A green and environmentally friendly heat-resistant photovoltaic cable and its preparation method

Abstract

The present invention provides a green and environmentally friendly heat-resistant photovoltaic cable and a preparation method thereof, which relates to the technical field of cable processing. The preparation method includes: S1, preparing a first PVC by suspension polymerization; S2-1, preparing a second PVC by emulsion method; S3, modifying porous PET with the second PVC to obtain modified PET; S4, melting and extruding raw materials including the first PVC and the modified PET, and coating the surface of the cable core as a sheath layer to obtain a photovoltaic cable. The photovoltaic cable obtained by the preparation method of the present invention has good degradability, and is not easily softened under higher ambient temperatures, and can maintain its size and shape at high temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of cable processing, and more particularly, to a green and environmentally friendly heat-resistant photovoltaic cable and a preparation method thereof. Background Art

[0002] Photovoltaic cables are special cables in solar power generation systems, mainly used for power transmission between components and between components and inverters. The basic structure of a photovoltaic cable includes: a conductor core, an insulating layer, and a sheath layer. The conductor usually uses high-purity oxygen-free copper or tin-plated copper, the material of the insulating layer is usually a polymer, and the sheath layer is made of a polymer or composite material.

[0003] The function of the sheath layer is to protect the cable core and prevent the cable core from being damaged due to stretching, bending, or extrusion during installation or use. In recent years, due to green environmental protection considerations, biodegradable polymer materials such as polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoates (PHA), and polyethylene terephthalate (PET) have gradually been applied in the cable sheath layer.

[0004] For example, the Chinese patent application with the publication number CN114729176A discloses a cable insulation material for automobiles mainly made of polyethylene terephthalate. The Chinese patent application with the publication number CN105348575A discloses a cable sheath rubber coating mainly made of natural rubber and polylactic acid. The Chinese patent application with the publication number CN117766215A discloses a cable sheath mainly made of a block copolymer composed of polylactic acid, terephthalic acid (PTA), and polyethylene glycol (PEG).

[0005] Considering problems such as weather resistance, cost, and mechanical strength, it is not realistic to completely use biodegradable materials to manufacture cable sheaths. Therefore, mixing traditional polymers and biodegradable polymers to prepare the cable sheath layer has become a development trend in this field.

[0006] For example, prior arts including Chinese patent applications such as CN104861352A and CN107090147A have all made attempts to prepare cable materials by mixing polyvinyl chloride (PVC) and polyethylene terephthalate and adding other additives.

[0007] Polyvinyl chloride materials have been widely used in the preparation of sheath layers, and polyethylene terephthalate can improve the degradability and heat resistance of polyvinyl chloride materials. However, in terms of chemical structure, polyethylene terephthalate is a thermoplastic polyester, while polyvinyl chloride is a polar plastic. The molecular chain structure and polarity of these two plastics are different, resulting in a lack of sufficient interaction between them, making it difficult to form good compatibility. Therefore, how to improve the compatibility between polyethylene terephthalate and polyvinyl chloride has always been a technical problem to be solved by technical personnel in the field, and is also the key to successfully obtaining a polyvinyl chloride and polyethylene terephthalate composite sheath material that is both environmentally friendly and heat-resistant. Summary of the invention

[0008] One of the problems solved by the present invention is how to provide an environmentally friendly and heat-resistant photovoltaic cable with polyvinyl chloride and polyethylene terephthalate as a composite sheath layer.

[0009] In order to solve at least one of the above problems, the present invention provides a method for preparing a green, environmentally friendly, heat-resistant photovoltaic cable, comprising:

[0010] S1, preparing a first PVC by suspension polymerization;

[0011] S2, preparing a second PVC by an emulsion method;

[0012] S3, using the second PVC to modify the porous PET to obtain modified PET;

[0013] S4. Melt-extrude the raw materials including the first PVC and the modified PET, and coat the surface of the cable core as a sheath layer to obtain a photovoltaic cable.

[0014] In any of the above technical solutions, the first PVC is hard PVC, and the second PVC is PVC paste resin.

[0015] In any of the above technical solutions, the porous PET is prepared by the following steps:

[0016] A1. Using acetylated chitosan as a porogen and inorganic non-metallic oxide as a flame retardant, adding acetic acid and water and mixing evenly to prepare a suspended first aqueous phase;

[0017] A2, using PET and organic solvent to prepare the first oil phase;

[0018] A3, obtaining a first emulsion by mixing and emulsifying the first water phase and the first oil phase;

[0019] A4. Add polyvinyl alcohol to the first emulsion, heat and stir evenly, let it stand, and then distill under reduced pressure to remove the solvent to obtain porous PET.

[0020] In any of the above technical solutions, in step S2, the raw materials used include glutamic acid.

[0021] In any of the above technical solutions, in step A1, by mass ratio, acetylated chitosan: inorganic non-metallic oxide: acetic acid: water = (1 - 2):(2 - 4):(4 - 8):100.

[0022] In any of the above technical solutions, in step A2, by mass ratio, PET: organic solvent = (6 - 12):100.

[0023] In any of the above technical solutions, in step A2, the organic solvent includes phenol and tetrachloroethane with a mass ratio of 1:1.

[0024] In any of the above technical solutions, in step A2, the first oil phase is prepared by heating PET and the organic solvent to 65°C to 75°C, holding the temperature and magnetically stirring at a speed of 400 rpm / min to 500 rpm / min until PET is completely dissolved.

[0025] In any of the above technical solutions, in step A3, by mass ratio, the first aqueous phase: the first oil phase = (80 - 120):100.

