Low smoke zero halogen flame retardant control cable

Abstract

The application relates to the cable technical field and discloses a low-smoke halogen-free flame-retardant control cable which comprises, from inside to outside, a conductor, an insulation layer, a shielding layer and a sheath layer; the sheath layer is prepared from the following components in parts by weight: linear low-density polyethylene 60-80 parts, ethylene-acrylate copolymer 20-25 parts, a compatibilizer 8-12 parts, a composite flame retardant 10-15 parts, an initiator 0.3-0.5 parts, a lubricant 1-3 parts and an antioxidant 1-1.5 parts; the composite flame retardant comprises, from inside to outside, kaolin, a phosphatized chitosan coating layer and a composite aerogel layer; the raw materials of the composite aerogel layer comprise sodium phytate, sodium alginate and polyvinyl alcohol in a mass ratio of 0.3-0.7:2:10. Through the technical scheme, the problem of poor flame-retardant performance of the sheath layer of the control cable in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and more specifically, to a low-smoke, halogen-free, flame-retardant control cable. Background Technology

[0002] Control cables are indispensable key components in power systems, industrial automation control, building power distribution, rail transportation, and various electrical equipment. They are primarily used to transmit control signals, monitoring signals, and small amounts of electricity. Their stability and safety directly affect the normal operation of the entire electrical system. Control cables are widely used in factories, mines, high-rise buildings, rail transportation, ships, aerospace, and many other important fields. Their safety performance is particularly critical in scenarios with dense populations, precision equipment, or high environmental requirements. Therefore, improving the flame-retardant properties of control cables is of great significance for ensuring the safety of electrical systems and reducing fire hazards.

[0003] In existing technologies, to improve the flame-retardant effect of control cables, the cable sheath layer often uses halogen-containing polymer materials such as polyvinyl chloride as the base material. Although these halogen-containing sheath materials can prevent the spread of flames to a certain extent and possess certain flame-retardant properties, they release a large amount of toxic and corrosive gases during combustion, while also producing dense black smoke. These toxic and harmful gases not only cause serious damage to the human respiratory system but also corrode surrounding electrical equipment and metal components, exacerbating secondary hazards after a fire and posing significant difficulties for personnel evacuation and fire fighting, which does not meet the modern environmental protection and safety development requirements. Therefore, there is a need to propose a low-smoke halogen-free flame-retardant control cable. Summary of the Invention

[0004] This invention proposes a low-smoke, halogen-free, flame-retardant control cable, which solves the problem of poor flame-retardant performance of the sheath layer in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a low-smoke halogen-free flame-retardant control cable, comprising, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60-80 parts of linear low-density polyethylene, 20-25 parts of ethylene-acrylate copolymer, 8-12 parts of compatibilizer, 10-15 parts of composite flame retardant, 0.3-0.5 parts of initiator, 1-3 parts of lubricant, and 1-1.5 parts of antioxidant; The composite flame retardant comprises, from the inside out, kaolin, a phosphorylated chitosan coating layer, and a composite aerogel layer; The raw materials for the composite aerogel layer include sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3~0.7:2:10.

[0006] As a further technical solution, the preparation method of the composite flame retardant includes the following steps: A1. After mixing chitosan, urea and phosphoric acid aqueous solution, the mixture is filtered, washed and dried to obtain phosphorylated chitosan; A2. Disperse kaolin in water, add the phosphorylated chitosan and mix, then filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; A3. Sodium phytate, sodium alginate and polyvinyl alcohol are dispersed in water to obtain a gel; phosphorylated chitosan-coated kaolin is dispersed in water, and the gel is added and mixed. After molding and freeze-drying, a composite aerogel layer is formed to obtain the composite flame retardant.

[0007] As a further technical solution, in step A1, the mass ratio of chitosan to urea is 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution is 1g:50mL; and the mass fraction of phosphoric acid aqueous solution is 85%.

[0008] As a further technical solution, in step A1, the mixing temperature is 110~130℃ and the mixing time is 2.5~3.5h.

[0009] As a further technical solution, in step A2, the mass ratio of kaolin to phosphorylated chitosan is 4~5:2, preferably 5:2.

[0010] As a further technical solution, in step A2, the mass-to-volume ratio of kaolin to water is 1g:15~20mL.

