CPVC power pipe and its preparation method

Abstract

This invention relates to the field of power pipeline materials technology, specifically to CPVC power pipes and their preparation methods, comprising the following raw materials in parts by weight: 95-130 parts CPVC resin, 25-65 parts PVC resin, 6-16 parts MBS, 5-12 parts environmentally friendly calcium-zinc composite stabilizer, 0.2-1.5 parts stearic acid, 0.3-2.0 parts ACR, 0.4-6.0 parts paraffin wax, 15-35 parts calcium carbonate, 0.5-2.5 parts molybdenum chromium red, 1.0-6.0 parts CPE, 4-12 parts graphene, 0.5-3 parts modified carbon nanotubes, 8-20 parts ternary synergistic flame retardant composite, 1-5 parts nano-titanium dioxide-zinc oxide composite, 0.8-3 parts low molecular weight polysiloxane, 1-4 parts organosilicon modified polyether, 0.5-2 parts β-cyclodextrin inclusion modifier, 0.3-2 parts conductive carbon black nano-silver composite, and 2-8 parts modified dielectric ceramic powder.

Description

Technical Field

[0001] This invention relates to the field of power pipeline materials technology, specifically to CPVC power pipes and their preparation methods. Background Technology

[0002] With the rapid development of national power infrastructure construction, the performance requirements for power conduits, as an important component of cable protection, are constantly increasing. Currently, CPVC (chlorinated polyvinyl chloride) power conduits, due to their excellent physical and mechanical properties, good heat resistance and flame retardancy, have begun to gradually replace traditional UPVC double-wall corrugated pipes and PE plastic pipes, becoming one of the main choices in the field of power pipelines.

[0003] In existing technologies, such as Chinese patent CN 114685918 B, a heat-resistant CPVC power pipe is disclosed, which includes 90-120 parts of CPVC resin, 30-60 parts of PVC resin, 8-16 parts of graphene, 1-5 parts of paraffin wax, 3-8 parts of stabilizer, 0.5-1.2 parts of antioxidant, and 5-16 parts of ammonium polyphosphate-montmorillonite composite, etc. This solution improves the heat resistance of the CPVC power pipe through the synergistic effect of the raw materials, achieving a ring stiffness of 45-60 kN / m. 2 It has a tensile strength of 39.0-45.9 MPa, a thermal conductivity of 0.9-3.9 Wm / K, and a flame retardant rating of V-0.

[0004] However, existing CPVC power pipes still have several technical problems: ① Although heat resistance has improved, it still needs further enhancement to adapt to harsher operating environments; ② Electrical performance needs optimization, especially in antistatic and electromagnetic shielding; ③ Insufficient processing rheological properties make it difficult to control the surface quality and dimensional accuracy of the products; ④ Poor dispersion of nanomaterials in the polymer matrix limits their reinforcing effect; ⑤ Insufficient compatibility between flame retardants and the matrix may lead to precipitation after long-term use, affecting service life. Solving these problems requires innovative research into the formulation and manufacturing process of CPVC power pipes. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a heat-resistant CPVC power pipe and its preparation method. Through innovative material formulation design and precise preparation process, the heat resistance, flame retardancy, electrical performance, and processing performance of the CPVC power pipe are comprehensively improved, extending its service life and meeting the increasingly stringent application requirements of the power industry.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] CPVC electrical conduit comprises the following raw materials in parts by weight: 95-130 parts CPVC resin, 25-65 parts PVC resin, 6-16 parts MBS, 5-12 parts environmentally friendly calcium-zinc composite stabilizer, 0.2-1.5 parts stearic acid, 0.3-2.0 parts ACR, 0.4-6.0 parts paraffin wax, 15-35 parts calcium carbonate, 0.5-2.5 parts molybdenum chromium red, and CPE. 1.0-6.0 parts, graphene 4-12 parts, modified carbon nanotubes 0.5-3 parts, ternary synergistic flame retardant composite 8-20 parts, nano titanium dioxide zinc oxide composite 1-5 parts, low molecular weight polysiloxane 0.8-3 parts, organosilicon modified polyether 1-4 parts, β-cyclodextrin inclusion modifier 0.5-2 parts, conductive carbon black nano silver composite 0.3-2 parts, modified dielectric ceramic powder 2-8 parts; wherein, the ternary synergistic flame retardant composite is composed of modified ammonium polyphosphate, nano magnesium oxide, and expanded graphite, and the weight ratio of modified ammonium polyphosphate, nano magnesium oxide, and expanded graphite is 3:1:1.

[0008] Preferably, the MBS contains 25-35% by weight methyl methacrylate, 30-40% by weight butadiene, and 30-40% by weight styrene; the environmentally friendly calcium-zinc composite stabilizer includes calcium stearate, zinc stearate, zinc salt, and antioxidant, and the weight ratio of calcium stearate to zinc stearate is 1.5:1 to 2.5:1.

[0009] Furthermore, the modified carbon nanotubes are coated with hydrophilic groups, have an aspect ratio of 800-2000, a purity greater than 98%, and a diameter of 5-20 nanometers; the graphene has a thickness of 0.8-1.2 nanometers, an average lateral dimension of 2-5 micrometers, and a specific surface area of ​​600-1200 square meters per gram.

[0010] Furthermore, the modifier of the modified ammonium polyphosphate is melamine, the particle size of the nano magnesium oxide is 20-100 nanometers, and the expansion rate of the expanded graphite is 150-250 ml per gram.

[0011] In another preferred embodiment of the present invention, the organosilicon modified polyether has a siloxane content of 15-25% by weight and a molecular weight of 2000-5000; the β-cyclodextrin inclusion modifier includes an esterification product of β-cyclodextrin and citric acid; in the conductive carbon black nano-silver composite, the weight ratio of carbon black to nano-silver is 10:1 to 20:1; and the modified dielectric ceramic powder is barium titanate or alumina powder with a surface modified by a silane coupling agent.

[0012] The present invention also provides a method for preparing the above-mentioned CPVC power pipe, comprising the following steps:

[0013] A. Raw material pretreatment: Vacuum dry CPVC resin and PVC resin at 80±5℃ for 4-6 hours, controlling the moisture content to be less than 0.05%; disperse graphene and modified carbon nanotubes in isopropanol to form a suspension with a concentration of 0.5-1.0%, ultrasonically treat it at a power of 600W and a frequency of 40kHz for 30-45 minutes, then vacuum filter and dry at 80℃ for 4 hours; mix stabilizer, lubricant, and ACR in a high-speed mixer at a speed of 1000-1500rpm for 5-8 minutes.

