WO2023176876A1 - Polyolefin microporous membrane, separator for batteries, nonaqueous electrolyte secondary battery and filter - Google Patents

Polyolefin microporous membrane, separator for batteries, nonaqueous electrolyte secondary battery and filter Download PDF

Info

Publication number
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
Authority
WO
WIPO (PCT)
Prior art keywords
molecular weight
polyolefin
microporous membrane
polyolefin microporous
membrane
Prior art date
Application number
PCT/JP2023/010054
Other languages
French (fr)
Japanese (ja)
Inventor
遼 下川床
琢也 久万
直哉 西村
龍太 中嶋
Original Assignee
東レ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 東レ株式会社 filed Critical 東レ株式会社
Publication of WO2023176876A1 publication Critical patent/WO2023176876A1/en

Links

Classifications

    • 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 OR LIGHT-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.

Abstract

The present invention provides a polyolefin microporous membrane which has a unit weight-converted puncture strength of 0.8 N/(g/m2) or more, wherein: in the molecular weight distribution of the polyolefin microporous membrane as obtained by a gel permeation chromatography method (GPC method), taking molecular weight on the horizontal axis and detected intensity on the vertical axis, if the total amount of all components is taken as 100%, the amount of components having a molecular weight of 10,000,000 or more is 1.0% or less; and if all detected intensities are normalized, while taking the maximum detected intensity as 1, and if K200 is the detected intensity at the molecular weight of 2,000,000 and K700 is the detected intensity at the molecular weight of 7,000,000, K200 and K700 satisfy the relational expression (K200 - K700) ≥ 0.4. The present invention provides a polyolefin microporous membrane which enables the achievement of excellent battery characteristics and excellent battery safety when used as a separator for a battery.

