WO1995015809A1 - Production of membranes - Google Patents
Production of membranes Download PDFInfo
- Publication number
- WO1995015809A1 WO1995015809A1 PCT/GB1994/002710 GB9402710W WO9515809A1 WO 1995015809 A1 WO1995015809 A1 WO 1995015809A1 GB 9402710 W GB9402710 W GB 9402710W WO 9515809 A1 WO9515809 A1 WO 9515809A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- polymer
- membrane
- strong acid
- solvent
- ether ketone
- Prior art date
Links
- 239000012528 membrane Substances 0.000 title claims abstract description 73
- 238000004519 manufacturing process Methods 0.000 title description 8
- 229920000642 polymer Polymers 0.000 claims abstract description 71
- 239000002253 acid Substances 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 28
- 229920001643 poly(ether ketone) Polymers 0.000 claims abstract description 25
- 239000002904 solvent Substances 0.000 claims abstract description 25
- -1 aromatic ether ketone Chemical class 0.000 claims abstract description 19
- 239000000654 additive Substances 0.000 claims abstract description 15
- 230000000996 additive effect Effects 0.000 claims abstract description 15
- 238000001879 gelation Methods 0.000 claims abstract description 15
- 239000000203 mixture Substances 0.000 claims abstract description 12
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims abstract description 12
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims abstract description 12
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- 239000004696 Poly ether ether ketone Substances 0.000 claims description 10
- 229920002530 polyetherether ketone Polymers 0.000 claims description 10
- 229920001657 poly(etheretherketoneketone) Polymers 0.000 claims description 3
- 229920001660 poly(etherketone-etherketoneketone) Polymers 0.000 claims description 3
- 230000002708 enhancing effect Effects 0.000 claims description 2
- 238000007493 shaping process Methods 0.000 claims description 2
- 239000011877 solvent mixture Substances 0.000 claims description 2
- JUPQTSLXMOCDHR-UHFFFAOYSA-N benzene-1,4-diol;bis(4-fluorophenyl)methanone Chemical compound OC1=CC=C(O)C=C1.C1=CC(F)=CC=C1C(=O)C1=CC=C(F)C=C1 JUPQTSLXMOCDHR-UHFFFAOYSA-N 0.000 claims 1
- 230000004907 flux Effects 0.000 abstract description 10
- 239000000243 solution Substances 0.000 description 21
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 15
- 125000003118 aryl group Chemical group 0.000 description 13
- 239000000835 fiber Substances 0.000 description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 10
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 10
- 239000001117 sulphuric acid Substances 0.000 description 10
- 235000011149 sulphuric acid Nutrition 0.000 description 10
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 9
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 9
- 230000008569 process Effects 0.000 description 8
- 238000011282 treatment Methods 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 5
- 239000002609 medium Substances 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 150000007513 acids Chemical class 0.000 description 4
- 229920001577 copolymer Polymers 0.000 description 4
- 229910001220 stainless steel Inorganic materials 0.000 description 4
- 239000010935 stainless steel Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- PBKONEOXTCPAFI-UHFFFAOYSA-N 1,2,4-trichlorobenzene Chemical compound ClC1=CC=C(Cl)C(Cl)=C1 PBKONEOXTCPAFI-UHFFFAOYSA-N 0.000 description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 description 3
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 3
- 239000012736 aqueous medium Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 150000002576 ketones Chemical class 0.000 description 3
- 238000000108 ultra-filtration Methods 0.000 description 3
- 229920003169 water-soluble polymer Polymers 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229920002307 Dextran Polymers 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000004793 Polystyrene Substances 0.000 description 2
- JUJWROOIHBZHMG-UHFFFAOYSA-N Pyridine Chemical compound C1=CC=NC=C1 JUJWROOIHBZHMG-UHFFFAOYSA-N 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 2
- 229920004695 VICTREX™ PEEK Polymers 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000000701 coagulant Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- JXTHNDFMNIQAHM-UHFFFAOYSA-N dichloroacetic acid Chemical compound OC(=O)C(Cl)Cl JXTHNDFMNIQAHM-UHFFFAOYSA-N 0.000 description 2
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N diphenyl Chemical compound C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 description 2
- 239000010408 film Substances 0.000 description 2
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920002223 polystyrene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 229940069328 povidone Drugs 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 125000001174 sulfone group Chemical group 0.000 description 2
- ITMCEJHCFYSIIV-UHFFFAOYSA-N triflic acid Chemical compound OS(=O)(=O)C(F)(F)F ITMCEJHCFYSIIV-UHFFFAOYSA-N 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- WSLDOOZREJYCGB-UHFFFAOYSA-N 1,2-Dichloroethane Chemical compound ClCCCl WSLDOOZREJYCGB-UHFFFAOYSA-N 0.000 description 1
- KGIGUEBEKRSTEW-UHFFFAOYSA-N 2-vinylpyridine Chemical compound C=CC1=CC=CC=N1 KGIGUEBEKRSTEW-UHFFFAOYSA-N 0.000 description 1
- KFDVPJUYSDEJTH-UHFFFAOYSA-N 4-ethenylpyridine Chemical compound C=CC1=CC=NC=C1 KFDVPJUYSDEJTH-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229920008285 Poly(ether ketone) PEK Polymers 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 229920000265 Polyparaphenylene Polymers 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000011260 aqueous acid Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 125000002619 bicyclic group Chemical group 0.000 description 1
- 239000004305 biphenyl Substances 0.000 description 1
- 235000010290 biphenyl Nutrition 0.000 description 1
- 210000001601 blood-air barrier Anatomy 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 229960005215 dichloroacetic acid Drugs 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 229920003247 engineering thermoplastic Polymers 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- BTZNPZMHENLISZ-UHFFFAOYSA-N fluoromethanesulfonic acid Chemical compound OS(=O)(=O)CF BTZNPZMHENLISZ-UHFFFAOYSA-N 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 125000000623 heterocyclic group Chemical group 0.000 description 1
- 238000001198 high resolution scanning electron microscopy Methods 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 238000001471 micro-filtration Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 125000001624 naphthyl group Chemical group 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000005373 pervaporation Methods 0.000 description 1
- 239000003880 polar aprotic solvent Substances 0.000 description 1
- 229920002939 poly(N,N-dimethylacrylamides) Polymers 0.000 description 1
- 229920001652 poly(etherketoneketone) Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- UMJSCPRVCHMLSP-UHFFFAOYSA-N pyridine Natural products COC1=CC=CN=C1 UMJSCPRVCHMLSP-UHFFFAOYSA-N 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007614 solvation Methods 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000004291 sulphur dioxide Substances 0.000 description 1
- 235000010269 sulphur dioxide Nutrition 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
Classifications
-
- 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
- B01D71/52—Polyethers
- B01D71/522—Aromatic polyethers
- B01D71/5222—Polyetherketone, polyetheretherketone, or polyaryletherketone
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0011—Casting solutions therefor
-
- 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
- B01D71/52—Polyethers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/12—Specific ratios of components used
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/20—Specific permeability or cut-off range
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/34—Molecular weight or degree of polymerisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2371/00—Characterised by the use of polyethers obtained by reactions forming an ether link in the main chain; Derivatives of such polymers
Definitions
- the present invention relates to the production of a porous membrane (particularly but not exclusively an asymmetric membrane) formed of an aromatic ether ketone polymer.
