JP2014177524A - Method for manufacturing porous polypropylene film roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous polypropylene film roll used for obtaining a porous polypropylene film having a favorable flatness and exhibiting excellent characteristics when used as a separator.SOLUTION: A porous polypropylene film is unwound from a porous polypropylene film roll, annealed within a temperature range of 60 to 100°C for 10-120 sec, and subsequently rewound.

Description

  The present invention relates to a method for producing a porous polypropylene film roll. Specifically, porous polypropylene that can be used suitably for separator applications in power storage devices that are easy to wrinkle during processing by improving the flatness of the film by unwinding and rewinding the porous film roll. The present invention relates to a method for producing a porous polypropylene film roll from which a film is obtained.

  Porous films include various separators such as batteries and electrolytic capacitors, various separation membranes (filters), absorbent articles represented by diapers and sanitary products, moisture-permeable waterproof members for clothing and medical use, members for heat-sensitive paper, inks There are various uses such as a receptor member, and a polyolefin-based porous film represented by polypropylene and polyethylene is mainly used. Porous polyolefin films are particularly used as power storage device separators because of their high permeability and low specific gravity.

  An electricity storage device is one of the extremely important electrical devices that support today's ubiquitous society because it can take out electrical energy whenever and wherever it is needed. On the other hand, with the widespread use of portable devices such as video cameras, personal computers, mobile phones, portable music players, and portable game machines, the need for high capacity, small size and light weight for power storage devices (especially secondary batteries) is increasing year by year. . Among them, lithium ion batteries have a high energy density per unit volume and mass as compared with other power storage devices, and have a high output density. Therefore, demand for lithium ion batteries is greatly increasing as power storage devices that satisfy the above needs.

Furthermore, in recent years, global warming, air pollution, oil depletion, CO ₂ emission regulations, and the like have become problems, and the environmental burden of automobiles is becoming a major problem. Therefore, electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles can be one of the solutions such as environmental measures (cleaning), energy saving measures (improvement of fuel consumption), and next-generation fuel measures (new energy development). Development and commercialization of (FCV) and the like are being actively studied. As these main power supply and auxiliary power supply, for example, lithium ion batteries, electric double layer capacitors, and the like are attracting attention, and application studies are being rapidly promoted.

  Here, as a required characteristic of the said lithium ion battery separator, the flatness of a film is mentioned. If the flatness is poor, wrinkles are generated during film processing for separator applications, which causes a loss in battery production.

  Patent Document 1 discloses a manufacturing method in which dimensional stability is improved by heat-treating a porous polyolefin film roll and adjusting the heat treatment temperature, the heat treatment time, and the tension at the time of winding the roll. However, although the thermal dimensional stability is improved by this method, it is insufficient for improving the flatness of the film.

  In patent document 2, in the manufacturing process of the film which added the inorganic filler to the polyethylene-type resin, after extending | stretching, the heat processing temperature and the heat processing time are adjusted, and it heat-processes, The thickness uniformity and the flexible porous The manufacturing method of an adhesive film is disclosed. However, there are concerns about the shutdown of the holes due to heat treatment in the vicinity of the softening point, there is a concern that the production conditions are not necessarily sufficient to fulfill the function as a separator, and the heat treatment is a description assuming immediately after stretching, This is a manufacturing method different from the present invention.

  Patent Document 3 discloses a method of annealing the uniaxially stretched polypropylene resin microporous film to suppress the heat shrinkage rate. However, since the treatment temperature is too high, wrinkles may be induced in the process, which is not sufficient as a technique for achieving both flatness and process wrinkles.

JP 2010-1000084 A JP 2002-128828 A JP 2012-64556 A

  An object of the present invention is to solve the above-described problems. That is, it is to provide a separator with improved planarity by unwinding a porous polypropylene film roll, heat-treating it, and rewinding it, whereby a porous polypropylene film that can be suitably used for a lithium ion secondary battery Is to provide a porous polypropylene film roll.

  The above-described problems can be achieved by a method for producing a porous polypropylene film roll that is wound up again after unwinding the porous polypropylene film roll and performing annealing treatment at 60 to 100 ° C. for 10 to 120 seconds. it can.

  The porous polypropylene film obtained from the porous polypropylene film roll produced by the present invention is excellent in flatness suitable for a separator for a lithium ion secondary battery, and can be suitably used as a separator.

  In the production method of the porous polypropylene film roll of the present invention, it is important to unwind the roll formed by winding the porous polypropylene film around the core from the viewpoint of improving the flatness and to perform the annealing treatment at a predetermined temperature and time. It is. By carrying out the annealing treatment, the shrinkage unevenness of the entire film can be improved and the flatness can be improved by causing sufficient shrinkage to occur even at the portion where the room temperature shrinkage is insufficient.

