A waterproof and anti-aging photovoltaic cable and its preparation process

Abstract

The present invention relates to the technical field of photovoltaic cables, and specifically to a waterproof and anti-aging photovoltaic cable and its preparation process, which includes the following processes: LDPE, LLDPE, modified EVA, inorganic filler, photoinitiator, crosslinking agent and additives are blended and kneaded to obtain insulating material; the insulating material is extruded, heated and irradiated to form an insulating layer, thus obtaining the photovoltaic cable; the modified EVA is obtained by alcoholysis of EVA and reaction with acyl chloride compounds, and the acyl chloride compounds include trimethylheptanoyl chloride and trimethylhexanoyl chloride. The present invention uses trimethylhexanoyl chloride and trimethylheptanoyl chloride to react with the alcoholysis product of EVA to prepare modified EVA. Tertiary carbonate isononanoate and neodecanoate have branched chains, making them have higher hydrolysis stability, effectively improving the water resistance of the insulating layer; and increasing the water channel barrier effect, which can prevent the penetration of moisture, reduce the slippage of moisture under extrusion pressure, and improve the water tree aging resistance of the insulating layer.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cables, and specifically to a waterproof and anti-aging photovoltaic cable and its preparation process. Background Art

[0002] In modern times, people's awareness of environmental protection energy has been increasing day by day, and new energy sources such as wind energy and solar energy have been continuously developed. As a clean, green, and renewable energy source, photovoltaic power generation utilizes the photovoltaic effect at the semiconductor interface to directly convert rich solar radiation energy into electrical energy. In order to meet the complex operating conditions of photovoltaic power stations, the performance of photovoltaic cables needs to be improved to adapt to the actual application environment. PE (polyethylene) has excellent mechanical and physical, electrical properties and good processing characteristics. By cross-linking it from a linear structure into a three-dimensional network structure, the thermoplasticity is transformed into thermosetting, and the mechanical properties, thermal stability, environmental stress cracking resistance, etc. of the prepared XLPE (cross-linked polyethylene) are further improved, while the thermal stability and heat resistance of the cable are also improved; however, this is still not sufficient to meet the harsh requirements for the electrical properties of cable insulating materials.

[0003] In a humid environment, the insulating layer of the cable will gradually absorb the surrounding moisture. Under the combined action of the electric field and water, dendritic traces will be generated inside the polymer dielectric of the cable insulating layer, which is called water tree. Its existence will seriously affect the electrical and mechanical properties of the cable insulating layer, and will cause the generation of electrical tree and insulation breakdown faults under certain conditions, resulting in the failure of the insulating layer, greatly shortening the service life of the cable, and seriously affecting the reliability of power supply. Research shows that EVA (ethylene-vinyl acetate copolymer) can inhibit the growth of water trees in XLPE, and its mixture has good anti-water tree aging performance. The polar polymer EVA has a greater attraction to water than the cohesive force of water molecules. Water molecules are adsorbed on the surface of the polar groups of EVA, and it is difficult for water to aggregate in the polymer, reducing the condensation of water in the amorphous region of XLPE, weakening the stretching deformation of water under the alternating electric field, and alleviating the stress damage formed by molecular chains, thus showing good water tree inhibition effect.

[0004] However, under long-term humid and water-immersed conditions, the adhesion between the filler and the matrix resin decreases, the molecular chains hydrolyze, the entanglement effect between molecular chains weakens, EVA absorbs water and swells, and the free volume increases, resulting in a decrease in the mechanical properties of the insulating layer; some fillers break away from the restraint of the matrix resin, causing a continuous decrease in the volume resistivity of the cable. Therefore, we propose a waterproof and anti-aging photovoltaic cable and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a waterproof and anti-aging photovoltaic cable and its preparation process to solve the problems raised in the above background art.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: A preparation process for a waterproof and anti-aging photovoltaic cable, including the following processes:

[0007] Mix LDPE, LLDPE, EVA, inorganic filler, photoinitiator, crosslinking agent and additives, and knead to obtain insulating material.

[0008] Extrude the insulating material so that the insulating material coats the conductor; heat and irradiate to form an insulating layer; extrude the sheath material so that the sheath material coats the insulating layer to form a sheath layer, and obtain a photovoltaic cable.

[0009] Furthermore, the photovoltaic cable sequentially includes the following structures from the inside to the outside: a conductor, an insulating layer and a sheath layer.

[0010] Furthermore, the process conditions for kneading are: temperature 145 - 160 °C, rotation speed 40 - 60 rmp, duration 20 - 30 min.

[0011] Furthermore, the process conditions for extrusion are: extrusion temperature 145 - 170 °C, monomer running speed 2.0 - 3.0 m / min.

[0012] Furthermore, the process conditions for heating are: temperature 155 - 170 °C, duration 44 - 76 s.

[0013] Furthermore, the process conditions for irradiation are: ultraviolet lamp power 1.0 W × 12 groups, duration 76 - 136 s.

[0014] In the above technical solutions, the crosslinking methods of PE include irradiation, peroxide, silane, etc. Among them, high-energy radiation crosslinking has the problem of low transmission depth and can only produce low-voltage and small-interface wire and cable. Silane crosslinking will increase the water content in the insulating layer, resulting in a relatively large polarity, which is not suitable for producing medium- and high-voltage power cables. Therefore, at present, the peroxide crosslinking method is mostly used to produce medium- and high-voltage XLPE insulated power cables; however, the by-products such as methane, cumyl alcohol, acetophenone, α-methylstyrene and water generated during the crosslinking reaction process will have a negative impact on the dielectric properties of the insulating layer; and it is also limited in the selection of PE resin and the single continuous processing time. The ultraviolet light crosslinking method has the characteristics of photoquantum effect and non-thermosensitivity of materials, and has the advantages of fast crosslinking speed, long continuous processing time, wide selection of insulating extrusion resins, low investment cost, energy saving and emission reduction, etc.

