Multilayer polypropylene film for capacitors

Abstract

To provide a film for a capacitor, which is excellent in high-temperature dielectric breakdown strength (high-temperature BDV), which has blocking resistance, and which restrains a nucleating agent and the like from bleeding out, even when it is preserved for long periods.SOLUTION: In a multi-layered polypropylene film for a capacitor according to the present invention, an obverse side layer or a reverse side layer, which is made from a propylene polymer (Y), is provided on at least one surface of a base layer made from a propylene polymer composition containing 0.0001-0.05 mass% of a propylene homopolymer (X) and a polymeric α-crystal nucleating agent (C), and the base layer and the obverse side layer or the reverse side layer are stretched.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Biaxially oriented polypropylene film has excellent mechanical properties, heat resistance, chemical stability, and insulating properties, and is therefore widely used not only for packaging and tape applications but also as capacitor film. Demand for capacitor film is increasing, primarily in the automotive and home appliance sectors, where there is a demand for further miniaturization, higher capacity, and higher reliability. In particular, when capacitors are used for high-power applications such as hybrid and electric vehicles, large currents flow through circuits such as transistors and capacitors, resulting in high operating temperatures. Therefore, capacitors must be able to withstand high voltages.

[0003] Various methods have been proposed to improve the properties of capacitor films, including a method of adding an α-nucleating agent to polypropylene with excellent stereoregularity to increase the heat distortion temperature of the biaxially oriented film and thereby improve heat resistance (e.g., Patent Document 1 and Patent Document 2), a method of adding an organic nucleating agent to polypropylene to improve the high voltage resistance and dielectric breakdown characteristics of the biaxially oriented film at high temperatures (Patent Document 3), and a method of laminating a surface layer made of polypropylene with excellent stereoregularity and silica particles to at least one side of a biaxially oriented film made of polypropylene with excellent stereoregularity and an α-nucleating agent to achieve a surface gloss of 140% or more (Patent Document 4).

[0004] However, none of these methods has been effective enough in improving the high-temperature dielectric breakdown strength (high-temperature BDV). In addition, when an organic nucleating agent is added, the organic nucleating agent may bleed out onto the surface of the biaxially stretched film, and the bleed-out material may contaminate production equipment such as casting rolls. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5586784 [Patent Document 2] Special Publication No. 2018-538373 [Patent Document 3] Japanese Patent Application Publication No. 2015-201616 [Patent Document 4] International Publication No. 2016 / 043217 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a film for a capacitor that has excellent high-temperature dielectric breakdown strength (high-temperature BDV), blocking resistance, and suppresses bleeding out of nucleating agents and the like even when stored for a long period of time. [Means for solving the problem]

[0007] The present invention relates to a multilayer polypropylene film for capacitors, characterized in that it has a surface layer or a back layer made of a propylene polymer (Y) on at least one side of a base layer made of a propylene polymer composition containing a propylene homopolymer (X) and 0.0001 to 0.05 mass % of a polymer-based α-crystal nucleating agent (C), and the base layer and the surface layer or the back layer are all stretched. [Effects of the Invention]

[0008] The multilayer polypropylene film for capacitors of the present invention is a multilayer film comprising a base layer containing a polymer-based α-crystal nucleating agent and a surface layer and / or a back layer made of a propylene-based polymer composition (the surface layer and back layer are layers in contact with the base layer). Therefore, even when stored for a long period of time, bleeding out of the α-crystal nucleating agent is suppressed, and the surface Roughness The larger the spherulite size, the more resistant it is to blocking, and the finer the spherulite size, which suppresses voids and achieves both high-temperature BDV and blocking resistance. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. [Propylene homopolymer (X)] The propylene homopolymer (X), which is one of the components contained in the propylene polymer composition forming the base layer of the multilayer polypropylene film for capacitors according to the present invention, is a homopolymer of propylene and preferably satisfies the following requirements (1) to (5):

[0010] <Requirement (1)> The MFR (ASTM D1238, 230°C, under a load of 2.16 kg) is in the range of 1 to 10 g / 10 min, preferably 2 to 6 g / 10 min, and more preferably 2.5 to 5 g / 10 min. If the MFR is less than 1.0 g / 10 min, it is difficult to form the raw film in an extruder, and the chuck may come off during film stretching, making it impossible to obtain the desired multilayer polypropylene film for capacitors. If the MFR exceeds 10.0 g / 10 min, the film may break frequently during stretching, significantly reducing the productivity of the stretched multilayer film. The MFR can be adjusted by adjusting the amount of hydrogen added during polymerization of the propylene homopolymer. Adjust by The MFR can be determined by the method described in the Examples below.

[0011] <Requirement (2)> 13 The mesopentad fraction (mmmm) determined by C-NMR is in the range of 0.930 to 0.999, preferably 0.940 to 0.998, and more preferably 0.950 to 0.997.

[0012] Propylene homopolymer in which mmmm is in the above range of By using this, the resulting multilayer polypropylene film for capacitors has excellent high-temperature voltage resistance. Here, the mesopentad fraction indicates the proportion of pentad isotactic structures in the molecular chain, and is the fraction of propylene structural units at the center of a chain in which five consecutive propylene monomer units have a mesostructure. The mesopentad fraction can be determined by the method described in the Examples below.

[0013] <Requirement (3)> The ash content is 50 ppm by mass or less, preferably 20 ppm by mass or less, and more preferably 10 ppm by mass or less.

[0014] If the ash content exceeds 50 ppm by mass, not only will the voltage resistance of the resulting multilayer polypropylene film for capacitors decrease, but the long-term capacitor characteristics will also decrease. The ash content was determined by placing the pellets in a crucible, burning them completely, and then incinerating the crucible in an electric furnace at 800°C for 2 hours, and measuring the ash remaining in the crucible to determine the ash content (ppm).

[0015] Ash is a component derived from the olefin polymerization catalyst contained in the propylene homopolymer. Propylene homopolymers with low ash content can be produced by using a highly active catalyst or by decomposing and / or removing the catalyst in the polymerized propylene homopolymer.

[0016] <Requirement (4)> The chlorine content is 2 ppm by mass or less, preferably 1.5 ppm by mass or less, and more preferably 1.2 ppm by mass or less.

[0017] If the chlorine content exceeds 2 ppm by mass, not only does the voltage resistance of the resulting multilayer polypropylene film for capacitors decrease, but the long-term capacitor characteristics also decrease. It is believed that the voltage resistance decreases because the electric field near the chlorine ions inside the film increases locally during use of the capacitor, making it more likely for dielectric breakdown to occur. Chlorine is caused by the catalyst used in homopolymerizing propylene, and can be controlled within the above range by controlling the type and amount of catalyst used and post-treating the propylene homopolymer.

[0018] The chlorine content was determined by combusting 0.8 g of propylene homopolymer at 400 to 900°C under an argon / oxygen stream using a Mitsubishi Chemical Corporation combustion apparatus, collecting the combustion gas with ultrapure water, concentrating the resulting sample solution, and measuring the chlorine content using a Nippon Dionex Corporation DIONEX-DX300 ion chromatograph and an AS4A-SC anion column (Dionex Corporation). Chlorine is a component derived from the olefin polymerization catalyst contained in the propylene homopolymer. Propylene homopolymers with a low chlorine content can be obtained by using a highly active catalyst or by removing the chlorine from the polymerized propylene homopolymer by washing with an appropriate solvent.

[0019] <Requirement (5)> The ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is in the range of 4.5 to 12.0, preferably 4.5 to 11.0, more preferably 4.5 to 10.5.

[0020] When the Mw / Mn is 4.5 or more, the stretchability is excellent when forming a stretched film, and a uniform film is easily obtained. On the other hand, when the Mw / Mn is 12.0 or less, the amount of low molecular weight components contained in the propylene homopolymer is small, and the film is easily formed into a uniform film. Ta This is preferable in terms of formability, since it suppresses adhesion and other problems. That is, when the Mw / Mn is within the above range, it is preferable from the viewpoints of formability and stretchability of the propylene homopolymer and uniformity of the thickness of the resulting capacitor film. The Mw / Mn can be determined by the method described in the examples below.

[0021] The propylene homopolymer (X) satisfying the above requirements (1) to (5) can be obtained, for example, by polymerizing propylene in the presence of an olefin polymerization catalyst described below.

