WO2021070917A1 - ポリオレフィン微多孔膜 - Google Patents

ポリオレフィン微多孔膜 Download PDF

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WO2021070917A1
WO2021070917A1 PCT/JP2020/038210 JP2020038210W WO2021070917A1 WO 2021070917 A1 WO2021070917 A1 WO 2021070917A1 JP 2020038210 W JP2020038210 W JP 2020038210W WO 2021070917 A1 WO2021070917 A1 WO 2021070917A1
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Prior art keywords
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polyolefin
microporous membrane
film
mass
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PCT/JP2020/038210
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English (en)
French (fr)
Japanese (ja)
Inventor
まな 川知
博 宮澤
学 関口
伸弥 久光
佳輝 小田
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Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
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Asahi Kasei Corp
Asahi Chemical Industry Co Ltd
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Priority to CN202080070450.1A priority Critical patent/CN114555687B/zh
Priority to EP20874698.2A priority patent/EP4043516A4/en
Priority to KR1020227008877A priority patent/KR102909894B1/ko
Priority to JP2021551709A priority patent/JP7140926B2/ja
Priority to US17/765,190 priority patent/US20220389203A1/en
Publication of WO2021070917A1 publication Critical patent/WO2021070917A1/ja
Anticipated expiration legal-status Critical
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    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
    • C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • C—CHEMISTRY; METALLURGY
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    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
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    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/20—Manufacture of shaped structures of ion-exchange resins
    • C08J5/22—Films, membranes or diaphragms
    • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
    • C08J5/2275—Heterogeneous membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
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    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
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    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B29C48/92—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/04—Monomers containing three or four carbon atoms
    • C08F210/06—Propene
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    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
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    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/10—Homopolymers or copolymers of propene
    • C08L23/12—Polypropene
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
    • B29C61/06—Making preforms having internal stresses, e.g. plastic memory
    • C—CHEMISTRY; METALLURGY
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    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
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    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene
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    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/04—Homopolymers or copolymers of ethene
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    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
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    • C08L2203/00—Applications
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    • C08L2205/00—Polymer mixtures characterised by other features
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    • C08L2207/062—HDPE
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a microporous polyolefin membrane.
  • Polyolefin microporous membranes are used for battery separators, capacitor separators, fuel cell materials, precision filtration membranes, etc. because they exhibit excellent electrical insulation and ion permeability, and are particularly used for lithium ion secondary batteries. It is used as a separator.
  • lithium-ion secondary batteries have also been used in small electronic devices such as mobile phones and notebook computers, and in electric vehicles such as electric vehicles and small electric motorcycles.
  • Lithium-ion secondary battery separators are required to have not only mechanical properties and ion permeability, but also high safety against collision tests and moderately low rigidity in the manufacturing process of square batteries.
  • control of physical properties by the strain rate at the time of stretching has been studied, and it has become possible to eliminate the trade-off of physical properties, which has been difficult to realize by controlling the strain rate (strain rate control).
  • Patent Document 1 proposes a method for producing a microporous polyolefin membrane having a small springback. It teaches that the internal stress of the entire film can be reduced and the springback can be reduced by performing a relaxation operation after the primary stretching. However, Patent Document 1 does not pay attention to the collision safety of the battery, and there is room for improvement in the collision safety.
  • Patent Document 2 defines the ratio of the thermal shrinkage rate at 120 ° C. to the thermal shrinkage rate at 130 ° C. in order to suppress thermal runaway of the battery, and the film maintains its dimensions at 120 ° C. and melts at 130 ° C.
  • the development of a membrane that can suppress the thermal runaway of the battery by shutting down is described.
  • the ratio of the strain rate of MD and TD at the time of biaxial stretching or sequential stretching is 1.2 or more and 1.8 or less, and the stretching strain in the heat fixing step is 20% / sec or more.
  • the relaxation rate is 10% / sec or less.
  • the film described in Patent Document 2 tends to sacrifice strength for controlling heat shrinkage, and there is room for improvement from the viewpoint of battery collision safety.
  • Patent Document 3 proposes a polyolefin microporous membrane having low puncture elongation and low TMA stress, and teaches that thermal runaway of a battery can be suppressed by controlling puncture elongation and stress within a specific range.
  • the strain rate ratio of TD in the primary stretching step and the heat fixing step is set to 2.0 or more and 10.0 or less, and the strain rate of MD during simultaneous biaxial stretching is 20% / sec or more and 50% or more. It is taught to set it to / sec or less.
  • Patent Document 3 does not study the strain rate of relaxation in the heat fixing step, and there is room for improvement in increasing the bending rigidity and the puncture strength of the film.
  • Patent Document 4 when the gel-like sheet is stretched, the strain rate is preferably set to 3% / sec or more to make the pore structure uniform and dense, and to realize both shutdown characteristics and heat resistance. Are considering. However, Patent Document 4 does not describe the strain rate of the relaxation treatment in the heat fixing step, nor does it mention the flexural rigidity of the polyolefin microporous film.
  • Patent Document 5 the composition of the surface layer and the intermediate layer in the laminated film is kept within a specified range, so that the heat shrinkage rate at 120 ° C. in TMA measurement is kept within 10% or more and 40% or less, whereby during hot pressing. It is described that the distortion of the battery or the deterioration of the cycle characteristics is suppressed.
  • Patent Document 5 has a film design that suppresses the strength in order to suppress the heat shrinkage rate, and there is room for improvement in battery safety.
  • Lithium-ion secondary batteries are available in various shapes such as cylindrical, square, and pouch types depending on the application.
  • the method of manufacturing a battery differs depending on the shape of the battery, but in manufacturing a square battery, there is a step of pressing a wound body or a laminated body of an electrode and a polyolefin film and inserting it into a rectangular parallelepiped outer can.
  • the wound body repels and springs back due to the rigidity of the polyolefin microporous film immediately after the press pressure is released.
  • the thickness of the wound body is larger than the thickness of the outer can. Therefore, when using a highly rigid polyolefin microporous film, it is necessary to reduce the number of wounds of the wound body in consideration of the springback amount. It was. Reducing the number of turns of the winder leads to a decrease in the energy density of the battery because the amount of electrodes used decreases. Therefore, development has been carried out to increase the number of turns of the wound body as much as possible.
  • the adoption of the zigzag method has been increasing in laminated bodies from the viewpoint of improving energy density.
  • the positive electrode and the negative electrode are inserted alternately while alternately folding back so that the upper and lower surfaces of the separator are interchanged.
  • the bent portion is springed back in an attempt to return to the original shape due to the rigidity of the polyolefin microporous film. Therefore, as in the case of the wound body, it is necessary to reduce the number of layers in consideration of the springback amount, so that the problem is that the energy density is lowered.
  • the problem to be solved by the present invention is to realize a high energy density of a square battery, and to ensure collision safety while having a high energy density. It is to provide a porous membrane.
  • the present inventors have found that the above problems can be solved by specifying the flexural rigidity and the puncture strength in terms of grain of the polyolefin microporous film, and have completed the present invention. That is, the present invention is as follows. [1] The bending coefficient is a value obtained by dividing the flexural rigidity (gf ⁇ cm 2 / cm) in the longitudinal direction (MD) by the cube of the film thickness ( ⁇ m) when the film thickness is 1.0 ⁇ m or more and 17.0 ⁇ m or less.
  • the present invention by controlling the flexural rigidity of the polyolefin microporous film to low rigidity, springback when inserting the wound body and the laminated body into the outer can in the manufacturing process of the square battery is suppressed, which in turn suppresses springback.
  • the number of turns and the number of layers can be increased. This makes it possible to increase the energy density of the square battery.
  • the microporous polyolefin membrane of the present invention can achieve both low rigidity and collision safety.
  • FIG. 1 is a schematic view for explaining the measurement mechanism of the pure bending test.
  • the point P is fixed, the point Q is movable, and the point Q moves as shown by the curve of FIG. 1 during the test to increase the bending rigidity.
  • the MD shown in FIG. 1 is a sample setting direction when measuring the flexural rigidity of the MD.
  • FIG. 2 is a schematic view of a collision test.
