High-temperature-resistant thin-film capacitor base film and preparation process thereof

Abstract

The invention relates to the technical field of capacitors, and particularly discloses a high-temperature-resistant thin-film capacitor base film and a preparation process thereof. The high-temperature-resistant thin-film capacitor base film comprises a thin film layer and a plating layer, and the thin film layer comprises the following raw materials in parts by weight: 150-170 parts of polyester; 30 to 50 parts of filler; 3-5 parts of an auxiliary agent; the filler comprises any one or more of nano calcium carbonate, fibrillated fiber, glass fiber and calcium borate; the preparation process comprises the following steps: S1, preparing the thin film layer; and S2, preparing the base membrane. The high-temperature-resistant thin-film capacitor base film can be used in a thin-film capacitor, and has the advantages of high temperature resistance, excellent mechanical properties and the like; in addition, in the preparation process, the base film has the advantages of better mechanical strength, high-temperature-resistant effect and the like in a film laminating manner.

Description

Technical Field

[0001] The present application relates to the technical field of capacitors, and more specifically, it relates to a high-temperature resistant base film for a thin-film capacitor and its preparation process. Background Art

[0002] Polymer thin-film capacitors have outstanding advantages such as simple processing, good flexibility, fast charge and discharge speed, and high power density. They can convert energy with the highest efficiency and are widely used in the field of electric power and electrical appliances. A thin-film capacitor is a capacitor with a structure in which metal foils are used as electrodes, and are overlapped at both ends with plastic base films such as polyethylene terephthalate, polypropylene, polystyrene, or polycarbonate and then wound into a cylindrical shape.

[0003] Among all plastic thin-film capacitors, polypropylene (PP) capacitors, polystyrene (PS) capacitors, and polyester (PET) capacitors have the most prominent characteristics. The capacitor core is the heart of the capacitor. Therefore, the core material of the capacitor must be a high-molecular polypropylene film with high-frequency resistance, high-temperature resistance, and the ability to withstand large current impacts to ensure the long-term stable operation of the whole machine. Summary of the Invention

[0004] In order to improve the high-temperature resistance effect of the thin film, the present application provides a high-temperature resistant base film for a thin-film capacitor and its preparation process, and adopts the following technical solutions: In the first aspect, the present application provides a high-temperature resistant base film for a thin-film capacitor. The capacitor base film includes a thin film layer and a coating layer. The thin film layer includes the following raw materials in parts by weight: 150 - 170 parts of polyester; 30 - 50 parts of filler; 3 - 5 parts of auxiliary agent; The filler includes any one or more of nano calcium carbonate, fibrillated fiber, glass fiber, and calcium borate.

[0005] By adopting the above technical solutions, preferably using nano calcium carbonate as the filler, nano calcium carbonate plays a role as a nucleation site in polyester, effectively improving the crystallinity of polyester, and thus effectively improving the high-temperature resistance effect of the thin film layer; and nano calcium carbonate can play a role in increasing viscosity in polyester, inhibiting the free movement of molecular chains, hindering the breakage of molecular chains, and further improving the high-temperature resistance effect of the thin film layer. And the introduction of nano calcium carbonate particles can trigger microcracks to absorb impact energy, and can also hinder the crack propagation caused by short fibers, effectively improving the toughness and mechanical strength of the thin film.

[0006] Preferably using fibrillated fiber as the filler, fibrillated fiber has better mechanical strength and heat resistance effect. Adding it to polyester can improve the mechanical strength of polyester by forming a cross-linked network structure in polyester, and can also effectively improve the heat resistance effect of polyester.

[0007] It is preferred to use glass fiber as the filler. Glass fiber has better mechanical strength, can build an interlaced network structure in the polyester to improve the mechanical strength of the polyester, and can improve the density of the polyester, thereby improving the high-temperature resistance effect of the polyester.

