WO2015083591A1 - Laminated porous film, and production method therefor - Google Patents

Laminated porous film, and production method therefor Download PDF

Info

Publication number
WO2015083591A1
WO2015083591A1 PCT/JP2014/081253 JP2014081253W WO2015083591A1 WO 2015083591 A1 WO2015083591 A1 WO 2015083591A1 JP 2014081253 W JP2014081253 W JP 2014081253W WO 2015083591 A1 WO2015083591 A1 WO 2015083591A1
Authority
WO
WIPO (PCT)
Prior art keywords
porous membrane
laminated
polyolefin
polyethylene
film
Prior art date
Application number
PCT/JP2014/081253
Other languages
French (fr)
Japanese (ja)
Inventor
水野　直樹
孝一 又野
Original Assignee
東レバッテリーセパレータフィルム株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 東レバッテリーセパレータフィルム株式会社 filed Critical 東レバッテリーセパレータフィルム株式会社
Priority to JP2015516303A priority Critical patent/JP5792914B1/en
Priority to CN201480065581.5A priority patent/CN105992691B/en
Priority to KR1020167014856A priority patent/KR102131009B1/en
Publication of WO2015083591A1 publication Critical patent/WO2015083591A1/en

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/32—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed at least two layers being foamed and next to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B29C48/914—Cooling of flat articles, e.g. using specially adapted supporting means cooling drums
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B29C48/915—Cooling of flat articles, e.g. using specially adapted supporting means with means for improving the adhesion to the supporting means
    • B29C48/9155—Pressure rollers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B29C55/16—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial simultaneously
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/42—Acrylic resins
    • 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
    • H01M50/423—Polyamide resins
    • 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
    • H01M50/426—Fluorocarbon polymers
    • 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
    • H01M50/429—Natural polymers
    • 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
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B29C55/14—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial successively
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
    • B32B2264/10—Inorganic particles
    • B32B2264/102—Oxide or hydroxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
    • B32B2264/10—Inorganic particles
    • B32B2264/104—Oxysalt, e.g. carbonate, sulfate, phosphate or nitrate particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2266/00—Composition of foam
    • B32B2266/02—Organic
    • B32B2266/0214—Materials belonging to B32B27/00
    • B32B2266/025—Polyolefin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/54—Yield strength; Tensile strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/726—Permeability to liquids, absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/10—Batteries
    • 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 present invention relates to a laminated porous membrane having a polyolefin porous membrane suitable for lamination of a modified porous layer and a modified porous layer, and a method for producing the same.
  • the laminated porous membrane of the present invention is a battery separator useful as a lithium ion battery separator.
  • a microporous membrane made of a thermoplastic resin is widely used as a material separation membrane, a permselective membrane, a separation membrane, and the like.
  • a separator for lithium ion secondary battery it has ion permeability by impregnating with electrolyte, has excellent electrical insulation, cuts off current at a temperature of about 120-150 ° C when the battery temperature rises abnormally, and excessive temperature rise
  • a polyethylene porous membrane having a pore closing effect that suppresses the above is suitably used.
  • the temperature continues to rise even after the hole is closed for some reason, a film breakage may occur due to the contraction of the film.
  • This phenomenon is not limited to a polyethylene microporous film, and even in the case of a microporous film using another thermoplastic resin, it cannot be avoided at a temperature equal to or higher than the melting point of the resin constituting the porous film.
  • lithium-ion battery separators are deeply involved in battery characteristics, battery productivity, and battery safety. Mechanical characteristics, heat resistance, permeability, dimensional stability, pore clogging characteristics (shutdown characteristics), melt-breaking characteristics ( Melt down characteristics) are required. Furthermore, in order to improve the cycle characteristics of the battery, it is required to improve the adhesion between the separator and the electrode material and the electrolyte permeability to improve the productivity.
  • the modified porous layer in the present invention refers to a layer containing a resin that imparts or improves at least one function such as heat resistance, adhesion to an electrode material, and electrolyte permeability.
  • Patent Document 1 polyvinylidene fluoride is applied to a polyethylene porous film having a thickness of 9 ⁇ m, and a part of the polyvinylidene fluoride appropriately bites into the pores of the polyethylene porous film so as to develop an anchor effect.
  • a composite porous membrane is disclosed in which the peel strength (T-type peel strength) at the interface between the membrane and the polyvinylidene fluoride coating layer is 1.0 to 5.3 N / 25 mm.
  • a heat resistant porous layer containing a self-crosslinking acrylic resin and plate boehmite is provided on a corona discharge-treated polyethylene porous film having a thickness of 16 ⁇ m, and the polyethylene porous film and the heat resistant porous layer are 180 °.
  • Example 1 of Patent Document 3 polyethylene having a viscosity average molecular weight of 200,000, 47.5 parts by mass, 2.5 parts by mass of polypropylene having a viscosity average molecular weight of 400,000, and 50 parts by mass of a composition comprising an antioxidant and flowing
  • a polyethylene resin solution consisting of 50 parts by mass of paraffin was extruded from an extruder at 200 ° C., and was taken up with a cooling roll adjusted to 25 ° C., to obtain a gel-like molded product, and then 7 ⁇ 6.4 times. Biaxial stretching is performed to obtain a polyolefin resin porous membrane.
  • a multilayer porous membrane obtained by laminating a coating layer made of polyvinyl alcohol and alumina particles on the surface of the polyolefin resin porous membrane is disclosed.
  • Example 6 of Patent Document 4 a polyethylene resin solution having a weight average molecular weight of 41.5 million, a weight average molecular weight of 560,000, a polyethylene composition of 30% by weight and a mixed solvent of liquid paraffin and decalin of 70% by weight is extruded. Extruded from the machine at 148 ° C., cooled in a water bath to obtain a gel-like molded article, and then biaxially stretched so as to be 5.5 ⁇ 11.0 times to obtain a polyethylene porous film. Next, a separator for a non-aqueous secondary battery obtained by further laminating a coating layer made of a meta-type wholly aromatic polyamide and alumina particles on the surface of the polyethylene porous membrane is disclosed.
  • Example 1 of Patent Document 5 47 parts by mass of homopolymer polyethylene having an Mv (viscosity average molecular weight) of 700,000, 46 parts by mass of polyethylene having an Mv of 250,000, and 7 parts by mass of polypropylene having an Mv of 400,000, Dry blended using a tumbler blender.
  • Mv viscosity average molecular weight
  • a polyethylene composition that has been dry-blended using a tumbler blender is melt-kneaded and extruded and cast onto a cooling roll controlled at a surface temperature of 25 ° C. to obtain a sheet-like polyolefin composition having a thickness of 2000 ⁇ m.
  • a multilayer porous membrane obtained by applying an aqueous dispersion of calcined kaolin and latex to a polyethylene porous membrane obtained by biaxial stretching so as to be ⁇ 7 times is disclosed.
  • JP 2012-037662 A Republished 2010-104127 Japanese Patent No. 4931083 Japanese Patent No. 4460028 JP 2011-000832 A
  • the battery assembly process will be accelerated in order to reduce costs.
  • high adhesion that can withstand high-speed processing is required between the polyolefin porous membrane and the modified porous layer.
  • the polyolefin porous membrane is sufficiently infiltrated with the resin contained in the modified porous layer in order to improve the adhesion, there is a problem that the increase in the air resistance increases.
  • the conventional technology uses locally modified porosity during slit processing and battery assembly processing As the layers peel, it is expected that ensuring safety will become increasingly difficult.
  • the polyolefin resin porous membrane becomes thinner, it becomes difficult to obtain a sufficient anchor effect of the modified porous layer for the polyolefin resin porous membrane, and thus it becomes more difficult to ensure safety.
  • the present invention aims to provide a laminated porous membrane having a polyolefin porous membrane suitable for lamination of a modified porous layer and a modified porous layer, and the laminated porous membrane used as a battery separator.
  • the peel strength as used herein means 0 ° peel strength between the polyolefin porous membrane and the modified porous layer, and is a value measured by the following method (hereinafter referred to as 0 ° peel strength). There is.)
  • FIG. 1 schematically shows a side view of a laminated sample of a polyolefin porous membrane and a modified porous layer in a state of being pulled by a tensile tester (not shown).
  • 1 is a laminated sample
  • 2 is a polyolefin porous membrane
  • 3 is a modified porous layer
  • 4 is a double-sided pressure-sensitive adhesive tape
  • the surface of the polyolefin porous membrane (2) of the porous membrane) is pasted so that 40 mm overlaps the end of one side of the 25 mm length of the aluminum plate (5), and the protruding portion is cut off.
  • a double-sided adhesive tape is attached to one side of an aluminum plate (5 ′) having a length of 100 mm, a width of 15 mm, and a thickness of 0.5 mm. From the end of one side of the aluminum plate (5) on the 25 mm-long sample side. Paste so that 20mm overlaps.
  • the aluminum plate (5) and the aluminum plate (5 ′) are pulled in parallel in opposite directions using a tensile tester at a tensile rate of 10 mm / min, and the strength when the modified porous layer is peeled is measured. If the peel strength is 130 N / 15 mm or more in this evaluation method, the laminated modified porous layer is peeled off during transportation or processing even when the thickness of the polyolefin porous membrane is 10 ⁇ m or less. The phenomenon hardly occurs.
  • the T-type peel strength or 180 ° peel strength conventionally used as a method for measuring peel strength is to peel the coating layer from the polyethylene porous film perpendicularly or obliquely backward from the surface of the polyethylene porous film. It is the peel force at the time. According to this evaluation method, it is possible to evaluate the abrasion resistance in the slit process and the battery assembly process more practically as compared with these conventional evaluation methods.
  • the laminated porous membrane of the present invention has the following configuration. That is, The projections made of polyolefin satisfy 5 ⁇ m ⁇ W ⁇ 50 ⁇ m (W is the size of the projection) and 0.5 ⁇ m ⁇ H (H is the height of the projection), and 3 / cm 2 or more per side on both sides, 200 / It is a laminated porous membrane in which a modified porous layer A is laminated on one side of a polyolefin porous membrane having a film thickness of 25 ⁇ m or less, and a modified porous layer B is laminated on the opposite side, which are irregularly scattered at a cm 2 or less.
  • At least the modified porous layer A is a laminated porous film containing a binder having a tensile strength of 5 N / mm 2 or more and inorganic particles.
  • the binder having a tensile strength of 5 N / mm 2 or more is preferably polyvinyl alcohol or an acrylic resin.
  • the inorganic particles preferably include at least one selected from the group consisting of calcium carbonate, alumina, titania, barium sulfate, mica and boehmite.
  • the polyolefin porous membrane preferably has a thickness of 20 ⁇ m or less.
  • the polyolefin porous membrane preferably has a thickness of 16 ⁇ m or less.
  • the laminated porous membrane of the present invention is preferably used as a battery separator.
  • the method for producing a laminated porous membrane of the present invention has the following configuration.
  • Step of adding a molding solvent to a polyolefin resin and then melt-kneading to prepare a polyolefin resin solution (b) Both sides of the polyolefin resin solution extruded into a film by extruding the polyolefin resin solution from a T-shaped die Step (c) of forming a gel-like molded product by cooling with a cooling roll having a surface from which the forming solvent is removed, and stretching the gel-like molded product in the machine direction and the width direction.
  • the forming solvent removing means is a doctor blade.
  • the modified porous layer A and the modified porous layer B may be simply referred to as a modified porous layer.
  • the polyolefin porous membrane used in the present invention is moderate on the surface obtained by preparing a specific polyolefin resin solution and highly controlling the cooling rate of the polyolefin resin solution extruded from the extruder via the T-die. It is a polyolefin porous membrane which has various shapes and a number of protrusions. Furthermore, when a modified porous layer containing inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more is laminated on the polyolefin porous film, extremely excellent peeling between the polyolefin porous film and the modified porous layer Strength can be obtained.
  • the projection referred to in the present invention is essentially different from the projection obtained by adding inorganic particles or the like to the polyolefin porous membrane.
  • the protrusions obtained by adding inorganic particles to the polyolefin porous membrane are usually extremely small in height, and if a protrusion having a height of 0.5 ⁇ m or more is to be formed by the same means, the thickness of the polyolefin porous film It is necessary to add particles having an equivalent or larger particle size. However, when such particles are added, the strength of the polyolefin porous membrane is lowered, which is not realistic.
  • the protrusions referred to in the present invention are those in which a part of the polyolefin porous film is grown to a moderately raised shape, and do not deteriorate the basic characteristics of the polyolefin porous film.
  • irregularly scattered in the present invention means that a regular or periodic arrangement obtained by passing an embossing roll before or after the stretching step in the production of a polyolefin porous membrane is clear.
  • Press work such as embossing is basically not preferred because it forms protrusions by compressing portions other than the protrusions and tends to cause a decrease in air resistance and electrolyte permeability.
  • the moderately shaped protrusion as used in the present invention means a protrusion having a size of 5 ⁇ m or more and 50 ⁇ m or less and a height of 0.5 ⁇ m or more. That is, 5 ⁇ m ⁇ W ⁇ 50 ⁇ m (W is the size of the protrusion) and 0.5 ⁇ m ⁇ H (H is the height of the protrusion).
  • Such protrusions function as anchors when the modified porous layer is laminated on the porous film, and as a result, the laminated porous film having a high 0 ° peel strength can be obtained.
  • the upper limit of the height is not particularly limited, but 3.0 ⁇ m is sufficient.
  • the 0 ° peel strength is affected by the number of protrusions having a height of 0.5 ⁇ m or more and the average height thereof.
  • the lower limit of the number of protrusions is preferably 3 / cm 2 , more preferably 5 / cm 2 , and still more preferably 10 / cm 2 .
  • the upper limit of the number of protrusions is preferably 200 / cm 2 , more preferably 150 / cm 2 .
  • the lower limit of the height of the protrusion is preferably 0.5 ⁇ m, more preferably 0.8 ⁇ m, and still more preferably 1.0 ⁇ m.
  • protrusion in this invention say the value measured with the measuring method mentioned later.
  • the range of increase in the air resistance referred to in the present invention means a difference in air resistance between the polyolefin porous membrane and the laminated porous membrane in which the modified porous layer is laminated. / 100ccAir or less is preferable.
  • the thickness of the polyolefin porous membrane of the present invention is preferably 25 ⁇ m or less, and the more preferable upper limit is 20 ⁇ m, and further preferably 16 ⁇ m.
  • the lower limit is 7 ⁇ m, preferably 9 ⁇ m. If the thickness of the polyolefin porous membrane is within the above preferred range, practical membrane strength and pore blocking function can be retained, and the area per unit volume of the battery case is not restricted, and will proceed in the future. Suitable for increasing the capacity of brazing batteries.
  • the upper limit of the air resistance of the polyolefin porous membrane is preferably 300 sec / 100 cc Air, more preferably 200 sec / 100 cc Air, still more preferably 150 sec / 100 cc Air, and the lower limit is preferably 50 sec / 100 cc Air, more preferably 70 sec / 100 cc Air, More preferably, it is 100 sec / 100 cc Air.
  • the upper limit of the porosity of the polyolefin porous membrane is preferably 70%, more preferably 60%, and even more preferably 55%.
  • the lower limit is preferably 30%, more preferably 35%, still more preferably 40%.
  • the average pore diameter of the polyolefin porous membrane is preferably 0.01 to 1.0 ⁇ m, more preferably 0.05 to 0.5 ⁇ m, still more preferably 0.1 to 0. 3 ⁇ m.
  • the 0 ° peel strength of the modified porous layer can be sufficiently obtained by the anchor effect of the functional resin, and air permeability can be obtained when the modified porous layer is laminated.
  • the resistance does not deteriorate significantly, the response to the temperature of the hole closing phenomenon does not become slow, and the hole closing temperature due to the temperature rising rate does not shift to a higher temperature side.
  • the polyolefin porous membrane needs to have a function of blocking pores when the charge / discharge reaction is abnormal. Therefore, the melting point (softening point) of the constituent resin is 70 to 150 ° C., more preferably 80 to 140 ° C., and still more preferably 100 to 130 ° C.
  • the melting point of the resin constituting the resin is within the above preferable range, the battery does not become unusable due to the occurrence of a hole closing function during normal use, and the hole closing function is exhibited during an abnormal reaction. Can be secured.
  • the polyolefin resin constituting the polyolefin porous membrane is preferably polyethylene or polypropylene. Further, it may be a single substance or a mixture of two or more different polyolefin resins, for example, a mixture of polyethylene and polypropylene, or a copolymer of different olefins. This is because, in addition to basic characteristics such as electrical insulation and ion permeability, it has a hole blocking effect that blocks current when the battery is abnormally heated and suppresses excessive temperature rise. Among these, polyethylene is particularly preferable from the viewpoint of excellent pore closing performance.
  • polyethylene will be described in detail as an example of the polyolefin resin used in the present invention.
  • the polyethylene include ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, and low density polyethylene.
  • the polymerization catalyst is not particularly limited, and examples thereof include a Ziegler-Natta catalyst, a Phillips catalyst, and a metallocene catalyst. These polyethylenes may be not only ethylene homopolymers but also copolymers containing small amounts of other ⁇ -olefins.
  • ⁇ -olefins other than ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, (meth) acrylic acid, esters of (meth) acrylic acid, styrene, etc. Is preferred.
  • Polyethylene may be a single material, but is preferably a mixture of two or more types of polyethylene.
  • a mixture containing two or more types of ultrahigh molecular weight polyethylenes having different weight average molecular weights (Mw) may be used, and similarly, a mixture of high density polyethylene, medium density polyethylene or low density polyethylene may be used. Good.
  • a mixture of two or more polyethylenes selected from the group consisting of ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene and low density polyethylene may also be used.
  • the polyethylene mixture a mixture composed of ultrahigh molecular weight polyethylene having a weight average molecular weight (Mw) of 5 ⁇ 10 5 or more and polyethylene having Mw of 1 ⁇ 10 4 or more and less than 5 ⁇ 10 5 is preferable.
  • the Mw of the ultra high molecular weight polyethylene is preferably 5 ⁇ 10 5 to 1 ⁇ 10 7 , more preferably 1 ⁇ 10 6 to 15 ⁇ 10 6 , and 1 ⁇ 10 6 to 5 ⁇ 10 6. Is more preferable.
  • the polyethylene having an Mw of 1 ⁇ 10 4 or more and less than 5 ⁇ 10 5 any of high density polyethylene, medium density polyethylene and low density polyethylene can be used, and it is particularly preferable to use high density polyethylene.
  • polyethylene having an Mw of 1 ⁇ 10 4 or more and less than 5 ⁇ 10 5 two or more types having different Mw may be used, or two or more types having different densities may be used.
  • the upper limit of Mw of the polyethylene mixture is set to 15 ⁇ 10 6 or less, melt extrusion can be facilitated.
  • the upper limit of the content of ultrahigh molecular weight polyethylene is preferably 40% by weight, more preferably 30% by weight, still more preferably 10% by weight, and the lower limit is preferably 1% by weight, more preferably 2% by weight. %, More preferably 5% by weight.
  • the content of ultrahigh molecular weight polyethylene is within the preferred range, a sufficiently high protrusion can be obtained.
  • the protrusion functions as an anchor, and extremely strong peeling resistance can be obtained with respect to a force applied in parallel to the plane direction of the polyethylene porous film. Further, even when the thickness of the polyethylene porous film is reduced, sufficient tensile strength can be obtained.
  • the tensile strength is preferably 100 MPa or more. There is no particular upper limit.
  • the specific molecular weight distribution (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyethylene resin is preferably in the range of 5 to 200, and more preferably in the range of 10 to 100. .
  • Mw / Mn is within the above preferred range, the polyethylene resin solution can be easily extruded and a sufficient number of protrusions can be obtained.
  • Mw / Mn is used as a measure of molecular weight distribution, that is, in the case of polyethylene consisting of a single substance, the larger this value, the wider the molecular weight distribution.
  • the Mw / Mn of polyethylene composed of a single substance can be appropriately adjusted by multistage polymerization of polyethylene. Moreover, Mw / Mn of the mixture of polyethylene can be suitably adjusted by adjusting the molecular weight and mixing ratio of each component.
  • the polyethylene porous film may be a single layer film or a layer structure composed of two or more layers having different molecular weights or average pore diameters.
  • a layer structure composed of two or more layers it is preferable that the molecular weight and molecular weight distribution of at least one outermost polyethylene resin satisfy the above.
  • the polyethylene porous membrane is within a range that satisfies the above-mentioned various characteristics, a production method according to the purpose can be freely selected.
  • the manufacturing method of polyolefin porous membrane includes foaming method, phase separation method, dissolution recrystallization method, stretch opening method, powder sintering method, etc. Among these, the uniform pores The phase separation method is preferable in view of cost and cost.
  • phase separation method for example, polyethylene and a molding solvent are heated, melted and kneaded, and the resulting molten mixture is extruded from a T-die and cooled to form a gel-like molded product.
  • the method include obtaining a porous film by performing stretching in at least a uniaxial direction on the shaped molding and removing the molding solvent.
  • each of the polyethylene constituting the a layer and the b layer is melt-kneaded with a molding solvent, and the obtained molten mixture is sent from each extruder to one T-die. It is possible to produce either a method in which the gel sheets constituting each component are integrated and co-extruded, or a method in which the gel sheets constituting each layer are superposed and heat-sealed.
  • the co-extrusion method is more preferable because it is easy to obtain a high interlayer adhesive strength, easily form communication holes between layers, easily maintain high permeability, and is excellent in productivity.
  • the manufacturing method of the polyolefin porous membrane used for this invention includes the following steps (a) to (e).
  • Step of preparing a polyethylene resin solution After adding a molding solvent to the polyethylene resin, it is melt-kneaded to prepare a polyethylene resin solution.
  • the molding solvent is not particularly limited as long as it can sufficiently dissolve polyethylene.
  • Nonvolatile solvents such as liquid paraffin are preferred for obtaining.
  • the dissolution by heating is performed by a method in which the polyethylene composition is completely dissolved and stirred and uniformly mixed in an extruder.
  • the temperature varies depending on the polymer and solvent to be used when it is dissolved in an extruder or in a solvent while stirring, but it is preferably in the range of 140 to 250 ° C., for example.
  • the concentration of the polyethylene resin is 25 to 40 parts by weight, preferably 28 to 35 parts by weight, with the total of the polyethylene resin and the molding solvent being 100 parts by weight.
  • concentration of the polyethylene resin is within the above preferable range, a sufficient number of crystal nuclei for forming protrusions are formed, and a sufficient number of protrusions are formed.
  • swell and neck-in are suppressed at the T-shaped die exit when the polyethylene resin solution is extruded, and the moldability and self-supporting property of the extruded product are maintained.
  • the method of melt kneading is not particularly limited, but it is usually carried out by uniformly kneading in an extruder. This method is suitable for preparing a high-concentration solution of polyethylene as described above.
  • the melting temperature is preferably within the range of the melting point of polyethylene + 10 ° C. to + 100 ° C. In general, the melting temperature is preferably in the range of 160 to 230 ° C, more preferably in the range of 170 to 200 ° C.
  • the melting point refers to a value obtained by differential scanning calorimetry (DSC) based on JIS K7121.
  • the molding solvent may be added before the start of kneading, or may be added from the middle of the extruder during the kneading and further melt kneaded, but it is preferably added before the start of kneading and preliminarily formed into a solution. In melt kneading, it is preferable to add an antioxidant to prevent oxidation of polyethylene.
  • Step B Step of forming a gel-like molded product
  • a melt-kneaded polyethylene resin solution is extruded from a T-shaped die, cooled by a cooling roll having a surface from which the molding solvent has been removed, by means of a molding solvent removal means, and gel A shaped molding is formed.
  • Extrusion from the T-type die is performed by directly melting or kneading the polyethylene resin solution from the extruder or through another extruder.
  • a T-shaped die for a sheet having a rectangular base shape is usually used as the T-shaped die.
  • a gel-like molded product is formed by bringing both surfaces of a polyethylene resin solution extruded from a T-shaped die into contact with a pair of rotating cooling rolls set at a surface temperature of 20 ° C. to 40 ° C. with a refrigerant. .
  • the extruded polyethylene resin solution is preferably cooled to 25 ° C. or lower.
  • the present invention it is important for protrusion formation to control the cooling rate in a temperature range where crystallization is substantially performed.
  • the present inventors consider the mechanism by which the projections are formed in the present invention as follows. The resin solution of the melted polyethylene resin and the molding solvent is extruded from the T-die, and at the same time, the crystallization of polyethylene is started. The crystallization speed is increased by coming into contact with the cooling roll and rapidly cooling. At this time, a spherulite having a symmetric structure having a crystal nucleus is formed (FIG. 2).
  • the extruded polyethylene resin solution is cooled at a cooling rate of 10 ° C./second or more in a temperature range where the surface of the polyethylene resin solution is substantially crystallized to obtain a gel-like molded product.
  • the cooling rate is preferably 20 ° C./second or more, more preferably 30 ° C./second or more, and further preferably 50 ° C./second or more.
  • the cooling rate in order to control the cooling rate, it is important to remove as much as possible the forming solvent adhering to the surface of the cooling roll in contact with the polyethylene resin solution extruded from the T-die. That is, as shown in FIG. 4, the polyethylene resin solution is cooled by being wound around a rotating cooling roll to become a gel-like molded product, but is formed on the surface of the cooling roll after being separated as a gel-like molded product. The solvent for use is attached, and it usually comes into contact with the polyethylene resin solution again as it is. However, if a large amount of the forming solvent adheres to the surface of the cooling roll, the cooling rate becomes slow due to the heat insulating effect, and it becomes difficult to form protrusions. Therefore, it is important to remove the forming solvent as much as possible before the cooling roll comes into contact with the polyethylene resin solution again.
  • the method of removing the molding solvent from the cooling roll (also referred to as a molding solvent removing means) is not particularly limited, but the doctor blade is placed on the cooling roll so as to be parallel to the width direction of the gel-like molded product.
  • a method is preferably employed in which the solvent for molding is scraped off to the surface of the cooling roll immediately after passing through the blade until the gel-like molded product comes into contact.
  • it can be removed by means such as blowing with compressed air, suction, or a combination of these methods.
  • the method of scraping off using a doctor blade is preferable because it can be carried out relatively easily, and it is more preferable to use a plurality of doctor blades in order to improve the removal efficiency of the forming solvent.
  • the material of the doctor blade is not particularly limited as long as it is resistant to the molding solvent, but is preferably made of resin or rubber rather than metal. This is because in the case of metal, the cooling roll may be scratched.
  • the resin doctor blade include polyester, polyacetal, and polyethylene.
  • the cooling rolls are two cooling rolls arranged on both sides of the polyethylene resin solution, and the rolls preferably have different diameters. Moreover, the height of the installation position of the rotating shaft of two cooling rolls differs with respect to the height of the installation position of the discharge port of the polyethylene resin solution of a T type die.
  • the height of the installation position of the rotating shaft of the cooling roll having a small diameter is preferably closer to the arrangement position of the discharge port of the polyethylene resin solution of the T-die than the cooling roll having a large diameter. This is because the distance from the position where the polyethylene resin solution discharge port of the T-type die is arranged to the position where the polyethylene resin solution is grounded onto the cooling roll having a large diameter is made as small as possible.