  • the longitudinal direction (MD) means the mechanical direction of continuous molding of the microporous membrane
  • the width direction (TD) means the direction across the MD of the microporous membrane at an angle of 90 °.
  • One aspect of the present invention is a polyolefin microporous membrane.
  • the polyolefin microporous membrane used in the square battery is preferably one having low flexural rigidity in consideration of springback when winding the electrode and the separator. Further, since the polyolefin microporous membrane can be used as a separator for a secondary battery, it is preferable that the piercing strength is high from the viewpoint of battery collision safety.
  • the microporous polyolefin membrane according to the embodiment of the present invention has a bending coefficient of 0.3 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or more and 1.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less. It is characterized by.
  • the bending coefficient is a value obtained by dividing the bending rigidity [gf ⁇ cm 2 / cm] in the longitudinal direction (MD) measured by a pure bending tester by the cube of the film thickness [ ⁇ m].
  • the bending coefficient is lower than 0.3 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 , the rigidity of the polyolefin microporous film becomes too weak, and wrinkles occur when the electrodes and separator are wound and laminated. .3 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or more is preferable. Further, by suppressing the bending coefficient to 1.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less, the spring back after pressing in the wound body and the spring bag in the folded portion in the zigzag laminated body. It is possible to improve the energy density because the number of times the electrodes are wound and the number of layers can be increased.
  • the polydispersity (Mw / Mn) of the polyolefin raw material In order to control the film thickness, bending coefficient, and puncture strength in terms of grain size in a good balance, the polydispersity (Mw / Mn) of the polyolefin raw material, the stretching ratio in the longitudinal direction in the stretching step, and the strain of stretching in the heat fixing step. It is important to control the speed, the strain rate of relaxation in the heat fixing step, and the temperature and stretching ratio in the fine stretching step.
  • Flexural rigidity is an index that indicates the difficulty of bending deformation of a material, and indicates the force that the material tries to return to its original shape when the material is bent.
  • the bending rigidity is proportional to the cube of the thickness.
  • the film thickness of the polyolefin microporous membrane is reduced in order to reduce the rigidity, the amount of resin per unit area is reduced and the safety of the battery is lowered. Therefore, in the present embodiment, we have developed a polyolefin microporous membrane that realizes low rigidity and can suppress springback and has good battery safety.
  • the flexural rigidity is defined as FIG. 1 as shown in FIG. 1 by fixing two opposing sides of a sample cut out to MD 20 cm ⁇ TD 20 cm with a chuck, fixing one of them, and moving one opposite side in a curved shape. It means the force that the sample tries to return to its original flat state when it is bent into a curved shape. Generally, this acting force is called “flexural rigidity" and is an index showing the flexibility of the sample with respect to the bending motion.
  • the present invention is characterized in that the value obtained by dividing the bending rigidity by the cube of the film thickness is small, and a film having high flexibility to bending is preferable.
  • the bending coefficient is 1.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less, springback does not occur in the electrode laminating process by the spiral folding method, and by extension, the spring is also used when inserting the wound body into the outer can of the battery. Since it is not necessary to consider the back amount, it is possible to increase the number of laminated electrodes by that amount, and the energy density is improved.
  • the rigidity of the film is low when the electrode and the polyolefin microporous film are wound, so that the wound body of the electrode and the microporous film is wound. Even if you press, it does not spring back, and it is not necessary to consider the springback amount when inserting the winding body into the outer can of the battery, so it is possible to increase the number of times the electrode is wound by that amount, and the battery It is possible to improve the energy density of.
  • the lower limit of the bending coefficient of the polyolefin microporous film is 0.3 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or more, and 0.4 ( ⁇ gf ⁇ cm). 2 / cm) / ⁇ m 3 or more is preferable, and 0.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or more is more preferable.
  • the upper limit is 1.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less, preferably 1.35 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less, as described above.
  • 1.1 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less is more preferable, 1.0 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less is further preferable, and 0.9 ( ⁇ gf ⁇ cm 2).
  • / Cm) / ⁇ m 3 or less is more preferable, 0.8 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less is particularly preferable, and 0.7 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less is most preferable.
  • the piercing strength (gf) is measured as the maximum piercing load using a handy compression tester KES-G5 (trademark) manufactured by Kato Tech, and the value obtained by dividing the piercing strength by the basis weight is defined as the basis weight equivalent puncture strength. did.
  • the basis weight equivalent puncture strength is 70 gf / (g / m 2 ) or more.
  • the puncture strength As the puncture strength is increased, the rate of shrinkage when the microporous membrane receives heat (hereinafter referred to as heat shrinkage) generally increases. From the viewpoint of suppressing heat shrinkage, the upper limit of the basis weight equivalent puncture strength is 160 gf / (g / m 2 ) or less.
  • polyolefin microporous film examples include a porous film containing a polyolefin resin, a resin such as polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene.
  • a porous membrane containing a polyolefin resin (hereinafter, also referred to as “polyolefin microporous membrane”) is preferable from the viewpoint of achieving both high puncture strength and low flexural rigidity.
  • the polyolefin resin porous membrane will be described.
  • the polyolefin resin porous film is a polyolefin in which the polyolefin resin accounts for 50% by mass or more and 100% by mass or less of the resin component constituting the porous film from the viewpoint of improving the shutdown performance when the polyolefin microporous film for a secondary battery is formed. It is preferably a porous membrane formed of the resin composition.
  • the proportion of the polyolefin resin in the polyolefin resin composition is more preferably 60% by mass or more and 100% by mass or less, further preferably 70% by mass or more and 100% by mass or less, and most preferably 95% by mass or more and 100% by mass. It is mass% or less.
  • the polyolefin resin contained in the polyolefin resin composition is not particularly limited, and for example, ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like are used as monomers. Examples thereof include the obtained homopolymer, copolymer, and multistage polymer. Further, these polyolefin resins may be used alone or in combination of two or more.
  • polyethylene, polypropylene, ethylene-propylene copolymer, copolymer of ethylene-propylene-other monomers, and a mixture thereof are preferable as the polyolefin resin.
  • polyethylene examples include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, and the like.
  • polypropylene examples include isotactic polypropylene, syndiotactic polypropylene, and tacticic. Polypropylene, etc.
  • copolymer examples include ethylene-propylene random copolymer and ethylene propylene rubber.
  • the polyolefin resin porous membrane has a polyethylene composition in which polyethylene accounts for 50% by mass or more and 100% by mass or less of the resin component constituting the microporous membrane from the viewpoint of increasing the puncture strength when the polyolefin microporous membrane for a secondary battery is formed. It is preferably a porous membrane formed of an object.
  • the proportion of polyethylene in the resin component constituting the porous membrane is more preferably 60% by mass or more and 100% by mass or less, further preferably 70% by mass or more and 100% by mass or less, and most preferably 90% by mass. It is 100% by mass or less.
  • the polyolefin resin is preferably polyethylene having a melting point in the range of 120 ° C. or higher and 150 ° C. or lower, more preferably 125 ° C. or higher and 140 ° C. or lower.
  • the proportion of polyethylene in the polyolefin resin is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and preferably 100% by mass or less, 97 It is more preferably mass% or less, and further preferably 95 mass% or less.
  • the proportion of polyethylene in the polyolefin resin is 100% by mass, it is preferable from the viewpoint of developing strength.
  • polyethylene as a polyolefin resin, particularly medium It is preferable to use high density polyethylene (MDPE) or high density polyethylene (HDPE).
  • MDPE high density polyethylene
  • HDPE high density polyethylene
  • the medium density polyethylene refers to polyethylene having a density of 0.930 to 0.942 g / cm 3
  • the high density polyethylene refers to polyethylene having a density of 0.942 to 0.970 g / cm 3 . From the viewpoint of further reducing the flexural rigidity, medium density polyethylene is preferable.
  • the density of polyethylene means a value measured according to the density gradient tube method described in JIS K7112 (1999).
  • a mixture of polyethylene and polypropylene may be used as the polyolefin resin.
  • the ratio of polypropylene to the total polyolefin resin in the polyolefin resin composition is larger than 0% by mass, 20% by mass or less, or 1% by mass or more and 20% by mass from the viewpoint of reducing the bending rigidity of the film. It is preferably 2% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less.
