JP6484959B2 - Biaxially oriented polypropylene film for capacitors - Google Patents

Description

  The present invention relates to a biaxially stretched polypropylene film for a capacitor having high withstand voltage at high temperatures and excellent dielectric breakdown characteristics. More specifically, the present invention relates to a biaxially oriented polypropylene film for a capacitor that can be suitably used for a high-capacitance capacitor to which a high voltage is applied at a high temperature, and preferably has a small thickness.

  Biaxially stretched polypropylene film makes use of the excellent electrical properties such as voltage resistance and low dielectric loss properties of polypropylene film and high moisture resistance, in electronic and electrical equipment, for example, high voltage capacitors, various switching power supplies, converters and It is preferably used as a dielectric film for a capacitor such as a filter capacitor such as an inverter and a smoothing capacitor. Polypropylene films have begun to be used as capacitors for inverter power supply devices that control drive motors of electric vehicles and hybrid vehicles, for which demand has been increasing in recent years.

  High-capacity capacitors for inverter power supply equipment used in automobiles and the like are required to be further reduced in size, weight, and capacity, while at a wide temperature range of −40 ° C. to 90 ° C., particularly at high temperatures Even when a high voltage is applied, it is required to have high voltage resistance, particularly high initial voltage resistance.

  Furthermore, in recent years, there has been an increasing demand for further miniaturization and higher capacity of the capacitor.For example, in order to improve the capacitance of the capacitor without changing the volume of the capacitor, There is a demand for thin films.

  By the way, it is known that when a plastic is processed by cooling and solidifying from a molten state, the crystalline polymer is crystallized to produce crystal phases such as spherulites and amorphous phases. It is known to affect the crystallization process of molecules. For example, Patent Document 1 discloses that with respect to polypropylene for electrical insulation, a nucleating agent is added to polypropylene, the spherulite size is adjusted to 20 μm or less, and the impulse breakdown electric field strength of polypropylene for electrical insulation is improved. Yes.

  When a film is produced by stretching a polymer, it is known that a polymer chain constituting the film is deformed by a stress during stretching and the polymer is oriented in the stretching direction. That is, due to the stress at the time of stretching, the polymer chain is deformed with the collapse of the crystalline phase such as spherulites, and the polymer is oriented in the stretching direction to form microcrystals, or it is amorphous by the stress at the time of stretching. The polymer chain of the phase is deformed, and the polymer is oriented in the stretching direction to form microcrystals. Therefore, there is no spherulite in the stretched film.

  Patent Document 2 describes a metallized biaxially oriented polypropylene film having at least one surface of a film surface having a base layer composed of textured irregularities and having a specific surface average roughness and glossiness. In Patent Document 2, a crystal nucleating agent is substantially added because it is difficult to obtain the desired surface roughness or may adversely affect electrical properties such as a decrease in volume resistivity at high temperatures. It is described that it is preferably not done.

JP-A-5-128915 JP2007-290380

High capacity capacitors to which high voltage is applied at high temperatures sufficiently satisfy the recent demand from the market for further miniaturization and higher voltage resistance at high temperatures, especially high initial voltage resistance. It was difficult to obtain a biaxially oriented polypropylene film for a capacitor.
Accordingly, an object of the present invention is to provide a biaxially stretched polypropylene film for a capacitor having a high withstand voltage at a high temperature and excellent in dielectric breakdown characteristics. It is another object of the present invention to provide a biaxially stretched polypropylene film for a capacitor that can be suitably used for a high-capacity capacitor to which a high voltage is applied at a high temperature, and preferably has a small thickness. Furthermore, the present invention provides a metallized polypropylene film for a capacitor in which the above-mentioned biaxially stretched polypropylene film for a capacitor is subjected to metal vapor deposition, and a capacitor having a withstand voltage at a high temperature manufactured using such a polypropylene film. It is to be.

As a result of intensive studies, the present inventors have found that the above object can be achieved by the means described below, and have completed the present invention.
That is, the present invention includes the following preferred embodiments.
[1] A biaxially stretched polypropylene film for a capacitor, comprising a polypropylene resin composition containing at least one polypropylene resin and at least one organic nucleating agent.
[2] The biaxially stretched polypropylene film for capacitors as described in [1] above, wherein the organic nucleating agent is a melting nucleating agent.
[3] The melting nucleating agent is at least one melting nucleating agent selected from the group consisting of a sorbitol nucleating agent, a nonitol nucleating agent and an amide nucleating agent, [2] 2. Biaxially stretched polypropylene film for capacitors described in 1.
[4] The biaxially stretched polypropylene film for capacitors according to [1], wherein the organic nucleating agent is a dispersion-type nucleating agent.
[5] The biaxially stretched polypropylene film for capacitors as described in [4], wherein the dispersive nucleating agent is at least one phosphate metal salt nucleating agent.
[6] The polypropylene resin composition is
The weight average molecular weight (Mw) is 250,000 to 450,000,
The molecular weight distribution (Mw / Mn) is 6 or more and 12 or less,
The biaxially stretched polypropylene film for capacitors according to any one of the above [1] to [5], comprising a polypropylene resin having a molecular weight distribution (Mz / Mn) of 20 or more and 70 or less.
[7] A metallized polypropylene film for capacitors, wherein metal deposition is performed on one or both sides of the biaxially stretched polypropylene film for capacitors according to any one of [1] to [6].
[8] A capacitor manufactured using the metallized polypropylene film for a capacitor according to [7].

  ADVANTAGE OF THE INVENTION According to this invention, the biaxially-stretched polypropylene film for capacitors which has the high voltage resistance in high temperature, especially the high initial voltage resistance in high temperature, and was excellent in the dielectric breakdown characteristic can be provided. In addition, it is possible to provide a biaxially oriented polypropylene film for a capacitor that can be suitably used for a high-capacity capacitor to which a high voltage is applied at a high temperature, and preferably has a small thickness.

  The biaxially stretched polypropylene film for capacitors of the present invention comprises a polypropylene resin composition and can be obtained by biaxially stretching the polypropylene resin composition. The polypropylene resin composition contains at least one polypropylene resin. The polypropylene resin composition may contain one type of polypropylene resin or a combination of two or more types of polypropylene resins.

  The polypropylene resin composition preferably contains a polypropylene resin having a weight average molecular weight (Mw) of 250,000 to 450,000. When such a polypropylene resin composition is used, moderate resin fluidity can be obtained at the time of biaxial stretching, the thickness of the cast raw sheet can be easily controlled, and suitable for, for example, a small and high capacity type capacitor, This is preferable because it is easy to obtain a biaxially stretched polypropylene film that is extremely thin. Moreover, since it becomes difficult to generate | occur | produce the nonuniformity of the thickness of a cast raw fabric sheet and a biaxially stretched polypropylene film, it is preferable. The weight average molecular weight (Mw) of the polypropylene resin is more preferably 300,000 or more from the viewpoints of thickness uniformity, mechanical properties, thermo-mechanical properties, etc. of the biaxially stretched polypropylene film. The weight average molecular weight (Mw) of the polypropylene resin is more preferably 400,000 or less from the viewpoint of the fluidity of the polypropylene resin composition and the stretchability when obtaining an ultrathin biaxially stretched polypropylene film.

  It is preferable that a polypropylene resin composition contains the polypropylene resin whose molecular weight distribution (Mw / Mn) calculated as ratio of a weight average molecular weight (Mw) and a number average molecular weight (Mn) is 6-12. The molecular weight distribution (Mw / Mn) is more preferably 7 or more, and further preferably 7.5 or more. The molecular weight distribution (Mw / Mn) is more preferably 11 or less, and still more preferably 10 or less. It is preferable to use such a polypropylene resin composition because an appropriate resin fluidity can be obtained at the time of biaxial stretching, and it becomes easy to obtain a very thin biaxially stretched polypropylene film having no thickness unevenness. Such a polypropylene resin composition is also preferable from the viewpoint of voltage resistance of the biaxially stretched polypropylene film.

  The polypropylene resin composition preferably contains a polypropylene resin having a molecular weight distribution (Mz / Mn) calculated as a ratio of the Z average molecular weight (Mz) and the number average molecular weight (Mn) of 20 or more and 70 or less. The molecular weight distribution (Mz / Mn) is more preferably 22.5 or more, and further preferably 25 or more. The molecular weight distribution (Mz / Mn) is more preferably 60 or less, and further preferably 50 or less. It is preferable to use such a polypropylene resin composition because an appropriate resin fluidity can be obtained at the time of biaxial stretching, and it becomes easy to obtain a very thin biaxially stretched polypropylene film having no thickness unevenness. Such a polypropylene resin composition is also preferable from the viewpoint of voltage resistance of the biaxially stretched polypropylene film.

