Halogen-free flame-retardant insulated cable and preparation method thereof

Abstract

The invention relates to a halogen-free flame-retardant insulated cable and a preparation method thereof. The halogen-free flame-retardant insulated cable comprises an inner core, a bonding layer coating the inner core and a protective layer coating the bonding layer, the protective layer comprises polyethylene resin, first mineral powder, glass powder, aluminum silicate fibers, a flame retardant, a ceramic forming aid, a binder and a compatilizer; the bonding layer comprises an ethylene-vinyl acetate copolymer, copolyamide, tackifying resin, bismaleimide resin, a thermoplastic polyurethane elastomer, silicon dioxide, second mineral powder, a conditioning agent and an antioxidant. The protective layer provided by the invention can play a role in flame retardance and high temperature resistance under a certain condition; when the temperature is too high, the protective layer can form a new ceramic body under the condition of high temperature, and the outer layer of the cable is coated with the new ceramic body, so that the heat insulation and flame retardant effects on the inner core and the bonding layer in the cable are achieved; meanwhile, under the high-temperature condition, the bonding layer can be heated and softened to bond the newly formed ceramic body, so that the overall mechanical strength of the cable is improved.

Description

Technical Field

[0001] The present application relates to the technical field of cable materials, and more specifically, to a halogen-free flame-retardant insulated cable and a preparation method thereof. Background Art

[0002] Cables are a general term for items such as optical cables and electrical cables. Cables are conductors consisting of multiple wires used to transmit electrical energy or signals, and are widely used in fields such as power generation, communications, and sensors. Different cable applications require different performance characteristics. Generally speaking, cables must exhibit excellent mechanical properties, aging resistance, and corrosion resistance. For use in crowded environments, in addition to these performance requirements, cables must also possess excellent flame retardancy.

[0003] Currently, flame retardants are commonly added to cable shielding materials to achieve flame retardancy. These typically include inorganic flame retardants such as aluminum hydroxide and organic flame retardants such as bromine and nitrogen-based flame retardants. However, while organic flame retardants are highly compatible with the cable shielding matrix, they tend to produce smoke and harmful gases when burned. While inorganic flame retardants offer good flame retardancy and smoke suppression, they have poor heat resistance and are typically used in large quantities. Adding large amounts of these flame retardants can also lead to a decrease in the mechanical properties of the cable material. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a halogen-free flame-retardant insulated cable and a preparation method thereof.

[0005] According to the first aspect of the present application, a halogen-free flame-retardant insulated cable is provided, which adopts the following technical solution:

[0006] A halogen-free flame-retardant insulated cable comprising an inner core, an adhesive layer covering the inner core, and a protective layer covering the adhesive layer;

[0007] The protective layer comprises the following raw materials in parts by weight:

[0008] 100-120 parts of polyethylene resin, 30-40 parts of first mineral powder, 10-20 parts of glass powder, 10-20 parts of aluminum silicate fiber, 20-30 parts of flame retardant, 20-30 parts of ceramic forming aid, 10-20 parts of binder and 1-5 parts of compatibilizer;

[0009] The bonding layer includes the following raw materials in parts by weight: 40-50 parts of ethylene-vinyl acetate copolymer, 20-30 parts of copolyamide, 20-30 parts of tackifying resin, 10-20 parts of bismaleimide resin, 5-10 parts of thermoplastic polyurethane elastomer, 15-25 parts of silicon dioxide, 10-20 parts of second mineral powder, 10-15 parts of regulator and 0.1-1 part of antioxidant.

[0010] In some embodiments of the present application, the first mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite; the second mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite.

[0011] In some embodiments of the present application, when the first mineral powder includes kaolin, sepiolite powder, and mica powder, the weight ratio of the kaolin, the sepiolite powder, and the mica powder is 10:(3-5):(1-3).

[0012] In some embodiments of the present application, when the second mineral powder includes attapulgite and sepiolite powder, the weight ratio of the attapulgite to the sepiolite powder is 1:(1-3).

