Highly insulating polyolefin composition, process for its preparation and use thereof

Abstract

The application discloses a kind of high insulation polyolefin composition and its preparation method and application, belong to high polymer material technical field.The polyolefin composition of the application includes the following weight parts of component: polyethylene 19-36 parts, ethylene-vinyl acetate copolymer 10-24 parts, polyethylene grafting silicone rubber 8-20 parts, hydroxide 45-60 parts, silane coupling agent coated mica powder 3-10 parts, montmorillonite 2-7 parts, irradiation initiator 1-2 parts, simultaneously have excellent high-temperature oil resistance, insulation performance and tensile strength, elongation at break and other mechanical properties, can also meet the flame retardant requirements of national standard GB / T 32129-2015, suitable for cable material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and particularly relates to a high-insulation polyolefin composition and a preparation method and application thereof. BACKGROUND

[0002] Low-smoke halogen-free polyolefin crosslinked insulation material is usually prepared by using a series of polyolefin resins such as PE / EVA / POE, and in order to meet the low-smoke halogen-free characteristics, a large amount of hydroxide flame retardant is often filled to meet the flame retardant requirements. For special cables under complex working conditions, the working environment often faces various oil liquids such as fuel oil and mineral oil, and the ordinary polyolefin material itself has poor oil resistance, and after adding a large amount of hydroxide, the compactness is damaged, resulting in poorer oil resistance.

[0003] At present, the oil resistance of cable materials is mainly improved by introducing strong polar resins, such as nitrile rubber, bisphenol A resin, polyphenylene sulfide, high-VA content EVA, etc., but the introduction of strong polar resins will cause the overall insulation performance of the material to be greatly reduced, which cannot meet the electrical resistance performance requirements of the insulation material. In addition, methyl vinyl silicone rubber can also be added to improve the oil resistance of the cable material, but the improvement of the oil resistance is limited.

[0004] Therefore, it is necessary to develop a polyolefin composition which has excellent oil resistance, insulation, flame retardance, and mechanical properties such as tensile strength and elongation at break. SUMMARY

[0005] Based on the defects of the prior art, the purpose of the present application is to provide a high-insulation polyolefin composition and a preparation method and application thereof, and the obtained polyolefin composition has excellent oil resistance, insulation, flame retardance, and mechanical properties such as tensile strength and elongation at break.

[0006] In order to achieve the above purpose, the present application provides a polyolefin composition comprising the following components by weight:

[0007] polyethylene 19-36 parts;

[0008]

[0009] Silicone rubber has good oil resistance and excellent insulation, but its compatibility with polyolefin material is poor. Directly adding silicone rubber or using conventional methods to improve compatibility (such as adding a coupling agent) in polyolefin material cannot obtain good compatibility, which leads to the inability to exert the advantages of silicone rubber in oil resistance and insulation, and also leads to poor mechanical properties and flame retardant properties of the material. The inventors have unexpectedly found that grafting polyethylene onto silicone rubber and tightly combining silicone rubber and polyethylene through chemical crosslinking can significantly improve the compatibility of silicone rubber and polyolefin material, effectively exert the advantages of silicone rubber in oil resistance and insulation, and reduce the impact of the addition of silicone rubber on the mechanical properties and flame retardant properties of the material.

[0010] Mica powder is mainly silicate, which has similar electric potential as silicone rubber, so mica powder can be well dispersed in silicone rubber. Compared with other layered silicates, the layered structure of mica powder is larger and has better barrier effect. Coating mica powder with a silane coupling agent can improve the compatibility of mica powder with the polyolefin system, so that it not only blocks solvents and improves the oil resistance of the material, but also enhances the compatibility of the overall system of the material, further improving the mechanical properties, oil resistance and other properties.

[0011] The polyolefin composition uses PE and EVA as the base resin, selects hydroxide and montmorillonite as the flame retardant, and adds PE-g-SiR, mica powder coated with a silane coupling agent, and an irradiation initiator, etc. It simultaneously has excellent high-temperature oil resistance, insulation, and tensile strength, elongation at break, and other mechanical properties, and can also meet the flame retardant requirements of national standard GB / T 32129-2015, and is suitable for use as a cable material.