[0026] In any of the above technical solutions, in step A3, the mixing and emulsifying method is: dropping the first aqueous phase into the first oil phase at 65°C to 75°C and stirring, after dropping, holding the temperature and ultrasonically emulsifying at a power of 400 W to 600 W and a frequency of 60 kHz to 80 kHz for 20 min to 40 min.

[0027] In any of the above technical solutions, in step A4, by mass ratio, the first emulsion: polyvinyl alcohol = 100:(6 - 12).

[0028] In any of the above technical solutions, in step A4, the heating and stirring evenly method is: magnetically stirring at a speed of 100 rpm / min to 200 rpm / min at a temperature of 95°C to 98°C until polyvinyl alcohol is completely dissolved.

[0029] In any of the above technical solutions, in step A4, during the standing process, it is naturally cooled, and the standing time is 20 min to 40 min.

[0030] In any of the above technical solutions, in step A4, after vacuum distillation, the solid matter is extracted, washed and dried to obtain porous PET.

[0031] In any of the above technical solutions, step S1 specifically includes:

[0032] S11. According to the mass ratio of dispersant: first initiator: water = (0.2 - 1):(1 - 3):100, dissolve the dispersant in water and disperse it evenly. After adjusting the pH value to 7 - 9, add the first initiator dissolved in an organic solvent and feed it into the polymerization kettle.

[0033] S12. According to the mass ratio of first vinyl chloride monomer: water = (200 - 300):100, and based on the amount of water added in S11, add the first vinyl chloride monomer to the polymerization kettle to form a suspension with water.

[0034] S13. Under the protection of an inert gas atmosphere, heat the sealed polymerization kettle to 55°C - 65°C to carry out the polymerization reaction and detect the pressure inside the polymerization kettle.

[0035] S14. When the real - time pressure inside the polymerization kettle drops to 25% - 30% of the peak pressure inside the polymerization kettle, terminate the polymerization reaction, cool down and release the pressure, separate the solid matter, wash and dry to obtain the first PVC.

[0036] In any of the above technical solutions, step S2 specifically includes:

[0037] S21. According to the mass ratio of glutamic acid: water = (4 - 6):100, dissolve glutamic acid in water to prepare the second aqueous phase.

[0038] S22. According to the mass ratio of stabilizer: second initiator: plasticizer: emulsifier: second vinyl chloride monomer = (8 - 12):(1 - 2):(1 - 2):(2 - 8):100, mix the stabilizer, second initiator, plasticizer, emulsifier and second vinyl chloride monomer evenly to prepare the second oil phase.

[0039] S23. According to the mass ratio of second aqueous phase: second oil phase = (100 - 150):100, drop the second aqueous phase into the second oil phase and emulsify it to obtain the second emulsion.

[0040] S24. Add polyvinyl alcohol and water to the second emulsion, heat, stir and react, then let it stand, and centrifuge the product, wash to obtain the second PVC.

[0041] In any of the above technical solutions, step S3 specifically includes:

[0042] S31. According to the mass ratio of second PVC: porous PET: water: tetrahydrofuran = (4 - 6):(20 - 25):(8 - 12):100, mix the second PVC evenly in tetrahydrofuran, add the mixture of porous PET and water, adjust the pH value to 7 - 8, and perform ultrasonic treatment.

[0043] S32. After the ultrasonic treatment, rotary evaporate tetrahydrofuran and water to obtain the modified PET.

[0044] In any of the above technical solutions, step S4 specifically includes:

[0045] S41. Pay out and preheat the cable core.

[0046] S42. According to the mass ratio of additive: modified PET: first PVC = (4 - 8):(10 - 15):100, melt and extrude raw materials including the additive, modified PET and first PVC under the temperature condition of 180°C to 200°C, coat the surface of the cable core, and take up the wire after cooling to obtain a photovoltaic cable.

[0047] The present invention also provides a green and environmentally friendly heat-resistant photovoltaic cable, which is obtained by using the preparation method of any of the above technical solutions.

[0048] Beneficial effects

[0049] The present invention provides a preparation method of a green and environmentally friendly heat-resistant photovoltaic cable. This method first prepares the first PVC by suspension polymerization and prepares the second PVC by emulsion polymerization. Then, the second PVC is used to modify the porous PET to obtain modified PET. Finally, the raw materials including the first PVC and the modified PET are melt-extruded and coated on the surface of the cable core as a sheath layer to obtain a photovoltaic cable.

[0050] First, polyvinyl chloride has the advantages of good electrical insulation, corrosion resistance, anti-aging, and good flame retardancy. And polyethylene terephthalate has better degradability and biocompatibility. Therefore, by adding polyethylene terephthalate, the degradability of the polyvinyl chloride material can be improved, its degradation speed can be increased, the degradation difficulty can be reduced, and it is more green and environmentally friendly. In addition, polyethylene terephthalate has good crystallinity. Adding it to polyvinyl chloride can reduce the thermal shrinkage rate of the material and improve the good dimensional stability of the cable in a high-temperature use environment. Finally, adding polyethylene terephthalate to polyvinyl chloride can enhance the mechanical properties of the cable material, especially the tensile strength and toughness, and thus make the cable more resistant to stretching and have a larger elongation at break. Therefore, by compounding polyvinyl chloride and polyethylene terephthalate, a sheath layer material with optimized environmental protection performance and heat resistance can be obtained, which is not only easier to degrade, but also can maintain dimensional stability in the natural environment in midsummer and is not easy to deform and damage.

