Flexible flame-retardant cable sheath material and preparation method thereof

Abstract

The invention provides a flexible flame-retardant cable sheath material and a preparation method thereof, and the flexible flame-retardant cable sheath material is prepared from the following raw materials in parts by weight: 100-140 parts of ethylene-vinyl acetate copolymer; 6 to 10 parts of a synergist; 35 to 50 parts of a flame retardant; 13 to 15 parts of epoxidized soybean oil; 0.5 to 0.7 part of other auxiliary agents; the synergist is prepared from the following raw materials: acetic acid, chitosan, ammonium polyphosphate, graphene oxide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, ethylenediamine and oxalic acid. The flame retardant is prepared from the following raw materials: phosphonitrilic chloride trimer, an alkaline substance, 3-amino-1, 2, 4-triazole and polyvinyl alcohol. The flexible flame-retardant cable sheath material provided by the invention has excellent flexibility, thermal stability and flame retardance.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable processing, and relates to a flexible flame-retardant cable sheath material and a preparation method thereof. Background Art

[0002] A cable is an electrical device used to transmit electrical energy, electrical signals, and achieve electromagnetic energy conversion, including four parts: a conductor, an insulating layer, a shielding layer, and a sheath layer. Among them, the conductor is usually made of a highly conductive metal material, and its function is to carry current and achieve the transmission of electrical energy or electrical signals; the insulating layer is a material with good insulation performance, wrapped around the conductor to prevent current leakage and short circuits between different conductors, ensuring the safety and stability of power transmission; the shielding layer is generally composed of a metal material, mainly used to reduce the interference of the internal electromagnetic field of the cable to the outside world, and at the same time can also prevent the influence of the external electromagnetic field on the internal signals of the cable, ensuring the quality of signal transmission; the sheath layer is located on the outermost layer of the cable, mainly playing a protective role. Cables are widely used in the power industry, industrial fields, construction industries, and communication fields. Therefore, the demand for cables is increasing, and the performance requirements are also getting higher and higher. For example, the connecting wires of electrical instruments and the transmission lines of automatic control systems need to have higher thermal stability, flexibility, and flame retardancy.

[0003] In order to improve the high-temperature resistance, aging resistance, etc. of cables, CN117894517BA discloses a high-temperature resistant and aging resistant cable and a preparation method thereof. The cable includes a cable sheath and a conductor material wrapped by the cable sheath; the sheath is sequentially provided with an insulating layer, a high-temperature resistant layer, and an aging resistant layer from the inside to the outside. Among them, the insulating layer is coated with a high-temperature resistant layer on the outside, and the high-temperature resistant layer is coated with an aging resistant layer on the outside; the high-temperature resistant layer is filled with expanded graphite material, and the aging resistant layer is filled with a hydrophobic fiber material. However, the flexibility, thermal stability, and flame retardancy of the cables prepared by these existing methods still need to be further improved.

[0004] Therefore, in this field, it is desirable to develop a flexible flame-retardant cable sheath material that simultaneously has excellent flexibility, thermal stability, and flame retardancy. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a flexible flame-retardant cable sheath material and a preparation method thereof.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a flexible flame-retardant cable sheath material. The preparation raw materials of the flexible flame-retardant cable sheath material include the following components according to weight parts:

[0008]

[0009] The raw materials for preparing the synergist include: acetic acid, chitosan, ammonium polyphosphate, graphene oxide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, ethylenediamine, and oxalic acid;

[0010] The raw materials for preparing the flame retardant include: phosphorus nitride trichloride, basic substance, 3-amino-1,2,4-triazole, and polyvinyl alcohol.

[0011] The raw materials for preparing the flexible flame retardant cable sheath material provided by the present invention include ethylene-vinyl acetate copolymer, synergist, flame retardant, epoxy soybean oil, and other additives. Through the screening and synergistic compounding of specific components, especially the introduction of specific synergist and specific flame retardant, the prepared cable sheath material has more excellent flexibility, thermal stability, and flame retardancy, making it have a wider application prospect.

[0012] In the present invention, based on weight parts, the amount of ethylene-vinyl acetate copolymer used in the raw materials for preparing the flexible flame retardant cable sheath material can be 100 parts, 102 parts, 104 parts, 106 parts, 108 parts, 110 parts, 112 parts, 114 parts, 116 parts, 118 parts, 120 parts, 122 parts, 124 parts, 126 parts, 128 parts, 130 parts, 132 parts, 134 parts, 136 parts, 138 parts, 140 parts, etc.

[0013] In the present invention, based on weight parts, the amount of synergist used in the raw materials for preparing the flexible flame retardant cable sheath material can be 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, etc.

[0014] In the present invention, based on weight parts, the amount of flame retardant used in the raw materials for preparing the flexible flame retardant cable sheath material can be 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 parts, 49 parts, 50 parts, etc.

[0015] In the present invention, based on weight parts, the amount of epoxy soybean oil used in the raw materials for preparing the flexible flame retardant cable sheath material can be 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, etc.

[0016] In the present invention, based on weight parts, the amount of other additives used in the raw materials for preparing the flexible flame retardant cable sheath material can be 0.5 parts, 0.55 parts, 0.6 parts, 0.65 parts, 0.7 parts, etc.

[0017] Preferably, the synergist is prepared by the following method:

[0018] Step A1: Add chitosan into an acetic acid solution and stir to obtain a chitosan gel;

[0019] Step A2: Mix ammonium polyphosphate with deionized water, then add (preferably dropwise) the chitosan gel, stir and then perform centrifugal separation. Dry the lower-layer precipitate to obtain a composite powder;

[0020] Step A3: Mix graphene oxide with a solvent and stir, then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and react. Then add an ethylenediamine solution, stir again, reflux, and after post-treatment, obtain modified graphene;

[0021] Step A4: Mix the modified graphene with deionized water and stir, then add oxalic acid and the composite powder, stir again, and after post-treatment, obtain the synergist.

[0022] In the present invention, during the preparation process of the modified graphene, the amino group of ethylenediamine reacts with carboxyl groups on the surface of graphene oxide, etc., effectively improving the uniform dispersion ability of graphene oxide, enabling graphene oxide to combine more closely with the matrix. At the same time, the introduction of ethylenediamine will change the combustion behavior of the material to a certain extent, promote the formation of a carbon layer, and further improve the flame retardancy effect. Combining with the inherent properties of graphene oxide, the modified graphene can effectively improve the tensile strength, elongation at break, flame retardancy, aging resistance, and antioxidant properties of the material.

