Irradiation crosslinking halogen-free flame-retardant polyolefin photovoltaic cable material and preparation method thereof

Abstract

The invention discloses an irradiation crosslinking halogen-free flame-retardant polyolefin photovoltaic cable material and a preparation method thereof, and belongs to the technical field of cable materials. Acrylonitrile, methyl methacrylate and azodiisobutyronitrile are stirred and mixed to obtain oily liquid; the nanotube composite flame-retardant powder, expanded graphite powder, magnesium nitrate, sodium hydroxide, lauryl sodium sulfate and deionized water are stirred, mixed and subjected to ultrasonic dispersion, dispersion liquid is obtained, then the dispersion liquid and oily liquid react to prepare composite flame-retardant microspheres, and the composite flame-retardant microspheres are applied to the photovoltaic cable material. Expanded graphite in the composite flame-retardant microspheres expands when heated, air can be blocked, the flame-retardant effect is further improved, the effect of blocking high-energy radiation can be achieved after the expanded graphite and the nanotube composite flame-retardant powder are compounded, the phosphorus-silicon flame retardant can be prevented from being decomposed in the irradiation crosslinking process, and the stability of the phosphorus-silicon flame retardant can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cable materials, and in particular relates to a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material and a preparation method thereof. Background Art

[0002] Solar energy technology is one of the green energy technologies. Photovoltaic cables are an indispensable part of the solar power generation system. The performance of photovoltaic cables directly affects the safety, stability and life of the entire system. The characteristics of photovoltaic cables are determined by the insulation and sheath materials used, which generally use cross-linked polyolefin materials. After the photovoltaic cable material is irradiated by the irradiation accelerator, the molecular structure of the cable material will change, which significantly improves the thermal stability and anti-aging performance of the material. Since photovoltaic cables are installed on roofs or on the ground for a long time, they may face the risk of high temperature and fire. Therefore, photovoltaic cable materials, like other cable materials, need to add flame retardants to improve their flame retardant properties.

[0003] Commonly used flame retardants include inorganic flame retardants, halogen flame retardants and phosphorus flame retardants. Due to the dual requirements of flame retardant effect and environmental protection, the more expensive phosphorus flame retardants are also widely used in the actual production process. However, phosphorus flame retardants are exposed to high-energy radiation during the irradiation cross-linking process and are easily decomposed, which is not conducive to the phosphorus flame retardant to stably exert its flame retardant effect. Summary of the invention

[0004] One of the purposes of the present invention is to provide a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, which is loaded with a phosphorus silicon flame retardant through halloysite nanotubes and then compounded with expanded graphite and coated with a polymer to block high-energy radiation and avoid affecting the stability of the phosphorus-based flame retardant; the second purpose of the present invention is to provide a method for preparing a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, comprising the following raw materials in parts by mass:

[0007] 60-80 parts of high-density polyethylene, 10-15 parts of low-density polyethylene, 30-40 parts of linear low-density polyethylene, 10-15 parts of maleic anhydride grafted polyethylene, 3-5 parts of triallyl cyanurate, 20-30 parts of carbon black, 5-10 parts of fumed silica, 8-14 parts of zinc stearate, 18-24 parts of composite flame retardant microspheres, 1.5-3 parts of silane coupling agent KH-560 and 1.5-3 parts of antioxidant 1010.

[0008] Furthermore, the composite flame retardant microspheres are prepared by the following steps:

[0009] Step 1: Add halloysite nanotubes, silane coupling agent KH-570 and 80% ethanol aqueous solution into a reactor, stir at 500-800 r / min for 5-10 min, then add phosphorus silicon flame retardant into the reactor, continue stirring at 85-90° C. for 3-4 h, filter under reduced pressure, wash the filter cake with anhydrous ethanol for 3-5 times, and vacuum dry at 50-60° C. to obtain nanotube composite flame retardant powder;

[0010] Step 2: acrylonitrile, methyl methacrylate and azobisisobutyronitrile as an initiator are stirred and mixed to obtain an oily liquid; nanotube composite flame retardant powder, expanded graphite powder, magnesium nitrate, sodium hydroxide, sodium dodecyl sulfate and deionized water are stirred and mixed and ultrasonically dispersed for 20-30 minutes to obtain a dispersion, and then the dispersion and the oily liquid are added to the reactor in a mass ratio of 2:1, stirred at 800-1200r / min for 10-15min, and then heated to 65-70°C, continued to stir and react for 6-8h, naturally cooled, filtered, and the product was washed with anhydrous ethanol 2-3 times, and dried to obtain composite flame retardant microspheres.

