Radiation crosslinked flame retardant polyolefin cable material and method of making

Abstract

This invention discloses an irradiated crosslinked flame-retardant polyolefin cable material and its preparation method, relating to the field of polymer materials technology. The irradiated crosslinked flame-retardant polyolefin cable composition comprises metallocene linear low-density polyethylene, ethylene-vinyl acetate copolymer, polyolefin thermoplastic elastomer, maleic anhydride-grafted POE, hydroxide flame retardant, compound flame retardant, and silane coupling agent. By incorporating maleic anhydride-grafted POE, silane coupling agent, and compound flame retardant, this invention improves the flame-retardant properties of the material and accelerates the irradiated crosslinking reaction, increasing the actual degree of crosslinking and thus reducing the required irradiation dose. This allows the polyolefin cable composition to crosslink under low irradiation doses, improving flame-retardant stability. Furthermore, the use of a combination of MCA and montmorillonite as a compound flame retardant enhances the flame-retardant stability of the material after irradiated crosslinking at low irradiation doses.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to an irradiated crosslinked flame-retardant polyolefin cable material and its preparation method. Background Technology

[0002] Irradiation-crosslinked polyolefins are high-performance materials obtained by using electron beam irradiation to cause network crosslinking of the polyolefin molecular chains. Compared with the uncrosslinked state, they exhibit improved temperature resistance and mechanical strength, thus significantly enhancing product reliability. Based on the superior performance brought by irradiation crosslinking technology, irradiation-crosslinked flame-retardant polyolefins play an important role in the wire and cable industry. However, in polyolefin systems, high irradiation doses are often used to ensure sufficient crosslinking. But after high-dose crosslinking, changes in the material's structural behavior due to crosslinking and degradation can lead to a certain degree of decrease in flame-retardant properties, with particularly significant negative impacts on the material's reliability and flame-retardant stability.

[0003] Currently, the main methods to improve flame retardant performance in the field of cable materials are to increase the content of flame retardants or add special flame retardants. However, increasing the content of flame retardants or introducing special flame retardant systems usually leads to a decrease in the compatibility between the material resin and the flame retardant, a significant decrease in mechanical properties, and difficulty in suppressing flame retardant failure after irradiation, resulting in poor flame retardant stability.

[0004] Patent CN113943453A discloses a high oil-resistant, high flame-retardant, irradiated cross-linked halogen-free, low-smoke polyolefin cable material for oil platform cables and its preparation method. It utilizes an ethylene-vinyl acetate copolymer with high and low VA (vinyl acetate) content to improve compatibility with flame-retardant fillers. By combining a halogen-free flame retardant with a nano-flame-retardant synergist, the total amount of flame retardant added can be reduced, ensuring the material's basic physicochemical properties such as mechanical properties, electrical properties, oil resistance, and low-temperature resistance. Maleic anhydride grafted products act as a "bond bridge" between the resin matrix and the filler powder, increasing the interfacial adhesion between them, giving the material excellent weather resistance and aging resistance. Its tensile strength is 16.1-18.2 MPa, elongation at break is 210-280%, and maximum heat release value is 158.37-181.37 kW / m. 2 However, its irradiation process involves 28 passes, 2.2 meva, 26 mA flow rate, and 30 m / min velocity, resulting in a thermal elongation of 15%-25% after irradiation. Although it exhibits good mechanical properties under this high irradiation intensity treatment, it cannot simultaneously guarantee flame retardant stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects and shortcomings of existing irradiated cross-linked flame-retardant polyolefin cables that cannot simultaneously achieve irradiation efficiency and flame-retardant stability, and to provide an irradiated cross-linked flame-retardant polyolefin cable composition.

[0006] Another object of the present invention is to provide a method for preparing an irradiated cross-linked flame-retardant polyolefin cable composition.

[0007] Another object of the present invention is to provide an irradiated cross-linked flame-retardant polyolefin cable material made by irradiating and cross-linking the above-mentioned irradiated cross-linked flame-retardant polyolefin cable composition.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] This invention protects an irradiated crosslinked flame-retardant polyolefin cable composition, comprising the following components in parts by weight:

[0010]

[0011] The compound flame retardant is composed of melamine cyanurate (MCA) and montmorillonite, and the mass ratio of melamine cyanurate to montmorillonite is (1-12):2.