[0023] In the present invention, the modified graphene and the composite powder undergo a cross-linking reaction to form an effective component with extremely excellent flame retardancy and thermal stability in the synergist; the synergist in a specific proportion will also have a synergistic effect with components such as flame retardants in the flexible flame-retardant cable sheath material, further enhancing the mechanical properties, flame retardancy, and thermal stability of the material.

[0024] Preferably, the dosage ratio of the acetic acid solution to chitosan in Step A1 is 300 - 450 mL: 10 - 15 g. 300 - 450 mL can be, for example, 300 mL, 320 mL, 340 mL, 350 mL, 360 mL, 380 mL, 400 mL, 420 mL, 440 mL, 450 mL, etc., and 10 - 15 g can be, for example, 10 g, 11 g, 12 g, 13 g, 14 g, 15 g, etc.

[0025] Preferably, the acetic acid solution in Step A1 includes an acetic acid aqueous solution.

[0026] Preferably, the mass concentration of the acetic acid solution in Step A1 is 0.5% - 2%, such as 0.5%, 1%, 1.5%, 2%, etc.

[0027] Preferably, the temperature of the stirring in step A1 is 60 - 80°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the time of the stirring is 60 - 70 min, such as 60 min, 65 min, 70 min, etc.

[0028] Preferably, the dosage ratio of ammonium polyphosphate to deionized water in step A2 is 20 - 30 g : 200 - 300 mL. 20 - 30 g can be, for example, 20 g, 22 g, 24 g, 26 g, 28 g, 30 g, etc., and 200 - 300 mL can be, for example, 200 mL, 220 mL, 240 mL, 250 mL, 260 mL, 280 mL, 300 mL, etc.

[0029] Preferably, the mass ratio of ammonium polyphosphate to chitosan gel in step A2 is 20 - 30 : 300 - 500. 20 - 30 can be, for example, 20, 22, 24, 26, 28, 30, etc., and 300 - 500 can be, for example, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 500, etc.

[0030] Preferably, the time of the stirring in step A2 is 60 - 70 min, such as 60 min, 65 min, 70 min, etc.

[0031] Preferably, the temperature of the drying in step A2 is 50 - 70°C, such as 50°C, 55°C, 60°C, 65°C, 70°C, etc.

[0032] Preferably, the dosage ratio of the solvent to graphene oxide in step A3 is 300 - 500 mL : 0.6 - 1 g. 300 - 500 mL can be, for example, 300 mL, 320 mL, 340 mL, 350 mL, 360 mL, 380 mL, 400 mL, 420 mL, 440 mL, 450 mL, 460 mL, 480 mL, 500 mL, etc., and 0.6 - 1 g can be, for example, 0.6 g, 0.7 g, 0.8 g, 0.9 g, 1 g, etc.

[0033] Preferably, the mass ratio of graphene oxide to 1-(3 - dimethylaminopropyl)-3 - ethylcarbodiimide hydrochloride in step A3 is 0.6 - 1 : 0.03 - 0.05. 0.6 - 1 can be, for example, 0.6, 0.7, 0.8, 0.9, 1, etc., and 0.03 - 0.05 can be, for example, 0.03, 0.035, 0.04, 0.045, 0.05, etc.

[0034] Preferably, the dosage ratio of the graphene oxide to the ethylenediamine solution in step A3 is 0.6 - 1 g: 900 - 1500 mL. 0.6 - 1 g can be, for example, 0.6 g, 0.7 g, 0.8 g, 0.9 g, 1 g, etc., and 900 - 1500 mL can be, for example, 900 mL, 1000 mL, 1100 mL, 1200 mL, 1300 mL, 1400 mL, 1500 mL, etc.

[0035] That is, the dosage ratio of the solvent, graphene oxide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and ethylenediamine solution in step A3 is 300 - 500 mL: 0.6 - 1 g: 0.03 - 0.05 g: 900 - 1500 mL.

[0036] Preferably, the solvent in step A3 includes N,N-dimethylformamide.

[0037] Preferably, the ethylenediamine solution in step A3 includes an aqueous ethylenediamine solution.

[0038] Preferably, the concentration of the ethylenediamine solution in step A3 is 0.4 - 1 mol / L, such as 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc.

[0039] Preferably, the rotation speed of the stirring in step A3 is 400 - 500 r / min, such as 400 r / min, 420 r / min, 440 r / min, 450 r / min, 460 r / min, 480 r / min, 500 r / min, etc., and the stirring time is 60 - 70 min, such as 60 min, 65 min, 70 min, etc.

[0040] Preferably, the reaction time in step A3 is 30 - 40 min, such as 30 min, 35 min, 40 min, etc.

[0041] Preferably, the time of the secondary stirring in step A3 is 60 - 70 min, such as 60 min, 65 min, 70 min, etc.

[0042] Preferably, the reflux temperature in step A3 is 60 - 70 °C, such as 60 °C, 65 °C, 70 °C, etc., and the reflux time is 6 - 10 h, such as 6 h, 7 h, 8 h, 9 h, 10 h, etc.

[0043] Preferably, the post-treatment in step A3 includes washing and drying.

[0044] Preferably, the dosage ratio of the deionized water to the modified graphene in step A4 is 500 - 600 mL: 0.4 - 0.6 g. 500 - 600 mL can be, for example, 500 mL, 520 mL, 540 mL, 550 mL, 560 mL, 580 mL, 600 mL, etc., and 0.4 - 0.6 g can be, for example, 0.4 g, 0.45 g, 0.5 g, 0.55 g, 0.6 g, etc.

[0045] Preferably, the mass ratio of the modified graphene to oxalic acid in step A4 is 0.4 - 0.6: 0.015 - 0.02. 0.4 - 0.6 can be, for example, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, 0.52, 0.54, 0.55, 0.56, 0.58, 0.6, etc., and 0.015 - 0.02 can be, for example, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, etc.

[0046] Preferably, the mass ratio of the modified graphene to the composite powder in step A4 is 0.4 - 0.6: 30 - 45. 0.4 - 0.6 can be, for example, 0.4, 0.42, 0.44, 0.45, 0.46, 0.48, 0.5, 0.52, 0.54, 0.55, 0.56, 0.58, 0.6, etc., and 30 - 45 can be, for example, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, etc.

[0047] That is, the dosage ratio of the deionized water, modified graphene, oxalic acid, and composite powder in step A4 is 500 - 600 mL: 0.4 - 0.6 g: 0.015 - 0.02 g: 30 - 45 g.

