Halogen-free flame-retardant polyolefin insulated cable material

Abstract

The invention discloses a halogen-free flame-retardant polyolefin insulated cable material and a cable with an insulating layer formed by the halogen-free flame-retardant polyolefin insulated cable material, and relates to the technical field of cable insulating materials. The halogen-free flame-retardant polyolefin insulated cable material provided by the invention comprises an insulating layer and a functional layer, wherein the functional layer comprises the following components in parts by weight: 60-100 parts of polyolefin resin; 2 to 10 parts of flame-retardant shielding filler; the flame-retardant shielding filler comprises long carbon nanotubes, short carbon nanotubes and a flame retardant, the short carbon nanotubes and the flame retardant form a core-shell structure compound, the shell is the short carbon nanotubes, and the core is the flame retardant; 1 to 3 parts of a toughening agent; 1-2 parts of a dispersant; and 0.25 to 1 part of an antioxidant. The cable material is used as an insulating material of a cable, cost is reduced, and the cable material has the advantages of good shielding performance, good flame retardance, high toughness and the like.

Description

Technical Field

[0001] The present application belongs to the technical field of cable insulation materials, and in particular relates to a halogen-free flame-retardant polyolefin insulated cable material and a cable having an insulation layer formed therefrom. Background Art

[0002] Extruded cables are the most mainstream transmission cables. Their insulation layer plays a pressure-bearing role and basically determines the operating scenario of the cable. In response to the problems of poor high-temperature insulation performance of traditional cable materials, the need for high-temperature cross-linking and degassing to remove residual by-products during cabling, and the difficulty in recycling retired insulation materials, many institutions and scholars have begun to study thermoplastic insulation materials. Polypropylene (PP) is a common thermoplastic material with good chemical corrosion resistance and electrical insulation, higher long-term operating temperature, and thermoplastic recyclability. In addition, as a general-purpose resin, polypropylene has the advantages of high output and low price. Compared with traditional cable materials, it eliminates the cross-linking and degassing processes, simplifies the production process, has low energy consumption, can increase the continuous extrusion length of the cable, and is conducive to reducing costs. At the same time, it can be recycled and reused.

[0003] Polypropylene molecular chains lack flexibility and are prone to crystallization, resulting in high modulus, strong rigidity, and poor toughness. This material is prone to brittle cracking in low-temperature environments. Existing polypropylene cable insulation technology requires the addition of 15% to 25% flame retardant to enhance the flame retardancy of wires and cables. However, excessive amounts make it difficult to evenly disperse the flame retardant within the matrix. Patent CN 117774474 A discloses a polypropylene cable insulation material and its preparation method. The polypropylene cable insulation material comprises, from the inside out, an insulating layer, a shielding layer, a flame retardant layer, and a protective layer. The flame retardant layer comprises: 49 to 61 parts polypropylene, 20 to 25 parts KN resin, 10 to 15 parts octabromosulfide, 1 part antioxidant, and 5 parts polyolefin modifier Elevast. This polypropylene cable insulation material has numerous structural layers, resulting in high production costs. Furthermore, the flame retardant component contains halogen, requiring a high dosage.

[0004] Therefore, it is of great significance to develop and research a polypropylene cable insulation material with low cost, excellent flexibility, flame retardancy and shielding performance. Summary of the Invention

[0005] The purpose of this application is to overcome the above-mentioned deficiencies of the prior art and provide a halogen-free flame-retardant polyolefin insulated cable material and its preparation method and application, so as to obtain a polypropylene cable insulation material with low cost and excellent flexibility, flame retardancy and shielding performance.

[0006] In order to achieve the above application objectives, the first aspect of the present application provides a halogen-free flame-retardant polyolefin insulated cable material, comprising an insulating layer and a functional layer, wherein the functional layer comprises, by weight:

[0007] Polyolefin resin: 60 to 100 parts;

[0008] Flame retardant shielding filler: 2 to 10 parts;

[0009] Toughening agent: 1 to 3 parts;

[0010] Dispersant: 1 to 2 parts;

[0011] Antioxidant: 0.25-1 part;

[0012] The flame retardant shielding filler comprises long carbon nanotubes, short carbon nanotubes and a flame retardant; the short carbon nanotubes and the flame retardant form a core-shell structure composite, the shell is the short carbon nanotubes and the core is the flame retardant; the flame retardant is a halogen-free flame retardant.

[0013] Furthermore, the weight ratio of the long carbon nanotubes, the short carbon nanotubes, and the flame retardant is in the range of 1:7-15:10-20; and the method for forming a core-shell structure composite of the short carbon nanotubes and the flame retardant comprises the following steps:

[0014] The short carbon nanotubes are firstly acid-washed and then surface-treated and modified with a silane coupling agent solution to form modified carbon nanotubes;

[0015] The modified carbon nanotubes are poured into the flame retardant solution, stirred and dispersed evenly, and then the solvent is removed by rotary evaporation and dried.

[0016] Furthermore, the flame retardant is selected from at least one of tributyl phosphate, triphenyl phosphate, bisphenol A-bis(diphenyl phosphate), dimethyl methylphosphonate, triphenyl phosphite, and resorcinol bis(diphenyl phosphate).

[0017] Furthermore, the polyolefin resin includes one or a mixture of two or more of polypropylene resin, polyethylene resin, poly-1-butene resin, and poly-4-methyl-1-pentene resin.

[0018] Furthermore, the polyolefin resin is a polypropylene resin, which is a compound of a high-flow polypropylene having a melt flow rate (MFR) of 10 to 20 g / 10 min and a low-flow polypropylene having a melt flow rate (MFR) of 0.5 to 5 g / 10 min. The measurement conditions are 230° C. and 2.16 kg.

[0019] Furthermore, the toughening agent is one or a mixture of two or more of ethylene-propylene-diene terpolymer, ethylene-propylene binary copolymer, butadiene rubber, and isobutylene rubber;

[0020] and / or,

[0021] The antioxidant includes at least one of an amine antioxidant and a phenolic antioxidant, and also includes at least one of an acid-containing metal salt, a sulfide, a thioester and a phosphite;

[0022] and / or,

[0023] The dispersant is obtained by mixing silicone oil with at least one of calcium stearate, barium sulfate, talc and polyethylene wax, and the silicone oil is at least one of methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, methylethoxy silicone oil, methylvinyl silicone oil, methylhydroxy silicone oil, ethyl hydrogen silicone oil and hydroxy hydrogen silicone oil.

