Thin-wall photovoltaic cable halogen-free flame-retardant insulating material, preparation method and photovoltaic cable

Abstract

This invention discloses a halogen-free flame-retardant insulating material for thin-walled photovoltaic cables, its preparation method, and the thin-walled photovoltaic cable itself, belonging to the field of polymer materials technology. The preparation method of the halogen-free flame-retardant insulating material for thin-walled photovoltaic cables includes: step S1, preparing double-crosslinked cable material A; step S2, preparing double-crosslinked cable material B; and step S3, mixing double-crosslinked cable material A and double-crosslinked cable material B in a specific ratio. The preparation method of the halogen-free flame-retardant insulating material for thin-walled photovoltaic cables in this invention is simple to operate and has high production efficiency. The flame retardant powder surface is double-coated with stearic acid and silane. During use, the initial self-crosslinking of silane gives the material a preliminary crosslinking network, and the subsequent irradiation crosslinking perfects the three-dimensional network structure of the material, improving the uniformity of the microstructure. The resulting halogen-free flame-retardant insulating material for thin-walled photovoltaic cables exhibits excellent mechanical properties, electrical properties, flame retardant properties, low smoke performance, weather resistance and aging resistance, acid and alkali resistance, and cut-through resistance.

Description

Technical Field

[0001] This invention application relates to the field of polymer materials technology, specifically to halogen-free flame-retardant insulation material for thin-walled photovoltaic cables, preparation method, and photovoltaic cables. Background Technology

[0002] Photovoltaic cables operate in harsh environments. Their overall structure consists of a conductor, insulation, and sheath. While the structure itself isn't complex, the performance requirements are high. Therefore, to ensure these performance requirements, the insulation materials used in photovoltaic cables on the market must have sufficient sheath thickness for stable use. The 4mm² insulation material, which is the most widely used in the domestic and international photovoltaic power generation market, is an example. 2 For products of similar specifications, the average insulation layer thickness is no less than 0.8mm. If the insulation layer thickness can be reduced by improving material performance without increasing material costs, the cable cost can be significantly reduced. For thin-walled photovoltaic cables, the insulation layer thickness is controlled at 0.5-0.6mm. Compared with conventional products, the insulation layer thickness of thin-walled photovoltaic cables can be reduced by more than 25%. Although this can significantly reduce cable costs, it places higher demands on the electrical insulation performance, flame retardant performance, high-temperature aging performance, low-temperature resistance, acid and alkali resistance, cut-through resistance, and extrusion processing performance of the insulation material.

[0003] Currently, there are two types of photovoltaic cable insulation materials on the market: 1) Irradiation cross-linked photovoltaic insulation materials. This type of material has a mature process, but its efficiency is low and its energy consumption is high. Photovoltaic cables basically adopt a single irradiation process, that is, after the insulation extrusion is completed, the sheath is extruded, and after the sheath extrusion is completed, irradiation cross-linking is performed. The problem arising from this is that if the cross-linking degree of the insulation layer is to be guaranteed so that it has qualified thermal elongation, a high irradiation dose is required. However, a high irradiation dose not only consumes more energy and time, but is also more likely to cause over-cross-linking of the sheath layer, affecting the sheath performance. At the same time, a high irradiation dose will also cause the risk of electron residue in the insulation due to the increased number of electrons, thus affecting the insulation performance of the cable. 2) Silane cross-linked photovoltaic insulation materials. This type of material does not require irradiation equipment and is mainly used in some areas where irradiation equipment is limited. Although the overall cost is reduced, the cross-linking stability is low, and the product quality is easily substandard due to insufficient cross-linking degree or uneven cross-linking.

[0004] For thin-walled photovoltaic cables, the performance requirements resulting from the thinner insulation layer cannot be met by currently available materials. This is primarily because the thinner insulation layer significantly reduces the cable's electrical properties (including insulation resistance, long-term DC stability), single-strand vertical combustion performance, and light transmittance. Furthermore, the cables face harsh environments such as high temperature and humidity, acids and alkalis, and low temperatures during use; the thinner insulation layer accelerates damage and affects the cable's lifespan. Additionally, during high-speed extrusion, the thinner insulation layer makes it difficult to control the cable's eccentricity and roundness. Therefore, these products require insulation materials with excellent extrusion processing properties, including low extrusion pressure, stable adhesive yield, and a smooth surface.

[0005] The dynamic puncture performance of photovoltaic cables is directly affected by the sheath thickness, in addition to the material itself. Thin-walled photovoltaic cables experience a significant decrease in dynamic puncture performance due to the reduced sheath thickness, which is a major reason why currently available materials cannot meet the requirements for thin-walled photovoltaic cables. The compound base material system adopted in this invention provides multiple supports in terms of material toughness, molecular weight, and crystallinity, thereby ensuring the dynamic puncture performance of thin-walled photovoltaic cables.

[0006] In view of the defects and deficiencies of the prior art, this invention application provides a halogen-free flame-retardant insulating material for thin-walled photovoltaic cables, a preparation method thereof, and a photovoltaic cable. Summary of the Invention

[0007] This invention provides a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables, a preparation method thereof, and the photovoltaic cable itself. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables possesses excellent mechanical properties, electrical properties, flame-retardant properties, low smoke performance, weather resistance and aging resistance, acid and alkali resistance, cut-through resistance, and good processing performance, meeting the various requirements of thin-walled photovoltaic cables. Furthermore, the preparation method of the halogen-free flame-retardant insulation material for thin-walled photovoltaic cables in this invention employs a double crosslinking process. Initially, silane self-crosslinking is used to establish a preliminary crosslinking network in the material. Later, irradiation crosslinking is used to perfect the three-dimensional network structure of the material, improving the uniformity of the microstructure and thus enhancing the material's various properties. This method emphasizes the uniformity and stability of the network structure after crosslinking, unlike existing methods that simply increase the irradiation crosslinking dosage. This ensures sufficient crosslinking degree while reducing irradiation energy consumption. More importantly, this double crosslinking method reduces the consumption of antioxidants and light stabilizers during crosslinking, lowers the structural damage to the material during irradiation crosslinking, reduces the risk of residual electrons within the insulation, and avoids the impact of over-crosslinking on sheath performance. The technical solution adopted in this invention is as follows:

[0008] Firstly, a halogen-free flame-retardant insulating material for thin-walled photovoltaic cables includes double cross-linked cable material A and double cross-linked cable material B.