[0008] It is preferred to use calcium borate as the filler. Calcium borate can combine with the polyester by means of a double in-situ reaction, can promote the uniform dispersion of the filler in the polyester, and can effectively improve the dielectric effect of the film, which is beneficial to the application of the film in capacitors.

[0009] It is preferred to use nano calcium carbonate, fibrillated fiber, glass fiber and calcium borate in combination as the filler. The fibrillated fiber and the glass fiber can interlace to build a network structure, and the two fibers can entangle with each other to form a three-dimensional network structure and have different surface structures and hydrophilic and lipophilic effects of the two, which can promote the uniform dispersion of the network structure in the polyester. The nano calcium carbonate and the calcium borate can break through the agglomeration by the fiber structure, and the calcium borate can adhere to the surface of the network structure, further improving the dispersion effect of the fiber in the polyester, which is beneficial to the polyester to obtain excellent mechanical strength and heat resistance effect.

[0010] Optionally, the calcium borate is a calcium borate dispersion liquid, and the calcium borate dispersion liquid is prepared by stirring and dispersing calcium borate and ethylene glycol.

[0011] By adopting the above technical scheme, it is preferred to use the calcium borate dispersion liquid as the filler. The boron-oxygen structure in the calcium borate can react with ethylene glycol to generate a colloid and be uniformly dispersed, which is beneficial to promoting the double in-situ reaction between the calcium borate and the polyester, and the dispersion liquid can also fully improve the dispersion effect of other fillers, enabling the fillers to fully fill the polyester, which is beneficial to the polyester to obtain a uniform high-temperature resistance effect.

[0012] Optionally, the filler further includes borate ester.

[0013] By adopting the above technical scheme, the borate ester has more boron-oxygen structures and can be thermally decomposed, providing conditions for the in-situ growth of new calcium borate, that is, promoting the double in-situ reaction between the calcium borate and the polyester, further improving the bonding strength between the filler and the polyester, so as to improve the mechanical strength of the film layer.

[0014] Optionally, the preparation of the borate ester is as follows: Mix calcium borate and ethylene glycol to prepare a dispersion liquid, gradually heat up to 230 - 250 °C, control the pressure, stir, and vacuum-extract the steam to obtain the borate ester.

[0015] Optionally, the preparation of the nano calcium carbonate is as follows: Calcinate limestone to obtain calcium oxide, mix the calcium oxide with water, carry out a digestion reaction, screen, age, adjust the concentration of the slurry, add sucrose and sodium stearate, and obtain the nano calcium carbonate through pressure filtration, drying and pulverization.

[0016] By adopting the above technical solutions, the preparation process of nano calcium carbonate is optimized. Through carbonation synthesis, the crystal particle size and morphology of calcium carbonate can be adjusted, enabling the nano calcium carbonate grains to obtain appropriate sizes and a large specific surface area. The introduction of sodium stearate can modify the surface of nano calcium carbonate. While improving the surface morphology of nano calcium carbonate particles, it also improves the dispersion uniformity of nano calcium carbonate in polyester, enabling nano calcium carbonate to uniformly improve the high-temperature resistance effect and mechanical strength of polyester.

[0017] Optionally, the addition amount of sucrose is 0.1 - 0.2%.

[0018] By adopting the above technical solutions, the addition amount of sucrose is optimized. An appropriate addition amount of sucrose can enable calcium carbonate to obtain a more regular cubic structure, enhance the chelation effect of calcium ions, promote crystal form refinement and modify the crystal form, enabling polyester to obtain better crystallinity and high-temperature resistance effect. And it can effectively reduce the number of irregular spindle-shaped bodies in polyester, make the internal stress distribution more uniform, enable the film to obtain excellent toughening effect, and avoid the possibility of film fracture.

[0019] Optionally, the glass fiber is a modified glass fiber modified by a modifier, and the modifier is selected from any one or more of vinyltrimethoxysilane, silane coupling agent KH550, or titanate coupling agent.