  The weight average molecular weight (Mw), number average molecular weight (Mn), and Z average molecular weight (Mz) of the polypropylene resin can be measured by a gel permeation chromatography (GPC) method. The GPC apparatus used in the GPC method is not particularly limited, and is a commercially available high-temperature GPC measuring instrument capable of analyzing the molecular weight of polyolefins, for example, a high-temperature GPC measuring instrument with a built-in differential refractometer (RI) manufactured by Tosoh Corporation. HLC-8121GPC-HT or the like can be used. In this case, for example, a GPC column manufactured by Tosoh Corporation and three connected TSKgelGMHHR-H (20) HT is used, the column temperature is set to 140 ° C., trichlorobenzene is used as an eluent, Measured at 1.0 ml / min. Usually, a calibration curve is prepared using standard polystyrene, and a weight average molecular weight (Mw), a number average molecular weight (Mn), and a Z average molecular weight (Mz) are obtained by polystyrene conversion. The molecular weight distribution (Mw / Mn) is calculated as the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), the weight average molecular weight (Mw) / number average molecular weight (Mn), and the molecular weight distribution (Mz / Mn). Is calculated as the ratio of Z average molecular weight (Mz) to number average molecular weight (Mn), Z average molecular weight (Mz) / number average molecular weight (Mn). The logarithmic value of the weight average molecular weight thus obtained is referred to as logarithmic molecular weight (“Log (M)”).

  Examples of the polypropylene resin include homopolymers of polypropylene such as isotactic polypropylene and syndiotactic polypropylene, and copolymers of polypropylene and polyethylene. From the viewpoint of heat resistance, the polypropylene resin is preferably isotactic polypropylene, and more preferably isotactic polypropylene obtained by homopolymerizing polypropylene in the presence of an olefin polymerization catalyst.

  The polypropylene resin composition preferably contains a polypropylene resin having a mesopentad fraction ([mmmm]) of 94.0% or more and less than 98.0%. The mesopentad fraction is more preferably 95.0% or more and 97.0% or less. When such a polypropylene resin composition is used, the crystallinity of the resin is moderately improved by a reasonably high stereoregularity, and the initial voltage resistance and the voltage resistance over a long period of time are improved. Desirable stretchability can be obtained at an appropriate solidification (crystallization) rate during molding.

The mesopentad fraction ([mmmm]) is an index of stereoregularity that can be obtained by high temperature nuclear magnetic resonance (NMR) measurement. Specifically, it can measure using the JEOL Co., Ltd. make, high temperature type Fourier-transform nuclear magnetic resonance apparatus (high temperature FT-NMR), and JNM-ECP500, for example. The observation nucleus is ¹³ C (125 MHz), the measurement temperature is 135 ° C., and o-dichlorobenzene (ODCB: ODCB and deuterated ODCB mixed solvent (mixing ratio = 4/1) is used as the solvent. For the measurement method by high temperature NMR, refer to, for example, the method described in “Japan Analytical Chemistry / Polymer Analysis Research Roundtable, New Edition Polymer Analysis Handbook, Kinokuniya, 1995, p. 610”. It can be carried out.

The measurement mode is single pulse proton broadband decoupling, the pulse width is 9.1 μsec (45 ° pulse), the pulse interval is 5.5 sec, the number of integration is 4500 times, and the shift reference is CH ₃ (mmmm) = 21.7 ppm. be able to. The meso pentad fraction is calculated as a percentage (%) from the integrated intensity of each signal derived from a combination of pentads (mmmm, mrrm, etc.). Regarding the attribution of each signal derived from mmmm, mrrm, etc., for example, description of spectra such as “T. Hayashi et al., Polymer, Vol. 29, p. 138 (1988)” may be referred to.

  The pentad fraction representing the degree of stereoregularity is a combination of mm (5 mm) and mrrm (5 mm and mrrm) of a consensus “meso (m)” arranged in the same direction and a consensus “lacemo (r)” arranged in the opposite direction. Etc.) based on the integrated value of the intensity of each signal derived from. Each signal derived from mmmm, mrrm and the like can be assigned with reference to, for example, “T. Hayashi et al., Polymer, 29, 138 (1988)”.

  The content of the polypropylene resin is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more based on the total mass of the polypropylene resin composition from the viewpoint of compatibility.

  In the present invention, the polypropylene resin composition contains at least one organic nucleating agent. Organic nucleating agents can be classified into dispersed nucleating agents and dissolved nucleating agents. The dispersion type nucleating agent is usually a solid nucleating agent at a temperature at which a polypropylene resin and a nucleating agent are melt-kneaded or a temperature at which a polypropylene film is molded, or the nucleating agent is a polypropylene resin. An organic nucleating agent that is not compatible (miscible). Soluble nucleating agents are usually organic systems in which the nucleating agent is compatible or compatible (mixed) in the polypropylene resin at the temperature at which the polypropylene resin and the nucleating agent are melt-kneaded or at the temperature at which the polypropylene film is molded. It is a nucleating agent.

  Examples of the dispersion-type nucleating agent include a phosphate ester metal salt nucleating agent, a carboxylic acid metal salt nucleating agent, and a rosin metal salt nucleating agent. Examples of the soluble nucleating agent include soluble nucleating agents such as a sorbitol nucleating agent, a nonitol nucleating agent, a xylitol nucleating agent, and an amide nucleating agent. The polypropylene resin composition may contain the above-mentioned dispersed nucleating agent or dissolved nucleating agent alone or in combination of two or more as the nucleating agent, or the dispersed nucleating agent and the dissolved nucleating agent. You may contain in combination with an agent. The organic nucleating agent is preferably a soluble nucleating agent from the viewpoint of miscibility with the polypropylene resin, and is selected from the group consisting of a sorbitol nucleating agent, a nonitol nucleating agent and an amide nucleating agent. More preferably, it comprises at least one selected melting nucleating agent. In addition, the organic nucleating agent is preferably a dispersion-type nucleating agent from the viewpoint of reducing the amount of the organic nucleating agent added and suppressing bleed out, and at least one phosphate metal salt type More preferably, a nucleating agent is included.

で示されるリン酸−２，２’−メチレンビス（４，６−ジ−ｔｅｒｔ−ブチルフェニル）ナトリウム、式（２）：

で示されるアルミニウムヒドロキシビス［２，２’−メチレンビス（４，６−ジ−ｔｅｒｔ−ブチルフェニル）ホスフェート］、リン酸−２，２’−メチレンビス（４，６−ジ−ｔｅｒｔ−ブチルフェニル）リチウム等が挙げられる。これらのリン酸エステル金属塩系造核剤は、例えば株式会社ＡＤＥＫＡより、アデカスタブＮＡ−１１（式（１）で示されるリン酸エステル金属塩系造核剤）、ＮＡ−２１（式（２）で示されるリン酸エステル金属塩系造核剤）、ＮＡ−７１（リン酸−２，２’−メチレンビス（４，６−ジ−ｔｅｒｔ−ブチルフェニル）リチウムを含むリン酸エステル金属塩系造核剤）、ＮＡ−２７等として市販されている。有機系造核剤として、これらのリン酸エステル金属塩系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 Examples of the phosphoric acid ester metal salt nucleating agent include the formula (1):

-2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate represented by the formula (2):

Aluminum hydroxybis [2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate], phosphoric acid-2,2′-methylenebis (4,6-di-tert-butylphenyl) lithium Etc. These phosphate ester metal salt nucleating agents are, for example, from ADEKA Corporation, ADK STAB NA-11 (phosphate ester metal salt nucleating agent represented by formula (1)), NA-21 (formula (2) Phosphate metal salt nucleating agent represented by the formula: NA-71 (phosphate-2,2′-methylenebis (4,6-di-tert-butylphenyl) lithium) Agent), NA-27 and the like. As the organic nucleating agent, these phosphate ester metal salt nucleating agents may be used alone or in combination of two or more.

  Examples of the carboxylic acid metal salt nucleating agent include aromatic carboxylic acid metal salt nucleating agents and alkyl fatty acid metal salt nucleating agents.