[0009] The double cross-linked cable material A comprises the following raw material components in parts by weight: 8-15 parts of ethylene-ethyl acrylate copolymer; 1-5 parts of ethylene-glycidyl methacrylate-vinyl acetate terpolymer; 5-15 parts of ethylene-vinyl acetate copolymer; 8-15 parts of thermoplastic elastomer; 35-55 parts of polyethylene; 5-12 parts of maleic anhydride graft; 1-6 parts of silicone masterbatch; 60-100 parts of halogen-free flame retardant; 3-6 parts of organophosphorus flame retardant; 10-30 parts of modified filler; 1-2 parts of surface treatment agent; 1-4 parts of antioxidant; 0.5-1 part of light stabilizer; 0.4-1.8 parts of unsaturated silane cross-linking agent; 0.2-0.8 parts of silane cross-linking initiator; 0.5-1.5 parts of radiation cross-linking sensitizer; and 0.5-2.5 parts of lubricant.

[0010] The double cross-linked cable material B comprises the following raw material components in parts by weight: 8-15 parts of ethylene-ethyl acrylate copolymer, 1-5 parts of ethylene-glycidyl methacrylate-vinyl acetate terpolymer, 5-15 parts of ethylene-vinyl acetate copolymer, 8-15 parts of thermoplastic elastomer, 35-55 parts of polyethylene, 5-12 parts of maleic anhydride graft, 1-6 parts of silicone masterbatch, 60-100 parts of halogen-free flame retardant, 3-6 parts of organophosphorus flame retardant, 10-30 parts of modified filler, 1-2 parts of surface treatment agent, 1-4 parts of antioxidant, 0.5-1 part of light stabilizer, 0.3-2 parts of silane cross-linking catalyst, 0.5-1.5 parts of irradiated cross-linking sensitizer, and 0.5-2.5 parts of lubricant;

[0011] The flame retardant includes the halogen-free flame retardant and the organophosphorus flame retardant. By using a combination of halogen-free flame retardant (metal hydroxide) and organophosphorus flame retardant, the total amount of flame retardant added can be reduced, ensuring the basic physical and chemical properties of the material, such as mechanical properties, electrical properties, weather resistance, aging resistance, and acid and alkali resistance. At the same time, the material can also have good crusting properties and anti-dripping properties, thereby significantly increasing the flame retardant properties and light transmittance of the material.

[0012] The surface treatment agent includes stearic acid and a silane coupling agent;

[0013] The mass ratio of stearic acid to flame retardant is 1:200-1:150;

[0014] The mass ratio of the silane coupling agent to the flame retardant is 1:150 to 1:80.

[0015] Optionally, the ethylene-ethyl acrylate copolymer has a melt index of 0.5-1.5 g / 10 min; and the ethylene-ethyl acrylate copolymer contains 15% EA.

[0016] Optionally, the ethylene-glyceryl methacrylate-vinyl acetate terpolymer has a melt index of 1.5-4.5 g / 10 min; in some more preferred embodiments, the ethylene-glyceryl methacrylate-vinyl acetate terpolymer contains 12% GMA and 5% VA, and the ethylene-vinyl acetate copolymer has a melt index of (1.8-2.8) g / 10 min.

[0017] Optionally, the ethylene-vinyl acetate copolymer is a mixture of ethylene-vinyl acetate copolymers with VA content of 14% and VA content of 18%; in some preferred embodiments, the ethylene-vinyl acetate copolymer is a mixture of ethylene-vinyl acetate copolymers with VA content of 14% and VA content of 18% in a mass ratio of 3:1 to 2:1.

[0018] Optionally, the thermoplastic elastomer is POP with an α-olefin content of less than 20% and a melt index of (1.0-5.0) g / 10min. Using POP elastomer with an α-olefin content of less than 20% as a toughening agent, compared to traditional POE elastomer, results in a higher melting point. This not only provides the material with the necessary elastic coating but also maintains better stability at high temperatures. Especially for the 90℃ electrical performance test required for photovoltaic cables, POE, due to its lower melting point, easily reduces its protective effect, while POP effectively compensates for this deficiency.

[0019] Optionally, the polyethylene is a mixture of linear low-density polyethylene, ultra-low-density polyethylene and bimodal polyethylene; the linear low-density polyethylene has a melt index of (1.0-2.8) g / 10 min, the ultra-low-density polyethylene has a melt index of (1.5-10.0) g / 10 min, and the bimodal polyethylene has a melt index of (0.2-2.0) g / 10 min.

[0020] Optionally, linear low-density polyethylene, ultra-low-density polyethylene, and bimodal polyethylene in a mass ratio of 3:1:2 can further improve the mechanical properties, electrical insulation properties, dynamic cutting performance, heat resistance, and extrusion processing performance of the cable material.

[0021] In some preferred embodiments, the use of a blend of linear low-density polyethylene, ultra-low-density polyethylene and bimodal polyethylene can ensure the mechanical and electrical properties of the material. At the same time, ultra-low-density polyethylene has a lower extrusion pressure and better processing performance, which can provide the material with better processing applicability and increase the extrusion speed. The high molecular weight and high crystallinity of bimodal polyethylene not only improve the heat resistance of the material, but more importantly, it can improve the puncture resistance of the material.

[0022] Currently, the matrix material for photovoltaic cable insulation is basically EVA+PE, and the types are relatively limited. This combination cannot meet the various requirements of thin-walled photovoltaic insulation materials. This invention application uses a compound of ethylene copolymer E-GMA-VA and EEA with long side chain structure as auxiliary modifiers. EEA not only has a high melting point, but also has the highest toughness and flexibility among polyolefin resins. Compared with EVA, it has higher toughness and better thermal stability, which can provide the material with better heat resistance, low temperature resistance, and puncture resistance. At the same time, it improves the extrusion processing performance of the material, making the cable extrusion surface smoother and faster. E-GMA-VA is a terpolymer with high reactivity, which can improve the crosslinking efficiency in the later stage and provide support for a more stable network structure. At the same time, E-GMA-VA has high adhesion, which can better connect the effects between the components and improve the overall performance of the material. However, the amount added to this system should not be too high. Only a small amount is needed to achieve the desired effect. Too much addition will lead to a decrease in the electrical insulation performance of the material.

