A High-Voltage-Resistant Film for Wind Power Capacitors and Its Preparation Method

Abstract

The present invention discloses a high-voltage-resistant film for wind power capacitors and a preparation method thereof, belonging to the technical field of capacitor films, and comprising the following raw materials in parts by weight: 50-80 parts of polypropylene resin, 3-5 parts of modified filler, 0.2-0.5 part of antioxidant, and 0.3-0.5 part of nucleating agent; mixing the raw materials evenly, melting at 170-190 °C, filtering and exhausting 10-12 times, hot pressing at 20 MPa to form a thick sheet, stretching to make a film, and obtaining the high-voltage-resistant film for wind power capacitors. When the modified filler is added to polypropylene, on the one hand, it can improve the high-temperature resistance of the polypropylene material, and on the other hand, it can improve the voltage resistance of the matrix. Moreover, by grafting a polymer on the surface of talcum powder, the compatibility with the matrix polypropylene can be improved.

Description

Technical Field

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

[0002] The existing films for metallized capacitors are widely used in multiple industries such as electronics, home appliances, communication, electric power, electrified railways, hybrid electric vehicles, wind power generation, and solar power generation. As an important energy storage device, capacitors have developed from the initial simple form to the complex devices today. Compared with batteries and electrochemical capacitors, dielectric capacitors have higher working voltages and power densities, longer lifetimes, and greater cycling stabilities. According to dielectric materials, they can be divided into: ceramic capacitors, electrolytic capacitors, paper capacitors, polymer film capacitors, etc. With the development of advanced electronic and power systems, film capacitors with high energy storage performance have become particularly important. Polymer-based materials stand out due to their flexibility, cost-effectiveness, and customizable functional characteristics and have become the main dielectrics for film capacitors. These film capacitors are gradually being widely used in fields such as smart grids and new energy vehicles due to their advantages such as high breakdown field strength, high power density, small dielectric loss, small volume, and low cost. However, due to their low dielectric constant, it is difficult to increase their capacitance and energy storage density, which hinders the further development of film capacitors.

[0003] Chinese Patent with application number 201710580920.9 discloses a preparation method of a polypropylene film for high-temperature-resistant capacitors. By putting polypropylene raw materials into an extruder for extrusion, casting, biaxial synchronous stretching, and heat setting to form a film, and then cooling, thickness measurement, edge trimming, corona treatment, winding, and secondary aging treatment, a polypropylene film for high-temperature-resistant capacitors is obtained; the above improvements to the film mainly focus on the preparation process, and the performance improvement of the prepared film is limited. Therefore, the research on new dielectric materials has become the focus of attention. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a high-voltage-resistant film for wind power capacitors and a preparation method thereof.

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

[0006] A high-voltage-resistant film for wind power capacitors, comprising the following raw materials in parts by weight: 50 - 80 parts of polypropylene resin, 3 - 5 parts of modified filler, 0.2 - 0.5 part of antioxidant, and 0.3 - 0.5 part of nucleating agent;

[0007] The modified filler is prepared through the following steps:

[0008] Step S1: Add talcum powder into an aqueous sodium hydroxide solution with a mass fraction of 20%, heat up to 80 - 90 °C, stir at high speed and react for 6 h. After the reaction, wash with deionized water to obtain modified talcum powder. Then add the obtained modified talcum powder into an aqueous ethanol solution with a volume fraction of 75%, adjust the pH of the system to 4 - 5, add KH570, heat up to 50 - 65 °C, stir evenly and react for 4 - 6 h. After the reaction, cool to room temperature to obtain modified talcum powder. Control the dosage ratio of talcum powder to aqueous sodium hydroxide solution as 5 - 10 g : 150 - 250 mL, and the dosage ratio of modified talcum powder, KH570 and aqueous ethanol solution as 5 - 10 g : 1 - 2 g : 100 mL;

[0009] In step S1, first treat the surface of talcum powder with sodium hydroxide to introduce hydroxyl groups on the surface of talcum powder. Then add silane coupling agent KH570. KH570 hydrolyzes and condenses with the hydroxyl groups on the surface of talcum powder, thereby introducing carbon - carbon double bonds on the surface of talcum powder to obtain modified talcum powder;

