[go: up one dir, main page]

WO2009038231A1 - Membranes microporeuses, procédés de fabrication et utilisation de telles membranes - Google Patents

Membranes microporeuses, procédés de fabrication et utilisation de telles membranes Download PDF

Info

Publication number
WO2009038231A1
WO2009038231A1 PCT/JP2008/067579 JP2008067579W WO2009038231A1 WO 2009038231 A1 WO2009038231 A1 WO 2009038231A1 JP 2008067579 W JP2008067579 W JP 2008067579W WO 2009038231 A1 WO2009038231 A1 WO 2009038231A1
Authority
WO
WIPO (PCT)
Prior art keywords
membrane
heat
microporous
stretching
microporous membrane
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/JP2008/067579
Other languages
English (en)
Inventor
Kotaro Takita
Shintaro Kikuchi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tonen Chemical Corp
Original Assignee
Tonen Sekiyu Kagaku KK
Tonen Chemical Corp
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
Priority claimed from US11/858,587 external-priority patent/US8304114B2/en
Priority claimed from US11/864,214 external-priority patent/US8021789B2/en
Priority claimed from US11/864,350 external-priority patent/US8273279B2/en
Priority claimed from US11/868,265 external-priority patent/US8715849B2/en
Application filed by Tonen Sekiyu Kagaku KK, Tonen Chemical Corp filed Critical Tonen Sekiyu Kagaku KK
Priority to JP2010525545A priority Critical patent/JP2010540691A/ja
Priority to KR1020107006155A priority patent/KR101135077B1/ko
Publication of WO2009038231A1 publication Critical patent/WO2009038231A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0025—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching
    • B01D67/0027—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching by stretching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/262—Polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • B01D71/421—Polyacrylonitrile
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • 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
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H01M50/406—Moulding; Embossing; Cutting
    • 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
    • H01M50/489—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
    • 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
    • H01M50/491—Porosity
    • 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
    • H01M50/494—Tensile strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/12—Specific ratios of components used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/0283—Pore size
    • B01D2325/02833—Pore size more than 10 and up to 100 nm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/0283—Pore size
    • B01D2325/02834—Pore size more than 0.1 and up to 1 µm
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/22—Thermal or heat-resistance properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/34—Molecular weight or degree of polymerisation
    • B01D2325/341—At least two polymers of same structure but different molecular weight
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention relates to a microporous membrane having suitable permeability, mechanical strength, electrolytic solution absorption characteristics, compression resistance, and heat shrinkage resistance; and methods for producing and using such a microporous polyolefin membrane. It also relates to battery separators comprising such a microporous polyolefin membrane, and to batteries utilizing such battery separators.
  • Microporous membranes are useful as separators for primary batteries and secondary batteries such as lithium ion secondary batteries, lithium-polymer secondary batteries, nickel-hydrogen secondary , batteries, nickel-cadmium secondary batteries, nickel-zinc secondary batteries, silver-zinc secondary batteries, etc.
  • the microporous polyolefin membrane is used as a battery separator, particularly for lithium ion batteries, the membrane's performance significantly affects the battery's properties, productivity, and safety. Accordingly, the microporous polyolefin membrane should have appropriate permeability, mechanical properties, heat resistance, dimensional stability, shutdown properties, meltdown properties, electrolytic solution absorption, etc.
  • JP6-240036A discloses a microporous polyolefin membrane having improved pore diameter and a sharp pore diameter distribution.
  • the membrane is made from a polyethylene resin containing 1% or more by mass of ultra-high molecular weight polyethylene having a weight-average molecular weight ("Mw") of 7 x 10 5 or more, the polyethylene resin having a molecular weight distribution (weight-average molecular weight/number-average molecular weight) of 10 to 300, and the microporous polyolefin membrane having a porosity of 35 to 95%, an average penetrating pore diameter of 0.05 to 0.2 ⁇ m, a rupture strength (15 mm width) of 0.2 kg or more, and a pore diameter distribution (maximum pore diameter/average penetrating pore diameter) of 1.5 or less.
  • Mw weight-average molecular weight
  • This microporous membrane is produced by extruding a melt-blend of the above polyethylene resin and a membrane-forming solvent through a die, stretching the gel-like sheet obtained by cooling at a temperature from the crystal dispersion temperature ("Ted") of the above polyethylene resin to the melting point +10°C, removing the membrane-forming solvent from the gel-like sheet, re-stretching the resultant membrane to 1.5 to 3 fold as an area magnification at a temperature of the melting point of the above polyethylene resin -10°C or less, and heat-setting it at a temperature from the crystal dispersion temperature of the above polyethylene resin to the melting point.
  • Ted crystal dispersion temperature
  • WO 1999/48959 discloses a microporous polyolefin membrane having suitable strength and permeability, as well as a uniformly porous surface without local permeability variations.
  • the membrane is made of a polyolefin resin, for instance, high density polyethylene, having an Mw of 50,000 or more and less than 5,000,000, and a molecular weight distribution of 1 or more to less than 30, which has a network structure with fine gaps formed by uniformly dispersed micro-fibrils, having an average micro-fibril size of 20 to 100 nm and an average micro-fibril distance of 40 to 400 nm.
  • This microporous membrane is produced by extruding a melt-blend of the above polyolefin resin and a membrane-forming solvent through a die, stretching a gel-like sheet obtained by cooling at a temperature of the melting point of the above polyolefin resin -50°C or higher and lower than the melting point, removing the membrane-forming solvent from the gel-like sheet, re-stretching it to 1.1-5 fold at a temperature of the melting point of the above polyolefin resin -50°C or higher and lower than the melting point, and heat-setting it at a temperature from the crystal dispersion temperature of the above polyolefin resin to the melting point.
  • WO 2000/20492 discloses a microporous polyolefin membrane of improved permeability which is characterized by fine polyethylene fibrils having an Mw of 5 x 10 5 or more, the composition comprising polyethylene.
  • the microporous polyolefin membrane has an average pore diameter of 0.05 to 5 ⁇ m, and the percentage of lamellas at angles ⁇ of 80 to 100° relative to the membrane surface is 40% or more in longitudinal and transverse cross sections.
  • This polyethylene composition comprises 1 to 69% by weight of ultra-high molecular weight polyethylene having a weight-average molecular weight of 7 x 10 5 or more, 1 to 98% by weight of high density polyethylene and 1 to 30% by weight of low density polyethylene.
  • This microporous membrane is produced by extruding a melt-blend of the above polyethylene composition and a membrane-forming solvent through a die, stretching a gel-like sheet obtained by cooling, heat-setting it at a temperature from the crystal dispersion temperature of the above polyethylene or its composition to the melting point +30°C, and removing the membrane-forming solvent.
  • WO 2002/072248 discloses a microporous membrane having improved permeability, particle-blocking properties and strength.
  • the membrane is made using a polyethylene resin having an Mw of less than 380,000.
  • the membrane has a porosity of 50 to 95% and an average pore diameter of 0.01 to 1 ⁇ m.
  • This microporous membrane has a three-dimensional network skeleton formed by micro-fibrils having an average diameter of 0.2 to 1 ⁇ m connected to each other throughout the overall microporous membrane, and openings defined by the skeleton to have an average diameter of 0.1 ⁇ m or more and less than 3 ⁇ m.
  • This microporous membrane is produced by extruding a melt-blend of the above polyethylene resin and a membrane-forming solvent through a die, removing the membrane-forming solvent from the gel-like sheet obtained by cooling, stretching it to 2 to 4 fold at a temperature of 20 to 140°C, and heat-treating the stretched membrane at a temperature of 80 to 140°C.
  • WO 2005/113657 discloses a microporous polyolef ⁇ n membrane having suitable shutdown properties, meltdown properties, dimensional stability, and high-temperature strength.
  • the membrane is made using a polyolefin composition comprising (a) polyethylene resin containing 8 to 60% by mass of a component having a molecular weight of 10,000 or less, and an Mw/Mn ratio of 11 to 100, wherein "Mn” is the number-average molecular weight of the polyethylene resin, and a viscosity-average molecular weight (“Mv”) of 100,000 to 1,000,000, and (b) polypropylene.
  • the membrane has a porosity of 20 to 95%, and a heat shrinkage ratio of 10% or less at 100 0 C.
  • This microporous polyolef ⁇ n membrane is produced by extruding a melt-blend of the above polyolefin and a membrane-forming solvent through a die, stretching the gel-like sheet obtained by cooling, removing the membrane-forming solvent, and annealing the sheet.
  • separators not only permeability, mechanical strength, dimensional stability, shutdown properties and meltdown properties, but also properties related to battery productivity such as electrolytic solution absorption, and battery cyclability, such as electrolytic solution retention properties, have recently been given importance.
  • electrodes for lithium ion batteries expand and shrink according to the intrusion and departure of lithium, and an increase in battery capacity leads to larger expansion ratios.
  • separators are compressed when the electrodes expand, it is desired that the separators when compressed suffer as little a decrease as possible in electrolytic solution retention.
  • improved microporous membranes are disclosed in JP6-240036A, WO 1999/48959, WO 2000/20492, WO 2002/072248, and WO 2005/113657, further improvements are still needed, particularly in membrane permeability, mechanical strength, heat shrinkage resistance, compression resistance, and electrolytic solution absorption properties. It is thus desired to form battery separators from microporous membranes having improved permeability, mechanical strength, heat shrinkage resistance, compression resistance, and electrolytic solution absorption.
  • the invention relates to the discovery of a microporous polymeric membrane, and a method for manufacturing same, having a good balance of permeability, mechanical strength, and electrolytic solution absorption, compression resistance, and heat shrinkage resistance properties.
  • An embodiment of the invention relates to a microporous membrane comprising pores characterized by a pore size (or pore diameter when the pores are approximately cylindrical) distribution curve obtained by mercury intrusion porosimetry having at least two peaks. It has been discovered that such a membrane has improved permeability, mechanical strength, heat shrinkage resistance, compression resistance, and electrolytic solution absorption characteristics.
  • the microporous polyolefin membrane can be produced by a method comprising (1) combining a polyolefin composition and at least one diluent (e.g., membrane-forming solvent) to form e.g., a polyolefin solution, the polyolefin composition comprising from about 73 wt. % to about 97 wt. % of a first polyethylene resin having a weight average molecular weight of less than 7 x 10 5 , e.g., in the range of from about 2.5 x 10 5 to 6 x 10 5 , and a molecular weight distribution of from about 5 to about 100, from about 3 wt. % to about 20 wt.
  • a polyolefin composition comprising from about 73 wt. % to about 97 wt. % of a first polyethylene resin having a weight average molecular weight of less than 7 x 10 5 , e.g., in the range of from about 2.5 x 10
