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WO2015083591A1 - Film poreux stratifié, et son procédé de production - Google Patents

Film poreux stratifié, et son procédé de production Download PDF

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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
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2014/081253
Other languages
English (en)
Japanese (ja)
Inventor
水野　直樹
孝一 又野
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toray Battery Separator Film Co Ltd
Original Assignee
Toray Battery Separator Film Co Ltd
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 Toray Battery Separator Film Co Ltd filed Critical Toray Battery Separator Film Co Ltd
Priority to KR1020167014856A priority Critical patent/KR102131009B1/ko
Priority to CN201480065581.5A priority patent/CN105992691B/zh
Priority to JP2015516303A priority patent/JP5792914B1/ja
Publication of WO2015083591A1 publication Critical patent/WO2015083591A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • 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
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B29C48/911—Cooling
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    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
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    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
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    • 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
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    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • 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
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    • H—ELECTRICITY
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    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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    • H—ELECTRICITY
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    • H01M50/409—Separators, membranes or diaphragms characterised by the material
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    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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    • 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
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    • 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
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    • 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
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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.

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Abstract

L'invention porte sur un film poreux stratifié, lequel film est obtenu par stratification, avec une couche poreuse modifiée (A), d'une surface d'un film poreux en polyoléfine, et stratification, avec une couche poreuse modifiée (B), d'une surface opposée du film poreux en polyoléfine. Le film poreux en polyoléfine a une épaisseur de film qui n'est pas supérieure à 25 µm, et a des saillies qui comprennent une polyoléfine, qui satisfont à 5 µm ≤ W ≤ 50 µm (W étant la taille de saillie) et à 0,5 µm ≤ H (H étant la hauteur de la saillie), et qui sont dispersées de façon irrégulière sur les deux surfaces du film poreux en polyoléfine sous une densité dans la plage 3/cm2 à 200/cm2 inclus par surface. Au moins la couche poreuse modifiée (A) comprend des particules minérales et un liant ayant une résistance à la traction d'au moins 5 N/mm2. La résistance à l'arrachage entre le film poreux en polyoléfine et les couches poreuses modifiées est extrêmement élevé, et, par conséquent, le film poreux stratifié est apte à un traitement à grande vitesse.
PCT/JP2014/081253 2013-12-03 2014-11-26 Film poreux stratifié, et son procédé de production Ceased WO2015083591A1 (fr)

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CN111834595A (zh) * 2019-04-16 2020-10-27 住友化学株式会社 非水电解液二次电池用多孔层
JP2020177771A (ja) * 2019-04-16 2020-10-29 住友化学株式会社 非水電解液二次電池用多孔質層
JP7215955B2 (ja) 2019-04-16 2023-01-31 住友化学株式会社 非水電解液二次電池用多孔質層
KR20220063114A (ko) 2019-09-27 2022-05-17 도레이 카부시키가이샤 스크레이퍼 장치, 제거 대상물 제거 기능을 갖는 회전 장치, 제거 대상물 제거 방법, 필름의 제조 방법 및 미다공막의 제조 방법
CN110690395A (zh) * 2019-11-06 2020-01-14 江苏厚生新能源科技有限公司 一种多层聚乙烯隔膜的制备方法
CN117937051A (zh) * 2024-03-21 2024-04-26 宁德新能源科技有限公司 一种隔离膜、二次电池和电子装置

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