Thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material and preparation method thereof

Abstract

The invention relates to the technical field of cable materials, in particular to a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material and a preparation method thereof. The modified thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material is prepared from the following components in parts by weight: 30 to 36 parts of polypropylene, 12 to 16 parts of toughening agent, 10 to 16 parts of POE (Polyolefin Elastomer) compatilizer, 88 to 102 parts of flame retardant, 0.5 to 0.9 part of antioxidant, 1 to 2 parts of lubricant and 3 to 6 parts of modified nano particles, the modified nano particles are prepared from nano silicon dioxide and methyl methacrylate through graft polymerization. By adding the modified nanoparticles, the performance of the cable material is remarkably improved, so that the cable material achieves better balance and effect in the aspects of mechanical property, flame retardant property, electrical property, aging property, low-temperature property and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, and particularly to a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material and a preparation method thereof. Background Art

[0002] In modern society, as a key component in the fields of power transmission, communication, industrial production, etc., the performance of cables directly affects the stable operation of the system. The commonly used cross-linked polyolefin cable materials for traditional 450 / 750V and below wires and cables have the problem of poor heat resistance, being prone to softening and deformation in high-temperature environments, endangering the safety of power transmission; at the same time, traditional polyvinyl chloride cables contain halogens, releasing toxic gases such as HCl when burning, and generating a large amount of smoke, which does not meet the modern fire safety requirements; moreover, the retired cross-linked polyolefin materials are difficult to be remelted and processed again, and improper treatment will cause environmental pollution and waste of resources.

[0003] Therefore, halogen-free flame-retardant polyolefins (such as PP, PE) have become the mainstream alternative materials. Although polypropylene (PP) has excellent electrical properties, a relatively high temperature resistance grade, simple processing technology and recyclability, etc., pure polypropylene has poor toughness, obvious low-temperature brittleness, and poor compatibility with flame retardants, which limits its application in the cable field. Existing technologies exist to improve performance by compounding phosphorus-nitrogen-based flame retardants or adding compatibilizers, but there are still defects such as low flame-retardant efficiency and high smoke density (>700).

[0004] The existing polypropylene cable materials face great difficulties in improving comprehensive performance and are difficult to achieve a balance in multiple aspects such as mechanical, flame-retardant, electrical, aging and low-temperature properties. Therefore, it is of great significance to develop new cable materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material and a preparation method thereof, aiming to solve the defects of traditional cross-linked polyolefin cable materials and at the same time overcome the deficiencies of polypropylene materials themselves. By optimizing the formula and preparation process, the cable material can achieve a better balance in mechanical properties, flame-retardant properties, electrical properties, aging properties and low-temperature properties, meet the diverse performance requirements of cables in complex environments, improve the service life and safety of cables, and provide reliable material guarantees for the fields of power transmission and communication, etc.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material, comprising the following components by weight parts: 30-36 parts of polypropylene, 12-16 parts of toughening agent, 10-16 parts of POE compatibilizer, 88-102 parts of flame retardant, 0.5-0.9 parts of antioxidant, 1-2 parts of lubricant, 3-6 parts of modified nanoparticles; the modified nanoparticles are prepared by graft polymerization of nano-silica and methyl methacrylate.

[0008] Preferably, the flame retardant includes aluminum hydroxide and nitrogen-based flame retardant. By weight parts, 85-95 parts of aluminum hydroxide and 3-7 parts of nitrogen-based flame retardant;

[0009] The antioxidant includes antioxidant 1010 and antioxidant 168. By weight parts, 0.45 parts of antioxidant 1010 and 0.15 parts of antioxidant 168.

[0010] Preferably, the polypropylene is polypropylene T30S, the toughening agent is toughening agent SBS, and the POE compatibilizer is POE compatibilizer MC509.

[0011] A method for preparing the above thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material, comprising the following steps:

[0012] a. Raw material pretreatment: drying the polypropylene and aluminum hydroxide;

[0013] b. Mixing and stirring: mixing the dried polypropylene, toughening agent, POE compatibilizer, antioxidant, lubricant and modified nanoparticles according to the formula ratio to make the components preliminarily mixed evenly;

[0014] c. Adding flame retardant: slowly stirring and adding the flame retardant to the mixture obtained in step b to avoid agglomeration, and stirring to make it evenly dispersed;

[0015] d. Melting and blending: adding the material obtained in step c into an extruder for melting and blending extrusion granulation;

[0016] e. Post-treatment: drying the obtained particles to remove the moisture absorbed during the granulation process to obtain the thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material;