  • % polypropylene resin having a weight average molecular weight of from about 3 x 10 to about 1.5 x 10 6 , a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1.0 to about 100, and from about 0 wt. % to about 7 wt.
  • the method can further comprise (6) stretching the membrane in at least one direction, and (7) heat-setting the stretched microporous membrane.
  • the microporous polyolefin membrane has dense domains corresponding to a main peak in a range of 0.01 to 0.08 ⁇ m in the pore size (or pore diameter when the pores are approximately cylindrical) distribution curve, and coarse domains corresponding to at least one sub-peak in a range of more than 0.08 ⁇ m to 1.5 ⁇ m in the pore size (or pore diameter when the pores are approximately cylindrical) distribution curve.
  • the pore volume ratio of the dense domains to the coarse domains is 0.5 to 49.
  • the microporous polyolefin membrane has surface roughness of 3 x 10 2 nm or more as the maximum height difference between any two points on the surface of the membrane.
  • the upper limit on the surface roughness of the microporous polyolefin membrane is 3 x 10 3 nm. With surface roughness within this range, the microporous membrane has a large contact area with an electrolytic solution when used as a battery separator, exhibiting desirable electrolytic solution absorption characteristics.
  • the polyolefin composition of the microporous membrane is produced or obtained from a mixture comprising from about 73 wt. % to about 97 wt. % high density polyethylene resin having a weight average molecular weight of from about 2.5 x 10 5 to about 4 x 10 5 and a molecular weight distribution of from about 5 to about 50, from about 3 wt.
  • polypropylene resin having a weight average molecular weight of from about 3 x 10 5 to about 1.5 x 10 6 , a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1.0 to about 100, and from about 0 wt. % to about 7 wt. % ultra-high molecular weight polyethylene resin having a weight average molecular weight of that is greater than that of the high density polyethylene, e.g., 7 x 10 5 or higher.
  • the high density polyethylene may, for example, have a weight average molecular weight of from about 2.5 x 10 5 to about 4 x 10 5 and a molecular weight distribution of from about 5 to about 30.
  • the microporous polyolef ⁇ n membrane comprises 3 wt. % to 20 wt. % of polypropylene obtained from polypropylene resin and 80 wt. % to 97 wt. % of polyethylene obtained from polyethylene resins, based on the weight of the microporous polyolefin membrane.
  • the microporous membrane is manufactured by a method comprising the steps of (1) combining a polyolefin composition and a membrane-forming solvent to form a polyolef ⁇ n solution, the polyolefin composition comprising from about 73 wt. % to about 97 wt. % of a first polyethylene resin having a weight average molecular weight of from about 2.5 x 10 5 to about 6 x 10 5 and a molecular weight distribution of from about 5 to about 100, from about 3 wt. % to about 20 wt.
  • polypropylene resin having a weight average molecular weight of from about 3 x 10 5 to about 1.5 x 10 6 , a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1.0 to about 100, and from about 0 wt. % to about 7 wt. % of a second polyethylene resin having a weight average molecular weight that is greater than that of the first polyethylene resin, e.g., in the range of from 7 x 10 5 to about 5 x 10 6 , percentages based on the weight of the polyolefin composition, with the polyolefin solution preferably having a solvent concentration of from about 25 wt. % to about 50 wt.
  • % based on the weight of the polyolefin solution (2) extruding the polyolefin solution through a die to form an extrudate, (3) cooling the extrudate to form a gel-like sheet having a high resin content, (4) stretching the gel-like sheet to a magnification of from about 9 to about 400 fold, for example from about 16 to about 49 fold, in at least one direction at a high stretching temperature of from about Ted to about Ted + 30 °C, for example from about Ted + 15 to about Ted + 25 °C, to form a stretched gel-like sheet, (5) removing the membrane-forming solvent from the stretched gel-like sheet to form a membrane, (6) stretching the membrane to a high magnification of from about 1.1 to about 1.8 fold, for example from about 1.2 to about 1.6 fold, in at least one direction to form a stretched membrane, and (7) heat-setting the stretched microporous membrane to form the microporous membrane.
  • the stretching of the microporous membrane in step (6) may be called “re-stretching,” because it is conducted after the stretching of the gel-like sheet in step (4).
  • the invention relates to a microporous membrane comprising polyethylene and polypropylene and having an electrolytic solution absorption speed > 4.3.
  • the inventions relate to a microporous membrane (or film) having enhanced properties, especially electrolyte injection, compression and heat resistance, e.g. melt down, properties.
  • a microporous membrane or film having enhanced properties, especially electrolyte injection, compression and heat resistance, e.g. melt down, properties.
  • certain specific polyethylene resin or resins and certain specific polypropylene resin are combined, e.g. by melt-blending, to form a polyolefin composition.
  • Polyolefin Composition is produced by combining (a) from about 73 wt. % to about 97 wt. % at a first polyethylene resin having a weight average molecular weight of from about 2.5 x 10 5 to about 6 x 10 5 and a molecular weight distribution of from about 5 to about 100, (b) from about 3 wt. % to about 20 wt.
  • polypropylene resin having a weight average molecular weight of from about 3 x 10 5 to about 1.5 x 10 6 , a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1.0 to about 100, and (c) from about 0 wt. % to about 7 wt. % of a second polyethylene resin having a weight average molecular weight greater than that of the first polyethylene resin, e.g., in the range of from about 7 x 10 5 to about 5 x 10 6 , and an MWD of 5-100, with the weight percents based on the weight of the polyolefin composition.
  • the amount the first polyethylene resin is in the range of 80 wt% to 90 wt%
  • the amount of polypropylene resin is in the range of about 5 wt% to about 15 wt%
  • the amount of the second polyethylene resin is in the range of 1 wt% to 5 wt%, based on the weight of the polyolefin composition.
  • the first polyethylene resin has a weight average molecular weight (“Mw”) ⁇ 7 x 10 5 , e.g., of from about 2.5 x 10 5 to about 6 x 10 5 and a molecular weight distribution ("MWD") of from about 5 to about 100.
  • Mw weight average molecular weight
  • MWD molecular weight distribution
  • a non-limiting example of the first polyethylene resin for use herein is one that has a Mw of from about 2.5 x 10 5 to about 4 x 10 5 and an MWD of from about 5 to about 50.
  • Another non-limiting example of the first polyethylene resin is one having an Mw of about 3 x 10 5 to 6 x 10 5 and an MWD of from about 5 to about 30.
  • the first polyethylene resin can be a high density polyethylene such as an ethylene homopolymer, or an ethylene/ ⁇ -olef ⁇ n copolymer, such as, for example, one containing a small amount, e.g. about 5 mole %, of a third ⁇ -olefin.
  • the third ⁇ -olefin, which is not ethylene, is preferably propylene, ctane-1, pentene-1, ctane-1, 4-methylpentene-l, ctane-1, vinyl acetate, methyl methacrylate, or styrene or combinations thereof.
  • a copolymer can be produced using a single-site catalyst.
  • the second polyethylene resin has an Mw greater than that of the first polyethylene resin, e.g., an Mw > 7 x 10 5 , and an MWD of from about 5 to about 100.
  • a non-limiting example of the second polyethylene resin for use herein is one that has an Mw of from about 5 x 10 5 to about 5 x 10 6 and an MWD of from about 5 to about 50.
  • Another non-limiting example of the second polyethylene resin is one having an Mw in the range of 1 x 10 6 to 2 x 10 6 and an MWD from about 4 to about 8.
  • the second polyethylene can be an ultra-high molecular weight polyethylene such as an ethylene homopolymer, or an ethylene/ ⁇ -olefin copolymer, such as, for example, one containing a small amount, e.g. about 5 mole %, of a third ⁇ -olefin.
  • the third ⁇ -olefin, which is not ethylene, is preferably propylene, ctane-1, pentene-1, ctane-1, 4-methylpentene-l, ctane-1, vinyl acetate, methyl methacrylate, or styrene or combinations thereof.
  • Such copolymer is preferably produced using a single-site catalyst.
  • MWD is equal to the ratio of Mw to the number-average molecular weight ("Mn").
  • Mn number-average molecular weight
  • the MWD of the polymers used to produce the microporous membrane can be controlled e.g., by a multi-stage polymerization.
  • the MWD of the polyethylene composition can be controlled by the molecular weights and mixing ratios of the polyethylene components.
  • Mw and Mn of the poly ethylenes are determined using a High Temperature Size Exclusion Chromatograph, or "SEC”, (GPC PL 220, Polymer Laboratories), equipped with a differential refractive index detector (DRI). Three PLgel Mixed-B columns (available from Polymer Laboratories) are used.
  • SEC High Temperature Size Exclusion Chromatograph
  • the nominal flow rate is 0.5 cm 3 /min, and the nominal injection volume was 300 ⁇ L. Transfer lines, columns, and the DRI detector were contained in an oven maintained at 145°C. The measurement is made in accordance with the procedure disclosed in "Macromolecules, Vol. 34, No. 19, pp. 6812-6820 (2001)".
  • the GPC solvent used is filtered Aldrich reagent grade 1 ,2,4-Trichlorobenzene (TCB) containing approximately 1000 ppm of butylated hydroxy toluene (BHT). The TCB was degassed with an online degasser prior to introduction into the SEC.
  • Polymer solutions were prepared by placing dry polymer in a glass container, adding the desired amount of above TCB solvent, then heating the mixture at 160°C with continuous agitation for about 2 hours.
  • concentration of UHMWPE solution was 0.25 to 0.75mg/ml.
  • Sample solution will be filtered off-line before injecting to GPC with 2 ⁇ m filter using a model SP260 Sample Prep Station (available from Polymer Laboratories).
  • the separation efficiency of the column set is calibrated with a calibration curve generated using a seventeen individual polystyrene standards ranging in Mp from about 580 to about 10,000,000, which is used to generate the calibration curve.
  • the polystyrene standards are obtained from Polymer Laboratories (Amherst, MA).
  • a calibration curve (logMp vs. retention volume) is generated by recording the retention volume at the peak in the DRI signal for each PS standard, and fitting this data set to a 2nd-order polynomial. Samples are analyzed using IGOR Pro, available from Wave Metrics, Inc.
  • the polypropylene for use herein has an Mw of from about 3 x 10 5 to about 1.5 x 10 6 , for example from about 6 x 10 5 to about 1.5 x 10 6 , a heat of fusion (" ⁇ Hm") of 80 J/g or higher, for non-limiting example from about 80 to about 200 J/g, and an MWD of from about 1.0 to about 100, for example from about 1.1 to about 50, and can be a propylene homopolymer or a copolymer of propylene and another, i.e. a fourth, olefin, though the homopolymer is preferable.
  • the copolymer may be a random or block copolymer.
  • the fourth olefin which is an olefin other than propylene, includes ⁇ -olefins such as ethylene, ctane-1, pentene-1, ctane-1, 4-methylpentene-l, ctane-1, vinyl acetate, methyl methacrylate, styrene, etc., and diolefins such as butadiene, 1,5-hexadiene, 1,7-octadiene, 1 ,9-decadiene, etc.
  • ⁇ -olefins such as ethylene, ctane-1, pentene-1, ctane-1, 4-methylpentene-l, ctane-1, vinyl acetate, methyl methacrylate, styrene, etc.
  • diolefins such as butadiene, 1,5-hexadiene, 1,7-octadiene, 1 ,9-decadiene, etc.
  • the percentage of the fourth olefin in the propylene copolymer is preferably in a range not deteriorating the properties of the microporous polyolefin membrane such as heat resistance, compression resistance, heat shrinkage resistance, etc., and is preferably less than about 10 mole %, e.g. from about 0 to less than about 10 mole %.
  • the MWD of polypropylene is from about 1.0 to about 100, for example from about 2 to about 50, or about 2.5 to 6.
  • the amount of polypropylene in the polyolefin composition can be from about 3 wt. % to about 20 wt. % based on the weight of the polyolefin composition.
  • the percentage of polypropylene may be, for example, from about 5 wt. % to about 15 wt. %, and for further example from about 7 wt. % to about 13 wt. %, based on the weight of the polyolefin composition.
