Process for producing a recycled polysulfone product from a thin-film composite membrane

Abstract

The invention relates to a process for producing a recycled polysulfone (PSU) product from a thin-film composite (TFC) membrane comprising a polyamide (PA) layer, a polysulfone (PSU) layer and a poly(ethylene phthalate) (PET) layer. The process includes selective dissolution of PSU and an optional color removal from PSU solution. The invention also relates to a recycled PSU product, its use, and an article selected from membranes, coatings, tubing and / or piping, comprising, or made from, the PSU product.

Description

[0001] Process for producing a recycled polysulfone product from a thin-film composite membrane

[0002] CROSS-REFERENCE TO RELATED APPLICATION(S)

[0003] This application claims priority to U.S. application No. 63 / 733712 filed on December 13, 2024, and to European application No. 25156703.8 filed on February 7, 2025, the entire content of these applications being incorporated herein by reference for all purposes.

[0004] TECHNICAL FIELD

[0005] The present invention relates to a recycled polysulfone product and a process for recovering it from a thin-film composite membrane containing 3 distinct polymeric layers including a selective polyamide layer and a supporting porous PSU layer.

[0006] BACKGROUND

[0007] Membrane technology has shown a promising role in combating water scarcity, a globally faced challenge. The escalating issue of water shortage has emerged as a worldwide threat owing to its crucial role in maintaining environmental sustainability and ecological systems . Desalination and wastewater reclamation utilizing membrane-based technologies are regarded as effective strategies for mitigating water scarcity. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD) are some of the classifications of membranes that are determined by the separation performance that is linked to the morphological structure and operational principle of the process.

[0008] For RO, thin-film composite (TFC) and thin film nanocomposite (TFN) polyamide (PA) membranes are dominating the market. TFC-PA membranes are widely used in the fields of desalination, wastewater treatment, and water softening. According to Lej arazu-Larranaga et al, “Thin Film Composite Polyamide Reverse Osmosis Membrane Technology towards a Circular Economy” in Membranes, 2022, vol. 12, p. 864, around 90% of commercially available RO membranes are TFC-PA membranes.

[0009] TFC membranes can also be used in ultrafiltration and nanofiltration processes for separating macromolecules, particles, and ions from liquids (food and beverage industry, wastewater treatment, pharmaceuticals); for gas separation applications (e.g., separation of hydrogen from various gas mixtures, carbon dioxide capture, and natural gas processing); for organic solvent

[0010] SSPU 2024 / 042 nanofiltration (industries like pharmaceuticals, fine chemicals, agrochemicals); for hemodialysis (in medical applications); in proton exchange membranes (fuel cells); and in vapor permeation (applications in dehydration processes for solvents and gases).

[0011] These polymeric membranes derived from fossil fuel inevitably encounter their end of life due to various factors, including the deposition of unanticipated fouling, mechanical / chemical persuaded defects, etc. As a consequence, appropriate disposal and replacement procedures become imperative. However, the disposal of end-of-life membrane modules is problematic because in general, the discarded membranes are disposed of in accordance with the waste management regulations of each country, which stipulate their incineration or landfill disposal as their final fate.

[0012] These disposal practices are neither economically nor environmentally sustainable. The environmental impact of both incineration and landfills remains detrimental. The disposal of plastic waste has become an emerging concern due to its slow degradation, occurrence in micron sizes in the aquatic and terrestrial environment, and accumulation in living organisms. For instance, the landfill degradation process for a frequently employed 8-inch spiral-wound RO membrane element (length 1 m; weight 18 kg) spanned several years. In regard to incineration, insufficient waste management and control may result in the production of greenhouse gases and other detrimental byproducts. The plastic components of the end-of-life RO membrane modules are prone to producing toxic and carcinogenic byproducts when incinerated, posing a risk to human health. This emphasizes the criticality of environmentally sustainable disposal approaches that adhere to the circular economy and sustainability principles on a global scale.

[0013] Sustainable Development Goal 12 of the United Nations endeavors to establish patterns of consumption and production that are sustainable. By reusing waste and membranes in the process of manufacturing them, not only could resources be conserved but also the environment could be safeguarded. Implementing this approach may greatly decrease the need for raw materials in the manufacturing process, as well as the environmental pollution that is linked to their production and disposal.

[0014] Thus recycling membranes and utilizing recycled polymeric material for their manufacturing is seen as a potential approach to address the aforementioned challenges. Membrane recycling refers to the reuse of polymeric membranes

[0015] SSPU 2024 / 042 (that are nearing the end of their lifespan) after undergoing chemical treatment for similar or upgraded / downgraded operation, whereas polymer recycling refers to the complete membrane deformation to recover polymer for re-preparation of membrane or other applications. In the case of membranes that have not suffered any significant damage, a number of different techniques, such as upcy cling, downcy cling, and regeneration, may be utilized, depending on the particular conditions.

[0016] RO membranes that have reached the end of their useful life can be, for example, downcy cled or regenerated to meet the specific needs of the user. Downcycling refers to the transformation of end-of-life membranes to directly prepare recycled membranes with lower sieving accuracy. It is considered the most convenient method when it comes to recycling NF / RO membranes to NF or UF membranes. Most commercial NF / RO membranes are spiral wounds and are packed with glass fiber casing to provide the mechanical support needed during high-pressure operation. Therefore, the end-of-life RO membranes can be readily downcycled without the need to alter the type of membrane modules. The primary approach involved in RO membrane downcycling is the partial or full destruction of the PA layer using oxidizing agents such as NaOCl, potassium permanganate (KMnO4), hydrogen peroxide (H2O2), and their mixture. The utilization of NaOCl is perhaps more common for RO membranes downcycling due to the susceptibility of PA to NaOCl, causing its degradation which is based on the mechanism of N-chlorination and hydrolysis of the amide bond, consequently causing oxidative degradation to the PA layer upon exposure to NaOCl.

[0017] In the event of significant membrane damage, it is advisable to “reprepare” a new membrane. The term “re-preparation” refers to the complete deformation of end-of-life membranes and refabrication of the same or different membrane types using the recovered material. This is performed by dissolving the membranes in organic solvents and then utilizing the resulting solution to produce new membranes using recycled polymer. This method is especially well suited for membranes that experience substantial damage, which greatly impairs their ability to selectively separate substances. The utilization of recycled waste for fabricating the membranes can help in reducing the environmental impact by 2* amount (i. e. , eliminate the use of polymer for membrane fabrication and its associated environmental impact and mitigating the effect of waste on the

[0018] SSPU 2024 / 042 environment via its utilization), thus helping in maintaining environmental sustainability.

[0019] While the re-preparation of polymeric membranes at the end of their life cycle is the best-suited pathway for sustainability inclusion in membrane technology, it may incur high costs and encounter implementation difficulties at the site.

[0020] TFC-PA membranes are those assembled with several layers of diverse polymeric materials, including an ultrathin dense selective polyamide layer formed on top of a thicker, porous support polysulfone layer and an even thicker backing polyester layer. The TFC-PA membranes constructed of different polymeric layers are inherently difficult to accurately and efficiently separate, rendering the recycling of these TFC-PA membranes difficult, as recovery of an individual polymer from such layered structure faces quite a few challenges as explained below.

[0021] The TFC membranes are designed to be chemically resistant to a wide range of substances, which can make them resistant to conventional recycling processes that rely on chemical treatments to break down materials.

[0022] During their use, the TFC membranes can become contaminated with various substances, including organic and inorganic compounds, which can complicate the recycling process. Effective cleaning and decontamination are required before recycling can occur.

[0023] The mechanical properties of TFC membranes, such as their flexibility and strength, can degrade over time. This degradation can make it challenging to recycle them into new, high-quality products.

[0024] The cost of recycling TFC membranes can be high due to the need for specialized equipment and processes. This can make recycling less economically viable compared to producing new membranes.

[0025] There is a lack of standardized recycling processes and infrastructure for TFC membranes. This can lead to inconsistencies in the quality of recycled materials and hinder the development of a robust recycling industry.

[0026] Some recycling processes may have environmental impacts, such as the release of harmful chemicals or high energy consumption. Finding environmentally friendly recycling methods is a significant challenge.

[0027] Moreover, the utilization of organic solvents for polymer dissolution is incongruent with the principle of sustainability. Therefore, the use of green solvents is strongly advised in order to have less environmental effects (i.e., non-

[0028] SSPU 2024 / 042 carcinogenic or toxic, biodegradable and non-accumulative, possess less potential for ozone layer depletion and greenhouse gas emissions, and exhibit negligible other adverse environmental effects) compared to traditional solvents, for the dissolution of damaged end-of-life membranes in order to prepare new membranes.

[0029] SUMMARY

[0030] The present invention thus addresses at least some of the challenges of PSU recovery from a TFC-PA membrane by a recycling process which efficiently separates the PSU polymer from the TFC membrane to produce a recycled PSU product of suitable quality for reuse in making a new polymeric article, such as a membrane.

[0031] The present invention thus relates to a process for producing a high value- added recycled polysulfone (PSU) product from TFC-PA membranes, as well as the recycled polysulfone (PSU) product itself.

[0032] The various aspects of the present invention are set out in the appended set of claims.

[0033] A first aspect of the invention relates to a process for producing a recycled polysulfone (PSU) product from athin-film composite (TFC) membrane.

[0034] A second aspect of the invention relates to a recycled polysulfone (PSU) product.

[0035] A third aspect of the invention relates to a recycled polysulfone (PSU) product obtained by such a process according to the first aspect of the present invention.

[0036] A fourth aspect of the invention relates to the use of the recycled polysulfone (PSU) product according to the second or third aspect of the present invention in the manufacture of membrane, coating, tubing and / or piping.

[0037] A further aspect of the invention relates to an article comprising or made from the recycled polysulfone (PSU) product according to the second or third aspect of the present invention.

[0038] More precisions and details about various embodiments, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description and examples.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 illustrates a first embodiment of the process according to the invention for recovery of a recycled PSU product from a TFC membrane or pieces thereof.

[0041] SSPU 2024 / 042 FIG. 2 illustrates a second embodiment of the process according to the invention for recovery of a recycled PSU product from a TFC membrane or pieces thereof.

[0042] FIG. 3 illustrates a third embodiment of the process according to the invention for recovery of a recycled PSU product from a TFC membrane or pieces thereof.

[0043] FIG. 4 is a plot of RED(PSU) versus RED(PA), related to the Hansen solubility parameter distances of PSU and PA for dimethylsulfoxide (DMSO), monochlorobenzene (MCB) and blends thereof.

[0044] FIG. 5 is a plot of RED(PSU) versus RED(PA), related to the Hansen solubility parameter distances of PSU and PA for DMSO, ortho-dichlorobenzene (ODCB) and blends thereof.

[0045] FIG. 6 is a plot of RED(PSU) versus RED(PA), related to the Hansen solubility parameter distances of PSU and PA for gamma-butyrolactone (GBL), ODCB and blends thereof.

[0046] FIG. 7 is a plot of RED(PSU) versus RED(PA), related to the Hansen solubility parameter distances of PSU and PA for cyclohexanone, ODCB and blends thereof.

[0047] FIG. 8 is a total ion chromatogram (TIC) using UPLC-MS from a filtrate obtained after dissolution of a recycled PSU (Example 9) according to the invention and coagulation of the resulting 15 wt% solution, to show impurities derived from TFC membrane.

[0048] FIG. 9 and FIG. 10 are comparative TIC using UPLC-MS, each TIC obtained from a filtrate obtained after dissolution of a commercial PSU product in NMP and coagulation of the resulting 15 wt% solution.

[0049] DETAILED DESCRIPTION

[0050] Definitions

[0051] In the present descriptive specification, some terms are intended to have the following meanings.

[0052] As used herein, the "Relative Energy Distance" (RED) parameter is defined as the ratio of the polymer / solvent distance in a 3-D Hansen solubility space to the radius of the solubility sphere.

[0053] As used herein, the term ‘ppm” means parts per million and unless otherwise stated, ppm is on weight basis.

[0054] In the present specification, the choice of an element from a group of elements (such as a Markush group) also explicitly describes:

[0055] SSPU 2024 / 042 - the choice of two or the choice of several elements from the group,

[0056] - the choice of an element from a subgroup of elements consisting of the group of elements from which one or more elements have been removed.

[0057] In the passages of the present specification which will follow, any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present disclosure. Each embodiment thus defined may be combined with another embodiment, unless otherwise indicated or clearly incompatible. In addition, it should be understood that the elements and / or the characteristics of a polymer, a reaction medium, a composition, a solution, a product or article, a process or a use, described in the present specification, may be combined in all possible ways with the other elements and / or characteristics of the polymer, reaction medium, composition, solution, product or article, process or use, explicitly or implicitly, this being done without departing from the scope of the present description.

[0058] In the present application, where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components. Any element or component recited in a list of elements or components may be omitted from such list. Further, it should be understood that elements, embodiments, and / or features of processes or methods described herein can be combined in a variety of ways without departing from the scope and disclosure of the present teaching, whether explicit or implicit herein.

[0059] In the present specification, the description of a range of values for a variable, defined by a bottom limit, or by a top limit, or by a bottom limit and a top limit, also comprises the embodiments where the variable is chosen, respectively, within the range of values: excluding the bottom limit, or excluding the top limit, or excluding the bottom limit and the top limit. Any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents.

[0060] The term "comprising" (or “comprise”) includes "consisting essentially of' (or “consist essentially of’) and also "consisting of' (or “consist of’).

[0061] The term “consisting essentially of’ in relation to a polymer, composition, product, polymer, solution, process, method, etc. is intended to mean that any

[0062] SSPU 2024 / 042 additional element or feature which may not be explicitly described herein and which does not materially affect the basic and novel characteristics of such a polymer, composition, product, polymer, solution, process, method, etc. can be included in such an embodiment.

[0063] The use of the singular ‘a’ or ‘one’ herein means “at least one” and includes the plural unless specifically stated otherwise.

[0064] The disclosure of all patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural or other details supplementary to those set forth herein. Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

[0065] PROCESS FOR RECOVERING A RECYCLED PSU

[0066] A first aspect of the present invention is directed to a process for recovering a recycled polysulfone (PSU) product from a thin-film composite (TFC) membrane [generally abbreviated as “TFC membrane”] comprising a polyamide (PA) layer, a polysulfone (PSU) layer and a polyethylene phthalate) (PET) layer, said process comprising the following steps: step a): contacting the TFC membrane or TFC membrane pieces with a solvent (SI) for a time sufficient to dissolve PSU, and optionally repeating the step (a), so as to obtain a slurry (SL) containing a liquid phase and solids, said solvent (SI) having a Relative Energy Distance value relative to PA (hereinafter “RED(PA)”) of at least 1.2 and a Relative Energy Distance value relative to PSU (hereinafter “RED(PSU)”) of at most 0.9, said Relative Energy Distance (RED) values being obtained by Hansen solubility spheres, said PET being insoluble in the solvent (SI), said liquid phase of the slurry (SL) comprising PSU, and said solids of the slurry (SL) comprising PA and PET; step (b): separating the liquid phase of the slurry (SL) obtained in step (a) from its solids to obtain a PSU solution (Spl), and optionally repeating the steps (a) and (b), so that the PSU solution (Spl) contains at least 5 wt% PSU dissolved in the solvent (SI), said wt% PSU in the PSU solution (Spl) being based on the combined weights of PSU and solvent (SI); step c): coagulating PSU from the PSU solution (Spl) in a precipitation bath comprising a non-solvent (NS) to form solid PSU particles; and

[0067] SSPU 2024 / 042 step d): recovering the solid PSU particles.

[0068] Thin-film composite (TFC) membrane

[0069] The TFC membrane has several layers of diverse polymeric materials: a selective layer, a support porous layer and a backing layer.

[0070] The selective layer in the TFC membrane is a polyamide layer (PA layer). This PA layer generally is an ultrathin, dense layer ~0.2 pm thick with a pore size < 1 nm.

