JP6269062B2 - Film roll - Google Patents

Description

  The present invention relates to a film roll wound around a separator film for an electricity storage device. Specifically, since there is no generation of tarmi or wrinkles after winding on a shaft, the film of the separator film for power storage devices has excellent flatness and is not restricted by the coating tension of the heat-resistant layer and the battery tension in the battery assembly process. Regarding roles.

  As an electricity storage device having excellent capacity density and output density, a lithium ion secondary battery has attracted attention, and various members constituting the battery have been vigorously studied. For example, in the case of a positive electrode member, a positive electrode member with an emphasis on capacity density has been adopted in the power supply application of a small mobile device such as a conventional mobile phone because the battery is intended to be downsized. Recently, when power density is more important than capacity for electric vehicle applications, etc., we are actively investigating positive electrode members suitable for high output and positive electrode members that have excellent thermal stability and can be used safely. Has been done.

  Among the members of lithium ion secondary batteries, various separators have been developed as members that contribute to both battery performance and safety. Conventional separators are mainly made of polyolefin porous films, and many porous films manufactured by various methods have been proposed (for example, see Patent Documents 1 to 3).

  A porous film used as a separator is a film roll wound around a shaft at the time of production, and is handled as a film roll as an intermediate product and a final product after slitting, and is secondarily processed by a user. Various problems may occur when wrinkles and tarmi are generated in the porous film formed as a film roll during the secondary processing by the user.

  As a technique for providing a film with little wrinkles and tarmi, it has been proposed to control the shape in a state of being wound as a film roll by the winding hardness (see, for example, Patent Document 4). According to Patent Document 4, it is possible to provide a film with less unevenness by controlling the shape of the film roll by controlling the amount of air that is wound between the films when winding. However, this proposal relates to a film that is not porous and does not have through-holes. In a porous film used for an electricity storage device, air passes through the film through the through-holes. The air escapes from the roll with time, and the roll shape cannot be controlled by the entrainment air.

  On the other hand, there has been proposed a wound product obtained by winding a porous film through which air passes in a roll shape (for example, see Patent Document 5). However, in this proposal, a wound product having excellent winding performance in the next process can be obtained by setting the maximum diameter and the minimum diameter of the wound product and the winding length to a predetermined relationship. Since attention is paid only to the maximum diameter and the minimum diameter, it is insufficient from the viewpoint of managing the flatness of the film influenced by the shape distribution in the film width direction.

  Moreover, the proposal which prescribed | regulated the curvature and loosening of a separator film in the specific range is made | formed (for example, refer patent document 6). In this proposal, in order to reduce slack and curvature, the intermediate product before slitting to the final product width is wound with low tension, and the annealing treatment is performed for 2 to 5 days to suppress the occurrence of the curvature. However, the deterioration in flatness due to the thickness unevenness in the central portion of the film is not necessarily improved by the present proposal. In some cases, the annealing treatment is too long, and the deterioration in flatness may be further advanced.

  Furthermore, the proposal which suppresses the flatness deterioration with time by controlling the width direction distribution of the roll hardness of the film roll which wound up the film is also made | formed (for example, refer patent document 7). However, this proposal is related to a film having no through-holes as in Patent Document 4, and in a porous film having through-holes and air permeability, air between the films escapes over time, and the roll hardness is low. Since it changes, it was difficult to prevent deterioration of flatness by the distribution of roll hardness in the width direction.

Japanese Patent Laid-Open No. 55-131028 Japanese Patent Publication No.55-32531 JP-A 63-199742 JP 2003-266525 A JP 2004-99799 A JP 2011-140633 A JP 2003-146696 A

  An object of the present invention is to solve the above-described problems. That is, the film roll of the separator film for electrical storage devices which is excellent in flatness in which the film is not wrinkled in the state of being wound up as a porous film roll and does not generate tarmi when the film is unwound from the roll is provided. It is to be.

The present invention for solving the above-described problems has the following features.
(1) A film roll obtained by slitting and winding a porous polyolefin film obtained by stretching at least uniaxially, wherein the porous polyolefin film is used as a separator film of an electricity storage device, and in the width direction of the film roll. when measuring the winding diameter distribution, [Delta] R is the difference between the small diameter adjacent maxima diameter of the pole winding diameter distribution curve ([mu] m) is, Ri 0.1~250μm der, winding length is not less than 1,100m film roll .
(2) The film roll according to (1), wherein an absolute value of an inclination of a straight line connecting adjacent maximum and minimum diameters is 0.01 to 10 μm / mm in the winding diameter distribution curve.
(3) The film roll according to (1) or (2), wherein a difference between the maximum roll diameter and the minimum roll diameter of the film roll is 0.1 to 500 μm.
(4) The film roll in any one of (1)-(3) whose width W of the said film roll is 200-4,000 mm.
(5) The film roll according to any one of (1) to (4), wherein the polyolefin constituting the porous polyolefin film is polypropylene.
(6) The porous polyolefin film has a ratio (TD / MD) of 5% elongation stress (F5 value) in the film longitudinal direction (MD) and 5% elongation stress (F5 value) in the film width direction (TD). The film roll in any one of (1)-(5) whose is 1.3-2.0.

  ADVANTAGE OF THE INVENTION According to this invention, when unwinding a film from a film roll, the separator film for electrical storage devices which can be handled by wrinkles, tarmi, etc., without deterioration in flatness can be provided.

