Thin film for capacitor, preparation method of thin film and thin film capacitor

Abstract

The invention relates to the technical field of thin films for capacitors, in particular to a thin film for a capacitor, a preparation method of the thin film and a thin film capacitor, and the preparation method comprises the following steps: (1) blending 10%-40% by mass of PMP (polymethylpentene), 2%-4% by mass of PP-g-MAH (maleic anhydride grafted PP) and 56%-88% by mass of PP, and then melting and biaxially stretching to form a film; (2) loading an antioxidant on the surface of silicon dioxide by adopting a dry method to prepare a silicon dioxide load with the antioxidant loaded on the surface; and (3) spraying the silicon dioxide load onto the surface of the capacitor film through a magnetron sputtering process. The capacitor film prepared by the method has excellent high temperature resistance and oxidation resistance, is low in manufacturing cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin films for capacitors, and particularly relates to thin films for capacitors, a preparation method thereof, and thin film capacitors. Background Art

[0002] With people paying more and more attention to the concept of low-carbon environmental protection, new energy vehicles have developed rapidly. As a key link in the development of new energy vehicles, energy storage has always been concerned by people. In the promotion of new energy vehicles, the driving force of the vehicle is crucial and largely determines the applicability of new energy vehicles. Supercapacitors are generally considered to be electrochemcial energy storage devices with development potential between ordinary capacitors and batteries, and are widely used in industrial production, military equipment, energy, transportation and other fields. At present, the application technology of supercapacitors for vehicles is becoming increasingly mature. Compared with traditional capacitors, they can store and release charges with high efficiency.

[0003] Biaxially oriented polypropylene film (BOPP) has excellent dielectric stability, high insulation strength and is easy to be produced and prepared on a large scale. Currently, it is the preferred dielectric material for supercapacitors. During the operation of capacitors, the thin film dielectric for BO capacitors is subjected to the coupling action of a complex strong electric field and a high-temperature thermal field. Under the dual action of high temperature and high field, the space charge injection and accumulation phenomena of the thin film dielectric are more serious, the leakage current of the insulating material increases, the conductance loss increases, and the internal electric field of the dielectric is severely distorted, resulting in thermal oxygen aging of the dielectric material and capacitor failure. Therefore, the performance of the capacitor thin film dielectric directly determines the performance and service life of the capacitor. Therefore, it is urgently needed to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a thin film for capacitors, a preparation method thereof, and a thin film capacitor. By designing the composition and cooperating with the corresponding preparation process, the prepared thin film for capacitors has good high-temperature resistance and antioxidant properties.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows. A thin film for capacitors, a preparation method thereof, and a thin film capacitor include the following raw materials in parts by weight: 10-40 parts of PMP pellets, 60-90 parts of PP pellets, and 0.1-1 part of silica load.

[0006] Further, the silica load is an antioxidant loaded on the surface of silica particles.

[0007] Further, the preparation method of the antioxidant loaded on the surface of the silica is to mix the silica and the antioxidant and stir and react at 80-120°C for 240-360 minutes to obtain the target product of the silica loaded antioxidant.

[0008] Furthermore, the antioxidant includes any one or more of phenolic antioxidants such as tert-butylphenol hydroxybenzoate, p-hydroxybenzoate, tri-tert-butyl hydroxybenzoate, 2,6-di-tert-butyl-4-methylphenol, [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4,4'-thiobis(6-tert-butyl-3-methylphenol), and the like, and the phenolic antioxidants are not limited to the above.

[0009] Furthermore, the mass ratio of the phenolic antioxidant to silicon dioxide is (5-25):100.

[0010] Further, the following steps are included:

[0011] 1) Extrusion:

[0012] 10%-40% by mass of PMP (polymethylpentene), 2%-4% by mass of PP-g-MAH, and 56%-88% by mass of PP are mechanically mixed and then added into a twin-screw for melt extrusion.

[0013] 2) Casting:

[0014] The blend melt in a viscous flow state from the extruder die is rapidly cooled to below its glass transition temperature on a uniformly rotating quenching roller to form a glassy cast sheet with uniform thickness.

[0015] 3) Stretching:

[0016] The cast sheet of a certain thickness is longitudinally stretched to a certain multiple under heating. The longitudinally stretched film is preheated, stretched, heat-set and cooled in a transverse stretching machine to complete the biaxial stretching of the film.

