WO2016104743A1 - 多孔質中空糸膜 - Google Patents
多孔質中空糸膜 Download PDFInfo
- Publication number
- WO2016104743A1 WO2016104743A1 PCT/JP2015/086332 JP2015086332W WO2016104743A1 WO 2016104743 A1 WO2016104743 A1 WO 2016104743A1 JP 2015086332 W JP2015086332 W JP 2015086332W WO 2016104743 A1 WO2016104743 A1 WO 2016104743A1
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- WIPO (PCT)
- Prior art keywords
- hollow fiber
- fiber membrane
- porous hollow
- columnar structure
- weight
- Prior art date
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- 239000012528 membrane Substances 0.000 title claims abstract description 273
- 239000012510 hollow fiber Substances 0.000 title claims abstract description 262
- 229920000642 polymer Polymers 0.000 claims abstract description 111
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 75
- 238000001816 cooling Methods 0.000 claims description 63
- 238000001069 Raman spectroscopy Methods 0.000 claims description 53
- 238000005259 measurement Methods 0.000 claims description 32
- 238000000034 method Methods 0.000 claims description 28
- 238000009826 distribution Methods 0.000 claims description 23
- 239000011550 stock solution Substances 0.000 claims description 21
- 238000004519 manufacturing process Methods 0.000 claims description 18
- 238000005191 phase separation Methods 0.000 claims description 17
- 239000013078 crystal Substances 0.000 claims description 16
- 238000002425 crystallisation Methods 0.000 claims description 16
- 230000008025 crystallization Effects 0.000 claims description 16
- 238000004736 wide-angle X-ray diffraction Methods 0.000 claims description 11
- 239000002033 PVDF binder Substances 0.000 claims description 10
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 8
- 238000002145 thermally induced phase separation Methods 0.000 claims description 8
- 230000035699 permeability Effects 0.000 abstract description 10
- 239000008213 purified water Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 63
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 56
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 56
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 56
- 229920001519 homopolymer Polymers 0.000 description 56
- 239000007864 aqueous solution Substances 0.000 description 40
- 239000002904 solvent Substances 0.000 description 32
- 239000002585 base Substances 0.000 description 26
- 229920005989 resin Polymers 0.000 description 22
- 239000011347 resin Substances 0.000 description 22
- 230000000717 retained effect Effects 0.000 description 15
- 238000011282 treatment Methods 0.000 description 15
- 239000011800 void material Substances 0.000 description 14
- 239000007788 liquid Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000000126 substance Substances 0.000 description 10
- 239000007787 solid Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- 229920001577 copolymer Polymers 0.000 description 6
- 239000003822 epoxy resin Substances 0.000 description 6
- 229920000647 polyepoxide Polymers 0.000 description 6
- 238000000746 purification Methods 0.000 description 6
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 239000008235 industrial water Substances 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 239000000178 monomer Substances 0.000 description 5
- 239000012071 phase Substances 0.000 description 5
- 230000010287 polarization Effects 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000003651 drinking water Substances 0.000 description 4
- 235000020188 drinking water Nutrition 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000000605 extraction Methods 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 229910052731 fluorine Inorganic materials 0.000 description 4
- 239000011737 fluorine Substances 0.000 description 4
- 239000000155 melt Substances 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-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
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- 239000002202 Polyethylene glycol Substances 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 238000010612 desalination reaction Methods 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000010884 ion-beam technique Methods 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 239000012046 mixed solvent Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 239000013535 sea water Substances 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- RFFLAFLAYFXFSW-UHFFFAOYSA-N 1,2-dichlorobenzene Chemical compound ClC1=CC=CC=C1Cl RFFLAFLAYFXFSW-UHFFFAOYSA-N 0.000 description 2
- FFWSICBKRCICMR-UHFFFAOYSA-N 5-methyl-2-hexanone Chemical compound CC(C)CCC(C)=O FFWSICBKRCICMR-UHFFFAOYSA-N 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 238000003841 Raman measurement Methods 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- CREMABGTGYGIQB-UHFFFAOYSA-N carbon carbon Chemical compound C.C CREMABGTGYGIQB-UHFFFAOYSA-N 0.000 description 2
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- 238000004043 dyeing Methods 0.000 description 2
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Natural products OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- HJOVHMDZYOCNQW-UHFFFAOYSA-N isophorone Chemical compound CC1=CC(=O)CC(C)(C)C1 HJOVHMDZYOCNQW-UHFFFAOYSA-N 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910052762 osmium Inorganic materials 0.000 description 2
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 2
- 239000004014 plasticizer Substances 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000009987 spinning Methods 0.000 description 2
- 150000005846 sugar alcohols Polymers 0.000 description 2
- 238000004781 supercooling Methods 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- PUPZLCDOIYMWBV-UHFFFAOYSA-N (+/-)-1,3-Butanediol Chemical compound CC(O)CCO PUPZLCDOIYMWBV-UHFFFAOYSA-N 0.000 description 1
- AVQQQNCBBIEMEU-UHFFFAOYSA-N 1,1,3,3-tetramethylurea Chemical compound CN(C)C(=O)N(C)C AVQQQNCBBIEMEU-UHFFFAOYSA-N 0.000 description 1
- 241000223935 Cryptosporidium Species 0.000 description 1
- 238000005169 Debye-Scherrer Methods 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
- 239000005977 Ethylene Substances 0.000 description 1
- 239000005708 Sodium hypochlorite Substances 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000001154 acute effect Effects 0.000 description 1
- 125000001931 aliphatic group Chemical group 0.000 description 1
- 150000001338 aliphatic hydrocarbons Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000003899 bactericide agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 150000008280 chlorinated hydrocarbons Chemical class 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 230000015271 coagulation Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000113 differential scanning calorimetry Methods 0.000 description 1
- 230000008034 disappearance Effects 0.000 description 1
- 239000012153 distilled water Substances 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
- 239000003792 electrolyte Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- XUCNUKMRBVNAPB-UHFFFAOYSA-N fluoroethene Chemical compound FC=C XUCNUKMRBVNAPB-UHFFFAOYSA-N 0.000 description 1
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000001891 gel spinning Methods 0.000 description 1
- HCDGVLDPFQMKDK-UHFFFAOYSA-N hexafluoropropylene Chemical group FC(F)=C(F)C(F)(F)F HCDGVLDPFQMKDK-UHFFFAOYSA-N 0.000 description 1
- ACCCMOQWYVYDOT-UHFFFAOYSA-N hexane-1,1-diol Chemical compound CCCCCC(O)O ACCCMOQWYVYDOT-UHFFFAOYSA-N 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 244000000010 microbial pathogen Species 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- BNIXVQGCZULYKV-UHFFFAOYSA-N pentachloroethane Chemical compound ClC(Cl)C(Cl)(Cl)Cl BNIXVQGCZULYKV-UHFFFAOYSA-N 0.000 description 1
- UWJJYHHHVWZFEP-UHFFFAOYSA-N pentane-1,1-diol Chemical compound CCCCC(O)O UWJJYHHHVWZFEP-UHFFFAOYSA-N 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 238000009287 sand filtration Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000010186 staining Methods 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- -1 trichloroethylene, ethylene Chemical group 0.000 description 1
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 1
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 description 1
- 238000000108 ultra-filtration Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/34—Polyvinylidene fluoride
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
- B01D67/00113—Pretreatment of the casting solutions, e.g. thermal treatment or ageing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0013—Casting processes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0016—Coagulation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0016—Coagulation
- B01D67/00165—Composition of the coagulation baths
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0018—Thermally induced processes [TIPS]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
- B01D67/0025—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching
- B01D67/0027—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching by stretching
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
- B01D69/087—Details relating to the spinning process
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D2323/10—Specific pressure applied
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D2325/00—Details relating to properties of membranes
- B01D2325/02—Details relating to pores or porosity of the membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/02—Details relating to pores or porosity of the membranes
- B01D2325/0281—Fibril, or microfibril structures
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/24—Mechanical properties, e.g. strength
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/30—Chemical resistance
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
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- B01D2325/32—Melting point or glass-transition temperatures
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/34—Molecular weight or degree of polymerisation
Definitions
- the present invention relates to a porous hollow fiber membrane suitable for various water treatments such as drinking water production, industrial water production, water purification treatment, wastewater treatment, seawater desalination, industrial water production and the like.
- porous membranes have been used in various fields such as water treatment fields such as water purification and wastewater treatment, medical applications such as blood purification, food industry, battery separators, charged membranes, fuel cell electrolyte membranes, etc. .
- water treatment such as water purification treatment, wastewater treatment and seawater desalination
- a porous membrane is used. Since the amount of treated water is large in these fields, if the water permeability of the porous membrane is excellent, it is possible to reduce the membrane area, and the equipment can be reduced because the device is compact, and the membrane replacement cost and installation area can be reduced. It becomes advantageous also from a point.
- porous membrane for water treatment one according to the size of the substance to be separated contained in the water to be treated is used.
- natural water contains many turbid components
- ultrafiltration membranes for removing turbid components in water are generally used.
- bactericides such as sodium hypochlorite are added to the separation membrane module for the purpose of sterilization of permeated water and biofouling of the separation membrane, and hydrochloric acid, citric acid,
- the separation membrane may be washed with an acid such as oxalic acid, an alkali such as an aqueous sodium hydroxide solution, chlorine, or a surfactant. Therefore, in recent years, a separation membrane using a fluororesin polymer represented by polyvinylidene fluoride has been developed and used as a material having high chemical resistance.
- Patent Document 1 discloses a wet solution method using a fluororesin polymer. Specifically, in Patent Document 1, a polymer solution in which a fluororesin-based polymer is dissolved in a good solvent is extruded from a die at a temperature considerably lower than the melting point of the fluororesin-based polymer, and the polymer solution is removed from the fluororesin-based polymer. An asymmetric porous structure is formed by contact with a liquid containing a non-solvent of the molecule by non-solvent-induced phase separation.
- the wet solution method has a problem that it is difficult to cause phase separation uniformly in the film thickness direction, and the strength is not sufficient because the film has an asymmetric three-dimensional network structure including macrovoids. Further, since there are many film forming condition factors to give to the film structure and film performance, there are drawbacks that the film forming process is difficult to control and the reproducibility is poor.
- Patent Document 2 discloses a melt extraction method. Specifically, Patent Document 2 describes the following method. A film-forming stock solution is obtained by melt-kneading inorganic fine particles and an organic liquid in a fluororesin polymer. This film-forming stock solution is extruded from the die at a temperature equal to or higher than the melting point of the fluororesin polymer, and then cooled and solidified. Thereafter, a porous structure is formed by extracting the organic liquid and the inorganic fine particles.
- the melt extraction method it is easy to control the porosity, and a film having a relatively homogeneous three-dimensional network structure is obtained without forming macrovoids. However, the strength is not sufficient, and if the dispersibility of the inorganic fine particles is poor, defects such as pinholes may occur. Furthermore, the melt extraction method has the disadvantage that the production cost is extremely high.
- Patent Document 3 also discloses a melt extraction method.
- two types of fluororesin-based polymers having different weight average molecular weights are used, a plasticizer and a good solvent are added, melt extruded into a hollow fiber membrane, the plasticizer is extracted after cooling and solidification, and further stretched Thus, a porous hollow fiber membrane in which a mixture of crystal orientation parts and crystal non-orientation parts is observed is obtained.
- Patent Document 4 a fluororesin polymer containing a fluororesin polymer and a poor solvent thereof and having a temperature equal to or higher than the phase separation temperature is discharged into a cooling bath below the phase separation temperature and solidified to form a hollow fiber membrane.
- a method of obtaining is disclosed.
- Patent Document 5 a fibrous structure having a diameter of 0.9 ⁇ m or more and 3 ⁇ m or less of a porous hollow fiber membrane made of a fluororesin-based polymer is 30% or more of the entire porous hollow fiber membrane. By occupying it, a porous hollow fiber membrane excellent in strength and pure water permeation performance is obtained.
- the present inventors provide a porous hollow fiber membrane having high strength while maintaining high pure water permeation performance using a fluorine resin polymer having high chemical resistance. Objective.
- the present invention has the following configurations (1) to (11).
- the porous hollow fiber membrane is oriented in the longitudinal direction of the porous hollow fiber membrane, and the molecular chain orientation degree ⁇ calculated based on the following formula (1) is 0.4 or more and less than 1.0.