で示されるジ−ｐ−ｔｅｒｔ−ブチル安息香酸ヒドロキシアルミニウム等が挙げられる。これらの安息香酸金属塩系造核剤は、例えばアデカ・パルマロール(AdekaPalmarole)社より、ＭＩ．ＮＡ．０８またはＭＩ．ＮＡ．２０として、クラリアントジャパン社よりＳａｎｄｏｓｔａｂ４０３０として市販されている。有機系造核剤として、これらの安息香酸金属塩系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 Examples of the aromatic carboxylic acid metal salt nucleating agent include a benzoic acid metal salt nucleating agent. Specifically, sodium benzoate, lithium benzoate, formula (3):

And di-p-tert-butylbenzoic acid hydroxyaluminum represented by the formula: These metal benzoate metal nucleating agents are available from, for example, Adeka Palmarole, MI. NA. 08 or MI. NA. 20 is commercially available as Sandostab 4030 from Clariant Japan. As the organic nucleating agent, these benzoic acid metal salt nucleating agents may be used alone or in combination of two or more.

  Examples of the alkyl fatty acid metal salt nucleating agent include a cycloalkyl carboxylic acid metal salt nucleating agent and a pimelic acid metal salt nucleating agent.

で示される化合物、式（５）：

で示される化合物等が挙げられる。これらのシクロアルキルカルボン酸金属塩系造核剤は、例えばミリケン・アンド・カンパニー社よりＨｙｐｅｒｆｏｒｍ（登録商標）６８Ｌ、Ｈｙｐｅｒｆｏｒｍ（登録商標）２０Ｅとして市販されている。有機系造核剤として、これらのシクロアルキルカルボン酸金属塩系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 As the cycloalkyl carboxylic acid metal salt nucleating agent, specifically, the formula (4):

A compound of formula (5):

And the like. These cycloalkyl carboxylic acid metal salt nucleating agents are commercially available from, for example, Milliken & Company as Hyperform (registered trademark) 68L and Hyperform (registered trademark) 20E. As the organic nucleating agent, these cycloalkyl carboxylic acid metal salt nucleating agents may be used alone or in combination of two or more.

  Examples of the pimelic acid metal salt nucleating agent include sodium pimelate and calcium pimelate. As the organic nucleating agent, these pimelic acid metal salt nucleating agents may be used alone or in combination of two or more.

  Examples of the rosin metal salt nucleating agent include magnesium dehydroabietic acid, calcium dehydroabietic acid, and alkali metal salts of dehydroabietic acid. These rosin metal salt nucleating agents are commercially available from, for example, Arakawa Chemical Industries as Pine Crystal KM-1500, Pine Crystal KM-1300, Pine Crystal KR-50M, and the like. As organic nucleating agents, these rosin metal salt nucleating agents may be used alone or in combination of two or more.

で示されるキナクリドンが挙げられる。 Other dispersed nucleating agents include, for example, formula (6):

The quinacridone shown by is mentioned.

  In one embodiment of the present invention in which a dispersion-type nucleating agent is used as the organic nucleating agent, the dispersion-type nucleating agent is a biaxially oriented polypropylene for a capacitor according to the present invention from the viewpoint of reducing the addition amount and suppressing bleed out. The film preferably has an average particle size of 2 μm or less. The average particle diameter is more preferably 1 μm, still more preferably 0.8 μm. Here, the particle diameter of the nucleating agent may be measured with an electron microscope or the like, and for example, it can be measured with reference to JIS Z8827-1 using a scanning electron microscope S-3000N manufactured by Hitachi High-Technologies Corporation.

［式中、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４は、互いに独立して、Ｈまたはメチルを表わす］
で示される化合物、ジベンジリデンソルビトール等が挙げられる。これらのソルビトール系造核剤は、例えばゲルオール（登録商標）Ｄ（新日本理化株式会社製）として市販されている１，３：２，４−ビス−Ｏ−（ベンジリデン）ソルビトール、ゲルオール（登録商標）ＭＤ（新日本理化株式会社製）として市販されている１，３：２，４−ビス−Ｏ−（４−メチルベンジリデン）ソルビトール、ゲルオール（登録商標）ＤＸＲ（新日本理化株式会社製）、Ｍｉｌｌａｄ３９８８（ミリケン・アンド・カンパニー社製）として市販されている１，３：２，４−ビス−Ｏ−（３，４−ジメチルベンジリデン）ソルビトール等が挙げられる。有機系造核剤として、これらのソルビトール系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 As a sorbitol nucleating agent, for example, the general formula (7):

[Wherein R ¹ , R ² , R ³ and R ⁴ independently of one another represent H or methyl]
The compound shown by these, dibenzylidene sorbitol, etc. are mentioned. These sorbitol-based nucleating agents are, for example, 1,3: 2,4-bis-O- (benzylidene) sorbitol and gelol (registered trademark) commercially available as Gelol (registered trademark) D (manufactured by Nippon Nippon Chemical Co., Ltd.). ) 1,3: 2,4-bis-O- (4-methylbenzylidene) sorbitol, Gelol (registered trademark) DXR (manufactured by Shin Nippon Rika Co., Ltd.), commercially available as MD (manufactured by Shin Nippon Rika Co., Ltd.), Examples include 1,3: 2,4-bis-O- (3,4-dimethylbenzylidene) sorbitol, which is commercially available as Millad 3988 (manufactured by Milliken & Company). As the organic nucleating agent, these sorbitol nucleating agents may be used alone or in combination of two or more.

で示される化合物等が挙げられる。このノニトール系造核剤は、例えばミリケン・アンド・カンパニー社より、ＮＸ-８０００として市販されている。有機系造核剤として、ノニトール系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 Examples of nonitol nucleating agents include formula (8):

And the like. This nonitol nucleating agent is commercially available, for example, as NX-8000 from Milliken & Company. As the organic nucleating agent, nonitol nucleating agents may be used alone or in combination of two or more.

  Examples of the xylitol nucleating agent include bis-1,3: 2,4- (5 ′, 6 ′, 7 ′, 8′-tetrahydro-2-naphthaldehydebenzylidene) 1-allylxylitol, bis-1,3. : 2,4- (3 ′, 4′-dimethylbenzylidene) 1-propylxylitol and the like. As the organic nucleating agent, these xylitol nucleating agents may be used alone or in combination of two or more.

で示される化合物、式（１０）：

で示される化合物等が挙げられる。これらのアミド系造核剤は、例えば新日本理化株式会社より、リカクリア（登録商標）ＰＣ−１（Ｎ，Ｎ’，Ｎ”−トリス［２−メチルシクロヘキサン−１−イル］−プロパン−１，２，３−トリイルカルボキサミド）（式（９）で示されるアミド系造核剤）として、ＢＡＳＦ社より、Ｉｒｇａｃｌｅａｒ ＸＴ３８６（式（１０）で示されるアミド系造核剤）として市販されている。有機系造核剤として、これらのアミド系造核剤を、単独であるいは２種以上を組み合わせて使用してよい。 As the amide nucleating agent, for example, the formula (9):

A compound of formula (10):

And the like. These amide-based nucleating agents are, for example, from Shin Nippon Rika Co., Ltd., Rikaclear (registered trademark) PC-1 (N, N ′, N ″ -tris [2-methylcyclohexane-1-yl] -propane-1, 2,3-triylcarboxamide) (an amide nucleating agent represented by formula (9)) is commercially available from BASF as Irgclear XT386 (an amide nucleating agent represented by formula (10)). As the organic nucleating agent, these amide nucleating agents may be used alone or in combination of two or more.

で示されるＮ，Ｎ’−ジシクロヘキシル−２，６−ナフタレンジカルボキサミド等が挙げられる。この化合物は、例えば新日本理化株式会社より、エヌジェスター（登録商標）ＮＵ−１００として市販されている。 Other soluble nucleating agents include, for example, formula (11):

N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide represented by This compound is commercially available as, for example, NJ Star (registered trademark) NU-100 from Shin Nippon Rika Co., Ltd.

  The above organic nucleating agents are classified into dispersed nucleating agents and dissolved nucleating agents, as well as α crystal nucleating agents that preferentially form polypropylene α crystals and polypropylene β crystals. It can also be classified as a β crystal nucleating agent. As the α crystal nucleating agent, the above-described phosphate ester metal salt nucleating agent, carboxylic acid metal salt nucleating agent, rosin metal salt nucleating agent, sorbitol nucleating agent, nonitol nucleating agent, Examples include xylitol nucleating agents and amide nucleating agents. Examples of the β crystal nucleating agent include quinacridone and N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide described above.

  The polypropylene resin composition preferably contains at least one α-crystal nucleating agent from the viewpoint of suppressing the occurrence of perforation.

