MPP power cable protection pipe and preparation process thereof

Abstract

The invention relates to the technical field of polymer composite materials, and discloses an MPP (modified polypropylene) power cable protection tube, which is prepared from the following raw materials in parts by weight: 100 parts of polyvinyl chloride resin; 15 to 30 parts of an ethylene-vinyl acetate copolymer; 5 to 15 parts of pre-crosslinked organic silicon microspheres; 20-40 parts of a composite inorganic filler; 0.5 to 2 parts of a silane coupling agent; 2-5 parts of a heat stabilizer; 1-3 parts of a lubricant; and 3-8 parts of a flame retardant. The polyvinyl chloride resin is used as a main body and is matched with the ethylene-vinyl acetate copolymer and the pre-crosslinked organic silicon microspheres with specific contents, a rigid matrix-elastic phase-organic silicon microsphere multiphase synergistic toughening and reinforcing system is constructed, and the pre-crosslinked organic silicon microspheres are used as second-phase elastic particles, so that crazing and shear bands can be effectively initiated, crack propagation is prevented, and the mechanical properties of the PVC pipe are improved. The impact toughness and the low-temperature performance of the material are remarkably improved, and the composite inorganic filler subjected to surface treatment by the silane coupling agent is matched, so that the interface bonding is further enhanced, and the rigidity, the wear resistance and the thermal stability are improved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to an MPP power cable protection pipe and its preparation process. Background Technology

[0002] Power cable protection pipes are widely used in power engineering for cable laying and protection. They are required to have good mechanical strength, impact resistance, wear resistance, flame retardancy and low temperature resistance. At present, most common cable protection pipes use polyvinyl chloride (PVC) as the base resin and add various modifiers and fillers to improve their comprehensive performance.

[0003] For example, Chinese patent application CN111363271A discloses a corrosion-resistant MPP power cable protection pipe material, which is a composite of polyvinyl chloride resin, propylene-ethylene random copolymer, fluorosilicone rubber, and other components, with the addition of a large amount of nanofillers and reinforcing fibers. Although this solution has certain improvements in strength, high temperature resistance, and wear resistance, it still has the following obvious shortcomings: 1. Complex composition and high cost: This solution uses more than a dozen raw materials, including various types of rubber, nanofillers and fibers. The formulation system is complicated, the raw material cost is high, and the compatibility and dispersibility between the components are difficult to guarantee, which can easily lead to unstable material performance.

[0004] 2. The process is complicated and energy-intensive: The preparation process requires multiple steps such as low-speed stirring, high-temperature mixing, and high-speed stirring at room temperature. The mixing temperature is as high as 160-180℃, and the high-speed stirring time is as long as 18-22 minutes. The overall process has high energy consumption and low efficiency, which is not conducive to large-scale production.

[0005] 3. Limited improvement in toughness and insufficient improvement in low-temperature brittleness: Despite the addition of toughening components such as fluorosilicone rubber, the material's notched impact strength and low-temperature embrittlement temperature are still not ideal due to the lack of effective interfacial compatibility design and elastomer network construction. It is prone to brittle failure in cold regions or under impact conditions. Summary of the Invention

[0006] The purpose of this invention is to provide an MPP power cable protection pipe and its manufacturing process to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an MPP power cable protection pipe, made from raw materials comprising the following parts by weight: 100 parts of polyvinyl chloride resin; 15-30 parts of ethylene-vinyl acetate copolymer; 5-15 parts of pre-crosslinked silicone microspheres; 20-40 parts of composite inorganic filler; 0.5-2 parts of silane coupling agent; 2-5 parts heat stabilizer; 1-3 parts lubricant; 3-8 parts flame retardant; The pre-crosslinked organosilicon microspheres are prepared by emulsion crosslinking of vinyl silicone oil and hydrogen-containing silicone oil under the action of platinum catalyst, with an average particle size of 1-10 μm; the composite inorganic filler is composed of silicon nitride, modified mica powder and fumed silica in a weight ratio of (1-3):(2-5):(1-2).

[0008] As a preferred embodiment of the present invention, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 18-28% by mass, and the melt flow rate is 3-10 g / 10 min.