[0011] As a further technical solution, in step A2, the mixing temperature is 65~75℃ and the mixing time is 8~10h.

[0012] As a further technical solution, in step A3, the mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to the volume ratio of water is 1g:30mL.

[0013] As a further technical solution, in step A3, the total mass of sodium phytate, sodium alginate and polyvinyl alcohol is 25% to 35% of the mass of kaolin, preferably 30%.

[0014] As a further technical solution, in step A3, the mixing temperature is 90~95℃ and the mixing time is 3.5~4.5h.

[0015] As a further technical solution, in step A3, the freeze-drying temperature is -65~-55℃, the pressure is 0.8~1.2Pa, and the time is 35~40h.

[0016] As a further technical solution, the ethylene-acrylate copolymer includes ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer.

[0017] As a further technical solution, the mass ratio of the ethylene-methyl acrylate copolymer to the ethylene-butyl acrylate copolymer is 5~7:1, preferably 6:1.

[0018] This invention improves the tensile strength of the sheath layer by limiting the mass ratio of ethylene-methyl acrylate copolymer to ethylene-butyl acrylate copolymer to 5-7:1. The ethylene-methyl acrylate copolymer has moderate main chain flexibility and good polarity, making it compatible with the polyethylene matrix and effectively enhancing the interfacial bonding force of the system. The ethylene-butyl acrylate copolymer has longer side chains and stronger internal plasticizing effect; adding a small amount can improve processing fluidity. Controlling the ratio of the two at 5-7:1 ensures compatibility and structural strength with the matrix through the ethylene-methyl acrylate copolymer, while optimizing processing performance with a small amount of ethylene-butyl acrylate copolymer. This avoids the problems of over-plasticization or insufficient compatibility of the single acrylate copolymer, resulting in a more uniform molecular chain arrangement and more efficient interfacial stress transfer in the sheath layer, thereby improving the tensile strength of the sheath layer.

[0019] As a further technical solution, the initiator includes one or both of dicumyl peroxide and tert-butyl peroxide.

[0020] As a further technical solution, the lubricant includes one or more of zinc stearate, calcium stearate, and polyethylene wax.

[0021] As a further technical solution, the antioxidant includes one or more of antioxidant 1010, antioxidant 168 and antioxidant 1076.

[0022] As a further technical solution, the compatibilizer is maleic anhydride-grafted polyethylene.

[0023] This invention also proposes a method for preparing a low-smoke halogen-free flame-retardant control cable, comprising the following steps: S1. Extruding insulating material onto the outside of the conductor to form an insulating layer; S2. Wrap the shielding layer material around the outside of the insulating layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form a sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0024] As a further technical solution, the conductor is a copper conductor, the insulating layer material is polyethylene, and the shielding layer material is aluminum-plastic composite tape.

[0025] The working principle and beneficial effects of this invention are as follows: This invention improves the flame-retardant performance of the control cable sheath by adding a composite flame retardant consisting of kaolin, a phosphorylated chitosan coating layer, and a composite aerogel layer, arranged sequentially from the inside out. The composite flame retardant coats the kaolin with phosphorylated chitosan, and then combines it with sodium phytate, sodium alginate, and polyvinyl alcohol to construct a porous composite aerogel structure. On one hand, the phosphate groups and chitosan can dehydrate and char at high temperatures, inhibiting the spread of combustion; the kaolin forms a dense barrier layer to isolate heat and oxygen; on the other hand, the porous structure of the aerogel further slows down heat transfer and adsorbs combustible gases. The synergistic effect of these components enhances the flame-retardant performance of the control cable sheath. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] In the following examples and comparative examples, linear low-density polyethylene (LDPE) is model CB9270; maleic anhydride-grafted polyethylene (GMPE) is model FT900E; polyethylene wax is model AC-6A; kaolin has a particle size of 1 μm; cross-linked polyethylene is model T3XL7420; ethylene-methyl acrylate copolymer is model HP441; ethylene-butyl acrylate copolymer is model 3117 AC; chitosan has a degree of deacetylation of 70%; and polyvinyl alcohol is model 18-88.

