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

Abstract

The invention relates to the technical field of polypropylene capacitance films and preparation methods thereof, in particular to a high-temperature-resistant polypropylene capacitance film and a preparation method thereof.The preparation method comprises the steps that a base film sheet comprising a first edge layer, a second edge layer and a heat-resistant layer is prepared through a three-layer co-extrusion extruder, and the heat-resistant layer is located between the first edge layer and the second edge layer; stretching the base film sheet to form a capacitance film base film; and plating a metal film on the surface of the capacitance film base film to obtain the capacitance film. According to the high-temperature-resistant polypropylene capacitor film prepared by the method, the heat-resistant layer can fundamentally improve the high-temperature-resistant performance of the base film of the capacitor film, so that the overall high-temperature-resistant performance of the capacitor film is improved, and the production is simple. Besides, metal ions and ash content are not introduced, the breakdown voltage of the capacitor film product is not reduced, the first edge layer and the second edge layer do not influence the processing performance of the high-temperature-resistant polypropylene capacitor film and the control of the surface roughness, and the subsequent process is not influenced.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene capacitor films and preparation methods thereof, in particular to high temperature resistant polypropylene capacitor films and preparation methods thereof. Background Art

[0002] Propylene (PP) capacitor film is a high-frequency dielectric insulating material with excellent electrical properties. It has many advantages such as thinness, roughness, low dielectric loss, stable dielectric constant, excellent moisture resistance, and low price, making it an important basic dielectric material in capacitor manufacturing. It is now widely used in national defense, electronics industry, national power grid construction, high-speed rail construction, and new energy electric vehicle manufacturing.

[0003] At present, the high temperature resistance of PP capacitor film in related technologies is relatively poor. Under 90°C and load conditions, it will soften and deform, causing the breakdown voltage to drop sharply, affecting the normal use of the capacitor. Summary of the invention

[0004] In view of this, the present application provides a method for preparing a high-temperature resistant polypropylene capacitor film and a high-temperature resistant polypropylene capacitor film, aiming to solve at least one of the technical problems existing in the prior art or related technology.

[0005] Specifically, the present application is implemented through the following technical solutions: According to the first aspect of the present application, a method for preparing a high-temperature resistant polypropylene capacitor film is provided, the preparation method comprising: using a three-layer co-extrusion extruder to prepare a base film sheet comprising a first side layer, a second side layer and a heat-resistant layer, the heat-resistant layer being located between the first side layer and the second side layer; stretching the base film sheet to form a capacitor film base film; and plating a metal film on the surface of the capacitor film base film to obtain a high-temperature resistant polypropylene capacitor film.

[0006] The present application provides a method for preparing a high-temperature resistant polypropylene capacitor film, which adopts a three-layer co-extrusion extruder to prepare a base film sheet including a first side layer, a second side layer and a heat-resistant layer, wherein the heat-resistant layer is located between the first side layer and the second side layer. That is to say, the base film sheet is extruded by a three-layer co-extrusion method, the base film sheet is stretched to form a capacitor film base film, and a metal film is plated on the surface of the capacitor film base film, thereby preparing a high-temperature resistant polypropylene capacitor film.

[0007] The heat-resistant polypropylene capacitor film prepared by the above method has a heat-resistant layer that can fundamentally improve the high-temperature resistance of the capacitor film base film, thereby improving the overall high-temperature resistance of the capacitor film, which is beneficial for the use of the high-temperature resistant polypropylene capacitor film in a higher temperature environment. Compared with the related technology that requires overheating during the preparation of the capacitor film, it can shorten the production cycle, improve production efficiency, and simplify production.

[0008] In addition, compared with the related art of adding other raw materials to the polypropylene resin for blending, the above-mentioned preparation method does not introduce metal ions and ash content, and thus will not reduce the breakdown voltage of the capacitor film product. The first side layer and the second side layer will not affect the processing performance and surface roughness control of the high temperature resistant polypropylene capacitor film, and will not affect subsequent processes.

[0009] In some embodiments, a three-layer co-extrusion extruder includes a first hopper, a second hopper, a third hopper and an extrusion end, and a three-layer co-extrusion extruder is used to prepare a base film sheet including a first side layer, a second side layer and a heat-resistant layer, specifically including: adding a special polypropylene material into the first hopper and the second hopper respectively to obtain a first side layer and a second side layer; mixing the special polypropylene material with an additive and adding the mixture into the third hopper to obtain a heat-resistant layer; and the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end to form a base film sheet.

