Polyester film for heat-resistant capacitor, preparation method and film capacitor

Abstract

The invention discloses a heat-resistant polyester film for a capacitor, a preparation method and a film capacitor, and belongs to the technical field of capacitor films, the heat-resistant polyester film comprises the following raw materials by weight: 50-70 parts of PET resin, 4-8 parts of a heat-resistant filler, 2-10 parts of a lubricant, and 1-5 parts of an antioxidant; the preparation method comprises the following steps: uniformly mixing the raw materials at 240-260 DEG C to prepare a mixture, then extruding through a mold, and casting into a membrane to prepare the heat-resistant polyester film for the capacitor. According to the polyester filler, mica powder is used as a matrix, and an intermediate structure capable of improving the heat resistance of the matrix and 4, 4 '-biphenyl are introduced; the polyester film has the advantages that the polyester film is prepared from mica powder, an intermediate and 4, 4 '-diphenyldicarboxylic acid, ternary synergistic interaction of the mica powder, the intermediate and the 4, 4'-diphenyldicarboxylic acid is achieved, the polyester film is endowed with excellent heat resistance, the use performance of the polyester film is improved, a structure similar to matrix PET resin can be formed through copolymerization on the surface of the mica powder, and the compatibility of the heat-resistant filler and a matrix is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor films, and in particular to a polyester film for heat-resistant capacitors, a preparation method and a film capacitor. Background Art

[0002] When polyester film is used as a dielectric for capacitors, it is usually made into a small shape, so it is wound together with metal foil or made into a metalized film with a metal layer pre-set on the surface of the polyester film and then wound, or it is made into a component by a lamination method, and then stamped, electrode processed, resin sealed, and encapsulated. In order to stabilize the electrical properties (mainly electrostatic capacitance), it is generally heat treated at a certain temperature.

[0003] Thus, when polyester film is used as a dielectric of a capacitor, it is subjected to various thermal and mechanical stresses until the capacitor is manufactured. As a result, the manufactured capacitor sometimes has lower characteristics than the expected capacitor in terms of insulation resistance and insulation breakdown voltage as a polyester film blank. In addition, if the performance of the polyester film itself is poor, it is inevitable that the capacitor characteristics will be reduced. Furthermore, the manufactured capacitor is actually assembled on a machine. Considering the safety of the machine, it will become a major problem if the function is reduced or damaged (short charged life) in the use environment.

[0004] In the past, the glass transition temperature of polyester film was around 120°C. When capacitors used this polyester film as a dielectric, the insulation breakdown voltage dropped significantly at temperatures above 120°C, which could easily cause damage to the capacitor. Therefore, in terms of the basic performance of the film, the operating temperature range was limited to below 120°C. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a polyester film for a heat-resistant capacitor, a preparation method and a film capacitor.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A polyester film for heat-resistant capacitors comprises the following raw materials in parts by weight: 50-70 parts of PET resin, 4-8 parts of heat-resistant filler, 2-10 parts of lubricant, and 1-5 parts of antioxidant; The heat-resistant filler is prepared by the following steps: Step S1, adding modified mica powder to N,N-dimethylformamide, stirring at a uniform speed and heating to 40-45° C., introducing nitrogen to expel air, adding diethanolamine and reacting for 24 hours while stirring, and obtaining modified mica powder after the reaction is completed; In step S1, the carbon-carbon double bonds on the modified mica powder react with the amino groups on the diethanolamine, and then the diol is connected to the surface of the mica powder to obtain the modified mica powder; Step S2, adding bisphenol A to N,N-dimethylformamide, adding TPP catalyst, stirring at a uniform speed and heating to 50-60° C., adding ethylene oxide, keeping warm and reacting for 1 hour, and after the reaction is completed, heating to 65-75° C., keeping warm and continuing to react for 3-4 hours, and obtaining an intermediate after the reaction is completed; In step S2, bisphenol A reacts with ethylene oxide under the catalytic action of a TPP catalyst to prepare an intermediate, which is a diol containing a diphenylpropane structure. The diphenylpropane structure can impart excellent heat resistance to the matrix.

[0007] Step S3, adding terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid into a polymerization kettle, adding a catalyst, heating to 240°C, keeping the temperature for reaction for 2 hours, then heating to 250°C, and continuing the reaction for 1 hour to obtain a heat-resistant filler.

[0008] In step S3, terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid are used as raw materials, and a polyester filler is prepared through an esterification copolymerization reaction under the action of a composite catalyst. The polyester filler uses mica powder as a matrix, and introduces an intermediate structure and 4,4'-biphenyl dicarboxylic acid that can improve the heat resistance of the matrix, thereby achieving a ternary synergistic effect of mica powder / intermediate / 4,4'-biphenyl dicarboxylic acid, and giving the polyester film excellent heat resistance.

