Weather-proof low-smoke halogen-free polyolefin composition for cable and preparation method of weather-proof low-smoke halogen-free polyolefin composition

Abstract

The invention discloses a weather-proof low-smoke halogen-free polyolefin composition for a cable and a preparation method of the weather-proof low-smoke halogen-free polyolefin composition. The formula of the weather-proof low-smoke halogen-free polyolefin composition for the cable comprises the following components in parts by weight: 40-80 parts of matrix resin; 30 to 150 parts of a halogen-free flame retardant; 0.5 to 8 parts of a weather-resistant additive; 0.5 to 5 parts of a coupling agent; 1 to 10 parts of a lubricant; and 2-20 parts of a processing aid. Compared with a traditional solid product, the weather-resistant flame-retardant cable material has the effect of synergistically improving weather resistance and flame-retardant efficiency, the ultraviolet light absorber and the hindered phenol / phosphite antioxidant are compounded according to a specific proportion, and the synergistic surface treatment technology of bis [3-(triethoxysilyl) propyl] tetrasulfide and the titanate coupling agent is combined, so that the weather-resistant flame-retardant cable material has the advantages that the weather resistance and the flame-retardant efficiency are improved, and the weather resistance and the flame-retardant efficiency are improved. The interface bonding force between the metal hydroxide and the matrix resin is obviously enhanced, and molecular chain degradation under ultraviolet radiation and a humid and hot environment is inhibited.

Description

Technical Field

[0001] The present invention belongs to the field of weather-resistant low-smoke halogen-free polyolefin compositions, and more specifically, relates to a weather-resistant low-smoke halogen-free polyolefin composition for cables. The present invention also relates to a method for preparing the weather-resistant low-smoke halogen-free polyolefin composition for cables. Background Art

[0002] As the cable industry's requirements for environmental protection and safety performance continue to increase, low-smoke, halogen-free, flame-retardant polyolefin materials, due to their low smoke and non-corrosive gas release during combustion, have become an important development direction for power and communication cable sheathing materials. However, conventional polyolefin compositions in existing technologies still suffer from insufficient weather resistance, difficulty balancing flame retardancy and mechanical properties, and susceptibility to frosting and precipitation during processing, limiting their long-term application in harsh outdoor environments.

[0003] Traditional low-smoke halogen-free cable materials mostly use metal hydroxides such as magnesium hydroxide and aluminum hydroxide as flame retardants, but their high filling content often leads to poor interfacial compatibility with the matrix resin and a significant decrease in material toughness. Although surface modification treatment schemes (such as single silane coupling agent treatment) have been proposed in patent literature, there are still defects such as uneven dispersion of flame retardants and insufficient thermal stability. In particular, under conditions of long-term exposure to heat or ultraviolet rays, flame retardant agglomeration and material embrittlement are prone to occur. On the other hand, the selection and ratio of existing weathering additives lack systematic optimization. Excessive addition can easily lead to deterioration of processing fluidity, while too little addition cannot effectively resist photo-oxidation aging.

[0004] Therefore, we propose a weather-resistant, low-smoke, halogen-free polyolefin composition for cables and a preparation method thereof to address the deficiencies of the existing technology and meet the technical upgrade needs of outdoor cable materials. Summary of the Invention

[0005] The purpose of the present invention is to address the shortcomings of the prior art and to propose a weather-resistant, low-smoke, halogen-free polyolefin composition for cables and a preparation method thereof. Through component collaborative design and process innovation, the weather resistance, flame retardancy and processing stability of the polyolefin material for cables are comprehensively improved.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A weather-resistant low-smoke halogen-free polyolefin composition for cables, comprising 40-80 parts of a base resin, 30-150 parts of a halogen-free flame retardant, 0.5-8 parts of a weather-resistant additive, 0.5-5 parts of a coupling agent, 1-10 parts of a lubricant, and 2-20 parts of a processing aid.