[0048] Preferably, the temperature of the stirring in step A4 is 40 - 50 °C, such as 40 °C, 45 °C, 50 °C, etc., and the time of the stirring is 30 - 40 min, such as 30 min, 35 min, 40 min, etc.

[0049] Preferably, the time of the re - stirring in step A4 is 12 - 24 h, such as 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc.

[0050] Preferably, the post - treatment in step A4 includes washing and drying.

[0051] Preferably, the flame retardant is prepared by the following method:

[0052] Step B1: Mix phosphonitrile trichloride with an organic solvent, then add an alkaline substance and a 3-amino-1,2,4-triazole solution, stir, heat to reflux, filter by suction, distill under reduced pressure, add absolute ethanol and heat to reflux, and after post-treatment, obtain a white solid.

[0053] Step B2: Mix deionized water with the white solid, perform ultrasonic treatment for the first time, then add a polyvinyl alcohol solution for secondary ultrasonic treatment to obtain the flame retardant.

[0054] In the present invention, during the preparation of the flame retardant, phosphonitrile trichloride reacts with 3-amino-1,2,4-triazole to generate a white solid with a toughening effect and containing flame retardant elements such as phosphorus and nitrogen. These elements can play a flame retardant role through various mechanisms such as gas-phase flame retardancy and condensed-phase flame retardancy during combustion; the polyvinyl alcohol solution will fully chemically crosslink with the white solid under the action of ultrasonic waves and will form a crosslinked structure with ethylene-vinyl acetate copolymer during the subsequent preparation process of the cable sheath material, thereby enhancing the cohesion of the material and improving the mechanical properties such as the tensile strength of the material. At the same time, the white solid in the flame retardant will absorb heat during the thermal decomposition process, thereby delaying the thermal decomposition rate of the material and improving the thermal stability of the material; polyvinyl alcohol will form a protective film on the surface of the cable sheath material at high temperature, reducing the heat transfer to the inside of the material, and further improving the stability of the material in a high-temperature environment, enabling the flexible flame retardant cable sheath material to withstand higher temperatures during use without deformation or performance degradation. Therefore, the addition of a flame retardant in a specific proportion can effectively improve the flexibility, flame retardancy and thermal stability of the cable sheath material.

[0055] Preferably, the dosage ratio of the phosphonitrile trichloride to the organic solvent in Step B1 is 5-6 g: 100-120 mL. 5-6 g can be, for example, 5 g, 5.2 g, 5.4 g, 5.5 g, 5.6 g, 5.8 g, 6 g, etc., and 100-120 mL can be, for example, 100 mL, 105 mL, 110 mL, 115 mL, 120 mL, etc.

[0056] Preferably, the mass ratio of the phosphonitrile trichloride to the alkaline substance in Step B1 is 5-6: 12-14.4. 5-6 can be, for example, 5, 5.2, 5.4, 5.5, 5.6, 5.8, 6, etc., and 12-14.4 can be, for example, 12, 12.2, 12.3, 12.5, 12.8, 13, 13.2, 13.3, 13.5, 13.8, 14, 14.2, 14.4, etc.

[0057] Preferably, the dosage ratio of the phosphonitrile chloride trimer described in step B1 to the 3-amino-1,2,4-triazole solution is 5-6 g: 50-60 mL. 5-6 g can be, for example, 5 g, 5.2 g, 5.4 g, 5.5 g, 5.6 g, 5.8 g, 6 g, etc., and 50-60 mL can be, for example, 50 mL, 52 mL, 54 mL, 55 mL, 56 mL, 58 mL, 60 mL, etc.

[0058] Preferably, the dosage ratio of the phosphonitrile chloride trimer described in step B1 to absolute ethanol is 5-6 g: 50-60 mL. 5-6 g can be, for example, 5 g, 5.2 g, 5.4 g, 5.5 g, 5.6 g, 5.8 g, 6 g, etc., and 50-60 mL can be, for example, 50 mL, 55 mL, 60 mL, etc.

[0059] That is, the dosage ratio of the phosphonitrile chloride trimer, organic solvent, basic substance, 3-amino-1,2,4-triazole solution, and absolute ethanol described in step B1 is 5-6 g: 100-120 mL: 12-14.4 g: 50-60 mL: 50-60 mL.

[0060] Preferably, the organic solvent described in step B1 includes tetrahydrofuran.

[0061] Preferably, the basic substance described in step B1 includes potassium carbonate.

[0062] Preferably, the 3-amino-1,2,4-triazole solution described in step B1 is prepared by the following method: Dissolve 8.4-10 g (such as 8.4 g, 8.6 g, 8.8 g, 9 g, 9.2 g, 9.4 g, 9.6 g, 9.8 g, 10 g, etc.) of 3-amino-1,2,4-triazole in 50-60 mL (such as 50 mL, 55 mL, 60 mL, etc.) of tetrahydrofuran.

[0063] Preferably, the stirring time in step B1 is 30-40 min, such as 30 min, 35 min, 40 min, etc.

[0064] Preferably, the heating to reflux in step B1 specifically includes: Heating to 60-70 °C (such as 60 °C, 65 °C, 70 °C, etc.) and refluxing for 24-25 h (such as 24 h, 24.5 h, 25 h, etc.).

[0065] Preferably, the suction filtration in step B1 is carried out at 25-30 °C (such as 25 °C, 26 °C, 28 °C, 30 °C, etc.).

[0066] Preferably, the temperature of the vacuum distillation in step B1 is 30 - 50 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, etc., the pressure is 3 - 5 kPa, such as 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, etc., and the duration is 1.5 - 2.5 h, such as 1.5 h, 2 h, 2.5 h, etc.

[0067] Preferably, the post-treatment in step B1 includes: hot filtration, and after the filtrate is cooled to 25 - 30 °C (such as 25 °C, 26 °C, 28 °C, 30 °C, etc.), it is placed at 3 - 5 °C (such as 3 °C, 4 °C, 5 °C, etc.) for 12 - 15 h (such as 12 h, 13 h, 14 h, 15 h, etc.), and then suction filtration, washing, and drying treatments are carried out.

[0068] Preferably, the mass ratio of the deionized water to the white solid in step B2 is 14 - 20:6 - 10, where 14 - 20 can be, for example, 14, 15, 16, 17, 18, 19, 20, etc., and 6 - 10 can be, for example, 6, 7, 8, 9, 10, etc.

