JP5320115B2 - Polypropylene film for film capacitor and film capacitor - Google Patents

Description

  The present invention relates to a polypropylene film for a film capacitor and a film capacitor. Specifically, the present invention relates to a polypropylene film for a film capacitor having a high dielectric breakdown voltage and a low thermal shrinkage rate, and a film capacitor including the film.

  Polypropylene is widely used as a film for a film capacitor because it has excellent stretching properties, insulation properties and voltage resistance. The demand for film capacitors is increasing mainly in the fields of automobiles and home appliances, and there is a demand for further miniaturization. Therefore, there is a demand for further improvement in dielectric breakdown voltage with respect to the films used.

  As a film for a film capacitor, for example, a film made of a composition mainly composed of highly stereoregular polypropylene (Patent Document 1), ash contained in polypropylene is 40 ppm by weight or less, and chlorine is 2 ppm by weight or less. High stereoregularity of polymer insulating material (Patent Document 2), a film made of propylene polymer having an aluminum residual content of less than 25 ppm and a boron residual content of less than 25 ppm (Patent Document 3), and a polypropylene having a long chain branch as a masterbatch A film obtained by adding to polypropylene and biaxially stretching (Patent Document 4) is disclosed.

  However, it is not possible to obtain a film having a sufficient dielectric breakdown voltage only by improving the stereoregularity of polypropylene, reducing impurities in polypropylene, or adding specific polypropylene, and obtain a capacitor that satisfies market requirements. I can't.

  In Patent Document 5, biaxial stretching is performed in order to suppress “wrinkles” that occur during heat treatment during capacitor element fabrication and significantly adversely affect the life of the capacitor to maintain the capacitor performance (breakdown voltage). A film for a film capacitor is disclosed in which the polypropylene film is irradiated with ultraviolet rays or an electron beam, and the thermal shrinkage in the longitudinal direction of the film is regulated within a specific range.

  However, since the polypropylene used in the examples has a stereoregularity of about 91%, when such a stereoregularity of about 91% is used, “wrinkles” are generated using this method. Even if suppressed, a film capacitor having a sufficient dielectric breakdown voltage cannot be obtained.

JP 61-110906 A Japanese Patent Laid-Open No. 06-236709 Special table 2009-500479 JP 2006-93688 A JP-A-54-109160

  The present invention is intended to solve the problems associated with the prior art as described above, has a low thermal shrinkage rate, is a thin film, and is also referred to as a dielectric breakdown voltage (BDV; hereinafter referred to as “Brake Down Voltage”). It is an object of the present invention to provide a polypropylene film for a film capacitor and a film capacitor including the film.

  The present inventors have intensively studied to solve the above problems. As a result, a polypropylene film for a film capacitor obtained by irradiating an electron beam with a specific absorbed dose to a stretched film formed using a specific propylene homopolymer has a low thermal shrinkage and a dielectric breakdown voltage. Therefore, the present invention has been found to be suitable for a film capacitor, and the present invention has been completed.

That is, the present invention includes the following matters.
[1] A film obtained by irradiating an electron beam with an absorbed dose of 0.1 to 500 kGy to a stretched film formed using a propylene homopolymer satisfying the following requirements (1) to (4) Polypropylene film for capacitors;
(1) Based on ASTM D1238, the melt flow rate (MFR) measured at 230 ° C. and a 2.16 kg load is in the range of 1 to 10 g / 10 min.
(2) The pentad isotactic fraction (mmmm fraction) measured using ¹³ C-NMR is 94% or more.
(3) The amount of ash obtained by complete combustion in air is 30 ppm or less.
(4) The amount of chlorine measured by ion chromatography is 10 ppm or less.

[2] The stretched film is preferably a stretched film formed by adding a crosslinking agent to the propylene homopolymer.
[3] The stretched film is preferably a stretched film formed by adding 0.01 to 10% by weight of a crosslinking agent to 100% by weight of the propylene homopolymer.

[4] The absorbed dose of the electron beam applied to the stretched film is preferably 1 to 300 kGy.
[5] The stretched film is preferably a biaxially stretched film.

[6] The thickness of the polypropylene film is preferably 1 to 20 μm.
[7] A film capacitor comprising the polypropylene film for a film capacitor.

  The polypropylene film for a film capacitor according to the present invention has a small heat shrinkage rate and is a thin film, and also has a high dielectric breakdown voltage. Therefore, a small and large capacity capacitor film can be provided. It can greatly contribute to higher output, smaller size, and lighter weight.

  Hereinafter, a polypropylene film for a film capacitor according to the present invention and a film capacitor including the film will be described in detail including preferred embodiments. The polypropylene film for a film capacitor is also simply referred to as “polypropylene film”.

[Polypropylene film for film capacitors]
The polypropylene film for film capacitors according to the present invention irradiates a stretched film formed using a propylene homopolymer satisfying requirements (1) to (4) described later with an electron beam at an absorbed dose of 0.1 to 500 kGy. It is characterized by being obtained. Since the dielectric breakdown voltage and the heat shrinkage rate of the polypropylene film are further improved, the stretched film is preferably a stretched film formed by adding a crosslinking agent to the propylene homopolymer.

<< stretched film >>
The stretched film is a propylene homopolymer that satisfies requirements (1) to (4) described later, preferably a stretched film formed by adding a crosslinking agent to the propylene homopolymer. More specifically, the stretched film stretches the original sheet made of a resin composition containing the propylene homopolymer, preferably the propylene homopolymer and a crosslinking agent (for example, uniaxial stretching, biaxial stretching), Preferably, it is formed by biaxial stretching. That is, the stretched film is preferably a biaxially stretched film.