[0011] Furthermore, in step 1, the usage ratio of halloysite nanotubes, silane coupling agent KH-570, ethanol aqueous solution, and phosphorus silicon flame retardant is 8-10g: 2-2.5g: 80-100mL: 5-6g.

[0012] Furthermore, in step 2, the mass ratio of acrylonitrile, methyl methacrylate and azobisisobutyronitrile is 70-75:25-30:0.06-0.1.

[0013] Furthermore, in step 2, the mass ratio of the nanotube composite flame retardant powder, expanded graphite powder, magnesium nitrate, sodium hydroxide, sodium dodecyl sulfate and deionized water is 20:12-15:4:2:0.01:35-40.

[0014] Furthermore, the preparation method of halloysite nanotubes is as follows: adding halloysite ore, deionized water and sodium hexametaphosphate into a reactor, stirring at 500-800 r / min for 4-5 hours, then standing for 10-12 hours, separating and collecting the upper suspension, centrifuging the suspension at a speed of 2500-2800 r / min for 5-8 minutes, discarding the precipitate, centrifuging the upper liquid at 8000 r / min for 12-15 minutes, collecting the precipitate and vacuum drying it at 60-80° C. to obtain halloysite nanotubes;

[0015] Furthermore, the mass ratio of the halloysite ore, deionized water and sodium hexametaphosphate is 40-50:160-200:1.

[0016] Furthermore, the phosphorus silicon flame retardant in step 1 is prepared by the following steps:

[0017] Step 1: Add diphenyl chlorophosphate into a reaction kettle, add anhydrous formic acid dropwise into the reaction kettle under nitrogen protection at 36-40°C, keep warm for 2-3 hours after the addition is complete, wash the reaction product with ether and deionized water for 2-3 times respectively, and fractionate under reduced pressure to obtain diphenyl phosphite monomer;

[0018] Step 2: Add vinyl triethoxysilane, 20% by mass hydrochloric acid aqueous solution and acetone to a reaction kettle, react at 40-42° C. for 20-24 hours, filter, wash the filter cake with acetone 2-3 times, and dry to obtain cage-like siloxane powder;

[0019] Step 3: Under nitrogen protection, add caged siloxane powder, toluene, diphenyl phosphite monomer and azobisisobutyronitrile as an initiator into a reactor, then stir and react at 75-80°C and 300-500r / min for 12-14h, cool naturally, and remove toluene as a solvent by reduced pressure distillation. Dissolve the remaining product with 1.5-2 times the volume of dichloromethane, add 15-20 times the volume of ethyl acetate and stir for 20-30min. Filter after precipitation, and vacuum dry the filter cake at 60-80°C to obtain a phosphorus silicon flame retardant.

[0020] Furthermore, in step 1, the mass ratio of diphenyl chlorophosphate to anhydrous formic acid is 2:0.7.

[0021] Furthermore, in step 2, the usage ratio of vinyltriethoxysilane, 20% by mass aqueous hydrochloric acid solution and acetone is 10-12 mL: 27.5-33 mL: 75-90 mL.

[0022] Furthermore, in step 3, the usage ratio of caged siloxane powder, toluene, diphenyl phosphite monomer and azobisisobutyronitrile is 15-20 g: 60-80 mL: 30-40 g: 0.75-0.8 g.

[0023] A method for preparing a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material comprises the following steps:

[0024] High-density polyethylene, low-density polyethylene, linear low-density polyethylene, maleic anhydride grafted polyethylene, triallyl cyanurate, carbon black, fumed silica, zinc stearate, composite flame-retardant microspheres, silane coupling agent KH-560 and antioxidant 1010 are mixed at 145-150° C. for 10-12 minutes, then compression molded in a mold at 155-160° C., and irradiated cross-linked at a irradiation dose of 75-80 kGy to prepare an irradiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material.