- Aromatic ether ketone polymers are polymers in which inter-ring ether linkages and inter-ring ketone linkings together provide at least a major proportion of the linkages between aromatic units in the polymer backbone.
- a portion of the aromatic rings may be replaced by a heterocyclic ring, eg pyridine, or a fused ring system such as naphthalene.
- Semi-crystalline aromatic polyetherketones are a family of high- performance engineering thermoplastics of exceptional stability, retaining their excellent mechanical properties of strength, stiffness and toughness at temperatures up to 300°C. They are moreover resistant to all conventional solvents at ambient temperatures and are highly resistant to the action of oxidising or hydrolysing agents.
- Porous membranes (particularly asymmetric membranes) fabricated from aromatic polyetherketones are useful in a range of filtration applications, eg ultrafiltration, microfiltration, gas separation, pervaporation and reverse osmosis.
- solutions of such polymers suitable for forming asymmetric membranes are obtainable only by use of strong acid solvents such as anhydrous methanesulphonic acid, trifluoromethanesulphonic acid, 98% sulphuric acid, or liquid hydrogen fluoride. Of these, 98% sulphuric acid is to be preferred on grounds of its low cost, low toxicity, and ease of handling.
- the gelation is normally effected in an aqueous medium.
- gelation in an aqueous medium an aromatic polyetherketone solution in a strong acid such as sulphuric acid generally gives a polyetherketone membrane of low overall porosity, so that although a surface pore-size suitable for ultrafiltration may be obtained, the density of pores is so low that the water- cr solvent- flux of the membrane can be severely limited.
- EP-A-0 382 356 discloses that a pore forming agent may be included in the polyetherketone.
- the pore forming agent may be a soluble organic polymer, e.g. a sulphonated polyetherethersulphone SPEES. It has however been found that SPEES does not produce any significant enhancement of permeability.
- the proble— may be that, although SPEES is water soluble and also soluble in concentrated sulphuric acid, it is not very soluble in medium-strength aqueous acid so it could precipitate under the gelation conditions.
- Membranes produced by the method of the invention have greatly improved overall performance and greatly improved flux at any given molecular weight cut-off (MCWO).
- the invention is particularly applicable to the fabrication of crystallisable polyetherketone membranes with pore-sizes in the ultrafiltration range (i.e. MCWO values in the range 1,000-500,000 Daltons).
- the invention is also particularly applicable to the production of asymmetric membranes.
- asymmetric membrane we mean a membrane (a) which comprises, on the side adjacent the solution to be filtered, a skin of thickness 0.02-2.0 microns supported on a substrate of thickness 25- 250 microns; (b) in which both the skin and the substrate comprise the same polymer; and (c) in which the pore sizes of the substrate are greater than the pore sizes of the skin.
- the polymer additive has a molecular weight of 1,000- 500,000 Daltons and is normally used at a concentration between 0.5% and 50% (more preferably 10-30%) by weight of that of the polyetherketone although it is possible to use values outside this range.
- the polymer additive can be very substantially removed from the final membrane by washing with an appropriate solvent medium. It has however been found that the higher the molecular weight of the polymer the more difficult is its removal from the membrane. For this reason it is generally preferred to use polymers towards the lower end of the 1,000-500,000 Dalton molecular weight range, e.g. 1000 to 100,000 especially 10,000 to 50,000.
- the gelation medium is aqueous and as such the polymer additive will be soluble in water, the strong acid, and mixtures thereof.
- the preferred polymer for use in an aqueous gelation medium is polyvinylpyrrolidone. It is particularly surprising that this polymer should be so useful in the method of the invention given the strong acid conditions in the solution of the polyetherketone.
- Other water soluble polymers which may be useful in the method of the invention include poly-2-vinylpyridine, poly-4- vinylpyridine, polyethylenesulphonic acid, polystyrenesulphonic acid, and poly(N,N-dimethylacrylamide).
- the process of the invention is applicable to the production of membranes formed from a wide range of aromatic polyetherketones using the procedures disclosed in EP-A-0 323 076.
- the aromatic polyetherketone may for example be a crystalline polymer.
