CN101568575A - Polyolefin microporous membrane - Google Patents

Polyolefin microporous membrane Download PDF

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Publication number
CN101568575A
CN101568575A CNA2007800448887A CN200780044888A CN101568575A CN 101568575 A CN101568575 A CN 101568575A CN A2007800448887 A CNA2007800448887 A CN A2007800448887A CN 200780044888 A CN200780044888 A CN 200780044888A CN 101568575 A CN101568575 A CN 101568575A
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film
polyolefin microporous
microporous film
extension
elongation
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CN101568575B (en
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稻垣大助
武田久
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Asahi Kasei Corp
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Asahi Chemical Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/22—After-treatment of expandable particles; Forming foamed products
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Cell Separators (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

Disclosed is a polyolefin microporous membrane having a bubble point of not more than 1 MPa, a tensile strength in the longitudinal direction of not less than 50 MPa, a tensile strength in the width direction of not less than 50 MPa, and a thermal shrinkage in the width direction at 130 DEG C of not more than 20%. This polyolefin microporous membrane is excellent in strength and low thermal shrinkage property, while having a large pore diameter.

Description

Polyolefin microporous film
Technical field
The micro-porous film of the isolated material of electrochemical reaction appts such as the separatory membrane of the present invention relates to be widely used as separating substances, selecting to see through etc., alkaline secondary cell, lithium secondary battery, fuel cell, electrical condenser etc.Especially, the present invention relates to be suitable as the membranous polyolefin microporous film of lithium ion battery.
Background technology
The isolation and selection that polyolefin microporous film is widely used as various materials see through separatory membrane and isolated material etc., and its purposes can be enumerated and for example comprise that secondary filter film, fuel cell separators, electrical condenser are with barrier film or be used for functional material is filled into the hole and show the mother metal, battery separator etc. of the functional membrane of new function.In these purposes, be preferably used as widely used lithium ion battery barrier film in notebook PC, portable phone, the digital camera etc. especially.As its reason, can enumerate this film and have physical strength and hole plug.
So-called hole plug is meant at inside battery and makes hole plug because of micro-porous film fusion when overheated such as the state of overcharging, the cut-out cell reaction, thus guarantee the performance of battery security.The temperature that hole plug takes place is low more, and the security effect is high more.
In addition, when the coiling barrier film, and in order to prevent because the foreign matter etc. in the battery causes short circuit, membranously pierce through intensity (piercing strength) and length direction (is meant operating direction, below also be called MD), the extension strength of width (be meant and the vertical direction of operating direction, below also be called TD) need have to a certain degree above intensity.In addition, in lithium-ion secondary cell in recent years,, but also require at high temperature have excellent heat-shrinkable because the high-output power and the high capacity of battery not only require membranous aperture to increase.
Membranous void content is high more and the aperture is big more, and the electrical characteristic of battery are good more, yet there are opposite relation in the increase of void content and the increase in aperture with the size and the intensity of percent thermal shrinkage.Therefore, have good battery electrical characteristic, also can have the problem of under the high temperature of battery baking oven test, shrinking big or undercapacity even implement the barrier film of high porosityization and wide apertureization.
As the means that address these problems, the applicant has proposed polymkeric substance and filler, softening agent mixing in patent documentation 1, makes it to be separated the method for extending after the extracting.Thus, provide high porosity and wide aperture and heat-shrinkable low micro-porous film, yet in the extension after extracting, these two is difficult to take into account to show full intensity and low thermal shrinkage behavior on whole directions.
In addition, in patent documentation 2, by via specific extracting and extension process, the applicant has proposed to have the special pore size distribution scope and has stipulated the micro-porous film of permeable amount/Air permenbility ratio.Yet, film via this extracting and extension process preparation not only has the tendency that percent thermal shrinkage increases, and under the permeable amount/Air permenbility described in the document, in lithium-ion secondary cell of in recent years high-output power etc., it is insufficient that electrical characteristic often become.
In patent documentation 3, proposed to use the prepared wide-aperture micro-porous film of high-molecular weight polyolefine, yet, do not obtain so far that so-called height is heat-resisting, high strength and the micro-porous film wide-aperture, that balance is excellent.
In addition, in patent documentation 4, high heat-resisting and wide-aperture micro-porous film has been proposed, yet, in this way, be difficult to realize the high strength of film.
In addition, in patent documentation 5, the high-intensity micro-porous film with specific polyolefin blend preparation has been proposed, yet, since the blend new LDPE (film grade), the difficulty so heat setting at high temperature becomes.
Patent documentation 1: No. 3258737 communiques of Japan's special permission
Patent documentation 2: TOHKEMY 2004-323820 communique
Patent documentation 3: Japanese kokai publication hei 10-258462 communique
Patent documentation 4: No. 3050021 communiques of Japan's special permission
Patent documentation 5: Japanese kokai publication hei 8-34873 communique
Summary of the invention
The problem that invention will solve
The purpose of this invention is to provide a kind of polyolefin microporous film, this film does not reduce the characteristic that polyolefin microporous film had in the past, owing to have the wide aperture and the electrical characteristic excellence, while intensity and low thermal shrinkage behavior excellence.
The scheme that is used to deal with problems
To achieve these goals, the inventor furthers investigate repeatedly, found that, the polyolefin microporous film that the percent thermal shrinkage of the extension strength of bubble point, length direction and width and the width under 130 ℃ is adjusted in the specified range has the wide aperture, and have excellent intensity and low thermal shrinkage behavior, thereby finished the present invention.That is to say that the present invention is as described below.
(1) a kind of polyolefin microporous film, the bubble point of wherein said micro-porous film are below the 1MPa, and the extension strength of length direction and the extension strength of width are respectively more than the 50MPa, and the percent thermal shrinkage of the width under 130 ℃ is below 20%.
(2) according to above-mentioned (1) described polyolefin microporous film, wherein, described micro-porous film comprises polypropylene.
