JP6620830B2 - Capacitor element manufacturing method - Google Patents

Description

  The present invention is a small-sized and large-capacity film capacitor element that is suitably used in an inverter power supply circuit for controlling a drive motor of an electric vehicle, a hybrid vehicle, etc., and has a high withstand voltage and a high temperature The present invention relates to a method for producing a capacitor element based on a metallized polypropylene film having a long-term durability.

  Film capacitor elements based on metallized polypropylene films are used for high voltage capacitors and various switching power supplies by taking advantage of the excellent voltage resistance performance, low dielectric loss characteristics, etc. of biaxially oriented polypropylene films, and high humidity resistance. It is preferably used as a filter capacitor and a smoothing capacitor for converters, inverters and the like. In particular, in an inverter power supply circuit that controls a drive motor of an electric vehicle, a hybrid vehicle, or the like that has been increasingly demanded in recent years, the film capacitor element has begun to be used as a smoothing capacitor.

  For such a capacitor for an inverter power supply device used in an automobile or the like, as the vehicle is reduced in size and weight, further miniaturization of the capacitor element itself constituting the capacitor is required. In order to reduce the size of the capacitor element, it is conceivable to use a polypropylene film having a high stretchability as a dielectric film for a capacitor and to make it extremely thin, for example, to a thickness of 1 to 6 μm. On the other hand, even if the film is extremely thin, it is required to have a high withstand voltage that does not break down even when a higher DC voltage is applied at a higher temperature, and a capacitor based on such a film. In an element, it is necessary to improve long-term durability (minimization of change in capacitance with time) that is not destroyed even when a higher voltage is applied for a longer time at a higher temperature.

  Patent Document 1 discloses an ultrathin biaxially stretched polypropylene film having a thickness of 1.0 to 8.0 μm, in order to obtain a dielectric film of a metallized film capacitor having high voltage resistance at high temperatures. In addition, it has been proposed to obtain a film having a specified molecular weight, molecular weight distribution, and mesopentad fraction. However, it may not always be sufficient for the recent high demand from the market regarding the further miniaturization of the capacitor element itself, the high voltage resistance at a high temperature and the long-term durability.

A method for achieving the improvement of the voltage resistance of the film capacitor element by improving the voltage resistance of the film itself has been proposed for a long time. However, even if the performance of the film itself is high, the performance may not be sufficiently exhibited depending on the method of manufacturing the capacitor element.
In addition, in capacitor elements based on metallized polypropylene films, the purpose of facilitating element winding when producing capacitors, the purpose of improving the slipperiness during processing, and the case of oil-impregnated capacitors are oil For the purpose of improving the impregnation property, the surface of the polypropylene film is appropriately finely roughened. However, when a capacitor element is produced by winding a finely roughened film, voids may be generated between the films. If a high voltage is applied between the electrodes in this state, corona discharge may occur in the gap, and the film may be deteriorated in discharge. As a result, the performance as a capacitor may be significantly adversely affected. There was something that even led to.

  For example, in Patent Document 2, in order to eliminate such voids, a heat treatment is performed on a capacitor element formed of a film containing an insulating material as a dielectric, so that the insulating material is separated from the surface of the dielectric so that the gap between the films is reduced. A method for filling the gap has been proposed. However, under severe conditions such as high temperature and high voltage, a substance mixed in the film may become a foreign substance and impair the insulation of the film itself, and conversely reduce the performance of the capacitor element.

  In Patent Document 3, a double-sided metallized film in which metal vapor deposition is formed on both sides of a polypropylene film having a specified heat shrinkage rate is wound so as to face a matching polypropylene film, and heat aging is performed. Therefore, it has been proposed to reduce the air gap between the film phases and improve the voltage resistance of the capacitor element at low temperatures. However, there is no specific description regarding the temperature and time of thermal aging, and the influence on the voltage resistance at high temperatures has not been studied. For example, it is difficult to perform double-sided vapor deposition for an extremely thin film of less than 6 μm, for example.

  In Patent Document 4, in a metallized polypropylene film capacitor, a capacitor element wound with a polypropylene film is hot-pressed under a specific pressure and temperature in order to reduce a beat sound when using a high voltage and a high frequency, After forming the film, a method of applying heat aging at a specific temperature has been proposed. However, with regard to the voltage resistance of the capacitor element, only the breakdown voltage after the energization test is examined, and no attention has been paid to the long-term durability that is regarded as important for the capacitor for inverter power supply equipment.

International Publication No. 2009/060944 JP-A-62-188212 JP 2002-367854 A JP 2009-21411 A

Thus, in a small and large-capacity capacitor element, a metallized polypropylene film capacitor element that sufficiently satisfies recent demands from the market regarding further miniaturization, high voltage resistance at high temperatures, and long-term durability. It was difficult to get.
Accordingly, an object of the present invention is a small and large-capacity film capacitor element, for example, at a high temperature at which a decrease in capacitance is small even when a high DC voltage is continuously applied for a long time at a high temperature. An object of the present invention is to provide a method for producing a film capacitor element based on a metallized polypropylene film having high voltage resistance and long-term durability at high temperatures.