[0020] By adopting the above technical solutions, it is preferably to use a silane coupling agent or a titanate coupling agent to modify the glass fiber, so that active groups can be grafted on the surface of the glass fiber. The active groups can combine with polyester, thereby effectively improving the bonding effect between the glass fiber and polyester. At the same time, the glass fiber can drive the fibrillation fibers intertwined with it to combine with polyester, that is, effectively improve the bonding strength between the filler and polyester.

[0021] Optionally, the preparation of the modified glass fiber is as follows: Mix the glass fiber with the modifier, adjust the pH, heat, reflux, wash, and add benzoyl peroxide to obtain the modified glass fiber.

[0022] By adopting the above technical solutions, it is preferably to add benzoyl peroxide to the glass fiber. Under the initiation of benzoyl peroxide, the active groups on the glass fiber can combine with polyester, stably improving the bonding effect between the glass fiber and polyester, increasing the bonding strength between the filler and polyester, and enabling the filler to stably improve the mechanical strength and high-temperature resistance effect of the film.

[0023] In a second aspect, the present application provides a preparation process for a high-temperature resistant thin film capacitor base film, adopting the following technical solutions: A preparation process for a high-temperature resistant thin film capacitor base film includes the following steps: S1. Preparation of the thin film layer: Take polyester, filler, and additives according to the above weight parts respectively, mix them evenly, and extrude and plasticize them to obtain modified polyester particles. Heat the conventional polyester and the modified polyester particles to the molten state respectively, and feed the two kinds of molten polyester particles into a lamination device for lamination, stretching, and winding to obtain the thin film layer; S2. Preparation of the base film: Gold plating is carried out on the surface of the thin film layer to obtain the base film.

[0024] By adopting the above technical solution, in this solution, it is preferably to use the lamination method to form a laminated structure of conventional polyester particles and modified polyester particles, which can endow the thin film layer with excellent reflection effect. And the composite structure of the laminated film can enable the thin film layer to obtain excellent high-temperature resistance performance while having excellent mechanical properties such as excellent tensile properties, improving the application performance of the thin film in many aspects.

[0025] Optionally, the temperature of the extrusion and plasticization is 150 - 160 °C.

[0026] In summary, the present application has the following beneficial effects: 1. Since the present application uses nano calcium carbonate as the filler, nano calcium carbonate plays a role as a nucleation site in the polyester, effectively improving the crystallinity of the polyester, thereby effectively improving the high-temperature resistance effect of the thin film layer; and nano calcium carbonate can play a role in increasing viscosity in the polyester, inhibiting the free movement of molecular chains, hindering the breakage of molecular chains, and further improving the high-temperature resistance effect of the thin film layer. And the introduction of nano calcium carbonate particles can trigger microcracks to absorb impact energy, and can hinder the crack propagation caused by short fibers, effectively improving the toughness and mechanical strength of the thin film.

[0027] 2. In the present application, it is preferably to use nano calcium carbonate, fibrillated fiber, glass fiber, and calcium borate in combination as the filler. The fibrillated fiber and the glass fiber can interlace and build a network structure, and the two fibers can entangle with each other to form a three-dimensional network structure and have different surface structures and hydrophilic and lipophilic effects, which can promote the uniform dispersion of the network structure in the polyester. Nano calcium carbonate and calcium borate can be broken through the agglomeration by the fiber structure, and calcium borate can adhere to the surface of the network structure, further improving the dispersion effect of the fiber in the polyester, which is beneficial for the polyester to obtain excellent mechanical strength and heat resistance effect.

[0028] 3. The present application uses a silane coupling agent or a titanate coupling agent to modify the glass fiber, so that the surface of the glass fiber can be grafted with active groups, and the active groups can combine with the polyester, thereby effectively improving the bonding effect between the glass fiber and the polyester. At the same time, the glass fiber can drive the fibrillated fiber intertwined with it to combine with the polyester, that is, effectively improving the bonding strength between the filler and the polyester.

