Halogen-free low-smoke flame-retardant class a crosslinked polyethylene insulated control cable

Abstract

The application provides a halogen-free low-smoke flame-retardant A-class crosslinked polyethylene insulated control cable, and relates to the field of cables.The halogen-free low-smoke flame-retardant A-class crosslinked polyethylene insulated control cable comprises, from inside to outside, a cable core, a cable core wrapping layer, a shielding layer and an outer sheath layer, wherein the outer sheath layer is made of a halogen-free low-smoke flame-retardant polyolefin sheath material composed of the following raw materials in parts by weight: 18-25 parts of ethylene-vinyl acetate resin, 6-12 parts of metallocene PE, 3-10 parts of a compatibilizer, 17-25 parts of silane coupling agent modified aluminum hydroxide, 25-35 parts of fluorine-containing surfactant modified magnesium hydroxide, 5-10 parts of fluorine-containing compound activated montmorillonite, 0.3-4 parts of black masterbatch, 0.5-5 parts of silicone masterbatch and 0.2-3 parts of polyethylene wax, wherein the fluorine-containing surfactant is at least one selected from perfluorooctanoic acid, perfluorooctane sulfonic acid and perfluorohexanoic acid, and the metallocene PE is Exceed TM Flow m 1020.RA.

Description

Technical Field

[0001] This invention belongs to the field of cable technology, specifically relating to a halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable. Background Technology

[0002] Control cables are widely used in densely populated areas with extremely high fire safety requirements, such as high-rise buildings, subways, tunnels, nuclear power plants, and large data centers. They are mainly used for control lines, signal transmission, and power distribution. Traditional control cables mostly use polyvinyl chloride (PVC) insulation sheath material. When this type of material burns, it releases a large amount of halogenated toxic gases and dense smoke, which can not only cause asphyxiation and injury but also corrode equipment and building structures. Furthermore, it does not meet modern environmental protection and fire safety standards.

[0003] Existing halogen-free, low-smoke, flame-retardant Class A control cables generally suffer from the following problems in order to ensure their Class A performance: Firstly, the cable structure is complex and poorly designed. The insulation uses halogen-free, low-smoke, flame-retardant polyolefin insulation, but the large addition of halogen-free flame retardants damages the molecular structure of the cross-linked polyethylene insulation layer, leading to decreased insulation resistance, poorer temperature resistance, and reduced mechanical strength. Furthermore, the cable still produces smoke during combustion, failing to achieve the synergistic effect of low smoke, non-toxicity, and high-efficiency flame retardancy. Secondly, the cable manufacturing process is cumbersome. For unarmored cables, the process includes an oxygen barrier layer and a halogen-free, low-smoke, flame-retardant wrapping layer, resulting in numerous production steps and low efficiency. In addition, the complex structural design leads to larger cable dimensions and heavier weight, violating the design principles of control cables: small outer diameter, light weight, and flexible laying.

[0004] Therefore, developing a cross-linked polyethylene insulated control cable that combines Class A flame retardancy, halogen-free low smoke, simple structure, small size, and high production efficiency has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable. By optimizing the formula of the outer sheath material and improving the overall structural design of the cable, the technical defects of traditional cables, such as insufficient flame retardancy, poor insulation performance, low mechanical strength, complex structure, and low production efficiency, are solved, thereby improving the comprehensive performance of the cable, such as halogen-free, low-smoke, Class A flame retardancy, thin wall thickness, and lightweight.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A first aspect of the present invention provides a halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable, characterized in that the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable comprises, from the inside out, a cable core, a core wrapping layer, a shielding layer, and an outer sheath layer, wherein the outer sheath layer is made of halogen-free, low-smoke, flame-retardant polyolefin sheath material. The halogen-free, low-smoke, flame-retardant polyolefin sheath material is composed of the following raw materials in parts by weight: 18-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 3-10 parts compatibilizer, 17-25 parts silane coupling agent modified aluminum hydroxide, 25-35 parts fluorinated surfactant modified magnesium hydroxide, 5-10 parts fluorinated compound activated montmorillonite, 0.3-4 parts black masterbatch, 0.5-5 parts silicone masterbatch, and 0.2-3 parts polyethylene wax. The fluorinated surfactant is selected from at least one of perfluorooctanoic acid, perfluorooctane sulfonic acid, and perfluorohexanoic acid, and the metallocene PE is Exceed PE purchased from Exxon. TM Flow m 1020.RA.