[0022] As will be described later, the propylene homopolymer (X) according to the present invention includes a propylene homopolymer (X1) and a propylene homopolymer (X2). <Olefin polymerization catalyst> The olefin polymerization catalyst used to produce the propylene homopolymer (X) according to the present invention is not particularly limited as long as it can produce the propylene homopolymer. For example, the catalyst may be a catalyst containing: (i) a solid titanium catalyst component containing magnesium, titanium, a halogen, and an electron donor and satisfying the following requirements (k1) to (k4): (ii) an organosilicon compound component represented by the following formula (II); (iii) a catalyst [A] containing an organometallic compound component containing an element belonging to Group 1, 2 or 13 of the periodic table, or Examples of the catalyst include a prepolymerized catalyst (p) obtained by prepolymerizing propylene on the catalyst (A), and a catalyst (B) containing the organosilicon compound component (ii) and the organometallic compound component (iii).

[0023] (k1) The titanium content is 2.5 mass% or less. (k2) The content of the electron donor is 8 to 30 mass %. (k3) The electron donor / titanium (mass ratio) is 7 or more.

[0024] (k4) Titanium is not substantially desorbed by washing with hexane at room temperature. R 1 Si(OR 2 )2(NR 3 R 4 ) (II) In formula (II), R 1 represents a secondary or tertiary hydrocarbon group having 1 to 20 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 3 represents a hydrocarbon group having 1 to 12 carbon atoms or a hydrogen atom, R 4 represents a hydrocarbon group having 1 to 12 carbon atoms.

[0025] Each component constituting the olefin polymerization catalyst will now be described. <Solid titanium catalyst component (i)> The solid titanium catalyst component (i) is (a) solid titanium containing magnesium, titanium, a halogen, and an electron donor, from which titanium does not desorb when washed with hexane at room temperature; (b) aromatic hydrocarbons, (c) liquid titanium, and (d) electron donor The compound can be prepared by a method comprising the step of contacting

[0026] (a) Solid titanium The solid titanium (a) can be produced by a known method for preparing a solid titanium catalyst component (see, for example, JP-A Nos. 4-096911, 58-83006, and 8-143580) by contacting a magnesium compound, a titanium compound, an electron donor (internal donor), and the like, by various methods.

[0027] The magnesium compound is preferably used in a solid state. This solid magnesium compound may be a magnesium compound itself in a solid state, or may be an adduct with an electron donor. Examples of the magnesium compound include the magnesium compounds described in JP-A-2004-2742, specifically magnesium chloride, ethoxy magnesium chloride, butoxy magnesium, etc. Furthermore, examples of the electron donor include the magnesium compounds described in JP-A-2004-2742. cormorant Examples of compounds capable of solubilizing magnesium compounds include alcohols, aldehydes, amines, carboxylic acids, and mixtures thereof. The amounts of the magnesium compound and electron donor used vary depending on the type, contact conditions, etc., but the magnesium compound can be used in an amount of 0.1 to 20 mol / L, preferably 0.5 to 5 mol / L, relative to the liquid electron donor.

[0028] The titanium compound is preferably used in a liquid state. Examples of such titanium compounds include tetravalent titanium compounds represented by the following formula (III): Ti(OR 5 ) g X4-g (III) In formula (III), R 5 is a hydrocarbon group, X is a halogen atom, and 0≦g≦4.

[0029] As the titanium compound, titanium tetrachloride is particularly preferred. Two or more of the titanium compounds may be used in combination. Examples of the electron donor (internal donor) include a compound represented by the following formula (IV) (hereinafter also referred to as "compound (IV)").

[0030] [ka]

[0031] In formula (IV), R represents a linear or branched alkyl group having 1 to 10 carbon atoms, preferably 2 to 8, and more preferably 3 to 6 carbon atoms, R' represents a linear or branched alkyl group having 1 to 10 carbon atoms, and n represents an integer of 0 to 4. In the present invention, a compound in which n is 0 is preferred.

[0032] Examples of alkyl groups for R and R' include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

[0033] Specific examples of the compound (IV) include dimethyl phthalate, methyl ethyl phthalate, diethyl phthalate, n-propyl phthalate, diisopropyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-n-pentyl phthalate, dineopentyl phthalate, di-n-hexyl phthalate, di-n-heptyl phthalate, di(methylhexyl) phthalate, di(dimethylpentyl) phthalate, di(ethylpentyl) phthalate, di(2,2,3-trimethylbutyl) phthalate, di-n-octyl phthalate, and di-2-ethylhexyl phthalate. Among these, diisobutyl phthalate is particularly preferred.

[0034] In the present invention, an electron donor other than the compound (IV) may be used as the electron donor (internal donor). Examples of the other electron donor include a compound having two or more ether bonds connected via multiple atoms (hereinafter also referred to as a "polyether compound").

[0035] Examples of the polyether compound include compounds in which the atoms between the ether bonds are carbon, silicon, oxygen, nitrogen, sulfur, phosphorus, boron, or two or more atoms selected from these. Among these, compounds in which a relatively bulky substituent is bonded to the atom between the ether bonds and the atoms between two or more ether bonds contain multiple carbon atoms are preferred. For example, polyether compounds represented by the following formula (3) are preferred.

[0036] [ka]

[0037] In the formula (3), m is an integer of 1 to 10, preferably an integer of 3 to 10, and more preferably an integer of 3 to 5. 11 , R 12 , R 31 ~R 36 R are each independently a hydrogen atom or a substituent having at least one element selected from carbon, hydrogen, oxygen, fluorine, chlorine, bromine, iodine, nitrogen, sulfur, phosphorus, boron, and silicon. 11 and R 12 are each independently preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms. 31 ~R 36 are each independently preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms.

[0038] R 11 and R 12Specific examples of R include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, isopentyl, neopentyl, hexyl, heptyl, octyl, 2-ethylhexyl, decyl, cyclopentyl, and cyclohexyl groups. Among these, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl groups are preferred. 31 ~R 36 Specific examples of R include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group. Among these, a hydrogen atom and a methyl group are preferred. 11 , R 12 , R 31 ~R 36 (preferably R 11 , R 12 ) may join together to form a ring other than a benzene ring, and the main chain may contain atoms other than carbon.

[0039] Specific examples of the polyether compound include 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, and 2,2-bis(2-cyclohexylethyl) -1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-di-s-butyl-1,3-dimethoxypropane, 2,2-di-t -butyl-1,3-dimethoxypropane, 2,2-dineopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane, 2,3-dicyclohexyl-1,4-diethoxybutane, 2,3-diisopropyl-1,4-diethoxybutane, 2,4-diisopropyl-1,5-dimethoxypentane, 2,4-diisobutyl-1,5-dimethoxypentane, 2,4-diisoamyl-1,5-dimethoxypentane, 3-methoxymethyl tetrahydrofuran, 3-methoxymethyldioxane, 1,2-diisobutoxypropane, 1,2-diisobutoxyethane, 1,3-diisoamyloxyethane, 1,3-diisoamyloxypropane, 1,3-diisoneopentyloxyethane, 1,3-dineopentyloxypropane, 2,2-tetramethylene-1,3-dimethoxypropane, 2,2-pentamethylene-1,3-dimethoxypropane, 2,2-hexamethylene-1,3-dimethoxypropane, 1,2-bis(methoxymethyl)cyclohexane, 2-cyclohexyl-2-ethoxymethyl-1,3-diethoxypropane, 2-cyclohexyl-2-methoxymethyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxycyclohexane, 2-isopropyl-2-isoamyl-1,3-dimethoxycyclohexane, 2-cyclohexyl-2-methoxymethyl-1,3-dimethoxycyclohexane, 2-isopropyl-2-methoxymethyl-1,3-dimethoxycyclohexane, 2-isobutyl-2-methoxymethyl-1,3-dimethoxycyclohexane, 2-cyclohexyl-2-methoxymethyl-1,3-dimethoxycyclohexane Examples of the cyclohexane include 2-cyclohexyl-2-ethoxymethyl-1,3-diethoxycyclohexane, 2-cyclohexyl-2-ethoxymethyl-1,3-dimethoxycyclohexane, 2-isopropyl-2-ethoxymethyl-1,3-diethoxycyclohexane, 2-isopropyl-2-ethoxymethyl-1,3-dimethoxycyclohexane, 2-isobutyl-2-ethoxymethyl-1,3-diethoxycyclohexane, and 2-isobutyl-2-ethoxymethyl-1,3-dimethoxycyclohexane.