[0069] Preferably, the mass ratio of the white solid to the polyvinyl alcohol solution in step B2 is 6 - 10:15 - 20, where 6 - 10 can be, for example, 6, 7, 8, 9, 10, etc., and 15 - 20 can be, for example, 15, 16, 17, 18, 19, 20, etc.

[0070] That is, the dosage ratio of the deionized water, white solid, and polyvinyl alcohol solution in step B2 is 14 - 20 g:6 - 10 g:15 - 20 g.

[0071] Preferably, the polyvinyl alcohol solution in step B2 is prepared by the following method: 3 - 5 g (such as 3 g, 3.5 g, 4 g, 4.5 g, 5 g, etc.) of polyvinyl alcohol is added to 12 - 15 g (such as 12 g, 13 g, 14 g, 15 g, etc.) of deionized water, and stirred at 90 - 95 °C (such as 90 °C, 92 °C, 93 °C, 95 °C, etc.) for 2 - 3 h (such as 2 h, 2.5 h, 3 h, etc.).

[0072] Preferably, the temperature of the first ultrasonic treatment in step B2 is 40 - 60 °C, such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc.

[0073] Preferably, the power of the first ultrasonic treatment in step B2 is 280 - 300 W, such as 280 W, 285 W, 290 W, 295 W, 300 W, etc., the frequency is 35 - 40 kHz, such as 35 kHz, 36 kHz, 38 kHz, 40 kHz, etc., and the duration is 2 - 3 h, such as 2 h, 2.5 h, 3 h, etc.

[0074] Preferably, the temperature of the secondary ultrasound in step B2 is 40-60 °C, such as 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, etc.

[0075] Preferably, the power of the secondary ultrasound in step B2 is 280-300 W, such as 280 W, 285 W, 290 W, 295 W, 300 W, etc., the frequency is 35-40 kHz, such as 35 kHz, 36 kHz, 38 kHz, 40 kHz, etc., and the duration is 10-12 h, such as 10 h, 11 h, 12 h, etc.

[0076] Preferably, the other additives include antioxidants and / or silane coupling agents.

[0077] Preferably, the other additives include 0.3-0.4 parts by weight of antioxidants (such as 0.3 parts, 0.35 parts, 0.4 parts, etc.) and 0.2-0.3 parts by weight of silane coupling agents (such as 0.2 parts, 0.25 parts, 0.3 parts, etc.).

[0078] Preferably, the antioxidant includes antioxidant 1010 and / or antioxidant 168.

[0079] Preferably, the antioxidant includes a composition of antioxidant 1010 and antioxidant 168 with a mass ratio of (0.1-0.2):0.2, and (0.1-0.2):0.2 can be, for example, 0.1:0.2, 0.12:0.2, 0.14:0.2, 0.16:0.2, 0.18:0.2, 0.2:0.2, etc.

[0080] When antioxidant 1010 and antioxidant 168 are used in combination, they have a good synergistic effect. The antioxidant compounded in a specific ratio in the present invention can not only capture free radicals generated during the thermal oxygen aging process of the material, interrupt the free radical chain reaction, thereby inhibiting the oxidation of the material, but also decompose hydroperoxides to prevent the further decomposition of hydroperoxides to generate new free radicals. After adding, it can further improve the thermal oxygen stability of the cable sheath material.

[0081] Preferably, the silane coupling agent includes silane coupling agent KH-550.

[0082] As a preferred technical solution of the present invention, the raw materials for preparing the flexible flame-retardant cable sheath material include the following components in parts by weight:

[0083]

[0084]

[0085] Second, the present invention provides a method for preparing the flexible flame-retardant cable sheath material as described in the first aspect, and the preparation method includes the following steps:

[0086] Step S1: Add ethylene-vinyl acetate copolymer into a twin-screw extruder for plasticization to obtain a pretreated copolymer;

[0087] Step S2: Knead the pretreated copolymer with a synergist, a flame retardant, epoxy soybean oil, and other additives, and then extrude, pelletize, and dry to obtain the flexible flame-retardant cable sheath material.

[0088] Preferably, the temperature of the plasticization in Step S1 is 130 - 150 °C, such as 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, etc.; the rotation speed of the plasticization is 150 - 200 r / min, such as 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, etc.; and the time of the plasticization is 8 - 10 min, such as 8 min, 9 min, 10 min, etc.

[0089] Preferably, the temperature of the kneading in Step S2 is 130 - 150 °C, such as 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, etc.; the rotation speed of the kneading is 150 - 200 r / min, such as 150 r / min, 160 r / min, 170 r / min, 180 r / min, 190 r / min, 200 r / min, etc.; and the time of the kneading is 8 - 10 min, such as 8 min, 9 min, 10 min, etc.

[0090] Preferably, the temperature of the drying in Step S2 is 80 - 90 °C, such as 80 °C, 85 °C, 90 °C, etc.; and the time of the drying is 2 - 3 h, such as 2 h, 2.5 h, 3 h, etc.

[0091] Compared with the prior art, the present invention has at least the following beneficial effects:

[0092] The preparation raw materials of the flexible flame-retardant cable sheath material provided by the present invention include ethylene-vinyl acetate copolymer, a synergist, a flame retardant, epoxy soybean oil, and other additives. Through the screening and synergistic compounding of specific components, especially the introduction of specific synergist and specific flame retardant, the prepared cable sheath material has more excellent flexibility, thermal stability, and flame retardancy, making it have a wider application prospect. Specific Embodiments

[0093] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0094] Unless otherwise specified, the information of some raw materials used in the following examples and comparative examples of the present invention is as follows:

[0095] Chitosan: Purchased from Shanghai Yuanye Bio-Technology Co., Ltd., product number: S11064-500g;

[0096] Ammonium polyphosphate: Purchased from Shanghai Yuanye Bio-Technology Co., Ltd., product number: S67475-100g;

[0097] Graphene oxide: Purchased from Shanghai Xiaohuang Nano-Technology Co., Ltd., product number: XH-C-2;

[0098] Phosphonitrile chloride trimer: Purchased from Henan Weiti Xi Chemical Technology Co., Ltd., product number: A940716;

[0099] Polyvinyl alcohol: Purchased from Shanghai Yuanye Bio-Technology Co., Ltd., product number: S30196-500g;

[0100] Ethylene-vinyl acetate copolymer: Purchased from Henan Weiti Xi Chemical Technology Co., Ltd., product number: A0937788;

[0101] Epoxidized soybean oil: Purchased from Shanghai Yuanye Bio-Technology Co., Ltd., product number: S50881-500ml.