[0024] Furthermore, the diameter of the long carbon nanotubes is in the range of 1 nm to 4 nm, the aspect ratio is in the range of 20000:1 to 100000:1, and the specific surface area is in the range of 600 m 2 / g~1000m 2 / g, Raman spectrum intensity ratio I D / I G The range is 0.5 to 0.7, and the powder resistivity range is 2mΩ·cm to 6mΩ·cm;

[0025] and / or,

[0026] The diameter of the short carbon nanotubes is in the range of 6nm to 15nm, the aspect ratio is in the range of 8000:1 to 15000:1, and the specific surface area is in the range of 250m 2 / g~350m 2 / g, Raman spectrum intensity ratio I D / I G The range is 0.7~1.0, and the powder resistivity range is 15mΩ·cm~25mΩ·cm.

[0027] Furthermore, the mass ratio of the high flow rate polypropylene to the low flow rate polypropylene is 1:4-8.

[0028] The second aspect of the present application provides a method for preparing the halogen-free flame-retardant polyolefin insulated cable material, comprising the following steps:

[0029] S1. Preparation of flame-retardant shielding filler: first, the short carbon nanotubes and the flame retardant form a core-shell structure composite, and then add the core-shell structure composite to the long carbon nanotube slurry, stirring and dispersing uniformly and drying;

[0030] S2. The flame retardant shielding filler is mixed with polypropylene resin and other raw materials, and then melt-extruded and granulated;

[0031] S3. The particles are formed into a functional layer and combined with the insulating layer.

[0032] The preparation of the long carbon nanotube slurry includes the following steps:

[0033] Formula: weight ratio of solvent: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder = (80-90): (1-3): (1-3): (1-3): (3-5); process: first add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and then mix until uniform; then transfer the mixed solution to a microfluidizer, set the flow rate to 10 L / h, the pressure to 2000-3000 Bar, and disperse for 1-2 hours; then continue to add the binder and stir at 4000 RPM for 30 minutes.

[0034] The third aspect of the present application provides a cable having an insulation layer formed of the halogen-free flame-retardant polyolefin insulated cable material, which has both flame-retardant and shielding properties and good toughness.

[0035] Compared with the existing technology, this application has the following technical effects:

[0036] The present invention innovatively prepares flame-retardant shielding fillers by forming a core-shell structure composite by short carbon nanotubes and halogen-free flame retardants, which can achieve good flame retardant effects while reducing the amount of halogen-free flame retardants used. At the same time, the long carbon nanotubes and short carbon nanotubes are combined to form a conductive path to provide electromagnetic shielding performance, which has both flame retardant and shielding effects. In addition, researchers have found that the core-shell structure formed by short carbon nanotubes and halogen-free flame retardants can improve the dispersibility of carbon nanotubes in the resin matrix, while improving the toughness of the resin matrix and reducing the amount of toughening agent used. The halogen-free flame retardant polyolefin insulated cable material of the present invention can be used as a flame retardant and shielding multifunctional material in cable materials, with low cost, high flame retardancy, good toughness, and excellent electromagnetic shielding performance. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0038] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0039] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c" can all mean: a, b, c, a~b (i.e. a and b), a~c, b~c or a~b~c, where a, b, c can be single or multiple.

[0040] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0041] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0042] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass in the examples of this application may be a well-known mass unit such as μg, mg, g, kg, etc.

[0043] The terms "first," "second," etc., are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the number of technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first," "second," etc., may explicitly or implicitly include one or more of such features.

[0044] A first aspect of the present application provides a halogen-free flame-retardant polyolefin insulated cable material, comprising an insulating layer and a functional layer, wherein the functional layer comprises, by weight:

[0045] Polyolefin resin: 60 to 100 parts;

[0046] Flame retardant shielding filler: 2 to 10 parts;

[0047] Toughening agent: 1 to 3 parts;

[0048] Dispersant: 1 to 2 parts;

[0049] Antioxidant: 0.25-1 part;

[0050] The flame retardant shielding filler comprises long carbon nanotubes, short carbon nanotubes and a flame retardant; the short carbon nanotubes and the flame retardant form a core-shell structure composite, the shell is the short carbon nanotubes and the core is the flame retardant; the flame retardant is a halogen-free flame retardant.

[0051] In the application, the weight proportions of the functional layer raw materials in the embodiment of the present application can be:

[0052] Polyolefin resin: 75 to 90 parts;

[0053] Flame retardant shielding filler: 6 to 10 parts;

[0054] Toughening agent: 2 to 3 parts;

[0055] Dispersant: 1 to 2 parts;

[0056] Antioxidant: 0.5-1 part.

[0057] For example, the polyolefin resin comprises 80 parts; the flame-retardant shielding filler comprises 9 parts; the toughening agent comprises 2.5 parts; the dispersant comprises 1.5 parts; and the antioxidant comprises 0.8 parts. Alternatively, the polyolefin resin comprises 85 parts; the flame-retardant shielding filler comprises 8 parts; the toughening agent comprises 2 parts; the dispersant comprises 1.5 parts; and the antioxidant comprises 0.6 parts. This halogen-free flame-retardant polyolefin insulated cable material significantly reduces the amount of conventional flame retardants and toughening agents, reducing raw material costs while maintaining excellent performance.

[0058] In application, the weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant described in the embodiments of this application ranges from 1:7-15:10-20; for example, the weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant can be 1:7:10, 1:15:20, 1:7:20, 1:15:10, 1:10:16, etc. Due to their high aspect ratio, long carbon nanotubes are easily entangled and difficult to disperse, so their usage is relatively small. Compared with long carbon nanotubes, short carbon nanotubes have improved dispersion performance, but their electrical conductivity is weakened; short carbon nanotubes and flame retardants form a core-shell structure composite, and the weight ratio of the two also needs to be optimized. This application studies the properties of long carbon nanotubes, short carbon nanotubes and flame retardants, and after a large number of experiments, obtains a weight ratio range of the three that is evenly dispersed in the substrate and has excellent flame retardant and shielding effects.

