CN118019788A - Polyolefin microporous membrane, separator for battery, and secondary battery - Google Patents
Polyolefin microporous membrane, separator for battery, and secondary battery Download PDFInfo
- Publication number
- CN118019788A CN118019788A CN202280065522.2A CN202280065522A CN118019788A CN 118019788 A CN118019788 A CN 118019788A CN 202280065522 A CN202280065522 A CN 202280065522A CN 118019788 A CN118019788 A CN 118019788A
- Authority
- CN
- China
- Prior art keywords
- microporous membrane
- polyolefin microporous
- temperature
- less
- polyolefin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229920000098 polyolefin Polymers 0.000 title claims abstract description 153
- 239000012982 microporous membrane Substances 0.000 title claims abstract description 140
- 238000002844 melting Methods 0.000 claims abstract description 132
- 230000008018 melting Effects 0.000 claims abstract description 132
- 238000005259 measurement Methods 0.000 claims abstract description 15
- 230000000630 rising effect Effects 0.000 claims abstract description 6
- -1 polyethylene Polymers 0.000 claims description 85
- 239000004698 Polyethylene Substances 0.000 claims description 74
- 229920000573 polyethylene Polymers 0.000 claims description 74
- 238000000034 method Methods 0.000 claims description 49
- 230000035699 permeability Effects 0.000 claims description 21
- 239000012528 membrane Substances 0.000 claims description 9
- 238000009826 distribution Methods 0.000 claims description 8
- 239000010408 film Substances 0.000 description 58
- 229920005672 polyolefin resin Polymers 0.000 description 58
- 239000002904 solvent Substances 0.000 description 34
- 239000002994 raw material Substances 0.000 description 29
- 239000000203 mixture Substances 0.000 description 27
- 239000013078 crystal Substances 0.000 description 22
- 239000000243 solution Substances 0.000 description 20
- 239000004705 High-molecular-weight polyethylene Substances 0.000 description 19
- 238000001816 cooling Methods 0.000 description 19
- 238000005406 washing Methods 0.000 description 18
- 239000004014 plasticizer Substances 0.000 description 16
- 239000000523 sample Substances 0.000 description 16
- 238000009998 heat setting Methods 0.000 description 13
- 230000000704 physical effect Effects 0.000 description 12
- 239000004743 Polypropylene Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 11
- 238000005227 gel permeation chromatography Methods 0.000 description 11
- 238000004898 kneading Methods 0.000 description 11
- 238000004519 manufacturing process Methods 0.000 description 11
- 238000002425 crystallisation Methods 0.000 description 10
- 230000008025 crystallization Effects 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 10
- 239000007788 liquid Substances 0.000 description 10
- 239000000463 material Substances 0.000 description 10
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 9
- 239000000155 melt Substances 0.000 description 9
- 238000011282 treatment Methods 0.000 description 9
- 229910052782 aluminium Inorganic materials 0.000 description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 8
- 239000003963 antioxidant agent Substances 0.000 description 8
- 230000003078 antioxidant effect Effects 0.000 description 8
- 230000004927 fusion Effects 0.000 description 8
- 229920001155 polypropylene Polymers 0.000 description 8
- 229920005989 resin Polymers 0.000 description 8
- 239000011347 resin Substances 0.000 description 8
- 230000006866 deterioration Effects 0.000 description 7
- 238000000113 differential scanning calorimetry Methods 0.000 description 7
- 238000011156 evaluation Methods 0.000 description 7
- 238000001953 recrystallisation Methods 0.000 description 7
- 238000001035 drying Methods 0.000 description 6
- 229940057995 liquid paraffin Drugs 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000004711 α-olefin Substances 0.000 description 6
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000010954 inorganic particle Substances 0.000 description 5
- 229920013716 polyethylene resin Polymers 0.000 description 5
- VXNZUUAINFGPBY-UHFFFAOYSA-N 1-Butene Chemical compound CCC=C VXNZUUAINFGPBY-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 238000001125 extrusion Methods 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 239000003643 water by type Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- ROHFBIREHKPELA-UHFFFAOYSA-N 2-[(3,5-ditert-butyl-4-hydroxyphenyl)methyl]prop-2-enoic acid;methane Chemical compound C.CC(C)(C)C1=CC(CC(=C)C(O)=O)=CC(C(C)(C)C)=C1O.CC(C)(C)C1=CC(CC(=C)C(O)=O)=CC(C(C)(C)C)=C1O.CC(C)(C)C1=CC(CC(=C)C(O)=O)=CC(C(C)(C)C)=C1O.CC(C)(C)C1=CC(CC(=C)C(O)=O)=CC(C(C)(C)C)=C1O ROHFBIREHKPELA-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 238000010030 laminating Methods 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000004094 surface-active agent Substances 0.000 description 3
- GBDZXPJXOMHESU-UHFFFAOYSA-N 1,2,3,4-tetrachlorobenzene Chemical compound ClC1=CC=C(Cl)C(Cl)=C1Cl GBDZXPJXOMHESU-UHFFFAOYSA-N 0.000 description 2
- LIKMAJRDDDTEIG-UHFFFAOYSA-N 1-hexene Chemical compound CCCCC=C LIKMAJRDDDTEIG-UHFFFAOYSA-N 0.000 description 2
- KWKAKUADMBZCLK-UHFFFAOYSA-N 1-octene Chemical compound CCCCCCC=C KWKAKUADMBZCLK-UHFFFAOYSA-N 0.000 description 2
- 238000001644 13C nuclear magnetic resonance spectroscopy Methods 0.000 description 2
- WSSSPWUEQFSQQG-UHFFFAOYSA-N 4-methyl-1-pentene Chemical compound CC(C)CC=C WSSSPWUEQFSQQG-UHFFFAOYSA-N 0.000 description 2
- NLZUEZXRPGMBCV-UHFFFAOYSA-N Butylhydroxytoluene Chemical compound CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 NLZUEZXRPGMBCV-UHFFFAOYSA-N 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- NNBZCPXTIHJBJL-UHFFFAOYSA-N decalin Chemical compound C1CCCC2CCCCC21 NNBZCPXTIHJBJL-UHFFFAOYSA-N 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
- DOIRQSBPFJWKBE-UHFFFAOYSA-N dibutyl phthalate Chemical compound CCCCOC(=O)C1=CC=CC=C1C(=O)OCCCC DOIRQSBPFJWKBE-UHFFFAOYSA-N 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- SNRUBQQJIBEYMU-UHFFFAOYSA-N dodecane Chemical compound CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000012760 heat stabilizer Substances 0.000 description 2
- IRHTZOCLLONTOC-UHFFFAOYSA-N hexacosan-1-ol Chemical compound CCCCCCCCCCCCCCCCCCCCCCCCCCO IRHTZOCLLONTOC-UHFFFAOYSA-N 0.000 description 2
- 229920001519 homopolymer Polymers 0.000 description 2
- 230000010220 ion permeability Effects 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- BKIMMITUMNQMOS-UHFFFAOYSA-N nonane Chemical compound CCCCCCCCC BKIMMITUMNQMOS-UHFFFAOYSA-N 0.000 description 2
- 239000002736 nonionic surfactant Substances 0.000 description 2
- GLDOVTGHNKAZLK-UHFFFAOYSA-N octadecan-1-ol Chemical compound CCCCCCCCCCCCCCCCCCO GLDOVTGHNKAZLK-UHFFFAOYSA-N 0.000 description 2
- YWAKXRMUMFPDSH-UHFFFAOYSA-N pentene Chemical compound CCCC=C YWAKXRMUMFPDSH-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 2
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- RSJKGSCJYJTIGS-UHFFFAOYSA-N undecane Chemical compound CCCCCCCCCCC RSJKGSCJYJTIGS-UHFFFAOYSA-N 0.000 description 2
- 230000037303 wrinkles Effects 0.000 description 2
- UJPMYEOUBPIPHQ-UHFFFAOYSA-N 1,1,1-trifluoroethane Chemical compound CC(F)(F)F UJPMYEOUBPIPHQ-UHFFFAOYSA-N 0.000 description 1
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical group FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 1
- VSAWBBYYMBQKIK-UHFFFAOYSA-N 4-[[3,5-bis[(3,5-ditert-butyl-4-hydroxyphenyl)methyl]-2,4,6-trimethylphenyl]methyl]-2,6-ditert-butylphenol Chemical compound CC1=C(CC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)C(C)=C(CC=2C=C(C(O)=C(C=2)C(C)(C)C)C(C)(C)C)C(C)=C1CC1=CC(C(C)(C)C)=C(O)C(C(C)(C)C)=C1 VSAWBBYYMBQKIK-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000178 Acrylic resin Polymers 0.000 description 1
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- 238000005481 NMR spectroscopy Methods 0.000 description 1
- 239000004962 Polyamide-imide Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000008186 active pharmaceutical agent Substances 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000003945 anionic surfactant Substances 0.000 description 1
- 239000002216 antistatic agent Substances 0.000 description 1
- 239000004760 aramid Substances 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 229920003235 aromatic polyamide Polymers 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000003093 cationic surfactant Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 150000008280 chlorinated hydrocarbons Chemical class 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- DIOQZVSQGTUSAI-NJFSPNSNSA-N decane Chemical compound CCCCCCCCC[14CH3] DIOQZVSQGTUSAI-NJFSPNSNSA-N 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000007606 doctor blade method Methods 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000005865 ionizing radiation Effects 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 1
- 239000001095 magnesium carbonate Substances 0.000 description 1
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 1
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 1
- 239000000347 magnesium hydroxide Substances 0.000 description 1
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002480 mineral oil Substances 0.000 description 1
- 235000010446 mineral oil Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- DIOQZVSQGTUSAI-UHFFFAOYSA-N n-butylhexane Natural products CCCCCCCCCC DIOQZVSQGTUSAI-UHFFFAOYSA-N 0.000 description 1
- GOQYKNQRPGWPLP-UHFFFAOYSA-N n-heptadecyl alcohol Natural products CCCCCCCCCCCCCCCCCO GOQYKNQRPGWPLP-UHFFFAOYSA-N 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 125000005498 phthalate group Chemical class 0.000 description 1
- 229920006122 polyamide resin Polymers 0.000 description 1
- 229920002312 polyamide-imide Polymers 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000009719 polyimide resin Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 229930195734 saturated hydrocarbon Natural products 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000006097 ultraviolet radiation absorber Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- PXXNTAGJWPJAGM-UHFFFAOYSA-N vertaline Natural products C1C2C=3C=C(OC)C(OC)=CC=3OC(C=C3)=CC=C3CCC(=O)OC1CC1N2CCCC1 PXXNTAGJWPJAGM-UHFFFAOYSA-N 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000002888 zwitterionic surfactant Substances 0.000 description 1
Classifications
-
- 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
- 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
- C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
-
- 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
-
- 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
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/04—Homopolymers or copolymers of ethene
- C08J2323/06—Polyethene
-
- 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
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Cell Separators (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The present invention relates to a polyolefin microporous membrane, wherein in a melting endothermic curve obtained by measurement with a differential scanning calorimeter at a temperature rising rate of 10 ℃/min, the temperature at the point of highest intensity at less than 145 ℃ is set as Tm B, and in a differential melting endothermic curve calculated from the melting endothermic curve, when the temperature showing the minimum value in the range of 145 ℃ or more and less than 155 ℃ is set as Tm A, Δtm (Δtm=tma-TmB) is 8.0 ℃ or more and 12.0 ℃ or less, and the ratio (Δs=s A/SB) of the intensity at Tm A (S A) to the intensity at Tm B (S B) in the melting endothermic curve exceeds 0.1 and is less than 0.5.