[0071] The PA layer is formed on top of a support polysulfone layer (PSU layer) and a backing polyester layer (PET layer). The PSU layer is a thick, porous layer (40-150 pm thick), and the PET layer is a non-woven considerably thicker layer (120-150 pm thick) which acts as mechanical support.

[0072] As used herein , a polysulfone [generally abbreviated as “PSU”] denotes any polymer of which of which at least 55 mol %, or at least 60 mol %, or at least 70 mol %, or at least 80 mol %, or at least 90 mol %, or at least 95 mol %, or at least 97 mol %, or at least 98 mol %, or all, of its recurring units are recurring units of formula (I): said mol. % being based on the total amount of moles of recurring unit in the PSU. The recurring unit of formula (I) of the PSU is formed from condensation of bisphenol A and di chlorodi phenylsulfone. Preferably, the PSU recurring units consist essentially of the recurring unit of formula (I). Poly sulfones are commercially available as UDEL® PSU from Solvay Specialty Polymers USA, LLC (SYENSQO group).

[0073] As used herein, a poly(ethylene naphthalate) [generally abbreviated as “PET”] denotes any polymer of which at least 55 mol %, or at least 60 mol %, or at least 70 mol %, or at least 80 mol %, or at least 90 mol %, or at least 95 mol %, or at least 97 mol %, or at least 98 mol %, or all, of its recurring units are recurring units of formula (III):

[0074] SSPU 2024 / 042 wherein the mol. % is based on the total number of moles of recurring units in the PET. Preferably, PET is formed by polycondensation of terephthalic acid and ethylene glycol.

[0075] As used herein, a polyamide [generally abbreviated as “PA”] denotes a crosslinked polyamide. Preferably, the polyamide is selected from two main types of fully-aromatic crosslinked polyamides used in commercial desalination membranes. The first type is a fully-aromatic crosslinked polyamide (“MPD- TMC”) made from M-phenylenediamine (MPD) and trimesoyl chloride (TMC). This MPD-TMC polyamide is commonly used in the PA layers of reverse osmosis (RO) membranes. The condensation and its resulting recurring unit of following formula are shown in the reaction scheme (IV) below:

[0076] (IV). The second type is a fully-aromatic crosslinked polypiperazine amide (PIP- TMC) made from piperazine (PIP) and trimesoyl chloride (TMC). This PIP- TMC polyamide is typically used in the PA layers of nanofiltration membranes such as commercially available from FilmTec NF270, Dupont. The condensation and its resulting recurring unit of following formula are shown in the reaction scheme (V) below:

[0077] (V). These two types of polyamides are highly networked due to crosslinks formed with each TMC unit due to its three functional groups.

[0078] The PSU layer is commonly prepared on top of the PET non-woven layer by a phase inversion method using organic solvents suitable to dissolve PSU, such as dimethylformamide (DMF), dimethyl acetamide (DMAc), N-methyl-2- pyrrolidone (NMP) as the solvent phase and water as the non-solvent phase.

[0079] SSPU 2024 / 042 Then, the thin selective PA layer is generally formed using a rapid polymerization reaction (generally, by interfacial polymerization) between a high concentration of aqueous aromatic amine monomer solution (e.g., m- phenylenediamine or piperazine) using water as a non-organic solvent and an organic solution of a trifunctional acyl chloride monomer (e.g., trimesoyl chloride) in immiscible organic solvent (e.g., in pentane, hexane, cyclohexane, heptane, octane, or isopar™ G, a high-purity isoparaffmic hydrocarbon solvent).

[0080] The PA layer preferably consists of a crosslinked polyamide which is either a crosslinked polyamide MPD-TMC made from M-phenylenediamine (MPD) and trimesoyl chloride (TMC), or a crosslinked polypiperazine amide (PIP-TMC) made from piperazine (PIP) and trimesoyl chloride (TMC). A TFC membrane with a MPD-TMC layer is generally utilized in reverse osmosis, while a TFC membrane with PIP-TMC layer is generally utilized in nanofiltration.

[0081] More preferably, the PA layer in the TFC membrane consists of a fully- aromatic crosslinked polyamide MPD-TMC.

[0082] At an industrial scale, the TFC membranes are commonly fabricated in a spiral wound module configuration with the objective to increase the membrane area in a reduced space and to confer to the module of high-pressure resistance.

[0083] More detailed description of a TFC membrane can be found in the article by Lejarazu-Larranaga et al, Membranes, 2022, vol. 12, p. 864.

[0084] Suitable TFC membranes are commercially available from Dupont (FilmTec), Toray, Hydranautics.

[0085] Optional step j): generating TFC membrane pieces

[0086] The process according to the invention may comprise, prior to step (a), a step (j) for generating TFC membrane pieces from a membrane module containing said TFC membrane, said step (j) comprising carrying out either step (jl) or step (j2):

[0087] - step (j 1): disassembling the membrane module to recover the TFC membrane, and carrying out a mechanical or physical modification of the TFC membrane to obtain TFC membrane pieces, or

[0088] - step (j 2): carrying out a mechanical or physical modification of the membrane module to form module fragments including TFC membrane pieces, and sorting out the module fragments to recover TFC membrane pieces.

[0089] When in step (j), the TFC membrane is transformed into small pieces of TFC membrane, this may permit decreasing the dissolution time of PSU during step (a).

[0090] SSPU 2024 / 042 The membrane module is preferably a reverse-osmosis (“RO”) membrane module or a nanofiltration (“NF”) membrane module, more preferably a RO membrane module.

[0091] Other than the TFC membranes which make up a large proportion of the membrane module, the membrane module typically includes other kinds of materials, such as acrylonitrile butadiene styrene (ABS), polypropylene (PP), rubber, fiberglass, and some glued parts containing epoxy -like components.

[0092] The mechanical or physical modification of the membrane module or of the TFC membrane used in step (j 1) or (j 2) to make membrane pieces preferably includes at least one of the following techniques selected from cutting, shredding, crushing, and / or grinding, in order to form TFC membrane pieces.

[0093] The TFC membrane pieces may have a maximum size of less than 50 mm, or less than 25 mm, preferably less than 15 mm, more preferably less than 10 mm, even preferably less than 5 mm.

[0094] In step (j2), the module fragments which are obtained after mechanical or physical modification of the membrane module and contains TFC membrane pieces may be fed into a sorting system. Density separation (e.g., flotation), optical separation (e.g., Near-Infrared “NIR” sorting), and mechanical separation (e.g., air classification) may be used for sorting the module fragments based on buoyancy, spectral properties, and weight, respectively. For example, an airsorting system (mechanical separation) uses a stream of air to separate the module fragments based on their weight, size, and material properties. The airsorting system should be calibrated to ensure that the lighter fragments are separated from the heavier fragments.

[0095] The sorted materials in step (j2) may be collected in separate bins for further processing or recycling. Throughout the dismantling and sorting steps, the separated fragments (or parts or pieces), and in particular the TFC membrane pieces, should be handled with care to avoid contamination and to ensure that the integrity of the separated TFC membrane pieces is maintained for their intended processing in the present process according to the invention.

[0096] Optional step k): pre-treating TFC membrane or pieces thereof

[0097] The process according to the invention may further comprise, before step (a), a step (k) for pre-treating the TFC membrane or TFC membrane pieces, said step (k) comprising carrying out at least one of following steps (kl), (k2) and (k3): step (kl): washing with a washing agent;

[0098] SSPU 2024 / 042 step (k2): treating with a cleaning agent selected from disinfectants and / or oxidizers; step (k3): sterilizing; followed by : step (k4): drying

[0099] Pretreating in step (k) is carried out before step (a), for the following reasons:

[0100] 1 / to ensure the removal of contaminants, biofilms, and / or any adherent substances including foulants without damaging the PSU polymer in the TFC membrane or pieces thereof;

[0101] 2 / to disinfect; and / or

[0102] 3 / optionally chemically degrade or transform, at least in part, the PA present in the PA layer initially present in the TFC membrane.

[0103] Pretreating in step (k) is preferably carried out before optional step (j).

[0104] The different options for the pretreating step (kl) or (k2) may include contacting with at least one pretreatment agent selected from the group consisting of washing agents (such as water, C1-C5 alcohol, an acid, and / or an alkali acids, bases); cleaning agents (such as disinfectants; and / or oxidizers), or combinations thereof.

[0105] When carrying out the pretreating step (kl) or (k2), the amount of the pretreatment agent and the time period sufficient for washing or cleaning may be selected depending on the nature of the contaminants and the desired outcome of the pre- treatment in step (k), and further in a manner that does not negatively impact the PSU polymer in the TFC membrane or pieces thereof, meaning which does not chemically modify or transform the PSU polymer by the pretreatment agent in a manner that would alter its properties, and in particular its solubility properties.

[0106] When the pretreating step (kl) includes contacting with an acid, the pretreatment agent may be an acidic solution selected from a citric acid solution, a dilute hydrochloric acid, or a dilute sulfuric acid. The acid can be used to remove mineral deposits, scale, and certain types of biofilms. The acidic solution helps in breaking down these deposits without harming the PSU polymeric structure if used in the correct concentration and for a controlled duration to avoid degradation of the PSU polymer. The TFC membrane or pieces thereof should be rinsed after such an acid washing in step (kl) to remove any residual acid, which could otherwise degrade the PSU polymer over time.

[0107] SSPU 2024 / 042 When the pretreating step (kl) includes contacting with a base, the pretreatment agent may be an alkaline solution comprising NaOH. The base can be used to remove organic contaminants, fats, and certain types of biofilms. The use of a base can also help in sanitizing the TFC membrane or pieces thereof. The concentration of the base and the exposure time should be carefully controlled to prevent the degradation of the PSU polymer in the TFC membrane or pieces thereof. After washing in step (kl) with a base, a thorough rinse with deionized water is preferred to neutralize any remaining alkaline residues.

[0108] When the pretreating step (k2) includes contacting with a disinfectant, the cleaning agent may be at least one disinfectant selected from peroxides such as hydrogen peroxide, peracids such as peracetic acid, or sodium hypochlorite. The disinfectant can be used to sanitize the TFC membrane or pieces thereof by killing bacteria and other microorganisms, and / or to help in breaking down organic contaminants. After cleaning, a thorough rinse with deionized water is preferred to remove any remaining disinfectant residues.

[0109] When the pretreating step (k2) includes contacting with an oxidizer, the cleaning agent may be at least one oxidizer selected from the group consisting of hypochlorite, perchlorate, chlorate, peracids such as peracetic acid, ozone, CIO2, Ch gas dissolved in water, and peroxides such as H2O2. The oxidizer can be used to degrade organic contaminants and disinfect the TFC membrane or pieces thereof. Oxidizers are particularly useful for breaking down complex organic molecules and biofilms. Proper rinsing after oxidation is necessary to remove any residual oxidizer. In case of use of hypochlorite in step (k2), the oxidizer may include an aqueous solution having at least 1,000 and up to 100,000 ppm, preferably at least 5,000 and up to 10,000 ppm sodium hypochlorite. In case of use of peroxide in step (k2), the oxidizer may include an aqueous solution of hydrogen peroxide.

[0110] It is to be understood that a cleaning agent used in step (k2) may be selected for having several functions. For example, a sodium hypochlorite solution may be used in step (k2) as an oxidizer to degrade organic contaminants and in particular chemically degrade or transform, at least in part, the PA initially present in the PA layer of the TFC membrane, as well as used as a disinfectant to sanitize the TFC membrane or pieces thereof by killing bacteria and other microorganisms.

[0111] For step (kl) or step (k2), the pre-treating step (k) is preferably carried out on the whole TFC membrane while it is inside a membrane module before its

[0112] SSPU 2024 / 042 disassembling such as in step (j). In such instances, the washing agent used in step (kl) or the oxidizing agent used in step (k2) may be passed through the TFC membrane.

[0113] For step (kl) or step (k2), the pre-treating step (k) may be carried out for a time period of at least 15 minutes, at least 20 min, at least 25 min or at least 30 min and at most 24 hours, at most 18 hours, at most 12 hours, or at most 6 hours. Preferably the time period for pre-treating in step (kl) or step (k2) may be from 20 minutes to 18 hours, more preferably from 25 minutes to 12 hours, still more preferably from 30 minutes to 6 hours.

[0114] The pre-treating step (kl) or (k2) may include soaking the entire membrane module which includes the TFC membrane with the washing agent and / or cleaning agent for such a time period, drain the washing agent and / or cleaning agent, and then let the membrane module dry.

[0115] While the sterilization step (k3) could be performed on TFC membrane pieces, the sterilization step (k) is preferably carried out on the whole TFC membrane in situ, meaning while it is still inside its membrane module, such as by passing ethylene oxide (EtO) gas and / or steam through the TFC membrane, or ex situ, meaning after the TFC membrane is removed from its membrane module.

[0116] Preferably, the sterilization step (k3) may use exposure to ethylene oxide (EtO) gas, irradiation and / or steam sterilization in an autoclave. The selected sterilization technique in step (k3) should not negatively impact the PSU polymer in the TFC membrane or pieces thereof, meaning not chemically modifying or transforming the PSU polymer. The sterilization in step (k3) may be carried out on the TFC membrane or pieces thereof such as those obtained from step (j), prior to or after washing in step (kl) and prior to or after cleaning in step (k2).

[0117] The autoclaving technique for sterilization step (k3) may be carried out at a temperature of up to 135 °C, preferably up to 121 °C. During autoclaving, the polymeric material or TFC membrane pieces such as those obtained from step (j) may be immersed in water.

[0118] The irradiation technique for sterilization step (k3) is generally gamma irradiation.

[0119] For step (k3) , the pre-treating step (k) is preferably carried out for a time period of at least 1 minute, at least 2 min, at least 5 min or at least 10 min and at most 1 hour, at most 50 min, at most 40 min, or at most 30 min. Preferably the

[0120] SSPU 2024 / 042 time period for pre-treating in step (kl) or step (k2) may be from 1 minute to 1 hour, more preferably from 2 minutes to 50 min, still more preferably from 3 minutes to 40 min.

[0121] An optional final rinse may be carried out before drying step (k4) in order to remove residues or remnants of the washing or cleaning agent used in steps (kl) or (k2), and / or to remove loosely bound impurities / contaminants originating from the manufacture (when the TFC membrane was unused) and / or from the use of the TFC membrane (such as in end-of-life TFC membrane). The final rinsing agent may be a volatile solvent such as deionized water and / or an organic solvent having a low boiling point (preferably < 100 °C) such as acetone, methanol, ethanol.

[0122] Preferably, drying in step (k4) uses a drying temperature which is higher than the boiling point (measured at atmospheric pressure) of any volatile solvent used in any of the steps (kl), (k2) or (k3) or optional final rinse, and preferably which is not higher than 150 °C. The drying in step (k4) may be done under vacuum or at atmospheric pressure.

[0123] Step a): contacting

[0124] The process according to the invention comprises: step (a): contacting the TFC membrane or TFC membrane pieces with a solvent (SI) for a time sufficient to dissolve PSU to obtain a slurry (SL) containing a liquid phase and solids,

[0125] While the contacting step (a) could be performed in situ on a whole TFC membrane, for example while the whole TFC membrane is still in place inside its membrane module, the contacting step (a) is preferably carried out ex situ on a whole TFC membrane or TFC membrane pieces, meaning after the TFC membrane is removed from its membrane module, or after the TFC membrane pieces are formed for example in optional step (j).

[0126] The contacting in step (a) may be carried out in batch mode or continuous mode.

[0127] The contacting in step (a) preferably takes place in a vessel which can operate at a temperature of up to 150 °C and at a pressure from 81 kPa (0.8 atm) up to 506 kPa (5 atm.).

[0128] The vessel may be a well-mixed vessel equipped with a stirring device, such as a turbine or agitator, or may not include an agitator.

