CA2886437A1 - Method for producing an integral-asymmetric hollow-fibre polymer membrane consisting of an amphiphilic block copolymer, the hollow-fibre membrane obtained and the use thereof - Google Patents
Method for producing an integral-asymmetric hollow-fibre polymer membrane consisting of an amphiphilic block copolymer, the hollow-fibre membrane obtained and the use thereof Download PDFInfo
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- CA2886437A1 CA2886437A1 CA 2886437 CA2886437A CA2886437A1 CA 2886437 A1 CA2886437 A1 CA 2886437A1 CA 2886437 CA2886437 CA 2886437 CA 2886437 A CA2886437 A CA 2886437A CA 2886437 A1 CA2886437 A1 CA 2886437A1
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- hollow
- fibre
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- 239000000835 fiber Substances 0.000 title claims abstract description 80
- 229920005597 polymer membrane Polymers 0.000 title claims abstract description 27
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 13
- 229920000469 amphiphilic block copolymer Polymers 0.000 title claims abstract description 8
- 239000012528 membrane Substances 0.000 title claims description 57
- 229920000642 polymer Polymers 0.000 claims abstract description 67
- 238000000034 method Methods 0.000 claims abstract description 44
- 239000002904 solvent Substances 0.000 claims abstract description 38
- 239000007788 liquid Substances 0.000 claims abstract description 36
- 238000001556 precipitation Methods 0.000 claims abstract description 35
- 230000000694 effects Effects 0.000 claims abstract description 11
- 238000001914 filtration Methods 0.000 claims abstract description 11
- 238000000578 dry spinning Methods 0.000 claims abstract description 8
- 238000002166 wet spinning Methods 0.000 claims abstract description 8
- 238000003825 pressing Methods 0.000 claims abstract description 3
- 210000004379 membrane Anatomy 0.000 claims description 53
- 239000000243 solution Substances 0.000 claims description 48
- 239000011148 porous material Substances 0.000 claims description 30
- 229920001400 block copolymer Polymers 0.000 claims description 24
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 21
- 239000000203 mixture Substances 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 16
- 230000015572 biosynthetic process Effects 0.000 claims description 15
- 238000005755 formation reaction Methods 0.000 claims description 15
- -1 polysiloxane Polymers 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 12
- 150000003839 salts Chemical class 0.000 claims description 12
- 150000001720 carbohydrates Chemical class 0.000 claims description 11
- 235000014633 carbohydrates Nutrition 0.000 claims description 11
- 229910052751 metal Inorganic materials 0.000 claims description 10
- 239000002184 metal Substances 0.000 claims description 10
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 9
- 238000000108 ultra-filtration Methods 0.000 claims description 9
- 238000001471 micro-filtration Methods 0.000 claims description 8
- 238000001728 nano-filtration Methods 0.000 claims description 8
- 239000000693 micelle Substances 0.000 claims description 7
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 229920006030 multiblock copolymer Polymers 0.000 claims description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 5
- 229910052791 calcium Inorganic materials 0.000 claims description 5
- 239000011575 calcium Substances 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- 239000011777 magnesium Substances 0.000 claims description 5
- 229910052712 strontium Inorganic materials 0.000 claims description 5
- CIOAGBVUUVVLOB-UHFFFAOYSA-N strontium atom Chemical compound [Sr] CIOAGBVUUVVLOB-UHFFFAOYSA-N 0.000 claims description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- 229920001577 copolymer Polymers 0.000 claims description 4
- 230000007704 transition Effects 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 229920000136 polysorbate Polymers 0.000 claims description 3
- 229920002223 polystyrene Polymers 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- KGIGUEBEKRSTEW-UHFFFAOYSA-N 2-vinylpyridine Chemical compound C=CC1=CC=CC=N1 KGIGUEBEKRSTEW-UHFFFAOYSA-N 0.000 claims description 2
- KFDVPJUYSDEJTH-UHFFFAOYSA-N 4-ethenylpyridine Chemical compound C=CC1=CC=NC=C1 KFDVPJUYSDEJTH-UHFFFAOYSA-N 0.000 claims description 2
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 2
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 claims description 2
- 229920002845 Poly(methacrylic acid) Polymers 0.000 claims description 2
- 239000005062 Polybutadiene Substances 0.000 claims description 2
- 239000004698 Polyethylene Substances 0.000 claims description 2
- 239000004793 Polystyrene Substances 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- 229920002125 Sokalan® Polymers 0.000 claims description 2
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 2
- 229930006000 Sucrose Natural products 0.000 claims description 2
- GZCGUPFRVQAUEE-SLPGGIOYSA-N aldehydo-D-glucose Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O GZCGUPFRVQAUEE-SLPGGIOYSA-N 0.000 claims description 2
- HFHDHCJBZVLPGP-RWMJIURBSA-N alpha-cyclodextrin Chemical compound OC[C@H]([C@H]([C@@H]([C@H]1O)O)O[C@H]2O[C@@H]([C@@H](O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O[C@H]3O[C@H](CO)[C@H]([C@@H]([C@H]3O)O)O3)[C@H](O)[C@H]2O)CO)O[C@@H]1O[C@H]1[C@H](O)[C@@H](O)[C@@H]3O[C@@H]1CO HFHDHCJBZVLPGP-RWMJIURBSA-N 0.000 claims description 2
- 235000013681 dietary sucrose Nutrition 0.000 claims description 2
- UEGPKNKPLBYCNK-UHFFFAOYSA-L magnesium acetate Chemical compound [Mg+2].CC([O-])=O.CC([O-])=O UEGPKNKPLBYCNK-UHFFFAOYSA-L 0.000 claims description 2
- 229940069446 magnesium acetate Drugs 0.000 claims description 2
- 235000011285 magnesium acetate Nutrition 0.000 claims description 2
- 239000011654 magnesium acetate Substances 0.000 claims description 2
- 239000012454 non-polar solvent Substances 0.000 claims description 2
- 239000002798 polar solvent Substances 0.000 claims description 2
- 229920002006 poly(N-vinylimidazole) polymer Polymers 0.000 claims description 2
- 229920000233 poly(alkylene oxides) Polymers 0.000 claims description 2
- 229920000747 poly(lactic acid) Polymers 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
- 239000004584 polyacrylic acid Substances 0.000 claims description 2
- 229920000767 polyaniline Polymers 0.000 claims description 2
- 229920002857 polybutadiene Polymers 0.000 claims description 2
- 229920000573 polyethylene Polymers 0.000 claims description 2
- 229920001195 polyisoprene Polymers 0.000 claims description 2
- 239000004626 polylactic acid Substances 0.000 claims description 2
- 229920001296 polysiloxane Polymers 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 2
- 108090000623 proteins and genes Proteins 0.000 claims description 2
- 102000004169 proteins and genes Human genes 0.000 claims description 2
- 229960004793 sucrose Drugs 0.000 claims description 2
- 229920002554 vinyl polymer Polymers 0.000 claims description 2
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 claims 1
- 239000005715 Fructose Substances 0.000 claims 1
- 125000005250 alkyl acrylate group Chemical group 0.000 claims 1
- 229920002338 polyhydroxyethylmethacrylate Polymers 0.000 claims 1
- NLVXSWCKKBEXTG-UHFFFAOYSA-N vinylsulfonic acid Chemical compound OS(=O)(=O)C=C NLVXSWCKKBEXTG-UHFFFAOYSA-N 0.000 claims 1
- 238000009987 spinning Methods 0.000 description 10
- 229940077731 carbohydrate nutrients Drugs 0.000 description 8
- 238000000926 separation method Methods 0.000 description 7
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 7
- 230000000875 corresponding effect Effects 0.000 description 5
- 238000007654 immersion Methods 0.000 description 5
- 238000001878 scanning electron micrograph Methods 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 230000001788 irregular Effects 0.000 description 3
- 238000005191 phase separation Methods 0.000 description 3
- 238000010008 shearing Methods 0.000 description 3
- 239000011877 solvent mixture Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000003125 aqueous solvent Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229940063557 methacrylate Drugs 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 1
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 229920000858 Cyclodextrin Polymers 0.000 description 1
- LKDRXBCSQODPBY-VRPWFDPXSA-N D-fructopyranose Chemical compound OCC1(O)OC[C@@H](O)[C@@H](O)[C@@H]1O LKDRXBCSQODPBY-VRPWFDPXSA-N 0.000 description 1
- CERQOIWHTDAKMF-UHFFFAOYSA-M Methacrylate Chemical compound CC(=C)C([O-])=O CERQOIWHTDAKMF-UHFFFAOYSA-M 0.000 description 1
- 208000036366 Sensation of pressure Diseases 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000009918 complex formation Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000000502 dialysis Methods 0.000 description 1
- 150000004985 diamines Chemical class 0.000 description 1
- 229940113088 dimethylacetamide Drugs 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 229960002737 fructose Drugs 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000012510 hollow fiber Substances 0.000 description 1
- 239000011796 hollow space material Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- CZFNISFYDPIDNM-UHFFFAOYSA-N n,n-dimethylformamide;oxolane Chemical compound CN(C)C=O.C1CCOC1 CZFNISFYDPIDNM-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- WCPAKWJPBJAGKN-UHFFFAOYSA-N oxadiazole Chemical compound C1=CON=N1 WCPAKWJPBJAGKN-UHFFFAOYSA-N 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920003228 poly(4-vinyl pyridine) Polymers 0.000 description 1
- 229920000075 poly(4-vinylpyridine) Polymers 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 229920006393 polyether sulfone Polymers 0.000 description 1
- 229920001601 polyetherimide Polymers 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- HFHDHCJBZVLPGP-UHFFFAOYSA-N schardinger α-dextrin Chemical compound O1C(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(O)C2O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC2C(O)C(O)C1OC2CO HFHDHCJBZVLPGP-UHFFFAOYSA-N 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000008093 supporting effect Effects 0.000 description 1
- 239000003021 water soluble solvent Substances 0.000 description 1
- PAPBSGBWRJIAAV-UHFFFAOYSA-N ε-Caprolactone Chemical compound O=C1CCCCCO1 PAPBSGBWRJIAAV-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- 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
-
- 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
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
- B01D71/80—Block polymers
-
- 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
- B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
- B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/15—Use of additives
- B01D2323/18—Pore-control agents or pore formers
-
- 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
-
- 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
- B01D2325/0283—Pore size
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/36—Hydrophilic membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/38—Hydrophobic membranes
Abstract
The invention relates to a method using a dry/wet spinning method for producing a self-supporting integral-asymmetric hollow-fibre polymer membrane (16) having an isoporous outer skin, a porous inner skin and a sponge-like inner structure. The invention further relates to an integral-asymmetric hollow-fibre polymer membrane (16), a filtration module and a use. The method according to the invention comprises the following method steps: production of a polymer solution having at least one solvent, in which at least one amphiphilic block copolymer having at least two different polymer blocks is dissolved; pressing the polymer solution through a spinneret (2) formed as a hollow-core nozzle or multiple hollow-core nozzle to form a hollow fibre (12), in the centre of which a liquid column is spun, which consists of a precipitant having reduced precipitation activity; and after passing through a precipitation section (13) in an atmosphere, immersing the spun hollow-fibre (12) in a precipitation bath (14) to form the hollow-fibre polymer membrane (16).