  • the cooling rate in the temperature range where the crystallization of the polyethylene resin solution extruded from the T-shaped die is substantially performed can be 10 ° C./second or more. .
  • the thickness of the polyethylene resin solution during extrusion is preferably 1500 ⁇ m or less, more preferably 1000 ⁇ m or less, and still more preferably 800 ⁇ m or less.
  • the cooling rate on the surface on the side of the cooling roll is preferably not slow.
  • the gel-shaped molded product is stretched in the machine direction (MD) and the width direction (TD) to obtain a stretched molded product.
  • Stretching is performed by heating the gel-like molded product and performing normal tenter method, roll method, or a combination of these methods at a predetermined magnification in two directions of MD and TD.
  • Stretching may be either MD and TD simultaneous stretching (simultaneous biaxial stretching) or sequential stretching. In the sequential stretching, the order of MD and TD is not limited, and at least one of MD and TD may be stretched in multiple stages.
  • the stretching temperature is the melting point of the polyolefin composition + 10 ° C. or less.
  • the surface ratio is preferably 9 times or more, more preferably 16 to 400 times.
  • stretching at the same MD and TD magnification such as 3 ⁇ 3, 5 ⁇ 5, and 7 ⁇ 7 is preferable.
  • the surface magnification is in the above preferred range, stretching is sufficient and a highly elastic, high strength porous membrane can be obtained.
  • a desired air resistance can be obtained by adjusting the stretching temperature.
  • (D) Step of obtaining a porous molded product The stretched molded product is treated with a washing solvent to remove the remaining molding solvent to obtain a porous film.
  • Cleaning solvents include hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Volatile ones can be used.
  • These washing solvents are appropriately selected according to the molding solvent used for dissolving polyethylene, and used alone or in combination.
  • the cleaning method can be performed by a method of immersing and extracting in a cleaning solvent, a method of showering the cleaning solvent, a method of sucking the cleaning solvent from the opposite side of the stretched molded product, or a method of a combination thereof. Washing as described above is performed until the residual solvent in the stretched molded product, which is a stretched molded product, is less than 1 wt%. Thereafter, the cleaning solvent is dried.
  • the cleaning solvent can be dried by heat drying, air drying, or the like.
  • Step of obtaining a polyethylene porous membrane A porous molded product obtained by drying is heat-treated to obtain a polyethylene porous membrane.
  • any of a tenter method, a roll method, a rolling method, and a free method can be adopted.
  • the heat treatment is preferably performed within a temperature range of 90 to 150 ° C.
  • the heat treatment temperature is in the above preferred range, the resulting polyolefin porous membrane is sufficiently secured to reduce the heat shrinkage rate and the air resistance.
  • the residence time of the heat treatment step is not particularly limited, but is usually 1 second to 10 minutes, preferably 3 seconds to 2 minutes or less.
  • the heat treatment step from the viewpoint of heat shrinkage, it is preferable to shrink in at least one of MD and TD while fixing both the machine direction (MD) and the width direction (TD).
  • the contraction rate for contracting in at least one direction of MD and TD is preferably 0.01 to 50%, more preferably 3 to 20%.
  • a function providing step such as a corona treatment step or a hydrophilization step may be provided as necessary.
  • the laminated porous membrane in the present invention is a laminated porous membrane in which the modified porous layer A is laminated on one side of the polyolefin porous membrane and the modified porous layer B is laminated on the opposite side.
  • the modified porous layer A and the modified porous layer B may be the same porous layer or may be different. However, it is important that at least the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more.
  • the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more, it is changed to the side where the stress is more strongly applied by the contact with the roll or bar in the subsequent process such as the slit process or the transport process.
  • the porous porous layer A is preferably laminated because the effect of the present invention is exhibited.
  • the modified porous layer referred to in the present invention imparts or improves at least one function such as heat resistance, adhesion to an electrode material, and electrolyte permeability.
  • At least the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more.
  • a binder having a tensile strength of 5 N / mm 2 or more By using a binder having a tensile strength of 5 N / mm 2 or more, a laminated porous membrane having an extremely excellent 0 ° peel strength can be obtained by the synergistic effect of the protrusions present on the surface of the polyolefin porous membrane and the tensile strength of the binder.
  • the air permeation resistance of the laminated porous membrane of the present invention is not significantly increased. This is because sufficient 0 ° peel strength can be obtained without allowing a large amount of binder to penetrate into the pores of the polyolefin porous membrane.
  • the lower limit of the tensile strength of the binder is preferably 10 N / mm 2, more preferably 20 N / mm 2, more preferably 30 N / mm 2. There is no particular upper limit, but 100 N / mm 2 is sufficient.
  • the tensile strength of the binder refers to a value measured by the method described later.
  • the use tensile strength of 5N / mm 2 or more binders in the present invention although the tensile strength is not particularly limited as long as 5N / mm 2 or more, e.g., polyvinyl alcohol, cellulose ether resins, and acrylic resins .
  • the cellulose ether resin include carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), carboxyethyl cellulose, methyl cellulose, ethyl cellulose, cyanethyl cellulose, oxyethyl cellulose, and the like.
  • the acrylic resin a cross-linked acrylic resin is preferable. Commercially available aqueous solutions or aqueous dispersions can also be used.
  • Examples of commercially available products include “POVACOAT” (registered trademark) manufactured by Nisshin Kasei Co., Ltd., “Jurimer” (registered trademark) AT-510, ET-410, FC-60 manufactured by Toa Gosei Co., Ltd. SEK-301, UW-223SX, UW-550CS, DIC Corporation WE-301, EC-906EF, CG-8490 manufactured by Taisei Fine Chemical Co., Ltd.
  • polyvinyl alcohol and acrylic resins having electrode adhesion, high affinity with non-aqueous electrolytes, suitable heat resistance, and relatively high tensile strength are preferable.
  • the binder used for the modified porous layer B may be the same as or different from that of the modified porous layer A.
  • heat-resistant resins such as polyamideimide resin, polyimide resin, and polyamide resin are used
  • fluorine-based resins such as polyvinylidene fluoride and its derivatives are used. be able to.
  • the coating solution in the present specification includes a binder having a tensile strength of 5 N / mm 2 or more, inorganic particles, and a solvent capable of dissolving or dispersing the binder, and is used for forming a modified porous layer.
  • the upper limit of the amount of inorganic particles added is preferably 98% by weight, more preferably 95% by weight.
  • the lower limit is preferably 80% by weight, more preferably 85% by weight.
  • Inorganic particles include calcium carbonate, calcium phosphate, amorphous silica, crystalline glass filler, kaolin, talc, titanium dioxide, alumina, silica-alumina composite oxide particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite , Molybdenum sulfide, mica, boehmite and the like.
  • the heat-resistant crosslinked polymer particles include crosslinked polystyrene particles, crosslinked acrylic resin particles, and crosslinked methyl methacrylate particles.
  • the shape of the inorganic particles includes a true sphere shape, a substantially spherical shape, a plate shape, a needle shape, and a polyhedral shape, but is not particularly limited.
  • the average particle size of these inorganic particles is preferably 1.5 to 50 times the average pore size of the polyolefin porous membrane. More preferably, it is 2.0 times or more and 20 times or less.
  • the average particle diameter of the particles is within the above-mentioned preferable range, the air resistance is maintained without blocking the pores of the polyolefin porous membrane in a state where the heat-resistant resin and the particles are mixed, and as a result, the battery is assembled. In the process, the particles are prevented from falling off and causing a serious defect of the battery.
  • the binder has at least the role of bonding inorganic particles and the role of bonding the polyolefin porous membrane and the modified porous layer.
  • the solvent include water, alcohols, acetone, n-methylpyrrolidone, and the like.
  • the solid content concentration of the coating solution is not particularly limited as long as it can be uniformly applied, but is preferably 50% by weight or more and 98% by weight or less, more preferably 80% by weight or more and 95% by weight or less.
  • the solid content concentration of the coating solution is in the above preferred range, the modified porous layer is prevented from becoming brittle, and a sufficient peel strength of 0 ° of the modified porous layer can be obtained.
  • the film thickness of the modified porous layer is preferably 1 to 5 ⁇ m, more preferably 1 to 4 ⁇ m, and still more preferably 1 to 3 ⁇ m.
  • the laminated porous film obtained by laminating the modified porous layer can ensure the film breaking strength and insulation when melted / shrinked at the melting point or higher, In addition, a sufficient hole blocking function can be obtained and abnormal reactions can be prevented.
  • the winding volume can be suppressed, which is suitable for increasing the battery capacity. In addition, suppressing curling leads to improved productivity in the battery assembly process.
  • the film thicknesses of the modified porous layers A and B may be the same or different, but the difference in film thickness is preferably 0.5 ⁇ m or less, more preferably 0.3 ⁇ m or less.
  • the porosity of the modified porous layer is preferably 30 to 90%, more preferably 40 to 70% from the viewpoint of battery characteristics.
  • the desired porosity can be obtained by appropriately adjusting the concentration of inorganic particles, the binder concentration, and the like.
  • the upper limit of the thickness of the laminated porous membrane obtained by laminating the modified porous layer is preferably 25 ⁇ m, more preferably 20 ⁇ m.
  • the lower limit is preferably 6 ⁇ m or more, more preferably 7 ⁇ m or more.
  • the air resistance of the laminated porous membrane is one of the most important characteristics, and is preferably 50 to 600 sec / 100 cc Air, more preferably 100 to 500 sec / 100 cc Air, and further preferably 100 to 400 sec / 100 cc Air.
  • the desired air resistance can be obtained by adjusting the porosity of the modified porous layer and adjusting the degree of penetration of the binder into the polyolefin porous membrane. If the air permeability resistance of the laminated porous membrane is within the above-mentioned preferable range, sufficient insulation can be obtained, and foreign matter clogging, short-circuiting and membrane breakage can be prevented. Further, by suppressing the film resistance, charge / discharge characteristics and life characteristics within a practically usable range can be obtained.
  • Lamination method of the modified porous layer on the polyolefin porous membrane Next, the lamination method of the modified porous layer on the polyolefin porous membrane in the present invention will be described.
  • a method of laminating the modified porous layer on the polyolefin porous membrane a known method can be used. Specifically, the coating solution is applied to the polyolefin porous film by a method described later so as to have a predetermined film thickness, and dried under conditions of a drying temperature of 40 to 80 ° C. and a drying time of 5 seconds to 60 seconds. Can be obtained by the method.
  • a coating solution in which the binder is soluble and dissolved in a solvent miscible with water is laminated on a predetermined polyolefin porous membrane using the coating method described later, and placed in a specific humidity environment to mix the binder and water. It is also possible to use a method in which the solvent to be phase-separated and further fed into a water bath (coagulation bath) to coagulate the binder.
  • Examples of methods for applying the coating liquid include dip method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, Mayer bar coating method, pipe doctor method , Blade coating method, die coating method and the like, and these methods can be carried out alone or in combination.
  • the laminated porous membrane of the present invention is desirably stored in a dry state, but when it is difficult to store in a completely dry state, it is preferable to perform a vacuum drying treatment at 100 ° C. or lower immediately before use.
  • the laminated porous membrane of the present invention includes a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-zinc battery, a silver-zinc battery, a secondary battery such as a lithium secondary battery, a lithium polymer secondary battery, and a plastic film capacitor, although it can be used as a separator for ceramic capacitors, electric double layer capacitors, etc., it is particularly preferred to be used as a separator for lithium ion secondary batteries.
  • a lithium ion secondary battery will be described as an example.
  • a positive electrode and a negative electrode are laminated via a separator, and the separator contains an electrolytic solution (electrolyte).
  • the structure of the electrode is not particularly limited, and may be a known structure.
  • the positive electrode usually has a current collector and a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium ions formed on the surface of the current collector.
  • the positive electrode active material include transition metal oxides, composite oxides of lithium and transition metals (lithium composite oxides), inorganic compounds such as transition metal sulfides, and the like.
  • the transition metal include V, Mn, Fe, Co, and Ni.
  • Preferred examples of the lithium composite oxide in the positive electrode active material include lithium nickelate, lithium cobaltate, lithium manganate, and a layered lithium composite oxide based on an ⁇ -NaFeO 2 type structure.
  • the negative electrode has a current collector and a negative electrode active material layer including a negative electrode active material formed on the surface of the current collector.
  • the negative electrode active material include carbonaceous materials such as natural graphite, artificial graphite, cokes, and carbon black.
  • the electrolytic solution can be obtained by dissolving a lithium salt in an organic solvent.
  • Lithium salts include 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 B 10 Cl 10 , LiN (C 2 F 5 SO 2 ) 2, LiPF 4 (CF 3) 2, LiPF 3 (C 2 F5) 3, lower aliphatic carboxylic acid lithium salts, and the like LiAlC l4 like. These may be used alone or in admixture of two or more.
  • organic solvent examples include high boiling point and high dielectric constant organic solvents such as ethylene carbonate, propylene carbonate, ethyl methyl carbonate, and ⁇ -butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, dioxolane, dimethyl carbonate, diethyl carbonate, and the like.
  • organic solvents having a low boiling point and a low viscosity These may be used alone or in admixture of two or more.
  • a high dielectric constant organic solvent has a high viscosity
  • a low viscosity organic solvent has a low dielectric constant. Therefore, it is preferable to use a mixture of both.
  • the separator of the present invention can be impregnated with an electrolytic solution to impart ion permeability to the separator.
  • the impregnation treatment is performed by immersing the microporous membrane in an electrolytic solution at room temperature.
  • a positive electrode sheet, a separator (composite porous membrane), and a negative electrode sheet are laminated in this order, and this laminate is wound from one end to form a wound electrode element.
  • a battery can be obtained by inserting this electrode element into a battery can, impregnating with the above electrolyte, and caulking a battery lid also serving as a positive electrode terminal provided with a safety valve via a gasket.
  • the measured value in an Example is a value measured with the following method.
  • protrusions The number and size of protrusions were measured after stabilizing the light source using a confocal microscope (HD100 manufactured by Lasertec) installed on a base isolation table.
  • a confocal microscope (HD100 manufactured by Lasertec) installed on a base isolation table.
  • A-side any one side of the battery separator obtained in the examples and comparative examples.
  • the surface on which the square frame was drawn was placed on the sample stage, and was fixed to the sample stage using an electrostatic contact apparatus attached to the confocal microscope.
  • a TOD 3 is displayed on a monitor as a two-dimensional image (referred to as a REAL screen in this apparatus), and the ring-shaped trace is displayed.
  • the position of the sample stage was adjusted so that the darkest part of was positioned almost at the center of the monitor screen.
  • the object of the projection height measurement was such that the major axis of the ring-shaped trace derived from the polyethylene spherulites was 0.2 mm or more.
  • the cursor was placed on both ends of the ring in the major axis direction in the two-dimensional image, and the length was read.
  • FIG. 1 schematically shows the evaluation method.
  • 1 is a laminated sample
  • 2 is a polyolefin porous membrane
  • 3 is a modified porous layer
  • 4 is a double-sided pressure-sensitive adhesive tape
  • 5 and 5 'are aluminum plates and the arrows in the figure are tensile directions.
  • a double-sided adhesive tape is attached to one side of an aluminum plate 5 ′ having a length of 100 mm, a width of 15 mm, and a thickness of 0.5 mm, so that 20 mm overlaps from the end of one side of the 25 mm long sample side of the aluminum plate 5. Pasted on. Thereafter, the aluminum plate 5 and the aluminum plate 5 ′ sandwiching the sample are attached to a tensile tester (Autograph AGS-J 1kN, manufactured by Shimadzu Corporation), and the aluminum plate 5 and the aluminum plate 5 ′ are respectively parallel and opposite to each other. The tensile strength was measured at 10 mm / min when the modified porous layer was peeled off.
  • Average pore diameter The average pore diameter of the polyolefin porous membrane was measured by the following method. The sample was fixed on the measurement cell using double-sided tape, platinum or gold was vacuum-deposited for several minutes, and the surface of the film was subjected to SEM measurement at an appropriate magnification. Arbitrary ten places were selected on the image obtained by SEM measurement, and the average value of the pore diameters at these ten places was taken as the average pore diameter of the sample.
  • Air permeability resistance (sec / 100ccAir) Using a Gurley Densometer Type B manufactured by Tester Sangyo Co., Ltd., fix the polyolefin porous film or laminated porous film so that there is no wrinkle between the clamping plate and the adapter plate, and measure according to JIS P8117 did.
  • the sample was a 10 cm square, the measurement points were a total of 5 points at the center and 4 corners of the sample, and the average value was used as the air resistance. When the length of one side of the sample is less than 10 cm, a value obtained by measuring five points at intervals of 5 cm may be used.
  • the increase width of the air permeability resistance was obtained from the following formula.
  • the peeling defects were counted and evaluated according to the following criteria.
  • the evaluation area was 100 mm wide ⁇ 500 m long. (When the width was less than 100 mm, the length was adjusted so that the same evaluation area was obtained.)
  • UHMWPE ultrahigh molecular weight polyethylene
  • HDPE high density polyethylene
  • a polyethylene composition (melting point: 135 ° C.) obtained by adding 0.375 parts by weight of an antioxidant was obtained.
  • 30 parts by weight of this polyethylene composition was put into a twin screw extruder. 70 parts by weight of liquid paraffin was supplied from the side feeder of this twin screw extruder, melt kneaded, and a polyethylene resin solution was prepared in the extruder.
  • the polyethylene resin solution was placed at the tip of the extruder and extruded from a T-die at 190 ° C. with an extrusion thickness of 825 ⁇ m, and the polyethylene resin solution extruded into a film was placed on both sides (see FIG. 4).
  • the gel-like molded object was formed, taking up with the two cooling rolls which maintained the cooling water temperature inside a cooling roll at 25 degreeC.
  • one polyester doctor blade is gelled between the point where the gel-like molded product is separated from the cooling roll and the point where the polyethylene resin solution extruded from the T-shaped die contacts the cooling roll.
  • the liquid paraffin adhering on the cooling roll was scraped off so as to be in contact with the cooling roll in parallel with the width direction of the shaped molding.
  • the gel-like molded product was simultaneously biaxially stretched 5 ⁇ 5 times while adjusting the temperature so as to obtain a desired air permeability resistance to obtain a stretched molded product.
  • the obtained stretched molded product was washed with methylene chloride to remove residual liquid paraffin and dried to obtain a porous molded product. After that, the porous film is held on the tenter, reduced in width by 10% only in the TD (width direction) direction, heat treated at 90 ° C.
  • Polyamideimide resin solution alumina particles having an average particle size of 0.5 ⁇ m, and N-methyl-2-pyrrolidone were blended in a weight ratio of 26:34:40, respectively, and zirconium oxide beads (“Traceram” manufactured by Toray Industries, Inc.) (Registered trademark) beads, 0.5 mm in diameter) were placed in a polypropylene container and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (b).
  • zirconium oxide beads (“Traceram” manufactured by Toray Industries, Inc.) (Registered trademark) beads, 0.5 mm in diameter) were placed in a polypropylene container and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits,
  • the coating liquid (a) was applied to one side (referred to as side A) of the polyethylene porous membrane by a gravure coating method to a thickness of 2 ⁇ m after drying, and dried by passing through a hot air drying oven at 50 ° C. for 10 seconds. .
  • 2.5 ⁇ m in thickness after drying was applied to the opposite surface (referred to as B surface), and after passing through a humidity control zone having a temperature of 25 ° C. and an absolute humidity of 12 g / m 3 for 5 seconds, N-methyl-2- It was immersed for 10 seconds in an aqueous solution containing 5% by weight of pyrrolidone.
  • it was dried by passing through a hot air drying furnace at 70 ° C. to obtain a laminated porous membrane having a final thickness of 20.5 ⁇ m.
  • Example 2 Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2 million and high density polyethylene (HDPE) having a weight average molecular weight of 350,000 was changed to 10:90 (weight% ratio). Thus, a laminated porous membrane was obtained.
  • UHMWPE ultra high molecular weight polyethylene
  • HDPE high density polyethylene
  • Example 3 Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) with a weight average molecular weight of 2 million and high density polyethylene (HDPE) with a weight average molecular weight of 350,000 was changed to 20:80 (weight% ratio). Thus, a laminated porous membrane was obtained.
  • UHMWPE ultra high molecular weight polyethylene
  • HDPE high density polyethylene
  • Example 4 Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) with a weight average molecular weight of 2 million and high density polyethylene (HDPE) with a weight average molecular weight of 350,000 was changed to 30:70 (weight% ratio). Thus, a laminated porous membrane was obtained.
  • UHMWPE ultra high molecular weight polyethylene
  • HDPE high density polyethylene
  • Example 5 Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2 million and high density polyethylene (HDPE) having a weight average molecular weight of 350,000 was changed to 40:60 (weight% ratio). Thus, a laminated porous membrane was obtained.
  • UHMWPE ultra high molecular weight polyethylene
  • HDPE high density polyethylene
  • Example 6 A laminated porous membrane was obtained in the same manner as in Example 1 except that two polyester doctor blades were applied to the cooling rolls at intervals of 20 mm for both of the two cooling rolls.
  • Example 7 A laminated porous membrane was obtained in the same manner as in Example 1 except that three polyester doctor blades were applied to the cooling rolls at intervals of 20 mm for each of the two cooling rolls.
  • Example 8 Two-part curable aqueous acrylic urethane resin (solid content concentration 45% by mass) composed of aqueous acrylic polyol and water-dispersible polyisocyanate (curing agent), alumina particles having an average particle size of 0.5 ⁇ m, and ion-exchanged water are respectively 10:40: 50 parts by weight, zirconium oxide beads (Toray Industries, Inc., “Traceram” (registered trademark) beads, 0.5 mm in diameter) are placed in a polypropylene container, and paint shaker (Toyo Seiki Co., Ltd.) ) For 6 hours. Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (c). A modified porous layer was laminated on both sides in the same manner as in Example 1 except that the coating solution (a) was changed to the coating solution (c) to obtain a laminated porous membrane having a final thickness of 20.5 ⁇ m.
  • curing agent aqueous acrylic polyo
  • POVACOAT polyvinyl alcohol, acrylic acid and methyl methacrylate
  • the coating liquid (a) was applied in the same manner as in Example 1 except that the coating liquid (d) was changed, and the modified porous layer was laminated on both surfaces to obtain a laminated porous film having a final thickness of 20.5 ⁇ m.
  • Example 10 KF polymer # 1120 (manufactured by Kureha Chemical Industry Co., Ltd., polyvinylidene fluoride resin solution (melting point 175 ° C., 12% N-methylpyrrolidone solution)) and alumina particles having an average particle size of 0.5 ⁇ m, N-methyl-2-pyrrolidone Were mixed in a weight ratio of 14:19:67, respectively, and placed in a polypropylene container together with zirconium oxide beads ("Traceram” (registered trademark) beads manufactured by Toray Industries, Inc., diameter 0.5 mm), and a paint shaker (( (Toyo Seiki Seisakusho Co., Ltd.) for 6 hours.
  • zirconium oxide beads (“Traceram” (registered trademark) beads manufactured by Toray Industries, Inc., diameter 0.5 mm)
  • the coating liquid (b) was coated in the same manner as in Example 1 except that the coating liquid (e) was replaced, and the modified porous layer was laminated on both surfaces to obtain a laminated porous film having a final thickness of 20.5 ⁇ m.
  • Example 11 A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 35 ° C.
  • Example 12 A laminated porous membrane having a final thickness of 24.5 ⁇ m was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 20 ⁇ m.
  • Example 13 A laminated porous membrane having a final thickness of 16.5 ⁇ m was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 12 ⁇ m.
  • Example 14 A laminated porous membrane having a final thickness of 13.5 ⁇ m was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 9 ⁇ m.
  • Example 15 A laminated porous membrane was formed in the same manner as in Example 1 except that 26 parts by weight of the polyethylene composition was charged into a twin screw extruder, 74 parts by weight of liquid paraffin was supplied from the side feeder of the twin screw extruder, and melt kneaded. Obtained.
  • Example 16 A laminated porous membrane was formed in the same manner as in Example 1 except that 35 parts by weight of a polyethylene composition was charged into a twin screw extruder, 65 parts by weight of liquid paraffin was supplied from a side feeder of the twin screw extruder, and melt kneaded. Obtained.
  • Example 17 A coating solution (f) was prepared by replacing the alumina particles with titanium oxide particles (average particle size 0.38 ⁇ m) in the coating solution (a).
  • a laminated porous membrane was obtained in the same manner as in Example 1 except that the coating solution (f) was used instead of the coating solution (a).
  • Example 18 A coating liquid (g) was prepared by replacing the alumina particles in the coating liquid (a) with plate-like boehmite fine particles (average particle diameter: 1.0 ⁇ m). A laminated porous membrane was obtained in the same manner as in Example 1 except that the coating solution (g) was used instead of the coating solution (a).
  • Example 19 A laminated porous membrane was obtained in the same manner as in Example 1 except that the coating liquid (a) was used on both sides.
  • Comparative Example 1 The polyethylene resin solution extruded from the T-shaped die is cooled with two cooling rolls, and when obtaining a gel-like molded product, neither the two cooling rolls use a doctor blade, but scrape the liquid paraffin adhering to the cooling roll. A laminated porous membrane was obtained in the same manner as in Example 1 except that it was not dropped.
  • HDPE high density polyethylene
  • Comparative Example 3 A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 0 ° C. and the doctor blade was not used.
  • Comparative Example 4 A laminated porous membrane was obtained in the same manner as in Example 1 except that the polyethylene resin solution extruded from the T-shaped die was immersed in water kept at 25 ° C. for 1 minute instead of being cooled with a cooling roll.
  • Comparative Example 5 50 parts by weight of the polyethylene composition used in Example 1 was put into a twin screw extruder, 50 parts by weight of liquid paraffin was supplied from the side feeder of the twin screw extruder, melted and kneaded, and the polyethylene resin was fed into the extruder. Although a solution was prepared and extrusion from a T-shaped die was attempted, it was not possible to extrude into a uniform film.
  • Comparative Example 6 A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 50 ° C.
  • Polyamideimide resin solution alumina particles having an average particle diameter of 0.5 ⁇ m, and N-methyl-2-pyrrolidone were blended in a weight ratio of 13:47:40, respectively, and zirconium oxide beads (“Traceram (registered trademark) manufactured by Toray Industries, Inc.) were mixed. ) Beads ”, 0.5 mm in diameter) and placed in a polypropylene container and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (h). A laminated porous membrane having a final thickness of 20.5 ⁇ m was obtained in the same manner as in Example 1 except that the coating solution (a) was changed to the coating solution (h).
  • Table 1 shows the production conditions of Examples 1 to 19 and Comparative Examples 1 to 7.
  • Table 2 shows the characteristics of the polyolefin porous membrane and the laminated porous membrane obtained in Examples 1 to 19 and Comparative Examples 1 to 7.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Cell Separators (AREA)
  • Laminated Bodies (AREA)
  • Extrusion Moulding Of Plastics Or The Like (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

This laminated porous film is obtained by laminating, with a modified porous layer (A), one surface of a polyolefin porous film, and laminating, with a modified porous layer (B), an opposite surface of the polyolefin porous film. The polyolefin porous film has a film thickness of not more than 25 µm, and has protrusions which comprise polyolefin, which satisfy 5 µm ≤ W ≤ 50 µm (W being the size of the protrusions) and 0.5 µm ≤ H (H being the height of the protrusion), and which are irregularly dispersed on both surfaces of the polyolefin porous film at a density in the range of 3/cm2 to 200/cm2 inclusive per surface. At least the modified porous layer (A) includes inorganic particles and a binder having a tensile strength of at least 5 N/mm2. The peel strength between the polyolefin porous film and the modified porous layers is extremely high, and thus the laminated porous film is suitable for high-speed processing.