  The annealing temperature of a film roll (hereinafter sometimes simply referred to as a film roll) wound with a porous polyolefin film is preferably 60 to 100 ° C, more preferably 70 to 90 ° C. If the heat treatment temperature is less than 60 ° C., the effect of the annealing treatment is not obtained, and the flatness may not be improved. Moreover, when it exceeds 100 degreeC, a film will unwind by a dimensional change, a wrinkle will enter during conveyance, and it may not wind up with a good winding form.

  As described above, in the annealing process, the flatness is improved, but wrinkles are generated.There is a trade-off between flatness improvement and wrinkle generation, but as a device to solve it, Introducing film wrinkle removal equipment in the process to achieve both improvement in flatness and suppression of wrinkle generation. The film wrinkle removal equipment includes an expander roller, an ear nip roller, and the like. The film wrinkle is conveyed by applying tension to the film in the TD direction (direction perpendicular to the film running direction (MD direction)). Winding wrinkles can be improved.

  The heat treatment time for the film roll is preferably 10 to 120 seconds, more preferably 20 to 100 seconds. If the heat treatment time is less than 10 seconds, there is a possibility that the heat treatment effect is not obtained and the improvement of the thermal dimensional stability cannot be achieved. If it exceeds 120 seconds, wrinkles may occur during conveyance and the roll may not be wound.

  As a method of annealing treatment, there are a method of heating a metal roll through a heat medium, a method of putting it in a hot air oven, etc., but any method can be used as long as it can be set to any temperature, and any method other than the above can also set the film to any temperature Therefore, any means capable of transferring heat may be used. The tension during conveyance is preferably 1 to 200 N / m, and more preferably 10 to 180 N / m. If the tension is less than 1 N / m, the conveyance may not be stable and may loosen in the oven and come into contact with the equipment. On the other hand, if the conveyance tension exceeds 200 N / m, the film may be pulled and wrinkles may occur.

  In the present invention, the porous polypropylene film has many fine through holes that penetrate both surfaces of the film and have air permeability. Examples of the monomer component constituting the polypropylene resin include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, and 4-methyl. -1-pentene, 5-ethyl-1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, vinyl Cyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene, and at least two copolymers selected from propylene as a main component from the above monomer components, and homopolymers thereof, Examples include, but are not limited to, blends of copolymers. In addition to the above monomer components, for example, vinyl alcohol, maleic anhydride or the like may be copolymerized or graft polymerized, but is not limited thereto.

  As a method for forming the through-hole in the film, either a wet method or a dry method may be used, but a dry method is desirable because the process can be simplified. As a dry method, for example, by adopting low-temperature extrusion and high draft ratio at the time of melt extrusion, the lamella structure in the film before stretching is controlled, and this is uniaxially stretched to cleave at the lamella interface. There is a method called lamellar stretching method for generating and forming voids. There is also a method in which a large amount of incompatible resin is added as particles to inorganic particles or polypropylene as a matrix resin, and a sheet is formed and stretched to cause cleavage at the particle-resin interface to form voids. It can be illustrated. Furthermore, it is called the β crystal method, in which voids are formed 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. A method can also be adopted. Among them, in the present invention, it is preferable to use the β crystal method from the viewpoint that the film is biaxially oriented and the physical properties are uniform and high strength can be maintained while being a thin film.

  In order to form through-holes in the film using the β crystal method, it is important to form a large amount of β crystals in the polypropylene resin. For this purpose, it is added to the polypropylene resin, which is called a β crystal nucleating agent. Thus, a crystallization nucleating agent that selectively forms β crystals is preferably used as an additive. Examples of the β crystal nucleating agent include various pigment compounds and amide compounds. In particular, amide compounds disclosed in JP-A-5-310665 can be preferably used. The addition amount of the β crystal nucleating agent is preferably 0.05 to 0.5 parts by mass, more preferably 0.1 to 0.3 parts by mass when the entire polypropylene resin is 100 parts by mass. .

  The polypropylene resin constituting the porous polypropylene film is an isotactic polypropylene resin having a melt flow rate (hereinafter referred to as MFR, measurement conditions are 230 ° C., 2.16 kg) in the range of 2 to 30 g / 10 min. preferable. If the MFR is out of the above preferred range, it may be difficult to obtain a biaxially stretched film. More preferably, the MFR is 3 to 20 g / 10 minutes.

