JP6988243B2 - Polypropylene film roll - Google Patents

Description

The present invention relates to a polypropylene film roll having excellent workability in a vapor deposition process and a capacitor manufacturing process when used as a dielectric for a film capacitor.

Since polypropylene film is excellent in transparency, mechanical properties, electrical properties, etc., it is used in various applications such as packaging applications, tape applications, cable wrapping, and electrical applications such as capacitors.

Among these, the capacitor application is particularly preferably used not only for DC applications and AC applications but also for high voltage capacitors because of its excellent withstand voltage characteristics and low loss characteristics. Recently, various electric equipments are being converted to inverters, and along with this, the demand for smaller capacitors and larger capacities is increasing. In response to the demands of such markets, especially automobile applications (including hybrid car applications), solar power generation, and wind power generation applications, it is essential to improve productivity and workability as well as the withstand voltage characteristics of polypropylene film. It is becoming.

It is considered effective to suppress wrinkles and unevenness of the polypropylene film roll as a means for improving the withstand voltage characteristics and workability. When a polypropylene film roll is made into a film capacitor through a vapor deposition process or a capacitor manufacturing process, if wrinkles or irregularities are present in the film roll, meandering or broken wrinkles occur during transportation, which is only inferior in workability. Since it also affects the withstand voltage characteristics, it is effective to use a film roll with a good winding shape with few wrinkles and irregularities in order to improve the withstand voltage characteristics and workability.

As described above, various studies have been conducted on methods for improving the winding shape of the film roll. For example, a method of improving the winding shape of a film roll by controlling the inner layer hardness distribution of the polyester film roll has been proposed (see, for example, Patent Document 1). However, even if an attempt was made to implement this condition with a polypropylene film having no stiffness, the winding shape was not improved, and the withstand voltage characteristics and workability could not be improved.

Further, a method for improving the winding shape of the film roll by controlling the hardness distribution in the width direction of the surface of the film roll has been proposed (see, for example, Patent Document 2). However, even if the hardness distribution in the width direction is controlled, the unevenness of the film roll surface cannot be completely improved, and although the withstand voltage characteristics and workability are improved, the effects are limited and satisfy the characteristics required for the current capacitors. It wasn't. Further, a method for improving the winding shape by reducing the difference in roll diameter in the width direction of the polypropylene film roll has been proposed (see, for example, Patent Document 3). However, even if the roll diameter in the width direction is controlled, the wrinkles of the film roll cannot be completely improved, and although the withstand voltage characteristics and workability are improved, the effects are limited and do not meet the characteristics required for the current capacitors. It was a thing.

Japanese Unexamined Patent Publication No. 2012-46736 Japanese Patent Application Laid-Open No. 2003-146494 Japanese Unexamined Patent Publication No. 2015-195367

An object of the present invention is to solve the above-mentioned problems. That is, since the film roll has few wrinkles and irregularities and has a good winding shape, it is possible to provide a polypropylene film roll that not only has excellent workability in the vapor deposition process and the capacitor manufacturing process but also has excellent withstand voltage characteristics as a film capacitor. be.

The above-mentioned problem is a polypropylene film roll formed by winding a polypropylene film containing a polypropylene resin as a main component around a core, and the thickness of the polypropylene film is 3.6 to 15 μm, from the center of the film roll toward both ends. When measuring points are set at intervals of 25 mm in the width direction (excluding the range of 25 mm from both ends of the film) and the surface layer hardness is measured sequentially from one end to the other, the surface hardness of the immediately preceding measurement points is the same as that of the adjacent measurement points. The ratio X / W of the number X of the locations where the difference is 1.0 ° or more and the film width W (m) is 1.1 or more and 7.6 or less, the surface layer hardness is 86 to 94 °, and the film length. It can be achieved by a polypropylene film roll having a size of 10,000 to 27,000 m and a film width W (m) of 0.62 to 0.92 m.

When the polypropylene film roll of the present invention is used as a dielectric for a capacitor, it is excellent in workability at the time of manufacturing a capacitor and withstand voltage characteristics, and can be suitably used as a dielectric for a capacitor.

Hereinafter, the polypropylene film roll of the present invention will be described in more detail.

The polypropylene film of the present invention contains a polypropylene resin as a main component. Further, the polypropylene resin also includes a copolymer described later and branched-chain polypropylene. The "main component" means that the ratio of the specific component to all the components is 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 90% by mass or more. It is 95% by mass or more. Examples of the components other than the polypropylene resin include additives such as antioxidants and lubricants, which will be described later.

The polypropylene resin is mainly composed of a homopolymer of propylene, but may contain a copolymerization component of other unsaturated hydrocarbons as long as the object of the present invention is not impaired, and propylene is not a single polymer. The coalescence may be blended. Examples of the monomer components constituting such copolymerization components and blends include ethylene, propylene (in the case of a copolymerized blend), 1-butene, 1-pentene, 3-methylpentene-1, 3 -Methylbutene-1,1-hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene , 1-eicosene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene and the like. The copolymerization amount or blend amount is preferably less than 1 mol% from the viewpoint of withstand voltage characteristics.

The cold xylene-soluble portion (hereinafter referred to as CXS) of the polypropylene resin constituting the polypropylene film of the present invention is preferably 4.0% by mass or less. Here, CXS refers to a polypropylene component dissolved in xylene when the film is completely dissolved in xylene at 135 ° C. and then precipitated at 20 ° C., and has low stereoregularity and low molecular weight. It is considered that it corresponds to a component that is difficult to crystallize due to such reasons. The CXS of the polypropylene resin is more preferably 3.0% by mass or less, further preferably 2.0% by mass or less, and particularly preferably 1.0% by mass or less. When CXS exceeds 4.0% by mass, the withstand voltage characteristics of the polypropylene film may be inferior. In order to keep the CXS of the polypropylene resin within the above range, there are a method of increasing the catalytic activity when obtaining the resin, a method of washing the obtained resin with a solvent or the propylene monomer itself, and the like.