  In the film roll of the present invention, a porous polyolefin film is continuously formed on a winding shaft called a core formed by molding a plastic such as paper or ABS (acrylonitrile-butadiene-styrene) resin, a carbon fiber reinforced plastic, or a metal into a cylindrical shape. It refers to an integrated body of a continuous film and a core that are wound up. In addition, this film roll was produced by winding a porous polyolefin film with a winder to produce an intermediate product (intermediate roll), and then adjusting the width with a slitter (making it narrow) and winding it up (product roll) Means.

  In the present invention, the main component of the resin composition constituting the porous polyolefin film includes homopolymers such as polyethylene, polypropylene, polybutene-1 and poly-4-methylpentene-1, and copolymers thereof. Can do. Here, the main component of the resin composition in the present invention is a component having the highest mass ratio in the resin composition. Among these, polypropylene is preferable in terms of the total balance of processability, handleability, and heat resistance. Among them, a preferable polypropylene is an isotactic polypropylene resin having a melt flow rate (MFR, condition 230 ° C., 2.16 kg) in a range of 2 to 30 g / 10 minutes. When the MFR is 2 to 30 g / 10 min, it is possible to achieve both the output performance as an electricity storage device and the stability (film processing suitability) during production. From this viewpoint, the more preferable range of MFR is 5 to 20 g / 10 minutes. Here, MFR is an index indicating the melt viscosity of a resin defined in JIS K 7210 (1999), and is widely used as a physical property value indicating the characteristics of polyolefin. In the case of polypropylene, the measurement is performed under condition M of JIS K 7210, that is, at a temperature of 230 ° C. and a load of 2.16 kg. In addition, you may use the mixed resin which mixed and adjusted several polypropylene from which MFR differs so that MFR of a resin composition may become the said preferable range.

  In addition, it is preferable that the isotactic index of the isotactic polypropylene resin is 90 to 99.9% because voids can be efficiently formed in the film because of high crystallinity. If the isotactic index is less than 90%, it may be difficult to obtain a highly permeable porous polyolefin film.

  The resin composition constituting the porous polyolefin film may be composed of 100% by mass of isotactic polypropylene resin. However, from the viewpoint of realizing high air permeability and porosity, 90 to 99.99. As long as 9 mass% is contained, polyolefins other than isotactic polypropylene resin may be included. From the viewpoint of heat resistance, it is more preferable that 92 to 99% by mass of the resin composition is isotactic polypropylene. Here, the polypropylene may be a polypropylene copolymer containing a comonomer residue as well as a homopolypropylene which is a homopolymer of propylene. The comonomer is preferably an unsaturated hydrocarbon, and examples thereof include 1-butene, 1-pentene, 4-methylpentene-1, and 1-octene which are ethylene and α-olefin. The copolymerization ratio of these comonomers to polypropylene is preferably 5% by mass or less, more preferably 3% by mass or less.

  The porous polyolefin film in the present invention preferably employs a β crystal method using a polypropylene resin, forms voids by sequential biaxial stretching, and forms through holes in the film. In that case, it is preferable that the β resin forming ability of the polypropylene resin is 50 to 100%. If the β-crystal forming ability is less than 50%, the amount of β-crystal formed at the time of film production is small, so the number of voids in the film formed by utilizing the transition to α-crystal is reduced, and as a result, the permeability is improved. An excellent film may not be obtained. From the viewpoint of transmission performance, the β-crystal forming ability is more preferably 60 to 100%.

  Here, the β crystal method is to form voids in the film by utilizing the crystal density difference and crystal transition between α-type crystal (α crystal) and β-type crystal (β crystal), which are polymorphs of polypropylene. Is the method. In particular, it is preferable to use a crystallization nucleating agent called a β crystal nucleating agent that selectively forms a β crystal of polypropylene by adding it to a polypropylene resin. As the β crystal nucleating agent, a compound in which the nucleating agent itself forms a needle crystal is preferably used. The β crystal nucleating agent is oriented by shearing by discharging from a T-die at the time of melt extrusion of a polypropylene resin, and at the time of producing an unstretched film, the surface of the oriented β crystal nucleating agent is used as a crystal nucleus to selectively select polypropylene molecules. The chain forms β crystals while the orientation is controlled. In this way, by stretching an unstretched film having a large amount of oriented β crystals of polypropylene, the orientation of polypropylene molecules is greatly changed simultaneously with the collapse of the β crystals of polypropylene and the transition to α crystals. The voids can be formed efficiently.

  In order to control the β crystal forming ability to 50 to 100%, it is preferable to use a polypropylene resin having a high isotactic index and a β crystal nucleating agent as an additive. As the β crystal nucleating agent, various pigment compounds and amide compounds can be preferably used. The content of the β crystal nucleating agent is preferably 0.01 to 0.5% by mass, more preferably 0.05 to 0.4% by mass, based on the entire resin composition. .

  As described above, the β-crystal nucleating agent used in the present invention is different from the appearance in which the nucleating agent itself is called a needle-like crystal, the appearance is a rod, and the ratio of the major axis to the minor axis has a value of 10 or more. Preferably, it is a compound having anisotropy, for example, an amide compound or a tetraoxaspiro compound having an aromatic dicarboxylic acid residue. Specific examples include N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide and 3,9-bis [4- (N-cyclohexylcarbamoyl) phenyl] -2,4,8,10-tetraoxaspiro [5. , 5] Undecane can be mentioned as a preferred β crystal nucleating agent.