  The raw sheet is obtained by, for example, melt-extruding (for example, 180 to 280 ° C.) or press-molding (for example, 180 to 280 ° C.) the propylene homopolymer or the resin composition in the form of powder, granules, or pellets. Obtained. In addition, it is preferable to carry out nitrogen sealing at the time of raw sheet forming or granulation (pelletizing).

  80-800 micrometers is preferable and, as for the thickness of the said original fabric sheet, 120-500 micrometers is more preferable. When the thickness of the original fabric sheet is less than the above range, it may break at the time of stretching, and when it exceeds the above range, a stretched thin film may not be obtained, so that it may not be suitable as a film for a film capacitor.

  Uniaxial stretching is preferably 2 to 10 times at 100 to 160 ° C., more preferably 3 to 8 times at 110 to 150 ° C., in the machine direction (the flow of the resin extruded when the raw sheet is formed) This is done by stretching in a parallel direction.

  As the biaxial stretching method, the film obtained by uniaxial stretching is further stretched at right angles to the machine direction under the same conditions as uniaxial stretching; stretching in the machine direction and the direction perpendicular to the machine direction. The simultaneous biaxial stretching method which performs simultaneously is mentioned. Specifically, conventionally known sequential biaxial stretching methods and simultaneous biaxial stretching methods such as a tenter method and a tubular film method can be used.

  In the tenter method, a molten sheet melt-extruded from a T-die is solidified with a cooling roll, and the sheet is preheated as necessary, and then introduced into a stretching zone, and then 3 to 7 times in the machine direction at a temperature of 100 to 160 ° C. The sheet is stretched 5 to 11 times in the transverse direction. The total stretched surface magnification is preferably 20 to 70 times, more preferably 30 to 50 times. If the stretched surface ratio is less than the above range, the film strength may not be increased, and if it exceeds the above range, voids are likely to be generated, the strength in the width direction is lowered, and the film is easily torn in the length direction.

  Moreover, heat-fixing at 160-190 degreeC is also performed as needed with respect to the film by which uniaxial stretching or biaxial stretching was carried out. Thereby, a polypropylene film with improved thermal dimensional stability, water resistance and wear resistance can be obtained. In addition, the stretched film formed as described above may be appropriately cut according to various conditions such as the equipment of the electron beam irradiation apparatus.

《Electron beam irradiation》
The polypropylene film according to the present invention is obtained by irradiating the stretched film with an electron beam at an absorbed dose of 0.1 to 500 kGy, preferably 1 to 300 kGy, more preferably 1 to 100 kGy. The absorbed dose (kGy) of the electron beam is a value calculated by the product of the acceleration voltage, current, and irradiation time of the electron beam irradiation apparatus. Further, the absorbed dose of the electron beam is a total amount, and the electron beam may be irradiated only once. If the total amount of the absorbed dose is within the above range, it may be irradiated in a plurality of times.

  If electron beam irradiation is made with respect to a stretched film, the timing etc. will not be specifically limited. For example, if the sequential biaxial stretching method is used, the film obtained by uniaxial stretching is irradiated with an electron beam, and further stretched at right angles to the machine direction under the same conditions as uniaxial stretching to form a biaxially stretched film. Also good. Moreover, you may extend | stretch the stretched film after electron beam irradiation further. In these, it is preferable to irradiate an electron beam to a biaxially stretched film.

  In addition, the propylene homopolymer or the resin composition in the form of powder, granules or pellets may be irradiated in advance with an electron beam as long as the object of the present invention is not impaired. A line may be irradiated.

  When the absorbed dose of the electron beam is lower than the above range, the effect of irradiation cannot be obtained, so that a polypropylene film having a high dielectric breakdown voltage and a film capacitor including the film may not be provided. If the absorbed dose of the electron beam exceeds the above range, the propylene homopolymer may be deteriorated, and further, it is necessary to increase the output of the electron beam irradiation, so that it is not appropriate from the viewpoint of productivity and economy.

  The stretched film may be irradiated with an electron beam on any surface, or only one surface or both surfaces. In addition, the stretched film has excellent flatness, and the stretched film can be uniformly irradiated with an electron beam at a low output voltage, so that a polypropylene film having a uniform dielectric breakdown voltage (non-uniformity) can be obtained. it can. That is, from the viewpoints of productivity and economy, electron beam irradiation on the stretched film is preferable.

  In the present invention, the reason why the breakdown voltage of the polypropylene film is remarkably improved by irradiating the stretched film with an electron beam in the above range is that the molecules in the amorphous part of the propylene homopolymer contained in the stretched film are cross-linked. By doing so, it is presumed that the entanglement between the molecules increases and the movement of the electrons is blocked by the molecules becoming difficult to move.

<< Physical properties and shape of polypropylene film >>
The polypropylene film according to the present invention has a higher dielectric breakdown voltage and a lower thermal shrinkage rate than conventionally known polypropylene films. For this reason, it can be suitably used as a small and large-capacity capacitor film, and can greatly contribute to, for example, high output, miniaturization, and weight reduction of a hybrid vehicle.

  The dielectric breakdown voltage (BDV) of the polypropylene film according to the present invention is specifically as described in Examples described later, and is superior to the BDV of conventionally known polypropylene films.

