High-temperature-resistant polypropylene capacitor film and preparation method thereof

Abstract

The invention relates to the technical field of capacitor films, in particular to a high-temperature-resistant polypropylene capacitor film and a preparation method thereof.The high-temperature-resistant polypropylene capacitor film is prepared from, by weight, 94-98 parts of polypropylene resin, 1-3 parts of filler-doped modified balance adjusting agent, 0.5-2 parts of boron nitride-glass fiber combined agent, 0.05-0.4 part of nucleating agent, 0.2-0.4 part of antioxidant and 0.1-0.4 part of silane coupling agent; the high-temperature-resistant polypropylene capacitor film is obtained through the processes of melting extrusion molding, cooling shaping, preheating, two-way stretching, heat shaping, rolling and the like of the raw material composition. The polypropylene resin, the nucleating agent, the antioxidant and the silane coupling agent are blended, the filler-doped modified balance adjusting agent and the boron nitride-glass fiber coupling agent are added, and the raw materials are blended and coordinated, so that high feasibility of a two-way stretching process is guaranteed, breakdown resistance, mechanical strength and dielectric loss performance of the product are optimized, and the product has good mechanical properties. And meanwhile, the high-temperature-resistant and corrosion-resistant stability effects 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. Seriously, in some applications, it even exceeds 120°C, such as capacitors used in 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 films. 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 proposed in the above background art.

[0004] The present invention solves the technical problems by adopting the following technical solutions: The present invention provides a high-temperature resistant polypropylene capacitor film, which 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.

[0005] Preferably, the antioxidant is antioxidant 1010; the polypropylene resin is linear polypropylene, with an isotactic index ≥ 97%, a melt flow rate of 3 - 5 g / 10 min, and an ash content ≤ 25 ppm; the nucleating agent is a sorbitol-based α nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0006] Preferably, the preparation method of the modified balance agent doped with fillers is as follows: 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; Mix the irradiated alumina, a lanthanum nitrate solution with a mass fraction of 3%, and the silane coupling agent KH550 evenly in a weight ratio of (3 - 5):(5 - 7):1 to obtain an alumina modifier; S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution in a weight ratio of 2:5. Subsequently, add modified carboxymethyl cellulose accounting for 10 - 15% of the total weight of the alumina modifier, and conduct 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; S03: Add 2 - 3 parts of a hydrochloric acid dopamine solution to 4 - 7 parts of a 4% chitosan solution by weight. Subsequently, add 1 - 3 parts of hollow glass microspheres and stir well to obtain a balancing solution; S04: Conduct secondary ball milling on the filler dopant and the balancing solution in 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 balancing agent doped with fillers.

[0007] Preferably, the mass fraction of the sodium dodecylbenzenesulfonate solution is 2 - 5%; the mass fraction of the hydrochloric acid dopamine solution is 4 - 6%.

[0008] Preferably, 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 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.

[0009] Preferably, the mass fraction of the sodium alginate solution is 2 - 5%.

[0010] Preferably, the preparation method of the boron nitride - glass fiber synergistic agent is as follows: S11: Mix boron nitride thoroughly in a sufficient amount of a sulfuric acid solution with a mass fraction of 5 - 8%. Then, wash with water and dry to obtain dried boron nitride; pre - heat 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 a urea solution by weight to 5 - 8 parts of a barium titanate solution and stir well to obtain a synergistic treatment solution; Mix barium titanate, a sodium silicate solution, and titanium oxide evenly in a weight ratio of (3 - 4):(5 - 8):2 to prepare a barium titanate solution; S13: Subject the pre - heated boron nitride and the synergistic treatment solution to ultrasonic treatment in a weight ratio of 3:(5 - 7) with an ultrasonic power of 400 - 450 W for 1 h. After the ultrasonic treatment is completed, perform suction filtration and drying to obtain a boron nitride - glass fiber synergistic agent.