  Further, the isotactic index of the isotactic polypropylene resin is preferably 90 to 99.9%, and if the isotactic index is less than 90%, the resin has low crystallinity and achieves high air permeability. It can be difficult. As the isotactic polypropylene resin, a commercially available resin can be used.

  Of course, homopolypropylene resin can be used for the polypropylene film, as well as ethylene component, butene, hexene, octene, etc., from the viewpoint of stability in the film-forming process, film-forming property, and uniformity of physical properties. The α-olefin component may be copolymerized within a range of 5% by mass or less. The form of the comonomer introduced into the polypropylene may be either random copolymerization or block copolymerization.

  Since the porous polypropylene film is preferably made porous by the β crystal method, the β crystal forming ability of the polypropylene resin constituting the film is preferably 30 to 100%. If the β-crystal forming ability is less than 30%, the amount of β-crystals is small at the time of film production, so the number of voids formed in the film is reduced by utilizing the transition to α-crystal, and as a result, only a film with low permeability is used. It may not be obtained. In order to make the β crystal forming ability in the range of 30 to 100%, it is preferable to add the above β crystal nucleating agent as well as using a polypropylene resin having a high isotactic index. The β-crystal forming ability is more preferably 35 to 90%.

  In the present invention, the above-described core for winding the porous polypropylene film into a roll shape is a cylindrical one, and the material thereof is not particularly limited, such as paper, plastic, a combination thereof, and foamed polyethylene. A simple cushion material may be applied evenly to the core surface. Moreover, a film roll means what wound up the said porous polyolefin film on a core. Examples of the winding method include a method of winding a porous polypropylene film around the core by applying a tension with a winding motor.

  The winding tension when winding the porous polypropylene film around the core is preferably 1 to 200 N / m, more preferably 5 to 100 N / m. When the winding tension is less than 1 N / m, the film roll may be displaced. On the other hand, when the winding tension exceeds 200 N / m, the porous film may be tightened and air permeability may be hindered.

  The winding length of the film roll in the present invention is preferably 100 to 10,000 m, and more preferably 300 to 1,000 m from the viewpoint of productivity. If the roll length of the film roll is less than 100 m, it may be difficult to maintain the shape as a film roll. Moreover, when it exceeds 10,000 m, the hole of a film may be crushed by dead weight.

  The porous polypropylene film of the present invention includes an antioxidant, a heat stabilizer, an antistatic agent, a lubricant composed of inorganic or organic particles, and further an antiblocking agent and a filler as long as the effects of the present invention are not impaired. Various additives such as an incompatible polymer may be contained. In particular, it is preferable to add 0.01 to 0.5 parts by mass of an antioxidant with respect to 100 parts by mass of the polypropylene resin for the purpose of suppressing oxidative degradation due to the thermal history of the polypropylene resin.

  Below, the manufacturing method of the porous polyolefin film of this invention is demonstrated concretely. As a polypropylene resin, 99.8 parts by mass of a commercially available homopolypropylene resin having an MFR of 8 g / 10 min was mixed with 0.2 part by mass of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide, and a twin screw extruder was used. Use to prepare raw materials mixed in advance at a predetermined ratio. At this time, the melting temperature is preferably 270 to 300 ° C.

  Next, the mixed raw material is supplied to a single-screw melt extruder, and melt extrusion is performed at 200 to 230 ° C. And after removing a foreign material, a modified polymer, 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. At this time, the surface temperature of the cast drum is preferably 105 to 130 ° C. from the viewpoint of controlling the β crystal fraction of the cast film to be high. At this time, particularly, the forming of the end portion of the sheet affects the subsequent stretchability, and therefore it is preferable that the end portion is sprayed with spot air to be in close contact with the drum. Further, air may be blown over the entire surface using an air knife as necessary from the state in which the entire sheet is in close contact with the drum.

  Next, the obtained unstretched sheet is biaxially oriented to form pores in the film. As a biaxial orientation method, the film is stretched in the longitudinal direction of the film and then stretched in the width direction, or the sequential biaxial stretching method in which the film is stretched in the width direction and then stretched in the longitudinal direction. The simultaneous biaxial stretching method can be used, but it is preferable to adopt the sequential biaxial stretching method in that it is easy to obtain a highly air permeable film, and in particular, stretching in the longitudinal direction and then stretching in the width direction. Is preferred.

