Film for film capacitor

Abstract

Provided is a film for a film capacitor, said film containing a resin composition that includes a 3-methyl-1-butene polymer.

Description

Film for film capacitors

[0001] The present invention relates to a film for a film capacitor.

[0002] Film capacitors using organic polymer films as dielectrics are widely known. Hydrocarbon-based resins such as polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polymethylpentene (PMP), and cycloolefin polymer (COP) have traditionally been used as resins for such capacitors. Furthermore, capacitor films using these hydrocarbon-based resins and fillers have been developed to improve physical properties such as dielectric constant, dielectric loss tangent, heat resistance, and breaking strength (see, for example, Patent Documents 1 to 5).

[0003] JP 2000-103870 A JP 2002-141246 A JP 2014-062244 A JP 2021-155596 A International Publication No. 2021 / 176930

[0004] Reflow soldering is a widely used surface mount technique for film capacitors. Because solder has a relatively high melting temperature, the temperature of the object to be soldered must be set high, at 260°C or higher, during reflow soldering. However, films made of resins with low heat resistance are difficult to surface mount. For example, films made of PPS, PET, etc. are known to be surface mountable, but their dielectric properties are insufficient and they are not suitable for use at high frequencies. On the other hand, films made of PP, PMP, COP, etc. are known to have excellent electrical properties, but their heat resistance is insufficient, making these resins unsuitable for surface mount technology.

[0005] In view of the current situation, an object of the present invention is to provide a film for a film capacitor that has a low relative dielectric constant and a low dielectric loss tangent and is capable of being surface mounted.

[0006] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved.

[0007] [1] A film for film capacitors comprising a resin composition containing a 3-methyl-1-butene polymer. [2] The film for film capacitors according to [1], wherein the 3-methyl-1-butene polymer is at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene with ethylene or an α-olefin, and the α-olefin has 3 to 20 carbon atoms. [3] The film for film capacitors according to [2], wherein the copolymer contains structural units derived from ethylene or the α-olefin in an amount of more than 0 mol% and not more than 20 mol%. [4] The film for film capacitors according to [2] or [3], wherein the copolymer contains structural units derived from ethylene or the α-olefin in an amount of more than 0 mol% and not more than 10 mol%. [5] The film for film capacitors according to any one of [1] to [4], wherein the dielectric loss tangent at 1 kHz to 200 GHz is less than 0.00100. [6] The film for film capacitors according to any one of [1] to [5], wherein the melting point of the 3-methyl-1-butene polymer is 260 to 310°C. [7] The film for film capacitors according to any one of [1] to [6], wherein the resin composition contains an alkyl radical scavenger. [8] The film for film capacitors according to [7], wherein the alkyl radical scavenger contains at least one selected from the group consisting of an acrylic phenol compound and a benzofuranone compound. [9] The film for film capacitors according to any one of [1] to [8], wherein the thickness is 0.01 to 40 μm.

[10] A film capacitor comprising the film for film capacitors according to any one of [1] to [9].

[11] The film capacitor according to

[10] , wherein the film is for surface mounting.

[0008] According to the present invention, it is possible to provide a film for a film capacitor that has a low relative dielectric constant and a low dielectric loss tangent and is capable of being surface mounted.

[0009] The following is a description based on one example of an embodiment of the present invention. However, the embodiment shown below is an example for embodying the technical idea of ​​the present invention, and the present invention is not limited to the following description. In this specification, preferred embodiments are shown, but a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters shown as numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. In this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less."

[0010] <Film for Film Capacitors> The film for film capacitors of this embodiment is characterized by containing a resin composition including a 3-methyl-1-butene polymer. That is, the film for film capacitors of this embodiment contains a 3-methyl-1-butene polymer. The resin composition contained in the film for film capacitors contains a 3-methyl-1-butene polymer, which enables surface mounting such as reflow soldering while maintaining a low relative dielectric constant and a low dielectric loss tangent. Furthermore, the resin composition contained in the film for film capacitors has excellent heat resistance, allowing it to be molded into any shape, and is expected to suppress an increase in the dielectric loss tangent while ensuring the prevention of blistering during surface mounting.

[0011] In addition, since the 3-methyl-1-butene polymer has low water absorption, the film for a film capacitor of this embodiment is less susceptible to the use environment and can exhibit stable physical properties. Furthermore, since the 3-methyl-1-butene polymer has a relatively low specific gravity, the film for a film capacitor of this embodiment can also contribute to reducing the weight of the film capacitor.

[0012] [Resin Composition] The resin composition contained in the film for a film capacitor of this embodiment contains a 3-methyl-1-butene polymer.

[0013] <3-Methyl-1-butene Polymer> The 3-methyl-1-butene polymer is a polymer containing at least a structural unit derived from 3-methyl-1-butene. The 3-methyl-1-butene polymer may be a 3-methyl-1-butene homopolymer or a copolymer of 3-methyl-1-butene and an unsaturated hydrocarbon. The unsaturated hydrocarbon may be one type or multiple types. Examples of the unsaturated hydrocarbon include ethylene or an α-olefin. In this embodiment, the α-olefin used in the 3-methyl-1-butene polymer refers to an α-olefin other than 3-methyl-1-butene. In other words, the α-olefin refers to an α-olefin other than 3-methyl-1-butene, and is also expressed as α-olefin (excluding 3-methyl-1-butene). From the viewpoint of good copolymerizability, the unsaturated hydrocarbon is preferably ethylene or an α-olefin having 3 to 20 carbon atoms. The α-olefin having 3 to 20 carbon atoms may be one type or multiple types. From the viewpoint of suitably exhibiting appropriate mechanical properties such as strength, flexibility, and impact resistance, the 3-methyl-1-butene polymer is preferably at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene with ethylene or an α-olefin having 3 to 20 carbon atoms, and more preferably a copolymer of 3-methyl-1-butene with ethylene or an α-olefin having 3 to 20 carbon atoms. A copolymer of 3-methyl-1-butene with ethylene or an α-olefin having 3 to 20 carbon atoms refers to a copolymer of 3-methyl-1-butene with ethylene or a copolymer of 3-methyl-1-butene with an α-olefin having 3 to 20 carbon atoms. Hereinafter, a copolymer of 3-methyl-1-butene with ethylene or an α-olefin will also be referred to simply as a "copolymer." The copolymer may be a random copolymer, a block copolymer, or an alternating copolymer. The method for producing the copolymer is not limited as long as it does not impair the effects of the present invention, and known copolymerization methods can be used.

[0014] When the 3-methyl-1-butene polymer is the copolymer, the content of structural units derived from ethylene or an α-olefin in 100 mol % of the copolymer is preferably more than 0 mol % and not more than 20 mol %. From the viewpoints of flexibility and impact resistance, the content of structural units derived from ethylene or an α-olefin in 100 mol % of the copolymer is more preferably 0.1 mol % or more, and even more preferably 0.5 mol % or more. Furthermore, from the viewpoint of heat resistance in surface mounting such as reflow soldering, the content of structural units derived from ethylene or an α-olefin in 100 mol % of the copolymer is more preferably 15 mol % or less, and even more preferably 10 mol % or less. From these viewpoints, the content of structural units derived from ethylene or an α-olefin in 100 mol % of the copolymer is more preferably 0.1 to 15 mol %, and even more preferably 0.5 to 10 mol %. In one embodiment, the content of structural units derived from ethylene or an α-olefin in 100 mol % of the copolymer is more preferably more than 0 mol % and not more than 10 mol %. The content of structural units derived from ethylene or α-olefin in the copolymer can be determined by Fourier transform infrared spectrophotometer (FT-IR). Specifically, it can be measured by the method described in the examples.