  The content of the organic nucleating agent is preferably 10 ppm or more, more preferably 25 ppm or more, and further preferably 50 ppm or more based on the total mass of the polypropylene resin composition from the viewpoint of the nucleation effect. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention in which a dispersed nucleating agent is used as the organic nucleating agent, the content of the dispersed nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 25 ppm or more, more preferably 50 ppm or more, and still more preferably 100 ppm or more. From the viewpoint of suppressing bleed out, the content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and still more preferably 0.2% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention in which a soluble nucleating agent is used as the organic nucleating agent, the content of the soluble nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 10 ppm or more, More preferably, it is 25 ppm or more, More preferably, it is 50 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention in which an α nucleating agent is used as the organic nucleating agent, the content of the α nucleating agent is preferably 10 ppm or more based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. More preferably, it is 20 ppm or more, More preferably, it is 25 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention using a β crystal nucleating agent as the organic nucleating agent, the content of the β crystal nucleating agent is preferably 10 ppm or more based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. More preferably, it is 20 ppm or more, More preferably, it is 25 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention using a sorbitol nucleating agent as the organic nucleating agent, the content of the sorbitol nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 50 ppm or more, More preferably, it is 100 ppm or more, More preferably, it is 200 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention using a nonitol nucleating agent as the organic nucleating agent, the content of the nonitol nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 50 ppm or more, More preferably, it is 100 ppm or more, More preferably, it is 200 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention using a xylitol nucleating agent as an organic nucleating agent, the content of the xylitol nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 50 ppm or more, More preferably, it is 100 ppm or more, More preferably, it is 200 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less, based on the total mass of the polypropylene resin composition.

  In one embodiment of the present invention using an amide nucleating agent as the organic nucleating agent, the content of the amide nucleating agent is preferably based on the total mass of the polypropylene resin composition from the viewpoint of the nucleating effect. It is 10 ppm or more, More preferably, it is 25 ppm or more, More preferably, it is 50 ppm or more. From the viewpoint of suppressing bleed out, it is preferably 0.3% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.1% by mass or less, based on the total mass of the polypropylene resin composition.

  In the present invention, the polypropylene resin composition includes, in addition to at least one polypropylene resin and at least one organic nucleating agent, other resins than the polypropylene resin (hereinafter also referred to as “other resins”). In the range which does not impair the effect. Here, the “other resin” is not particularly limited, and a conventionally known resin that is a resin other than a polypropylene resin and is suitable for a capacitor application can be appropriately used in the present invention. Other resins include, for example, polyolefins other than polypropylene, such as polyethylene, poly (1-butene), polyisobutene, poly (1-pentene), and poly (1-methylpentene), ethylene-propylene copolymers, and propylene. -Copolymers of α-olefins such as butene copolymers and ethylene-butene copolymers, vinyl monomers such as styrene-butadiene random copolymers, random copolymers of diene monomers, styrene-butadiene -Vinyl monomers, such as a styrene block copolymer-Diene monomer-Vinyl monomer random copolymer, etc. are mentioned. It is preferable that the compounding quantity of such other resin is 10 mass parts or less with respect to 100 mass parts of resin which comprises a film, More preferably, it is 5 mass parts or less.

  In the present invention, the polypropylene resin composition may contain at least one additive as required in addition to at least one polypropylene resin and at least one organic nucleating agent. In general, the additive is not particularly limited as long as it is an additive used for a polypropylene resin. Such additives include, for example, stabilizers such as antioxidants, chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, colorants and the like. Such an additive may be added to the polypropylene resin as long as the effects of the present invention are not impaired.

  The “antioxidant” is not particularly limited as long as it is normally used for polypropylene. Antioxidants are generally used for two purposes. One purpose is to suppress thermal deterioration and oxidation deterioration in the extruder, and the other purpose is to contribute to suppression of deterioration and improvement of capacitor performance in long-term use as a film capacitor. An antioxidant that suppresses thermal degradation and oxidative degradation in the extruder is also referred to as a “primary agent”, and an antioxidant that contributes to improvement of capacitor performance is also referred to as a “secondary agent”. Two types of antioxidants may be used for these two purposes, and one type of antioxidant may be used for the two purposes.

  When two kinds of antioxidants are used, the polypropylene resin is, for example, 2,6-di-tert-butyl-para-cresol (generic name: BHT) as a primary agent, based on the polypropylene resin (100 mass). Part), about 1000 ppm to 4000 ppm can be contained. Most of the antioxidant for this purpose is consumed in the molding process in the extruder, and hardly remains in the film after film formation (generally, the residual amount is less than 100 ppm).

  As the secondary agent, a hindered phenol-based antioxidant having a carbonyl group can be used. Although it does not restrict | limit especially as a hindered phenolic antioxidant which has a carbonyl group which can be used in this invention, For example, triethyleneglycol-bis [3- (3-tertiary-butyl-5-methyl-4-hydroxyphenyl) ) Propionate] (trade name: Irganox 245), 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 259) , Pentaerythrityl tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010), 2,2-thio-diethylenebis [3- (3 5-Di-tertiary-butyl-4-hydroxyphenyl) propionate] (product) : Irganox 1035), octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: Irganox 1076), N, N′-hexamethylenebis (3,5- Di-tertiary-butyl-4-hydroxy-hydrocinnamamide) (trade name: Irganox 1098). Among them, pentaerythryl tetrakis [3- (3,5-di-tertiarybutyl-4-hydroxyphenyl) propionate having a high molecular weight, high compatibility with polypropylene, low volatility and excellent heat resistance. ] Is most preferred.

  The hindered phenol-based antioxidant having a carbonyl group is preferably not less than 2000 ppm and not more than 7000 ppm, more preferably not less than 3000 ppm and not more than 7000 ppm, based on 100 parts by mass of the polypropylene resin, considering that it is consumed in the extruder. In the polypropylene resin composition.

  When a polypropylene resin composition does not contain a primary agent, more hindered phenolic antioxidants having a carbonyl group can be used. In this case, the hindered phenol-based antioxidant having a carbonyl group in the extruder increases the consumption amount of the hindered phenol-based antioxidant having a carbonyl group. It is preferable to be included in the polypropylene resin composition in the following amounts.

  The “chlorine absorbent” is not particularly limited as long as it is normally used for polypropylene. Examples of the chlorine absorbent include metal soaps such as calcium stearate.

  The “ultraviolet absorber” is not particularly limited as long as it is usually used for polypropylene. Examples of the ultraviolet absorber include benzotriazole (such as Tinuvin 328 manufactured by BASF), benzophenone (such as Cysorb UV-531 manufactured by Cytec), and hydroxybenzoate (such as UV-CHEK-AM-340 manufactured by Ferro).

  The “lubricant” is not particularly limited as long as it is normally used for polypropylene. Examples of the lubricant include primary amides (such as stearic acid amides), secondary amides (such as N-stearyl stearic acid amides), ethylene bisamides (such as N, N'-ethylene bisstearic acid amides), and the like.

  The “plasticizer” is not particularly limited as long as it is one normally used for polypropylene. As a plasticizer, PP random copolymer etc. can be illustrated, for example.

  The “flame retardant” is not particularly limited as long as it is normally used for polypropylene. Examples of the flame retardant include halogen compounds, aluminum hydroxide, magnesium hydroxide, phosphates, borates, and antimony oxides.

  The “antistatic agent” is not particularly limited as long as it is usually used for polypropylene. Examples of the antistatic agent include glycerin monoester (glycerin monostearate and the like), ethoxylated secondary amine and the like.

  The “coloring agent” is not particularly limited as long as it is usually used for polypropylene. Examples of the colorant include cadmium and chromium-containing inorganic compounds to azo and quinacridone organic pigments.

  In the present invention, the film contains one or more hindered phenolic antioxidants (secondary agents) having a carbonyl group for the purpose of suppressing deterioration that progresses with time during long-term use of the biaxially stretched polypropylene film. The content is preferably from 1000 ppm to 6000 ppm, preferably from 1500 ppm to 6000 ppm, based on 100 parts by mass of the polypropylene resin.

  Film capacitors containing hindered phenolic antioxidants with carbonyl groups that have good compatibility with polypropylene at the molecular level and in the optimum specified range are very high temperatures while maintaining high withstand voltage performance. In the life promotion test, the electrostatic capacity is not decreased (deterioration does not proceed) and the long-term durability is improved over a long period of time, which is preferable.

