An anti-ultraviolet aging photovoltaic cable and its preparation method

Abstract

The present invention provides an anti-ultraviolet aging photovoltaic cable and a preparation method thereof, which relates to the technical field of cable processing. The preparation method includes: mixing and granulating raw materials including polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, modified magnesium aluminum hydrotalcite, titanium dioxide and additives to obtain masterbatch; melting and extruding the masterbatch and coating it on the surface of the cable core as a sheath layer to obtain a photovoltaic cable; wherein, the modified magnesium aluminum hydrotalcite is subjected to intercalation treatment, and the intercalating agent used for the intercalation treatment includes ammonium salt and hydroxydibenzophenone. The sheath layer obtained by the above method has improved anti-ultraviolet performance. Therefore, the photovoltaic cable obtained by the preparation method of the present invention is particularly suitable for laying under high altitude conditions, and it is not easy to age and has a long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of cable processing, and more specifically, to an anti-ultraviolet aging 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] Since photovoltaic cables are often used in outdoor strong light environments, after long-term use, the sheath layer of such cables is prone to aging due to poor anti-ultraviolet performance, resulting in ineffective guarantee of the safety of photovoltaic cables. How to improve the anti-ultraviolet performance of the sheath layer material of photovoltaic cables is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] One of the problems solved by the present invention is how to provide a photovoltaic cable with excellent anti-ultraviolet performance.

[0005] To solve at least one of the above problems, the present invention provides a preparation method for an anti-ultraviolet aging photovoltaic cable, including:

[0006] S1. Mixing and granulating raw materials including polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, modified magnesium aluminum hydrotalcite, titanium dioxide, and additives to obtain masterbatch;

[0007] S2. Melting and extruding the masterbatch and coating it on the surface of the cable core as the sheath layer to obtain a photovoltaic cable;

[0008] Among them, the modified magnesium aluminum hydrotalcite is subjected to intercalation treatment, and the intercalating agent used for the intercalation treatment includes ammonium salt and hydroxybenzophenone.

[0009] In any of the above technical solutions, based on the total addition amount of titanium dioxide being 100 wt%, the titanium dioxide includes: titanium dioxide powder A, 20 wt% to 25 wt%; titanium dioxide powder B, 45 wt% to 50 wt%; titanium dioxide powder C, 30 wt% to 35 wt%; among them, the average particle size D50 of titanium dioxide powder A A is smaller than the average particle size D50 of titanium dioxide powder B B , and the average particle size D50 of titanium dioxide powder B B is smaller than the average particle size D50 of titanium dioxide powder C C .

[0010] In any of the above technical solutions, the particle size range of the titanium dioxide powder A is greater than 50 nm and less than 100 nm, the particle size range of the titanium dioxide powder B is greater than 100 nm and less than 200 nm, and the particle size range of the titanium dioxide powder C is greater than 200 nm and less than 350 nm.

[0011] In any of the above technical solutions, in S1, by mass ratio, polyvinyl chloride: polyethylene: ethylene-vinyl acetate copolymer: modified magnesium aluminum hydrotalcite: titanium dioxide: additive = 100: (30 - 35): (20 - 25): (6 - 12): (4 - 6): (2 - 6).

[0012] In any of the above technical solutions, in S1, based on the total addition amount of the additive being 100 wt%, the additive includes: 35 wt% to 40 wt% of the plasticizer diisodecyl phthalate, 25 wt% to 30 wt% of the stabilizer calcium zinc dimer acid, 10 wt% to 20 wt% of the antioxidant pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 15 wt% to 25 wt% of the lubricant glycerol monostearate.

[0013] In any of the above technical solutions, in S1, the polyethylene is linear low-density polyethylene.

[0014] In any of the above technical solutions, the cable core sequentially includes from inside to outside: a conductor, a conductor shielding layer, an insulating layer, and an insulating shielding layer.

[0015] In any of the above technical solutions, in S1, the mixing temperature for mixing and pelletizing is 80°C to 100°C, the mixing speed is 400 r / min to 800 r / min, and the mixing time is 20 min to 30 min.

[0016] In any of the above technical solutions, in S2, the melting temperature for melt extrusion is 160°C to 220°C, and the melting time is 20 min to 40 min.

[0017] In any of the above technical solutions, the polyvinyl chloride is subjected to carboxylation modification treatment, the intercalating agent further includes serine, and the polyvinyl chloride and the modified magnesium aluminum hydrotalcite are organically linked through an esterification reaction.

[0018] In any of the above technical solutions, the carboxylation modification treatment includes: using a compound having at least one carboxyl group and at least one mercapto group, and heating and refluxing with polyvinyl chloride particles in a solvent system.

[0019] In any of the above technical solutions, the esterification reaction is carried out under heating conditions using an inorganic acid as a catalyst.

[0020] In any of the above technical solutions, S1 specifically includes:

[0021] S11. Mix polyvinyl chloride and modified magnesium aluminum hydrotalcite, use an acid as a catalyst, and heat and reflux in a solvent system to obtain a first mixture;

[0022] S12. Knead and pelletize the first mixture with polyethylene, ethylene-vinyl acetate copolymer, titanium dioxide, and additives to obtain a masterbatch.

[0023] In any of the above technical solutions, the modified magnesium aluminum hydrotalcite is prepared by the following steps:

[0024] A1. Dissolve an ammonium salt and serine in water to obtain an aqueous phase;

[0025] A2. Dissolve hydroxybenzophenone in N-methylpyrrolidone to obtain an organic phase;

[0026] A3. First, ultrasonically disperse magnesium aluminum hydrotalcite, the aqueous phase, and sodium dodecyl sulfate evenly, then add the organic phase and cyclohexane, mix and ultrasonically emulsify to obtain an emulsion;

[0027] A4. Feed the emulsion into a reaction kettle, and carry out hydrothermal treatment under heating and pressurization conditions to obtain the modified magnesium aluminum hydrotalcite.