The mesopentad fraction (mm mm) of the polypropylene film of the present invention and the polypropylene resin constituting the film is preferably in the range of 0.950 to 0.995 from the viewpoint of withstand voltage characteristics, preferably 0.960 to 0.995. It is more preferably 0.990, further preferably 0.970 to 0.990, and particularly preferably 0.980 to 0.990. The mesopentad fraction is an index showing the stereoregularity of the polypropylene crystal phase measured by the nuclear magnetic resonance method (so-called NMR method), and the higher the value, the higher the crystallinity and melting point, and not only the room temperature but also the high temperature. However, it is preferable because it has excellent withstand voltage characteristics. When the mesopentad fraction of the polypropylene resin and the polypropylene film is less than 0.950, the withstand voltage characteristics may be inferior. On the other hand, when the mesopentad fraction of the polypropylene resin and the polypropylene film exceeds 0.995, the film-forming property may be poor and a polypropylene film may not be stably obtained. In order to keep the mesopentad fraction of polypropylene resin and polypropylene film within the above range, the method of cleaning the resin powder obtained with a solvent such as n-heptane, the selection of catalyst and / or co-catalyst, and the composition of the A method of appropriately selecting is preferably adopted.

The melt flow rate (hereinafter referred to as MFR) of the polypropylene resin constituting the polypropylene film of the present invention was measured in accordance with the condition M (230 ° C., 2.16 kg) of JIS K 7210 (1995). It is preferably 50 to 10 g / 10 minutes, more preferably 1.0 to 8.0 g / 10 minutes, still more preferably 1.5 to 5.0 g / 10 minutes, and 2.0 to 5. It is particularly preferable that it is 0 g / 10 minutes. If the MFR of the polypropylene resin is less than 0.50 g / 10 minutes, the film-forming property may be poor and a polypropylene film may not be stably obtained. On the other hand, when the MFR of the polypropylene resin exceeds 10 g / 10 minutes, the withstand voltage characteristics may be inferior. In order to keep the MFR of the polypropylene resin within the above range, a method of controlling the average molecular weight and the molecular weight distribution is preferably adopted.

The polypropylene film of the present invention has a film thickness of 3.6 to 15 μm. The film thickness is more preferably 4.0 to 12 μm, further preferably 4.5 to 9.0 μm, and particularly preferably 5.0 to 7.0 μm. If the film thickness is less than 3.6 μm, wrinkles are likely to occur when the film is wound as a film roll, and the processability may be inferior in the vapor deposition process or the capacitor manufacturing process. On the other hand, when the film thickness exceeds 15 μm, the capacity per volume may become small when used as a dielectric for a capacitor. In addition, the height of the protrusions generated on the film surface becomes too high, and as a result, the glossiness described later may decrease and the withstand voltage characteristics may be inferior. In order to keep the film thickness within the above range, it can be appropriately set by adjusting the discharge amount of the resin or adjusting the draft ratio when forming the sheet, but the thinner the film thickness, the more. Since the film is likely to break during film formation, the polypropylene resin described above is used to stably form a film by setting the longitudinal stretching step and the transverse stretching step during film forming as specific conditions as described later. It becomes possible.

The polypropylene film roll of the present invention is formed by winding a polypropylene film around a core. As the material of the core, a plastic having little deformation, a fiber reinforced plastic, and a metal are preferable, and it is more preferable to use a fiber reinforced plastic from the viewpoint of strength. Examples of the fiber-reinforced plastic core include a resin-impregnated type core in which carbon fiber or glass fiber is wound into a cylindrical shape, impregnated with a thermoplastic resin such as unsaturated polyester resin, and cured. Be done.

In the polypropylene film roll of the present invention, measurement points are set at intervals of 25 mm in the width direction from the center of the film roll toward both ends, and the surface layer hardness is measured sequentially from one end to the other (from both ends of the film). (Excluding the range of 25 mm), the ratio X / W of the number X of the points where the difference from the surface hardness of the adjacent measurement points is 1.0 ° or more and the film width W (unit: m) is 1.1. It is 7.6 or less. X / W is more preferable to be 1.0 or more on the 7.0 or less, more preferable to be 1.0 or more on the 6.0 or less, and particularly preferably 1.0 or more on 5.0. The details of the measurement method will be described later. When the X / W is 1.1 or more and 7.6 or less , there are no wrinkles or irregularities on the polypropylene film roll, no meandering or bending wrinkles during transportation in the vapor deposition process or the capacitor manufacturing process, and the workability is good. Is. As a result, the withstand voltage characteristics are also good. In order to keep the X / W within the above range, the surface condition of the polypropylene film is set by using the above-mentioned polypropylene resin and setting the casting step and the longitudinal stretching step at the time of film formation as specific conditions as described later. This can be achieved by controlling the above and setting the slitting process as a specific condition as described later.

In the polypropylene film roll of the present invention, measurement points are set at intervals of 25 mm in the width direction from the center of the film roll toward both ends, and the surface layer hardness is measured sequentially from one end to the other (from both ends of the film). (Excluding the range of 25 mm), it is preferable that the maximum value of the difference from the surface hardness of the immediately preceding measurement points adjacent to each other is 1.5 ° or less. The maximum value of the difference from the surface hardness of the adjacent measurement points immediately before is more preferably 1.4 ° or less, further preferably 1.3 ° or less, and particularly preferably 1.2 ° or less. When the maximum value of the difference from the surface hardness of the adjacent measurement points exceeds 1.5 °, it means that the degree of wrinkles and unevenness existing on the film is strong, and it means that the degree of wrinkles and irregularities is strong in the vapor deposition process and the capacitor manufacturing process. Workability may be inferior due to meandering or bending wrinkles during transportation. As a result, the withstand voltage characteristics may be inferior. In order to keep the maximum value of the difference from the surface hardness of the adjacent measurement points within the above range, the above-mentioned polypropylene resin is used, and the casting step and the longitudinal stretching step at the time of film formation are performed as described later. It can be achieved by controlling the surface condition of the polypropylene film by setting specific conditions and by setting the slitting process to specific conditions as described later.