[0051] Second aspect: Considering the poor compatibility between polyethylene terephthalate and polyvinyl chloride, the present invention improves the compatibility between polyethylene terephthalate and polyvinyl chloride through the following process. First, the present invention treats polyethylene terephthalate to form a porous state, namely porous PET. Second, the present invention uses the PVC paste resin (i.e., the second PVC) prepared by the emulsion method to modify the porous PET. The pore structure makes the specific surface area of the porous PET larger and the adsorption performance better. The PVC paste resin prepared by the emulsion method of the present invention has smaller particle size and better fluidity. Using it to treat the porous PET makes it easier for the small-sized PVC to adhere to the surface of the porous PET. The present invention uses the rigid PVC (i.e., the first PVC) prepared by suspension polymerization as the main material of the sheath layer. The compatibility between the porous PET modified by the second PVC and the first PVC is improved and enhanced, so that a sheath layer material with uniform and stable properties, better performance, and longer service life can be prepared.

[0052] Third aspect: In some key processes of the present invention, the emulsion method of water-oil mixing is used to prepare an emulsion, and the hydrophilicity of polyvinyl alcohol is used to extract the water phase in the emulsion. Thus, the present invention can add the modifying substance to the water phase and prepare the substance to be modified into the oil phase. Through the extraction of the water phase by polyvinyl alcohol, the modifying substance can modify the substance to be modified. Specifically, in order to prepare porous PET, the present invention dissolves PET in an organic solvent to form an oil phase, and dissolves chitosan in water under the action of acetic acid. Through water-oil mixing and emulsification, a water-in-oil emulsion is formed. During the process of adding polyvinyl alcohol to the emulsion and heating and stirring, polyvinyl alcohol gradually dissolves, and the water phase carrying chitosan wrapped by the oil phase in the emulsion moves outwards from the inner core through the oil phase, forming pores in the PET, thereby forming porous PET with uniform pore distribution. During the process of preparing the second PVC by the emulsion method, vinyl chloride monomer is formulated as the oil phase, and glutamic acid is formulated as the water phase. Through water-oil mixing and emulsification, a water-in-oil emulsion is formed. During the process of adding polyvinyl alcohol to the emulsion and diluting with water, glutamic acid moves outwards from the inner core through the oil phase following the water phase, and heating drives the polymerization reaction to proceed, obtaining the second PVC modified by glutamic acid. The porous PET contains a small amount of chitosan that exhibits cationic characteristics when encountering water, while glutamic acid dissociates hydrogen ions from its carboxyl group in a neutral or weakly alkaline environment after encountering water, thus having anionic characteristics. Therefore, during the process of treating the porous PET obtained from A1 to A4 with the second PVC obtained from S21 to S23 in S31, the electrostatic adsorption of anions and cations helps the porous PET to uniformly adsorb the second PVC, further improving the compatibility between the modified PET and the first PVC during the melt extrusion process.

[0053] Fourthly, although a small amount of chitosan remaining in the porous PET can be decomposed during the melting process at nearly 200°C, considering ordinary chitosan with hydroxyl groups, dehydration will occur during the melting process. The polyethylene terephthalate material is prone to degradation when encountering water under high-temperature conditions, resulting in a reduction in the mechanical properties of the sheath layer. To avoid the above situation, the present invention adopts acetylated chitosan. By replacing the hydroxyl groups in the chitosan molecule with acetyl groups, the degradation of the polyethylene terephthalate material under high-temperature melting conditions is avoided, and the mechanical properties of the sheath layer are improved.

[0054] Fifthly, the flame retardancy of polyethylene terephthalate is weaker than that of polyvinyl chloride. This means that in extreme situations such as fires, the polyvinyl chloride material containing polyethylene terephthalate is more likely to burn and spread compared to pure polyvinyl chloride material. Therefore, during the modification of the porous PET in the present invention, an inorganic non-metallic oxide is added to the aqueous phase as a flame retardant. By jointly formulating the aqueous phase with the flame retardant and chitosan, under the aqueous phase extraction action of polyvinyl alcohol, the flame retardant can be uniformly mixed in the PET material and adhere to the pores inside and on the surface of the porous PET, improving the flame retardancy of the sheath layer. Specific Embodiments

[0055] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will make a detailed description in combination with the specific embodiments of the present invention.

[0056] Unless otherwise specified, the reagents and raw materials used in the present invention can be purchased through commercial channels. The experimental methods without specific conditions noted in the following examples are carried out according to conventional methods and conditions, or selected according to the product instructions.

[0057] The present invention provides a preparation method for a green and environmentally friendly heat-resistant photovoltaic cable. The photovoltaic cable at least includes a cable core and a sheath layer. Among them, the core structure of the cable core is a conductor, and an insulating layer is wrapped around the outer periphery of the conductor. A conductor shielding layer can be provided between the conductor and the insulating layer. An insulating shielding layer can also be wrapped around the outer periphery of the insulating layer. In addition, a water-blocking tape layer can also be provided outside the insulating shielding layer. The conductor is generally made of high-purity oxygen-free copper or tinned copper stranded together. The insulating layer is generally prepared from high-molecular compounds such as polyvinyl chloride, polyethylene, ethylene-propylene rubber, or their combinations. The conductor shielding layer and the insulating shielding layer are used to smooth the electric field distribution, prevent partial discharge and electromagnetic interference, and generally can be made of metal materials or semiconductor materials. The water-blocking tape layer is usually made of highly absorbent fibers or non-woven fabrics impregnated with highly absorbent resins.

[0058] The present invention uses polyvinyl chloride (hereinafter referred to as PVC) and polyethylene terephthalate (hereinafter referred to as PET) as the main raw materials for the sheath layer, and prepares a photovoltaic cable by melting and extruding the preheated cable core.

[0059] Specifically, the preparation method of the present invention includes:

[0060] S1. Prepare the first PVC by suspension polymerization;

[0061] S2. Prepare the second PVC by emulsion method;

[0062] S3. Modify the porous PET with the second PVC to obtain modified PET;

[0063] S4. Melt and extrude the raw materials including the first PVC and the modified PET, and coat the surface of the cable core as a sheath layer to obtain a photovoltaic cable.

