An anti-aging halogen-free flame-retardant polyethylene cable material and its production process

Abstract

This application relates to the technical field of cable materials, and specifically discloses an anti-aging halogen-free flame-retardant polyethylene cable material and its production process. The cable material is obtained by heating and mixing, extruding and pelletizing, and drying a mixture. The mixture includes a matrix rubber, a resin base, a reinforcing fiber, a flame retardant, a flame retardant synergist, and an auxiliary agent. The matrix rubber includes ethylene propylene diene monomer rubber. The mass fraction of magnesium hydroxide in the flame retardant is 75%. The reinforcing fiber is an inorganic fiber grafted with carboxyl groups on the surface. After adding the reinforcing fiber in this application, the magnesium hydroxide particles play an anchoring role on the reinforcing fiber, increasing the resistance that needs to be overcome when the reinforcing fiber slips, hindering the slipping of the reinforcing fiber, improving the tensile strength of the cable material, and improving the crack resistance of the cable material.

Description

Technical Field

[0001] The present application relates to the technical field of cable materials, and more specifically, to an anti-aging halogen-free flame-retardant polyethylene cable material and a production process thereof. Background Art

[0002] Plastics used for insulation and sheathing of wires and cables, also known as cable materials, are one of the key materials in cable production. Traditional cable materials are mainly made of raw materials such as polyolefins and rubber, which have the defect of being flammable, so flame retardants need to be added to the cable materials in advance. When selecting flame retardant ingredients, in order to reduce the impact on the environment, halogen-free flame retardants such as magnesium hydroxide are usually selected. When used alone, magnesium hydroxide needs to be added in an amount of 60% of the total weight to produce a good flame retardant effect. However, adding magnesium hydroxide at this amount has a significant impact on the tensile strength of the cable material, which can easily cause the cable to crack under tension. Therefore, if you want to achieve good crack resistance while using magnesium hydroxide as a flame retardant component, you usually need to try to reduce the proportion of magnesium hydroxide in the cable material while maintaining the flame retardant effect.

[0003] Chinese patent publication number CN114891303A discloses a flame-retardant cable material for charging piles and its preparation method. The cable material is prepared by mixing the raw materials, heating and kneading them at 170-175°C for 15-20 minutes, followed by extrusion, granulation, and drying. The raw materials for the cable material are composed of the following components by weight: 55-70 parts base rubber, 33-57 parts resin base, 60-90 parts flame retardant, 20-30 parts flame retardant synergist, and 2.6-4.2 parts additives. The base rubber is EPDM rubber, and the resin base material includes the following components in parts by weight: 10-20 parts of POE resin (ethylene-octene copolymer resin), 8-12 parts of MAH-POE resin (maleic anhydride modified ethylene-octene copolymer resin), 8-10 parts of cross-linked modified resin, 5-10 parts of polyethylene-vinyl acetate, and 2-5 parts of polyphenylene ether; the flame retardant is a mixture of diethyl phosphinate aluminum and magnesium hydroxide in a weight ratio of 1:3, and the flame retardant synergist is a mixture of silane coupling agent and melamine polyphosphate; the auxiliary agents include the following components in parts by weight: 0.5-1.0 parts of polyethylene wax, 1.2-2.0 parts of antioxidant, and 0.9-1.2 parts of cross-linking agent.

[0004] Regarding the above-mentioned related technologies, the inventors believe that although the proportion of magnesium hydroxide in the cable material is reduced by compounding two flame retardants and adding flame retardant synergists in the related technologies, the proportion of magnesium hydroxide is still close to 1 / 4 of the total weight of the raw materials. Under this dosage condition, magnesium hydroxide still has a certain impact on the tensile strength of the cable material, which is not conducive to fully improving the crack resistance of the cable material. Summary of the Invention

[0005] In the related art, magnesium hydroxide has a certain impact on the tensile strength of cable materials, which is not conducive to fully improving the crack resistance of cable materials. To improve this defect, the present application provides an anti-aging halogen-free flame-retardant polyethylene cable material and its production process.