[0025] Beneficial effects of the present invention:

[0026] The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable of the present invention adopts a homemade phosphorus silicon flame retardant as a flame retardant material, and no halogen elements are released during the combustion process, which is more environmentally friendly; compared with common organic phosphorus flame retardants, the phosphorus silicon flame retardant can form a solid carbon layer and a glassy layer on the surface of the photovoltaic cable material during the flame retardant process to inhibit heat and mass transfer; the expanded graphite in the composite flame retardant microspheres expands when heated, which helps to block the air and further improve the flame retardant effect; and the expanded graphite and the nanotube composite flame retardant powder can be compounded to block high-energy radiation, which helps to prevent the phosphorus silicon flame retardant from decomposing during the radiation cross-linking process and helps to improve the stability of the phosphorus silicon flame retardant.

[0027] Phosphorus silicon flame retardant with halloysite nanotubes as carrier helps to improve the mechanical properties of photovoltaic cable materials; nanotube composite flame retardant powder and expanded graphite are combined with each other through intermolecular forces during ultrasonic dispersion, and sodium hydroxide and magnesium nitrate react to form magnesium hydroxide, which plays an anchoring role, so that the nanotube composite flame retardant powder is stably loaded on the surface of expanded graphite particles and serves as a template particle. Then, under the action of an initiator, acrylonitrile and methyl methacrylate are cross-linked and polymerized to form a coating film to prepare composite flame retardant microspheres, which helps to increase the compatibility of flame retardant substances and other raw materials and helps to improve the performance of photovoltaic cable materials. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Example 1: This example provides a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, which is prepared by the following steps:

[0030] Step 1: Add 400 kg of halloysite ore, 1600 kg of deionized water and 10 kg of sodium hexametaphosphate into a reactor, stir at 500 r / min for 4 hours, then let stand for 10 hours, separate and collect the upper suspension, centrifuge the suspension at 2500 r / min for 5 minutes, discard the precipitate, centrifuge the upper liquid at 8000 r / min for 12 minutes, collect the precipitate and vacuum dry it at 60°C to obtain halloysite nanotubes.

[0031] Step 2: Add 40 kg of diphenyl chlorophosphate into a reactor, and drop 14 kg of anhydrous formic acid into the reactor under nitrogen protection and 36°C. After the dropwise addition is completed, keep the reaction warm for 2 hours. Wash the reaction product twice with ether and deionized water respectively, and perform vacuum distillation to obtain diphenyl phosphite monomer.

[0032] Step 3: Add 100 L of vinyl triethoxysilane, 275 L of 20% hydrochloric acid aqueous solution and 750 L of acetone to the reactor, react at 40° C. for 20 h, filter, wash the filter cake twice with acetone, and dry to obtain cage-like siloxane powder.

[0033] Step 4: Under nitrogen protection, 7.5 kg of caged siloxane powder, 30 L of toluene, 15 kg of diphenyl phosphite monomer and 375 g of azobisisobutyronitrile as an initiator are added to the reactor, and then stirred at 75 ° C and 300 r / min for 12 hours, cooled naturally, and toluene as a solvent is removed by vacuum distillation. The remaining product is dissolved with 1.5 times the volume of dichloromethane, and then 15 times the volume of ethyl acetate is added and stirred for 20 minutes. After the precipitate is precipitated, it is filtered and the filter cake is vacuum dried at 60 ° C to obtain a phosphorus silicon flame retardant.

[0034] Step 5: Add 8 kg of halloysite nanotubes, 2 kg of silane coupling agent KH-570 and 80 L of 80% ethanol aqueous solution into the reactor, stir at 500 r / min for 5 minutes, then add 5 kg of phosphorus silicon flame retardant into the reactor, continue stirring at 85 ° C for 3 hours, filter under reduced pressure, wash the filter cake with anhydrous ethanol 3 times, and vacuum dry at 50 ° C to obtain nanotube composite flame retardant powder.

[0035] Step six: stir and mix 7kg of acrylonitrile, 2.5kg of methyl methacrylate and 6g of azobisisobutyronitrile as an initiator to obtain an oily liquid; stir and mix 2kg of nanotube composite flame retardant powder, 1.2kg of expanded graphite powder, 0.4kg of magnesium nitrate, 2kg of sodium hydroxide, 1g of sodium dodecyl sulfate and 3.5kg of deionized water and ultrasonically disperse for 20 minutes to obtain a dispersion, then add 6kg of the dispersion and 3kg of the oily liquid into the reactor, stir at 800r / min for 10min, then heat to 65°C, continue stirring and reacting for 6h, cool naturally, filter, wash the product twice with anhydrous ethanol, and dry to obtain composite flame retardant microspheres.