  • the propylene has a ⁇ Hm in the range of about 110 J/g to 120 J/g.
  • the Mw, MWD and the ⁇ Hm of the polypropylene are measured in accordance with the procedures described in patent publication US 2008/0057389, which is incorporated by reference herein in its entirety.
  • T Other components
  • the polyolefin composition can contain (a) additional polyolefin and/or (b) heat-resistant polymer resins having melting points or glass transition temperatures ("Tg") of about 170 0 C or higher, in amounts not deteriorating the properties of the microporous membrane, for example 10 wt. % based on the weight of the polyolefin composition.
  • Tg melting points or glass transition temperatures
  • the additional polyolefin can be at least one of (a) polybutene-1, polypentene-1, poly-4-methylpentene-l, polyhexene-1, polyoctene-1, polyvinyl acetate, polymethyl methacrylate, polystyrene and an ethylene/ ⁇ -olef ⁇ n copolymer, each of which may have an Mw of from 1 x 10 4 to 4 x 10 6 , and (b) a polyethylene wax having an Mw of from 1 x 10 3 to 1 x 10 4 .
  • Polybutene-1, polypentene-1, poly-4-methylpentene-l, polyhexene-1, polyoctene-1, polyvinyl acetate, polymethyl methacrylate and polystyrene are not restricted to homopolymers, but may be copolymers containing still other ⁇ -olefins.
  • the heat-resistant resins are preferably (i) amorphous resins having melting points of about 170°C or higher, which may be partially crystalline, and (ii) completely amorphous resins having a Tg of about 170°C or higher and mixtures thereof.
  • the melting point and Tg are determined by differential scanning calorimetry (DSC) according to method JIS K7121.
  • the heat-resistant resins include polyesters such as polybutylene terephthalate (melting point: about 160-230°C), polyethylene terephthalate (melting point: about 250-270°C), etc., fluororesins, polyamides (melting point: 215-265°C), polyarylene sulfide, polyimides (Tg: 280°C or higher), polyamideimides (Tg: 280°C), polyether sulfone (Tg: 223 0 C), polyetheretherketone (melting point: 334°C), polycarbonates (melting point: 220-240 0 C), cellulose acetate (melting point: 220 0 C), cellulose triacetate (melting point: 300°C), polysulfone (Tg: 190°C), polyetherimide (melting point: 216°C), etc. (c) Content
  • the total amount of the additional polyolefin and the heat-resistant resin is preferably 20% or less, for example from about 0 wt. % to about 20 wt. %, based on the weight of the polyolefin composition.
  • the invention relates to a method for producing the microporous membrane having desirable electrolytic solution absorption, compression and heat resistance, e.g. melt down, properties, comprising the steps of (1) combining a certain specific polyolefin composition and at least one diluent, (2) extruding the combined diluent and polyolefin composition through a die to form an extrudate, (3) cooling the extrudate to form a cooler extrudate sheet, (4) stretching the extrudate to form a stretched extrudate, (5) removing at least a portion of the diluent from the stretched extrudate to form a solvent-removed membrane, (6) stretching the solvent-removed membrane at a certain specific temperature and to a certain specific high magnification to form a stretched membrane, and (7) heat-setting the stretched membrane to form the finished microporous membrane.
  • a heat-setting treatment step (4i), a heat roll treatment step (4ii), and/or a hot solvent treatment step (4iii) may be conducted between the steps (4) and (5), if desired.
  • a heat-setting treatment step (5i) may be conducted between the steps (5) and (6).
  • a step (5ii) of cross-linking with ionizing radiations following step (5i) prior to step (6), and a hydrophilizing treatment step (7i) and a surface-coating treatment step (7ii) may be conducted after the step (7), if desired.
  • the polyolefin composition comprising polyethylene and polypropylene is blended with at least one diluent to form a mixture.
  • the mixture may contain various additives such as anti-oxidants, fine silicate powder (pore-forming material), etc., in ranges not deteriorating the effects of the present invention, if desired.
  • the diluent can be preferably liquid at room temperature.
  • the diluent is a solvent for one or more of the polymers in the mixture, it can be called a “solvent” or “membrane-forming solvent”.
  • the diluent is a solvent (or membrane-forming solvent)
  • the mixture can be called a "polyolefin solution”.
  • the diluent can be, for example, aliphatic, alicyclic or aromatic hydrocarbons such as nonane, decane, decalin, p-xylene, undecane, dodecane, liquid paraffin, mineral oil distillates having boiling points comparable to those of the above hydrocarbons, and phthalates liquid at room temperature such as dibutyl phthalate, dioctyl phthalate, etc.
  • a non- volatile liquid solvent such as liquid paraffin.
  • one or more solid solvents which are miscible with the polyolefin composition during melt-blending but solid at room temperature may be added to the liquid solvent.
  • Such solid solvents are preferably stearyl alcohol, ceryl alcohol, paraffin waxes, etc.
  • solid solvent can be used without liquid solvent. However, when only the solid solvent is used, uneven stretching, etc., can occur.
  • the viscosity of the liquid solvent is preferably from about 30 to about 500 cSt, more preferably from about 30 to about 200 cSt, when measured at a temperature of 25°C.
  • the viscosity at 25°C is less than 30 cSt, the polyolefin solution may foam, resulting in difficulty in blending.
  • the viscosity is more than 500 cSt, the removal of the liquid solvent can be difficult.
  • the polyolefin solution is preferably melt-blended in a double-screw extruder to prepare a high resin concentration polyolefin solution.
  • the membrane-forming solvent may be added before starting melt-blending, or supplied to the double-screw extruder in an intermediate portion during blending, though the latter is preferable.
  • the melt-blending temperature of the polyolefin solution is preferably in a range of the melting point ("Tm") of the polyethylene resin +10°C to Tm +12O 0 C.
  • the melting point can be measured by differential scanning calorimetry (DSC) according to JIS K7121.
  • the melt-blending temperature is from about 140 to about 25O 0 C, preferably from about 170 to about 240 0 C, particularly where the polyethylene resin has a melting point of about 130 to about 140 0 C.
  • the concentration of the polyolefin composition in the polyolefin solution is preferably from about 25 wt. % to about 50 wt. %, for example from about 25 wt. % to about 45 wt. %, based on the weight of the polyolefin solution.
  • the ratio L/D of the screw length L to the screw diameter D in the double-screw extruder is preferably in a range of from about 20 to about 100, more preferably in a range of from about 35 to about 70. When L/D is less than 20, melt-blending can be inefficient.
  • the cylinder of the double-screw extruder preferably has an inner diameter of from about 40 to about 100 mm.
  • the ratio Q/Ns of the amount Q (kg/h) of the polyolefin solution charged to the number of revolution Ns (rpm) of a screw is preferably from about 0.1 to about 0.55 kg/h/rpm.
  • Q/Ns is less than 0.1 kg/h/rpm, the polyolefin can be damaged by shearing, resulting in decrease in strength and meltdown temperature.
  • Q/Ns is more than 0.55 kg/h/rpm, uniform blending cannot be achieved.
  • Q/Ns is more preferably from about 0.2 to about 0.5 kg/h/rpm.
  • the number of revolutions Ns of the screw is preferably 180 rpm or more. Though not particularly critical, the upper limit of the number of revolutions Ns of the screw is preferably about 500 rpm.
  • the polyolefin solution can be melt-blended in the extruder and extruded from a die.
  • the polyolefin can be extruded and then pelletized.
  • the pellets can be melt-blended and extruded in a second extrusion to make the gel-like molding or sheet.
  • the die may be a sheet-forming die having a rectangular orifice, a double-cylindrical, hollow die, an inflation die, etc.
  • the die gap is preferably from about 0.1 to about 5 mm.
  • the extrusion temperature is preferably from about 140 to about 250 0 C, and the extruding speed is preferably from about 0.2 to about 15 m/minute.
  • the direction of extrusion i.e., the direction of extrudate travel during extrusion and steps downstream of extrusion
  • MD machine direction
  • TD transverse direction
  • the extrudate produced from the die is cooled to form a cooled extrudate, e.g., a high resin content gel-like molding or sheet.
  • Cooling can be conducted by exposing the extrudate to a temperature ⁇ the extrudate's gelation temperature at a cooling rate of about 50°C/minute or more. Cooling can be preferably conducted to about 25°C or lower.
  • Such cooling sets the micro-phase of the polyolef ⁇ n separated by the membrane-forming solvent.
  • the slower cooling rate provides the gel-like sheet with larger pseudo-cell units, resulting in a coarser higher-order structure.
  • a higher cooling rate results in denser cell units.
  • a cooling rate of less than 50°C/minute can lead to increased crystallinity, making it more difficult to provide the gel-like sheet with suitable stretchability.
  • Usable cooling methods include bringing the extrudate into contact with a cooling medium such as cooling air, cooling water, etc.; bringing the extrudate into contact with cooling rollers; etc. (4) Stretching the cooled extrudate
  • the cooled extrudate can be stretched in at least one direction. While not wishing to be bound by any theory or model, it is believed that the cooled extrudate (e.g., a gel-liked sheet) can be uniformly stretched because the sheet contains the membrane-forming solvent.
  • the gel-like sheet is preferably stretched to a predetermined magnification after heating by, for example, a tenter method, a roll method, an inflation method or a combination thereof.
  • the stretching may be conducted monoaxially or biaxially, though biaxial stretching is preferable. In the case of biaxial stretching, any of simultaneous biaxial stretching, sequential stretching or multi-stage stretching (for instance, a combination of the simultaneous biaxial stretching and the sequential stretching) may be used, though simultaneous biaxial stretching is preferable.
  • the stretching magnification of this first stretching step is preferably 2 fold or more, more preferably 3 to 30 fold in the case of monoaxial stretching.
  • the stretching magnification is preferably 3 fold or more in any direction, namely 9 fold or more, more preferably 16 fold or more, most preferably 25 fold or more, in area magnification.
  • the cooled extrudate is simultaneously stretched 3 to 7 fold (e.g., 5 fold) in MD and 3 to 7 fold (e.g., 5 fold) in TD.
  • An example for this first stretching step would include stretching from about 9 fold to about 400 fold.
  • a further example would be stretching from about 16 to about 49 fold.
  • the pin puncture strength of the microporous membrane is improved.
  • the area magnification is more than 400 fold, stretching apparatuses, stretching operations, etc., involve large-sized stretching apparatuses, which can be difficult to operate.
  • the extrudate can be exposed to a temperature in the range of from about the crystal dispersion temperature ("Ted") of the polyethylene used to produce the extrudate to about Ted + 30 °C, e.g. in a range of Ted of the combined polyethylene content of the cooled extrudate to Ted + 25°C, more preferably in a range of Ted + 10°C to Ted + 25°C, most preferably in a range of Ted + 15°C to Ted + 25°C.
  • Ted crystal dispersion temperature
  • the crystal dispersion temperature is determined by measuring the temperature characteristics of dynamic viscoelasticity according to ASTM D 4065. Because the polyethylene resin has a crystal dispersion temperature of about 90 to 100°C, the stretching temperature is from about 90 to 125°C; preferably form about 100 to 125°C, more preferably from 105 to 125°C. [0047] The above stretching causes cleavage between polyethylene lamellas, making the polyethylene phases finer and forming large numbers of fibrils. The fibrils form a three-dimensional network structure. The stretching is believed to improve the mechanical strength of the final microporous membrane and expands its pores, making the microporous membrane suitable for use as a battery separator.
  • stretching may be conducted with a temperature distribution in a thickness direction, to provide the final microporous membrane with further improved mechanical strength.
