Flame-retardant modified metallized film for capacitor and preparation method of flame-retardant modified metallized film

Abstract

The invention relates to a flame-retardant modified metallized film for a capacitor and a preparation method of the flame-retardant modified metallized film, and belongs to the technical field of capacitor materials. The metallized film is prepared from the following components in parts by weight: 50 to 60 parts of terephthalic acid, 30 to 40 parts of ethylene glycol, 5 to 10 parts of cyclobutane-1, 3-dicarboxylic acid, 0.5 to 1 part of antimony trioxide, 0.5 to 1 part of a stabilizer, 4 to 6 parts of a composite flame retardant, 0.1 to 0.3 part of 4-dimethylaminopyridine and 0.1 to 0.2 part of polyhedral oligomeric silsesquioxane. The metallized film prepared by the invention has excellent flame retardant property.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of capacitor materials and relates to a flame-retardant modified metallized film for capacitors and a preparation method thereof. BACKGROUND

[0002] As a key component in electronic circuits, thin film capacitors are widely used in consumer electronics, industrial automation, new energy and other fields. With the development of electronic devices towards miniaturization and high performance, the performance requirements of thin film capacitors are increasingly improved. Traditional metallized thin film capacitors are prone to problems such as insufficient flame retardant performance and poor thermal stability in harsh environments such as high temperature and high humidity, leading to capacitor failure and even safety accidents. At present, although there are some studies on flame-retardant modified metallized films in the prior art, there are generally problems such as uneven dispersion of flame retardants, insufficient thermal stability and poor mechanical properties, which affect the reliability and service life of capacitors.

[0003] Therefore, it is of great significance to develop a flame-retardant modified metallized film for capacitors and a preparation method thereof. SUMMARY

[0004] The application aims to provide a flame-retardant modified metallized film for capacitors and a preparation method thereof, which has excellent flame-retardant performance.

[0005] The application can be achieved by the following technical solutions. A flame-retardant modified metallized film for capacitors, the metallized film comprising the following components in parts by weight: 50-60 parts of terephthalic acid, 30-40 parts of ethylene glycol, 5-10 parts of cyclobutane-1,3-dicarboxylic acid, 0.5-1 part of antimony trioxide, 0.5-1 part of stabilizer, 4-6 parts of composite flame retardant, 0.1-0.3 parts of 4-dimethylaminopyridine, and 0.1-0.2 parts of cage polysilsesquioxane. The preparation method of the composite flame retardant is as follows, S1-1: Dissolve magnesium nitrate and aluminum nitrate in deionized water at a molar ratio of 2:1, add urea, stir at 90-95 DEG C for 10-12 h, wash with deionized water and vacuum dry at 60 DEG C for 10-14 h to obtain powder A; S1-2: Disperse powder A in an aqueous solution containing 10-20% by mass of ammonium polyphosphate, ultrasonically treat at 45-55 DEG C for 4-6 h, wash with deionized water and dry at 60 DEG C for 10-14 h to obtain powder B; S1-3: Mix powder B with modified boron nitride, add 1-3% of silane coupling agent KH550 based on the mass of powder B, ball mill at a speed of 200-300 rpm for 1-2 h, and then vacuum dry at 60 DEG C for 10-14 h to obtain the composite flame retardant.

[0006] Further, the preparation method of the modified boron nitride in S1-3 is as follows, S2-1: dispersing boron nitride in an ethanol solution with a mass fraction of 50-60%, adding silane coupling agent KH550, stirring at 80°C for 6 h, washing with deionized water and drying at 60°C for 10-14 h to obtain powder C; S2-2: mixing diethyl phosphoacetic acid with powder C according to a molar ratio of (5-7):1, adding to a MES buffer with a pH of 5-6, then adding EDC and NHS, stirring at 45-55°C for 4-6 h, washing with deionized water and drying at 60°C for 10-14 h to obtain modified boron nitride.