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 method for producing a capacitor element based on a metallized polypropylene film,
A step of forming a metallized polypropylene film by forming a metal vapor-deposited film on one side of a biaxially stretched polypropylene film having a thickness of 1 to 6 μm,
Two metallized polypropylene films are paired together, wound and stacked so that metal vapor deposition films and polypropylene films are alternately stacked, and then a pair of metallized electrodes is formed on both end surfaces by metal spraying to form a film capacitor A step of manufacturing an element; and
A step of heat treating the film capacitor element at a temperature of 80 to 115 ° C. for more than 30 hours;
Including methods.
[2] In the above-mentioned process for producing a film capacitor element, the obtained wound product is subjected to a heat treatment for 5 hours or more at a temperature of 100 to 120 ° C. under a pressure of 10 × 10 ^{4 to} 450 × 10 ⁴ Pa. The method according to [1] above.
[3] The polypropylene resin constituting the polypropylene film is
-The weight average molecular weight Mw is from 250,000 to 450,000,
The molecular weight distribution Mw / Mn calculated from the ratio of the weight average molecular weight Mw / number average molecular weight Mn is 5 to 12, and the differential distribution value when the logarithmic molecular weight Log (M) = 4.5 in the molecular weight distribution curve. The method according to [1] or [2] above, comprising a polypropylene resin A having a difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from 8.0% to 18.0% .
[4] The polypropylene resin constituting the polypropylene film is
-The weight average molecular weight Mw is from 300,000 to 400,000
The molecular weight distribution Mw / Mn calculated from the ratio of the weight average molecular weight Mw / number average molecular weight Mn is from 7 to 9,
In the molecular weight distribution curve, the difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when log molecular weight Log (M) = 4.5 is 1.0% or more and 8.0. The method according to [3], further comprising a polypropylene resin C that is less than%.

According to the present invention, a small and large-capacity film capacitor element for producing a capacitor element based on a metallized polypropylene film having high voltage resistance at high temperature and long-term durability at high temperature. Can provide a way.
The capacitor element obtained by the method of the present invention can be preferably used for a small-sized and large-capacity capacitor used in automobiles and electric power applications that require high voltage and heat resistance.

In one Embodiment of this invention, the schematic sectional drawing which shows the metallized polypropylene film of a pair of 2 sheets obtained by superimposing so that a metal vapor deposition film and a polypropylene film may be laminated | stacked alternately

The present invention is a method of manufacturing a capacitor element based on a metallized polypropylene film,
A step of forming a metallized polypropylene film by forming a metal vapor-deposited film on one side of a biaxially stretched polypropylene film having a thickness of 1 to 6 μm,
A pair of metallized polypropylene films, stacked and wound so that metal vapor deposition films and polypropylene films are alternately stacked, and then a pair of metallicon electrodes is formed on both end surfaces by metal spraying to form a film capacitor A step of manufacturing an element; and
A step of heat treating the film capacitor element at a temperature of 80 to 115 ° C. for more than 30 hours;
including.

In the step of producing a metallized polypropylene film, a metal vapor deposition film is formed on one side of a biaxially stretched polypropylene film having a thickness of 1 to 6 μm.
The polypropylene resin constituting the polypropylene film may be only one kind of polypropylene resin, but may be two or more kinds of polypropylene resins.

  It is preferable that the polypropylene resin which comprises a polypropylene film contains the polypropylene resin A whose weight average molecular weight Mw is 250,000-450,000. When a polypropylene resin containing the polypropylene resin A is used, an appropriate resin fluidity can be obtained during biaxial stretching, so that the thickness of the cast raw sheet can be easily controlled, and it is suitable for forming a small and large capacity type capacitor element. It becomes easy to obtain a biaxially stretched polypropylene film that is extremely thinned. Moreover, since the thickness nonuniformity of a cast raw fabric sheet and a stretched film becomes difficult to generate | occur | produce, it is preferable. The weight average molecular weight Mw of the polypropylene resin A is more preferably 300,000 or more in terms of uniformity of thickness of the biaxially stretched polypropylene film, mechanical properties, thermo-mechanical properties, etc., and the resin fluidity is excellent. It is more preferable that it is 400,000 or less at the point which is excellent in the drawability at the time of obtaining the thinned biaxially-stretched polypropylene film.

  The polypropylene resin A preferably further has a molecular weight distribution Mw / Mn calculated from a ratio of weight average molecular weight Mw / number average molecular weight Mn of 5 or more and 12 or less. When the polypropylene resin A has a molecular weight distribution in the above range, an appropriate resin fluidity can be obtained during biaxial stretching, and it becomes easy to obtain a biaxially stretched polypropylene film with no thickness unevenness and withstand voltage. A biaxially stretched polypropylene film having good properties can be obtained. The molecular weight distribution Mw / Mn of the polypropylene resin A is more preferably 7 or more, further preferably 7.5 or more, preferably 12 or less, and more preferably 11 or less.