[0007] In some embodiments, the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable further includes: An inner liner layer, wherein the inner liner layer is disposed on the outer periphery of the shielding layer and is made of a halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler with an oxygen index ≥40; and An armor layer, disposed between the inner liner and the outer sheath, and comprising at least one of galvanized steel strip armor and steel wire armor. The thickness of the inner lining layer is 1.0-1.2 mm.

[0008] In some embodiments, the halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler is composed of the following parts by weight of raw materials: 15-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 5-10 parts compatibilizer, 18-25 parts aluminum hydroxide, 28-36 parts magnesium hydroxide, 0.5-4 parts black masterbatch, 0.3-2 parts silane coupling agent, 0.9-3 parts silicone masterbatch, and 0.8-2 parts polyethylene wax.

[0009] In some embodiments, the cable core includes a filler material and a silane cross-linked polyethylene insulated single wire, the silane cross-linked polyethylene insulated single wire being composed of a conductor and a silane cross-linked polyethylene insulation layer extruded onto the conductor.

[0010] In some embodiments, the conductor is made of stranded soft round copper wire, and the silane cross-linked polyethylene insulation layer comprises a mixture of silane cross-linked polyethylene graft material A and silane cross-linking catalyst masterbatch B in a mass ratio of 95:5, and the minimum median tensile strength of the silane cross-linked polyethylene insulation layer is 18 N / mm².2 The minimum median value of elongation at break is 400%.

[0011] In some embodiments, the filler material is a non-hygroscopic flame-retardant filler rope.

[0012] In some embodiments, the cable core is formed by twisting together multiple cross-linked polyethylene insulated single wires with a filler material.

[0013] In some embodiments, the thickness of the outer sheath layer is 1.8-2.3 mm.

[0014] In some embodiments, the halogen-free, low-smoke, flame-retardant polyolefin sheath material has an oxygen index ≥38, a tensile strength ≥18MPa, and an elongation at break ≥200%.

[0015] In some embodiments, the bundled combustion carbonization height of the insulated control cable is ≤1.0m.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention achieves synergistic effects among the three flame-retardant components by adding a modified inorganic flame-retardant composite consisting of modified aluminum hydroxide, modified magnesium hydroxide, and modified montmorillonite to the halogen-free, low-smoke flame-retardant polyolefin sheath material. This improves the overall performance of the halogen-free, low-smoke flame-retardant polyolefin sheath material while ensuring good flame-retardant performance. Furthermore, by employing a differentiated modification strategy of modifying aluminum hydroxide with silane coupling agents, magnesium hydroxide with fluorinated surfactants, and montmorillonite with fluorinated compounds, targeted surface properties are imparted to each flame-retardant component, significantly improving its dispersibility, compatibility, and interfacial bonding in the polyolefin matrix.

[0017] (2) This invention employs a resin system composed of EVA and metallocene PE, and achieves a balance between mechanical and processing properties by optimizing the mass ratio between the two. Specifically, Exceed™ Flow m 1020.RA metallocene polyethylene is selected, with a density of 0.920 g / cm³ and a melt index of 1.0 g / 10min, which can further improve the processing performance of the halogen-free, low-smoke, flame-retardant polyolefin sheathing material. Furthermore, the resin matrix composed of EVA and metallocene PE exhibits good compatibility in halogen-free, low-smoke, flame-retardant polyolefin sheathing materials, enhancing mechanical properties such as tensile strength, elongation, tear resistance, and crack resistance.

