WO2023176876A1 - Membrane microporeuse en polyoléfine, séparateur pour batteries, batterie secondaire à électrolyte non aqueux et filtre - Google Patents

Membrane microporeuse en polyoléfine, séparateur pour batteries, batterie secondaire à électrolyte non aqueux et filtre Download PDF

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WO2023176876A1
WO2023176876A1 PCT/JP2023/010054 JP2023010054W WO2023176876A1 WO 2023176876 A1 WO2023176876 A1 WO 2023176876A1 JP 2023010054 W JP2023010054 W JP 2023010054W WO 2023176876 A1 WO2023176876 A1 WO 2023176876A1
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molecular weight
polyolefin
microporous membrane
polyolefin microporous
membrane
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PCT/JP2023/010054
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English (en)
Japanese (ja)
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遼 下川床
琢也 久万
直哉 西村
龍太 中嶋
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東レ株式会社
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    • C—CHEMISTRY; METALLURGY
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • 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
    • 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
    • H01M50/431—Inorganic material
    • 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
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H01M8/0239—Organic resins; Organic polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1058—Polymeric electrolyte materials characterised by a porous support having no ion-conducting properties
    • H01M8/1062—Polymeric electrolyte materials characterised by a porous support having no ion-conducting properties characterised by the physical properties of the porous support, e.g. its porosity or thickness

Definitions

  • the present invention relates to a microporous polyolefin membrane, a battery separator, a non-aqueous electrolyte secondary battery, and a filter.
  • Polyolefin microporous membranes are widely used as substance separation membranes, selectively permeable membranes, separation membranes, etc.
  • Specific applications of polyolefin microporous membranes include separators for non-aqueous electrolyte secondary batteries (e.g. lithium ion secondary batteries, nickel-hydrogen batteries, nickel-cadmium batteries, polymer batteries, etc.) and separators for electric double layer capacitors.
  • various filters reverse osmosis filtration membranes, ultrafiltration membranes, precision filtration membranes, etc.
  • moisture permeable and waterproof clothing e.g., medical materials, supports for fuel cells, etc.
  • microporous polyolefin membranes are widely used as separators for lithium ion secondary batteries. Its characteristics include excellent ion permeability (hereinafter ion permeability is sometimes simply referred to as "permeability”), which is directly linked to battery performance, and mechanical strength that greatly contributes to battery safety and productivity. It can also be mentioned that it is excellent. In recent years, with the miniaturization and increase in capacity of batteries, separators have become thinner, and the demand for microporous polyolefin membranes with higher mechanical strength is increasing.
  • One way to increase the strength is to reduce the porosity in the microporous membrane and increase the amount of resin in the membrane, but ion permeability decreases due to pore blockage and a decrease in the amount of electrolyte retained.
  • ultra-high molecular weight polyethylene containing components with a molecular weight of 1 million or more ultra-high molecular weight polyethylene is difficult to form into a film due to difficulty in processability.
  • the challenge is to improve the quality of microporous membranes.
  • One of the challenges for microporous polyolefin membranes is to increase their strength while maintaining ion permeability and membrane quality.
  • the polyolefin microporous membrane has a pore-closing function (shutdown characteristic) that automatically blocks ion permeation at temperatures of approximately 130 to 150°C and suppresses excessive temperature rises in the event of an abnormal reaction inside/outside the battery.
  • a pore-closing function shutdown characteristic
  • shutdown property if the high temperature state is maintained for a certain period of time, the microporous polyolefin membrane after pore-blocking will partially flow due to melting and will no longer be able to maintain pore-blocking, causing ions to be released. A phenomenon of transmission (meltdown) can be seen.
  • Meltdown resistance which increases the temperature at which meltdown occurs, is also considered an important issue for polyolefin microporous membranes. It is important to lower the shutdown temperature and higher the meltdown temperature to improve battery safety, but these are trade-offs with the mechanical strength and ion permeability of the microporous membrane. be.
  • microporous polyolefin membranes As described above, as battery separators become thinner, microporous polyolefin membranes have improved mechanical strength while offering advanced membrane quality, ion permeability, shutdown characteristics, and meltdown resistance. It is necessary to maintain balance.
  • Patent Document 1 uses a polyolefin with high viscosity (high molecular weight) as a method for increasing strength, but the balance between mechanical strength and shutdown temperature is poor and it cannot be used as a separator for high-output/high-capacity batteries. There was a case. Moreover, if the molecular weight is further increased and the stretching ratio is increased in order to improve mechanical strength, there is a concern that the shutdown temperature will further rise.
  • high molecular weight high viscosity
  • Patent Document 2 uses raw materials with low molecular weight and low melting point to increase the amount of closed pore components in the microporous membrane.
  • shutdown temperature since it contains many low molecular weight components, although it has an excellent pore closing temperature (shutdown temperature), it is estimated that its mechanical strength is insufficient for use as current thin film separators.
  • the mechanical strength is improved by a method such as lowering the porosity, there is a concern that the pores will be excessively blocked and the ion permeability will deteriorate.
  • shutdown temperature a method for lowering the shutdown temperature
  • Patent Document 3 a method of adding a highly heat-resistant raw material such as polypropylene is taken in order to improve meltdown resistance, but it is difficult to maintain film quality and mechanical strength.
  • the object of the present invention is to maintain membrane quality while maintaining excellent ion permeability, which contributes to battery output characteristics, mechanical strength, shutdown characteristics, and meltdown resistance, which contribute to safety characteristics, and when used as a battery separator.
  • the purpose of the present invention is to provide a polyolefin microporous membrane having excellent output characteristics and safety.
  • microporous polyolefin membrane of the present invention maintains permeability, membrane quality, and shutdown characteristics better than conventional microporous polyolefin membranes. At the same time, we have found that it is possible to achieve both high levels of mechanical strength and meltdown resistance.
  • the present invention has the following configuration.
  • [I] A polyolefin having a puncture strength converted to unit weight of 0.8 N/(g/m 2 ) or more and obtained by gel permeation chromatography (GPC method), with the horizontal axis representing the molecular weight and the vertical axis representing the detection strength.
  • GPC method gel permeation chromatography
  • [II] In the molecular weight distribution of polyolefin microporous membrane obtained by GPC method, with the horizontal axis as the molecular weight and the vertical axis as the detection intensity, the detection of a molecular weight of 200 when the maximum detection intensity is 1 and the overall detection intensity is normalized.
  • Strength The polyolefin microporous membrane according to [I], which has a K200 of 0.6 or more.