[0064] The purpose of the present invention is to use the second PVC prepared by the emulsion method to modify the porous PET, in order to improve the compatibility between the porous PET and the first PVC, thereby improving the homogeneity degree, performance parameters and service life of the sheath layer.

[0065] The key factor for the above purpose to be achieved is: enabling the surface of the porous PET to uniformly, effectively and abundantly adhere to the second PVC. The present invention starts from the following three aspects and ensures the above purpose is achieved through process improvement: ensuring that the second PVC has a smaller particle size and better fluidity through the emulsion method; ensuring that the pores and pore sizes of the porous PET are uniform through the emulsification method and aqueous phase extraction; promoting the mutual adsorption between the second PVC and the modified PET through electrostatic interaction.

[0066] Before introducing the modification method of the PET material, the present invention first introduces the manufacturing method of the first PVC, which is the main material of the sheath layer. The first PVC is rigid PVC, and in cable engineering, rigid PVC sheaths are widely used in power cables and communication cables. Its electrical insulation performance, flame retardant performance and corrosion resistance are all good.

[0067] Rigid PVC is generally prepared by suspension polymerization. The PVC obtained by the suspension polymerization process has a relatively large particle size (generally about 100 to 150 microns), its structure is dense, it is easy to process, and its strength is also relatively high.

[0068] The principle of suspension polymerization is that the vinyl chloride monomer dissolved with an initiator is dispersed in a medium (usually water) in the form of small droplets under the action of a suspending agent, and the polymerization reaction occurs. During the reaction, each small droplet is equivalent to a small bulk polymerization unit, and the polymerization reaction occurs within each small droplet.

[0069] The specific suspension polymerization process parameters adopted by the present invention are as follows:

[0070] S11. According to the mass ratio of dispersant: first initiator: water = (0.2 - 1):(1 - 3):100, dissolve the dispersant in water and disperse it evenly. After adjusting the pH value to 7 to 9, add the first initiator dissolved in an organic solvent and feed it into the polymerization kettle.

[0071] S12. According to the mass ratio of first vinyl chloride monomer: water = (200 - 300):100, and based on the amount of water added in S11, add the first vinyl chloride monomer to the polymerization kettle to form a suspension with water.

[0072] S13. Under the atmosphere protected by an inert gas, heat the sealed polymerization kettle to 55°C to 65°C to carry out the polymerization reaction and detect the pressure inside the polymerization kettle.

[0073] S14. When the real-time pressure inside the polymerization kettle drops to 25% to 30% of the peak pressure inside the polymerization kettle, terminate the polymerization reaction, cool down and relieve the pressure, separate the solid matter, wash and dry to obtain the first PVC.

[0074] Among them, the dispersant used in the present invention is specifically a mixture of polyvinyl alcohol and hydroxypropyl methylcellulose prepared according to the mass ratio of 1:2. The first initiator and the second initiator used below can be the same or different. The first initiator can specifically be benzoyl peroxide or azobisisobutyronitrile.

[0075] The pH regulator in S11 can be selected as an aqueous solution of sodium hydroxide or potassium hydroxide with a relatively low concentration (3wt% to 6wt%), or an aqueous solution of sodium bicarbonate with weak alkalinity.

[0076] The amount of the organic solvent in S11 can be selected by those skilled in the art, as long as it is sufficient to dissolve the first initiator. Among them, the organic solvent in S11 can be selected as toluene.

[0077] The purity of the first vinyl chloride monomer and the second vinyl chloride monomer below needs to be greater than 99.9%. When preparing the suspension, the first vinyl chloride monomer can be evenly dispersed in water by stirring.

[0078] The inert gas protection atmosphere of the polymerization kettle is created by nitrogen. First, the polymerization kettle needs to be sealed, and nitrogen is introduced to remove air. After heating up, during the polymerization reaction, the pressure inside the polymerization kettle can reach up to 0.8MPa to 1MPa at most. Monitor the pressure inside the polymerization kettle in real time. When the real-time pressure inside the polymerization kettle drops to 25% to 30% of the peak pressure inside the polymerization kettle (about 0.2MPa to 0.3MPa), it indicates that the polymerization reaction is nearly completed. At this time, add a terminator to terminate the polymerization reaction, cool down and relieve the pressure, separate the solid matter, wash and dry to obtain the first PVC.

[0079] Among them, the terminator is specifically diethylhydroxylamine. After cooling and depressurizing, the unreacted first vinyl chloride monomer can be recovered through a condenser. The method for separating solids is centrifugal separation, and the dispersant and the first initiator are removed by washing. The drying of the first PVC needs to ensure that its water content is less than 0.5%.

[0080] In order to ensure that the second PVC used for modifying PET has a smaller particle size and better fluidity, the second PVC is prepared by an emulsion method in the present invention. The second PVC is a PVC paste resin, and its preparation process is as follows:

[0081] S21. Dissolve glutamic acid in water according to the mass ratio of glutamic acid: water = (4 - 6):100 to prepare a second aqueous phase;

[0082] S22. Mix the stabilizer, the second initiator, the plasticizer, the emulsifier, and the second vinyl chloride monomer evenly according to the mass ratio of stabilizer: second initiator: plasticizer: emulsifier: second vinyl chloride monomer = (8 - 12):(1 - 2):(1 - 2):(2 - 8):100 to prepare a second oil phase;

[0083] S23. Drop the second aqueous phase into the second oil phase and emulsify it according to the mass ratio of second aqueous phase: second oil phase = (100 - 150):100 to obtain a second emulsion;

[0084] S24. Add polyvinyl alcohol and water to the second emulsion, heat and stir for reaction, and after standing, centrifuge the product and wash it to obtain the second PVC.

