Nanometer reinforced pipe and preparation method thereof

Abstract

The invention relates to the technical field of pipe manufacturing, and provides a nano reinforced pipe and a preparation method thereof, the nano reinforced pipe comprises an inner layer and an outer layer; the inner layer is prepared from the following raw materials in parts by weight: 75 to 100 parts of engineering plastic, 5 to 80 parts of PVC-C resin, 1 to 35 parts of a modified nano material, 0.5 to 15 parts of a coupling agent, 0.5 to 15 parts of an active agent, 0.5 to 3.0 parts of a lubricating agent and 0.8 to 8 parts of a stabilizer; 1 to 10 parts of compatilizer, 0.5 to 2.0 parts of pigment and 1.0 to 3.0 parts of titanium dioxide; the outer layer is prepared from the following raw materials in parts by weight: 75-100 parts of PVC resin, 5-15 parts of a modified nano material, 0.5-5 parts of a coupling agent, 0.5-5 parts of an active agent, 0.5-3.0 parts of a lubricant, 3-8 parts of a stabilizer, 0.5-2.0 parts of pigment and 1.0-3.0 parts of titanium dioxide; the preparation method comprises the following steps: respectively preparing the inner-layer material and the outer-layer material, and co-extruding. The high-strength, high-toughness and heat-resistant characteristics of the pipe can be guaranteed while the using amount of the compatilizer is reduced, the full life cycle of the pipe is better guaranteed, and the purposes of energy conservation, emission reduction and green ecological environmental protection are achieved.

Description

Technical Field

[0001] This invention relates to the field of pipe manufacturing technology, and more specifically, to a nano-reinforced pipe and its preparation method. Background Technology

[0002] Power cable conduits (also known as cable pipes, cable protection pipes, cement cable pipes, etc.) are conduits used for laying underground cables in power plants, transportation infrastructure, bridges, industrial parks, and other locations. They are made from materials such as vinylon fiber and high-grade cement, using an electro-expansion process. They feature high strength (flexural load ≥12000N, external pressure load ≥15000N), low coefficient of friction (<0.35), and high current carrying capacity, with a strength increase of 40% compared to ordinary conduits.

[0003] The materials used for electrical conduits are primarily polyethylene, polypropylene, polyvinyl chloride (PVC), and chlorinated PVC. Due to their lightweight, corrosion resistance, ease of installation, and moderate cost, they are widely used in municipal, chemical, and construction industries. Among these, PVC and chlorinated PVC are the most common. PVC and chlorinated PVC are general-purpose plastics polymerized from vinyl chloride monomers through free radical polymerization. By adding appropriate additives, they can be made into rigid and flexible products for various applications and are widely used in power, communications, industry, agriculture, construction, daily necessities, and packaging. Major products include pipes and fittings, door and window profiles, sheets and plates, wire insulation, medical supplies, films, and sealing strips. However, PVC pipes have drawbacks such as poor high-temperature ring stiffness and low tensile strength, while PVC-C has high low-temperature brittleness. Polyethylene and polypropylene can be processed into pipes using conventional methods, and they have good processing performance. However, they have low high-temperature ring stiffness, low tensile strength, and fast aging. This is mainly due to the poor compatibility between the matrix and other components. If a large amount of compatibilizer is added to meet the aging resistance requirements, not only will the cost be high, but the physical and mechanical properties will also be greatly sacrificed.

[0004] However, with the upgrading of industrial technology and the expansion of application scenarios, the inherent defects of traditional polymer pipes have become increasingly prominent, such as: insufficient mechanical properties, low impact strength, tensile strength and high temperature ring stiffness, and poor durability, making them prone to damage and cracking during transportation, installation and use; limited heat resistance, which easily leads to safety problems such as pipe aging, embrittlement and leakage. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a nano-reinforced pipe and its preparation method, which can reduce the amount of compatibilizer used while ensuring the pipe's high strength, high toughness, heat resistance, and aging resistance, thus better guaranteeing the pipe's entire life cycle and achieving the goals of energy conservation, emission reduction, and green ecological environmental protection.

[0006] The embodiments of the present invention are achieved through the following technical solutions:

[0007] A nano-reinforced pipe, the pipe wall of which is composed of a double-layer structure, including an inner layer and an outer layer; by weight, the inner layer raw materials include: 75-100 parts of engineering plastic, 5-80 parts of PVC-C resin, 1-35 parts of modified nanomaterials, 0.5-15 parts of coupling agent, 0.5-15 parts of activator, 0.5-3.0 parts of lubricant, 0.8-8 parts of stabilizer, 1-10 parts of compatibilizer, 0.5-2.0 parts of pigment, and 1.0-3.0 parts of titanium dioxide; The outer layer raw materials include: 75-100 parts of PVC resin, 5-15 parts of modified nanomaterials, 0.5-5 parts of coupling agent, 0.5-5 parts of activator, 0.5-3.0 parts of lubricant, 3-8 parts of stabilizer, 0.5-2.0 parts of pigment, and 1.0-3.0 parts of titanium dioxide.

[0008] The modified nanomaterial is a composite of modified graphene nanoparticles and modified boron nitride nanoparticles, and the mass ratio of the modified graphene nanoparticles to the modified boron nitride nanoparticles is 2-7:1.