  • the detailed description of this method is given by Japanese Patent 3347854.
  • any convenient method can be used for removing at least a portion of the diluent from the cooled extrudate.
  • the diluent can be removed (e.g., washed, displaced, or dissolved) using a washing solvent. Because the polyolefin composition phase is phase-separated from a membrane-forming solvent phase, the removal of the diluent provides a microporous membrane.
  • the removal of the liquid solvent can be conducted by using one or more suitable washing solvents, i.e., one capable of displacing the liquid solvent from the membrane.
  • washing solvents include volatile solvents, e.g., saturated hydrocarbons such as pentane, hexane, heptane, etc., chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, etc., ethers such as diethyl ether, dioxane, etc., ketones such as methyl ethyl ketone, etc., linear fluorocarbons such as trifluoroethane, C 6 F ]4 , etc., cyclic hydrofluorocarbons such as C 5 H 3 F 7 , etc., hydrofluoroethers such as C 4 F 9 OCH 3 , C 4 F 9 OC 2 Hs, etc., perfluoroethers such as C 4 F 9 OCF 3 , C 4 F 9 OC 2 F 5 , etc., and mixtures thereof.
  • volatile solvents e.g., saturated hydrocarbons such as pentane, hexane, heptane,
  • the washing of the stretched membrane can be conducted by immersion in the washing solvent and/or showering with the washing solvent.
  • the washing solvent used is preferably from about 300 to about 30,000 parts by mass per 100 parts by mass of the stretched membrane.
  • the washing temperature is usually from about 15 to about 30°C, and if desired, heating may be conducted during washing. The heating temperature during washing is preferably about 80°C or lower. Washing is preferably conducted until the amount of the remaining liquid solvent becomes less than 1 wt. % of the amount of liquid solvent that was present in polyolefin solution prior to extrusion.
  • the microporous membrane deprived of the membrane-forming solvent can be dried by a heat-drying method, a wind-drying (e.g., air drying using moving air) method, etc. Any drying method capable of removing a significant amount of the washing solvent can be used. Preferably, substantially all of the washing solvent is removed during drying.
  • the membrane can be exposed to a temperature that is preferably equal to or lower than Ted, more preferably 5°C or more lower than Ted. Drying is conducted until the remaining washing solvent becomes preferably 5 wt. % or less, more preferably 3 wt. %, based on the weight (on a dry basis) of the microporous membrane. Insufficient drying can be recognized because it results in an undesirable decrease in the porosity of the microporous membrane.
  • the dried microporous membrane is stretched in a second stretching step (re-stretched) at least monoaxially at high magnification.
  • the re-stretching of the microporous membrane can be conducted, for example, while heating, by a tenter method, etc., as in the first stretching step.
  • the re-stretching may be monoaxial or biaxial. In the case of biaxial stretching, any one of simultaneous biaxial stretching or sequential stretching may be used, though simultaneous biaxial stretching is preferable.
  • the second stretching is conducted while exposing the membrane at a second temperature preferably equal to Tm or lower, more preferably in a range of Ted to Tm, (the "second stretching temperature").
  • the second stretching temperature is higher than Tm, it is believed that the melt viscosity is generally too low to conduct good stretching, resulting in low permeability.
  • Ted it is believed that the polyolefin is insufficiently softened so that the membrane might be broken by stretching, i.e., a failure to achieve uniform stretching.
  • the second stretching temperature is usually from about 90 to about 135°C, for example from about 95 to about 130°C.
  • the monoaxial second stretching magnification of the microporous membrane in this step, as mentioned above, is preferably from about 1.1 to about 1.8 fold.
  • a magnification of 1.1 to 1.8 fold generally provides the microporous membrane of the present invention with a hybrid structure having a large average pore size.
  • the magnification can be form 1.1 to 1.8 fold in a longitudinal or transverse direction.
  • the microporous membrane may be stretched at the same or different magnifications, though preferably the same, as long as the stretching magnifications in both directions are form 1.1 to 1.8 fold.
  • the second stretching magnification of the microporous membrane is less than 1.1 fold, it can be more difficult to produce a membrane having a hybrid structure, and having good permeability, electrolytic solution absorption capability, and compression resistance in the finished membrane.
  • the stretching rate is preferably 3%/second or more in the stretching direction. In the case of monoaxial stretching, stretching rate is 3%/second or more in a MD or TD. In the case of biaxial stretching, stretching rate is 3%/second or more in both MD and TD. A stretching rate of less than 3%/second can make it more difficult to produce a membrane having good permeability without undue permeability variation across TD.
  • the stretching rate is preferably 5%/second or more, more preferably 10%/second or more. Though not particularly critical, the upper limit of the stretching rate is e.g., 50%/second to avoid membrane rupture during stretching. (7) Heat treatment
  • the dried microporous membrane can be thermally treated (heat-set) to stabilize crystals and make uniform lamellas in the membrane.
  • the heat-setting can be conducted by a tenter method or a roll method.
  • the heat-setting temperature can be conducted while exposing the membrane to a temperature in a range of the second stretching temperature ⁇ 5°C, more preferably in a range of the second stretching temperature ⁇ 3°C. It is believed that too low a heat-setting temperature makes it more difficult to produce a membrane having the desired pin puncture strength, tensile rupture strength, tensile rupture elongation and heat shrinkage resistance, while too high a heat-setting temperature can adversely affect membrane permeability.
  • An annealing treatment can be conducted after the heat-setting step.
  • the annealing is a heat treatment with no load applied to the microporous membrane, and may be conducted by using, for example, a heating chamber with a belt conveyer or an air-floating-type heating chamber.
  • the annealing may also be conducted continuously after the heat-setting with the tenter slackened.
  • the annealing can be conducted while exposing the membrane to a temperature of Tm or lower, more preferably in a range from about 60 0 C to about Tm -5°C. Annealing is believed to provide the microporous membrane with improved permeability and strength.
  • the membrane can be annealed without prior heat-setting.
  • At least one surface of the stretched extrudate step (4) may be brought into contact with one or more heat rollers following any of steps (4) to (7).
  • the roller temperature is preferably in a range of from Ted +10°C to Tm.
  • the contact time of the heat roll with the stretched extrudate is preferably from about 0.5 second to about 1 minute.
  • the heat roll may have a flat or rough surface.
  • the heat roll may have a suction functionality to remove the solvent.
  • one example of a roller-heating system may comprise holding heated oil in contact with a roller surface.
  • the stretched extrudate may be contacted with a hot solvent between steps (4) and (5).
  • a hot solvent treatment turns fibrils formed by stretching to a leaf vein form with relatively thick fiber trunks, providing the microporous membrane with large pore size and suitable strength and permeability.
  • the term "leaf vein form” means that the fibrils have thick fiber trunks, and thin fibers extending in a complicated network structure from the trunks. The details of the hot solvent treatment method are described in WO 2000/20493.
  • the microporous membrane containing at least a portion of the washing solvent can be heat set between the steps (5) and (6) if desired.
  • the heat-setting procedure can be the same as described above in step (7).
  • the heat-set microporous membrane can be cross-linked by ionizing radiation rays such as ⁇ -rays, ⁇ -rays, ⁇ -rays, electron beams, etc.
  • ionizing radiation rays such as ⁇ -rays, ⁇ -rays, ⁇ -rays, electron beams, etc.
  • the amount of electron beams is preferably from about 0.1 to about 100 Mrad, and the accelerating voltage is preferably form about 100 to about 300 kV.
  • the cross-linking treatment is believed to elevate the meltdown temperature of the microporous membrane. (13) Hvdrophilizing treatment
  • the heat-set microporous membrane may be subjected to a hydrophilizing treatment (a treatment that makes the membrane more hydrophilic).
  • the hydrophilizing treatment may be a monomer-grafting treatment, a surfactant treatment, a corona-discharging treatment, etc.
  • the monomer-grafting treatment is conducted after the cross-linking treatment.
  • any of nonionic surfactants, cationic surfactants, anionic surfactants and amphoteric surfactants may be used, and the nonionic surfactants are preferred.
  • the microporous membrane can be dipped in a solution of the surfactant in water or a lower alcohol such as methanol, ethanol, isopropyl alcohol, etc., or coated with the solution by a doctor blade method.
  • the heat-set microporous membrane resulting from step (7) can be coated with porous polypropylene, porous fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, porous polyimides, porous polyphenylene sulfide, etc., to improve meltdown properties when the membrane is used as a battery separator.
  • the polypropylene used for the coating preferably has Mw of form about 5,000 to about 500,000, and a solubility of about 0.5 grams or more in 100 grams of toluene at 25°C.
  • Such polypropylene more preferably has a racemic diade fraction of from about 0.12 to about 0.88, the racemic diade being a structural unit in which two adjacent monomer units are mirror-image isomers to each other.
  • the surface-coating layer may be applied, for instance, by applying a solution of the above coating resin in a good solvent to the microporous membrane, removing part of the solvent to increase a resin concentration, thereby forming a structure in which a resin phase and a solvent phase are separated, and removing the remainder of the solvent.
  • the good solvents for this purpose include aromatic compounds, such as toluene, xylene.
  • microporous polyolefin membrane of this invention has a hybrid structure derived from the polyethylene, in which its pore size distribution represented as a differential pore volume obtained by mercury intrusion porosimetry has at least two peaks (main peak and at least one sub-peak).
  • pore size is analogous to the pore diameter in the case where the pores are approximately cylindrical.
  • the main peak and sub-peak respectively correspond to the dense domains and coarse domains of the polyethylene phase.
  • the microporous membrane produced by the above-described method has a relatively wide pore size distribution when plotted as a differential pore volume curve. Pore size distribution can be measured, e.g., by conventional methods such as mercury porosimetry.
  • mercury porosimetry When mercury porosimetry is used to measure the distribution of pore sizes and pore volume in the membrane, it is conventional to measure pore diameter, pore volume, and the specific surface area of the membrane. The measurements can be used to
  • a differential pore volume expressed as K- ⁇ - where Vp is the pore volume, dLog ⁇ r) and r is the pore radius, assuming cylindrical pores.
  • the differential pore volume when plotted on the y axis with pore diameter on the x axis is conventionally referred to as the "pore size distribution.”
  • pore size distribution For membranes exhibiting a hybrid structure, at least about 25%, or at least about 30%, or at least about 40%, or at least about 50%, or at least about 60%, of the differential pore volume is associated with pores that are about 100 nanometers in size
  • the dLogyr fraction of the area under the curve from a pore diameter of about 100 nanometers to about 1,000 nanometers is at least about 25%, or at least about 30%, or at least about 40%, or at least about 50%, or at least about 60% of the total area under that curve for pore sizes (or diameters assuming cylindrical pores) of from about 10 nanometers to about 1,000 nanometers.