[0085] Among them, S21, S22, and S23 are all carried out at room temperature. The stabilizer used in S22 is specifically octadecane. The second initiator used in S22 is specifically azobisisobutyronitrile. The plasticizer used in S22 is specifically dioctyl phthalate. The emulsifier used in S22 is specifically Tween 80.

[0086] The emulsification in S23 needs to be carried out at a relatively high magnetic stirring speed or under certain ultrasonic conditions. Specifically, if magnetic stirring is used, the stirring speed needs to reach at least 4000 rpm / min to 5000 rpm / min. If ultrasonic emulsification is used, the ultrasonic power needs to reach at least 400 W to 600 W, and the ultrasonic frequency needs to reach at least 1400 Hz. Regardless of magnetic stirring or ultrasonic treatment, the treatment time can be selected by those skilled in the art as long as sufficient emulsification can be achieved.

[0087] By dropping the second aqueous phase into the second oil phase, water-in-oil droplets are obtained. In order to achieve aqueous phase extraction using hydrophilic polyvinyl alcohol, in S24, the mass of the added polyvinyl alcohol is 6% to 8% of the mass of the water added in S21. In S24, the mass of the added water is 200% to 250% of the mass of the water added in S21. In S24, the polyvinyl alcohol and water are added in the following manner: Add the polyvinyl alcohol and one-third of the water to the second emulsion and mix evenly, heat them together to 95°C to 98°C, then add the remaining two-thirds of the water, and stir and react at a temperature of 95°C to 98°C for 2 h to 4 h. The reaction is carried out under low-speed stirring at 100 rpm / min to 200 rpm / min. After the heating and stirring reaction is completed, the standing time is 20 min to 40 min. After washing, the product of S24 is preferably dried. The drying temperature does not exceed 100°C.

[0088] In order to ensure the uniformity of the pores and pore sizes of the porous PET, the porous PET of the present invention is prepared by the following steps:

[0089] A1. Use acetylated chitosan as a pore-forming agent, use inorganic non-metallic oxides as a flame retardant, add acetic acid and water and mix them evenly to prepare a turbid first aqueous phase;

[0090] A2. Use PET and an organic solvent to prepare a first oil phase;

[0091] A3. By mixing and emulsifying the first aqueous phase and the first oil phase, a first emulsion is obtained;

[0092] A4. Add polyvinyl alcohol to the first emulsion, heat and stir evenly, and after standing, remove the solvent by vacuum distillation to obtain porous PET.

[0093] Specifically, in step A1, by mass ratio, acetylated chitosan: inorganic non-metallic oxide: acetic acid: water = (1 - 2): (2 - 4): (4 - 8): 100. The acetic acid used in A1 is 100% pure acetic acid.

[0094] In order to avoid the degradation of PET caused by dehydration of ordinary chitosan containing hydroxyl groups in the melting process, the present invention prepared acetylated chitosan in the following manner:

[0095] B1. Disperse chitosan evenly in acetic acid and heat it to 45°C to 65°C, dropwise add concentrated sulfuric acid and stir, after stirring is completed, keep warm for 20 min to 30 min, then dropwise add acetic anhydride and stir and keep warm for reaction for 1.5 h to 2.5 h;

[0096] B2. Remove acetic acid by vacuum distillation, wash the solid matter, and dry it to obtain acetylated chitosan.

[0097] At B1, by mass ratio, concentrated sulfuric acid: acetic anhydride: chitosan: acetic acid = (2 - 3):(4 - 5):(8 - 12):100. The concentration of concentrated sulfuric acid is 98%. The acetic acid is pure acetic acid with a concentration of 100%.

[0098] The purpose of dropping and stirring concentrated sulfuric acid is to activate the hydroxyl groups of chitosan by using concentrated sulfuric acid, and then through an esterification reaction, to form ester bonds between the hydroxyl groups of chitosan and the acyl groups of acetic anhydride to obtain acetylated chitosan.

[0099] In order to improve the flame retardancy of porous PET, a flame retardant is also added when preparing the first aqueous phase. The advantage of using inorganic non - metallic oxides as the flame retardant is that it is environmentally friendly and pollution - free, and it is helpful to improve the mechanical properties of the sheath layer. The inorganic non - metallic oxides can be selected from materials such as alumina, magnesia, and antimony oxide. Considering that flame retardants such as aluminum hydroxide and magnesium hydroxide will release interlayer free water at high temperatures, resulting in the degradation of PET, the present invention does not use hydroxide flame retardants to treat porous PET. Preferably, the inorganic non - metallic oxide of the present invention is magnesia.

[0100] In step A2, by mass ratio, PET: organic solvent = (6 - 12):100, and the organic solvent includes phenol and tetrachloroethane with a mass ratio of 1:1. In step A2, the method of preparing the first oil phase is: heating PET and the organic solvent to 65°C to 75°C, keeping warm and magnetically stirring at a speed of 400 rpm / min to 500 rpm / min until PET is completely dissolved.

[0101] In step A3, by mass ratio, the first aqueous phase: the first oil phase = (80 - 120):100. In step A3, the method of mixing and emulsifying is: dropping the first aqueous phase into the first oil phase at 65°C to 75°C and stirring, and after dropping, keeping warm and performing ultrasonic emulsification at a power of 400W to 600W and a frequency of 60kHz to 80kHz for 20min to 40min.

[0102] In step A4, by mass ratio, the first emulsion: polyvinyl alcohol = 100:(6 - 12). In step A4, the method of heating and stirring evenly is: magnetically stirring at a speed of 100 rpm / min to 200 rpm / min at a temperature of 95°C to 98°C until polyvinyl alcohol is completely dissolved. In step A4, it is naturally cooled during the standing process, and the standing time is 20min to 40min. In step A4, after vacuum distillation, the solid matter is extracted, washed and dried to obtain porous PET.