[0009] A method for preparing a nano-reinforced tube includes the following steps: A. Inner layer preparation: A1: First, put the modified nanomaterials into a mixer and control the temperature at 50-90℃. Then add the coupling agent, lubricant, and activator. Then raise the temperature to 100-130℃, add a positive pressure of 0.01-0.05MPa, and cook for 1-10 minutes. Continue to raise the temperature to 150-160℃ and react for 0.5-1 hour. Then cool to 20-45℃ and pack for later use. By applying pressure and gradient temperature control, the material swells and penetrates, improving the compatibility interface and ensuring the activity of the material, thereby improving the dispersibility and compatibility of the material. A2: Place the engineering plastic and a portion of the compatibilizer into a mixer, control the temperature at 100-120℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 130-150℃ and react for 0.5-1 hour. After that, cool to 20-45℃ and bag for later use. This improves the interfacial dispersibility and compatibility of the engineering plastic, and enhances its compatibility when blended with other materials. A3: Preparation method of chlorinated polyvinyl chloride: Place chlorinated polyvinyl chloride resin, stabilizer, and remaining compatibilizer into a mixer, control the temperature at 100-120℃, apply positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 120-130℃ and react for 0.5-1 hour. After cooling to 20-45℃, package for later use. This improves the interfacial dispersibility and compatibility of chlorinated polyvinyl chloride, and enhances the compatibility of engineering plastics when blended with other materials. A4: Place the engineering plastics and chlorinated polyvinyl chloride prepared in steps A2 and A3 into a mixer, control the temperature at 80℃-100℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 110-115℃ and react for 0.5-1 hours. Then add the nanomaterials prepared in step A1 and the remaining raw materials, continue to apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, continue to raise the temperature to 120-130℃, and then cool to 20-45℃ to obtain the inner layer material. B. Outer layer preparation: B1. The preparation method of modified nanomaterials is the same as that of A1; B2. Except for the modified nanomaterials, put the remaining outer layer raw materials and the modified nanomaterials into a mixer, control the temperature at 100-125℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, and then cool to 20-45℃ to obtain the outer layer material. C. Processing C1. Feed the inner layer material into the extruder and set the extruder main machine temperature to 160-235℃, the die temperature to 170-235℃, the screw speed to 10-45 rpm, and the main machine current to 32-80A; the inner layer material is extruded through the inner layer flow channel of the co-extrusion die to form the inner layer. C2. The outer layer material is fed into the extruder, and the extruder main machine temperature is set to 160-200℃, the die temperature to 170-235℃, the screw speed to 10-45 rpm, and the main machine current to 32-70A; the inner layer material is extruded through the outer layer flow channel of the co-extrusion die to form the outer layer. C3. The outer and inner layers are compounded at the discharge port of the co-extrusion die, with the core temperature at 160-170℃, the traction machine speed at 0.5-1.8m / min, and the cooling water temperature in the water tank at 15-35℃, to obtain the nano-reinforced tube.

[0010] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: 1. The pipe material of this invention utilizes the synergistic effect of multiple components, especially the modification of nanomaterials, to promote the dispersion and compatibility of active functional groups of nanomaterials and the compatibility and synergy between multiple components. Compared with existing PVC pipes, the prepared pipe material reduces the amount of compatibilizer used while still maintaining high ring stiffness when heated, ensuring greater dimensional stability, preventing instability during repair after high-temperature extrusion deformation, and addressing the problem of difficulty in dragging when replacing cables. Furthermore, the pipe material of this invention is high in strength and toughness, heat resistant, and better ensures the entire life cycle, achieving energy conservation, emission reduction, and green ecological environmental protection goals, and can be applied to many fields.

[0011] 2. The pipe of this invention uses PVC-C resin as the matrix. During the extrusion, molding, and shaping processes, a combination of positive pressure and gradient heating is applied internally. The core is to solve the core problems in pipe molding, such as uneven wall thickness, internal surface defects, low molecular particle density, stress concentration, and poor dimensional accuracy, through the coordinated control of the "pressure field and temperature field". At the same time, it realizes the directional optimization of the pipe's microstructure, improves the mechanical properties, sealing performance, and service stability of the finished product, and can greatly reduce the amount of compatibilizer used in the preparation process, thus solving the drawbacks of using a large amount of compatibilizer in the prior art. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The following is a detailed description of a nano-reinforced pipe and its preparation method provided by an embodiment of the present invention.

[0014] A nano-reinforced pipe, the pipe wall of which is composed of a double-layer structure, including an inner layer and an outer layer; by weight, the inner layer raw materials include: 75-100 parts engineering plastic, 5-80 parts PVC-C resin, 1-35 parts modified nanomaterials, 0.5-15 parts coupling agent, 0.5-15 parts activator, 0.5-3.0 parts lubricant, 0.8-8 parts stabilizer, 1-10 parts compatibilizer, 0.5-2.0 parts scarlet pigment, and 1.0-3.0 parts titanium dioxide; the outer layer raw materials include: 75-100 parts PVC resin, 5-15 parts modified nanomaterials, 0.5-5 parts coupling agent, 0.5-5 parts activator, 0.5-3.0 parts lubricant, 3-8 parts stabilizer, and 0.5-2.0 parts scarlet pigment. The inner layer raw materials include: 75-90 parts engineering plastic, 5-50 parts PVC-C resin, 1-20 parts modified nanomaterials, 0.5-10 parts coupling agent, 0.5-10 parts activator, 0.5-1.0 parts lubricant, 0.8-5 parts stabilizer, 1-5 parts compatibilizer, 0.5-1.0 parts pigment, and 1.0-2.0 parts titanium dioxide; the outer layer raw materials include: 75-90 parts PVC resin, 5-10 parts modified nanomaterials, 0.5-3 parts coupling agent, 0.5-2 parts activator, 0.5-2.0 parts lubricant, 3-5 parts stabilizer, 0.5-1.0 parts pigment, and 1.0-2.0 parts titanium dioxide.

