Modification formula and production process of impact-resistant and high-heat-resistant MPP cable protection pipe

Abstract

The invention relates to the technical field of high polymer material modification and processing, in particular to a modification formula and production process of an impact-resistant and high-heat-resistant MPP cable protection tube, and the formula comprises 60-80 parts of a polypropylene base material, 8-15 parts of a nano-composite reinforcing agent, 5-12 parts of a heat-resistant modifier, 3-8 parts of an impact-resistant modifier and the like. The production process comprises the steps of nanofiller surface functionalization, multi-stage melt blending, dynamic vulcanization forming, pulse type vacuum setting and online detection, and the prepared pipe is excellent in impact resistance and heat resistance and high in size precision. The pipe provided by the invention has the advantages of zero fracture in drop hammer impact, vicat softening temperature of 152 DEG C, ring stiffness of 60.16 kN / m < 2 > and small dimensional deviation; the process improves filler dispersity, has low rejection rate and energy consumption, has comprehensive performance superior to that of traditional products, and is suitable for complex working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material modification and processing, and in particular to a modified formula and production process of an impact-resistant and highly heat-resistant MPP cable protection tube. Background Art

[0002] MPP (modified polypropylene) cable protection tubing is widely used in cable laying projects in the power, communications, and other fields due to its excellent insulation properties, chemical resistance, and ease of construction. With the acceleration of urbanization and the upgrading of infrastructure construction, the cable laying environment is becoming increasingly complex, placing higher demands on the performance of the protection tubing. In particular, when crossing high-load areas such as roads and bridges, and in harsh operating conditions such as high temperature and high humidity, traditional MPP cable protection tubing has exposed defects such as insufficient impact resistance and poor thermal stability. These defects can easily lead to cracking and deformation of the tubing, which can cause cable failures, increase maintenance costs, and pose safety risks.

[0003] From the perspective of materials, traditional MPP formulas mainly rely on a single polypropylene substrate and lack an efficient reinforcement and toughening system. Although existing technologies improve rigidity by adding fillers such as calcium carbonate and talc, the problem of nano-scale dispersion leads to weak interfacial bonding, and the material is prone to stress concentration, and the improvement in impact resistance is limited (such as the breakage rate in the drop hammer impact test is as high as 30%). In terms of heat resistance, the Vicat softening temperature of ordinary polypropylene is only about 130°C, which is difficult to meet the needs of long-term service in an environment above 60°C. Creep deformation is prone to occur at high temperatures, affecting cable safety. In addition, problems such as uneven melt blending and insufficient control of molding stress in traditional production processes further aggravate the discreteness of product performance.

[0004] Existing improvement technologies mostly focus on adjusting a single component. For example, improving impact resistance by adding rubber elastomers can easily lead to a decrease in heat resistance; or enhancing heat resistance by introducing glass fiber, but uneven fiber dispersion can cause processing difficulties and deterioration of mechanical properties. At the same time, the production process lacks precise control over the material's microstructure, making it difficult to achieve a synergistic improvement in impact resistance and heat resistance. For example, conventional extrusion molding cannot construct a gradient structure, resulting in poor overall performance balance of the pipe, making it unable to adapt to the differentiated needs of complex service environments.

[0005] With the rapid development of new energy, smart grid and other fields, the market has put forward clear requirements for the performance of MPP cable protection pipes: impact resistance must meet the conditions of zero cracking under the conditions of a drop weight of 15kg and an impact height of 1.2m (such as DL / T 802.7-2023 standard), Vicat softening temperature must be ≥150℃, and at the same time, it must have excellent dimensional stability (longitudinal shrinkage rate ≤3%) and long-term load resistance (ring stiffness ≥40kN / m 2). Traditional technical routes are no longer able to meet the above indicators. There is an urgent need to develop a comprehensive innovative solution from formulation design to production process, which can achieve a leapfrog improvement in material performance through multi-component synergistic modification and multi-field regulation technology. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In view of the shortcomings of the existing technology, the present invention provides a modified formula and production process of an impact-resistant and highly heat-resistant MPP cable protection tube.