Description

ポリオレフィン微多孔膜、電池用セパレータ、非水電解液二次電池およびフィルターPolyolefin microporous membranes, battery separators, non-aqueous electrolyte secondary batteries and filters
　本発明は、ポリオレフィン微多孔膜、電池用セパレータ、非水電解液二次電池およびフィルターに関する。 The present invention relates to a microporous polyolefin membrane, a battery separator, a non-aqueous electrolyte secondary battery, and a filter.
　ポリオレフィン微多孔膜は物質の分離膜、選択透過膜、および隔離膜等として広く用いられている。ポリオレフィン微多孔膜の具体的な用途は、非水電解液二次電池（例えば、リチウムイオン二次電池、ニッケル－水素電池、ニッケル－カドミウム電池、ポリマー電池等）用セパレータ、電気二重層コンデンサ用セパレータ、各種フィルター（逆浸透濾過膜、限外濾過膜、精密濾過膜等）、透湿防水衣料、医療用材料、燃料電池用支持体などである。 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, medical materials, supports for fuel cells, etc.
　特にリチウムイオン二次電池用セパレータとして、ポリオレフィン微多孔膜が広く採用されている。その特徴として、電池性能に直結するイオン透過性（以下、イオン透過性を単に「透過性」という場合がある）などに優れながら、電池の安全性に優れ、生産性に大きく寄与する機械的強度にも優れることが挙げられる。近年、電池の小型化および高容量化に伴い、セパレータの更なる薄膜化が進み、より高い機械的強度をもつポリオレフィン微多孔膜の需要が高まっている。 In particular, 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.
　高強度化の手法として、微多孔膜中の空孔率を低下させ、微多孔膜中の樹脂量を増やす方法もあるが、孔の閉塞や電解液保持量の低下によりイオン透過性が低下するという問題がある。また、分子量１００万以上の成分を含む超高分子量ポリエチレンを適用し、微多孔膜構造自体を強化する検討が進められているものの、超高分子量ポリエチレンは加工性の難しさから製膜難度が高く、微多孔膜の高品位化が課題となっている。イオン透過性と膜品位を維持したまま、高強度化させることがポリオレフィン微多孔膜の課題の一つである。 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. There is a problem. In addition, although studies are underway to strengthen the microporous membrane structure by applying 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.
　さらに、ポリオレフィン微多孔膜は、電池の外部／内部の異常反応時には１３０～１５０℃程度の温度において自動的にイオンの透過を遮断し、過度の温度上昇を抑制する孔閉塞機能（シャットダウン特性）を備えている。孔閉塞機能（シャットダウン特性）が発現された後、さらに高温の状態が一定時間保持されると、孔閉塞後のポリオレフィン微多孔膜が溶融により部分的に流動して孔閉塞を維持できなくなりイオンを透過してしまう現象（メルトダウン）が見られる。このメルトダウンが起こる温度を高くする耐メルトダウン特性もポリオレフィン微多孔膜の課題として重要視されている。シャットダウン温度をより低く、メルトダウン温度をより高くすることが電池の安全性を向上させる上で重要とされているが、これらは微多孔膜の機械的強度やイオン透過性とトレードオフの関係である。 Furthermore, 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. We are prepared. After the pore-blocking function (shutdown property) is developed, 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.
　以上のように、電池用セパレータの更なる薄膜化に対して、ポリオレフィン微多孔膜には、機械的強度を向上させつつも、膜品位、イオン透過性、シャットダウン特性および耐メルトダウン特性において高度なバランスを維持することが求められている。 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.
特開２００９－１０８３２３号公報Japanese Patent Application Publication No. 2009-108323 特開２０００－２０４１８８号公報Japanese Patent Application Publication No. 2000-204188 特開２００４－１９６８７１号公報Japanese Patent Application Publication No. 2004-196871
　高強度化の手法として、特許文献１では、高粘度（高分子量）のポリオレフィンを用いているが、機械的強度およびシャットダウン温度のバランスが悪く、高出力・高容量用電池のセパレータとしては使用できない場合があった。また、機械的強度を向上させるために更なる高分子量化および延伸倍率増加をすると、シャットダウン温度がさらに上昇する懸念がある。 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.
　シャットダウン温度を低くする手法として、特許文献２においては、低分子量や低融点の原料を使用して、微多孔膜への閉孔成分の増加等が行われている。しかしながら、低分子量成分が多いため、閉孔温度（シャットダウン温度）には優れているものの、現在の薄膜化したセパレータとして使用するには機械強度が不十分であると推定される。また、空孔率を下げる等の方法で機械的強度を向上させた場合、孔が過度に塞がり、イオン透過性の悪化が懸念される。以上のように、微多孔膜のシャットダウン特性と、機械強度や透過性はトレードオフの関係にあり、両者を高いレベルで両立することは困難であった。 As a method for lowering the shutdown temperature, 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. However, 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. Furthermore, if 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. As described above, there is a trade-off relationship between the shutdown characteristics of microporous membranes, mechanical strength, and permeability, and it has been difficult to achieve both at a high level.
　さらに、特許文献３においては、耐メルトダウン特性を向上させるためにポリプロピレンなどの高耐熱原料を添加する手法がとられているものの、膜品位や機械的強度の維持が難しい。 Furthermore, in 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.
　本発明の課題は、膜品位を維持しながら、電池の出力特性に寄与するイオン透過性、安全特性に寄与する機械的強度やシャットダウン特性、耐メルトダウン特性に優れ、電池用セパレータとして用いたとき、優れた出力特性と安全性を有するポリオレフィン微多孔膜を提供することにある。 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.
　本発明者らは上述の問題点を解決するために鋭意検討を重ねた結果、本発明のポリオレフィン微多孔膜は従来のポリオレフィン微多孔膜と比べて、透過性や膜品位、シャットダウン特性を維持しつつ、機械的強度と耐メルトダウン特性が高いレベルで両立が可能となることを見出した。 The present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that the 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.
　すなわち本発明は、次の構成を有する。
［Ｉ］単位目付換算突刺強度が０．８Ｎ／（ｇ／ｍ２）以上であり、かつゲル浸透クロマトグラフィー法（ＧＰＣ法）により得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、全体の成分量を１００質量％とした時に分子量１０００万以上の成分量が１．０％質量以下であり、かつ最大検出強度を１として分子量分布の検出強度を規格化し、分子量２００万における検出強度をＫ２００、分子量７００万における検出強度をＫ７００としたとき、Ｋ２００－Ｋ７００≧０．４であるポリオレフィン微多孔膜。
［ＩＩ］ＧＰＣ法より得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度を１として全体の検出強度を規格化した時の分子量２００の検出強度：Ｋ２００が０．６以上である［Ｉ］に記載のポリオレフィン微多孔膜。
［ＩＩＩ］ＧＰＣ法より得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度が分子量１０万から５０万の領域に存在する［Ｉ］または［ＩＩ］に記載のポリオレフィン微多孔膜。
［ＩＶ］ＪＩＳ　Ｋ　３８３２－１９９０に基づくパームポロメーター測定により得られる平均孔径と最大孔径の比（平均孔径／最大孔径）が０．６５以上である［Ｉ］から［ＩＩＩ］のいずれかに記載のポリオレフィン微多孔膜。
［Ｖ］昇温速度５℃／ｍｉｎ条件の熱機械分析測定（ＴＭＡ測定）から得られる横軸を温度、縦軸を応力としたポリオレフィン微多孔膜の温度－応力曲線において、最大応力をＰｍａｘ、温度１５０℃における応力をＰ１５０とした時、Ｐ１５０／Ｐｍａｘ≧０．６である［Ｉ］から［ＩＶ］のいずれかに記載のポリオレフィン微多孔膜。
［ＶＩ］ハフニウムを０．２ｐｐｍ以上含む［Ｉ］から［Ｖ］のいずれかに記載のポリオレフィン微多孔膜。
［ＶＩＩ］［Ｉ］から［ＶＩ］のいずれかに記載のポリオレフィン微多孔膜に、さらに多孔質層が積層された積層体。
［ＶＩＩＩ］［Ｉ］から［ＶＩ］のいずれかに記載のポリオレフィン微多孔膜、または［ＶＩＩ］に記載の積層体を用いた、電池用セパレータ。
［ＩＸ］［ＶＩＩＩ］に記載の電池用セパレータを有する、非水電解液二次電池。
［Ｘ］［Ｉ］から［ＶＩ］のいずれかに記載のポリオレフィン微多孔膜を用いた、フィルター。
［ＸＩ］［Ｘ］に記載の液体用ろ過フィルターを用いたろ過ユニット。 That is, 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. In the molecular weight distribution of a microporous membrane, when the total component amount is 100% by mass, the amount of components with a molecular weight of 10 million or more is 1.0% by mass or less, and the maximum detection intensity is 1, and the detection intensity of the molecular weight distribution is standard. A microporous polyolefin membrane in which K200-K700≧0.4, where the detection intensity at a molecular weight of 2 million is K200 and the detection intensity at a molecular weight of 7 million is K700.
[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.
[III] In the molecular weight distribution of a polyolefin microporous membrane obtained by the GPC method, with the horizontal axis representing the molecular weight and the vertical axis representing the detection intensity, the maximum detection intensity exists in the molecular weight region of 100,000 to 500,000 [I] or [ II].
[IV] Any one of [I] to [III], wherein the ratio of average pore diameter to maximum pore diameter (average pore diameter/maximum pore diameter) obtained by palm porometer measurement based on JIS K 3832-1990 is 0.65 or more. microporous polyolefin membrane.
[V] In the 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, the maximum stress is Pmax, The polyolefin microporous membrane according to any one of [I] to [IV], wherein P150/Pmax≧0.6, where P150 is stress at a temperature of 150°C.
[VI] The polyolefin microporous membrane according to any one of [I] to [V], containing 0.2 ppm or more of hafnium.
[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].
　本発明のポリオレフィン微多孔膜は、電池の出力特性に寄与するイオン透過性、安全特性に寄与する機械的強度やシャットダウン特性および耐メルトダウン特性に優れる。したがって、高エネルギー密度化、高容量化および高出力化を必要とする二次電池用のセパレータとして好適に使用することができる。 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.
　また、本発明のポリオレフィン微多孔膜は、均一な孔構造を有していることから、フィルター用途としても好適に使用することができる。 Furthermore, since the polyolefin microporous membrane of the present invention has a uniform pore structure, it can also be suitably used as a filter.
　以下、本発明の実施形態について説明する。 Hereinafter, embodiments of the present invention will be described.
　なお、本発明においては、ポリオレフィン微多孔膜の製膜する方向に平行な方向を製膜方向、長手方向あるいはＭＤ方向と称し、ポリオレフィン微多孔膜面内で製膜方向に直交する方向を幅方向あるいはＴＤ方向と称する。 In the present invention, 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. Alternatively, it is referred to as the TD direction.
　本発明のポリオレフィン微多孔膜に用いる原料としては超高分子量ポリエチレン（ＵＨＰＥ）を少なくとも１種類含むことが好ましい。本発明のポリオレフィン微多孔膜の樹脂成分中の超高分子量ポリエチレンの割合は５０質量％以上が好ましく、６０質量％以上が好ましく、７０質量％以上がさらに好ましく、９０質量％以上が特に好ましい。 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). 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.
　本発明において原料として用いる超高分子量ポリエチレンは、エチレンの単独重合体でもよいし、後述のように融点を低下させるために、他のα－オレフィンを含有する共重合体でもよい。他のα－オレフィンとしては、例えば、プロピレン、ブテン－１、ヘキセン－１、ペンテン－１、４－メチルペンテン－１、オクテン、酢酸ビニル、メタクリル酸メチル、スチレンが挙げられる。α－オレフィンの存在や種類は、Ｃ１３－ＮＭＲで測定することで確認できる。 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 α-olefins in order to lower the melting point as described below. Other α-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 α-olefin can be confirmed by measuring with C 13 -NMR.
　本発明において原料として用いる超高分子量ポリエチレンは、後述する条件におけるゲルパーミエーションクロマトグラフィー（ＧＰＣ）測定から得られる重量平均分子量（Ｍｗ）が８０万以上であることが好ましく、１００万以上がより好ましく、１２０万以上がさらに好ましい。また、Ｍｗは２００万以下が好ましく、１５０万以下がより好ましい。Ｍｗが上記範囲内であると、溶融混練によって分子量が調整された後も延伸応力が効率よく伝わり、ポリオレフィン微多孔膜に高強度化に必要な分子量成分を維持することが可能である。 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.
　本発明において原料として用いる超高分子量ポリエチレンは、後述する条件におけるＧＰＣ測定から得られる分子量分布において、１０万以上１００万未満の領域と１００万以上１０００万以下の領域の二つの領域にピークを持つことが好ましい。低分子量側の範囲は１０万以上５０万以下がより好ましく、高分子量側の範囲は１００万以上５００万以下がより好ましい。上記両方の分子量範囲にピークがあることで、高強度化を促進するが、可塑剤と相溶しにくい高分子量成分を低分子量成分がサポートし、可塑剤と相溶しやすくすることが可能であり、ポリオレフィン微多孔膜の品位と高強度化の両立が可能となる。 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.
　本発明において原料として用いる超高分子量ポリエチレンは、後述する条件におけるＧＰＣ測定から得られる分子量分布において、最大検出強度を１として分子量分布の検出強度を規格化し、分子量３００万における検出強度をＫ３００、分子量７００万における検出強度をＫ７００としたとき、その比：Ｋ３００／Ｋ７００が２．０以上であることが好ましく、３．０以上がより好ましく、４．０以上がさらに好ましい。このＫ３００／Ｋ７００は高分子量側の分子量均一性を示しており、この値が大きいほどシャープな分布の高分子量成分を有する。この値が範囲内にあることで、溶融混練によって分子量が調整された際もポリオレフィン微多孔膜に高強度化に必要な分子量成分を維持することが可能である。また、高分子量成分の均一性が高くなることで、分子の絡み合いも強固となり、溶融後も形態を維持しやすい。 In the ultra-high molecular weight polyethylene used as a raw material in the present invention, in the molecular weight distribution obtained from GPC measurement under the conditions described below, 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. When the detection intensity at 7 million is K700, 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. When this value is within this range, even when the molecular weight is adjusted by melt-kneading, it is possible to maintain the molecular weight components necessary for increasing the strength of the polyolefin microporous membrane. In addition, by increasing the uniformity of the high molecular weight components, the entanglement of molecules becomes strong, and the shape is easily maintained even after melting.
　本発明において原料として用いる超高分子量ポリエチレンは、ＧＰＣ測定から得られた分子量分布において、分子量１０００万以上の成分量は４．０質量％以下が好ましく、より好ましくは２．０質量％以下、さらに好ましくは１．０質量％以下である。この分子量１０００万以上の成分を均一に延伸するには、現在の生産条件よりも大幅に高い延伸倍率が必要であり、不均一な延伸の要因となる。そのため、分子量１０００万以上の成分は、高強度化への関与は低い一方で熱収縮悪化の要因になると懸念される。よって、この成分量が上記の範囲内にあることで、溶融混練によって分子量が調整された際も、ポリオレフィン微多孔膜に高強度化に必要な分子量成分を維持することが可能である。 In the ultra-high molecular weight polyethylene used as a raw material in the present invention, 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. In order to uniformly stretch 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.
　本発明において原料として用いる超高分子量ポリエチレンはメタロセン触媒を用いて重合されることが好ましい。メタロセン触媒を用いて重合されたポリエチレンは、分子量分布が狭く、上記Ｋ３００／Ｋ７００や分子量１０００万以上の成分量を上述した範囲に調整しやすい。なお、メタロセン触媒を用いて重合されたポリエチレンはその触媒残渣であるＨｆ（ハフニウム）やＣｒ（クロム）などを含む。 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. Note that polyethylene polymerized using a metallocene catalyst contains catalyst residues such as Hf (hafnium) and Cr (chromium).
　本発明において原料として用いる超高分子量ポリエチレンは、示差走査熱量計（ＤＳＣ）から得られる融点が１３４℃以上であることが好ましく、１３５℃以上がより好ましく、さらに好ましくは１３５．５℃以上である。また、融点は、１４０℃以下が好ましく、１３７．５℃以下がより好ましく、１３６．０以下がさらに好ましい。融点が上記範囲内であると、熱固定工程での透過性の悪化やシャットダウン温度の過度な上昇が抑制でき、各種物性の両立が可能となる。 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.
　本発明において原料として用いる超高分子量ポリエチレンは、後述する条件における示差走査熱量計（ＤＳＣ）から得られるΔＨ（Ｊ／ｇ）が１５０Ｊ／ｇ以上であることが好ましく、１５５Ｊ／ｇ以上であることがより好ましい。また、ΔＨは、２００Ｊ／ｇ以下が好ましく、１９０Ｊ／ｇ以下がより好ましく、１８０Ｊ／ｇ以下がさらに好ましい。ΔＨが上記範囲内であると、熱固定工程での透過性の悪化やシャットダウン温度の過度な上昇が抑制でき、各種物性の両立が可能となる。 The ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a ΔH (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. Moreover, ΔH is preferably 200 J/g or less, more preferably 190 J/g or less, and even more preferably 180 J/g or less. When ΔH is within the above range, deterioration of permeability and excessive rise in shutdown temperature in the heat setting process can be suppressed, and various physical properties can be achieved simultaneously.
　本発明のポリオレフィン微多孔膜は超高分子量ポリエチレン（ＵＨＰＥ）以外のポリオレフィンを含んでもよい。このポリオレフィンとしては超高分子量ポリエチレンとの相溶性の観点からポリエチレンが好ましい。 The microporous polyolefin membrane of the present invention may contain polyolefins other than ultra-high molecular weight polyethylene (UHPE). As this polyolefin, polyethylene is preferable from the viewpoint of compatibility with ultra-high molecular weight polyethylene.
　本発明において原料として用いる超高分子量ポリエチレン以外のポリエチレンについて、後述する条件におけるゲルパーミエーションクロマトグラフィー（ＧＰＣ）測定から得られる重量平均分子量（Ｍｗ）は１万以上が好ましく、５万以上がより好ましい。また、Ｍｗは３０万以下が好ましく、２０万以下がより好ましい。Ｍｗが上記範囲内であると、高分子量ポリオレフィンが形成する構造を過度に阻害しないため、機械的強度を維持しつつ、シャットダウンや熱収縮特性の更なる向上が可能となる。 Regarding polyethylene other than ultra-high molecular weight polyethylene used as a raw material in the present invention, 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.
　本発明において原料として用いる超高分子量ポリエチレン以外のポリエチレンは、示差走査熱量計（ＤＳＣ）から得られる融点が１３６℃以下であることが好ましく、１３４℃以下がより好ましく、さらに好ましくは１３３℃以下である。また、融点は１２５℃以上が好ましく、１３０℃以上がより好ましく、１３１℃以上がさらに好ましい。融点が上記範囲内であると、熱固定工程での透過性の過度な悪化を抑制しつつ、シャットダウン特性を向上でき、各種物性の両立が可能となる。 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.
　本発明において原料として用いる超高分子量ポリエチレン以外のポリエチレンは、示差走査熱量計（ＤＳＣ）から得られるΔＨ（Ｊ／ｇ）が１８０Ｊ／ｇ以上であることが好ましく、２００Ｊ／ｇ以上であることがより好ましく、２２０Ｊ／ｇ以上であることがさらに好ましい。また、ΔＨは、２５０Ｊ／ｇ以下が好ましく、２４０Ｊ／ｇ以下がより好ましい。ΔＨが上記範囲内であると、熱固定工程での透過性の過度な悪化を抑制しつつ、シャットダウン特性を向上でき、各種物性の両立が可能となる。 The polyethylene other than ultra-high molecular weight polyethylene used as a raw material in the present invention preferably has a ΔH (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, ΔH is preferably 250 J/g or less, more preferably 240 J/g or less. When ΔH 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.