(3) according to above-mentioned (1) or (2) described polyolefin microporous film, wherein, the summation that MD extends elongation and TD extension elongation is 20～250%.
(4) according to above-mentioned (1) or (2) described polyolefin microporous film, wherein, the summation that MD extends elongation and TD extension elongation is 20～200%.
(5) according to each described polyolefin microporous films of above-mentioned (1)～(4), wherein, it is that ultrahigh molecular weight polyethylene(UHMWPE) and viscosity-average molecular weight more than 500,000 is lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
(6) according to each described polyolefin microporous films of above-mentioned (1)～(5), wherein, described void content is more than 20% below 60%.
(7) a kind of battery separator, described barrier film comprise each described polyolefin microporous film of above-mentioned (1)～(6).
(8) a kind of nonaqueous electrolytic solution secondary battery, it has above-mentioned (7) described barrier film.
(9) a kind of total elongation multiplying power manufacture method that is the polyolefin microporous film more than 50 times, described method comprise the resin combination melting mixing that will contain polyolefine and softening agent at least, extrude and obtain the operation of flap; Extend described flap and obtain the operation of film; The operation of extracting elasticizer from described flap or described film; And with the operation of described film heat setting.
The effect of invention
Compare with existing polyolefin microporous film, polyolefin microporous film of the present invention is the wide apertureization, and has excellent intensity and low thermal shrinkage behavior.Therefore, by polyolefin microporous film of the present invention is used for battery separator, can improve battery behavior and battery security.
Description of drawings
Fig. 1 shows the sectional view of employed battery in the determination test of the hot rupture of membranes of high speed (anti-rupture of membranes).
Description of reference numerals
1... barrier film; 2... nickel foil A; 3... nickel foil B; 4...Aramica film; 5... sheet glass; 6... slide glass; 7... thermopair; 8...10 the window of * 10mm
Embodiment
Hereinafter describe in detail and be used to implement preferred forms of the present invention (following also be called " present embodiment ").In addition, the invention is not restricted to following embodiment, in its purport scope, can have various modification.
The bubble point of the polyolefin microporous film of present embodiment is below 1MPa, and the extension strength of length direction and the extension strength of width are respectively more than the 50MPa, and the percent thermal shrinkage of the width under 130 ℃ is below 20%.
In order not make the hole become excessively fine and close, the bubble point of the micro-porous film of polyolefine system need be preferably below the 0.8MPa below 1.0MPa.The lower limit of bubble point is preferably more than the 0.1MPa, more preferably more than the 0.3MPa.When bubble point was lower than 0.1MPa, hole thickization that become might cause film toughness to reduce.
This bubble point method is known as the simple and easy method of expression maximum diameter of hole, and is different with the viewpoint of bubble point, has dependency between the permeable amount of micro-porous film and ratio of Air permenbility (permeable amount/Air permenbility) and the mean pore size.This ratio is preferably 1.7 * 10 -3More than.Be lower than 1.7 * 10 at this ratio -3The time, it is insufficient that perviousness becomes easily, and the capacity sustainment rate of battery has the tendency of reduction.The upper limit to this ratio is unqualified, preferably less than 2.3 * 10 -3, be more preferably less than 2.1 * 10 -3Scope.At this ratio is 2.3 * 10 -3When above, might become excessive in the hole, undercapacity is perhaps easily because lithium dentrite (dendrite) produces short circuit.At bubble point is below the 1.0MPa and permeable amount/Air permenbility in above-mentioned scope the time, because it is harmonious and have high strength and low thermal shrinkage behavior under the state of perviousness keeping to have excellent mean pore size, for lithium ion battery is in recent years given superperformance, therefore preferred especially.
In addition, the extension strength of the polyolefin microporous film of present embodiment on length direction (MD) and width (TD) need be more than 50MPa, more preferably more than 70MPa, more preferably more than the 100MPa.When extension strength low (being lower than 50MPa), the battery winding variation is easily owing to be short-circuited from the battery shock test of outside generation, the foreign matter in the battery etc.
In addition, from guaranteeing the security of baking oven test etc., the polyolefin microporous film of present embodiment percent thermal shrinkage at width (TD) under 130 ℃ is below 20%, is preferably below 17%, more preferably below 15%.Percent thermal shrinkage to the length direction under 130 ℃ (MD) does not have specific limited, and is identical with width, from guaranteeing security, is preferably below 20%, more preferably below 17%, more preferably below 15%.
The polyolefin microporous film of present embodiment preferably includes polypropylene.By in micro-porous film, containing polypropylene, not only can improve thermotolerance, even and under high extension ratio, also often be difficult to rupture.In addition, can be easily MD described later and TD be extended elongation and be adjusted in the suitable scope, the result can improve the shock-resistance of gained battery, lowers short risk.Polyacrylic content is preferably with respect to 1～80 quality % of polymer materials, more preferably 2～50 quality %, further preferred 3～30 quality %.When polypropylene content is lower than 1 quality %, often is difficult to expression effect, and when polypropylene content surpasses 80 quality %, often is difficult to guarantee perviousness.
In addition, the MD of the polyolefin microporous film of present embodiment and TD extend elongation and are preferably 10～200% separately, and more preferably 10～150%, further preferred 10～120%.MD extends the summation that elongation and TD extend elongation and is preferably 20～250%, and more preferably 20～230%, further preferred 20～200%.MD and TD extend the micro-porous film of elongation in above-mentioned scope and not only have good battery winding, and coiling body is difficult to deform in battery shock test etc.When extending elongation and surpass above-mentioned scope, the elongation of micro-porous film increases, deform easily for the repeated stock in the battery shock test etc., and the result, the risk that is short-circuited might increase.
Extend the micro-porous film of elongation in above-mentioned scope in order to obtain MT and TD, need the combination several method.For example, can realize by regulating extension after extension ratio described later, the extracting and the various conditions in the relaxation operation.In addition as mentioned above, polypropylene also is a kind of effective means in polymkeric substance.