[0007] Further, the stabilizer is triphenyl phosphite.

[0008] Further, the total molar ratio of urea to metal salt in S1-1 is (1-3):1.

[0009] Further, the mass ratio of powder B to modified boron nitride in S1-3 is (2-4):1.

[0010] Further, the mass ratio of silane coupling agent KH550 to boron nitride in S2-1 is 1:(8-10).

[0011] Further, the molar ratio of diethyl phosphoacetic acid, EDC and NHS is 2:2:(1-2).

[0012] A preparation method of a flame-retardant modified metallized film for capacitors, the specific steps of the preparation method are as follows, S8-1: according to the formula proportion, adding terephthalic acid, ethylene glycol, cyclobutane-1,3-dicarboxylic acid, antimony trioxide and stabilizer into a reaction kettle, purging with nitrogen and heating to 210-230°C, pressure 0.3-0.5 MPa; S8-2: then adding a composite flame retardant, 4-dimethylaminopyridine and a cage polysilsesquioxane into the reaction kettle, stirring for 5-10 min, heating to 230-250°C, stirring for 30-40 min, further heating to 265-270°C, and continuing to stir for 4-6 h to obtain a modified polyester material; S8-3: extruding the modified polyester material through a flat die of an extruder at 230-240°C to form a sheet with a thickness of 80-120 μm, and then performing bidirectional stretching treatment to obtain a bidirectional stretched film; S8-4: heat setting the film, then annealing at 110-120°C for 30-60 min to obtain the flame-retardant modified metallized film for capacitors.

[0013] Further, the bidirectional stretching treatment step in S8-3 is to heat the sheet to 80-100°C, longitudinally stretch at a stretching ratio of 1:(3-5), and then transversely stretch at 100-120°C at a stretching ratio of 1:(3-4).

[0014] Further, the heat setting time in S8-4 is 5-10 s, and the temperature is 180-200°C.

[0015] The interlayer crystalline water of MgAl-LDH is removed at high temperature, absorbing a large amount of heat, and releasing CO2 and H2O to dilute the concentration of combustible gas. At the same time, MgO and Al2O3 generated by pyrolysis of LDH have Lewis acid sites, which can catalyze the β-scission of polyester molecular chains to generate olefin radicals, promote crosslinking to form carbon, and form a dense heat insulation layer. Ammonium polyphosphate decomposes into polyphosphoric acid and NH3 at high temperature, and polyphosphoric acid combines with the terminal hydroxyl group of polyester through esterification reaction to enhance the graphitization degree of carbon layer. Polyphosphoric acid reacts with the hydroxyl group on the surface of LDH to form a covalent bond, which improves the shear strength of the carbon layer and the matrix. The layered structure of LDH physically adsorbs ammonium polyphosphate molecules through van der Waals force, reducing its hygroscopicity, and the cavitation effect generated by ultrasonic treatment makes ammonium polyphosphate intercalate into the interlayer of LDH, improving the uniformity of dispersion. In addition, LDH and ammonium polyphosphate also have further synergistic effect. The acid sites of LDH promote the decomposition of ammonium polyphosphate, and the polyphosphoric acid further reacts with the MgO generated by LDH to form magnesium phosphate, forming a three-dimensional network structure, which improves the compressive strength of the carbon layer.

[0016] Boron nitride has high thermal conductivity, which can improve the heat dissipation performance of the film and avoid local overheating to cause breakdown. Silane coupling agent KH550 hydrolyzes to generate Si-OH, which condenses with the hydroxyl group on the surface of boron nitride to form Si-O-BN bond, and the amino group adsorbs LDH nanosheet through electrostatic attraction, realizing the chemical bonding of boron nitride and flame retardant. Diethyl phosphoacetic acid reacts with boron nitride to form amide under the catalysis of EDC / NHS, introducing phosphorus element to form P-N-B synergistic flame retardant system. The hexagonal structure of boron nitride is retained intact through KH550 modification, which constructs a heat conduction path in the polyester matrix. Diethyl phosphoacetic acid generates PO· free radicals to inhibit the chain reaction of combustion, and releases NH3 to dilute the oxygen concentration. Modified boron nitride reacts with polyphosphoric acid generated by the decomposition of ammonium polyphosphate to form borophosphate, which enhances the density of carbon layer and significantly improves the flame retardant effect of the film.