[0008] (2) Technical solution

[0009] A modified formula for an impact-resistant and high-heat-resistant MPP cable protection tube comprises the following components by weight: 60-80 parts of a polypropylene base material; 8-15 parts of a nanocomposite reinforcing agent; 5-12 parts of a heat-resistant modifier; 3-8 parts of an impact-resistant modifier; 1-3 parts of a stabilizer; 0.5-2 parts of a coupling agent; 0.3-1 parts of a lubricant; and 0.2-1 parts of an innovative functional additive.

[0010] The nanocomposite reinforcing agent is 0.5-2 parts of graphene, 3-6 parts of nano-silicon dioxide, and 2-5 parts of carbon fiber; the heat-resistant modifier is 3-8 parts of maleic anhydride grafted polypropylene, 2-4 parts of silicone resin, and 1-3 parts of silicon carbide whiskers; the impact modifier is 2-5 parts of EPDM rubber, 1-3 parts of hydrogenated styrene-butadiene block copolymer, and 0.5-2 parts of liquid nitrile rubber;

[0011] The stabilizer is 0.5-1.5 parts of calcium stearate, 0.3-1 parts of hindered phenol antioxidant, 0.2-0.5 parts of ultraviolet absorber, and 0.3-1 parts of nano-montmorillonite; the coupling agent is 0.3-1.2 parts of silane coupling (KH-560), 0.2-0.8 parts of titanate coupling (NDZ-101), and 0.1-0.5 parts of aluminate coupling agent (DL-411); the lubricant is 0.1-0.6 parts of polyethylene wax, 0.2-0.4 parts of stearic acid; the carbon nanotube dispersion is 0.1-0.5 parts, and the nano-boron nitride is 0.1-0.5 parts.

[0012] Preferably, the silicon carbide whisker has a diameter of 0.5-2 μm, a length of 10-50 μm, an aspect ratio of ≥10:1, and a heat-resistant temperature of ≥1600°C.

[0013] Preferably, the liquid nitrile rubber has an acrylonitrile content of 25%-40% and a molecular weight of 3000-8000, and forms an elastomeric microsphere dispersed phase during blending.

[0014] Preferably, the interlayer spacing of the nano-montmorillonite is ≥1.5 nm, and the cation exchange capacity is 90-120 mmol / 100 g after intercalation treatment with an organic quaternary ammonium salt.

[0015] Preferably, the modified formula production process of the impact-resistant and high-heat-resistant MPP cable protection tube comprises the following steps:

[0016] S1: Multi-stage melt blending

[0017] The MPP substrate and the heat-resistant modifier and impact modifier were melted and plasticized at 190°C in a single-screw extruder to form a basic masterbatch; the basic masterbatch and the nanocomposite reinforcing agent, stabilizer and functional additive were added to the twin-screw extruder, and the three-zone temperature was set at 200°C, 220°C and 230°C, the screw speed was 400 rpm, and the blending time was 15 minutes;

[0018] S2: Dynamic vulcanization molding

[0019] A dynamic vulcanization unit is set up in front of the extrusion die, and nitrogen protection is introduced to form an interpenetrating network structure between EPDM and SEBS at a pressure of 10-20 MPa and a temperature of 200-220°C;

[0020] S3: Pulse vacuum setting

[0021] During cooling and shaping, a pulsed vacuum system is used with a vacuum degree of -0.05 to -0.08 MPa and a pulse frequency of 1-3 times / minute to promote rapid and uniform cooling of the inner and outer surfaces of the pipe;

[0022] S4: Online Defect Detection

[0023] Laser diameter gauge and industrial CT are used to detect the dimensional accuracy and internal defects of pipes online, with a scrap rate of ≤0.5%.

[0024] Preferably, the method further comprises treating the nano-silica carbon fiber and the silane coupling agent KH-560 in a high-speed mixer in proportion before melt blending to form a core-shell structure filler with the surface coated with the silane coupling agent.

