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
  • B01D69/12—Composite membranes; Ultra-thin membranes
• • 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
• • 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
  • B01D69/081—Hollow fibre membranes characterised by the fibre diameter
• • 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
  • B01D69/10—Supported membranes; Membrane supports
  • B01D69/107—Organic support material
• • 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
  • B01D71/28—Polymers of vinyl aromatic compounds
  • B01D71/281—Polystyrene
• • 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
  • B01D71/28—Polymers of vinyl aromatic compounds
  • B01D71/283—Polyvinylpyridine
• • 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
  • B01D2323/00—Details relating to membrane preparation
  • B01D2323/02—Hydrophilization
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2323/00—Details relating to membrane preparation
  • B01D2323/42—Details of membrane preparation apparatus
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/26—Electrical 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
  • B01D69/10—Supported membranes; Membrane supports
  • B01D69/105—Support pretreatment

Definitions

• the present invention relates to coated hollow fiber membranes which have an isoporous inner skin and a porous outer support membrane, i.e. an inside-out isoporous composite hollow fiber membrane, and to a method of preparing such membranes.
• the invention further relates to the use of the coated hollow fiber membrane according to the present invention for filtra ⁇ tion, such as in particular for microfiltration, ultrafiltration, nanofiltration and/or reverse osmosis, in particular for ultrafiltration.
• Membrane separation is widely used in the food technology, bi ⁇ otechnology and pharmaceutical industries for mechanical sepa ⁇ ration of fluid, e.g. gaseous or liquid streams.
• Membrane separation technology using a separation membrane having a hollow fiber structure has been applied to water purification and sewage and wastewater processes.
• membranes useful in particular for water treatment can be classified into the fol ⁇ lowing categories: polymer membranes, ceramic membranes, and metal membranes.
• Such membranes are used for microfiltration (MF) , ultrafiltration (UF) , nanofiltration (NF) , and reverse osmosis (RO) .
• MF microfiltration
• UF ultrafiltration
• NF nanofiltration
• RO reverse osmosis
• Ultrafiltration membranes allow small molecules and ions to be permeated, but remove high molecular polymer particles or bacteria and viruses, and may vary according to the requirements of use. They usually have a pore size in a range of from 0.01 to 0.1 ⁇ .
• Ultrafiltration membranes having such characteristics have a wide application range, but are particularly interesting for pretreatment of process water or ultrapure water, reuse, sewage and wastewater treatment and water purification. Also in wastewater treatment, membrane technology is becoming increasingly important. With the help of ultrafiltration or microfiltration it is possible to remove particles, colloids and macromolecules , so that wastewater can be disinfected in this way.
• Such membranes have a porous separation layer on top wherein the size and size distribution (regularity) of the pores de ⁇ termine filtration selectivity.
• the fluid stream is passed along the outside of the hollow fiber polymer membrane, and the permeate stream is collected from the inside of the hollow fiber poly ⁇ mer membrane.
• This outside-in separation is undesirable for a number of reasons, including the difficulty to control concen ⁇ tration polarization and membrane fouling. Therefore, in many cases an opposite filtration direction is desirable. This is because of protection of selective surface, better distribution of feed on the lumen side during filtration, and ease of processing and maintenance. For example, cleaning of membranes with isoporous inner skin by backwashing or forward aeration will be easier, and the overall fouling and clogging by bacteria and other foulants may thereby be re ⁇ cuted in comparison to hollow fiber polymer membranes having an isoporous outer skin.
• European patent application 3,147,024 Al discloses a hollow fiber polymer membrane having a novel structure with an isoporous inner skin and a porous outer skin as well as a nov ⁇ el method for its production.
• the method described in EP 3,147,024 Al comprises providing a polymer solution of at least one amphiphilic block copolymer in a solvent or solvent mixture, extruding the polymer solution through a first annular die in a spinneret while simultaneously passing a core gas stream through at least one orifice encircled by the first die and extruding that sheath liquid comprising at least one pre ⁇ cipitant from a second die encircling the first annular die into air, and subsequently into an aqueous precipitation bath.