[0017] The nano-cage structure of the cage polysilsesquioxane forms a dense SiO2 reinforced carbon layer during combustion, which synergistically flame-retardant with antimony trioxide, ammonium polyphosphate and the like, so as to improve the oxygen index of the film; the Si-O bond vibration and the polyester chain resonance construct an efficient heat conduction path, and meanwhile the SiO2 core maintains high insulation; the rigid cage body enhances the tensile strength of the film through physical / chemical crosslinking, optimizes the melt flowability in nanometer size, reduces the viscosity, and improves the thickness uniformity; the hydrophobic Si-O-Si skeleton reduces the water absorption, suppresses the dielectric loss during hygrothermal aging, and the strength after thermal aging still remains at a high level.

[0018] The beneficial effects of the present application are as follows: The present application significantly improves the flame-retardant and comprehensive performance of the film through the synergistic effect of MgAl-LDH, ammonium polyphosphate, boron nitride and cage polysilsesquioxane. The interlayer dehydration endothermic of LDH releases CO2 / H2O to dilute combustible gas, and the pyrolysis product MgO / Al2O3 catalyzes carbonization to form a covalent bond with ammonium polyphosphate, enhances the graphitization of the carbon layer and the interfacial bonding force, and improves the dispersibility through ultrasonic intercalation technology; the modified boron nitride by KH550 and diethyl phosphoacetic acid constructs a P-N-B synergistic flame-retardant system, the hexagonal crystal structure retains high thermal conductivity, and at the same time releases NH3 to dilute oxygen and generates borophosphate to strengthen the carbon layer; the cage polysilsesquioxane enhances the density of the carbon layer through the nano-cage SiO2, and synergistically flame-retardant with antimony trioxide, the Si-O bond vibration optimizes the heat conduction path, the rigid cage body enhances the tensile strength, and the hydrophobic skeleton reduces the water absorption and suppresses the dielectric loss during hygrothermal aging, and the strength after thermal aging still remains at a high level. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined object, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0020] In the examples and comparative examples of the present application: Terephthalic acid: purchased from Shanghai Aldrin Biochemical Technology Co., Ltd.; Ethylene glycol: purchased from Shanghai Aldrin Biochemical Technology Co., Ltd.; Cyclobutane-1,3-dicarboxylic acid: purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd.; Antimony trioxide: purchased from Beijing Hailiyang Chemical Technology Co., Ltd.; Triphenyl phosphite: purchased from Changhe Chemical New Materials (Jiangsu) Co., Ltd.; 4-dimethylamino pyridine: purchased from Shanghai Kaisai Chemical Co., Ltd.; Cage polysilsesquioxane: purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.; Ammonium polyphosphate: purchased from Guangzhou Haoyu International Trade Co., Ltd.; Silane coupling agent KH550: purchased from Jiangxi Hongbai New Material Co., Ltd. Boron nitride: purchased from Fosman Technology (Beijing) Co., Ltd. Diethyl phosphoacetic acid: purchased from Shanghai Boteng Pharmaceutical Technology Co., Ltd. EDC: purchased from Shanghai Xijia Biological Technology Co., Ltd. NHS: purchased from Shanghai Changming Pharmaceutical Technology Co., Ltd. MES buffer: purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0021] Example 1