  The polypropylene resin A preferably further has a molecular weight distribution Mz / Mn calculated from a ratio of Z average molecular weight Mz / number average molecular weight Mn of 20 or more and 70 or less. When the polypropylene resin A has a molecular weight distribution in the above range, an appropriate resin fluidity can be obtained during biaxial stretching, and it becomes easy to obtain a biaxially stretched polypropylene film with no thickness unevenness and withstand voltage. A biaxially stretched polypropylene film having good properties can be obtained. The molecular weight distribution Mz / Mn of the polypropylene resin A is more preferably 25 or more, further preferably 30 or more, preferably 60 or less, and more preferably 50 or less.

  The weight average molecular weight Mw, the number average molecular weight Mn, the molecular weight distribution Mw / Mn and the molecular weight distribution Mz / Mn of the polypropylene resin can be measured by a gel permeation chromatograph (GPC) method. The GPC apparatus used in the GPC method is not particularly limited, and is a commercially available high-temperature GPC apparatus capable of analyzing the molecular weight of polyolefins, such as a high-temperature GPC measurement machine with a built-in differential refractometer (RI) manufactured by Tosoh Corporation. HLC-8121GPC-HT etc. can be used. In this case, for example, a GPC column manufactured by Tosoh Corporation and three TSKgel GMHHR-H (20) HT connected is used, the column temperature is set to 140 ° C., and trichlorobenzene is used as the eluent. , Measured at a flow rate of 1.0 ml / min. Usually, standard polystyrene is used to prepare a calibration curve, and the measurement result is converted into a polypropylene value. The logarithmic value of the weight average molecular weight thus obtained is referred to as logarithmic molecular weight (“Log (M)”).

  In the molecular weight differential distribution curve, the polypropylene resin A is obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log (M) = 4.5. However, it is 8.0% or more and 18.0% or less, and 10.0% or more and 17.0% or less with respect to the differential distribution value 100% (reference) when Log (M) = 6.0 It is preferably 12.0% or more and 16.0% or less. This is because the distribution value of the component having a logarithmic molecular weight Log (M) of 4 to 5, that is, a molecular weight of 10,000 to 100,000 on the lower molecular weight side than the weight average molecular weight (hereinafter also referred to as a low molecular weight component) is This means that the structure is somewhat higher than the distribution value of a component (hereinafter also referred to as a high molecular weight component) of Log (M) = about 6 (molecular weight around 1 million) on the high molecular weight side from the molecular weight. Here, the differential distribution value at Log (M) = 4.5 is adopted as the representative value of the low molecular weight component, and the differential distribution value at Log (M) = 6 is adopted as the representative value of the high molecular weight component.

  Logarithmic molecular weight Log is a typical distribution value of components having a molecular weight of 10,000 to 100,000 on the low molecular weight side (hereinafter also referred to as “low molecular weight component”) from the Mw value (250,000 to 450,000) of the polypropylene resin A. Component (M) = 4.5 is a component with Log (M) = 6.0 as a typical distribution value of a component having a molecular weight of about 1 million on the high molecular weight side (hereinafter also referred to as “high molecular weight component”). It is understood that the low molecular weight component is larger at a ratio of 8.0% to 18.0%.

  In other words, even if the range of the molecular weight distribution Mw / Mn is defined, it merely represents the breadth of the molecular weight distribution width and does not represent the quantitative relationship between the high molecular weight component and the low molecular weight component therein. Absent. Therefore, the polypropylene resin A in the present invention has a predetermined molecular weight distribution, and at the same time, as described above, a component having a molecular weight of 10,000 to 100,000 is 8.0% or more and 18% compared with a component having a molecular weight of 1,000,000. It is preferable to contain a large amount at a ratio of 0.0% or less.

  As described above, the difference in the polypropylene resin A obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log (M) = 4.5 is Log (M ) = 6.0, the differential distribution value is within a predetermined range with respect to 100% (reference), so that a large amount of low molecular weight components are contained in a predetermined ratio as compared with high molecular weight components. As a result, the crystallite size becomes smaller, and it becomes easier to obtain a desired orientation and a roughened surface, which is preferable.

  Such differential distribution values can be obtained using GPC as follows. A curve (in general, also referred to as “elution curve”) showing an intensity with respect to time obtained by a differential refractometer (RI detector) of GPC is plotted on a time axis using a calibration curve obtained using standard polystyrene. Is converted to a logarithmic molecular weight (Log (M)) to convert the elution curve to a curve showing the intensity against Log (M). Since the RI detection intensity is proportional to the component concentration, an integral distribution curve with respect to the logarithmic molecular weight Log (M) can be obtained when the total area of the curve indicating the intensity is 100%. The differential distribution curve is obtained by differentiating the integral distribution curve with Log (M). Therefore, “differential distribution” means a differential distribution with respect to the molecular weight of the concentration fraction. In the present invention, the differential distribution value at a specific Log (M) is read from this curve.

  The polypropylene resin constituting the polypropylene film is preferably 55% by mass or more, more preferably 60% by mass or more, preferably 90% by mass or less, more preferably 85% by mass, based on 100% by mass of the entire polypropylene resin. Hereinafter, more preferably, 80% by mass or less of polypropylene resin A is contained as the main polypropylene resin.