• the spinning solution is precipitated in the precipitation bath to form the hollow fiber polymer membrane having an isoporous inner skin and a porous outer skin.
• the fluid stream is passed along the inside of the hollow fiber polymer membrane, and the permeate stream is removed from the outside of the fiber, which is less complex .
• CA 2,886,437 and EP 3,147,024 Al self- assembly of the block copolymers and non-solvent induced phase separation (SNIPS) form the isoporous skin on the site oppo ⁇ site to where the non-solvent is contacted with the polymer solution.
• SNIPS non-solvent induced phase separation
• the hollow fiber membrane is formed entirely by the block-copolymer .
• CA 2,886,437 and EP 3,147,024 Al highly concentrated block copolymer solution is required, and the production of isoporous hollow fibers by the spinning process CA 2,886,437 and EP 3,147,024 Al is comparatively expensive.
• a method for producing a coat ⁇ ed hollow fiber membrane having an isoporous inner skin com- prising providing a hollow fiber support membrane having a lumen surrounded by the support membrane, and coating the inner surface thereof by first passing a polymer solution of at least one amphiphilic block copolymer in a suitable solvent through the lumen of the hollow fiber support membrane and along the inner surface thereof, thereafter pressing a core gas stream through the lumen of the coated hollow fiber membrane, and thereafter passing a non-solvent (precipitant) through the lumen of the coated hollow fiber membrane.
• the membranes according to the present invention are self- supporting and have an isoporous inner skin, a porous outer skin, and a sponge-like inner structure.
• the inner skin is typically of a different material than the outer skin of the coated hollow fiber membrane.
• Hollow fiber support membrane having a lumen to be coated with an isoporous inner skin of a block copolymer is preferably a polymeric membrane such as a cellulose acetate (CA) membrane, a polyethersulfone (PES) membrane, a polyetherimide (PEI) mem ⁇ brane, a polyvinylidene fluoride (PVDF) membrane, a polysulfone (PSf) membrane, a polyacrylonitrile (PAN) mem ⁇ brane, a polyamide-imide (PAI) membrane, a modified cellulose acetate (mCA) membrane, a modified polyethersulfone (mPES) membrane, a modified polyetherimide (mPEI) membrane, a modi ⁇ fied polyvinylidene fluoride (mPVDF) membrane, a modified polysulfone (mPSf) membrane, a modified polyacrylonitrile (mPAN) membrane, a modified polyamide-imide (
• the hollow fiber support membrane may preferably have a diame ⁇ ter ranging from 0.2 to 3.0 mm, preferably from 0.5 to 1.5 mm, and the lumen of the hollow fiber support membrane may prefer ⁇ ably have a diameter of from 0.1 to 2.5 mm, preferably from 0.3 to 1.49 mm.
• the length of the hollow fiber support mem ⁇ brane may be from few centimeters to few meters.
• the hollow fiber support membrane has a length of from 5 to 50 cm, more preferably from 10 to 25 cm.
• the hollow fiber support membrane has a median pore size of from 20 nm to 20 ym, more preferably from 50 nm to 1 ym, as determined by electron microscopy.
• the pore size of the hollow fiber support membrane is, however, not critical for many ap ⁇ plications .
• the at least one amphiphilic block copolymer used for making the isoporous inner skin of the coated hollow fiber membrane may be the same as used in EP 3,147,024 Al, which is fully in ⁇ corporated by reference herewith.
• Further amphiphilic block copolymers useful for making the isoporous inner skin of the coated hollow fiber membrane are those disclosed in S. Saleem et al .
• PS-b-PSMA Polystyrene-b- poly (solketal methacrylate)
• PS-b-PGMA Amphiphilic Poly- styrene-b-poly (glyceryl methacrylate)
• preferred pore forming polymer blocks are selected from poly (N, -dimethylacrylamide) (PDMA) , poly (acrylic acid), poly (glutamic acid) (PGA), poly-Y-glutamic acid ( ⁇ -PGA) , Polyaspartic acid (polyaminoacid) , poly (ethyleneoxide) (PEO) , poly[(allyl glycidyl ether) -co-PDMA) , poly (N, -dimethylacrylamide) (PDMA) , poly (acrylic acid), poly (glutamic acid) (PGA), poly-Y-glutamic acid ( ⁇ -PGA) , Polyaspartic acid (polyaminoacid) , poly (ethyleneoxide) (PEO) , poly[(allyl glycidyl ether) -co-
• triphenylamine polyphenylalanine, poly(N- isopropylacrylamide) (PNIPAM) , poly (N, -dimethylaminoethyl meth- acrylate) (PDMAEMA) , poly (poly (ethylene glycol ) methyl ether methacrylate) ( P ( PEGMA) ) .