  As specific stretching conditions, first, the temperature is controlled so that the unstretched sheet is stretched in the longitudinal direction. As a temperature control method, a method using a temperature-controlled rotating roll, a method using a hot air oven, or the like can be adopted. The stretching temperature in the longitudinal direction is preferably 90 to 120 ° C, more preferably 95 to 110 ° C. As a draw ratio, it is 3-6 times, More preferably, it is 3-5 times. Next, after cooling, the end of the film is gripped and introduced into a stenter type stretching machine. And it heats to 140-155 degreeC preferably, and extends 5 to 12 times in the width direction, More preferably, it extends 6 to 10 times. The transverse stretching speed at this time is preferably 100 to 4,000% / min, more preferably 100 to 2,000% / min. Subsequently, heat setting is performed in the stenter as it is, and the temperature is preferably from the transverse stretching temperature to 160 ° C. Further, the heat setting may be performed 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 preferably 7 to 12% from the viewpoint of thermal dimensional stability.

  Next, the obtained biaxially stretched film is rolled up by a winder to obtain a film roll. The film roll is slit to a predetermined width, and is wound around the core under a certain winding tension.

  The film roll of the present invention may be annealed while being slit from a winder to a predetermined width and wound, or after the slit roll is unwound, annealed and wound again. In addition, when wrinkles are generated when the roll is wound, facilities for preventing the generation of wrinkles by applying tension in the TD direction such as an expander roller and an ear nip roller may be introduced.

  The porous polypropylene film thus obtained has good flatness and excellent processing suitability, and can be suitably used as a separator for an electricity storage device.

  The method for producing a porous polypropylene film roll of the present invention can improve the flatness of the porous film by a simple means. Therefore, the porous polypropylene film obtained from the porous polypropylene film roll of the present invention can be suitably used as a separator for an electricity storage device.

  Here, examples of the electricity storage device include a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery, and an electric double layer capacitor such as a lithium ion capacitor. 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 vehicles, and the like. The electricity storage device using the porous polyolefin film obtained by the present invention as a separator can suppress internal short circuit and improve safety.

  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 on an aluminum pan and measured using a differential scanning calorimeter (RDC220 manufactured by Seiko Denshi Kogyo). First, the temperature is raised from room temperature to 240 ° C. at 10 ° C./min (first run) in a nitrogen atmosphere, held for 10 minutes, and then cooled to 30 ° C. at 10 ° C./min. After holding for 5 minutes, the melting peak observed when the temperature is raised again at 10 ° C./min (second run) is the melting peak of the β crystal at 145 ° C. to 157 ° C., 158 ° C. The melting at which the peak is observed is defined as the melting peak of the α crystal, and the melting heat amount of the α crystal is obtained from the baseline and the area of the region surrounded by the peak drawn from the flat portion on the high temperature side. Is the ΔHα, and the heat of fusion of the β crystal is ΔHβ, the value calculated by the following formula 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) Melt flow rate (MFR)
The MFR of polypropylene and thermoplastic elastomer is measured according to the condition M (230 ° C., 2.16 kg) of JIS K 7210 (1995). The polyethylene resin is measured in accordance with the condition D (190 ° C., 2.16 kg) of JIS K 7210 (1995).

(3) Planarity The planarity of the porous polypropylene film roll can be confirmed visually by unwinding the film roll for 1 hour and then unwinding the film roll for 1 m and applying a load. It was evaluated as follows according to the load mass. For example, 1 kg / m means a load of 1 kg per 1 m of roll width.

◎: Tarmi disappears at less than 0.5 kg / m ○: Tarmi disappears at from 0.5 kg / m to less than 1.5 kg / m Δ: Tarmi disappears at from 1.5 kg / m to less than 3 kg / m ×: 3.0 kg / m (4) Process wrinkle The wrinkles generated on the film roll after being transported, wound, and wound are visually evaluated according to the following criteria.

◎: No wrinkle on the roll, during winding, and film roll after winding ○: Wrinkles are observed on some transport rolls, but there is no wrinkle on the film roll during and after winding △: Wrinkles are seen on some of the transport rolls, and slight wrinkles are seen on the film roll being wound, but it cannot be confirmed as a film roll after winding.

  X: Wrinkles are observed even during winding of the transport roll, and wrinkles can also be confirmed on the film roll after winding.

(Experimental example 1)
As a raw material resin for porous polypropylene film, 99.8 parts by mass of homopolypropylene FSX80E4 manufactured by Sumitomo Chemical Co., Ltd., and N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide as a β crystal nucleating agent Rika Co., Ltd. (Nu-100) 0.2 parts by mass, and further, the antioxidants BASF IRGANOX1010 and IRGAFOS168 are mixed at a ratio of 0.15 and 0.1 parts by mass, respectively. The raw material was supplied from the hopper to the twin screw extruder, melt kneaded at 300 ° C., discharged from the die in a strand shape, cooled and solidified in a 25 ° C. water bath, cut into a chip shape, and used as a chip raw material.