[0013] In some embodiments of the present application, the fineness of the first mineral powder is 500-800 mesh, and the fineness of the glass powder is 500-800 mesh;

[0014] The fineness of the second mineral powder is 800-1000 mesh, and the fineness of the silicon dioxide is 1000-2000 mesh.

[0015] In some embodiments of the present application, the flame retardant is composed of alumina trihydrate, ammonium polyphosphate and aluminum hydroxide in a weight ratio of 1:(1-3):(10-15).

[0016] In some embodiments of the present application, the density of the polyethylene resin is 0.940-0.960 g / cm 3 , melt index is 0.8-1.2g / 10min;

[0017] The vinyl acetate content in the ethylene-vinyl acetate copolymer is 15-30%.

[0018] In some embodiments of the present application, the inner core includes a wire and an insulation layer covering the wire;

[0019] The insulating layer comprises the following raw materials in parts by weight: 100-120 parts of polyethylene resin, 20-30 parts of polystyrene resin, 20-30 parts of glass powder, 10-15 parts of regulator and 1-5 parts of compatibilizer.

[0020] In some embodiments of the present application, the potting aid includes one of zinc borate and sodium borate;

[0021] The binder includes a combination of one or more of polyvinyl alcohol, phenolic resin, polyvinyl butyral, polymethyl methacrylate, and epoxy resin;

[0022] The compatibilizer includes a combination of one or more of a silane coupling agent, a titanate coupling agent, and stearic acid;

[0023] The tackifying resin comprises a combination of one or more of terpene resin, petroleum resin and hydrogenated petroleum resin;

[0024] The conditioning agent includes a combination of one or more of paraffin wax, microcrystalline wax, and polyethylene wax;

[0025] The antioxidant includes a combination of one or more of tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, tris[2,4-di-tert-butylphenyl]phosphite, and distearyl thiodipropionate.

[0026] According to a second aspect of the present application, a method for preparing a halogen-free flame-retardant insulated cable is provided, comprising the following steps:

[0027] Stirring and melting the raw materials of the bonding layer, and coating the surface of the inner core to form the bonding layer;

[0028] The raw materials of the protective layer are stirred and melted, and then coated on the surface of the bonding layer to form the protective layer.

[0029] The present application has the following beneficial effects: the protective layer of the present application can play a flame retardant and high temperature resistant role under certain conditions; when the temperature is too high, the protective layer can form a new ceramic body under high temperature conditions, which is coated on the outer layer of the cable to provide heat insulation and flame retardancy to the inner core and bonding layer inside the cable; at the same time, under high temperature conditions, the bonding layer can be softened by heat and bonded to the newly formed ceramic body, thereby improving the overall mechanical strength of the cable. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be arbitrarily combined with each other.

[0031] In an exemplary embodiment, the present application provides a halogen-free flame-retardant insulated cable, comprising an inner core, an adhesive layer coated on the inner core, and a protective layer coated on the adhesive layer;

[0032] The protective layer comprises the following raw materials in parts by weight:

[0033] 100-120 parts of polyethylene resin, 30-40 parts of first mineral powder, 10-20 parts of glass powder, 10-20 parts of aluminum silicate fiber, 20-30 parts of flame retardant, 20-30 parts of ceramic forming aid, and 1-5 parts of compatibilizer;

[0034] The bonding layer includes the following raw materials in parts by weight: 40-50 parts of ethylene-vinyl acetate copolymer, 20-30 parts of copolyamide, 20-30 parts of tackifying resin, 10-20 parts of bismaleimide resin, 5-10 parts of thermoplastic polyurethane elastomer, 15-25 parts of silicon dioxide, 10-20 parts of second mineral powder, 10-15 parts of regulator and 0.1-1 part of antioxidant.

[0035] In this embodiment, the protective layer uses polyethylene resin as its base material. The flame retardant and aluminum silicate fibers enhance the polyethylene resin's heat resistance and flame retardancy at certain temperatures. When the temperature is too high, the first mineral powder, glass powder, and ceramic-forming additive in the protective layer react to form a new ceramic. The aluminum silicate fibers dispersed in the protective layer serve as a mesh support structure, and the molten polyethylene resin and binder bond the newly formed ceramic, forming a hard ceramic structure on the cable exterior.