  • [VII] A laminate in which a porous layer is further laminated on the microporous polyolefin membrane according to any one of [I] to [VI].
  • [VIII] A battery separator using the polyolefin microporous membrane according to any one of [I] to [VI] or the laminate according to [VII].
  • [IX] A non-aqueous electrolyte secondary battery comprising the battery separator according to [VIII].
  • [X] A filter using the polyolefin microporous membrane according to any one of [I] to [VI].
  • [XI] A filtration unit using the liquid filtration filter according to [X].
  • the microporous polyolefin membrane of the present invention is excellent in ion permeability, which contributes to the output characteristics of a battery, and mechanical strength, shutdown characteristics, and meltdown resistance characteristics, which contribute to safety characteristics. Therefore, it can be suitably used as a separator for secondary batteries that require high energy density, high capacity, and high output.
  • the polyolefin microporous membrane of the present invention has a uniform pore structure, it can also be suitably used as a filter.
  • the direction parallel to the direction in which the microporous polyolefin membrane is formed is referred to as the film-forming direction, longitudinal direction, or MD direction, and the direction perpendicular to the film-forming direction within the surface of the microporous polyolefin membrane is referred to as the width direction.
  • the TD direction the direction perpendicular to the film-forming direction within the surface of the microporous polyolefin membrane.
  • the raw material used for the polyolefin microporous membrane of the present invention preferably contains at least one type of ultra-high molecular weight polyethylene (UHPE).
  • UHPE ultra-high molecular weight polyethylene
  • the proportion of ultra-high molecular weight polyethylene in the resin component of the polyolefin microporous membrane of the present invention is preferably 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more.
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention may be an ethylene homopolymer, or may be a copolymer containing other ⁇ -olefins in order to lower the melting point as described below.
  • Other ⁇ -olefins include, for example, propylene, butene-1, hexene-1, pentene-1, 4-methylpentene-1, octene, vinyl acetate, methyl methacrylate, and styrene.
  • the presence and type of ⁇ -olefin can be confirmed by measuring with C 13 -NMR.
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a weight average molecular weight (Mw) of 800,000 or more, more preferably 1,000,000 or more, as determined by gel permeation chromatography (GPC) measurement under the conditions described below. , 1.2 million or more is more preferable. Moreover, Mw is preferably 2 million or less, more preferably 1.5 million or less. When Mw is within the above range, the stretching stress is efficiently transmitted even after the molecular weight is adjusted by melt-kneading, and it is possible to maintain the molecular weight component necessary for high strength in the polyolefin microporous membrane.
  • Mw weight average molecular weight
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention has peaks in two regions: 100,000 to less than 1 million, and 1 million to 10 million, in the molecular weight distribution obtained from GPC measurement under the conditions described below. It is preferable.
  • the range on the low molecular weight side is more preferably 100,000 to 500,000, and the range on the high molecular weight side is more preferably 1 million to 5 million. Having peaks in both of the above molecular weight ranges promotes high strength, but low molecular weight components support high molecular weight components that are difficult to miscible with plasticizers, making them more compatible with plasticizers. This makes it possible to achieve both high quality and high strength of the polyolefin microporous membrane.
  • the detection intensity of the molecular weight distribution is normalized by setting the maximum detection intensity to 1, and the detection intensity at a molecular weight of 3 million is K300.
  • the ratio: K300/K700 is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 4.0 or more. This K300/K700 indicates molecular weight uniformity on the high molecular weight side, and the larger this value is, the sharper the distribution of high molecular weight components is.
  • the amount of components having a molecular weight of 10 million or more in the molecular weight distribution obtained from GPC measurement is preferably 4.0% by mass or less, more preferably 2.0% by mass or less, and Preferably it is 1.0% by mass or less.
  • this component having a molecular weight of 10 million or more a much higher stretching ratio than the current production conditions is required, which causes non-uniform stretching. Therefore, although components having a molecular weight of 10 million or more have little contribution to increasing strength, there is concern that they may be a factor in worsening thermal shrinkage. Therefore, when the amount of this component is within the above range, even when the molecular weight is adjusted by melt-kneading, it is possible to maintain the molecular weight component necessary for increasing the strength of the polyolefin microporous membrane.
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention is preferably polymerized using a metallocene catalyst.
  • Polyethylene polymerized using a metallocene catalyst has a narrow molecular weight distribution, and the amount of K300/K700 or components having a molecular weight of 10 million or more can be easily adjusted to the above range.
  • polyethylene polymerized using a metallocene catalyst contains catalyst residues such as Hf (hafnium) and Cr (chromium).
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a melting point of 134°C or higher, more preferably 135°C or higher, and even more preferably 135.5°C or higher, as determined by differential scanning calorimetry (DSC). . Further, the melting point is preferably 140°C or lower, more preferably 137.5°C or lower, and even more preferably 136.0 or lower. When the melting point is within the above range, deterioration of permeability and excessive increase in shutdown temperature in the heat setting process can be suppressed, and various physical properties can be achieved simultaneously.
  • the ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a ⁇ H (J/g) of 150 J/g or more, preferably 155 J/g or more, obtained from a differential scanning calorimeter (DSC) under the conditions described below. is more preferable.
  • ⁇ H is preferably 200 J/g or less, more preferably 190 J/g or less, and even more preferably 180 J/g or less.
  • the microporous polyolefin membrane of the present invention may contain polyolefins other than ultra-high molecular weight polyethylene (UHPE).
  • UHPE ultra-high molecular weight polyethylene
  • polyethylene is preferable from the viewpoint of compatibility with ultra-high molecular weight polyethylene.
  • the weight average molecular weight (Mw) obtained from gel permeation chromatography (GPC) measurement under the conditions described below is preferably 10,000 or more, more preferably 50,000 or more. . Moreover, Mw is preferably 300,000 or less, more preferably 200,000 or less. When Mw is within the above range, the structure formed by the high molecular weight polyolefin is not excessively inhibited, so that it is possible to further improve shutdown and heat shrinkage characteristics while maintaining mechanical strength.
  • the polyethylene other than ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a melting point of 136°C or lower, more preferably 134°C or lower, and even more preferably 133°C or lower, as determined by differential scanning calorimetry (DSC). be. Further, the melting point is preferably 125°C or higher, more preferably 130°C or higher, and even more preferably 131°C or higher. When the melting point is within the above range, the shutdown characteristics can be improved while suppressing excessive deterioration of permeability in the heat setting process, and various physical properties can be achieved at the same time.