- Figure 1 illustrates polymers chains in which the aromatic rings are joined by ether or ketone bonds ((I-VI);
- Figure 2 illustrates polymer chains in which a portion of the aromatic rings are joined by direct links (VII-IX)) or are bicyclic rings (X);
- Figure 3 illustrates copolymer units bearing intercyclic -S0 2 - bonds (XI-XII);
- Figure 4 illustrates certain copolymers containing ketone and ether links (XV and XVII) or in addition a mixture of biphenyl and sulphone linkages (XIV and XVI).
- Figs 5a and 5b are electron micrographs of the product obtained in Example 3.
- Fig 6 is a GPC trace illustrating the results of Example 4.
- E represents an ether linkage
- K represents a ketone linkage
- D represents a direct linkage
- m represents a meta substituted aromatic ring
- N represents a naphthalene ring
- the membrane is preferably formed of a homopolymer, most preferably PEK, PEEK, PEEKK, or PEKEKK.
- PEK and PEEK are available from Imperial Chemical Industries pic, PEEKK from Hoechst, and PEKEKK from BASF.
- the membrane may be fabricated from a copolymer eg. PEEK/PEK, PEEK/PES, PEK/PES, PEEK/PEES, PEKK/PE-m-KK wherein the copolymer units are represented by the General Formulae XI-XII and XVII in the drawings.
- a copolymer eg. PEEK/PEK, PEEK/PES, PEK/PES, PEEK/PEES, PEKK/PE-m-KK wherein the copolymer units are represented by the General Formulae XI-XII and XVII in the drawings.
- the membrane may be formed from a mixture of polymers, eg. PEEK/PEK or PEK/PES.
- the strong acid is a substantially non-sulphonating reagent towards the aromatic ether ketone polymer.
- the aromatic ether ketone polymer is PEEK
- the strong acid is typically methanesulphonic acid.
- the solution is formed by dissolving the polyetherketone typically in particulate form, together with the water soluble polymer in the strong acid under an inert atmosphere, at a temperature and timespan sufficient to completely dissolve the polymers.
- the membrane may for example be formed as a sheet or a capillary or a tube.
- the sheet membrane is typically formed by casting the polymer solution as a thin liquid film, typically of thickness between 20 and 500 ⁇ m, onto a suitable substrate which is not attacked by the strong acid solution.
- the membrane can be supported by a porous fabric e.g. of polyethylene, polypropylene, polyester, PTFE, polyphenylene sulphide, or carbon fibre.
- the membrane can be unsupported in which case the film would be cast onto a plane non- porous surface, e.g. a band of stainless steel, PTFE of polypropylene or a sheet of glass.
- the polymer is then precipitated by treating the shaped solution with non-solvent under suitable conditions, e.g. it may be immersed in non-solvent liquid in a gelation bath, or non-solvent vapour may be allowed or caused to diffuse into it.
- suitable conditions e.g. it may be immersed in non-solvent liquid in a gelation bath, or non-solvent vapour may be allowed or caused to diffuse into it.
- a capillary membrane which typically has an internal diameter of 0.03 mm
- a capillary membrane which typically has an internal diameter of 0.03 mm
- suitable fluid e.g. an inert gas or liquid, which is a non- solvent for the polymer.
- a tubular membrane (which typically has an internal diameter of at least 5 mm) may be formed by coating the polymer solution as a thin film on the inner or outer wall of a porous tube and immersing the coated tube in a non-solvent to precipitate the membrane.
- the porous tube may for example be of sintered carbon, stainless steel, or a polymer which is substantially inert to the strong acid solvent.
- the precipitated membrane is then allowed to remain in contact with the non-solvent for a time sufficient to allow substantially complete gelation of the polymer, then removed from the non-solvent.
- the residual strong acid/non-solvent is removed from the membrane by treatment with an aqueous medium, e.g. water or an aqueous base, at an appropriate temperature, e.g. between room temperature and the belling point of water. Often further treatment with an organic medium, e.g. acetone, is necessary to reduce the amount of acid present in the membrane further.
- an aqueous medium e.g. water or an aqueous base
- the membrane ay be subjected to a treatment to enhance crystallinity.
- a treatment to enhance crystallinity may be mentioned inter alia heating dry above the Tg of the polymer; treatment with a polar aprotic solvent, e.g. acetone, dimethylformamide (DMF) or dimethylacetamide (DMA). Where DMF or DMA is used in such treatments it is later removed by a suitable further treatment, e.g. by washing with acetone.
- a suitable further treatment e.g. by washing with acetone.
- the strong acid is water-free although we do not exclude the possibility that it may contain a small amount, for example up to about 10% of water.
- the strong acid will be chosen in the light of the structure of the polymer. For example, it should not react chemically with the polymer to unduly reduce the crystallinity thereof. For example, whereas 98% sulphuric acid reacts unduly with polyetheretherketone (PEEK) and should not be used therewith, it can advantageously be used with polyetherketone (PEK) in the process according to the present invention.
- PEEK polyetheretherketone
- PEK polyetherketone
- the strong acid should be a good solvent for the polymer and, after membrane formation, should be readily extractable therefrom.
- the strong acid may be a mixture of acids, e.g. sulphuric acid and acetic acid. It will be appreciated that where one of the acids in the mixture is non-solvent for the polymer the concentration thereof will be insufficient to inhibit solvation of the polymer in the mixture. For example, where the strong acid is a mixture of sulphuric acid and acetic acid, the concentration of acetic acid is typically less than 15% w/w.
- strong acids for use in the process of the present invention may be mentioned - inter alia sulphuric acid, liquid hydrogen fluoride, methane sulphonic acid, fluoromethane sulphonic acid, and di- and tri-fluoromethane sulphonic acid.