[0028] The present invention also provides an anti-ultraviolet aging photovoltaic cable, which is obtained by using the preparation method of any of the above technical solutions.

[0029] Beneficial effects

[0030] The present invention provides a preparation method for an anti-ultraviolet aging photovoltaic cable. This method first uses raw materials including polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, modified magnesium aluminum hydrotalcite, titanium dioxide, and additives to knead and pelletize to obtain a masterbatch. Then, the masterbatch is melt-extruded and coated on the surface of the cable core as a sheath layer to obtain a photovoltaic cable. Among them, the modified magnesium aluminum hydrotalcite has been intercalated, and the intercalating agent used for the intercalation treatment includes an ammonium salt and hydroxybenzophenone.

[0031] In the first aspect, the present invention controls the basic components and ratios of the sheath layer material used for the photovoltaic cable. The three main polymer raw materials used for this sheath layer material are polyvinyl chloride, polyethylene, and ethylene-vinyl acetate copolymer. Among many polymer materials, polyvinyl chloride has relatively excellent thermal stability, chemical stability, and mechanical strength. There is a certain compatibility between polyethylene and polyvinyl chloride during the processing process. Adding an appropriate amount of polyethylene can improve the processing performance of polyvinyl chloride, and improve its fluidity and extrusion efficiency. Adding ethylene-vinyl acetate copolymer to the polyvinyl chloride material can enhance the flexibility of the polyvinyl chloride material, thereby improving its tensile performance.

[0032] Second aspect, the present invention improves the inorganic additive components of the sheath layer material used for photovoltaic cables. For the cable sheath layer mainly made of polymers, it is prone to decomposition, aging, loss of elasticity and reduction of mechanical properties under long-term illumination of natural light. The main reasons for the above phenomena are that ultraviolet rays with higher photon energy in natural light will break the chemical bonds in plastic molecules, resulting in chain breakage, and will also cause chromophores to form in plastic polymer materials, resulting in color change. Therefore, polymer materials will become brittle under long-term high-intensity natural light illumination, and their strength, elasticity and durability will all decrease. In order to avoid or slow down the above phenomena, anti-ultraviolet components are usually added to the sheath layer material. Among them, titanium dioxide is a relatively widely used anti-ultraviolet component. The mechanism of its anti-ultraviolet effect is mainly because titanium dioxide has a high refractive index, which enables it to effectively reflect and scatter ultraviolet rays. When ultraviolet rays irradiate the surface of the material containing titanium dioxide, a considerable part of the ultraviolet rays will be reflected back or scattered in other directions, thereby reducing the direct irradiation of ultraviolet rays on the material. Considering that the effect of titanium dioxide on ultraviolet light is only limited to reflection and scattering, the present invention further introduces hydroxybenzophenone into the sheath layer mainly made of polyvinyl chloride. As an ultraviolet absorber, hydroxybenzophenone contains a conjugated system in its molecular structure, and such a structure enables it to effectively absorb ultraviolet rays. The present invention improves the anti-ultraviolet performance of the sheath layer by introducing titanium dioxide and hydroxybenzophenone into the sheath layer at the same time. Due to the high altitude in the plateau area, the atmosphere is thinner, the solar radiation intensity is high, and the photovoltaic equipment can obtain more solar energy and has higher power generation efficiency. Therefore, there is a large demand for laying photovoltaic cables in the plateau area. The blocking effect of the ozone layer on ultraviolet rays in the plateau area is weakened, so the ultraviolet penetration ability in the plateau area is significantly enhanced. The treatment method of the present invention that jointly introduces ultraviolet-reflecting substances and ultraviolet-absorbing substances into polymer materials is more helpful to obtain photovoltaic cables suitable for the erection of photovoltaic equipment in the plateau area.

[0033] Third aspect, the present invention introduces hydroxybenzophenone into the interlayer of magnesium aluminum hydrotalcite through intercalation treatment. Considering that hydroxybenzophenone, as an organic ultraviolet absorber, has problems such as easy migration and poor thermal stability. Since the interlayer region of magnesium aluminum hydrotalcite contains a large amount of water molecules that will desorb and absorb heat at high temperatures, introducing hydroxybenzophenone into the interlayer of magnesium aluminum hydrotalcite not only helps to fix hydroxybenzophenone, limit its migration, but also can provide high-temperature protection for it to avoid its failure under long-term high-temperature natural conditions. Detailed implementation manners

[0034] In order 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.

[0035] Unless otherwise specified, the reagents and raw materials used in the present invention can be purchased through commercial channels. For the experimental methods without specific conditions indicated in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product instructions.

[0036] The present invention provides a preparation method of an anti-ultraviolet aging photovoltaic cable, and 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 by stranding. The insulating layer is generally prepared from high-molecular compounds such as polyvinyl chloride, polyethylene, ethylene-propylene rubber or their compositions. 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.

[0037] The sheath layer is usually made of high-molecular polymers or composite materials, and its function 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 addition, the sheath layer usually also needs to have functions such as waterproofing, moisture-proofing, corrosion resistance, heat resistance, fire resistance and flame retardancy, and anti-ultraviolet.

[0038] The present invention uses polyvinyl chloride, polyethylene, and ethylene-vinyl acetate copolymer as the main raw materials to prepare the sheath layer of the photovoltaic cable. The overall preparation process of the present invention is to weigh the above raw materials and necessary inorganic or organic additives and then mix and knead them to make masterbatch, and then melt the masterbatch and extrude it through a screw device to coat the surface of the cable core, thus forming the sheath layer.