[0011] Preferably, the mass fraction of the urea solution is 2-4%; the mass fraction of the sodium silicate solution is 5-8%.

[0012] The present invention also provides a method for preparing a high-temperature resistant polypropylene capacitor film, comprising the following steps: Step 1, prepare a raw material composition for the high-temperature resistant polypropylene capacitor film according to the above-mentioned weight parts of raw materials for the high-temperature resistant polypropylene capacitor film; Step 2, melt and extrude the raw material composition for the high-temperature resistant polypropylene capacitor film through an extruder, with the average temperature of each section of the extruder being 245-255°C, to obtain a viscous flow state melt, and then extrude it into a T-shaped die head with a die head temperature of 240°C to form a sheet-like melt; Step 3, shape the sheet-like melt under the cooling of a chill roll and an air knife in a 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, and a cast sheet is obtained; 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 a 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; In the 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; 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; The heat setting temperature of the first stage is 165°C, the second stage is 166°C, and the third stage is 163°C; 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.

[0013] 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 balancing agent doped with fillers and a boron nitride-glass fiber synergistic agent. Through the coordination of raw materials, the breakdown resistance, mechanical strength and dielectric loss performance of the product are optimized. At the same time, the product has remarkable high-temperature resistance and corrosion resistance stability effects; The modified balancing agent of the doped filler is made of alumina irradiated with protons to stimulate its active efficiency, and is prepared by mixing 3% by mass of lanthanum nitrate solution and silane coupling agent KH550 to prepare an alumina modifier, and the alumina modifier is used to adjust sodium dodecylbenzene sulfonate solution and modified carboxymethyl cellulose to prepare a filler dopant, and the ball milling of the balancing liquid is improved and optimized, and the chitosan solution, dopamine hydrochloride solution and hollow glass microspheres in the balancing liquid are blended and improved, and the modified carboxymethyl cellulose is made of carboxymethyl cellulose, nano-silica sol and sodium alginate solution, and is combined with silicon carbide and talcum powder. Through the blending improvement between the raw materials, carboxymethyl cellulose is combined with silicon carbide and talcum powder to fill the system, so that the prepared filler dopant further strengthens the system performance in the system, so that the performance of the product is further improved; The boron nitride-glass fiber synergist adopts boron nitride, which is fully mixed in a sulfuric acid solution and then preheated at 55-60°C for 1h to optimize the activity of boron nitride. The glass fiber in the synergistic treatment solution is combined with urea solution and barium titanate solution. At the same time, the barium titanate, sodium silicate solution and titanium oxide in the barium titanate solution are blended and optimized. Barium titanate is used as a matrix, combined with titanium oxide and other raw materials, and blended with glass fiber. The improved boron nitride-glass fiber synergist can better coordinate with the modified balancing agent of the doped filler, so that the performance of the product is further improved. DETAILED DESCRIPTION

[0014] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with specific embodiments. 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.

[0015] Embodiment 1: A high temperature resistant polypropylene capacitor film, comprising the following raw materials in parts by weight: 94 parts of polypropylene resin, 1 part of modified balancing agent doped with fillers, 0.5 parts of boron nitride-glass fiber synergist, 0.05 parts of nucleating agent, 0.2 parts of antioxidant, and 0.1 parts of silane coupling agent.

[0016] The antioxidant in this embodiment is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index of linear polypropylene is ≥97%, the melt flow rate is 3g / 10min, and the ash content is ≤25ppm; the nucleating agent is a sorbitol α nucleating agent; and the silane coupling agent is silane coupling agent KH560.