[0028] Example 1 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0029] Example 2 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 70 parts linear low-density polyethylene, 23 parts ethylene-methyl acrylate copolymer, 10 parts maleic anhydride grafted polyethylene, 13 parts composite flame retardant, 0.4 parts tert-butyl cumene peroxide, 2 parts calcium stearate, and 1.2 parts antioxidant 168; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 120℃ for 3h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 70℃ for 9 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:18mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 93°C for 4 hours, the mixture was shaped and then freeze-dried at -60°C and 1 Pa for 38 hours to obtain a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL. The total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0030] Example 3 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 80 parts linear low-density polyethylene, 25 parts ethylene-methyl acrylate copolymer, 12 parts maleic anhydride grafted polyethylene, 15 parts composite flame retardant, 0.5 parts dicumyl peroxide, 3 parts polyethylene wax, and 10761.5 parts antioxidant. The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 130℃ for 2.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 75℃ for 8 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:20mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 95°C for 3.5 hours, the mixture was shaped and then freeze-dried at -55°C and 1.2 Pa for 40 hours to obtain a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL. The total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0031] Example 4 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.5:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0032] Example 5 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.7:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0033] Example 6 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-acrylate copolymer, 8 parts maleic anhydride-grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; the ethylene-acrylate copolymer is composed of ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer in a mass ratio of 5:1; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0034] Example 7 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-acrylate copolymer, 8 parts maleic anhydride-grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; the ethylene-acrylate copolymer is composed of ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer in a mass ratio of 6:1; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0035] Example 8 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-acrylate copolymer, 8 parts maleic anhydride-grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; the ethylene-acrylate copolymer is composed of ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer in a mass ratio of 7:1; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0036] Example 9 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-butyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A3. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Phosphorylated chitosan-coated kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer, thus obtaining a composite flame retardant. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL; the total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0037] Comparative Example 1 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Disperse kaolin in water, add phosphorylated chitosan, mix at 65℃ for 10 hours, filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain a composite flame retardant; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0038] Comparative Example 2 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts composite flame retardant, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; The preparation method of the composite flame retardant includes the following steps: A1. Chitosan, urea and 85wt% phosphoric acid aqueous solution were mixed at 110℃ for 3.5h, and then filtered, washed and dried to obtain phosphorylated chitosan; the mass ratio of chitosan to urea was 1:5; the mass-volume ratio of chitosan to phosphoric acid aqueous solution was 1g:50mL. A2. Sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3:2:10 were dispersed in water to obtain a gel. Kaolin was dispersed in water, and the gel was added. After mixing at 90°C for 4.5 hours, the mixture was shaped and then freeze-dried at -65°C and 0.8 Pa for 35 hours to form a composite aerogel layer. The composite aerogel layer coating kaolin was obtained. The mass ratio of sodium phytate, sodium alginate, and polyvinyl alcohol to water was 1 g:30 mL. The total mass of sodium phytate, sodium alginate, and polyvinyl alcohol was 30% of the mass of kaolin. A3. The composite aerogel layer coated with kaolin is dispersed in water, phosphorylated chitosan is added, and after mixing at 65℃ for 10 hours, it is filtered, washed and dried to form a phosphorylated chitosan coating layer, thus obtaining a composite flame retardant; the mass ratio of kaolin to phosphorylated chitosan is 5:2; the mass-volume ratio of kaolin to water is 1g:15mL. A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0039] Comparative Example 3 A low-smoke halogen-free flame-retardant control cable comprises, from the inside out, a conductor, an insulation layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60 parts linear low-density polyethylene, 20 parts ethylene-methyl acrylate copolymer, 8 parts maleic anhydride grafted polyethylene, 10 parts kaolin, 0.3 parts dicumyl peroxide, 1 part zinc stearate, and 1 part antioxidant 1010; A method for preparing a low-smoke halogen-free flame-retardant control cable includes the following steps: S1. Cross-linked polyethylene is extruded onto the outside of the copper conductor to form an insulating layer; S2. Wrap the aluminum-plastic composite tape around the outside of the insulation layer to form a shielding layer; S3. After mixing the raw materials for the sheath layer, extrude them onto the outside of the shielding layer to form the sheath layer, thus obtaining a low-smoke halogen-free flame-retardant control cable.