- the pure water permeation performance at 50 kPa and 25 ° C. is 0.7 m 3 / m 2 / hr or more, and the breaking strength is 25 MPa or more, according to any one of the above (1) to (7) Porous hollow fiber membrane.
- a method for producing a porous hollow fiber membrane comprising the following steps 1) and 2). 1) Porous structure having a columnar structure that is oriented in the length direction by heat-induced phase separation and has a thickness uniformity of 0.60 or more and less than 1.00 from a film-forming stock solution containing a fluororesin polymer. Step of forming hollow fiber 2) Step of stretching the porous hollow fiber obtained in 1) in the longitudinal direction by 2.0 times to 5.0 times (11) Thermally induced phase separation in step 1)
- a porous hollow fiber membrane having both excellent physical durability and high pure water permeation performance while having excellent chemical durability due to a fluorochemical polymer having high chemical resistance.
- FIG. 2 is a diagram showing Raman orientation parameters at each measurement location of the porous hollow fiber membrane of Example 4.
- 3 is a view showing a cross-sectional photograph in the longitudinal direction of the porous hollow fiber membrane of Example 4.
- FIG. 4 is a view showing a cross-sectional photograph in the longitudinal direction of the porous hollow fiber membrane of Comparative Example 1.
- FIG. 2 is a diagram showing Raman orientation parameters at each measurement location of the porous hollow fiber membrane of Example 4.
- 3 is a view showing a cross-sectional photograph in the longitudinal direction of the porous hollow fiber membrane of Example 4.
- FIG. 4 is a view showing a cross-sectional photograph in the longitudinal direction
- porous hollow fiber membrane (1-1) Fluororesin polymer
- the porous hollow fiber membrane of the present invention contains a fluororesin polymer.
- the fluororesin-based polymer means a resin containing at least one of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer.
- the fluororesin polymer may contain a plurality of types of vinylidene fluoride copolymers.
- the vinylidene fluoride copolymer is a polymer having a vinylidene fluoride residue structure, and is typically a copolymer of a vinylidene fluoride monomer and other fluorine-based monomers.
- Examples of such a copolymer include a copolymer of vinylidene fluoride and one or more monomers selected from vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and trichloroethylene chloride. It is done.
- a monomer such as ethylene other than the fluorine-based monomer may be copolymerized to such an extent that the effects of the present invention are not impaired.
- the weight average molecular weight of the fluororesin-based polymer may be appropriately selected depending on the required strength and water permeability of the polymer separation membrane, but as the weight average molecular weight increases, the water permeability performance decreases and the weight average molecular weight decreases. As a result, the strength decreases. For this reason, the weight average molecular weight is preferably from 50,000 to 1,000,000. In the case of a water treatment application where the polymer separation membrane is exposed to chemical cleaning, the weight average molecular weight is preferably from 100,000 to 700,000, more preferably from 150,000 to 600,000.
- the porous hollow fiber membrane preferably contains a fluororesin-based polymer as a main component, and the proportion of the fluororesin-based polymer in the porous hollow fiber membrane is preferably 80% by weight or more, and 90% by weight or more. More preferably, it is more preferably 95% by weight or more. Moreover, the porous hollow fiber membrane may be comprised only with the fluororesin type polymer.
- the “porous hollow fiber membrane containing a fluororesin-based polymer as a main component” is also referred to as “a porous hollow fiber membrane based on a fluororesin-based polymer”. In this specification, the explanation that “X contains Y as a main component” is described for other elements as well, but in these cases, X can be rephrased as “Y based”. .
- the molecular chain of the fluororesin polymer is oriented in the longitudinal direction of the porous hollow fiber membrane.
- orientation degree ⁇ of the molecular chain is 0.4 or more and less than 1.0.
- the degree of orientation ⁇ is calculated from the half width H (°) obtained by wide-angle X-ray diffraction measurement based on the following formula (1).
- Orientation degree ⁇ (180 ° ⁇ H) / 180 ° (1) (However, H is the half width (°) of the diffraction intensity distribution in the circumferential direction of the wide-angle X-ray diffraction image.)
- the orientation of the molecular chain in the longitudinal direction of the porous hollow fiber membrane and the method for measuring the orientation degree ⁇ will be specifically described below.
- it is attached to the fiber sample stage so that the longitudinal direction of the porous hollow fiber membrane is vertical.
- the short direction of the porous hollow fiber membrane is a direction parallel to the radial direction of the hollow fiber
- the long direction is a direction perpendicular to the short direction.
- the short direction can be rephrased as a direction parallel to the hollow surface, that is, the in-plane direction of the hollow surface
- the longitudinal direction can be rephrased as a direction perpendicular to the hollow surface.
- the diffraction angle 2 ⁇ 20.
- a peak can be seen in the vicinity of °.
- the horizontal axis of the diffraction pattern obtained at this time is the X-ray diffraction angle 2 ⁇ , and the vertical axis is the diffraction intensity.
- the horizontal axis indicates the azimuth angle ⁇ and the vertical axis indicates the diffraction pattern (that is, the diffraction intensity).
- a diffraction intensity distribution along the circumferential direction of the Debye ring at a diffraction angle 2 ⁇ 20 °. In the non-oriented sample, the diffraction intensity is substantially constant over the entire 360 ° circumferential direction of the Debye ring.
- the position of the diffraction peak in the radial direction of the Debye ring (that is, the value of 2 ⁇ corresponding to the diffraction peak) is “near 20 °” in the above description.
- the value of 2 ⁇ varies depending on the structure and composition of the polymer and may be in the range of 15 to 25 °.
- the derived diffraction peak is seen.
- the intensity distribution in the azimuth angle direction can be obtained by fixing the value of the diffraction angle 2 ⁇ and further measuring the intensity from 0 ° to 360 ° in the azimuth angle direction (circumferential direction).
- This intensity distribution can be said to be an intensity distribution obtained by scanning a crystal peak in a diffraction image in the circumferential direction.
- a peak is considered to exist.
- a width (half-value width H) at a position half the peak height is obtained.
- the degree of orientation ⁇ is calculated by substituting this half width H into the above equation (1).
- the degree of orientation ⁇ of the molecular chain of the porous hollow fiber membrane of the present invention in the longitudinal direction of the porous hollow fiber membrane is in the range of 0.4 or more and less than 1.0, preferably 0.5 or more and less than 1.0. More preferably, it is 0.6 or more and less than 1.0.
- the degree of orientation ⁇ is 0.4 or more, the mechanical strength of the porous hollow fiber membrane is increased.
- the degree of orientation ⁇ is not less than 0.4 and less than 1.0 at 80% or more of measurement points when the wide-angle X-ray diffraction measurement is performed at measurement points of 1 cm intervals in the longitudinal direction of the porous hollow fiber membrane. Preferably there is.
- the ratio of the intensity at the azimuth angle of 180 ° and the intensity at the azimuth angle of 90 ° exceeds 0.80 and is less than 1.25. Assumes no peak. That is, in this case, it is determined that the fluororesin polymer is non-oriented.
- the orientation of the molecular chain of the present invention can be determined by orientation analysis by Raman spectroscopy.
- the number of measurement points in one columnar structure is a value obtained by dividing the longitudinal length ( ⁇ m) of a columnar structure described later by 1 ⁇ m (rounded down to the nearest decimal point). For example, when the longitudinal length of the columnar structure is 20.5 ⁇ m, the number of measurement points is 20.
- the Raman band near 1270 cm ⁇ 1 belongs to the coupling mode of CF 2 (fluorocarbon) stretching vibration and CC (carbon-carbon) stretching vibration. .
- the vibration direction of these vibrations is a mode parallel to the molecular chain.
- the vibration direction of the Raman band near 840 cm ⁇ 1 is perpendicular to the molecular chain. Since Raman scattering is strongly obtained when the vibration direction of the molecular chain coincides with the polarization direction of the incident light, the ratio of the scattering intensities of these vibration modes changes in correlation with the degree of orientation. For this reason, an orientation parameter is computable by following formula (2).
- the orientation parameter has a larger value as the orientation of the porous hollow fiber membrane in the longitudinal direction is higher, 1 when no orientation is performed, and 1 when the orientation in the lateral direction is high.
- Orientation parameter (I1270 / I840) parallel / (I1270 / I840) vertical (2)
- Parallel condition the longitudinal direction of the porous hollow fiber membrane is parallel to the polarization direction
- Vertical condition the longitudinal direction of the porous hollow fiber membrane is orthogonal to the polarization direction
- I1270 parallel the intensity of the 1270 cm ⁇ 1 Raman band under the parallel condition
- I1270 perpendicular intensity of Raman bands of 1270 cm -1 when the vertical condition
- I840 parallel the intensity of the Raman bands of 840 cm -1 at collinear condition
- I840 vertical the intensity of the Raman bands of 840 cm -1 at a vertical condition.
- the Raman orientation parameter ⁇ of the molecular chain of the porous hollow fiber membrane of the present invention in the longitudinal direction of the porous hollow fiber membrane is preferably 3.0 or more, more preferably 3.4 or more, and still more preferably 3. 7 or more.
- the degree of orientation ⁇ is 3.0 or more, the strength of the porous hollow fiber membrane is increased.
- M and m are considered to represent the main orientation location in the columnar structure and the power point during stretching, respectively. For this reason, considering the balance of the performance of the obtained porous hollow fiber membrane such as strength, elongation, water permeability and the like, M and m may be in an appropriate range. This is preferable because the orientation of the film tends to increase and the strength of the porous hollow fiber membrane tends to increase. Therefore, in the present invention, M / m is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more.
- the degree of orientation ⁇ obtained by wide-angle X-ray diffraction measurement represents the orientation of the molecular chains of the entire porous hollow fiber membrane
- the Raman orientation parameter ⁇ obtained by Raman spectroscopy focuses on the columnar structure of the porous hollow fiber membrane. It tends to represent the orientation of molecular chains when hit, that is, the orientation of local molecular chains.
- the strength of the porous hollow fiber membrane is increased, and the orientation degree ⁇ is in the range of 0.6 or more and less than 1.0, and
- the Raman orientation parameter ⁇ is preferably 3.4 or more, and the degree of orientation ⁇ is in the range of 0.7 or more and less than 1.0, and the Raman orientation parameter ⁇ is 3.7 or more. Is preferred.
- the porous hollow fiber membrane has a columnar structure oriented in the longitudinal direction of the porous hollow fiber membrane.
- a “columnar structure” is a solid that is long in one direction.
- the aspect ratio (longitudinal length / short side length) of the columnar structure is preferably 3 or more.
- longitudinal length refers to the length of the columnar tissue in the longitudinal direction.
- short length is an average length in the short direction of the columnar structure.
- the long length and short length can be measured as follows.
- the hollow fiber membrane is cut along the longitudinal direction of the hollow fiber membrane.
- the obtained cross section is observed using a scanning electron microscope (SEM).
- SEM scanning electron microscope
- the magnification can be changed according to the length of the columnar structure, and is such that five, preferably ten, whole columnar structures are included in the longitudinal direction in the visual field.
- the maximum length in the longitudinal direction may be measured as the longitudinal length.
- the short length is obtained by measuring the length in each short direction at a predetermined number of arbitrary measurement points in one columnar structure and calculating the average value thereof.
- the number of measurement points is a value obtained by dividing the longitudinal length ( ⁇ m) by 1 ⁇ m (rounded down after the decimal point). For example, when the longitudinal length of the columnar structure is 20.5 ⁇ m, the number of measurement points is 20. However, if this value is 21 or more, any 20 locations may be measured.
- the longitudinal length of the columnar structure is not particularly limited, but is preferably 7 ⁇ m or more, more preferably 10 ⁇ m or more, and further preferably 15 ⁇ m or more.
- the longitudinal length of the columnar tissue is preferably, for example, 50 ⁇ m or less, and more preferably 40 ⁇ m or less.
- the short length of the columnar structure is preferably 0.5 ⁇ m or more and 3 ⁇ m or less. It is preferable for the short length to be in the above range since high strength performance and high pure water permeation performance can be obtained. Since the physical strength of the columnar structure itself is increased when the short length of the columnar structure is 0.5 ⁇ m or more, high strength can be obtained. Moreover, since the space
- the short length of the columnar structure is more preferably 0.7 ⁇ m or more and 2.5 ⁇ m or less, and further preferably 1 ⁇ m or more and 2 ⁇ m or less.