The polypropylene film roll of the present invention has a surface hardness of 86 to 94 ° . Surface hardness is more preferable to be 87 to 93 °, and particularly preferably 88 to 92 °. If the surface hardness is less than 86 ° , the film roll may be too soft and unwinding may occur during transportation or vapor deposition. On the other hand, when the surface hardness exceeds 94 ° , blocking may occur between the film layers, and the film may not be stable at the time of unwinding and film breakage may occur. In order to keep the surface hardness within the above range, it can be achieved by setting the slit step as a specific condition as described later.

The polypropylene film roll of the present invention has a polypropylene film film length of 10,000 to 27,000 m . If the film length is less than 10,000 m, productivity may deteriorate. On the other hand, if the film length El super a 27,000M, easily wrinkle is generated in the slitting step, meandering and bending wrinkles in the transport in some cases generated workability is poor in a subsequent deposition process and the capacitor manufacturing process. As a result, the withstand voltage characteristics may be inferior.

In the polypropylene film roll of the present invention, the film width of the polypropylene film is 0.62 to 0.92 m. If the film width is less than 0.62 m, productivity may deteriorate. On the other hand, if the film width is Exceeding the 0.92 m, easily wrinkle is generated in the slitting step, meandering and bending wrinkles in the transport in some cases generated workability is poor in a subsequent deposition process and the capacitor manufacturing process. As a result, the withstand voltage characteristics may be inferior.

The polypropylene film of the present invention preferably has a young ratio of 2.0 GPa to 5.0 GPa in both the longitudinal direction (the direction in which the film flows during film formation) and the width direction (the direction orthogonal to the longitudinal direction on the film plane). .. The Young's modulus in both the longitudinal direction and the width direction is more preferably 2.2 to 5.0 GPa, further preferably 2.4 to 5.0 GPa, and particularly preferably 2.6 to 5.0 GPa. When the Young's modulus in either the longitudinal direction or the width direction is less than 2.0 GPa, transfer wrinkles are likely to occur in the film transfer process during film formation and processing, which deteriorates the winding shape of the film roll and, in some cases, the film It may break. Further, it may be inferior in withstand voltage characteristics. The Young's modulus of the polypropylene film of the present invention is substantially up to 5.0 GPa in either direction. In order to keep the Young's modulus in the above range in both the longitudinal direction and the width direction, the polypropylene resin described above is used, and the longitudinal stretching step, the transverse stretching step, and the heat treatment step at the time of film formation are set as specific conditions as described later. It can be achieved by doing.

The polypropylene film of the present invention preferably has a glossiness of 100 to 150% on both sides. The glossiness is more preferably 105 to 145% on both sides, further preferably 110 to 140% on both sides, and particularly preferably 115 to 135% on both sides. When the glossiness of at least one side is less than 100%, it means that the density of light scattering on the film surface increases, that is, there are many protrusions on the film surface, and the withstand voltage characteristics may be deteriorated due to the protrusions. be. On the other hand, when the glossiness of at least one side exceeds 150%, the film surface has few protrusions, so that the slipperiness is inferior, and transfer wrinkles are likely to occur in the film transfer process during film formation and processing, which deteriorates the winding shape of the film roll. In some cases, the film may break. In order to keep the glossiness within the above range on both sides, it can be achieved by using the above-mentioned polypropylene resin and setting the casting step and the longitudinal stretching step at the time of film formation as specific conditions as described later. can.

The polypropylene film of the present invention may contain branched chain polypropylene for the purpose of improving the film forming property and controlling the film surface shape. In this case, the branched-chain polypropylene satisfies the relational expression that the melt tension (MS) and the melt flow rate (MFR) when measured at 230 ° C. are log (MS)> −0.56 log (MFR) +0.74. Branched chain polypropylene is preferred. To obtain a branched chain polypropylene in which the melt tension (MS) and melt flow rate (MFR) measured at 230 ° C. satisfy the relational expression of log (MS)> −0.56 log (MFR) +0.74, A method of blending polypropylene containing a large amount of high molecular weight components, a method of blending an oligomer or a polymer having a branched structure, and introducing a long-chain branched structure into a polypropylene molecule as described in Japanese Patent Application Laid-Open No. 62-121704. A method, a method as described in Japanese Patent No. 2869606, or the like is preferably used. Specific examples thereof include "Profax ™ PF-814" manufactured by Basell and "Daploy ™ HMS-PP" (WB130HMS, WB135HMS, etc.) manufactured by Borealis, which are obtained by the electron beam cross-linking method. The resin to be used is preferably used because the gel component in the resin is small. The branched-chain polypropylene referred to here is polypropylene having 5 or less internal tri-substituted olefins in 10,000 carbon atoms, and the presence of these internal tri-substituted olefins is present in the ¹ H-NMR spectrum. It can be confirmed by the proton ratio. The branched-chain polypropylene has an action as an α-crystal nucleating agent, and can form a rough surface in a crystal form if the amount added is within a certain range. Specifically, the spherulite size of polypropylene produced in the cooling process of the melt-extruded resin sheet can be controlled to be small, the generation of insulation defects generated in the stretching process can be suppressed, and a polypropylene film having excellent withstand voltage characteristics can be obtained. ..

When the polypropylene film of the present invention contains branched polypropylene, the content is preferably 0.05 to 3% by mass, more preferably 0.1 to 2% by mass, and 0.3 to 1. It is more preferably 5% by mass, and particularly preferably 0.5 to 1% by mass. If the content of the branched-chain polypropylene is less than 0.05% by mass, the above-mentioned effect may not be obtained. On the other hand, when the content of the branched chain polypropylene exceeds 3% by mass, the steric regularity of the polypropylene film is lowered, and the withstand voltage characteristics may be inferior.

The polypropylene resin constituting the polypropylene of the present invention contains various additives such as a crystal nucleating agent, an antioxidant, a heat stabilizer, an easy lubricant, an antistatic agent, and an antiblocking agent as long as the object of the present invention is not impaired. It is also preferable to contain a filler, a viscosity modifier, an anticoloring agent and the like.