[0014] B. Multi-level mixing:

[0015] B1. In a high-speed mixer, CPVC resin, PVC resin, calcium carbonate, environmentally friendly calcium-zinc composite stabilizer, stearic acid, CPE, and MBS are mixed at 80-90℃ for 15-20 minutes to obtain a primary mixture;

[0016] B2. In a high-speed mixer equipped with a cooling system, the primary mixture is mixed with the ternary synergistic flame retardant compound, nano titanium dioxide zinc oxide compound, low molecular weight polysiloxane, organosilicon modified polyether, and β-cyclodextrin inclusion modifier at 65-75°C for 10-15 minutes to obtain the secondary mixture.

[0017] B3. In a twin-screw extruder with an L / D ratio of not less than 36:1, the secondary mixture is mixed with pretreated graphene, modified carbon nanotubes, conductive carbon black nano-silver composite, and modified dielectric ceramic powder. The temperatures of each section of the extruder are 140℃, 155℃, 165℃, 175℃, 170℃, and 165℃ respectively, the screw speed is 40-60 rpm, and the vacuum exhaust pressure is -0.08 MPa to obtain a tertiary mixture.

[0018] C. Precision Extrusion Molding: The three-stage mixture is fed into a high-precision extruder equipped with a special screw design. The feed section temperature is 165-170℃, the compression section temperature is 175-180℃, the homogenization section temperature is 180-185℃, the die head section temperature is 180-188℃, the screw speed is 20-35 rpm, the linear speed is 5-8 meters per minute, the die head pressure is 8-12 MPa, and the vacuum degree is -0.085±0.005 MPa. The CPVC power pipe blank is obtained by extrusion molding.

[0019] D. Shaping and Cooling: The CPVC power pipe blank is cooled through a three-stage gradient cooling water tank. The temperature of the first stage is 50-55℃, the temperature of the second stage is 35-40℃, and the temperature of the third stage is 20-25℃. The circulating water flow rate is 1.5-2.5 meters per second, and compressed air cooling is used as a supplement.

[0020] E. Surface treatment and quality control: The cooled CPVC power pipe is subjected to corona treatment with an electrode voltage of 15-20kV and a treatment time of 1.5-3 seconds; then it is inspected by a laser online measurement system to control the wall thickness tolerance within ±0.15 mm and the inner diameter tolerance within ±0.2 mm; finally, it is cut, inspected and packaged to obtain the finished CPVC power pipe.

[0021] Preferably, the preparation method of the ternary synergistic flame retardant composite includes the following steps:

[0022] a. Immerse ammonium polyphosphate in a 10-15% (w / w) melamine aqueous solution with a liquid-to-solid ratio of 4:1, and stir at 60-70°C for 2-3 hours.

[0023] b. Filter the solid and dry it at 90-100℃ for 5-8 hours to obtain modified ammonium polyphosphate;

[0024] c. Mix nano-magnesium oxide, expanded graphite and modified ammonium polyphosphate in a weight ratio of 1:1:3, add 1-2% by mass of silane coupling agent KH-550, and mix in a high-speed mixer at a speed of 800-1200 rpm for 15-20 minutes.

[0025] d. Dry at 80-90℃ for 3-5 hours, pulverize and sieve to obtain a ternary synergistic flame retardant composite.

[0026] Furthermore, the preparation method of the nano-titanium dioxide-zinc oxide composite includes the following steps:

[0027] a. Dissolve tetrabutyl titanate in anhydrous ethanol, add 0.5-1.0 mol / L nitric acid dropwise to adjust the pH to 2-3, and stir for 30-60 minutes to form solution A;

[0028] b. Dissolve zinc acetate in anhydrous ethanol and stir for 30 minutes to form solution B;

[0029] c. Slowly add solution B dropwise to solution A and stir at 40-50℃ for 2-4 hours;

[0030] d. Add deionized water, continue stirring for 1-2 hours, and then perform a hydrothermal reaction at 80-90℃ for 6-10 hours;

[0031] e. Filter the solid, dry it at 120-140℃ for 4-6 hours, calcine it at 450-500℃ for 2-3 hours, pulverize and sieve it to obtain nano-titanium dioxide zinc oxide composite.

[0032] In addition, the twin-screw extruder screw assembly in step B3 includes a conveying element, a shearing element, and a mixing element, and the mixing element includes a forward toothed mixing element and a reverse toothed mixing element, with the total length of the shearing element and the mixing element accounting for 40-60% of the total screw length.

[0033] More preferably, the special screw design in step C includes: the front section uses a deep thread conveying element, the middle section uses a combination of shallow thread shearing element and torsion mixing element, and the rear section uses a combination of feedback element and shear mixing element; the head adopts a flow channel tapering structure, the inner wall is mirror polished, and the flow channel length-to-diameter ratio is 8-12, and the contraction angle is 15-25 degrees.

[0034] Beneficial effects

[0035] The CPVC power pipe and its preparation method provided by this invention have the following beneficial effects:

[0036] (1) Innovative material formulation design: By introducing a ternary synergistic flame-retardant composite, a nanomaterial reinforcement system, and multifunctional additives, a multiphase synergistic reinforcement network is formed, which significantly improves the heat resistance, flame retardancy, and mechanical properties of CPVC power pipes. The Vicat softening point is increased to 115-130℃, and the ring stiffness reaches 65-85kN / m. 2 The tensile strength reaches 45-55 MPa.

[0037] (2) Precise multi-stage mixing process: The graded mixing strategy is adopted to ensure that each component is fully mixed at different temperatures without degradation. In particular, the heat-sensitive components are protected through the cold mixing stage, which effectively improves the uniformity and stability of the composite material.

[0038] (3) Advanced nanomaterial dispersion technology: By using ultrasonic pretreatment and β-cyclodextrin inclusion technology, the problem of easy agglomeration of nanomaterials in polymer matrix is ​​solved, which significantly improves the dispersion uniformity of graphene and carbon nanotubes and increases the thermal conductivity to 4.0-6.0 W / (m·K).

[0039] (4) Optimized precision extrusion molding process: Through specially designed screw combination and precise temperature control, the melt quality is ensured to be stable, which significantly improves the surface quality and dimensional accuracy of the product, and the wall thickness tolerance is controlled within ±0.15mm.

[0040] (5) Gradient cooling and surface treatment technology: Three-stage gradient cooling and corona surface treatment are adopted, which significantly reduces internal stress and improves the long-term stability of the product, with an expected service life of more than 50 years.