[0040] Among these, 1,3-diethers are preferred, and 2-isopropyl-2-isobutyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, and 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane are more preferred. These compounds may be used alone or in combination of two or more. <<Preparation of solid titanium (a)>> The solid titanium (a) can be prepared by contacting the magnesium compound, the titanium compound, and the electron donor. In this case, it is preferable to use a solid magnesium compound suspended in a hydrocarbon solvent. When contacting these components, a liquid titanium compound may be used once to produce solid material (1), or the resulting solid material (1) may be contacted with another liquid titanium compound to produce solid material (2). Furthermore, it is preferable to wash the solid material (1) or (2) with a hydrocarbon solvent as needed before preparing solid titanium (a).

[0041] The contact of the above components is usually carried out at temperatures of −70° C. to +200° C., preferably −50° C. to +150° C., and more preferably −30° C. to +130° C. The amounts of the components used in preparing solid titanium (a) vary depending on the preparation method and cannot be generally defined, but for example, the electron donor can be used in an amount of 0.01 to 10 mol, preferably 0.1 to 5 mol, and the titanium compound can be used in an amount of 0.01 to 1000 mol, preferably 0.1 to 200 mol, per 1 mol of the magnesium compound.

[0042] In the present invention, the solid (1) or (2) thus obtained can be used as solid titanium (i) as it is, but it is preferable to wash this solid with a hydrocarbon solvent at 0 to 150°C.

[0043] Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, and cetane, non-halogenated aromatic hydrocarbon solvents such as toluene, xylene, and benzene, and halogen-containing aromatic hydrocarbon solvents. Of these, aliphatic hydrocarbon solvents and halogen-free aromatic hydrocarbon solvents are preferably used.

[0044] When washing solids, the amount of hydrocarbon solvent is usually 10 to 500 ml per 1 g of solids. 、 It is preferably used in an amount of 20 to 100 ml. The solid titanium (a) thus obtained contains magnesium, titanium, a halogen, and an electron donor. In this solid titanium (a), the electron donor / titanium (mass ratio) is preferably 6 or less.

[0045] The solid titanium (a) thus obtained does not lose its titanium when washed with hexane at room temperature. (b) Aromatic hydrocarbons Examples of the aromatic hydrocarbon (b) used in contact with the solid titanium (a) include benzene, toluene, xylene, ethylbenzene, and halogen-containing hydrocarbons thereof. Among these, xylene (particularly paraxylene) is preferred. By contacting the solid titanium (a) with such an aromatic hydrocarbon (b), it is possible to reduce the amount of so-called "excess titanium compounds" that produce low stereoregularity components as by-products. (c) Liquid titanium The liquid titanium (c) used for contact with the solid titanium (a) may be the same as the titanium compound used for preparing the solid titanium (a). Among them, titanium tetrahalides are preferred, and titanium tetrachloride is particularly preferred. (d) electron donor Examples of the electron donor (d) used in contact with the solid titanium (a) include the same electron donors (internal donors) as those exemplified above. Among them, it is preferable to use the same electron donor as that used in preparing the solid titanium (a).

[0046] <Method for preparing solid titanium catalyst component (i)> The contact of the solid titanium (a), aromatic hydrocarbon (b), liquid titanium (c) and electron donor (d) is carried out usually at a temperature of 110 to 160°C, preferably 115 to 150°C, for 1 minute to 10 hours, preferably 10 minutes to 5 hours.

[0047] In this contact, the aromatic hydrocarbon (b) is used in an amount of usually 1 to 10,000 ml, preferably 5 to 5,000 ml, per gram of solid titanium (a). 、 It is more preferably used in an amount of 10 to 1000 ml. Liquid titanium (c) is usually used in an amount of 0.1 to 50 ml, preferably 0.2 to 20 ml, and particularly preferably 0.3 to 10 ml, per 100 ml of aromatic hydrocarbon (b). Electron donor (d) is usually used in an amount of 0.01 to 10 ml, preferably 0.02 to 5 ml, and particularly preferably 0.03 to 3 ml, per 100 ml of aromatic hydrocarbon (b).

[0048] The order of contacting the solid titanium (a), aromatic hydrocarbon (b), liquid titanium (c) and electron donor (d) is not particularly limited, and they can be contacted simultaneously or sequentially. The solid titanium (a), aromatic hydrocarbon (b), liquid titanium (c), and electron donor (d) are preferably contacted under stirring in an inert gas atmosphere. For example, it is desirable to contact the solid titanium (a), aromatic hydrocarbon (b), liquid titanium (c), and electron donor (d) by stirring a slurry of the solid titanium (a), aromatic hydrocarbon (b), liquid titanium (c), and electron donor (d) in a glass flask equipped with a stirrer that has been thoroughly substituted with nitrogen at the above-mentioned temperature and at a rotation speed of 100 to 1000 rpm, preferably 200 to 800 rpm, for the above-mentioned period of time.

[0049] After contact, the solid titanium (a) and the aromatic hydrocarbon (b) can be separated by filtration. By contacting the solid titanium (a) with the aromatic hydrocarbon (b), a solid titanium catalyst component (i) having a titanium content reduced by 25% by mass or more, preferably 30 to 95% by mass, compared to the solid titanium (a) can be obtained. 、 More preferably, 40 to 90% less solid titanium catalyst component (i) is obtained.

[0050] The solid titanium catalyst component (i) obtained as described above contains magnesium, titanium, a halogen, and an electron donor, and satisfies the following requirements (k1) to (k4), and preferably further satisfies the following requirement (k5). (k1) The titanium content of the solid titanium catalyst component (i) is 2.5 mass % or less, preferably 2.2 to 0.1 mass %, more preferably 2.0 to 0.2 mass %, particularly preferably 1.8 to 0.3 mass %, and most preferably 1.5 to 0.4 mass %. The content of the (k2) electron donor is 8 to 30% by mass, preferably 9 to 25% by mass, and more preferably 10 to 20% by mass. (k3) The electron donor / titanium (mass ratio) is 7 or more, preferably 7.5 to 35, more preferably 8 to 30, and particularly preferably 8.5 to 25. (k4) The solid titanium catalyst component (i) is not substantially desorbed of titanium by washing with hexane at room temperature. Washing the solid titanium catalyst component (i) with hexane means washing for 5 minutes with hexane in an amount of typically 10 to 500 ml, preferably 20 to 100 ml, per gram of the solid titanium catalyst component (i). Room temperature is 15 to 25°C. The phrase "not substantially desorbing titanium" means that the titanium concentration in the hexane washings is 0.1 g / L or less. (k5) The solid titanium catalyst component (i) has an average particle size of 5 to 70 μm, preferably 7 to 65 μm, more preferably 8 to 60 μm, and particularly preferably 10 to 55 μm.

[0051] The amounts of magnesium, halogen, titanium, and electron donor are each expressed in mass% per unit mass of the solid titanium catalyst component (i), and the amounts of magnesium, halogen, and titanium are determined by inductively coupled plasma emission spectrometry (ICP), and the amount of electron donor is determined by gas chromatography. The average particle size of the catalyst is measured by centrifugal sedimentation using decalin as a solvent.

[0052] When the above-mentioned solid titanium catalyst component (i) is used as a catalyst component for olefin polymerization, it is possible to polymerize propylene with high activity, and also possible to stably produce a propylene homopolymer with high stereoregularity while reducing the amount of propylene homopolymer with low stereoregularity produced.

[0053] <Organosilicon compound component (ii)> The organosilicon compound component (ii) constituting the olefin polymerization catalyst of the present invention is represented by the following formula (II):

[0054] R 1 Si(OR 2 )2(NR 3 R 4 ) (II) In formula (II), R 1 represents a secondary or tertiary hydrocarbon group having 1 to 20 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 3 represents a hydrocarbon group having 1 to 12 carbon atoms or a hydrogen atom, and R 4 represents a hydrocarbon group having 1 to 12 carbon atoms.

[0055] R 1 Examples of the alkyl group include alicyclic hydrocarbon groups such as cyclobutyl, cyclopentyl, cyclopentenyl, cyclopentadienyl, cyclohexyl, and cyclohexyl groups. S Examples of the aryl group include a substituted aryl group and these groups having a substituent.

