Extreme-cold resistant low-fume halogen-free flame-retardant polyolefin sheath, preparation method therefor, and cable

Abstract

An extreme-cold resistant low-fume halogen-free flame-retardant polyolefin sheath, a preparation method therefor, and a cable. The sheath comprises the following raw materials in parts by mass: 4-16 parts of an ethylene-vinyl acetate copolymer, 7-13 parts of a phosphate group functionalized linear low-density polyethylene, 9-15 parts of an ethylene-octene copolymer, 5-10 parts of a maleic anhydride-grafted ethylene-methyl methacrylate copolymer, 10-15 parts of magnesium hydroxide, 40-50 parts of aluminum hydroxide, etc. The preparation method for the phosphate group functionalized linear low-density polyethylene comprises: adding a catalyst to a pre-cooled ethylene monomer, adding a vinyl phosphate ester and an initiator after the reaction, and reacting for 1-2 hours at a temperature of 65-75°C and a pressure of 15-35 Mpa and then terminating the reaction, thereby obtaining the phosphate group functionalized linear low-density polyethylene. Compared with unfunctionalized polyethylene, the phosphate group functionalized polyethylene used has greatly improved low-temperature and flame-retardant performance, and can improve the overall flame-retardant and low-temperature performance of the formula.

Description

Cold-resistant low-smoke halogen-free flame-retardant polyolefin sheath, preparation method thereof and cable TECHNICAL FIELD

[0001] The present application relates to cold-resistant cable, in particular to a cold-resistant low-smoke halogen-free flame-retardant polyolefin sheath, a preparation method thereof and a cable. BACKGROUND

[0002] Wire and cable is a wire product used to transmit electric energy, information and realize electromagnetic energy conversion. In a broad sense, wire and cable is also simply referred to as cable, and in a narrow sense, cable is defined as: a collection of one or more insulated cores, and their respective possible cladding layers, total protective layer and outer sheath, and cable can also have additional conductors without insulation.

[0003] Since part of the wire and cable needs to be placed outdoors for a long time, it is unavoidable to be disturbed by severe cold. A big problem in the use of existing wire and cable is that the wire and cable has poor cold resistance. When used at a very low temperature for a long time, the outer skin of the wire and cable is easily damaged, thereby causing line damage and economic loss.

[0004] With the increasing changes in the international environment, the continuous sanctions of Russia by Europe and the United States, and the implementation of many embargo measures, Russia has lost most of its traditional cable suppliers. Due to the extremely cold environment caused by the geographical environment of Russia, the cable market in the extremely cold environment is open to us, but there is a lack of similar extremely cold working conditions in China, and there is a general lack of corresponding products and technical reserves. SUMMARY

[0005] In order to solve the problem of lack of corresponding cable products in the extremely cold working condition in China, the present application provides a cold-resistant low-smoke halogen-free flame-retardant polyolefin sheath, a preparation method thereof and a preparation application in a cold-resistant-52℃ low-smoke halogen-free flame-retardant class A cable in an extremely cold area. The addition of phosphoric acid group functionalized polyethylene in the sheath greatly improves the low temperature and flame retardant properties.

[0006] In order to achieve the above purpose, the present application provides a cold-resistant low-smoke halogen-free flame-retardant polyolefin sheath, which comprises the following raw materials in parts by mass: ethylene-vinyl acetate copolymer 4-16 parts, phosphoric acid group functionalized linear low density polyethylene 7-13 parts, ethylene-octene copolymer 9-15 parts, maleic anhydride grafted ethylene-methyl methacrylate copolymer 5-10 parts, magnesium hydroxide 10-15 parts, aluminum hydroxide 40-50 parts, char-forming agent (such as kaolin, sepiolite) 2-5 parts, lubricant (such as erucic acid amide) 1-2 parts, antioxidant (such as antioxidant 1010, antioxidant 1024) 0.1-0.2 parts, colorant (such as carbon black masterbatch) 2-3 parts, coupling agent (such as Dow Corning 11-100) 1-2 parts.