[0018] (3) In this invention, an inner lining layer made of halogen-free, low-smoke, flame-retardant, Class A cross-linked polyethylene insulated armored control cable with oxygen index ≥40 is introduced. When halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler is used as the inner lining layer, the oxygen-barrier filler forms a dense carbonized oxygen-barrier layer when heated, which isolates oxygen from the cable core and prevents the flame from spreading inward, thereby improving the flame-retardant performance of the cable.

[0019] (4) The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention has a bundled combustion carbonization height of ≤1.0m, and has the advantages of excellent overall flame retardant performance, simple structure, small bending radius, easy installation and use, low production cost, and simple production process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the first embodiment of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention; Figure 2 This is a schematic diagram of a second embodiment of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention; Figure 3 The figures show the bundled combustion performance test results of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention. Among them, (a) shows the bundled combustion performance test results of the cable with model WDZA-KYJYP2-23 450 / 750V and specification 37×1.5(B), (b) shows the bundled combustion performance test results of the cable with model WDZA-KYJYP2 450 / 750V and specification 37×1.5(B), and (c) shows the bundled combustion performance test results of the cable with model WDZA-KYJYP2 450 / 750V and specification 8×1.5(B).

[0021] Wherein: 100—Halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable; 110—Cable core; 111—Filling material; 112—Silane cross-linked polyethylene insulated single wire; 1121—Conductor; 1122—Silane cross-linked polyethylene insulation layer; 120—Cable core wrapping layer; 130—Shielding layer; 140—Inner lining layer; 150—Armor layer; 160—Outer sheath layer. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] Existing halogen-free, low-smoke, flame-retardant Class A control cables generally suffer from the following problems in order to ensure their Class A performance: Firstly, the cable structure is complex and poorly designed. The insulation uses halogen-free, low-smoke, flame-retardant polyolefin insulation, but the large addition of halogen-free flame retardants damages the molecular structure of the cross-linked polyethylene insulation layer, leading to decreased insulation resistance, poorer temperature resistance, and reduced mechanical strength. Furthermore, the cable still produces smoke during combustion, failing to achieve the synergistic effect of low smoke, non-toxicity, and high-efficiency flame retardancy. Secondly, the cable manufacturing process is cumbersome. For unarmored cables, the process includes an oxygen barrier layer and a halogen-free, low-smoke, flame-retardant wrapping layer, resulting in numerous production steps and low efficiency. In addition, the complex structural design leads to larger cable dimensions and heavier weight, violating the design principles of control cables: small outer diameter, light weight, and flexible laying.

[0025] To address the aforementioned problems of existing control cables, patent CN102637473A provides a low-smoke, halogen-free, flame-retardant Class A stainless steel armored cable and its manufacturing method. The cable includes a core and a sheath. The core is wrapped with non-woven fabric tape, which is then wrapped with a rubberized fabric buffer layer. The buffer layer is covered with corrugated stainless steel, which is longitudinally welded onto the buffer layer. An aluminum sheath is extruded with a flame-retardant inner sheath, and the inner sheath is extruded with a cross-linked flame-retardant polyolefin outer sheath. The core is composed of stranded insulated and shielded wire cores, with inorganic fiber fillers in the gaps. The insulated and shielded wire core consists of a conductor shielding layer, a cross-linked polyethylene insulation layer extruded over the conductor shielding layer, an aluminum-plastic composite tape insulation shielding layer, and a copper strip wrapped around the insulation shielding layer. The copper strip has colored stripes. This product exhibits good flame-retardant performance, meeting Class A flame-retardant requirements, and has excellent resistance to mechanical impact. The process is simple and easy to manufacture.

[0026] However, the control cables obtained by the above methods rely on multi-layer composite structures (such as non-woven fabric wrapping tape and coated fabric tape buffer layers), which involve complex production processes and high costs. In addition, the control cables have an aluminum-plastic composite tape insulation shielding layer outside the insulation layer, and copper tape is wrapped around the insulation shielding layer, which affects the flexibility and processability of the materials, and the cables are prone to cracking when bent.

