CN101568575B - Polyolefin microporous membrane - Google Patents

Polyolefin microporous membrane Download PDF

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Publication number
CN101568575B
CN101568575B CN2007800448887A CN200780044888A CN101568575B CN 101568575 B CN101568575 B CN 101568575B CN 2007800448887 A CN2007800448887 A CN 2007800448887A CN 200780044888 A CN200780044888 A CN 200780044888A CN 101568575 B CN101568575 B CN 101568575B
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polyolefin microporous
molecular weight
microporous film
manufacture method
polyethylene
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CN101568575A (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)
  • Polymers & Plastics (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Cell Separators (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (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 the 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 polyolefin microporous film that lithium ion battery is used barrier film.
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 such as comprising secondary filter film, fuel cell separators, electrical condenser with barrier film or being used for functional material is filled into the hole and showing the mother metal, battery separator etc. of the functional membrane of new function.In these purposes, particularly preferably as widely used lithium ion battery barrier film in notebook PC, portable phone, digital camera etc.As its reason, can enumerate this film and have physical strength and hole plug.
So-called hole plug refers at inside battery to make hole plug because of micro-porous film melting 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 occurs is lower, and the security effect is higher.
In addition, when the coiling barrier film, and in order to prevent because foreign matter in battery etc. causes short circuit, barrier film pierce through intensity (piercing strength) and length direction (refers to operating direction, below also be called MD), the extension strength of width (refer to the direction vertical with operating direction, below also be called TD) need to have to a certain degree above intensity.In addition, in lithium-ion secondary cell in recent years, due to high-output power and the high capacity of battery, not only require the aperture of barrier film to increase, but also require at high temperature have excellent heat-shrinkable.
The void content of barrier film is higher and the aperture is larger, and the electrical characteristic of battery are better, yet there are opposite relation in the increase of void content and the increase in aperture with size and the intensity of percent thermal shrinkage.Therefore, have good battery electrical characteristic even implement the barrier film of high porosity and wide aperture, also can have the problem of shrinking large or undercapacity under the high temperature of battery oven test.
As the means that address these problems, the applicant has proposed polymkeric substance and filler, softening agent mixing in patent documentation 1, make it to be separated, and the method for extending after 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 sufficient 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.
Proposed to use the polyolefine prepared wide-aperture micro-porous film of high molecular in patent documentation 3, 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, due to the blend Low Density Polyethylene, the difficulty so heat fixation 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 in the past has, and electrical characteristic are excellent owing to having the wide aperture, and intensity and low thermal shrinkage behavior are excellent simultaneously.
For the scheme of dealing 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 specified range has the wide aperture, and have excellent intensity and low thermal shrinkage behavior, thereby completed the present invention.That is to say, 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 1MPa, and more than the extension strength of length direction and the extension strength of width were respectively 50MPa, the percent thermal shrinkage of the width under 130 ℃ was 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 the described polyolefin microporous film of any one of above-mentioned (1)～(4), wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
(6) according to the described polyolefin microporous film of any one 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 the described polyolefin microporous film of any one 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 at least polyolefine and softening agent, 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 the operation that described film thermal is fixing.
The effect of invention
Compare with existing polyolefin microporous film, polyolefin microporous film of the present invention is the wide aperture, 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 the battery that uses 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 for implementing preferred forms of the present invention (following also be called " present embodiment ").In addition, the invention is not restricted to following embodiment, can have various modification in its purport scope.
