A high-temperature resistant polypropylene capacitor film and its preparation method

Abstract

The present invention relates to the technical field of capacitor films, and specifically relates to a high-temperature resistant polypropylene capacitor film and a preparation method thereof. The high-temperature resistant polypropylene capacitor film comprises the following raw materials in parts by weight: 94-98 parts of polypropylene resin, 1-3 parts of a modified balance agent doped with fillers, 0.5-2 parts of a boron nitride-glass fiber synergistic agent, 0.05-0.4 parts of a nucleating agent, 0.2-0.4 parts of an antioxidant, and 0.1-0.4 parts of a silane coupling agent. The raw material composition is subjected to processes such as melting and extrusion molding, cooling and shaping, preheating, biaxial stretching, heat setting, and winding to obtain the high-temperature resistant polypropylene capacitor film. The present invention is formulated with polypropylene resin, a nucleating agent, an antioxidant, and a silane coupling agent, and a modified balance agent doped with fillers and a boron nitride-glass fiber synergistic agent are added. Through the coordination of the raw materials, the feasibility of the high biaxial stretching process is ensured, and the breakdown resistance, mechanical strength, and dielectric loss performance of the product are optimized. At the same time, the effects of high temperature resistance and corrosion resistance stability are remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor films, and particularly relates to a high-temperature resistant polypropylene capacitor film and a preparation method thereof. Background Art

[0002] With the development of electrical equipment towards large capacity, high power and miniaturization, the operating temperature of capacitors has been continuously rising, reaching above 100°C. In severe cases, the application in some fields even exceeds 120°C, such as capacitors for electric vehicles. Polypropylene resin (PP) is a widely used material for capacitor films. Due to the characteristics of its intrinsic structure, polypropylene has always had the problem of poor high-temperature resistance. The problems exposed by biaxially oriented polypropylene capacitor films at high temperatures are severe. The breakdown strength decreases rapidly with the increase of temperature, especially after the temperature > 100°C, which brings many potential safety hazards and performance losses to the use of capacitors. For the problem of poor breakdown resistance of polypropylene materials for capacitor films at high temperatures, the existing technical means to improve the breakdown performance of products are likely to lead to poor mechanical strength and dielectric loss of the capacitor film. It is very difficult to balance and coordinate the breakdown resistance, mechanical strength and dielectric loss of the products, which limits the use efficiency of the products. Summary of the Invention

[0003] Aiming at the defects of the prior art, the purpose of the present invention is to provide a high-temperature resistant polypropylene capacitor film and a preparation method thereof to solve the problems raised in the above background art.

[0004] The present invention adopts the following technical solutions to solve the technical problems:

[0005] The present invention provides a high-temperature resistant polypropylene capacitor film, which comprises the following raw materials in parts by weight:

[0006] 94 - 98 parts of polypropylene resin, 1 - 3 parts of a modified balance agent doped with fillers, 0.5 - 2 parts of a boron nitride-glass fiber synergist, 0.05 - 0.4 parts of a nucleating agent, 0.2 - 0.4 parts of an antioxidant, and 0.1 - 0.4 parts of a silane coupling agent.

[0007] Preferably, the antioxidant is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index ≥ 97%, the melt flow rate is 3 - 5 g / 10min, and the ash content ≤ 25 ppm; the nucleating agent is a sorbitol-based α nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0008] Preferably, the preparation method of the modified balance agent doped with fillers is as follows:

[0009] S01: Place alumina in a proton irradiation chamber for irradiation for 25 min, with an irradiation power of 350 - 400 W. After the irradiation ends, obtain irradiated alumina;

[0010] Mix the irradiated alumina, a lanthanum nitrate solution with a mass fraction of 3%, and the silane coupling agent KH550 evenly according to a weight ratio of (3 - 5):(5 - 7):1 to obtain an alumina modifier;

[0011] S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution according to a weight ratio of 2:5. Subsequently, add modified carboxymethyl cellulose accounting for 10 - 15% of the total weight of the alumina modifier, and perform primary ball milling at a ball milling speed of 1000 r / min for 1 h. After the ball milling is completed, perform suction filtration and drying to obtain a filler dopant;

[0012] S03: Add 2 - 3 parts of a hydrochloric acid dopamine solution to 4 - 7 parts of a chitosan solution with a mass fraction of 4% by weight. Subsequently, add 1 - 3 parts of hollow glass microspheres and stir well to obtain a balance adjusting solution;

[0013] S04: Perform secondary ball milling on the filler dopant and the balance adjusting solution according to a weight ratio of 5:3 at a ball milling speed of 1500 r / min for 2 h. After the ball milling is completed, perform suction filtration and drying to obtain a modified balance adjusting agent doped with fillers.