[0012] Preferably, the mass percentage content of silicone rubber in the polyethylene grafted silicone rubber is 28%-72%, such as 28%, 30%, 40%, 50%, 60%, 70%, or 72%, etc. Not only can silicone rubber be used to better improve high-temperature oil resistance, but also can make silicone rubber more easily dispersed in the polyolefin system, avoid self-crosslinking of silicone rubber, and better improve the compatibility of silicone rubber with the polyolefin system.

[0013] More preferably, the mass percentage content of silicone rubber in the polyethylene grafted silicone rubber is 38%-62%, such as 38%, 40%, 45%, 50%, 55%, 60%, or 62%, etc. to better improve the balance between the mechanical properties and high-temperature oil resistance of the material.

[0014] Optionally, the preparation method of the polyethylene grafted silicone rubber comprises the following steps: mixing and dispersing polyethylene and silicone rubber, then performing first opening and mixing, adding an initiator, then performing second opening and mixing, and then extruding and granulating to obtain the polyethylene grafted silicone rubber. Illustratively, the silicone rubber has at least one of a methyl group, a vinyl group, and a phenyl group.

[0015] Preferably, the mass of the used silicon rubber is 28% to 72%, such as 28%, 30%, 40%, 50%, 60%, 70% or 72%, of the total mass of the used polyethylene and silicon rubber when preparing the polyethylene grafted silicon rubber.

[0016] Preferably, the mass of the used initiator is 0.05% to 1% of the total mass of the used polyethylene and silicon rubber when preparing the polyethylene grafted silicon rubber.

[0017] Preferably, the temperature of the first mixing is 100 to 120°C, and the mixing time is 5 to 10 minutes.

[0018] Preferably, the temperature of the second mixing is 110 to 130°C, and the mixing time is 10 to 15 minutes.

[0019] Preferably, the temperature of the extrusion is 160 to 180°C when preparing the polyethylene grafted silicon rubber.

[0020] Preferably, the granulation is performed underwater when preparing the polyethylene grafted silicon rubber.

[0021] Preferably, the initiator used when preparing the polyethylene grafted silicon rubber is an organic peroxide. As an example, the organic peroxide includes at least one of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, and di-tert-butyl peroxide isopropylbenzene.

[0022] Preferably, the polyethylene used when preparing the polyethylene grafted silicon rubber includes a metallocene linear low density polyethylene.

[0023] Preferably, the mass percentage of the silane coupling agent in the silane coupling agent coated mica powder is 0.3% to 4%, such as 0.3%, 0.5%, 1%, 2%, 3% or 4%, to avoid self-crosslinking of the silane coupling agent and to better improve the compatibility of the mica powder with the polyolefin system and to improve the mechanical properties of the material.

[0024] More preferably, the mass percentage of the silane coupling agent in the silane coupling agent coated mica powder is 0.8% to 2.2%, such as 0.8%, 1%, 1.5%, 2% or 2.2%, to further improve the mechanical properties of the material.

[0025] The mass percentage of the silane coupling agent in the silane coupling agent coated mica powder = (W1-W0 / W0)*100%, wherein W1 represents the weight of the silane coupling agent coated mica powder, and W0 represents the weight of the mica powder before the coating treatment.

[0026] The silane coupling agent can be selected from silane coupling agents containing an epoxy group or silane coupling agents not containing an epoxy group. For example, in one embodiment, the silane coupling agent includes at least one of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, gamma-(2,3-epoxypropoxy)propyl trimethoxysilane, 3-(2,3-epoxypropoxy)propyl triethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, and 3-acryloyloxypropyl trimethoxysilane.

[0027] Preferably, the silane coupling agent contains an epoxy group. The epoxy group in the epoxy silane coupling agent has strong polarity, which forms a strong interaction with EVA, thereby improving the dispersibility and the mechanical properties such as tensile strength, elongation at break, and insulation performance of the material.

[0028] As an example, the silane coupling agent containing an epoxy group includes at least one of 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, gamma-(2,3-epoxypropoxy)propyl trimethoxysilane, and 3-(2,3-epoxypropoxy)propyl triethoxysilane.

[0029] Optionally, the method for preparing the mica powder coated with a silane coupling agent includes the following steps: soaking the mica powder in a solution containing a silane coupling agent, heating and stirring to perform a coating grafting reaction, then performing solid-liquid separation, drying the obtained solid to obtain the mica powder coated with a silane coupling agent on the surface.

[0030] Preferably, the mass fraction of the silane coupling agent in the solution containing a silane coupling agent is 0.8wt%-3wt%.