- the preferred ranges of the representative values of the longitudinal length and the short length of the columnar structures are respectively the longitudinal lengths and the short lengths of the individual columnar structures described above. It is the same as the preferred range.
- the representative value of the longitudinal length is measured as follows. Similar to the measurement of the longitudinal length, the longitudinal length is measured for 5 columnar structures, preferably 10 columnar structures, at 3 positions, preferably 5 positions in the hollow fiber membrane. By obtaining an average value of the obtained longitudinal length values, it is possible to obtain a representative value of the longitudinal length of the columnar structure.
- the representative value of the short length is obtained by measuring the short length (calculated as an average value) as described above and calculating the average value of the columnar structure that is the target of measurement of the representative value of the long length. Is determined.
- the representative value of the aspect ratio of the columnar structure calculated from the representative value of the longitudinal length and the representative value of the short length is preferably 3 or more, more preferably It is 5 or more, more preferably 10 or more, and particularly preferably 20 or more.
- the short length of the columnar structure is preferably 0.5 ⁇ m or more and 3 ⁇ m or less, and the aspect ratio of the columnar structure is preferably 3 or more.
- the porous hollow fiber membrane of the present invention can be produced by forming a hollow fiber from a film-forming stock solution containing a polymer and stretching the hollow fiber. .
- the state before stretching is called “hollow fiber”, and the state after stretching is called “hollow fiber membrane”.
- Thickness uniformity (average value D described later) of the columnar structure in the hollow fiber membrane after stretching is preferably 0.60 or more, more preferably 0.70 or more, and further preferably 0.80 or more, Especially preferably, it is 0.90 or more.
- the thickness uniformity is 1.0 at the maximum, but the columnar structure may have a thickness uniformity of less than 1.0.
- the columnar structure has high thickness uniformity, that is, the number of constricted portions of the columnar structure is small, so that the elongation of the hollow fiber membrane is increased. It is preferable that the porous hollow fiber membrane after stretching retains a high degree of elongation because it is difficult for the yarn to break even when a sudden load is applied.
- the breaking elongation of the porous hollow fiber membrane is preferably 50% or more, and more preferably 80% or more.
- the thickness uniformity of the columnar structure can be obtained by comparing the first and second cross sections parallel to the short direction of the porous hollow fiber membrane. This will be specifically described below.
- a first cross section and a second cross section that are parallel to each other are selected.
- the distance between the first surface and the second surface is 5 ⁇ m.
- the resin portion and the void portion are distinguished, and the resin portion area and the void portion area are measured.
- the first cross section is projected onto the second cross section, the area of the portion where the resin portion in the first cross section overlaps the resin portion in the second cross section, that is, the overlapping area is obtained.
- thickness uniformity A and B are determined for any 20 sets of the first cross section and the second cross section for one hollow fiber membrane.
- Thickness uniformity A (overlapping area) / (resin partial area of the second cross section) (3)
- Thickness uniformity B (overlap area) / (resin partial area of the first cross section) (4)
- the porous hollow fiber membrane is embedded in advance with an epoxy resin or the like, and the epoxy resin or the like is stained with osmium or the like. It is preferable to process.
- the void portion is filled with epoxy resin or the like, and when the cross-section processing by the focused ion beam described later, the portion made of fluororesin-based polymer and the void portion (that is, epoxy resin portion) ) Can be clearly distinguished from each other, and the observation accuracy is increased.
- a scanning electron microscope (SEM) equipped with a focused ion beam (FIB) may be used.
- SEM scanning electron microscope
- FIB focused ion beam
- a plane parallel to the short side direction of the porous hollow fiber membrane is cut out using FIB, and cutting and SEM observation by FIB are repeated 200 times at 50 nm intervals in the longitudinal direction of the porous hollow fiber membrane.
- Information of a depth of 10 ⁇ m can be obtained by such continuous section observation.
- interval of 5 micrometers are selected, and thickness uniformity is calculated
- the observation magnification may be any magnification that allows a columnar structure and a spherical structure to be clearly confirmed. For example, a magnification of 1000 to 5000 may be used.
- the columnar structure contains a fluororesin polymer.
- the columnar structure preferably contains a fluororesin polymer as a main component, and the proportion of the fluororesin polymer in the columnar structure is preferably 80% by weight or more, more preferably 90% by weight or more, and 95% by weight. It is still more preferable that it is above.
- the columnar structure may be composed of only a fluororesin polymer.
- the porous hollow fiber membrane has a solid content containing a fluororesin polymer, and at least a part of the solid content constitutes a columnar structure.
- All of the solid content containing the fluororesin-based polymer may constitute a columnar structure, or a part thereof may have a shape that does not correspond to the columnar structure.
- the proportion of the solid content of the fluororesin polymer is preferably 80% by weight or more, more preferably 90% by weight or more, and 95% by weight. It is still more preferable that it is above.
- the main structure is preferably a columnar structure.
- the proportion of the columnar structure is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more.
- the porous hollow fiber membrane may be comprised only by the columnar structure
- the porous hollow fiber membrane can also be expressed as an assembly of columnar structures.
- orienting in the longitudinal direction means that the acute angle of the longitudinal direction of the columnar structure and the longitudinal direction of the porous hollow fiber membrane is within 20 degrees.
- the porous hollow fiber membrane of the present invention has a porosity of preferably 40% or more and 90% or less, and preferably 50% or more and 80% or less in order to achieve both high pure water permeability and high strength. More preferably, it is 50% or more and 70% or less.
- the porosity of the porous hollow fiber membrane is obtained by the following formula (5) using the resin partial area and the void partial area in the cross section described above.
- Porosity (%) ⁇ 100 ⁇ (void partial area) ⁇ / ⁇ (resin partial area) + (void partial area) ⁇ (5)
- the porous hollow fiber membrane of the present invention may contain a structure other than the columnar structure described above without departing from the object of the present invention.
- Examples of the structure other than the columnar structure include a spherical structure having an aspect ratio (long length / short length) of less than 3.
- the short length and the long length of the spherical structure are preferably in the range of 0.5 ⁇ m to 3 ⁇ m.
- the proportion of the spherical structure having an aspect ratio of less than 3 in the porous hollow fiber membrane increases, the connection between the spherical structures increases and the constriction increases, making it difficult to stretch at high magnification. In addition, it tends to be difficult to maintain the elongation after stretching. For this reason, the proportion of the spherical structure in the porous hollow fiber membrane is preferably as small as possible, preferably less than 20%, more preferably less than 10%, and even more preferably less than 1%, and none at all. Is the best.
- the occupation ratio (%) of each structure is a magnification at which the columnar structure and the spherical structure can be clearly confirmed using a SEM or the like, preferably 1000 to 5000 times, with respect to the longitudinal section of the porous hollow fiber membrane.
- the image is taken and calculated by the following formula (6).
- Occupancy rate (%) ⁇ (area occupied by each tissue) / (area of the entire photograph) ⁇ ⁇ 100 (6)
- a method of obtaining the area of the entire photograph and the area occupied by the tissue by replacing with the corresponding weight of each photographed tissue can be preferably employed.
- the photographed photograph may be printed on paper, and the weight of the paper corresponding to the entire photograph and the weight of the paper corresponding to the tissue portion cut out from the photograph may be measured.
- the porous hollow fiber membrane of the present invention may be one in which the above-described layer having a columnar structure and a layer having another structure are laminated without departing from the object of the present invention.
- the thickness of a layer having another structure is thicker than that of a layer having a columnar structure, it becomes difficult to exert the object / effect of the present invention.
- the thickness ratio is preferably 0.3 or less, and more preferably 0.2 or less.
- the porous hollow fiber membrane of the present invention preferably has a pure water permeation performance at 50 kPa and 25 ° C. of 0.7 m 3 / m 2 / hr or more and a breaking strength of 25 MPa or more. More preferably, the pure water permeation performance at 50 kPa and 25 ° C. is 0.7 m 3 / m 2 / hr or more, and the breaking strength is 30 MPa or more. In particular, from the viewpoint of achieving a high-performance hollow fiber membrane that achieves both high pure water permeation performance and high strength performance, the pure water permeation performance at 50 kPa and 25 ° C. is 0.7 m 3 / m 2 / hr or more and 5.0 m.
- the breaking strength is preferably in the range of 25 MPa or more and 70 MPa or less, more preferably 50 kPa, pure water permeability at 25 ° C. of 0.7 m 3 / m 2 / hr or more and 5.0 m 3 / m 2 / hr or less, and the breaking strength is in the range of 30 MPa to 70 MPa.
- the pure water permeation performance is measured by producing a 200 mm long miniature module composed of four porous hollow fiber membranes. Under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, the external pressure total filtration of the reverse osmosis membrane filtrate is performed for 10 minutes, and the permeation amount (m 3 ) is obtained. By converting the permeation amount (m 3 ) into a value per unit time (h) and effective membrane area (m 2 ), and further multiplying by (50/16), it is converted into a value at a pressure of 50 kPa to obtain pure water. Find the transmission performance.
- the methods for measuring the breaking strength and breaking elongation are not particularly limited. For example, using a tensile tester, a sample having a measurement length of 50 mm is subjected to a tensile test at a pulling speed of 50 mm / min, and the sample is changed to 5 It can be measured by performing the measurement more than once and obtaining the average value of the breaking strength and the average value of the breaking elongation.
- the porous hollow fiber membrane described above has pure water permeability, strength and elongation sufficient for various water treatments such as drinking water production, industrial water production, water purification treatment, wastewater treatment, seawater desalination, industrial water production, etc. Have.
- the method for producing the porous hollow fiber membrane of the present invention is exemplified below.
- the manufacturing method of the porous hollow fiber membrane is at least: 1) A hollow fiber having a columnar structure which is oriented in the length direction by heat-induced phase separation and has a thickness uniformity of 0.60 or more and less than 1.00 from a film-forming stock solution containing a fluororesin polymer. And 2) a step of stretching the porous hollow fiber obtained in 1) above by 2.0 times or more and 5.0 times or less in the longitudinal direction.
- the method for producing a porous hollow fiber membrane in the present invention further comprises a step of preparing a fluororesin polymer solution. Fluororesin polymer is dissolved in a poor or good solvent of the fluororesin polymer at a relatively high temperature above the crystallization temperature. To prepare a film-forming stock solution).
- the concentration of the fluororesin polymer is preferably 20% by weight or more and 60% by weight or less, and more preferably 30% by weight or more and 50% by weight or less.
- a poor solvent means that a fluororesin polymer cannot be dissolved at 5% by weight or more at a low temperature of 60 ° C. or lower, but it is 60 ° C. or higher and below the melting point of the fluororesin polymer (for example, It is a solvent that can be dissolved in an amount of 5% by weight or more in a high temperature region of about 178 ° C. when the vinylidene fluoride homopolymer is constituted alone.
- a good solvent is a solvent capable of dissolving 5% by weight or more of a fluororesin-based polymer even in a low temperature region of 60 ° C. or lower, and a non-solvent is fluorine up to the melting point of the fluororesin-based polymer or the boiling point of the solvent. It is defined as a solvent that does not dissolve or swell resin-based polymers.
- examples of the poor solvent for the fluororesin-based polymer include cyclohexanone, isophorone, ⁇ -butyrolactone, methyl isoamyl ketone, propylene carbonate, dimethyl sulfoxide and the like and mixed solvents thereof.
- examples of the good solvent include N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, trimethyl phosphate, and a mixed solvent thereof.
- Non-solvents include water, hexane, pentane, benzene, toluene, methanol, ethanol, carbon tetrachloride, o-dichlorobenzene, trichloroethylene, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, Hexanediol, aliphatic hydrocarbons such as low molecular weight polyethylene glycol, aromatic hydrocarbons, aliphatic polyhydric alcohols, aromatic polyhydric alcohols, chlorinated hydrocarbons, other chlorinated organic liquids, and mixed solvents thereof Is mentioned.
- a hollow fiber is formed from a membrane-forming stock solution containing a fluororesin polymer using a thermally induced phase separation method in which phase separation is induced by temperature change. Get.
- the hollow fiber has a columnar structure oriented in the length direction, and the thickness uniformity of the columnar structure is 0.60 or more. Preferably it is less than 00.