[0023] Optionally, the grafting rate of the maleic anhydride graft is 0.8%-1.2%;

[0024] Optionally, the maleic anhydride graft is a mixture of maleic anhydride-grafted LLDPE and maleic anhydride-grafted EVA. The maleic anhydride graft product can act as a "bond bridge" between the resin matrix and the filler powder, increasing the interfacial adhesion between the two and thus improving the overall performance of the material. Using a combination of maleic anhydride-grafted LLDPE and maleic anhydride-grafted EVA allows for better utilization of the respective matrix components.

[0025] Optionally, to further improve the compatibility between the materials, the maleic anhydride grafted product is a mixture of maleic anhydride-grafted mLLDPE and maleic anhydride-grafted EVA (the VA content of the EVA used is 14%) in a 2:1 ratio.

[0026] Optionally, the silicone masterbatch is an LLDPE carrier with a silicone content of 40-60%. This can effectively improve the processing performance of cable materials.

[0027] Optionally, the halogen-free flame retardant is a metal hydroxide flame retardant; in order to improve the uniformity of the cable material and better balance the mechanical properties, electrical properties, flame retardancy and formulation cost of the cable material, the halogen-free flame retardant is preferably aluminum hydroxide with an average particle size of 1.0-1.8μm.

[0028] In some embodiments of this invention, in order to reduce the total amount of flame retardant and improve the overall performance of cable materials, the organophosphorus flame retardant is selected from one or a combination of phosphite esters, phosphorus oxides, and phosphorus-nitrogen compounds; the thermal decomposition products of the organophosphorus flame retardant have a strong dehydrating effect, which can carbonize the surface of the covered polymer to form a carbon mold, isolate air and heat on the polymer surface, and form a good synergistic effect with metal hydroxides, thereby achieving the purpose of high flame retardancy, low smoke emission, and low toxicity.

[0029] In some embodiments of this invention, the modified filler is mica powder and kaolin, wherein the average particle size of the mica powder is 5-15 μm, the oil absorption is 28-35 G / 100 G, and the kaolin is calcined kaolin. Using mica powder and kaolin as modified fillers, the mica powder, belonging to the monoclinic crystal system, crystallizes in thin flakes, which can improve the damping characteristics of the material and increase its tensile and flexural modulus. Therefore, in the dynamic puncture test of cables, the addition of mica powder can provide more resistance during the puncture process. Simultaneously, mica powder also has good heat resistance, acid and alkali resistance, UV protection, radiation protection, and electrical insulation properties, all of which support the development of thin-walled photovoltaic insulation materials. The addition of kaolin further improves the electrical insulation performance of the material. Furthermore, kaolin has a layered structure, which can act as cross-linking grid points during the later irradiation cross-linking process, thus giving the material a more complete three-dimensional network structure, improving its mechanical properties, heat resistance, and puncture resistance, resulting in a higher long-term service temperature and a longer service life.

[0030] In some embodiments of this invention application, in order to further improve the mechanical properties, heat resistance, puncture resistance, UV protection, radiation protection and electrical insulation properties of the material, the modified filler is a mixture of mica powder and kaolin in a 1:1 ratio.

[0031] In some embodiments of this invention, the antioxidant is a mixture of antioxidant 1035, antioxidant 626, antioxidant 1024, and antioxidant DNP in a mass ratio of 1.0:0.5:(0.2-0.5):(0.4-0.8). For photovoltaic cable insulation materials, due to the outer sheath protection, long-term research has focused only on the thermal aging performance of the insulation material, neglecting its photo-aging performance. However, the sheath layer of thin-walled photovoltaic cables is thin, and long-term ultraviolet radiation poses a risk of penetrating the sheath layer and affecting the insulation material. This invention employs a combination of various antioxidants and light stabilizers, which can achieve a good synergistic effect, thereby giving the material excellent weather resistance and aging resistance, significantly increasing its service life.

[0032] In some embodiments of this invention, the light stabilizer is selected from a combination of UV944, UV622, UV1164, and 2020. This improves the UV protection performance of the cable material, increases its weather resistance, reduces photo-oxidative aging, and extends its service life.

[0033] In some embodiments of this invention application, the unsaturated silane crosslinking agent is selected from one or a combination of vinyltrimethoxysilane, vinylmethyldimethoxysilane, and octyltriethoxysilane.

[0034] In some embodiments of this invention application, the silane crosslinking initiator is an organic peroxide;

[0035] In some embodiments of this invention, the silane crosslinking catalyst is selected from at least one of dibutyltin dilaurate, dialkyltin thiolate, and stannous 2-ethylhexanoate;

[0036] In some embodiments of this invention application, the irradiation crosslinking sensitizer is selected from at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate;

[0037] In some embodiments of this invention application, the silane coupling agent is selected from at least one of vinyl silane coupling agents, amino silane coupling agents, and epoxy silane coupling agents.

[0038] Using the irradiation crosslinking sensitizer, unsaturated silane crosslinking agent, silane crosslinking initiator, and silane crosslinking catalyst described above, the material forms a uniform, stable, and perfect three-dimensional network structure, further improving the crosslinking efficiency, heat resistance, aging resistance, cut-through resistance, and electrical insulation performance of the cable material. Further optimization is achieved by adding 0.6-0.9 parts of the unsaturated silane crosslinking agent, 0.3-0.5 parts of the silane crosslinking initiator, 1.2-1.8 parts of the silane crosslinking catalyst, and 0.8-1.2 parts of the irradiation crosslinking sensitizer.

[0039] In order to improve processing fluidity and enhance powder dispersibility, in some embodiments of this invention, the lubricant is selected from one or a combination of oxidized polyethylene wax, phenyl silicone oil, and oleamide.

[0040] In some embodiments of this invention, the components of material A or material B include: 10-15 parts of ethylene-ethyl acrylate copolymer, 1-3 parts of ethylene-glycidyl methacrylate-vinyl acetate terpolymer, 7-13 parts of ethylene-vinyl acetate copolymer, 10-15 parts of thermoplastic elastomer, 37-50 parts of polyethylene, 5-10 parts of maleic anhydride graft, 1-4 parts of silicone masterbatch, and 60-90 parts of halogen-free flame retardant. The composition includes 4-6 parts organophosphorus flame retardant, 15-25 parts modified filler, 0.8-1.5 parts surface treatment agent, 0.6-1.0 parts unsaturated silane crosslinking agent, 0.3-0.6 parts silane crosslinking initiator, 0.8-1.8 parts silane crosslinking catalyst, 0.6-1.2 parts radiation crosslinking sensitizer, 1.2-2.5 parts antioxidant, 0.6-2.0 parts lubricant, and 0.5-0.8 parts light stabilizer; all parts are by weight. This composition further ensures the overall performance of the material.

