B1 grade low-smoke halogen-free flame-retardant cable material for small-diameter cables and preparation method thereof

Abstract

The application relates to the technical field of high polymer composite materials, and discloses a B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables and a preparation method thereof. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables comprises the following components by weight: ethylene-vinyl acetate copolymer, a compatilizer, metallocene-catalyzed polyethylene, an olefin copolymer, a flame retardant, aluminum diethyl phosphinate, cyanuric acid melamine, hydrotalcite, zinc oxide, an alkoxyl-substituted hindered amine stabilizer, a silicone master batch, an antioxidant and a crosslinking agent. The compatilizer is composed of first POE grafted maleic anhydride and second POE grafted maleic anhydride, and the grafting rates of the first POE grafted maleic anhydride and the second POE grafted maleic anhydride are different. Through the technical scheme, the problem of poor flame-retardant performance of the cable material for small-diameter cables in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, specifically to a B1 grade low-smoke halogen-free flame-retardant cable material for small-diameter cables and its preparation method. Background Technology

[0002] Small-diameter cables refer to cables with relatively small wire diameters. Copper-core PVC insulated cables are a common type of small-diameter cable used in daily life and are also the main type of cable for low-voltage power transmission in households. Currently, small-diameter cable materials generally suffer from problems such as high density, slow extrusion processing speed, high acidity of gases released during combustion, and poor flame retardant performance. In existing technologies, adding flame retardants is often used to address the poor flame retardant performance of cable materials. However, with excessive amounts of flame retardants added, the dispersibility and compatibility with the matrix material become critical issues, severely affecting the flame retardant's effectiveness. Therefore, surface modification of the flame retardant or the addition of compatibilizers is often necessary. Since surface modification of flame retardants is relatively complex, the commonly used method is to add compatibilizers. However, the flammability of compatibilizers limits the flame retardancy of the material to some extent, and the dispersing effect of compatibilizers on flame retardants is limited. With large amounts of flame retardants added, achieving good dispersion and compatibility is difficult. Cable materials with poor flame retardant properties not only increase the risk of fire spread, but may also cause electrical system failures and equipment damage, endangering public safety. Therefore, it is necessary to develop a low-smoke halogen-free cable material for small-diameter cables with high flame retardant properties. Summary of the Invention

[0003] This invention proposes a B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables and its preparation method, which solves the problem of poor flame-retardant performance of cable materials for small-diameter cables in related technologies.

[0004] The technical solution of this invention is as follows: This invention proposes a B1 grade low-smoke halogen-free flame-retardant cable material for small-diameter cables, comprising the following raw materials in parts by weight: 40-60 parts of ethylene-vinyl acetate copolymer, 8-14 parts of compatibilizer, 10-20 parts of metallocene-catalyzed polyethylene, 12-35 parts of olefin copolymer, 120-160 parts of flame retardant, 3-6 parts of aluminum diethylphosphines, 1-3 parts of melamine cyanurate, 2-4 parts of hydrotalcite, 1-3 parts of zinc oxide, 1-4 parts of alkoxy-substituted hindered amine stabilizer, 1.4-2.4 parts of silicone masterbatch, 0.8-2.0 parts of antioxidant, and 1.2-2.0 parts of crosslinking agent; the compatibilizer is composed of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride, wherein the grafting rates of the first POE grafted with maleic anhydride and the second POE grafted with maleic anhydride are different.

[0005] In this invention, alkoxy-substituted hindered amine stabilizers are used to enhance the material's ability to quench free radicals, thereby further improving the material's flame retardant properties, especially its gas-phase flame retardant effect.

[0006] As a further technical solution, the mass ratio of the first POE grafted with maleic anhydride to the second POE grafted with maleic anhydride is 1:2~3, and the grafting rate of the first POE grafted with maleic anhydride is < the grafting rate of the second POE grafted with maleic anhydride.

[0007] In this invention, POE-grafted maleic anhydride is polyolefin elastomer-grafted maleic anhydride. By adjusting the mass ratio of the first POE-grafted maleic anhydride and the second POE-grafted maleic anhydride, their synergistic effect is brought into play. The combination of the first POE-grafted maleic anhydride with a low grafting rate and the second POE-grafted maleic anhydride with a high grafting rate can more effectively enhance the bonding force between the components, enabling the components of the cable material to be more uniformly dispersed and fused. This not only helps to improve the processing performance of the cable material, making it easier to plasticize and mold during the preparation process, but also ensures that additives such as flame retardants can play a full role, thereby significantly improving the overall performance of cable material for small-diameter cables.