[0102] Example 1

[0103] In this example, a flexible flame-retardant cable sheath material is provided, and the preparation method includes the following steps:

[0104] S1: Add 10 g of chitosan to 300 mL of acetic acid aqueous solution with a mass concentration of 1%, and stir at 70 °C for 60 min to obtain chitosan gel;

[0105] S2: At 25 °C, dissolve 20 g of ammonium polyphosphate in 200 mL of deionized water, and then drop it into all the chitosan gel synthesized in step S1 at a speed of 5 mL / min. After stirring for 60 min, centrifuge and separate. The lower layer precipitate is dried at 60 °C to obtain composite powder;

[0106] S3: At 25 °C, add 0.6 g of graphene oxide to 300 mL of N,N-dimethylformamide and stir at 400 r / min for 60 min. Then add 0.03 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, react for 30 min, add 900 mL of ethylenediamine aqueous solution with a concentration of 0.5 mol / L and stir for 60 min. Then reflux at 60 °C for 6 h. Finally, wash with deionized water by centrifugation 4 times and dry at 50 °C to obtain modified graphene;

[0107] S4: Add 0.4 g of modified graphene into 500 mL of deionized water and stir for 30 min at 45 °C. Then add 0.015 g of oxalic acid and 30 g of composite powder and stir for 12 h. Wash with distilled water three times and dry at 50 °C to obtain the synergist.

[0108] S5: Dissolve 8.4 g of 3 - amino - 1,2,4 - triazole in 50 mL of tetrahydrofuran to obtain a 3 - amino - 1,2,4 - triazole solution.

[0109] S6: Dissolve 5 g of phosphorus pentachloride in 100 mL of tetrahydrofuran. Then slowly add 12 g of potassium carbonate, dropwise add 50 mL of the 3 - amino - 1,2,4 - triazole solution at a rate of 0.1 mL / min and stir for 30 min. Then raise the temperature to 65 °C and reflux for 24 h. After cooling to 25 °C, perform suction filtration and carry out vacuum distillation on the filtrate at 40 °C and 4 kPa for 1.5 h. Then add 50 mL of absolute ethanol and heat to reflux. Filter while it is hot. After the filtrate cools to 25 °C, place it at 3 °C for 12 h. Finally, perform suction filtration and wash the crystals three times with absolute ethanol at 3 °C. Vacuum dry at 60 °C for 6 h to obtain a white solid.

[0110] S7: Add 3 g of polyvinyl alcohol into 12 g of deionized water and stir for 2 h at 90 °C to obtain a polyvinyl alcohol solution.

[0111] S8: Add 6 g of the white solid into 14 g of deionized water and perform the first ultrasonic treatment at 50 °C with a power of 280 W and a frequency of 35 kHz for 2 h. Then add 15 g of the polyvinyl alcohol solution and perform the second ultrasonic treatment at 50 °C with a power of 280 W and a frequency of 30 kHz for 10 h to obtain the flame retardant.

[0112] S9: Mix 0.1 g of antioxidant 1010 and 0.2 g of antioxidant 168 evenly to obtain the antioxidant.

[0113] S10: Add 100 g of ethylene - vinyl acetate copolymer into a twin - screw extruder, plasticize at 130 °C and 150 r / min for 8 min. Then add 6 g of the synergist, 35 g of the flame retardant, 0.3 g of the antioxidant, 13 g of epoxidized soybean oil, 0.2 g of silane coupling agent KH - 550. Continue to mix at 130 °C and 150 r / min for 8 min. Then extrude, pelletize, and perform drying treatment at 80 °C for 2 h to obtain the flexible flame - retardant cable sheath material.

[0114] Example 2

[0115] In this example, a flexible flame - retardant cable sheath material is provided, and the preparation method includes the following steps:

[0116] S1: Add 12.5 g of chitosan to 375 mL of acetic acid aqueous solution with a mass concentration of 1%, and stir at 70 °C for 65 min to obtain chitosan gel;

[0117] S2: At 28 °C, dissolve 25 g of ammonium polyphosphate in 250 mL of deionized water, and then drop all the chitosan gel synthesized in step S1 at a rate of 6 mL / min. After stirring for 65 min, centrifuge and separate. The lower layer precipitate is dried at 60 °C to obtain composite powder;

[0118] S3: At 25 °C, add 0.8 g of graphene oxide to 400 mL of N,N-dimethylformamide and stir at 450 r / min for 65 min. Then add 0.04 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. After reacting for 35 min, add 1200 mL of ethylenediamine aqueous solution with a concentration of 0.5 mol / L and stir for 65 min. Then reflux at 60 °C for 8 h. Finally, wash with deionized water by centrifugation 5 times and dry at 50 °C to obtain modified graphene;

[0119] S4: Add 0.5 g of modified graphene to 550 mL of deionized water and stir at 45 °C for 35 min. Then add 0.018 g of oxalic acid and 37.5 g of composite powder and stir for 18 h. Then wash with distilled water 4 times and dry at 50 °C to obtain a synergist;

[0120] S5: Dissolve 9.2 g of 3-amino-1,2,4-triazole in 55 mL of tetrahydrofuran to obtain a 3-amino-1,2,4-triazole solution;

[0121] S6: Dissolve 5.5 g of phosphorus pentachloride in 110 mL of tetrahydrofuran, then slowly add 13.2 g of potassium carbonate, drop 55 mL of 3-amino-1,2,4-triazole solution at a rate of 0.2 mL / min and stir to react for 35 min. Then raise the temperature to 65 °C and reflux for 24.5 h. After cooling to 28 °C, perform suction filtration and carry out vacuum distillation on the filtrate at 40 °C and 4 kPa for 2 h. Then add 55 mL of absolute ethanol and heat to reflux. Filter while it is hot. After the filtrate cools to 28 °C, place it at 4 °C for 14 h. Finally, perform suction filtration and wash the crystals 4 times with absolute ethanol at 4 °C, and vacuum dry at 60 °C for 6.5 h to obtain a white solid;

[0122] S7: Add 4 g of polyvinyl alcohol to 13 g of deionized water and stir at 93 °C for 2.5 h to obtain a polyvinyl alcohol solution;

[0123] S8: Add 8 g of white solid to 17 g of deionized water and conduct the first ultrasonic treatment at 50 °C with a power of 290 W and a frequency of 38 kHz for 2.5 h. Then add 17 g of polyvinyl alcohol solution and conduct the second ultrasonic treatment at 50 °C with a power of 290 W and a frequency of 35 kHz for 11 h to obtain the flame retardant;

[0124] S9: Mix 0.15 g of antioxidant 1010 and 0.2 g of antioxidant 168 evenly to obtain the antioxidant;

[0125] S10: Add 120 g of ethylene-vinyl acetate copolymer to a twin-screw extruder, plasticize at 140 °C and 180 r / min for 9 min. Then add 8 g of synergist, 42.5 g of flame retardant, 0.35 g of antioxidant, 14 g of epoxy soybean oil, and 0.25 g of silane coupling agent KH-550, continue to mix at 140 °C and 180 r / min for 9 min, and then conduct extrusion, granulation, and drying treatment at 85 °C for 2.5 h to obtain the flexible flame-retardant cable sheath material.

