High-temperature and high-humidity-resistant metallized polypropylene film for capacitor and preparation method and application thereof

Abstract

The application belongs to the technical field of capacitor films, and relates to a metalized polypropylene film for high-temperature and high-humidity-resistant capacitors, a preparation method and application thereof. The metalized polypropylene film comprises a polypropylene film and a metal layer, the metal layer is composed of a first copper layer, a first zinc layer, a second copper layer and a second zinc layer, the first copper layer is located on the surface of the polypropylene film, the first zinc layer covers the surface of the first copper layer, the second copper layer covers the surface of the first zinc layer, and the second zinc layer covers the surface of the second copper layer. The special metal layer structure formed by the copper-zinc layers alternately on the surface of the polypropylene film can endow the metal layer with more excellent oxidation resistance compared with a copper-zinc composite layer, and improve the high-temperature and high-humidity resistance of the capacitor.

Description

Technical Field

[0001] This invention belongs to the field of capacitor film technology, and relates to a metallized polypropylene film for high temperature and high humidity resistant capacitors, its preparation method and application. Background Technology

[0002] Metallized film capacitors are capacitors made by depositing one or more layers of metal film onto the surface of an organic plastic film as the dielectric, replacing traditional metal foil as electrodes, and then winding them. The thickness of the metallized film layer is much smaller than that of the metal foil, resulting in a much smaller overall volume compared to metal foil capacitors. Although common organic plastic film materials include polyester, polypropylene, polycarbonate, and polyethylene terephthalate, metallized film capacitors made of polypropylene are low-cost and possess excellent electrical characteristics, high stability, and long lifespan. Metallized polypropylene film capacitors are increasingly replacing aluminum electrolytic capacitors in various applications and are rapidly developing in the new energy market, represented by wind power generation, solar power generation, and electric vehicles.

[0003] Currently, zinc is commonly used as the main metal layer for the electrode plates in the metallized film capacitor industry. However, zinc has poor adhesion and is difficult to deposit directly onto the film surface. A layer of metal, alloy, or oxide must first be deposited as an underlayer. For example, Chinese patent application CN114277335A discloses a method for manufacturing a metallized capacitor film, in which a layer of aluminum is first deposited on the base film surface as an underlayer, followed by a layer of zinc, thus forming an aluminum and zinc composite coating on the base film surface, resulting in an Al and Zn composite metallized capacitor film. Another example is Chinese patent CN111146001B, which discloses a method for preparing a metallized film for capacitors, in which an aluminum-magnesium alloy layer is deposited on the surface of a substrate film using vacuum evaporation, followed by a zinc layer being deposited on the aluminum-magnesium alloy evaporation film surface using vacuum evaporation, resulting in an aluminum-magnesium alloy and zinc composite metallized base film. Chinese patent application CN114050052A discloses a metallized thin film for capacitors, which includes a base film layer, an Al2O3 underlayer covering the base film layer, a zinc layer covering the Al2O3 underlayer, and an Al2O3 protective layer covering the zinc layer. This invention effectively solves the problem of poor zinc adhesion by first depositing an Al2O3 layer on the base film as an underlayer.

[0004] However, when current metal coatings are affected by external factors, such as operating in high temperature (85℃) and high humidity (85%RH) environments (i.e., so-called "double 85" resistance), the area of ​​the metallized film layer decreases, leading to a reduction in the capacitance of the film capacitor. This is because, under high temperature and high humidity conditions, when external moisture penetrates the air between the film layers, the breakdown potential of the air decreases, accelerating air ionization and generating a large amount of ozone. Since the metal coating of the metallized film is composed of Zn / Al, upon encountering the oxygen produced by ozone decomposition, the Zn / Al metal is immediately oxidized, generating non-conductive metal oxides ZnO and Al2O3. This reduces the area of ​​the metal coating of the metallized film, causing a rapid decrease in the capacitor's capacitance.

[0005] Existing methods for improving the performance of metallized film capacitors under high temperature and high humidity conditions include special treatment of the metallized coating and specialization of the capacitor manufacturing process. For example, Chinese patent application CN110289167A discloses a high-temperature and high-humidity resistant film capacitor, which has a dense and solid Parylene film (nanoscale) attached to the surface of the metallized coating. This film blocks the rate at which moisture penetrates the coating. Compared to zinc-aluminum metallized coatings, moisture is less likely to corrode the zinc-aluminum film, thus slowing down the capacitance decay and improving capacitor stability. Another example is Chinese patent CN10640950. 7B discloses a processing method for a thin-film capacitor suitable for high-temperature and high-humidity applications. The processing method includes a vapor deposition process, a heat setting process, and a potting process. The plasma treatment technology in the vapor deposition process allows the metallized film to adhere more tightly after the core is shaped, preventing moisture residue from causing film oxidation and greatly improving its oxidation resistance. The heat setting process allows the film to shrink fully, and the potting is carried out in a vacuum environment, effectively isolating the core from the influence of moisture in the air and improving its oxidation resistance under high-temperature and high-humidity conditions. Finally, the processed thin-film capacitor still meets the requirements of long life and reliability under high-temperature and high-humidity conditions, and its safety and stability are improved. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a metallized polypropylene film for high-temperature and high-humidity capacitors. This metallized polypropylene film has two layers of copper and two layers of zinc plated on its surface, and capacitors made from it can maintain excellent performance when operating in high-temperature and high-humidity environments.