[0056] Also, R 1 Examples of hydrocarbon groups in which the carbon adjacent to Si is a secondary carbon include an i-propyl group, an s-butyl group, an s-amyl group, and an α-methylbenzyl group. Examples of hydrocarbon groups in which the carbon adjacent to Si is a tertiary carbon include a tert-butyl group, a tert-amyl group, an α,α'-dimethylbenzyl group, and an α-methylbenzyl group. Da Examples include a mantyl group.

[0057] Of these, cyclopentyl and cyclobutyl are preferred, with cyclopentyl being particularly preferred. R 2 Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tertiary alkyl group, and the like. t Examples of the alkyl group include butyl, sec-butyl, n-pentyl, iso-pentyl, cyclopentyl, n-hexyl, and cyclohexyl groups. Among these, methyl and ethyl groups are particularly preferred.

[0058] R 3 Examples of the alkyl group include hydrogen, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tertiary alkyl group, and the like. tExamples of the alkyl group include butyl, sec-butyl, n-pentyl, iso-pentyl, cyclopentyl, n-hexyl, cyclohexyl, and octyl groups. Among these, the ethyl group is particularly preferred.

[0059] R 4 Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tertiary alkyl group, and the like. t Examples of the alkyl group include butyl, sec-butyl, n-pentyl, iso-pentyl, cyclopentyl, n-hexyl, cyclohexyl, and octyl groups. Among these, the ethyl group is particularly preferred.

[0060] Specific examples of the organosilicon compound represented by formula (II) include cyclopentyldiethylaminodimethoxysilane, cyclopentenyldiethylaminodimethoxysilane, cyclopentadienyldiethylaminodimethoxysilane, cyclohexyldiethylaminodimethoxysilane, isopropyldiethylaminodimethoxysilane, and tert-butyldiethylaminodimethoxysilane.

[0061] Among the organosilicon compounds represented by the formula (II), cyclopentyldiethylaminodimethoxysilane is preferred from the viewpoints of high stereoregularity, particularly a long meso chain length and increasing the proportion of high-temperature elution in cross-fractional chromatography (CFC).

[0062] The organosilicon compound component (ii) may be used alone or in combination of two or more. By using the solid titanium catalyst component (i) in combination with the organosilicon compound component (ii), it is possible to obtain a propylene-based polymer having a high stereoregularity at a level never before seen.

[0063] ≪Organometallic compound component (iii)≫ The organometallic compound component (iii) constituting the olefin polymerization catalyst of the present invention is an organometallic compound containing a metal belonging to Group 1, Group 2 or Group 13 of the periodic table, and examples thereof include organoaluminum compounds, alkyl complex compounds of Group 1 metals with aluminum, organometallic compounds of Group 2 metals, etc. Two or more types of organometallic compound component (iii) may be used in combination. <Organoaluminum compounds> The organoaluminum compound is represented by, for example, the following formula:

[0064] R a n AlX 3-n In the formula, R a is a hydrocarbon group having 1 to 12 carbon atoms, X is a halogen or hydrogen, and n is 1 to 3.

[0065] R a is a hydrocarbon group having 1 to 12 carbon atoms, such as an alkyl group, a cycloalkyl group, or an aryl group, and specific examples thereof include methyl, ethyl, n-propyl, isopropyl, isobutyl, pentyl, hexyl, octyl, cyclopentyl, cyclohexyl, phenyl, and tolyl.

[0066] Further, examples of the organoaluminum compound include compounds represented by the following formula: R a n AlY 3-n In the formula, R a is the same as above, and Y is -OR b Group, -OSiR c 3 groups, -OAlR d 2 units, -NR e 2 units, -SiR f 3 groups or -N(R g )AlR h 2 groups, n is 1 to 2, and R b , R c , R d and R his a methyl group, an ethyl group, an isopropyl group, an isobutyl group, a cyclohexyl group, a phenyl group, etc., and R e is hydrogen, methyl group, ethyl group, isopropyl group, phenyl group, trimethylsilyl group, etc., and R f and R g is a methyl group, an ethyl group, etc.

[0067] Specific examples of such organoaluminum compounds include the following compounds: (1)R a n Al(OR b ) 3-n Compounds represented by the formula (I) above, for example, dimethylaluminum methoxide, diethylaluminum ethoxide, diisobutylaluminum methoxide, etc. (2)R a n Al(OSiR c ) 3-n Compounds represented by the formula (I), such as Et2Al(OSiMe3), (iso-Bu)2Al(OSiMe3), and (iso-Bu)2Al(OSiEt3). (3)R a n Al(OAlR d 2) 3-n Compounds represented by the formula: Et2AlOAlEt2, (iso-Bu)2AlOAl(iso-Bu)2, etc.

[0068] Among the above-mentioned organoaluminum compounds, R a An organoaluminum compound represented by 3Al is preferably used. <<Method for producing an olefin polymerization catalyst>> The olefin polymerization catalyst can be produced by a method comprising the step of contacting the solid titanium catalyst component (i), the organosilicon compound component (ii), and the organometallic compound component (iii).

[0069] In the present invention, when forming an olefin polymerization catalyst from these components (i), (ii) and (iii), other components may also be used as necessary. In the present invention, a prepolymerization catalyst (p) may be formed from the above-mentioned components. The prepolymerization catalyst (p) is formed by prepolymerizing an olefin such as propylene in the presence of the above-mentioned components (i), (ii), and (iii) and other components used as needed. Such a prepolymerization catalyst (p) usually forms an olefin polymerization catalyst together with an organosilicon compound (ii) and an organometallic compound (iii), but in some cases the prepolymerization catalyst (p) alone can be used as an olefin polymerization catalyst.

[0070] <Method for producing propylene homopolymer (X)> In the method for producing the propylene homopolymer (X), propylene is polymerized in the presence of the above-mentioned olefin polymerization catalyst.

[0071] In the present invention, the polymerization can be carried out by either a liquid phase polymerization method such as solution polymerization or suspension polymerization, or a gas phase polymerization method. When the polymerization is carried out in the form of a slurry polymerization reaction, an inert organic solvent can be used as the reaction solvent, or propylene that is liquid at the reaction temperature can be used.

[0072] Specific examples of the inert organic solvent include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons; aromatic hydrocarbons; halogenated hydrocarbons; and contact products thereof. Of these, it is particularly preferred to use aliphatic hydrocarbons.

[0073] In the polymerization, the solid titanium catalyst component (i) or the prepolymerized catalyst (p) is usually about 1 x 10 titanium atoms per liter of polymerization volume. -5 ~1 mmol, preferably about 1 x 10 -4 It is used in an amount of .about.0.1 millimolar.

[0074] The organosilicon compound (ii) is usually used in an amount of about 0.001 to 10 moles, preferably 0.01 to 5 moles, per mole of metal atom in the organometallic compound (iii). The organometallic compound (iii) is used in an amount such that the metal atom in the compound (iii) is usually about 1 to 2000 mol, preferably about 2 to 500 mol, per mol of titanium atom in the polymerization system.

[0075] If a prepolymerization catalyst (p) is used in this polymerization, it may be unnecessary to add the organosilicon compound (ii) and / or the organometallic compound (iii). When an olefin polymerization catalyst is formed from the prepolymerization catalyst (p), component (ii) and component (iii), these components (ii) and (iii) can be used in the amounts described above.

[0076] If hydrogen is used during polymerization, the molecular weight of the resulting propylene homopolymer can be adjusted, and a polymer with a high MFR can be obtained. In the present invention, the polymerization is usually carried out at a temperature of about 20 to 150°C, preferably about 50 to 100°C, and at a pressure of normal pressure to 100 kg / cm. 2 , preferably about 2 to 50 kg / cm 2 This is done under pressure.

[0077] In the present invention, the polymerization can be carried out by any of batch, semi-continuous and continuous methods. Furthermore, the polymerization can be carried out in two or more stages by changing the reaction conditions. <Polymer-based α-crystal nucleating agent (C)> The polymer-based α-crystal nucleating agent (C) contained in the propylene polymer composition forming the base layer of the multilayer polypropylene film for capacitors according to the present invention is a nucleating agent consisting of a polymer, preferably a polymer produced by prepolymerization of a catalyst used to obtain a propylene homopolymer, more preferably a polymer having a glass transition temperature and / or melting point (Tm) of 200°C or higher, and even more preferably 280°C or higher.