[0031] Preferably, the mass ratio of the mica powder to the solution containing a silane coupling agent is 1:(0.5-5).

[0032] Preferably, the soaking time is 5-10min.

[0033] Preferably, the heating and stirring temperature is 70-90℃, and the heating and stirring time is 0.5-2h.

[0034] As an example, the solvent in the solution containing a silane coupling agent includes at least one of ethanol, acetone, and methanol.

[0035] Preferably, the melt flow rate of the polyethylene under a load of 2.16kg at 190℃ is 0.5-4g / 10min, such as 0.5g / 10min, 1g / 10min, 1.5g / 10min, 2g / 10min, 2.5g / 10min, 3g / 10min, or 4g / 10min, etc. The melt flow rate is measured according to GB / T3682.1-2018.

[0036] Preferably, the mass percentage of the polyethylene in the polyolefin composition is above 13%, such as 13%, 15%, 20% or 25%, etc.

[0037] Preferably, the polyethylene is metallocene linear low density polyethylene.

[0038] Preferably, the mass percentage of vinyl acetate in the ethylene-vinyl acetate copolymer is 25%-35%, such as 25%, 27%, 30%, 33% or 35%, etc.

[0039] Preferably, the hydroxide includes at least one of aluminum hydroxide and magnesium hydroxide.

[0040] Preferably, the irradiation initiator includes at least one of TAIC (triallyl isocyanurate), TMPTMA (trimethylolpropane trimethylacrylate), TMPTA (trimethylolpropane triacrylate).

[0041] Preferably, the polyolefin composition further includes 2-5 parts by weight of an antioxidant, which includes at least one of hindered phenol antioxidant, phosphite antioxidant and sulfide antioxidant.

[0042] The polyolefin composition described in the present application can contain common additives such as color powder, lubricant, anti-UV agent, etc. without impairing the effects of the present application.

[0043] Optionally, the method for preparing the polyolefin composition includes the following steps: mixing and dispersing raw materials except for hydroxide, montmorillonite and mica powder coated with silane coupling agent to obtain a premix;

[0044] Mixing the premix with hydroxide, montmorillonite and mica powder coated with silane coupling agent in proportion, and then densifying, extruding and granulating to obtain the polyolefin composition.

[0045] Preferably, the densifying temperature is 130-140℃, and the extruding temperature is 140-160℃.

[0046] Optionally, the rotating speed for mixing and dispersing during the preparation of the premix is 1000-2000 rpm.

[0047] Optionally, the extruding and granulating is performed in a double-stage single-screw extruder.

[0048] The present application also provides the use of the polyolefin composition in cable materials.

[0049] Compared with the prior art, the present application has the following advantages:

[0050] (1) The application improves the oil resistance and insulation of the system by adding polyethylene grafted silicone rubber in the polyethylene and ethylene-vinyl acetate copolymer system; and improves the oil resistance and mechanical properties of the system by adding mica powder coated with silane coupling agent.

[0051] (2) The polyolefin composition of the application has excellent high-temperature oil resistance and insulation performance, excellent tensile strength and elongation at break, and meets the flame retardation requirements of national standard GB / T 32129-2015, and is suitable for cable materials. DETAILED DESCRIPTION

[0052] In order to better illustrate the purpose, technical scheme and advantages of the application, the application will be further described below in combination with specific examples and comparative examples, the purpose of which is to understand the content of the application in detail, rather than to limit the application. All other examples obtained by those of ordinary skill in the art without creative labor fall within the scope of the application. The experimental reagents and instruments involved in the implementation of the application are common ordinary reagents and instruments unless otherwise specified. In the application, the open description of the technical features includes the closed technical solution consisting of the listed features, and also includes the open technical solution containing the listed features.

[0053] Examples and comparative examples

[0054] Each example and comparative example provides a polyolefin composition, the composition of which is shown in Tables 1-2, and the preparation method comprises the following steps:

[0055] The metallocene linear low density polyethylene, ethylene-vinyl acetate copolymer, polyethylene grafted silicone rubber (or silicone rubber, if any), irradiation initiator and antioxidant are proportionally put into a high-speed mixer for mixing and dispersion at a speed of 1500 rpm to obtain a premix;

[0056] The obtained premix is proportionally put into a banbury mixer with hydroxide, montmorillonite and mica powder coated with silane coupling agent (or mica powder, if any), and after banburying, it is extruded and granulated by a double-stage single-screw extruder to obtain a polyolefin composition, wherein the temperature of the banbury mixer is controlled at 135°C, and the temperature of the single-screw extruder is controlled at 140-160°C. The preparation method of each example and comparative example is the same as the steps and process parameters used unless otherwise specified.