  The thermal contraction rate (%) of the polypropylene film according to the present invention is preferably −2.0 to + 2.0%, more preferably −1.5 to + 1.5%. If the thermal shrinkage rate is less than the above range, the element may not be sufficiently tightened and it may be difficult to maintain the shape, or a void may be generated and the element may be deteriorated. When the thermal shrinkage rate exceeds the above range, the element is deformed, and a void is generated due to the deformation, which may cause deterioration or further destruction of the element. Here, the polypropylene film was cut to a length of 100 mm with a width of 10 mm in the resin flow direction (MD direction), and the cut one was put into a 120 ° C. hot air oven and heated for 15 minutes, and contracted to the original length. The ratio of length (+ when contracted and-when expanded) was defined as the thermal contraction rate (%).

  The thickness of the polypropylene film according to the present invention is preferably 1 to 20 μm, more preferably 1 to 15 μm, still more preferably 2 to 8 μm, and particularly preferably 2 to 4 μm. A polypropylene film having a thickness in the above range (preferably 8 μm or less, particularly preferably 4 μm or less) exhibits better electrical characteristics (dielectric breakdown voltage) than when a conventionally known material is used. Films with a thickness below the above range may be difficult to mold with current technology, and when a film with a thickness above the above range is used, the film capacitor becomes large and the current capacitor is downsized. May not be able to meet the demands for.

"material"
Hereinafter, the propylene homopolymer used as a raw material in the present invention, the crosslinking agent preferably used, and other additives will be described. When forming a stretched film, the propylene homopolymer may be used as it is, or may be used as a resin composition containing the propylene homopolymer and a crosslinking agent or other additives.

  The shape of the propylene homopolymer or resin composition may be any of powder, granules and pellets. Powders and granules are obtained directly from the propylene homopolymer or resin composition, and pellets are obtained by granulating the powders and granules.

  If it is a powder, the average particle size is, for example, about 50 to 150 μm. If it is a granule, the average particle size is, for example, about 150 to 2000 μm. If it is a pellet, the average particle size is about 2 to 10 mm. The height is about 1 to 5 mm.

<Propylene homopolymer>
The propylene homopolymer used in the present invention satisfies the following requirements (1) to (4). It is preferable that the following requirement (5) and / or (6) is further satisfied because the moldability is improved and the withstand voltage is improved.

  (1) Based on ASTM D1238, the melt flow rate (MFR) measured at 230 ° C. and a 2.16 kg load is in the range of 1 to 10 g / 10 minutes, preferably 2 to 5 g / 10 minutes. If the MFR is less than the above range, the formability of the sheet is inferior, and the sheet is not easily stretched. If it exceeds the above range, breakage may occur when the sheet is stretched. In addition, it is considered that the breakage is caused by insufficient melt tension.

(2) The pentad isotactic fraction (mmmm fraction) measured using ¹³ C-NMR is 94% or more, preferably 96% or more, more preferably 98% or more. When the pentad isotactic fraction (mmmm fraction) of the polypropylene homopolymer is less than the above value, a polypropylene film having a high dielectric breakdown voltage and a film capacitor including the film cannot be obtained even when irradiated with an electron beam. . This is presumed to be due to the fact that there are many amorphous parts that easily conduct electricity because the pentad isotactic fraction is low. The upper limit of the pentad isotactic fraction is not particularly limited, but is usually about 99.5%.

The pentad isotactic fraction (mmmm fraction) The proportion of isotactic linkages in pentad units in the molecular chain as determined by assignments shown in Zamelli et al. Macromolecules, 8, 687 (1975) and measured using ¹³ C-NMR. Pentad isotactic fraction = (peak area at 21.7 ppm) / (peak area at 19 to 23 ppm).

  (3) The amount of ash obtained by complete combustion in air is 30 ppm or less, preferably 25 ppm or less, more preferably 20 ppm or less. When the ash content exceeds the above value, a polypropylene film having a high dielectric breakdown voltage may not be obtained. This is presumed to be due to the fact that voids tend to form when there is a large amount of ash, thus affecting the breakdown voltage.

  (4) The amount of chlorine measured by ion chromatography is 10 ppm or less, preferably 5 ppm or less, more preferably 2 ppm or less. When the amount of chlorine exceeds the above value, a polypropylene film having a high breakdown voltage may not be obtained. This is presumed to be because chlorine becomes hydrochloric acid and gradually destroys polypropylene, affecting the breakdown voltage during long-term use.

  (5) The melting point (Tm) obtained by differential scanning calorimeter (DSC) measurement is preferably 155 ° C. or higher, more preferably 160 ° C. or higher, and further preferably 163 ° C. or higher. The upper limit of Tm is not particularly limited, but is usually about 170 ° C. When Tm is in the above-described range, a polypropylene film having excellent heat shrinkage and breakdown voltage can be obtained. This is presumably because there are few amorphous parts that can move freely.

  (6) The molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) measured by gel permeation chromatography (GPC) is preferably 4.0 or more, more preferably 4.5-9. 0.0, more preferably 4.5 to 7.5. When the molecular weight distribution Mw / Mn is in the above range, a sheet excellent in moldability and stretchability can be obtained.

-Propylene homopolymer production method-
A propylene homopolymer satisfying the requirements (1) to (4) (preferably further the requirements (5) and / or (6)) is produced by a propylene polymerization method using a conventionally known propylene polymerization catalyst. Among them, a production method using a supported titanium catalyst is preferable.

