A single-core B1 grade isolated fire-resistant cable

Abstract

The present invention discloses a single-core B1-level isolated fire-resistant cable, comprising a wire core, an insulating layer, an isolation layer, an anti-dropping sheath, and an outer sheath arranged in sequence from the inside to the outside, wherein the outer sheath contains a halogen-free intumescent flame retardant, the anti-dropping sheath is a surface-modified aluminum alloy, the anti-dropping sheath and the outer sheath are bonded by a polyurethane crosslinking agent, and the preparation method of the surface-modified aluminum is: (1) pretreatment; (2) acid immersion; (3) surface modification. The wire core is wrapped in a protective layer using a multi-layer structure, and the intumescent flame retardant in the outer sheath and the oxygen barrier effect of the isolation layer are used, and the anti-dropping sheath is used to prevent the internal structure from falling off during the combustion process, so that the cable meets the B1-level flame retardant requirements, is halogen-free and non-toxic at high temperatures or when burning, and the combustion smoke is non-toxic and non-corrosive, will not cause corrosion to precision equipment, and will not cause pollution to the atmospheric environment, and can 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, in particular to a single-core B1 grade isolated fire-resistant cable. Background Art

[0002] As the urbanization process accelerates significantly, rail transit has become the most important means of transportation to solve urban congestion and ensure smooth travel for citizens. Cables are essential basic components for transmitting power, information, and manufacturing various electrical appliances and instruments in transportation, and are basic products for electrification and informatization.

[0003] The national standard GB 51348-2019 "Electrical Design Code for Civil Buildings" specifies that B1 cables must be used in a variety of environments; the "Technical Requirements for Strengthened Fire Protection Design of Civil Buildings with a Building Height of More Than 250m (Trial)" issued by the Fire Department of the Ministry of Public Security specifies the use environment of fire-resistant B1 cables with a flame retardant grade of B1 and a fire resistance of 3h; the national standard GB / T19666-2019 "General Rules for Flame Retardant and Fire Resistant Wires, Cables or Optical Cables" specifies the test requirements for fire resistance plus impact and fire resistance plus spraying. 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 wrapped around 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, such isolated fire-resistant cables are directly extruded with flame-retardant polyolefin sheath materials outside the isolation layer. When the cable burns, the isolation layer gradually forms a ceramic structure, and the isolation layer expands as a whole, causing the sheath material to fall off, making the product combustion dripping level unable to meet the d0 requirement. At the same time, for cable products used in rail transit, while meeting the B1 flame retardant effect, due to the special use environment of rail transit cables, the cables should also have moisture-proof, rat-proof, ant-proof, and UV-resistant properties. The existing technology cannot meet the performance requirements. Summary of the invention

[0005] The present invention aims to overcome the problems of insufficient flame retardant performance, poor moisture resistance and isolation capacity of existing cables, and provides a single-core B1-level isolated fire-resistant cable. The cable core is wrapped in a protective layer by a multi-layer structure, and the cable passes the B1-level flame retardant test and meets the standard requirements through the expansion flame retardant in the outer sheath and the oxygen-blocking flame retardant effect of the isolation layer; an anti-falling sheath is designed between the outer sheath and the isolation layer to prevent the internal structure from falling off due to volume expansion during the combustion process, thereby affecting the flame retardant effect of the cable; the anti-falling sheath is surface modified to enhance its bonding ability with the outer sheath, and a polyurethane cross-linking agent is used to ensure that the anti-falling sheath is closely fitted to the outer sheath to reduce the production defect rate.