• PIPAM poly(N- isopropylacrylamide)
• PDMAEMA poly (N, -dimethylaminoethyl meth- acrylate)
• PEGMA poly (poly (ethylene glycol ) methyl ether methacrylate)
• Further amphiphilic block copolymers useful for making the isoporous inner skin of the coated hollow fiber membrane are selected from diblock copolymers such as polystyrene-jb- poly ( solketal methacrylate) (PS-b-PSMA) , polystyrene-jb- poly (glyceryl methacrylate) (PS-b-PGMA) , polystyrene-jb-poly (2- ethylhexyl methacrylate) (PS-b-PEHMA) , poly (glutamic Acid) -b- Polyphenylalanine, polystyrene-jb-poly [ (allyl glycidyl ether) - co- (ethylene oxide)] (PS-jb-P (AGE-co-EO) ) , polystyrene-jb-poly (N- isopropylacrylamide) (PS-PNIPAM) , poly (ethylene oxide) -b- poly (N,
• PDMAEMA poly (2- (2-guanidinoethoxy) ethyl methacrylate) -£>- ⁇ -£>- poly (2- (2-guanidinoethoxy) -ethyl methacrylate) (PGn-jb-PEO-jb-PGn) , polyisoprene-j -polystyrene-j -poly (4-vinylpyridine) (PI-jb-PS-jb- P4VP) , poly (isoprene-j -styrene-j - (4-vinylpyridine) ) P(I-jb-S-jb- 4VP) , polystyrene-jb-polybutadiene-jb-poly (tert-butyl methacry ⁇ late) (PS-jb-PB-jb-PTMA) , polystyrene-jb-poly (4-vinylpyridine) -b-b-
• Preferred star triblock terporlymers for making the isoporous inner skin of the coated hollow fiber membrane are polysty- rene-jb-poly (2-vinylpyridine) 3 (PS-jb-P2VP) 3 , polystyrene-jb- poly (2-vinylpyridine) -jb-polyethyleneoxide) 3 ( ⁇ 3-£>- ⁇ 2 ⁇ " ⁇ -£>- ⁇ ) 3 , and polystyrene-jb-poly (2-vinylpyridine) -jb-jbis-poly- ethyleneoxide) 3 ( PS-&-P2VP-&- (PEO) 2 ) 3 .
• polystyrene-jblocJf-poly (4- vinylpyridine) (PS-jb-P4VP) block copolymers are preferred polystyrene-jblocJf-poly (4- vinylpyridine) (PS-jb-P4VP) block copolymers.
• PS-jb-P4VP polystyrene-jblocJf-poly (4- vinylpyridine)
• the styrene comonomer component is present in 75-85 wt . % of the polymer and the 4-vinylpyridine component is present in 15-25 wt . % of the polymer.
• the polymer has a molec ⁇ ular weight between 50 and 300 kg/mol.
• the polymer preferably makes up a percentage by weight between 1 wt . % and 10 wt.%, more preferably between 1 wt . % and 5 wt.%, and most preferably between 1 wt.% and 3 wt.% of the polymer solution such as around 2 wt.% of the polymer solution.
• solvents are suitable for preparing the polymer solu ⁇ tion.
• Preferred solvents include diethyl ether, N, N-dimethy1- formamide (DMF) , dimethylacetamide, W-methylpyrrolidone, dime- thyl-sulfoxide, acetonitrile, dioxane, acetone, tetrahydro- furane (THF) , and mixtures thereof.
• More preferred solvents include a solvent mixture such as dioxane/THF, dioxane/DMF, dioxane/DMF/THF or dioxane/DMF/acetone .
