JP5929469B2 - Aromatic polyamide porous membrane, battery separator and method for producing the same - Google Patents
Aromatic polyamide porous membrane, battery separator and method for producing the same Download PDFInfo
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- JP5929469B2 JP5929469B2 JP2012099416A JP2012099416A JP5929469B2 JP 5929469 B2 JP5929469 B2 JP 5929469B2 JP 2012099416 A JP2012099416 A JP 2012099416A JP 2012099416 A JP2012099416 A JP 2012099416A JP 5929469 B2 JP5929469 B2 JP 5929469B2
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- aromatic polyamide
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- 239000012528 membrane Substances 0.000 title claims description 77
- 239000004760 aramid Substances 0.000 title claims description 73
- 229920003235 aromatic polyamide Polymers 0.000 title claims description 73
- 238000004519 manufacturing process Methods 0.000 title claims description 24
- 239000011148 porous material Substances 0.000 claims description 93
- 238000000034 method Methods 0.000 claims description 50
- 230000035699 permeability Effects 0.000 claims description 11
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 claims description 9
- 229910052753 mercury Inorganic materials 0.000 claims description 9
- 239000002798 polar solvent Substances 0.000 claims description 8
- 239000011550 stock solution Substances 0.000 description 28
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 27
- 229920000642 polymer Polymers 0.000 description 25
- 239000000243 solution Substances 0.000 description 21
- 239000010410 layer Substances 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 19
- 238000011156 evaluation Methods 0.000 description 18
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 14
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 14
- 238000010438 heat treatment Methods 0.000 description 13
- 150000002500 ions Chemical class 0.000 description 13
- 229920001477 hydrophilic polymer Polymers 0.000 description 11
- 230000002829 reductive effect Effects 0.000 description 11
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 10
- 125000003118 aryl group Chemical group 0.000 description 10
- 229910001416 lithium ion Inorganic materials 0.000 description 10
- 239000002904 solvent Substances 0.000 description 10
- 238000010521 absorption reaction Methods 0.000 description 9
- 230000007423 decrease Effects 0.000 description 9
- 238000001035 drying Methods 0.000 description 9
- 238000006116 polymerization reaction Methods 0.000 description 9
- 239000011248 coating agent Substances 0.000 description 8
- 238000000576 coating method Methods 0.000 description 8
- 238000007599 discharging Methods 0.000 description 8
- 239000008151 electrolyte solution Substances 0.000 description 8
- 238000005259 measurement Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 239000000523 sample Substances 0.000 description 8
- 239000000126 substance Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000009826 distribution Methods 0.000 description 7
- 238000012545 processing Methods 0.000 description 7
- 229910001220 stainless steel Inorganic materials 0.000 description 7
- 239000010935 stainless steel Substances 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 238000009472 formulation Methods 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229920000098 polyolefin Polymers 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 125000001424 substituent group Chemical group 0.000 description 4
- HLBLWEWZXPIGSM-UHFFFAOYSA-N 4-Aminophenyl ether Chemical compound C1=CC(N)=CC=C1OC1=CC=C(N)C=C1 HLBLWEWZXPIGSM-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
- 230000008602 contraction Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 150000004985 diamines Chemical class 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 3
- 230000020169 heat generation Effects 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 238000005191 phase separation Methods 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000003860 storage Methods 0.000 description 3
- NGNBDVOYPDDBFK-UHFFFAOYSA-N 2-[2,4-di(pentan-2-yl)phenoxy]acetyl chloride Chemical compound CCCC(C)C1=CC=C(OCC(Cl)=O)C(C(C)CCC)=C1 NGNBDVOYPDDBFK-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical group [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052801 chlorine Chemical group 0.000 description 2
- 239000000460 chlorine Chemical group 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000004320 controlled atmosphere Methods 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 239000002003 electrode paste Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 238000001465 metallisation Methods 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 239000004745 nonwoven fabric Substances 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 2
- IOLCXVTUBQKXJR-UHFFFAOYSA-M potassium bromide Chemical compound [K+].[Br-] IOLCXVTUBQKXJR-UHFFFAOYSA-M 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- CBCKQZAAMUWICA-UHFFFAOYSA-N 1,4-phenylenediamine Chemical compound NC1=CC=C(N)C=C1 CBCKQZAAMUWICA-UHFFFAOYSA-N 0.000 description 1
- MGLZGLAFFOMWPB-UHFFFAOYSA-N 2-chloro-1,4-phenylenediamine Chemical compound NC1=CC=C(N)C(Cl)=C1 MGLZGLAFFOMWPB-UHFFFAOYSA-N 0.000 description 1
- MSWAXXJAPIGEGZ-UHFFFAOYSA-N 2-chlorobenzene-1,4-dicarbonyl chloride Chemical compound ClC(=O)C1=CC=C(C(Cl)=O)C(Cl)=C1 MSWAXXJAPIGEGZ-UHFFFAOYSA-N 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical group [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000012695 Interfacial polymerization Methods 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 229920002873 Polyethylenimine Polymers 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- GOOHAUXETOMSMM-UHFFFAOYSA-N Propylene oxide Chemical compound CC1CO1 GOOHAUXETOMSMM-UHFFFAOYSA-N 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 101000804816 Xenopus laevis Werner syndrome ATP-dependent helicase homolog Proteins 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 125000002252 acyl group Chemical group 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910001508 alkali metal halide Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 229910001615 alkaline earth metal halide Inorganic materials 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- FDQSRULYDNDXQB-UHFFFAOYSA-N benzene-1,3-dicarbonyl chloride Chemical compound ClC(=O)C1=CC=CC(C(Cl)=O)=C1 FDQSRULYDNDXQB-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Chemical group BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 239000000920 calcium hydroxide Substances 0.000 description 1
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001186 cumulative effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- BXKDSDJJOVIHMX-UHFFFAOYSA-N edrophonium chloride Chemical compound [Cl-].CC[N+](C)(C)C1=CC=CC(O)=C1 BXKDSDJJOVIHMX-UHFFFAOYSA-N 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 125000001301 ethoxy group Chemical group [H]C([H])([H])C([H])([H])O* 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000009477 glass transition Effects 0.000 description 1
- 125000005843 halogen group Chemical group 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 239000010954 inorganic particle Substances 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 229910001867 inorganic solvent Inorganic materials 0.000 description 1
- 239000003049 inorganic solvent Substances 0.000 description 1
- 230000010220 ion permeability Effects 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000002931 mesocarbon microbead Substances 0.000 description 1
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 1
- 239000011325 microbead Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 1
- 239000011146 organic particle Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 238000000710 polymer precipitation Methods 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 239000001103 potassium chloride Substances 0.000 description 1
- 235000011164 potassium chloride Nutrition 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 125000002572 propoxy group Chemical group [*]OC([H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- 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
Landscapes
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Cell Separators (AREA)
Description
本発明は、芳香族ポリアミド多孔質膜に関するものであり、特に電池などの蓄電デバイスのセパレータとして好適に使用できる芳香族ポリアミド多孔質膜に関するものである。 The present invention relates to an aromatic polyamide porous membrane, and more particularly to an aromatic polyamide porous membrane that can be suitably used as a separator for an electricity storage device such as a battery.
リチウムイオン二次電池（ＬＩＢ）などの非水系二次電池は、携帯機器用途を中心に広範に普及しており、今後は電気自動車（ＥＶ）やハイブリッド電気自動車（ＨＥＶ）などの車載用途にも急速に拡大すると考えられる。そのため、ＬＩＢの開発においては、更なる高容量化、高出力化、大型化が進められる一方で、これまで以上に高い安全性が求められている。それに伴い、セパレータにも優れたイオン透過性と同時に、安全性の付与が強く求められている。 Non-aqueous secondary batteries such as lithium ion secondary batteries (LIBs) are widely used mainly for portable devices, and will be used in in-vehicle applications such as electric vehicles (EV) and hybrid electric vehicles (HEV) in the future. Expected to expand rapidly. Therefore, in the development of LIB, while further increasing the capacity, increasing the output, and increasing the size, higher safety is required than ever. Along with this, there is a strong demand for providing separators with safety as well as excellent ion permeability.
セパレータによる安全性付与に関して、従来のポリオレフィン系のセパレータには、電池が異常発熱した際に孔が閉塞して電流を遮断する、いわゆるシャットダウン（ＳＤ）機構が備わっている。しかしながら、電池内部の温度がポリオレフィンの融点を超えた場合、セパレータの溶融によりその機能を失い（メルトダウン）、電池が熱暴走し発火につながる危険性がある。また、電池を大型化した際、異常発熱時に孔の閉塞が不十分な領域が残ると、その部分に電流が集中し、かえって危険であるとの考えもあり、車載用などの高度な安全性が求められるＬＩＢではセパレータを耐熱化する方向で開発が進んでいる。 Regarding the provision of safety by the separator, the conventional polyolefin-based separator is provided with a so-called shutdown (SD) mechanism in which the hole is closed and the current is cut off when the battery abnormally generates heat. However, when the temperature inside the battery exceeds the melting point of the polyolefin, there is a risk that the function of the separator is lost due to melting of the separator (meltdown), and the battery runs out of heat and leads to ignition. In addition, when a battery is enlarged, if there is an area where the hole is not sufficiently closed during abnormal heat generation, the current concentrates in that area, which may be dangerous. LIB is required to be developed in a direction to increase the heat resistance of the separator.
そこで、ポリオレフィン多孔膜の片面または両面に耐熱層（ＨＲＬ）を設けたセパレータが開示されている（例えば、特許文献１）。しかしながら、このＨＲＬの効果は限定的で、大面積におけるポリオレフィン層のメルトダウン時にセパレータの収縮を有効に阻止できないことがあり、特に端部において短絡を起こす可能性がある。さらに、積層体であるため一般的に薄膜化が困難である。 Then, the separator which provided the heat-resistant layer (HRL) on the single side | surface or both surfaces of the polyolefin porous membrane is disclosed (for example, patent document 1). However, the effect of this HRL is limited, and the shrinkage of the separator may not be effectively prevented when the polyolefin layer is melted down in a large area, and there is a possibility of causing a short circuit particularly at the end portion. Furthermore, since it is a laminated body, it is generally difficult to reduce the thickness.
一方、例えば特許文献２〜４には、耐熱性に優れる芳香族ポリアミドを単体でセパレータに用いることが開示されている。特許文献２はアラミド不織布やアラミドペーパーのセパレータとしての用途を開示した例であるが、不織布や紙状シートでは５０μｍ以下の薄い厚みで、かつ十分な強度を持ち、繊維間の空隙が緻密なものを工業的に製造することは困難である。また、特許文献３および４はアラミド多孔質フィルムからなるセパレータを開示した例であるが、アラミドからなる多孔質膜において、高空孔率でありながら緻密かつ厚み方向に均一な孔構造を有するものは得られていない。 On the other hand, for example, Patent Documents 2 to 4 disclose that an aromatic polyamide having excellent heat resistance is used alone as a separator. Patent Document 2 is an example disclosing the use as an aramid non-woven fabric or aramid paper separator, but the non-woven fabric or paper-like sheet has a thin thickness of 50 μm or less, sufficient strength, and a fine gap between fibers. Is difficult to produce industrially. Patent Documents 3 and 4 are examples in which a separator made of an aramid porous film is disclosed, but a porous film made of aramid has a high porosity and a uniform pore structure in the thickness direction. Not obtained.
本発明は、高気孔率でありながら緻密な孔構造を有し、かつその孔構造が厚み方向に均一である、芳香族ポリアミドを構成成分とする多孔質膜ならびにそれを用いた電池用セパレータおよびその製造方法を提供することを目的とする。 The present invention has a dense pore structure with a high air porosity, and the pore structure is uniform in the thickness direction, the porous membrane and a battery separator using the same as a constituent component an aromatic polyamide And it aims at providing the manufacturing method.
上記目的を達成するための本発明は、以下の特徴を有する。 In order to achieve the above object, the present invention has the following features.