The bubble point of the polyolefin microporous film of present embodiment is below 1MPa, and more than the extension strength of length direction and the extension strength of width were respectively 50MPa, the percent thermal shrinkage of the width under 130 ℃ was 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 to below 1.0MPa, be preferably below 0.8MPa.More than the lower limit of bubble point is preferably 0.1MPa, more preferably more than 0.3MPa.At bubble point during 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 from the viewpoint of bubble point, has dependency between the permeable amount of micro-porous film and the ratio of Air permenbility (permeable amount/Air permenbility) and mean pore size.This ratio is preferably 1.7 * 10 -3Above.At this ratio lower than 1.7 * 10 -3The time, it is insufficient that perviousness easily becomes, and the capacity dimension holdup of battery has the tendency of reduction.The upper limit to this ratio does not limit, preferably less than 2.3 * 10 -3, be more preferably less than 2.1 * 10 -3Scope.Be 2.3 * 10 at this ratio -3When above, might become excessive in the hole, undercapacity is perhaps easily because lithium dentrite (dendrite) produces short circuit.Be below 1.0MPa and permeable amount/Air permenbility in above-mentioned scope the time at bubble point, harmonious and have high strength and low thermal shrinkage behavior under the state of perviousness keeping owing to having excellent mean pore size, for lithium ion battery is in recent years given superperformance, therefore particularly preferably.
In addition, the extension strength of the polyolefin microporous film of present embodiment on length direction (MD) and width (TD) need to be more than 50MPa, more preferably more than 70MPa, more preferably more than 100MPa.When extension strength low (lower than 50MPa), the battery winding variation is easily because the battery shock test that occurs from the outside, the foreign matter in battery etc. are short-circuited.
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 contain polypropylene in micro-porous film, not only can improve thermotolerance, even and also often be difficult to fracture under high extension ratio.In addition, can be easily MD described later and TD be extended elongation and be adjusted in suitable scope, result can improve the shock-resistance of gained battery, lowers the risk of short circuit.Polyacrylic content is preferably with respect to 1～80 quality % of polymer materials, more preferably 2～50 quality %, further preferred 3～30 quality %.During lower than 1 quality %, often be difficult to expression effect in polypropylene content, and when polypropylene content surpasses 80 quality %, often be difficult to guarantee perviousness.
In addition, the MD of the polyolefin microporous film of present embodiment and TD extend elongation and are preferably separately 10～200%, 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, easily deform for the repeated stock in battery shock test etc., and 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, extracting and the various conditions in the relaxation operation.In addition as mentioned above, polypropylene is also a kind of effective means in polymkeric substance.
It is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight 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 melting increases, and has by the early stage relaxation of melting tension force the tendency that improves anti-rupture of membranes.
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 more low more preferred, but from the viewpoint of the balance of thickness and void content, more than being preferably 1sec, more preferably more than 50sec.In addition, from the viewpoint of perviousness, this Gas permeability is preferably below 1000sec, more preferably below 500sec.
From the viewpoint of film toughness, more than the thickness of the polyolefin microporous film of present embodiment is preferably 1 μ m, more preferably more than 5 μ m.In addition, from the viewpoint of perviousness, this thickness is preferably below 50 μ m, more preferably below 30 μ m.
In addition, the piercing through more than intensity is preferably 0.2N/ μ m of the polyolefin microporous film of present embodiment is more preferably more than 0.22N/ μ m.When piercing through intensity lower (lower than 0.2N/ μ m), in the situation that as battery diaphragm, micro-porous film is thrust in the sharp keen section of electrode materials etc., easily produces pinprick or be full of cracks, has the yielding tendency of appearance the battery shock test that occurs 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 fixation 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 at least polyolefine and softening agent 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 the operation that described film thermal is fixing.
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 axle.
(d) extend after, extracting elasticizer and inorganics as required.
(e) then carry out heat fixation and thermal treatment.
The polyolefine that uses in 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, can be also the mixture of above-mentioned polymkeric substance.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 supplying with, preferably with two or more polyolefin blends.Can control thus melt temperature and short circuit temperature.More preferably, with two or more polyethylene blends, preferably comprise viscosity-average molecular weight (Mw) and be ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight (Mv) lower than 500,000 polyethylene.Never plugging hole, can carry out the viewpoint of heat fixation under higher temperature, 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.Lower than 100,000 o'clock, the anti-rupture of membranes during melting might become insufficient in viscosity-average molecular weight (Mv), and surpassed at 1,200,000 o'clock in viscosity-average molecular weight, possiblely was, extruded the operation difficulty that becomes, and the relaxation of the convergent force during melting is slow, and thermotolerance is inferior.