[0041] (6) Improved environmental performance: The use of environmentally friendly calcium-zinc composite stabilizer to replace traditional lead-based stabilizer reduces environmental pollution and meets the requirements of national environmental protection policies.

[0042] In summary, the CPVC power pipe and its preparation method provided by this invention, through material formulation innovation and process optimization, comprehensively improve the performance and stability of the product, meet the increasingly stringent requirements of the power industry for pipe materials, and have significant economic and social benefits. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0044] The main raw materials used in this invention are as follows:

[0045] CPVC resin: model TempRite 677×88, chlorine content 67%, K value 56-60.

[0046] PVC resin: Model SG-5, produced by Xinjiang Tianye Co., Ltd., K value 65-67, particle size 100-120μm.

[0047] MBS: Model MB-358, produced by Kumho Petrochemical Company, with 30% methyl methacrylate, 35% butadiene, and 35% styrene.

[0048] Environmentally friendly calcium-zinc composite stabilizer: model CZ-988, the main components are calcium stearate, zinc stearate, zinc salt and antioxidant, and the weight ratio of calcium stearate to zinc stearate is 2:1.

[0049] Stearic acid: Model SA-1801, purity ≥98.5%.

[0050] ACR: Model ACR-401, manufactured by ROHM Chemical Company, is an acrylate processing modifier with a molecular weight of approximately 25,000.

[0051] Paraffin wax: Grade 58, melting point 58-60℃.

[0052] Calcium carbonate: Model GCC-800, average particle size 0.8μm, surface treated with stearic acid.

[0053] Molybdenum Chromium Red: Model CR-840, average particle size 5-8μm.

[0054] CPE: Model CPE-135A, chlorine content 35%, melt index 2.0g / 10min.

[0055] Graphene: Model GNP-H5, thickness 1.0 nm, lateral dimension 3 μm, specific surface area 800 m² 2 / g.

[0056] Modified carbon nanotubes: model CNT-OH, surface coated with hydroxyl groups, aspect ratio 1500, purity 99%, diameter 10-15nm.

[0057] Nano magnesium oxide: Model NMgO-50, produced by Shanghai Maclean Biochemical Technology Co., Ltd., particle size 50nm, purity ≥99.9%.

[0058] Expanded graphite: Model EG-180, expansion rate 180mL / g, carbon content ≥99%.

[0059] Tetrabutyl titanate: Model TBT-98, manufactured by Sinopharm Chemical Reagent Co., Ltd., purity ≥98%.

[0060] Zinc acetate: Model ZnAc-99, manufactured by Aladdin Reagent Co., Ltd., purity ≥99%.

[0061] Ammonium polyphosphate: Model APP-II, produced by Zhejiang Wansheng Co., Ltd., with a phosphorus content of 31-32% and a nitrogen content of 14-15%.

[0062] Melamine: Model M-99, manufactured by BASF Chemicals, purity ≥99.8%.

[0063] β-Cyclodextrin: Model β-CD, purity ≥98%.

[0064] Citric acid: Model CA-99, manufactured by Aladdin Reagent Co., Ltd., purity ≥99%.

[0065] Low molecular weight polysiloxane: Model PDMS-3000, manufactured by Dow Corning, molecular weight 3000.

[0066] Organosilicon modified polyether: Model SPE-2500, manufactured by Wacker Chemie, with 20% siloxane content and a molecular weight of 2500.

[0067] Conductive carbon black: Model EC-600, manufactured by Cabot Corporation, specific surface area 600m² 2 / g, DBP oil absorption value 120mL / 100g.

[0068] Nano silver: Model NS-30, particle size 30nm, purity ≥99.9%.

[0069] Barium titanate: Model BT-100, average particle size 100nm, purity ≥99.5%.

[0070] Silane coupling agent KH-550: Model A-1100, manufactured by Dow Corning, with a purity of ≥98%.

[0071] Example 1

[0072] CPVC power pipe comprises the following raw materials in parts by weight: 95 parts CPVC resin, 25 parts PVC resin, 6 parts MBS, 5 parts environmentally friendly calcium-zinc composite stabilizer, 0.2 parts stearic acid, 0.3 parts ACR, 0.4 parts paraffin wax, 15 parts calcium carbonate, 0.5 parts molybdenum chromium red, 1.0 part CPE, 4 parts graphene, 0.5 parts modified carbon nanotubes, 8 parts ternary synergistic flame retardant composite, 1 part nano titanium dioxide zinc oxide composite, 0.8 parts low molecular weight polysiloxane, 1 part organosilicon modified polyether, 0.5 parts β-cyclodextrin inclusion modifier, 0.3 parts conductive carbon black nano silver composite, and 2 parts modified dielectric ceramic powder.

[0073] The preparation method of the ternary synergistic flame retardant composite is as follows:

[0074] (1) Immerse 200g of ammonium polyphosphate in 1000g of 10% melamine aqueous solution (liquid-solid ratio of 5:1) and stir at 60°C for 2 hours.

[0075] (2) Filter the solid and dry it at 90°C for 5 hours to obtain modified ammonium polyphosphate;

[0076] (3) Mix 50g of nano magnesium oxide, 50g of expanded graphite and 150g of modified ammonium polyphosphate, add 5g of 1% KH-550 silane coupling agent solution, and mix in a high-speed mixer at 800rpm for 15 minutes.

[0077] (4) Dry at 80℃ for 3 hours, pulverize and pass through a 200-mesh sieve to obtain a ternary synergistic flame retardant composite.

[0078] The preparation method of the nano-titanium dioxide-zinc oxide composite is as follows:

[0079] (1) Dissolve 34g of tetrabutyl titanate in 200mL of anhydrous ethanol, add 0.5mol / L nitric acid dropwise to adjust the pH to 2, and stir for 30 minutes to form solution A;

[0080] (2) Dissolve 22g of zinc acetate in 100mL of anhydrous ethanol and stir for 30 minutes to form solution B;

[0081] (3) Slowly add solution B dropwise to solution A and stir at 40°C for 2 hours;

[0082] (4) Add 300 mL of deionized water, continue stirring for 1 hour, and then perform hydrothermal reaction at 80 °C for 6 hours;

[0083] (5) The solid was filtered and dried at 120°C for 4 hours, calcined at 450°C for 2 hours, and then pulverized through a 400-mesh sieve to obtain nano-titanium dioxide zinc oxide composite.

[0084] The preparation method of the β-cyclodextrin inclusion modifier is as follows:

[0085] (1) Mix 10g of β-cyclodextrin with 2g of citric acid, add 50mL of anhydrous ethanol, and stir to dissolve at 60℃;

[0086] (2) Evaporate the solvent to a paste and react at 130°C for 2 hours;

[0087] (3) Cool to room temperature, pulverize, wash with deionized water 3 times, and dry at 60°C for 12 hours to obtain β-cyclodextrin inclusion modifier.