[0009] As a preferred embodiment of the present invention, in the pre-crosslinked organosilicon microspheres, the mass ratio of vinyl silicone oil to hydrogen-containing silicone oil is (5-8):1, the viscosity of the vinyl silicone oil is 10000-50000 mPa·s, and the vinyl molar content is 1.5-3.0%; the viscosity of the hydrogen-containing silicone oil is 20-50 mm² / s, and the active hydrogen content is 0.8-1.5%. The emulsion crosslinking method uses a nonionic surfactant as the emulsifier, the reaction temperature is 60-80℃, and the reaction time is 2-4 hours.

[0010] As a preferred embodiment of the present invention, the modified mica powder is flaky mica that has been surface-treated with a silane coupling agent, and the particle size D50 is 800-1500 mesh.

[0011] As a preferred embodiment of the present invention, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0012] As a preferred embodiment of the present invention, the heat stabilizer is a calcium-zinc composite stabilizer; the lubricant is polyethylene wax or oxidized polyethylene wax; and the flame retardant is at least one of ammonium polyphosphate and melamine cyanurate.

[0013] A manufacturing process for an MPP power cable protection pipe as described in any of the above claims includes the following steps: S1. Preparation of pre-crosslinked organosilicon microspheres: Vinyl silicone oil, hydrogen-containing silicone oil, emulsifier and water are mixed and emulsified by high-speed shearing to form a stable emulsion. Platinum catalyst is added and reacted at 60-80℃ for 2-4 hours. After washing and drying, pre-crosslinked organosilicon microspheres are obtained. S2. Pretreatment of filler: Silicon nitride, modified mica powder, silica and silane coupling agent are mixed in a high-speed mixer at 90-110℃ for 5-15 minutes to obtain surface-treated composite inorganic filler. S3. High-speed hot mixing: Polyvinyl chloride resin and ethylene-vinyl acetate copolymer are added to a high-speed mixer. After heating to 90-110℃, the pre-crosslinked organosilicon microspheres obtained in step S1, the surface-treated composite inorganic filler obtained in step S2, heat stabilizer, lubricant and flame retardant are added in sequence. The mixture is continued at a speed of 800-1200 rpm until the material temperature reaches 115-125℃ to obtain a uniform premix. S4. Melt Extrusion and Molding: The premixed material is fed into a twin-screw extruder and melt-plasticized, extruded and granulated within a processing temperature range of 150-190℃ to obtain masterbatch; the masterbatch is then fed into a pipe extruder and, under a die temperature of 175-185℃ and a vacuum shaping pressure of -0.06 to -0.08MPa, is extruded, shaped, cooled, drawn and cut to obtain MPP power cable protection pipe.

[0014] As a preferred embodiment of the present invention, the total mixing time of the high-speed thermal mixing in step S3 is 8-15 minutes.

[0015] As a preferred technical solution of the present invention, the specific processing temperature of the twin-screw extruder in step S4 is set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, Zone 4 175-185℃, and Die head 180-190℃.

[0016] As a preferred embodiment of the present invention, the screw speed of the pipe extruder in step S4 is 15-25 rpm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. By using polyvinyl chloride resin as the main body, combined with a specific amount of ethylene-vinyl acetate copolymer and pre-crosslinked organosilicon microspheres, a multiphase synergistic toughening and reinforcement system of rigid matrix-elastic phase-organosilicon microspheres was constructed. The pre-crosslinked organosilicon microspheres, as the second phase elastic particles, can effectively induce crazes and shear bands, prevent crack propagation, and significantly improve the impact toughness and low-temperature performance of the material. Combined with composite inorganic fillers with silane coupling agent surface treatment, the interfacial bonding is further enhanced, and the rigidity, wear resistance and thermal stability are improved.

[0018] 2. This invention uses pre-crosslinked organosilicon microspheres for pre-preparation, and pre-mixes them with surface-treated fillers, resins, etc. through high-speed hot mixing in one step. The process steps are simplified, the temperature control of the entire mixing and extrusion process is reasonable, and it is far lower than the high-temperature mixing process in the comparative document. The energy consumption is significantly reduced, the total working time is short, the production efficiency is high, and it is suitable for continuous and large-scale production.

[0019] 3. The protective tube prepared by this invention maintains high bending strength, bending modulus and ring stiffness, while also having excellent notched impact strength and extremely low embrittlement temperature, achieving a good balance between high toughness and high rigidity. At the same time, the material also exhibits good wear resistance, flame retardancy and thermal stability, which can meet the long-term use requirements in complex and harsh environments.