[0006] In a first aspect, the present application provides an anti-aging halogen-free flame-retardant polyethylene cable material, adopting the following technical solution: An anti-aging halogen-free flame-retardant polyethylene cable material, which is obtained by heating and mixing, extruding and pelletizing, and drying a mixture. The mixture includes the following components in parts by weight: 55-70 parts of matrix rubber, 33-57 parts of resin base material, 16-28 parts of reinforcing fiber, 60-90 parts of flame retardant, 20-30 parts of flame retardant synergist, and 2.6-4.2 parts of auxiliary agent; the matrix rubber includes ethylene propylene diene monomer (EPDM), the mass fraction of magnesium hydroxide in the flame retardant is 75%, the reinforcing fiber is an inorganic fiber grafted with carboxyl groups on the surface, and the carboxyl groups are provided by unsaturated carboxylic acid monomers including oleic acid.

[0007] By adopting the above technical solution, the present application adds a reinforcing fiber to the raw material system of the cable material. After heating and mixing, the carboxyl groups on the surface of the reinforcing fiber will adsorb on the surface of magnesium hydroxide particles, and a part of the carboxyl groups on the surface of the reinforcing fiber can also undergo an esterification reaction with the hydroxyl groups on the surface of magnesium hydroxide during the heating and mixing process, thereby realizing the combination of magnesium hydroxide particles and the reinforcing fiber. When the cable material (and the products made of the cable material, the same below) bears tensile stress, the reinforcing fiber and the cable material jointly bear the tensile stress. At the same time, the magnesium hydroxide particles combined with the reinforcing fiber play a certain mechanical anchoring role in the cable material, increasing the resistance that needs to be overcome when the reinforcing fiber slips and hindering the slipping of the reinforcing fiber. In summary, the synergistic effect of the reinforcing fiber and magnesium hydroxide enhances the resistance effect of the cable material to tensile stress, improves the tensile strength of the cable material, and improves the crack resistance of the cable material.

[0008] Under the condition that the tensile strength is improved, the cable material of the present application overcomes the influence of using the halogen-free flame retardant magnesium hydroxide on the crack resistance performance, and has both good flame retardant performance and tensile and crack resistance performance. Moreover, ethylene propylene diene monomer (EPDM) endows the cable material of the present application with good high and low temperature resistance and aging resistance. Therefore, the cable material of the present application has good application prospects.

[0009] Preferably, the reinforcing fiber is prepared according to the following method:

[0010] (1) Mix ethanol, water and vinyltriethoxysilane to obtain a silane modification solution for standby; add monomers to water to obtain a monomer dispersion solution for standby; the molar ratio of the monomers to vinyltriethoxysilane is 5:1, and the monomers are a mixture of oleic acid and acrylic acid in a molar ratio of 4:1;

[0011] (2) Mix the inorganic fiber with the silane modification solution, stir and heat at 50 - 70 °C for 1 - 2 h, then perform suction filtration and drying to obtain silanized fiber;

[0012] (3) Mix the silanized fiber, monomer dispersion liquid and initiator, heat at 75 - 85 °C for 4 - 5 h, then perform suction filtration and drying to obtain reinforcing fiber.

[0013] By adopting the above technical solution, in this application, the inorganic fiber is modified with vinyltriethoxysilane, vinyl is grafted on the surface of the inorganic fiber to obtain silanized fiber, and then under the action of the initiator, the monomer polymerizes with the vinyl, and the copolymer of oleic acid and acrylic acid is grafted on the surface of the inorganic fiber to obtain reinforcing fiber.

[0014] Preferably, in step (2) of preparing the reinforcing fiber, the weight ratio between the inorganic fiber added to the silane modification solution and vinyltriethoxysilane in the silane modification solution is 2:1.