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

[0007] A single-core B1-level isolated fire-resistant cable comprises a wire core, an insulating layer, an isolation layer, an anti-shedding sheath, and an outer sheath which are sequentially arranged from the inside to the outside, wherein the outer sheath contains a halogen-free intumescent flame retardant, the anti-shedding sheath is a surface-modified aluminum alloy, the anti-shedding sheath and the outer sheath are bonded by a polyurethane cross-linking agent, and the preparation method of the surface-modified aluminum is as follows:

[0008] (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface;

[0009] (2) Acid soaking: soaking the aluminum alloy obtained in step (1) in a 3-5 mol / L nitric acid solution for 30-60 seconds at a temperature of 20-30°C, followed by washing and drying;

[0010] (3) Surface modification: a surface modification liquid containing 10 to 15 g / L of cerium salt is added dropwise to the surface of the aluminum alloy obtained in step (2), and the mixture is reacted for 10 to 30 min, and then washed and dried to obtain a surface-modified aluminum alloy.

[0011] The core is wrapped in a protective layer using a multilayer structure to provide mechanical and flame retardant protection for the core. A halogen-free intumescent flame retardant is added to the outer sheath of the cable, and its special intumescent flame retardant mechanism is used to achieve a flame retardant effect, and an isolation layer is set in the inner layer of the outer sheath to further isolate oxygen from the outside of the core during the combustion process, reduce damage to the internal core, and achieve a better flame retardant effect. The anti-shedding sheath can protect the cable structure under fire and external force, prevent the internal isolation layer, insulation layer, etc. from falling off, and achieve better fire resistance. In addition, the anti-shedding sheath has a dense structure and also has good moisture resistance. If aluminum alloy material is directly used as the anti-shedding sheath, the outer sheath and the anti-shedding sheath cannot be tightly combined due to the excessive smoothness of the aluminum alloy surface and insufficient adsorption performance, so that the sheath is stripped, the extrusion is unstable, and the thickness uniformity decreases, so that the cable has certain safety hazards. The present invention performs surface modification on the aluminum alloy, and a certain rough structure is formed on the surface of the aluminum alloy through the surface modification process to enhance the interaction with the outer sheath. During the surface modification process, the aluminum alloy surface is first treated with acid to create certain tiny pores, and then a surface modification liquid is added. The cerium salt in the surface modification liquid reacts with aluminum through the primary battery to form a layer of serrated magnesium oxide, thereby increasing the roughness of the aluminum alloy surface and increasing its effective surface area.

[0012] In addition, in order to enhance the bonding strength between the anti-dropping sheath and the outer sheath, the present invention uses a polyurethane crosslinking agent for bonding between the two layers. Since the aluminum alloy surface is modified, the interaction between it and the polyurethane crosslinking agent is significantly enhanced, so that the polyurethane crosslinking agent can play a better bonding role therein. The polyurethane crosslinking agent can also be used as part of the carbon source component in the intumescent flame retardant during the flame retardant process to better exert the flame retardant effect. At the same time, due to the hygroscopic effect of the polyurethane crosslinking 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 cable from being reduced in a humid environment, and at the same time effectively improving the insulation performance of the cable.

[0013] Preferably, the cerium salt is one of cerium sulfate and cerium nitrate, and the surface modification solution further contains ammonium persulfate and sodium phosphate, wherein the concentration of the ammonium persulfate is 0.1-0.5 g. / L, and the concentration of the sodium phosphate is 0.1-0.5 g / L. Ammonium persulfate and sodium phosphate can promote the primary battery reaction between cerium and aluminum, accelerate the reaction efficiency, and promote the formation of an oxide film.

[0014] 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 cable may be reduced, affecting its use; if the thickness of the outer sheath is too thin, a good flame retardant effect cannot be achieved.

[0015] Preferably, the wire core is made of oxygen-free copper, and the insulating layer comprises an outer insulating layer and an inner insulating layer.

[0016] Preferably, the outer insulating layer is made of ceramic polyolefin, and the inner insulating layer is made of magnesium oxide. The double-layer insulating material can form a sufficient insulating layer between the anti-drip sheath and the wire core to ensure good insulation performance of the cable.

[0017] Preferably, the isolation layer is a polyolefin oxygen isolation layer, and the isolation layer further comprises a filler, and the filler is one or a combination of nano-montmorillonite, polysilsesquioxane, azo compound, kaolin and sepiolite.