[0017] The preparation method of the modified nanoparticles is as follows:

[0018] ① Surface treatment of nano-silica: adding nano-silica into anhydrous ethanol, ultrasonic dispersion, then adding silane coupling agent to the dispersion liquid, heating and stirring for reaction for 2h-4h, after the reaction is completed, carrying out centrifugal separation, washing and drying to obtain the surface-treated nano-silica;

[0019] ②Graft polymerization reaction: Add the surface-treated nano-silica into methyl methacrylate solution, and simultaneously add benzoyl peroxide, then heat and stir for 3 h - 6 h; after the reaction, add a precipitant to precipitate the product, and then filter, wash, and dry to obtain the modified nano-particles.

[0020] Preferably, in the drying treatment operation of step a, the polypropylene is dried at a temperature of 80°C - 100°C for 2 h - 4 h, and the aluminum hydroxide is dried at a temperature of 120°C - 150°C for 3 h - 5 h.

[0021] Preferably, in step b, the stirring is carried out in a high-speed mixer, and the stirring rate of the high-speed mixer is set to 800 r / min - 1200 r / min, and the stirring duration is 10 min - 15 min.

[0022] Preferably, in step c, after adding the flame retardant to the mixture obtained in step b, the stirring duration is set to 5 min - 10 min to enable the flame retardant to be evenly dispersed in the system.

[0023] Preferably, in step d, the extruder is a twin-screw extruder, and the temperatures of each section of the extruder are set as follows: the first section is 160°C - 180°C, the second section is 180°C - 200°C, the third section is 200°C - 220°C, the fourth section is 220°C - 240°C, the head temperature is 230°C - 250°C, and the screw speed is 300 r / min - 500 r / min.

[0024] Preferably, in the drying treatment operation of step e, the prepared particles are dried at a temperature of 40°C - 60°C for 4 h - 6 h.

[0025] Preferably, the preparation method of the modified nano-particles is as follows:

[0026] ①Surface treatment of nano-silica: Add nano-silica into absolute ethanol, ultrasonically disperse for 30 min - 60 min, then add an amino-silane coupling agent to the dispersion, and the dosage of the amino-silane coupling agent is 1% - 5% of the mass of nano-silica, and carry out stirring reaction for 2 h - 4 h under the condition of 50°C - 80°C. After the reaction, carry out centrifugal separation, washing, and drying. The washing is carried out with absolute ethanol for 5 times, and the drying is carried out in a vacuum drying oven for 6 h - 10 h, and the drying temperature is 60°C - 80°C, thus obtaining the surface-treated nano-silica;

[0027] ②Graft polymerization reaction: Add the surface-treated nano-silica into the methyl methacrylate solution, and simultaneously add benzoyl peroxide. The addition amount of benzoyl peroxide is 0.5%-2% of the mass of the surface-treated nano-silica obtained in step 1; protect by passing nitrogen, control the reaction temperature at 80°C - 120°C, and stir and react for 3h - 6h; after the reaction is completed, add acetone to precipitate the product, then filter, wash, and dry. The washing is carried out 5 times with methanol, and the drying is carried out in a vacuum drying oven for 8h - 12h at a drying temperature of 60°C - 80°C to obtain the modified nanoparticles.

[0028] In summary, specific modified nanoparticles are added to the formulation of the present invention, which are prepared by first surface-treating nano-silica and then graft-polymerizing with an organic compound containing an unsaturated double bond; the addition of these modified nanoparticles significantly improves the flame retardancy of the cable material; not only the tensile strength and elongation at break are significantly increased; at the same time, the retention rates of the tensile strength and elongation at break after aging are significantly increased; the low-temperature performance is improved, and the impact embrittlement temperature is reduced; the flame retardancy is improved, the oxygen index is increased and the smoke density is reduced; the environmental performance is better, the content of halogen acid gas is reduced, and the pH value is more suitable. Description of the Drawings

[0029] Figure 1 is the microscopic image of the modified nanoparticles of the present invention from the first perspective;

[0030] Figure 2 is the microscopic image of the modified nanoparticles of the present invention from the second perspective;

[0031] Figure 3 is the microscopic image of the modified nanoparticles of the present invention from the third perspective;

[0032] Figure 4 is the microscopic image of the modified nanoparticles of the present invention from the fourth perspective; Detailed Embodiments

[0033] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following is described in conjunction with the embodiments, but it does not constitute a limitation to the protection scope of the present invention.

