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

Abstract

The invention relates to the technical field of capacitors, and discloses a high-temperature-resistant metal polypropylene film capacitor and a preparation method thereof.A metal polypropylene film is formed by plating an aluminum layer on the surface of a biaxially oriented polypropylene composite film through a sputter coating technology. The biaxially oriented polypropylene composite film contains a cross-linked modified material and a modified nano-filler, can interact with a compatilizer maleic anhydride grafted polypropylene in a high-temperature melting process, and forms a mutually entangled cross-linked network structure with an isotactic polypropylene molecular chain, so that the advantages of the two-way oriented polypropylene composite film and the isotactic polypropylene molecular chain are efficiently exerted; the prepared biaxially oriented polypropylene film not only has excellent temperature resistance, but also has good mechanical properties and dielectric properties, so that a finally prepared capacitor can maintain a stable working state in a high-temperature environment.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to a metal polypropylene film capacitor with high temperature resistance and a preparation method thereof. Background Art

[0002] Film capacitors are electrostatic energy storage capacitors 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, aerospace, etc. Due to their excellent insulation properties, biaxially oriented polypropylene film capacitors have developed rapidly in recent years. Due to the reflow soldering process used in the welding process of film capacitors, the capacitors will experience a high temperature process. In addition, due to the small size of film capacitors and the high packing density per unit space, the heat dissipation conditions become worse. This requires that the biaxially oriented polypropylene used in film capacitors must have good temperature resistance. Otherwise, under high temperature conditions, the performance of the biaxially oriented polypropylene film will deteriorate, which will directly lead to a serious decrease in the energy storage density of the capacitor, and even failures and safety hazards.

[0003] In order to solve the problem of poor heat resistance of polypropylene film, we can start from the structure of polypropylene film. For example, the invention patent publication number CN111564312B discloses a polypropylene film for high temperature capacitor and its preparation method. By connecting a high temperature resistant layer on one side of the polypropylene base film and plating a weather resistant layer on the other side, the high temperature resistant layer has a honeycomb structure and contains manganese elements and nanographene that can produce synergistic effects, so that the prepared polypropylene film has significant high temperature resistance. In addition, we can also start from the components of polypropylene, by adjusting the formula, for example, by adding α nucleating agent, to increase the crystallinity of polypropylene, so that the density of polypropylene is increased, and the heat resistance of polypropylene film is improved. However, the addition of nucleating agent will affect the mechanical properties and processing properties of polypropylene, which is not conducive to practical application.

[0004] Based on this, the present invention provides a biaxially oriented polypropylene composite film, which can be directly used to make 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 technology, the object of the present invention is to provide a metal polypropylene film capacitor with high temperature resistance and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a metal polypropylene film capacitor with high temperature resistance, comprising 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 0.2-0.5 μm 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, wind it into a capacitor core by a winder, and then use a gold spraying machine to spray gold on the end surface of the capacitor core; Step 3: After the gold spraying is completed, the capacitor core is tested using an energizer, and then the capacitor core and lead wires are welded using a reflow soldering process to form a core group. The fourth step is to assemble the core into the shell to form a capacitor, and then encapsulate, polish, clean and paint the capacitor to form a metal polypropylene film capacitor.

[0007] A metal polypropylene film capacitor with high temperature resistance is prepared by the preparation method.

[0008] As a further solution of the present invention, in the first step, the biaxially oriented polypropylene composite film is made of raw materials including the following parts by weight: Isotactic polypropylene 65-75 parts; 2.5-4 parts of cross-linked modified material; 0.5-1 part of modified nanofiller; Maleic anhydride grafted polypropylene 10-15 parts; 0.5-1.5 parts of antioxidant; Calcium stearate 1-2 parts; The method for preparing the biaxially oriented polypropylene composite film comprises the following steps: S1. Prepare all the raw materials by weight, mix them evenly in a mixer, and feed them into a twin-screw extruder for extrusion granulation to form masterbatch; S2, placing the masterbatch in an extruder, setting the extruder temperature to 220-240° C., the die temperature to 220-230° C., melting, and then casting a sheet to form a polypropylene sheet; S3. Place the cast sheet in the fixture of the biaxial stretching equipment, first stretch it longitudinally, then stretch it transversely, keep it relaxed after forming, and perform heat setting treatment at 160-170°C, and finally mature it at room temperature for 30 minutes to obtain a biaxially stretched polypropylene composite film.

[0009] As a further embodiment of the present invention, the preparation method of the cross-linked modified material is as follows: Add 2,5-furandicarboxylic acid and tetrahydrofuran to a reactor filled with nitrogen, start stirring to form a uniform liquid phase, then add a phase transfer catalyst to the reactor. After the addition, start heating to maintain the temperature at 60-65°C, then slowly add epoxy soybean oil dropwise to the reactor. After the addition is completed, continue stirring for 6-9 hours, evaporate and remove the solvent, cool and discharge the material, and then the cross-linked modified material can be obtained.