- liquid sulphur dioxide 1,2,4-trichlorobenzene
- 1,2- dichloroethane 1,2- dichloroethane
- dichloromethane 1,2- dichloroethane
- dichloroacetic acid trifluoroacetic acid
- a 9.5% w/w solution of polyetherketone (ICI Victrex PEK-220G) and 3.0% w/w polyvinylpyrrolidone (Povidone, 44,000 MW) in 98% sulphuric acid was spun under pressure through a stainless steel tube-in-hole spinneret (hole diameter 0.65 mm; tube o.d. 0.36 mm, tube i.d. 0.19 mm) into a water-bath.
- Aqueous sulphuric acid (55% w/w) was used as the internal coagulant.
- the resulting hollow-fibre membrane was washed with water, soaked in a 10% w/w aqueous solution of glycerol, dried, and potted in nylon tubing before evaluation under cross-flow conditions in terms of water-flux and molecular weight cut-off (dextran challenge).
- the fibre had an internal diameter of ⁇ .Zo mm, a wall-thickness of 0.125 mm, water flux (at 2 bar transmembrane pressure) of 293 l/m 2 /hr, and a MWCO of 16,000 Daltons.
- a hollow-fibre membrane was prepared as in Example 1, but omitting polyvinylpyrrolidone.
- the resulting fibre had an internal diameter of 0.33 mm, a wall- thickness of 0.135 mm, a water flux (at 2 bar transmembrane pressure) of 145 1/rrJ/hr, and a MWCO of 30,000 Daltons.
- a hollow-fibre membrane was prepared as in Example 1, but now using a 9.0% w/w solution of PEK, containing 2% w/w of PVP (MW 44,000).
- the resulting fibre had an internal diameter of 0.35 mm, a wall- thickness of 0.125 mm, a water flux (at 2 bar transmembrane pressure) of 384 1/ ⁇ J/hr, and a MWCO of 30,000 Daltons.
- a hollow-fibre membrane was prepared as in Example 2, but omitting polyvinylpyrrolidone.
- the resulting fibre had an internal diameter of 0.32 mm, a wall- thickness of 0.140 mm, a water flu (at 2 bar transmembrane pressure) of 118 l/m 2 /hr, and a MWCO of 115,000 Daltons.
- polyetherketone membranes of substantially improved performance can be obtained by incorporation of a water-soluble polymer such as polyvinylpyrrolidone into the membrane-spinning solution.
- a water-soluble polymer such as polyvinylpyrrolidone
- the MWCO of the new type of membrane is sharply lowered, effectively increasing its selectivity, and moreover the water-flux is in each case two to three times greater than that of the comparative membrane prepared in the absence of PVP. Since the lowering of MWCO in a membrane is conventionally accompanied by a reduction in flux, it is clear that the membranes of the present invention represent a significant advance in performance over the prior art.
- a 9.0% w/w solution of polyetherketone (ICI Victrex PEK-220) containing 2.5% w/w of PVP (Povidone) was spun under pressure through a stainless steel tube-in-hole spinneret (hole diameter 0.90 mm, tube o.d. 0.51 mm, tube i.d. 0.25 mm) into a deionised-water bath.
- Deionised water was also used as the internal coagulant, and the resulting hollow fibre membrane had an internal diameter of 0.70 mm and a wall thickness of 0.10 mm.
- This membrane was subjected to a post- fabrication crystallisation process, as described in our U.K. Patent Application No. 9323671.9, to give a membrane with water flux at 2 bar of 115 l/m 2 /hr and a MWCO of 10,000 daltons.
- This membrane was determined by high resolution scanning electron microscopy.
- An oblique cross-section of the fibre at low magnification is shown in Figure 5a, from which it can be seen that the membrane is skinned on both its outer and inner surfaces, and has a highly porous internal structure, which may account, in part, for the excellent permeability of the membrane.
- An orthogonal cross-section of the inner surface of the membrane is shown at high magnification in Figure 5b. From this micrograph it can be seen that the relatively dense inner skin, (which forms the separating layer in membranes of this type), is quite exceptionally uniform, suggesting that the process of the invention is capable of providing an intrinsically consistent and reproducible product.
- Example 3 The membrane produced in Example 3 was used to concentrate and fractionate a toluene solution containing a mixture of polystyrenes (0.1% w/w of each fraction) of nominal molecular weights 4,000, 12,000, 24,000, 32,000, and 50,000. After flushing the membrane successively with water, acetone, and then toluene, a steady toluene flu.x of 120 l/m 2 /hr at 1 bar was obtained. On permeating the toluene/polystyrene solution, the flux fell to 100 l/m 2 /hr, and to 80 1/ ⁇ J/hr as the total polymer concentration in the feed rose to ca. 1%.
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Abstract
A porous membrane is produced by gelation in a non-solvent medium of an aromatic ether ketone polymer dissolved in a strong acid which is substantially non-sulphonating to the polymer. The polyether ketone solution includes a polymer additive which is not substantially degraded by the strong acid and which is soluble both in the strong acid, the non-solvent and mixtures thereof. The gelation medium may, for example, be aqueous and the polymer additive may be polyvinylpyrrolidone. Membranes produced by the method of the invention have good overall performance and flux at any given molecular weight cut-off.
Description
PRODUCTION OF MEMBRANES
The present invention relates to the production of a porous membrane (particularly but not exclusively an asymmetric membrane) formed of an aromatic ether ketone polymer.
Aromatic ether ketone polymers (also referred to herein as an aromatic polyetherketones) are polymers in which inter-ring ether linkages and inter-ring ketone linkings together provide at least a major proportion of the linkages between aromatic units in the polymer backbone. We do not exclude the possibility that a portion of the aromatic rings may be replaced by a heterocyclic ring, eg pyridine, or a fused ring system such as naphthalene.