[0015] When the 3-methyl-1-butene polymer is the copolymer, the content of structural units derived from 3-methyl-1-butene in 100 mol% of the copolymer is preferably 80 mol% or more but less than 100 mol%. Alternatively, it is preferably more than 50 mol%, more preferably 70 mol% or more, even more preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, still more preferably 92 mol% or more, and even more preferably 93 mol% or more. From the viewpoint of heat resistance in surface mounting such as reflow soldering, the content of structural units derived from 3-methyl-1-butene in 100 mol% of the copolymer is more preferably 85 mol% or more, even more preferably 90 mol% or more. Furthermore, from the viewpoint of flexibility and impact resistance, the content of structural units derived from 3-methyl-1-butene in 100 mol% of the copolymer is more preferably 99.9 mol% or less, even more preferably 99.5 mol% or less, still more preferably 99.0 mol% or less, and even more preferably 95.0 mol% or less. From these viewpoints, the content of structural units derived from 3-methyl-1-butene in 100 mol% of the copolymer is preferably 85 to 99.9 mol%, more preferably 90 to 99.5 mol%, even more preferably 92 to 99.5 mol%, still more preferably 93 to 99.5 mol%, still more preferably 93 to 99.0 mol%, and most preferably 93.0 to 95.0%.

[0016] From the viewpoint of favorably exhibiting the physical properties of the 3-methyl-1-butene polymer, the ethylene or α-olefin is preferably an α-olefin having 3 to 20 carbon atoms, more preferably an α-olefin having 4 to 16 carbon atoms, even more preferably an α-olefin having 4 to 12 carbon atoms, still more preferably an α-olefin having 4 to 10 carbon atoms, and still more preferably an α-olefin having 6 to 10 carbon atoms. The α-olefin may be linear, branched, cyclic, or may contain a cyclic moiety.

[0017] Examples of the α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, vinylcyclohexene, and vinylnorbornane. The α-olefin having 3 to 20 carbon atoms is preferably a linear α-olefin, more preferably at least one selected from the group consisting of 1-butene, 1-octene, 1-nonene, and 1-decene, even more preferably at least one selected from the group consisting of 1-octene, 1-nonene, and 1-decene, and even more preferably 1-decene. Ethylene or the α-olefin having 3 to 20 carbon atoms may be used alone or in combination of two or more.

[0018] The melting point of the 3-methyl-1-butene polymer is preferably 260 to 310°C. When the melting point of the 3-methyl-1-butene polymer is within this range, the resin composition can be easily molded by extrusion molding or the like, and warping, melting, and blistering of the film for film capacitors due to surface mounting such as reflow soldering can be further suppressed, resulting in better heat resistance. The melting point of the 3-methyl-1-butene polymer refers to the peak temperature measured using a differential scanning calorimeter by heating a test piece (3-methyl-1-butene polymer) from 30°C to 320°C at a rate of 10°C / min under a nitrogen flow rate (100 mL / min), holding at 320°C for 5 minutes, cooling to -70°C at 10°C / min, holding at -70°C for 5 minutes, and then heating to 320°C at a rate of 10°C / min. Specifically, it can be measured by the method described in the Examples. From the viewpoint of a balance between processability and heat resistance, the melting point of the 3-methyl-1-butene polymer is preferably 270 to 305°C, more preferably 280 to 305°C, and even more preferably 280 to 300°C.

[0019] The melt viscosity of the 3-methyl-1-butene polymer of this embodiment is preferably 10 to 1,000 Pa·s. When the melt viscosity of the 3-methyl-1-butene polymer is 10 Pa·s or more, the mechanical strength is further improved, and when it is 1,000 Pa·s or less, good fluidity during molding is easily obtained. From the viewpoint of the balance between mechanical strength and fluidity during molding, the melt viscosity of the 3-methyl-1-butene polymer is more preferably 30 to 500 Pa·s, even more preferably 50 to 300 Pa·s, still more preferably 50 to 200 Pa·s, and even more preferably 70 to 150 Pa·s. The melt viscosity of the 3-methyl-1-butene polymer is measured using a capillary rheometer at a barrel temperature of 320°C and a shear rate of 1,220 sec －１ The term "capillary" refers to a value measured under the conditions of (capillary: inner diameter 1.0 mm x length 10 mm, extrusion rate 10 mm / min), and specifically can be measured by the method described in the examples.

[0020] The content of the 3-methyl-1-butene polymer in 100% by mass of the resin composition is preferably 50.0 to 99.9% by mass, more preferably 60.0 to 99.9% by mass, and even more preferably 65.0 to 99.9% by mass, from the viewpoint of obtaining a film for a film capacitor having a lower relative dielectric constant and a lower dielectric loss tangent. The content of the 3-methyl-1-butene polymer in the film for a film capacitor is the same as above.

[0021] 3-methyl-1-butene polymers have a relatively low specific gravity and can contribute to weight reduction of film capacitors. Furthermore, 3-methyl-1-butene polymers do not generate harmful gases when incinerated. Furthermore, the decomposition products of 3-methyl-1-butene polymers in an inert atmosphere are low-molecular-weight hydrocarbons, making them suitable for chemical recycling.

[0022] <Alkyl Radical Scavenger> The resin composition may contain an alkyl radical scavenger to exhibit better mechanical properties. In this case, the film for film capacitors of this embodiment also contains an alkyl radical scavenger, its reaction product, or its decomposition product. In this embodiment, the term "alkyl radical scavenger" refers to a compound that reacts with alkyl radicals derived from a 3-methyl-1-butene polymer and subsequently stabilizes the radicals, thereby suppressing chain reactions of main chain scission initiated by the alkyl radicals. In order to exhibit better mechanical properties, the alkyl radical scavenger preferably contains at least one compound selected from the group consisting of an acrylic phenol compound and a benzofuranone compound. One alkyl radical scavenger may be used alone, or two or more alkyl radical scavengers may be used in combination.

[0023] (Acrylphenol Compound) The acrylic phenol compound used in this embodiment can be represented by, for example, the following general formula (I).

[0024]

[0025] In general formula (I), R １ represents a hydrogen atom or a methyl group, and R ２ represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R ３ , R ４ , R ５ and R ６ each independently represents an alkyl group having 1 to 9 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. The alkyl group having 1 to 9 carbon atoms may be linear or branched. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-nonyl group. R １is preferably a hydrogen atom. ２ is preferably a hydrogen atom or a methyl group, more preferably a methyl group. ３ , R ４ , R ５ and R ６ are each independently preferably an alkyl group having 3 to 8 carbon atoms, more preferably a t-butyl group or an alkyl group having 5 carbon atoms, and even more preferably a 1,1-dimethylpropyl group.

[0026] Examples of the acrylic phenol compound represented by general formula (I) include 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate, 2,4-di-t-butyl-6-[1-(3,5-di-t-butyl-2-hydroxyphenyl)ethyl]phenyl acrylate, and 2-t-butyl-6-[(3-t-butyl-2-hydroxy-5-methylphenyl)methyl]-4-methylphenyl acrylate. Commercially available alkyl radical scavengers may be used, and examples of the acrylic phenol compound represented by general formula (I) include those available under the trade names "Sumilizer (registered trademark) GS" and "Sumilizer (registered trademark) GM" manufactured by Sumitomo Chemical Co., Ltd.

[0027] (Benzofuranone Compound) The benzofuranone compound used in this embodiment can be represented by, for example, the following general formula (II).

[0028]

[0029] In general formula (II), R ７ and R ８ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R ９ and R １０each independently represents an alkyl group having 1 to 9 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, and a t-butyl group. The alkyl group having 1 to 9 carbon atoms may be linear or branched. Examples of the alkyl group having 1 to 9 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, and an n-nonyl group. R ７ and R ８ are each independently preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. ９ and R １０ are each independently preferably an alkyl group having 1 to 4 carbon atoms, more preferably a t-butyl group.

[0030] Examples of the benzofuranone compound represented by general formula (II) include 5,7-di-t-butyl-3-(3,4-di-methyl-phenyl)-3H-benzofuran-2-one, 5,7-di(t-butyl)-3-(3,4-di-propyl-phenyl)-3H-benzofuran-2-one, etc. Commercially available alkyl radical scavengers may be used, and examples of the benzofuranone compound represented by general formula (II) include "Irganox (registered trademark) HP-136" manufactured by BASF Japan Ltd. and "Revonox (registered trademark) 501" manufactured by Chitec Corporation.