  The supported titanium catalyst includes a solid titanium catalyst component containing titanium, magnesium, halogen and an internally added electron donating compound, and an organic metal containing a metal selected from Groups I, II and III of the periodic table A polymerization catalyst comprising a compound and an externally added electron donating compound is preferably used.

  More specifically, a catalyst used for industrially producing a propylene polymer containing polypropylene is used as the polymerization catalyst. For example, a material in which titanium trichloride or titanium tetrachloride is supported on a support such as magnesium halide and an organoaluminum compound are used. Among these, it is particularly preferable to use a catalyst that is highly active and has a low titanium component.

  Since the propylene homopolymer is used for a film capacitor, when the amount of polymer produced per unit amount of the catalyst is small, it is necessary to perform post-treatment to remove the catalyst residue. Further, even if the amount of polymer produced is large due to the high activity of the catalyst, it is preferable to carry out post-treatment to remove the catalyst residue. Examples of the post-treatment method include a method of washing a propylene homopolymer obtained by polymerization with liquid propylene, butane, hexane, heptane or the like. At this time, water, alcohol compounds, ketone compounds, ether compounds, ester compounds, amine compounds, organic acid compounds or inorganic acid compounds may be added to solubilize and easily extract catalyst components such as titanium and magnesium. Good. It is also preferable to wash with a polar compound such as water or alcohol.

  Furthermore, the propylene homopolymer obtained by the above polymerization is preferably dehalogenated. In particular, dehalogenation treatment using an epoxy compound is preferable. Here, as the epoxy compound, for example, alkoxy oxides such as ethylene oxide, propylene oxide, butene oxide or cyclohexene oxide, glycidyl alcohol, glycidyl acid or glycidyl ester are preferably used. When performing a dechlorination treatment of a propylene homopolymer using these epoxy compounds, it is very effective to use a compound having an hydroxyl group (OH group) of equimolar or more with the epoxy compound. Examples of the compound having an OH group include water and alcohol.

  Furthermore, it can also be produced by multistage polymerization in the presence of a highly stereoregular propylene polymerization catalyst. That is, the propylene homopolymer used in the present invention is obtained by polymerizing propylene in the presence or absence of hydrogen in the presence of a supported titanium catalyst, so that the propylene homopolymer part has two or more stages. It can be produced by multistage polymerization. Moreover, when producing a propylene homopolymer, preliminary polymerization can be carried out in advance.

  The polymerization conditions are a polymerization temperature in the range of about −50 to + 200 ° C., preferably about 20 to 100 ° C., and a polymerization pressure of atmospheric pressure to 9.8 MPa (gauge pressure), preferably about 0.2 to 4.9 MPa. It is appropriately selected within the range of (gauge pressure). As the polymerization medium, inert hydrocarbons may be used, and liquid propylene may be used as the polymerization medium. The method for adjusting the molecular weight is not particularly limited, but a method using hydrogen as the molecular weight adjusting agent is preferred.

<Crosslinking agent>
In the present invention, a crosslinking agent can be preferably used. By adding a crosslinking agent to the propylene homopolymer, a polypropylene film having a higher breakdown voltage can be obtained. This is because the molecular cutting of the propylene homopolymer by electron beam irradiation is reduced by crosslinking with a crosslinking agent, so that the absorbed dose of the electron beam is increased to the point where the effect of breakdown voltage is more manifested. It is estimated that

The crosslinking agent is preferably a crosslinking monomer having two or more polymerizable double bonds. Examples of the crosslinkable monomer include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6 -Hexanediol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2'-bis (4-acryloxypropyloxyphenyl) Diacrylate compounds such as propane, 2,2′-bis (4-acryloxydiethoxyphenyl) propane;
Triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate;
Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate;
Hexaacrylate compounds such as dipentaerythritol hexaacrylate;
Ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol Dimethacrylate compounds such as dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, 2,2′-bis (4-methacryloxydiethoxyphenyl) propane;
Trimethacrylate compounds such as trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate;
Examples include glycerin-α-allyl ether, triallyl isocyanurate, trimethallyl isocyanurate, methylene bisacrylamide, and divinylbenzene.

  Among these, 1,3-butylene glycol dimethacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, polyethylene glycol diacrylate, 1,6-hexane glycol diacrylate, glycerin-α-allyl Ether, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, trimethallyl isocyanurate, tetramethylol methane tetraacrylate are preferred, the volatilization amount during sheet and film molding is small, and the reaction during electron beam irradiation Is gentle, and therefore triallyl isocyanurate is more preferable because it is easy to handle.

  In the present invention, the crosslinking agent is preferably added in an amount of 0.01 to 10% by weight, more preferably 0.5 to 5% by weight with respect to 100% by weight of the propylene homopolymer. When the addition amount of the crosslinking agent is less than the above range, the effect of adding the crosslinking agent may not be obtained. When the addition amount of the crosslinking agent exceeds the above range, it may be difficult to form the resin composition into a sheet shape.

<Other additives>
In the present invention, to the propylene homopolymer, an antioxidant (Irganox 1010, BHT (dibutylhydroxytoluene), Irgaphos 168, etc.), hydrochloric acid absorbent (calcium stearate, etc.), Additives such as weather resistance stabilizer, heat resistance stabilizer, antistatic agent, anti-slip agent, anti-blocking agent, anti-fogging agent, nucleating agent, lubricant, pigment, dye, plasticizer, anti-aging agent may be added .