[0015] Furthermore, the insulating material includes the following mass components: 50 - 90 parts of LDPE (low density polyethylene), 10 - 50 parts of LLDPE (linear low density polyethylene), 6 - 12 parts of EVA (ethylene-vinyl acetate copolymer), 1 - 3 parts of photoinitiator, 1 - 3 parts of crosslinking agent, 0.5 - 3.0 parts of inorganic filler, 0.2 - 0.5 parts of additive.

[0016] In the above technical solution, compared with LDPE (low density polyethylene) and HDPE (high density polyethylene), LLDPE (linear low density polyethylene) has a dense short branched chain molecular structure, which can promote the entanglement between lamellae. In the amorphous phase of LLDPE, water requires more energy and time to break these entangled molecular chains, and the entangled molecular chains can, to a certain extent, inhibit the slip of lamellae under the extrusion pressure of water, thereby weakening the destructive effect brought by electro-induced stress, inhibiting the growth of water trees, and endowing LLDPE with stronger resistance to water tree aging. However, the extrusion processing performance of LLDPE is poor, which will affect the comprehensive performance of the extrudate. Therefore, a mixture of LDPE and LLDPE is used as the base resin of XLPE.

[0017] Furthermore, the photoinitiator is one of benzophenone and 4-hydroxybenzophenone laurate.

[0018] Furthermore, the crosslinking agent is one or a mixture of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate, diallyl phthalate, pentaerythritol triallyl ether, and pentaerythritol tetraallyl ether.

[0019] In the above technical solution, the irradiation process enables the photoinitiator to function, crosslink and combine polyethylene with the crosslinking agent to generate XLPE (crosslinked polyethylene). The three-dimensional network structure formed by crosslinking can effectively hinder the penetration of water into the interior of XLPE under the action of electric field force, narrow the water tree channels, enhance the barrier effect, and improve the water resistance and anti-water tree performance of XLPE. The formed crosslinking bonds strengthen the β relaxation of XLPE, can buffer the impact of water on the amorphous phase of XLPE under the action of electric field force, reduce the growth rate of water trees; the entanglement behavior of molecular chains in the amorphous region is enhanced, and the difficulty of slip and damage between lamellae under the action of electro-induced stress increases, thereby improving the ability of the insulating layer to inhibit water trees. A macromolecular photoinitiator is selected, which has better thermal stability, is not easily volatilized by heat, and has better photo-crosslinking reaction efficiency.

[0020] Furthermore, the inorganic filler is one or a mixture of silica, montmorillonite, and alumina.

[0021] In the above technical solution, adding an appropriate amount of inorganic filler can promote the heterogeneous nucleation of XLPE, improve the crystallization morphology of XLPE, reduce the amorphous phase region, inhibit the penetration of water, and enhance the water tree resistance of XLPE.

[0022] Furthermore, the additive is one or a mixture of antioxidant 1010, antioxidant 300, and antioxidant 1035.

[0023] Further, the EVA is modified, and the specific process is as follows:

[0024] Mix EVA and toluene, heat to 60 - 70 °C, and stir to dissolve; slowly add sodium hydroxide / methanol solution and finish adding within 10 min, then stir and react for 100 - 150 min; cool, filter by suction, wash the precipitate, and dry to obtain the alcoholysis product of EVA.

[0025] Mix the alcoholysis product of EVA and toluene, under the protection of nitrogen atmosphere, heat to 60 - 70 °C, and stir for 30 - 60 min; slowly add 2,5,5 - trimethylheptanoyl chloride, 3,5,5 - trimethylhexanoyl chloride, and acryloyl chloride, stir and react for 120 - 150 min; add an acid-binding agent and react for 90 - 120 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry to obtain vinyl EVA.

[0026] Mix vinyl EVA and toluene, add a dithiol compound and a photoinitiator, stir and irradiate with an ultraviolet lamp for 2 - 4 h; add a vinyl carbazole compound and continue irradiating for 8 - 12 h; wash and dry to obtain the modified EVA.

[0027] Further, the ratio of EVA, toluene, and sodium hydroxide / methanol solution is (5 - 6) g:100 mL:50 mL.

[0028] The concentration of the sodium hydroxide / methanol solution is 5 wt%.

[0029] Further, the ratio of the alcoholysis product of EVA and toluene is (1 - 2) g:100 mL.

[0030] The acid-binding agent is triethanolamine.

[0031] The vinyl EVA includes the following mass components: 100 parts of the alcoholysis product of EVA, 1 - 4 parts of 3,5,5 - trimethylhexanoyl chloride (isononanoyl chloride, CAS No. 36727 - 29 - 4), 0 - 3 parts of 2,5,5 - trimethylheptanoyl chloride (neodecanoyl chloride, CAS No. 40292 - 82 - 8), 4.5 - 6.0 parts of acryloyl chloride, and 12 - 13 parts of the acid-binding agent triethanolamine.

[0032] Further, the ratio of vinyl EVA and toluene is 10 g / 100 mL.

[0033] The dithiol compound is one of alkyl dithiol, 1,4 - benzenedithiol, and hexa(ethylene glycol) dithiol.

[0034] The modified EVA includes the following mass components: 100 parts of vinyl EVA, 10 - 22 parts of vinyl carbazole compound, 5.6 - 22.1 parts of dithiol compound, and 2.4 - 11.0 parts of photoinitiator.

[0035] The photoinitiator is benzoin dimethyl ether.

[0036] Furthermore, the vinylcarbazole compound is prepared by the following process:

[0037] Mix 2-hydroxycarbazole and triethylamine in dichloromethane, and slowly add 5-norbornene-2-carbonyl chloride at a temperature of 0 - 8 °C within 20 min. Restore the temperature to 20 - 30 °C and react for 90 - 120 min. Wash, let it stand for layering, take the lower-layer liquid, and dry it to obtain the polymerization monomer.

[0038] Under the protection of a nitrogen atmosphere, mix the polymerization monomer and the cyclic catalyst in dichloromethane, heat up to 50 - 60 °C, and react for 96 - 100 h. Cool to -20 °C and precipitate with cold methanol to obtain the vinylcarbazole compound.