These polyethylene with not only can improve thermotolerance as fusing point higher than blend such as poly polyolefinic polypropylene, and in the extension after extracting and relaxation operation, can operate at the temperature higher than polyvinyl monomer, in addition, when keeping the intensity of micro-porous film, percent thermal shrinkage, aperture, can reduce to extend elongation.In addition, although reason is unclear, also being difficult to even have the effect that ruptures under high extension ratio, is therefore particularly preferred.
Improve thermotolerance and the application's low thermal shrinkage behavior combination by above-mentioned blend, anti-rupture of membranes at high temperature becomes better, is therefore preferred.
In addition, can mix the known additives such as metal soap, UV light absorber, photostabilizer, static inhibitor, antifogging agent, tinting pigment such as using calcium stearate, Zinic stearas.
In addition, can also add inorganics take aluminum oxide, titanium dioxide etc. as representative.Can be at this inorganics of 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 present embodiment is can form with polyolefine the organic compound of homogeneous solution at the temperature below boiling point, 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, from the viewpoint of the void content of gained micro-porous film, more than the ratio of softening agent is preferably 20 quality %; From the viewpoint of viscosity, more than being preferably 90 quality %, 50 quality %～70 quality % more preferably.
Be the good solvent of polyolefinic poor solvent and softening agent as the extraction solvent that is used for extracting elasticizer, and boiling point is desirable than polyolefinic low-melting solvent.As this extraction solvent, such as enumerating the hydro carbons such as normal hexane, hexanaphthene, the halogenated hydrocarbons such as methylene dichloride, 1，1，1-trichloroethane, fluorohydrocarbon class, the alcohols such as ethanol, Virahol, the 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 after extracting elasticizer etc. regenerates and reuses.
From the perviousness of film and the viewpoint of masking, the gross weight ratio that softening agent and inorganics account for the entire mixture of melting mixing is preferably 20～95 quality %, more preferably 30～80 quality %.
In addition, the viewpoint of the thermal degradation when when preventing melting mixing and the quality variation that causes thus, the preferred oxidation inhibitor that coordinates in mixture.Oxidation inhibitor is with respect to the concentration of whole polyolefine weight preferably more than 0.3 quality %, more preferably more than 0.5 quality %.In addition, this concentration is preferably below 5.0 quality %, more preferably below 3.0 quality %.
As oxidation inhibitor, be preferred as the phenolic antioxidant of primary antioxidant, 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 (2,4-di-tert-butyl-phenyl) ester, four (2 can be enumerated, the 4-di-tert-butyl-phenyl)-4, the sulfur type antioxidants such as the Phosphorus oxidation inhibitor such as 4-biphenylene diphosphites, dilauryl thiodipropionate etc.
At first melting mixing and the method for extruding comprise that the starting material with part or all are pre-mixed with Henschel mixer, belt blending machine, tumbler mixer etc. as required.Can stir with hand under a few cases.Then, carry out melting mixing with the screw extrusion presss such as single screw extrusion machine, twin screw extruder, mixing roll, mixing machine etc., with T shape die head, annular die is first-class extrudes.
Preferably, with after predetermined concentration mixing oxidation inhibitor, be replaced as nitrogen atmosphere and carry out melting mixing under the state of nitrogen atmosphere keeping in stock polymer.Temperature during melting mixing is preferably more than 160 ℃, more preferably more than 180 ℃.In addition, this temperature is preferably lower than 300 ℃, more preferably less than 240 ℃, also more preferably less than 230 ℃.
But the inorganics that can contain the not melting of extracting in inorganics extracting operation in the melts described in present embodiment.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 cooling melting mixing and the melts extruded are solidified by compressing.As method of cooling, can enumerate the heat-eliminating mediums such as direct contact cold wind, water coolant method, with method that contacts with the cooling roller of heat-eliminating medium or press etc.From the viewpoint of gauge control excellence, be preferred with the method that contacts with the cooling roller of heat-eliminating medium or press.