Semi-crystalline aromatic polyetherketones are a family of high- performance engineering thermoplastics of exceptional stability, retaining their excellent mechanical properties of strength, stiffness and toughness at temperatures up to 300°C. They are moreover resistant to all conventional solvents at ambient temperatures and are highly resistant to the action of oxidising or hydrolysing agents.
Porous membranes (particularly asymmetric membranes) fabricated from aromatic polyetherketones are useful in a range of filtration applications, eg ultrafiltration, microfiltration, gas separation, pervaporation and reverse osmosis.
Processes for the production of asymmetric aromatic polyether ketone membranes are disclosed in EP-A-O 3S2 356 (ICI) and EP-A- 368 003 (Dow). As disclosed in these prior specifications, the process comprises forming a solution of the polymer into a desired shape and then treating the solution with a non-solvent for the polymer so as to cause gelation thereof and thus precipitation of the membrane.
Because of the insolubility of crystalline aromatic polyetherketones in conventional organic solvents (noted above), solutions of such polymers suitable for forming asymmetric membranes are obtainable only by use of strong acid solvents such as anhydrous methanesulphonic acid, trifluoromethanesulphonic acid, 98% sulphuric acid, or liquid hydrogen fluoride. Of these, 98% sulphuric acid is to be preferred on grounds of its low cost, low toxicity, and ease of handling.
The gelation is normally effected in an aqueous medium.
However, gelation in an aqueous medium c an aromatic polyetherketone solution in a strong acid such as sulphuric acid generally gives a polyetherketone membrane of low overall porosity, so that although a surface pore-size suitable for ultrafiltration may be obtained, the density of pores is so low that the water- cr solvent- flux of the membrane can be severely limited.
EP-A-0 382 356 discloses that a pore forming agent may be included in the polyetherketone. The pore forming agent may be a soluble organic polymer, e.g. a sulphonated polyetherethersulphone SPEES. It has however been found that SPEES does not produce any significant enhancement of permeability. The proble— may be that, although SPEES is water soluble and also soluble in concentrated sulphuric acid, it is not very soluble in medium-strength aqueous acid so it could precipitate under the gelation conditions.
It is therefore an object of the present invention to obviate or mitigate the abovementioned disadvantages.
According to the present invention there is provided a method of producing a porous membrane comprising the steps of
(a) shaping into a desired shape a solution of an aromatic ether ketone polymer in a strong acid which is substantially non- sulphonating to the polymer,
(b) contacting the shaped solution with a gelation medium containing a non-solvent for the polymer so as to form a membrane, and
(c) removing the membrane from strong acid/non-solvent mixture, characterised in that said solution of the aromatic ether ketone polymer includes a polymer additive which is not substantially degraded by the strong acid and which is soluble both in the strong acid, the non-solvent and mixtures thereof so as to remain soluble under the gelation conditions.
We have established that the use of the aforesaid polymer additive avoids the problems associated with the use of SPEES where the polymer is soluble in the strong acid and in the non-solvent but not in the mixture of the two which occurs during membrane formation.
Membranes produced by the method of the invention have greatly
improved overall performance and greatly improved flux at any given molecular weight cut-off (MCWO).
The invention is particularly applicable to the fabrication of crystallisable polyetherketone membranes with pore-sizes in the ultrafiltration range (i.e. MCWO values in the range 1,000-500,000 Daltons).
The invention is also particularly applicable to the production of asymmetric membranes.
By "asymmetric membrane" we mean a membrane (a) which comprises, on the side adjacent the solution to be filtered, a skin of thickness 0.02-2.0 microns supported on a substrate of thickness 25- 250 microns; (b) in which both the skin and the substrate comprise the same polymer; and (c) in which the pore sizes of the substrate are greater than the pore sizes of the skin.
Preferably the polymer additive has a molecular weight of 1,000- 500,000 Daltons and is normally used at a concentration between 0.5% and 50% (more preferably 10-30%) by weight of that of the polyetherketone although it is possible to use values outside this range.
The polymer additive can be very substantially removed from the final membrane by washing with an appropriate solvent medium. It has however been found that the higher the molecular weight of the polymer the more difficult is its removal from the membrane. For this reason it is generally preferred to use polymers towards the lower end of the 1,000-500,000 Dalton molecular weight range, e.g. 1000 to 100,000 especially 10,000 to 50,000.
Generally the gelation medium is aqueous and as such the polymer additive will be soluble in water, the strong acid, and mixtures thereof. The preferred polymer for use in an aqueous gelation medium is polyvinylpyrrolidone. It is particularly surprising that this polymer should be so useful in the method of the invention given the strong acid conditions in the solution of the polyetherketone. Other water soluble polymers which may be useful in the method of the invention include poly-2-vinylpyridine, poly-4- vinylpyridine, polyethylenesulphonic acid, polystyrenesulphonic acid, and poly(N,N-dimethylacrylamide).
The process of the invention is applicable to the production of
membranes formed from a wide range of aromatic polyetherketones using the procedures disclosed in EP-A-0 323 076. The aromatic polyetherketone may for example be a crystalline polymer.
The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 illustrates polymers chains in which the aromatic rings are joined by ether or ketone bonds ((I-VI);
Figure 2 illustrates polymer chains in which a portion of the aromatic rings are joined by direct links (VII-IX)) or are bicyclic rings (X);
Figure 3 illustrates copolymer units bearing intercyclic -S02- bonds (XI-XII);
Figure 4 illustrates certain copolymers containing ketone and ether links (XV and XVII) or in addition a mixture of biphenyl and sulphone linkages (XIV and XVI).