  In the present invention, the polypropylene resin contained in the polypropylene resin composition can be produced using a conventionally known method, and examples of the polymerization method include a gas phase polymerization method, a bulk polymerization method, and a slurry polymerization method. . The polymerization may be one-stage polymerization using one polymerization reactor, or may be multistage polymerization using two or more polymerization reactors. Moreover, you may superpose | polymerize by adding hydrogen or a comonomer as a molecular weight regulator in a reactor. A conventionally known Ziegler-Natta catalyst can be used as the polymerization catalyst, and the polymerization catalyst may contain a promoter component and a donor. The molecular weight, molecular weight distribution, stereoregularity and the like of the polypropylene resin can be controlled by appropriately adjusting the polymerization catalyst and other polymerization conditions.

  Further, as a method of adjusting the molecular weight distribution of the polypropylene resin, for example, a method by adjusting the molecular weight distribution by adjusting the polymerization conditions, a method using a decomposing agent, a method of selectively decomposing a high molecular weight component, Examples include a method of blending resins having different molecular weights.

  When the molecular weight distribution is adjusted depending on the polymerization conditions, it is preferable to use a polymerization catalyst described later because the molecular weight distribution and the molecular weight configuration can be easily adjusted. In the case of obtaining a polypropylene resin by a multistage polymerization reaction, for example, the following method can be exemplified. In the presence of a catalyst, the polymerization reaction is carried out in a plurality of reactors, a polymerization reactor for high molecular weight components and a reactor for low molecular weight or medium molecular weight components. Multiple reactors can be used, for example, in series or in parallel. First, propylene and a catalyst are supplied into the reactor. Together with these components, a first polymerization reaction is carried out by mixing a molecular weight adjusting agent, for example, hydrogen, in an amount necessary to reach the required molecular weight of the polymer. In the case of slurry polymerization, for example, the reaction temperature is about 70 to 100 ° C., and the residence time is about 20 to 100 minutes. The product of the first polymerization reaction is sequentially or continuously sent to the next reactor together with additional propylene, a catalyst, and a molecular weight regulator so that a product having a lower molecular weight or higher molecular weight than the first polymerization reaction can be obtained. And the second polymerization reaction is carried out. The molecular weight distribution can be adjusted by adjusting the yield (production amount) of the first and second polymerization reactions.

  As the catalyst, a general Ziegler-Natta catalyst is preferably used. The catalyst used may contain a promoter component and a donor. The molecular weight distribution can be controlled by appropriately adjusting the catalyst and polymerization conditions.

  When adjusting the molecular weight distribution of the polypropylene raw material resin by peroxidative decomposition, it is preferable to employ a method of performing a peroxidation treatment using a decomposing agent such as hydrogen peroxide or an organic oxide. When a peroxide is added to a collapsible polymer such as polypropylene, a hydrogen abstraction reaction occurs from the polymer, and the resulting polymer radical partially recombines to cause a crosslinking reaction, but most radicals undergo secondary decomposition (β cleavage). ) And is divided into two polymers having smaller molecular weights. Therefore, the decomposition from the high molecular weight component proceeds with a high probability, and as a result, the low molecular weight component increases, whereby the structure of the molecular weight distribution can be adjusted. Examples of a method for obtaining a resin containing a low molecular weight component appropriately by oxidative decomposition include the following methods. That is, the polypropylene resin powder or pellets obtained by the polymerization reaction and the organic peroxide, for example, 1,3-bis- (tertiary-butyl peroxide isopropyl) -benzene or the like is 0.001% by mass to 0%. About 5 mass%, adjusting and adding in consideration of the target molecular weight distribution, and melt-kneading at about 180 ° C. to 300 ° C. in a melt kneader machine.

  When the content of the low molecular weight component is adjusted by blending resins, it is preferable to mix at least two types of resins having different molecular weights in a dry or molten state. For example, with respect to 100% by mass of the resin as the main component, a method of mixing about 1 to 40% by mass of an additive resin having a higher or lower average molecular weight to obtain a mixed system of two types of polypropylene resin has a low molecular weight. Since the adjustment of the component amount is easy, it is preferably employed.

  When the content of the low molecular weight component is adjusted by blending the resin, melt flow rate (MFR) may be used as a measure of the average molecular weight. In this case, the MFR difference between the resin as the main component and the additive resin is preferably about 1 to 30 g / 10 minutes.

  It is preferable that the total ash content due to the polymerization catalyst residue and the like contained in the polypropylene raw material resin in the present invention is as small as possible in order to improve electrical characteristics. The total ash content is preferably 100 ppm or less, more preferably 50 ppm or less, still more preferably 40 ppm or less, and particularly preferably 30 ppm or less, based on the polypropylene resin (100 parts by mass).

The method for obtaining a biaxially stretched polypropylene film by adding an organic nucleating agent to the polypropylene resin in the present invention to obtain a polypropylene resin composition is not particularly limited, and examples thereof include the following methods.
(1) A method in which a polypropylene resin and an organic nucleating agent are kneaded to produce a polypropylene resin composition pellet, the polypropylene resin composition pellet is melt-kneaded and biaxially stretched to obtain a film.
(2) A method of preparing a master batch pellet by pre-kneading a polypropylene resin and an organic nucleating agent, melt-kneading the master batch pellet and the propylene resin pellet, and biaxially stretching to obtain a film.
(3) A method in which a polypropylene resin and an organic nucleating agent are melt-kneaded and biaxially stretched to form a film when forming a polypropylene resin by biaxial stretching without forming a masterbatch.
It is preferable to use the method (1) or (2) because the vicinity of the stretching machine can be maintained in a clean environment.

In the above (1) to (3), before melt-kneading, a powdery or pellet-like resin and a powdery organic nucleating agent may be dry blended with a mixer or the like. An organic nucleating agent may be added to.
The mixer that can be used is not particularly limited, and a Henschel mixer, a ribbon blender, a Banbury mixer, and the like can be used.

  In the above (1) and (2), the polypropylene resin and the organic nucleating agent are melt-kneaded when producing the polypropylene resin composition pellets or the master batch pellet containing the polypropylene resin and the organic nucleating agent. For example, a powdered or pelleted resin and an organic nucleating agent are melt-kneaded in a kneader, and the melt-kneaded resin is pelletized to an appropriate size using a known granulator. The method of obtaining the masterbatch pellet containing the pellet of a polypropylene resin composition or a polypropylene resin, and an organic type nucleating agent by the thing etc. is mentioned.

  There are no particular limitations on the kneader that can be used, and any of a single screw type, a twin screw type, or a multi-screw type higher than that can be used. In the case of a screw type of two or more axes, any kneading type rotating in the same direction or in different directions can be used.

  In the case of blending by melt kneading, the kneading temperature is not particularly limited as long as even good kneading can be obtained, but it is generally in the range of 200 ° C. to 300 ° C., preferably 230 ° C. to 270 ° C. Kneading at an excessively high temperature is not preferable because the resin may be deteriorated. In order to suppress deterioration during resin kneading and mixing, an inert gas such as nitrogen may be purged into the kneader.

  The biaxially stretched polypropylene film of the present invention can be obtained by biaxially stretching the polypropylene resin composition prepared as described above according to an ordinary method.

In the present invention, first, it is preferable to form a “cast original fabric sheet before stretching” for producing a biaxially stretched polypropylene film using a known method.
For example, in the method (1), the obtained polypropylene resin composition pellets are supplied to an extruder and melted by heating. In the method (2), master batch pellets and polypropylene resin pellets are supplied to an extruder and melted by heating. In the above method (3), polypropylene resin pellets and / or powder dry-mixed with an organic nucleating agent are supplied to an extruder and melted by heating, or polypropylene resin pellets are supplied to an extruder. Heat and melt, add organic nucleating agent, melt and knead the heated melt.
Next, after the heated melt is passed through a filtration filter, it is heated and melted at 170 ° C. to 320 ° C., preferably 200 ° C. to 300 ° C., and melt-extruded from the T die, and usually 80 ° C. to 140 ° C. An unstretched cast raw sheet can be formed by cooling and solidifying at least one metal drum maintained at 120 ° C., more preferably 90 ° C. to 105 ° C. The thickness of the cast original fabric sheet is preferably 0.05 mm to 2 mm, and more preferably 0.1 mm to 1 mm.