（１）水銀圧入法を用いて測定した気孔率が５０〜９５％であり、細孔径のピーク直径が０．０１〜０．２０μｍであり、ガーレ透気度が０．５〜２００秒／１００ｍｌであり、かつ対数微分細孔容積が０．２ｃｍ２／ｇ以上である細孔のうち最大細孔直径と最小細孔直径の差が０．０〜０．６μｍである、芳香族ポリアミド多孔質膜。 (1) The porosity measured using the mercury intrusion method is 50 to 95%, the peak diameter of the pore diameter is 0.01 to 0.20 μm, and the Gurley air permeability is 0.5 to 200 seconds / 100 ml. And the difference between the maximum pore diameter and the minimum pore diameter among the pores having a logarithmic differential pore volume of 0.2 cm 2 / g or more is 0.0 to 0.6 μm. film.
（２）膜厚が６〜４０μｍであり、一方の表面から膜の厚み方向２μｍまでの層、もう一方の表面から膜の厚み方向２μｍまでの層、および厚み方向中心部の厚み２μｍの層の３領域における空孔率の標準偏差が０．０〜５．０％である、上記（１）に記載の芳香族ポリアミド多孔質膜。 (2) A film thickness of 6 to 40 μm, a layer from one surface to a thickness direction of 2 μm, a layer from the other surface to a thickness direction of 2 μm, and a layer having a thickness of 2 μm at the center in the thickness direction The aromatic polyamide porous membrane according to (1) above, wherein the standard deviation of porosity in the three regions is 0.0 to 5.0%.
（３）上記（１）または（２）に記載の芳香族ポリアミド多孔質膜を用いてなる電池用セパレータ。 (3) A battery separator using the aromatic polyamide porous membrane according to (1) or (2).
（４）有機極性溶媒に溶解させた芳香族ポリアミド溶液を、表面積１ｍ２あたりの熱容量が１．０ｋＪ／Ｋ以上の支持体上に塗布した後、温度３０〜８０℃、相対湿度５０〜９５％ＲＨの雰囲気中で吸湿させることにより孔構造を形成させる、上記（１）または（２）に記載の芳香族ポリアミド多孔質膜の製造方法。 (4) After applying an aromatic polyamide solution dissolved in an organic polar solvent on a support having a heat capacity per 1 m 2 of surface area of 1.0 kJ / K or more, a temperature of 30 to 80 ° C. and a relative humidity of 50 to 95%. The method for producing an aromatic polyamide porous membrane according to the above (1) or (2), wherein a pore structure is formed by absorbing moisture in an RH atmosphere.
本発明によれば、以下に説明するとおり、高気孔率でありながら緻密な孔構造を有し、かつその構造が厚み方向に均一である多孔質膜が得られ、リチウムイオン二次電池などの電池用セパレータに好適に用いることができる。多孔質膜が緻密な孔構造を有することで、電池の使用時に析出したリチウム金属やその他製造工程で混入した異物などによる正負極の短絡を防止することができる。また、気孔率が高く、孔構造が厚み方向に均一であることで、リチウムイオンの移動度が膜中において均一となり、イオン伝導が効率良く行われる。さらに、イオンの透過経路の偏在化を抑制することにつながり、長期使用時のリチウム金属析出による孔の閉塞、微小短絡を防止することができる。 According to the present invention, as described below, it has a dense pore structure with a high air porosity, and a uniform porous film can be obtained in its structure the thickness direction, such as a lithium ion secondary battery It can use suitably for the battery separator. Since the porous film has a dense pore structure, it is possible to prevent short-circuiting of the positive and negative electrodes due to lithium metal deposited during use of the battery and other foreign matters mixed in the manufacturing process. Further, since the porosity is high and the pore structure is uniform in the thickness direction, the mobility of lithium ions is uniform in the film, and ion conduction is performed efficiently. Further, uneven distribution of ion permeation paths is suppressed, and pore clogging and micro short-circuiting due to lithium metal precipitation during long-term use can be prevented.
本発明において用いる芳香族ポリアミドとしては、次の化学式（１）および／または化学式（２）で表される繰り返し単位を有するものが好適である。
化学式（１）：
As the aromatic polyamide used in the present invention, those having a repeating unit represented by the following chemical formula (1) and / or chemical formula (2) are preferable.
Chemical formula (1):
化学式（２）： Chemical formula (2):
ここで、Ａｒ１、Ａｒ２、Ａｒ３の基としては、例えば、次の化学式（３）〜（７）などが挙げられる。
化学式（３）〜（７）：
Here, examples of the groups Ar 1 , Ar 2 , and Ar 3 include the following chemical formulas (3) to (7).
Chemical formulas (3) to (7):
また、Ｘ、Ｙの基は、
Ａ群： −Ｏ−、−ＣＯ−、−ＣＯ２−、−ＳＯ２−、
Ｂ群： −ＣＨ２−、−Ｓ−、−Ｃ（ＣＨ３）２−
などから選択することができる。
The X and Y groups are
Group A: -O -, - CO -, - CO 2 -, - SO 2 -,
Group B: —CH 2 —, —S—, —C (CH 3 ) 2 —
Etc. can be selected.
さらに、これら芳香環上の水素原子の一部が、フッ素や臭素、塩素などのハロゲン基（特に塩素）、ニトロ基、メチルやエチル、プロピルなどのアルキル基（特にメチル基）、メトキシやエトキシ、プロポキシなどのアルコキシ基等の置換基で置換されているものが、溶媒への溶解性が向上すること、および吸湿率を低下させ湿度変化による寸法変化が小さくなることから好ましい。また、重合体を構成するアミド結合中の水素が他の置換基によって置換されていてもよい。 Furthermore, some of the hydrogen atoms on these aromatic rings are halogen groups such as fluorine, bromine and chlorine (especially chlorine), nitro groups, alkyl groups such as methyl, ethyl and propyl (especially methyl groups), methoxy and ethoxy, Those substituted with a substituent such as an alkoxy group such as propoxy are preferable because the solubility in a solvent is improved, and the dimensional change due to a change in humidity is reduced by reducing the moisture absorption rate. In addition, hydrogen in the amide bond constituting the polymer may be substituted with another substituent.
本発明に用いられる芳香族ポリアミドは、上記の芳香環がパラ配向性を有しているものが、全芳香環の５０モル％以上を占めていることが好ましく、６０モル％以上を占めていることがより好ましい。ここでいうパラ配向性とは、芳香環上主鎖を構成する２価の結合手が互いに同軸または平行にある状態をいう。このパラ配向性が５０モル％未満の場合、芳香族ポリアミド多孔質膜（以下、単に多孔質膜ということがある。）の剛性および耐熱性が不十分となったり、孔径が大きくなる場合がある。さらに、芳香族ポリアミドが下記化学式（８）で表される繰り返し単位を４０モル％以上含有する場合、多孔質膜の特性が特に優れることから好ましい。
化学式（８）：
In the aromatic polyamide used in the present invention, the above aromatic ring having para-orientation preferably accounts for 50 mol% or more of the total aromatic ring, and accounts for 60 mol% or more. It is more preferable. Para-orientation here means a state in which the divalent bonds constituting the main chain on the aromatic ring are coaxial or parallel to each other. When this para-orientation is less than 50 mol%, the rigidity and heat resistance of the aromatic polyamide porous film (hereinafter sometimes simply referred to as a porous film) may be insufficient, or the pore diameter may be increased. . Further, when the aromatic polyamide contains 40 mol% or more of the repeating unit represented by the following chemical formula (8), it is preferable because the characteristics of the porous membrane are particularly excellent.
Chemical formula (8):
本発明の芳香族ポリアミド多孔質膜は、水銀圧入法を用いて測定した気孔率が５０〜９５％であることが好ましい。より好ましくは６０〜９５％であり、さらに好ましくは７０〜８５％である。気孔率が５０％未満であると、電池用セパレータとして用いたときに、電解液の保液量が少なく、充放電を繰り返した際に液枯れによる性能低下が起きることがある。また、多孔質膜の細孔径を本発明の範囲としたときに気孔率が５０％未満であると、イオン伝導の抵抗が大きく、電池用セパレータとして使用した際に膜の劣化が起きたり、内部抵抗が上昇し十分な出力が得られないことがある。気孔率が９５％を超えると、機械強度が不足し、セパレータとして現実的に使用することが困難になる。気孔率を上記範囲内とするため、製膜原液の処方、多孔化方法を後述の範囲内とすることが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has a porosity of 50 to 95% measured using a mercury intrusion method. More preferably, it is 60-95%, More preferably, it is 70-85%. When the porosity is less than 50%, when used as a battery separator, there is a small amount of electrolyte solution retained, and performance deterioration due to liquid drainage may occur when charging and discharging are repeated. Further, when the porosity of the porous membrane is within the range of the present invention, if the porosity is less than 50%, the resistance of ionic conduction is large, and when used as a battery separator, deterioration of the membrane occurs, Resistance may increase and sufficient output may not be obtained. When the porosity exceeds 95%, the mechanical strength is insufficient, and it becomes difficult to practically use as a separator. In order to keep the porosity within the above range, it is preferable that the formulation of the film-forming stock solution and the method for making the pores are within the ranges described below.
本発明の芳香族ポリアミド多孔質膜は、水銀圧入法を用いて測定した細孔径のピーク直径が０．０１〜０．２０μｍであることが好ましい。より好ましくは０．０２〜０．１０μｍであり、さらに好ましくは０．０３〜０．０８μｍである。細孔径のピーク直径が０．２０μｍを超えると、電池用セパレータとして用いて充放電を繰り返した際に、リチウム金属のデンドライト状結晶によるものと思われる微小短絡が起き、サイクル特性や保存特性が低下することがある。また、製造工程などで混入した異物による正負極の短絡が起きることがある。さらに、膜構造が脆弱となることで破断伸度などの機械特性も低下することがある。細孔径のピーク直径が０．０１μｍ未満であると、電池用セパレータとして用いた際に目詰まりが起き、電池特性が低下することがある。ピーク直径を上記範囲内とするため、多孔化方法、特に多孔化時の製膜原液温度の制御を後述の方法で行うことが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has a peak diameter of 0.01 to 0.20 μm measured using a mercury intrusion method. More preferably, it is 0.02-0.10 micrometer, More preferably, it is 0.03-0.08 micrometer. If the peak diameter of the pore exceeds 0.20 μm, a short-circuit that may be caused by dendritic crystals of lithium metal occurs when charging and discharging are repeated as a battery separator, resulting in poor cycle characteristics and storage characteristics. There are things to do. Moreover, the positive and negative electrodes may be short-circuited due to foreign matters mixed in the manufacturing process. Furthermore, mechanical properties such as elongation at break may be reduced due to the weak membrane structure. When the peak diameter of the pore diameter is less than 0.01 μm, clogging may occur when used as a battery separator, and battery characteristics may deteriorate. In order to keep the peak diameter within the above range, it is preferable to control the temperature of the film forming stock solution at the time of porous formation by the method described later.