[0010] In some embodiments, the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end to form a base film sheet, specifically including: the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end and cooled at a first preset temperature to form a base film sheet.

[0011] In some embodiments, the first preset temperature is 90°C to 100°C.

[0012] In some embodiments, the additive is an aryl dicarboxamide or a derivative thereof.

[0013] In some embodiments, the special polypropylene material is a polypropylene with a melt index of 2.5 g / 10 min to 3.5 g / 10 min, an isotactic index of 98.0% to 98.5%, an ash content of ≤0.003%, and a molecular weight distribution of 4 to 6.

[0014] In some embodiments, when preparing the heat-resistant layer, the ratio of the amount of the polypropylene special material to the amount of the additive is 100: (0.1 to 0.2).

[0015] In some embodiments, the heating temperature of the three-layer coextrusion extruder is 225°C to 245°C.

[0016] In some embodiments, the base film is stretched, specifically including: longitudinally stretching the base film at a second preset temperature and a first preset ratio; transversely stretching the base film at a third preset temperature and a second preset ratio; wherein the longitudinal stretching and transverse stretching are performed simultaneously, or the base film is first longitudinally stretched and then transversely stretched.

[0017] In some embodiments, the second preset temperature is 125°C to 145°C.

[0018] In some embodiments, the first preset magnification is 4 to 5.

[0019] In some embodiments, the third preset temperature is 155°C to 175°C.

[0020] In some embodiments, the second preset magnification is 9 to 10.

[0021] In some embodiments, stretching the base film to form a capacitive film base film further includes: cooling the base film at a fourth preset temperature after stretching the base film to form a capacitive film base film.

[0022] In some embodiments, the fourth preset temperature is 25°C to 35°C.

[0023] In some embodiments, the metal film includes an aluminum film or a zinc film.

[0024] According to the second aspect of the present application, the present application provides a high temperature resistant polypropylene capacitor film, which is prepared by the preparation method of the high temperature resistant polypropylene capacitor film provided by any of the above technical solutions.

[0025] In some embodiments, a high temperature resistant polypropylene capacitor film base film comprises: a first side layer and a second side layer; a heat resistant layer located between the first side layer and the second side layer and connected to the first side layer and the second side layer.

[0026] In some embodiments, the thickness of the first side layer is the same as the thickness of the second side layer; the ratio of the thickness of the first side layer or the thickness of the second side layer to the thickness of the heat-resistant layer is (1 to 2): (6 to 8).

[0027] In some embodiments, a three-layer co-extrusion method is used to form a base film including a first side layer, a second side layer and a heat-resistant layer.

[0028] The technical solution provided by this application brings at least the following beneficial effects: The heat-resistant polypropylene capacitor film prepared by the above method has a heat-resistant layer that can fundamentally improve the high-temperature resistance of the capacitor film base film, thereby improving the overall high-temperature resistance of the capacitor film, which is beneficial for the use of the high-temperature polypropylene capacitor film in a higher temperature environment, and compared with the need for overheating during the preparation of the capacitor film in the related art, it can shorten the production cycle, improve production efficiency, and simplify production. In addition, compared with the related art of adding other raw materials to the polypropylene resin for blending, the above preparation method does not introduce metal ions and ash content, so it will not reduce the breakdown voltage of the capacitor film product, and the first side layer and the second side layer will not affect the processing performance and surface roughness control of the high-temperature resistant polypropylene capacitor film, and will not affect the subsequent process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0031] Figure 1 A flow chart showing a method for preparing a high temperature resistant polypropylene capacitor film according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] The present invention is not limited by the following embodiments, and specific implementation methods can be determined according to the technical scheme of the present invention and actual conditions. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art.

[0034] As attached Figure 1 The present invention provides a method for preparing a high temperature resistant polypropylene capacitor film, the method comprising the following steps: S102, using a three-layer co-extrusion extruder to prepare a base film including a first side layer, a second side layer and a heat-resistant layer, wherein the heat-resistant layer is located between the first side layer and the second side layer; S104, stretching the base film to form a capacitor film base film; S106, coating a metal film on the surface of the capacitor film base film to obtain a capacitor film.