[0015] By adopting the above technical solution, the dosage ratio of the inorganic fiber and vinyltriethoxysilane is optimized. When there are silanol groups on the surface of the inorganic fiber available for reaction with the silane coupling agent, adopting this dosage ratio is beneficial to the full reaction between the inorganic fiber and vinyltriethoxysilane.

[0016] Preferably, the inorganic fiber is selected as the chopped strand of basalt fiber after being calcined to remove oil.

[0017] By adopting the above technical solution, the chopped strand of basalt fiber has good mechanical properties, and there are a certain number of silanol groups on the surface of the chopped strand of basalt fiber, which can couple with vinyltriethoxysilane and can be used as the raw material for producing reinforcing fiber after being calcined to remove oil.

[0018] Preferably, the inorganic fiber is selected as modified basalt fiber, and the modified basalt fiber is prepared according to the following method:

[0019] (1) Cut the continuous basalt fiber to obtain basalt fiber monofilaments, bundle the basalt fiber monofilaments into a tow, and calcine and degrease the tow for standby; Mix Portland cement, retarder and water and stir to obtain cement slurry, and detect the initial setting time of the cement slurry;

[0020] (2) Re-prepare the cement slurry in step (1), then immerse the tow in the cement slurry and stir, and then cure the mixture of the tow and the cement slurry under the conditions of relative humidity 95% ± 1% and temperature 20 ± 2 °C, and take out the tow for washing and drying 30 min before the initial setting time measured in step (1), and then perform cutting processing to obtain modified basalt fiber.

[0021] By adopting the above technical solution, inorganic fiber is preferably modified basalt fiber in this application. There is a retarder in the cement slurry prepared according to the above method. Therefore, it can maintain a fluid state before initial setting for a long time and is suitable for soaking and modifying the tow. When the degreased tow contacts the cement slurry, calcium hydroxide in the cement slurry reacts with silica on the surface of the tow to produce calcium silicate, increasing the surface roughness of the tow. At the same time, calcium hydroxide destroys a part of the Si-O-Si bonds, generating new silanol groups on the surface of the tow. After cutting and processing these tows, the obtained modified basalt fiber can couple with more silane molecules compared with the unmodified basalt fiber, which helps to increase the total amount of unsaturated carboxylic acid monomers actually grafted onto the fiber surface, thereby enhancing the binding effect between the reinforcing fiber and magnesium hydroxide and contributing to improving the tensile strength of the cable compound.

[0022] Preferably, the retarder is sucrose, and the dosage of the sucrose is 0.15% of the weight of the cement.

[0023] By adopting the above technical solution, sucrose is preferably used as the retarder, and the addition amount of sucrose is optimized, which is beneficial to maintaining the flowable state of the cement slurry for a long time and also beneficial to the full reaction of silica on the surface of the tow with calcium hydroxide in the cement slurry.

[0024] Preferably, when preparing the cement slurry, the portland cement and water are first mixed and stirred for 120 s, and then the retarder is added.

[0025] By adopting the above technical solution, delaying the addition of sucrose retarder during the preparation of the cement slurry can reduce the procoagulant effect of sucrose, thereby prolonging the initial setting time of the cement slurry and being beneficial to the full reaction of silica on the surface of the tow with calcium hydroxide in the cement slurry.

[0026] Preferably, the matrix rubber is composed of ethylene propylene diene monomer rubber (EPDM) and carboxyl nitrile butadiene rubber (XNBR) according to a weight ratio of 9:1.

[0027] By adopting the above technical solution, by mixing carboxyl nitrile butadiene rubber and ethylene propylene diene monomer rubber, a part of carboxyl is also contained in the matrix rubber, which can improve the compatibility between magnesium hydroxide and the rubber matrix.

[0028] Preferably, the components of the resin base material include POE resin and MAH-POE resin.