It is that ultrahigh molecular weight polyethylene(UHMWPE) and viscosity-average molecular weight more than 500,000 is lower than 500,000 polyethylene that the polyolefin microporous film of present embodiment preferably contains viscosity-average molecular weight.By containing above-mentioned various polyethylene, not only the melt viscosity during the barrier film fusion increases, and has the tendency that improves anti-rupture of membranes by the early stage relaxation of fusion tensile.
From the viewpoint of perviousness, the void content of the polyolefin microporous film of present embodiment is preferably more than 20%; From the viewpoint of film toughness, proof voltage and percent thermal shrinkage, this void content is preferably below 60%.This void content more preferably 25%～60%, more preferably 30%～55%.
The Gas permeability of the polyolefin microporous film of present embodiment is low more preferred more, but from the viewpoint of the balance of thickness and void content, is preferably more than the 1sec, more preferably more than the 50sec.In addition, from the viewpoint of perviousness, this Gas permeability is preferably below the 1000sec, more preferably below the 500sec.
From the viewpoint of film toughness, the thickness of the polyolefin microporous film of present embodiment is preferably more than the 1 μ m, more preferably more than the 5 μ m.In addition, from the viewpoint of perviousness, this thickness is preferably below the 50 μ m, more preferably below the 30 μ m.
In addition, the intensity that pierces through of the polyolefin microporous film of present embodiment is preferably more than the 0.2N/ μ m, more preferably more than the 0.22N/ μ m.When piercing through intensity lower (being lower than 0.2N/ μ m), as under the situation of battery diaphragm, micro-porous film is thrust in the sharp keen portion of electrode materials etc., is easy to generate pinprick or be full of cracks, has the tendency of easy deformation the battery shock test that takes place from the outside etc.
Next the manufacture method of the polyolefin microporous film of present embodiment is described; As long as the gained micro-porous film has above-mentioned characteristic, to type of polymer, solvent species, extrusion method, extension method, method for extracting, boring method, heat setting and heat treating method etc. without any restriction.
The manufacture method of the polyolefin microporous film of present embodiment preferably includes following operation: the resin combination melting mixing that will contain polyolefine and softening agent at least obtains the operation of flap with extruding; Extend described flap and obtain the operation of film; The operation of extracting elasticizer from described flap or film; And with the operation of described film heat setting.
The polyolefin microporous film of present embodiment for example can obtain by the method that comprises following operation (a)～(e).
(a) any polymer materials with polyolefine monomer, polyolefin blend, polyolefine solvent mixture and the mixing thing of polyolefine carries out melting mixing.
(b) melts is extruded, is configured as sheet and make its cooling curing.Extracting elasticizer and inorganics as required.
(c) resulting sheet is extended on a direction more than the axle.
(d) extend after, extracting elasticizer and inorganics as required.
(e) then carry out heat setting and thermal treatment.
The polyolefine that uses in the present embodiment is the homopolymer of ethene or propylene, and perhaps the multipolymer of ethene, propylene, 1-butylene, 4-methyl-1-pentene, 1-hexene, 1-octene, norbornylene also can be above-mentioned mixture of polymers.Wherein, from the viewpoint of the performance that improves micro-porous film, polyethylene and multipolymer thereof are preferred.As this polyolefinic polymerizing catalyst, can enumerate ziegler-natta type catalyzer, Phillips type catalyzer, metalloscene catalyst etc.Polyolefine can obtain by one-step polymerization method, perhaps obtains by the multistep polymerization method.
As the composition of the polymkeric substance of being supplied with, preferably with two or more polyolefin blends.Can control melt temperature and short circuit temperature thus.More preferably, with two or more polyethylene blends, the ultrahigh molecular weight polyethylene(UHMWPE) and the viscosity-average molecular weight (Mv) that preferably comprise viscosity-average molecular weight (Mw) and be more than 500,000 are lower than 500,000 polyethylene.Never plugging hole, under higher temperature, can carry out the viewpoint of heat setting, the polyethylene of blend is the high-density homopolymer preferably.
In addition, the overall viscosity-average molecular weight (Mv) of polymer materials is preferably more than 100,000 to below 1,200,000, more preferably more than 300,000 to below 800,000.(Mv) is lower than at 100,000 o'clock in viscosity-average molecular weight, and the anti-rupture of membranes during fusion might become insufficient, and surpasses at 1,200,000 o'clock in viscosity-average molecular weight, possiblely is, extrudes the operation difficulty that becomes, and the relaxation of the convergent force during fusion is slow, and thermotolerance is inferior.
These polyethylene not only can improve thermotolerance with blend such as being higher than poly polyolefinic polypropylene as fusing point, and in extension after extracting and the relaxation operation, can under the temperature higher, operate than polyvinyl monomer, in addition, when keeping the intensity of micro-porous film, percent thermal shrinkage, aperture, can reduce to extend elongation.In addition, though reason is unclear, also being difficult to the effect that ruptures even have under high extension ratio, is particularly preferred therefore.
By the low thermal shrinkage behavior combination that above-mentioned blend improves thermotolerance and the application, anti-rupture of membranes at high temperature becomes better, is preferred therefore.
In addition, can mix known additives such as metallic soap class, UV light absorber, photostabilizer, static inhibitor, antifogging agent, tinting pigment such as using calcium stearate, Zinic stearas.
In addition, can also add with aluminum oxide, titanium dioxide etc. be the inorganics of representative.Can be at this inorganics of an extracting full dose in any one of whole in-process or a part, this inorganics also can be residual in product.
The softening agent that uses in the present embodiment is the organic compound that can form homogeneous solution under the temperature below the boiling point with polyolefine, particularly, can enumerate perhydronaphthalene, dimethylbenzene, dioctyl phthalate (DOP), dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, phenyl ether, n-decane, n-dodecane, paraffin wet goods.In the middle of these, paraffin oil, dioctyl phthalate (DOP) are preferred.