  The polypropylene resin A as the main polypropylene resin contained in the polypropylene resin constituting the polypropylene film is preferably isotactic polypropylene, which is obtained by polymerizing polypropylene alone in the presence of an olefin polymerization catalyst. A homopolymer of tic polypropylene is more preferable.

  The polypropylene resin A as the main polypropylene resin preferably has a mesopentad fraction ([mmmm]) of 94.0% or more and less than 98.0%, and preferably 95.0% or more and 97.0% or less. More preferred. With such a mesopentad fraction ([mmmm]), 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 by an appropriate solidification (crystallization) rate when the raw sheet is formed.

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 pentad fraction representing the degree of stereoregularity is a combination of the quintet (pentad) of the consensus “meso (m)” arranged in the same direction and the consensus “rasemo (r)” arranged in the opposite direction (mmmm and mrrm). 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)”.

In one embodiment of the present invention, the polypropylene resin constituting the polypropylene film is preferably two or more kinds of polypropylene resins including the polypropylene resin A.
Among the polypropylene resins constituting the polypropylene film, the polypropylene resin suitably used together with the polypropylene resin A as the main polypropylene resin includes a long-chain branched polypropylene resin (hereinafter also referred to as “added polypropylene resin B”), and a polypropylene resin A. And polypropylene resins having different molecular weight differential distribution curves (hereinafter also referred to as “added polypropylene resin C”). These resins are mixed according to any non-limiting mixing method including a method of dry blending the polymerized powder or pellets with a mixer, a method of obtaining the blended resin by melt-kneading the polymerized powder or pellets with a kneader. You can do it.

  Long chain branched polypropylene resin (added polypropylene resin B) increases the tension in the molten state by mixing high molecular weight components or components having a branched structure into the polypropylene resin or by copolymerizing polypropylene with long chain branched components. The polypropylene resin can be used together with the polypropylene resin A for the purpose of improving the surface smoothness and heat resistance of the polypropylene film. Examples of commercially available products of such a long-chain branched polypropylene resin include Profax PF-814 manufactured by Basell, and Daploy HMS-PP (WB130HMS, WB135HMS, WB140HMS, etc.) manufactured by Borealis.

  The long-chain branched polypropylene resin as the added polypropylene resin B is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, based on 100% by mass of the whole polypropylene resin for the above purpose, Is blended in an amount of 5% by mass or less, more preferably 4% by mass or less, and still more preferably 2.5% by mass. By blending the additive polypropylene resin B, the surface of the resulting film can be smoothed appropriately, and the heat resistance can be improved because the melting point of the film is increased.

  The above-mentioned added polypropylene resin C is a polypropylene resin having a molecular weight differential distribution curve different from that of polypropylene resin A, and its weight average molecular weight Mw is preferably 300,000 to 400,000, more preferably 330,000 to 380,000. The molecular weight distribution Mw / Mn calculated from the ratio of the weight average molecular weight Mw / number average molecular weight Mn is preferably 7 or more and 9 or less, more preferably 7.5 or more and 8.5 or less.

  The added polypropylene resin C preferably further has a molecular weight distribution Mz / Mn calculated from a ratio of Z average molecular weight Mz / number average molecular weight Mn of 20 or more and 70 or less. When the added polypropylene resin C has a molecular weight distribution in the above range, an appropriate resin fluidity can be obtained during biaxial stretching, and it becomes easy to obtain a very thin biaxially stretched polypropylene film having no thickness unevenness. A biaxially stretched polypropylene film having good voltage characteristics is obtained. The molecular weight distribution Mz / Mn of the added polypropylene resin C is more preferably 25 or more, further preferably 30 or more, preferably 60 or less, and more preferably 50 or less.

  The added polypropylene resin C further has a difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when the logarithmic molecular weight Log (M) = 4.5 in the molecular weight differential distribution curve. Is 1.0% or more and less than 8.0% and 3.0% or more and 7.5% or less with respect to the differential distribution value of 100% (reference) when Log (M) = 6.0 It is preferably 5.0% or more and 7.5% or less. In this respect, the added polypropylene resin C is clearly distinguished from the polypropylene resin A described above.

  When the polypropylene resin constituting the polypropylene film includes the above-described polypropylene resin A and the added polypropylene resin C, it includes two types of polypropylene resins having different differential distribution values, that is, different molecular weight distribution configurations. . If the quantitative relationship between the high molecular weight component and the low molecular weight component contained in the two types of polypropylene resin is slightly different, a certain fine mixing (phase separation) state will occur in the resulting polypropylene film, and it will be suitably miniaturized. It is thought that the crystal size formed is formed. As a result, even when the film is stretched at the same stretch ratio, it is preferable because a highly oriented film is easily obtained because the film is highly oriented.

  The weight average molecular weight Mw, number average molecular weight Mn, molecular weight distribution (Mw / Mn and Mz / Mn) of the added polypropylene resin C and the differential distribution value in the molecular weight differential distribution curve are the same as in the case of the polypropylene resin A. It can be measured by a chromatographic (GPC) method.