[0034] Based on the problems of the existing technology, our research team conducted a number of targeted experiments and explored the thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material and its preparation method of the present invention, which are specifically as follows:

[0035] 1. Problems with existing technologies: Traditional cross-linked polyolefin cable materials have poor heat resistance and cannot work properly in high temperature environments, affecting the safety of power transmission; they are difficult to handle after retirement, causing environmental pollution and waste of resources. Polypropylene cable materials have poor toughness, obvious low-temperature brittleness, poor compatibility with flame retardants, and are difficult to balance and optimize their comprehensive performance. They are easily damaged in actual applications and cannot meet the needs of complex environments.

[0036] 2. Improvement methods: In response to the existing problems, the first step is to screen out suitable toughening agents, compatibilizers, flame retardants and other ingredients, and optimize their ratios. In a large number of experiments, the effects of different toughening agents on the toughness of polypropylene were studied, the improvement effects of various compatibilizers on the compatibility of each component were compared, and the flame retardant properties of different flame retardant compound systems were tested. At the same time, the preparation process and addition effect of new modified nanoparticles were focused on, and the best solution was determined by continuously adjusting the preparation parameters and addition amount. In terms of the preparation process, the raw material pretreatment temperature and time, mixing speed and time, temperature of each section of the extruder and screw speed and other parameters are precisely controlled to ensure uniform dispersion and good interaction of each component.

[0037] 3. Get the solution: During the preparation process, strictly control the quality and order of addition of each raw material. Pre-treat the raw materials first to ensure the removal of moisture and improve dispersibility. During mixing and stirring, ensure that all components are fully mixed. When adding flame retardants, add slowly and stir thoroughly to achieve uniform dispersion. During melt blending, accurately control the temperature and screw speed to ensure that the materials are fully mixed and reacted. In the post-processing stage, strictly control the drying temperature and time to remove moisture and stabilize the material properties. Through precise control of each link, the optimal balance of the comprehensive performance of cable materials can be achieved.

[0038] The invention discloses a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material, which adopts the following technical scheme and comprises the following components by weight: 30-36 parts of polypropylene (brand T30S), 12-16 parts of toughening agent (SBS, brand 7551), 10-16 parts of POE compatibilizer (MC509), 88-102 parts of flame retardant (including 85-95 parts of aluminum hydroxide (brand 01DH) and 3-7 parts of nitrogen flame retardant (MCA-100), 0.5-0.9 parts of antioxidant (0.4-0.6 parts of antioxidant 1010 and 0.1-0.3 parts of antioxidant 168), 1-2 parts of lubricant (silicone masterbatch), and 3-6 parts of modified nanoparticles. The modified nanoparticles are prepared by treating the surface of nano-silicon dioxide with a silane coupling agent and then grafting and polymerizing with an organic compound containing an unsaturated double bond, and can effectively enhance the mechanical properties and flame retardant properties of the material.

[0039] The modified nanoparticle preparation method is as follows:

[0040] ① Surface treatment of nano-silica: Add 30 g of nano-silica into absolute ethanol, and ultrasonically disperse it for 30 min - 60 min. Then add an amino-silane coupling agent to the dispersion liquid. The dosage of the amino-silane coupling agent is 1% - 5% of the mass of the nano-silica. Carry out a stirring reaction at 50 °C - 80 °C for 2 h - 4 h. After the reaction ends, carry out centrifugal separation, washing, and drying. Select absolute ethanol for washing 5 times, and dry in a vacuum drying oven for 6 h - 10 h at a drying temperature of 60 °C - 80 °C to obtain the surface-treated nano-silica;

[0041] ② Graft polymerization reaction: Add the surface-treated nano-silica into a methyl methacrylate solution, and at the same time add benzoyl peroxide. The addition amount of benzoyl peroxide is 0.5% - 2% of the mass of the surface-treated nano-silica obtained in step 1; Protect with nitrogen, control the reaction temperature at 80 °C - 120 °C, and stir and react for 3 h - 6 h; After the reaction ends, add acetone to precipitate the product, then filter, wash, and dry. Select methanol for washing 5 times, 10 g each time, and dry in a vacuum drying oven for 8 h - 12 h at a drying temperature of 60 °C - 80 °C to obtain the modified nano-particles.

[0042] The preparation method of a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material of the present invention is as follows:

[0043] a. Raw material pretreatment: Dry polypropylene (T30S) at 80 °C - 100 °C for 2 h - 4 h to remove moisture and avoid affecting the material properties during subsequent processing, such as causing problems like bubble generation. Dry aluminum hydroxide (01DH) at 120 °C - 150 °C for 3 h - 5 h to improve its dispersibility and make it more evenly distributed in the system during subsequent mixing.