Description
Technical Field
The present invention relates to a polyolefin microporous membrane, a separator for a battery, and a secondary battery.
Background
The polyolefin microporous membrane is used as a filter, a separator for a fuel cell, a separator for a capacitor, or the like. The polyolefin microporous membrane is particularly suitable for use as a separator for lithium ion batteries widely used in notebook personal computers, smart phones, electric vehicles, and the like. The reason for this is that the polyolefin microporous membrane has excellent mechanical strength and shutdown characteristics, and has characteristics suitable for ensuring the safety of the battery. In particular, in lithium ion secondary batteries, recent developments have been made with the aim of increasing the size of the batteries and increasing the energy density, the capacity and the output, mainly for vehicle-mounted applications. Along with this, the demand for safety for the separator is also higher.
As characteristics that entail safety of the battery, there are shutdown characteristics and melting characteristics. The shutdown characteristic is a characteristic in which the inside of the battery becomes excessively charged and the inside of the battery becomes abnormally high Wen Huashi such as overheating, and the separator is closed with holes. The separator closes the hole to increase the resistance, and the battery reaction is blocked, so that the safety of the battery can be ensured. In general, the lower the shutdown temperature, the higher the safety is considered to be. On the other hand, when the temperature in the battery is further increased, the polymer in the microporous membrane melts and shrinks, and the blocking of the pores cannot be maintained, and the phenomenon of decrease in resistance is called melting. Further, the temperature at which the resistance value is lower than a predetermined value is set as the melting temperature. Regarding the melting characteristics, the higher the melting temperature and the higher the resistance value at high temperature, the more excellent the effect on the battery safety is considered.
Patent document 1 describes that a microporous film having excellent melting characteristics can be provided by mixing polyethylene with polypropylene having a weight average molecular weight of 50 ten thousand or more.
Patent document 2 describes that a microporous film having both shutdown characteristics and melting characteristics can be provided by laminating a polypropylene-containing layer.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2004-196871
Patent document 2: japanese patent laid-open No. 2015-208894
Disclosure of Invention
Problems to be solved by the invention
As described in the above document, conventionally, a resin having high heat resistance such as polypropylene is combined with polyethylene, thereby achieving both of the shutdown property and the melting property. However, in such a method, there is a problem that film forming properties such as uneven appearance occur when forming a microporous film due to differences in melting points and crystallization rates of polypropylene and polyethylene. Further, as the capacity and output of the battery are increased, the necessity of increasing the thickness (for example, the thickness of 10 μm or less), the mechanical strength, the permeability, and the like of the battery separator is considered, and thus, the microporous membrane described in the above patent document needs to be further improved in terms of various physical properties such as thickness and mechanical strength.
In view of the above, the present invention has an object to provide a polyolefin microporous membrane having excellent safety and output characteristics when used as a separator for a battery, which has high levels of both puncture strength and permeability in addition to shutdown characteristics and meltdown characteristics without impairing the film forming properties.
Means for solving the problems
The present inventors have conducted intensive studies and as a result, have found that a polyolefin microporous membrane satisfying predetermined requirements according to Δtm and Δs described below can achieve both melting characteristics and other characteristics without impairing the film forming properties of the microporous membrane even if a heat-resistant raw material such as polypropylene is not contained in a large amount, and have completed the present invention.
In order to solve the above problems, the present invention includes the following configurations 1 to 9.
1. A polyolefin microporous membrane, wherein, in a melting endothermic curve obtained by measurement with a differential scanning calorimeter at a temperature rising rate of 10 ℃/min, the temperature at the point of highest intensity at less than 145 ℃ is set as Tm B, and, in a differential melting endothermic curve calculated from the melting endothermic curve, when the temperature showing the minimum value in the range of 145 ℃ or more and less than 155 ℃ is set as Tm A, ΔTm (ΔTm=Tm A-TmB) is 8.0 ℃ or more and 12.0 ℃ or less, and the ratio (ΔS=S A/SB) of the intensity at Tm A (S A) to the intensity at Tm B (S B) in the melting endothermic curve is more than 0.1 and less than 0.5.
2. The polyolefin microporous membrane according to the above 1, wherein tan delta at 130℃obtained by dynamic viscoelasticity measurement is 0.35 or more.
3. The polyolefin microporous membrane according to the above 1 or 2, which has a puncture strength of 400 mN/(g/m 2) or more in terms of weight per unit area.
4. The polyolefin microporous membrane according to any one of the above 1 to 3, which has a permeability of 50 seconds/100 cm 3/(g/m2 or less in terms of weight per unit area.
5. The microporous polyolefin membrane according to any one of 1 to 4, which comprises polyethylene as a main component.
6. The microporous polyolefin membrane according to any one of the above 1 to 5, which has no peak at 155℃or higher in the melting endothermic curve.
7. The polyolefin microporous membrane according to any of the above 1 to 6, wherein the molecular weight distribution of the polyethylene measured by GPC method comprises 10 mass% or more of a polyethylene component having a molecular weight of 5 ten thousand or less and 15 mass% or more of a polyethylene component having a molecular weight of 100 ten thousand or more.
8. A separator for a battery, which uses the polyolefin microporous membrane according to any one of the above 1 to 7.
9. A secondary battery using the battery separator according to 8.
ADVANTAGEOUS EFFECTS OF INVENTION
The polyolefin microporous membrane according to the present invention can have both puncture strength and permeability at a high level in addition to shutdown characteristics and meltdown characteristics without impairing the film forming properties. When used as a separator for a battery, the polyolefin microporous membrane can be suitably used while maintaining safety and output characteristics.
Detailed Description
Hereinafter, embodiments of the present invention will be described.
In the polyolefin microporous membrane according to the embodiment of the present invention, tm (Δtm=tm A-TmB) is 8.0 ℃ to 12.0 ℃ in the case where Tm B is the temperature at the highest point of the melting endothermic curve obtained by measurement with a differential scanning calorimeter at a temperature rise rate of 10 ℃/min and Tm A is the temperature at which the minimum value is displayed in the range of 145 ℃ to 155 ℃ in the differential melting endothermic curve calculated from the melting endothermic curve, and the ratio (Δs=s A/SB) of the intensity at Tm A (S A) to the intensity at Tm B (S B) in the melting endothermic curve is more than 0.1 and less than 0.5.
Δtm refers to the difference between Tm A and Tm B, and specifically is represented by Δtm=tm A-TmB. In the polyolefin microporous membrane according to the embodiment of the present invention, Δtm is 8.0 or more and 12.0 or less. The Δtm is 8.0 or more, preferably 8.5 or more, and more preferably 9.0 or more. Further, Δtm is 12.0 or less, preferably 11.5 or less, and more preferably 11.0 or less. The Δtm is within the above range, and means that a crystal structure having different characteristics with respect to thermal stability is formed in the polyolefin microporous membrane. That is, when Δtm is within the above range, it is preferable that both the shutdown property and the melting property are easily achieved within a range where the mechanical strength and the permeability are not deteriorated.
Δs is a ratio of the intensity at Tm A (S A) to the intensity at Tm B (S B) in the melting endothermic curve, and specifically, Δs=s A/SB. In the polyolefin microporous membrane, Δs exceeds 0.1 and is less than 0.5.Δs exceeds 0.1, preferably exceeds 0.15, more preferably exceeds 0.2.Δs is less than 0.5, preferably less than 0.4, more preferably less than 0.35, and even more preferably less than 0.3. If the Δs is within the above range, the ratio of the structure having the property of melting at a relatively low temperature, which contributes to the shutdown property, to the structure having the property of maintaining the structure up to a relatively high temperature, which contributes to the melting property, tends to be appropriate, and the shutdown property and the melting property tend to be combined. In order to set the Δtm and Δs to the above ranges, it is preferable to set the raw material composition of the polyolefin microporous membrane to the below-described range, and to set the stretching conditions and heat setting conditions in the production of the polyolefin microporous membrane to the below-described range.
It is suggested that the polyolefin microporous membrane according to the embodiment of the present invention has a structure contributing to the shutdown property and the melting property in a balanced manner by the above Δtm and Δs falling within the above ranges. When the polyolefin microporous membrane of the present invention is used as a separator for a battery, it has high safety, and therefore, it can be suitably used as a separator for a battery for a secondary battery.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has a tan δ of 0.35 or more at 130 ℃. In the present specification, tan δ at 130 ℃ means a value obtained by dynamic viscoelasticity measurement at a temperature rising rate of 10 ℃/min and a frequency of 10 Hz. The tan δ at 130 ℃ is more preferably 0.37 or more, and still more preferably 0.40 or more. The upper limit of tan δ at 130 ℃ is not particularly limited, but is preferably 1.0 or less if polyolefin is considered as the main component. When tan δ at 130 ℃ is within the above range, structural changes such as film breakage in a high temperature region are small, and melting characteristics are easily exhibited. In order to set the tan δ at 130 ℃ within the above range, it is preferable to set the raw material composition of the polyolefin microporous membrane to the below-described range, as well as the stretching conditions and heat setting conditions when the polyolefin microporous membrane is formed as described below.
