A B1-level flame-retardant and environmentally friendly portable power cord

Abstract

The invention discloses a B1-level flame-retardant and environmentally friendly portable power cord, comprising an outer sheath, an oxygen-isolating layer, a cable wrapping tape and a plurality of wire cores arranged in sequence from the outside to the inside, wherein the outer sheath contains a halogen-free intumescent flame retardant, and the halogen-free intumescent flame retardant comprises the following components in parts by weight: 60 to 80 parts of ammonium polyphosphate, 10 to 15 parts of melamine, 10 to 15 parts of a polyurethane cross-linking agent, and 1 to 5 parts of a compatibilizer. The wire core is wrapped in a protective layer by a multilayer structure, and the power cord passes the B1-level flame retardant test and meets the standard requirements through the oxygen-blocking and flame-retardant effects of the intumescent flame retardant in the outer sheath and the oxygen-isolating layer; a polyurethane cross-linking agent is added to the intumescent flame retardant as a carbon source to enhance the safety and stability of the power cord; the power cord is halogen-free and non-toxic at high temperatures or when burning, and the smoke from the burning is non-toxic and non-corrosive, and will not corrode precision equipment or pollute the atmospheric environment, so as to meet the use of important places with concentrated personnel and high safety requirements.

Description

Technical Field

[0001] The invention relates to the field of cable production technology, and in particular to a B1-level flame-retardant and environment-friendly movable power cord. Background Art

[0002] With the rapid development of social economy, the use of power equipment in production and life is increasing, and almost all equipment cannot do without power cords. Wires and cables are essential basic components for transmitting electrical energy, transmitting information, and manufacturing various electrical appliances and instruments. They are basic products of electrification and informatization.

[0003] According to the latest version of DGJ 08-2048-2016 "Electrical Fire Protection Design Code for Civil Buildings" and GB 50016-2018 "Code for Fire Protection Design of Buildings", B1 cables must be used in super high-rise buildings and Class I high-rise buildings in civil buildings. At the same time, B1 cables will be widely used in high-rise buildings, shopping malls, schools, subway stations, airports, stadiums, exhibition halls, hospitals and other densely populated public places. Compared with other grades or categories of flame-retardant cables, B1 flame-retardant cables have higher flame-retardant requirements.

[0004] In the currently commonly used B1-level flame-retardant cables or power cords, in order to make the cables meet the corresponding flame-retardant requirements, inorganic flame retardants (including magnesium hydroxide, aluminum hydroxide, etc.) are usually added to the cable materials. However, the addition of these flame retardants will increase the content of mineral materials in the cable materials, increase the water absorption of the materials, reduce the insulation resistance, and greatly increase the risk of leakage of the cables. Chinese patent publication number "CN106024168A" discloses a flame-retardant four-core cable with high insulation resistance, including a cable core, an insulation layer and a sheath. The number of the cable cores is four groups, which are twisted by bundle twisting. The four groups of cable cores are composed of a conductor bundle formed by twisting a number of conductor wires and a high insulation resistance layer coated on the outer periphery of the conductor bundle. The number of conductor wires on each group of cable cores is 18 to 20. The insulation layer is coated on the outer periphery of the four groups of cable cores, and the sheath is coated on the outer layer of the insulation layer. It has high insulation resistance and mechanical strength, strong corrosion resistance, and also has a high temperature resistance grade and oil resistance and crack resistance, which prolongs the service life of the four-core cable. However, for power cords, since they move more frequently than other types of cables during use, small cracks are prone to appear on their surfaces, further increasing the possibility of inorganic flame retardants absorbing water, affecting the safety and flame retardant effect of the cables. At the same time, it will also cause the internal structure of the cables to be exposed, reducing their service life. Summary of the invention

[0005] The present invention aims to overcome the problems of insufficient flame retardancy of existing power cords and the tendency to crack when moved frequently, and provides a B1-level flame retardant and environmentally friendly movable power cord. The present invention adopts a multi-layer design, adds a halogen-free intumescent flame retardant in the outer sheath, and adopts polyurethane as one of the carbon source and gas source of the intumescent flame retardant. While achieving the flame retardant effect, the small cracks in the power cord can be repaired, thereby extending the service life of the power supply and preventing the internal structure from being exposed and causing the flame retardant performance to decrease.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A B1-level flame-retardant and environment-friendly portable power cord comprises an outer sheath, an oxygen-isolating layer, a cable wrapping tape and a plurality of wire cores which are arranged in sequence from the outside to the inside. The outer sheath contains a halogen-free intumescent flame retardant, and the halogen-free intumescent flame retardant comprises the following components in parts by weight: 60 to 80 parts of ammonium polyphosphate, 10 to 15 parts of melamine, 10 to 15 parts of a polyurethane cross-linking agent, and 1 to 5 parts of a compatibilizer.

