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WO2025008223A1 - Solution de polymères de sulfone dans du méthyl-1-méthyl-2-oxopyrrolidone-4-carboxylate pour l'utilisation de membranes - Google Patents

Solution de polymères de sulfone dans du méthyl-1-méthyl-2-oxopyrrolidone-4-carboxylate pour l'utilisation de membranes Download PDF

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WO2025008223A1
WO2025008223A1 PCT/EP2024/067768 EP2024067768W WO2025008223A1 WO 2025008223 A1 WO2025008223 A1 WO 2025008223A1 EP 2024067768 W EP2024067768 W EP 2024067768W WO 2025008223 A1 WO2025008223 A1 WO 2025008223A1
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solution
polymer
methyl
water
polyarylsulfone
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Oliver Gronwald
Radoslaw Kierat
Dieter Rodewald
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BASF SE
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BASF SE
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
    • B01D71/68—Polysulfones; Polyethersulfones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives
    • C08G65/38—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives derived from phenols
    • C08G65/40—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives derived from phenols from phenols (I) and other compounds (II), e.g. OH-Ar-OH + X-Ar-X, where X is halogen atom, i.e. leaving group
    • C08G65/4012—Other compound (II) containing a ketone group, e.g. X-Ar-C(=O)-Ar-X for polyetherketones
    • C08G65/4056—(I) or (II) containing sulfur
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G75/00—Macromolecular compounds obtained by reactions forming a linkage containing sulfur with or without nitrogen, oxygen, or carbon in the main chain of the macromolecule
    • C08G75/20—Polysulfones
    • C08G75/23—Polyethersulfones
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L81/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing sulfur with or without nitrogen, oxygen or carbon only; Compositions of polysulfones; Compositions of derivatives of such polymers
    • C08L81/06—Polysulfones; Polyethersulfones
    • 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

Definitions

  • the present application relates to a solution comprising at least one polyarylsulfone selected from the group of polyethersulfone and polysulfone as polymer and methyl-1-methyl-2- oxopyrrodlidone -4-carboxylate (MMOC), the process of making a membrane and the use of this membrane for separation processes.
  • MMOC methyl-1-methyl-2- oxopyrrodlidone -4-carboxylate
  • Polyarylsulfone polymers such as polysulfones (i.a. merchandized under the trade names: III- trason® S, UJU Paryls®) and polyethersulfones (i.a. merchandized under the trade names: III- trason® E, Veradel®, Sumicaexel®) are high performance polymers which are used in a variety of technical applications because of their mechanical properties and their chemical and thermal stability.
  • One major technical application of polyarylsulfone polymers is their usage as raw materials for the production of polymer membranes, for example, dialysis or ultrafiltration membranes. Polymer membranes are used in separation processes and are widely applied, e.g., in medical applications, the food technology, biotechnology, pharmaceutical industries, and water treatment.
  • WO 2019042749 A1 discloses a process for making a membrane by bringing a polymer solution comprising a polymer, a first solvent, and a co-solvent in contact with a coagulating agent.
  • a polymer solution comprising a polymer, a first solvent, and a co-solvent in contact with a coagulating agent.
  • first solvent N-methylpyrrolidone and N-ethylpyrrolidone is claimed.
  • Polyvinylpyrrolidone is used as a water-soluble polymer.
  • a membrane obtained by this process is disclosed.
  • the workup of the membrane includes an oxidizing step with sodium hypochlorite.
  • the manufacturing of membranes from a polymer solution is furthermore described in WO 2015056145 A1.
  • WO 2021191043 describes the use of N-n-butyl-2-pyrrolidone as alternative solvent for different polymer classes, including polyarylsulfone polymers.
  • PCT/EP2021/082449 describes a solution comprising at least one sulfone polymer and N-tert-butyl-2-pyrrolidone as alternative solvent.
  • the use of such solutions in combination with a water-soluble polymer in membrane fabrication as well as the use of such solutions in combination with a water-soluble polymer in membrane fabrication are also described in WO 2021191043 as well as in PCT/EP2021/082449.
  • But nei- ther WO 2021191043 nor PCT/EP2021/082449 describe the use of MMOC as possible solvent for the membrane production.
  • Methyl-1-methyl-2-oxopyrrodlidone -4-carboxylate is prepared from itaconic acid with methylamine. Itaconic acid is obtained on an industrial scale from sugar and can therefore be prepared in an environmentally friendly manner based on renewable raw materials. On the other hand, itaconic acid can also prepared by different chemical synthesis pathways like carbonylation of propargyl chloride, oxidation of mesityl oxide with an additional isomerization of the citraconic acid to itaconic acid, thermolysis of citric acid to itaconic acid or oxidation of isoprene.
  • DE 2452536A1 describes the synthesis of MMOC and derivates thereof from itaconic acid with different kind of alkylamines. The synthesis of MMOC from itaconic acid with methylamine is also described and the use of MMOC and derivates thereof as solvents for pesticide preparations.
  • US2012/0269750A1 describes the use of MMOC and derivates of it as an ingredient in a composition used for cosmetic sun protection formulations comprising a lipophilic UV-screening agent of the benzophenone type.
  • WO 2012/034688 describes the use of N-Alkyl-2-pyrrolidone-4 carboxylic acid and their esters with not more than C1-C7 alkyl groups as solvent which can replace the polar and water-soluble but toxicological critical solvent N-Methylpyrrolidone (NMP).
  • NMP N-Methylpyrrolidone
  • N-alkyl-2- pyrrolidone 4- carboxylic acid esters are mentioned as preferred solvent for the preparation of coatings, paint, printing ink, agrochemical, pharmaceutical, petrochemical, electronics or photovoltaic industries, binder systems, in cleaners, in paint strippers or graffiti removers, in gas scrubing, for adhesives or adhesive removers, for degreasing, for extraction or purification of substance mixtures, in chemical or pharmaceutical synthesis and for manufacture of pigments or in pigment preparations.
  • N-Alkyl-2-pyrrolidone carboxylic esters MMOC is mentioned for the above-described applications.
  • MMOC MMOC
  • polyarylsulfon polymer for the preparation of membranes which show higher water permeability values in combination with molecular weight cutoff (MWCO) values in the ultrafiltration range are not mentioned in WO2012/034688.
  • MMOC is biodegradable with a degree of biodegration of 77 ⁇ 19 % CO2/ThCO2 after 28 days, which is comparable to the degree of biodegradation of aniline after 14 days (78% CO2/ThCO2), which was used as reference substance and measured according to OECD 301 B with International Standard ISO 9439.
  • NMP N-methyl-2-pyrrolidone
  • the solution containing water-soluble polymers should be stable and clear, since this influences the pore structure and thus the quality of the membranes obtained from these solutions.
  • the solvents conventionally used for membrane fabrication result in low viscous polymer solutions, which are difficult to cast, there is also the demand for solvent systems leading to polymer solutions with higher viscosity.
  • the solvents utilized for membrane production by non-solvent induced phase inversion show complete miscibility with water which is used as coagulant.
  • the water permeability of such membranes should be as high as possible combined with a molecular weight cutoff which is in the ultrafiltration range.
  • these solutions can be used for the preparation of membranes used in the RO-application without any defects in the cross-section of the membranes.
  • a solution comprising a) a polyarylsulfone polymer selected from the group of polyethersulfone polymers comprising repeating unit of formula (I) and polysulfone polymer comprising repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95 wt.-% of the repeating units of formula (I) and/or (II) based on the total weight of the polyarylsulfone polymer, and b) Methyl-1-methyl-2-oxopyrrolidone-4-carboxylate.
