A high-toughness, low-smoke, halogen-free flame-retardant wire and cable sheath material

Abstract

This invention relates to a high-toughness, low-smoke, halogen-free flame-retardant wire and cable sheath material, comprising the following raw materials in parts by weight: 27-36 parts phosphorus-nitrogen flame retardant, 2-4 parts flame retardant synergist, 0.2-0.5 parts antioxidant, 0.3-0.5 parts silane coupling agent, 20-40 parts linear low-density polyethylene, and 20-40 parts ethylene-vinyl acetate copolymer; wherein the phosphorus-nitrogen flame retardant is a mixture of piperazine pyrophosphate, aluminum hypophosphite, and melamine pyrophosphate. This invention has selected a flame-retardant formulation with excellent flame-retardant performance, good cost-effectiveness, and low smoke, exhibiting higher flame-retardant efficiency than ammonium polyphosphate flame retardants; it also possesses excellent flexibility and processing performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of flame-retardant cable materials, and particularly relates to a high-toughness low-smoke halogen-free flame-retardant electric wire and cable sheath material. BACKGROUND

[0002] Electric wires and cables are widely used in national production, including high-voltage cables for transmitting power, control cables for operating equipment, rubber cables for ports and mines, flexible cables for robots, high-temperature cables for aerospace, etc. Although China's cable industry started late, it has developed rapidly and has a huge output. Since the 1980s, flame-retardant cables using polyvinyl chloride (PVC) as a sheath material have dominated the market. Halogen-containing cables have good flame-retardant effect, high efficiency, and low cost, but their combustion process releases a large amount of smoke, toxic gas, and corrosive gas, which not only corrodes and damages equipment, but also harms the health of personnel, causing "secondary damage". In recent years, with the proposal of low-smoke halogen-free flame-retardant electric wires and cables, the use of halogen-containing cables has gradually decreased, and the use of low-smoke halogen-free environmentally friendly flame-retardant electric wires and cables has increased year by year. It is estimated that the annual demand for halogen-free flame-retardant cable materials will reach about 350 kt in 2025. Domestic manufacturers and research institutions have also increased their efforts to develop low-smoke halogen-free flame-retardant electric wire and cable materials. At present, the low-smoke halogen-free flame-retardant method for polyolefin cable sheath materials can be divided into intrinsic flame retardation and additive flame retardation. Introducing flame-retardant elements or groups containing flame-retardant elements into the polyolefin chain through block, grafting, etc. can give the material more efficient flame-retardant properties, but the preparation process is complicated, expensive, and harsh. The additive flame-retardant process is simpler and less expensive, making it suitable for rapid promotion. Currently, low-smoke halogen-free flame retardants commonly used in electric wire and cable materials include metal hydroxides, phosphorus-based, nitrogen-based, borides, silicon-based, etc. Research has found that phosphorus-nitrogen-based flame retardants have the advantage of lower addition amount compared to metal hydroxides while meeting the same halogen-free flame-retardant conditions, making them suitable for preparing low-smoke halogen-free electric wire and cable sheath materials with high mechanical performance requirements.