[0088] The preparation method of the conductive carbon black nano-silver composite is as follows:

[0089] (1) Disperse 19g of conductive carbon black in 500mL of deionized water and sonicate for 30 minutes;

[0090] (2) Dissolve 1g of silver nitrate in 100mL of deionized water, and slowly add it dropwise to the carbon black suspension, stirring for 30 minutes;

[0091] (3) Add an appropriate amount of ascorbic acid as a reducing agent and react at 70°C for 1 hour;

[0092] (4) Filter by suction and dry at 80°C for 12 hours to obtain conductive carbon black nano-silver composite.

[0093] The preparation method of the CPVC power pipe includes the following steps:

[0094] A. Raw material pretreatment:

[0095] (1) The CPVC resin and PVC resin were vacuum dried at 80°C for 5 hours, and the moisture content was controlled to be 0.03%;

[0096] (2) 4g of graphene and 0.5g of modified carbon nanotubes were dispersed in 500mL of isopropanol to form a suspension with a concentration of 0.9%. The suspension was ultrasonically treated for 40 minutes at a power of 600W and a frequency of 40kHz, then vacuum filtered and dried at 80℃ for 4 hours.

[0097] (3) Mix the environmentally friendly calcium-zinc composite stabilizer, stearic acid, and ACR in a high-speed mixer at a speed of 1000 rpm for 5 minutes.

[0098] B. Multi-level mixing:

[0099] (1) In a high-speed mixer, CPVC resin, PVC resin, calcium carbonate, environmentally friendly calcium-zinc composite stabilizer, stearic acid, CPE and MBS are mixed at 85°C for 15 minutes to obtain a primary mixture;

[0100] (2) In a high-speed mixer equipped with a cooling system, the primary mixture is mixed with the ternary synergistic flame retardant compound, nano titanium dioxide zinc oxide compound, low molecular weight polysiloxane, organosilicon modified polyether, and β-cyclodextrin inclusion modifier at 70°C for 10 minutes to obtain the secondary mixture.

[0101] (3) In a twin-screw extruder with an L / D ratio of 40:1, the secondary mixture was mixed with pretreated graphene, modified carbon nanotubes, conductive carbon black nano-silver composite and modified dielectric ceramic powder. The temperatures of each section of the extruder were 140℃, 155℃, 165℃, 175℃, 170℃ and 165℃ respectively. The screw speed was 40 rpm and the vacuum exhaust pressure was -0.08 MPa to obtain the tertiary mixture.

[0102] C. Precision extrusion molding:

[0103] The three-stage mixture is fed into a high-precision extruder equipped with a special screw design. The feed section temperature is 165℃, the compression section temperature is 175℃, the homogenization section temperature is 180℃, the die head section temperature is 180℃, the screw speed is 20rpm, the linear speed is 5m / min, the die head pressure is 8MPa, and the vacuum degree is -0.085MPa. The extrusion molding process yields CPVC power pipe blanks.

[0104] D. Shaping and cooling:

[0105] The CPVC power pipe blank is cooled through a three-stage gradient cooling water tank. The temperature of the first stage is 50℃, the temperature of the second stage is 35℃, and the temperature of the third stage is 20℃. The circulating water flow rate is 1.5 m / s, and compressed air cooling is also used.

[0106] E. Surface treatment and quality control:

[0107] The cooled CPVC power pipe is subjected to corona treatment with an electrode voltage of 15kV and a treatment time of 1.5 seconds. Then, it is inspected by a laser online measurement system to control the wall thickness tolerance within ±0.15 mm and the inner diameter tolerance within ±0.2 mm. Finally, it is cut, inspected, and packaged to obtain the finished CPVC power pipe.

[0108] Example 2

[0109] CPVC power pipe comprises the following raw materials in parts by weight: 110 parts CPVC resin, 40 parts PVC resin, 10 parts MBS, 8 parts environmentally friendly calcium-zinc composite stabilizer, 0.8 parts stearic acid, 1.0 part ACR, 2.0 parts paraffin wax, 25 parts calcium carbonate, 1.5 parts molybdenum chromium red, 3.0 parts CPE, 8 parts graphene, 1.5 parts modified carbon nanotubes, 12 parts ternary synergistic flame retardant composite, 3 parts nano titanium dioxide zinc oxide composite, 1.5 parts low molecular weight polysiloxane, 2 parts organosilicon modified polyether, 1.0 part β-cyclodextrin inclusion modifier, 1.0 part conductive carbon black nano silver composite, and 5 parts modified dielectric ceramic powder.

[0110] The preparation method of the ternary synergistic flame retardant composite and the nano-titanium dioxide-zinc oxide composite is the same as in Example 1. In this example, the amount of citric acid in the β-cyclodextrin inclusion modifier is 3g, and the other steps are the same as in Example 1.

[0111] The preparation method of the CPVC power pipe includes the following steps:

[0112] A. Raw material pretreatment:

[0113] (1) The CPVC resin and PVC resin were vacuum dried at 80°C for 6 hours, and the moisture content was controlled to be 0.02%;

[0114] (2) Disperse 8g of graphene and 1.5g of modified carbon nanotubes in 800mL of isopropanol to form a suspension with a concentration of 1.0%. Sonicate for 45 minutes at a power of 600W and a frequency of 40kHz, then vacuum filter and dry at 80℃ for 4 hours.

[0115] (3) Mix the environmentally friendly calcium-zinc composite stabilizer, stearic acid, and ACR in a high-speed mixer at a speed of 1200 rpm for 6 minutes.

[0116] B. Multi-level mixing:

[0117] (1) In a high-speed mixer, CPVC resin, PVC resin, calcium carbonate, environmentally friendly calcium-zinc composite stabilizer, stearic acid, CPE and MBS are mixed at 90°C for 18 minutes to obtain a primary mixture.

[0118] (2) In a high-speed mixer equipped with a cooling system, the primary mixture is mixed with the ternary synergistic flame retardant compound, nano titanium dioxide zinc oxide compound, low molecular weight polysiloxane, organosilicon modified polyether, and β-cyclodextrin inclusion modifier at 65°C for 12 minutes to obtain the secondary mixture.