  • the inventive solution will be advantageous, if the solution comprises 10 to 25wt.-% of polyarylsulfone polymer based on the total weight of the solution.
  • the inventive solution will be advantageous, if the solution comprises 60 to 90 wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the inventive solution will be advantageous, if the solution comprises a water-soluble polymer showing a solubility in water at 21 °C of at least 10 g per 100 g water.
  • the inventive solution comprises a water-soluble polymer showing a solubility in water at 21°C of at least 10g per 100g water will be advantageous, if the solution comprises 0.1 to 15 wt.-% of a water-soluble polymer and 60 to 89.9wt.% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the inventive solution comprising a water soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the water soluble polymer is selected from polyvinylpyrrolidone, poly(alkylene glycol) with a Mw of at least 2000 g/mol or mixtures thereof.
  • the inventive solution will be advantageous, if the solution comprises 0.1 to 15wt.-% of an additive, in which the polyarylsulfone polymer is soluble at 21 °C at concentration of ⁇ 1 g polyarylsulfone polymer per 100 g additive and 60 to 89.9 wt.-% of methyl-1-methyl-2-oxopyrrolidone-4- carboxylate both based on the total weight of the solution.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the solution comprises an additive, in which the polyarylsulfone polymer is soluble at 21 °C at con- centrations of ⁇ 1g polyarylsulfone polymer per 100 g additive and 60 to 89.8 wt.-% of methyl-1- methyl-2-oxypyrrolidone-4-carboxylate both based on the total weight of the solution.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the additive is selected form the group of water, C1-C4 alkanols, C2-C8 alkandiols, oligo(alkylene glycol)s, polyethylene glycol with a M w of not more than 2000 g/mol and C3-C12 alkantriols or mixtures thereof.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the solution shows a solution viscosity of 1 to 70 Pa*s as determined with a Brookfield Viscometer DV- 1 Prime with RV 6 spindle at 60°C and 5-100 rpm.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the solution shows a solution turbidity of 0 to 3 NTU as determined with a turbidimeter employing a filter of 860 nm at 60°C.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the used methyl-1-methyl-2-oxopyrrolidone-4-carboxylate is produced by using itaconic acid from a renewable source.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the used methyl-1-methyl-2-oxopyrrolidone-4-carboxylate is produced by using itaconic acid from a renewable and non-renewable source.
  • inventive solution as well as the inventive solution comprising a water-soluble polymer showing a solubility in water at 21 °C of at least 10g per 100g water will be advantageous, if the used methyl-1-methyl-2-oxopyrrolidone-4-carboxylate is produced by using itaconic acid from a non-renewable source.
  • Another embodiment of the invention is a process for the preparation of a membrane using the inventive solution or the inventive solution comprising a water-soluble polymer showing a solubility in water at 21°C of at least 10g per 100g water.
  • the inventive process comprising the following steps: a1) Preparing the inventive solution, wherein the polyarylsulfon polymere is a polysulfone polymer comprises repeating units of formula (II) and wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol based on the total weight of the polyarylsulfone polymer, b) Preparing a polymer film from the inventive solution of step a1) by applying the inventive solution of step a1) to a substrate, and c) exposing the polymer film to a coagulant.
  • the inventive process comprising the following steps: a2) Preparing the inventive solution comprises a water-soluble polymer showing a solubility in water at 21°C of at least 10g per 100g water, b) Preparing a polymer film from the inventive solution of step a2) by applying the inventive solution of step a2) to a substrate, and c) exposing the polymer film to a coagulant.
  • a further embodiment is the use of the inventive membranes received by any of the inventive processes for drinking water purification, treatment of industrial or municipal wastewater, desalination of sea or brackish water, dialysis, purification of pharmaceutical products, plasmolysis and food processing.
  • the polyarylsulfone polymer comprises at least 95wt.-% (% per weight), preferably at least 97wt.-%, more preferably at least 98wt.-%, and particularly preferably at least 99wt.-% of the repeating units of formula (I) and/or (II) based on the total weight of the polyarylsulfone polymer.
  • the polyarylsulfone polymer comprises aromatic groups. Beside 1 ,4-phenylene units, the polyarylsulfone polymer can also comprise units based on minor isomers, like 1 ,2-phenylene or 1 ,3- phenylene units.
  • the polyarylsulfone polymer comprises endgroups at the polymer chain ends, like CI-, OH-, MeO-, tert. butyl-, or arylgroups.
  • the different chain ends may comprise different endgroups.
  • the polyarylsulfone polymer usually comprises 0.02 to 1wt.-% (% by weight) endgroups, preferably 0.03 to 0.8wt.-% based on the total weight of the polyarylsulfone polymer.
  • the polyarylsulfone polymer comprises ⁇ 5wt.-% further chemical groups, which are not represented by the repeating units of formula (I) and/or (II), preferably ⁇ 3wt.-%, more preferably ⁇ 2wt.-%, and particularly preferably ⁇ 1wt.-% based on the total weight of the polyarylsulfone polymer.
  • These further chemical groups typically are endgroups or minor aromatic isomers as described above.
  • Ultra- son® E grades available from BASF SE, like Ultrason® E 3010, Ultrason® E 6020 P or Ultra- son® E 7020 P are mentioned.
  • Ultrason® S grades available from BASF SE like Ultrason® S 6010 or UJU Paryls®, which is a polysulfone polymere comprising the repeating unit of formula (II) available from UJU New Materials, are mentioned.
  • the weight average molecular weight M w of a polymer is based on the summarized mass of molecules having a certain molecular mass. To this value, larger, i.e. higher mass molecules have a larger contribution than smaller, i.e. lower mass molecules. M w and its determination are well known in the art. M w can be, for example, determined by gel permeation chromatography (GPC), using a suitable column (stationary phase), solvent (liquid phase), and detector (e.g., via refractive index or UV). These chromatography units have to be calibrated using standard polymers of known molecular weight (e.g., polystyrene).
  • GPC gel permeation chromatography
  • the detector calculates the chromatogram which represents the molecular weight distribution of the respective sample.
  • the molecular weight distribution describes the number of molecules present in a sample versus their molar mass.
  • M w and the number average molecular weight M n are received via computational analysis.
  • M n is based on the number of molecules bearing a specific mass.
  • PDI M w /M n
  • the polyarylsulfone polymers show weight-average molecular weight values M w of 40000 to 105000 g/mol, preferably 45000 to 100000 g/mol, and more preferably 50000 to 95000 g/mol as determined via gel permeation chromatography (GPC) in tetrahydrofuran (THF) and polystyrene (PS) as standard.
  • GPC gel permeation chromatography
  • the preferred polyethersulfone polymers comprising the repeating unit of formula (I) show weight-average molecular weight values of 40000 to 100000 g/mol, preferably 48000 to 92000 g/mol and the preferred polysulfone polymers comprising the repeating unit of formula (II) show weight-average molecular weight values of 45000 to 75000 g/mol, preferably 51000 to 60000 g/mol as determined via GPC in THF and PS as standard.
  • the preferred polyarylsulfone polymers show polydispersity indices of 2 to 5, preferably 2.5 to 4.7.
  • the preferred polyethersulfone polymers comprising the repeating unit of formula (I) show PDI-values of 2.7 to 3.8, preferably 2.8 to 3.6 and the preferred polysulfone polymers comprising the repeating unit of formula (II) show PDI-values of 2.8 to 4.7, preferably 3.0 to 4.5.
  • the glass transition temperature T g is the temperature region at which polymer chain segments become mobile and the sample undergoes a reversible transition from solid, amorphous regions to a softer state of higher flexibility.