[0029] 4. Preferably, the present application adopts a laminated manner to form a laminated structure of conventional polyester particles and modified polyester particles, which can endow the film layer with excellent reflection effect. And the composite structure of the laminated film can enable the film layer to obtain excellent high-temperature resistance performance while having excellent mechanical properties such as tensile properties, improving the application performance of the film in many aspects. Detailed Embodiments

[0030] The present application will be further described in detail below with reference to embodiments.

[0031] Preparation Examples Preparation Example of Calcium Borate Dispersion Preparation Example 1 Take 7 g of calcium borate and mix it with 100 mL of ethylene glycol, stir at 270 r / min at 170 °C for 4 h to obtain a calcium borate dispersion with a mass ratio of 7%.

[0032] Preparation Example of Borate Preparation Example 2 Mix 7 g of calcium borate with 100 mL of ethylene glycol, stir at 270 r / min at 170 °C for 4 h to obtain a calcium borate dispersion with a mass ratio of 7%. Gradually raise the temperature to 230 - 250 °C, control the pressure at 0.33 MPa, stir for 3 h, and vacuum-extract ethylene glycol vapor to obtain borate.

[0033] Preparation Example of Nano Calcium Carbonate Preparation Example 3 Place limestone in a muffle furnace and calcine it at 1200 °C for 2.5 h. React the obtained calcium oxide with tap water according to the mass ratio of ash to water of 1:6 for digestion reaction. After sieving through a 200-mesh sieve to remove impurities, age for 72 h. Adjust the concentration of the aged calcium hydroxide slurry to 8.5%. Take 20 °C as the initial carbonation temperature, add 3.5% (calculated based on the calcium carbonate content) of sodium stearate and 0.1% (calculated based on the calcium carbonate content) of sucrose. Filter, dry, and pulverize the NCC slurry to obtain nano calcium carbonate.

[0034] Preparation Example 4 Place limestone in a muffle furnace and calcine it at 1200 °C for 2.5 h. React the obtained calcium oxide with tap water according to the mass ratio of ash to water of 1:6 for digestion reaction. After sieving through a 200-mesh sieve to remove impurities, age for 72 h. Adjust the concentration of the aged calcium hydroxide slurry to 8.5%. Take 20 °C as the initial carbonation temperature, add 3.5% (calculated based on the calcium carbonate content) of sodium stearate and 0.15% (calculated based on the calcium carbonate content) of sucrose to obtain a nano calcium carbonate slurry. Filter, dry, and pulverize the nano calcium carbonate slurry to obtain nano calcium carbonate.

[0035] Preparation Example 5 The limestone is calcined at a high temperature of 1200 °C in a muffle furnace for 2.5 h. The obtained calcium oxide reacts with tap water in a lime-water mass ratio of 1:6 for digestion reaction. After sieving through a 200-mesh sieve to remove impurities, it is aged for 72 h. The concentration of the aged calcium hydroxide slurry is adjusted to 8.5%. With 20 °C as the initial carbonation temperature, 3.5% (calculated based on the calcium carbonate content) of sodium stearate and 0.20% of sucrose (calculated based on the calcium carbonate content) are added to obtain a nano-calcium carbonate slurry. The nano-calcium carbonate slurry is filtered, dried, and pulverized to obtain nano-calcium carbonate.

[0036] Preparation Example of Modified Glass Fiber Preparation Example 6 The glass fiber is calcined in a muffle furnace at 600 °C for 30 min, and washed thoroughly three times with deionized water to remove the sizing agent on the surface of the glass fiber, and then dried for standby. Respectively, 10 g of the calcined glass fiber is taken and soaked in an impregnating solution with a mass fraction of KH-550 of 5.0 wt% for 4 h, and the modified glass fiber is washed thoroughly 3 times with water and ethanol solution, and benzoyl peroxide is added and mixed to obtain the modified glass fiber.