[0057] The raw material information used in each example and comparative example is as follows:

[0058] MLLDPE 1: Melt flow rate of 3.5 g / 10 min, LLDPE Exceed 3518PA, Exxon Mobil;

[0059] MLLDPE 2: Melt flow rate of 2 g / 10 min, LLDPE Exceed 2012MA, ExxonMobil;

[0060] MLLDPE 3: Melt flow rate of 1 g / 10 min, LLDPE ENABLE 2010PA, ExxonMobil;

[0061] EVA: Vinyl acetate mass percentage of 27%, EVA UL00328, ExxonMobil;

[0062] Silicone rubber: Methyl vinyl silicone rubber, CHN3500U, Shin-Etsu, Japan;

[0063] PE-g-SiR 1 : Silicone rubber mass percentage of 40%, self-made, the specific preparation method comprising the following steps: mixing and dispersing the above-mentioned MLLDPE 1 and silicone rubber according to a weight ratio of 6:4, placing in an open mill to open mill at a temperature of 110°C to make the two materials melt fully mixed, then adding 0.1wt% of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane based on the total weight of MLLDPE 1 and silicone rubber, continuously opening mill at a temperature of 120°C, extruding the opened mixture with a twin-screw extruder at a temperature of 170°C and cutting it into particles under water, to obtain PE-g-SiR 1 ;

[0064] PE-g-SiR 2: Silicone rubber mass percentage of 50%, self-made, the difference between its preparation method and that of PE-g-SiR1 is that the mass ratio of MLLDPE 1 to silicone rubber used is 5:5;

[0065] PE-g-SiR 3: Silicone rubber mass percentage of 60%, self-made, the difference between its preparation method and that of PE-g-SiR1 is that the mass ratio of MLLDPE 1 to silicone rubber used is 4:6;

[0066] PE-g-SiR 4: Silicone rubber mass percentage of 30%, self-made, the difference between its preparation method and that of PE-g-SiR1 is that the mass ratio of MLLDPE 1 to silicone rubber used is 7:3;

[0067] PE-g-SiR 5: Silicone rubber mass percentage of 70%, self-made, the difference between its preparation method and that of PE-g-SiR1 is that the mass ratio of MLLDPE 1 to silicone rubber used is 3:7;

[0068] Mica powder: MICA C-4000, IMERYS;

[0069] Mica powder coated with silane coupling agent 1: the mass percentage of silane coupling agent is 1.5%, self-made, the specific preparation method comprises the following steps: dissolving the silane coupling agent in ethanol to obtain a solution with a mass fraction of 2% of the silane coupling agent, and soaking the above-mentioned mica powder in the solution according to a solid-liquid ratio of 3g:4g, and then performing a coating and grafting reaction by heating and stirring at 80°C for 1h after soaking for 10min, and then performing solid-liquid separation, and drying the obtained solid, at this time, the powder and the silane coupling agent form a firm chemical bond, and the mica powder coated with the silane coupling agent 1 is obtained, wherein the silane coupling agent used is 2-(3,4-epoxycyclohexyl) ethyl trimethoxysilane, KBM-303, Japan Shin-Etsu;

[0070] Mica powder coated with silane coupling agent 2: the mass percentage of silane coupling agent is 1%, self-made, and the difference between the preparation method and the preparation method of the mica powder coated with silane coupling agent 1 is that the specific preparation method comprises the following steps: dissolving the silane coupling agent in ethanol to obtain a solution with a mass fraction of 2% of the silane coupling agent, and soaking the above-mentioned mica powder in the solution according to a solid-liquid ratio of 1g:1g;

[0071] Mica powder coated with silane coupling agent 3: the mass percentage of silane coupling agent is 2%, self-made, and the difference between the preparation method and the preparation method of the mica powder coated with silane coupling agent 1 is that the specific preparation method comprises the following steps: dissolving the silane coupling agent in ethanol to obtain a solution with a mass fraction of 2% of the silane coupling agent, and soaking the above-mentioned mica powder in the solution according to a solid-liquid ratio of 1g:2g;