[0059] The diameter of the long carbon nanotubes can be in the range of 1 nm to 4 nm, the aspect ratio can be in the range of 20000:1 to 100000:1, and the specific surface area can be in the range of 600 m 2 / g~1000m 2 / g, Raman spectrum intensity ratio I D / I G The range of the short carbon nanotubes can be 0.5 to 0.7, the range of the powder resistivity can be 2 mΩ·cm to 6 mΩ·cm; the diameter of the short carbon nanotubes can be 6 nm to 15 nm, the aspect ratio can be 8000:1 to 15000:1, and the specific surface area can be 250 m 2 / g~350m 2 / g, Raman spectrum intensity ratio I D / I G The range can be 0.7 to 1.0, and the powder resistivity can range from 15 mΩ·cm to 25 mΩ·cm.

[0060] For example, the diameter of the long carbon nanotubes can be 1 nm, 2 nm, 3 nm or 4 nm; the aspect ratio can be 20,000:1, 40,000:1, 60,000:1, 80,000:1 or 100,000:1; the specific surface area can be 600 m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g or 1000m 2 / g, etc.; Raman spectrum intensity ratio I D / I G The resistivity of the powder can be 2mΩ·cm, 3mΩ·cm, 4mΩ·cm, 5mΩ·cm or 6mΩ·cm. The diameter of the short carbon nanotubes can be 6nm, 8nm, 9nm, 11nm, 13nm or 15nm. The aspect ratio can be 8000:1, 10000:1, 11000:1, 13000:1 or 15000:1. The specific surface area can be 250m 2 / g, 280m 2 / g、300m 2 / g or 350m 2 / g, etc.; Raman spectrum intensity ratio I D / I G It can be 0.7, 0.8, 0.9 or 1.0, etc.; the powder resistivity can be 15mΩ·cm, 18mΩ·cm, 21mΩ·cm or 25mΩ·cm, etc.

[0061] The flame retardant may be at least one of tributyl phosphate, triphenyl phosphate, bisphenol A-bis(diphenyl phosphate), dimethyl methylphosphonate, triphenyl phosphite, and resorcinol bis(diphenyl phosphate).

[0062] The selection of specifications for long and short carbon nanotubes, as well as the flame retardant, in this application is based on achieving excellent dispersibility in polyolefin resins, good nucleation properties of the short carbon nanotubes and flame retardant, and resin toughening properties. Compared to other flame retardants, phosphate flame retardants, especially those containing phenyl groups, can form highly stable core-shell composites due to the affinity of their phenyl structures with the conjugated polycyclic tubular structures of carbon nanotubes (surface π-π conjugated adsorption, reducing surface energy and inhibiting carbon nanotube aggregation).

[0063] In application, the method for forming a core-shell structure composite of the short carbon nanotubes and the flame retardant in the embodiment of the present application includes the following steps:

[0064] The short carbon nanotubes are firstly acid-washed and then surface-treated and modified with a silane coupling agent solution to form modified carbon nanotubes;

[0065] The modified carbon nanotubes are poured into the flame retardant solution, stirred and dispersed evenly, and then the solvent is removed by rotary evaporation and dried.

[0066] Optionally, the pickling process uses a sulfuric acid solution with a concentration of 38% or greater by mass as the pickling solution, with the carbon nanotubes added in an amount of 3-6% of the total pickling solution. Stirring is performed continuously during the pickling process at a stirring rate of 2000-3000 rpm for 1-4 hours. After pickling, the carbon nanotubes are washed multiple times with anhydrous ethanol, centrifuged, and dried. The carbon nanotubes are then added to a silane coupling agent solution and stirred for 0.5-3 hours at a stirring rate of 800-1500 rpm. After the reaction, the modified carbon nanotubes are washed multiple times with anhydrous ethanol, centrifuged, and dried to form the modified carbon nanotubes. The carbon nanotubes are then added to a flame retardant solution and stirred for another 1-3 hours. The stirring speed and time can be adjusted as needed to control the size and shape of the core-shell structure composite. The composite is concentrated by rotary evaporation to a quarter of its original volume or to a solvent-free state, and then dried to obtain the result.

[0067] The silane coupling agent may include a silane coupling agent containing one of the functional groups such as isocyanate, amino, carboxyl, epoxy, and mercapto. For example, the silane coupling agent may be γ-glycidoxypropyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane (A-187), γ-aminopropyltriethoxysilane (KH-550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), etc. The mass concentration of the silane coupling agent in the silane coupling agent solution is 3-5wt%, and the solvent may be ethanol, water, etc.

[0068] The flame retardant solution includes a flame retardant, a solvent, and a binder. The flame retardant has a mass concentration of 5-15 wt%. The solvent can be a conventional alcohol solution or water. The binder can include silicone oil, etc., with a mass concentration of 4-8 wt%. The binder can effectively bond the modified carbon nanotubes and the flame retardant to form a core-shell structure.

[0069] Specifically, through the treatment of silane coupling agent, the short carbon nanotubes further improve their surface affinity with the flame retardant and can form a stable core-shell structure complex with the flame retardant. The interaction between the two can not only further improve the dispersion performance of the short carbon nanotubes, but also improve the flame retardant effect of the flame retardant.

[0070] In the embodiments of the present application, the polyolefin resin includes one or a mixture of two or more of polypropylene resin, polyethylene resin, poly-1-butene resin, and poly-4-methyl-1-pentene resin. For example, the polyolefin resin may be 60 parts, 65 parts, 75 parts, 85 parts, 90 parts, or 100 parts by weight.

[0071] Furthermore, the polyolefin resin is a polypropylene resin, which is a compound of a high-flow polypropylene with a melt flow rate (MFR) of 10 to 20 g / 10 min and a low-flow polypropylene with a melt flow rate (MFR) of 0.5 to 5 g / 10 min. Furthermore, the mass ratio of the high-flow polypropylene to the low-flow polypropylene is 1:4-8. For example, the mass ratio of the high-flow polypropylene to the low-flow polypropylene can be 1:4, 1:5, 1:6, or 1:8, etc.