  • the ratio of polypropylene to the total polyolefin resin in the polyolefin resin composition is preferably 3% by mass or more and 10% by mass or less, and preferably 5% by mass or more and 10% by mass or less.
  • Additives include, for example, polymers other than polyolefin resins; inorganic fillers; antioxidants such as phenol-based, phosphorus-based, and sulfur-based; metal soaps such as calcium stearate and zinc stearate; ultraviolet absorbers; light stabilizers. ; Antistatic agent; Antifogging agent; Colored pigment and the like.
  • the total amount of these additives added is preferably 20% by mass or less with respect to 100% by mass of the polyolefin resin from the viewpoint of improving shutdown performance and the like, more preferably 10% by mass or less, still more preferably 5% by mass. % Or less.
  • the viscosity average molecular weight (Mv) of the polyolefin resin used as a raw material is preferably 30,000 or more and 5,000,000 or less, more preferably 80,000 or more and 3 It is less than ⁇ 1,000,000, more preferably 150,000 or more and less than 2,000,000.
  • the viscosity average molecular weight is 30,000 or more, the strength tends to be high due to the entanglement of the polymers, which is preferable.
  • the viscosity average molecular weight is 5,000,000 or less, it is preferable from the viewpoint of controlling the rigidity of the polyolefin microporous film.
  • the polyolefin microporous membrane according to the embodiment of the present invention can be produced by a method for producing a polyolefin microporous membrane including the steps (A) to (E) described below as an example of the production method thereof.
  • the polydispersity (Mw / Mn) of the polyolefin raw material is preferably 4.0 or more and 12.0 or less.
  • the polydispersity (Mw / Mn) is measured according to a measurement method described later. When the polydispersity (Mw / Mn) is within this range, a certain amount of each of the high molecular weight component and the low molecular weight component is present, and the bending rigidity of the polyolefin microporous film is reduced while ensuring the puncture strength and heat resistance. It is preferable because it tends to be possible.
  • the lower limit of the polydispersity (Mw / Mn) of the polyolefin raw material is preferably 6.0 or more, more preferably 7.0 or more.
  • the upper limit thereof is preferably 12.0 or less, more preferably 10.0 or less, from the viewpoint of reducing the porosity during the heat fixing (HS) step. Therefore, the range of polydispersity of the polyolefin raw material is 6.0 or more and 12.0 or less, 7.0 or more and 12.0 or less, 4.0 or more and 10.0 or less, 6.0 or more and 10.0 or less, 7 It is preferable in the order of 0.0 or more and 10.0 or less.
  • the flexural rigidity to low rigidity it is preferable to contain 50% by mass or more of the raw materials having a polydispersity (Mw / Mn) of 4.0 or more and 12.0 or less, and 70% by mass or more. More preferred.
  • the polyolefin raw material for controlling the polydispersity is preferably polyethylene.
  • the ratio (Mz / Mw) of the Z average molecular weight and the weight average molecular weight of the polyolefin raw material is preferably 2.0 or more and 7.0 or less.
  • the ratio (Mz / Mw) is measured according to the measurement method in the examples described later.
  • the Mz / Mw of the polyolefin raw material is more preferably 4.0 or more, and further preferably 5.0 or more. Therefore, the range of Mz / Mw of the polyolefin raw material is preferably 4.0 or more and 7.0 or less, and 5.0 or more and 7.0 or less in this order.
  • the polyolefin microporous membrane Since the polyolefin microporous membrane has a porous structure in which a large number of very small pores are gathered to form dense communication pores, the polyolefin microporous membrane has excellent ion permeability and high strength in a state containing an electrolytic solution. It has the feature.
  • the microporous membrane may be a monolayer membrane made of the above-mentioned materials or a laminated membrane.
  • the lower limit of the film thickness of the microporous membrane is 1 ⁇ m (1.0 ⁇ m) or more in order to have mechanical strength and maintain insulation.
  • the film thickness is preferably 2 ⁇ m (2.0 ⁇ m) or more, and more preferably 3 ⁇ m (3.0 ⁇ m) or more.
  • the film thickness is preferably 6 ⁇ m (6.0 ⁇ m) or more.
  • the film thickness of the microporous membrane is 17.0 ⁇ m or less, preferably 15 ⁇ m (15.0 ⁇ m) or less, and more preferably 11 ⁇ m (11.0 ⁇ m) or less from the viewpoint of increasing the capacity of the secondary battery.
  • the film thickness of the microporous film can be adjusted by controlling the distance between the rolls of the cast roll, the stretching ratio in the stretching step, and the like.
  • the porosity of the microporous membrane is preferably 25% or more and 60% or less, more preferably 30% or more and 50% or less, and further preferably 35% or more and 45% or less.
  • the porosity of the microporous membrane is preferably 25% or more, more preferably 30% or more, still more preferably 35% or more from the viewpoint of output. From the viewpoint of battery safety, the porosity of the microporous membrane is preferably 60% or less, more preferably 50% or less, still more preferably 45% or less.
  • the pore ratio of the microporous film controls the mixing ratio of the polyolefin resin composition and the plasticizer, the stretching temperature, the stretching ratio, the heat fixing temperature, the stretching ratio at the time of heat fixing, the relaxation rate at the time of heat fixing, etc., or these Can be adjusted by combining.
  • the air permeability of the microporous film is preferably is preferably 30 sec / 100 cm 3 or more 250 sec / 100 cm 3 or less, more preferably 70 sec / 100 cm 3 or more 200 sec / 100 cm 3 or less, more preferably of 80 sec / 100 cm 3 or more 180 sec / 100 cm 3 , more preferably not more than 90 sec / 100 cm 3 or more 150 sec / 100 cm 3.
  • the air permeability of the microporous membrane is preferably 70 sec / 100 cm 3 or more from the viewpoint of ensuring puncture strength, and is preferably 200 sec / 100 cm 3 or less from the viewpoint of output characteristics.
  • the average pore size of the microporous membrane is preferably 0.010 ⁇ m or more and 0.080 ⁇ m or less, more preferably 0.020 ⁇ m or more, in order to achieve high ion permeability, excellent withstand voltage and high strength. It is more preferably 0.030 ⁇ m or more, particularly preferably 0.035 ⁇ m or more, or 0.040 ⁇ m or more, and most preferably 0.045 ⁇ m or more.
  • the upper limit of the average pore size is more preferably 0.075 ⁇ m or less, further preferably 0.070 ⁇ m or less, and particularly preferably 0.065 ⁇ m or less.
  • the average pore size can be adjusted by controlling the stretching temperature, stretching ratio, heat fixing temperature, stretching ratio at the time of heat fixing, relaxation rate at the time of heat fixing, or a combination thereof.
  • the puncture strength not converted into the basis weight of the microporous membrane is preferably 100 gf or more and 950 gf or less.
  • the puncture strength is preferably 100 gf or more from the viewpoint of battery safety, and is preferably 950 gf or less from the viewpoint of flexural rigidity and heat shrinkage of the polyolefin microporous membrane.
  • the lower limit of the puncture strength of the microporous membrane is more preferably 300 gf or more, and by setting it to 300 gf or more, when the battery collides or foreign matter is mixed between the electrode and the polyolefin microporous membrane.
  • the upper limit of the puncture strength of the microporous film is more preferably 870 gf or less, and by setting it to 870 gf or less, the polyolefin film is thermally shrunk even when the temperature inside the battery cell rises for some reason. It is more preferable because the insulation property is maintained and the safety is improved.
  • the puncture strength is more preferably 360 gf or more and 800 gf or less, particularly preferably 400 gf or more and less than 740 gf, and most preferably 450 gf or more and 700 gf or less.
  • the basis weight in terms of puncture strength of the microporous film is preferably 70gf / (g / m 2) or more from the viewpoint of safety in the battery, in view of the low rigidity of the film 160gf / (g / m 2 ) The following is preferable.