[0017] The preparation method of the modified balancing agent doped with fillers in this embodiment is as follows: S01: placing the aluminum oxide in a proton irradiation box and irradiating it for 25 minutes at an irradiation power of 350 W, and then completing the irradiation to obtain irradiated aluminum oxide; The irradiated alumina, 3% by mass lanthanum nitrate solution and silane coupling agent KH550 are uniformly mixed in a weight ratio of 3:5:1 to obtain an alumina modifier; S02: adding an alumina modifier to a sodium dodecylbenzene sulfonate solution at a weight ratio of 2:5, and then adding modified carboxymethyl cellulose in an amount of 10% of the total weight of the alumina modifier, and subjecting the mixture to primary ball milling at a ball milling speed of 1000 r / min for 1 h. After the ball milling is completed, the mixture is filtered and dried to obtain a filler dopant; S03: Add 2 parts of dopamine hydrochloride solution to 4 parts of 4% chitosan solution by weight, and then add 1 part of hollow glass microspheres, stir well, and obtain a balanced solution; S04: The filler dopant and the balancing liquid are subjected to secondary ball milling at a weight ratio of 5:3, with a ball milling speed of 1500 r / min and ball milling for 2 hours. After the ball milling is completed, the mixture is filtered and dried to obtain a modified balancing agent doped with a filler.

[0018] The mass fraction of the sodium dodecylbenzenesulfonate solution in this embodiment is 2%; the mass fraction of the dopamine hydrochloride solution is 4%.

[0019] The preparation method of the modified carboxymethyl cellulose of this embodiment is: 3 parts of carboxymethyl cellulose and 1 part of nano-silica sol are added to 5 parts of sodium alginate solution by weight, and then 2 parts of silicon carbide and 3 parts of talc are added and blended thoroughly, and then filtered and dried to obtain modified carboxymethyl cellulose.

[0020] The mass fraction of the sodium alginate solution in this embodiment is 2%.

[0021] The preparation method of the boron nitride-glass fiber synergist of this embodiment is as follows: S11: Boron nitride is mixed thoroughly in a sufficient amount of a 5% by mass sulfuric acid solution, and then washed with water and dried to obtain dry boron nitride; the dry boron nitride is preheated at 55° C. for 1 hour to obtain preheated boron nitride; S12: adding 3 parts of glass fiber and 2 parts of urea solution to 5 parts of barium titanate solution by weight and stirring thoroughly to obtain a combined treatment solution; The barium titanate, sodium silicate solution and titanium oxide are uniformly mixed in a weight ratio of 3:5:2 to prepare a barium titanate solution; S13: ultrasonically treat the preheated boron nitride and the synergistic treatment liquid in a weight ratio of 3:5, with an ultrasonic power of 400 W for 1 hour. After the ultrasonic treatment is completed, the mixture is filtered and dried to obtain a boron nitride-glass fiber synergist.

[0022] The mass fraction of the urea solution in this embodiment is 2%; the mass fraction of the sodium silicate solution is 5%.

[0023] A preparation method of a high-temperature resistant polypropylene capacitor film according to this embodiment includes the following steps: 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; Step 2, melt and 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-shaped die head. The temperature of the die head is 240 °C to form a sheet-like melt; Step 3, shape the sheet-like melt under the cooling of a chill roll and an 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 tightly adheres to the surface of the chill roll to achieve cooling and shaping, and a cast sheet is obtained; 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; 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; 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; The heat setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C; 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.

[0024] Example 2: A high-temperature resistant polypropylene capacitor film includes the following weight parts of raw materials: 98 parts of polypropylene resin, 3 parts of a modified balance agent doped with fillers, 2 parts of a boron nitride-glass fiber synergistic agent, 0.4 part of a nucleating agent, 0.4 part of an antioxidant, and 0.4 part of a silane coupling agent.

[0025] 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.