[0007] The first objective of this invention is achieved through the following technical solution:

[0008] A metallized polypropylene film for high-temperature and high-humidity capacitors includes a polypropylene film and a metal layer. The metal layer is composed of a first copper layer, a first zinc layer, a second copper layer, and a second zinc layer. The first copper layer is located on the surface of the polypropylene film, the first zinc layer covers the surface of the first copper layer, the second copper layer covers the surface of the first zinc layer, and the second zinc layer covers the surface of the second copper layer.

[0009] The copper layer formed by vapor deposition on the polypropylene film can serve as a base layer, which is beneficial for the subsequent vapor deposition of the zinc layer. The special metal layer structure formed by vapor deposition, which consists of alternating copper and zinc layers (first copper layer, first zinc layer, second copper layer, and second zinc layer), can impart better oxidation resistance to the metal layer and improve the film's resistance to high temperature and high humidity compared to a copper and zinc composite layer.

[0010] Preferably, the zinc content in the metal layer is greater than the copper content.

[0011] Preferably, in the metal layer, the zinc content is 60–99.9 wt%, the copper content is 0.1–40 wt%, and the total zinc and copper content is 100 wt%. More preferably, the zinc content is 80–99.5 wt%, and the copper content is 0.5–20 wt%. Even more preferably, the zinc content is 90–99 wt%, and the copper content is 1–10 wt%. Optionally, the copper content can be any one of 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, and 10 wt%, or a value within a range of any two values.

[0012] Preferably, the mass of the first copper layer accounts for 30-70 wt% of the total mass of the first copper layer and the second copper layer, and the mass of the first zinc layer accounts for 10-50 wt% of the total mass of the first zinc layer and the second zinc layer.

[0013] The copper and zinc layers of this invention are formed by vacuum evaporation coating technology. Vacuum evaporation coating involves heating the coating material in a vacuum environment, causing it to evaporate in a very short time. The evaporated coating material molecules are deposited on the plastic surface to form a coating layer.

[0014] The second objective of this invention is achieved through the following technical solution:

[0015] A method for preparing a metallized polypropylene film for high-temperature and high-humidity resistant capacitors includes the following steps:

[0016] S1. Place the polypropylene film in a vacuum evaporation coating machine and evacuate the vacuum evaporation coating machine.

[0017] S2. The zinc block is placed in the crucible, and the copper wire is transferred to the copper evaporation boat. The copper evaporation boat and the crucible are heated, and the copper wire and zinc block are evaporated by the heat. The polypropylene film winding system is started, and the polypropylene film begins to move. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, and the first evaporation is completed.

[0018] S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evacuate the vacuum evaporation coating machine.

[0019] S4. The zinc block is placed in the crucible, and the copper wire is transferred to the copper evaporation boat. The copper evaporation boat and the crucible are heated, and the copper wire and zinc block are evaporated by heat. The polypropylene film winding system is started, and the polypropylene film begins to move. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, and the second evaporation is completed.

[0020] S5. Cutting and packaging yields the finished metallized polypropylene film.

[0021] The present invention deposits copper and zinc layers separately in two stages to form a metal layer structure consisting of a first copper layer, a first zinc layer, a second copper layer, and a second zinc layer. This improves the bonding between the deposited layers, resulting in a more robust and stable metal layer.

[0022] Preferably, the copper evaporation boat used in this invention undergoes pretreatment, which includes the following steps: coating an evaporation paste onto the groove surface of the copper evaporation boat and drying it to obtain a copper evaporation boat with a coating; the evaporation paste includes Mo, TiB2 and water.

[0023] The groove in the copper evaporation boat is where the copper wire is placed.

[0024] Copper wires undergo melting and then vaporization in a hot evaporation boat. However, copper is incompatible with the evaporation boat's materials, resulting in spherical copper deposits within the boat with a small coverage area, affecting subsequent vaporization and consequently impacting evaporation efficiency and uniformity. This invention addresses this by treating the copper evaporation boat with an evaporation paste, forming a coating on the grooved surface. The molten copper then wets this coating, effectively spreading the molten copper evenly throughout the evaporation boat, thus increasing the copper coverage area and improving evaporation efficiency and uniformity.

[0025] Preferably, the coating thickness is 80–300 μm.

[0026] The composition of the evaporation paste has a significant impact on the wetting effect on copper. Preferably, the composition and content of the evaporation paste are controlled as follows:

[0027] Mo: 50~80wt%, TiB2: 10~25wt%, H2O: 10~25wt%.

[0028] Preferably, in steps S1 and S3, the vacuum evaporation coating machine is evacuated to a vacuum level of 0.01 × 10⁻⁶. -3 ~5×10 -3 Pa, vapor deposition under high vacuum helps to improve the coating quality.