Description

積層多孔質膜及びその製造方法Laminated porous membrane and method for producing the same
　本発明は、改質多孔層の積層に適したポリオレフィン多孔質膜と改質多孔層とを有する積層多孔質膜及びその製造方法に関する。本発明の積層多孔質膜はリチウムイオン電池用セパレータとして有用な電池用セパレータである。 The present invention relates to a laminated porous membrane having a polyolefin porous membrane suitable for lamination of a modified porous layer and a modified porous layer, and a method for producing the same. The laminated porous membrane of the present invention is a battery separator useful as a lithium ion battery separator.
　熱可塑性樹脂からなる微多孔膜は、物質の分離膜や選択透過膜及び隔離膜等として広く用いられている。例えば、リチウムイオン二次電池、ニッケル－水素電池、ニッケル‐カドミウム電池、ポリマー電池に用いる電池用セパレータや、電気二重層コンデンサ用セパレータ、逆浸透濾過膜、限外濾過膜、精密濾過膜等の各種フィルター、透湿防水衣料、医療用材料等などである。特にリチウムイオン二次電池用セパレータとしては、電解液含浸によりイオン透過性を有し、電気絶縁性に優れ、電池異常昇温時に１２０～１５０℃程度の温度において電流を遮断し、過度の昇温を抑制する孔閉塞効果を備えているポリエチレン製多孔質膜が好適に使用されている。しかしながら、何らかの原因で孔閉塞後も昇温が続く場合、膜の収縮により破膜を生じることがある。この現象はポリエチレン製微多孔膜に限定された現象ではなく、他の熱可塑性樹脂を用いた微多孔膜の場合においても、その多孔質膜を構成する樹脂の融点以上では避けることができない。 A microporous membrane made of a thermoplastic resin is widely used as a material separation membrane, a permselective membrane, a separation membrane, and the like. For example, battery separators for lithium ion secondary batteries, nickel-hydrogen batteries, nickel-cadmium batteries, polymer batteries, separators for electric double layer capacitors, reverse osmosis filtration membranes, ultrafiltration membranes, microfiltration membranes, etc. Filters, moisture permeable waterproof clothing, medical materials, etc. Especially as a separator for lithium ion secondary battery, it has ion permeability by impregnating with electrolyte, has excellent electrical insulation, cuts off current at a temperature of about 120-150 ° C when the battery temperature rises abnormally, and excessive temperature rise A polyethylene porous membrane having a pore closing effect that suppresses the above is suitably used. However, if the temperature continues to rise even after the hole is closed for some reason, a film breakage may occur due to the contraction of the film. This phenomenon is not limited to a polyethylene microporous film, and even in the case of a microporous film using another thermoplastic resin, it cannot be avoided at a temperature equal to or higher than the melting point of the resin constituting the porous film.
　特にリチウムイオン電池用セパレータは電池特性、電池生産性及び電池安全性に深く関わっており、機械的特性、耐熱性、透過性、寸法安定性、孔閉塞特性（シャットダウン特性）、溶融破膜特性（メルトダウン特性）等が要求される。さらに、電池のサイクル特性向上のためにセパレータと電極材料との密着性向上や生産性向上のための電解液浸透性の向上などが要求される。 In particular, lithium-ion battery separators are deeply involved in battery characteristics, battery productivity, and battery safety. Mechanical characteristics, heat resistance, permeability, dimensional stability, pore clogging characteristics (shutdown characteristics), melt-breaking characteristics ( Melt down characteristics) are required. Furthermore, in order to improve the cycle characteristics of the battery, it is required to improve the adhesion between the separator and the electrode material and the electrolyte permeability to improve the productivity.
　そのため、これまでにポリオレフィン多孔質膜に改質多孔層を積層する検討がなされている。改質多孔層に含まれる樹脂としては、耐熱性及び電解液浸透性を併せ持つポリアミドイミド樹脂、ポリイミド樹脂、ポリアミド樹脂、電極密着性に優れたフッ素系樹脂などが好適に用いられている。また、比較的簡易な水洗工程、乾燥工程を用いて改質多孔層が積層できる水溶性または水分散性バインダーも広く用いられている。
　なお、本発明でいう改質多孔層とは、耐熱性、電極材料との密着性、電解液浸透性などの機能を少なくとも一つ以上、付与または向上させる樹脂を含む層をいう。 Therefore, studies have been made so far to laminate a modified porous layer on a polyolefin porous membrane. As the resin contained in the modified porous layer, polyamideimide resin, polyimide resin, polyamide resin, fluorine resin excellent in electrode adhesion, etc. having both heat resistance and electrolyte solution permeability are preferably used. In addition, a water-soluble or water-dispersible binder capable of laminating a modified porous layer using a relatively simple washing step and drying step is also widely used.
The modified porous layer in the present invention refers to a layer containing a resin that imparts or improves at least one function such as heat resistance, adhesion to an electrode material, and electrolyte permeability.
　特許文献１では、厚み９μｍのポリエチレン製多孔質膜にポリフッ化ビニリデンを塗布し、ポリフッ化ビニリデンの一部がポリエチレン製多孔膜の細孔に適度に食い込みアンカー効果を発現させることによって、ポリエチレン製多孔膜とポリフッ化ビニリデンの塗布層界面での剥離強度（Ｔ型剥離強度）が１．０～５．３Ｎ／２５ｍｍのとなる複合多孔質膜を開示している。 In Patent Document 1, polyvinylidene fluoride is applied to a polyethylene porous film having a thickness of 9 μm, and a part of the polyvinylidene fluoride appropriately bites into the pores of the polyethylene porous film so as to develop an anchor effect. A composite porous membrane is disclosed in which the peel strength (T-type peel strength) at the interface between the membrane and the polyvinylidene fluoride coating layer is 1.0 to 5.3 N / 25 mm.
　特許文献２では、厚みが１６μｍのコロナ放電処理されたポリエチレン製多孔質膜に自己架橋性のアクリル樹脂と板状ベーマイトを含む耐熱多孔層を設け、ポリエチレン製多孔質膜と耐熱多孔層の１８０°での剥離強度（Ｔ型剥離強度）が１．１～３．０Ｎ／１０ｍｍのセパレータが開示されている。 In Patent Document 2, a heat resistant porous layer containing a self-crosslinking acrylic resin and plate boehmite is provided on a corona discharge-treated polyethylene porous film having a thickness of 16 μm, and the polyethylene porous film and the heat resistant porous layer are 180 °. Discloses a separator having a peel strength (T-type peel strength) of 1.1 to 3.0 N / 10 mm.
　特許文献３の実施例１では、粘度平均分子量２０万のポリエチレン、４７．５質量部と粘度平均分子量４０万のポリプロピレン２．５質量部、および、酸化防止剤からなる組成物５０質量部と流動パラフィン５０質量部からなるポリエチレン樹脂溶液を押出機から２００℃で押出し、２５℃に温調された冷却ロールで引き取りながら、ゲル状成形物を得て、次いで７×６．４倍になるように二軸延伸を行い、ポリオレフィン樹脂多孔膜を得る。次いでこのポリオレフィン樹脂多孔質膜の表面にポリビニルアルコール、アルミナ粒子からなる塗布層を積層して得た多層多孔質膜が開示されている。 In Example 1 of Patent Document 3, polyethylene having a viscosity average molecular weight of 200,000, 47.5 parts by mass, 2.5 parts by mass of polypropylene having a viscosity average molecular weight of 400,000, and 50 parts by mass of a composition comprising an antioxidant and flowing A polyethylene resin solution consisting of 50 parts by mass of paraffin was extruded from an extruder at 200 ° C., and was taken up with a cooling roll adjusted to 25 ° C., to obtain a gel-like molded product, and then 7 × 6.4 times. Biaxial stretching is performed to obtain a polyolefin resin porous membrane. Next, a multilayer porous membrane obtained by laminating a coating layer made of polyvinyl alcohol and alumina particles on the surface of the polyolefin resin porous membrane is disclosed.
　特許文献４の実施例６では、重量平均分子量４１５万と重量平均分子量５６万、重量比１：９のポリエチレン組成物３０重量％と流動パラフィンとデカリンの混合溶媒７０重量％のポリエチレン樹脂溶液を押出機から１４８℃で押出し、水浴中で冷却し、ゲル状成形物を得て、次いで５．５×１１．０倍になるように二軸延伸を行い、ポリエチレン多孔質膜を得る。次いでさらにこのポリエチレン多孔質膜の表面にメタ型全芳香族ポリアミドとアルミナ粒子からなる塗布層を積層して得た非水系二次電池用セパレータが開示されている。 In Example 6 of Patent Document 4, a polyethylene resin solution having a weight average molecular weight of 41.5 million, a weight average molecular weight of 560,000, a polyethylene composition of 30% by weight and a mixed solvent of liquid paraffin and decalin of 70% by weight is extruded. Extruded from the machine at 148 ° C., cooled in a water bath to obtain a gel-like molded article, and then biaxially stretched so as to be 5.5 × 11.0 times to obtain a polyethylene porous film. Next, a separator for a non-aqueous secondary battery obtained by further laminating a coating layer made of a meta-type wholly aromatic polyamide and alumina particles on the surface of the polyethylene porous membrane is disclosed.
　特許文献５の実施例１では、Ｍｖ（粘度平均分子量）７０万のホモポリマーのポリエチレン４７質量部とＭｖ２５万のホモポリマーのポリエチレン４６質量部とＭｖ４０万のホモポリマーのポリプロピレン７質量部とを、タンブラーブレンダーを用いてドライブレンドした。得られた純ポリマー混合物９９質量％に、酸化防止剤としてペンタエリスリチル‐テトラキス‐［３‐（３，５‐ジ‐ｔ‐ブチル‐４‐ヒドロキシフェニル）プロピオネート］を１質量％添加し、再度タンブラーブレンダーを用いてドライブレンドしたポリエチレン組成物を溶融混練し、表面温度２５℃に制御された冷却ロール上に押出しキャストすることにより、厚さ２０００μｍのシート状のポリオレフィン組成物を得て、次いで７×７倍になるように二軸延伸を行なって得たポリエチレン多孔質膜に焼成カオリンとラテックスの水分散液を塗工することによって得られる多層多孔膜が開示されている。 In Example 1 of Patent Document 5, 47 parts by mass of homopolymer polyethylene having an Mv (viscosity average molecular weight) of 700,000, 46 parts by mass of polyethylene having an Mv of 250,000, and 7 parts by mass of polypropylene having an Mv of 400,000, Dry blended using a tumbler blender. 1% by mass of pentaerythrityl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] as an antioxidant was added to 99% by mass of the obtained pure polymer mixture, and again A polyethylene composition that has been dry-blended using a tumbler blender is melt-kneaded and extruded and cast onto a cooling roll controlled at a surface temperature of 25 ° C. to obtain a sheet-like polyolefin composition having a thickness of 2000 μm. A multilayer porous membrane obtained by applying an aqueous dispersion of calcined kaolin and latex to a polyethylene porous membrane obtained by biaxial stretching so as to be × 7 times is disclosed.
特開２０１２‐０４３７６２号公報JP 2012-037662 A 再公表２０１０‐１０４１２７号公報Republished 2010-104127 特許第４９３１０８３号公報Japanese Patent No. 4931083 特許第４４６００２８号公報Japanese Patent No. 4460028 特開２０１１‐０００８３２号公報JP 2011-000832 A
　今後、電池容量の向上のため、電極シートのみならず、セパレータにおいても容器内に充填できる面積を増加させる必要があり、よりいっそうの薄膜化が進むことが予測されている。しかしながら、多孔質膜の薄膜化が進むと平面方向に変形しやすくなるため、加工中やスリット工程あるいは電池組み立て工程において、薄膜の多孔質膜に積層した改質多孔層が剥離することがあり、安全性の確保がより困難となる。 In the future, in order to improve the battery capacity, it is necessary to increase not only the electrode sheet, but also the separator, the area that can be filled in the container, and it is predicted that further thinning will progress. However, as the porous film becomes thinner, it tends to be deformed in the plane direction, so the modified porous layer laminated on the thin porous film may be peeled off during processing or in the slit process or battery assembly process. Ensuring safety is more difficult.
　また、低コスト化に対応するため、電池組み立て工程を高速化することが予想される。高速加工においても改質多孔層の剥離等のトラブルが少ないセパレータを得るために、ポリオレフィン多孔質膜と改質多孔層との間に高速加工に耐えうる高い密着性が求められる。しかしながら、密着性の向上を図るために、ポリオレフィン多孔質膜に改質多孔層に含まれる樹脂を十分に浸透させると、透気抵抗度の上昇幅が大きくなってしまうという問題がある。 Also, it is expected that the battery assembly process will be accelerated in order to reduce costs. In order to obtain a separator with few troubles such as peeling of the modified porous layer even in high-speed processing, high adhesion that can withstand high-speed processing is required between the polyolefin porous membrane and the modified porous layer. However, when the polyolefin porous membrane is sufficiently infiltrated with the resin contained in the modified porous layer in order to improve the adhesion, there is a problem that the increase in the air resistance increases.
　今後、急速に進むであろう低コスト化、高容量化に伴う、高速加工化、セパレータの薄膜化の要求に対して、従来の技術ではスリット加工や電池組み立て加工中に局所的に改質多孔層が剥離するため、安全性を確保することはますます困難となることが予想される。特にポリオレフィン樹脂多孔質膜が薄くなれば改質多孔層のポリオレフィン樹脂多孔質膜に対する十分なアンカー効果が得にくくなるため、いっそう安全性の確保は困難となる。 In the future, in response to demands for high-speed processing and thinning of the separator due to cost reduction and high capacity that will progress rapidly in the future, the conventional technology uses locally modified porosity during slit processing and battery assembly processing As the layers peel, it is expected that ensuring safety will become increasingly difficult. In particular, when the polyolefin resin porous membrane becomes thinner, it becomes difficult to obtain a sufficient anchor effect of the modified porous layer for the polyolefin resin porous membrane, and thus it becomes more difficult to ensure safety.
　本発明者らは電池用セパレータが今後ますます薄膜化と低コスト化が進んだ場合を想定し、改質多孔層との剥離強度が極めて高く、スリット工程や電池組み立て工程における高速加工に適した、改質多孔層の積層に適したポリオレフィン多孔質膜と改質多孔層とを有する積層多孔質膜及び電池用セパレータとして用いる前記積層多孔質膜の提供を目指したものである。 Assuming that battery separators will become increasingly thinner and lower in cost, the present inventors have extremely high peel strength from the modified porous layer and are suitable for high-speed processing in the slit process and battery assembly process. The present invention aims to provide a laminated porous membrane having a polyolefin porous membrane suitable for lamination of a modified porous layer and a modified porous layer, and the laminated porous membrane used as a battery separator.
　本明細書でいう剥離強度とは、ポリオレフィン多孔質膜と改質多孔層との間の０°剥離強度を意味し、以下の方法により測定される値である（以下、０°剥離強度という場合がある。）。 The peel strength as used herein means 0 ° peel strength between the polyolefin porous membrane and the modified porous layer, and is a value measured by the following method (hereinafter referred to as 0 ° peel strength). There is.)
　図１に、引張試験機（図示しない）によって引っ張った状態のポリオレフィン多孔質膜と改質多孔層の積層試料の側面の様子を模式的に示している。１が積層試料、２がポリオレフィン多孔質膜、３が改質多孔層、４が両面粘着テープ、５及び５'がアルミニウム板であり、図中の矢印が引張方向である。大きさ５０ｍｍ×２５ｍｍ、厚さ０．５ｍｍのアルミニウム板（５）に同じ大きさの両面粘着テープ（４）を貼り付け、その上に幅５０ｍｍ×長さ１００ｍｍに切り出した試料（１）（積層多孔質膜）のポリオレフィン多孔質膜（２）の面を前記アルミニウム板（５）の２５ｍｍ長さの片辺の端から４０ｍｍが重なるように貼り付け、はみ出た部分を切り取る。次いで、長さ１００ｍｍ、幅１５ｍｍ、厚さ０．５ｍｍのアルミニウム板（５'）の片面に両面粘着テープを貼り付け、前記アルミニウム板（５）の２５ｍｍ長さの試料側の片辺の端から２０ｍｍが重なるように貼り付ける。その後、アルミニウム板（５）とアルミニウム板（５'）を平行に反対方向に引張試験機を用いて、引張速度１０ｍｍ／ｍｉｎで引っ張り、改質多孔層が剥離したときの強度を測定する。本評価方法で剥離強度が１３０Ｎ／１５ｍｍ以上であれば、ポリオレフィン多孔質膜の厚さが１０μｍ以下のような場合であっても、積層された改質多孔層が搬送中、あるいは加工中に剥がれ現象はほとんど生じない。 FIG. 1 schematically shows a side view of a laminated sample of a polyolefin porous membrane and a modified porous layer in a state of being pulled by a tensile tester (not shown). 1 is a laminated sample, 2 is a polyolefin porous membrane, 3 is a modified porous layer, 4 is a double-sided pressure-sensitive adhesive tape, 5 and 5 'are aluminum plates, and the arrows in the figure are tensile directions. A sample (1) (laminated) having a double-sided adhesive tape (4) of the same size applied to an aluminum plate (5) having a size of 50 mm × 25 mm and a thickness of 0.5 mm, and cut into a width of 50 mm × length of 100 mm. The surface of the polyolefin porous membrane (2) of the porous membrane) is pasted so that 40 mm overlaps the end of one side of the 25 mm length of the aluminum plate (5), and the protruding portion is cut off. Next, a double-sided adhesive tape is attached to one side of an aluminum plate (5 ′) having a length of 100 mm, a width of 15 mm, and a thickness of 0.5 mm. From the end of one side of the aluminum plate (5) on the 25 mm-long sample side. Paste so that 20mm overlaps. Thereafter, the aluminum plate (5) and the aluminum plate (5 ′) are pulled in parallel in opposite directions using a tensile tester at a tensile rate of 10 mm / min, and the strength when the modified porous layer is peeled is measured. If the peel strength is 130 N / 15 mm or more in this evaluation method, the laminated modified porous layer is peeled off during transportation or processing even when the thickness of the polyolefin porous membrane is 10 μm or less. The phenomenon hardly occurs.
　剥離強度の測定法として従来から用いられているＴ型剥離強度または１８０°での剥離強度は、ポリエチレン製多孔膜から塗布層をポリエチレン製多孔膜表面に対して垂直または垂直から斜め後方に引きはがす時の剥離力である。本評価方法によれば、これら従来の評価方法に比べてスリット工程や電池組み立て工程における擦れ耐性をより実際に即して評価することができる。 The T-type peel strength or 180 ° peel strength conventionally used as a method for measuring peel strength is to peel the coating layer from the polyethylene porous film perpendicularly or obliquely backward from the surface of the polyethylene porous film. It is the peel force at the time. According to this evaluation method, it is possible to evaluate the abrasion resistance in the slit process and the battery assembly process more practically as compared with these conventional evaluation methods.
　上記課題を解決するために本発明の積層多孔質膜は以下の構成を有する。すなわち、
　ポリオレフィンからなる突起が５μｍ≦Ｗ≦５０μｍ（Ｗは突起の大きさ）および０．５μｍ≦Ｈ（Ｈは突起の高さ）をみたし、両面に片面あたり３個／ｃｍ２以上、２００個／ｃｍ２以下で不規則に点在し、かつ膜厚が２５μｍ以下であるポリオレフィン多孔質膜の片面に改質多孔層Ａ、反対面に改質多孔層Ｂを積層した積層多孔質膜であり、少なくとも改質多孔層Ａは引っ張り強度が５Ｎ／ｍｍ２以上のバインダーと無機粒子とを含む積層多孔質膜、である。
　本発明の積層多孔質膜は、前記引っ張り強度が５Ｎ／ｍｍ２以上のバインダーがポリビニルアルコール又はアクリル系樹脂であることが好ましい。
　本発明の積層多孔質膜は、前記無機粒子が炭酸カルシウム、アルミナ、チタニア、硫酸バリウム、マイカ及びベーマイトからなる群から選ばれる少なくとも１種を含むことが好ましい。
　本発明の積層多孔質膜は、ポリオレフィン多孔質膜の厚さが２０μｍ以下であることが好ましい。
　本発明の積層多孔質膜は、ポリオレフィン多孔質膜の厚さが１６μｍ以下であることが好ましい。
　本発明の積層多孔質膜は、電池用セパレータとして用いることが好ましい。
　上記課題を解決するために本発明の積層多孔質膜の製造方法は以下の構成を有する。すなわち、
（ａ）ポリオレフィン樹脂に成形用溶剤を添加した後、溶融混練し、ポリオレフィン樹脂溶液を調製する工程
（ｂ）前記ポリオレフィン樹脂溶液をＴ型ダイより押出し、フィルム状に押し出されたポリオレフィン樹脂溶液の両面に配置された形成用溶剤が除去された表面を有する冷却ロールにて冷却し、ゲル状成形物を形成する工程
（ｃ）前記ゲル状成形物を機械方向および幅方向に延伸し、延伸成形物を得る工程
（ｄ）前記延伸成形物から前記成形用溶剤を除去し、乾燥し、多孔質成形物を得る工程
（ｅ）前記多孔質成形物を熱処理し、ポリオレフィン多孔質膜を得る工程
（ｆ）前記ポリオレフィン多孔質膜の少なくとも片面に、引っ張り強度が５Ｎ／ｍｍ２以上のバインダー、前記バインダーを溶解または分散しうる溶媒及び無機粒子とを含む塗布液を用いて積層膜を形成し、乾燥する工程。
　本発明の積層多孔質膜の製造方法は、成形用溶剤の除去手段がドクターブレードであることが好ましい。
　なお、本明細書では改質多孔層Ａおよび改質多孔層Ｂを単に改質多孔層と略記する場合がある。 In order to solve the above problems, the laminated porous membrane of the present invention has the following configuration. That is,
The projections made of polyolefin satisfy 5 μm ≦ W ≦ 50 μm (W is the size of the projection) and 0.5 μm ≦ H (H is the height of the projection), and 3 / cm 2 or more per side on both sides, 200 / It is a laminated porous membrane in which a modified porous layer A is laminated on one side of a polyolefin porous membrane having a film thickness of 25 μm or less, and a modified porous layer B is laminated on the opposite side, which are irregularly scattered at a cm 2 or less. At least the modified porous layer A is a laminated porous film containing a binder having a tensile strength of 5 N / mm 2 or more and inorganic particles.
In the laminated porous membrane of the present invention, the binder having a tensile strength of 5 N / mm 2 or more is preferably polyvinyl alcohol or an acrylic resin.
In the laminated porous membrane of the present invention, the inorganic particles preferably include at least one selected from the group consisting of calcium carbonate, alumina, titania, barium sulfate, mica and boehmite.
In the laminated porous membrane of the present invention, the polyolefin porous membrane preferably has a thickness of 20 μm or less.
In the laminated porous membrane of the present invention, the polyolefin porous membrane preferably has a thickness of 16 μm or less.
The laminated porous membrane of the present invention is preferably used as a battery separator.
In order to solve the above problems, the method for producing a laminated porous membrane of the present invention has the following configuration. That is,
(A) Step of adding a molding solvent to a polyolefin resin and then melt-kneading to prepare a polyolefin resin solution (b) Both sides of the polyolefin resin solution extruded into a film by extruding the polyolefin resin solution from a T-shaped die Step (c) of forming a gel-like molded product by cooling with a cooling roll having a surface from which the forming solvent is removed, and stretching the gel-like molded product in the machine direction and the width direction. (D) removing the molding solvent from the stretched molded product and drying it to obtain a porous molded product (e) heat treating the porous molded product to obtain a polyolefin porous membrane (f ) On at least one surface of the polyolefin porous membrane, a binder having a tensile strength of 5 N / mm 2 or more, a solvent capable of dissolving or dispersing the binder, and inorganic particles The process of forming a laminated film using the coating liquid containing this, and drying.
In the method for producing a laminated porous membrane of the present invention, it is preferable that the forming solvent removing means is a doctor blade.
In the present specification, the modified porous layer A and the modified porous layer B may be simply referred to as a modified porous layer.
　本発明によれば、改質多孔層との密着性に極めて優れたポリオレフィン多孔質膜と改質多孔層とを有する積層多孔質膜及び当該積層多孔質膜を用いた高速搬送時においても剥離が生じない電池用セパレータが得られる。 According to the present invention, a laminated porous membrane having a polyolefin porous membrane and a modified porous layer having excellent adhesion to the modified porous layer, and peeling at the time of high-speed conveyance using the laminated porous membrane. A battery separator that does not occur is obtained.
０°剥離強度の測定方法を示す概略図。Schematic which shows the measuring method of 0 degree peeling strength. ポリエチレン多孔質膜におけるポリエチレンの球晶構造および結晶核を示す概略図。Schematic which shows the spherulite structure and crystal nucleus of polyethylene in a polyethylene porous membrane. ポリエチレン多孔質膜におけるポリエチレンの球晶に由来するリング状痕の顕微鏡写真。The microscope picture of the ring-shaped trace derived from the spherulite of polyethylene in a polyethylene porous membrane. ポリエチレン樹脂溶液を押出機の先端に設置されたＴ型ダイから押出し、冷却ロールで冷却しながらゲル状成形物を形成する工程を示す概略図。Schematic which shows the process of extruding a polyethylene resin solution from the T-type die installed in the front-end | tip of an extruder, and forming a gel-like molded product, cooling with a cooling roll.
　本発明に用いるポリオレフィン多孔質膜は、特定のポリオレフィン樹脂溶液を調整し、押出機からＴ型ダイを経由して押し出されたポリオレフィン樹脂溶液の冷却速度を高度に制御することで得られる表面に適度な形状と数の突起を有するポリオレフィン多孔質膜である。さらに、無機粒子及び引っ張り強度が５Ｎ／ｍｍ２以上のバインダーを含む改質多孔層を該ポリオレフィン多孔質膜に積層した場合において、ポリオレフィン多孔質膜と改質多孔層との間で極めて優れた剥離強度を得ることができる。 The polyolefin porous membrane used in the present invention is moderate on the surface obtained by preparing a specific polyolefin resin solution and highly controlling the cooling rate of the polyolefin resin solution extruded from the extruder via the T-die. It is a polyolefin porous membrane which has various shapes and a number of protrusions. Furthermore, when a modified porous layer containing inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more is laminated on the polyolefin porous film, extremely excellent peeling between the polyolefin porous film and the modified porous layer Strength can be obtained.
　本発明でいう突起とは、ポリオレフィン多孔質膜に、例えば無機粒子等を添加して得られる突起とは本質的に異なる。ポリオレフィン多孔質膜に無機粒子を添加して得られる突起は通常、極めて高さが小さいものであり、同手段で高さ０．５μｍ以上の突起を形成しようとすればポリオレフィン多孔質膜の厚さと同等かそれ以上の粒径を有する粒子の添加が必要となる。しかし、このような粒子を添加するとポリオレフィン多孔質膜の強度が低下してしまい現実的ではない。 The projection referred to in the present invention is essentially different from the projection obtained by adding inorganic particles or the like to the polyolefin porous membrane. The protrusions obtained by adding inorganic particles to the polyolefin porous membrane are usually extremely small in height, and if a protrusion having a height of 0.5 μm or more is to be formed by the same means, the thickness of the polyolefin porous film It is necessary to add particles having an equivalent or larger particle size. However, when such particles are added, the strength of the polyolefin porous membrane is lowered, which is not realistic.
　本発明でいう突起とは、ポリオレフィン多孔質膜の一部を適度な形状の***に成長させたものであり、ポリオレフィン多孔質膜の基本的な特性を低下させるものではない。 The protrusions referred to in the present invention are those in which a part of the polyolefin porous film is grown to a moderately raised shape, and do not deteriorate the basic characteristics of the polyolefin porous film.