　本発明のポリオレフィン微多孔膜には、本発明の効果を損なわない範囲において、酸化防止剤、熱安定剤や帯電防止剤、紫外線吸収剤、ブロッキング防止剤や充填材等の各種添加剤を含有させてもよい。 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.
　特に、ポリオレフィン樹脂の熱履歴による酸化劣化を抑制する目的で、酸化防止剤を添加することが好ましい。酸化防止剤としては例えば、２，６－ジ－ｔ－ブチル－ｐ－クレゾール（ＢＨＴ：分子量２２０．４）、１，３，５－トリメチル－２，４，６－トリス（３，５－ジ－ｔ－ブチル－４－ヒドロキシベンジル）ベンゼン（例えばＢＡＳＦ社製“Ｉｒｇａｎｏｘ”（登録商標）１３３０：分子量７７５．２）、テトラキス［メチレン－３（３，５－ジ－ｔ－ブチル－４－ヒドロキシフェニル）プロピオネート］メタン（例えばＢＡＳＦ社製“Ｉｒｇａｎｏｘ”（登録商標）１０１０：分子量１１７７．７）等から選ばれる１種類以上を用いることが好ましい。 In particular, it is preferable to add an antioxidant for the purpose of suppressing oxidative deterioration of the polyolefin resin due to thermal history. Examples of 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).
　本発明のポリオレフィン微多孔膜は、単位目付換算突刺強度が０．８Ｎ／（ｇ／ｍ２）以上であり、好ましくは０．８５Ｎ／（ｇ／ｍ２）以上、より好ましくは０．９Ｎ／（ｇ／ｍ２）以上であり、さらに好ましくは１．０Ｎ／（ｇ／ｍ２）以上である。また、前記単位目付換算突刺強度は１．８Ｎ／（ｇ／ｍ２）以下が好ましく、より好ましくは１．５Ｎ／（ｇ／ｍ２）以下である。 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.
　ポリオレフィン微多孔膜の単位目付換算突刺強度を０．８Ｎ／（ｇ／ｍ２）以上とすることで、高空孔率においても、ポリオレフィン微多孔膜としての突刺強度を維持しやすく、イオン透過性と機械的強度の両立が可能となる。また、薄膜化した際もポリオレフィ微多孔膜としての突刺強度を維持しやすく、耐異物性に優れた電池用セパレータとして使用可能である。さらに、フィルターとして用いた際に、前記単位目付換算突刺強度が０．８Ｎ／（ｇ／ｍ２）以上であると、高空孔率化および薄膜化がしやすくなり、濾過抵抗を抑えながら、濾過流量を多くすることが可能であり、好ましい。 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. Furthermore, when used as a filter, if 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.
　ポリオレフィン微多孔膜の単位目付換算突刺強度を上記範囲とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや製膜条件を後述する範囲とすることが好ましい。 In order to make the puncture strength of the polyolefin microporous membrane in terms of unit weight within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、後述する条件におけるゲル浸透クロマトグラフィー法（ＧＰＣ法）により得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、全体の成分量を１００質量％とした時に分子量１０００万以上の成分量が１．０質量％以下である。 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. When the amount is 100% by mass, the amount of components having a molecular weight of 10 million or more is 1.0% by mass or less.
　この分子量１０００万以上の成分量は、好ましくは０．７質量％以下、より好ましくは０．５質量％以下、さらに好ましくは０．３質量％以下、特に好ましくは０質量％である。 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.
　本発明のポリオレフィン微多孔膜は、ゲル浸透クロマトグラフィー法（ＧＰＣ法）により得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度を１として全体の検出強度を規格化し、分子量２００万における検出強度をＫ２００、分子量７００万における検出強度をＫ７００としたとき、Ｋ２００－Ｋ７００≧０．４である。 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. When the detection intensity is normalized and the detection intensity at a molecular weight of 2 million is K200 and the detection intensity at a molecular weight of 7 million is K700, K200-K700≧0.4.
　前記Ｋ２００－Ｋ７００は、好ましくは０．４５以上、より好ましくは０．５以上、さらに好ましくは０．５５以上である。また、前記Ｋ２００－Ｋ７００は０．９以下であることが好ましく、より好ましくは０．８以下である。 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.
　ポリオレフィン微多孔膜の分子量１０００万以上の成分量とＫ２００－Ｋ７００を上記範囲内とすることで、微多孔膜全体を延伸初期から均一に延伸することが可能であり、膜品位を維持したまま、ポリオレフィン微多孔膜の機械的強度を向上させることができる。また、ポリオレフィン微多孔膜において未延伸部分が減り、イオン透過性を向上させることができる。また、Ｋ２００－Ｋ７００を上記範囲内とすることで、高分子量成分がより均一となり、溶融後も形態維持しやすくなるため、耐メルトダウン特性が向上しやすくなる。 By setting 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. Moreover, the unstretched portion of the polyolefin microporous membrane is reduced, and ion permeability can be improved. Further, by setting 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.
　分子量１０００万以上の成分量とＫ２００－Ｋ７００を上記範囲とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや混練条件を後述する範囲とすることが好ましい。 In order to keep the amount of components with a molecular weight of 10 million or more and K200-K700 within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、前記Ｋ２００が０．６以上であることが好ましい。Ｋ２００は、好ましくは０．６５以上、より好ましくは０．７以上である。また、１．０以下が好ましく、０．９５以下がより好ましく、０．９以下が特に好ましい。 In the polyolefin microporous membrane of the present invention, 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.
　ポリオレフィン微多孔膜のＫ２００を上記範囲内とすることで、延伸時の応力が高くなり、より均一延伸が促進され、膜品位を維持したまま、ポリオレフィン微多孔膜の機械的強度をさらに向上させることが可能である。 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.
　前記Ｋ２００を上記範囲内とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや混練条件を後述する範囲とすることが好ましい。 In order to keep the K200 within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、後述する測定方法におけるゲル浸透クロマトグラフィー法（ＧＰＣ法）により得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度が分子量１０万以上５０万以下の領域に存在することが好ましい。 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.
　この最大検出強度は、好ましくは分子量２０万以上４０万以下の領域、より好ましくは分子量２０万以上３０万以下の領域に存在することが好ましい。 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.
　ポリオレフィン微多孔膜の分子量の最大検出強度を上記分子量範囲内とすることで、可塑剤との相溶性の高い比較的低分子量の成分が多くなり、微多孔膜構造の骨格を形成する高分子量成分の可塑剤との相溶を促進するため、ポリオレフィン微多孔膜のフィルム外観等の膜品位を維持しつつ、機械的強度を向上させることが可能となる。 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.
　前記分子量の最大検出強度を上記の分子量範囲内とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや混練条件を後述する範囲とすることが好ましい。 In order to keep the maximum detection intensity of the molecular weight within the above molecular weight range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、ハフニウム元素を０．２ｐｐｍ以上含有することが好ましい。 The polyolefin microporous membrane of the present invention preferably contains 0.2 ppm or more of hafnium element.
　このハフニウム元素含有量は、より好ましくは０．５ｐｐｍ以上、さらに好ましくは０．８ｐｐｍ以上であり、特に好ましくは１．０ｐｐｍ以上である。また、ハフニウム元素含有量は５．０ｐｐｍ以下が好ましく、より好ましくは３．０ｐｐｍ以下である。 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.
　ポリオレフィン微多孔膜のハフニウム元素含有量を上記範囲内とすることで、電池性能に悪影響を与えることなく、ポリオレフィン微多孔膜のＫ２００－Ｋ７００などの分子量分布を適切な状態に調整することができる。 By setting the hafnium element content of the polyolefin microporous membrane within the above range, 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.
　ポリオレフィン微多孔膜のハフニウム元素含有量を上記範囲とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや混練条件を後述する範囲とすることが好ましい。 In order to make the hafnium element content of the polyolefin microporous membrane within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、ＪＩＳ　Ｋ　３８３２－１９９０に基づくパームポロメーターによる測定から得られる平均孔径と最大孔径の比（平均孔径／最大孔径）が０．６５以上であることが好ましい。 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.
　この平均孔径／最大孔径は、より好ましくは０．６７以上、さらに好ましくは０．６９以上であり、特に好ましくは０．７１以上である。また、この平均孔径／最大孔径は０．９以下が好ましく、より好ましくは０．８以下である。 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.
　ポリオレフィン微多孔膜の平均孔径／最大孔径が上記範囲内であることは、より均一な孔構造を有することを示し、ポリオレフィン微多孔膜の機械的強度を向上させることができる上に、孔の曲路率も低減するためイオン透過性も向上させることが可能である。さらに、フィルターとして用いた際に、前記平均孔径／最大孔径が０．６５以上であると、フィルム面での孔径の分布が均一であるため、濾過精度の向上が可能であり、好ましい。 When 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.
　前記平均孔径／最大孔径を上記の分子量範囲内とするには、ポリオレフィン微多孔膜の原料組成を前記の範囲とすることや製膜条件を後述する範囲とすることが好ましい。 In order to keep the average pore diameter/maximum pore diameter within the above molecular weight range, it is preferable to set the raw material composition of the microporous polyolefin membrane to the above range and to set the film forming conditions to the ranges described below.
　本発明のポリオレフィン微多孔膜は、空孔率が３０％以上であることが好ましい。空孔率は、より好ましくは３５％以上、さらに好ましくは３７％以上であり、さらに好ましくは４０％以上である。空孔率が上記範囲内であることで、ポリオレフィン微多孔膜の機械的強度とイオン透過性を維持できるため、電池用セパレータとして用いた時に電池の出力特性と安全性の維持が可能である。また空孔率は、６０％以下であることがポリオレフィン微多孔膜の機械的強度の点から好ましい。 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. When 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. Further, the porosity is preferably 60% or less from the viewpoint of mechanical strength of the microporous polyolefin membrane.
　空孔率を上記範囲とするには、ポリオレフィン微多孔膜の原料組成を前記の範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件や熱固定条件を後述する範囲内とすることが好ましい。 In order to keep the porosity within the above range, it is preferable that 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. .
　本発明のポリオレフィン微多孔膜は、ＪＩＳ　Ｐ－８１１７：２００９の王研式試験機法により測定される、１００ｃｍ３の空気を通過させる際の透気抵抗度が厚み１０μｍに換算して３００秒以下であることが好ましい。厚み１０μｍ換算の透気抵抗度は、より好ましくは２５０秒以下、さらに好ましくは２１０秒以下である。透気抵抗度が上記範囲内であることで、ポリオレフィン微多孔膜のイオン透過性を維持でき、電池用セパレータとして用いた際の出力特性が向上する。また、厚み１０μｍ換算の透気抵抗度が５０秒以上であることで、強度や耐熱性とのバランスにも優れる。 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 μm. It is preferable that The air permeability resistance when converted to a thickness of 10 μm 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 μm, it has an excellent balance with strength and heat resistance.
　厚み１０μｍ換算の透気抵抗度を上記範囲とするには、ポリオレフィン微多孔膜の原料組成を前記の範囲とすることや積層構成を後述する範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件や熱固定条件を後述する範囲内とすることが好ましい。 In order to maintain the air permeability resistance in the above range when converted to a thickness of 10 μm, 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.
　本発明のポリオレフィン微多孔膜は、膜厚が１μｍ以上２５μｍ以下であることが好ましい。膜厚が上記範囲内であると、ポリオレフィン微多孔膜のハンドリング性や生産性がよく、また電池にした際の安全性を維持し、出力特性の悪化を抑制できる。膜厚は、１２μｍ以下であることがより好ましく、１０μｍ以下であることがさらに好ましく、７μｍ以下であることが特に好ましく、５μｍ以下であることが最も好ましい。 The polyolefin microporous membrane of the present invention preferably has a thickness of 1 μm or more and 25 μm or less. When the film thickness is within the above range, the polyolefin microporous film has good handling properties and productivity, maintains safety when used as a battery, and suppresses deterioration of output characteristics. The film thickness is more preferably 12 μm or less, even more preferably 10 μm or less, particularly preferably 7 μm or less, and most preferably 5 μm or less.
　膜厚は他の物性を悪化させない範囲内で、押出機のスクリュー回転数、未延伸シートの幅、製膜速度、延伸倍率などにより調整可能である。 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.
　本発明のポリオレフィン微多孔膜は、厚み１０μｍ換算の突刺強度が５．０Ｎ以上であることが好ましい。前記突刺強度はより好ましくは５．５Ｎ以上、さらに好ましくは６．０Ｎ以上、特に好ましくは６．５Ｎ以上、最も好ましくは７．０以上である。突刺強度が上記範囲内であることで、ポリオレフィン微多孔膜を薄膜化したときに捲回時や電池内の異物などによる短絡を抑制でき、電池の安全性が向上する。また、前記突刺強度は１０Ｎ以下が、シャットダウン特性の向上の点からは好ましい。さらに、フィルターとして用いた際に、前記突刺強度が５．０Ｎ以上であると、薄膜化がしやすくなり、濾過流量を多くすることが可能であり、好ましい。 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 μm. 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. When the puncture strength is within the above range, when the polyolefin microporous membrane is made thin, short circuits due to winding or foreign matter inside the battery can be suppressed, and the safety of the battery is improved. Further, the puncture strength is preferably 10 N or less from the viewpoint of improving the shutdown characteristics. Furthermore, when used as a filter, it is preferable that 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.
　突刺強度を上記範囲とするには、ポリオレフィン微多孔膜の原料組成を前記の範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件を後述する範囲内とすることが好ましい。 In order to have the puncture strength within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、昇温速度５℃／ｍｉｎの条件の熱機械分析測定（ＴＭＡ測定）から得られる横軸を温度、縦軸を応力としたポリオレフィン微多孔膜の温度－応力曲線において、最大応力をＰｍａｘ、温度１５０℃における応力をＰ１５０とした時、Ｐ１５０／Ｐｍａｘ≧０．６であることが好ましい。Ｐ１５０／Ｐｍａｘは、より好ましくは０．７以上、さらに好ましくは０．７５以上であり、最も好ましくは０．８以上である。また、Ｐ１５０／Ｐｍａｘが０．９５以下であることが好ましい。Ｐ１５０／Ｐｍａｘが上記範囲内であると、ポリオレフィン微多孔膜が溶融する温度でも分子鎖の絡み合いが保持され、形態を維持することが可能であり、ポリオレフィン微多孔膜上に耐熱層を積層した際に更なる耐メルトダウン特性の向上が可能となる。 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. In this case, when the maximum stress is P max and the stress at a temperature of 150° C. is P 150 , it is preferable that 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. Moreover, it is preferable that P 150 /P max is 0.95 or less. When P 150 /P max is within the above range, the entanglement of molecular chains is maintained even at the temperature at which the microporous polyolefin membrane melts, and the shape can be maintained, making it possible to laminate a heat-resistant layer on the microporous polyolefin membrane. When this happens, it becomes possible to further improve the meltdown resistance.
　Ｐ１５０／Ｐｍａｘを上記の範囲内とするには、ポリオレフィン微多孔膜に使用する原料やその組成を前記の範囲とすることや混練条件を後述する範囲とすることが好ましい。 In order to keep P 150 /P max within the above range, it is preferable that 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.
　本発明のポリオレフィン微多孔膜は、昇温透気度法によるシャットダウン温度が１４４℃以下であることが好ましい。シャットダウン温度はより好ましくは１４２℃以下、さらに好ましくは１４０℃以下、特に好ましくは１３８℃以下である。シャットダウン温度が１４４℃以下であることで、電気自動車などの高エネルギー密度化・高容量化・高出力化を必要とする二次電池用の電池用セパレータとして用いたときに、安全性が高い電池を提供することができる。また、シャットダウン温度は１００℃以上が好ましく、より好ましくは１２０℃以上である。ポリオレフィン微多孔膜のシャットダウン温度が１００℃以上であることで、通常の使用環境下や電池作成工程においても孔が閉じて出力特性が悪化してしまうのを防ぐことができる。 It is preferable that 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. With a shutdown temperature of 144℃ or less, this battery is highly safe when used as a battery separator for secondary batteries that require high energy density, high capacity, and high output such as in electric vehicles. can be provided. Further, the shutdown temperature is preferably 100°C or higher, more preferably 120°C or higher. By setting the shutdown temperature of the polyolefin microporous membrane to 100° C. or higher, it is possible to prevent the pores from closing and deteriorating the output characteristics even under normal usage environments or during the battery manufacturing process.
　シャットダウン温度を上記範囲内とするには、ポリオレフィン微多孔膜を構成する原料組成を前記の範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件や熱固定条件を後述する範囲内とすることが好ましい。 In order to keep the shutdown temperature within the above range, 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.
　本発明のポリオレフィン微多孔膜の膜厚測定によって得られた膜均一性は、０．２０以下であることが好ましく、より好ましくは０．１０以下、さらに好ましくは０．０５以下である。ポリオレフィン微多孔膜の膜均一性が０．２０以下であると、著しい物性のバラつきも少なく、薄膜化した電池用セパレータとして、好適に用いることができる。膜均一性の測定方法は後述する。 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. When 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.
　膜均一性を上記範囲内とするには、ポリオレフィン微多孔膜を構成する原料組成を前記の範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件や熱固定条件を後述する範囲内とすることが好ましい。 In order to keep the film uniformity within the above range, 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.