- the lower limit of the thickness uniformity of the columnar structure is more preferably 0.70 or more, further preferably 0.80 or more, and particularly preferably 0.90 or more.
- phase separation mechanisms Two types are mainly used in the thermally induced phase separation method.
- One is a liquid-liquid phase in which a polymer solution that is uniformly dissolved at a high temperature is separated into a polymer-rich phase and a polymer-dilute phase due to a decrease in solution solubility when the temperature is lowered, and then the structure is fixed by crystallization Separation method.
- the other is a solid-liquid phase separation method in which a polymer solution that is uniformly dissolved at a high temperature causes the polymer to crystallize when the temperature falls and phase-separates into a polymer solid phase and a solvent phase.
- the former method mainly forms a three-dimensional network structure
- the latter method forms a spherical structure mainly composed of a spherical structure.
- the latter phase separation mechanism is preferably used. Therefore, the polymer concentration and solvent that induce solid-liquid phase separation are selected.
- the former phase separation mechanism it is difficult to develop a columnar structure oriented in the length direction of the hollow fiber membrane as described above. This is because the polymer-rich phase forms a very fine phase by phase separation before the structure is fixed, and cannot be made columnar.
- the above-mentioned membrane-forming solution is discharged from the outer tube of the double tube die for spinning the porous hollow fiber membrane, while the hollow portion forming liquid is discharged from the inner tube of the double tube die. Discharge.
- the membrane forming stock solution thus discharged is cooled and solidified in a cooling bath to obtain a porous hollow fiber membrane.
- the fluororesin-based polymer solution is placed under a specific temperature condition for a certain period of time while being pressurized before being discharged from the die.
- the pressure is preferably 0.5 MPa or more, and more preferably 1.0 MPa or more.
- the temperature T of the polymer solution preferably satisfies Tc + 35 ° C. ⁇ T ⁇ Tc + 60 ° C., and more preferably satisfies Tc + 40 ° C. ⁇ T ⁇ Tc + 55 ° C.
- Tc is the crystallization temperature of the fluororesin polymer solution.
- the time for which the polymer solution is held under this pressure and temperature is preferably 10 seconds or more, and more preferably 20 seconds or more.
- a retention part for retaining the polymer solution is provided in any part of the liquid feed line for sending the polymer solution to the die, and a pressurizing means for pressurizing the retained polymer solution,
- a temperature adjusting means for example, a heating means for adjusting the temperature of the polymer solution.
- the pump include a piston pump, a plunger pump, a diaphragm pump, a wing pump, a gear pump, a rotary pump, and a screw pump, and two or more kinds may be used.
- the crystal growth Since pressure is applied under conditions where crystallization is likely to occur in this step, the crystal growth has anisotropy, and the structure oriented in the length direction of the porous hollow fiber membrane is not an isotropic spherical structure. It is assumed that a columnar structure is obtained as a result.
- the crystallization temperature Tc of the fluororesin polymer solution is defined as follows. Using a differential scanning calorimetry (DSC measurement) device, a mixture of the same composition as the film-forming polymer stock solution, such as a fluororesin polymer and a solvent, is sealed in a sealed DSC vessel and dissolved at a heating rate of 10 ° C./min. The rising temperature of the crystallization peak observed in the process of lowering the temperature at a temperature lowering rate of 10 ° C./min after the temperature is raised to the temperature, kept for 30 minutes and uniformly dissolved, is Tc.
- DSC measurement differential scanning calorimetry
- a cooling bath for cooling the fluororesin polymer solution discharged from the die will be described.
- the cooling bath it is preferable to use a mixed liquid composed of a poor solvent or a good solvent having a concentration of 50 to 95% by weight and a non-solvent having a concentration of 5 to 50% by weight. Further, it is preferable to use the same poor solvent as the polymer solution as the poor solvent.
- the hollow portion forming liquid it is preferable to use a mixed liquid composed of a poor solvent or a good solvent having a concentration of 50 to 95% by weight and a non-solvent having a concentration of 5 to 50% by weight, like the cooling bath. Further, it is preferable to use the same poor solvent as the polymer solution as the poor solvent.
- the polymer-incorporated growth into the constricted part leads to the disappearance of the constricted part having a high interfacial energy and is stabilized in terms of energy, and therefore can be preferentially generated over the growth other than the constricted part.
- the headline and the method for improving the thickness uniformity were intensively studied.
- the thermally induced phase separation includes at least one of the following cooling steps a) and b) as a method for promoting the polymer uptake growth in the constricted portion.
- the cooling and solidification is gradually advanced by performing the cooling and solidification in the cooling bath in the vicinity of the crystallization temperature of the polymer solution.
- the temperature Tb of the cooling bath is set so as to satisfy Tc ⁇ 30 ° C. ⁇ Tb ⁇ Tc, where Tc is the crystallization temperature of the fluororesin polymer solution, and Tc ⁇ 20 ° C. ⁇ More preferably, Tb ⁇ Tc.
- the passage time of the cooling bath (that is, the immersion time in the cooling bath) is not particularly limited as long as sufficient time can be secured to complete the heat-induced phase separation including the polymer uptake and growth into the constricted portion. It may be determined experimentally in consideration of spinning speed, bath ratio, cooling capacity, and the like.
- the passage time as long as possible in the above-described cooling bath temperature range, for example, 10 seconds or more, preferably 20 seconds or more, more preferably 30 seconds or more. It is good to do.
- the cooling step includes a step of cooling using a first cooling bath that promotes crystal nucleation and growth by increasing the degree of supercooling, and then a second step that promotes polymer uptake and growth in the constricted portion. Cooling with a cooling bath may be included. The cooling step by the second cooling bath utilizes the phenomenon that the polymer uptake and growth into the constricted part occurs preferentially during the structural coarsening process of phase separation.
- Tb1 of the first cooling bath that cools the fluororesin polymer solution discharged from the die satisfies Tb1 ⁇ Tc ⁇ 30 ° C.
- the degree of supercooling is increased and the generation and growth of crystal nuclei are increased.
- Tb2 of the second cooling bath a temperature near the crystallization temperature (specifically, Tc-30 ° C ⁇ Tb2 ⁇ Tc, more preferably Tc-20 ° C ⁇ Tb2 ⁇ Tc
- the passage time of each cooling bath can be changed, for example, the passage time of the first cooling bath is 1 second to 20 seconds, preferably 3 seconds to 15 seconds, more preferably 5 seconds to 10 seconds. And the passage time of the second cooling bath is 10 seconds or longer, preferably 20 seconds or longer, more preferably 30 seconds or longer.
- Patent Document 5 Japanese Patent Application Laid-Open No. 2006-297383
- Patent Document 5 Japanese Patent Application Laid-Open No. 2006-297383
- the present inventors have attempted to increase the strength by stretching it. However, it was found that the film could not be stretched uniformly and the strength could not be increased.
- a porous membrane used for water treatment has a large number of voids for allowing water to permeate, and at the time of stretching, the destruction of the structure proceeds from the voids, so that the stretching itself is very difficult.
- the porous hollow fiber membrane has a phase-separated porous structure obtained by dry-wet spinning using the principle of non-solvent induced phase separation or thermally induced phase separation, there are many fine voids and the porosity This tendency is remarkable because of
- the present inventors are not a fibrous structure having a number of constricted portions described in Patent Document 5, a network structure described in Patent Document 3, or a spherical structure described in Patent Document 4, and is uniform.
- a hollow fiber having a columnar structure having a thickness found that the entire columnar structure could be uniformly stretched, and high-strength stretching of 2.0 times or more was made possible.
- a porous hollow fiber membrane made of a fluororesin-based polymer having a columnar structure obtained by the above method is stretched at a high magnification to thereby form a molecular chain of the polymer. Oriented in the longitudinal direction of the hollow fiber membrane.
- the draw ratio is 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, and particularly preferably 2.5 to 3.5 times.
- the draw ratio is less than 2.0 times, the orientation of the molecular chain by drawing is not sufficient, and when it exceeds 5.0 times, the elongation decreases greatly.
- the stretching temperature is preferably 60 to 140 ° C., more preferably 70 to 120 ° C., and further preferably 80 to 100 ° C.
- the stretching temperature is preferably 60 to 140 ° C., more preferably 70 to 120 ° C., and further preferably 80 to 100 ° C.
- Stretching is preferably performed in a liquid because temperature control is easy, but may be performed in a gas such as steam.
- a liquid water is convenient and preferable, but when stretching at about 90 ° C. or higher, it is also possible to preferably employ a low molecular weight polyethylene glycol or the like.
- the orientation parameter of the polyvinylidene fluoride homopolymer in the porous hollow fiber membrane was determined by the following operation. The cross section in the longitudinal direction of the porous hollow fiber membrane was sectioned by cutting with a microtome. While selecting 10 columnar structures per porous hollow fiber membrane and confirming the columnar structures with an optical microscope, the scattering intensity of each columnar structure is measured by laser Raman spectroscopy at intervals of 1 ⁇ m along the longitudinal direction. Was measured. Each orientation parameter was calculated by the formula (2), and the average value of each orientation parameter was defined as the Raman orientation parameter ⁇ .
- Orientation parameter (I1270 / I840) parallel / (I1270 / I840) vertical
- Parallel condition the longitudinal direction of the porous hollow fiber membrane is parallel to the polarization direction
- Vertical condition the longitudinal direction of the porous hollow fiber membrane is orthogonal to the polarization direction
- I1270 parallel the intensity of the 1270 cm ⁇ 1 Raman band under the parallel condition
- I1270 perpendicular intensity of Raman bands of 1270 cm -1 when the vertical condition
- I840 parallel the intensity of the Raman bands of 840 cm -1 at collinear condition
- I840 vertical intensity laser Raman spectrometer and measurement conditions of the Raman band at 840 cm -1 at a vertical condition
- the above photographing was performed at five locations, and the longitudinal length and the short length were determined for each of the 10 columnar structures, and a total of 50 long lengths and a total of 50 short lengths were obtained. Next, an average value of a total of 50 longitudinal lengths was calculated and used as a representative value of the longitudinal length, and an average value of a total of 50 short lengths was calculated and used as a representative value of the short length.
- the porous hollow fiber membrane was resin-embedded with an epoxy resin, and the void portion was filled with the epoxy resin by osmium staining treatment.
- SEM scanning electron microscope
- FIB focused ion beam
- Thickness uniformity was determined by comparing the first and second sections parallel to the short direction of the porous hollow fiber membrane obtained by continuous section observation using the FIB.
- 20 sets were selected so that the first cross section and the second cross section were parallel to each other with an interval of 5 ⁇ m.
- the resin part and the void part are distinguished, the resin part area and the void part area are obtained, and then the first cross section is viewed from the direction perpendicular to both cross sections.
- the area of the portion where the portion made of the resin of the first cross section and the portion made of the resin of the second cross section overlap was determined, and was defined as the overlapping area.
- Crystallization temperature Tc of fluororesin polymer solution Using a DSC-6200 manufactured by Seiko Denshi Kogyo Co., Ltd., a mixture of the same composition as the film-forming polymer stock solution, such as a fluororesin polymer and a solvent, is sealed in a sealed DSC vessel and dissolved at a heating rate of 10 ° C./min. The temperature was raised to the temperature, kept for 30 minutes and dissolved uniformly, and then the rising temperature of the crystallization peak observed in the process of lowering the temperature at a temperature lowering rate of 10 ° C./min was defined as the crystallization temperature Tc.
- Example 1 36% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 64% by weight of ⁇ -butyrolactone were dissolved at 150 ° C.
- the Tc of this vinylidene fluoride homopolymer solution was 48 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.62, a columnar structure occupation ratio of 86%, and a spherical structure occupation ratio of 14%. Subsequently, the porous hollow fiber membrane obtained above was stretched 2.5 times in 95 ° C. water.
- the porous hollow fiber membrane When the porous hollow fiber membrane after stretching was observed, a columnar structure was observed.
- the porous hollow fiber membrane has a columnar structure with a typical value of 16 ⁇ m in the longitudinal length, a representative value of 2.2 ⁇ m in the short length, and a thickness uniformity of 0.61, has a porosity of 55%, and vinylidene fluoride.