  • Basis weight in terms of puncture strength, in view of the balance between safety and thermal contraction of the battery 75gf / (g / m 2 ) or more 150gf / (g / m 2) and more preferably less, 80gf / (g / m 2 ) or more 140 gf / (g / m 2 ) or less is more preferable, 85 gf / (g / m 2 ) or more and 130 gf / (g / m 2 ) or less is particularly preferable, and 90 gf / (g / m 2 ) or more and 120 gf / (g / m 2) or more. 2 ) The following is most preferable.
  • the basis weight of the polyolefin microporous film is preferably 0.1 g / m 2 or more from the viewpoint of suppressing thermal runaway of the battery, and 20 g / m 2 or less from the viewpoint of increasing the capacity of the battery. More preferably, the basis weight of the polyolefin microporous membrane is 1 g / m 2 or more and 10 g / m 2 or less.
  • the absolute value of the withstand voltage of the microporous membrane is preferably 0.5 kV or more, more preferably 0.7 kV or more, further preferably 0.9 kV or more, and most preferably 1.1 kV or more from the viewpoint of battery safety.
  • the withstand voltage per unit film thickness of the microporous membrane is preferably 0.130 kV / ⁇ m or more, more preferably 0.140 kV / ⁇ m or more, and further preferably 0.150 kV / ⁇ m or more.
  • the meltdown temperature of the microporous membrane is preferably 150 ° C. or higher, more preferably 160 ° C. or higher, and even more preferably 170 ° C. or higher.
  • a meltdown temperature of 150 ° C. or higher means that the microporous membrane does not break up to 150 ° C., so that the safety of the secondary battery can be ensured.
  • the meltdown temperature can be adjusted within the range of 150 ° C. or higher depending on the molecular weight of the polyolefin, stretching and heat fixing conditions.
  • the shutdown temperature of the microporous membrane is preferably 150 ° C. or lower, more preferably 147 ° C. or lower, still more preferably 143 ° C. or lower, and most preferably 140 ° C. or lower.
  • a shutdown temperature of 150 ° C. or lower means that when some abnormal reaction occurs and the temperature inside the battery rises, the separator holes are closed by the time the temperature reaches 150 ° C. Therefore, the lower the shutdown temperature, the faster the flow of lithium ions between the electrodes stops at a low temperature, which improves safety.
  • the shutdown temperature of the microporous membrane is preferably 125 ° C. or higher, more preferably 130 ° C. or higher.
  • Tensile strength of the microporous membrane, MD, TD together is preferably 500 kgf / cm 2 or more, preferably 700 kgf / cm 2 or more, preferably 1000 kgf / cm 2 or more, or 1000 kgf / cm It is preferably 2 or more and 5000 kgf / cm 2 or less.
  • the membrane cannot withstand the stress applied when the electrode and the polyolefin microporous membrane are wound, and the membrane may break. From the viewpoint of suppressing thermal shrinkage of the polyolefin microporous membrane. Is preferably lower than 5000 kgf / cm 2.
  • the MD / TD tensile strength ratio of the polyolefin microporous membrane is preferably 0.80 or more and 1.20 or less, more preferably 0.85 to 1.15, and further preferably 0.90 or more 1 .10 or less, most preferably 0.95 or more and 1.05 or less.
  • the tensile elongation of the microporous membrane is preferably 10% or more, more preferably 30% or more, and most preferably 50% or more for both MD and TD. If the tensile elongation is lower than 10%, when the battery is deformed due to an external impact or the like, the deformation cannot be followed and the film breaks, so that the electrodes may come into contact with each other and cause a short circuit.
  • the production method of the present invention is not particularly limited, and an example thereof includes a method including the following steps: (A) A step of extruding a polyolefin composition containing a polyolefin resin and a pore-forming material to form a gel-like sheet; (B) A step of biaxially stretching a gel-like sheet to form a stretched sheet; (C) A step of extracting a pore-forming material from a stretched sheet to form a porous film; (D) A step of heat-fixing the porous film; and (E) A step of finely stretching the porous film to MD.
  • step (A) a polyolefin raw material having a polydispersity of 4.0 or more and 12.0 or less is used in an amount of 50% by mass or more, and the magnification in the longitudinal direction in step (B) is increased. It is 6 times or more and 10 times or less, and the stretching operation and the relaxation operation are included at least once in the step (D), and the strain rate of stretching in the step (D) is 11% / sec or less, and the stretching operation in the step (D).
  • the strain rate of relaxation is 10% / sec or less
  • MD microstretching of 1.0 to 5.0% is carried out at a temperature of the melting point of the polyolefin microporous film of ⁇ 70 ° C. to the melting point of ⁇ 30 ° C. It is characterized by that.
  • the manufacturing process and preferred embodiments of the polyolefin microporous membrane will be described below.
  • step (A) the polyolefin composition is extruded to form a gel-like sheet.
  • the polyolefin composition may contain a polyolefin resin, a pore-forming agent, and the like.
  • the gel-like sheet can be obtained by melt-kneading the polyolefin resin and the pore-forming material to form a sheet.
  • the polyolefin resin and the pore-forming material are melt-kneaded.
  • a melt-kneading method for example, a polyolefin resin and, if necessary, other additives are put into a resin kneading device such as an extruder, a kneader, a lab plast mill, a kneading roll, or a Banbury mixer to heat and melt the resin components.
  • a resin kneading device such as an extruder, a kneader, a lab plast mill, a kneading roll, or a Banbury mixer to heat and melt the resin components.
  • a method of introducing a pore-forming material at an arbitrary ratio and kneading include a method of introducing a pore-forming material at an arbitrary ratio and kneading.
  • the polyolefin resin contained in the polyolefin composition can be determined according to a predetermined resin raw material of the obtained polyolefin microporous film.
  • the polyolefin resin used in the extrusion step (A) may be the polyolefin resin described in relation to the polyolefin microporous membrane according to the embodiment of the present invention.
  • the proportion of the polyolefin resin in the polyolefin composition is preferably 10 to 80% by mass, more preferably 15 to 60% by mass, still more preferably 20 to 40, based on the mass of the polyolefin composition. It is mass%.
  • the polyolefin raw material preferably has a polydispersity (Mw / Mn) of 4.0 or more and 12.0 or less, and Mw / Mn of 4.0 or more and 12. Polyethylene of 0 or less is more preferable.
  • Mw / Mn polydispersity
  • the polyolefin resin contained in the polyolefin composition for step (A) can include polyethylene, or can include polyethylene and polypropylene.
  • the proportion of polyethylene may be 50% by mass or more and 100% by mass or less, and the proportion of polypropylene may be 0% or more and 20% by mass or less.
  • pore-forming material examples include plasticizers, inorganic materials, and combinations thereof.
  • the plasticizer is not particularly limited, but it is preferable to use a non-volatile solvent capable of forming a uniform solution above the melting point of polyolefin.
  • a non-volatile solvent capable of forming a uniform solution above the melting point of polyolefin.
  • specific examples of the non-volatile solvent include hydrocarbons such as liquid paraffin and paraffin wax; esters such as dioctyl phthalate and dibutyl phthalate; higher alcohols such as oleyl alcohol and stearyl alcohol. After extraction, these plasticizers may be recovered and reused by an operation such as distillation.
  • liquid paraffin has high compatibility with polyethylene or polypropylene when the polyolefin resin is polyethylene, and even if the melt-kneaded product is stretched, interfacial peeling between the resin and the plasticizer is unlikely to occur, and uniform stretching is possible. It is preferable because it tends to be easy to carry out.
  • the ratio of the polyolefin resin composition to the plasticizer can be determined according to the uniform melt-kneading and sheet moldability.
  • the mass fraction of the plasticizer in the composition composed of the polyolefin resin composition and the plasticizer is preferably 20 to 90% by mass, more preferably 50 to 70% by mass.
  • the mass fraction of the plasticizer is 90% by mass or less, the melt tension during melt molding tends to be sufficient for improving the moldability.
  • the mass fraction of the plasticizer is 20% by mass or more, the polyolefin molecular chain is not broken even when the mixture of the polyolefin resin composition and the plasticizer is stretched at a high magnification, and a uniform and fine pore structure is formed. It is easy to do, and the strength is also easy to increase.
  • the non-equipment is not particularly limited, and for example, oxide-based ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, itria, zinc oxide, and iron oxide; silicon nitride, titanium nitride, nitride.
