Highly heat-conductive pipe and method for manufacturing the same

Abstract

The application provides a high-thermal-conductivity pipe and a preparation method thereof, and belongs to the technical field of pipe production. The method comprises the following steps: adding boron carbide into a hydrogen peroxide solution, washing with water, drying, dispersing in anhydrous toluene, adding yttrium isopropylate, aminophenyl silsesquioxane and 4-dimethylaminopyridine, centrifugal separation, washing, drying, and obtaining a composite filler; mixing 1-allyl imidazole, 1-bromododecane and anhydrous acetonitrile, rotary evaporation, pouring into anhydrous ether, suction filtration, vacuum drying, adding EPDM particles, dicumyl peroxide and maleic anhydride, stirring, melt kneading, and obtaining modified EPDM particles; uniformly mixing PE-RT resin particles, the composite filler, the modified EPDM particles and zinc stearate, melting, cooling, cutting, drying, and obtaining a composite master batch; melting the composite master batch, extruding, cooling, and obtaining the high-thermal-conductivity pipe. The application can improve the thermal conductivity, tensile yield strength and elongation at break of the pipe.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipe production, in particular to a high-thermal-conductivity pipe and a preparation method thereof. BACKGROUND

[0002] With the rapid development of urban infrastructure construction and new energy industry, high polymer pipes are widely used in floor heating, central heating, industrial heat exchange and new energy equipment due to their light weight, corrosion resistance, convenient construction and other advantages. However, traditional polyolefin pipes (such as polyethylene PE) have low thermal conductivity, insufficient aging resistance and limited mechanical properties, which cannot meet the needs of efficient heat transfer and long-term service.

[0003] In existing research, inorganic high-thermal-conductivity fillers (such as alumina, boron nitride and silicon carbide) are usually introduced into the polyolefin matrix to improve the thermal conductivity of the pipe. However, due to the strong inertness of the inorganic filler surface and the poor interfacial adhesion between the polyolefin resin, the inorganic filler often agglomerates seriously in the matrix, making it difficult to form a continuous thermal conduction network, thereby limiting the thermal conduction efficiency. At the same time, uneven dispersion of the filler also causes interfacial defects, which weakens the mechanical properties of the pipe, especially the tensile yield strength and elongation at break.

[0004] Secondly, polyolefin pipes are prone to thermal oxidative aging under long-term hot water or high temperature working conditions. Existing technologies usually improve the thermal stability of the material by directly adding hindered phenolic or phosphite antioxidants, but these small molecule antioxidants are prone to migration and consumption during processing or service, making it difficult to maintain antioxidant effect for a long time, thereby affecting the service life of the pipe.

[0005] Thirdly, the toughness of traditional polyolefin materials is limited, and when the pipe is subjected to internal pressure impact or bending deformation, cracks may easily expand due to stress concentration, affecting the elongation at break and overall safety. Existing methods often use thermoplastic elastomers (such as SEBS) as toughening phase, but conventional elastomers have poor compatibility with the polyolefin matrix and large dispersion particle size, making it difficult to balance the improvement of toughness and the maintenance of strength.

[0006] In summary, it is necessary to provide a high-thermal-conductivity pipe and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0007] Therefore, the present application provides a high-thermal-conductivity pipe and a preparation method thereof to improve the thermal conductivity, tensile yield strength and elongation at break of the pipe.

[0008] To achieve the above-mentioned purpose, the present application provides a high-thermal-conductivity pipe and a preparation method thereof, comprising the following steps:

[0009] S1, boron carbide is added to hydrogen peroxide solution, stirred, washed with water, dried, dispersed in anhydrous toluene, yttrium isopropoxide, aminosilica cage and 4-dimethylamino pyridine are added, stirred and reacted, centrifuged, dried to obtain a composite filler;

[0010] S2, 1-allyl imidazole, 1-bromododecane and anhydrous acetonitrile are mixed, reacted, rotary evaporated, poured into anhydrous ether, filtered, added to ternary ethylene propylene rubber particles, dicumyl peroxide and maleic anhydride, melt mixed to obtain modified EPDM particles;

[0011] S3, PE-RT resin particles, composite filler, modified EPDM particles and zinc stearate are uniformly mixed, extruded, cooled, cut into particles and dried to obtain a composite master batch;

[0012] S4, the composite master batch is melted, extruded, cooled and prepared into a high thermal conductivity pipe material.