[0017] 4) Corona:

[0018] The stretched film is subjected to corona treatment at a certain voltage to activate the film surface.

[0019] 5) Time limit:

[0020] The corona treated film is placed in an aging warehouse for a certain period of aging treatment.

[0021] 6) Magnetron sputtering:

[0022] SiO2 or SiO2 load is used as target material, and SiO2 or SiO2 load is deposited on the surface of PP film by magnetron sputtering technology.

[0023] 7) Coating;

[0024] The metal is evaporated and deposited on the PP film by heating or electron beam in a vacuum environment.

[0025] Further, in step 4), the corona voltage is controlled to be 15 kV - 30 kV.

[0026] Further, in step 5), the aging treatment temperature is controlled at 20 - 40 °C and the time is 12 - 36 h.

[0027] Further, in step 6), the pressure of magnetron sputtering is controlled at 1.0 - 2.0 Pa and the sputtering time is 1 - 2 h.

[0028] Further, the capacitor includes the capacitor film as described above.

[0029] The beneficial effects of the present invention are embodied in:

[0030] (1) By introducing PMP, PP-g-MAH and silica loadings and adopting a specific raw material ratio, PMP has a relatively high melting point. Adding a compatibilizer PP-g-MAH improves the compatibility between PMP and PP and enhances the high-temperature resistance of the PP film. SiO2 has excellent insulation properties. An antioxidant is loaded on the surface of SiO2, and a silica loading is grown on the surface of the PP film through a magnetron sputtering process, so that the obtained capacitor film has good high-temperature resistance and antioxidant properties.

[0031] (2) The capacitor film provided by the present invention has low preparation cost and mature process, and is suitable for large-scale production. Specific Embodiments

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] The capacitor film mainly consists of the following raw materials by weight parts:

[0034] 10 - 40 parts of PMP pellets, 2 - 4 parts of PP-g-MAH pellets, 56 - 88 parts of PP pellets, and 0.1 - 1 part of silica loading.

[0035] Through specific components and corresponding dosages, the obtained capacitor film has good high-temperature resistance and antioxidant properties.

[0036] In a specific embodiment of the present invention, in the preparation of the antioxidant loaded on the surface of silica, the reaction temperature can be 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C and the like; the reaction time can be 240min, 260min, 280min, 300min, 320min, 340min, 360min.

[0037] In a specific embodiment of the present invention, the antioxidant includes tert-butylphenol hydroxybenzoate, p-hydroxybenzoate, tri-tert-butyl hydroxybenzoate, 2,6-di-tert-butyl-4-methylphenol, [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate n-octadecyl alcohol ester,

[0038] Any one or more of phenolic antioxidants such as 4,4'-thiobis(6-tert-butyl-3-methylphenol), the phenolic antioxidants are not limited to the above;

[0039] In a specific embodiment of the present invention, the mass ratio of silica support: phenolic antioxidant to silica is (5-25):100.

[0040] For example, in different embodiments, the mass ratio of antioxidant to silicon dioxide can be 5:100, 10:100, 15:100, 20:100, 25:100, and the like.

[0041] In a specific embodiment of the present invention, the method for preparing a capacitor film mainly comprises the following steps:

[0042] Extrusion; casting; stretching; corona; magnetron sputtering; aging treatment; slitting; coating; packaging.

[0043] For example, in different embodiments, in the corona step, the arc voltage of the corona treatment can be 15kv, 18kv, 21kv, 24kv, 27kv, 30kv, etc.

[0044] For example, in different embodiments, in the magnetron sputtering step, the magnetron sputtering gas pressure can be 1.0Pa, 1.2Pa, 1.4Pa, 1.6Pa, 1.8Pa, 2.0Pa, and the magnetron sputtering time can be 60min, 70min, 80min, 90min, 100min, 110min, 120min.

[0045] For example, in different embodiments, in the aging treatment step, the aging treatment temperature may be 20° C., 24° C., 28° C., 32° C., 36° C., 40° C. The aging treatment time may be 12 h, 16 h, 20 h, 24 h, 28 h, 32 h, 36 h.