[0029] The purity of the copper wire needs to be controlled. If the copper wire has a high impurity content, these impurities will deposit on the surface of the polypropylene film or penetrate into the polypropylene film, reducing the adhesion between the copper and the film and causing uneven copper plating. Preferably, the purity of the copper wire is ≥99.99%. Preferably, the purity of the zinc block is ≥99.9%.

[0030] Optionally, during the first and second vapor deposition processes, the vapor deposition distance is 40–50 cm, the moving speed of the polypropylene film is 5–15 m / min, the diameter of the copper wire is 1.0–2.0 mm, and the conveying speed of the copper wire is 100–500 mm / min.

[0031] The parameters in the above evaporation coating process will affect the metal evaporation amount. By controlling the above parameters to a suitable value, the zinc content in the metal layer is 90-99 wt%, the copper content is 1-10 wt%, and the mass of the first copper layer accounts for 30-70 wt% of the total mass of the first and second copper layers, and the mass of the first zinc layer accounts for 10-50 wt% of the total mass of the first and second zinc layers.

[0032] Preferably, the heating temperature of the copper evaporation boat is 1400–1600°C, and the heating temperature of the crucible is 650–800°C. At these temperatures, copper and zinc are heated and evaporated into a gaseous state.

[0033] Preferably, after the first evaporation coating is completed, the metallized polypropylene film is placed in an environment with a cleanliness level of 10,000 or below, a temperature of -10 to 0°C, and a humidity of 10 to 40% for 20 to 30 hours, and then placed in an environment with a cleanliness level of 10,000 or below, and a temperature of 20 to 40% for 10 to 30 hours, and then placed in a vacuum evaporation coating machine.

[0034] Preferably, after the second vapor deposition, the metallized polypropylene film is placed in an environment with a cleanliness level of 10,000 or below, a temperature of -10 to 0°C, and a humidity of 10 to 40% for 20 to 30 hours, and then placed in an environment with a cleanliness level of 10,000 or below, a temperature of 20 to 40°C, and a humidity of 10 to 40% for 10 to 30 hours, and then cut and packaged to obtain the final product.

[0035] The inventors discovered that placing the metallized polypropylene film in a low-temperature environment after each vapor deposition process results in a denser coating structure, more stable metal atoms, and tighter bonding between metal layers. Capacitors made from metallized polypropylene films that have undergone this low-temperature treatment exhibit excellent resistance to high temperatures and humidity.

[0036] Preferably, the thickness of the polypropylene film of the present invention is ≤4μm.

[0037] The following detailed description of the preparation method of polypropylene film is for illustrative purposes only and is not intended to limit the preparation method of polypropylene film of the present invention.

[0038] The preparation method of polypropylene film includes the following steps:

[0039] 1) Polypropylene raw material is fed into an extruder and melt-extruded to obtain a melt. The die temperature of the extruder is 230-250℃, the isotactic index of the polypropylene raw material is ≥98.0%, the melt flow index (MFR) is 3.2-4.0 g / 10min (230℃, 2.16 kg), and the ash content is ≤20ppm.

[0040] 2) Cooling and shaping by quenching rollers and air shower: The melt obtained in step 1) is cooled and shaped by quenching rollers and air shower to obtain a casting. The temperature of the quenching rollers is 95-110℃, and the thickness of the casting is 200.0-400.0μm.

[0041] 3) Longitudinal stretching step: The casting obtained in step 2) is subjected to longitudinal preheating, longitudinal stretching and longitudinal shaping in sequence. The longitudinal preheating temperature is 100-135℃, the longitudinal stretching temperature is 140-145℃ and the longitudinal shaping temperature is 142-148℃. The longitudinal stretching ratio is 5-8 times.

[0042] 4) Transverse stretching step: The film obtained in step 3) is subjected to transverse preheating, transverse stretching and transverse setting in sequence. The transverse preheating temperature is 160-175℃, the transverse stretching temperature is 155-160℃ and the transverse setting temperature is 165-175℃, and the transverse stretching ratio is 7-10 times.

[0043] 5) Thickness Measurement, Edge Trimming, and Corona Treatment: The thickness of the thin film is measured, and one side of the film is corona treated using electrodes. During corona treatment, the electrode output power is 5–18 kW, the output voltage is 5–10 kV, the pulse frequency is 10–30 kHz, and the electrode bombardment intensity is 7–15 W·min / m. 2 ;

[0044] 6) Winding: Winding tension is 10-30%, and winding pressure is 20-50%;

[0045] 7) First aging treatment: The rolled-up film is treated in a cleanroom of Class 10,000 or below at 20-40°C for 30-100 hours;

[0046] 8) Slitting: According to requirements, the film after the first aging treatment is slitted into small rolls of film of a certain width;

[0047] 9) Second aging treatment: The slit rolls of film are treated in a cleanroom of Class 10,000 or below at 20-40°C for 15-40 hours to obtain the finished polypropylene film.

[0048] The third objective of this invention is achieved through the following technical solution:

[0049] A metallized polypropylene film for high-temperature and high-humidity capacitors is applied in capacitors.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The present invention forms a special metal layer structure on the surface of a polypropylene film by vapor deposition of alternating copper and zinc layers, namely a first copper layer, a first zinc layer, a second copper layer, and a second zinc layer. Compared with the copper and zinc composite layer, the metal layer can be endowed with better oxidation resistance and improve the high temperature and high humidity resistance of the capacitor.