Description
Method for Producing an Integral-Asymmetric Hollow-Fibre Polymer Mem-brane Consisting of an Amphiphilic Block Copolmyer, The Hollow-Fibre Membrane obtained and the Use thereof Description The invention relates to a method for producing a self-supporting integral-asymmetric hollow-fibre polymer membrane having an isoporous outer skin, a porous inner skin and a sponge-like inner structure in a dry/wet spinning method. The invention further relates to an integral-asymmetric hollow-fibre polymer membrane, a filtration module and a use.
The invention thus relates to the field of membrane-support microfiltration, ultrafiltration and nanofiltration. Such membranes have a porous separa-tion layer, wherein the size and regularity of the pores determine both the separation limit as well as the selectivity. The most isoporous possible membrane is hereby desired, i.e. a membrane with a most regular possi-ble structure of pores, the diameter of which is as uniform as possible.
Corresponding membranes are producible in different manners. Mem-¨ 2 ¨
' branes produced according to a so-called phase inversion process are predominantly used. These membranes have a more or less large statisti-cal variance during the distribution of the pore size. In addition to a low selectivity, such membranes also tend to so-called "fouling". This is a fast blocking of the large pores, since a larger portion of the liquid passing through the membrane first passes through these large pores. The fouling is also considerably reduced for isoporous membranes.
In German patent no. 10 2006 045 282 by the applicant, which has been published as DE 10 2006 045 282 Al, a method is disclosed by means of which polymer membranes can be produced with isoporous separation-active surfaces. For this purpose, an amphiphilic block copolymer is dis-solved in a casting solution with one or more solvents, spread into a film, and the film is immersed in a precipitation bath.
This method exploits the fact that the polymer blocks of the amphiphilic block copolymer are not miscible with each other. The block copolymers therefore form microphases in the casting solution such as a known mi-celle structure with spherical or cylindrical micelles. Within a short evapo-ration time, part of the liquid solvent close to the surface evaporates such that the microphase morphology hardens in a layer of the film close to the surface that has formed due to the self-organization of the polymer blocks of the block copolymers, whereas the block copolymers remain dissolved within the bulk of the casting solution.
By dipping this film in a precipitation bath, the rest of the solvent is dis-placed, and a known phase inversion process occurs which results in a known sponge-like structure. In some cases, the previously assumed mi-crophase-separated isoporous structure of the layer close to the surface is retained despite being dipped in the precipitation bath. This then transi-tions directly into the sponge-like structure. Additional descriptions are contained in DE 10 2006 045 282 Al, the entire disclosed content of which ¨ 3 ¨
is incorporated in the present application.
An overview of other different methods for producing isoporous mem-branes is also included in DE 10 2006 045 282 Al of the applicant.
However, up until now, this concept of flat membranes has not been suc-cessfully transferred to hollow-fibre membranes. Due to its considerably larger ratio of separation surface to packing volume in one module, hollow-fibre membranes are very interesting for the economical application, in particular for applications that require large membrane surfaces, such as drinking water treatment or dialysis.
Up until now, hollow-fibre membranes for the ultrafiltration of aqueous sys-tems are mainly produced based on polysulfone or respectively polyether-sulfones or polyether imides, polyvinylidene fluorides (PVDF) or poly-acrylnitrile (PAN) through phase inversion of corresponding polymer solu-tions, which are spun as hollow fibres and precipitated in water. These membranes show no isoporous structure and for this reason have a great-er tendency for fouling.
An overview of new developments in the production of polymeric hollow fibres is provided in the article Na Peng et al., "Evolution of polymeric hol-low fibers as sustainable technologies: Past, present, and future", Pro-gress in Polymer Science 37 (2012), 1401 ¨ 1424. It describes the tech-nique of spinning hollow fibres, in which a spinning solution with at least one polymer is directed through an annular spinneret, wherein another liquid is directed concentrically on the inside through the spinneret and penetrates the hollow space of the hollow fibre formed in this manner. De-pending on the selection of the polymers and of the solutions, which act from outside or respectively inside on the hollow fibres, mainly impermea-ble surfaces are achieved.
¨ 4 ¨
Based on this state of the art, the object of the present invention is to make available hollow-fibre membranes with an isoporous pore structure in a separation-active surface, which are usable for microfiltration, ultrafil-tration or nanofiltration.
The object is solved by a method for producing a self-supporting integral-asymmetric hollow-fibre polymer membrane having an isoporous outer skin, a porous inner skin and a sponge-like inner structure in a dry/wet spinning method with the following method steps:
¨ Production of a polymer solution having at least one solvent, in which at least one amphiphilic block copolymer having at least two different polymer blocks is dissolved, - Pressing the polymer solution through a spinneret formed as a hol-low-core nozzle or multiple hollow-core nozzle to form a hollow fibre, in the centre of which a liquid column is spun, which consists of a precipitant having reduced precipitation activity, - After passing through a fall section in an atmosphere, immersing the spun hollow fibre in a precipitation bath to form the hollow-fibre poly-mer membrane.
The method according to the invention corresponds with a dry/wet spin-fling method insofar, as after the extruding the hollow fibre passes through a fall section without external contacting of a liquid precipitation bath first ("dry") and is then immersed into a bath of a liquid precipitant ("wet").
The execution of the method according to the invention leads to the pro-duction of polymer hollow-fibre membranes with an isoporous outer sur-face, which is based on the self-organization of the tailored block copoly-¨ 5 ¨
mers in microphases of the so-called microphase separation. This isopo-rous separation-active outer surface transitions into a typical sponge-like structure of a membrane produced through precipitant-induced phase in-version. This sponge-like structures gives the hollow-fibre membrane its stability and permeability so that the hollow-fibre membrane is self-supporting or respectively self-carrying. The passing of a fall section in an atmosphere, i.e. a dry part of the process at first, thereby leads to part of the solvent of the polymer solution evaporating and a microphase-separated structure being able to solidify at the outer surface, which sur-vives the immersion into the precipitation bath after passing through the fall section.
According to the invention, a precipitant with reduced precipitation activity is used for the inner surface of the hollow-fibre membrane. Tests have shown that a conventional precipitant such as water leads to the formation of a mainly impermeable or respectively almost impermeable inner skin.
The inner skin formed in this manner is then so impermeable that it still holds onto particles, which can pass through the separation-active outer skin. With such a liquid-impermeable inner skin, the hollow-fibre mem-brane designed in this manner is generally unsuitable for filtration. The use of a precipitant with reduced precipitation activity causes the surface for-mation to progress with lower kinetics than for a normally used precipitant.
The reaction thereby has enough time for a partial separation on the inner surface so that pores can form inside the surface so that use for filtration is enabled.
The liquid column preferably consists of a mixture of at least one precipi-tant for the at least one block copolymer and at least one solvent mixable with the precipitant for the at least one block copolymer. Due to the fact that the solvent or the solvents is or respectively are mixable with the pre-cipitant in the liquid column, the precipitation activity of the precipitant is reduced considerably. The separation of the copolymer from the polymer ¨ 6 ¨
solution thereby leads to the desired pore formation on the inner boundary surface. The liquid column can preferably also contain at least one pore forming material, in particular polyethylene glycol (PEG). This can support the pore formation on the inner surface of the hollow fibre.
Additionally, at least one metal salt is preferably dissolved in the polymer solution, wherein one of the polymer blocks forms complexes with the metal, wherein the metal is preferably a main group element of the second main group in particular magnesium, calcium or strontium, wherein the salt is in particular advantageously magnesium acetate or another organic salt of magnesium, calcium or strontium. The metals of the second main group are more biocompatible than transition metals so that they are preferred for hollow-fibre membranes with biological applications. Magnesium and calcium in particular occur in comparatively large amounts in the human body. Strontium also occurs in small amounts in the body and is not toxic.
The supported effect of the salt in the phase separation is attributed to the fact that the added salt leads to the formation of partially charged polyelec-trolytic micelle cores, which positively impact the non-solvent-induced phase separation.
Alternatively or additional, it is advantageously provided that at least one carbohydrate is additionally dissolved in the polymer solution, in particular saccharose, D(+)-glucose, D(-)-fructose and/or cyclodextrin, in particular a-cyclodextrin. These substances are more biocompatible than the transi-tion metals and their salts. For use in the method according to the inven-tion, the carbohydrates show a clear stabilization of the isoporous separa-tion-active surface during the phase inversion through immersion in a pre-cipitation bath.