Next the extension carried out and order, method and the number of times of softening agent extracting or extension and softening agent extracting and inorganics extracting do not had 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 successively twin shaft 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 particularly preferably more than 40 times.Wherein, simultaneously or successively 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 fully dry.
The heat fixation 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.The TD that the relaxation operation refers at film and/or the reduction operation on the TD direction.The relaxation rate refers to that the MD size of the film after the relaxation operation is divided by the resulting value of MD size of preoperative film, the perhaps value that obtains divided by the TD size of preoperative film of the TD size after relaxation operation, perhaps in the situation that MD and TD both direction enterprising Henan that runs, it is 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 only direction of MD or TD is enterprising, not only can reduce the percent thermal shrinkage of direction of operating, but also can reduce the percent thermal shrinkage on the direction vertical with direction of operating.By carried out more than 1.5 times before the operation of this relaxation, the more preferably extension more than 1.8 times, can easily obtain the micro-porous film of high strength and wide aperture.
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 aperture, 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, be in poly situation at polyolefine, extend near fusing point and the relaxation operation, compare with micro-porous film in the past, easily obtain the micro-porous film of wide aperture and low heat shrinkage.In addition, although agnogenio, even the film of low elongation also easily obtains the micro-porous film of rupture of membranes excellence.From can be at this from the past different higher temperature condition downward-extension and relaxations, even also be difficult in addition the viewpoint of breaking under the large condition of total elongation multiplying power, as polyolefine, preferably go back co-blend polypropylene except polyethylene.
In addition, the polyolefin micro porous polyolefin membrane of present embodiment can carry out the surface treatments such as electron rays irradiation, plasma irradiating, tensio-active agent coating, chemical modification.
Embodiment
Illustrate in greater detail by the following examples the present embodiment.
[measuring method]
The measuring method of the physical property 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)
Use miniature thickness measuring device KBM (trade mark) that Japan's essence machine makes to measure under 23 ± 2 ℃ of room temperatures.
(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 (Japan's essence device (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
Be arranged in the saturating liquid pool of stainless steel of diameter 41mm being immersed in advance micro-porous film in ethanol, after water cleans the ethanol of this film, under the pressure reduction of about 50000Pa, water seen through, the permeable amount (cm by through 120 second 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 2SecPa))=permeable degree/100
(7) (pierce through intensity (N/ μ m)
Use KATO TECH Co., the Portable compressed 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 under the condition of speed 2mm/sec and 25 ℃ of atmosphere, the central part to fixing micro-porous film carries out puncture test, 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 work packing シ ス テ system (strain) that sample adopts spacing jig to be set as 50mm, sample both ends (each 25mm) is made, trade(brand)name: sample N.29).And, for the slip of sample in preventing from testing, the inboard viton of pasting thickness 1mm of the fixture of elongation test machine.
Extend elongation (%) and reach elongation (mm) when rupturing divided by spacing jig (50mm) by use, then multiply by 100 and obtain.
The sample section of the intensity of extension strength (MPa) by will rupture the time before divided by test amasss to obtain.
In addition, extend the summation (%) of elongation and TD extension elongation by the value addition of MD and TD being calculated MD.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 the baking oven of 130 ℃ standing 1 hour.At this moment, directly blow to sample in order not make hot blast, with sample holder between two pieces of paper.Take out and cooling rear measured length (mm) from baking oven, 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, measure in alcohol solvent.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, 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 arranges the window of 10mm * 10mm in electrolytic solution.
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, standing in baking oven.After this, the speed intensification with 5 ℃/min kept 1 hour under 150 ℃ after reaching 150 ℃.Measure the resistance change of this moment with the LCR meter under the condition that exchanges 10mV, 1kHz.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, the E that is evaluated as of 5 minutes 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 above-mentioned solvent.
[making of battery and evaluation]
(1) anodal making
Disperse the lithium cobalt composite oxide LiCoO as active substance of 92.2 quality % in N-Methyl pyrrolidone (NMP) 2, be respectively the poly(vinylidene fluoride) as binding agent (PVDF) as the flaky graphite of conductive agent and acetylene black, 3.2 quality % of 2.3 quality %, preparation slurry.With die coater, this slurry is coated on the face of aluminium foil of the thickness 20 μ m that consist of positive electrode collector, under 130 ℃ dry 3 minutes, then used the roll squeezer compression molding.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 approximately band shape of 40mm of width.