[0039] Furthermore, the molar ratio of 2-hydroxycarbazole, 5-norbornene-2-carbonyl chloride, and triethylamine is 1:(1.0 - 1.1):(1.0 - 1.1);

[0040] The ratio of 2-hydroxycarbazole to dichloromethane is 3 g / 100 mL.

[0041] Furthermore, the dosage of the cyclic catalyst is 0.20 - 0.25% of the mass of the polymerization monomer;

[0042] The ratio of the polymerization monomer to dichloromethane is 30 g / 100 mL;

[0043] The cyclic catalyst is a cycloalkyl ruthenium catalyst, prepared with reference to 6cyc in the literature "Boydston A J, Xia Y, Kornfield JA, et al. Cyclic ruthenium-alkylidene catalysts for ringexpansion metathesispolymerization [J]. Journal of the American Chemical Society, 2008, 130(38):12775 - 12782".

[0044] In the above technical solution, the alcoholysis product of EVA is reacted with 3,5,5-trimethylhexanoyl chloride, 2,5,5-trimethylheptanoyl chloride and acryloyl chloride to obtain vinyl EVA. As tertiary carbonates, isononanoate and neodecanoate have branched chains. While maintaining the hydrophilicity of the ester group, they have higher hydrolysis stability, which can effectively improve the water resistance of the insulating layer; the water channel blocking effect is increased, which can effectively prevent the penetration of moisture, and the slippage of moisture under extrusion is reduced, improving the water tree aging resistance of the insulating layer. Introducing isononanoate with a hard segment and neodecanoate with a soft segment into EVA can also synergistically improve the rigidity and toughness of the EVA molecular chain.

[0045] In the preparation of the benzophenone acyl chloride compound, 2-hydroxycarbazole reacts with 5-norbornene-2-carbonyl chloride. Through the nucleophilic addition between the acyl chloride and the hydroxyl group, a norbornene acyloxycarbazole compound is formed, denoted as the polymerization monomer. The polymerization monomer undergoes metathesis polymerization under the action of a ring-opening catalyst to form a tough cyclic polymer, denoted as the vinyl carbazole compound. When it is introduced into the insulating layer structure, mechanical interlocking is formed after interpenetrating ultraviolet cross-linking with linear polymers (LDPE, LLDPE, EVA), which can delay the relaxation of the molecular chain and slow down the diffusion of moisture; and it can absorb the energy of the initiation and growth of microcracks in XLPE to a certain extent, inhibit the initiation and growth of water trees, thereby effectively improving the water tree resistance and water aging resistance of the prepared insulating layer. In addition, the π-electron system in the carbazole structure helps to capture and inhibit the movement of the same-polarity charges, reduce charge migration, improve the insulation strength of the insulating layer, and increase its breakdown field strength; it can inhibit the initiation and further growth of water trees, effectively extending the service life of the cable.

[0046] Through a dithiol compound, vinyl EVA and vinyl carbazole compound are cross-linked by a thiol-ene click reaction to obtain modified EVA, making it and the insulating layer prepared therefrom have good toughness and water tree resistance and water aging resistance.

[0047] Furthermore, the inorganic filler is modified, and the specific process is as follows:

[0048] Mix the cross-linking agent and tetrahydrofuran, under the protection of a nitrogen atmosphere, adjust the system temperature to 0-8 °C, add mercapto siloxane and triethylamine, stir and restore to room temperature, and keep the reaction at this temperature for 24-27 h; carry out vacuum distillation to obtain allyl siloxane;

[0049] Place the inorganic filler in an ethanol solution and ultrasonically disperse it for 20-30 min. Adjust the pH of the system to 3.6-4.2 with hydrochloric acid, add allyl siloxane, raise the temperature to 70-80 °C, and stir and react for 8-12 h; wash, filter by suction, and dry to obtain the modified filler.

[0050] Further, the molar ratio of the crosslinking agent, mercapto siloxane, and triethylamine is 1:1:(1.8 - 2.5);

[0051] The mercapto siloxane is one of γ-mercaptopropyltrimethoxysilane and 11-mercaptoundecyltrimethoxysilane;

[0052] The ratio of the crosslinking agent to tetrahydrofuran is 5 g / 10 mL.

[0053] Further, the allyl siloxane is 10 - 60 wt% of the mass of the inorganic filler;

[0054] The ratio of the inorganic filler to the ethanol solution is 10 g / 100 mL;

[0055] The concentration of the ethanol solution is 60 - 75 v%.

[0056] In the above technical solution, the modified inorganic filler can serve as a physical crosslinking point in XLPE, form a crosslinking bond with PE and the crosslinking agent during the irradiation process, increase the crosslinking density of the system, and effectively improve the strength and toughness of the insulating layer. The prepared modified filler has a strong interfacial interaction with XLPE, can effectively prevent the inorganic filler from being released from the XLPE matrix, improve the water resistance of the insulating layer, and enhance its resistance to water aging. The large specific surface area of the inorganic filler and its interfacial interaction with XLPE enhance the binding effect of the insulating layer on carriers, inhibit the migration of carriers, shorten the free path of electrons, reduce the conductivity of the insulating layer, and increase the breakdown field strength; the binding of molecular chains is increased, the penetration and diffusion of moisture in the insulating layer are inhibited, and the water tree resistance of the insulating layer is further improved.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] A waterproof and anti-aging photovoltaic cable and its preparation process of the present invention prepare vinyl EVA by nucleophilic addition of 3,5,5-trimethylhexanoyl chloride and 2,5,5-trimethylheptanoyl chloride to the alcoholysis product of EVA. The tertiary carbonate isononanoate and neodecanoate have branched chains, which endow them with higher hydrolysis stability, effectively improve the water resistance of the insulating layer; and increase the water channel blocking effect, can prevent the penetration of moisture, reduce the slip of moisture under extrusion pressure, and improve the water tree aging resistance of the insulating layer. Specific Embodiments