  • the area under the curve for pore diameters of from about 100 nanometers to about 1,000 nanometers is in the range of about 25% to about 60%, or about 30% to about 55%, or about 35% to about 50% of the total area under the curve for pore diameters of from about 10 nanometers to about 1,000 nanometers.
  • dense domains (relatively small pores) and coarse domains (relatively large pores) are irregularly entangled to form a hybrid structure in any cross sections of the microporous polyolef ⁇ n membrane viewed in longitudinal and transverse directions.
  • the hybrid structure can be observed by a transmission electron microscope (TEM), etc.
  • the microporous membrane of the present invention has relatively large internal space and openings due to coarse domains, it has suitable permeability and electrolytic solution absorption, with little air permeability variation when compressed.
  • This microporous membrane also has relatively small internal space and openings which influence safety properties of the membrane when used as a battery separator, such as shutdown temperature and shutdown speed. Accordingly, lithium ion batteries such as lithium ion secondary batteries comprising separators formed by such microporous membrane have suitable productivity and cyclability while retaining their high safety performance.
  • the mercury intrusion porosimetry method used to determine the microporous membrane structure involves use of a Pore Sizer 9320 (Micromeritics Company, Ltd.), a pressure range of from 3.6 kPa to 207 MPa, and a cell volume of 15 cm 3 .
  • a contact angle of mercury of 141.3 and a surface tension of mercury of 484 dynes/cm was employed.
  • the parameters obtained by this included pore volume, surface area ratio, peak top of pore size, average pore size and porosity. References teaching this method include Raymond P. Mayer and Robert A. Stowe, J. Phys. Chem.70,12(1966); L. C. Drake, Ind.Eng.Chem., 41,780(1949); H. L. Ritter and L. C. Drake, Ind.Eng.Chem.AnaL, 17,782(1945) and E. W. Washburn,
  • L is the depth and r is the radius of the pores, assuming the pores are cylindrical.
  • the contact angle of the mercury is expressed as ⁇ .
  • the surface tension of mercury is expressed as ⁇ , which is generally recognized as 0.48Nm "1 . Consequently, according to the Washbum model, pore radius r can be expressed as a function of the pressure P according to the equation
  • the volume V of mercury intruded into the pores is measure as a function of pressure P.
  • the measured value of P is used to calculate pore radius r, as described above.
  • P is increased incrementally, and the volume of mercury is determined at each value of P.
  • a table can be constructed showing the pore volume associated with pores of a particular r, tabulated over the range of r as determined by the range of P selected for the measurement.
  • the tabulated values of r can be conveniently converted to Log (r).
  • Pore volume Vp is generally expressed as cm 3 per gram of the microporous
  • microporous polyolefin membrane has relatively large internal space and openings due to coarse domains, it has suitable permeability and electrolytic solution absorption, with little air permeability variation when compressed. Accordingly, lithium ion batteries such as lithium ion secondary batteries comprising separators formed by such microporous polyolefin membrane have suitable productivity and cyclability.
  • the microporous polyolefin membrane is a single-layer membrane, where the has a hybrid structure, e.g., the microporous layer material is characterized by a differential pore volume curve having an area under the curve over the range of pore diameters of from about 100 run to about 1,000 nm that is about 25% or more of a total area under the curve over the range of pore diameters of from about 10 nm to about 1,000 nm
  • a hybrid structure is more difficult to produce when the percentage of the first polyethylene in the membrane is more than 97 wt. % based on the total weight of polyolefin in the membrane.
  • a hybrid structure is also more difficult to produce when the percentage of polypropylene in the membrane is more than 20 wt. %based on the total weight of polyolefin in the membrane.
  • a hybrid structure is more difficult to produce when the percentage of the second polyethylene in the membrane is more than 7 wt. %, based on the total weight of polyolefin in the membrane.
  • Membranes having a hybrid structure generally have better electrolytic solution absorption characteristics than membranes that do not have a hybrid structure.
  • the main peak is in a pore size range of 0.01 to 0.08 ⁇ m, and at least one sub-peak is in a pore size ranging from more than 0.08 ⁇ m to 1.5 ⁇ m. In other words, at least one sub-peak has a pore size of greater than 0.08 ⁇ m to 1.5 ⁇ m or less.
  • the main peak is a first peak in a pore size range of about 0.04 to 0.07 ⁇ m
  • the sub-peaks comprise a second peak in a pore size range of about 0.1 to 0.11 ⁇ m, a third peak at a pore size of about 0.7 ⁇ m, and a fourth peak in a pore size range of about 1 to 1.1 ⁇ m.
  • the sub-peaks need not have the third and fourth peaks.
  • the pore size distribution curve may have first to fourth peaks at about 0.06 ⁇ m, about 0.1 ⁇ m, about 0.7 ⁇ m, and about 1.1 ⁇ m, respectively.
  • the approximate positions can be obtained using, e.g., conventional peak deconvolution analysis.
  • the first derivative of the curve representing the number of pores on the y axis and the pore size on the x axis can be used to more clearly identify a change in slope (e.g., an inflection) on the curve.
  • the pore volume ratio of the dense domains to the coarse domains of the microporous polyolefin membrane of the present invention is determined by standard methods using a transmission electron microscope (TEM), mercury porosimetry, etc, as described in PCT Patent Application No. WO2008/016174, which is incorporated by reference herein in its entirety.
  • TEM transmission electron microscope
  • WO2008/016174 which is incorporated by reference herein in its entirety.
  • a hatched area Si (as shown in the PCT publication) on the smaller diameter side and a vertical line Li passing the first peak corresponds to the pore volume of the dense domains
  • a hatched area S 2 on the larger diameter side and a vertical line L 2 passing the second peak corresponds to the pore volume of the coarse domains.
  • the pore volume ratio Si /S 2 of the dense domains to the coarse domains is preferably from about 0.5 to about 49, more preferably from about 0.6 to about 10, most preferably from 0.7 to 2.
  • dense domains and coarse domains are irregularly entangled to form a hybrid structure in any cross sections of the microporous polyolefin membrane viewed in longitudinal and transverse directions.
  • the thickness of the final membrane is generally in the range of 3 ⁇ m to 200 ⁇ m.
  • the membrane can have a thickness in the range of from about 5 ⁇ m to about 50 ⁇ m, e.g., from about 15 ⁇ m to about 30 ⁇ m.
  • the thickness of the microporous membrane can be measured, e.g., by a contact thickness meter at 1 cm longitudinal intervals over the width of 10 cm, and then averaged to yield the membrane thickness. Thickness meters such as the Litematic available from Mitsutoyo Corporation are suitable. Non-contact thickness measurement methods are also suitable, e.g. optical thickness measurement methods.
  • the membrane's air permeability is measured according to JIS P8117.
  • the membrane's air permeability is in the range of from 20 to 400 seconds/ 100 cm 3 .
  • the membrane's pin puncture strength (converted to the value at membrane thickness of 20 ⁇ m) is represented by the maximum load measured when the microporous membrane is pricked with a needle of 1 mm in diameter with a spherical end surface (radius R of curvature: 0.5 mm) at a speed of 2 mm/second.
  • the pin puncture strength is less than 2,000 mN/20 ⁇ m, short-circuiting might occur in batteries with separators formed by the microporous membrane.
  • the membrane's pin puncture strength (converted to 20 ⁇ m) is in the range of 4,000 to 5,000 mN.
  • the maximum load is measured when each microporous membrane having a thickness of Ti is pricked with a needle of 1 mm in diameter with a spherical end surface (radius R of curvature: 0.5 mm) at a speed of 2 mm/second.
  • a tensile strength of 49,000 kPa or more in both longitudinal and transverse directions is characteristic of suitable durable microporous membranes, particularly when used as battery separators.
  • the tensile rupture strength is preferably about 80,000 kPa or more.
  • a tensile elongation of 100% or more in both longitudinal and transverse directions is characteristic of suitably durable microporous membranes, particularly when used as battery separators.
  • the heat shrinkage ratio of the microporous membrane orthogonal planar directions (e.g., machine direction or transverse direction) at 105°C is measured as follows: (i) Measure the size of a test piece of microporous membrane at ambient temperature in both the machine direction and transverse direction, (ii) equilibrate the test piece of the microporous membrane at a temperature of 105 0 C for 8 hours with no applied load, and then (iii) measure the size of the membrane in both the machine and transverse directions.
  • the heat (or "thermal") shrinkage ratio in either the machine or transverse directions can be obtained by dividing the result of measurement (i) by the result of measurement (ii) and expressing the resulting quotient as a percent.
  • the microporous membrane has a TD heat shrinkage ratio at 105°C in the range of 3% to 10%, e.g., 3.5% to 5%; and an MD heat shrinkage ratio at 105 0 C in the range of 1% to 8%, e.g., 1.5% to 3%.
  • Thickness variation ratio of 21% or less after heat compression (expressed as an absolute value)
  • the thickness variation ratio after heat compression at 90°C under pressure of 2.2 MPa for 5 minutes is generally 20% or less per 100% of the thickness before compression.
  • Batteries comprising microporous membrane separators with a thickness variation ratio of 20% or less have suitably large capacity and good cyclability.
  • the membrane's thickness variation ratio is in the range of 10% to 20%.
  • a microporous membrane sample is situated between a pair of highly flat plates, and heat-compressed by a press machine under a pressure of 2.2 MPa (22 kgf/cm 2 ) at 90 0 C for 5 minutes, to determine an average thickness in the same manner as above.
  • a thickness variation ratio is calculated by the formula of (average thickness after compression - average thickness before compression) / (average thickness before compression) x 100.
  • Air permeability after heat compression of 700 sec/ 100 cm 3 or less Air permeability after heat compression of 700 sec/ 100 cm 3 or less
  • the microporous polyolefin membrane when heat-compressed under the above conditions generally has air permeability (Gurley value) of 700 sec/ 100 cm 3 or less.
  • Air permeability after heat compression is measured according to JIS P8117. (i) Surface roughness of 3 x 10 2 nm or more
  • the surface roughness of the membrane measured by an atomic force microscope (AFM) in a dynamic force mode is generally 3 x 10 2 nm or more (measured as the average maximum height difference across the membrane).
  • the membrane's surface roughness is preferably 3.5 x 10 2 nm or more, e.g., in the range of 400 nm to 700 nm.
  • Melt down temperature is measured by the following procedure: A rectangular sample of 3 mm x 50 mm is cut out of the microporous membrane such that the long axis of the sample is aligned with the transverse direction of the microporous membrane as it is produced in the process and the short axis is aligned with the machine direction.
  • the sample is set in a thermomechanical analyzer (TMA/SS6000 available from Seiko Instruments, Inc.) at a chuck distance of 10 mm, i.e., the distance from the upper chuck to the lower chuck is 10mm.
  • the lower chuck is fixed and a load of 19.6mN applied to the sample at the upper chuck.
  • the chucks and sample are enclosed in a tube which can be heated.
  • the temperature inside the tube is elevated at a rate of 5°C/minute, and sample length change under the 19.6mN load is measured at intervals of 0.5 second and recorded as temperature is increased.
  • the temperature is increased to 200 0 C.
  • the melt down temperature of the sample is defined as the temperature at which the sample breaks, generally at a temperature in the range of about 145°C to about 200°C. [0095] In an embodiment, the meltdown temperature is in the range of from 160 0 C to 20O 0 C 5 e.g., in the range of 17O 0 C to 18O 0 C.