[0010] Step S2: Add the obtained modified talcum powder and maleimide into ethyl acetate, disperse ultrasonically and add benzoyl peroxide. Heat up to 70 - 90 °C, stir evenly and react for 1 h. After the reaction, obtain grafted talcum powder. Control the dosage ratio of modified talcum powder, maleimide and ethyl acetate as 5 - 10 g : 2 - 3 g : 100 mL;

[0011] In step S2, the carbon - carbon double bonds on the modified talcum powder polymerize with the unsaturated carbon - carbon double bonds on maleimide, thereby grafting a prepolymer containing maleimide structure onto the surface of talcum powder to obtain grafted talcum powder.

[0012] Step S3: Add 4,4'-dichlorobenzil and grafted talcum powder into N,N - dimethylformamide, stir evenly and add copper iodide and N,N - dimethyl - 1,2 - ethylenediamine. After mixing evenly, heat up to 100 °C and react for 24 h under a nitrogen atmosphere to obtain modified filler. Control the dosage ratio of grafted talcum powder, 4,4'-dichlorobenzil and N,N - dimethylformamide as 5 - 10 g : 3 - 5 g : 50 - 80 mL, the weight ratio of copper iodide to N,N - dimethyl - 1,2 - ethylenediamine as 1:1, and the sum of the weights of copper iodide and N,N - dimethyl - 1,2 - ethylenediamine is 3 - 5% of the weight of grafted talcum powder.

[0013] In step S3, cuprous iodide and N,N-dimethyl-1,2-ethylenediamine are used as a catalyst system. The chlorine on 4,4'-dichlorobenzil reacts with the imine on the grafted talc powder, and a benzil compound is grafted onto the surface of the talc powder. The talc powder can be used as an excellent heat-resistant modifier to improve the heat resistance of polypropylene. Moreover, the grafted benzil compound can act as a voltage stabilizer. When the modified filler is added to polypropylene, on the one hand, it can improve the high-temperature resistance of the polypropylene material, and on the other hand, it can improve the voltage resistance of the matrix. Additionally, by grafting a polymer onto the surface of the talc powder, the compatibility with the matrix polypropylene can be improved.

[0014] Further, the antioxidant is antioxidant 1010 or antioxidant 168.

[0015] Further, the nucleating agent is a long-chain linear saturated carboxylate nucleating agent.

[0016] A preparation method of a high-voltage-resistant film for a wind power capacitor includes the following steps:

[0017] Mix all the raw materials evenly, melt them at 170 - 190 °C, filter and degas 10 - 12 times, hot press them at 20 MPa to form a thick sheet, and then stretch it to make a film, thus obtaining the high-voltage-resistant film for a wind power capacitor.

[0018] Further, during degassing, control it to be once every 8 - 10 s.

[0019] The beneficial effects of the present invention: The present invention prepares a high-voltage-resistant film. Using polypropylene as the matrix, excellent properties are imparted to the film by adding a modified filler. During the preparation process of this modified filler, the surface of the talc powder is first treated with sodium hydroxide to introduce hydroxyl groups onto the surface of the talc powder. Then, silane coupling agent KH570 is added. KH570 hydrolyzes and condenses with the hydroxyl groups on the surface of the talc powder, thereby introducing carbon-carbon double bonds onto the surface of the talc powder to obtain modified talc powder. Subsequently, the carbon-carbon double bonds on the modified talc powder polymerize with the unsaturated carbon-carbon double bonds on maleimide, and a prepolymer containing a maleimide structure is grafted onto the surface of the talc powder to obtain grafted talc powder. Finally, under the action of cuprous iodide and N,N-dimethyl-1,2-ethylenediamine as catalysts, the chlorine on 4,4'-dichlorobenzil reacts with the imine on the grafted talc powder, and a benzil compound is grafted onto the surface of the talc powder. The talc powder can be used as an excellent heat-resistant modifier to improve the heat resistance of polypropylene. Moreover, the grafted benzil compound can act as a voltage stabilizer. When the modified filler is added to polypropylene, on the one hand, it can improve the high-temperature resistance of the polypropylene material, and on the other hand, it can improve the voltage resistance of the matrix. Additionally, by grafting a polymer onto the surface of the talc powder, the compatibility with the matrix polypropylene can be improved. Specific embodiments