[0031] (Alkyl Radical Scavenger Content) The content of the alkyl radical scavenger in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is preferably 0.01 to 1.00 parts by mass. The content ratio of the alkyl radical scavenger in the film for film capacitors is the same as above. When the content of the alkyl radical scavenger is 0.01 parts by mass or more, the physical properties of the resin composition can be more stably maintained during melt-kneading of the resin composition. Furthermore, generation of decomposition gas during melt molding, which can result in molding defects, can be suppressed. Furthermore, when the content of the alkyl radical scavenger is 1.00 parts by mass or less, a film for film capacitors with superior mechanical properties can be easily obtained. Furthermore, impairment of the physical properties required of the resin composition, such as bleeding out of the alkyl radical scavenger or deterioration of water absorbency, can be suppressed.

[0032] From the viewpoint of maintaining the physical properties of the resin composition more stably during melt-kneading, the content of the alkyl radical scavenger in the resin composition per 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.02 parts by mass or more, and even more preferably 0.05 parts by mass or more. Furthermore, from the viewpoint of balancing maintaining the stability of the physical properties of the resin composition with economic efficiency, and from the viewpoint of obtaining a film for a film capacitor having a lower dielectric constant and a lower dielectric loss tangent, the content of the alkyl radical scavenger in the resin composition per 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.80 parts by mass or less, and even more preferably 0.70 parts by mass or less. From these viewpoints, the content of the alkyl radical scavenger in the resin composition per 100 parts by mass of the 3-methyl-1-butene polymer is more preferably 0.02 to 0.80 parts by mass, and even more preferably 0.05 to 0.70 parts by mass. When two or more alkyl radical scavengers are contained, the content of the alkyl radical scavengers refers to the total content of the alkyl radical scavengers.

[0033] <Antioxidant> The resin composition may contain an antioxidant from the viewpoint of ensuring the stability of the polymer. The antioxidant preferably contains at least one selected from the group consisting of phenolic antioxidants and phosphorus-based antioxidants. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0034] (Phenol-Based Antioxidant) Examples of the phenol-based antioxidant include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3,5-tris[(4-t-butyl-3-hydroxy-2,6-xylyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, thiodiethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], 3,3',3'',5,5',5''-hexa-t-butyl-α,α',α''-(mesitylene-2,4,6-triyl)tri-p-butyl Resole, ethylene bis(oxyethylene) bis[3-(5-t-butyl-4-hydroxy-m-tolyl)propionate], hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,6-di-t-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, 3,9-bis[2-(3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy) -1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro(5,5)undecane, 4,4',4''-(1-methylpropanyl-3-ylidene)tris(6-t-butyl-m-cresol), 6,6'-di-t-butyl-4,4'-butylidene-m-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate, and 3,5-bis-(1,1-dimethylethyl)-4-hydroxy-C benzenepropanoate ７ -C ９ Branched alkyl esters and the like are included.

[0035] As the phenolic antioxidant, commercially available products may be used, such as "ADEKA STAB (registered trademark) AO series" manufactured by ADEKA Corporation and "Irganox (registered trademark) series" manufactured by BASF Japan Ltd.

[0036] (Phosphorus-Based Antioxidant) Examples of the phosphorus-based antioxidant include 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, tetrakis(2,4-di-t-butyl-phenyl)-4,4′-biphenylenephosphonite, 2,2-methylenebis(4,6-di-t-butylphenyl)octyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl ester phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis( 2,4-dicumylphenyl)pentaerythritol diphosphite, di-t-butyl-m-cresyl phosphonite, diethyl [(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl]phosphonate, tris(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, 3,9-bis(octadecyoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite, tetra-C １２ -C １５ -alkyl(propane-2,2-diylbis(4,1-phenylene))bis(phosphite), 2-ethylhexyldiphenyl phosphite, isodecyldiphenyl phosphite, trisisodecyl phosphite, triphenyl phosphite, and 3,9-bis[2,4-bis(1-methyl-1-phenylethyl)phenoxy]-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane.

[0037] As the phosphorus-based antioxidant, commercially available products may be used, and examples thereof include "ADK STAB (registered trademark) PEP series" and "ADK STAB (registered trademark) HP series" manufactured by ADEKA Corporation, "Irgafos (registered trademark) series" manufactured by BASF Japan Ltd., and "HOSTANOX (registered trademark) P-EPQ" manufactured by Clariant.

[0038] (Sulfur-Based Antioxidants) Examples of sulfur-based antioxidants include dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3′-thiodipropionate, laurylstearyl 3,3′-thiodipropionate, pentaerythritol-tetrakis-(β-lauryl-thio-propionate), 3,9-bis(2-dodecylthioethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, and the like.

[0039] (Other Antioxidants) The resin composition may contain other antioxidants besides the phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants, as long as the effects of the present invention are not impaired. Examples of antioxidants other than the phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants include amine-based antioxidants.

[0040] (Antioxidant Content) The content of the antioxidant in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer is preferably 0.01 parts by mass or more, more preferably 0.10 parts by mass or more, from the viewpoint of ensuring the stability of the 3-methyl-1-butene polymer. From the viewpoint of the relative dielectric constant and the dielectric loss tangent, the content is preferably 1.00 parts by mass or less, more preferably 0.80 parts by mass or less. That is, the content is preferably 0.01 to 1.00 parts by mass, more preferably 0.10 to 0.80 parts by mass. The content ratio of the antioxidant in the film for film capacitors is the same as above. Note that when the resin composition contains two or more antioxidants, the content of the antioxidants refers to the total content of the antioxidants.

[0041] <Other Additives> The resin composition may contain additives other than the alkyl radical scavenger and the antioxidant, as long as the effects of the present invention are not impaired. Examples of other additives include antacids, fillers, light stabilizers, antistatic agents, flame retardants, pigments, polymerization inhibitors, heavy metal deactivators, UV absorbers, nucleating agents, clarifying agents, lubricants, fluorescent brighteners, rust inhibitors, and sliding agents. One type of other additive may be used alone, or two or more types may be used in combination.

[0042] (Antacid Agent) From the viewpoint of suppressing deterioration due to acid components generated from residual metals and the like during melt-kneading, the resin composition preferably contains an antacid. Examples of antacid agents include barium laurate, calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, zinc oleate, and magnesium 12-hydroxystearate. One type of antacid agent may be used alone, or two or more types may be used in combination.

[0043] The content of the antacid in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be determined appropriately and may be, for example, 0.01 to 200 parts by mass, 0.01 to 2.0 parts by mass, or 0.01 to 1.0 part by mass. Alternatively, it may be 0.01 to 0.5 parts by mass, or 0.01 to 0.3 parts by mass. The content of the antacid in the film for a film capacitor is the same as above.

[0044] (Antistatic Agent) Examples of the antistatic agent include sodium alkylsulfonate, phosphonium alkylsulfonate, and fatty acid ester hydroxyamine compounds, which are glycerin esters of stearic acid.

[0045] The content of the antistatic agent in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 5 parts by mass or less. The content of the antistatic agent in the film for a film capacitor is the same as above.

[0046] (Filler) Examples of fillers include fibrous compounds such as glass fiber, alumina fiber, resin fiber, carbon fiber, and cellulose fiber; flat compounds such as mica, talc, montmorillonite, and tabular aluminum; spherical compounds such as glass beads, shirasu balloons, and acrylic balloons; needle-shaped compounds such as acicular metal titanate, wollastonite, acicular silica, and tin oxide; and powdered compounds such as powdered metal titanate, finely divided wood chips, titanium oxide, calcium carbonate, silica, and alumina. These fillers may be surface-treated with, for example, a silane coupling agent. A compatibilizer may also be used to enhance the dispersibility of the filler. One filler may be used alone, or two or more fillers may be used in combination.

[0047] The content of the filler in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.01 to 300 parts by mass or 0.1 to 100 parts by mass. The content of the filler in the film for a film capacitor is the same as above.