[0014] Preferably, the mass fraction of the sodium dodecylbenzenesulfonate solution is 2 - 5%; the mass fraction of the hydrochloric acid dopamine solution is 4 - 6%.

[0015] Preferably, the preparation method of the modified carboxymethyl cellulose is as follows:

[0016] Add 3 - 5 parts of carboxymethyl cellulose and 1 - 3 parts of nano - silica sol by weight to 5 - 8 parts of a sodium alginate solution. Subsequently, add 2 - 5 parts of silicon carbide and 3 - 4 parts of talcum powder and mix well. Then perform suction filtration and drying to obtain modified carboxymethyl cellulose.

[0017] Preferably, the mass fraction of the sodium alginate solution is 2 - 5%.

[0018] Preferably, the preparation method of the boron nitride - glass fiber synergistic agent is as follows:

[0019] S11: Mix boron nitride thoroughly in a sulfuric acid solution with a mass fraction of 5 - 8% in sufficient quantity, then wash with water and dry to obtain dried boron nitride; preheat the dried boron nitride at 55 - 60 °C for 1 h to obtain preheated boron nitride;

[0020] S12: Add 3 - 5 parts of glass fiber and 2 - 3 parts of a urea solution by weight to 5 - 8 parts of a barium titanate solution and stir well to obtain a synergistic treatment solution;

[0021] Mix barium titanate, a sodium silicate solution, and titanium oxide evenly according to a weight ratio of (3 - 4):(5 - 8):2 to prepare a barium titanate solution;

[0022] S13: Ultrasonically treat the preheated boron nitride and the synergistic treatment liquid at a weight ratio of 3:(5 - 7), with an ultrasonic power of 400 - 450 W for 1 h. After the ultrasonic treatment ends, perform suction filtration and drying to obtain the boron nitride - glass fiber synergist.

[0023] Preferably, the mass fraction of the urea solution is 2 - 4%; the mass fraction of the sodium silicate solution is 5 - 8%.

[0024] The present invention also provides a method for preparing a high - temperature resistant polypropylene capacitor film, comprising the following steps:

[0025] Step 1: Prepare the raw material composition of the high - temperature resistant polypropylene capacitor film according to the above weight parts of the raw materials of the high - temperature resistant polypropylene capacitor film;

[0026] Step 2: Melt - extrude the raw material composition of the high - temperature resistant polypropylene capacitor film through an extruder. The average temperature of each section of the extruder is 245 - 255 °C to obtain a viscous - flow melt, and then extrude it into a T - die head with a die head temperature of 240 °C to form a sheet - like melt;

[0027] Step 3: Shape the sheet - like melt under the cooling of the chill roll and the air knife in the casting machine. The cooling temperature of the chill roll is 85 - 95 °C, and the gas pressure of the air knife is 120 - 140 mbar, so that the sheet - like melt tightly adheres to the surface of the chill roll to achieve cooling and shaping, obtaining a cast sheet;

[0028] Step 4: Send the cast sheet into the stretching zone for preheating, biaxial stretching and heat setting, then perform corona treatment and winding to obtain a capacitor base film; then perform room - temperature aging treatment on the capacitor base film for 72 h, and finally perform unwinding, slitting and winding to obtain the high - temperature resistant polypropylene capacitor film;

[0029] During biaxial stretching, the preheating temperature of the first stage is 135 °C, the second stage is 140 °C, and the third stage is 145 °C;

[0030] The stretching temperature of the first stage is 155 °C, the second stage is 160 °C, the third stage is 160 °C, and the fourth stage is 164 °C;

[0031] The heat - setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C;

[0032] The longitudinal stretching ratio of the film is 4.5 times, the transverse stretching ratio is 6.5 times, and the production line speed is 200 m / min.

[0033] The high - temperature resistant polypropylene capacitor film of the present invention is prepared by blending polypropylene resin, nucleating agent, antioxidant, silane coupling agent, adding a modified balance agent with doped fillers and a boron nitride - glass fiber synergist. Through the coordination of raw materials, the breakdown resistance, mechanical strength and dielectric loss performance of the product are optimized, and at the same time, the product has remarkable high - temperature resistance and corrosion - resistant stability effects;

[0034] The modified balance regulator with doped filler uses alumina irradiated by protons to stimulate its active efficacy. At the same time, an alumina modifier is prepared by mixing a lanthanum nitrate solution with a mass fraction of 3% and a silane coupling agent KH550. The alumina modifier is used to blend a sodium dodecylbenzenesulfonate solution and modified carboxymethyl cellulose to form a filler dopant. At the same time, it is further improved and optimized by ball milling with a balance liquid. In the balance liquid, a chitosan solution, a hydrochloric acid dopamine solution, and hollow glass microspheres are blended and improved. At the same time, the modified carboxymethyl cellulose uses carboxymethyl cellulose, nano-silica sol, and sodium alginate solution, and at the same time, silicon carbide and talcum powder are further blended. Through the blending improvement of raw materials, carboxymethyl cellulose is combined with silicon carbide and talcum powder to fill into the system, so that the filler dopant prepared can further strengthen the system performance in the system, and thus the performance of the product is further improved;