  • oxide-based ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, itria, zinc oxide, and iron oxide
  • Nitride ceramics such as boron; silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite.
  • silica is particularly preferable because it is easy to extract.
  • the ratio of the polyolefin resin composition to the inorganic material is preferably 3% by mass or more, and more preferably 10% by mass or more, based on the total mass of these, from the viewpoint of obtaining good isolation.
  • it is preferably 60% by mass or less, and more preferably 50% by mass or less.
  • the melt-kneaded product is molded into a sheet to obtain a gel-like sheet.
  • the ratio of the extrusion speed of the polyolefin composition that is, the discharge rate Q: kg / hour of the extruder
  • the screw rotation speed N (rpm) of the extruder Q / N
  • the unit: kg / (h ⁇ rpm)) is preferably 0.1 or more and 7.0 or less, more preferably 0.5 or more and 6.0 or less, and further preferably 1.0 or more and 5.0 or less.
  • the melt-kneaded product is extruded into a sheet shape via a T-die or the like, brought into contact with a heat conductor, and cooled to a temperature sufficiently lower than the crystallization temperature of the resin component.
  • a heat conductor used for cooling and solidifying
  • the heat conductor used for cooling and solidifying include metals, water, air, and plasticizers.
  • sandwiching it between the rolls further enhances the efficiency of heat conduction, and the sheet is oriented to increase the film strength and the surface smoothness of the sheet.
  • the distance between the rolls of the cast rolls when the melt-kneaded product is extruded from the T-die into a sheet is preferably 200 ⁇ m or more and 3,000 ⁇ m or less, and more preferably 500 ⁇ m or more and 2,500 ⁇ m or less.
  • the distance between rolls of the cast roll is 200 ⁇ m or more, the risk of film breakage can be reduced in the subsequent stretching step, and when the distance between rolls is 3,000 ⁇ m or less, the cooling rate is high and uneven cooling can be prevented.
  • the extruded sheet-shaped molded product or gel-like sheet may be rolled. Rolling can be carried out by, for example, a method using a roll or the like.
  • the rolled surface magnification is preferably more than 1 time and 3 times or less, and more preferably more than 1 time and 2 times or less.
  • the rolling ratio exceeds 1 times, the plane orientation tends to increase, and the film strength of the finally obtained porous film tends to increase.
  • the rolling ratio is 3 times or less, the orientation difference between the surface layer portion and the inside of the center is small, and a uniform porous structure tends to be formed in the thickness direction of the film.
  • step (B) In the step (B), the gel-like sheet obtained in the step (A) is stretched. The step (B) is performed before the step (C) of extracting the pore-forming material from the sheet. In the step (B), the stretching treatment of the gel-like sheet is performed at least once in the longitudinal direction and the width direction (that is, by biaxial stretching) from the viewpoint of controlling the flexural rigidity of the polyolefin microporous film.
  • the stretching ratio in the longitudinal direction is preferably 6 times or more from the viewpoint of reducing the flexural rigidity in the longitudinal direction.
  • the plasticizer tends to suppress the orientation in the stretching direction as compared with the case where the resin and the plasticizer are stretched alone. There is a tendency to reduce the rigidity.
  • the strain rate in the longitudinal direction and the width direction in the step (B) is not particularly limited, but is preferably 3% / sec or more and less than 50% / sec, and 10 from the viewpoint of achieving both low rigidity and high strength. Most preferably% / sec or more and 30% / sec or less.
  • step (B) in order to facilitate the bending coefficient value of 0.3 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or more and 1.5 ( ⁇ gf ⁇ cm 2 / cm) / ⁇ m 3 or less, the longitudinal direction
  • the draw ratio of (MD) can be 6 times or more and 10 times or less.
  • the stretching ratio in the longitudinal direction is preferably 6 times or more and 9 times or less, and more preferably 7 times or more and 8 times. It is as follows.
  • stretching method examples include simultaneous biaxial stretching, sequential biaxial stretching, multi-stage stretching, and multiple stretching. Above all, simultaneous biaxial stretching is preferable from the viewpoint of improving the puncture strength, the uniformity of stretching, and the reduction of flexural rigidity.
  • simultaneous biaxial stretching refers to a stretching method in which stretching in the longitudinal direction and stretching in the width direction are performed at the same time, and the stretching ratio in each direction may be different.
  • Sequential biaxial stretching refers to a stretching method in which stretching in the longitudinal direction and the width direction is performed independently, and when stretching is performed in the longitudinal direction or the width direction, the other direction is in an unconstrained state or a constant length. It is assumed that it is fixed to.
  • the draw ratio in the step (B) is preferably in the range of 12 times or more and 120 times or less in terms of surface magnification, and more preferably in the range of 36 times or more and 65 times or less.
  • the stretching ratio in each axial direction is preferably in the range of 6 times or more and 10 times or less in the longitudinal direction and 2 times or more and 12 times or less in the width direction, 7 times or more and 9 times or less in the longitudinal direction, and 6 times in the width direction. It is more preferable that the range is 9 times or more.
  • the total area magnification is 12 times or more, sufficient strength tends to be imparted to the obtained porous film, while when the total area magnification is higher than 120 times, the rigidity of the film is difficult to control. Therefore, it is preferably 120 times or less.
  • the stretching temperature of the step (B) is preferably 90 to 150 ° C., more preferably 100 to 140 ° C., still more preferably 110 to 130 ° C. from the viewpoint of meltability and film forming property of the polyolefin resin.
  • the pore-forming material is removed from the sheet-shaped molded product to obtain a porous film.
  • the method for removing the pore-forming material include a method in which a sheet-shaped molded product is immersed in an extraction solvent to extract the pore-forming material and sufficiently dried.
  • the method for extracting the pore-forming material may be either a batch method or a continuous method.
  • the residual amount of the pore-forming material in the porous membrane is preferably less than 1% by mass with respect to the total mass of the porous membrane.
  • the extraction solvent used when extracting the pore-forming material it is preferable to use a solvent that is poor with respect to the polyolefin resin, is a good solvent with respect to the pore-forming material, and has a boiling point lower than that of the polyolefin resin.
  • examples of such an extraction solvent include hydrocarbons such as n-hexane and cyclohexane; halogenated hydrocarbons such as methylene chloride and 1,1,1-trichloroethane; non-chlorine type such as hydrofluoroether and hydrofluorocarbon.
  • Hydrocarbon solvents such as ethanol and isopropanol
  • ethers such as diethyl ether and tetrahydrofuran
  • ketones such as acetone and methyl ethyl ketone
  • an aqueous solution of sodium hydroxide, potassium hydroxide or the like can be used as the extraction solvent.
  • Heat fixing step (D) In the heat fixing step (D), in order to suppress the shrinkage of the polyolefin microporous film, after extracting the plasticizer in the step (C), the microporous film is heat-treated for the purpose of heat fixing.
  • the heat treatment of the porous membrane includes a stretching operation performed at a predetermined temperature atmosphere and a predetermined stretching ratio for the purpose of adjusting physical properties, and / or a predetermined temperature atmosphere and a predetermined relaxation for the purpose of reducing stretching stress. There is a mitigation operation performed at a rate. These heat treatments can be performed using a tenter or a roll stretching machine. It is preferable that heat fixing including stretching and relaxation operation after extraction of the plasticizer is performed in the width direction.
  • the stretching ratio of the film is 1.1 times or more, more preferably 1.3 times or more, and most preferably 1.5 times or more in the longitudinal direction and / or width direction of the film. This is preferable from the viewpoint of obtaining a porous film having higher strength and higher porosity.
  • the relaxation ratio is preferably 0.8 to 2.5 times, more preferably 1.2 to 2.3 times, and even more preferably 1.5 to 2.0 times.
  • the relaxation ratio referred to in the present specification is a value obtained by dividing the film width direction dimension (mm) at the stretcher outlet of the heat fixing step by the film width direction dimension (mm) at the stretcher inlet.