[0013] In the present application, after boron carbide (B4C) is oxidized by hydrogen peroxide, -OH groups are introduced on the surface, which improves the surface energy and provides active sites for condensation. Subsequent hydrolysis of yttrium isopropoxide in anhydrous toluene system produces yttrium ions, which form "Y-O" bonds with the -OH groups on the surface of boron carbide. On this basis, aminosilica cage (POSS-NH2) is bridged with "Y-O" to obtain modified boron carbide, so as to build an "inorganic-organic bridge-polyhydrocarbon matrix" interfacial transition layer between the modified boron carbide and the PE-RT resin particles. The steric hindrance of the cage body of aminosilica cage (POSS-NH2) in the transition layer reduces the agglomeration of modified boron carbide, improves the dispersion uniformity of modified boron carbide, promotes the formation of a coherent heat conduction path, so that the modified boron carbide can more effectively transfer heat to the polyhydrocarbon matrix. At the same time, the surface of the modified boron carbide has good hydrophobicity, which improves the compatibility and bonding force of the modified boron carbide and the PE-RT resin, and further improves the tensile yield strength of the pipe material.

[0014] In the present application, grafting reaction occurs between ternary ethylene propylene rubber (EPDM) and 1-allyl imidazole, and polar imidazolium groups are introduced on the EPDM, so that the EPDM has both flexible segments and polar group characteristics. The polar groups enhance the interfacial compatibility of EPDM and PE-RT, allowing the EPDM rubber particles to be refined and uniformly dispersed in PE-RT, avoiding the formation of stress concentration points. When stretched, the EPDM rubber phase as a flexible phase is elongated and deformed, which can absorb and disperse external loads, thereby delaying the initiation and propagation of cracks. At the same time, the dynamic combination between imidazolium groups and molecular segments can occur reversible relaxation and recombination when subjected to a larger external force. This process can gradually release and absorb energy during the material stretching process, thereby playing a buffering role and effectively improving the ductility and elongation at break of the pipe material.

[0015] Optionally, in step S3, a slow-release agent is added to the modified EPDM particles. The slow-release agent is prepared by cross-linking tannins with glutaraldehyde to form porous microspheres and loading tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite.

[0016] Optionally, the sustained-release agent is prepared by dissolving tannin powder in a 70 vol% ethanol solution, stirring until homogeneous, adding glutaraldehyde, reacting at room temperature for 1-3 hours, centrifuging, washing with ethanol, vacuum drying at 60-70°C for 6-8 hours, dispersing in butyl acetate, adding tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite, stirring at 40-60°C for 30-50 minutes, ultrasonically dispersing, and vacuum drying at 50-60°C for 8-10 hours.

[0017] The sustained-release agent prepared in this invention utilizes porous microspheres formed by tannin molecules under the action of glutaraldehyde, and is loaded with tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite (THP-EPQ). The abundant hydroxyl and phenolic hydroxyl groups in the tannin molecules interact with THP-EPQ, thereby ensuring the stable distribution of THP-EPQ within the porous microspheres. Furthermore, with subsequent oxidation reactions, THP-EPQ is gradually released from the tannin microspheres, continuously exerting its antioxidant effect. Simultaneously, the polyphenolic structure of the tannin molecules themselves also possesses strong antioxidant capacity. The sustained-release antioxidant effect of the tannin molecules and THP-EPQ forms a synergistic effect, thereby improving the antioxidant performance of the material.

[0018] Optionally, in step S1, boron carbide powder is added to hydrogen peroxide solution and stirred at 60-80℃ for 60-90 min. After washing with water until neutral, it is vacuum dried at 80-100℃ for 5-9 h, dispersed in anhydrous toluene, and yttrium isopropoxide solution is added. The mixture is stirred at 70-100℃ for 2 h, centrifuged, washed with deionized water, and dried at 100-110℃. The mixture is then dispersed in anhydrous toluene, and amino-modified cage-like silsesquioxane and 4-dimethylaminopyridine are added. The mixture is stirred and reacted at 80-100℃ for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 90-110℃ for 6-10 h to obtain the composite filler.

[0019] Optionally, in step S2, 1-allylimidazolium, 1-bromododecane, and anhydrous acetonitrile are mixed and stirred at 70-85°C for 10-12 hours under nitrogen protection. The mixture is then rotary evaporated, anhydrous diethyl ether is added, and the mixture is filtered. After vacuum drying at 60-80°C for 8-10 hours, EPDM rubber particles, dicumyl peroxide, and maleic anhydride are added and stirred until homogeneous. The mixture is then fed into a mixer for melt mixing, cooled, pulverized, and vacuum dried to obtain modified EPDM particles.