　本発明のポリオレフィン微多孔膜は、後述する条件により求められる室温における電気抵抗値が、膜厚１０μｍ換算で１．５Ω・ｃｍ２以下であることが好ましく、より好ましくは１．２Ω・ｃｍ２以下、さらに好ましくは１．０Ω・ｃｍ２以下、特に好ましくは０．８Ω・ｃｍ２以下である。ポリオレフィン微多孔膜の室温における抵抗値が膜厚１０μｍで１．５Ω・ｃｍ２以下であると、電気自動車などの高出力化を必要とする二次電池用の電池用セパレータとして好適に用いることができる。 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 Ω·cm 2 or less, more preferably 1.2 Ω·cm 2 or less when converted to a film thickness of 10 μm. , more preferably 1.0 Ω·cm 2 or less, particularly preferably 0.8 Ω·cm 2 or less. When the resistance value of the polyolefin microporous membrane at room temperature is 1.5 Ω cm 2 or less at a film thickness of 10 μm, it can be suitably used as a battery separator for secondary batteries that require high output such as electric vehicles. can.
　上記換算抵抗値を上記範囲内とするには、ポリオレフィン微多孔膜を構成する原料組成を前記の範囲とし、また、ポリオレフィン微多孔膜製膜時の延伸条件や熱固定条件を後述する範囲内とすることが好ましい。 In order to keep the above converted resistance value within the above range, 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.
　本発明のポリオレフィン微多孔膜は、フィルター、燃料電池用セパレータ、コンデンサ用セパレータなど様々な用途で用いることができる。特に、電池用セパレータとして用いたとき安全性および出力特性に優れることから、電気自動車などの高エネルギー密度、高容量、および高出力を必要とする二次電池用の電池用セパレータとして好ましく用いることができる。 The microporous polyolefin membrane of the present invention can be used in various applications such as filters, fuel cell separators, and capacitor separators. In particular, 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.
　以下に、上記原料を用いたポリオレフィン微多孔膜の製膜方法について例を説明する。ただし、本発明のポリオレフィン微多孔膜は、以下に示す製造方法により得られるもののみに限定されるものではない。本発明のポリオレフィン微多孔膜の製造方法は、以下の（ａ）～（ｆ）の工程からなることが好ましい。 An example of a method for forming a microporous polyolefin membrane using the above raw materials will be described below. However, the polyolefin microporous membrane of the present invention is not limited to that obtained by the manufacturing method shown below. The method for producing a polyolefin microporous membrane of the present invention preferably comprises the following steps (a) to (f).
　（ａ）ポリオレフィン樹脂溶液の調製
　ポリオレフィン樹脂および各種添加剤を可塑剤に加熱溶解させて、ポリオレフィン樹脂溶液を調製する。 (a) Preparation of polyolefin resin solution A polyolefin resin solution is prepared by heating and dissolving a polyolefin resin and various additives in a plasticizer.
　可塑剤としては、ポリオレフィン樹脂を十分に溶解できる溶剤であればよい。延伸ムラを抑え比較的高倍率の延伸を可能とするために、可塑剤として、室温で液体である液体溶剤が好ましい。液体溶剤としては、ノナン、デカン、デカリン、パラキシレン、ウンデカン、ドデカン、流動パラフィン等の脂肪族、環式脂肪族または芳香族の炭化水素、および沸点がこれらに対応する鉱油留分、並びにジブチルフタレート、ジオクチルフタレート等の室温では液状のフタル酸エステルが挙げられる。なかでも、液体溶剤の含有量が安定なゲル状シートを得るために、流動パラフィンのような不揮発性の液体溶剤が好ましい。 The plasticizer may be any solvent as long as it can sufficiently dissolve the polyolefin resin. In order to suppress stretching unevenness and enable relatively high stretching, 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. Among these, a nonvolatile liquid solvent such as liquid paraffin is preferred in order to obtain a gel-like sheet with a stable liquid solvent content.
　液体溶剤の粘度は４０℃において２０ｃＳｔ以上２００ｃＳｔ以下であることが好ましい。前記粘度を２０ｃＳｔ以上とすれば、ダイからポリオレフィン樹脂溶液を押し出して得られるシートが不均一になりにくい。一方、前記粘度を２００ｃＳｔ以下とすれば液体溶剤の除去が容易である。 The viscosity of the liquid solvent is preferably 20 cSt or more and 200 cSt or less at 40°C. When 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. On the other hand, if the viscosity is set to 200 cSt or less, the liquid solvent can be easily removed.
　液体溶剤の粘度は、ウベローデ粘度計を用いて４０℃で測定することができる。 The viscosity of the liquid solvent can be measured at 40°C using an Ubbelohde viscometer.
　溶融混練状態ではポリオレフィンと混和するが室温では固体の固体溶剤を、液体溶剤に混合して用いてもよい。固体溶剤としては例えば、ステアリルアルコール、セリルアルコール、パラフィンワックス等が挙げられる。 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. Examples of the solid solvent include stearyl alcohol, ceryl alcohol, and paraffin wax.
　可塑剤の配合割合は、ポリオレフィン樹脂と可塑剤との合計を１００質量％として５０質量％以上が好ましく、７０質量％以上がより好ましく、７５％以上がさらに好ましい。また、可塑剤の配合割合は、９０質量％以下が好ましい。可塑剤を５０質量％以上とすることで、ポリオレフィン樹脂溶液をシート状に成形する際の厚み方向の収縮を抑え、成形加工性を向上させることができる。また、可塑剤を９０質量％以下とすることで、ポリオレフィン樹脂溶液をシート状に成形する際の口金の出口でのスウエルやネックインが大きくなるのを抑え、シートの成形性、製膜性を向上させることができる。 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. By setting the plasticizer content to 50% by mass or more, shrinkage in the thickness direction when molding the polyolefin resin solution into a sheet shape can be suppressed, and molding processability can be improved. In addition, by controlling the plasticizer content to 90% by mass or less, when molding a polyolefin resin solution into a sheet, swell and neck-in at the outlet of the die are suppressed, and the moldability and film-forming properties of the sheet are improved. can be improved.
　ポリオレフィン樹脂溶液の溶融混練は、二軸押出機中で行うことが、高濃度のポリオレフィン樹脂溶液を調製する上で好ましい。 It is preferable to melt-knead the polyolefin resin solution in a twin-screw extruder in order to prepare a highly concentrated polyolefin resin solution.
　押出機内のポリオレフィン樹脂へ可塑剤を投入する際に、添加する可塑剤を複数回に分けて押出機へ投入しても良いが、超高分子量ポリエチレンと可塑剤の相溶性を高めるためには、押出機への超高分子量ポリエチレン投入直後に、多くの可塑剤を添加することが好ましい。可塑剤全量のうち、押出機への超高分子量ポリエチレンの投入直後に添加する可塑剤の割合（以下、初期添加割合と記載することがある）は、添加する可塑剤全量を１００質量％として、６０質量％以上が好ましく、７０質量％以上がより好ましく、特に好ましくは９０質量％以上である。なお、押出機への超高分子量ポリエチレン投入直後とは、二軸押出機における可塑剤の投入口を、超高分子量ポリエチレンの投入口より下流に設ける場合において、超高分子量ポリエチレンの投入口から可塑剤の投入口までの距離が１００ｃｍ以内にあることを言う。 When adding the plasticizer to the polyolefin resin in the extruder, 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. Of the total amount of plasticizer, 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. 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.
　押出機中では、ポリオレフィン樹脂が完全に溶融する温度で、ポリオレフィン樹脂溶液を均一に混合することが好ましい。 In the extruder, it is preferable to uniformly mix the polyolefin resin solution at a temperature at which the polyolefin resin completely melts.
　溶融混練温度は、（ポリオレフィン樹脂の融点＋１０℃）～（ポリオレフィン樹脂の融点＋１２０℃）とするのが好ましい。より好ましくは（ポリオレフィン樹脂の融点＋２０℃）～（ポリオレフィン樹脂の融点＋１００℃）である。例えば、ポリオレフィン樹脂がポリエチレン樹脂である場合、ポリエチレン樹脂は約１３０～１４０℃の融点を有するので、溶融混練温度は１４０～２５０℃が好ましい。溶融混練温度は、より好ましくは１５０～２１０℃、さらに好ましくは１６０～２３０℃、特に好ましくは１７０～２００℃である。 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). For example, when the polyolefin resin is a polyethylene resin, since the polyethylene resin has a melting point of about 130 to 140°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.
　樹脂の劣化を抑制する観点から溶融混練温度は低い方が好ましいが、上述の温度よりも低いとダイから押出された押出物に未溶融物が発生し、後の延伸工程で破膜等を引き起こす原因となる場合がある。また、上述の温度より高いと、ポリオレフィン樹脂の熱分解が激しくなり、得られるポリオレフィン微多孔膜の物性、例えば、強度や空孔率等が劣る場合がある。また、分解物がチルロールや延伸工程上のロールなどに析出し、シートに付着することで外観悪化につながる。そのため、上記範囲内で混練することが好ましい。 From the viewpoint of suppressing resin deterioration, it is preferable that 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.
　融点は、ＪＩＳ　Ｋ７１２１：２０１２に基づき、ＤＳＣにより測定する。 The melting point is measured by DSC based on JIS K7121:2012.
　溶融混練の後、フィルターにて異物や変性したポリマーを除去することが好ましい。 After melt-kneading, it is preferable to remove foreign substances and modified polymers using a filter.
　（ｂ）ゲル状シートの形成
　溶融混練された樹脂溶液をダイより押し出し、冷却することによりゲル状シートを得る。冷却により、可塑剤によって分離されたポリオレフィン樹脂のミクロ相を固定化することができる。冷却工程においてゲル状シートを１０～５０℃まで冷却するのが好ましい。これは、最終冷却温度をポリオレフィン樹脂の結晶化終了温度以下とするのが、ゲル状シートの高次構造を細かくする上で好ましいためである。高次構造を細かくすることで、その後の延伸においてゲル状シートの均一延伸が行いやすくなる。そのため、冷却は少なくともゲル化温度以下までは３０℃／分以上の速度で行うのが好ましい。冷却速度が３０℃／分未満では、結晶化度が上昇し、延伸に適したゲル状シートとなりにくい。一般に冷却速度が遅いと、比較的大きな結晶が形成されるので、ゲル状シートの高次構造が粗くなり、それを形成するゲル構造も大きなものとなる。対して冷却速度が速いと、比較的小さな結晶が形成されるので、ゲル状シートの高次構造が密となり、均一延伸が行いやすくなるのに加え、フィルムの強度および伸度の向上につながる。 (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. In the cooling step, 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. If 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. Generally, when 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. On the other hand, when 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.
　ゲル状シートを冷却する方法としては、例えば、冷風、冷却水、その他の冷却媒体に直接接触させる方法、冷媒で冷却したロールに接触させる方法、キャスティングドラムを用いる方法等がある。 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.
　（ｃ）延伸
　得られたゲル状シートを二軸延伸する。二軸延伸の方法としては、インフレーション法、同時二軸延伸法、逐次二軸延伸法のいずれも用いることができる。その中でも、製膜安定性、厚み均一性ならびにフィルムの剛性および寸法安定性を制御する点において同時二軸延伸法または逐次二軸延伸法を採用することが好ましい。同時二軸延伸法としては例えば、同時二軸テンターによる方法が挙げられる。また、逐次二軸延伸法としては例えば、ロール延伸機によるＭＤ延伸およびテンターによるＴＤ延伸の組み合わせによる方法、またはテンターとテンターとの組み合わせによる方法が挙げられる。 (c) Stretching The obtained gel-like sheet is biaxially stretched. As 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. Examples of 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.
　延伸倍率は、ＭＤ／ＴＤいずれの方向についても５倍以上とすることが好ましい。 The stretching ratio is preferably 5 times or more in both MD/TD directions.
　延伸の面積倍率としては、２５倍以上が好ましい。面積倍率を２５倍以上、より好ましくは３６倍以上、さらに好ましくは４９倍以上、特に好ましくは６４倍とすることで、膜の均一性も得られ易い上に、未延伸部分も残りにくいため、機械的強度、電気抵抗の観点からも優れたポリオレフィン微多孔膜を得ることができる。また、面積倍率は１５０倍以下が好ましく、１００倍以下がより好ましい。延伸の面積倍率を１５０倍以下とすることで、ポリオレフィン微多孔膜の製造中に破れが生じるのを抑え、生産性が向上するとともに、配向が過度に進むのを抑え、ポリオレフィン微多孔膜の融点の上昇によるシャットダウン温度の上昇を抑えることができる。 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.
　延伸温度はゲル状シートの融点＋１０℃以下にするのが好ましく、（ポリオレフィン樹脂の結晶分散温度Ｔｃｄ）～（ゲル状シートの融点＋５℃）の範囲にするのがより好ましい。具体的には、ポリオレフィン樹脂がポリエチレン樹脂である場合は約９０～１００℃の結晶分散温度を有するので、延伸温度は好ましくは９０～１３５℃であり、より好ましくは９０～１３０℃である。延伸温度を９０℃以上とすることで、開孔が十分なものとなり膜厚の均一性が得られやすく、空孔率も高くなる。延伸温度を１３５℃以下とすることで、シートの融解による孔の閉塞を防ぐことができる。結晶分散温度ＴｃｄはＡＳＴＭ　Ｄ４０６５－２０（２０２０）に従って測定した動的粘弾性の温度特性から求める。 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). Specifically, when 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. By setting the stretching temperature to 90° C. or higher, the pores are sufficient, the film thickness becomes more uniform, and the porosity becomes higher. By setting the stretching temperature to 135° C. or lower, it is possible to prevent the pores from clogging due to melting of the sheet. The crystal dispersion temperature Tcd is determined from the temperature characteristics of dynamic viscoelasticity measured according to ASTM D4065-20 (2020).
　以上のような延伸により、ゲル状シートに形成された高次構造に開裂が起こり、結晶相が微細化し、多数のフィブリルが形成される。フィブリルは三次元的に不規則に連結した網目構造を形成する。ゲル状シートの延伸により、得られるポリオレフィン微多孔膜の機械的強度が向上するとともに、細孔が拡大するので、電池用セパレータとして好適になる。また、可塑剤を除去する前に延伸することによって、ポリオレフィン樹脂が十分に可塑化し軟化した状態であるために、高次構造の開裂がスムーズになり、結晶相の微細化を均一に行うことができる。また、開裂が容易であるために、延伸時のひずみが残りにくく、可塑剤を除去した後に延伸する場合に比べて得られるポリオレフィン微多孔膜の熱収縮率を低くすることができる。 By stretching as described above, cleavage occurs in the higher-order structure formed in the gel-like sheet, the crystal phase becomes finer, and a large number of fibrils are formed. Fibrils form a three-dimensionally irregularly connected network structure. By stretching the gel-like sheet, the mechanical strength of the resulting microporous polyolefin membrane is improved and the pores are enlarged, making it suitable for use as a battery separator. In addition, by stretching the polyolefin resin before removing the plasticizer, the polyolefin resin is sufficiently plasticized and softened, so that the higher-order structure can be cleaved smoothly and the crystal phase can be uniformly refined. can. Furthermore, since it is easily cleaved, strain is less likely to remain during stretching, and the heat shrinkage rate of the resulting microporous polyolefin membrane can be lowered compared to when stretching is performed after removing the plasticizer.
　（ｄ）可塑剤抽出（洗浄）
　ゲル状シート中に残留する可塑剤（溶剤）を、洗浄溶剤を用いて除去する。ポリオレフィン樹脂相と溶剤相とは分離しているので、溶剤の除去によりポリオレフィン微多孔膜が得られる。 (d) 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.
　洗浄溶剤としては、例えばペンタン、ヘキサン、ヘプタン等の飽和炭化水素；塩化メチレン、四塩化炭素等の塩素化炭化水素；ジエチルエーテル、ジオキサン等のエーテル類；メチルエチルケトン等のケトン類；三フッ化エタン等の鎖状フルオロカーボンなどがあげられる。これらの洗浄溶剤は低い表面張力（例えば、２５℃で２４ｍＮ／ｍ以下）を有することが好ましい。低い表面張力の洗浄溶剤を用いることにより、微多孔を形成する網状構造が洗浄後の乾燥時において、気－液界面で表面張力により収縮することを抑制し、空孔率および透過性を有するポリオレフィン微多孔膜が得られる。これらの洗浄溶剤は可塑剤に応じて適宜選択し、単独でまたは複数を混合して用いる。 Examples of cleaning solvents 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. Preferably, these cleaning solvents have a low surface tension (eg, 24 mN/m or less at 25°C). By using a cleaning solvent with low surface tension, 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. These cleaning solvents are appropriately selected depending on the plasticizer and used alone or in combination.
　洗浄方法としては例えば、ゲル状シートを洗浄溶剤に浸漬する方法、ゲル状シートに洗浄溶剤をシャワーする方法、またはこれらの組み合わせによる方法を挙げることができる。 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.
　洗浄溶剤の使用量は洗浄方法により異なるが、一般にゲル状シート１００質量部に対して３００質量部以上であるのが好ましい。 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.
　洗浄温度は１５～３０℃が好ましく、必要に応じて８０℃以下に加熱する。この時、溶剤の洗浄効果を高める観点、得られるポリオレフィン微多孔膜の物性のＴＤ方向および／またはＭＤ方向の微多孔膜物性が不均一にならないようにする観点、ポリオレフィン微多孔膜の機械的物性および電気的物性を向上させる観点から、ゲル状シートが洗浄溶剤に接触している時間は長ければ長い方が良い。上述のような洗浄は、洗浄後のゲル状シート、すなわちポリオレフィン微多孔膜中の可塑剤の残存量が１質量％未満になるまで行うのが好ましい。 The washing temperature is preferably 15 to 30°C, and if necessary, it is heated to 80°C or lower. At this time, the viewpoints of improving the cleaning effect of the solvent, preventing the physical properties of the obtained microporous polyolefin membrane from becoming uneven in the TD direction and/or MD direction, and the mechanical properties of the microporous polyolefin membrane And from the viewpoint of improving electrical properties, the longer the time the gel-like sheet is in contact with the cleaning solvent, the better. 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.
　（ｅ）乾燥
　乾燥工程でポリオレフィン微多孔膜を乾燥させ、ポリオレフィン微多孔膜中の溶剤を除去する。乾燥が不十分であると、後の熱処理でポリオレフィン微多孔膜の空孔率が低下し、透過性が悪化する。乾燥方法としては、金属加熱ロールを用いる方法や熱風を用いる方法などを選択することができる。 (e) Drying In the drying step, 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. As the drying method, a method using a metal heating roll, a method using hot air, etc. can be selected.
　（ｆ）熱処理／再延伸工程
　乾燥したポリオレフィン微多孔膜を少なくとも一軸方向に延伸（再延伸）してもよい。再延伸は、ポリオレフィン微多孔膜を加熱しながら上述の延伸と同様にテンター法等により行うことができる。再延伸は一軸延伸でも二軸延伸でもよい。多段延伸の場合は、同時二軸または／および逐次延伸を組み合わせることにより行う。 (f) Heat treatment/re-stretching step 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.
　再延伸の温度は、ポリオレフィン樹脂の融点以下とすることが好ましく、（ポリオレフィン樹脂の結晶分散温度Ｔｃｄ－２０℃）～融点の範囲内にするのがより好ましい。具体的には、７０～１４０℃が好ましく、１１０～１３８℃がより好ましく、さらに好ましくは１２０～１３５℃である。 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.