[0010] 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 the two, continuous and uninterrupted bridging connection can be achieved between them to form a polymer material with alternating chains of soybean oil and furan heterocycles, namely a cross-linked modified material.

[0011] As a further embodiment of the present invention, the molar ratio of the 2,5-furandicarboxylic acid to the epoxidized soybean oil is 1-1.5:1.

[0012] As a further embodiment of the present invention, the phase transfer catalyst is at least one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, tetramethylammonium bromide or N,N-dimethylbenzylamine.

[0013] As a further embodiment of the present invention, the preparation method of the modified nanofiller is as follows: S10, ultrasonically dispersing nano-titanium dioxide in chloroform, adding diacyl chloride to the dispersion, and adding pyridine as a catalyst, stirring at a temperature of 55-60° C. for 3-6 hours, centrifuging the nano-material, and obtaining acyl chloride-modified nano-titanium dioxide; S20, mixing the acyl chloride modified nano titanium dioxide with acetone, forming a uniform dispersion by ultrasonication, and then adding polyetheramine to the dispersion. After the addition, stirring and mixing at room temperature for 2-4 hours, centrifuging out the solid material, and obtaining the modified nano filler.

[0014] 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 and utilizing the high reactivity of the terminal primary amine group in its structure, the acyl chloride-modified nano-titanium dioxide is further modified to finally obtain a modified nano-filler.

[0015] As a further embodiment of the present invention, in step S10, the diacyl chloride is any one of succinyl chloride, glutaryl chloride or adipoyl chloride.

[0016] As a further embodiment of the present invention, in step S20, the number average molecular weight of the polyetheramine is 1000.

[0017] As a further embodiment of the present invention, the antioxidant is at least one of antioxidant 1010, antioxidant 1076 or antioxidant 168.

[0018] Beneficial effects of the present invention: (1) The cross-linked modified material structure 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 then can form an entangled cross-linked network structure with the isotactic polypropylene molecular chain. On the one hand, such a network structure has a positive effect on the improvement of the density of the isotactic polypropylene molecular chain, which is conducive to the final biaxially oriented polypropylene composite film to maintain structural stability under high temperature conditions. In addition, the rich furan heterocyclic structure contained in the cross-linked modified material structure exhibits rigidity, which can also improve the heat resistance of the polypropylene film. The presence of the furan ring can also generate deep traps in the polypropylene film, limiting the jumping conductivity of the carriers, thereby further improving the high temperature resistance of the polypropylene film, so that it can maintain a stable working state in a high temperature environment.

[0019] (2) The surface of the modified nanofiller prepared by the present invention contains a large number of polyetheramine molecular chains. First, the primary amine in the polyetheramine molecular chain 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 a high degree of bonding with each other in this way, and the 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 the polypropylene, and then can effectively utilize the advantages of nano-titanium dioxide, reduce the conductivity loss of the polypropylene film under high temperature conditions, weaken the electric field distortion, thereby improving 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, the nano-titanium dioxide in the form of chemical crosslinking points can also effectively improve the mechanical properties of the polypropylene film.

[0020] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 This is the infrared analysis diagram of the cross-linked modified material. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1: Preparation of cross-linked modified material Add 0.5 g of 2,5-furandicarboxylic acid and tetrahydrofuran to a reactor filled with nitrogen, start stirring to form a uniform liquid phase, then add 0.2 g of tetrabutylammonium bromide to the reactor. After the addition, turn on the heating and maintain the temperature at 65°C. Then, slowly add 3.1 g of epoxidized soybean oil dropwise to the reactor. After the addition is completed, continue stirring for 8 hours, evaporate to remove the solvent, cool and discharge the material to obtain a cross-linked modified material.

[0025] The cross-linked modified material was made into test samples using the potassium bromide tableting method and infrared testing was performed. The results are shown in Figure 1 The absorption peak at 3401cm-1 is the characteristic absorption peak of the hydroxyl group, the absorption peak at 3000cm-1~3100cm-1 is the characteristic absorption peak of CH of the unsaturated carbon-carbon double bond in the furan ring, and the absorption peak at 1747cm-1 is the characteristic absorption peak of the ester group C=O produced by the ring-opening esterification reaction.

[0026] Example 2: The preparation method of the modified nanofiller is as follows: S10, ultrasonically dispersing 1.5 g of nano titanium dioxide in chloroform, adding 2.4 g of adipoyl chloride to the dispersion, and adding 0.2 g of pyridine as a catalyst, stirring at 60° C. for 4 h, centrifuging the nano material, and obtaining acyl chloride-modified nano titanium dioxide; S20, 1.2g of acyl chloride modified nano titanium dioxide was mixed with acetone, and after ultrasonication to form a uniform dispersion, 4.5g of polyetheramine with a number average molecular weight of 1000 was added to the dispersion. After the addition, the mixture was stirred at room temperature for 3h, and the solid material was centrifuged to obtain the modified nano filler.

