High-toughness low-smoke halogen-free flame-retardant cable composite material and preparation process thereof
Patent Information
- Application Number
- CN202611269106.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-20
- Publication Date
- 2026-11-03
AI Technical Summary
Existing low-smoke halogen-free flame-retardant cable composite materials have shortcomings in terms of high flame retardancy, toughness, weather resistance and processing performance. They cannot achieve a comprehensive performance of high flame retardancy, high toughness, low smoke and non-toxicity, high weather resistance and easy processing. In addition, traditional materials are prone to brittle fracture, powder agglomeration, component stratification and many processing defects in low-temperature environments, and cannot adapt to dynamic bending and high-speed production.
The toughness, flame retardancy, weather resistance and processing performance of the material are improved by combining a ternary polyolefin toughening matrix with a phosphorus-nitrogen-silicon composite synergistic flame retardant, a nanocomposite reinforcing filler, a composite interface coupling agent, a multi-level weather-resistant and anti-aging additive, and a rheology lubrication processing aid, through powder activation pretreatment, closed gradient premixing and twin-screw segmented melt mixing process.
It achieves a balance between rigidity and toughness in materials, improves flame retardant efficiency, reduces smoke density, improves interfacial compatibility, extends service life, and is suitable for high-speed industrial production, solving the problems of brittle fracture and processing defects of traditional materials in low-temperature environments.
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Figure CN123026848A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer composite materials for cables, specifically to a high-toughness, low-smoke, halogen-free flame-retardant cable composite material and its preparation process. Background Technology
[0002] With the rapid development of rail transit, municipal engineering, new energy, tunnel construction, and other fields, the market's requirements for the flame retardancy, environmental friendliness, mechanical properties, and weather resistance of cable materials are continuously increasing. Low-smoke halogen-free flame-retardant cable materials have become the mainstream development direction for cable insulation and sheathing materials due to their advantages of being halogen-free, producing low smoke during combustion, being non-toxic and harmless, and being flame-retardant and safe.
[0003] Currently, traditional low-smoke halogen-free flame-retardant cable composite materials have significant technical defects: First, to meet flame-retardant requirements, a large amount of inorganic flame-retardant powder needs to be filled, which disrupts the continuity of the material matrix, significantly reduces toughness, tear resistance, and fatigue resistance, and makes them prone to cracking and brittle fracture in low-temperature environments, making them unsuitable for dynamic bending and high-altitude cold-weather service scenarios; Second, single flame-retardant systems have low flame-retardant efficiency and high smoke density, and are prone to producing molten droplets during combustion, posing secondary safety hazards; Third, the inorganic filler has poor interfacial compatibility with the organic polyolefin matrix, which easily leads to powder agglomeration and component stratification, resulting in uneven mechanical properties and poor stability of the material; Fourth, traditional materials have a single aging resistance system, and are prone to performance degradation, hardening cracking, and short service life under long-term outdoor ultraviolet radiation, humid heat, and thermo-oxidative environments; Fifth, the large amount of powder filling results in poor melt flowability, and extrusion processing is prone to defects such as surface roughness, porosity, and eccentricity, making them unsuitable for high-speed industrial production.
[0004] Most existing technologies only optimize a single flame-retardant property or a single mechanical property, failing to achieve a comprehensive balance of properties such as high flame retardancy, high toughness, low smoke and non-toxicity, high weather resistance, and ease of processing. The industry has consistently faced a technical bottleneck in achieving both high flame retardancy and high toughness. Therefore, developing a cable composite material that combines excellent toughness, low smoke and halogen-free flame retardancy, high weather resistance, and excellent processing performance has significant engineering application value. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-toughness, low-smoke, halogen-free flame-retardant cable composite material and its preparation process. This invention solves the problems of traditional materials, such as large flame-retardant filler content, poor toughness, high smoke density, poor interfacial compatibility, weak weather resistance, and many processing defects. It achieves a balance of rigidity and toughness, low smoke and high flame retardancy, long-term aging resistance, and compatibility with high-speed extrusion production, thus meeting the needs of cables used in complex working conditions.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A high-toughness, low-smoke, halogen-free flame-retardant cable composite material is prepared from the following raw materials in parts by weight:
[0008] 40-55 parts of ternary polyolefin toughening matrix; 30-40 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 5-12 parts of nano-composite reinforcing filler; 0.4-1.3 parts of composite interface coupling agent; 1.4-3.2 parts of multi-level weather-resistant and anti-aging additives; 0.7-2.1 parts of rheology lubrication processing aids.
[0009] Furthermore, the ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene and polyolefin elastomer in a mass ratio of (3.5-4.5):(1.5-2.5):(0.8-1.2).