[0072] Mica powder coated with silane coupling agent 4: the mass percentage of silane coupling agent is 0.5%, self-made, and the difference between the preparation method and the preparation method of the mica powder coated with silane coupling agent 1 is that the specific preparation method comprises the following steps: dissolving the silane coupling agent in ethanol to obtain a solution with a mass fraction of 2% of the silane coupling agent, and soaking the above-mentioned mica powder in the solution according to a solid-liquid ratio of 3g:2g;

[0073] Mica powder coated with silane coupling agent 5: the mass percentage of silane coupling agent is 3%, self-made, and the difference between the preparation method and the preparation method of the mica powder coated with silane coupling agent 1 is that the specific preparation method comprises the following steps: dissolving the silane coupling agent in ethanol to obtain a solution with a mass fraction of 2% of the silane coupling agent, and soaking the above-mentioned mica powder in the solution according to a solid-liquid ratio of 1g:4g;

[0074] Mica powder coated with silane coupling agent 6: the mass percentage of silane coupling agent is 1%, self-made, and the difference between the preparation method and the preparation method of the mica powder coated with silane coupling agent 2 is that the silane coupling agent used is 3-(2,3-epoxypropoxy) propyl triethoxysilane, model GX-560, purchased from Anhui Sibao Organic Silicon New Material Co., Ltd.;

[0075] Mica powder coated with silane coupling agent 7: the mass percentage content of silane coupling agent is 1%, which is self-made, and the difference between its preparation method and that of mica powder coated with silane coupling agent 2 is that the silane coupling agent used is γ-(2,3-epoxypropoxy) propyl trimethoxysilane, model GX-561, purchased from Anhui Silibao Organic Silicon New Material Co., Ltd.;

[0076] Mica powder coated with silane coupling agent 8: the mass percentage content of silane coupling agent is 1%, which is self-made, and the difference between its preparation method and that of mica powder coated with silane coupling agent 2 is that the silane coupling agent used is vinyl silane coupling agent, model SG-SI 172, manufacturer Nanjing Shuguang Chemical;

[0077] Montmorillonite: DK-1, Zhejiang Fenghong;

[0078] Irradiation initiator: TAIC, commercially available;

[0079] Antioxidant: a mixture of antioxidant 3114, antioxidant PEP-36 and antioxidant IRGANOX PS 802FD, the mass ratio of the three is 1:1:1, all commercially available.

[0080] The melt flow rate of each MLLDPE described above is measured according to GB / T 3682.1-2018, and the test conditions are as follows: 190°C, 2.16 kg load;

[0081] The mass percentage content of silane coupling agent in each mica powder coated with silane coupling agent described above is calculated according to the following formula: mass percentage content of silane coupling agent in mica powder coated with silane coupling agent = (W1-W0 / W0)*100%, wherein W1 represents the weight of mica powder coated with silane coupling agent, and W0 represents the weight of mica powder before coating treatment.

[0082] Unless otherwise specified, the component raw materials used in each embodiment and comparative example of the present application are the same.

[0083] The polyolefin composition obtained in each example and comparative example is pressed into a sheet on a flat vulcanizing machine at 180°C*10min, the pressure is 15MPa, the thickness of the sample sheet is 1mm, and after being placed at 25°C for 16h, high-energy electron beam irradiation is carried out, the irradiation dose is 15Mrad, and the irradiated sample sheet is subjected to the following performance tests:

[0084] Tensile strength and elongation at break before oil swelling: refer to standard GB / T 1040.2-2018;

[0085] Oil resistance experiment: immerse the sample strip in 903# mineral oil at 100°C and keep for 72h, and then test the tensile strength and elongation at break of the material after oil swelling according to the above method,

[0086] Retention rate of tensile strength after oil resistance = tensile strength before oil immersion / tensile strength after oil immersion * 100%,

[0087] Retention rate of elongation at break after oil resistance = elongation at break before oil immersion / elongation at break after oil immersion * 100%;

[0088] Flame retardant grade test: GB / T 32129-2015;

[0089] Volume resistivity test: GBT 1410-2006.

[0090] The test results are shown in Tables 1-2.