  The added polypropylene resin C further preferably has a mesopentad fraction ([mmmm]) of 94.0% or more and less than 98.0%, more preferably 95.0% or more and 97.0% or less. . For the measurement of the mesopentad fraction and the like, reference is made to the matters described for the polypropylene resin A.

  The added polypropylene resin C is preferably 25% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, preferably 50% by mass or less, based on 100% by mass of the entire polypropylene resin. Preferably, it is blended in an amount of 45% by mass or less, more preferably 40% by mass. By blending in such an amount, the crystallite size becomes finer and it becomes easy to achieve high orientation, and a further effect of improving withstand voltage can be obtained.

  In the present invention, the polypropylene resin constituting the polypropylene film is a polypropylene resin other than the above-mentioned polypropylene resin A, added polypropylene resin B, and added polypropylene resin C (hereinafter also referred to as “other polypropylene resin”), and the effects of the present invention are impaired. It can also be included within the range. Here, the “other polypropylene resin” is not particularly limited, and a conventionally known polypropylene resin that is suitable for capacitor use can also be used as appropriate in the present invention.

  In this invention, the polypropylene resin which comprises a polypropylene film can contain other resin (henceforth "other resin") other than a polypropylene resin within the range which does not impair the effect of this invention. 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 above-mentioned various polypropylene resins constituting the polypropylene film 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. it can. 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.

  In addition, in the polypropylene resin, as a method for causing a difference in differential distribution value, that is, a difference in the composition of the molecular weight distribution, for example, a method by adjusting the molecular weight distribution by adjusting the polymerization conditions, a decomposition agent is used. A method of selectively decomposing a high molecular weight component, a method of blending resins having different molecular weights, and the like.

  When adjusting the structure of the molecular weight distribution depending on the polymerization conditions, it is preferable to use a polymerization catalyst described later, since the molecular weight distribution and the structure of the molecular weight 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 sent sequentially or continuously 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 composition (configuration) of the high molecular weight component and the low molecular weight component 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 the composition of the molecular weight distribution of the polypropylene raw resin is adjusted by peroxidative decomposition, it is preferable to employ a method of performing a peroxidation treatment using a decomposing agent such as hydrogen peroxide or 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 composition (configuration) of the target high molecular weight component and low molecular weight component, 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, a method of obtaining about 1 to 40% by mass of an additive resin having a higher or lower average molecular weight with respect to 100% by mass of a resin as a main component to obtain a two-type polypropylene resin mixed system is a low molecular weight component amount. This is preferably employed because it is easy to adjust.

  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.

  The method of mixing a plurality of polypropylene raw resins (main polypropylene resin A and additive polypropylene resin B etc.) in the present invention is not particularly limited, but a method of dry blending each resin in powder form or pellet form with a mixer or the like, Examples thereof include a method of obtaining a blend resin by melting and kneading each resin in a powder or pellet form in a kneader.

  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. Moreover, there is no restriction | limiting in particular also in the kneading machine which can be used, Any of a 1 axis screw type, a 2 axis screw type, or the multi-screw type more than it can also be used. In the case of a screw type having two or more axes, any kneading type rotating in the same direction or 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 melt-kneaded resin is pelletized to an appropriate size using a known granulator, whereby mixed polypropylene raw material resin pellets can be obtained.

  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 50 ppm or less, more preferably 40 ppm or less, and particularly preferably 30 ppm or less, based on the polypropylene resin (100 parts by mass).

  In the present invention, the polypropylene resin constituting the polypropylene film may contain additives as necessary. The “additive” is not particularly limited as long as it is generally an additive used for polypropylene resin. Additives include, for example, stabilizers such as antioxidants, chlorine absorbers, ultraviolet absorbers, lubricants, plasticizers, flame retardants, antistatic agents, 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 the suppression of deterioration and the improvement of capacitor performance in the 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 wt. 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.

  Considering that the hindered phenol-based antioxidant having a carbonyl group is consumed in the extruder, it is preferably 5000 ppm to 7000 ppm, more preferably 5500 ppm to 7000 ppm, based on 100 parts by mass of the polypropylene resin. In the polypropylene resin.

  When a polypropylene resin does not contain a primary agent, more hindered phenolic antioxidants having a carbonyl group can be used. In this case, the amount of hindered phenol antioxidant having a carbonyl group in the extruder increases, so that the hindered phenol antioxidant having a carbonyl group is 6000 ppm or more and 8000 ppm based on 100 parts by mass of the polypropylene resin. It is preferable to be contained in the polypropylene resin in the following amounts.

  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 4000 ppm to 6000 ppm, preferably 4500 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. Also in the life promotion test, it is preferable because the electrostatic capacity is not lowered (deterioration does not proceed) and long-term durability is improved over a long period of time.

  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.