- the degree of orientation ⁇ of the homopolymer molecular chain in the longitudinal direction of the porous hollow fiber membrane was 0.61
- the Raman orientation parameter ⁇ was 3.12
- M / m was 3.1. Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- the Tc of this vinylidene fluoride homopolymer solution was 48 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.65, a columnar structure occupation ratio of 87%, and a spherical structure occupation ratio of 13%.
- the porous hollow fiber membrane obtained above was stretched 3 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a columnar structure with a long length of 19 ⁇ m, a short length of 1.8 ⁇ m, and a thickness uniformity of 0.66, a porosity of 61%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.77
- the Raman orientation parameter ⁇ was 3.74
- M / m was 4.2. Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- Example 3 > 38% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 62% by weight of ⁇ -butyrolactone were dissolved at 150 ° C.
- the vinylidene fluoride homopolymer solution had a Tc of 51 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.66, a columnar structure occupancy of 91%, and a spherical structure occupancy of 9%.
- the porous hollow fiber membrane obtained above was stretched 3 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a columnar structure with a long length of 24 ⁇ m, a short length of 1.6 ⁇ m, and a thickness uniformity of 0.66, a porosity of 59%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.85
- the Raman orientation parameter ⁇ was 4.37
- M / m was 5.0. Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- Example 4 38% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 62% by weight of ⁇ -butyrolactone were dissolved at 150 ° C.
- the vinylidene fluoride homopolymer solution had a Tc of 51 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.66, a columnar structure occupancy of 91%, and a spherical structure occupancy of 9%.
- the porous hollow fiber membrane obtained above was stretched 3.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a columnar structure with a longitudinal length of 28 ⁇ m, a short length of 1.3 ⁇ m, and a thickness uniformity of 0.62, a porosity of 61%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.89
- the Raman orientation parameter ⁇ was 4.42
- M / m was 5.1.
- Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching. In addition, FIG.
- FIG. 2 shows the Raman orientation parameter at each measurement location of the porous hollow fiber membrane
- FIG. Cross-sectional photographs of the longitudinal direction of the yarn membrane are shown in FIG.
- Example 5 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000
- porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.62, a columnar structure occupation ratio of 93%, and a spherical structure occupation ratio of 7%. Subsequently, the porous hollow fiber membrane obtained above was stretched 2.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a columnar structure having a long length of 20 ⁇ m, a short length of 2.1 ⁇ m, and a thickness uniformity of 0.61, a porosity of 64%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.66
- the Raman orientation parameter ⁇ was 3.40
- M / m was 3.5.
- Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- Example 6 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000
- a 90% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube base, and was kept in a first cooling bath composed of 85% by weight aqueous solution of dimethyl sulfoxide at a temperature of -5 ° C. for 10 seconds, and then 85% by weight of dimethyl sulfoxide. It was allowed to stay for 30 seconds in a second cooling bath made of a 15% aqueous solution at a temperature of 15 ° C. and solidified.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.72, a columnar structure occupancy of 92%, and a spherical structure occupancy of 8%.
- the porous hollow fiber membrane obtained above was stretched 3 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a columnar structure with a long length of 27 ⁇ m, a short length of 1.7 ⁇ m, and a thickness uniformity of 0.69, a porosity of 64%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.86
- the Raman orientation parameter ⁇ was 4.38
- Example 7 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000
- a 90% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube base, and was kept in a first cooling bath composed of 85% by weight aqueous solution of dimethyl sulfoxide at a temperature of -5 ° C. for 10 seconds, and then 85% by weight of dimethyl sulfoxide. It was allowed to stay for 50 seconds in a second cooling bath consisting of a 20% aqueous solution at a temperature of 20 ° C. and solidified.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.72, a columnar structure occupation ratio of 95%, and a spherical structure occupation ratio of 5%.
- the porous hollow fiber membrane obtained above was stretched 3.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a columnar structure with a long length of 35 ⁇ m, a short length of 1.5 ⁇ m, and a thickness uniformity of 0.67, a porosity of 65%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.91, the Raman orientation parameter ⁇ was 4.62, and M / m was 5.8.
- Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- Example 8> 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- a 90% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube base, and was kept in a first cooling bath composed of 85% by weight aqueous solution of dimethyl sulfoxide at a temperature of -5 ° C. for 10 seconds, and then 85% by weight of dimethyl sulfoxide. It was allowed to stay for 50 seconds in a second cooling bath consisting of a 20% aqueous solution at a temperature of 20 ° C. and solidified.
- the obtained porous hollow fiber membrane had a columnar structure with a thickness uniformity of 0.72, a columnar structure occupation ratio of 95%, and a spherical structure occupation ratio of 5%.
- the porous hollow fiber membrane obtained above was stretched 4 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a columnar structure with a long length of 40 ⁇ m, a short length of 1.1 ⁇ m, and a thickness uniformity of 0.63, a porosity of 66%, and a vinylidene fluoride homopolymer molecular chain.
- the degree of orientation ⁇ in the longitudinal direction of the porous hollow fiber membrane was 0.92, the Raman orientation parameter ⁇ was 4.76, and M / m was 6.2.
- Table 1 shows the structure and performance of the porous hollow fiber membrane after stretching.
- Example 9 15% by weight of vinylidene fluoride homopolymer (KF 1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000), 3% by weight of polyethylene glycol having a weight average molecular weight of 20,000, N—
- a polymer solution was prepared by mixing and dissolving 80% by weight of methyl-2-pyrrolidone and 2% by weight of water at a temperature of 95 ° C. This polymer solution was uniformly applied to the surface of the hollow fiber membrane (outer diameter: 1240 ⁇ m, inner diameter: 740 ⁇ m, film thickness: 250 ⁇ m) obtained after stretching in Example 2, and immediately solidified in a water bath to form a columnar shape.
- a porous hollow fiber membrane in which a layer having a three-dimensional network structure (film thickness: 30 ⁇ m) was formed on a layer having a structure was produced.
- the thickness of the three-dimensional network structure layer with respect to the thickness of the layer having a columnar structure was 0.12.
- the layer having the columnar structure of this porous hollow fiber membrane it has a columnar structure with a long length of 40 ⁇ m, a short length of 1.1 ⁇ m, and a thickness uniformity of 0.63, and the columnar structure occupation ratio is 87%.
- the spherical tissue occupancy is 13%
- the porosity is 66%
- the Raman orientation parameter ⁇ is 4.75
- M / m is 6.0
- the three-dimensional network structure layer can be formed.
- Example 2 the degree of orientation ⁇ of the vinylidene fluoride homopolymer molecular chain in the longitudinal direction of the porous hollow fiber membrane was 0.89, and even when a three-dimensional network structure layer was formed, there was almost no change from Example 2.
- the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.47, a fibrous tissue occupation ratio of 91%, and a spherical tissue occupation ratio of 9%. Subsequently, the porous hollow fiber membrane obtained above was stretched 1.5 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 15 ⁇ m, a short length of 2.2 ⁇ m, and a thickness uniformity of 0.45, a porosity of 63%, and a vinylidene fluoride homopolymer molecular chain was non-oriented, Raman orientation parameter ⁇ was 1.01, and M / m was 1.0.
- the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.47, a fibrous tissue occupation ratio of 91%, and a spherical tissue occupation ratio of 9%. Subsequently, the porous hollow fiber membrane obtained above was stretched 2.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 18 ⁇ m, a short length of 1.7 ⁇ m, and a thickness uniformity of 0.42, a porosity of 65%, and a vinylidene fluoride homopolymer molecular chain.
- Raman orientation parameter ⁇ was 1.03
- M / m was 1.1. Table 2 shows the structure and performance of the porous hollow fiber membrane after stretching.
- the vinylidene fluoride homopolymer solution had a Tc of 51 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 99-101 ° C.
- porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.47, a fibrous tissue occupation ratio of 91%, and a spherical tissue occupation ratio of 9%. Subsequently, when the porous hollow fiber membrane obtained above was stretched 3.5 times in water at 95 ° C., yarn breakage occurred and the porous hollow fiber membrane could not be stretched.
- the Tc of this vinylidene fluoride homopolymer solution was 48 ° C.
- the solution was pressurized to 0.2 MPa on the line between them, held at 99-101 ° C. for 20 seconds, and then discharged from the outer pipe of the double-tube type die.
- a 85% by weight aqueous solution of ⁇ -butyrolactone was discharged from the inner tube of the double-tube base, and was retained in a cooling bath composed of an 85% by weight aqueous solution of ⁇ -butyrolactone at a temperature of 25 ° C. for 20 seconds to solidify.
- the obtained porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.42, a fibrous tissue occupation ratio of 24%, and a spherical tissue occupation ratio of 76%. Subsequently, when the porous hollow fiber membrane obtained above was stretched twice in water at 95 ° C., thread breakage occurred and the porous hollow fiber membrane could not be stretched.
- ⁇ Comparative Example 5> 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.56, a fibrous tissue occupation ratio of 84%, and a spherical tissue occupation ratio of 16%. Subsequently, the porous hollow fiber membrane obtained above was stretched 1.5 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 18 ⁇ m, a short length of 1.2 ⁇ m, and a thickness uniformity of 0.53, a porosity of 64%, and a vinylidene fluoride homopolymer molecular chain.
- Raman orientation parameter ⁇ was 1.03
- M / m was 1.1. Table 2 shows the structure and performance of the porous hollow fiber membrane after stretching.
- ⁇ Comparative Example 6> 40% by weight of vinylidene fluoride homopolymer (KF1300 manufactured by Kureha Co., Ltd., weight average molecular weight: 417,000, number average molecular weight: 221,000) and 60% by weight of dimethyl sulfoxide were dissolved at 130 ° C. Tc of this vinylidene fluoride homopolymer solution was 30 ° C. By installing two gear pumps, the solution was pressurized to 2.0 MPa on the line between them and allowed to stay at 78-80 ° C.
- porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.56, a fibrous tissue occupation ratio of 84%, and a spherical tissue occupation ratio of 16%. Subsequently, the porous hollow fiber membrane obtained above was stretched 2.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 22 ⁇ m, a short length of 1.0 ⁇ m, and a thickness uniformity of 0.51, a porosity of 65%, and a vinylidene fluoride homopolymer molecular chain.
- Raman orientation parameter ⁇ was 1.05
- M / m was 1.1. Table 2 shows the structure and performance of the porous hollow fiber membrane after stretching.
- a 90% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube type die, and was retained in a cooling bath composed of 85% by weight aqueous solution of dimethyl sulfoxide at a temperature of 0 ° C. for 20 seconds to solidify.
- the obtained porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.42, a fibrous tissue occupation ratio of 88%, and a spherical tissue occupation ratio of 12%. Subsequently, the porous hollow fiber membrane obtained above was stretched 1.5 times in water at 95 ° C.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 14 ⁇ m, a short length of 1.2 ⁇ m, and a thickness uniformity of 0.41, a porosity of 71%, and a vinylidene fluoride homopolymer molecular chain was non-oriented, Raman orientation parameter ⁇ was 1.04, and M / m was 1.1.
- Table 2 shows the structure and performance of the porous hollow fiber membrane after stretching.
- a 90% by weight aqueous solution of dimethyl sulfoxide was discharged from the inner tube of the double-tube type die, and was retained in a cooling bath composed of 85% by weight aqueous solution of dimethyl sulfoxide at a temperature of 0 ° C. for 20 seconds to solidify.
- the obtained porous hollow fiber membrane had a fibrous structure with a thickness uniformity of 0.42, a fibrous tissue occupation ratio of 88%, and a spherical tissue occupation ratio of 12%. Subsequently, the porous hollow fiber membrane obtained above was stretched 2.5 times in 95 ° C. water.
- the stretched porous hollow fiber membrane has a fibrous structure having a long length of 19 ⁇ m, a short length of 0.8 ⁇ m, and a thickness uniformity of 0.37, a porosity of 73%, and a vinylidene fluoride homopolymer molecular chain.
- Raman orientation parameter ⁇ was 1.06
- M / m was 1.2. Table 2 shows the structure and performance of the porous hollow fiber membrane after stretching.
- This vinylidene fluoride homopolymer solution did not have Tc because dimethylacetamide is a good solvent for vinylidene fluoride homopolymer.
- the solution was pressurized to 0.2 MPa on the line between them, held at 99-101 ° C. for 20 seconds, and then discharged from the outer pipe of the double-tube type die.