  • the glass transition temperature and its determination is well known in the art. It can be determined for example by differential scanning calorimetry (DSC), measuring the heat capacity versus the temperature, whereby the temperature is changed at constant speed (e.g., 10 K/min). Usually, the sample is first cooled and then heated with the same speed. The glass transition temperature can be received from the resulting diagram by geometrical or computational analysis.
  • the preferred polyarylsulfone polymers show glass transition temperatures of 160 to 250 °C, preferably 170 to 240 °C, and more preferably from 180 to 230 °C, measured via differential scanning calorimetry (DSC) according to ISO 11357-1 (2017) and11357-2 (2020) at a heating rate of 10 K/min.
  • DSC differential scanning calorimetry
  • the viscosity number correlates with the molecular weight of the polymer and can be measured based on ISO 1628-5 (1998) in a 1wt.-% polymer solution in N-methylpyrrolidone.
  • the elution time (t) of a defined volume of the polymer solution in an Ubbelohde 1C-capillary is related to the running time of the pure solvent (to) and normalized afterwards with the polymer concentration (c in g/ml) according to equation 1 :
  • the viscosity number is given in ml/g.
  • the preferred polyarylsulfone polymers show viscosity numbers of 40 to 130 ml/g, preferably 50 to 120 ml/g, and most preferably of 60 to 110 ml/g, based on ISO 1628-5 (1998) in a 1wt.-% polymer solution in N-methylpyrrolidone.
  • the inventive solution comprises methyl-1-methyl-2-oxopyrrolidone-4-carboxylate (MMOC) (CAS-No. 59857-86-2) as solvent.
  • MMOC is prepared from itaconic dimethylester with methylamine or by direct reaction of itaconic methylester with methylamine as described in DE2452536 and in the literature by Wu; Feldkamp; Journal of Organic Chemistry; vol. 26; (1961); p. 1519.
  • Itaconic acid is obtained on an industrial scale from sugar or citric acid and can therefore be prepared in an environmentally friendly manner based on renewable raw materials.
  • Cis-aconitate is converted to the thermodynamically favoured transaconitate via aconitate-A-isomerase.
  • Trans-Aconitate is further decarboxylated to itaconate by trans-aconitate-decarboxylase.
  • itaconic acid can also prepared by different chemical synthesis pathways like carbonylation of propargyl chloride described in US 3,025,320, oxidation of mesityl oxide with an additional isomerization of the citraconic acid to itaconic acid described in US 4,100,179, thermolysis of citric acid to itaconic acid described in Erddl Kohle Erdgas Petrochemie 20 (3) p. 188 or oxidation of isoprene described by A.H. Blatt in Organic Syntheses; John Wiley & Sons, New York 1943, Vol. II. p. 328.
  • MMOC can be prepared from itaconic acid that was received from a renewable source like sugar or citric acid (MMOC from a renewable source) as well as from chemical synthesis and non-renewable precursors (MMOC from non-renewable source). Also, a mixture of itaconic acid from a renewable source and from non-renewable source (MMOC from a renewable and a non-renewable source) is proper to prepare MMOC.
  • the biodegradability of MMOC was measured according to OECD 301 B with International Standard ISO 9439. MMOC was biodegradable with a degree of biodegradation of ⁇ S. D: 77 ⁇ 19% CO2/ThCO2 after 28 days (non-OECD evaluation) compared to the reference substance aniline which shows a degree of biodegradable of 78% CO2/ThCO2 after 14 days.
  • Polyarylsulfone polymers and mixtures of polyarylsulfone polymers with water-soluble polymers can be well dissolved by MMOC leading to clear solutions showing surprisingly high viscosities. Both, transparency, and a minimum viscosity are requirements for the preparation of high- quality membranes from such solutions.
  • the inventive solution comprises preferably 60-90wt.-% of methyl-1-methyl-2oxopyrrolidon- 4- carboxylate (MMOC), more preferably 60-89.9wt.-%, particularly preferably 62-87wt.-%, very particularly preferably 63-86wt.-%, and most preferably 64-85wt.-% based on the total weight of the solution.
  • the inventive solution comprises 10 to 40wt.-%, preferably 10 to 25wt.-%, more preferably 11 to 24wt.-%, particularly preferably 12 to 23wt.-%, and very particularly preferably 14 to 20wt.-% polyarylsulfone polymer based on the total weight of the solution.
  • the inventive solution may further comprise a water-soluble polymer, i.e., a polymer that can be readily dissolved in water to give a clear solution in concentrations of at least 10 g polymer per 100 g water at 21 °C.
  • a water-soluble polymer i.e., a polymer that can be readily dissolved in water to give a clear solution in concentrations of at least 10 g polymer per 100 g water at 21 °C.
  • These water-soluble polymers influence the solution viscosity and therefore act as viscosity modifiers.
  • these water-soluble polymers act as pore forming agent in the process of membrane preparation and therefore strongly influence the membrane characteristics.
  • the water-soluble polymers filling the formed pores are removed in a work-up step of membrane preparation. This step can comprise different washing and/or oxidizing steps to remove the water-soluble polymers, which, after removal, leave the empty pores. Beside other parameters, polymer type and molecular weight strongly influence the effort necessary for removal of the water-soluble poly
  • the water-soluble polymer is selected from the group of polyvinylpyrrolidone and poly(alkylene glycol)s or mixtures thereof usually showing a weight-average molecular weight values M w of at least 2000 g/mol. More preferably, the water-soluble polymer is selected from the group of polyvinylpyrrolidone, poly(ethylene oxide), polypropylene oxide), and poly(ethylene oxide)/poly(propylene oxide)-block-copolymers or mixtures thereof showing a Mw of at least 2000 g/mol.
  • the water-soluble polymer is selected from the group of polyvinylpyrrolidone and poly(ethylene oxide) or mixtures thereof with Mw of at least 2000 g/mol and, in the case of polyvinylpyrrolidone with a solution viscosity characterized by the K-value of 12 or higher determined according to the method of Fikentscher described by Fikentscher in Cellulosechemie 13, 1932 (58). The K-value is determined by viscosity measurements of polymer solutions as described by Fikentscher and is known in the art.
  • a very particularly preferred water-soluble polymer is a polyvinylpyrrolidone with Mw of at least 2000 g/mol and a solution viscosity characterized by the K-value of 12 or higher determined according to the method of Fikentscher described by Fikentscher in Cellulosechemie 13, 1932 (58).
  • the solution comprises 0.1 to 15wt.-% of water-soluble polymer, more preferably 2 to 10wt.-%, and particularly preferably 3 to 7wt.-% based on the total weight of the solution.
  • the solution comprises 0.1 to 15wt.-% of water-soluble polymer selected from the group of water-soluble polyvinylpyrrolidone and water-soluble poly(alkylene glycol)s or mixtures thereof, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • water-soluble polymer selected from the group of water-soluble polyvinylpyrrolidone and water-soluble poly(alkylene glycol)s or mixtures thereof, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • the solution comprises 0.1 to 15wt.-% of water-soluble polymer selected from the group of water-soluble polyvinylpyrrolidone, water-soluble poly(ethylene oxide), water- soluble polypropylene oxide), and water-soluble poly(ethylene oxide)/poly(propylene oxide)- block-copolymers or mixtures thereof, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • water-soluble polymer selected from the group of water-soluble polyvinylpyrrolidone, water-soluble poly(ethylene oxide), water- soluble polypropylene oxide), and water-soluble poly(ethylene oxide)/poly(propylene oxide)- block-copolymers or mixtures thereof, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • the solution comprises 0.1 to 15wt.-% of water-soluble polymer selected from the group of water-soluble polyvinylpyrrolidone and water-soluble poly(ethylene oxide) or mixtures thereof, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • the solution comprises 0.1 to 15wt.-% of water-soluble polyvinylpyrrolidone, preferably 2 to 10wt.-%, and more preferably 3 to 7wt.-% based on the total weight of the solution.