[0126] Example 3

[0127] In this example, a flexible flame-retardant cable sheath material is provided, and the preparation method includes the following steps:

[0128] S1: Add 15 g of chitosan to 450 mL of acetic acid aqueous solution with a mass concentration of 1%, and stir at 70 °C for 70 min to obtain chitosan gel;

[0129] S2: At 30 °C, dissolve 30 g of ammonium polyphosphate in 300 mL of deionized water, and then drop all the chitosan gel synthesized in step S1 at a speed of 7 mL / min. After stirring for 70 min, conduct centrifugal separation. The lower layer precipitate is dried at 60 °C to obtain the composite powder;

[0130] S3: At 25 °C, add 1 g of graphene oxide to 500 mL of N,N-dimethylformamide and stir at 500 r / min for 70 min. Then add 0.05 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, react for 40 min, add 1500 mL of ethylenediamine aqueous solution with a concentration of 0.5 mol / L and stir for 70 min, then reflux at 60 °C for 10 h, and finally wash 6 times with deionized water by centrifugation and dry at 50 °C to obtain modified graphene;

[0131] S4: Add 0.6 g of modified graphene to 600 mL of deionized water and stir at 45 °C for 40 min. Then add 0.02 g of oxalic acid and 45 g of composite powder and stir for 24 h. Then wash 5 times with distilled water and dry at 50 °C to obtain the synergist;

[0132] S5: Dissolve 10 g of 3 - amino - 1,2,4 - triazole in 60 mL of tetrahydrofuran to obtain a 3 - amino - 1,2,4 - triazole solution;

[0133] S6: Dissolve 6 g of phosphorus oxychloride - triphosphazene in 120 mL of tetrahydrofuran, then slowly add 14.4 g of potassium carbonate, dropwise add 60 mL of the 3 - amino - 1,2,4 - triazole solution at a rate of 0.3 mL / min and stir for reaction for 40 min, then raise the temperature to 65 °C and reflux for 25 h. After cooling to 30 °C, perform suction filtration and carry out vacuum distillation on the filtrate at 40 °C and 4 kPa for 2.5 h. Then add 60 mL of absolute ethanol and heat to reflux, filter while it is hot. After the filtrate cools to 30 °C, place it at 5 °C for 15 h, and finally perform suction filtration and wash the crystals 5 times with absolute ethanol at 5 °C, and dry in vacuum at 60 °C for 7 h to obtain a white solid;

[0134] S7: Add 5 g of polyvinyl alcohol to 15 g of deionized water and stir at 95 °C for 3 h to obtain a polyvinyl alcohol solution;

[0135] S8: Add 10 g of the white solid to 20 g of deionized water and perform the first ultrasonic treatment at 50 °C with a power of 300 W and a frequency of 40 kHz for 3 h. Then add 20 g of the polyvinyl alcohol solution and perform the second ultrasonic treatment at 50 °C with a power of 300 W and a frequency of 40 kHz for 12 h to obtain a flame retardant;

[0136] S9: Mix 0.2 g of antioxidant 1010 and 0.2 g of antioxidant 168 evenly to obtain an antioxidant;

[0137] S10: Add 140 g of ethylene - vinyl acetate copolymer to a twin - screw extruder, plasticize at 150 °C and 200 r / min for 10 min. Then add 10 g of a synergist, 50 g of the flame retardant, 0.4 g of the antioxidant, 15 g of epoxidized soybean oil, 0.3 g of silane coupling agent KH - 550, continue to mix at 150 °C and 200 r / min for 10 min, and then extrude, pelletize, and perform a drying treatment at 90 °C for 3 h to obtain a flexible flame - retardant cable sheath material.

[0138] Example 4

[0139] The difference between this example and Example 1 is only that in the preparation process of the synergist, the "modified graphene" added in step S4 is replaced with "graphene oxide" of equal weight. Accordingly, step S3 is not included.

[0140] Example 5

[0141] The difference between this example and Example 1 is only that in the preparation process of the synergist, the step "add 0.4 g of modified graphene to 500 mL of deionized water, stir at 45 °C for 30 min, then add 0.015 g of oxalic acid and 30 g of composite powder and stir for 12 h" in step S4 is replaced by "add 10.4 g of modified graphene to 500 mL of deionized water, stir at 45 °C for 30 min, then add 0.015 g of oxalic acid and 20 g of composite powder and stir for 12 h".

[0142] Example 6

[0143] The difference between this example and Example 1 is only that in the preparation process of the flame retardant, the step "add 6 g of white solid to 14 g of deionized water, perform the first ultrasonic wave for 2 h with a power of 280 W and a frequency of 35 kHz at 50 °C, then add 15 g of polyvinyl alcohol solution and perform the second ultrasonic wave for 10 h with a power of 280 W and a frequency of 30 kHz at 50 °C" in step S8 is replaced by "add 16 g of white solid to 14 g of deionized water, perform the first ultrasonic wave for 2 h with a power of 280 W and a frequency of 35 kHz at 50 °C, then add 5 g of polyvinyl alcohol solution and perform the second ultrasonic wave for 10 h with a power of 280 W and a frequency of 30 kHz at 50 °C".

[0144] Example 7

[0145] The difference between this example and Example 1 is only that in the preparation process of the flame retardant, the step "add 6 g of white solid to 14 g of deionized water, perform the first ultrasonic wave for 2 h with a power of 280 W and a frequency of 35 kHz at 50 °C, then add 15 g of polyvinyl alcohol solution and perform the second ultrasonic wave for 10 h with a power of 280 W and a frequency of 30 kHz at 50 °C" in step S8 is replaced by "add 6 g of white solid to 14 g of deionized water, perform the first ultrasonic wave for 2 h with a power of 280 W and a frequency of 35 kHz at 50 °C, then add 15 g of polyvinyl alcohol solution and stir at 50 °C at a rotation speed of 400 r / min for 10 h".