[0036] In order to avoid the polyethylene resin and adhesive from decomposing too quickly at high temperatures, which may result in a poor bonding effect on the ceramic body, in this embodiment, a bonding layer is further provided between the inner core and the protective layer; under normal conditions, the provision of the bonding layer can increase the bonding strength between the protective layer and the inner core, thereby improving the stability of the overall strength of the cable; under high temperature conditions, the protective layer blocks heat, thereby avoiding thermal decomposition of the bonding layer caused by excessively high temperatures, and the temperature causes the bonding layer to soften and melt due to the heat, thereby providing a bonding effect on the newly formed ceramic body, thereby improving the integrity of the sintered material, and further improving the overall mechanical strength of the cable.

[0037] In this embodiment, the adhesive layer is based on ethylene-vinyl acetate copolymer, which exhibits excellent bonding properties, particularly to the inner core, protective layer, and newly formed ceramic body. Copolyamide, tackifying resin, bismaleimide resin, and thermoplastic polyurethane elastomer not only exhibit excellent bonding properties but also possess excellent heat resistance. The combination of these resins and elastomers enhances the high-temperature bonding performance of the adhesive layer.

[0038] In an exemplary embodiment, the first mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite; the second mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite.

[0039] In this embodiment, the addition of a first mineral powder to the protective layer can reduce the firing temperature of the ceramic, thereby improving the mechanical strength and chemical stability of the resulting ceramic body. The addition of a second mineral powder to the bonding layer can not only fill and reinforce the bonding layer, but also improve the bond strength between the bonding layer and the protective layer. The first and second mineral powders can have the same or different components.

[0040] In an exemplary embodiment, when the first mineral powder includes kaolin, sepiolite powder, and mica powder, the weight ratio of the kaolin, the sepiolite powder, and the mica powder is 10:(3-5):(1-3).

[0041] The main mineral component of kaolin is kaolinite, and its main chemical components include SiO2 and Al2O3, which has good fire resistance and electrical insulation. The main components of sepiolite powder include SiO2 and MgO, which has the advantages of low shrinkage and high thermal stability. The main chemical components of mica powder include SiO2 and Al2O3, which has good high temperature resistance, toughness enhancement and electrical insulation. In this embodiment, by using kaolin, sepiolite powder and mica powder with a weight ratio of 10: (3-5): (1-3) as the first mineral powder, on the one hand, it can improve the mechanical strength and chemical stability of the formed ceramic body, and on the other hand, it can play a role in heat resistance and flame retardancy.

[0042] In an exemplary embodiment, when the second mineral powder includes attapulgite and sepiolite powder, the weight ratio of the attapulgite to the sepiolite powder is 1:(1-3).

[0043] Attapulgite, also known as palygorskite, has the main chemical components of SiO2 and MgO, and has the advantages of strong adsorption and good heat resistance. Sepiolite powder is composed of very fine and short fibers or fibrous aggregates, and therefore also has strong adsorption capacity. In this embodiment, by using attapulgite and sepiolite powder in a weight ratio of 1: (1-3) as the second mineral powder, on the one hand, the second mineral powder and silica as inorganic fillers in the bonding layer have similar chemical compositions to the first mineral powder and glass powder containing more Si in the protective layer, which can improve the bonding force between the bonding layer and the protective layer; on the other hand, the porous structure of the second mineral powder has a certain adsorption effect on the odor of the burning cable, thereby reducing the emission of harmful gases when the cable burns.

[0044] In an exemplary embodiment, the fineness of the first mineral powder is 500-800 mesh, and the fineness of the glass powder is 800-2000 mesh; the fineness of the second mineral powder is 800-1000 mesh, and the fineness of the silicon dioxide is 1000-2000 mesh.

[0045] In this embodiment, the mechanical strength of the protective layer can be improved by controlling the fineness of the first mineral powder and glass powder in the protective layer to 500-800 mesh and 800-2000 mesh, respectively. The fineness of the second mineral powder and silicon dioxide is controlled to 800-1000 mesh and 1000-2000 mesh, respectively, to increase the specific surface area of ​​the second mineral powder and silicon dioxide, thereby improving the bonding strength of the bonding layer.