[0020] Optionally, in step S3, PE-RT resin particles, composite filler, modified EPDM particles, slow-release agent, and zinc stearate are added to a high-speed mixer and mixed at 60-70°C for 15-20 minutes. The mixture is then fed into a co-rotating twin-screw extruder for extrusion. The extrudate is water-cooled and pelletized, and then vacuum-dried at 60-65°C for 4-5 hours to obtain composite masterbatch.

[0021] High-speed mixing and vacuum drying processes are employed to ensure uniform distribution of the composite filler, modified EPDM, and slow-release agent in the composite masterbatch, guaranteeing effective moisture removal. This not only improves the consistency of the extruded composite masterbatch but also enhances its dispersion, ensuring the stability of the mechanical and thermal conductivity properties of the subsequent pipe extrusion.

[0022] Optionally, in step S4, the composite masterbatch is fed into a single-screw extruder to melt at a melt temperature of 195±2℃ and extruded at a traction speed of 3.0~4.0m / min to obtain a high thermal conductivity pipe.

[0023] By melting and extruding the composite masterbatch at a melt temperature of 195±2℃ in a single screw extruder and forming it at a traction speed of 3.0~4.0m / min, it is beneficial to improve the extrusion stability of the pipe and avoid uneven wall thickness or surface defects.

[0024] Optionally, in step S1, the boron carbide includes two types: granular boron carbide and short whisker boron carbide, and the weight ratio of granular boron carbide to short whisker boron carbide is 70~80:20~30.

[0025] This invention employs a combination of granular boron carbide and short whisker boron carbide. The granular type acts as a skeleton reinforcement, while the short whisker type improves the toughness of the material through bridging and toughening. The combination of the two can further improve the tensile yield strength and elongation at break of the pipe.

[0026] Optionally, the high thermal conductivity pipe material comprises the following raw materials in parts by weight: 100-110 parts of PE-RT resin particles, 15-18 parts of composite filler, 4-4.5 parts of modified EPDM particles, 1.2-1.5 parts of slow-release agent, and 0.5-0.8 parts of zinc stearate.

[0027] The composite filler comprises the following raw materials in parts by weight: 100-110 parts boron carbide powder, 500-550 parts hydrogen peroxide solution, 2000-2100 parts anhydrous toluene, 2-2.5 parts yttrium isopropoxide solution, 50-60 parts aminated cage-like silsesquioxane, and 0.05-0.08 parts 4-dimethylaminopyridine.

[0028] Optionally, the modified EPDM particles comprise the following raw materials in parts by weight: 10-12 parts of 1-allylimidazolium, 10.5-13 parts of 1-bromododecane, 120-140 parts of anhydrous acetonitrile, 100-110 parts of EPDM rubber particles, 0.5-0.7 parts of dicumyl peroxide, and 0.5-0.7 parts of maleic anhydride;

[0029] The sustained-release agent comprises the following raw materials in parts by weight: 100-105 parts tannin powder, 800-820 parts ethanol, 5-6 parts glutaraldehyde, 600-630 parts butyl acetate, and 40-45 parts tetrakis(2,4-di-tert-butylphenol)-4,4'-biphenyl diphosphite.

[0030] The above-described technical solution of the present invention has at least the following beneficial effects:

[0031] In this invention, modified boron carbide is prepared by POSS-NH2 condensation and used to construct an "inorganic-organic bridge-polyhydrocarbon" transition layer in the PE-RT matrix. The steric hindrance provided by the cage-like structure of POSS-NH2 effectively inhibits boron carbide agglomeration, improves the uniformity of filler dispersion in the resin, and promotes the continuous formation of thermal conductivity pathways, thereby improving thermal conductivity efficiency. At the same time, the surface structure of POSS-NH2 endows the modified boron carbide with good hydrophobicity and interfacial compatibility, making its bond with PE-RT stronger and enhancing the tensile yield strength of the pipe.

[0032] This invention grafts imidazolium monomers onto ethylene propylene diene monomer (EPDM), endowing EPDM with both flexible chain segments and polar groups. This results in finer and more uniformly dispersed rubber particles within the PE-RT, preventing stress concentration points. Under tension, the EPDM rubber phase absorbs and disperses external loads, thus delaying crack initiation and propagation. Simultaneously, the dynamic bond between the imidazolium groups and molecular segments undergoes reversible relaxation and recombination under significant external forces, providing a buffering effect and effectively improving the pipe's ductility and elongation at break. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0034] Example 1

[0035] 100 parts of boron carbide powder (70% by weight of granular boron carbide with a particle size of 310 μm and 30% by weight of short whisker boron carbide with a length of 30 μm and a diameter of 1.5 μm) were added to 500 parts of 30 wt% hydrogen peroxide solution, stirred at 60 °C for 90 min, washed with water until neutral, and then vacuum dried at 100 °C for 6 h. The powder was then dispersed in 2000 parts of anhydrous toluene, and 2 parts of 0.05 mol / L yttrium isopropoxide solution, 50 parts of aminated cage-like silsesquioxane (POSS-NH2), and 0.05 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 85 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 90 °C for 8 h to obtain the composite filler.