[0035] Capacitor films are divided into two categories: metallized films (MPP) and roughened films (RPP). Metallized films account for the vast majority, and are also called electronic films. The production of PP metallized films is to first make the melt of high molecular weight PP into sheets or thick films through a narrow and long die, and then stretch it in two vertical directions (longitudinal and transverse) at a certain temperature and set speed in a special stretching machine at the same time or in steps, and after appropriate cooling, form a PP metallized base film. In order to facilitate later processing, the surface of the base film needs to be controlled to have a certain degree of roughness (mainly to control the β-crystal content on the surface of the base film. Due to its instability, certain grooves are formed during the transformation to the α-crystal). In the later stage of the process, the base film is subjected to corona treatment and a layer of metal film such as aluminum, zinc, etc. is plated on the surface of the film.

[0036] At present, the high temperature resistance of PP capacitor film is poor. Under 90℃ and load conditions, it will soften and deform, causing the breakdown voltage to drop sharply, affecting the normal use of the capacitor. During the use of capacitors, not only should the internal heating of the capacitor components be suppressed, but also the ambient temperature should be considered. With the widespread application of compensation capacitors for lamps (operating temperature 90℃ to 120℃), induction cooker capacitors (operating temperature 85℃ to 120℃), high-frequency furnace capacitors (operating temperature around 100℃) and other special capacitors such as locomotive capacitors, it is urgent to increase the operating temperature of polypropylene film capacitors.

[0037] In order to improve the high temperature resistance of the capacitor film in the related technology, one is to adjust the process parameters. For example, the polypropylene raw material is placed in an extruder, heated at 200°C to 220°C for 1 hour to 3 hours, and then extruded to form a melt, cooled at 75°C to 90°C, and heated at 125°C to 145°C for 8 to 12 minutes during transverse and longitudinal stretching. This method requires the polypropylene raw material to be heated in the extruder for a long time, which leads to a longer production cycle, lower efficiency, and limited improvement in the high temperature resistance of the base film.

[0038] The second method is to add other raw materials to the polypropylene resin for blending. For example, isotactic polypropylene, polylactic acid, tung oil, sodium silicate, and tetrabutylammonium bromide are blended and heated to melt, and then additives and other components are added and fully stirred, and then sent to an extruder for melting and filtering, and then the sheet melt is extruded through an extruder, and then a high-temperature resistant and antioxidant metallized film is obtained after subsequent treatment. In this way, too much monomer is added, and there are certain problems in the dispersion between the components. At the same time, it will affect the crystallization order of polypropylene, reduce its crystallization performance, and is not conducive to the roughness control of the surface of the capacitor film product. In addition, the introduction of metal ion components will increase the ash content of the product, and while improving the high-temperature resistance, it may reduce the breakdown voltage of the capacitor film.

[0039] The present application provides a method for preparing a high-temperature resistant polypropylene capacitor film, which adopts a three-layer co-extrusion extruder to prepare a base film sheet including a first side layer, a second side layer and a heat-resistant layer, wherein the heat-resistant layer is located between the first side layer and the second side layer. That is to say, the base film sheet is extruded by a three-layer co-extrusion method, the base film sheet is stretched to form a capacitor film base film, and a metal film is plated on the surface of the capacitor film base film, thereby preparing a high-temperature resistant polypropylene capacitor film.

[0040] The heat-resistant polypropylene capacitor film prepared by the above method has a heat-resistant layer that can fundamentally improve the high-temperature resistance of the capacitor film base film, thereby improving the overall high-temperature resistance of the capacitor film, which is beneficial for the use of the high-temperature resistant polypropylene capacitor film in a higher temperature environment. Compared with the related technology that requires overheating during the preparation of the capacitor film, it can shorten the production cycle, improve production efficiency, and simplify production.

[0041] In addition, compared with the related art of adding other raw materials to the polypropylene resin for blending, the above-mentioned preparation method does not introduce metal ions and ash content, and thus will not reduce the breakdown voltage of the capacitor film product. The first side layer and the second side layer will not affect the processing performance and surface roughness control of the high temperature resistant polypropylene capacitor film, and will not affect subsequent processes.