  In the present invention, the porous polyolefin film is desirably stretched at least uniaxially. As a method of making the polyolefin film porous, as a method other than the β crystal method described above, a wet process in which a plasticizer is mixed with a resin to form a sheet, and the plasticizer is extracted in an extraction liquid to form a void in the resin. A method called a method (or an extraction method), a method of forming a void by breaking the crystal lamella itself by stretching, a method of forming a void by cleaving the crystal grain interface by low-temperature low-speed stretching, adding particles, A technique called a dry method such as forming a void at the interface is known, but in order to obtain a porous film with excellent permeation performance by forming a through hole by either the wet method or the dry method, the film is stretched at least uniaxially. Further, it is more preferable to use a biaxially stretched film in terms of dimensional stability.

  The film roll of the present invention in which a porous polyolefin film is wound around a core is an adjacent maximum in the winding diameter distribution curve in the width direction of the film roll which is unwound from an intermediate product (intermediate roll) and wound by slitting. The difference ΔR (μm) between the diameter and the minimum diameter is 0.1 to 250 μm. When the ΔR exceeds 250 μm, there is a case where tarmi or wrinkles are generated on the film. Moreover, although it is desirable that ΔR is small, it is practically difficult to make ΔR less than 0.1 μm.

  The roll diameter distribution curve of a film roll indicates a change in the roll diameter in the width direction of the roll by continuously measuring the outer diameter (wind diameter) of the film roll in the width direction. Ideally, a film roll having a uniform winding diameter can be obtained by uniformly winding a film having no thickness unevenness around a core made of a perfect circle. Actually, the roll diameter of the film roll has a distribution due to the influence of variations in thickness existing in the width direction and longitudinal direction of the film.

  The maximum and minimum diameters of the winding diameter distribution curve are the winding diameters at the point (peak or valley) where the change in winding diameter changes from increasing to decreasing or decreasing to increasing. The former is the maximum diameter and the latter is the minimum diameter. . In the present inventors, the difference ΔR between the adjacent maximum diameter and the minimum diameter among the plurality of maximum diameters and minimum diameters usually present in the film roll strongly affects the flatness of the film. It has been found that by setting the small diameter difference ΔR to 0.1 to 250 μm, a film having no wrinkles and no tarmi and excellent in flatness can be obtained. ΔR is more preferably 0.1 to 200 μm, and further preferably 0.1 to 180 μm. The lower limit of ΔR is preferably as small as possible, but it is difficult to control the lower limit to be less than 10 μm. Therefore, it is practically preferable that ΔR is 10 to 150 μm.

  Furthermore, in the winding diameter distribution curve of the film roll of the present invention, it is preferable that the absolute value of the slope of the straight line connecting the adjacent maximum and minimum diameters is 0.01 to 10 μm / mm. The slope of the straight line connecting the adjacent maximum diameter and the minimum diameter is the slope of a straight line connecting the points indicating the adjacent maximum diameter and the minimum diameter. ΔR is the distance in the width direction between the maximum diameter and the minimum diameter (mm ) Divided by. That this numerical value is small indicates that ΔR is small or that the distance between the adjacent maximum and minimum diameters is long. When the absolute value of the slope of the straight line connecting the adjacent maximum and minimum diameters exceeds 10 μm / mm, tarmi may occur if the tension at the time of unwinding the film is weakened. The absolute value of the slope of the straight line connecting the adjacent maximum and minimum diameters is more preferably 0.01 to 7 μm / mm. The absolute value of the slope of the straight line connecting the adjacent maximum and minimum diameters is preferably as small as possible. However, in practice, it is difficult to control it to less than 0.1, so that it may be 0.1 to 7 μm / mm. Is particularly preferred.

  In the film roll of the present invention, the difference between the maximum winding diameter and the minimum winding diameter is preferably 0.1 to 500 μm. The maximum winding diameter is the largest winding diameter among the maximum diameters, and the minimum winding diameter is the smallest winding diameter among the minimum diameters. If the difference between the maximum winding diameter and the minimum winding diameter exceeds 500 μm, the film may be bent or meandering when being unwound and conveyed. The difference between the maximum winding diameter and the minimum winding diameter is more preferably 0.1 to 300 μm. The smaller the difference between the maximum winding diameter and the minimum winding diameter, the better. However, it is practically difficult to make the difference less than 0.1 μm. Actually, it is difficult to control to less than 10 μm like ΔR, and therefore the difference between the maximum winding diameter and the minimum winding diameter is particularly preferably 10 to 300 μm.