〔Film capacitor〕
The film capacitor according to the present invention includes the polypropylene film for a film capacitor. That is, in the present invention, the polypropylene film for a film capacitor can be used for a known film capacitor. The polypropylene film for a film capacitor according to the present invention exhibits a small thermal contraction rate and a high dielectric breakdown voltage even in a thin film, so that a small and large capacity capacitor film can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by an Example. In the examples and comparative examples, each physical property was measured as follows. (1) to (6) are physical properties of a propylene homopolymer used as a raw material, and (7) to (8) are physical properties of a biaxially stretched film or a biaxially stretched film after electron beam irradiation.

(1) Melt flow rate (MFR)
The MFR of the sample (propylene homopolymer) was measured at 230 ° C. and a 2.16 kg load in accordance with ASTM D1238.

(2) Pentad isotactic fraction (mmmm fraction)
The pentad isotactic fraction (mmmm fraction) of the sample (propylene homopolymer) is Based on the assignment shown in Zamelli et al., Macromolecules, 8, 687 (1975), measured using ¹³ C-NMR under the following conditions, the pentad isotactic fraction = (peak area at 21.7 ppm) / (Peak area at 19 to 23 ppm).

<Measurement condition>
Type: JNM-Lambada400 (manufactured by JEOL Ltd.)
Resolution: 400MHz
Measurement temperature: 125 ° C
Solvent: 1,2,4-trichlorobenzene / deuterated benzene = 7/4 (volume ratio)
Pulse width: 7.8 μsec
Pulse interval: 5 sec
Integration count: 2000 shift standard: TMS = 0ppm
Mode: Single pulse broadband decoupling

(3) Ash content 100 g of a sample (propylene homopolymer) was placed in a magnetic crucible, heated on an electric heater to burn the sample, and placed in an electric furnace at 750 ° C. for 30 minutes for complete ashing. After the crucible was cooled in a desiccator for 1 hour, the weight of ash was measured to the nearest 0.1 mg with a precision balance, and the amount of ash (ppm) relative to the sample was calculated.

(4) Chlorine amount Set about 0.7 g of sample (propylene homopolymer) in the sample combustion device (Mitsubishi Chemical Corporation QF-02), and slowly burn it under the condition of complete combustion. The gas was passed through an absorption liquid (ultra pure water) to collect chlorine. The absorbing solution was introduced into an ion chromatograph equipped with a concentrating device (DX-300 manufactured by Nippon Dionex Co., Ltd.), and the amount of chlorine was calculated from the area of the obtained chromatogram. The detection limit is 1 ppm.

(5) Melting point (Tm)
About 0.40 g of a sample (propylene homopolymer) was put in a 0.2 mm-thick film mold, heated at 240 ° C. for 7 minutes, and then cold-pressed to prepare a film. 5.0 mg ± 0.5 mg was cut from the obtained film and crimped with a dedicated aluminum pan to obtain a measurement sample. The sample was held at 30 ° C. for 0.5 minutes under a nitrogen stream using a DSC7 manufactured by PerkinElmer, Inc., then heated from 30 ° C. to 240 ° C. at 30 ° C./min, and then held at 240 ° C. for 10 minutes. The temperature was lowered from 240 ° C. to 30 ° C. at 10 ° C./min, held at 30 ° C. for 2 minutes, and then the melting point (Tm) was determined from the endothermic curve when the temperature was raised at 10 ° C./min.

(6) Molecular weight distribution (Mw / Mn)
The molecular weight distribution (Mw / Mn) of the propylene homopolymer was measured as follows using a gel permeation chromatograph Alliance GPC-2000 manufactured by Waters. The separation columns are two TSKgel GNH6-HT and two TSKgel GNH6-HTL, the column size is 7.5 mm in diameter and 300 mm in length, the column temperature is 140 ° C., and the mobile phase is o -Use dichlorobenzene and 0.025% by weight of BHT as an antioxidant, move at 1.0 ml / min, set the sample (propylene homopolymer) concentration to 15 mg / 10 mL, set the sample injection volume to 500 μL, and use the differential as the detector. A refractometer was used. The standard polystyrene used was manufactured by Tosoh Corporation for molecular weights of Mw <1000 and Mw> 4 × 10 ⁶ , and used by Pressure Chemical Co. for 1000 ≦ Mw ≦ 4 × 10 ⁶ .

(7) Thermal contraction rate The films obtained in Examples and Comparative Examples were cut in the MD direction to a length of 10 mm and a width of 10 mm. The cut one was placed in a 120 ° C. hot air oven and heated for 15 minutes. The thermal contraction rate (%) was determined by the ratio of the contracted length to the original length.

(8) Dielectric breakdown voltage (BDV)
In accordance with JIS C2330, using a Kasuga Electric Co., Ltd. 6-point DC / AC switching type 15 KV withstand voltage tester, with a voltage increase of 100 to 500 V / sec at a temperature of 80 ° C., in Examples and Comparative Examples A voltage was applied to the obtained film (cut to 250 mm × 300 mm, thickness 15 μm) to measure a dielectric breakdown voltage, and a withstand voltage characteristic was obtained. The upper electrode was a brass cylinder having a mass of 500 g and 25 mmφ as the (+) electrode, and the lower electrode was wound around silicon rubber with an aluminum foil defined in JIS H4160, which was used as the (−) electrode. In addition, the measurement was performed on 6 films for 1 film and 3 films, and the average value was defined as the BDV value. The breakdown voltage is obtained by dividing the measured breakdown voltage (V) by the thickness (μm) of the film.