[0129] Alternatively although not preferred, the vessel does not have moving parts but rather uses a whole TFC membrane or a packed bed of TFC membrane

[0130] SSPU 2024 / 042 pieces through which the solvent (SI) passes. For example, the vessel may be the membrane module in which the TFC membrane was initially installed.

[0131] Preferably, TFC membrane pieces and the solvent (SI) may be added simultaneously or sequentially to a vessel equipped with a stirring device where the contacting step (a) takes place.

[0132] Particularly, TFC membrane pieces and the solvent (SI) are loaded into the vessel, then the vessel is closed and pre-heated, and pressurized if needed, to achieve the desired dissolution temperature and pressure, and then these dissolution conditions are held for a time sufficient to dissolve PSU from the PSU layer into the solvent (SI).

[0133] The contacting time sufficient to dissolve PSU into the solvent (SI) during step (a) may be at least 15 minutes, at least 20 min, at least 25 min or at least 30 min and at most 6 hours, at most 4 hours, at most 2 hours, at most 1.5 hours, at most 1.25 hours, or at most 1 hour. Preferably the time period for step (a) may be from 15 minutes to 6 hours, preferably from 20 minutes to 4 hours, more preferably from 25 minutes to 2 hours, still more preferably from 25 minutes to 1.5 hours, yet more preferably from 30 minutes to 1.25 hour.

[0134] The temperature during step (a) should not exceed the boiling point of the solvent (SI). In particular, the temperature during step (a) may be not more than 130°C. Preferably the temperature during step (a) may be at least 20°C, at least 22°C, at least 24°C, at least 26°C, at least 28°C, or at least 30°C, and at most 100°C, at most 90°C, at most 80°C, at most 70°C, at most 60°C, at most 50°C, at most 45°C, or at most 40°C. More preferably, the temperature during step (a) may be from 20°C up to 90°C, from 20°C up to 80°C, from 20°C up to 70°C, from 25°C up to 60°C, from 25°C up to 60°C, or from 25°C up to 50°C. Still more preferably, the temperature during step (a) may be from 20°C up to 45°C.

[0135] The pressure during step (a) should not exceed 500 kPa. In particular the pressure during step (a) may be at least 90 kPa, at least 95 kPa, at least 101 kPa, at least 105 kPa, or at least 110 kPa and up to 400 kPa, up to 300 kPa, up to 200 kPa, or up to 150 kPa. Preferably, the pressure during step (a) may be from 95 kPa up to 300 kPa, or from 100 kPa up to 200 kPa.

[0136] During step (a), the weight ratio (w:w) of the solvent (SI) relative to the TFC membrane or pieces thereof may be at least 3:2, at least 2: 1, at least 3: 1, or at least 10:3 and at most 20: 1, at most 15: 1, at most 12: 1, at most 10: 1, at most 9: 1, at most 8: 1, most 7: 1, at most 6: 1, at most 5: 1, at most 9:2 or at most 4: 1. Preferably the weight ratio (w:w) of the solvent (SI) relative to the TFC

[0137] SSPU 2024 / 042 membrane or pieces thereof may be from 3:2 up to 20: 1, or from 2: 1 to 20: 1, or from 5:2 to 15:1, or from 3:1 to 10:1.

[0138] Solvent (SI)

[0139] The step (a) comprises contacting the TFC membrane or pieces thereof with the solvent (SI).

[0140] The solvent (SI) selected for step (a) should be soluble in the non-solvent (NS) used in the coagulation step (c). If the solvent (SI) is not soluble in the nonsolvent (NS), then the coagulation step (c) will not be very effective.

[0141] For example, when the precipitation bath in coagulation step (c) comprises water (as non-solvent), such as > 25 wt% water, preferably > 50 wt% water, more preferably > 70 wt% water, said wt% being based on total weight of precipitation bath, it is preferable not to select a solvent (SI), whether it be a pure solvent or a solvent blend, having too low polarity (e.g., a dielectric constant of less than 12) which would render it incompatible in operation with the coagulation step (c) in the precipitation bath comprising water.

[0142] The solvent (SI) has a RED value relative to PA [hereinafter “RED(PA)”] of at least 1.2, preferably at least 1.25 or at least 1.3, more preferably at least 1.35 or at least 1.4, still more preferably at least 1.45 or at least 1.5, such RED(PA) value being obtained by the Hansen solubility sphere of PA in the solvent (SI).

[0143] The solvent (SI) has a RED value relative to PSU in the solvent (SI) [hereinafter “RED(PSU)”] at most 0.9, or at most 0.85, or at most 0.8, preferably at most 0.75, more preferably at most 0.7, still more preferably at most 0.65, yet still more preferably at most 0.6, such RED(PSU) value being obtained by the Hansen solubility sphere of PSU in the solvent (SI).

[0144] Particularly, the solvent (SI) may have a RED(PA) value of at least 1.2 and a RED(PSU) of at most 0.85, preferably a RED(PA) value of at least 1.25 and a RED(PSU) of at most 0.8, more preferably a RED(PA) value of at least 1.3 and a RED(PSU) of at most 0.75, still more preferably a RED(PA) value of at least 1.4 and a RED(PSU) of at most 0.7, even more preferably a RED(PA) value of at least 1.5 and a RED(PSU) of at most 0.65.

[0145] The solvent (SI) having the maximum RED(PSU) value and the minimum RED(PA) value as described above may be:

[0146] - a pure solvent soluble in the non-solvent (NS) used in the coagulation step (c), or

[0147] SSPU 2024 / 042 - a blend of at least one non-polar solvent and at least one polar solvent, such a blend being soluble in the non-solvent (NS) used in the coagulation step (c).

[0148] Generally, the dielectric constant (symbol: e) of a solvent may be used as a measure of its polarity. The higher the dielectric constant of a solvent, the more polar it is. A solvent's dielectric constant (e) can help predict how well a solute molecule will dissolve in it. As a general rule, if e of a solvent is high, it is more likely to dissolve polar / ionic compounds. If e is low, the solvent is more suited for dissolving non-polar (non-ionic compounds).

[0149] As used herein, a solvent with a dielectric constant of at least 12 is considered "polar" and a solvent with a dielectric constant of less than 12 is considered "non-polar”.

[0150] Table 1 provides examples of polar and non-polar solvents with their dielectric constant and polarity (P: polar ; NP: non-polar).

[0151] Table 1

[0152] SSPU 2024 / 042

[0153] Particularly, the solvent (SI) may be:

[0154] - a pure polar solvent selected from dimethyl isosorbide (DMI), cyclohexanone, cycloheptanone, cyclopentanone, or N-Butyl Pyrrolidone (NBP), preferably being DMI or cyclohexanone, more preferably being cyclohexanone, or

[0155] - a blend of at least one non-polar solvent and at least one polar solvent.

[0156] The solvent (SI) is preferably a blend of at least one non-polar solvent and at least one polar solvent.

[0157] When the solvent (SI) is a blend of at least one non-polar solvent and a polar solvent, the polar solvent is selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N-methyl-2- pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone, and / or the non-polar solvent is selected from the group consisting of o-dichlorobenzene (ODCB), monochlorobenzene (MCB), and toluene.

[0158] Particularly, the solvent (SI) may be selected from:

[0159] - a pure polar solvent selected from dimethyl isosorbide (DMI), cyclohexanone, cycloheptanone, cyclopentanone, or N-Butyl Pyrrolidone (NBP), preferably being DMI or cyclohexanone, more preferably being cyclohexanone,

[0160] - blends of o-dichlorobenzene (ODCB) with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone;

[0161] SSPU 2024 / 042 - blends of monochlorobenzene (MCB) with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone; or

[0162] - blends of toluene with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma- Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone.

[0163] More particularly, the solvent (SI) is a blend of a non-polar solvent and a polar solvent, said blend being selected from:

[0164] - blends of o-dichlorobenzene (ODCB) with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone;

[0165] - blends of monochlorobenzene (MCB) with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone; or

[0166] - blends of toluene with a polar solvent selected from the group consisting of DMAc, DMF, NMP, DMSO, dimethyl ether isosorbide (DMI), gamma- Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone.

[0167] When the solvent (SI) is a DMSO blend or a NMP blend with anon-polar solvent, the volumetric ratio of the non-polar solvent in the blend is preferably greater than 50 vol.% and less than 95 vol.%, said vol.% being based on the total volume of the solvent (SI). In such instances, the non-polar solvent is preferably ODCB, MCB, or toluene, more preferably MCB.

[0168] When the solvent (SI) is a GBL blend with a non-polar solvent, the volumetric ratio of the non-polar solvent in the blend is preferably greater than 29 vol.%, more preferably at least 34 vol.%, still more preferably at least 39 vol% and less than 95 vol.%, said vol.% being based on the total volume of the solvent (SI).

[0169] Step b): separating

[0170] At the end of step (a), a slurry (SL) containing a liquid phase and solids is obtained. As it would be appreciated by those of ordinary skill in the art, the solids portion of the resulting slurry (SL) includes the insoluble PA and PET originating from their respective layers of the TFC membrane, while the liquid phase of the resulting slurry (SL) contains PSU dissolved in the solvent (SI).

[0171] SSPU 2024 / 042 Step (b) includes separating the liquid phase of the slurry (SL) obtained in step (a) from its solids.

[0172] Any suitable a solid / liquid separation can be used to remove solids from the liquid phase of the slurry (SL). The solid / liquid separation preferably includes filtration, but other solid / liquid separation techniques such as centrifugation may be employed.

[0173] When the solid / liquid separation includes filtration, the insoluble PA and PET are collected as filtered solids, and the filtrate generates a PSU solution (Spl).

[0174] The filtration can be performed in a variety of ways, such as vacuum filtering or any form of filtering as desired.

[0175] The PSU solution (Spl) obtained in step (b) should contain at least 5 wt% PSU, at least 7 wt% PSU, or at least 10 wt% PSU, and at most 25 wt% PSU, at most 23 wt% PSU, or at most 22 wt% PSU, or at most 20 wt% PSU dissolved in the solvent (SI), said wt% PSU in the PSU solution (Spl) being based on the combined weights of PSU and solvent (SI).

[0176] In order to achieve at least a minimum of 5 wt% PSU in the PSU solution (Spl) before it is subjected to the coagulation step (c), it may be desirable to repeat the steps (a) and (b). In such instances a first-obtained PSU solution (Spl) which contains insufficient content of PSU (< 5 wt% PSU) may be subjected to yet another contacting step (a) with an additional amount of TFC membrane or pieces thereof, in order to further dissolve PSU and enrich the solution in PSU, thus forming a subsequent enriched PSU solution (Spl).

[0177] Step (c): coagulating

[0178] The recycled PSU of the invention can be isolated by methods well known and widely employed in the art such as, for example, coagulation, solvent evaporation and the like.

[0179] In step (c) however, coagulation of PSU is preferred.

[0180] Coagulation is based on precipitation of the PSU polymer present in the PSU solution (Spl) with the use of anon-solvent (NS) or poor solvent.

[0181] The solvent (SI) in the PSU solution (Spl) should be soluble in the nonsolvent (NS).

[0182] This coagulation (c) is preferably carried out by forming droplets of the PSU solution into a precipitation bath which comprises the non-solvent “NS” or poor solvent to form a coagulated PSU, generally in the form of PSU beads.

[0183] SSPU 2024 / 042 The non-solvent (NS) in the precipitation bath may be selected from Cl- C5 alcohol such as methanol, ethanol, n-propanol, isopropanol, butanol, ethyl acetate, methyl acetate, acetone, butanone, water, or any mixture thereof.

[0184] A preferred non-solvent (NS) may be ethanol, methanol, water, or any mixture thereof. The non-solvent (NS) is more preferably water and / or methanol. The non-solvent (NS) is yet more preferably methanol.

[0185] In the context of the present invention, a poor solvent is defined as a mixture of at least one non-solvent (NS) which does not dissolve PSU and at least one solvent which dissolves PSU.

[0186] Precipitation Bath

[0187] The precipitation bath may comprise at least 50 wt%, preferably at least 60 wt%, of anon-solvent (NS), such as water and / or at least one C1-C5 alcohol.

[0188] The precipitation bath preferably comprises at least 50 wt%, or at least 60 wt%, or at least 70 wt%, of water and / or methanol as non-solvent (NS).

[0189] The precipitation bath may consist of at least one non-solvent (NS) or may consist of a poor solvent which is a mixture of at least one non-solvent (NS) and a solvent which dissolves PSU such as the solvent (SI), said poor solvent preferably having at least 50 wt%, preferably at least 60 wt%, of the at least one non-solvent (NS), the remainder wt% being for the solvent which dissolves PSU such as the solvent (SI).

[0190] Step d): recovering the solid PSU

[0191] The recovery step (d) comprises:

[0192] • (dl) removing the solid PSU particles from the precipitation bath;

[0193] • (d2) washing the solid PSU particles; and

[0194] • (d3) drying the washed solid PSU particles at a temperature of from 80°C to 130°C.

[0195] Step (dl) may involve filtration, or centrifugation, or successive steps of filtration and centrifugation, preferably filtration.

[0196] In step (d2), the recovered solid PSU can be subjected to one or more washes with a washing liquid to further remove salts or other ingredients that remain in the polymer solids. The washing liquid is preferably water and / or Cl- C5 alcohol (e.g., methanol, ethanol, n-propanol, isopropanol), more preferably water and / or methanol.

[0197] The washing liquid used in step (d2) is preferably at a temperature of at least 50°C, or at least 60°C, or at least 65°C. The washing liquid should be at a temperature not exceeding its boiling point. The washing liquid is preferably at a

[0198] SSPU 2024 / 042 temperature of at most 90°C, or at most 85°C, or at most 80°C, or at most 75°C. The washing liquid is more preferably water at a temperature of from 60°C to 80°C, or from 65°C to 75°C. There may be two or more washes in step d2), using different washing liquids, such as first one or more washes with water and subsequently one or more washes with methanol.

[0199] In step (d3) the recovered solid PSU may be dried at a temperature generally from about 50°C to 120°C, preferably from about 80°C to 120°C, more preferably at about 90-120°C, yet more preferably at about 90-110°C, preferably under vacuum.

[0200] The dried recycled PSU solid can be used for preparing an article, such as, but not limited to, a fiber, a sheet, a film, or a membrane.

[0201] Optional shaping after drying

[0202] The resulting dried recycled PSU solid obtained after drying step (d3) may be further processed by grinding, extruding and / or pelletizing. A pelletized product may subsequently be subjected to further melt processing such as injection molding and / or sheet extrusion. The conditions for molding, extruding, and thermoforming the resulting recycled PSU are well known in the art.

[0203] The shaped recycled PSU solid can be used for preparing an article, such as, but not limited to, a fiber, a sheet, a film, or a membrane.

[0204] Step (f): color removal treatment

[0205] The process may further comprise a color removal step (f) by carrying out either or both of following step (fl) and step (f2):

[0206] • step (fl): removing color from the PSU solution (Spl) to obtain a treated (“decolorized”) PSU solution (Spl*), and / or

[0207] • step (f2): dissolving the solid PSU particles obtained in step (d) into a solvent (S2) to obtain a second PSU solution (Sp2), and removing color from the second PSU solution (Sp2) to obtain a treated (“decolorized”) PSU solution (Sp2*).

[0208] In step (f2), the solvent (S2) is preferably selected from the group consisting of DMF, DMAC, NMP, DMSO, dimethyl ether Isosorbide (DMI), N- n-Butyl Pyrrolidone (NBP), gamma-Butyrolactone (GBL), Cyclopentanone, Cycloheptanone, Cyclohexanone, more preferably selected from the group consisting of DMF, DMAC, NMP, DMSO, DMI, NBP, and GBL.

[0209] The color removal treatment in step (fl) or (f2) is preferably carried out by contacting the PSU solution (Spl) or (Sp2) with an adsorbent.

