A method for preventing contamination of the corona treated surface of capacitor film
By setting a polypropylene film with a specific surface roughness on the surface of the traction roller, the problem of adhering to the traction roller after the corona treatment is solved, and the effect of reducing contamination and damage to the corona treatment surface is achieved, and the performance and production efficiency of the capacitor are improved.
Patent Information
- Application Number
- CN202411829627.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-04-08
AI Technical Summary
After corona treatment, the metallized film of capacitors is easily adhered to the traction roller, resulting in contamination, abrasions and damage to the corona treatment surface, affecting the quality of the film and the performance of the capacitor.
A polypropylene film is provided on the surface of the traction roller, with a surface roughness of 0.55-0.65. The traction roller is wrapped by spiral winding to reduce the adhesion between the film and the traction roller.
It effectively prevents the adhesion between the film and the traction roller, reduces the abrasion and damage of the corona treatment surface, improves the quality of the film and the performance of the capacitor, and reduces production costs.
Smart Images
Figure CN119773218A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of thin films, and in particular relates to a method for preventing the corona treatment surface of a capacitor film from being contaminated. Background Art
[0002] During the preparation of metallized film for capacitors, a dense metal layer needs to be evaporated on the film substrate after corona treatment. As the electrode of the capacitor, the quality of its metal adhesion will affect the square resistance of the film. If the coating falls off, it will directly cause the capacitor capacity to decay, affecting the performance and service life of the capacitor. After the film is evaporated, a magnifying glass is generally used to check the adhesion of the coating, and it is required that the coating should not fall off.
[0003] Among them, corona treatment is to polarize the surface of the film substrate through corona discharge, increase its surface wetting tension, and thus improve the metal adhesion of the film substrate. However, the surface of the film substrate after corona treatment is easily polarized by high voltage, resulting in increased surface molecular activity and high viscosity, which makes it easy to stick to the subsequent traction roller in contact with it. The stickiness of the roller will cause tension fluctuations, resulting in contamination, scratches, damage, and decreased adhesion of the corona treatment surface, and cause quality abnormalities such as light spots, dark stripes, and metal layer shedding during downstream evaporation.
[0004] At present, the adhesion between the film and the traction roller is usually reduced by frequently stopping the machine to clean the traction roller or changing the corona treatment parameters, thereby reducing the scratches and damage on the corona treated surface. However, these methods often cause additional losses and increase production costs; they may also affect other properties of the film, such as metal adhesion and thermal stability.
[0005] Therefore, how to effectively prevent the corona-treated surface of the metallized film for capacitors from being contaminated and damaged is still a technical problem that needs to be solved urgently in this field. Summary of the invention
[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preventing the contamination of the corona treated surface of the capacitor film, which can effectively prevent the adhesion of the corona treated film to the traction roller, reduce the scratches and damage of the corona treated surface, thereby improving the quality of the capacitor film and further reducing the loss value of the capacitor.
[0007] A first aspect of the present invention provides a method for preventing contamination of a corona treated surface of a capacitor film, comprising the following steps:
[0008] A polypropylene film is arranged on the surface of a traction roller, and the corona-treated film substrate is tractioned by the traction roller and then transported to the next process;
[0009] The surface roughness of the polypropylene film is 0.55-0.65.
[0010] Specifically, a polypropylene film with a specific surface roughness is arranged on the surface of the traction roller, which can reduce the contact area with the film substrate and reduce the stickiness with the corona treated surface. The polypropylene film is a non-polar material, and is not easy to adhere to the polar surface (the surface of the film substrate after corona treatment), which can effectively prevent the contamination of the corona treated surface of the film substrate, reduce the increase of the surface molecular activity of the film substrate caused by the corona treatment, and reduce the viscosity, which is easy to stick to the traction roller, causing tension fluctuations, and causing the corona treated surface to be scratched and damaged. And under the premise of not affecting other properties of the film substrate (such as mechanical strength, thermal stability, etc.), the subsequent evaporation quality of the film substrate is improved, and the problem of coating shedding caused by the contamination of the corona treated surface is solved.
[0011] In some embodiments of the present invention, the polypropylene film is wrapped on the surface of the traction roller in a spiral winding manner.