  In the method of the present invention, the biaxially stretched polypropylene film 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, after supplying polypropylene resin pellets, dry-mixed polypropylene resin pellets and / or powder, or mixed polypropylene resin pellets prepared by pre-melting and kneading to an extruder, heating and melting, and passing through a filtration filter 170 ° C. to 320 ° C., preferably 200 ° C. to 300 ° C., and melt-extruded from the T die, usually 80 ° C. to 140 ° C., preferably 90 ° C. to 120 ° C., more preferably 90 ° C. to 105 ° C. An unstretched cast raw sheet can be formed by cooling and solidifying with at least one held metal drum. 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 orienting vertically and horizontally 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. By appropriately adjusting the temperature of this longitudinal stretching step, the β crystal melts and transitions to the α crystal, and the unevenness can be made obvious. 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.

  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 preferably has a surface roughness of 0.03 μm or more and 0.08 μm or less in centerline average roughness (Ra) on at least one surface, and a maximum height (Rz, It is preferable that the surface is finely roughened to 0.3 μm or more and 0.8 μm or less as Rmax) in the old JIS definition. 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” (Rmax defined in the former JIS definition) are, for example, a stylus type surface roughness meter that is generally widely used by a method defined in JIS-B0601: 2001 or the like. 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 thickness of the biaxially stretched polypropylene film used for producing the metallized polypropylene film is 1 to 6 μm in terms 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. The biaxially stretched polypropylene film to be used is desirably made 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.

  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 process. 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 a metallized polypropylene film, a metal vapor deposition film is formed on one side of a biaxially stretched polypropylene film having a thickness of 1 to 6 μm. 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, as shown in FIG. 1, two pairs of metallized polypropylene films are stacked so that metal vapor deposition portions and polypropylene films are alternately laminated, and further, an insulation margin portion is on the opposite side. Wind together. 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. When the film capacitor element is tightly wound and the crystal structure is appropriately changed by hot pressing, mechanical and thermal stability can be obtained. 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. , still more preferably ^{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 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 thermal 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 performed on the metallized polypropylene film capacitor element produced by the above-described method. That is, the method of the present invention includes a step of subjecting the film capacitor element to a heat treatment for more than 30 hours 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.

  In the above process, the film capacitor element is subjected to heat treatment for more than 30 hours. The heat treatment time is preferably 35 hours or more, preferably 40 hours or more, and more preferably 45 hours or more. When the heat treatment time is shorter than the predetermined time, the above-mentioned effect due to thermal aging cannot be obtained sufficiently, and in particular, the effect of improving the voltage resistance at high temperature cannot be obtained. The heat treatment time is desirably as long as possible as long as it exceeds 30 hours, but from the viewpoint of workability and efficiency, it is preferably 200 hours or less, more preferably 100 hours or less, and 80 hours or less. More preferably.

  As a method for 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 and large-capacity film capacitor element based on a metallized polypropylene film, and has high voltage resistance at high temperature and long-term durability at high temperature. is there. Examples of test methods for examining the durability of the capacitor element include “step-up test”, “life test”, and the like, both of which are test methods for evaluating the durability at a high temperature of 100 ° C. or higher. . “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. Details of each test method are as described later.

  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 higher than 1450 V, more preferably 1460 V or higher, still more preferably 1470 V or higher, and 1480 V or higher. It is particularly preferred that

Further, the capacitor element obtained by the method of the present invention preferably has a capacity change rate ΔC (after 7 hours) after voltage application evaluated according to the “life test” of −10% or more, and −8% or more. More preferably, it is more preferably -6% or more, and particularly preferably -3% or more. Rated voltage of the capacitor of the high voltage type for hybrid vehicles because 400～800V _DC is common, and a 750V _DC applied voltages in the "Life Test" in the present invention.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, the scope of the present invention is not limited to these. Unless otherwise specified, the terms “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) Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn, Mz / Mn), and differential distribution value Molecular weight (Mw) and molecular weight distribution (Mw / Mn) of a polypropylene resin forming a biaxially stretched polypropylene film , Mz / Mn), and evaluation of the differential distribution value of the distribution curve was performed using GPC (gel permeation chromatography) under the following conditions. For the production of the calibration curve, standard polystyrene manufactured by Tosoh Corporation was used, and the measurement results were converted into polypropylene values.
Measuring machine: High temperature GPC with built-in differential refractometer (RI) manufactured by Tosoh Corporation
HLC-8121GPC-HT type column: manufactured by Tosoh Corporation, connecting three TSKgel GMHHR-H (20) HT Column temperature: 140 ° C.
Eluent: Trichlorobenzene Flow rate: 1.0 ml / min

  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) Mesopentad fraction ([mmmm])
The polypropylene film was dissolved in the following solvent, and the mesopentad fraction ([mmmm]) was determined under the following conditions using a high-temperature Fourier transform nuclear magnetic resonance apparatus (high-temperature FT-NMR).
Measuring instrument: JEOL Ltd., high temperature FT-NMR JNM-ECP500
Observation nucleus: ¹³ C (125 MHz)
Measurement temperature: 135 ° C
Solvent: Ortho-dichlorobenzene [ODCB: Mixed solvent of ODCB and deuterated ODCB (4/1)]
Measurement mode: Single pulse proton broadband decoupling Pulse width: 9.1 μsec (45 ° pulse)
Pulse interval: 5.5 sec
Integration count: 4500 shift standard: CH ₃ (mmmm) = 21.7 ppm
It calculated by the percentage (%) from the intensity | strength integral value of each signal derived from the combination (mmmm, mrrm, etc.) of a pentad (pentad). Regarding the attribution of each signal derived from mmmm, mrrm, etc., for example, the description of spectra such as “T. Hayashi et al., Polymer, 29, 138 (1988)” was referred to.