The puncture strength of the polyolefin microporous membrane according to the embodiment of the present invention in terms of weight per unit area is preferably 400 mN/(g/m 2) or more. The lower limit of the puncture strength in terms of weight per unit area is more preferably 450 mN/(g/m 2) or more, still more preferably 500 mN/(g/m 2) or more, still more preferably 600 mN/(g/m 2) or more, particularly preferably 650 mN/(g/m 2) or more, and still more preferably 700 mN/(g/m 2) or more. The upper limit of the puncture strength in terms of weight per unit area is not particularly limited, but is preferably 1800 mN/(g/m 2) or less if the balance of various physical properties such as heat shrinkage with the polyolefin microporous membrane is considered. If the puncture strength in terms of weight per unit area falls within the above range, the battery separator has high resistance to film breakage by foreign matter when used as a battery separator, and the short-circuit resistance is easily improved. Thus, a battery with higher safety can be provided. In order to set the puncture strength of the polyolefin microporous membrane in terms of weight per unit area within the above-mentioned range, it is preferable that the raw material composition of the polyolefin microporous membrane be within the below-mentioned range as well as the stretching conditions and heat setting conditions at the time of forming the polyolefin microporous membrane as described later.
The polyolefin microporous membrane according to the embodiment of the present invention preferably contains polyethylene as a main component. Specifically, the polyolefin microporous membrane preferably has a polyethylene content of 93 mass% or more in polyolefin. The polyethylene content in the polyolefin microporous membrane is more preferably 96 mass% or more, still more preferably 99 mass% or more, and particularly preferably 100 mass%. When the polyethylene ratio in the polyolefin is within the above range, the film forming property can be easily improved, and a polyolefin microporous film excellent in puncture strength and shutdown characteristics can be easily obtained.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has no peak at 155 ℃ or higher in a melting endothermic curve obtained by measurement with a differential scanning calorimeter at a temperature rising rate of 10 ℃/min. The polyolefin microporous membrane having no peak at 155℃or higher, which facilitates improvement of the film forming property, and is excellent in puncture strength and shutdown characteristics. In order to prevent the polyolefin microporous membrane from having a peak at 155℃or higher, the raw material composition of the polyolefin microporous membrane is preferably as described below.
The polyolefin microporous membrane according to the embodiment of the present invention preferably contains 10 mass% or more of a polyethylene component having a molecular weight of 5 ten thousand or less and 15 mass% or more of a polyethylene component having a molecular weight of 100 ten thousand or more in the molecular weight distribution of the polyethylene measured by GPC. The polyethylene component having a molecular weight of 5 ten thousand or less is preferably 10 mass% or more, more preferably 13 mass% or more, and still more preferably 15 mass% or more. The polyethylene component having a molecular weight of 5 ten thousand or less is preferably 30 mass% or less, more preferably 25 mass% or less, and still more preferably 20 mass% or less. The polyethylene component having a molecular weight of 100 ten thousand or more is preferably 15 mass% or more, more preferably 20 mass% or more, and still more preferably 23 mass% or more. The polyethylene component having a molecular weight of 100 ten thousand or more is preferably 35 mass% or less, more preferably 30 mass% or less, and still more preferably 25 mass% or less.
Further, in the polyolefin microporous membrane according to the embodiment of the present invention, in the molecular weight distribution of polyethylene measured by GPC method, the polyethylene component having a molecular weight of 200 ten thousand or more is preferably 5 mass% or more and 20 mass% or less. The polyethylene component having a molecular weight of 200 ten thousand or more is preferably 5 mass% or more, more preferably 7 mass% or more, and still more preferably 9 mass% or more. The polyethylene component having a molecular weight of 200 ten thousand or more is preferably 20 mass% or less, more preferably 15 mass% or less, and still more preferably 10 mass% or less.
By setting the molecular weight distribution of the polyethylene to the above range, the relaxation behavior at high temperature can be easily controlled appropriately while maintaining the puncture strength and the shutdown characteristics of the polyolefin microporous membrane. This can improve the melting characteristics. In order to set the molecular weight distribution of the polyethylene of the polyolefin microporous membrane as measured by GPC method to the above range, it is preferable to set the raw material composition of the polyolefin microporous membrane to the below range and set the membrane-forming condition of the polyolefin microporous membrane to the below range.
The polyolefin microporous membrane according to the embodiment of the present invention has an air permeability of preferably 50 seconds/100 cm 3/(g/m2) or less, more preferably 40 seconds/100 cm 3/(g/m2) or less, still more preferably 30 seconds/100 cm 3/(g/m2) or less, particularly preferably 25 seconds/100 cm 3/(g/m2) or less in terms of weight per unit area. If the air permeability in terms of weight per unit area is 50 seconds/100 cm 3/(g/m2) or less, the ion permeability is easily maintained, and deterioration of output characteristics when used as a battery separator can be suppressed. The lower the air permeability in terms of weight per unit area, the more preferable from the viewpoint of output characteristics, but about 10 seconds/100 cm 3/(g/m2) is the lower limit from the viewpoint of balance with strength and heat resistance. In order to set the air permeability in terms of weight per unit area to the above range, it is preferable to set the raw material composition and the laminate composition of the microporous membrane to the below range, and the stretching conditions and the heat setting conditions in the case of forming the polyolefin microporous membrane to the below range.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has a porosity of 25% or more. The porosity is more preferably 30% or more, still more preferably 35% or more, and particularly preferably 37% or more. The upper limit of the porosity is not particularly limited, but if the mechanical strength of the microporous membrane is considered, 60% or less is substantially the upper limit. If the porosity is within the above range, mechanical strength and ion permeability are easily maintained when used as a separator for a battery. Thus, when used in a battery, the output characteristics and safety can be maintained. In order to set the porosity to the above range, it is preferable that the raw material composition of the polyolefin microporous membrane be within the range described below, and the stretching conditions and heat setting conditions when the polyolefin microporous membrane is formed are within the range described below.
The thickness of the polyolefin microporous membrane according to the embodiment of the present invention is appropriately adjusted according to the application, and is not particularly limited. For example, the film thickness is preferably 1 μm or more and 25 μm or less. When the film thickness is within the above range, the operability and productivity are good, and deterioration of safety and output characteristics in the production of a battery can be suppressed. The film thickness is more preferably 2 μm to 15 μm, still more preferably 2 μm to 12 μm, particularly preferably 2 μm to 10 μm, and most preferably 2 μm to 9 μm. The film thickness can be adjusted by the screw speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretching ratio, and the like within a range that does not deteriorate other physical properties.
The weight per unit area of the polyolefin microporous membrane according to the embodiment of the present invention is appropriately adjusted according to the application, and is not particularly limited. For example, the weight per unit area is preferably 1.0g/m 2 or more and 10.0g/m 2 or less. When the weight per unit area is within the above range, the operability and productivity are good, and deterioration of safety and output characteristics in the production of a battery can be suppressed. The weight per unit area is more preferably 1.5g/m 2 to 7.0g/m 2, still more preferably 2.0g/m 2 to 6.5g/m 2. The weight per unit area can be adjusted by the screw speed, the draw ratio, and the like of the extruder within a range that does not deteriorate other physical properties.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has a shutdown temperature of 140 ℃ or lower, which is obtained by a temperature-rising resistance method. The shutdown temperature is more preferably 139℃or lower, still more preferably 137℃or lower, and particularly preferably 135℃or lower. When the shutdown temperature is 140 ℃ or lower, a battery with high safety can be provided when the battery separator is used as a battery separator for a secondary battery requiring high energy density, high capacity and high output, such as an electric vehicle. If the shutdown temperature is 100 ℃ or less, the pores may be closed even in a normal use environment in a battery manufacturing process, and the output characteristics may be deteriorated, so that the shutdown temperature is a lower limit of about 100 ℃. In order to set the shutdown temperature to the above range, it is preferable to set the raw material composition constituting the polyolefin microporous membrane to the below range, and to set the stretching conditions and heat setting conditions in the production of the polyolefin microporous membrane to the below range.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has a resistance value at 160 ℃ of 1.0x10 3Ω·cm2 or more, more preferably 1.2x10 3Ω·cm2 or more, and still more preferably 1.5x10 3Ω·cm2 or more, which is obtained by a temperature-rising resistance method. When the resistance value at 160℃obtained by the temperature-increasing impedance method is 1.0X10 3Ω·cm2 or more, a battery with high safety can be provided when the battery separator is used as a battery separator for a secondary battery requiring high energy density, high capacity and high output, such as an electric automobile. The higher the resistance value at 160℃obtained by the temperature-rising resistance method, the higher the upper limit of the resistance value is, however, about 1.0X10 6Ω·cm2 when the weight per unit area of the polyolefin microporous membrane is taken into consideration. In order to set the resistance value at 160℃obtained by the temperature-rising resistance method to the above range, it is preferable that the raw material composition constituting the polyolefin microporous membrane be within the range described below, and that the stretching conditions and heat-setting conditions at the time of forming the polyolefin microporous membrane be within the range described below.
The polyolefin microporous membrane according to the embodiment of the present invention preferably has a resistance value at 180 ℃ of 1.0x10 2Ω·cm2 or more, more preferably 2.0x10 2Ω·cm2 or more, still more preferably 4.0x10 2Ω·cm2 or more, and particularly preferably 6.0x10 2Ω·cm2 or more, which is obtained by a temperature-rising resistance method. When the resistance value at 180℃obtained by the temperature-rising impedance method is 1.0X10 2Ω·cm2 or more, a battery with high safety can be provided when the battery separator is used as a battery separator for a secondary battery requiring high energy density, high capacity and high output, such as an electric automobile. The resistance value at 180℃obtained by the temperature-rising resistance method is considered to be as high as possible, but the upper limit thereof is about 1.0X10 5Ω·cm2 when considering the weight per unit area of the polyolefin microporous membrane. In order to set the resistance value at 180℃obtained by the temperature-rising resistance method to the above range, it is preferable that the raw material composition constituting the polyolefin microporous membrane be within the range described below, and that the stretching conditions and heat-setting conditions at the time of forming the polyolefin microporous membrane be within the range described below.
Next, specific configurations of the polyolefin microporous membrane according to the embodiment of the present invention will be described, but the present invention is not necessarily limited thereto.
The polyolefin microporous membrane according to the embodiment of the present invention preferably contains a high molecular weight polyethylene and a low molecular weight polyethylene as described below. The high molecular weight polyethylene and the low molecular weight polyethylene may be a mixture of 2 or more kinds, respectively, and are more preferably composed of 1 kind of polyethylene raw material, respectively, from the viewpoints of structural uniformity and physical properties of the polyolefin microporous membrane.
The proportion of the high molecular weight polyethylene in the polyolefin microporous membrane according to the embodiment of the present invention is preferably 60 mass% or more, more preferably 70 mass% or more, and still more preferably 75 mass% or more.
The high molecular weight polyethylene used in the embodiment of the present invention is preferably a homopolymer of ethylene, but may be a copolymer containing other α -olefin as long as the melting point of the raw material is not excessively lowered as described later. Examples of the other α -olefin include propylene, butene-1, hexene-1, pentene-1, 4-methylpentene-1, octene, vinyl acetate, methyl methacrylate, and styrene. In addition, alpha-olefins can be confirmed by C 13 -NMR measurements.