Among the above-mentioned additives, the selection of the type of antioxidant and the amount to be added is important from the viewpoint of long-term heat resistance. That is, the antioxidant is preferably a phenolic agent having steric hindrance, and at least one of them is a high molecular weight type having a molecular weight of 500 or more. Specifically, for example, 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4), 1,3,5-trimethyl-2,4,6-tris (3,5-di). -T-Butyl-4-hydroxybenzyl) benzene (eg, BASF's Irganox® 1330: molecular weight 775.2), tetrakis [methylene-3 (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] It is preferable to use or use methane (for example, Irganox 1010 manufactured by BASF: molecular weight 1177.7) alone or in combination. The total content of these antioxidants is preferably 0.03 to 1.0% by mass, more preferably 0.1 to 0.9% by mass, and 0.15 to 0% based on the total amount of the polypropylene resin. It is more preferably 8.8% by mass, and particularly preferably 0.15 to 0.6% by mass. When the content of the antioxidant in the polypropylene resin is less than 0.03% by mass, the effect of preventing oxidation is difficult to obtain and the long-term heat resistance may be inferior. On the other hand, when the content of the antioxidant in the polypropylene resin exceeds 1.0% by mass, the withstand voltage characteristics at high temperatures may be inferior.

The polypropylene film of the present invention preferably has an ash content of 50 ppm (mass basis, the same applies hereinafter) or less, more preferably 40 ppm or less, further preferably 30 ppm or less, and particularly preferably 20 ppm or less. If the ash content exceeds 50 ppm, the withstand voltage characteristics of the polypropylene film may be inferior. In order to keep the ash content in the above range, it is important to use a raw material with a small amount of catalyst residue, but a method for reducing contamination from the extrusion system during film formation as much as possible, for example, undamaged before starting film formation A method of sufficiently cleaning the flow path of the polymer with the polypropylene resin of No. 1 can be preferably adopted.

The polypropylene film of the present invention preferably has a surface wetting tension of at least one side of 37 to 50 mN / m, more preferably 38 to 49 mN / m, further preferably 39 to 48 mN / m, and even more preferably 40 to 47 mN. It is particularly preferable that it is / m. If the surface wetting tension is less than 37 mN / m, the adhesion with the metal may be insufficient when the metal is vapor-deposited. On the other hand, when the surface wetting tension exceeds 50 mN / m, the withstand voltage characteristics may be inferior. The polypropylene film usually has a low surface energy and a surface wetting tension of about 30 mN / m. In order to keep the surface wetting tension within the above range, a method of applying a surface treatment after biaxial stretching at the time of film formation is preferably adopted. Specifically, corona discharge treatment, plasma treatment, glow treatment, flame treatment and the like can be adopted.

The polypropylene film of the present invention is preferably obtained by preparing a sheet containing the above-mentioned polypropylene resin as a main component and biaxially stretching the sheet. As a biaxial stretching method, any of the inflation simultaneous biaxial stretching method, the tenter simultaneous biaxial stretching method, and the tenter sequential biaxial stretching method can be obtained, but from the viewpoint of film forming stability and thickness uniformity, the tenter sequential biaxial stretching method can be obtained. It is preferable to adopt the axial stretching method. In particular, it is preferable to stretch in the longitudinal direction and then in the width direction.

The polypropylene film of the present invention may have a functional layer laminated on at least one surface for the purpose of imparting various effects. The laminated structure may be two-layered, three-layered, or more laminated. As the laminating method, for example, a feed block method or a multi-manifold method by coextrusion, or a method of laminating polypropylene films by laminating may be used. In particular, for the purpose of improving the processability of a polypropylene film, for example, it is preferable to laminate an easy-to-slip layer in which fine particles are uniformly arranged within a range that does not deteriorate the withstand voltage characteristics.

Next, the method for producing the polypropylene film roll of the present invention will be described below, but the present invention is not necessarily limited thereto.

First, the above-mentioned preferable polypropylene resin is supplied to a single-screw melt extruder, and melt extrusion is performed at 230 to 260 ° C. Next, after removing foreign matter and modified polymer with a filter installed in the middle of the polymer tube, the unstretched sheet is obtained by discharging the foreign matter and the modified polymer from the T die onto the cast drum. Further, the cast drum preferably has a surface temperature of 60 to 120 ° C. from the viewpoint that the glossiness can be controlled in an appropriate range. The temperature is more preferably 65 to 110 ° C, further preferably 70 to 100 ° C, and particularly preferably 75 to 90 ° C. The time during which the molten sheet discharged from the T-die lands on the cast drum and is in close contact with the cast drum is preferably 1.0 second or longer from the viewpoint of solidifying the molten sheet and promoting crystal growth. 5.5 seconds is more preferable, 2.0 seconds or more is further preferable, and 2.5 seconds or more is particularly preferable.

As a method for bringing the sheet into close contact with the cast drum, a method such as an electrostatic application method, an air knife method, a nip roll method, or an underwater casting method can be adopted, but the air knife method is preferable from the viewpoint of high-speed film formation. Further, as a method of bringing the sheet into close contact with the cast drum, a close contact assisting device such as an end nip roll, an end spot air, or an air chamber can be adopted, but the end spot air is preferable from the viewpoint of high-speed film formation.

Next, the obtained unstretched sheet is biaxially stretched and biaxially oriented. As specific stretching conditions, first, the temperature at which the unstretched sheet is stretched in the longitudinal direction is controlled. As the temperature control method, a method using a temperature-controlled rotary roll, a method using a hot air oven, or the like can be adopted. The film temperature when stretched in the longitudinal direction is preferably 120 to 155 ° C., more preferably 125 to 154 ° C., and even more preferably 130 to 153 ° C. from the viewpoint of controlling the glossiness and stable film forming property. Particularly preferably, it is 135 to 152 ° C. The draw ratio is preferably 4.0 to 6.0 times, more preferably 4.2 to 5.8 times, and even more preferably 4.4 to 5. It is 6 times, particularly preferably 4.6 to 5.4 times. The higher the draw ratio, the higher the Young's modulus in the longitudinal direction and the better the withstand voltage characteristics. It may be easier to get up.