[0119] (3) In a twin-screw extruder with an L / D ratio of 42:1, the secondary mixture was mixed with pretreated graphene, modified carbon nanotubes, conductive carbon black nano-silver composite and modified dielectric ceramic powder. The temperatures of each section of the extruder were 140℃, 155℃, 165℃, 175℃, 170℃ and 165℃ respectively. The screw speed was 50 rpm and the vacuum exhaust pressure was -0.08 MPa to obtain a tertiary mixture.

[0120] Steps C, D, and E are similar to those in Example 1, but in the precision extrusion molding stage, the linear speed is increased to 6 m / min and the die head pressure is 10 MPa.

[0121] Example 3

[0122] CPVC power pipe comprises the following raw materials in parts by weight: 130 parts CPVC resin, 65 parts PVC resin, 16 parts MBS, 12 parts environmentally friendly calcium-zinc composite stabilizer, 1.5 parts stearic acid, 2.0 parts ACR, 6.0 parts paraffin wax, 35 parts calcium carbonate, 2.5 parts molybdenum chromium red, 6.0 parts CPE, 12 parts graphene, 3 parts modified carbon nanotubes, 20 parts ternary synergistic flame retardant composite, 5 parts nano titanium dioxide zinc oxide composite, 3 parts low molecular weight polysiloxane, 4 parts organosilicon modified polyether, 2 parts β-cyclodextrin inclusion modifier, 2 parts conductive carbon black nano silver composite, and 8 parts modified dielectric ceramic powder.

[0123] In this embodiment, in the preparation method of the ternary synergistic flame retardant composite, the concentration of melamine aqueous solution is increased to 15%, the reaction temperature is 70°C, and the reaction time is 3 hours. In the preparation of the nano-titanium dioxide-zinc oxide composite, the hydrothermal reaction time is extended to 10 hours, the calcination temperature is increased to 500°C, and the time is extended to 3 hours.

[0124] The preparation method is basically the same as in Examples 1-2, but in the multi-stage mixing stage, the screw speed of the twin-screw extruder is increased to 60 rpm, and in the precision extrusion molding stage, the temperature of each section is increased by 5°C, the linear speed is increased to 8 m / min, and the die head pressure is 12 MPa.

[0125] Example 4

[0126] CPVC power pipe comprises the following raw materials in parts by weight: 120 parts CPVC resin, 50 parts PVC resin, 12 parts MBS, 10 parts environmentally friendly calcium-zinc composite stabilizer, 1.2 parts stearic acid, 1.5 parts ACR, 4.0 parts paraffin wax, 30 parts calcium carbonate, 2.0 parts molybdenum chromium red, 4.5 parts CPE, 10 parts graphene, 2 parts modified carbon nanotubes, 15 parts ternary synergistic flame retardant composite, 4 parts nano titanium dioxide-zinc oxide composite, 2 parts low molecular weight polysiloxane, 3 parts organosilicon modified polyether, 1.5 parts β-cyclodextrin inclusion modifier, 1.5 parts conductive carbon black nano silver composite, and 6 parts modified dielectric ceramic powder.

[0127] In this embodiment, the modified dielectric ceramic powder is alumina powder with an average particle size of 150 nm, which has been modified with KH-550. The preparation method is as follows: 100 g of alumina powder is dispersed in 500 mL of anhydrous ethanol, 5 g of KH-550 is added, the mixture is stirred at 60 °C for 4 hours, filtered, and dried at 120 °C for 8 hours to obtain the modified dielectric ceramic powder.

[0128] The preparation method is basically the same as the previous embodiment, but during the shaping and cooling stage, the temperature of each section of the water tank is adjusted to 52℃, 38℃ and 23℃, and the circulating water flow rate is increased to 2.0 m / s.

[0129] Example 5

[0130] CPVC power pipe comprises the following raw materials in parts by weight: 100 parts CPVC resin, 35 parts PVC resin, 8 parts MBS, 7 parts environmentally friendly calcium-zinc composite stabilizer, 1.0 part stearic acid, 1.2 parts ACR, 3.0 parts paraffin wax, 20 parts calcium carbonate, 1.0 part molybdenum chromium red, 2.5 parts CPE, 6 parts graphene, 1 part modified carbon nanotube, 10 parts ternary synergistic flame retardant composite, 2 parts nano titanium dioxide zinc oxide composite, 1.2 parts low molecular weight polysiloxane, 1.5 parts organosilicon modified polyether, 0.8 parts β-cyclodextrin inclusion modifier, 0.8 parts conductive carbon black nano silver composite, and 4 parts modified dielectric ceramic powder.

[0131] In this embodiment, the weight ratio of carbon black to silver nitrate in the preparation method of the conductive carbon black nano-silver composite is adjusted to 15:1. Other preparation methods are basically the same as those in the previous embodiments.

[0132] Comparative Example 1

[0133] CPVC power pipes comprise the following raw materials in parts by weight: 100 parts CPVC resin, 35 parts PVC resin, 8 parts MBS, 7 parts environmentally friendly calcium-zinc composite stabilizer, 1.0 part stearic acid, 1.2 parts ACR, 3.0 parts paraffin wax, 20 parts calcium carbonate, 1.0 part molybdenum chromium red, and 2.5 parts CPE.

[0134] In this comparative example, no graphene, modified carbon nanotubes, ternary synergistic flame retardant composite, nano-titanium dioxide zinc oxide composite, low molecular weight polysiloxane, organosilicon modified polyether, β-cyclodextrin inclusion modifier, conductive carbon black nano-silver composite, or modified dielectric ceramic powder were added.

[0135] The preparation method is similar to that in Example 5, but the ultrasonic dispersion step of nanomaterials in the raw material pretreatment and the steps related to nanomaterials in the multi-stage mixing are omitted.

[0136] Comparative Example 2

[0137] CPVC power pipe comprises the following raw materials in parts by weight: 100 parts CPVC resin, 35 parts PVC resin, 8 parts MBS, 7 parts environmentally friendly calcium-zinc composite stabilizer, 1.0 part stearic acid, 1.2 parts ACR, 3.0 parts paraffin wax, 20 parts calcium carbonate, 1.0 part molybdenum chromium red, 2.5 parts CPE, 6 parts graphene, and 1 part modified carbon nanotubes.

[0138] In this comparative example, graphene and modified carbon nanotubes were added, but ternary synergistic flame retardant composite, nano-titanium dioxide zinc oxide composite, low molecular weight polysiloxane, organosilicon modified polyether, β-cyclodextrin inclusion modifier, conductive carbon black nano-silver composite and modified dielectric ceramic powder were not added.

[0139] The preparation method is similar to that in Example 5, but the step of adding functional additives such as the ternary synergistic flame retardant compound is omitted.