[0020] 4. The raw material system is relatively simple, mainly using polyvinyl chloride resin, EVA, specific inorganic fillers and conventional additives, avoiding the use of expensive and diverse nanofillers and special rubbers. The overall raw material cost is effectively controlled, and the performance is better than or equivalent to complex formulation systems, with higher cost performance and market competitiveness. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the manufacturing process of an MPP power cable protection pipe according to the present invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0023] An MPP power cable protection conduit is made from raw materials comprising the following parts by weight: 100 parts of polyvinyl chloride resin; 15-30 parts of ethylene-vinyl acetate copolymer; 5-15 parts of pre-crosslinked silicone microspheres; 20-40 parts of composite inorganic filler; 0.5-2 parts of silane coupling agent; 2-5 parts heat stabilizer; 1-3 parts lubricant; 3-8 parts flame retardant; Among them, the pre-crosslinked organosilicon microspheres are prepared by emulsion crosslinking of vinyl silicone oil and hydrogen-containing silicone oil under the action of platinum catalyst, with an average particle size of 1-10μm; the composite inorganic filler is composed of silicon nitride, modified mica powder and fumed silica in a weight ratio of (1-3):(2-5):(1-2).

[0024] Furthermore, the vinyl acetate content in the ethylene-vinyl acetate copolymer is 18-28% by mass, and the melt flow rate is 3-10 g / 10 min.

[0025] Furthermore, in the pre-crosslinked organosilicon microspheres, the mass ratio of vinyl silicone oil to hydrogen-containing silicone oil is (5-8):1. The viscosity of the vinyl silicone oil is 10000-50000 mPa·s, and the vinyl molar content is 1.5-3.0%. The viscosity of the hydrogen-containing silicone oil is 20-50 mm² / s, and the active hydrogen content is 0.8-1.5%. The emulsion crosslinking method uses a nonionic surfactant as the emulsifier, the reaction temperature is 60-80℃, and the reaction time is 2-4 hours.

[0026] Furthermore, the modified mica powder is flaky mica with a particle size D50 of 800-1500 mesh, which has been surface-treated with a silane coupling agent.

[0027] Furthermore, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

[0028] Furthermore, the heat stabilizer is a calcium-zinc composite stabilizer; the lubricant is polyethylene wax or oxidized polyethylene wax; and the flame retardant is at least one of ammonium polyphosphate and melamine cyanurate.

[0029] A manufacturing process for an MPP power cable protection pipe as described above includes the following steps: S1. Preparation of pre-crosslinked organosilicon microspheres: Vinyl silicone oil, hydrogen-containing silicone oil, emulsifier and water are mixed and emulsified by high-speed shearing to form a stable emulsion. Platinum catalyst is added and reacted at 60-80℃ for 2-4 hours. After washing and drying, pre-crosslinked organosilicon microspheres are obtained. S2. Pretreatment of filler: Silicon nitride, modified mica powder, silica and silane coupling agent are mixed in a high-speed mixer at 90-110℃ for 5-15 minutes to obtain surface-treated composite inorganic filler. S3. High-speed hot mixing: Polyvinyl chloride resin and ethylene-vinyl acetate copolymer are added to a high-speed mixer. After heating to 90-110℃, the pre-crosslinked organosilicon microspheres obtained in step S1, the surface-treated composite inorganic filler obtained in step S2, heat stabilizer, lubricant and flame retardant are added in sequence. The mixture is continued at a speed of 800-1200 rpm until the material temperature reaches 115-125℃ to obtain a uniform premix. S4. Melt Extrusion and Molding: The premixed material is fed into a twin-screw extruder and melt-plasticized, extruded and granulated within a processing temperature range of 150-190℃ to obtain masterbatch; the masterbatch is then fed into a pipe extruder and, under a die temperature of 175-185℃ and a vacuum shaping pressure of -0.06 to -0.08MPa, is extruded, shaped, cooled, drawn and cut to obtain MPP power cable protection pipe.

[0030] Furthermore, the total mixing time for high-speed hot mixing in step S3 is 8-15 minutes.

[0031] Furthermore, the specific processing temperatures of the twin-screw extruder in step S4 are set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, Zone 4 175-185℃, and Die head 180-190℃.