[0039] Specifically, the preparation method of the present invention includes:

[0040] S1. Mix and granulate the raw materials including polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, modified magnesium aluminum hydrotalcite, titanium dioxide and additives to obtain the masterbatch;

[0041] S2. Melt and extrude the masterbatch and coat it on the surface of the cable core as the sheath layer to obtain the photovoltaic cable.

[0042] The present invention preferably uses polyvinyl chloride with an average molecular weight of 50,000 - 100,000. The polyethylene used in the present invention is preferably linear low-density polyethylene. The additives used in the present invention include plasticizers, stabilizers, antioxidants and lubricants. Among them, the functions of the above additives belong to the prior art, and the present invention will not elaborate here.

[0043] Preferably, in S1, based on the total additive amount of the additives being 100 wt%, the additives include: 35 wt% to 40 wt% of the plasticizer diisodecyl phthalate, 25 wt% to 30 wt% of the stabilizer calcium zinc dimerate, 10 wt% to 20 wt% of the antioxidant pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 15 wt% to 25 wt% of the lubricant glycerol monostearate.

[0044] More preferably, in S1, based on the total additive amount of the additives being 100 wt%, the additives include: 40 wt% of the plasticizer diisodecyl phthalate, 25 wt% of the stabilizer calcium zinc dimerate, 20 wt% of the antioxidant pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 15 wt% of the lubricant glycerol monostearate.

[0045] Regarding the component ratio, preferably, in S1, by mass ratio, polyvinyl chloride: polyethylene: ethylene-vinyl acetate copolymer: modified magnesium aluminum hydrotalcite: titanium dioxide: additives = 100: (30 - 35): (20 - 25): (6 - 12): (4 - 6): (2 - 6).

[0046] It can be understood that in the sheath material of the present invention, the main raw material is polyvinyl chloride. Appropriate polyethylene can improve the processing performance of polyvinyl chloride, enhance its fluidity and extrusion efficiency, while the ethylene-vinyl acetate copolymer is used to improve the flexibility and tensile strength of the sheath layer.

[0047] In the present invention, the modified magnesium aluminum hydrotalcite is subjected to intercalation treatment. The intercalating agent used for the intercalation treatment includes ammonium salts and hydroxybenzophenone. Preferably, the intercalating agent further includes serine. Magnesium aluminum hydrotalcite belongs to layered double hydroxides (LDH), which is a compound with a special layered structure. Magnesium aluminum hydrotalcite itself can be used as a flame retardant. The conjugated structure of hydroxybenzophenone can absorb ultraviolet light and convert it into heat energy or other forms of energy. Considering that the conjugated structure (benzene ring and carbonyl group) of hydroxybenzophenone can absorb ultraviolet light and convert it into heat energy or other forms of energy. Considering the problems of easy migration and poor thermal stability of hydroxybenzophenone, in the present invention, hydroxybenzophenone is inserted into the interlayer of magnesium aluminum hydrotalcite. In order to ensure smooth intercalation, ammonium salts are used as auxiliary intercalating agents to assist in opening the layer spacing of magnesium aluminum hydrotalcite. Serine can cooperate with ammonium salts to assist in achieving intercalation by releasing ammonium ions. By inserting hydroxybenzophenone into the interlayer of magnesium aluminum hydrotalcite, it not only helps to fix hydroxybenzophenone, restrict its migration, but also can provide high-temperature protection for it to avoid its failure under natural conditions of long-term high temperature.

[0048] In addition to using ultraviolet absorbers in combination with titanium dioxide, the present invention also screens and controls the particle size of titanium dioxide. This is because the reflection and scattering effects of titanium dioxide on ultraviolet light are related to its particle size. Generally speaking, titanium dioxide with a particle size less than 400 nm has relatively good reflection and scattering effects on ultraviolet light. Titanium dioxide with a particle size greater than 400 nm has enhanced covering power but weakened ultraviolet resistance. Moreover, there are also differences in the reflection and scattering effects of titanium dioxide with different particle sizes on ultraviolet light. Titanium dioxide with a particle size greater than 100 nm is mainly Mie scattering, which has certain effects on both the reflection and scattering of ultraviolet light, but excessive addition will result in a whitening phenomenon. Titanium dioxide with a particle size less than 100 nm is mainly Rayleigh scattering, and its scattering effect on ultraviolet light is very significant. However, excessive addition will lead to poor dispersibility, and small-particle-size titanium dioxide is more active and prone to generating too many free radicals, which are captured by hydrogen chloride slowly released during the long-term use of polyvinyl chloride, resulting in the aging of polyvinyl chloride materials.

[0049] Therefore, the titanium dioxide used in the present invention includes three kinds of powder materials with different particle sizes. Based on the total addition amount of titanium dioxide being 100 wt%, the added titanium dioxide in the present invention includes: titanium dioxide powder A, 20 wt% to 25 wt%; titanium dioxide powder B, 45 wt% to 50 wt%; titanium dioxide powder C, 30 wt% to 35 wt%. Among them, the average particle size D50 of titanium dioxide powder A A is less than the average particle size D50 of the said titanium dioxide powder B B , and the average particle size D50 of titanium dioxide powder B B is less than the average particle size D50 of titanium dioxide powder C C .

[0050] Specifically, the particle size range of titanium dioxide powder A is greater than 50 nm and less than 100 nm, the particle size range of titanium dioxide powder B is greater than 100 nm and less than 200 nm, and the particle size range of titanium dioxide powder C is greater than 200 nm and less than 350 nm.