[0026] The preparation method of the modified balance agent doped with fillers in this embodiment is: S01: Place alumina in a proton irradiation chamber for irradiation for 25 min, the irradiation power is 400 W, and after irradiation, the irradiated alumina is obtained; Mix the irradiated alumina, a 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; S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution in a weight ratio of 2:5. Subsequently, add the modified carboxymethyl cellulose which is 15% of the total weight of the alumina modifier. Perform primary ball milling treatment 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 the filler dopant; S03: Add 3 parts of hydrochloric acid dopamine solution to 7 parts of chitosan solution with a mass fraction of 4% by weight. Subsequently, add 3 parts of hollow glass microspheres and stir thoroughly to obtain the balance adjusting liquid; S04: Perform secondary ball milling treatment on the filler dopant and the balance adjusting liquid in 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 the modified balance adjusting agent doped with fillers.

[0027] In this example, the mass fraction of the sodium dodecylbenzenesulfonate solution is 5%; the mass fraction of the hydrochloric acid dopamine solution is 6%.

[0028] The preparation method of the modified carboxymethyl cellulose in this example is as follows: Add 5 parts of carboxymethyl cellulose and 3 parts of nano-silica sol to 8 parts of sodium alginate solution by weight. Subsequently, add 5 parts of silicon carbide and 4 parts of talc powder and mix thoroughly. Then perform suction filtration and drying to obtain the modified carboxymethyl cellulose.

[0029] In this example, the mass fraction of the sodium alginate solution is 5%.

[0030] The preparation method of the boron nitride - glass fiber synergistic agent in this example is as follows: S11: Mix boron nitride thoroughly in a sufficient amount of sulfuric acid solution with a mass fraction of 8%. 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; S12: Add 5 parts of glass fiber and 3 parts of urea solution to 8 parts of barium titanate solution by weight and stir thoroughly to obtain the synergistic treatment liquid; Prepare the barium titanate solution by uniformly blending barium titanate, sodium silicate solution, and titanium oxide in a weight ratio of 4:8:2; S13: Perform ultrasonic treatment on the preheated boron nitride and the synergistic treatment liquid in a weight ratio of 3:7 at an ultrasonic power of 450 W for 1 h. After the ultrasonic treatment is completed, perform suction filtration and drying to obtain the boron nitride - glass fiber synergistic agent.

[0031] In this example, the mass fraction of the urea solution is 4%; the mass fraction of the sodium silicate solution is 8%.

[0032] The preparation method of a high-temperature resistant polypropylene capacitor film in this example includes the following steps: Step 1, prepare the raw material composition of the high-temperature resistant polypropylene capacitor film according to the above-mentioned weight parts of raw materials for the high-temperature resistant polypropylene capacitor film; Step 2: Melt and 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-shaped die head with a die head temperature of 240 °C to form a sheet-like melt. 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, and obtain a cast sheet. Step 4: Send the cast sheet into the stretching area 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 unwind, slit and wind to obtain a high-temperature resistant polypropylene capacitor film. 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. 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. The heat setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C. 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] Example 3: A high-temperature resistant polypropylene capacitor film, comprising the following raw materials in parts by weight: 96 parts of polypropylene resin, 2 parts of modified balance agent doped with fillers, 1.25 parts of boron nitride-glass fiber synergist, 0.23 part of nucleating agent, 0.3 part of antioxidant, 0.25 part of silane coupling agent.

[0034] The antioxidant in this example is antioxidant 1010; the polypropylene resin is linear polypropylene, the isotactic index of the linear polypropylene ≥ 97%, the melt flow rate is 4 g / 10 min, and the ash content ≤ 25 ppm; the nucleating agent is sorbitol-based α nucleating agent; the silane coupling agent is silane coupling agent KH560.