[0046] Example 1

[0047] This example provides a method for preparing a capacitor film, which includes the following steps:

[0048] Weigh p-hydroxybenzoate and silica powder with a mass ratio of 5:100, and stir and react at 80 °C for 240 min to obtain a silica-loaded product.

[0049] Weigh 10 parts of PMP pellets, 2 parts of PP-g-MAH, and 88 parts of PP pellets by weight, mix them evenly, and then successively perform extrusion, casting, stretching, corona treatment, aging treatment, magnetron sputtering, and coating to obtain a film for metallized capacitors.

[0050] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of the silica-loaded product is weighed, the sputtering pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0051] Example 2

[0052] This example provides a method for preparing a capacitor film, which includes the following steps:

[0053] (1) Weigh p-hydroxybenzoate and silica powder with a mass ratio of 20:100, and stir and react at 80 °C for 240 min to obtain a silica-loaded product.

[0054] (2) Weigh 10 parts of PMP pellets, 2 parts of PP-g-MAH, and 88 parts of PP pellets by weight, mix them evenly, and then successively perform extrusion, casting, stretching, corona treatment, aging treatment, magnetron sputtering, and coating to obtain a film for metallized capacitors.

[0055] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of the silica-loaded product is weighed, the sputtering pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0056] Example 3

[0057] This example provides a method for preparing a capacitor film, which includes the following steps:

[0058] (1) Weigh p-hydroxybenzoate and silica powder with a mass ratio of 20:100, and stir and react at 80 °C for 240 min to obtain a silica-loaded product.

[0059] (2) Weigh 30 parts of PMP pellets, 4 parts of PP-g-MAH pellets and 66 parts of PP pellets by weight. After mixing evenly, successively through extrusion, casting, stretching, corona treatment, aging treatment, magnetron sputtering, and coating, a film for metallized capacitors is prepared.

[0060] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of the silica load is weighed, the sputtering gas pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0061] Example 4

[0062] This example provides a method for preparing a capacitor film, including the following steps:

[0063] (1) Weigh p-hydroxybenzoate and silica powder in a mass ratio of 25:100, and stir and react at 80 °C for 240 min to obtain a silica load.

[0064] (2) Weigh 40 parts of PMP pellets, 4 parts of PP-g-MAH pellets and 56 parts of PP pellets by weight. After mixing evenly, successively through extrusion, casting, stretching, corona treatment, aging treatment, magnetron sputtering, and coating, a film for metallized capacitors is prepared.

[0065] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of the silica load is weighed, the sputtering gas pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0066] Comparative Example 1

[0067] This example provides a method for preparing a capacitor film, including the following steps:

[0068] (1) Weigh p-hydroxybenzoate and silica powder in a mass ratio of 20:100, and stir and react at 80 °C for 240 min to obtain a silica load.

[0069] (2) Weigh 100 parts of PP pellets by weight, and successively through extrusion, casting, stretching, corona treatment, aging treatment, magnetron sputtering, and coating, a film for metallized capacitors is prepared.

[0070] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of the silica load is weighed, the sputtering gas pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0071] Comparative Example 2

[0072] This embodiment provides a method for preparing a capacitor film, comprising the following steps:

[0073] Weigh 40 parts of PMP pellets, 4 parts of PP-g-MAH pellets and 56 parts of PP pellets by weight. After mixing evenly, extrude, cast, stretch, corona treat, age, magnetron sputter, and coat in sequence to obtain a film for metallized capacitors.

[0074] In the above steps, the arc voltage of the corona treatment is 20 kV, 0.5 part of pure silica is weighed, the sputtering gas pressure is 2 Pa, the sputtering time is 100 min, the temperature of the aging treatment is 28 °C, and the time is 24 h.