[0103] In order to promote the mutual adsorption between the second PVC and the modified PET, step S3 specifically includes:

[0104] S31. Mix the second PVC evenly in tetrahydrofuran according to the mass ratio of the second PVC: porous PET: water: tetrahydrofuran = (4 - 6):(20 - 25):(8 - 12):100, add the mixture of porous PET and water, adjust the pH value to 7 - 8, and perform ultrasonic treatment.

[0105] S32. After the ultrasonic treatment, rotary evaporate tetrahydrofuran and water to obtain modified PET.

[0106] Among them, the conditions of the ultrasonic treatment are at a power of 200W - 400W and a frequency of 800Hz - 1000Hz, and the ultrasonic treatment is carried out for 15min - 30min. The purpose of adjusting the pH value to 7 - 8 is to ensure a neutral or weakly alkaline environment to achieve the mutual adsorption between the second PVC and the porous PET based on electrostatic interaction.

[0107] After obtaining the first PVC and the modified PET, a sheath layer can be formed on the surface of the cable core by melt extrusion. Step S4 specifically includes:

[0108] S41. Pay off and preheat the cable core.

[0109] S42. According to the mass ratio of additives: modified PET: first PVC = (4 - 8):(10 - 15):100, melt - extrude the raw materials including additives, modified PET and the first PVC at a temperature of 180°C - 200°C, coat the surface of the cable core, take up the wire after cooling to obtain a photovoltaic cable.

[0110] The preheating temperature of S41 does not exceed 160°C. The additives in S42 can be selected and added by those skilled in the art. The additives mainly include antioxidants, plasticizers, lubricants, stabilizers, inorganic fillers, etc. The selection of the above additives belongs to the prior art and will not be elaborated here. The melt extrusion is carried out by using a melting device and a screw extrusion device. The temperature range of the melting device and the rotation speed of the screw extrusion device can be selected and adjusted by those skilled in the art. The melting time is preferably 20min - 40min.

[0111] Specific examples are given below. The water used in the following specific examples is deionized water, and the acetic acid is 100% pure acetic acid.

[0112] Example 1

[0113] In this example, an acetylated chitosan was prepared, and its preparation process is as follows:

[0114] According to the mass ratio of concentrated sulfuric acid: acetic anhydride: chitosan: acetic acid = 2:4:10:100, disperse chitosan in acetic acid and stir until completely dissolved. After heating to 50 °C, gradually add 98% concentrated sulfuric acid and slowly stir with a stirring rod. After the addition and stirring are completed, keep warm for 20 min, then gradually add acetic anhydride and also stir slowly with a stirring rod. After the addition is completed, start magnetic stirring, stir at a speed of 180 rpm / min, and keep warm and react at 50 °C for 2 h; after the reaction is completed, remove acetic acid by reduced pressure distillation, wash the solid with ethanol and water, and dry it by infrared drying below 80 °C to obtain acetylated chitosan.

[0115] Example Two

[0116] In this example, a PVC material was prepared for use as the first PVC in the subsequent examples. The preparation process is as follows:

[0117] 1. According to the mass ratio of polyvinyl alcohol: hydroxypropyl methylcellulose: azobisisobutyronitrile: water = 0.3:0.6:2:100, dissolve and disperse polyvinyl alcohol and hydroxypropyl methylcellulose in water. After adjusting the pH value to 8 by dropping sodium bicarbonate aqueous solution, add toluene dissolved in toluene and feed it into the polymerization kettle.

[0118] 2. According to the mass ratio of the first vinyl chloride monomer: water = 250:100, and based on the amount of water added in the above steps, add the first vinyl chloride monomer to the polymerization kettle and stir to form a suspension with water.

[0119] 3. Seal the polymerization kettle, introduce nitrogen to remove air, heat the polymerization kettle to 60 °C, keep warm and monitor the pressure in the polymerization kettle in real time. Given that the peak pressure in the polymerization kettle is 0.86 Mpa, when the pressure in the polymerization kettle drops to 0.25 Mpa, add diethylhydroxylamine to terminate the polymerization reaction, cool down and release the pressure, recover the unreacted first vinyl chloride monomer, centrifuge and separate the solid, wash the solid with ethanol and water, and dry it by infrared drying below 80 °C to obtain the first PVC.

[0120] Example Three

[0121] In this example, a PVC material was prepared for use as the second PVC in the subsequent examples. The preparation process is as follows:

[0122] 1. According to the mass ratio of glutamic acid: water = 5:100, stir glutamic acid in water at room temperature until completely dissolved to prepare the second aqueous phase.

[0123] 2. According to the mass ratio of octadecane: azobisisobutyronitrile: dioctyl phthalate: Tween 80: the second vinyl chloride monomer = (8 - 12):(1 - 2):(1 - 2):(2 - 8):100, mix octadecane, azobisisobutyronitrile, dioctyl phthalate, Tween 80 and the second vinyl chloride monomer evenly to prepare the second oil phase.

[0124] 3. Dropwise add the second aqueous phase into the second oil phase at a mass ratio of the second aqueous phase: the second oil phase = 150:100, and simultaneously stir with a stirring rod. After the addition is complete, perform ultrasonic emulsification at a power of 500 W and a frequency of 1600 Hz for 20 min to obtain a second emulsion.