  • the inventive solution may further comprise an additive, i.e. , one or more additives or mixtures thereof.
  • Additives are compounds, which modify the solubility of the polyarylsulfone polymer solutions selected from the group of polyethersulfone comprising repeating units of formula (I) and polysulfone polymer comprising repeating units of formula (II) or mixtures thereof only at low concentrations of ⁇ 1 g polyarylsulfone polymer per 100 g additive at 21 °C and have a Mw ⁇ 2000 g/mol.
  • additives influence the velocity of solvent exchange and thus of the precipitation process and therefore control membrane properties like pore size and number.
  • the additive is selected from the group of water, C1-C4 alkanols, C2-C8 alkanediols, oligo(alkylene glycol)s, poly(alkylene glycol)s with a Mw ⁇ 2000 g/mol and C3-C12 alkanetriols or mixtures thereof.
  • More preferred additives are methanol, ethanol, propanol, isopropanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, ethylene glycol, di(ethylene glycol), tri(ethylene glycol), tetra(ethylene glycol), polyethylene glycol with a Mw ⁇ 2000 g/mol, propane-1 , 2-diol, di(propylene glycol), tri(propylene glycol), tetra(propylene glycol), propane-1 , 3-diol, butane-
  • the solution comprises 0.1 to 15 wt.-%, more preferably 1 to 13 wt.-%, particularly preferably 2 to 12 wt.-% and very particularly preferably 5 to 10 wt.-% of the additive based on the total weight of the solution.
  • the inventive solution may comprise further solvents herein designated as cosolvents.
  • cosolvents influence the velocity of solvent exchange and thus of the precipitation process and therefore control membrane properties like pore size and number.
  • Preferred cosolvents are solvents that are readily miscible with methyl-1-methyl-2- oxopyrrolidone-4-carboxylate at any ratio. More preferred suitable cosolvents are, for example, selected from high-boiling ethers, esters, ketones, asymmetrically halogenated hydrocarbons, anisole, gamma-valerolactone, N,N-dimethylformamide, dimethylsulfoxide, dihydrolevoglu- cosenone, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate, sulfolane, N-methyl- 2-pyrrolidone, N-ethyl-2-pyrrolidone, N-n-butyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone, N-(-2’- hydroxyethyl)-2-pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide, and
  • cosolvents are gamma-valerolactone, N-tert- butyl-2-pyrrolidone, N-n-butyl-2-pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide and N-(- 2’-hydroxyethyl)-2-pyrrolidone.
  • At least 10wt.-%, more preferably at least 50wt.-%, particularly preferably at least 80wt.-%, and very particularly preferably at least 90wt.-% of the total weight amount of all solvents of the solution is methyl-1-methyl-2-oxopyrrolidone-4-carboxylate.
  • the solution of the invention can be easily prepared by combining the different components of the solution.
  • the solution of the invention can be prepared by combining all the components, i.e. polyarylsulfone polymer, methyl-1-methyl-2-oxopyrrolidone-4-carboxylate, and if need be, further components like water-soluble polymer, additives or cosolvents and dissolving all compounds according to any process known in the art.
  • the solution process may, for example, advantageously be supported or accelerated by increasing the temperature of the mixture and/or by mechanical operations like stirring, shaking, subjection to ultrasound (e.g. by using an ultrasonification bath) etc.
  • the polyarylsulfone is dissolved in methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate and subsequently, the water-soluble polymer and additives are added and stirred until a clear solution is received.
  • the inventive solution usually shows a viscosity of 0.1 to 80 Pa s, preferably 0.5 to 70 Pa s, particularly preferably 1 to 50 Pa s, and most preferably of 2 to 49 Pa s as determined with a Brookfield Viscometer DV-I Prime from Brookfield Engineering Laboratories, Inc. Middleboro, USA) with RV 6 spindle at 60 °C with 5-100 rpm (rounds per minute).
  • the shear rate i.e. , rounds per minute, is usually selected depending on the viscosity of the sample. Typically, low viscous samples are measured at higher shear rates, whereas higher viscous samples are measured at lower shear rates.
  • High solution viscosities are beneficial for the casting process during membrane preparation by leading to better film quality. Furthermore, in case of high solution viscosities, during membrane preparation there is generally no need to use high molecular weight water-soluble polymers to (further) increase the viscosity. This is realized by preparing membranes for reverse Osmosis (RO).
  • RO reverse Osmosis
  • a measure for turbidity is the nephelometric turbidity unit (NTU) determined with a calibrated nephelometer or turbidimeter, expressing the amount of light reaching a detector at the side of a light beam after being scattered of the sample.
  • NTU nephelometric turbidity unit
  • the inventive solution shows a turbidity of 0 to 3 NTU, more preferably of 0 to 2.7 NTU, particularly preferably of 0 to 1 .5 NTU as determined with a turbidimeter 2100 AN (Hach Lange GmbH, Dusseldorf, Germany) employing a filter of 860 nm at 60 °C.
  • a low solution turbidity is a prerequisite for the preparation of high-quality films and thus, high performance membranes, because hereby macrovoids and defects in the membranes are avoided which would affect the balance between pure water permeability and molecular weight cut-off.
  • a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyaryl- sulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and/or (II) based on the total weight of the polyarylsulfone polymer and methyl- 1-methyl-2-oxopyrrolidone-4- carboxylate,
  • a membrane shall be understood to be a semipermeable structure capable of separating two fluids or separating molecular and/or ionic components or particles from a liquid.
  • a membrane acts as a selective barrier, allowing some particles, substances or chemicals to pass through, while retaining others.
  • the membrane may have various geometries such as flat sheet, spiral wound, pillows, tubular, single bore hollow fiber or multiple bore hollow fiber.
  • Separation by using membranes can be operated in different ways, e.g., driven by pressure, by concentration gradients or by gradients like electric potential or temperature gradients.
  • Examples for pressure driven operations are micro-, ultra- or nanofiltration or reverse osmosis operations.
  • Examples for concentration-based operations are hemodialysis or forward osmosis.
  • Preferred membranes are ultrafiltration and hemodialysis membranes.
  • the inventive solution without a water-soluble polymer and/ or additive and/or a cosolvent is needed if the inventive solution of polyarylsufone polymere dissolved in methyl-1-methyl-2-oxopyrrolidone-4- carboxylate used in step a1) of the inventive process shows a viscosity of > 1 Pa s
  • Membranes can be prepared by different methods, like phase separation (phase inversion) of polymers, sol-gel process, interface reaction, stretching, extrusion, track-etching, microfabrication, etc.
  • the membranes according to the invention are prepared by liquid nonsolvent- induced phase separation (NIPS), which comprises the following steps: a1) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and/or (II) based on the total weight of the polyarylsulfone polymer and methyl- 1- methyl-2-oxopyrrolidon-4-carboxylate a2) and optionally a water-soluble polymer.
  • NIPS liquid nonsolvent- induced phase separation
  • Step b) Shaping the polymer solution into a certain geometry, like, for example, fiber, tubular or flat sheet geometries, by methods like, for example, extrusion of the polymer solution or preparation of a film from or casting the polymer solution, c) Solidifying the geometry shaped in Step b) by exposing the polymer solution to a coagulant.
  • step a1) corresponds to a polymer solution as described above.
  • step a2) corresponds to a polymer solution as described above wherein additionally a water-soluble polymer is included.