本発明の芳香族ポリアミド多孔質膜は、水銀圧入法を用いて測定した対数微分細孔容積が０．２ｃｍ２／ｇ以上である細孔のうち、最大細孔直径と最小細孔直径の差が０．０〜０．６μｍであることが好ましい。より好ましくは０．０〜０．３μｍである。最大細孔直径と最小細孔直径の差が０．６μｍを超えると、多孔質膜中の細孔直径の斑が大きく、細孔直径の小さい領域のイオン透過が律速となり、十分なイオン伝導性が得られないことがある。また、充放電時にリチウムイオンが正負極間を移動する際、このイオン透過が律速となる領域の一部分でイオンが停滞するため、Ｌｉ金属の析出が起こりやすくなり、微小短絡などが起きることがある。孔構造が膜中で均一であることで、リチウムイオンの移動度が膜中において均一となり、イオン伝導が効率良く行われる。最大細孔直径と最小細孔直径の差を上記範囲内とするため、多孔化方法、特に多孔化時の製膜原液温度の制御を後述の方法で行うことが好ましい。ここで、対数微分細孔容積（またはｌｏｇ微分細孔容積）とは、差分細孔容積を、細孔径の対数差分値で除した値である。 The aromatic polyamide porous membrane of the present invention has a difference between the maximum pore diameter and the minimum pore diameter among pores having a logarithmic differential pore volume of 0.2 cm 2 / g or more measured using a mercury intrusion method. Is preferably 0.0 to 0.6 μm. More preferably, it is 0.0-0.3 micrometer. When the difference between the maximum pore diameter and the minimum pore diameter exceeds 0.6 μm, the pore diameter spots in the porous membrane are large, and the ion permeation of the small pore diameter region becomes rate limiting, and sufficient ion conductivity is achieved. May not be obtained. In addition, when lithium ions move between the positive and negative electrodes during charge and discharge, the ions stagnate in a part of the region where the ion permeation is rate-determining, so that Li metal is likely to precipitate and a micro short circuit may occur. . Since the pore structure is uniform in the film, the mobility of lithium ions is uniform in the film, and ion conduction is performed efficiently. In order to make the difference between the maximum pore diameter and the minimum pore diameter within the above range, it is preferable to control the temperature of the film-forming stock solution at the time of the porous formation by the method described later. Here, the logarithmic differential pore volume (or log differential pore volume) is a value obtained by dividing the differential pore volume by the logarithmic difference value of the pore diameter.
本発明の芳香族ポリアミド多孔質膜の厚みは、６〜４０μｍであることが好ましく、より好ましくは１０〜４０μｍである。６μｍ未満であると強度が不足し、加工時にフィルムの破断が起きたり、セパレータとして使用した際に電極間が短絡する可能性がある。４０μｍを超えるとセパレータとして使用した際に内部抵抗の上昇により出力が低下したり、電池内に組み込める活物質層の厚みが薄くなり容量が小さくなることがある。 The thickness of the aromatic polyamide porous membrane of the present invention is preferably 6 to 40 μm, more preferably 10 to 40 μm. If the thickness is less than 6 μm, the strength may be insufficient, and the film may be broken during processing, or the electrodes may be short-circuited when used as a separator. When it exceeds 40 μm, when used as a separator, the output may decrease due to an increase in internal resistance, or the thickness of the active material layer that can be incorporated into the battery may become thin, resulting in a decrease in capacity.
本発明の芳香族ポリアミド多孔質膜は、一方の表面から膜の厚み方向２μｍまでの層、もう一方の表面から膜の厚み方向２μｍまでの層、および厚み方向中心部の厚み２μｍの層の３領域における空孔率の標準偏差が０．０〜５．０％であることが好ましい。より好ましくは０．０〜４．０％であり、さらに好ましくは０．０〜３．０％である。標準偏差は各値のばらつきを表す尺度であり、３領域における空孔率が同値である場合、標準偏差は０．０％である。空孔率の標準偏差が５．０％を超えると、多孔質膜中の厚み方向における空孔率の斑が大きく、空孔率の大きい領域と小さい領域が生じる。その結果、空孔率の小さい領域のイオン透過が律速となり、十分なイオン伝導性が得られないことがある。また、このイオン透過が律速となる領域でイオンが停滞するため、充放電を繰り返した際にＬｉ金属の析出が起こりやすくなり、微小短絡などが起きることがある。さらに、空孔率の小さい領域において電解液の保液量が少なく、充放電を繰り返した際に液枯れによる性能低下が起きることがある。空孔率の標準偏差を上記範囲内とするため、製膜原液処方、多孔化方法、特に多孔化時の製膜原液温度の制御を後述の方法で行うことが好ましい。なお、上記した３領域のうち、厚み方向中心部の厚み２μｍの層とは、厚み方向の中点から両表面方向に各々１μｍ進んだところを境界とする層である。 The aromatic polyamide porous membrane of the present invention comprises a layer from one surface to a thickness direction of 2 μm, a layer from the other surface to a thickness direction of 2 μm, and a layer having a thickness of 2 μm at the center in the thickness direction. The standard deviation of the porosity in the region is preferably 0.0 to 5.0%. More preferably, it is 0.0-4.0%, More preferably, it is 0.0-3.0%. The standard deviation is a scale representing the variation of each value, and when the porosity in the three regions is the same value, the standard deviation is 0.0%. When the standard deviation of the porosity exceeds 5.0%, the unevenness of the porosity in the thickness direction in the porous film is large, and a region having a large porosity and a region having a small porosity are generated. As a result, ion permeation in a region with a low porosity becomes rate limiting, and sufficient ion conductivity may not be obtained. In addition, since ions stagnate in a region where the ion permeation is rate-determining, Li metal is likely to be deposited when charging and discharging are repeated, and a micro short circuit may occur. Furthermore, the amount of the electrolyte solution retained is small in the region where the porosity is small, and performance degradation may occur due to liquid drainage when charging and discharging are repeated. In order to set the standard deviation of the porosity within the above range, it is preferable to control the film-forming stock solution formulation and the porosity forming method, particularly the film-forming stock solution temperature at the time of porosity formation by the method described later. Of the three regions described above, the layer having a thickness of 2 μm at the central portion in the thickness direction is a layer having a boundary at a position advanced by 1 μm from the middle point in the thickness direction in both surface directions.
本発明の芳香族ポリアミド多孔質膜は、電解液の吸い上げ性が１０〜２００ｍｍ／１０ｍｉｎであることが好ましい。より好ましくは３０〜２００ｍｍ／１０ｍｉｎ、さらに好ましくは５０〜２００ｍｍ／１０ｍｉｎである。電解液の吸い上げ性が１０ｍｍ／１０ｍｉｎ未満であると、電池用セパレータとして使用した際、部分的に電解液が不足したときに平均化が速やかに行われず、液枯れによる性能低下が起きることがある。また、吸い上げ性が１０ｍｍ／１０ｍｉｎ未満である場合、面方向のイオン透過経路が不十分となることが予想され、イオン伝導が効率良く行われず、出力やサイクル特性が低下することがある。上限は特に定めないが、測定法上２００ｍｍ／１０ｍｉｎを超えることは困難である。吸い上げ性を上記範囲内とするため、製膜原液の処方、多孔化方法を後述の範囲内とし、高空孔率かつ緻密な孔構造を形成することが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has an electrolyte uptake of 10 to 200 mm / 10 min. More preferably, it is 30-200 mm / 10min, More preferably, it is 50-200 mm / 10min. When the electrolyte absorbability is less than 10 mm / 10 min, when used as a battery separator, when the electrolyte is partially insufficient, averaging is not performed quickly, and performance degradation due to liquid drainage may occur. . Further, when the wicking property is less than 10 mm / 10 min, it is expected that the ion transmission path in the plane direction is insufficient, ion conduction is not performed efficiently, and output and cycle characteristics may be deteriorated. Although the upper limit is not particularly defined, it is difficult to exceed 200 mm / 10 min in the measurement method. In order to make the wicking property within the above range, it is preferable to set the formulation of the film-forming stock solution and the method for making the pores within the ranges described later, and to form a highly porous and dense pore structure.
本発明の芳香族ポリアミド多孔質膜は、ガーレ透気度が０．５〜３００秒／１００ｍｌであることが好ましい。より好ましくは０．５〜２００秒／１００ｍｌであり、さらに好ましくは０．５〜１５０秒／１００ｍｌである。ガーレ透気度が０．５秒／１００ｍｌより小さいと強度が著しく低下し、３００秒／１００ｍｌより大きいとイオン伝導の抵抗が大きく、電池用セパレータとして使用した際に十分な出力が得られないことがある。ガーレ透気度を上記範囲内とするため、製膜原液処方、多孔化方法を後述のとおりとし、厚み方向に均一な孔構造であり、高抵抗の領域を形成させないことが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has a Gurley air permeability of 0.5 to 300 seconds / 100 ml. More preferably, it is 0.5-200 seconds / 100 ml, More preferably, it is 0.5-150 seconds / 100 ml. If the Gurley air permeability is less than 0.5 sec / 100 ml, the strength is significantly reduced. If the Gurley permeability is greater than 300 sec / 100 ml, the resistance of ionic conduction is large, and sufficient output cannot be obtained when used as a battery separator. There is. In order to make the Gurley air permeability within the above-mentioned range, it is preferable that the film-forming stock solution formulation and the porosity forming method are as described later, have a uniform pore structure in the thickness direction, and do not form a high-resistance region.
本発明の芳香族ポリアミド多孔質膜は、２００℃における長手方向（ＭＤ）および幅方向（ＴＤ）の熱収縮率のいずれもが−０．５〜２．０％、より好ましくは−０．５〜１．０％であることが好ましい。熱収縮率が２．０％を超える場合、電池の異常発熱時にセパレータの収縮により、電池端部において短絡が起こることがある。熱収縮率を上記範囲内とするため、本発明の芳香族ポリアミド多孔質膜は、芳香族ポリアミドの芳香環がパラ配向性を有しているものが全芳香環の５０モル％以上を占めていることが好ましい。また、製膜原液処方、多孔化方法を後述のとおりとし、緻密かつ均一な孔構造を形成させることが好ましい。さらに、熱処理時にリラックスを施すことも効果的である。 In the aromatic polyamide porous membrane of the present invention, both the heat shrinkage in the longitudinal direction (MD) and the width direction (TD) at 200 ° C. are −0.5 to 2.0%, more preferably −0.5. It is preferable that it is -1.0%. When the thermal shrinkage rate exceeds 2.0%, a short circuit may occur at the end of the battery due to the shrinkage of the separator during abnormal heat generation of the battery. In order to make the heat shrinkage rate within the above range, in the aromatic polyamide porous membrane of the present invention, the aromatic polyamide aromatic ring having para-orientation accounts for 50 mol% or more of the total aromatic ring. Preferably it is. Moreover, it is preferable to make the film-forming stock solution formulation and the porosity forming method as described later to form a dense and uniform pore structure. Furthermore, it is effective to relax during the heat treatment.
本発明の芳香族ポリアミド多孔質膜は、少なくとも一方向のヤング率が３００ＭＰａ以上であることが好ましい。ヤング率が高いことにより、薄膜化しても、加工時のハンドリング性を良好に保つことができる。また、電池用セパレータとして使用する際、充放電によりセパレータが圧迫されても、構造を維持することができる。ヤング率は５００ＭＰａ以上であることがより好ましく、７００ＭＰａ以上であることがさらに好ましい。上限は特に定めることはないが、多孔質膜であれば一般的に１０ＧＰａ程度が限界である。ヤング率を上記範囲内とするため、本発明の芳香族ポリアミドは、芳香環がパラ配向性を有しているものが全芳香環の５０モル％以上を占めていることが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has a Young's modulus in at least one direction of 300 MPa or more. Due to the high Young's modulus, it is possible to maintain good handling properties during processing even if the film thickness is reduced. Further, when used as a battery separator, the structure can be maintained even if the separator is pressed by charge / discharge. The Young's modulus is more preferably 500 MPa or more, and further preferably 700 MPa or more. The upper limit is not particularly defined, but generally about 10 GPa is the limit if it is a porous film. In order for the Young's modulus to be within the above range, it is preferable that the aromatic polyamide of the present invention has 50% by mole or more of the aromatic ring in which the aromatic ring has para-orientation.
本発明の芳香族ポリアミド多孔質膜は、少なくとも一方向の破断点応力が１０ＭＰａ以上であることが好ましい。破断点応力が１０ＭＰａ未満の場合、加工時の高張力、張力変動などによりフィルムが破断し、生産性が低下することがある。生産性がより良くなることから、破断点応力は２０ＭＰａ以上であることがより好ましく、３０ＭＰａ以上であることがさらに好ましい。上限は特に定めることはないが、多孔質膜であれば一般的に１ＧＰａ程度が限界である。破断点応力を上記範囲内とするため、本発明の芳香族ポリアミドは、芳香環がパラ配向性を有しているものが全芳香環の５０モル％以上を占めていることが好ましい。 The aromatic polyamide porous membrane of the present invention preferably has a stress at break in at least one direction of 10 MPa or more. When the stress at break is less than 10 MPa, the film may be broken due to high tension and fluctuation in tension during processing, and productivity may be reduced. From the viewpoint of improving productivity, the stress at break is more preferably 20 MPa or more, and further preferably 30 MPa or more. The upper limit is not particularly defined, but generally about 1 GPa is the limit if it is a porous film. In order to make the stress at break within the above range, it is preferable that the aromatic polyamide of the present invention has 50% by mole or more of the aromatic ring in which the aromatic ring has para-orientation.