[0036] 100 parts of tannin powder were dissolved in 800 parts of 70 vol% ethanol solution, stirred evenly, and then 5 parts of glutaraldehyde were added. The mixture was reacted at room temperature for 2 hours. After centrifugation, washing with ethanol, and vacuum drying at 60°C for 6 hours, the mixture was dispersed in 600 parts of butyl acetate. 40 parts of tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite were added, stirred at 45°C for 40 minutes, and then ultrasonically dispersed. The mixture was then vacuum dried at 50°C for 10 hours to obtain the sustained-release agent.

[0037] 10 parts of 1-allylimidazolium, 10.5 parts of 1-bromododecane, and 120 parts of anhydrous acetonitrile were mixed and reacted at 70°C for 12 hours under nitrogen protection. After removing the solvent by rotary evaporation, the mixture was poured into excess anhydrous diethyl ether to precipitate. The precipitate was filtered and dried under vacuum at 60°C for 10 hours. It was then mixed with 100 parts of ethylene propylene diene monomer (EPDM) granules, 0.5 parts of dicumyl peroxide (DCP), and 0.5 parts of maleic anhydride and stirred evenly. The mixture was fed into an internal mixer and melt-mixed at 180°C for 15 minutes. After cooling, pulverizing, and vacuum drying at 75°C for 4 hours, modified EPDM granules were obtained.

[0038] 100 parts of PE-RT resin granules (commercially purchased PE-RT underfloor heating material LG Chem SP980 extrusion pipe grade LLDPE hot and cold water pipe raw material granules), 15 parts of composite filler, 4 parts of modified EPDM granules, 1.2 parts of slow-release agent, and 0.5 parts of zinc stearate were added to a high-speed mixer and mixed at 60°C for 15 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 180°C, mixing zone 195°C, and die head zone 190°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 4 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 60°C for 4 hours to obtain composite masterbatch.

[0039] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 195℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 3.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0040] Example 2

[0041] 105 parts of boron carbide powder (80% by weight of granular boron carbide with a particle size of 310 μm and 20% by weight of short whisker boron carbide with a length of 20 μm and a diameter of 1.0 μm) were added to 520 parts of 30 wt% hydrogen peroxide solution. The mixture was stirred at 70 °C for 75 min, washed with water until neutral, and then vacuum dried at 90 °C for 6 h. The powder was then dispersed in 2100 parts of anhydrous toluene, and 2.2 parts of 0.06 mol / L yttrium isopropoxide solution, 55 parts of aminated silsesquioxane cage (POSS-NH2), and 0.06 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 90 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 100 °C for 9 h to obtain the composite filler.

[0042] 105 parts of tannin powder were dissolved in 810 parts of 70 vol% ethanol solution, stirred evenly, and then 5.5 parts of glutaraldehyde were added. The mixture was reacted at room temperature for 2 hours. After centrifugation, washing with ethanol, and vacuum drying at 65°C for 7 hours, the mixture was dispersed in 620 parts of butyl acetate. 43 parts of tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite were added, stirred at 50°C for 45 minutes, and then ultrasonically dispersed. The mixture was then vacuum dried at 60°C for 9 hours to obtain the sustained-release agent.

[0043] 11 parts of 1-allylimidazolium, 12 parts of 1-bromododecane, and 130 parts of anhydrous acetonitrile were mixed and reacted at 75°C for 10 hours under nitrogen protection. After removing the solvent by rotary evaporation, the precipitate was poured into excess anhydrous diethyl ether and filtered. The precipitate was then vacuum dried at 70°C for 9 hours. It was then mixed with 105 parts of ethylene propylene diene monomer (EPDM) granules, 0.6 parts of dicumyl peroxide (DCP), and 0.6 parts of maleic anhydride and stirred evenly. The mixture was then fed into an internal mixer and melt-mixed at 185°C for 15 minutes. After cooling, pulverizing, and vacuum drying at 70°C for 4 hours, modified EPDM granules were obtained.