[0029] By adopting the above technical solution, POE resin is a copolymer of ethylene and octene, and has good compatibility with ethylene propylene diene monomer rubber. MAH-POE resin is a POE resin modified by grafting maleic anhydride, introducing polar groups. The structure of MAH-POE resin is similar to that of POE resin. While maintaining good compatibility with POE resin, it also has good compatibility with carboxyl nitrile rubber which also contains polar groups. Therefore, the synergistic use of POE resin and MAH-POE resin can improve the compatibility between carboxyl nitrile rubber and ethylene propylene diene monomer rubber, and contribute to improving the tensile strength of cable compound.

[0030] In a second aspect, the present application provides a production process for an anti-aging halogen-free flame-retardant polyethylene cable compound, adopting the following technical solution.

[0031] A production process for an anti-aging halogen-free flame-retardant polyethylene cable compound includes the following steps:

[0032] (1) Mix the matrix rubber, resin base material, reinforcing fiber, flame retardant, flame retardant synergist, and auxiliary agent to obtain a mixed material;

[0033] (2) Heat and knead the mixed material at 170 - 175 °C for 15 - 20 min, then perform extrusion granulation and drying to obtain the anti-aging halogen-free flame-retardant polyethylene cable compound described in any one of the above.

[0034] By adopting the above technical solution, in the present application, the raw materials are first mixed to obtain a mixed material, and then through heat kneading and extrusion granulation processing, the anti-aging halogen-free flame-retardant polyethylene cable compound is obtained.

[0035] In summary, the present application has the following beneficial effects:

[0036] 1. In the present application, reinforcing fiber and magnesium hydroxide are used simultaneously in the raw materials of the cable compound. When the cable compound bears tensile stress, the reinforcing fiber and the cable compound bear the tensile stress together, and the magnesium hydroxide particles combined with the reinforcing fiber can play a mechanical anchoring role, thereby increasing the resistance that needs to be overcome during the slippage of the reinforcing fiber, hindering the slippage of the reinforcing fiber, improving the tensile strength of the cable compound, and improving the crack resistance of the cable compound.

[0037] 2. In the present application, it is preferred to pretreat the tow of basalt fiber with cement slurry, so that the basalt fiber can react with more silane molecules to couple, which helps to increase the total amount of unsaturated carboxylic acid monomers actually grafted onto the surface of the basalt fiber, thereby enhancing the binding effect between the reinforcing fiber and magnesium hydroxide, and contributing to improving the tensile strength of the cable compound. Specific embodiments

[0038] The present application will be further described in detail below with reference to examples, preparation examples, and comparative examples. The raw materials involved in the present application can all be obtained through commercial channels.

[0039] Preparation Example of Reinforcing Fiber

[0040] Taking Preparation Example 1 as an example, the following is an illustration.

[0041] Preparation Example 1

[0042] In this preparation example, the reinforcing fiber is prepared according to the following method:

[0043] (1) Ethanol, water and vinyltriethoxysilane are mixed to obtain a silane-modified solution for standby. The mass fraction of vinyltriethoxysilane is 0.75%, and the weight ratio of ethanol to water is 1:20. The monomer is added to water to obtain a monomer dispersion with a monomer mass fraction of 10% for standby. The molar ratio of the monomer to vinyltriethoxysilane is 5:1, and the monomer is composed of oleic acid and acrylic acid mixed in a molar ratio of 4:1.

[0044] (2) The inorganic fiber is mixed with the silane-modified solution, stirred and heated at 65 °C for 1.5 h, and then subjected to suction filtration and drying to obtain silanized fiber. The inorganic fiber is chopped basalt fiber yarn with a single filament diameter of 13 μm and an average length of 3 mm, and is calcined to remove oil to a constant weight. The weight ratio between the inorganic fiber added to the silane-modified solution and vinyltriethoxysilane in the silane-modified solution is 1:1.

[0045] (3) The silanized fiber, monomer dispersion and initiator are mixed, heated at 80 °C for 5 h, and then subjected to suction filtration and drying to obtain the reinforcing fiber.