[0015] The modified nanomaterial is a composite of modified graphene nanoparticles and modified boron nitride nanoparticles, and the mass ratio of the modified graphene nanoparticles to the modified boron nitride nanoparticles is 2-7:1.

[0016] To improve the compatibility between nanoparticles and the matrix material, this invention uses surface-modified graphene nanoparticles and boron nitride nanoparticles as reinforcing agents. On one hand, the three-dimensional network structure of graphene oxide connects the matrix, while the oxygen-containing functional groups such as hydroxyl and carboxyl groups on its surface serve as "anchoring points," inducing the adsorption of metal ions and the in-situ generation of phosphate-intercalated hydrotalcite crystals under alkaline conditions. This achieves bonding with graphene oxide, improving the dispersibility of graphene oxide in the system. Simultaneously, phosphate ions between the hydrotalcite layers can be released and dispersed from the modified graphene oxide layers. Between the matrix and the substrate, the compatibility between the nano-boron nitride particles is greatly improved. On the other hand, the surface of the boron nitride nanoparticles is modified by titanate coupling agent, which changes the surface polarity of the boron nitride particles to match the polarity of the polymer matrix. At the same time, the surface energy of the boron nitride particles is reduced, which effectively inhibits the aggregation of boron nitride particles. The synergistic effect of the compounded nano-reinforcing agent and compatibilizer further enhances the interfacial bonding force between the nanoparticles and the polymer matrix, realizes the uniform dispersion of nanoparticles in the polymer matrix, gives full play to the reinforcing effect of nanoparticles, and avoids agglomerates becoming weak links in the pipe. Furthermore, the modified nanographene is prepared as follows: ① Put Mg 2+ Solution and Al 3+ The solution was mixed at a molar ratio of 2-4:1 and then added to the graphene oxide suspension to obtain mixture A; this maintained a stable layered structure for the metal ions, which then bound to the oxygen-containing functional groups on the graphene oxide surface through electrostatic adsorption; more specifically, Mg 2+ With Al 3+ In aqueous solution, it exists as a hydrated ion, undergoing electrostatic adsorption and coordination with numerous oxygen-containing functional groups on the surface of graphene oxide. The metal ions can form a hydrotalcite-like precursor structure between and on the surface of graphene oxide sheets, playing an intercalation, supporting, and bridging role, and enhancing the subsequent bonding force with phosphates and matrix materials. The total concentration of the metal salt is controlled between 0.2 and 0.8 mol / L; through Mg... 2+ Solution and Al 3+ Solutions mixed at a molar ratio of 2-4:1 readily form homogeneous, highly crystalline layered metal hydroxides; however, if the ratio is too low (Al... 3+ Excessive amounts of Mg can easily lead to impurities and agglomeration; excessively high proportions (Mg) can also cause problems. 2+ Excessive charge on the layers leads to insufficient charge and reduced modification effect. ② Mix phosphate, deionized water, and alkaline solution, and control the pH of the system to 9-11 to obtain mixture B; the molar ratio of phosphate to alkaline solution is 1:3-5; phosphate provides a phosphate ion precipitant, and alkaline solution (such as NaOH or ammonia) regulates the pH to keep the system in the suitable range for metal phosphate / hydroxide co-precipitation; by controlling the molar ratio of phosphate to alkaline solution to 1:3-5, the pH of the system is quickly stabilized at 9-11, avoiding uneven precipitation caused by local over-acidity / over-alkalinity; excess alkaline solution is beneficial for the full precipitation of metal ions and the formation of a layered phase with higher crystallinity; by forming a stable and homogeneous precipitation precursor solution, the subsequent in-situ growth is ensured to be uniform; ③ Slowly add mixture B to mixture A, maintaining the pH between 9 and 11 throughout the process. Then, stir continuously at 60-80℃ for 0.5-1 h, and crystallize at 60-100℃ for 6-24 h. Filter and wash until neutral, then dry at 60-80℃ to obtain modified nano-graphene; PO4 3- OH - Mg² adsorbed on the GO surface + Al³ + A coprecipitation reaction occurs, generating magnesium aluminum phosphate / hydrotalcite-like phases in situ. Heating promotes complete precipitation and uniform diffusion, reducing agglomeration. After crystallization at 60–100 °C for 6–24 h, the amorphous precipitate rearranges and crystallizes under hydrothermal conditions, forming an inorganic modified layer with complete crystal structure and stability. pH 9–11 is the optimal range for coprecipitation and phase stability in the Mg-Al-PO system. If the pH is too low, precipitation is incomplete; if the pH is too high, heterogeneous hydroxides are easily formed. By growing uniform inorganic layers in situ on the graphene surface / interlayer, intercalation exfoliation and surface functionalization are achieved, significantly improving the dispersibility, compatibility, thermal stability, and bonding strength with the matrix of graphene.