[0078] The polymeric α-crystal nucleating agent (C) according to the present invention is produced by prepolymerization and is finely dispersed to the sub-nano order, so it exerts its nucleating effect in a very small amount. When the glass transition temperature and / or melting point (Tm) is 200°C or higher, the spherulite size of the propylene homopolymer becomes small and the crystallinity becomes high, resulting in an excellent nucleating effect. Furthermore, when the temperature is 280°C or higher, these effects are even more pronounced.

[0079] <Polymer produced by prepolymerization> The polymer produced by prepolymerization according to the present invention is an olefin polymer formed by prepolymerization of a catalyst for polymerizing propylene. The olefin used in preparing the prepolymerization catalyst component is a compound represented by the following formula (i) or (ii), specifically, an olefin having a branched structure such as 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, allylnaphthalene, allylnorbornane, vinylnaphthalenes, allyltoluenes, allylbenzene, vinylcyclohexane, vinylcyclopentane, vinylcycloheptane, or allyltrialkylsilanes. The glass transition temperature of the resulting olefin polymer, / Or the crystalline melting point is 200°C or higher.

[0080] [ka]

[0081] <Propylene polymer composition> The propylene polymer composition constituting the base layer of the multilayer polypropylene film for capacitors of the present invention is a composition containing the above propylene homopolymer (X) and the above polymeric α-crystal nucleating agent (C) in an amount of 0.0001 to 0.05 mass %, preferably 0.0001 to 0.03 mass %, more preferably 0.0001 to 0.01 mass % (however, the propylene homopolymer (X) and the polymer system α crystal formationThe total amount of the nucleating agent (C) is taken as 100% by mass.

[0082] The propylene polymer composition of the present invention can be obtained by mixing the propylene homopolymer (X) and the polymeric α-crystal nucleating agent (C) in the above ranges. Preferably, in the method for producing an olefin polymerization catalyst for producing the propylene homopolymer (X), an olefin polymer (polymeric α-crystal nucleating agent) produced by prepolymerizing an olefin represented by the above formula (i) or (ii) as a prepolymerization catalyst is used, since the olefin polymer is finely dispersed in the propylene homopolymer (X1).

[0083] As described above, the propylene polymer composition according to the present invention may use, as a prepolymerization catalyst, a propylene polymer composition in which an olefin polymer (polymer-based α-crystal nucleating agent) produced by prepolymerizing an olefin represented by the above formula (i) or (ii) is finely dispersed in a propylene homopolymer (X1). However, in the method for producing the propylene homopolymer (X), a propylene homopolymer (X2) obtained by using, as a prepolymerization catalyst (p), an olefin other than the compound represented by the above formula (i) or (ii), for example, an olefin such as propylene, may be blended with the propylene homopolymer (X1) containing the olefin polymer (polymer-based α-crystal nucleating agent, and the amount of the polymer-based α-crystal nucleating agent contained therein may be appropriately adjusted.

[0084] The propylene polymer composition of the present invention may contain additives such as weathering stabilizers, heat stabilizers, antistatic agents, antislip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, plasticizers, antioxidants, hydrochloric acid absorbers, antioxidants, etc., within the scope of the invention. Preferably, the propylene polymer composition of the present invention is blended by melt extrusion at a temperature of 180 to 280°C while adding various additives such as various antioxidants (Irganox 1010, BHT (dibutylhydroxytoluene), Irgafos 168, etc.) and calcium stearate.

[0085] [Propylene polymer (Y)] The propylene-based polymer forming the surface layer of the multilayer polypropylene film for capacitors according to the present invention may be the propylene homopolymer (X) forming the base layer, or a random copolymer containing typically 8 mol % or less, preferably 6 mol % or less, of ethylene and an α-olefin having 4 or more carbon atoms, such as an olefin having 2 to 8 carbon atoms, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, or 3-methyl-1-butene.

[0086] The propylene polymer (Y) according to the present invention preferably satisfies the above requirements (1) to (5) that the propylene homopolymer (X) forming the base layer satisfies. However, when the propylene homopolymer (X) is used in the front or back layer of the multilayer polypropylene film for a capacitor of the present invention, it is preferable that the propylene homopolymer (X) is a polymer that does not contain the polymer-based α-crystal nucleating agent (C), for example, the propylene homopolymer (X2) or the polymer-based α-crystal nucleating agent (C) of Even when it is contained, a propylene homopolymer having a polymer-based α-crystal nucleating agent (C) content of less than 0.00001% by mass is used.

[0087] When the propylene polymer (Y) according to the present invention is used in the front and back layers of the multilayer polypropylene film for capacitors, the propylene polymer (Y) used in the front layer and the propylene polymer (Y) used in the back layer may be the same, or may be a propylene polymer (Y) having different properties within the range of the above-mentioned properties.

[0088] The propylene polymer (Y) according to the present invention can be produced by the above-mentioned method for producing the propylene homopolymer (X), but can also be produced by various known production methods. The propylene polymer (Y) forming the front and back layers of the multilayer polypropylene film for capacitors according to the present invention may contain additives such as weathering stabilizers, heat stabilizers, antistatic agents, antislip agents, antiblocking agents, antifogging agents, lubricants, pigments, dyes, plasticizers, antioxidants, hydrochloric acid absorbers, and antioxidants, provided that the object of the invention is not impaired. Preferably, the polymers are blended by melt extrusion at a temperature in the range of 180 to 280°C while adding various additives such as various antioxidants (e.g., Irganox 1010, BHT (dibutylhydroxytoluene), Irgafos 168), calcium stearate, and the like.

[0089] [Multi-layer polypropylene film for capacitors] The multilayer polypropylene film for a capacitor of the present invention has a surface layer or a back layer made of a propylene polymer (Y) on at least one side of a base layer made of a propylene polymer composition containing the above-mentioned propylene homopolymer (X) and 0.0001 to 0.05 mass % of a polymer-based α-crystal nucleating agent (C), and and, Surface or lining and All of these are stretched multilayer films.

[0090] The multilayer polypropylene film for capacitors of the present invention preferably has a surface layer on one side of a base layer and a backing layer on the other side of the base layer. The total thickness of the multilayer film is usually in the range of 1 to 20 μm, preferably in the range of 1.5 to 10 μm, and more preferably in the range of 2 to 5 μm, and the thickness ratio of the base layer to the surface layer or back layer of the multilayer film is usually in the range of 9:1 to 6:1, preferably in the range of 9:1 to 7:3, and more preferably in the range of 9:1 to 8:2.

[0091] The multilayer polypropylene film for a capacitor of the present invention preferably has a surface roughness Ra of 0.2 on the front or back layer. μm or more, more preferably 0.3 μm Surface roughness Ra is 0.2 or more. μm If the thickness is more than this, the contact area between the films becomes small, which is preferable in terms of blocking resistance.

[0092] The multilayer polypropylene film for capacitors of the present invention preferably has a breakdown voltage (V / μm) at 100° C. of 540 V / μm or more. The multilayer polypropylene film for capacitors of the present invention does not cause bleeding out of the nucleating agent onto the surface.

[0093] <Method of manufacturing multilayer polypropylene film for capacitors> The multilayer polypropylene film for capacitors of the present invention can be produced by various known methods, such as stretching a multilayer sheet obtained by coextrusion molding the propylene polymer composition as a base layer and the propylene-based polymer (Y) as a top or bottom layer. The multilayer sheet can be stretched by uniaxial stretching or biaxial stretching, with biaxial stretching being preferred. Examples of biaxial stretching include sequential biaxial stretching, in which the film is uniaxially stretched in the machine direction and then stretched in a direction perpendicular to the machine direction, and simultaneous biaxial stretching, in which the film is simultaneously stretched in both the machine direction and a direction perpendicular to the machine direction. Specifically, sequential biaxial stretching methods such as the tenter method and the tubular film method, and simultaneous biaxial stretching methods can be used.