[0012] The polyolefin cable composition of the present invention improves the flame-retardant stability of the material by incorporating maleic anhydride-grafted POE, a silane coupling agent, and a compound flame retardant into a hydroxide flame-retardant system and optimizing the component ratio. Specifically, maleic anhydride-grafted POE increases the reaction point for cross-linking and accelerates the irradiation cross-linking reaction; the silane coupling agent modifies the hydroxide flame retardant, improves its dispersibility, and enables it to form covalent bonds with the resin system, promoting irradiation cross-linking efficiency; the montmorillonite in the compound flame retardant helps suppress the release of degradation molecules during flame retardation, reducing the degree of combustion aggression and improving flame-retardant stability; MCA forms hydrogen bonds with maleic anhydride-grafted POE, the silane coupling agent, and montmorillonite, and even at low irradiation doses, it can assist in compatibilizing the flame retardant with the resin matrix, facilitating the dispersion of the compound flame retardant in the system and further improving the stability of the system during flame retardation. The flame retardant obtained by compounding melamine cyanurate and montmorillonite has a synergistic effect with the hydroxide flame retardant, and can exhibit high flame retardant performance under low radiation dose treatment, and also has high flame retardant stability.

[0013] The inventors discovered that polyolefin cable compositions, after undergoing an irradiation crosslinking reaction, can form polyolefin cable materials with high mechanical properties. However, high irradiation doses can also lead to molecular chain breakage, resulting in flame retardant degradation and reduced flame retardant stability. By adding maleic anhydride-grafted POE and a silane coupling agent, the reaction point for the crosslinking reaction can be increased, accelerating the irradiation crosslinking reaction and increasing the actual degree of crosslinking. This reduces the actual required irradiation dose, allowing the polyolefin cable composition to undergo crosslinking at low irradiation doses and improving flame retardant stability. Simultaneously, the use of a combination of MCA and montmorillonite as a compound flame retardant enables the polyolefin cable composition to exhibit high flame retardant and mechanical properties, as well as high flame retardant stability, even under low irradiation dose treatment.

[0014] In some embodiments, the silane coupling agent is an epoxy silane coupling agent and / or a vinyl silane coupling agent; specifically, the silane coupling agent includes, but is not limited to, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, vinyltris(methoxyethoxy)silane, and FD-71.

[0015] In some embodiments, the content of maleic anhydride-grafted POE is 5-16 wt% of the total amount of the resin system formed by LLDPE, EVA, POE and maleic anhydride-grafted POE; preferably 8-12 wt%. This content can ensure the radiation crosslinking reaction of the composition system, reduce the actual required radiation dose, and improve flame retardant stability. Excessive maleic anhydride-grafted POE will not further increase the actual degree of crosslinking, but will instead lead to a significant decrease in aging resistance.

[0016] Furthermore, the use of metallocene linear low-density polyethylene, ethylene-vinyl acetate copolymer and POE thermoplastic elastomer provides excellent compatibility with flame retardants. At the same time, the molecular chains in the system are prone to undergo network cross-linking reaction under irradiation, giving the finished product excellent mechanical properties.

[0017] In some embodiments, the content of metallocene linear low-density polyethylene (LLDPE) that enables the achievement of the present invention can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, or 15 parts.

[0018] In some embodiments, the content of ethylene-vinyl acetate copolymer (EVA) that enables the present invention to achieve its purpose can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, or 30 parts.

[0019] In some embodiments, the polyolefin thermoplastic elastomer (POE) content that enables the achievement of the present invention can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, or 30 parts.

[0020] In some embodiments, the content of maleic anhydride-grafted POE that enables the achievement of the present invention can be 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, or 8 parts.

[0021] In some embodiments, the content of the irradiated catalyst that can achieve the purpose of the present invention can be 1 part, 2 parts, 3 parts, 4 parts, or 5 parts.

[0022] In some embodiments, the mass ratio of melamine cyanurate and montmorillonite to achieve the purpose of the present invention can be 1:2, 1:1, 3:2, 2:1, 5:2, 3:1, 7:2, 4:1, 9:2, or 5:1.

[0023] In some embodiments, the mass ratio of melamine cyanurate to montmorillonite is (3-7):2. This is beneficial for improving the flame retardant stability of the product.

[0024] Preferably, the mass ratio of melamine cyanurate to montmorillonite can be 3:2, 2:1, 5:2, 3:1, or 7:2.

[0025] In some embodiments, the mass ratio of aluminum hydroxide to magnesium hydroxide is (3-7):3.