[0018] The polyolefin oxygen barrier layer has a high oxygen index and excellent heat insulation and oxygen insulation. Adding 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 fillers from being directly exposed to the cable surface, which increases the hygroscopicity of the cable surface, thereby causing the intumescent flame retardant to precipitate and affect the flame retardant effect of the outer sheath.

[0019] Preferably, the halogen-free intumescent flame retardant comprises the following components in parts by weight: 60-80 parts of ammonium polyphosphate, 15-20 parts of melamine, and 1-5 parts of a compatibilizer.

[0020] Preferably, the compatibilizer is one of ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and maleic anhydride grafted polyethylene.

[0021] Preferably, the polyurethane crosslinking agent comprises the following components in parts by weight: 50-100 parts of polyphenyl polymethylene polyisocyanate, 80-120 parts of polyether polyol, 1-3 parts of chain extender, and 1-5 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%. Therefore, the polyurethane crosslinking agent contains a large amount of phenyl, which can be used as a carbon source in an intumescent flame retardant and play a role as a carbon-forming agent during the combustion process.

[0022] Preferably, the polyether polyol is one of trihydroxy polyoxypropylene ether, polyoxypropylene triol, and polyoxypropylene diol, the number average molecular weight of the polyether polyol is 2000-5000, the chain extender is one of 1,4-butanediol, ethylene glycol, hexanediol, ethylenediamine, and 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, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, or a combination thereof.

[0023] Therefore, the present invention has the following beneficial effects: (1) The wire core is wrapped in a protective layer by a multi-layer structure, and the intumescent flame retardant in the outer sheath and the oxygen-blocking flame retardant effect of the isolation layer enable the cable to pass the B1 flame retardant test and meet the standard requirements; (2) An anti-falling sheath is designed between the outer sheath and the isolation layer to prevent the internal structure from falling off due to volume expansion during combustion, thereby affecting the flame retardant effect of the cable; (3) The surface of the anti-falling sheath is modified to enhance its bonding ability with the outer sheath, and a polyurethane cross-linking agent is used to ensure that the anti-falling sheath is tightly fitted to the outer sheath, thereby reducing the production defect rate; (4) It is halogen-free and non-toxic at high temperatures or when burning, and the combustion smoke is non-toxic and non-corrosive, and will not corrode precision equipment or pollute the atmospheric environment, thus meeting the requirements for use in important places where personnel are concentrated and safety requirements are high. DETAILED DESCRIPTION

[0024] 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 adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions adopted in conventional experiments.

[0025] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0026] Example 1

[0027] A single-core B1-level isolated fire-resistant cable comprises a wire core, an insulating layer, an isolation layer, an anti-dropping sheath, and an outer sheath which are sequentially arranged from the inside to the outside. The wire core is made of oxygen-free copper, the insulating layer comprises an outer insulating layer and an inner insulating layer, the outer insulating layer is made of ceramicized polyolefin, the inner insulating layer is made of magnesium oxide, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, the oxygen-isolating layer further comprises a filler nano-montmorillonite with a mass fraction of 5%, the outer sheath comprises a halogen-free intumescent flame retardant, the halogen-free intumescent flame retardant comprises the following components in parts by weight: 70 parts of ammonium polyphosphate, 18 parts of melamine, and 3 parts of a compatibilizer ethylene-ethyl acrylate copolymer; the thickness ratio between the outer sheath and the isolation layer is 1.7:1.5, the anti-dropping sheath is a surface-modified aluminum alloy, and the preparation method of the surface-modified aluminum is as follows:

[0028] (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface;

[0029] (2) Acid soaking: soak the aluminum alloy obtained in step (1) in 4 mol / L nitric acid solution for 45 seconds at a temperature of 25°C, followed by washing and drying;

[0030] (3) Surface modification: adding a surface modification liquid containing 13 g / L cerium nitrate, 0.3 g / L ammonium persulfate and 0.3 g / L sodium phosphate to the surface of the aluminum alloy obtained in step (2), reacting for 20 min, washing and drying to obtain a surface modified aluminum alloy;