[0072] This application uses a compound of high-flow rate polypropylene and low-flow rate polypropylene, which can improve the processing performance of polypropylene and play a certain role in increasing the flexibility of the resin; in addition, when the flame-retardant shielding filler mentioned above is added, it is conducive to the uniform dispersion of the filler in the resin, forming a good carbon nanotube conductive path structure in the resin, with good electromagnetic shielding performance, and obtaining nano-synergistic flame retardancy and good flame retardant effect.

[0073] In the embodiments of the present application, the toughening agent is one or a mixture of two or more of ethylene-propylene-diene terpolymer, ethylene-propylene copolymer, butadiene rubber, and isobutylene rubber. Exemplarily, the toughening agent may be 1 part, 1.2 parts, 1.6 parts, 2.0 parts, 2.5 parts, or 3 parts by weight. The antioxidant includes at least one of an amine antioxidant and a phenolic antioxidant, and also includes at least one of an acid-containing metal salt, a sulfide, a thioester, and a phosphite. Exemplarily, the antioxidant may be 0.25 parts, 0.4 parts, 0.6 parts, 0.8 parts, 0.9 parts, or 1 part by weight. The dispersant is a mixture of silicone oil and at least one of calcium stearate, barium sulfate, talc, and polyethylene wax. The silicone oil is at least one of methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, methylethoxy silicone oil, methylvinyl silicone oil, methylhydroxy silicone oil, ethyl hydrogen silicone oil, and hydroxy hydrogen silicone oil. For example, the dispersant can be 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts or 2 parts by weight. The weight ratio of silicone oil to other dispersants is 1:2-5; for example, the weight ratio of silicone oil to talc can be 1:2, 1:3, 1:4 or 1:5, and the weight ratio of silicone oil to calcium stearate can be 1:2, 1:3, 1:4 or 1:5.

[0074] The main function of the above dispersant is to improve the dispersion uniformity of the long carbon nanotubes, short carbon nanotube flame retardants, etc. in the resin matrix.

[0075] The halogen-free flame-retardant polyolefin insulated cable material of this application has the following characteristics: 1. Fire resistance reaches V0; 2. Surface resistance value is less than 106, and electromagnetic shielding performance reaches 30dB; 3. Notched impact strength ≥9KJ / m 2 ; 4. Tensile elongation at break ≥ 110%.

[0076] The second aspect of the present application provides a method for preparing the halogen-free flame-retardant polyolefin insulated cable material, comprising the following steps:

[0077] S1. Preparation of flame-retardant shielding filler: first, the short carbon nanotubes and the flame retardant form a core-shell structure composite, and then add the core-shell structure composite to the long carbon nanotube slurry, stirring and dispersing uniformly and drying;

[0078] S2. The flame retardant shielding filler is mixed with polypropylene resin and other raw materials, and then melt-extruded and granulated;

[0079] S3. The particles are formed into a functional layer and combined with the insulating layer.

[0080] In application, the preparation of the long carbon nanotube slurry described in the embodiment of the present application includes the following steps:

[0081] Formula: Weight ratio of solvent: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder = (80-90): (1-3): (1-3): (1-3): (3-5); Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and mix until uniform; then transfer the mixture to a microfluidizer, set the flow rate to 10 L / h, the pressure to 2000-3000 Bar, and disperse for 1-2 hours; then continue to add the binder and stir at 4000 RPM for 30 minutes. For example, solvent: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder = 80:1:1:1:3, 90:3:3:3:5, 85:2:2:2:4, 83:1:2:2:3, etc.

[0082] The solvent may be a conventional alcohol solution or water, for example, ethanol, propanol, propylene glycol, deionized water, etc. The binder may be a polyacrylic acid or polyacrylate binder.

[0083] The above-mentioned long carbon nanotube slurry of the present application optimizes the preparation process parameters and the selection of long carbon nanotube dispersing materials. The long carbon nanotubes are evenly dispersed in the solution. After adding the short carbon nanotube flame retardant core-shell structure complex, the long carbon nanotubes can be cross-distributed in each core-shell structure particle. After combining them and adding them to the resin matrix, the conductivity and flame retardancy can be better improved, while the interface strength between the flame retardant shielding filler and the resin is increased, thereby improving the toughness of the resin.

[0084] In the application, the uniform mixing and melt extrusion granulation described in Example S2 of the present application includes the following steps:

[0085] S21. The flame retardant shielding filler and polypropylene resin and other raw materials are added to a high mixer and mixed uniformly, the specific mixing temperature is 25 to 60 ℃, the speed is 120 to 600 rpm, and the mixing time is 3 to 10 minutes;

[0086] S22. The mixture is added to a twin-screw extruder for melt plasticization and mixing, and then extruded into granules; the temperature at the feed port position of the first zone of the twin-screw extruder is 80-120°C, the temperature of the remaining zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 40-48, and the screw speed is 350-600 rpm.

[0087] The design of process parameters such as mixing of raw materials and melt granulation of the functional layer in the embodiment of the present application is based on the melt processing characteristics of the polypropylene material itself and the properties of each filler, especially the dispersion uniformity of the flame retardant shielding filler in the resin matrix. Targeted optimization and adjustment are carried out to ensure that each filler is evenly dispersed in the polypropylene resin to achieve a synergistic effect.

[0088] The following uses a number of specific examples to illustrate the preparation methods and applications of the halogen-free flame-retardant polyolefin insulated cable materials of the present application and the polyolefin insulated cable materials of the comparative examples. All raw materials, unless otherwise specified, are commercially available.

[0089] Example 1

[0090] 1. Recipe

[0091] For the insulation layer, you can just buy regular polypropylene insulation material.

[0092] The functional layer material formula is as follows:

[0093] 75 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 15 g / 10 min and polypropylene with an MFR of 3 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:4);

[0094] Flame retardant shielding filler: 6Kg;

[0095] Toughening agent ethylene-propylene-diene terpolymer: 2 kg;

[0096] Dispersant 1 kg (methyl silicone oil and talc, weight ratio of methyl silicone oil: talc is 1:2);

[0097] 0.5 kg of antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio of amine antioxidant 186:phosphite antioxidant 168=5:1).