  • DSC differential scanning calorimetry
  • the polyethylene other than ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a ⁇ H (J/g) of 180 J/g or more, preferably 200 J/g or more, as determined by a differential scanning calorimeter (DSC). More preferably, it is 220 J/g or more. Moreover, ⁇ H is preferably 250 J/g or less, more preferably 240 J/g or less. When ⁇ H is within the above range, the shutdown characteristics can be improved while suppressing excessive deterioration of permeability in the heat setting process, and various physical properties can be achieved at the same time.
  • DSC differential scanning calorimeter
  • the polyolefin microporous membrane of the present invention may contain various additives such as antioxidants, heat stabilizers, antistatic agents, ultraviolet absorbers, antiblocking agents, and fillers within the range that does not impair the effects of the present invention. It's okay.
  • antioxidants for the purpose of suppressing oxidative deterioration of the polyolefin resin due to thermal history.
  • antioxidants include 2,6-di-t-butyl-p-cresol (BHT: molecular weight 220.4), 1,3,5-trimethyl-2,4,6-tris (3,5-di -t-butyl-4-hydroxybenzyl)benzene (for example, "Irganox” (registered trademark) 1330 manufactured by BASF: molecular weight 775.2), tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxy) It is preferable to use one or more types selected from phenyl)propionate]methane (for example, "Irganox” (registered trademark) 1010 manufactured by BASF, molecular weight 1177.7).
  • the microporous polyolefin membrane of the present invention has a puncture strength in terms of unit weight of 0.8 N/(g/m 2 ) or more, preferably 0.85 N/(g/m 2 ) or more, more preferably 0.9 N/m 2 . (g/m 2 ) or more, more preferably 1.0 N/(g/m 2 ) or more. Further, the puncture strength in terms of unit area weight is preferably 1.8 N/(g/m 2 ) or less, more preferably 1.5 N/(g/m 2 ) or less.
  • the puncture strength of the polyolefin microporous membrane By setting the puncture strength of the polyolefin microporous membrane to 0.8 N/(g/m 2 ) or more in terms of unit area weight, it is easy to maintain the puncture strength as a polyolefin microporous membrane even at high porosity, and the ion permeability and It is possible to achieve both mechanical strength. Furthermore, even when the film is made thin, it easily maintains the puncture strength as a microporous polyolefin film, and can be used as a battery separator with excellent foreign object resistance.
  • the puncture strength in terms of unit weight is 0.8 N/(g/m 2 ) or more, it will be easier to increase the porosity and make the film thinner, thereby reducing filtration resistance while suppressing filtration resistance. It is possible and preferable to increase the flow rate.
  • the raw materials used for the polyolefin microporous membrane and its composition be in the above ranges, and that the film forming conditions be in the ranges described below.
  • the polyolefin microporous membrane of the present invention has a molecular weight distribution of the polyolefin microporous membrane obtained by gel permeation chromatography (GPC method) under the conditions described below, with the horizontal axis representing the molecular weight and the vertical axis representing the detection intensity.
  • GPC method gel permeation chromatography
  • the amount of this component having a molecular weight of 10 million or more is preferably 0.7% by mass or less, more preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, and particularly preferably 0% by mass.
  • the polyolefin microporous membrane of the present invention is obtained by a gel permeation chromatography method (GPC method), and the molecular weight distribution of the polyolefin microporous membrane, where the horizontal axis is the molecular weight and the vertical axis is the detection intensity, is determined as follows, with the maximum detection intensity being 1.
  • GPC method gel permeation chromatography method
  • the above K200-K700 is preferably 0.45 or more, more preferably 0.5 or more, and even more preferably 0.55 or more. Further, the K200-K700 is preferably 0.9 or less, more preferably 0.8 or less.
  • the amount of components With a molecular weight of 10 million or more and K200-K700 within the above range of the polyolefin microporous membrane, it is possible to uniformly stretch the entire microporous membrane from the initial stage of stretching, while maintaining the membrane quality.
  • the mechanical strength of the polyolefin microporous membrane can be improved.
  • the unstretched portion of the polyolefin microporous membrane is reduced, and ion permeability can be improved.
  • K200-K700 within the above range, the high molecular weight component becomes more uniform and the shape is easily maintained even after melting, so that the meltdown resistance properties are easily improved.
  • the raw materials used for the polyolefin microporous membrane and their composition be within the above range, and that the kneading conditions be within the ranges described below.
  • the K200 is preferably 0.6 or more.
  • K200 is preferably 0.65 or more, more preferably 0.7 or more. Further, it is preferably 1.0 or less, more preferably 0.95 or less, and particularly preferably 0.9 or less.
  • the K200 of the polyolefin microporous membrane By setting the K200 of the polyolefin microporous membrane within the above range, the stress during stretching is increased, more uniform stretching is promoted, and the mechanical strength of the polyolefin microporous membrane is further improved while maintaining membrane quality. is possible.
  • the raw materials used for the polyolefin microporous membrane and their composition be within the above ranges, and that the kneading conditions be within the ranges described below.
  • the polyolefin microporous membrane of the present invention has a maximum detection value in the molecular weight distribution of the polyolefin microporous membrane obtained by gel permeation chromatography (GPC method) in the measurement method described below, with the horizontal axis representing the molecular weight and the vertical axis representing the detection intensity. It is preferable that the strength exists in a molecular weight range of 100,000 to 500,000.
  • This maximum detection intensity is preferably present in a molecular weight range of 200,000 to 400,000, more preferably in a molecular weight range of 200,000 to 300,000.
  • the maximum molecular weight detection intensity of the polyolefin microporous membrane By setting the maximum molecular weight detection intensity of the polyolefin microporous membrane within the above molecular weight range, relatively low molecular weight components that are highly compatible with plasticizers are increased, and high molecular weight components that form the skeleton of the microporous membrane structure are increased. In order to promote compatibility with the plasticizer, it becomes possible to improve the mechanical strength of the polyolefin microporous membrane while maintaining the film quality such as the film appearance.
  • the raw materials used for the microporous polyolefin membrane and their composition be within the above ranges, and that the kneading conditions be within the ranges described below.
  • the polyolefin microporous membrane of the present invention preferably contains 0.2 ppm or more of hafnium element.
  • This hafnium element content is more preferably 0.5 ppm or more, still more preferably 0.8 ppm or more, and particularly preferably 1.0 ppm or more. Further, the hafnium element content is preferably 5.0 ppm or less, more preferably 3.0 ppm or less.