[0008] The wire core is wrapped in a protective layer using a multi-layer structure to provide mechanical and flame retardant protection for the wire core. Halogen-free intumescent flame retardant is added to the outer sheath of the power cord, and its special intumescent flame retardant mechanism is used to achieve flame retardant effect. In addition, an oxygen-isolating layer is set in the inner layer of the outer sheath to further isolate oxygen from the outside of the wire core during combustion, reduce damage to the internal wire core, and achieve better flame retardant effect. Conventional intumescent flame retardants have poor dispersibility in cable base resins. By adding polyurethane crosslinking agents as carbon sources to the intumescent flame retardants and adding some compatibilizers, the dispersibility of intumescent flame retardants in cable base resins is enhanced. During the use of the power cord, when small gaps appear on the surface of the power cord due to movement or handling, the polyurethane crosslinking agent component is exposed and wet-cured under the action of water in the air, which repairs the small gaps and prevents the decrease in the flame retardant performance of the material due to the increase in small gaps. At the same time, due to the hygroscopic effect of the polyurethane cross-linking agent, the precipitation of other components of the intumescent flame retardant due to the humid environment can be reduced, preventing the flame retardant performance of the power cord from being reduced in a humid environment, and at the same time effectively improving the insulation performance of the power cord.

[0009] Preferably, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, and the oxygen-isolating layer further comprises an inorganic filler, and the inorganic filler is one or a combination of nano-montmorillonite, polysilsesquioxane, azo compound, kaolin and sepiolite.

[0010] The polyolefin oxygen barrier layer has a high oxygen index and excellent heat insulation and oxygen insulation. Adding inorganic fillers to the oxygen barrier layer can, on the one hand, further enhance the flame retardant effect of the oxygen barrier layer, and on the other hand, prevent the inorganic fillers from being directly exposed to the surface of the power cord, which increases the hygroscopicity of the power cord surface, thereby causing the intumescent flame retardant to precipitate and affect the flame retardant effect of the outer sheath.

[0011] Preferably, the wire core comprises a conductor and an insulating layer covering the conductor, the conductor is made of oxygen-free copper, and the insulating layer is made of silane cross-linked polyethylene.

[0012] Preferably, the number of the wire cores is 2 to 5.

[0013] Preferably, the thickness ratio between the outer sheath and the isolation layer is (1-1.2): 1. If the thickness of the outer sheath is too thick, the flexibility of the power cord may be reduced, affecting its use; if the thickness of the outer sheath is too thin, a good flame retardant effect cannot be achieved.

[0014] Preferably, the compatibilizer is one of ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and maleic anhydride grafted polyethylene.

[0015] Preferably, the polyurethane crosslinking agent comprises the following components in parts by weight: 50 to 100 parts of polyphenyl polymethylene polyisocyanate, 80 to 120 parts of polyether polyol, 1 to 3 parts of chain extender, and 1 to 5 parts of coupling agent. Polyphenyl polymethylene polyisocyanate is a mixture of diphenylmethane diisocyanate and other polyisocyanates with a functionality greater than 2, wherein the mass fraction of diphenylmethane diisocyanate is about 50%. Since it contains a large amount of phenyl, it can be used as a carbon source in intumescent flame retardants and acts as a carbon-forming agent during the combustion process. At the same time, it has good adhesive properties and can be cured under the catalysis of water to repair the small gaps in the power cord.

[0016] Preferably, the polyether polyol is one of trihydroxy polyoxypropylene ether, polyoxypropylene triol and polyoxypropylene diol, and the number average molecular weight of the polyether polyol is 2000-5000.