[0037] Preparation Example 7 The glass fiber is calcined in a muffle furnace at 600 °C for 30 min, and washed thoroughly three times with deionized water to remove the sizing agent on the surface of the glass fiber, and then dried for standby. Respectively, 10 g of the calcined glass fiber is taken and soaked in an impregnating solution with a mass fraction of titanate coupling agent TMC-7 of 5.0 wt% for 4 h, and the modified glass fiber is washed thoroughly 3 times with water and ethanol solution, and benzoyl peroxide is added and mixed to obtain the modified glass fiber.

[0038] Preparation Example 8 The limestone is calcined at a high temperature of 1200 °C in a muffle furnace for 2.5 h. The obtained calcium oxide reacts with tap water in a lime-water mass ratio of 1:6 for digestion reaction. After sieving through a 200-mesh sieve to remove impurities, it is aged for 72 h. The concentration of the aged calcium hydroxide slurry is adjusted to 8.5%. With 18 °C as the initial carbonation temperature, 3.5% (calculated based on the calcium carbonate content) of sodium stearate is added. The NCC slurry is filtered, dried, and pulverized to obtain nano-calcium carbonate.

[0039] Examples Examples 1 - 3 On the one hand, the present application provides a high-temperature resistant base film for a thin film capacitor. The capacitor base film includes a thin film layer and a coating layer. The thin film layer includes the following raw materials: polyester PET, filler, and additives. The specific masses are shown in the following table.

[0040] Among them, the filler includes nano-calcium carbonate, fibrillated fiber, glass fiber, and calcium borate prepared in Preparation Example 8 with a mass ratio of 5:2:2:1. The calcium borate is the calcium borate dispersion prepared in Preparation Example 1.

[0041] The auxiliaries include an ultraviolet absorber (phenyl salicylate) and an antioxidant (antioxidant 1076) in equal mass.

[0042] On the other hand, the present application provides a preparation process of a high-temperature resistant base film for a film capacitor, including the following steps: S1. Preparation of the film layer: Respectively take polyester, filler and auxiliaries. First, mix nano calcium carbonate, fibrillated fiber, glass fiber and calcium borate dispersion to obtain a uniformly mixed filler, then add the uniformly mixed filler and auxiliaries to polyester in batches, mix well, extrude and plasticize at 155 °C to obtain modified polyester particles. Take conventional polyester and modified polyester particles and heat them to the molten state respectively, and feed the two kinds of molten polyester particles into a lamination device for lamination, stretching and winding to obtain a film layer; S2. Preparation of the base film: Gold plating is carried out on the surface of the film layer to obtain a base film.

[0043] Table 1 Composition of Examples 1-3 Example 4 On the one hand, the present application provides a high-temperature resistant base film for a film capacitor. The capacitor base film includes a film layer and a coating layer. The film layer includes the following raw materials: 160 kg of polyester PET, 40 kg of filler and 4 kg of auxiliaries.

[0044] Among them, the filler includes nano calcium carbonate, fibrillated fiber, glass fiber, calcium borate and borate ester prepared in Preparation Example 2 with a mass ratio of 5:2:2:1:0.5. The calcium borate is the calcium borate dispersion prepared in Preparation Example 1.

[0045] The auxiliaries include an ultraviolet absorber (phenyl salicylate) and an antioxidant (antioxidant 1076) in equal mass.

[0046] On the other hand, the present application provides a preparation process of a high-temperature resistant base film for a film capacitor, including the following steps: S1. Preparation of the film layer: Respectively take polyester, filler and auxiliaries. First, mix nano calcium carbonate, fibrillated fiber, glass fiber and calcium borate dispersion to obtain a uniformly mixed filler, then add the uniformly mixed filler and auxiliaries to polyester in batches, mix well, extrude and plasticize at 155 °C to obtain modified polyester particles. Take conventional polyester and modified polyester particles and heat them to the molten state respectively, and feed the two kinds of molten polyester particles into a lamination device for lamination, stretching and winding to obtain a film layer; S2. Preparation of the base film: Gold plating is carried out on the surface of the film layer to obtain a base film.