[0022] A flame-retardant modified metallized film for capacitors, the metallized film comprising the following components, in parts by weight, terephthalic acid 55 parts, ethylene glycol 35 parts, cyclobutane-1,3-dicarboxylic acid 8 parts, antimony trioxide 0.8 parts, triphenyl phosphite 0.8 parts, composite flame retardant 5 parts, 4-dimethylamino pyridine 0.2 parts, cage polysilsesquioxane 0.15 parts; The preparation method of the composite flame retardant is as follows, S1-1: Dissolve magnesium nitrate and aluminum nitrate in deionized water at a molar ratio of 2:1, add urea, the total molar ratio of urea to metal salt is 2:1, stir at 92 ℃ for 11 h, wash with deionized water and vacuum dry at 60 ℃ for 12 h to obtain powder A; S1-2: Disperse powder A in an aqueous solution containing 15% by mass of ammonium polyphosphate, ultrasonic treatment at 50 ℃ for 5 h, wash with deionized water and dry at 60 ℃ for 12 h to obtain powder B; S1-3: Mix powder B with modified boron nitride at a mass ratio of 3:1, add 2% of silane coupling agent KH550 based on the mass of powder B, ball mill at a speed of 250 rpm for 1.5 h, and then vacuum dry at 60 ℃ for 12 h to obtain the composite flame retardant.

[0023] The preparation method of the modified boron nitride in S1-3 is as follows, S2-1: Disperse boron nitride in an ethanol solution with a mass fraction of 55%, add silane coupling agent KH550, the mass ratio of silane coupling agent KH550 to boron nitride is 1:9, stir at 80 ℃ for 6 h, wash with deionized water and dry at 60 ℃ for 12 h to obtain powder C; S2-2: Diethyl phosphoacetic acid and powder C were mixed in a molar ratio of 6:1, added to a MES buffer with a pH of 5.5, followed by the addition of EDC and NHS, the molar ratio of diethyl phosphoacetic acid, EDC and NHS being 2:2:1.5, stirred at 50°C for 5 h, washed with deionized water and dried at 60°C for 12 h to obtain the modified boron nitride.

[0024] A preparation method of a flame-retardant modified metallized film for capacitors, the specific steps of the preparation method are as follows, S8-1: According to the formula proportion, terephthalic acid, ethylene glycol, cyclobutane-1,3-dicarboxylic acid, antimony trioxide and stabilizer were added into the reaction kettle, nitrogen was introduced and the temperature was raised to 220°C, the pressure was 0.4 MPa; S8-2: Then, the composite flame retardant, 4-dimethylaminopyridine and cage polysilsesquioxane were added into the reaction kettle, stirred for 8 min, the temperature was raised to 240°C, stirred for 35 min, the temperature was further raised to 268°C, and stirred for 5 h to obtain the modified polyester material; S8-3: The modified polyester material was extruded through the flat die of the extruder at 235°C to form a sheet with a thickness of 100 μm, then the sheet was heated to 90°C and stretched longitudinally at a stretching ratio of 1:4, and then stretched transversely at 110°C at a stretching ratio of 1:3.5 to obtain a biaxially stretched film; S8-4: The film was heat set for 8 s at a temperature of 190°C, and then annealed at 115°C for 45 min to obtain the flame-retardant modified metallized film for capacitors.

[0025] Example 2

[0026] A flame-retardant modified metallized film for capacitors, the metallized film comprises the following components by weight: terephthalic acid 50 parts, ethylene glycol 30 parts, cyclobutane-1,3-dicarboxylic acid 5 parts, antimony trioxide 0.5 parts, triphenyl phosphite 0.5 parts, composite flame retardant 4 parts, 4-dimethylaminopyridine 0.1 parts, cage polysilsesquioxane 0.1 parts; The preparation method of the composite flame retardant is as follows, S1-1: Magnesium nitrate and aluminum nitrate were dissolved in deionized water in a molar ratio of 2:1, urea was added, the total molar ratio of urea to metal salt was 1:1, stirred at 90°C for 10 h, washed with deionized water and vacuum dried at 60°C for 10 h to obtain powder A; S1-2: Powder A was dispersed in an aqueous solution containing 10% ammonium polyphosphate by mass fraction, ultrasonic treated at 45°C for 4 h, washed with deionized water and dried at 60°C for 10 h to obtain powder B; S1-3: mixing powder B with modified boron nitride at a mass ratio of 2:1, adding 1% of silane coupling agent KH550 by mass of powder B, ball milling for 1 h at a ball milling speed of 200 rpm, and vacuum drying at 60°C for 10 h to obtain the composite flame retardant.