  In the present invention, as a method for controlling the winding diameter distribution curve of the film roll wound with the porous polyolefin film within the above-described preferred range, first, primarily in the longitudinal direction and the width direction of the porous polyolefin film itself. It is important to reduce the thickness variation. Since thickness variation cannot be eliminated completely, it is important to moderate the thickness change rate and reduce steep unevenness. It is also important not to have a fixed thick part or thin part at a specific part. Specifically, in order to prevent thickness fluctuations from occurring in a specific cycle in the longitudinal direction, it is important to manage equipment drive so that output fluctuations in a specific cycle do not occur. In order to prevent thickness fluctuations corresponding to the section period, it is desirable to employ a stretching temperature and a magnification at which stretching unevenness is unlikely to occur. In the width direction, when the resin is melt-extruded, if unevenness occurs in the width direction, it directly affects the thickness variation of the final product. It is important to manage so that it does not. Furthermore, even if a thick part or thin part occurs at the fixed position, in order to eliminate the influence as much as possible, while winding the film while moving the winding position in the width direction, while applying so-called oscillation It is preferable to employ a winding method. It is also important to control the outer diameter of the core to be used, and to suppress fluctuations in speed and tension during winding. The diameter of the core to be used is a 6-inch core (inner diameter is 152.4 mm) larger than a 3-inch core (inner diameter is 76.2 mm) or a large-diameter core having an 8-inch core (inner diameter is 203.2 mm) or more. It is preferable. Further, even if the inner diameter is 3 inches, a large-diameter core having an inner diameter-outer diameter difference such as 8 inches (203.2 mm) or 10 inches (254 mm) may be used.

  The film roll of the present invention preferably has a product width W of 200 to 4,000 mm. Lithium ion secondary batteries used in power storage devices for electric vehicles and hybrid electric vehicles often have a size of 100 mm square or more, so the separator film is expected to be supplied in a larger size. The In addition, when coating a separator film with a heat-resistant resin layer or a heat-resistant layer containing inorganic particles for the purpose of improving safety, it is possible to produce a wide film and then slit into a narrow film. Therefore, the product width W of the film roll (product roll) is preferably in the above range.

  In the film roll of the present invention, the porous polyolefin film wound around the core is 5% elongation stress (F5 value) in the film longitudinal direction (MD) and 5% elongation stress (F5 value) in the film width direction (TD). The ratio (TD / MD) is preferably 1.3 to 2.0. After winding the film formed as an intermediate roll with a winder, aging is usually performed to stabilize the physical properties of the film. During aging, the planarity of the film may change over time due to strain and stress remaining in the film wound on the intermediate roll. When the TD / MD value of the F5 value is within the above preferable range, it is possible to reduce deterioration in flatness due to the occurrence of tarmi, wrinkles, and stripes over time. If TD / MD is less than 1.3, the residual stress in the MD direction is high, and winding tightening tends to proceed with an intermediate roll (film roll), and a large number of tarmi may occur due to minute thickness spots. Further, when TD / MD exceeds 2.0, the orientation in the MD direction is insufficient, so that there is a case where it is deformed by the transport tension in the assembly process of the electricity storage device. More preferably, when the TD / MD value of the F5 value is 1.4 to 1.8, the flatness is hardly deteriorated.

  In the present invention, in order to make the ratio of the F5 value in the MD direction and the TD direction of the porous polyolefin film within the above-mentioned preferable range, the stretching temperature and magnification in the production process of the porous polyolefin film are within the following preferable ranges. It is desirable to do.

  In the present invention, the porous polyolefin film preferably has an air permeability resistance of 50 to 500 seconds from the viewpoint of exhibiting excellent battery performance as a separator. More preferably, it is 80 to 350 seconds. The air permeation resistance can be controlled by the temperature during stretching, the magnification condition, and the heat setting condition after stretching.

  In the present invention, the film thickness of the porous polyolefin film is preferably 5 to 40 μm. If the thickness is less than 5 μm, self-discharge in the electricity storage device increases, and it may not be possible to store for a long time in a charged state. Moreover, when thickness exceeds 40 micrometers, the volume ratio of the porous polyolefin film which occupies in an electrical storage device will become high too much, and it will become impossible to obtain a high energy density. The film thickness is more preferably 8 to 30 μm, and still more preferably 10 to 20 μm.

  For the porous polyolefin film, an antioxidant, a thermal stabilizer, an antistatic agent, a lubricant composed of inorganic or organic particles, an antiblocking agent, a filler, an incompatible polymer, as long as the effects of the present invention are not impaired. You may contain various additives, such as. In particular, for the purpose of suppressing oxidative deterioration due to the thermal history of the resin composition constituting the porous polyolefin film, 0.01 to 0.5 parts by mass of an antioxidant is added to 100 parts by mass of the resin composition. Is preferred.

  Below, the manufacturing method of the film roll of this invention is demonstrated concretely. In addition, the manufacturing method of the film roll of this invention is not limited to this.

  First, as polypropylene resin, 99.7 parts by mass of MFR 7 g / 10 min isotactic polypropylene resin 9 parts by mass of N crystal, N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide 0.3 parts by mass is mixed. A raw material mixed in advance at a predetermined ratio using a twin-screw extruder is prepared. At this time, the melting temperature is preferably 290 to 305 ° C., and after quenching with cooling water at 25 ° C., it is preferably processed into a chip shape with a chip cutter to obtain a raw material resin.

  Next, the above-mentioned raw material resin is supplied to a uniaxial melt extruder, and melt extrusion is performed at 200 to 230 ° C. And after removing a foreign material etc. with the filter installed in the middle of the polymer pipe | tube, it discharges on a cast drum from T-die, and an unstretched sheet is obtained. The cast drum at this time preferably has a surface temperature of 110 to 130 ° C. from the viewpoint of controlling the β crystal fraction in the unstretched sheet to be high. At this time, in particular, since the forming of the end portion of the sheet affects the subsequent stretchability, it is preferable that the end portion is sprayed with spot air to be in close contact with the drum. Moreover, in order to make the contact | adherence state to the drum of the whole sheet | seat uniform, you may spray air using an air knife to the sheet | seat full width as needed. Further, casting by electrostatic application may be performed.