[0051] Preferably, the particle size range of titanium dioxide powder A is greater than 50 nm and less than 80 nm, the particle size range of titanium dioxide powder B is greater than 120 nm and less than 150 nm, and the particle size range of titanium dioxide powder C is greater than 200 nm and less than 250 nm.

[0052] It can be understood that the titanium dioxide powder materials with different particle sizes used in the present invention can be directly obtained by purchasing, or can be obtained by air classification or wet classification.

[0053] Preferably, in the present invention, polyvinyl chloride is carboxylated and modified, and polyvinyl chloride and modified magnesium aluminum hydrotalcite are organically linked through an esterification reaction. The purpose of the above treatment method is: on the one hand, through the organic linkage of polyvinyl chloride and modified magnesium aluminum hydrotalcite, the agglomeration of magnesium aluminum hydrotalcite in the polymer material can be avoided or prevented; on the other hand, magnesium aluminum hydrotalcite can be used to prevent or reduce the contact between polyvinyl chloride and titanium dioxide, and the ultraviolet absorber between the layers of magnesium aluminum hydrotalcite can absorb the remaining small amount of ultraviolet light that cannot be scattered or reflected by titanium dioxide, which helps to limit or prevent the contact between ultraviolet light and polyvinyl chloride material.

[0054] Specifically, titanium dioxide (especially nano-scale titanium dioxide) not only reflects and scatters ultraviolet light, but also has a certain absorption of ultraviolet light. By absorbing ultraviolet light, the valence band electrons of titanium dioxide jump to the conduction band, forming electron-hole pairs. The holes react with water molecules or hydroxyl groups adsorbed on the material surface to generate hydroxyl radicals. The electrons react with oxygen adsorbed on the material surface to generate superoxide radicals, and further reactions will also generate hydroxyl radicals. For polymer materials such as polyvinyl chloride, hydrogen chloride is slowly released during long-term use, and hydrogen chloride can capture the active radicals generated by titanium dioxide, resulting in and accelerating the degradation of polyvinyl chloride. By organically linking magnesium aluminum hydrotalcite on the surface of polyvinyl chloride, not only can the contact between polyvinyl chloride and titanium dioxide be prevented or reduced, but also the hydroxyl benzophenone between the layers of magnesium aluminum hydrotalcite can be used to absorb the ultraviolet light that cannot be reflected or scattered by titanium dioxide, further protecting polyvinyl chloride and preventing its chemical bond breakage and decomposition caused by ultraviolet light excitation.

[0055] The above organic linkage is achieved through an esterification reaction. The esterification reaction is carried out under heating conditions with an inorganic acid as a catalyst. In order to achieve the esterification reaction, ensure the chemical linkage effect, and avoid the agglomeration of hydrotalcite, polyvinyl chloride needs to be carboxylated and try to promote more serine and hydroxyl benzophenone to enter the interlayer of magnesium aluminum hydrotalcite.

[0056] The carboxylation modification treatment of polyvinyl chloride includes: reacting a compound having at least one carboxyl group and at least one mercapto group with polyvinyl chloride particles by heating and refluxing in a solvent system. Exemplarily, glutathione can be used to treat polyvinyl chloride to obtain carboxylated polyvinyl chloride.

[0057] Specifically, the method of treating polyvinyl chloride with glutathione is as follows: Dissolve glutathione in water, add triethanolamine, polyvinyl alcohol, polyvinyl chloride, and ethanol, and carry out a heating reflux reaction to obtain carboxylated polyvinyl chloride. After obtaining the carboxylated polyvinyl chloride, the solvent can be removed under negative pressure, and the solvent and acid-binding agent can be recycled. Preferably, by mass ratio, triethanolamine: polyvinyl alcohol: glutathione: polyvinyl chloride: water: ethanol = (2 - 4): (4 - 6): (6 - 8): (20 - 30): (10 - 15): 100. The temperature of the heating reflux reaction is preferably 80°C to 90°C, and the time is 8 h to 12 h.

[0058] Glutathione is formed by the condensation of three amino acids, namely glutamic acid, cysteine, and glycine, through peptide bonds, and it has two carboxyl groups and one mercapto group. In the above steps, triethanolamine and polyvinyl alcohol are used as acid-binding agents, and ethanol is mainly used as the reaction medium. Through heating reflux, the nucleophilic substitution reaction occurs between the mercapto group of glutathione and the chlorine atom of polyvinyl chloride, thereby introducing the carboxyl group of glutathione into the macromolecular chain of polyvinyl chloride to obtain carboxylated polyvinyl chloride.

[0059] Before explaining the intercalation process, first, the preparation process of the magnesium-aluminum hydrotalcite of the present invention will be described. Magnesium-aluminum hydrotalcite can be prepared by a chemical method using magnesium salts and aluminum salts as raw materials in an alkaline environment.

[0060] Specifically, the magnesium-aluminum hydrotalcite in the present invention can be prepared through the following steps: According to the mass ratio of magnesium chloride: aluminum nitrate: water = (10 - 15): (20 - 25): 100, disperse magnesium chloride and aluminum nitrate evenly in water to obtain a magnesium-aluminum salt solution; add an aqueous solution of an alkali metal hydroxide with a concentration of 6 wt% to 12 wt% to the magnesium-aluminum salt solution and stir until the pH value reaches 10 to 12. After standing and aging for 2 h to 4 h, filter the solid matter, wash, and dry to obtain magnesium-aluminum hydrotalcite; wherein, the aqueous solution of the alkali metal hydroxide is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0061] In order to promote more hydroxybenzophenone to enter the interlayer of magnesium-aluminum hydrotalcite, the present invention uses a small molecule ammonium salt and serine with amino and carboxyl groups to open the layer spacing of magnesium-aluminum hydrotalcite. Specifically, the modified magnesium-aluminum hydrotalcite of the present invention is prepared through the following steps:

[0062] A1. Dissolve the ammonium salt and serine in water to obtain an aqueous phase;

[0063] A2. Dissolve hydroxybenzophenone in N-methylpyrrolidone to obtain an organic phase;

[0064] A3. First, ultrasonically disperse magnesium-aluminum hydrotalcite, the aqueous phase, and sodium dodecyl sulfate evenly, then add the organic phase and cyclohexane and mix and ultrasonically emulsify to obtain an emulsion;

[0065] A4. Feed the emulsion into a reaction kettle and conduct hydrothermal treatment under heating and pressurization conditions to obtain modified magnesium aluminum hydrotalcite.