[0125] 4. Weigh polyvinyl alcohol with a mass of 6% of the mass of the water in step 1, and water with a mass twice that of the water in step 1. Add all of the polyvinyl alcohol and one-third of the water weighed in this step to the second emulsion and mix evenly. Heat the mixture to 96 °C, then add the remaining two-thirds of the water, heat to 96 °C again, and stir at a low speed of 100 rpm / min for 2 h. After the reaction ends, let it stand for 20 min, wash the product with ethanol and water, and perform infrared drying below 80 °C to obtain the second PVC sample 1.

[0126] Example 4

[0127] In this example, a PVC material was prepared for use as the second PVC in subsequent examples. The difference between it and the second PVC sample 1 prepared in Example 3 is that glutamic acid was replaced with sodium chloride. Other preparation processes are the same as those in Example 3, and the second PVC sample 2 was obtained in this example.

[0128] Example 5

[0129] In this example, a series of modified porous PET samples 1 to 4 were prepared. The raw material selection and ratio are listed in Table 1, and the preparation process is as follows:

[0130] 1. Mix chitosan, a flame retardant, acetic acid, and water, and stir at room temperature until the chitosan is completely dissolved to prepare a turbid first aqueous phase.

[0131] 2. Mix PET, phenol, and tetrachloroethane, heat to 65 °C, keep warm and stir magnetically at a speed of 400 rpm / min until the PET is completely dissolved to prepare a first oil phase.

[0132] 3. Dropwise add the first aqueous phase into the first oil phase at 70 °C at a mass ratio of the first aqueous phase: the first oil phase = 100:100, and stir simultaneously. After the addition is complete, keep warm and perform ultrasonic emulsification at a power of 500 W and a frequency of 80 kHz for 20 min to obtain a first emulsion.

[0133] 4. Add polyvinyl alcohol to the first emulsion, heat to 96 °C, and stir magnetically at a speed of 100 rpm / min until the polyvinyl alcohol is completely dissolved. Let it stand for 30 min and cool naturally, remove the solvent by vacuum distillation, extract the solid matter, wash the solid matter with ethanol and water, and perform infrared drying below 80 °C to obtain porous PET.

[0134] 5. Mix the second PVC sample 1 obtained in Example 3 evenly in tetrahydrofuran according to the mass ratio of second PVC: porous PET: water: tetrahydrofuran = 4:25:10:100. Add the mixture of porous PET and water, adjust the pH value to 8, and perform ultrasonic treatment for 15 min at a power of 200 W and a frequency of 800 Hz. 6. After the ultrasonic treatment, rotate and evaporate tetrahydrofuran and water to obtain modified porous PET samples 1 to 4.

[0135] Table 1

[0136]

[0137] In this example, porous PET sample 5 was prepared. The raw material selection, raw material ratio, and preparation process were basically the same as those of porous PET sample 3. The only difference was that the second PVC used was the second PVC sample 2 obtained in Example 4.

[0138] Example 7

[0139] In this example, porous PET sample 6 was prepared. The raw material selection, raw material ratio, and preparation process were basically the same as those of porous PET sample 3. The only difference was that the flame retardant used was magnesium hydroxide.

[0140] Example 8

[0141] In this example, porous PET sample 7 was prepared. The raw material selection, raw material ratio, and preparation process were basically the same as those of porous PET sample 3. The only difference was that the magnesium oxide flame retardant was replaced with silicon dioxide.

[0142] Example 9

[0143] In this example, sheath samples 1 to 7 that can be used as sheath layer materials were prepared. The difference between sheath samples 1 to 7 was that porous PET samples 1 to 7 were used correspondingly in sequence. The preparation method of sheath samples 1 to 7 is as follows:

[0144] According to the mass ratio of diisodecyl phthalate: calcium zinc dimerate: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: glycerol monostearate: porous PET: first PVC = 1:1:1:1:15:100, melt and extrude the above raw materials at a temperature of 180°C to 200°C to obtain sheath samples. Among them, the first PVC was prepared through Example 2.

[0145] It can be understood that if the extruded material is coated on the surface of the cable core in the above steps, a photovoltaic cable can be obtained. In this example, for testing the performance of the sheath material, it was directly extruded and then cooled and formed.

[0146] Performance Test

[0147] The particle size of PVC was measured using a laser diffraction particle size analyzer (Mastersizer 3000) in this invention. Among them, the average particle sizes (obtained by calculating the weighted average diameter of particle volume) of the samples obtained in Example 2, Example 3, and Example 4 were 183 microns, 23 microns, and 25 microns, respectively.

[0148] The properties of sheath samples 1 to 7 were tested in this invention. The detection standards for tensile strength and elongation at break referred to GB / T 1701 - 2001, and the detection standard for limiting oxygen index referred to GB / T 2406.1 - 2008. To measure the anti - aging effect of the samples, the aging test conditions (temperature 80°C, time 144 h) referred to the aging conditions of the non - electrical test of polyvinyl chloride sheaths in GB / T 5023.

[0149] The test results of the flame retardant properties of sheath samples 1 to 7 are shown in Table 2. The test results show that samples 1 to 6 added with flame retardants all exhibited acceptable flame retardant properties. Among them, sample 6 added with magnesium hydroxide flame retardant had the best flame retardant property. Sample 7 added with silicon dioxide performed poorly in terms of flame retardant property.

[0150] Table 2

[0151]

[0152] The test results of the tensile strength and elongation at break of sheath samples 1 to 7 are shown in Table 3. In terms of tensile strength and elongation at break, samples 1, 2, 3, 4, 6, and 7 all performed well. Sample 5 performed poorly, which may be due to the poor bonding force and compatibility between the porous PET sample 5 and the first PVC sample in Example 2. After aging treatment, samples 3, 4, 6, and 7 all performed well. The change rates of samples 1 and 2 were relatively high, which may be due to the fact that chitosan was not acetylated.