  Next, the obtained unstretched sheet is biaxially stretched to form pores (through holes) in the film. As the biaxial stretching method, the film is stretched in the longitudinal (longitudinal) direction and then stretched in the width (transverse) direction, or the stretched in the width (transverse) direction and then stretched in the longitudinal (longitudinal) direction, or the film A simultaneous biaxial stretching method in which the longitudinal (longitudinal) direction and the width (transverse) direction are stretched almost simultaneously can be used. The sequential biaxial stretching method is preferably employed from the viewpoint that high air permeability is easily obtained, and it is particularly desirable to stretch in the width (transverse) direction after stretching in the longitudinal (longitudinal) direction.

  As specific stretching conditions, a sequential biaxial stretching method in which stretching in the longitudinal direction and then stretching in the transverse direction will be described as an example. First, the temperature is controlled so that the unstretched sheet can be stretched in the longitudinal direction. As a temperature control method, a method using a heated rotating roll, a method using a hot air oven, or the like can be adopted. As the stretching temperature in the machine direction, it is preferable to employ a temperature of 110 to 140 ° C., more preferably 115 to 130 ° C., from the viewpoint of film characteristics and uniformity. The stretching ratio is preferably 4.5 times or more. More preferably, it is 4.8 times or more, and further preferably 5 times or more. The upper limit of the vertical magnification is not limited, but is preferably 6 times or less. When the magnification exceeding 6 times is adopted, the film may frequently break in the next transverse stretching step.

  Next, the above-mentioned uniaxially stretched polypropylene film is introduced by gripping the end of the film with a stenter type stretching machine. And it is preferable from the viewpoint of not only air permeability variation but thickness uniformity that it is preferably heated to 140 to 160 ° C. and stretched by 8 times or more in the transverse direction. The stretching ratio in the transverse direction is more preferably 8.5 times or more. The upper limit of the stretching ratio in the transverse direction is not limited, but is preferably 12 times or less from the viewpoint of avoiding film breakage during stretching. It is particularly preferable that the stretching ratio in the transverse direction is 9 to 11 times. The stretching temperature in the transverse direction is more preferably stretched at 145 to 155 ° C.

  Next, heat setting is performed in the stenter. The heat setting temperature is preferably from the transverse stretching temperature to 165 ° C., and the heat setting time is preferably 5 to 30 seconds. Further, the heat setting may be performed while relaxing in the longitudinal direction and / or the lateral direction of the film. The relaxation rate in the lateral direction is preferably 5 to 20%, more preferably 8 to 18%, from the viewpoint of coexistence of thermal dimensional stability and physical property variations. When the heat setting temperature exceeds 165 ° C., the air permeability may be lowered. The heat setting temperature is more preferably 158 to 164 ° C.

  In addition, while transporting the film after stretching and heat setting, the thickness of the film is measured while scanning in the width direction with a non-contact continuous thickness meter using infrared rays, visible light, β rays, etc. Therefore, it is preferable to control the gap in the slit portion where the resin at the tip of the T die is discharged in the width direction so that the thickness variation in the width direction becomes uniform.

  About the film obtained as mentioned above, the film edge part currently hold | gripped with the stenter can be cut, and only the center flat part can be wound around a core with a winder, and an intermediate product (intermediate roll) can be obtained. At this time, it is important to set the film length of the intermediate roll in consideration of the production efficiency and the collapse of the porous film, and preferably 1,000 to 10,000 m. More preferably, it is 1,500-8,000m. In addition, it is preferable to perform the oscillation at the stage of winding the intermediate product from the viewpoint of preventing the flatness from deteriorating before the slit in the subsequent process. The movement width of the oscillation is preferably 20 to 500 mm in total width, and more preferably 30 to 300 mm. If the intermediate product is wound up without oscillating and aged for a long time, the flatness may deteriorate during the aging, so use the oscillation in the first winding process during film production. It is preferable.

  The intermediate product of the porous polyolefin film obtained as described above is cut into a predetermined product width by a slit according to secondary processing or customer request, and wound around a core, and a film roll (product roll) and Is done. When the film is wound, if the winding tension is too high, the film tightens strongly, resulting in a film roll with inferior flatness with an uneven film appearance. Conversely, if the winding tension is too low, the film is loosened. In other words, wrinkles may occur or film tears may occur. When no oscillation is performed when winding the intermediate product, it is preferable to perform the oscillation when performing the slitting. As the movement width of the oscillation, it is preferable to perform the oscillation at a ratio of 1 to 30% with respect to the product width after the slit from the viewpoint of obtaining a film having excellent flatness. The proportion of oscillation is more preferably 5 to 25%. If the oscillation exceeds the preferred range, the film may be curved or meander.

  It is preferable to set the moving speed in the width direction so that the oscillation performed at the time of winding the intermediate product or slitting is one cycle when the film length is 50 to 500 m. If it is less than 50 m / cycle, the moving speed may be too high, and conveyance wrinkles may occur. On the other hand, if it exceeds 500 m / cycle, the moving speed is too slow, and it may be difficult to obtain the effect of employing oscillation. More preferably, it is 100-400 m / cycle, and it is especially preferable if it is 100-300 m / cycle.