[0036] Step seven: knead and mix 6kg high-density polyethylene, 1kg low-density polyethylene, 3kg linear low-density polyethylene, 1kg maleic anhydride grafted polyethylene, 0.3kg triallyl cyanurate, 2kg carbon black, 0.5kg fumed silica, 0.8kg zinc stearate, 1.8kg composite flame-retardant microspheres, 0.15kg silane coupling agent KH-560 and 0.15kg antioxidant 1010 at 145°C for 10 minutes, then compression mold them in a mold at 155°C, and irradiate cross-link them at a irradiation dose of 75kGy to prepare irradiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable materials.

[0037] Example 2: This example provides a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, which is prepared by the following steps:

[0038] Step 1: Add 450 kg of halloysite ore, 1800 kg of deionized water and 10 kg of sodium hexametaphosphate into a reactor, stir at 650 r / min for 4.5 hours, then let stand for 11 hours, separate and collect the upper suspension, centrifuge the suspension at 2650 r / min for 6 minutes, discard the precipitate, centrifuge the upper liquid at 8000 r / min for 13 minutes, collect the precipitate and vacuum dry it at 70°C to obtain halloysite nanotubes.

[0039] Step 2: Add 40 kg of diphenyl chlorophosphate into a reactor, and drop 14 kg of anhydrous formic acid into the reactor under nitrogen protection and 38°C. After the addition is completed, keep the reaction warm for 2.5 hours. Wash the reaction product twice with ether and deionized water respectively, and perform vacuum distillation to obtain diphenyl phosphite monomer.

[0040] Step 3: Add 110 L of vinyl triethoxysilane, 300 L of 20% hydrochloric acid aqueous solution and 820 L of acetone to the reactor, react at 41° C. for 22 h, filter, wash the filter cake twice with acetone, and dry to obtain cage-like siloxane powder.

[0041] Step 4: Under nitrogen protection, 10 kg of caged siloxane powder, 35 L of toluene, 18 kg of diphenyl phosphite monomer and 385 g of azobisisobutyronitrile as an initiator are added to the reactor, and then stirred at 78 ° C and 400 r / min for 13 hours, cooled naturally, and toluene as a solvent is removed by vacuum distillation. The remaining product is dissolved with 1.8 times the volume of dichloromethane, and then 18 times the volume of ethyl acetate is added and stirred for 25 minutes. After the precipitate is precipitated, it is filtered and the filter cake is vacuum dried at 70 ° C to obtain a phosphorus silicon flame retardant.

[0042] Step 5: Add 9 kg of halloysite nanotubes, 2.2 kg of silane coupling agent KH-570 and 90 L of 80% ethanol aqueous solution into the reactor, stir at 650 r / min for 8 min, then add 5.5 kg of phosphorus silicon flame retardant into the reactor, continue stirring at 88 ° C for 3.5 h, filter under reduced pressure, wash the filter cake with anhydrous ethanol 4 times, and vacuum dry at 55 ° C to obtain nanotube composite flame retardant powder.

[0043] Step six: stir and mix 7.2kg of acrylonitrile, 2.8kg of methyl methacrylate and 8g of azobisisobutyronitrile as an initiator to obtain an oily liquid; stir and mix 2kg of nanotube composite flame retardant powder, 1.35kg of expanded graphite powder, 0.4kg of magnesium nitrate, 2kg of sodium hydroxide, 1g of sodium dodecyl sulfate and 3.8kg of deionized water and ultrasonically disperse for 25 minutes to obtain a dispersion, then add 6kg of the dispersion and 3kg of the oily liquid into the reactor, stir at 1000r / min for 12min, then heat to 68°C, continue stirring and reacting for 7h, cool naturally, filter, wash the product twice with anhydrous ethanol, and dry to obtain composite flame retardant microspheres.