　再延伸の倍率は、一軸延伸の場合、１．０１～３．０倍が好ましい。特にＴＤ方向は１．０１～２．０倍が好ましく、１．２～１．８倍がより好ましく、１．３～１．６倍が特に好ましい。二軸延伸の場合、ＭＤ方向およびＴＤ方向にそれぞれ１．０１～１．６倍とするのが好ましい。再延伸の倍率は、ＭＤ方向とＴＤ方向で異なってもよい。上述の範囲内で延伸することで、機械的強度と電気抵抗を向上させることができる。また、結晶配向が進んでポリオレフィン微多孔膜の融点が上昇することによるシャットダウン温度の上昇を抑えることができる。 In the case of uniaxial stretching, the re-stretching ratio is preferably 1.01 to 3.0 times. In particular, 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. In the case of biaxial stretching, 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. By stretching within the above range, mechanical strength and electrical resistance can be improved. Further, it is possible to suppress an increase in the shutdown temperature due to an increase in the melting point of the polyolefin microporous membrane due to progress of crystal orientation.
　さらに膜を加熱中にＭＤ方向やＴＤ方向に熱収縮させる緩和処理を施すことも好ましい。緩和処理における緩和率は、緩和処理後の膜の寸法を緩和処理前の膜の寸法で除した値のことであり、ＭＤおよびＴＤ方向への緩和率はいずれも、１．０以下であることが好ましく、より好ましくは０．９以下であり、さらに好ましくは０．８５以下である。緩和率を上記範囲とすることで、熱収縮を抑え、しわやたるみも抑えることができる。また、緩和率は０．７以上とすることで、しわの発生や透過性の悪化を抑えることができる。 Furthermore, it is also preferable to perform a relaxation treatment to thermally shrink the film in the MD direction or TD direction while heating the film. 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. By setting the relaxation rate within the above range, thermal shrinkage can be suppressed, and wrinkles and sagging can also be suppressed. Further, by setting the relaxation rate to 0.7 or more, it is possible to suppress the occurrence of wrinkles and deterioration of permeability.
　（ｇ）その他の工程
　さらに、その他用途に応じて、ポリオレフィン微多孔膜に架橋処理や親水化処理を施すこともできる。 (g) Other steps Furthermore, the microporous polyolefin membrane may be subjected to crosslinking treatment or hydrophilic treatment depending on the intended use.
　架橋処理によりポリオレフィン微多孔膜のメルトダウン温度が上昇する。架橋処理は、ポリオレフィン微多孔膜に対して、α線、β線、γ線、電子線等の電離放射線を照射することにより施すことができる。電子線の照射の場合、０．１～１００Ｍｒａｄの電子線量が好ましく、１００～３００ｋＶの加速電圧が好ましい。 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 α rays, β rays, γ rays, and electron beams. In the case of 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.
　親水化処理は、モノマーグラフト、界面活性剤処理、コロナ放電等により行うことができる。モノマーグラフトは架橋処理後に行うのが好ましい。 The hydrophilization treatment can be performed by monomer grafting, surfactant treatment, corona discharge, etc. Monomer grafting is preferably carried out after crosslinking treatment.
　界面活性剤処理の場合、ノニオン系界面活性剤、カチオン系界面活性剤、アニオン系界面活性剤および両イオン系界面活性剤から選ばれるいずれも使用できるが、ノニオン系界面活性剤が好ましい。界面活性剤を水またはメタノール、エタノール、イソプロピルアルコール等の低級アルコールに溶解してなる溶液中にポリオレフィン微多孔膜を浸漬するか、ポリオレフィン微多孔膜にドクターブレード法により前記溶液を塗布する方法が好ましい。 In the case of surfactant treatment, any one selected from nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants can be used, but nonionic surfactants are preferred. Preferably, 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. .
　本発明のポリオレフィン微多孔膜は、耐メルトダウン特性や耐熱性、接着性などの機能を付与する目的で、ポリオレフィン樹脂以外の他の樹脂を含む多孔質層を積層した積層体としてもよい。多孔質層の積層は、コーティングや蒸着などで行うことができる。 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.
　多孔質層としては例えば、バインダーと無機粒子とを含む無機粒子層を積層してもよい。無機粒子層を構成するバインダー成分としては、例えば、アクリル樹脂、ポリフッ化ビニリデン樹脂、ポリアミドイミド樹脂、ポリアミド樹脂、芳香族ポリアミド樹脂、ポリイミド樹脂などを用いることができる。無機粒子層を構成する無機粒子としては、例えば、アルミナ、ベーマイト、硫酸バリウム、酸化マグネシウム、水酸化マグネシウム、炭酸マグネシウム、ケイ素などからなる粒子を用いることができる。 As the porous layer, for example, an inorganic particle layer containing a binder and inorganic particles may be laminated. As 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. As 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.
　多孔質層としては、前記バインダーとして例示された樹脂が多孔質化したものであってもよい。 The porous layer may be one in which the resin exemplified as the binder is made porous.
　以上のようにして得られた本発明のポリオレフィン微多孔膜は、フィルター、燃料電池用セパレータ、コンデンサ用セパレータなど様々な用途で用いることができる。 The 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.
　本発明のポリオレフィン微多孔膜は、特に電池用セパレータとして用いたとき電池特性および電池安全性に優れることから、電気自動車などの高エネルギー密度化、高容量化、および高出力化を必要とする非水電解液二次電池用セパレータとして好ましく用いることができる。非水電解液二次電池は、正極、負極、電解液およびセパレータを少なくとも備え、正極と負極の間の絶縁を保つようセパレータが配置され、電解液は有機溶媒と電解質からなり、これらを容器に封入したものである。本発明のポリオレフィン微多孔膜はそのままでも非水電解液二次電池のセパレータとして好適に使用できるが、不織布や耐熱性コーティング層等を積層して用いてもよい。 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.
　また、本発明のポリオレフィン微多孔膜は、液体フィルター用途に用いたとき、ろ過精度と高透過性に優れることから、高精度ろ過が求められる半導体レジスト用向けの液体用フィルターとして好ましく用いることができる。本発明のポリオレフィン微多孔膜は、シート状、管状、プリーツ状などのろ過ユニット用の液体用フィルターとして用いることができる。ろ過面積を大きくできることからプリーツ状ろ過ユニットに用いることが好ましい。プリーツ状ろ過ユニットに組み込む際は、本発明のポリオレフィン微多孔膜の少なくとも片面に樹脂素材を用いたメッシュや多孔質体からなる補強膜を積層することが好ましい。本発明のポリオレフィン微多孔膜を、補強膜と加熱ロールなどで貼り合わせた後、山谷の折り目をつけてプリーツ状に織り込み、ろ過ユニットに組み込んで使用することができる。 In addition, 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. When incorporated into a pleated filtration unit, it is preferable to laminate 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. After 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.
　以下、本発明を実施例によりさらに詳細に説明する。ただし、本発明はこれらの例のみに限定されるものではない。 Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited only to these examples.
　先ず、測定方法と評価方法について説明する。なお、特に記載がない限りは温度：２５±２℃（室温）、湿度：５０±１０％で実施した。 First, the measurement method and evaluation method will be explained. In addition, unless otherwise specified, the experiments were carried out at a temperature of 25±2° C. (room temperature) and a humidity of 50±10%.
　（１）ポリオレフィン原料の融点およびΔＨ
　原料のポリオレフィン原料の融点は、ＪＩＳ　Ｋ７１２１：２０１２に基づき、示差走査熱量分析（ＤＳＣ）法により測定した。アルミパンに６．０ｍｇの試料を封入し、ＰａｒｋｉｎＥｌｍｅｒ製　ＰＹＲＩＳ　Ｄｉａｍｏｎｄ　ＤＳＣを用いて、窒素雰囲気下、温度３０℃から２３０℃まで１０℃／ｍｉｎで昇温（１回目の昇温）後、２３０℃で５分間保持した。続いて、１０℃／分の速度で３０℃まで冷却し、再度１０℃／分の昇温速度で３０℃から２３０℃まで昇温し（２回目の昇温）、各融解吸熱曲線を得た。２回目の昇温で得られた融解吸熱曲線上のピークトップの温度をポリオレフィン原料の融点（℃）とし、融解曲線とベースラインで囲まれた面積から融解エンタルピーであるΔＨ（Ｊ／ｇ）を算出した。 (1) Melting point and ΔH of polyolefin raw materials
The melting point of the raw polyolefin raw material was measured by differential scanning calorimetry (DSC) based on JIS K7121:2012. A 6.0 mg sample was sealed in an aluminum pan, and the temperature was raised from 30°C to 230°C at a rate of 10°C/min (first temperature rise) in a nitrogen atmosphere using a PYRIS Diamond DSC manufactured by ParkinElmer, and then heated to 230°C. It was held for 5 minutes. Subsequently, it was cooled to 30°C at a rate of 10°C/min, and then raised again from 30°C to 230°C at a heating rate of 10°C/min (second temperature increase) to obtain each melting endothermic curve. . The temperature at the top of the peak on the melting endothermic curve obtained in the second temperature increase is taken as the melting point (°C) of the polyolefin raw material, and the enthalpy of melting ΔH (J/g) is calculated from the area surrounded by the melting curve and the baseline. Calculated.
　（２）ポリオレフィン原料およびポリオレフィン微多孔膜の分子量分布
　ポリオレフィン原料やポリオレフィン微多孔膜の分子量分布は以下の条件でゲルパーミエーションクロマトグラフィー（ＧＰＣ）法により求めた。また、分子量分布から得られたパラメーターの算出方法を下記（ａ）～（ｄ）に示す。
・測定装置：Ｗａｔｅｒｓ　Ｃｏｒｐｏｒａｔｉｏｎ製ＧＰＣ－１５０Ｃ
・カラム：昭和電工株式会社製Ｓｈｏｄｅｘ　ＵＴ８０６Ｍ
・カラム温度：１６０℃
・溶媒（移動相）：１，２，４－トリクロロベンゼン
・溶媒流速：１．０ｍｌ／分
・試料濃度：０．１質量％（溶解条件：１６０℃／１ｈ）
・インジェクション量：５００μｌ
・検出器：Ｗａｔｅｒｓ　Ｃｏｒｐｏｒａｔｉｏｎ製ディファレンシャルリフラクトメーター（ＲＩ検出器）
・検量線：単分散ポリスチレン標準試料を用いて得られた分子量に、ポリエチレン換算係数（０．４６）を乗じることにより検量線を作成した。 (2) Molecular weight distribution of polyolefin raw material and polyolefin microporous membrane The molecular weight distribution of polyolefin raw material and polyolefin microporous membrane was determined by gel permeation chromatography (GPC) method under the following conditions. Further, methods for calculating parameters obtained from the molecular weight distribution are shown in (a) to (d) below.
・Measuring device: GPC-150C manufactured by Waters Corporation
・Column: Shodex UT806M manufactured by Showa Denko Co., Ltd.
・Column temperature: 160℃
・Solvent (mobile phase): 1,2,4-trichlorobenzene ・Solvent flow rate: 1.0ml/min ・Sample concentration: 0.1% by mass (dissolution conditions: 160°C/1h)
・Injection volume: 500μl
・Detector: Waters Corporation differential refractometer (RI detector)
- Calibration curve: A calibration curve was created by multiplying the molecular weight obtained using a monodisperse polystyrene standard sample by a polyethylene conversion factor (0.46).
　（ａ）分子量１０００万以上の成分の割合（質量％）
　上記のように得られた分子量分布を用いて下記式により算出した。
分子量１０００万以上の成分の割合（質量％）＝（分子量１０００万以上の成分量）÷（全分子量の成分量）×１００
　（ｂ）ポリオレフィン原料およびポリオレフィン微多孔膜の分子量の規格化検出強度：Ｋ２００、Ｋ３００、Ｋ７００
　上記のように得られた分子量分布について、検出強度の最大値で全体を規格化した際の分子量２００万における検出強度をＫ２００、分子量３００万における検出強度をＫ３００、分子量７００万における検出強度をＫ７００とした。 (a) Proportion of components with a molecular weight of 10 million or more (mass%)
It was calculated by the following formula using the molecular weight distribution obtained as described above.
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
(b) Normalized detection intensity of molecular weight of polyolefin raw material and polyolefin microporous membrane: K200, K300, K700
Regarding the molecular weight distribution obtained as above, when the whole is normalized by the maximum value of detection intensity, the detection intensity at a molecular weight of 2 million is K200, the detection intensity at a molecular weight of 3 million is K300, and the detection intensity at a molecular weight of 7 million is K700. And so.
　（ｃ）ポリオレフィン原料の分子量３００万における検出強度と分子量７００万における検出強度の検出強度比（Ｋ３００／Ｋ７００）
　上記のように得られたポリオレフィン原料のＫ３００とＫ７００を用いてＫ３００／Ｋ７００を算出した。 (c) Detection intensity ratio between the detection intensity at a molecular weight of 3 million and the detection intensity at a molecular weight of 7 million of polyolefin raw materials (K300/K700)
K300/K700 was calculated using K300 and K700 of the polyolefin raw materials obtained as described above.
　（ｄ）ポリオレフィン微多孔膜の分子量２００万と７００万の検出強度差：Ｋ２００－Ｋ７００
　上記のように得られたポリオレフィン微多孔膜のＫ２００とＫ７００を用いて、Ｋ２００－Ｋ７００を算出した。 (d) 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.
　（３）製膜性
　ポリレフィン微多孔膜を上記の工程に基づいて製膜した際の製膜性について、以下のようにＡ、Ｂ、Ｃ評価した。
Ａ：ポリオレフィン樹脂溶液やゲル状シートの外観に問題なく、延伸や熱処理工程を問題なく実施した。
Ｂ：ポリオレフィン樹脂溶液やゲル状シートに未溶融物やムラ等が発生したが、後の延伸や熱処理工程を問題なく実施した。
Ｃ：ポリオレフィン樹脂溶液やゲル状シートの外観にムラ等が発生し、ゲル状シートの製膜が断続的になったため、製膜可能な部分のみを採取し、後の延伸や熱処理工程を実施した。 (3) Film-forming properties The film-forming properties of microporous polyolefin membranes formed based on the above steps were evaluated as A, B, and C as follows.
A: There were no problems with the appearance of the polyolefin resin solution or gel-like sheet, and the stretching and heat treatment steps were carried out without problems.
B: Although unmelted substances and unevenness occurred in the polyolefin resin solution and gel-like sheet, the subsequent stretching and heat treatment steps were carried out without any problems.
C: Unevenness occurred in the appearance of the polyolefin resin solution and gel-like sheet, and film formation of the gel-like sheet became intermittent, so only the parts that could be formed into film were collected and the subsequent stretching and heat treatment processes were performed. .
　（４）ポリオレフィン微多孔膜中のハフニウム含有量（ｐｐｍ）
　ポリオレフィン微多孔膜を秤量し、硫酸－硝酸－過塩素酸を用いて分解後、希王水で加温・溶解したものを測定溶液とした。得られた溶液について、四重極型ＩＣＰ質量分析装置（パーキンエルマー社製　ＮｅｘＩＯＮ　２０００）を用いて、ＩＣＰ質量分析法でハフニウム含有量を測定した。 (4) 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).
　（５）平均孔径／最大孔径
　以下の測定を同じポリオレフィン微多孔膜中の異なる箇所で３点行い、平均孔径と最大孔径との平均値を求め、平均孔径を最大孔径で除して算出した。 (5) 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.
　ＪＩＳ　Ｋ　３８３２：１９９０に基づき、パームポロメーター（ＰＭＩ社製、ＣＦＰ－１５００Ａ）を用いて、ＤＲＹ－ＵＰ、ＷＥＴ－ＵＰの順で、バブルポイント孔径および平均孔径を測定した。ＷＥＴ－ＵＰには表面張力が既知のＰＭＩ社製ＧＡＬＷＩＣＫ（商品名）で十分に浸したポリオレフィン微多孔膜に圧力をかけ、空気が貫通し始める圧力から換算される孔径を最大孔径とした。平均孔径については、ＤＲＹ－ＵＰ測定で圧力、流量曲線の１／２の傾きを示す曲線と、ＷＥＴ－ＵＰ測定の曲線が交わる点の圧力から孔径を換算した。圧力と平均孔径の換算は下記の数式を用いた。
Ｄ＝Ｃ・Γ／Ｐ
Ｄ：ポリオレフィン微多孔膜の平均孔径（ｎｍ）
Γ：液体の表面張力（１５．９Ｎ／ｍ）
Ｐ：圧力（Ｐａ）
Ｃ：定数（２．８６×１０３）。 Based on JIS K 3832:1990, the bubble point pore size and average pore size were measured in the order of DRY-UP and WET-UP using a palm porometer (manufactured by PMI, CFP-1500A). For WET-UP, pressure was applied to a polyolefin microporous membrane sufficiently soaked with GALWICK (trade name) manufactured by PMI, whose surface tension was known, and the pore diameter calculated from the pressure at which air began to penetrate was taken as the maximum pore diameter. The average pore diameter was calculated from the pressure at the point where the curve showing the slope of 1/2 of the pressure/flow curve in the DRY-UP measurement intersects with the curve in the WET-UP measurement. The following formula was used to convert pressure and average pore diameter.
D=C・Γ/P
D: Average pore diameter (nm) of polyolefin microporous membrane
Γ: Surface tension of liquid (15.9N/m)
P: Pressure (Pa)
C: constant (2.86×10 3 ).
　（６）膜厚
　ポリオレフィン微多孔膜の５０ｍｍ×５０ｍｍの範囲内における５点の膜厚を接触厚み計（株式会社ミツトヨ製“ライトマチック”ＶＬ－５０、１０．５ｍｍφ超硬球面測定子）を用いて測定荷重０．０１Ｎにより測定し、平均値を膜厚（μｍ）とした。 (6) 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 (μm).
　（７）空孔率
　ポリオレフィン微多孔膜から５ｃｍ×５ｃｍ角を切り取って試験片とし、室温２５℃におけるその体積（ｃｍ３）および質量（ｇ）を測定した。ポリオレフィンの密度０．９９ｇ／ｃｍ３として、これらの値から、ポリオレフィン微多孔膜の空孔率を次式により算出した。
空孔率（％）＝（試験片の体積－試験片の質量／ポリオレフィンの密度）／試験片の体積×１００　…（式）。 (7) Porosity A 5 cm x 5 cm square was cut from the polyolefin microporous membrane to prepare a test piece, and its volume (cm 3 ) and mass (g) at room temperature of 25° C. were measured. Assuming that the density of the polyolefin is 0.99 g/cm 3 , the porosity of the microporous polyolefin membrane was calculated from these values using the following formula.
Porosity (%) = (volume of test piece - mass of test piece / density of polyolefin) / volume of test piece x 100 (formula).
　（８）１０μｍ換算透気抵抗度
　ＪＩＳ　Ｐ－８１１７：２００９の王研式試験機法により測定した。王研式透気抵抗度計（旭精工株式会社製、ＥＧＯ－１Ｔ）を用いて測定圧力０．０５ＭＰａで、１００ｃｍ３の空気を通過させる際のポリオレフィン微多孔膜の透気抵抗度Ｐ１（秒）を測定した。そして下記式により、膜厚１０μｍに換算した透気抵抗度Ｐ２を算出した。
Ｐ２＝（Ｐ１×１０）／Ｔ
Ｐ２：１０μｍ換算透気抵抗度（秒／１０μｍ）