  • the molecular weight distribution such as K200-K700 of the polyolefin microporous membrane can be adjusted to an appropriate state without adversely affecting battery performance.
  • the raw materials used for the polyolefin microporous membrane and its composition be within the above range, and that the kneading conditions be within the ranges described below.
  • the polyolefin microporous membrane of the present invention preferably has a ratio of average pore diameter to maximum pore diameter (average pore diameter/maximum pore diameter) of 0.65 or more as measured by a palm porometer based on JIS K 3832-1990.
  • This average pore diameter/maximum pore diameter is more preferably 0.67 or more, still more preferably 0.69 or more, and particularly preferably 0.71 or more. Moreover, this average pore diameter/maximum pore diameter is preferably 0.9 or less, more preferably 0.8 or less.
  • the average pore diameter/maximum pore diameter of the polyolefin microporous membrane is within the above range, it indicates that the polyolefin microporous membrane has a more uniform pore structure, which not only improves the mechanical strength of the polyolefin microporous membrane, but also reduces the curvature of the pores. Since the path ratio is also reduced, it is possible to improve ion permeability. Furthermore, when used as a filter, it is preferable that the average pore diameter/maximum pore diameter is 0.65 or more, since the distribution of pore diameters on the film surface is uniform, so that filtration accuracy can be improved.
  • the polyolefin microporous membrane of the present invention preferably has a porosity of 30% or more.
  • the porosity is more preferably 35% or more, still more preferably 37% or more, and still more preferably 40% or more.
  • the porosity is within the above range, the mechanical strength and ion permeability of the polyolefin microporous membrane can be maintained, so that when used as a battery separator, the output characteristics and safety of the battery can be maintained.
  • the porosity is preferably 60% or less from the viewpoint of mechanical strength of the microporous polyolefin membrane.
  • the raw material composition of the microporous polyolefin membrane be within the above range, and the stretching conditions and heat setting conditions during film production of the microporous polyolefin membrane be within the ranges described below. .
  • the polyolefin microporous membrane of the present invention has an air permeability resistance of 300 seconds or less when 100 cm 3 of air is passed through it, as measured by the Oken tester method of JIS P-8117:2009, when converted to a thickness of 10 ⁇ m. It is preferable that The air permeability resistance when converted to a thickness of 10 ⁇ m is more preferably 250 seconds or less, and even more preferably 210 seconds or less. When the air permeability resistance is within the above range, the ion permeability of the polyolefin microporous membrane can be maintained, and the output characteristics when used as a battery separator are improved. Furthermore, since the air permeability resistance is 50 seconds or more when converted to a thickness of 10 ⁇ m, it has an excellent balance with strength and heat resistance.
  • the raw material composition of the microporous polyolefin membrane must be within the range described above, the laminated structure must be within the range described below, and the stretching during production of the microporous polyolefin membrane must be adjusted. It is preferable that the conditions and heat setting conditions are within the ranges described below.
  • the polyolefin microporous membrane of the present invention preferably has a thickness of 1 ⁇ m or more and 25 ⁇ m or less.
  • the film thickness is more preferably 12 ⁇ m or less, even more preferably 10 ⁇ m or less, particularly preferably 7 ⁇ m or less, and most preferably 5 ⁇ m or less.
  • the film thickness can be adjusted by adjusting the screw rotation speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretching ratio, etc. within a range that does not deteriorate other physical properties.
  • the polyolefin microporous membrane of the present invention preferably has a puncture strength of 5.0 N or more when converted to a thickness of 10 ⁇ m.
  • the puncture strength is more preferably 5.5N or more, still more preferably 6.0N or more, particularly preferably 6.5N or more, and most preferably 7.0 or more.
  • the puncture strength is preferably 10 N or less from the viewpoint of improving the shutdown characteristics.
  • the puncture strength is 5.0 N or more, since this makes it easier to form a thin film and increases the filtration flow rate.
  • the raw material composition of the microporous polyolefin membrane is within the above range, and the stretching conditions during the production of the microporous polyolefin membrane are within the ranges described below.
  • the polyolefin microporous membrane of the present invention has a temperature-stress curve of the polyolefin microporous membrane, where the horizontal axis is temperature and the vertical axis is stress, obtained from thermomechanical analysis measurement (TMA measurement) at a heating rate of 5°C/min.
  • TMA measurement thermomechanical analysis measurement
  • P 150 /P max ⁇ 0.6.
  • P 150 /P max is more preferably 0.7 or more, still more preferably 0.75 or more, and most preferably 0.8 or more.
  • P 150 /P max is 0.95 or less.
  • the raw materials used for the microporous polyolefin membrane and their composition be within the above ranges, and that the kneading conditions be within the ranges described below.
  • the microporous polyolefin membrane of the present invention has a shutdown temperature of 144° C. or lower as determined by the temperature-elevated air permeability method.
  • the shutdown temperature is more preferably 142°C or lower, further preferably 140°C or lower, particularly preferably 138°C or lower.
  • the shutdown temperature is preferably 100°C or higher, more preferably 120°C or higher.
  • the raw material composition constituting the microporous polyolefin membrane must be within the range described above, and the stretching conditions and heat setting conditions during production of the microporous polyolefin membrane must be within the ranges described below. is preferred.
  • the film uniformity obtained by measuring the film thickness of the polyolefin microporous membrane of the present invention is preferably 0.20 or less, more preferably 0.10 or less, and still more preferably 0.05 or less.
  • the film uniformity of the polyolefin microporous film is 0.20 or less, there is little variation in physical properties, and it can be suitably used as a thin battery separator. The method for measuring film uniformity will be described later.
  • the raw material composition constituting the microporous polyolefin membrane should be within the above range, and the stretching conditions and heat setting conditions during film formation of the microporous polyolefin film should be within the ranges described below. It is preferable.
  • the polyolefin microporous membrane of the present invention preferably has an electrical resistance value at room temperature determined by the conditions described below of 1.5 ⁇ cm 2 or less, more preferably 1.2 ⁇ cm 2 or less when converted to a film thickness of 10 ⁇ m. , more preferably 1.0 ⁇ cm 2 or less, particularly preferably 0.8 ⁇ cm 2 or less.
  • the resistance value of the polyolefin microporous membrane at room temperature is 1.5 ⁇ cm 2 or less at a film thickness of 10 ⁇ m, it can be suitably used as a battery separator for secondary batteries that require high output such as electric vehicles. can.