[0044] b. Mixing and stirring: According to the formula ratio, add the dried polypropylene, toughening agent, POE compatibilizer, antioxidant, lubricant, and modified nano-particles into a high-speed mixer, and stir at a speed of 800 r / min - 1200 r / min for 10 min - 15 min to initially mix each component evenly and lay a foundation for subsequent uniform dispersion.

[0045] c. Adding flame retardant: Slowly add the flame retardant to the mixture obtained in step b, and continue stirring for 5 min - 10 min. Slowly adding is to ensure that the flame retardant can be evenly dispersed in the system, avoid agglomeration, and ensure uniform flame retardant performance of the material.

[0046] d. Melt blending: Add the uniformly mixed materials into a twin-screw extruder. Set the temperatures of each section of the extruder as follows: the first section is 160°C - 180°C, the second section is 180°C - 200°C, the third section is 200°C - 220°C, the fourth section is 220°C - 240°C, the head temperature is 230°C - 250°C, and the screw speed is 300 r / min - 500 r / min. Then carry out melt blending and pelletizing. Precisely control the temperature and screw speed to ensure that the materials are fully mixed in the molten state, achieve good interaction between components, and improve the comprehensive performance of the material.

[0047] e. Post-treatment: Dry the obtained pellets at 40°C - 60°C for 4 h - 6 h to remove the moisture absorbed during the pelletizing process, and obtain a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material. Through post-treatment, the stability and reliability of the material can be further improved.

[0048] The specific implementation methods are as follows:

[0049] Example 1

[0050] 1. Formula: 34 parts of polypropylene (T30S), 14 parts of toughening agent (SBS, grade 7551), 16 parts of POE compatibilizer (MC509), 95 parts of flame retardant (including 90 parts of aluminum hydroxide (grade 01DH) and 5 parts of nitrogen-based flame retardant (MCA-100)), 0.6 parts of antioxidant (0.45 parts of antioxidant 1010 and 0.15 parts of antioxidant 168), 1 part of lubricant (silicone masterbatch), and 5 parts of modified nano-particles.

[0051] 2. Preparation method: First, dry the polypropylene at 90°C for 3 h and the aluminum hydroxide at 130°C for 4 h. Stir the raw materials in a high-speed mixer at a speed of 1200 r / min for 10 min to preliminarily mix them, and then slowly add the flame retardant and stir for 5 min. Set the temperatures of each section of the twin-screw extruder as 180°C for the first section, 200°C for the second section, 220°C for the third section, 240°C for the fourth section, 250°C for the head temperature, and the screw speed is 500 r / min for melt blending and pelletizing. Dry the pellets at 60°C for 4 h to obtain the cable material.

[0052] 3. Performance test results (for the main performance tests and reference standards, see Table 1 below): Conduct performance tests on the obtained cable material, and the results are as follows: The tensile strength is 14 MPa, the elongation at break is 200%, the retention rate of tensile strength after the aging performance test (135°C × 168 h) is 80%, the retention rate of elongation at break is 120%, the low-temperature impact embrittlement temperature is -22°C, the dielectric strength is 38 MV / m, and the volume resistivity at 20°C is 5×10 14Ω·cm, the oxygen index is 30%, the flame smoke density is 180, the flameless smoke density is 250, the halogen acid gas content is 0.2%, the pH value is 6.2, and the conductivity is 6 μS / mm. All performance indicators meet the standards of heat-resistant 125 °C rated voltage 450 / 750 V and below insulated wires and cables and the performance requirements of users. The specific data comparison is shown in Table 2.

[0053] Example 2

[0054] 1. Formula: 30 parts of polypropylene (T30S), 12 parts of toughening agent (SBS, grade 7551), 10 parts of POE compatibilizer (MC509), 89 parts of flame retardant (including 86 parts of aluminum hydroxide (grade 01DH) and 3 parts of nitrogen-based flame retardant (MCA-100)), 0.6 parts of antioxidant (0.4 parts of antioxidant 1010 and 0.2 parts of antioxidant 168), 1 part of lubricant (silicone masterbatch), 3 parts of modified nanoparticles.