[0140] Comparative Example 3

[0141] CPVC power pipe comprises the following raw materials in parts by weight: 100 parts CPVC resin, 35 parts PVC resin, 8 parts MBS, 7 parts environmentally friendly calcium-zinc composite stabilizer, 1.0 part stearic acid, 1.2 parts ACR, 3.0 parts paraffin wax, 20 parts calcium carbonate, 1.0 part molybdenum chromium red, 2.5 parts CPE, and 8 parts ammonium polyphosphate.

[0142] In this comparative example, a ternary synergistic flame retardant compound was not used; instead, unmodified ammonium polyphosphate was used directly as the flame retardant, and no other nanomaterials or functional additives were added.

[0143] The preparation method is similar to that in Example 5, but the preparation steps of the ternary synergistic flame retardant compound and the addition steps of other functional additives are omitted.

[0144] Performance testing methods

[0145] The following performance tests were performed on the CPVC power pipes prepared in the above embodiments and comparative examples:

[0146] (1) Vicat softening point: Tested according to GB / T 1633-2000 "Determination of Vicat softening temperature of thermoplastic plastics".

[0147] (2) Ring stiffness: Tested in accordance with GB / T 9647-2003 "Determination of ring stiffness of thermoplastic pipes".

[0148] (3) Tensile strength: Tested in accordance with GB / T 8804.2-2003 "Determination of tensile properties of thermoplastic pipes - Part 2: Extruded plastic pipes".

[0149] (4) Thermal conductivity: Tested according to GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials by hot wire method".

[0150] (5) Flame retardancy rating: tested according to UL 94 standard.

[0151] (6) Electrical performance: Tested in accordance with GB / T 1408.1-2016 "Electrical strength test method for solid insulating materials - Part 1: Test at power frequency" and GB / T 1410-2006 "Test method for volume resistivity and surface resistivity of solid insulating materials".

[0152] (7) Aging performance: The test was conducted in accordance with GB / T 9651-2009 "Plastics exposed to laboratory light source - Part 3: Fluorescent ultraviolet lamps", and the aging time was 1000 hours.

[0153] Table 1: Key performance test results of Examples 1-5 and Comparative Examples 1-3

[0154] sample Vicat softening point (°C) <![CDATA[Ring stiffness (kN / m 2 )]]> Tensile strength (MPa) Thermal conductivity (W / m·K) Flame retardant rating Breakdown voltage (kV / mm) Strength retention rate after aging (%) Example 1 115 65 45.2 4 V-0 25.2 92.5 Example 2 120 70 48.5 4.8 V-0 27.8 94.2 Example 3 130 85 55 6 V-0 30.5 96.8 Example 4 125 78 52.3 5.5 V-0 29 95.5 Example 5 118 72 49.8 4.5 V-0 26.5 93.8 Comparative Example 1 98 42 38.2 0.3 V-2 18.5 75.2 Comparative Example 2 102 48 40.5 2.8 V-1 20.2 80.5 Comparative Example 3 100 45 39.4 0.5 V-1 19.8 78.3

[0155] Table 2: Test results of electrical and processing performance of Examples 1-5

[0156] sample Volume resistivity (Ω·cm) Surface resistivity (Ω) Antistatic properties (s) Dimensional stability (%) Surface gloss (%) Processing fluidity (g / 10min) Example 1 <![CDATA[2.5×10 15 ]]> <![CDATA[3.2×10 13 ]]> 8.5 ±0.12 85 3.2 Example 2 <![CDATA[1.8×10 15 ]]> <![CDATA[2.5×10 13 ]]> 6.2 ±0.10 88 4.5 Example 3 <![CDATA[1.2×10 15 ]]> <![CDATA[1.8×10 13 ]]> 3.5 ±0.08 92 6.8 Example 4 <![CDATA[1.5×10 15 ]]> <![CDATA[2.0×10 13 ]]> 4.8 ±0.09 90 5.5 Example 5 <![CDATA[2.0×10 15 ]]> <![CDATA[2.8×10 13 ]]> 7 ±0.11 87 4 Comparative Example 1 <![CDATA[5.2×10 15 ]]> <![CDATA[8.5×10 13 ]]> 25.2 ±0.35 70 2 Comparative Example 2 <![CDATA[4.0×10 15 ]]> <![CDATA[6.2×10 13 ]]> 18.5 ±0.28 75 2.5 Comparative Example 3 <![CDATA[4.5×10 15 ]]> <![CDATA[7.0×10 13 ]]> 20.2 ±0.30 72 2.2

[0157] The test results above show that:

[0158] (1) The CPVC power pipes of Examples 1-5 are significantly superior to those of Comparative Examples 1-3 in terms of Vicat softening point, ring stiffness, tensile strength, and thermal conductivity. In particular, Example 3 achieved the best performance, with a Vicat softening point as high as 130℃ and a ring stiffness of 85kN / m. 2 The tensile strength reaches 55.0 MPa and the thermal conductivity reaches 6.0 W / m·K. These performance indicators significantly exceed those of the comparative sample and existing technology.

[0159] (2) In terms of flame retardant performance, Examples 1-5 all achieved the UL 94 V-0 level, while Comparative Examples 1-3 only achieved the V-1 or V-2 level. This demonstrates the high efficiency of the ternary synergistic flame retardant composite of the present invention.

[0160] (3) In terms of electrical performance, the breakdown voltage, volume resistivity, and surface resistivity of Examples 1-5 are significantly better than those of the comparative examples, indicating that the power tube of the present invention has better insulation performance. In particular, the antistatic performance is better; the electrostatic decay time of Example 3 is only 3.5 seconds, while that of Comparative Example 1 is as high as 25.2 seconds.

[0161] (4) In terms of aging performance, the strength retention rate of Examples 1-5 after 1000 hours of UV accelerated aging test is all above 90%, while that of the comparative examples is only 75-80%, indicating that the power tube of the present invention has a longer service life.

[0162] (5) In terms of processing performance, the dimensional stability, surface gloss and processing fluidity of Examples 1-5 are better than those of the comparative examples, indicating that the multi-stage mixing process and precision extrusion molding process of the present invention can effectively improve product quality and production efficiency.

[0163] The superior performance of the CPVC power pipe of this invention is achieved through multiple synergistic mechanisms:

[0164] (1) Mechanism for improving heat resistance:

[0165] An environmentally friendly calcium-zinc composite stabilizer forms a thermally stable network structure with low-molecular-weight polysiloxane, effectively capturing free radicals generated during thermal decomposition. Simultaneously, graphene and modified carbon nanotubes form a three-dimensional thermally conductive network, accelerating heat dissipation and preventing localized overheating. Under high-temperature conditions, β-cyclodextrin encapsulates the modifier, slowly releasing citrate esters to neutralize residual acidic degradation products, further improving thermal stability. This multi-layered thermal stabilization strategy increases the Vicat softening point from the traditional 95-100℃ to 115-130℃.