[0059] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0060] In the following specific embodiments,

[0061] LDPE: DJ210, sourced from Shanghai Jinshan Petrochemical Company;

[0062] LLDPE: DFDA - 7042, sourced from Qilu Petrochemical Company;

[0063] EVA: EVA28 - 150, with a VA content of 28%, sourced from Beijing Orient Petrochemical Co., Ltd.;

[0064] The photoinitiator is benzophenone; the cross - linker is triallyl isocyanurate;

[0065] The inorganic filler is nano - silica: fumed silica, with an average particle size of 12 nm, sourced from Degussa (China) Investment Co., Ltd.;

[0066] The additives are a mixture of antioxidant 1010 and antioxidant 300, with a mass ratio of 1:1;

[0067] The cyclic catalyst is a cycloalkyl ruthenium catalyst, prepared with reference to 6cyc in the literature "Boydston A J, Xia Y, Kornfield JA, et al. Cyclic ruthenium - alkylidene catalysts for ring - expansion metathesis polymerization [J]. Journal of the American Chemical Society, 2008, 130(38):12775 - 12782";

[0068] The sheath material: 9323, sourced from Jiangsu Dewei New Materials Co., Ltd.;

[0069] The thicknesses of both the insulating layer and the sheath layer are 1.5 mm.

[0070] Example 1: A preparation process for a waterproof and anti - aging photovoltaic cable, including the following processes:

[0071] Step 1. Preparation of modified EVA:

[0072] 1.1. Mix 15 g of 2 - hydroxycarbazole and triethylamine in 500 mL of dichloromethane. Slowly add 5 - norbornene - 2 - carbonyl chloride at 8 °C within 20 min. Restore the temperature to 20 °C and react for 120 min. Wash, let it stand for layer separation, take the lower - layer liquid, and dry to obtain the polymerization monomer; the molar ratio of 2 - hydroxycarbazole, 5 - norbornene - 2 - carbonyl chloride, and triethylamine is 1:1:1;

[0073] Under the protection of nitrogen atmosphere, 30 g of polymerization monomer and 6.0 g of cyclic catalyst were mixed in 100 mL of dichloromethane, heated to 50 °C, and reacted for 100 h; cooled to -20 °C, and precipitated with cold methanol to obtain an alkenyl carbazole compound;

[0074] 1.2. Mix 15 g of EVA and 300 mL of toluene, heat to 60 °C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution, add it within 10 min, and stir and react for 150 min; cool, filter by suction, wash the precipitate, and dry it to obtain an EVA alcoholysis product;

[0075] Mix 10 g of EVA alcoholysis product and 1 L of toluene, heat to 60 °C under the protection of nitrogen atmosphere, and stir for 60 min; slowly add 2,5,5-trimethylheptanoyl chloride, 3,5,5-trimethylhexanoyl chloride, and acryloyl chloride, stir and react for 150 min; add the acid-binding agent triethanolamine, and react for 120 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry it to obtain alkenyl EVA; alkenyl EVA includes the following mass components: 100 parts of EVA alcoholysis product, 1 part of 3,5,5-trimethylhexanoyl chloride, 3 parts of 2,5,5-trimethylheptanoyl chloride, 4.5 parts of acryloyl chloride, and 12 parts of acid-binding agent triethanolamine;

[0076] Mix 10 g of alkenyl EVA and 100 mL of toluene, add a dithiol compound and the photoinitiator benzoin dimethyl ether, stir and irradiate with an ultraviolet lamp for 2 h; add the alkenyl carbazole compound, and continue to irradiate for 12 h; wash and dry to obtain modified EVA; the dithiol compound is 1,4-benzenedithiol; modified EVA includes the following mass components: 100 parts of alkenyl EVA, 10 parts of alkenyl carbazole compound, 5.6 parts of dithiol compound, and 2.4 parts of photoinitiator;

[0077] Step 2: Preparation of modified inorganic filler:

[0078] Mix 5 g of crosslinking agent and 10 mL of tetrahydrofuran, adjust the system temperature to 8 °C under the protection of nitrogen atmosphere, add γ-mercaptopropyltrimethoxysilane and triethylamine, stir and restore to room temperature, and keep the reaction at a constant temperature for 24 h; distill under reduced pressure to obtain allyl siloxane; the molar ratio of crosslinking agent, γ-mercaptopropyltrimethoxysilane, and triethylamine is 1:1:1.8;

[0079] Place 10 g of inorganic filler in 100 mL of 60 v% ethanol solution and ultrasonically disperse for 20 min, adjust the pH of the system to 3.6 with hydrochloric acid, add 1 g of allyl siloxane, heat to 70 °C, and stir and react for 12 h; wash, filter by suction, and dry to obtain modified filler;

[0080] Step 3: Preparation of photovoltaic cable:

[0081] Mix LDPE, LLDPE, modified EVA, modified filler, photoinitiator, crosslinking agent and additives, and then conduct mixing and kneading. The process conditions for kneading are as follows: temperature 145 °C, rotation speed 40 rmp, duration 30 min, to obtain insulating material; the insulating material includes the following mass components: 80 parts of LDPE, 20 parts of LLDPE, 6 parts of modified EVA, 1 part of photoinitiator, 1 part of crosslinking agent, 0.5 part of modified filler, 0.2 part of additives;

[0082] Extrude the insulating material to coat the conductor. The process conditions for extrusion are as follows: extrusion temperature 145 °C, monomer wire-walking speed 3.0 m / min; heat and irradiate to form an insulating layer. The process conditions for heating are as follows: temperature 155 °C, duration 76 s; the process conditions for irradiation are as follows: ultraviolet lamp power 1.0 W × 12 groups, duration 76 s;

[0083] Extrude the sheath material to coat the insulating layer to form a sheath layer, and obtain a photovoltaic cable.