[0025] Preferably, a gradient structure design is also included: during extrusion molding, the outer layer of the pipe contains 30%-50% nano-composite reinforcing agent and the inner layer contains 10%-20% impact modifier through the layered feeding device inside the mold, forming a gradient structure that is strong on the outside and tough on the inside.

[0026] Preferably, the residence time of the dynamic vulcanization unit in step S3 is 30-60 seconds, and the degree of vulcanization is controlled at 80%-90%.

[0027] Preferably, in step S4, the cooling water tank has a length of ≥5 m, a water temperature of 10-15° C. in the front section, and a water temperature of 15-20° C. in the rear section, and is equipped with an ultrasonic descaling device.

[0028] Preferably, in the step S5, a laser diameter gauge monitors the average inner diameter and wall thickness out-of-roundness of the pipe in real time, and the data is fed back to the extruder traction speed control system to achieve closed-loop control.

[0029] (3) Beneficial technical effects

[0030] Compared with the existing technology, the beneficial effects of the present invention are:

[0031] 1. By introducing a composite impact-resistant system consisting of EPDM rubber, hydrogenated styrene-butadiene block copolymer, and liquid nitrile rubber, combined with a dynamic vulcanization process, a dispersed phase of nano-elastomer microspheres is formed within the material, effectively absorbing impact energy. Testing showed that none of the ten specimens tested under a 15kg drop weight and an impact height of 1200mm exhibited crack resistance, demonstrating improved impact resistance. Furthermore, the gradient structural design enhances the rigidity of the pipe's outer layer and enhances the toughness of its inner layer, creating a "strong exterior, tough interior" impact-resistant barrier that is particularly suitable for high-load installations.

[0032] 2. A heat-resistant modified system composed of maleic anhydride-grafted polypropylene, silicone resin, and silicon carbide whiskers enhances inter-molecular chain forces and high-temperature rigidity through the dual effects of chemical grafting and physical filling. The Vicat softening temperature reaches 152°C. In a constant-temperature load test at 80°C, the pipe's deformation rate is significantly lower than that of conventional products. Its long-term heat resistance meets the heat dissipation requirements of high-voltage cables. Furthermore, the incorporation of nano-boron nitride creates a highly efficient thermal conductivity network, resulting in excellent heat dissipation performance. At room temperature, both the inner and outer wall temperatures remain ≤30°C, preventing potential safety hazards associated with cable overheating.

[0033] 3. The nanocomposite reinforcement, treated with a silane coupling agent for surface functionalization, forms a strong interfacial bond with the polypropylene substrate, achieving the required ring stiffness and tensile strength required for high-strength installation. The production process utilizes multi-stage melt blending and pulsed vacuum shaping technology, resulting in enhanced nanofiller dispersion uniformity and significantly improved pipe dimensional accuracy, with a curvature of only 0.2%, facilitating installation and joint sealing.

[0034] 4. The formula utilizes environmentally friendly stabilizers and recyclable additives, resulting in a production process that releases no hazardous substances and complies with RoHS standards. The process utilizes online defect detection and a closed-loop control system to minimize scrap rates. Cooling water recycling and energy recovery technologies also reduce energy consumption. Overall, the product's lifespan is extended, and its lifecycle costs are lower than those of traditional processes, achieving both economic benefits and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a process flow chart for producing a modified formula of an impact-resistant and heat-resistant MPP cable protection tube disclosed by the present invention;

[0036] Figure 21. is a broken line comparison diagram of ring stiffness and elongation at break of the embodiment and the comparative example;

[0037] Figure 3 1. This is a comparison chart of the qualified number of drop hammer impact and the longitudinal shrinkage rate of the embodiment and the comparative example;

[0038] Figure 4 1. It is a bar graph comparing the out-of-roundness and curvature of the embodiment and the comparative example;

[0039] Figure 5 This is a radar comparison chart made after the dimensional accuracy data of the embodiment and the comparative example were unified in dimension. DETAILED DESCRIPTION

[0040] according to Figures 1 to 5 , the specific implementation methods of the present invention are as follows:

[0041] 1. Example 1: Preparation of MPP Cable Protection Tube by Standard Formula and Process