[0046] Preparation Example 2

[0047] The difference between this preparation example and Preparation Example 1 is that the weight ratio between the inorganic fiber added to the silane-modified solution and vinyltriethoxysilane in the silane-modified solution is 1:2.

[0048] Preparation Example 3

[0049] The difference between this preparation example and Preparation Example 2 is that the inorganic fiber is selected as modified basalt fiber, and the modified basalt fiber is prepared according to the following method:

[0050] (1) Continuous basalt fiber with a single filament diameter of 13 μm is cut into basalt fiber filaments with a length of 100 mm. The basalt fiber filaments are bundled into a filament bundle, and the filament bundle is calcined to remove oil (to a constant weight) for standby. Portland cement, retarder and water are simultaneously added to a container and mixed and stirred to obtain a cement paste with a water-cement ratio of 0.5, and the initial setting time of the cement paste is detected. In this step, the retarder is sucrose (dosage is 0.15% of the cement weight), and the Portland cement used meets the regulations in Appendix A of 《GB 8076-2008 Concrete Admixtures》.

[0051] (2) Re-prepare the cement slurry in step (1), then immerse the tow in the cement slurry and stir, and then cure the mixture of the tow and the cement slurry under the conditions of relative humidity of 95% ± 1% and temperature of 20 ± 2°C. When there are still 30 minutes left until the initial setting time measured in step (1), take out the tow, wash it with water and dry it, and then perform cutting processing to obtain modified basalt fibers with an average length of 3 mm.

[0052] Preparation Example 4

[0053] The difference between this preparation example and Preparation Example 3 is that when preparing the cement slurry, first mix and stir the portland cement and water for 120 s, and then add the retarder.

[0054] Examples

[0055] Examples 1-5

[0056] The following takes Example 1 as an example for illustration.

[0057] Example 1

[0058] In this example, the anti-aging halogen-free flame-retardant polyethylene cable material is prepared according to the following steps:

[0059] (1) Mix the matrix rubber, resin base material, reinforcing fiber, flame retardant, flame retardant synergist, and auxiliary agent to obtain a mixture;

[0060] (2) Heat and knead the mixture in a mixer at a temperature of 175°C for 20 minutes, then extrude and pelletize it with a twin-screw extruder, and then dry it to obtain the anti-aging halogen-free flame-retardant polyethylene cable material; in this step, a seven-temperature-section twin-screw extruder can be used for extrusion and pelletization, and the seven temperature sections can be set to 100°C, 145°C, 155°C, 165°C, 165°C, 160°C, and 160°C in sequence.

[0061] In this example, the mixture includes the following components: 55 kg of matrix rubber, 33 kg of resin base material, 16 kg of reinforcing fiber, 60 kg of flame retardant, 20 kg of flame retardant synergist, and 2.6 kg of auxiliary agent.

[0062] In this embodiment, the matrix rubber is ethylene propylene diene monomer rubber (EPDM), and the resin base material is composed of 10 kg of POE resin, 8 kg of maleic anhydride grafted POE (MAH-POE) resin, 8 kg of crosslinked modified resin, 5 kg of ethylene-vinyl acetate copolymer, and 2 kg of polyphenylene ether. The model of the POE resin is ExxonMobil 6102FL, and the MAH-POE resin is DuPont 493D from the United States. The reinforcing fiber is prepared according to the method of Preparation Example 1. The flame retardant is composed of aluminum diethyl phosphinate and magnesium hydroxide mixed in a weight ratio of 1:3, and the average particle size of magnesium hydroxide is 0.5 μm. The flame retardant synergist is a mixture of methyltriethoxysilane and melamine polyphosphate, and the dosage of methyltriethoxysilane is 0.3% of the weight of melamine polyphosphate. The additives are composed of 0.5 kg of polyethylene wax, 1.2 kg of antioxidant, and 0.9 kg of crosslinking agent. The antioxidant is composed of pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and dilauryl thiodipropionate mixed in a weight ratio of 2:3, and the crosslinking agent is triallyl isocyanurate.