[0008] The halogen-free flame retardant is a metal hydroxide, which is prepared from magnesium hydroxide and aluminum hydroxide, wherein the median particle size D50 of the magnesium hydroxide is 1-5 μm and the specific surface area is 5-20 m 2 / g; the median particle size D50 of aluminum hydroxide is 0.5-3μm, and the specific surface area is 8-25m 2 / g, the matrix resin is ethylene-vinyl acetate copolymer, the VA content thereof is 15-40wt%, and the melt index is 1-10g / 10min.

[0009] Preferably, the weathering additive comprises an ultraviolet absorber and an antioxidant in a weight ratio of 1:0.5-1:3; the ultraviolet absorber is selected from benzotriazole or triazine compounds; and the antioxidant is selected from hindered phenols or phosphite compounds.

[0010] Preferably, the coupling agent is silane coupling agent KH-550 or KH-570, and the application amount is 0.3-1.5% of the total weight of the inorganic filler; the lubricant is a compound of zinc stearate and oxidized polyethylene wax, and the weight ratio of the two is 1:0.5-1:2.

[0011] Preferably, the processing aid is a compound system of silicone masterbatch and fluoropolymer, with a weight ratio of 1:0.5-1:3, wherein the viscosity of the silicone masterbatch is 500-3000 cSt, and the fluoropolymer is polyvinylidene fluoride or ethylene-tetrafluoroethylene copolymer.

[0012] Preferably, the metal hydroxide is surface treated, the treating agent is a synergistic system of bis[3-(triethoxysilyl)propyl]tetrasulfide and a titanate coupling agent, and the total amount of the treating agent added is 0.5-3.0% of the total weight of the metal hydroxide.

[0013] A method for preparing a weather-resistant low-smoke halogen-free polyolefin composition for cables, wherein the weather-resistant low-smoke halogen-free polyolefin composition for cables is prepared using the above-mentioned materials, and comprises the following steps:

[0014] S1. Optimize and prepare the material according to the formula of the weather-resistant low-smoke halogen-free polyolefin composition for cables, and perform flame retardant surface pretreatment at the same time;

[0015] S2, preheating and modification of base resin;

[0016] S3, pre-dispersion of functional additives;

[0017] S4, multi-stage blending extrusion;

[0018] S5, post-processing, the extruded product is water-cooled and pelletized, and then immersed in a cold soaking tank containing erucamide frosting inhibitor with a concentration of 0.1-0.5wt%, the cooling water temperature is controlled at 10-25°C, and the soaking time is 5-10 seconds; after drying, it is matured at 50-70°C for 4-8 hours.

[0019] Preferably, step S1 is specifically:

[0020] Magnesium hydroxide and aluminum hydroxide are placed in a high-speed mixer respectively, the speed is adjusted to 800-1200 r / min, and after heating to 60-80° C., a surface treatment agent composed of bis[3-(triethoxysulfide)propyl]tetrasulfide and a titanate coupling agent is sprayed, and the total amount of the treatment agent is 0.5-3.0% of the total weight of the metal hydroxide. Stir for 15-25 minutes until the surface is evenly coated, then cool to below 40° C., sieve to remove lumps, and set aside. The titanate coupling agent is selected from isopropyl tris(dioctyl pyrophosphate acyloxy) titanate (TCA-101);

[0021] Step S2 is specifically as follows:

[0022] Ethylene-vinyl acetate copolymer is placed in a vacuum oven and preheated at 80-100°C for 30-60 minutes with the vacuum degree controlled at -0.08-0.05 MPa to reduce the resin moisture content to below 0.05wt%. The preheated resin is then transferred to an internal mixer and polyolefin elastomer (POE) with a Shore hardness of 50-85A is added. The internal mixer temperature is controlled at 110-130°C and the rotor speed at 30-50 rpm. The mixture is mixed for 10-15 minutes until a uniform molten matrix is ​​formed.