[0052] (2) The present invention deposits copper and zinc layers in two separate vapor deposition processes to form a metal layer structure consisting of a first copper layer, a first zinc layer, a second copper layer, and a second zinc layer. This is beneficial to improving the vapor deposition bonding between the layers, resulting in a metal layer with higher bonding and greater stability.

[0053] (3) The present invention uses an evaporation paste with appropriate composition and content to treat the copper evaporation boat, forming a coating on the groove surface of the copper evaporation boat, increasing the area of ​​copper liquid wetting the evaporation boat, which is beneficial to improving the evaporation efficiency and evaporation uniformity.

[0054] (4) The present invention places the metallized polypropylene film after vapor deposition in a low temperature environment of -10 to 0°C. The capacitor made of the metallized polypropylene film after low temperature treatment has excellent high temperature and high humidity resistance.

[0055] (5) The capacitor made from the metallized polypropylene film of the present invention has excellent high temperature and high voltage resistance. After operating for 500 hours under high temperature and high humidity (temperature 85°C, relative humidity 85%RH) conditions, the capacitance change rate is <-0.6% and the loss tangent change value (△DF) is ≤0.05%. Detailed Implementation

[0056] The technical solution of the present invention will be further described and illustrated below through specific embodiments. It should be understood that the specific embodiments described herein are only for the purpose of helping to understand the present invention and are not intended to limit the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0057] Polypropylene raw material: Borealis, model HC300BF.

[0058] The polypropylene films in the following examples and comparative examples were prepared by the following methods:

[0059] 1) Polypropylene raw material is fed into an extruder and melted and extruded to obtain a melt. The die temperature of the extruder is 240℃.

[0060] 2) Cooling and shaping with quenching rollers and air shower: The melt obtained in step 1) is cooled and shaped by quenching rollers and air shower to obtain a casting. The temperature of the quenching rollers is 100℃.

[0061] 3) Longitudinal stretching step: The casting obtained in step 2) is subjected to longitudinal preheating, longitudinal stretching, and longitudinal shaping in sequence. Longitudinal preheating uses 8 rollers: the temperature of rollers 1-2 is set to 106℃, rollers 3-4 to 122℃, rollers 5-6 to 128℃, and rollers 7-8 to 133℃. Longitudinal stretching uses 6 rollers: the temperature of rollers 1-2 is set to 141℃, rollers 3-4 to 144℃, and rollers 5-6 to 142℃. Longitudinal shaping uses 4 rollers: the temperature of rollers 1-2 is set to 145℃, and rollers 3-4 to 147℃. The longitudinal stretching ratio is 6 times.

[0062] 4) Transverse stretching step: The film obtained in step 3) is subjected to transverse preheating, transverse stretching, and transverse setting in sequence. The transverse preheating has 8 sections, with the temperature set to 165℃ for sections 1-3, 170℃ for sections 4-6, and 172℃ for sections 7-8. The transverse stretching has 6 sections, with the temperature set to 156℃ for sections 1-2, 158℃ for sections 3-4, and 160℃ for sections 5-6. The transverse setting has 5 sections, with the temperature set to 170℃ for sections 1-3 and 174℃ for sections 4-5. The transverse stretching ratio is 9 times.

[0063] 5) Thickness measurement, edge trimming, and corona treatment: The film thickness was measured to be 3.5 μm. One side of the film was corona treated using an electrode. During corona treatment, the electrode output power was 8 kW, the output voltage was 8 kV, the pulse frequency was 15 kHz, and the electrode bombardment intensity was 8 W·min / m. 2 ;

[0064] 6) Winding: Winding tension is 20%, winding pressure is 40%;

[0065] 7) First aging treatment: The rolled-up film is aged for 72 hours in an environment with a dust level of 10,000 and a temperature of 35°C.

[0066] 8) Slitting: According to requirements, the film after the first aging treatment is slitted into small rolls of film of a certain width;

[0067] 9) Second aging treatment: The slit rolls of film are aged for 22 hours in a cleanroom environment of 10,000 class and 32°C to obtain the finished polypropylene film.

[0068] In the following examples and comparative examples:

[0069] The copper wire was purchased from Beijing Xingrongyuan Technology Co., Ltd., with a purity of 99.995% and a diameter of 1.6mm; the zinc block was purchased from Shijiazhuang Zhongli Zinc Industry Co., Ltd., with a purity of 99.99%.

[0070] The vacuum evaporation coating machine is a German Leybold 650, and the copper evaporation boat was purchased from Stek, with dimensions of 10mm*30mm*130mm.

[0071] Example 1

[0072] The copper evaporation boat used in this embodiment has undergone pretreatment, which involves coating an evaporation paste onto the groove surface of the copper evaporation boat and drying it to obtain a copper evaporation boat with a coating thickness of 160 μm. The evaporation paste is composed of: Mo: 70 wt%, TiB2: 15 wt%, and H2O: 15 wt%.