[0063] The crosslinked modified resin is prepared according to the following method: Put ULDPE resin and diisopropylbenzene peroxide into a blender and stir for 2 minutes, then add the obtained mixture into a twin-screw extruder for processing to obtain the crosslinked modified resin. The dosage of diisopropylbenzene peroxide is 0.3% of the weight of ULDPE resin. When processing the crosslinked modified resin, a twin-screw extruder with six temperature zones can be used. When using this type of extruder, the temperatures of the six temperature zones can be set to 100 °C, 160 °C, 175 °C, 175 °C, 175 °C, and 180 °C respectively.

[0064] As shown in Table 1, the main difference between Examples 1-5 lies in the different raw material ratios of the mixture.

[0065] Table 1 Raw material ratios of the mixture

[0066]

[0067] Example 6

[0068] The difference between this embodiment and Example 5 is that the reinforcing fiber is prepared according to the method of Preparation Example 2.

[0069] Example 7

[0070] The difference between this embodiment and Example 6 is that the reinforcing fiber is prepared according to the method of Preparation Example 3.

[0071] Example 8

[0072] The difference between this embodiment and Example 7 is that the reinforcing fiber is prepared according to the method of Preparation Example 4.

[0073] Example 9

[0074] The difference between this embodiment and Embodiment 8 is that the matrix rubber is composed of ethylene propylene diene monomer rubber (EPDM) and carboxy nitrile butadiene rubber (XNBR) according to a weight ratio of 9:1.

[0075] Embodiment 10

[0076] The difference between this embodiment and Embodiment 9 is that the MAH-POE resin is replaced with an equal weight of POE resin.

[0077] Comparative Example

[0078] Comparative Example 1

[0079] The difference between this comparative example and Embodiment 1 is that the components of the mixture do not include reinforcing fibers.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Embodiment 1 is that without changing the composition ratio of the flame retardant, the amount of the flame retardant is increased so that the mass fraction of magnesium hydroxide in the mixture reaches 27%.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Embodiment 1 is that the reinforcing fibers are replaced with chopped basalt fiber yarns with a monofilament diameter of 13 μm, an average length of 3 mm, and which have been calcined to remove oil until constant weight.

[0084] Performance Detection Test Method

[0085] I. Tensile Strength Performance Test

[0086] Referring to the records of "GB / T 1040.1-2018 Plastics - Determination of tensile properties - Part 1: General principles", a tensile testing machine is used to detect the tensile strength of the cable compound, and then the ratio between the tensile strength of each embodiment and comparative example and the tensile strength measured in Comparative Example 1 is calculated. This ratio is recorded as the relative tensile strength, and the results are shown in Table 2.

[0087] II. Flame Retardant Performance Test

[0088] Referring to "GB / T 2408-2008 Plastics - Determination of burning behavior - Horizontal and vertical methods" to detect the flame retardant grade of the cable compound, and the results are shown in Table 2.

[0089] Table 2

[0090] Sample Relative Tensile Strength / % Flame Retardant Grade Example 1 123.8 V-0 Example 2 127.5 V-0 Example 3 133.9 V-0 Example 4 136.7 V-0 Example 5 138.2 V-0 Example 6 138.4 V-0 Example 7 151.6 V-0 Example 8 154.7 V-0 Example 9 160.8 V-0 Example 10 155.7 V-0 Comparative Example 1 100.0 V-0 Comparative Example 2 122.4 V-0 Comparative Example 3 107.8 V-0

[0091] Combined with Example 1 and Comparative Example 1 and with reference to Table 2, it can be seen that the relative tensile strength measured in Example 1 is greater than that in Comparative Example 1, indicating that the cable material of the present application has a higher tensile strength compared with the cable materials in the related art, and has a stronger resistance to tensile cracking. Therefore, the cable material of the present application has better anti-cracking performance.