  • the solution further contains additives and/or cosolvents as described above.
  • the preparation of the solution of step a1) or step a2) can be performed as described above.
  • the solution of step a1) comprises 10 to 25wt.-% of the polyarylsulfone polymer, 75 to 90wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the preparation of the solution of step a2) comprises 10 to 25 wt.-% polyarylsulfone polymer, 60 to 89.9 wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate and 0.1 to 15wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution of step a1) comprises 14 to 20 wt.-% of polyarylsulfone polymer and 80 to 86 wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the solution of step a2) comprises 14 to 20wt.-% of the polyarylsulfone polymer, 60 to 83wt.-% of methyl- 1-methyl-2- oxopyrrolidone-4-carboxylate and 3 to 8wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution may be degassed and/or heated before proceeding to the next step.
  • Steps b) and c) can either be performed continuously, i.e. not as separated steps, for example, in case of the continuous extrusion of the polymer solution into a coagulation bath, or in separated steps, for example first forming a polymer film, which is then transferred to a coagulation bath after a certain drying time.
  • the shaped polymer solution still contains the polyarylsulfone polymer, methyl- 1-methyl-2- oxopyrrolidone-4-carboxylate and optionally the water-soluble polymers and other additives and/or cosolvents.
  • the phase separation of polymer and solvent has not started or is not yet completed, i.e. the polymer is not yet completely solidified.
  • the polymer solution is brought into a fiber- or tubular-shaped geometry.
  • the polymer solution is brought into a flat sheet geometry.
  • the exposition of the shaped polymer solution to the coagulant (step c) can, for example, take place in a coagulation bath containing a coagulant.
  • the polyarylsulfone polymer should have a low solubility in the coagulant, i.e. ⁇ 1 g polyarylsulfone polymer per 100 g of coagulant at 21 °C.
  • the contact to the coagulant induces the nonsolvent-induced de-mixing of the homogeneous polymer solution, which results in the solidification of the polymer and thus the membrane formation in the respective geometry of the shape of the polymer solution.
  • the membrane structure and morphology is strongly dependent on the process parameters used hereby, as well as on the nature and presence of the different chemical compounds present in the solution.
  • the water-soluble polymer and the additives have mainly two functions: on the one hand side they adjust the solution viscosity on a high level which makes film formation, e.g., by casting easier, on the other side they function as pore formation agents, strongly determining the membrane’s performance properties.
  • Suitable coagulants are, for example, liquid water, water vapor and mixtures of water with alcohols, cosolvents, and/or methyl-1-methyl-2-oxopyrrolidone-4-carbonxylate, the solvent of the inventive solution.
  • Suitable alcohols are, for example, mono-, di- or trialcohols selected from the group of C1-C4 alkanols, C2-C8 alkanediols, oligo(alkylene glycol)s, C3-C12 alkanetriols as they can be used as additives in the inventive solution (see above), or polyalkylenglycole with M w of 200 to 2,000,000 g/mol.
  • Suitable cosolvents are, for example, selected from high-boiling ethers, esters, ketones, asymmetrically halogenated hydrocarbons, anisole, gamma-valerolactone, N,N-dimethylformamide, dimethylsulfoxide, sulfolane, dihydrolevoglucosenone, methyl-5-(dimethylamino)-2-methyl-5- oxopentanoate, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-n-butyl-2-pyrrolidone, N-tert- butyl-2-pyrrolidone, N-(2’-hydroxyethyl)-2-pyrrolidone, N,N-dimethyl-2-hydroxypropanoic amide, and N,N-diethyl-2-hydroxypropanoic amide.
  • Preferred cosolvents are gamma-valerolactone, N,N-dimethyl-2-hydroxypropanoic amide, N-tert-butyl-2-pyrrolidone, N-n-butyl-2-pyrrolidone and N-(2’-hydroxyethyl)-2-pyrrolidone.
  • coagulants are selected from the group of mixtures comprising liquid water and the solvent methyl- 1-methyl-2-oxopyrrolidine-4-carboxylate, mixtures comprising liquid water and alcohols, (e.g., polyalkylen glycol with a M w of 200 to 2,000,000 g/mol and mixtures comprising liquid water and cosolvents. More preferably, coagulants are mixtures comprising liquid water and the solvent methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate.
  • the coagulant comprises from 10 to 90wt.-% water and 90 to 10wt.-% alcohol and/or co-solvent(s) or the solvent methyl-1-methyl-2-oxopyrollidone-4-carboxylate, preferably 30 to 70wt.-% water and 70 to 30wt.-% alcohol and/or co-solvent(s) or the solvent methyl-1-methyl-2- oxopyrrolidone-4-carboxylate, based on the total weight of the coagulant. Generally, the amount of all components of the coagulant adds up to 100%.
  • process steps a1), a2) and b) depend on the desired geometrical structure of the membrane and the scale of production, which includes lab scale or commercial/industrial scale.
  • a flat sheet membrane is prepared.
  • This process comprises: a1) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polysulfone comprising the repeating unit of formula (II), wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula based on the total weight of the polyarylsulfone polymer and methyl-1-methyl-2- oxopyrrolidone-4-carboxylate, and a water-soluble polymer.
  • Exposing the polymer film to a coagulant is provided.
  • the solution of step a1) corresponds to a polymer solution as described above.
  • the solution of step a1) can contain further additives and/or cosolvents as described above, but preferably the solution only contains the polyarylsulfon and the solvent methyl-1-methyl-2-oxopyrrolidone-4- carboxylate.
  • the preparation of the solution of step a1) can be performed as described above.
  • the solution of step a1) comprises 5 to 25wt.-% of the polyarylsulfone polymer, 75 to 95wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the solution of step a1) comprises 14 to 20wt.-% of the polyarylsulfone polymer and 60 to 86wt.-% of methyl-1-methyl-2-oxopyrrolidone-4-carboxylate based on the total weight of the solution.
  • the solution is be prepared under stirring at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C.
  • the ready solution typically is degassed for 2 to 24 h, preferably 6 to 20 h, more preferably 10 to 14 h.
  • the solution is preferably re-heated at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C for 1 to 4 h, preferably 1.5 to 3 h.
  • the preparation of a polymer film from the inventive solution can be performed, for example, by casting or other methods like rolling, spraying etc., preferably by casting onto a substrate, preferably, a polymeric substrate (like, e.g., polymer films from biaxially oriented poly(ethylene terephthalate), e.g., under trade name Hostaphan®), a glass substrate, or metal substrates (e.g., metal conveyor belt) using, for example, a casting knife and, optionally, an automated coating machine at a temperature of 40 to 90 °C, preferably 50 to 70 °C.
  • a polymeric substrate like, e.g., polymer films from biaxially oriented poly(ethylene terephthalate), e.g., under trade name Hostaphan®
  • a glass substrate e.g., under trade name Hostaphan®
  • metal substrates e.g., metal conveyor belt
  • the polymer film is generated by casting, using a casting knife with an aperture of 100 to 500 pm, more preferably of 200 to 400 pm.
  • the polymer film is allowed to rest for 5 to 150 s, preferably 10 to 100 s, more preferably 20 to 60 s and is then subjected to the coagulation bath containing a coagulant as described above.
  • the immersion takes place at 10 to 50 °C, preferably 15 to 40 °C, more preferably at 20 to 30 °C for 3 to 20 min, preferably for 5 to 15 min.
  • the membrane is washed with water at temperature in the range 40 to 90°C preferably 50 to 70°C. Subsequently, the membrane is detached from the substrate and usually subjected to work-up.
  • a flat sheet membrane is prepared.