[0041] In a second aspect, a method for preparing a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables, used to prepare any of the halogen-free flame-retardant insulation materials for thin-walled photovoltaic cables described in the first aspect, comprising:

[0042] Step S1: Prepare double cross-linked cable material A;

[0043] Step S2: Prepare double cross-linked cable material B;

[0044] Step S3: Mix double cross-linked cable material A and double cross-linked cable material B in a certain proportion;

[0045] Step S1 includes:

[0046] Step S11: Stearic acid is sprayed onto the flame retardant and then mixed for the first time in a high-speed mixer; the treated flame retardant is graded using an air jet mill; then silane coupling agent is sprayed onto the graded mixed flame retardant and then mixed for the second time in a high-speed mixer to obtain a surface-coated mixed flame retardant.

[0047] Step S12: Take the surface-coated mixed flame retardant obtained in step S11 and add mica powder, kaolin, antioxidant, lubricant, light stabilizer, radiation crosslinking sensitizer, unsaturated silane crosslinking agent and silane crosslinking initiator, and mix to obtain mixed flame retardant filler A;

[0048] Step S13: At least the mixed flame retardant filler A and resin base obtained in step S12 are mixed, extruded and granulated in a reciprocating mixing extruder in proportion to obtain double cross-linked cable material A.

[0049] Step S2 includes:

[0050] Step S21: Stearic acid is sprayed onto the flame retardant and then mixed for the first time in a high-speed mixer; the treated flame retardant is graded using an air jet mill; then silane coupling agent is sprayed onto the graded mixed flame retardant and then mixed for the second time in a high-speed mixer to obtain a surface-coated mixed flame retardant.

[0051] Step S22: Take the surface-coated mixed flame retardant obtained in step S21 and add mica powder, kaolin, antioxidant, lubricant, light stabilizer, irradiation crosslinking sensitizer, and silane crosslinking catalyst. After mixing, the mixed flame retardant filler B is obtained.

[0052] Step S23: At least the mixed flame retardant filler B and resin base obtained in step S22 are mixed, extruded and granulated in a reciprocating mixing extruder in proportion to obtain double cross-linked cable material B.

[0053] Surface pretreatment of fillers during production to form surface-modified fillers can improve the compatibility between the matrix resin and the flame-retardant filler, improve the dispersibility of the powder, and enhance the mechanical, electrical, flame-retardant, and processing properties of the material. The powder surface treatment method adopted in this invention is a double coating: first, the powder is coated with stearic acid, which improves the processing performance of the material; then, after stearic acid coating, the powder is graded using an air jet mill, which significantly reduces powder agglomeration; finally, the powder is coated with silane, which connects the hydrophilic groups of the powder filler, making the powder surface hydrophobic and improving its interfacial compatibility with the matrix resin. This double coating method can fundamentally solve the problem of decreased electrical properties and various conventional properties after the material is immersed in water.

[0054] To further balance the mechanical, flame-retardant, and electrical properties of the cable material, the surface treatment in step S11 or step S21 is a double coating of stearic acid and silane coupling agent. This can improve the interfacial compatibility between the resin base and the flame-retardant powder, so that the cable material forms a hydrophobic phase.

[0055] In some embodiments of this invention application, in step S11 or step S21, the first mixing is carried out in a high-speed mixer at a speed of 300±50 rpm for 420-500 s, and the processing temperature is 70-90℃.

[0056] In some embodiments of this invention application, the second mixing is carried out in a high-speed mixer at a speed of 300±50 rpm for 300-400 s, and the processing temperature is 70-90℃.

[0057] In some embodiments of this invention application, in step S12 or step S22, the mixture is stirred at a speed of 300±50 rpm for 100-150 s and the processing temperature is 70-90℃.

[0058] In some embodiments of this invention application, in step S13 or step S23, the temperature range of the reciprocating compounding extruder is 100-155°C.

[0059] This invention employs a dual crosslinking method. First, silane self-crosslinking establishes a preliminary crosslinked network. Then, irradiation crosslinking refines the material's three-dimensional network structure, improving the uniformity of the microstructure and creating a highly elastic, strong, and structurally complete network of interwoven C-C bonds and Si-O-Si bonds, resulting in excellent heat and puncture resistance. This method emphasizes the uniformity and stability of the crosslinked network structure. While the initial silane self-crosslinking process requires high crosslinking efficiency, the overall degree of crosslinking does not need to be too high; only a preliminary crosslinking framework needs to be formed. Therefore, the amount of unsaturated silane crosslinking agent and silane crosslinking initiator needs to be reduced compared to conventional silane crosslinking processes, while the amount of silane crosslinking catalyst needs to be increased. This ensures that the material can rapidly complete self-crosslinking under standard temperature and humidity conditions during the initial silane crosslinking process, without requiring a high degree of crosslinking. This process does not require boiling. After the silane self-crosslinking process, the sample undergoes subsequent irradiation crosslinking using an electron beam. This method focuses on the uniformity and stability of the network structure after material cross-linking, rather than simply increasing the irradiation cross-linking dose. This ensures sufficient cross-linking degree of the material while reducing irradiation energy consumption. More importantly, this dual cross-linking method reduces the consumption of antioxidants and light stabilizers during the cross-linking process, reduces structural damage to the material during irradiation cross-linking, reduces the risk of residual electrons in the insulation, and also avoids affecting the sheath performance due to over-cross-linking.

[0060] In some embodiments of this invention application, step S3 is followed by step S4: after pressing the thin-walled photovoltaic cable halogen-free flame-retardant insulation material into sheets, the sheets are left to stand in a standard environment for 12-24 hours to complete the preliminary silane self-crosslinking process. After the crosslinking is completed, the samples are subjected to electron beam irradiation crosslinking. The standard environment is a temperature of 23±2℃ and a humidity of 45%-55%. The electron beam irradiation process is 28 passes, 2.0 meV energy, 12 mA current, and 35 m / min speed.

[0061] Thirdly, a thin-walled photovoltaic cable includes a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables as described in any of the first aspects above, wherein the sheath thickness of the thin-walled photovoltaic cable is less than or equal to 0.55 mm.

[0062] Compared with the prior art, the beneficial effects of this invention application are at least as follows:

[0063] (1) In this invention application, the double cross-linked halogen-free flame-retardant insulation material of thin-walled photovoltaic cable has excellent mechanical properties, electrical properties, flame-retardant properties, low smoke properties, weather resistance and aging resistance, acid and alkali resistance, cut-through resistance and good processing performance; and the cable material does not contain any halogen-containing components, and has low smoke and non-toxicity when burning, meeting environmental protection requirements.