[0166] (2) Flame retardant synergistic mechanism:

[0167] In the ternary synergistic flame-retardant composite, modified ammonium polyphosphate decomposes at high temperatures to release phosphoric acid, catalyzing the formation of a char layer on CPVC / PVC; simultaneously, it releases ammonia and nitrogen, diluting the oxygen concentration in the combustion zone; nano-magnesium oxide absorbs a large amount of heat and releases water vapor, reducing the surface temperature of the material; and expanded graphite rapidly expands when heated, forming a honeycomb-like heat insulation barrier. The synergistic effect of these three flame-retardant components achieves a multi-dimensional flame-retardant mechanism of "gas-phase dilution + solid-phase barrier + catalytic char formation," enabling the flame retardant rating to reach UL 94 V-0.

[0168] (3) Conductivity / insulation balance mechanism:

[0169] The conductive carbon black nano-silver composite forms a uniformly distributed but discontinuous conductive network within the matrix, giving the material sufficient surface conductivity to dissipate static electricity without affecting the volume resistivity and maintaining good insulation properties. Simultaneously, the modified dielectric ceramic powder improves the material's dielectric strength and enhances its resistance to electrical breakdown. This ingenious design of electrical property balance gives the material both excellent insulation and antistatic properties.

[0170] (4) Dispersion and reinforcement mechanism of nanomaterials:

[0171] β-Cyclodextrin inclusion modifiers significantly improve the dispersibility of nanomaterials in polymer matrices by forming host-guest inclusion complexes. The hydrophobic cavities of β-cyclodextrin within the inclusion complex form non-covalent interactions with the nanomaterial surface, while its hydrophilic outer walls undergo hydrogen bonding with polar groups, forming a ternary composite structure of "nanomaterial-β-cyclodextrin-polymer," effectively preventing nanomaterial aggregation. This innovative dispersion technology allows the reinforcing effect of nanomaterials to be fully realized.

[0172] (5) Mechanism for optimizing processing performance:

[0173] Organosilicon-modified polyethers (ACRs) form a microphase structure in the melt, enhancing the compatibility of CPVC and PVC while reducing melt viscosity and improving flowability. Simultaneously, ACRs reduce melt elasticity during processing, minimizing the occurrence of "sharkskin" defects. Multi-stage mixing processes, through temperature-controlled stages, ensure that each component is mixed at its optimal temperature, preventing degradation of heat-sensitive components. These innovative measures significantly improve the surface quality and dimensional accuracy of the product.

[0174] Based on the above test results and mechanism analysis, Example 3 exhibits the best overall performance and can be considered the optimal implementation scheme of this invention. In this scheme, the proportions of each component reach the optimal balance, with the amount of the ternary synergistic flame retardant composite being 20 parts, forming the best synergistic effect with graphene (12 parts) and modified carbon nanotubes (3 parts). Simultaneously, the amounts of nano-titanium dioxide zinc oxide composite (5 parts), low molecular weight polysiloxane (3 parts), organosilicon modified polyether (4 parts), β-cyclodextrin inclusion modifier (2 parts), conductive carbon black nano-silver composite (2 parts), and modified dielectric ceramic powder (8 parts) also reach the optimal level, forming a perfect synergistic effect among the functional components.

[0175] Regarding the manufacturing process, Example 3 employed optimal process parameters, including optimal pretreatment conditions, multi-stage mixing temperature and time, precision extrusion molding parameters, and setting and cooling conditions. These optimized process parameters ensured the high quality and stability of the product.

[0176] The CPVC power pipe prepared according to this optimal implementation scheme has a Vicat softening point of 130℃ and a ring stiffness of 85kN / m. 2 The tensile strength reaches 55.0 MPa, the thermal conductivity reaches 6.0 W / m·K, the flame retardant rating is V-0, the breakdown voltage is 30.5 kV / mm, and the strength retention rate after aging is 96.8%. These performance indicators all significantly exceed the existing technical level and meet or even exceed the stringent requirements of the power industry for CPVC power pipes.

[0177] The CPVC power pipe and its preparation method provided by this invention comprehensively improve the heat resistance, flame retardancy, electrical properties, and processing performance of CPVC power pipes through innovative material formulation design and precise preparation processes, thereby extending their service life. In particular, by introducing a ternary synergistic flame-retardant composite, a nanomaterial reinforcement system, and multifunctional additives, a multiphase synergistic reinforcement network is formed, achieving a qualitative leap in performance. Simultaneously, multi-stage mixing processes, precision extrusion molding processes, and gradient cooling technology ensure the high quality and stability of the product.

[0178] Compared with existing technologies, the CPVC power pipe of the present invention has significant advantages such as high Vicat softening point, large ring stiffness, high tensile strength, large thermal conductivity, excellent flame retardant rating, good electrical performance, and excellent aging performance. It can meet the increasingly stringent application requirements of the power industry and has important economic value and social benefits.

[0179] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A CPVC electrical power pipe, characterized in that, The CPVC power pipe comprises the following raw materials by weight: CPVC resin 95-130 parts, PVC resin 25-65 parts, MBS 6-16 parts, environmentally friendly calcium-zinc composite stabilizer 5-12 parts, stearic acid 0.2-1.5 parts, ACR 0.3-2.0 parts, paraffin 0.4-6.0 parts, calcium carbonate 15-35 parts, molybdenum-chromium red 0.5-2.5 parts, CPE 1.0-6.0 parts, graphene 4-12 parts, modified carbon nanotube 0.5-3 parts, ternary synergistic flame-retardant composite 8-20 parts, nano-titanium dioxide-zinc oxide composite 1-5 parts, low molecular weight polysiloxane 0.8-3 parts, silicone modified polyether 1-4 parts, beta-cyclodextrin inclusion modifier 0.5-2 parts, conductive carbon black nano-silver composite 0.3-2 parts, and modified dielectric ceramic powder 2-8 parts; wherein the ternary synergistic flame-retardant composite is composed of modified ammonium polyphosphate, nano-magnesium oxide and intumescent graphite, and the weight ratio of the modified ammonium polyphosphate, nano-magnesium oxide and intumescent graphite is 3:1:1; The modified carbon nanotube is coated with a hydrophilic group on the surface, has an aspect ratio of 800-2000, a purity of greater than 98%, and a diameter of 5-20 nanometers; the graphene has a thickness of 0.8-1.2 nanometers, an average lateral size of 2-5 micrometers, and a specific surface area of 600-1200 square meters per gram; The modifier of the modified ammonium polyphosphate is melamine, the nano-magnesium oxide has a particle size of 20-100 nanometers, and the intumescent graphite has an expansion rate of 150-250 milliliters per gram; The silicone content of the silicone modified polyether is 15-25 weight percent, and the molecular weight is 2000-5000; the beta-cyclodextrin inclusion modifier comprises an esterification product of beta-cyclodextrin and citric acid; in the conductive carbon black nano-silver composite, the weight ratio of carbon black to nano-silver is 10:1 to 20:1; and the modified dielectric ceramic powder is barium titanate or aluminum oxide powder modified by a silane coupling agent on the surface.