[0027] Patent CN107742549A discloses a halogen-free, low-smoke, flame-retardant Class A computer cable, comprising several cores, sequentially wrapped with a fiberglass tape sheath, a copper wire braided shielding layer, and a flame-retardant Class A halogen-free, low-smoke polyolefin sheath. Each core comprises two sets of mini-cores, each consisting of several bare copper conductors wrapped with polyethylene insulation. Sequentially wrapped with a fiberglass tape sheath, a copper wire braided sub-shielding layer, and another fiberglass tape sheath. A fiberglass rope filler layer is placed between the cores and the fiberglass tape sheath; a fiberglass rope filler layer is placed between the polyethylene insulation layer and the fiberglass tape sheath. This invention features excellent insulation performance, good environmental friendliness, good flame retardancy, good heat resistance, good transmission performance, and effectively isolates external interference while preventing internal signal leakage from interfering with other wire pairs.

[0028] However, the fiberglass tape wrapping around the core of the aforementioned cable comes into contact with the copper wire, and under conditions such as high temperature and current flow, electrochemical corrosion will occur, reducing the insulation performance. Furthermore, fiberglass ropes and tapes are brittle, prone to shedding powder, not environmentally friendly, can cause itching when in contact with skin, have a poor processing experience, and are not compatible with copper materials.

[0029] Patent CN112992437A discloses a method for manufacturing an insulated halogen-free, low-smoke, flame-retardant Class A power cable. The method includes: manufacturing a conductor; extruding an insulation layer; performing electron beam cross-linking on the extruded insulation layer; manufacturing a core wrapping layer; extruding an inner sheath layer; performing electron beam cross-linking on the extruded inner sheath layer; manufacturing a copper wire braided armor layer; extruding a sheath layer; performing electron beam cross-linking on the extruded sheath layer; and finally, packaging. Using this method, the cable core is wrapped to form a core wrapping layer, and an inner sheath layer, copper wire braided armor layer, and sheath layer are sequentially arranged outside the core wrapping layer. Through extrusion followed by electron beam cross-linking, the insulation layer of the conductor can be effectively prevented from burning in a fire. This method is simple in structure, easy to manufacture, and produces a power cable that achieves halogen-free, low-smoke, and flame-retardant properties, meeting the requirements for power cable use.

[0030] The insulation layer, inner sheath, and outer sheath of the power cable obtained by the above method all require electron irradiation crosslinking processing. For a single cable, this adds three processes, increasing production costs. Furthermore, since the insulation material, inner sheath material, and outer sheath material are all irradiated materials, this further increases material costs.

[0031] To address the shortcomings of existing technologies, this invention provides a halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable. By optimizing the outer sheath material formula and improving the overall cable structure design, it solves the technical defects of traditional cables, such as insufficient flame retardancy, poor insulation performance, low mechanical strength, complex structure, and low production efficiency, thereby improving the cable's comprehensive performance, including halogen-free, low-smoke, Class A flame retardancy, thin wall thickness, and lightweight design.

[0032] Figure 1 A first embodiment of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention is shown. See also Figure 1 In the first embodiment of the present invention, the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable 100 comprises, from the inside out, a cable core 110, a core wrapping layer 120, a shielding layer 130, and an outer sheath layer 160. The various layers of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable 100 will be described in detail below.