[0042] 1. Modified formula (by weight)

[0043] Polypropylene substrate: 70 parts;

[0044] Nanocomposite reinforcing agent: 12 parts (graphene 1 part, nano-silica 5 parts, carbon fiber 6 parts);

[0045] Heat-resistant modifier: 8 parts (maleic anhydride grafted polypropylene 5 parts, silicone resin 2 parts, silicon carbide whisker 1 part);

[0046] Impact modifier: 5 parts (3 parts EPDM rubber, 1.5 parts hydrogenated styrene-butadiene block copolymer, 0.5 parts liquid nitrile rubber);

[0047] Stabilizer: 2 parts (1 part calcium stearate, 0.6 part hindered phenol antioxidant, 0.3 part ultraviolet absorber, 0.1 part nano-montmorillonite);

[0048] Coupling agent: 1.2 parts (0.8 parts of silane coupling agent KH-560, 0.3 parts of titanate coupling agent NDZ-101, and 0.1 parts of aluminate coupling agent DL-411);

[0049] Lubricant: 0.5 parts (0.3 parts of polyethylene wax, 0.2 parts of stearic acid);

[0050] Innovative functional additives: 0.6 parts (0.3 parts of carbon nanotube dispersion, 0.3 parts of nano-boron nitride);

[0051] 2. The entire production process

[0052] S1: Surface functionalization of nanofillers

[0053] Graphene, nano-silica (particle size 30 nm), carbon fiber (diameter 8 μm, length 1 mm), silane coupling agent KH-560, and titanate coupling agent NDZ-101 were put into a high-speed mixer in a ratio of 10:0.8:0.3. The temperature was set at 120°C and the speed was 1500 rpm. The mixture was processed for 30 minutes to graft silane and titanate functional groups on the filler surface to form a core-shell structure with enhanced dispersibility.

[0054] S2: Multi-stage melt blending

[0055] Step 1: Put the polypropylene substrate, maleic anhydride grafted polypropylene, EPDM rubber, etc. into a single screw extruder, set the temperature to 190℃, the screw speed to 200rpm, melt and plasticize for 30 minutes to obtain a uniform basic masterbatch;

[0056] Step 2: Add the base masterbatch, nano-composite reinforcing agent, stabilizer, innovative functional additives, etc. into a twin-screw extruder (model: co-rotating parallel twin screw, L / D = 40:1), set the temperature of zone 1 to 200°C, zone 2 to 220°C, zone 3 to 230°C, and the screw speed to 400 rpm. Blend for 15 minutes. The melt is monitored by a pressure sensor and the pressure is controlled at 8-10 MPa.

[0057] S3: Dynamic vulcanization molding

[0058] A dynamic vulcanization unit was installed in the front section of the extrusion die, and nitrogen (purity ≥99.9%) was introduced. The pressure was set at 15 MPa and the temperature was set at 210°C. Under the action of shear force, EPDM rubber (ethylene content 60%) and hydrogenated styrene-butadiene block copolymer (styrene content 25%) formed an interpenetrating network structure. The residence time was 45 seconds and the degree of vulcanization was 85%. The die adopted a streamlined flow channel design (compression ratio 4:1). The melt was extruded through the die into a tubular billet with an outer diameter of 250 mm and a wall thickness of 22 mm. The pulling speed was 2 m / min, and 0.1 MPa compressed air was simultaneously introduced to maintain the tube shape.

[0059] S4: Pulse vacuum setting

[0060] The cooling water tank is 6 meters long, with water temperatures of 12°C in the front section and 18°C ​​in the back section. It is equipped with a pulsed vacuum system (vacuum degree -0.06MPa, pulse frequency 2 times / minute). As the billet passes through the tank, vacuum pulses promote uniform cooling of the inner and outer surfaces. The cooling time is 8 minutes, and the final pipe surface temperature is 35°C.

[0061] S5: Online Defect Detection

[0062] Laser diameter measuring instruments monitor the pipes' average inner diameter (250.3mm), wall thickness (22.1mm), and out-of-roundness (0.5mm). Industrial CT scans confirm no internal defects, such as bubbles or cracks, with a scrap rate of 0.3%. The pipes are cut into 9-meter lengths and packaged after passing inspection.