The supporting effect of the carbohydrates in the phase separation is at-tributed to the fact that the carbohydrates can form hydrogen bonds to the ¨ 7 ¨
hydrophilic block of the block copolymers. Through the hydrogen bonds, the viscosity of the polymer solution is greatly increased so that a lower concentration of the block copolymers in the solution is sufficient to form the structure according to the invention with the isoporous separation-active layer.
In the case of both types of additives, i.e. metal salts or carbohydrates, a moderate, thermo-reversible linking of a block type in the polymer solution, in particular of the pore-forming component, thus takes place for example through hydrogen bonds or complex formation.
The problem of a permanently belated release of toxic metal ions through the membrane during its use is thus no longer relevant through the use of carbohydrates for improving the membrane structure. Since carbohydrates are non-toxic, the use of the membrane for medically or respectively bio-logically relevant processes is thus harmless.
Due to the increased viscosity, it is also hereby possible to work with lower block copolymer concentrations in the polymer solution, which leads to material savings for the relatively expensive block copolymers. The clean-ing of the membrane produced with carbohydrates is unproblematic.
Both the membranes produced with metal salts and those produced with carbohydrates show adjustable pore sizes in a few cases. Thus, the water flow through the membrane can be adjusted in a broad range via a change in the pH value of a solution flowing through the pores. The control over the pH value works when the pore-forming polymer block reacts to chang-es in the pH value, for example expands or contracts and thus narrows or widens the pores.
The at least one block copolymer preferably comprises two or more differ-ent polymer blocks A, B or A, B and C or A, B, C and D of the configura-¨ 8 ¨
tion A-B, A-B-A, A-B-C, A-B-C-B-A, A-B-C-D, A-B-C-D-C-B-A or multiblock copolymers based on the aforementioned configurations, wherein the pol-ymer blocks are respectively selected from the group of polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly(ethylene-stat-butylene), poly(ethylene-alt-propylene), polysiloxane, polyalkylene oxide, poly-e-caprolactone, polylactic acid, poly alkyl methac-rylate, polymethacrylic acid, polyalkyl acrylate, polyacrylic acid, polyhy-droxyethyl methacrylate, polyacrylamide, poly-N-alkylacrylamide, polysul-fone, polyaniline, polypyrrole, polytriazole, polyvinylimidazole, polyte-trazole, polyethylene diamine, polyvinyl alcohol, polyvinylpyrrolidone, poly-oxadiazole, polyvinylsulfonic acid, polyvinyl phosphonic acid or polymers.
Multiblock copolymers comprise structures of the base configurations that repeat multiple times. Thus, a multiblock copolymer based on the configu-ration A-B has a structure A-B-A-B etc. or a multiblock copolymer based on the configuration A-B-C the structure A-B-C-A-B-C etc. The multiblock copolymers also form the microphases underlying the invention.
The block copolymers and the polymer blocks preferably have a low poly-dispersity, in particular less than 1.5, in particular less than 1.2. The self-organization of the block copolymers and the microphase formation is thus supported.
The polymer lengths of the at least two polymer blocks of the amphiphilic block copolymers are preferably selected relative with respect to each oth-er so that a self-organization in the solvent leads to the formation of a spherical, cylindrical or co-continuous, in particular gyroidal, micelle struc-ture or microphase structure in the solvent, in particular a length ratio be-tween approximately 2:1 and approximately 10:1, in particular between approx. 3:1 and 6:1. These length ratios of the majority components to the minority components of the block copolymers lead to the desired micelle structure, i.e. to the inclusion of individual spherical micelles of the minority components in the bulk of the majority components or to cylindrical or co-¨ 9 ¨
continuous, for example gyroidal, micelle structures, in which the minority components form the cylinders or respectively gyroidal filaments or re-spectively branchings in the bulk of the majority components.
The block copolymer preferably has a molecular weight between 100 kDa and 600 kDa, in particular between 170 kDa and 320 kDa. In this range, the pore size can be adjusted in a particular fine manner through selection of the molecular weight.
The polymer preferably makes up a percentage by weight between 10 wt.-% and 40 wt.-%, in particular between 15 M.-% and 25 wt.-%, of the solu-tion.
In the dry/wet spinning process, the polymer solution is particularly prefer-ably pressed through the spinneret with an excess press of 0.01 to 0.5 bar, in particular between 0.05 and 0.25 bar. A very regular hollow-fibre membrane can thus be produced, wherein the required excess pressure depends among other things on the viscosity of the polymer solution. The geometry, i.e. in particular radius, gap width and shape, of the spinneret also plays a role, so that for a selected system the excess pressure or re-spectively the throughput can be determined securely and simply through series of tests.
The hollow-core nozzle or multiple hollow-core nozzle to be used accord-ing to the invention has in the simplest case an annular-slit-shaped, outer nozzle opening, which is arranged in particular concentrically around a central nozzle opening. Other hollow-fibre cross-sections can also be cre-ated by suitable geometries of the hollow-core nozzle or multiple hollow-core nozzle, for example elliptical, polygonal, star-shaped with 3 or more rays among other things. With triple- or multi-layered multiple hollow-core nozzles, it is also possible to co-extrude for example carrier and mem-brane and, if applicable, even other layers. Such carrier layers are to be ¨
arranged on the outside and/or inside of the layer according to the inven-tion.
The fall section preferably has a length of between 1 cm and 100 cm, in 5 particular between 10 cm and 100 cm. Depending on the set excess pres-sure or respectively throughput and of the set spinning rate, this means that there is advantageously an evaporation time of between 10 seconds and 60 seconds before immersion in the precipitation bath. The fall section can also be determined securely and optimal through a series of tests.
Several solvents are preferably used, wherein the polymer blocks of the block copolymers in the different solvents are soluble to different degrees and the solvents are volatile to different degrees. The use of different sol-vents, which represent solvents of differing quality in particular for the dif-ferent blocks of the block copolymers, supports the solidification of the self-organization and microphase formation on the outer surface of the hollow fibre before immersion in the precipitation bath.
Respectively a polar or non-polar precipitant or precipitant mixture is ad-vantageously used as precipitant in the liquid column and in the precipita-tion bath after the fall section independently of each other, in particular water and/or methanol and/or ethanol and/or acetone and/or a mixture of two or more of the precipitants or diethyl ether, and respectively a polar or non-polar solvent, in particular dimethylformamide and/or dimethylacetam-ide and/or N-methylpyrrolidone and/or dimethylsulfoxide and/or tetrahydro-furane or a mixture of two or more of the solvents, are used as solvent in the polymer solution and in the liquid column independently of each other, wherein the solvent(s) in the liquid column is or respectively are mixable with the precipitant(s) in the liquid column.
The precipitants or respectively solvents used in the respective precipitant or precipitant mixture and the respective solvent or solvent mixture are - 11 ¨
also respectively intermixable so that the respectively used precipitant mix-ture or respectively solvent mixture is single-phase, i.e. homogeneous.
Diethyl ether is an example of a water-insoluble precipitant. For some pol-ymers, non-aqueous solvents and precipitants are more suitable than aqueous solvents and precipitants.
The object underlying the invention is also solved by an integral-asymmetric hollow-fibre polymer membrane, in particular micro-, ultra- or nanofiltration membrane, produced or producible in an, in particular as described above according to the invention, dry/wet spinning process, wherein the hollow-fibre polymer membrane has an isoporous, separation-active outer surface, which is based on a microphase formation through self-organization of an amphiphilic copolymer, which transitions into a non-solvent-induced, phase-inversion-formed, sponge-like inner structure, wherein an inner surface of the hollow-fibre polymer membrane is formed porously based on a precipitation with an inner liquid column from a pre-cipitant with reduced precipitation activity.
The pores of the separation-active outer surface preferably have a ratio of the maximum pore diameter to the minimum pore diameter of less than 3.
The object underlying the invention is also solved by a filtration module, in particular microfiltration module, ultrafiltration module or nanofiltration module, with at least one of the hollow-fibre polymer membranes de-scribed above according to the invention, as well as by a use of a corre-sponding integral-asymmetric hollow-fibre polymer membrane according to the invention for microfiltration, ultrafiltration or nanofiltration, in particular for filtering out proteins or other nanoparticulate substances.
The advantages, properties and characteristics named for the individual invention objects, i.e. the method, the integral-asymmetric hollow-fibre pol-ymer membrane, the filtration module and the use, also apply without re-¨ 12 ¨
striction to the respective other invention objects, which relate to each oth-er.
Further characteristics of the invention will become apparent from the de-scription of embodiments according to the invention together with the claims and the included drawings.
The invention is described below in an exemplary manner, without restrict-ing the general intent of the invention, based on exemplary embodiments in reference to drawings and figures, wherein we expressly refer to the drawings with regard to the disclosure of all details according to the inven-tion that are not explained in greater detail in the text. The figures shown in:
Fig. 1 a schematic representation of a hollow-fibre-membrane spinning system, Fig. 2a), b) SEM images of cross-sections through a hollow-fibre poly-mer membrane produced according to the invention in two different enlargement stages, Fig. 3a), b) SEM images of the outer surface of a hollow-fibre polymer membrane produced according to the invention in two differ-ent enlargement stages, Fig. 4a), b) SEM images of the inner surface of a hollow-fibre polymer membrane produced according to the invention in two differ-ent enlargement stages and Fig. 5a)-c) SEM images of the cross-section, outer surface and inner surface of a further hollow-fibre polymer membrane pro-duced according to the invention.
¨ 13 ¨
It will be illustrated below using examples how the hollow-fibre membranes according to the invention are produced as completely self-supporting in-tegral-asymmetric membranes.