[0010] Furthermore, the phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of an intumescent phosphorus-nitrogen flame retardant, nano-magnesium hydroxide, and organosilicon flame retardant in a mass ratio of (4.5-5.5):(2.5-3.5):(1.5-2.5).
[0011] Furthermore, the nanocomposite reinforcing filler is composed of fumed nano-silica and organic modified montmorillonite in a mass ratio of (1.5-2.5):(0.8-1.2).
[0012] Furthermore, the composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of (1-3):(0.5-2).
[0013] Furthermore, the multi-level weather-resistant and anti-aging additive is composed of hindered phenolic primary antioxidant, phosphite secondary antioxidant, hindered amine light stabilizer and benzotriazole ultraviolet absorber in a mass ratio of (1-2):(1-2):(0.5-1.5):(0.5-1.5).
[0014] Furthermore, the rheological lubrication processing aid is composed of polyethylene wax, zinc stearate and organosilicon rheology modifier in a mass ratio of (1-3):(0.5-1.5):(0.5-1.5).
[0015] A process for preparing a high-toughness, low-smoke, halogen-free flame-retardant cable composite material includes the following steps:
[0016] S1. Powder activation pretreatment: Select phosphorus-nitrogen-silicon composite synergistic flame retardant and nano-composite reinforcing filler according to the formula. After sieving to remove agglomerates and large particles, put them into a high-speed mixer. Add the formula amount of composite interface coupling agent, seal the mixer cavity and maintain a slight positive pressure in the cavity. After uniformly heating to the set temperature, stir and modify at high speed and constant temperature. After stirring is completed, cool naturally to room temperature to obtain activated and modified composite powder. Seal and let stand for later use.
[0017] S2. Closed gradient premixing: The activated modified composite powder, multi-stage weather-resistant and anti-aging additives, rheology lubrication processing aids, and ternary polyolefin toughening matrix prepared in step S1 are sequentially added to a closed horizontal mixer. After the equipment is closed, the temperature is raised to the preset temperature. First, low-speed stirring is used to achieve preliminary uniform dispersion of the additives, and then high-speed stirring is switched to complete the macroscopic homogeneous blending of the multi-components to obtain the composite premixed material, which is then conveyed to a twin-screw extruder in a closed manner.
[0018] S3. Twin-screw segmented melt mixing: The composite premixed material is fed into the co-rotating twin-screw extruder in a uniform and continuous feeding manner. The four-stage gradient precise temperature control mode is adopted, combined with the equipment cavity pressure stabilization treatment. By setting the screw speed, the shear rate of the system is controlled, so that the material is gradually melted and plasticized through multi-stage shearing, extrusion and kneading to obtain a homogeneous melt.
[0019] S4. Extrusion, water cooling, shaping and pelletizing: The twin-screw extruder head is controlled to output homogeneous molten material at a constant pressure. The molten material is extruded into strips at a uniform speed through the die head. The strips are immediately sent to a constant temperature cold water bath for water cooling and shaping. After solidification, they are removed from the water bath and air-dried under high pressure to remove surface free moisture. Finally, they are sent to a pelletizer to be cut into uniform cylindrical composite material semi-finished particles.
[0020] S5. Constant temperature drying and curing and sieving: The composite material semi-finished particles are evenly spread in a hot air circulating oven. The thickness of the spread material is controlled, and constant temperature hot air circulation is set for drying and curing. After completion, the oven is naturally cooled to room temperature. The particles are then sieved through a double-layer grading screen to remove powder, large particles and broken particles, and finally, a high-toughness, low-smoke, halogen-free flame-retardant cable composite material is obtained.
[0021] Furthermore, in step S1, a 100-mesh sieve is used for powder sieving, the positive pressure of the cavity is controlled at 0.02-0.03 MPa, the system heating temperature is 80-90℃ with a temperature control accuracy of ±1℃, the high-speed stirring speed is 2900-3300 r / min, and the constant temperature stirring time is 15-22 min.
[0022] Furthermore, in step S2, the mixer temperature is 100-112℃ with a temperature control accuracy of ±1℃, the low-speed stirring speed is 400-500 r / min and the stirring time is 10 min, and the high-speed stirring speed is 1200-1500 r / min and the stirring time is 18 min.
[0023] Furthermore, in step S3, the material feeding rate is 80–100 kg / h with a feeding fluctuation error controlled within ±2 kg / h. The four-stage gradient temperature control is as follows: feeding stage 135–140℃, plasticizing stage 140–148℃, homogenizing stage 148–152℃, and die head stage 152–155℃. The temperature control accuracy of each zone is ±0.5℃. The equipment cavity pressure is maintained at 0.3–0.5 MPa, the screw speed is 300–400 r / min, and the system shear rate is stably controlled at 1200–1600 r / min. .