[0098] 2. Preparation of halogen-free flame retardant polyolefin insulated cable materials:

[0099] (1) Preparation of flame retardant shielding filler:

[0100] 1. Preparation of core-shell structure complex

[0101] The short carbon nanotubes were first pickled using a 60% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 4% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000-3000 rpm. The pickling time was 2 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (KH-550 silane coupling agent solution, mass concentration of 3wt%) was then added. ，The mixture was stirred in an aqueous solution (solvent water) for 1 hour at 1000 rpm. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (composition of the flame retardant triphenyl phosphate, solvent ethanol, and binder methyl silicone oil, with a flame retardant concentration of 10 wt% and a binder concentration of 5 wt%) was then added and stirred for another 2 hours at 700 rpm. The mixture was concentrated by rotary evaporation to a quarter of the original volume and then dried to obtain the modified carbon nanotubes.

[0102] 2. Preparation of long carbon nanotube slurry:

[0103] Formula: Weight ratio of ethanol: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 80:1:1:1:3; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and mix until uniform. Then, transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours. Then, continue to add polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0104] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0105] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:7:10; the diameter of the long carbon nanotubes is in the range of 2nm to 4nm, the aspect ratio is in the range of 80000:1 to 100000:1, and the specific surface area is 785m 2 / g, Raman spectrum intensity ratio ID / IG is 0.65, powder resistivity is 4.8mΩ·cm; the diameter range of the short carbon nanotubes is 10nm~15nm, the aspect ratio range is 10000:1~13000:1, and the specific surface area is 290m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.9, and the powder resistivity is 19mΩ·cm.

[0106] (2) Raw material mixing, melt extrusion and granulation

[0107] 1. Add the prepared flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 50-60°C, the speed is 400 rpm, and the mixing time is 6 minutes.

[0108] 2. Add the above mixture into a twin-screw extruder for melting, plasticizing and mixing, and then extrude and granulate; the temperature at the feed port of the first zone of the twin-screw extruder is 120°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 48, and the screw speed is 450 rpm.

[0109] (3) Combination of functional layer and insulating layer

[0110] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0111] Example 2

[0112] 1. Recipe

[0113] Functional layer material formula:

[0114] 90 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 13 g / 10 min and polypropylene with an MFR of 4 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:8);

[0115] Flame retardant shielding filler: 10Kg;

[0116] Toughening agent ethylene-propylene copolymer: 3Kg;

[0117] 2 kg of dispersant (methyl silicone oil and calcium stearate, weight ratio of methyl silicone oil to calcium stearate is 1:5);

[0118] 1 kg of antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio 186:168 = 6:1).

[0119] For the insulation layer, you can just buy regular polypropylene insulation material.

[0120] 2. Preparation of halogen-free flame retardant polyolefin insulated cable materials:

[0121] (1) Preparation of flame retardant shielding filler:

[0122] 1. Preparation of core-shell structure complex

[0123] The short carbon nanotubes were first pickled using a 65% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 5% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000-3000 rpm. The pickling time was 3 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (KH-560 silane coupling agent solution, mass concentration of 5wt%) was then added. ，The modified carbon nanotubes were stirred in an aqueous solution (solvent) at 1200 rpm for 2 hours. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (comprising bisphenol A-bis(diphenyl phosphate), aqueous solution, and binder methyl silicone oil, with a flame retardant concentration of 12 wt% and a binder concentration of 6 wt%) was then added and stirred for another 3 hours at 800 rpm. The mixture was concentrated by rotary evaporation until no solvent was present, and finally dried to obtain the modified carbon nanotubes.

[0124] 2. Preparation of long carbon nanotube slurry:

[0125] Formula: Weight ratio of water: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 90:3:3:3:5; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent water, stir at 3000 RPM for 30 minutes, and mix until uniform. Then transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours. Then, continue to add the binder polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0126] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0127] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:15:20; the diameter of the long carbon nanotubes is in the range of 3nm to 4nm, the aspect ratio is in the range of 70000:1 to 90000:1, and the specific surface area is 705m 2 / g, Raman spectrum intensity ratio ID / IG is 0.60, powder resistivity is 5.3mΩ·cm; the diameter range of the short carbon nanotubes is 9nm~13nm, the aspect ratio range is 11000:1~14000:1, and the specific surface area is 302m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.86, and the powder resistivity is 21mΩ·cm.

[0128] (2) Raw material mixing, melt extrusion and granulation

[0129] 1. Add the flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 40-50°C, the speed is 450 rpm, and the mixing time is 5 minutes.

[0130] 2. Add the above mixture into a twin-screw extruder for melting, plasticizing and mixing, and then extrude and granulate; the temperature at the feed port of the first zone of the twin-screw extruder is 110°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 45, and the screw speed is 400 rpm.

[0131] (3) Combination of functional layer and insulating layer

[0132] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0133] Example 3

[0134] 1. Recipe

[0135] Functional layer material formula:

[0136] 85 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 12 g / 10 min and polypropylene with an MFR of 5 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:6);

[0137] Flame retardant shielding filler: 8Kg;

[0138] Toughening agent butadiene rubber: 2.5Kg;

[0139] Dispersant 1.5 kg (ethyl silicone oil and talc, weight ratio of ethyl silicone oil: talc is 1:3);

[0140] 0.75 kg of antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio 186:168=7:1).

[0141] For the insulation layer, you can just buy regular polypropylene insulation material.

[0142] 2. Preparation of halogen-free flame retardant polyolefin insulated cable materials:

[0143] (1) Preparation of flame retardant shielding filler:

[0144] 1. Preparation of core-shell structure complex

[0145] The short carbon nanotubes were first pickled using a 68% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 3% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000-3000 rpm. The pickling time was 2.5 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (A-187 silane coupling agent solution, mass concentration of 4wt%) was then added. ，The modified carbon nanotubes were stirred in an aqueous solution (solvent: ethanol) for 2.5 hours at 900 rpm. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (composition of the flame retardant triphenyl phosphite, solvent: ethanol, and binder: methyl silicone oil, with a flame retardant concentration of 15 wt% and a binder concentration of 8 wt%) was then added and stirred for another 3 hours at 1000 rpm. The mixture was concentrated by rotary evaporation until no solvent was present, and finally dried to obtain the modified carbon nanotubes.