[0008] As a further technical solution, the grafting rate of the first POE grafted with maleic anhydride is 0.712%, and the grafting rate of the second POE grafted with maleic anhydride is 1.2%.

[0009] In this invention, the first POE grafted with maleic anhydride at a grafting rate of 0.712% has relatively low activity, which can reduce the interfacial tension in the system, making it easier for flame retardant particles to disperse in the cable material and avoiding the agglomeration of flame retardants. The second POE grafted with maleic anhydride at a grafting rate of 1.2% has stronger activity due to its higher grafting rate, which can further refine the dispersion of flame retardants and form a more stable and dense carbon layer structure at high temperatures. The dense carbon layer can effectively isolate the transfer of heat and oxygen, prevent the further spread of flames, and thus greatly improve the flame retardant performance of the cable material.

[0010] As a further technical solution, the olefin copolymer is composed of olefin copolymer A and olefin copolymer B, wherein olefin copolymer A includes one or more of ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer; and olefin copolymer B is ethylene-α-olefin copolymer.

[0011] As a further technical solution, the mass ratio of the olefin copolymer A to the olefin copolymer B is 5~7.5:1.

[0012] In this invention, olefin copolymer A has a relatively short branched chain structure, which can impart good flexibility and plasticity to the cable material. Olefin copolymer B has a good molecular structure regularity, which can improve the crystallinity of the material to a certain extent. When the two are in the range of 5~7.5:1, a good balance can be achieved between flexibility and crystallinity, making the material easy to plasticize and mold, which can meet the complex processing requirements of small diameter cables, and can also ensure that the cable has a certain rigidity and shape stability after molding, avoiding problems such as cable deformation.

[0013] As a further technical solution, the antioxidant includes one or more of antioxidant 1010, antioxidant 168, and antioxidant DSTP, preferably composed of antioxidant 1010, antioxidant 168, and antioxidant DSTP in a mass ratio of 1:0.2:0.2 to 1:0.5:0.4.

[0014] In this invention, a composite antioxidant is added. Different types of antioxidants have different antioxidant mechanisms. These different antioxidant mechanisms work together and synergistically to block the oxidation reaction process from multiple dimensions. This is more comprehensive and efficient than the effect of a single antioxidant, and can more effectively protect the polymer matrix in the cable material from oxidative damage and slow down the aging rate of the cable material.

[0015] As a further technical solution, the crosslinking agent includes one or two of triallyl isocyanurate and trimethylolpropane trimethacrylate.

[0016] In this invention, a crosslinking agent is added. The crosslinking agent can promote the formation of chemical bonds between polymer molecular chains in the cable material, and build a three-dimensional network crosslinking structure, making the cable material less prone to thermal deformation and thermal decomposition under high temperature environment, thus effectively improving the stability of the cable material.

[0017] As a further technical solution, the flame retardant is composed of aluminum hydroxide and magnesium hydroxide, and the mass ratio of aluminum hydroxide to magnesium hydroxide is 9:7 to 7:5.

[0018] In this invention, magnesium hydroxide and aluminum hydroxide are added as flame retardants. Magnesium hydroxide, due to its special hexagonal plate structure, serves as the main flame retardant charring agent and smoke suppressant. Aluminum hydroxide can absorb heat and lower the temperature, decompose and dilute oxygen and combustible gases. The two work synergistically to more effectively reduce the generation and release of smoke, reduce the harm of smoke to personnel in a fire, improve fire safety, and further improve the flame retardant performance of cable materials. Moreover, aluminum hydroxide and magnesium hydroxide are both inorganic flame retardants. Compared with organic flame retardants, they do not produce toxic and harmful gases and substances during combustion, which meets environmental protection requirements.

[0019] As a further technical solution, the hydrotalcite includes one or more of magnesium aluminum hydrotalcite, zinc aluminum hydrotalcite, and calcium aluminum hydrotalcite, preferably magnesium aluminum hydrotalcite.