[0003] Most of the conventional low-smoke halogen-free cable materials add hydroxides, because hydroxide flame-retardant smoke is clean and non-toxic, and magnesium hydroxide and aluminum hydroxide are cheap, but the high load of hydroxide flame-retardant low-smoke halogen-free cable material limits the higher requirement application of low-smoke halogen-free flame-retardant cable material. Therefore, the invention patent of most low-smoke halogen-free flame-retardant cable material mainly improves the low-smoke halogen-free cable material with metal hydroxide flame retardant, still mainly uses metal hydroxide as the flame retardant, adds phosphorus-containing flame retardant, nitrogen-containing flame retardant, nanocomposite, etc. as the synergistic flame retardant, and performs surface treatment on the metal hydroxide. However, when the flame-retardant demand is met, the total addition proportion of inorganic substances is still high, and many properties of the material are deteriorated, that is, additives, elastomers, etc. are added, and these methods cannot fundamentally solve the adverse effects of the large amount of inorganic substances on the properties other than the flame-retardant property. The preparation scheme of a low-smoke halogen-free cable material is introduced in the authorized Chinese patent CN116622155A. The scheme uses at least one of aluminum hydroxide, silicon dioxide, ammonium molybdate, manganese dioxide, or cobalt sesquioxide to prepare a composite flame retardant, and adds 0.5-1 parts of a coupling agent, 1-2 parts of a stabilizer, 6-10 parts of a compatibilizer, and other additives. Because the amount of inorganic substances added is huge, an open two-roll plasticator is used for sufficient mixing. The preparation scheme of a low-smoke halogen-free polyolefin sheath material is disclosed in the authorized Chinese patent CN116589782A. The inorganic flame retardant added in the scheme is a mixture of micron-sized aluminum hydroxide, magnesium hydroxide, sulfate, expanded graphite, and microencapsulated red phosphorus. To alleviate the negative effects of hydroxides and the like on processing performance and mechanical properties, 1-3 parts of a surface treatment agent, 1-2 parts of a compatibilizer, 1-3 parts of a lubricant, and 1-3 parts of a crosslinking agent are added in the invention. The preparation scheme of a low-smoke halogen-free polyolefin cable material for photovoltaics is introduced in the published Chinese patent CN116554589A. The flame retardant in the scheme is a mixture of aluminum hydroxide, magnesium hydroxide, nitrogen-phosphorus intumescent flame retardant, expanded graphite, and microencapsulated red phosphorus, and the mass fraction of the flame retardant is more than 40wt%. The preparation method of a low-smoke halogen-free soft fireproof cable material is introduced in the published Chinese patent CN116496564A. The flame retardant in the invention is a mixture of magnesium hydroxide, calcium oxide, and zinc oxide, the mica powder contains 50%-55% silicon dioxide and 30%-35% aluminum hydroxide, the total mass fraction of the flame retardant and the mica powder is 48wt%, and about 10wt% of glass fiber is added to improve the mechanical properties.

[0004] The metal hydroxide is used as the main flame retardant, and the phosphorus-containing flame retardant is added to improve the carbonization capacity in the combustion process. The inorganic aluminum hypophosphite and organic aluminum hypophosphite are mainly used as the phosphorus-containing flame retardant, because the decomposition product of aluminum hypophosphite, such as aluminum phosphate, can play a role in bonding aluminum oxide and magnesium oxide, thereby improving the adhesion, density and integrity of the carbon layer, and avoiding the secondary risk caused by powdering and falling. The Chinese published patent CN112210157B introduces a halogen-free flame-retardant polyolefin sheath material and a preparation method thereof. In this scheme, the flame retardant is still a metal hydroxide, but the aluminum diethyl hypophosphite and ammonium polyphosphate are used as the phosphorus-containing flame retardant as a synergistic flame retardant. The Chinese published patent CN113201179B introduces a high oxygen index low smoke halogen-free cable material and a preparation method thereof. In this method, aluminum hydroxide is used as the main flame retardant, and the organic hypophosphite and nitrogen-containing flame retardant are used as the oxygen index synergistic agent in an amount of about twice that of aluminum hydroxide. The Chinese granted high-value patent CN103865165B introduces a low smoke halogen-free flame-retardant polyolefin cable material and a preparation method thereof. In this method, the metal hydroxide is used as the main flame retardant, and melamine, zinc borate, ammonium polyphosphate and melamine polyphosphate are used as the flame-retardant synergistic agent.

[0005] In halogen-free flame retardation, phosphorus-nitrogen flame retardants have more excellent flame retardant efficiency than metal hydroxides, and their lower addition amount reduces the adverse effects of inorganic substances on the performance of cable materials. Generally, the addition of about 30% of the total weight of the composite phosphorus-containing flame retardant can make the material have good flame retardant performance. In addition, phosphorus-containing flame retardants are more easily modified organically to improve the compatibility of the flame retardant with the matrix, which is more conducive to reducing the impact on mechanical properties. At present, there are fewer granted invention patents on low smoke halogen-free flame-retardant wire and cable materials using full phosphorus-nitrogen flame retardants. The first reason is that the current cable materials mainly use polyolefins without oxygen, which is not conducive to the flame-retardant mechanism of phosphorus-containing flame retardants. The second reason is that nitrogen-containing flame retardants have a significant gas-phase flame-retardant effect, which is easy to produce more smoke. The Chinese granted patent CN104629175A introduces a low smoke halogen-free flame-retardant polypropylene cable material and a preparation method thereof. In this method, about 40wt% of piperazine phosphate flame retardant and a small amount of nano-clay are added. The sample passes the VW-1 test and has excellent flame retardant performance, 25kW non-flame smoke density less than 200, and elongation at break more than 490%, with excellent flexibility.