  • the raw material composition constituting the microporous polyolefin membrane should be within the above range, and the stretching conditions and heat setting conditions during film formation of the microporous polyolefin membrane should be within the ranges described below. It is preferable to do so.
  • the microporous polyolefin membrane of the present invention can be used in various applications such as filters, fuel cell separators, and capacitor separators.
  • it since it has excellent safety and output characteristics when used as a battery separator, it is preferably used as a battery separator for secondary batteries that require high energy density, high capacity, and high output such as for electric vehicles. can.
  • the method for producing a polyolefin microporous membrane of the present invention preferably comprises the following steps (a) to (f).
  • a polyolefin resin solution is prepared by heating and dissolving a polyolefin resin and various additives in a plasticizer.
  • the plasticizer may be any solvent as long as it can sufficiently dissolve the polyolefin resin.
  • a liquid solvent that is liquid at room temperature is preferred as the plasticizer.
  • Liquid solvents include aliphatic, cycloaliphatic or aromatic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, liquid paraffin, mineral oil fractions with corresponding boiling points, and dibutyl phthalate. Examples include phthalic acid esters that are liquid at room temperature, such as dioctyl phthalate.
  • a nonvolatile liquid solvent such as liquid paraffin is preferred in order to obtain a gel-like sheet with a stable liquid solvent content.
  • the viscosity of the liquid solvent is preferably 20 cSt or more and 200 cSt or less at 40°C.
  • the viscosity is 20 cSt or more, the sheet obtained by extruding the polyolefin resin solution from a die is less likely to be non-uniform.
  • the viscosity is set to 200 cSt or less, the liquid solvent can be easily removed.
  • the viscosity of the liquid solvent can be measured at 40°C using an Ubbelohde viscometer.
  • a solid solvent that is miscible with the polyolefin in a melt-kneaded state but is solid at room temperature may be used by mixing it with a liquid solvent.
  • the solid solvent include stearyl alcohol, ceryl alcohol, and paraffin wax.
  • the blending ratio of the plasticizer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 75% or more, based on the total of the polyolefin resin and plasticizer being 100% by mass. Further, the blending ratio of the plasticizer is preferably 90% by mass or less.
  • the plasticizer to be added may be added to the extruder in multiple batches, but in order to increase the compatibility between the ultra-high molecular weight polyethylene and the plasticizer, It is preferred to add most of the plasticizer immediately after charging the ultra-high molecular weight polyethylene to the extruder.
  • the proportion of plasticizer added immediately after charging the ultra-high molecular weight polyethylene to the extruder (hereinafter sometimes referred to as initial addition proportion) is based on the total amount of plasticizer to be added as 100% by mass, The content is preferably 60% by mass or more, more preferably 70% by mass or more, particularly preferably 90% by mass or more.
  • the ultra-high molecular weight polyethylene Immediately after the ultra-high molecular weight polyethylene is charged into the extruder means that when the plasticizer input port in the twin-screw extruder is provided downstream from the ultra-high molecular weight polyethylene input port, This means that the distance to the drug inlet is within 100 cm.
  • the extruder it is preferable to uniformly mix the polyolefin resin solution at a temperature at which the polyolefin resin completely melts.
  • the melt-kneading temperature is preferably from (melting point of polyolefin resin +10°C) to (melting point of polyolefin resin +120°C). More preferably, it is from (melting point of polyolefin resin +20°C) to (melting point of polyolefin resin +100°C).
  • the melt-kneading temperature is preferably 140 to 250°C.
  • the melt-kneading temperature is more preferably 150 to 210°C, still more preferably 160 to 230°C, particularly preferably 170 to 200°C.
  • the melt-kneading temperature is lower, but if the temperature is lower than the above-mentioned temperature, unmelted material will be generated in the extrudate extruded from the die, causing membrane rupture in the subsequent stretching process. It may be the cause. Moreover, if the temperature is higher than the above-mentioned temperature, thermal decomposition of the polyolefin resin becomes severe, and the physical properties of the resulting microporous polyolefin membrane, such as strength and porosity, may be inferior. In addition, decomposition products precipitate on chill rolls, rolls during the stretching process, etc., and adhere to the sheet, leading to deterioration in appearance. Therefore, it is preferable to knead within the above range.
  • the melting point is measured by DSC based on JIS K7121:2012.
  • (b) Formation of gel-like sheet A gel-like sheet is obtained by extruding the melt-kneaded resin solution through a die and cooling it. Cooling allows the microphase of the polyolefin resin separated by the plasticizer to be immobilized.
  • the gel-like sheet is preferably cooled to 10 to 50°C. This is because it is preferable to keep the final cooling temperature below the crystallization end temperature of the polyolefin resin in order to refine the higher-order structure of the gel-like sheet. By making the higher-order structure fine, it becomes easier to uniformly stretch the gel-like sheet in subsequent stretching. Therefore, cooling is preferably performed at a rate of 30° C./min or more until at least the gelling temperature or lower.
  • the cooling rate is less than 30° C./min, the crystallinity will increase and it will be difficult to form a gel-like sheet suitable for stretching.
  • the cooling rate is slow, relatively large crystals are formed, so that the higher-order structure of the gel-like sheet becomes coarse and the gel structure forming it also becomes large.
  • the cooling rate is fast, relatively small crystals are formed, so the higher-order structure of the gel-like sheet becomes denser, which not only facilitates uniform stretching but also improves the strength and elongation of the film.
  • Methods for cooling the gel-like sheet include, for example, a method in which it is brought into direct contact with cold air, cooling water, or other cooling medium, a method in which it is brought into contact with a roll cooled with a refrigerant, and a method in which a casting drum is used.
  • the obtained gel-like sheet is biaxially stretched.
  • the biaxial stretching method any of an inflation method, a simultaneous biaxial stretching method, and a sequential biaxial stretching method can be used. Among these, it is preferable to employ the simultaneous biaxial stretching method or the sequential biaxial stretching method in terms of controlling film forming stability, thickness uniformity, and film rigidity and dimensional stability.
  • the simultaneous biaxial stretching method include a method using a simultaneous biaxial tenter.
  • Examples of the sequential biaxial stretching method include a method using a combination of MD stretching using a roll stretching machine and TD stretching using a tenter, or a method using a combination of tenters.
  • the stretching ratio is preferably 5 times or more in both MD/TD directions.