[0020] In this invention, the hydrotalcite is preferably magnesium aluminum hydrotalcite. Magnesium aluminum hydrotalcite has a suitable thermal decomposition temperature range. During the combustion process of cable material, it can decompose and absorb heat at the appropriate time, effectively reducing the surface temperature of the material and inhibiting the combustion reaction. Compared with zinc aluminum hydrotalcite and calcium aluminum hydrotalcite, magnesium aluminum hydrotalcite absorbs more heat during decomposition and has a better effect on delaying the combustion process.

[0021] In this invention, hydrotalcite and zinc oxide are used to improve the char residue rate of the material and reduce heat conduction during combustion, thereby improving the flame retardant performance of the cable material.

[0022] As a further technical solution, when the hydrotalcite is magnesium aluminum hydrotalcite, the magnesium-aluminum ratio of the magnesium aluminum hydrotalcite is 2~3.

[0023] In this invention, the magnesium-aluminum ratio refers to the molar ratio of magnesium to aluminum in magnesium-aluminum hydrotalcite. By limiting the magnesium-aluminum ratio of magnesium-aluminum hydrotalcite, a more stable flame-retardant structure is formed when the hydrotalcite is heated, the decomposition temperature and rate of hydrotalcite are coordinated, and the flame-retardant performance of the cable material is further improved.

[0024] This invention also proposes a method for preparing low-smoke halogen-free flame-retardant cable material for small-diameter cables, comprising the following steps:

[0025] S1. Weigh all raw materials except the crosslinking agent, mix them evenly, then add the crosslinking agent and knead them to obtain a mixed rubber compound.

[0026] S2. After extrusion and granulation, the mixed rubber compound yields low-smoke halogen-free flame-retardant cable material.

[0027] As a further technical solution, the mixing time is 2 minutes.

[0028] As a further technical solution, the mixing temperature is 150~165℃, and the mixing time is 10~20min.

[0029] As a further technical solution, in step S1, after the raw materials other than olefin copolymer B and crosslinking agent are mixed evenly, olefin copolymer B and crosslinking agent are added and the mixture is intensively mixed to obtain a mixed rubber compound.

[0030] The working principle and beneficial effects of this invention are as follows:

[0031] Existing technologies for improving flame retardant properties in cable materials by adding compatibilizers have limited effectiveness, especially when the amount of flame retardant used is too large. It becomes difficult for the compatibilizer to achieve uniform dispersion and compatibility with the matrix material. Furthermore, excessive compatibilizer addition can further reduce the flame retardant properties of the cable material due to its flammability. This invention addresses this issue by adding a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride at different grafting rates to prepare a cable material that improves its flame retardant properties. In this invention, by adjusting the grafting rates of the first POE grafted with maleic anhydride and the second POE grafted with maleic anhydride, the synergistic effect of the two is achieved. The POE grafted with maleic anhydride with a higher grafting rate, due to its outstanding polarity and reactivity, tightly binds the flame retardant to the matrix resin, enhancing the compatibility of the flame retardant with matrices such as ethylene-vinyl acetate copolymer and metallocene-catalyzed polyethylene. The POE grafted with maleic anhydride with a lower grafting rate, utilizing its good flexibility, reduces the viscosity of the system during the mixing of various components of the cable material, allowing for smoother and more uniform mixing of the components and ensuring the uniform distribution of the flame retardant throughout the system. The synergistic effect of the two reduces the impact of the compatibilizer's flammability on the flame retardant performance of the cable material, while ensuring uniform dispersion of the flame retardant and good compatibility with the matrix material. The use of both POE grafted with maleic anhydride allows the uniformly dispersed flame retardant to respond rapidly, quickly forming an insulating layer on the material surface, preventing contact between oxygen and flammable substances, and inhibiting the generation of flammable gases, thereby effectively suppressing the spread of combustion and greatly improving the flame retardant effect. Furthermore, its flammability rating can reach the B1 level in the GB 31247-2014 standard "Classification of Flammability of Cables and Optical Fibers". Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following examples and comparative examples:

[0034] Ethylene-vinyl acetate copolymer: vinyl acetate monomer content is 28wt%, model is MV1055;

[0035] The first POE grafted with maleic anhydride has a grafting rate of 0.712%, model number FB521A, and is manufactured by Jia Yi Rong Polymer (Shanghai) Co., Ltd.

[0036] The second POE was grafted with maleic anhydride, with a grafting rate of 1.2%, and the manufacturer was Dongguan Kadar Plastic Raw Materials Co., Ltd.

[0037] Metallocene-catalyzed polyethylene: model SP0540, manufactured by Mitsui Chemicals Co., Ltd.