[0012] Specifically, on the traction roller in contact with the corona treated surface of the film substrate, according to the direction of rotation of the roller, from the end of the traction roller where no film substrate passes, the polypropylene film is wrapped around the entire traction roller in a spiral winding manner at about 30 degrees to ensure that each circle overlaps during the film wrapping process and the roller surface is not exposed, while avoiding wrinkles after wrapping.
[0013] In some embodiments of the present invention, the polypropylene film has a thickness of 12-15 μm.
[0014] Specifically, if the thickness of the polypropylene film is less than 12 μm, the polypropylene film is easily damaged and broken during high-speed production and cannot be used continuously; if the thickness is greater than 15 μm, during the process of wrapping the polypropylene film around the traction roller, the thickness difference between the overlapping area and the non-overlapping area of the polypropylene film is too large, and wrinkles will be generated at this position during production. Therefore, the thickness of the polypropylene film selected by the present invention is best in the range of 12-15 μm.
[0015] In some embodiments of the present invention, the width of the polypropylene film is 140-200 mm.
[0016] Specifically, if the width of the polypropylene film is less than 140 mm, it is easy to produce empty areas on the surface of the traction roller during the wrapping process, making it difficult to achieve full coverage, and the uncovered areas will cause corona treatment surface damage; if the width is greater than 200 mm, wrinkles are easy to be produced during the wrapping process, and such wrinkles will cause the polypropylene film to wrinkle, affecting subsequent slitting and vapor deposition.
[0017] In some embodiments of the present invention, the polypropylene film is prepared by a preparation method comprising the following steps:
[0018] The polypropylene raw material is heated and melted to obtain a melt;
[0019] The melt flows out as a sheet after passing through the die head, and then forms a casting sheet after being cooled;
[0020] The cast sheet is longitudinally stretched, transversely stretched, heat-set, and rolled up to obtain the polypropylene film.
[0021] Specifically, the present invention does not add other additives during the preparation of the polypropylene film, because impurities will affect the withstand voltage of the metallized film for capacitors, and the precipitation of additives will cause the electrical properties of the product to be unqualified and unusable.
[0022] In some embodiments of the present invention, the ash content of the polypropylene raw material is below 30 ppm, the oxidation half-life is between 15 and 25 minutes, the isotacticity is between 97.0% and 98.5%, and the melt index is between 2.8 and 3.5.
[0023] In some embodiments of the present invention, the temperature of the longitudinal stretching is 138-145°C.
[0024] In some embodiments of the present invention, the longitudinal stretching multiple is 5-6 times.
[0025] In some embodiments of the present invention, the temperature of the transverse stretching is 160-165°C.
[0026] In some embodiments of the present invention, the transverse stretching ratio is 8-10 times.
[0027] In some embodiments of the present invention, the temperature of the heat setting is 120-140°C.
[0028] In some embodiments of the present invention, an aging treatment is further performed after winding, and the conditions of the aging treatment include: a temperature of 20-35° C., a humidity of 50-60%, and a time of ≥48 h.
[0029] In some embodiments of the present invention, the material of the film substrate includes biaxially oriented polypropylene film (BOPP), polyethylene or polycarbonate.
[0030] The second aspect of the present invention provides the use of the method described in the first aspect of the present invention in preparing a metallized film for a capacitor.
[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0032] 1. The present invention arranges a polypropylene film with a specific surface roughness on the surface of the traction roller, which can effectively prevent the film substrate from adhering to the traction roller, reduce the scratches and damages on the corona treated surface, and ensure that the film substrate has sufficient friction when passing through, and will not slip and cause damage to the corona treated surface.
[0033] 2. The polypropylene film used in the present invention can be replaced once a week, and each replacement takes about 20 minutes, which greatly reduces the frequent cleaning loss of the traditional traction roller, improves efficiency, and reduces production costs.
[0034] 3. The present invention does not require changing the corona treatment parameters and will not affect other properties of the film substrate, such as mechanical strength, thermal stability, etc., thereby improving the quality of the capacitor film and further reducing the loss value of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 This is a magnifying glass observation picture after the method of Example 1 is used to treat and evaporate metal;
[0036] Figure 2 This is a magnifying glass observation picture after the method of comparative example 1 was used to treat and evaporate metal;
[0037] Figure 3 This is a magnifying glass observation picture after the method of Comparative Example 2 was used to treat and evaporate metal. DETAILED DESCRIPTION
[0038] The present invention is further described in detail below by specific examples. The raw materials, reagents or devices used in the examples can be obtained from conventional commercial sources or by prior art methods unless otherwise specified. Unless otherwise specified, the experiments or test methods are conventional methods in the art.