[0026] In some of these embodiments, the following components by mass fraction are included:

[0027]

[0028] This invention further optimizes the component content and appropriately controls the irradiation catalyst content at a high level, which can reduce the irradiation dose required to achieve the same degree of crosslinking, thus improving irradiation efficiency. Under the condition of lower irradiation dose, the degree of irradiation degradation can be reduced, the degree of molecular chain breakage is significantly reduced, the peak change rate of heat release rate after irradiation is reduced, and the flame retardant stability before and after irradiation is increased.

[0029] In some embodiments, the metallocene linear low-density polyethylene has a melt index of 0.1-10 g / 10 min, preferably 0.5-4 g / 10 min, at 190°C and 2.16 kg.

[0030] In some embodiments, the grafting rate of maleic anhydride-grafted POE is 0.5-1.5%; preferably, the grafting rate is 0.8-1.2%.

[0031] The maleic anhydride-grafted POE described in this invention can be selected from commercially available products or prepared in-house.

[0032] In some embodiments, the method for preparing the self-made maleic anhydride-grafted POE is as follows: maleic anhydride and POE resin are mixed and an initiator is added to react. After the reaction is complete, the reaction product is dried at 75-85°C for 5-7 hours to obtain the product.

[0033] Preferably, the preparation method of the self-made maleic anhydride grafted POE includes the following steps: premixing maleic anhydride powder with an organic peroxide initiator, wherein the concentration of the organic peroxide initiator is 5-15%, and after thorough mixing, adding POE resin and mixing, wherein the mass ratio of maleic anhydride powder to POE resin is (1-2):100, melt-blending and extruding at 170-180℃, underwater pelletizing, and drying at 75-85℃ for 5-7 hours to obtain the final product.

[0034] Preferably, the melt blending extrusion is performed using a twin-screw extruder at a temperature of 160-190°C, followed by drying at 75-85°C for 5.5-6.5 hours.

[0035] In some embodiments, the VA content of the ethylene-vinyl acetate copolymer is 15-30 wt%.

[0036] In some embodiments, the irradiation catalyst is one or more of divinylbenzene, trimethylolpropane trimethacrylate, triallyl isocyanurate, or triallyl cyanurate.

[0037] In some embodiments, the hydroxide flame retardant is aluminum hydroxide and magnesium hydroxide in a mass ratio of (3-7):(2-6); preferably, the hydroxide flame retardant is in a mass ratio of (3-7):3.

[0038] In some embodiments, the irradiated crosslinked flame-retardant polyolefin cable composition may contain 0.1-12 parts of conventional additives acceptable to plastics.

[0039] In some embodiments, the additive includes at least one of a silane coupling agent, an antioxidant, and a lubricant.

[0040] Optionally, the antioxidant is primarily a hindered phenolic antioxidant, with phosphite antioxidants and / or thioester antioxidants used as auxiliary antioxidants. Preferably, the hindered phenolic antioxidant is at least one of antioxidant 1010, antioxidant 1076, antioxidant 1098, and antioxidant 1024; the phosphite antioxidant is selected from antioxidant 168; and the thioester antioxidant is selected from antioxidant DSTDP. More preferably, the mass ratio of the hindered phenolic antioxidant, phosphite antioxidant, and thioester antioxidant is (1.5-2.5):(0.8-1.2):1, exhibiting excellent antioxidant properties and improving flame retardant stability.

[0041] This invention protects a method for preparing an irradiated crosslinked flame-retardant polyolefin cable composition, comprising the following steps:

[0042] Metallocene linear low-density polyethylene, ethylene-vinyl acetate copolymer, polyolefin thermoplastic elastomer, maleic anhydride-grafted POE, melamine cyanurate, irradiation catalyst and additives are mixed and stirred evenly. Then, hydroxide flame retardant and montmorillonite are added, and the mixture is kneaded and extruded to obtain irradiated crosslinked flame-retardant polyolefin cable material.

[0043] In some embodiments, the stirring speed is 100-140 rpm.

[0044] In some embodiments, the mixing temperature is 120-140°C.

[0045] In some embodiments, the extrusion temperature is 150-170°C.

[0046] This invention protects an irradiated cross-linked flame-retardant polyolefin cable material, which is made by irradiation cross-linking of the aforementioned irradiated cross-linked flame-retardant polyolefin cable composition.