Ratio to softening agent does not have specific limited, and from the viewpoint of the void content of gained micro-porous film, the ratio of softening agent is preferably more than the 20 quality %; From the viewpoint of viscosity, be preferably more than the 90 quality %, more preferably 50 quality %～70 quality %.
As the extraction solvent that is used for extracting elasticizer is the good solvent of polyolefinic poor solvent and softening agent, and boiling point is an ideal than polyolefinic low-melting solvent.As this extraction solvent, for example can enumerate hydro carbons such as normal hexane, hexanaphthene, halogenated hydrocarbons such as methylene dichloride, 1, fluorohydrocarbon class, alcohols such as ethanol, Virahol, ketones such as acetone, 2-butanone.Can select in the middle of these a kind of or select multiple mixing to use.These extraction solvents can distill to wait after extracting elasticizer and regenerate and reuse.
From the perviousness of film and the viewpoint of system film, the gross weight ratio that softening agent and inorganics account for whole mixtures of melting mixing is preferably 20～95 quality %, more preferably 30～80 quality %.
In addition, the viewpoint of thermal degradation when when preventing melting mixing and the quality variation that causes thus, the preferred oxidation inhibitor that cooperates in mixture.Oxidation inhibitor is with respect to the concentration of whole polyolefine weight preferably more than the 0.3 quality %, more preferably more than the 0.5 quality %.In addition, this concentration is preferably below the 5.0 quality %, more preferably below the 3.0 quality %.
As oxidation inhibitor, as the phenolic antioxidant of primary antioxidant is preferred, can enumerate 2,6 di tert butyl 4 methyl phenol, [3-(3 for tetramethylolmethane-four, 5-di-t-butyl-4-hydroxyphenyl) propionic ester], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionic ester etc.In addition, secondary oxidation inhibitor can be used in combination, tricresyl phosphite (2, the 4-di-tert-butyl-phenyl) ester, four (2, the 4-di-tert-butyl-phenyl)-4 can be enumerated, sulfur type antioxidants such as Phosphorus oxidation inhibitor such as 4-biphenylene diphosphites, dilauryl thiodipropionate etc.
Melting mixing and the method for extruding comprise that at first the starting material with part or all are pre-mixed with Henschel mixer, belt blending machine, tumbler mixer etc. as required.Under a few cases, can stir with hand.Then, carry out melting mixing, with T shape die head, annular die is first-class extrudes with screw extrusion presss such as single screw extrusion machine, twin screw extruder, mixing roll, mixing machine etc.
Preferably, in stock polymer,, be replaced as nitrogen atmosphere and carry out melting mixing under the state of nitrogen atmosphere keeping with after the predetermined concentration mixing oxidation inhibitor.Temperature during melting mixing is preferably more than 160 ℃, more preferably more than 180 ℃.In addition, this temperature preferably is lower than 300 ℃, more preferably less than 240 ℃, also more preferably less than 230 ℃.
Can contain in the melts described in the present embodiment can extractive not fused inorganics in inorganics extracting operation.In addition, in order to improve film quality, preferably make melting mixing and the melts of homogenizing is crossed screen cloth.
Next the shaping of gel sheet is described.As the manufacturing process of gel sheet, preferably melting mixing and the melts of extruding are solidified by the compression cooling.As method of cooling, can enumerate heat-eliminating mediums such as direct contact cold wind, water coolant method, with method that contacts with heat-eliminating medium refrigerative roller or press etc.From the viewpoint of gauge control excellence, be preferred with the method that contacts with heat-eliminating medium refrigerative roller or press.
Next the extension carried out and softening agent extracting or extension and softening agent extracting and the extractive order of inorganics, method and number of times there is not specific limited.As required, can not carry out the inorganics extracting.
As extension method, can enumerate MD uniaxial extension with the roller elongator, with the TD uniaxial extension of tenter machine, the twin shaft one by one that carries out with the combination of the combination of roller elongator and tenter machine or tenter machine and tenter machine extend, twin shaft extension etc. with biaxial stenter or blow molding simultaneously the time.In order to obtain required extension strength and extension elongation, with total face dynameter, extension ratio is preferably more than 8 times, more preferably more than 15 times, more preferably more than 30 times, is preferably especially more than 40 times.Wherein, simultaneously or one by one twin shaft to extend be preferred.In addition, by the same token, all the total elongation multiplying power of operation is preferably more than 50 times, more preferably more than 60 times.
In the softening agent extracting, come extracting elasticizer by dipping in extraction solvent or spray.After this thorough drying.
The heat setting method is carried out the relaxation operation with predetermined relaxation rate under preset temperature atmosphere.Can use tenter machine or roller elongator to carry out.TD that the relaxation operation is meant at film and/or the reduction operation on the TD direction.The relaxation rate is meant the MD size resulting value of the MD size of the film after the relaxation operation divided by preoperative film, the perhaps value that obtained divided by the TD size of preoperative film of the TD size after the relaxation operation, perhaps under the enterprising situation that runs Henan of MD and TD both direction, be the value that the relaxation rate of the relaxation rate of MD and TD multiplies each other.From the viewpoint of percent thermal shrinkage, predetermined relaxation rate is preferably below 0.9, more preferably below 0.8.In addition, from preventing the viewpoint of gauffer generation, void content and perviousness, this predetermined relaxation rate is preferably more than 0.6.Relaxation operation can be carried out on MD and TD both direction, even run the Henan operation in that only direction of MD or TD is enterprising, not only can reduce the percent thermal shrinkage of direction of operating, but also can reduce with the vertical direction of direction of operating on percent thermal shrinkage.By before the operation of this relaxation, carry out more than 1.5 times, the more preferably extension more than 1.8 times, can easily obtain the micro-porous film of high strength and wide apertureization.