[0044] 105 parts of PE-RT resin granules (commercially purchased PE-RT underfloor heating material LG Chem SP980 extrusion pipe grade LLDPE hot and cold water pipe raw material granules), 16 parts of composite filler, 4.2 parts of modified EPDM granules, 1.4 parts of slow-release agent, and 0.6 parts of zinc stearate were added to a high-speed mixer and mixed at 70°C for 20 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 185°C, mixing zone 200°C, and die head zone 195°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 3 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 65°C for 4 hours to obtain composite masterbatch.

[0045] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 195℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 4.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0046] Example 3

[0047] 110 parts of boron carbide powder (75% by weight of granular boron carbide with a particle size of 330 μm and 25% by weight of short whisker boron carbide with a length of 20 μm and a diameter of 0.5 μm) were added to 500 parts of 30 wt% hydrogen peroxide solution, stirred at 60 °C for 90 min, washed with water until neutral, and then vacuum dried at 80 °C for 9 h. The powder was then dispersed in 2200 parts of anhydrous toluene, and 2.5 parts of 0.05 mol / L yttrium isopropoxide solution, 60 parts of aminated silsesquioxane cage (POSS-NH2), and 0.08 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 100 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 110 °C for 7 h to obtain the composite filler.

[0048] 110 parts of tannin powder were dissolved in 820 parts of 70 vol% ethanol solution, stirred evenly, and then 6 parts of glutaraldehyde were added. The mixture was reacted at room temperature for 1.5 h. After centrifugation, washing with ethanol, and vacuum drying at 65 °C for 7 h, the mixture was dispersed in 630 parts of butyl acetate. 45 parts of tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite were added, stirred at 50 °C for 40 min, and then ultrasonically dispersed. The mixture was then vacuum dried at 50 °C for 8 h to obtain the sustained-release agent.

[0049] 12 parts of 1-allylimidazolium, 13 parts of 1-bromododecane, and 140 parts of anhydrous acetonitrile were mixed and reacted at 70°C for 10 hours under nitrogen protection. After removing the solvent by rotary evaporation, the precipitate was poured into excess anhydrous diethyl ether and filtered. The precipitate was then vacuum dried at 80°C for 10 hours and mixed with 105 parts of ethylene propylene diene monomer (EPDM) granules, 0.7 parts of dicumyl peroxide (DCP), and 0.7 parts of maleic anhydride. The mixture was stirred evenly and fed into an internal mixer. The mixture was melt-mixed at 180°C for 10 minutes, cooled, pulverized, and vacuum dried at 75°C for 5 hours to obtain modified EPDM granules.

[0050] 110 parts of PE-RT resin granules (commercially purchased PE-RT underfloor heating material LG Chem SP980 extrusion pipe grade LLDPE hot and cold water pipe raw material granules), 18 parts of composite filler, 4.5 parts of modified EPDM granules, 1.5 parts of slow-release agent, and 0.8 parts of zinc stearate were added to a high-speed mixer and mixed at 65°C for 18 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 185°C, mixing zone 195°C, and die head zone 190°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 3 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 62°C for 4.5 hours to obtain composite masterbatch.

[0051] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 196℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 3.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0052] Example 4

[0053] 100 parts of boron carbide powder (70% by weight of granular boron carbide with a particle size of 310 μm and 30% by weight of short whisker boron carbide with a length of 30 μm and a diameter of 1.5 μm) were added to 500 parts of 30 wt% hydrogen peroxide solution, stirred at 60 °C for 90 min, washed with water until neutral, and then vacuum dried at 100 °C for 6 h. The powder was then dispersed in 2000 parts of anhydrous toluene, and 2 parts of 0.05 mol / L yttrium isopropoxide solution, 50 parts of aminated cage-like silsesquioxane (POSS-NH2), and 0.05 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 85 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 90 °C for 8 h to obtain the composite filler.

[0054] 10 parts of 1-allylimidazolium, 10.5 parts of 1-bromododecane, and 120 parts of anhydrous acetonitrile were mixed and reacted at 70°C for 12 hours under nitrogen protection. After removing the solvent by rotary evaporation, the mixture was poured into excess anhydrous diethyl ether to precipitate. The precipitate was filtered and dried under vacuum at 60°C for 10 hours. It was then mixed with 100 parts of ethylene propylene diene monomer (EPDM) granules, 0.5 parts of dicumyl peroxide (DCP), and 0.5 parts of maleic anhydride and stirred evenly. The mixture was fed into an internal mixer and melt-mixed at 180°C for 15 minutes. After cooling, pulverizing, and vacuum drying at 75°C for 4 hours, modified EPDM granules were obtained.