[0039] The polypropylene film used in the embodiment of the present invention is prepared by a preparation method comprising the following steps:
[0040] (1) Select polypropylene pellets with an ash content of less than 30 ppm, an oxidation half-life of 15-25 minutes, an isotacticity of 97.0%-98.5%, and a melt index of 2.8-3.5;
[0041] (2) adding polypropylene pellets into the feed port of the screw extruder, heating and melting the polypropylene pellets by the screw extruder 1, and then melting and conveying them through the extruder 2, and then the melt passes through the metering pump and the fine filter in sequence, and enters the hanger die through the flow channel;
[0042] (3) The melt after passing through the die is cooled by a cold drum to obtain a thick sheet, the thick sheet is peeled off from the cold drum, and the peeled thick sheet is passed through a tension control roller to obtain a cast sheet;
[0043] (4) Stretching: The cast sheet is placed in a longitudinal stretching machine for longitudinal stretching to form a film. The temperature of the longitudinal stretching is 138-145°C. The longitudinally stretched film is longitudinally heat-set on the surface of a shaping roller (120-140°C). The longitudinal stretching ratio of the formed film is 5-6 times; after longitudinal stretching, the film enters a transverse stretching machine. At the entrance of the transverse stretching machine, the film is clamped on both sides by chain clamps. The chain clamps pull the film forward. The width of the chain clamps becomes wider in the stretching zone, so that the film is transversely stretched. The temperature of the transverse stretching is 160-165°C. The transverse stretching ratio of the formed film is 8-10 times. The stretched film is transversely heat-set (120-140°C) on the shaping roller and then cooled; the pressure of the air pressure rollers of the longitudinal stretching machine and the transverse stretching machine is 0.4-0.5MPa;
[0044] (5) Traction: The film is fed into the traction process by rollers, the thickness is tested by a thickness gauge, and the trimming device cuts off the edge material;
[0045] (6) using a winding device to wind up the film to form a film roll (without corona treatment), wherein the film is pulled by a traction roller and then conveyed to a tension roller and a pressure roller, and then enters the winding device;
[0046] (7) Aging treatment: Place the film roll in an aging treatment rack for aging treatment, maintain the temperature at 20-35°C, humidity at 50-60%, and time ≥48h;
[0047] (8) Finished product: The processed film rolls are cut and packaged to obtain the finished product.
[0048] It is understandable that the surface roughness, thickness and width of the prepared polypropylene film can be adjusted by adjusting the preparation process parameters of the above-mentioned polypropylene film.
[0049] Example 1
[0050] A method for preventing contamination of a corona treated surface of a capacitor film comprises the following steps:
[0051] On the traction roller in contact with the corona-treated surface of the film substrate (BOPP), according to the rotation direction of the roller, from the end of the traction roller where no film substrate passes, the polypropylene film is wrapped around the entire traction roller in a spiral winding manner at about 30 degrees, ensuring that each circle overlaps during the film coating process and does not expose the roller surface, and at the same time, wrinkles are avoided after wrapping, and the corona-treated film substrate is pulled by the traction roller wrapped with the polypropylene film and then transported to the next process;
[0052] The surface roughness of the polypropylene film is 0.6, the thickness is 13 μm, and the width is 180 mm.
[0053] Example 2
[0054] A method for preventing contamination of a corona treated surface of a capacitor film comprises the following steps:
[0055] On the traction roller in contact with the corona-treated surface of the film substrate (BOPP), according to the rotation direction of the roller, from the end of the traction roller where no film substrate passes, the polypropylene film is wrapped around the entire traction roller in a spiral winding manner at about 30 degrees, ensuring that each circle overlaps during the film coating process and does not expose the roller surface, and at the same time, wrinkles are avoided after wrapping, and the corona-treated film substrate is pulled by the traction roller wrapped with the polypropylene film and then transported to the next process;
[0056] The surface roughness of the polypropylene film is 0.55, the thickness is 12 μm, and the width is 140 mm.