[0006] Pyrophosphoric acid piperazine was first produced industrially in Japan and applied to flame retardation. The pyrophosphoric acid piperazine with the "three sources in one" has excellent flame retardation performance, and the flame retardation efficiency is superior to that of the traditional ammonium polyphosphate flame retardation system. Chinese authorized patents CN104629175B, CN107207806B and CN107075378B introduce the scheme of (poly) phosphoric acid melamine and (poly) phosphoric acid piperazine used in polyolefin for flame retardation, which reflects the excellent flame retardation efficiency of phosphorus-nitrogen flame retardant and the lower addition amount compared with metal hydroxide. However, (poly) pyrophosphoric acid piperazine not only has high price, but also has insufficient carbon layer strength, so that the carbon layer is easy to collapse and break, a large number of incomplete combustion particles are taken out from the broken part by the hot gas flow, and the smoke release amount increases sharply, which is not conducive to smoke suppression. SUMMARY

[0007] The application provides a high-toughness low-smoke halogen-free wire and cable material and a preparation method thereof. 2 Below, the solid residual weight ratio of the cone calorimeter is increased by about one time for the polyolefin flame-retarded by pyrophosphoric acid piperazine and polyphosphoric acid piperazine.

[0008] The application is achieved by the following technical solutions.

[0009] A high-toughness low-smoke halogen-free flame-retardant wire and cable sheath material comprises the following raw materials in parts by mass: 27-36 parts of phosphorus-nitrogen flame retardant, 2-4 parts of flame-retardant synergist, 0.2-0.5 parts of antioxidant, 0.3-0.5 parts of silane coupling agent, 20-40 parts of linear low-density polyethylene, and 20-40 parts of ethylene-vinyl acetate copolymer; the phosphorus-nitrogen flame retardant is a mixture of pyrophosphoric acid piperazine, aluminum hypophosphite and melamine pyrophosphate.

[0010] Preferably, the mass ratio of pyrophosphoric acid piperazine, aluminum hypophosphite and melamine pyrophosphate is 12-15:3-4:10-13, and more preferably 12:3:10. The inventors have found that the phosphorus-nitrogen flame retardant in the above combination can play a synergistic flame-retardant effect of nitrogen and phosphorus, can achieve good flame-retardant effect with less flame retardant, and also has a smoke suppression effect.

[0011] The aluminum hypophosphite requires a particle size D50 of less than 10 μm.

[0012] The flame-retardant synergist is at least one of nano-montmorillonite, 3.5 hydrated zinc borate, attapulgite, and corundum; preferably, the particle size D50 of the nano-montmorillonite and 3.5 hydrated zinc borate is 2-10 μm; the size of the attapulgite is 10-30 μm; and the particle size D50 of the corundum is 0.3-0.7 μm.

[0013] Preferably, the flame-retardant synergist is one of nano-montmorillonite and 3.5 hydrated zinc borate or a mixture thereof, attapulgite, and corundum compounded in a mass ratio of 1-2:1-2:1-2. The inventors have found that the above flame-retardant synergist compounded with three different particle sizes can achieve the best performance in flame-retardation and smoke suppression.

[0014] The antioxidant is at least one of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, tris(2,4-di-tert-butylphenyl) phosphite, N,N-1,6-hexylidene-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, and n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0015] The silane coupling agent is an alkenyl silane coupling agent, specifically at least one of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(β-methoxyethoxy)silane.

[0016] The linear low-density polyethylene has a melt index of 2.0-2.5 g / 10 min.

[0017] The ethylene-vinyl acetate copolymer has a VA content of 25-30 wt%, such as 28 wt%.