[0032] Furthermore, in step S4, the screw speed of the pipe extruder is 15-25 rpm. Example 2

[0033] High-toughness MPP power cable protection pipe This embodiment aims to provide an MPP power cable protection pipe that maintains good rigidity while highlighting high toughness and low temperature resistance, making it particularly suitable for areas with cold winters or large temperature differences between day and night, such as some areas of Heilongjiang Province, China.

[0034] 1. Raw materials and proportions: Polyvinyl chloride resin: 100 parts by weight, using Qilu Petrochemical S-1000 type with a degree of polymerization of 1300.

[0035] Ethylene-vinyl acetate copolymer: 28 parts by weight, using Formosa Plastics UE630 with a vinyl acetate content of 26% and a melt flow rate of 5.0 g / 10 min.

[0036] Pre-crosslinked silicone microspheres: 12 parts by weight, prepared as follows: Vinyl silicone oil: Dow Corning PMX-200 series, viscosity 20000 mPa·s, vinyl content 2.5%.

[0037] Hydrogen-containing silicone oil: Dow Corning HMS-501 series hydrogen-containing silicone oil with a viscosity of 30 mm was selected. 2 / s, with an active hydrogen content of 1.2%.

[0038] Mix vinyl silicone oil and hydrogen-containing silicone oil at a mass ratio of 7:1.

[0039] Emulsifier: OP-10, a nonionic emulsifier of fatty alcohol polyoxyethylene ether, is used.

[0040] In a reaction vessel, the above mixture is emulsified with water and emulsifier at a high speed of 3000 rpm for 20 minutes to form a stable emulsion.

[0041] A solution of isopropanol chloroplatinate at 0.3% of the mass of vinyl silicone oil was added as a platinum catalyst.

[0042] The reaction was carried out at a constant temperature of 75°C for 3.5 hours.

[0043] After the reaction was completed, the microspheres were centrifuged, washed, and dried under vacuum at 80°C for 12 hours to obtain pre-crosslinked organosilicon microspheres with an average particle size of about 5 μm.

[0044] Composite inorganic filler: 28 parts by weight, composed of silicon nitride, modified mica powder, and precipitated silica in a weight ratio of 1.5:4:1.5. The silicon nitride is UB-E05 grade from Tokuyama Corporation of Japan, the modified mica powder has a particle size D50 of 1000 mesh and has been treated with γ-aminopropyltriethoxysilane, and the precipitated silica is Aerosil 200 from Evonik Industries of Germany.

[0045] Silane coupling agent: 1.2 parts by weight, using γ-aminopropyltriethoxysilane.

[0046] Heat stabilizer: 3 parts by weight, using Baeropan MC 8368 KA type calcium-zinc composite stabilizer.

[0047] Lubricant: 2 parts by weight, using Clariant's Licowax PE 520 oxidized polyethylene wax.

[0048] Flame retardant: 5 parts by weight, made by compounding ammonium polyphosphate and melamine cyanurate in a 1:1 mass ratio.

[0049] 2. Preparation process: S2. Pretreatment of filler: Add the composite inorganic filler and silane coupling agent to a high-speed mixer and mix at 105℃ and 600rpm for 10 minutes.

[0050] S3. High-speed hot mixing: Add PVC resin and EVA to a high-speed mixer, heat to 100°C, and then add pre-crosslinked silicone microspheres, pretreated composite inorganic fillers, heat stabilizers, lubricants and flame retardants in sequence. Increase the speed to 1000 rpm and mix for 12 minutes until the material temperature reaches 120°C to obtain a premix.

[0051] S4. Melt extrusion and molding: Granulation: The premixed material is fed into a co-rotating twin-screw extruder, and the temperature is set to 155℃ in zone 1, 165℃ in zone 2, 175℃ in zone 3, 180℃ in zone 4, and 185℃ at the die head. The material is melt-extruded, water-cooled, and pelletized to obtain masterbatch.

[0052] Pipe forming: The masterbatch is fed into a single-screw pipe extruder, the screw speed is set to 20 rpm, the die temperature is set to 180℃, and the vacuum forming chamber pressure is set to -0.07MPa. After extrusion, vacuum forming, spray cooling, traction, and fixed-length cutting, an MPP power cable protection pipe with an outer diameter of 110mm and a wall thickness of 5mm is obtained. Example 3

[0053] High wear-resistant and high rigidity MPP power cable protection pipe This embodiment aims to provide an MPP power cable protection pipe with excellent wear resistance, high ring stiffness and long-term thermal stability when used in complex geological conditions or areas with high traffic volume.