[0031] The anti-dropping sheath is bonded to the outer sheath by a polyurethane crosslinking agent, wherein 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, wherein 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; the preparation method of the polyurethane crosslinking agent is:

[0032] (a) weighing each component according to the stated weight parts;

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

[0034] (c) 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] A single-core B1-level isolated fire-resistant cable comprises a wire core, an insulating layer, an isolation layer, an anti-dropping sheath, and an outer sheath which are sequentially arranged from the inside to the outside. The wire core is made of oxygen-free copper, the insulating layer comprises an outer insulating layer and an inner insulating layer, the outer insulating layer is made of ceramicized polyolefin, the inner insulating layer is made of magnesium oxide, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, the oxygen-isolating layer further comprises a filler polysilsesquioxane having a mass fraction of 10%, the outer sheath comprises a halogen-free intumescent flame retardant, the halogen-free intumescent flame retardant comprises the following components in parts by weight: 60 parts of ammonium polyphosphate, 15 parts of melamine, and 1 part of a compatibilizer ethylene-acrylic acid copolymer; the thickness ratio between the outer sheath and the isolation layer is 1.2:1, the anti-dropping sheath is a surface-modified aluminum alloy, and the preparation method of the surface-modified aluminum is as follows:

[0037] (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface;

[0038] (2) Acid soaking: soak the aluminum alloy obtained in step (1) in 5 mol / L nitric acid solution for 30 seconds at a temperature of 20°C, followed by washing and drying;

[0039] (3) Surface modification: adding a surface modification liquid containing 15 g / L cerium nitrate, 0.5 g / L ammonium persulfate and 0.1 g / L sodium phosphate to the surface of the aluminum alloy obtained in step (2), reacting for 30 min, washing and drying to obtain a surface modified aluminum alloy;

[0040] The anti-falling sheath is bonded to the outer sheath by a polyurethane cross-linking agent, and 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. The polyether polyol is polyoxypropylene triol with a number average molecular weight of 5000, the chain extender is ethylene glycol and hexanediol in a mass ratio of 1:1, and the coupling agent is vinyl trimethoxy silane. The preparation method of the polyurethane cross-linking agent is the same as that in Example 1.

[0041] Example 3

[0042] A single-core B1-level isolated fire-resistant cable comprises a wire core, an insulating layer, an isolation layer, an anti-dropping sheath, and an outer sheath which are sequentially arranged from the inside to the outside. The wire core is made of oxygen-free copper, the insulating layer comprises an outer insulating layer and an inner insulating layer, the outer insulating layer is made of ceramicized polyolefin, the inner insulating layer is made of magnesium oxide, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, the oxygen-isolating layer further comprises a filler having a mass fraction of 5%, the filler being kaolin and sepiolite in a mass ratio of 1:1, the outer sheath comprises a halogen-free intumescent flame retardant, the halogen-free intumescent flame retardant comprises the following components in parts by weight: 80 parts of ammonium polyphosphate, 20 parts of melamine, and 5 parts of compatibilizer maleic anhydride grafted polyethylene; the thickness ratio between the outer sheath and the isolation layer is 1:1, the anti-dropping sheath is a surface-modified aluminum alloy, and the preparation method of the surface-modified aluminum is as follows:

[0043] (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface;

[0044] (2) Acid soaking: soaking the aluminum alloy obtained in step (1) in 3 mol / L nitric acid solution for 60 seconds at a temperature of 30°C, followed by washing and drying;

[0045] (3) Surface modification: adding a surface modification liquid containing 10 g / L cerium nitrate, 0.1 g / L ammonium persulfate and 0.5 g / L sodium phosphate to the surface of the aluminum alloy obtained in step (2), reacting for 10 min, washing and drying to obtain a surface modified aluminum alloy;

[0046] The anti-falling sheath is bonded to the outer sheath by a polyurethane cross-linking agent, and 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. 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. The preparation method of the polyurethane cross-linking agent is the same as that in Example 1.