[0055] 2. Preparation method: Dry polypropylene at 80 °C for 4 h and dry aluminum hydroxide at 120 °C for 5 h. Add each raw material to a high-speed mixer according to the formula ratio, stir at a speed of 800 r / min for 15 min, and then slowly add the flame retardant and stir for 10 min. Add the mixed material to a twin-screw extruder, set the temperature of the first section of the extruder at 160 °C, the second section at 180 °C, the third section at 200 °C, the fourth section at 220 °C, and the head temperature at 230 °C, and the screw speed at 300 r / min for melt blending and pelletizing. Finally, dry the obtained pellets at 40 °C for 6 h to obtain the cable material.

[0056] 3. Performance test results (for main performance tests and reference standards, see Table 1 below): Tensile strength is 12 MPa, elongation at break is 180%, the retention rate of tensile strength after aging performance test (135 °C × 168 h) is 75%, the retention rate of elongation at break is 110%, the low-temperature impact embrittlement temperature is -18 °C, the dielectric strength is 35 MV / m, and the volume resistivity at 20 °C is 4×10 12 Ω·m, the oxygen index is 28%, the flame smoke density is 190, the flameless smoke density is 280, the halogen acid gas content is 0.3%, the pH value is 5.8, and the conductivity is 7 μS / mm.

[0057] Example 3

[0058] 1. Formula: 36 parts of polypropylene (T30S), 16 parts of toughening agent (SBS, grade 7551), 16 parts of POE compatibilizer (MC509), 95 parts of flame retardant (including 88 parts of aluminum hydroxide (grade 01DH) and 7 parts of nitrogen-based flame retardant (MCA-100)), 0.9 parts of antioxidant (0.6 parts of antioxidant 1010 and 0.3 parts of antioxidant 168), 2 parts of lubricant (silicone masterbatch), 6 parts of modified nanoparticles.

[0059] 2. Preparation method: Polypropylene is dried at 100 °C for 2 h, and aluminum hydroxide is dried at 150 °C for 3 h. The raw materials are preliminarily mixed in a high-speed mixer at a speed of 1200 r / min for 10 min, and then the flame retardant is slowly added and stirred for 5 min. The temperature of each section of the twin-screw extruder is set as follows: the first section is 180 °C, the second section is 200 °C, the third section is 220 °C, the fourth section is 240 °C, the head temperature is 250 °C, and the screw speed is 500 r / min for melt blending and pelletizing. The pellets are dried at 60 °C for 4 h to obtain the cable material.

[0060] 3. Performance test results (the main performance tests and reference standards are shown in Table 1 below): The tensile strength is 15 MPa, the elongation at break is 220%, the retention rate of tensile strength after the aging performance test (135 °C × 168 h) is 85%, the retention rate of elongation at break is 130%, the low-temperature impact embrittlement temperature is -25 °C, the dielectric strength is 40 MV / m, the volume resistivity at 20 °C is 6×10 12 Ω·m, the oxygen index is 32%, the flame smoke density is 170, the non-flame smoke density is 230, the halogen acid gas content is 0.15%, the pH value is 6.5, and the conductivity is 5 μS / mm.

[0061] In the formula of the present invention, specific modified nanoparticles are added. First, the surface of nano-silica is treated, and then it is graft-polymerized with an organic compound containing an unsaturated double bond. These particles have a unique microstructure, can be tightly combined with the polypropylene matrix, and play a key role in enhancing the internal structural strength of the material. At the same time, their special chemical composition and structure enable them to effectively block heat and inhibit flame spread during combustion, significantly improving the flame retardant performance of the material.

[0062] In the present invention, the microstructure of the modified nanoparticles has highly ordered and fine surface textures and internal lattice arrangements (see Appendix Figures 1-4 ), which is significantly different from conventional nanoparticles. This microstructure can enable them to generate strong intermolecular forces with the polypropylene matrix, forming a stable interfacial bond, like countless tiny anchor points, greatly enhancing the internal structural strength of the material.

[0063] In terms of chemical composition, due to the graft polymerization with an organic compound containing an unsaturated double bond, it has a special functional group distribution. These functional groups can rapidly undergo a series of endothermic chemical reactions during combustion, thereby effectively blocking heat transfer; at the same time, the inert gases released can dilute the oxygen concentration and inhibit flame spread, significantly improving the flame retardant performance of the material.

[0064] The functions of the modified nanoparticles in the present invention are specifically as follows:

[0065] I. Interaction with Polypropylene Matrix

[0066] 1. Physical action: The modified nanoparticles have a very large specific surface area, which can generate strong van der Waals forces with the polypropylene matrix. At the same time, they can be evenly dispersed in the polypropylene matrix. Just like a "filler", they fill the gaps between the polypropylene molecular chains, restricting the movement of the molecular chains and increasing the rigidity of the material.

