A metal polypropylene film capacitor with high temperature resistance and a preparation method thereof

Abstract

The application relates to the technical field of capacitors, and discloses a metal polypropylene film capacitor with high-temperature-resistant characteristics and a preparation method thereof. The metal polypropylene film is formed by sputtering and plating an aluminum layer on the surface of a biaxially-stretched polypropylene composite film. The biaxially-stretched polypropylene composite film contains cross-linking modified material and modified nano filler, can interact with the compatible agent maleic anhydride grafted polypropylene in a high-temperature melting process, form a cross-linking network structure with the isotactic polypropylene molecular chain, and efficiently play the respective advantages of each other. The biaxially-stretched polypropylene film prepared by the method has excellent temperature resistance, good mechanical properties and dielectric properties, and the capacitor prepared finally can maintain a stable working state in a high-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, specifically to a high-temperature resistant metal polypropylene film capacitor and its preparation method. Background Technology

[0002] Film capacitors are a type of electrostatic energy storage capacitor with high energy density and reliability, as well as unique self-healing properties. Therefore, they are widely used in many fields such as power systems, pulse power, automotive electronics, power equipment, and aerospace. Due to the excellent insulation properties of biaxially oriented polypropylene (BOP) film capacitors, their development has been rapid in recent years. However, the reflow soldering process used in film capacitor welding exposes the capacitor to high temperatures. Furthermore, the small size and high packing density of film capacitors lead to poor heat dissipation. This necessitates that the BOP used in film capacitors possess excellent temperature resistance. Otherwise, under high-temperature conditions, the performance of the BOP film deteriorates, directly causing a significant decrease in the capacitor's energy density, and even leading to malfunctions and safety hazards.

[0003] To address the poor temperature resistance of polypropylene (PP) films, one approach is to modify their structure. For example, Chinese Patent Publication No. CN111564312B discloses a high-temperature resistant polypropylene film for capacitors and its preparation method. This method involves attaching a high-temperature resistant layer to one side of a PP base film and depositing a weather-resistant layer on the other side. Because the high-temperature resistant layer has a honeycomb structure and contains manganese and nano-graphene that produce synergistic effects, the prepared PP film exhibits significant high-temperature resistance. Alternatively, one can adjust the composition of the PP by modifying the formulation, such as by adding an α-nucleating agent, to increase the crystallinity of the PP and thus its density, thereby improving the temperature resistance of the PP film. However, the addition of a nucleating agent can negatively impact the mechanical and processing properties of the PP, hindering practical applications.

[0004] Based on this, the present invention provides a biaxially oriented polypropylene composite film that can be directly used to manufacture metal polypropylene film capacitors and exhibits good high-temperature resistance. Summary of the Invention

[0005] In order to solve the problems mentioned in the background art, the purpose of this invention is to provide a metal polypropylene film capacitor with high temperature resistance and a method for preparing the same.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a high-temperature resistant metal polypropylene film capacitor includes the following steps:

[0008] The first step is to fix the biaxially oriented polypropylene composite film in a vacuum coating machine, and then use a sputtering coating process to form an aluminum metal layer with a thickness of 0.2-0.5μm on its surface to form a metal polypropylene film.

[0009] The second step is to cut the metal polypropylene film into films of a predetermined width, then wind them into capacitor cores using a winding machine, and finally spray gold onto the end face of the capacitor cores using a gold spraying machine.

[0010] The third step, after the gold spraying is completed, uses an energy-enhancing machine to test the capacitor core, and then uses a reflow soldering process to weld the capacitor core and leads to form a core assembly.

[0011] The fourth step is to assemble the core into the housing to form a capacitor. Then, the capacitor is encapsulated, polished, cleaned, and painted to form a metal polypropylene film capacitor.

[0012] A high-temperature resistant metal polypropylene film capacitor is prepared using the above-described method.

[0013] As a further aspect of the present invention, in the first step, the biaxially oriented polypropylene composite film is made from raw materials comprising the following parts by weight:

[0014] 65-75 parts of isotactic polypropylene;

[0015] Crosslinked modified material 2.5-4 parts;

[0016] 0.5-1 part of modified nanofiller;

[0017] 10-15 parts of maleic anhydride-grafted polypropylene;

[0018] Antioxidant 0.5-1.5 parts;

[0019] 1-2 parts calcium stearate;

[0020] The preparation method of the biaxially oriented polypropylene composite film includes the following steps:

[0021] S1. Prepare all the raw materials according to the weight proportions, mix them evenly in a mixer, and then feed them into a twin-screw extruder for extrusion granulation to form masterbatch;

[0022] S2. Place the masterbatch in an extruder, set the extruder temperature to 220-240℃ and the die head temperature to 220-230℃, melt it, and then cast it into polypropylene sheets.