The high molecular weight polyethylene used in the embodiment of the present invention preferably has a weight average molecular weight (hereinafter referred to as Mw) of 8.0×10 5 or more, more preferably 9.0×10 5 or more, and still more preferably 1.0×10 6 or more, as measured by high temperature GPC or the like. The Mw of the high molecular weight polyethylene is preferably 2.0×10 6 or less, more preferably 1.5×10 6 or less, and even more preferably 1.2×10 6 or less. If Mw is within the above range, the tensile stress tends to propagate efficiently. This can improve mechanical strength while suppressing an increase in the shrinkage force of the polyolefin microporous membrane.
The melting point of the high molecular weight polyethylene used in the embodiment of the present invention obtained by a Differential Scanning Calorimeter (DSC) is preferably 135 ℃ or higher, more preferably 135.5 ℃ or higher. The melting point is preferably 138℃or lower. When the melting point is within the above range, the polyolefin microporous membrane tends to have high thermal stability when produced, and the melting characteristics can be improved.
The heat of fusion ΔH (J/g) obtained by a Differential Scanning Calorimeter (DSC) of the high molecular weight polyethylene used in the embodiment of the present invention is preferably 160J/g or more, more preferably 170J/g or more, and still more preferably 180J/g or more. The upper limit of ΔH is not particularly limited, but is typically 250J/g or less in terms of the characteristics of the high molecular weight polyethylene. If Δh is within the above range, the structure is easily stabilized and deterioration of the permeability can be suppressed when used in a polyolefin microporous membrane, which is preferable.
In addition to the above melting point range, the high molecular weight polyethylene used in the embodiment of the present invention is preferably high in recrystallization ability in order to improve the melting characteristics. This recrystallization ability can be observed by a Differential Scanning Calorimeter (DSC) under high-speed cooling conditions described later. Specifically, a polyethylene having a high recrystallization ability may observe a peak or shoulder considered to originate from recrystallization at a temperature higher than the peak top temperature. Regarding the recrystallization ability of the polyethylene resin, the crystal melting ratio (hereinafter also referred to as high-temperature crystal melting ratio: H.) of 135 ℃ or higher as measured by a Differential Scanning Calorimeter (DSC) under the above-mentioned high-speed cooling condition can be effectively used as a simple index. The high-temperature crystalline melting ratio (H) of the high-molecular-weight polyethylene used in the embodiment of the present invention is preferably 5.0% or more, more preferably 10.0% or more, and even more preferably 13.0% or more. The upper limit is not particularly limited, but is typically 30% or less in terms of the characteristics of polyethylene. If the high-temperature crystal melting ratio (H) is within the above range, crystals having a higher melting point than the melting point of the raw material tend to be formed when the crystals are stabilized during or after stretching. Thus, the structure contributing to the melting characteristics of the polyolefin microporous membrane can be controlled to an appropriate range. Examples of specific conditions are described in detail in the examples as high-speed cooling conditions.
The proportion of the low-molecular-weight polyethylene in the polyolefin microporous membrane according to the embodiment of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 30% by mass or more.
The low molecular weight polyethylene used in the embodiment of the present invention may be a homopolymer of ethylene, and may be a copolymer containing other α -olefin in order to lower the melting point of the raw material as described later. Examples of the other α -olefin include propylene, butene-1, hexene-1, pentene-1, 4-methylpentene-1, octene, vinyl acetate, methyl methacrylate, and styrene. Further, the alpha-olefin can be confirmed by measurement by C 13 -NMR.
The weight average molecular weight (hereinafter referred to as Mw) of the low molecular weight polyethylene used in the embodiment of the present invention, which is obtained by high temperature GPC measurement or the like, is preferably 12×10 4 or less, more preferably 9.0×10 4 or less, and further preferably 7.0×10 4 or less. The Mw of the low molecular weight polyethylene is preferably 1.0×10 4 or more, more preferably 3.0×10 4 or more, and even more preferably 5.0×10 4 or more. If Mw falls within the above range, the structure of the high molecular weight polyethylene is not easily damaged, and the formation of crystals with a low melting point and the reduction of shrinkage force upon melting can be easily performed. This can combine mechanical strength, closing properties, and melting properties.
The low molecular weight polyethylene used in the embodiment of the present invention preferably has a melting point (. Degree.C.) obtained by a Differential Scanning Calorimeter (DSC) of 134℃or lower, more preferably 133℃or lower, and still more preferably 132℃or lower. The melting point of the low-molecular-weight polyethylene is preferably 125℃or higher, more preferably 127℃or higher, still more preferably 130℃or higher, and particularly preferably 131℃or higher. If the melting point of the low molecular weight polyethylene is within the above range, the melting point of the structure before stretching can be reduced within an appropriate range, and the structure of the high molecular weight polyethylene is not easily damaged when the polyolefin microporous membrane is produced, and crystallization with a low melting point can be easily performed. This can improve the shutdown characteristics of the polyolefin microporous membrane.
The low molecular weight polyethylene used in the embodiment of the present invention preferably has a heat of fusion Δh (J/g) of 200J/g or more, more preferably 210J/g or more, still more preferably 220J/g or more, obtained by a Differential Scanning Calorimeter (DSC). The upper limit of ΔH is not particularly limited, but is typically 260J/g or less in terms of the characteristics of polyethylene. If Δh is within the above range, the formation of crystals with a low melting point can be easily performed without excessively decreasing the amount of crystals in the polyolefin microporous membrane. This allows both the closing property and the permeability to be achieved.
The half width of the maximum peak on the melting endothermic curve obtained by a Differential Scanning Calorimeter (DSC) of the low molecular weight polyethylene used in the embodiment of the present invention is preferably 6.0℃or less, more preferably 5.5℃or less, further preferably 5.0℃or less, further preferably 4.5℃or less. The lower limit of the half width is preferably 1.0℃or higher, more preferably 3.0℃or higher. If the half width is within the above range, excessive lowmelting point of the polyolefin microporous membrane can be easily suppressed. This allows both the closing property and the permeability to be achieved.
In addition to the above melting point range, the low molecular weight polyethylene used in the embodiment of the present invention is preferably low in recrystallization ability in order to improve shutdown characteristics. Regarding the recrystallization ability of polyethylene, the crystal melting ratio (hereinafter also referred to as high-temperature crystal melting ratio: H.) of 135℃or higher as measured by a Differential Scanning Calorimeter (DSC) under the above-mentioned high-speed cooling condition can be effectively used as a simple index. The high-temperature crystalline melting ratio (H) of the low-molecular-weight polyethylene used in the embodiment of the present invention is preferably 3.0% or less, more preferably 1.0% or less, and still more preferably 0.5% or less. The lower limit of the high-temperature crystallization melting ratio (H) is 0% or more. If the high-temperature crystal melting ratio (H) of the low-molecular weight polyethylene is within the above range, excessive increase in melting point of the crystals contributing to shutdown properties as shown by the peak B can be suppressed mainly at the time of stretching or at the time of stabilizing the crystals after stretching, and shutdown properties of the polyolefin microporous membrane can be improved.
The polyolefin microporous membrane according to the embodiment of the present invention may further contain other polyolefin resin raw materials such as polypropylene for the purpose of improving the melting characteristics and the like, as long as it contains the high molecular weight polyethylene and the low molecular weight polyethylene. However, from the viewpoint of making the film-forming property and the physical properties of the polyolefin microporous film in the proper ranges, the ratio of the polyolefin resin raw material other than the high molecular weight polyethylene and the low molecular weight polyethylene is preferably less than 7.5 mass%, more preferably less than 5 mass%, still more preferably less than 1 mass%, particularly preferably 0 mass% in the polyolefin microporous film. From the same viewpoint, the proportion of polypropylene is preferably less than 7.5 mass%, more preferably less than 5 mass%, even more preferably less than 1 mass%, and particularly preferably 0 mass% in the polyolefin microporous membrane.
The polyolefin resin used for the polyolefin microporous film according to the embodiment of the present invention may contain various additives such as an antioxidant, a heat stabilizer, an antistatic agent, an ultraviolet absorber, an antiblocking agent, and a filler, within a range that does not impair the effects of the present invention. In particular, for the purpose of suppressing oxidative deterioration due to the thermal history of the polyethylene resin, it is preferable to add an antioxidant. As the antioxidant, for example, 1 or more selected from 2, 6-di-t-butyl-p-cresol (BHT: molecular weight 220.4), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene (for example, "Irganox" (registered trademark) 1330 by BASF Co., ltd., "molecular weight 775.2), tetrakis [ methylene-3 (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] methane (for example," Irganox "(registered trademark) 1010 by BASF Co., ltd.," molecular weight 1177.7 ") and the like are preferably used. The proper selection of the kind and addition amount of the antioxidant and the heat stabilizer is important as the adjustment or enhancement of the properties of the polyolefin microporous membrane.
The polyolefin microporous membrane according to the embodiment of the present invention is obtained, for example, by biaxially stretching using the above raw materials. The biaxial stretching method may be any of inflation method, simultaneous biaxial stretching method and sequential biaxial stretching method, but among them, simultaneous biaxial stretching method or sequential biaxial stretching method is preferably used in terms of controlling film-forming stability, thickness uniformity, high rigidity of the film and dimensional stability. Specifically, for example, the polyolefin microporous membrane is preferably produced by a method comprising the following steps (a) to (e). Hereinafter, examples of a method for producing a polyolefin microporous membrane using the above raw materials will be described, but the method is not necessarily limited thereto. In the following description, the film forming direction is referred to as MD direction, and the film width direction perpendicular to the MD direction is referred to as TD direction.
(A) And a step of preparing a polyolefin resin solution by melt-kneading a material containing a polyolefin resin and a plasticizer (solvent).
(B) And a step of forming the polyolefin resin solution, cooling and solidifying the solution to form a gel sheet.
(C) And stretching the gel sheet.
(D) And a step of extracting (washing) the plasticizer from the stretched gel sheet and drying the same.
(E) And optionally, performing at least one of heat treatment and re-stretching.
Hereinafter, each step will be described.