[0007] The preparation method of the phosphonic group functionalized linear low-density polyethylene is as follows: adding a catalyst into pre-cooled ethylene monomer, adding vinyl phosphate and an initiator after reaction, and terminating the reaction under the condition of temperature of 65-75 DEG C and pressure of 15-35 Mpa for 1-2 hours.

[0008] In the present application, the phosphonic group functionalized polyethylene has greater improvement in low-temperature and flame-retardant properties compared with the unfunctionalized polyethylene, and can improve the overall flame-retardant and low-temperature properties of the formula. The introduction of the phosphonic group functionalized polyethylene can reduce the addition amount of the powder flame retardant in the sheath material, and under the condition of the same flame-retardant effect as the original, the low-temperature performance of the cable material is improved due to the reduction of the powder flame retardant.

[0009] In the preparation process of the phosphonic group functionalized linear low-density polyethylene, the phosphonic group content can be improved by introducing the phosphonic group in the polyethylene monomer polymerization process, which can greatly improve the low-temperature brittleness of the cable sheath on the basis of enhancing the flame retardation.

[0010] Preferably, the catalyst is vinyl titanium trichloride, methylaluminoxane or vinyl hafnium tetrachloride; and / or

[0011] The initiator is benzoyl peroxide or dicumyl peroxide.

[0012] Preferably, the molar ratio of the ethylene monomer, the catalyst, the vinyl phosphate and the initiator is 1000: (1-1.1): (12-15): (3-5).

[0013] Preferably, after the reaction is terminated, the product is filtered and separated to remove the unreacted monomer and catalyst residues, and then purified and stabilized to obtain the phosphonic group functionalized linear low-density polyethylene. Specifically, the polymer is dissolved in toluene for further purification. Insoluble impurities are removed by precipitation, filtration and the like. A stabilizer BHT (2,6-di-tert-butyl-p-cresol) is added to prevent the oxidation and degradation of the polymer. After drying treatment, the pure phosphonic group functionalized linear low-density polyethylene is obtained.

[0014] Preferably, the grafting rate of the maleic anhydride grafted ethylene-methyl methacrylate copolymer is 3-5%. The methyl methacrylate copolymer as the matrix can guarantee the overall low-temperature performance, and the grafting rate of the maleic anhydride within the range can minimize the influence on the mechanical properties on the premise of guaranteeing the low-temperature performance of the overall cable material.

[0015] Preferably, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 9-12%.

[0016] Preferably, the elongation at break of the ethylene-octene copolymer is ≥800%. The excellent low-temperature performance itself and the high elongation can compensate for the relatively low elongation at break of the phosphoric acid functionalized polyethylene.

[0017] Preferably, the purity of the aluminum hydroxide is ≥99%, and the particle size D50 is ≤1 micron. The low particle size further improves the overall low-temperature performance while ensuring the flame-retardant performance.

[0018] The magnesium hydroxide is surface-modified by phosphoric acid ester and has an average particle size ≤1 micron. The flame-retardant performance is further improved while ensuring the low-temperature performance. The modification method of the magnesium hydroxide is: phosphoric acid ester and magnesium ion complex reaction to form phosphate to deposit and coat the magnesium hydroxide.

[0019] The second aspect of the present application provides a preparation method of the above-mentioned low-smoke halogen-free flame-retardant polyolefin sheath resistant to extreme cold, which comprises the following steps: mixing raw materials at 10-12 Hz for 2-3 min and at 45-55 Hz for 5-8 min at 50-60℃, then mixing the mixture in a banbury mixer for 20-25 min, placing the banbury product in a screw extruder for extrusion, the upper stage barrel temperature is 120-130℃, the lower stage barrel temperature is 135-150℃, placing the double-screw product in a single-screw extruder for extrusion, the barrel temperature is 130-145℃, and granulating and packaging.