[0035] The preparation method of the modified balance agent doped with fillers in this example is as follows: S01: Place alumina in a proton irradiation chamber for irradiation for 25 min with an irradiation power of 375 W. After irradiation, obtain irradiated alumina. Mix the irradiated alumina, 3% lanthanum nitrate solution by mass fraction and silane coupling agent KH550 evenly according to a weight ratio of 4:6:1 to obtain an alumina modifier. S02: Add the alumina modifier to the sodium dodecylbenzenesulfonate solution according to a weight ratio of 2:5. Subsequently, add the modified carboxymethyl cellulose which is 12.5% of the total weight of the alumina modifier, and perform primary ball milling. The ball milling speed is 1000 r / min, and the ball milling time is 1 h. After the ball milling is completed, perform suction filtration and drying to obtain the filler dopant; S03: Add 2.5 parts of hydrochloric acid dopamine solution to 5.5 parts of a 4% chitosan solution by weight. Subsequently, add 2 parts of hollow glass microspheres and stir well to obtain the balance adjusting liquid; S04: Perform secondary ball milling on the filler dopant and the balance adjusting liquid according to a weight ratio of 5:3. The ball milling speed is 1500 r / min, and the ball milling time is 2 h. After the ball milling is completed, perform suction filtration and drying to obtain the modified balance adjusting agent doped with fillers.

[0036] In this example, the mass fraction of the sodium dodecylbenzenesulfonate solution is 3.5%; the mass fraction of the hydrochloric acid dopamine solution is 5%.

[0037] The preparation method of the modified carboxymethyl cellulose in this example is as follows: Add 4 parts of carboxymethyl cellulose and 2 parts of nano-silica sol to 6.5 parts of sodium alginate solution by weight. Subsequently, add 3.5 parts of silicon carbide and 3.5 parts of talc powder and mix well. Then perform suction filtration and drying to obtain the modified carboxymethyl cellulose.

[0038] In this example, the mass fraction of the sodium alginate solution is 3.5%.

[0039] The preparation method of the boron nitride - glass fiber synergistic agent in this example is as follows: S11: Mix boron nitride thoroughly in a sufficient amount of 6.5% sulfuric acid solution by mass fraction, 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; S12: Add 4 parts of glass fiber and 2.5 parts of urea solution to 6.5 parts of barium titanate solution by weight and stir well to obtain the synergistic treatment liquid; Mix barium titanate, sodium silicate solution and titanium oxide evenly according to a weight ratio of 3.5:6.5:2 to prepare the barium titanate solution; S13: Perform ultrasonic treatment on the preheated boron nitride and the synergistic treatment liquid according to a weight ratio of 3:6. The ultrasonic power is 425 W, and the ultrasonic treatment time is 1 h. After the ultrasonic treatment is completed, perform suction filtration and drying to obtain the boron nitride - glass fiber synergistic agent.

[0040] In this example, the mass fraction of the urea solution is 3%; the mass fraction of the sodium silicate solution is 6%.

[0041] The preparation method of a high-temperature resistant polypropylene capacitor film in this example includes the following steps: Step 1: Prepare a raw material composition for a high-temperature resistant polypropylene capacitor film according to the above weight parts of raw materials for the high-temperature resistant polypropylene capacitor film; Step 2: Melt and 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 250 °C to obtain a viscous flow state melt, and then extrude it into a T-shaped die head with a die head temperature of 240 °C to form a sheet-like melt; 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 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; 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 unwind, slit and wind to obtain a high-temperature resistant polypropylene capacitor film; 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; 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; The heat setting temperature of the first stage is 165 °C, the second stage is 166 °C, and the third stage is 163 °C; 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.

[0042] Comparative Example 1: The difference from Example 3 is that the modified balance agent without doping filler is not added.

[0043] Comparative Example 2: The difference from Example 3 is that the filler dopant is not added during the preparation of the modified balance agent with doping filler.

[0044] Comparative Example 3: The difference from Example 3 is that the alumina modifier is not added to the filler dopant.

[0045] Comparative Example 4: The difference from Example 3 is that the lanthanum nitrate solution and silane coupling agent KH550 are not added during the preparation of the alumina modifier.

[0046] Comparative Example 5: The difference from Example 3 is that the modified carboxymethyl cellulose is not added to the filler dopant.

[0047] Comparative Example 6: The difference from Example 3 is that carboxymethyl cellulose and nano-silica sol are not added during the preparation of the modified carboxymethyl cellulose.