[0035] The boron nitride-glass fiber synergistic agent is prepared by mixing boron nitride thoroughly in a sulfuric acid solution and then preheating it at 55-60 °C for 1 h to optimize the active efficacy of boron nitride. In the synergistic treatment liquid, glass fiber is combined with a urea solution and a barium titanate solution. At the same time, barium titanate, sodium silicate solution, and titanium oxide in the barium titanate solution are blended and optimized. Using barium titanate as the matrix and combining raw materials such as titanium oxide, and blending with glass fiber, the improved boron nitride-glass fiber synergistic agent can better cooperate with the modified balance regulator with doped filler, and thus the performance of the product is further improved. Specific embodiments

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0037] Example 1: A high-temperature resistant polypropylene capacitor film, comprising the following raw materials in parts by weight:

[0038] 94 parts of polypropylene resin, 1 part of modified balance regulator with doped filler, 0.5 part of boron nitride-glass fiber synergistic agent, 0.05 part of nucleating agent, 0.2 part of antioxidant, and 0.1 part of silane coupling agent.

[0039] The antioxidant in this example is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index of the linear polypropylene is ≥97%, the melt flow rate is 3 g / 10 min, and the ash content is ≤25 ppm; the nucleating agent is a sorbitol-based α nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0040] The preparation method of the modified balance regulator with doped filler in this example is as follows:

[0041] S01: Place alumina in a proton irradiation chamber and irradiate it for 25 minutes at an irradiation power of 350 W. After irradiation, the irradiated alumina is obtained.

[0042] Mix the irradiated alumina, a 3% lanthanum nitrate solution by mass fraction, and the silane coupling agent KH550 evenly at a weight ratio of 3:5:1 to obtain an alumina modifier.

[0043] S02: Add the alumina modifier to a sodium dodecylbenzenesulfonate solution at a weight ratio of 2:5. Then, add 10% of the total weight of the alumina modifier of modified carboxymethyl cellulose. Conduct primary ball milling at a ball milling speed of 1000 r / min for 1 hour. After ball milling, perform suction filtration and drying to obtain a filler dopant.

[0044] S03: Add 2 parts of a hydrochloric acid dopamine solution to 4 parts of a 4% chitosan solution by weight. Then, add 1 part of hollow glass microspheres and stir well to obtain a balance adjusting solution.

[0045] S04: Conduct secondary ball milling on the filler dopant and the balance adjusting solution at a weight ratio of 5:3 at a ball milling speed of 1500 r / min for 2 hours. After ball milling, perform suction filtration and drying to obtain a modified balance adjusting agent doped with fillers.

[0046] In this example, the mass fraction of the sodium dodecylbenzenesulfonate solution is 2%; the mass fraction of the hydrochloric acid dopamine solution is 4%.

[0047] The preparation method of the modified carboxymethyl cellulose in this example is as follows:

[0048] Add 3 parts of carboxymethyl cellulose and 1 part of nano-silica sol to 5 parts of a sodium alginate solution by weight. Then, add 2 parts of silicon carbide and 3 parts of talc powder and mix well. Then, perform suction filtration and drying to obtain modified carboxymethyl cellulose.

[0049] In this example, the mass fraction of the sodium alginate solution is 2%.

[0050] The preparation method of the boron nitride - glass fiber synergistic agent in this example is as follows:

[0051] S11: Mix boron nitride thoroughly in a sufficient amount of a 5% sulfuric acid solution by mass fraction, then wash it with water and dry it to obtain dried boron nitride; preheat the dried boron nitride at 55 °C for 1 hour to obtain preheated boron nitride.

[0052] S12: Add 3 parts of glass fiber and 2 parts of a urea solution to 5 parts of a barium titanate solution by weight and stir well to obtain a synergistic treatment solution.

[0053] Mix barium titanate, a sodium silicate solution, and titanium oxide evenly at a weight ratio of 3:5:2 to prepare a barium titanate solution.

[0054] S13: Ultrasonically treat the preheated boron nitride and the synergistic treatment solution at a weight ratio of 3:5. The ultrasonic power is 400 W, and the ultrasonic treatment lasts for 1 h. After the ultrasonic treatment ends, perform suction filtration and drying to obtain the boron nitride - glass fiber synergist.

[0055] In this example, the mass fraction of the urea solution is 2%; the mass fraction of the sodium silicate solution is 5%.