  • This other process comprises a2) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and (II) based on the total weight of the polyarylsulfone polymer, methyl- 1-methyl-2- oxopyrrolidone-4-carboxylate and a water-soluble polymer.
  • Exposing the polymer film to a coagulant is a
  • the solution of step a2) corresponds to a polymer solution as described above.
  • the solution further contains additives and/or cosolvents as described above.
  • the preparation of the solution of step a2) can be performed as described above.
  • the solution of step a2) comprises 10 to 25wt.-% of the polyarylsulfone polymer, 60 to 89.9wt.-% of methyl-1-methyl-2-oxopyrrolidone-4-carbonxylate and 0.1 to 15wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution of step a2) comprises 14 to 20wt.-% of the polyarylsulfone polymer, 60 to 83wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate and 3 to 7wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution is be prepared under stirring at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C.
  • the ready solution typically is degassed for 2 to 24 h, preferably 6 to 20 h, more preferably 10 to 14 h.
  • the solution is preferably re-heated at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C for 1 to 4 h, preferably 1.5 to 3 h.
  • Step b) and step c) for this other preferred process are the same as described above for the process where step a1) is used.
  • a non-flat sheet membrane is prepared.
  • This process comprises: a2) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and (II) based on the total weight of the polyarylsulfone polymer, methyl- 1-methyl-2- oxopyrrolidone-4-carboxylate, and a water-soluble polymer.
  • the solution of step a2) corresponds to a polymer solution as described above.
  • the solution further contains additives and/or cosolvents as described above.
  • the preparation of the solution of step a2) can be performed as described above.
  • the solution of step a2) comprises 10 to 25wt.-% of the polyarylsulfone polymer, 60 to 89.9wt.-% of methyl-1-methyl-2-oxopyrrolidone-4-carboxylate and 0.1 to 15wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution of step a2) comprises 14 to 20wt.-% of the polyarylsulfone polymer, 60 to 83wt.-% of methyl- 1-methyl-2-oxopyrrolidone-4-carboxylate and 3 to 7wt.-% of water-soluble polymer based on the total weight of the solution.
  • the solution is be prepared under stirring at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C.
  • the ready solution typically is degassed for 2 to 24 h, preferably 6 to 20 h, more preferably 10 to 14 h.
  • the solution is preferably re-heated at a temperature of 20 to 100 °C, preferably 40 to 90 °C, more preferably 50 to 70 °C for 1 to 4 h, preferably 1.5 to 3 h.
  • Shaping of the solution of step a1) or a2) to a non-flat geometry can, for example, be performed via extrusion of the solution through an extrusion nozzle, to get, for example, a fiber-like geometry.
  • the polymer solution is usually extruded directly into a coagulation bath containing a coagulant as described above, which induces de-mixing of polymer and solvent and thus polymer solidification in the desired shape.
  • a solution of a coagulant is injected to the inside of the developing fibers, single- or multi-tubular geometries are obtained as described in the following.
  • Preferred membranes showing a non-flat geometry are hollow fiber membranes (single bore hollow fibers or multiple bore hollow fibers). They can be prepared by different spinning technologies, for example by melt spinning, dry spinning or wet spinning.
  • the solution obtained in above mentioned step a2) is extruded through an extrusion nozzle (also called spinneret) containing the required number of hollow needles (step d).
  • the coagulation liquid is injected in the middle of the hollow needles into the extruded polymer during extrusion.
  • the extruded polymer membrane gets a hollow cylindrical geometry and parallel continuous channels extending in extrusion direction are formed in the extruded polymer.
  • the porous structure on the inner surface of the extruded membrane is formed by bringing the inner surface of the extruded hollow polymer fiber in contact with a mild coagulation agent as for example water vapor such that the shape is fixed without an active layer, i.e., a highly porous filtration layer, on the inner surface. Subsequently, the membrane is brought in contact with a coagulation agent.
  • a mild coagulation agent as for example water vapor
  • a coagulation agent i.e., a highly porous filtration layer
  • the parameters of the process like extrusion speed, temperature, nozzle geometry, type of coagulant, concentrations have an effect on and thus can be used to control pore size and distribution as well as the membrane’s shape and thickness and thus the perfor- mance of the membrane.
  • Hollow fiber membranes can be optionally wound up onto rolls and/or bundled to bundles of hollow fibers.
  • the membranes prepared by the procedures described above are usually worked up by washing and/or optional oxidizing steps.
  • the membrane prepared by the processes described above is exposed, after an optional washing step, to a solution containing an oxidatively active component.
  • the solution containing an oxidatively active component preferably is an aqueous solution.
  • washing is performed after the oxidation step.
  • a water-soluble oxidant such as, e.g., sodium hypochlorite or halogens, especially chlorine in a concentration range of 500 to 5000wt.-ppm, more preferably from 1000 to 4000wt.-ppm and particularly preferably from 1500 to 3500wt.-ppm based on the total weight of the aqueous oxidation solution.
  • the membrane is oxidized with hypochlorite solution or gaseous chlorine at 20 to 90 °C, preferably 35 to 80 °C, more preferably 50 to 70 °C and at a pH of 9 to 10, preferably 9.3 to 9.7 for 0.5 to 4 h, preferably 1 to 3 h, more preferably 1 .5 to 2.5 h, and subsequently washed with water.
  • hypochlorite solution or gaseous chlorine at 20 to 90 °C, preferably 35 to 80 °C, more preferably 50 to 70 °C and at a pH of 9 to 10, preferably 9.3 to 9.7 for 0.5 to 4 h, preferably 1 to 3 h, more preferably 1 .5 to 2.5 h, and subsequently washed with water.
  • Washing with water is typically performed in a water bath for 2 to 24 h, preferably for 4 to 20 h, more preferably for 8 to 16 h, and subsequently usually one to five times, preferably three times with water at 20 to 90 °C, preferably 35 to 80 °C and more preferably 50 to 70 °C.
  • inventive solution based on methyl-1-methyl-2- oxopyrrolidone-4-carboxylate can also use middle and high molecular weight water-soluble polymers with which membranes will be received that show better PWP and MWCO values as those where N-methylpyrrolidone was used as solvent.
  • a membrane was found, which is prepared using the inventive solution comprising a polyarylsulfone polymer selected from the group of polysulfone comprising the repeating unit of formula (II), wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (II) based on the total weight of the polyarylsulfone polymer and methyl-1-methyl-2-oxopyrrolidone-4-carboxylate.
  • the membrane preparation preferably comprises the following steps a1) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (II) based on the total weight of the polyarylsulfone polymer and methyl-1-methyl-2-oxopyrrolidone-4-carboxylate.
  • Step b) Shaping the polymer solution into a certain geometry, like, for example, fiber, tubular or flat sheet geometries, by methods like, for example, extrusion of the polymer solution or preparation of a film from or casting the polymer solution.
  • Step b) Solidifying the geometry shaped in Step b) by exposing the polymer solution to a coagulant.
  • a membrane which is prepared using the inventive solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and (II) based on the total weight of the polyarylsulfone polymer, methyl-1-methyl-2-oxopyrrolidone-4-carboxylate and a water-soluble polymer.
  • a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular
  • the membrane preparation preferably comprises the following steps a2) Preparing a solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating unit of formula (II) or mixtures thereof, wherein the weight average molecular weight M w of the polyarylsulfone polymer is in the range from 40000 to 105000 g/mol and the polyarylsulfone polymer comprises at least 95wt.-% of the repeating units of formula (I) and (II) based on the total weight of the polyarylsulfone polymer, methyl-1-methyl-2- oxopyrrolidone-4-carboxylate and a water-soluble polymer.