[0066] Among them, the ammonium salt is specifically ammonium sulfate, and the hydroxybenzophenone is specifically 2,2',4,4'-tetrahydroxybenzophenone. In A1, by mass ratio, ammonium salt: serine: water = (2 - 4): (10 - 20): 100. In A2, by mass ratio, hydroxybenzophenone: N-methylpyrrolidone = (6 - 12): 100. In A3, by mass ratio, magnesium aluminum hydrotalcite: aqueous phase: organic phase: sodium dodecyl sulfate: cyclohexane = (10 - 20): (40 - 60): (20 - 40): (2 - 4): (30 - 50). In A3, the frequency and power of ultrasonic dispersion can be selected and adjusted by those skilled in the art, as long as uniform dispersion can be achieved. In addition to ultrasonic dispersion, magnetic stirring or manual stirring can also achieve the same purpose. The frequency of ultrasonic treatment is 60 kHz to 80 kHz, and the power is 400 W to 600 W. Sodium dodecyl sulfate serves as a surfactant and emulsifier. The purpose of ultrasonic treatment is to prepare the above-mentioned raw materials used in A3 into an emulsion by ultrasonic waves, so as to improve the uniformity of the hydrothermal reaction and achieve uniform intercalation of the intercalating agent. The temperature of hydrothermal treatment is 140 °C to 160 °C, and the pressure is 3 MPa to 5 Mpa. The time of hydrothermal treatment is 2 h to 3 h. After the hydrothermal treatment, it is necessary to cool down and relieve pressure, filter the solid matter, wash it repeatedly with organic solvent and deionized water in turn, and dry the solid matter to obtain modified magnesium aluminum hydrotalcite.

[0067] The layer spacing of magnesium aluminum hydrotalcite is about 0.77 nm, and the van der Waals diameter of serine is above 0.56 nm. The van der Waals diameter of serine is smaller than the layer spacing of magnesium aluminum hydrotalcite, and intercalation is theoretically feasible. However, in order to improve the intercalation effect, the present invention also adds small-molecule ammonium sulfate as an intercalating agent. During the ultrasonic treatment process, ammonium sulfate chemically intercalates magnesium aluminum hydrotalcite, promoting the entry of its ammonium ions into the interlayer of magnesium aluminum hydrotalcite and opening the layer spacing.

[0068] Serine contains amino and carboxyl groups. Ammonium sulfate produces hydrogen ions due to the hydrolysis of ammonium ions in water, thus creating an acidic environment. Under acidic conditions, a proton in the carboxyl group of serine will transfer into the amino group to form an ammonium ion. The further increased number of ammonium ions can exchange more with the cations in the interlayer of hydrotalcite, helping to open the layer spacing of hydrotalcite and promoting the intercalation of serine itself and 2,2',4,4'-tetrahydroxybenzophenone into magnesium aluminum hydrotalcite. Therefore, in the present invention, ammonium sulfate and serine need to be mixed and stirred with magnesium aluminum hydrotalcite in the aqueous phase first, and then 2,2',4,4'-tetrahydroxybenzophenone is added and ultrasonically emulsified to promote 2,2',4,4'-tetrahydroxybenzophenone to enter the interlayer of magnesium aluminum hydrotalcite whose layer spacing has been pre-opened by ammonium sulfate and serine.

[0069] As mentioned above, in order to achieve the organic connection between magnesium aluminum hydrotalcite and polyvinyl chloride, it is necessary to drive the esterification reaction. Specifically, by heating under reflux in an acidic condition, the carboxyl group of the modified polyvinyl chloride is chemically connected to the hydroxyl groups of serine and tetrahydroxybenzophenone inserted into the interlayer of magnesium aluminum hydrotalcite through an esterification reaction, so that the intercalated modified magnesium aluminum hydrotalcite protects polyvinyl chloride and restricts and reduces its contact with titanium dioxide and ultraviolet light.

[0070] The esterification reaction needs to be carried out under the catalysis of inorganic acid and heating conditions. In the present invention, S1 specifically includes:

[0071] S11. Mix polyvinyl chloride and modified magnesium aluminum hydrotalcite, use an acid as a catalyst, and heat under reflux in a solvent system to obtain a first mixture;

[0072] S12. Knead and granulate the first mixture with polyethylene, ethylene-vinyl acetate copolymer, titanium dioxide and additives to obtain masterbatch.

[0073] The acid in S11 is phosphoric acid, and the solvent system is ethanol. In S11, by mass ratio, phosphoric acid: modified magnesium aluminum hydrotalcite: polyvinyl chloride: ethanol = (5 - 15): (6 - 12): 100: 300. The temperature of the heating under reflux reaction is 80 °C to 90 °C, and the time of the heating under reflux reaction is 2 h to 4 h. During the heating under reflux reaction, a water-carrying agent can be used to dehydrate in time. The water-carrying agent can be molecular sieve or an organic water-carrying agent such as cyclohexane.