[0047] Example 4

[0048] A single-core B1-level isolated fire-resistant cable comprises a wire core, an insulating layer, an isolation layer, an anti-dropping sheath, and an outer sheath which are sequentially arranged from the inside to the outside. The wire core is made of oxygen-free copper, the insulating layer comprises an outer insulating layer and an inner insulating layer, the outer insulating layer is made of ceramicized polyolefin, the inner insulating layer is made of magnesium oxide, the oxygen-isolating layer is a polyolefin oxygen-isolating layer, the oxygen-isolating layer further comprises a filler nano-montmorillonite with a mass fraction of 5%, the material of the outer sheath comprises a halogen-free intumescent flame retardant, the halogen-free intumescent flame retardant comprises the following components in parts by weight: 75 parts of ammonium polyphosphate, 17 parts of melamine, and 4 parts of compatibilizer maleic anhydride grafted polyethylene; the thickness ratio between the outer sheath and the isolation layer is 1.1:1, the anti-dropping sheath is a surface-modified aluminum alloy, and the preparation method of the surface-modified aluminum is as follows:

[0049] (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface;

[0050] (2) Acid soaking: soaking the aluminum alloy obtained in step (1) in 4 mol / L nitric acid solution for 50 s at a temperature of 25° C., followed by washing and drying;

[0051] (3) Surface modification: adding a surface modification liquid containing 12 g / L cerium nitrate, 0.4 g. / L ammonium persulfate and 0.2 g. / L sodium phosphate to the surface of the aluminum alloy obtained in step (2), reacting for 10 min, washing and drying to obtain a surface modified aluminum alloy;

[0052] The anti-falling sheath and the outer sheath are bonded by a polyurethane cross-linking agent. 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. The preparation method of the polyurethane cross-linking agent is the same as that in Example 1.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is that no anti-dropping sheath is provided in the cable.

[0055] Comparative Example 2

[0056] The only difference between this comparative example and Example 1 is that the anti-dropping sheath is made of aluminum alloy without surface modification.

[0057] Comparative Example 3

[0058] The only difference between this comparative example and Example 1 is that the anti-dropping sheath and the outer sheath are not bonded by using a polyurethane cross-linking agent.

[0059] Comparative Example 4

[0060] The only difference between this comparative example and Example 1 is that no halogen-free intumescent flame retardant is added to the cable outer sheath.

[0061] The cables 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, burning droplets / particles level, and also 20°C conductor DC resistance and withstand voltage performance. The test methods for combustion performance level and combustion performance index refer to GB8624-2012 "Classification of Combustion Performance of Building Materials and Products" and GB / T 31248-2014 "Test Methods for Flame Spread, Heat Release and Smoke Generation Characteristics of Cables or Optical Cables under Fire Conditions", the test method for 20°C conductor DC resistance refers to GB / T 3956-2008 "Conductors of Cables", and the withstand voltage performance test method refers to GB / T 3048.8-2007 "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] As can be seen from Table 1, the cables prepared in Examples 1-4 have good flame retardant properties and meet the B1 flame retardant standard, wherein the flame spread FS≤1.5m; the peak heat release rate HRR peak ≤30kW; the combustion growth rate index FIGRA≤150W / s; the minimum light transmittance ≥70%; and the burning droplets / particles level are all d0 level. At the same time, the 20°C conductor DC resistance also meets the requirements of GB / T 3956-2008 "Conductors of Cables", and will not be broken down in the withstand voltage test. It shows that the cables prepared in Examples 1-4 can achieve very good flame retardant effects due to the flame retardant structure settings of the outer sheath, anti-dropping sheath, and oxygen barrier layer and the use of good flame retardant materials, meeting the use requirements of transportation and other places. In the comparative example 1, the anti-dropping sheath was not used in the cable preparation process, so during the combustion process, the internal insulation layer, especially the ceramic polyolefin insulation layer, may affect the intumescent flame retardant of the outer layer due to the volume expansion, causing its burning droplets / particles level to fail to meet the standard requirements. Comparative Example 2 uses aluminum alloy without surface modification as the anti-dropping sheath. Due to the smooth surface and poor adsorption of the aluminum alloy, the outer sheath extrusion is unstable and uneven during the cable preparation process, which reduces its flame retardant performance and cannot meet the B1 flame retardant requirements. Comparative Example 3 does not use a polyurethane cross-linking agent to bond the anti-dropping sheath and the outer sheath during the preparation process. Although the cable can meet the B1 flame retardant requirements, after a long time, the lack of polyurethane flame retardant will cause the moisture resistance of the cable to decrease, resulting in the flame retardant performance in the later stage failing to meet the requirements. Comparative Example 4 does not use a halogen-free intumescent flame retardant, so its flame retardant performance is poor and does not meet the use requirements.