[0210] SSPU 2024 / 042 Preferably, contacting in step (fl) or (f2) may include forming a slurry (SL1) or (SL2) by mixing the PSU solution (Spl) or (Sp2), respectively, with an adsorbent in solid form.

[0211] Alternatively, contacting in step (fl) or (f2) may include passing the PSU solution (Spl) or (Sp2) through the adsorbent in a stationary particulate or monolithic arrangement such as a bed of adsorbent particles.

[0212] The adsorbent may be activated carbon, silica-alumina complex, activated clay, diatomaceous earth, and / or perlite. Two or more adsorbents may be used. A preferred adsorbent comprises, or consists of, at least one activated carbon. A preferred specific surface area (preferably BET surface area) of the adsorbent may be from about 100 cm2 / g to 100,000 cm2 / g.

[0213] The amount of the adsorbent in step (1) is not particularly limited. The amount of the adsorbent in step (1) is usually from 1 to 10 wt%, preferably from 2 to 5 wt%, more preferably from 2 to 4 wt%, of the absorbent based on the weight of the PSU solution (Spl) or (Sp2) to be treated.

[0214] The temperature in step (1) at which the PSU solution (Spl) or (Sp2) is brought in contact with the adsorbent is not particularly limited. The temperature in step (1) is usually from 10 to 120 °C, preferably from 20 to 100 °C, more preferably from 25 to 90 °C, still more preferably from 50 to 85 °C.

[0215] The time period to carry out the step (1) is not particularly limited. The time period to carry out the step (1) is usually from about 0.5 to 10 hours, preferably from 1 to 5 hours, more preferably from 2 to 4 hours.

[0216] After completion of the step (1) that includes forming a slurry (SL1) or (SL2) with the adsorbent is completed, the treated slurry (SL1*) or (SL2*) is separated in a separation step (b2) to remove the adsorbent , for example, by filtration, centrifugation, decantation or the like to obtain a treated PSU solution (Spl*) for step (fl) or (Sp2*) for step (f2)

[0217] The treated PSU solution (Spl*) obtained from step (fl) may be directly subjected to coagulation in step (c) or may be first subjected to an optional evaporation step (e) before being subjected to coagulation in step (c).

[0218] The treated PSU solution (Sp2*) obtained from step (f2) may be directly subjected to another coagulation with anon-solvent in a secondary step (c2) and then further separated in a secondary separation step (d2) to obtain a solid recycled PSU product which is purified compared to the solid PSU particles which were obtained in step (d).

[0219] SSPU 2024 / 042 When the step (f) is carried out, a PSU solution (SPf), which is obtained when the final recycled PSU product is dissolved in NMP with a content of 5 wt% PSU, has :

[0220] - a Yellowness Index of less than 8, or less than 5, or less than 4, or less than 3; and / or

[0221] - a color coordinate b* and / or a chroma C* of less than 14, or at most 12, or at most 10, or at most 8, or at most 7, or at most 6, or at most 5, or at most 4, or at most 3, or at most 2.

[0222] A particularly suitable CIE Color measurement method to provide the color coordinate b* and the chroma C* is CIE D65-10 provided in the examples section.

[0223] The method ASTM E313-20 is a standard for calculating yellowness and whiteness indices from instrumentally measured CIE color coordinates and is particularly suitable for determining the Yellowness Index (which can be labelled as ‘YI E313”) based on the CIE Color measurement.

[0224] Optional step (e): PSU concentration before step (c)

[0225] The process may further comprise a concentration step (e), preferably carried out before coagulation to obtain a concentrated PSU solution (SpT).

[0226] The evaporation in step (e) preferably comprises subjecting the PSU solution (Spl) or treated PSU solution (Spl *) to heating and / or applying vacuum.

[0227] The step (e) preferably includes evaporating at least a portion of the solvent (SI) from the PSU solution (Spl) obtained after step (b) or from the treated PSU solution (Spl*) obtained in optional color removal step (fl), thereby increasing the PSU content in the resulting concentrated PSU solution (SpT).

[0228] The concentration step (e) may be carried out to increase the PSU content of the PSU solution which is intended to be coagulated to at least 20 wt% PSU (wt% being based on the total weight of solution) . The step (e) is thus preferably carried out when the PSU content in the PSU solution (Spl) or the treated PSU solution (Spl*) obtained in optional color removal step (fl) is less than 20 wt% PSU.

[0229] When the solvent (SI) comprises a blend of a polar solvent and a nonpolar solvent having a lower boiling point [“bp”] than the polar solvent, the concentration step (e) may be carried out to particularly remove the more volatile non-polar solvent. Such evaporation step (e) would be particularly advantageous when the precipitation bath comprises water, preferably at least 50 wt% water,

[0230] SSPU 2024 / 042 because the non-polar solvent in the PSU solution (Spl) or treated PSU solution (Spl*) may not be compatible for an effective coagulation step (c) in a precipitation bath containing water. As an example, when the solvent (SI) comprises a blend of DMSO (polar solvent having a bp of 191 °C) and MCB (non-polar solvent having a bp of 132 °C) with an initial DMSO:MCB volumetric ratio of 25:75, the evaporating step (e) may be effective to remove a larger proportion of MCB compared to DMSO, so that the resulting DMSO:MCB volumetric ratio in the concentrated PSU solution (SpT) is increased, for example to 35:65, or to 40:60, or to 45:55, to 50:50, or even to 60:40.

[0231] When a more volatile non-polar solvent is present in solvent (SI), the evaporation step (e) thus could reduce the non-polar solvent content in the concentrated PSU solution (SpT), and increase the polar solvent: non-polar solvent volumetric ratio in the concentrated PSU solution (SpT).

[0232] The various embodiments of the process according to the invention are illustrated in FIG. 1 to 3.

[0233] FIG. 1 represents an embodiment of the process according to the invention in which a thin-film composite (TFC) membrane 10 is subjected to the process according to the invention in order to produce a recycled PSU product 70.

[0234] TFC membrane 10 or pretreated TFC membrane 15 or optionally- pretreated TFC membranes pieces 20 are directed to contact unit 100 to which solvent (SI) 25 is added. The TFC membrane is generally in form of sheets and consists of PET-PSU-PA layers. The TFC membrane 10 may be subjected to a pretreatment [step (k)] in unit 500 to form pretreated membrane 15. Pretreatment unit 500 may be the membrane module from which the TFC membrane originates or be another vessel used when the TFC membrane has been dismantled from its module.

[0235] Prior to being fed to unit 500, the TFC membrane 10 may be subjected to mechanical or physical modification [step (j)] in unit 600 to form membrane fragments 20. Mechanical or physical modification in unit 600 may include cutting, shredding, crushing, and / or grinding. The membrane pieces 20 may have a maximum size lower than 50 mm, lower than 25 mm, preferably lower than 15 mm, more preferably lower than 10 mm, even preferably lower than 5 mm.

[0236] If the TFC membrane 10 or pretreated membrane 15 is still in its membrane module, then the membrane module may be dissembled to recover the TFC membrane (10 or 15), and then the TFC membrane (10 or 15) may be subjected to mechanical or physical modification in unit 600 to obtain TFC membrane pieces

[0237] SSPU 2024 / 042 20. Alternatively, the membrane module including the TFC membrane (10 or 15) is subjected to the mechanical or physical modification in unit 600 to form module fragments including TFC membrane pieces, and then the module fragments are sorted out (such as via an air-jet sorting system) to recover TFC membrane pieces 20.

[0238] The TFC membrane or pieces thereof are stirred in contact unit 100 [step (a)] with the solvent SI to dissolve at least some of the PSU from the PSU layer and to generate a slurry (SL1) 30.

[0239] The slurry (SL1) 30 may be subjected to a solid / liquid separation in separation unit 200 (preferably including filtration) to provide a PSU solution (Spl) 40 and to remove solids (Wl) 45 containing the solid PET and PA layers.

[0240] The PSU dissolution in unit 100 and solid / liquid separation in unit 200 can be repeated by way of a PSU enrichment loop 48, until the content of PSU in the PSU solution (Spl) 40 is at least 5 wt% PSU.

[0241] The PSU solution (Spl) 40 or an optionally-concentrated PSU solution (Spl’) 50 is then coagulated [step (c)] in coagulation unit 300 containing a precipitation bath fed by anon-solvent 55 (preferably using anon-sol vent / soluti on volumetric ratio of from 2 / 1 to 10 / 1 v. / v.) to obtain coagulated PSU 60.

[0242] The coagulated PSU 60 is washed with a non-solvent (preferably methanol or water), filtered and dried [step (d)] in post-coagulation unit 400 from which the recycled PSU product 70 is collected. The post-coagulation unit 400 generally contains separate units / vessels for the washing, filtering and drying.

[0243] In the process of FIG.l, when the PSU solution (Spl) 40 exiting unit 200 is less than 20 wt% PSU, it may be subjected to concentration [step (e)] in optional unit 700 to form a concentrated PSU solution (Spl’) 50 before being sent to the coagulation unit 300.

[0244] Additionally or alternatively when the PSU solution (Spl) 40 exiting unit 200 comprises a polar solvent and a more-volatile non-polar solvent (such nonpolar solvent originating from solvent (SI) in stream 25), the PSU solution (Spl) 40 may be subjected to evaporation [step (e)] in optional unit 700 in order to volatilize some, and in particular a majority, of the non-polar solvent, to form a concentrated PSU solution (Spl’) 50 which has a higher polar solvent to non-polar solvent volumetric ratio than the PSU solution (Spl) 40.

[0245] FIG. 2 represents another embodiment of the process according to the invention in which a thin-film composite (TFC) membrane 10 is subjected to produce a recycled PSU product 70. The process in FIG. 2 is similar to the process

[0246] SSPU 2024 / 042 in FIG. 1, except that this embodiment of the process further contains a color removal step (fl) with an adsorbent 75 in unit 800 and a further separation in unit 900. The PSU solution (Spl) 40 exiting unit 200 is treated with the adsorbent in unit 800 to form a treated PSU slurry (SL1*) 80 exiting unit 800, which is then separated from solids (W2) 85 and form the treated PSU solution (Spl*) 87.

[0247] Similarly to what is described in the process of FIG.l, when the treated PSU solution (Spl*) 87 exiting unit 900 is less than 20 wt% PSU, it may be subjected to concentration [step (e)] in optional unit 700 to form an optionally-concentrated PSU solution (SpT) 50 before being sent to coagulation unit 300.

[0248] Additionally or alternatively when the treated PSU solution (Spl*) 90 exiting unit 900 comprises a polar solvent and a more-volatile non-polar solvent (such non-polar solvent originating from solvent (SI) in stream 25), the treated PSU solution (Spl*) 87 may be subjected to evaporation [step (e)] in optional unit 700 in order to volatilize some, and in particular a majority, of the non-polar solvent, to form an optionally-concentrated PSU solution (SpT) 50 which has a higher polar solvent to non-polar solvent volumetric ratio than the treated PSU solution (Spl*) 90. The PSU solution (Spl) 40 or the optionally-concentrated PSU solution (SpT) 50 is then coagulated [step (c)] with non-solvent 55 in coagulation unit 300. Then the coagulated PSU 60 is washed with a non-solvent (preferably methanol or water), filtered and dried [step (d)] in post-coagulation unit 400, as previously described for FIG. 1.

[0249] FIG. 3 represents yet another embodiment of the process according to the invention which produces a purified recycled PSU product 95.

[0250] The process in FIG. 3 is similar to the process in FIG. 1, except that after a first coagulation (step (c)) in unit 300, there is a PSU dissolution with a solvent (S2) and a color removal treatment (step (f2)) in unit 850 with an adsorbent 75 followed by a second separation (step (b2)) in unit 900, a second coagulation (step (c2)) in unit 350 and a second recovery (step (d2)) in unit 450

[0251] The PSU product exiting unit 400 in FIG. 3 is intermediate product 70. Optionally, a portion 70a of intermediate PSU product 70 may be collected and used ‘as is’. Another portion 70b, or preferably all, of the PSU product 70 exiting unit 400 is dissolved with a solvent (S2) 72 to form a PSU solution (Sp2) 74. This PSU solution (Sp2) 74 is then treated with adsorbent 75 in unit 850 to form a treated slurry (SL2*) 82, which is then separated in unit 900 to remove solids (W2) 85 and to form treated PSU solution (Sp2*) 88. The treated PSU solution (Sp2*) 88 is then subjected to another coagulation with non-solvent 55b (which

[0252] SSPU 2024 / 042 may be the same or different than non-solvent 55 used in unit 300) in unit 350 to form coagulated purified PSU 90, which is then washed, filtered and dried [step (d)] in unit 450 to obtain purified recycled PSU product 95. The non-solvent 55b (preferably water or methanol) used in unit 350 may be the same or different than non-solvent 55 used in unit 300.

[0253] RECYCLED PSU PRODUCT

[0254] Another aspect of the present invention is related to a polysulfone (PSU) product obtained by the process according to the present invention.

[0255] The recycled PSU according to the present invention features all the benefits of the currently sold poly sulfones while also unexpectedly featuring a low content in combined BPA and DCDPS monomers, and optionally furthermore in a low content in cyclic dimers.

[0256] The recycled polysulfone (PSU) product comprises a combined content of bisphenol A (BPA) and dichlorodiphenylsulfone (DCDPS) monomers of > 0 to less than 10 ppm. The contents of BPA and DCDPS in the PSU product can be measured by Gas Chromatography (GC). A particularly suitable GC method for measuring the combined content of BPA and DCDPS is provided in the examples section. The combined BPA and DCDPS content in the recycled PSU product is preferably much less than commercial PSU products. The evidence is provided in Table 5 for Examples 6-9.

[0257] The recycled PSU product may further comprise <0.95 wt%, pref. <0.90 wt%, more pref. <0.75 wt% or <0.7 wt% of cyclic dimers, said wt% being based on the total weight of the PSU product. The cyclic dimers content in the PSU product can be measured by Gel Permeation Chromatography (GPC). A particularly suitable GPC method for measuring the cyclic dimers content is provided in the examples section. The cyclic dimers content in the recycled PSU product is preferably less than what is typically measured for commercial PSU products. The evidence is provided in Table 4 for Examples 2-9.

[0258] When the recycled PSU product is dissolved in NMP with a content of 5 wt% PSU, the resulting 5 wt% PSU solution (SP1) in NMP preferably has :

[0259] - a color coordinate b* of at most 18, or at most 15, or at most 14;

[0260] - a chroma C* of at most 18, or at most 15, or at most 14; and / or

[0261] - a Yellowness Index (YI) of at most 35, or at most 33, or at most 28.

[0262] When the step (1) is carried out in the process of the present invention, the 5 wt% PSU solution (SP1) in NMP may have :

[0263] SSPU 2024 / 042 - a color coordinate b* of less than 14, or at most 12, or at most 10, or at most 8, or at most 7, or at most 6, or at most 5, or at most 4, or at most 3, or at most 2;

[0264] - a chroma C* of less than 14, or at most 12, or at most 10, or at most 8, or at most 7, or at most 6, or at most 5, or at most 4, or at most 3, or at most 2; and / or

[0265] - a Yellowness Index based on a CIE Color measurement of less than 8, or less than 5, or less than 4, or less than 3.

[0266] A particularly suitable CIE Color measurement method to provide the color coordinates L*, a*, b*, hue angle h° and chroma C* is CIE D65-10 provided in the examples section.

[0267] The method ASTM E313-20 is a standard for calculating yellowness and whiteness indices from instrumentally measured CIE color coordinates and is particularly suitable for determining the Yellowness Index (which can be labelled as ‘YI E313”) based on the CIE Color measurement.

[0268] Measured color coordinates L*, a*, b*, hue angle h°, chroma C* and YI E313 for 5 wt% PSU solutions (SPf) in NMP are provided in Table 3 in the Examples section.

[0269] The recycled PSU product may further comprise the presence of impurities originating from the TFC membrane. These TFC membrane impurities in the recycled PSU product are preferably separated and detected by ultra-performance liquid chromatography (UPLC) operating at ultra-high pressure with high resolution mass spectrometry (HRMS).