[0047] In some embodiments, the irradiation dose during the irradiation crosslinking treatment is not greater than 7 Mrad; preferably, the irradiation dose is 5-7 Mrad.

[0048] Compared with the prior art, the beneficial effects of the present invention are:

[0049] This invention provides a polyolefin cable composition. By incorporating maleic anhydride-grafted POE, a silane coupling agent, and a compound flame retardant into a hydroxide flame retardant system and optimizing the component ratio, the flame retardant stability of the material can be improved. Specifically, maleic anhydride-grafted POE increases the reaction point for crosslinking and accelerates the irradiation crosslinking reaction; the silane coupling agent modifies the hydroxide flame retardant, improving its dispersibility and enabling it to form covalent bonds with the resin system, thus promoting irradiation crosslinking efficiency; in the compound flame retardant, a combination of MCA and montmorillonite is used. This combination synergistically enhances the flame retardant performance with the inorganic hydroxide, while the addition of the layered montmorillonite helps maintain the integrity of the char layer and inhibits the release of degradation molecules, particularly improving the flame retardant stability of the material after irradiation crosslinking under low irradiation doses.

[0050] The polyolefin cable material of this invention is made by irradiation crosslinking of the aforementioned polyolefin cable composition. It exhibits a tensile strength ≥11.8 MPa, elongation ≥180%, and a minimum irradiation dose ≤7 Mrad required to achieve 85% gel content. Furthermore, the flame retardant failure rate is no greater than 36%, demonstrating excellent flame retardant stability. After heat aging, the tensile strength retention rate is ≥94.2%, and the elongation at break retention rate is ≥82%, indicating good heat aging resistance. Detailed Implementation

[0051] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0052] The raw materials used in the following examples and comparative examples are as follows:

[0053] Metallocene linear low-density polyethylene (LLDPE): LLDPE ENGAGE 3518PA, ExxonMobil; melt index of 3.5 g / 10 min at 190℃ / 2.16 kg.

[0054] Ethylene-vinyl acetate copolymer (EVA): EVA 00328, ExxonMobil; its VA content is 28 wt%.

[0055] Polyolefin thermoplastic elastomer (POE): POE ENGAGE 8842, Dow Chemical Company.

[0056] Aluminum hydroxide: Chow Bosch, USA, MARTINAL ON-310.

[0057] Magnesium hydroxide: Albemarle, MAGNIFIN H-5IV.

[0058] Melamine cyanurate: MCA, Mitsui Chemicals Co., Ltd.

[0059] Montmorillonite: DK-1, Zhejiang Fenghong Company.

[0060] Meerschaum: Clay 20, commercially available.

[0061] Irradiation catalyst: TAIC, commercially available.

[0062] Silane coupling agent: KBM-303, Shin-Etsu Chemical Co., Ltd., Japan.

[0063] Compound antioxidants: Antioxidant 1010, Antioxidant 168, and Antioxidant DSTDP in a mass ratio of 2:1:1, commercially available.

[0064] Lubricant: CS-12N, commercially available.

[0065] Maleic anhydride-grafted POE-1, prepared in-house, with a grafting rate of 0.8%, exhibits a melt index of 0.7 g / 10 min at 190℃ / 2.16 kg, demonstrating excellent flowability and processing properties. The preparation method includes: premixing maleic anhydride powder with an organic peroxide initiator (bis(2,5-diphenyl)sulfide agent) at a concentration of 10 wt%. After thorough mixing, the mixture is added to a high-speed mixer, followed by the addition of POE resin. The mass ratio of maleic anhydride powder to POE resin is 1.5:100. The mixture is extruded using a twin-screw extruder at 175℃ and pelletized using underwater cutting. After drying at 80℃ for 6 hours, the maleic anhydride-grafted POE copolymer is obtained.

[0066] Maleic anhydride grafted POE-2: Model PC-28, manufactured by Nanhai Baichen Company.

[0067] Maleic anhydride-grafted PE: Model number MC218, manufactured by Ningbo Nengzhiguang Company.

[0068] A method for preparing an irradiated crosslinked flame-retardant polyolefin cable composition includes the following steps: metallocene linear low-density polyethylene, ethylene-vinyl acetate copolymer, POE thermoplastic elastomer, maleic anhydride-grafted POE, melamine cyanurate, and irradiation catalyst are added to a high-speed mixer in proportion and mixed evenly at a speed of 120 rpm. The final mixture is then added to a mixing mill with a hydroxide flame retardant and montmorillonite in proportion. After mixing in the mixing mill, the mixture is extruded and granulated using a two-stage single-screw extruder. The temperature of the mixing mill is controlled at 130°C, and the temperature of the single-screw extruder is controlled at 160°C.