[0047] Example 5 The difference from Example 4 lies in that: nano calcium carbonate prepared in Preparation Example 3 with equal mass is used to replace the nano calcium carbonate in Example 4 to prepare the base film.

[0048] Example 6 The difference from Example 4 lies in that: nano calcium carbonate prepared in Preparation Example 4 with equal mass is used to replace the nano calcium carbonate in Example 4 to prepare the base film.

[0049] Example 7 The difference from Example 4 lies in that: nano calcium carbonate prepared in Preparation Example 5 with equal mass is used to replace the nano calcium carbonate in Example 4 to prepare the base film.

[0050] Example 8 On the one hand, the present application provides a high-temperature resistant thin film capacitor base film. The capacitor base film includes a thin film layer and a coating layer. The thin film layer includes the following raw materials: 160 kg of polyester PET, 40 kg of filler, and 4 kg of auxiliary agent.

[0051] Among them, the filler includes nano calcium carbonate prepared in Preparation Example 5, fibrillated fiber, modified glass fiber prepared in Preparation Example 6, calcium borate, and borate ester prepared in Preparation Example 2 with a mass ratio of 5:2:2:1:0.5. The calcium borate is the calcium borate dispersion prepared in Preparation Example 1.

[0052] The auxiliary agent includes equal mass of ultraviolet absorber (phenyl salicylate) and antioxidant (antioxidant 1076).

[0053] On the other hand, the present application provides a preparation process for a high-temperature resistant thin film capacitor base film, including the following steps: S1. Preparation of the thin film layer: Respectively take polyester, filler, and auxiliary agent. First, pre-stir and mix the fibrillated fiber and the modified glass fiber to obtain a mixed fiber material. Then, mix the mixed fiber material, nano calcium carbonate, and calcium borate dispersion to obtain a uniformly mixed filler. Then, add the uniformly mixed filler and auxiliary agent to the polyester in batches, mix well, extrude and plasticize at 155 °C to obtain modified polyester particles. Take conventional polyester and modified polyester particles and heat them to the molten state respectively, and feed the two kinds of molten polyester particles into a lamination device for lamination, stretching, and winding to obtain the thin film layer; S2. Preparation of the base film: Gold plating is carried out on the surface of the thin film layer to obtain the base film.

[0054] Example 9 On the one hand, the present application provides a high-temperature resistant thin film capacitor base film. The capacitor base film includes a thin film layer and a coating layer. The thin film layer includes the following raw materials: 160 kg of polyester PET, 40 kg of filler, and 4 kg of auxiliary agent.

[0055] Among them, the filler includes nano-calcium carbonate, fibrillated fiber, modified glass fiber, calcium borate, and borate ester prepared in Preparation Example 2, which are prepared in Preparation Example 5 with a mass ratio of 5:2:2:1:0.5. The calcium borate is the calcium borate dispersion prepared in Preparation Example 1.

[0056] The auxiliaries include equal masses of an ultraviolet absorber (phenyl salicylate) and an antioxidant (antioxidant 1076).

[0057] On the other hand, the present application provides a preparation process for a high-temperature resistant thin film capacitor base film, which includes the following steps: S1. Preparation of the thin film layer: Respectively take polyester, filler, and auxiliaries. First, pre-stir and mix the fibrillated fiber and the modified glass fiber to obtain a mixed fiber material. Then, mix the mixed fiber material, nano-calcium carbonate, and calcium borate dispersion to obtain a uniformly mixed filler. Then, add the uniformly mixed filler and auxiliaries to the polyester in batches, mix well, and extrude and plasticize at 155°C to obtain modified polyester particles. Heat the conventional polyester and the modified polyester particles to the molten state respectively, and send the two molten polyester particles into a laminating device for laminating, stretching, and winding to obtain a thin film layer; S2. Preparation of the base film: Gold plating is performed on the surface of the thin film layer to obtain a base film.