[0017] Preferably, the chain extender is one of 1,4-butanediol, ethylene glycol, hexylene glycol, ethylenediamine, triethanolamine or a combination thereof, and the coupling agent is one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltri(b-methoxyethoxy)silane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane or a combination thereof.

[0018] Preferably, the preparation method of the polyurethane crosslinking agent is:

[0019] (1) Weighing each component according to the stated weight proportions;

[0020] (2) adding polyphenyl polymethylene polyisocyanate and polyether polyol into a reaction kettle in sequence, heating to 70-80° C. and reacting for 2-4 hours;

[0021] (3) After cooling to 50-60°C, add the chain extender, continue stirring and reacting for 1-2 hours, cool to 20-30°C, add the coupling agent, and stir evenly to obtain the polyurethane crosslinking agent.

[0022] During the preparation process, polyphenyl polymethylene polyisocyanate and polyether polyol are first added to the reactor to cause a certain degree of prepolymerization reaction, and then a chain extender is added to extend the polyurethane molecular chain, increase its molecular weight, and improve the mechanical properties of the polyurethane during the bonding process. Finally, a coupling agent is added to improve the compatibility between the polyurethane and other components.

[0023] Therefore, the present invention has the following beneficial effects: (1) a multi-layer structure is adopted to wrap the wire core in a protective layer, and the flame retardant effect of the intumescent flame retardant in the outer sheath and the oxygen-isolating layer is utilized to enable the power cord to pass the B1 flame retardant test and meet the standard requirements; (2) a polyurethane cross-linking agent is added to the intumescent flame retardant as a carbon source, which, on the one hand, improves the flame retardant effect of the intumescent flame retardant, and, on the other hand, acts as a cross-linking agent to repair the fine gaps on the surface of the power cord, thereby enhancing the safety and stability of the power cord; (3) the water absorption effect of the polyurethane cross-linking agent prevents other components of the intumescent flame retardant from precipitating in a humid environment, thereby enhancing the flame retardant performance of the power cord in a humid environment; (4) the power cord is halogen-free and non-toxic at high temperatures or when burning, and the smoke generated by the combustion is non-toxic and non-corrosive, and will not cause corrosion to precision equipment or pollution to the atmospheric environment, thereby meeting the requirements for use in important places where personnel are concentrated and safety requirements are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional view of the B1-level flame-retardant and environment-friendly portable power cord of the present invention.

[0025] In the figure: 1 outer sheath, 2 oxygen insulation layer, 3 cable wrapping tape, 4 core, 41 insulation layer, 42 conductor. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are suitable for illustrating the basic principles, main features and advantages of the present invention, and the present invention is not limited by the scope of the following embodiments; the implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions used in conventional experiments.

[0027] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0028] Example 1

[0029] This embodiment provides a B1-level flame-retardant and environmentally friendly portable power cord, such as Figure 1 As shown, it includes an outer sheath 1, an oxygen barrier layer 2, a cabling tape 3 and four cores 4 arranged in sequence from the outside to the inside, the thickness ratio between the outer sheath and the isolation layer is 1.7:1.5, and the core includes a conductor 42 and an insulating layer 41 covering the conductor. The conductor is made of oxygen-free copper, the insulating layer is made of silane cross-linked polyethylene, the oxygen barrier layer is a polyolefin oxygen barrier layer, and the oxygen barrier layer also includes 5% by mass of inorganic filler nano-montmorillonite;

[0030] The material of the outer sheath includes a halogen-free intumescent flame retardant, and the halogen-free intumescent flame retardant includes the following components in parts by weight: 70 parts of ammonium polyphosphate, 12 parts of melamine, 12 parts of polyurethane cross-linking agent, and 3 parts of compatibilizer ethylene-ethyl acrylate copolymer; the polyurethane cross-linking agent includes the following components in parts by weight: 75 parts of polyphenyl polymethylene polyisocyanate, 100 parts of polyether polyol, 2 parts of chain extender, and 3 parts of coupling agent, the polyether polyol is trihydroxy polyoxypropylene ether with a number average molecular weight of 3000, the chain extender is 1,4-butanediol, and the coupling agent is 3-aminopropyl triethoxysilane;

[0031] The preparation method of the polyurethane crosslinking agent is:

[0032] (1) Weigh each component according to the stated weight parts;

[0033] (2) adding polyphenyl polymethylene polyisocyanate and polyether polyol into a reaction kettle in sequence, heating to 75° C. and reacting for 3 hours;

[0034] (3) After cooling to 55°C, a chain extender was added, and the reaction was continued with stirring for 1.5 hours. After cooling to 25°C, a coupling agent was added, and the mixture was stirred evenly to obtain a polyurethane crosslinking agent.