  Usually, the polyolefin film is aged at room temperature for about 0.5 to 5 days from the winding of the intermediate product to the slitting. The porous polyolefin film of the present invention is also preferably slit after aging. On the other hand, if the oscillation is not performed when winding the intermediate product, the aging is preferably within 3 days because the flatness may deteriorate if the aging time is too long. A more preferable aging period is 0.5 to 2 days.

  Examples of the electricity storage device in the present invention include non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries, electric double layer capacitors such as lithium ion capacitors, and the like. Since such an electricity storage device can be repeatedly used by charging and discharging, it can be used as a power supply device for industrial devices, household equipment, electric vehicles, hybrid electric vehicles, and the like. The porous polyolefin film of the present invention can be suitably used especially for lithium ion secondary batteries, and particularly suitably used as a separator for lithium ion secondary batteries that require high output such as industrial equipment and automobiles. be able to.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) β-crystal forming ability 5 mg of resin or film was sampled in an aluminum pan and measured using a differential scanning calorimeter (Seiko Denshi Kogyo RDC220). First, the temperature is raised from room temperature to 280 ° C. at 20 ° C./min (first run) in a nitrogen atmosphere, held for 15 minutes, and then cooled to 20 ° C. at 20 ° C./min. After melting for 10 minutes, the melting peak (rounded off after the decimal point) observed when the temperature is raised at 20 ° C./min (second run) is the melting point of the β crystal. The melting at which the peak is observed at 158 ° C. or higher is defined as the melting peak of the α crystal, and the amount of heat of fusion is determined from the baseline and the area of the region surrounded by the peak with reference to the flat portion on the high temperature side. When the heat of fusion of the crystal is ΔHα and the heat of fusion of the β crystal is ΔHβ, the value calculated by the following equation is the β crystal forming ability. The heat of fusion was calibrated using indium.
β crystal forming ability (%) = [ΔHβ / (ΔHα + ΔHβ)] × 100
In addition, the β crystal fraction in the state of the sample can be calculated by calculating the abundance ratio of the β crystal in the same manner from the melting peak observed in the first run.

(2) Air permeability resistance A square having a size of 100 mm × 100 mm was cut out from the porous polyolefin film and used as a sample. Using the Oken type testing machine method of JIS P 8117 (2009), the air resistance resistance instruction value was measured at 23 ° C. and relative humidity 65%. The measurement was performed 10 times at different locations, and the average value was taken as the air resistance of the porous polypropylene film.

(3) Thickness The thickness was measured with a contact-type film thickness meter, Mitsutyo Lightmatic VL-50A (10.5 mmφ carbide spherical surface probe, measurement load 0.06 N). The measurement was performed 10 times at different locations, and the average value was taken as the thickness of the porous polypropylene film.

(4) F5 value From the porous polyolefin film immediately before the slit, rectangles having lengths of 150 mm × 10 mm and 10 mm × 150 mm in the longitudinal direction and the width direction were respectively cut out and used as samples. Using a tensile tester (Orientec Tensilon UCT-100), the tensile test was performed in the longitudinal direction and the width direction of the film at an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. The load applied to the film when the sample was extended by 5% (when the distance between chucks became 52.5 mm) was read, and the value divided by the cross-sectional area (film thickness × 10 mm) of the sample before the test was defined as F5 value. . The measurement was performed for five samples in each direction, and the average value was evaluated.

(5) The roll diameter distribution curve in the width direction of a film roll About the film roll after a slit, the outer diameter (winding diameter) measurement of the film roll was performed over the roll full width using the bulk shape measuring apparatus by Kitano Planning Co., Ltd. . Specifically, the measurement was performed by bringing a linear gauge as a detector of the measuring device into contact with the roll surface and running on a dedicated rail at a speed of 12.5 mm / sec. Data from the linear gauge was collected as digital data using a digital recorder at intervals of 0.01 seconds.
The collected digital data is graphed as a winding diameter distribution curve by smoothing using the average value of a total of 41 points of 20 points before and after by the adjacent average method on the spreadsheet software, and the winding diameter distribution curve data (above) The maximum point and the minimum point of the outer diameter were read out from the digital data after the smoothing process), and the difference ΔR between the outer diameter (maximum diameter) of the adjacent maximum point and the outer diameter (minimum diameter) of the minimum point was calculated. Also, by reading the distance in the width direction between adjacent maximum and minimum points from the smoothed digital data and dividing ΔR by the distance, the absolute value of the slope of the straight line connecting the adjacent maximum and minimum diameters is calculated. did.
Furthermore, the difference was calculated by setting the largest winding diameter among the maximum diameters as the maximum winding diameter and the smallest winding diameter among the minimum diameters as the minimum winding diameter.
The maximum and minimum diameters of the winding diameter distribution curve are points where the change in winding diameter changes from increasing to decreasing or decreasing to increasing. The diameter corresponding to the former is the maximum diameter, and the diameter corresponding to the latter is the minimum diameter. It is.