[0069] Examples 1-13

[0070] This embodiment provides a series of irradiated cross-linked flame-retardant polyolefin cable compositions, the components of which are shown in Table 1.

[0071] Table 1. Components (parts by weight) of Examples 1-13

[0072]

[0073]

[0074] Comparative Examples 1-10

[0075] This comparative example provides a series of irradiated cross-linked flame-retardant polyolefin cable compositions, the components of which are shown in Table 2.

[0076] Table 2. Components (parts by weight) of Comparative Examples 1–10

[0077]

[0078] Performance testing

[0079] The materials from Examples 1-13 and Comparative Examples 1-10 were pressed into tablets at 180°C for 10 minutes on a flat vulcanizing machine at a pressure of 15 MPa, with a tablet thickness of 3 mm. After being placed at room temperature for 24 hours, the tablets were irradiated with a high-energy electron beam until the gel content of the tablets reached 85%. Then, the following tests were performed:

[0080] 1. Mechanical property testing: The tensile strength and elongation at break of the irradiated sample were tested according to the test method of standard GB / T 1040.2.

[0081] 2. Flame retardant stability test: Using a cone calorimeter, according to the test method of standard ASTM 1354-04a, at 50kW / m³... 2 The generation of smoke, CO, and CO2 was measured under a heat flux, and the heat release rate (HRR) before and after irradiation was tested. The change rate of flame retardant failure before and after irradiation was calculated. The higher the change rate, the more obvious the flame retardant failure. The calculation formula is: Change rate of flame retardant failure = (peak heat release rate after irradiation - peak heat release rate before irradiation / peak heat release rate before irradiation) * 100%.

[0082] 3. Heat aging test: Place the sample in an oven at 135℃ and keep it for 168 hours. Then test the tensile strength and elongation at break of the material after heat aging. The retention rate of tensile strength after heat aging = tensile strength after heat aging / tensile strength before aging * 100%; the retention rate of elongation after heat aging = elongation after heat aging / elongation before aging * 100%.

[0083] Minimum required radiation dose test: with a source intensity of 3.7 × 10⁻⁶ 15 Bq's γ 60Using Co as the radiation source, samples were treated for 2 minutes under different irradiation doses (0-15 Mrad) at room temperature and in an N2 atmosphere. The gel content of the samples was then tested, and an irradiation dose-gel content curve was obtained. The minimum irradiation dose (rounded down) corresponding to a gel content of 85% is the minimum irradiation dose required to meet the crosslinking requirements of the cable test. The gel content test method is as follows: the sample weight m1 is weighed, the sample is immersed in xylene at 120℃, refluxed, and maintained for 48 hours. The insoluble matter after immersion is removed, vacuum dried, and the weight of the insoluble matter m2 is weighed. The gel content is calculated as m2 / m1*100%.

[0084] The test results are shown in Table 3-4.

[0085] Table 3

[0086]

[0087]

[0088] Table 4

[0089]

[0090] As shown in Tables 3-4, the minimum irradiation dose required for the irradiated crosslinked flame-retardant polyolefin cable composition of the present invention to achieve an 85% gel content is less than 7 Mrad, indicating high irradiation efficiency; the tensile strength is greater than 11.8 MPa, and the elongation at break is greater than 180%, demonstrating excellent mechanical properties; the flame-retardant failure rate is less than 36%, indicating high flame-retardant stability. The tensile strength retention rate after heat aging is greater than 94.2%, and the elongation at break retention rate after heat aging is greater than 82%, exhibiting good heat aging resistance.

[0091] Comparing Comparative Example 1 and Example 1, it can be seen that when the maleic anhydride grafted with POE is excessive, it does not significantly improve the flame retardant stability of the material, and it also leads to a significant decrease in the retention rate of tensile strength and elongation after heat aging, resulting in poor heat aging resistance.

[0092] Comparing Comparative Examples 2-3 and Example 1, it can be seen that adding maleic anhydride-grafted POE can increase the reaction point where the crosslinking reaction occurs, reduce the actual required irradiation dose, and increase the flame retardant failure rate. While increasing the dose of the irradiation catalyst without adding maleic anhydride-grafted POE can improve the efficiency of the crosslinking reaction to some extent and help reduce the actual required irradiation dose, it will lead to a significant decrease in the mechanical properties of the product.