[0270] Preferably, the following ultra-performance liquid chromatography method with mass spectrometry detection (UPLC-MS) and sample preparation are used to detect these impurities.

[0271] Preferably to prepare a sample to be analyzed by UPLC-MS, the recycled PSU product is dissolved in a solvent (preferably NMP) at room temperature to obtain a 15 wt% PSU solution. The 15 wt% PSU solution is then coagulated into a non-solvent mixture of methanol and acetone (80 v. / 20 v.) using a volumetric ratio of non-solvent to PSU solution of 2: 1 (v:v). The precipitated PSU polymer is then removed via filtration, and the filtrate in the solvent is collected and analyzed by UPLC-MS.

[0272] For a preferred UPLC-MS method, a reversed-phase chromatography is preferably employed, utilizing a Waters Acquity UPLC BEH Cl 8 (2.1 mm x 100 mm x 1.7 pm) column as the stationary phase and using a mobile phase gradient starting with 95% A and 5% B (A= 0.1% formic acid in water, B= 0.1% formic

[0273] SSPU 2024 / 042 acid in acetonitrile) initially held for 1 minute. The mobile phase gradient is then increased to achieve 100% B over 13 minutes, held at 100% B for 2 minutes, followed by returning to the starting mobile phase ratio (95% A; 5% B) for the next 16.5 minutes. The column can be re-equilibrated at the starting mobile phase ratio (95% A and 5% B) for at least 3.5 minutes prior to the next sample analysis. The mobile phase flow rate is set to 0.350 mL min'1, the column temperature is maintained at 40 °C and the sample injection volume is set to 2 pL.

[0274] The total ion chromatogram (TIC) can be used to detect the presence of TFC membrane impurities in the recycled PSU product. When using the preferred sample preparation and UPLC-MS method as previously described, these TFC membrane impurities present in the recycled PSU product are detected in the retention time region of 7.0-9.0 minutes.

[0275] USE OF RECYCLED PSU PRODUCT

[0276] Another aspect of the present invention is directed to the use of the recycled PSU product according to the invention for making a polymer solution such as a dope solution and / or for manufacturing articles such as membrane, coating, tubing and / or piping.

[0277] POLYMER COMPOSITION

[0278] The present invention also concerns polymer compositions that include at least one recycled PSU product according to the invention and at least one other ingredient.

[0279] The polymer composition comprises advantageously more than 1 wt%, preferably more than 10 wt%, still more preferably more than 50 wt%, and the most preferably more than 90 wt%, said wt% being relative to the total weight of the composition, of the recycled PSU product according to the invention.

[0280] Such another ingredient can be one or more commercially available PPSU, PSU and / or PES polymers.

[0281] Such another ingredient can also be a polymer other than a sulfone polymer such as polyvinylpyrrolidone or a polyethylene glycol.

[0282] Such another ingredient can also be a non-polymeric ingredient such as a solvent, a filler, a lubricant, a mold release agent, an antistatic agent, a flame retardant, an anti-fogging agent, a matting agent, a pigment, a dye and an optical brightener.

[0283] Dope Solution

[0284] An example of such polymer composition is a dope polymer solution suitable for the preparation of membranes. A dope polymer solution is intended

[0285] SSPU 2024 / 042 to denote a polymer solution that is used to prepare a membrane, i.e. by casting, spinning, etc.

[0286] The dope solution for preparing a membrane preferably comprises the recycled PSU product according to the invention in a polar organic solvent.

[0287] Suitable polar organic solvents for the dope solution may be any of the polar aprotic solvent described herein for the reaction’s solvent. The polar organic solvent in the dope solution may be selected from a group consisting of 1,3- dimethyl-2-imidazolidinone, dimethylsulfoxide (DMSO), dimethylsulfone (DMSO2), diphenylsulfone, diethylsulfoxide, diethylsulfone, diisopropylsulfone, tetrahydrothiophene- 1, 1 -dioxide (commonly called tetramethylene sulfone or sulfolane), N-Methyl-2-pyrrolidone (NMP), N-butylpyrrolidone (NBP), N- ethylpyrrolidone (NEP), N,N-dimethylacetamide (DMAc), N,N'- dimethylpropyleneurea (DMPU), N,N-dimethylformamide (DMF), N- methylcaprolactame, N-ethylcaprolactame, tetrahydrothiophene- 1 -monoxide, dimethyl isosorbide, and mixtures thereof. The polar organic solvent in the dope solution may preferably be DMAc or NMP.

[0288] The overall concentration of the polar organic solvent in the dope solution may be at least 20 wt%, preferably at least 30 wt%, based on the total weight of the polymer solution. Typically the concentration of the solvent in the dope solution does not exceed 85 wt%; preferably, it does not exceed 75 wt%; more preferably, it does not exceed 70 wt%, more preferably, it does not exceed 65 wt%, most preferably, it does not exceed 60 wt% based on the total weight of the dope solution.

[0289] The overall concentration of the recycled PSU product according to the invention in the dope solution is preferably at least 8 wt%, more preferably at least 12 wt%, based on the total weight of the dope solution. Typically, the concentration of the recycled PSU product in the dope solution does not exceed 50 wt%; preferably, it does not exceed 40 wt%; more preferably, it does not exceed 30 wt%, based on the total weight of the dope solution.

[0290] Concentrations of the recycled PSU product ranging between 15 and 25 wt%, and more preferably between 16 and 22 wt%, with respect to the total weight of dope solution have been found particularly advantageous.

[0291] The polymer dope solution may further comprise at least one additional polymer distinct form the recycled PSU product described herein, for example a commercially available or non-recycled sulfone polymer, e.g., polysulfone (PSU), polyethersulfone (PES), poly(biphenyl ether sulfone) (PPSU), polyvinyl acetate,

[0292] SSPU 2024 / 042 polyvinyl alcohol, a polyphenylene sulfide (PPS), a poly(aryl ether ketone) (PAEK), e.g., a poly(ether ether ketone) (PEEK), a poly(ether ketone ketone) (PEKK), a poly(ether ketone) (PEK) or a copolymer of PEEK and poly(diphenyl ether ketone) (PEEK-PEDEK copolymer), a poly etherimide (PEI), and / or a polycarbonate (PC). The other polymeric ingredient can also include or be a polyvinylpyrrolidone and / or a polyethyleneglycol (PEG) having a molecular weight of at least 200 g / mol.

[0293] In such instances, the concentration of the at least one additional polymer and the recycled PSU product in the dope solution does not exceed 50 wt%; preferably, it does not exceed 40 wt%; more preferably, it does not exceed 30 wt%, based on the total weight of the dope solution.

[0294] The dope solution may comprise another ingredient such as glycerol, di ethylene glycol (DEG), and / or tri ethylene glycol (TEG).

[0295] For porous membranes, the dope solution may further comprise a poreforming agent, such as polyvinylpyrrolidone or a polyethylene glycol.

[0296] The dope solution may contain additional components, such as nucleating agents, fillers and the like.

[0297] The Applicant has surprisingly found that the recycled PSU product of the present invention or the polymer composition of the present invention as detailed above, exhibiting excellent properties which are useful in providing high performance polymeric membranes.

[0298] The dope solution of the present invention comprising the recycled PSU product of the present invention is preferably used for fabrication of membranes. ARTICLE

[0299] Another aspect of the present invention also concerns an article comprising the recycled PSU product of the present invention or the polymer composition as above described.

[0300] The recycled PSU product of the present invention may be used for the manufacture of membranes or a component thereof, coatings, films, sheets, and three-dimensional molded parts, in particular transparent or coloured parts.

[0301] Among applications of use wherein injection molded parts can be used, mention can be made of healthcare applications, in particular medical and dental applications, wherein shaped articles made from the recycled PSU product according to the present invention, can advantageously be used for replacing metal, glass and other traditional materials in single-use and reusable instruments and devices.

[0302] SSPU 2024 / 042 Particular shaped articles which comprise, or are made from, the recycled PSU product of the present invention may be selected from the group consisting of membranes, melt processed films, solution processed films, melt process monofilaments and fibers, solution processed monofilaments, hollow fibers and solid fibers, coatings, printed objects, and injection and compression molded objects.

[0303] The article may also be a food contact article such as a plumbing article such as a fitting, a valve, a manifold or a faucet, a food tray, a water bottle or a baby bottle, a cookware.

[0304] The article may also be an electronic part.

[0305] The article may also be a housing or cover for a mobile electronic device.

[0306] The article may also be a medical tray or an animal cage.

[0307] The recycled PSU product of the invention or the polymer composition of the present invention as detailed above may be also useful in optical applications. The article may also be optical articles such as notably sunglass lenses, eyeglass lenses, optical lenses, optical discs.

[0308] The recycled PSU product of the invention or the polymer composition of the present invention as detailed above may be also useful used for manufacturing sheets and films. These are particularly useful as specialized optical films or sheets, and / or suitable for packaging.

[0309] The recycled PSU product of the present invention and the polymer composition comprised in the article according to the present invention have the same characteristics respectively as the recycled PSU product of the present invention and the polymer composition according to the present invention, in all their embodiments, as above detailed.

[0310] Membrane (as article)

[0311] The article is preferably a membrane.

[0312] Membranes suitable for the purpose of the invention include, without limitation, isotropic or anisotropic membranes, porous or non-porous membranes, composite membranes, or symmetric or non-symmetric membranes. Such membranes may be in the form of flat structures, corrugated structures, (such as corrugated sheets), tubular structures, or hollow fibers. The membranes according to the present invention can be manufactured using any of the conventionally known membrane preparation methods, for example, by a solution casting or solution spinning method.

[0313] The article is more preferably a porous membrane.

[0314] SSPU 2024 / 042 Non limitative examples of membrane applications include water purification, wastewater treatment, pharmaceutical production, blood purification, in particular hemodialysis and a variety of industrial process separations, such as food and beverage processing, electropaint recovery and gas separation.

[0315] Particular preferred shaped articles which comprise, or are made from, the recycled PSU product of the present invention may be membranes being selected from membranes for bioprocessing and medical flitrations (such as hemodialysis membranes), membranes for food and beverage processing, membranes for water purification, membranes for waste water treatment, and / or membranes for industrial process separations involving aqueous media.

[0316] Among membranes, the recycled PSU according to the present invention is particularly suitable for manufacturing membranes intended for contact with an aqueous medium. The aqueous medium may include a biological fluid, such as whole blood or a blood product (e.g., serum, plasma), or a food product, such as beverages (e.g., fruit juice, milk, beer, wine).

[0317] From an architectural perspective, membranes comprising the recycled PSU may be provided in the form of flat structures (e.g. films or sheets), corrugated structures (such as corrugated sheets), tubular structures, or hollow fibers; as per the pore size is concerned, full range of membranes (non-porous and porous, including for microfiltration, ultrafiltration, nanofiltration, and reverse osmosis) can be advantageously manufactured with the recycled PSU, the pore distribution can be isotropic or anisotropic.

[0318] A membrane may be a microporous membrane that can be characterized by its average pore diameter and porosity, i.e., the fraction of the total membrane that is porous.

[0319] The membrane may have a gravimetric porosity (%) of from 20 to 90 % and comprises pores, wherein at least 90 % by volume of the said pores has an average pore diameter of less than 5 pm. Gravimetric porosity of the membrane is defined as the volume of the pores divided by the total volume of the membrane.

[0320] Membranes having a uniform structure throughout their thickness are generally known as symmetrical membranes; membranes having pores that are not homogeneously distributed throughout their thickness are generally known as asymmetric membranes. Asymmetric membranes are characterized by a thin selective layer (0.1-1 pm thick) and a highly-porous, thick layer (100-200 pm

[0321] SSPU 2024 / 042 thick) which acts as a support and has little effect on the separation characteristics of the membrane.

[0322] Membranes can be in the form of a flat sheets or the form of tubes.

[0323] A membrane may be formed using a plurality of films or fibers.

[0324] Tubular membranes are classified based on their dimensions in tubular membranes having a diameter greater than 3 mm; capillary membranes, having a diameter comprised between 0.5 mm and 3 mm; and hollow fibers having a diameter of less than 0.5 mm. Capillary membranes are otherwise referred to as hollow fibers.

[0325] Hollow fibers are particularly advantageous in applications where compact modules with high surface areas are required.

[0326] The membrane, fiber, or film according to the present invention can be manufactured using any of the conventionally known membrane, fiber, or film preparation methods.

[0327] A membrane or film according to the present invention may be prepared by a phase inversion method occurring in a liquid phase, said method comprising the following steps: preparing a polymer solution comprising the recycled PSU described herein and a polar solvent, processing said polymer solution into a film; and contacting said film with a non-solvent bath.

[0328] The membranes according to the present invention can be manufactured using any of the conventionally known membrane preparation methods, for example, by a solution casting or solution spinning method.

[0329] Preferably, the membranes according to the present invention are prepared by a phase inversion method occurring in the liquid phase, said method comprising the following steps:

[0330] (i) preparing a dope solution comprising the recycled PSU product described herein and a polar solvent,

[0331] (ii) processing said dope solution into a film;

[0332] (iii) contacting said film with a non-solvent bath.

[0333] The membrane of the present invention may comprise the recycled PSU product described herein in an amount of at least 1 wt%, for example at least 5 wt%, at least 10 wt%, at least 15 wt%, at least 20 wt%, at least 25 wt%, or at least 30 wt%, based on the total weight of the membrane.

[0334] The membrane of the present invention may comprise the recycled PSU product described herein in an amount of more than 50 wt%, for example more than 55 wt%, more than 60 wt%, more than 65 wt%, more than 70 wt%, more than

[0335] SSPU 2024 / 042 75 wt%, more than 80 wt. %, more than 85 wt%, more than 90 wt%, more than 95 wt% or more than 99 wt%, said wt% being based on the total weight of the membrane.

[0336] According to an embodiment, the membrane of the present invention may comprise the recycled PSU product described herein in an amount ranging from 1 wt% to 99 wt%, for example from 3 wt% to 96 wt%, from 6 wt% to 92 wt% or from 12 wt% to 88 wt%, said wt% being based on the total weight of the membrane.

[0337] The membrane of the present invention may further comprise at least one polymer distinct from the recycled PSU product described herein, for example another commercially available or non-recycled sulfone polymer, e.g., poly sulfone (PSU), polyethersulfone (PES), poly(biphenyl ether sulfone) (PPSU), polyvinyl acetate, polyvinyl alcohol, a polyphenylene sulfide (PPS), a poly(aryl ether ketone) (PAEK), e.g., a poly (ether ether ketone) (PEEK), a poly (ether ketone ketone) (PEKK), a poly(ether ketone) (PEK) or a copolymer of PEEK and poly(diphenyl ether ketone) (PEEK-PEDEK copolymer), polyetherimide (PEI), and / or polycarbonate (PC). The other polymeric ingredient can also be polyvinylpyrrolidone and / or polyethylene glycol.

[0338] The membrane may also further comprise at least one non-polymeric ingredient such as a solvent, a filler, a lubricant, a mold release, an antistatic agent, a flame retardant, an anti -fogging agent, a matting agent, a pigment, a dye and / or an optical brightener.

[0339] A suitable example of a method for forming a membrane from a poly(aryl ether sulfone) polymer is described in US2019 / 054429A1 by Solvay Specialty Polymers USA (SYENSQO group), incorporated herein by reference.

[0340] EXAMPLES

[0341] The invention will now be described with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the invention. As used in the Examples, “E” denotes an example embodiment of the present invention and “CE” denotes a counter-example.

[0342] The following examples demonstrate the unexpected merits of the invented process and of the recycled PSU product.

[0343] Raw Materials

[0344] All solvents used in the examples were sourced from Sigma Aldrich.

[0345] Activated charcoal was sourced from Spectrum.