[0056] A preparation method of a high - temperature resistant polypropylene capacitor film in this example includes the following steps:

[0057] Step 1: Prepare a raw material composition for the high - temperature resistant polypropylene capacitor film according to the above weight parts of raw materials for the high - temperature resistant polypropylene capacitor film;

[0058] Step 2: Melt - extrude the raw material composition for the high - temperature resistant polypropylene capacitor film through an extruder. The average temperature of each section of the extruder is 245 °C to obtain a viscous - flow state melt, and then extrude it into a T - die head. The temperature of the die head is 240 °C to form a sheet - like melt;

[0059] Step 3: Shape and set the sheet - like melt under the cooling of the chill roll and air knife in a casting machine. The cooling temperature of the chill roll is 85 °C, and the gas pressure of the air knife is 120 mbar, so that the melt adheres tightly to the surface of the chill roll to achieve cooling and shaping, obtaining a cast sheet;

[0060] Step 4: Send the cast sheet into the stretching zone for preheating, biaxial stretching and heat setting, then perform corona treatment and winding to obtain a capacitor base film; then perform room - temperature aging treatment on the capacitor base film for 72 h, and finally perform unwinding, slitting and winding to obtain the high - temperature resistant polypropylene capacitor film;

[0061] During biaxial stretching, the preheating temperature of the first stage is 135 °C, the second stage is 140 °C, and the third stage is 145 °C;

[0062] The stretching temperature of the first stage is 155 °C, the second stage is 160 °C, the third stage is 160 °C, and the fourth stage is 164 °C;

[0063] The heat - setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C;

[0064] The longitudinal stretching ratio of the film is 4.5 times, the transverse stretching ratio is 6.5 times, and the production line speed is 200 m / min.

[0065] Example 2: A high - temperature resistant polypropylene capacitor film, including the following weight parts of raw materials:

[0066] 98 parts of polypropylene resin, 3 parts of a modified balancing agent doped with a filler, 2 parts of a boron nitride - glass fiber synergist, 0.4 part of a nucleating agent, 0.4 part of an antioxidant, and 0.4 part of a silane coupling agent.

[0067] The antioxidant in this embodiment is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index of the linear polypropylene is ≥97%, the melt flow rate is 5 g / 10 min, and the ash content is ≤25 ppm; the nucleating agent is a sorbitol-based α-nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0068] The preparation method of the modified balance agent doped with fillers in this embodiment is as follows:

[0069] S01: Place alumina in a proton irradiation chamber and irradiate it for 25 min with an irradiation power of 400 W. After the irradiation ends, obtain irradiated alumina;

[0070] Mix the irradiated alumina, 3% lanthanum nitrate solution by mass fraction, and silane coupling agent KH550 evenly according to a weight ratio of 5:7:1 to obtain an alumina modifier;

[0071] S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution according to a weight ratio of 2:5, and then add 15% of the total weight of the alumina modifier of modified carboxymethyl cellulose. Perform primary ball milling at a ball milling speed of 1000 r / min for 1 h. After the ball milling ends, filter and dry to obtain a filler dopant;

[0072] S03: Add 3 parts of hydrochloric acid dopamine solution to 7 parts of 4% chitosan solution by weight, and then add 3 parts of hollow glass microspheres and stir well to obtain a balance liquid;

[0073] S04: Perform secondary ball milling on the filler dopant and the balance liquid according to a weight ratio of 5:3 at a ball milling speed of 1500 r / min for 2 h. After the ball milling ends, filter and dry to obtain a modified balance agent doped with fillers.

[0074] The mass fraction of the sodium dodecylbenzenesulfonate solution in this embodiment is 5%; the mass fraction of the hydrochloric acid dopamine solution is 6%.

[0075] The preparation method of the modified carboxymethyl cellulose in this embodiment is as follows:

[0076] Add 5 parts of carboxymethyl cellulose and 3 parts of nano-silica sol to 8 parts of sodium alginate solution by weight, then add 5 parts of silicon carbide and 4 parts of talc powder and mix well, and then filter and dry to obtain modified carboxymethyl cellulose.

[0077] The mass fraction of the sodium alginate solution in this embodiment is 5%.

[0078] The preparation method of the boron nitride-glass fiber synergist in this embodiment is as follows:

[0079] S11: Mix boron nitride thoroughly in a sufficient amount of 8% sulfuric acid solution by mass fraction, then wash with water and dry to obtain dried boron nitride; preheat the dried boron nitride at 60 °C for 1 h to obtain preheated boron nitride;

[0080] S12: Add 5 parts of glass fiber and 3 parts of urea solution by weight to 8 parts of barium titanate solution and stir thoroughly to obtain a synergistic treatment solution;

[0081] Mix barium titanate, sodium silicate solution and titanium oxide uniformly in a weight ratio of 4:8:2 to prepare barium titanate solution;

[0082] S13: Ultrasonically treat the preheated boron nitride and the synergistic treatment solution in a weight ratio of 3:7, with an ultrasonic power of 450 W for 1 h. After the ultrasonic treatment, perform suction filtration and drying to obtain a boron nitride - glass fiber synergistic agent.