[0024] Furthermore, in step S4, the extruder head pressure is stabilized at 2.0–2.5 MPa, the melt temperature is maintained at 152–155°C, the die diameter is 3–4 mm, the material extrusion rate is 15–20 m / min, the cold water tank temperature is 15–25°C, the water cooling and shaping time is 8–12 s, the air drying speed is 12–15 m / s, the air drying time is 3–5 s, the pelletizer speed is 800–1000 r / min, and the pellet length is 3–5 mm.
[0025] Furthermore, in step S5, the thickness of the semi-finished granules is no more than 3cm, the drying temperature of the oven is 70-82℃ with a temperature control accuracy of ±1℃, the hot air circulation speed is 6-8m / s, and the constant temperature drying and maturation time is 2.5-3.5h; a double-layer grading sieve of 40 mesh and 80 mesh is used for screening, and the screening rate is 50-60kg / h.
[0026] The present invention has the following beneficial effects:
[0027] This invention uses a ternary polyolefin toughening matrix matched with a phosphorus-nitrogen-silicon composite synergistic flame retardant. While achieving flame retardant performance, it protects the continuous phase structure of the polymer matrix as much as possible, alleviates the problem of material toughness deterioration caused by the large amount of inorganic flame retardant powder filling in traditional technology, improves the material's bending resistance, alleviates low-temperature brittle fracture defects, and to a certain extent breaks through the industry bottleneck of the difficulty in achieving both high flame retardancy and high toughness. It can adapt to complex operating conditions such as dynamic bending and high cold.
[0028] This invention uses a phosphorus-nitrogen-silicon composite synergistic flame retardant, which differs from traditional single flame retardant systems. It relies on the synergistic effect of multiple components to improve flame retardant efficiency, reduce combustion smoke release, inhibit the generation of combustion droplets, eliminate secondary safety hazards caused by droplets, and achieve low-smoke, halogen-free flame retardant effects.
[0029] The formulation of this invention introduces nanocomposite reinforcing fillers and composite interface coupling agents. At the same time, the preparation process includes a powder activation pretreatment step, and the inorganic powder is surface modified by the coupling agent to improve the interfacial compatibility between the inorganic filler and the organic polyolefin matrix, alleviate the problems of powder agglomeration and component stratification, improve the dispersion uniformity of internal components of the composite material, and improve the overall performance stability of the material.
[0030] This invention adds multi-level weather-resistant and anti-aging additives, which can protect against multiple aging factors such as heat and oxygen, ultraviolet rays, and damp heat, inhibit the performance degradation and hardening cracking of materials during long-term service, improve the weather resistance of cable materials, and extend the service life of materials in tunnels, outdoor and other scenarios.
[0031] This invention combines rheological lubrication processing aids to improve the melt flowability of the system; combined with a closed gradient premixing and twin-screw segmented melt mixing process, it achieves progressive melt plasticization through multi-stage shearing and blending, reducing processing defects such as surface roughness, porosity, and eccentricity during extrusion molding, and is suitable for high-speed industrial extrusion production of cable materials. Attached Figure Description
[0032] Figure 1 This is a flowchart illustrating the preparation process of a high-toughness, low-smoke, halogen-free flame-retardant cable composite material proposed in this invention. Detailed Implementation
[0033] The present invention will be further described in detail below with reference to specific embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0034] Example 1:
[0035] A high-toughness, low-smoke, halogen-free flame-retardant cable composite material is prepared from the following raw materials in parts by weight:
[0036] 40-55 parts of ternary polyolefin toughening matrix; 30-40 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 5-12 parts of nano-composite reinforcing filler; 0.4-1.3 parts of composite interface coupling agent; 1.4-3.2 parts of multi-level weather-resistant and anti-aging additives; 0.7-2.1 parts of rheology lubrication processing aids.
[0037] The ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene, and polyolefin elastomer in a mass ratio of (3.5–4.5):(1.5–2.5):(0.8–1.2). EVA improves powder compatibility and low-temperature flexibility; LLDPE provides basic tensile strength, abrasion resistance, and heat resistance; POE elastomer significantly improves resistance to torsion, fatigue, and tearing.
[0038] The phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of intumescent phosphorus-nitrogen flame retardant, nano-magnesium hydroxide, and organosilicon flame retardant in a mass ratio of (4.5–5.5):(2.5–3.5):(1.5–2.5). The phosphorus-nitrogen flame retardant expands at high temperatures to form a dense char layer, providing heat and oxygen insulation and blocking combustion; nano-magnesium hydroxide absorbs heat, lowers the temperature, and adsorbs smoke and dust, achieving a low-smoke effect; the organosilicon flame retardant strengthens the char layer structure and prevents combustion dripping. The three components work synergistically to achieve low filler content, high flame retardancy, low smoke, and non-toxicity.