[0063] 2. Example 2: High Heat-Resistant Formula Optimization Process

[0064] 1. Modified formula adjustment (by weight)

[0065] Heat-resistant modifier: 12 parts (8 parts maleic anhydride grafted polypropylene, 3 parts silicone resin, 1 part silicon carbide whisker);

[0066] Nanocomposite reinforcing agent: 15 parts (graphene 2 parts, nano-silica 6 parts, carbon fiber 7 parts);

[0067] Innovative functional additives: 1 part (0.5 parts of carbon nanotube dispersion, 0.5 parts of nano-boron nitride);

[0068] Polypropylene substrate: 70 parts;

[0069] Impact modifier: 5 parts (3 parts EPDM rubber, 1.5 parts hydrogenated styrene-butadiene block copolymer, 0.5 parts liquid nitrile rubber);

[0070] Stabilizer: 2 parts (1 part calcium stearate, 0.6 part hindered phenol antioxidant, 0.3 part ultraviolet absorber, 0.1 part nano-montmorillonite);

[0071] Coupling agent: 1.2 parts (0.8 parts of silane coupling agent KH-560, 0.3 parts of titanate coupling agent NDZ-101, and 0.1 parts of aluminate coupling agent DL-411);

[0072] Lubricant: 0.5 parts (0.3 parts of polyethylene wax, 0.2 parts of stearic acid).

[0073] 2. The entire production process

[0074] S1: Surface functionalization of nanofillers

[0075] Graphene, nano-silica (particle size 30 nm), carbon fiber (diameter 8 μm, length 1 mm), silane coupling agent KH-560, and titanate coupling agent NDZ-101 were put into a high-speed mixer in a ratio of 10:0.8:0.3. The temperature was set at 120°C and the speed was 1500 rpm. The mixture was processed for 30 minutes to graft silane and titanate functional groups on the filler surface to form a core-shell structure with enhanced dispersibility.

[0076] S2: Multi-stage melt blending

[0077] Step 1: Put the polypropylene substrate, maleic anhydride grafted polypropylene, EPDM rubber, etc. into a single screw extruder, set the temperature to 190℃, the screw speed to 200rpm, melt and plasticize for 30 minutes to obtain a uniform basic masterbatch;

[0078] Step 2: Add the base masterbatch, nano-composite reinforcing agent, stabilizer, innovative functional additives, etc. into a twin-screw extruder (model: co-rotating parallel twin screw, L / D = 40:1), set the temperature of zone 1 to 200°C, zone 2 to 225°C, zone 3 to 235°C, and the screw speed to 450rpm. Blend for 20 minutes. The melt is monitored by a pressure sensor and the pressure is controlled at 8-10MPa to enhance the dispersion of silicon carbide whiskers (aspect ratio 15:1).

[0079] S3: Dynamic vulcanization molding

[0080] A dynamic vulcanization unit was installed in the front section of the extrusion die, and nitrogen (purity ≥99.9%) was introduced. The pressure was set at 20 MPa and the temperature was set at 220°C. Under the action of shear force, EPDM rubber (ethylene content 60%) and hydrogenated styrene-butadiene block copolymer (styrene content 25%) formed an interpenetrating network structure. The residence time was 60 seconds and the vulcanization degree was 90%, forming a denser elastomer network.

[0081] The mold adopts a streamlined flow channel design (compression ratio 4:1). The melt is extruded through the mold into a tubular billet with an outer diameter of 250 mm and a wall thickness of 22 mm. The pulling speed is 2 m / min, and 0.1 MPa compressed air is introduced simultaneously to maintain the tube shape.

[0082] S4: Pulse vacuum setting

[0083] The cooling water tank is 6 meters long, with water temperatures of 10°C in the front section and 15°C in the back section. It is equipped with a pulsed vacuum system (vacuum degree -0.08MPa, pulse frequency 3 times / minute). As the billet passes through the water tank, vacuum pulses promote uniform cooling of the inner and outer surfaces. The cooling time is 6 minutes, and the final pipe surface temperature is 35°C.