[0020] The third aspect of the present application provides a low-smoke halogen-free flame-retardant A-class cable resistant to -52℃ cold in extremely cold regions comprising the above-mentioned low-smoke halogen-free flame-retardant polyolefin sheath resistant to extreme cold. In a preferred technical solution of the present application, the cable is composed of a conductor, crosslinked polyethylene insulation, elastomer filling strip, and low-smoke halogen-free flame-retardant polyolefin sheath resistant to extreme cold. The elastomer filling strip is poly(methyl methacrylate) extruded. The elastomer filling strip can provide sufficient rebound space for the cable at low temperature. In the sheath, phosphoric acid group functionalized linear low-density polyethylene prepared by in-situ polymerization is introduced to ensure more outstanding low-temperature performance on the basis of flame-retardant performance, ensuring that the cable can adapt to the use environment in extremely cold regions.

[0021] Through the above technical solution, the present application achieves the following beneficial effects:

[0022] Compared with the unfunctionalized polyethylene, the phosphoric acid group functionalized polyethylene has greater improvement in low temperature and flame retardant performance, and can improve the overall flame retardant and low temperature performance of the formula. The introduction of the phosphoric acid group functionalized polyethylene can reduce the addition amount of the particle flame retardant in the sheath material, and in the case of the same flame retardant effect as before, the low temperature performance of the cable material is improved due to the reduction of the addition amount of the powder flame retardant. In the preparation process of the phosphoric acid group functionalized linear low density polyethylene by the method of the application, the phosphoric acid group content can be increased by introducing the phosphoric acid group during the polymerization of the polyethylene monomer, so that the low temperature brittleness of the cable sheath can be greatly improved on the basis of enhancing the flame retardant. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural schematic diagram of a preferred embodiment of the cable of the application.

[0024] BRIEF DESCRIPTION OF DRAWINGS

[0025] 1, conductor; 2, insulation layer; 3, filler strip; 4, sheath. Embodiment of the application

[0026] The specific embodiments of the application will be described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only for illustration and explanation of the application, and are not intended to limit the application.

[0027] Example 1

[0028] 1. Preparation of phosphoric acid group functionalized linear low density polyethylene

[0029] Dissolve methylaluminoxane in toluene to prepare a catalyst solution. Dissolve the initiator dicumyl peroxide in toluene to prepare an initiator solution.

[0030] Clean the reaction kettle to ensure that there is no impurity and moisture. Under the protection of argon, the reaction kettle is pretreated.

[0031] Introduce ethylene monomer into the reaction kettle and precool at 0°C. Slowly add the catalyst solution and stir uniformly. After 10 minutes of reaction, slowly add the ethylene phosphate and continue to stir. The molar ratio of ethylene monomer, methylaluminoxane, ethylene phosphate and dicumyl peroxide is 1000:1:12:3. Control the reaction temperature at 65°C and the pressure at 35 MPa. During or after the introduction of the phosphate, slowly add the initiator solution to control the polymerization rate and molecular weight distribution. Maintain the reaction temperature and pressure and continue the reaction for 1 hour. Terminate the polymerization reaction by adding ethanol. Release the pressure of the reaction kettle and cool to room temperature. Separate the product by filtration to remove unreacted monomer and catalyst residue.

[0032] The polymer is dissolved in toluene for further purification. Insoluble impurities are removed by precipitation, filtration and other methods. A stabilizer BHT is added to prevent oxidative degradation of the polymer. Drying treatment is performed to obtain pure phosphonic acid functionalized low density polyethylene.

[0033] 2. Preparation of low smoke halogen-free flame retardant polyolefin sheath for extremely cold area

[0034] The sheath comprises the following raw materials in parts by mass: ethylene-vinyl acetate copolymer 16 parts, phosphonic acid group functionalized linear low density polyethylene 7 parts, ethylene-octene copolymer 9 parts, maleic anhydride grafted ethylene-methyl methacrylate copolymer 5 parts, phosphate modified magnesium hydroxide 10 parts, aluminum hydroxide 40 parts, char-forming agent kaolin 2 parts, lubricant erucic acid amide 1 part, antioxidant 1010 0.1 part, carbon black masterbatch 2 parts, coupling agent Dow Corning 11-100 1 part.