[0046] In one exemplary embodiment, the flame retardant is composed of alumina trihydrate, ammonium polyphosphate, and aluminum hydroxide in a weight ratio of 1:(1-3):(10-15).

[0047] The flame retardant used in this embodiment is a halogen-free flame retardant, which has the advantages of low smoke and environmental protection. Aluminum hydroxide has the advantages of low price and good flame retardancy, which can improve the flame retardancy of the cable; however, it has poor heat resistance. Therefore, it is combined with the heat-resistant aluminum trihydrate and ammonium polyphosphate to achieve flame retardancy, isolate oxygen, and reduce smoke generation.

[0048] In an exemplary embodiment, the density of the polyethylene resin is 0.940-0.960 g / cm 3 , the melt index is 0.8-1.2g / 10min; the vinyl acetate content in the ethylene-vinyl acetate copolymer is 15-30%.

[0049] In this embodiment, high-density polyethylene resin is used as the base material of the protective layer. It has good wear resistance, electrical insulation, rigidity, and toughness, which can effectively protect the inner core of the cable. Ethylene-vinyl acetate copolymer with a vinyl acetate content of 15-30% has good flexibility and bonding properties.

[0050] In an exemplary embodiment, the inner core includes a conductive wire and an insulation layer covering the conductive wire;

[0051] The insulating layer comprises the following raw materials in parts by weight: 100-120 parts of polyethylene resin, 20-30 parts of polystyrene resin, 20-30 parts of glass powder, 10-15 parts of regulator and 1-5 parts of compatibilizer.

[0052] By coating the conductor with an insulating layer, the insulation performance of the cable can be improved. In this embodiment, the adhesive layer is coated on the insulating layer, and the insulating layer uses polyethylene resin as a base material, which can improve the bonding strength between the insulating layer and the adhesive layer.

[0053] In an exemplary embodiment, the potting aid includes one of zinc borate and sodium borate;

[0054] The binder includes a combination of one or more of polyvinyl alcohol, phenolic resin, polyvinyl butyral, polymethyl methacrylate, and epoxy resin;

[0055] The compatibilizer includes a combination of one or more of a silane coupling agent, a titanate coupling agent, and stearic acid;

[0056] The tackifying resin includes a combination of one or more of a terpene resin, a petroleum resin, and a hydrogenated petroleum resin;

[0057] The conditioning agent includes a combination of one or more of paraffin wax, microcrystalline wax, and polyethylene wax;

[0058] The antioxidant includes a combination of one or more of pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, tris[2,4-di-tert-butylphenyl]phosphite, and distearyl thiodipropionate.

[0059] Adhesives, compatibilizers, regulators and antioxidants serve as functional additives and enhance the performance of the protective layer or bonding layer. The addition of tackifying resin can improve the bonding performance of the bonding layer to increase the bonding strength between the inner core and the protective layer.

[0060] In an exemplary embodiment, the present application provides a method for preparing a halogen-free flame-retardant insulated cable, comprising the following steps:

[0061] The raw materials of the bonding layer are stirred and melted, and then coated on the surface of the inner core to form a bonding layer;

[0062] The raw materials of the protective layer are stirred and melted, and then coated on the surface of the adhesive layer to form the protective layer.

[0063] In this embodiment, conventional methods can be used to prepare the cable. Cables typically have single-core, two-core, three-core, four-core, or five-core cores, and different cable preparation methods can be used depending on the number of cores. For example, in a single-core cable, the raw materials for the bonding layer are stirred, melted, extruded, and press-formed, and then wrapped around the outer periphery of the inner core to form the bonding layer. The raw materials for the protective layer are then stirred, melted, extruded, and press-formed, and then wrapped around the surface of the bonding layer to form the protective layer.

[0064] When the cable has a multi-core structure such as two-core or three-core, before forming the bonding layer, the multiple inner cores are first twisted together, and then the gaps between the multiple inner cores are filled with glass fiber ropes; then the pressed bonding layer is wrapped around the outer periphery of the inner core to form a bonding layer.