(3) Film thickness The thickness of the film was measured based on JIS-C2330 using a paper thickness measuring device MEI-11 manufactured by Citizen Seimitsu Co., Ltd.

(4) Step-up test for capacitor element A step-up test for a capacitor element at a high temperature was performed according to the following procedure.
The capacitor element was preheated at a test environment temperature (105 ° C.) for 15 hours in advance, and the initial capacitance before the test was measured with an LCR high tester 3522-50 manufactured by Hioki Electric Co., Ltd. Next, a DC voltage of 600 V was applied to the capacitor element for 1 minute in a constant temperature bath at 105 ° C. using a high voltage power source. The capacitance of the capacitor element after voltage application was measured with the tester, and the capacitance change rate before and after voltage application was calculated. Next, the capacitor element was returned to the thermostatic chamber, a voltage of DC 700 V was applied for 1 minute, and the capacity change rate (cumulative) was calculated in the same manner as described above. Similarly, the voltage application for 1 minute and the calculation of the capacity change rate (cumulative) were repeated every 100V until reaching 1000V and every 50V after reaching 1000V. The test was terminated when the capacitance change rate of the capacitor element exceeded -95%. The voltage at which the capacitance change rate of the capacitor element was −5% and −95% was evaluated by the average value of the three capacitor elements.

(5) Life (Life) Test for Capacitor Element A life test for the capacitor element was performed according to the following procedure.
The capacitor element was preheated at a test environment temperature (105 ° C.) for 15 hours in advance, and the initial capacitance before the test was 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 750 V was continuously applied to the capacitor element for 7 hours in a constant temperature bath at 105 ° C. The capacitance of the capacitor element after 7 hours was measured with the above tester, and the rate of change in capacitance before and after voltage application was calculated. The capacity change rate of the capacitor element after the elapse of 7 hours was evaluated by an average value of three capacitor elements.

[Polypropylene resin]
The polypropylene resins used for producing the polypropylene films of Examples and Comparative Examples are shown below.
The resin A1 shown in Table 1 is an isotactic polypropylene resin manufactured by Prime Polymer Co., Ltd., and the resin C1 is a polypropylene resin manufactured by Korea Oil Chemical Co., Ltd. (trade name “HPT-1”). The polypropylene resin A1 corresponds to the polypropylene resin A, and the polypropylene resin C1 corresponds to the polypropylene resin C. Further, as the long-chain branched polypropylene (polypropylene resin B), a long-chain branched polymer (trade name “WB135HMS”) (hereinafter referred to as “polypropylene resin B1”) manufactured by Borealis was used.

Table 1 shows the weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), molecular weight distribution (Mz / Mn), differential distribution value difference, and mesopentad fraction ([mmmm]) of these polypropylene resins A1 and C1. Indicated.
These values are values in the form of raw material resin pellets. In addition, polypropylene resins A1 and C1 are both hindered phenols having 2000 ppm of 2,6-di-t-butyl-p-cresol (generic name: BHT) and carbonyl groups as antioxidants (primary agents). As a system antioxidant (secondary agent), pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: Irganox 1010) is contained in 5000 to 6500 ppm. To do.

[Example 1]
<Production of biaxially stretched polypropylene film>
Resin A1 described in Table 1 as the raw material polypropylene resin A (weight average molecular weight Mw = 3.4 × 10 ⁵ , molecular weight distribution Mw / Mn = 10.0) and resin B1 described in Table 1 as the added polypropylene resin B ( A dry blend obtained by continuously weighing and mixing a weight average molecular weight Mw = 7.0 × 10 ⁴ and a molecular weight distribution Mw / Mn = 2.0) at a ratio of 97.5 to 2.5 (mass ratio). Then, the resin is heated and melted so that the resin temperature becomes 250 ° C. in an extruder, and then extruded from a T die, wound around a metal drum maintained at a surface temperature of 92 ° C. and solidified, and a 125 μm thick cast raw sheet is obtained. Produced. The cast raw sheet is heated to 140 ° C. and stretched 5 times in the flow direction, and then stretched 10 times in the transverse direction at a temperature of 165 ° C. with a tenter to form a biaxial shaft having a thickness of 2.5 μm. A stretched polypropylene film was obtained.

<Production of metallized polypropylene film>
The biaxially stretched polypropylene film thus obtained was subjected to aluminum vapor deposition at a T margin vapor deposition pattern of 12Ω / □ to obtain a metallized polypropylene film. Pattern deposition was performed according to a vacuum deposition method using a wire method, and heavy edge deposition was performed according to a vacuum deposition method using a crucible method.