[0033] The cable core 110, as the core component for transmitting electrical energy, includes filler material 111 and silane-crosslinked polyethylene insulated single wires 112. For example... Figure 1 As shown, the cable core 110 is formed by stranding six silane cross-linked polyethylene insulated single wires 112, with filler material 111 filling the gaps formed by the stranded silane cross-linked polyethylene insulated single wires 112. The filler material 111 is composed of non-hygroscopic flame-retardant filler rope to ensure the roundness of the cable core 110. The silane cross-linked polyethylene insulated single wire 112 consists of a conductor 1121 and a silane cross-linked polyethylene insulation layer 1122 extruded onto the conductor 1121. The conductor can be formed by stranding multiple strands of soft round copper wire. The silane cross-linked polyethylene insulation layer 1122 comprises a mixture of silane cross-linked polyethylene graft A material and silane cross-linking catalyst masterbatch B in a mass ratio of 95:5. As an example, the silane cross-linked polyethylene insulation layer 1122 is formed by mixing silane cross-linked polyethylene graft A material and silane cross-linking catalyst masterbatch B material in a 95:5 ratio, extruding it onto the conductor, and then steaming it in a steam oven at 60-70°C for 3-4 hours. The minimum median tensile strength of the obtained silane cross-linked polyethylene insulation layer 1122 is 18 N / mm. 2 The minimum median elongation at break is 400%. Furthermore, the silane cross-linked polyethylene insulation layer 1122 on the outer side of conductor 1121 prevents leakage and forms an isolating "safety barrier," ensuring that current flows only within the conductor. In addition, silane cross-linked polyethylene has the characteristics of low production cost, high insulation resistance, high breakdown strength, and excellent mechanical properties.

[0034] The cable core wrapping layer 120 consists of two overlapping layers of polyester film wrapped around the cable core 110 to secure the stranded silane cross-linked polyethylene insulated single wires 112 within the cable core 110. This prevents the stranded silane cross-linked polyethylene insulated single wires 112 from loosening or misaligning during bending, movement, or processing of the cable core 110. Furthermore, the cable core wrapping layer 120 also helps maintain the cross-section of the cable core 110 as circular or near-circular, facilitating subsequent processes such as sheathing and armoring, and simplifying on-site installation.

[0035] As an example, the polyester film of the cable core sheath layer 120 is 30 The polyester film is wrapped around the outer wall of cable core 110 at a 45° angle, with an overlap of 30%. 50%, with two layers of wrapping; the first layer is wrapped to the left on the outside of the cable core 110, and the second layer is wrapped to the right on the outer wall of the first layer. The double layers of polyester film are wrapped in opposite directions on the outer wall of the cable core 110, making the cross-section of the cable core round and tight, not easy to loosen, and enhancing the reliability of the cable.

[0036] The shielding layer 130, acting as an "electromagnetic shield" to resist interference, is located on the outer periphery of the cable core wrapping layer 120. The shielding layer 130 can be formed by overlapping soft copper tape or braiding soft round copper wire, thereby reducing internal and external electromagnetic interference.

[0037] The outer sheath layer 160 is disposed on the outer periphery of the shielding layer 130. As a "robust armor" against external forces, the outer sheath layer 160 protects the internal structure of the cable from mechanical, chemical, and environmental damage. Furthermore, the outer sheath layer 160 is made of halogen-free, low-smoke, flame-retardant polyolefin sheath material. This material possesses excellent processing performance and high flame retardancy. In this embodiment, the halogen-free, low-smoke, flame-retardant polyolefin sheath material comprises a modified inorganic flame-retardant composite material composed of modified aluminum hydroxide, modified magnesium hydroxide, and modified montmorillonite, thereby giving it high flame-retardant properties and an oxygen index of not less than 38. This ensures the cable's Class A bundled high flame retardancy, resulting in an outer sheath layer 160 with excellent mechanical properties, halogen-free properties, oil resistance, low smoke, Class A flame retardancy, thin wall thickness, and lightweight properties.

[0038] Specifically, the halogen-free, low-smoke, flame-retardant polyolefin sheathing material is composed of the following raw materials in parts by weight: 18-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 3-10 parts compatibilizer, 17-25 parts silane coupling agent modified aluminum hydroxide, 25-35 parts fluorinated surfactant modified magnesium hydroxide, 5-10 parts fluorinated compound activated montmorillonite, 0.3-4 parts black masterbatch, 0.5-5 parts silicone masterbatch, and 0.2-3 parts polyethylene wax. The fluorinated surfactant is selected from at least one of perfluorooctanoic acid, perfluorooctane sulfonic acid, and perfluorohexanoic acid, and the metallocene PE is Exceed PE purchased from ExxonMobil. TMFlow m1020.RA.