[0042] In some embodiments, a three-layer co-extrusion extruder includes a first hopper, a second hopper, a third hopper and an extrusion end, and a three-layer co-extrusion extruder is used to prepare a base film sheet including a first side layer, a second side layer and a heat-resistant layer, specifically including: adding a special polypropylene material into the first hopper and the second hopper respectively to obtain a first side layer and a second side layer; mixing the special polypropylene material with an additive and adding the mixture into the third hopper to obtain a heat-resistant layer; and the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end to form a base film sheet.

[0043] In this embodiment, special polypropylene material is put into the first hopper and the second hopper, so that the upper and lower side layers of the prepared base membrane sheet, i.e., the first side layer and the second side layer, will not affect the processing performance and surface roughness control of the high temperature resistant polypropylene capacitor film, and will not affect the subsequent process.

[0044] After the additives are mixed into the special polypropylene material, the material is put into the third hopper to obtain a heat-resistant intermediate layer, i.e., a heat-resistant layer, which can fundamentally improve the high temperature resistance of the capacitor film base film, thereby improving the overall high temperature resistance of the capacitor film, which is beneficial to the use of the high temperature resistant polypropylene capacitor film in a higher temperature environment.

[0045] The base film is prepared by a three-layer co-extrusion method, that is, a base film having three layers (a first side layer, a second side layer and a heat-resistant layer) can be directly obtained by a three-layer co-extrusion extruder.

[0046] In some embodiments, the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end to form a base film sheet, specifically including: the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end and cooled at a first preset temperature to form a base film sheet.

[0047] In some embodiments, the first preset temperature is 90°C to 100°C.

[0048] In some embodiments, the additive is an aryl dicarboxamide or a derivative thereof.

[0049] In some embodiments, the special polypropylene material is a polypropylene with a melt index of 2.5 g / 10 min to 3.5 g / 10 min, an isotactic index of 98.0% to 98.5%, an ash content of ≤0.003%, and a molecular weight distribution of 4 to 6.

[0050] In some embodiments, when preparing the heat-resistant layer, the ratio of the amount of the polypropylene special material to the amount of the additive is 100: (0.1 to 0.2).

[0051] In this embodiment, the amount of the polypropylene special material is 100 parts, and the amount of the additive is 0.1 part to 0.2 part.

[0052] In some embodiments, the heating temperature of the three-layer coextrusion extruder is 225°C to 245°C.

[0053] In some embodiments, the base film is stretched, specifically including: longitudinally stretching the base film at a second preset temperature and a first preset ratio; transversely stretching the base film at a third preset temperature and a second preset ratio; wherein the longitudinal stretching and transverse stretching are performed simultaneously, or the base film is first longitudinally stretched and then transversely stretched.

[0054] In some embodiments, the second preset temperature is 125°C to 145°C.

[0055] In some embodiments, the first preset magnification is 4 to 5.

[0056] In some embodiments, the third preset temperature is 155°C to 175°C.

[0057] In some embodiments, the second preset magnification is 9 to 10.

[0058] In this embodiment, the base film is longitudinally stretched at a stretching temperature of 125° C. to 145° C. and a stretching ratio of 4 to 5, and transversely stretched at a stretching temperature of 155° C. to 175° C. and a stretching ratio of 9 to 10. It can be understood that the transverse and longitudinal directions are two mutually perpendicular directions, and the longitudinal stretching and the transverse stretching can be performed simultaneously or in steps, which can be specifically set according to actual needs.

[0059] In some embodiments, stretching the base film to form a capacitive film base film further includes: cooling the base film at a fourth preset temperature after stretching the base film to form a capacitive film base film.

[0060] In some embodiments, the fourth preset temperature is 25°C to 35°C.

[0061] In some embodiments, the metal film includes an aluminum film or a zinc film.

[0062] In this embodiment, the capacitive film base film is subjected to corona treatment and then a metal film is plated on the surface of the film. Specifically, the metal film can be made of aluminum, zinc or the like.