[0055] 100 parts of PE-RT resin granules (commercially purchased PE-RT underfloor heating material LG Chem SP980 extrusion pipe-grade LLDPE raw material granules for hot and cold water pipes), 15 parts of composite filler, 4 parts of modified EPDM granules, and 0.5 parts of zinc stearate were added to a high-speed mixer and mixed at 60°C for 15 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 180°C, mixing zone 195°C, and die head zone 190°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 4 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 60°C for 4 hours to obtain composite masterbatch.

[0056] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 195℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 3.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0057] Example 5

[0058] 105 parts of boron carbide powder (80% by weight of granular boron carbide with a particle size of 310 μm and 20% by weight of short whisker boron carbide with a length of 20 μm and a diameter of 1.0 μm) were added to 520 parts of 30 wt% hydrogen peroxide solution. The mixture was stirred at 70 °C for 75 min, washed with water until neutral, and then vacuum dried at 90 °C for 6 h. The powder was then dispersed in 2100 parts of anhydrous toluene, and 2.2 parts of 0.06 mol / L yttrium isopropoxide solution, 55 parts of aminated silsesquioxane cage (POSS-NH2), and 0.06 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 90 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 100 °C for 9 h to obtain the composite filler.

[0059] 11 parts of 1-allylimidazolium, 12 parts of 1-bromododecane, and 130 parts of anhydrous acetonitrile were mixed and reacted at 75°C for 10 hours under nitrogen protection. After removing the solvent by rotary evaporation, the precipitate was poured into excess anhydrous diethyl ether and filtered. The precipitate was then vacuum dried at 70°C for 9 hours. It was then mixed with 105 parts of ethylene propylene diene monomer (EPDM) granules, 0.6 parts of dicumyl peroxide (DCP), and 0.6 parts of maleic anhydride and stirred evenly. The mixture was then fed into an internal mixer and melt-mixed at 185°C for 15 minutes. After cooling, pulverizing, and vacuum drying at 70°C for 4 hours, modified EPDM granules were obtained.

[0060] 105 parts of PE-RT resin granules (commercially purchased LG Chem SP980 extrusion pipe-grade LLDPE raw material granules for hot and cold water pipes), 16 parts of composite filler, 4.2 parts of modified EPDM granules, and 0.6 parts of zinc stearate were added to a high-speed mixer and mixed at 70°C for 20 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 185°C, mixing zone 200°C, and die head zone 195°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 3 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 65°C for 4 hours to obtain the composite masterbatch.

[0061] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 195℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 4.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0062] Example 6

[0063] 110 parts of boron carbide powder (75% by weight of granular boron carbide with a particle size of 330 μm and 25% by weight of short whisker boron carbide with a length of 20 μm and a diameter of 0.5 μm) were added to 500 parts of 30 wt% hydrogen peroxide solution, stirred at 60 °C for 90 min, washed with water until neutral, and then vacuum dried at 80 °C for 9 h. The powder was then dispersed in 2200 parts of anhydrous toluene, and 2.5 parts of 0.05 mol / L yttrium isopropoxide solution, 60 parts of aminated silsesquioxane cage (POSS-NH2), and 0.08 parts of 4-dimethylaminopyridine (DMAP) were added. The mixture was stirred at 100 °C for 3 h under nitrogen protection, centrifuged, washed three times with ethanol, and vacuum dried at 110 °C for 7 h to obtain the composite filler.

[0064] 12 parts of 1-allylimidazolium, 13 parts of 1-bromododecane, and 140 parts of anhydrous acetonitrile were mixed and reacted at 70°C for 10 hours under nitrogen protection. After removing the solvent by rotary evaporation, the precipitate was poured into excess anhydrous diethyl ether and filtered. The precipitate was then vacuum dried at 80°C for 10 hours and mixed with 105 parts of ethylene propylene diene monomer (EPDM) granules, 0.7 parts of dicumyl peroxide (DCP), and 0.7 parts of maleic anhydride. The mixture was stirred evenly and fed into an internal mixer. The mixture was melt-mixed at 180°C for 10 minutes, cooled, pulverized, and vacuum dried at 75°C for 5 hours to obtain modified EPDM granules.

[0065] 110 parts of PE-RT resin granules (commercially purchased PE-RT underfloor heating material LG Chem SP980 extrusion pipe grade LLDPE hot and cold water pipe raw material granules), 18 parts of composite filler, 4.5 parts of modified EPDM granules, and 0.8 parts of zinc stearate were added to a high-speed mixer and mixed at 65°C for 18 minutes. The mixture was then fed into a co-rotating twin-screw extruder for processing. The temperature zones were sequentially: feeding zone 160°C, melting zone 185°C, mixing zone 195°C, and die head zone 190°C. During the mixing zone, a vacuum devolatilization of -0.08 MPa was applied and maintained for approximately 3 minutes. The extrudate was water-cooled and pelletized, then vacuum-dried at 62°C for 4.5 hours to obtain composite masterbatch.