[Production Example of Propylene Homopolymer]
(1) Preparation of Solid Titanium Catalyst Component 952 g of anhydrous magnesium chloride, 4420 mL of decane and 3906 g of 2-ethylhexyl alcohol were heated at 130 ° C. for 2 hours to obtain a uniform solution. To this solution, 213 g of phthalic anhydride was added, and further stirred and mixed at 130 ° C. for 1 hour to dissolve phthalic anhydride. After cooling the obtained uniform solution to 23 degreeC, 750 mL of this uniform solution was dripped in 2000 mL titanium tetrachloride hold | maintained at -20 degreeC over 1 hour. After the dropping, the temperature of the obtained mixture was raised to 110 ° C. over 4 hours, and when it reached 110 ° C., 52.2 g of diisobutyl phthalate (DIBP) was added and heated at the same temperature for 2 hours. Next, the solid part is collected by hot filtration, and the solid part is resuspended in 2750 mL of titanium tetrachloride, and then the titanium compound is no longer detected in the washing solution using decane and hexane at 110 ° C. Until washed. The solid titanium catalyst component thus adjusted is stored as a hexane slurry. A portion of this hexane slurry was dried and the catalyst composition was examined. The solid titanium catalyst component contained 2% by weight of titanium, 57% by weight of chlorine, 21% by weight of magnesium and 20% by weight of DIBP. It was.

(2) Production of prepolymerization catalyst 120 g of transition metal catalyst component (solid titanium catalyst component), 20.5 mL of triethylaluminum and 120 L of heptane were placed in an autoclave equipped with a stirrer with an internal volume of 200 L, while maintaining the internal temperature at 5 ° C. 720 g was added and reacted by stirring for 60 minutes. After completion of the polymerization, the solid component was precipitated, and the supernatant was removed and washed with heptane twice. The obtained prepolymerized catalyst was resuspended in purified heptane so that the transition metal catalyst component concentration was 1 g / L. This prepolymerization catalyst contained 6 g of propylene polymer per 1 g of the transition metal catalyst component.

(3) Main polymerization Into a vessel polymerization vessel with an internal volume of 100 L, 110 kg / hour of propylene, 1.4 g / hour of the catalyst slurry prepared in (2) as a transition metal catalyst component, and 5.8 mL / triethylaluminum. Time and dicyclopentyldimethoxysilane were continuously supplied at 2.6 mL / hour, and hydrogen was supplied so that the hydrogen concentration in the gas phase was 0.9 mol%. Polymerization was carried out at a polymerization temperature of 73 ° C. and a pressure of 3.2 MPa / G. The obtained slurry was sent to a vessel polymerization vessel with a stirrer having an internal volume of 1000 L, and further polymerization was performed. Propylene was supplied at 30 kg / hour, and hydrogen was supplied to the polymerization reactor so that the hydrogen concentration in the gas phase was 1.3 mol%. Polymerization was performed at a polymerization temperature of 71 ° C. and a pressure of 3.0 MPa / G. The obtained slurry was sent to a vessel having an internal volume of 500 L with a stirrer, and further polymerized. 46 kg / hour of propylene and hydrogen were supplied to the polymerization reactor so that the hydrogen concentration in the gas phase was 1.3 mol%. Polymerization was performed at a polymerization temperature of 69 ° C. and a pressure of 2.9 MPa / G. The resulting slurry was deactivated and then sent to a liquid propylene washing tank to wash the propylene homopolymer powder. After the slurry was vaporized, gas-solid separation was performed to obtain a propylene homopolymer. The resulting propylene homopolymer was introduced into a conical dryer and vacuum dried at 80 ° C. Next, 35.9 g of pure water and 0.63 L of propylene oxide were added to 100 kg of this product, dechlorinated at 90 ° C. for 2 hours, and then vacuum dried at 80 ° C. to produce a propylene homopolymer I got a powder.

  The physical properties of the obtained propylene homopolymer were MFR: 4.2 g / 10 min, mmmm: 98%, ash content: 20 ppm, chlorine content: 1 ppm, Tm: 166 ° C., Mw / Mn: 6.5. It was.

[Comparative Example 1]
The propylene homopolymer pellets (average particle size 3 mm) obtained in the above production example were melted at a molding temperature of 210 ° C. using a 30 mmφ extruder (extruded sheet molding machine manufactured by GM Engineering), The sheet was extruded from a T-die and cooled with a cooling roll maintained at a cooling temperature of 30 ° C. under a take-up speed of 1.0 m / min, to obtain a sheet having a thickness of 0.5 mm.

  This sheet was cut into 85 mm × 85 mm, and using a biaxial stretching machine (KARO IV manufactured by Bruckner), preheating temperature 154 ° C., preheating time 60 seconds, stretching temperature 154 ° C., stretching ratio 5 × 7 times (MD direction) : 5 times, TD direction: 7 times), and biaxially stretched sequentially under conditions of a stretching speed of 6 m / min, to obtain a biaxially stretched film having a thickness of 15 μm. About the obtained biaxially stretched film, an evaluation result (it is related with a thermal contraction rate and BDV. The following is same) is shown in Table 1.