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Embodiment 1: A high-voltage-resistant film for wind power capacitors, comprising the following raw materials in parts by weight: 50 parts of polypropylene resin, 3 parts of modified filler, 0.2 part of antioxidant, and 0.3 part of nucleating agent;

[0022] A preparation method of a high-voltage-resistant film for wind power capacitors, comprising the following steps:

[0023] Mix the raw materials evenly, melt them at 170 °C, filter and exhaust 10 times, hot press and form at 20 MPa to form a thick sheet, stretch it to make a film, and obtain a high-voltage-resistant film for wind power capacitors. Control the exhaust time to be once every 8 s.

[0024] The modified filler is prepared through the following steps:

[0025] Step S1: Add talcum powder into an aqueous sodium hydroxide solution with a mass fraction of 20%, heat it up to 80 °C, stir at high speed and react for 6 h. After the reaction, wash it with deionized water to obtain modified talcum powder. Then add the obtained modified talcum powder into an aqueous ethanol solution with a volume fraction of 75%, adjust the pH of the system to 4 - 5, add KH570, heat it up to 50 °C, stir evenly and react for 4 h. After the reaction, cool it to room temperature to obtain modified talcum powder. Control the dosage ratio of talcum powder to aqueous sodium hydroxide solution to be 5 g: 150 mL, and the dosage ratio of modified talcum powder, KH570 and aqueous ethanol solution to be 5 g: 1 g: 100 mL;

[0026] Step S2: Add the obtained modified talcum powder and maleimide into ethyl acetate, ultrasonically disperse and add benzoyl peroxide, heat it up to 70 °C, stir evenly and react for 1 h. After the reaction, obtain grafted talcum powder. Control the dosage ratio of modified talcum powder, maleimide and ethyl acetate to be 5 g: 2 g: 100 mL;

[0027] Step S3: Add 4,4'-dichlorobenzil and grafted talcum powder into N,N-dimethylformamide, stir evenly and add copper iodide and N,N-dimethyl-1,2-ethylenediamine. After mixing evenly, heat it up to 100 °C and react for 24 h under a nitrogen atmosphere to obtain a modified filler. Control the dosage ratio of grafted talcum powder, 4,4'-dichlorobenzil and N,N-dimethylformamide to be 5 g: 3 g: 50 mL, and the weight ratio of copper iodide to N,N-dimethyl-1,2-ethylenediamine to be 1:1. The sum of the weights of copper iodide and N,N-dimethyl-1,2-ethylenediamine is 3% of the weight of grafted talcum powder.

[0028] The antioxidant is antioxidant 1010 or antioxidant 168.

[0029] The nucleating agent is a long-chain linear saturated carboxylate nucleating agent with the model number HAV101.

[0030] Example 2: A high-voltage-resistant film for wind power capacitors, comprising the following raw materials in parts by weight: 65 parts of polypropylene resin, 4 parts of modified filler, 0.4 part of antioxidant, and 0.4 part of nucleating agent;

[0031] A preparation method of a high-voltage-resistant film for wind power capacitors, comprising the following steps:

[0032] Mix the raw materials evenly, melt them at 180°C, filter and exhaust 11 times, hot press them at 20 MPa to form a thick sheet, stretch it to make a film, and obtain the high-voltage-resistant film for wind power capacitors. Control the exhaust time to be once every 8 s.