[0039] The nanocomposite reinforcing filler is composed of fumed nano-silica and organically modified montmorillonite in a mass ratio of (1.5–2.5):(0.8–1.2). The nanoparticles construct a microscopic network support structure in the matrix, slightly improving the material's strength, heat distortion temperature, and wear resistance without affecting its flexibility, thus achieving a balance between rigidity and toughness.
[0040] The composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of (1-3):(0.5-2). It is used to surface-activate and modify flame-retardant powders and nanofillers, eliminating powder agglomeration, strengthening the interfacial bonding between inorganic fillers and the organic matrix, and improving the overall uniformity and stability of the material.
[0041] The multi-stage weather-resistant and anti-aging additive is composed of hindered phenolic primary antioxidant, phosphite secondary antioxidant, hindered amine light stabilizer, and benzotriazole UV absorber in a mass ratio of (1-2):(1-2):(0.5-1.5):(0.5-1.5). The synergistic effect of these multiple additives simultaneously inhibits thermo-oxidative aging, UV aging, and damp-heat aging, significantly delaying the degradation of material mechanical properties and extending the service life of cables in outdoor, tunnel, and extremely cold environments.
[0042] The rheology processing aid is composed of polyethylene wax, zinc stearate, and organosilicon rheology modifier in a mass ratio of (1-3):(0.5-1.5):(0.5-1.5). It reduces melt processing torque and internal friction, improves fluidity and molding stability, eliminates defects such as roughness, porosity, and eccentricity on cable surfaces, and is suitable for high-speed industrial extrusion production.
[0043] Example 2:
[0044] A process for preparing a high-toughness, low-smoke, halogen-free flame-retardant cable composite material includes the following steps:
[0045] S1. Powder activation pretreatment: Select phosphorus-nitrogen-silicon composite synergistic flame retardant and nano-composite reinforcing filler according to the formula. After sieving to remove agglomerates and large particles, put them into a high-speed mixer. Add the formula amount of composite interface coupling agent, seal the mixer cavity and maintain a slight positive pressure in the cavity. After uniformly heating to the set temperature, stir and modify at high speed and constant temperature. After stirring is completed, cool naturally to room temperature to obtain activated and modified composite powder. Seal and let stand for later use.
[0046] S2. Closed gradient premixing: The activated modified composite powder, multi-stage weather-resistant and anti-aging additives, rheology lubrication processing aids, and ternary polyolefin toughening matrix prepared in step S1 are sequentially added to a closed horizontal mixer. After the equipment is closed, the temperature is raised to the preset temperature. First, low-speed stirring is used to achieve preliminary uniform dispersion of the additives, and then high-speed stirring is switched to complete the macroscopic homogeneous blending of the multi-components to obtain the composite premixed material, which is then conveyed to a twin-screw extruder in a closed manner.
[0047] S3. Twin-screw segmented melt mixing: The composite premixed material is fed into the co-rotating twin-screw extruder in a uniform and continuous feeding manner. The four-stage gradient precise temperature control mode is adopted, combined with the equipment cavity pressure stabilization treatment. By setting the screw speed, the shear rate of the system is controlled, so that the material is gradually melted and plasticized through multi-stage shearing, extrusion and kneading to obtain a homogeneous melt.
[0048] S4. Extrusion, water cooling, shaping and pelletizing: The twin-screw extruder head is controlled to output homogeneous molten material at a constant pressure. The molten material is extruded into strips at a uniform speed through the die head. The strips are immediately sent to a constant temperature cold water bath for water cooling and shaping. After solidification, they are removed from the water bath and air-dried under high pressure to remove surface free moisture. Finally, they are sent to a pelletizer to be cut into uniform cylindrical composite material semi-finished particles.
[0049] S5. Constant temperature drying and curing and sieving: The composite material semi-finished particles are evenly spread in a hot air circulating oven. The thickness of the spread material is controlled, and constant temperature hot air circulation is set for drying and curing. After completion, the oven is naturally cooled to room temperature. The particles are then sieved through a double-layer grading screen to remove powder, large particles and broken particles, and finally, a high-toughness, low-smoke, halogen-free flame-retardant cable composite material is obtained.
[0050] In step S1, the powder is sieved using a 100-mesh sieve, the positive pressure in the cavity is controlled at 0.02-0.03 MPa, the system temperature is 80-90℃ with a temperature control accuracy of ±1℃, the high-speed stirring speed is 2900-3300 r / min, and the constant temperature stirring time is 15-22 min.