  • the relaxation operation is a reduction operation of the film in the longitudinal direction and / or the width direction after the stretching operation
  • the relaxation rate is a value obtained by dividing the relaxation rate in the heat fixing step by the stretching rate, and the relaxation rate is It is preferably 1.0 or less, more preferably 0.90 or less, and even more preferably 0.85 or less.
  • the relaxation rate is preferably 0.5 or more from the viewpoint of increasing the strength of the film.
  • the relaxation operation may be performed in both the longitudinal direction and the width direction, or only in one of the longitudinal direction and the width direction.
  • the strain rate is preferably 11% / sec or less, more preferably 2% / sec or more and 11% / sec or less, and further preferably 3% / sec or more and 9%. It is / sec or less, most preferably 5% / sec or more and 8% / sec or less.
  • the strain rate in the relaxation operation is preferably 10% / sec or less, more preferably 0.1% / sec or more and 10% / sec or less, and further preferably 0.5% / sec or more and 7% / sec or less. Most preferably, it is 1.0% / sec or more and 5.0% / sec or less.
  • the strain rate means the rate of change of an object per unit time before and after being subjected to a specific process.
  • the flexural rigidity and the piercing strength of the microporous membrane can be controlled by setting the strain rate of the stretching operation and the relaxation operation to a certain value or less, whereby both low rigidity and high strength can be achieved. It becomes.
  • the strain rate at the time of stretching is large, the rigidity of the film becomes high because the resin is pulled without being entangled with each other. It was also found that when the strain rate at the time of relaxation is large, the bending rigidity becomes high because the boeing of the film becomes large. The method of calculating the strain rate and the ratio of the strain rate will be described later in Examples.
  • the temperature of heat fixation including stretching and relaxation operations is preferably in the range of 100 to 170 ° C. from the viewpoint of the melting point of the polyolefin resin.
  • the lower limit of the heat fixing temperature is more preferably 110 ° C. or higher, further preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and the upper limit thereof is more preferably 170 ° C. or lower, further preferably 160 ° C. or lower, and more. More preferably, it is 150 ° C. or lower, and most preferably 145 ° C. or lower.
  • step (E) It is important that the method for producing the polyolefin microporous membrane includes step (E).
  • step (E) in order to control the rigidity of the film, after the step (D), fine stretching of 1.0% or more and 5.0% or less in the longitudinal direction is performed by a roll stretching machine or a tenter stretching machine. Is preferable, MD is slightly stretched by 1.5 to 4.0%, MD is slightly stretched by 2.0% or more and 4.0% or less, and MD is particularly preferably 2 Fine stretching is performed at 0.0 to 3.5%.
  • the bending coefficient can be controlled within a predetermined range by performing fine stretching of 1.0% or more and 5.0% or less in the step (E).
  • the stretching temperature in the step (E) it is preferable to perform microstretching within a temperature range of (melting point ⁇ 70) ° C. or higher and (melting point ⁇ 30) ° C. or lower of the polyolefin microporous membrane.
  • the temperature range for microstretching is more preferably (melting point -60) ° C. or higher and (melting point -40) ° C. or lower for the film.
  • the stretching ratio in the step (B) and each strain rate in the step (C) are set in a preferable range, and then the fine stretching is performed in the above temperature range in the step (E). It was found that the bending coefficient can be controlled within the specified range.
  • an inorganic coating layer can be provided on the surface of the polyolefin microporous film.
  • the inorganic coating layer is a layer containing an inorganic component such as inorganic particles, and may optionally contain a binder resin that binds the inorganic particles to each other, a dispersant that disperses the inorganic particles in the binder resin, and the like.
  • the inorganic particles include oxide-based ceramics such as alumina, silica, titania, zirconia, magnesia, ceria, itria, zinc oxide, and iron oxide; nitride-based ceramics such as silicon nitride, titanium nitride, and boron nitride; Silicon carbide, calcium carbonate, magnesium sulfate, aluminum sulfate, barium sulfate, aluminum hydroxide, aluminum hydroxide, aluminum hydroxide, potassium titanate, talc, kaolinite, dikite, nacrite, halloysite, pyrophyllite, montmorillonite, cericite, mica, Ceramics such as amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; as well as glass fiber and the like.
  • oxide-based ceramics such as alumina, silica, titania, zirconia,
  • the inorganic particles may be used alone or in combination of two or more.
  • the binder resin include conjugated diene-based polymers, acrylic-based polymers, polyvinyl alcohol-based resins, and fluororesins.
  • the binder resin can be in the form of latex and can contain water or an aqueous solvent.
  • the dispersant is one that adsorbs to the surface of the inorganic particles in the slurry and stabilizes the inorganic particles by electrostatic repulsion or the like, and is, for example, a polycarboxylic acid salt, a sulfonate, a polyoxy ether, a surfactant, or the like. ..
  • the inorganic coating layer can be formed, for example, by applying and drying the slurry of the contained components described above on the surface of the polyolefin microporous film.
  • an adhesive layer that further exhibits adhesiveness to the electrode may be attached to the polyolefin microporous film or the inorganic coating layer, and when the adhesive layer is provided, for example, deformation in a laminated battery, etc. Can be suppressed.
  • the polyolefin microporous membrane according to the embodiment of the present invention can be used as a separator for a lithium ion secondary battery.
  • thermal runaway of the lithium ion secondary battery can be suppressed.
  • the above-mentioned measured values of various physical properties are values measured according to the measuring method in the examples described later.
  • a PL-GPC200 manufactured by Agilent which incorporates a differential refractometer (RI) and a light scattering detector (PD2040), was used.
  • RI differential refractometer
  • PD2040 light scattering detector
  • two Agilent PLgel MIXED-A 13 ⁇ m, 7.5 mm ID ⁇ 30 cm were connected and used.
  • 1,2,4-trichlorobenzene 0.05 wt% 4,4'-Thiobis (containing 6-tert-butyl-3-methylphenol) was added as an eluent at a flow rate of 1.0 ml.
  • Measurements were made under the conditions of / min and an injection volume of 500 ⁇ L, and RI chromatograms and light scattering chromatograms with scattering angles of 15 ° and 90 ° were obtained. From the obtained chromatograms, the number average molecular weight (number average molecular weight ( Mn), weight average molecular weight (Mw) and Z average molecular weight (Mz) were obtained. Using the values of Mz and Mw, the ratio of Z average molecular weight to weight average molecular weight (Mz / Mw) was obtained, and Mw and Mn were obtained. The degree of polydispersity (Mw / Mn) was obtained using the value of. The value of the increase in the refractive index of polyethylene was 0.053 ml / g.
  • DSC measurement differential scanning calorimetry
  • the DSC was measured using a DSC60 manufactured by Shimadzu Corporation.
  • a PO microporous membrane was punched into a circle having a diameter of 5 mm, and several sheets were stacked to make 3 mg, which was used as a measurement sample.
  • This sample was laid on an aluminum open sample pan having a diameter of 5 mm, a clamping cover was placed on the sample, and the sample was fixed in the aluminum pan by a sample sealer.
  • the temperature is raised from 30 ° C to 200 ° C at a heating rate of 10 ° C / min (first temperature rise), held at 200 ° C for 5 minutes, and then from 200 ° C to 30 ° C at a temperature lowering rate of 10 ° C / min. The temperature has dropped. Subsequently, after holding at 30 ° C. for 5 minutes, the temperature was raised again from 30 ° C. to 200 ° C. at a heating rate of 10 ° C./min (second temperature rise). In the melting endothermic curve of the second temperature rise, the maximum temperature was taken as the melting point of the PO microporous membrane. When there were a plurality of maximum values, the temperature at which the maximum value of the largest melting endothermic curve was obtained was adopted as the melting point (Tm) of the PO microporous membrane.
  • Tm melting point
  • the basis weight is the weight (g) of the polyolefin microporous membrane per unit area (1 m 2). After sampling to 1 m ⁇ 1 m, the weight was measured with an electronic balance (AUW120D) manufactured by Shimadzu Corporation. When sampling to 1 m ⁇ 1 m was not possible, the sample was cut into an appropriate area, the weight was measured, and then converted to the weight (g) per unit area (1 m 2).