[0092] Combined with Example 1 and Comparative Example 2 and with reference to Table 2, it can be seen that the relative tensile strength of Comparative Example 2 is close to that of Example 1, and the proportion of magnesium hydroxide in the cable material of Comparative Example 2 is already higher than that in the related art. This shows that the decrease in the proportion of magnesium hydroxide caused by the addition of reinforcing fibers is not the main reason for the improvement of tensile strength.

[0093] Combined with Example 1 and Comparative Example 3 and with reference to Table 2, it can be seen that the relative tensile strength of Comparative Example 3 is significantly lower than that of Example 1. Since basalt fiber itself has a relatively high tensile strength, it indicates that in the cable material of Comparative Example 3, the basalt fiber does not form a tight bond with the other components, and relatively easily slips, resulting in limited improvement in tensile strength by the basalt fiber. When the cable material of the present application is subjected to tension, the magnesium hydroxide particles combined with the reinforcing fibers can play a mechanical anchoring role, increasing the resistance that needs to be overcome during the slipping of the reinforcing fibers, hindering the slipping of the reinforcing fibers, and improving the tensile strength of the cable material. Therefore, the cable material of the present application has a stronger resistance to tensile cracking and better anti-cracking performance.

[0094] Combined with Example 5 and Example 6 and with reference to Table 2, it can be seen that the relative tensile strength measured in Example 5 is close to that in Example 6, indicating that the effect of combining the basalt fiber chopped strand only treated by burning and degreasing with the silane coupling agent is limited, and it is difficult to couple with more silane coupling agent molecules on the surface even if the amount of the silane coupling agent is increased.

[0095] Combined with Example 6 and Example 7 and with reference to Table 2, it can be seen that the relative tensile strength measured in Example 7 is higher than that in Example 6, indicating that compared with the basalt fiber chopped strands used in Preparation Examples 1-2, the modified basalt fiber in Preparation Example 3 can couple with more silane coupling agent molecules, which helps to increase the total amount of unsaturated carboxylic acid monomers actually grafted onto the fiber surface, thereby enhancing the bonding effect between the reinforcing fiber and magnesium hydroxide and improving the tensile strength of the cable material.

[0096] Combined with Example 7 and Example 8 and with reference to Table 2, it can be seen that the relative tensile strength measured in Example 8 is higher than that in Example 7, indicating that adding the retarder 120 s later is beneficial for the retarder to fully exert its retarding effect, prolongs the soaking time of the basalt fiber bundle in the cement slurry, improves the modification effect of the cement slurry on the basalt fiber, increases the total amount of unsaturated carboxylic acid monomers actually grafted onto the fiber surface, improves the bonding effect between the reinforcing fiber and magnesium hydroxide, and improves the tensile strength of the cable material.

[0097] Combined with Example 8, Examples 9 - 10 and Table 2, it can be seen that the relative tensile strength measured in Example 9 is higher than that in Example 8, while the relative tensile strength measured in Example 10 is lower than that in Example 9, indicating that the synergistic use of POE resin and MAH - POE resin can improve the compatibility between carboxylated nitrile rubber and ethylene - propylene - diene monomer rubber, and carboxylated nitrile rubber can enhance the compatibility between matrix rubber and magnesium hydroxide, which helps to improve the tensile strength of cable compounds. After replacing MAH - POE resin with POE resin, the poor compatibility between carboxylated nitrile rubber and ethylene - propylene - diene monomer rubber is not fully improved, thus affecting the mechanical properties of cable compounds and resulting in a decrease in the tensile strength of cable compounds.

[0098] Combined with Examples 1 - 10, Comparative Examples 1 - 3 and Table 2, it can be seen that while improving the tensile property of cable compounds, the present application also maintains the flame - retardant property of cable compounds.