[0017] Further, the preparation method of the modified boron nitride nanoparticles is as follows: Take 100 parts of boron nitride nanoparticles, add 400-600 parts of solvent (such as anhydrous ethanol), and ultrasonically disperse for 0.5-1 h (ultrasonic power 200-300W) to form a stable suspension, thereby obtaining highly dispersed nano-BN, providing sufficient reaction sites for surface modification; then add 3-6 parts of titanate coupling agent (NDZ-101 or NDZ-311). If too little is added, the coating will be incomplete and the modification insufficient; if too much is added, it will form... Multilayer physical adsorption, on the contrary, reduces interfacial interaction and introduces impurities. The reaction is carried out under reflux at 60-100℃ and 400-600 r / min for 1.5-2.5 h. Heating accelerates the hydrolysis, condensation, and chemisorption of the coupling agent, resulting in a stable chemical bond between the coupling agent and the BN surface, rather than a simple physical coating. After the reaction, the solvent is removed by vacuum distillation, and the resulting solid is vacuum dried at 90-110℃ for 3-5 h, pulverized, and passed through a 200-mesh sieve to obtain surface-modified boron nitride nanoparticles. The boron nitride nanoparticles have weak surface polarity and poor compatibility with the matrix; while the titanate coupling agent has an inorganic-loving group at one end, bonding with hydroxyl groups / defects on the BN surface; and an organic-loving group at the other end, improving interfacial compatibility. Essentially, the coupling agent undergoes chemisorption and condensation reactions on the BN surface to form a monomolecular coating layer.

[0018] Furthermore, the preparation method of the modified nanomaterial is as follows: the modified nanographene and modified nanoboron nitride prepared above are mixed at a mass ratio of 2-7:1. If the ratio is too low (too much boron nitride), the reinforcing, conductive, and adsorption advantages of graphene will be weakened, the overall filler performance will be more inert, and the composite reinforcement effect will decrease. If the ratio is too high (too much graphene), the aggregation of graphene sheets cannot be effectively inhibited, local conductive pathways will easily form, and the insulation and dispersion stability will deteriorate. However, with the modified nanographene and modified nanoboron nitride of this invention combined at a mass ratio of 2-7:1, the conductivity can be improved. An optimal balance is achieved between thermal enhancement, mechanical enhancement, dispersibility, and insulation, realizing a spatially complementary structure between sheet-like graphene and particulate boron nitride. This reduces agglomeration while maintaining high thermal conductivity, adjustable electrical / insulating properties, high dispersibility, and high interfacial bonding strength, and significantly improves compatibility with polymer / resin / coating matrices. The material is then placed in a high-speed mixer and mixed for 15-25 minutes at a speed of 1000-1500 r / min and a temperature of 80-100℃, allowing the coupling layer and inorganic layer on the surfaces of the two modified fillers to mutually wet and anchor, thus obtaining surface-modified nanomaterials. By utilizing the hydrogen bonds, polar adsorption, interfacial entanglement, and mechanical coating effects between the polar functional groups, inorganic modified layers, and organic coupling layers introduced on the surfaces of two nanomaterials, uniform composite and interfacial compatibility of two high thermal conductivity and high stability nanofillers are achieved at the microscale. This forms a synergistic modified nanocomposite filler that combines the high specific surface area of ​​graphene with the high insulation and high chemical stability of boron nitride, thereby improving the thermal stability and dispersion stability of the composite nanomaterial.

[0019] Furthermore, the pigment can be selected from pigments of suitable colors as needed, such as bright red pigment, blue pigment, etc., and the present invention does not impose any restrictions.

[0020] Furthermore, the engineering plastic is ABS and / or PC.

[0021] Furthermore, the coupling agent is one or more of silane coupling agents, aluminate coupling agents, and titanate coupling agents.

[0022] Further, the activator is one or more of stearic acid, calcium stearate, zinc stearate, barium stearate, and zinc stearate.

[0023] Furthermore, the stabilizer is one or more of rare earth stabilizers, calcium-zinc stabilizers, and organotin stabilizers.

[0024] Furthermore, the lubricant is one or more of stearic acid, paraffin wax, polyethylene wax, and oxidized polyethylene wax.

[0025] Further, the compatibilizer is one or more of the following: ethylene-vinyl acetate copolymer, glycidyl methacrylate radiation graft copolymer, styrene-maleic anhydride copolymer, ethylene-propylene copolymer, acrylonitrile-butadiene-styrene graft copolymer, polypropylene-caprolactone graft copolymer, polypropylene-styrene graft copolymer, maleic anhydride graft copolymer (such as maleic anhydride grafted polyethylene / polypropylene / ethylene / vinyl acetate / styrene / butadiene / styrene block copolymer, the same below), polypropylene-methacrylate graft copolymer, polypropylene-acrylonitrile graft copolymer, chloromethylstyrene graft copolymer, acrylate epoxy ester graft copolymer, chlorinated polyethylene (CPE), maleic anhydride graft copolymer, and MBS.