[0084] Example 2: A preparation process of a waterproof and anti-aging photovoltaic cable, including the following processes:

[0085] Step 1: Preparation of modified EVA:

[0086] 1.1. Mix 15 g of 2-hydroxycarbazole and triethylamine in 500 mL of dichloromethane, and slowly add 5-norbornene-2-carbonyl chloride at 4 °C within 20 min; restore the temperature to 25 °C and react for 105 min; wash, let it stand for layer separation, take the lower-layer liquid, and dry to obtain a polymerization monomer; the molar ratio of 2-hydroxycarbazole, 5-norbornene-2-carbonyl chloride, and triethylamine is 1:1.05:1.05;

[0087] Under the protection of a nitrogen atmosphere, mix 30 g of the polymerization monomer and 6.8 g of a cyclic catalyst in 100 mL of dichloromethane, heat to 55 °C, and react for 98 h; cool to -20 °C and precipitate with cold methanol to obtain an alkenylcarbazole compound;

[0088] 1.2. Mix 16 g of EVA and 300 mL of toluene, heat to 65 °C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution within 10 min, stir and react for 120 min; cool, filter by suction, wash the precipitate, and dry to obtain an EVA alcoholysis product;

[0089] Mix 15 g of the EVA alcoholysis product with 1 L of toluene, heat to 65 °C under a nitrogen atmosphere, and stir for 45 min; slowly add 2,5,5-trimethylheptanoyl chloride, 3,5,5-trimethylhexanoyl chloride, and acryloyl chloride, and stir and react for 135 min; add the acid-binding agent triethanolamine and react for 105 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry to obtain vinyl EVA; the vinyl EVA includes the following mass components: 100 parts of the EVA alcoholysis product, 2.5 parts of 3,5,5-trimethylhexanoyl chloride, 1.5 parts of 2,5,5-trimethylheptanoyl chloride, 5 parts of acryloyl chloride, and 12.5 parts of the acid-binding agent triethanolamine;

[0090] Mix 10 g of vinyl EVA with 100 mL of toluene, add a dithiol compound and the photoinitiator benzoin dimethyl ether, stir and irradiate with an ultraviolet lamp for 3 h; add a vinyl carbazole compound and continue irradiating for 9 h; wash and dry to obtain modified EVA; the dithiol compound is 1,4-benzenedithiol; the modified EVA includes the following mass components: 100 parts of vinyl EVA, 16 parts of vinyl carbazole compound, 9.0 parts of dithiol compound, and 4.0 parts of photoinitiator;

[0091] Step 2: Preparation of modified inorganic filler:

[0092] Mix 5 g of crosslinking agent with 10 mL of tetrahydrofuran, adjust the system temperature to 4 °C under a nitrogen atmosphere, add γ-mercaptopropyltrimethoxysilane and triethylamine, stir and return to room temperature, and keep the reaction at a constant temperature for 25 h; carry out vacuum distillation to obtain allyl siloxane; the molar ratio of the crosslinking agent, γ-mercaptopropyltrimethoxysilane, and triethylamine is 1:1:2.1;

[0093] Place 10 g of inorganic filler in a 100 mL 66 v% ethanol solution and ultrasonically disperse for 25 min, adjust the pH of the system to 4.0 with hydrochloric acid, add 3.5 g of allyl siloxane, raise the temperature to 75 °C, and stir and react for 10 h; wash, filter by suction, and dry to obtain modified filler;

[0094] Step 3: Preparation of photovoltaic cable:

[0095] Mix LDPE, LLDPE, modified EVA, modified filler, photoinitiator, crosslinking agent, and additives, and carry out mixing and kneading. The process conditions for kneading are: temperature 150 °C, rotation speed 50 rmp, and duration 25 min to obtain insulating material; the insulating material includes the following mass components: 80 parts of LDPE, 20 parts of LLDPE, 9 parts of modified EVA, 2 parts of photoinitiator, 2 parts of crosslinking agent, 1.5 parts of modified filler, and 0.3 part of additive;

[0096] Extrude the insulating material so that the insulating material coats the conductor. The extrusion process conditions are as follows: extrusion temperature 155°C, monomer running speed 3.0 m / min; heat and irradiate to form an insulating layer. The heating process conditions are: temperature 160°C, duration 60; the irradiation process conditions are: ultraviolet lamp power 1.0 W × 12 groups, duration 406 s;

[0097] Extrude the sheath material so that the sheath material coats the insulating layer to form a sheath layer, obtaining a photovoltaic cable.

[0098] Example 3: A preparation process for a waterproof and anti-aging photovoltaic cable, including the following processes:

[0099] Step 1. Preparation of modified EVA:

[0100] 1.1. Mix 15 g of 2-hydroxycarbazole and triethylamine in 500 mL of dichloromethane. At 0°C, slowly add 5-norbornene-2-carbonyl chloride, and finish adding it in 20 min; restore the temperature to 30°C and react for 90 min; wash, let it stand for layer separation, take the lower-layer liquid, dry it to obtain a polymerization monomer; the molar ratio of 2-hydroxycarbazole, 5-norbornene-2-carbonyl chloride, and triethylamine is 1:1.1:1.1;

[0101] Under the protection of a nitrogen atmosphere, mix 30 g of the polymerization monomer and 7.5 g of a cyclic catalyst in 100 mL of dichloromethane, heat up to 60°C, and react for 96 h; cool to -20°C, precipitate with cold methanol to obtain a vinylcarbazole compound;

[0102] 1.2. Mix 18 g of EVA and 300 mL of toluene, heat to 70°C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution, finish adding it within 10 min, and stir and react for 100 min; cool, filter by suction, wash the precipitate, and dry it to obtain an EVA alcoholysis product;

[0103] Mix 20 g of the EVA alcoholysis product and 1 L of toluene, under the protection of a nitrogen atmosphere, heat to 70°C, and stir for 30 min; slowly add 3,5,5-trimethylhexanoyl chloride and acryloyl chloride, stir and react for 120 min; add the acid-binding agent triethanolamine and react for 90 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry it to obtain vinyl EVA; vinyl EVA includes the following mass components: 100 parts of EVA alcoholysis product, 4 parts of 3,5,5-trimethylhexanoyl chloride, 6.0 parts of acryloyl chloride, and 13 parts of the acid-binding agent triethanolamine;