[Examples 1 to 3, Comparative Example 2]
The biaxially stretched film obtained in Comparative Example 1 was irradiated with an electron beam with an absorbed dose shown in Table 1 using an electron beam irradiator (EBC300-60 manufactured by NHV Corporation, the same applies hereinafter). Table 1 shows the evaluation results of the obtained film. In Comparative Example 2, since the biaxially stretched film was deteriorated by electron beam irradiation, the above evaluation could not be performed on the obtained film.

[Comparative Example 3]
In Comparative Example 1, propylene homopolymer (MFR: 2.9 g / 10 min, mmmm: 94%, ash content: 23 ppm, chlorine content: 1 ppm, Tm: 163 ° C., Mw / Mn: 5.0) as pellets. A biaxially stretched film was produced in the same manner as in Comparative Example 1 except that pellets (average particle size: 3 mm) were used and the preheating temperature and stretching temperature of the biaxial stretching machine were set to 151 ° C. Table 1 shows the evaluation results of the obtained biaxially stretched film.

[ Reference Example 4]
The biaxially stretched film obtained in Comparative Example 3 was irradiated with an electron beam with an absorbed dose shown in Table 1 using an electron beam irradiator. Table 1 shows the evaluation results of the obtained film.

[Comparative Example 4]
In Comparative Example 1, propylene homopolymer (MFR: 2.8 g / 10 min, mmmm: 91%, ash content: 27 ppm, chlorine content: 3 ppm, Tm: 160 ° C., Mw / Mn: 8.0) as pellets A biaxially stretched film was produced in the same manner as in Comparative Example 1 except that pellets (average particle size 3 mm) were used and the preheating temperature and stretching temperature of the biaxial stretching machine were set to 147 ° C. Table 1 shows the evaluation results of the obtained biaxially stretched film.

[Comparative Example 5]
The biaxially stretched film obtained in Comparative Example 4 was irradiated with an electron beam with an absorbed dose shown in Table 1 using an electron beam irradiator. Table 1 shows the evaluation results of the obtained film.

[Comparative Example 6]
Propylene homopolymer obtained in the above production example (MFR: 4.2 g / 10 min, mmmm: 98%, ash content: 20 ppm, chlorine content: 1 ppm, Tm: 166 ° C., Mw / Mn: 6.5) 99% by weight of pellets (average particle size 3 mm), propylene homopolymer (polypropylene PF-814 manufactured by Basel, MFR: 3.2 g / 10 min, mmmm: 91.0%, ash content: 220 ppm, chlorine content: 24 ppm , Tm: 158 ° C., Mw / Mn: 8.5) 1% by weight using a twin-screw extruder (HYPERKTX30, 30 mmφ × 2 manufactured by Kobe Steel Co., Ltd.) at a molding temperature of 210 ° C. And pellets were obtained.

  In Comparative Example 1, a biaxially stretched film was produced in the same manner as Comparative Example 1 except that the pellet obtained in Comparative Example 6 was used as the pellet. Table 1 shows the evaluation results of the obtained biaxially stretched film.

[Comparative Example 7]
In Comparative Example 1, propylene homopolymer (MFR: 3.0 g / 10 min, mmmm: 98.5%, ash content: 300 ppm, chlorine content: 70 ppm, Tm: 167 ° C., Mw / Mn: 5.0 as pellets A biaxially stretched film was produced in the same manner as in Comparative Example 1 except that the pellets (average particle size 3 mm) were used. Table 1 shows the evaluation results of the obtained biaxially stretched film.

[Comparative Example 8]
Propylene homopolymer (polypropylene PF-814 (trade name) manufactured by Basel Co., Ltd., MFR: 3.2 g / 10 min, mmmm: 91.0%, ash content: 220 ppm, chlorine content: 24 ppm, Tm: 158 ° C., Mw / Using a press molding machine (SFA-20 type, manufactured by Shindo Metal Industry Co., Ltd.), the pellets of Mn: 8.5) were preheated / pressurized temperature 210 ° C., preheated time 5 minutes, pressurized time 2 minutes, Pressing was performed under conditions of a pressure of 10 MPa and a cooling time of 3 minutes to obtain a 0.5 mm press sheet.

  This press sheet is cut into 85 mm × 85 mm, and using a biaxial stretching machine (KARO IV manufactured by Brookner), preheating temperature 150 ° C., preheating time 60 seconds, stretching temperature 150 ° C., stretching ratio 5 × 7 times (MD Direction: 5 times, TD direction: 7 times) and a stretching speed of 6 m / min were successively biaxially stretched to obtain a biaxially stretched film having a thickness of 15 μm. Table 1 shows the evaluation results of the obtained biaxially stretched film.

［比較例９］
前記製造例で得られたプロピレン単独重合体（ＭＦＲ：４．２ｇ／１０分、ｍｍｍｍ：９８％、灰分量：２０ｐｐｍ、塩素量：１ｐｐｍ、Ｔｍ：１６６℃、Ｍｗ／Ｍｎ：６．５）のペレット（平均粒径３ｍｍ）１００重量％と、トリアリルイソシアヌレート（日本化成（株）社製、ＴＡＩＣ）０．５重量％とを、二軸押出機（神戸製鋼（株）社製ＨＹＰＥＲＫＴＸ３０、３０ｍｍφ×２）を用いて、成形温度２１０℃にて溶融混練し、ペレットを得た。

[Comparative Example 9]
Propylene homopolymer obtained in the above production example (MFR: 4.2 g / 10 min, mmmm: 98%, ash content: 20 ppm, chlorine content: 1 ppm, Tm: 166 ° C., Mw / Mn: 6.5) Pellet (average particle size 3 mm) 100% by weight and triallyl isocyanurate (Nihon Kasei Co., Ltd., TAIC) 0.5% by weight, twin screw extruder (Kobe Steel Co., Ltd. HYPERKTX30, 30mmφ) × 2) was melt kneaded at a molding temperature of 210 ° C. to obtain pellets.