(6) Evaluation of flatness The evaluation is carried out as follows by applying the evaluation of the winding property of item 7 of JIS C 2151 (2008). As shown in FIG. 2 of JIS C 2151, the film is passed between two rolls and a load is applied. The load was increased stepwise by 200 g per 300 mm film width, and the flatness was evaluated according to the following criteria with the load at which the tarmi was not visible.
Class A: Tarmi disappeared under a load of 400 g / 300 mm width or less.
Class B: Tarmi disappeared with a load of 401 g / 300 mm width to 800 g / 300 mm width or less.
Class C: A load of 801 g / 300 mm width or more was necessary for the tarmi to disappear.

(7) Curvature A porous polypropylene film is unrolled 5 m in the longitudinal direction from a porous polyolefin film roll and brought into close contact with a glass plate placed on a horizontal table. The distance between the film side and the octopus yarn at the middle point in the longitudinal direction (position 2.5 m from both ends) with respect to this straight line (octopus yarn) is connected to a straight line with an octopus yarn between two points 5m apart on one side of the film width direction (Mm) was measured using calipers.

Example 1
99.2 parts by mass of homopolypropylene FLX80E4 (MFR: 8 g / 10 min, hereinafter referred to as high MFR-PP) manufactured by Sumitomo Chemical Co., Ltd. as a raw material resin for porous polyolefin film, and N, N ′ as β crystal nucleating agent -0.3 part by mass of dicyclohexyl-2,6-naphthalenedicarboxamide (manufactured by Shin Nippon Rika Co., Ltd., Nu-100, hereinafter simply referred to as β crystal nucleating agent), and further, an antioxidant IRGANOX 1010 manufactured by BASF Japan And IRGAFOS 168 are supplied to the twin screw extruder from the weighing hopper so that 0.1 and 0.2 parts by mass of each are mixed at this ratio, melt kneaded at 300 ° C., and discharged from the die into strands. Then, it was cooled and solidified in a water bath whose temperature was controlled at 20 ° C., cut into a chip shape, and used as a chip raw material.
The chip raw material was supplied to a single screw extruder whose temperature was controlled at 220 ° C., and melt extrusion was performed. Then, the molten polymer was guided to a 20 μm cut sintered filter through a polymer tube, and after removing foreign matters, it was discharged from a T-die and cast on a cast drum whose temperature was adjusted to 125 ° C. to obtain an unstretched sheet. . At this time, the molten polymer was brought into close contact with the drum by using an air knife, and the temperature was maintained on the drum for 12 seconds.
Next, the unstretched sheet is heated using a hard chrome roll heated to 125 ° C., and the longitudinal direction of the film is obtained by utilizing the peripheral speed difference between the roll similarly heated to 125 ° C. and the roll temperature-controlled to 45 ° C. The film was stretched 5 times and cooled once.
Furthermore, the end of the film stretched in the longitudinal direction was introduced into a tenter-type stretching machine by holding it with a clip, and stretched 9.5 times in the width direction at 148 ° C. Then, the film after biaxial stretching was heat-treated at 162 ° C. for 15 seconds while relaxing 10% in the width direction, and then both ends of the film held by the clips were cut, and the center of the film was cut Only the portion was continuously wound on a core having an outer diameter of 172 mm to obtain an intermediate roll. The porous film wound up as an intermediate roll had a length of 5,000 m and a thickness of 20 μm.
After leaving the intermediate roll at room temperature for 24 hours, it was placed on a slitter and slit so that the product width was 500 mm and the length was 1,200 m. At that time, the film was wound around a core made of ABS resin having an outer diameter of 162 mm while applying oscillation at a full width of 140 mm (± 70 mm from the reference position) and a film length of 300 m / cycle to obtain a film roll.

(Example 2)
In Example 1, a film roll was obtained under the same conditions except that the oscillation at the time of slitting was 80 mm (± 40 mm from the reference position).

(Example 3)
A porous polyolefin film having a thickness of 20 μm was obtained in the same manner as in Example 1, except that the stretching ratio in the width direction was 9.3 times and the relaxation was 17%.
After leaving the intermediate roll at room temperature for 24 hours, it was placed on a slitter and slit so that the product width was 800 mm and the length was 2,400 m. At that time, the film was wound around a core made of carbon fiber reinforced plastic and having an outer diameter of 166 mm while applying oscillation at a full width of 200 mm (± 100 mm from the reference position) and a film length of 300 m / cycle to obtain a film roll.

Example 4
A porous film having a thickness of 25 μm was obtained in the same manner as in Example 1, except that the draw ratio in the width direction was 8.5 times and the relaxation was 15%.
After leaving the intermediate roll at room temperature for 24 hours, it was placed on a slitter and slit so that the product width was 600 mm and the length was 500 m. At that time, the film was wound around a paper core having an outer diameter of 172 mm while applying oscillation at a full width of 150 mm (± 75 mm from the reference position) and a film length of 300 m / cycle to obtain a film roll.

(Comparative Example 1)
In Example 1, slitting was performed without performing oscillation during slitting.

(Comparative Example 2)
In Example 2, the film roll was used under the same conditions except that the winding length of the intermediate roll was 10,500 m, the product length after slitting was 5,000 m, and the winding shaft was a paper core having an outer diameter of 170 mm. Got.

(Comparative Example 3)
A porous film having a thickness of 20 μm was obtained in the same manner as in Example 3 except that the relaxation rate was 25%. Next, at the time of slitting, the film was wound around a core made of paper having an outer diameter of 96 mm with an oscillation of 50 mm in total width (± 25 mm from the reference position) and a film length of 300 m / cycle, thereby obtaining a film roll.