[0074] After the heating under reflux reaction is completed, the solvent and the catalyst are recovered, the solid matter is extracted and washed and dried to obtain the first mixture. This first mixture includes polyvinyl chloride organically connected with modified magnesium aluminum hydrotalcite, and also includes a small part of polyvinyl chloride and modified magnesium aluminum hydrotalcite particles that did not participate in the reaction or did not fully participate in the reaction.

[0075] In S12, polyethylene: ethylene-vinyl acetate copolymer: titanium dioxide: additives = (30 - 35): (20 - 25): (4 - 6): (2 - 6). Among them, based on the mass of polyvinyl chloride used in S11, the usage amount of polyethylene in S12 is controlled at about one-third of the mass of polyvinyl chloride in S11.

[0076] The mixing and pelletizing of raw materials such as polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, etc. can be carried out using a mixer and a pelletizing device. The preferred size of the pellets is 0.5 mm to 2 mm. The melt extrusion is carried out 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. Preferably, in S1, the mixing temperature for mixing and pelletizing is 80°C to 100°C, the mixing speed is 400 r / min to 800 r / min, and the mixing time is 20 min to 30 min.

[0077] The process of melting and extruding the masterbatch and coating it on the surface of the cable core is a relatively common existing technology, and the present invention will not elaborate on this. Preferably, in S2, the melting temperature for melt extrusion is 160°C to 220°C, and the melting time is 20 min to 40 min.

[0078] Example 1

[0079] In this example, a magnesium-aluminum hydrotalcite sample was prepared, and the preparation steps are as follows:

[0080] 1. According to the mass ratio of magnesium chloride: aluminum nitrate: water = 10:20:100, disperse magnesium chloride and aluminum nitrate in distilled water, and stir evenly with magnetic force to obtain a magnesium-aluminum salt solution;

[0081] 2. Dropwise add an 8 wt% aqueous sodium hydroxide solution to the magnesium-aluminum salt solution and stir until the pH value reaches 11. Let it stand for aging for 2 h, then filter the solid matter, wash it once with ethanol and twice with water, and dry it by infrared at 110°C to obtain magnesium-aluminum hydrotalcite sample 1.

[0082] Example 2

[0083] In this example, a carboxylated polyvinyl chloride sample was prepared, and the preparation steps are as follows:

[0084] 1. According to the mass ratio of triethanolamine: polyvinyl alcohol: glutathione: polyvinyl chloride: water: ethanol = 2:6:6:20:10:100, dissolve glutathione in water, and then add triethanolamine, polyvinyl alcohol, polyvinyl chloride and ethanol and mix evenly to obtain a mixture;

[0085] 2. Heat the mixture under reflux at a temperature of 85°C for 10 h to remove the solvent. Wash the reaction product once with ethanol, twice with water, and dry it by hot air at 80°C to obtain carboxylated polyvinyl chloride sample 1.

[0086] Example 3

[0087] In this example, a carboxylated polyvinyl chloride sample was prepared, and the preparation steps are as follows:

[0088] 1. Dissolve glutathione in water according to the mass ratio of triethanolamine: polyvinyl alcohol: glutathione: polyvinyl chloride: water: ethanol = 4:4:8:30:15:100, and then add triethanolamine, polyvinyl alcohol, polyvinyl chloride and ethanol and mix evenly to obtain a mixture;

[0089] 2. The same as step 2 of Example 2 to obtain carboxylated polyvinyl chloride sample 2.

[0090] Example 4

[0091] In this example, a modified magnesium aluminum hydrotalcite sample was prepared, and the preparation steps are as follows:

[0092] 1. Dissolve ammonium sulfate and serine in water at room temperature according to the mass ratio of ammonium sulfate: serine: water = 2:15:100 and stir evenly to obtain an aqueous phase;

[0093] 2. Dissolve 2,2',4,4'-tetrahydroxybenzophenone in N-methylpyrrolidone at room temperature according to the mass ratio of 2,2',4,4'-tetrahydroxybenzophenone: N-methylpyrrolidone = 6:100 and stir evenly to obtain an organic phase;

[0094] 3. According to the mass ratio of magnesium aluminum hydrotalcite: aqueous phase: organic phase: sodium dodecyl sulfate: cyclohexane = 15:50:30:3:40, ultrasonically disperse the magnesium aluminum hydrotalcite, aqueous phase and sodium dodecyl sulfate prepared in Example 1 for 20 min, then add the organic phase and cyclohexane and mix, and use an ultrasonic device with 400 W to ultrasonically treat at a frequency of 60 kHz for 20 min to obtain an emulsion. Feed the emulsion into a reaction kettle, carry out hydrothermal treatment for 2.5 h under the temperature condition of 140 and the pressure condition of 3.5 Mpa. After the hydrothermal treatment, cool down and release the pressure, filter the solid, wash it twice with acetone and water respectively, and dry the solid to obtain modified magnesium aluminum hydrotalcite sample 1.

[0095] Example 5

[0096] In this example, a modified magnesium aluminum hydrotalcite sample was prepared, and the preparation steps are as follows:

[0097] 1. Dissolve ammonium sulfate and serine in water at room temperature according to the mass ratio of ammonium sulfate: serine: water = 2:10:100 and stir evenly to obtain an aqueous phase;

[0098] 2. Dissolve 2,2',4,4'-tetrahydroxybenzophenone in N-methylpyrrolidone at room temperature according to the mass ratio of 2,2',4,4'-tetrahydroxybenzophenone: N-methylpyrrolidone = 12:100 and stir evenly to obtain an organic phase;

[0099] 3. The same as step 3 of Example 4 to obtain the modified magnesium aluminum hydrotalcite sample 2.