Claims

1. A single-core B1 grade isolated fire-resistant cable, characterized in that: The invention comprises a wire core, an insulating layer, an isolation layer, an anti-shedding sheath, and an outer sheath which are arranged in sequence from the inside to the outside. The outer sheath contains a halogen-free intumescent flame retardant. The anti-shedding sheath is a surface-modified aluminum alloy. The anti-shedding sheath and the outer sheath are bonded by a polyurethane cross-linking agent. The preparation method of the surface-modified aluminum alloy is as follows: (1) Pretreatment: Clean, degrease, degrease and then dry the aluminum alloy surface; (2) Acid soaking: soaking the aluminum alloy obtained in step (1) in a 3-5 mol / L nitric acid solution for 30-60 seconds at a temperature of 20-30°C, followed by washing and drying; (3) Surface modification: a surface modification liquid containing 10 to 15 g / L of cerium salt is added dropwise to the surface of the aluminum alloy obtained in step (2), and the mixture is reacted for 10 to 30 min, and then washed and dried to obtain a surface-modified aluminum alloy.

2. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The cerium salt is one of cerium sulfate and cerium nitrate. The surface modification liquid also contains ammonium persulfate and sodium phosphate. The concentration of the ammonium persulfate is 0.1-0.5 g / L, and the concentration of the sodium phosphate is 0.1-0.5 g / L.

3. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The thickness ratio between the outer sheath and the isolation layer is (1~1.2):

1.

4. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The wire core is made of oxygen-free copper, and the insulating layer comprises an outer insulating layer and an inner insulating layer.

5. A single-core B1-level isolated fire-resistant cable according to claim 4, characterized in that: The material of the outer insulating layer is ceramic polyolefin, and the material of the inner insulating layer is magnesium oxide.

6. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The isolation layer is a polyolefin oxygen isolation layer, and the isolation layer also includes a filler, which is one of nano-montmorillonite, polysilsesquioxane, azo compound, kaolin and sepiolite, or a combination thereof.

7. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The halogen-free intumescent flame retardant comprises the following components in parts by weight: 60-80 parts of ammonium polyphosphate, 15-20 parts of melamine, and 1-5 parts of a compatibilizer.

8. A single-core B1-level isolated fire-resistant cable according to claim 7, characterized in that: The compatibilizer is one of ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and maleic anhydride grafted polyethylene.

9. A single-core B1-level isolated fire-resistant cable according to claim 1, characterized in that: The polyurethane crosslinking agent comprises the following components in parts by weight: 50-100 parts of polyphenyl polymethylene polyisocyanate, 80-120 parts of polyether polyol, 1-3 parts of chain extender, and 1-5 parts of coupling agent.

10. A single-core B1-level isolated fire-resistant cable according to claim 9, characterized in that: The polyether polyol is one of trihydroxy polyoxypropylene ether, polyoxypropylene triol, and polyoxypropylene diol. The number average molecular weight of the polyether polyol is 2000-5000. The chain extender is one of 1,4-butanediol, ethylene glycol, hexanediol, ethylenediamine, and 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, and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, or a combination thereof.

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