[0084] S5: Online Defect Detection

[0085] A laser diameter gauge (accuracy ±0.01mm) monitors the average inner diameter, wall thickness, and out-of-roundness of the pipe in real time. Industrial CT scans confirm that there are no bubbles, cracks, or other defects inside the pipe. The pipe is cut into 9-meter lengths and packaged after passing the inspection.

[0086] 1. Modified formula adjustment (by weight)

[0087] Impact modifier: 8 parts (5 parts EPDM rubber, 2 parts hydrogenated styrene-butadiene block copolymer, 1 part liquid nitrile rubber, liquid nitrile rubber acrylonitrile content 35%, molecular weight 5000);

[0088] Nanocomposite reinforcing agent: 8 parts (0.5 parts of graphene, 3 parts of nano-silica, 4.5 parts of carbon fiber);

[0089] Polypropylene substrate: 70 parts;

[0090] Heat-resistant modifier: 8 parts (maleic anhydride grafted polypropylene 5 parts, silicone resin 2 parts, silicon carbide whisker 1 part);

[0091] Stabilizer: 2 parts (1 part calcium stearate, 0.6 part hindered phenol antioxidant, 0.3 part ultraviolet absorber, 0.1 part nano-montmorillonite);

[0092] Coupling agent: 1.2 parts (0.8 parts of silane coupling agent KH-560, 0.3 parts of titanate coupling agent NDZ-101, and 0.1 parts of aluminate coupling agent DL-411);

[0093] Lubricant: 0.5 parts (0.3 parts of polyethylene wax, 0.2 parts of stearic acid);

[0094] Innovative functional additives: 0.6 parts (0.3 parts of carbon nanotube dispersion, 0.3 parts of nano-boron nitride).

[0095] 2. The entire production process

[0096] S1: Surface functionalization of nanofillers

[0097] Nano-silica (particle size 30 nm) and silane coupling agent KH-560 were put into a high-speed mixer in a ratio of 10:1.2, the temperature was set at 120°C and the speed was 2000 rpm, and the mixture was treated for 30 minutes to form a silane coating layer with a thickness of 50 nm; graphene, carbon fiber, silane coupling agent KH-560, and titanate coupling agent NDZ-101 were put into a high-speed mixer in a ratio of 10:0.8:0.3, the temperature was set at 120°C and the speed was 1500 rpm, and the mixture was treated for 30 minutes to graft silane and titanate functional groups on the filler surface.

[0098] S2: Multi-stage melt blending

[0099] Step 1: Put the polypropylene substrate, maleic anhydride grafted polypropylene, EPDM rubber, etc. into a single screw extruder, set the temperature to 190℃, the screw speed to 200rpm, melt and plasticize for 30 minutes to obtain a uniform basic masterbatch.

[0100] Step 2: Add the base masterbatch, nano-composite reinforcing agent, stabilizer, innovative functional additives, etc. into a twin-screw extruder (model: co-rotating parallel twin screw, L / D = 40:1), set the temperature of zone 1 to 200°C, zone 2 to 220°C, zone 3 to 230°C, and the screw speed to 400 rpm. Blend for 15 minutes. The melt is monitored by a pressure sensor and the pressure is controlled at 8-10 MPa.

[0101] S3: Dynamic vulcanization molding

[0102] A dynamic vulcanization unit was installed in front of the extrusion die. Nitrogen (purity ≥ 99.9%) was introduced, and the pressure was set at 10 MPa and the temperature at 200°C. This allowed EPDM rubber (ethylene content 60%) and hydrogenated styrene-butadiene block copolymer (styrene content 25%) to form an interpenetrating network structure under the action of shear force. The residence time was 30 seconds, and the degree of vulcanization was 80%, retaining more active groups in the elastomer.