　また、本発明でいう不規則に点在するとは、ポリオレフィン多孔質膜の製造に際して、延伸工程の前、あるいは後にエンボス加工ロールを通過させて得られる規則性、あるいは周期性のある配置とは明確に異なる。エンボス加工等のプレス加工は基本的に突起以外の部分を圧縮することによって突起を形成するものであり、透気抵抗度、電解液浸透性の低下を生じやすいため好ましくない。 In addition, irregularly scattered in the present invention means that a regular or periodic arrangement obtained by passing an embossing roll before or after the stretching step in the production of a polyolefin porous membrane is clear. Different. Press work such as embossing is basically not preferred because it forms protrusions by compressing portions other than the protrusions and tends to cause a decrease in air resistance and electrolyte permeability.
　本発明でいう適度な形状の突起とは、大きさ５μｍ以上、５０μｍ以下、高さ０．５μｍ以上の突起を意味する。すなわち、５μｍ≦Ｗ≦５０μｍ（Ｗは突起の大きさ）、且つ０．５μｍ≦Ｈ（Ｈは突起の高さ）である。このような突起は多孔質膜に改質多孔層を積層した際、アンカーとして機能し、その結果、前記０°剥離強度の大きい積層多孔質膜が得られる。一方、高さの上限は特に限定されないが、３．０μｍもあれば十分である。十分な高さの突起が数多くあるほど前述の０°剥離強度は高くなる傾向にある。すなわち、０°剥離強度は高さ０．５μｍ以上の突起の数とその平均高さに影響される。突起の数の下限は３個／ｃｍ２が好ましく、より好ましくは５個／ｃｍ２、さらに好ましくは１０個／ｃｍ２である。突起の数の上限は２００個／ｃｍ２が好ましく、より好ましくは１５０個／ｃｍ２である。突起の高さの下限は０．５μｍが好ましく、より好ましくは０．８μｍ、さらに好ましくは１．０μｍである。
　なお、本発明における突起の大きさ及び高さは、後述する測定方法で測定した値をいう。 The moderately shaped protrusion as used in the present invention means a protrusion having a size of 5 μm or more and 50 μm or less and a height of 0.5 μm or more. That is, 5 μm ≦ W ≦ 50 μm (W is the size of the protrusion) and 0.5 μm ≦ H (H is the height of the protrusion). Such protrusions function as anchors when the modified porous layer is laminated on the porous film, and as a result, the laminated porous film having a high 0 ° peel strength can be obtained. On the other hand, the upper limit of the height is not particularly limited, but 3.0 μm is sufficient. The more the protrusions are sufficiently high, the higher the 0 ° peel strength described above tends to be. That is, the 0 ° peel strength is affected by the number of protrusions having a height of 0.5 μm or more and the average height thereof. The lower limit of the number of protrusions is preferably 3 / cm 2 , more preferably 5 / cm 2 , and still more preferably 10 / cm 2 . The upper limit of the number of protrusions is preferably 200 / cm 2 , more preferably 150 / cm 2 . The lower limit of the height of the protrusion is preferably 0.5 μm, more preferably 0.8 μm, and still more preferably 1.0 μm.
In addition, the magnitude | size and height of a processus | protrusion in this invention say the value measured with the measuring method mentioned later.
　本発明でいう透気抵抗度の上昇幅とは、ポリオレフィン多孔質膜の透気抵抗度と改質多孔層が積層された積層多孔質膜との透気抵抗度の差を意味し、１００秒／１００ｃｃＡｉｒ以下が好ましい。 The range of increase in the air resistance referred to in the present invention means a difference in air resistance between the polyolefin porous membrane and the laminated porous membrane in which the modified porous layer is laminated. / 100ccAir or less is preferable.
　本発明のポリオレフィン多孔質膜と改質多孔層とを有する積層多孔質膜及び電池用セパレータとして用いる前記積層多孔質膜について概要を説明するが、当然この代表例に限定されるものではない。 The outline of the laminated porous membrane having the polyolefin porous membrane and the modified porous layer of the present invention and the laminated porous membrane used as a battery separator will be described, but it is naturally not limited to this representative example.
１．ポリオレフィン多孔質膜
　まず、本発明のポリオレフィン多孔質膜について説明する。
　本発明のポリオレフィン多孔質膜の厚さは、２５μｍ以下が好ましく、より好ましい上限は２０μｍ、さらに好ましくは１６μｍである。下限は７μｍ、好ましくは９μｍである。ポリオレフィン多孔質膜の厚さが上記好ましい範囲であると、実用的な膜強度と孔閉塞機能を保有させることが出来き、電池ケースの単位容積当たりの面積が制約されず、今後、進むであろう電池の高容量化には適する。 1. Polyolefin Porous Membrane First, the polyolefin porous membrane of the present invention will be described.
The thickness of the polyolefin porous membrane of the present invention is preferably 25 μm or less, and the more preferable upper limit is 20 μm, and further preferably 16 μm. The lower limit is 7 μm, preferably 9 μm. If the thickness of the polyolefin porous membrane is within the above preferred range, practical membrane strength and pore blocking function can be retained, and the area per unit volume of the battery case is not restricted, and will proceed in the future. Suitable for increasing the capacity of brazing batteries.
　ポリオレフィン多孔質膜の透気抵抗度の上限は、３００ｓｅｃ／１００ｃｃＡｉｒが好ましく、より好ましくは２００ｓｅｃ／１００ｃｃＡｉｒ、さらに好ましくは１５０ｓｅｃ／１００ｃｃＡｉｒであり、下限は５０ｓｅｃ／１００ｃｃＡｉｒが好ましく、より好ましくは７０ｓｅｃ／１００ｃｃＡｉｒ、さらに好ましくは１００ｓｅｃ／１００ｃｃＡｉｒである。 The upper limit of the air resistance of the polyolefin porous membrane is preferably 300 sec / 100 cc Air, more preferably 200 sec / 100 cc Air, still more preferably 150 sec / 100 cc Air, and the lower limit is preferably 50 sec / 100 cc Air, more preferably 70 sec / 100 cc Air, More preferably, it is 100 sec / 100 cc Air.
　ポリオレフィン多孔質膜の空孔率は、上限は７０％が好ましく、より好ましくは６０％、さらに好ましくは５５％である。下限は好ましくは３０％が好ましく、より好ましくは３５％、さらに好ましくは４０％である。透気抵抗度および空孔率が上記好ましい範囲であると、十分な電池の充放電特性、特にイオン透過性（充放電作動電圧）および電池の寿命（電解液の保持量と密接に関係する）において十分であり、電池としての機能を十分に発揮することができ、十分な機械的強度と絶縁性が得られることで充放電時に短絡が起こる可能性が低くなる。 The upper limit of the porosity of the polyolefin porous membrane is preferably 70%, more preferably 60%, and even more preferably 55%. The lower limit is preferably 30%, more preferably 35%, still more preferably 40%. When the air permeability resistance and the porosity are within the above preferred ranges, sufficient battery charge / discharge characteristics, particularly ion permeability (charge / discharge operating voltage) and battery life (closely related to the amount of electrolyte retained) In this case, the function as a battery can be sufficiently exerted, and sufficient mechanical strength and insulation can be obtained, so that the possibility of a short circuit during charge / discharge is reduced.
　ポリオレフィン多孔質膜の平均孔径については、孔閉塞性能に大きく影響を与えるため、０．０１～１．０μｍが好ましく、より好ましくは０．０５～０．５μｍ、さらに好ましくは０．１～０．３μｍである。ポリオレフィン多孔質膜の平均孔径が上記好ましい範囲であると、機能性樹脂のアンカー効果により十分な改質多孔層の前記０°の剥離強度が得られ、改質多孔層を積層した際に透気抵抗度が大幅に悪化せず、かつ、孔閉塞現象の温度に対する応答が緩慢になることもなく、昇温速度による孔閉塞温度がより高温側にシフトすることもない。 The average pore diameter of the polyolefin porous membrane is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.5 μm, still more preferably 0.1 to 0. 3 μm. When the average pore diameter of the polyolefin porous membrane is within the above preferred range, the 0 ° peel strength of the modified porous layer can be sufficiently obtained by the anchor effect of the functional resin, and air permeability can be obtained when the modified porous layer is laminated. The resistance does not deteriorate significantly, the response to the temperature of the hole closing phenomenon does not become slow, and the hole closing temperature due to the temperature rising rate does not shift to a higher temperature side.
　ポリオレフィン多孔質膜は、充放電反応の異常時に孔が閉塞する機能を有することが必要である。従って、構成する樹脂の融点（軟化点）は、７０～１５０℃、より好ましくは８０～１４０℃、さらに好ましくは１００～１３０℃である。構成する樹脂の融点が上記好ましい範囲であると、正常使用時に孔閉塞機能が発現してしまって電池が使用不可になることがなく、また、異常反応時に孔閉塞機能が発現することで安全性を確保できる。 The polyolefin porous membrane needs to have a function of blocking pores when the charge / discharge reaction is abnormal. Therefore, the melting point (softening point) of the constituent resin is 70 to 150 ° C., more preferably 80 to 140 ° C., and still more preferably 100 to 130 ° C. When the melting point of the resin constituting the resin is within the above preferable range, the battery does not become unusable due to the occurrence of a hole closing function during normal use, and the hole closing function is exhibited during an abnormal reaction. Can be secured.
　ポリオレフィン多孔質膜を構成するポリオレフィン樹脂としては、ポリエチレンやポリプロピレンが好ましい。また、単一物又は２種以上の異なるポリオレフィン樹脂の混合物、例えばポリエチレンとポリプロピレンの混合物であってもよいし、異なるオレフィンの共重合体でもよい。電気絶縁性、イオン透過性などの基本特性に加え、電池異常昇温時において電流を遮断し、過度の昇温を抑制する孔閉塞効果を具備しているからである。なかでもポリエチレンが優れた孔閉塞性能の観点から特に好ましい。 The polyolefin resin constituting the polyolefin porous membrane is preferably polyethylene or polypropylene. Further, it may be a single substance or a mixture of two or more different polyolefin resins, for example, a mixture of polyethylene and polypropylene, or a copolymer of different olefins. This is because, in addition to basic characteristics such as electrical insulation and ion permeability, it has a hole blocking effect that blocks current when the battery is abnormally heated and suppresses excessive temperature rise. Among these, polyethylene is particularly preferable from the viewpoint of excellent pore closing performance.
　以下、本発明で用いるポリオレフィン樹脂としてポリエチレンを例に詳述する。
　ポリエチレンは、超高分子量ポリエチレン、高密度ポリエチレン、中密度ポリエチレン及び低密度ポリエチレンなどが挙げられる。また重合触媒にも特に制限はなく、チーグラー・ナッタ系触媒やフィリップス系触媒やメタロセン系触媒などが挙げられる。これらのポリエチレンはエチレンの単独重合体のみならず、他のα‐オレフィンを少量含有する共重合体であってもよい。エチレン以外のα‐オレフィンとしてはプロピレン、１‐ブテン、１‐ペンテン、１‐ヘキセン、４‐メチル‐１‐ペンテン、１‐オクテン、（メタ）アクリル酸、（メタ）アクリル酸のエステル、スチレン等が好適である。 Hereinafter, polyethylene will be described in detail as an example of the polyolefin resin used in the present invention.
Examples of the polyethylene include ultra high molecular weight polyethylene, high density polyethylene, medium density polyethylene, and low density polyethylene. The polymerization catalyst is not particularly limited, and examples thereof include a Ziegler-Natta catalyst, a Phillips catalyst, and a metallocene catalyst. These polyethylenes may be not only ethylene homopolymers but also copolymers containing small amounts of other α-olefins. Α-olefins other than ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, (meth) acrylic acid, esters of (meth) acrylic acid, styrene, etc. Is preferred.
　ポリエチレンは単一物でもよいが、２種以上のポリエチレンからなる混合物であることが好ましい。ポリエチレン混合物としては、重量平均分子量（Ｍｗ）の異なる２種類以上の超高分子量ポリエチレンを含む混合物を用いてもよいし、同様に高密度ポリエチレン、中密度ポリエチレン又は低密度ポリエチレンの混合物を用いてもよい。また、超高分子量ポリエチレン、高密度ポリエチレン、中密度ポリエチレン及び低密度ポリエチレンからなる群から選ばれた２種以上ポリエチレンの混合物を用いてもよい。 Polyethylene may be a single material, but is preferably a mixture of two or more types of polyethylene. As the polyethylene mixture, a mixture containing two or more types of ultrahigh molecular weight polyethylenes having different weight average molecular weights (Mw) may be used, and similarly, a mixture of high density polyethylene, medium density polyethylene or low density polyethylene may be used. Good. A mixture of two or more polyethylenes selected from the group consisting of ultrahigh molecular weight polyethylene, high density polyethylene, medium density polyethylene and low density polyethylene may also be used.
　ポリエチレン混合物としては、重量平均分子量（Ｍｗ）が５×１０５以上の超高分子量ポリエチレンとＭｗが１×１０４以上～５×１０５未満のポリエチレンからなる混合物が好ましい。超高分子量ポリエチレンのＭｗは５×１０５～１×１０７であることが好ましく、１×１０６～１５×１０６であることがより好ましく、１×１０６～５×１０６であることがさらに好ましい。Ｍｗが１×１０４以上～５×１０５未満のポリエチレンとしては、高密度ポリエチレン、中密度ポリエチレン及び低密度ポリエチレンのいずれも使用することが出来るが、特に高密度ポリエチレンを使用することが好ましい。Ｍｗが１×１０４以上～５×１０５未満のポリエチレンとしてはＭｗが異なるものを２種以上使用してもよいし、密度の異なるものを２種以上使用してもよい。ポリエチレン混合物のＭｗの上限を１５×１０６以下にすることにより、溶融押出を容易にすることが出来る。 As the polyethylene mixture, a mixture composed of ultrahigh molecular weight polyethylene having a weight average molecular weight (Mw) of 5 × 10 5 or more and polyethylene having Mw of 1 × 10 4 or more and less than 5 × 10 5 is preferable. The Mw of the ultra high molecular weight polyethylene is preferably 5 × 10 5 to 1 × 10 7 , more preferably 1 × 10 6 to 15 × 10 6 , and 1 × 10 6 to 5 × 10 6. Is more preferable. As the polyethylene having an Mw of 1 × 10 4 or more and less than 5 × 10 5 , any of high density polyethylene, medium density polyethylene and low density polyethylene can be used, and it is particularly preferable to use high density polyethylene. As polyethylene having an Mw of 1 × 10 4 or more and less than 5 × 10 5 , two or more types having different Mw may be used, or two or more types having different densities may be used. By setting the upper limit of Mw of the polyethylene mixture to 15 × 10 6 or less, melt extrusion can be facilitated.
　本発明においては超高分子量ポリエチレンの含有量の上限は、４０重量％が好ましく、より好ましくは３０重量％、さらに好ましくは１０重量％であり、下限は１重量％が好ましく、より好ましくは２重量％、さらに好ましくは５重量％である。 In the present invention, the upper limit of the content of ultrahigh molecular weight polyethylene is preferably 40% by weight, more preferably 30% by weight, still more preferably 10% by weight, and the lower limit is preferably 1% by weight, more preferably 2% by weight. %, More preferably 5% by weight.
　超高分子量ポリエチレンの含有量が好ましい範囲内であると、十分な高さの突起が得られる。この突起によって改質多孔層を積層した場合に突起がアンカーとして機能し、ポリエチレン多孔質膜の面方向に平行に加わる力に対し極めて強い剥離耐性を得ることができる。また、ポリエチレン多孔質膜の厚さを薄膜化させた場合であっても、十分な引っ張り強度が得られる。引っ張り強度は１００ＭＰａ以上が好ましい。上限は特に定めない。 When the content of ultrahigh molecular weight polyethylene is within the preferred range, a sufficiently high protrusion can be obtained. When the modified porous layer is laminated by this protrusion, the protrusion functions as an anchor, and extremely strong peeling resistance can be obtained with respect to a force applied in parallel to the plane direction of the polyethylene porous film. Further, even when the thickness of the polyethylene porous film is reduced, sufficient tensile strength can be obtained. The tensile strength is preferably 100 MPa or more. There is no particular upper limit.
　ポリエチレン樹脂の重量平均分子量（Ｍｗ）と数平均分子量（Ｍｎ）の比分子量分布（Ｍｗ／Ｍｎ）は５～２００の範囲内であることが好ましく、１０～１００の範囲内であることがより好ましい。Ｍｗ／Ｍｎの範囲が上記好ましい範囲であると、ポリエチレン樹脂溶液の押出しが容易であり、また十分な数の突起が得られる。さらに、ポリエチレン多孔質膜の厚さを薄膜化させた場合、十分な機械的強度が得られる。Ｍｗ／Ｍｎは分子量分布の尺度として用いられるものであり、すなわち単一物からなるポリエチレンの場合、この値が大きい程分子量分布の幅が大きい。単一物からなるポリエチレンのＭｗ／Ｍｎはポリエチレンの多段重合により適宜調整することができる。またポリエチレンの混合物のＭｗ／Ｍｎは各成分の分子量や混合割合を調整することにより適宜調整することができる。 The specific molecular weight distribution (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polyethylene resin is preferably in the range of 5 to 200, and more preferably in the range of 10 to 100. . When the range of Mw / Mn is within the above preferred range, the polyethylene resin solution can be easily extruded and a sufficient number of protrusions can be obtained. Furthermore, when the thickness of the polyethylene porous film is reduced, sufficient mechanical strength can be obtained. Mw / Mn is used as a measure of molecular weight distribution, that is, in the case of polyethylene consisting of a single substance, the larger this value, the wider the molecular weight distribution. The Mw / Mn of polyethylene composed of a single substance can be appropriately adjusted by multistage polymerization of polyethylene. Moreover, Mw / Mn of the mixture of polyethylene can be suitably adjusted by adjusting the molecular weight and mixing ratio of each component.
　前記ポリエチレン多孔質膜は単層膜であってもよいし、分子量あるいは平均細孔径の異なる二層以上からなる層構成であってもよい。二層以上からなる層構成の場合、少なくとも一つの最外層のポリエチレン樹脂の分子量、および分子量分布が前記を満足することが好ましい。ポリエチレン多孔質膜は、上記の各種特徴を満足する範囲内ならば、目的に応じた製造方法を自由に選択することができる。 The polyethylene porous film may be a single layer film or a layer structure composed of two or more layers having different molecular weights or average pore diameters. In the case of a layer structure composed of two or more layers, it is preferable that the molecular weight and molecular weight distribution of at least one outermost polyethylene resin satisfy the above. As long as the polyethylene porous membrane is within a range that satisfies the above-mentioned various characteristics, a production method according to the purpose can be freely selected.
２．ポリオレフィン多孔質膜の製造方法
　ポリオレフィン多孔質膜の製造方法としては、発泡法、相分離法、溶解再結晶法、延伸開孔法、粉末焼結法などがあり、これらの中では微細孔の均一化、コストの点で相分離法が好ましい。 2. Manufacturing method of polyolefin porous membrane The manufacturing method of polyolefin porous membrane includes foaming method, phase separation method, dissolution recrystallization method, stretch opening method, powder sintering method, etc. Among these, the uniform pores The phase separation method is preferable in view of cost and cost.
　相分離法による製造方法としては、例えばポリエチレンと成形用溶剤とを加熱溶融混練し、得られた溶融混合物をＴ型ダイより押出し、冷却することによりゲル状成形物を形成し、得られたゲル状成形物に対して少なくとも一軸方向に延伸を実施し、前記成形用溶剤を除去することによって多孔質膜を得る方法などが挙げられる。 As a production method by the phase separation method, for example, polyethylene and a molding solvent are heated, melted and kneaded, and the resulting molten mixture is extruded from a T-die and cooled to form a gel-like molded product. Examples of the method include obtaining a porous film by performing stretching in at least a uniaxial direction on the shaped molding and removing the molding solvent.
　二層以上からなる多層膜の製造方法としては、例えばａ層及びｂ層を構成するポリエチレンのそれぞれを成形用溶剤と溶融混練し、得られた溶融混合物をそれぞれの押出機から１つのＴ型ダイに供給し各成分を構成するゲルシートを一体化させて共押出する方法、各層を構成するゲルシートを重ね合わせて熱融着する方法のいずれでも作製できる。共押出法の方が、高い層間接着強度を得やすく、層間に連通孔を形成しやすいために高い透過性を維持しやすく、生産性にも優れているためにより好ましい。 As a method for producing a multilayer film composed of two or more layers, for example, each of the polyethylene constituting the a layer and the b layer is melt-kneaded with a molding solvent, and the obtained molten mixture is sent from each extruder to one T-die. It is possible to produce either a method in which the gel sheets constituting each component are integrated and co-extruded, or a method in which the gel sheets constituting each layer are superposed and heat-sealed. The co-extrusion method is more preferable because it is easy to obtain a high interlayer adhesive strength, easily form communication holes between layers, easily maintain high permeability, and is excellent in productivity.
　本発明に用いるポリオレフィン多孔質膜の製造方法について詳述する。
　本発明に用いるポリオレフィン多孔質膜の製造方法は以下の（ａ）～（ｅ）の工程を含むものである。
（ａ）ポリオレフィン樹脂に成形用溶剤を添加した後、溶融混練し、ポリオレフィン樹脂溶液を調製する工程
（ｂ）前記ポリエチレン溶液をＴ型ダイより押出し、フィルム状に押し出されたポリオレフィン樹脂溶液の両面に配置された成形用溶剤が除去された表面を有する冷却ロールにて冷却し、ゲル状成形物を形成する工程
（ｃ）前記ゲル状成形物を機械方向（ＭＤ）および幅方向（ＴＤ）に延伸し、延伸成形物を得る工程
（ｄ）前記延伸成形物から前記成形用溶剤を除去し、乾燥し、多孔質成形物を得る工程
（ｅ）前記多孔質成形物を熱処理し、ポリオレフィン多孔質膜を得る工程。
 更に（ａ）～（ｅ）の工程の後、必要に応じてコロナ処理工程等を設けてもよい。 The manufacturing method of the polyolefin porous membrane used for this invention is explained in full detail.
The method for producing a polyolefin porous membrane used in the present invention includes the following steps (a) to (e).
(A) Step of adding a molding solvent to a polyolefin resin and then melt-kneading to prepare a polyolefin resin solution (b) Extruding the polyethylene solution from a T-shaped die, on both sides of the polyolefin resin solution extruded into a film Step (c) forming a gel-like product by cooling with a cooling roll having a surface from which the molding solvent has been removed, and stretching the gel-like product in the machine direction (MD) and the width direction (TD) (D) removing the molding solvent from the stretched molded product and drying it to obtain a porous molded product (e) heat treating the porous molded product to obtain a polyolefin porous membrane Obtaining.
Further, after the steps (a) to (e), a corona treatment step or the like may be provided as necessary.
　各工程について、ポリオレフィン樹脂としてポリエチレン樹脂を使用した例で以下に説明する。
（ａ）ポリエチレン樹脂溶液を調製する工程
　ポリエチレン樹脂に成形用溶剤を添加した後、溶融混練して、ポリエチレン樹脂溶液を調製する。
　成形用溶剤としては、ポリエチレンを十分に溶解できるものであれば特に限定されない。例えば、ノナン、デカン、ウンデカン、ドデカン、流動パラフィンなどの脂肪族または環式の炭化水素、あるいは沸点がこれらに対応する鉱油留分などがあげられるが、溶剤含有量が安定なゲル状成形物を得るためには流動パラフィンのような不揮発性の溶剤が好ましい。加熱溶解は、ポリエチレン組成物が完全に溶解する温度で攪拌または押出機中で均一混合して溶解する方法で行う。その温度は、押出機中又は溶媒中で攪拌しながら溶解する場合は使用する重合体及び溶媒により異なるが、例えば１４０～２５０℃の範囲が好ましい。 Each step will be described below using an example in which a polyethylene resin is used as the polyolefin resin.
(A) Step of preparing a polyethylene resin solution After adding a molding solvent to the polyethylene resin, it is melt-kneaded to prepare a polyethylene resin solution.
The molding solvent is not particularly limited as long as it can sufficiently dissolve polyethylene. For example, nonane, decane, undecane, dodecane, liquid paraffin and other aliphatic or cyclic hydrocarbons, or mineral oil fractions with boiling points corresponding to these, gel-like molded products with a stable solvent content Nonvolatile solvents such as liquid paraffin are preferred for obtaining. The dissolution by heating is performed by a method in which the polyethylene composition is completely dissolved and stirred and uniformly mixed in an extruder. The temperature varies depending on the polymer and solvent to be used when it is dissolved in an extruder or in a solvent while stirring, but it is preferably in the range of 140 to 250 ° C., for example.
　ポリエチレン樹脂の濃度は、ポリエチレン樹脂と成形用溶剤の合計を１００重量部として、２５～４０重量部であり、好ましくは２８～３５重量部である。ポリエチレン樹脂の濃度が上記の好ましい範囲であると、突起を形成するための結晶核の数が十分形成され、十分な数の突起が形成される。また、ポリエチレン樹脂溶液を押し出す際のＴ型ダイ出口でスウェルやネックインを抑え、押出し成形体の成形性及び自己支持性が維持される。 The concentration of the polyethylene resin is 25 to 40 parts by weight, preferably 28 to 35 parts by weight, with the total of the polyethylene resin and the molding solvent being 100 parts by weight. When the concentration of the polyethylene resin is within the above preferable range, a sufficient number of crystal nuclei for forming protrusions are formed, and a sufficient number of protrusions are formed. In addition, swell and neck-in are suppressed at the T-shaped die exit when the polyethylene resin solution is extruded, and the moldability and self-supporting property of the extruded product are maintained.
　溶融混練の方法としては、特に限定されないが、通常は押出機中で均一に混練することにより行う。この方法は、前述のようなポリエチレンの高濃度溶液を調製するのに適する。溶融温度はポリエチレンの融点＋１０℃～＋１００℃の範囲内であるのが好ましい。一般的に溶融温度は１６０～２３０℃の範囲内であることが好ましく、より好ましくは１７０～２００℃の範囲内である。ここで融点とは、ＪＩＳ　Ｋ７１２１に基づいて示差走査熱量測定（ＤＳＣ）により求められる値をいう。成形用溶剤は混練開始前に添加しても、混練中に押出機の途中から添加しさらに溶融混練してもよいが、混練開始前に添加して予め溶液化するのが好ましい。溶融混練にあたってはポリエチレンの酸化を防止するために酸化防止剤を添加するのが好ましい。 The method of melt kneading is not particularly limited, but it is usually carried out by uniformly kneading in an extruder. This method is suitable for preparing a high-concentration solution of polyethylene as described above. The melting temperature is preferably within the range of the melting point of polyethylene + 10 ° C. to + 100 ° C. In general, the melting temperature is preferably in the range of 160 to 230 ° C, more preferably in the range of 170 to 200 ° C. Here, the melting point refers to a value obtained by differential scanning calorimetry (DSC) based on JIS K7121. The molding solvent may be added before the start of kneading, or may be added from the middle of the extruder during the kneading and further melt kneaded, but it is preferably added before the start of kneading and preliminarily formed into a solution. In melt kneading, it is preferable to add an antioxidant to prevent oxidation of polyethylene.
（ｂ）ゲル状成形物を形成する工程
　溶融混練したポリエチレン樹脂溶液をＴ型ダイより押出し、成形用溶剤の除去手段により、成形用溶剤を除去した表面を有する冷却ロールにて冷却して、ゲル状成形物を形成する。Ｔ型ダイからの押出しは、溶融混練したポリエチレン樹脂溶液を押出機から直接的に又は別の押出機を介して行う。Ｔ型ダイとしては、通常は長方形の口金形状をしたシート用Ｔ型ダイを用いる。 (B) Step of forming a gel-like molded product A melt-kneaded polyethylene resin solution is extruded from a T-shaped die, cooled by a cooling roll having a surface from which the molding solvent has been removed, by means of a molding solvent removal means, and gel A shaped molding is formed. Extrusion from the T-type die is performed by directly melting or kneading the polyethylene resin solution from the extruder or through another extruder. As the T-shaped die, a T-shaped die for a sheet having a rectangular base shape is usually used.
　次に、冷媒で表面温度２０℃から４０℃に設定した回転する一対の冷却ロールに、Ｔ型ダイからフィルム状に押し出されたポリエチレン樹脂溶液の両面を接触させることでゲル状成形物を形成する。押出されたポリエチレン樹脂溶液は２５℃以下まで冷却するのが好ましい。 Next, a gel-like molded product is formed by bringing both surfaces of a polyethylene resin solution extruded from a T-shaped die into contact with a pair of rotating cooling rolls set at a surface temperature of 20 ° C. to 40 ° C. with a refrigerant. . The extruded polyethylene resin solution is preferably cooled to 25 ° C. or lower.