[0044] Step seven: knead and mix 7kg high-density polyethylene, 1.2kg low-density polyethylene, 3.5kg linear low-density polyethylene, 1.2kg maleic anhydride grafted polyethylene, 0.4kg triallyl cyanurate, 2.5kg carbon black, 0.8kg fumed silica, 1.1kg zinc stearate, 2.1kg composite flame-retardant microspheres, 0.22kg silane coupling agent KH-560 and 0.23kg antioxidant 1010 at 148°C for 11 minutes, then compression mold them in a mold at 158°C, and irradiate cross-link them at a irradiation dose of 78kGy to prepare irradiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable materials.

[0045] Example 3: This example provides a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, which is prepared by the following steps:

[0046] Step 1: Add 500 kg of halloysite ore, 2000 kg of deionized water and 10 kg of sodium hexametaphosphate into a reactor, stir at 800 r / min for 5 hours, then let stand for 12 hours, separate and collect the upper suspension, centrifuge the suspension at 2800 r / min for 8 minutes, discard the precipitate, centrifuge the upper liquid at 8000 r / min for 15 minutes, collect the precipitate and vacuum dry it at 80°C to obtain halloysite nanotubes.

[0047] Step 2: Add 40 kg of diphenyl chlorophosphate into a reactor, and drop 14 kg of anhydrous formic acid into the reactor under nitrogen protection and 40°C. After the addition is completed, keep the reaction warm for 3 hours. Wash the reaction product with ether and deionized water for 3 times respectively, and perform vacuum distillation to obtain diphenyl phosphite monomer.

[0048] Step 3: Add 120L of vinyltriethoxysilane, 330L of 20% hydrochloric acid aqueous solution and 900L of acetone into the reactor, react at 42°C for 24h, filter, wash the filter cake with acetone three times, and dry to obtain cage-like siloxane powder.

[0049] Step 4: Under nitrogen protection, 15 kg of caged siloxane powder, 40 L of toluene, 20 kg of diphenyl phosphite monomer and 400 g of azobisisobutyronitrile as an initiator are added to the reactor, and then stirred for 14 hours at 80 ° C and 500 r / min. After natural cooling, the toluene as a solvent is removed by reduced pressure distillation, and the remaining product is dissolved with 2 times the volume of dichloromethane, and then 20 times the volume of ethyl acetate is added and stirred for 30 minutes. After the precipitate is precipitated, it is filtered and the filter cake is vacuum dried at 80 ° C to obtain a phosphorus silicon flame retardant.

[0050] Step 5: Add 10 kg of halloysite nanotubes, 2.5 kg of silane coupling agent KH-570 and 100 L of 80% ethanol aqueous solution into the reactor, stir at 800 r / min for 10 min, then add 6 kg of phosphorus silicon flame retardant into the reactor, continue stirring at 90 ° C for 4 h, filter under reduced pressure, wash the filter cake with anhydrous ethanol 5 times, and vacuum dry at 60 ° C to obtain nanotube composite flame retardant powder.

[0051] Step six: stir and mix 7.5kg of acrylonitrile, 3kg of methyl methacrylate and 10g of azobisisobutyronitrile as an initiator to obtain an oily liquid; stir and mix 2kg of nanotube composite flame retardant powder, 1.5kg of expanded graphite powder, 0.4kg of magnesium nitrate, 2kg of sodium hydroxide, 1g of sodium dodecyl sulfate and 4kg of deionized water and ultrasonically disperse for 30 minutes to obtain a dispersion, then add 6kg of the dispersion and 3kg of the oily liquid into the reactor, stir at 1200r / min for 15min, then heat to 70°C, continue stirring and reacting for 8h, cool naturally, filter, wash the product with anhydrous ethanol 3 times, and dry to obtain composite flame retardant microspheres.

[0052] Step seven: 8kg high-density polyethylene, 1.5kg low-density polyethylene, 4kg linear low-density polyethylene, 1.5kg maleic anhydride grafted polyethylene, 0.5kg triallyl cyanurate, 3kg carbon black, 1kg fumed silica, 1.4kg zinc stearate, 2.4kg composite flame-retardant microspheres, 0.3kg silane coupling agent KH-560 and 0.3kg antioxidant 1010 are mixed at 150°C for 12 minutes, then compression molded in a mold at 160°C, and irradiated cross-linked at a irradiation dose of 80kGy to prepare an irradiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material.