[0065] In an exemplary embodiment, the present application provides a method for preparing a halogen-free flame-retardant insulated cable, comprising the following steps:

[0066] After drawing and annealing, the wire is obtained;

[0067] The raw materials of the insulating layer are stirred and melted, and then coated on the surface of the wire to form an insulating layer to obtain an inner core;

[0068] The raw materials of the bonding layer are stirred and melted, and then coated on the surface of the inner core to form a bonding layer;

[0069] The raw materials of the protective layer are stirred and melted, and then coated on the surface of the adhesive layer to form the protective layer.

[0070] In this embodiment, the conductor can be a copper wire. Drawing and annealing the copper wire can reduce its hardness and increase its toughness and plasticity. By coating the conductor with an insulating layer, short circuits between the conductor and external media or other conductors can be avoided, thereby ensuring safe operation of the cable.

[0071] In order to more clearly explain the technical solution of the present application, the present application lists specific embodiments of halogen-free flame-retardant insulated cables, and the beneficial effects of selecting the above-mentioned ranges of the content of each component will be illustrated by providing specific experimental data through specific embodiments.

[0072] It should be noted that, unless otherwise specified, the raw materials used in the following examples are commercially available. Furthermore, the protective layer, adhesive layer, and insulating layer all use the same polyethylene resin, the same compatibilizer, the same conditioning agent, and the same glass frit.

[0073] The polyethylene resin is HDPE, brand 5000S; the ceramic-forming additive is zinc borate; the binder is polyvinyl alcohol, model PVA17-88; the compatibilizer is silane coupling agent KH-550; the ethylene-vinyl acetate copolymer is 7A50H from Formosa Plastics, with a VA content of 19%; and the copolyamide is Arkema's copolyamide hot melt adhesive Platamid. B409; the tackifying resin is selected from T100 terpene resin; the bismaleimide resin is BMI resin with CAS number 13676-54-5; the thermoplastic polyurethane elastomer is selected from DP1080AU of Covestro of Germany; the regulator is microcrystalline wax; the antioxidant is pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; the polystyrene resin is selected from Idemitsu SW130 of Japan; the fineness of the first mineral powder is 500 mesh; the fineness of the glass powder is 1500 mesh; the fineness of the second mineral powder is 1000 mesh; and the fineness of the silicon dioxide is 2000 mesh.

[0074] Example 1: A method for preparing a halogen-free flame-retardant insulated cable, comprising the following steps:

[0075] (1) 100 kg of polyethylene resin, 20 kg of polystyrene resin, 20 kg of glass powder, 10 kg of a regulator, and 1 kg of a compatibilizer were mixed and stirred uniformly, heated to 180° C., melt-extruded, and pressed into shape to obtain an insulating layer raw material;

[0076] 40 kg of ethylene-vinyl acetate copolymer, 20 kg of copolyamide, 20 kg of tackifying resin, 10 kg of bismaleimide resin, 5 kg of thermoplastic polyurethane elastomer, 15 kg of silica, 10 kg of second mineral powder, 10 kg of regulator and 0.1 kg of ethylene-vinyl acetate copolymer were mixed and stirred uniformly, heated to 180° C., melt-extruded, and pressed to obtain a bonding layer raw material;

[0077] 100 kg of polyethylene resin, 30 kg of first mineral powder, 10 kg of glass powder, 10 kg of aluminum silicate fiber, 20 kg of flame retardant, 20 kg of ceramic additive, 10 kg of binder and 1 kg of compatibilizer were mixed and stirred uniformly, heated to 180° C., melt-extruded, and pressed into shape to obtain a protective layer raw material;

[0078] (2) Drawing and annealing the copper wire to obtain a conductor;

[0079] (3) Wrapping the insulating layer material around the outer periphery of the wire to obtain an inner core;

[0080] (4) Wrapping the bonding layer material around the outer periphery of the inner core to form a bonding layer;

[0081] (5) Wrapping the protective layer material around the outer periphery of the adhesive layer to form a protective layer, thereby obtaining a halogen-free flame-retardant insulated cable, wherein the thickness of the insulating layer is 0.2 mm, the thickness of the adhesive layer is 0.2 mm, and the thickness of the protective layer is 2 mm.