[0058] Comparative Example Comparative Example 1 The difference between this comparative example and Example 2 is that in this comparative example, the filler includes nano-calcium carbonate and glass fiber with a mass ratio of 5:2, and a base film is prepared.

[0059] Comparative Example 2 On the one hand, the present application provides a high-temperature resistant thin film capacitor base film. The capacitor base film includes a thin film layer and a plating layer. The thin film layer includes the following raw materials: 160 kg of polyester PET, 40 kg of filler, and 4 kg of auxiliaries.

[0060] Among them, the filler includes nano-calcium carbonate, fibrillated fiber, glass fiber, and calcium borate with a mass ratio of 5:2:2:1. The calcium borate is the calcium borate dispersion prepared in Preparation Example 1.

[0061] The auxiliaries include equal masses of an ultraviolet absorber (phenyl salicylate) and an antioxidant (antioxidant 1076).

[0062] On the other hand, the present application provides a preparation process for a high-temperature resistant thin film capacitor base film, which includes the following steps: S1. Preparation of the thin film layer: Polyester, fillers, and additives were separately taken. The fibrillated fiber and glass fiber were pre-stirred and mixed in advance to obtain a mixed fiber material. Then, the mixed fiber material, nano-calcium carbonate, and calcium borate dispersion were mixed to obtain a uniformly mixed filler. The uniformly mixed filler and additives were added to the polyester in portions and mixed evenly. After extrusion and plasticization at 155 °C, modified polyester particles were obtained, which were stretched and wound to obtain the thin film layer; S2. Preparation of the base film: Gold plating was performed on the surface of the thin film layer to obtain the base film.

[0063] Performance detection test (1) Heat resistance test: The transverse heat shrinkage rate was the transverse heat shrinkage rate measured when the thin film layer was placed at 300 °C and left standing for 20 min.

[0064] (2) Mechanical property detection: The thin film layer was subjected to a tensile test using a universal tensile tester; Table 2 Performance detection It can be found from the performance detection comparison in Table 2 that: 1. By comparing Examples 1-3 with Comparative Examples 1-2, it can be found that the heat resistance and mechanical strength of the thin film layers prepared in Examples 1-3 have been improved. This shows that in this application, using nano-calcium carbonate, fibrillated fiber, glass fiber, and calcium borate in combination as fillers, the fibrillated fiber and glass fiber can interleave and build a network structure, and the two fibers can entangle with each other to form a three-dimensional network structure and can utilize their different surface structures and hydrophilic-lipophilic effects, thereby promoting the uniform dispersion of the network structure in the polyester. Nano-calcium carbonate and calcium borate can be broken through the agglomeration by the fiber structure, and calcium borate can adhere to the surface of the network structure, further improving the dispersion effect of the fiber in the polyester, which is beneficial for the polyester to obtain excellent mechanical strength and heat resistance. By using a laminated method to form a laminated structure of conventional polyester particles and modified polyester particles, the thin film layer can be given excellent reflection effect, and the composite structure of the laminated film can endow the thin film layer with excellent high-temperature resistance while having excellent mechanical properties such as tensile properties, improving the application performance of the thin film in many aspects.

[0065] 2. By comparing Example 4 with Example 2, it can be found that the heat resistance and mechanical strength of the thin film layer prepared in Example 4 have been improved. This shows that in this application, the borate has more boron-oxygen structures and can be decomposed by heat, providing conditions for the in-situ growth of new calcium borate, that is, promoting the double in-situ reaction between calcium borate and polyester, further improving the bonding strength between the filler and the polyester, so as to enhance the mechanical strength of the thin film layer.