[0027] Take M (g) modified nanofiller sample and test the amino content by using acid-base titration method. The specific operation steps are as follows: mix the sample with T (mL) HCl standard solution with concentration C1, ultrasonicate for 30 min, and then let it stand for 1 h. Take 5 mL of dispersion, mix it with 5 mL of deionized water, and add 0.02 mL of phenolphthalein as an indicator. Use NaOH standard solution with concentration C2 to titrate. Stop when the dispersion changes color, record the consumption of NaOH standard solution Ws (mL), and calculate the amino content using the formula (T×C1-4×C2×Ws) / M. The measured result is 4.518 mmol / g.

[0028] Example 3: Preparation of biaxially oriented polypropylene composite film S1, 65 parts of isotactic polypropylene, 2.5 parts of the cross-linked modified material prepared in Example 1, 0.5 parts of the 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 are placed in a mixer and mixed evenly, and then fed into a twin-screw extruder for extrusion granulation, and the temperature of each zone is controlled to be 190°C, 200°C, 220°C, 230°C, 240°C, 230°C, and 220°C, and the screw speed is 300rpm to form a masterbatch; S2, placing the masterbatch in an extruder, setting the melt temperature of the extruder to 220° C., the head temperature to 220° C., melting, and then casting a sheet to form a polypropylene sheet with a thickness of 0.5 mm; S3. Place the cast sheet in the fixture of the biaxial stretching equipment, control the temperature to 160°C, the stretching rate to 100% / s, the stretching ratio to 5 times, first perform longitudinal stretching, then perform transverse stretching, keep it relaxed after forming, and perform heat setting treatment at 160°C, and finally mature at room temperature for 30 minutes to obtain a biaxially stretched polypropylene composite film.

[0029] Example 4: Preparation of biaxially oriented polypropylene composite film S1, 70 parts of isotactic polypropylene, 3.5 parts of the cross-linked modified material prepared in Example 1, 0.8 parts of the 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 placed in a mixer and mixed evenly, and then fed into a twin-screw extruder for extrusion granulation, and the temperature of each zone is controlled to be 190°C, 200°C, 220°C, 230°C, 240°C, 230°C, and 220°C, and the screw speed is 300rpm to form a masterbatch; S2, placing the masterbatch in an extruder, setting the melt temperature of the extruder to 230° C. and the head temperature to 220° C., melting, and then casting a sheet to form a polypropylene sheet with a thickness of 0.5 mm; S3. Place the cast sheet in the fixture of the biaxial stretching equipment, control the temperature to 160°C, the stretching rate to 100% / s, the stretching ratio to 5 times, first perform longitudinal stretching, then perform transverse stretching, keep it relaxed after forming, and perform heat setting treatment at 165°C, and finally mature at room temperature for 30 minutes to obtain a biaxially stretched polypropylene composite film.

[0030] Example 5: Preparation of biaxially oriented polypropylene composite film S1, 75 parts of isotactic polypropylene, 4 parts of the cross-linked modified material prepared in Example 1, 1 part of the 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 placed in a mixer and mixed evenly, and then fed into a twin-screw extruder for extrusion granulation, and the temperature of each zone is controlled to be 190° C., 200° C., 220° C., 230° C., 240° C., 230° C., and 220° C., and the screw speed is 300 rpm to form a masterbatch; S2, placing the masterbatch in an extruder, setting the melt temperature of the extruder to 240° C. and the head temperature to 230° C., melting, and then casting a sheet to form a polypropylene sheet with a thickness of 0.5 mm; S3. Place the cast sheet in the fixture of the biaxial stretching equipment, control the temperature to 160°C, the stretching rate to 100% / s, the stretching ratio to 5 times, first perform longitudinal stretching, then perform transverse stretching, keep it relaxed after forming, and perform heat setting treatment at 170°C, and finally mature at room temperature for 30 minutes to obtain a biaxially stretched polypropylene composite film.

[0031] Comparative Example 1 The biaxially oriented polypropylene composite film prepared in this comparative example is different from that in Example 4 in that the cross-linking modified material in the raw material is removed, and the rest remains unchanged.

[0032] Comparative Example 2 The biaxially oriented polypropylene composite film prepared in this comparative example is different from that in Example 4 in that the modified nanofiller in the raw material is removed, and the rest remains unchanged.

[0033] Comparative Example 3 The biaxially oriented polypropylene composite film prepared in this comparative example is different from that in Example 4 in that the modified nanofiller in the raw material is replaced with nano-titanium dioxide, and the rest remains unchanged.