[0038] Ethylene-butene copolymer: Model number Exact™ 9071;

[0039] Ethylene-hexene copolymer: model number Exceed™ mPE 0015XC;

[0040] Ethylene-octene copolymer: Model number ENGAGE™ POE 8150;

[0041] Ethylene-α-olefin copolymer: Model name LUCANT™, manufactured by Mitsui Chemicals Co., Ltd.

[0042] Aluminum hydroxide: Silane-surface-treated aluminum hydroxide with an average particle size of 1.1 nm;

[0043] Magnesium hydroxide: average particle size 3.5μm, type S-6, manufacturer: Kamishima Chemical, Japan;

[0044] Zinc-magnesium-aluminum ternary hydrotalcite: average particle size is 0.8 μm;

[0045] Calcium aluminum hydrotalcite: average particle size is 0.8 μm;

[0046] Magnesium aluminum hydrotalcite: average particle size is 0.8 μm;

[0047] Alkoxy-substituted hindered amine stabilizer: model number NOR116;

[0048] Silicone masterbatch: 50wt% active ingredient content, manufactured by Shanghai Canhui Trading Co., Ltd.

[0049] Example 1

[0050] A method for preparing B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables includes the following steps:

[0051] S1. Weigh 40 parts of ethylene-vinyl acetate copolymer, 8 parts of compatibilizer, 10 parts of metallocene-catalyzed polyethylene, 10 parts of ethylene-butene copolymer, 70 parts of aluminum hydroxide, 50 parts of magnesium hydroxide, 3 parts of aluminum diethylphosphinic acid, 1 part of melamine cyanurate, 2 parts of calcium aluminum hydrotalcite, 1 part of zinc oxide, 1 part of alkoxy-substituted hindered amine stabilizer, 1.4 parts of silicone masterbatch, and 0.8 parts of antioxidant. Mix for 2 minutes, then add 2 parts of ethylene-α-olefin copolymer and 1.2 parts of triallyl isocyanurate. Mix at 150°C for 20 minutes to obtain a mixed rubber compound. The compatibilizer consists of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride in a mass ratio of 1:2. The antioxidant consists of antioxidant 1010, antioxidant 168, and antioxidant DSTP in a mass ratio of 1:0.2:0.2.

[0052] S2. After the mixed rubber compound is extruded by a two-stage twin-screw extruder followed by a single-screw extruder, low-smoke halogen-free flame-retardant cable material is obtained.

[0053] The operating parameters of the two-stage twin-screw to single-screw are as follows: the temperatures of zones one through six in the twin-screw are set to 110℃, 120℃, 130℃, 140℃, 145℃, and 140℃ respectively, and the temperatures of zones one through six in the single-screw are set to 100℃, 110℃, 120℃, 130℃, 120℃, and 120℃ respectively.

[0054] Example 2

[0055] A method for preparing B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables includes the following steps:

[0056] S1. Weigh 50 parts of ethylene-vinyl acetate copolymer, 10 parts of compatibilizer, 15 parts of metallocene-catalyzed polyethylene, 20 parts of ethylene-hexene copolymer, 80 parts of aluminum hydroxide, 60 parts of magnesium hydroxide, 5 parts of aluminum diethylphosphinic acid, 2 parts of melamine cyanurate, 3 parts of calcium aluminum hydrotalcite, 2 parts of zinc oxide, 2 parts of alkoxy-substituted hindered amine stabilizer, 2 parts of silicone masterbatch, and 1.5 parts of antioxidant. Mix for 2 minutes, then add 3 parts of ethylene-α-olefin copolymer and 1.5 parts of triallyl isocyanurate. Mix at 160°C for 15 minutes to obtain a mixed rubber compound. The compatibilizer consists of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride in a mass ratio of 1:2. The antioxidant consists of antioxidant 1010, antioxidant 168, and antioxidant DSTP in a mass ratio of 1:0.4:0.3.

[0057] S2. After the mixed rubber compound is extruded by a two-stage twin-screw extruder followed by a single-screw extruder, low-smoke halogen-free flame-retardant cable material is obtained.

[0058] The operating parameters of the two-stage twin-screw to single-screw are as follows: the temperatures of zones one through six in the twin-screw are set to 110℃, 120℃, 130℃, 140℃, 145℃, and 140℃ respectively, and the temperatures of zones one through six in the single-screw are set to 100℃, 110℃, 120℃, 130℃, 120℃, and 120℃ respectively.