[0035] Example 2

[0036] This embodiment provides a B1-level flame-retardant and environmentally friendly portable power cord, such as Figure 1 As shown, it includes an outer sheath 1, an oxygen barrier layer 2, a cabling tape 3 and four cores 4 arranged in sequence from the outside to the inside, the thickness ratio between the outer sheath and the isolation layer is 1.2:1, and the core includes a conductor 42 and an insulating layer 41 covering the conductor. The conductor is made of oxygen-free copper, the insulating layer is made of silane cross-linked polyethylene, the oxygen barrier layer is a polyolefin oxygen barrier layer, and the oxygen barrier layer also includes 10% by mass of an inorganic filler polysilsesquioxane;

[0037] The material of the outer sheath contains a halogen-free intumescent flame retardant, which includes the following components in parts by weight: 60 parts of ammonium polyphosphate, 10 parts of melamine, 10 parts of polyurethane cross-linking agent, and 1 part of compatibilizer ethylene-acrylic acid copolymer; the polyurethane cross-linking agent includes the following components in parts by weight: 100 parts of polyphenyl polymethylene polyisocyanate, 120 parts of polyether polyol, 3 parts of chain extender, and 5 parts of coupling agent, wherein the polyether polyol is polyoxypropylene triol with a number average molecular weight of 5000, the chain extender is ethylene glycol and hexanediol with a mass ratio of 1:1, and the coupling agent is vinyl trimethoxy silane;

[0038] The preparation method of the polyurethane crosslinking agent is:

[0039] (1) Weigh each component according to the stated weight parts;

[0040] (2) adding polyphenyl polymethylene polyisocyanate and polyether polyol into a reaction kettle in sequence, heating to 70° C. and reacting for 4 hours;

[0041] (3) After cooling to 50°C, a chain extender is added, and the reaction is continued with stirring for 2 hours. After cooling to 20°C, a coupling agent is added, and the mixture is stirred evenly to obtain a polyurethane crosslinking agent.

[0042] Example 3

[0043] This embodiment provides a B1-level flame-retardant and environmentally friendly portable power cord, comprising an outer sheath 1, an oxygen-isolating layer 2, a cabling tape 3 and five cores 4 arranged in sequence from the outside to the inside, the thickness ratio between the outer sheath and the isolation layer is 1:1, and the core comprises a conductor 42 and an insulating layer 41 covering the conductor. The conductor is made of oxygen-free copper, the insulating layer is made of silane cross-linked polyethylene, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, and the oxygen-isolating layer further comprises an inorganic filler with a mass fraction of 5%, and the inorganic filler is kaolin and sepiolite with a mass ratio of 1:1;

[0044] The material of the outer sheath includes a halogen-free intumescent flame retardant, which includes the following components in parts by weight: 80 parts of ammonium polyphosphate, 15 parts of melamine, 15 parts of polyurethane cross-linking agent, and 5 parts of compatibilizer maleic anhydride grafted polyethylene; the polyurethane cross-linking agent includes the following components in parts by weight: 50 parts of polyphenyl polymethylene polyisocyanate, 80 parts of polyether polyol, 1 part of chain extender, and 1 part of coupling agent, wherein the polyether polyol is polyoxypropylene glycol with a number average molecular weight of 2000, the chain extender is ethylenediamine and triethanolamine in a mass ratio of 1:1, and the coupling agent is vinyltrimethoxysilane;

[0045] The preparation method of the polyurethane crosslinking agent is:

[0046] (1) Weigh each component according to the stated weight parts;

[0047] (2) adding polyphenyl polymethylene polyisocyanate and polyether polyol into a reaction kettle in sequence, heating to 80° C. and reacting for 2 h;

[0048] (3) After cooling to 60°C, a chain extender is added, and the reaction is continued with stirring for 1 hour. After cooling to 30°C, a coupling agent is added, and the mixture is stirred evenly to obtain a polyurethane crosslinking agent.