[0051] In step S2, the mixer temperature is 100-112℃ with a temperature control accuracy of ±1℃, the low-speed stirring speed is 400-500 r / min and the stirring time is 10 min, and the high-speed stirring speed is 1200-1500 r / min and the stirring time is 18 min.
[0052] In step S3, the material feeding rate is 80–100 kg / h with a feeding fluctuation error controlled within ±2 kg / h. The four-stage gradient temperature control is as follows: feeding stage 135–140℃, plasticizing stage 140–148℃, homogenizing stage 148–152℃, and die head stage 152–155℃. The temperature control accuracy of each zone is ±0.5℃. The equipment cavity pressure is maintained at 0.3–0.5 MPa, the screw speed is 300–400 r / min, and the system shear rate is stably controlled at 1200–1600 r / min. .
[0053] In step S4, the extruder head pressure is stabilized at 2.0-2.5 MPa, the melt temperature is maintained at 152-155℃, the die diameter is 3-4 mm, the material extrusion rate is 15-20 m / min, the water temperature in the cold water tank is 15-25℃, the water cooling and shaping time is 8-12 s, the air drying speed is 12-15 m / s, the air drying time is 3-5 s, the pelletizer speed is 800-1000 r / min, and the length of the cut pellets is 3-5 mm.
[0054] In step S5, the thickness of the semi-finished granules should not exceed 3cm, the drying temperature of the oven should be 70-82℃ with a temperature control accuracy of ±1℃, the hot air circulation speed should be 6-8m / s, and the constant temperature drying and maturation time should be 2.5-3.5h; a double-layer grading sieve of 40 mesh and 80 mesh should be used for sieving, and the sieving rate should be 50-60kg / h.
[0055] Example 3:
[0056] A high-toughness, low-smoke, halogen-free flame-retardant cable composite material is prepared from the following raw materials in parts by weight: 48 parts of ternary polyolefin toughening matrix; 36 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 8 parts of nano-composite reinforcing filler; 0.9 parts of composite interface coupling agent; 2.3 parts of multi-level weather-resistant and anti-aging additives; and 1.4 parts of rheology lubrication processing aid.
[0057] The ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene and polyolefin elastomer in a mass ratio of 4.0:2.0:1.0.
[0058] The phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of intumescent phosphorus-nitrogen flame retardant, nano magnesium hydroxide and organosilicon flame retardant in a mass ratio of 5.0:3.0:2.0.
[0059] The nanocomposite reinforcing filler is composed of fumed nano silica and organic modified montmorillonite in a mass ratio of 2.0:1.0.
[0060] The composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of 2.0:1.0.
[0061] The multi-level weather-resistant and anti-aging additive is composed of hindered phenol as the main antioxidant, phosphite as the auxiliary antioxidant, hindered amine as the light stabilizer, and benzotriazole as the ultraviolet absorber in a mass ratio of 1.5:1.5:1.0:1.0.
[0062] The rheological lubrication processing aid is composed of polyethylene wax, zinc stearate and organosilicon rheology modifier in a mass ratio of 2.0:1.0:1.0.
[0063] The composite material preparation process in this embodiment is completely the same as that in Example 2, and will not be repeated here.
[0064] Example 4:
[0065] A high-toughness, low-smoke, halogen-free flame-retardant cable composite material is prepared from the following raw materials in parts by weight: 42 parts of ternary polyolefin toughening matrix; 31 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 6 parts of nano-composite reinforcing filler; 0.5 parts of composite interface coupling agent; 1.6 parts of multi-level weather-resistant and anti-aging additives; and 0.9 parts of rheology lubrication processing aids.
[0066] The ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene and polyolefin elastomer in a mass ratio of 3.6:1.6:0.9.
[0067] The phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of intumescent phosphorus-nitrogen flame retardant, nano magnesium hydroxide and organosilicon flame retardant in a mass ratio of 4.6:2.6:1.6.
[0068] The nanocomposite reinforcing filler is composed of fumed nano silica and organic modified montmorillonite in a mass ratio of 1.6:0.9.
[0069] The composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of 1.2:0.6.
[0070] The multi-level weather-resistant and anti-aging additive is composed of hindered phenol as the main antioxidant, phosphite as the auxiliary antioxidant, hindered amine as the light stabilizer, and benzotriazole as the ultraviolet absorber in a mass ratio of 1.1:1.1:0.6:0.6.
[0071] The rheological lubrication processing aid is composed of polyethylene wax, zinc stearate and organosilicon rheology modifier in a mass ratio of 1.2:0.6:0.6.
[0072] The composite material preparation process in this embodiment is completely the same as that in Example 2, and will not be repeated here.