  • AUW120D electronic balance
  • the thickness was measured at an ambient temperature of 23 ⁇ 2 ° C. using a micro-thickness measuring instrument (type KBN, terminal diameter ⁇ 5 mm) manufactured by Toyo Seiki.
  • a micro-thickness measuring instrument type KBN, terminal diameter ⁇ 5 mm manufactured by Toyo Seiki.
  • When measuring the thickness after sampling the microporous membrane to 10 cm ⁇ 10 cm, multiple microporous membranes are stacked so as to be 15 ⁇ m or more, and 9 points are measured and averaged, and the average thereof is taken. The value obtained by dividing the value by the number of overlapping values is taken as the thickness of one sheet.
  • Porosity (%) (volume-mass / density of mixed composition) / volume x 100 The density of the mixed composition used was a value calculated from the densities and mixing ratios of the polyolefin resin used and the other components.
  • Air permeability (seconds / 100 cm 3 ) The air permeability was measured with the Oken type air permeability measuring machine "EGO2" of Asahi Seiko Co., Ltd.
  • the measured value of the air permeability is a value obtained by measuring the air permeability at a total of three points, 5 cm from both ends and one point in the center, along the width direction of the membrane, and calculating the average value thereof.
  • the piercing strength (gf) was measured as a load, and the displacement (mm) of the needle from the time the needle touched the microporous membrane until the maximum stress (piercing strength) was reached was measured as the piercing elongation.
  • the measured value of the puncture test is a value obtained by measuring a total of three points, 5 cm from both ends and one point in the center, along the width direction of the membrane, and calculating the average value thereof.
  • the flexural rigidity value of the membrane sample was measured at an atmospheric temperature of 23 ⁇ 2 ° C. and an atmospheric humidity of 40 ⁇ 2% using a pure bending tester KES-FB2-A of Kato Tech. Cut the sample into MD 20 cm x TD 20 cm, chuck both ends of the TD to the fixed chuck (2) and the moving chuck (3) as shown in FIG. 1, and measure the flexural rigidity value of the MD according to the instruction manual. It was. Each setting is as follows.
  • the flexural rigidity value of TD chuck both ends of the MD of the sample cut out to MD 20 cm ⁇ TD 20 cm, and measure in the same manner as described above.
  • the flexural rigidity shall be measured after excluding those coating layers from the microporous film.
  • Ni foils (A, B) were pasted together, and both sides were pressed with clips with two glass plates.
  • the Ni foil electrode thus produced was placed in an oven at 25 ° C. and heated to 200 ° C. at 2 ° C./min.
  • the impedance change at this time was measured under the condition of 1 V and 1 kHz using an electric resistance measuring device "AG-4311" (manufactured by Ando Electric Co. Ltd.).
  • the temperature at which the impedance value reached 1000 ⁇ in this measurement was defined as the shutdown temperature (° C.).
  • a fluororubber having a thickness of 1 mm was attached to the inside of the chuck of the tensile tester. The measurement was carried out under the conditions of a temperature of 23 ⁇ 2 ° C., a chuck pressure of 0.40 MPa, and a tensile speed of 100 mm / min.
  • the tensile strength (MPa) was determined by dividing the strength of the polyolefin microporous membrane at break by the sample cross-sectional area before the test.
  • the tensile elongation (%) was determined by dividing the elongation amount (mm) leading to fracture by the inter-chuck distance (50 mm) and multiplying by 100.
  • strain rate (% / sec) (stretching ratio -1) x 100 / (stretching length (m) / ((pre-stretching line speed (m / sec) + post-stretching line speed (m / sec)) / 2))
  • the stretching length refers to the distance that the film moves in the longitudinal direction (MD) from the start of stretching to the end of stretching in steps (B) and (D).
  • the strain rates of the stretching operation and the relaxation operation are calculated respectively.
  • Springback value 100- (thickness of laminated body after 3 seconds / thickness of laminated body after 1 minute x 100) [%]
  • the springback value was evaluated according to the following criteria. (Evaluation criteria) A: Less than 1% B: Less than 1 to 3% C: 3 to 5% or more D: 5 to 7% or more E: 7% or more
  • Negative Electrode A slurry was prepared by dispersing artificial graphite as a negative electrode active material and an ammonium salt of carboxymethyl cellulose and a styrene-butadiene copolymer latex as a binder in purified water. This slurry was applied to a copper foil serving as a negative electrode current collector with a die coater, dried at 120 ° C. for 3 minutes, and then compression-molded with a roll press machine. The obtained molded product was slit to a width of 58.5 mm to obtain a negative electrode. c.
  • the solution was prepared.
  • Battery assembly After winding the positive electrode, the porous film and the negative electrode obtained in Examples or Comparative Examples, a wound electrode body was prepared by a conventional method and pressed with a press so as to fit in an outer can. The number of turns was adjusted according to the thickness of the polyolefin microporous film and the degree of springback.
  • the outermost peripheral end of the obtained wound electrode body was fixed by attaching an insulating tape.
  • the negative electrode lead was welded to the battery can and the positive electrode lead was welded to the safety valve, and the wound electrode body was inserted into the battery can.
  • 5 g of a non-aqueous electrolyte solution was injected into the battery can, and the lid was crimped to the battery can via a gasket to obtain a square secondary having a width of 42.0 mm, a height of 63.0 mm, and a thickness of 10.5 mm. I got a battery.
  • This square secondary battery is charged to a battery voltage of 4.2 V at a current value of 0.2 C (current 0.2 times the 1-hour rate (1 C) of the rated electric capacity) in an atmosphere of 25 ° C., and after reaching the battery voltage of 4.2 V. Charging was carried out for a total of 3 hours by a method of starting to throttle the current value so as to hold 4.2 V. Subsequently, the battery was discharged to a battery voltage of 3.0 V with a current value of 0.2 C.
  • FIG. 2 is a schematic view of a collision test.
  • ⁇ 15.8 mm
  • the procedure of the collision test in Examples and Comparative Examples will be described below with reference to FIG.
  • the secondary battery obtained in the above item was charged with a constant current of 1C, reached 4.2V, and then charged with a constant voltage of 4.2V for a total of 3 hours.
  • the secondary battery was placed sideways on a flat surface, and a stainless steel round bar 5 having a diameter of 15.8 mm was arranged so as to cross the central portion of the secondary battery.
  • the round bar 5 is arranged so that its long axis is parallel to the longitudinal direction (MD) of the separator.
  • a 18.2 kg weight 6 was dropped from a height of 61 cm so that an impact was applied at a right angle to the vertical axis direction of the secondary battery from the round bar 5 arranged at the center of the secondary battery.
  • the surface temperature of the secondary battery was measured 3 seconds and 3 minutes after the collision.
  • the test was conducted 5 cells at a time and evaluated according to the following criteria. For this evaluation item, A, B, and C were used as acceptance criteria.
  • the surface temperature of the secondary battery is a temperature measured by a thermocouple (K-type seal type) at a position 1 cm from the bottom side of the exterior body of the secondary battery.
  • E Surface temperature exceeds 100 ° C or ignites in one or more cells.
  • the secondary battery obtained in the above item was charged with a constant current of 1C in an environment of 25 ° C. and reached 4.2V. After that, the battery was charged at a constant voltage of 4.2 V for a total of 3 hours. The charged battery was heated from room temperature to a predetermined temperature at 5 ° C./min and left at a predetermined temperature for 60 minutes to check the ignition status. Three batteries were prepared and the results were evaluated according to the following criteria. A: None of the batteries ignited at 136 ° C. B: None of the batteries ignited at 134 ° C. C: None of the batteries ignited at 132 ° C. D: None of the batteries ignited at 130 ° C. E: At least one battery ignited at 130 ° C.
  • Example 1 High-density polyethylene (PE5) having an Mv of 700,000 and a polydispersity (Mw / Mn) of 7.9 by 45% by mass, a high-density polyethylene (PE2) having an Mv of 250,000 and a polydispersity (Mw / Mn) of 7.2. 45% by mass, Mv 400,000, and 10% by mass of homopolypropylene (PP1) having a polydispersity (Mw / Mn) of 4.5 were dry-blended using a tumbler blender to obtain a raw material resin mixture.