[0075] To compare and illustrate the performance of the capacitor films prepared in different embodiments and comparative examples of the present invention, the following performance tests are carried out on the capacitor films prepared in each embodiment and comparative example. Among them, the test methods for each test item are as follows:

[0076] The test method for tensile strength reference: carried out according to the relevant regulations in Chapter 11 of GB / T13542.2-2009;

[0077] The test method for thermal shrinkage rate reference: carried out according to the relevant regulations in Chapter 23 of GB / T13542.2-2009;

[0078] The test method for Vicat softening point temperature reference: carried out according to the relevant regulations in GB / T1633-2000;

[0079] The test method for dielectric strength reference: carried out according to the relevant regulations in Chapter 18 of GB / T13542.2-2009;

[0080] Adhesion of the metal layer: For the adhesion test, use a tape with an adhesion strength of 2 N / cm2 - 10 N / cm2. Conduct the test on a 1000 mm long specimen. Place the specimen on a flat surface with a rubber pad, and evenly paste the above tape on the metal coating of the specimen. The bonding length is 100 mm. When pasting, the force should be even to make the tape fully adhere to the metal layer. Then, gently and vertically tear off the tape, and observe whether there is any obvious peeling phenomenon on the metal coating;

[0081] Test conditions for aging performance: After 720 h at 80 °C, test the tensile strength.

[0082] The test results are shown in Table 1 below.

[0083] Table 1 Performance test results of different capacitor films

[0084]

[0085] It can be seen from Examples 1-4 and Comparative Example 1 that as the content of PMP increases, and the introduction of PP-g-MAH improves the compatibility between PMP and PP, the Vicat softening point of the film also shows an upward trend. The film exhibits excellent heat resistance, and PMP can improve the mechanical properties of the film to a certain extent. It can be seen from Example 4 and Comparative Example 2 that after the film is aged, the deposited silica-supported antioxidant can significantly improve the aging resistance of the film. The performance of the film for capacitors of the present invention meets the requirements of national standards. Compared with similar products on the market, it shows excellent high-temperature resistance and antioxidant properties, and has broad application prospects.

[0086] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A film for capacitors, characterized in that: The invention comprises the following raw materials in parts by weight: 10-40 parts of PMP granules, 2-4 parts of PP-g-MAH granules, 56-88 parts of PP granules and 0.1-1 part of silicon dioxide loading material.

2. The capacitor film according to claim 1, wherein: The silica loading material is an antioxidant loaded on the surface of silica particles.

3. The capacitor film according to claim 2, wherein: The silicon dioxide surface-loaded antioxidant is prepared by mixing silicon dioxide and an antioxidant and stirring the mixture at 80-120° C. for 240 min-360 min.

4. The capacitor film according to claim 3, wherein: The antioxidant includes any one or more of phenolic antioxidants such as tert-butylphenol hydroxybenzoate, p-hydroxybenzoate, tri-tert-butyl hydroxybenzoate, 2,6-di-tert-butyl-4-methylphenol, [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4,4'-thiobis(6-tert-butyl-3-methylphenol), etc.

5. The capacitor film according to claim 4, wherein: The mass ratio of the phenolic antioxidant to silicon dioxide is (5-25):

100.

6. The method for preparing a capacitor film according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Extrusion: 10%-40% by mass of PMP, 2%-4% by mass of PP-g-MAH, and 56%-88% by mass of PP are mechanically mixed and then added into a twin-screw for melt extrusion; 2) Casting: The blend melt in a viscous flow state from the extruder die is rapidly cooled to below its glass transition temperature on a uniformly rotating quenching roller to form a glassy cast sheet; 3) Stretching: The cast sheet is longitudinally stretched in a heated state, and the longitudinally stretched film is preheated, tentered, heat-set and cooled in a transverse stretching machine to complete the biaxial stretching of the film; 4) Corona: The stretched film is subjected to a voltage corona treatment to activate the film surface; 5) Time limit: The corona-treated film is placed in an aging warehouse for aging treatment; 6) Magnetron sputtering: Using SiO2 or SiO2 load as target material, SiO2 or SiO2 load is deposited on the surface of PP film by magnetron sputtering technology; 7) Coating; The metal is evaporated and deposited on the PP film by heating or electron beam in a vacuum environment.

7. The method for preparing a capacitor film according to claim 6, characterized in that: In step 4), the corona voltage is controlled to be 15kv-30kv.

8. The method for preparing a capacitor film according to claim 6, characterized in that: In step 5), the temperature of the aging treatment is controlled at 20-40° C. and the time is 12-36 hours.

9. The method for preparing a capacitor film according to claim 6, characterized in that: In step 6), the gas pressure of magnetron sputtering is controlled to be 1.0-2.0 Pa, and the sputtering time is 1-2 h.

10. A film capacitor, characterized in that: The capacitor comprises the capacitor film according to any one of claims 1 to 5.

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