[0100] Example 6

[0101] In this example, a polyvinyl chloride sheath material was prepared, and the preparation steps are as follows:

[0102] 1. According to the mass ratio of phosphoric acid: modified magnesium aluminum hydrotalcite: polyvinyl chloride: ethanol = 10:6:100:300, mix 98 wt% phosphoric acid, the modified magnesium aluminum hydrotalcite sample 1 obtained in Example 4, the carboxylated polyvinyl chloride sample 1 obtained in Example 2, and ethanol, heat and reflux at 85 °C for 2 h, use cyclohexane as a water-carrying agent to dehydrate in a timely manner during the reaction, recover phosphoric acid and ethanol after the reaction, extract the solid matter, wash it once with water, and dry it by infrared drying at 100 °C or below to obtain the first mixture;

[0103] 2. According to the mass ratio of polyvinyl chloride: polyethylene: ethylene-vinyl acetate copolymer: titanium dioxide: diisodecyl phthalate: calcium zinc dimerate: pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]: glycerol monostearate = 100:33:20:4:4:1.6:1:0.8:0.6, weigh the above raw materials except polyvinyl chloride according to the addition amount of polyvinyl chloride in S1, mix them with the first mixture obtained in step 1, send them into a mixer, and mix at a rotation speed of 600 r / min at 80 °C or above and 100 °C for 20 min, and extrude and pelletize to obtain masterbatch between 0.5 mm and 1 mm; among them, titanium dioxide is obtained by commercial procurement, and its particle size range is between 50 nm and 80 nm;

[0104] 3. Send the masterbatch into a melting device, melt it in the temperature range of 180 °C to 200 °C for 20 min, and extrude it with a single-screw device to obtain the polyvinyl chloride sheath material sample 1.

[0105] It can be understood that if the extruded material is coated on the surface of the cable core in the above step 3, a photovoltaic cable can be obtained. In this example, in order to test the performance of the polyvinyl chloride sheath material, it is directly extruded and then cooled and formed.

[0106] Example 7

[0107] In this example, a polyvinyl chloride sheath material was prepared, and the preparation steps are the same as those of Example 6, except that in this example, the modified magnesium aluminum hydrotalcite sample 2 obtained in Example 5 and the carboxylated polyvinyl chloride sample 2 obtained in Example 3 were used to obtain the polyvinyl chloride sheath material sample 2.

[0108] Example 8

[0109] In this example, a polyvinyl chloride sheath material was prepared. The preparation steps were the same as those in Example 6, except that in this example, the modified magnesium aluminum hydrotalcite sample 2 obtained in Example 5 and the carboxylated polyvinyl chloride sample 1 obtained in Example 2 were used to obtain the polyvinyl chloride sheath material sample 3.

[0110] Example 9

[0111] In this example, a polyvinyl chloride sheath material was prepared. The preparation steps were the same as those in Example 6, except that in this example, the modified magnesium aluminum hydrotalcite sample 1 obtained in Example 4 and the carboxylated polyvinyl chloride sample 2 obtained in Example 3 were used to obtain the polyvinyl chloride sheath material sample 4.

[0112] Example 10

[0113] In this example, a polyvinyl chloride sheath material was prepared. The preparation steps and the raw material selection of the modified magnesium aluminum hydrotalcite sample 1 and the carboxylated polyvinyl chloride sample 1 were the same as those in Example 6, except that the titanium dioxide used in this example was different from that in Example 6. The titanium dioxide selected in this example was a titanium dioxide powder prepared from three different particle size powders obtained by cyclone classification, and the polyvinyl chloride sheath material sample 5 was obtained.

[0114] The preparation method of the titanium dioxide selected in this example is as follows: taking 100 g as an example, every 100 g of titanium dioxide includes: 20 g of titanium dioxide powder A, 50 g of titanium dioxide powder B, and 30 g of titanium dioxide powder C. The particle size range of titanium dioxide powder A is between 50 nm and 80 nm, the particle size range of titanium dioxide powder B is between 120 nm and 150 nm, and the particle size range of titanium dioxide powder C is between 200 nm and 250 nm.

[0115] Example 11

[0116] In this example, a polyvinyl chloride sheath material was prepared. The preparation steps were the same as those in Example 6, and the polyvinyl chloride sheath material sample 6 was obtained. The difference is that the polyvinyl chloride used in this example was obtained through commercial procurement and was not carboxylated. The magnesium aluminum hydrotalcite sample used in this example was prepared through the following steps:

[0117] 1. According to the mass ratio of ammonium sulfate: water = 2:100, dissolve ammonium sulfate in water at room temperature and stir evenly to obtain an aqueous phase;

[0118] 2. According to the mass ratio of 2,2’,4,4’-tetrahydroxybenzophenone: N-methylpyrrolidone = 6:100, dissolve 2,2’,4,4’-tetrahydroxybenzophenone in N-methylpyrrolidone at room temperature and stir evenly to obtain an organic phase;

[0119] 3. According to the mass ratio of magnesium-aluminum hydrotalcite: aqueous phase: organic phase: sodium dodecyl sulfate: cyclohexane = 15:50:30:3:40, ultrasonically disperse the magnesium-aluminum hydrotalcite, aqueous phase, and sodium dodecyl sulfate prepared in Example 1 for 20 min, then add the organic phase and cyclohexane and mix. Using a 400 W ultrasonic device, ultrasonically treat at a frequency of 60 kHz for 20 min to obtain an emulsion. Feed the emulsion into a reaction kettle, and perform hydrothermal treatment for 2.5 h under the temperature condition of 140 °C and the pressure condition of 3.5 Mpa. After the hydrothermal treatment, cool down and release the pressure, filter the solid matter, wash it twice with acetone and water respectively, and dry the solid matter to obtain magnesium-aluminum hydrotalcite.