本発明の芳香族ポリアミド多孔質膜は、長手方向（ＭＤ）および幅方向（ＴＤ）の破断点伸度がいずれも５％以上であることが好ましい。伸度が高いことにより、加工工程でのフィルム破れを低減することができ、高速で加工することが可能となる。また、電池用セパレータとして使用する際、充放電時の電極の膨張収縮に破断することなく追随でき、電池の耐久性や安全性が確保できる。加工性、耐久性、および安全性がより向上することから、破断伸度は２０％以上であることがより好ましく、４０％以上であることがさらに好ましい。上限は特に定めることはないが、多孔質膜であれば一般的に２００％程度が限界である。破断点伸度を上記範囲内とするため、製膜原液処方、多孔化方法を後述のとおりとし、緻密かつ均一な孔構造を形成させることが好ましい。さらに、熱処理条件を後述する条件で施し、その際にリラックスを施すことも効果的である。 The aromatic polyamide porous membrane of the present invention preferably has an elongation at break in the longitudinal direction (MD) and the width direction (TD) of 5% or more. Since the elongation is high, film breakage in the processing step can be reduced, and processing at high speed becomes possible. Further, when used as a battery separator, the battery can follow the expansion and contraction of the electrode during charge and discharge without breaking, and the durability and safety of the battery can be ensured. Since workability, durability, and safety are further improved, the breaking elongation is more preferably 20% or more, and further preferably 40% or more. The upper limit is not particularly defined, but generally about 200% is the limit for porous membranes. In order to make the elongation at break within the above-mentioned range, it is preferable to form a dense and uniform pore structure by setting the film forming stock solution formulation and the pore forming method as described later. Furthermore, it is also effective to apply heat treatment conditions under the conditions described later, and to relax at that time.
次に、本発明の芳香族ポリアミド多孔質膜の製造方法について、以下説明する。 Next, the manufacturing method of the aromatic polyamide porous membrane of this invention is demonstrated below.
まず、芳香族ポリアミドの重合方法として、例えば、酸クロライドとジアミンから得る場合には、Ｎ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルアセトアミド、ジメチルホルムアミド、ジメチルスルホキシド等の非プロトン性有機極性溶媒中で溶液重合により合成する方法や、水系媒体を使用する界面重合で合成する方法等をとることができる。ただし、ポリマーの分子量を制御しやすいことから、非プロトン性有機極性溶媒中での溶液重合が好ましい。 First, as a method for polymerizing an aromatic polyamide, for example, when it is obtained from an acid chloride and a diamine, an aprotic organic polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylformamide, dimethylsulfoxide, etc. Among them, a method of synthesis by solution polymerization, a method of synthesis by interfacial polymerization using an aqueous medium, and the like can be employed. However, solution polymerization in an aprotic organic polar solvent is preferable because the molecular weight of the polymer can be easily controlled.
溶液重合の場合、フィルムの自己支持性が発現するのに必要な分子量のポリマーを得るために、重合に使用する溶媒の水分率を５００ｐｐｍ以下（質量基準、以下同様）とすることが好ましく、２００ｐｐｍ以下とすることがより好ましい。使用するジアミン及び酸クロライドは、純度の高いものを用いることは言うまでもないが、両者を等量用いると超高分子量のポリマーが生成する傾向にあるため、モル比を、一方が他方の９７．０〜９９．５％、より好ましくは９８．０〜９９．０％になるように調整することが好ましい。また、芳香族ポリアミドの重合反応は発熱を伴うが、重合中の溶液の温度を４０℃以下にすることが好ましい。４０℃を超えると、副反応が起きて、重合度が十分に上がらないことがある。重合中の溶液の温度は３０℃以下にすることがより好ましい。さらに、重合反応に伴って塩化水素が副生するが、これを中和する場合には炭酸リチウム、炭酸カルシウム、水酸化カルシウムなどの無機の中和剤、またエチレンオキサイド、プロピレンオキサイド、アンモニア、トリエチルアミン、トリエタノールアミン、ジエタノールアミン等の有機の中和剤を使用するとよい。本発明の芳香族ポリアミド多孔質膜を得るためにはポリマーの対数粘度ηｉｎｈ（ポリマー０．５ｇを９８質量％硫酸中で１００ｍｌの溶液として３０℃で測定した値）は、０．５（ｄｌ／ｇ）以上であることが、多孔質膜とした時に剛性、靱性が高く、ハンドリング性が良くなるので好ましい。対数粘度は１．０以上であることがより好ましく、２．０以上であることがさらに好ましい。 In the case of solution polymerization, in order to obtain a polymer having a molecular weight necessary for developing the self-supporting property of the film, the water content of the solvent used for the polymerization is preferably 500 ppm or less (mass basis, the same applies hereinafter), and 200 ppm More preferably, it is as follows. Needless to say, the diamine and acid chloride to be used are of high purity, but if they are used in an equal amount, an ultrahigh molecular weight polymer tends to be formed, so that the molar ratio is 97.0 for the other. It is preferable to adjust it to ˜99.5%, more preferably 98.0 to 99.0%. The polymerization reaction of the aromatic polyamide is accompanied by heat generation, but the temperature of the solution during polymerization is preferably 40 ° C. or lower. When it exceeds 40 degreeC, a side reaction may occur and polymerization degree may not fully go up. The temperature of the solution during polymerization is more preferably 30 ° C. or lower. In addition, hydrogen chloride is produced as a by-product of the polymerization reaction. When neutralizing this, inorganic neutralizers such as lithium carbonate, calcium carbonate, calcium hydroxide, ethylene oxide, propylene oxide, ammonia, triethylamine are used. Organic neutralizers such as triethanolamine and diethanolamine may be used. In order to obtain the aromatic polyamide porous membrane of the present invention, the logarithmic viscosity η inh of the polymer (value measured at 30 ° C. as a 100 ml solution in 98% by mass sulfuric acid in 0.5 g of polymer) is 0.5 (dl / G) or more is preferable because the rigidity and toughness are high when the porous film is formed, and the handling property is improved. The logarithmic viscosity is more preferably 1.0 or more, and further preferably 2.0 or more.
次に、本発明の芳香族ポリアミド多孔質膜の製膜原液（以下、単に製膜原液ということがある。）について、説明する。 Next, a raw film forming solution for the aromatic polyamide porous membrane of the present invention (hereinafter sometimes simply referred to as a film forming raw solution) will be described.
本発明の芳香族ポリアミド多孔質膜の製膜原液には重合後のポリマー溶液をそのまま使用してもよく、あるいはポリマーを一度単離してから上述の非プロトン性有機極性溶媒や硫酸などの無機溶剤に再溶解して使用してもよい。芳香族ポリアミドを単離する方法としては、特に限定しないが、重合後の芳香族ポリアミド溶液を多量の水中に投入することで溶媒および中和塩を水中に抽出し、析出した芳香族ポリアミドのみを分離した後、乾燥させる方法などが挙げられる。また、再溶解時に溶解助剤として金属塩などを添加してもよい。金属塩としては、非プロトン性有機極性溶媒に溶解するアルカリ金属またはアルカリ土類金属のハロゲン化物が好ましく、例えば、塩化リチウム、臭化リチウム、塩化ナトリウム、臭化ナトリウム、塩化カリウム、臭化カリウム等が挙げられる。製膜原液１００質量部中の芳香族ポリアミドの含有量は、１０〜２０質量部が好ましく、より好ましくは１０〜１５質量部である。 The polymer solution after polymerization may be used as it is for the raw material solution for forming the aromatic polyamide porous membrane of the present invention, or the polymer is once isolated and then the above-mentioned aprotic organic polar solvent or inorganic solvent such as sulfuric acid. It may be redissolved and used. The method for isolating the aromatic polyamide is not particularly limited, but the solvent and neutralized salt are extracted into water by introducing the polymerized aromatic polyamide solution into a large amount of water, and only the precipitated aromatic polyamide is removed. The method of drying after isolate | separating is mentioned. Further, a metal salt or the like may be added as a dissolution aid during re-dissolution. The metal salt is preferably an alkali metal or alkaline earth metal halide dissolved in an aprotic organic polar solvent, such as lithium chloride, lithium bromide, sodium chloride, sodium bromide, potassium chloride, potassium bromide, etc. Is mentioned. The content of the aromatic polyamide in 100 parts by mass of the film-forming stock solution is preferably 10 to 20 parts by mass, more preferably 10 to 15 parts by mass.
本発明の芳香族ポリアミド多孔質膜の製膜原液には孔形成能を向上させる目的で、親水性ポリマーを混合してもよい。親水性ポリマーを混合することで、製膜原液からの多孔質化の過程において、芳香族ポリアミド分子の凝集を抑え、孔形成を誘起し、気孔率を本発明の範囲とすることができる。混合する親水性ポリマーは芳香族ポリアミド１００質量部に対して１０〜３００質量部であることが好ましい。製膜原液における親水性ポリマーの含有量が芳香族ポリアミド１００質量部に対して１０質量部未満の場合、多孔質化の際に芳香族ポリアミド分子が凝集し、孔構造が制御できず、気孔率が本発明の範囲内とならないことがあり、含有量が芳香族ポリアミド１００質量部に対して３００質量部を超える場合、最終的に多孔質膜中の親水性ポリマーの残存量が多くなり耐熱性や剛性の低下、親水性ポリマーの電解液中への溶出などが起きることがある。本発明に用いる親水性ポリマーとしては、非プロトン性有機極性溶媒に溶解するポリマーのうち、極性の置換基、特に、水酸基、アシル基およびアミノ基からなる群から選ばれる少なくとも１種の置換基を含有するポリマーであることが好ましい。このようなポリマーとして、例えば、ポリビニルピロリドン（以下、ＰＶＰと記すことがある。）、ポリエチレングリコール、ポリビニルアルコール、ポリアクリルアミド、ポリアクリル酸、ポリエチレンイミン等が挙げられるが、芳香族ポリアミドとの相溶性が良いＰＶＰを用いることがより好ましい。さらに、本発明で用いるＰＶＰとしては重量平均分子量２０万〜２００万であることが好ましい。重量平均分子量が２０万未満であると、低分子量のＰＶＰが多孔質膜に残った場合、多孔質膜の耐熱性が低下したり、セパレータとして使用した際にＰＶＰが電解液中に溶出したりする恐れがある。重量平均分子量が２００万を超えると、製膜原液の溶液粘度が上昇し、生産性が低下したり、透気性が低下することがある。親水性ポリマーは重合後の芳香族ポリアミド溶液あるいは再溶解した芳香族ポリアミド溶液中に投入しても、単離した芳香族ポリアミドとともに非プロトン性有機極性溶媒中に投入してもよい。 For the purpose of improving the pore forming ability, a hydrophilic polymer may be mixed in the stock solution for forming the aromatic polyamide porous membrane of the present invention. By mixing the hydrophilic polymer, it is possible to suppress the agglomeration of the aromatic polyamide molecules and induce pore formation in the process of making the porous film from the film-forming stock solution, and to set the porosity within the range of the present invention. The hydrophilic polymer to be mixed is preferably 10 to 300 parts by mass with respect to 100 parts by mass of the aromatic polyamide. When the content of the hydrophilic polymer in the raw film forming solution is less than 10 parts by mass with respect to 100 parts by mass of the aromatic polyamide, the aromatic polyamide molecules aggregate when making the porous structure, the pore structure cannot be controlled, and the porosity May not fall within the scope of the present invention, and when the content exceeds 300 parts by mass with respect to 100 parts by mass of the aromatic polyamide, the residual amount of the hydrophilic polymer in the porous membrane will eventually increase, resulting in heat resistance. In some cases, a decrease in rigidity and elution of hydrophilic polymer into the electrolyte may occur. The hydrophilic polymer used in the present invention includes at least one substituent selected from the group consisting of a polar substituent, particularly a hydroxyl group, an acyl group, and an amino group, among polymers dissolved in an aprotic organic polar solvent. It is preferable that it is a polymer to contain. Examples of such polymers include polyvinyl pyrrolidone (hereinafter sometimes referred to as PVP), polyethylene glycol, polyvinyl alcohol, polyacrylamide, polyacrylic acid, polyethyleneimine, etc., but are compatible with aromatic polyamides. It is more preferable to use good PVP. Furthermore, the PVP used in the present invention preferably has a weight average molecular weight of 200,000 to 2,000,000. When the weight average molecular weight is less than 200,000, when low molecular weight PVP remains in the porous membrane, the heat resistance of the porous membrane is reduced, or when used as a separator, PVP is eluted into the electrolyte solution. There is a fear. When the weight average molecular weight exceeds 2 million, the solution viscosity of the film-forming stock solution increases, and the productivity may decrease or the air permeability may decrease. The hydrophilic polymer may be introduced into the aromatic polyamide solution after polymerization or the redissolved aromatic polyamide solution, or may be introduced into the aprotic organic polar solvent together with the isolated aromatic polyamide.