  In Comparative Example 1, a biaxially stretched film was produced in the same manner as Comparative Example 1 except that the pellet produced in Comparative Example 9 was used as the pellet. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[Examples 5 to 8, Comparative Example 10]
The biaxially stretched film obtained in Comparative Example 9 was irradiated with an electron beam at an absorbed dose shown in Table 2 using an electron beam irradiator. The evaluation results are shown in Table 2 for the obtained film. In Comparative Example 10, since the biaxially stretched film was deteriorated by electron beam irradiation, the above evaluation could not be performed on the obtained film.

[Comparative Example 11]
In Comparative Example 9, a biaxially stretched film was produced in the same manner as in Comparative Example 9, except that the amount of the crosslinking agent TAIC used was 1% by weight. The evaluation results of the obtained biaxially stretched film are shown in Table 2.

[Examples 9 to 10]
The biaxially stretched film obtained in Comparative Example 11 was irradiated with an electron beam with an absorbed dose shown in Table 2 using an electron beam irradiator. The evaluation results are shown in Table 2 for the obtained film.

[Example 11]
In Comparative Example 9, a biaxially stretched film was produced in the same manner as in Comparative Example 9, except that the amount of the crosslinking agent TAIC used was 5% by weight. The biaxially stretched film was irradiated with an electron beam at an absorbed dose shown in Table 2 using an electron beam irradiator. The evaluation results are shown in Table 2 for the obtained film.

[ Reference Example 12]
In Comparative Example 9, propylene homopolymer (MFR: 2.9 g / 10 min, mmmm: 94%, ash content: 23 ppm, chlorine content: 1 ppm, Tm: 163 ° C., Mw / Mn: 5.0) as pellets A pellet obtained by adding 1% by weight of TAIC to 100% by weight of pellets (average particle size 3 mm) was used in the same manner as in Comparative Example 9 except that the preheating temperature and the stretching temperature of the biaxial stretching machine were set to 151 ° C. A biaxially stretched film was produced. The biaxially stretched film was irradiated with an electron beam at an absorbed dose shown in Table 2 using an electron beam irradiator. The evaluation results are shown in Table 2 for the obtained film.

[Comparative Example 12]
In Comparative Example 9, propylene homopolymer (MFR: 2.8 g / 10 min, mmmm: 91%, ash content: 27 ppm, chlorine content: 3 ppm, Tm: 160 ° C., Mw / Mn: 8.0) as pellets A pellet obtained by adding 1% by weight of TAIC to 100% by weight of pellets (average particle size 3 mm) was used in the same manner as in Comparative Example 9 except that the preheating temperature and the stretching temperature of the biaxial stretching machine were set to 147 ° C. A biaxially stretched film was produced. The biaxially stretched film was irradiated with an electron beam at an absorbed dose shown in Table 2 using an electron beam irradiator. The evaluation results are shown in Table 2 for the obtained film.

[Comparative Example 13]
In Comparative Example 9, the amount of the crosslinking agent TAIC used was 15% by weight. However, since the amount of the crosslinking agent was too large, pelletization could not be performed and a biaxially stretched film could not be produced.

  The polypropylene film for a film capacitor according to the present invention exhibits a small thermal shrinkage rate and a high dielectric breakdown voltage even in a thin film, and thus can provide a small and large-capacity capacitor film. For example, high output of a hybrid vehicle , Can greatly contribute to miniaturization and weight reduction.

Claims (7)

A polypropylene for a film capacitor obtained by irradiating an electron beam with an absorbed dose of 0.1 to 500 kGy to a stretched film formed using a propylene homopolymer satisfying the following requirements (1) to (4) the film;
(1) Based on ASTM D1238, the melt flow rate (MFR) measured at 230 ° C. and a 2.16 kg load is in the range of 1 to 10 g / 10 min.
(2) The pentad isotactic fraction (mmmm fraction) measured using ¹³ C-NMR is 98% or more .
(3) The amount of ash obtained by complete combustion in air is 30 ppm or less.
(4) The amount of chlorine measured by ion chromatography is 10 ppm or less.   The polypropylene film for a film capacitor according to claim 1, wherein the stretched film is a stretched film formed by adding a crosslinking agent to the propylene homopolymer.   3. The film capacitor according to claim 2, wherein the stretched film is a stretched film formed by adding 0.01 to 10% by weight of a crosslinking agent to 100% by weight of the propylene homopolymer. Polypropylene film.   The polypropylene film for a film capacitor according to any one of claims 1 to 3, wherein the absorbed dose of the electron beam applied to the stretched film is 1 to 300 kGy.   The polypropylene film for a film capacitor according to any one of claims 1 to 4, wherein the stretched film is a biaxially stretched film.   The polypropylene film for a film capacitor according to any one of claims 1 to 5, wherein the thickness is 1 to 20 µm.   A film capacitor comprising the polypropylene film for a film capacitor according to claim 1.