[0023] Preferably, step S3 is specifically:

[0024] The ultraviolet absorber UV-531 and the antioxidant 1076 in the weathering additive are pre-mixed in a weight ratio of 1:0.5-1:3, placed in a three-dimensional motion mixer, and silicone masterbatch, viscosity 500-3000 cSt, fluoropolymer polyvinylidene fluoride and zinc stearate / oxidized polyethylene wax composite lubricant are added. The mixture is mixed under nitrogen protection for 20-40 minutes at a mixing temperature of 50-70°C and a rotation speed of 200-400 rpm to obtain a homogeneous pre-mixed additive package;

[0025] Step S4 is specifically as follows:

[0026] The pretreated base resin, metal hydroxide flame retardant and the premixed additive package obtained in step 3 are put into a twin-screw extruder, and the barrel temperature is controlled in sections: 150-160°C in zone 1, 165-175°C in zone 2, 170-180°C in zone 3, and 175-185°C in zone 4, and the screw speed is 250-400 rpm; a liquid silane coupling agent is injected at the end of zone 4, and nano-scale dispersion is achieved through a high-shear mixing die.

[0027] Preferably, the optimization described in step S1 optimizes the components by the following weighted calculation model, specifically:

[0028] Comprehensive performance index

[0029] Constraints:

[0030] Where σ b is the tensile strength, OI is the oxygen index, and SD is the smoke density. The subscript ref is the reference value of each parameter, and the weight ω is dynamically allocated according to the cable application scenario.

[0031] Technical effects and advantages of the present invention: The weather-resistant low-smoke halogen-free polyolefin composition for cables provided by the present invention has the following effects compared with traditional solid products:

[0032] Synergistic improvement in weather resistance and flame retardancy: By compounding a UV absorber with a hindered phenol / phosphite antioxidant in a specific ratio, and combining it with a synergistic surface treatment technology of bis[3-(triethoxysilyl)propyl]tetrasulfide and a titanate coupling agent, the interfacial bonding between the metal hydroxide and the matrix resin is significantly enhanced, inhibiting molecular chain degradation under UV radiation and humid and hot environments;

[0033] Balanced optimization of processing performance and mechanical properties: A processing aid system based on a combination of silicone masterbatch and fluoropolymer, combined with a segmented, precise temperature-controlled extrusion process, significantly improves the melt flowability of the highly filled flame retardant system. By optimizing the lubricant compounding ratio, the risk of scorching caused by shear heat is reduced.

[0034] Long-term stability and anti-precipitation properties: By introducing a low-temperature cold dip tank and gradient aging process, the migration tendency of low molecular weight components such as silane coupling agents and lubricants is suppressed;

[0035] Dynamic component optimization and process adaptability: A dynamic weighted calculation model based on tensile strength, oxygen index, and smoke density can adjust the proportions of each component and the weights of process parameters for different cable application scenarios, enabling rapid iterative optimization of formula design and breaking through the efficiency bottleneck of traditional trial-and-error methods. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] The present invention provides a weather-resistant low-smoke halogen-free polyolefin composition for cables and a preparation method thereof. The formula of the weather-resistant low-smoke halogen-free polyolefin composition for cables consists of a base resin, a halogen-free flame retardant, a weather-resistant additive, a coupling agent, a lubricant, and a processing aid.

[0038] Among them, the halogen-free flame retardant is a metal hydroxide, which is prepared from magnesium hydroxide and aluminum hydroxide. The median particle size D50 of the magnesium hydroxide is 1-5 μm, and the specific surface area is 5-20 m 2 / g; the median particle size D50 of aluminum hydroxide is 0.5-3μm, and the specific surface area is 8-25m 2 / g, the base resin is ethylene-vinyl acetate copolymer, the VA content thereof is 15-40wt%, and the melt index is 1-10g / 10min; the weathering additive comprises a UV absorber and an antioxidant, the weight ratio of the two being 1:0.5-1:3; the UV absorber is selected from benzotriazole or triazine compounds;

[0039] The antioxidant is selected from hindered phenols or phosphite compounds; the weathering additive comprises an ultraviolet absorber and an antioxidant, and the weight ratio of the two is 1:0.5-1:3; the ultraviolet absorber is selected from benzotriazole or triazine compounds; the antioxidant is selected from hindered phenols or phosphite compounds; the metal hydroxide is surface-treated, and the treating agent is a synergistic system of bis[3-(triethoxysilyl)propyl]tetrasulfide and a titanate coupling agent, and the total added amount of the treating agent is 0.5-3.0% of the total weight of the metal hydroxide.