また、多孔質膜の静摩擦係数を低減し加工性を向上させる目的で、製膜原液に無機粒子または有機粒子を添加し、表面に突起を形成してもよい。 Further, for the purpose of reducing the static friction coefficient of the porous film and improving the workability, inorganic or organic particles may be added to the film forming stock solution to form protrusions on the surface.
上記のようにして調製された製膜原液は、いわゆる溶液製膜法により、多孔質膜化が行われる。溶液製膜による多孔質膜化の方法として、代表的には湿式法、析出法などが挙げられるが、凝固浴を用いる湿式法では、厚み方向で孔の形状が異なったり、膜表面に緻密な被膜層が形成されたり、凝固条件の変動で孔構造にバラツキが生じる場合がある。そのため、孔構造を本発明の範囲内とするには、多孔質膜の孔構造を任意に制御しやすい析出法で製膜することが好ましい。 The film-forming stock solution prepared as described above is made into a porous film by a so-called solution film-forming method. Typical examples of the method for forming a porous film by solution casting include a wet method and a deposition method. However, in the wet method using a coagulation bath, the shape of the pores varies in the thickness direction or the film surface is dense. A coating layer may be formed or the pore structure may vary due to fluctuations in solidification conditions. Therefore, in order to make the pore structure within the scope of the present invention, it is preferable to form a film by a deposition method in which the pore structure of the porous membrane can be arbitrarily controlled.
析出法による多孔質膜化を行う場合、まず、製膜原液を口金やダイコーターを用いて、支持体上にキャスト（流延）し、膜形状とする。次に析出による孔構造形成を行うが、その方法として、調温調湿雰囲気下で吸湿させて析出させる方法、冷却によりポリマーの溶解性を低下させて相分離または析出させる方法、霧状の水を吹き付けて析出させる方法などが挙げられる。これらの中で、調温調湿雰囲気下で吸湿させる方法が、水の供給速度および量を細かく制御可能で、均質な多孔質構造を短時間で形成させることができることから、より好ましい。 When forming a porous film by the precipitation method, first, the film-forming stock solution is cast (cast) on a support using a die or a die coater to obtain a film shape. Next, the pore structure is formed by precipitation. As a method for this, a method of absorbing and precipitating in a temperature-controlled humidity atmosphere, a method of decreasing the solubility of the polymer by cooling to cause phase separation or precipitation, or atomized water The method of spraying and depositing is mentioned. Among these, a method of absorbing moisture in a temperature-controlled humidity atmosphere is more preferable because the supply rate and amount of water can be finely controlled and a homogeneous porous structure can be formed in a short time.
調温調湿雰囲気下で吸湿させて孔構造を形成させる方法では、雰囲気の温度を２０〜８０℃、相対湿度を５０〜９５％ＲＨとすることが好ましい。温度が２０℃未満では、絶対湿度が低く、吸湿によるポリマーの析出が穏やかに進行する結果、多孔質化に時間を要し、孔構造の粗大化や厚み方向の孔構造の不均一化が進行することがある。また、生産性が低下することがある。８０℃を超えると表面の吸湿が急激に起こることで緻密な層ができ、孔構造およびガーレ透気度が本発明の範囲外となることや、貫通孔が形成されないことがある。また、相対湿度が５０％ＲＨ未満では、吸湿よりも溶媒の乾燥が進行することで多孔質構造が形成されないことがあり、９５％ＲＨを超えると、表面の吸湿が急激に起こることで緻密な層ができて、孔構造およびガーレ透気度が本発明の範囲外となることや、貫通孔が形成されないことがある。 In the method of absorbing moisture in a temperature-controlled and humidity-controlled atmosphere to form a pore structure, it is preferable that the temperature of the atmosphere is 20 to 80 ° C. and the relative humidity is 50 to 95% RH. If the temperature is less than 20 ° C, the absolute humidity is low, and polymer precipitation due to moisture absorption proceeds gently. As a result, it takes time to make it porous, and the pore structure becomes coarser and the pore structure becomes uneven in the thickness direction. There are things to do. In addition, productivity may be reduced. When the temperature exceeds 80 ° C., moisture absorption on the surface suddenly occurs to form a dense layer, and the pore structure and Gurley air permeability may be out of the scope of the present invention, or through holes may not be formed. In addition, when the relative humidity is less than 50% RH, the porous structure may not be formed due to the drying of the solvent rather than the moisture absorption. When the relative humidity exceeds 95% RH, moisture absorption on the surface occurs rapidly and becomes dense. A layer may be formed, and the pore structure and Gurley air permeability may be out of the scope of the present invention, or the through hole may not be formed.
ここで、多孔質膜の孔構造を、本発明の範囲を満たす緻密かつ厚み方向に均一なものとする方法について説明する。吸湿によりポリマーを析出させる方法は、ポリマーと水との間に相分離を誘起させることで孔構造を得るものであり、形成される孔構造の大きさは、ポリマーの析出が完了し、構造が固定化されるまでの相分離の進行度によって決まる。また、吸湿の方法として、支持体にキャストした膜を支持体に接していない表面側から吸湿させるため、水濃度は表面側から上昇していき、ポリマーの移動度が高いとポリマーはより安定な裏面側（支持体側）に移動する。その結果、厚み方向にポリマーの濃度勾配が生じ、支持体に接していない側（表面側）の孔構造が粗大となり、支持体に接している側の孔構造が極めて緻密あるいは閉塞した構造となることがある。以上のことから、孔構造の肥大化および厚み方向の孔構造の不均一化を抑制する方法の一つとして、溶液の温度を低く抑えた状態で速やかに構造を固定化することが挙げられる。一方で、吸湿の際、水と溶媒との溶解熱により製膜原液の温度は大きく上昇するため、この温度上昇を抑制することが重要な要素となる。 Here, a method for making the pore structure of the porous membrane dense and uniform in the thickness direction that satisfies the scope of the present invention will be described. In the method of precipitating a polymer by moisture absorption, a pore structure is obtained by inducing phase separation between the polymer and water. The size of the pore structure formed is such that the precipitation of the polymer is completed and the structure is It depends on the degree of progress of phase separation until immobilization. Also, as a method of moisture absorption, the membrane cast on the support is absorbed from the surface side not in contact with the support, so the water concentration increases from the surface side, and the polymer is more stable when the polymer mobility is high. Move to the back side (support side). As a result, a polymer concentration gradient occurs in the thickness direction, the pore structure on the side not in contact with the support (surface side) becomes coarse, and the pore structure on the side in contact with the support becomes extremely dense or closed. Sometimes. From the above, as one method for suppressing the enlargement of the pore structure and the non-uniformity of the pore structure in the thickness direction, it is possible to quickly fix the structure while keeping the temperature of the solution low. On the other hand, when the moisture is absorbed, the temperature of the film-forming stock solution greatly increases due to the heat of dissolution of water and the solvent. Therefore, it is important to suppress this temperature increase.
吸湿による製膜原液温度の上昇を抑制する方法としては、吸湿工程において連続的に支持体を冷却する方法、支持体を熱容量の大きいものとする方法などが挙げられる。生産性の点から、支持体を熱容量の大きいものとする方法がより好ましい。なお、調温調湿雰囲気の温度条件を低くすることも考えられるが、製膜原液温度の上昇を抑制する効果が限定的であり、また、雰囲気の絶対湿度が低下し析出までの時間が長くなる結果、構造の粗大化や不均一化が進行することがあるため、適用に関しては限定的である。連続的に支持体を冷却する方法を用いる場合、支持体に熱伝導性が１０Ｗ／ｍ・Ｋ以上のものを用いることが好ましい。このような支持体として、例えば、アルミニウム（熱伝導性２０４Ｗ／ｍ・Ｋ）、ステンレス（熱伝導率１７Ｗ／ｍ・Ｋ）などが挙げられる。一方、支持体を熱容量の大きいものとする方法を用いる場合、支持体の表面積１ｍ２あたりの熱容量が１．０ｋＪ／Ｋ以上のものを用いることが好ましい。２．０ｋＪ／Ｋ以上であることがより好ましく、３．０ｋＪ／Ｋ以上であることがさらに好ましい。支持体の熱容量は支持体の素材（これにより比熱と密度が決まる。）および厚みで制御できる。このような支持体として、例えば、ガラスを用いる場合は厚み０．５ｍｍ（表面積１ｍ２あたりの熱容量１．１ｋＪ／Ｋ）以上、ステンレス（ＳＵＳ３０４、ＳＵＳ３１６）を用いる場合は厚み０．３ｍｍ（表面積１ｍ２あたりの熱容量１．４ｋＪ／Ｋ）以上のものが挙げられる。また、支持体全体としての熱容量が上記範囲内であれば、異素材を積層したものを用いても良い。 Examples of a method for suppressing an increase in the temperature of the film forming stock solution due to moisture absorption include a method of continuously cooling the support in the moisture absorption step, a method of increasing the heat capacity of the support, and the like. From the viewpoint of productivity, a method in which the support has a large heat capacity is more preferable. Although it is conceivable to lower the temperature condition of the temperature and humidity control atmosphere, the effect of suppressing an increase in the temperature of the film forming stock solution is limited, and the absolute humidity of the atmosphere decreases and the time until precipitation is long. As a result, the coarsening and non-uniformity of the structure may progress, and the application is limited. When the method of continuously cooling the support is used, it is preferable to use a support having a thermal conductivity of 10 W / m · K or more. Examples of such a support include aluminum (thermal conductivity 204 W / m · K), stainless steel (thermal conductivity 17 W / m · K), and the like. On the other hand, when using the method of making the support have a large heat capacity, it is preferable to use a support having a heat capacity of 1.0 kJ / K or more per 1 m 2 of the surface area of the support. It is more preferably 2.0 kJ / K or more, and further preferably 3.0 kJ / K or more. The heat capacity of the support can be controlled by the material of the support (which determines the specific heat and density) and the thickness. As such a support, for example, when glass is used, the thickness is 0.5 mm (heat capacity 1.1 kJ / K per 1 m 2 surface area) or more, and when stainless steel (SUS304, SUS316) is used, the thickness is 0.3 mm (surface area 1 m). The heat capacity per 2 is 1.4 kJ / K) or more. In addition, if the heat capacity of the entire support is within the above range, a laminate of different materials may be used.