[0091] Table 1

[0092]

[0093]

[0094]

[0095] Table 2

[0096]

[0097]

[0098] From the above data, it can be seen that the tensile strength of the polyolefin composition obtained by each embodiment of the application is above 12 MPa, the elongation at break is above 190%, the flame retardant grade is B1, the retention rate of tensile strength after oil resistance is above 80%, the retention rate of elongation at break after oil resistance is above 80%, and the volume resistivity is above 4*10 13

[0099] Comparative Example 1 directly uses silicone rubber without grafting it on polyethylene, resulting in poor compatibility with polyolefin, and thus low mechanical properties such as tensile strength and elongation at break, poor flame retardancy, poor oil resistance, and poor insulation.

[0100] Comparative Example 2 directly uses mica powder without coating it with silane coupling agent, resulting in poor compatibility between the mica powder and the polyolefin system, and thus low mechanical properties such as tensile strength and elongation at break, poor oil resistance, and poor insulation.

[0101] Comparative Examples 3 and 4 do not add mica powder or silicone rubber, resulting in low mechanical properties such as tensile strength and elongation at break, poor oil resistance, and poor insulation.

[0102] ​Comparative Example 5 has a high amount of polyethylene grafted silicone rubber, which causes the silicone rubber to easily coagulate and produce phase separation, resulting in low tensile strength, elongation at break and other mechanical properties; Comparative Example 6 has a high amount of mica powder coated with silane coupling agent, which results in low tensile strength, elongation at break and other mechanical properties, and a decrease in volume resistivity.

[0103] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application.

Claims

1. A polyolefin composition, characterized in that, The components include the following parts by weight: 19-36 parts of polyethylene; 10-24 parts of ethylene-vinyl acetate copolymer; 8-20 parts of polyethylene-grafted silicone rubber; 45-60 parts of hydroxide; 3-10 parts of mica powder coated with silane coupling agent; 2-7 parts of montmorillonite; 1-2 parts of irradiation initiator; The hydroxide is selected from at least one of aluminum hydroxide and magnesium hydroxide; The silicone rubber in the polyethylene-grafted silicone rubber has a silicone rubber mass percentage of 28%-72%; The mica powder coated with the silane coupling agent has a silane coupling agent content of 0.3%-4% by mass.

2. The polyolefin composition according to claim 1, characterized in that, The silicone rubber in the polyethylene-grafted silicone rubber has a silicone rubber content of 38%-62% by mass.

3. The polyolefin composition according to claim 1, characterized in that, The mica powder coated with the silane coupling agent has a silane coupling agent content of 0.8%-2.2% by mass.

4. The polyolefin composition according to claim 1, characterized in that, The silane coupling agent in the mica powder coated with the silane coupling agent contains epoxy groups.

5. The polyolefin composition according to claim 4, characterized in that, The silane coupling agent in the mica powder coated with the silane coupling agent includes at least one of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(2,3-epoxypropoxy)propyltriethoxysilane.

6. The polyolefin composition according to claim 1, characterized in that, The polyethylene has a melt flow rate of 0.5-3 g / 10 min at 190°C and a load of 2.16 kg.

7. The polyolefin composition according to claim 1, characterized in that, Satisfy at least one of (a)-(e): (a) The polyethylene is metallocene linear low-density polyethylene; (b) The irradiation initiator includes at least one of TAIC, TMPTMA, and TMPTA; (c) The polyolefin composition further comprises 2-5 parts by weight of an antioxidant, wherein the antioxidant includes at least one of hindered phenolic antioxidants, phosphite antioxidants, and thioether antioxidants; (d) The preparation method of the polyethylene-grafted silicone rubber includes the following steps: after mixing and dispersing polyethylene and silicone rubber, a first open milling is performed, then an initiator is added, a second open milling is performed, and then extrusion granulation is performed to obtain polyethylene-grafted silicone rubber.

8. The method for preparing the polyolefin composition according to any one of claims 1 to 7, characterized in that, Includes the following steps: The raw materials, excluding hydroxide, montmorillonite, and mica powder coated with silane coupling agent, are mixed and dispersed to obtain a premix. The premix is ​​mixed and kneaded with hydroxide, montmorillonite and mica powder coated with silane coupling agent in a certain proportion, and then extruded and granulated to obtain a polyolefin composition.

9. The method for preparing the polyolefin composition according to claim 8, characterized in that, The mixing temperature is 130-140℃; the extrusion temperature is 140-160℃.

10. The use of the polyolefin composition according to any one of claims 1 to 7 or the polyolefin composition prepared by the preparation method according to any one of claims 8 to 9 in cable materials.

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