[0039] In halogen-free, low-smoke flame-retardant polyolefin sheathing materials, silane coupling agent-modified aluminum hydroxide significantly improves interfacial compatibility with the resin matrix, enhancing mechanical properties while reducing hygroscopicity and maintaining dehydration and flame-retardant function. Fluorinated surfactant-modified magnesium hydroxide achieves extremely low hygroscopicity and excellent anti-agglomeration properties through its superhydrophobic surface, significantly improving processing flowability. Simultaneously, it enhances flame-retardant and smoke-suppressing effects through free radical capture and charring. Furthermore, in fluorinated compound-activated montmorillonite, the excellent properties of fluorine (such as extremely low surface energy, excellent weather resistance, and chemical resistance) are combined with the nano-reinforcing effect of montmorillonite, significantly improving the flame-retardant efficiency of magnesium-aluminum flame retardants and reducing smoke density. It also exhibits better charring and anti-dripping effects, reducing heat release. Therefore, the halogen-free, low-smoke flame-retardant polyolefin sheathing material achieves good charring and anti-dripping performance, resulting in high flame-retardant performance.

[0040] As an example, a method for preparing magnesium hydroxide modified with a fluorinated surfactant includes: adding nanosheet magnesium hydroxide prepared by a hydrothermal method to deionized water, heating to 40-60°C and stirring for a period of time to obtain a magnesium hydroxide dispersion; adding a fluorinated surfactant to the magnesium hydroxide dispersion and reacting to obtain a reactant mixture; continuing to stir the reactant mixture at 60°C for 5 hours to ensure that the fluorinated segments are fully coated on the surface of the magnesium hydroxide to obtain a reaction product; and drying the reaction product in a 60°C oven at a constant temperature for 24 hours to obtain the modified magnesium hydroxide.

[0041] Furthermore, in the silane coupling agent modified aluminum hydroxide, the silane coupling agent can be a KH-550 type silane coupling agent.

[0042] In addition, metallocene PE uses Exceed PE purchased from Exxon. TM Flow m 1020.RA. Compared to the commonly used Exxon 3518CB, Exceed TM Finished products made from Flow m 1020.RA have a soft feel, reduced actual hardness, better processing performance, higher crack resistance, and also reduce the risk of cracking in finished cables.

[0043] As an example, a method for preparing halogen-free, low-smoke, flame-retardant polyolefin sheathing materials may include: S1. Add ethylene-vinyl acetate resin, metallocene PE, compatibilizer, fluorinated surfactant-modified magnesium hydroxide (60%), and silane coupling agent-modified aluminum hydroxide (60%) to the main feed port of a Φ75 twin-screw mixer for mixing. S2. Add 40% magnesium hydroxide modified with fluorinated surfactant, 40% aluminum hydroxide modified with silane coupling agent, montmorillonite modified with fluorinated compound, black masterbatch, silicone masterbatch, and a mixture of polyethylene wax to the auxiliary feed port of a Φ75 twin-screw mixer. Under conditions of 105-160℃ and a mixing speed of 5-20Hz, thoroughly mix using the Φ75 twin-screw mixer to obtain a uniformly mixed compound. This ensures that the inorganic powders and resin in the formulation are fully mixed, thereby guaranteeing the uniformity and consistency of the formulation. S3. Then, the material is extruded and granulated at a temperature of 100-170℃ using a Φ200 single screw extruder at a production speed of 15Hz-30Hz to obtain 3mm×3mm cylindrical halogen-free low-smoke flame-retardant sheath material granules, resulting in halogen-free low-smoke flame-retardant polyolefin sheaths with an oxygen index ≥38, tensile strength ≥18MPa, and elongation at break ≥200%.