(2) making of negative pole
The synthetic graphite as active substance of middle dispersion 96.9 quality % of purifying waste water, 1.4 quality % as the ammonium salt of the carboxymethyl cellulose of binding agent and the styrene-butadiene copolymer latex of 1.7 quality %, the preparation slurry.With die coater, this slurry is coated on the face of Copper Foil that the thickness that consists of negative electrode collector is 12 μ m, under 120 ℃ dry 3 minutes, then used the roll squeezer compression molding.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 approximately band shape of 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 to make its concentration be 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 the order of banded negative pole, barrier film, banded positive pole and barrier film with using, and repeatedly reel to form spirrillum, thereby make the plate electrode layer laminate.This plate electrode layer laminate is compressed to tabular, then puts into aluminium vessel, derive the aluminum lead-in wire from positive electrode collector, be welded on battery cover, derive nickel making line from negative electrode collector, be welded in container bottom.In addition, above-mentioned nonaqueous electrolytic solution is injected in this container and sealing.The lithium ion battery of making like this is designed to the size of length direction (thickness) 6.3mm, horizontal 30mm and height 48mm, 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, place 1 week (aging) under 25 ℃ of atmosphere.
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, then is being discharged to cell voltage 3.0V under certain current value (CC) 620mA.The loading capacity of this moment is set as first loading capacity.
(a) further repeat above-mentioned circulation 300 times.In this circulation, the loading capacity of the 300th circulation is the capacity dimension holdup with respect to the ratio (%) of first loading capacity.This capacity dimension holdup is high 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 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 is evaluated as C.
[embodiment 1]
Use 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 dry mixed.[3-(3 to add the tetramethylolmethane as oxidation inhibitor-four of 1 quality % in the resulting straight polymer mixture of 99 quality %, 5-di-t-butyl-4-hydroxyphenyl) propionic ester], again be dry mixed with tumbler mixer, obtain thus the mixtures such as polymkeric substance.The mixtures such as resulting polymers supply to twin screw extruder by material feeder with after 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 extruder barrel.
Regulate material feeder and pump, the ratio that makes the whiteruss amount account for melting mixing and the entire mixture of extruding is 65 quality %.The melting mixing condition is the design temperature of 200 ℃, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, through T shape die head, the melting mixing thing is expressed into surface temperature control on the cooling roller of 25 ℃, casts, obtain the gel sheet of thickness 2000 μ m.
Then, import in 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 then dry, removes methylethylketone.
Then be directed on the TD tenter machine, carry out heat fixation.Carry out under elongating temperature when the heat fixation of 128 ℃ and the extension ratio of 2.0 times, after this temperature during relaxation is 133 ℃, and the relaxation rate is 0.80.
The physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 2]
Except the twin shaft elongating temperature is 120 ℃, carry out similarly to Example 1.The physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 3]
Former film thickness after extruding is that 900 μ m, twin shaft elongating temperature are 122 ℃, the elongating temperature during heat fixation 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 physical property of gained polyolefin microporous film is shown in 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 %, elongating temperature when the former film thickness after extruding is 2400 μ m, heat fixation 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 physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 5]
Temperature when using Mv to be 500,000 homopolymer polyethylene, heat fixation in 99 quality % straight polymer mixtures is carried out being 125 ℃ similarly to Example 1.The physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 6]
Former film thickness after extruding is that 1800 μ m, twin shaft extension ratio are that 5 * 5 times, twin shaft elongating temperature are 115 ℃, the elongating temperature during heat fixation 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 physical property of gained polyolefin microporous film is shown in 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 physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 8]
Except the Mv that the uses 45 quality % Mv that is 700,000 homopolymer polyethylene, 40 quality % the Mv that is 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 physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 9]
Except the Mv that the uses 45 quality % Mv that is 700,000 homopolymer polyethylene, 30 quality % the Mv that is 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 physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 10]
Elongating temperature when being 1600 μ m, heat fixation except gel sheet thickness be 125 ℃ and after this temperature during relaxation be 130 ℃, to carry out similarly to Example 1.The physical property of gained polyolefin microporous film is shown in table 1.