In order to achieve the above-mentioned high-magnification stretching without breaking the film, it is preferable to introduce a mechanism for assisting stretching by applying a local amount of heat immediately before stretching by a radiation heater. In particular, in the case of high-magnification stretching, the orientation is strongly applied. Therefore, applying heat from at least one side of the film immediately before stretching to achieve the above-mentioned high-magnification stretching from the viewpoint of improving the stretchability of the film. It is more preferable. When the film is stretched in the longitudinal direction, a phenomenon called neck down is observed in which the film width decreases. However, in order to reduce the thickness unevenness in the longitudinal direction and the width direction, the neck down rate (after stretching) is observed. The film width / film width before stretching × 100) is preferably 90 to 99%.

Next, the film end is gripped by a tenter type stretching machine and introduced. Then, from the viewpoint of stable film forming property, it is preferably heated to 140 to 170 ° C., more preferably 145 to 173 ° C., further preferably 150 to 171 ° C., particularly preferably 155 to 170 ° C., and 8 to 15 times in the width direction. , More preferably 9 to 14 times, still more preferably 10 to 13 times, and particularly preferably 10 to 12 times.

Then, the heat treatment may be performed in the tenter as it is, but the temperature is preferably 147 to 173 ° C, more preferably 150 to 172 ° C, and 152 to 172 ° C from the viewpoint of controlling the Young's modulus in an appropriate range. The temperature is more preferably 171 ° C, and particularly preferably 155 to 170 ° C. Further, the heat treatment may be carried out while relaxing in the longitudinal direction and / or the width direction of the film, and in particular, the relaxation rate in the width direction is 5 to 15%, more preferably 8 to 13%, still more preferably 9 to 12%. , Particularly preferably 10 to 12%, from the viewpoint of the balance between Young's modulus and dimensional stability.

Next, from the viewpoint of improving the adhesion of the vapor-deposited metal to the surface to be vapor-deposited, a corona discharge treatment is performed on a biaxially stretched polypropylene film in air, nitrogen, carbon dioxide gas, or a mixed gas thereof. Obtain a polypropylene film of.

Finally, the polypropylene film described above is slit into a predetermined width and length in a slitting step, and is wound around a core as a film roll. The slit speed in the slit step is preferably 350 to 550 m / min, more preferably 370 to 500 m / min, and more preferably 400 to 450 m / min from the viewpoint of controlling the surface hardness and productivity. More preferred. When the slit speed is less than 350 m / min, the amount of air entrained between the film layers is small, and the surface hardness is high, so that blocking may easily occur. On the other hand, when the slit speed exceeds 550 m / min, wrinkles are likely to occur during transportation, and meandering or bending wrinkles during transportation may occur in the subsequent vapor deposition process or capacitor manufacturing process, resulting in poor workability. As a result, the withstand voltage characteristics may be inferior. The unwinding tension in the slit step is preferably 400 to 550 N / m, more preferably 410 to 520 N / m, and even more preferably 420 to 500 N / m, from the viewpoint of suppressing wrinkles during transportation. .. When the unwinding tension is less than 400 N / m, wrinkles are likely to occur during transportation, and meandering or bending wrinkles during transportation may occur in the subsequent vapor deposition process or capacitor manufacturing process, resulting in poor workability. As a result, the withstand voltage characteristics may be inferior. On the other hand, even when the unwinding tension exceeds 550 N / m, wrinkles are likely to occur during transportation, and meandering or bending wrinkles during transportation occur in the subsequent vapor deposition process or capacitor manufacturing process, resulting in poor workability. There is. As a result, the withstand voltage characteristics may be inferior. The initial take-up tension in the slit step is preferably 20 to 70 N / m, more preferably 30 to 67 N / m, and more preferably 40 to 65 N / m from the viewpoint of suppressing the generation of wrinkles during take-up. And even more preferable. When the initial winding tension is less than 20 N / m, wrinkles are likely to occur during winding, and meandering or broken wrinkles during transportation may occur in the subsequent vapor deposition process or capacitor manufacturing process, resulting in poor workability. As a result, the withstand voltage characteristics may be inferior. On the other hand, even when the initial winding tension exceeds 70 N / m, wrinkles are likely to occur during winding, and meandering and bending wrinkles during transportation occur in the subsequent vapor deposition process and capacitor manufacturing process, resulting in workability. It may be inferior. As a result, the withstand voltage characteristics may be inferior.

The take-up tension taper in the slit process (winding tension when the film roll is wound / initial take-up tension x 100) suppresses the occurrence of wrinkles during transportation, and in particular, the number of wrinkles and irregularities present in the polypropylene film roll. It is preferably 40 to 59% from the viewpoint of suppressing the maximum value of X / W, which is an index of the above, and the difference between adjacent hardnesses, which is an index of the degree of wrinkles and unevenness, to be small. The take-up tension taper is more preferably 42 to 57% and even more preferably 44 to 55%. If the take-up tension taper is less than 40%, the hardness of the polypropylene film roll surface layer becomes too soft, which may cause buckling or unwinding. In addition, transport wrinkles may occur due to a sudden change in winding tension. On the other hand, when the take-up tension taper exceeds 59%, wrinkles and irregularities are likely to occur especially in the vicinity of the polypropylene film roll surface layer, and meandering and bending wrinkles during transportation occur in the subsequent vapor deposition process and capacitor manufacturing process, resulting in workability. May be inferior. As a result, the withstand voltage characteristics may be inferior.