[0040] The preparation method of the weather-resistant low-smoke halogen-free polyolefin composition for the cable comprises the following steps:

[0041] S1. Optimize and prepare the material according to the formula of the weather-resistant low-smoke halogen-free polyolefin composition for cables, and perform flame retardant surface pretreatment at the same time; Step S1 is specifically:

[0042] Magnesium hydroxide and aluminum hydroxide are placed in a high-speed mixer respectively, and the speed is adjusted to 800-1200 r / min. After heating to 60-80° C., a surface treatment agent composed of bis[3-(triethoxysulfide)propyl]tetrasulfide and a titanate coupling agent is sprayed, and the total amount of the treatment agent is 0.5-3.0% of the total weight of the metal hydroxide. Stir for 15-25 minutes until the surface is evenly coated, then cool to below 40° C., sieve to remove lumps, and set aside. The titanate coupling agent is selected from isopropyl tris(dioctyl pyrophosphate) titanate (TCA-101).

[0043] In addition, the optimization of step S1 optimizes the components through the following weighted calculation model, specifically:

[0044] Comprehensive performance index

[0045] Constraints:

[0046] Where σ b is the tensile strength, OI is the oxygen index, and SD is the smoke density. The subscript ref is the reference value of each parameter, and the weight ω is dynamically allocated according to the cable application scenario.

[0047] S2, preheating and modifying the matrix resin; Step S2, specifically:

[0048] Ethylene-vinyl acetate copolymer is placed in a vacuum oven and preheated at 80-100°C for 30-60 minutes with the vacuum degree controlled at -0.08-0.05 MPa to reduce the resin moisture content to below 0.05wt%. The preheated resin is then transferred to an internal mixer and polyolefin elastomer (POE) with a Shore hardness of 50-85A is added. The internal mixer temperature is controlled at 110-130°C and the rotor speed at 30-50 rpm. The mixture is mixed for 10-15 minutes until a uniform molten matrix is ​​formed.

[0049] S3, pre-dispersion of functional additives; Step S3, specifically:

[0050] The ultraviolet absorber UV-531 and the antioxidant 1076 in the weathering additive are premixed in a weight ratio of 1:0.5-1:3, placed in a three-dimensional motion mixer, and silicone masterbatch, viscosity 500-3000 cSt, fluoropolymer polyvinylidene fluoride and zinc stearate / oxidized polyethylene wax composite lubricant are added. The mixture is mixed under nitrogen protection for 20-40 minutes at a mixing temperature of 50-70°C and a rotation speed of 200-400 rpm to obtain a homogeneous premixed additive package.

[0051] S4, multi-stage blending extrusion; the pretreated base resin, metal hydroxide flame retardant and the premixed additive package obtained in step 3 are put into a twin-screw extruder, and the barrel temperature is controlled in sections: 150-160°C in zone 1, 165-175°C in zone 2, 170-180°C in zone 3, and 175-185°C in zone 4, and the screw speed is 250-400 rpm; liquid silane coupling agent is injected at the end of zone 4, and nano-scale dispersion is achieved through a high shear mixing die.

[0052] S5, post-processing, the extruded product is water-cooled and pelletized, and then immersed in a cold soaking tank containing erucamide frosting inhibitor with a concentration of 0.1-0.5wt%, the cooling water temperature is controlled at 10-25°C, and the soaking time is 5-10 seconds; after drying, it is matured at 50-70°C for 4-8 hours.