[0067] 2. Chemical action: Through surface modification, functional groups capable of reacting chemically with the polypropylene matrix are introduced onto the surface of the modified nanoparticles.

[0068] II. Enhancement of Mechanical Properties

[0069] 1. Load transfer: The modified nanoparticles are well combined with the polypropylene matrix. When the material is subjected to external forces, the nanoparticles can effectively bear part of the load and transfer it to the surrounding polypropylene matrix, making the stress evenly distributed, avoiding stress concentration, and thus improving the strength and toughness of the material.

[0070] 2. Hindrance to crack propagation: The modified nanoparticles in the polypropylene matrix are like "obstacles". When a crack propagates to the nanoparticles, it will change the propagation direction, increase the path length of crack propagation, and consume more energy, thereby improving the fracture resistance of the material.

[0071] III. Improvement of Flame Retardancy

[0072] 1. Isolation effect: The nanoparticles are evenly dispersed in the polypropylene matrix. During combustion, a dense protective film will be formed on the surface of the material, isolating the internal polypropylene from oxygen and heat in the outside world and slowing down the combustion speed.

[0073] 2. Catalytic carbonization: Metal oxides can catalyze the carbonization reaction of polypropylene during combustion, forming a hard carbonized layer on the surface of the material. The carbonized layer can not only prevent the transfer of heat and oxygen but also reduce the release of combustible gases, thereby improving the flame retardancy of the material.

[0074] 3. Free radical capture: The modified nanoparticles can capture free radicals during combustion, inhibiting the chain propagation of the combustion reaction, thereby achieving the purpose of flame retardancy.

[0075] The prior art could not achieve this technical effect. However, with the development of materials science and nanotechnology, breakthroughs have been made in the surface treatment technology of nano-silica, enabling precise control of surface modification and improving its reactivity with organic compounds. At the same time, the graft polymerization process has been continuously optimized to achieve efficient and stable polymerization reactions, preparing modified nanoparticles with excellent properties. In addition, advanced analytical and testing means can deeply study the action mechanism of nanoparticles in cable materials, providing a basis for determining their reasonable addition amount and application method.

[0076] After adding this modified nanoparticle to the formulation of the present invention, the effect is significantly improved (see Table 2 below for detailed data), specifically as follows: The mechanical properties of the material are significantly improved, the tensile strength is increased by 15%-20%, and the elongation at break is increased by 18%-25%, enhancing the anti-external force ability of the cable during installation and use. In terms of flame retardancy performance, the oxygen index is increased by 3%-5%, and both the flame smoke density and the non-flame smoke density are reduced by 15%-20%, greatly improving the fire safety of the cable and reducing the hazards during a fire.

[0077] To verify the performance advantages of the thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material of the present invention, two existing similar cable materials on the market (marked as Comparative Example 1 and Comparative Example 2 respectively) were selected for performance comparison tests. At the same time, a comparative example (Comparative Example 3) of a cable material prepared with the same formulation as that of Example 1 but without adding modified nanoparticles was also set up.

[0078] Comparative Example 1 is a traditional cross-linked polyolefin cable material of a well-known brand, and Comparative Example 2 is a common polypropylene cable material of another brand. The test items include tensile strength, elongation at break, aging performance (tensile strength retention rate, elongation at break retention rate), low-temperature impact embrittlement temperature, dielectric strength, volume resistivity, oxygen index, smoke density, halogen acid gas content, pH value, and conductivity, etc.

[0079] Comparative Example 1 is a 105°C halogen-free low-smoke flame-retardant cross-linked polyolefin insulating material: model WDZ-Y-J105, oxygen index ≥ 35, and this product is commonly used in the market for insulating wires and cables with a rated voltage of 450 / 750V and below.

[0080] Comparative Example 2 is a 90°C halogen-free low-smoke flame-retardant polypropylene cable material: model WDZ-Y-J90, oxygen index ≥ 32, and it is mainly applied in the market for insulating wires and cables with a rated voltage of 450 / 750V and below.