- a 85% by weight aqueous solution of dimethylacetamide was discharged from the inner tube of the double-tube type mouthpiece, and was retained in a cooling bath made of 85% by weight aqueous solution of dimethylacetamide at a temperature of 25 ° C. for 40 seconds to solidify.
- the obtained porous hollow fiber membrane did not have any of a spherical structure, a fibrous structure, and a columnar structure, and had a three-dimensional network structure. Subsequently, when the porous hollow fiber membrane obtained above was stretched twice in water at 95 ° C., thread breakage occurred and the porous hollow fiber membrane could not be stretched.
- a porous hollow fiber membrane having both excellent physical durability and high pure water permeation performance while having excellent chemical durability due to a fluorochemical polymer having high chemical resistance.
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Abstract
Description
(1)フッ素樹脂系高分子を含有する多孔質中空糸膜であって、前記多孔質中空糸膜の長手方向に配向する柱状組織を有し、前記フッ素樹脂系高分子の分子鎖が前記多孔質中空糸膜の長手方向に配向しており、下記式(1)に基づき算出される分子鎖の配向度πが、0.4以上1.0未満である多孔質中空糸膜。
配向度π=(180°-H)/180° ・・・(1)
(ただし、Hは広角X線回折像の円周方向における回折強度分布の半値幅(°)である。)
(2)前記柱状組織の短手長さが0.5μm以上3μm以下、且つ、該柱状組織のアスペクト比が3以上である、前記(1)に記載の多孔質中空糸膜。
(3)前記柱状組織の太さ均一性が0.60以上である、前記(1)または(2)に記載の多孔質中空糸膜。
(4)前記半値幅Hは、広角X線回折測定によるポリフッ化ビニリデンの(110)面由来の結晶ピーク(2θ=20.4°)を円周方向にスキャンして得られる強度分布の半値幅である、前記(1)~(3)のいずれか1つに記載の多孔質中空糸膜。
(5)前記多孔質中空糸膜の長手方向に1cm間隔の測定点で広角X線回折測定を行った際に、80%以上の前記測定点で、前記配向度πが0.4以上1.0未満である、前記(1)~(4)のいずれか1つに記載の多孔質中空糸膜。
(6)前記フッ素樹脂系高分子がポリフッ化ビニリデンであり、ラマン分光法によって得られる分子鎖のラマン配向パラメータνが3.0以上である、前記(1)~(5)のいずれか1つに記載の多孔質中空糸膜。
(7)空隙率が50%以上80%以下である、前記(1)~(6)のいずれか1つに記載の多孔質中空糸膜。
(8)50kPa、25℃における純水透過性能が0.7m3/m2/hr以上であり、破断強度が25MPa以上である、前記(1)~(7)のいずれか1つに記載の多孔質中空糸膜。
(9)熱誘起相分離によって形成される、前記(1)~(8)のいずれか1つに記載の多孔質中空糸膜。
(10)下記1)および2)の工程を備える多孔質中空糸膜の製造方法。
1)フッ素樹脂系高分子を含有する製膜原液から、熱誘起相分離により、長さ方向に配向し、かつ0.60以上1.00未満の太さ均一性を有する柱状組織を有する多孔質中空糸を形成する工程
2)前記1)で得られた多孔質中空糸を長手方向に2.0倍以上5.0倍以下で延伸する工程
(11)前記工程1)の熱誘起相分離が下記a)およびb)の冷却工程のうちの少なくとも一方を備える、前記(10)に記載の多孔質中空糸膜の製造方法。
a)前記製膜原液をTc-30℃<Tb≦Tcを満たす温度Tbの冷却浴に浸す工程
b)前記製膜原液をTb1≦Tc-30℃を満たす温度Tb1の冷却浴に浸した後、Tc-30℃<Tb2≦Tcを満たす温度Tb2の冷却浴に浸す工程
(ただし、Tcは前記フッ素樹脂系高分子を含有する製膜原液の結晶化温度である。)
(1-1)フッ素樹脂系高分子
本発明の多孔質中空糸膜は、フッ素樹脂系高分子を含有する。
本書において、フッ素樹脂系高分子とは、フッ化ビニリデンホモポリマーおよびフッ化ビニリデン共重合体のうちの少なくとも1つを含有する樹脂を意味する。フッ素系樹脂高分子は、複数の種類のフッ化ビニリデン共重合体を含有してもよい。
なお、「フッ素樹脂系高分子を主成分として含有する多孔質中空糸膜」とは、「フッ素樹脂系高分子をベースとする多孔質中空糸膜」とも言い換えられる。本明細書では、他の要素についても「XがYを主成分として含有する」という説明が記載されているが、これらについても同様に、Xについて「Yをベースとする」と言い換えることができる。
本発明の多孔質中空糸膜において、フッ素樹脂系高分子の分子鎖は、多孔質中空糸膜の長手方向に配向している。また、分子鎖の配向度πは、0.4以上1.0未満である。配向度πは、下記式(1)に基づき、広角X線回折測定によって得られた半値幅H(°)から算出される。
配向度π=(180°-H)/180° ・・・(1)
(ただし、Hは広角X線回折像の円周方向における回折強度分布の半値幅(°)である。)
配向度πを算出するためには、多孔質中空糸膜の長手方向が鉛直となるように繊維試料台に取り付ける。なお、多孔質中空糸膜の短手方向とは、中空糸の径方向と平行な方向であり、長手方向とは、短手方向に垂直な方向である。また、短手方向は、中空面と平行な方向、すなわち中空面の面内方向と言い換えることができ、長手方向とは、中空面に垂直な方向と言い換えることができる。
本発明の多孔質中空糸膜の分子鎖の多孔質中空糸膜の長手方向への配向度πは、0.4以上1.0未満の範囲であり、好ましくは0.5以上1.0未満であり、より好ましくは0.6以上1.0未満である。配向度πが0.4以上であることで、多孔質中空糸膜の機械的強度が大きくなる。なお、配向度πは、多孔質中空糸膜の長手方向に1cm間隔の測定点で広角X線回折測定を行った際に、80%以上の測定点で、0.4以上1.0未満であることが好ましい。
このため、配向パラメータを、下記式(2)で算出することができる。配向パラメータは、多孔質中空糸膜の長手方向への配向が高いほど大きな値となり、無配向時には1、短手方向への配向が高いと1よりも小さな値を示す。
配向パラメータ=(I1270/I840)平行/(I1270/I840)垂直 ・・・(2)
式(2)において、
平行条件:多孔質中空糸膜の長手方向と偏光方向が平行
垂直条件:多孔質中空糸膜の長手方向と偏光方向が直交
I1270平行:平行条件時の1270cm-1のラマンバンドの強度
I1270垂直:垂直条件時の1270cm-1のラマンバンドの強度
I840平行:平行条件時の840cm-1のラマンバンドの強度
I840垂直:垂直条件時の840cm-1のラマンバンドの強度
である。
(a)寸法
多孔質中空糸膜は、多孔質中空糸膜の長手方向に配向する柱状組織を有する。「柱状組織」とは、一方向に長い形状の固形物である。柱状組織のアスペクト比(長手長さ/短手長さ)は3以上であることが好ましい。
ここで、「長手長さ」とは柱状組織の長手方向の長さを指す。また、「短手長さ」とは柱状組織の短手方向の平均長さである。
長手長さの代表値は、以下のように測定する。長手長さの測定と同様にして、中空糸膜における3箇所、好ましくは5箇所の位置で、1箇所につき5個、好ましくは10個の柱状組織について、長手長さを測定する。得られた長手長さの値について平均値を求めることで、柱状組織の長手長さの代表値とすることができる。
また、短手長さの代表値は、長手長さの代表値の測定の対象とした柱状組織について、上述のとおり短手長さ(平均値として算出される)を測定し、その平均値を算出することで決定される。
後述するように、本発明の多孔質中空糸膜は、高分子を含有する製膜原液から中空糸を形成し、その中空糸を延伸することで、製造可能である。便宜上、延伸前の状態を「中空糸」と呼び、延伸後の状態を「中空糸膜」と呼ぶ。
延伸後の多孔質中空糸膜が高い伸度を保持していると、急激な荷重が掛かった際にも糸切れしにくいため好ましい。多孔質中空糸膜の破断伸度は、50%以上であることが好ましく、80%以上であることがより好ましい。
太さ均一性A=(重なり面積)/(第二の断面の樹脂部分面積) ・・・(3)
太さ均一性B=(重なり面積)/(第一の断面の樹脂部分面積) ・・・(4)
柱状組織は、フッ素樹脂系高分子を含有する。柱状組織は、フッ素樹脂系高分子を主成分として含有することが好ましく、柱状組織においてフッ素樹脂系高分子が占める割合は、80重量%以上が好ましく、90重量%以上がより好ましく、95重量%以上であることが更に好ましい。また、柱状組織は、フッ素樹脂系高分子のみで構成されていてもよい。
言い換えると、多孔質中空糸膜はフッ素樹脂系高分子を含有する固形分を有しており、その固形分の少なくとも一部が柱状組織を構成している。フッ素樹脂系高分子を含有する固形分は、その全てが柱状組織を構成していてもよいし、その一部が柱状組織に該当しない形状を有していてもよい。多孔質中空糸膜において、フッ素樹脂系高分子を含有する固形分のうち、柱状組織を構成する固形分が占める割合は、80重量%以上が好ましく、90重量%以上がより好ましく、95重量%以上であることが更に好ましい。
多孔質中空糸膜において、主たる構造が柱状組織であることが好ましい。多孔質中空糸膜において、柱状組織が占める割合は、80重量%以上が好ましく、90重量%以上がより好ましく、95重量%以上であることが更に好ましい。また、多孔質中空糸膜は、柱状組織のみで構成されていてもよい。
より具体的には、多孔質中空糸膜は、その主たる構造として、フッ素樹脂系高分子を主成分として含有する柱状組織を有することが好ましい。
多孔質中空糸膜は、柱状組織の集合体である、とも表現できる。
本発明の多孔質中空糸膜は、高い純水透過性能と高い強度を両立するために、空隙率は40%以上90%以下が好ましく、50%以上80%以下がより好ましく、50%以上70%以下がさらに好ましい。空隙率が、40%未満だと純水透過性能が低くなり、90%を超えると強度が著しく低下するため、水処理用の多孔質中空糸膜としての適性を欠く。多孔質中空糸膜の空隙率は、上述した断面における樹脂部分面積と空隙部分面積を用いて、下記式(5)によって求められる。精度を高めるために、任意の20点以上、好ましくは30点以上の断面について空隙率を求め、それらの平均値を用いることが好ましい。
空隙率(%)={100×(空隙部分面積)}/{(樹脂部分面積)+(空隙部分面積)} ・・・(5)
本発明の多孔質中空糸膜は、本発明の目的を逸脱しない範囲で、上述した柱状組織以外の組織を含有していてもよい。柱状組織以外の構造としては、例えば、アスペクト比(長手長さ/短手長さ)が3未満の球状組織が挙げられる。球状組織の短手長さおよび長手長さは、0.5μm以上3μm以下の範囲であることが好ましい。球状組織を用いる場合に、その短手長さおよび長手長さが前記範囲であれば、多孔質中空糸膜の強度の低下が抑制され、かつ良好な純水透過性能を維持することができる。
占有率(%)={(各組織の占める面積)/(写真全体の面積)}×100 ・・・(6)
ここで、写真全体の面積および組織の占める面積は、写真撮影された各組織の対応する重量に置き換えて求める方法などが好ましく採用できる。すなわち、撮影された写真を紙に印刷し、写真全体に対応する紙の重量およびそこから切り取った組織部分に対応する紙の重量を測定すればよい。また、SEM等による写真撮影に先立ち、上述したような樹脂包埋・染色処理、FIBによる切削加工を施すと、観察精度が高くなるため好ましい。
本発明の多孔質中空糸膜を製造する方法について、以下に例示する。多孔質中空糸膜の製造方法は、少なくとも、
1)フッ素樹脂系高分子を含有する製膜原液から、熱誘起相分離により、長さ方向に配向し、かつ0.60以上1.00未満の太さ均一性を有する柱状組織を有する中空糸を形成する工程、および
2)上記1)で得られた多孔質中空糸を長手方向に2.0倍以上5.0倍以下で延伸する工程
を備える。
本発明における多孔質中空糸膜の製造方法は、フッ素樹脂系高分子溶液を調整する工程をさらに備える。フッ素樹脂系高分子を、フッ素樹脂系高分子の貧溶媒または良溶媒に、結晶化温度以上の比較的高温で溶解することで、フッ素樹脂系高分子溶液(つまり、フッ素樹脂系高分子を含有する製膜原液)を調製する。
中空糸の形成工程においては、温度変化により相分離を誘起する熱誘起相分離法を利用して、フッ素樹脂系高分子を含有する製膜原液から、中空糸を得る。後述する2.0倍以上の高倍率延伸を行うためには、中空糸は、その長さ方向に配向する柱状組織を有し、かつ、柱状組織の太さ均一性は0.60以上1.00未満であることが好ましい。柱状組織の太さ均一性の下限は、0.70以上であることがより好ましく、0.80以上であることが更に好ましく、0.90以上であることが特に好ましい。
前者の方法では主に三次元網目構造が、後者の方法では主に球状組織で構成された球状構造が形成される。本発明の中空糸膜の製造では、後者の相分離機構が好ましく利用される。よって、固-液相分離が誘起される高分子濃度および溶媒が選択される。前者の相分離機構では、上述したような中空糸膜の長さ方向に配向した柱状組織を発現させることは困難である。これは構造が固定される前の相分離でポリマー濃厚相は非常に微細な相を形成し、柱状にすることができないためである。
a)前記製膜原液をTc-30℃<Tb≦Tcを満たす温度Tbの冷却浴に浸す工程
b)Tb1≦Tc-30℃を満たす温度Tb1の冷却浴に浸した後、Tc-30℃<Tb2≦Tcを満たす温度Tb2の冷却浴に浸す工程
(ただし、Tcは前記フッ素樹脂系高分子を含有する製膜原液の結晶化温度である。)
最後に、本発明では、以上の方法で得られる柱状組織を有するフッ素樹脂系高分子からなる多孔質中空糸膜を高倍率延伸することで、該高分子の分子鎖を該中空糸膜の長手方向に配向させる。
多孔質中空糸膜4本からなる有効長さ200mmの小型モジュールを作製した。このモジュールに、温度25℃、ろ過差圧16kPaの条件で、1時間にわたって蒸留水を送液し得られた透過水量(m3)を測定し、単位時間(h)および単位膜面積(m2)当たりの数値に換算し、さらに圧力(50kPa)換算して純水透過性能(m3/m2/h)とした。なお、単位膜面積は平均外径と多孔質中空糸膜の有効長から算出した。
引っ張り試験機(TENSILON(登録商標)/RTM-100、東洋ボールドウィン株式会社製)を用い、測定長さ50mmの試料を引っ張り速度50mm/分で、試料を変えて5回以上試験し、破断強度、破断伸度の平均値を求めることで算出した。
多孔質中空糸膜の長手方向が鉛直となるように繊維試料台に取り付け、X線回折装置(Rigaku社製、高分子用SmartLab、CuKα線)を用いて、X線回折測定(2θ/θスキャン、βスキャン)を行った。まず、2θ/θスキャンで、2θ=20.4°にピークトップがあることを確認した。次に、βスキャンにて、2θ=20.4°の回折ピークに対し、方位角方向に0°から360°までの強度を測定することにより、方位角方向の強度分布を得た。ここで、方位角180°の強度と方位角90°の強度の比が0.80以下、または、1.25以上となる場合にピークが存在するとみなし、この方位角方向の強度分布において、ピーク高さの半分の位置における幅(半値幅H)を求め、下記式(1)によって配向度πを算出した。なお、βスキャンにおける強度の極小値が0°と180°付近に見られたため、これらを通る直線をベースラインとした。