[0094] The tenter method can be carried out, for example, by the following method. A molten multilayer sheet melt-extruded from a T-die is solidified by a cooling roll typically at 40 to 120°C, preferably 50 to 100°C, and more preferably 60 to 90°C. The multilayer sheet is then preheated, if necessary, and introduced into a stretching zone. The sheet is then stretched 3 to 9 times in the machine direction (longitudinal direction) at a temperature of 120 to 160°C and 5 to 11 times in the transverse direction (transverse direction) at a temperature of 150 to 190°C. The total areal stretching ratio is 30 to 80 times, preferably 35 to 75 times, more preferably 35 to 70 times, and even more preferably 35 to 50 times. If the areal stretching ratio is less than 30 times, it may be difficult to achieve the desired strength and thickness accuracy. If the areal stretching ratio exceeds 80 times, breakage may occur easily during stretching, resulting in poor productivity.

[0095] If necessary, the biaxially stretched multilayer polypropylene film for a capacitor can be heat-set at 160 to 190° C. This allows for the production of a multilayer polypropylene film for a capacitor with improved thermal dimensional stability, abrasion resistance, and the like. [Example]

[0096] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring various physical properties described in the examples are as follows.

[0097] [Physical Properties of Propylene Homopolymers and Propylene-Based Polymers] <Melt flow rate (MFR)> The test was conducted in accordance with ASTM D1238E, with a measurement temperature of 230°C and a load of 2.16 kg.

[0098] <Mesopentad fraction (mmmm (noise removal method))> 1. Measurement conditions Equipment: Bruker BioSpin AVANCE III cryo-500 nuclear magnetic resonance spectrometer Measurement nuclei: 13 C(125MHz) Measurement mode: Single pulse proton broadband decoupling Pulse width: 45° (5.00 microseconds) Repeat time: 5.5 seconds Number of times accumulated: 256 Measurement solvent: o-dichlorobenzene / heavy benzene (80 / 20% by volume) mixed solvent Sample concentration: 50 mg / 0.6 mL Measurement temperature: 120℃ Chemical shift reference: 21.59 ppm (mesopentad methyl peak shifts) 2. Calculation method The mesopentad fraction (mmmm, %), which is one of the indicators of the stereoregularity of a polymer and which was used to examine its microtacticity, was calculated from the peak intensity ratio of the 13C-NMR spectrum obtained under the measurement conditions described in 1 above.

[0099] Here, in the case of polypropylene with an unprecedentedly high level of stereoregularity, such as the object of measurement in the present invention, if the rmmr, mmrm, rmrr, rmrm, and mrrr regions are included in the integral value, the influence of "noise" on the integral value will be large, and S2 in general calculation methods will be overestimated, that is, mmmm (%) will be underestimated. Prog. Polym. Sci. 26 (2001), 443-533 also reports that in the case of polypropylene with a stereoregularity of 95% or more, if certain requirements are met, the integral values of the rmmr, mmrm, rmrr, rmrm, and mrrr regions will theoretically be 0.1% or less in total, suggesting that this will lead to an overestimation of S2 in general calculation methods.

[0100] Therefore, in the present invention, calculations were made according to the following (Equation 1). The rmmr, mmrm, rmrr, rmrm, and mrrr regions were excluded from the calculations in accordance with the suggestion in Prog. Polym. Sci. 26 (2001), 443-533. Hereinafter, this calculation method in this specification will be referred to as the "noise removal method."

[0101] mmmm (noise removal method) (%) = S1 / S2 * 100 (Equation 1) S1 = (peak containing mmmm, mmmr) - (n-propyl end) - (n-butyl end) - mrrm * 2 S2=S1+mmmr+mmrr+mrrm+rrrr =S1+5*mrrm+rrrr When calculating using the above formula 1, the following assignments were made, for example: Note that the mmmm peak overlaps with the mmmr peak and the (n-propyl terminal) and (n-butyl terminal) peaks.

[0102] Peaks containing mmmm and mmmr: Peak area from 21.2 to 22.0 ppm mmmr=mrrm*2 mmrr=mrrm*2 mrrm: Peak area of 19.5 to 19.7 ppm rrrr: Peak area between 20.0 and 20.2 ppm n-Propyl terminal: (A1+A3) / 2 A1: Peak area of 14.2 ppm A3: Peak area of 39.4 ppm n-Butyl terminal: Peak area at 36.7 ppm <Ash content> The ash content was determined by placing the pellets in a crucible, completely burning them, and then incinerating the crucible in an electric furnace at 800°C for 2 hours, and measuring the ash remaining in the crucible to determine the ash content (ppm).

[0103] <Chlorine content> 0.8 g of sample was combusted at 400 to 900°C under an argon / oxygen flow using a Mitsubishi Chemical Corporation combustion apparatus. The combustion gas was then captured with ultrapure water, and the concentrated sample solution was analyzed using a DIONEX-DX300 ion chromatograph (trade name, Nippon Dionec). vinegar Co., Ltd.) and anion column AS4A-SC (trade name, Dionec vinegar The chlorine content was determined by measuring using a chlorine analyzer (manufactured by the company).

[0104] <Molecular weight distribution> The Mw / Mn value, which is an index of molecular weight distribution, was obtained by analyzing a chromatogram measured under the following conditions by a known method.

[0105] Apparatus: Waters gel permeation chromatograph Alliance GPC2000 Column: Tosoh TSKgel GMH6-HT x 2 + TSKgel GMH6-HTL x 2 Mobile phase: o-dichlorobenzene (containing 0.025% BHT) Flow rate: 1.0ml / min Temperature: 140℃ Column calibration: Tosoh monodisperse polystyrene Sample concentration: 0.15% (w / v) Injection volume: 0.4 ml <<Production of a propylene polymer composition containing a propylene homopolymer and a polymeric α-crystal nucleating agent>> The propylene polymer compositions containing a polymeric α-crystal nucleating agent used in the examples were produced in the following production examples.

[0106] [Manufacturing Example 1] <Preparation of solid titanium catalyst component> 4.5m 3 A reactor was charged with 240 kg of anhydrous magnesium chloride, 1,100 liters of decane, and 990 kg of 2-ethylhexyl alcohol, and heated to 130°C to form a homogeneous solution. 54 kg of phthalic anhydride was then added to the solution, and the mixture was stirred at 130°C to dissolve the phthalic anhydride. The homogeneous solution thus obtained was cooled to room temperature, and then 6.7 ml of titanium tetrachloride kept at -25°C was added. 3 The entire amount of this homogeneous solution was added dropwise to the mixture while stirring. After the addition, the temperature was about -20°C. Next, the temperature of this mixture was raised to 110°C over 4 hours, and when it reached 110°C, 13 kg of diisobutyl phthalate (DIBP) was added, and the mixture was maintained at the same temperature with stirring for the next 2 hours. After the 2-hour reaction was completed, the solid portion was collected by hot filtration, and 7.3 ml of this solid portion was added. 3 The resulting mixture was resuspended in titanium tetrachloride and then heated at 110°C for 2 hours. After the reaction was complete, the solid was collected by hot filtration again and thoroughly washed with decane and hexane at 110°C until no free titanium compounds were detected in the solution. This procedure yielded a solid titanium catalyst component (A).

[0107] The composition of the obtained solid titanium catalyst component (A) was as follows: titanium: 2.2% by weight, chlorine: 61% by weight, magnesium: 19% by weight, and DIBP: 12.7% by weight. <Preparation of Prepolymerization Catalyst> An 80-liter reactor equipped with a stirrer was charged with 40 liters of purified hexane, 3.0 moles of triethylaluminum, 3.0 moles of trimethylmethoxysilane, and 0.3 moles of the above-mentioned solid titanium catalyst component (A) in terms of titanium atoms under a nitrogen atmosphere. Then, 1.5 kg of 3-methyl-1-butene (3MB-1) was fed into the reactor at 20°C, and prepolymerization was carried out for 2 hours. After the reaction was completed, the reactor was purged with nitrogen, and a washing procedure consisting of removing the supernatant and adding purified hexane was carried out three times to obtain prepolymerization catalyst (B) containing the polymer α-crystal nucleating agent 3MB-1. This prepolymerization catalyst (B) was resuspended in purified hexane and stored.