[0346] SSPU 2024 / 042 TFC-PA RO membranes in the following examples were from two different suppliers, one a manufacturer of RO membranes and the other, an end user. For end-of-life TFC RO membranes, the TFC membrane was autoclaved before any of the procedures below is carried out.

[0347] Polysulfone PSU Udel® P-3500 LCD MB7 and Udel® 1700NT PSU are commercially available from Solvay Specialty Polymers (SYENSQO group).

[0348] Polysulfone PSU Ultrason® S6010 is commercially available from BASF.

[0349] Methods for Analysis

[0350] Gel Permeation Chromatography (GPC) to measure Mw, Mn, PSI, cyclic dimers content of PSU product:

[0351] The molecular weights (number average molecular weight Mn and weight average molecular weight Mw) were measured by gel permeation chromatography (GPC), using methylene chloride as a mobile phase. Two 5 pl mixed D Size Exclusion Chromatography (SEC) columns with guard column from Agilent Technologies were used for separation. An ultraviolet detector of 254 nm was used to obtain the chromatogram. A flow rate of 1.5 mL / min and injection volume of 20 pL of a 0.2 w / v% solution in mobile phase was selected. Calibration was performed with 10 or 12 narrow molecular weight polystyrene standards from Agilent Technologies (Peak molecular weight range: 371,000 to 580 g / mol).

[0352] CIE Color Measurements to measure Yellow Index in PSU solution:

[0353] Solution color was measured using an X-rite Ci7800 spectrophotometer equipped with a pulsed xenon lamp. The software Color IQC Software program was used to the color data. The recovered PSU sample was prepared in HPLC grade NMP at a 5 wt% polymer concentration in a Stama Colorimeter cell with a 10 mm path length and 25 mL volume size.

[0354] Gas Chromatography (GC) Method to measure Residual Monomer content (BPA, DCDPS) in PSU product:

[0355] The residual monomers content (BPA and DCDPS) was quantified using a Hewlett-Packard 6890 gas chromatography system with an FID detector and Restek RTX-5MS, 30 m, 0.25 mm I.D., 0.25 urn film thickness capillary column. Polysulfone was dissolved into chloroform at 5 wt% and mixed for 30 minutes. The sample was put into a GC vial and added to a Hewlett Packard auto-sampler. The injection volume was 2 pL with a 3:1 split ratio. The temperature ramp program started with an initial temperature of 35 °C, hold for 1 minute, then a 20 °C / min ramp to 325 °C and then hold for 10 minutes. The injection port

[0356] SSPU 2024 / 042 temperature is 290 °C and detection temperature is 300 °C. The instrument was calibrated with BPA and DCDPS standards.

[0357] Example 1:

[0358] Preliminary PSU extraction tests were performed on fresh TFC-PA RO membranes of Supplier 1 using dissolution, filtration and coagulation according to the following Procedure 1 on a small scale in order to determine optimal extraction conditions at a temperature of at most 125 °C down to 30 °C (mild temperature condition).

[0359] Procedure 1 (dissolution, filtration and coagulation):

[0360] A thin-film composite (TFC) reverse-osmosis (RO) membrane module was dismantled and the TFC RO membrane was removed. The TFC RO was in form of sheets and consisted of PET-PSU-PA layers. The sheets were then shredded using a paper shredder into strips that were smaller than 13 cm (ca. 5 inches). The shredded TFC strips were added into a solvent [see solvent selection in Table 2] using different weight ratios of solvent / TFC strips: 6:1, 10:1 and 20:1. The strips were stirred in the solvent for a time period of 30 min or 1 hour with an overhead stirrer at a temperature selected from 125 °C to 30 °C to dissolve at least some of the PSU from the PSU layer and to generate a solution. The solution was then filtered to remove solids containing the solid PET and PA layers. The dissolution and filtration steps were repeated until the content of PSU in the solution was at least 5% by weight. The PSU solution was then coagulated into a non-solvent (methanol) bath using a methanol / solution volumetric ratio of 4 / 1 v. / v., and then the coagulated PSU was washed with methanol four times. The washed coagulated PSU was filtered and dried at 120 °C for 14 hours to obtain a recycled PSU product.

[0361] The PSU extractions were performed in following tests A to K. The conditions (choice of solvent, ratio of solvents when used, solvent weight, total weight of TFC membrane, time and temperature for dissolution, overall PSU yield) are provided in Table 2.

[0362] The overall PSU yield was calculated based on the presence of 25 wt% of initial PSU content in the TFC membranes In some cases, the TFC pieces were extracted a second time with the same amount of solvent.

[0363] In Table 2, the following abbreviations are used:

[0364] DMAc: dimethylacetamide;

[0365] DMF : dimethylformamide;

[0366] DMSO: dimethylsulfoxide;

[0367] MCB: monochlorobenzene;

[0368] SSPU 2024 / 042 NMP: N-methyl-2-pyrrolidone;

[0369] DMSO / MCB : a blend of DMSO and MCB.

[0370] Based on these preliminary tests, it was noted that the PSU dissolution was not improved at a temperature above 40°C. It was noted that the extractions with the pure solvents generated colored solutions from brownish to brownish-orange, and it was observed that the higher temperatures cause more color in the solutions.

[0371] The extraction (dissolution and filtration) of PSU with the blend of 25:75 v:v DMSO / MCB provided a consistent overall yield of 60-63% using a mild temperature (30°C - 40°C) at 1 hour and a 10: 1 weight ratio of solvent: TFC pieces.

[0372] Table 2. Small scale PSU extraction results membrane

[0373] Examples 2- 9:

[0374] The following Examples 2-9 were used to demonstrate the difference in colored impurities between a polar solvent extraction versus a solvent mixture with a nonpolar solvent, as well as recovering PSU using 3 different procedures:

[0375] - dissolution and coagulation (Procedure 1),

[0376] - dissolution, color removal and coagulation (Procedure 2), and

[0377] - dissolution, 1stcoagulation, color removal, and 2ndcoagulation (Procedure 3).

[0378] Example 2:

[0379] SSPU 2024 / 042 In this example, PSU was recovered from end-of-life (autoclaved) TFC RO membranes of Supplier 2 using dissolution, filtration and coagulation similarly to Procedure 1 used in Example 1, except that the conditions were altered slightly due to DMF’s ability to solubilize PSU at higher concentrations at room temperature.

[0380] The used (autoclaved) TFC RO membranes were shredded and added to 500 g of DMF using 25 g of TFC membrane pieces per extraction. The mixture (membrane pieces + solvent) was gently mixed with an overhead stirrer for one hour at room temperature (about 20°C). Afterward, the solids (insolubles) were filtered off using a coarse glass fiber filter to collect a filtrate containing PSU. The PSU extraction (dissolution and filtration) was repeated using the filtrate solution obtained from one extraction to dissolve more membrane pieces in a subsequent extraction until a PSU concentration of approximately 5 wt% was achieved (after a total of 6 extractions). For atotal of 6 extractions, 150 g of TFC membrane pieces were used. Next, the PSU solution obtained after the last (6th) extraction was coagulated into methanol (non-solvent) using amethanol / solution volumetric ratio of 4 / 1 v. / v.. The coagulated solid was filtered off and then washed with methanol four times to remove DMF. Finally, the washed white / powdery PSU was dried in an oven at 120 °C for 12 hours. A total of 7.5 g of recycled PSU product was isolated.

[0381] The characteristics of the recycled PSU product (CIE data, GPC data) obtained in Example 2 can be found in Tables 3 and 4, respectively.

[0382] Example 3:

[0383] In this example, the same procedure was used as described in Example 2 to recover PSU from 150 g of membrane pieces of the same used (autoclaved) TFC RO membranes of Supplier 2, except that 500 g of NMP was used instead of 500 g of DMF until a PSU concentration of approximately 5 wt% was achieved after 6 extractions (25 g of TFC membrane pieces per extraction). The PSU solution obtained after the last (6th) extraction was coagulated into methanol (nonsolvent) using a methanol / solution volumetric ratio of 4 / 1 v. / v.. The coagulated solid was recovered by filtration and then washed with methanol four times to remove NMP. Finally, the washed white / powdery PSU solid was dried in an oven at 120 °C for 12 hours. A total of 14.6 g of recycled PSU product was isolated.

[0384] The characteristics of the recycled PSU product (CIE data, GPC data) obtained in Example 3 can be found in Tables 3 and 4, respectively.

[0385] SSPU 2024 / 042 Example 4:

[0386] In this example, the same procedure was used as described in Example 2 to recover PSU from 150 g of membrane pieces of the same end-of-life (autoclaved) TFC RO membranes of Supplier 2, except that 500 g of a 25 / 75 v / v NMP / MCB blend (solvent (SI)) was used instead of 500 g of DMF until a PSU concentration of approximately 5 wt% was achieved after 6 extractions (using 25 g of TFC membrane pieces per extraction). The PSU solution obtained after the last (6th) extraction was coagulated into methanol (non-solvent) using a methanol / solution volumetric ratio of 4 / 1 v. / v.. The coagulated solid was recovered by filtration and then washed with methanol four times to remove the solvent blend. Finally, the washed white / powdery PSU solid was dried in an oven at 120 °C for 12 hours. A total of 13.1 g of recycled PSU product was isolated.

[0387] The characteristics of the recycled PSU product (CIE data, GPC data) obtained in Example 4 can be found in TABLES 3 and 4, respectively.

[0388] Example 5:

[0389] In this example, the same procedure was used as described in Example 2 to recover PSU from 150 g of membrane pieces of the same used (autoclaved) TFC RO membranes of Supplier 2, except that 500 g of a 25 / 75 v / v DMSO / MCB blend (solvent (SI)) was used instead of 500 g of DMF until a PSU concentration of approximately 5 wt% was achieved after 6 extractions (25 g of TFC membrane pieces per extraction). The PSU solution obtained after the last (6th) extraction was coagulated into methanol (non-solvent) using a methanol / solution volumetric ratio of 4 / 1 v. / v.. The coagulated solid was recovered by filtration and then washed with methanol four times to remove the solvent blend. Finally, the washed white / powdery PSU solid was dried in an oven at 120 °C for 12 hours. A total of 16.5 g of recycled PSU product was isolated.

[0390] The characteristics of the recycled PSU product (CIE data, GPC data) obtained in Example 5 can be found in TABLES 3 and 4, respectively.

[0391] Example 6 :

[0392] In this example, the following Procedure 3 was used to recover PSU from fresh (not-used) TFC RO membranes of Supplier 1 using dissolution, 1stcoagulation, color removal, and 2ndcoagulation.

[0393] Procedure 3 (dissolution, 1stcoagulation, color removal, and 2ndcoagulation)'.

[0394] A fresh (not-used) thin-film composite (TFC) reverse-osmosis (RO) membrane module was dismantled and the TFC RO membrane was removed. The

[0395] SSPU 2024 / 042 fresh (not-used) TFC RO was in form of sheets and consisted of PET-PSU-PA layers. The fresh (unused) TFC RO membranes were shredded and added to 1000 grams of a solvent (SI) consisting of a 25 / 75 v / v DMSO / MCB blend using 50 g membrane pieces per extraction (successive steps of PSU dissolution and filtration). The mixture (membrane pieces + solvent (SI)) was gently mixed with an overhead stirrer for one hour at room temperature (about 20°C). Afterward, the solids were filtered off using a coarse glass fiber filter to collect a filtrate containing PSU. The PSU extraction (dissolution and filtration) was repeated using the filtrate solution obtained from an extraction to dissolve more membrane pieces in a subsequent extraction until a PSU concentration of approximately 5 wt% was achieved in the final PSU solution (after a total of 6 extractions using a total of 300 g of TFC membrane pieces). The PSU solution obtained after the last (6th) extraction was coagulated into methanol (non-solvent) using a methanol / solution volumetric ratio of 4 / 1 v. / v.. The coagulated solid was recovered by filtration and then washed with methanol four times to remove the solvent blend. Finally, the washed white / powdery PSU was dried in an oven at 120 °C for 14 hours.

[0396] Next, the dried PSU was redissolved into a 25 / 75 v / v DMSO / MCB mixture to achieve a solution having a content of 10 wt% PSU. Activated charcoal (AC) in the form of a powder was added to the 10 wt% PSU solution to achieve an AC loading of 2 wt% AC based on the total weight of solution The resulting slurry (AC + solution) was stirred and heated at 80 °C for 3 hours. Afterward, the activated charcoal was filtered off, and the filtrate (treated PSU solution) was coagulated into methanol (non-solvent), and washed with methanol (4 times). Finally, the coagulated white / powdery PSU was dried in an oven at 120 °C for 12 hours. A total of 39.5 g of recycled PSU product was isolated for a 53% yield.

[0397] The characteristics of the recycled PSU product (CIE data, GPC data, GC data) obtained in Example 6 can be found in Tables 3, 4 and 5, respectively.

[0398] Example 7:

[0399] In this example, the following Procedure 2 was used to recover PSU from fresh (not-used) TFC RO membranes of Supplier 1 using dissolution, color removal and coagulation).

[0400] Procedure 2 (dissolution, color removal and coagulation) '.

[0401] The fresh (unused) TFC RO membranes of Supplier 1 were shredded and added to 1000 g of a solvent (SI) consisting of a 25 / 75 v / v DMSO / MCB mixture at 50 g TFC membrane pieces per extraction. The mixture (membrane pieces +

[0402] SSPU 2024 / 042 solvent (SI)) was gently mixed with an overhead stirrer for one hour at room temperature (about 20°C). Afterward, the solids were filtered off using a coarse glass fiber filter to collect a filtrate containing PSU. The PSU extraction (dissolution and filtration) was repeated using the filtrate solution obtained from an extraction to dissolve more membrane pieces in a subsequent extraction until a PSU concentration of approximately 5 wt% was achieved (after a total of 6 extractions for a total of 300 g of membrane pieces). Next, activated charcoal (AC) in the form of a powder was added to the last PSU solution obtained after 6 extractions to achieve a loading of 4 wt% AC based on the total weight of solution. The resulting slurry (AC + solution) was stirred and heated at 80 °C for 3 hours. Afterward, the activated charcoal was filtered off. The filtrate (treated PSU solution) was coagulated into methanol (non-solvent) and washed with methanol (4 times). Finally, the coagulated white / powdery PSU was dried in an oven at 120 °C for 12 hours. A total of 38.8 g of recycled PSU product was isolated for a yield of 52%.

[0403] The characteristics of the recycled PSU product (CIE data, GPC data, GC data) obtained in Example 7 can be found in Tables 3, 4 and 5, respectively.

[0404] Example 8:

[0405] In this example, the same procedure was used as described in Example 7 to recover PSU, except that 300 g of shredded used (autoclaved) TFC RO membranes of Supplier 2 were used. A total of 34.5 g of recycled PSU product was isolated for a yield of 46%.

[0406] The characteristics of the recycled PSU product (CIE data, GPC data, GC data) obtained in Example 8 can be found in Tables 3, 4 and 5, respectively.

[0407] Example 9:

[0408] In this example, a recycled PSU product was recovered using dissolution, color removal and coagulation (Procedure 2} from end-of-life (autoclaved) TFC- PA RO membranes of Supplier 2. The same procedure was used as described in Example 7 to recover PSU, except at a larger scale in that 2000 g of a solvent (SI) consisting of a 25 / 75 v. / v. DMSO / MCB blend were used, and 600 g membrane pieces were used (100 g per extraction) for a total of 6 extractions.

[0409] A total of 67.5 g of recycled PSU product was isolated for an overall yield of 45%. The characteristics of the recycled PSU product (CIE data, GPC data, GC data) obtained in Example 9 can be found in Tables 3, 4 and 5, respectively.

[0410] SSPU 2024 / 042 The detection of impurities originating from the TFC membrane was carried out for the recycled PSU product obtained in this example using LC-MS, as shown in Example 10.

[0411] As shown in Example 11, a membrane was made using the recycled PSU product of Example 9 and is characterized in Example 12.