Figs 5a and 5b are electron micrographs of the product obtained in Example 3; and
Fig 6 is a GPC trace illustrating the results of Example 4.
Examples of polymers from which the membranes may be fabricated are shown in Figs. 1-4 of the drawings.
It will be appreciated that in figures 1-4,
E represents an ether linkage;
K represents a ketone linkage;
D represents a direct linkage; m represents a meta substituted aromatic ring;
N represents a naphthalene ring;
S represents a sulphone linkage except where it is used as a prefix to the polymer trivial name where it represents "sulphonatedJ
We do not exclude the possibility that at least a portion of the ether linkages in the polymers illustrated in Figures 1-4 may be replaced by thioether linkages.
The preparation of polymers illustrated in certain Figures of the drawings are described inter alia in Journal of Macromolecular Science Review of Macromelecular Chem. Phys., (27 (2), 313-341, 1987 (General Formulae I-VIII); European Patent Specification No. 0,323,076 (General Formula IX); Polymer 1984, Vol 25 (August, 1151 (General Formula X); EPA 0,194,062 (General Formulae XIV) and British Patent Application No.
8910549 (General Formulae XVI)).
The membrane is preferably formed of a homopolymer, most preferably PEK, PEEK, PEEKK, or PEKEKK. PEK and PEEK are available from Imperial Chemical Industries pic, PEEKK from Hoechst, and PEKEKK from BASF.
We do not however exclude the possibility that the membrane may be fabricated from a copolymer eg. PEEK/PEK, PEEK/PES, PEK/PES, PEEK/PEES, PEKK/PE-m-KK wherein the copolymer units are represented by the General Formulae XI-XII and XVII in the drawings.
Furthermore we do not exclude the possibility that the membrane may be formed from a mixture of polymers, eg. PEEK/PEK or PEK/PES.
In the process according to the present invention, the strong acid is a substantially non-sulphonating reagent towards the aromatic ether ketone polymer. For example, where the aromatic ether ketone polymer is PEEK the strong acid is typically methanesulphonic acid.
The solution is formed by dissolving the polyetherketone typically in particulate form, together with the water soluble polymer in the strong acid under an inert atmosphere, at a temperature and timespan sufficient to completely dissolve the polymers.
The membrane may for example be formed as a sheet or a capillary or a tube.
The sheet membrane is typically formed by casting the polymer solution as a thin liquid film, typically of thickness between 20 and 500 μm, onto a suitable substrate which is not attacked by the strong acid solution. The membrane can be supported by a porous fabric e.g. of polyethylene, polypropylene, polyester, PTFE, polyphenylene sulphide, or carbon fibre. Alternatively, the membrane can be unsupported in which case the film would be cast onto a plane non- porous surface, e.g. a band of stainless steel, PTFE of polypropylene or a sheet of glass.
The polymer is then precipitated by treating the shaped solution with non-solvent under suitable conditions, e.g. it may be immersed in non-solvent liquid in a gelation bath, or non-solvent vapour may be allowed or caused to diffuse into it.
A capillary membrane which typically has an internal diameter of 0.03 mm) may be formed by extruding the polymer solution through the outer annulus of a coaxial die. Through the inner nozzle there is
a flow of suitable fluid, e.g. an inert gas or liquid, which is a non- solvent for the polymer.
A tubular membrane (which typically has an internal diameter of at least 5 mm) may be formed by coating the polymer solution as a thin film on the inner or outer wall of a porous tube and immersing the coated tube in a non-solvent to precipitate the membrane. The porous tube may for example be of sintered carbon, stainless steel, or a polymer which is substantially inert to the strong acid solvent.
The precipitated membrane is then allowed to remain in contact with the non-solvent for a time sufficient to allow substantially complete gelation of the polymer, then removed from the non-solvent.
The residual strong acid/non-solvent is removed from the membrane by treatment with an aqueous medium, e.g. water or an aqueous base, at an appropriate temperature, e.g. between room temperature and the belling point of water. Often further treatment with an organic medium, e.g. acetone, is necessary to reduce the amount of acid present in the membrane further.
The membrane ay be subjected to a treatment to enhance crystallinity. As examples of such treatment may be mentioned inter alia heating dry above the Tg of the polymer; treatment with a polar aprotic solvent, e.g. acetone, dimethylformamide (DMF) or dimethylacetamide (DMA). Where DMF or DMA is used in such treatments it is later removed by a suitable further treatment, e.g. by washing with acetone. An alternative procedure for enhancing membrane crystallinity is disclosed in our U.K. Patent Application No. 9323671.9.
Preferably the strong acid is water-free although we do not exclude the possibility that it may contain a small amount, for example up to about 10% of water.
It will be appreciated that the strong acid will be chosen in the light of the structure of the polymer. For example, it should not react chemically with the polymer to unduly reduce the crystallinity thereof. For example, whereas 98% sulphuric acid reacts unduly with polyetheretherketone (PEEK) and should not be used therewith, it can advantageously be used with polyetherketone (PEK) in the process according to the present invention. The strong acid should be a good solvent for the polymer and, after membrane formation, should be
readily extractable therefrom.
We do not exclude the possibility that the strong acid may be a mixture of acids, e.g. sulphuric acid and acetic acid. It will be appreciated that where one of the acids in the mixture is non-solvent for the polymer the concentration thereof will be insufficient to inhibit solvation of the polymer in the mixture. For example, where the strong acid is a mixture of sulphuric acid and acetic acid, the concentration of acetic acid is typically less than 15% w/w.
As examples of strong acids for use in the process of the present invention may be mentioned - inter alia sulphuric acid, liquid hydrogen fluoride, methane sulphonic acid, fluoromethane sulphonic acid, and di- and tri-fluoromethane sulphonic acid.