[0063] The present invention will be further described below in conjunction with embodiments: Comparative Example A three-layer co-extrusion extruder was selected, and a special material for capacitor film (polypropylene special material) with a melt index of 2.5g / 10min, an isotactic index of 98.0, an ash content of 0.003%, and a molecular weight distribution of 4 was directly added to the hopper of each extruder. The feeding ratio of the upper and lower side layer (first side layer and second side layer) extruder and the middle layer (heat-resistant layer) extruder was set to 1:1:1. The three layers were co-extruded at 230°C to form a thick sheet (base film sheet), and the thick sheet was cooled at 95°C. The cooled thick sheet was longitudinally stretched at a stretching temperature of 130°C and a stretching ratio of 4.5, and transversely stretched at a stretching temperature of 160°C and a stretching ratio of 9.5. The film was cooled at 30°C to form a PP metallized base film (capacitor film), and the capacitor film was tested for breakdown voltage under different temperature conditions. The results are shown in Table 1.

[0064] Example 1 Select a three-layer co-extrusion extruder, add 0.1 parts of aromatic dicarbonamide to 100 parts of special material for capacitor film (special material for polypropylene) with a melt index of 2.5g / 10min, an isotactic index of 98.0, an ash content of 0.003%, and a molecular weight distribution of 4, mix well and add to the middle layer (heat-resistant layer) extruder hopper. A special capacitor film material with a melt index of 2.5 g / 10 min, an isotactic index of 98.0, an ash content of 0.003%, and a molecular weight distribution of 4 was directly added to the upper and lower side layer (first side layer and second side layer) extruder hoppers, and the feeding ratio of the upper and lower side layer extruders to the middle layer extruder was set to 1:1:8. The three layers were co-extruded at 230° C. to form a thick sheet (base film sheet), and the thick sheet was cooled at 90° C. The cooled thick sheet was longitudinally stretched at a stretching temperature of 125° C. and a stretching ratio of 4, and transversely stretched at a stretching temperature of 155° C. and a stretching ratio of 9. The film was cooled at 25° C. to form a PP metallized base film (capacitor film), that is, a high temperature resistant polypropylene capacitor film of the present invention (the same applies to subsequent embodiments), and the capacitor film was tested for breakdown voltage under different temperature conditions. The results are shown in Table 1.

[0065] Example 2 Select a three-layer co-extrusion extruder, add 0.2 parts of aromatic dicarbonamide to 100 parts of special material for capacitor film (special material for polypropylene) with a melt index of 3.5g / 10min, an isotactic index of 98.5, an ash content of 0.0015%, and a molecular weight distribution of 6, mix well and add to the middle layer (heat-resistant layer) extruder hopper. A special capacitor film material with a melt index of 3.5 g / 10 min, an isotactic index of 98.5, an ash content of 0.002% and a molecular weight distribution of 6 was directly added to the upper and lower side layer (first side layer and second side layer) extruder hoppers. The feeding ratio of the upper and lower side layer extruders and the middle layer extruder was set to 2:2:6. The three layers were co-extruded at 230°C to form a thick sheet (base film sheet). The thick sheet was cooled at 100°C. The cooled thick sheet was longitudinally stretched at a stretching temperature of 125°C and a stretching ratio of 5, and transversely stretched at a stretching temperature of 155°C and a stretching ratio of 10. The film was cooled at 35°C to form a PP metallized base film (capacitor film). The breakdown voltage of the capacitor film was tested under different temperature conditions. The results are shown in Table 1.

[0066] Embodiment 3 Select a three-layer co-extrusion extruder, add 0.15 parts of aromatic dicarbonamide to 100 parts of special material for capacitor film (special material for polypropylene) with a melt index of 2.5g / 10min, an isotactic index of 98.5, an ash content of 0.002%, and a molecular weight distribution of 5, mix well and add to the middle layer (heat-resistant layer) extruder hopper. A special capacitor film material with a melt index of 2.5 g / 10 min, an isotactic index of 98.5, an ash content of 0.002% and a molecular weight distribution of 5 was directly added to the upper and lower side layer (first side layer and second side layer) extruder hoppers. The feeding ratio of the upper and lower side layer extruders and the middle layer extruder was set to 1.5:1.5:7. The three layers were co-extruded at 230°C to form a thick sheet (base film sheet). The thick sheet was cooled at 90°C, and the cooled thick sheet was longitudinally stretched at a stretching temperature of 145°C and a stretching ratio of 4, and transversely stretched at a stretching temperature of 175°C and a stretching ratio of 9. The film was cooled at 25°C to form a PP metallized base film (capacitor film). The breakdown voltage of the capacitor film was tested under different temperature conditions. The results are shown in Table 1.