  • a2 Preparing a solution comprising a polyarylsulfone polymer selected from the group of polyethersulfone comprising the repeating unit of formula (I) and polysulfone comprising the repeating
  • Step b) Shaping the polymer solution into a certain geometry, like, for example, fiber, tubular or flat sheet geometries, by methods like, for example, extrusion of the polymer solution or preparation of a film from or casting the polymer solution.
  • Step b) Solidifying the geometry shaped in Step b) by exposing the polymer solution to a coagulant.
  • the solution used for the membrane production further contains additives and/or cosolvents as described above.
  • the preparation of the solution of step a1) or step a2) can be performed as described above.
  • the membrane is worked up by different washing and/or oxidizing steps as described above.
  • the performance of a membrane can be specified by its pure water permeability (PWP) and its molecular weight cut-off.
  • PWP pure water permeability
  • the PWP reflects the permeability of the membrane towards pure water in dependance on the membrane area, the applied pressure, and time of the permeation experiment according to the following formula (equation 2):
  • PWP pure water permeability [kg I bar h m 2 ] m: mass of permeated water [kg] A: membrane area [m 2 ] P: pressure [bar] t: time of the permeation experiment [h].
  • the membranes according to the invention preferably comprise a high PWP of more than 100 kg/h m 2 bar, more preferably more than 125 kg/h m 2 bar, and particularly preferably more than 150 kg/h m 2 bar for ultrafiltration membranes and preferably more than 25 kg/h m 2 bar, more preferably more than 50 kg/h m 2 bar, and particularly preferably more than 100 kg/h m 2 bar for nanofiltration membranes.
  • the pure water permeability of the membrane is determined before the determination of its molecular weight cut-off, to avoid limited permeation values due to clogging/fouling of the pores by the polymer used in the molecular weight cut-off determination.
  • the weight average molecular weight cut-off of the membranes is the molecular weight of the poly(ethylene oxide) standard of the lowest weight-average molecular weight (M w ) which is withhold to at least 90% by the membrane. It is usually given in kilo-Daltons (kDa)
  • a MWCO of 18.4 kDa means that poly(ethylene oxide) of M w of 18.4 kDa and higher is withhold to at least 90%.
  • the MWCO of the membranes according to the invention is typically 2-200 kDa, for ultrafiltration membranes, preferably 10-200 kDa, and more preferably 10-100 kDa, and for nanofiltration membranes the upper MWCO limit is typically ⁇ 10 kDa and the lower MWCO limit is preferably at least 5kDa, more preferably at least 3 kDa and particularly preferably at least 2 kDa.
  • the inventive membranes can be used for any kind of separation process of gaseous or liquid mixtures, for example water treatment applications like drinking water purification, treatment of industrial or municipal wastewater, desalination of sea or brackish water, dialysis, purification of pharmaceutical products, plasmolysis, and food processing.
  • polyethersulfone comprising the repeating unit of formula (I) with a weight average molecular weight of 48000 to 90000 g/mol is mixed with methyl-1-methyl-2-oxopyrrolidone-4-carboxylate and polyvinylpyrrolidone showing a K-value of at least 12.
  • the different polymers are used in an amount such that the resulting solution comprises 10 to 25wt.-% of the polyethersulfone and 1 to 10wt.-% of polyvinylpyrrolidone.
  • the mixture is heated under stirring at a temperature of 50 to 70 °C until a homogeneous clear viscous solution is obtained.
  • the solution is then degassed for 10 to 14 h and re-heated at 50 to 70 °C for 1.5 to 3 h. Subsequently, the solution is casted onto a glass plate with a casting knife with an aperture of 200 to 400 pm at a temperature of 50 to 70 °C. The resulting film is allowed to rest for 20 to 60 s and then subjected to a water-based coagulation bath comprising 45 to 55wt.-% water and 45 to 55wt.-% of glycerol at 20 to 30 °C for 5 to 15 min.
  • the membrane After detachment of the glass substrate, the membrane is exposed to an aqueous solution comprising 1500 to 3500wt.-ppm NaOCI at 50 to 70 °C and a pH of 9.3 to 9.7 for 1 to 3 h (oxidative posttreamtent) or the membrane is washed with water for three times at 50 to 70 °C (water posttreatmnet).
  • the membrane is stored in a wet state.
  • polysulfone comprising the repeating unit of formula (II) with a weight average molecular weight of 50000 to 70000 g/mol is mixed with methyl-1-methyl-2-oxopyrrolidone-4-carboxylate.
  • the poly- arylsulfon and the solvent are used in an amount such that the resulting solution comprises 10 to 20wt.-% of the polysulfone and 80 to 90wt.-% of methyl-1-methyl-2-oxopyrrolidone-4- carboxylate.
  • the mixture is heated under stirring at a temperature of 40 to 90 °C until a homogeneous clear viscous solution is obtained.
  • the solution is then degassed for 10 to 14 h, and subsequently re-heated at 40 to 90 °C for 1.5 to 3 h.
  • the solution is casted onto a glass plate with a casting knife with an aperture of 200 to 400 pm at a temperature of 50 to 70 °C.
  • the resulting film is allowed to rest for 20 to 60 s and then subjected to a water coagulation bath at 20 to 30 °C for 5 to 15 min.
  • the membrane After detachment of the glass substrate, the membrane is transferred into a water bath at room temperature, left there for 8 to 16 h, subsequently washed three times with water at 50 to 70 °C, and stored in a wet state. It was found that the solvent methyl-1-methyl-2-oxopyrrolidone-4-carboxylate readily dissolves polyarylsulfone polymers, even such polyarylsulfone polymers that included higher amounts of cyclic dimers that are normally insoluble and cause imperfections on the membrane surface during the membrane manufacturing process, leading to solutions of low turbidity.
  • methyl-1-methyl-2-oxopyrrolidone-4-carboxylate is easily accessible over a renewable source and of low toxicological concern compared, for example, with the frequently used N- methylpyrrolidone. Furthermore, it shows good biodegradable properties.
  • the resulting inventive solutions show high viscosities, which are beneficial for the casting process during membrane preparation by leading to better film quality.
  • inventive solution without any water-soluble polymer can be used for reverse osmosis (RO) applications as the resulting membranes show defect-free cross sections comparable to solutions containing the standard solvents.
  • RO reverse osmosis
  • the inventive solution comprising the poylarylsulfon polymer, methyl- 1-methyl-2- oxopyrrolidone-4-carboxylate and a water-soluble polymer, form membranes where the amounts of high molecular weight water-soluble polymers can be reduced in order to get membranes with pure water permeability and molecular weight cut-off values in the ultrafiltration area comparable to solutions using standard solvents like N-methylpyrrolidone that did not reach such advantages values in the ultrafiltration area.
  • Luvitec® K90 Polyvinylpyrrolidone with a molecular weight M w of 1000000 to 1500000 g/mol and a solution viscosity characterized by the K-value of 90, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)), which is abbreviated as “K90” Luvitec® K85 Polyvinylpyrrolidone with a molecular weight M w of 1100000 g/mol and a solution viscosity characterized by the K-value of 85, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)), which is abbreviated as “K85”
  • Luvitec® K30 Polyvinylpyrrolidone with a molecular weight M w of 44000 to 54000 g/mol and a solution viscosity characterized by the K-value of 30, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)), which is abbreviated as “K30”
  • Luvitec® K12 Polyvinylpyrrolidone with a molecular weight M w of 2000 to 3000 g/mol and a solution viscosity characterized by the K-value of 12, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)), which is abbreviated as “K12”
  • the polymer solution turbidity was measured with a turbidimeter 2100AN (Hach Lange GmbH, Dusseldorf, Germany) employing a filter of 860 nm at 60 °C and expressed in nephelometric turbidity units (NTU). NTU values below 3 are preferred.