[0073] Example 5:
[0074] A high-toughness, low-smoke, halogen-free flame-retardant cable composite material is prepared from the following raw materials in parts by weight: 54 parts of ternary polyolefin toughening matrix; 39 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 11 parts of nano-composite reinforcing filler; 1.2 parts of composite interface coupling agent; 3.0 parts of multi-level weather-resistant and anti-aging additives; and 2.0 parts of rheology lubrication processing aids.
[0075] The ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene and polyolefin elastomer in a mass ratio of 4.4:2.4:1.1.
[0076] The phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of intumescent phosphorus-nitrogen flame retardant, nano magnesium hydroxide and organosilicon flame retardant in a mass ratio of 5.4:3.4:2.4.
[0077] The nanocomposite reinforcing filler is composed of fumed nano silica and organic modified montmorillonite in a mass ratio of 2.4:1.1.
[0078] The composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of 2.8:1.8.
[0079] The multi-stage weather-resistant and anti-aging additive is composed of hindered phenol as the main antioxidant, phosphite as the auxiliary antioxidant, hindered amine as the light stabilizer, and benzotriazole as the ultraviolet absorber in a mass ratio of 1.9:1.9:1.4:1.4.
[0080] The rheological lubrication processing aid is composed of polyethylene wax, zinc stearate and organosilicon rheology modifier in a mass ratio of 2.8:1.4:1.4.
[0081] The composite material preparation process in this embodiment is completely the same as that in Example 2, and will not be repeated here.
[0082] Comparative example:
[0083] Traditional halogen-free flame retardant materials for rail transit are prepared using a conventional single EVA matrix + highly filled aluminum hydroxide flame retardant system and conventional mixing and granulation processes.
[0084] Performance test data:
[0085] Performance tests were conducted on Examples 3, 4, and 5, as well as the comparative example. The results are as follows:
[0086]
[0087] Application example:
[0088] A preparation process for a high-toughness, low-smoke, halogen-free flame-retardant cable composite material, comprising the following specific steps:
[0089] Step 1: Powder Activation Pretreatment
[0090] According to the specified weight ratio, a phosphorus-nitrogen-silicon composite synergistic flame retardant and a nano-composite reinforcing filler were selected and screened through a 100-mesh sieve to remove impurities, lumps, and large particles before being added to a high-speed mixer. The specified amount of composite interfacial coupling agent was added to the mixer, the chamber was sealed, and a slight positive pressure of 0.02–0.03 MPa was maintained. The system temperature was raised to 80–90℃ using a uniform heating mode, with a temperature control accuracy of ±1℃. After reaching the set temperature, a high-speed stirrer at 2900–3300 r / min was started, and stirring was continued at a constant temperature for 15–22 minutes.
[0091] After stirring, the modified powder is allowed to cool naturally to room temperature to obtain a dry, uniformly dispersed activated modified composite powder, which is then sealed and left to stand for later use.
[0092] Step 2: Closed-loop gradient premixing
[0093] The activated modified composite powder prepared in step one, the multi-stage weather-resistant and anti-aging additives, the rheology lubrication processing aids, and the ternary polyolefin toughening matrix are sequentially added to a closed horizontal mixer according to the specified ratio to avoid local enrichment of trace additives and sedimentation and segregation of heavy fillers. After the materials are added, the closed mixer is heated to 100-112℃ with a temperature control accuracy of ±1℃.
[0094] First, the mixture is stirred at a low speed of 400–500 rpm for 10 minutes to ensure that trace amounts of weather-resistant and lubricating agents are uniformly adsorbed onto the surface of the powder and matrix particles, achieving initial uniform dispersion. Then, the mixture is stirred at a high speed of 1200–1500 rpm for 18 minutes. By utilizing the difference in rheological gradient, the interfacial resistance of the multi-component mixture is broken down, achieving macroscopic homogeneous blending of rigid inorganic powder, flexible polyolefin matrix, and various functional additives. After premixing, a composite premixed material with uniform components, no segregation, and no agglomeration is obtained and conveyed in a closed system to the feed end of a twin-screw extruder.
[0095] Step 3: Twin-screw segmented melt mixing
[0096] A co-rotating twin-screw extruder is used for continuous melt plasticizing of the premixed material. A continuous, uniform feed mode is set, with the feed rate controlled at 80–100 kg / h, and the feed fluctuation error not exceeding ±2 kg / h. Based on the melting characteristics of the toughened ternary polyolefin matrix, a four-stage gradient precise temperature control is employed: feeding stage 135–140℃, plasticizing stage 140–148℃, homogenizing stage 148–152℃, and die head stage 152–155℃. The temperature control accuracy for each zone is ±0.5℃, and the equipment cavity pressure is maintained at 0.3–0.5 MPa.