  • Electrolytic solution absorption speed of 4.3 or greater
  • a microporous membrane sample is immersed in an electrolytic solution for 600 seconds (electrolyte: 1 mol/L of LiPF 6 , solvent: ethylene carbonate/dimethyl carbonate at a volume ratio of 3/7) kept at 18°C, to determine an electrolytic solution absorption speed by the formula of [weight (in grams) of microporous membrane after immersion / weight (in grams) of microporous membrane before immersion].
  • the electrolytic solution absorption speed is expressed by a relative value, assuming that the electrolytic solution absorption rate in the microporous membrane of Comparative Example 6 is 1.
  • the membrane's electrolytic solution absorption speed is in the range of 4.3 to 6.
  • the pore size distribution of the microporous membrane is determined by mercury intrusion porosimetry. At least about 25% of the differential pore volume is associated with pores larger than 100 nanometers (nm). (m) Surface roughness
  • the microporous membrane has good electrolytic solution absorption, compression and heat resistance properties and comprises (a) from about 73 wt. % to about 97 wt. % of a first polyethylene having an Mw of from about 2.5 x 10 5 to about 6 x 10 5 and an MWD of from about 5 to about 100, for example, an Mw of from about 2.5 x 10 5 to about 4 x 10 5 and an MWD of from about 5 to about 50; and (b) from about 3 wt. % to about 20 wt.
  • polypropylene resin having an Mw of from about 3 x 10 5 to about 1.5 x 10 6 , a heat of fusion of 80 J/g or higher, and an MWD of from about 1 to about 100, for example, an Mw of from about 3 x 10 5 to about 5 x 10 5 and an MWD of from about 1.1 to about 50; and (c) from about 0 wt. % to about 7 wt. % of a second polyethylene having a weight average molecular weight of 5 x 10 5 or higher, for example, an Mw of from about 5 x 10 5 to about 5 x 10 6 ; the weight percents being based on the combined weight of the polyethylene and the polypropylene in the membrane.
  • the microporous membrane generally comprises the same polymers used to produce the polymeric composition, in generally the same relative amounts. Washing solvent and/or process solvent (diluent) can also be present, generally in amounts less than 1 wt% based on the weight of the microporous membrane. A small amount of polymer molecular weight degradation might occur during processing, but this is acceptable. In an embodiment where the polymer is polyolef ⁇ n and the membrane is produced in a wet process, molecular weight degradation during processing, if any, causes the MWD value of the polymers in the membrane to differ from the Mw/Mn of the polymers used to produce the membrane by no more than about 5%, or no more than about 1%, or no more than about 0.1%.
  • the battery separator formed from any of the above microporous polyolef ⁇ n membranes of the present invention has a thickness of from about 3 to about 200 ⁇ m, or from about 5 to about 50 ⁇ m, or from about 7 to about 35 ⁇ m, though the most suitable thickness is properly selected depending on the type of battery to be manufactured.
  • microporous polyolefin membranes of the present invention may be used as separators for primary and secondary batteries, particularly such as lithium ion secondary batteries, lithium-polymer secondary batteries, nickel-hydrogen secondary batteries, nickel-cadmium secondary batteries, nickel-zinc secondary batteries, silver-zinc secondary batteries, particularly for lithium ion secondary batteries.
  • primary and secondary batteries particularly such as lithium ion secondary batteries, lithium-polymer secondary batteries, nickel-hydrogen secondary batteries, nickel-cadmium secondary batteries, nickel-zinc secondary batteries, silver-zinc secondary batteries, particularly for lithium ion secondary batteries.
  • the lithium ion secondary battery comprises a cathode and an anode laminated via a separator, and the separator contains an electrolyte, usually in the form of an electrolytic solution ("electrolyte").
  • electrolyte usually in the form of an electrolytic solution
  • the electrode structure is not critical and conventional structures are suitable.
  • the electrode structure may be, for instance, a coin type in which a disc-shaped positive and anodes are opposing, a laminate type in which planar positive and anodes are alternately laminated, a toroidal type in which ribbon-shaped positive and anodes are wound, etc.
  • the cathode usually comprises a current collector, and a cathodic active material layer capable of absorbing and discharging lithium ions which is formed on the current collector.
  • the cathodic active materials may be inorganic compounds such as transition metal oxides, composite oxides of lithium and transition metals (lithium composite oxides), transition metal sulfides, etc.
  • the transition metals may be V, Mn, Fe, Co, Ni, etc.
  • Preferred examples of the lithium composite oxides are lithium nickelate, lithium cobaltate, lithium manganate, laminar lithium composite oxides based on Ci-NaFeO 2 , etc.
  • the anode comprises a current collector, and a negative-electrode active material layer formed on the current collector.
  • the negative-electrode active materials may be carbonaceous materials such as natural graphite, artificial graphite, coke, carbon black, etc.
  • the electrolytic solution can be a solution obtained by dissolving a lithium salt in an organic solvent.
  • the lithium salt may be LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , Li 2 Bi 0 CIi 0 , LiN(C 2 F 5 SO 2 ) 2 , LiPF 4 (CF 3 ) 2 , LiPF 3 (C 2 Fs) 3 , lower aliphatic carboxylates of lithium, LiAlCl 4 , etc.
  • These lithium salts may be used alone or in combination.
  • the organic solvent may be an organic solvent having a high boiling point and high dielectric constant such as ethylene carbonate, propylene carbonate, ethylmethyl carbonate, ⁇ -butyrolactone, etc.; and/or organic solvents having low boiling points and low viscosity such as tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, dioxolane, dimethyl carbonate, dimethyl carbonate, etc. These organic solvents may be used alone or in combination. Because the organic solvents having high dielectric constants generally have high viscosity, while those having low viscosity generally have low dielectric constants, their mixtures are preferably used.
  • the separator When the battery is assembled, the separator is impregnated with the electrolytic solution, so that the separator (microporous polyolefin membrane) is provided with ion permeability.
  • the impregnation treatment is usually conducted by immersing the microporous membrane in the electrolytic solution at room temperature.
  • a cathode sheet, a microporous membrane separator and an anode sheet are laminated in this order, and the resultant laminate is wound to a toroidal-type electrode assembly.
  • the resultant electrode assembly is charged/formed into a battery can and then impregnated with the above electrolytic solution, and the battery lid acting as a cathode terminal provided with a safety valve is caulked to the battery can via a gasket to produce a battery.
  • Dry-blended are 100 parts by mass of polyolefin composition
  • a polyethylene (PE) composition comprising (a) 2% by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 2 x 10 and a molecular weight distribution (Mw/Mn) of 8, and (b) 88% by mass of high density polyethylene (HDPE) having an Mw of 3.0 x 10 5 and Mw/Mn of 8.6, and (ii) a polypropylene (PP) composition comprising 10% by mass of polypropylene having an Mw of 6.6 x 10 5 and a heat of fusion ( ⁇ Hm) of 83.3 J/g, and 0.2 parts by mass of tetrakis[methylene-3-(3,5-ditertiary-butyl-4-hydroxyphenyl)-propionate] methane as an antioxidant.
  • the polyethylene in the mixture has a melting point of 135°C and a
  • the gel-like sheet is simultaneously biaxially stretched at 118.5°C to 5 fold in both longitudinal and transverse directions.
  • the stretched gel-like sheet is fixed to an aluminum frame of 20 cm x 20 cm, immersed in a bath of methylene chloride controlled at 25 0 C to remove the liquid paraffin with vibration of 100 rpm for 3 minutes, and dried by an air flow at room temperature.
  • the dried membrane is re-stretched by a batch-stretching machine to a magnification of 1.5 fold in a transverse direction at 129°C.
  • the re-stretched membrane which remains fixed to the batch-stretching machine, is heat-set at 129°C for 30 seconds to produce a microporous polyethylene membrane.
  • Example 2
  • Example 1 is repeated except for the polyolefin composition comprising 90 % by mass of the HDPE resin having a weight average molecular weight of 3 x 10 5 and a molecular weight distribution of 8.6; and 10 % by mass of the PP resin having a weight average molecular weight of 6.6 x 10 5 and a ⁇ Hm of 83.3 J/g; the re-stretching is to a magnification of 1.5 fold at 128.5 °C; and the heat setting is at 128.5 °C.
  • Example 3
  • Example 1 is repeated except for the polyolefin composition comprising 2% by mass of the UHMWPE resin having a weight average molecular weight (Mw) of 2 x 10 6 and a molecular weight distribution of 8; 88 % by mass of the HDPE resin having a weight average molecular weight of 3 x 10 D and a molecular weight distribution of 8.6; and 10 % by mass of a PP resin having a weight average molecular weight of 1.35 x 10 6 and a ⁇ Hm of 97.9 J/g; the re-stretching is to a magnification of 1.5 fold at 127.5 °C; and the heat setting is at 127.5 °C. Comparative Example 1
  • Example 1 is repeated except for the polyolefin composition comprising 5% by mass of the UHMWPE resin having a weight average molecular weight (Mw) of 2 x 10 6 and a molecular weight distribution of 8; and 95 % by mass of the HDPE resin having a weight average molecular weight of 3 x 10 5 and a molecular weight distribution of 8.6. No PP is included in this Comparative Example. Comparative Example 2
  • Example 1 is repeated except for the polyolefin composition comprising 100 % by mass of the HDPE resin having a weight average molecular weight of 3 x 10 3 and a molecular weight distribution of 8.6; the stretching is done at 118 °C; and the re-stretching is to a magnification of 1.4 fold at 129 0 C. No PP or UHMWPE are included in this Comparative Example. Comparative Example 3
  • Example 1 is repeated except for the polyolefin composition comprising 3% by mass of the UHMWPE resin having a weight average molecular weight of 2 x 10 6 and a molecular weight distribution of 8; 92 % by mass of the HDPE resin having a weight average molecular weight of 3 x 10 5 and a molecular weight distribution of 8.6; and 5 % by mass of a PP resin having a weight average molecular weight of 5.3 x 10 5 and a ⁇ Hm of only 77.2 J/g; the stretching is at 116 0 C; the re-stretching is to a magnification of 1.4 fold at 127 °C; and the heat setting is at 127 °C.
  • Another exception from Example 1 for this Comparative Example 3 is that 35 parts by mass of the resultant polyolefin composition and 65 parts by mass of the liquid paraffin (50 cst at 40°C) is charged into the double-screw extruder.
  • the microporous membrane of the present invention exhibits a pore size distribution curve obtained by mercury intrusion porosimetry having a first peak at a pore size of from 0.01 to 0.08 ⁇ m, and second to fourth peaks at pore sizes of more than 0.08 ⁇ m and 1.5 ⁇ m or less, and the surface roughness as a maximum height difference was 3 x 10 2 nm or more.
  • the microporous membrane of the present invention has suitable air permeability, pin puncture strength, tensile rupture strength, tensile rupture elongation, as well as excellent electrolytic solution absorption, compression properties and heat shrinkage resistance, with little variation of thickness and air permeability after heat compression.
  • the microporous membrane of the product of the Comparative Examples has lower electrolytic solution absorption and lower melt-down temperatures. Accordingly, the microporous membrane of the Comparative Example does not perform as well as that of the present invention.
  • the microporous polyolefin membrane of the present invention has suitable permeability and mechanical strength, and excellent electrolytic solution absorption, compression resistance and heat shrinkage resistance. Separators formed by the microporous polyolefin membrane of the present invention provide batteries with suitable safety, heat resistance, storage properties and productivity.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Cell Separators (AREA)
  • Coating Of Shaped Articles Made Of Macromolecular Substances (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Secondary Cells (AREA)