  • a polyolefin composition was obtained by blending 32% by mass of the raw material resin mixture, 68% by mass of liquid paraffin and 0.1% by mass of the antioxidant.
  • the polyolefin composition was put into a twin-screw extruder, and the melted polyolefin composition was extruded at a distance of 900 ⁇ m between cast rolls to form a gel-like sheet, which was then cooled and solidified by the cast rolls.
  • B Using a simultaneous biaxial stretching machine, a stretched sheet is obtained by stretching a cooled and solidified sheet at a set temperature of 119 ° C. and a surface magnification of 64 times (longitudinal stretching magnification 8 times, width direction stretching magnification 8 times). It was.
  • C Then, the stretched sheet was immersed in methylene chloride to extract and remove liquid paraffin, and then dried to make it porous.
  • Examples 2 to 21 and Comparative Examples 1 to 21 A microporous polyolefin membrane was obtained and evaluated in the same manner as in Example 1 except that the production conditions shown in Tables 1 and 2 were used. The evaluation results are shown in Tables 1 and 2 below. However, in Comparative Example 18, the relaxation operation was not performed in the step (D). In Comparative Example 3 and Comparative Example 13, MD microstretching was not performed in the step (E).
  • step (B) after stretching a cooled and solidified sheet at a set temperature of 115 ° C. and a longitudinal stretching ratio of 6 times using a roll stretching machine, a set temperature of 120 ° C. and a width direction stretching ratio of 7 times are subsequently used using a tenter.
  • a polyolefin microporous film was obtained and evaluated by the same method as in Example 1 except that the MD microstretching was not carried out in the step (E). The evaluation results are shown in Tables 1 and 2 below.
  • the annealed film was uniaxially stretched 1.2 times in the longitudinal direction at a temperature of 25 ° C. to obtain a stretched film.
  • the stretched film was uniaxially stretched 2.5 times in the longitudinal direction at a temperature of 140 ° C., heat-fixed at 150 ° C., and then the microporous film was wound up.

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2023161496A (ja) * 2022-04-25 2023-11-07 旭化成株式会社 ポリオレフィン微多孔膜

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN121729794A (zh) * 2023-08-21 2026-03-24 国际人造丝公司 多孔膜及其制备所用的聚合物共混物
CN119650881A (zh) * 2024-11-04 2025-03-18 中创新航科技集团股份有限公司 电芯及电池及电池模组

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11279324A (ja) * 1998-03-30 1999-10-12 Asahi Chem Ind Co Ltd ポリエチレン微多孔膜
JP2003105122A (ja) * 2001-09-28 2003-04-09 Tonen Chem Corp ポリオレフィン微多孔膜及びその製造方法
JP2010538097A (ja) * 2007-08-31 2010-12-09 東燃化学株式会社 ポリオレフィン微多孔膜、その製造方法、電池用セパレータ及び電池
JP2016102203A (ja) * 2014-11-12 2016-06-02 東レ株式会社 多孔性フィルム、および透湿防水シート
JP2016102201A (ja) * 2014-11-12 2016-06-02 東レ株式会社 多孔性フィルム
JP2016191006A (ja) 2015-03-31 2016-11-10 旭化成株式会社 ポリオレフィン微多孔膜の製造方法、電池用セパレータ、及び非水電解液二次電池
JP2017027945A (ja) * 2015-07-24 2017-02-02 旭化成株式会社 蓄電デバイス用セパレータ
WO2019045077A1 (ja) * 2017-08-31 2019-03-07 旭化成株式会社 ポリオレフィン微多孔膜
WO2019107119A1 (ja) * 2017-11-28 2019-06-06 旭化成株式会社 蓄電デバイス用セパレータ及びその製造方法、並びに蓄電デバイス及びその製造方法
JP2019157060A (ja) * 2018-03-16 2019-09-19 東レ株式会社 ポリオレフィン微多孔膜

Family Cites Families (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5325405B2 (ja) * 2007-10-09 2013-10-23 旭化成イーマテリアルズ株式会社 ポリオレフィン製微多孔膜
JP2009149710A (ja) * 2007-12-19 2009-07-09 Asahi Kasei E-Materials Corp ポリオレフィン製微多孔膜
US8298465B2 (en) * 2008-07-31 2012-10-30 Asahi Kasei E-Materials Corporation Microporous film and method for producing the same
CN102257048B (zh) * 2008-12-19 2016-01-20 旭化成电子材料株式会社 聚烯烃制微多孔膜及锂离子二次电池用分隔件
JP6222083B2 (ja) * 2012-03-30 2017-11-01 東レ株式会社 ポリエチレン微多孔膜およびその製造方法
KR101807377B1 (ko) * 2012-11-13 2017-12-08 아사히 가세이 이-매터리얼즈 가부시키가이샤 레독스 플로우 이차 전지용 격막 및 그것을 사용한 레독스 플로우 이차 전지
JP2015208893A (ja) 2014-04-24 2015-11-24 東レバッテリーセパレータフィルム株式会社 ポリオレフィン製積層微多孔膜
EP3085531B1 (en) * 2014-05-30 2018-05-02 Toray Industries, Inc. Polyolefin multilayer microporous membrane and battery separator
JP6208187B2 (ja) * 2015-09-03 2017-10-04 旭化成株式会社 ポリオレフィン微多孔膜、蓄電デバイス用セパレータ、及び蓄電デバイス
EP3505560A4 (en) * 2016-08-29 2020-04-15 Toray Industries, Inc. MICROPOROUS MEMBRANE, LITHIUM-ION SECONDARY BATTERY AND METHOD FOR PRODUCING A MICROPOROUS MEMBRANE
JP7045862B2 (ja) * 2017-03-24 2022-04-01 旭化成株式会社 ポリオレフィン微多孔膜及びポリオレフィン微多孔膜の製造方法
KR102264032B1 (ko) 2017-03-27 2021-06-11 아사히 가세이 가부시키가이샤 폴리올레핀 미다공막 및 폴리올레핀 미다공막의 제조 방법
KR102290094B1 (ko) * 2017-05-26 2021-08-18 아사히 가세이 가부시키가이샤 폴리올레핀 미다공막, 축전 디바이스용 세퍼레이터 및 축전 디바이스
CN111212734B (zh) 2017-10-13 2023-04-25 旭化成株式会社 聚烯烃微多孔膜以及使用其的锂离子二次电池
TW201940528A (zh) * 2018-02-23 2019-10-16 日商東麗股份有限公司 多孔性聚烯烴薄膜

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11279324A (ja) * 1998-03-30 1999-10-12 Asahi Chem Ind Co Ltd ポリエチレン微多孔膜
JP2003105122A (ja) * 2001-09-28 2003-04-09 Tonen Chem Corp ポリオレフィン微多孔膜及びその製造方法
JP2010538097A (ja) * 2007-08-31 2010-12-09 東燃化学株式会社 ポリオレフィン微多孔膜、その製造方法、電池用セパレータ及び電池
JP2016102203A (ja) * 2014-11-12 2016-06-02 東レ株式会社 多孔性フィルム、および透湿防水シート
JP2016102201A (ja) * 2014-11-12 2016-06-02 東レ株式会社 多孔性フィルム
JP2016191006A (ja) 2015-03-31 2016-11-10 旭化成株式会社 ポリオレフィン微多孔膜の製造方法、電池用セパレータ、及び非水電解液二次電池
JP2017027945A (ja) * 2015-07-24 2017-02-02 旭化成株式会社 蓄電デバイス用セパレータ
WO2019045077A1 (ja) * 2017-08-31 2019-03-07 旭化成株式会社 ポリオレフィン微多孔膜
WO2019107119A1 (ja) * 2017-11-28 2019-06-06 旭化成株式会社 蓄電デバイス用セパレータ及びその製造方法、並びに蓄電デバイス及びその製造方法
JP2019157060A (ja) * 2018-03-16 2019-09-19 東レ株式会社 ポリオレフィン微多孔膜

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4043516A4

Cited By (1)

* Cited by examiner, † Cited by third party
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JP2023161496A (ja) * 2022-04-25 2023-11-07 旭化成株式会社 ポリオレフィン微多孔膜

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