[0103] The mold adopts a streamlined flow channel design (compression ratio 4:1). The melt is extruded through the mold into a tubular billet with an outer diameter of 250 mm and a wall thickness of 22 mm. The pulling speed is 2 m / min, and 0.1 MPa compressed air is introduced simultaneously to maintain the tube shape.

[0104] S4: Pulse vacuum setting

[0105] The cooling water tank is 6 meters long, with water temperatures of 12°C in the front section and 18°C ​​in the back section. It is equipped with a pulsed vacuum system (vacuum degree -0.06MPa, pulse frequency 2 times / minute). As the billet passes through the tank, vacuum pulses promote uniform cooling of the inner and outer surfaces. The cooling time is 8 minutes, and the final pipe surface temperature is 35°C.

[0106] S5: Gradient structure forming and online detection

[0107] The material is fed in layers through the mold, with the outer layer containing 45% nanocomposite reinforcement and the inner layer containing 18% impact modifier, forming a gradient structure with a hard outer layer and a soft inner layer. A laser diameter gauge (accuracy ±0.01mm) monitors the pipe's dimensional parameters in real time, and an industrial CT scan detects internal defects. The pipe is cut into 9-meter lengths and packaged after passing inspection.

[0108] 1. Formulation and process

[0109] Formula: 90 parts of polypropylene base material, 10 parts of calcium carbonate, 1 part of calcium stearate;

[0110] Process: single screw extruder melt blending (temperature 180℃), ordinary die extrusion, room temperature cooling, no nano fillers and dynamic vulcanization.

[0111] The performance comparison of the embodiment and the comparative example is shown in the following table:

[0112] Table 1

[0113] Test items Example 1 Example 2 Example 3 Comparative Example Vicat softening temperature (℃) 152 155 150 135 Drop hammer impact (15kg, 1.2m) 10 / 10 passed 10 / 10 passed 10 / 10 passed 6 / 10 rupture <![CDATA[Ring stiffness (kN / m 2 )]]> 60.16 65.2 58.5 35 Elongation at break (%) 177 165 177 130 Longitudinal shrinkage rate (%) 0.9 0.8 1.0 2.8

[0114] The Vicat softening temperatures of Examples 1-3 are all ≥150°C, and all are qualified in drop hammer impact tests. The ring stiffness is 67%-86% higher than that of the traditional process, the elongation at break is increased by 35%-36%, and the longitudinal shrinkage is reduced by 64%-71%. The comprehensive performance is significantly better than that of the comparative example.

[0115] The dimensional accuracy comparison between the embodiment and the comparative example is shown in the following table:

[0116] Table 2

[0117] Test items Standard requirements Example 1 Example 2 Example 3 Comparative Example Average inner diameter (mm) 250.0-251.5 250.3 250.1 250.5 252.1 Wall thickness (mm) 22±2.0 22.1 22.3 22.0 23.5 Out-of-roundness (mm) ≤4.2 0.5 0.4 0.6 3.8 Curvature (%) ≤0.5 0.2 0.15 0.25 1.1

[0118] The average inner diameter and wall thickness of Examples 1-3 are all controlled within the standard range, the out-of-roundness is ≤0.6 mm, the curvature is ≤0.25%, and the dimensional accuracy is significantly better than that of the traditional process.

[0119] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A modified formula of an impact-resistant and high-heat-resistant MPP cable protection tube, characterized in that: The components include the following by weight: 60-80 parts of polypropylene base material; 8-15 parts of nanocomposite reinforcing agent; 5-12 parts of heat-resistant modifier; 3-8 parts of impact modifier; 1-3 parts of stabilizer; 0.5-2 parts of coupling agent; 0.3-1 parts of lubricant; 0.2-1 parts of innovative functional additives; The nanocomposite reinforcing agent is 0.5-2 parts of graphene, 3-6 parts of nano-silicon dioxide, and 2-5 parts of carbon fiber; the heat-resistant modifier is 3-8 parts of maleic anhydride grafted polypropylene, 2-4 parts of silicone resin, and 1-3 parts of silicon carbide whiskers; the impact modifier is 2-5 parts of EPDM rubber, 1-3 parts of hydrogenated styrene-butadiene block copolymer, and 0.5-2 parts of liquid nitrile rubber; The stabilizer is 0.5-1.5 parts of calcium stearate, 0.3-1 parts of hindered phenol antioxidant, 0.2-0.5 parts of ultraviolet absorber, and 0.3-1 parts of nano-montmorillonite; the coupling agent is 0.3-1.2 parts of silane coupling (KH-560), 0.2-0.8 parts of titanate coupling (NDZ-101), and 0.1-0.5 parts of aluminate coupling agent (DL-411); the lubricant is 0.1-0.6 parts of polyethylene wax, 0.2-0.4 parts of stearic acid; the carbon nanotube dispersion is 0.1-0.5 parts, and the nano-boron nitride is 0.1-0.5 parts.