[0066] The composite masterbatch was melted in a single-screw extruder, and the melt temperature was controlled at 196℃. The pipe with an outer diameter of 20mm and a wall thickness of 2.0mm was extruded under the condition of a traction speed of 3.0m / min. The pipe was then shaped and cooled using a spray cooling system with a length of 6m and a spray liquid temperature of 15℃ to obtain a high thermal conductivity pipe.

[0067] The present invention also includes comparative examples and related experiments.

[0068] Comparative Example 1

[0069] The only difference from Example 1 is that no composite filler was added to the composite masterbatch; the other components and preparation steps are completely the same, resulting in a high thermal conductivity pipe.

[0070] Comparative Example 2

[0071] The only difference from Example 2 is that the composite masterbatch did not contain modified EPDM particles, while the other components and preparation steps were completely the same, resulting in a high thermal conductivity pipe.

[0072] Comparative Example 3

[0073] The only difference from Example 3 is that aminated cage-like silsesquioxane was not added during the preparation of the composite filler. The other components and preparation steps are completely the same, and a high thermal conductivity pipe is obtained.

[0074] Comparative Example 4

[0075] The only difference from Example 1 is that 1-allylimidazol was not added during the preparation of the modified EPDM particles. All other components and preparation steps were completely the same, and a high thermal conductivity pipe was obtained.

[0076] The high thermal conductivity pipes prepared in Examples 1-6 and Comparative Examples 1-4 were subjected to relevant performance tests. Thermal conductivity was tested according to the national standard GB / T 3399-1982 "Test Method for Thermal Conductivity of Plastics - Heat-Protected Plate Method". Tensile yield strength and elongation at break were tested according to the national standard GB / T 8804.3-2003 "Determination of Tensile Properties of Thermoplastic Pipes - Part 3: Polyolefin Pipes (OCR)". Oxidation induction time (OIT) was tested according to the national standard GB / T 19466.6-2009 "Differential Scanning Calorimetry (DSC) for Plastics". The results of the relevant performance tests are shown in Table 1.

[0077] Table 1

[0078]

[0079] It should be understood that the oxidation resistance of high thermal conductivity pipes is reflected by the oxidation induction time.

[0080] Referring to Table 1, compared with Examples 4-6, Examples 1-3 introduced a slow-release agent, which allowed the antioxidant effect to be sustained, thereby significantly extending the oxidation induction time and enhancing the antioxidant performance of the high thermal conductivity pipe. Comparing Example 1 and Comparative Example 1, it can be seen that adding composite fillers to the composite masterbatch significantly improves the thermal conductivity and tensile yield strength of the prepared high thermal conductivity pipe. Comparing Example 2 and Comparative Example 2, it can be seen that adding modified EPDM particles to the composite masterbatch significantly increases the elongation at break of the prepared high thermal conductivity pipe. Comparing Example 3 and Comparative Example 3, it can be seen that adding aminated cage-like silsesquioxane to the composite filler significantly improves the tensile yield strength of the prepared high thermal conductivity pipe. Comparing Example 1 and Comparative Example 4, it can be seen that adding 1-allylimidazolium to the modified EPDM particles significantly increases the elongation at break of the prepared high thermal conductivity pipe.

[0081] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high thermal conductivity pipe, characterized in that, Includes the following steps: S1. Add boron carbide to hydrogen peroxide solution, stir, wash with water, dry, disperse in anhydrous toluene, add yttrium isopropoxide, aminated cage-like silsesquioxane and 4-dimethylaminopyridine, stir to react, centrifuge, dry, and obtain composite filler; S2. Mix 1-allylimidazolium, 1-bromododecane and anhydrous acetonitrile, stir and react, rotary evaporate, pour in anhydrous diethyl ether, filter, vacuum dry, add EPDM rubber particles, dicumyl peroxide and maleic anhydride, stir, melt and knead to obtain modified EPDM particles. S3. Mix PE-RT resin particles, composite filler, modified EPDM particles, and zinc stearate evenly, extrude, cool, pelletize, and dry to obtain composite masterbatch. S4. Melt the composite masterbatch, extrude it, and cool it to obtain a high thermal conductivity pipe. In step S3, a sustained-release agent is also added. The sustained-release agent is a porous microsphere formed by cross-linking tannin with glutaraldehyde and loaded with tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite.