[0040] Experimental Example 1 The sheaths of the low-smoke halogen-free flame-retardant control cables prepared in Examples 1-5 and Comparative Examples 1-3 were tested for oxygen index according to standard GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test". The sample type was I, and the ignition method was A. The average of the results of three samples in each group was taken as the final result, and the results were rounded to one decimal place. The test results are shown in Table 1. Table 1. Test results of oxygen index of sheath layer of low-smoke halogen-free flame-retardant control cable

[0041] The results in Table 1 show that by adding a composite flame retardant consisting of kaolin, a phosphorylated chitosan coating layer, and a composite aerogel layer from the inside out to the sheath layer of the control cable, the present invention can improve the flame retardant effect of the sheath layer of the low-smoke halogen-free flame-retardant control cable.

[0042] Experiment Example 2 Referring to the methods in GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods - Thickness and Dimensional Measurement - Mechanical Properties Test", the sheath layers of the low-smoke halogen-free flame-retardant control cables prepared in Examples 1, 6-9 were made into dumbbell specimens with a thickness of 2 mm for tensile strength testing; the total spacing between the clamps was 34 mm, and the clamp moving speed was 25 mm / min; the test results are shown in Table 2. Table 2. Test results of tensile strength of sheath layer of low-smoke halogen-free flame-retardant control cable

[0043] The results in Table 2 show that when the ethylene-acrylate copolymer in the sheath of the control cable is composed of ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer, the tensile strength of the sheath of the low-smoke halogen-free flame-retardant control cable can be improved.

[0044] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low smoke, halogen-free, flame-retardant control cable, characterized in that, From the inside out, it includes a conductor, an insulating layer, a shielding layer, and a sheath layer; the sheath layer comprises the following raw materials in parts by weight: 60-80 parts linear low-density polyethylene, 20-25 parts ethylene-acrylate copolymer, 8-12 parts compatibilizer, 10-15 parts composite flame retardant, 0.3-0.5 parts initiator, 1-3 parts lubricant, and 1-1.5 parts antioxidant; The composite flame retardant comprises, from the inside out, kaolin, a phosphorylated chitosan coating layer, and a composite aerogel layer; The raw materials for the composite aerogel layer include sodium phytate, sodium alginate, and polyvinyl alcohol in a mass ratio of 0.3~0.7:2:

10.

2. The low-smoke halogen-free flame-retardant control cable according to claim 1, characterized in that, The preparation method of the composite flame retardant includes the following steps: A1. After mixing chitosan, urea and phosphoric acid aqueous solution, the mixture is filtered, washed and dried to obtain phosphorylated chitosan; A2. Disperse kaolin in water, add the phosphorylated chitosan and mix, then filter, wash and dry to form a phosphorylated chitosan coating layer, and obtain phosphorylated chitosan coated kaolin; A3. Sodium phytate, sodium alginate and polyvinyl alcohol are dispersed in water to obtain a gel; phosphorylated chitosan-coated kaolin is dispersed in water, and the gel is added and mixed. After molding and freeze-drying, a composite aerogel layer is formed to obtain the composite flame retardant.

3. The low-smoke halogen-free flame-retardant control cable according to claim 2, characterized in that, In step A2, the mass ratio of kaolin to phosphorylated chitosan is 4~5:

2.

4. The low-smoke halogen-free flame-retardant control cable according to claim 2, characterized in that, In step A3, the mixing temperature is 90~95℃ and the mixing time is 3.5~4.5h.

5. A low-smoke halogen-free flame-retardant control cable according to claim 2, characterized in that, In step A3, the freeze-drying temperature is -65~-55℃, the pressure is 0.8~1.2Pa, and the time is 35~40h.

6. The low-smoke halogen-free flame-retardant control cable according to claim 1, characterized in that, The ethylene-acrylate copolymers include ethylene-methyl acrylate copolymers and ethylene-butyl acrylate copolymers.

7. A low-smoke halogen-free flame-retardant control cable according to claim 6, characterized in that, The mass ratio of the ethylene-methyl acrylate copolymer to the ethylene-butyl acrylate copolymer is 5~7:

1.

8. The low-smoke halogen-free flame-retardant control cable according to claim 1, characterized in that, The initiator includes one or both of dicumyl peroxide and tert-butyl peroxide.

9. A low-smoke halogen-free flame-retardant control cable according to claim 1, characterized in that, The lubricant includes one or more of zinc stearate, calcium stearate, and polyethylene wax.

10. A low-smoke halogen-free flame-retardant control cable according to claim 1, characterized in that, The antioxidant includes one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076.

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