調温調湿雰囲気下で析出した芳香族ポリアミド膜は、支持体ごとあるいは支持体から剥離して湿式浴に導入され、溶媒、取り込まれなかった親水性ポリマー、および無機塩等の添加剤の除去が行われる。浴組成は特に限定されないが、水、あるいは有機溶媒／水の混合系を用いることが、経済性、取扱いの容易さから好ましい。また、湿式浴中には無機塩が含まれていてもよい。この時、同時に延伸あるいはリラックスを行ってもよいし、フィルムの幅方向を把持せずに湿式浴に導入し、自由収縮させてもよい。 The aromatic polyamide film deposited in a temperature-controlled and humidity-controlled atmosphere is peeled off from the support or from the support and introduced into a wet bath to remove solvents, hydrophilic polymers that have not been incorporated, and additives such as inorganic salts. Is done. The bath composition is not particularly limited, but it is preferable to use water or an organic solvent / water mixed system in view of economy and ease of handling. Further, the wet bath may contain an inorganic salt. At this time, stretching or relaxation may be performed at the same time, or the film may be introduced into a wet bath without gripping the width direction of the film and freely contracted.
湿式浴温度は、溶媒等を効率的に除去できることから、２０℃以上であることが好ましい。浴温度が２０℃未満であると、溶媒が残存し、熱処理時に突沸して靱性を低下させたり、取り込まれなかった親水性ポリマーが残存し、セパレータとして使用した際に電解液中へ溶出することがある。浴温度の上限は特に定めることはないが、水の蒸発や沸騰による気泡の発生の影響を考えると、９０℃までに抑えることが効率的である。導入時間は、１〜２０分にすることが好ましい。 The wet bath temperature is preferably 20 ° C. or higher because the solvent and the like can be efficiently removed. When the bath temperature is less than 20 ° C, the solvent remains, and bumping occurs during heat treatment to reduce toughness, or the hydrophilic polymer that has not been taken in remains, and is eluted into the electrolyte when used as a separator. There is. Although the upper limit of the bath temperature is not particularly defined, it is efficient to suppress the temperature to 90 ° C. in consideration of the generation of bubbles due to water evaporation or boiling. The introduction time is preferably 1 to 20 minutes.
次に、脱溶媒を終えた多孔質膜は、テンターなどで熱処理が行われる。この時、まず１００〜２１０℃で予備乾燥させた後、２２０〜３００℃で高温熱処理を施すことが、靱性と耐熱性を両立させるために好ましい。ここで、予備乾燥はポリマー内部に取り込まれている水分を、高温での熱処理前に取り除く目的で行う。予備乾燥温度が１００℃未満であると、ポリマー内部の水分まで取り除くことができず、次工程の高温での熱処理時に水分が突沸し発泡することで破断伸度などの機械特性が低下することがある。一方で、２１０℃を超えると、予備乾燥時に内部の水分が突沸し、機械特性が低下することがある。乾燥温度は上記範囲内において高い方が好ましく、より好ましくは１５０〜２１０℃である。さらに、予備乾燥を親水性ポリマーのガラス転移温度以上（例えばＰＶＰを用いる場合、１８０℃以上）で施すと、内部に含有する水分をより効率的に除去でき、次工程で高温熱処理を施しても機械特性の低下を抑えることができるため、最も好ましい。 Next, the porous film that has been desolvated is heat-treated with a tenter or the like. At this time, after preliminarily drying at 100 to 210 ° C., it is preferable to perform high-temperature heat treatment at 220 to 300 ° C. in order to achieve both toughness and heat resistance. Here, the preliminary drying is performed for the purpose of removing moisture taken in the polymer before the heat treatment at a high temperature. If the pre-drying temperature is less than 100 ° C., moisture inside the polymer cannot be removed, and mechanical properties such as elongation at break may deteriorate due to water bumping and foaming during heat treatment at a high temperature in the next step. is there. On the other hand, if it exceeds 210 ° C., the internal moisture may bump up during the preliminary drying, and the mechanical properties may deteriorate. The drying temperature is preferably higher within the above range, more preferably 150 to 210 ° C. Furthermore, when pre-drying is performed at a temperature higher than the glass transition temperature of the hydrophilic polymer (for example, 180 ° C. or higher when PVP is used), moisture contained therein can be removed more efficiently, and high-temperature heat treatment is performed in the next step. Since it is possible to suppress a decrease in mechanical properties, it is most preferable.
予備乾燥後の高温熱処理は２２０〜３００℃で施すのが好ましい。高温熱処理温度が２２０℃未満であると、耐熱性が不十分となり、熱収縮率が大きくなることがある。高温熱処理温度が高いほど耐熱性は向上するが、３００℃を超えると、ポリマーの分解などにより、破断伸度などの機械特性が低下することがある。また、この時、幅方向への延伸およびリラックスが施されてもよい。 The high temperature heat treatment after the preliminary drying is preferably performed at 220 to 300 ° C. When the high-temperature heat treatment temperature is less than 220 ° C., the heat resistance may be insufficient and the heat shrinkage rate may be increased. The higher the high-temperature heat treatment temperature, the better the heat resistance. However, when the temperature exceeds 300 ° C., mechanical properties such as elongation at break may be deteriorated due to polymer decomposition. At this time, stretching in the width direction and relaxation may be performed.
本発明の芳香族ポリアミド多孔質膜は、高空孔率でありながら緻密な孔構造を有し、かつその孔構造が厚み方向に均一であるため、リチウムイオン二次電池などの電池用セパレータとして好適に使用できる。本発明の芳香族ポリアミド多孔質膜を電池用セパレータとして用いた場合、イオン伝導が効率良く行われるため優れた出力特性が得られるとともに、長期使用時のリチウム金属析出による孔の閉塞、微小短絡、電解液の枯渇を抑制することができ、電池容量の低下を低減することができる。 The aromatic polyamide porous membrane of the present invention has a high porosity and a dense pore structure, and the pore structure is uniform in the thickness direction. Therefore, it is suitable as a separator for batteries such as lithium ion secondary batteries. Can be used for When the aromatic polyamide porous membrane of the present invention is used as a battery separator, excellent output characteristics can be obtained because ionic conduction is efficiently performed, pore clogging due to lithium metal deposition during long-term use, micro short circuit, The depletion of the electrolytic solution can be suppressed, and the decrease in battery capacity can be reduced.
［物性の測定方法ならびに効果の評価方法］
実施例における物性の測定方法は次の方法に従って行った。
[Methods for measuring physical properties and methods for evaluating effects]
The physical properties were measured in the examples according to the following method.
（１）細孔径分布
以下の条件の下、水銀圧入法を用いて求めた。
(1) Pore size distribution It calculated | required using the mercury intrusion method under the following conditions.
装置 ：オートポアＩＶ９５１０（マイクロメリティックス社製）
水銀圧入圧力 ：約４ｋＰａ〜４００ＭＰａ
測定細孔直径 ：約４ｎｍ〜１０μｍ
測定モード ：昇圧（圧入）過程
測定セル容積 ：約５，０００ｍｍ３
水銀接触角 ：１４１．３°
水銀表面張力 ：４．８４Ｎ／ｍ
試料体積 ：５０〜１００ｍｍ３
得られた細孔径分布から、各細孔パラメータを求めた。
Apparatus: Autopore IV9510 (manufactured by Micromeritics)
Mercury pressure: about 4 kPa to 400 MPa
Measurement pore diameter: about 4 nm to 10 μm
Measurement mode: Pressurization (press-fit) process Measurement cell volume: Approximately 5,000 mm 3
Mercury contact angle: 141.3 °
Mercury surface tension: 4.84 N / m
Sample volume: 50 to 100 mm 3
Each pore parameter was determined from the obtained pore size distribution.
Ａ．気孔率
下式により求めた。
A. Porosity Calculated by the following formula.
気孔率（％）＝（Ｖｐ×Ｗ×１００）／Ｖ
Ｖｐ：解析範囲内の累積細孔・間隙容積（ｍｍ３／ｇ）
Ｗ：試料重量（ｇ）
Ｖ：試料体積（ｍｍ３）
Ｂ．ピーク直径
縦軸を対数微分細孔容積、横軸を細孔直径として細孔径分布曲線をプロットし、解析範囲内の分布ピークトップ直径をピーク直径とした。ピークが複数ある場合は対数微分細孔容積が最大のものをピークとした。ここで、対数微分細孔容積（またはｌｏｇ微分細孔容積）とは、測定点間の細孔容積の増加分である差分細孔容積ｄＶを、細孔径の対数扱いの差分値ｄ（ｌｏｇＤ）で除した値であり、ｄＶ／ｄ（ｌｏｇＤ）で表される。
Porosity (%) = (V p × W × 100) / V
V p : Cumulative pore / gap volume within the analysis range (mm 3 / g)
W: Sample weight (g)
V: Sample volume (mm 3 )
B. Peak diameter The logarithmic differential pore volume is plotted on the vertical axis and the pore diameter distribution curve is plotted with the horizontal axis being the pore diameter, and the distribution peak top diameter within the analysis range is taken as the peak diameter. When there were a plurality of peaks, the peak with the largest logarithmic differential pore volume was taken as the peak. Here, the logarithmic differential pore volume (or log differential pore volume) is a difference pore volume dV that is an increase in pore volume between measurement points, and a difference value d (logD) that is a logarithm of pore diameter. It is a value divided by and expressed by dV / d (logD).
Ｃ．最大細孔直径と最小細孔直径の差
縦軸を対数微分細孔容積、横軸を細孔直径として細孔径分布曲線をプロットし、解析範囲内に存在する最大細孔直径と最小細孔直径の差を求めることで、多孔質膜中の細孔径の分布幅を評価した。ここで、ノイズを除去するため、対数微分細孔容積が０．２ｃｍ２／ｇ以上である細孔に限定して評価を行った。
C. Difference between the maximum and minimum pore diameters Plot the pore size distribution curve with the logarithmic differential pore volume on the vertical axis and the pore diameter on the horizontal axis, and the maximum and minimum pore diameters existing in the analysis range The distribution width of the pore diameter in the porous membrane was evaluated by calculating the difference between the two. Here, in order to remove noise, evaluation was limited to pores having a logarithmic differential pore volume of 0.2 cm 2 / g or more.
（２）膜厚
定圧厚み測定器ＦＦＡ−１（尾崎製作所製）を用いて、測定子径５ｍｍ、測定荷重１．２５Ｎで測定した。幅方向に、２０ｍｍ間隔で１０箇所測定し、平均値を求めた。ここで、平均値とは相加平均により求めた値のことをいう。（以下、特に断りのない限りにおいて、同様である。）
（３）空孔率の標準偏差
初めに、以下の条件の下、試料の長手方向−厚み方向断面および幅方向−厚み方向断面の断面像を得た。
(2) Film thickness Using a constant pressure thickness measuring instrument FFA-1 (manufactured by Ozaki Mfg. Co., Ltd.), the film thickness was measured with a probe diameter of 5 mm and a measurement load of 1.25 N. Ten points were measured at intervals of 20 mm in the width direction, and the average value was obtained. Here, an average value means the value calculated | required by the arithmetic mean. (The same applies hereinafter unless otherwise specified.)
(3) Standard Deviation of Porosity First, cross-sectional images of a longitudinal direction-thickness direction cross section and a width direction-thickness direction cross section of the sample were obtained under the following conditions.
装置 ：透過型電子顕微鏡Ｈ−７１００ＦＡ（日立社製）
加速電圧 ：１００ｋＶ
試料調製 ：超薄切片法（空孔部：樹脂包埋）
得られた断面像のうち、一方の表面から膜の厚み方向２μｍまでの層、もう一方の表面から膜の厚み方向２μｍまでの層、および厚み方向中心部の厚み２μｍの層の各層の、長手方向（または幅方向）に５μｍの領域について解析を行い、空孔の面積を解析領域の面積（１０μｍ２）で除することで各層の空孔率を求めた。各層の空孔率は、長手方向−厚み方向断面から求めた値と幅方向−厚み方向断面から求めた値の平均値とした。
Apparatus: Transmission electron microscope H-7100FA (manufactured by Hitachi)
Acceleration voltage: 100 kV
Sample preparation: Ultra-thin section method (hole part: resin embedding)
Among the obtained cross-sectional images, the length of each layer of the layer from one surface to the thickness direction of 2 μm, the layer from the other surface to the thickness direction of 2 μm, and the layer having a thickness of 2 μm at the center in the thickness direction The region of 5 μm in the direction (or the width direction) was analyzed, and the porosity of each layer was determined by dividing the area of the pores by the area of the analysis region (10 μm 2 ). The porosity of each layer was an average value of a value obtained from the longitudinal direction-thickness direction cross section and a value obtained from the width direction-thickness direction cross section.