[0082] In order to more clearly explain the technical solution of the present application, the present application also lists Examples 2-6 of the preparation method of the halogen-free flame-retardant insulated cable, wherein the formula of Example 2-3 is shown in Table 1.

[0083] It should be noted that, except for the data in Table 1, the raw material amounts and process parameters in Examples 2-3 are basically the same as those in Example 1.

[0084] Table 1 Raw material usage of Examples 1-3 (unit: kg)

[0085]

[0086] Example 4: The main difference between this example and Example 1 is that the first mineral powder is composed of kaolin, sepiolite powder and mica powder in a weight ratio of 1:1:1; the second mineral powder is composed of attapulgite and sepiolite powder in a weight ratio of 1:5.

[0087] Example 5: The main difference between this example and Example 1 is that the second mineral powder is composed of kaolin, sepiolite powder and mica powder in a weight ratio of 10:3:1.

[0088] Example 6: The main difference between this example and Example 1 is that the first mineral powder is only kaolin and the second mineral powder is only kaolin.

[0089] Comparative Example 1: The main difference between this comparative example and Example 1 is that no bonding layer is provided between the inner core and the protective layer, that is, the cable includes an inner core and a protective layer coated on the inner core, wherein the formula of the insulation layer of the inner core and the formula of the protective layer are the same as those in Example 1.

[0090] Comparative Example 2: The main difference between this comparative example and Example 1 is that in the raw materials of the bonding layer, the copolyamide and bismaleimide resin are replaced with ethylene-vinyl acetate copolymer in equal amounts. That is, the raw materials of the bonding layer in Comparative Example 2 are prepared by the following method:

[0091] 70 kg of ethylene-vinyl acetate copolymer, 20 kg of tackifying resin, 5 kg of thermoplastic polyurethane elastomer, 15 kg of silica, 10 kg of second mineral powder, 10 kg of regulator and 0.1 kg were mixed and stirred evenly, heated to 180° C., melt-extruded, and pressed into shape to obtain a bonding layer raw material.

[0092] Comparative Example 3: The main difference between this comparative example and Example 1 is that in the raw materials of the bonding layer, an equal amount of the second mineral powder is replaced by silicon dioxide.

[0093] Comparative Example 4: The main difference between this comparative example and Example 1 is that in the raw materials of the protective layer, an equal amount of aluminum silicate fiber is replaced by glass powder.

[0094] Performance Testing

[0095] High-temperature resistance: Cables were prepared according to the methods of Examples 1-6 and Comparative Examples 1-4, and subjected to ignition temperatures of 800°C and 1200°C for 150 minutes, respectively, according to the method in "Test for Line Integrity of Electrical or Optical Cables under Flame Conditions" GB / T 19216.21-2003. The integrity of the sintered material and any line damage were observed.

[0096] Flame retardant performance: Cut the cable into 15 cm lengths one by one, and then burn it in a vertical position with a 500W blowtorch for 15 seconds with a flame height of 125mm, then stop for 15 seconds. Repeat this five times and record the flame burning time.

[0097] Smoke density: According to GB / T8323.2-2008 "Plastic Smoke Generation Part 2: Single Chamber Test Method for Determination of Smoke Density", the smoke density of the cable when burning is tested.

[0098] The performance test results are shown in Table 2.

[0099] Table 2 Performance test table of the cables of the embodiment and comparative example

[0100]

[0101] According to the data in Table 2 and in combination with Examples 1-6, it can be seen that the cable prepared by the method of the embodiment of the present application has excellent high temperature resistance and flame retardant properties. The sintered material at high temperature can form a complete, dense, and crack-free ceramic coating structure to protect the inner core structure of the cable. In addition, the cable of the present application uses a halogen-free flame retardant, and has a lower odor and lower smoke density when the cable burns.