[embodiment 11]
Extension when being 400,000 polypropylene and heat fixation except the Mv that the uses 30 quality % Mv that is 2,500,000 homopolymer polyethylene, 60 quality % the Mv that is 250,000 homopolymer polyethylene and 10 quality % and relaxation temperature are carried out being 128 ℃ and 133 ℃ similarly to Example 4.The physical property of gained polyolefin microporous film is shown in table 1.
[comparative example 1]
Elongating temperature during except heat fixation 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 physical property of gained polyolefin microporous film is shown in table 1.
[comparative example 2]
Elongating temperature during except heat fixation is 122 ℃ and is 1.3 times and does not carry out carrying out similarly to Example 2 relaxation with extension ratio.The physical property of gained polyolefin microporous film is shown in table 1.
[comparative example 3]
Use 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 dry mixed.Add the tetramethylolmethane as oxidation inhibitor-four [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionic ester] of 1 quality % in the 99 resulting straight polymer mixtures of quality %, again be dry mixed with cylindrical blender, obtain the mixtures such as polymkeric substance.The mixtures such as resulting polymers supply to twin screw extruder by material feeder with after 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 extruder barrel.
Regulate material feeder and pump, the ratio that makes the whiteruss amount account for melting mixing and the entire mixture of extruding is 62 quality %.The melting mixing condition is the design temperature of 200 ℃, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, through T shape die head, the melting mixing thing is expressed into surface temperature control on the cooling roller of 25 ℃, casts with 4 times of calendering ratios, obtain the gel sheet of thickness 200 μ m.
Then, resulting sheet is directed in TD tentering elongator, carries out horizontal expansion before extracting with the extension ratio of the elongating temperatures of 115 ℃ and 5 times, then carry out 10% hot relaxation.
Then, import in the methylethylketone groove, fully flood in methylethylketone, whiteruss is removed in extracting, and is then dry, removes methylethylketone.
Then the film after above-mentioned extracting being directed on multistage roll-type length direction elongator, is to carry out extending after extracting under the condition of 2 times at 110 ℃ of elongating temperatures and MD direction extension ratio, obtains micro-porous film.
The physical property of gained polyolefin microporous film is shown in 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.The mixtures such as resulting polymers are supplied with twin screw extruder by material feeder with after nitrogen replacement under nitrogen atmosphere.
The melting mixing condition is the design temperature of 200 ℃, the screw rod revolution of 240rpm and the spray volume of 12kg/h.
Then, through T shape die head, the melting mixing thing is expressed into surface temperature control on the cooling roller of 80 ℃, casts, obtain the gel sheet of thickness 110 μ m.
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 lower length directions, then be directed on the TD tenter machine, laterally extend 2 times under 130 ℃.After this, the TD relaxation rate under 130 ℃ is 0.80.
The physical property of gained polyolefin microporous film is shown in table 1.
* 1 find that almost the rear disintegration of test, coiling body distortion are evaluated as A; After finding test, slight disintegration and coiling body distortion is evaluated as B; Confirm that easily distortion is evaluated as C.
* the state of insulation evaluation more than 2 1000 Ω that keep more than 60 minutes is A; Keep the above state of insulation of 1000 Ω more than 30 minutes to be evaluated as B; Keep the above state of insulation of 1000 Ω more than 10 minutes to be evaluated as C; Keep the above state of insulation of 1000 Ω more than 5 minutes to be evaluated as D; The above state of insulation of 1000 Ω that can not keep 5 minutes 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 specified range has good shock-resistance and the balance of anti-rupture of membranes, and the battery that uses their to make has excellent capacity dimension holdup.