[0049] Example 4

[0050] The present embodiment provides a B1-level flame-retardant and environmentally friendly portable power cord, comprising an outer sheath 1, an oxygen isolation layer 2, a cabling tape 3 and two cores 4 arranged in sequence from the outside to the inside, the thickness ratio between the outer sheath and the isolation layer is 1.1:1, and the core comprises a conductor 42 and an insulating layer 41 covering the conductor. The conductor is made of oxygen-free copper, the insulating layer is made of silane cross-linked polyethylene, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, and the oxygen-isolating layer also includes 5% by mass of inorganic filler nano-montmorillonite; the outer sheath is made of a halogen-free intumescent flame retardant, and the halogen-free intumescent flame retardant includes the following components in parts by weight: 75 parts of ammonium polyphosphate, 10 parts of melamine, 15 parts of polyurethane cross-linking agent, and 4 parts of compatibilizer maleic anhydride grafted polyethylene; the polyurethane cross-linking agent includes the following components in parts by weight: 80 parts of polyphenyl polymethylene polyisocyanate, 90 parts of polyether polyol, 2 parts of chain extender, and 2 parts of coupling agent, the polyether polyol is trihydroxy polyoxypropylene ether with a number average molecular weight of 3000, the chain extender is triethanolamine, and the coupling agent is N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane;

[0051] The preparation method of the polyurethane crosslinking agent is the same as that in Example 1.

[0052] Example 5

[0053] The present embodiment provides a B1-level flame-retardant and environmentally friendly portable power cord, comprising an outer sheath 1, an oxygen isolation layer 2, a cabling tape 3 and three cores 4 arranged in sequence from the outside to the inside, the thickness ratio between the outer sheath and the isolation layer is 1.7:1.5, and the core comprises a conductor 42 and an insulating layer 41 covering the conductor. The material of the conductor is oxygen-free copper, the material of the insulating layer is silane cross-linked polyethylene, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, and the oxygen-isolating layer also includes 5% by mass of inorganic filler nano-montmorillonite; the material of the outer sheath includes a halogen-free intumescent flame retardant, and the halogen-free intumescent flame retardant includes the following components in parts by weight: 65 parts of ammonium polyphosphate, 10 parts of melamine, 13 parts of polyurethane cross-linking agent, and 2 parts of compatibilizer maleic anhydride grafted polyethylene; the polyurethane cross-linking agent includes the following components in parts by weight: 90 parts of polyphenyl polymethylene polyisocyanate, 100 parts of polyether polyol, 3 parts of chain extender, and 4 parts of coupling agent, the polyether polyol is trihydroxy polyoxypropylene ether with a number average molecular weight of 2000, the chain extender is hexanediol, and the coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane;

[0054] The preparation method of the polyurethane crosslinking agent is the same as that in Example 1.

[0055] Comparative Example 1

[0056] The only difference between this comparative example and Example 1 is that no oxygen isolation layer is provided in the power line.

[0057] Comparative Example 2

[0058] The only difference between this comparative example and Example 1 is that no halogen-free intumescent flame retardant is added to the outer sheath of the power cord.

[0059] Comparative Example 3

[0060] The difference between this comparative example and Example 1 is that the halogen-free intumescent flame retardant of the outer sheath of the power cord uses melamine of the same mass instead of the polyurethane cross-linking agent.

[0061] The power cords obtained from the above embodiments and comparative examples were subjected to performance tests, including combustion performance level and combustion performance indexes: flame spread FS, heat release rate peak HRR peak, combustion growth rate index FIGRA, smoke density: minimum light transmittance, vertical flame spread H, as well as 20°C conductor DC resistance and withstand voltage performance. The test methods for combustion performance level and combustion performance indexes refer to GB8624-2012 "Classification of Combustion Performance of Building Materials and Products", the test method for 20°C conductor DC resistance refers to GB / T 3048.4-2007 "Conductor DC Resistance Test", and the withstand voltage performance test method refers to GB / T3048.8-2007 "AC Voltage Test", and the test parameters are 3.5KV, 5min. The test results are shown in Table 1.