[0026] Through theoretical research and numerous practical applications, the inventors discovered that poor compatibility among multiple material components in pipes often leads to poor mechanical and durability properties. While existing methods of increasing compatibilizer concentration can address this issue, they also introduce significant problems: excessive addition forms a loose, low-strength pure compatibilizer interface layer, transforming the material interface from a "strong bond" to a "weak interface layer," thus negating the core function of the compatibilizer and consequently sacrificing some of the material's mechanical properties. Furthermore, excessive compatibilizer addition significantly increases pipe manufacturing costs. This invention addresses this issue by modifying the nanomaterials in the formulation to improve their dispersibility and compatibility with the matrix, and by employing a pressurized and gradient-heated approach during the preparation process. Specifically, this invention also provides a method for preparing nano-reinforced pipes, comprising the following steps: A. Inner layer preparation: A1: First, put the modified nanomaterials into a mixer and control the temperature at 50-90℃. Then add the coupling agent, lubricant, and activator. Then raise the temperature to 100-130℃, add a positive pressure of 0.01-0.05MPa, and cook for 1-10 minutes. Continue to raise the temperature to 150-160℃ and react for 0.5-1 hour. Then cool to 20-45℃ and pack for later use. By applying pressure and gradient temperature control, the material swells and penetrates, improving the compatibility interface and ensuring the activity of the material, thereby improving the dispersibility and compatibility of the material. A2: Place the engineering plastic and a portion of the compatibilizer into a mixer, control the temperature at 100-120℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 130-150℃ and react for 0.5-1 hour. After that, cool to 20-45℃ and bag for later use. This improves the interfacial dispersibility and compatibility of the engineering plastic, and enhances its compatibility when blended with other materials. A3: Place the chlorinated polyvinyl chloride resin, stabilizer, and remaining compatibilizer into a mixer, control the temperature at 100-120℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 120-130℃ and react for 0.5-1 hour. After that, cool to 20-45℃ and bag for later use. This improves the interfacial dispersibility and compatibility of chlorinated polyvinyl chloride, and enhances the compatibility of engineering plastics when blended with other materials. A4: Place the engineering plastics and chlorinated polyvinyl chloride obtained in steps A2 and A3 into a mixer, control the temperature at 80℃-100℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 110-115℃ and react for 0.5-1 hours. Then add the modified nanomaterials obtained in step A1 and the remaining raw materials, continue to apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, continue to raise the temperature to 120-130℃ and react for 0.5-1 hours. Finally, cool to 20-45℃ to obtain the inner layer material. B. Outer layer preparation: B1. The preparation method of modified nanomaterials is the same as that of A1; B2. Place the outer layer material into a mixer, control the temperature at 100-125℃, apply positive pressure of 0.01-0.05MPa for 1-10 minutes, and then cool it to 20-45℃ to obtain the outer layer material. C. Processing C1. Feed the inner layer material into the extruder and set the extruder main machine temperature to 160-235℃, the die temperature to 170-235℃, the screw speed to 10-45 rpm, and the main machine current to 32-80A; the inner layer material is extruded through the inner layer flow channel of the co-extrusion die to form the inner layer. C2. Feed the outer layer material into the extruder and set the extruder main machine temperature to 160-200℃, the die temperature to 170-235℃, the screw speed to 10-45 rpm, and the main machine current to 32-70A; the inner layer material is extruded through the outer flow channel of the co-extrusion die to form the outer layer. C3. The outer and inner layers are compounded at the discharge port of the co-extrusion die, with the core temperature at 160-170℃, the traction machine speed at 0.5-1.8m / min, and the cooling water temperature in the water tank at 15-35℃, to obtain the nano-reinforced tube.

[0027] This invention relates to a pipe made from PVC-C resin. During extrusion, molding, and shaping, a combination of positive pressure and gradient heating is applied internally. The core of this process is to address key issues in pipe forming, such as uneven wall thickness, internal surface defects, low molecular particle density, stress concentration, and poor dimensional accuracy, through the coordinated control of the "pressure field" and "temperature field." Simultaneously, it achieves targeted optimization of the pipe's microstructure, improving the finished product's mechanical properties, sealing performance, and service stability. The two processes are not simply superimposed; rather, the gradient heating creates the thermodynamic and kinetic conditions for effective positive pressure transfer, plastic flow of the material, and particle densification, while the positive pressure provides the driving force for structural rearrangement and defect elimination during the gradient heating process, ultimately achieving simultaneous control of the pipe's "shape, properties, and density." This invention employs gradient heating and pressurization during the preparation process at different stages. The gradient heating causes the materials at the interlayer interfaces to reach their diffusion temperature first, activating and diffusing the interlayer molecules (forming a "transition layer" at the interface). Meanwhile, the radial compressive stress applied by the positive pressure promotes close contact between the interlayer materials, increasing the diffusion area and diffusion rate at the interface. This upgrades the interlayer bonding from "physical bonding" to chemical bonding, significantly improving the material's compatibility. Therefore, the amount of compatibilizer used in the preparation process can be greatly reduced, solving the drawbacks of using large amounts of compatibilizer in existing technologies.

[0028] Example 1 A nano-reinforced pipe, the pipe wall of which is composed of a double-layer structure, including an inner layer and an outer layer; the raw materials of the inner layer include: 750 kg of ABS resin, 100 kg of PC, 100 kg of PVC-C resin, 50 kg of modified nano-graphite, 10 kg of modified nano-boron nitride, 30 kg of MBS, 15 kg of titanate coupling agent, 5 kg of stearic acid, 5 kg of calcium stearate, 5 kg of zinc stearate, 8.0 kg of calcium-zinc stabilizer, 15 kg of maleic anhydride grafted polyethylene, 5 kg of scarlet pigment, and 10 kg of titanium dioxide; The outer layer raw materials include: 1000 kg of PVC, 100 kg of modified nano-graphite, 20 kg of modified nano-boron nitride, 10 kg of silane coupling agent, 5 kg of stearic acid, 5 kg of oxidized polyethylene wax, 50 kg of calcium zinc stabilizer, 5 kg of scarlet pigment, and 10 kg of titanium dioxide.

[0029] The preparation method of modified nanomaterials is as follows: (1) Preparation of modified nanographite ① Take graphene oxide powder, add deionized water to prepare a dispersion with a concentration of 1 mg / ml, sonicate for 60 min to obtain a uniform and stable graphene oxide suspension, then mix magnesium nitrate solution and aluminum nitrate solution at a molar ratio of 3:1 and stir for 1 h, add to the graphene oxide suspension, control the total concentration of metal salts to 0.5 mol / L, and obtain mixture A. ② Mix sodium phosphate, deionized water, and sodium hydroxide solution, and control the pH of the system to 10 to obtain mixture B; ③ Slowly add mixture B to mixture A, maintaining the pH between 9 and 11 throughout the process. Then, stir continuously at 70°C for 1 hour and crystallize at 80°C for 24 hours. Filter, wash until neutral, and dry and grind at 70°C to obtain modified graphene oxide.