2. The method for preparing a high thermal conductivity pipe according to claim 1, characterized in that, The sustained-release agent is prepared by dissolving tannin powder in a 70 vol% ethanol solution, stirring until homogeneous, adding glutaraldehyde, reacting at room temperature for 1-3 hours, centrifuging, washing with ethanol, vacuum drying at 60-70°C for 6-8 hours, dispersing in butyl acetate, adding tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite, stirring at 40-60°C for 30-50 minutes, ultrasonically dispersing, and vacuum drying at 50-60°C for 8-10 hours.

3. The method for preparing a high thermal conductivity pipe according to claim 1, characterized in that, In step S1, boron carbide powder is added to hydrogen peroxide solution and stirred at 60-80℃ for 60-90 min. After washing with water until neutral, it is vacuum dried at 80-100℃ for 5-9 h and then dispersed in anhydrous toluene. Isopropanol yttrium solution, aminated cage-like silsesquioxane and 4-dimethylaminopyridine are added. The mixture is stirred and reacted at 80-100℃ for 3 h under nitrogen protection. After centrifugation, the mixture is washed three times with ethanol and vacuum dried at 90-110℃ for 6-10 h to obtain the composite filler.

4. The method for preparing a high thermal conductivity pipe according to claim 1, characterized in that, In step S2, 1-allylimidazolium, 1-bromododecane, and anhydrous acetonitrile are mixed and stirred at 70-85°C for 10-12 hours under nitrogen protection. The mixture is then rotary evaporated, anhydrous diethyl ether is added, and the mixture is filtered. After vacuum drying at 60-80°C for 8-10 hours, EPDM rubber particles, dicumyl peroxide, and maleic anhydride are added and stirred until homogeneous. The mixture is then fed into a mixer for melt mixing, cooled, pulverized, and vacuum dried to obtain modified EPDM particles.

5. The method for preparing a high thermal conductivity pipe according to claim 1, characterized in that, In step S3, PE-RT resin particles, composite filler, modified EPDM particles, slow-release agent, and zinc stearate are added to a high-speed mixer and mixed at 60-70°C for 15-20 minutes. The mixture is then fed into a co-rotating twin-screw extruder for extrusion. The extrudate is water-cooled and pelletized, and then vacuum-dried at 60-65°C for 4-5 hours to obtain composite masterbatch.

6. The method for preparing a high thermal conductivity pipe according to claim 3, characterized in that, In step S4, the composite masterbatch is fed into a single-screw extruder to melt at a melt temperature of 195±2℃ and extruded at a traction speed of 3.0~4.0m / min to obtain a high thermal conductivity pipe.

7. The method for preparing a high thermal conductivity pipe according to claim 1, characterized in that, In step S1, the boron carbide includes two types: granular boron carbide and short whisker boron carbide, and the weight ratio of granular boron carbide to short whisker boron carbide is 70~80:20~30.

8. A high thermal conductivity pipe, prepared by the method for preparing a high thermal conductivity pipe according to any one of claims 1 to 7, characterized in that, The raw materials include the following parts by weight: 100-110 parts of PE-RT resin granules, 15-18 parts of composite filler, 4-4.5 parts of modified EPDM granules, 1.2-1.5 parts of slow-release agent, and 0.5-0.8 parts of zinc stearate; The composite filler comprises the following raw materials in parts by weight: 100-110 parts boron carbide powder, 500-550 parts hydrogen peroxide solution, 2000-2200 parts anhydrous toluene, 2-2.5 parts yttrium isopropoxide solution, 50-60 parts aminated cage-like silsesquioxane, and 0.05-0.08 parts 4-dimethylaminopyridine.

9. A high thermal conductivity pipe according to claim 8, characterized in that, The modified EPDM particles comprise the following raw materials in parts by weight: 10-12 parts of 1-allylimidazolium, 10.5-13 parts of 1-bromododecane, 120-140 parts of anhydrous acetonitrile, 100-110 parts of EPDM rubber particles, 0.5-0.7 parts of dicumyl peroxide, and 0.5-0.7 parts of maleic anhydride; The sustained-release agent comprises the following raw materials in parts by weight: 100-110 parts of tannin powder, 800-820 parts of ethanol, 5-6 parts of glutaraldehyde, 600-630 parts of butyl acetate, and 40-45 parts of tetrakis(2,4-di-tert-butylphenol)-4,4'-biphenyl diphosphite.

Images