[0067] Example 4 Select a three-layer co-extrusion extruder, add 0.2 parts of aromatic dicarbonamide to 100 parts of special material for capacitor film (special material for polypropylene) with a melt index of 3.0g / 10min, an isotactic index of 98.5, an ash content of 0.002%, and a molecular weight distribution of 5, mix well and add to the middle layer (heat-resistant layer) extruder hopper. The capacitor film special material with a melt index of 3.0 g / 10 min, an isotactic index of 98.5, an ash content of 0.002% and a molecular weight distribution of 5 was directly added to the upper and lower side layer (first side layer and second side layer) extruder hoppers. The feeding ratio of the upper and lower side layer extruders and the middle layer extruder was set to 1.5:1.5:7. The three layers were co-extruded at 230°C to form a thick sheet (base film sheet). The thick sheet was cooled at 95°C. The cooled thick sheet was longitudinally stretched at a stretching temperature of 135°C and a stretching ratio of 4.5, and transversely stretched at a stretching temperature of 165°C and a stretching ratio of 9.5. The film was cooled at 30°C to form a PP metallized base film (capacitor film). The breakdown voltage of the capacitor film was tested under different temperature conditions. The results are shown in Table 1.

[0068] It can be seen from Table 1 that compared with the capacitor film prepared in the comparative example, the breakdown voltage of the high temperature resistant polypropylene capacitor film prepared according to Examples 1 to 4 at different temperatures is higher than that of the comparative example to varying degrees, that is, at the same test temperature, the breakdown voltage of the high temperature resistant polypropylene capacitor film prepared in Examples 1 to 4 is higher, indicating that the high temperature resistant polypropylene capacitor film prepared according to the method of the present invention has better temperature resistance.

[0069] According to the second aspect of the present application, the present application provides a high temperature resistant polypropylene capacitor film, which is prepared by the preparation method of the high temperature resistant polypropylene capacitor film provided by any of the above technical solutions.

[0070] In some embodiments, the high temperature resistant polypropylene capacitor film includes a base film, which includes: a first side layer and a second side layer; a heat resistant layer located between the first side layer and the second side layer and connected to the first side layer and the second side layer.

[0071] In this embodiment, the upper and lower side layers of the capacitor film, namely the first side layer and the second side layer, are prepared using a special polypropylene material, so that the processing performance and surface roughness control of the high temperature resistant polypropylene capacitor film are not affected, and the subsequent processes are not affected.

[0072] Mixing additives into the polypropylene special material to prepare a heat-resistant layer can fundamentally improve the high temperature resistance of the capacitor film base film, thereby improving the overall high temperature resistance of the capacitor film, which is beneficial to the use of the high temperature resistant polypropylene capacitor film in a higher temperature environment.

[0073] In some embodiments, the thickness of the first side layer is the same as the thickness of the second side layer; the ratio of the thickness of the first side layer or the thickness of the second side layer to the thickness of the heat-resistant layer is (1 to 2): (6 to 8).

[0074] In some embodiments, a three-layer co-extrusion method is used to form a base film including a first side layer, a second side layer and a heat-resistant layer.

[0075] In this embodiment, a base film sheet including a first side layer, a second side layer and a heat-resistant layer is prepared by a three-layer co-extrusion method, the base film sheet is stretched to obtain a capacitor film base film, and a metal film is plated on the surface of the capacitor film base film to form a capacitor film. The prepared high-temperature resistant polypropylene capacitor film has a heat-resistant layer that can fundamentally improve the high-temperature resistance of the capacitor film base film, thereby improving the overall high-temperature resistance of the capacitor film, which is beneficial to the use of the high-temperature resistant polypropylene capacitor film in a higher temperature environment. Compared with the related technology that requires overheating during the preparation of the capacitor film, it can shorten the production cycle, improve production efficiency, and simplify production.