Ｐ１：透気抵抗度（秒）
Ｔ：ポリオレフィン微多孔膜の膜厚（μｍ）。 (8) 10 μm equivalent air permeability resistance Measured by the Oken tester method of JIS P-8117:2009. Air permeability resistance P 1 ( seconds) was measured. Then, the air permeability resistance P 2 was calculated based on the film thickness of 10 μm using the following formula.
P 2 =(P 1 ×10)/T
P 2 : 10 μm equivalent air permeability resistance (sec/10 μm)
P 1 : Air permeability resistance (seconds)
T: Film thickness (μm) of polyolefin microporous membrane.
　（９）単位目付換算突刺強度
　ポリオレフィン微多孔膜から５．０ｃｍ×５．０ｃｍ角を切り取り、室温２５℃での質量（ｇ）を測定した。その値から、ポリオレフィン微多孔膜の目付を次式により算出した。
目付（ｇ／ｍ２）＝質量（ｇ／０．００２５ｍ２）×４００
　そして、試験速度を２ｍｍ／秒としたことを除いて、ＪＩＳ　Ｚ　１７０７：２０１９に準拠して測定した。フォースゲージ（株式会社イマダ製　ＤＳ２－２０Ｎ）を用いて、先端が球面（曲率半径Ｒ：０．５ｍｍ）の直径１．０ｍｍの針で、ポリオレフィン微多孔膜を２５℃の雰囲気下で突刺したときの最大荷重（Ｎ）を計測し、下記式から単位目付に換算した突刺強度を算出した。
単位目付換算突刺強度（Ｎ／（ｇ／ｍ２））＝最大荷重（Ｎ）／Ｓ（ｇ／ｍ２）
Ｓ：ポリオレフィン微多孔膜の目付（ｇ／ｍ２）。 (9) Puncture strength in terms of unit basis weight A 5.0 cm x 5.0 cm square was cut from the polyolefin microporous membrane, and its mass (g) at room temperature of 25° C. was measured. From that value, the basis weight of the polyolefin microporous membrane was calculated using the following formula.
Area weight (g/m 2 ) = Mass (g/0.0025m 2 ) x 400
The measurement was conducted in accordance with JIS Z 1707:2019, except that the test speed was 2 mm/sec. When using a force gauge (DS2-20N manufactured by Imada Co., Ltd.) to pierce a microporous polyolefin membrane in an atmosphere of 25°C with a needle with a diameter of 1.0 mm and a spherical tip (radius of curvature R: 0.5 mm). The maximum load (N) was measured, and the puncture strength converted to unit area weight was calculated from the following formula.
Puncture strength converted to unit weight (N/(g/m 2 )) = Maximum load (N)/S (g/m 2 )
S: Area weight (g/m 2 ) of the polyolefin microporous membrane.
　（１０）１０μｍ換算突刺強度
　試験速度を２ｍｍ／秒としたことを除いて、ＪＩＳ　Ｚ　１７０７：２０１９に準拠して測定した。フォースゲージ（株式会社イマダ製　ＤＳ２－２０Ｎ）を用いて、先端が球面（曲率半径Ｒ：０．５ｍｍ）の直径１．０ｍｍの針で、ポリオレフィン微多孔膜を２５℃の雰囲気下で突刺したときの最大荷重（Ｎ）を計測し、下記式から膜厚１０μｍに換算した突刺強度を算出した。
１０μｍ換算突刺強度（Ｎ／１０μｍ）＝最大荷重（Ｎ）×１０／Ｔ
Ｔ：ポリオレフィン微多孔膜の膜厚（μｍ）。 (10) 10 μm conversion puncture strength Measured in accordance with JIS Z 1707:2019, except that the test speed was 2 mm/sec. When using a force gauge (DS2-20N manufactured by Imada Co., Ltd.) to pierce a microporous polyolefin membrane in an atmosphere of 25°C with a needle with a diameter of 1.0 mm and a spherical tip (radius of curvature R: 0.5 mm). The maximum load (N) was measured, and the puncture strength converted to a film thickness of 10 μm was calculated from the following formula.
10μm equivalent puncture strength (N/10μm) = maximum load (N) x 10/T
T: Film thickness (μm) of polyolefin microporous membrane.
　（１１）Ｐ１５０℃／ＰＭａｘ（耐メルトダウン特性評価）
　ポリオレフィン微多孔膜を長軸１５ｍｍ、短軸３ｍｍに切り出して評価用サンプルを作製した。その後、日立ハイテクノロジー社製「ＴＭＡ７１００」を用いて、チャック間距離が１０ｍｍになるように評価用サンプルをチャックに固定し、初期荷重９．８ｍＮの定長モードで３０℃から２００℃まで５℃／分の速度で昇温させた。２００℃まで昇温させた際の温度と収縮力を１秒間隔で測定し、得られたチャートから１５０℃における収縮力と最大収縮力を求めた。そして、１５０℃における収縮力を最大収縮力で除算してＰ１５０℃／ＰＭａｘを求めた。 (11) P 150℃ /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 .
　（１２）シャットダウン温度（シャットダウン特性評価）
　ポリオレフィン微多孔膜を５℃／ｍｉｎの昇温速度で加熱しながら、透気度計（旭精工株式会社製、ＥＧＯ－１Ｔ）により透気抵抗度を測定し、透気抵抗度が検出限界である１．０×１０５秒／１００ｃｍ３Ａｉｒに到達した温度を求め、昇温透気度法によるシャットダウン温度（℃）とした。測定セルはアルミブロックで構成され、ポリオレフィン微多孔膜の直下に熱電対を有する構造とし、サンプルを５０ｍｍ×５０ｍｍ角に切り取り、周囲をОリングで固定しながら昇温測定した。 (12) Shutdown temperature (shutdown characteristics evaluation)
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.
　（１３）膜均一性
　ポリオレフィン微多孔膜の１００ｍｍ×１００ｍｍの範囲内において、間隔が１０ｍｍ以上離れた、任意の１５点の膜厚を接触厚み計（株式会社ミツトヨ製“ライトマチック”（登録商標）ＶＬ－５０、１０．５ｍｍφ超硬球面測定子）を用いて測定荷重０．０１Ｎの条件で測定した。得られた１５点の膜厚の平均値と標準偏差を求め、標準偏差を平均値で除した値を膜均一性とした。 (13) Film uniformity Within a 100 mm x 100 mm area of the microporous polyolefin film, measure the film thickness at any 15 points separated by 10 mm or more using a contact thickness meter (“Lightmatic” (registered trademark) manufactured by Mitutoyo Co., Ltd.) The measurement was carried out using a VL-50 (10.5 mmφ carbide spherical probe) under a measurement load of 0.01N. The average value and standard deviation of the film thicknesses obtained at the 15 points were determined, and the value obtained by dividing the standard deviation by the average value was defined as the film uniformity.
　（１４）室温抵抗値
　以下、室温抵抗値評価用セルの作製手順を示す。該作業はいずれも露点温度を－３５℃以下としたドライルーム内にて行った。ポリオレフィン微多孔膜を直径１９ｍｍの円形にカットし、試験片とした。２０３２型コインセルの部材（上蓋、下蓋、ガスケット（ＰＦＡ製）、スペーサー（直径１５．５ｍｍ、厚み１．０ｍｍの円柱状）、ウェーブワッシャー）を用意した。上記２０３２型コインセルの部材は、いずれも宝泉株式会社から購入した。２０３２型コインセルの部材の下蓋の内側底部に、下蓋側から順に、試験片、ガスケットを載置した。次にＥＣとＥＭＣとの体積比が４：６の混合溶媒にＬｉＰＦ６の濃度が１ｍｏｌ／Ｌとなるよう溶解させた電解液を前述のコインセルに０．１５ｍＬ注液した。各略称はそれぞれ以下の意味である。
ＬｉＰＦ６：六フッ化リン酸リチウム
ＥＣ：炭酸エチレン
ＥＭＣ：炭酸エチルメチル
次いで、ガスケット中空部の測定用サンプルの上にスペーサーを設置した後、ゲージ圧で－５０ｋＰａの環境下、１分間静置する作業を２回行い、ポリオレフィン微多孔膜に電解液を含浸させた。その後、スペーサーの上に、スペーサー側から順に、ウェーブワッシャー、上蓋を載置し、コインセルカシメ機（宝泉株式会社製）で密閉して評価用セルを作製した。 (14) Room-temperature resistance value The procedure for manufacturing a cell for evaluating room-temperature resistance value will be described below. All of these operations were carried out in a dry room with a dew point temperature of -35°C or lower. A polyolefin microporous membrane was cut into a circular shape with a diameter of 19 mm to prepare a test piece. The members of a 2032 type coin cell (upper lid, lower lid, gasket (made of PFA), spacer (cylindrical shape with a diameter of 15.5 mm and a thickness of 1.0 mm), and a wave washer) were prepared. All components of the 2032 type coin cell were purchased from Hosen Co., Ltd. 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. Next, 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. Each abbreviation has the following meaning.
LiPF 6 : Lithium hexafluorophosphate EC : Ethylene carbonate EMC : Ethyl methyl carbonate Next, after installing a spacer on top of the measurement sample in the hollow part of the gasket, it is left standing for 1 minute in an environment of -50 kPa gauge pressure. 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.
　作成したコイン電池の電気抵抗値を、２５℃の雰囲気でインピーダンスアナライザにより周波数２００ｋＨｚにて測定した。 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.
　上記測定方法により得られた抵抗値には、ケースや電極などポリオレフィン微多孔膜以外の抵抗の寄与も含まれているため、コイン電池に入れるポリオレフィン微多孔膜の試験片の枚数を３枚、４枚、５枚としたコイン電池をそれぞれ作製し、各コイン電池の抵抗値から、ポリオレフィン微多孔膜１枚あたりの抵抗値（Ω・ｃｍ２）を算出した。そして下記式により、膜厚１０μｍに換算した抵抗値を算出した。
Ｒ２＝Ｒ１×１０／Ｔ
Ｒ２：１０μｍ換算の抵抗値（Ω・ｃｍ２／１０μｍ）
Ｒ１：ポリオレフィン微多孔膜１枚あたりの抵抗値（Ω・ｃｍ２）
Ｔ：ポリオレフィン微多孔膜の膜厚（μｍ）。 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 (Ω·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 μm was calculated using the following formula.
R2 =R1×10/T
R 2 : Resistance value converted to 10 μm (Ω・cm 2 /10 μm)
R 1 : Resistance value per polyolefin microporous membrane (Ω・cm 2 )
T: Film thickness (μm) of polyolefin microporous membrane.
　（１５）耐異物性
　負極／ポリオレフィン微多孔膜／直径５００μｍのクロム球／アルミ箔の順にセットした簡易電池に、１．５Ｖキャパシタおよびデータロガーを接続し、引張試験機（ＳＨＩＭＡＺＵ製“ＡＵＴＯＧＲＡＰＨ”（登録商標）ＡＧＳ－Ｘ）を用いて０．３ｍｍ／ｍｉｎの条件でプレスし、電池がショートするまでの変位量を測定した。高い変位量でもショートしないサンプルほど耐異物性が良好である。電池がショートするまでの変位量と耐異物性の関係は下記４段階で評価した。
Ａ：変位量（ｍｍ）／セパレータ厚み（μｍ）が０．０７以上であった。
Ｂ：変位量（ｍｍ）／セパレータ厚み（μｍ）が０．０５以上０．０７未満であった。
Ｃ：変位量（ｍｍ）／セパレータ厚み（μｍ）が０．０３以上０．０５未満であった。
Ｄ：変位量（ｍｍ）／セパレータ厚み（μｍ）が０．０３未満であった。 (15) Foreign object resistance A 1.5V capacitor and a data logger were connected to a simple battery set in the following order: negative electrode/polyolefin microporous membrane/chromium bulb with a diameter of 500 μm/aluminum foil. (registered trademark) AGS-X) at a pressure of 0.3 mm/min, and the amount of displacement until the battery short-circuited was measured. A sample that does not short-circuit even with a large amount of displacement has better foreign object resistance. The relationship between the amount of displacement until the battery short-circuited and foreign object resistance was evaluated on the following four levels.
A: Displacement amount (mm)/separator thickness (μm) was 0.07 or more.
B: Displacement amount (mm)/separator thickness (μm) was 0.05 or more and less than 0.07.
C: Displacement amount (mm)/separator thickness (μm) was 0.03 or more and less than 0.05.
D: Displacement amount (mm)/separator thickness (μm) was less than 0.03.
　実施例に用いた原料を表１、２に示した。 The raw materials used in the examples are shown in Tables 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　［実施例１］
　（混合物の調製）
　超高分子量ポリエチレンとしてＵＨＰＥａを１００質量％含んでなるポリオレフィン樹脂１００質量部に、酸化防止剤テトラキス［メチレン－３－（３，５－ジターシャリーブチル－４－ヒドロキシフェニル）－プロピオネート］メタン０．５質量部を配合し、混合物を調製した。得られた混合物２０質量部を、強混練タイプの二軸押出機（内径５８ｍｍ、Ｌ／Ｄ＝４２）に投入し、二軸押出機のサイドフィーダーから流動パラフィン（４０℃における粘度３５ｃＳｔ）８０質量部を分割せずに初期添加割合１００質量％で供給し、１９０℃で溶融混練して、ポリオレフィン樹脂溶液を調製した。 [Example 1]
(Preparation of mixture)
To 100 parts by mass of a polyolefin resin containing 100% by mass of UHPEa as ultra-high molecular weight polyethylene, 0.5% of the antioxidant tetrakis[methylene-3-(3,5-ditertiarybutyl-4-hydroxyphenyl)-propionate]methane was added. Parts by mass were blended to prepare a mixture. 20 parts by mass of the obtained mixture was put into a strong kneading type twin-screw extruder (inner diameter 58 mm, L/D=42), and 80 parts by mass of liquid paraffin (viscosity 35 cSt at 40°C) was added from the side feeder of the twin-screw extruder. A polyolefin resin solution was prepared by supplying the mixture at an initial addition ratio of 100% by mass without dividing the parts and melt-kneading at 190°C.
　（ゲル状シートの形成）
　前記ポリオレフィン樹脂溶液を、フィルターを通して異物を除去後、ギアポンプにより送り量を調節しながら、二軸押出機から、２３０℃に設定したＴダイに供給した。一部ポリオレフィン樹脂溶液は排出弁からパージした。Ｔダイから押し出された成形体を、３０℃に温調した冷却ロールを用いて引き取り速度５ｍ／ｍｉｎで引き取りながら冷却し、ゲル状シートを形成した。 (Formation of gel-like sheet)
After removing foreign matter from the polyolefin resin solution through a filter, it was supplied from a twin-screw extruder to a T-die set at 230° C. while adjusting the feed rate with a gear pump. A portion of the polyolefin resin solution was purged through a drain valve. The molded product extruded from the T-die was cooled while being taken off at a take-up speed of 5 m/min using a cooling roll whose temperature was controlled at 30° C. to form a gel-like sheet.
　（延伸）
　前記ゲル状シートを、テンター延伸機を用いて１１５℃でＭＤ方向およびＴＤ方向ともに８倍に同時二軸延伸した。 (Stretching)
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.
　（洗浄・乾燥）
　延伸されたゲル状シートを３０ｃｍ×３０ｃｍのアルミニウム枠板に固定し、２５℃に温調した塩化メチレン浴中に浸漬した。塩化メチレン浴中で２分間揺動しながら流動パラフィンを除去した後、室温で風乾し、乾燥膜を得た。 (washing/drying)
The stretched gel-like sheet was fixed to a 30 cm x 30 cm aluminum frame plate and immersed in a methylene chloride bath whose temperature was controlled at 25°C. The liquid paraffin was removed while rocking in a methylene chloride bath for 2 minutes, and then air-dried at room temperature to obtain a dry film.
　（熱処理）
　前記乾燥膜に１３０℃で３分、熱固定処理を行い、ポリオレフィン微多孔膜を得た。得られたポリオレフィン微多孔膜の厚みは８μｍであった。構成する各成分の配合割合、製造条件、評価結果等を表３に示す。 (Heat treatment)
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 μm. Table 3 shows the blending ratio of each constituent component, manufacturing conditions, evaluation results, etc.
　（実施例２～６）
　表３で示した原料配合や工程条件に変更した以外は実施例１と同様に製膜し、ポリオレフィン微多孔膜を得た。なお、実施例５はゲル状シートの時点で外観ムラが発生していたが、後工程の実施は可能であったので製膜性をＢとした。 (Examples 2 to 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 3. In 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.
　（比較例１～６）
　表４で示した原料配合や工程条件に変更した以外は実施例１と同様に製膜し、ポリオレフィン微多孔膜を得た。なお、比較例４はゲル状シートの時点で外観ムラが発生していたが、後工程の実施は可能であったので製膜性をＢとした。また、比較例５では、溶融混練後のポリオレフィン樹脂溶液の時点で、未溶融物が多量に発生し、ゲル状シートの製膜が断続的であり、ポリオレフィン微多孔膜にも未溶融物が存在したため、製膜性をＣとした。さらに、比較例６では、溶融混練後のポリオレフィン樹脂溶液の時点で、未溶融物が発生したが、後工程の実施は可能であったので製膜性をＢとした。 (Comparative Examples 1 to 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. In addition, in 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. In addition, in 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. Furthermore, in 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.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　実施例１～４のポリオレフィン微多孔膜は、優れた機械的強度を持ちながら、シャットダウン特性と耐メルトダウン特性との両立を確認でき、電池用セパレータとしても優れた膜品位やイオン透過性、耐異物性を有していた。また、実施例５はシャットダウン特性を維持しながら、優れた機械的強度と耐メルトダウン特性を確認できたものの、膜均一性が他の実施例と比べ、劣っていた。また、実施例６は優れた機械的強度と膜均一性は有していたものの、耐メルトダウン特性や平均孔径／最大孔径、室温抵抗値が他の実施例と比べ劣っていた。 The 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.
　一方、比較例１～４、６のポリオレフィン微多孔膜は必要とされる各特性の少なくとも１つが悪化しており、両立されていないことが示された。比較例５については、ポリオレフィン微多孔膜として製膜したものの、膜均一性が他のものより大きく劣っており、一部の評価を実施しなかった。 On the other hand, 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. Regarding 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.
　以上、本発明の実施の形態を説明したが、上述した実施の形態は本発明を実施するための例示に過ぎない。よって、本発明は上述した実施の形態に限定されることなく、その趣旨を逸脱しない範囲内で上述した実施の形態を適宜変形して実施することが可能である。 Although the embodiments of the present invention have been described above, the embodiments described above are merely examples for implementing the present invention. Therefore, the present invention is not limited to the embodiments described above, and can be implemented by appropriately modifying the embodiments described above without departing from the spirit thereof.
　本発明のポリオレフィン微多孔膜は、優れた機械的強度を持ちながら、シャットダウン特性と耐メルトダウン特性とを両立している。電池用セパレータとして優れた膜品位やイオン透過性、耐異物性を有しており、電池特性と電池安全性の高いレベルでの両立が可能となる。したがって、電池高容量化が要求される二次電池用セパレータに好適に用いることができる。また、本発明のポリオレフィン微多孔膜をセパレータとして有する非水電解液二次電池は、ポリオレフィン微多孔膜の特性を活かして、電池安全性を高いレベルで維持しながら、電池容量を高めることができる。 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. .
　また、本発明のポリオレフィン微多孔膜は、その特性を活かして、各種フィルター（逆浸透濾過膜、限外濾過膜、精密濾過膜等）に好適に用いることができる。本発明のポリオレフィン微多孔膜を有する各種フィルターは、機械的強度が高く薄膜化が可能であり、かつ均一な孔構造をしていることから、濾過流量を高いレベルで維持しつつ、濾過精度にも優れる。 Furthermore, 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. 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.