  A biaxially stretched polypropylene film can be produced by subjecting the polypropylene cast original fabric sheet to stretching. Stretching is performed biaxially and longitudinally and laterally biaxially, and examples of the stretching method include simultaneous or sequential biaxial stretching methods, and a sequential biaxial stretching method is preferred. As the sequential biaxial stretching method, for example, the cast raw sheet is first maintained at a temperature of 100 to 160 ° C., passed between rolls provided with a speed difference, stretched 3 to 7 times in the flow direction, and immediately cooled to room temperature. To do. Subsequently, the stretched film is guided to a tenter and stretched 3 to 11 times in the width direction at a temperature of 160 ° C. or higher, and then relaxed and heat-set, and wound up. The wound film can be cut to a desired product width after being subjected to an aging treatment in an atmosphere of about 20 to 45 ° C.

  The thickness of the biaxially stretched polypropylene film used for production of the metallized polypropylene film is preferably 1 to 6 μm from the viewpoint of obtaining a small and large capacity capacitor element. It is preferable to use a biaxially stretched polypropylene film having a thickness of 1.5 μm or more. Moreover, it is desirable that the biaxially stretched polypropylene film to be used is extremely thin, and the thickness thereof is preferably 5 μm or less, more preferably 4 μm or less, and further preferably 3 μm or less. The thickness of the film can be measured according to JIS-C2330 using, for example, a paper thickness measuring instrument, a micrometer (JIS-B7502) or the like.

  By such a stretching process, a film having excellent mechanical strength and rigidity is obtained, and the unevenness of the surface is further clarified, resulting in a stretched film that is finely roughened. The surface of the biaxially stretched polypropylene film is preferably provided with an appropriate surface roughness that improves the winding properties and also improves the capacitor characteristics.

  The biaxially stretched polypropylene film for capacitors of the present invention is calculated from the half-value width of the α crystal (040) plane reflection peak measured by the wide-angle X-ray diffraction method from the viewpoint of voltage endurance using the Scherrer equation. It preferably has a crystallite size of 0.0 nm or less.

  In the present invention, the “crystallite size” of the polypropylene film is determined from the half-value width of the diffraction reflection peak of the α crystal (040) plane of the polypropylene film, which is measured using a wide-angle X-ray diffraction method (XRD method). It refers to the crystallite size calculated using the Scherrer equation described below.

  The crystallite size of the polypropylene film is more preferably 15.5 nm or less. Using a polypropylene film with a small crystallite size within the above range reduces the leakage current and suppresses the occurrence of structural destruction due to Joule heat generation, so that the heat resistance, voltage resistance and long-term heat resistance and voltage resistance can be reduced. It is preferable from the viewpoint. From the viewpoint of maintaining the mechanical strength and melting point of the polypropylene film, the crystallite size of the polypropylene film is preferably 10.0 nm or more, and more preferably 10.5 nm or more.

［ここで、Ｄは、結晶子サイズ（ｎｍ）、Ｋは定数（形状因子）、λは使用Ｘ線波長（ｎｍ）、βは求めた半価幅、θは回折ブラッグ角である。］ Specifically, the “crystallite size” of the polypropylene film of the present invention can be determined as follows. First, wide-angle X-ray diffraction of the biaxially stretched polypropylene film or its metallized film was performed, and the half width of the diffraction reflection peak of the obtained α crystal (040) plane was determined. Next, from the half width of the diffraction reflection peak of the obtained α crystal (040) plane, the crystallite size is obtained using the Scherrer equation shown in the following equation (1). In the present invention, the shape factor constant K is 0.94.

[Where D is the crystallite size (nm), K is a constant (shape factor), λ is the used X-ray wavelength (nm), β is the calculated half-value width, and θ is the diffraction Bragg angle. ]

  The biaxially oriented polypropylene film for capacitors of the present invention preferably has a surface roughness of at least 0.01 μm or more and 0.08 μm or less in terms of centerline average roughness (Ra) on at least one surface. It is preferable that the surface is finely roughened to have a height (Rz, Rmax in the old JIS definition) of 0.1 μm or more and 0.8 μm or less. When Ra and Rz are in the above-mentioned preferable ranges, the surface can be a finely roughened surface, and during capacitor processing, it is difficult to cause winding wrinkles in element winding processing, and the surface can be preferably wound up. it can. Furthermore, since uniform contact is also possible between the films, the voltage resistance and the voltage resistance over a long period of time can be improved.

  Here, “Ra” and “Rz” (formerly JIS-defined Rmax) are, for example, stylus type surface roughness meters that are generally widely used by the method defined in JIS-B0601: 2001, etc. The value measured using a stylus type surface roughness meter (for example, a diamond needle). More specifically, “Ra” and “Rz” are, for example, a method defined in JIS-B0601: 2001 using a three-dimensional surface roughness meter Surfcom 1400D-3DF-12 manufactured by Tokyo Seimitsu Co., Ltd. It can be determined in compliance.

  As a method for giving fine irregularities on the film surface, various known roughening methods such as an embossing method and an etching method can be employed, and among them, a roughening using β crystals that do not require the incorporation of impurities. The surface method is preferred. The production rate of β crystals can be generally controlled by changing the casting temperature and the casting speed. In addition, the melting / transition ratio of the β crystal can be controlled by the roll temperature in the longitudinal stretching process, and fine roughening can be achieved by selecting optimum production conditions for these two parameters of β crystal formation and its melting / transition. Surface property can be obtained.

  The biaxially stretched polypropylene film can be subjected to a corona discharge treatment on-line or off-line after the end of the stretching and heat setting steps for the purpose of enhancing adhesive properties in the subsequent steps such as a metal vapor deposition processing step. The corona discharge treatment can be performed using a known method. As the atmospheric gas, it is preferable to use air, carbon dioxide gas, nitrogen gas, and a mixed gas thereof.

  In the step of producing the metallized polypropylene film, a metal vapor deposition film is formed on one side of the biaxially stretched polypropylene film. Examples of a method for providing a metal vapor deposition film on a biaxially stretched polypropylene film include a vacuum vapor deposition method and a sputtering method, and the vacuum vapor deposition method is preferable from the viewpoint of productivity and economy. When providing a metal vapor deposition film by a vacuum vapor deposition method, it carries out by selecting suitably from well-known systems, such as a crucible system and a wire system. As the metal constituting the metal vapor deposition film, it is possible to use a single metal such as zinc, lead, silver, chromium, aluminum, copper, nickel, a mixture or an alloy composed of a plurality of kinds of metals selected from these metals. it can. From the standpoints of environment, economy, and film capacitor performance, especially temperature characteristics and frequency characteristics of capacitance and insulation resistance, a simple metal or metal selected from zinc and aluminum as the metal constituting the metal deposition film It is preferable to employ a mixture or an alloy.

  The film resistance of the metal vapor deposition film is preferably 1 to 100Ω / □ from the viewpoint of the electric characteristics of the capacitor. A higher value within this range is desirable from the viewpoint of self-healing (self-healing) characteristics, and the film resistance is more preferably 5Ω / □ or more, and further preferably 10Ω / □ or more. Further, from the viewpoint of safety as a capacitor element, the membrane resistance is more preferably 50Ω / □ or less, and further preferably 20Ω / □ or less. The film resistance of a metal vapor deposition film can be measured during metal vapor deposition, for example, by the two-terminal method known to those skilled in the art. The film resistance of the metal vapor deposition film can be adjusted, for example, by adjusting the output of the evaporation source and adjusting the evaporation amount.

  When forming a metal vapor-deposited film on one side of the film, an insulating margin is formed without vapor-depositing a certain width from one end of the film so that a capacitor is formed when the film is wound. Furthermore, in order to strengthen the bonding between the metallized polypropylene film and the metallicon electrode, it is preferable to form a heavy edge structure at the end opposite to the insulation margin, and the film resistance of the heavy edge is usually 2 to 8Ω / □. Yes, preferably 3 to 6 Ω / □.

  The margin pattern of the metal vapor deposition film to be formed is not particularly limited. However, from the viewpoint of the security of the film capacitor, a pattern including a so-called special margin such as a fish net pattern or a T margin pattern is preferable. It is preferable to form a metal vapor-deposited film with a pattern including a special margin on one side of a biaxially stretched polypropylene film because the security of the obtained film capacitor is improved and the breakdown and short-circuit of the film capacitor can be suppressed. As a method for forming the margin, a known method such as a tape method in which masking is performed with a tape at the time of vapor deposition or an oil method in which masking is performed by application of oil can be used without any limitation.