[0083] In this example, the mass fraction of the urea solution is 4%; the mass fraction of the sodium silicate solution is 8%.

[0084] A preparation method of a high - temperature resistant polypropylene capacitor film in this example includes the following steps:

[0085] Step 1, prepare a high - temperature resistant polypropylene capacitor film raw material composition according to the above - mentioned weight - part raw materials of the high - temperature resistant polypropylene capacitor film;

[0086] Step 2, melt - extrude the high - temperature resistant polypropylene capacitor film raw material composition through an extruder. The average temperature of each section of the extruder is 255 °C to obtain a viscous - flow state melt, and then extrude it into a T - die head with a die head temperature of 240 °C to form a sheet - like melt;

[0087] Step 3, shape the sheet - like melt under the cooling of the chill roll and air knife in the casting machine. The cooling temperature of the chill roll is 95 °C, and the gas pressure of the air knife is 140 mbar, so that the sheet - like melt tightly adheres to the surface of the chill roll to achieve cooling and shaping, obtaining a cast sheet;

[0088] Step 4, send the cast sheet into the stretching zone for preheating, biaxial stretching and heat setting, then perform corona treatment and winding to obtain a capacitor base film; then perform room - temperature aging treatment on the capacitor base film for 72 h, and finally perform unwinding, slitting and winding to obtain a high - temperature resistant polypropylene capacitor film;

[0089] During biaxial stretching, the preheating temperature of the first stage is 135 °C, the second stage is 140 °C, and the third stage is 145 °C;

[0090] The stretching temperature of the first stage is 155 °C, the second stage is 160 °C, the third stage is 160 °C, and the fourth stage is 164 °C;

[0091] The heat - setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C;

[0092] The longitudinal stretching ratio of the film is 4.5 times, the transverse stretching ratio is 6.5 times, and the production line speed is 200 m / min.

[0093] Example 3: A high-temperature resistant polypropylene capacitor film, comprising the following raw materials in parts by weight:

[0094] 96 parts of polypropylene resin, 2 parts of a modified balancing agent doped with fillers, 1.25 parts of a boron nitride-glass fiber synergistic agent, 0.23 parts of a nucleating agent, 0.3 parts of an antioxidant, and 0.25 parts of a silane coupling agent.

[0095] The antioxidant in this example is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index of the linear polypropylene is ≥97%, the melt flow rate is 4 g / 10 min, and the ash content is ≤25 ppm; the nucleating agent is a sorbitol-based α nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0096] The preparation method of the modified balancing agent doped with fillers in this example is as follows:

[0097] S01: Place alumina in a proton irradiation chamber and irradiate for 25 min at an irradiation power of 375 W. After irradiation, obtain irradiated alumina;

[0098] Mix the irradiated alumina, a 3% lanthanum nitrate solution by mass fraction, and silane coupling agent KH550 uniformly in a weight ratio of 4:6:1 to obtain an alumina modifier;

[0099] S02: Add the alumina modifier to a sodium dodecylbenzenesulfonate solution in a weight ratio of 2:5, and then add 12.5% of the total weight of the alumina modifier of modified carboxymethyl cellulose. Perform primary ball milling at a ball milling speed of 1000 r / min for 1 h. After ball milling, perform suction filtration and drying to obtain a filler dopant;

[0100] S03: Add 2.5 parts of a hydrochloric acid dopamine solution to 5.5 parts of a 4% chitosan solution by mass fraction, and then add 2 parts of hollow glass microspheres, and stir well to obtain a balancing liquid;

[0101] S04: Perform secondary ball milling on the filler dopant and the balancing liquid in a weight ratio of 5:3 at a ball milling speed of 1500 r / min for 2 h. After ball milling, perform suction filtration and drying to obtain a modified balancing agent doped with fillers.

[0102] The mass fraction of the sodium dodecylbenzenesulfonate solution in this example is 3.5%; the mass fraction of the hydrochloric acid dopamine solution is 5%.

[0103] The preparation method of the modified carboxymethyl cellulose in this example is as follows:

[0104] Add 4 parts of carboxymethyl cellulose and 2 parts of nano-silica sol by weight to 6.5 parts of sodium alginate solution, then add 3.5 parts of silicon carbide and 3.5 parts of talcum powder and mix well. Then, perform suction filtration and drying to obtain modified carboxymethyl cellulose.