2. The modified formula of the impact-resistant and heat-resistant MPP cable protection tube according to claim 1 is characterized in that: The silicon carbide whisker has a diameter of 0.5-2 μm, a length of 10-50 μm, an aspect ratio of ≥10:1, and a heat-resistant temperature of ≥1600°C.

3. The modified formula of the impact-resistant and heat-resistant MPP cable protection tube according to claim 1, characterized in that: The liquid nitrile rubber has an acrylonitrile content of 25%-40% and a molecular weight of 3000-8000, and forms an elastomer microsphere dispersed phase during blending.

4. The modified formula of the impact-resistant and heat-resistant MPP cable protection tube according to claim 1, characterized in that: The interlayer distance of the nano-montmorillonite is ≥1.5nm, and the cation exchange capacity is 90-120mmol / 100g after intercalation treatment with an organic quaternary ammonium salt.

5. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 1 is characterized in that: The following steps are involved: S1: Multi-stage melt blending The MPP substrate and the heat-resistant modifier and impact modifier were melted and plasticized at 190°C in a single-screw extruder to form a basic masterbatch; the basic masterbatch and the nanocomposite reinforcing agent, stabilizer and functional additive were added to the twin-screw extruder, and the three-zone temperature was set at 200°C, 220°C and 230°C, the screw speed was 400 rpm, and the blending time was 15 minutes; S2: Dynamic vulcanization molding A dynamic vulcanization unit is set up in front of the extrusion die, and nitrogen protection is introduced to form an interpenetrating network structure between EPDM and SEBS at a pressure of 10-20 MPa and a temperature of 200-220°C; S3: Pulse vacuum setting During cooling and shaping, a pulsed vacuum system is used with a vacuum degree of -0.05 to -0.08 MPa and a pulse frequency of 1-3 times / minute to promote rapid and uniform cooling of the inner and outer surfaces of the pipe; S4: Online Defect Detection Laser diameter gauge and industrial CT are used to detect the dimensional accuracy and internal defects of pipes online, with a scrap rate of ≤0.5%.

6. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 5 is characterized in that: The method also includes processing the nano silicon dioxide carbon fiber and the silane coupling agent KH-560 in a high-speed mixer in proportion before melt blending to form a core-shell structure filler with the surface coated with the silane coupling agent.

7. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 5 is characterized in that: It also includes a gradient structure design: during extrusion molding, the layered feeding device inside the mold is used to make the outer layer of the pipe contain 30%-50% nano-composite reinforcement and the inner layer contain 10%-20% impact modifier, forming a gradient structure that is strong on the outside and tough on the inside.

8. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 5 is characterized in that: The residence time of the dynamic vulcanization unit in the step S3 is 30-60 seconds, and the degree of vulcanization is controlled at 80%-90%.

9. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 7 is characterized in that: In the step S4, the cooling water tank is ≥5m long, the water temperature in the front section is 10-15°C, the water temperature in the rear section is 15-20°C, and is equipped with an ultrasonic descaling device.

10. The modified formula production process of the impact-resistant and heat-resistant MPP cable protection tube according to claim 7, characterized in that: In the step S5, the laser diameter measuring instrument monitors the average inner diameter and wall thickness out-of-roundness of the pipe in real time, and the data is fed back to the extruder traction speed control system to achieve closed-loop control.

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