[0104] Mix 10 g of vinyl EVA and 100 mL of toluene, add a dithiol compound and the photoinitiator benzoin dimethyl ether, stir and irradiate with an ultraviolet lamp for 4 h; add a vinyl carbazole compound and continue irradiating for 12 h; wash and dry to obtain modified EVA; the dithiol compound is 1,4-benzenedithiol; the modified EVA includes the following mass components: 100 parts of vinyl EVA, 22 parts of vinyl carbazole compound, 12.3 parts of dithiol compound, and 5.3 parts of photoinitiator;

[0105] Step 2: Preparation of modified inorganic filler:

[0106] Mix 5 g of crosslinking agent and 10 mL of tetrahydrofuran, under the protection of a nitrogen atmosphere, adjust the system temperature to 0 °C, add γ-mercaptopropyltrimethoxysilane and triethylamine, stir and restore to room temperature, and keep the reaction at a constant temperature for 27 h; carry out vacuum distillation to obtain allyl siloxane; the molar ratio of the crosslinking agent, γ-mercaptopropyltrimethoxysilane, and triethylamine is 1:1:2.5;

[0107] Place 10 g of inorganic filler in 100 mL of 75 v% ethanol solution and ultrasonically disperse for 30 min, adjust the pH of the system to 4.2 with hydrochloric acid, add 6 g of allyl siloxane, raise the temperature to 80 °C, and stir and react for 8 h; wash, filter by suction, and dry to obtain modified filler;

[0108] Step 3: Preparation of photovoltaic cable:

[0109] Mix LDPE, LLDPE, modified EVA, modified filler, photoinitiator, crosslinking agent, and additives, and carry out mixing and kneading. The process conditions for kneading are: temperature 160 °C, rotation speed 60 rmp, duration 20 min, to obtain insulating material; the insulating material includes the following mass components: 80 parts of LDPE, 20 parts of LLDPE, 12 parts of modified EVA, 3 parts of photoinitiator, 3 parts of crosslinking agent, 3.0 parts of modified filler, and 0.5 part of additive;

[0110] Extrude the insulating material so that the insulating material coats the conductor. The process conditions for extrusion are: extrusion temperature 170 °C, monomer wire feeding speed 3.0 m / min; heat and irradiate to form an insulating layer. The process conditions for heating are: temperature 170 °C, duration 44 s; the process conditions for irradiation are: ultraviolet lamp power 1.0 W × 12 groups, duration 76 s;

[0111] Extrude the sheath material so that the sheath material coats the insulating layer to form a sheath layer, and obtain the photovoltaic cable.

[0112] Comparative Example 1: A preparation process for a waterproof and anti-aging photovoltaic cable, including the following processes:

[0113] Step 2: Preparation of modified inorganic filler:

[0114] Disperse 10 g of inorganic filler in 100 mL of 60 v% ethanol solution by ultrasonic for 20 min. Adjust the pH of the system to 3.6 with hydrochloric acid, add 1 g of silane coupling agent A151, heat up to 70 °C, and stir and react for 12 h; wash, filter by suction, and dry to obtain the modified filler;

[0115] Steps 1 and 3 are the same as those in Example 1 to obtain the photovoltaic cable.

[0116] Comparative Example 2: A preparation process of a waterproof and anti-aging photovoltaic cable, including the following processes:

[0117] Step 1, Preparation of modified EVA:

[0118] 1.1. Under the protection of nitrogen atmosphere, mix 30 g of methyl 5-norbornene-2-carboxylate and 6.0 g of cyclic catalyst in 100 mL of dichloromethane, heat up to 50 °C, and react for 100 h; cool to -20 °C and precipitate with cold methanol to obtain the cyclic polymer;

[0119] 1.2. Mix 15 g of EVA and 300 mL of toluene, heat to 60 °C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution within 10 min, finish adding within 10 min, and stir and react for 150 min; cool, filter by suction, wash the precipitate, and dry to obtain the EVA alcoholysis product;

[0120] Mix 10 g of the EVA alcoholysis product and 1 L of toluene, heat to 60 °C under the protection of nitrogen atmosphere, and stir for 60 min; slowly add 2,5,5-trimethylheptanoyl chloride, 3,5,5-trimethylhexanoyl chloride, and acryloyl chloride, and stir and react for 150 min; add the acid-binding agent triethanolamine and react for 120 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry to obtain vinyl EVA; vinyl EVA includes the following mass components: 100 parts of EVA alcoholysis product, 1 part of 3,5,5-trimethylhexanoyl chloride, 3 parts of 2,5,5-trimethylheptanoyl chloride, 4.5 parts of acryloyl chloride, and 12 parts of acid-binding agent triethanolamine;

[0121] Mix 10 g of vinyl EVA and 100 mL of toluene, add a dithiol compound and the photoinitiator benzoin dimethyl ether, stir and irradiate with an ultraviolet lamp for 2 h; add the cyclic polymer and continue irradiating for 12 h; wash and dry to obtain the modified EVA; the dithiol compound is 1,4-benzenedithiol; the modified EVA includes the following mass components: 100 parts of vinyl EVA, 10 parts of cyclic polymer, 5.6 parts of dithiol compound, and 2.4 parts of photoinitiator;

[0122] Steps 2 and 3 are the same as those in Comparative Example 1 to obtain the photovoltaic cable.