[0030] (2) Preparation of modified boron nitride nanoparticles: Take 100 parts of boron nitride nanoparticles, add 500 parts of anhydrous ethanol, and ultrasonically disperse at 250W power for 1h. Then add 5 parts of NDZ-311 titanate coupling agent and reflux at 80℃ and 500r / min for 2h. After the reaction is completed, remove the solvent by vacuum distillation. The obtained solid is vacuum dried at 100℃ for 4h, pulverized and passed through a 200-mesh sieve to obtain surface-modified boron nitride nanoparticles. (3) Mixing: The modified nano-graphene and modified nano-boron nitride prepared above are mixed at a mass ratio of 5:1 and placed in a high-speed mixer. The mixture is mixed for 20 minutes at a speed of 1200 r / min and a temperature of 90℃ to obtain the surface modified nanomaterial.

[0031] The preparation method of the above-mentioned nano-reinforced tubing is as follows: A. Inner layer preparation: A1: First, put the modified nanomaterials into the mixer and control the temperature at 80℃. Then add the coupling agent, lubricant, and activator. Then raise the temperature to 120℃, add a positive pressure of 0.03MPa for 5 minutes, and continue to raise the temperature to 155℃. After reacting for 1 hour, cool to 30℃ and pack into bags for later use. A2: Put ABS resin, PC, and 50% maleic anhydride-grafted polyethylene into a mixer, control the temperature at 110℃, apply a positive pressure of 0.03MPa for 5 minutes, then raise the temperature to 140℃, react for 0.8 hours, cool to 30℃, and pack for later use. A3: Place chlorinated polyvinyl chloride resin, calcium-zinc stabilizer and the remaining maleic anhydride-grafted polyethylene into a mixer, control the temperature at 110℃, apply positive pressure of 0.03MPa for 5 minutes, then raise the temperature to 125℃, react for 0.5 hours, cool to 30℃, and pack for later use. A4: The engineering plastics and chlorinated polyvinyl chloride prepared in steps A2 and A3 are placed in a mixer, the temperature is controlled at 90℃, positive pressure is applied at 0.02MPa for 6 minutes, and then the temperature is raised to 113℃. After reacting for 1 hour, the modified nanomaterials obtained in step A1 and the remaining raw materials are added, and positive pressure is applied at 0.04MPa for 5 minutes. The temperature is raised to 125℃ and reacted for 1 hour. Then the mixture is cooled to 30℃ to obtain the inner layer material. B. Outer layer preparation: B1. The preparation method of modified nanomaterials is the same as that of A1; B2. Place the outer layer material into a mixer, control the temperature at 100-125℃, apply positive pressure of 0.01-0.05MPa for 1-10 minutes, and then cool it to 20-45℃ to obtain the outer layer material. C. Processing C1. The inner layer material is fed into the extruder, and the extruder main machine temperature is set to 190℃ in zone 1, 180℃ in zone 2, 165℃ in zone 3, and 160℃ in zone 4, the screw speed is 10 rpm, and the main machine current is 55A; the inner layer material is extruded through the inner layer flow channel of the co-extrusion die to form the inner layer. C2. Feed the outer layer material into the extruder and set the extruder temperature to 190℃ in zone 1, 180℃ in zone 2, 165℃ in zone 3, and 160℃ in zone 4, the screw speed to 10 rpm, and the main machine current to 55A; the inner layer material is extruded through the outer flow channel of the co-extrusion die to form the outer layer. C3. The molten material is extruded through the inner and outer main extruders to form a confluence core. The melt enters the co-extrusion die through the confluence core, passes through the exit die, and is cooled and shaped into a pipe by vacuum spraying after passing through the sizing sleeve. The temperature of the confluence core is controlled at 165℃, the speed of the traction machine is 0.5 m / min, and the cooling water temperature in the water tank is 25℃. The pipe specification is: ID100x5mm.

[0032] Using the same testing method, the performance of PVC-C pipes based on existing technology (industry standard DLT 802.3-2023) and the pipes obtained in this embodiment were compared. The results are shown in Table 1. Table 1 - Comparison of performance between existing PVC-C pipes and pipes from Example 1

[0033] Example 2 The difference between this embodiment and Embodiment 1 is that: The outer layer of the nano-reinforced pipe in this embodiment includes: 1000 kg of PVC, 100 kg of modified nano-graphite, 20 kg of modified nano-boron nitride, 50 kg of MBS, 10 kg of silane coupling agent, 5 kg of stearic acid, 5 kg of oxidized polyethylene wax, 50 kg of calcium zinc stabilizer, 5 kg of scarlet pigment, and 10 kg of titanium dioxide; the inner layer includes: 100 kg of ABS resin, 850 kg of PC, 50 kg of chlorinated polyvinyl chloride, 150 kg of modified nano-graphite, 30 kg of modified nano-boron nitride, 15 kg of titanate coupling agent, 15 kg of calcium stearate, 15 kg of polyethylene wax, 10 parts of rare earth stabilizer, 15 kg of maleic anhydride-grafted polypropylene, 5 kg of scarlet pigment, and 10 kg of titanium dioxide; the final pipe specification is ID150x8 mm.