For this, Fig. 1 shows a spinning system with a spinneret 2 designed as a hollow-core nozzle, which has a central opening and an annular-slit-shaped nozzle or respectively annular nozzle arranged around it concen-trically. Through the annular nozzle, a polymer solution with at least one amphiphilic block copolymer exits, which is kept ready in a polymer solu-tion container 4. The polymer solution is pressed into the spinneret 2 by means of a gas under excess pressure P, in this case nitrogene (N2), which is supplied to a pressure connection 6 on the container 4. Instead of an overpressurized gas, a pump can alternatively be used, which controls the throughput of the polymer solution through the spinneret 2.
Through the central opening or respectively the spinneret 2, a liquid pre-cipitant solution exits a precipitant container 8. A central liquid column is thereby spun. The precipitant introduced in the central opening of the spun hollow fibre 12 is introduced through a pump 10.
A hollow fibre 12 thus exits the spinneret 2, the inner opening or respec-tively lumen of which is filled with a liquid column of the precipitant from the container 8, which brings about a precipitation of the polymer from in-side. The hollow fibre 12 immerses after a fall section 13 into a precipita-tion bath 14 with a further precipitant, for example water. A liquid-induced phase-inversion process takes place there and the hollow-fibre polymer membrane 16 according to the invention is formed from the hollow fibre 12.
Process parameters herein are among other things the selection of the spinneret 2 or respectively annular-slit nozzle, the polymer solution, the ¨ 14 ¨
liquid column, the excess pressure P or respectively the throughput of pol-ymer solution, the fall section 13, the precipitant in the precipitation bath 14, the different concentrations or the local shear rate in the spinneret gap.
The parameters are selected such that a mechanically stable hollow fibre 12 is created as soon as it leaves the spinneret 2 in the direction of the precipitation bath 14 and a formation of a impermeable skin on the inside of the hollow fibre 12 is avoided.
Several processes take place thermodynamically in quick succession. A
slowed liquid-induced phase inversion process without a dry phase first takes place on the inside. Irregular and large pores hereby occur due to the reduced precipitation activity of the inner precipitant. The formation of the cylindrical pore structures on the outside takes place between the spinneret 2 and the precipitation bath 14 through evaporation of a solvent.
Since the hollow fibre 12 is spun downwards, gravity also impacts the -structure formation. After the immersion of the hollow fibre 12 into the pre-cipitation bath 14, a second liquid-induced phase inversion process occurs on the outside surface of the hollow fibre 12, which leads to the final for-mation of the hollow-fibre polymer membrane 16.
The scanning electron microscope (SEM) images in Figures 2 to 5 show a relatively narrow pore size distribution on the outer skin, which is caused by the microphase separation and the solvent-precipitant exchange. In contrast, the inner skin shows elliptical pore structures, which were creat-ed due to the slowed phase inversion on the inside of the hollow fibre 12 and aligned parallel to the spinning direction due to the shearing in the gap. In certain cases, considerable hollow spaces occur here, which cre-ate a porosity, which is needed for the filtration.
It was found that pure water is not suitable as a core liquid. In contrast, water mixtures with the solvents of the block copolymer solution are suita-ble for a corresponding coarsely porous inner skin.
¨ 15 ¨
Examples according to the invention are described below.
Production of a Polymer Solution In order to produce a polymer solution with different concentrations and solvent mixtures, a polystyrene-block-poly(4-vinylpyridine) block copoly-mer (PS-b-P4VP) was solved in a mixture of N,N-Dimethylformamide (DMF) and tetrahydrofuran (THF) at room temperature for one day under constant stirring with a magnetic stirrer, until the polymer solution became homogeneous.
Before the spinning of the hollow fibre, the polymer solution was stored at room temperature without stirring for 12 hours in order to remove the shearing effect of the stirring and fine air bubbles, which were trapped in the solution.
A copolymer PS-b-P4VP with a total molecular weight of 154 kg/mol (kDa) was used as the polymer, whereby 82.7 wt.-% was polystyrol and 17.3 wt.-Yo were P4VP. The solution contained 27 wt.-% polymer and 73 wt.-% sol-vent DMF and THF in a ratio of 60:40 wt.-% DMF:THF.
Spinning of the Integral-Asymmetric Hollow-Fibre Membrane PS-b-P4VP hollow-fibre membranes were spun in a dry/wet spinning method at different fall heights. The fall heights were 30, 50, 70 and 90 cm. The experimental system is shown in Fig. 1.
The spinneret has a structure with an individual opening in the opening in a concentric arrangement with diameter of 0.212 mm for the inner liquid column. The inner diameter of the annular nozzle is 0.353 mm and the outer diameter 0.702 mm; the nozzle length is 1 mm.
¨ 16 ¨
The polymer solution was pressed out through the opening of the spinner-et or respectively annular nozzle using nitrogen under excess pressure.
The extrusion rate of the polymer solution was set by the pressure of the nitrogen gas between 0.05 and 1 bar. The polymer solution flowed through the annular nozzle or respectively hollow-core nozzle while, as liquid col-umn, a mixture of water and different water-soluble solvents as internal precipitant was directed through the inner opening of the spinneret under controlled flow rates.
The created hollow fibres came from the tip of the spinning nozzle and passed through a fall section of a certain length before they immersed into a precipitation bath with pure water.
The variation in the fall section between the spinneret and the precipitation bath served to let the solvent from the polymer solution evaporate in the outer area of the hollow-fibre membrane. The hollow-fibre membranes then reached the precipitation bath with their fall speed, without being supplied externally with a tractive force.
Both the internal and the external precipitants were held at room tempera-ture.
The hollow-fibre polymer membranes were then held in the water contain-er for 24 hours at room temperature in order to remove residual solvent (DMF) and then dried in a vacuum oven at 60 Celsius for more than 24 hours.
Parameters of some test arrangements are shown in the following table:
¨ 17 ¨
Fall section 90 cm Flow of the col-0.5 ml/min umns Pressure P
0.2 0.1 0.05 0.2 0.1 (bar) Liquid Water/ Water/ Water/ Water/mix Water/mix column DMF THF THE (DMF/THF) (DMF/THF) Mix 80/20 60/40 ratio (60/40) (60/40) In these cases, a hollow-fibre membrane according to the invention with isoporous outer skin and porous inner skin was obtained. Examples of this are shown in the following.
SEM Images The following figures show electron-microscope images of results from two experiments. They concern the two experiments in which the liquid col-umns had a mixture of water and THF at a weight ratio of 80 wt-% to 20 wt.-%. The fall section was 90 cm, the flow rate of the liquid column 0.5 ml/min.
It is thereby shown that a lower shear rate in the spinneret leads to a more regular structure of the pores on the outer surface of the hollow-fibre membrane.
Fig. 2a) and 2b) show the cross-section through the hollow-fibre mem-brane for an excess pressure of 0.1 bar in two different enlargements. In particular, the sponge-like structure inside the hollow-fibre membrane can be clearly seen.
Fig. 3a) and 3b) show the outer surface of the same membrane as in Fig.
¨18-
The invention thus relates to the field of membrane-support microfiltration, ultrafiltration and nanofiltration. Such membranes have a porous separa-tion layer, wherein the size and regularity of the pores determine both the separation limit as well as the selectivity. The most isoporous possible membrane is hereby desired, i.e. a membrane with a most regular possi-ble structure of pores, the diameter of which is as uniform as possible.
Corresponding membranes are producible in different manners. Mem-¨ 2 ¨
' branes produced according to a so-called phase inversion process are predominantly used. These membranes have a more or less large statisti-cal variance during the distribution of the pore size. In addition to a low selectivity, such membranes also tend to so-called "fouling". This is a fast blocking of the large pores, since a larger portion of the liquid passing through the membrane first passes through these large pores. The fouling is also considerably reduced for isoporous membranes.
In German patent no. 10 2006 045 282 by the applicant, which has been published as DE 10 2006 045 282 Al, a method is disclosed by means of which polymer membranes can be produced with isoporous separation-active surfaces. For this purpose, an amphiphilic block copolymer is dis-solved in a casting solution with one or more solvents, spread into a film, and the film is immersed in a precipitation bath.
This method exploits the fact that the polymer blocks of the amphiphilic block copolymer are not miscible with each other. The block copolymers therefore form microphases in the casting solution such as a known mi-celle structure with spherical or cylindrical micelles. Within a short evapo-ration time, part of the liquid solvent close to the surface evaporates such that the microphase morphology hardens in a layer of the film close to the surface that has formed due to the self-organization of the polymer blocks of the block copolymers, whereas the block copolymers remain dissolved within the bulk of the casting solution.
By dipping this film in a precipitation bath, the rest of the solvent is dis-placed, and a known phase inversion process occurs which results in a known sponge-like structure. In some cases, the previously assumed mi-crophase-separated isoporous structure of the layer close to the surface is retained despite being dipped in the precipitation bath. This then transi-tions directly into the sponge-like structure. Additional descriptions are contained in DE 10 2006 045 282 Al, the entire disclosed content of which ¨ 3 ¨
is incorporated in the present application.
An overview of other different methods for producing isoporous mem-branes is also included in DE 10 2006 045 282 Al of the applicant.
However, up until now, this concept of flat membranes has not been suc-cessfully transferred to hollow-fibre membranes. Due to its considerably larger ratio of separation surface to packing volume in one module, hollow-fibre membranes are very interesting for the economical application, in particular for applications that require large membrane surfaces, such as drinking water treatment or dialysis.
Up until now, hollow-fibre membranes for the ultrafiltration of aqueous sys-tems are mainly produced based on polysulfone or respectively polyether-sulfones or polyether imides, polyvinylidene fluorides (PVDF) or poly-acrylnitrile (PAN) through phase inversion of corresponding polymer solu-tions, which are spun as hollow fibres and precipitated in water. These membranes show no isoporous structure and for this reason have a great-er tendency for fouling.