[0120] Performance Test

[0121] The present invention tests the performance of polyvinyl chloride sheath material samples 1 to 6. The detection standards for tensile strength and elongation at break refer to GB / T 1701-2001. In order to measure the effect of the samples against ultraviolet aging, the aging test conditions (temperature 80 °C, time 144 h) refer to the aging conditions of the non-electrical test of polyvinyl chloride sheath in GB / T 5023, and 254 nm short-wave ultraviolet irradiation with a power density of 100 W / cm² is applied during the aging treatment process.

[0122] The results of the above performance tests are shown in Table 1. The test results show that although the mechanical properties of sample 5 obtained in Example 10 are the best before aging treatment, the mechanical properties of the 5 samples prepared in Examples 6 to 10 have little difference before aging treatment. After aging treatment, both sample 5 obtained in Example 10 and sample 1 obtained in Example 6 maintain relatively good mechanical properties. The mechanical properties of sample 6 obtained in Example 11 decline the most after aging treatment, indicating its poor performance against ultraviolet aging.

[0123] It should be noted that the formula and test adopted in this embodiment are only used to verify the feasibility of the technical solution of this application. Based on the technical solution of this application, those skilled in the art can continue to add other fillers according to actual needs to improve the mechanical properties or other properties of the material.

[0124] Table 1

[0125]

[0126] 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 photovoltaic cable resistant to ultraviolet aging, characterized in that: include: S1, mixing and granulating raw materials including polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, modified magnesium aluminum hydrotalcite, titanium dioxide and additives to obtain masterbatch; S2, melt-extrude the masterbatch, and coat the masterbatch on the surface of the cable core as a sheath layer to obtain the photovoltaic cable; The modified magnesium aluminum hydrotalcite is subjected to intercalation treatment, and the intercalation agent used in the intercalation treatment includes ammonium salt, hydroxybenzophenone, and serine; the modified magnesium aluminum hydrotalcite is prepared by the following steps: A1, dissolving the ammonium salt and the serine in water to obtain an aqueous phase; A2, dissolving the hydroxybenzophenone in N-methylpyrrolidone to obtain an organic phase; A3, firstly uniformly dispersing the magnesium aluminum hydrotalcite, the aqueous phase and sodium dodecyl sulfate by ultrasonication, then adding the organic phase and cyclohexane, mixing and ultrasonically emulsifying to obtain an emulsion; A4, sending the emulsion into a reactor, and performing hydrothermal treatment under heating and pressurization conditions to obtain the modified magnesium aluminum hydrotalcite; The polyvinyl chloride is subjected to a carboxyl modification treatment, wherein the carboxyl modification treatment comprises: using a compound having at least one carboxyl group and at least one thiol group to heat and reflux with polyvinyl chloride particles in a solvent system; The polyvinyl chloride and the modified magnesium aluminum hydrotalcite are organically linked through an esterification reaction; the esterification reaction is carried out under heating conditions with an inorganic acid as a catalyst.

2. The preparation method according to claim 1, characterized in that: Taking the total addition amount of the titanium dioxide as 100wt%, the titanium dioxide comprises: Titanium dioxide powder A, 20wt% to 25wt%; Titanium dioxide powder B, 45wt% to 50wt%; Titanium dioxide powder C, 30wt% to 35wt%; Wherein, the average particle size D50 of the titanium dioxide powder A is A Smaller than the average particle size D50 of the titanium dioxide powder B B The average particle size D50 of the titanium dioxide powder B is B Smaller than the average particle size D50 of the titanium dioxide powder C C .

3. The preparation method according to claim 2, characterized in that: The particle size range of the titanium dioxide powder A is greater than 50 nm and less than 100 nm, the particle size range of the titanium dioxide powder B is greater than 100 nm and less than 200 nm, and the particle size range of the titanium dioxide powder C is greater than 200 nm and less than 350 nm.

4. The preparation method according to claim 1, characterized in that: In S1, by mass ratio, polyvinyl chloride: Polyethylene: ethylene-vinyl acetate copolymer: modified magnesium aluminum hydrotalcite: titanium dioxide: additive = 100: (30-35): (20-25): (6-12): (4-6): (2-6); and / or In S1, based on the total amount of the additives added as 100wt%, the additives include: 35wt% to 40wt% of a plasticizer, diisodecyl phthalate, 25wt% to 30wt% of a stabilizer, calcium zinc dimerate, 10wt% to 20wt% of an antioxidant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 15wt% to 25wt% of a lubricant, glyceryl monostearate; and / or In S1, the polyethylene is a linear low density polyethylene; and / or The cable core comprises, from inside to outside, a conductor, a conductor shielding layer, an insulating layer, and an insulating shielding layer.

5. The preparation method according to claim 1, characterized in that: In S1, the mixing temperature of the mixing and granulation is 80° C. to 100° C., the mixing speed is 400 r / min to 800 r / min, and the mixing time is 20 min to 30 min; and / or In S2, the melt extrusion has a melting temperature of 160°C to 220°C and a melting time of 20min to 40min.

6. The preparation method according to claim 1, characterized in that: S1 specifically includes: S11, mixing the polyvinyl chloride and the modified magnesium aluminum hydrotalcite, using an acid as a catalyst, heating and refluxing in a solvent system to obtain a first mixture; S12, mixing and granulating the first mixture with the polyethylene, the ethylene-vinyl acetate copolymer, the titanium dioxide and the auxiliary agent to obtain the masterbatch.

7. A photovoltaic cable resistant to ultraviolet aging, characterized in that: The UV-resistant photovoltaic cable is obtained by the preparation method according to any one of claims 1 to 6.

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