[0035] The raw materials are mixed at 50°C for 3 min at low speed of 12 Hz and at high speed of 45 Hz for 5 min, and then the mixture is subjected to mixing in a Banbury mixer for 20 min. The mixing product is subjected to extrusion in a screw extruder, with the upper stage barrel temperature ranging from 120°C and the lower stage barrel temperature ranging from 135°C. The double screw product is subjected to extrusion in a single screw extruder, with the barrel temperature being 130°C. The product is pelletized and packaged.

[0036] 3. Preparation of low smoke halogen-free flame retardant class A cable for extremely cold area

[0037] A single screw extruder is used to extrude a crosslinked polyethylene insulation layer 2 with a thickness of 0.85 mm outside a 2.5 mm2conductor 1.

[0038] The semi-finished product after extrusion insulation is subjected to irradiation (irradiation dose 12-16 Mrad), and the deformation of the irradiated insulation layer 2 under thermal extension load is less than 100%, and the permanent deformation is less than 10%.

[0039] The irradiated semi-finished product is twisted into a cable together with a methyl methacrylate filling strip 3.

[0040] A single screw extruder is used to extrude a sheath 4 with a thickness of 1.8-2.0 mm outside the cabling line.

[0041] Example 2

[0042] 1. Preparation of phosphonic acid group functionalized linear low density polyethylene

[0043] Ethylene-based titanium trichloride is dissolved in toluene to prepare a catalyst solution. The initiator benzoyl peroxide is dissolved in toluene to prepare an initiator solution.

[0044] The reaction kettle is cleaned to ensure that there is no impurity and moisture. The reaction kettle is pretreated under argon protection.

[0045] Ethylene monomer was introduced into the reactor and pre-cooled at 0°C. Catalyst solution was added slowly and stirred uniformly. After 15 minutes of reaction initiation, vinyl phosphate was added slowly and stirring was continued. The molar ratio of ethylene monomer, vinyl titanium trichloride, vinyl phosphate, and benzoyl peroxide was controlled at 1000:1:15:5. The reaction temperature was controlled at 70°C and the pressure was controlled at 25 MPa. Initiator solution was added slowly during or after the introduction of phosphate to control the polymerization rate and molecular weight distribution. The reaction temperature and pressure were maintained and the reaction was continued for 2 hours. The polymerization reaction was terminated by adding ethanol. The reactor pressure was released and cooled to room temperature. The product was separated by filtration to remove unreacted monomer and catalyst residue.

[0046] The polymer was dissolved in toluene for further purification. Insoluble impurities were removed by precipitation, filtration, and the like. A stabilizer, BHT, was added to prevent oxidative degradation of the polymer. Drying treatment was performed to obtain pure phosphoric acid functionalized low density polyethylene.

[0047] 2. Preparation of low smoke halogen-free flame-retardant polyolefin sheath resistant to extremely cold temperatures

[0048] The sheath includes the following raw materials in parts by mass: ethylene-vinyl acetate copolymer 10 parts, phosphoric acid group functionalized linear low density polyethylene 10 parts, ethylene-octene copolymer 12 parts, maleic anhydride grafted ethylene-methyl methacrylate copolymer 6 parts, phosphate modified magnesium hydroxide 10 parts, aluminum hydroxide 45 parts, char-forming agent kaolin 3 parts, lubricant erucic acid amide 1 part, antioxidant 1010 0.2 parts, carbon black color masterbatch 2 parts, and coupling agent Dow Corning 11-100 1 part.

[0049] The raw materials were mixed at 60°C for 2 minutes at low speed of 10 Hz and 5 minutes at high speed of 50 Hz, and then the mixture was subjected to banburying in a banburying machine for 25 minutes. The banburying product was subjected to extrusion in a screw extruder, with the temperature of the upper stage of the cylinder being 130°C and the temperature of the lower stage of the cylinder being 140°C. The double-screw product was subjected to extrusion in a single-screw extruder, with the temperature of the cylinder being 145°C. The product was pelletized and packaged.