[0073] In this embodiment, metallic copper is deposited onto the surface of a polypropylene film. The steps are as follows:

[0074] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0075] S2. Heat the copper evaporation boat to 1600℃. The copper wire is conveyed to the copper evaporation boat at a speed of 400mm / min, and the copper wire evaporates upon heating. Start the polypropylene film winding system. The polypropylene film begins to move at a speed of 8m / min. Open the copper baffle to allow gaseous copper to deposit on the surface of the moving polypropylene film to form a copper layer. Turn off the vacuum pump to release the vacuum and make the pressure of the vacuum evaporation coating machine equal to atmospheric pressure.

[0076] The copper-plated polypropylene film sample was tested for coating adhesion, and the copper adhesion amount was found to be 8 mg / m³. 2 .

[0077] Comparative Example 1

[0078] The only difference between Comparative Example 1 and Example 1 is that the copper evaporation boat in Comparative Example 1 was not pretreated.

[0079] The copper-plated polypropylene film sample from Comparative Example 1 was tested for coating adhesion. The copper adhesion amount in Comparative Example 1 was found to be 4.2 mg / m³. 2 .

[0080] Comparative Example 2

[0081] The only difference between Comparative Example 2 and Example 1 is that the copper evaporation boat in Comparative Example 2 was pretreated. The evaporation paste used in the pretreatment was: Mo: 85wt%, H2O: 15wt%.

[0082] The copper-plated polypropylene film sample from Comparative Example 2 was tested for coating adhesion. The copper adhesion amount in Comparative Example 2 was found to be 5.6 mg / m³. 2 .

[0083] Comparative Example 3

[0084] The only difference between Comparative Example 3 and Example 1 is that the copper evaporation boat in Comparative Example 3 was pretreated, and the evaporation paste used for the pretreatment was: TiB2: 85wt%, H2O: 15wt%.

[0085] The copper-plated polypropylene film sample of Comparative Example 3 was tested for coating adhesion, and the copper adhesion amount of Comparative Example 3 was found to be 5.0 mg / m³. 2 .

[0086] Comparative Example 4

[0087] The only difference between Comparative Example 4 and Example 1 is that the copper evaporation boat in Comparative Example 4 was pretreated. The evaporation paste used for the pretreatment was: TiB2: 70wt%, Mo: 15wt%, H2O: 15wt%.

[0088] The copper-plated polypropylene film sample of Comparative Example 4 was tested for coating adhesion. The results showed that the copper adhesion in Comparative Example 4 was 6.5 mg / m³. 2 .

[0089] Comparative Example 5

[0090] The only difference between Comparative Example 5 and Example 1 is that the copper evaporation boat of Comparative Example 5 was pretreated, and the evaporation paste used for the pretreatment was: WB: 85wt%, H2O: 15wt%.

[0091] The copper-plated polypropylene film sample of Comparative Example 5 was tested for coating adhesion, and the copper adhesion amount of Comparative Example 5 was found to be 6.0 mg / m³. 2 .

[0092] By comparing the copper adhesion amounts in Example 1 and Comparative Example 1, it can be seen that coating the surface of the copper evaporation boat with evaporation paste to form a coating is beneficial to improving the copper evaporation efficiency. Comparing the copper adhesion amount data of Example 1 and Comparative Examples 2-5, it is clear that applying the evaporation paste with the composition content of the present invention results in a better copper evaporation effect.

[0093] Example 2

[0094] The copper evaporation boat used in this embodiment has undergone pretreatment, which involves coating an evaporation paste onto the groove surface of the copper evaporation boat and drying it to obtain a copper evaporation boat with a coating thickness of 180 μm. The evaporation paste is composed of: Mo: 70 wt%, TiB2: 15 wt%, and H2O: 15 wt%.

[0095] The steps of the preparation method of the metallized polypropylene film for high temperature and high humidity resistant capacitors in this embodiment are as follows:

[0096] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0097] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 300 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 14 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The first evaporation coating is completed.

[0098] The metallized polypropylene film deposited for the first time was placed in a cleanroom of Class 10,000 with a temperature of -6°C and a humidity of 30% for 24 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 30°C and a humidity of 30% for another 24 hours.

[0099] The coating adhesion of a polypropylene film sample after the first vapor deposition was tested, and the copper adhesion was found to be 3.8 mg / m³. 2 The zinc adhesion amount was 62.5 mg / m³. 2 .

[0100] S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evaporate the vacuum evaporation coating machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0101] S4. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 220 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 10 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The second evaporation coating is completed.

[0102] The metallized polypropylene film after the second vapor deposition was placed in a cleanroom of Class 10,000 with a temperature of -6°C and a humidity of 30% for 24 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 30°C and a humidity of 30% for another 24 hours.

[0103] The coating adhesion of the polypropylene film sample after the second vapor deposition was tested, and the copper adhesion was found to be 4.5 mg / m³. 2 The zinc adhesion amount was 87.2 mg / m³. 2 ;

[0104] Then it is cut and packaged into metallized polypropylene film products.