Abstract

La présente invention concerne une membrane microporeuse présentant une perméabilité, une résistance mécanique, des propriétés d'absorption de solution électrolytique, une résistance à la compression, et une résistance à la rétraction thermique appropriées, ainsi que des procédés permettant de produire et d'utiliser une telle membrane de polyoléfine microporeuse. L'invention concerne également des séparateurs de batterie comprenant une telle membrane de polyoléfine microporeuse, et des batteries utilisant de tels séparateurs de batterie.
PCT/JP2008/067579 2007-09-20 2008-09-19 Membranes microporeuses, procédés de fabrication et utilisation de telles membranes Ceased WO2009038231A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2010525545A JP2010540691A (ja) 2007-09-20 2008-09-19 微多孔膜およびそのような膜を製造し使用する方法
KR1020107006155A KR101135077B1 (ko) 2007-09-20 2008-09-19 미세다공성 막, 그것의 제조방법 및 그것의 사용방법

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
US11/858,587 2007-09-20
US11/858,587 US8304114B2 (en) 2007-09-20 2007-09-20 Microporous polyolefin membrane and manufacturing method
US11/864,214 US8021789B2 (en) 2007-09-28 2007-09-28 Microporous membrane and manufacturing method
US11/864,350 US8273279B2 (en) 2007-09-28 2007-09-28 Microporous polyolefin membrane and manufacturing method
US11/864,214 2007-09-28
US11/864,350 2007-09-28
US11/868,265 US8715849B2 (en) 2007-10-05 2007-10-05 Microporous polymer membrane
US11/868,265 2007-10-05

Publications (1)

Publication Number Publication Date
WO2009038231A1 true WO2009038231A1 (fr) 2009-03-26

Family

ID=40084208

Family Applications (3)

Application Number Title Priority Date Filing Date
PCT/JP2008/067575 Ceased WO2009038229A1 (fr) 2007-09-20 2008-09-19 Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes
PCT/JP2008/067579 Ceased WO2009038231A1 (fr) 2007-09-20 2008-09-19 Membranes microporeuses, procédés de fabrication et utilisation de telles membranes
PCT/JP2008/067581 Ceased WO2009038233A1 (fr) 2007-09-20 2008-09-19 Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes

Family Applications Before (1)

Application Number Title Priority Date Filing Date
PCT/JP2008/067575 Ceased WO2009038229A1 (fr) 2007-09-20 2008-09-19 Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes

Family Applications After (1)

Application Number Title Priority Date Filing Date
PCT/JP2008/067581 Ceased WO2009038233A1 (fr) 2007-09-20 2008-09-19 Membranes microporeuses et procédés de fabrication et d'utilisation de telles membranes

Country Status (3)

Country Link
JP (3) JP2010540690A (fr)
KR (3) KR101160462B1 (fr)
WO (3) WO2009038229A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011114664A1 (fr) * 2010-03-15 2011-09-22 Toray Tonen Specialty Separator Godo Kaisha Membranes microporeuses, leurs procédés de fabrication, et utilisation desdites membranes en tant que films de séparation d'éléments de batterie
US11139533B2 (en) 2016-02-09 2021-10-05 Ube Industries, Ltd. Polyolefin micro-porous film, separator film for power-storage device, and power-storage device