[0018] The application screens out three halogen-free phosphorus-nitrogen flame retardants, pyrophosphoric acid piperazine, aluminum hypophosphite and pyrophosphoric acid melamine, combines the unique properties of each to prepare a composite flame retardant which is relatively low in price, low in addition amount, excellent in flame retardant efficiency, low in smoke and halogen-free and safe. Pyrophosphoric acid piperazine (PAPP) has the advantages of "three sources in one", i.e. acid source, gas source and carbon source, and the flame retardant efficiency is higher than that of conventional ammonium polyphosphate (APP), and the presence of organic piperazine ring also makes its anti-precipitation performance obviously improved compared with conventional inorganic flame retardants, and the flame retardant performance is more excellent when PAPP is used in combination with other phosphorus-nitrogen flame retardants; inorganic aluminum hypophosphite (AHP) has excellent condensed phase carbonization capacity, and in the combustion process, it not only makes the carbon layer more dense and thick, but also makes the phosphoric acid aluminum and other substances precipitate on the surface of the carbon layer, which is more helpful to enhance the heat insulation capacity. Although aluminum hypophosphite is inexpensive, it is difficult to meet the basic flame retardant requirements of cable materials when used alone, and it releases toxic phosphine gas when heated, so it is not suitable for large-scale addition; pyrophosphoric acid melamine (MPP) contains more nitrogen and phosphorus elements, and is often used in combination with other phosphorus-nitrogen intumescent flame retardants, and is a cost-effective gas source and acid source supplement. The three have a positive synergistic flame retardant effect on each other, and the flame retardant efficiency of the prepared composite phosphorus-containing flame retardant is obviously better than that of any single component under the same addition amount. The three complement each other's advantages and show excellent comprehensive flame retardant performance. In the oxygen index test process, the surface rapidly carbonizes and expands to wrap and isolate the internal unburned melt, and the non-combustible gas generated by the decomposition of the added nitrogen-containing substances continuously blows out the surface flame and dilutes the nearby oxygen concentration. The inside of the ablated residual carbon layer presents a foamed structure with vertical and horizontal interlaced holes, so that the self-supporting strength and heat insulation capacity of the carbon layer are obviously improved compared with polyphosphoric acid ammonium polyphosphate intumescent flame retardant. The carbonized structure of the surface layer is more dense and tough, so that the smoke and other incomplete decomposition products generated in the combustion process are difficult to escape, further enhancing the suppression ability. The application obtains a high-toughness low-smoke halogen-free flame-retardant wire and cable sheath material with excellent comprehensive performance through reasonable compounding of raw materials, which has high flame retardancy, high toughness and strong suppression ability, and is an extremely practical and suitable for industrialization halogen-free flame-retardant wire and cable sheath material.

[0019] The application also provides a preparation method of the high-toughness low-smoke halogen-free flame-retardant wire and cable sheath material, which comprises the following steps: fully stirring and pre-mixing phosphorus-nitrogen flame retardants, flame retardant synergists, antioxidants, silane coupling agents, linear low-density polyethylene and polyvinyl acetate in a high-speed stirrer; then adopting double-screw extrusion, pelletization, drying and injection molding, or adopting a banbury mixer to melt blend and then molding by a flat vulcanizing machine.

[0020] The double screw extruder is a double screw extruder with a screw diameter of 20 mm of Model SHJ-20 manufactured by Nanjing Jiantai Machinery and Electrical Co., Ltd., and the temperature from below the hopper to the extruder head is set as follows: 155℃ for zone 1, 165℃ for zone 2, 170℃ for zone 3, 175℃ for zone 4, 175℃ for zone 5, and 170℃ for the head. The injection molding machine is an injection molding machine of Model HTF80X1 manufactured by Ningbo Haitian Group Co., Ltd., and the extrusion temperature is set as follows from the hopper section to the nozzle: 160℃, 165℃, 170℃, 175℃ and 180℃, and the cooling time is set to 15-20s.

[0021] The internal mixer is a Plastograph EC internal mixer manufactured by Brabender, and the processing conditions are as follows: total weight of single feeding is 50g, temperature is 160℃, kneading time is 12min, and rotating speed is 40r / min. The working conditions of the flat plate vulcanizing machine are as follows: temperature is 140℃, pressure is 10bar, time is 3min, and exhaust is three times.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The present application adopts halogen-free flame retardant which is mature in production technology, suitable in price, stable and safe in nature, and selects a flame retardant ratio which has excellent flame retardant performance, good cost performance and low smoke under the premise of as low cost and simple as possible, and has higher flame retardant efficiency than polyammonium phosphate flame retardant. The prepared LLDPE / EVA wire and cable material has excellent flame retardant performance, and the preparation method adopts conventional preparation means, so that special equipment needs to be purchased almost without increasing for enterprises, and the cost is reduced. In addition, when the addition amount of the flame retardant in the cable sheath material prepared according to the present application is 30wt%, the limiting oxygen index is higher than 32%, there is no obvious melting drop, the average heat release rate during flame combustion can be lower than 150kW / m 2 , the solid residual weight of the cone calorimeter is increased by about one time compared with that without adding carbon-enhancing agent and gas source acid source supplementing agent, and the cable material has excellent flexibility and processing performance, and the breaking elongation at a stretching speed of 50mm / min is more than 350%. Compared with the cable material with hydroxide flame retardant, the cable material in the present application can be smoothly processed without adding processing aids such as extrusion and injection molding, and the sample has no obvious white frost phenomenon on the surface after long time storage. The cable material has good flame retardant performance, and also has good mechanical performance and electrical performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The photos of the sample of Example 1 before, during and after the combustion test. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in detail below. The following examples facilitate better understanding of the present application, but do not limit the present application. The experimental methods in the following examples are all conventional methods, unless otherwise specified.