[0048] (Ultraviolet Absorber) Examples of the ultraviolet absorber include 2,2,6,6-tetramethyl-4-piperidyl benzoate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate, 4-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)-1-(2-(3-(3,5- hindered amine-based ultraviolet absorbers such as (di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl)-2,2,6,6-tetramethylpiperidine; benzotriazole-based ultraviolet absorbers such as 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole; benzoate-based ultraviolet absorbers such as 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; and the like.

[0049] The content of the ultraviolet absorber in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.001 to 5 parts by mass or 0.01 to 1 part by mass. The content of the ultraviolet absorber in the film for a film capacitor is the same as above.

[0050] (Lubricant) Inorganic fine particles are generally used as the lubricant. Examples of the inorganic fine particles include particles of oxides, hydroxides, sulfides, nitrides, halides, carbonates, sulfates, acetates, phosphates, phosphites, organic carboxylates, silicates, titanates, borates, and hydrated compounds thereof, composite compounds mainly composed of these, and natural minerals, of elements of Groups 1, 2, 4, 6, 7, 8 to 10, 11, 12, 13, and 14 of the periodic table.

[0051] Examples of inorganic fine particles include Group 1 element compounds such as lithium fluoride and borax (sodium borate hydrate); Group 2 element compounds such as magnesium carbonate, magnesium phosphate, magnesium oxide (magnesiu), magnesium chloride, magnesium acetate, magnesium fluoride, magnesium titanate, magnesium silicate, magnesium silicate hydrate (talc), calcium carbonate, calcium phosphate, calcium phosphite, calcium sulfate (gypsum), calcium acetate, calcium terephthalate, calcium hydroxide, calcium silicate, calcium fluoride, calcium titanate, strontium titanate, barium titanate, zinc titanate, lanthanum titanate, bismuth titanate, lead titanate, barium carbonate, barium phosphate, barium sulfate, and barium phosphite; titanium dioxide (titania Group 4 element compounds such as titanium monoxide, titanium nitride, zirconium dioxide (zirconia), and zirconium monoxide; Group 6 element compounds such as molybdenum dioxide, molybdenum trioxide, and molybdenum sulfide; Group 7 element compounds such as manganese chloride and manganese acetate; Group 8 to 10 element compounds such as cobalt chloride and cobalt acetate; Group 11 element compounds such as cuprous iodide; Group 12 element compounds such as zinc oxide and zinc acetate; Group 13 element compounds such as aluminum oxide (alumina), aluminum hydroxide, aluminum fluoride, and aluminosilicates (alumina silicate, kaolin, and kaolinite); Group 14 element compounds such as silicon oxide (silica, silica gel), graphite, carbon, graphite, and glass; and fine particles of natural minerals such as karnalite, kainite, mica, and byrrosite. There are no particular limitations on the average particle size of the inorganic fine particles, but it is preferably 0.01 to 3 μm.

[0052] The content of the lubricant in the resin composition relative to 100 parts by mass of the 3-methyl-1-butene polymer can be appropriately determined and may be, for example, 0.001 to 5 parts by mass or 0.005 to 3 parts by mass. The content of the lubricant in the film for a film capacitor is the same as above.

[0053] <Other Resins> The resin composition may or may not contain a resin other than the 3-methyl-1-butene polymer. In order to improve the dispersibility of additives containing polar groups, the resin composition may contain other resins other than the 3-methyl-1-butene polymer, such as a vinyl acetate-ethylene copolymer or a modified polyolefin obtained by partially oxidizing a polyolefin and / or modifying it with a reactive functional group such as maleic acid. Examples of polyolefins constituting the modified polyolefin modified with a reactive functional group include polyethylene, polypropylene, and polyolefins having a structural unit of an α-olefin having 3 to 20 carbon atoms. Examples of α-olefins having 3 to 20 carbon atoms include those described above in the <3-methyl-1-butene polymer> section. These may be homopolymers or copolymers. Furthermore, these polyolefins may be high-density or low-density and may be polymerized using at least one catalyst selected from the group consisting of a Ziegler-Natta catalyst and a metallocene catalyst. Among these, the resin other than the 3-methyl-1-butene polymer is preferably at least one selected from the group consisting of polyethylene or polypropylene, more preferably at least one selected from the group consisting of modified polyethylene or modified polypropylene, more preferably at least one selected from the group consisting of modified polyethylene or modified polypropylene in which polyolefin is partially oxidized and / or modified with a reactive functional group such as maleic acid, and even more preferably maleic anhydride-modified polypropylene.

[0054] From the viewpoint of further exerting the effects of the present invention, the content of the vinyl acetate-ethylene copolymer and the modified polyolefin obtained by partially oxidizing a polyolefin and / or modifying a polyolefin with a reactive functional group such as maleic acid in the resin composition is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the 3-methyl-1-butene polymer. The content of the vinyl acetate-ethylene copolymer and the modified polyolefin obtained by partially oxidizing a polyolefin and / or modifying a polyolefin with a reactive functional group such as maleic acid in the film for film capacitors is also the same as above.

[0055] Examples of resins other than vinyl acetate-ethylene copolymers and modified polyolefins in which polyolefins are partially oxidized and / or modified with reactive functional groups such as maleic acid include polyolefins such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, very low-density polyethylene, polypropylene, syndiotactic polypropylene, polybutene, and polypentene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6 and nylon 66; ethylene-ethyl acrylate copolymers, polystyrene, syndiotactic polystyrene, polyphenylene sulfide, polyphenylene ether, polycarbonate, and thermoplastic elastomers. Examples of thermoplastic elastomers include random or block copolymers of aromatic vinyl monomers and conjugated diene monomers, such as styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, and styrene-butadiene random copolymers; polyisoprene rubber; polyolefin rubbers, such as ethylene-propylene copolymers, ethylene-α-olefin copolymers, and propylene-α-olefin copolymers; diene copolymers, such as ethylene-propylene-diene copolymers, α-olefin-diene copolymers, diene copolymers, isobutylene-isoprene copolymers, and isobutylene-diene copolymers; norbornene rubbery polymers, such as copolymers of norbornene monomers and ethylene or α-olefins, terpolymers of norbornene monomers, ethylene and α-olefins, and ring-opening polymers of norbornene monomers, and hydrogenated versions of these.

[0056] In order to further improve the flexibility, bendability, and impact resistance of the film for a film capacitor, the resin composition may contain a thermoplastic elastomer. When the resin composition contains a thermoplastic elastomer, the film for a film capacitor is less susceptible to distortion and impact, and cracking can be suppressed.

[0057] From the viewpoint of impact resistance, the thermoplastic elastomer preferably has a glass transition temperature (Tg) of 40°C or lower. Some block copolymers have two or more Tg points, but they can be preferably used as long as one of the Tg points is 40°C or lower. The number-average molecular weight of the thermoplastic elastomer is preferably 10,000 or higher, more preferably 20,000 or higher, even more preferably 30,000 or higher, and preferably 200,000 or lower. A number-average molecular weight of 10,000 or higher provides superior mechanical properties, while a number-average molecular weight of 200,000 or lower facilitates production. From the viewpoint of compatibility with the 3-methyl-1-butene polymer, the thermoplastic elastomer is preferably non-polar, i.e., composed only of carbon and hydrogen.

[0058] From the viewpoint of obtaining a film for a film capacitor having a low dielectric constant and a low dielectric loss tangent, it is preferable that the resin composition has a reduced amount of metal elements. Therefore, from the viewpoint of easily reducing the amount of metal elements, the thermoplastic elastomer is preferably a copolymer of an aromatic vinyl monomer and a conjugated diene monomer, more preferably a block copolymer thereof. Furthermore, from the viewpoint of improving weather resistance, a hydrogenated product thereof is even more preferable.