[0009] Furthermore, the lubricant is montan wax-E wax or montan wax-OP wax.

[0010] Furthermore, the antioxidant is antioxidant 168 or antioxidant 1010.

[0011] Furthermore, the modified mica powder in step S1 is mica powder grafted and modified with silane coupling agent KH570.

[0012] Furthermore, in step S1, the dosage ratio of the modified mica powder, diethanolamine and N,N-dimethylformamide is controlled to be 2-4 g: 0.5-1 g: 10-15 mL.

[0013] Furthermore, in step S2, the dosage ratio of bisphenol A, ethylene oxide and N,N-dimethylformamide is controlled to be 1-1.5mmol:2-2.5mmol:10-15mL, and the dosage of TPP catalyst is 3-5% of the weight of bisphenol A.

[0014] Furthermore, in step S3, the dosage ratio of terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyldicarboxylic acid is controlled to be 2-4 g: 1-2 mmol: 3-5 mmol: 2-2.4 mmol, and the dosage of the catalyst is 10-12% of the weight of terephthalic acid.

[0015] Furthermore, the catalyst in step S3 is a mixture of antimony ethylene glycol and anhydrous sodium acetate in a weight ratio of 1:1.

[0016] A method for preparing a heat-resistant polyester film for a capacitor comprises the following steps: The raw materials are mixed uniformly at 240-260° C. to obtain a mixture, which is then extruded through a die and cast into a film to obtain a heat-resistant polyester film for capacitors.

[0017] A film capacitor comprises the above-mentioned heat-resistant polyester film for capacitors.

[0018] Beneficial effects of the present invention: The present invention prepares a polyester film for heat-resistant capacitors, using PET resin as a matrix, and adding a heat-resistant filler to significantly improve the heat resistance of the film. During the preparation process, the heat-resistant filler first reacts the carbon-carbon double bonds on the modified mica powder with the amino groups on the diethanolamine, and then connects the diol on the surface of the mica powder to obtain the modified mica powder. Then, bisphenol A reacts with ethylene oxide under the catalytic action of the TPP catalyst to prepare an intermediate, which is a diol containing a diphenylpropane structure. The diphenylpropane structure can give the matrix excellent heat resistance. Finally, the terephthalate is used as the intermediate. Acid, modified mica powder, intermediate and 4,4'-biphenyldicarboxylic acid are used as raw materials, and a polyester filler is prepared through esterification copolymerization reaction under the action of a composite catalyst. The polyester filler uses mica powder as a matrix, and introduces an intermediate structure and 4,4'-biphenyldicarboxylic acid that can improve the heat resistance of the matrix, thereby achieving ternary synergistic enhancement of mica powder / intermediate / 4,4'-biphenyldicarboxylic acid, giving the polyester film excellent heat resistance, and improving the performance of the polyester film. In addition, through copolymerization on the surface of mica powder, a structure similar to the matrix PET resin can be formed, thereby improving the compatibility of the heat-resistant filler and the matrix. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0020] Example 1: A polyester film for heat-resistant capacitors comprises the following raw materials in parts by weight: 50 parts of PET resin, 4 parts of heat-resistant filler, 2 parts of lubricant, and 1 part of antioxidant; A method for preparing a heat-resistant polyester film for a capacitor comprises the following steps: The raw materials were mixed uniformly at 240° C. to obtain a mixed material, which was then extruded through a die and cast into a film to obtain a heat-resistant polyester film for capacitors.

[0021] The heat-resistant filler is prepared by the following steps: Step S1, adding modified mica powder to N,N-dimethylformamide, stirring at a uniform speed and heating to 40°C, introducing nitrogen to expel air, adding diethanolamine and reacting for 24 hours while stirring, and obtaining modified mica powder after the reaction is completed, wherein the amount ratio of modified mica powder, diethanolamine and N,N-dimethylformamide is controlled to be 2g:0.5g:10mL; The modified mica powder is mica powder grafted and modified by silane coupling agent KH570.

[0022] Step S2, adding bisphenol A to N, N-dimethylformamide, adding TPP catalyst, stirring at a uniform speed and heating to 50° C., adding ethylene oxide, keeping warm and reacting for 1 hour, and after the reaction is completed, heating to 65-75° C., keeping warm and continuing to react for 3 hours, and obtaining an intermediate after the reaction is completed, controlling the dosage ratio of bisphenol A, ethylene oxide and N, N-dimethylformamide to be 1 mmol: 2 mmol: 10 mL, and the dosage of TPP catalyst to be 3% of the weight of bisphenol A; Step S3, adding terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid into a polymerization kettle, adding a catalyst, heating to 240°C, keeping the temperature for reaction for 2 hours, then heating to 250°C, and continuing the reaction for 1 hour to obtain a heat-resistant filler, wherein the dosage ratio of terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid is controlled to be 2g:1mmol:3mmol:2mmol, and the dosage of the catalyst is 10% of the weight of terephthalic acid.