Extension after this softening agent extracting and relaxation operation are preferably carried out on the TD direction.From the viewpoint of percent thermal shrinkage and wide apertureization, the temperature of relaxation operation and the preoperative extension process of relaxation preferably is more than 125 ℃, and any one is preferably more than 130 ℃ at least, more preferably more than 132 ℃.When the temperature of relaxation operation and the preoperative extension process of relaxation is in above-mentioned scope, at polyolefine is under the poly situation, near fusing point, extend and the relaxation operation, compare, obtain the micro-porous film of wide aperture and low heat shrinkage easily with micro-porous film in the past.In addition, though agnogenio, even the film of low elongation also obtains the micro-porous film of rupture of membranes excellence easily.From can under this with different in the past higher temperature conditions, extending and relaxation,,, preferably except polyethylene, go back co-blend polypropylene as polyolefine even under the big condition of total elongation multiplying power, also be difficult to the disruptive viewpoint in addition.
In addition, the polyolefin micro porous polyolefin membrane of present embodiment can carry out surface treatments such as electron rays irradiation, plasma irradiating, tensio-active agent coating, chemical modification.
Embodiment
Illustrate in greater detail the present embodiment by the following examples.
[measuring method]
The measuring method of the rerum natura in this specification sheets etc. is as described below.
(1) viscosity-average molecular weight (Mv)
Obtain the limiting viscosity under 135 ℃ [η] in the perhydronaphthalene solvent according to ASTM-D4020.Calculate poly Mv by following formula.
[η]＝6.77×10 -4Mv 0.67
Polyacrylic Mv calculates by following formula.
[η]＝1.10×10 -4Mv 0.80
(2) thickness (μ m)
The miniature thickness measuring device KBM (trade mark) that uses the smart machine of Japan to make measures down for 23 ± 2 ℃ in room temperature.
(3) void content (%)
Cut the square test portion of 10cm * 10cm from micro-porous film, obtain its volume (cm 3) and quality (g), use following formula by this volume, quality and film density (g/cm 3) the calculating void content.
Void content=(volume-quality)/volume * 100
In addition, film density calculates by density of material.
(4) Gas permeability (sec)
According to JIS P-8117, use Gurley formula Gas permeability meter (the smart device of Japan (strain) is made, G-B2 (trade mark)).Measure the 100ml air by inner core weight 567g, diameter 28.6mm, 645mm 2Time of area.
(5) Air permenbility
The penetration speed constant Rgas of air uses following formula to be obtained by Gas permeability (sec).Being determined at the indoor of 23 ℃ of room temperatures carries out.
Rgas (m 3/ (m 2SecPa))=0.0001/ Gas permeability/0.0006424/ (0.01276 * 101325)
(6) permeable amount
To be immersed in advance in the saturating liquid pool of stainless steel that micro-porous film in the ethanol is arranged on diameter 41mm, water cleans after the ethanol of this film, under the pressure reduction of about 50000Pa water is seen through, the permeable amount (cm by through 120 seconds the time 3) calculate the permeable amount of time per unit unit pressure unit surface, with it as permeable degree (cm 3/ (cm 2SecPa)).Being determined at the indoor of 23 ℃ of room temperatures carries out.The penetration speed constant Rliq of water uses following formula by permeable degree (cm 3/ (cm 2SecPa)) obtain.
Rliq (cm 3/ (cm 2.sec.Pa))=permeable degree/100
(7) (pierce through intensity (N/ μ m)
Use KATO TECH Co., the portable compressing tester KE S-G5 (trade mark) that Ltd. makes fixes micro-porous film with the test portion clamper of peristome diameter 11.3mm.Then at the radius-of-curvature 0.5mm of needle point, pierce through that the central part to the fixed micro-porous film carries out puncture test under the condition of speed 2mm/sec and 25 ℃ of atmosphere, that calculates that maximum pierces through that load (N) multiply by 1/ thickness (μ m) pierces through intensity (N/ μ m).
(8) extension strength (MPa) and extension elongation (%)
According to JIS K7127, the elongation test machine Autograph AG-A type (trade mark) that uses Shimadzu Seisakusho Ltd. to make is measured MD and TD sample (shape; Width 10mm * length 100mm).In addition, the face sticking glass paper self-adhesive tape (Ri East Electricity worker that sample adopts spacing jig to be set at 50mm, sample both ends (each 25mm) packs シ ス テ system (strain) manufacturing, trade(brand)name: sample N.29).And, for the slip of sample in preventing to test, the inboard viton of pasting thickness 1mm of the anchor clamps of elongation test machine.
Elongation (mm) when extension elongation (%) reaches fracture by using multiply by 100 again and obtains divided by spacing jig (50mm).
The sample section of the intensity of extension strength (MPa) by will rupture the time before divided by test amasss to be obtained.
In addition, by the value addition of MD and TD being calculated the summation (%) that MD extends elongation and TD extension elongation.In addition, mensuration is to carry out under the condition of 23 ± 2 ℃ of temperature, chucking pressure 0.30MPa, extension speed 200mm/min (for the sample that can not guarantee spacing jig 50mm, rate of straining is 400%/minute).
(9) 130 ℃ of percent thermal shrinkages (%)
Cut 100mm on the MD direction, on the TD direction sample of 100mm, in 130 ℃ baking oven, left standstill 1 hour.At this moment, directly blow to sample in order not make hot blast, with sample holder between two pieces of paper.From baking oven, take out and cooling back measured length (mm), calculate the percent thermal shrinkage of MD and TD with following formula.(in the time that sample length can not be guaranteed, use the long as far as possible sample in 100mm * 100mm scope.)
MD percent thermal shrinkage (%)=(the MD length after the 100-heating)/100 * 100
TD percent thermal shrinkage (%)=(the TD length after the 100-heating)/100 * 100
(10) bubble point (MPa)
According to ASTM F316-86, in alcohol solvent, measure.Confirm that the point of bubble is set to bubble point continuously.