[0059] The content of the other resins other than the thermoplastic elastomer, vinyl acetate-ethylene copolymer, and modified polyolefin obtained by partially oxidizing polyolefin and / or modifying with a reactive functional group such as maleic acid in the resin composition is preferably 1 to 100 parts by mass, more preferably 2 to 50 parts by mass, and even more preferably 3 to 30 parts by mass, per 100 parts by mass of the 3-methyl-1-butene polymer. The content of the other resins other than the thermoplastic elastomer, vinyl acetate-ethylene copolymer, and modified polyolefin obtained by partially oxidizing polyolefin and / or modifying with a reactive functional group such as maleic acid in the film for film capacitors is also the same as above. Within the above range, the excellent physical properties of the 3-methyl-1-butene polymer, such as heat resistance and chemical resistance, are easily exhibited.

[0060] <Melting Point of Resin Composition> The melting point of the resin composition of this embodiment is preferably 260 to 310°C. When the melting point of the resin composition is within the above range, molding can be facilitated and reflow heat resistance can be further improved. The melting point of the resin composition refers to the peak temperature when measured using a method similar to that used to measure the melting point of a 3-methyl-1-butene polymer. Specifically, it can be measured using the method for measuring the melting point of a 3-methyl-1-butene polymer described in the Examples. From the viewpoint of a balance between processability and heat resistance, the melting point of the resin composition is preferably 270 to 305°C, more preferably 280 to 305°C, and even more preferably 280 to 300°C. The melting point of the resin composition of this embodiment is almost the same as that of the 3-methyl-1-butene polymer. Therefore, in this specification, the melting point of the 3-methyl-1-butene polymer can be considered to be the melting point of the resin composition.

[0061] <Method for Producing Resin Composition> The method for producing the resin composition of this embodiment is not particularly limited as long as it can produce a resin composition containing a 3-methyl-1-butene polymer. More specifically, the method for producing the resin composition includes a step of obtaining a 3-methyl-1-butene polymer and a step of obtaining a resin composition. Details of each step can be found in the sections [Step of Obtaining a 3-methyl-1-butene Polymer] and [Step of Obtaining a Resin Composition] described below.

[0062] [Film for film capacitors] The film for film capacitors of this embodiment contains the resin composition of this embodiment. The film for film capacitors of this embodiment contains a 3-methyl-1-butene polymer. The film for film capacitors of this embodiment may consist of only the resin composition, or may contain components other than the resin composition.

[0063] <Dielectric Loss Tangent of Film for Film Capacitor> The dielectric loss tangent of the film for film capacitor of this embodiment refers to the dielectric loss tangent measured at a specific frequency, specifically, the dielectric loss tangent measured at a frequency of 1 kHz to 200 GHz. The dielectric loss tangent of the film for film capacitor of this embodiment at 1 kHz to 200 GHz is preferably 0.00010 or more, more preferably 0.00013 or more, and even more preferably 0.00015 or more. From the viewpoint of reducing transmission loss, the dielectric loss tangent of the film for film capacitor is preferably less than 0.00100, more preferably 0.00080 or less, and even more preferably 0.00060 or less. That is, the dielectric loss tangent of the film for film capacitor at 1 kHz to 200 GHz is preferably 0.00010 to less than 0.00100, more preferably 0.00013 to 0.00080, and even more preferably 0.00015 to 0.00060. The dielectric loss tangent of a film for a film capacitor at 1 kHz to 200 GHz refers to a value measured by a common method, such as a capacitance method, a resonance method, or a frequency variation method. Specifically, it can be measured by the method described in the Examples. When the measurement frequency is 1 kHz to 1 GHz, measurement is preferably performed by the capacitance method. When the measurement frequency is greater than 1 GHz and equal to or less than 50 GHz, measurement is preferably performed by the resonance method. When the measurement frequency is greater than 50 GHz and equal to or less than 200 GHz, measurement is preferably performed by the frequency variation method. In one aspect, the dielectric loss tangent of the film for a film capacitor of this embodiment at 1 MHz, measured by the capacitance method, is 0.00010 to less than 0.00100, preferably 0.00013 to 0.00080, and more preferably 0.00015 to 0.00060. In one aspect, the dielectric loss tangent of the film for a film capacitor of this embodiment at 10 GHz measured by a resonance method is 0.00010 to less than 0.00100, preferably 0.00013 to 0.00080, more preferably 0.00015 to 0.00060. In another aspect, the dielectric loss tangent of the film for a film capacitor of this embodiment at 100 GHz measured by a frequency variation method is 0.00010 to less than 0.00100, preferably 0.00013 to 0.00080, more preferably 0.00015 to 0.00060.In one aspect, the film for a film capacitor of the present embodiment has a dielectric loss tangent at 200 GHz measured by a frequency variation method of 0.00010 to less than 0.00100, preferably 0.00013 to 0.00080, more preferably 0.00015 to 0.00060.

[0064] <Dielectric Constant of Film for Film Capacitor> The dielectric loss tangent of the film for film capacitor of this embodiment refers to the dielectric loss tangent measured at a specific frequency, specifically, the dielectric loss tangent measured at a frequency of 1 kHz to 200 GHz. The dielectric constant of the film for film capacitor of this embodiment at 1 kHz to 200 GHz is preferably 0.5 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. From the viewpoint of reducing transmission loss, the dielectric constant of the film for film capacitor is preferably 5.0 or less, more preferably 4.0 or less, more preferably 3.8 or less, and even more preferably 3.5 or less. That is, the dielectric constant of the film for film capacitor at 1 kHz to 200 GHz is preferably 0.5 to 5.0, more preferably 1.5 to 4.0, and even more preferably 2.0 to 3.5. The dielectric constant of the film for film capacitor at 1 kHz to 200 GHz refers to a value measured by a common method such as a capacitance method, a resonance method, or a frequency variation method. Specifically, it can be measured by the method described in the examples. When the measurement frequency is 1 kHz to 1 GHz, measurement is preferably performed by a capacitance method. When the measurement frequency is greater than 1 GHz and equal to or less than 50 GHz, measurement is preferably performed by a resonance method. When the measurement frequency is greater than 50 GHz and equal to or less than 200 GHz, measurement is preferably performed by a frequency variation method. In one aspect, the film for a film capacitor of this embodiment has a relative dielectric constant at 1 MHz measured by a capacitance method of 0.5 to 5.0, preferably 1.5 to 4.0, and more preferably 2.0 to 3.5. In one aspect, the film for a film capacitor of this embodiment has a relative dielectric constant at 10 GHz measured by a resonance method of 0.5 to 5.0, preferably 1.5 to 4.0, and more preferably 2.0 to 3.5. In one aspect, the film for a film capacitor of this embodiment has a relative dielectric constant at 100 GHz measured by a frequency variation method of 0.5 to 5.0, preferably 1.5 to 4.0, and more preferably 2.0 to 3.5. In one aspect, the film for a film capacitor of the present embodiment has a relative dielectric constant at 200 GHz measured by a frequency variation method of 0.5 to 5.0, preferably 1.5 to 4.0, and more preferably 2.0 to 3.5.

[0065] <Thickness of Film for Film Capacitor> The thickness of the film for a film capacitor of this embodiment can be set appropriately depending on the type, size, etc. of the film capacitor. For example, from the viewpoint of advantageously miniaturizing the film capacitor while ensuring good capacitance, the thickness of the film for a film capacitor is preferably 0.01 to 40 μm, more preferably 0.1 to 40 μm, and even more preferably 0.1 to 20 μm.

[0066] <Water Absorption of Film for Film Capacitor> The water absorption of the film for film capacitor of this embodiment is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0.1% by mass or less. If the water absorption of the film for film capacitor is within the above range, the occurrence of blisters during surface mounting such as reflow soldering can be further suppressed. Storage management before surface mounting is also facilitated. The water absorption of the film for film capacitor means a value measured in accordance with JIS K-7209:2000 Method A, and specifically can be measured by the method described in the Examples.

[0067] <Method for Producing Film for Film Capacitor> The method for producing the film for film capacitor of the present embodiment can be a known method and is not particularly limited. From the viewpoint of obtaining a film for film capacitor that has a low relative dielectric constant and a low dielectric loss tangent and that can be surface-mounted by reflow soldering or the like, the method for producing the film for film capacitor preferably includes a step of obtaining a 3-methyl-1-butene polymer, a step of obtaining a resin composition, and a step of obtaining a film for film capacitor.