<Production of film capacitor element>
After slitting the obtained metallized polypropylene film to a small width (620 mm width), two metallized polypropylene films were paired so that metal vapor deposition films and polypropylene films were alternately laminated. Using an automatic winder 3KAW-N2 manufactured by Seisakusho, 1360 turns were wound at a winding tension of 200 g.
By applying a heat treatment (heat press) for 12 hours at 120 ° C. while applying a pressure of 100 × 10 ⁴ Pa to the element wound (winding material), the zinc metal is sprayed on both end faces thereof A pair of metallicon electrodes was formed to obtain a flat film capacitor element.

<Heat treatment (thermal aging) for film capacitor element>
The obtained film capacitor element was put in a thermostat in an air atmosphere and subjected to heat treatment at a temperature of 105 ° C. for 35 hours.

  Table 2 summarizes the results of the step-up test and the life test performed on the capacitor element obtained as described above.

[Example 2]
Instead of the added polypropylene resin B, the resin C1 shown in Table 1 (weight average molecular weight Mw = 3.5 × 10 ⁵ , molecular weight distribution Mw / Mn = 8.0) was used as the added polypropylene resin C, and the raw material polypropylene resin A A capacitor element was obtained in the same manner as in Example 1 except that the mixing ratio of the added polypropylene resin C was set to a ratio of 65 to 35 (mass ratio).
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

Example 3
A capacitor element was obtained in the same manner as in Example 2 except that the heat treatment (thermal aging) time was changed to 50 hours.
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

Example 4
A capacitor element was obtained in the same manner as in Example 2 except that the heat treatment (thermal aging) time was changed to 1500 hours.
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

[Comparative Example 1]
A capacitor element was obtained in the same manner as in Example 1 except that the heat treatment (thermal aging) time was changed to 2 hours.
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

[Comparative Example 2]
A capacitor element was obtained in the same manner as in Example 1 except that the heat treatment (thermal aging) time was changed to 20 hours.
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

[Comparative Example 3]
A metallized polypropylene film capacitor element was obtained in the same manner as in Example 2 except that the heat treatment (thermal aging) time was changed to 15 hours.
Table 2 summarizes the results of the step-up test and the life test for the obtained capacitor element.

  As is clear from the results of Examples 1 to 4, the capacitor element obtained according to the method of the present invention is a small and large-capacity film capacitor element, which has high withstand voltage at high temperature and long-term durability at high temperature. It was a highly practical one with the property. This capacitor element was suitable as a smoothing capacitor used in an inverter power supply circuit for controlling a drive motor of an electric vehicle, a hybrid vehicle, or the like.

  On the other hand, in Comparative Examples 1 to 3, since the heat treatment (thermal aging) was performed only for a short time, the obtained capacitor element had a high withstand voltage at high temperatures from the result of the step-up test. The result of the example was lower. In particular, in the life test, all capacitor elements were punctured (a phenomenon in which the capacitor elements were destroyed and the performance as a capacitor was lost).

  The metallized polypropylene film capacitor element of the present invention can be preferably used for a small-sized and large-capacity capacitor used for automobiles and electric power applications that require high voltage and heat resistance.

1 Polypropylene film 2 Metal deposition part 3 Heavy edge

Claims (3)

A film capacitor element comprising a metallized polypropylene film and a metallicon electrode,
The metallized polypropylene film has a metal vapor deposition film on one side of a biaxially stretched polypropylene film having a thickness of 1 to 6 μm,
The film capacitor element is a pair of the metallized polypropylene films, and the metal vapor deposition films and the polypropylene films are overlapped and wound so that they are alternately stacked, and a pair of metal sprays is applied to both end faces. The metallicon electrode is formed,
The film capacitor element has been subjected to a heat treatment for over 30 hours at a temperature of 80 to 115 ° C. ,
The wound body laminated so that the metal vapor-deposited film and the polypropylene film of the metallized polypropylene film are alternately laminated is 100 to 120 ° C. under a pressure of 10 × 10 ^{4 to} 450 × 10 ⁴ Pa. A film capacitor element that has been heat-treated for 5 hours or more at a temperature . The polypropylene resin constituting the polypropylene film is
-The weight average molecular weight Mw is from 250,000 to 450,000,
The molecular weight distribution Mw / Mn calculated from the ratio of the weight average molecular weight Mw / number average molecular weight Mn is 5 to 12, and the differential distribution value when the logarithmic molecular weight Log (M) = 4.5 in the molecular weight distribution curve. from including Log (M) = 6.0 polypropylene resin a difference obtained by subtracting the differential distribution value is 18.0% or less 8.0% or more when the film capacitor element of claim 1. The polypropylene resin constituting the polypropylene film is
-The weight average molecular weight Mw is from 300,000 to 400,000
The molecular weight distribution Mw / Mn calculated from the ratio of the weight average molecular weight Mw / number average molecular weight Mn is from 7 to 9,
In the molecular weight distribution curve, the difference obtained by subtracting the differential distribution value when Log (M) = 6.0 from the differential distribution value when log molecular weight Log (M) = 4.5 is 1.0% or more and 8.0. The film capacitor element according to claim 2 , further comprising a polypropylene resin C that is less than%.

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