[0054] 1. Raw materials and proportions: Polyvinyl chloride resin: 100 parts by weight, using Tianjin Dagu Chemical DG-800 type with a degree of polymerization of 1200.

[0055] Ethylene-vinyl acetate copolymer: 18 parts by weight, using Yangzi BASF V4110J with a vinyl acetate content of 20% and a melt flow rate of 8.0 g / 10 min.

[0056] Pre-crosslinked silicone microspheres: 8 parts by weight, prepared as follows: Vinyl silicone oil: XHG-802 from Blue Star Fire Chemical Co., Ltd. was selected, with a viscosity of 45000 mPa·s and a vinyl molar content of 2.8%.

[0057] Hydrogen-containing silicone oil: XHG-301 from Blue Star Spark Chemical Co., Ltd., with a viscosity of 45 mm. 2 / s, with an active hydrogen content of 1.0%.

[0058] The mass ratio of vinyl silicone oil to hydrogen-containing silicone oil is 5.5:1.

[0059] Emulsifier: TX-10, an alkylphenol polyoxyethylene ether emulsifier, is used.

[0060] The emulsification and reaction process was the same as in Example 2, with the reaction temperature set at 70°C and the reaction time at 3 hours.

[0061] Pre-crosslinked silicone microspheres with an average particle size of approximately 3 μm were obtained.

[0062] Composite inorganic filler: 38 parts by weight, made of silicon nitride, modified mica powder and precipitated silica mixed in a weight ratio of 2.5:3:1.5. The modified mica powder has a particle size D50 of 1200 mesh and is treated with γ-glycidoxypropyltrimethoxysilane.

[0063] Silane coupling agent: 1.8 parts by weight, using γ-glycidoxypropyltrimethoxysilane.

[0064] Heat stabilizer: 4.5 parts by weight, using ADK ST-3000S type calcium-zinc composite stabilizer.

[0065] Lubricant: 1.5 parts by weight, using Honeywell AC 6A polyethylene wax.

[0066] Flame retardant: 7 parts by weight, all of which are ammonium polyphosphate.

[0067] 2. Preparation process: S2. Packing pretreatment: Mix and treat at 100℃ and 500rpm for 12 minutes.

[0068] S3, High-speed hot mixing: Mixing speed 1100 rpm, mixing time 10 minutes, final temperature 118℃.

[0069] S4. Melt extrusion and molding: Granulation: The extruder temperature is set as follows: Zone 1 150℃, Zone 2 160℃, Zone 3 170℃, Zone 4 175℃, and Die head 182℃.

[0070] Tube forming: Screw speed 18 rpm, mold temperature 178℃, vacuum forming pressure -0.075MPa, to produce protective tubes of the same specifications.

[0071] Compare with Example 1 For a fair comparison, the polyvinyl chloride resin of Example 1 was used as a benchmark, and a complex formulation approach using multiple traditional toughening agents and fillers in the prior art was adopted, using a mixed extrusion process similar to that of the present invention.

[0072] Raw materials: 100 parts polyvinyl chloride resin, 25 parts propylene-ethylene random copolymer, 12 parts fluorosilicone rubber, 15 parts oxidized polyethylene wax, 8 parts nano-silica powder, 5 parts nano-calcium carbonate, 6 parts fumed silica, 12 parts silicon nitride, 10 parts silicon carbide, 3 parts mica powder, 6 parts carbon fiber, 10 parts expandable graphite, 3 parts CPE flame retardant, and 6 parts lithium ceramic stone powder.

[0073] Preparation: All powdered fillers were pre-mixed at low speed. PVC, propylene-ethylene copolymer, fluorosilicone rubber, and oxidized polyethylene wax were mixed at 165°C for 25 minutes. All components were then mixed and stirred at 5000 rpm at room temperature for 20 minutes. The subsequent extrusion granulation and pipe forming process parameters were kept as consistent as possible with those in Example 1.

[0074] Compare with Example 2 For a fair comparison, the polyvinyl chloride resin of Example 1 was used as a benchmark, and reference was made to a prior art formulation and method that uses a PVC / CPVC / EVA alloy combined with a long-term in-situ crosslinking process.