[0044] The outer sheath layer 160 is extruded using the prepared halogen-free, low-smoke, flame-retardant polyolefin sheath material, and the thickness of the outer sheath layer 160 can be 1.8-2.3 mm.

[0045] The resulting halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable has a char height of ≤1.0m when burned in a bundle. It has advantages such as excellent overall flame retardant performance, simple structure, small bending radius, easy installation and use, low production cost, and simple production process.

[0046] Figure 2 This is a schematic diagram of a second embodiment of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable of the present invention. Since in the following description, [the following text is incomplete and likely refers to...]. Figure 1 The examples mentioned in the description will be understood as independent inventions; therefore, although the same configuration is mentioned, they will be understood as different technical features. However, no further... Figure 1 The repeated concepts of similar components mentioned in the description will be elaborated upon here.

[0047] See Figure 2 In the second embodiment of the present invention, the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable 100 comprises, from the inside out, a cable core 110, a core wrapping layer 120, a shielding layer 130, an inner liner layer 140, an armor layer 150, and an outer sheath layer 160. The inner liner layer 140 and the armor layer 150 of the halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable 100 will be described in detail below.

[0048] The inner lining layer 140, serving as the inner sheath of the armored cable, is disposed around the outer periphery of the shielding layer 130 and inside the armoring layer 150. This prevents damage to the shielding layer from the armoring layer and provides functions such as moisture protection, corrosion prevention, and electrical isolation. The inner lining layer 140 is made of halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler. This filler isolates oxygen from the cable core, preventing the flame from spreading inward and thus improving the cable's flame-retardant performance. In this embodiment, a composite flame retardant composed of aluminum hydroxide and magnesium hydroxide is added to the halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler, giving it high flame-retardant properties and an oxygen index of not less than 40, further ensuring the cable's Class A bundled high flame retardancy.

[0049] Specifically, the halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler is composed of the following raw materials in parts by weight: 15-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 5-10 parts compatibilizer, 18-25 parts aluminum hydroxide, 28-36 parts magnesium hydroxide, 0.5-4 parts black masterbatch, 0.3-2 parts silane coupling agent, 0.9-3 parts silicone masterbatch, and 0.8-2 parts polyethylene wax.

[0050] The inner liner 140 is extruded using the above-mentioned halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler, and the thickness of the inner liner 140 can be 1.0-1.2 mm.

[0051] To protect the cable's structural integrity and electrical performance, and to extend its service life, an armor layer 150 is wrapped around the outer wall of the inner liner 140 to provide mechanical protection when the cable is bent. The armor layer 150 is made of galvanized steel tape or steel wire armor. Armored cables exhibit good mechanical properties, tensile strength, and compressive strength, and high strength, thus protecting the internal structure and ensuring its integrity. Furthermore, in this embodiment, steel wire armor is preferred. Compared to conventional steel tape armor, using a steel wire mesh as the armor layer provides both high protective performance and good flexibility, facilitating cable laying and meeting the requirements for cable installation in confined spaces.

[0052] The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cables of the first and second embodiments of the present invention reduce redundant structures outside the cable core without changing the internal structure of the cable core, and feature high flame retardancy, thin walls, and lightweight characteristics. Furthermore, the halogen-free, low-smoke, flame-retardant polyolefin sheath material of the present invention has excellent extrusion performance, ensuring that the cable can pass the Class A flame-retardant bundled burning test, with the char height of the bundled burning not exceeding 1 meter. The outer sheath layer can pass the 8kg crack resistance test, meeting the design concept of small outer diameter, light weight, and flexible laying of control cables. The overall structure is simple, production efficiency is high, cost is low, and bundled flame-retardant performance is good.

[0053] Furthermore, the inventors prepared halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cables with the following specifications: WDZA-KYJYP2-23 450 / 750V 37×1.5(B), WDZA-KYJYP2 450 / 750V 37×1.5(B), and WDZA-KYJYP2450 / 750V 8×1.5(B), according to the structures of the first and second embodiments described above. The mechanical properties of these halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cables were tested according to GB / T 9330-2020, and the results are shown in Table 1. Furthermore, the bundled combustion performance of these halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cables was tested according to GB / T 19666-2019, and the results are shown in Table 2 and... Figure 3 As shown.