[0059] Example 3

[0060] A method for preparing B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables includes the following steps:

[0061] S1. Weigh 60 parts of ethylene-vinyl acetate copolymer, 14 parts of compatibilizer, 20 parts of metallocene-catalyzed polyethylene, 30 parts of ethylene-octene copolymer, 90 parts of aluminum hydroxide, 70 parts of magnesium hydroxide, 6 parts of aluminum diethylphosphinic acid, 3 parts of melamine cyanurate, 4 parts of calcium aluminum hydrotalcite, 3 parts of zinc oxide, 4 parts of alkoxy-substituted hindered amine stabilizer, 2.4 parts of silicone masterbatch, 2.0 parts of antioxidant, and 4 parts of ethylene-α-olefin copolymer. Mix for 2 minutes, then add 2 parts of trimethylolpropane trimethacrylate. Mix at 165°C for 10 minutes to obtain a mixed rubber compound. The compatibilizer consists of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride in a mass ratio of 1:2. The antioxidant consists of antioxidant 1010, antioxidant 168, and antioxidant DSTP in a mass ratio of 1:0.5:0.4.

[0062] S2. After the mixed rubber compound is extruded by a two-stage twin-screw extruder followed by a single-screw extruder, low-smoke halogen-free flame-retardant cable material is obtained.

[0063] The operating parameters of the two-stage twin-screw to single-screw are as follows: the temperatures of zones one through six in the twin-screw are set to 110℃, 120℃, 130℃, 140℃, 145℃, and 140℃ respectively, and the temperatures of zones one through six in the single-screw are set to 100℃, 110℃, 120℃, 130℃, 120℃, and 120℃ respectively.

[0064] Example 4

[0065] The difference between Example 4 and Example 2 is that the compatibilizer consists of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride in a mass ratio of 1:3.

[0066] Example 5

[0067] The difference between Example 5 and Example 2 is that the compatibilizer consists of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride in a mass ratio of 1:2.5.

[0068] Example 6

[0069] The difference between Example 6 and Example 5 is that calcium aluminum hydrotalcite is replaced with an equal amount of zinc magnesium aluminum ternary hydrotalcite.

[0070] Example 7

[0071] The difference between Example 7 and Example 5 is that calcium aluminum hydrotalcite is replaced with an equal amount of magnesium aluminum hydrotalcite, wherein the magnesium-aluminum ratio of the magnesium aluminum hydrotalcite is 1.78.

[0072] Example 8

[0073] The difference between Example 8 and Example 7 is that the magnesium-aluminum ratio of the magnesium-aluminum hydrotalcite is 2.

[0074] Example 9

[0075] The difference between Example 9 and Example 7 is that the magnesium-aluminum ratio of the magnesium-aluminum hydrotalcite is 3.

[0076] Example 10

[0077] The difference between Example 10 and Example 7 is that the magnesium-aluminum ratio of the magnesium-aluminum hydrotalcite is 4.5.

[0078] Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 2 is that the compatibilizer is a first POE grafted with maleic anhydride.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 and Example 2 is that the compatibilizer is a second POE grafted with maleic anhydride.

[0082] Experimental Example 1

[0083] After extrusion, the low-smoke halogen-free flame-retardant cable materials prepared in Examples 1-10 and Comparative Examples 1-2 were used to obtain cable material samples. The cable material samples were prepared into Type IV samples according to the test method specified in GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The oxygen index of the samples was tested using Method B in 8.2.2.

[0084] The test results are shown in Table 1:

[0085] Table 1 Performance test results of low-smoke halogen-free flame-retardant cable materials prepared in Examples 1-10 and Comparative Examples 1-2

[0086]

[0087] Compared with Comparative Examples 1 and 2, the oxygen index of Example 2 is better than that of Comparative Examples 1 and 2, indicating that the first POE grafted with maleic anhydride and the second POE grafted with maleic anhydride have a synergistic effect, which can improve the flame retardant properties of the cable material.

[0088] In Examples 2, 4, and 5, the oxygen index of Example 5 is better than that of Examples 2 and 4, indicating that when the mass ratio of the first POE grafted with maleic anhydride and the second POE grafted with maleic anhydride is 1:2.5, the resulting cable material has better flame retardant properties.