[0105] Example 3

[0106] The copper evaporation boat used in this embodiment has undergone pretreatment, which involves coating an evaporation paste onto the groove surface of the copper evaporation boat and drying it to obtain a copper evaporation boat with a coating thickness of 200 μm. The evaporation paste is composed of: Mo: 70 wt%, TiB2: 15 wt%, and H2O: 15 wt%.

[0107] The steps of the preparation method of the metallized polypropylene film for high temperature and high humidity resistant capacitors in this embodiment are as follows:

[0108] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0109] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 330 mm / min. The copper evaporation boat is heated to 1550℃, and the crucible is heated to 680℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 13 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The first evaporation coating is completed.

[0110] The metallized polypropylene film deposited for the first time was placed in a cleanroom of Class 10,000 with a temperature of -8°C and a humidity of 30% for 28 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 32°C and a humidity of 30% for 22 hours.

[0111] The coating adhesion of a polypropylene film sample after the first vapor deposition was tested, and the copper adhesion was found to be 4.4 mg / m³. 2 The zinc adhesion amount was 65.9 mg / m³. 2 .

[0112] S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evaporate the vacuum evaporation coating machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0113] S4. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 220 mm / min. The copper evaporation boat is heated to 1550℃, and the crucible is heated to 680℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 9 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The second evaporation coating is completed.

[0114] The metallized polypropylene film after the second vapor deposition was placed in a cleanroom of Class 10,000 with a temperature of -8°C and a humidity of 30% for 24 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 32°C and a humidity of 30% for 30 hours.

[0115] The coating adhesion of the polypropylene film sample after the second vapor deposition was tested, and the copper adhesion was found to be 5.5 mg / m³. 2 The zinc adhesion amount was 94.2 mg / m³. 2 ;

[0116] Then it is cut and packaged into metallized polypropylene film products.

[0117] Comparative Example 6

[0118] The copper evaporation boat used in this implementation was not pretreated.

[0119] The difference between the preparation method of the metallized polypropylene film for high-temperature and high-humidity capacitors in this embodiment and that in Embodiment 2 is:

[0120] In Comparative Example 6, during the first vapor deposition, the copper wire conveying speed was 495 mm / min and the temperature was 1600°C; during the second vapor deposition, the copper wire conveying speed was 350 mm / min and the temperature was 1600°C. Everything else was the same as in Example 2.

[0121] The coating adhesion of a polypropylene film sample after the first vapor deposition was tested, and the copper adhesion was found to be 3.8 mg / m³. 2 The zinc adhesion amount was 62.5 mg / m³. 2 .

[0122] The coating adhesion of the polypropylene film sample after the second vapor deposition was tested, and the copper adhesion was found to be 4.5 mg / m³. 2 The zinc adhesion amount was 87.2 mg / m³. 2 .

[0123] Comparative Example 7

[0124] The copper evaporation boat used in Comparative Example 7 underwent pretreatment, and the pretreatment steps were the same as those in Example 2.

[0125] The preparation method of the metallized polypropylene film in Comparative Example 7 differs from that in Example 2 in that Comparative Example 7 involves a single vapor deposition process without cold treatment. The specific steps are as follows:

[0126] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0127] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 285 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 6 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form a copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form a zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The evaporation coating is complete.

[0128] The metallized polypropylene film was placed in an environment with a cleanliness level of 10,000, a temperature of 30°C, and a humidity of 30% for 48 hours.

[0129] The adhesion of the coated polypropylene film sample after vapor deposition was tested, and the copper adhesion was found to be 8.3 mg / m³. 2 The zinc adhesion amount was 149.7 mg / m³. 2 ;

[0130] Then it is cut and packaged into metallized polypropylene film products.

[0131] Comparative Example 8

[0132] The copper evaporation boat used in Comparative Example 8 underwent pretreatment, and the pretreatment steps were the same as those in Example 2.

[0133] The difference between the preparation method of the metallized polypropylene film in Comparative Example 8 and Example 2 is that Comparative Example 8 involves a single vapor deposition process, the specific steps of which are as follows:

[0134] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0135] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 285 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 6 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form a copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form a zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The evaporation coating is complete.

[0136] The metallized polypropylene film was placed in a cleanroom environment of Class 10,000, temperature of -6℃ and humidity of 30% for 24 hours, and then placed in a cleanroom environment of Class 10,000, temperature of 30℃ and humidity of 30% for 24 hours.

[0137] The adhesion of the coated polypropylene film sample after vapor deposition was tested, and the copper adhesion was found to be 8.3 mg / m³. 2 The zinc adhesion amount was 149.7 mg / m³. 2 ;

[0138] Then it is cut and packaged into metallized polypropylene film products.

[0139] Comparative Example 9

[0140] The copper evaporation boat used in Comparative Example 9 underwent pretreatment, and the pretreatment steps were the same as those in Example 2.

[0141] The preparation method of the metallized polypropylene film in Comparative Example 9 differs from that in Example 2 in that Comparative Example 9 did not undergo cold treatment. The specific steps are as follows:

[0142] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0143] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 300 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 14 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The first evaporation coating is completed.