  The biaxially stretched polypropylene film provided with the metal vapor-deposited film is processed into a metallized polypropylene film capacitor through a winding process of winding along the longitudinal direction of the film. That is, in the method of the present invention, two metallized polypropylene films produced as described above are paired and wound so that metal vapor deposition films and polypropylene films are alternately stacked, Forming a pair of metallicon electrodes on the surface by metal spraying to produce a film capacitor element;

  In the process of producing the film capacitor element, a film winding process is performed. For example, two pairs of metallized polypropylene films are overlapped and wound so that metal vapor deposition portions and polypropylene films are alternately laminated, and further, the insulation margin portions are on the opposite side. At this time, it is preferable to laminate a pair of two metallized polypropylene films with a shift of 1 to 2 mm. The winding machine to be used is not particularly limited, and for example, an automatic winder 3KAW-N2 manufactured by Minato Co., Ltd. can be used.

After winding, heat treatment (hereinafter sometimes referred to as “hot pressing”) is usually performed while applying pressure to the obtained wound product. Mechanical and thermal stability can be obtained when the film capacitor element is tightly wound and the crystal structure is appropriately changed by hot pressing. However, when the element is excessively tightened or the crystal structure is changed by hot pressing, the film loses heat and shrinks, which may cause problems such as molding defects such as heat wrinkles and molding. From such a point, the optimum value of the applied pressure varies depending on the thickness of the polypropylene film, etc., but is preferably 10 × 10 ^{4 to} 450 × 10 ⁴ Pa, more preferably 30 × 10 ^{4 to} 300 × 10 ⁴ Pa. , more preferably from ^{40 × 10 4 ~150 × 10 4} Pa. Moreover, it is preferable that the temperature of heat processing shall be 100-120 degreeC. The time for performing the heat treatment is preferably 5 hours or more, more preferably 10 hours or more from the viewpoint of obtaining mechanical and thermal stability, but it prevents molding defects such as heat wrinkles and molding. In this respect, it is preferably 20 hours or less, and more preferably 15 hours or less.

  Subsequently, a metal capacitor electrode is provided by spraying metal on both end faces of the wound product, thereby producing a film capacitor element. A lead wire is usually welded to the metallicon electrode. In addition, in order to provide weather resistance and particularly prevent deterioration of humidity, it is preferable to enclose the capacitor element in a case and pot it with an epoxy resin.

  In the method of the present invention, a predetermined heat treatment is further applied to the metallized polypropylene film capacitor element produced by the method described above. That is, the method of the present invention includes a step of subjecting the film capacitor element to a heat treatment for 1 hour or longer at a temperature of 80 to 115 ° C. (hereinafter sometimes referred to as “thermal aging”).

  In the above-described step of performing the heat treatment on the film capacitor element, the temperature of the heat treatment is preferably 80 ° C. or higher and preferably 90 ° C. or higher, while 115 ° C. or lower and 110 ° C. or lower. preferable. The effect of heat aging can be obtained by performing heat treatment at the above temperature. Specifically, the gap between the films constituting the capacitor element based on the metallized polypropylene film is reduced, corona discharge is suppressed, and metal It is considered that the internal structure of the fluorinated polypropylene film changes and crystallization proceeds, and as a result, the withstand voltage is improved. When the temperature of the heat treatment is lower than the predetermined temperature, the above effect due to thermal aging cannot be obtained sufficiently. On the other hand, when the temperature of the heat treatment is higher than a predetermined temperature, the polypropylene film may be thermally decomposed or oxidized and deteriorated.

  As a method of performing heat treatment on the film capacitor element, for example, from a known method including a method using a thermostatic bath or a method using high-frequency induction heating in an air atmosphere, a vacuum atmosphere, or an inert gas atmosphere Although it may be selected as appropriate, it is preferable to employ a method using a thermostatic bath.

  The capacitor element obtained by the method of the present invention is a small-sized and large-capacity film capacitor element based on a metallized polypropylene film, and has a high withstand voltage at high temperatures.

  Examples of test methods for investigating the durability of capacitor elements include “step-up test” and “life (life) test”. These are test methods for evaluating the durability at a high temperature of 100 ° C. or higher. is there. “Step-up test” is a test method in which a constant voltage is repeatedly applied to a capacitor element for a certain period (short time) while gradually increasing the voltage value. This is an evaluation method from the viewpoint of voltage. On the other hand, the “life test” is a test method in which a constant voltage is applied to the capacitor element over a long period of time, and the long-term voltage resistance, that is, the durability of the capacitor element is reduced by the capacitance. It is a method of evaluation from the viewpoint of the time when no runaway occurs.

  Although the capacitor element obtained by the method of the present invention depends on the film thickness, for example, when the thickness is 2.5 μm, the voltage when the capacity change rate ΔC = −5% evaluated according to the “step-up test” is 1100 V. Preferably, it is 1120 V or more, more preferably 1150 V or more, and particularly preferably 1180 V or more. Further, the voltage when the capacity change rate ΔC = −95% evaluated according to the “step-up test” is preferably over 1450 V, more preferably 1460 V or more, further preferably 1470 V or more, and 1480 V or more. It is particularly preferred that

The capacitor element obtained by the method of the present invention preferably has a capacity change rate ΔC (after 200 hours) after voltage application evaluated according to the “life test” of −10% or more, and −8% or more. More preferably, it is -6% or more, and particularly preferably -5% or more. Rated voltage of the high voltage capacitor types for hybrid vehicles because 400～800V _DC is common, for example, the applied voltage in the "Life Test" may be evaluated as 600V _DC.
Specifically, a life test for the capacitor element may be performed according to the following procedure.
The capacitor element is preheated at a test environment temperature (for example, 105 ° C.) in advance, and the initial capacitance before the test is measured with an LCR high tester 3522-50 manufactured by Hioki Electric Co., Ltd. Next, using a high-voltage power source, a DC voltage of 600 V is continuously applied to the capacitor element for 200 hours in a constant temperature bath at 105 ° C. The capacitance of the capacitor element after the elapse of 200 hours is measured by the tester, and the capacitance change rate (ΔC) before and after voltage application is calculated. The capacity change rate of the capacitor element after the elapse of 200 hours is evaluated by the average value of the three capacitor elements.

  EXAMPLES Next, the present invention will be described more specifically with reference to examples, but these examples are for explaining the present invention and do not limit the present invention in any way. Unless otherwise specified, the descriptions “parts” and “%” indicate “parts by mass” and “% by mass”, respectively.

[Evaluation method for each characteristic value]
The evaluation method of each characteristic value in the examples is as follows.

(1) Measurement of weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn, Mz / Mn) Using GPC (gel permeation chromatography), measurement was performed under the following conditions.
Measuring instrument: manufactured by Tosoh Corporation, differential refractometer (RI) built-in high-temperature GPC HLC-8121GPC-HT type Column: manufactured by Tosoh Corporation, three TSKgel GMHHR-H (20) HTs connected Column temperature: 140 ° C
Eluent: Trichlorobenzene Flow rate: 1.0 ml / min In addition, the measurement result was obtained by polystyrene conversion using the standard polystyrene by Tosoh Corporation for preparation of a calibration curve. However, the molecular weight was converted to the molecular weight of polypropylene using a Q-factor.

  The differential distribution value was obtained by the following method. First, a time curve (elution curve) of the intensity distribution detected by the RI detector was used as a distribution curve with respect to the weight average molecular weight (Log (M)) using a calibration curve. Next, after obtaining an integral distribution curve for Log (M) when the total area of the distribution curve is 100%, the differential distribution for Log (M) is obtained by differentiating the integral distribution curve with Log (M). A curve was obtained. From this differential distribution curve, differential distribution values when Log (M) = 4.5 and Log (M) = 6.0 were read. In addition, a series of operations until obtaining the differential distribution curve can be normally performed using analysis software built in the GPC measurement apparatus.

(2) Thickness of film The thickness of the film was measured based on JIS-C2330 using the paper thickness measuring device MEI-11 made by Citizen Seimitsu Co., Ltd.

［ここで、Ｄは、結晶子サイズ（ｎｍ）、Ｋは定数（形状因子）、λは使用Ｘ線波長（ｎｍ）、βは求めた半価幅、θは回折ブラッグ角である。］ (3) Crystallite size The crystallite size of the biaxially stretched polypropylene film was measured according to the following using an XRD (wide angle X-ray diffraction) apparatus.
Measuring device: Disstop X-ray diffractometer “MiniFlex300” manufactured by Rigaku Corporation
X-ray generation output: 30KV, 10mA
Irradiation X-ray: Monochromator monochromated CuKα ray (wavelength 0.15418 nm)
Detector: Scintillation counter goniometer scan: 2θ / θ interlocking scan From the obtained data, diffraction diffraction of α crystal (040) plane using analysis computer and integrated powder X-ray analysis software PDXL The half width of the peak was calculated.
From the half width of the diffraction reflection peak of the obtained α crystal (040) plane, the crystallite size was determined using the Scherrer equation of the following equation (1). In the present invention, the shape factor constant K is 0.94.