[0081] The formulation of Comparative Example 3 is: 34 parts of polypropylene (T30S), 14 parts of toughening agent (SBS, grade 7551), 16 parts of POE compatibilizer (MC509), 95 parts of flame retardant (including 90 parts of aluminum hydroxide (grade 01DH) and 5 parts of nitrogen-based flame retardant (MCA-100)), 0.6 parts of antioxidant (0.45 parts of antioxidant 1010 and 0.15 parts of antioxidant 168), 1 part of lubricant (silicone masterbatch);

[0082] The preparation method is as follows: First, polypropylene is dried at 90°C for 3 hours, and aluminum hydroxide is dried at 130°C for 4 hours. The raw materials are preliminarily mixed in a high-speed mixer at a speed of 1200 r / min for 10 minutes, and then the flame retardant is slowly added and stirred for 5 minutes. The temperatures of each section of the twin-screw extruder are set as follows: the first section is 180°C, the second section is 200°C, the third section is 220°C, the fourth section is 240°C, the head temperature is 250°C, and the screw speed is 500 r / min for melt blending and pelletizing. The pellets are dried at 60°C for 4 hours to obtain the cable material.

[0083]

[0084]

[0085]

[0086] By comparing the data of the examples of the present invention with Comparative Example 1 and Comparative Example 2, it can be seen that the cable material of the present invention is superior to Comparative Example 1 and Comparative Example 2 in various performance indicators. In terms of mechanical properties, the tensile strength and elongation at break are higher, and the performance retention rate after aging is also significantly improved, indicating that the material of the present invention has obvious advantages in withstanding external forces and resisting aging. In terms of low-temperature performance, the lower impact embrittlement temperature makes it more suitable for cold environments. In terms of flame retardancy, the higher oxygen index and lower smoke density mean better fire safety. In terms of environmental protection performance, the content of halogen acid gas is lower, the pH value is better, and the conductivity is also within the standard range, causing less harm to the environment.

[0087] By comparing the data of the examples of the present invention with Comparative Example 3, it can be seen that after adding the modified nanoparticles, in terms of the mechanical properties of the cable material of the present invention, the tensile strength and elongation at break are significantly improved, enhancing the anti-external force ability of the cable during installation and use; in terms of aging performance, the retention rates of tensile strength and elongation at break after aging are higher, and the aging resistance ability is stronger; in terms of low-temperature performance, the impact embrittlement temperature is reduced, making it more suitable for cold environments; in terms of flame retardancy, the oxygen index is increased, and the flame and non-flame smoke densities are reduced, greatly improving the fire safety; in terms of environmental protection performance, the content of halogen acid gas is reduced, the pH value is better, and the harm to the environment is further reduced, fully reflecting the beneficial effects brought by adding the modified nanoparticles to the present invention.

[0088] From the above data, it can be seen that compared with the prior art, the performance of the present invention is significantly improved, as follows:

[0089] 1. The mechanical properties of the material are significantly improved: the tensile strength is increased by 15%-20%, and the elongation at break is increased by 18%-25%, enhancing the anti-external force ability of the cable during installation and use.

[0090] 2. Improved flame retardancy: The oxygen index is increased by 3% - 5%, and both the flaming smoke density and the non - flaming smoke density are reduced by 15% - 20%, greatly enhancing the fire safety of the cable and reducing the hazards during a fire.

[0091] 3. Improved processing performance: By optimizing the process and the synergistic effect of components, the material is more evenly dispersed during melt blending, has better processing fluidity, reduces processing energy consumption, improves production efficiency, and reduces the defective rate.

[0092] 4. Outstanding environmental protection advantages: It meets the requirements of low - smoke and halogen - free environmental protection. Indicators such as the content of halogen - acid gas, pH value, and conductivity are superior to existing standards, reducing the harm to the environment during use and waste treatment.

[0093] The above embodiments only represent several implementation modes of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material, characterized in that, It comprises the following components by weight parts: 30 - 36 parts of polypropylene, 12 - 16 parts of toughening agent, 10 - 16 parts of POE compatibilizer, 88 - 102 parts of flame retardant, 0.5 - 0.9 part of antioxidant, 1 - 2 parts of lubricant, 3 - 6 parts of modified nanoparticles; The modified nanoparticles are prepared by graft polymerization of nano - silica and methyl methacrylate.

2. The thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 1, wherein: The flame retardant includes aluminum hydroxide and nitrogen - based flame retardant. By weight parts, aluminum hydroxide is 85 - 95 parts and nitrogen - based flame retardant is 3 - 7 parts; The antioxidant includes antioxidant 1010 and antioxidant 168. By weight parts, antioxidant 1010 is 0.45 part and antioxidant 168 is 0.15 part.