[0146] Example 8

[0147] The difference between this example and Example 1 is only that in the preparation process of the antioxidant in step S9, the step "mix 0.1 g of antioxidant 1010 and 0.2 g of antioxidant 168 evenly" is replaced by "mix 0.25 g of antioxidant 1010 and 0.05 g of antioxidant 168 evenly".

[0148] Comparative Example 1

[0149] The only difference between this comparative example and Example 1 is that the "afterwards adding 6 g of synergist, 35 g of flame retardant, 0.3 g of antioxidant, 13 g of epoxy soybean oil, and 0.2 g of silane coupling agent KH-550" in the preparation process of the flexible flame-retardant cable sheath material in step S10 is replaced by "afterwards adding 0.6 g of synergist, 35 g of flame retardant, 0.7 g of antioxidant, 15 g of epoxy soybean oil, and 3.2 g of silane coupling agent KH-550".

[0150] Comparative Example 2

[0151] The only difference between this comparative example and Example 1 is that the phrase "add 6 g synergist, 35 g flame retardant, 0.3 g antioxidant, 13 g epoxy soybean oil, and 0.2 g silane coupling agent KH-550" in the preparation process of the flexible flame-retardant cable sheath material in step S10 is replaced by "add 6 g synergist, 3 g flame retardant, 0.3 g antioxidant, 13 g epoxy soybean oil, and 0.2 g silane coupling agent KH-550".

[0152] Comparative Example 3

[0153] The only difference between this comparative example and Example 1 is that, in the process of preparing the synergist, step S3 does not include the step of "adding 0.03 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and reacting for 30 minutes".

[0154] Comparative Example 4

[0155] The only difference between this comparative example and Example 1 is that, in the process of preparing the flame retardant, step S6 does not include the step of "dropping 50 mL of 3-amino-1,2,4-triazole solution at 0.1 mL / min and stirring the reaction for 30 min".

[0156] Performance testing:

[0157] The cable sheath materials prepared in the embodiment and the comparative example were respectively added into an injection molding machine (the temperature of the injection molding machine was set to 170°C, the injection pressure was 100 MPa, the injection time was 15 s, and the holding time was 8 s) for injection molding, and then vulcanized at 5 MPa and 120°C for 2 h. A cable sheath material sample (thickness of 1 mm) was prepared in this way, and then the cable sheath material sample was tested as follows:

[0158] (1) Determination of limiting oxygen index:

[0159] According to GB / T2406.2-2009 "Determination of Combustion Behavior of Plastics by Oxygen Index Method Part 2: Room Temperature Test" standard, the limiting oxygen index (%) test was carried out on the cable sheath material samples;

[0160] (2) Determination of Tensile Strength and Elongation at Break before and after Aging:

[0161] Referring to the standard of GB / T2951.12-2008 "General Test Methods for Insulating and Sheathing Materials of Cables and Optical Fibre Cables - Part 12: General Test Methods - Thermal Aging Test", the aging resistance test of the cable sheath material sample was carried out, and the tensile strength (MPa) and elongation at break (%) of the cable sheath material before and after aging at 150 °C for 480 h were recorded.

[0162] The performance test results are shown in Table 1.

[0163] Table 1

[0164]

[0165]

[0166] It can be seen from Table 1 that the flexible flame-retardant cable sheath material provided by the embodiment of the present invention has a relatively high limiting oxygen index (29.7% - 41.5%, preferably 41.2% - 41.5%), tensile strength (19.8 - 26.5 MPa, preferably 25.9 - 26.5 MPa), elongation at break (530% - 621%, preferably 611% - 621%), tensile strength retention rate after thermal aging (90.1% - 98.9%, preferably 98.8% - 98.9%), and elongation at break retention rate after thermal aging (88.9% - 98.2%, preferably 98.2%). That is, the flexible flame-retardant cable sheath material provided by the present invention has excellent flexibility, flame-retardant ability and thermal stability.

[0167] Compared with Example 1, the flexibility, flame-retardant ability and thermal stability of the cable sheath materials provided in Comparative Examples 1 - 4 are significantly decreased.

[0168] The applicant declares that the present invention uses the above embodiments to illustrate the flexible flame-retardant cable sheath material and its preparation method of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A flexible flame-retardant cable sheath material, characterized in that, The raw materials for preparing the flexible flame-retardant cable sheath material include the following components in parts by weight: The raw materials for preparing the synergist include: acetic acid, chitosan, ammonium polyphosphate, graphene oxide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, ethylenediamine, and oxalic acid; The raw materials for preparing the flame retardant include: tripolyphosphazene chloride, alkaline substances, 3-amino-1,2,4-triazole and polyvinyl alcohol.

2. The flexible flame-retardant cable sheath material according to claim 1, wherein The synergist is prepared by the following method: Step A1: adding chitosan to an acetic acid solution and stirring to obtain a chitosan gel; Step A2: mixing ammonium polyphosphate with deionized water, then adding chitosan gel, stirring and centrifuging, and drying the lower precipitate to obtain a composite powder; Step A3: mixing graphene oxide with a solvent, stirring, then adding 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, reacting, then adding ethylenediamine solution, stirring again, refluxing, and post-treating to obtain modified graphene; Step A4: Mix the modified graphene with deionized water, stir, then add oxalic acid and composite powder, stir again, and obtain the synergist after post-treatment.

3. The flexible flame-retardant cable sheath material according to claim 2, characterized in that, The usage ratio of the acetic acid solution and chitosan in step A1 is 300-450 mL: 10-15 g; Preferably, the acetic acid solution in step A1 comprises an acetic acid aqueous solution; Preferably, the mass concentration of the acetic acid solution in step A1 is 0.5%-2%; Preferably, the stirring temperature in step A1 is 60-80° C., and the stirring time is 60-70 min; Preferably, the usage ratio of the ammonium polyphosphate and deionized water in step A2 is 20-30 g: 200-300 mL; Preferably, the mass ratio of ammonium polyphosphate to chitosan gel in step A2 is 20-30:300-500; Preferably, the stirring time in step A2 is 60-70 min; Preferably, the drying temperature in step A2 is 50-70°C.