[0153] Table 3

[0154]

[0155] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A method for preparing a green, environmentally friendly, heat-resistant photovoltaic cable, characterized in that: include: S1. preparing a first PVC by suspension polymerization, wherein the first PVC is a hard PVC; S2, preparing a second PVC by an emulsion method, wherein the second PVC is a PVC paste resin; S3, using the second PVC to modify the porous PET to obtain modified PET; S4, melt-extrude the raw materials including the first PVC and the modified PET, and coat the raw materials on the surface of the cable core as a sheath layer to obtain the photovoltaic cable; The porous PET is prepared by the following steps: A1. Using acetylated chitosan as a porogen and inorganic non-metallic oxide as a flame retardant, adding acetic acid and water and mixing evenly to prepare a suspended first aqueous phase; A2, using PET and organic solvent to prepare the first oil phase; A3, obtaining a first emulsion by mixing and emulsifying the first aqueous phase and the first oil phase; A4, adding polyvinyl alcohol to the first emulsion, heating and stirring, and letting it stand, and then distilling under reduced pressure to remove the solvent to obtain the porous PET; Step S3 specifically includes: S31, mixing the second PVC in the tetrahydrofuran in a mass ratio of second PVC: porous PET: water: tetrahydrofuran = (4-6): (20-25): (8-12): 100, adding the mixture of the porous PET and the water, adjusting the pH value to 7 to 8, and performing ultrasonic treatment; S32, after the ultrasonic treatment is completed, the tetrahydrofuran and the water are removed by rotary evaporation to obtain the modified PET.

2. The preparation method according to claim 1, characterized in that: In step S2, the raw materials used include glutamic acid.

3. The preparation method according to claim 1, characterized in that: In step A1, the mass ratio of acetylated chitosan: inorganic non-metallic oxide: acetic acid: water is (1-2): (2-4): (4-8): 100; and / or In step A2, the mass ratio of PET: organic solvent = (6-12): 100; and / or In step A2, the organic solvent comprises phenol and tetrachloroethane in a mass ratio of 1:1; and / or In step A2, the first oil phase is prepared by heating the PET and the organic solvent to 65° C. to 75° C., keeping the temperature and magnetically stirring at 400 rpm to 500 rpm until the PET is completely dissolved; and / or In step A3, the mass ratio of the first aqueous phase to the first oil phase is (80-120): 100; and / or In step A3, the mixing and emulsification is carried out by dropping the first aqueous phase into the first oil phase at 65° C. to 75° C. and stirring, and after the dropping is completed, keeping the temperature and ultrasonically emulsifying at a power of 400 W to 600 W and a frequency of 60 kHz to 80 kHz for 20 min to 40 min; and / or In step A4, the mass ratio of the first emulsion to polyvinyl alcohol is 100: (6-12); and / or In step A4, the heating and stirring are performed uniformly by: magnetically stirring at a temperature of 95° C. to 98° C. and a speed of 100 rpm to 200 rpm until the polyvinyl alcohol is completely dissolved; and / or In step A4, the step of cooling the device naturally during the standing process is performed, and the standing time is 20 to 40 minutes; and / or In step A4, after the reduced pressure distillation, the solid matter is extracted, washed and dried to obtain the porous PET.

4. The preparation method according to any one of claims 1 to 3, characterized in that Step S1 specifically includes: S11, dissolving and uniformly dispersing the dispersant in the water at a mass ratio of dispersant: first initiator: water = (0.2-1): (1-3): 100, adjusting the pH value to 7 to 9, adding the first initiator dissolved in an organic solvent, and feeding into a polymerization kettle; S12, adding the first vinyl chloride monomer to the polymerization kettle at a mass ratio of the first vinyl chloride monomer: water = (200-300): 100 and according to the amount of water added in S11 to form a suspension with the water; S13, in an inert gas atmosphere, heating the sealed polymerization kettle to 55° C. to 65° C. to carry out a polymerization reaction and detecting the pressure in the polymerization kettle; S14. When the real-time pressure in the polymerization kettle drops to 25% to 30% of the peak pressure in the polymerization kettle, the polymerization reaction is terminated, the temperature is reduced and the pressure is released, the solid is separated, and the solid is washed and dried to obtain the first PVC.

5. The preparation method according to any one of claims 1 to 3, characterized in that: Step S2 specifically includes: S21, dissolving the glutamic acid in the water at a mass ratio of glutamic acid: water = (4-6): 100 to prepare a second aqueous phase; S22, mixing the stabilizer, the second initiator, the plasticizer, the emulsifier and the second vinyl chloride monomer uniformly according to a mass ratio of stabilizer: second initiator: plasticizer: emulsifier: second vinyl chloride monomer = (8-12): (1-2): (1-2): (2-8): 100 to prepare a second oil phase; S23, adding the second aqueous phase dropwise into the second oil phase and emulsifying the second oil phase at a mass ratio of second aqueous phase: second oil phase = (100-150): 100 to obtain a second emulsion; S24, adding polyvinyl alcohol and water to the second emulsion, heating and stirring to react and standing, centrifuging and separating the product, washing, and obtaining the second PVC.

6. The preparation method according to any one of claims 1 to 3, characterized in that: Step S4 specifically includes: S41, laying out and preheating the cable core; S42. According to the mass ratio of auxiliary agent: modified PET: first PVC = (4-8): (10-15): 100, the raw materials including the auxiliary agent, the modified PET and the first PVC are melt-extruded at a temperature of 180° C. to 200° C., coated on the surface of the cable core, and then wound up after cooling to obtain the photovoltaic cable.

7. A green, environmentally friendly, heat-resistant photovoltaic cable, characterized in that: The green, environmentally friendly, heat-resistant photovoltaic cable is obtained by the preparation method as described in any one of claims 1 to 6.

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