  • the area magnification for stretching is preferably 25 times or more. By setting the area magnification to 25 times or more, more preferably 36 times or more, still more preferably 49 times or more, and particularly preferably 64 times, uniformity of the film can be easily obtained, and unstretched parts are less likely to remain. A microporous polyolefin membrane having excellent mechanical strength and electrical resistance can be obtained. Further, the area magnification is preferably 150 times or less, more preferably 100 times or less. By setting the area magnification of stretching to 150 times or less, it is possible to suppress the occurrence of tears during the production of the microporous polyolefin membrane, improve productivity, suppress the excessive progress of orientation, and improve the melting point of the microporous polyolefin membrane. It is possible to suppress the increase in the shutdown temperature due to the increase in the temperature.
  • the stretching temperature is preferably below the melting point of the gel-like sheet +10°C, and more preferably within the range of (crystal dispersion temperature Tcd of the polyolefin resin) to (melting point of the gel-like sheet +5°C).
  • the polyolefin resin is a polyethylene resin, it has a crystal dispersion temperature of about 90 to 100°C, so the stretching temperature is preferably 90 to 135°C, more preferably 90 to 130°C.
  • the stretching temperature Tcd is determined from the temperature characteristics of dynamic viscoelasticity measured according to ASTM D4065-20 (2020).
  • Plasticizer extraction cleaning
  • the plasticizer (solvent) remaining in the gel sheet is removed using a cleaning solvent. Since the polyolefin resin phase and the solvent phase are separated, a microporous polyolefin membrane can be obtained by removing the solvent.
  • cleaning solvents examples include saturated hydrocarbons such as pentane, hexane, and heptane; chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride; ethers such as diethyl ether and dioxane; ketones such as methyl ethyl ketone; trifluoroethane, etc.
  • examples include chain fluorocarbons.
  • these cleaning solvents have a low surface tension (eg, 24 mN/m or less at 25°C).
  • the network structure that forms micropores is prevented from shrinking due to surface tension at the air-liquid interface during drying after cleaning, creating a polyolefin with high porosity and permeability.
  • a microporous membrane is obtained.
  • Examples of the cleaning method include immersing the gel sheet in a cleaning solvent, showering the gel sheet with a cleaning solvent, or a combination thereof.
  • the amount of cleaning solvent used varies depending on the cleaning method, but is generally preferably 300 parts by mass or more per 100 parts by mass of the gel sheet.
  • the washing temperature is preferably 15 to 30°C, and if necessary, it is heated to 80°C or lower.
  • the above-mentioned washing is preferably carried out until the amount of plasticizer remaining in the gel sheet, that is, the polyolefin microporous membrane after washing, becomes less than 1% by mass.
  • the polyolefin microporous membrane is dried to remove the solvent in the polyolefin microporous membrane. If the drying is insufficient, the porosity of the polyolefin microporous membrane decreases during the subsequent heat treatment, resulting in poor permeability.
  • a method using a metal heating roll, a method using hot air, etc. can be selected.
  • the dried microporous polyolefin membrane may be stretched (re-stretched) in at least one direction.
  • Re-stretching can be carried out by the tenter method or the like in the same manner as the above-mentioned stretching while heating the polyolefin microporous membrane.
  • the re-stretching may be uniaxial or biaxial stretching. In the case of multi-stage stretching, it is carried out by combining simultaneous biaxial stretching and/or sequential stretching.
  • the re-stretching temperature is preferably below the melting point of the polyolefin resin, and more preferably within the range of (crystal dispersion temperature Tcd of the polyolefin resin - 20°C) to the melting point. Specifically, the temperature is preferably 70 to 140°C, more preferably 110 to 138°C, and still more preferably 120 to 135°C.
  • the re-stretching ratio is preferably 1.01 to 3.0 times.
  • the TD direction is preferably 1.01 to 2.0 times, more preferably 1.2 to 1.8 times, particularly preferably 1.3 to 1.6 times.
  • the stretching is preferably 1.01 to 1.6 times in the MD direction and in the TD direction, respectively.
  • the re-stretching magnification may be different in the MD direction and the TD direction.
  • the relaxation rate in relaxation treatment is the value obtained by dividing the dimension of the film after relaxation treatment by the dimension of the film before relaxation treatment, and the relaxation rate in both MD and TD directions must be 1.0 or less. is preferable, more preferably 0.9 or less, still more preferably 0.85 or less.
  • microporous polyolefin membrane may be subjected to crosslinking treatment or hydrophilic treatment depending on the intended use.
  • Crosslinking treatment increases the meltdown temperature of the polyolefin microporous membrane.
  • the crosslinking treatment can be performed by irradiating the polyolefin microporous membrane with ionizing radiation such as ⁇ rays, ⁇ rays, ⁇ rays, and electron beams.
  • ionizing radiation such as ⁇ rays, ⁇ rays, ⁇ rays, and electron beams.
  • electron beam irradiation an electron beam dose of 0.1 to 100 Mrad is preferred, and an accelerating voltage of 100 to 300 kV is preferred.
  • the hydrophilization treatment can be performed by monomer grafting, surfactant treatment, corona discharge, etc.
  • Monomer grafting is preferably carried out after crosslinking treatment.
  • any one selected from nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used, but nonionic surfactants are preferred.
  • the polyolefin microporous membrane is immersed in a solution prepared by dissolving a surfactant in water or a lower alcohol such as methanol, ethanol, or isopropyl alcohol, or the solution is applied to the polyolefin microporous membrane by a doctor blade method. .
  • the microporous polyolefin membrane of the present invention may be a laminate in which porous layers containing resins other than polyolefin resin are laminated for the purpose of imparting functions such as meltdown resistance, heat resistance, and adhesiveness. Lamination of porous layers can be performed by coating, vapor deposition, or the like.
  • an inorganic particle layer containing a binder and inorganic particles may be laminated.
  • the binder component constituting the inorganic particle layer for example, acrylic resin, polyvinylidene fluoride resin, polyamideimide resin, polyamide resin, aromatic polyamide resin, polyimide resin, etc. can be used.
  • the inorganic particles constituting the inorganic particle layer for example, particles made of alumina, boehmite, barium sulfate, magnesium oxide, magnesium hydroxide, magnesium carbonate, silicon, etc. can be used.
  • the porous layer may be one in which the resin exemplified as the binder is made porous.
  • microporous polyolefin membrane of the present invention obtained as described above can be used in various applications such as filters, separators for fuel cells, and separators for capacitors.
  • the polyolefin microporous membrane of the present invention has excellent battery characteristics and battery safety especially when used as a battery separator. It can be preferably used as a separator for aqueous electrolyte secondary batteries.