[0097] The screw speed was set to 300–400 r / min, and the system shear rate was stably controlled between 1200 and 1600 r / min. The material undergoes multi-stage shearing, extrusion, and kneading inside the extruder to achieve progressive melting and plasticization. This process avoids problems such as matrix aging, additive failure, and flame retardant component decomposition caused by high temperatures. It also thoroughly breaks down residual micro-agglomerates, eliminates the stratification of multiphase components, and promotes the micro-scale compatibility and fusion of inorganic flame retardants, reinforcing components, and organic matrix, resulting in a homogeneous melt with uniform rheology, no bubbles, and no impurities.
[0098] Step 4: Extrusion, water cooling, shaping, and pelletizing
[0099] The twin-screw extruder outputs a homogeneous molten material through a pressure-stabilized die head, maintaining a pressure of 2.0–2.5 MPa and a melt temperature of 152–155°C. The melt is uniformly extruded into strips through a 3–4 mm orifice die at a rate controlled at 15–20 m / min. The strips are then immediately fed into a constant-temperature cooling water bath at 15–25°C for 8–12 seconds of water cooling and solidification. This rapid temperature difference solidification locks in the material's microscopic homogeneous structure, suppressing secondary component migration and material deformation defects such as voids.
[0100] After the shaped strip material is removed from the water tank, it is air-dried at a wind speed of 12-15 m / s for 3-5 seconds to remove free moisture from the surface of the material. Then it is sent to a pelletizer and the pelletizer speed is adjusted to 800-1000 r / min to cut cylindrical composite material semi-finished particles with a length of 3-5 mm and uniform size.
[0101] Step 5: Constant temperature drying and ripening followed by sieving and impurity removal
[0102] The semi-finished granules are evenly spread in the material tray of a hot air circulating oven, with a thickness not exceeding 3 cm to ensure uniform hot air penetration. The oven is set to a constant temperature of 70–82℃, with a temperature control accuracy of ±1℃, and a hot air circulation speed of 6–8 m / s. The constant temperature drying and curing process lasts for 2.5–3.5 hours. This low-temperature curing process can completely remove trace amounts of bound water and residual moisture in the pores of the granules, while slowly releasing the mechanical stress generated during the extrusion and pelletizing processes, repairing microstructural defects, and fully activating the material's toughening properties, flame retardant properties, and weather resistance.
[0103] After drying and maturation, the material is naturally cooled to room temperature in the furnace and then screened to remove impurities using a double-layer 40-mesh and 80-mesh grading sieve. The screening rate is controlled at 50-60 kg / h to remove ultrafine powder, large particles, and broken particles, ultimately obtaining a high-toughness, low-smoke, halogen-free flame-retardant cable composite material with a moisture content of ≤0.05%, uniform size, and stable performance.
[0104] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A high-toughness, low-smoke, halogen-free flame-retardant cable composite material, characterized in that: Prepared from the following raw materials in parts by weight: 40-55 parts of ternary polyolefin toughening matrix; 30-40 parts of phosphorus-nitrogen-silicon composite synergistic flame retardant; 5-12 parts of nano-composite reinforcing filler; 0.4-1.3 parts of composite interface coupling agent; 1.4-3.2 parts of multi-level weather-resistant and anti-aging additives; 0.7-2.1 parts of rheology lubrication processing aids.
2. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The ternary polyolefin toughening matrix is composed of ethylene-vinyl acetate copolymer, linear low-density polyethylene and polyolefin elastomer in a mass ratio of (3.5-4.5):(1.5-2.5):(0.8-1.2).
3. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The phosphorus-nitrogen-silicon composite synergistic flame retardant is composed of an intumescent phosphorus-nitrogen flame retardant, nano-magnesium hydroxide, and organosilicon flame retardant in a mass ratio of (4.5-5.5):(2.5-3.5):(1.5-2.5).
4. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The nanocomposite reinforcing filler is composed of fumed nano silica and organic modified montmorillonite in a mass ratio of (1.5-2.5):(0.8-1.2).
5. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The composite interface coupling agent is composed of silane coupling agent KH-550 and titanate coupling agent in a mass ratio of (1-3):(0.5-2).
6. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The multi-stage weather-resistant and anti-aging additive is composed of hindered phenolic primary antioxidant, phosphite secondary antioxidant, hindered amine light stabilizer and benzotriazole ultraviolet absorber in a mass ratio of (1-2):(1-2):(0.5-1.5):(0.5-1.5).
7. The high-toughness, low-smoke, halogen-free flame-retardant cable composite material according to claim 1, characterized in that: The rheological lubrication processing aid is composed of polyethylene wax, zinc stearate and organosilicon rheology modifier in a mass ratio of (1-3):(0.5-1.5):(0.5-1.5).