[0053] Example 1

[0054] Formula and process parameters:

[0055] Matrix resin, ethylene-vinyl acetate copolymer (VA content 28%, melt index 5g / 10min), 60 parts;

[0056] Halogen-free flame retardant: magnesium hydroxide (D50 = 3 μm, specific surface area 12m 2 / g) + aluminum hydroxide (D50 = 2 μm, specific surface area 16m 2 / g), with a total addition amount of 90 parts (mass ratio 1:1);

[0057] Weathering additives: 4.5 parts of benzotriazole UV-326 and antioxidant 1076 (weight ratio 1:1.5);

[0058] Coupling agent: silane coupling agent KH-570, accounting for 0.8% of the total weight of the flame retardant;

[0059] Lubricant: zinc stearate and oxidized polyethylene wax (1:1), 5 parts;

[0060] Processing aid: silicone masterbatch (viscosity 1500 cSt): polyvinylidene fluoride = 1:1, 12 parts;

[0061] Process characteristics:

[0062] Metal hydroxide surface treatment agent (disulfide: titanate TCA-101 = 1:1), treatment amount 1.8%;

[0063] Mixing temperature is 120℃, speed is 40rpm; temperature of extruder zone 4 is 155℃-170℃-175℃-180℃155℃-170℃-175℃-180℃, screw speed is 300rpm;

[0064] The cold soak tank has an erucamide concentration of 0.3 wt%, an immersion time of 8 seconds, and an aging temperature of 60°C for 6 hours.

[0065] The properties of the prepared materials are shown in the following table:

[0066]

[0067]

[0068] Example 2

[0069] Formula and process parameters:

[0070] Halogen-free flame retardant: magnesium hydroxide (D50 = 4.5 μm, specific surface area 8m 2 / g) + aluminum hydroxide (D50 = 2.5 μm, specific surface area 22m 2 / g), with a total addition amount of 130 parts (mass ratio 2:1);

[0071] Matrix resin: EVA with VA content of 35% and melt index of 2g / 10min, 55 parts;

[0072] Weathering additive: triazine UV-1164 and phosphite 168 (1:2), 6 parts;

[0073] Lubricant formula: zinc stearate: oxidized polyethylene wax = 1:1.5, 8 parts;

[0074] Processing aid: high viscosity silicone masterbatch (2500 cSt): ETFE = 1:2, 18 parts;

[0075] Process characteristics:

[0076] The proportion of disulfide in the surface treatment is increased (accounting for 65% of the treatment agent), and the total treatment amount is 2.5%;

[0077] The temperature of the four zones of the extruder is raised to:

[0078] 158℃-173℃-178℃-185℃158℃-173℃-178℃-185℃, screw speed 350rpm;

[0079] The water temperature of the cold soaking tank is 15°C and the aging time is 7 hours;

[0080] The properties of the prepared materials are shown in the following table:

[0081]

[0082] Example 3

[0083] Formula and process parameters:

[0084] Halogen-free flame retardant: ultrafine aluminum hydroxide (D50 = 1.2 μm, specific surface area 24m 2 / g) as the main additive, with a total addition of 70 parts; base resin: high-flow EVA (melt index 8g / 10min) and POE elastomer (Shore hardness 75A) compounded, accounting for 30% of the total base resin; weathering additives: UV-531 and antioxidant 1010 (1:3), 7 parts; lubricant: oxidized polyethylene wax with an increased ratio (1:2), 6 parts;

[0085] Processing aid: silicone masterbatch (2000cSt): PVDF = 1:3, 15 parts;

[0086] Process characteristics: Surface treatment is dominated by titanate (accounting for 70% of the treatment agent); the mixing stage is extended to 18 minutes, the mixing temperature is 125°C; the aging stage is a gradient temperature increase (50°C → 70°C, 8 hours);

[0087]

[0088] Example 1 achieves simultaneous improvement of mechanical strength, flame retardancy and weather resistance through particle size distribution optimization and balanced coupling agent ratio, and is suitable for general-purpose building cables.