  This chip is supplied to a single screw extruder and melt extruded at 220 ° C. After removing foreign matter with a 30 μm cut sintered filter, it is discharged from a T-die to a cast drum whose surface temperature is controlled at 120 ° C. An unstretched sheet was obtained by casting for 15 seconds. Next, preheating was performed using a ceramic roll heated to 100 ° C., and the film was stretched 5 times in the longitudinal direction of the film. After cooling, the end portion was introduced into a tenter-type stretching machine by holding it with a clip, and stretched 6 times at 150 ° C. at a stretching rate of 1,500% / min. As it was, heat treatment was performed at 155 ° C. for 7 seconds while relaxing 5% in the width direction to obtain a porous polypropylene film having a width of 1 m and a thickness of 20 μm.

Example 1
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 80 ° C. for 60 seconds, wound at a winding tension of 100 N / m, and then evaluated for process wrinkles and flatness of the obtained film roll, and the results are shown. It was shown in 1.

(Example 2)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 60 ° C. for 10 seconds, and taken up at a take-up tension of 100 N / m. It was shown in 1.

(Example 3)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 100 ° C. for 120 seconds, and wound at a winding tension of 100 N / m, and then the process wrinkles and flatness of the obtained film roll were evaluated to show the results. It was shown in 1.

Example 4
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 80 ° C. for 60 seconds, and wound at a winding tension of 1 N / m. It was shown in 1.

(Example 5)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 80 ° C. for 60 seconds, an expander roller was used as the treated conveyance roll, and the film roll was obtained with a winding tension of 1 N / m. The process wrinkles and flatness were evaluated, and the results are shown in Table 1.

(Example 6)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 80 ° C. for 60 seconds, and wound at a winding tension of 200 N / m. It was shown in 1.

(Example 7)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 80 ° C. for 60 seconds, wound up at a winding tension of 250 N / m, and then the process wrinkles and flatness of the obtained film roll are evaluated to show the results. It was shown in 1.

(Example 8)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 100 m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 80 ° C. for 60 seconds, and wound at a winding tension of 100 N / m. It was shown in 1.

Example 9
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 10,000 m winding film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 80 ° C. for 60 seconds, wound at a winding tension of 100 N / m, and then evaluated for process wrinkles and flatness of the obtained film roll, and the results are shown. It was shown in 1.

(Example 10)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 12,000 m winding film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll is unwound, annealed while being conveyed at 80 ° C. for 60 seconds, wound at a winding tension of 100 N / m, and then evaluated for process wrinkles and flatness of the obtained film roll, and the results are shown. It was shown in 1.

(Comparative Example 1)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000 m winding film roll was obtained at a winding tension of 100 N / m on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. The process wrinkles and flatness of the obtained film roll were evaluated and the results are shown in Table 1.

(Comparative Example 2)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 50 ° C. for 60 seconds, and wound at a winding tension of 100 N / m, and then the process wrinkles and flatness of the obtained film roll were evaluated, and the results were shown. It was shown in 1.

(Comparative Example 3)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 110 ° C. for 60 seconds, and wound at a winding tension of 100 N / m, and then the process wrinkles and flatness of the obtained film roll were evaluated, and the results were shown. It was shown in 1.

(Comparative Example 4)
The porous polypropylene film produced in Experimental Example 1 was slit to a width of 700 mm, and a 5,000-m roll film roll was obtained on a plastic core having an inner diameter of 152.4 mm and an outer diameter of 172.4 mm. Next, the film roll was unwound, annealed while being conveyed at 80 ° C. for 130 seconds, and wound at a winding tension of 100 N / m. Then, the resulting film roll was evaluated for process wrinkles and flatness, and the results were shown. It was shown in 1.

  The porous film obtained by the production method of the present invention can be provided as a porous film having excellent thermal dimensional stability and good battery characteristics.

Claims (4)

A method for producing a porous polypropylene film roll, comprising unwinding a porous polypropylene film from a porous polypropylene film roll, performing annealing treatment at a temperature of 60 to 100 ° C. for 10 to 120 seconds, and then rewinding. The manufacturing method of the porous polypropylene film roll of Claim 1 whose winding tension | tensile_strength is 1-200 N / m. The manufacturing method of the porous polypropylene film roll of Claim 1 or 2 whose winding length is 100-10,000m. The separator for electrical storage devices which uses the porous polypropylene film obtained from the porous polypropylene film roll manufactured by the method in any one of Claims 1-3.