[0123] Comparative Example 3: A preparation process of a waterproof and anti-aging photovoltaic cable, including the following processes:

[0124] Step 1, preparation of modified EVA:

[0125] Mix 15 g of EVA and 300 mL of toluene, heat to 60 °C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution, add it within 10 min, and stir and react for 150 min; cool, filter by suction, wash the precipitate, and dry to obtain the EVA alcoholysis product;

[0126] Mix 10 g of the EVA alcoholysis product and 1 L of toluene, heat to 60 °C under a nitrogen atmosphere protection, and stir for 60 min; slowly add 2,5,5-trimethylheptanoyl chloride, 3,5,5-trimethylhexanoyl chloride, and acryloyl chloride, and stir and react for 150 min; add the acid-binding agent triethanolamine, and react for 120 min; cool, precipitate with ethanol, filter by suction, wash the precipitate, and dry to obtain vinyl EVA; the vinyl EVA includes the following mass components: 100 parts of EVA alcoholysis product, 1 part of 3,5,5-trimethylhexanoyl chloride, 3 parts of 2,5,5-trimethylheptanoyl chloride, 4.5 parts of acryloyl chloride, and 12 parts of acid-binding agent triethanolamine;

[0127] Mix 10 g of vinyl EVA and 100 mL of toluene, add a dithiol compound and the photoinitiator benzoin dimethyl ether, stir and irradiate with an ultraviolet lamp for 2 h; add N-vinylcarbazole, and continue irradiating for 12 h; wash and dry to obtain modified EVA; the dithiol compound is 1,4-benzenedithiol; the modified EVA includes the following mass components: 100 parts of vinyl EVA, 6 parts of N-vinylcarbazole, 5.6 parts of dithiol compound, and 2.4 parts of photoinitiator;

[0128] Steps 2 and 3 are the same as those in Comparative Example 1 to obtain a photovoltaic cable.

[0129] Comparative Example 4: A preparation process of a waterproof and anti-aging photovoltaic cable, including the following processes:

[0130] Step 1, preparation of modified EVA:

[0131] Mix 15 g of EVA and 300 mL of toluene, heat to 60 °C, and stir to dissolve; slowly add 50 mL of 5 wt% sodium hydroxide / methanol solution, add it within 10 min, and stir and react for 150 min; cool, filter by suction, wash the precipitate, and dry to obtain the EVA alcoholysis product;

[0132] Mix 10 g of the alcoholysis product of EVA with 1 L of toluene. Under the protection of a nitrogen atmosphere, heat the mixture to 60 °C and stir for 60 min. Slowly add 2,5,5-trimethylheptanoyl chloride and 3,5,5-trimethylhexanoyl chloride, and stir the reaction for 150 min. Add the acid-binding agent triethanolamine and react for 120 min. Cool the mixture, precipitate it with ethanol, filter it by suction, wash the precipitate, and dry it to obtain modified EVA.

[0133] Steps 2 and 3 are the same as those in Comparative Example 1 to obtain a photovoltaic cable.

[0134] Comparative Example 5: A preparation process of a waterproof and anti-aging photovoltaic cable, including the following processes:

[0135] Step 1, the preparation of modified filler, is the same as that in Comparative Example 1 to obtain modified filler.

[0136] Step 2, the preparation of photovoltaic cable:

[0137] Mix LDPE, LLDPE, EVA, modified filler, photoinitiator, crosslinking agent, and additives, and knead them. The kneading process conditions are: temperature 145 °C, rotation speed 40 rmp, duration 30 min, to obtain insulating material. The insulating material includes the following mass components: 80 parts of LDPE, 20 parts of LLDPE, 6 parts of EVA, 1 part of photoinitiator, 1 part of crosslinking agent, 0.5 part of modified filler, and 0.2 part of additive.

[0138] Extrude the insulating material so that the insulating material coats the conductor. The extrusion process conditions are: extrusion temperature 145 °C, monomer running speed 3.0 m / min; heat and irradiate to form an insulating layer. The heating process conditions are: temperature 155 °C, duration 76 s; the irradiation process conditions are: ultraviolet lamp power 1.0 W × 12 groups, duration 76 s.

[0139] Extrude the sheath material so that the sheath material coats the insulating layer to form a sheath layer to obtain a photovoltaic cable.

[0140] Experiment: Take the photovoltaic cables obtained in Examples 1-3 and Comparative Examples 1-5, prepare specimens, and detect and record the test results of their properties respectively:

[0141] Mechanical property test: Referring to GB / T 2951.11 as the reference standard, use an electronic universal testing machine to detect the tensile properties of the insulating layer specimens. The tensile rate is 250 mm / min, the test temperature is 23 °C, the specimens are type II dumbbell-shaped pieces with dimensions of 25 mm × 4 mm × 1.0 mm.

[0142] Volume resistivity test: Use a high resistance meter to detect the volume resistivity of the insulating layer specimens. The test voltage is 1 kV, and the specimen size is Φ100 mm × 1.0 mm.

[0143] AC breakdown field strength test: Aluminum was plated on both sides of the insulating layer sample with a thickness of 100 μm as electrodes, and the sample was placed in silicone oil. The voltage was increased at a rate of 4 kV / s until the sample broke down, and the characteristic breakdown field strength with a 63.2% failure probability was used as the performance data;

[0144] Water resistance performance test: The insulating layer sample was immersed in deionized water for 30 d, and its performance was detected again;

[0145] Water tree aging performance test: Needles were inserted on the surface of the insulating layer sample. The sample size was 100 mm × 100 mm × 5.0 mm, the number of inserted needles was 30, the needle penetration depth was 3 mm, and the needle insertion angle was 60°. These were used as the starting points for the initiation and growth of water trees. The sample was placed at 90 °C for 4 h to eliminate stress; The needle hole surface was contacted with 10 wt% NaCl solution, and aluminum was plated on the other side of the insulating layer as a grounding electrode. The current was applied for 21 d, the voltage was 4 kV, and the frequency was 6000 Hz; After taking it out, it was impregnated and dyed with 5 wt% potassium permanganate solution, and the average length of the water tree (in the direction of the electric field) was detected. The ratio of the number of needle holes that initiated water trees to the total number of needle holes was used as the water tree growth probability.