[0093] A comparison of Comparative Examples 4-7 and Example 1 shows that adding a compound flame retardant can reduce the actual required irradiation dose, improve the flame retardant stability of the material, and maintain good mechanical properties and aging resistance. While using montmorillonite alone as a flame retardant can also reduce the actual required irradiation dose, it significantly damages the mechanical properties of the material. Using MCA alone as a flame retardant has limited improvement on flame retardant stability. In Comparative Example 7, the combination of MCA and montmorillonite improved flame retardant stability to some extent, but the high proportion of montmorillonite indicates that its mechanical properties need further improvement.

[0094] Comparing Comparative Example 8 and Example 1, it can be seen that replacing maleic anhydride-grafted POE-1 with maleic anhydride-grafted PE did not effectively reduce the actual required irradiation dose or improve the flame retardant failure rate.

[0095] Comparing Comparative Example 9 and Example 1, it can be seen that the addition of silane coupling agent can improve the compatibility of the system; more importantly, it enables the composition to be molded under irradiation treatment with a lower irradiation dose, reduces the rate of change of flame retardant failure, and can also improve the tensile strength and elongation at break of the material.

[0096] Comparing Comparative Example 10 and Example 1, it can be seen that after replacing montmorillonite with sepiolite, sepiolite failed to work effectively with MCA to improve the flame retardant failure rate, and sepiolite would lead to a certain degree of loss in the material's mechanical properties and heat aging resistance.

[0097] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A radiation-crosslinked flame-retardant polyolefin cable composition, characterized in that, Includes the following components by mass: 5-15 parts of metallocene linear low-density polyethylene 10-30 parts of ethylene-vinyl acetate copolymer 10-30 parts of polyolefin thermoplastic elastomer, Maleic anhydride grafted with POE 3-8 parts 75-130 parts of hydroxide flame retardant, Compound flame retardant 3-14 parts, Irradiation catalyst 1-5 parts, 0.1-3 parts of silane coupling agent; The compound flame retardant is composed of melamine cyanurate and montmorillonite, and the mass ratio of melamine cyanurate to montmorillonite is (1-6):

2.

2. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that, The mass ratio of melamine cyanurate to montmorillonite is (3-6):

2.

3. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that, The content of maleic anhydride-grafted POE is 5-16 wt% of the total amount of the resin system formed by LLDPE, EVA, POE and maleic anhydride-grafted POE.

4. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that, Includes the following components by mass: 7-13 parts of metallocene linear low-density polyethylene 17-23 parts of ethylene-vinyl acetate copolymer, 12-18 parts of polyolefin thermoplastic elastomer, Maleic anhydride grafted with 4-6 parts of POE 75-85 parts of hydroxide flame retardant, Compound flame retardant 5-10 parts, Irradiated catalyst 2.5-3.5 parts, 0.5-2 parts of silane coupling agent.

5. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that, The grafting rate of maleic anhydride-grafted POE is 0.5-1.5%.

6. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that: The hydroxide flame retardant is aluminum hydroxide and magnesium hydroxide in a mass ratio of (3-7):(2-6).

7. The irradiated cross-linked flame-retardant polyolefin cable composition according to claim 1, characterized in that: The irradiation catalyst is one or more of divinylbenzene, trimethylolpropane trimethacrylate, triallyl isocyanurate, or triallyl cyanurate.

8. A method for preparing the irradiated crosslinked flame-retardant polyolefin cable composition according to any one of claims 1-7, characterized in that, Includes the following steps: Metallocene linear low-density polyethylene, ethylene-vinyl acetate copolymer, polyolefin thermoplastic elastomer, maleic anhydride-grafted POE, melamine cyanurate, irradiation catalyst and silane coupling agent are mixed and stirred evenly. Then, hydroxide flame retardant and montmorillonite are added, and the mixture is kneaded and extruded to obtain irradiated crosslinked flame-retardant polyolefin cable material.

9. An irradiated cross-linked flame-retardant polyolefin cable material, characterized in that, The irradiated crosslinked flame-retardant polyolefin cable composition according to any one of claims 1-7 is prepared by irradiation crosslinking treatment.

10. The irradiated cross-linked flame-retardant polyolefin cable material according to claim 9, characterized in that: During the irradiation crosslinking treatment, the irradiation dose is no greater than 7 Mrad.

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