配向度π=(180°-H)/180° ・・・(1)
多孔質中空糸膜中のポリフッ化ビニリデンホモポリマーの配向のパラメータを以下の操作により求めた。
多孔質中空糸膜の長手方向の断面を、ミクロトームによる切削により切片化した。多孔質中空糸膜1本あたり10個の柱状組織を選択し、光学顕微鏡で柱状組織を確認しながら、それぞれの柱状組織について、その長手方向に沿って、1μm間隔でレーザーラマン分光法により散乱強度の測定を行った。
それぞれの配向パラメータを式(2)により算出し、各配向パラメータの平均値をラマン配向パラメータνとした。また、10個の相異なる柱状組織の中で、最も大きな配向パラメータと最も小さな配向パラメータを選び、それらについてそれぞれ平均値を求め、最大ラマン配向パラメータM、最小ラマン配向パラメータmとし、M/mを算出した。
配向パラメータ=(I1270/I840)平行/(I1270/I840)垂直 ・・・(2)
平行条件:多孔質中空糸膜の長手方向と偏光方向が平行
垂直条件:多孔質中空糸膜の長手方向と偏光方向が直交
I1270平行:平行条件時の1270cm-1のラマンバンドの強度
I1270垂直:垂直条件時の1270cm-1のラマンバンドの強度
I840平行:平行条件時の840cm-1のラマンバンドの強度
I840垂直:垂直条件時の840cm-1のラマンバンドの強度
レーザーラマン分光装置および測定条件は以下の通りである。
装置:Jobin Yvon/愛宕物産 T-64000
条件:測定モード;顕微ラマン
対物レンズ;×100
ビーム径;1μm
光源;Ar+レーザー/514.5nm
レーザーパワー;100mW
回折格子;Single 600gr/mm
スリット;100μm
検出器;CCD/Jobin Yvon 1024×256
各例で作製した多孔質中空糸膜について、その長手方向に沿った断面を、走査型電子顕微鏡を用いて3000倍で撮影した。撮影された画像から、任意に10個の柱状組織を選択し、それぞれの長手長さ、短手長さを測定した。ここで、各柱状組織の長手長さとしては、長手方向の最大長さを測定した。また、上述したように、各柱状組織の長手長さを1μmで除して小数点以下を切り捨てることで得られた値を測定点数とし、短手方向の長さを測定し、それらの平均値を算出することで、各柱状組織の短手長さを求めた。
上記撮影を5箇所で行い、それぞれ任意の10個の柱状組織について長手長さと短手長さを求め、合計50個の長手長さと合計50個の短手長さを得た。ついで、合計50個の長手長さの平均値を算出し、長手長さの代表値とし、合計50個の短手長さの平均値を算出し、短手長さの代表値とした。
まず、多孔質中空糸膜をエポキシ樹脂で樹脂包埋し、オスミウム染色処理することで、空隙部分をエポキシ樹脂で埋めた。次に、集束イオンビーム(FIB)を備えた走査型電子顕微鏡(SEM)を用いて、多孔質中空糸膜の短手方向に平行な面を、FIBを用いて切り出し、FIBによる切削加工とSEM観察を、多孔質中空糸膜の長手方向に向かって50nm間隔で繰り返し200回実施し、10μmの深さの情報を得た。
太さ均一性A=(重なり面積)/(第二の断面の樹脂部分面積) ・・・(3)
太さ均一性B=(重なり面積)/(第一の断面の樹脂部分面積) ・・・(4)
空隙率は、「(6)太さ均一性」で得た20組の第一の断面と第二の断面、すなわち、合計40点の断面から、任意の20点の断面について、樹脂部分面積と空隙部分面積を用いて、下記式(5)によって求め、それらの平均値を用いた。
空隙率(%)={100×(空隙部分面積)}/{(樹脂部分面積)+(空隙部分面積)} ・・・(5)
多孔質中空糸膜の長手方向の断面を、走査型電子顕微鏡を用いて3000倍で任意の20カ所の写真を撮影し、下記式(6)でそれぞれ求め、それらの平均値を採用した。ここで写真全体の面積および組織の占める面積は、撮影された写真を紙に印刷し、写真全体に対応する紙の重量およびそこから切り取った組織部分に対応する紙の重量としてそれぞれ置き換えて求めた。
占有率(%)={(各組織の占める面積)/(写真全体の面積)}×100 ・・・(6)
セイコー電子工業株式会社製DSC-6200を用いて、フッ素樹脂系高分子と溶媒など製膜高分子原液組成と同組成の混合物を密封式DSC容器に密封し、昇温速度10℃/minで溶解温度まで昇温し、30分保持して均一に溶解した後に、降温速度10℃/minで降温する過程で観察される結晶化ピークの立ち上がり温度を結晶化温度Tcとした。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)36重量%とγ-ブチロラクトン64重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは48℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度25℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.62の柱状組織を有し、柱状組織の占有率は86%であり、球状組織占有率は14%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2.5倍に延伸した。延伸後の多孔質中空糸膜を観察したところ、柱状組織が認められた。また、多孔質中空糸膜において、長手長さの代表値16μm、短手長さの代表値2.2μm、太さ均一性0.61の柱状組織を有し、空隙率が55%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.61、ラマン配向パラメータνは3.12、M/mは3.1であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)36重量%とγ-ブチロラクトン64重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは48℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の第1冷却浴中に10秒間滞留させ、ついで、γ-ブチロラクトン85重量%水溶液からなる温度25℃の第2冷却浴中に20秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.65の柱状組織を有し、柱状組織占有率は87%であり、球状組織占有率は13%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ19μm、短手長さ1.8μm、太さ均一性0.66の柱状組織を有し、空隙率が61%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.77、ラマン配向パラメータνは3.74、M/mは4.2であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)38重量%とγ-ブチロラクトン62重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは51℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の第1冷却浴中に10秒間滞留させ、ついで、γ-ブチロラクトン85重量%水溶液からなる温度35℃の第2冷却浴中に50秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.66の柱状組織を有し、柱状組織占有率は91%であり、球状組織占有率は9%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ24μm、短手長さ1.6μm、太さ均一性0.66の柱状組織を有し、空隙率が59%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.85、ラマン配向パラメータνは4.37、M/mは5.0であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)38重量%とγ-ブチロラクトン62重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは51℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の第1冷却浴中に10秒間滞留させ、ついで、γ-ブチロラクトン85重量%水溶液からなる温度35℃の第2冷却浴中に50秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.66の柱状組織を有し、柱状組織占有率は91%であり、球状組織占有率は9%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ28μm、短手長さ1.3μm、太さ均一性0.62の柱状組織を有し、空隙率が61%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.89、ラマン配向パラメータνは4.42、M/mは5.1であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
また、延伸後の多孔質中空糸膜の2θ=20.4°における方位角方向の強度分布を図1に、多孔質中空糸膜の各測定箇所におけるラマン配向パラメータを図2に、多孔質中空糸膜の長手方向の断面写真を図3にそれぞれ示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度30℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.62の柱状組織を有し、柱状組織占有率は93%であり、球状組織占有率は7%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ20μm、短手長さ2.1μm、太さ均一性0.61の柱状組織を有し、空隙率が64%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.66、ラマン配向パラメータνは3.40、M/mは3.5であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度-5℃の第1冷却浴中に10秒間滞留させ、ついで、ジメチルスルホキシド85重量%水溶液からなる温度15℃の第2冷却浴中に30秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.72の柱状組織を有し、柱状組織占有率は92%であり、球状組織占有率は8%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ27μm、短手長さ1.7μm、太さ均一性0.69の柱状組織を有し、空隙率が64%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.86、ラマン配向パラメータνは4.38、M/mは5.1であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度-5℃の第1冷却浴中に10秒間滞留させ、ついで、ジメチルスルホキシド85重量%水溶液からなる温度20℃の第2冷却浴中に50秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.72の柱状組織を有し、柱状組織占有率は95%であり、球状組織占有率は5%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ35μm、短手長さ1.5μm、太さ均一性0.67の柱状組織を有し、空隙率が65%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.91、ラマン配向パラメータνは4.62、M/mは5.8であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度-5℃の第1冷却浴中に10秒間滞留させ、ついで、ジメチルスルホキシド85重量%水溶液からなる温度20℃の第2冷却浴中に50秒間滞留させ、固化させた。得られた多孔質中空糸膜は、太さ均一性0.72の柱状組織を有し、柱状組織占有率は95%であり、球状組織占有率は5%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を4倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ40μm、短手長さ1.1μm、太さ均一性0.63の柱状組織を有し、空隙率が66%、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.92、ラマン配向パラメータνは4.76、M/mは6.2であった。延伸後の多孔質中空糸膜の構造と性能を表1に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)を15重量%、重量平均分子量2万のポリエチレングリコールを3重量%、N-メチル-2-ピロリドンを80重量%、水を2重量%の割合で95℃の温度で混合溶解してポリマー溶液を調製した。
このポリマー溶液を、実施例2で延伸後に得られた中空糸膜(外径:1240μm、内径:740μm、膜厚:250μm)の表面に均一に塗布し、すぐに水浴中で凝固させて、柱状組織を有する層の上に三次元網目構造(膜厚:30μm)からなる層を形成させた多孔質中空糸膜を作製した。ここで、柱状組織を有する層の厚みに対する三次元網目構造層の厚みは、0.12であった。この多孔質中空糸膜の柱状組織を有する層を見ると、長手長さ40μm、短手長さ1.1μm、太さ均一性0.63の柱状組織を有し、柱状組織占有率は87%であり、球状組織占有率は13%であり、空隙率が66%、ラマン配向パラメータνは4.75、M/mは6.0であり、三次元網目構造層を形成させても、実施例2とほぼ変化なかった。
また、フッ化ビニリデンホモポリマー分子鎖の多孔質中空糸膜の長手方向への配向度πは0.89であり、三次元網目構造層を形成させても、実施例2とほぼ変化なかった。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)38重量%とγ-ブチロラクトン62重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは51℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.47の繊維状組織を有し、繊維状組織占有率は91%であり、球状組織占有率は9%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を1.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ15μm、短手長さ2.2μm、太さ均一性0.45の繊維状組織を有し、空隙率が63%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.01、M/mは1.0であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