[0033] The modified filler is prepared through the following steps:

[0034] Step S1: Add talcum powder into a 20% sodium hydroxide aqueous solution by mass fraction, heat it up to 85°C, stir at high speed and react for 6 h. After the reaction, wash it with deionized water to obtain modified talcum powder. Then add the obtained modified talcum powder into a 75% ethanol aqueous solution by volume fraction, adjust the pH of the system to 4-5, add KH570, heat it up to 60°C, stir evenly and react for 5 h. After the reaction, cool it to room temperature to obtain modified talcum powder. Control the dosage ratio of talcum powder to sodium hydroxide aqueous solution to be 8 g: 200 mL, and the dosage ratio of modified talcum powder, KH570 and ethanol aqueous solution to be 8 g: 1.5 g: 100 mL;

[0035] Step S2: Add the obtained modified talcum powder and maleimide into ethyl acetate, ultrasonically disperse them and add benzoyl peroxide, heat it up to 80°C, stir evenly and react for 1 h. After the reaction, obtain grafted talcum powder. Control the dosage ratio of modified talcum powder, maleimide and ethyl acetate to be 8 g: 2.5 g: 100 mL;

[0036] Step S3: Add 4,4'-dichlorobenzil and grafted talcum powder into N,N-dimethylformamide, stir evenly and add copper iodide and N,N-dimethyl-1,2-ethylenediamine. After mixing evenly, heat it up to 100°C and react for 24 h under a nitrogen atmosphere to obtain the modified filler. Control the dosage ratio of grafted talcum powder, 4,4'-dichlorobenzil and N,N-dimethylformamide to be 8 g: 4 g: 60 mL, and the weight ratio of copper iodide to N,N-dimethyl-1,2-ethylenediamine to be 1:1. The sum of the weights of copper iodide and N,N-dimethyl-1,2-ethylenediamine is 4% of the weight of the grafted talcum powder.

[0037] The antioxidant is antioxidant 1010 or antioxidant 168.

[0038] The nucleating agent is a long-chain linear saturated carboxylate nucleating agent with the model number HAV101.

[0039] Example 3: A high-voltage-resistant film for wind power capacitors, comprising the following raw materials in parts by weight: 80 parts of polypropylene resin, 5 parts of modified filler, 0.5 part of antioxidant, and 0.5 part of nucleating agent;

[0040] A preparation method of a high-voltage-resistant film for wind power capacitors, comprising the following steps:

[0041] Mix the raw materials evenly, melt them at 190°C, filter and exhaust 12 times, hot-press and form at 20 MPa to form a thick sheet, stretch it to make a film, and obtain the high-voltage-resistant film for wind power capacitors. Control the exhaust time to be once every 10 s.

[0042] The modified filler is prepared through the following steps:

[0043] Step S1: Add talcum powder to a 20% sodium hydroxide aqueous solution by mass fraction, heat it to 90°C, stir at high speed and react for 6 h. After the reaction, wash it with deionized water to obtain modified talcum powder. Then add the obtained modified talcum powder to a 75% ethanol aqueous solution by volume fraction, adjust the pH of the system to 5, add KH570, heat it to 65°C, stir evenly and react for 6 h. After the reaction, cool it to room temperature to obtain modified talcum powder. Control the dosage ratio of talcum powder to sodium hydroxide aqueous solution to be 10 g:250 mL, and the dosage ratio of modified talcum powder, KH570 and ethanol aqueous solution to be 10 g:2 g:100 mL;

[0044] Step S2: Add the obtained modified talcum powder and maleimide to ethyl acetate, ultrasonically disperse and add benzoyl peroxide, heat it to 90°C, stir evenly and react for 1 h. After the reaction, obtain grafted talcum powder. Control the dosage ratio of modified talcum powder, maleimide and ethyl acetate to be 10 g:3 g:100 mL;

[0045] Step S3: Add 4,4'-dichlorobenzil and grafted talcum powder to N,N-dimethylformamide, stir evenly and add copper iodide and N,N-dimethyl-1,2-ethylenediamine. After mixing evenly, heat it to 100°C and react for 24 h under a nitrogen atmosphere to obtain the modified filler. Control the dosage ratio of grafted talcum powder, 4,4'-dichlorobenzil and N,N-dimethylformamide to be 10 g:5 g:80 mL, the weight ratio of copper iodide and N,N-dimethyl-1,2-ethylenediamine to be 1:1, and the sum of the weights of copper iodide and N,N-dimethyl-1,2-ethylenediamine to be 5% of the weight of grafted talcum powder.

[0046] The antioxidant is antioxidant 1010 or antioxidant 168.

[0047] The nucleating agent is a long-chain linear saturated carboxylate nucleating agent with the model number HAV101.