[0068] [Step of Obtaining a 3-methyl-1-butene Polymer] In this embodiment, the step of obtaining a 3-methyl-1-butene polymer is not particularly limited as long as it is a step that allows the production of a 3-methyl-1-butene polymer. The method of obtaining a 3-methyl-1-butene polymer is not particularly limited, and the polymer can be produced using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. More specifically, the step of obtaining a 3-methyl-1-butene polymer is a step of preparing a raw material containing 3-methyl-1-butene and polymerizing this raw material to obtain a 3-methyl-1-butene polymer. A method of obtaining a 3-methyl-1-butene polymer, for example, as described in JP-A-61-103910, involves homopolymerizing 3-methyl-1-butene in the presence of a catalyst, or copolymerizing 3-methyl-1-butene with ethylene or one of the above-mentioned α-olefins, thereby obtaining a powder. In the case of homopolymerization, the raw material contains at least 3-methyl-1-butene and may further contain a catalyst. In the case of copolymerization, the raw materials contain at least 3-methyl-1-butene and ethylene or the above-mentioned α-olefin, and may further contain a catalyst. The stereoregularity of the 3-methyl-1-butene polymer may be isotactic or syndiotactic.

[0069] [Step of Obtaining Resin Composition] In this embodiment, the step of obtaining a resin composition refers to a step of blending and mixing other components, such as additives, in addition to a 3-methyl-1-butene polymer to obtain a resin composition. Specifically, this is a step of obtaining a resin composition containing a 3-methyl-1-butene polymer and other components. The resin composition is obtained by blending a 3-methyl-1-butene polymer with other components. The blending method is not particularly limited, and a melt-kneading method using a twin-screw kneading extruder can be used. Furthermore, the raw materials may be dry-blended before melt-kneading. Note that when no other components other than the 3-methyl-1-butene polymer are blended, the resin composition is composed of the 3-methyl-1-butene polymer, and the film for a film capacitor is produced using the 3-methyl-1-butene polymer, so the step of obtaining a resin composition is not necessary. In this case, the method of producing a film for a film capacitor includes a step of obtaining a 3-methyl-1-butene polymer and a step of obtaining a film for a film capacitor. Examples of the additives include those similar to those described in the above [Resin Composition], such as alkyl radical scavengers, antioxidants, antacids, fillers, light stabilizers, antistatic agents, flame retardants, pigments, polymerization inhibitors, heavy metal deactivators, ultraviolet absorbers, nucleating agents, clarifying agents, lubricants, fluorescent brighteners, rust inhibitors, and sliding agents.

[0070] <Melt-Kneading Conditions> The melt-kneading conditions are not particularly limited. However, it is preferable to perform the melt-kneading in an oxygen-lower state than the atmosphere. It is more preferable to perform the melt-kneading by injecting an inert gas into the melt-kneader or by degassing the inside of the melt-kneader under reduced pressure. To suppress the deterioration of the physical properties of the resin composition due to oxygen and produce a film for a film capacitor with better mechanical properties, it is preferable to perform the melt-kneading in an inert atmosphere or a low-oxygen state. In this embodiment, the "low-oxygen state" refers to a state in which the oxygen concentration is lowered by degassing the inside of the melt-kneader under reduced pressure compared to before degassing. Alternatively, it refers to a state in which the oxygen concentration is lowered by injecting an inert gas such as nitrogen gas compared to before the injection. In the "low-oxygen state," the oxygen concentration inside the melt-kneader is preferably 5% or less, more preferably 2% or less, and even more preferably 1% or less. The oxygen concentration is measured using an oxygen concentration meter such as a diaphragm-type galvanic oxygen meter.

[0071] The method of melt-kneading by injecting an inert gas into the melt kneader may involve, for example, introducing each component into the melt kneader while injecting the inert gas, or introducing each component into the melt kneader and then injecting the inert gas to perform melt kneading. Furthermore, the inert gas may be continuously injected into the melt kneader during melt kneading. The inert gas may be injected according to the equipment of each melt kneader. For example, the inert gas may be injected from a gas supply section such as an inert gas provided in the melt kneader, from a supply section for each component provided in the melt kneader, or from a gas vent provided in the melt kneader. There are no limitations on the injection method as long as the inert gas can be injected into the entire area from the inert gas supply section to the heating section where melt kneading is performed, thereby enabling melt kneading. Examples of inert gases include nitrogen gas, helium gas, neon gas, argon gas, krypton gas, and carbon dioxide gas. Nitrogen gas is preferred from the viewpoints of availability and versatility.

[0072] The method of degassing the inside of the melt kneader under reduced pressure to melt and knead may be, for example, to add each component to the inside of the melt kneader, and then degas the inside of the melt kneader under reduced pressure to perform melt kneading. Moreover, during melt kneading, degassing the inside of the melt kneader under reduced pressure may be performed intermittently or continuously. The method of degassing the inside of the melt kneader under reduced pressure can be performed depending on the equipment provided in each melt kneader, and may be performed, for example, through a vacuum vent. When degassing under reduced pressure, the inside of the melt kneader can be placed in a vacuum state of, for example, 0.1 kPa or more and 50 kPa or less.

[0073] The melt kneader may be a single-screw extruder, a multi-screw extruder, a kneader, a Banbury mixer, or the like, which is equipped with equipment capable of melt-kneading by injecting an inert gas into the inside of the melt kneader, or equipment capable of melt-kneading by degassing the inside of the melt kneader under reduced pressure.

[0074] The melt-kneading temperature is preferably 300 to 380°C. When the melt-kneading temperature is 300°C or higher, the 3-methyl-1-butene polymer can be sufficiently melted, and additives and the like can be easily dispersed. When the melt-kneading temperature is 380°C or lower, thermal decomposition of the 3-methyl-1-butene polymer and additives can be suppressed. From the viewpoint of sufficiently dispersing the additives throughout the 3-methyl-1-butene polymer, the melt-kneading temperature is more preferably 300°C or higher, and even more preferably 310°C or higher. Furthermore, from the viewpoint of suppressing significant decomposition of the raw materials, the melt-kneading temperature is more preferably 380°C or lower, and even more preferably 360°C or lower.

[0075] The melt-kneading time can be adjusted depending on the size of the kneading apparatus, etc. For example, it may be 1 to 15 minutes, but is not limited to this numerical range of the melt-kneading time. In this embodiment, the "melt-kneading time" refers to the time during which the mixer is rotating in a batch-type kneader, and refers to the residence time of the raw materials in the apparatus in the case of a continuous extrusion-type kneader.

[0076] The rotation speed of the mixer during melt-kneading may be 80 rpm or more or 100 rpm or more, and may be 300 rpm or less or 250 rpm or less. After melt-kneading, the resin composition is removed from the melt-kneader and cooled.

[0077] [Step of Obtaining a Film for a Film Capacitor] In this embodiment, the step of obtaining a film for a film capacitor is a step of obtaining a film for a film capacitor by molding a resin composition. The method of molding the film is not particularly limited as long as it does not impair the effects of the present invention, and known film molding methods can be used. The above-mentioned resin composition is thermoplastic and can be melt-molded. Therefore, methods for molding the film include extrusion molding and heat press molding. Among these, extrusion molding is preferred as the method of molding the film from the viewpoint of obtaining a film with excellent ease of production and dimensional accuracy.

[0078] <Film Capacitor> The film capacitor of this embodiment includes the above-described film for a film capacitor. The film capacitor of this embodiment is configured to have at least the above-described film for a film capacitor and electrodes, with the film for a film capacitor being included as a dielectric. The film capacitor may further include lead terminals, an exterior case that encapsulates the film for a film capacitor and the electrodes, and the like. In the film capacitor, the film for a film capacitor and the electrodes may be alternately laminated, or the film for a film capacitor may be wound around the electrodes.

[0079] Furthermore, before providing an electrode on the surface of the film for a film capacitor, the surface of the film for a film capacitor may be subjected to a pretreatment such as a degreasing treatment, a plasma treatment, a UV ozone treatment, a laser treatment, a corona discharge treatment, etc. The treatment conditions for the pretreatment are not limited as long as they do not impair the effects of the present invention.