[0034] Test Case (A) According to standard GB / T 1040.3-2006, the tensile strength of the biaxially oriented polypropylene composite films in Examples 3 to 5 and Comparative Examples 1 to 3 was tested; (B) According to standard GB / T 13542.2-2021, test the breakdown strength; (C) Use WK65120B high-precision impedance analyzer to test the dielectric constant; The results are recorded in Table 1; Table 1 - Test results

[0035] According to the results in Table 1, the biaxially oriented polypropylene composite film prepared by containing cross-linked modified materials and modified nanofillers in the components has obviously better comprehensive properties such as mechanical properties, breakdown strength and temperature resistance. However, when the modified nanofillers are replaced by nano-titanium dioxide without surface modification, there is an obvious compatibility problem. The poor interface bonding force causes the nano-titanium dioxide to be unable to efficiently exert its own advantages, so the performance of various properties is poor.

[0036] The biaxially oriented polypropylene composite film in Example 4 of the present invention is used to prepare a metal polypropylene film capacitor, and the preparation method is as follows: The first step is to fix the biaxially oriented polypropylene composite film in a vacuum coating machine, and then adopt a sputtering coating process, control the heating current of the aluminum evaporator evaporation boat to 80A, and control the aluminum feeding rate to 500mm / min, to form an aluminum metal layer with a thickness of 0.2μm 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, wind it into a capacitor core by a winder, and then use a gold spraying machine to spray gold on the end surface of the capacitor core; Step 3: After the gold spraying is completed, the capacitor core is tested using an energizer, and then the capacitor core and lead wires are welded using a reflow soldering process to form a core group. The fourth step is to assemble the core into the shell to form a capacitor, and then encapsulate, polish, clean and paint the capacitor to form a metal polypropylene film capacitor.

[0037] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a metal polypropylene film capacitor with high temperature resistance, characterized in that: The following steps are involved: 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 0.2-0.5 μm 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, wind it into a capacitor core by a winder, and then use a gold spraying machine to spray gold on the end surface of the capacitor core; Step 3: After the gold spraying is completed, the capacitor core is tested using an energizer, and then the capacitor core and lead wires are welded using a reflow soldering process to form a core group. The fourth step is to assemble the core into the shell to form a capacitor, and then encapsulate, polish, clean and paint the capacitor to form a metal polypropylene film capacitor.

2. A metal polypropylene film capacitor with high temperature resistance, characterized in that: The method is prepared according to claim 1.

3. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 1, characterized in that: In the first step, the biaxially oriented polypropylene composite film is made of the following raw materials in parts by weight: Isotactic polypropylene 65-75 parts; 2.5-4 parts of cross-linked modified material; 0.5-1 part of modified nanofiller; Maleic anhydride grafted polypropylene 10-15 parts; 0.5-1.5 parts of antioxidant; Calcium stearate 1-2 parts; The method for preparing the biaxially oriented polypropylene composite film comprises the following steps: S1. Prepare all the raw materials by weight, mix them evenly in a mixer, and feed them into a twin-screw extruder for extrusion granulation to form masterbatch; S2, placing the masterbatch in an extruder, setting the extruder temperature to 220-240° C., the die temperature to 220-230° C., melting, and then casting a sheet to form a polypropylene sheet; S3. Place the cast sheet in the fixture of the biaxial stretching equipment, first stretch it longitudinally, then stretch it transversely, keep it relaxed after forming, and perform heat setting treatment at 160-170°C, and finally mature it at room temperature for 30 minutes to obtain a biaxially stretched polypropylene composite film.

4. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 3, characterized in that: The cross-linked modified material is prepared by branching polymerization of 2,5-furandicarboxylic acid and epoxidized soybean oil under the catalytic condition of a phase transfer catalyst.

5. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 4, characterized in that: The molar ratio of the 2,5-furandicarboxylic acid to the epoxidized soybean oil is 1-1.5:

1.

6. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 4, characterized in that: The phase transfer catalyst is at least one of tetrabutylammonium hydrogen sulfate, tetrabutylammonium bromide, tetrabutylammonium chloride, tetramethylammonium bromide or N,N-dimethylbenzylamine.

7. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 3, characterized in that: The preparation method of the modified nanofiller is as follows: S10, firstly using diacyl chloride to modify the surface of nano titanium dioxide to form acyl chloride modified nano titanium dioxide; S20, further modifying the acyl chloride-modified nano titanium dioxide using polyetheramine to obtain a modified nano filler.

8. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 7, characterized in that: In step S10, the diacyl chloride is any one of succinyl chloride, glutaryl chloride or adipoyl chloride.

9. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 7, characterized in that: In step S20, the number average molecular weight of the polyetheramine is 1000.

10. The method for preparing a metal polypropylene film capacitor with high temperature resistance according to claim 3, characterized in that: The antioxidant is at least one of antioxidant 1010 , antioxidant 1076 or antioxidant 168 .

Images