[0048] Comparative Example 1: Compared with Example 1, talcum powder was used to replace the modified filler, and the rest was the same as in Example 1.

[0049] The properties of the polypropylene films prepared in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1 below:

[0050] The thermal shrinkage rate was measured after heating at 120 °C for 15 min;

[0051] Table 1

[0052]

[0053] It can be seen from Table 1 above that the polypropylene films prepared in Examples 1-3 of the present invention have excellent mechanical properties and heat resistance.

[0054] The polypropylene films prepared in Examples 1-4 and Comparative Example 1 were applied to the preparation of capacitors. All detection tests were carried out on the premise of ensuring safety, and relevant performance tests were carried out on the prepared capacitors. Among them, a programmed withstand voltage tester was used to test the breakdown strength, and a radio frequency impedance material analyzer was used to test the dielectric constant. The test results are shown in Table 2:

[0055] Table 2

[0056]

[0057] It can be seen from Table 2 above that the polypropylene film prepared by the present invention has a higher breakdown strength and is more suitable for the field of capacitors.

[0058] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of the present technology make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. A high voltage film for wind power capacitors, characterized in that: The invention comprises the following raw materials in parts by weight: 50-80 parts of polypropylene resin, 3-5 parts of modified filler, 0.2-0.5 parts of antioxidant, and 0.3-0.5 parts of nucleating agent; The modified filler is prepared by the following steps: Step S1, adding talcum powder to a 20% by mass sodium hydroxide aqueous solution, heating to 80-90° C., stirring at high speed and reacting for 6 hours, washing with deionized water after the reaction to obtain modified talcum powder, then adding the obtained modified talcum powder to a 75% by volume ethanol aqueous solution, adjusting the system pH to 4-5, adding KH570, heating to 50-65° C., stirring at a uniform speed and reacting for 4-6 hours, cooling to room temperature after the reaction to obtain modified talcum powder, controlling the dosage ratio of talcum powder to sodium hydroxide aqueous solution to be 5-10 g: 150-250 mL, and the dosage ratio of modified talcum powder, KH570 and ethanol aqueous solution to be 5-10 g: 1-2 g: 100 mL; Step S2, adding the prepared modified talc and maleimide to ethyl acetate, ultrasonically dispersing and adding dibenzoyl peroxide, heating to 70-90° C., stirring at a uniform speed and reacting for 1 hour, and obtaining grafted talc after the reaction, wherein the amount ratio of modified talc, maleimide and ethyl acetate is controlled to be 5-10 g: 2-3 g: 100 mL; Step S3, adding 4,4'-dichlorobenzil and grafted talc to N,N-dimethylformamide, stirring at a uniform speed, adding cuprous iodide and N,N-dimethyl-1,2-ethylenediamine, mixing evenly, heating to 100°C, reacting for 24 hours under a nitrogen atmosphere to obtain a modified filler, wherein the amount ratio of grafted talc, 4,4'-dichlorobenzil and N,N-dimethylformamide is controlled to be 5-10g:3-5g:50-80mL, the weight ratio of cuprous iodide and N,N-dimethyl-1,2-ethylenediamine is 1:1, and the sum of the weight of cuprous iodide and N,N-dimethyl-1,2-ethylenediamine is 3-5% of the weight of the grafted talc.

2. A high voltage film for wind power capacitors according to claim 1, characterized in that: The antioxidant is antioxidant 1010 or antioxidant 168.

3. The high voltage-resistant film for wind power capacitor according to claim 1, characterized in that: The nucleating agent is a long-chain linear saturated carboxylic acid sodium salt nucleating agent.

4. The method for preparing a high-voltage film for a wind power capacitor according to claim 1, characterized in that: The steps include: The raw materials are mixed uniformly, melted at 170-190° C., filtered and vented 10-12 times, hot-pressed at 20 MPa to form a thick sheet, stretched and made into a film, thereby obtaining a high-voltage film for wind power capacitors.

5. The method for preparing a high voltage-resistant film for wind power capacitors according to claim 4, characterized in that: The exhaust should be controlled every 8-10 seconds.

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