[0064] (2) In this invention application, the method for preparing double-crosslinked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables firstly involves double coating the surface of the flame retardant powder with stearic acid and silane, fundamentally solving the problem of decreased electrical performance and various conventional properties after immersion in water; then, double-crosslinked cable material A and double-crosslinked cable material B are prepared separately; after being mixed in proportion, the material initially adopts a silane self-crosslinking method to give it a preliminary crosslinking network, and later adopts an irradiation crosslinking method to improve the three-dimensional network structure of the material, thereby improving the uniformity of the micro-network structure and forming an interpenetrating network of C-C bonds and Si-O-Si bonds with high elasticity, high strength, and perfect structure, thus giving the material excellent heat resistance and puncture resistance. The cable material can meet the standard requirements after being processed by the double-crosslinking process; the preparation method is simple to operate, has high production efficiency, and high automation, and can meet the various requirements of thin-walled photovoltaic cables.

[0065] (3) In this application, a thin-walled photovoltaic cable is prepared using a double cross-linked halogen-free flame-retardant insulating material for thin-walled photovoltaic cables. When the sheath thickness of the photovoltaic cable is less than or equal to 0.55 mm, it still has excellent mechanical properties, aging properties, thermal elongation properties, high and low temperature electrical properties, low temperature tensile properties, and dynamic cutting properties. Detailed Implementation

[0066] To make the above-mentioned objects, features, and advantages of this invention application more apparent and understandable, the specific embodiments of this invention application are described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of this invention application; however, this invention application can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this invention application. Therefore, this invention application is not limited to the specific embodiments disclosed below.

[0067] In some embodiments of this invention application, the halogen-free flame-retardant insulation material of the thin-walled photovoltaic cable includes double cross-linked cable material A and double cross-linked cable material B; or, the halogen-free flame-retardant insulation material of the thin-walled photovoltaic cable includes double cross-linked cable material A, double cross-linked cable material B, and the remainder is auxiliary material, and the mass ratio of double cross-linked cable material A to double cross-linked cable material B is (90-98):(2-8), preferably, the mass ratio of double cross-linked cable material A to double cross-linked cable material B is 95:5.

[0068] In each embodiment:

[0069] The ethylene-ethyl acrylate copolymer (EEA) is A1150 (REXPEARL) with an EA content of 15%;

[0070] Ethylene-glycidyl methacrylate-vinyl acetate terpolymer (E-GMA-VA) is BF-2B (IGETABOND) with 12% GMA and 5% VA content;

[0071] The ethylene-vinyl acetate copolymer (EVA) is a mixture of 14-2 (Yanshan Petrochemical) and 5110J (Yangzi Petrochemical) with a VA content of 14% in a 2:1 ratio;

[0072] The thermoplastic elastomer is VL0003 (Daelin);

[0073] The linear low-density polyethylene is 7042 (Sinopec);

[0074] The ultra-low density polyethylene is CB1001 (Sumitomo);

[0075] The bimodal polyethylene is FK2715 (Borouge);

[0076] Maleic anhydride graft MG9215 (Ruicheng);

[0077] Silicone masterbatch MB50 (Dow Corning);

[0078] The halogen-free flame retardant is aluminum hydroxide LY05AH (Rheinstein);

[0079] The organophosphorus flame retardant is diethylaluminum hypophosphite FR-ADP02C (Guangzhou Yinyuan New Materials);

[0080] The mica powder is WJ-4 (Baota Sericite Mining);

[0081] Kaolin is GY650-12 (Ousena Chemicals);

[0082] The surface treatment agents are stearic acid SA 1801 (Shanyi Plastics) and silane coupling agent SIC 6285 (Sloco);

[0083] The antioxidant is a mixture of antioxidant 1035, antioxidant 626, antioxidant 1024 and antioxidant DNP in a mass ratio of 1.0:0.5:(0.2-0.5):(0.4-0.8);

[0084] The unsaturated silane crosslinking agent is vinylmethyldimethoxysilane, the silane crosslinking initiator is dicumyl peroxide, and the silane crosslinking catalyst is dibutyltin dilaurate;

[0085] The irradiation crosslinking sensitizer is trimethylolpropane trimethacrylate (TMPTMA);

[0086] The lubricant is a mixture of Honeywell 316A and SIC6468F (Sloco) in a 3:1 ratio;

[0087] The light stabilizer is a mixture of UV622 and 2020 in a mass ratio of 1:1.

[0088] The formulations of each embodiment are shown in Table 1 below: (Since there are many identical components in materials A and B, the identical components are not repeated, and only the different components are specifically marked).

[0089] Table 1

[0090]

[0091] Example 1: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0092] Step 1: Stearic acid is evenly sprayed onto the mixed flame retardant of aluminum hydroxide and organophosphorus flame retardant at the appropriate mass ratio, and then mixed in a high-speed mixer at a speed of 300±50 rpm for 450 s at a processing temperature of 80℃. The treated mixed flame retardant is then graded using an air jet mill to screen out mixed flame retardants with uniform particle size and no agglomeration. Subsequently, silane coupling agent is evenly sprayed onto the graded mixed flame retardant at the appropriate mass ratio, and then mixed in a high-speed mixer at a speed of 300±50 rpm for 350 s at a processing temperature of 80℃.

[0093] Step 2: Add mica powder, kaolin, antioxidant, lubricant, light stabilizer, radiation crosslinking sensitizer, unsaturated silane crosslinking agent and silane crosslinking initiator to the surface coating mixed flame retardant after the first step of mixing, and continue mixing for 120 seconds at a processing temperature of 80℃; to obtain mixed flame retardant filler A;

[0094] Step 3: Add mica powder, kaolin, antioxidant, lubricant, light stabilizer, radiation crosslinking sensitizer and silane crosslinking catalyst to the surface coating mixed flame retardant after the first step of mixing, continue mixing for 100s, and the treatment temperature is 80℃ to obtain mixed flame retardant filler B.

[0095] Step 4: At least the mixed flame retardant filler A and resin base obtained in step 2 are mixed, extruded and granulated in a reciprocating mixing extruder in a certain proportion to obtain double cross-linked cable material A.