(A) Preparing a polyolefin resin solution
In the step (a), a material containing a polyolefin resin and a plasticizer (solvent) is melt kneaded to prepare a polyolefin resin solution in which the polyolefin resin is dissolved in the plasticizer by heating. The plasticizer is not particularly limited as long as it is a solvent capable of sufficiently dissolving the polyolefin resin, but the solvent is preferably a liquid at room temperature in order to enable stretching at a high magnification. Examples of the solvent include aliphatic, cyclic aliphatic or aromatic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, and liquid paraffin, mineral oil fractions having boiling points corresponding to these hydrocarbons, and phthalates such as dibutyl phthalate and dioctyl phthalate which are liquid at room temperature. In order to obtain a gel-like sheet having a stable content of the liquid solvent, a nonvolatile liquid solvent such as liquid paraffin is preferably used. Although the resin is mixed with the polyolefin resin in a melt-kneaded state, a solvent that is solid at room temperature may be mixed with a liquid solvent. Examples of such solid solvents include stearyl alcohol, ceryl alcohol, and paraffin wax. However, if only a solid solvent is used, stretching unevenness may occur.
The viscosity of the liquid solvent is preferably 20 to 200cSt at 40 ℃. When the viscosity at 40℃is 20cSt or more, the sheet obtained by extruding the polyolefin resin solution from the die is less likely to become uneven. On the other hand, if 200cSt or less, the liquid solvent is easily removed. The viscosity of the liquid solvent was measured at 40℃using an Ubbelohde viscometer.
The blending ratio of the polyolefin resin and the plasticizer is preferably in the following range, with the total of the polyolefin resin and the plasticizer being 100 mass%. The content of the polyolefin resin may be appropriately selected within a range not impairing the molding processability, but is preferably 10 to 50% by mass, more preferably 15 to 30% by mass. When the polyolefin resin is less than 10 mass%, or when the plasticizer is 90 mass% or more, the expansion and the shrinkage tend to be large at the outlet of the die when the sheet is formed, and the moldability of the sheet tends to be deteriorated to lower the film formability. On the other hand, when the polyolefin resin exceeds 50 mass%, or when the plasticizer is 50 mass% or less, shrinkage in the thickness direction tends to be large, and molding processability tends to be low.
The specific method for uniformly melt-kneading the polyolefin resin solution is not particularly limited, but in the case where a high-concentration polyolefin resin solution is to be prepared, it is preferable to carry out the melt-kneading in a twin-screw extruder. If necessary, various additives such as an antioxidant may be added to the polyolefin resin solution within a range that does not impair the effects of the present invention. In particular, in order to prevent oxidation of the polyolefin-based resin, an antioxidant is preferably added.
In particular, when materials having greatly different viscosities at the time of melting are melt-kneaded, such as high molecular weight polyethylene, low molecular weight polyethylene, and liquid solvent, for example, used in the embodiments of the present invention, it is preferable to set the screw diameter and the shape and number of screw members in the twin-screw extruder as in the following (1) to (3). By setting the content within the following range, the amount of unmelted material in the polyolefin resin solution after melting can be reduced, the outflow from the vent hole can be easily suppressed, and the quality such as the discharge accuracy can be improved. In addition, the polyolefin microporous membrane can be made with less unevenness of various physical properties such as film thickness and weight per unit area, and can be improved in quality and physical properties.
(1) When the outermost diameter of the screw is D, the distance between the tip of the screw and the vent hole is 1.0D to 15.0D.
(2) At least 1 screw member having a length in the raw material conveying direction of 0.2D to 0.9D is used between the tip of the screw and the distance between the vent hole.
(3) No screw members having a length of 1.5D or more in the direction of feed of 2 or more materials are used.
The polyolefin resin solution is uniformly mixed in an extruder at a temperature at which the polyolefin resin is completely melted. The melt kneading temperature varies depending on the polyolefin resin used, but is preferably from (the melting point of the polyolefin resin +10℃) to (the melting point of the polyolefin resin +120℃). The melt kneading temperature is more preferably from (melting point of polyolefin resin +20℃) to (melting point of polyolefin resin +100℃). The melting point herein refers to a value measured by DSC (hereinafter, the same applies) based on JIS K7121 (1987). For example, when the polyolefin resin is a polyethylene resin, the melt kneading temperature is preferably in the range of 140 to 250 ℃. In this case, the melt kneading temperature is more preferably 160 to 230℃and most preferably 170 to 200 ℃. Specifically, since the polyethylene composition has a melting point of about 130 to 140 ℃, the melt kneading temperature is preferably 140 to 250 ℃, and more preferably 150 to 210 ℃.
From the viewpoint of suppressing deterioration of the resin, the melt kneading temperature is preferably low, but if the temperature is lower than the above temperature, unmelted matter may be generated in the extrudate extruded from the die, and this may cause film breakage or the like in the subsequent stretching step. If the melt kneading temperature is higher than the above temperature, thermal decomposition of polyolefin may be severe, and physical properties of the obtained microporous membrane such as strength and porosity may be poor. Further, the decomposed product may be deposited on a cooling roll, a roll in a stretching process, or the like, and adhere to the sheet, thereby deteriorating the appearance. Therefore, the melt kneading temperature is preferably within the above range. Further, it is preferable to remove foreign matters and modified polymers by a filter.
(B) Step of Forming gel sheet
Next, in the step (b), the polyolefin resin solution is molded and cooled to solidify, thereby forming a gel-like sheet. Typically, the gel-like sheet is obtained by extruding a polyolefin resin solution to form an extrudate, and cooling the extrudate. By cooling, the microphase of the polyethylene resin separated by the solvent can be immobilized. Preferably, the cooling step is performed to a temperature of 10 to 50 ℃. This is because the final cooling temperature is preferably equal to or lower than the crystallization completion temperature. That is, by making the higher-order structure thin, uniform stretching is easy to perform in the subsequent stretching. From this viewpoint, the cooling is preferably performed at a rate of 30 ℃/min or more to at least the gelation temperature or less. If the cooling rate is less than 30℃per minute, the crystallinity tends to increase, and the gel-like sheet is not easily stretched. Generally, if the cooling rate is low, a relatively large crystal is formed, and therefore, the higher-order structure of the gel-like sheet becomes thicker, and the gel structure thereof becomes larger. On the other hand, if the cooling rate is high, relatively small crystals are formed, and therefore the higher-order structure of the gel-like sheet becomes dense, and the strength and elongation of the film are improved in addition to uniform stretching. The melting point of the gel-like sheet as observed by a Differential Scanning Calorimeter (DSC) is preferably 128℃or lower, more preferably 127℃or lower. The lower limit of the melting point is preferably 115℃or higher, if the influence on heat setting after stretching is considered. If the melting point of the gel-like sheet is within the above range, the shutdown temperature can be easily controlled in the direction of lowering the temperature. The melting point of the gel-like sheet can be adjusted by the melting point of the polyolefin resin, the proportion of the plasticizer, the cooling conditions, and the like.
As the cooling method, there are a method of directly contacting with cold air, cooling water, other cooling medium, a method of contacting with a roll cooled with a cooling medium, a method of using a casting drum, and the like.
(C) Stretching the gel sheet
In the step (c), the gel-like sheet obtained in the step (b) is stretched. Examples of the stretching method used include MD uniaxial stretching using a roll stretcher, TD uniaxial stretching using a tenter, sequential biaxial stretching using a combination of a roll stretcher and a tenter, or a tenter and a tenter, simultaneous biaxial stretching using a simultaneous biaxial tenter, and the like. The stretching ratio varies depending on the thickness of the gel sheet, but is preferably 5 times or more in any direction from the viewpoint of uniformity of the film thickness. The area magnification is preferably 25 times or more, more preferably 49 times or more, and even more preferably 64 times or more. The draw ratio is 25 times or more, and thus the stretching tends to be sufficient. Thus, uniformity of the film is easily improved, and unstretched portions are less likely to remain. Therefore, from the viewpoint of strength and electrical resistance, an excellent microporous membrane is also easily obtained. The area magnification is preferably 150 times or less. By having an area ratio of 150 times or less, cracking in the production of the microporous membrane can be easily suppressed, and productivity can be improved. Further, by setting the area ratio to 150 times or less, it is possible to suppress an excessive progress of orientation and an increase in the melting point of the microporous membrane and an increase in the shutdown temperature.
The stretching temperature is preferably not higher than +10℃ for the gel-like sheet, and more preferably in the range of (crystalline dispersion temperature Tcd of the polyolefin-based resin) to (melting point +5℃ for the gel-like sheet). Specifically, in the case of the polyethylene composition, since the polyethylene composition has a crystal dispersion temperature of about 90 to 100 ℃, the stretching temperature is preferably 90 to 125 ℃, more preferably 90 to 120 ℃. The crystal dispersion temperature Tcd is obtained from the dynamic viscoelasticity temperature characteristics measured in accordance with ASTM D4065. Or the crystal dispersion temperature Tcd may be obtained by NMR. The stretching temperature is 90 ℃ or higher, whereby the opening is liable to become sufficient. Thus, uniformity of film thickness can be easily obtained, and the porosity can be appropriately increased. By the stretching temperature being 125 ℃ or lower, melting of the sheet is less likely to occur, and blocking of the pores can be suppressed.
When the tensile stress is excessively high, residual strain tends to remain, and the shrinkage force at the time of melting in the production of the microporous film is high, so that the melting property is not easily exerted. Therefore, in order to suppress residual strain and promote structural change due to stretching, it is particularly preferable that the tensile stress increase rate of the region 1 to 5 times in each direction exceeds 0.05 MPa/time and is less than 0.1 MPa/time. The tensile stress increase rate is a value obtained by using an initial cross-sectional area to determine tensile stress (MPa) with respect to a load at each magnification in each direction, which is detected by a load detector or the like at the time of stretching, and by the following equation.
(Tensile stress increase rate) = (tensile stress at 5 times)/(tensile stress at 1 time)
According to the stretching described above, the higher structure formed in the gel-like sheet breaks, and the crystal phase becomes finer, thereby forming a plurality of fibrils. The fibrils form a three-dimensionally irregularly connected network. Such stretching increases the mechanical strength and enlarges the pores, so that the separator is suitable for a battery. Further, since the polyolefin resin is sufficiently plasticized and softened by stretching before removing the plasticizer, the higher-order structure is broken smoothly, and the crystal phase can be uniformly miniaturized. Further, since the fracture is easy, strain at the time of stretching is less likely to remain, and the heat shrinkage rate can be made lower than in the case of stretching after removing the plasticizer.