[Where D is the crystallite size (nm), K is a constant (shape factor), λ is the used X-ray wavelength (nm), β is the calculated half-value width, and θ is the diffraction Bragg angle. ]

(4) Dielectric breakdown voltage According to JIS C2330 (2001) 7.4.11.2 B method (plate electrode method), an AC power source was used, and the dielectric breakdown voltage value was measured 12 times at 100 ° C. The dielectric breakdown voltage value (V _AC ) is divided by the film thickness (μm), and the average value of 8 times excluding the upper 2 times and the lower 2 times among the 12 measurement results is calculated as the breakdown voltage (V _AC / μm).

[Polypropylene resin]
Polypropylene resins having the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), and molecular weight distribution (Mz / Mn) shown in Table 1 below were used for the production of the polypropylene films of Examples and Comparative Examples. These values are values measured in accordance with the above measurement method in the form of raw material resin pellets.
Polypropylene resin PP-1: Isotactic polypropylene (manufactured by Prime Polymer Co., Ltd.)
Polypropylene resin PP-2: Isotactic polypropylene (manufactured by Korea Oil Chemical Co., Ltd.)

  Any of the above polypropylene resins is an antioxidant (primary agent), 2,6-di-t-butyl-p-cresol (generic name: BHT) 2000 ppm, hindered phenolic antioxidant having a carbonyl group. As an agent (secondary agent), pentaerythrityl tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010) is contained in an amount of 3000 to 6500 ppm.

[Organic nucleating agent]
The organic nucleating agents used to produce the polypropylene films of the examples are shown in Table 2 below.

A polypropylene resin composition having the composition shown in Table 3 was produced using the above polypropylene resin and organic nucleating agent. The obtained polypropylene resin composition was biaxially stretched to produce polypropylene films of Examples 2, 3 and 9, Examples (Reference Examples) 1 , 4 to 8 and 10, and Comparative Examples 1 and 2. Details of the manufacture are shown below. Moreover, about the obtained polypropylene film, the crystallite size and the dielectric breakdown voltage were evaluated according to the said method. The obtained evaluation results are shown in Table 3.

Example 1 (Reference Example)
An organic nucleating agent NA-S1 and polypropylene resin PP-1 (5000 ppm of Irganox 1010 added as an antioxidant) were masterbatched by preliminary kneading. Thereafter, the masterbatch and the polypropylene resin PP-1 are weighed and mixed at a ratio such that the concentration of the nucleating agent is 2500 ppm, supplied to the extruder, and heated and melted so that the resin temperature becomes 230 ° C. Then, it was extruded from a T die, wound around a metal drum maintained at a surface temperature of 45 ° C., and solidified to produce a cast raw sheet having a thickness of about 1 mm. The cast original fabric sheet was stretched 5 times in the flow direction and 10 times in the transverse direction at a temperature of 165 ° C. to obtain a biaxially stretched polypropylene film having a thickness of 20 μm. In the present example and the following examples and comparative examples, evaluation was performed using a biaxially stretched polypropylene film having a thickness of 20 μm from the viewpoint of increasing the accuracy of dielectric breakdown voltage measurement. In addition, it is also possible to obtain an ultrathin polypropylene film having a thickness of 10 μm or less from the polypropylene resin compositions shown in this example and the following examples.

Example 2
In the same manner as in Example 1, except that NA-D1 was used in place of NA-S1 as the organic nucleating agent and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 500 ppm. An axially stretched polypropylene film was obtained.

Example 3
In the same manner as in Example 1, except that NA-D2 was used instead of NA-D1 as the organic nucleating agent, and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 500 ppm. An axially stretched polypropylene film was obtained.

Example 4 (Reference Example)
An organic nucleating agent NA-S1 and polypropylene resin PP-1 (5000 ppm of Irganox 1010 added as an antioxidant) were masterbatched by preliminary kneading. Thereafter, the ratio of polypropylene resin PP-1 (5000 ppm of Irganox 1010 added as an antioxidant) to polypropylene resin PP-2 (5000 ppm added Irganox 1010 as an antioxidant) was PP-1 / PP-2 = 50. / 50 (mass ratio), the master batch and the polypropylene resins PP-1 and PP-2 are weighed and mixed at a ratio such that the concentration of the nucleating agent is 2500 ppm, and the resin temperature is After being melted by heating to 230 ° C., it was extruded from a T-die, wound around a metal drum maintained at a surface temperature of 45 ° C., and solidified to produce a cast raw sheet having a thickness of about 1 mm. The cast original fabric sheet was stretched 5 times in the flow direction and 10 times in the transverse direction at a temperature of 165 ° C. to obtain a biaxially stretched polypropylene film having a thickness of 20 μm.

Example 5 (Reference Example)
In the same manner as in Example 4, except that NA-S2 was used as an organic nucleating agent instead of NA-S1, and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 1000 ppm. An axially stretched polypropylene film was obtained.

Example 6 (Reference Example)
In the same manner as in Example 4, except that NA-S3 was used instead of NA-S1 as the organic nucleating agent, and the mixture was measured and mixed so that the concentration of the nucleating agent was 1000 ppm. An axially stretched polypropylene film was obtained.

Example 7 (Reference Example)
In the same manner as in Example 1, except that NA-S4 was used instead of NA-S1 as an organic nucleating agent, and the mixture was measured and mixed so that the concentration of the nucleating agent was 200 ppm. An axially stretched polypropylene film was obtained.

Example 8 (Reference Example)
In the same manner as in Example 1, except that NA-S5 was used instead of NA-S1 as an organic nucleating agent, and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 200 ppm. An axially stretched polypropylene film was obtained.

Example 9
In the same manner as in Example 1, except that NA-D3 was used instead of NA-S1 as the organic nucleating agent, and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 500 ppm. An axially stretched polypropylene film was obtained.

Example 10 (Reference Example)
In the same manner as in Example 1, except that NA-D4 was used instead of NA-S1 as the organic nucleating agent, and the mixture was measured and mixed at a ratio such that the concentration of the nucleating agent was 500 ppm. An axially stretched polypropylene film was obtained.

Comparative Example 1
A biaxially stretched polypropylene film was obtained in the same manner as in Example 1 except that no organic nucleating agent was added.

Comparative Example 2
A biaxially stretched polypropylene film was obtained in the same manner as in Example 4 except that no organic nucleating agent was added.

As shown in Table 3, the biaxially stretched polypropylene films of the present invention in Examples 2, 3 and 9 have a higher breakdown voltage compared to Comparative Examples 1 and 2, and better insulation. It can be seen that it has destructive properties. The biaxially stretched polypropylene films of Examples 2, 3 and 9 having excellent dielectric breakdown characteristics are extremely suitable as a biaxially stretched polypropylene film for capacitors.

  Since the biaxially stretched polypropylene film for capacitors of the present invention is excellent in dielectric breakdown voltage, the use of this film to produce a capacitor is expected to improve the voltage resistance at high temperatures, particularly the initial voltage resistance. Furthermore, since the biaxially stretched polypropylene film for capacitors of the present invention is excellent in dielectric breakdown voltage and can be reduced in thickness, it can be preferably used for small and high-capacity capacitors that require high voltage resistance. is there.

Claims (4)

A polypropylene resin composition comprising at least one polypropylene resin and at least one organic nucleating agent, wherein the organic nucleating agent is represented by the formula (1):

-2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate represented by formula (2):

At least one phosphate ester metal salt nucleating agent selected from the group consisting of aluminum hydroxybis [2,2′-methylenebis (4,6-di-tert-butylphenyl) phosphate] represented by Biaxially oriented polypropylene film for capacitors. The polypropylene resin composition is
The weight average molecular weight (Mw) is 250,000 to 450,000,
The molecular weight distribution (Mw / Mn) is 6 or more and 12 or less,
The biaxially stretched polypropylene film for capacitors according to claim 1, comprising a polypropylene resin having a molecular weight distribution (Mz / Mn) of 20 or more and 70 or less. A metallized polypropylene film for capacitors, wherein metal deposition is performed on one side or both sides of the biaxially oriented polypropylene film for capacitors according to claim 1 or 2 . A capacitor manufactured using the metallized polypropylene film for a capacitor according to claim 3 .