　本発明において、実質的に結晶化が行われる温度域での冷却速度を制御することが突起形成に重要となる。
　本発明でいう突起が形成されるメカニズムについて、本発明者らは以下のように考えている。溶融したポリエチレン樹脂と成形用溶剤との樹脂溶液がＴ型ダイから押し出されると同時にポリエチレンの結晶化が開始され、冷却ロールに接触し急冷されることで結晶化速度は増大する。この時、結晶核を有する対称構造の球晶が形成される（図２）。冷却ロール表面と前記溶融したポリエチレン樹脂間の熱伝達速度が比較的小さい場合は結晶化速度は小さく、その結果、比較的小さい結晶核を有する球晶となる。熱伝達速度が大きい場合は比較的大きい結晶核を有する球晶となる。これら球晶の結晶核は後工程であるＴＤ（幅方向）及び／又はＭＤ（機械方向）延伸時に突起となる。また、球晶はポリエチレン多孔質膜表面にリング状痕となって現れる（図３）。 In the present invention, it is important for protrusion formation to control the cooling rate in a temperature range where crystallization is substantially performed.
The present inventors consider the mechanism by which the projections are formed in the present invention as follows. The resin solution of the melted polyethylene resin and the molding solvent is extruded from the T-die, and at the same time, the crystallization of polyethylene is started. The crystallization speed is increased by coming into contact with the cooling roll and rapidly cooling. At this time, a spherulite having a symmetric structure having a crystal nucleus is formed (FIG. 2). When the heat transfer rate between the cooling roll surface and the molten polyethylene resin is relatively low, the crystallization rate is low, and as a result, spherulites having relatively small crystal nuclei are formed. When the heat transfer rate is high, the spherulite has a relatively large crystal nucleus. The crystal nuclei of these spherulites become protrusions during TD (width direction) and / or MD (machine direction) stretching, which is a subsequent process. Spherulites appear as ring-shaped marks on the surface of the polyethylene porous membrane (FIG. 3).
　本発明では、例えば、ポリエチレン樹脂溶液の表面が実質的に結晶化される温度域での冷却速度が１０℃／秒以上で、押し出されたポリエチレン樹脂溶液を冷却し、ゲル状成形物を得る。冷却速度は、２０℃／秒以上が好ましく、より好ましくは３０℃／秒以上、さらに好ましくは５０℃／秒以上である。このような冷却を行うことによりポリエチレン相が溶剤によりミクロ相分離された構造を固定化し、冷却ロールと接していたゲル状成形物の表面に比較的大きな核を有する球晶が形成され、延伸後に適度な形状の突起を形成することができる。冷却ロール上の冷却速度は、ポリオレフィン樹脂溶液の熱伝導度、厚み、成形用溶剤、冷却ロールと空気の熱伝達率によりシミュレーションすることによって推定できる。 In the present invention, for example, the extruded polyethylene resin solution is cooled at a cooling rate of 10 ° C./second or more in a temperature range where the surface of the polyethylene resin solution is substantially crystallized to obtain a gel-like molded product. The cooling rate is preferably 20 ° C./second or more, more preferably 30 ° C./second or more, and further preferably 50 ° C./second or more. By carrying out such cooling, the structure in which the polyethylene phase is microphase-separated by the solvent is fixed, and spherulites having relatively large nuclei are formed on the surface of the gel-like molded product in contact with the cooling roll. Appropriately shaped protrusions can be formed. The cooling rate on the cooling roll can be estimated by simulating the thermal conductivity, thickness, molding solvent, heat transfer coefficient between the cooling roll and air of the polyolefin resin solution.
　本発明において、冷却速度を制御するために、Ｔ型ダイから押出したポリエチレン樹脂溶液と接する部分の冷却ロール表面に付着している成形用溶剤を極力除去しておくことが重要である。すなわち、図４に示すように、ポリエチレン樹脂溶液は回転する冷却ロールに巻きつくことにより冷却されゲル状成形物となるが、ゲル状成形物となって引き離された後の冷却ロール表面には成形用溶剤が付着しており、通常はそのままの状態で再びポリエチレン樹脂溶液と接触することになる。しかし、成形用溶剤が冷却ロール表面に多く付着しているとその断熱効果により、冷却速度が緩慢になり、突起が形成されにくくなる。そのため、冷却ロールが再びポリエチレン樹脂溶液と接触するまでに成形用溶剤を極力除去しておくことが重要となる。 In the present invention, in order to control the cooling rate, it is important to remove as much as possible the forming solvent adhering to the surface of the cooling roll in contact with the polyethylene resin solution extruded from the T-die. That is, as shown in FIG. 4, the polyethylene resin solution is cooled by being wound around a rotating cooling roll to become a gel-like molded product, but is formed on the surface of the cooling roll after being separated as a gel-like molded product. The solvent for use is attached, and it usually comes into contact with the polyethylene resin solution again as it is. However, if a large amount of the forming solvent adheres to the surface of the cooling roll, the cooling rate becomes slow due to the heat insulating effect, and it becomes difficult to form protrusions. Therefore, it is important to remove the forming solvent as much as possible before the cooling roll comes into contact with the polyethylene resin solution again.
　成形用溶剤を冷却ロールから除去する方法（成形用溶剤の除去手段ともいう）は特に限定されないが、冷却ロール上にドクターブレードをゲル状成形物の幅方向と平行になるようにあてて、ドクターブレードを通過した直後からゲル状成形物が接するまでの冷却ロール表面に成形用溶剤が視認できない程度に掻き落とす方法が好ましく採用される。あるいは圧縮空気で吹き飛ばす、吸引する、またはこれらの方法を組み合わせる等の手段で除去することもできる。なかでもドクターブレードを用いて掻き落とす方法は比較的容易に実施できるため好ましく、ドクターブレードは１枚より複数枚用いるのが成形用溶剤の除去効率を向上させる上でさらに好ましい。 The method of removing the molding solvent from the cooling roll (also referred to as a molding solvent removing means) is not particularly limited, but the doctor blade is placed on the cooling roll so as to be parallel to the width direction of the gel-like molded product. A method is preferably employed in which the solvent for molding is scraped off to the surface of the cooling roll immediately after passing through the blade until the gel-like molded product comes into contact. Alternatively, it can be removed by means such as blowing with compressed air, suction, or a combination of these methods. Among them, the method of scraping off using a doctor blade is preferable because it can be carried out relatively easily, and it is more preferable to use a plurality of doctor blades in order to improve the removal efficiency of the forming solvent.
　ドクターブレードの材質は成形用溶剤に耐性を有するものであれば特に限定されないが金属製より樹脂製、あるいはゴム製のものが好ましい。金属製の場合、冷却ロールをキズつけてしまう恐れがあるためである。樹脂製ドクターブレードとしてはポリエステル製、ポリアセタール製、ポリエチレン製などが挙げられる。 The material of the doctor blade is not particularly limited as long as it is resistant to the molding solvent, but is preferably made of resin or rubber rather than metal. This is because in the case of metal, the cooling roll may be scratched. Examples of the resin doctor blade include polyester, polyacetal, and polyethylene.
　冷却ロールの温度を２０℃未満に設定しても、これだけでは成形用溶剤の断熱効果により、十分な冷却速度が得られないだけでなく、冷却ロールへの結露の付着によって、ゲル状成形物に表面荒れを引き起こす場合がある。 Even if the temperature of the cooling roll is set to less than 20 ° C., this alone does not provide a sufficient cooling rate due to the heat insulating effect of the molding solvent, but also causes the gel-like molded product to adhere to the condensation due to the condensation on the cooling roll. It may cause surface roughness.
　冷却ロールはポリエチレン樹脂溶液の両面に配置する２つの冷却ロールであり、各ロールの直径は異なる方が好ましい。また、Ｔ型ダイのポリエチレン樹脂溶液の吐出口の設置位置の高さに対して、２つの冷却ロールの回転軸の設置位置の高さは異なる。直径が小さい冷却ロールの回転軸の設置位置の高さは、直径が大きい冷却ロールよりＴ型ダイのポリエチレン樹脂溶液の吐出口の配置位置に近い方が好ましい。これはＴ型ダイのポリエチレン樹脂溶液の吐出口の配置位置から直径の大きい冷却ロール上へのポリエチレン樹脂溶液の接地位置までの距離をできるだけ小さくするためである。例えば、図４のような配置にすることによって、Ｔ型ダイから押出したポリエチレン樹脂溶液の実質的に結晶化が行われる温度域での冷却速度を１０℃／秒以上にすることが可能となる。 The cooling rolls are two cooling rolls arranged on both sides of the polyethylene resin solution, and the rolls preferably have different diameters. Moreover, the height of the installation position of the rotating shaft of two cooling rolls differs with respect to the height of the installation position of the discharge port of the polyethylene resin solution of a T type die. The height of the installation position of the rotating shaft of the cooling roll having a small diameter is preferably closer to the arrangement position of the discharge port of the polyethylene resin solution of the T-die than the cooling roll having a large diameter. This is because the distance from the position where the polyethylene resin solution discharge port of the T-type die is arranged to the position where the polyethylene resin solution is grounded onto the cooling roll having a large diameter is made as small as possible. For example, with the arrangement as shown in FIG. 4, the cooling rate in the temperature range where the crystallization of the polyethylene resin solution extruded from the T-shaped die is substantially performed can be 10 ° C./second or more. .
　押出し時のポリエチレン樹脂溶液の厚みは、１５００μｍ以下が好ましく、より好ましくは１０００μｍ以下、さらに好ましくは８００μｍ以下である。押出し時のポリエチレン樹脂溶液の厚みが上記範囲内であると、冷却ロール側の面の冷却速度が緩慢にならず好ましい。 The thickness of the polyethylene resin solution during extrusion is preferably 1500 μm or less, more preferably 1000 μm or less, and still more preferably 800 μm or less. When the thickness of the polyethylene resin solution at the time of extrusion is within the above range, the cooling rate on the surface on the side of the cooling roll is preferably not slow.
（ｃ）延伸成形物を得る工程
　次に、このゲル状成形物を機械方向（ＭＤ）および幅方向（ＴＤ）に延伸し、延伸成形物とする。延伸は、ゲル状成形物を加熱し、通常のテンター法、ロール法、もしくはこれらの方法の組み合わせによってＭＤ及びＴＤの二方向に所定の倍率で行う。延伸は、ＭＤ及びＴＤ同時延伸（同時二軸延伸）または逐次延伸のいずれでもよい。逐次延伸はＭＤとＴＤの順序は問わず、ＭＤ及びＴＤの少なくとも一方を多段で延伸してもよい。延伸温度は、ポリオレフィン組成物の融点＋１０℃以下である。延伸倍率は、原反の厚さによって異なるが面倍率で９倍以上が好ましく、より好ましくは１６～４００倍である。ＭＤ及びＴＤ同時延伸（同時二軸延伸）であれば、３×３、５×５及び７×７などのＭＤ及びＴＤ同倍率での延伸が好ましい。面倍率が上記好ましい範囲であると、延伸が十分であり高弾性、高強度の多孔質膜が得られる。また、延伸温度を調整することによって所望の透気抵抗度を得ることができる。 (C) Step of obtaining stretched molded product Next, the gel-shaped molded product is stretched in the machine direction (MD) and the width direction (TD) to obtain a stretched molded product. Stretching is performed by heating the gel-like molded product and performing normal tenter method, roll method, or a combination of these methods at a predetermined magnification in two directions of MD and TD. Stretching may be either MD and TD simultaneous stretching (simultaneous biaxial stretching) or sequential stretching. In the sequential stretching, the order of MD and TD is not limited, and at least one of MD and TD may be stretched in multiple stages. The stretching temperature is the melting point of the polyolefin composition + 10 ° C. or less. Although the draw ratio varies depending on the thickness of the original fabric, the surface ratio is preferably 9 times or more, more preferably 16 to 400 times. For MD and TD simultaneous stretching (simultaneous biaxial stretching), stretching at the same MD and TD magnification such as 3 × 3, 5 × 5, and 7 × 7 is preferable. When the surface magnification is in the above preferred range, stretching is sufficient and a highly elastic, high strength porous membrane can be obtained. Moreover, a desired air resistance can be obtained by adjusting the stretching temperature.
（ｄ）多孔質成形物を得る工程
　延伸された延伸成形物を洗浄溶剤で処理して残留する成形用溶剤を除去し、多孔質膜を得る。洗浄溶剤としては、ペンタン、ヘキサン、ヘプタンなどの炭化水素、塩化メチレン、四塩化炭素などの塩素化炭化水素、三フッ化エタンなどのフッ化炭化水素、ジエチルエーテル、ジオキサンなどのエーテル類などの易揮発性のものを用いることができる。これらの洗浄溶剤はポリエチレンの溶解に用いた成形用溶剤に応じて適宜選択し、単独もしくは混合して用いる。洗浄方法は、洗浄溶剤に浸漬し抽出する方法、洗浄溶剤をシャワーする方法、洗浄溶剤を延伸成形物の反対側から吸引する方法、またはこれらの組合せによる方法などにより行うことができる。上述のような洗浄は、延伸成形物である延伸成形物中の残留溶剤が１重量％未満になるまで行う。その後、洗浄溶剤を乾燥するが、洗浄溶剤の乾燥方法は加熱乾燥、風乾などの方法で行うことができる。 (D) Step of obtaining a porous molded product The stretched molded product is treated with a washing solvent to remove the remaining molding solvent to obtain a porous film. Cleaning solvents include hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorinated hydrocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Volatile ones can be used. These washing solvents are appropriately selected according to the molding solvent used for dissolving polyethylene, and used alone or in combination. The cleaning method can be performed by a method of immersing and extracting in a cleaning solvent, a method of showering the cleaning solvent, a method of sucking the cleaning solvent from the opposite side of the stretched molded product, or a method of a combination thereof. Washing as described above is performed until the residual solvent in the stretched molded product, which is a stretched molded product, is less than 1 wt%. Thereafter, the cleaning solvent is dried. The cleaning solvent can be dried by heat drying, air drying, or the like.
（ｅ）ポリエチレン多孔質膜を得る工程
　乾燥して得られた多孔質成形物を熱処理し、ポリエチレン多孔質膜を得る。熱処理は、テンター方式、ロール方式、圧延方式、フリー方式のいずれも採用できる。熱処理は、９０～１５０℃の温度範囲内で行うのが好ましい。熱処理温度が上記好ましい範囲であると、得られたポリオレフィン多孔質膜の熱収縮率低減および透気抵抗度が十分確保される。熱処理工程の滞留時間は、特に限定されることはないが、通常は１秒以上１０分以下、好ましくは３秒から２分以下で行われる。 (E) Step of obtaining a polyethylene porous membrane A porous molded product obtained by drying is heat-treated to obtain a polyethylene porous membrane. For the heat treatment, any of a tenter method, a roll method, a rolling method, and a free method can be adopted. The heat treatment is preferably performed within a temperature range of 90 to 150 ° C. When the heat treatment temperature is in the above preferred range, the resulting polyolefin porous membrane is sufficiently secured to reduce the heat shrinkage rate and the air resistance. The residence time of the heat treatment step is not particularly limited, but is usually 1 second to 10 minutes, preferably 3 seconds to 2 minutes or less.
　さらに、熱処理工程では、熱収縮の観点から、機械方向（ＭＤ）、幅方向（ＴＤ）の両方向を固定しながら、ＭＤ、ＴＤの少なくとも一方向に収縮させるのが好ましい。ＭＤ、ＴＤの少なくとも一方向に収縮させる収縮率は、０．０１～５０％が好ましく、より好ましくは３～２０％である。
　なお、（ａ）～（ｅ）の工程の後、必要に応じてコロナ処理工程や親水化工程等の機能付与工程を設けてもよい。 Furthermore, in the heat treatment step, from the viewpoint of heat shrinkage, it is preferable to shrink in at least one of MD and TD while fixing both the machine direction (MD) and the width direction (TD). The contraction rate for contracting in at least one direction of MD and TD is preferably 0.01 to 50%, more preferably 3 to 20%.
In addition, after the steps (a) to (e), a function providing step such as a corona treatment step or a hydrophilization step may be provided as necessary.
３．改質多孔層
　次に、本発明に用いる改質多孔層について説明する。
　本発明における積層多孔質膜は、上記ポリオレフィン多孔質膜の片面に改質多孔層Ａ、反対面に改質多孔層Ｂを積層した積層多孔質膜である。
　改質多孔層Ａおよび改質多孔層Ｂは同じ多孔質層であってもよいし、異なっていてもよい。ただし、少なくとも改質多孔層Ａには無機粒子と引っ張り強度が５Ｎ／ｍｍ２以上のバインダーとを含むことが重要である。改質多孔層Ａのみ無機粒子と引っ張り強度が５Ｎ／ｍｍ２以上のバインダーとを含む場合はスリット工程や搬送工程などの後工程において、ロールやバーなどの接触によってより強く応力がかかる側に改質多孔層Ａを積層するのが、本発明による効果が発揮されるため好ましい。 3. Modified porous layer Next, the modified porous layer used in the present invention will be described.
The laminated porous membrane in the present invention is a laminated porous membrane in which the modified porous layer A is laminated on one side of the polyolefin porous membrane and the modified porous layer B is laminated on the opposite side.
The modified porous layer A and the modified porous layer B may be the same porous layer or may be different. However, it is important that at least the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more. When only the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more, it is changed to the side where the stress is more strongly applied by the contact with the roll or bar in the subsequent process such as the slit process or the transport process. The porous porous layer A is preferably laminated because the effect of the present invention is exhibited.
　本発明でいう改質多孔層とは、耐熱性、電極材料との密着性、電解液浸透性などの機能を少なくとも一つ付与、または向上させるものである。少なくとも改質多孔層Ａには無機粒子と引っ張り強度が５Ｎ／ｍｍ２以上のバインダーとを含む。引っ張り強度が５Ｎ／ｍｍ２以上のバインダーを用いることによってポリオレフィン多孔質膜の表面に存在する突起と該バインダーの抗張力の相乗効果で前記０°剥離強度が極めて優れた積層多孔質膜が得られる。また、ポリオレフィン多孔質膜の透気抵抗度と比較して、本発明の積層多孔質膜は大幅に透気抵抗度が上昇しない。これはポリオレフィン多孔質膜の細孔内に多くのバインダーを浸透させなくとも十分な０°剥離強度が得られるためである。 The modified porous layer referred to in the present invention imparts or improves at least one function such as heat resistance, adhesion to an electrode material, and electrolyte permeability. At least the modified porous layer A contains inorganic particles and a binder having a tensile strength of 5 N / mm 2 or more. By using a binder having a tensile strength of 5 N / mm 2 or more, a laminated porous membrane having an extremely excellent 0 ° peel strength can be obtained by the synergistic effect of the protrusions present on the surface of the polyolefin porous membrane and the tensile strength of the binder. Moreover, compared with the air permeation resistance of the polyolefin porous membrane, the air permeation resistance of the laminated porous membrane of the present invention is not significantly increased. This is because sufficient 0 ° peel strength can be obtained without allowing a large amount of binder to penetrate into the pores of the polyolefin porous membrane.
　バインダーの引っ張り強度の下限は１０Ｎ／ｍｍ２が好ましく、より好ましくは２０Ｎ／ｍｍ２、さらに好ましくは３０Ｎ／ｍｍ２である。上限は特に定めないが１００Ｎ／ｍｍ２もあれば十分である。バインダーの引っ張り強度は後述する方法で測定した値をいう。 The lower limit of the tensile strength of the binder is preferably 10 N / mm 2, more preferably 20 N / mm 2, more preferably 30 N / mm 2. There is no particular upper limit, but 100 N / mm 2 is sufficient. The tensile strength of the binder refers to a value measured by the method described later.
　本発明に用いる引っ張り強度が５Ｎ／ｍｍ２以上のバインダーとしては、引っ張り強度が５Ｎ／ｍｍ２以上であれば特に限定されないが、例えば、ポリビニルアルコール、セルロースエーテル系樹脂、アクリル系樹脂などが挙げられる。セルロースエーテル系樹脂としてはカルボキシメチルセルロース（ＣＭＣ）、ヒドロキシエチルセルロース（ＨＥＣ）、カルボキシエチルセルロース、メチルセルロース、エチルセルロース、シアンエチルセルロース、オキシエチルセルロース等が挙げられ、アクリル系樹脂としては架橋型アクリル樹脂が好ましい。また、市販されている水溶液または水分散液を用いることもできる。市販されているものとしては、例えば、日新化成（株）製“ＰＯＶＡＣＯＡＴ”（登録商標）、東亜合成（株）製“ジュリマー”（登録商標）ＡＴ－５１０、ＥＴ－４１０、ＦＣ－６０、ＳＥＫ－３０１、大成ファインケミカル（株）製ＵＷ－２２３ＳＸ、ＵＷ－５５０ＣＳ、ＤＩＣ（株）ＷＥ－３０１、ＥＣ－９０６ＥＦ、ＣＧ－８４９０などが挙げられる。なかでも、電極接着性を有し、非水電解液とも親和性が高く、しかも耐熱性が適切であり、比較的大きい引っ張り強度を有するポリビニルアルコール、アクリル系樹脂が好適である。 The use tensile strength of 5N / mm 2 or more binders in the present invention, although the tensile strength is not particularly limited as long as 5N / mm 2 or more, e.g., polyvinyl alcohol, cellulose ether resins, and acrylic resins . Examples of the cellulose ether resin include carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), carboxyethyl cellulose, methyl cellulose, ethyl cellulose, cyanethyl cellulose, oxyethyl cellulose, and the like. As the acrylic resin, a cross-linked acrylic resin is preferable. Commercially available aqueous solutions or aqueous dispersions can also be used. Examples of commercially available products include “POVACOAT” (registered trademark) manufactured by Nisshin Kasei Co., Ltd., “Jurimer” (registered trademark) AT-510, ET-410, FC-60 manufactured by Toa Gosei Co., Ltd. SEK-301, UW-223SX, UW-550CS, DIC Corporation WE-301, EC-906EF, CG-8490 manufactured by Taisei Fine Chemical Co., Ltd. Of these, polyvinyl alcohol and acrylic resins having electrode adhesion, high affinity with non-aqueous electrolytes, suitable heat resistance, and relatively high tensile strength are preferable.
　改質多孔層Ｂに用いるバインダーとしては、改質多孔層Ａと同じであってもよいが、異なっていてもよい。例えば、優れた耐熱性を付与させる場合はポリアミドイミド樹脂、ポリイミド樹脂、ポリアミド樹脂などの耐熱性樹脂を用い、電極密着性を付与させる場合はポリフッ化ビニリデンやその誘導体などのフッ素系樹脂などを用いることができる。 The binder used for the modified porous layer B may be the same as or different from that of the modified porous layer A. For example, when imparting excellent heat resistance, heat-resistant resins such as polyamideimide resin, polyimide resin, and polyamide resin are used, and when imparting electrode adhesion, fluorine-based resins such as polyvinylidene fluoride and its derivatives are used. be able to.
　積層多孔質膜のカールを低減させるために、改質多孔層を形成するための塗布液に無機粒子を添加することが重要である。本明細書における塗布液とは、引っ張り強度が５Ｎ／ｍｍ２以上のバインダー、無機粒子及び前記バインダーを溶解または分散しうる溶媒を含むものであり、改質多孔層を形成するために用いる。 In order to reduce curling of the laminated porous membrane, it is important to add inorganic particles to the coating solution for forming the modified porous layer. The coating solution in the present specification includes a binder having a tensile strength of 5 N / mm 2 or more, inorganic particles, and a solvent capable of dissolving or dispersing the binder, and is used for forming a modified porous layer.
　無機粒子の添加量の上限としては９８重量％が好ましく、より好ましくは９５重量％である。下限は８０重量％が好ましく、より好ましくは８５重量％である。無機粒子の添加量が上記好ましい範囲であるとカール低減効果が十分であり、改質多孔層の総体積に対して機能性樹脂の割合が最適であり、かつ、改質多孔層の十分な０°の剥離強度が得られる。 The upper limit of the amount of inorganic particles added is preferably 98% by weight, more preferably 95% by weight. The lower limit is preferably 80% by weight, more preferably 85% by weight. When the addition amount of the inorganic particles is within the above preferable range, the curl reduction effect is sufficient, the ratio of the functional resin is optimal with respect to the total volume of the modified porous layer, and sufficient 0% of the modified porous layer is obtained. A peel strength of ° can be obtained.
　無機粒子としては、炭酸カルシウム、リン酸カルシウム、非晶性シリカ、結晶性のガラスフィラー、カオリン、タルク、二酸化チタン、アルミナ、シリカーアルミナ複合酸化物粒子、硫酸バリウム、フッ化カルシウム、フッ化リチウム、ゼオライト、硫化モリブデン、マイカ、ベーマイトなどが挙げられる。また、必要に応じて耐熱性架橋高分子粒子を添加してもよい。耐熱性架橋高分子粒子としては、架橋ポリスチレン粒子、架橋アクリル系樹脂粒子、架橋メタクリル酸メチル系粒子などが挙げられる。 Inorganic particles include calcium carbonate, calcium phosphate, amorphous silica, crystalline glass filler, kaolin, talc, titanium dioxide, alumina, silica-alumina composite oxide particles, barium sulfate, calcium fluoride, lithium fluoride, zeolite , Molybdenum sulfide, mica, boehmite and the like. Moreover, you may add a heat resistant crosslinked polymer particle as needed. Examples of the heat-resistant crosslinked polymer particles include crosslinked polystyrene particles, crosslinked acrylic resin particles, and crosslinked methyl methacrylate particles.
　無機粒子の形状は真球形状、略球形状、板状、針状、多面体形状が挙げられるが特に限定されない。 The shape of the inorganic particles includes a true sphere shape, a substantially spherical shape, a plate shape, a needle shape, and a polyhedral shape, but is not particularly limited.
　これら無機粒子の平均粒径はポリオレフィン多孔質膜の平均細孔径の１．５倍以上、５０倍以下であることが好ましい。より好ましくは２．０倍以上、２０倍以下である。粒子の平均粒径が上記好ましい範囲であると、耐熱性樹脂と粒子が混在した状態でポリオレフィン多孔質膜の細孔を塞いでしまうことなく、結果として透気抵抗度を維持し、さらに電池組み立て工程において該粒子が脱落、電池の重大な欠陥を招くのを防ぐ。 The average particle size of these inorganic particles is preferably 1.5 to 50 times the average pore size of the polyolefin porous membrane. More preferably, it is 2.0 times or more and 20 times or less. When the average particle diameter of the particles is within the above-mentioned preferable range, the air resistance is maintained without blocking the pores of the polyolefin porous membrane in a state where the heat-resistant resin and the particles are mixed, and as a result, the battery is assembled. In the process, the particles are prevented from falling off and causing a serious defect of the battery.
　バインダーとは、少なくとも無機粒子同士を結合させる役割及びポリオレフィン多孔質膜と改質多孔層とを結合させる役割を有するものである。溶媒とは、例えば、水、アルコール類、アセトン又はｎ‐メチルピロリドンなどが挙げられる。塗布液に無機粒子を添加することによって、電池の内部における電極の樹枝状結晶の成長に起因する内部短絡の防止効果（デンドライト防止効果）、熱収縮率を低減、滑り性付与などの効果も得ることができる。 The binder has at least the role of bonding inorganic particles and the role of bonding the polyolefin porous membrane and the modified porous layer. Examples of the solvent include water, alcohols, acetone, n-methylpyrrolidone, and the like. By adding inorganic particles to the coating solution, the effect of preventing internal short circuit (dendrite prevention effect) due to the growth of the dendritic crystals of the electrode inside the battery, the effect of reducing the heat shrinkage, and the provision of slipperiness are also obtained. be able to.