[0027] The preparation method of the modified boron nitride in S1-3 is as follows, S2-1: dispersing boron nitride in an ethanol solution with a mass fraction of 50%, adding silane coupling agent KH550, the mass ratio of silane coupling agent KH550 to boron nitride being 1:8, stirring at 80°C for 6 h, washing with deionized water, and drying at 60°C for 10 h to obtain powder C; S2-2: mixing diethyl phosphoacetic acid with powder C at a molar ratio of 5:1, adding to a MES buffer solution with a pH of 5, then adding EDC and NHS, the molar ratio of diethyl phosphoacetic acid, EDC and NHS being 2:2:1, stirring at 45°C for 4 h, washing with deionized water, and drying at 60°C for 10 h to obtain modified boron nitride.

[0028] A preparation method of a flame-retardant modified metallized film for capacitors, the specific steps of the preparation method being as follows, S8-1: adding terephthalic acid, ethylene glycol, cyclobutane-1,3-dicarboxylic acid, antimony trioxide and stabilizer into a reaction kettle according to the formula ratio, introducing nitrogen and heating to 210°C, the pressure being 0.3 MPa; S8-2: then adding the composite flame retardant, 4-dimethylaminopyridine and cage polysilsesquioxane into the reaction kettle, stirring for 5 min, heating to 230°C, stirring for 30 min, further heating to 265°C, and continuing to stir for 4 h to obtain a modified polyester material; S8-3: extruding the modified polyester material through a flat die of an extruder at 230°C to form a sheet with a thickness of 80 μm, then performing bidirectional stretching treatment, heating the sheet to 80°C, performing longitudinal stretching at a stretching ratio of 1:3, and then performing transverse stretching at 100°C at a stretching ratio of 1:3 to obtain a bidirectional stretched film; S8-4: heat setting the film, the heat setting time being 5 s and the temperature being 180°C, then annealing at 110°C for 30 min to obtain the flame-retardant modified metallized film for capacitors.

[0029] Example 3

[0030] A flame-retardant modified metallized film for capacitors, the metallized film comprising the following components, in parts by weight, terephthalic acid 60 parts, ethylene glycol 40 parts, cyclobutane-1,3-dicarboxylic acid 10 parts, antimony trioxide 1 part, triphenyl phosphite 1 part, composite flame retardant 6 parts, 4-dimethylamino pyridine 0.3 parts, cage polysilsesquioxane 0.2 parts; The preparation method of the composite flame retardant is as follows, S1-1: Dissolve magnesium nitrate and aluminum nitrate in deionized water at a molar ratio of 2:1, add urea, the total molar ratio of urea to metal salt is 3:1, stir at 95 ℃ for 12 h, wash with deionized water and vacuum dry at 60 ℃ for 14 h to obtain powder A; S1-2: Disperse powder A in an aqueous solution containing 20% by mass of ammonium polyphosphate, ultrasonic treatment at 55 ℃ for 6 h, wash with deionized water and dry at 60 ℃ for 14 h to obtain powder B; S1-3: Mix powder B with modified boron nitride at a mass ratio of 4:1, add 3% of silane coupling agent KH550 based on the mass of powder B, ball mill for 2 h at a speed of 300 rpm, and then vacuum dry at 60 ℃ for 14 h to obtain the composite flame retardant.