解析は、画像解析ソフト「ＩｍａｇｅＪ １．４４ｐ」（アメリカ国立衛生研究所）を用いて、以下の手順で行った。まず、８ビット化した各画像について、空孔部と構成ポリマー部との二値化処理を行った。二値化処理における閾値設定のパラメータとして、「Ｄｅｆａｕｌｔ」を使用した。次に、スケール設定を行った後、計測条件を「Ｌｉｍｉｔ ｔｏ Ｔｈｒｅｓｈｏｌｄ」として、「Ｍｅａｓｕｒｅ」により、ポリマー部のみの面積を求めた。 The analysis was performed by the following procedure using image analysis software “ImageJ 1.44p” (National Institutes of Health, USA). First, for each 8-bit image, binarization processing of a hole portion and a constituent polymer portion was performed. “Default” was used as a threshold setting parameter in the binarization process. Next, after setting the scale, the area of only the polymer portion was determined by “Measure” with the measurement condition “Limit to Threshold”.
各層について得られた空孔率から下式により標準偏差を求めた。 The standard deviation was calculated from the porosity obtained for each layer according to the following equation.
標準偏差（％）＝［｛Σ（Ｘｉ−Ｘａｖ）２｝／ｎ］０．５
Ｘｉ（ｉ＝１，２，３，・・・，ｎ）：各データ
Ｘａｖ：平均値
ｎ：データ数（ここではｎ＝３）。
Standard deviation (%) = [{Σ (X i −X av ) 2 } / n] 0.5
X i (i = 1, 2, 3,..., N): Each data X av : Average value n: Number of data (here, n = 3).
（４）電解液吸い上げ性
試験液を水からエチレンカーボネート３０質量部、ジメチルカーボネート７０質量部の混合液に変更した以外は、ＪＩＳ−Ｐ８１４１（２００４）に規定された方法を用いて測定した。
(4) Electrolyte wicking property Measured using the method defined in JIS-P8141 (2004) except that the test solution was changed from water to a mixed solution of 30 parts by mass of ethylene carbonate and 70 parts by mass of dimethyl carbonate.
（５）ガーレ透気度
Ｂ型ガーレーデンソメーター（安田精機製作所製）を使用し、ＪＩＳ−Ｐ８１１７（１９９８）に規定された方法に従って測定を行った。試料の多孔質膜を直径２８．６ｍｍ、面積６４５ｍｍ２の円孔に締め付け、内筒により（内筒質量５６７ｇ）、筒内の空気を試験円孔部から筒外へ通過させ、空気１００ｍｌが通過する時間を測定することでガーレ透気度とした。
(5) Gurley air permeability A B-type Gurley Densometer (manufactured by Yasuda Seiki Seisakusho) was used, and measurement was performed according to the method defined in JIS-P8117 (1998). The porous membrane of the sample is clamped to a circular hole with a diameter of 28.6 mm and an area of 645 mm 2 , and the air inside the cylinder is passed from the test hole to the outside of the cylinder by the inner cylinder (inner cylinder mass 567 g), and 100 ml of air passes. The Gurley air permeability was determined by measuring the time to perform.
（６）熱収縮率
試料の多孔質膜を、幅１０ｍｍ、長さ２２０ｍｍの短冊状に、長辺が測定方向になるように切り取った。長辺の両端から約１０ｍｍの部分に印をつけ、印の間隔をＬ１とした。２００℃の熱風オーブン中で１０分間、実質的に張力を掛けない状態で熱処理を行った後の印の間隔をＬ２とし、次式で計算した。フィルムの長手方向および幅方向にそれぞれ５回測定し、それぞれ平均値を求めた。
(6) Thermal contraction rate The porous film of the sample was cut into a strip shape having a width of 10 mm and a length of 220 mm so that the long side was in the measurement direction. Marked from both ends of the long side portion approximately 10 mm, the distance between the marks was L 1. 200 ° C. 10 min in a hot air oven, a distance between the mark after the heat treatment with no over substantially tension and L 2, was calculated by the following equation. The film was measured five times in the longitudinal direction and in the width direction, and the average value was obtained.
熱収縮率（％）＝（（Ｌ１−Ｌ２）／Ｌ１）×１００。 Thermal contraction rate (%) = ((L 1 −L 2 ) / L 1 ) × 100.
（７）ヤング率、破断点応力、破断点伸度
幅１０ｍｍ、長さ１５０ｍｍに切断したフィルムを、ロボットテンシロンＡＭＦ／ＲＴＡ−１００（オリエンテック製）を用いてチャック間距離５０ｍｍ、引張速度３００ｍｍ／分、温度２３℃、相対湿度６５％の条件下で引張試験を行うことで求めた。フィルムの長手方向および幅方向にそれぞれ５回測定し、それぞれの値について平均値を求めた。
(7) Young's modulus, stress at break, elongation at break 10 mm in width, 150 mm in length using robot Tensilon AMF / RTA-100 (manufactured by Orientec), distance between chucks 50 mm, tensile speed 300 mm / It was determined by conducting a tensile test under the conditions of minute, temperature 23 ° C. and relative humidity 65%. The film was measured five times in the longitudinal direction and in the width direction, and the average value was determined for each value.
（８）電池評価
以下の通り、リチウムイオン二次電池を作製し、評価を行った。
(8) Battery evaluation A lithium ion secondary battery was prepared and evaluated as follows.
・正極
コバルト酸リチウム（ＬｉＣｏＯ２、日本化学工業社製）８９．５質量部と、アセチレンブラック（電気化学工業社製）４．５質量部およびポリフッ化ビニリデン（ＰＶｄＦ、クレハ社製）の乾燥質量が６質量部となるように、６質量％のＰＶｄＦのＮ−メチル−２−ピロリドン（ＮＭＰ）溶液を用い、正極剤ペーストを作製した。得られたペーストを集電体である厚さ２０μｍのアルミニウム箔上に塗布、乾燥後、直径１３ｍｍの円形に打ち抜き加工を行うことで正極を得た。
・ Positive electrode Lithium cobaltate (LiCoO 2 , manufactured by Nippon Kagaku Kogyo Co., Ltd.) 89.5 parts by mass, acetylene black (Electrochemical Co., Ltd.) 4.5 parts by mass and polyvinylidene fluoride (PVdF, manufactured by Kureha Co., Ltd.) A positive electrode paste was prepared using 6% by mass of an N-methyl-2-pyrrolidone (NMP) solution of PVdF in an amount of 6 parts by mass. The obtained paste was applied to a 20 μm thick aluminum foil as a current collector, dried, and then punched into a circle having a diameter of 13 mm to obtain a positive electrode.
・負極
メソフェーズカーボンマイクロビーズ（ＭＣＭＢ、大阪ガスケミカル社製）８７質量部と、アセチレンブラック３質量部およびＰＶｄＦの乾燥質量が１０質量部となるように、６質量％のＰＶｄＦのＮＭＰ溶液を用い、負極剤ペーストを作製した。得られたペーストを集電体である厚さ１８μｍの銅箔上に塗布、乾燥後、直径１４．５ｍｍの円形に打ち抜き加工を行うことで負極を得た。
-Negative electrode Mesophase carbon microbeads (MCMB, manufactured by Osaka Gas Chemical Co., Ltd.) 87 parts by mass, acetylene black 3 parts by mass and PVdF dry mass of 10 parts by mass, using 6% by mass PVdF NMP solution, A negative electrode paste was prepared. The obtained paste was applied onto a 18 μm thick copper foil as a current collector, dried, and then punched into a circle having a diameter of 14.5 mm to obtain a negative electrode.
・電解液
エチレンカーボネート３０質量部、ジメチルカーボネート７０質量部の混合液にＬｉＰＦ６が１ｍｏｌ／Ｌとなるように溶解させたものを用いた。
Electrolytic solution of ethylene carbonate 30 parts by mass, LiPF 6 in a mixture of dimethyl carbonate 70 parts by mass was used dissolved at a 1 mol / L.
・組み立て
封口板の上に上記負極を負極剤が上になるように静置し、上から電解液を注液した。その上に実施例および比較例で作製したセパレータ（直径１７ｍｍの円形）を静置し、さらにセパレータ上から電解液を注液した。次に正極を正極剤が下になるように静置し、ケースを静置した。これをカシメ機で封口し、直径２０ｍｍ、厚み３．２ｍｍのコイン型電池を作製した。
-Assembly The said negative electrode was left still on a sealing board so that a negative electrode agent might become the top, and electrolyte solution was inject | poured from the top. On top of that, the separators (circular shape with a diameter of 17 mm) prepared in Examples and Comparative Examples were allowed to stand, and an electrolytic solution was injected from above the separators. Next, the positive electrode was allowed to stand with the positive electrode agent facing down, and the case was allowed to stand. This was sealed with a caulking machine to produce a coin-type battery having a diameter of 20 mm and a thickness of 3.2 mm.
Ａ．高温サイクル特性
作製した各リチウムイオン二次電池について、１２０℃の雰囲気下、定電流１ｍＡ（０．２Ｃ）で電池電圧が４．２Ｖになるまで充電を行い、充電後、１時間放置した。その後、定電流０．２Ｃで電池電圧が３．０Ｖになるまで放電を行い、放電後、１時間放置した。この充放電を１サイクルとし、１サイクル目の放電容量を基準とし、１００サイクル目の放電容量を以下の基準で評価した。○または△が実用範囲である。
A. High-temperature cycle characteristics Each of the produced lithium ion secondary batteries was charged at a constant current of 1 mA (0.2 C) at 120 ° C. until the battery voltage reached 4.2 V, and left for 1 hour after charging. Thereafter, the battery was discharged at a constant current of 0.2 C until the battery voltage reached 3.0 V, and left for 1 hour after the discharge. This charging / discharging was defined as one cycle, the discharge capacity at the first cycle was used as a reference, and the discharge capacity at the 100th cycle was evaluated according to the following criteria. ○ or Δ is a practical range.
○：８０％以上
△：７０％以上８０％未満
×：７０％未満
Ｂ．高温保存特性
作製した各リチウムイオン二次電池について、１２０℃の雰囲気下、定電流０．２Ｃで電池電圧が４．２Ｖになるまで充電を行い、充電後、１時間放置した。その後、定電流０．２Ｃで電池電圧が３．０Ｖになるまで放電を行い、放電後、１時間放置した。この充放電を１サイクルとし、２サイクル行った後、定電流０．２Ｃで電池電圧が４．２Ｖになるまで充電した。この充電状態の電池を１２０℃の雰囲気下に１０日間放置した。放置後、定電流０．２Ｃで電池電圧が３．０Ｖになるまで放電を行い、放電後、１時間放置した。その後、再度１サイクルの充放電を行い、放電容量を測定した。１０日間放置前の２サイクル目の放電容量を基準とし、放置後の放電容量を以下の基準で評価した。○または△が実用範囲である。
○: 80% or more Δ: 70% or more and less than 80% ×: less than 70% High-temperature storage characteristics Each of the produced lithium ion secondary batteries was charged at a constant current of 0.2 C until the battery voltage reached 4.2 V in an atmosphere of 120 ° C., and left for 1 hour after charging. Thereafter, the battery was discharged at a constant current of 0.2 C until the battery voltage reached 3.0 V, and left for 1 hour after the discharge. This charging / discharging was defined as 1 cycle, and after 2 cycles, the battery was charged at a constant current of 0.2 C until the battery voltage reached 4.2V. The charged battery was left in an atmosphere of 120 ° C. for 10 days. After being left, discharging was performed at a constant current of 0.2 C until the battery voltage reached 3.0 V, and after discharging, the battery was left for 1 hour. Then, 1 cycle charge / discharge was performed again and the discharge capacity was measured. The discharge capacity at the second cycle before standing for 10 days was used as a reference, and the discharge capacity after standing was evaluated according to the following criteria. ○ or Δ is a practical range.