The initial take-up surface pressure in the slit step is preferably 300 to 550 N / m, more preferably 330 to 520 N / m, and even more preferably 350 to 500 N / m from the viewpoint of controlling the surface hardness. .. If the initial take-up surface pressure is less than 300 N / m, the surface hardness of the polypropylene film roll becomes too soft, which may cause buckling or unwinding. On the other hand, when the initial take-up surface pressure exceeds 550 N / m, the surface hardness of the polypropylene film roll becomes too high, and blocking occurs between the film layers. As a result, the film is not stable during unwinding in the vapor deposition process. Breakage may occur. The take-up surface pressure taper in the slit process (winding surface pressure at the time of film roll winding / initial take-up surface pressure × 100) is preferably 100 to 120% from the viewpoint of controlling the surface hardness, and is preferably 100 to 120%. It is more preferably 115%, and even more preferably 100 to 110%. If the take-up surface pressure taper is less than 100%, the surface hardness of the polypropylene film roll becomes too soft, which may cause buckling or unwinding. On the other hand, when the take-up surface pressure taper exceeds 120%, the surface hardness of the polypropylene film roll becomes too high, and blocking occurs between the film layers. As a result, the film is not stable during unwinding in the vapor deposition process and the film breaks. May occur. The deceleration in the slitting process is preferably 1.1 to 6.0 m / min / sec, preferably 1.1 to 6.0 m / min / sec, from the viewpoint of suppressing wrinkles during winding, controlling the surface hardness, and productivity. It is more preferably ~ 5.0 m / min / sec, and even more preferably 1.5 to 4.5 m / min / sec. If the deceleration of the slit is less than 1.1 m / min / sec, the productivity is poor or the surface hardness of the polypropylene film roll becomes too high, resulting in blocking between the film layers, resulting in unwinding in the vapor deposition process. The film may not be stable and film breakage may occur. On the other hand, when the deceleration exceeds 6.0 m / min / sec, winding wrinkles are likely to occur due to the rapid deceleration of the slit speed, and meandering or broken wrinkles during transportation in the subsequent vapor deposition process or capacitor manufacturing process. May occur and the workability may be inferior. As a result, the withstand voltage characteristics may be inferior.

When the polypropylene film has thickness spots in the slitting step, unevenness due to the thickness spots may easily occur on the wound film roll. In order to solve this problem, it is preferable to carry out so-called oscillation in which the unwinding film or the unwinding film roll is repeatedly moved in the width direction to smooth out the thickness unevenness. The oscillation width in the slit step is preferably 10 to 100 mm from the viewpoint of smoothing the thickness unevenness and productivity, and the oscillation speed is preferably 5 to 70 mm / min.

The polypropylene film roll of the present invention is preferably used as a dielectric for a capacitor, but is not limited to the type of the capacitor. Specifically, from the viewpoint of the electrode configuration, it may be either a foil-wound capacitor or a metal vapor-deposited film capacitor, and is also preferable for an oil-immersed type capacitor containing insulating oil and a dry capacitor that does not use insulating oil at all. Used. Further, from the viewpoint of shape, it may be a winding type or a laminated type. Due to the characteristics of the polypropylene film of the present invention, it is particularly preferably used as a metal vapor deposition film capacitor.

In the present invention, it is preferable to provide a metal film on the surface of the polypropylene film described above to form a metal film laminated film. The method is not particularly limited, but for example, a method in which aluminum is vapor-deposited on at least one surface of the film to provide a metal film such as an aluminum-deposited film as an internal electrode of a film capacitor is preferably used. At this time, other metal components such as nickel, copper, gold, silver, chromium, and zinc can be vapor-deposited simultaneously or sequentially with aluminum. Further, a protective layer may be provided on the vapor-filmed film with oil or the like.

The thickness of the metal film of the metal film laminated film is preferably 20 to 100 nm from the viewpoint of the electrical characteristics of the film capacitor and the self-healing property. Further, for the same reason, the surface resistance value of the metal film is preferably 1 to 20 Ω / □. The surface resistance value can be controlled by the metal type and film thickness used.

In the present invention, after forming the metal film, if necessary, the metal film laminated film can be aged or heat-treated at a specific temperature. Further, at least one side of the metal film laminated film may be coated with polyphenylene sulfide or the like for insulation or other purposes.

The metal film laminated film thus obtained can be laminated or wound by various methods to obtain a film capacitor. A preferred method for manufacturing a wound capacitor will be described below, but the method is not necessarily limited thereto.

Aluminum is vacuum-deposited on one side of the polypropylene film of the present invention. At that time, the film is deposited in a striped shape having a margin portion running in the longitudinal direction of the film. Next, a blade is inserted into the center of each vapor deposition portion and the center of each margin portion on the surface to slit the reel, and a tape-shaped take-up reel having a margin on one side of the surface is produced. Two tape-shaped take-up reels with a left or right margin, one for the left margin and one for the right margin, are overlapped and wound so that the vapor-deposited portion protrudes from the margin portion in the width direction. Get the body. The core material was removed from this winding body and pressed, and metallicon was sprayed on both ends to form an external electrode. Then, the lead wire can be welded to the metallikon to obtain a wound film capacitor. The use of the film capacitor is wide-ranging, such as for vehicles, home appliances (televisions, refrigerators, etc.), general miscellaneous protection, automobiles (hybrid cars, power windows, wipers, etc.), and power supplies. Film rolls can also be suitably used for these applications.

Hereinafter, the present invention will be described in detail with reference to Examples. The characteristics were measured and evaluated by the following methods.

(1) Cold xylene soluble part (CXS)
0.5 g of a polypropylene resin sample is dissolved in 100 ml of xylene at 135 ° C., allowed to cool, recrystallized in a constant temperature water bath at 20 ° C. for 1 hour, and then the polypropylene-based component dissolved in the filtrate is subjected to a liquid chromatograph method. Quantify (X (g)).

CXS (%) = (X / X ₀ ) x 100
It was calculated from the above formula using the precision value (X _{0 (g)) of 0.5 g of the sample.}

(2) Mesopentad fraction (mmmm)
A polypropylene resin or polypropylene film was used as a sample and dissolved in a solvent, and the ^{mesopentad fraction (mm mm) was determined under the following conditions using 13} C-NMR (Reference: New Edition Polymer Analysis Handbook Japan Analytical Chemistry) Meeting / Polymer Analysis Research Roundtable, ed. 1995, pp. 609-611).