Families Citing this family (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010540690A (ja) * 2007-09-20 2010-12-24 東燃化学株式会社 微多孔膜およびそのような膜を製造し使用する方法
US8715849B2 (en) 2007-10-05 2014-05-06 Toray Battery Separator Film Co., Ltd. Microporous polymer membrane
EP2414085B1 (fr) * 2009-03-30 2019-01-16 Toray Industries, Inc. Membranes microporeuses et procédé de fabrication associé
US9184429B2 (en) * 2009-08-25 2015-11-10 Asahi Kasei E-Materials Corporation Microporous membrane winding and method for manufacturing the same
JP2012043629A (ja) * 2010-08-18 2012-03-01 Mitsubishi Chemicals Corp 非水系電解液二次電池用セパレータ及び非水系電解液二次電池
JP5742135B2 (ja) * 2010-08-25 2015-07-01 ソニー株式会社 セパレータおよびこれを用いた非水電解質電池
JP2012102198A (ja) * 2010-11-08 2012-05-31 Asahi Kasei E-Materials Corp ポリオレフィン微多孔膜、及び蓄電デバイス
JP5942127B2 (ja) * 2010-11-08 2016-06-29 旭化成株式会社 ポリオレフィン微多孔膜、及び蓄電デバイス
JP2012190729A (ja) * 2011-03-13 2012-10-04 Seiko Instruments Inc コイン型非水電解質二次電池
CA2810168C (fr) * 2011-04-05 2016-04-26 W-Scope Corporation Membrane poreuse et son procede de production
JP5670854B2 (ja) * 2011-09-29 2015-02-18 株式会社東芝 二次電池の製造方法
CN102779965B (zh) * 2012-08-09 2014-08-13 常州大学 一种具有亲水交联表层的锂离子电池隔膜及其制备方法
CN102850573B (zh) * 2012-09-21 2014-08-13 中国乐凯集团有限公司 一种湿法制备聚烯烃微孔膜的方法
KR20140062690A (ko) * 2012-11-14 2014-05-26 류수선 폴리올레핀 미세 다공막의 제조방법
KR101611229B1 (ko) 2013-01-31 2016-04-11 제일모직 주식회사 분리막의 제조 방법과 그 분리막, 및 이를 이용한 전지
JP6102380B2 (ja) * 2013-03-18 2017-03-29 日本ポリエチレン株式会社 微多孔フィルム、及びそれを用いたリチウムイオン電池用セパレータ
US9419265B2 (en) 2013-10-31 2016-08-16 Lg Chem, Ltd. High-strength electrospun microfiber non-woven web for a separator of a secondary battery, a separator comprising the same and a method for manufacturing the same
HUE051622T2 (hu) * 2015-02-20 2021-03-01 Toray Industries Eljárás mikropórusos mûanyag film elõállítására
JP2016160267A (ja) 2015-02-26 2016-09-05 株式会社日本製鋼所 微多孔性膜又は微多孔延伸フィルムの製造方法及び微多孔フィルム又は二軸微多孔延伸フィルム
JP6004037B2 (ja) * 2015-05-01 2016-10-05 ソニー株式会社 セパレータおよびこれを用いた非水電解質電池
JP6859952B2 (ja) * 2015-06-05 2021-04-14 東レ株式会社 微多孔膜製造方法、微多孔膜、電池用セパレータ及び二次電池
WO2017051514A1 (fr) * 2015-09-25 2017-03-30 三洋電機株式会社 Batterie secondaire à électrolyte non aqueux cylindrique
WO2017138512A1 (fr) * 2016-02-09 2017-08-17 宇部興産株式会社 Membrane microporeuse de polyoléfine, film de séparateur pour dispositif de stockage, et dispositif de stockage
WO2018043335A1 (fr) 2016-08-29 2018-03-08 東レ株式会社 Film microporeux ainsi que procédé de fabrication de celui-ci, et batterie secondaire au lithium-ion
JP7047382B2 (ja) 2016-08-29 2022-04-05 東レ株式会社 ポリオレフィン微多孔膜、リチウムイオン二次電池及びポリオレフィン微多孔膜製造方法
CN106832529B (zh) * 2017-03-06 2020-11-10 四川天邑康和通信股份有限公司 一种用于机械化补口的热缩带基片材料及其制备方法
CN108398647B (zh) * 2018-03-01 2020-07-24 杭州高特新能源技术有限公司 锂电池不同充放电曲线获取方法
CN109509856B (zh) * 2018-04-04 2021-06-22 深圳市合壹新能技术有限公司 一种芳香族聚酰胺微孔膜及其制备方法和用途
CN108807821B (zh) * 2018-06-20 2021-03-19 宁德新能源科技有限公司 隔离膜和电化学装置
CN109054149A (zh) * 2018-06-29 2018-12-21 怀宁县日升塑业有限公司 一种耐撕裂塑料袋的制备方法
KR102869816B1 (ko) * 2019-01-07 2025-10-13 주식회사 엘지화학 가교 폴리올레핀 분리막 및 이의 제조방법
CN110295402B (zh) * 2019-06-11 2021-02-09 宜宾天原集团股份有限公司 一种聚苯硫醚纤维的制备方法
CN112886138A (zh) * 2021-01-05 2021-06-01 中材锂膜有限公司 一种两面微孔不同的微孔膜及其制备方法
CN116093545B (zh) * 2023-03-15 2023-06-23 中材锂膜(南京)有限公司 一种聚烯烃微孔膜及其制备方法、电池隔膜、电化学装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4670341A (en) * 1985-05-17 1987-06-02 W. R. Grace & Co. Hollow fiber
US20030031924A1 (en) * 2000-01-10 2003-02-13 Sang-Young Lee High crystalline polypropylene microporous membrane, multicomponent microporous membrane and method for preparing the same
US6824865B1 (en) * 1998-10-01 2004-11-30 Tonen Chemical Corporation Microporous polyolefin film and process for producing the same
WO2005113657A1 (fr) * 2004-05-20 2005-12-01 Asahi Kasei Chemicals Corporation Membrane microporeuse constituée de polyoléfines

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5922492A (en) * 1996-06-04 1999-07-13 Tonen Chemical Corporation Microporous polyolefin battery separator
JP2002194132A (ja) * 2000-12-26 2002-07-10 Tonen Chem Corp ポリオレフィン微多孔膜及びその製造方法
JP4121846B2 (ja) * 2002-12-16 2008-07-23 東燃化学株式会社 ポリオレフィン微多孔膜及びその製造方法並びに用途
JP5202826B2 (ja) * 2005-08-04 2013-06-05 東レバッテリーセパレータフィルム株式会社 ポリエチレン微多孔膜及びその製造方法並びに電池用セパレータ
JP2010540690A (ja) * 2007-09-20 2010-12-24 東燃化学株式会社 微多孔膜およびそのような膜を製造し使用する方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4670341A (en) * 1985-05-17 1987-06-02 W. R. Grace & Co. Hollow fiber
US6824865B1 (en) * 1998-10-01 2004-11-30 Tonen Chemical Corporation Microporous polyolefin film and process for producing the same
US20030031924A1 (en) * 2000-01-10 2003-02-13 Sang-Young Lee High crystalline polypropylene microporous membrane, multicomponent microporous membrane and method for preparing the same
WO2005113657A1 (fr) * 2004-05-20 2005-12-01 Asahi Kasei Chemicals Corporation Membrane microporeuse constituée de polyoléfines

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011114664A1 (fr) * 2010-03-15 2011-09-22 Toray Tonen Specialty Separator Godo Kaisha Membranes microporeuses, leurs procédés de fabrication, et utilisation desdites membranes en tant que films de séparation d'éléments de batterie
CN102884116A (zh) * 2010-03-15 2013-01-16 东丽电池隔膜株式会社 微孔膜、该膜的生产方法、以及该膜作为电池隔膜的应用
JP2013522379A (ja) * 2010-03-15 2013-06-13 東レバッテリーセパレータフィルム株式会社 微多孔膜、これらの膜の作製方法、およびバッテリーセパレーターフィルムとしてのこれらの膜の使用
CN102884116B (zh) * 2010-03-15 2014-08-13 东丽电池隔膜株式会社 微孔膜、该膜的生产方法、以及该膜作为电池隔膜的应用
JP2015221904A (ja) * 2010-03-15 2015-12-10 東レバッテリーセパレータフィルム株式会社 微多孔膜
KR101841513B1 (ko) * 2010-03-15 2018-03-23 도레이 카부시키가이샤 미세다공막, 이들 막의 제조방법, 및 전지 세퍼레이터 필름으로서 이들 막의 사용
US11139533B2 (en) 2016-02-09 2021-10-05 Ube Industries, Ltd. Polyolefin micro-porous film, separator film for power-storage device, and power-storage device

Also Published As

Publication number Publication date
JP2010540692A (ja) 2010-12-24
KR101135077B1 (ko) 2012-04-16
JP2010540691A (ja) 2010-12-24
JP5453272B2 (ja) 2014-03-26
KR20100066516A (ko) 2010-06-17
WO2009038229A1 (fr) 2009-03-26
KR20100066517A (ko) 2010-06-17
KR101160462B1 (ko) 2012-06-28
KR20100066518A (ko) 2010-06-17
JP2010540690A (ja) 2010-12-24
KR101138860B1 (ko) 2012-05-14
WO2009038233A1 (fr) 2009-03-26

Similar Documents

Publication Publication Date Title
EP2212946B1 (fr) Membranes microporeuses et procédés de production et d'utilisation desdites membranes
EP2004740B1 (fr) Membrane microporeuse polyoléfinique, procédé de production de celle-ci, separateur d'accumulateur, et accumulateur
US8304114B2 (en) Microporous polyolefin membrane and manufacturing method
WO2009038231A1 (fr) Membranes microporeuses, procédés de fabrication et utilisation de telles membranes
KR101143106B1 (ko) 미세다공성 중합체 막
US8338017B2 (en) Microporous membrane and manufacturing method
US8715849B2 (en) Microporous polymer membrane
EP1956041B1 (fr) Membrane microporeuse polyolefinique, procede de production, separateur de cellule, et cellule
EP2263275A1 (fr) Membrane microporeuse, séparateur de batterie et batterie
EP2263277A1 (fr) Membrane microporeuse, séparateur de batterie et batterie
WO2009069534A2 (fr) Membrane polymère microporeuse, séparateur d'accumulateur et accumulateur
EP1956040B1 (fr) Membrane microporeuse polyolefinique, procede de production, separateur de cellule, et cellule
US8273279B2 (en) Microporous polyolefin membrane and manufacturing method
US8021789B2 (en) Microporous membrane and manufacturing method
EP2111909A1 (fr) Membrane microporeuse de polyoléfine et son procédé de fabrication
EP2111908A1 (fr) Membrane microporeuse et son procédé de fabrication
EP2111912A1 (fr) Membrane microporeuse de polyoléfine et son procédé de fabrication
EP2111913A1 (fr) Membrane microporeuse et son procédé de fabrication
WO2008035806A1 (fr) Assemblage d'électrodes et batterie à électrolyte non aqueux

Legal Events

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

Ref document number: 08832722

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 20107006155

Country of ref document: KR

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2010525545

Country of ref document: JP

122 Ep: pct application non-entry in european phase

Ref document number: 08832722

Country of ref document: EP

Kind code of ref document: A1