[0105] The mass fraction of the sodium alginate solution in this example is 3.5%.

[0106] The preparation method of the boron nitride - glass fiber synergistic agent in this example is as follows:

[0107] S11: Mix boron nitride thoroughly in a sufficient amount of sulfuric acid solution with a mass fraction of 6.5%, then wash with water and dry to obtain dried boron nitride; preheat the dried boron nitride at 57.5 °C for 1 h to obtain preheated boron nitride;

[0108] S12: Add 4 parts of glass fiber and 2.5 parts of urea solution by weight to 6.5 parts of barium titanate solution and stir well to obtain a synergistic treatment solution;

[0109] Mix barium titanate, sodium silicate solution and titanium oxide evenly according to the weight ratio of 3.5:6.5:2 to prepare barium titanate solution;

[0110] S13: Ultrasonically treat the preheated boron nitride and the synergistic treatment solution according to the weight ratio of 3:6, with an ultrasonic power of 425 W and ultrasonic treatment for 1 h. After the ultrasonic treatment, perform suction filtration and drying to obtain the boron nitride - glass fiber synergistic agent.

[0111] The mass fraction of the urea solution in this example is 3%; the mass fraction of the sodium silicate solution is 6%.

[0112] The preparation method of a high - temperature resistant polypropylene capacitor film in this example includes the following steps:

[0113] Step 1, prepare a high - temperature resistant polypropylene capacitor film raw material composition according to the above weight parts of raw materials for the high - temperature resistant polypropylene capacitor film;

[0114] Step 2, melt - extrude the high - temperature resistant polypropylene capacitor film raw material composition through an extruder. The average temperature of each section of the extruder is 250 °C to obtain a viscous - flow melt, and then extrude it into a T - die head. The die head temperature is 240 °C to form a sheet - like melt;

[0115] Step 3, shape the sheet - like melt under the cooling of the chill roll and air knife in a casting machine. The cooling temperature of the chill roll is 90 °C, and the gas pressure of the air knife is 130 mbar, so that the sheet - like melt adheres tightly to the surface of the chill roll to achieve cooling and shaping, and obtain a cast sheet;

[0116] Step 4: Feed the cast film into the stretching zone for preheating, biaxial stretching and heat setting, then perform corona treatment and winding to obtain the capacitor base film; then perform room temperature aging treatment on the capacitor base film for 72 hours, and finally unwind, slit and wind to obtain the high-temperature resistant polypropylene capacitor film.

[0117] During biaxial stretching, the preheating temperature for the first stage is 135 °C, the second stage is 140 °C, and the third stage is 145 °C.

[0118] The stretching temperature for the first stage is 155 °C, the second stage is 160 °C, the third stage is 160 °C, and the fourth stage is 164 °C.

[0119] The heat setting temperature for the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C.

[0120] The longitudinal stretching ratio of the film is 4.5 times, the transverse stretching ratio is 6.5 times, and the production line speed is 200 m / min.

[0121] Comparative Example 1:

[0122] It is different from Example 3 in that the modified balance adjuster without doping filler is used.

[0123] Comparative Example 2:

[0124] It is different from Example 3 in that the filler dopant is not added during the preparation of the modified balance adjuster with doping filler.

[0125] Comparative Example 3:

[0126] It is different from Example 3 in that the alumina modifier is not added to the filler dopant.

[0127] Comparative Example 4:

[0128] It is different from Example 3 in that the lanthanum nitrate solution and the silane coupling agent KH550 are not added during the preparation of the alumina modifier.

[0129] Comparative Example 5:

[0130] It is different from Example 3 in that the modified carboxymethyl cellulose is not added to the filler dopant.

[0131] Comparative Example 6:

[0132] It is different from Example 3 in that the carboxymethyl cellulose and the nano-silica sol are not added during the preparation of the modified carboxymethyl cellulose.

[0133] Comparative Example 7:

[0134] It is different from Example 3 in that the silicon carbide and the talcum powder are not added during the preparation of the modified carboxymethyl cellulose.

[0135] Comparative Example 8:

[0136] It is different from Example 3 in that the balance adjusting liquid is not added during the preparation of the modified balance adjuster with doping filler.

[0137] Comparative Example 9:

[0138] It is different from Example 3 in that hollow glass microspheres and chitosan solution are not added to the leveling liquid.

[0139] Comparative Example 10:

[0140] It is different from Example 3 in that the boron nitride - glass fiber synergistic agent is not added.

[0141] Comparative Example 11:

[0142] It is different from Example 3 in that preheated boron nitride is not added in the preparation of the boron nitride - glass fiber synergistic agent.

[0143] Comparative Example 12:

[0144] It is different from Example 3 in that the synergistic treatment liquid is not added in the preparation of the boron nitride - glass fiber synergistic agent.