[0034] Using the same testing method, the performance of PVC-C pipes based on existing technology (industry standard DLT 802.3-2023) and the pipes obtained in this embodiment were compared. The results are shown in Table 2. Table 2 - Comparison of performance between existing PVC-C pipes and pipes from Example 2

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that: The outer layer of the nano-reinforced pipe in this embodiment includes: 1000 kg of PVC resin, 80 kg of modified nano-graphite, 20 kg of modified nano-boron nitride, 10 kg of titanate coupling agent, 5 kg of stearic acid, 6 kg of oxidized polyethylene wax, 80 kg of calcium zinc stabilizer, 5 kg of scarlet pigment, and 10 kg of titanium dioxide; the inner layer includes: 100 kg of ABS resin, 850 kg of PC, 50 kg of chlorinated polyvinyl chloride, 50 kg of modified nano-graphite, 10 kg of modified nano-boron nitride, 15 kg of titanate coupling agent, 15 kg of calcium stearate, 15 kg of polyethylene wax, 10 parts of rare earth stabilizer, 15 kg of acrylonitrile-butadiene-styrene graft, 5 kg of scarlet pigment, and 10 kg of titanium dioxide; the final pipe specification is ID200x11 mm.

[0036] Using the same testing method, the performance of PVC-C pipes based on existing technology (industry standard DLT 802.3-2023) and the pipes obtained in this embodiment were compared. The results are shown in Table 3. Table 3 - Comparison of performance between existing PVC-C pipes and pipes from Example 3

[0037] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not contain modified nano-graphite and modified nano-boron nitride.

[0038] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not contain modified nano boron nitride.

[0039] Comparative Example 3 The difference between this comparative example and Example 1 is that: in the preparation process, the temperature was kept constant at 150°C throughout step A1; no positive pressure was applied in step A2; and no positive pressure was applied in step A3, while the temperature was kept constant at 120°C, and finally cooled to 30°C.

[0040] Experimental Example 1 Using the same testing method, the pipe performance of each comparative example was compared, and the results are shown in Table 4. Table 4 - Comparison Results of Pipe Performance in Various Comparative Examples

[0041] As shown in Tables 1-4, the ring stiffness of the pipe of this invention is increased by 50%-100% even with a 100-400% increase in heating time for high-temperature ring stiffness adjustment. This means that while the industry standard SN12 is ≥SN12 qualified at 80℃, the pipe of this invention achieves a 200% improvement. Simultaneously, the drop hammer impact requirement is increased by 100%, the flattening test by 100%, and the tensile strength reaches 60-78MPa. The longitudinal shrinkage rate is within 2% of the industry standard (≤5%). The Vicat softening point is 125-155℃, higher than the 93℃ of existing PVC-C power pipes. This ensures high ring stiffness when heated, guarantees greater dimensional stability, prevents difficulty in dragging during repairs and cable replacement after high-temperature extrusion deformation, and provides high strength, high toughness, and heat resistance, better guaranteeing the entire life cycle and achieving energy conservation, emission reduction, and green environmental protection goals.

[0042] Comparative Example 1, which did not contain modified nano-graphite or modified nano-boron nitride, exhibited the worst overall performance. Comparative Example 2, also without modified nano-boron nitride, showed slightly better overall performance than Comparative Example 1, but its overall performance remained unsatisfactory. This demonstrates that the combination of modified nano-graphite and modified nano-boron nitride has a significant impact on the overall performance of the pipe material. Its significant improvement in mechanical properties is attributed to the invention's modification of the nanomaterials, which enhances their dispersibility and compatibility with the matrix, thereby greatly improving the mechanical and durability properties of the pipe material. In Comparative Example 3, although the raw materials... The nanomaterials were modified, but the preparation process did not involve a combination of positive pressure and gradient heating, i.e., it did not utilize the synergistic control of the "pressure field and temperature field". Although the overall performance was significantly improved compared to Comparative Examples 1-2, it still lagged behind Example 1. This shows that the preparation method of the present invention, through the synergistic control of the "pressure field and temperature field", significantly addresses the core issues in pipe forming, such as uneven wall thickness, internal surface defects, low molecular particle density, stress concentration, and poor dimensional accuracy. Furthermore, the synergistic effect of the raw material composition and the preparation method has a significant impact on improving the overall performance of the pipe.

[0043] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention, such as replacing PVC-C resin with polyethylene, polypropylene, polybutene, polyvinyl chloride, etc., should be included within the scope of protection of the present invention.

Claims

1. A nanoreinforced pipe, characterized in that, The pipe wall is composed of a double-layer structure, including an inner layer and an outer layer; by weight, the inner layer raw materials include: 75-100 parts engineering plastic, 5-80 parts PVC-C resin, 1-35 parts modified nanomaterials, 0.5-15 parts coupling agent, 0.5-15 parts activator, 0.5-3.0 parts lubricant, 0.8-8 parts stabilizer, 1-10 parts compatibilizer, 0.5-2.0 parts pigment, and 1.0-3.0 parts titanium dioxide; The outer layer raw materials include: 75-100 parts of PVC resin, 5-15 parts of modified nanomaterials, 0.5-5 parts of coupling agent, 0.5-5 parts of activator, 0.5-3.0 parts of lubricant, 3-8 parts of stabilizer, 0.5-2.0 parts of pigment, and 1.0-3.0 parts of titanium dioxide.