[0062] Table 1 Cable performance test results

[0063]

[0064]

[0065] As can be seen from Table 1, the power cords prepared in Examples 1-5 have good flame retardant properties and meet the B1 flame retardant standard, with flame spread FS≤1.5m; heat release rate peak HRR peak ≤30kW; combustion growth rate index FIGRA≤150W / s; minimum light transmittance ≥70%; vertical flame spread H≤425mm. At the same time, its 20°C conductor DC resistance also meets the requirements of GB / T3956-2008 "Conductors of Cables", and will not be broken down in the withstand voltage test. This shows that the power cords prepared in Examples 1-5 can achieve very good flame retardant effects due to the double-layer flame retardant structure of the outer sheath and the oxygen-isolating layer and the flame retardant components used therein, meeting the use requirements of densely populated public places. Comparative Example 1 does not use an oxygen barrier layer in the power cord, which reduces its flame retardant performance during the combustion process and cannot provide subsequent flame retardant effects after the components such as the intumescent flame retardant in the outer sheath are burned, resulting in the flame retardant performance of the power cord failing to meet the B1 level requirements; Comparative Example 2 does not add an intumescent flame retardant component to the outer sheath of the power cord, which significantly reduces its flame retardant effect, also resulting in the flame retardant performance of the power cord failing to meet the B1 level requirements. Comparative Example 3 uses melamine instead of a polyurethane crosslinking agent as the gas source in the flame retardant. Although it does not affect the flame retardant performance of the power cord, it is found that it ages significantly after long-term use during use, and subsequent safety is difficult to guarantee.

Claims

1. A B1 flame retardant and environmentally friendly portable power cord, characterized in that: The invention comprises an outer sheath (1), an oxygen barrier layer (2), a cabling tape (3) and a plurality of wire cores (4) which are arranged in sequence from the outside to the inside. The outer sheath contains a halogen-free intumescent flame retardant, which comprises the following components in parts by weight: 60 to 80 parts of ammonium polyphosphate, 10 to 15 parts of melamine, 10 to 15 parts of a polyurethane crosslinking agent and 1 to 5 parts of a compatibilizer; the oxygen barrier layer is a polyolefin oxygen barrier layer, and the oxygen barrier layer further comprises an inorganic filler, which is one of nano-montmorillonite, polysilsesquioxane, an azo compound, kaolin and sepiolite or a combination thereof; the polyurethane crosslinking agent comprises the following components in parts by weight: 50 to 100 parts of polyphenyl polymethylene polyisocyanate, 80 to 120 parts of polyether polyol, 1 to 3 parts of a chain extender and 1 to 5 parts of a coupling agent.

2. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The wire core comprises a conductor (42) and an insulating layer (41) covering the conductor; the conductor is made of oxygen-free copper, and the insulating layer is made of silane cross-linked polyethylene.

3. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The number of the wire cores is 2 to 5.

4. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The thickness ratio between the outer sheath and the isolation layer is (1~1.2):

1.

5. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The compatibilizer is one of ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and maleic anhydride grafted polyethylene.

6. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The polyurethane crosslinking agent comprises the following components in parts by weight: 75 parts of polyphenyl polymethylene polyisocyanate, 100 parts of polyether polyol, 2 parts of chain extender, and 3 parts of coupling agent.

7. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 6, characterized in that: The polyether polyol is one of trihydroxy polyoxypropylene ether, polyoxypropylene triol and polyoxypropylene diol, and the number average molecular weight of the polyether polyol is 2000-5000.

8. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 6, characterized in that: The chain extender is one of 1,4-butanediol, ethylene glycol, hexylene glycol, ethylenediamine, triethanolamine or a combination thereof; the coupling agent is one of 3-aminopropyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltrimethoxysilane, vinyltri(b-methoxyethoxy)silane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane or a combination thereof.

9. The B1-level flame-retardant and environmentally friendly portable power cord according to claim 1, characterized in that: The preparation method of the polyurethane crosslinking agent is: (1) Weigh each component according to the stated weight proportions; (2) Add polyphenyl polymethylene polyisocyanate and polyether polyol into the reaction kettle in sequence, heat to 70-80°C and react for 2-4 hours; (3) After cooling to 50-60°C, add the chain extender and continue stirring the reaction for 1-2 hours. After cooling to 20-30°C, add the coupling agent and stir evenly to obtain the polyurethane crosslinker.

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