  • a non-aqueous electrolyte secondary battery includes at least a positive electrode, a negative electrode, an electrolytic solution, and a separator. The separator is arranged to maintain insulation between the positive electrode and the negative electrode.
  • the electrolytic solution consists of an organic solvent and an electrolyte, and these are placed in a container. It is enclosed.
  • the polyolefin microporous membrane of the present invention can be suitably used as a separator for nonaqueous electrolyte secondary batteries as it is, but it may also be used by laminating a nonwoven fabric, a heat-resistant coating layer, or the like.
  • the polyolefin microporous membrane of the present invention has excellent filtration accuracy and high permeability when used as a liquid filter, so it can be preferably used as a liquid filter for semiconductor resists that requires high-precision filtration.
  • the microporous polyolefin membrane of the present invention can be used as a liquid filter for a filtration unit in the form of a sheet, a tube, a pleat, or the like. It is preferable to use it in a pleated filtration unit because the filtration area can be increased.
  • a reinforcing membrane made of a mesh or porous material using a resin material on at least one side of the microporous polyolefin membrane of the present invention.
  • the microporous polyolefin membrane of the present invention is laminated with a reinforcing membrane using a heating roll or the like, it can be woven into a pleat shape with creases at peaks and valleys, and then incorporated into a filtration unit for use.
  • Proportion of components with a molecular weight of 10 million or more (mass%) (amount of components with a molecular weight of 10 million or more) ⁇ (amount of components with a total molecular weight) x 100
  • the detection intensity at a molecular weight of 2 million is K200
  • the detection intensity at a molecular weight of 3 million is K300
  • the detection intensity at a molecular weight of 7 million is K700. And so.
  • K200-K700 Difference in detection intensity between polyolefin microporous membranes with molecular weights of 2 million and 7 million: K200-K700 Using K200 and K700 of the polyolefin microporous membrane obtained as described above, K200-K700 was calculated.
  • Hafnium content (ppm) in polyolefin microporous membrane A microporous polyolefin membrane was weighed, decomposed using sulfuric acid, nitric acid, and perchloric acid, and then heated and dissolved in dilute aqua regia to provide a measurement solution. The hafnium content of the obtained solution was measured by ICP mass spectrometry using a quadrupole ICP mass spectrometer (PerkinElmer NexION 2000).
  • Average pore diameter/maximum pore diameter The following measurements were performed at three different locations in the same microporous polyolefin membrane, the average value of the average pore diameter and the maximum pore diameter was determined, and the average pore diameter was divided by the maximum pore diameter.
  • Film thickness Measure the film thickness at 5 points within a 50 mm x 50 mm area of the microporous polyolefin film using a contact thickness meter (“Lightmatic” VL-50 manufactured by Mitutoyo Co., Ltd., 10.5 mm diameter carbide spherical measuring tip). The average value was taken as the film thickness ( ⁇ m).
  • P 150°C /P Max (Meltdown resistance characteristic evaluation)
  • a sample for evaluation was prepared by cutting a polyolefin microporous membrane into a piece with a long axis of 15 mm and a short axis of 3 mm. After that, using "TMA7100" manufactured by Hitachi High-Technology, the evaluation sample was fixed on the chuck so that the distance between the chucks was 10 mm, and the temperature was increased from 30 °C to 200 °C at 5 °C in constant length mode with an initial load of 9.8 mN. The temperature was raised at a rate of /min.
  • the temperature and shrinkage force when the temperature was raised to 200°C were measured at 1 second intervals, and the shrinkage force and maximum shrinkage force at 150°C were determined from the obtained chart. Then, the contractile force at 150°C was divided by the maximum contractile force to obtain P 150°C /P Max .
  • shutdown temperature While heating the polyolefin microporous membrane at a temperature increase rate of 5°C/min, the air permeability resistance was measured using an air permeability meter (manufactured by Asahi Seiko Co., Ltd., EGO-1T), and the air permeation resistance was at the detection limit. The temperature at which a certain 1.0 ⁇ 10 5 seconds/100 cm 3 Air was reached was determined and set as the shutdown temperature (° C.) by the temperature-rising air permeability method.
  • the measurement cell was composed of an aluminum block and had a structure with a thermocouple directly under the microporous polyolefin membrane.
  • the sample was cut into a 50 mm x 50 mm square, and the temperature was measured while fixing the periphery with an O-ring.
  • a test piece and a gasket were placed on the inner bottom of the lower lid of a 2032 type coin cell member in order from the lower lid side.
  • 0.15 mL of an electrolytic solution in which LiPF 6 was dissolved in a mixed solvent with a volume ratio of EC and EMC of 4:6 to a concentration of 1 mol/L was poured into the coin cell.
  • LiPF 6 Lithium hexafluorophosphate
  • EC Ethylene carbonate
  • EMC Ethyl methyl carbonate
  • the operation was performed twice to impregnate the polyolefin microporous membrane with the electrolyte. Thereafter, a wave washer and a top lid were placed on the spacer in this order from the spacer side, and sealed using a coin cell crimping machine (manufactured by Hosen Co., Ltd.) to produce an evaluation cell.
  • a coin cell crimping machine manufactured by Hosen Co., Ltd.
  • the electrical resistance value of the produced coin battery was measured at a frequency of 200 kHz using an impedance analyzer in an atmosphere of 25°C.
  • the resistance value obtained by the above measurement method includes the contribution of resistance other than the polyolefin microporous membrane, such as the case and electrodes, so the number of polyolefin microporous membrane test pieces to be placed in the coin battery is 3 and 4.
  • Five coin batteries were prepared, and the resistance value ( ⁇ cm 2 ) per microporous polyolefin membrane was calculated from the resistance value of each coin battery. Then, the resistance value converted to a film thickness of 10 ⁇ m was calculated using the following formula.
  • R2 R1 ⁇ 10/T
  • R 2 Resistance value converted to 10 ⁇ m ( ⁇ cm 2 /10 ⁇ m)
  • R 1 Resistance value per polyolefin microporous membrane ( ⁇ cm 2 )
  • T Film thickness ( ⁇ m) of polyolefin microporous membrane.
  • B Displacement amount (mm)/separator thickness ( ⁇ m) was 0.05 or more and less than 0.07.
  • C Displacement amount (mm)/separator thickness ( ⁇ m) was 0.03 or more and less than 0.05.
  • D Displacement amount (mm)/separator thickness ( ⁇ m) was less than 0.03.
  • the gel-like sheet was simultaneously biaxially stretched 8 times in both the MD direction and the TD direction at 115° C. using a tenter stretching machine.