[0144] The metallized polypropylene film deposited for the first time was placed in an environment with a cleanliness level of 10,000, a temperature of 30°C, and a humidity of 30% for 48 hours.

[0145] The coating adhesion of a polypropylene film sample after the first vapor deposition was tested, and the copper adhesion was found to be 3.8 mg / m³. 2 The zinc adhesion amount was 62.5 mg / m³. 2 .

[0146] S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evaporate the vacuum evaporation coating machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0147] S4. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 220 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 10 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The second evaporation coating is completed.

[0148] The metallized polypropylene film after the second vapor deposition was placed in a cleanroom environment of Class 10,000 and a temperature of 30°C for 48 hours.

[0149] The coating adhesion of the polypropylene film sample after the second vapor deposition was tested, and the copper adhesion was found to be 4.5 mg / m³. 2 The zinc adhesion amount was 87.2 mg / m³. 2 .

[0150] Then it is cut and packaged into metallized polypropylene film products.

[0151] Comparative Example 10

[0152] The copper evaporation boat used in Comparative Example 10 underwent pretreatment, and the pretreatment steps were the same as those in Example 2.

[0153] The preparation steps of the metallized polypropylene film of Comparative Example 10 are as follows:

[0154] S1. Place the polypropylene film in a vacuum evaporation coating machine and evaporate the machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0155] S2. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 300 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 14 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The first evaporation coating is completed.

[0156] The metallized polypropylene film deposited for the first time was placed in a cleanroom of Class 10,000 with a temperature of 6°C and a humidity of 30% for 24 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 30°C and a humidity of 30% for another 24 hours.

[0157] The coating adhesion of a polypropylene film sample after the first vapor deposition was tested, and the copper adhesion was found to be 3.8 mg / m³. 2 The zinc adhesion amount was 62.5 mg / m³. 2 .

[0158] S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evaporate the vacuum evaporation coating machine to a vacuum level of 1×10⁻⁶. -3 Pa;

[0159] S4. The zinc block is placed in the crucible, and the copper wire is conveyed to the copper evaporation boat at a speed of 200 mm / min. The copper evaporation boat is heated to 1500℃, and the crucible is heated to 700℃. The copper and zinc wires evaporate due to the heat. The polypropylene film winding system is started, and the polypropylene film begins to move at a speed of 10 m / min. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, the vacuum is released, and the pressure of the vacuum evaporation coating machine is made equal to atmospheric pressure. The second evaporation coating is completed.

[0160] The metallized polypropylene film after the second vapor deposition was placed in a cleanroom of Class 10,000 with a temperature of 6°C and a humidity of 30% for 24 hours, and then placed in a cleanroom of Class 10,000 with a temperature of 30°C and a humidity of 30% for another 24 hours.

[0161] The coating adhesion of the polypropylene film sample after the second vapor deposition was tested, and the copper adhesion was found to be 4.5 mg / m³. 2 The zinc adhesion amount was 87.2 mg / m³. 2 .

[0162] Then it is cut and packaged into metallized polypropylene film products.

[0163] The metallized polypropylene films prepared in Examples 2-3 and Comparative Examples 6-10 were wound into capacitor core packages, hot-pressed, and flattened. A metal contact layer (tin-zinc alloy) was sprayed onto the electrode portions at both ends of the capacitor core package. The leads were soldered onto the metal contact layer. The capacitor core package was inserted into a plastic shell, and potting compound was poured into the plastic shell for encapsulation to obtain a capacitor.

[0164] High temperature and high humidity load test of capacitors:

[0165] Testing instruments: Constant temperature and humidity test chamber (QP08), LCR bridge (LQC09)

[0166] Test temperature: 85℃, relative humidity: 85%RH, test voltage: ACR.V = 275VAC, current: 3A, test frequency: CS = 1KHz, DF = 1KHz.

[0167] For each example and comparative example, 10 samples of the capacitors were tested at 85°C and 85%RH for 500 hours. The capacitance change rate (ΔC / C0) and loss tangent (ΔDF) change value (ΔDF) were measured and the average value was taken. The results are shown in Table 1.

[0168] Table 1. High temperature and high humidity resistance of capacitors prepared in the examples and comparative examples.

[0169]

[0170] The absence of evaporation paste in the copper evaporation boat to form a coating will affect the amount of copper deposited on the film. By comparing Example 2 and Comparative Example 6, it can be seen that by adjusting the evaporation temperature and increasing the copper wire conveying speed, the same amount of copper can be achieved. However, there is incompletely evaporated copper, which is obviously a waste of raw materials. In addition, the copper liquid exists in a spherical shape, and the uneven wetting of the evaporation boat will also lead to uneven copper deposit, which in turn affects the performance of the capacitor.

[0171] By comparing Comparative Examples 7 and 8 with Comparative Examples 2 and 9, it can be seen that the metallized polypropylene film that undergoes cold treatment after metal vapor deposition produces capacitors with better high temperature and high humidity resistance. This may be because the cold treatment makes the metal coatings bond more tightly, the coating structure more compact, and the metal atoms on the coating more stable, thus reducing the adverse effects of water vapor and air on the metal coating.