An overview of new developments in the production of polymeric hollow fibres is provided in the article Na Peng et al., "Evolution of polymeric hol-low fibers as sustainable technologies: Past, present, and future", Pro-gress in Polymer Science 37 (2012), 1401 ¨ 1424. It describes the tech-nique of spinning hollow fibres, in which a spinning solution with at least one polymer is directed through an annular spinneret, wherein another liquid is directed concentrically on the inside through the spinneret and penetrates the hollow space of the hollow fibre formed in this manner. De-pending on the selection of the polymers and of the solutions, which act from outside or respectively inside on the hollow fibres, mainly impermea-ble surfaces are achieved.
¨ 4 ¨
Based on this state of the art, the object of the present invention is to make available hollow-fibre membranes with an isoporous pore structure in a separation-active surface, which are usable for microfiltration, ultrafil-tration or nanofiltration.
The object is solved by a method for producing a self-supporting integral-asymmetric hollow-fibre polymer membrane having an isoporous outer skin, a porous inner skin and a sponge-like inner structure in a dry/wet spinning method with the following method steps:
¨ Production of a polymer solution having at least one solvent, in which at least one amphiphilic block copolymer having at least two different polymer blocks is dissolved, - Pressing the polymer solution through a spinneret formed as a hol-low-core nozzle or multiple hollow-core nozzle to form a hollow fibre, in the centre of which a liquid column is spun, which consists of a precipitant having reduced precipitation activity, - After passing through a fall section in an atmosphere, immersing the spun hollow fibre in a precipitation bath to form the hollow-fibre poly-mer membrane.
The method according to the invention corresponds with a dry/wet spin-fling method insofar, as after the extruding the hollow fibre passes through a fall section without external contacting of a liquid precipitation bath first ("dry") and is then immersed into a bath of a liquid precipitant ("wet").
The execution of the method according to the invention leads to the pro-duction of polymer hollow-fibre membranes with an isoporous outer sur-face, which is based on the self-organization of the tailored block copoly-¨ 5 ¨
mers in microphases of the so-called microphase separation. This isopo-rous separation-active outer surface transitions into a typical sponge-like structure of a membrane produced through precipitant-induced phase in-version. This sponge-like structures gives the hollow-fibre membrane its stability and permeability so that the hollow-fibre membrane is self-supporting or respectively self-carrying. The passing of a fall section in an atmosphere, i.e. a dry part of the process at first, thereby leads to part of the solvent of the polymer solution evaporating and a microphase-separated structure being able to solidify at the outer surface, which sur-vives the immersion into the precipitation bath after passing through the fall section.
According to the invention, a precipitant with reduced precipitation activity is used for the inner surface of the hollow-fibre membrane. Tests have shown that a conventional precipitant such as water leads to the formation of a mainly impermeable or respectively almost impermeable inner skin.
The inner skin formed in this manner is then so impermeable that it still holds onto particles, which can pass through the separation-active outer skin. With such a liquid-impermeable inner skin, the hollow-fibre mem-brane designed in this manner is generally unsuitable for filtration. The use of a precipitant with reduced precipitation activity causes the surface for-mation to progress with lower kinetics than for a normally used precipitant.
The reaction thereby has enough time for a partial separation on the inner surface so that pores can form inside the surface so that use for filtration is enabled.
The liquid column preferably consists of a mixture of at least one precipi-tant for the at least one block copolymer and at least one solvent mixable with the precipitant for the at least one block copolymer. Due to the fact that the solvent or the solvents is or respectively are mixable with the pre-cipitant in the liquid column, the precipitation activity of the precipitant is reduced considerably. The separation of the copolymer from the polymer ¨ 6 ¨
solution thereby leads to the desired pore formation on the inner boundary surface. The liquid column can preferably also contain at least one pore forming material, in particular polyethylene glycol (PEG). This can support the pore formation on the inner surface of the hollow fibre.
Additionally, at least one metal salt is preferably dissolved in the polymer solution, wherein one of the polymer blocks forms complexes with the metal, wherein the metal is preferably a main group element of the second main group in particular magnesium, calcium or strontium, wherein the salt is in particular advantageously magnesium acetate or another organic salt of magnesium, calcium or strontium. The metals of the second main group are more biocompatible than transition metals so that they are preferred for hollow-fibre membranes with biological applications. Magnesium and calcium in particular occur in comparatively large amounts in the human body. Strontium also occurs in small amounts in the body and is not toxic.
The supported effect of the salt in the phase separation is attributed to the fact that the added salt leads to the formation of partially charged polyelec-trolytic micelle cores, which positively impact the non-solvent-induced phase separation.
Alternatively or additional, it is advantageously provided that at least one carbohydrate is additionally dissolved in the polymer solution, in particular saccharose, D(+)-glucose, D(-)-fructose and/or cyclodextrin, in particular a-cyclodextrin. These substances are more biocompatible than the transi-tion metals and their salts. For use in the method according to the inven-tion, the carbohydrates show a clear stabilization of the isoporous separa-tion-active surface during the phase inversion through immersion in a pre-cipitation bath.
The supporting effect of the carbohydrates in the phase separation is at-tributed to the fact that the carbohydrates can form hydrogen bonds to the ¨ 7 ¨
hydrophilic block of the block copolymers. Through the hydrogen bonds, the viscosity of the polymer solution is greatly increased so that a lower concentration of the block copolymers in the solution is sufficient to form the structure according to the invention with the isoporous separation-active layer.
In the case of both types of additives, i.e. metal salts or carbohydrates, a moderate, thermo-reversible linking of a block type in the polymer solution, in particular of the pore-forming component, thus takes place for example through hydrogen bonds or complex formation.
The problem of a permanently belated release of toxic metal ions through the membrane during its use is thus no longer relevant through the use of carbohydrates for improving the membrane structure. Since carbohydrates are non-toxic, the use of the membrane for medically or respectively bio-logically relevant processes is thus harmless.
Due to the increased viscosity, it is also hereby possible to work with lower block copolymer concentrations in the polymer solution, which leads to material savings for the relatively expensive block copolymers. The clean-ing of the membrane produced with carbohydrates is unproblematic.
Both the membranes produced with metal salts and those produced with carbohydrates show adjustable pore sizes in a few cases. Thus, the water flow through the membrane can be adjusted in a broad range via a change in the pH value of a solution flowing through the pores. The control over the pH value works when the pore-forming polymer block reacts to chang-es in the pH value, for example expands or contracts and thus narrows or widens the pores.
The at least one block copolymer preferably comprises two or more differ-ent polymer blocks A, B or A, B and C or A, B, C and D of the configura-¨ 8 ¨
tion A-B, A-B-A, A-B-C, A-B-C-B-A, A-B-C-D, A-B-C-D-C-B-A or multiblock copolymers based on the aforementioned configurations, wherein the pol-ymer blocks are respectively selected from the group of polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly(ethylene-stat-butylene), poly(ethylene-alt-propylene), polysiloxane, polyalkylene oxide, poly-e-caprolactone, polylactic acid, poly alkyl methac-rylate, polymethacrylic acid, polyalkyl acrylate, polyacrylic acid, polyhy-droxyethyl methacrylate, polyacrylamide, poly-N-alkylacrylamide, polysul-fone, polyaniline, polypyrrole, polytriazole, polyvinylimidazole, polyte-trazole, polyethylene diamine, polyvinyl alcohol, polyvinylpyrrolidone, poly-oxadiazole, polyvinylsulfonic acid, polyvinyl phosphonic acid or polymers.
Multiblock copolymers comprise structures of the base configurations that repeat multiple times. Thus, a multiblock copolymer based on the configu-ration A-B has a structure A-B-A-B etc. or a multiblock copolymer based on the configuration A-B-C the structure A-B-C-A-B-C etc. The multiblock copolymers also form the microphases underlying the invention.
The block copolymers and the polymer blocks preferably have a low poly-dispersity, in particular less than 1.5, in particular less than 1.2. The self-organization of the block copolymers and the microphase formation is thus supported.
The polymer lengths of the at least two polymer blocks of the amphiphilic block copolymers are preferably selected relative with respect to each oth-er so that a self-organization in the solvent leads to the formation of a spherical, cylindrical or co-continuous, in particular gyroidal, micelle struc-ture or microphase structure in the solvent, in particular a length ratio be-tween approximately 2:1 and approximately 10:1, in particular between approx. 3:1 and 6:1. These length ratios of the majority components to the minority components of the block copolymers lead to the desired micelle structure, i.e. to the inclusion of individual spherical micelles of the minority components in the bulk of the majority components or to cylindrical or co-¨ 9 ¨
continuous, for example gyroidal, micelle structures, in which the minority components form the cylinders or respectively gyroidal filaments or re-spectively branchings in the bulk of the majority components.
The block copolymer preferably has a molecular weight between 100 kDa and 600 kDa, in particular between 170 kDa and 320 kDa. In this range, the pore size can be adjusted in a particular fine manner through selection of the molecular weight.
The polymer preferably makes up a percentage by weight between 10 wt.-% and 40 wt.-%, in particular between 15 M.-% and 25 wt.-%, of the solu-tion.
In the dry/wet spinning process, the polymer solution is particularly prefer-ably pressed through the spinneret with an excess press of 0.01 to 0.5 bar, in particular between 0.05 and 0.25 bar. A very regular hollow-fibre membrane can thus be produced, wherein the required excess pressure depends among other things on the viscosity of the polymer solution. The geometry, i.e. in particular radius, gap width and shape, of the spinneret also plays a role, so that for a selected system the excess pressure or re-spectively the throughput can be determined securely and simply through series of tests.