[0412] Characteristics of recycled PSU products

[0413] The characteristics of the recycled PSU product (CIE data, GPC data, GC data) obtained in Examples 2 to 9 can be found in Tables 3, 4 and 5, respectively.

[0414] Table 3: CIE color coordinates and yellowness index in NMP at 5 wt% recovered PSU.

[0415] (a) CIE D65: A standard illuminant that simulates average daylight with a color temperature of approximately 6,500 K, and “10” refers to the 10° standard observer, a measurement condition that approximates how humans perceive color, which differs slightly from the 2° observer; (b) L* represents lightness, ranging from 0 (black) to 100 (white);

[0416] (c) a*represents the red-green axis in which positive values are red, and negative values are green;

[0417] (d) represents the yellow-blue axis in which positive values are yellow and negative values are blue;

[0418] SSPU 2024 / 042 (e) h° represents the hue angle, representing the color's position on a circle (e.g., 0° is red, 90° is yellow, 180° is green, 270° is blue);

[0419] (f) C* is the chroma, representing the saturation or intensity of the color;

[0420] (g)ASTM E313-20 is a standard for calculating yellowness and whiteness indices from instrumentally measured CIE color coordinates.

[0421] Table 4: GPC data for Recycled PSU from Examples 2-9

[0422] Table 5: GC data : residual content in combined BPA and DCDPS (monomer concentration).

[0423] Example 10 Ultra-performance liquid chromatography (UPLC) operating at ultra-high pressure with high resolution mass spectrometry (HRMS) detector was used for the separation and detection of TFC membrane impurities in PSU product.

[0424] UPLC-MS Method

[0425] An ultra-performance liquid chromatography-mass spectrometry (UPLC- MS) analysis was carried out on the recycled PSU product obtained in Example 9 and compared with the two commercially-available PSU samples.

[0426] To prepare the samples to be analyzed by UPLC-MS, each PSU (solid form) was dissolved inNMP at room temperature to obtain a 15 wt% PSU solution. Each

[0427] SSPU 2024 / 042 PSU solution was then coagulated into a non-solvent mixture of methanol and acetone (80 v. / 20 v.) using a volumetric ratio of non-solvent to PSU solution of 2:1 (v:v). The precipitated PSU polymer was then removed via filtration and the filtrate in NMP was collected. Each filtrate in NMP served as the sample which was analyzed by UPLC-MS.

[0428] Reversed-phase chromatography was employed, utilizing a Waters Acquity UPLC BEH C18 (2.1 mmx 100 mmx 1.7 pm) column as the stationary phase and using a mobile phase gradient starting with 95% A and 5% B (A= 0.1% formic acid in water, B= 0.1% formic acid in acetonitrile) initially held for 1 minute. The mobile phase gradient was then increased to achieve 100% B over 13 minutes, held at 100% B for 2 minutes, followed by returning to the starting mobile phase ratio (95% A; 5% B) for the next 16.5 minutes. The column was re-equilibrated at the starting mobile phase ratio for 3.5 minutes prior to the next sample analysis for a total sample analysis time of 20 minutes. The mobile phase flow rate was set to 0.350 mL min'1, the column temperature was maintained at 40 °C and the sample injection volume was set to 2 pL.

[0429] The total ion chromatogram (TIC) was used to locate the impurities originating from the TFC membrane. The TIC for the 3 analyzed samples are provided in FIG. 8 (recycled PSU obtained in Example 9), FIG. 9 (PSU Udel® P-3500 LCD MB7) and FIG. 10 (PSU Ultrason® S6010). These impurities originating from the TFC membrane were found in the retention time region of 7.0-9.0 minutes (see various peaks in the region A in FIG. 8), and these impurities were observed only in the PSU obtained in Example 9.

[0430] Example 11: Preparation of porous membranes made from polymeric solutions comprising 16 wt% of PSU polymer

[0431] Raw Materials

[0432] • DMF (N,N-dimethylformamide) obtained from Sigma- Aldrich

[0433] • PSU (polysulfone) Udel® P-3500 LCD MB7 obtained from Solvay Specialty Polymers (Syensqo group)

[0434] • Recycled PSU (poly sulfone) from Example 9

[0435] • PVP K90 (polyvinylpyrrolidone K90) obtained from Sigma-Aldrich

[0436] • BSA (bovine serum albumin) from Sigma-Aldrich

[0437] • Phosphate buffered saline P4417 from Sigma-Aldrich Solution preparation for membrane manufacturing

[0438] Dope polymeric solution to make porous membranes was prepared by dissolving the recycled PSU polymer described in Example 9, in DMF and stirring

[0439] SSPU 2024 / 042 with a magnetic stirrer at 65°C. The polymeric solution of PSU polymer was 16 wt%, said wt% being relative to the combined weights of PSU polymer + DMF. The solution (100 grams) was made by stirring the PSU polymer and DMF solvent, so as to contain 16 wt% PSU + 84 wt% DMF.

[0440] Additionally, a reference polymeric solution was made with commercial PSU Udel® P-3500 LCD MB7 (Solvay Specially Polymers, SYENSQO group) for making comparative membranes using the same amount of PSU and DMF. Porous membrane preparation

[0441] A4 size flat sheet porous membranes were prepared by filming 20 grams of a polymeric dope solution (polymer + solvent) as described above, over a suitable smooth glass support by means of an automatized casting knife.

[0442] Membrane casting was performed by holding dope solutions, the casting knife and the support temperatures at 25°C. The knife gap was set to 200 pm. After casting, the polymeric porous films were immediately immersed in a coagulation bath at 20°C in order to induce phase inversion. The coagulation bath consisted of pure de-ionized water. After coagulation the porous films (membranes) were washed several times in pure water during several days to remove residual traces of solvent. The membranes were stored (wet) in water.

[0443] Table 6 provides the compositions of the polymeric solutions used to make membrane samples.

[0444] Table 6

[0445] Example 12. Properties of porous membranes

[0446] Methods

[0447] Thickness measurement on wet membrane

[0448] Thickness was measured on wet membranes by using ABSOLUTE Digimatic Thickness Gauges provided by Mitutoyo. The thickness of each flat membrane was the average of at least 5 measures on different positions.

[0449] Permeability measurements on flat membrane

[0450] SSPU 2024 / 042 Water flux (J) through each membrane at given pressure, was defined as the volume which permeates per unit area and per unit time. The flux was calculated with the following equation:

[0451] V

[0452] J =

[0453] A fit wherein:

[0454] - V (L) is the volume of permeate,

[0455] - A (m2) is the membrane area, and

[0456] - At (h) is the operation time.

[0457] Water flux measurements were conducted at room temperature using a dead-end configuration system under a constant nitrogen pressure of 1 bar using pure MilliQ water. Membrane discs with an effective area of 11.3 cm2were cut from the membrane sheets (stored in water) and placed on a metal plate. For each sample, the flux was the average of measurements obtained on at least three different discs. The flux was expressed in LMH (liters / square meter x hour or L / m2h).

[0458] Each permeability test was carried out by applying pressure for 30 minutes on wet membranes which were previously stored in water.

[0459] Rejection testing

[0460] A person skilled in the art of membrane manufacturing may correlate an increased permeate flow to an increase of the dimensions of the pores. Membrane rejection tests were performed by measuring the retention of the membranes of specific molecules (bovine serum albumin (“BSA”) or PVP k90) with well- defined dimensions.

[0461] Rejection measurement method:

[0462] A dead-end stirred cell filtration system was designed to characterize the filtration performance of membranes. The system consisted of a 180-ml filtration cell (model 8200, Amicon, W.R. Grace, Beverly, MA). All filtration experiments were conducted at a constant driven pressure of 1 bar (by N2 gas line) and a stirring rate of 200 rpm at room temperature with :

[0463] - a feed of 0.1 g / L bovine serum albumin (BSA) in phosphate buffered saline

[0464] (PBS) at pH 7.4; or

[0465] - a feed of 0.1 g / L PVP K90 in deionized water.

[0466] The permeate flux was calculated by gravimetric method versus time considering a membrane sample area equal to 26.41 cm2. All the rejection % values referred to the sampling after the first 7.5 minutes.

[0467] SSPU 2024 / 042 Gravimetric porosity method on porous membranes:

[0468] 1. Gravimetric porosity of a porous membrane is defined as the volume of the pores divided by the total volume of the membrane.

[0469] 2. Membrane porosity (E) was determined according to the gravimetric method detailed below.

[0470] 3. Perfectly dry membrane pieces were weighed and impregnated in isopropyl alcohol (IPA) for 24h. After this time, the excess of the liquid was removed with tissue paper, and membrane weight was measured again. The porosities were measured using IPA (isopropyl alcohol) as wetting fluid according to the procedure described in Appendix of the article by Smolders & Franken entitled “Terminology for Membrane Distillation . in Desalination, vol. 72 (1989) pp. 249-262. where ‘Wet’ is the weight of the wetted membrane, ‘Dry’ is the weight of dry membrane, pPolymer is the density of PSU (1.37 g / cm3) and piiquid is the density of IPA (0.78 g / cm3).

[0471] Pure water flux (at 1 bar), wet membrane thickness, gravimetric porosity, BSA rejection and PVP K90 rejection are reported in TABLE 7.

[0472] T able 7. Properties of membranes

[0473] Example 13

[0474] The inventors have found that polar organic solvents which are typically used to dissolve PSU, particularly NMP, DMSO, DMAc, or DMF, did not result

[0475] SSPU 2024 / 042 in a good outcome for PSU recovery from a TFC-PA membrane when used during the contacting step (a) in preliminary tests.

[0476] The solutions obtained after filtration in step (b) were highly colored (brown to brownish orange) and it was apparent that several polymeric materials, namely PSU and PA, were dissolved in the solutions. However the color of the filtrate was more or less intense depending on the single polar solvents used, NMP and DMF being the worst.

[0477] The inventors have thus realized that the typical solvents NMP, DMSO, DMAc, DMF used to dissolve PSU also dissolve some of the PA from the thin selective layer.

[0478] On the other end, a 25:75 v / v blend of DMSO with a non-polar solvent, monochlorobenzene (MCB) 25:75 v / v not only was found to be more efficient in recovering PSU and also led to less color in the dissolved PSU.

[0479] Because a non-polar organic solvent or a blend of non-polar solvents is not compatible with the subsequent step (c) for PSU recovery which relies on the coagulation of the PSU solution with a polar non-solvent (water and / or C1-C5 alcohol), the selection of the solvent (SI) needed to be studied for the selective dissolution of PSU without dissolution of PA and PET.

[0480] However in view of the numerous possible options for solvent blends, it was decided to perform a Hansen parameter sphere evaluation as it should be particularly useful to better predict the solvent blend space for very good solubility of PSU and very low / no solubility of PA without the need for extensive empirical testing.

[0481] The Hansen Solubility Parameters (HSP) developed by Charles Hansen in 1967 provide a method to predict the compatibility of solvents and polymers by considering the contributions from dispersion forces, polar forces, and hydrogen bonding. The HSP are represented by three parameters: 6D (dispersion), 6P (polar), and 6H (hydrogen bonding). These parameters can be visualized in a three-dimensional space, often referred to as the Hansen space.

[0482] The evaluation of a polymer's solubility or compatibility with a solvent using the Hansen Solubility parameters involves comparing the distance (Ra) between the polymer's and the solvent's position in the Hansen space. This distance Ra is calculated using the differences in their respective 6D, 6P, and 6H values according to Equation 1 : Ra2=4(6Ds-6Dp)2+(6Ps-6Pp)2+(6Hs-6Hp)2Equation 1

[0483] SSPU 2024 / 042 wherein, in Equation 1,

[0484] • Ra is a Hansen solubility parameter distance (expressed in MPa1 2),

[0485] • 6Ds is a dispersion energy parameter (expressed in MPa1 / 2) for the solvent,

[0486] • 6Dpis a dispersion energy parameter (expressed in MPa1 / 2) for the polymer,

[0487] • 6Ps is a polar-dipolar energy parameter (expressed in MPa1 / 2) for the solvent,

[0488] • 6Pp is a polar-dipolar energy parameter (expressed in MPa1 / 2) for the polymer,

[0489] • 6Hs is a hydrogen bonding energy parameter (expressed in MPa1 / 2) for the solvent, and

[0490] • 6Hp is a hydrogen bonding energy parameter (expressed in MPa1 / 2) for the polymer.

[0491] The RED value (Relative Energy Distance) is a normalized form of the distance (Ra) and is calculated according to Equation 2:

[0492] RED = Ra / Ro Equation 2 where Ro is the radius of the Hansen sphere for the polymer (either PSU or PA), representing the limit of solubility. Solvents with RED < 1 shall then be good solvents of the considered polymer.

[0493] To estimate the RED value for a specific polymer in a solvent, the Hansen parameters (6D, 6P, 6H) are needed for both the polymer and the solvent, as well as the polymer's solubility radius Ro. With these values, the distance (Ra) and subsequently the RED value can be calculated to assess the compatibility or solubility of the polymer in the solvent.

[0494] Determination of HSP sphere radius Ro for PSU

[0495] The sphere parameters (6D, 6P, 6H and Ro) for the PSU were determined experimentally on two commercial PSU products: Udel® 1700NT PSU and Udel® 3500 NT LCD from Syensqo Specialty Polymers USA.

[0496] In 8-ml vials, an amount of PSU was placed in 1 mL of a solvent to achieve a concentration of 50 mg / ml, 200 mg / ml or 500 mg / ml. each sample was stirred for 24 hours at room temperature (25 °C), for 4 hours at 50 °C and for 4 hours at 80 °C.

[0497] The list of 48 solvents (see Table 7) used to determine the HSP of PSU by solubility tests is similar to the list reported in Table (SI) of the supporting information document available at https: / / pubs.acs.org / doi / 10.1021 / acs.langmuir.0c01312 for the article by Laurens, Julien, et al. "Competitive adsorption between a polymer and solvents onto silica." Langmuir 36.26 (2020): 7669-7680.

[0498] SSPU 2024 / 042 Table 7. List of solvents used to characterize HSP data for PSU

[0499] SSPU 2024 / 042

[0500] Then visual observations were recorded on a scale of 1 to 6 being as follows:

[0501] 1: perfect vial without grain

[0502] 2: vial with 2 / 3 grains at the bottom

[0503] 3: vial with some grains at the bottom and on the walls

[0504] 4: vial with a bit of muddy powder at the bottom 5: vial with a lot of muddy powder at the bottom 6: no solubilization at all

[0505] The HSP data (6D, 6P, 6H and Ro) for the PSU are reported in Table 8 below. Determination of HSP sphere radius Ro for PA

[0506] The HSP sphere parameters (6D, 6P, 6H and Ro) for the crosslinked PA were extracted from a 2023 paper by Shin, “Solvent transport model for polyamide nanofilm membranes based on accurate Hansen solubility parameters'’'’, Journal of Membrane Science 674 (2023) 121505. This paper describes the determination method for accurate Hansen solubility parameters for PA based on swelling (membranes fabricated by forming an ultrathin, crosslinked PA permselective layer through the interfacial polymerization (IP) of difunctional amine (e.g., m-phenylenediamine [MPD]) and trifunctional acyl chloride (e.g., trimesoyl chloride [TMC]) monomers on a porous support).

[0507] The HSP data (6D, 6P, 6H and Ro) for the crosslinked PA are shown in Table 8 below.

[0508] SSPU 2024 / 042 Table 8. HSP data (6D, 6P, 6H and Ro) for PSU and crosslinked PA

[0509] Determination of solubility for non-woven PET

[0510] The solubility of non-woven PET was evaluated with the same 48 standard solvents provided in TABLE 7 and additionally two blends of DMSO / MCB (50:50, 25:75 v:v) in a 1-ml solvent sample using a 1cm2non-woven PET paper available from Hirose Paper Mfg Co. (product name: 05™-100, having a thickness of 162 microns and a surface weight of 98 g / m2

[0511] The solubility test conditions were 1 w / w% for 24 hours under agitation at 24 hours, at ambient temperature, then 4h at 50°C and 4h at 80°C.