[0050] 3. Preparation of low smoke halogen-free flame-retardant class A cable resistant to extremely cold temperatures of -52°C for use in extremely cold regions

[0051] A single-screw extruder was used to extrude a crosslinked polyethylene insulation layer 2 having a thickness of 0.85 mm outside a conductor 1 having a cross-sectional area of 2.5 mm2.

[0052] The semi-finished product after extrusion insulation was subjected to irradiation (irradiation dose 12-16 Mrad), and the deformation of the irradiated insulation layer 2 under thermal extension load was less than 100%, and the permanent deformation was less than 10%.

[0053] The irradiated semi-finished product is cabled together with the methyl methacrylate filling strip 3;

[0054] A single-screw extruder is used to extrude a sheath 4 with a thickness of 1.8-2.0 mm outside the cabled wire, forming a cable as shown in Fig. 1.

[0055] Example 3

[0056] 1. Preparation of phosphonic group functionalized linear low density polyethylene

[0057] Vinyl hafnium tetrachloride is dissolved in toluene to prepare a catalyst solution. Initiator benzoyl peroxide is dissolved in toluene to prepare an initiator solution.

[0058] The reactor is cleaned to ensure no impurities and moisture. The reactor is pre-treated under argon protection.

[0059] Ethylene monomer is introduced into the reactor and pre-cooled at 0°C. The catalyst solution is slowly added and stirred uniformly. After 10 minutes from the start of the reaction, vinyl phosphate is slowly added and stirring is continued. The molar ratio of the ethylene monomer, vinyl hafnium tetrachloride, vinyl phosphate, and benzoyl peroxide is controlled at 1000:1.1:15:5. The reaction temperature is controlled at 75°C and the pressure is controlled at 15 MPa. The initiator solution is slowly added during or after the introduction of the phosphate to control the polymerization rate and molecular weight distribution. The reaction temperature and pressure are maintained and the reaction is continued for 2 hours. The polymerization reaction is terminated by adding ethanol. The reactor pressure is released and cooled to room temperature. The product is separated by filtration to remove unreacted monomer and catalyst residues.

[0060] The polymer is dissolved in toluene for further purification. Insoluble impurities are removed by methods such as precipitation and filtration. A stabilizer BHT is added to prevent oxidative degradation of the polymer. Drying treatment is performed to obtain pure phosphonic group functionalized low density polyethylene.

[0061] 2. Preparation of extremely cold resistant low smoke halogen-free flame retardant polyolefin sheath:

[0062] The sheath includes the following raw materials in parts by mass: ethylene-vinyl acetate copolymer 4 parts, phosphonic group functionalized linear low density polyethylene 13 parts, ethylene-octene copolymer 15 parts, maleic anhydride grafted ethylene-methyl methacrylate copolymer 0 parts, phosphate modified magnesium hydroxide 15 parts, aluminum hydroxide 50 parts, carbonaceous agent kaolin 5 parts, lubricant erucic acid amide 2 parts, antioxidant 1010 0.2 parts, carbon black color masterbatch 3 parts, coupling agent Dow Corning 11-100 2 parts.

[0063] The raw materials were mixed at 50°C for 3 minutes at low speed of 10 Hz, and at high speed of 55 Hz for 8 minutes, and then the mixture was mixed in an internal mixer for 25 minutes. The mixed product was extruded in a screw extruder, with the temperature of the upper stage of the cylinder being 130°C and the temperature of the lower stage of the cylinder being 150°C. The product of the twin-screw extruder was extruded in a single-screw extruder, with the temperature of the cylinder being 145°C. The product was granulated and packaged.

[0064] 3. Preparation of a low-smoke halogen-free flame-retardant A-class cable resistant to cold of -52°C for use in extremely cold regions

[0065] A cross-linked polyethylene insulation layer 2 with a thickness of 0.85 mm was extruded outside the conductor 1 with a cross-section of 2.5 mm2using a single-screw extruder;

[0066] The semi-finished product after the extruded insulation was irradiated (irradiation dose: 12-16 Mrad), and the deformation of the irradiated insulation layer 2 under thermal extension load was less than 100%, and the permanent deformation was less than 10%.