The hollow-core nozzle or multiple hollow-core nozzle to be used accord-ing to the invention has in the simplest case an annular-slit-shaped, outer nozzle opening, which is arranged in particular concentrically around a central nozzle opening. Other hollow-fibre cross-sections can also be cre-ated by suitable geometries of the hollow-core nozzle or multiple hollow-core nozzle, for example elliptical, polygonal, star-shaped with 3 or more rays among other things. With triple- or multi-layered multiple hollow-core nozzles, it is also possible to co-extrude for example carrier and mem-brane and, if applicable, even other layers. Such carrier layers are to be ¨
arranged on the outside and/or inside of the layer according to the inven-tion.
The fall section preferably has a length of between 1 cm and 100 cm, in 5 particular between 10 cm and 100 cm. Depending on the set excess pres-sure or respectively throughput and of the set spinning rate, this means that there is advantageously an evaporation time of between 10 seconds and 60 seconds before immersion in the precipitation bath. The fall section can also be determined securely and optimal through a series of tests.
Several solvents are preferably used, wherein the polymer blocks of the block copolymers in the different solvents are soluble to different degrees and the solvents are volatile to different degrees. The use of different sol-vents, which represent solvents of differing quality in particular for the dif-ferent blocks of the block copolymers, supports the solidification of the self-organization and microphase formation on the outer surface of the hollow fibre before immersion in the precipitation bath.
Respectively a polar or non-polar precipitant or precipitant mixture is ad-vantageously used as precipitant in the liquid column and in the precipita-tion bath after the fall section independently of each other, in particular water and/or methanol and/or ethanol and/or acetone and/or a mixture of two or more of the precipitants or diethyl ether, and respectively a polar or non-polar solvent, in particular dimethylformamide and/or dimethylacetam-ide and/or N-methylpyrrolidone and/or dimethylsulfoxide and/or tetrahydro-furane or a mixture of two or more of the solvents, are used as solvent in the polymer solution and in the liquid column independently of each other, wherein the solvent(s) in the liquid column is or respectively are mixable with the precipitant(s) in the liquid column.
The precipitants or respectively solvents used in the respective precipitant or precipitant mixture and the respective solvent or solvent mixture are - 11 ¨
also respectively intermixable so that the respectively used precipitant mix-ture or respectively solvent mixture is single-phase, i.e. homogeneous.
Diethyl ether is an example of a water-insoluble precipitant. For some pol-ymers, non-aqueous solvents and precipitants are more suitable than aqueous solvents and precipitants.
The object underlying the invention is also solved by an integral-asymmetric hollow-fibre polymer membrane, in particular micro-, ultra- or nanofiltration membrane, produced or producible in an, in particular as described above according to the invention, dry/wet spinning process, wherein the hollow-fibre polymer membrane has an isoporous, separation-active outer surface, which is based on a microphase formation through self-organization of an amphiphilic copolymer, which transitions into a non-solvent-induced, phase-inversion-formed, sponge-like inner structure, wherein an inner surface of the hollow-fibre polymer membrane is formed porously based on a precipitation with an inner liquid column from a pre-cipitant with reduced precipitation activity.
The pores of the separation-active outer surface preferably have a ratio of the maximum pore diameter to the minimum pore diameter of less than 3.
The object underlying the invention is also solved by a filtration module, in particular microfiltration module, ultrafiltration module or nanofiltration module, with at least one of the hollow-fibre polymer membranes de-scribed above according to the invention, as well as by a use of a corre-sponding integral-asymmetric hollow-fibre polymer membrane according to the invention for microfiltration, ultrafiltration or nanofiltration, in particular for filtering out proteins or other nanoparticulate substances.
The advantages, properties and characteristics named for the individual invention objects, i.e. the method, the integral-asymmetric hollow-fibre pol-ymer membrane, the filtration module and the use, also apply without re-¨ 12 ¨
striction to the respective other invention objects, which relate to each oth-er.
Further characteristics of the invention will become apparent from the de-scription of embodiments according to the invention together with the claims and the included drawings.
The invention is described below in an exemplary manner, without restrict-ing the general intent of the invention, based on exemplary embodiments in reference to drawings and figures, wherein we expressly refer to the drawings with regard to the disclosure of all details according to the inven-tion that are not explained in greater detail in the text. The figures shown in:
Fig. 1 a schematic representation of a hollow-fibre-membrane spinning system, Fig. 2a), b) SEM images of cross-sections through a hollow-fibre poly-mer membrane produced according to the invention in two different enlargement stages, Fig. 3a), b) SEM images of the outer surface of a hollow-fibre polymer membrane produced according to the invention in two differ-ent enlargement stages, Fig. 4a), b) SEM images of the inner surface of a hollow-fibre polymer membrane produced according to the invention in two differ-ent enlargement stages and Fig. 5a)-c) SEM images of the cross-section, outer surface and inner surface of a further hollow-fibre polymer membrane pro-duced according to the invention.
¨ 13 ¨
It will be illustrated below using examples how the hollow-fibre membranes according to the invention are produced as completely self-supporting in-tegral-asymmetric membranes.
For this, Fig. 1 shows a spinning system with a spinneret 2 designed as a hollow-core nozzle, which has a central opening and an annular-slit-shaped nozzle or respectively annular nozzle arranged around it concen-trically. Through the annular nozzle, a polymer solution with at least one amphiphilic block copolymer exits, which is kept ready in a polymer solu-tion container 4. The polymer solution is pressed into the spinneret 2 by means of a gas under excess pressure P, in this case nitrogene (N2), which is supplied to a pressure connection 6 on the container 4. Instead of an overpressurized gas, a pump can alternatively be used, which controls the throughput of the polymer solution through the spinneret 2.
Through the central opening or respectively the spinneret 2, a liquid pre-cipitant solution exits a precipitant container 8. A central liquid column is thereby spun. The precipitant introduced in the central opening of the spun hollow fibre 12 is introduced through a pump 10.
A hollow fibre 12 thus exits the spinneret 2, the inner opening or respec-tively lumen of which is filled with a liquid column of the precipitant from the container 8, which brings about a precipitation of the polymer from in-side. The hollow fibre 12 immerses after a fall section 13 into a precipita-tion bath 14 with a further precipitant, for example water. A liquid-induced phase-inversion process takes place there and the hollow-fibre polymer membrane 16 according to the invention is formed from the hollow fibre 12.
Process parameters herein are among other things the selection of the spinneret 2 or respectively annular-slit nozzle, the polymer solution, the ¨ 14 ¨
liquid column, the excess pressure P or respectively the throughput of pol-ymer solution, the fall section 13, the precipitant in the precipitation bath 14, the different concentrations or the local shear rate in the spinneret gap.
The parameters are selected such that a mechanically stable hollow fibre 12 is created as soon as it leaves the spinneret 2 in the direction of the precipitation bath 14 and a formation of a impermeable skin on the inside of the hollow fibre 12 is avoided.
Several processes take place thermodynamically in quick succession. A
slowed liquid-induced phase inversion process without a dry phase first takes place on the inside. Irregular and large pores hereby occur due to the reduced precipitation activity of the inner precipitant. The formation of the cylindrical pore structures on the outside takes place between the spinneret 2 and the precipitation bath 14 through evaporation of a solvent.
Since the hollow fibre 12 is spun downwards, gravity also impacts the -structure formation. After the immersion of the hollow fibre 12 into the pre-cipitation bath 14, a second liquid-induced phase inversion process occurs on the outside surface of the hollow fibre 12, which leads to the final for-mation of the hollow-fibre polymer membrane 16.
The scanning electron microscope (SEM) images in Figures 2 to 5 show a relatively narrow pore size distribution on the outer skin, which is caused by the microphase separation and the solvent-precipitant exchange. In contrast, the inner skin shows elliptical pore structures, which were creat-ed due to the slowed phase inversion on the inside of the hollow fibre 12 and aligned parallel to the spinning direction due to the shearing in the gap. In certain cases, considerable hollow spaces occur here, which cre-ate a porosity, which is needed for the filtration.
It was found that pure water is not suitable as a core liquid. In contrast, water mixtures with the solvents of the block copolymer solution are suita-ble for a corresponding coarsely porous inner skin.
¨ 15 ¨
Examples according to the invention are described below.
Production of a Polymer Solution In order to produce a polymer solution with different concentrations and solvent mixtures, a polystyrene-block-poly(4-vinylpyridine) block copoly-mer (PS-b-P4VP) was solved in a mixture of N,N-Dimethylformamide (DMF) and tetrahydrofuran (THF) at room temperature for one day under constant stirring with a magnetic stirrer, until the polymer solution became homogeneous.
Before the spinning of the hollow fibre, the polymer solution was stored at room temperature without stirring for 12 hours in order to remove the shearing effect of the stirring and fine air bubbles, which were trapped in the solution.
A copolymer PS-b-P4VP with a total molecular weight of 154 kg/mol (kDa) was used as the polymer, whereby 82.7 wt.-% was polystyrol and 17.3 wt.-Yo were P4VP. The solution contained 27 wt.-% polymer and 73 wt.-% sol-vent DMF and THF in a ratio of 60:40 wt.-% DMF:THF.
Spinning of the Integral-Asymmetric Hollow-Fibre Membrane PS-b-P4VP hollow-fibre membranes were spun in a dry/wet spinning method at different fall heights. The fall heights were 30, 50, 70 and 90 cm. The experimental system is shown in Fig. 1.
The spinneret has a structure with an individual opening in the opening in a concentric arrangement with diameter of 0.212 mm for the inner liquid column. The inner diameter of the annular nozzle is 0.353 mm and the outer diameter 0.702 mm; the nozzle length is 1 mm.
¨ 16 ¨
The polymer solution was pressed out through the opening of the spinner-et or respectively annular nozzle using nitrogen under excess pressure.