[0099] This specific embodiment is only an interpretation of the present application and is not a limitation thereof. Those skilled in the art can make modifications without creative contributions to this embodiment as needed after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A halogen-free flame-retardant polyethylene cable compound for anti-aging, characterized in that, The cable material is obtained by heating and kneading, extruding and pelletizing, and drying a mixture. The mixture comprises the following components in parts by weight: 55-70 parts of matrix rubber, 33-57 parts of resin base material, 16-28 parts of reinforcing fiber, 60-90 parts of flame retardant, 20-30 parts of flame retardant synergist, and 2.6-4.2 parts of auxiliary agent; the matrix rubber comprises ethylene propylene diene monomer rubber (EPDM), the mass fraction of magnesium hydroxide in the flame retardant is 75%, the reinforcing fiber is an inorganic fiber grafted with carboxyl groups on the surface, and the carboxyl groups are provided by unsaturated carboxylic acid monomers including oleic acid; The reinforcing fiber is prepared according to the following method: (1) Mix ethanol, water and vinyltriethoxysilane to obtain a silane modification solution for standby; add monomers into water to obtain a monomer dispersion solution for standby; the molar ratio of the monomers to vinyltriethoxysilane is 5:1, and the monomers are a mixture of oleic acid and acrylic acid in a molar ratio of 4:1; (2) Mix the inorganic fiber with the silane modification solution, stir and heat at 50-70 °C for 1-2 h, then carry out suction filtration and drying to obtain silanized fiber; (3) Mix the silanized fiber, the monomer dispersion solution and an initiator, heat at 75-85 °C for 4-5 h, then carry out suction filtration and drying to obtain the reinforcing fiber.

2. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 1, wherein In step (2) of preparing the reinforcing fiber, the weight ratio of the inorganic fiber added to the vinyltriethoxysilane in the silane modification solution is 2:

1.

3. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 2, wherein The inorganic fiber is selected as a chopped strand of basalt fiber that has been calcined to remove oil.

4. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 2, characterized in that The inorganic fiber is selected as modified basalt fiber, and the modified basalt fiber is prepared according to the following method: (1) Cut continuous basalt fiber to obtain basalt fiber monofilaments, bundle the basalt fiber monofilaments into a filament bundle, and calcine and degrease the filament bundle for standby; mix portland cement, a retarder and water and stir to obtain a cement slurry, and detect the initial setting time of the cement slurry; (2) Re-prepare the cement slurry in step (1), then immerse the filament bundle in the cement slurry and stir, then cure the mixture of the filament bundle and the cement slurry under the conditions of a relative humidity of 95% ± 1% and a temperature of 20 ± 2 °C, and take out the filament bundle for washing and drying 30 min before the initial setting time measured in step (1), and then carry out cutting processing to obtain the modified basalt fiber.

5. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 4, wherein The retarder is selected as sucrose, and the dosage of the sucrose is 0.15% of the weight of the cement.

6. The anti-aging halogen-free flame-retardant polyethylene cable compound according to claim 5, characterized in that, When preparing the cement slurry, first mix and stir portland cement and water for 120 s, and then add the retarder.

7. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 1, wherein The matrix rubber is composed of ethylene propylene diene monomer rubber (EPDM) and carboxyl nitrile rubber in a weight ratio of 9:

1.

8. The anti-aging halogen-free flame-retardant polyethylene cable material according to claim 7, characterized in that The components of the resin base material include POE resin and MAH-POE resin.

9. The production process of an anti-aging halogen-free flame-retardant polyethylene cable compound is characterized in that, It includes the following steps: (1) Mix the matrix rubber, the resin base material, the reinforcing fiber, the flame retardant, the flame retardant synergist and the auxiliary agent to obtain a mixture; (2) Carry out heating and kneading on the mixture at 170-175 °C for 15-20 min, then carry out extrusion and pelletizing and drying to obtain the anti-aging halogen-free flame-retardant polyethylene cable material according to any one of claims 1-8.

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