Claims (13)

  1. 単位目付換算突刺強度が０．８Ｎ／（ｇ／ｍ２）以上であり、かつゲル浸透クロマトグラフィー法（ＧＰＣ法）により得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、全体の成分量を１００質量％とした時に分子量１０００万以上の成分量が１．０％質量以下であり、かつ最大検出強度を１として分子量分布の検出強度を規格化し、分子量２００万における検出強度をＫ２００、分子量７００万における検出強度をＫ７００としたとき、Ｋ２００－Ｋ７００≧０．４であるポリオレフィン微多孔膜。 A polyolefin microporous membrane 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. In the molecular weight distribution, when the total component amount is 100% by mass, the amount of components with a molecular weight of 10 million or more is 1.0% by mass or less, and the maximum detection intensity is 1. The detection intensity of the molecular weight distribution is normalized, and the molecular weight A polyolefin microporous membrane in which K200-K700≧0.4, where the detection intensity at a molecular weight of 2 million is K200 and the detection intensity at a molecular weight of 7 million is K700.
  2. ＧＰＣ法より得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度を１として全体の検出強度を規格化した時の分子量２００の検出強度：Ｋ２００が０．６以上である請求項１に記載のポリオレフィン微多孔膜。 In the molecular weight distribution of a polyolefin microporous membrane obtained by the GPC method, with the horizontal axis as the molecular weight and the vertical axis as the detection intensity, the detection intensity at a molecular weight of 200 when the maximum detection intensity is 1 and the overall detection intensity is normalized: K200 The microporous polyolefin membrane according to claim 1, wherein is 0.6 or more.
  3. ＧＰＣ法より得られる、横軸を分子量、縦軸を検出強度としたポリオレフィン微多孔膜の分子量分布において、最大検出強度が分子量１０万から５０万の領域に存在する請求項１または請求項２に記載のポリオレフィン微多孔膜。 According to claim 1 or claim 2, in the molecular weight distribution of the polyolefin microporous membrane obtained by the GPC method, with the horizontal axis being the molecular weight and the vertical axis being the detection intensity, the maximum detection intensity exists in the region of molecular weight from 100,000 to 500,000. The polyolefin microporous membrane described.
  4. ＪＩＳ　Ｋ　３８３２－１９９０に基づくパームポロメーター測定により得られる平均孔径と最大孔径の比（平均孔径／最大孔径）が０．６５以上である請求項１または請求項２に記載のポリオレフィン微多孔膜。 The microporous polyolefin membrane according to claim 1 or 2, wherein the ratio of the average pore diameter to the maximum pore diameter (average pore diameter/maximum pore diameter) obtained by palm porometer measurement based on JIS K 3832-1990 is 0.65 or more.
  5. 昇温速度５℃／ｍｉｎ条件の熱機械分析測定（ＴＭＡ測定）から得られる横軸を温度、縦軸を応力としたポリオレフィン微多孔膜の温度－応力曲線において、最大応力をＰｍａｘ、温度１５０℃における応力をＰ１５０とした時、Ｐ１５０／Ｐｍａｘ≧０．６である請求項１または請求項２に記載のポリオレフィン微多孔膜。 In the temperature-stress curve of the polyolefin microporous membrane, where the horizontal axis is the temperature and the vertical axis is the stress, obtained from thermomechanical analysis measurement (TMA measurement) at a heating rate of 5°C/min, the maximum stress is Pmax, and the temperature is 150°C. The polyolefin microporous membrane according to claim 1 or 2, wherein P150/Pmax≧0.6, where P150 is the stress at P150.
  6. ハフニウムを０．２ｐｐｍ以上含む請求項１または請求項２に記載のポリオレフィン微多孔膜。 The microporous polyolefin membrane according to claim 1 or 2, containing 0.2 ppm or more of hafnium.
  7. 請求項１または請求項２に記載のポリオレフィン微多孔膜に、さらに多孔質層が積層された積層体。 A laminate comprising the polyolefin microporous membrane according to claim 1 or 2 further laminated with a porous layer.
  8. 請求項１または請求項２に記載のポリオレフィン微多孔膜を用いた、電池用セパレータ。 A battery separator using the polyolefin microporous membrane according to claim 1 or 2.
  9. 請求項７に記載の積層体を用いた、電池用セパレータ。 A battery separator using the laminate according to claim 7.
  10. 請求項８に記載の電池用セパレータを有する、非水電解液二次電池。 A non-aqueous electrolyte secondary battery comprising the battery separator according to claim 8.
  11. 請求項９に記載の電池用セパレータを有する、非水電解液二次電池。 A non-aqueous electrolyte secondary battery comprising the battery separator according to claim 9.
  12. 請求項１または請求項２に記載のポリオレフィン微多孔膜を用いた、フィルター。 A filter using the polyolefin microporous membrane according to claim 1 or 2.
  13. 請求項１２に記載のフィルターを用いたろ過ユニット。 A filtration unit using the filter according to claim 12.
PCT/JP2023/010054 2022-03-18 2023-03-15 Polyolefin microporous membrane, separator for batteries, nonaqueous electrolyte secondary battery and filter WO2023176876A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2022043406 2022-03-18
JP2022-043406 2022-03-18