3. The thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 1 or 2, characterized in that: The polypropylene is polypropylene T30S, the toughening agent is toughening agent SBS, and the POE compatibilizer is POE compatibilizer MC509.

4. A method for preparing a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material as described in claim 3, characterized in that, It includes the following steps: a. Raw material pretreatment: drying polypropylene and aluminum hydroxide; b. Mixing and stirring: according to the formula ratio, mixing the dried polypropylene, toughening agent, POE compatibilizer, antioxidant, lubricant and modified nanoparticles to make each component preliminarily mixed evenly; c. Adding flame retardant: slowly stirring and adding the flame retardant into the mixture obtained in step b to avoid agglomeration, and stirring to make it evenly dispersed; d. Melt blending: adding the material obtained in step c into an extruder for melt blending and pelletizing; e. Post - treatment: drying the prepared pellets to remove the moisture absorbed during the pelletizing process to obtain a thermoplastic low - smoke and halogen - free flame - retardant polypropylene cable material; The preparation method of the modified nanoparticles is as follows:

1. Surface treatment of nano - silica: adding nano - silica into anhydrous ethanol, ultrasonic dispersion, then adding silane coupling agent into the dispersion liquid, heating and stirring for reaction for 2h - 4h. After the reaction ends, centrifugal separation, washing and drying are carried out to obtain surface - treated nano - silica; 2. Graft polymerization reaction: adding the surface - treated nano - silica into methyl methacrylate solution, and at the same time adding benzoyl peroxide, heating and stirring for reaction for 3h - 6h; after the reaction ends, adding a precipitant to precipitate the product, then filtering, washing and drying to obtain modified nanoparticles.

5. The preparation method of a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 4, characterized in that: In the drying treatment operation in step a, polypropylene is dried at a temperature of 80℃ - 100℃ for 2h - 4h, and aluminum hydroxide is dried at a temperature of 120℃ - 150℃ for 3h - 5h.

6. The preparation method of a thermoplastic low-smoke and halogen-free flame-retardant polypropylene cable material according to claim 4 or 5, characterized in that: In step b, the stirring is carried out in a high - speed mixer, and the stirring rate of the high - speed mixer is set at 800r / min - 1200r / min and the stirring time is 10min - 15min.

7. The preparation method of a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 6, characterized in that: In step c, after the flame retardant is added to the mixture obtained in step b, the stirring time is set at 5min - 10min to enable the flame retardant to be evenly dispersed in the system.

8. The preparation method of a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 4 or 5 or 7, characterized in that: In step d, the extruder is a twin-screw extruder. The temperatures of each section of the extruder are set as follows: the first section is 160°C - 180°C, the second section is 180°C - 200°C, the third section is 200°C - 220°C, the fourth section is 220°C - 240°C, the head temperature is 230°C - 250°C, and the screw speed is 300 r / min - 500 r / min.

9. The preparation method of a thermoplastic low-smoke halogen-free flame-retardant polypropylene cable material according to claim 8, characterized in that: The drying treatment operation in step e is to dry the obtained particles at a temperature of 40°C - 60°C for 4 h - 6 h.

10. The preparation method of a thermoplastic low-smoke and halogen-free flame-retardant polypropylene cable material according to claim 4 or 5 or 7 or 9, characterized in that: The preparation method of the modified nanoparticles is as follows:

1. Surface treatment of nano-silica: Add nano-silica into anhydrous ethanol, ultrasonically disperse for 30 min - 60 min, then add an amino-silane coupling agent to the dispersion. The dosage of the amino-silane coupling agent is 1% - 5% of the mass of nano-silica. Carry out stirring reaction for 2 h - 4 h at 50°C - 80°C. After the reaction ends, carry out centrifugal separation, washing, and drying. Select anhydrous ethanol for washing 5 times. Dry in a vacuum drying oven for 6 h - 10 h, and the drying temperature is 60°C - 80°C, thus obtaining the surface-treated nano-silica.

2. Graft polymerization reaction: Add the surface-treated nano-silica into a methyl methacrylate solution, and at the same time add benzoyl peroxide. The addition amount of benzoyl peroxide is 0.5% - 2% of the mass of the surface-treated nano-silica obtained in step 1. Protect with nitrogen, control the reaction temperature at 80°C - 120°C, and stir and react for 3 h - 6 h. After the reaction ends, add acetone to precipitate the product, then filter, wash, and dry. Select methanol for washing 5 times. Dry in a vacuum drying oven for 8 h - 12 h, and the drying temperature is 60°C - 80°C, thus obtaining the modified nanoparticles.

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