[0075] Raw materials: Prepare 100 parts of PVC-CPVC-EVA alloy, wherein the mass ratio of PVC, CPVC and EVA is 1:1.5:0.1, the chlorine content of CPVC is 68% and the degree of polymerization is 650, the number average molecular weight of EVA is 242k, 10 parts of reinforcing fiber, 25 parts of inorganic filler, 10 parts of organosilicon crosslinking system, 1 part of plasticizer, and 3 parts of lubricant.

[0076] Preparation: The process strictly follows conventional methods, including premixing, long-term vacuum melt crosslinking, and remixing and extrusion.

[0077] Compare with Example 3 This comparative example aims to verify the necessity of the key component, pre-crosslinked silicone microspheres. Its formulation is basically the same as that of Example 1, but the preparation and addition steps of the pre-crosslinked silicone microspheres are omitted, and their weight parts are replaced with an equal amount of ethylene-vinyl acetate copolymer. At the same time, the silane coupling agent is omitted, and steps S1 and S2 are omitted in the preparation process.

[0078] Experimental Data and Effect Analysis The power cable protection pipes prepared by the above embodiments and the control examples were tested in a unified manner, and the results are shown in the table below.

[0079] Table 1: Comparison of Performance Test Results of MPP Power Cable Protection Pipes Test Project Example 1 Example 2 Example 3 Compare with Example 1 Compare with Example 2 Compare with Example 3 <![CDATA[Notch impact strength, kJ / m 2 > 85.2 92.5 78.8 65.1 72.4 58.3 Bending strength, MPa 79.8 76.5 83.2 82.1 77.6 71.0 Flexural modulus, MPa 2850 2610 3120 2980 2740 2430 <![CDATA[Ring stiffness, kN / m 2 > 24.5 23.2 26.8 25.1 23.8 21.5 Embrittlement temperature, ℃ -52 -58 -48 -41 -45 -38 Heat distortion temperature, °C 78 75 82 80 76 72 Wear amount, mg 11.5 13.2 9.8 15.8 12.1 18.7 Oxygen index, % 34.5 33.8 35.2 32.0 33.5 31.5 Total preparation time, h 4.5 4.5 4.5 4.0 17.0 3.5 Raw material cost index 100 105 108 125 115 95 As can be seen from the table above: 1. The notched impact strength and embrittlement temperature of Examples 1 to 3 are significantly better than those of all control examples. In Example 2, by increasing the content of ethylene-vinyl acetate copolymer and optimizing the ratio of organosilicon microspheres to fillers, the impact strength reached 92.5 kJ / m. 2 With an embrittlement temperature as low as -58°C, it exhibits the best toughness. Comparative Example 1 uses a variety of traditional toughening agents and fillers, but lacks the synergistic toughening network of the pre-crosslinked organosilicon microspheres and ethylene-vinyl acetate copolymer of this invention, as well as the strong interface constructed by the silane coupling agent, resulting in the lowest impact toughness. Comparative Example 2 uses in-situ crosslinked organosilicon, but the process is complex and takes up to 17 hours, and the chlorinated polyvinyl chloride emulsion itself has poor toughness, so the final impact performance is still lower than that of this invention. Comparative Example 3 directly proves the key role of the pre-crosslinked organosilicon microspheres. Using only ethylene-vinyl acetate copolymer for toughening, the material has the worst impact strength and low-temperature brittleness, indicating that the toughening effect of a single rubber phase is limited, while organosilicon microspheres, as a second-phase elastomer, can more effectively induce crazes and shear bands and prevent crack propagation.

[0080] 2. Example 3 achieved the highest flexural strength of 83.2 MPa, flexural modulus of 3120 MPa, and ring stiffness of 26.8 kN / m by increasing the proportion of high-hardness silicon nitride and optimizing the filler gradation. 2 The lowest wear loss was 9.8 mg, and the heat distortion temperature reached 82℃. Although the rigidity index of Comparative Example 1 was acceptable, its filler system was complex and had not undergone system interface treatment, resulting in significantly worse wear resistance than that of the present invention. The rigidity and wear resistance of Comparative Example 2 were between those of the embodiments of the present invention, but its high energy consumption and long cycle caused by its process were significant drawbacks. The modified mica powder of the present invention played an important role. The lamellar mica formed a physical barrier in the matrix, formed a composite reinforcement system with silicon nitride and silica, and interacted with the organosilicon microspheres grafted with silane coupling agent, jointly contributing high rigidity, high wear resistance and good flame retardancy.