(11) the hot rupture of membranes of high speed (anti-rupture of membranes)
Prepare nickel foil A (length 100mm * width 25mm), the nickel foil B (length 100mm * width 15mm) of thickness 10 μ m, in electrolytic solution, soak the barrier film (MD length 75mm * TD length 25mm) more than 30 minutes, Aramica film (trade mark), slide glass (length 75mm * width 25mm), the sheet glass (length 25mm * width 20mm) that the center is provided with the window of 10mm * 10mm.
As shown in Figure 1, superimposed according to the order of slide glass, nickel foil A, barrier film, Aramica film, nickel foil B, sheet glass, fix with clip.
Above-mentioned battery is connected with thermopair, in baking oven, leaves standstill.After this, the speed intensification with 5 ℃/min kept 1 hour down at 150 ℃ after reaching 150 ℃.Under the condition that exchanges 10mV, 1kHz, measure the resistance change of this moment with the LCR meter.In this is measured, when remaining on 150 ℃, impedance can keep the A that is evaluated as more than 60 minutes at the state of insulation more than 1000 Ω, keep the B that is evaluated as more than 30 minutes, can keep the C that is evaluated as more than 10 minutes, the D that is evaluated as more than 5 minutes can be kept, 5 minutes the E that is evaluated as can not be kept.
In addition, the ratio of components of regulation electrolytic solution is as described below.
The ratio of components of solvent (volume ratio): dipropyl carbonate/diethyl carbonate/gamma-butyrolactone=1/1/2
The ratio of components of solute: with LiBF 4Concentration with 1mol/L is dissolved in the above-mentioned solvent.
[making of battery and evaluation]
(1) anodal is made
The lithium cobalt composite oxide LiCoO that in N-Methyl pyrrolidone (NMP), disperses 92.2 quality % as active substance 2, be respectively the poly(vinylidene fluoride) as binding agent (PVDF) of 2.3 quality %, preparation slurry as the flaky graphite of conductive agent and acetylene black, 3.2 quality %.With die coater this slurry is coated on the face of aluminium foil of the thickness 20 μ m that constitute positive electrode collector, 130 ℃ dry 3 minutes down, use the roll squeezer compression molding then.At this moment, anodal active substance glue spread is 250g/m 2, the active substance volume density is 3.00g/cm 3It is cut to the band shape of the about 40mm of width.
(2) making of negative pole
In purifying waste water, disperse 96.9 quality % the synthetic graphite as active substance, 1.4 quality % as the ammonium salt of the carboxymethyl cellulose of binding agent and the styrene-butadiene copolymer latex of 1.7 quality %, preparation slurry.With die coater this slurry is coated on the face of Copper Foil that the thickness that constitutes negative electrode collector is 12 μ m, 120 ℃ dry 3 minutes down, use the roll squeezer compression molding then.At this moment, the active substance glue spread of negative pole is 106g/m 2, the active substance volume density is 1.35g/cm 3It is cut to the band shape of the about 40mm of width.
(3) preparation of nonaqueous electrolytic solution
At diethyl carbonate: in the mixed solvent of Methyl ethyl carbonate=1: 2 (volume ratio), dissolving is as the LiPF of solute 6, and make that its concentration is 1.0mol/L, the preparation nonaqueous electrolytic solution.
(4) battery assembling
Barrier film, banded positive pole and the banded negative pole of polyolefin microporous film are superimposed according to banded negative pole, barrier film, banded positive pole and membranous order with using, and repeatedly reel to form spirrillum, thereby make battery lead plate lamination body.This battery lead plate lamination body is compressed to tabular, puts into aluminium vessel then, derive the aluminum lead-in wire, be welded on the battery cover, derive nickel making line, be welded in container bottom from negative electrode collector from positive electrode collector.In addition, be injected into above-mentioned nonaqueous electrolytic solution in this container and seal.The lithium ion battery of Zhi Zuoing is designed to the size of length direction (thickness) 6.3mm, horizontal 30mm and height 48mm like this, and the nominal loading capacity is 620mAh.
(5) cell evaluation (under 25 ℃ of atmosphere)
In the lithium ion battery of assembling as mentioned above, continuous current constant voltage (CCCV) charging is 6 hours under the condition of current value 310mA (0.5C), termination cell voltage 4.2V.At this moment, the current value before charging finishes is about 0 value.After this, under 25 ℃ of atmosphere, place 1 week (wearing out).
After this, carry out following circulation: continuous current constant voltage (CCCV) charging is 3 hours under the condition of current value 620mA (1.0C), termination cell voltage 4.2V, is being discharged to cell voltage 3.0V again under certain current value (CC) 620mA.The loading capacity of this moment is set at first loading capacity.
(a) further repeat above-mentioned circulation 300 times.In this circulation, the 300th round-robin loading capacity is the capacity sustainment rate with respect to the ratio (%) of first loading capacity.This capacity sustainment rate height means that cycle characteristics is good.
(b) in addition, the battery shock test for before the round-robin test of carrying out (a) drops on the concrete floor its height from 1.9m, and repeats 10 times.Then battery is taken apart and observed.Almost not seeing the coiling body deformation evaluating is A, sees slight deformation and is evaluated as B, can confirm easily that distortion then is evaluated as C.
[embodiment 1]
Using tumbler mixer that the polypropylene of the Mv40 ten thousand of the homopolymer polyethylene of the Mv30 ten thousand of the homopolymer polyethylene of the Mv70 ten thousand of 47 quality %, 46 quality % and 7 quality % is done mixes.In the resulting straight polymer mixture of 99 quality %, add the tetramethylolmethane as oxidation inhibitor-four [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionic ester] of 1 quality %, do with tumbler mixer once more and mix, obtain mixtures such as polymkeric substance thus.Mixtures such as resulting polymers supply to twin screw extruder by material feeder with after the nitrogen replacement under nitrogen atmosphere.In addition, (dynamic viscosity under 37.78 ℃ is 7.59 * 10 with whiteruss by ram pump (plunger pump) -5m 2/ s) be injected in the extruder barrel.