  • the pure water permeance (PWP) of the membranes was tested using a pressure cell with a diameter of 74 mm using ultrapure water (salt-free water, filtered by a Millipore UF-system) at 23 °C and 1 bar water pressure.
  • the pure water permeation (PWP) is calculated as follows (equation 1)
  • PWP pure water permeance [kg I bar h m 2 ]
  • m mass of permeated water [kg]
  • A membrane area [m 2 ]
  • a high PWP allows a high flow rate of more than 150 kg/h m 2 bar is desired.
  • MWCO weight average molecular weight cut-off of the membranes
  • Example 1-5 Viscosity and turbidity of polyarylsulfone polymer solutions in different solvents Into a three-neck flask equipped with a magnetic stirrer there were added 80 or 84 ml of Solvent S1 and 20 or 16 g polymer as given in table 1. The mixture was heated under gentle stirring at 60°C until a homogeneous clear viscous solution, usually referred to as solution was obtained. The solution was degassed overnight at room temperature.
  • Polymer solutions of S6010 in MMOC are clearer and more transparent compared to solutions in DMF over time.
  • Higher contents of cyclic dimers such as in Paryls are better dissolved by MMOC and more stable over time compared to DMF as shown by solution turbidity. Over time the solution turbidity increases in DMF while in MMOC it remains stable.
  • the membrane solution was reheated at 60°C for 2 hours and casted onto a glass plate with a casting knife (300 microns) at 60°C using an Erichsen Coating machine (Coatmaster 510, Erichsen GmbH & Co KG, Hemer, Germany) operating at a speed of 5 mm/s.
  • the membrane film was allowed to rest for 30 seconds before immersion in a water-based coagulation bath at 25°C for 10 minutes. After the membrane had detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Afterwards the membrane was washed with water at 60°C three times and stored wet.
  • Table 3 Compositions and properties of Ultrason® E 3010 membranes prepared with PVP K30 and K90; Posttreatment A (NaOCI). Coagulation water-glycerol (50/50 wt/wt)
  • Table 4 Compositions and properties of Ultrason® E 3010 membranes prepared with 6 g PVP K30 and K90; 10 g 1 ,2-propandiol, Posttreatment B (water). Coagulation water-glycerol (50/50 wt/wt)
  • Table 5 Compositions and properties of Ultrason® E 6020P membranes prepared with 6 g PVP K12, K30 and K90; Posttreatment B (water). Coagulation water-glycerol (50/50 wt/wt) Table 6: Compositions and properties of Ultrason® S 6010/Paryls membranes prepared from MMOC and DMF solutions; Posttreatment B (water). Coagulation water
  • Polymer solutions produced with MMOC according to the invention show higher solution viscosity and membranes fabricated thereof showed higher water permeability values of higher than 100 kg/h m 2 bar in combination with MWCO values in the ultrafiltration (5 -100 kDa) range compared to membranes made of solutions with NMP as solvent as it is shown in table 3 and 4.
  • Table 5 shows that, even if the viscosity of the solutions including MMOC are comparable to those including NMP as solvent, the resulting membranes of these solutions will not reach the values of PWP and MWCO, if NMP as solvent is used, compared to the membranes, where MMOC as solvent was used, during the preparation process.
  • table 5 shows that with MMOC as solvent also water-soluble polymers can be used.
  • table 5 show that the resulting PWP and MWCO values of the resulting membranes, where MMOC as solvents was used, are in the nanofiltration (water permeability values of higher than 100 kg/h m 2 bar and MWCO values from 2 to ⁇ 10 KDa) range, while the use of solutions, where NMP was used as solvents, do not reach such nanofiltration range according to the PWP values.
  • Table 6 shows that with the inventive solutions also membranes are producible that can be used for RO-applications, as no water-soluble polymer is used and only water post-treatment is used. The comparable membranes made from solutions where DMF ,the state of the art solvents for the RO-application membranes, don't reach such high PWP values as those where MMOC was used as solvent in the preparation process.
  • FIG. 1 shows a scanning electron micrograph of a membrane of example 10 according to the invention which shows a well-established nano porous filtration layer on the top supported by a sponge-type substructure with increasing pore sizes from top to bottom. No defects or macrovoids are visible in die cross-section.
  • Figure 2 shows a scanning electron micrograph of a membrane of comparative example 12 showing numerous macrovoids inside the macroporous support level.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

La présente invention concerne une solution comprenant au moins un polyarylsulfone choisi dans le groupe du polyéthersulfone et du polysulfone en tant que polymère et du méthyl-1-méthyl-2-oxopyrrodlidone-4-carboxylate (MMOC), le procédé de fabrication d'une membrane et l'utilisation de cette membrane pour des procédés de séparation.
PCT/EP2024/067768 2023-07-05 2024-06-25 Solution de polymères de sulfone dans du méthyl-1-méthyl-2-oxopyrrolidone-4-carboxylate pour l'utilisation de membranes Pending WO2025008223A1 (fr)

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US3025320A (en) 1958-07-04 1962-03-13 Montedison Spa Process for preparing itaconic acid, and 2, 3-butadienoic acid
DE2452536A1 (de) 1974-11-06 1976-05-13 Hoechst Ag Pyrrolidone und verfahren zu ihrer herstellung
US4100179A (en) 1974-06-24 1978-07-11 Pfizer Inc. Preparation of citraconic anhydride
WO2012034688A1 (fr) 2010-09-16 2012-03-22 Clariant International Ltd Utilisation d'esters de l'acide 2-pyrrolidone-4-carboxylique n-substitués en tant que solvant
US20120269750A1 (en) 2009-11-05 2012-10-25 L'oreal Cosmetic compositions comprising an ester derived from 4-carboxy-2-pyrrolidinone and a lipophilic screening agent; use of said derivative as a solvent for a benzophenone lipophilic screening agent
WO2015056145A1 (fr) 2013-10-15 2015-04-23 Basf Se Amélioration de la stabilité chimique de membranes de filtration
WO2017045985A1 (fr) 2015-09-17 2017-03-23 Basf Se Procédé de fabrication de membranes à l'aide de solvants à base de lactame ide
WO2019042749A1 (fr) 2017-08-28 2019-03-07 Basf Se Fabrication de membrane avec un cosolvant dans la solution de dopage de polymère
WO2021191043A1 (fr) 2020-03-25 2021-09-30 Basf Se Solution de polysulfones dans une n-n-butyl-2-pyrrolidone pour l'utilisation de membranes
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US3025320A (en) 1958-07-04 1962-03-13 Montedison Spa Process for preparing itaconic acid, and 2, 3-butadienoic acid
US4100179A (en) 1974-06-24 1978-07-11 Pfizer Inc. Preparation of citraconic anhydride
DE2452536A1 (de) 1974-11-06 1976-05-13 Hoechst Ag Pyrrolidone und verfahren zu ihrer herstellung
US20120269750A1 (en) 2009-11-05 2012-10-25 L'oreal Cosmetic compositions comprising an ester derived from 4-carboxy-2-pyrrolidinone and a lipophilic screening agent; use of said derivative as a solvent for a benzophenone lipophilic screening agent
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WO2019042749A1 (fr) 2017-08-28 2019-03-07 Basf Se Fabrication de membrane avec un cosolvant dans la solution de dopage de polymère
WO2021191043A1 (fr) 2020-03-25 2021-09-30 Basf Se Solution de polysulfones dans une n-n-butyl-2-pyrrolidone pour l'utilisation de membranes
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