(Comparative Example 4)
In Example 2, a film roll was obtained in the same manner except that the time from the winding of the intermediate roll to the slitting was 5 days.

(Example 5)
79.3 parts by mass of high MFR-PP, 20 parts by mass of Prime Polymer Polypropylene Resin Prime Polypro F133A (MFR = 3 g / 10 min), 0.2 parts by mass of β crystal nucleating agent, and antioxidant The raw material, BASF Japan IRGANOX1010 and IRGAFOS168, are mixed at a ratio of 0.15 parts by mass, and the raw material is supplied from the weighing hopper to the twin-screw extruder, melt-kneaded at 295 ° C, and dies in a strand shape. Then, it was cooled and solidified in a water bath whose temperature was controlled at 25 ° C., cut into a chip shape, and used as a chip raw material.
The chip raw material was supplied to a single screw extruder whose temperature was controlled at 220 ° C., and melt extrusion was performed. Then, after passing the molten polymer through a 20 μm cut sintered filter through a polymer tube, the molten polymer was discharged from a T-die and cast on a mirror surface metal cast drum whose surface temperature was adjusted to 125 ° C. to obtain an unstretched sheet. At this time, the molten polymer was brought into close contact with the metal drum by using an air knife, and the temperature was kept on the drum for 12 seconds.
Next, the unstretched sheet is heated using a hard chrome roll heated to 125 ° C., and the longitudinal direction of the film is obtained by utilizing the peripheral speed difference between the roll similarly heated to 125 ° C. and the roll temperature-controlled to 45 ° C. The film was stretched 5 times and cooled once.
Further, the end of the film stretched in the longitudinal direction was introduced into a tenter-type stretching machine by holding it with a clip, and stretched 9 times in the width direction at 148 ° C. Then, the film after biaxial stretching was heat-treated at 160 ° C. for 15 seconds while relaxing 12% in the width direction, and then both ends held by the clips were cut to remove only the central part of the film. The intermediate roll was continuously wound around a core having an outer diameter of 172 mm while applying oscillation at a full width of 80 mm (± 40 mm from the reference position) and a film length of 500 m / cycle. The porous film wound up as an intermediate roll had a length of 5,000 m and a thickness of 20 μm.
The intermediate roll was allowed to stand at room temperature for 24 hours, and then slitted with a slitter so that the product width was 500 mm and the length was 1,100 m. At that time, the film was wound around a core having an outer diameter of 162 mm made of ABS resin to obtain a film roll.

(Example 6)
In Example 5, with respect to the film after heat treatment, the thickness can be continuously measured while scanning in the width direction set in the film forming apparatus, the thickness is measured using a β-ray thickness meter, and the result The film was formed while controlling the slit gap of the T die so that the thickness in the width direction becomes uniform by feeding back to the T die. After waiting until the thickness variation in the width direction measured by the β-ray thickness meter was less than 5%, both ends of the film were cut while applying oscillation at 120 mm (± 60 mm from the reference position) and a film length of 200 m / cycle. The central portion of the film was continuously wound around a core having an outer diameter of 172 mm to form an intermediate roll. The porous film wound up as an intermediate roll had a length of 3,000 m and a thickness of 20 μm.
The intermediate roll was allowed to stand at room temperature for 24 hours, and then slitted with a slitter so that the product width was 600 mm and the length was 550 m. At that time, the film was wound around a core made of ABS resin and having an outer diameter of 162 mm to obtain a film roll.

(Comparative Example 5)
In Example 2, a film roll was obtained by setting the moving speed of oscillation when slitting to a film length of 600 m / cycle.

(Comparative Example 6)
In Example 5, when the movement speed of the oscillation was set to 40 m / cycle, the wrinkles were generated on the transport roll, and the film was wound around the intermediate roll with the wrinkles remaining. When slitting, notches were formed in the wrinkled part due to poor cutting, and film tearing occurred starting from there.

Claims (6)

A film roll obtained by slitting and winding a porous polyolefin film obtained by stretching at least uniaxially,
The porous polyolefin film is used as a separator film for an electricity storage device,
Wherein when the winding diameter distribution in the width direction of the film roll was measured, [Delta] R is the difference in diameter adjacent maxima diameter of the pole winding diameter distribution curve ([mu] m) is, 0.1～250Myuemu der is, winding length 1 , 100m or more film roll.   The film roll of Claim 1 whose absolute value of the inclination of the straight line which connects the adjacent maximum diameter and minimum diameter in the said winding diameter distribution curve is 0.01-10 micrometers / mm.   The film roll according to claim 1 or 2, wherein a difference between the maximum roll diameter and the minimum roll diameter of the film roll is 0.1 to 500 µm.   The film roll in any one of Claims 1-3 whose width W of the said film roll is 200-4,000 mm.   The film roll in any one of Claims 1-4 whose polyolefin which comprises the said porous polyolefin film is a polypropylene.   The porous polyolefin film has a ratio (TD / MD) of 5% elongation stress (F5 value) in the film longitudinal direction (MD) to 5% elongation stress (F5 value) in the film width direction (TD) (TD / MD). The film roll in any one of Claims 1-5 which is 3-2.0.