[0066] 3. By comparing Examples 5 - 7 with Example 2, it can be found that the heat resistance and mechanical strength of the film layer prepared in Examples 5 - 7 have been improved. This shows that in this application, the addition amount of sucrose is optimized. An appropriate addition amount of sucrose can enable calcium carbonate to obtain a more regular cubic structure, enhance the chelation effect of calcium ions, promote crystal refinement and modify the crystal form, so that the polyester obtains better crystallinity and high-temperature resistance effect. And it can effectively reduce the number of irregular spindles in the polyester, make the internal stress distribution more uniform, enable the film to obtain an excellent toughening effect, and avoid the possibility of film fracture.

[0067] 4. By comparing Examples 8 - 9 with Example 2, it can be found that the heat resistance and mechanical strength of the film layer prepared in Examples 8 - 9 have been improved. This shows that in this application, the glass fiber is modified with a silane coupling agent or a titanate coupling agent, so that active groups can be grafted on the surface of the glass fiber. The active groups can combine with the polyester, thereby effectively improving the bonding effect between the glass fiber and the polyester. At the same time, the glass fiber can drive the fibrillation fibers intertwined with it to combine with the polyester, that is, effectively improve the bonding strength between the filler and the polyester.

[0068] This specific embodiment is only an interpretation of this application, and it is not a limitation of this application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of this application, it is protected by the patent law.

Claims

1. A high temperature resistant film capacitor base film, characterized in that: The capacitor base film includes a film layer and a coating layer, wherein the film layer includes the following raw materials in parts by weight: Polyester 150-170 parts; 30-50 parts of filler; 3-5 parts of additives; The filler includes any one or more of nano calcium carbonate, fibrillated fiber, glass fiber and calcium borate; The calcium borate is a calcium borate dispersion; The glass fiber is a modified glass fiber modified by a coupling agent; The filler further comprises borate ester, and the borate ester is prepared from the calcium borate dispersion.

2. The high temperature resistant film capacitor base film according to claim 1, characterized in that: The calcium borate dispersion is prepared by stirring and dispersing calcium borate and ethylene glycol.

3. The high temperature resistant film capacitor base film according to claim 1, characterized in that: The boric acid ester is prepared as follows: calcium borate and ethylene glycol are mixed to prepare a dispersion, the dispersion is gradually heated to 230-250° C., the pressure is controlled, the mixture is stirred, and the steam is removed by vacuum to obtain the boric acid ester.

4. The high temperature resistant film capacitor base film according to claim 1, characterized in that: The preparation of the nano calcium carbonate is as follows: limestone is calcined to obtain calcium oxide, the calcium oxide is mixed with water, digested, sieved, aged, the slurry concentration is adjusted, sucrose and sodium stearate are added, and the nano calcium carbonate is obtained by filter pressing, drying and crushing.

5. The high temperature resistant film capacitor base film according to claim 4, characterized in that: The added amount of the sucrose is 0.1-0.2%.

6. The high temperature resistant film capacitor base film according to claim 1, characterized in that: The coupling agent is selected from any one or more of vinyltrimethoxysilane, silane coupling agent KH550 or titanate coupling agent.

7. The high temperature resistant film capacitor base film according to claim 6, characterized in that: The modified glass fiber is prepared as follows: glass fiber is mixed with a modifier, pH is adjusted, heating, refluxing, washing, and toluoyl peroxide is added and mixed to obtain the modified glass fiber.

8. A process for preparing a high temperature resistant film capacitor base film according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, preparation of film layer: taking polyester, filler and additives according to the above weight parts respectively, mixing, extruding and plasticizing to obtain modified polyester particles, taking conventional polyester and modified polyester particles respectively and heating them to a molten state, sending the two polyester particles in a molten state into a lamination device for lamination, stretching and winding to obtain a film layer; S2. Preparation of base film: Gold is plated on the surface of the thin film layer to obtain a base film.

9. The process for preparing a high temperature resistant film capacitor base film according to claim 8, characterized in that: The temperature of the extrusion plasticization is 150-160°C.

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