　塗布液の固形分濃度は、均一に塗布できれば特に制限されないが５０重量％以上、９８重量％以下が好ましく、８０重量％以上、９５重量％以下がより好ましい。塗布液の固形分濃度が上記好ましい範囲であると、改質多孔層が脆くなるのを防ぎ、改質多孔層の十分な０°の剥離強度が得られる。 The solid content concentration of the coating solution is not particularly limited as long as it can be uniformly applied, but is preferably 50% by weight or more and 98% by weight or less, more preferably 80% by weight or more and 95% by weight or less. When the solid content concentration of the coating solution is in the above preferred range, the modified porous layer is prevented from becoming brittle, and a sufficient peel strength of 0 ° of the modified porous layer can be obtained.
　改質多孔層の膜厚は１～５μｍが好ましく、より好ましくは１～４μｍ、さらに好ましくは１～３μｍである。改質多孔層の膜厚が上記好ましい範囲であると、改質多孔層を積層して得られた積層多孔質膜は融点以上で溶融・収縮した際の破膜強度と絶縁性を確保でき、また十分な孔閉塞機能が得られ異常反応を防ぐことができる。また、巻き嵩を抑制することができ電池の高容量化には適する。さらにカールを抑えることで電池組み立て工程での生産性の向上に繋がる。改質多孔層ＡおよびＢの膜厚は同じであっても異なっていてもよいが、膜厚の差は０．５μｍ以下が好ましく、さらに好ましくは０．３μｍ以下である。 The film thickness of the modified porous layer is preferably 1 to 5 μm, more preferably 1 to 4 μm, and still more preferably 1 to 3 μm. When the film thickness of the modified porous layer is in the above preferred range, the laminated porous film obtained by laminating the modified porous layer can ensure the film breaking strength and insulation when melted / shrinked at the melting point or higher, In addition, a sufficient hole blocking function can be obtained and abnormal reactions can be prevented. Moreover, the winding volume can be suppressed, which is suitable for increasing the battery capacity. In addition, suppressing curling leads to improved productivity in the battery assembly process. The film thicknesses of the modified porous layers A and B may be the same or different, but the difference in film thickness is preferably 0.5 μm or less, more preferably 0.3 μm or less.
　改質多孔層の空孔率は、電池特性の観点から３０～９０％が好ましく、より好ましくは４０～７０％である。所望の空孔率にするには、無機粒子の濃度、バインダー濃度などを適宜調整することにより得られる。 The porosity of the modified porous layer is preferably 30 to 90%, more preferably 40 to 70% from the viewpoint of battery characteristics. The desired porosity can be obtained by appropriately adjusting the concentration of inorganic particles, the binder concentration, and the like.
　改質多孔層を積層して得られた積層多孔質膜の膜厚の上限は２５μｍが好ましく、より好ましくは２０μｍである。下限は６μｍ以上が好ましく、より好ましくは７μｍ以上である。積層多孔質膜の膜厚が上記好ましい範囲であると、改質多孔層を積層して得られた積層多孔質膜は十分な機械強度と絶縁性を確保できる。また、容器内に充填できる電極面積が減少することにより容量の低下を回避できる。 The upper limit of the thickness of the laminated porous membrane obtained by laminating the modified porous layer is preferably 25 μm, more preferably 20 μm. The lower limit is preferably 6 μm or more, more preferably 7 μm or more. When the film thickness of the laminated porous film is within the above preferred range, the laminated porous film obtained by laminating the modified porous layer can ensure sufficient mechanical strength and insulation. In addition, a decrease in capacity can be avoided by reducing the electrode area that can be filled in the container.
　積層多孔質膜の透気抵抗度は、もっとも重要な特性のひとつであり、好ましくは５０～６００ｓｅｃ／１００ｃｃＡｉｒ、より好ましくは１００～５００ｓｅｃ／１００ｃｃＡｉｒ、さらに好ましくは１００～４００ｓｅｃ／１００ｃｃＡｉｒである。所望の透気抵抗度にするには、改質多孔層の空孔率を調整し、バインダーのポリオレフィン多孔質膜への浸み込み程度を調整することにより得られる。積層多孔質膜の透気抵抗度が上記好ましい範囲であると、十分な絶縁性が得られ、異物詰まり、短絡および破膜を防ぐ。また、膜抵抗を抑えることで実使用可能な範囲の充放電特性、寿命特性が得られる。 The air resistance of the laminated porous membrane is one of the most important characteristics, and is preferably 50 to 600 sec / 100 cc Air, more preferably 100 to 500 sec / 100 cc Air, and further preferably 100 to 400 sec / 100 cc Air. The desired air resistance can be obtained by adjusting the porosity of the modified porous layer and adjusting the degree of penetration of the binder into the polyolefin porous membrane. If the air permeability resistance of the laminated porous membrane is within the above-mentioned preferable range, sufficient insulation can be obtained, and foreign matter clogging, short-circuiting and membrane breakage can be prevented. Further, by suppressing the film resistance, charge / discharge characteristics and life characteristics within a practically usable range can be obtained.
４．ポリオレフィン多孔質膜への改質多孔層の積層方法
　次に本発明におけるポリオレフィン多孔質膜への改質多孔層の積層方法について説明する。
　ポリオレフィン多孔質膜へ改質多孔層を積層する方法は、公知の方法を用いることができる。具体的には、前記塗布液をポリオレフィン多孔質膜に所定の膜厚になるように後述する方法で塗工し、乾燥温度４０～８０℃、乾燥時間５秒から６０秒の条件下で乾燥させる方法で得ることができる。また、バインダーが可溶でかつ水と混和する溶媒で溶解した塗布液を所定のポリオレフィン多孔質膜に後述する塗布法を用いて積層し、特定の湿度環境下に置き、バインダーと水とを混和する溶媒を相分離させ、さらに水浴（凝固浴）に投入してバインダーを凝固させる方法も用いることができる。 4). Lamination method of the modified porous layer on the polyolefin porous membrane Next, the lamination method of the modified porous layer on the polyolefin porous membrane in the present invention will be described.
As a method of laminating the modified porous layer on the polyolefin porous membrane, a known method can be used. Specifically, the coating solution is applied to the polyolefin porous film by a method described later so as to have a predetermined film thickness, and dried under conditions of a drying temperature of 40 to 80 ° C. and a drying time of 5 seconds to 60 seconds. Can be obtained by the method. In addition, a coating solution in which the binder is soluble and dissolved in a solvent miscible with water is laminated on a predetermined polyolefin porous membrane using the coating method described later, and placed in a specific humidity environment to mix the binder and water. It is also possible to use a method in which the solvent to be phase-separated and further fed into a water bath (coagulation bath) to coagulate the binder.
　塗布液を塗布する方法としては、例えば、ディップ法、リバースロール・コート法、グラビア・コート法、キス・コート法、ロールブラッシュ法、スプレーコート法、エアナイフコート法、マイヤーバーコート法、パイプドクター法、ブレードコート法およびダイコート法などが挙げられ、これらの方法は単独又は組み合わせて行うことができる。 Examples of methods for applying the coating liquid include dip method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, Mayer bar coating method, pipe doctor method , Blade coating method, die coating method and the like, and these methods can be carried out alone or in combination.
　本発明の積層多孔質膜は、乾燥状態で保存することが望ましいが、絶乾状態での保存が困難な場合は、使用の直前に１００℃以下の減圧乾燥処理を行うことが好ましい。 The laminated porous membrane of the present invention is desirably stored in a dry state, but when it is difficult to store in a completely dry state, it is preferable to perform a vacuum drying treatment at 100 ° C. or lower immediately before use.
　本発明の積層多孔質膜は、ニッケル‐水素電池、ニッケル－カドミウム電池、ニッケル‐亜鉛電池、銀－亜鉛電池、リチウム二次電池、リチウムポリマー二次電池等の二次電池、およびプラスチックフィルムコンデンサ、セラミックコンデンサ、電気二重層コンデンサなどのセパレータとして用いることができるが、特にリチウムイオン二次電池のセパレータとして用いるのが好ましい。以下にリチウムイオン二次電池を例にとって説明する。 The laminated porous membrane of the present invention includes a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-zinc battery, a silver-zinc battery, a secondary battery such as a lithium secondary battery, a lithium polymer secondary battery, and a plastic film capacitor, Although it can be used as a separator for ceramic capacitors, electric double layer capacitors, etc., it is particularly preferred to be used as a separator for lithium ion secondary batteries. Hereinafter, a lithium ion secondary battery will be described as an example.
　リチウムイオン二次電池は、正極と負極がセパレータを介して積層されており、セパレータは電解液（電解質）を含有している。電極の構造は特に限定されず、公知の構造であってよい。例えば、円盤状の正極及び負極が対向するように配設された電極構造（コイン型）、平板状の正極及び負極が交互に積層された電極構造（積層型）、帯状の正極及び負極が重ねられて巻回された電極構造（巻回型）等の構造とすることができる。 In a lithium ion secondary battery, a positive electrode and a negative electrode are laminated via a separator, and the separator contains an electrolytic solution (electrolyte). The structure of the electrode is not particularly limited, and may be a known structure. For example, an electrode structure (coin type) in which disc-shaped positive electrodes and negative electrodes are opposed to each other, an electrode structure in which flat plate-like positive electrodes and negative electrodes are alternately stacked (stacked type), and belt-shaped positive electrodes and negative electrodes are stacked. It can be set as a structure such as a wound electrode structure (winding type).
　正極は、通常集電体とその表面に形成されたリチウムイオンを吸蔵放出可能な正極活物質を含む正極活物質層とを有する。正極活物質としては、遷移金属酸化物、リチウムと遷移金属との複合酸化物（リチウム複合酸化物）、遷移金属硫化物等の無機化合物等が挙げられる。遷移金属としては、Ｖ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ等が挙げられる。正極活物質の中でリチウム複合酸化物の好ましい例としては、ニッケル酸リチウム、コバルト酸リチウム、マンガン酸リチウム、α‐ＮａＦｅＯ２型構造を母体とする層状リチウム複合酸化物等が挙げられる。 The positive electrode usually has a current collector and a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium ions formed on the surface of the current collector. Examples of the positive electrode active material include transition metal oxides, composite oxides of lithium and transition metals (lithium composite oxides), inorganic compounds such as transition metal sulfides, and the like. Examples of the transition metal include V, Mn, Fe, Co, and Ni. Preferred examples of the lithium composite oxide in the positive electrode active material include lithium nickelate, lithium cobaltate, lithium manganate, and a layered lithium composite oxide based on an α-NaFeO 2 type structure.
　負極は、集電体とその表面に形成された負極活物質を含む負極活物質層とを有する。負極活物質としては、天然黒鉛、人造黒鉛、コークス類、カーボンブラック等の炭素質材料が挙げられる。電解液はリチウム塩を有機溶媒に溶解することにより得られる。リチウム塩としては、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、Ｌｉ２Ｂ１０Ｃｌ１０、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２、ＬｉＰＦ４（ＣＦ３）２、ＬｉＰＦ３（Ｃ２Ｆ５）３、低級脂肪族カルボン酸リチウム塩、ＬｉＡｌＣｌ４等が挙げられる。これらは単独で用いても２種以上を混合して用いてもよい。有機溶媒としては、エチレンカーボネート、プロピレンカーボネート、エチルメチルカーボネート、γ‐ブチロラクトン等の高沸点及び高誘電率の有機溶媒や、テトラヒドロフラン、２‐メチルテトラヒドロフラン、ジメトキシエタン、ジオキソラン、ジメチルカーボネート、ジエチルカーボネート等の低沸点及び低粘度の有機溶媒が挙げられる。これらは単独で用いても２種以上を混合して用いてもよい。特に高誘電率の有機溶媒は粘度が高く、低粘度の有機溶媒は誘電率が低いため、両者を混合して用いるのが好ましい。 The negative electrode has a current collector and a negative electrode active material layer including a negative electrode active material formed on the surface of the current collector. Examples of the negative electrode active material include carbonaceous materials such as natural graphite, artificial graphite, cokes, and carbon black. The electrolytic solution can be obtained by dissolving a lithium salt in an organic solvent. Lithium salts include 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 B 10 Cl 10 , LiN (C 2 F 5 SO 2 ) 2, LiPF 4 (CF 3) 2, LiPF 3 (C 2 F5) 3, lower aliphatic carboxylic acid lithium salts, and the like LiAlC l4 like. These may be used alone or in admixture of two or more. Examples of the organic solvent include high boiling point and high dielectric constant organic solvents such as ethylene carbonate, propylene carbonate, ethyl methyl carbonate, and γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxyethane, dioxolane, dimethyl carbonate, diethyl carbonate, and the like. Examples include organic solvents having a low boiling point and a low viscosity. These may be used alone or in admixture of two or more. In particular, a high dielectric constant organic solvent has a high viscosity, and a low viscosity organic solvent has a low dielectric constant. Therefore, it is preferable to use a mixture of both.
　電池を組み立てる際に、本発明のセパレータに電解液を含浸させ、セパレータにイオン透過性を付与することができる。通常、含浸処理は微多孔膜を常温で電解液に浸漬して行う。例えば、円筒型電池を組み立てる場合、まず正極シート、セパレータ（複合多孔質膜）、及び負極シートをこの順に積層し、この積層体を一端より巻き取って巻回型電極素子とする。次にこの電極素子を電池缶に挿入し、上記電解液を含浸させ、さらに安全弁を備えた正極端子を兼ねる電池蓋を、ガスケットを介してかしめることにより電池を得ることができる。 When assembling the battery, the separator of the present invention can be impregnated with an electrolytic solution to impart ion permeability to the separator. Usually, the impregnation treatment is performed by immersing the microporous membrane in an electrolytic solution at room temperature. For example, when assembling a cylindrical battery, first, a positive electrode sheet, a separator (composite porous membrane), and a negative electrode sheet are laminated in this order, and this laminate is wound from one end to form a wound electrode element. Next, a battery can be obtained by inserting this electrode element into a battery can, impregnating with the above electrolyte, and caulking a battery lid also serving as a positive electrode terminal provided with a safety valve via a gasket.
　以下、実施例を示して具体的に説明するが、本発明はこれらの実施例よって何ら制限されるものではない。なお、実施例中の測定値は以下の方法で測定した値である。 Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In addition, the measured value in an Example is a value measured with the following method.
１．バインダーの引っ張り強度（Ｎ／ｍｍ２）
　実施例および比較例で用いたバインダーが可溶な溶媒に十分溶解または水分散させ、ＪＩＳ　Ｋ７１１３に規定の２号形試験片作製用のダンベル型に乾燥後の膜厚が約１００μｍになるように入れて２５℃で自然乾燥させ、さらに２５℃で８時間真空乾燥（真空度３ｍｍＨｇ）を行って溶媒を十分除去して得られた試料シートを引っ張り強度測定に供した。引張試験機（（株）島津製作所製　Ａｕｔｏｇｒａｐｈ　ＡＧＳ-Ｊ　ロードセル容量１ｋＮ）を用いて以下の条件で測定した。サンプルフィルム、測定条件は以下の通りであり、３回測定を行い、その平均値をバインダーの引っ張り強度とした。
　チャック間距離：４０ｍｍ
　試験速度：２０ｍｍ／ｍｉｎ
　測定環境：気温２０℃、相対湿度６０％ 1. Tensile strength of binder (N / mm 2 )
The binder used in the examples and comparative examples is sufficiently dissolved or dispersed in a soluble solvent so that the film thickness after drying is about 100 μm to the dumbbell type for preparing No. 2 type test piece defined in JIS K7113. Then, the sample sheet was naturally dried at 25 ° C. and further vacuum-dried (vacuum degree 3 mmHg) at 25 ° C. for 8 hours to sufficiently remove the solvent, and the sample sheet was subjected to tensile strength measurement. Measurement was performed under the following conditions using a tensile tester (Autograph AGS-J, load cell capacity: 1 kN, manufactured by Shimadzu Corporation). The sample film and measurement conditions were as follows. The measurement was performed three times, and the average value was defined as the tensile strength of the binder.
Distance between chucks: 40mm
Test speed: 20 mm / min
Measurement environment: temperature 20 ° C, relative humidity 60%
２．突起の数
　突起の数と大きさは免震台上に設置したコンフォーカル（共焦点）顕微鏡（Ｌａｓｅｒｔｅｃ社製　ＨＤ１００）を用いて、光源を安定化させた後に測定した。
（手順）
（１）実施例および比較例で得られた電池用セパレータの任意の片面（Ａ面とする）に１ｃｍ×１ｃｍの正方形の枠を極細油性ペンで描いた。
（２）上記正方形の枠を描いた面を上にしてサンプルステージに載せ、コンフォーカル顕微鏡付属の静電気密着装置を用いてサンプルステージに密着固定させた。
（３）倍率５倍の対物レンズを用いて、図３のようなポリエチレンの球晶に由来するリング状痕をモニターに二次元画像（本装置ではＲＥＡＬ画面と称す）として表示させ、リング状痕の最も色の濃い部分がモニター画面のほぼ中央に位置するようにサンプルステージ位置を調整した。リング状痕が２つ連なっている場合はその接点に合わせた。突起高さ測定の対象は前記ポリエチレンの球晶に由来するリング状痕の長径が０．２ｍｍ以上のものとした。リング状痕の長径は前記二次元画像にて長径方向にリングの両端にカーソルを合わせ、その長さを読み取った。
（４）対物レンズを２０倍レンズに替え、モニター画面の中央部にフォーカスを合わせて（本装置ではモニター画面の中央部が最も明るく表示されようにする）、この高さ位置を基準高さとした（本装置ではＲＥＦ ＳＥＴと称す）。
（５）高さ方向の測定範囲は前記基準高さを０μｍとして上下１５μｍに設定した。また、スキャン時間１２０秒、ＳＴＥＰ移動距離０．１μｍ／Ｓｔｅｐとし、三次元データを取り込んだ。
（６）三次元データ取り込み後、データ処理用画像（本装置ではＺ画像と称す）を表示させ、スムージング処理を行った（スムージング条件：フィルタサイズ３ｘ３、マトリックスタイプ　SMOOTH3_0、回数1回）。また、必要に応じて水平補正画面にて水平補正を行った。
（７）データ処理用画像にて最も高い突起を通る位置（最も明るい部分）に水平方向にカーソルを置き、前記カーソルに対応した断面プロファイルを、断面プロファイル画像に表示させた。
（８）断面プロファイル画像にて垂直方向に２本のカーソルを突起の両袖の変曲点に合わせ両カーソル間の距離を突起の大きさとした。
（９）断面プロファイル画像にて水平方向に２本のカーソルを突起の頂点と突起の両袖の変曲点に合わせ（突起の両袖の変曲点の高さが異なる場合は低い方）両カーソル間の距離を突起の高さとした。
（１０）前記操作を前記１ｃｍ×１ｃｍの正方形の枠内で繰り返し、大きさ５μｍ以上、５０μｍ以下、高さ０．５μｍ以上、３．０μｍ以下の突起の数を数え１ｃｍ２当たりのＡ面の突起数を求め、さらにその突起の高さ平均値を求めてＡ面の平均突起高さとした。Ａ面と反対面（Ｂ面とする。）についても同様の操作を行いＢ面の突起数と平均突起高さを求めた。 2. Number of protrusions The number and size of protrusions were measured after stabilizing the light source using a confocal microscope (HD100 manufactured by Lasertec) installed on a base isolation table.
(procedure)
(1) A square frame of 1 cm × 1 cm was drawn with an ultrafine oil pen on any one side (referred to as A-side) of the battery separator obtained in the examples and comparative examples.
(2) The surface on which the square frame was drawn was placed on the sample stage, and was fixed to the sample stage using an electrostatic contact apparatus attached to the confocal microscope.
(3) Using an objective lens with a magnification of 5 times, a ring-shaped trace derived from a polyethylene spherulite as shown in FIG. 3 is displayed on a monitor as a two-dimensional image (referred to as a REAL screen in this apparatus), and the ring-shaped trace is displayed. The position of the sample stage was adjusted so that the darkest part of was positioned almost at the center of the monitor screen. When two ring-shaped marks were connected, the contact was made. The object of the projection height measurement was such that the major axis of the ring-shaped trace derived from the polyethylene spherulites was 0.2 mm or more. As for the major axis of the ring-shaped mark, the cursor was placed on both ends of the ring in the major axis direction in the two-dimensional image, and the length was read.
(4) Change the objective lens to a 20x lens and focus on the center of the monitor screen (in this device, the center of the monitor screen is displayed brightest), and this height position is used as the reference height (This device is called REF SET).
(5) The measurement range in the height direction was set to 15 μm above and below, with the reference height being 0 μm. Also, the scan time was 120 seconds, the STEP moving distance was 0.1 μm / Step, and the three-dimensional data was captured.
(6) After capturing the three-dimensional data, a data processing image (referred to as a Z image in the present apparatus) was displayed and smoothing processing was performed (smoothing condition: filter size 3 × 3, matrix type SMOOTH3_0, number of times once). In addition, horizontal correction was performed on the horizontal correction screen as necessary.
(7) A cursor was placed in a horizontal direction at a position (the brightest part) passing through the highest protrusion in the data processing image, and a cross-sectional profile corresponding to the cursor was displayed on the cross-sectional profile image.
(8) In the cross-sectional profile image, the two cursors were aligned with the inflection points of the sleeves of the protrusions in the vertical direction, and the distance between the cursors was taken as the protrusion size.
(9) In the cross-sectional profile image, align the two cursors in the horizontal direction with the inflection points of the top of the protrusion and the sleeves of the protrusion (if the height of the inflection points of the sleeves of the protrusion is different) The distance between the cursors was the height of the protrusion.
(10) The operation was repeated within the framework of the square of the 1 cm × 1 cm, the size 5μm or more, 50 [mu] m or less, the height 0.5μm or more, the surface A per 1 cm 2 counts the number of the following projection 3.0μm The number of protrusions was determined, and the average height of the protrusions was determined as the average protrusion height of the A surface. The same operation was performed on the surface opposite to the A surface (referred to as the B surface), and the number of protrusions and the average protrusion height on the B surface were obtained.
３．改質多孔層の０°の剥離強度
　任意の面（例えばＡ面）を測定するために、反対面（Ｂ面）の改質多孔層を予め粘着テープで剥離し、ポリオレフィン多孔質膜一方の表面を露出させて試料に供した。
　図１に、評価方法を模式的に示す。１が積層試料、２がポリオレフィン多孔質膜、３が改質多孔層、４が両面粘着テープ、５及び５’がアルミニウム板であり、図中の矢印が引張方向である。大きさ５０ｍｍ×２５ｍｍ、厚さ０．５ｍｍのアルミニウム板５に同じ大きさの両面粘着テープ（ニチバン（株）製ＮＷ‐Ｋ５０）４を貼り付けた。その上に幅５０ｍｍ×長さ１００ｍｍに切り出した試料１（電池用セパレータ）のポリオレフィン多孔質膜２の面を前記アルミニウム板５の２５ｍｍ長さの片辺の端から４０ｍｍが重なるように貼り付け、はみ出た部分を切り取った。次いで、長さ１００ｍｍ、幅１５ｍｍ、厚さ０．５ｍｍのアルミニウム板５’の片面に両面粘着テープを貼り付け、前記アルミニウム板５の２５ｍｍ長さの試料側の片辺の端から２０ｍｍが重なるように貼り付けた。その後、試料を挟持したアルミニウム板５とアルミニウム板５’を引張試験機（（株）島津製作所製Ａｕｔｏｇｒａｐｈ　ＡＧＳ-Ｊ　１ｋＮ）に取り付け、アルミニウム板５とアルミニウム板５’のそれぞれを平行に反対方向に引張速度１０ｍｍ／ｍｉｎで引っ張り、改質多孔層が剥離したときの強度を測定した。この測定を長手方向に３０ｃｍ以上の間隔を空けた任意の３点について行い、その平均値をＡ面の改質多孔層の０°の剥離強度とした。Ｂ面についても同様に改質多孔層の０°の剥離強度を求めた。 3. 0 ° peel strength of the modified porous layer In order to measure an arbitrary surface (for example, A surface), the modified porous layer on the opposite surface (B surface) was previously peeled off with an adhesive tape, and one surface of the polyolefin porous membrane Was exposed to a sample.
FIG. 1 schematically shows the evaluation method. 1 is a laminated sample, 2 is a polyolefin porous membrane, 3 is a modified porous layer, 4 is a double-sided pressure-sensitive adhesive tape, 5 and 5 'are aluminum plates, and the arrows in the figure are tensile directions. A double-sided adhesive tape (NW-K50 manufactured by Nichiban Co., Ltd.) 4 having the same size was attached to an aluminum plate 5 having a size of 50 mm × 25 mm and a thickness of 0.5 mm. The surface of the polyolefin porous membrane 2 of the sample 1 (battery separator) cut out to a width of 50 mm and a length of 100 mm was pasted thereon so that 40 mm overlapped from the edge of one side of the 25 mm length of the aluminum plate 5, The protruding part was cut off. Next, a double-sided adhesive tape is attached to one side of an aluminum plate 5 ′ having a length of 100 mm, a width of 15 mm, and a thickness of 0.5 mm, so that 20 mm overlaps from the end of one side of the 25 mm long sample side of the aluminum plate 5. Pasted on. Thereafter, the aluminum plate 5 and the aluminum plate 5 ′ sandwiching the sample are attached to a tensile tester (Autograph AGS-J 1kN, manufactured by Shimadzu Corporation), and the aluminum plate 5 and the aluminum plate 5 ′ are respectively parallel and opposite to each other. The tensile strength was measured at 10 mm / min when the modified porous layer was peeled off. This measurement was performed for any three points spaced 30 cm or more in the longitudinal direction, and the average value was defined as the 0 ° peel strength of the modified porous layer on the A surface. Similarly, the peel strength at 0 ° of the modified porous layer was also obtained for the B surface.
４．膜厚
　接触式膜厚計（（株）ミツトヨ製ライトマチックｓｅｒｉｅｓ３１８）を使用して２０点の測定値を平均することによって求めた。超硬球面測定子φ９．５ｍｍを用い、加重０．０１Ｎの条件で測定した。 4). Film thickness It calculated | required by averaging the measured value of 20 points | pieces using the contact-type film thickness meter (Corporation | KK Mitutoyo lightmatic series318). The measurement was performed under the condition of a weight of 0.01 N using a carbide spherical measuring element φ9.5 mm.
５．平均孔径
　ポリオレフィン多孔質膜の平均孔径は以下の方法で測定した。試料を測定用セルの上に両面テープを用いて固定し、プラチナまたは金を数分間真空蒸着させ、適度な倍率で膜の表面をＳＥＭ測定した。ＳＥＭ測定で得られた画像上で任意の１０箇所を選択し、それら１０箇所の孔径の平均値を試料の平均孔径とした。 5. Average pore diameter The average pore diameter of the polyolefin porous membrane was measured by the following method. The sample was fixed on the measurement cell using double-sided tape, platinum or gold was vacuum-deposited for several minutes, and the surface of the film was subjected to SEM measurement at an appropriate magnification. Arbitrary ten places were selected on the image obtained by SEM measurement, and the average value of the pore diameters at these ten places was taken as the average pore diameter of the sample.
６．透気抵抗度（ｓｅｃ／１００ｃｃＡｉｒ）
　テスター産業（株）製のガーレー式デンソメーターＢ型を使用して、ポリオレフィン多孔質膜又は積層多孔質膜をクランピングプレートとアダプタープレートの間にシワが入らないように固定し、ＪＩＳ　Ｐ８１１７に従って測定した。試料は１０ｃｍ角とし、測定点は試料の中央部と４隅の計５点として、その平均値を透気抵抗度として用いた。なお、試料の１辺の長さが１０ｃｍに満たない場合は５ｃｍ間隔で５点測定した値を用いてもよい。透気抵抗度の上昇幅は下記の式より求めた。