[0089] Example 2 targets high flame retardancy scenarios (such as subway tunnels) and utilizes ultrafine flame retardant compounding and surface treatment enhancement. The smoke density is lower than the general industry level (industry benchmark value 110), and the O index exceeds 40.

[0090] Example 3 uses "high VA content resin + POE elastomer toughening" compounded with weather-resistant additives to achieve a performance attenuation rate of ≤5% under extreme climates, meeting the harsh environmental requirements of my country's western plateau and southeastern coastal areas.

[0091] All embodiments meet the core invention effects of smoke density Ds ≤ 100 (ASTM E662) and oxygen index ≥ 32 (ASTM D2863), and the practical effectiveness of the weighted calculation model is demonstrated through examples.

[0092] In summary, the present invention has the following effects:

[0093] Synergistic improvement in weather resistance and flame retardancy: By compounding a UV absorber with a hindered phenol / phosphite antioxidant in a specific ratio, and combining it with a synergistic surface treatment technology of bis[3-(triethoxysilyl)propyl]tetrasulfide and a titanate coupling agent, the interfacial bonding between the metal hydroxide and the matrix resin is significantly enhanced, inhibiting molecular chain degradation under UV radiation and humid and hot environments;

[0094] Balanced optimization of processing performance and mechanical properties: A processing aid system based on a combination of silicone masterbatch and fluoropolymer, combined with a segmented, precise temperature-controlled extrusion process, significantly improves the melt flowability of the highly filled flame retardant system. By optimizing the lubricant compounding ratio, the risk of scorching caused by shear heat is reduced.

[0095] Long-term stability and anti-precipitation properties: By introducing a low-temperature cold dip tank and gradient aging process, the migration tendency of low molecular weight components such as silane coupling agents and lubricants is suppressed;

[0096] Dynamic component optimization and process adaptability: A dynamic weighted calculation model based on tensile strength, oxygen index, and smoke density can adjust the proportions of each component and the weights of process parameters for different cable application scenarios, enabling rapid iterative optimization of formula design and breaking through the efficiency bottleneck of traditional trial-and-error methods.

[0097] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A weather-resistant low-smoke halogen-free polyolefin composition for cables, characterized by: The formula of the weather-resistant low-smoke halogen-free polyolefin composition for cables is as follows: base resin: 40-80 parts; halogen-free flame retardant: 30-150 parts; weather-resistant additive: 0.5-8 parts; Coupling agent: 0.5-5 parts; Lubricant: 1-10 parts; processing aid: 2-20 parts; The halogen-free flame retardant is a metal hydroxide, which is prepared from magnesium hydroxide and aluminum hydroxide, wherein the median particle size D50 of the magnesium hydroxide is 1-5 μm and the specific surface area is 5-20 m 2 / g; the median particle size D50 of aluminum hydroxide is 0.5-3μm, and the specific surface area is 8-25m 2 / g, the matrix resin is ethylene-vinyl acetate copolymer, the VA content thereof is 15-40wt%, and the melt index is 1-10g / 10min.

2. The weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 1, characterized in that: The weathering-resistant additive comprises an ultraviolet absorber and an antioxidant, and the weight ratio of the two is 1:0.5-1:3; the ultraviolet absorber is selected from benzotriazole or triazine compounds; and the antioxidant is selected from hindered phenols or phosphite compounds.

3. The weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 1, characterized in that: The coupling agent is silane coupling agent KH-550 or KH-570, and the application amount is 0.3-1.5% of the total weight of the inorganic filler; the lubricant is a compound of zinc stearate and oxidized polyethylene wax, and the weight ratio of the two is 1:0.5-1:

2.

4. The weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 1, characterized in that: The processing aid is a compound system of silicone masterbatch and fluoropolymer, with a weight ratio of 1:0.5-1:

3. The viscosity of the silicone masterbatch is 500-3000 cSt, and the fluoropolymer is polyvinylidene fluoride or ethylene-tetrafluoroethylene copolymer.