[0108] <Propylene polymerization> A 1000-liter reactor equipped with a stirrer was charged with 450 liters of purified n-hexane, and then charged with 500 mmol of triethylaluminum, 500 mmol of dicyclopentyldimethoxysilane, and 10 mmol of prepolymerization catalyst (B) in terms of titanium atom Ti in a propylene atmosphere at 60°C. 250 liters of hydrogen was introduced, and the temperature was raised to 80°C. This was maintained for 4 hours to carry out propylene polymerization. The pressure during polymerization was 6 kg / cm. 2 The temperature was kept at G. After the polymerization was completed, the pressure was released, and the slurry containing the produced solid was centrifuged and dried in a dryer to obtain 200 kg of a white powdery propylene polymer composition containing a polymeric α-crystal nucleating agent.

[0109] The melt flow rate of the obtained propylene polymer composition containing a polymeric α-crystal nucleating agent was 2 g / 10 min, the stereoregularity index [M5] of the boiling heptane insoluble component was 0.986, the content of 3MB-1 polymer as a polymeric α-crystal nucleating agent was 300 ppm, and the density was 0.919 g / cm 3 It was.

[0110] The melting point of the 3MB-1 polymer was 310°C. The propylene polymer composition containing a polymer-based α-crystal nucleating agent obtained in Production Example 1 contains propylene homopolymer (X1) which is a propylene homopolymer (X) and 300 ppm of 3MB-1 polymer which is a polymer-based α-crystal nucleating agent (C). In the examples, this composition is called propylene polymer composition (Z).

[0111] The propylene polymer composition (Z) contains, relative to 100 parts by mass of the composition, 0.2 parts by mass of 3,5-di-t-butyl-4-hydroxytoluene as an antioxidant, 0.65 parts by mass of tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane as an antioxidant, and 0.005 parts by mass of calcium stearate as a neutralizer. mass The components were blended and melt-kneaded at a resin temperature of 230°C using a single-screw extruder to form a composition. tree The fat was pelletized. The single-screw extruder used was GMZ50-32 (L / D=32) manufactured by GM Engineering Co., Ltd.

[0112] Table 1 shows the physical properties of the propylene homopolymer (X1-1), which is the propylene homopolymer (X1) contained in the obtained propylene polymer composition (Z). [Propylene polymers used in examples and comparative examples] <Production of propylene homopolymer> [Manufacturing Example 2] <Preparation of solid titanium (a-1)> A 2-liter high-speed stirring apparatus (manufactured by Tokushu Kika Kogyo) was thoroughly purged with nitrogen, and then charged with 700 ml of refined kerosene, 10 g of magnesium chloride, 24.2 g of ethanol, and 3 g of sorbitan distearate ("Emersol 320" manufactured by Kao Atlas Corporation). The system was heated with stirring and stirred at 120°C and 800 rpm for 30 minutes. With high-speed stirring, the mixture was transferred using a 5 mm inner diameter Teflon (registered trademark) tube to a 2-liter glass flask (equipped with a stirrer) containing 1 liter of refined kerosene pre-cooled to -10°C. The resulting solid was filtered and thoroughly washed with purified n-hexane to obtain a solid adduct in which 2.8 moles of ethanol were coordinated to 1 mole of magnesium chloride.

[0113] Next, the solid adduct (45 mmol in terms of magnesium atoms) was suspended in 20 ml of decane, and the entire amount was introduced into 195 ml of titanium tetrachloride kept at -20°C while stirring. The mixture was heated to 80°C over 5 hours, and 1.8 ml (6.2 mmol) of diisobutyl phthalate was added. The temperature was then raised to 110°C and stirred for 1.5 hours.

[0114] After 1.5 hours of reaction, the solid was collected by hot filtration and washed with decane at 100°C and hexane at room temperature until no titanium was detected in the filtrate. In this way, solid titanium (a-1) containing 3.8% by mass of titanium, 16% by mass of magnesium, 18.2% by mass of diisobutyl phthalate, and 1.1% by mass of ethanol residue was obtained.

[0115] <Preparation of solid titanium catalyst component (i-1)> A 200 ml glass reactor thoroughly purged with nitrogen was charged with 6.8 g of the obtained solid titanium (a-1), 113 ml of paraxylene, 11 ml of decane, 2.5 ml (23 mmol) of titanium tetrachloride, and 0.34 ml (1.2 mmol) of diisobutyl phthalate. The temperature inside the reactor was raised to 130°C, and the mixture was stirred at that temperature for 1 hour to effect a contact treatment. The solid was then collected by hot filtration. This solid was resuspended in 101 ml of paraxylene, and 1.7 ml (15 mmol) of titanium tetrachloride and 0.22 ml (0.8 mmol) of diisobutyl phthalate were added.

[0116] The mixture was then heated to 130°C and stirred for 1 hour while maintaining the temperature to allow the reaction to proceed. After the reaction was completed, solid-liquid separation was again carried out by hot filtration, and the resulting solid was washed with decane at 100°C and hexane at room temperature until the paraxylene content in the catalyst was 1% by mass or less. In this way, a solid titanium catalyst component (i-1) containing 1.3% by mass of titanium, 20% by mass of magnesium, and 13.8% by mass of diisobutyl phthalate was obtained.

[0117] <Preparation of prepolymerization catalyst (p-1)> A 200 ml glass reactor purged with nitrogen was charged with 50 ml of hexane, 2.5 mmol of triethylaluminum, 0.5 mmol of cyclopentyldiethylaminodimethoxysilane, and 0.25 mmol of the solid titanium catalyst component (i-1) obtained above in terms of titanium atom, and then propylene was fed at a rate of 1.47 L / hour for 1 hour while maintaining the temperature in the system at 20° C. This operation yielded a prepolymerized catalyst (p-1) in which 3 g of propylene had been prepolymerized per 1 g of the solid titanium catalyst component (i-1).

[0118] <Main polymerization> 500 g of propylene and 3.5 L of hydrogen were charged into a 2-L autoclave, and the temperature inside the system was raised to 60°C. Polymerization was then initiated by adding 1.4 mmol of triethylaluminum, 0.7 mmol of cyclopentyldiethylaminodimethoxysilane, and 0.0028 mmol of the prepolymerization catalyst (p-1) obtained above in terms of titanium atom. Polymerization was carried out for 1 hour while maintaining the temperature inside the system at 70°C. Ethanol was then added to terminate the polymerization, and unreacted propylene was purged to obtain 248 g of propylene homopolymer.

[0119] The same procedure was repeated several times to obtain a total of 5 kg of propylene homopolymer. 0.6 g of pure water and 5.4 mL of propylene oxide were added to 1 kg of the obtained propylene homopolymer, and the mixture was subjected to a dechlorination treatment at 90°C for 2 hours, followed by vacuum drying at 80°C to obtain a propylene homopolymer powder. The physical properties of the obtained propylene homopolymer were evaluated, and the results are shown in Table 1.

[0120] In the present invention, the propylene polymer (Y) used in the surface layer contains a propylene homopolymer (X). Therefore, when the propylene homopolymer obtained in Production Example 2 is used in the surface layer, it is represented as a propylene polymer (Y1). When the propylene homopolymer is used as a part of the propylene polymer composition containing a polymer-based α-crystal nucleating agent in the base layer, the propylene homopolymer (X2) is represented as a propylene homopolymer (X2-1).

[0121] Table 1 shows the physical properties of the propylene homopolymer (X2-1), the propylene homopolymer (X1-1), and the propylene-based polymer (Y1). The propylene homopolymer (X2-1) and the propylene-based polymer (Y1) are the same propylene homopolymer.

[0122] <Additive blending and granulation> Next, 100 parts by mass of the obtained propylene homopolymer were dry-blended with 0.2 parts by mass of 3,5-di-tert-butyl-4-hydroxytoluene as an antioxidant, 0.2 parts by mass of tetrakis[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane as an antioxidant, and 0.01 parts by mass of calcium stearate as a neutralizer. Then, the mixture was melt-kneaded at a resin temperature of 230°C using a single-screw extruder to obtain a composition. tree The fat was pelletized. The single-screw extruder used was GMZ50-32 (L / D=32) manufactured by GM Engineering Co., Ltd.

[0123] The physical properties of the propylene homopolymer (X1), propylene polymer composition (Z) and propylene homopolymer (X2) obtained in Production Examples 1 and 2 were measured by the methods described above. The results are shown in Table 1.