[0023] S3. Place the casting in the fixture of the biaxial stretching equipment, stretch it longitudinally first, then stretch it transversely, keep it relaxed after forming, and heat set it at 160-170℃. Finally, cure it at room temperature for 30 minutes to obtain the biaxially stretched polypropylene composite film.

[0024] As a further aspect of the present invention, the preparation method of the crosslinked modified material is as follows:

[0025] Add 2,5-furandicarboxylic acid and tetrahydrofuran to a nitrogen-filled reactor, start stirring, and after they form a uniform liquid phase, add a phase transfer catalyst to the reactor. After the addition is complete, start heating and maintain the temperature at 60-65℃. Then, slowly add epoxidized soybean oil dropwise to the reactor. After the addition is complete, continue stirring for 6-9 hours, evaporate and remove the solvent, cool down and discharge the material to obtain the cross-linked modified material.

[0026] Specifically, a phase transfer catalyst is used to catalyze the ring-opening esterification reaction of the substituted carboxyl group in the 2,5-furandicarboxylic acid structure and the epoxy group in the epoxidized soybean oil structure. By controlling the amount of each, continuous and uninterrupted cross-linking can occur between them to form a polymeric material with alternating segments of soybean oil and furan heterocycles, i.e., a cross-linked modified material.

[0027] As a further aspect of the present invention, the molar ratio of 2,5-furandicarboxylic acid and epoxidized soybean oil is 1-1.5:1.

[0028] As a further embodiment of the present invention, the phase transfer catalyst is at least one of tetrabutylammonium bisulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, tetramethylammonium bromide, or N,N-dimethylbenzylamine.

[0029] As a further aspect of the present invention, the preparation method of the modified nanofiller is as follows:

[0030] S10. Disperse nano-titanium dioxide in chloroform by ultrasonication, then add diacyl chloride to the dispersion and add pyridine as a catalyst. After the addition is complete, stir at 55-60℃ for 3-6 hours, centrifuge to remove the nano material, and obtain acyl chloride modified nano-titanium dioxide.

[0031] S20. Mix acyl chloride-modified nano-titanium dioxide with acetone, sonicate to form a uniform dispersion, then add polyetheramine to the dispersion. After the addition is complete, stir and mix at room temperature for 2-4 hours, centrifuge to remove the solid material, and the modified nanofiller can be obtained.

[0032] Specifically, the surface of nano-titanium dioxide contains reactive active hydroxyl groups, which can condense with the acyl chloride group at one end of the diacyl chloride structure to form acyl chloride-modified nano-titanium dioxide. Then, by using polyetheramine as a modifier, the high reactivity of the terminal primary amine group in its structure is utilized to further modify the acyl chloride-modified nano-titanium dioxide, and finally, modified nanofiller is obtained.

[0033] As a further aspect of the present invention, in step S10, the diacyl chloride is any one of succinyl chloride, glutaryl chloride, or adipyl chloride.

[0034] As a further aspect of the present invention, in step S20, the number-average molecular weight of the polyetheramine is 1000.

[0035] As a further aspect of the present invention, the antioxidant is at least one of antioxidant 1010, antioxidant 1076, or antioxidant 168.

[0036] The beneficial effects of the present invention are as follows: (1) The crosslinked modified material prepared by the present invention contains a large number of substituted hydroxyl groups generated by the ring-opening esterification reaction, which can interact with the compatibilizer maleic anhydride grafted polypropylene during the high-temperature melting process, and thus form an entangled crosslinked network structure with the isotactic polypropylene molecular chains. On the one hand, such a network structure has a positive effect on improving the density of isotactic polypropylene molecular chains, which is conducive to maintaining the structural stability of the final biaxially oriented polypropylene composite film under high temperature conditions. In addition, the rich furan heterocyclic structure contained in the crosslinked modified material structure is rigid, which can also improve the temperature resistance of the polypropylene film. Furthermore, the presence of furan rings can also generate deep traps in the polypropylene film, restricting the jumping conductivity of charge carriers, thereby further improving the high temperature resistance of the polypropylene film and enabling it to maintain a stable working state in a high-temperature environment.