[0080] Examples of metal materials constituting the electrodes include copper, silver, gold, platinum, iron, nickel, aluminum, magnesium, titanium, etc. Generally, aluminum is preferred from the viewpoints of good electrical conductivity, etching properties, cost, etc. Known methods can be used to provide electrodes on the surface of the film for film capacitors, and examples thereof include ion plating, sputtering, and vacuum deposition.

[0081] The film for a film capacitor of this embodiment has a low relative dielectric constant and a low dielectric loss tangent, and is highly heat-resistant, allowing for surface mounting by reflow soldering or the like. Therefore, the film capacitor of this embodiment can be used in, for example, environmentally-related equipment such as electric vehicles, hybrid vehicles, solar power generation systems, and wind power generation systems, as well as home appliances such as televisions and refrigerators. The film capacitor of this embodiment is particularly suitable for surface mounting.

[0082] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0083] <Measurement and Evaluation Methods> Various physical properties were measured or evaluated by the following methods.

[0084] [Content of structural units derived from comonomers] The content of structural units derived from 1-decene (comonomer), which is an α-olefin other than 3-methyl-1-butene, in the polymers (3-methyl-1-butene copolymers) obtained in Production Examples 1 and 2 was determined by IR measurement using an FT-IR analyzer (manufactured by Ailent Technologies, device name "Cary 600 series FTIR spectrometer") by the ATR method, as follows: Deformation vibration of 1,461 cm derived from the main chain methylene group of 3-methyl-1-butene homopolymer －１ and the bending vibration of 727 cm originating from the side chain methylene group of the α-olefin homopolymer. －１A calibration curve was created from the ratio of the peak area of ​​the copolymer (A) obtained in Production Example 1 to the peak area of ​​the copolymer (B) obtained in Production Example 2, and the ratio of the added polymers (3-methyl-1-butene copolymer and α-olefin) to the peak area of ​​the copolymer (A) obtained in Production Example 1 and the copolymer (B) obtained in Production Example 2. The above-mentioned IR measurement was carried out for each of the copolymers, and the obtained measured values ​​(peak area ratios) were inserted into the calibration curve to determine the content of structural units derived from α-olefins other than 3-methyl-1-butene (1-decene).

[0085] [Melting Point] Using a differential scanning calorimeter ("DSC25" manufactured by TA Instrument) the polymers (3-methyl-1-butene copolymers) obtained in Production Examples 1 and 2 were heated from 30°C to 320°C at a rate of 10°C / min under a nitrogen flow rate (100 mL / min), held at 320°C for 5 minutes, and then cooled to -70°C at a rate of 10°C / min. After holding at -70°C for 5 minutes, the polymers were heated to 320°C at a rate of 10°C / min, and the peak temperature of the endothermic peak accompanying melting was measured, and this temperature was taken as the melting point.

[0086] [Melt Viscosity] The melt viscosity (Pa·s) of the polymers (3-methyl-1-butene copolymers) obtained in Production Examples 1 and 2 was measured using a capillary rheometer ("Capillography 1C" manufactured by Toyo Seiki Seisaku-sho, Ltd.) at a barrel temperature of 320°C and a shear rate of 1220 sec. －１ The measurement was carried out under the following conditions: (capillary: inner diameter 1.0 mm x length 10 mm, extrusion speed 10 mm / min).

[0087] [Specific Gravity] Test pieces (length: 40 mm, width: 40 mm) were prepared by cutting out each of the films for film capacitors obtained in Examples 1 and 2 and Comparative Examples 1 to 3. Using the test pieces, specific gravity was measured in accordance with Method A of JIS K 7112:1999.

[0088] [Water Absorption Rate] Test pieces (length: 60 mm, width: 60 mm) were prepared by cutting out each of the films for film capacitors obtained in Examples 1 and 2 and Comparative Examples 1 to 3. The test pieces were dried under reduced pressure at 100°C for 10 hours, and then stored at 23°C and 50% RH for 1 week, and the water absorption rate of the films was measured using a Karl Fischer moisture meter.

[0089] [Dielectric Constant and Dielectric Loss Tangent] Test pieces (length: 40 mm, width: 40 mm) were prepared by cutting out each of the film capacitor films obtained in Examples 1 and 2. Using these test pieces, the dielectric constant and dielectric loss tangent at a measurement frequency of 1 MHz were measured by the capacitance method using a precision LCR meter "Keysight E4980A." Test pieces (length: 40 mm, width: 40 mm) were prepared by cutting out each of the film capacitor films obtained in Examples 1 and 2 and Comparative Examples 1 to 3. Using these test pieces, the dielectric constant and dielectric loss tangent at a measurement frequency of 10 GHz were measured by the TE resonance method using a vector network analyzer "Keysight PNA N5227A." Test pieces (length: 40 mm, width: 40 mm) were also prepared by cutting out each of the film capacitor films obtained in Examples 1 and 2. Using the test specimen, the relative permittivity and dielectric loss tangent at a measurement frequency of 100 GHz were measured by the open-type resonant Fabry-Perot method using a vector network analyzer "WR10" manufactured by Virginia Diodes Inc. The pellet-shaped resin compositions obtained in Examples 1 and 2 were melt-kneaded using an electric injection molding machine "SE18DU" (manufactured by SUMITOMO Heavy Industries, Ltd.) under a nitrogen atmosphere at 40 rpm and a cylinder temperature of 310°C, and then injection-molded under conditions of an injection pressure of 45 MPa, a mold retention time of 33 seconds, and a mold temperature of 160°C to prepare test specimens (length: 100 mm, width: 100 mm, thickness: 2 mm). Using the test piece, the relative permittivity and dielectric loss tangent were measured at a measurement frequency of 200 GHz by a frequency change method using a vector network analyzer "Anritsu ME7838G 70 kHz-220 GHz".

[0090] [Reflow Heat Resistance] The film capacitor films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were left to stand for 7 days in an atmosphere of 85°C and 85% RH. After standing, the test specimens were heat-treated using a high-temperature observation device "SMT Scope Light SL-1" (manufactured by Sanyo Seiko Co., Ltd.) according to the following reflow temperature profile, and the appearance of the test specimens was observed and evaluated. Specifically, specimens that showed at least one of warping, melting, and blisters were rated "B," and specimens that showed no warping, melting, or blisters were rated "A." Reflow temperature profile: The temperature was raised from 25°C to 150°C over 60 seconds, then raised to 180°C over 80 seconds, and further raised to 280°C over 60 seconds, and held at 280°C for 10 seconds. Air cooling was then performed.

[0091] [Catalyst Preparation] Preparation of Titanium Catalyst Component 47.6 g (500 mmol) of anhydrous magnesium chloride, 250 mL of decane, and 234 mL (1.5 mol) of 2-ethylhexyl alcohol were heated at 130°C for 2 hours to form a homogeneous solution. The resulting homogeneous solution was cooled to room temperature (23°C) and then added dropwise over 1 hour to 2 L (18 mol) of titanium tetrachloride maintained at -20°C. After the dropwise addition was completed, the temperature of the mixture was raised to 90°C over 2 hours. Upon reaching 90°C, 11.4 mL (80 mmol) of ethyl benzoate was added and the mixture was maintained at the same temperature for 2 hours with stirring. After the 2-hour reaction, the mixture was allowed to stand and the supernatant was removed. Decane and hexane were added, and the solid component was washed three times. After that, it was resuspended in 2 L of titanium tetrachloride and again heated at 90°C for 2 hours. After the reaction was complete, the mixture was again left to stand using decane and hexane, and the supernatant was repeatedly removed, followed by thorough washing until no free titanium compound was detected in the washings. The resulting suspension was dried under reduced pressure at room temperature for 6 hours to obtain a titanium catalyst component. The composition of the resulting titanium catalyst component was 4.0% by mass of titanium, 56.0% by mass of chlorine, 17.0% by mass of magnesium, 10.4% by mass of ethyl benzoate, and 12.6% by mass of a hydrocarbon solvent consisting of decane and hexane.

