogen atmosphere, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and p-hydroxybenzaldehyde were added to toluene and stirred for 30-40 min. Then p-toluenesulfonic acid was added and refluxed at 110 °C for 4-6 h. After cooling, toluene was removed by rotary evaporation under reduced pressure. Then it was added to deionized water at 5-15 °C and stirred for 30-40 min. After filtration, washing and drying, the intermediate was obtained. B2: Under a nitrogen atmosphere, add the intermediate, cyanuric chloride, and triethylamine to acetonitrile and stir at 0-5℃ for 2 hours, then stir at 45℃ for 2 hours. Then add γ-aminopropyltriethoxysilane and triethylamine at 25℃ and stir at 65℃ for 6 hours. After filtration and rotary evaporation, add the filtrate dropwise to petroleum ether, stir for 20-30 minutes, filter, and dry to obtain the modified intermediate. B3: Under a nitrogen atmosphere, add the modified intermediate and glycidyl methacrylate to toluene and stir for 20-30 min. Then add hydroquinone, triethylamine, and trimethylchlorosilane and reflux at 90°C under a nitrogen atmosphere for 10-12 h. After cooling, wash and then dry the organic phase with anhydrous magnesium sulfate. After filtration and rotary evaporation to remove toluene, dry to obtain the composite flame retardant.

2. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 1, characterized in that, The modified nanotubes are prepared as follows: A1: Under a nitrogen atmosphere, multi-walled carbon nanotubes were added to an aqueous nitric acid solution and stirred at 60°C for 4-6 hours. After centrifugation, washing, and drying, pretreated nanotubes were obtained. A2: Add tetrabutyl titanate to anhydrous ethanol and stir for 5-7 min, then add acetic acid and continue stirring for 10 min, then add aluminum nitrate nonahydrate and stir for 10-15 min, then add deionized water and stir for 30-50 min, age for 2 h, then add pretreated nanotubes and ultrasonically disperse for 1-2 h, evaporate the solvent by rotary evaporation, grind and sieve, then heat to 800℃ under a nitrogen atmosphere, and finally keep warm at 800℃ under a mixed atmosphere of methane, nitrogen and ammonia for 2-3 h, and cool under a nitrogen atmosphere to obtain modified nanotubes.

3. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 2, characterized in that, The ratio of nitric acid aqueous solution to multi-walled carbon nanotubes in A1 is 1900-2000 mL: 20 g; The mass fraction of the nitric acid aqueous solution described in A1 is 10%-12%.

4. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 2, characterized in that, The ratio of anhydrous ethanol, tetrabutyl titanate, acetic acid, aluminum nitrate nonahydrate, deionized water, and pretreated nanotubes in A2 is 400-420 mL: 8 g: 8 mL: 6 g: 8 mL: 20 g; The volume ratio of methane, nitrogen, and ammonia in the mixture described in A2 is 10:70-80:10-20, and the total flow rate of the mixture is 200 sccm.

5. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 1, characterized in that, The ratio of toluene, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde, p-toluenesulfonic acid, and deionized water in B1 is 150 mL: 21.6 g: 18.4 g: 0.5 g: 200-300 mL.

6. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 1, characterized in that, The ratio of acetonitrile, intermediate, cyanuric chloride, triethylamine, γ-aminopropyltriethoxysilane, triethylamine, and petroleum ether in B2 is 200mL: 28-30g: 18.4g: 3g: 22.2g: 3g: 500mL.

7. The wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 1, characterized in that, The ratio of toluene, modified intermediate, glycidyl methacrylate, hydroquinone, triethylamine, and trimethylchlorosilane described in B3 is 75-80 mL: 25 g: 5.75 g: 0.05 g: 0.15 g: 0.25 g.

8. The method for preparing the wear-resistant and corrosion-resistant modified polyethylene special pipe according to any one of claims 1-7, characterized in that, Includes the following steps: Ethylene-1-octene copolymer, modified nanotubes, composite flame retardant, cold-resistant toughening agent, antioxidant 1010, and antioxidant 168 are mixed and dry-mixed at 50-60℃ for 8-10 minutes. Then, the mixture is melt-extruded, water-cooled, pelletized, and mixed with high-density polyethylene at 90℃ for 5-7 minutes. After cooling, it is melt-extruded again and then hot-pressed to obtain wear-resistant and corrosion-resistant modified polyethylene special pipes.

9. The method for preparing the wear-resistant and corrosion-resistant modified polyethylene special pipe according to claim 8, characterized in that, The hot pressing process is as follows: the extrudate is placed in a pipe mold at 185°C, preheated for 3 minutes, and then hot-pressed at 5-10 MPa pressure for 10-12 minutes. After that, it is cooled to 50°C at 5-10 MPa pressure and demolded. After sizing at room temperature for 30-50 minutes, it is vacuum heat-treated at 100°C for 2-3 hours, and finally treated at 80°C for 1 hour.