[0096] Step 5: At least the mixed flame retardant filler B and resin base obtained in step 3 are mixed, extruded and granulated in a reciprocating mixing extruder in a certain proportion to obtain double cross-linked cable material B;

[0097] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed in a ratio of 95:5 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0098] Example 2: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0099] Step 1: Stearic acid is evenly sprayed onto the mixed flame retardant of aluminum hydroxide and organophosphorus flame retardant at the appropriate mass ratio, and then mixed in a high-speed mixer at a speed of 300±50 rpm for 500 s at a processing temperature of 75℃. The treated mixed flame retardant is then graded using an air jet mill to screen out mixed flame retardants with uniform particle size and no agglomeration. Then, silane coupling agent is evenly sprayed onto the graded mixed flame retardant at the appropriate mass ratio, and then mixed in a high-speed mixer at a speed of 300±50 rpm for 400 s at a processing temperature of 75℃.

[0100] Step 2: Same as Example 1;

[0101] Step 3: Same as Example 1;

[0102] Step 4: Same as Example 1;

[0103] Step 5: Same as Example 1;

[0104] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed in a ratio of 92:4 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0105] Example 3: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0106] Step 1: Same as Example 1

[0107] Step 2: The difference from Example 1 is that the mixing time is 100 seconds and the processing temperature is 90°C;

[0108] Step 3: The difference from Example 1 is that the mixing time is 100 seconds and the processing temperature is 90°C;

[0109] Step 4: Same as Example 1;

[0110] Step 5: Same as Example 1;

[0111] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed in a ratio of 90:6 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0112] Example 4: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0113] The steps from the first to the fifth are the same as in Example 1;

[0114] A double-crosslinked cable material A and double-crosslinked cable material B are mixed in a ratio of 98:8 to obtain a double-crosslinked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0115] Examples 5-6: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows:

[0116] The preparation method is the same as in Example 1 (the proportions of each raw material are shown in Table 1);

[0117] A double-crosslinked cable material A and double-crosslinked cable material B are mixed in a ratio of 95:5 to obtain a double-crosslinked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0118] The cable materials prepared in Examples 1-6 were pressed into sheets and then left to stand for 12-24 hours under standard conditions (temperature 23±2℃, humidity 45%-55%) to complete the initial silane self-crosslinking process. After this crosslinking, the thermal elongation of the materials was between 100% and 70%. After the silane self-crosslinking, the samples were subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, 2.0 mevav, 12 mA current, and 35 m / min velocity. The thermal elongation after irradiation was between 20% and 35%, which meets the standard requirements.

[0119] Example 7: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0120] Step 1: Same as Example 1

[0121] Step 2: The difference from Step 2 of Example 1 is that mica powder and kaolin were not added;

[0122] Step 3: The difference from Step 3 of Example 1 is that mica powder and kaolin were not added;

[0123] Step 4: Same as Example 1;

[0124] Step 5: Same as Example 1;

[0125] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed at a mass ratio of 95:5 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0126] The cable material obtained above was pressed into sheets and left to stand for 12-24 hours under standard conditions (temperature 23±2℃, humidity 45%-55%) to complete the initial silane self-crosslinking process. After this crosslinking, the material's thermal elongation was 110%-70%. After the silane self-crosslinking, the samples were subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, 2.0 meva, 12 mA current, and 35 m / min velocity. The thermal elongation after irradiation was 35%, which meets the standard requirements.

[0127] Example 8: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0128] Step 1: The difference from Step 1 of Example 1 is that only stearic acid is used to coat the flame retardant, without the silane coating step.

[0129] Step 2: Same as Example 1;

[0130] Step 3: Same as Example 1;

[0131] Step 4: Same as Example 1;

[0132] Step 5: Same as Example 1;

[0133] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed at a mass ratio of 95:5 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0134] The cable material obtained above was pressed into sheets and left to stand for 12-24 hours under standard conditions (temperature 23±2℃, humidity 45%-55%) to complete the initial silane self-crosslinking process. After this crosslinking, the material's thermal elongation was 110%-70%. After the silane self-crosslinking, the samples were subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, 2.0 meva, 12 mA current, and 35 m / min velocity. The thermal elongation after irradiation was 35%, which meets the standard requirements.

[0135] Example 9: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0136] Step 1: The difference from Step 1 of Example 1 is that only silane is used to coat the flame retardant; there is no stearic acid coating step.

[0137] Step 2: Same as Example 1;

[0138] Step 3: Same as Example 1;

[0139] Step 4: Same as Example 1;

[0140] Step 5: Same as Example 1;

[0141] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed at a mass ratio of 95:5 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0142] The cable material obtained above was pressed into sheets and left to stand for 12-24 hours under standard conditions (temperature 23±2℃, humidity 45%-55%) to complete the initial silane self-crosslinking process. After this crosslinking, the material's thermal elongation was 100%-70%. After the silane self-crosslinking, the sample was subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, 2.0 meva, 12 mA current, and 35 m / min velocity. The thermal elongation after irradiation was 20%, which meets the standard requirements.

[0143] Example 10: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0144] Step 1: Spray stearic acid evenly onto the mixed flame retardant of aluminum hydroxide and organophosphorus flame retardant at the appropriate mass ratio, and then mix in a high-speed mixer at a speed of 300±50 rpm for 420-500 s, with a processing temperature of 70-90℃; classify the treated mixed flame retardant using an air jet mill to screen out mixed flame retardants with uniform particle size and no agglomerated particles; then spray silane coupling agent evenly onto the graded mixed flame retardant at the appropriate mass ratio, and then mix in a high-speed mixer at a speed of 300±50 rpm for 300-400 s, with a processing temperature of 70-90℃;

[0145] Step 2: Add mica powder, kaolin, antioxidant, lubricant, light stabilizer, and radiation crosslinking sensitizer to the surface coating flame retardant after the first step of mixing, and continue mixing for 100-150 seconds to obtain the mixed flame retardant filler.

[0146] Step 3: At least the mixed flame-retardant filler and resin base obtained in step 2 are mixed, extruded and granulated in a reciprocating mixing extruder in proportion to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0147] After the cable material obtained above was pressed into sheets, it was left to stand in a standard environment (temperature 23±2℃, humidity 45%-55%) for 12-24 hours, and then the samples were subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, 2.0 meva, 12 mA current, and 35 m / min speed. The thermal elongation after irradiation was 80%.