[0092] [Production Example 1] Production of Copolymer (A) 8.0 kg of 3-methyl-1-butene, 0.6 kg of 1-decene, 50 g of triethylaluminum diluted with hexane to a concentration of 1 mol / L, and 4 g of the titanium catalyst component produced in the above [Catalyst Preparation] were added to a 20 L stainless steel autoclave, and a polymerization reaction was carried out at 70 °C for 4 hours. During the polymerization reaction, hydrogen was continuously fed at a rate of 40 mL / min. After 4 hours, 200 g of 3-methyl-1-butanol was injected to stop the reaction and expel excess unreacted monomer. Next, 2 kg of normal heptane was introduced, and the mixture was stirred at 60 °C for 30 minutes, after which the solids were filtered off using a pressure filter. This procedure was repeated twice, and then the solvent was changed from 2 kg of normal heptane to 3 kg of 2-propanol, and the same procedure was repeated twice. 7.7 kg of the obtained crude polymer was placed in a 50 L vessel equipped with a stirrer, followed by the addition of 8 kg of 1 mol / L hydrochloric acid and 16 kg of 2-propanol, followed by stirring for 1 hour. This suspension was filtered by vacuum filtration and washed with 10 kg of 2-propanol. This crude polymer was placed in a 50 L vessel equipped with a stirrer, followed by the addition of 20 kg of 2-propanol, followed by stirring for 1 hour. This suspension was filtered by vacuum filtration and washed with 10 kg of 2-propanol. The washed polymer obtained was dried under reduced pressure at 80°C for 2 days to obtain 3.2 kg of copolymer (A), a copolymer of 3-methyl-1-butene and 1-decene. The above-mentioned measurements were performed on the obtained copolymer (A), and the melting point was 286°C and the melt viscosity was 104 Pa s. Furthermore, the content of structural units derived from the comonomer 1-decene in copolymer (A) was 1.1 mol%.

[0093] [Production Example 2] Production of Copolymer (B) The same procedure as in Production Example 1 was carried out, except that 0.6 kg of 1-decene was changed to 3.6 kg of 1-decene, to obtain 2.8 kg of copolymer (B), a copolymer of 3-methyl-1-butene and 1-decene. When the above-mentioned measurements were carried out on the obtained copolymer (B), it was found that the melting point was 281°C and the melt viscosity was 99 Pa s. Furthermore, the content of structural units derived from the comonomer 1-decene in copolymer (B) was 6.4 mol%.

[0094] Example 1 To 100 parts by mass of the copolymer (A) obtained in Production Example 1, 0.2 parts by mass of pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] ("AO-60", manufactured by ADEKA Corporation) as a phenol-based antioxidant, 0.2 parts by mass of 3,9-bis(2,6-di-t-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane ("PEP-36", manufactured by ADEKA Corporation) as a phosphorus-based antioxidant, 0.1 part by mass of 2,4-di-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl]phenyl acrylate (Sumilizer (registered trademark) GS, manufactured by Sumitomo Chemical Co., Ltd.) as an alkyl radical scavenger (acrylic phenol compound) and 0.25 part by mass of zinc stearate (antacid) were dry blended, and then the mixture was melt-kneaded at a cylinder temperature of 320°C using a twin-screw kneading extruder KZW15-45 (manufactured by Technovel Corporation) to obtain a pellet-shaped resin composition (M1).

[0095] The obtained pellet-like resin composition (M1) was molded under the following film-forming conditions to obtain a biaxially stretched film. Specifically, the pellets were fed into a twin-screw extruder "KZW15-45" (manufactured by Technovel Corporation), melt-kneaded at 310°C, and melt-extruded into a film from a T-die. The resulting film was then cooled and solidified on a cooling roll at 110°C to obtain an unstretched film with a thickness of 200 μm. The unstretched film obtained here was heated with a heating roll at 200°C and stretched three times longitudinally between a pair of rolls with a difference in peripheral speed to obtain a uniaxially stretched film. Next, both ends of the uniaxial film in the width direction were gripped, heated in a heating oven at 200°C, and then transversely stretched seven times in the width direction to obtain a biaxially stretched film. A film for a film capacitor (thickness 10 μm) was produced. Both ends of the obtained film for a film capacitor were cut and then subjected to a corona discharge treatment. This film was introduced into a resistance heating evaporation apparatus (manufactured by MBRAUN) and －６ An aluminum layer of 80 nm was vacuum-deposited under reduced pressure conditions of 1000 psi (1000 bar), and the metal-deposited film was wound up to prepare a film capacitor. The results of the above evaluations are shown in Table 1.

[0096] [Example 2] A resin composition (M2), a film for a film capacitor, and a film capacitor were produced in the same manner as in Example 1, except that the copolymer (B) obtained in Production Example 2 was used instead of the copolymer (A). The film for a film capacitor had a thickness of 10 μm. The results of the above evaluations are shown in Table 1.

[0097]

[0098] [Comparative Example 1] A polypropylene (PP) film "#25A-KW37" (manufactured by Toray Industries, Inc.) was used as a film for a film capacitor, and after corona discharge treatment in the same manner as in Example 1, an aluminum layer was vacuum-deposited using a resistance heating vapor deposition device to produce a film capacitor. The results of the above evaluations are shown in Table 2.

[0099] Comparative Example 2 A film for a film capacitor was produced in the same manner as in Example 1, except that polymethylpentene (PMP) "TPX (registered trademark) MX0020" (manufactured by Mitsui Chemicals, Inc.) was used instead of the resin composition (M1) in Example 1, and the film formation conditions for obtaining the resin composition were a cylinder temperature of 270°C, a cooling roll temperature of 80°C, a heating roll temperature of 190°C, and a heating oven temperature of 190°C. A film for a film capacitor was produced in the same manner as in Example 1 using the obtained film for a film capacitor. The results of the above evaluations are shown in Table 2.

[0100] [Comparative Example 3] A cycloolefin polymer (COP) film "ZEONORfilm (registered trademark) ZF16" (manufactured by Zeon Corporation) was used as a film for a film capacitor, and a film capacitor was produced by forming a metallized film in the same manner as in Comparative Example 1. The results of the above evaluations are shown in Table 2.

[0101]

[0102] As shown in the examples, a film for a film capacitor containing a resin composition containing a 3-methyl-1-butene polymer of this embodiment has a low dielectric constant and a low dielectric loss tangent, and is surface mountable. Therefore, the film for a film capacitor of this embodiment is highly industrially useful.

Claims

1. A film for a film capacitor comprising a resin composition containing a 3-methyl-1-butene polymer.

2. The 3-methyl-1-butene polymer is at least one selected from the group consisting of a 3-methyl-1-butene homopolymer and a copolymer of 3-methyl-1-butene with ethylene or an α-olefin, and the α-olefin has 3 to 20 carbon atoms. The film for film capacitors according to claim 1.

3. The film for film capacitors according to claim 2, wherein the content of structural units derived from the ethylene or the α-olefin in the copolymer is more than 0 mol% and 20 mol% or less.

4. The film for film capacitors according to claim 2, wherein the content of structural units derived from the ethylene or the α-olefin in the copolymer is more than 0 mol% and 10 mol% or less.

5. The film for a film capacitor according to claim 1, wherein the dielectric loss tangent at 1 kHz to 200 GHz is less than 0.00100.

6. 2. The film for a film capacitor according to claim 1, wherein the melting point of the 3-methyl-1-butene polymer is 260 to 310°C.

7. The film for a film capacitor according to claim 1 , wherein the resin composition contains an alkyl radical scavenger.

8. 8. The film for a film capacitor according to claim 7, wherein the alkyl radical scavenger comprises at least one selected from the group consisting of an acrylic phenol compound and a benzofuranone compound.

9. The film for a film capacitor according to claim 1, having a thickness of 0.01 to 40 μm.

10. A film capacitor comprising the film for a film capacitor according to any one of claims 1 to 9.

11. The film capacitor according to claim 10, which is for surface mounting.