[0037] (2) The modified nanofiller prepared in this invention contains a large number of polyetheramine molecular chains on its surface. First, the primary amine in the polyetheramine molecular chains can also interact with the compatibilizer under molten conditions, thereby inserting nano-titanium dioxide into the polypropylene film in the form of chemical crosslinking points. On the one hand, they can achieve high bonding through this method, and nano-titanium dioxide can be highly dispersed in the polypropylene film, solving the interface problem caused by the dielectric constant mismatch between the wide-bandgap nano-titanium dioxide and polypropylene. In this way, the advantages of nano-titanium dioxide can be efficiently utilized to reduce the conductivity loss of the polypropylene film under high temperature conditions, weaken the electric field distortion, and thus improve the dielectric constant and breakdown field strength of the polypropylene film, so that the final prepared capacitor has a higher energy density. On the other hand, nano-titanium dioxide existing in the form of chemical crosslinking points can also effectively improve the mechanical properties of the polypropylene film.

[0038] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is an infrared analysis diagram of the crosslinked modified material. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Example 1: Preparation of crosslinked modified material

[0043] Add 0.5g of 2,5-furandicarboxylic acid and tetrahydrofuran to a nitrogen-filled reactor, start stirring, and after they form a uniform liquid phase, add 0.2g of tetrabutylammonium bromide to the reactor. After the addition is complete, start heating and maintain the temperature at 65℃. Then, slowly add 3.1g of epoxidized soybean oil to the reactor. After the addition is complete, continue stirring for 8 hours, evaporate to remove the solvent, cool down and discharge the material to obtain the cross-linked modified material.

[0044] The crosslinked modified material was prepared into test samples using the potassium bromide tableting method, and infrared spectroscopy was performed. The results are shown below. Figure 1 The absorption peak at 3401 cm⁻¹ is the characteristic absorption peak of hydroxyl groups, the absorption peaks at 3000 cm⁻¹ to 3100 cm⁻¹ are the characteristic absorption peaks of CH in the unsaturated carbon-carbon double bond in the furan ring, and the absorption peak at 1747 cm⁻¹ is the characteristic absorption peak of C=O of the ester group produced by the ring-opening esterification reaction.

[0045] Example 2: The preparation method of the modified nanofiller is shown below:

[0046] S10. 1.5g of nano-titanium dioxide was ultrasonically dispersed in chloroform, and then 2.4g of adipic acid chloride and 0.2g of pyridine were added to the dispersion as a catalyst. After the addition was complete, the mixture was stirred at 60℃ for 4h, and the nanomaterial was centrifuged to obtain acyl chloride modified nano-titanium dioxide.

[0047] S20. Mix 1.2g of acyl chloride modified nano-titanium dioxide with acetone, and sonicate to form a uniform dispersion. Then add 4.5g of polyetheramine with a number average molecular weight of 1000 to the dispersion. After the addition is complete, stir and mix at room temperature for 3 hours. Centrifuge to remove the solid material to obtain the modified nanofiller.

[0048] Take M(g) of modified nanofiller sample and test the amino content by acid-base titration. The specific operation steps are as follows: mix the sample with T(mL) of HCl standard solution with concentration C1, sonicate for 30 min, and then let stand for 1 h. Take 5 mL of dispersion, mix with 5 mL of deionized water, and add 0.02 mL of phenolphthalein as an indicator. Titrate with NaOH standard solution with concentration C2. Stop when the dispersion changes color. Record the consumption of NaOH standard solution Ws(mL). Calculate the amino content using the formula (T×C1-4×C2×Ws) / M. The result is 4.518 mmol / g.

[0049] Example 3: Preparation of biaxially oriented polypropylene composite film

[0050] S1. Mix 65 parts of isotactic polypropylene, 2.5 parts of crosslinked modified material prepared in Example 1, 0.5 parts of modified nanofiller prepared in Example 2, 10 parts of maleic anhydride grafted polypropylene, 0.5 parts of antioxidant 1010, and 1 part of calcium stearate in a mixer until homogeneous. Then feed the mixture into a twin-screw extruder for extrusion granulation. Control the temperature of each zone to be 190℃, 200℃, 220℃, 230℃, 240℃, 230℃, and 220℃, and the screw speed to be 300 rpm to form masterbatch.

[0051] S2. Place the masterbatch in an extruder, set the extruder's melt temperature to 220℃ and the die head temperature to 220℃, melt the masterbatch, and then cast it into a polypropylene sheet with a thickness of 0.5mm.