It will be appreciated that the skilled man will take appropriate precautions where he uses any of the above acids.
We do not exclude the possibility that a further solvent may be used in combination with the strong acid, with the proviso that it does not unduly impair the solvent power of the strong acid, or react with the strong acid or unduly react with the polymer in the presence of the strong acid.
As typical examples of such further solvents may be mentioned inter alia liquid sulphur dioxide, 1,2,4-trichlorobenzene, 1,2- dichloroethane, dichloromethane, dichloroacetic acid and trifluoroacetic acid.
The invention will be illustrated by the following non-limiting Examples.
Example 1
A 9.5% w/w solution of polyetherketone (ICI Victrex PEK-220G) and 3.0% w/w polyvinylpyrrolidone (Povidone, 44,000 MW) in 98% sulphuric acid was spun under pressure through a stainless steel tube-in-hole spinneret (hole diameter 0.65 mm; tube o.d. 0.36 mm, tube i.d. 0.19 mm) into a water-bath. Aqueous sulphuric acid (55% w/w) was used as the internal coagulant.
The resulting hollow-fibre membrane was washed with water, soaked in a 10% w/w aqueous solution of glycerol, dried, and potted in nylon tubing before evaluation under cross-flow conditions in terms of water-flux and molecular weight cut-off (dextran challenge).
The fibre had an internal diameter of ύ.Zo mm, a wall-thickness of 0.125 mm, water flux (at 2 bar transmembrane pressure) of 293 l/m2/hr, and a MWCO of 16,000 Daltons.
Comparative Example No. 1
A hollow-fibre membrane was prepared as in Example 1, but omitting polyvinylpyrrolidone.
The resulting fibre had an internal diameter of 0.33 mm, a wall- thickness of 0.135 mm, a water flux (at 2 bar transmembrane pressure) of 145 1/rrJ/hr, and a MWCO of 30,000 Daltons.
Example 2
A hollow-fibre membrane was prepared as in Example 1, but now using a 9.0% w/w solution of PEK, containing 2% w/w of PVP (MW 44,000).
The resulting fibre had an internal diameter of 0.35 mm, a wall- thickness of 0.125 mm, a water flux (at 2 bar transmembrane pressure) of 384 1/πJ/hr, and a MWCO of 30,000 Daltons.
Comparative Example No. 2
A hollow-fibre membrane was prepared as in Example 2, but omitting polyvinylpyrrolidone.
The resulting fibre had an internal diameter of 0.32 mm, a wall- thickness of 0.140 mm, a water flu (at 2 bar transmembrane pressure) of 118 l/m2/hr, and a MWCO of 115,000 Daltons.
The above examples clearly demonstrate that polyetherketone membranes of substantially improved performance can be obtained by incorporation of a water-soluble polymer such as polyvinylpyrrolidone into the membrane-spinning solution. In particular, the MWCO of the new type of membrane is sharply lowered, effectively increasing its selectivity, and moreover the water-flux is in each case two to three times greater than that of the comparative membrane prepared in the absence of PVP. Since the lowering of MWCO in a membrane is conventionally accompanied by a reduction in flux, it is clear that the membranes of the present invention represent a significant advance in performance over the prior art.
Example 3
A 9.0% w/w solution of polyetherketone (ICI Victrex PEK-220) containing 2.5% w/w of PVP (Povidone) was spun under pressure through a stainless steel tube-in-hole spinneret (hole diameter 0.90 mm, tube o.d. 0.51 mm, tube i.d. 0.25 mm) into a deionised-water bath. Deionised water was also used as the internal coagulant, and the resulting hollow fibre membrane had an internal diameter of 0.70 mm and a wall thickness of 0.10 mm. This membrane was subjected to a post- fabrication crystallisation process, as described in our U.K. Patent Application No. 9323671.9, to give a membrane with water flux at 2 bar of 115 l/m2/hr and a MWCO of 10,000 daltons.
The structure of this membrane was determined by high resolution scanning electron microscopy. An oblique cross-section of the fibre at low magnification is shown in Figure 5a, from which it can be seen that the membrane is skinned on both its outer and inner surfaces, and has a highly porous internal structure, which may account, in part, for the excellent permeability of the membrane. An orthogonal cross-section of the inner surface of the membrane is shown at high magnification in Figure 5b. From this micrograph it can be seen that the relatively dense inner skin, (which forms the separating layer in membranes of this type), is quite exceptionally uniform, suggesting that the process of the invention is capable of providing an intrinsically consistent and reproducible product.
Example 4
Ability of the membrane to operate in aqueous or non-aqueous solvents.
The membrane produced in Example 3 was used to concentrate and fractionate a toluene solution containing a mixture of polystyrenes (0.1% w/w of each fraction) of nominal molecular weights 4,000, 12,000, 24,000, 32,000, and 50,000. After flushing the membrane successively with water, acetone, and then toluene, a steady toluene flu.x of 120 l/m2/hr at 1 bar was obtained. On permeating the toluene/polystyrene solution, the flux fell to 100 l/m2/hr, and to 80 1/πJ/hr as the total polymer concentration in the feed rose to ca. 1%.
Gel permeation chromatograms of the feed and permeate are shown in Figure 6, from which it can be seen that the membrane
retains essentially 100% of the polymers witn MW greater than 24,000 and about 95% of the 12,000 MW fraction. Only some 60% of the 4 ,000 MW fraction however is retained by the membrane. These results confirm that the MWCO of the membrane (for 90% rejection) remains at around 10,000, whether the membrane is operating in aqueous or organic media.
Following the fractionation experiment, the membrane was flushed with pure toluene, then acetone, and finally water. Its water flux and MWCO for aqueous dextrans were essentially unchanged from their initial values as determined in Example 3.