Regulate material feeder and pump, the ratio that makes the whiteruss amount account for melting mixing and whole mixtures of extruding is 65 quality %.The melting mixing condition is 200 ℃ design temperature, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, the melting mixing thing is expressed into surface temperature control on 25 ℃ cooling roller, casts, obtain the gel sheet of thickness 2000 μ m through T shape die head.
Then, import in the while twin shaft tentering elongator, carry out twin shaft and extend.The extension condition of setting is that 7.0 times of MD multiplying powers, 7.0 times of TD multiplying powers, design temperature are 125 ℃.
Then, import in the methylethylketone groove, fully flood in methylethylketone, whiteruss is removed in extracting, and is dry then, removes methylethylketone.
Be directed into then on the TD tenter machine, carry out heat setting.Carry out under the extension ratio of the periodic elongating temperature of 128 ℃ thermosetting and 2.0 times, after this temperature during relaxation is 133 ℃, and the relaxation rate is 0.80.
The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 2]
Except the twin shaft elongating temperature is 120 ℃, carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 3]
Former film thickness after extruding be 900 μ m, twin shaft elongating temperature be 122 ℃, the periodic elongating temperature of thermosetting be 130 ℃ and extension ratio be 2.0 times and after this temperature during relaxation be that 135 ℃ and relaxation rate are 0.80, carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 4]
Homopolymer polyethylene except the Mv25 ten thousand of the homopolymer polyethylene of the Mv250 ten thousand that uses 30 quality %, 70 quality %, former film thickness after extruding be 2400 μ m, the periodic elongating temperature of thermosetting be 125 ℃ and extension ratio be 1.9 times and after this temperature during relaxation be that 132 ℃ and relaxation rate are beyond 0.7, carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 5]
Except in 99 quality % straight polymer mixtures, using Mv 500,000 the periodic temperature of homopolymer polyethylene, thermosetting is 125 ℃, to carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 6]
Former film thickness after extruding be 1800 μ m, twin shaft extension ratio be 5 * 5 times, twin shaft elongating temperature be 115 ℃, the periodic elongating temperature of thermosetting be 125 ℃ and extension ratio be 1.7 times and after this temperature during relaxation be that 131 ℃ and relaxation rate are 0.70, carry out similarly to Example 4.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 7]
Except using Mv 1,200,000 homopolymer polyethylene and twin shaft elongating temperature are 128 ℃, to carry out similarly to Example 5.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 8]
Except the Mv that uses 45 quality % is that the Mv of 700,000 homopolymer polyethylene, 40 quality % is that the Mv of 300,000 homopolymer polyethylene and 15 quality % 400,000 polyacrylic blend and twin shaft elongating temperature are 123 ℃, carries out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 9]
Except the Mv that uses 45 quality % is that the Mv of 700,000 homopolymer polyethylene, 30 quality % is that the Mv of 300,000 homopolymer polyethylene and 25 quality % 400,000 polyacrylic blend and twin shaft elongating temperature are 123 ℃, carries out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 10]
Except gel sheet thickness is that 1600 μ m, the periodic elongating temperature of thermosetting are 125 ℃ and after this temperature during relaxation is 130 ℃, carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[embodiment 11]
Except the Mv that uses 30 quality % is that the Mv of 2,500,000 homopolymer polyethylene, 60 quality % is that the Mv of 250,000 homopolymer polyethylene and 10 quality % 400,000 polypropylene and the periodic extension of thermosetting and relaxation temperature are 128 ℃ and 133 ℃, carries out similarly to Example 4.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[comparative example 1]
Except the periodic elongating temperature of thermosetting be 120 ℃ and extension ratio be 1.5 times and after this temperature during relaxation be that 125 ℃ and relaxation rate are 0.80, carry out similarly to Example 1.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[comparative example 2]
Except the periodic elongating temperature of thermosetting is that 122 ℃ and extension ratio are 1.3 times and do not carry out carrying out similarly to Example 2 the relaxation.The rerum natura of gained polyolefin microporous film is shown in the table 1.
[comparative example 3]
Using tumbler mixer that the homopolymer of the Mv95 ten thousand of the homopolymer of the Mv27 ten thousand of 60 quality % and 40 quality % is done mixes.In the resulting straight polymer mixture of 99 quality %, add the tetramethylolmethane as oxidation inhibitor-four [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionic ester] of 1 quality %, do with cylindrical blender once more and mix, obtain mixtures such as polymkeric substance.Mixtures such as resulting polymers supply to twin screw extruder by material feeder with after the nitrogen replacement under nitrogen atmosphere.In addition, (dynamic viscosity under 37.78 ℃ is 7.59 * 10 with whiteruss by ram pump -5m 2/ s) be injected in the extruder barrel.
Regulate material feeder and pump, the ratio that makes the whiteruss amount account for melting mixing and whole mixtures of extruding is 62 quality %.The melting mixing condition is 200 ℃ design temperature, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, the melting mixing thing is expressed into surface temperature control on 25 ℃ cooling roller, prolongs than casting, obtain the gel sheet of thickness 200 μ m with 4 multiplication of voltages through T shape die head.
Then, resulting sheet is directed in the TD tentering elongator, carries out horizontal expansion before the extracting, carry out 10% hot relaxation then with the extension ratio of 115 ℃ elongating temperatures and 5 times.
Then, import in the methylethylketone groove, fully flood in methylethylketone, whiteruss is removed in extracting, and is dry then, removes methylethylketone.
Then the film after the above-mentioned extracting being directed on the multistage roll-type length direction elongator, is to carry out extending after the extracting under 2 times the condition at 110 ℃ of elongating temperatures and MD direction extension ratio, obtains micro-porous film.
The rerum natura of gained polyolefin microporous film is shown in the table 1.