[0067] The semi-finished product after the irradiation was twisted into a cable together with a methyl methacrylate filling strip 3.

[0068] A sheath 4 with a thickness of 1.8-2.0 mm was extruded outside the cabling line using a single-screw extruder.

[0069] Comparative Example 1

[0070] The other conditions were the same as in Example 2, except that the preparation process of the phosphonic group functionalized linear low-density polyethylene was as follows: 50 g of LDPE (low-density polyethylene) and 100 ml of dimethylbenzene solvent were added to a three-necked flask, and the LDPE was dissolved by heating and stirring. Generally, the temperature was heated to about 120°C to completely dissolve the LDPE. Under the protection of nitrogen, 5 g of acrylic acid and 10 g of methyl methacrylate were sequentially added, and the mixture was continuously stirred until it was uniform. 0.5 g of dicumyl peroxide (DCP) was slowly added as an initiator. The temperature of the reaction system was raised to 150°C, and the reaction was carried out at this temperature. During the reaction, continuous stirring and nitrogen flow were maintained to prevent oxidation. The reaction time was generally controlled to be 3-5 hours. After the reaction was completed, the product was cooled to room temperature. The reaction product was washed with ethanol to remove unreacted monomers and initiators. After multiple washings, the product was dried in a vacuum drying oven at 60°C for 24 hours to remove residual solvents and other volatile substances.

[0071] Comparative Example 2

[0072] The other conditions were the same as in Example 2, except that the sheath was a common halogen-free A-class sheath (model WDZA-H90-04).

[0073] Performance test

[0074] The sheath materials in the above examples and comparative examples were subjected to tensile strength (GB / T 1040.3), elongation at break (GB / T 1040.3), -52℃ low temperature tensile elongation (GB / T 2951.14) tests, the cables were subjected to -52℃ low temperature impact, -52℃ low temperature winding (IEC 60811-1-4), class A flame retardant test (GB / T 18380.3), and the test results are as follows.

[0075] Table 1 Performance test results

[0076]

[0077] From the above results, it can be seen that the phosphoric acid group functionalized linear low density polyethylene prepared by the preparation method of the present application is added to the sheath material, and the tensile strength, elongation at break and low temperature tensile elongation are all significantly increased compared to the comparative example method, and the overall flame retardant and low temperature performance of the cable is improved.

[0078] The preferred embodiments of the present application are described in detail above in combination with examples, however, the present application is not limited to the specific details in the above described embodiments, and within the technical concept scope of the present application, the technical solutions of the present application can be subjected to various simple modifications, and these simple modifications all belong to the protection scope of the present application.

[0079] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any suitable manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combination manners.

[0080] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the technical concept of the present application, and it should be considered as disclosed content of the present application.

Claims

1. An extremely cold resistant, low smoke, halogen-free, flame retardant polyolefin jacketing characterized in that, By mass parts, including the following raw materials: ethylene-vinyl acetate copolymer 4~16 parts, phosphonic acid group functionalized linear low density polyethylene 7~13 parts, ethylene-octene copolymer 9~15 parts, maleic anhydride grafted ethylene-methyl methacrylate copolymer 5~10 parts, magnesium hydroxide 10~15 parts, aluminum hydroxide 40~50 parts, char-forming agent 2~5 parts, lubricant 1~2 parts, antioxidant 0.1~0.2 parts, colorant 2~3 parts, coupling agent 1~2 parts; The preparation method of the phosphonic acid group functionalized linear low density polyethylene is as follows: adding a catalyst in a pre-cooled ethylene monomer, adding vinyl phosphate and an initiator after reaction, and terminating the reaction under the conditions of a temperature of 65~75℃ and a pressure of 15~35 Mpa for 1~2 hours.