[0089] Compared with Examples 5 and 6, the oxygen index of Example 7 is better than that of Examples 5 and 6, indicating that when the added hydrotalcite is magnesium aluminum hydrotalcite, the flame retardant properties of the cable material can be further improved.

[0090] Compared with Examples 7 and 10, the oxygen index of Examples 8 and 9 is better than that of Examples 7 and 10, indicating that when the magnesium-aluminum ratio of magnesium-aluminum hydrotalcite is 2 to 3, the flame retardant properties of the obtained cable material are better.

[0091] Experiment Example 2

[0092] After extruding the low-smoke halogen-free flame-retardant cable materials prepared in Examples 1-10, small-diameter wire and cable samples were obtained. The combustion performance rating of the samples was tested according to the test methods specified in GB 31247-2014 "Classification of Combustion Performance of Cables and Optical Fibers".

[0093] The test results are shown in Table 2:

[0094] Table 2. Test results of the combustion performance of small-diameter wires and cables prepared in Examples 1-10

[0095]

[0096] Tests showed that samples 1-10 all achieved a B1 flammability rating.

[0097] Experimental Example 3

[0098] 1. Tensile strength and elongation at break: In accordance with the provisions of GB / T 32129-2015, the cable material sample prepared in Example 1 was prepared into a specified test sample, and the tensile strength and elongation at break of the test specimen were tested.

[0099] 2. Volume resistivity: The volume resistivity of the cable material prepared in Example 1 was tested according to the test method specified in GB / T 31838.2-2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity". The test temperature was 20℃.

[0100] 3. Hardness: The hardness of the cable material prepared in Example 1 was tested according to the test method specified in ISO 868-2003.

[0101] The test results are shown in Table 3:

[0102] Table 3 Performance test results of the low-smoke halogen-free flame-retardant cable material prepared in Example 1

[0103]

[0104] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. 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 B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables, characterized in that, The raw materials include the following components by weight: 40-60 parts of ethylene-vinyl acetate copolymer, 8-14 parts of compatibilizer, 10-20 parts of metallocene-catalyzed polyethylene, 12-35 parts of olefin copolymer, 120-160 parts of flame retardant, 3-6 parts of aluminum diethylphosphinate, 1-3 parts of melamine cyanurate, 2-4 parts of hydrotalcite, 1-3 parts of zinc oxide, 1-4 parts of alkoxy-substituted hindered amine stabilizer, 1.4-2.4 parts of silicone masterbatch, 0.8-2.0 parts of antioxidant, and 1.2-2.0 parts of crosslinking agent; the compatibilizer is composed of a first POE grafted with maleic anhydride and a second POE grafted with maleic anhydride, wherein the grafting rates of the first POE grafted with maleic anhydride and the second POE grafted with maleic anhydride are different; The mass ratio of the first POE grafted with maleic anhydride to the second POE grafted with maleic anhydride is 1:2~3, the grafting rate of the first POE grafted with maleic anhydride is 0.712%, and the grafting rate of the second POE grafted with maleic anhydride is 1.2%.

2. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 1, characterized in that, The olefin copolymer is composed of olefin copolymer A and olefin copolymer B. olefin copolymer A includes one or more of ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer; olefin copolymer B is an ethylene-α-olefin copolymer.

3. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 1, characterized in that, The antioxidants include one or more of antioxidant 1010, antioxidant 168, and antioxidant DSTP.

4. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 1, characterized in that, The crosslinking agent includes one or both of triallyl isocyanurate and trimethylolpropane trimethacrylate.

5. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 1, characterized in that, The hydrotalcite includes one or more of magnesium aluminum hydrotalcite, zinc magnesium aluminum ternary hydrotalcite, and calcium aluminum hydrotalcite.

6. The B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 5, characterized in that, When the hydrotalcite is magnesium aluminum hydrotalcite, the magnesium-aluminum ratio of the magnesium aluminum hydrotalcite is 2 to 3.

7. A method for preparing a B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. After mixing the raw materials except for the crosslinking agent evenly, add the crosslinking agent and mix thoroughly to obtain the mixed rubber compound; S2. After extrusion and granulation, the mixed rubber compound yields low-smoke halogen-free flame-retardant cable material.

8. The method for preparing a B1-grade low-smoke halogen-free flame-retardant cable material for small-diameter cables according to claim 7, characterized in that, The mixing temperature is 150~165℃, and the mixing time is 10~20min.

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