• the solvent is dioxane or a mixture including dioxane.
• the polymer solution is pressed or sucked through the lumen of the support membrane with a flow rate between 0.1 mL/min and 5 mL/min, preferably between 0.2 mL/min and 1.0 mL/min .
• the polymer solution comprises at least one metal salt.
• the metal is selected from an element of the second main group of the periodic system of elements, such as Mg, Ca or Sr or from non-toxic transition metals such as Fe .
• the salt is an organic salt of Mg, Ca or Sr, most preferably magnesium acetate.
• the metals of the second main group of the periodic system are biocompatible making them preferred for coated hollow fiber membranes with biologi ⁇ cal applications. The supporting effect of the salt in the phase separation can probably be explained in that the metal salt leads to the formation of partially charged polyelectrolytic micelle cores, which positively impact the precipitant-induced phase separation.
• the polymer solution comprises at least one carbohydrate, multifunctional phenol and/or multifunctional organic acid.
• Preferred carbohy ⁇ drates include saccharose, D (+) -glucose, D (-) -fructose and/or cyclodextrin, in particular -cyclodextrin .
• Carbohydrates as used in the present invention lead to a stabilization of the isoporous separation-active surface during the phase inver ⁇ sion. The supporting effect of the at least one carbohydrate in phase separation can probably be explained in that the car- bohydrates form hydrogen bonds with the hydrophilic block of the block copolymers.
• the block copolymer solution may also comprise of any non- solvent such as polyethylene glycol (PEG) , polyvinylpyrrolidone (PVP) glycerol, ⁇ -butyrolactone (GBL) in order to increase the viscosity of solution and to reduce overall requirement of block copolymer concentration.
• PEG polyethylene glycol
• PVP polyvinylpyrrolidone
• GBL ⁇ -butyrolactone
• the core gas may be selected from any gas which does not react with the polymer of the membrane.
• the core gas is selected from compressed air, nitrogen (N 2 ) , a noble gas, such as argon or helium, and/or carbon dioxide (C0 2 ) ; most prefera ⁇ bly the core gas is nitrogen.
• the core gas is pressed or sucked through the lumen of the support membrane with a flow rate between 0.1 mL/min and 5 mL/min depending on the lumen volume of support fiber, preferably between 0.2 mL/min and 1.0 mL/min.
• the non-solvent comprises water, methanol, ethanol or a mixture of two or more thereof in ad ⁇ mixture with any one or more of diethyl ether, more preferably in admixture with at least one pore forming material such as polyethylene glycol (PEG) , polyvinylpyrrolidone (PVP) or glyc ⁇ erol.
• the precipitation bath comprises or is comprised of a mixture of water and glycerol.
• the non-solvent (precipitant) is water.
• the non- solvent is pressed or sucked through the lumen of the support membrane with a flow rate between 0.1 mL/min and 5 mL/min, preferably between 0.2 mL/min and 1.0 mL/min.
• the so-obtained coated hollow fiber membranes are preferably washed using water, prior to use.
• the hollow fiber support membrane is preferably also pretreat- ed by passing a non-solvent for support membrane through the lumen thereof, where non-solvent for support membrane prefera ⁇ bly shows good miscibility with the block copolymer solution, such as dioxane or dioxane/acetone .
• This pretreatment is in ⁇ tended to reduce the infiltration of dilute block copolymer solution. While passing the polymer solution for coating on the top most inner skin of support membrane, the infiltration decreases the porosity of support membrane.
• the inner surface or lumen of the hollow fiber support membrane is preferably coated from top to bottom or from bottom to top, coating from top to bottom being preferred.
• the method according to the present invention makes it possible to achieve coated hollow fiber composite membranes having advan ⁇ tageous characteristics as set out below.