[0145] Comparative Example 13:

[0146] It is different from Example 3 in that glass fiber and urea solution are not added in the preparation of the synergistic treatment liquid.

[0147] Comparative Example 14:

[0148] It is different from Example 3 in that barium titanate solution is not added in the preparation of the synergistic treatment liquid.

[0149] Comparative Example 15:

[0150] It is different from Example 3 in that titanium oxide and barium titanate are not added to the barium titanate solution.

[0151] The products of Examples 1 - 3 and Comparative Examples 1 - 15 were tested for breakdown resistance, mechanical strength and dielectric loss performance under conventional conditions, high temperature resistance and corrosion resistance conditions. The high temperature resistance and corrosion resistance conditions were to place the products at 75 °C for 12 h, and then at 5% hydrochloric acid mist conditions for 24 h. The test results are shown in Table 1.

[0152] Table 1 Test results of the product performance of Examples 1 - 3 and Comparative Examples 1 - 15:

[0153]

[0154] It can be seen from Comparative Examples 1 - 15 and Examples 1 - 3 that the product of Example 3 has excellent tensile strength, and at the same time, excellent breakdown strength and dielectric loss performance. The three can be coordinately improved. In addition, under high temperature resistance and corrosion resistance conditions, the product has excellent performance stability, and the product can achieve an integrated coordinated improvement;

[0155] It can be seen from Comparative Examples 1 to 15 and Example 3 that when a modified balancing agent without a doping filler or a boron nitride-glass fiber synergistic agent is not added to the product, the performance of the product deteriorates significantly. When the two are coordinated, the performance effect of the product is the most obvious;

[0156] When a filler dopant is not added in the preparation of the modified balancing agent with a doping filler, an alumina modifier is not added to the filler dopant, a lanthanum nitrate solution and a silane coupling agent KH550 are not added in the preparation of the alumina modifier, a modified carboxymethyl cellulose is not added to the filler dopant, carboxymethyl cellulose is not added in the preparation of the modified carboxymethyl cellulose, nano-silica sol, silicon carbide and talcum powder are not added in the preparation of the modified carboxymethyl cellulose, the performance of the product shows a deteriorating trend to varying degrees. The performance effect of the product is the most significant when the modified carboxymethyl cellulose obtained by the specific method of the present invention is combined with the alumina modifier and the modified balancing agent with a doping filler made of specific raw materials. Using other methods instead is not as obvious as the effect of the present invention;

[0157] When a balancing liquid is not added in the preparation of the modified balancing agent with a doping filler, and hollow glass microspheres and a chitosan solution are not added to the balancing liquid, the performance of the product shows a deteriorating trend;

[0158] When preheated boron nitride is not added in the preparation of the boron nitride-glass fiber synergistic agent, a synergistic treatment liquid is not added in the preparation of the boron nitride-glass fiber synergistic agent, glass fiber, urea solution are not added in the preparation of the synergistic treatment liquid, a barium titanate liquid is not added in the preparation of the synergistic treatment liquid, and titanium oxide and barium titanate are not added to the barium titanate liquid, the performance of the product shows a deteriorating trend to varying degrees. The performance effect of the product is the most significant when the barium titanate liquid obtained by the specific method of the present invention is used to prepare the synergistic treatment liquid, and the boron nitride-glass fiber synergistic agent is prepared by improving the preheated boron nitride with the synergistic treatment liquid.

[0159] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

[0160] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A high-temperature resistant polypropylene capacitor film, characterized in that, It comprises the following raw materials in parts by weight: 94 - 98 parts of polypropylene resin, 1 - 3 parts of modified balance regulator doped with filler, 0.5 - 2 parts of boron nitride - glass fiber synergist, 0.05 - 0.4 parts of nucleating agent, 0.2 - 0.4 parts of antioxidant, 0.1 - 0.4 parts of silane coupling agent; The preparation method of the modified balance regulator doped with filler is as follows: S01: Place alumina in a proton irradiation chamber and irradiate for 25 min with an irradiation power of 350 - 400 W. After irradiation, obtain irradiated alumina; Mix the irradiated alumina, lanthanum nitrate solution with a mass fraction of 3%, and silane coupling agent KH550 evenly according to the weight ratio of (3 - 5):(5 - 7):1 to obtain an alumina modifier; S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution according to the weight ratio of 2:

5. Then add 10 - 15% of the total weight of the alumina modifier of modified carboxymethyl cellulose, and perform primary ball - milling treatment at a ball - milling speed of 1000 r / min for 1 h. After ball - milling, perform suction filtration and drying to obtain a filler dopant; The preparation method of the modified carboxymethyl cellulose is as follows: Add 3 - 5 parts of carboxymethyl cellulose and 1 - 3 parts of nano - silica sol by weight to 5 - 8 parts of sodium alginate solution. Then add 2 - 5 parts of silicon carbide and 3 - 4 parts of talc powder and mix thoroughly. Then perform suction filtration and drying to obtain modified carboxymethyl cellulose; S03: Add 2 - 3 parts of hydrochloric acid dopamine solution to 4 - 7 parts of chitosan solution with a mass fraction of 4% by weight. Then add 1 - 3 parts of hollow glass microspheres and stir thoroughly to obtain a balance - adjusting liquid; S04: Perform secondary ball - milling treatment on the filler dopant and the balance - adjusting liquid according to the weight ratio of 5:3 at a ball - milling speed of 1500 r / min for 2 h. After ball - milling, perform suction filtration and drying to obtain a modified balance regulator doped with filler; The preparation method of the boron nitride - glass fiber synergist is as follows: S11: Mix boron nitride thoroughly in a sufficient amount of sulfuric acid solution with a mass fraction of 5 - 8%. Then wash with water and dry to obtain dried boron nitride. Preheat the dried boron nitride at 55 - 60 °C for 1 h to obtain pre - heated boron nitride; S12: Add 3 - 5 parts of glass fiber and 2 - 3 parts of urea solution by weight to 5 - 8 parts of barium titanate solution and stir thoroughly to obtain a synergistic treatment liquid; Mix barium titanate, sodium silicate solution and titanium oxide evenly according to the weight ratio of (3 - 4):(5 - 8):2 to prepare barium titanate solution; S13: Perform ultrasonic treatment on the pre - heated boron nitride and the synergistic treatment liquid according to the weight ratio of 3:(5 - 7) with an ultrasonic power of 400 - 450 W for 1 h. After ultrasonic treatment, perform suction filtration and drying to obtain a boron nitride - glass fiber synergist.

2. The high-temperature resistant polypropylene capacitor film according to claim 1, wherein The polypropylene resin is linear polypropylene, the isotactic index of the linear polypropylene ≥ 97%, the melt flow rate is 3 - 5 g / 10 min, and the ash content ≤ 25 ppm.

3. A high-temperature resistant polypropylene capacitor film according to claim 1, characterized in that, The antioxidant is antioxidant 1010; the nucleating agent is a sorbitol - type α - nucleating agent; the silane coupling agent is silane coupling agent KH560.

4. A high-temperature resistant polypropylene capacitor film according to claim 1, characterized in that The mass fraction of the sodium dodecylbenzenesulfonate solution is 2 - 5%; the mass fraction of the hydrochloric acid dopamine solution is 4 - 6%.

5. A high-temperature resistant polypropylene capacitor film according to claim 1, characterized in that, The mass fraction of the sodium alginate solution is 2-5%.

6. The high-temperature resistant polypropylene capacitor film according to claim 1, wherein The mass fraction of the urea solution is 2-4%; the mass fraction of the sodium silicate solution is 5-8%.

7. A preparation method of a high-temperature resistant polypropylene capacitor film for preparing a high-temperature resistant polypropylene capacitor film according to any one of claims 1 to 6, characterized in that, It includes the following steps: Step 1, prepare the raw material composition of the high-temperature resistant polypropylene capacitor film according to the above weight parts of raw materials of the high-temperature resistant polypropylene capacitor film; Step 2, melt and extrude the raw material composition of the high-temperature resistant polypropylene capacitor film through an extruder. The average temperature of each section of the extruder is 245-255°C to obtain a viscous molten state melt, and then extrude it into a T-shaped die head with a die head temperature of 240°C to form a sheet-shaped melt; Step 3, shape the sheet-shaped melt under the cooling of the chill roll and air knife in the casting machine. The cooling temperature of the chill roll is 85-95°C, and the gas pressure of the air knife is 120-140 mbar, so that the sheet-shaped melt tightly adheres to the surface of the chill roll to achieve cooling and shaping, and obtain a cast sheet; Step 4, send the cast sheet into the stretching zone for preheating, biaxial stretching and heat setting, then perform corona treatment and winding to obtain a capacitor base film; then perform room temperature aging treatment on the capacitor base film for 72 hours, and finally perform unwinding, slitting and winding to obtain a high-temperature resistant polypropylene capacitor film; During biaxial stretching, the longitudinal stretching ratio of the cast sheet is 4.5 times, the transverse stretching ratio is 6.5 times, and the production line speed is 200 m / min; The preheating temperature of the first stage is 135°C, the second stage is 140°C, and the third stage is 145°C; The biaxial stretching temperature of the first stage is 155°C, the second stage is 160°C, the third stage is 160°C, and the fourth stage is 164°C; The heat setting temperature of the first stage is 165°C, the second stage is 166°C, and the third stage is 163°C.

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