(2) bubble point of comparative example 1 and 2 polyolefin microporous film surpasses 1MPa, owing to not having sufficient aperture, so the capacity dimension holdup 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) lower than 50MPa, the summation of MD extension elongation and TD extension elongation surpasses 250% to the polyolefin microporous film of comparative example 4 in addition due to the TD extension strength, and therefore, micro-porous film easily is out of shape repeated stock, and shock-resistance is not good.
(5) compare with 7 with embodiment 5, the polyolefin microporous film of embodiment 11 due to use Mv be polyethylene 500,000 or more and Mv lower than 500,000 polyethylene, and further with polypropene blended, so anti-rupture of membranes and shock-resistance are all excellent.
(6) with embodiment 1 relatively, the polypropylene content of embodiment 8 and 9 polyolefin microporous film is high.As a result, heat fixation at high temperature not only, and extend the elongation step-down, anti-rupture of membranes and shock-resistance are all excellent.
(7) compare with embodiment 6, therefore the polyolefin microporous film of embodiment 4 has excellent shock-resistance because the total elongation multiplying power is high low with the extension elongation.
(8) with embodiment 10 relatively, although the polyolefin microporous film of embodiment 1 because void content is low, the capacity dimension holdup can be slightly poor, due to the low heat shrinkage under high strength, therefore anti-rupture of membranes and shock-resistance are all excellent.
As can be seen from the above results, the polyolefin microporous film of present embodiment has the wide aperture, has simultaneously intensity, extension elongation and the low thermal shrinkage behavior of balance excellence.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 industry
The present invention relates to for separating substances and select to see through separatory membrane and the polyolefin microporous film of isolated material etc., especially can be used as the barrier film that uses in lithium ion battery etc. in industrial utilization.

Claims (14)

1. the manufacture method of a polyolefin microporous film, the bubble point of wherein said micro-porous film is below 1MPa, more than the extension strength of length direction and the extension strength of width were respectively 50MPa, the percent thermal shrinkage of the width under 130 ℃ was below 20%, and 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
The operation that described film thermal is fixing,
Described heat fixation operation has relaxation operation and the preoperative extension process of relaxation of described film,
Carry out the extension more than 1.5 times before relaxation operation in described heat fixation operation,
The temperature of relaxation operation and the preoperative extension process of relaxation is more than 125 ℃, and any one is more than 130 ℃ at least.
2. the manufacture method of polyolefin microporous film according to claim 1, wherein, described micro-porous film comprises polypropylene.
3. the manufacture method of polyolefin microporous film according to claim 1, wherein, it is 20～250% that the MD of described micro-porous film extends the summation that elongation and TD extend elongation.
4. the manufacture method of polyolefin microporous film according to claim 3, wherein, it is 20-200% that the MD of described micro-porous film extends the summation that elongation and TD extend elongation.
5. the manufacture method of polyolefin microporous film according to claim 1, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
6. the manufacture method of polyolefin microporous film according to claim 2, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
7. the manufacture method of polyolefin microporous film according to claim 3, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
8. the manufacture method of polyolefin microporous film according to claim 4, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
9. the manufacture method of polyolefin microporous film according to claim 2, wherein, it is 20～250% that the MD of described micro-porous film extends the summation that elongation and TD extend elongation.
10. the manufacture method of polyolefin microporous film according to claim 9, wherein, it is 20-200% that the MD of described micro-porous film extends the summation that elongation and TD extend elongation.
11. the manufacture method of polyolefin microporous film according to claim 9, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
12. the manufacture method of polyolefin microporous film according to claim 10, wherein, it is ultrahigh molecular weight polyethylene(UHMWPE) more than 500,000 and viscosity-average molecular weight lower than 500,000 polyethylene that described micro-porous film contains viscosity-average molecular weight.
13. the manufacture method of according to claim 1～12 the described polyolefin microporous film of any one, wherein, the void content of described micro-porous film is more than 20% below 60%.
14. the manufacture method of polyolefin microporous film according to claim 1, wherein, all the total elongation multiplying power of operation is more than 50 times.
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