  • the dried membrane was heat-set at 130° C. for 3 minutes to obtain a microporous polyolefin membrane.
  • the thickness of the obtained microporous polyolefin membrane was 8 ⁇ m. Table 3 shows the blending ratio of each constituent component, manufacturing conditions, evaluation results, etc.
  • Example 2 A microporous polyolefin membrane was obtained by forming a film in the same manner as in Example 1 except for changing the raw material composition and process conditions shown in Table 3.
  • Example 5 appearance unevenness occurred at the time of forming the gel-like sheet, but since it was possible to perform the post-process, the film formability was rated B.
  • Example 6 A microporous polyolefin membrane was obtained by forming a film in the same manner as in Example 1, except for changing the raw material composition and process conditions shown in Table 4.
  • Comparative Example 4 appearance unevenness occurred at the time of forming the gel-like sheet, but since it was possible to perform the post-process, the film formability was rated B.
  • Comparative Example 5 a large amount of unmelted material was generated in the polyolefin resin solution after melt-kneading, and the formation of the gel-like sheet was intermittent, and unmelted material was also present in the polyolefin microporous membrane. Therefore, the film formability was rated C.
  • Comparative Example 6 unmelted substances were generated in the polyolefin resin solution after melt-kneading, but the post-process could be carried out, so the film formability was rated B.
  • microporous polyolefin membranes of Examples 1 to 4 were confirmed to have both shutdown characteristics and meltdown resistance while having excellent mechanical strength, and also had excellent membrane quality, ion permeability, and resistance as battery separators. It had foreign material properties. Further, in Example 5, excellent mechanical strength and meltdown resistance were confirmed while maintaining shutdown characteristics, but film uniformity was inferior compared to other Examples. Further, although Example 6 had excellent mechanical strength and film uniformity, it was inferior to other Examples in meltdown resistance, average pore diameter/maximum pore diameter, and room temperature resistance value.
  • the polyolefin microporous membranes of Comparative Examples 1 to 4 and 6 had at least one of the required characteristics deteriorated, indicating that they were not compatible.
  • Comparative Example 5 although it was formed as a polyolefin microporous membrane, the membrane uniformity was significantly inferior to the others, and some evaluations were not performed.
  • the microporous polyolefin membrane of the present invention has excellent mechanical strength while also achieving both shutdown characteristics and meltdown resistance characteristics. It has excellent membrane quality, ion permeability, and foreign object resistance as a battery separator, making it possible to achieve both high levels of battery characteristics and battery safety. Therefore, it can be suitably used in separators for secondary batteries that require high battery capacity. Furthermore, a non-aqueous electrolyte secondary battery having the polyolefin microporous membrane of the present invention as a separator can increase battery capacity while maintaining a high level of battery safety by taking advantage of the characteristics of the polyolefin microporous membrane. .
  • the microporous polyolefin membrane of the present invention can be suitably used in various filters (reverse osmosis filtration membranes, ultrafiltration membranes, precision filtration membranes, etc.) by taking advantage of its properties.
  • filters reverse osmosis filtration membranes, ultrafiltration membranes, precision filtration membranes, etc.
  • Various filters using the polyolefin microporous membrane of the present invention have high mechanical strength, can be made into thin films, and have a uniform pore structure, so they maintain filtration flow rate at a high level and improve filtration accuracy. Also excellent.

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Abstract

La présente invention concerne une membrane microporeuse en polyoléfine qui présente une résistance à la perforation convertie en poids unitaire de 0,8 N/(g/m2) ou plus, dans laquelle : dans la distribution de poids moléculaire de la membrane microporeuse en polyoléfine obtenue par un procédé de chromatographie par perméation de gel (procédé GPC), le poids moléculaire étant sur l'axe horizontal et l'intensité détectée sur l'axe vertical, si la quantité totale de tous les composants est considérée comme étant 100 %, la quantité de composants ayant un poids moléculaire de 10 000 000 ou plus est de 1,0 % ou moins ; et si toutes les intensités détectées sont normalisées, en considérant l'intensité maximale détectée comme étant 1, et si K200 est l'intensité détectée au poids moléculaire de 2 000 000 et K700 est l'Intensité détectée au poids moléculaire de 7 000 000, K200 et K700 satisfont à l'expression relationnelle (K200-K700) ≥ 0,4. La présente invention concerne une membrane microporeuse en polyoléfine qui permet d'obtenir d'excellentes caractéristiques de batterie et une excellente sécurité de batterie lorsqu'elle est utilisée en tant que séparateur pour une batterie.
PCT/JP2023/010054 2022-03-18 2023-03-15 Membrane microporeuse en polyoléfine, séparateur pour batteries, batterie secondaire à électrolyte non aqueux et filtre WO2023176876A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010079784A1 (fr) * 2009-01-07 2010-07-15 三井化学株式会社 Composition de résine de polypropylène pour la formation de films microporeux
WO2018164056A1 (fr) * 2017-03-08 2018-09-13 東レ株式会社 Film microporeux polyoléfinique
WO2018164057A1 (fr) * 2017-03-08 2018-09-13 東レ株式会社 Membrane de polyoléfine microporeuse, membrane de polyoléfine microporeuse multicouche, membrane de polyoléfine microporeuse stratifiée et séparateur
WO2018173904A1 (fr) * 2017-03-22 2018-09-27 東レ株式会社 Membrane microporeuse en polyoléfine et batterie la comprenant
JP2018162438A (ja) * 2017-03-24 2018-10-18 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
WO2020256138A1 (fr) * 2019-06-21 2020-12-24 旭化成株式会社 Membrane microporeuse en polyoléfine

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010079784A1 (fr) * 2009-01-07 2010-07-15 三井化学株式会社 Composition de résine de polypropylène pour la formation de films microporeux
WO2018164056A1 (fr) * 2017-03-08 2018-09-13 東レ株式会社 Film microporeux polyoléfinique
WO2018164057A1 (fr) * 2017-03-08 2018-09-13 東レ株式会社 Membrane de polyoléfine microporeuse, membrane de polyoléfine microporeuse multicouche, membrane de polyoléfine microporeuse stratifiée et séparateur
WO2018173904A1 (fr) * 2017-03-22 2018-09-27 東レ株式会社 Membrane microporeuse en polyoléfine et batterie la comprenant
JP2018162438A (ja) * 2017-03-24 2018-10-18 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
WO2020256138A1 (fr) * 2019-06-21 2020-12-24 旭化成株式会社 Membrane microporeuse en polyoléfine

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