[0102] According to the data in Table 2 and in combination with Examples 1-6 and Comparative Examples 1-4, it can be seen that by providing a bonding layer between the inner core and the protective layer, the integrity of the sintered material after high-temperature calcination of the protective layer can be significantly improved, and by adjusting the type of resin in the bonding layer, as well as the type of the second mineral powder in the bonding layer and the first mineral powder in the protective layer, the high temperature resistance and flame retardant properties of the cable can be further improved, which is beneficial to extending the service life of the cable.

[0103] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A halogen-free flame-retardant insulated cable, characterized in that: It comprises an inner core, an adhesive layer covering the inner core, and a protective layer covering the adhesive layer; The protective layer comprises the following raw materials in parts by weight: 100-120 parts of polyethylene resin, 30-40 parts of first mineral powder, 10-20 parts of glass powder, 10-20 parts of aluminum silicate fiber, 20-30 parts of flame retardant, 20-30 parts of ceramic forming aid, 10-20 parts of binder and 1-5 parts of compatibilizer; The bonding layer includes the following raw materials in parts by weight: 40-50 parts of ethylene-vinyl acetate copolymer, 20-30 parts of copolyamide, 20-30 parts of tackifying resin, 10-20 parts of bismaleimide resin, 5-10 parts of thermoplastic polyurethane elastomer, 15-25 parts of silicon dioxide, 10-20 parts of second mineral powder, 10-15 parts of regulator and 0.1-1 part of antioxidant.

2. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The first mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite; the second mineral powder includes a combination of one or more of kaolin, sepiolite powder, mica powder, montmorillonite, talc, bentonite, and attapulgite.

3. The halogen-free flame-retardant insulated cable according to claim 2, characterized in that: When the first mineral powder includes kaolin, sepiolite powder and mica powder, the weight ratio of the kaolin, the sepiolite powder and the mica powder is 10:(3-5):(1-3).

4. The halogen-free flame-retardant insulated cable according to claim 2, characterized in that: When the second mineral powder includes attapulgite and sepiolite powder, the weight ratio of the attapulgite to the sepiolite powder is 1:(1-3).

5. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The fineness of the first mineral powder is 500-800 mesh, and the fineness of the glass powder is 800-2000 mesh; The fineness of the second mineral powder is 800-1000 mesh, and the fineness of the silicon dioxide is 1000-2000 mesh.

6. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The flame retardant consists of aluminum oxide trihydrate, ammonium polyphosphate and aluminum hydroxide in a weight ratio of 1:(1-3):(10-15).

7. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The density of the polyethylene resin is 0.940-0.960 g / cm 3 , melt index is 0.8-1.2g / 10min; The vinyl acetate content in the ethylene-vinyl acetate copolymer is 15-30%.

8. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The inner core includes a conductive wire and an insulating layer covering the conductive wire; The insulating layer comprises the following raw materials in parts by weight: 100-120 parts of polyethylene resin, 20-30 parts of polystyrene resin, 20-30 parts of glass powder, 10-15 parts of regulator and 1-5 parts of compatibilizer.

9. The halogen-free flame-retardant insulated cable according to claim 1, characterized in that: The potting aid includes one of zinc borate and sodium borate; The binder includes a combination of one or more of polyvinyl alcohol, phenolic resin, polyvinyl butyral, polymethyl methacrylate, and epoxy resin; The compatibilizer includes a combination of one or more of a silane coupling agent, a titanate coupling agent, and stearic acid; The tackifying resin comprises a combination of one or more of terpene resin, petroleum resin and hydrogenated petroleum resin; The conditioning agent includes a combination of one or more of paraffin wax, microcrystalline wax, and polyethylene wax; The antioxidant includes a combination of one or more of tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol, tris[2,4-di-tert-butylphenyl]phosphite, and distearyl thiodipropionate.

10. A method for preparing a halogen-free flame-retardant insulated cable according to any one of claims 1 to 9, characterized in that: The steps include: Stirring and melting the raw materials of the bonding layer, and coating the surface of the inner core to form the bonding layer; The raw materials of the protective layer are stirred and melted, and then coated on the surface of the bonding layer to form the protective layer.

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