[0172] Comparative Examples 2 and 8, and Comparative Examples 7 and 9, show that the special metal layer structure formed by vapor deposition of the present invention, in which the first copper layer, the first zinc layer, the second copper layer, and the second zinc layer alternate, can effectively improve the high temperature and high humidity resistance of the capacitor compared to the copper and zinc composite layer.

[0173] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0174] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0175] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing a metallized polypropylene film for high-temperature and high-humidity resistant capacitors, characterized in that, Includes the following steps: S1. Place the polypropylene film in a vacuum evaporation coating machine and evacuate the vacuum evaporation coating machine. S2. The zinc block is placed in the crucible, and the copper wire is transferred to the copper evaporation boat. The copper evaporation boat and the crucible are heated, and the copper wire and zinc block are evaporated by the heat. The polypropylene film winding system is started, and the polypropylene film begins to move. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the moving polypropylene film to form the first copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the first copper layer to form the first zinc layer. The vacuum pump is turned off, and the first evaporation is completed. S3. Place the polypropylene film after the first vapor deposition into the vacuum evaporation coating machine again, and evacuate the vacuum evaporation coating machine. S4. The zinc block is placed in the crucible, and the copper wire is transferred to the copper evaporation boat. The copper evaporation boat and the crucible are heated, and the copper wire and zinc block are evaporated by heat. The polypropylene film winding system is started, and the polypropylene film begins to move. The copper baffle is opened to allow gaseous copper to be deposited on the surface of the first zinc layer to form a second copper layer. The zinc baffle is opened to allow gaseous zinc to be deposited on the surface of the second copper layer to form a second zinc layer. The vacuum pump is turned off, and the second evaporation is completed. S5. Cutting and packaging yields the finished metallized polypropylene film. The copper evaporation boat undergoes pretreatment, which includes the following steps: applying evaporation paste to the groove surface of the copper evaporation boat and drying it to obtain a copper evaporation boat with a coating. The composition and content of the evaporating paste are as follows: Mo: 50~80wt%, TiB2: 10~25wt%, H2O: 10~25wt%.

2. The preparation method according to claim 1, characterized in that, The coating thickness is 80~300μm.

3. The preparation method according to claim 1, characterized in that, In steps S1 and S3, the vacuum evaporation coating machine is evacuated to a vacuum level of 0.01 × 10⁻⁶. -3 ~5×10 -3 Pa.

4. The preparation method according to claim 1, characterized in that, The purity of the copper wire is ≥99.99%, and the purity of the zinc block is ≥99.9%.

5. The preparation method according to claim 1, characterized in that, During the first and second vapor deposition processes, the vapor deposition distance is 40~50cm, the moving speed of the polypropylene film is 5~15m / min, the diameter of the copper wire is 1.0~2.0mm, and the conveying speed of the copper wire is 100~500mm / min.

6. The preparation method according to claim 1, characterized in that, The heating temperature of the copper evaporation boat is 1400~1600℃, and the heating temperature of the crucible is 650~800℃.

7. The preparation method according to claim 1, characterized in that, After the first vapor deposition, the metallized polypropylene film is placed in an environment with a cleanliness level of less than 10,000, a temperature of -10 to 0°C, and a humidity of 10 to 40% for 20 to 30 hours, and then placed in an environment with a cleanliness level of less than 10,000, and a temperature of 20 to 40°C for 10 to 30 hours.

8. The preparation method according to claim 1 or 7, characterized in that, After the second vapor deposition, the metallized polypropylene film is placed in an environment with a cleanliness level of less than 10,000, a temperature of -10 to 0℃, and a humidity of 10 to 40% for 20 to 30 hours, and then placed in an environment with a cleanliness level of less than 10,000, a temperature of 20 to 40℃, and a humidity of 10 to 40% for 10 to 30 hours.

9. A metallized polypropylene film for high-temperature and high-humidity resistant capacitors, characterized in that, It is prepared by the preparation method as described in claim 1. The metallized polypropylene film includes a polypropylene film and a metal layer. The metal layer is composed of a first copper layer, a first zinc layer, a second copper layer and a second zinc layer. The first copper layer is located on the surface of the polypropylene film. The first zinc layer covers the surface of the first copper layer. The second copper layer covers the surface of the first zinc layer and the second zinc layer covers the surface of the second copper layer.

10. The metallized polypropylene film according to claim 9, characterized in that, In the metal layer, the zinc content is greater than the copper content.

11. The metallized polypropylene film according to claim 9, characterized in that, The metal layer contains 60-99.9 wt% zinc, 0.1-40 wt% copper, and a total of 100 wt% zinc and copper.

12. The metallized polypropylene film according to claim 11, characterized in that, The metal layer contains 90-99 wt% zinc and 1-10 wt% copper.

13. The metallized polypropylene film according to claim 9, characterized in that, The mass of the first copper layer accounts for 30 to 70 wt% of the total mass of the first and second copper layers, and the mass of the first zinc layer accounts for 10 to 50 wt% of the total mass of the first and second zinc layers.

14. The metallized polypropylene film for high-temperature and high-humidity capacitors as described in claim 9 is applied in capacitors.

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