[0146] 2. Preparation of long carbon nanotube slurry:

[0147] Formula: Weight ratio of water: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 85:2:2:2:4; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and mix until uniform. Then, transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours. Then, continue to add the binder polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0148] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0149] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:10:16; the diameter of the long carbon nanotubes is in the range of 2nm to 3nm, the aspect ratio is in the range of 80000:1 to 90000:1, and the specific surface area is 755m 2 / g, Raman spectrum intensity ratio ID / IG is 0.63, powder resistivity is 4.7mΩ·cm; the diameter range of the short carbon nanotubes is 12nm~15nm, the aspect ratio range is 10000:1~12000:1, and the specific surface area is 286m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.88, and the powder resistivity is 22mΩ·cm.

[0150] (2) Raw material mixing, melt extrusion and granulation

[0151] 1. Add the flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 25-30°C, the speed is 600 rpm, and the mixing time is 4 minutes.

[0152] 2. Add the above mixture into a twin-screw extruder for melt plasticization and mixing, and then extrude and granulate; the temperature at the feed port position of the first zone of the twin-screw extruder is 120°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 40, and the screw speed is 500 rpm.

[0153] (3) Combination of functional layer and insulating layer

[0154] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0155] Example 4

[0156] 1. Recipe

[0157] Functional layer material formula:

[0158] 80 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 16 g / 10 min and polypropylene with an MFR of 2.5 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:5);

[0159] Flame retardant shielding filler: 9Kg;

[0160] Toughening agent isobutylene rubber: 2.3Kg;

[0161] Dispersant 1.3 kg (methylhydroxy silicone oil and talc, weight ratio of methylhydroxy silicone oil: talc is 1:4);

[0162] Antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio 186:168=4:1): 0.6 kg.

[0163] For the insulation layer, you can just buy regular polypropylene insulation material.

[0164] 2. Preparation of halogen-free flame retardant polyolefin insulated cable materials:

[0165] (1) Preparation of flame retardant shielding filler:

[0166] 1. Preparation of core-shell structure complex

[0167] The short carbon nanotubes were first pickled using a 75% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 4% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000-3000 rpm. The pickling time was 4 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (γ-glycidyloxypropyltrimethoxysilane, mass concentration 3.5wt%) was then added. ，The mixture was stirred in an aqueous solvent (solvent water) for 3 hours at a stirring rate of 1100 rpm. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (composition of the flame retardant resorcinol bis(diphenyl phosphate), aqueous solvent, and binder methyl silicone oil, with a flame retardant concentration of 13 wt% and a binder concentration of 7 wt%) was then added and stirred for another 2.5 hours at a stirring rate of 800 rpm. The mixture was concentrated by rotary evaporation to a quarter of the original volume and finally dried to obtain the modified carbon nanotubes.

[0168] 2. Preparation of long carbon nanotube slurry:

[0169] Formula: Solvent ethanol: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 83:1:2:2:3; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and mix until uniform. Then transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours. Then, continue to add the binder polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0170] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0171] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:7:20; the diameter of the long carbon nanotubes is in the range of 2nm to 3nm, the aspect ratio is in the range of 80000:1 to 95000:1, and the specific surface area is 732m 2 / g, Raman spectrum intensity ratio ID / IG is 0.67, powder resistivity is 4.1mΩ·cm; the diameter range of the short carbon nanotubes is 12nm~14nm, the aspect ratio range is 10000:1~12000:1, and the specific surface area is 293m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.90, and the powder resistivity is 19mΩ·cm.

[0172] (2) Raw material mixing, melt extrusion and granulation

[0173] 1. Add the flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 30-40°C, the speed is 450 rpm, and the mixing time is 5 minutes.

[0174] 2. Add the above mixture into a twin-screw extruder for melt plasticization and mixing, and then extrude and granulate; the temperature at the feed port position of the first zone of the twin-screw extruder is 90°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 44, and the screw speed is 430 rpm.

[0175] (3) Combination of functional layer and insulating layer

[0176] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0177] Example 5

[0178] 1. Recipe

[0179] Functional layer material formula:

[0180] 83 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 17 g / 10 min and polypropylene with an MFR of 3.5 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:6);

[0181] Flame retardant shielding filler: 9Kg;

[0182] Toughening agent ethylene-propylene-diene terpolymer: 2.3Kg;

[0183] Dispersant 1.2 kg (methyl silicone oil and talc, weight ratio of methyl silicone oil: talc is 1:4);

[0184] 0.9 kg of antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio 186:168=7:2).

[0185] For the insulation layer, you can just buy regular polypropylene insulation material.

[0186] 2. Preparation of halogen-free flame retardant polyolefin insulated cable materials:

[0187] (1) Preparation of flame retardant shielding filler:

[0188] 1. Preparation of core-shell structure complex

[0189] The short carbon nanotubes were first pickled using a 70% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 5% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000 rpm. The pickling time was 2 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (KH-550 silane coupling agent solution, mass concentration 5wt%) was then added. ，The modified carbon nanotubes were stirred in an aqueous solution (solvent: ethanol) for 2.5 hours at 1200 rpm. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (composition of the flame retardant triphenyl phosphate, solvent: ethanol, and binder: methyl silicone oil, with a flame retardant concentration of 9 wt% and a binder concentration of 5 wt%) was then added and stirred for another 2 hours at 800 rpm. The mixture was concentrated by rotary evaporation until no solvent was present, and finally dried to obtain the modified carbon nanotubes.

[0190] 2. Preparation of long carbon nanotube slurry:

[0191] Formula: Weight ratio of solvent water: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 88:2.5:2:2.5:3.5; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent water, stir at 3000 RPM for 30 minutes, and mix until uniform; then transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours; then continue to add the binder polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0192] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0193] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:15:10. The diameter of the long carbon nanotubes is in the range of 2nm to 4nm, the aspect ratio is in the range of 50000:1 to 80000:1, and the specific surface area is 687m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.63, and the powder resistivity is 5.3mΩ·cm; the diameter of the short carbon nanotubes is in the range of 12nm to 15nm, the aspect ratio is in the range of 13000:1 to 15000:1, and the specific surface area is 292m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.85, and the powder resistivity is 23mΩ·cm.