A. Measurement conditions Equipment: Bruker DRX-500
Measurement nucleus: ¹³ C nucleus (resonance frequency: 125.8 MHz)
Measured concentration: 10 wt%
Solvent: Benzene / heavy orthodichlorobenzene = mass ratio 1: 3 mixed solution Measurement temperature: 130 ° C
Spin speed: 12Hz
NMR sample tube: 5 mm tube Pulse width: 45 ° (4.5 μs)
Pulse repetition time: 10 seconds Data point: 64K
Number of conversions: 10,000 times Measurement mode: complete decoupling
B. The Fourier transform was performed with the analysis condition LB (line broadening factor) set to 1.0, and the mmmm peak was set to 21.86 ppm. Peak division is performed using WINFIT software (manufactured by Bruker). At that time, the peak was divided from the peak on the high magnetic field side as follows, and the attached software was automatically fitted.
Peak (a) mrrm
(B) (c) rrrm (divided as two peaks)
(D) rrrrr
(E) mrmr
(F) mrmm + rmrr
(G) mmrr
(H) rmmr
(I) mmml
(J) mmmm
After optimizing the peak division, the total peak fraction of mm mm was calculated. The above measurement was performed 5 times, and the average value was taken as the mesopentad fraction (mm mm) of this sample.

(3) Melt flow rate (MFR)
The measurement was performed according to the condition M (230 ° C., 2.16 kg) of JIS K7210 (1995).

(4) Melt tension (MS)
The measurement was performed according to the device for MFR measurement shown in JIS K7210 (1999). A resin sample was heated to 230 ° C. using a melt tension tester manufactured by Toyo Seiki Co., Ltd., and the molten polymer was discharged at an extrusion speed of 15 mm / min to form a strand. The tension when the strand was taken up at a speed of 6.5 m / min was measured, and the melt tension was determined.

(5) Film thickness The micrometer method thickness was measured according to 7.4.1.1 of JIS C2330 (2001).

(6) The maximum difference between the surface hardness, the ratio X / W of the number X of the points where the difference between the surface hardness and the measurement points immediately before the adjacent measurement points is 1.0 ° or more and the film roll width W, and the adjacent surface hardness. Value The surface hardness of the surface of the polypropylene film roll was measured using a rubber hardness meter (ASKER “TypeC”) manufactured by Polymer Meter Co., Ltd. specified in JIS K-6301. As the measurement points, the central portion in the width direction of the polypropylene film roll was first determined, and then the measurement points were set at intervals of 25 mm toward both ends in the width direction (the measurement points were marked with a marker). However, the range 25 mm from both ends of the polypropylene film roll was excluded from the measurement range. The surface hardness of the above measurement points was measured sequentially from one end to the other. The average value of each surface hardness obtained by the measurement was taken as the surface hardness of the polypropylene film roll of the present invention.

Further, in each surface layer hardness, the number of points where the difference in surface hardness between the immediately preceding measurement points adjacent to each other was 1.0 ° or more was defined as X, and the ratio X / W to the film roll width W was determined. The unit of the film roll width was (m).

Further, in each surface layer hardness, the adjacent hardness difference was obtained, and the highest value among the respective hardness differences was obtained as the maximum value.

(7) Young's modulus Five samples were cut out so that the measurement direction was 200 mm and the direction perpendicular to the measurement direction was 10 mm in the longitudinal direction or width direction of the polypropylene film, and marks were made at positions 50 mm from both ends to make a trial length of 100 mm. did. It was measured at a tensile speed of 300 mm / min in an atmosphere of 23 ° C. and 65% RH using a film strength elongation measuring device (AMF / RTA-100) manufactured by Orientec Co., Ltd. The Young's modulus of the polypropylene film of the present invention was taken as the average value of 5 samples in both the longitudinal direction and the width direction.

(8) Glossiness According to JIS K7105 (1981), the measurement was performed using a digital variable angle gloss meter UGV-5D manufactured by Suga Test Instruments Co., Ltd. under the conditions of an incident angle of 60 ° and a light receiving angle of 60 °. This measurement was performed 5 times on both sides, and the average value of each was taken as the glossiness of the polypropylene film of the present invention.

(9) Element Workability in Capacitor Manufacturing Aluminum was vacuum-deposited to 8Ω / □ on one side of the polypropylene film obtained in each of the examples and comparative examples described later with a vacuum vapor deposition machine manufactured by ULVAC, Inc. At that time, the film was deposited in a striped shape having a margin portion running in the longitudinal direction (repetition of a width of the vapor deposition portion of 39.0 mm and a width of the margin portion of 1.0 mm). Then, a blade was inserted into the center of each vapor-film deposition portion and the center of each margin portion to slit the reel, and a tape-shaped take-up reel having a total width of 20 mm having a margin portion of 0.5 mm at either the left or right end was produced. The left margin and the right margin of the obtained reels are wound one by one on top of each other so that the vapor-filmed portion protrudes 0.5 mm from the margin portion in the width direction, and the reel has a capacitance of 10 μF. Got KAW-4NHB manufactured by Minato Seisakusho Co., Ltd. was used for element winding.

When manufacturing the above capacitors, the process from the start to the end of winding was visually observed, and those with wrinkles or deviations were regarded as rejected (defective products), and the element processability was evaluated by the number of rejected products. Fifty capacitor elements were manufactured and evaluated according to the following criteria.

◯: Element defect rate 0% or more and less than 2% Δ: Element defect rate 2% or more and less than 5% ×: Element defect rate 5% or more and 100% or less The defect rate was used.
Element defect rate = number of defects / 50 [pieces] x 100 [%]
The formula for the element defect rate is as described above.