[0124] [Table 1]

[0125] Example 1 <Preparation of raw sheet> The propylene polymer (Y) forming the front and back layers was the propylene homopolymer (Y1) obtained in Production Example 2, and the propylene polymer composition (Z) containing a polymeric α-crystal nucleating agent obtained in Production Example 1 was used as the propylene polymer composition forming the base layer (intermediate layer). These were melted at 270°C in a two-kind, three-layer, 25mmφ / 30mmφ multilayer T-die sheet molding machine (manufactured by GM Engineering Co., Ltd.), extruded, and cooled at a pulling speed of 1.0 m / min using a single chill roll maintained at 65°C to obtain a 315μm thick raw sheet. The thickness ratio of the intermediate layer to the front and back layers was 1:8:1 (front layer:intermediate layer:reverse layer).

[0126] <Preparation of multi-layer polypropylene film for capacitors> The obtained raw sheet was cut into a size of 95 mm x 95 mm and biaxially stretched under the following conditions to obtain a multilayer biaxially stretched film (multilayer polypropylene film for capacitors) with a thickness of 7 μm. The thickness was adjusted by changing the preheating temperature.

[0127] <Stretching conditions> Stretching device: KARO IV (product name, manufactured by Bruckner) Preheat temperature: 153-162℃ Preheat time: 60 seconds Stretching ratio: 5x longitudinal (machine direction) x 9x transverse (sequential biaxial stretching) (stretching area ratio: 45x) Stretching speed: 6m / min The physical properties of the obtained film were evaluated according to the methods described below, and the results are shown in Table 2.

[0128] [Physical properties of multi-layer polypropylene film for capacitors] <Bleed amount> After melting at 270°C using a 25mmφ / 30mmφ multilayer T-die sheet molding machine (manufactured by GM Engineering Co., Ltd.), the extruded sheet is cooled at a pulling speed of 1.0 m / min using a single cooling roll maintained at 65°C to obtain a raw sheet with a thickness of 315 μm. The obtained raw sheet is aged for 48 hours in an oven heated to 120°C. After aging, the raw sheet is cut into a length x width of 30 cm x 18 cm. doBoth sides of these 10 cut sheets are washed with dichloromethane and collected. After removing the solvent, the washed and collected material is weighed, and this amount is the total amount of bleed. The washed and collected material is subjected to HPLC (UV 254 nm) to quantify the amount of nucleating agent.

[0129] <Surface roughness> Measurements were carried out in accordance with JIS B0601-1994. <Dielectric strength (BDV)> The BDV of the obtained stretched film was measured in accordance with JIS-C2330. The breakdown voltage of the biaxially stretched film was measured at 100°C and 120°C. The withstand voltage (BDV, V / μm) was calculated by dividing the breakdown voltage by the film thickness.

[0130] <Internal Haze> S In a glass cell containing cyclohexanol , the obtained stretched film The test piece was immersed and the haze was measured in accordance with JIS K7136.

[0131] <Surface roughness> The average surface area in the MD direction of the surface layer of the obtained stretched film Roughness Ra was measured using a surface roughness measuring instrument in accordance with JIS-B0601:1994 at a measurement speed of 0.15 mm / min (n=3) and the arithmetic average was calculated.

[0132] Example 2 A multilayer polypropylene film for a capacitor was obtained in the same manner as in Example 1, except that a propylene polymer composition in which 6 parts by mass of the propylene polymer composition (Z) used in Example 1 was blended with 94 parts by mass of the propylene homopolymer (X2-1) obtained in Production Example 2 was used instead of the propylene polymer composition used in Example 1 to form the base layer (intermediate layer).

[0133] The evaluation results are shown in Table 2. Example 3 A multilayer polypropylene film for a capacitor was obtained in the same manner as in Example 1, except that a propylene polymer composition in which 3 parts by mass of the propylene polymer composition (Z) used in Example 1 was blended with 97 parts by mass of the propylene homopolymer (X2-1) obtained in Production Example 2 was used instead of the propylene polymer composition used in Example 1 to form the base layer (intermediate layer).

[0134] The evaluation results are shown in Table 2. Comparative Example 1 The same procedure as in Example 1 was carried out except that the propylene polymer composition used in Example 1 to form the base layer (intermediate layer) was replaced by the propylene homopolymer (X2-1) obtained in Production Example 2 alone, to obtain a one-kind, three-layer multilayer polypropylene film for capacitors, in which the base layer and front and back layers were made of the propylene homopolymer (X2-1).

[0135] The evaluation results are shown in Table 2. Comparative Example 2 The procedure of Example 1 was repeated except that, instead of the two surface layers and the intermediate layer (base layer) used in Example 1, a composition (W1) prepared by adding 0.05 parts by mass of an organic α-crystal nucleating agent (manufactured by Milliken, product name: NX8000J) to 100 parts by mass of a propylene-based homopolymer (X2-1) as a crystal nucleating agent was used for the surface and back layers and the intermediate layer (base layer), and a one-kind, three-layer multilayer polypropylene film for capacitors was obtained, in which the base layer and the surface and back layers were made of the above composition.

[0136] The evaluation results are shown in Table 2. Comparative Example 3 The procedure of Example 1 was repeated except that, instead of the front and back layers and intermediate layer (base layer) used in Example 1, a composition (W2) was used for the front and back layers and intermediate layer (base layer), in which 100 parts by mass of a propylene-based homopolymer (X2-1) was mixed with 0.1 parts by mass of an organic α-crystal nucleating agent (manufactured by Milliken, product name: NX8000J) as a crystal nucleating agent. A one-kind, three-layer multilayer polypropylene film for capacitors was obtained, in which the base layer and front and back layers were made of the above composition.

[0137] The evaluation results are shown in Table 2. Comparative Example 4 A one-kind, three-layer multilayer polypropylene film for capacitors was obtained in the same manner as in Example 1, except that a propylene polymer composition prepared by blending 3 parts by mass of the propylene polymer composition (Z) used in the base layer (intermediate layer) of Example 3 with 97 parts by mass of the propylene homopolymer (X2-1) obtained in Production Example 2 was used for both surface layers and the intermediate layer (substrate layer) instead of the front and back layers and intermediate layer (substrate layer) used in Example 1.

[0138] The evaluation results are shown in Table 2. Comparative Example 5 Instead of the propylene polymer composition used in Example 1 to form the base layer (intermediate layer), 100% of the propylene homopolymer (X2-1) used in Comparative Example 1 was used as the propylene polymer composition. mass A two-kind, three-layer multilayer polypropylene film for capacitors was obtained in the same manner as in Example 1, except that a composition (W2) was used in which 0.1 parts by mass of an organic α-crystal nucleating agent (manufactured by Milliken, trade name: NX8000J) was added to the remaining 1 part by mass.

[0139] The evaluation results are shown in Table 2.

[0140] [Table 2]

Claims

1. a surface layer on one side of a base layer made of a propylene polymer composition containing a propylene homopolymer (X) and a polymeric α-crystal nucleating agent (C) in an amount of 0.0001 to 0.05% by mass, and a back layer on the other side of the base layer; the front layer and the back layer are each made of a propylene-based polymer (Y) alone or a propylene-based polymer (Y) and an additive selected from the group consisting of a neutralizing agent and an antioxidant; The base layer, the front layer, and the back layer are all stretched, and A multilayer polypropylene film for capacitors, characterized in that the surface roughness Ra of the front and back layers is 0.2 μm or more.

2. 2. The multilayer polypropylene film for capacitors according to claim 1, wherein the propylene polymer (Y) forming the surface layer and the back layer is a polymer that does not contain a polymer-based α-crystal nucleating agent (C), or is a propylene homopolymer having a content of the polymer-based α-crystal nucleating agent (C) of less than 0.00001 mass%.

3. 3. The multilayer polypropylene film for capacitors according to claim 1, wherein the polymer-based α-crystal nucleating agent (C) is a polymer having a glass transition temperature and / or melting point (Tm) of 280° C. or higher.

4. The multilayer polypropylene film for capacitors according to any one of claims 1 to 3, wherein the propylene homopolymer (X) satisfies the following requirements (1) to (5): (1) Melt flow rate (MFR) (ASTM D1238, 230°C, under a load of 2.16 kg) in the range of 1 to 10 g / 10 min; (2) 13 mmmm measured using C-NMR is in the range of 0.930 to 0.999, (3) Ash content is 50 mass ppm or less, (4) A chlorine content of 5 ppm by mass or less, and (5) The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is in the range of 4.5 to 12.0.

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