[0048] Comparative Example 7: Different from Example 3, silicon carbide and talcum powder were not added in the preparation of modified carboxymethyl cellulose.

[0049] Comparative Example 8: Different from Example 3, the balance adjusting liquid was not added in the preparation of the modified balance adjusting agent doped with fillers.

[0050] Comparative Example 9: Different from Example 3, hollow glass microspheres and chitosan solution were not added to the balance adjusting liquid.

[0051] Comparative Example 10: Different from Example 3, the boron nitride - glass fiber synergistic agent was not added.

[0052] Comparative Example 11: Different from Example 3, preheated boron nitride was not added in the preparation of the boron nitride - glass fiber synergistic agent.

[0053] Comparative Example 12: Different from Example 3, the synergistic treatment liquid was not added in the preparation of the boron nitride - glass fiber synergistic agent.

[0054] Comparative Example 13: Different from Example 3, glass fiber and urea solution were not added in the preparation of the synergistic treatment liquid.

[0055] Comparative Example 14: Different from Example 3, barium titanate solution was not added in the preparation of the synergistic treatment liquid.

[0056] Comparative Example 15: Different from Example 3, titanium oxide and barium titanate were not added to the barium titanate solution.

[0057] The products of Examples 1 - 3 and Comparative Examples 1 - 15 were tested for breakdown resistance, mechanical strength, and dielectric loss performance under normal conditions, high - temperature resistance, and corrosion resistance conditions. The high - temperature 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.

[0058] Table 1 Test results of the product performance of Examples 1 - 3 and Comparative Examples 1 - 15:

[0059] 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 and corrosion - resistant conditions, the product has excellent performance stability, and the product can achieve an integrated coordinated improvement; It can be seen from Comparative Examples 1 to 15 and Example 3 that when a modified balance agent without doped fillers 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 and combined, the performance effect of the product is the most obvious; When the filler dopant is not added in the preparation of the modified balance agent with doped fillers, the alumina modifier is not added in the filler dopant, the lanthanum nitrate solution and the silane coupling agent KH550 are not added in the preparation of the alumina modifier, the modified carboxymethyl cellulose is not added in the filler dopant, the carboxymethyl cellulose is not added in the preparation of the modified carboxymethyl cellulose, the nano-silica sol is not added, the 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 balance agent with doped fillers made of specific raw materials. Using other methods instead is not as obvious as the effect of the present invention; When the balance liquid is not added in the preparation of the modified balance agent with doped fillers, and the hollow glass microspheres and the chitosan solution are not added in the balance liquid, the performance of the product shows a deteriorating trend; When the preheated boron nitride is not added in the preparation of the boron nitride-glass fiber synergistic agent, the synergistic treatment liquid is not added in the preparation of the boron nitride-glass fiber synergistic agent, the glass fiber, the urea solution are not added in the preparation of the synergistic treatment liquid, the barium titanate liquid is not added in the preparation of the synergistic treatment liquid, and the titanium oxide and barium titanate are not added in 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.

[0060] 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 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 included in the present invention.

[0061] 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 includes the following raw materials in parts by weight: 94-98 parts of polypropylene resin, 1-3 parts of modified balancing agent doped with fillers, 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, and 0.1-0.4 parts of silane coupling agent; The preparation method of the modified balancing agent doped with fillers is as follows: S01: placing the aluminum oxide in a proton irradiation box for 25 minutes, with an irradiation power of 350-400W, and obtaining irradiated aluminum oxide after the irradiation is completed; The irradiated alumina, 3% by mass lanthanum nitrate solution and silane coupling agent KH550 are uniformly mixed in a weight ratio of (3-5):(5-7):1 to obtain an alumina modifier; S02: adding an alumina modifier to a sodium dodecylbenzene sulfonate solution at a weight ratio of 2:5, and then adding 10-15% of the total weight of the alumina modifier to modified carboxymethyl cellulose, and subjecting the mixture to primary ball milling at a ball milling speed of 1000 r / min for 1 h. After the ball milling is completed, the mixture is filtered and dried to obtain a filler dopant; S03: Add 2 to 3 parts of dopamine hydrochloride solution to 4 to 7 parts of 4% chitosan solution by weight, and then add 1 to 3 parts of hollow glass microspheres, stir well, and obtain a balanced solution; S04: The filler dopant and the balancing liquid are subjected to secondary ball milling at a weight ratio of 5:3, with a ball milling speed of 1500 r / min and ball milling for 2 hours. After the ball milling is completed, the mixture is filtered and dried to obtain a modified balancing agent doped with a filler.