2. The extremely cold resistant low smoke halogen-free flame retardant polyolefin jacketing of claim 1, wherein, The catalyst is vinyl titanium trichloride, methylaluminoxane or vinyl hafnium tetrachloride; and / or The initiator is benzoyl peroxide or dicumyl peroxide.

3. The extremely cold resistant low smoke halogen-free flame retardant polyolefin jacketing of claim 2, wherein, The molar ratio of the ethylene monomer, the catalyst, the vinyl phosphate and the initiator is 1000: (1~1.1): (12~15): (3~5).

4. The extremely cold resistant, low smoke, halogen-free, flame retardant polyolefin jacketing of claim 1, wherein, After terminating the reaction, the product is separated by filtration to remove unreacted monomers and catalyst residues, and then purified and stabilized to obtain the phosphonic acid group functionalized linear low density polyethylene.

5. The extreme cold resistant low smoke halogen-free flame retardant polyolefin jacketing of any one of claims 1 to 4, characterized in that, The grafting rate of the maleic anhydride grafted ethylene-methyl methacrylate copolymer is 3~5%.

6. The extreme cold resistant low smoke halogen-free flame retardant polyolefin jacketing of any one of claims 1 to 4, characterized in that, The ethylene-vinyl acetate copolymer has a vinyl acetate content of 9~12%.

7. The extreme cold resistant low smoke halogen-free flame retardant polyolefin jacketing of any one of claims 1 to 4, wherein, The ethylene-octene copolymer has an elongation at break ≥800%.

8. The extreme cold resistant low smoke halogen-free flame retardant polyolefin jacketing of any one of claims 1 to 4, characterized in that, The purity of the aluminum hydroxide is ≥99%, and the particle size D50 is ≤1 micron; and / or The magnesium hydroxide is surface modified by phosphate and has an average particle size ≤1 micron.

9. Process for the production of the extremely cold-resistant low smoke halogen-free flame-retardant polyolefin sheath according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: mixing the raw materials at 10~12 Hz for 2~3 min and at 45~55 Hz for 5~8 min under the environment of 50~60℃, then mixing the mixture in a banbury mixer for 20~25 min, placing the mixed product in a screw extruder for extrusion, setting the temperature of the upper stage barrel to 120~130℃ and the temperature of the lower stage barrel to 135~150℃, placing the twin-screw product in a single-screw extruder for extrusion, and setting the barrel temperature to 130~145℃.

10. A cold resistant -52°C low smoke and halogen free flame retardant class A cable for use in extremely cold regions, characterized in that, The method comprises the following steps: mixing the raw materials at 10~12 Hz for 2~3 min and at 45~55 Hz for 5~8 min under the environment of 50~60℃, then mixing the mixture in a banbury mixer for 20~25 min, placing the mixed product in a screw extruder for extrusion, setting the temperature of the upper stage barrel to 120~130℃ and the temperature of the lower stage barrel to 135~150℃, placing the twin-screw product in a single-screw extruder for extrusion, and setting the barrel temperature to 130~145℃. The method comprises the following steps: mixing the raw materials at 10~12 Hz for 2~3 min and at 45~55 Hz for 5~8 min under the environment of 50~60℃, then mixing the mixture in a banbury mixer for 20~25 min, placing the mixed product in a screw extruder for extrusion, setting the temperature of the upper stage barrel to 120~130℃ and the temperature of the lower stage barrel to 135~150℃, placing the twin-screw product in a single-screw extruder for extrusion, and setting the barrel temperature to 130~145℃. The method comprises the following steps: mixing the raw materials at 10~12 Hz for 2~3 min and at 45~55 Hz for 5~8 min under the environment of 50~60℃, then mixing the mixture in a banbury mixer for 20~25 min, placing the mixed product in a screw extruder for extrusion, setting the temperature of the upper stage barrel to 120~130℃ and the temperature of the lower stage barrel to 135~150℃, placing the twin-screw product in a single-screw extruder for extrusion, and setting the barrel temperature to 130~145℃.

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