[0148] Example 11: The preparation method of double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables is as follows (the proportions of each raw material are shown in Table 1):

[0149] Step 1: Same as Example 1;

[0150] Step 2: Unlike Step 2 of Example 1, no irradiation crosslinking sensitizer was added;

[0151] Step 3: Unlike Step 3 of Example 1, no irradiation crosslinking sensitizer was added;

[0152] Step 4: Same as Example 1;

[0153] Step 5: Same as Example 1;

[0154] The above-mentioned double cross-linked cable material A and double cross-linked cable material B are mixed at a mass ratio of 95:5 to obtain a double cross-linked halogen-free flame-retardant insulation material for thin-walled photovoltaic cables.

[0155] After the cable material obtained above is pressed into sheets, it is left to stand in a standard environment (temperature 23±2℃, humidity 45%-55%) for 12-24 hours to complete the silane self-crosslinking process. After the crosslinking is completed, the material has a thermal elongation of 100%.

[0156] The main performance indicators of the materials obtained in each embodiment are shown in Table 2:

[0157] Table 2

[0158]

[0159]

[0160] As can be seen from the data in Table 2, the double cross-linked halogen-free flame-retardant insulating materials prepared in Examples 1-4 all have relatively balanced mechanical properties, aging properties, low-temperature properties, electrical properties and cut-through resistance, and have excellent overall performance.

[0161] The performance comparisons of Examples 1 and 5 show that, compared to EVA alone, the use of a blend of EEA, EVA, and E-GMA-VA in the base material system significantly improves the material's mechanical properties, aging properties, low-temperature properties, electrical properties, crosslinking efficiency, and cut-through resistance. The performance comparisons of Examples 1 and 6 show that, compared to linear low-density polyethylene alone, the use of a blend of linear low-density polyethylene, ultra-low-density polyethylene, and bimodal polyethylene significantly improves the material's aging properties and dynamic cut-through resistance.

[0162] The performance comparison between Examples 1 and 7 shows that the addition of modified fillers mica powder and kaolin significantly improves the electrical properties and dynamic puncture performance of the material. This is because mica powder can improve the damping characteristics of the material and increase its tensile and flexural modulus. Therefore, in the dynamic puncture test of the cable, the addition of mica powder can provide more resistance during the puncture process. Kaolin, with its layered structure, can act as a cross-linking grid point in the later irradiation cross-linking process of the material, thereby giving the material a more complete three-dimensional network structure and improving its electrical properties and aging performance.

[0163] The performance comparison of Examples 1 and 8 / 9 shows that, compared with the surface treatment of stearic acid or silane coupling agent alone, the double coating method of both can make the powder form a hydrophobic surface and improve its interfacial compatibility with the matrix resin. This double coating method of powder can fundamentally solve the problem of the decline in electrical properties and various conventional properties of the material after immersion in water.

[0164] The performance comparison of Examples 1 and 10 / 11 shows that, compared with single silane crosslinking or irradiation crosslinking, the dual crosslinking method adopted in this invention can significantly improve the crosslinking efficiency of the product, improve electrical performance and dynamic cut-through performance. This method focuses on the uniformity and stability of the network structure after material crosslinking, rather than simply increasing the irradiation crosslinking dose. This ensures sufficient crosslinking degree of the material and reduces irradiation energy consumption. More importantly, this dual crosslinking method reduces the consumption of antioxidants and light stabilizers during the crosslinking process, reduces the structural damage to the material during irradiation crosslinking, reduces the risk of residual electrons in the insulation, and also avoids the impact of over-crosslinking on the sheath performance.

[0165] Example 12: The material obtained in Example 1 was verified by coating extrusion on a cable extrusion production line. The extrusion temperature was set as follows: Zone 1 110-120℃, Zone 2 130-140℃, Zone 3 145-155℃, Zone 4 155-165℃, and die head 160-170℃. After extrusion, the cable was left to stand in a standard environment for 12-24 hours to complete the initial silane self-crosslinking process. After this crosslinking, the sample was subjected to electron beam irradiation crosslinking. The irradiation process was 28 passes, energy 2.0 mevav, current 12 mA, and speed 70 m / min. The verification wire gauge was photovoltaic cable PV1-F 1*4 with a sheath thickness of 0.55 mm. The main performance indicators of the finished cable obtained in Example 12 are compared with those of cables made from commercially available materials in Table 3 below.

[0166] Table 3

[0167]

[0168]

[0169] As shown in Table 3, the double-crosslinked halogen-free flame-retardant insulation material prepared in Example 1, when used to make thin-walled photovoltaic cables with a sheath thickness of 0.55 mm, exhibits significantly superior mechanical strength compared to commercially available thin-walled cables. After aging at 150℃ for 168 hours, the mechanical properties show no significant change. After aging at 185℃ for 100 hours, the mechanical properties decrease slightly, but are still significantly better than commercially available products. Thermal elongation performance is also excellent, recovering upon cooling. High and low temperature electrical properties, low-temperature tensile properties, and dynamic cut-through properties are all significantly superior to commercially available products.

[0170] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the present invention.

Claims

1. A halogen-free flame-retardant insulation material for thin-walled photovoltaic cables, characterized in that, Including double cross-linked cable material A and double cross-linked cable material B; The double cross-linked cable material A comprises the following raw material components in parts by weight: 8-15 parts of ethylene-ethyl acrylate copolymer; 1-5 parts of ethylene-glycidyl methacrylate-vinyl acetate terpolymer; 5-15 parts of ethylene-vinyl acetate copolymer; and 12-15 parts of thermoplastic elastomer. Polyethylene 35-55 parts; maleic anhydride graft 5-12 parts; silicone masterbatch 1-6 parts; halogen-free flame retardant 60-100 parts; organophosphorus flame retardant 3-6 parts; modified filler 10-30 parts; surface treatment agent 1-2 parts; antioxidant 1-4 parts; light stabilizer 0.5-1 part; unsaturated silane crosslinking agent 0.4-1.8 parts; silane crosslinking initiator 0.2-0.8 parts; irradiation crosslinking sensitizer 0.5-1.5 parts; lubricant 0.5-2.5 parts; The B material of the double cross-linked cable comprises the following raw material components in parts by weight: 8-15 parts of ethylene-ethyl acrylate copolymer, 1-5 parts of ethylene-glycidyl methacrylate-vinyl acetate terpolymer, 5-15 parts of ethylene-vinyl acetate copolymer, 12-15 parts of thermoplastic elastomer, 35-55 parts of polyethylene, 5-12 parts of maleic anhydride graft, 1-6 parts of silicone masterbatch, 60-100 parts of halogen-free flame retardant, 3-6 parts of organophosphorus flame retardant, 10-30 parts of modified filler, 1-2 parts of surface treatment agent, 1-4 parts of antioxidant, 0.5-1 part of light stabilizer, 0.3-2 parts of silane cross-linking catalyst, 0.5-1.5 parts of irradiated cross-linking sensitizer, and 0.5-2.5 parts of lubricant; The thermoplastic elastomer is POP with an α-olefin content of less than 20%; The polyethylene is a mixture of linear low-density polyethylene, ultra-low-density polyethylene and bimodal polyethylene; The flame retardant is the halogen-free flame retardant and the organophosphorus flame retardant; The surface treatment agent includes stearic acid and a silane coupling agent; The mass ratio of stearic acid to flame retardant is 1:200-1:150; The mass ratio of the silane coupling agent to the flame retardant is 1:150-1:80; The modified filler is mica powder and kaolin, wherein the average particle size of the mica powder is 5-15μm and the oil absorption is 28-35G / 100G, and the kaolin is calcined kaolin. Stearic acid was sprayed onto the flame retardant and then mixed for the first time in a high-speed mixer. The treated flame retardant was then graded using an air jet mill. A silane coupling agent was then sprayed onto the graded flame retardant mixture and then mixed for the second time in a high-speed mixer.

2. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 1, characterized in that, The ethylene-ethyl acrylate copolymer has a melt index of 0.5-1.5 g / 10 min; And / or, the melt index of the ethylene-vinyl acetate copolymer is 1.8-2.8 g / 10 min; And / or, the ethylene-glyceryl glycidyl acrylate-vinyl acetate terpolymer has a melt index of 1.5-4.5 g / 10 min.

3. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 1, characterized in that, The melt index of the thermoplastic elastomer is 1.0-5.0 g / 10 min; And / or, the melt index of the linear low-density polyethylene is 1.0-2.8 g / 10 min, the melt index of the ultra-low-density polyethylene is 1.5-10.0 g / 10 min, and the melt index of the bimodal polyethylene is 0.2-2.0 g / 10 min; And / or, the grafting rate of the maleic anhydride graft is 0.8%-1.2%; And / or, the silicone masterbatch is an LLDPE carrier with a silicone content of 40-60%.

4. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 1, characterized in that, The halogen-free flame retardant is a metal hydroxide flame retardant; the metal hydroxide flame retardant is aluminum hydroxide with an average particle size of 1.0-1.8 μm.

5. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 1, characterized in that, The antioxidant is a mixture of antioxidant 1035, antioxidant 626, antioxidant 1024 and antioxidant DNP in a mass ratio of 1.0:0.5:0.2-0.5:0.4-0.8; And / or, the light stabilizer is selected from one or a combination of UV944, UV622, UV1164 and 2020; And / or, the unsaturated silane crosslinking agent is selected from one or a combination of vinyltrimethoxysilane and vinylmethyldimethoxysilane.

6. The halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 1, characterized in that, The silane crosslinking initiator is an organic peroxide; The silane crosslinking catalyst is selected from at least one of dibutyltin dilaurate, dialkyltin thiolate, and stannous 2-ethylhexanoate; And / or, the irradiation crosslinking sensitizer is selected from at least one of triallyl isocyanurate and trimethylolpropane trimethacrylate; And / or, the silane coupling agent is selected from at least one of vinyl silane coupling agents, amino silane coupling agents, and epoxy silane coupling agents; And / or, the lubricant is selected from one or a combination of oxidized polyethylene wax, phenyl silicone oil and oleamide.

7. A method for preparing a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables, used to prepare the halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to any one of claims 1-6, characterized in that, include: Step S1: Prepare double cross-linked cable material A; Step S2: Prepare double cross-linked cable material B; Step S3: Mix double cross-linked cable material A and double cross-linked cable material B in a certain proportion; Step S1 includes: Step S11: Stearic acid is sprayed onto the flame retardant and then mixed for the first time in a high-speed mixer; the treated flame retardant is graded using an air jet mill; then silane coupling agent is sprayed onto the graded mixed flame retardant and then mixed for the second time in a high-speed mixer to obtain a surface-coated mixed flame retardant. Step S12: Take the surface-coated mixed flame retardant obtained in step S11 and add mica powder, kaolin, antioxidant, lubricant, light stabilizer, radiation crosslinking sensitizer, unsaturated silane crosslinking agent and silane crosslinking initiator, and mix to obtain mixed flame retardant filler A; Step S13: At least the mixed flame retardant filler A and resin base obtained in step S12 are mixed, extruded and granulated in a reciprocating mixing extruder in proportion to obtain double cross-linked cable material A. Step S2 includes: Step S21: Stearic acid is sprayed onto the flame retardant and then mixed for the first time in a high-speed mixer; the treated flame retardant is graded using an air jet mill; then silane coupling agent is sprayed onto the graded mixed flame retardant and then mixed for the second time in a high-speed mixer to obtain a surface-coated mixed flame retardant. Step S22: Take the surface-coated mixed flame retardant obtained in step S21 and add mica powder, kaolin, antioxidant, lubricant, light stabilizer, irradiation crosslinking sensitizer, and silane crosslinking catalyst. After mixing, the mixed flame retardant filler B is obtained. Step S23: At least the mixed flame-retardant filler B and resin base obtained in step S22 are mixed, extruded and granulated in a reciprocating mixing extruder in proportion to obtain double cross-linked cable material B.

8. The method for preparing a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 7, characterized in that, In step S11 or step S21, the first mixing is carried out in a high-speed mixer at a speed of 300±50 rpm for 420-500 s and the processing temperature is 70-90℃; and / or, the second mixing is carried out in a high-speed mixer at a speed of 300±50 rpm for 300-400 s and the processing temperature is 70-90℃.

9. The method for preparing a halogen-free flame-retardant insulation material for thin-walled photovoltaic cables according to claim 7, characterized in that, In step S12 or step S22, the mixture is mixed at a speed of 300±50 rpm for 100-150 s and the processing temperature is 70-90℃; and / or, in step S13 or step S23, the temperature range of the reciprocating mixing extruder is 100-155℃.

10. A thin-walled photovoltaic cable, comprising the halogen-free flame-retardant insulation material for thin-walled photovoltaic cables as described in any one of claims 1-6, characterized in that, The sheath thickness of the thin-walled photovoltaic cable is less than or equal to 0.55 mm.

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