○：８０％以上
△：７０％以上８０％未満
×：７０％未満
以下に実施例に基づいて本発明をより具体的に説明するが、本発明はこれらに限定されるものでない。
○: 80% or more Δ: 70% or more and less than 80% ×: less than 70% The present invention will be described more specifically based on examples below, but the present invention is not limited thereto.
（実施例１）
脱水したＮ−メチル−２−ピロリドン（ＮＭＰ）に、８５モル％に相当する２−クロルパラフェニレンジアミンと１５モル％に相当する４，４’−ジアミノジフェニルエーテルを溶解させ、これに９８．５モル％に相当する２−クロルテレフタル酸クロリドを添加して、３０℃以下で約２時間の撹拌を行い、芳香族ポリアミドを重合した。この重合溶液を炭酸リチウム、ジエタノールアミン、トリエタノールアミンにより中和することで芳香族ポリアミドの溶液を得た。この溶液を水とともにミキサーに投入し、攪拌しながらポリマーを沈殿させて取り出した。取り出したポリマーを水洗し、減圧１２０℃下で２４時間乾燥させ、芳香族ポリアミドを単離した。
Example 1
In dehydrated N-methyl-2-pyrrolidone (NMP), 2-chloroparaphenylenediamine corresponding to 85 mol% and 4,4′-diaminodiphenyl ether corresponding to 15 mol% were dissolved, and 98.5 mol was dissolved in this. % 2-chloroterephthalic acid chloride was added and stirred for about 2 hours at 30 ° C. or lower to polymerize the aromatic polyamide. The polymerization solution was neutralized with lithium carbonate, diethanolamine, and triethanolamine to obtain an aromatic polyamide solution. This solution was poured into a mixer together with water, and the polymer was precipitated while stirring. The polymer taken out was washed with water and dried under reduced pressure at 120 ° C. for 24 hours to isolate the aromatic polyamide.
得られた芳香族ポリアミドおよびポリビニルピロリドン（ＰＶＰ、重量平均分子量１２０万、ＩＳＰ社製）をＮＭＰ中に投入し、６０℃で７時間撹拌することで均一で透明な製膜原液を得た。それぞれの添加量は芳香族ポリアミド１０質量部、ＰＶＰ５質量部、ＮＭＰ８５質量部とした。 The obtained aromatic polyamide and polyvinyl pyrrolidone (PVP, weight average molecular weight 1,200,000, manufactured by ISP) were put into NMP and stirred at 60 ° C. for 7 hours to obtain a uniform and transparent film forming stock solution. Each addition amount was 10 parts by mass of aromatic polyamide, 5 parts by mass of PVP, and 85 parts by mass of NMP.
この製膜原液を、口金から支持体である厚み１ｍｍのステンレス（ＳＵＳ３１６）ベルト上に厚み約５０μｍの膜状に塗布し、温度５０℃、相対湿度８５％ＲＨの調温調湿空気中で１分間、塗布膜が失透するまで処理した。次に、失透した塗布膜をベルトから剥離し、６０℃の水浴に２分間導入することで溶媒の抽出を行った。続いて、テンター中で２００℃において１分、２３０℃において幅方向に５％収縮させながら２分、熱処理を行い、多孔質膜を得た。 This film-forming stock solution is applied in the form of a film having a thickness of about 50 μm from a base to a stainless steel (SUS316) belt having a thickness of 1 mm, which is a support, and is 1 in a temperature-conditioned air with a temperature of 50 ° C. and a relative humidity of 85% RH. Processing was continued for a minute until the coating film was devitrified. Next, the devitrified coating film was peeled off from the belt and introduced into a 60 ° C. water bath for 2 minutes to extract the solvent. Subsequently, heat treatment was performed in a tenter at 200 ° C. for 1 minute and at 230 ° C. for 2 minutes while shrinking 5% in the width direction to obtain a porous film.
得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。 Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例２、３）
塗布厚みを表１に記載の通りとすること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Examples 2 and 3)
A porous membrane was obtained in the same manner as in Example 1 except that the coating thickness was as described in Table 1. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例４）
実施例１と同様の製膜原液を用いて、支持体である厚み０．５ｍｍのステンレス（ＳＵＳ３０４）板上にアプリケーターで厚み約７０μｍの膜状に塗布した。その後、温度５０℃、相対湿度８５％ＲＨの調温調湿空気中で１分間、塗布膜が失透するまで処理した。次に、失透した塗布膜を支持体から剥離し、ステンレス製の枠に固定した後、６０℃の水浴に１０分間浸漬することで溶媒の抽出を行った。続いて、枠に固定したまま、熱風オーブンを用いて２００℃において１分、２３０℃において２分、熱処理を行い、多孔質膜を得た。
Example 4
Using the same film-forming stock solution as in Example 1, it was applied to a support having a thickness of about 70 μm on a 0.5 mm-thick stainless steel (SUS304) plate with an applicator. Then, it processed in the temperature-controlled humidity air of temperature 50 degreeC and relative humidity 85% RH for 1 minute until the coating film devitrified. Next, the devitrified coating film was peeled from the support, fixed to a stainless steel frame, and then immersed in a 60 ° C. water bath for 10 minutes to extract the solvent. Subsequently, heat treatment was performed for 1 minute at 200 ° C. and 2 minutes at 230 ° C. using a hot air oven while being fixed to the frame to obtain a porous film.
得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。 Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例５、６）
支持体を表１に記載の通りとすること以外は実施例４と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Examples 5 and 6)
A porous membrane was obtained in the same manner as in Example 4 except that the support was as shown in Table 1. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例７）
芳香族ポリアミド中の４、４’−ジアミノジフェニルエーテルの量を、ジアミン全量に対して５０モル％とし、製膜原液を芳香族ポリアミド１１質量部、ＰＶＰ５質量部、ＮＭＰ８４質量部とすること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Example 7)
Implemented except that the amount of 4,4′-diaminodiphenyl ether in the aromatic polyamide is 50 mol% with respect to the total amount of the diamine, and the film forming stock solution is 11 parts by mass of aromatic polyamide, 5 parts by mass of PVP, and 84 parts by mass of NMP. In the same manner as in Example 1, a porous membrane was obtained. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例８）
芳香族ポリアミドを、７５モル％に相当する４，４’−ジアミノジフェニルエーテルと２５モル％に相当するパラフェニレンジアミン、および９８．５モル％に相当するイソフタル酸クロライドから重合し、製膜原液を芳香族ポリアミド１２質量部、ＰＶＰ４質量部、ＮＭＰ８４質量部とすること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Example 8)
Aromatic polyamide was polymerized from 4,4′-diaminodiphenyl ether equivalent to 75 mol%, paraphenylenediamine equivalent to 25 mol%, and isophthalic acid chloride equivalent to 98.5 mol%, and the film-forming stock solution was aromatized. A porous membrane was obtained in the same manner as in Example 1 except that 12 parts by mass of the polyamide group, 4 parts by mass of PVP, and 84 parts by mass of NMP were used. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（参考例９）
製膜原液を芳香族ポリアミド１０質量部、ポリエチレングリコール（ＰＥＧ、重量平均分子量３００、第一工業製薬社製）２０質量部、ＮＭＰ７０質量部とし、厚み約１００μｍの膜状に塗布した後、温度２０℃、相対湿度８０％ＲＨの調温調湿空気中で１５分間処理すること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
( Reference Example 9)
The stock solution was applied to 10 parts by weight of aromatic polyamide, 20 parts by weight of polyethylene glycol (PEG, weight average molecular weight 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 70 parts by weight of NMP. A porous membrane was obtained in the same manner as in Example 1 except that the treatment was carried out in a temperature-conditioned air of 15 ° C. and relative humidity of 80% RH for 15 minutes. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例１０）
製膜原液を芳香族ポリアミド１４質量部、ＰＶＰ４質量部、ＮＭＰ８２質量部とすること以外は実施例７と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Example 10)
A porous membrane was obtained in the same manner as in Example 7 except that the membrane-forming stock solution was 14 parts by mass of aromatic polyamide, 4 parts by mass of PVP, and 82 parts by mass of NMP. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例１１）
塗布厚みを２０μｍとすること以外は実施例７と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Example 11)
A porous membrane was obtained in the same manner as in Example 7 except that the coating thickness was 20 μm. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（実施例１２、１３）
調温調湿条件を表１に記載の通りとすること以外は実施例７と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Examples 12 and 13)
A porous membrane was obtained in the same manner as in Example 7 except that the temperature and humidity control conditions were as described in Table 1. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例１〜４）
支持体を表１に記載の通りとすること以外は実施例４と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Examples 1-4)
A porous membrane was obtained in the same manner as in Example 4 except that the support was as shown in Table 1. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例５）
支持体を厚み５０μｍのステンレス（ＳＵＳ３０４）箔とし、温度２０℃、相対湿度８５％ＲＨの調温調湿空気中で２分間処理すること以外は実施例４と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Example 5)
A porous membrane is obtained in the same manner as in Example 4 except that the support is made of stainless steel (SUS304) foil having a thickness of 50 μm and treated in temperature-conditioned air at a temperature of 20 ° C. and a relative humidity of 85% RH for 2 minutes. It was. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例６）
実施例１と同様の製膜原液を用いて、支持体である厚み５ｍｍのガラス板上にアプリケーターで厚み約１００μｍの膜状に塗布した。その後、水５０質量部、ＮＭＰ５０質量部で温度４０℃の凝固液中に浸漬し、失透した塗布膜を支持体から剥離した。以降は実施例４と同様にステンレス製の枠に固定し、水洗、熱処理を行い、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Example 6)
Using the same film-forming stock solution as in Example 1, a film having a thickness of about 100 μm was coated on a glass plate having a thickness of 5 mm as a support with an applicator. Thereafter, the film was immersed in a coagulating liquid having a temperature of 40 ° C. with 50 parts by mass of water and 50 parts by mass of NMP, and the devitrified coating film was peeled off from the support. Thereafter, it was fixed to a stainless steel frame in the same manner as in Example 4, washed with water and heat-treated to obtain a porous membrane. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例７）
製膜原液を芳香族ポリアミド８質量部、ＰＶＰ４質量部、ＮＭＰ８８質量部とすること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Example 7)
A porous membrane was obtained in the same manner as in Example 1 except that the membrane-forming stock solution was 8 parts by mass of aromatic polyamide, 4 parts by mass of PVP, and 88 parts by mass of NMP. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例８）
塗布厚みを１５０μｍとすること以外は実施例１と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Example 8)
A porous membrane was obtained in the same manner as in Example 1 except that the coating thickness was 150 μm. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
（比較例９〜１１）
調温調湿条件を表１に記載の通りとすること以外は実施例７と同様にして、多孔質膜を得た。得られた多孔質膜の、主な製造条件を表１に、評価結果を表２に示す。
(Comparative Examples 9-11)
A porous membrane was obtained in the same manner as in Example 7 except that the temperature and humidity control conditions were as described in Table 1. Table 1 shows the main production conditions of the obtained porous membrane, and Table 2 shows the evaluation results.
本発明の芳香族ポリアミド多孔質膜は、高空孔率でありながら緻密な孔構造を有し、かつその孔構造が厚み方向に均一であるため、リチウムイオン二次電池などの電池用セパレータとして好適に使用できる。本発明の芳香族ポリアミド多孔質膜を電池用セパレータとして用いた場合、イオン伝導が効率良く行われるため優れた出力特性が得られるとともに、長期使用時のリチウム金属析出による孔の閉塞、微小短絡、電解液の枯渇を抑制することができ、電池容量の低下を低減することができる。 The aromatic polyamide porous membrane of the present invention has a high porosity and a dense pore structure, and the pore structure is uniform in the thickness direction. Therefore, it is suitable as a separator for batteries such as lithium ion secondary batteries. Can be used for When the aromatic polyamide porous membrane of the present invention is used as a battery separator, excellent output characteristics can be obtained because ionic conduction is efficiently performed, pore clogging due to lithium metal deposition during long-term use, micro short circuit, The depletion of the electrolytic solution can be suppressed, and the decrease in battery capacity can be reduced.
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