(D) A step of extracting (washing) and drying the plasticizer
Next, in step (d), the plasticizer is extracted (washed) from the stretched gel-like sheet stretched in step (c), and dried. First, the plasticizer (solvent) remaining in the gel-like sheet is removed using a washing solvent. Since the polyolefin-based resin phase is separated from the solvent phase, a microporous membrane is obtained by removal of the solvent. Examples of the washing solvent include saturated hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, diethyl ether and diethyl etherEthers such as alkanes, ketones such as methyl ethyl ketone, and chain fluorocarbons such as trifluoroethane. These washing solvents have a comparatively low surface tension (for example, 24mN/m or less at 25 ℃). By using a relatively low surface tension washing solvent, shrinkage of the network structure forming micropores by the surface tension of the gas-liquid interface is suppressed at the time of drying after washing, and a microporous membrane having suitable porosity and permeability can be obtained. These washing solvents may be appropriately selected depending on the plasticizer, and used alone or in combination.
Examples of the washing method include a method of immersing the gel-like sheet in a washing solvent and extracting the same, a method of spraying the washing solvent onto the gel-like sheet, and a method using a combination of these. The amount of the washing solvent used varies depending on the washing method, but is generally preferably 300 parts by mass or more based on 100 parts by mass of the gel-like sheet. The washing temperature may be, for example, 15 to 30℃and, if necessary, 80℃or lower. In this case, from the viewpoint of improving the washing effect of the solvent, the viewpoint of preventing the obtained microporous membrane from becoming uneven in physical properties in the TD direction and/or MD direction of the physical properties of the polyolefin microporous membrane, and the viewpoint of improving the mechanical properties and electrical properties of the polyolefin microporous membrane, the longer the time for immersing the gel-like sheet in the washing solvent is, the better. The washing as described above is preferably performed until the residual solvent in the gel-like sheet after washing, i.e., the polyolefin microporous membrane becomes less than 1 mass%.
Then, in the drying step, the solvent in the polyolefin microporous membrane is dried and removed. The drying method is not particularly limited, and a method using a metal heating roller, a method using hot air, or the like may be selected. If the drying is insufficient, the porosity of the polyolefin microporous membrane may be lowered by the subsequent heat treatment, and the permeability may be deteriorated.
(E) A step of performing at least one of heat treatment and redrawing
In the step (e), at least one of heat treatment and re-stretching is performed as needed. For example, the dried polyolefin microporous membrane may be stretched (re-stretched) at least in the uniaxial direction. The re-stretching may be performed by a tenter method or the like in the same manner as the stretching described above while heating the polyolefin microporous film. The re-stretching may be uniaxial stretching or biaxial stretching. In the case of multi-stage stretching, simultaneous biaxial or/and sequential stretching are combined.
The temperature for redrawing is preferably not higher than the melting point of the polyethylene composition, and more preferably within the range of (Tcd-20 ℃) to the melting point. Specifically, the temperature is preferably 70 to 140℃and more preferably 110 to 138 ℃. Most preferably 120 to 135 ℃.
In the case of uniaxial stretching, the ratio of the stretching is preferably 1.01 to 3.0 times, particularly preferably 1.01 to 2.0 times, more preferably 1.2 to 1.8 times, particularly preferably 1.3 to 1.6 times in the TD direction. In the case of biaxial stretching, it is preferably 1.01 to 1.6 times in the MD direction and the TD direction, respectively. In addition, the re-stretching magnification may be different in the MD direction and the TD direction. Stretching in the above range can improve mechanical strength and electrical resistance. On the other hand, if stretching is performed at a magnification of not less than the above range, crystal orientation tends to progress, the melting point of the microporous film increases, and the shutdown temperature increases.
From the viewpoints of heat shrinkage, wrinkles, and relaxation, the relaxation rate from the maximum re-stretching ratio is preferably 0.9 or less, and more preferably 0.85 or less. If the relaxation rate is too low, wrinkles may be generated and permeability may be deteriorated, so that the relaxation rate is preferably 0.7 or more.
In addition, the re-stretched polyolefin microporous membrane may be subjected to a heat treatment (heat setting treatment) in order to adjust the heat shrinkage rate and shrinkage stress. Alternatively, the dried polyolefin microporous membrane may be heat-set without re-stretching. When the heat-setting temperature is a temperature having a polyethylene resin as a main component, it is preferably 125 to 140 ℃. Further, the second heat-setting treatment may be further performed in a direction different from the direction in which the relaxation adjustment was performed in the first heat-setting treatment.
(F) Other procedures
Further, according to other applications, other steps such as a step of subjecting the polyolefin microporous membrane to various treatments may be included. For example, the polyolefin microporous membrane may be hydrophilized according to the application. The hydrophilization treatment may be performed by monomer grafting, surfactant treatment, corona discharge, or the like. The monomer grafting is preferably carried out after the crosslinking treatment. The polyolefin microporous membrane is preferably crosslinked by irradiation with ionizing radiation such as α rays, β rays, γ rays, and electron rays. In the case of irradiation with electron beams, the electron beam quantity is preferably 0.1 to 100Mrad, and the acceleration voltage is preferably 100 to 300 kV. The melting temperature of the polyolefin microporous membrane is raised by the crosslinking treatment.
In the case of the surfactant treatment, a nonionic surfactant, a cationic surfactant, an anionic surfactant, or a zwitterionic surfactant may be used, but a nonionic surfactant is preferable. The polyolefin microporous membrane is immersed in a solution in which a surfactant is dissolved in water or a lower alcohol such as methanol, ethanol, isopropanol, or the like, or the solution is applied to the polyolefin microporous membrane by a doctor blade method.
The polyolefin microporous membrane according to the embodiment of the present invention can be produced into a multilayer polyolefin porous membrane by laminating porous layers containing resins other than polyolefin resins by coating, vapor deposition, or the like for the purpose of imparting functions such as melting characteristics, heat resistance, and adhesiveness. The other porous layer is not particularly limited, and examples thereof include a porous layer such as an inorganic particle layer containing a binder and inorganic particles. The binder component constituting the inorganic particle layer is not particularly limited, and known components may be used, and for example, acrylic resins, poly-1, 1-difluoroethylene resins, polyamide-imide resins, polyamide resins, aromatic polyamide resins, polyimide resins, and the like may be used. The inorganic particles constituting the inorganic particle layer are not particularly limited, and known materials can be used, and for example, alumina, boehmite, barium sulfate, magnesium oxide, magnesium hydroxide, magnesium carbonate, silicon, and the like can be used. The multilayered polyolefin porous film may be a film obtained by laminating the binder resin having been made porous on at least one surface of a polyolefin microporous film.
The polyolefin microporous membrane obtained in the above-described manner can be used in various applications such as filters, separators for fuel cells, separators for capacitors, and the like. In particular, since the separator is excellent in safety and output characteristics when used as a battery separator, the separator can be preferably used as a battery separator for a secondary battery requiring high energy density, high capacity, and high output, such as an electric vehicle.
Examples
The present invention will be described in further detail with reference to examples. The present invention is not limited to these examples.
Initially, a measurement method and an evaluation method will be described. Unless otherwise specified, the temperature is: 25+ -2deg.C (room temperature), humidity: 50.+ -. 10% of the total weight of the sample.
[ Film thickness ]
The thickness of 5 points of a polyolefin microporous membrane in the range of 50mm×50mm was measured by a contact thickness meter (m.c. m.m. for 10.5mm phi superhard spherical probe, measuring load 0.01N), and the average value was set as the thickness (μm).
[ Weight per unit area ]
Samples were obtained by cutting 5cm×5cm square from the polyolefin microporous membrane, and the mass (g) at room temperature of 25℃was measured. From this value, the weight per unit area of the polyolefin microporous membrane was calculated by the following formula.
Weight per unit area (g/m 2) =mass (g/0.0025 m 2) ×400
[ Porosity ]
Samples were obtained by cutting 5cm×5cm square from the polyolefin microporous membrane, and the volume (cm 3) and mass (g) thereof at room temperature of 25℃were measured. From their values and film densities (g/cm 3), the porosity of the polyolefin microporous films was calculated by the following formula.
In addition, the film density was calculated assuming a constant value of 0.99g/cm 3.
Porosity (%) = { (volume-mass/membrane density)/volume } ×100
[ Puncture Strength in terms of weight per unit area ]
The test speed was set at 2 mm/sec, except that the test speed was measured in accordance with JIS Z1707 (2019). The maximum load (mN) of the polyolefin microporous membrane when the membrane was punctured at 25℃was measured with a needle having a diameter of 1.0mm and a spherical surface (radius of curvature R:0.5 mm) at the tip thereof using a dynamometer (DS 2-20N manufactured by DOWN Co., ltd.) and the puncture strength per unit area weight (mN/(g/m 2)) was calculated from the following formula.
The formula: weight per unit area conversion puncture strength=maximum load (mN)/weight per unit area of polyolefin microporous membrane (g/m 2)
[ Air permeability in terms of weight per unit area ]
The polyolefin microporous membrane having a weight per unit area T (g/m 2) was measured for air permeability P 1 (sec/100 cm 3) by means of an air permeability resistance meter (manufactured by Asahi Kabushiki Kaisha, EGO-1T) in accordance with JIS P-8117 (2009). Furthermore, by the formula: p 2＝P1/T, and calculated as air permeability per unit area weight, P 2 (sec/100 cm 3/(g/m2)).
[ Molecular weight of polyolefin resin Material ]
The molecular weight of the polyolefin resin was determined by Gel Permeation Chromatography (GPC) under the following conditions.
Measurement device: GPC-150C manufactured by Waters Corporation
Column: shodex UT806M manufactured by Showa Denko Co., ltd
Column temperature: 160 DEG C
Solvent (mobile phase): 1,2, 4-trichlorochlorobenzene
Solvent flow rate: 1.0 mL/min
Sample concentration: 0.1wt% (dissolution conditions: 160 ℃ C./1 h)
Sample introduction amount: 500 mu L
Detector: waters Corporation differential refractometer (RI detector)
Standard curve: a standard curve obtained by using a monodisperse polystyrene standard sample was prepared using a polyethylene conversion factor (0.46).
[ Melting Point of gel-like sheet (before stretching) ]
The melting point (. Degree. C.) of the gel-like sheet before stretching of the polyolefin microporous membrane was measured by the differential scanning calorimetric analysis (DSC) method based on JIS K7121. A20 mg sample was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute using PARKING ELMER: PYRISDiamond DSC, to obtain a melting endothermic curve. The temperature of the peak top on the obtained melting endothermic curve was set as the melting point (. Degree. C.) of the gel-like sheet (before stretching).
[ Proportion of polyethylene component having molecular weight of 5 ten thousand or less in polyolefin microporous film ]
The proportion of the polyethylene component having a molecular weight of 5 ten thousand or less in the polyolefin microporous membrane was calculated using a molecular weight distribution obtained by a Gel Permeation Chromatography (GPC) method measured under the following conditions. Specifically, the following expression is adopted.