2. The CPVC electrical power pipe according to claim 1, characterized in that, The MBS has a methyl methacrylate content of 25-35 weight percent, a butadiene content of 30-40 weight percent, and a styrene content of 30-40 weight percent; and the environmentally friendly calcium-zinc composite stabilizer comprises calcium stearate, zinc stearate, a zinc salt, and an antioxidant, and the weight ratio of calcium stearate to zinc stearate is 1.5:1 to 2.5:

1.

3. A method of making the CPVC electrical power pipe according to any one of claims 1-2, characterized in that, The method comprises the following steps: A. Raw material pretreatment: vacuum drying CPVC resin and PVC resin at 80±5℃ for 4-6 hours to control the moisture content to be less than 0.05%; dispersing graphene and modified carbon nanotube in isopropyl alcohol to form a suspension with a concentration of 0.5-1.0%, ultrasonic treatment for 30-45 minutes under the conditions of power 600W and frequency 40kHz, then vacuum filtration and drying at 80℃ for 4 hours; mixing stabilizers, lubricants and ACR in a high-speed mixer at a speed of 1000-1500 rpm for 5-8 minutes; B. Multi-stage mixing: B1. In a high-speed mixer, mix CPVC resin, PVC resin, calcium carbonate, environmentally friendly calcium-zinc composite stabilizer, stearic acid, CPE, MBS at 80-90℃ for 15-20 minutes to obtain a first mixture; B2. In a high-speed mixer equipped with a cooling system, mix the first mixture with a ternary synergistic flame retardant compound, nano-titanium dioxide zinc oxide compound, low molecular weight polysiloxane, silicone modified polyether, β-cyclodextrin inclusion modifier at 65-75℃ for 10-15 minutes to obtain a second mixture; B3. In a twin-screw extruder with an L / D ratio not less than 36:1, mix the second mixture with pretreated graphene, modified carbon nanotubes, conductive carbon black nano-silver compound, modified dielectric ceramic powder, the temperature of each section of the extruder is 140℃, 155℃, 165℃, 175℃, 170℃, 165℃ respectively, the screw speed is 40-60rpm, the vacuum exhaust pressure is-0.08MPa, to obtain a third mixture; C. Precision extrusion molding: feed the third mixture into a high-precision extruder equipped with special screw design, the temperature of the feeding section is 165-170℃, the temperature of the compression section is 175-180℃, the temperature of the homogenization section is 180-185℃, the temperature of the die head section is 180-188℃, the screw speed is 20-35rpm, the linear speed is 5-8 meters per minute, the die head pressure is 8-12MPa, the vacuum degree is-0.085±0.005MPa, and the CPVC power pipe blank is obtained by extrusion molding; the special screw design includes: deep thread conveying elements are used in the front section, shallow thread shearing elements and torsional mixing elements are alternately arranged in the middle section, and feedback elements and shear mixing elements are combined in the rear section; the die head adopts a gradually tapered flow channel structure, the inner wall is mirror polished, and the length-diameter ratio of the flow channel is 8-12 and the contraction angle is 15-25 degrees; D. Shaping and cooling: cool the CPVC power pipe blank through a three-stage gradient cooling water tank, the first stage temperature is 50-55℃, the second stage temperature is 35-40℃, the third stage temperature is 20-25℃, the circulating water flow rate is 1.5-2.5 meters per second, and compressed air cooling is assisted; E. Surface treatment and quality control: the cooled CPVC power pipe is subjected to corona treatment, the electrode voltage is 15-20kV, and the treatment time is 1.5-3 seconds; then it is detected by a laser online measurement system to control the wall thickness tolerance within ±0.15mm and the inner diameter tolerance within ±0.2mm; finally, it is cut, inspected, and packaged to obtain the finished CPVC power pipe.

4. The method of claim 3, wherein, The preparation method of the ternary synergistic flame retardant compound comprises the following steps: a. Immerse the ammonium polyphosphate in a 10-15% by mass fraction melamine aqueous solution, the liquid-solid ratio is 4:1, and stir and react at 60-70℃ for 2-3 hours; b. Filter and dry the solid at 90-100℃ for 5-8 hours to obtain modified ammonium polyphosphate; c. Mix the nano-magnesium oxide, expanded graphite and modified ammonium polyphosphate according to the weight ratio of 1:1:3, add 1-2% of silane coupling agent KH-550, mix in a high-speed mixer at a speed of 800-1200 rpm for 15-20 minutes; d. Dry at 80-90℃ for 3-5 hours, crush and sieve to obtain the ternary synergistic flame-retardant composite.

5. The method of claim 3, wherein, The preparation method of the nano-titanium dioxide zinc oxide composite comprises the following steps: a. Dissolve tetrabutyl titanate in anhydrous ethanol, drop 0.5-1.0 mol / L of nitric acid to adjust the pH value to 2-3, and stir for 30-60 minutes to form solution A; b. Dissolve zinc acetate in anhydrous ethanol and stir for 30 minutes to form solution B; c. Slowly drop solution B into solution A and stir at 40-50℃ for 2-4 hours; d. Add deionized water and continue to stir for 1-2 hours, and then hydrothermally react at 80-90℃ for 6-10 hours; e. Filter, dry the obtained solid at 120-140℃ for 4-6 hours, calcine at 450-500℃ for 2-3 hours, crush and sieve to obtain the nano-titanium dioxide zinc oxide composite.

6. The method of claim 3, wherein, The screw combination of the twin-screw extruder in step B3 comprises conveying elements, shearing elements and mixing elements, and the mixing elements comprise forward tooth-shaped mixing elements and reverse tooth-shaped mixing elements, and the total length of the shearing elements and the mixing elements accounts for 40-60% of the total length of the screw.