透気抵抗度の上昇幅＝（Ｙ）－（Ｘ）ｓｅｃ／１００ｃｃＡｉｒ
ポリオレフィン多孔質膜の透気抵抗度度（Ｘ）ｓｅｃ／１００ｃｃＡｉｒ
積層多孔質膜の透気抵抗度度（Ｙ）ｓｅｃ／１００ｃｃＡｉｒ 6). Air permeability resistance (sec / 100ccAir)
Using a Gurley Densometer Type B manufactured by Tester Sangyo Co., Ltd., fix the polyolefin porous film or laminated porous film so that there is no wrinkle between the clamping plate and the adapter plate, and measure according to JIS P8117 did. The sample was a 10 cm square, the measurement points were a total of 5 points at the center and 4 corners of the sample, and the average value was used as the air resistance. When the length of one side of the sample is less than 10 cm, a value obtained by measuring five points at intervals of 5 cm may be used. The increase width of the air permeability resistance was obtained from the following formula.
Increasing width of air resistance = (Y) − (X) sec / 100 cc Air
Air permeability resistance of polyolefin porous membrane (X) sec / 100ccAir
Degree of air permeability of laminated porous membrane (Y) sec / 100ccAir
７．ポリオレフィン多孔質膜の空孔率
　１０ｃｍ角の試料を用意し、その試料体積（ｃｍ３）と質量（ｇ）を測定し得られた結
果から次式を用いて空孔率（％）を計算した。
空孔率＝（１－質量／（樹脂密度×試料体積））×１００ 7). Porosity of Polyolefin Porous Membrane A 10 cm square sample was prepared, and the sample volume (cm 3 ) and mass (g) were measured. From the results obtained, the porosity (%) was calculated using the following formula. .
Porosity = (1−mass / (resin density × sample volume)) × 100
８．耐擦れ性
　実施例及び比較例で得られたロール状積層多孔質膜を巻きだしながら、両端をスリット加工した。スリット加工はスリッター（（株）西村製作所製　ＷＡ１７７Ａ型）を用いて速度２０ｍ／分、張力６０Ｎ／１００ｍｍの条件で行った。加工中、塗工面に接触するロールはハードクロムメッキロール２本（いずれもフリーロール）とした。次いで、スリット加工済のロール状積層多孔質膜を巻き戻しながら目視、および拡大率１０倍のスケール付きルーペ（ＰＥＡＫ社ＳＣＡＬＥ ＬＵＰＥ×１０）を用いて、長径０．５ｍｍ以上の改質多孔層の剥離欠点を数え、以下の判定基準で評価した。評価面積は幅１００ｍｍ×長さ５００ｍとした。（幅が１００ｍｍに満たない場合は長さを調整し、同様の評価面積になるようにした。）
判定基準
○（極めて良好）：５ヶ以下
△（良好）：６～１５ヶ
×（不良）：１６ヶ以上 8). Scratch resistance Both ends were slit while rolling the roll-shaped laminated porous membrane obtained in the examples and comparative examples. Slit processing was performed using a slitter (WA177A model manufactured by Nishimura Seisakusho Co., Ltd.) under conditions of a speed of 20 m / min and a tension of 60 N / 100 mm. During processing, the rolls that contact the coated surface were two hard chrome plating rolls (both free rolls). Next, using a magnifying glass with a scale of 10 times magnification (PEAK SCALE LUPE × 10) while rewinding the roll-shaped laminated porous membrane after slitting, the modified porous layer having a major axis of 0.5 mm or more was used. The peeling defects were counted and evaluated according to the following criteria. The evaluation area was 100 mm wide × 500 m long. (When the width was less than 100 mm, the length was adjusted so that the same evaluation area was obtained.)
Judgment criteria ○ (very good): 5 or less △ (good): 6 to 15 × (defect): 16 or more
実施例１
　重量平均分子量が２００万の超高分子量ポリエチレン（ＵＨＭＷＰＥ）２重量％及び重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）９８重量％からなる組成物（Ｍｗ／Ｍｎ＝１６．０）１００重量部に、酸化防止剤０．３７５重量部を加えたポリエチレン組成物（融点１３５℃）を得た。このポリエチレン組成物３０重量部を二軸押出機に投入した。この二軸押出機のサイドフィーダーから流動パラフィン７０重量部を供給し、溶融混練して、押出機中にてポリエチレン樹脂溶液を調製した。続いて、ポリエチレン樹脂溶液を押出機の先端に設置されＴ型ダイから１９０℃、押出し厚さ８２５μｍで押出し、フィルム状に押し出されたポリエチレン樹脂溶液を、その両側に配置され（図４参照）、かつ冷却ロール内部冷却水温度を２５℃に保った２つの冷却ロールで引き取りながらゲル状成形物を形成した。この時、それぞれの冷却ロールにおいて、ゲル状成形物が冷却ロールから離れる点からＴ型ダイから押し出されたポリエチレン樹脂溶液と冷却ロールとが接する点までの間に１枚のポリエステル製ドクターブレードをゲル状成形物の幅方向と平行に冷却ロールに接するようにあてて、冷却ロール上に付着している流動パラフィンを掻き落とした。続いてこのゲル状成形物を、所望の透気抵抗度になるように温度を調節しながら５×５倍に同時２軸延伸を行い、延伸成形物を得た。得られた延伸成形物を塩化メチレンで洗浄して残留する流動パラフィンを除去し、乾燥して多孔質成形物を得た。その後、テンターに多孔質膜を保持し、ＴＤ（幅方向）方向にのみ１０％縮幅し、９０℃、３秒間熱処理し、厚さ１６μｍ、空孔率４５％、平均孔径０．１５μｍ、透気抵抗度２４０ｓｅｃ／１００ｃｃＡｉｒのポリエチレン多孔質膜を得た。
　(塗布液Ａの調合)
　ポリビニルアルコール（平均重合度１７００、ケン化度９９％以上）、平均粒径０．５μｍのアルミナ粒子、イオン交換水をそれぞれ６：５４：４０の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製“トレセラム”（登録商標）ビーズ、直径０．５ｍｍ）と共にポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、塗布液（ａ）を得た。
　（塗布液Ｂの調合）
　温度計、冷却管、窒素ガス導入管のついた４ツ口フラスコにトリメリット酸無水物（ＴＭＡ）１モル、ｏ‐トリジンジイソシアネート（ＴＯＤＩ）０．８モル、２，４‐トリレンジイソシアネート（ＴＤＩ）０．２モル、フッ化カリウム０．０１モルを固形分濃度が１４％となるようにＮ‐メチル‐２‐ピロリドンと共に仕込み、１００℃で５時間攪拌した後、固形分濃度が１４％となるようにＮ‐メチル‐２‐ピロリドンで希釈してポリアミドイミド樹脂溶液を合成した。得られたポリアミドイミド樹脂の対数粘度は１．３５ｄｌ／ｇ、ガラス転移温度は３２０℃であった。 Example 1
100 parts by weight of a composition (Mw / Mn = 16.0) comprising 2% by weight of ultrahigh molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2 million and 98% by weight of high density polyethylene (HDPE) having a weight average molecular weight of 350,000 In addition, a polyethylene composition (melting point: 135 ° C.) obtained by adding 0.375 parts by weight of an antioxidant was obtained. 30 parts by weight of this polyethylene composition was put into a twin screw extruder. 70 parts by weight of liquid paraffin was supplied from the side feeder of this twin screw extruder, melt kneaded, and a polyethylene resin solution was prepared in the extruder. Subsequently, the polyethylene resin solution was placed at the tip of the extruder and extruded from a T-die at 190 ° C. with an extrusion thickness of 825 μm, and the polyethylene resin solution extruded into a film was placed on both sides (see FIG. 4). And the gel-like molded object was formed, taking up with the two cooling rolls which maintained the cooling water temperature inside a cooling roll at 25 degreeC. At this time, in each cooling roll, one polyester doctor blade is gelled between the point where the gel-like molded product is separated from the cooling roll and the point where the polyethylene resin solution extruded from the T-shaped die contacts the cooling roll. The liquid paraffin adhering on the cooling roll was scraped off so as to be in contact with the cooling roll in parallel with the width direction of the shaped molding. Subsequently, the gel-like molded product was simultaneously biaxially stretched 5 × 5 times while adjusting the temperature so as to obtain a desired air permeability resistance to obtain a stretched molded product. The obtained stretched molded product was washed with methylene chloride to remove residual liquid paraffin and dried to obtain a porous molded product. After that, the porous film is held on the tenter, reduced in width by 10% only in the TD (width direction) direction, heat treated at 90 ° C. for 3 seconds, thickness 16 μm, porosity 45%, average pore diameter 0.15 μm, transparent A polyethylene porous membrane having a gas resistance of 240 sec / 100 cc Air was obtained.
(Preparation of coating solution A)
Polyvinyl alcohol (average polymerization degree 1700, saponification degree 99% or more), alumina particles having an average particle diameter of 0.5 μm, and ion-exchanged water were blended in a weight ratio of 6:54:40, respectively, and zirconium oxide beads (Toray Industries, Inc. ) “Traceram” (registered trademark) beads, 0.5 mm in diameter) and placed in a polypropylene container, and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (a).
(Preparation of coating solution B)
In a four-necked flask equipped with a thermometer, a condenser tube, and a nitrogen gas inlet tube, 1 mole of trimellitic anhydride (TMA), 0.8 mole of o-tolidine diisocyanate (TODI), 2,4-tolylene diisocyanate (TDI) ) 0.2 mol and 0.01 mol of potassium fluoride were charged together with N-methyl-2-pyrrolidone so that the solid concentration was 14%, and stirred at 100 ° C. for 5 hours. A polyamide-imide resin solution was synthesized by diluting with N-methyl-2-pyrrolidone. The obtained polyamideimide resin had a logarithmic viscosity of 1.35 dl / g and a glass transition temperature of 320 ° C.
　ポリアミドイミド樹脂溶液及び平均粒径０．５μｍのアルミナ粒子、Ｎ‐メチル‐２‐ピロリドンをそれぞれ２６：３４：４０の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製、“トレセラム”（登録商標）ビーズ、直径０．５ｍｍ）と共にポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、塗布液（ｂ）を得た。前記ポリエチレン多孔質膜の片面（Ａ面とする）に塗布液（ａ）をグラビアコート法にて乾燥後の厚みで２μｍ塗布し、５０℃の熱風乾燥炉を１０秒間通過させることで乾燥させた。次いで反対面（Ｂ面とする）に乾燥後の厚みで２．５μｍ塗布し、温度２５℃、絶対湿度１２ｇ／ｍ３の調湿ゾーンを５秒間で通過させた後、Ｎ‐メチル‐２‐ピロリドンを５重量％含有する水溶液中に１０秒間浸漬した。さらに、純水で洗浄した後、７０℃の熱風乾燥炉を通過させることで乾燥して、最終厚み２０．５μｍの積層多孔質膜を得た。 Polyamideimide resin solution, alumina particles having an average particle size of 0.5 μm, and N-methyl-2-pyrrolidone were blended in a weight ratio of 26:34:40, respectively, and zirconium oxide beads (“Traceram” manufactured by Toray Industries, Inc.) (Registered trademark) beads, 0.5 mm in diameter) were placed in a polypropylene container and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (b). The coating liquid (a) was applied to one side (referred to as side A) of the polyethylene porous membrane by a gravure coating method to a thickness of 2 μm after drying, and dried by passing through a hot air drying oven at 50 ° C. for 10 seconds. . Next, 2.5 μm in thickness after drying was applied to the opposite surface (referred to as B surface), and after passing through a humidity control zone having a temperature of 25 ° C. and an absolute humidity of 12 g / m 3 for 5 seconds, N-methyl-2- It was immersed for 10 seconds in an aqueous solution containing 5% by weight of pyrrolidone. Furthermore, after washing with pure water, it was dried by passing through a hot air drying furnace at 70 ° C. to obtain a laminated porous membrane having a final thickness of 20.5 μm.
実施例２
　重量平均分子量が２００万の超高分子量ポリエチレン（ＵＨＭＷＰＥ）と重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）の配合比を１０：９０（重量％比）に変更した以外は実施例１と同様にして積層多孔質膜を得た。 Example 2
Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2 million and high density polyethylene (HDPE) having a weight average molecular weight of 350,000 was changed to 10:90 (weight% ratio). Thus, a laminated porous membrane was obtained.
実施例３
　重量平均分子量が２００万の超高分子量ポリエチレン（ＵＨＭＷＰＥ）と重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）の配合比を２０：８０（重量％比）に変更した以外は実施例１と同様にして積層多孔質膜を得た。 Example 3
Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) with a weight average molecular weight of 2 million and high density polyethylene (HDPE) with a weight average molecular weight of 350,000 was changed to 20:80 (weight% ratio). Thus, a laminated porous membrane was obtained.
実施例４
　重量平均分子量が２００万の超高分子量ポリエチレン（ＵＨＭＷＰＥ）と重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）の配合比を３０：７０（重量％比）に変更した以外は実施例１と同様にして積層多孔質膜を得た。 Example 4
Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) with a weight average molecular weight of 2 million and high density polyethylene (HDPE) with a weight average molecular weight of 350,000 was changed to 30:70 (weight% ratio). Thus, a laminated porous membrane was obtained.
実施例５
　重量平均分子量が２００万の超高分子量ポリエチレン（ＵＨＭＷＰＥ）と重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）の配合比を４０：６０（重量％比）に変更した以外は実施例１と同様にして積層多孔質膜を得た。 Example 5
Example 1 except that the blending ratio of ultra high molecular weight polyethylene (UHMWPE) having a weight average molecular weight of 2 million and high density polyethylene (HDPE) having a weight average molecular weight of 350,000 was changed to 40:60 (weight% ratio). Thus, a laminated porous membrane was obtained.
実施例６
　２つの冷却ロールとも２枚のポリエステル製ドクターブレードを２０ｍｍの間隔で冷却ロールにあてた以外は実施例１と同様にして積層多孔質膜を得た。 Example 6
A laminated porous membrane was obtained in the same manner as in Example 1 except that two polyester doctor blades were applied to the cooling rolls at intervals of 20 mm for both of the two cooling rolls.
実施例７
　２つの冷却ロールとも３枚のポリエステル製ドクターブレードをそれぞれ２０ｍｍの間隔で冷却ロールにあてた以外は実施例１と同様にして積層多孔質膜を得た。 Example 7
A laminated porous membrane was obtained in the same manner as in Example 1 except that three polyester doctor blades were applied to the cooling rolls at intervals of 20 mm for each of the two cooling rolls.
実施例８
　水性アクリルポリオールと水分散性ポリイソシアネート（硬化剤）からなる２液硬化型水性アクリルウレタン樹脂（固形分濃度４５質量％）平均粒径０．５μｍのアルミナ粒子、イオン交換水をそれぞれ１０：４０：５０の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製、“トレセラム”（登録商標）ビーズ、直径０．５ｍｍ）と共にポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、塗布液（ｃ）を得た。塗布液（ａ）を塗布液（ｃ）に替えた以外は実施例１と同様に両面に改質多孔層を積層させ、最終厚み２０．５μｍの積層多孔質膜を得た。 Example 8
Two-part curable aqueous acrylic urethane resin (solid content concentration 45% by mass) composed of aqueous acrylic polyol and water-dispersible polyisocyanate (curing agent), alumina particles having an average particle size of 0.5 μm, and ion-exchanged water are respectively 10:40: 50 parts by weight, zirconium oxide beads (Toray Industries, Inc., “Traceram” (registered trademark) beads, 0.5 mm in diameter) are placed in a polypropylene container, and paint shaker (Toyo Seiki Co., Ltd.) ) For 6 hours. Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (c). A modified porous layer was laminated on both sides in the same manner as in Example 1 except that the coating solution (a) was changed to the coating solution (c) to obtain a laminated porous membrane having a final thickness of 20.5 μm.
実施例９
　ポリビニルアルコールとアクリル酸、メタクリル酸メチルの共重合体（日新化成（株）製“ＰＯＶＡＣＯＡＴ”（登録商標））、平均粒径０．５μｍのアルミナ粒子、溶媒（イオン交換水：エタノール＝７０：３０）をそれぞれ５：４５：５０の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製“トレセラム”（登録商標）ビーズ、直径０．５ｍｍ）と共にポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、塗布液（ｄ）を得た。塗布液（ａ）を塗布液（ｄ）に替えた以外は実施例１と同様に塗布し、両面に改質多孔層を積層させ、最終厚み２０．５μｍの積層多孔質膜を得た。 Example 9
Copolymer of polyvinyl alcohol, acrylic acid and methyl methacrylate (“POVACOAT” (registered trademark) manufactured by Nisshin Kasei Co., Ltd.), alumina particles having an average particle size of 0.5 μm, solvent (ion-exchanged water: ethanol = 70: 30) were mixed at a weight ratio of 5:45:50, respectively, and placed in a polypropylene container together with zirconium oxide beads ("Traceram" (registered trademark) beads, diameter 0.5 mm) manufactured by Toray Industries, Inc.) (Toyo Seiki Seisakusho Co., Ltd.) for 6 hours. Subsequently, it filtered with the filter of the filtration limit 5 micrometers, and obtained the coating liquid (d). The coating liquid (a) was applied in the same manner as in Example 1 except that the coating liquid (d) was changed, and the modified porous layer was laminated on both surfaces to obtain a laminated porous film having a final thickness of 20.5 μm.
実施例１０
　ＫＦポリマー＃１１２０（呉羽化学工業（株）製、ポリフッ化ビニリデン樹脂溶液（融点１７５℃、１２％Ｎ‐メチルピロリドン溶液））及び平均粒径０．５μｍのアルミナ粒子、Ｎ‐メチル‐２‐ピロリドンをそれぞれ１４：１９：６７の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製“トレセラム”（登録商標）ビーズ、直径０．５ｍｍ）と共に、ポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、ワニス（ｅ）を調合した。塗布液（ｂ）を塗布液（ｅ）に替えた以外は実施例１と同様に塗布し、両面に改質多孔層を積層させ、最終厚み２０．５μｍの積層多孔質膜を得た。 Example 10
KF polymer # 1120 (manufactured by Kureha Chemical Industry Co., Ltd., polyvinylidene fluoride resin solution (melting point 175 ° C., 12% N-methylpyrrolidone solution)) and alumina particles having an average particle size of 0.5 μm, N-methyl-2-pyrrolidone Were mixed in a weight ratio of 14:19:67, respectively, and placed in a polypropylene container together with zirconium oxide beads ("Traceram" (registered trademark) beads manufactured by Toray Industries, Inc., diameter 0.5 mm), and a paint shaker (( (Toyo Seiki Seisakusho Co., Ltd.) for 6 hours. Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and prepared the varnish (e). The coating liquid (b) was coated in the same manner as in Example 1 except that the coating liquid (e) was replaced, and the modified porous layer was laminated on both surfaces to obtain a laminated porous film having a final thickness of 20.5 μm.
実施例１１
　冷却ロールの内部冷却水温度を３５℃に保った以外は実施例１と同様にして積層多孔質膜を得た。 Example 11
A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 35 ° C.
実施例１２
　ポリエチレン樹脂溶液の押出し量を調整し、厚さ２０μｍのポリエチレン多孔質膜を得た以外は実施例１と同様にして、最終厚み２４．５μｍの積層多孔質膜を得た。 Example 12
A laminated porous membrane having a final thickness of 24.5 μm was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 20 μm.
実施例１３
　ポリエチレン樹脂溶液の押出し量を調整し、厚さ１２μｍのポリエチレン多孔質膜を得た以外は実施例１と同様にして、最終厚み１６．５μｍの積層多孔質膜を得た。 Example 13
A laminated porous membrane having a final thickness of 16.5 μm was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 12 μm.
実施例１４
　ポリエチレン樹脂溶液の押出し量を調整し、厚さ９μｍのポリエチレン多孔質膜を得た以外は実施例１と同様にして、最終厚み１３．５μｍの積層多孔質膜を得た。 Example 14
A laminated porous membrane having a final thickness of 13.5 μm was obtained in the same manner as in Example 1 except that the extrusion amount of the polyethylene resin solution was adjusted to obtain a polyethylene porous membrane having a thickness of 9 μm.
実施例１５
　ポリエチレン組成物２６重量部を二軸押出機に投入し、二軸押出機のサイドフィーダーから流動パラフィン７４重量部を供給し、溶融混練した以外は実施例１と同様にして、積層多孔質膜を得た。 Example 15
A laminated porous membrane was formed in the same manner as in Example 1 except that 26 parts by weight of the polyethylene composition was charged into a twin screw extruder, 74 parts by weight of liquid paraffin was supplied from the side feeder of the twin screw extruder, and melt kneaded. Obtained.
実施例１６
　ポリエチレン組成物３５重量部を二軸押出機に投入し、二軸押出機のサイドフィーダーから流動パラフィン６５重量部を供給し、溶融混練した以外は実施例１と同様にして、積層多孔質膜を得た。 Example 16
A laminated porous membrane was formed in the same manner as in Example 1 except that 35 parts by weight of a polyethylene composition was charged into a twin screw extruder, 65 parts by weight of liquid paraffin was supplied from a side feeder of the twin screw extruder, and melt kneaded. Obtained.
実施例１７
　塗布液（ａ）においてアルミナ粒子を酸化チタン粒子（平均粒子径０．３８μｍ）に替えた塗布液（ｆ）を調合した。塗布液（ａ）の替わりに塗布液（ｆ）を用いた以外は実施例１と同様にして、積層多孔質膜を得た。 Example 17
A coating solution (f) was prepared by replacing the alumina particles with titanium oxide particles (average particle size 0.38 μm) in the coating solution (a). A laminated porous membrane was obtained in the same manner as in Example 1 except that the coating solution (f) was used instead of the coating solution (a).
実施例１８
　塗布液（ａ）においてアルミナ粒子を板状ベーマイト微粒子（平均粒子径１．０μｍ）替えた塗布液（ｇ）を調合した。塗布液（ａ）の替わりに塗布液（ｇ）を用いた以外は実施例１と同様にして、積層多孔質膜を得た。 Example 18
A coating liquid (g) was prepared by replacing the alumina particles in the coating liquid (a) with plate-like boehmite fine particles (average particle diameter: 1.0 μm). A laminated porous membrane was obtained in the same manner as in Example 1 except that the coating solution (g) was used instead of the coating solution (a).
　実施例１９
　両面とも塗布液（ａ）用いた以外は実施例１と同様にして、積層多孔質膜を得た。 Example 19
A laminated porous membrane was obtained in the same manner as in Example 1 except that the coating liquid (a) was used on both sides.
比較例１
　Ｔ型ダイから押し出されたポリエチレン樹脂溶液を２つの冷却ロールで冷却し、ゲル状成形物を得る際に２つの冷却ロールともドクターブレードを用いず、冷却ロール上に付着している流動パラフィンを掻き落とさなかった以外は実施例１と同様にして、積層多孔質膜を得た。 Comparative Example 1
The polyethylene resin solution extruded from the T-shaped die is cooled with two cooling rolls, and when obtaining a gel-like molded product, neither the two cooling rolls use a doctor blade, but scrape the liquid paraffin adhering to the cooling roll. A laminated porous membrane was obtained in the same manner as in Example 1 except that it was not dropped.
比較例２
　ポリエチレン組成物を重量平均分子量が３５万の高密度ポリエチレン（ＨＤＰＥ）１００重量％からなる組成物（Ｍｗ／Ｍｎ＝１６．０）１００重量部に、酸化防止剤０．３７５重量部を加えたポリエチレン組成物（融点１３５℃）を用いた以外は実施例１と同様にして、積層多孔質膜を得た。 Comparative Example 2
Polyethylene obtained by adding 0.375 parts by weight of an antioxidant to 100 parts by weight of a composition (Mw / Mn = 16.0) comprising 100% by weight of high density polyethylene (HDPE) having a weight average molecular weight of 350,000 A laminated porous membrane was obtained in the same manner as in Example 1 except that the composition (melting point: 135 ° C.) was used.
比較例３
　冷却ロールの内部冷却水温度を０℃に保ち、ドクターブレードを用いなかった以外は実施例１と同様にして、積層多孔質膜を得た。 Comparative Example 3
A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 0 ° C. and the doctor blade was not used.
比較例４
　Ｔ型ダイから押し出されたポリエチレン樹脂溶液を冷却ロールで冷却する替わりに、２５℃に保った水中に１分間浸漬した以外は実施例１と同様にして、積層多孔質膜を得た。 Comparative Example 4
A laminated porous membrane was obtained in the same manner as in Example 1 except that the polyethylene resin solution extruded from the T-shaped die was immersed in water kept at 25 ° C. for 1 minute instead of being cooled with a cooling roll.
比較例５
　実施例１で用いたポリエチレン組成物５０重量部を二軸押出機に投入し、二軸押出機のサイドフィーダーから流動パラフィン５０重量部を供給し、溶融混練して、押出機中にてポリエチレン樹脂溶液を調製しＴ型ダイからの押出しを試みたが、均一なフィルム状に押し出せなかった。 Comparative Example 5
50 parts by weight of the polyethylene composition used in Example 1 was put into a twin screw extruder, 50 parts by weight of liquid paraffin was supplied from the side feeder of the twin screw extruder, melted and kneaded, and the polyethylene resin was fed into the extruder. Although a solution was prepared and extrusion from a T-shaped die was attempted, it was not possible to extrude into a uniform film.
比較例６
　冷却ロールの内部冷却水温度を５０℃に保った以外は実施例１と同様にして、積層多孔質膜を得た。 Comparative Example 6
A laminated porous membrane was obtained in the same manner as in Example 1 except that the internal cooling water temperature of the cooling roll was kept at 50 ° C.
比較例７
　温度計、冷却管、窒素ガス導入管のついた４ツ口フラスコにトリメリット酸無水物（ＴＭＡ）１モル、ｏ‐トリジンジイソシアネート（ＴＯＤＩ）０．８モル、２，４‐トリレンジイソシアネート（ＴＤＩ）０．２モル、フッ化カリウム０．０１モルを固形分濃度が１４％となるようにＮ‐メチル‐２‐ピロリドンと共に仕込み、１００℃で５時間攪拌した後、固形分濃度が１４％となるようにＮ‐メチル‐２‐ピロリドンで希釈してポリアミドイミド樹脂溶液を合成した。
　ポリアミドイミド樹脂溶液及び平均粒径０．５μｍのアルミナ粒子、Ｎ‐メチル‐２‐ピロリドンをそれぞれ１３：４７：４０の重量比率で配合し、酸化ジルコニウムビーズ（東レ（株）製“トレセラム（登録商標）ビーズ”、直径０．５ｍｍ）と共にポリプロピレン製の容器に入れ、ペイントシェーカー（（株）東洋精機製作所製）で６時間分散させた。次いで、濾過限界５μｍのフィルターで濾過し、塗布液（ｈ）を得た。塗布液（ａ）を塗布液（ｈ）に替えた以外は実施例１と同様にして最終厚み２０．５μｍの積層多孔質膜を得た。 Comparative Example 7
In a four-necked flask equipped with a thermometer, a condenser tube, and a nitrogen gas inlet tube, 1 mole of trimellitic anhydride (TMA), 0.8 mole of o-tolidine diisocyanate (TODI), 2,4-tolylene diisocyanate (TDI) ) 0.2 mol and 0.01 mol of potassium fluoride were charged together with N-methyl-2-pyrrolidone so that the solid concentration was 14%, and stirred at 100 ° C. for 5 hours. A polyamide-imide resin solution was synthesized by diluting with N-methyl-2-pyrrolidone.
Polyamideimide resin solution, alumina particles having an average particle diameter of 0.5 μm, and N-methyl-2-pyrrolidone were blended in a weight ratio of 13:47:40, respectively, and zirconium oxide beads (“Traceram (registered trademark) manufactured by Toray Industries, Inc.) were mixed. ) Beads ”, 0.5 mm in diameter) and placed in a polypropylene container and dispersed for 6 hours with a paint shaker (manufactured by Toyo Seiki Seisakusho). Subsequently, it filtered with the filter of 5 micrometers of filtration limits, and obtained the coating liquid (h). A laminated porous membrane having a final thickness of 20.5 μm was obtained in the same manner as in Example 1 except that the coating solution (a) was changed to the coating solution (h).
　実施例１～１９、比較例１～７の製造条件を表１に示す。 Table 1 shows the production conditions of Examples 1 to 19 and Comparative Examples 1 to 7.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　実施例１～１９、比較例１～７で得られたポリオレフィン多孔質膜および積層多孔質膜の特性を表２に示す。 Table 2 shows the characteristics of the polyolefin porous membrane and the laminated porous membrane obtained in Examples 1 to 19 and Comparative Examples 1 to 7.
Figure JPOXMLDOC01-appb-T000002
  