[0057] Example 3
[0058] A method for preventing contamination of a corona treated surface of a capacitor film comprises the following steps:
[0059] On the traction roller in contact with the corona-treated surface of the film substrate (BOPP), according to the rotation direction of the roller, from the end of the traction roller where no film substrate passes, the polypropylene film is wrapped around the entire traction roller in a spiral winding manner at about 30 degrees, ensuring that each circle overlaps during the film coating process and does not expose the roller surface, and at the same time, wrinkles are avoided after wrapping, and the corona-treated film substrate is pulled by the traction roller wrapped with the polypropylene film and then transported to the next process;
[0060] The polypropylene film has a surface roughness of 0.65, a thickness of 15 μm, and a width of 200 mm.
[0061] Comparative Example 1
[0062] The only difference from Example 1 is that the surface roughness of the polypropylene film used in Comparative Example 1 is 0.4.
[0063] Comparative Example 2
[0064] The only difference from Example 1 is that the surface roughness of the polypropylene film used in Comparative Example 2 is 0.8.
[0065] Test Example 1
[0066] After being treated by the methods of Examples 1-3 and Comparative Examples 1-2, conventional metal evaporation was performed on the corona treated surface to obtain a metallized film for capacitors, and the coating was observed.
[0067] The results show that: using the methods of Examples 1-3, the coating is intact, without damage or shedding; among them, using the method of Example 1, the coating is as follows Figure 1 As shown (observed with a 40x magnifying glass).
[0068] The surface of the polypropylene film of Comparative Example 1 is too smooth, and relative sliding is likely to occur between the polypropylene film and the film substrate, which will also cause damage to the coating. This damage has no definite rules, and the shedding shape is generally irregular, such as Figure 2 As shown, Figure 2 The white part in the middle is the fallen part (observed under a 100x magnifying glass).
[0069] The surface roughness of the polypropylene film of Comparative Example 2 is too large, and the edge of the crystal peak is obviously protruding, which will cause scratches on the corona treated surface in the protruding area. After evaporation, a large number of dense dot-shaped coatings will fall off (white dot-shaped parts), such as Figure 3 As shown (observed with a 40x magnifying glass).
[0070] Test Example 2
[0071] After being treated by the methods of Examples 1-3 and Comparative Examples 1-2, conventional metal evaporation was performed on the corona treated surface to obtain a metallized film for capacitors, which was then further conventionally made into capacitors. The loss values were tested, and the data are shown in Tables 1 and 2.
[0072] Table 1
[0073]
[0074] Table 2
[0075]
[0076]
[0077] It can be seen from the data in Table 1 and Table 2 that there is no significant difference in 1KHz loss, but the 10KHz loss test results show that after being processed by the method of the present invention, the loss is significantly reduced and reaches the loss requirement range.
[0078] The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.
Claims
1. A method for preventing contamination of a corona treated surface of a capacitor film, characterized in that: The following steps are involved: A polypropylene film is arranged on the surface of a traction roller, and the corona-treated film substrate is tractioned by the traction roller and then transported to the next process; The surface roughness of the polypropylene film is 0.55-0.
65.
2. The method according to claim 1, characterized in that The thickness of the polypropylene film is 12-15 μm.
3. The method according to claim 1, characterized in that The width of the polypropylene film is 140-200 mm.
4. The method according to claim 1, characterized in that: The polypropylene film is prepared by a preparation method comprising the following steps: The polypropylene raw material is heated and melted to obtain a melt; The melt flows out as a sheet after passing through the die head, and then forms a casting sheet after being cooled; The cast sheet is longitudinally stretched, transversely stretched, heat-set, and rolled up to obtain the polypropylene film.
5. The method according to claim 4, characterized in that The temperature of the longitudinal stretching is 138-145°C.
6. The method according to claim 4, characterized in that The multiple of the longitudinal stretching is 5-6 times.
7. The method according to claim 4, characterized in that The temperature of the transverse stretching is 160-165°C.
8. The method according to claim 4, characterized in that The transverse stretching ratio is 8-10 times.
9. The method according to claim 4, characterized in that After winding, an aging treatment is also performed, and the conditions of the aging treatment include: a temperature of 20-35° C., a humidity of 50-60%, and a time of ≥48 hours.
10. Use of the method according to any one of claims 1 to 9 in preparing a metallized film for capacitors.