[0146]

[0147] According to the data in the above table, the following conclusions can be clearly obtained:

[0148] The photovoltaic cables obtained in Examples 1-3 were compared with the photovoltaic cables obtained in Comparative Examples 1-5. The test results showed that

[0149] Compared with the comparative examples, for the photovoltaic cables obtained in Examples 1-3, their insulating layers had better tensile strength and volume resistivity data before and after immersion in water, and the average length of their water trees and the water tree growth probability were lower. This fully demonstrates that the present invention has achieved an improvement in the water resistance, water tree resistance, and anti-aging performance of the insulating layer, and the manufactured photovoltaic cables have better water resistance and anti-aging capabilities.

[0150] Compared with Example 1, the inorganic filler in Comparative Example 1 was surface-modified with silane coupling agent A151. Compared with Comparative Example 1, the modified EVA in Comparative Example 2 was prepared from vinyl EVA, a cyclic polymer obtained by metathesis polymerization of methyl 5-norbornene-2-carboxylate, and a dimercapto compound; the modified EVA in Comparative Example 3 was prepared from vinyl EVA, N-vinylcarbazole, and a dimercapto compound; the modified EVA in Comparative Example 4 was prepared from an alcoholysis product of EVA, 3,5,5-trimethylhexanoyl chloride, and 2,5,5-trimethylheptanoyl chloride; the EVA in Comparative Example 5 was not modified. Compared with Example 1, for the photovoltaic cables obtained in Comparative Examples 1-5, the tensile strength and volume resistivity data of their insulating layers were lower before and after immersion in water; the average length and growth probability of water trees increased. It can be seen that the modification process of EVA and the components used in the present invention can promote the improvement of the water resistance, water tree resistance, and anti-aging performance of the insulating layer, and contribute to the improvement of the water and anti-aging resistance of the photovoltaic cable.

[0151] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0152] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation process of a waterproof and anti-aging photovoltaic cable, characterized in that: It includes the following processes: Mix LDPE, LLDPE, modified EVA, inorganic filler, photoinitiator, crosslinking agent and auxiliary agent, and then carry out kneading to obtain insulating material; Extrude the insulating material so that it coats the conductor; heat and irradiate to form an insulating layer; extrude the sheath material so that it coats the insulating layer to form a sheath layer, and obtain a photovoltaic cable; The modified EVA is prepared by the following process: Mix EVA and toluene, heat to 60 - 70 °C, and stir to dissolve; slowly add sodium hydroxide / methanol solution and finish adding it within 10 min, and then stir and react for 100 - 150 min to obtain an EVA alcoholysis product; Mix the EVA alcoholysis product and toluene, under the protection of nitrogen atmosphere, heat to 60 - 70 °C, and stir for 30 - 60 min; slowly add 2,5,5 - trimethylheptanoyl chloride, 3,5,5 - trimethylhexanoyl chloride and acryloyl chloride, and stir and react for 120 - 150 min; add an acid-binding agent and react for 90 - 120 min to obtain alkenyl EVA; Mix the alkenyl EVA and toluene, add a dithiol compound and a photoinitiator, stir and irradiate with an ultraviolet lamp for 2 - 4 h; add an alkenyl carbazole compound and continue to irradiate for 8 - 12 h to obtain modified EVA; The alkenyl carbazole compound is prepared by the following process: Mix 2 - hydroxycarbazole and triethylamine in dichloromethane, and slowly add 5 - norbornene - 2 - acyl chloride at 0 - 8 °C within 20 min; restore the temperature to 20 - 30 °C and react for 90 - 120 min to obtain a polymerization monomer; Under the protection of nitrogen atmosphere, mix the polymerization monomer and a cyclic catalyst in dichloromethane, heat to 50 - 60 °C, and react for 96 - 100 h to obtain an alkenyl carbazole compound.

2. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 1, characterized in that: The inorganic filler is modified, and the specific process is as follows: Mix a crosslinking agent and tetrahydrofuran, under the protection of nitrogen atmosphere, adjust the system temperature to 0 - 8 °C, add a mercapto siloxane and triethylamine, stir and restore to room temperature, and keep the temperature for reaction for 24 - 27 h; carry out vacuum distillation to obtain allyl siloxane; Place the inorganic filler in an ethanol solution and carry out ultrasonic dispersion for 20 - 30 min, adjust the pH of the system to 3.6 - 4.2 with hydrochloric acid, add allyl siloxane, heat to 70 - 80 °C, and stir and react for 8 - 12 h; Wash, filter by suction, and dry to obtain a modified filler.

3. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 2, characterized in that: The insulating material includes the following mass components: 50 - 90 parts of LDPE, 10 - 50 parts of LLDPE, 6 - 12 parts of modified EVA, 1 - 3 parts of photoinitiator, 1 - 3 parts of crosslinking agent, 0.5 - 3.0 parts of modified filler, 0.2 - 0.5 parts of auxiliary agent.

4. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 1, characterized in that: The process conditions for heating are: temperature 155 - 170 °C, duration 44 - 76 s.

5. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 1, wherein: The process conditions for irradiation are: ultraviolet lamp power 1.0 W × 12 groups, duration 76 - 136 s.

6. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 1, characterized in that: The alkenyl EVA includes the following mass components: 100 parts of EVA alcoholysis product, 1 - 4 parts of 3,5,5 - trimethylhexanoyl chloride, 0 - 3 parts of 2,5,5 - trimethylheptanoyl chloride, 4.5 - 6.0 parts of acryloyl chloride, 12 - 13 parts of acid-binding agent.

7. The preparation process of a waterproof and anti-aging photovoltaic cable according to claim 1, characterized in that: The modified EVA comprises the following mass components: 100 parts of vinyl EVA, 10 to 22 parts of vinyl carbazole compound, 5.6 to 22.1 parts of dithiol compound, and 2.4 to 11.0 parts of photoinitiator.

8. A waterproof and anti-aging photovoltaic cable, characterized in that: It is prepared by using the preparation process described in any one of claims 1-7.

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