[0031] The preparation method of the modified boron nitride in S1-3 is as follows, S2-1: Disperse boron nitride in an ethanol solution with a mass fraction of 60%, add silane coupling agent KH550, the mass ratio of silane coupling agent KH550 to boron nitride is 1:10, stir at 80 ℃ for 6 h, wash with deionized water and dry at 60 ℃ for 14 h to obtain powder C; S2-2: Mix diethyl phosphoacetic acid with powder C at a molar ratio of 7:1, add to a MES buffer solution with a pH of 6, then add EDC and NHS, the molar ratio of diethyl phosphoacetic acid, EDC and NHS is 1:1:1, stir at 55 ℃ for 6 h, wash with deionized water and dry at 60 ℃ for 14 h to obtain modified boron nitride.

[0032] A preparation method of a flame-retardant modified metallized film for capacitors, the specific steps of the preparation method are as follows, S8-1: Add terephthalic acid, ethylene glycol, cyclobutane-1,3-dicarboxylic acid, antimony trioxide and stabilizer into a reaction kettle according to the formula ratio, introduce nitrogen and heat to 230 ℃, pressure 0.5 MPa; S8-2: Then add composite flame retardant, 4-dimethylamino pyridine and cage polysilsesquioxane into the reaction kettle, stir for 10 min, then heat to 250 ℃, stir for 40 min, further heat to 270 ℃, continue to stir for 6 h to obtain a modified polyester material; S8-3: The modified polyester material was extruded through a flat die of an extruder at 240℃ to form a sheet with a thickness of 120 μm, and then a biaxial stretching treatment was performed, the sheet was heated to 100℃, and longitudinal stretching was performed at a stretching ratio of 1:5, and then transverse stretching was performed at 120℃ at a stretching ratio of 1:4 to obtain a biaxially stretched film; S8-4: The film was heat set for 10 s at a temperature of 200℃, and then annealed at 120℃ for 60 min to obtain the flame-retardant modified metallized film for capacitors.

[0033] Comparative Example 1 The preparation of the composite flame retardant did not add ammonium polyphosphate, and the remaining steps were consistent with Example 1.

[0034] Comparative Example 2 The preparation of the composite flame retardant did not add modified boron nitride, and the remaining steps were consistent with Example 1.

[0035] Comparative Example 3 The boron nitride was not modified, and the remaining steps were consistent with Example 1.

[0036] Comparative Example 4 The preparation of the modified boron nitride did not add diethyl phosphoacetic acid, and the remaining steps were consistent with Example 1.

[0037] Comparative Example 5 The cage polysilsesquioxane was not added, and the remaining steps were consistent with Example 1.

[0038] Comparative Example 6 The composite flame retardant was not added, and the remaining steps were consistent with Example 1.

[0039] Flame Retardant Performance Test According to the GB / T 2406.2-2009 standard, the limiting oxygen index of the film prepared in the examples and comparative examples was determined using an oxygen index instrument, each group of samples was tested 3 times, and the average value was taken, and the experimental data is recorded in the following table;

[0040] As can be seen from the data of the examples and comparative examples, the metallized film prepared by the present application has excellent flame retardant performance.

[0041] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A flame retardant modified metallized film for capacitors, characterized in that: The metallized film comprises the following components, in parts by weight: 50-60 parts of terephthalic acid, 30-40 parts of ethylene glycol, 5-10 parts of cyclobutane-1,3-dicarboxylic acid, 0.5-1 part of antimony trioxide, 0.5-1 part of stabilizer, 4-6 parts of composite flame retardant, 0.1-0.3 parts of 4-dimethylaminopyridine, and 0.1-0.2 parts of cage-type polysilsesquioxane; The preparation method of the composite flame retardant is as follows: S1-1: Dissolve magnesium nitrate and aluminum nitrate in deionized water at a molar ratio of 2:1, add urea, stir at 90-95°C for 10-12 h, wash with deionized water, and vacuum dry at 60°C for 10-14 h to obtain powder A; S1-2: Powder A was dispersed in an aqueous solution containing 10-20% by mass of ammonium polyphosphate, ultrasonically treated at 45-55°C for 4-6 h, washed with deionized water, and dried at 60°C for 10-14 h to obtain powder B. S1-3: Powder B and modified boron nitride were mixed, 1 to 3% by weight of powder B as a silane coupling agent KH550 was added, ball milling was performed for 1 to 2 hours at a ball milling speed of 200 to 300 rpm, and vacuum drying was performed at 60°C for 10 to 14 hours to obtain the composite flame retardant.