• the self-supporting hollow fiber composite membranes having an isoporous inner skin and an outer porous support membrane ac ⁇ cording to the present invention have preferably an inner skin of at least one amphiphilic block copolymer and outer porous support membrane is preferably a polymer material selected from the group consisting of a cellulose acetate (CA) mem ⁇ brane, a polyethersulfone (PES) membrane, a polyetherimide
• PEI polyvinylidene fluoride
• PVDF polyvinylidene fluoride
• PSf polysulfone
• PAN polyacrylonitrile mem ⁇ brane
• PAI polyamide-imide
• mCA modified cellulose acetate
• mPES modified polyethersulfone
• mPEI modified polyetherimide
• mPVDF modi ⁇ fied polyvinylidene fluoride
• mPSf modified polysulfone
• the pore size of the inner skin is smaller than the pore size of the outer porous support membrane.
• the isopores of the separation- active inner skin preferably have a ratio of the maximum pore diameter to the minimum pore diameter (pore size dispersity) of less than 10, more preferably less than 5, most preferably less than 3; and preferably a median pore size ranging from 1 nm to 70 nm, preferably from 2 nm to 40 nm, more preferably from 10 to 30 nm.
• the membranes may be kept in water for 1 to 2 days and washed pri ⁇ or to use.
• the coated hollow fiber composite membrane according to the present invention may have a flux from 1000 to 30,000 dm 3 / (m 2 -h-MPa) , such as 3000 to 20000 dm 3 / (m 2 ⁇ h ⁇ MPa) . At this flux, the coated hollow fiber membrane according to the pre ⁇ sent invention still maintains high selectivity.
• the proposed method of the coating can be also applied to pre ⁇ pare isoporous surfaces in multibore membranes and the lumens having different architected shapes such as triangular-polygon or star-shaped in order to increase surface area for separa ⁇ tion.
• the process holds the potential to coat a bundle of hol ⁇ low fiber support membranes together.
• two opposite elec ⁇ trolytes can be added to support membrane and in the coating solution in order to produce an electro-conductive isoporous composite hollow fiber membrane.
• Membranes having isoporous surfaces on both sides could be beneficial for instance for applications in bioprocessing .
• the outer surface of inside-out isoporous composite hol ⁇ low fibers can also be coated which will result in a membrane having isoporous inner and outer surfaces.
• the coating of the outer surface could be performed by the methods described in the article by Y. Liu et al . "Fabrication of a Novel PS4VP/PVDF Dual-layer Hollow Fiber Ultrafiltration Membrane” , Journal of Membrane Science 506, 1-10, 2016. Further methods for producing a coating on outer surface are disclosed in: Y. Zhang et al .
• the present invention provides a filtration mod ⁇ ule, in particular a microfiltration module, an ultrafiltration module, or a nanofiltration module, comprising at least one of the hollow fiber polymer membranes according to the present invention.
• the coated hollow fiber membranes according to the present invention are e.g. useful for pretreatment of process water or ultrapure water, reuse, sewage and wastewater treatment and water purification.
• the mem ⁇ branes can be produced having different charges in the support membrane and coating membrane.
• Figure 1 is a schematic diagram of the method according to the present invention, wherein the hollow fiber support membrane is preferably coated from top to bottom.
• Figure 2 is a schematic diagram of the method according to the present invention, wherein the hollow fiber support membrane is preferably coated from bottom to top.
• Figure 3a shows an SEM of the cross-section of a PEI support membrane coated top-bottom with 1.5 wt% ⁇ 3 7 9 -£>- ⁇ 4 ⁇ " ⁇ 2 ⁇ 701 ⁇ in dioxane:
• Q dox 0.2 mL/min;
• Q p 0.2 mL/min;
• Q C o2 0.2 mL/min;
• Q w 0.5 mL/min;
• T dox 10 s;
• T p 15 s;
• T C0 2 15 s.
• Figure 3b shows the cross-section near the inner surface of the coated membrane of Figure 3a.
• the coating thickness is about 13 ym.
• Figure 3c shows the morphology of the inner surface of the coated membrane of Figure 3a in top view.
• Figure 4a shows an SEM of the cross-section of a PES support membrane coated top-bottom with 1.5 wt% ⁇ 3 7 9 -£>- ⁇ 4 ⁇ " ⁇ 2 ⁇ 701 ⁇ in dioxane:
• Q dox 1.0 mL/min;
• Q p 1.0 mL/min;
• Q C o2 1.0 mL/min;
• Q w 1.0 mL/min;
• T dox 15 s;
• T p 25 s;
• T C o2 15 s.