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

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

4. The 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 dopamine hydrochloride solution is 4-6%.

5. The high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The preparation method of the modified carboxymethyl cellulose is: 3-5 parts of carboxymethyl cellulose and 1-3 parts of nano-silica sol are added to 5-8 parts of sodium alginate solution by weight, and then 2-5 parts of silicon carbide and 3-4 parts of talc are added and mixed thoroughly, and then filtered and dried to obtain modified carboxymethyl cellulose.

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

7. The high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The preparation method of the boron nitride-glass fiber synergist is as follows: S11: mixing the boron nitride in a sufficient amount of a sulfuric acid solution having a mass fraction of 5-8%, and then washing and drying to obtain dry boron nitride; preheating the dry boron nitride at 55-60° C. for 1 h to obtain preheated boron nitride; S12: adding 3 to 5 parts of glass fiber and 2 to 3 parts of urea solution to 5 to 8 parts of barium titanate solution by weight and stirring thoroughly to obtain a combined effect treatment solution; The barium titanate, sodium silicate solution and titanium oxide are uniformly mixed in a weight ratio of (3-4):(5-8):2 to prepare a barium titanate solution; S13: ultrasonically treat the preheated boron nitride and the synergistic treatment liquid in a weight ratio of 3:(5-7), with an ultrasonic power of 400-450W for 1 hour. After the ultrasonic treatment is completed, the boron nitride-glass fiber synergist is obtained by suction filtration and drying.

8. The high temperature resistant polypropylene capacitor film according to claim 7, characterized in that: The mass fraction of the urea solution is 2-4%; the mass fraction of the sodium silicate solution is 5-8%.

9. A method for preparing a high temperature resistant polypropylene capacitor film, used for preparing a high temperature resistant polypropylene capacitor film as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1, preparing a high temperature resistant polypropylene capacitor film raw material composition according to the above-mentioned raw materials in parts by weight of the high temperature resistant polypropylene capacitor film; Step 2: melt and extrude the high temperature resistant polypropylene capacitor film raw material composition through an extruder, with the average temperature of each section of the extruder being 245-255° C., to obtain a viscous melt, and then squeeze it into a T-die with a die temperature of 240° C. to form a sheet melt; Step 3, shaping the molten sheet under the cooling of the chill roller and the air knife in the sheet casting machine, the cooling temperature of the chill roller is 85-95°C, the gas pressure of the air knife is 120-140 mbar, so that the molten sheet is tightly attached to the surface of the chill roller to achieve cooling and shaping, and obtain a cast sheet; Step 4, sending the cast sheet into the stretching zone for preheating, biaxial stretching and heat setting, and then performing corona treatment and winding to obtain a capacitor base film; then performing room temperature aging treatment on the capacitor base film for 72 hours, and finally performing unwinding, slitting and winding to obtain a high temperature resistant polypropylene capacitor film; Preheating in biaxial stretching is 135℃ for the first stage, 140℃ for the second stage, and 145℃ for the third stage; Stretching stage 1: 155℃, stage 2: 160℃, stage 3: 160℃, stage 4: 164℃; Heat setting stage 1: 165℃, stage 2: 166℃, stage 3: 163℃; 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 200m / min.

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