[0023] The catalyst is prepared by mixing antimony ethylene glycol and anhydrous sodium acetate in a weight ratio of 1:1.

[0024] The lubricant is montan wax-E wax.

[0025] The antioxidant is antioxidant 168.

[0026] A film capacitor comprises the above-mentioned heat-resistant polyester film for capacitors.

[0027] Example 2: A polyester film for heat-resistant capacitors, comprising the following raw materials in parts by weight: 60 parts of PET resin, 5 parts of heat-resistant filler, 6 parts of lubricant, and 3 parts of antioxidant; A method for preparing a heat-resistant polyester film for a capacitor comprises the following steps: The raw materials were mixed uniformly at 250° C. to obtain a mixed material, which was then extruded through a die and cast into a film to obtain a heat-resistant polyester film for capacitors.

[0028] The heat-resistant filler is prepared by the following steps: Step S1, adding modified mica powder to N,N-dimethylformamide, stirring at a uniform speed and heating to 42°C, introducing nitrogen to expel air, adding diethanolamine and reacting for 24 hours while stirring, and obtaining modified mica powder after the reaction is completed, wherein the amount ratio of modified mica powder, diethanolamine and N,N-dimethylformamide is controlled to be 3g:0.8g:14mL; The modified mica powder is mica powder grafted and modified by silane coupling agent KH570.

[0029] Step S2, adding bisphenol A to N,N-dimethylformamide, adding TPP catalyst, stirring at a uniform speed and heating to 55°C, adding ethylene oxide, keeping warm and reacting for 1 hour, and after the reaction is completed, heating to 65-75°C, keeping warm and continuing to react for 3 hours, and obtaining an intermediate after the reaction is completed, controlling the dosage ratio of bisphenol A, ethylene oxide and N,N-dimethylformamide to be 1.2mmol:2.2mmol:10mL, and the dosage of TPP catalyst to be 4% of the weight of bisphenol A; Step S3, adding terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid into a polymerization kettle, adding a catalyst, heating to 240°C, keeping the temperature for reaction for 2 hours, then heating to 250°C, and continuing the reaction for 1 hour to obtain a heat-resistant filler, wherein the amount ratio of terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid is controlled to be 3g:1.5mmol:4mmol:2.2mmol, and the amount of the catalyst is 10% of the weight of terephthalic acid.

[0030] The catalyst is prepared by mixing antimony ethylene glycol and anhydrous sodium acetate in a weight ratio of 1:1.

[0031] The lubricant is montan wax-OP wax.

[0032] The antioxidant is antioxidant 1010.

[0033] A film capacitor comprises the above-mentioned heat-resistant polyester film for capacitors.

[0034] Example 3: A polyester film for heat-resistant capacitors, comprising the following raw materials in parts by weight: 70 parts of PET resin, 8 parts of heat-resistant filler, 10 parts of lubricant, and 5 parts of antioxidant; A method for preparing a heat-resistant polyester film for a capacitor comprises the following steps: The raw materials were mixed uniformly at 260° C. to obtain a mixed material, which was then extruded through a die and cast into a film to obtain a heat-resistant polyester film for capacitors.

[0035] The heat-resistant filler is prepared by the following steps: Step S1, adding modified mica powder to N,N-dimethylformamide, stirring at a uniform speed and heating to 45°C, introducing nitrogen to expel air, adding diethanolamine and reacting for 24 hours while stirring, and obtaining modified mica powder after the reaction is completed, wherein the amount ratio of modified mica powder, diethanolamine and N,N-dimethylformamide is controlled to be 4g:1g:15mL; The modified mica powder is mica powder grafted and modified by silane coupling agent KH570.

[0036] Step S2, adding bisphenol A to N,N-dimethylformamide, adding TPP catalyst, stirring at a uniform speed and heating to 60°C, adding ethylene oxide, keeping warm and reacting for 1 hour, and after the reaction is completed, heating to 65-75°C, keeping warm and continuing to react for 4 hours, and obtaining an intermediate after the reaction is completed, controlling the dosage ratio of bisphenol A, ethylene oxide and N,N-dimethylformamide to be 1.5mmol:2.5mmol:15mL, and the dosage of TPP catalyst to be 5% of the weight of bisphenol A; Step S3, adding terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid into a polymerization kettle, adding a catalyst, heating to 240°C, keeping the temperature for reaction for 2 hours, then heating to 250°C, and continuing the reaction for 1 hour to obtain a heat-resistant filler, wherein the amount ratio of terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid is controlled to be 4g:2mmol:5mmol:2.4mmol, and the amount of the catalyst is 12% of the weight of terephthalic acid.