Ratio (mass%) of polyethylene component having a molecular weight of 5 ten thousand or less in the polyolefin microporous membrane = (component amount of polyethylene having a molecular weight of 5 ten thousand or less)/(component amount of polyethylene having a total molecular weight) ×100
Measurement device: GPC-150C manufactured by Waters Corporation
Column: shodex UT806M manufactured by Showa Denko Co., ltd
Column temperature: 160 DEG C
Solvent (mobile phase): 1,2, 4-trichlorochlorobenzene
Solvent flow rate: 1.0 mL/min
Sample concentration: 0.1wt% (dissolution conditions: 160 ℃ C./1 h)
Sample introduction amount: 500 mu L
Detector: waters Corporation differential refractometer (RI detector)
Standard curve: a standard curve obtained by using a monodisperse polystyrene standard sample was prepared using a polyethylene conversion factor (0.46).
[ Proportion of polyethylene having a molecular weight of 100 ten thousand or more and proportion of polyethylene component having a molecular weight of 200 ten thousand or more ] in polyolefin microporous film
The proportion of polyethylene having a molecular weight of 100 ten thousand or more and the proportion of polyethylene having a molecular weight of 200 ten thousand or more in the polyolefin microporous membrane were calculated using the molecular weight distribution measured under the same conditions as in the GPC method described above. Specifically, the following expression is adopted.
The proportion (mass%) of polyethylene having a molecular weight of 100 ten thousand or more in the polyolefin microporous membrane = (the component amount of polyethylene having a molecular weight of 100 ten thousand or more)/(the component amount of polyethylene having a total molecular weight) ×100
The proportion (mass%) of polyethylene having a molecular weight of 200 ten thousand or more in the polyolefin microporous membrane = (the component amount of polyethylene having a molecular weight of 200 ten thousand or more)/(the component amount of polyethylene having a total molecular weight) ×100
[ Peak temperature Difference (DeltaTm) and Peak Strength Difference (DeltaS) of polyolefin microporous Membrane ]
The melting endothermic curve of the polyolefin microporous membrane was obtained by Differential Scanning Calorimetry (DSC) method based on JIS K7121 at a heating rate of 10 ℃/min, and the peak temperature difference (DeltaTm) and the peak intensity difference (DeltaS) were calculated. The intensity obtained by the differential scanning calorimetric analysis (DSC) method in the present specification means a heat flow rate (mW) at a peak temperature on a melting endothermic curve described later. First, 6.0mg of a polyolefin microporous membrane was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute (data number: 30/. Degree.C.) using PARKING ELMER: PYRIS Diamond DSC as a differential scanning calorimeter, thereby obtaining a melting endothermic curve. Further, a linear base line was set in a range of 60 to 160℃with respect to the melting endothermic curve, and correction was performed. Further, the obtained melting endothermic curve was squared with a value obtained by differentiating the temperature, and then, 5 parts of data of continuous temperatures were averaged (smoothed) to obtain a differential melting endothermic curve. In the obtained temperature differential melting endothermic curve, a temperature which becomes a minimum value in a range of 145 ℃ or more and less than 155 ℃ is set as a peak temperature a (Tm A). In addition, in the case where the differential melting endothermic curve has a minimum value in a range of 145 ℃ or more and less than 155 ℃, tm A is also set to be absent when a value 10% or more higher than the minimum value is not present in a range of more than the temperature showing the minimum value and less than 155 ℃. When the temperature satisfying the above conditions of Tm A is 2 or more, the lower temperature is set to Tm A. Assuming that the highest intensity point at less than 145 ℃ in the melting endothermic curve corrected with the base line is peak B, the temperature is set to Tm B, and Tm B is subtracted from Tm A to obtain Δtm (c, tm A-TmB). Further, in the melting endothermic curve corrected by the base line, the intensity at Tm A is S A, the intensity at Tm B is S B, and the intensity ratio (S A/SB) is Δs. In addition, the presence or absence of a peak at 155℃or higher in the obtained melting endothermic curve was also confirmed.
[ Tan delta at 130 ℃ of polyolefin microporous film ]
Dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring machine (TA end RSA-G2), and tan δ (loss modulus/storage modulus) at 130 ℃ was obtained using loss modulus and storage modulus at 130 ℃. The measurement conditions were that the sample shape: width 10mm x length 50mm, initial inter-chuck distance: 20mm, initial strain: 0.1%, frequency: 10Hz, temperature sweep range: 30-180 ℃, and the temperature rising speed is as follows: 5 ℃/min, initial tension: 50gf, the minimum strain for the automatic strain adjustment procedure: 0.1%, maximum strain: 1.5%, minimum tension: 1.0g, maximum tension: 300.0g. The above measurement was carried out at different positions in the same film in the TD direction, 3 points were measured, and the average value was set to be tan delta at 130 ℃.
[ Melting Point of polyolefin-based resin Material ]
The melting point of the polyolefin-based resin of the raw material was measured by differential scanning calorimetric analysis (DSC) method based on JIS K7121. 6.0mg of a sample was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute (1 st temperature rise) under a nitrogen atmosphere using PYRISDiamond DSC prepared by PARKING ELMER, then the mixture was kept at 230℃for 5 minutes, cooled at a rate of 10℃per minute, and again raised from 30℃to 230℃at a rate of 10℃per minute (2 nd temperature rise), whereby respective melting endothermic curves were obtained. The temperature of the peak top on the melting endothermic curve obtained by the 2 nd temperature rise was set as the melting point of the polyolefin resin raw material.
[ DeltaH of polyolefin resin Material ]
The melting point of the polyolefin-based resin of the raw material was measured by differential scanning calorimetric analysis (DSC) method based on JIS K7121. 6.0mg of a sample was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute (1 st temperature rise) under a nitrogen atmosphere using PYRISDiamond DSC prepared by PARKING ELMER, then the mixture was kept at 230℃for 5 minutes, cooled at a rate of 10℃per minute, and again raised from 30℃to 230℃at a rate of 10℃per minute (2 nd temperature rise), whereby respective melting endothermic curves were obtained. The heat of fusion on the heat absorption curve of fusion obtained by the 2 nd temperature rise is integrated to 60 to 160 ℃, and ΔH (J/g) of the polyolefin resin raw material is obtained.
[ Half width of melting Peak of polyolefin resin Material ]
The melting point of the polyolefin-based resin of the raw material was measured by differential scanning calorimetric analysis (DSC) method based on JIS K7121. 6.0mg of a sample was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute (1 st temperature rise) under a nitrogen atmosphere using PYRISDiamond DSC prepared by PARKING ELMER, then the mixture was kept at 230℃for 5 minutes, cooled at a rate of 10℃per minute, and again raised from 30℃to 230℃at a rate of 10℃per minute (2 nd temperature rise), whereby respective melting endothermic curves were obtained. The absolute value of the difference between 2 temperatures showing 50% of the peak top strength on the melting endothermic curve obtained by the 2 nd temperature rise was set as the melting peak half width (. Degree. C.) of the polyolefin-based resin raw material.
[ High-temperature crystalline melting ratio of polyolefin resin: h ]
The high-temperature crystallization melting ratio (H) of the polyolefin-based resin was measured by the differential scanning calorimetric analysis (DSC) method under the following high-speed cooling conditions. 6.0mg of a sample was sealed in an aluminum pan, and the temperature was raised from 30℃to 230℃at 10℃per minute (1 st temperature rise) under a nitrogen atmosphere using PYRISDiamond DSC prepared by PARKING ELMER, then the mixture was kept at 230℃for 5 minutes, cooled at a rate of 300℃per minute, and again raised from 30℃to 230℃at a rate of 10℃per minute (2 nd temperature rise), whereby respective melting endothermic curves were obtained. Regarding a melting heat absorption curve at the time of melting obtained by the 2 nd temperature rise, a linear base line was set in a range of 60 to 160 ℃, and heat was calculated from the area of a portion surrounded by such linear base line and melting heat absorption curve, and the heat was converted to a unit mass of sample to calculate the entire heat of fusion H all. The heat was calculated from the area of the portion surrounded by such a linear base line and a melting endothermic curve after 135 ℃, and converted to a mass per unit sample to calculate the high temperature crystallization heat of fusion H 135℃over. The obtained total heat of fusion H all and heat of high-temperature crystallization heat of fusion H ht were substituted into the following formula to determine the high-temperature crystallization heat ratio (H) of the polyolefin resin.
H(％)＝(H135℃over/Hall)×100
[ Resistance values at shutdown temperature and 160 ℃ and 180 ]
After cutting the polyolefin microporous membrane to a diameter of 19mm in an atmosphere having a humidity of 30% + -10%, the membrane was added to a coin cell (CR 2032 standard), and the electrolyte was injected, and the membrane was vacuum-impregnated with a vacuum drier at a pressure of-50 kPa for 1 minute. Then, the battery was sealed by a coin cell caulking machine, heated at a heating rate of 5 ℃/min, and measured for resistance. A 1mol/L solution of LiPF 6 (EC: emc=4:6v%) was used as the electrolyte (LiPF 6: lithium hexafluorophosphate, EC: ethylene carbonate, EMC: ethylmethyl carbonate). The measurement conditions were elevated from room temperature (25 ℃) to 180℃using a constant temperature bath for 30 minutes. The resistance values of the respective temperatures were read by an impedance analyzer at a frequency of 200kHz, and the initial temperature at which 1000 Ω·cm 2 was reached was set as the off temperature.
The raw materials used in examples are shown in tables 1 and 2, and the screw specifications of the twin-screw extruder used are shown in table 3.
Example 1
A mixture was prepared by mixing 100 parts by mass of a polyolefin resin containing 80% by mass of PEa as a high molecular weight polyethylene and PEd% by mass as a low molecular weight polyethylene with 0.5 part by mass of tetrakis [ methylene-3- (3, 5-di-t-butyl-4-hydroxyphenyl) -propionate ] methane as an antioxidant. 20 parts by mass of the obtained mixture was fed into a twin-screw extruder (internal diameter: 58mm, screw gauge A), 80 parts by mass of liquid paraffin [35cst (40 ℃ C.) ] was fed from a side feeder of the twin-screw extruder, and melt-kneaded at 180 ℃ and 200rpm to prepare a polyolefin resin solution.
After foreign matter was removed from each twin-screw extruder through a filter, the polyolefin resin solution was supplied to a T-die, and the extrusion molded body was cooled while being pulled at a pulling rate of 5 m/min by a cooling roll having a temperature of 15 ℃.