5. The weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 1, characterized in that: The metal hydroxide is surface treated, the treating agent is a synergistic system of bis[3-(triethoxysilyl)propyl]tetrasulfide and titanate coupling agent, and the total addition amount of the treating agent is 0.5-3.0% of the total weight of the metal hydroxide.

6. A method for preparing a weather-resistant low-smoke halogen-free polyolefin composition for cables, characterized in that: The method for preparing the weather-resistant low-smoke halogen-free polyolefin composition for cables is prepared by using the material according to any one of claims 1 to 5, comprising the following steps: S1. Optimize and prepare the material according to the formula of the weather-resistant low-smoke halogen-free polyolefin composition for cables, and perform flame retardant surface pretreatment at the same time; S2, preheating and modification of base resin; S3, pre-dispersion of functional additives; S4, multi-stage blending extrusion; S5, post-processing, the extruded product is water-cooled and pelletized, and then immersed in a cold soaking tank containing erucamide frosting inhibitor with a concentration of 0.1-0.5wt%, the cooling water temperature is controlled at 10-25°C, and the soaking time is 5-10 seconds; after drying, it is matured at 50-70°C for 4-8 hours.

7. The method for preparing a weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 6, characterized in that: Step S1 is specifically as follows: Magnesium hydroxide and aluminum hydroxide are placed in a high-speed mixer respectively, the speed is adjusted to 800-1200 r / min, and after heating to 60-80° C., a surface treatment agent composed of bis[3-(triethoxysulfide)propyl]tetrasulfide and a titanate coupling agent is sprayed, and the total amount of the treatment agent is 0.5-3.0% of the total weight of the metal hydroxide. Stir for 15-25 minutes until the surface is evenly coated, then cool to below 40° C., sieve to remove lumps, and set aside. The titanate coupling agent is selected from isopropyl tris(dioctyl pyrophosphate acyloxy) titanate (TCA-101); Step S2 is specifically as follows: Put the ethylene-vinyl acetate copolymer into a vacuum oven and preheat it at 80-100°C for 30-60 minutes, with the vacuum degree controlled at -0.08-0.05MPa, so that the water content of the resin is reduced to below 0.05wt%; The preheated resin is then transferred to an internal mixer, and polyolefin elastomer POE with a Shore hardness of 50-85A is added. The internal mixing temperature is controlled at 110-130°C and the rotor speed is 30-50 rpm. The mixture is mixed for 10-15 minutes until a uniform molten matrix is ​​formed.

8. The method for preparing a weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 6, characterized in that: Step S3 is specifically as follows: The ultraviolet absorber UV-531 and the antioxidant 1076 in the weathering additive are pre-mixed in a weight ratio of 1:0.5-1:3, placed in a three-dimensional motion mixer, and silicone masterbatch, viscosity 500-3000 cSt, fluoropolymer polyvinylidene fluoride and zinc stearate / oxidized polyethylene wax composite lubricant are added. The mixture is mixed under nitrogen protection for 20-40 minutes at a mixing temperature of 50-70°C and a rotation speed of 200-400 rpm to obtain a homogeneous pre-mixed additive package; Step S4 is specifically as follows: The pretreated base resin, metal hydroxide flame retardant and the premixed additive package obtained in step 3 are put into a twin-screw extruder, and the barrel temperature is controlled in sections: 150-160°C in zone 1, 165-175°C in zone 2, 170-180°C in zone 3, and 175-185°C in zone 4, and the screw speed is 250-400 rpm; a liquid silane coupling agent is injected at the end of zone 4, and nano-scale dispersion is achieved through a high-shear mixing die.

9. The method for preparing a weather-resistant low-smoke halogen-free polyolefin composition for cables according to claim 6, characterized in that: The optimization described in step S1 optimizes the components through the following weighted calculation model, specifically: Comprehensive performance index Constraints: 0.25≤w i ≤0.65; Where, σ b is the tensile strength, OI is the oxygen index, and SD is the smoke density. The subscript ref is the reference value of each parameter, and the weight ω is dynamically allocated according to the cable application scenario.

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