[0026] Example 1

[0027] 36 parts by mass of phosphorus-nitrogen flame retardant (17.28 parts by mass of piperazine pyrophosphate, 4.32 parts by mass of aluminum hypophosphite, 14.4 parts by mass of melamine pyrophosphate), 4 parts by mass of montmorillonite with D50 of 5 μm, 0.1 part by mass of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, 0.2 part by mass of tris(2,4-di-tert-butylphenyl) phosphite, 0.4 part by mass of vinyltriethoxysilane, 29.65 parts by mass of linear low-density polyethylene, 29.65 parts by mass of ethylene-vinyl acetate copolymer, are pre-mixed at room temperature with high-speed stirring, then melt blended in a twin-screw extruder and injection molded to obtain a high-toughness low-smoke halogen-free flame-retardant wire and cable sheath material.

[0028] Example 2

[0029] The other conditions are the same as in Example 1, except that the montmorillonite is replaced by attapulgite with size of 12 μm.

[0030] Example 3

[0031] The other conditions are the same as in Example 1, except that the montmorillonite is replaced by 3.5 zinc borate hydrate with D50 of 3 μm.

[0032] Example 4

[0033] The other conditions are the same as in Example 1, except that the montmorillonite is replaced by corundum with D50 of 0.5 μm.

[0034] Example 5

[0035] 27 parts by mass of phosphorus-nitrogen flame retardant (12.96 parts by mass of piperazine pyrophosphate, 3.24 parts by mass of aluminum hypophosphite, 10.8 parts by mass of melamine pyrophosphate), 3 parts by mass of 3.5 zinc borate hydrate with D50 of 3 μm, 0.1 part by mass of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester, 0.2 part by mass of tris(2,4-di-tert-butylphenyl) phosphite, 0.3 part by mass of vinyltriethoxysilane, 36 parts by mass of linear low-density polyethylene, 36 parts by mass of ethylene-vinyl acetate copolymer, are pre-mixed at room temperature with high-speed stirring, then melt blended in a twin-screw extruder and injection molded to obtain a high-toughness low-smoke halogen-free flame-retardant wire and cable sheath material.

[0036] Example 6

[0037] Other components, allocation ratio and conditions are the same as example 1, the difference is that 4 parts by mass of D50 of 5 μm montmorillonite is replaced by 2 parts by mass of D50 of 5 μm montmorillonite, 1 part by mass of size of 12 μm attapulgite, 1 part by mass of D50 of 0.5 μm corundum.

[0038] Comparative example 1

[0039] Other conditions are the same as example 1, the difference is that 36 parts by mass of phosphorus-nitrogen flame retardant is 28.8 parts by mass of piperazine pyrophosphate, 7.2 parts by mass of aluminum hypophosphite. That is, no melamine pyrophosphate is added.

[0040] Comparative example 2

[0041] Other conditions are the same as example 1, the difference is that 36 parts by mass of phosphorus-nitrogen flame retardant is 19.64 piperazine pyrophosphate and 16.36 parts by mass of melamine pyrophosphate, that is, no aluminum hypophosphite is added.

[0042] Comparative example 3

[0043] Other conditions are the same as example 1, the difference is that 36 parts by mass of phosphorus-nitrogen flame retardant is 8.31 parts by mass of aluminum hypophosphite, 27.69 parts by mass of melamine pyrophosphate, that is, no piperazine pyrophosphate is added.

[0044] Comparative example 4

[0045] Other conditions are the same as comparative example 1, the difference is that piperazine pyrophosphate is replaced by ammonium polyphosphate.