The extrusion rate of the polymer solution was set by the pressure of the nitrogen gas between 0.05 and 1 bar. The polymer solution flowed through the annular nozzle or respectively hollow-core nozzle while, as liquid col-umn, a mixture of water and different water-soluble solvents as internal precipitant was directed through the inner opening of the spinneret under controlled flow rates.
The created hollow fibres came from the tip of the spinning nozzle and passed through a fall section of a certain length before they immersed into a precipitation bath with pure water.
The variation in the fall section between the spinneret and the precipitation bath served to let the solvent from the polymer solution evaporate in the outer area of the hollow-fibre membrane. The hollow-fibre membranes then reached the precipitation bath with their fall speed, without being supplied externally with a tractive force.
Both the internal and the external precipitants were held at room tempera-ture.
The hollow-fibre polymer membranes were then held in the water contain-er for 24 hours at room temperature in order to remove residual solvent (DMF) and then dried in a vacuum oven at 60 Celsius for more than 24 hours.
Parameters of some test arrangements are shown in the following table:
¨ 17 ¨
Fall section 90 cm Flow of the col-0.5 ml/min umns Pressure P
0.2 0.1 0.05 0.2 0.1 (bar) Liquid Water/ Water/ Water/ Water/mix Water/mix column DMF THF THE (DMF/THF) (DMF/THF) Mix 80/20 60/40 ratio (60/40) (60/40) In these cases, a hollow-fibre membrane according to the invention with isoporous outer skin and porous inner skin was obtained. Examples of this are shown in the following.
SEM Images The following figures show electron-microscope images of results from two experiments. They concern the two experiments in which the liquid col-umns had a mixture of water and THF at a weight ratio of 80 wt-% to 20 wt.-%. The fall section was 90 cm, the flow rate of the liquid column 0.5 ml/min.
It is thereby shown that a lower shear rate in the spinneret leads to a more regular structure of the pores on the outer surface of the hollow-fibre membrane.
Fig. 2a) and 2b) show the cross-section through the hollow-fibre mem-brane for an excess pressure of 0.1 bar in two different enlargements. In particular, the sponge-like structure inside the hollow-fibre membrane can be clearly seen.
Fig. 3a) and 3b) show the outer surface of the same membrane as in Fig.
¨18-
2 in two different enlargement stages. A pore structure with pores having a very uniform size results in particular for the large enlargement. This struc-ture is come across over a large area of the outer surface.
Fig. 4a) and 4b) show in different enlargement stages images of the inner surface of the hollow-fibre membrane from Fig. 2 and 3, wherein the irreg-ular pore structure from the shearing in the spinneret is shown elongated as in the spinning direction. This irregular pore structure has no separa-tion-active effect, but is necessary so that the corresponding membrane can be used at all for filtration.
Fig. 5 shows the cross-section, the outer surface and the inner surface in respectively larger scales finally for a case, in which a hollow-fibre mem-brane was extruded with an excess pressure of 0.05 bar, wherein the structures of a mainly isoporous outer surface and a porous inner surface according to the invention as well as a sponge-like structure occur in be-tween.
All named characteristics, including those taken from the drawings alone and also individual characteristics, which are disclosed in combination with other characteristics, are considered alone and in combination as essential for the invention. Embodiments according to the invention can be realized by individual characteristics, or a combination of several characteristics.
¨ 19 ¨
Reference Numbers 2 Spinneret 4 Container for polymer solution 6 Pressure connection 8 Container for inner precipitant solution 10 Pump 12 Hollow fibre 13 Fall section 14 Precipitation bath 16 Hollow-fibre polymer membrane
Fig. 4a) and 4b) show in different enlargement stages images of the inner surface of the hollow-fibre membrane from Fig. 2 and 3, wherein the irreg-ular pore structure from the shearing in the spinneret is shown elongated as in the spinning direction. This irregular pore structure has no separa-tion-active effect, but is necessary so that the corresponding membrane can be used at all for filtration.
Fig. 5 shows the cross-section, the outer surface and the inner surface in respectively larger scales finally for a case, in which a hollow-fibre mem-brane was extruded with an excess pressure of 0.05 bar, wherein the structures of a mainly isoporous outer surface and a porous inner surface according to the invention as well as a sponge-like structure occur in be-tween.
All named characteristics, including those taken from the drawings alone and also individual characteristics, which are disclosed in combination with other characteristics, are considered alone and in combination as essential for the invention. Embodiments according to the invention can be realized by individual characteristics, or a combination of several characteristics.
¨ 19 ¨
Reference Numbers 2 Spinneret 4 Container for polymer solution 6 Pressure connection 8 Container for inner precipitant solution 10 Pump 12 Hollow fibre 13 Fall section 14 Precipitation bath 16 Hollow-fibre polymer membrane
Claims (18)
Method for Producing an Integral-Asymmetric Hollow-Fibre Polymer Mem-brane Consisting of an Amphiphilic Block Copolmyer, The Hollow-Fibre Membrane obtained and the Use thereof
1. A method for producing a self-supporting integral-asymmetric hollow-fibre polymer membrane (16) having an isoporous outer skin, a po-rous inner skin and a sponge-like inner structure in a dry/wet spin-ning method with the following method steps:
Production of a polymer solution having at least one solvent, in which at least one amphiphilic block copolymer having at least two different polymer blocks is dissolved, Pressing the polymer solution through a spinneret (2) formed as a hollow-core nozzle or multiple hollow-core nozzle to form a hollow fibre (12), in the centre of which a liquid column is spun, which consists of a precipitant having reduced precipitation ac-tivity, After passing through a fall section (13) in an atmosphere, ¨ 21 ¨
immersing the spun hollow fibre (12) in a precipitation bath (14) to form the hollow-fibre polymer membrane (16).
Production of a polymer solution having at least one solvent, in which at least one amphiphilic block copolymer having at least two different polymer blocks is dissolved, Pressing the polymer solution through a spinneret (2) formed as a hollow-core nozzle or multiple hollow-core nozzle to form a hollow fibre (12), in the centre of which a liquid column is spun, which consists of a precipitant having reduced precipitation ac-tivity, After passing through a fall section (13) in an atmosphere, ¨ 21 ¨
immersing the spun hollow fibre (12) in a precipitation bath (14) to form the hollow-fibre polymer membrane (16).
2. The method according to claim 1, characterized in that the liquid col-umn consists of a mixture of mainly a precipitant for the at least one block copolymer and at least one solvent mixable with the precipitant for the at least one block copolymer, wherein in particular additionally at least one pore forming material, in particular polyethylene glycol, is present in the liquid column.
3. The method according to claim 1 or 2, characterized in that at least one metal salt is dissolved in the polymer solution, wherein one of the polymer blocks forms complexes with the metal, wherein the metal is in particular a main group element of the second main group in particular magnesium, calcium or strontium, wherein the salt is in particular magnesium acetate or another organic salt of magnesium, calcium or strontium.
4. The method according to one of claims 1 to 3, characterized in that at least one carbohydrate is additionally dissolved in the polymer solu-tion, in particular saccharose, D(+)-glucose, DH-fructose and/or cy-clodextrin, in particular a-cyclodextrin.
5. The method according to claim 3 or 4, characterized in that the metal salt and/or the carbohydrate makes up a percentage by weight be-tween 0.1 wt.-% and 5 wt.-%, in particular between 0.5 wt.-% and 2 wt.-%, of the solution.
6. The method according to one of claims 1 to 5, characterized in that the at least one block copolymer comprises two or more different polymer blocks A, B or A, B and C or A, B, C and D of the configura-tion A-B, A-B-A, A-B-C, A-B-C-B-A, A-B-C-D, A-B-C-D-C-B-A or ¨ 22 ¨
multiblock copolymers based on the aforementioned configurations, wherein the polymer blocks are respectively selected from the group polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly(ethylene-stat-butylene), poly(ethylene-alt-propylene), polysiloxane, polyalkylene oxide, poly-c-caprolactone, polylactic acid, poly alkyl methacrylate, polymethacrylic acid, poly-alkyl acrylate, polyacrylic acid, polyhydroxyethyl methacrylate, poly-acrylamide, poly-N-alkylacrylamide, polysulfone, polyaniline, polypyr-role, polytriazole, polyvinylimidazole, polytetrazole, polyethylene di-amine, polyvinyl alcohol, polyvinylpyrrolidone, polyoxadiazole, poly-vinylsulfonic acid, polyvinyl phosphonic acid or polymers.
multiblock copolymers based on the aforementioned configurations, wherein the polymer blocks are respectively selected from the group polystyrene, poly-4-vinylpyridine, poly-2-vinylpyridine, polybutadiene, polyisoprene, poly(ethylene-stat-butylene), poly(ethylene-alt-propylene), polysiloxane, polyalkylene oxide, poly-c-caprolactone, polylactic acid, poly alkyl methacrylate, polymethacrylic acid, poly-alkyl acrylate, polyacrylic acid, polyhydroxyethyl methacrylate, poly-acrylamide, poly-N-alkylacrylamide, polysulfone, polyaniline, polypyr-role, polytriazole, polyvinylimidazole, polytetrazole, polyethylene di-amine, polyvinyl alcohol, polyvinylpyrrolidone, polyoxadiazole, poly-vinylsulfonic acid, polyvinyl phosphonic acid or polymers.
7. The method according to one of claims 1 to 6, characterized in that the block copolymers and the polymer blocks have a lower polydis-persity, in particular less than 1.5, in particular less than 1.2.
8. The method according to one of claims 1 to 7, characterized in that the polymer lengths of the at least two polymer blocks of the am-phiphilic block copolymers are preferably selected relative to each other such that a self-organization in the solvent leads to the for-mation of a spherical, cylindrical or co-continuous, in particular gy-roidal, micelle structure or microphase structure in the solvent, in par-ticular a length ratio between approximately 2:1 and approximately 1, in particular between approx. 31 and 6:1.