また、延伸後の多孔質中空糸膜の2θ=20.4°における方位角方向の強度分布を図1に、多孔質中空糸膜の長手方向の断面写真を図4にそれぞれ示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)38重量%とγ-ブチロラクトン62重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは51℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.47の繊維状組織を有し、繊維状組織占有率は91%であり、球状組織占有率は9%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ18μm、短手長さ1.7μm、太さ均一性0.42の繊維状組織を有し、空隙率が65%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.03、M/mは1.1であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)38重量%とγ-ブチロラクトン62重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは51℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度5℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.47の繊維状組織を有し、繊維状組織占有率は91%であり、球状組織占有率は9%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を3.5倍に延伸したところ糸切れが発生し延伸することができなかった。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)36重量%とγ-ブチロラクトン64重量%を150℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは48℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で0.2MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にγ-ブチロラクトン85重量%水溶液を二重管式口金の内側の管から吐出し、γ-ブチロラクトン85重量%水溶液からなる温度25℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.42の繊維状組織を有し、繊維状組織占有率は24%であり、球状組織占有率は76%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2倍に延伸したところ糸切れが発生し延伸することができなかった。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度0℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.56の繊維状組織を有し、繊維状組織占有率は84%であり、球状組織占有率は16%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を1.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ18μm、短手長さ1.2μm、太さ均一性0.53の繊維状組織を有し、空隙率が64%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.03、M/mは1.1であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)40重量%とジメチルスルホキシド60重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは30℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、78~80℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度0℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.56の繊維状組織を有し、繊維状組織占有率は84%であり、球状組織占有率は16%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ22μm、短手長さ1.0μm、太さ均一性0.51の繊維状組織を有し、空隙率が65%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.05、M/mは1.1であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)28重量%とジメチルスルホキシド72重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは20℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、64~66℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度0℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.42の繊維状組織を有し、繊維状組織占有率は88%であり、球状組織占有率は12%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を1.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ14μm、短手長さ1.2μm、太さ均一性0.41の繊維状組織を有し、空隙率が71%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.04、M/mは1.1であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)28重量%とジメチルスルホキシド72重量%を130℃で溶解した。このフッ化ビニリデンホモポリマー溶液のTcは20℃であった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で2.0MPaに加圧し、64~66℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルスルホキシド90重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルスルホキシド85重量%水溶液からなる温度0℃の冷却浴中に20秒間滞留させ固化させた。得られた多孔質中空糸膜は、太さ均一性0.42の繊維状組織を有し、繊維状組織占有率は88%であり、球状組織占有率は12%であった。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2.5倍に延伸した。延伸後の多孔質中空糸膜は、長手長さ19μm、短手長さ0.8μm、太さ均一性0.37の繊維状組織を有し、空隙率が73%、フッ化ビニリデンホモポリマー分子鎖は無配向、ラマン配向パラメータνは1.06、M/mは1.2であった。延伸後の多孔質中空糸膜の構造と性能を表2に示す。
フッ化ビニリデンホモポリマー(株式会社クレハ製KF1300、重量平均分子量:41.7万、数平均分子量:22.1万)15重量%とジメチルアセトアミド85重量%を100℃で溶解した。このフッ化ビニリデンホモポリマー溶液は、ジメチルアセトアミドがフッ化ビニリデンホモポリマーの良溶媒であるため、Tcを有さなかった。該溶液を2つのギヤーポンプを設置することにより、その間のライン上で0.2MPaに加圧し、99~101℃で20秒間滞留させた後、二重管式口金の外側の管から吐出し、同時にジメチルアセトアミド85重量%水溶液を二重管式口金の内側の管から吐出し、ジメチルアセトアミド85重量%水溶液からなる温度25℃の冷却浴中に40秒間滞留させ固化させた。得られた多孔質中空糸膜は、球状組織、繊維状組織、柱状組織のいずれも有さず、三次元網目状構造を有していた。
ついで、95℃の水中にて、上記で得られた多孔質中空糸膜を2倍に延伸したところ糸切れが発生し延伸することができなかった。
Claims (11)
- フッ素樹脂系高分子を含有する多孔質中空糸膜であって、
前記多孔質中空糸膜の長手方向に配向する柱状組織を有し、
前記フッ素樹脂系高分子の分子鎖が前記多孔質中空糸膜の長手方向に配向しており、
下記式(1)に基づき算出される分子鎖の配向度πが、0.4以上1.0未満である多孔質中空糸膜。
配向度π=(180°-H)/180° ・・・(1)
(ただし、Hは広角X線回折像の円周方向における回折強度分布の半値幅(°)である。) - 前記柱状組織の短手長さが0.5μm以上3μm以下、且つ、該柱状組織のアスペクト比が3以上である、請求項1に記載の多孔質中空糸膜。
- 前記柱状組織の太さ均一性が0.60以上である、請求項1または2に記載の多孔質中空糸膜。
- 前記半値幅Hは、広角X線回折測定によるポリフッ化ビニリデンの(110)面由来の結晶ピーク(2θ=20.4°)を円周方向にスキャンして得られる強度分布の半値幅である、請求項1~3のいずれか1項に記載の多孔質中空糸膜。
- 前記多孔質中空糸膜の長手方向に1cm間隔の測定点で広角X線回折測定を行った際に、80%以上の前記測定点で、前記配向度πが0.4以上1.0未満である、請求項1~4のいずれか1項に記載の多孔質中空糸膜。
- 前記フッ素樹脂系高分子がポリフッ化ビニリデンであり、ラマン分光法によって得られる分子鎖のラマン配向パラメータνが3.0以上である、請求項1~5のいずれか1項に記載の多孔質中空糸膜。
- 空隙率が50%以上80%以下である、請求項1~6のいずれか1項に記載の多孔質中空糸膜。
- 50kPa、25℃における純水透過性能が0.7m3/m2/hr以上であり、破断強度が25MPa以上である、請求項1~7のいずれか1項に記載の多孔質中空糸膜。
- 熱誘起相分離によって形成される、請求項1~8のいずれか1項に記載の多孔質中空糸膜。
- 下記1)および2)の工程を備える多孔質中空糸膜の製造方法。
1)フッ素樹脂系高分子を含有する製膜原液から、熱誘起相分離により、長さ方向に配向し、かつ0.60以上1.00未満の太さ均一性を有する柱状組織を有する多孔質中空糸を形成する工程
2)前記1)で得られた多孔質中空糸を長手方向に2.0倍以上5.0倍以下で延伸する工程 - 前記工程1)の熱誘起相分離が下記a)およびb)の冷却工程のうちの少なくとも一方を備える、請求項10に記載の多孔質中空糸膜の製造方法。
a)前記製膜原液をTc-30℃<Tb≦Tcを満たす温度Tbの冷却浴に浸す工程
b)前記製膜原液をTb1≦Tc-30℃を満たす温度Tb1の冷却浴に浸した後、Tc-30℃<Tb2≦Tcを満たす温度Tb2の冷却浴に浸す工程
(ただし、Tcは前記フッ素樹脂系高分子を含有する製膜原液の結晶化温度である。)
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US10456753B2 (en) | 2015-08-31 | 2019-10-29 | Toray Industries, Inc. | Porous hollow fiber membrane |
WO2017038224A1 (ja) * | 2015-08-31 | 2017-03-09 | 東レ株式会社 | 多孔質中空糸膜 |
WO2017056594A1 (ja) * | 2015-09-29 | 2017-04-06 | 東レ株式会社 | 多孔質成形体 |
WO2017115769A1 (ja) * | 2015-12-28 | 2017-07-06 | 東レ株式会社 | 中空糸膜モジュールおよびその運転方法 |
EP3398674B1 (en) * | 2015-12-28 | 2023-02-15 | Toray Industries, Inc. | Hollow fiber membrane module and method for operating same |
JP6191790B1 (ja) * | 2015-12-28 | 2017-09-06 | 東レ株式会社 | 中空糸膜モジュールおよびその運転方法 |
US11141698B2 (en) | 2015-12-28 | 2021-10-12 | Toray Industries, Inc. | Hollow fiber membrane module and method for operating same |
US11058996B2 (en) | 2016-02-25 | 2021-07-13 | Toray Industries, Inc. | Porous hollow fiber membrane |
JPWO2017146211A1 (ja) * | 2016-02-25 | 2018-12-13 | 東レ株式会社 | 多孔質中空糸膜 |
WO2017146211A1 (ja) * | 2016-02-25 | 2017-08-31 | 東レ株式会社 | 多孔質中空糸膜 |
JPWO2017209151A1 (ja) * | 2016-05-31 | 2019-03-28 | 東レ株式会社 | 多孔質中空糸膜およびその製造方法 |
US11077407B2 (en) | 2016-05-31 | 2021-08-03 | Toray Industries, Inc. | Porous hollow-fiber membrane and production process therefor |
WO2017209151A1 (ja) * | 2016-05-31 | 2017-12-07 | 東レ株式会社 | 多孔質中空糸膜およびその製造方法 |
JPWO2017222062A1 (ja) * | 2016-06-24 | 2019-04-11 | 東レ株式会社 | 複合多孔質中空糸膜、複合多孔質中空糸膜の製造方法、複合多孔質中空糸膜モジュール及び複合多孔質中空糸膜モジュールの運転方法 |
US11020709B2 (en) | 2016-06-24 | 2021-06-01 | Toray Industries, Inc. | Composite porous hollow fiber membrane, production method for composite porous hollow fiber membrane, composite porous hollow fiber membrane module, and operation method for composite porous hollow fiber membrane module |
WO2017222062A1 (ja) * | 2016-06-24 | 2017-12-28 | 東レ株式会社 | 複合多孔質中空糸膜、複合多孔質中空糸膜の製造方法、複合多孔質中空糸膜モジュール及び複合多孔質中空糸膜モジュールの運転方法 |
Also Published As
Publication number | Publication date |
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KR101969663B1 (ko) | 2019-04-16 |
AU2015368335B2 (en) | 2018-06-14 |
EP3238814A4 (en) | 2018-06-27 |
JPWO2016104743A1 (ja) | 2017-06-08 |
KR101784141B1 (ko) | 2017-10-10 |
CN107106998A (zh) | 2017-08-29 |
KR20170083637A (ko) | 2017-07-18 |
US9901883B2 (en) | 2018-02-27 |
US20170348649A1 (en) | 2017-12-07 |
KR20170116165A (ko) | 2017-10-18 |
HUE051691T2 (hu) | 2021-10-28 |
EP3238814B1 (en) | 2020-08-12 |
JP6245281B2 (ja) | 2017-12-13 |
EP3238814A1 (en) | 2017-11-01 |
CN107106998B (zh) | 2018-06-12 |
AU2015368335A1 (en) | 2017-07-13 |
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