[comparative example 4]
The Mv that adds 30 quality % be the Mv of 700,000 homopolymer polyethylene, 15 quality % be the Mv of 300,000 homopolymer polyethylene, 5 quality % be 400,000 homopolymer polypropylene, 30.6 quality % dioctyl phthalate (DOP) (DOP), 18.4 quality % micro mist silicas and 1 quality % the tetramethylolmethane as oxidation inhibitor-four [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionic ester] and mix.Mixtures such as resulting polymers are supplied with twin screw extruder by material feeder with after the nitrogen replacement under nitrogen atmosphere.
The melting mixing condition is 200 ℃ design temperature, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, the melting mixing thing is expressed into surface temperature control on 80 ℃ cooling roller, casts, obtain the gel sheet of thickness 110 μ m through T shape die head.
DOP and micro mist silica are removed in extracting from this gel sheet, obtain micro-porous film.This micro-porous film of 2 is overlapping, extend 5 times at 110 ℃ of following length directions, be directed into then on the TD tenter machine, 2 times of 130 ℃ of following horizontal expansions.After this, the TD relaxation rate under 130 ℃ is 0.80.
The rerum natura of gained polyolefin microporous film is shown in the table 1.
Figure A20078004488800251
*1 does not find that almost disintegrate in the test back, the coiling body distortion then is evaluated as A; Find that disintegration and coiling body distortion that the test back is slight then are evaluated as B; Confirm that easily distortion then is evaluated as C.
*State of insulation evaluation more than 2 1000 Ω that keep more than 60 minutes then is A; Keep the above state of insulation of 1000 Ω more than 30 minutes then to be evaluated as B; Keep the above state of insulation of 1000 Ω more than 10 minutes then to be evaluated as C; Keep the above state of insulation of 1000 Ω more than 5 minutes then to be evaluated as D; The above state of insulation of 1000 Ω that can not keep 5 minutes then is evaluated as E.
Can draw to draw a conclusion from the result of table 1:
(1) percent thermal shrinkage of the extension strength of bubble point, length direction and width and the width under the 130 ℃ polyolefin microporous film that is adjusted in the embodiment 1～11 in the specified range has the good shock-resistance and the balance of anti-rupture of membranes, and the battery that uses their to make has excellent capacity sustainment rate.
(2) bubble point of comparative example 1 and 2 polyolefin microporous film surpasses 1MPa, owing to do not have sufficient aperture, so the capacity sustainment rate is inferior.
(3) polyolefin microporous film of comparative example 3 is because the TD percent thermal shrinkage under 130 ℃ surpasses 20%, and in addition, piercing through intensity is that 0.20N/ μ m is following and intensity is insufficient, and therefore, the balance of shock-resistance and anti-rupture of membranes is inferior.
(4) polyolefin microporous film of comparative example 4 is because the TD extension strength is lower than 50MPa, and the summation of MD extension elongation and TD extension elongation surpasses 250% in addition, and therefore, micro-porous film is to the repeated stock easy deformation, and shock-resistance is not good.
(5) compare with 7 with embodiment 5, the polyolefin microporous film of embodiment 11 is because to use Mv be that polyethylene and Mv 500,000 or more is lower than 500,000 polyethylene, and further with polypropene blended, so anti-rupture of membranes and shock-resistance all are excellent.
(6) with embodiment 1 relatively, the polypropylene content height of embodiment 8 and 9 polyolefin microporous film.As a result, heat setting at high temperature not only, and extend the elongation step-down, anti-rupture of membranes and shock-resistance all are excellent.
(7) compare with embodiment 6, therefore the polyolefin microporous film of embodiment 4 has excellent in impact resistance because the total elongation multiplying power is high and the extension elongation is low.
(8) compare with embodiment 10, though the polyolefin microporous film of embodiment 1 is low owing to void content, the capacity sustainment rate can be poor slightly, because the low heat shrinkage under high strength, therefore anti-rupture of membranes and shock-resistance all are excellent.
As can be seen from the above results, the polyolefin microporous film of present embodiment has the wide aperture, has intensity, extension elongation and the low thermal shrinkage behavior of balance excellence simultaneously.Therefore, the polyolefin microporous film by using present embodiment can obtain the harmonious excellent secondary cell of battery behavior and battery security as battery separator.
Utilizability on the industry
The present invention relates to see through diffusion barrier and isolated material for separating substances and selection Deng polyolefin microporous film, especially can be used as and use in the lithium ion battery etc. Barrier film is in industrial utilization.

Claims (9)

1. polyolefin microporous film, the bubble point of wherein said micro-porous film is below the 1MPa, and the extension strength of length direction and the extension strength of width are respectively more than the 50MPa, and the percent thermal shrinkage of the width under 130 ℃ is below 20%.
2. polyolefin microporous film according to claim 1, wherein, described micro-porous film comprises polypropylene.
3. polyolefin microporous film according to claim 1 and 2, wherein, the summation that MD extends elongation and TD extension elongation is 20～250%.
4. polyolefin microporous film according to claim 3, wherein, the summation that MD extends elongation and TD extension elongation is 20-200%.
5. according to each described polyolefin microporous film of claim 1～4, wherein, it is that ultrahigh molecular weight polyethylene(UHMWPE) and viscosity-average molecular weight more than 500,000 is lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
6. according to each described polyolefin microporous film of claim 1～5, wherein, void content is more than 20% below 60%.
7. battery separator, described barrier film is formed by each described polyolefin microporous film of claim 1～6.
8. nonaqueous electrolytic solution secondary battery, it has battery separator according to claim 7.
9. manufacture method that the total elongation multiplying power is the polyolefin microporous film more than 50 times, described method comprises:
With contain at least polyolefine and softening agent the resin combination melting mixing, extrude and obtain the operation of flap;
Extend described flap and obtain the operation of film;
The operation of extracting elasticizer from described flap or described film; And
Operation with described film heat setting.
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