9. The method according to one of claims 1 to 8, characterized in that the block copolymer has a molecular weight between 100 kDa and 600 kDa, in particular between 170 kDa and 320 kDa.
10. The method according to one of claims 1 to 9, characterized in that the polymer makes up a percentage by weight between 10 wt.-% and 40 wt.-%, in particular between 15 wt.-% and 25 wt.-%, of the solu-¨ 23 ¨
tion.
tion.
11. The method according to one of claims 1 to 10, characterized in that the polymer solution is pressed through the spinneret with an excess pressure of 0.01 to 0.5 bar, in particular between 0.05 and 0.25 bar.
12. The method according to one of claims 1 to 11, characterized in that the fall section (13) has a length of between 1 cm and 100 cm, in par-ticular between 10 cm and 100 cm.
13. The method according to one of claims 1 to 12, characterized in that several solvents are used, wherein the polymer blocks of the block copolymer in the different solvents are soluble to different degrees and the solvents are volatile to different degrees.
14. The method according to one of claims 1 to 13, characterized in that respectively a polar or non-polar precipitant or precipitant mixture is used as precipitant in the liquid column and in the precipitation bath (14) after the fall section (13) independently of each other, in particu-lar water and/or methanol and/or ethanol and/or acetone and/or a mixture of two or more of the precipitants or diethyl ether, and re-spectively a polar or non-polar solvent, in particular dimethylforma-mide and/or dimethylacetamide and/or N-methylpyrrolidone and/or dimethylsulfoxide and/or tetrahydrofurane or a mixture of two or more of the solvents, are used as solvent in the polymer solution and in the liquid column independently of each other, wherein the solvent(s) in the liquid column are mixable with the precipitant(s) in the liquid col-umn.
15. The integral-asymmetric hollow-fibre polymer membrane (16), in par-ticular micro-, ultra- or nanofiltration membrane, produced or produc-ible in a dry/wet spinning process, in particular a method according to ¨ 24 ¨
one of claims 1 to 14, wherein the hollow-fibre polymer membrane (16) has an isoporous separation-active outer surface, which is based on a microphase formation through self-organization of an amphiphilic copolymer, which transitions into a non-solvent-induced, phase-inversion-formed, sponge-like inner structure, wherein an in-ner surface of the hollow-fibre polymer membrane (16) is formed po-rously based on a precipitation with an inner liquid column from a precipitant with reduced precipitation activity.
one of claims 1 to 14, wherein the hollow-fibre polymer membrane (16) has an isoporous separation-active outer surface, which is based on a microphase formation through self-organization of an amphiphilic copolymer, which transitions into a non-solvent-induced, phase-inversion-formed, sponge-like inner structure, wherein an in-ner surface of the hollow-fibre polymer membrane (16) is formed po-rously based on a precipitation with an inner liquid column from a precipitant with reduced precipitation activity.
16. The integral-asymmetric hollow-fibre polymer membrane (16) accord-ing to claim 15, characterized in that the pores of the separation-active outer surface have a ratio of the maximum pore diameter to the minimum pore diameter of less than 3.
17. A filtration module, in particular microfiltration module, ultrafiltration module or nanofiltration module, with at least one hollow-fibre poly-mer membrane (16) according to claim 15 or 16.
18. A use of an integral-asymmetric hollow-fibre polymer membrane (16) according to claim 15 or 16 for microfiltration, ultrafiltration or nanofil-tration, in particular for filtering out proteins or other nanoparticulate substances.
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| DE102012221378.3 | 2012-11-22 | ||
| DE102012221378.3A DE102012221378A1 (en) | 2012-11-22 | 2012-11-22 | A method of making an integral asymmetric hollow fiber polymer membrane, integral asymmetric hollow fiber polymer membrane, filtration module and use |
| PCT/EP2013/003320 WO2014079538A1 (en) | 2012-11-22 | 2013-11-05 | Method for producing an integral-asymmetric hollow-fibre polymer membrane consisting of an amphiphilic block copolymer, the hollow-fibre membrane obtained and the use thereof |
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| EP (1) | EP2922620B1 (en) |
| KR (1) | KR20150086244A (en) |
| BR (1) | BR112015008965A2 (en) |
| CA (1) | CA2886437A1 (en) |
| DE (1) | DE102012221378A1 (en) |
| DK (1) | DK2922620T3 (en) |
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| WO2009076174A1 (en) * | 2007-12-05 | 2009-06-18 | The Board Of Trustees Of The University Of Illinois | Highly permeable polymer membranes |
| JP5519684B2 (en) * | 2008-10-28 | 2014-06-11 | アーケマ・インコーポレイテッド | Moisture flowable polymer membrane |
| US9914099B2 (en) * | 2010-02-11 | 2018-03-13 | Klaus-Viktor Peinemann | Self-assembled block copolymer membrane |
| CN102432782B (en) * | 2011-09-01 | 2013-03-27 | 四川大学 | Amphiphilic triblock copolymer, preparation method thereof, and polyethersulfone hollow fiber membrane blend-modified by using amphiphilic triblock copolymer |
-
2012
- 2012-11-22 DE DE102012221378.3A patent/DE102012221378A1/en not_active Withdrawn
-
2013
- 2013-11-05 ES ES13786173.8T patent/ES2662804T3/en active Active
- 2013-11-05 IN IN2834DEN2015 patent/IN2015DN02834A/en unknown
- 2013-11-05 EP EP13786173.8A patent/EP2922620B1/en active Active
- 2013-11-05 KR KR1020157010669A patent/KR20150086244A/en not_active Application Discontinuation
- 2013-11-05 WO PCT/EP2013/003320 patent/WO2014079538A1/en active Application Filing
- 2013-11-05 BR BR112015008965A patent/BR112015008965A2/en not_active IP Right Cessation
- 2013-11-05 DK DK13786173.8T patent/DK2922620T3/en active
- 2013-11-05 CA CA 2886437 patent/CA2886437A1/en not_active Abandoned
-
2015
- 2015-04-26 IL IL238457A patent/IL238457A0/en unknown
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| US11466134B2 (en) | 2011-05-04 | 2022-10-11 | Cornell University | Multiblock copolymer films, methods of making same, and uses thereof |
| EP3147024A1 (en) | 2015-09-25 | 2017-03-29 | Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH | Hollow-fibre polymer membrane |
| US10967332B2 (en) | 2015-12-23 | 2021-04-06 | Pall Corporation | Filter device |
| US11628409B2 (en) | 2016-04-28 | 2023-04-18 | Terapore Technologies, Inc. | Charged isoporous materials for electrostatic separations |
| US11802200B2 (en) | 2016-11-17 | 2023-10-31 | Terapore Technologies, Inc. | Isoporous self-assembled block copolymer films containing high molecular weight hydrophilic additives and methods of making the same |
| US11401411B2 (en) | 2016-11-17 | 2022-08-02 | Terapore Technologies, Inc. | Isoporous self-assembled block copolymer films containing high molecular weight hydrophilic additives and methods of making the same |
| US10781279B2 (en) | 2016-11-22 | 2020-09-22 | 3M Innovative Properties Company | Pentablock copolymers |
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| CN109996598A (en) * | 2016-11-22 | 2019-07-09 | 3M创新有限公司 | Perforated membrane and preparation method thereof comprising five block copolymers |
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| JP7223691B2 (en) | 2016-11-22 | 2023-02-16 | スリーエム イノベイティブ プロパティズ カンパニー | Porous membrane containing pentablock copolymer and method for producing the same |
| US11567072B2 (en) | 2017-02-22 | 2023-01-31 | Terapore Technologies, Inc. | Ligand bound MBP membranes, uses and method of manufacturing |
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| EP3398675A1 (en) | 2017-05-02 | 2018-11-07 | Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH | Macroporous or mesoporous polymer films in hollow fiber or flat sheet geometry |
| US11572424B2 (en) | 2017-05-12 | 2023-02-07 | Terapore Technologies, Inc. | Chemically resistant fluorinated multiblock polymer structures, methods of manufacturing and use |
| EP3434357A1 (en) | 2017-07-27 | 2019-01-30 | Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH | Method for preparing isoporous hollow fiber composite membranes |
| US11185828B2 (en) | 2017-07-27 | 2021-11-30 | Helmholtz-Zentrum Hereon Gmbh | Method for preparing isoporous hollow fiber composite membranes |
| WO2019020278A1 (en) | 2017-07-27 | 2019-01-31 | Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH | Method for preparing isoporous hollow fiber composite membranes |
| CN110913978A (en) * | 2017-07-27 | 2020-03-24 | 亥姆霍兹材料研究与海岸研究盖斯特哈赫特中心 | Method for preparing uniform-hole hollow fiber composite membrane |
| US11571667B2 (en) | 2018-03-12 | 2023-02-07 | Terapore Technologies, Inc. | Isoporous mesoporous asymmetric block copolymer materials with macrovoids and method of making the same |
| WO2019178077A1 (en) * | 2018-03-12 | 2019-09-19 | Terapore Technologies, Inc. | Free standing pleatable block copolymer materials and method of making the same |
Also Published As
| Publication number | Publication date |
|---|---|
| DK2922620T3 (en) | 2018-04-16 |
| IL238457A0 (en) | 2015-06-30 |
| DE102012221378A1 (en) | 2014-05-22 |
| EP2922620A1 (en) | 2015-09-30 |
| EP2922620B1 (en) | 2018-01-10 |
| IN2015DN02834A (en) | 2015-09-11 |
| BR112015008965A2 (en) | 2017-07-04 |
| KR20150086244A (en) | 2015-07-27 |
| ES2662804T3 (en) | 2018-04-09 |
| WO2014079538A1 (en) | 2014-05-30 |
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