Figure JPOXMLDOC01-appb-T000002
  
１　 積層多孔質膜
２　 ポリオレフィン多孔質膜
３　 改質多孔層
４　 両面粘着テープ
５　 アルミニウム板
５’ アルミニウム板
６　 ポリエチレン球晶の結晶核
７　 Ｔ型ダイ
８　 ポリオレフィン樹脂溶液
９　 冷却ロール
９’ 冷却ロール
１０ ドクターブレード
１１ ゲル状成形物
  DESCRIPTION OF SYMBOLS 1 Laminated porous membrane 2 Polyolefin porous membrane 3 Modified porous layer 4 Double-sided adhesive tape 5 Aluminum plate 5 'Aluminum plate 6 Crystal nuclei of polyethylene spherulite 7 T-type die 8 Polyolefin resin solution 9 Cooling roll 9' Cooling roll 10 Doctor Blade 11 Gel-like molded product

Claims (8)

  1. ポリオレフィンからなる突起が５μｍ≦Ｗ≦５０μｍ（Ｗは突起の大きさ）および０．５μｍ≦Ｈ（Ｈは突起の高さ）をみたし、両面に片面あたり３個／ｃｍ２以上、２００個／ｃｍ２以下で不規則に点在し、かつ膜厚が２５μｍ以下であるポリオレフィン多孔質膜の片面に改質多孔層Ａ,反対面に改質多孔層Ｂを積層した積層多孔質膜であり、少なくとも改質多孔層Ａは引っ張り強度が５Ｎ／ｍｍ２以上のバインダーと無機粒子とを含む積層多孔質膜。 The projections made of polyolefin satisfy 5 μm ≦ W ≦ 50 μm (W is the size of the projection) and 0.5 μm ≦ H (H is the height of the projection), and 3 / cm 2 or more per side on both sides, 200 / a laminated porous membrane in which a modified porous layer A is laminated on one side of a polyolefin porous membrane having a film thickness of 25 μm or less, and the modified porous layer B is laminated on the opposite side, and is irregularly scattered at a cm 2 or less; At least the modified porous layer A is a laminated porous film containing a binder having a tensile strength of 5 N / mm 2 or more and inorganic particles.
  2. 前記引っ張り強度が５Ｎ／ｍｍ２以上のバインダーがポリビニルアルコール又はアクリル系樹脂である請求項１に記載の積層多孔質膜。 The laminated porous membrane according to claim 1, wherein the binder having a tensile strength of 5 N / mm 2 or more is polyvinyl alcohol or an acrylic resin.
  3. 前記無機粒子が炭酸カルシウム、アルミナ、チタニア、硫酸バリウム、マイカ及びベーマイトからなる群から選ばれる少なくとも１種を含む請求項１または請求項２に記載の積層多孔質膜。 The laminated porous membrane according to claim 1 or 2, wherein the inorganic particles include at least one selected from the group consisting of calcium carbonate, alumina, titania, barium sulfate, mica, and boehmite.
  4. ポリオレフィン多孔質膜の厚さが２０μｍ以下である請求項１～３のいずれかに記載の積層多孔質膜。 4. The laminated porous membrane according to claim 1, wherein the polyolefin porous membrane has a thickness of 20 μm or less.
  5. ポリオレフィン多孔質膜の厚さが１６μｍ以下である請求項１～３のいずれかに記載の積層多孔質膜。 4. The laminated porous membrane according to claim 1, wherein the polyolefin porous membrane has a thickness of 16 μm or less.
  6. 電池用セパレータとして用いる請求項１～５のいずれかに記載の積層多孔質膜。 The laminated porous membrane according to any one of claims 1 to 5, which is used as a battery separator.
  7. （ａ）ポリオレフィン樹脂に成形用溶剤を添加した後、溶融混練し、ポリオレフィン樹脂溶液を調製する工程
    （ｂ）前記ポリオレフィン樹脂溶液をＴ型ダイより押出し、フィルム状に押し出されたポリオレフィン樹脂溶液の両面に配置されたポリオレフィン樹脂溶液が除去された表面を有する冷却ロールにて冷却し、ゲル状成形物を形成する工程
    （ｃ）前記ゲル状成形物を機械方向および幅方向に延伸し、延伸成形物を得る工程
    （ｄ）前記延伸成形物から前記成形用溶剤を除去し、乾燥し、多孔質成形物を得る工程
    （ｅ）前記多孔質成形物を熱処理し、ポリオレフィン多孔質膜を得る工程
    （ｆ）前記ポリオレフィン多孔質膜の少なくとも片面に、引っ張り強度が５Ｎ／ｍｍ２以上のバインダー、前記バインダーを溶解または分散しうる溶媒及び無機粒子とを含む塗布液を用いて積層膜を形成し、乾燥する工程を含む、
    請求項１～６のいずれかに記載の積層多孔質膜の製造方法。     (A) Step of adding a molding solvent to a polyolefin resin and then melt-kneading to prepare a polyolefin resin solution (b) Both sides of the polyolefin resin solution extruded into a film by extruding the polyolefin resin solution from a T-shaped die Step (c) of forming a gel-like molded product by cooling with a cooling roll having a surface from which the polyolefin resin solution disposed in is removed, and stretching the gel-like molded product in the machine direction and the width direction. (D) removing the molding solvent from the stretched molded product and drying it to obtain a porous molded product (e) heat treating the porous molded product to obtain a polyolefin porous membrane (f ) On at least one surface of the polyolefin porous membrane, a binder having a tensile strength of 5 N / mm 2 or more, a solvent capable of dissolving or dispersing the binder, and Including a step of forming a laminated film using a coating liquid containing inorganic particles and drying,
    The method for producing a laminated porous membrane according to any one of claims 1 to 6.
  8. 前記（ｂ）工程における成形用溶剤の除去手段がドクターブレードである請求項７の積層多孔質膜の製造方法。
          The method for producing a laminated porous membrane according to claim 7, wherein the forming solvent removing means in the step (b) is a doctor blade.
PCT/JP2014/081253 2013-12-03 2014-11-26 Laminated porous film, and production method therefor WO2015083591A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2015516303A JP5792914B1 (en) 2013-12-03 2014-11-26 Laminated porous membrane and method for producing the same
CN201480065581.5A CN105992691B (en) 2013-12-03 2014-11-26 Lamination multiple aperture plasma membrane and its manufacture method
KR1020167014856A KR102131009B1 (en) 2013-12-03 2014-11-26 Laminated porous film, and production method therefor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2013-250403 2013-12-03
JP2013250403 2013-12-03

Publications (1)

Publication Number Publication Date
WO2015083591A1 true WO2015083591A1 (en) 2015-06-11

Family

ID=53273354

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2014/081253 WO2015083591A1 (en) 2013-12-03 2014-11-26 Laminated porous film, and production method therefor

Country Status (4)

Country Link
JP (1) JP5792914B1 (en)
KR (1) KR102131009B1 (en)
CN (1) CN105992691B (en)
WO (1) WO2015083591A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110690395A (en) * 2019-11-06 2020-01-14 江苏厚生新能源科技有限公司 Preparation method of multilayer polyethylene diaphragm
CN111834595A (en) * 2019-04-16 2020-10-27 住友化学株式会社 Porous layer for nonaqueous electrolyte secondary battery
KR20220063114A (en) 2019-09-27 2022-05-17 도레이 카부시키가이샤 A scraper device, a rotating device having an object removal function, a method for removing an object to be removed, a method for manufacturing a film, and a method for manufacturing a microporous membrane
CN117937051A (en) * 2024-03-21 2024-04-26 宁德新能源科技有限公司 Separator, secondary battery and electronic device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6398328B2 (en) * 2014-05-28 2018-10-03 東レ株式会社 Battery separator and method for producing the same
CN113839147A (en) * 2021-08-27 2021-12-24 湖北亿纬动力有限公司 Diaphragm, preparation method thereof and lithium ion secondary battery

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005022674A1 (en) * 2003-08-29 2005-03-10 Ube Industries, Ltd. Battery separator and lithium secondary battery
JP2007106992A (en) * 2005-09-16 2007-04-26 Tonen Chem Corp Microporous polyethylene membrane and method for producing the same, and battery separator
WO2007049568A1 (en) * 2005-10-24 2007-05-03 Tonen Chemical Corporation Polyolefin multilayer microporous film, method for producing same and battery separator
WO2011118735A1 (en) * 2010-03-24 2011-09-29 帝人株式会社 Polyolefin microporous membrane, method for producing same, separator for nonaqueous secondary battery and nonaqueous secondary battery
JP2012119225A (en) * 2010-12-02 2012-06-21 Teijin Ltd Separator for nonaqueous electrolyte battery, and nonaqueous electrolyte battery
WO2013146342A1 (en) * 2012-03-26 2013-10-03 三菱樹脂株式会社 Multilayer porous film, separator for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4931083B1 (en) 1970-08-17 1974-08-19
US4460028A (en) 1983-04-12 1984-07-17 Henry Richard T Log handling device and method therefor
JP4440548B2 (en) * 2002-02-13 2010-03-24 パナソニック株式会社 Battery and manufacturing method thereof
CN1792126A (en) * 2003-05-19 2006-06-21 大日本印刷株式会社 Double-sided wiring board and manufacturing method of double-sided wiring board
JP2008186721A (en) * 2007-01-30 2008-08-14 Asahi Kasei Chemicals Corp Porous membrane having high thermal resistance and high permeability, and its manufacturing method
EP2517880B1 (en) * 2007-06-06 2014-03-26 Asahi Kasei E-materials Corporation Multilayer porous film
JP2009035690A (en) * 2007-08-03 2009-02-19 Nitto Denko Corp Aluminum electrolytic capacitor lead electrode protecting tape using porous base material
JP2010192391A (en) * 2009-02-20 2010-09-02 Sumitomo Chemical Co Ltd Porous membrane complex for fuel cell, electrolyte membrane-electrode-porous membrane complex for fuel cell, and manufacturing method of them
KR101044700B1 (en) 2009-03-16 2011-06-28 (주)베이직테크 Power suppling apparatus of light emitted diode dispaly and the methoe thereof
CN102341238B (en) * 2009-05-21 2015-09-16 旭化成电子材料株式会社 Multilayer porous film
KR20110000832A (en) 2009-06-29 2011-01-06 크루셜텍 (주) Portable terminal with optical joystick and control method thereof
JP5495210B2 (en) 2010-07-21 2014-05-21 東レバッテリーセパレータフィルム株式会社 Composite porous membrane, method for producing composite porous membrane, and battery separator using the same

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005022674A1 (en) * 2003-08-29 2005-03-10 Ube Industries, Ltd. Battery separator and lithium secondary battery
JP2007106992A (en) * 2005-09-16 2007-04-26 Tonen Chem Corp Microporous polyethylene membrane and method for producing the same, and battery separator
WO2007049568A1 (en) * 2005-10-24 2007-05-03 Tonen Chemical Corporation Polyolefin multilayer microporous film, method for producing same and battery separator
WO2011118735A1 (en) * 2010-03-24 2011-09-29 帝人株式会社 Polyolefin microporous membrane, method for producing same, separator for nonaqueous secondary battery and nonaqueous secondary battery
JP2012119225A (en) * 2010-12-02 2012-06-21 Teijin Ltd Separator for nonaqueous electrolyte battery, and nonaqueous electrolyte battery
WO2013146342A1 (en) * 2012-03-26 2013-10-03 三菱樹脂株式会社 Multilayer porous film, separator for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111834595A (en) * 2019-04-16 2020-10-27 住友化学株式会社 Porous layer for nonaqueous electrolyte secondary battery
JP2020177771A (en) * 2019-04-16 2020-10-29 住友化学株式会社 Porous layer for nonaqueous electrolyte secondary battery
JP7215955B2 (en) 2019-04-16 2023-01-31 住友化学株式会社 Porous layer for non-aqueous electrolyte secondary battery
KR20220063114A (en) 2019-09-27 2022-05-17 도레이 카부시키가이샤 A scraper device, a rotating device having an object removal function, a method for removing an object to be removed, a method for manufacturing a film, and a method for manufacturing a microporous membrane
CN110690395A (en) * 2019-11-06 2020-01-14 江苏厚生新能源科技有限公司 Preparation method of multilayer polyethylene diaphragm
CN117937051A (en) * 2024-03-21 2024-04-26 宁德新能源科技有限公司 Separator, secondary battery and electronic device

Also Published As

Publication number Publication date
KR20160091917A (en) 2016-08-03
CN105992691B (en) 2017-12-01
KR102131009B1 (en) 2020-07-07
JP5792914B1 (en) 2015-10-14
JPWO2015083591A1 (en) 2017-03-16
CN105992691A (en) 2016-10-05

Similar Documents

Publication Publication Date Title
JP5857155B2 (en) Polyolefin porous membrane, battery separator using the same, and production method thereof
JP6323449B2 (en) Laminated porous membrane, method for producing the same, and battery separator
JP5857151B2 (en) Polyolefin porous membrane, battery separator using the same, and production method thereof
JP5876629B1 (en) Battery separator and method for producing the same
JP5876628B1 (en) Battery separator and method for producing the same
JP5845381B1 (en) Polyolefin laminated porous membrane, battery separator using the same, and method for producing polyolefin laminated porous membrane
JP5801983B1 (en) Battery separator and method for producing the same
JP5792914B1 (en) Laminated porous membrane and method for producing the same
JP6558363B2 (en) Polyolefin laminated porous membrane, battery separator using the same, and production method thereof
JP6398498B2 (en) Battery separator using polyolefin laminated porous membrane and method for producing the same
JP6398328B2 (en) Battery separator and method for producing the same

Legal Events

Date Code Title Description
ENP Entry into the national phase

Ref document number: 2015516303

Country of ref document: JP

Kind code of ref document: A

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

Ref document number: 14868274

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 20167014856

Country of ref document: KR

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 14868274

Country of ref document: EP

Kind code of ref document: A1