2. The flame retardant modified metallized film for capacitors according to claim 1, characterized in that: The preparation method of the modified boron nitride in S1-3 is as follows: S2-1: Boron nitride was dispersed in a 50-60% by mass ethanol solution, silane coupling agent KH550 was added, and the mixture was stirred at 80°C for 6 h. The mixture was washed with deionized water and dried at 60°C for 10-14 h to obtain powder C. S2-2: Diethylphosphoacetic acid and powder C were mixed in a molar ratio of (5-7):1, added to MES buffer with a pH of 5-6, and then EDC and NHS were added. The mixture was stirred at 45-55°C for 4-6 hours, washed with deionized water, and dried at 60°C for 10-14 hours to obtain modified boron nitride.

3. The flame retardant modified metallized film for capacitors according to claim 1, characterized in that: The stabilizer is triphenyl phosphite.

4. The flame retardant modified metallized film for capacitors according to claim 1, characterized in that: The total molar ratio of urea to metal salt in S1-1 is (1-3):

1.

5. The flame retardant modified metallized film for capacitors according to claim 1, characterized in that: The powder B in S1-3 is mixed with modified boron nitride in a mass ratio of (2-4):

1.

6. The flame retardant modified metallized film for capacitors according to claim 2, characterized in that: The mass ratio of the silane coupling agent KH550 to the boron nitride in the S2-1 is 1:(8-10).

7. The flame retardant modified metallized film for capacitors according to claim 2, characterized in that: The molar ratio of the diethylphosphoacetic acid, EDC and NHS is 2:2:(1-2).

8. A method for preparing a flame-retardant modified metallized film for capacitors according to any one of claims 1 to 7, characterized in that: The specific steps of the preparation method are as follows: S8-1: Add terephthalic acid, ethylene glycol, cyclobutane-1,3-dicarboxylic acid, antimony trioxide, and stabilizer into a reactor according to the formula ratio, introduce nitrogen, and raise the temperature to 210-230°C and the pressure to 0.3-0.5 MPa; S8-2: Then, the composite flame retardant, 4-dimethylaminopyridine and cage-type polysilsesquioxane were added to the reactor, stirred for 5 to 10 minutes, then heated to 230 to 250°C, stirred for 30 to 40 minutes, further heated to 265 to 270°C, and stirred for 4 to 6 hours to obtain a modified polyester material; S8-3: Extruding the modified polyester material through a flat die of an extruder at 230-240° C. to form a sheet having a thickness of 80-120 μm, and then biaxially stretching the sheet to obtain a biaxially stretched film; S8-4: heat-setting the film, and then annealing it at 110-120° C. for 30-60 min to obtain the flame-retardant modified metallized film for capacitors.

9. The method for preparing a flame-retardant modified metallized film for capacitors according to claim 8, characterized in that: The biaxial stretching treatment step in S8-3 is to heat the sheet to 80-100°C, stretch it longitudinally at a stretching ratio of 1:(3-5), and then stretch it transversely at 100-120°C at a stretching ratio of 1:(3-4).

10. The method for preparing a flame-retardant modified metallized film for capacitors according to claim 8, characterized in that: The heat setting time in S8-4 is 5 to 10 seconds, and the temperature is 180 to 200°C.

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