• Figure 4b shows the cross-section near the inner surface of the coated membrane of Figure 4 a .
• the coating thickness is about 5 ym.
• Figure 4c shows the morphology of the inner surface of the coated membrane of Figure 4 a in top view.
• Figure 5b shows the cross-section near the inner surface of the coated membrane of Figure 5a.
• the coating thickness is about 3 ym.
• Figure 5c shows the morphology of the inner surface of the coated membrane of Figure 5a in cross-sectional view.
• Figure 5d shows the morphology of the inner surface of the coated membrane of Figure 5a in top view.
• Figure 6a shows an SEM of the cross-section of a mPES (commercially available) support membrane coated bottom-top with 2 wt% PS 82 .7- J b-P4VP 17 .3 168k and 1 wt% MgAc in dioxane:
• Q p 1.0 mL/min;
• Q N2 0.5 mL/min;
• Q w 0.5 mL/min;
• T p 10 s;
• T N2 20 s.
• Figure 6b shows the cross-section near the inner surface of the coated membrane of Figure 6a.
• the coating thickness is about 3 ym.
• Figure 6c shows the morphology of the inner surface of the coated membrane of Figure 6a in cross-sectional view.
• Figure 6d shows the morphology of the inner surface of the coated membrane of Figure 6a in top view.
• a hollow fiber support membrane having a lumen surrounded by the support membrane is provided.
• a module which consists of transparent PVC U-tubes having an outer diameter of about 6 mm and thickness of about 1 mm were provided in the present case.
• the tubes were preferentially pierced at every 3 cm distance, using a bore of 2.4 mm in order to fasten the exchange of solvent/non- solvent, to lead away the water filtered through the coated membrane and to avoid floating of the modules in the precipi ⁇ tation bath.
• To hold and straighten the support fibers both ends of PVC modules were sealed using epoxy resin.
• the effec ⁇ tive length was varied in the range of 10-20 cm and a typical preparation procedure started with modules having one support membrane. A larger module can contain bundle of longer fibers as well.
• the hollow fiber support membrane may thereafter be pretreated with a non-solvent for support membrane and which shows good miscibility with the block copolymer solution, such as dioxane or dioxane/acetone .
• steps B, C and D three fluids were pumped from top to bot ⁇ tom (Fig. 1) or bottom to top (Fig. 2) , respectively, as indicated by the arrows, for a certain time period through the module to achieve isoporous surface on the inner side: in step B the polymer solution as coating material; in step C a core gas for removal of superfluous polymer solutions and for providing sufficient evaporation time for self-assembly; in step D a non-solvent, such as water, for precipitation of the coated layer. Fibers with newly developed thin selective layer were then washed and kept in DI water. In step C, nitrogen (N 2 ) and carbon dioxide (C0 2 ) were used as gaseous fluid.
• Dioxane pretreatment flow rate Q dox
• polymer solution flow rate Q p
• nitrogen ( N 2 ) flow rate QN2
• carbon dioxide C0 2
• flow rate Qco 2
• water flow rate Q w
• time of dioxane pre ⁇ treatment T dox
• time of flow for polymer solution T p
• time of flow for N 2 T N2
• time of flow for water T w
• Figs. 3a to 6d show the results of four samples prepared using the method according to the present invention.
• Figs. 3a to 5d display results of the coating experiments performed in top- bottom direction on three different support hollow fiber membranes: PEI, PES and mPES, while Figs. 6a to 6d show the re ⁇ sults of the coating performed in bottom-top direction on mPES support.
• the cross-section images highlight uniform coating of thicknesses ranging from 3 to 15 ym (see description of Figures) .
• Inner surface morphology shows that the method provides inside-out isoporous composite hollow fiber membranes.
• the po ⁇ rosity on inner surface can be increased by e.g. increasing the amount of additives, and variation in coating parameters e.g., flow rate and time of flow for gas stream.

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• 2017
  • 2017-07-27 EP EP17183511.9A patent/EP3434357A1/en not_active Withdrawn
• 2018
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  • 2018-06-18 DK DK18732063.5T patent/DK3606651T3/da active
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