[0054] Table 1

[0055] Table 2

[0056] As can be seen from Tables 1 and 2 above, the halogen-free, low-smoke, flame-retardant polyolefin sheath material and cable structure of the present invention produce halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cables with excellent sheath mechanical properties and can ensure that the cables pass the Class A bundled burning test. Further, see... Figure 3 It can be seen that the carbonization height of the cable bundled Class A test does not exceed 1.0m, which meets the requirements of GB / T19666-2019 standard.

[0057] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable, characterized in that, From the inside out, it includes a cable core, a core wrapping layer, a shielding layer, and an outer sheath layer, wherein the outer sheath layer is made of halogen-free, low-smoke, flame-retardant polyolefin sheath material. The halogen-free, low-smoke, flame-retardant polyolefin sheath material is composed of the following raw materials in parts by weight: 18-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 3-10 parts compatibilizer, 17-25 parts silane coupling agent modified aluminum hydroxide, 25-35 parts fluorinated surfactant modified magnesium hydroxide, 5-10 parts fluorinated compound activated montmorillonite, 0.3-4 parts black masterbatch, 0.5-5 parts silicone masterbatch, and 0.2-3 parts polyethylene wax. The fluorinated surfactant is selected from at least one of perfluorooctanoic acid, perfluorooctane sulfonic acid, and perfluorohexanoic acid, and the metallocene PE is Exceed PE purchased from Exxon. TM Flow m 1020.RA.

2. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable also includes: An inner liner layer, wherein the inner liner layer is disposed on the outer periphery of the shielding layer and is made of a halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler with an oxygen index ≥40; and An armor layer, disposed between the inner liner and the outer sheath, and comprising at least one of galvanized steel strip armor and steel wire armor. The thickness of the inner lining layer is 1.0-1.2 mm.

3. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 2, characterized in that, The halogen-free, low-smoke, flame-retardant, and oxygen-barrier filler is composed of the following raw materials in parts by weight: 15-25 parts ethylene-vinyl acetate resin, 6-12 parts metallocene PE, 5-10 parts compatibilizer, 18-25 parts aluminum hydroxide, 28-36 parts magnesium hydroxide, 0.5-4 parts black masterbatch, 0.3-2 parts silane coupling agent, 0.9-3 parts silicone masterbatch, and 0.8-2 parts polyethylene wax.

4. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The cable core includes a filler material and a silane cross-linked polyethylene insulated single wire, wherein the silane cross-linked polyethylene insulated single wire consists of a conductor and a silane cross-linked polyethylene insulation layer extruded on the conductor.

5. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 4, characterized in that, The conductor is made of multiple strands of soft, round copper wire twisted together, and The silane cross-linked polyethylene insulation layer comprises a mixture of silane cross-linked polyethylene graft material A and silane cross-linking catalyst masterbatch B in a mass ratio of 95:5, and the minimum median tensile strength of the silane cross-linked polyethylene insulation layer is 18 N / mm². 2 The minimum median value of elongation at break is 400%.

6. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 4, characterized in that, The filling material is a non-hygroscopic flame-retardant filling rope.

7. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The cable core is formed by twisting multiple cross-linked polyethylene insulated single wires together with filler material.

8. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The thickness of the outer sheath layer is 1.8-2.3 mm.

9. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The halogen-free, low-smoke, flame-retardant polyolefin sheath material has an oxygen index ≥38, a tensile strength ≥18MPa, and an elongation at break ≥200%.

10. The halogen-free, low-smoke, flame-retardant Class A cross-linked polyethylene insulated control cable according to claim 1, characterized in that, The bundled combustion carbonization height of the insulated control cable is ≤1.0m.

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