4. The flexible flame-retardant cable sheath material according to claim 2 or 3, characterized in that, The ratio of the solvent to graphene oxide in step A3 is 300-500 mL: 0.6-1 g; Preferably, the mass ratio of graphene oxide to 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride in step A3 is 0.6-1:0.03-0.05; Preferably, the ratio of graphene oxide to ethylenediamine solution in step A3 is 0.6-1 g: 900-1500 mL; Preferably, the solvent in step A3 comprises N,N-dimethylformamide; Preferably, the ethylenediamine solution in step A3 comprises an ethylenediamine aqueous solution; Preferably, the concentration of the ethylenediamine solution in step A3 is 0.4-1 mol / L; Preferably, the stirring speed in step A3 is 400-500 r / min, and the stirring time is 60-70 min; Preferably, the reaction time in step A3 is 30-40 min; Preferably, the stirring time in step A3 is 60-70 minutes; Preferably, the reflux temperature in step A3 is 60-70° C., and the reflux time is 6-10 h; Preferably, the post-treatment in step A3 includes washing and drying; Preferably, the dosage ratio of the deionized water to the modified graphene in step A4 is 500 - 600 mL: 0.4 - 0.6 g; Preferably, the mass ratio of the modified graphene to oxalic acid in step A4 is 0.4 - 0.6: 0.015 - 0.02; Preferably, the mass ratio of the modified graphene to the composite powder in step A4 is 0.4 - 0.6: 30 - 45; Preferably, the temperature of the stirring in step A4 is 40 - 50 °C, and the stirring time is 30 - 40 min; Preferably, the time of the re-stirring in step A4 is 12 - 24 h; Preferably, the post-treatment in step A4 includes washing and drying.

5. The flexible flame-retardant cable sheath material according to any one of claims 1-4, characterized in that The flame retardant is prepared by the following method: Step B1: Mix phosphonitrile trichloride with an organic solvent, then add an alkaline substance and a 3-amino-1,2,4-triazole solution, stir, heat to reflux, filter by suction, distill under reduced pressure, then add absolute ethanol and heat to reflux, and after post-treatment, obtain a white solid; Step B2: Mix deionized water with the white solid, perform primary ultrasonic treatment, and then add a polyvinyl alcohol solution for secondary ultrasonic treatment to obtain the flame retardant.

6. The flexible flame-retardant cable sheath material according to claim 5, characterized in that The dosage ratio of the phosphonitrile trichloride to the organic solvent in step B1 is 5 - 6 g: 100 - 120 mL; Preferably, the mass ratio of the phosphonitrile trichloride to the alkaline substance in step B1 is 5 - 6: 12 - 14.4; Preferably, the dosage ratio of the phosphonitrile trichloride to the 3-amino-1,2,4-triazole solution in step B1 is 5 - 6 g: 50 - 60 mL; Preferably, the dosage ratio of the phosphonitrile trichloride to the absolute ethanol in step B1 is 5 - 6 g: 50 - 60 mL; Preferably, the organic solvent in step B1 includes tetrahydrofuran; Preferably, the alkaline substance in step B1 includes potassium carbonate; Preferably, the 3-amino-1,2,4-triazole solution in step B1 is prepared by the following method: Dissolve 8.4 - 10 g of 3-amino-1,2,4-triazole in 50 - 60 mL of tetrahydrofuran; Preferably, the stirring time in step B1 is 30 - 40 min; Preferably, the heat-up reflux in step B1 specifically includes: Heating to 60 - 70 °C and refluxing for 24 - 25 h; Preferably, the suction filtration in step B1 is carried out at 25 - 30 °C; Preferably, the temperature of the distillation under reduced pressure in step B1 is 30 - 50 °C, the pressure is 3 - 5 kPa, and the duration is 1.5 - 2.5 h; Preferably, the post-treatment in step B1 includes: Filtering while it is hot, and after the filtrate cools to 25 - 30 °C, placing it at 3 - 5 °C for 12 - 15 h, and then performing suction filtration, washing, and drying treatments.

7. The flexible flame-retardant cable sheath material according to claim 5 or 6, characterized in that, The mass ratio of the deionized water to the white solid in step B2 is 14 - 20: 6 - 10; Preferably, the mass ratio of the white solid to the polyvinyl alcohol solution in step B2 is 6 - 10: 15 - 20; Preferably, the polyvinyl alcohol solution in step B2 is prepared by the following method: Add 3 - 5 g of polyvinyl alcohol to 12 - 15 g of deionized water and stir at 90 - 95 °C for 2 - 3 h; Preferably, the temperature of the primary ultrasonic treatment in step B2 is 40 - 60 °C; Preferably, the power of the first ultrasonic wave in step B2 is 280 - 300 W, the frequency is 35 - 40 kHz, and the duration is 2 - 3 h; Preferably, the temperature of the second ultrasonic wave in step B2 is 40 - 60 °C; Preferably, the power of the second ultrasonic wave in step B2 is 280 - 300 W, the frequency is 35 - 40 kHz, and the duration is 10 - 12 h.

8. The flexible flame-retardant cable sheath material according to any one of claims 1-7, characterized in that The other additives include antioxidants and / or silane coupling agents; Preferably, the other additives include 0.3 - 0.4 parts of antioxidant and 0.2 - 0.3 parts of silane coupling agent; Preferably, the antioxidant includes antioxidant 1010 and / or antioxidant 168; Preferably, the antioxidant includes a composition of antioxidant 1010 and antioxidant 168 with a mass ratio of (0.1 - 0.2):0.2; Preferably, the silane coupling agent includes silane coupling agent KH - 550; Preferably, the raw materials for preparing the flexible flame - retardant cable sheath material include the following components by weight:

9. A method for preparing a flexible flame-retardant cable sheath material as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: Step S1: Add ethylene - vinyl acetate copolymer into a twin - screw extruder for plasticization to obtain a pretreated copolymer; Step S2: Mix the pretreated copolymer with a synergist, a flame retardant, epoxy soybean oil, and other additives, and then extrude, pelletize, and dry to obtain the flexible flame - retardant cable sheath material.

10. The preparation method according to claim 9, characterized in that, The temperature of the plasticization in step S1 is 130 - 150 °C, the rotation speed of the plasticization is 150 - 200 r / min, and the time of the plasticization is 8 - 10 min; Preferably, the temperature of the mixing in step S2 is 130 - 150 °C, the rotation speed of the mixing is 150 - 200 r / min, and the time of the mixing is 8 - 10 min; Preferably, the temperature of the drying in step S2 is 80 - 90 °C, and the time of the drying is 2 - 3 h.

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