[0052] S3. Place the casting in the fixture of the biaxial stretching equipment, control the temperature at 160℃, the stretching rate at 100% / s, and the stretching ratio at 5 times. First, perform longitudinal stretching, and then perform transverse stretching. After forming, keep it relaxed and perform heat setting treatment at 160℃. Finally, cure at room temperature for 30 minutes to obtain the biaxially stretched polypropylene composite film.

[0053] Example 4: Preparation of biaxially oriented polypropylene composite film

[0054] S1. 70 parts of isotactic polypropylene, 3.5 parts of crosslinked modified material prepared in Example 1, 0.8 parts of modified nanofiller prepared in Example 2, 12 parts of maleic anhydride grafted polypropylene, 1 part of antioxidant 1010, and 1.5 parts of calcium stearate are mixed evenly in a mixer and then fed into a twin-screw extruder for extrusion granulation. The temperature of each zone is controlled at 190℃, 200℃, 220℃, 230℃, 240℃, 230℃, and 220℃, and the screw speed is 300 rpm to form masterbatch.

[0055] S2. Place the masterbatch in an extruder, set the extruder's melt temperature to 230℃ and the die head temperature to 220℃, melt it, and then cast it into a polypropylene sheet with a thickness of 0.5mm.

[0056] S3. Place the casting in the fixture of the biaxial stretching equipment, control the temperature at 160℃, the stretching rate at 100% / s, and the stretching ratio at 5 times. First, perform longitudinal stretching, and then perform transverse stretching. After forming, keep it relaxed and perform heat setting treatment at 165℃. Finally, cure at room temperature for 30 minutes to obtain the biaxially stretched polypropylene composite film.

[0057] Example 5: Preparation of biaxially oriented polypropylene composite film

[0058] S1. 75 parts of isotactic polypropylene, 4 parts of crosslinked modified material prepared in Example 1, 1 part of modified nanofiller prepared in Example 2, 15 parts of maleic anhydride grafted polypropylene, 1.5 parts of antioxidant 1010, and 2 parts of calcium stearate are mixed evenly in a mixer and then fed into a twin-screw extruder for extrusion granulation. The temperature of each zone is controlled at 190℃, 200℃, 220℃, 230℃, 240℃, 230℃, and 220℃, and the screw speed is 300 rpm to form masterbatch.

[0059] S2. Place the masterbatch in an extruder, set the extruder's melt temperature to 240℃ and the die head temperature to 230℃, melt it, and then cast it into a polypropylene sheet with a thickness of 0.5mm.

[0060] S3. Place the casting in the fixture of the biaxial stretching equipment, control the temperature at 160℃, the stretching rate at 100% / s, and the stretching ratio at 5 times. First, perform longitudinal stretching, and then perform transverse stretching. After forming, keep it relaxed and perform heat setting treatment at 170℃. Finally, cure at room temperature for 30 minutes to obtain the biaxially stretched polypropylene composite film.

[0061] Comparative Example 1

[0062] The biaxially oriented polypropylene composite film prepared in this comparative example differs from that in Example 4 in that the crosslinking modifier in the raw materials is removed, while the rest remains unchanged.

[0063] Comparative Example 2

[0064] The biaxially oriented polypropylene composite film prepared in this comparative example differs from that in Example 4 in that the modified nanofiller in the raw materials is removed, while the rest remains unchanged.

[0065] Comparative Example 3

[0066] The biaxially oriented polypropylene composite film prepared in this comparative example differs from that in Example 4 in that the modified nanofiller in the raw materials is replaced with nano-titanium dioxide, while the rest remains unchanged.

[0067] Test case

[0068] (A) The tensile strength of the biaxially oriented polypropylene composite films in Examples 3-5 and Comparative Examples 1-3 were tested according to standard GB / T 1040.3-2006.

[0069] (B) Test the breakdown strength according to standard GB / T 13542.2-2021;

[0070] (C) Use a WK65120B high-precision impedance analyzer to test the dielectric constant;

[0071] The results are recorded in Table 1;

[0072] Table 1 - Test Results

[0073]

[0074] According to the results in Table 1, the biaxially oriented polypropylene composite film prepared with cross-linked modified material and modified nanofiller has significantly better comprehensive properties such as mechanical properties, breakdown strength and temperature resistance. However, when unmodified nano-titanium dioxide is used to replace the modified nanofiller, there are obvious compatibility problems. The poor interfacial bonding force prevents the nano-titanium dioxide from efficiently exerting its advantages, resulting in poor performance in various aspects.