The gel sheet was simultaneously biaxially stretched by a tenter at 115 ℃ so that both MD and TD directions became 8 times. The tensile stress increase rates in the regions 1 to 5 times in the MD direction and the TD direction at the time of stretching were 0.080 MPa/time and 0.075 MPa/time, respectively. The stretched gel sheet was fixed to a 30cm×30cm aluminum frame plate, immersed in a methylene chloride bath at a temperature of 25 ℃, and the liquid paraffin was removed while shaking at 100rpm for 10 minutes, and then air-dried at room temperature.
The obtained dried film was heat-set at 125℃for 10 minutes. The thickness of the obtained polyolefin microporous membrane was 8.4. Mu.m, and the blending ratio, production conditions, evaluation results, and the like of each component of the composition are shown in Table 4.
Examples 2 to 6
A polyolefin microporous membrane was produced in the same manner as in example 1, except that the raw material mixture and the process conditions shown in table 4 were changed.
Comparative examples 1 to 4
A polyolefin microporous membrane was produced in the same manner as in example 1, except that the raw material mixture and the process conditions shown in table 5 were changed.
Comparative example 5
To 100 parts by mass of a polyolefin resin containing 30 parts by mass of PEc as a high molecular weight polyethylene, PEe 62.5.5 parts by mass of a low molecular weight polyethylene, and 7.5 parts by mass of PP as another polyolefin, 0.5 parts by mass of tetrakis [ methylene-3- (3, 5-di-t-butyl-4-hydroxyphenyl) -propionate ] methane as an antioxidant was mixed to prepare a mixture. 25 parts by mass of the obtained mixture was fed into a twin-screw extruder (internal diameter: 58mm, screw gauge A), 75 parts by mass of liquid paraffin [35cst (40 ℃ C.) ] was fed from a side feeder of the twin-screw extruder, and melt-kneaded at 180 ℃ and 200rpm to prepare a polyolefin resin solution.
After foreign matter was removed from each twin-screw extruder through a filter, the polyolefin resin solution was supplied to a T-die, and the extrusion molded body was cooled while being pulled at a pulling rate of 5 m/min by a cooling roll having a temperature of 15 ℃.
The gel sheet was simultaneously biaxially stretched by a tenter at 115 ℃ so that both MD and TD directions became 7 times. The tensile stress increase rates in the regions 1 to 5 times in the MD direction and the TD direction at the time of stretching were 0.150 MPa/time and 0.080 MPa/time, respectively. The stretched gel sheet was fixed to a 30cm×30cm aluminum frame plate, immersed in a methylene chloride bath at a temperature of 25 ℃, and the liquid paraffin was removed while shaking at 100rpm for 10 minutes, and then air-dried at room temperature.
The obtained dried film was heat-set at 125℃for 10 minutes. The resulting polyolefin microporous membrane had a thickness of 8.6. Mu.m, and was scattered with spots, and if compared with examples 1 to 4 and comparative examples 1 to 4, the appearance was deteriorated. The blending ratio, production conditions, evaluation results, and the like of each component are shown in table 5. In the table, regarding the item of the film forming property, the term "o" is used when there is no problem in the film forming property, the term "Δ" is used when there is a problem in the film forming property, and the term "x" is used when there is a significant problem in the film forming property or when the film forming is difficult.
Comparative example 6
A film was produced in the same manner as in comparative example 1, except that 23 parts by mass of PEc was used as the high molecular weight polyethylene, 55 parts by mass of PEe parts by mass as the low molecular weight polyethylene, and 22 parts by mass of PP was used as the other polyolefin. The resulting polyolefin microporous membrane had a thickness of 8.7 μm and a large number of scattered spots, and if compared with examples 1 to 4 and comparative examples 1 to 4, the appearance was significantly deteriorated. The blending ratio, production conditions, evaluation results, and the like of each component are shown in table 4.
Comparative example 7
A film was produced in the same manner as in example 1 except that the screw gauge of the twin-screw extruder was set to C, but vent flash (vent up) during extrusion was severe, and a uniform gel sheet was not obtained, so that evaluation after stretching was abandoned.
Comparative example 8
A film was produced in the same manner as in example 3 except that the screw gauge of the twin-screw extruder was set to D, but vent flash during extrusion was severe, and a uniform gel sheet was not obtained, so that evaluation after stretching was abandoned.
TABLE 1
| Unit (B) | PEa | PEb | PEc | |
| Mw | (×104) | 100 | 150 | 250 |
| Melting point | ℃ | 136.0 | 136.0 | 133.5 |
| Half width of | ℃ | 6.4 | 6.5 | 8.2 |
| ΔH | J/g | 190 | 178 | 159 |
| High temperature crystallization to melting ratio | ％ | 14.5 | 15.0 | 3.1 |
TABLE 2
| Unit (B) | PEd | PEe | PEf | PP | |
| Mw | (×104) | 8 | 35 | 4 | 100 |
| Melting point | ℃ | 131.5 | 135.2 | 126.0 | 163.0 |
| Half width of | ℃ | 4.3 | 5.8 | 3.3 | - |
| ΔH | J/g | 225 | 200 | 192 | - |
| High temperature crystallization to melting ratio | ％ | 0.5 | 13 | 0.8 | - |
TABLE 3 Table 3
(Evaluation)
It is suggested that the polyolefin microporous films of examples 1 to 6 achieve low shutdown temperature and high temperature resistance without deteriorating film forming properties, such as appearance deterioration. Among these, it was confirmed that examples 1 to 4 were more excellent in appearance and maintained other physical properties such as puncture strength and permeability at a high level as compared with examples 5 and 6. On the other hand, the resistances were significantly deteriorated at high temperatures in comparative examples 1 to 4. In comparative examples 5 and 6, polypropylene was added to improve the electrical resistance at high temperature as compared with comparative examples 1 to 4, but it was confirmed that the appearance was poor due to the specks and the film forming property was deteriorated.
Industrial applicability
The polyolefin microporous membrane of the present invention is excellent in shutdown characteristics and meltdown characteristics without impairing the film forming property, and is excellent in safety when used as a separator for a battery. Therefore, the present invention can be suitably used for a separator for a secondary battery, which is required to have a high capacity and a thin film.
While the application has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. The present application is based on japanese patent application (japanese patent application publication No. 2021-160023), filed on 9/29 of 2021, the contents of which are incorporated herein by reference.
Claims (9)
1. A polyolefin microporous film, wherein in a melting endothermic curve obtained by measurement with a differential scanning calorimeter at a temperature rising rate of 10 ℃/min, the temperature at the point of highest intensity at less than 145 ℃ is set as Tm B, and in a differential melting endothermic curve calculated from the melting endothermic curve, when the temperature showing the minimum value in the range of 145 ℃ or more and less than 155 ℃ is set as Tm A, ΔTm, namely ΔTm=Tm A-TmB, is 8.0 ℃ or more and 12.0 ℃ or less, and the ratio of the intensity S A at Tm A to the intensity S B at Tm B, namely ΔS=S A/SB, in the melting endothermic curve exceeds 0.1 and is less than 0.5.
2. The microporous polyolefin membrane according to claim 1, wherein tan delta at 130 ℃ measured by dynamic viscoelasticity is 0.35 or more.
3. The microporous polyolefin membrane according to claim 1 or 2, which has a puncture strength of 400 mN/(g/m 2) or more in terms of weight per unit area.
4. The polyolefin microporous membrane according to claim 1 or 2, having a permeability of 50 seconds/100 cm 3/(g/m2) or less in terms of weight per unit area.
5. The polyolefin microporous membrane according to claim 1 or 2, which comprises polyethylene as a main component.
6. The polyolefin microporous membrane according to claim 1 or 2, having no peak at 155 ℃ or more in the melting endothermic curve.
7. The polyolefin microporous membrane according to claim 1 or 2, comprising 10 mass% or more of a polyethylene component having a molecular weight of 5 ten thousand or less and 15 mass% or more of a polyethylene component having a molecular weight of 100 ten thousand or more in a molecular weight distribution of polyethylene measured by GPC method.
8. A separator for a battery using the polyolefin microporous film according to claim 1 or 2.
9. A secondary battery using the separator for a battery according to claim 8.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2021-160023 | 2021-09-29 | ||
| JP2021160023 | 2021-09-29 | ||
| PCT/JP2022/035269 WO2023054139A1 (en) | 2021-09-29 | 2022-09-21 | Microporous polyolefin membrane, separator for batteries, and secondary battery |
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| Publication Number | Publication Date |
|---|---|
| CN118019788A true CN118019788A (en) | 2024-05-10 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202280065522.2A Pending CN118019788A (en) | 2021-09-29 | 2022-09-21 | Polyolefin microporous membrane, separator for battery, and secondary battery |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPWO2023054139A1 (en) |
| KR (1) | KR20240087644A (en) |
| CN (1) | CN118019788A (en) |
| WO (1) | WO2023054139A1 (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3348965B2 (en) * | 1994-03-31 | 2002-11-20 | 三井化学株式会社 | Microporous biaxially stretched film comprising a composition of high molecular weight polyethylene and high molecular weight polypropylene, its production method and its use |
| JP2004018838A (en) * | 2002-06-20 | 2004-01-22 | Asahi Kasei Corp | Microporous polyolefin membrane |
| JP4195810B2 (en) | 2002-12-16 | 2008-12-17 | 東燃化学株式会社 | Polyolefin microporous membrane and production method and use thereof |
| JP6170181B2 (en) * | 2013-01-30 | 2017-07-26 | ダブリュ．エル．ゴア アンド アソシエイツ，インコーポレイティドＷ．Ｌ． Ｇｏｒｅ ＆ Ａｓｓｏｃｉａｔｅｓ， Ｉｎｃｏｒｐｏｒａｔｅｄ | Method for producing porous article derived from ultra-high molecular weight polyethylene |
| JP2015208894A (en) | 2014-04-24 | 2015-11-24 | 東レバッテリーセパレータフィルム株式会社 | Polyolefin-made laminated microporous film |
| KR102404990B1 (en) * | 2018-07-13 | 2022-06-07 | 주식회사 엘지에너지솔루션 | A separator for an electrochemical device and an electrochemical device comprising the same |
| WO2021065283A1 (en) * | 2019-09-30 | 2021-04-08 | 東レ株式会社 | Polyolefin microporous film, separator for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery |
-
2022
- 2022-09-21 WO PCT/JP2022/035269 patent/WO2023054139A1/en active Application Filing
- 2022-09-21 JP JP2022558195A patent/JPWO2023054139A1/ja active Pending
- 2022-09-21 CN CN202280065522.2A patent/CN118019788A/en active Pending
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| WO2023054139A1 (en) | 2023-04-06 |
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| JPWO2023054139A1 (en) | 2023-04-06 |
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