Claims
1. A method of producing a porous membrane comprising the steps of
(a) shaping into a desired shape a solution of an aromatic ether ketone polymer in a strong acid which is substantially non- sulphonating to the polymer,
(b) contacting the shaped solution with a gelation medium containing a non-solvent for the polymer so as to form a membrane, and
(c) removing the membrane from strong acid/non-solvent mixture, characterised in that said solution of the aromatic ether ketone polymer includes a polymer additive which is not substantially degraded by the strong acid and which is soluble both in the strong acid, the non-solvent and mixtures thereof so as to remain soluble under the gelation conditions.
2. A method as claimed in claim 1 wherein the polymer additive has a molecular weight of 1,000 to 500,000.
3. A method as claimed in claim 2 wherein the polymer additive has a molecular weight of 1,000 to 100,000.
4. A method as claimed in claim 3 wherein the polymer additive has a molecular weight of 10,000 to 50,000.
5. A method as claimed in any one of claims 1 to 4 wherein the polymer additive is used at a concentration between 0.5% and 50% of that of the aromatic ether ketone polymer.
6. A method as claimed in claim 5 wherein the polymer additive is used at a concentration between 10% and 30% of that of the aromatic ether ketone polymer.
7. A method as claimed in any one of claims 1 to 6 wherein the gelation medium is aqueous and the polymer additive is water soluble.
8. A method as claimed in claim 7 wherein the polymer additive is polyvinylpyrrolidone.
9. A method as claimed in any one of claims 1 to 8 wherein the membrane has a molecular weight cut-off in the range 1,000 to 500,000.
10. A method as claimed in any one of claims 1 to 9 wherein the membrane is an asymmetric membrane.
11. A method as claimed in any one of claims 1 to 10 wherein the aromatic ether ketone polymer is a crystalline polymer.
12. A method as claimed in any one of claims 1 to 11 wherein the aromatic ether ketone polymer is PEK, PEEK, PEEKK, or PEKEKK.
13. A method as claimed in any one of claims 1 to 12 comprising the further step of enhancing the crystallinity of the membrane.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU11973/95A AU1197395A (en) | 1993-12-10 | 1994-12-12 | Production of membranes |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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GB9325344.1 | 1993-12-10 | ||
GB939325344A GB9325344D0 (en) | 1993-12-10 | 1993-12-10 | Production of membranes |
Publications (1)
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WO1995015809A1 true WO1995015809A1 (en) | 1995-06-15 |
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PCT/GB1994/002710 WO1995015809A1 (en) | 1993-12-10 | 1994-12-12 | Production of membranes |
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AU (1) | AU1197395A (en) |
GB (1) | GB9325344D0 (en) |
WO (1) | WO1995015809A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003000390A2 (en) * | 2001-06-26 | 2003-01-03 | Victrex Manufacturing Limited | Membranes and their manufacture |
KR100446211B1 (en) * | 2001-08-29 | 2004-08-30 | 박기용 | Process for preparing of a proton-conducting polyvinylidene fluoride membrane |
WO2012106583A3 (en) * | 2011-02-04 | 2013-03-21 | Fresenius Medical Care Holdings, Inc. | Performance enhancing additives for fiber formation and polysulfone fibers |
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EP0261734A1 (en) * | 1986-09-23 | 1988-03-30 | X-Flow B.V. | A process for the preparation of hydrophilic membranes and such membranes |
EP0382356A2 (en) * | 1989-01-26 | 1990-08-16 | North West Water Group Plc | Membranes |
EP0417287A1 (en) * | 1988-09-29 | 1991-03-20 | Toray Industries, Inc. | Porous membrane and process for its manufacture |
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EP0492446A2 (en) * | 1990-12-21 | 1992-07-01 | The Dow Chemical Company | Microporous membranes from poly(ether-etherketone)-type polymers and low melting point crystallizable polymers, and a process for making the same |
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1993
- 1993-12-10 GB GB939325344A patent/GB9325344D0/en active Pending
-
1994
- 1994-12-12 WO PCT/GB1994/002710 patent/WO1995015809A1/en active Application Filing
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EP0382356A2 (en) * | 1989-01-26 | 1990-08-16 | North West Water Group Plc | Membranes |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003000390A2 (en) * | 2001-06-26 | 2003-01-03 | Victrex Manufacturing Limited | Membranes and their manufacture |
WO2003000390A3 (en) * | 2001-06-26 | 2003-10-16 | Victrex Mfg Ltd | Membranes and their manufacture |
US7407609B2 (en) | 2001-06-26 | 2008-08-05 | Victrex Manufacturing Limited | Membranes and their manufacture |
KR100446211B1 (en) * | 2001-08-29 | 2004-08-30 | 박기용 | Process for preparing of a proton-conducting polyvinylidene fluoride membrane |
WO2012106583A3 (en) * | 2011-02-04 | 2013-03-21 | Fresenius Medical Care Holdings, Inc. | Performance enhancing additives for fiber formation and polysulfone fibers |
AU2012212102B2 (en) * | 2011-02-04 | 2016-01-07 | Fresenius Medical Care Holdings, Inc. | Performance enhancing additives for fiber formation and polysulfone fibers |
US9617421B2 (en) | 2011-02-04 | 2017-04-11 | Fresenius Medical Care Holdings, Inc. | Performance enhancing additives for fiber formation and polysulfone fibers |
USRE48703E1 (en) | 2011-02-04 | 2021-08-24 | Fresenius Medical Care Holdings, Inc. | Performance enhancing additives for fiber formation and polysulfone fibers |
Also Published As
Publication number | Publication date |
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AU1197395A (en) | 1995-06-27 |
GB9325344D0 (en) | 1994-02-16 |
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