[0076] In the description of this specification, all quantities involving temperature, including expressions, are in degrees Celsius. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance unless otherwise clearly specified and limited; the terms "connection", "installation", "fixation", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0077] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0078] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for preparing a high temperature resistant polypropylene capacitor film, characterized in that: The preparation method comprises: A three-layer co-extrusion extruder is used to prepare a base film including a first side layer, a second side layer and a heat-resistant layer, wherein the heat-resistant layer is located between the first side layer and the second side layer, and the extrusion raw material of the heat-resistant layer is a mixture of a special polypropylene material and an additive; Performing a stretching process on the base film to form a capacitive film base film; The high temperature resistant polypropylene capacitor film is obtained by coating a metal film on the surface of the capacitor film base film.

2. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The three-layer co-extrusion extruder comprises a first hopper, a second hopper, a third hopper and an extrusion end. The three-layer co-extrusion extruder is used to prepare a base film comprising a first side layer, a second side layer and a heat-resistant layer, specifically comprising: The polypropylene special material is respectively put into the first hopper and the second hopper to obtain the first side layer and the second side layer; the polypropylene special material is mixed with additives and then put into the third hopper to obtain the heat-resistant layer; the first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end to form the base film sheet.

3. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 2, characterized in that: The first side layer, the heat-resistant layer and the second side layer are extruded through the extrusion end and then cooled at a first preset temperature to form the base film.

4. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 3, characterized in that: The first preset temperature is 90°C to 100°C.

5. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The additive is aryl dicarboxamide or a derivative thereof.

6. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The special polypropylene material is a polypropylene with a melt index of 2.5g / 10min to 3.5g / 10min, an isotactic index of 98.0% to 98.5%, an ash content of ≤0.003%, and a molecular weight distribution of 4 to 6.

7. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 1, characterized in that: The mass ratio of the special polypropylene material to the additive is 100:(0.1 to 0.2).

8. The method for preparing a high temperature resistant polypropylene capacitor film according to any one of claims 1 to 7, characterized in that: The heating temperature of the three-layer co-extrusion extruder is 225°C to 245°C.

9. The method for preparing a high temperature resistant polypropylene capacitor film according to any one of claims 1 to 7, characterized in that: The base film is subjected to a stretching process, specifically comprising: The base film is longitudinally stretched at a second preset temperature and a first preset ratio; Transversely stretching the base film at a third preset temperature and a second preset ratio; The longitudinal stretching and the transverse stretching are performed simultaneously, or the base film is firstly subjected to the longitudinal stretching and then subjected to the transverse stretching.

10. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 9, characterized in that: The second preset temperature is 125°C to 145°C.

11. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 9, characterized in that: The first preset magnification is 4 to 5.

12. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 9, characterized in that: The third preset temperature is 155°C to 175°C.

13. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 9, characterized in that: The second preset magnification is 9 to 10.

14. The method for preparing a high temperature resistant polypropylene capacitor film according to any one of claims 1 to 7, characterized in that: The method of stretching the base film to form a capacitive film base film further comprises: After the base film is stretched, it is cooled at a fourth preset temperature to form the capacitor film base film.

15. The method for preparing a high temperature resistant polypropylene capacitor film according to claim 14, characterized in that: The fourth preset temperature is 25°C to 35°C.

16. The method for preparing a high temperature resistant polypropylene capacitor film according to any one of claims 1 to 7, characterized in that: The metal film is an aluminum film or a zinc film.

17. A high temperature resistant polypropylene capacitor film, characterized in that: The high temperature resistant polypropylene capacitor film is prepared by the method for preparing a high temperature resistant polypropylene capacitor film according to any one of claims 1 to 16.

18. The high temperature resistant polypropylene capacitor film according to claim 17, characterized in that: The high temperature resistant polypropylene capacitor film comprises a base film, and the base film comprises: a first side layer and a second side layer; The heat-resistant layer is located between the first side layer and the second side layer, and is connected to the first side layer and the second side layer.

19. The high temperature resistant polypropylene capacitor film according to claim 18, characterized in that: The thickness of the first side layer is the same as the thickness of the second side layer; The ratio of the thickness of the first side layer or the thickness of the second side layer to the thickness of the heat-resistant layer is (1 to 2): (6 to 8).

20. The high temperature resistant polypropylene capacitor film according to claim 18, characterized in that: The base film including the first side layer, the second side layer and the heat-resistant layer is formed by three-layer co-extrusion.

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