[0194] (2) Raw material mixing, melt extrusion and granulation

[0195] 1. Add the flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 55-60°C, the speed is 450 rpm, and the mixing time is 7 minutes.

[0196] 2. Add the above mixture into a twin-screw extruder for melt plasticization and mixing, and then extrude and granulate; the temperature at the feed port position of the first zone of the twin-screw extruder is 110°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 12, and the screw speed is 500 rpm.

[0197] (3) Combination of functional layer and insulating layer

[0198] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0199] Example 6

[0200] 1. Recipe

[0201] Functional layer material formula:

[0202] 90 kg of polypropylene resin (composed of polypropylene with a melt flow rate (MFR) of 13 g / 10 min and polypropylene with an MFR of 4 g / 10 min, with a mass ratio of high flow rate to low flow rate of 1:8);

[0203] Flame retardant shielding filler: 10Kg;

[0204] Toughening agent ethylene-propylene copolymer: 3Kg;

[0205] 2 kg of dispersant (methyl silicone oil and calcium stearate, weight ratio of methyl silicone oil to calcium stearate is 1:5);

[0206] 1 kg of antioxidant (amine antioxidant 186 and phosphite antioxidant 168, weight ratio 186:168 = 6:1).

[0207] For the insulation layer, you can just buy regular polypropylene insulation material.

[0208] 2. Preparation process of halogen-free flame retardant polyolefin insulated cable material:

[0209] (1) Preparation of flame retardant shielding filler:

[0210] 1. Preparation of core-shell structure complex

[0211] The short carbon nanotubes were first pickled using a 68% mass concentration sulfuric acid solution as the pickling solution. The amount of carbon nanotubes added was 3% of the total amount of the pickling solution. Stirring was continued during the pickling process at a stirring rate of 2000-3000 rpm. The pickling time was 2.5 hours. After pickling, the carbon nanotubes were washed several times with anhydrous ethanol, centrifuged, and dried. A silane coupling agent solution (A-187 silane coupling agent solution, mass concentration of 4wt%) was then added. ，The modified carbon nanotubes were stirred in an aqueous solution (solvent: ethanol) for 2.5 hours at 900 rpm. After the reaction, the mixture was washed multiple times with anhydrous ethanol, centrifuged, and dried to form modified carbon nanotubes. A flame retardant solution (composition of the flame retardant triphenyl phosphite, solvent: ethanol, and binder: methyl silicone oil, with a flame retardant concentration of 15 wt% and a binder concentration of 8 wt%) was then added and stirred for another 3 hours at 1000 rpm. The mixture was concentrated by rotary evaporation until no solvent was present, and finally dried to obtain the modified carbon nanotubes.

[0212] 2. Preparation of long carbon nanotube slurry:

[0213] Formula: Solvent ethanol: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder polyacrylic acid = 83:1:2:2:3; Process: First, add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and mix until uniform. Then transfer the mixture to a microfluidizer with a set flow rate of 10 L / h and a pressure of 2000-3000 Bar, and disperse for 1-2 hours. Then, continue to add the binder polyacrylic acid and stir at 4000 RPM for 30 minutes.

[0214] 3. Adding the core-shell structure composite into the long carbon nanotube slurry, stirring and dispersing it evenly and then drying it to obtain a flame retardant shielding filler.

[0215] The weight ratio of the long carbon nanotubes, short carbon nanotubes and flame retardant is 1:7:10; the diameter of the long carbon nanotubes is in the range of 2nm to 4nm, the aspect ratio is in the range of 80000:1 to 100000:1, and the specific surface area is 785m 2 / g, Raman spectrum intensity ratio ID / IG is 0.65, powder resistivity is 4.8mΩ·cm; the diameter range of the short carbon nanotubes is 10nm~15nm, the aspect ratio range is 10000:1~13000:1, and the specific surface area is 290m 2 / g, the Raman spectrum intensity ratio ID / IG is 0.9, and the powder resistivity is 19mΩ·cm.

[0216] (2) Raw material mixing, melt extrusion and granulation

[0217] 1. Add the flame retardant shielding filler, polypropylene resin and other raw materials into a high-speed mixer and mix them evenly. The specific mixing temperature is 50-55°C, the speed is 450 rpm, and the mixing time is 6 minutes.

[0218] 2. Add the above mixture into a twin-screw extruder for melt plasticization and mixing, and then extrude and granulate; the temperature at the feed port position of the first zone of the twin-screw extruder is 110°C, the temperature of the other zones is 210-240°C, the head temperature is 240-260°C, the aspect ratio of the twin-screw extruder is 12, and the screw speed is 500 rpm.

[0219] (3) Combination of functional layer and insulating layer

[0220] The particles are extruded to form a functional layer, which is combined with the insulating layer.

[0221] Comparative Example 1

[0222] Compared with Example 1, the short carbon nanotubes and the flame retardant do not form a core-shell structure composite. Instead, the short carbon nanotubes, the flame retardant and the long carbon nanotubes are simply mixed evenly and used as a flame-retardant shielding filler.

[0223] Comparative Example 2

[0224] Compared with Example 1, all long carbon nanotubes were replaced with short carbon nanotubes, and other operations remained unchanged.

[0225] Comparative Example 3

[0226] Compared with Example 1, the weight ratio of long carbon nanotubes, short carbon nanotubes and flame retardant is 1:3:5, and other operations remain unchanged.

[0227] Comparative Example 4

[0228] Compared with Example 1, the weight ratio of long carbon nanotubes, short carbon nanotubes and flame retardant is 1:20:25, and other operations remain unchanged.

[0229] Performance Testing

[0230] The functional layer particles prepared in Examples 1 to 6 and Comparative Examples 1 to 4 were injection molded into standard samples, and then the tensile strength, elongation at break, notched impact strength (GB / T 1843-2008, pendulum energy 2.75 J), surface resistance, UL94 flame retardancy, and electromagnetic shielding performance were tested.

[0231] Among them, tensile strength and elongation at break test: the composite material is injection molded into standard specimens and tested in accordance with GB / T1040-2018, with a tensile rate of 10 mm / min.