[0046] Effect example

[0047] The halogen-free flame-retardant wire and cable sheath material prepared in the above examples and comparative examples is tested for performance (50 kW / m 2 conical calorimetry), and the results are shown in Table 1 below:

[0048] Table 1 Performance test of low-smoke halogen-free flame-retardant wire and cable sheath material

[0049]

[0050]

[0051] As can be seen from the data in Table 1, when piperazine pyrophosphate, aluminum hypophosphite, and melamine pyrophosphate are compounded in a certain proportion as nitrogen and phosphorus-containing flame retardants, a synergistic effect can be achieved, and the flame-retardant and smoke-suppressing properties of the material are significantly improved. As can be seen from examples and comparative examples 1-4, when any one of the above three substances is missing, the flame-retardant and / or smoke-suppressing properties will decrease under the same total amount of flame retardant, which fully illustrates the synergistic effect between the three.

[0052] Figure 1 100 x 100 x 3 mm 3 Photos of the sample before, during and after the test. The combustion behavior of other example groups is similar to it, which expands rapidly after being ignited to form a foaming structure with dense surface, and the carbon shell has a certain strength and toughness, fully wraps and protects the internal unburned part, and reduces the fire.

Claims

1. A high toughness, low smoke, halogen-free, flame retardant wire and cable jacketing compound characterized in that, The raw materials include the following quality parts: 27-36 parts of phosphorus-nitrogen flame retardant, 2-4 parts of flame retardant synergist, 0.2-0.5 parts of antioxidant, 0.3-0.5 parts of silane coupling agent, 20-40 parts of linear low density polyethylene, 20-40 parts of ethylene-vinyl acetate copolymer; the phosphorus-nitrogen flame retardant is a mixture of piperazine pyrophosphate, aluminum hypophosphite, and melamine pyrophosphate; the mass ratio of piperazine pyrophosphate, aluminum hypophosphite, and melamine pyrophosphate is 12-15:3-4:10-13.

2. The high toughness, low smoke, zero halogen, flame retardant wire and cable jacketing compound of claim 1, wherein, The flame retardant synergist is at least one of nano-montmorillonite, 3.5 hydrated zinc borate, attapulgite, and diamond sand.

3. The high toughness, low smoke, zero halogen, flame retardant wire and cable jacketing material of claim 2, wherein, The particle size D50 of the nano-montmorillonite and 3.5 hydrated zinc borate is 2-10 μm; the size of the attapulgite is 10-30 μm; the particle size D50 of the diamond sand is 0.3-0.7 μm.

4. The high toughness, low smoke, zero halogen, flame retardant electrical wire and cable jacketing material of claim 1 wherein, The flame retardant synergist is a mixture of one or both of nano-montmorillonite and 3.5 hydrated zinc borate, attapulgite, and diamond sand in a mass ratio of 1-2:1-2:1-2.

5. The high toughness, low smoke, zero halogen, flame retardant wire and cable jacketing material of claim 1 wherein, The antioxidant is at least one of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol ester, tris(2,4-di-tert-butylphenyl) phosphite, N,N-1,6-hexanediyl-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide, n-octadecanol β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

6. The high toughness, low smoke, zero halogen, flame retardant electrical wire and cable jacketing material of claim 1 wherein, The silane coupling agent is an alkenyl silane coupling agent.

7. The high toughness, low smoke, zero halogen, flame retardant wire and cable jacketing material of claim 6 wherein, The alkenyl silane coupling agent is at least one of vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(β-methoxyethoxy)silane.

8. The high toughness, low smoke, zero halogen, flame retardant electrical wire and cable jacketing material of claim 1 wherein, The linear low density polyethylene has a melt index of 2.0-2.5 g / 10 min.

9. The high toughness, low smoke, zero halogen, flame retardant wire and cable jacketing material of claim 1 wherein, The ethylene-vinyl acetate copolymer has a VA content of 25-30 wt%.

10. The process for the preparation of a high flexibility low smoke halogen-free flame retardant sheath for electric wire and cable as claimed in any one of claims 1 to 9, characterized in that, The method includes the following steps: The phosphorus-nitrogen flame retardant, flame retardant synergist, antioxidant, silane coupling agent, linear low density polyethylene, and ethylene-vinyl acetate copolymer are pre-mixed by being fully stirred in a high-speed mixer; then, double-screw extrusion, granulation, drying, and injection molding are adopted, or a mixer is used for melt blending, and then a flat vulcanizing machine is used for molding.

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