[0037] The catalyst is prepared by mixing antimony ethylene glycol and anhydrous sodium acetate in a weight ratio of 1:1.

[0038] The lubricant is montan wax-E wax.

[0039] The antioxidant is antioxidant 1010.

[0040] A film capacitor comprises the above-mentioned heat-resistant polyester film for capacitors.

[0041] Comparative Example 1: Compared with Example 1, this comparative example uses commercially available mica powder instead of the heat-resistant filler, and the rest is the same as Example 1.

[0042] The properties of the polyester films (thickness 2.5 μm) prepared in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in Table 1 below: Tensile strength: Tested according to ASTMD882 test standard: Softening temperature: Using the heat deformation temperature test method, the PET film sample is placed in a heat deformation temperature tester, a load of 0.45 MPa is applied, and heating is performed at a heating rate of 2°C / min, and the temperature when the sample reaches a deformation of 0.25 mm is recorded.

[0043] Table 1 It can be seen from Table 1 above that the polyester films prepared in Examples 1-3 of the present invention have good mechanical properties and heat resistance.

[0044] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A heat-resistant polyester film for capacitors, characterized in that: The raw materials include the following parts by weight: 50-70 parts of PET resin, 4-8 parts of heat-resistant filler, 2-10 parts of lubricant, and 1-5 parts of antioxidant; The heat-resistant filler is prepared by the following steps: Step S1, adding modified mica powder to N,N-dimethylformamide, stirring at a uniform speed and heating to 40-45° C., introducing nitrogen to expel air, adding diethanolamine and reacting for 24 hours while stirring, and obtaining modified mica powder after the reaction is completed; Step S2, adding bisphenol A to N,N-dimethylformamide, adding TPP catalyst, stirring at a uniform speed and heating to 50-60° C., adding ethylene oxide, keeping warm and reacting for 1 hour, and after the reaction is completed, heating to 65-75° C., keeping warm and continuing to react for 3-4 hours, and obtaining an intermediate after the reaction is completed; Step S3, adding terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyl dicarboxylic acid into a polymerization kettle, adding a catalyst, heating to 240°C, keeping the temperature for reaction for 2 hours, then heating to 250°C, and continuing the reaction for 1 hour to obtain a heat-resistant filler.

2. The heat-resistant polyester film for capacitors according to claim 1, wherein The lubricant is montan wax-E wax or montan wax-OP wax.

3. The heat-resistant polyester film for capacitors according to claim 1, wherein The antioxidant is antioxidant 168 or antioxidant 1010.

4. The heat-resistant polyester film for capacitors according to claim 1, wherein: The modified mica powder in step S1 is mica powder grafted and modified by silane coupling agent KH570.

5. The heat-resistant polyester film for capacitors according to claim 1, wherein In step S1, the dosage ratio of the modified mica powder, diethanolamine and N,N-dimethylformamide is controlled to be 2-4 g: 0.5-1 g: 10-15 mL.

6. The heat-resistant polyester film for capacitors according to claim 1, wherein In step S2, the dosage ratio of bisphenol A, ethylene oxide and N,N-dimethylformamide is controlled to be 1-1.5 mmol: 2-2.5 mmol: 10-15 mL, and the dosage of TPP catalyst is 3-5% of the weight of bisphenol A.

7. The heat-resistant polyester film for capacitors according to claim 1, wherein: In step S3, the dosage ratio of terephthalic acid, modified mica powder, intermediate and 4,4'-biphenyldicarboxylic acid is controlled to be 2-4 g: 1-2 mmol: 3-5 mmol: 2-2.4 mmol, and the dosage of the catalyst is 10-12% of the weight of terephthalic acid.

8. The heat-resistant polyester film for capacitors according to claim 1, wherein The catalyst in step S3 is a mixture of antimony ethylene glycol and anhydrous sodium acetate in a weight ratio of 1:

1.

9. A method for preparing a heat-resistant polyester film for a capacitor according to claim 1, characterized in that: The steps include: The raw materials are mixed uniformly at 240-260° C. to obtain a mixture, which is then extruded through a die and cast into a film to obtain a heat-resistant polyester film for capacitors.

10. A film capacitor, characterized in that: A heat-resistant polyester film for capacitors comprising any one of claims 1 to 8.

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