2. The nano-reinforced tubing according to claim 1, characterized in that, By weight, the inner layer raw materials include: 75-90 parts engineering plastic, 5-50 parts PVC-C resin, 1-20 parts modified nanomaterials, 0.5-10 parts coupling agent, 0.5-10 parts activator, 0.5-1.0 parts lubricant, 0.8-5 parts stabilizer, 1-5 parts compatibilizer, 0.5-1.0 parts pigment, and 1.0-2.0 parts titanium dioxide; The outer layer raw materials include: 75-90 parts of PVC resin, 5-10 parts of modified nanomaterials, 0.5-3 parts of coupling agent, 0.5-2 parts of activator, 0.5-2.0 parts of lubricant, 3-5 parts of stabilizer, 0.5-1.0 parts of pigment, and 1.0-2.0 parts of titanium dioxide.

3. The nano-reinforced tubing according to claim 1, characterized in that, The modified nanomaterial is a composite of modified graphene nanoparticles and modified boron nitride nanoparticles, and the mass ratio of the modified graphene nanoparticles to the modified boron nitride nanoparticles is 2-7:

1.

4. The nano-reinforced tubing according to claim 3, characterized in that, The modified graphene nanoparticles are prepared as follows: ①Then Mg 2+ solution is mixed with Al 2+ solution, and the mixture is added to the graphene oxide suspension to obtain a mixed solution A; ② Mix phosphate, deionized water, and alkaline solution, and control the pH of the system to 9-11 to obtain mixture B; ③ Slowly add mixture B to mixture A, maintaining the pH at an alkaline level throughout the process. After mixing thoroughly, filter, wash until neutral, and then dry to obtain modified graphene oxide.

5. The nano-reinforced tubing according to claim 3, characterized in that, The modified boron nitride nanoparticles are prepared as follows: boron nitride nanoparticles are added to a solvent, dispersed by ultrasonication, and then a titanate coupling agent is added. After reflux reaction, the solvent is removed by vacuum distillation, and the resulting solid is dried to obtain surface-modified boron nitride nanoparticles.

6. The nano-reinforced tubing according to claim 1, characterized in that, The engineering plastic is ABS and / or PC; The coupling agent is one or more of silane coupling agents, aluminate coupling agents, and titanate coupling agents; The activator is one or more of stearic acid, calcium stearate, zinc stearate, barium stearate, and zinc stearate; The stabilizer is one or more of rare earth stabilizers, calcium-zinc stabilizers, and organotin stabilizers; The lubricant is one or more of stearic acid, paraffin wax, polyethylene wax, and oxidized polyethylene wax; The compatibilizer is one or more of the following: ethylene-vinyl acetate copolymer, glycidyl methacrylate radiation graft copolymer, styrene-maleic anhydride copolymer, ethylene-propylene copolymer, acrylonitrile-butadiene-styrene graft copolymer, polypropylene-caprolactone graft copolymer, polypropylene-styrene graft copolymer, maleic anhydride graft copolymer, polypropylene-methacrylate graft copolymer, polypropylene-acrylonitrile graft copolymer, chloromethylstyrene graft copolymer, epoxy acrylate graft copolymer, chlorinated polyethylene, maleic anhydride graft copolymer, and MBS.

7. A method for preparing a nano-reinforced tubular material according to any one of claims 1-6, characterized in that, Includes the following steps: A. Inner layer preparation: A1: First, control the temperature of the modified nanomaterials, then add coupling agent, lubricant, and activator and mix. Then, raise the temperature, apply positive pressure, continue to raise the temperature, react for a period of time, and then cool for later use. A2: Mix engineering plastics and some compatibilizer, control the temperature and apply positive pressure, then heat up and react for a period of time, then cool and set aside. A3: Mix chlorinated polyvinyl chloride resin, stabilizer and remaining compatibilizer, control the temperature and apply positive pressure, then heat and react for a period of time, then cool and set aside. A4: Mix the materials obtained in steps A2 and A3, control the temperature and apply positive pressure, then heat and react for a period of time, add the material obtained in step A1, and add pigment and titanium dioxide, continue to apply positive pressure and heat, react for a period of time and then cool to obtain the inner layer material. B. Outer layer preparation: B1. The preparation method of modified nanomaterials is the same as that of A1; B2. Mix the outer layer raw materials, control the temperature and apply positive pressure to react for a period of time, and then cool to obtain the outer layer material; C. Processing: The inner layer material and the outer layer material are fed into the extruder respectively, and then compounded at the discharge port of the co-extrusion die. After co-extrusion, traction and cooling, the nano-reinforced tube is obtained.

8. The method for preparing the nano-reinforced tubing according to claim 7, characterized in that, In step A1, control the temperature at 50-90℃, then add coupling agent, lubricant, and activator, then raise the temperature to 100-130℃, apply a positive pressure of 0.01-0.05MPa, for 1-10 minutes, then continue to raise the temperature to 150-160℃, react for 0.5-1 hour, and then cool to 20-45℃. In step A2, control the temperature at 100-120℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 130-150℃, react for 0.5-1 hour, and then cool to 20-45℃. In step A3, control the temperature at 100-120℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 120-130℃, react for 0.5-1 hour, and then cool to 20-45℃. In step A4, control the temperature at 80℃-100℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, then raise the temperature to 110-115℃ and react for 0.5-1 hours. Then add the material obtained in step A1 and the remaining raw materials, continue to apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, continue to raise the temperature to 120-130℃, and then cool to 20-45℃.

9. The method for preparing the nano-reinforced tubing according to claim 7, characterized in that, In step B2, control the temperature at 100-125℃, apply a positive pressure of 0.01-0.05MPa for 1-10 minutes, and then cool to 20-45℃.

10. The method for preparing the nano-reinforced tubing according to claim 7, characterized in that, In step C, the co-extrusion temperature is 160-170℃, the traction machine speed is 0.5-1.8m / min, and the water tank cooling water temperature is 15-35℃.

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