[0232] The electromagnetic shielding performance test is in accordance with GB / T30142-2013.

[0233] Surface resistance test: Use four-probe square resistance test.

[0234] UL94 flame retardant performance: UL94 flame retardant performance increases step by step from HB, V2, V1 to V0, among which HB is the lowest flame retardant grade in the UL94 standard, requiring that for samples with a thickness of 3mm to 13mm, the burning speed is less than 40mm / min, and for samples with a thickness of less than 3mm, the burning speed is less than 70mm / min, or it is extinguished before the 100mm mark; V2: After two 10s burning tests on the sample, the flame goes out within 60s and can ignite the cotton wool 30cm below; V1: After two 10s burning tests on the sample, the flame goes out within 60s and cannot ignite the cotton wool 30cm below; V0: After two 10s burning tests on the sample, the flame goes out within 30s and no burning objects can fall.

[0235] The above performance test results are shown in Table 1 below.

[0236] Table 1

[0237]

[0238]

[0239] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A halogen-free flame-retardant polyolefin insulated cable material, characterized in that: It includes an insulating layer and a functional layer, and the functional layer includes, by weight: Polyolefin resin: 60 to 100 parts; Flame retardant shielding filler: 2 to 10 parts; Toughening agent: 1 to 3 parts; Dispersant: 1 to 2 parts; Antioxidant: 0.25-1 part; The flame retardant shielding filler comprises long carbon nanotubes, short carbon nanotubes and a flame retardant; the short carbon nanotubes and the flame retardant form a core-shell structure composite, the shell is the short carbon nanotubes and the core is the flame retardant; the flame retardant is a halogen-free flame retardant.

2. The halogen-free flame-retardant polyolefin insulated cable material according to claim 1, characterized in that: The weight ratio of the long carbon nanotubes, the short carbon nanotubes and the flame retardant is in the range of 1:7-15:10-20; and the method for forming a core-shell structure composite of the short carbon nanotubes and the flame retardant comprises the following steps: The short carbon nanotubes are firstly acid-washed and then surface-treated and modified with a silane coupling agent solution to form modified carbon nanotubes; The modified carbon nanotubes are poured into the flame retardant solution, stirred and dispersed evenly, and then the solvent is removed by rotary evaporation and dried.

3. The halogen-free flame-retardant polyolefin insulated cable material according to claim 1 or 2, characterized in that: The polyolefin resin includes one or a mixture of two or more of polypropylene resin, polyethylene resin, poly-1-butene resin, and poly-4-methyl-1-pentene resin.

4. The halogen-free flame-retardant polyolefin insulated cable material according to claim 3, characterized in that: The polyolefin resin is a polypropylene resin, which is obtained by compounding a high-flow-rate polypropylene with a melt flow rate (MFR) of 10 to 20 g / 10 min and a low-flow-rate polypropylene with a melt flow rate (MFR) of 0.5 to 5 g / 10 min.

5. The halogen-free flame-retardant polyolefin insulated cable material according to claim 1 or 2, characterized in that: The toughening agent is one or a mixture of two or more of ethylene-propylene-diene terpolymer, ethylene-propylene binary copolymer, butadiene rubber, and isobutylene rubber; and / or, The antioxidant includes at least one of an amine antioxidant and a phenolic antioxidant, and also includes at least one of an acid-containing metal salt, a sulfide, a thioester and a phosphite; and / or, The dispersant is obtained by mixing silicone oil with at least one of calcium stearate, barium sulfate, talc and polyethylene wax, and the silicone oil is at least one of methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, methylethoxy silicone oil, methylvinyl silicone oil, methylhydroxy silicone oil, ethyl hydrogen silicone oil and hydroxy hydrogen silicone oil.

6. The halogen-free flame-retardant polyolefin insulated cable material according to claim 1 or 2, characterized in that: The diameter of the long carbon nanotubes is in the range of 1 nm to 4 nm, the aspect ratio is in the range of 20,000:1 to 100,000:1, and the specific surface area is in the range of 600 m 2 / g~1000m 2 / g, Raman spectrum intensity ratio I D / I G The range is 0.5 to 0.7, and the powder resistivity range is 2mΩ·cm to 6mΩ·cm; and / or, The diameter of the short carbon nanotubes is in the range of 6nm to 15nm, the aspect ratio is in the range of 8000:1 to 15000:1, and the specific surface area is in the range of 250m 2 / g~350m 2 / g, Raman spectrum intensity ratio I D / I G The range is 0.7~1.0, and the powder resistivity range is 15mΩ·cm~25mΩ·cm.

7. The halogen-free flame-retardant polyolefin insulated cable material according to claim 4, characterized in that: The mass ratio of the high flow rate polypropylene to the low flow rate polypropylene is 1:4-8.

8. The method for preparing the halogen-free flame-retardant polyolefin insulated cable material according to any one of claims 1 to 7, characterized in that: The steps include: S1. Preparation of flame-retardant shielding filler: first, the short carbon nanotubes and the flame retardant form a core-shell structure composite, and then add the core-shell structure composite to the long carbon nanotube slurry, stirring and dispersing uniformly and drying; S2. The flame retardant shielding filler is mixed with polypropylene resin and other raw materials, and then melt-extruded and granulated; S3. The particles are formed into a functional layer and combined with the insulating layer.

9. The method for preparing a halogen-free flame-retardant polyolefin insulated cable material according to claim 8, characterized in that: The preparation of the long carbon nanotube slurry includes the following steps: Formula: weight ratio of solvent: sodium carboxymethyl cellulose: sodium dodecyl sulfate: long carbon nanotubes: binder = (80-90): (1-3): (1-3): (1-3): (3-5); process: first add sodium carboxymethyl cellulose and sodium dodecyl sulfate to the solvent, stir at 3000 RPM for 30 minutes, and then mix until uniform; then transfer the mixed solution to a microfluidizer, set the flow rate to 10 L / h, the pressure to 2000-3000 Bar, and disperse for 1-2 hours; then continue to add the binder and stir at 4000 RPM for 30 minutes.

10. A cable having an insulation layer formed from the halogen-free flame-retardant polyolefin insulated cable material according to any one of claims 1 to 7.

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