8. A preparation process for a high-toughness, low-smoke, halogen-free flame-retardant cable composite material, characterized in that: Includes the following steps: S1. Powder activation pretreatment: Select phosphorus-nitrogen-silicon composite synergistic flame retardant and nano-composite reinforcing filler according to the formula. After sieving to remove agglomerates and large particles, put them into a high-speed mixer. Add the formula amount of composite interface coupling agent, seal the mixer cavity and maintain a slight positive pressure in the cavity. After uniformly heating to the set temperature, stir and modify at high speed and constant temperature. After stirring is completed, cool naturally to room temperature to obtain activated and modified composite powder. Seal and let stand for later use. S2. Closed gradient premixing: The activated modified composite powder, multi-stage weather-resistant and anti-aging additives, rheology lubrication processing aids, and ternary polyolefin toughening matrix prepared in step S1 are sequentially added to a closed horizontal mixer. After the equipment is closed, the temperature is raised to the preset temperature. First, low-speed stirring is used to achieve preliminary uniform dispersion of the additives, and then high-speed stirring is switched to complete the macroscopic homogeneous blending of the multi-components to obtain the composite premixed material, which is then conveyed to a twin-screw extruder in a closed manner. S3. Twin-screw segmented melt mixing: The composite premixed material is fed into the co-rotating twin-screw extruder in a uniform and continuous feeding manner. The four-stage gradient precise temperature control mode is adopted, combined with the equipment cavity pressure stabilization treatment. By setting the screw speed, the shear rate of the system is controlled, so that the material is gradually melted and plasticized through multi-stage shearing, extrusion and kneading to obtain a homogeneous melt. S4. Extrusion, water cooling, shaping and pelletizing: The twin-screw extruder head is controlled to output homogeneous molten material at a constant pressure. The molten material is extruded into strips at a uniform speed through the die head. The strips are immediately sent to a constant temperature cold water bath for water cooling and shaping. After solidification, they are removed from the water bath and air-dried under high pressure to remove surface free moisture. Finally, they are sent to a pelletizer to be cut into uniform cylindrical composite material semi-finished particles. S5. Constant temperature drying and curing and sieving: The composite material semi-finished particles are evenly spread in a hot air circulating oven. The thickness of the spread material is controlled, and constant temperature hot air circulation is set for drying and curing. After completion, the oven is naturally cooled to room temperature. The particles are then sieved through a double-layer grading screen to remove powder, large particles and broken particles, and finally, a high-toughness, low-smoke, halogen-free flame-retardant cable composite material is obtained.
9. The preparation process according to claim 8, characterized in that: In step S1, the powder is sieved using a 100-mesh sieve, the positive pressure in the cavity is controlled at 0.02-0.03 MPa, the system temperature is 80-90℃ with a temperature control accuracy of ±1℃, the high-speed stirring speed is 2900-3300 r / min, and the constant temperature stirring time is 15-22 min. In step S2, the mixer temperature is 100-112℃ with a temperature control accuracy of ±1℃, the low-speed stirring speed is 400-500 r / min and the stirring time is 10 min, and the high-speed stirring speed is 1200-1500 r / min and the stirring time is 18 min. In step S3, the material feeding rate is 80–100 kg / h with a feeding fluctuation error controlled within ±2 kg / h. The four-stage gradient temperature control is as follows: feeding stage 135–140℃, plasticizing stage 140–148℃, homogenizing stage 148–152℃, and die head stage 152–155℃. The temperature control accuracy of each zone is ±0.5℃. The equipment cavity pressure is maintained at 0.3–0.5 MPa, the screw speed is 300–400 r / min, and the system shear rate is stably controlled at 1200–1600 r / min. .
10. The preparation process according to claim 8, characterized in that: In step S4, the extruder head pressure is stabilized at 2.0-2.5 MPa, the melt temperature is maintained at 152-155℃, the die diameter is 3-4 mm, the material extrusion rate is 15-20 m / min, the water temperature in the cold water tank is 15-25℃, the water cooling and shaping time is 8-12 s, the air drying speed is 12-15 m / s, the air drying time is 3-5 s, the pelletizer speed is 800-1000 r / min, and the length of the cut pellets is 3-5 mm. In step S5, the thickness of the semi-finished granules should not exceed 3cm, the drying temperature of the oven should be 70-82℃ with a temperature control accuracy of ±1℃, the hot air circulation speed should be 6-8m / s, and the constant temperature drying and maturation time should be 2.5-3.5h; a double-layer grading sieve of 40 mesh and 80 mesh should be used for sieving, and the sieving rate should be 50-60kg / h.