[0053] Comparative Example 1: Based on Example 3, the nanotube composite flame retardant powder in step five is directly used to replace the composite flame retardant microspheres in step seven, and the other steps remain unchanged to prepare a photovoltaic cable material.

[0054] Comparative Example 2: Based on Example 3, no expanded graphite powder is added during the preparation of composite flame-retardant microspheres in step six, and then the prepared composite flame-retardant microspheres are used as the final raw material, and the remaining steps remain unchanged to prepare photovoltaic cable materials.

[0055] Comparative Example 3: Based on Example 3, in step six, the expanded graphite powder is replaced with ordinary graphite powder during the preparation of composite flame-retardant microspheres, and the prepared composite flame-retardant microspheres are used as the final raw material. The remaining steps remain unchanged to prepare photovoltaic cable materials.

[0056] Comparative Example 4: Based on Example 3, in the process of preparing composite flame retardant microspheres in step six, the phosphorus silicon flame retardant in step four is used instead of the nanotube composite flame retardant powder, and then the prepared composite flame retardant microspheres are used as the final raw material, and the other steps remain unchanged to prepare photovoltaic cable materials.

[0057] Performance tests were performed on Examples 1 to 3 and Comparative Examples 1 to 4. Different tensile specimens were prepared from different photovoltaic cable materials according to GB / T1040.1-2018, and then the tensile strength and elongation at break of the different tensile specimens were tested; different combustion specimens were prepared from different photovoltaic cable materials according to GB / T 18380-2022, and the self-extinguishing time of the different combustion specimens was recorded. The flame retardancy of the different combustion specimens was tested according to the UL94 standard, and the V0 level flame retardancy was the best. Each group of tests was repeated 3 times, and the results were averaged. The results are shown in Table 1:

[0058] Table 1

[0059] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Tensile strength(MPa) 42.6 43.8 43.2 40.5 43.5 43.3 38.7 Elongation at break (%) 283 295 290 274 291 290 255 Self-extinguishing time(s) 2.5 2.3 2.4 10.7 11.2 5.6 2.9 Flame retardancy (UL94) V0 V0 V0 V1 V1 V0 V0

[0060] According to Table 1, it can be seen that the photovoltaic cable materials in Examples 1 to 3 have better mechanical properties than those in Comparative Example 1, because the nanotube composite flame retardant powder has better compatibility and dispersibility with the other raw materials after coating, thereby improving its mechanical properties; the self-extinguishing time in Comparative Example 1 and Comparative Example 2 is prolonged, because the nanotube composite flame retardant powder that has not been coated is partially decomposed by high-energy radiation during the irradiation cross-linking process, resulting in a decrease in flame retardant performance; the self-extinguishing time in Comparative Example 3 is longer than that in the comparative example, because the expanded graphite powder can not only block high-energy radiation to protect the phosphosilicate flame retardant, but also can expand to block open flames and photovoltaic cable materials, thereby improving the flame retardant effect; the tensile strength and elongation at break in Comparative Example 4 are reduced, because the halloysite nanotubes, as a carrier of the phosphosilicate flame retardant, can increase the mechanical properties of the photovoltaic cable materials.

[0061] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material, characterized in that: The following raw materials are included by mass: 60-80 parts of high-density polyethylene, 10-15 parts of low-density polyethylene, 30-40 parts of linear low-density polyethylene, 10-15 parts of maleic anhydride grafted polyethylene, 3-5 parts of triallyl cyanurate, 20-30 parts of carbon black, 5-10 parts of fumed silica, 8-14 parts of zinc stearate, 18-24 parts of composite flame-retardant microspheres, 1.5-3 parts of silane coupling agent KH-560 and 1.5-3 parts of antioxidant 1010; The composite flame retardant microspheres are prepared by the following steps: Acrylonitrile, methyl methacrylate and azobisisobutyronitrile are stirred and mixed to obtain an oily liquid, nanotube composite flame retardant powder, expanded graphite powder, magnesium nitrate, sodium hydroxide, sodium dodecyl sulfate and deionized water are stirred and mixed and ultrasonically dispersed for 20-30 minutes to obtain a dispersion, and then the dispersion and the oily liquid are added into a reactor at a mass ratio of 2:1, stirred at 800-1200r / min for 10-15min, heated to 65-70°C and continued to stir and react for 6-8h, naturally cooled, filtered, washed and dried to obtain composite flame retardant microspheres.

2. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 1, characterized in that: The mass ratio of acrylonitrile, methyl methacrylate and azobisisobutyronitrile is 70-75:25-30:0.06-0.

1.

3. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 1, characterized in that: The mass ratio of the nanotube composite flame retardant powder, expanded graphite powder, magnesium nitrate, sodium hydroxide, sodium dodecyl sulfate and deionized water is 20:12-15:4:2:0.01:35-40.

4. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 1, characterized in that: The nanotube composite flame retardant powder is prepared by the following steps: Adding halloysite ore, deionized water and sodium hexametaphosphate into a reactor in a mass ratio of 40-50:160-200:1, stirring at 500-800 r / min for 4-5 hours, standing for 10-12 hours, separating and collecting the upper suspension, centrifuging the suspension at 2500-2800 r / min for 5-8 minutes, centrifuging the upper liquid at 8000 r / min for 12-15 minutes, collecting the precipitate and vacuum drying to obtain halloysite nanotubes; Halloysite nanotubes, silane coupling agent KH-570 and 80wt% ethanol aqueous solution are added into a reactor, stirred at 500-800r / min for 5-10min, then phosphorus silicon flame retardant is added, stirred at 85-90℃ for 3-4h, filtered under reduced pressure, washed and vacuum dried to obtain nanotube composite flame retardant powder.

5. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 4, characterized in that: The usage ratio of the halloysite nanotube, the silane coupling agent KH-570, the ethanol aqueous solution and the phosphorus silicon flame retardant is 8-10g: 2-2.5g: 80-100mL: 5-6g.

6. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 4, characterized in that: The phosphorus silicon flame retardant is prepared by the following steps: Under nitrogen protection, caged siloxane powder, toluene, diphenyl phosphite monomer and azobisisobutyronitrile are added into a reactor, stirred at 75-80°C and 300-500r / min for 12-14h, cooled naturally, and toluene is removed by vacuum distillation. The remaining product is dissolved with 1.5-2 times the volume of dichloromethane, and then 15-20 times the volume of ethyl acetate is added and stirred for 20-30min. After the precipitate is separated, it is filtered and the filter cake is vacuum dried to obtain a phosphorus silicon flame retardant.

7. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 6, characterized in that: The usage ratio of the caged siloxane powder, toluene, diphenyl phosphite monomer and azobisisobutyronitrile is 15-20 g: 60-80 mL: 30-40 g: 0.75-0.8 g.

8. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 6, characterized in that: The caged siloxane powder is prepared by the following steps: Add vinyl triethoxysilane, 20 wt% hydrochloric acid aqueous solution and acetone into a reaction kettle, react at 40-42° C. for 20-24 hours, filter, wash the filter cake with acetone 2-3 times, and dry to obtain cage-shaped siloxane powder; the amount ratio of vinyl triethoxysilane, 20% hydrochloric acid aqueous solution by mass fraction and acetone is 10-12 mL: 27.5-33 mL: 75-90 mL.

9. The radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 6, characterized in that: The diphenyl phosphite monomer is prepared by the following steps: Add diphenyl chlorophosphate into a reactor, and drop anhydrous formic acid into the reactor under nitrogen protection at 36-40°C. After the dropwise addition is completed, keep the reaction warm for 2-3 hours. Wash the reaction product with ether and deionized water for 2-3 times respectively, and perform vacuum distillation to obtain diphenyl phosphite monomer. The mass ratio of diphenyl chlorophosphate to anhydrous formic acid is 2:0.

7.

10. The method for preparing a radiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material according to claim 1, characterized in that: The steps include: High-density polyethylene, low-density polyethylene, linear low-density polyethylene, maleic anhydride grafted polyethylene, triallyl cyanurate, carbon black, fumed silica, zinc stearate, composite flame-retardant microspheres, silane coupling agent KH-560 and antioxidant 1010 are mixed at 145-150° C. for 10-12 minutes, then compression molded in a mold at 155-160° C., and irradiated cross-linked at a irradiation dose of 75-80 kGy to prepare an irradiation cross-linked halogen-free flame-retardant polyolefin photovoltaic cable material.