[0081] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. An MPP power cable protection pipe, characterized in that, Made from the following ingredients in parts by weight: 100 parts of polyvinyl chloride resin; 15-30 parts of ethylene-vinyl acetate copolymer; 5-15 parts of pre-crosslinked silicone microspheres; 20-40 parts of composite inorganic filler; 0.5-2 parts of silane coupling agent; 2-5 parts heat stabilizer; 1-3 parts lubricant; 3-8 parts flame retardant; The pre-crosslinked organosilicon microspheres are prepared by emulsion crosslinking of vinyl silicone oil and hydrogen-containing silicone oil under the action of platinum catalyst, with an average particle size of 1-10 μm; the composite inorganic filler is composed of silicon nitride, modified mica powder and fumed silica in a weight ratio of (1-3):(2-5):(1-2).

2. The MPP power cable protection pipe according to claim 1, characterized in that, The ethylene-vinyl acetate copolymer has a vinyl acetate content of 18-28% by mass and a melt flow rate of 3-10 g / 10 min.

3. The MPP power cable protection pipe according to claim 1, characterized in that, In the pre-crosslinked organosilicon microspheres, the mass ratio of vinyl silicone oil to hydrogen-containing silicone oil is (5-8):

1. The viscosity of the vinyl silicone oil is 10000-50000 mPa·s, and the vinyl molar content is 1.5-3.0%. The viscosity of the hydrogen-containing silicone oil is 20-50 mm² / s, and the active hydrogen content is 0.8-1.5%. The emulsion crosslinking method uses a nonionic surfactant as the emulsifier, the reaction temperature is 60-80℃, and the reaction time is 2-4 hours.

4. The MPP power cable protection pipe according to claim 1, characterized in that, The modified mica powder is flaky mica that has been surface-treated with a silane coupling agent, with a particle size D50 of 800-1500 mesh.

5. The MPP power cable protection pipe according to claim 1, characterized in that, The silane coupling agent is at least one of γ-aminopropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane.

6. The MPP power cable protection pipe according to claim 1, characterized in that, The heat stabilizer is a calcium-zinc composite stabilizer; the lubricant is polyethylene wax or oxidized polyethylene wax; and the flame retardant is at least one of ammonium polyphosphate and melamine cyanurate.

7. A manufacturing process for an MPP power cable protection pipe as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of pre-crosslinked organosilicon microspheres: Vinyl silicone oil, hydrogen-containing silicone oil, emulsifier and water are mixed and emulsified by high-speed shearing to form a stable emulsion. Platinum catalyst is added and reacted at 60-80℃ for 2-4 hours. After washing and drying, pre-crosslinked organosilicon microspheres are obtained. S2. Pretreatment of filler: Silicon nitride, modified mica powder, silica and silane coupling agent are mixed in a high-speed mixer at 90-110℃ for 5-15 minutes to obtain surface-treated composite inorganic filler. S3. High-speed hot mixing: Polyvinyl chloride resin and ethylene-vinyl acetate copolymer are added to a high-speed mixer. After heating to 90-110℃, the pre-crosslinked organosilicon microspheres obtained in step S1, the surface-treated composite inorganic filler obtained in step S2, heat stabilizer, lubricant and flame retardant are added in sequence. The mixture is continued at a speed of 800-1200 rpm until the material temperature reaches 115-125℃ to obtain a uniform premix. S4. Melt Extrusion and Molding: The premixed material is fed into a twin-screw extruder and melt-plasticized, extruded and granulated within a processing temperature range of 150-190℃ to obtain masterbatch; the masterbatch is then fed into a pipe extruder and, under a die temperature of 175-185℃ and a vacuum shaping pressure of -0.06 to -0.08MPa, is extruded, shaped, cooled, drawn and cut to obtain MPP power cable protection pipe.

8. The preparation process according to claim 7, characterized in that, The total mixing time for high-speed thermal mixing in step S3 is 8-15 minutes.

9. The preparation process according to claim 7, characterized in that, The specific processing temperatures of the twin-screw extruder in step S4 are set as follows: Zone 1 150-160℃, Zone 2 160-170℃, Zone 3 170-180℃, Zone 4 175-185℃, and Die head 180-190℃.

10. The preparation process according to claim 7, characterized in that, In step S4, the screw speed of the pipe extruder is 15-25 rpm.

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