[0075] Metallic polypropylene film capacitors are prepared using the biaxially oriented polypropylene composite film of Example 4 of this invention. The preparation method is as follows:

[0076] The first step is to fix the biaxially oriented polypropylene composite film in a vacuum coating machine, and then use a sputtering coating process to control the heating current of the aluminum evaporator boat to 80A and the aluminum feeding rate to 500mm / min to form an aluminum metal layer with a thickness of 0.2μm on its surface, thus forming a metal polypropylene film.

[0077] The second step is to cut the metal polypropylene film into films of a predetermined width, then wind them into capacitor cores using a winding machine, and finally spray gold onto the end face of the capacitor cores using a gold spraying machine.

[0078] The third step, after the gold spraying is completed, uses an energy-enhancing machine to test the capacitor core, and then uses a reflow soldering process to weld the capacitor core and leads to form a core assembly.

[0079] The fourth step is to assemble the core into the housing to form a capacitor. Then, the capacitor is encapsulated, polished, cleaned, and painted to form a metal polypropylene film capacitor.

[0080] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a high-temperature resistant metal polypropylene film capacitor, characterized in that, Includes the following steps: The first step is to fix the biaxially oriented polypropylene composite film in a vacuum coating machine, and then use a sputtering coating process to form an aluminum metal layer with a thickness of 0.2-0.5μm on its surface to form a metal polypropylene film. The second step is to cut the metal polypropylene film into films of a predetermined width, then wind them into capacitor cores using a winding machine, and finally spray gold onto the end face of the capacitor cores using a gold spraying machine. The third step, after the gold spraying is completed, uses an energy-enhancing machine to test the capacitor core, and then uses a reflow soldering process to weld the capacitor core and leads to form a core assembly. The fourth step is to assemble the core into the housing to form a capacitor. Then, the capacitor is encapsulated, polished, cleaned, and painted to form a metal polypropylene film capacitor. The biaxially oriented polypropylene composite film is made from raw materials comprising the following parts by weight: 65-75 parts of isotactic polypropylene; Crosslinked modified material 2.5-4 parts; 0.5-1 part of modified nanofiller; 10-15 parts of maleic anhydride-grafted polypropylene; Antioxidant 0.5-1.5 parts; 1-2 parts calcium stearate; The preparation method of the biaxially oriented polypropylene composite film includes the following steps: S1. Prepare all the raw materials according to the weight proportions, mix them evenly in a mixer, and then feed them into a twin-screw extruder for extrusion granulation to form masterbatch; S2. Place the masterbatch in an extruder, set the extruder temperature to 220-240℃ and the die head temperature to 220-230℃, melt it, and then cast it into polypropylene sheets. S3. Place the casting in the fixture of the biaxial stretching equipment, stretch it longitudinally first, then stretch it transversely, keep it relaxed after forming, and heat set it at 160-170℃. Finally, cure it at room temperature for 30 minutes to obtain the biaxially stretched polypropylene composite film. The crosslinked modified material is prepared by branching polymerization of 2,5-furandicarboxylic acid and epoxidized soybean oil under the catalytic conditions of a phase transfer catalyst. The preparation method of the modified nanofiller is as follows: S10. First, the surface of nano-titanium dioxide is modified with diacyl chloride to form acyl chloride-modified nano-titanium dioxide. S20. Polyetheramine is used to further modify the acyl chloride-modified nano-titanium dioxide to obtain modified nanofiller.

2. The method for preparing a high-temperature resistant metal polypropylene film capacitor according to claim 1, characterized in that, The molar ratio of 2,5-furandicarboxylic acid and epoxidized soybean oil is 1-1.5:

1.

3. The method for preparing a high-temperature resistant metal polypropylene film capacitor according to claim 1, characterized in that, The phase transfer catalyst is at least one of tetrabutylammonium bisulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, tetramethylammonium bromide, or N,N-dimethylbenzylamine.

4. The method for preparing a high-temperature resistant metal polypropylene film capacitor according to claim 1, characterized in that, In step S10, the diacyl chloride is any one of succinyl chloride, glutaryl chloride, or adipyl chloride.

5. The method for preparing a high-temperature resistant metal polypropylene film capacitor according to claim 1, characterized in that, In step S20, the number-average molecular weight of the polyetheramine is 1000.

6. The method for preparing a high-temperature resistant metal polypropylene film capacitor according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 1076, or antioxidant 168.

7. A high-temperature resistant metal polypropylene film capacitor, characterized in that, It was prepared by the method described in claim 1.

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