(10) High temperature withstand voltage characteristics According to JIS C2330 (2001), electrodes were placed in a hot air oven whose temperature was adjusted to 125 ° C., and the dielectric breakdown voltage of the polypropylene film was measured. This measurement was performed 5 times, the average value was obtained, and the high-temperature dielectric breakdown voltage (V / μm) per 1 μm was obtained by dividing by the film thickness obtained in the above item (5). The high temperature withstand voltage characteristic was evaluated by evaluating the high temperature dielectric breakdown voltage according to the following criteria: ◯: 450V / μm or more Δ: 400V / μm or more, less than 450V / μm ×: less than 400V / μm.

(Example 1)
100% by mass of polypropylene resin (manufactured by Prime Polymer Co., Ltd., melting point: 166 ° C., MFR: 3.5 g / 10 minutes, mmmm: 0.985) was supplied to a single-screw melt extruder, and melt extrusion was performed at 250 ° C. Foreign matter was removed with a 25 μm cut sintered filter. The molten sheet discharged from the T-die was brought into close contact with a cast drum whose surface temperature was controlled to 80 ° C., and cast to the cast drum so as to be indirect for 3.0 seconds to obtain an unstretched sheet. At this time, an air knife and end spot air were used to bring the molten sheet into close contact with the cast drum. Then, preheating was performed using a ceramic roll heated to 150 ° C., and the film was stretched 5.0 times in the longitudinal direction. The neck down rate at this time was 98%. Further, by applying a heat amount by a radiation heater immediately before the film stretching for the purpose of improving the stretchability of the film, no film tear occurred in the vertical stretching. Next, the end portion was gripped with a clip and stretched 11 times in the width direction at 165 ° C. Further, heat treatment was performed at 163 ° C. for 7 seconds, and relaxation was performed by 11% in the width direction. Then, after cooling to room temperature, one side of the film ^{was subjected to a corona discharge treatment with a processing strength of 25 W · min / m 2} , and the selvage portion of the film gripped with a clip was cut and removed. The surface-treated surface is referred to as the A surface, and the untreated surface is referred to as the B surface. The film from which the end was removed was wound with a winder to obtain a polypropylene film having a thickness of 6.0 μm.
Then, with a slitter, the slit speed is 430 m / min, the take-up tension is 440 N / m, the initial take-up tension is 60 N / m, the take-up tension taper is 50%, the initial take-up surface pressure is 440 N / m, and the take-up surface pressure taper is 100%. Under the conditions of deceleration of 3.0 m / min / sec, oscillation width of 40 mm, and oscillation speed of 60 mm / min, the polypropylene film is slit so that the film length is 27,000 m and the film width is 0.62 m. Wrapped around the core as a roll. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 2)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 44%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 3)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 55%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 4)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 42%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 5)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 57%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 6)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was set to 40%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 7)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 59%. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 8)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the surface temperature of the cast drum was set to 60 ° C. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 9)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the stretching temperature in the longitudinal direction was set to 155 ° C. Table 1 shows the physical characteristics of the obtained polypropylene film roll.

(Example 10)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the draw ratio in the longitudinal direction was set to 3.8 times. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Example 11)
A polypropylene film roll having a film length of 27,000 m and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the discharge amount at the time of melt extrusion was adjusted to make the film thickness 3.6 μm. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Example 12)
A polypropylene film roll having a film length of 27,000 m and a film width of 0.62 m was produced in the same manner as in Example 1 except that the discharge amount at the time of melt extrusion was adjusted to set the film thickness to 15 μm. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Example 13)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained under the same conditions as in Example 1 except that the oscillation width at the time of slitting was 80 mm. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Comparative Example 1)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was set to 60%. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Comparative Example 2)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the take-up tension taper at the time of slitting was 39%. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Comparative Example 3)
A polypropylene film roll having a film thickness of 6.0 μm, a film length of 27,000 m, and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the surface temperature of the cast drum was 55 ° C. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Comparative Example 4)
A polypropylene film roll having a film length of 27,000 m and a film width of 0.92 m was obtained in the same manner as in Example 1 except that the discharge amount at the time of melt extrusion was adjusted to make the film thickness 3.5 μm. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

(Comparative Example 5)
A polypropylene film roll having a film length of 27,000 m and a film width of 0.62 m was obtained in the same manner as in Example 1 except that the discharge amount at the time of melt extrusion was adjusted to make the film thickness 16.0 μm. Table 2 shows the physical characteristics of the obtained polypropylene film roll.

When the polypropylene film roll of the present invention is used as a dielectric for a capacitor, the polypropylene film roll is provided as a polypropylene film roll having a good winding shape, less wrinkles and unevenness, and therefore excellent workability and withstand voltage characteristics. be able to.

Claims (5)

It is a polypropylene film roll formed by winding a polypropylene film containing polypropylene resin as a main component around a core, and the thickness of the polypropylene film is 3.6 to 15 μm, and the distance is 25 mm in the width direction from the center of the film roll toward both ends. When the measurement points are set with (excluding the range of 25 mm from both ends of the film) and the surface layer hardness is measured sequentially from one end to the other end, the difference in surface layer hardness from the immediately preceding measurement points adjacent to each other is 1.0. The ratio X / W of the number of locations X of ° or more and the film width W (m) is 1.1 or more and 7.6 or less, the surface layer hardness is 86 to 94 °, and the film length is 10,000. A polypropylene film roll having a film width W (m) of about 27,000 m and a film width W (m) of 0.62 to 0.92 m. When the surface hardness is measured at intervals of 25 mm in the width direction from the center of the film roll (excluding the range of 25 mm from both ends of the film), the maximum value of the difference between adjacent surface hardness is 1.5 ° or less. The polypropylene film roll described in . The polypropylene film roll according to claim 1 or 2 , wherein the polypropylene film has a Young's modulus of 2.0 to 5.0 GPa in both the longitudinal direction and the width direction. The polypropylene film roll according to any one of claims 1 to 3 , wherein the polypropylene film has a glossiness of 100 to 150% on both sides. The polypropylene film roll according to any one of claims 1 to 4 , wherein the polypropylene film is used as a dielectric for a capacitor.