Publications (1)

Publication Number Publication Date
WO2023176876A1 true WO2023176876A1 (en) 2023-09-21

Family

ID=88023902

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2023/010054 WO2023176876A1 (en) 2022-03-18 2023-03-15 Polyolefin microporous membrane, separator for batteries, nonaqueous electrolyte secondary battery and filter

Country Status (1)

Country Link
WO (1) WO2023176876A1 (en)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010079784A1 (en) * 2009-01-07 2010-07-15 三井化学株式会社 Polypropylene resin composition for microporous film formation
WO2018164057A1 (en) * 2017-03-08 2018-09-13 東レ株式会社 Microporous polyolefin membrane, multilayer microporous polyolefin membrane, laminated microporous polyolefin membrane and separator
WO2018164056A1 (en) * 2017-03-08 2018-09-13 東レ株式会社 Polyolefin microporous film
WO2018173904A1 (en) * 2017-03-22 2018-09-27 東レ株式会社 Microporous polyolefin membrane and battery including same
JP2018162438A (en) * 2017-03-24 2018-10-18 旭化成株式会社 Polyolefin microporous film and method for producing polyolefin microporous film
WO2020256138A1 (en) * 2019-06-21 2020-12-24 旭化成株式会社 Polyolefin microporous membrane

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010079784A1 (en) * 2009-01-07 2010-07-15 三井化学株式会社 Polypropylene resin composition for microporous film formation
WO2018164057A1 (en) * 2017-03-08 2018-09-13 東レ株式会社 Microporous polyolefin membrane, multilayer microporous polyolefin membrane, laminated microporous polyolefin membrane and separator
WO2018164056A1 (en) * 2017-03-08 2018-09-13 東レ株式会社 Polyolefin microporous film
WO2018173904A1 (en) * 2017-03-22 2018-09-27 東レ株式会社 Microporous polyolefin membrane and battery including same
JP2018162438A (en) * 2017-03-24 2018-10-18 旭化成株式会社 Polyolefin microporous film and method for producing polyolefin microporous film
WO2020256138A1 (en) * 2019-06-21 2020-12-24 旭化成株式会社 Polyolefin microporous membrane

Similar Documents

Publication Publication Date Title
JP5202948B2 (en) Method for producing polyolefin microporous membrane
JP5967589B2 (en) Polyolefin microporous membrane and method for producing the same
JP4902455B2 (en) Polyolefin multilayer microporous membrane, method for producing the same, battery separator and battery
JP4121846B2 (en) Polyolefin microporous membrane and production method and use thereof
JP6680206B2 (en) Polyolefin microporous membrane, battery separator and battery
US10079378B2 (en) Polyolefin microporous membrane and production method thereof
JP2004196871A (en) Polyolefin fine porous membrane and method for producing the same and use
JPWO2006106783A1 (en) Polyolefin microporous membrane and method for producing the same
JP7395827B2 (en) porous polyolefin film
JP2002194132A (en) Polyolefin fine porous film and method of manufacturing the same
JP2002284918A (en) Polyolefin microporous film, method for producing the same and use thereof
JP4234392B2 (en) Microporous membrane, production method and use thereof
JP2004161899A (en) Film with minute pore and its manufacturing method and use
US20220298314A1 (en) Polyolefin microporous film, layered body, and battery
JP5450944B2 (en) Polyolefin microporous membrane, battery separator and battery
JP2021038379A (en) Porous polyolefin film
CN110382605B (en) Polyolefin microporous membrane and battery using the same
JP2003105121A (en) Polyolefin minute porous film and method of its manufacture
CN114516982B (en) Polyolefin microporous membrane, separator for battery, and secondary battery
JP5057414B2 (en) Method for producing microporous membrane and use of microporous membrane obtained by the production method
JP7380553B2 (en) Polyolefin microporous membrane, battery separator and secondary battery
WO2023176876A1 (en) Polyolefin microporous membrane, separator for batteries, nonaqueous electrolyte secondary battery and filter
WO2021033733A1 (en) Polyolefin micro porous film, laminate, and battery
WO2023176880A1 (en) Polyolefin microporous film, non-aqueous electrolyte secondary battery, and filter
CN114207004B (en) Polyolefin microporous membrane, separator for battery, and secondary battery

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 2023521523

Country of ref document: JP

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23770829

Country of ref document: EP

Kind code of ref document: A1