[0512] For all of the 48 solvents tested and the two DMSO / MCB blends, the scores were 6.

[0513] Experimentally, there were no good solvents for PET, and the visual observations indicated no swelling or any impact on the PET paper, whatever the temperature level.

[0514] Determination of RED(PSU) and RED(PA) for pure solvents

[0515] The RED(PSU) and RED(PA) were calculated as follows: 1 / determining the Ra value based on Equation 1 using the HSP data (6D, 6P, 6H) for each pure solvent and 2 / determining their respective RED values for PSU and PA based on Equation 2 using the respective Ro for PSU and PA (see Table 8) for the following pure solvents including green solvents. The results for 6D, 6P, 6H (all in MPa1 2), RED(PSU) and RED(PA) are shown in Table 9.

[0516] These results confirmed that while DMSO, DMF, NMP, DMAC are good solvents for PSU, DMF and DMAC should also dissolve the crosslinked PA as their RED(PA) values are well below 1 (0.45 and 0.63), and NMP and DMSO should also partially dissolve PA as their RED(PA) values are slightly above 1 (1.01 and 1.03).

[0517] Out of these pure solvents, 10 pure solvents stood out with RED (PSU) <0.9 and RED (PA) >1.20 as best solvent candidates for PSU selective dissolution as shown below in Table 10. Five of these pure solvents are nonpolar ; they have a low dielectric constant (<12).

[0518] SSPU 2024 / 042 Table 9. RED(PSU) and RED(PA) for pure solvents

[0519] SSPU 2024 / 042 Table 10. Pure solvents with RED (PSU) <0.9 and RED (PA) >1.20

[0520] Because the subsequent coagulation step (c) may use a polar non-solvent, it is recommended for the suitable pure solvent (SI) used in the contacting step (a) to be compatible with the subsequent coagulation step (c). For that reason, particularly when the coagulation step (c) uses water as nonsolvent, a pure solvent selected for solvent (SI) should preferably have a dielectric constant of at least 12, preferably at least 13, more preferably at least 15.

[0521] Therefore when the solvent (SI) is a pure solvent, the solvent (SI) is preferably selected from DMI, cyclohexanone, cycloheptanone, cyclopentanone, or NBP, more preferably selected from DMI or cyclohexanone, still more preferably being cyclohexanone.

[0522] Determination of RED(PSU) and RED(PA) for solvent blends

[0523] Since experimentally the 25 / 75 v / v DMSO / MCB blend has provided good PSU extraction data and good PSU recovery after precipitation in methanol, the values of RED(PSU) and RED(PA) for blends of low polar solvents (ODCB, MCB, toluene) with other solvents (polar solvents as well as green solvents) were determined.

[0524] While wishing not to be bound by this theory, it is believed that the nonpolar solvents (e.g., ODCB, MCB) favor a bigger distance to PA swelling sphere, and thus the presence of a non-polar solvent in a solvent blend with another solvent should increase the RED(PA) of the solvent blend compared to the RED(PA) value of the other solvent.

[0525] The results for 6D, 6P, 6H, RED(PSU) and RED(PA) are provided for blends with MCB (Table 11), blends with ODCB (Table 12), and blends with toluene (Table 13) in which xA, xB are volumetric fractions in the blends and the HSP data (6D, 6P, 6H) are in MPa1 2.

[0526] SSPU 2024 / 042 In Tables 11, 12, 13, the following abbreviations are used:

[0527] DMAc: dimethylacetamide ; DMF: dimethylformamide; DMI: dimethyl isosorbide; DMSO: dimethylsulfoxide; GBL: gamma-butyrolactone

[0528] MCB: monochlorobenzene; NMP: N-methyl-2-pyrrolidone; ODCB: ortho- dichlorobenzene.

[0529] The dimethyl isosorbide (DMI) and gamma-butyrolactone (GBL) are good green solvent candidates for blends using a non-polar solvent such as ODCB or MCB.

[0530] Table 11: Blends with MCB (a): xA, xB: volumetric fractions of solvent A and solvent B, respectively, based on total volume of solvents A+B(b): 6D, 6P, 6H in MPa1 / 2

[0531] SSPU 2024 / 042 As shown in Table 11, some of the MCB blends with DMSO did not have suitable RED(PA) (<1.2), likely because their volume fraction of MCB was low (20 to 35 vol%). When the MCB comprised the majority of the blend, meaning when the volume fraction of MCB was higher than 50 vol%, the RED(PA) values of the MCB:DMSO blends clearly improved (increased).

[0532] This is illustrated in FIG. 4 which is a plot of RED(PSU) versus RED(PA) for various MCB / DMSO blends. Confirming the experimental data with MCB and DMSO, the pure solvents were not selective enough for the dissolution of PSU and not of PA. The same was true for blends containing a large amount of DMSO- see 35:65 MCB:DMSO and 20:80 MCB:DMSO blends.

[0533] However the blends with a majority of MCB, meaning a volumetric ratio greater than 50:50 v:v MCB:DMSO were favorable for selective PSU dissolution with very low PA dissolution (RED(PA) > 1.2). More preferred MCB:DMSO blends had a volumetric ratio greater than 60:40 v:v MCB:DMSO (with a RED(PA) > 1.5).

[0534] As shown in Table 12 for blends of ODCB, some of the ODCB blends with DMSO did not have suitable RED(PA) (<1.2), likely because the volume fraction of ODCB was low (24 or 41 vol%). When the ODCB comprises the majority of the blend, meaning when the volume fraction of ODCB was higher than 50 vol%, the RED(PA) values of the ODCB:DMSO blends clearly improved (> 1.2).

[0535] This is illustrated in FIG. 5 which is a plot of RED(PSU) versus RED(PA) for various ODCB / DMSO blends. Confirming the experimental data with DMSO, the pure DMSO solvent was not selective enough for the dissolution of PSU as it still permitted the partial dissolution of PA. The same was true for blends containing a large amount of DMSO - see the 41:59 ODCB:DMSO and 24:76 ODCB:DMSO blends.

[0536] While ODCB seemed a good solvent for selective dissolution of PSU and no dissolution of PA (preferably RED(PSU)< 0.7 and RED(PA)>1.5), unfortunately its non-polarity made it unsuitable to be used as a pure solvent for the coagulation step which was subsequent to the removal of insolubles from the PSU solution.

[0537] However the blends with a majority of ODCB, meaning a volumetric ratio greater than 50:50 v:v ODCB:DMSO were favorable for selective PSU dissolution with very low PA dissolution (RED(PA) > 1.3). More preferred

[0538] SSPU 2024 / 042 ODCB:DMSO blends have a volumetric ratio of at least 70:30 v:v

[0539] ODCB:DMSO (with a RED(PA) > 1.5).

[0540] Table 12: Blends with ODCB

[0541] (a): xA, xB: volumetric fractions of solvent A and solvent B, respectively, based on total volume of solvents A+B

[0542] (b): 6D, 6P, 6H in MPa1 / 2

[0543] SSPU 2024 / 042 The green solvent GBL had a RED(PSU) = 0.99 and RED(PA) = 1.32, so it was identified as a suitable solvent to serve as a base for a blend, since PSU is soluble in GBL and PA has limited solubility. It was shown in Table 12 and illustrated in FIG. 6 that resulting ODCB:GBL blends could improve the solubility in PSU and further increase its RED(PA), thus reducing the risk of PA solubilization during the contacting step (a) of the TFC-PA membrane (or pieces thereof).

[0544] As shown in Table 12 and illustrated in FIG. 7, all of the blends of ODCB and cyclohexanone (with ODCB : cyclohexanone volumetric ratios of 0.91:0.09 to 0.11:0.89) had a RED(PSU) of from 0.57 to 0.61 and a RED(PA) of from 1.98 to 1.53. All were suitable for selective dissolution of PSU.

[0545] Table 13: Blends with toluene

[0546] (a): xA, xB: volumetric fractions of solvent A and solvent B, respectively, based on total volume of solvents A+B(b): 6D, 6P, 6H in MPa1 / 2

[0547] As shown in Table 13 for blends with toluene, some of the toluene blends did not have suitable RED(PA) (<1.2) especially with DMAc, DMF or DMSO. However since the volume fraction of toluene was low (32 to 43 vol%), the RED(PA) values of the blends would improve, should toluene comprise the

[0548] SSPU 2024 / 042 majority of the blend, meaning when the volume fraction of toluene is higher than 50 vol%.

[0549] As shown in Table 13, all of the blends of toluene and cyclohexanone (with toluene : cyclohexanone volumetric ratios of from 0.36:0.64 to 0.04:0.96) had a RED(PSU) of from 0.59 to 0.78 and a RED(PA) of from 1.87 to 1.48. All were suitable for selective dissolution of PSU.

[0550] As explained previously, when the solvent blend is identified as being suitable for selective dissolution of PSU, the selection for its use in step (a) is contingent upon its compatibility with the subsequent coagulation step (c). For that reason, the solvent blend selected to be used as solvent (SI) in step (a) should be soluble in the non-solvent (NS) used in the subsequent coagulation step (c).

[0551] In particular, when the non-solvent is water, it may be recommended to select a solvent blend (to be used as solvent (SI) in the contacting step (a)) having a dielectric constant of at least 12, preferably at least 13, more preferably at least 15, such minimum dielectric constant providing a further selection criterion for compatibility of solvent (SI) with the subsequent coagulation step (c) when the precipitation bath comprises or consists of water.

[0552] What is claimed is:

[0553] SSPU 2024 / 042

Claims

C L A I M S1 . A process for producing a recycled polysulfone (PSU) product from a thin- film composite (TFC) membrane [hereinafter “TFC membrane”] comprising a polyamide (PA) layer, a polysulfone (PSU) layer and a poly(ethylene phthalate) (PET) layer, said process comprising the following steps: step (a): contacting the TFC membrane or TFC membrane pieces with a solvent (SI) for a time sufficient to dissolve PSU to obtain a slurry SL containing a liquid phase and solids, said solvent (SI) having a Relative Energy Distance value relative to PA [“RED(PA)”] of at least 1.2, of at least 1.25, at least 1.3, at least 1.35, or at least 1.4, and a Relative Energy Distance value relative to PSU [“RED(PSU)”] of at most 0.9, at most 0.85, at most 0.8, at most 0.75, or at most 0.7, said RED values for PA and PSU being obtained by Hansen solubility parameter spheres, said PET being insoluble in the solvent (SI), said liquid phase of the slurry (SL) comprising PSU, and said solids of the slurry (SL) comprising PA and PET; step (b): separating the liquid phase of the slurry (SL) obtained in step (a) from its solids to obtain a PSU solution (Spl), and optionally repeating the steps (a) and (b), so that the PSU solution (Spl) contains at least 5 wt% PSU dissolved in the solvent (SI), said wt% PSU in the PSU solution (Spl) being based on the combined weights of PSU and solvent (SI); step c): coagulating PSU from the PSU solution (Spl) in a precipitation bath comprising anon-solvent (NS) to form solid PSU particles, wherein the solvent (SI) is soluble in the non-solvent (NS); and step d): collecting a recycled PSU product.

2. The process according to claim 1, further comprising, prior to step (a), a step (j) for generating TFC membrane pieces from a membrane module containing said TFC membrane, said step (j) comprising carrying out either step (jl) or step (j2):SSPU 2024 / 042step (j 1): disassembling the membrane module to recover the TFC membrane, and carrying out a mechanical or physical modification of the TFC membrane to obtain TFC membrane pieces, or step (j2): carrying out a mechanical or physical modification of the membrane module to form module fragments including TFC membrane pieces, and sorting out the module fragments to recover TFC membrane pieces.

3. The process according to claim 1 or 2, further comprising, before step (a), a step (k) for pre-treating the TFC membrane or membranes pieces, said step (k) comprising carrying out at least one of following steps (kl), (k2) and (k3): step (kl): washing with a washing agent such as water, C1-C5 alcohol, an acid, and / or a base, step (k2): treating with a cleaning agent selected from disinfectants and / or an oxidizers such as sodium hypochlorite, and step (k3): sterilization, followed by : step (k4): drying4. The process according to any one of claims 1 to 3, wherein the solvent (SI) is a blend of a polar solvent and a non-polar solvent.

5. The process according to any one of claims 1 to 4, wherein the solvent (SI) is selected from:- a pure polar solvent selected from dimethyl isosorbide (DMI), cyclohexanone, cycloheptanone, cyclopentanone, or N-Butyl Pyrrolidone (NBP), preferably being DMI or cyclohexanone, more preferably being cyclohexanone;- blends of o-dichlorobenzene (ODCB) with a polar solvent selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N- methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone;SSPU 2024 / 042- blends of monochlorobenzene (MCB) with a polar solvent selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N- methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone; or- blends of toluene with another solvent selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N-methyl-2- pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone.

6. The process according to claim 4, wherein the polar solvent in the solvent (SI) is selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), gamma-Butyrolactone (GBL), cyclopentanone, cycloheptanone, and cyclohexanone; and / or the non-polar solvent in the solvent (SI) is selected from the group consisting of o- dichlorobenzene (ODCB), monochlorobenzene (MCB), and toluene.

7. The process according to claim 4 or 5, wherein the solvent (SI) is a blend of a nonpolar solvent and a polar solvent selected from DMSO or NMP, having a volumetric ratio of the non-polar solvent being greater than 50 vol.% and less than 95 vol.%, based on the total volume of the solvent (SI).

8. The process according to any one of claims 1 to 7, wherein the non-solvent (NS) is water and / or a C1-C5 alcohol, preferably water and / or methanol.

9. The process according to any one of claims 1 to 8, wherein the PSU solution (Spl) has a PSU content of at least 7 wt%, or at least 10 wt%, and at most 25 wt%, or at most 23 wt%, or at most 22 wt%, or at most 20 wt%, said wt% PSU in the PSU solution (Spl) being based on the combined weights of PSU and solvent (SI).SSPU 2024 / 042lO.The process according to any one of claims 1 to 9, further comprising, before step (c), carrying out a concentration step (e) to increase the PSU content to at least 20 wt% PSU.1 l.The process according to any one of claims 1 to 10, further comprising a color removal step (1) by carrying out either or both of following step (fl) and step (f2):- step (fl): before steps (c) and (d) and preferably before an optional concentration step (e), removing color from the PSU solution (Spl) to obtain a treated PSU solution (Spl*), and / or- step (f2): dissolving the PSU product obtained in step d) into a solvent (S2) to obtain a second PSU solution (Sp2), and removing color from the second PSU solution (Sp2) to obtain a treated PSU solution (Sp2*), preferably wherein the solvent (S2) in step (f2) is selected from the group consisting of dimethylacetamide (DMAC), dimethylformamide (DMF), N- methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), dimethyl ether isosorbide (DMI), N-n-Butyl Pyrrolidone (NBP), g-Butyrolactone (GBL), Cyclopentanone, Cycloheptanone, Cyclohexanone.12.The process according to claim 11, wherein removing color in step (fl) or (f2) is carried out by contacting with activated carbon, and wherein when step (1) is carried out, a PSU solution (SP1) containing 5 wt% of the recycled PSU product dissolved in NMP has a Yellowness Index, measured according to ATSM E313-20 based on a CIE Color Measurement, of less than 8, or less than 5, or less than 4, or less than 3.

13. The process according to any one of claims 1 to 12, wherein the recovery step d) comprises: dl) removing the coagulated PSU particles from the precipitation bath; d2) washing the coagulated PSU particles with water and / or a C1-C5 alcohol, preferably water and / or methanol; and d3) drying the washed coagulated PSU particles at a temperature of from 80°C to 130°C.SSPU 2024 / 04214. A poly sulfone (PSU) product, preferably obtained by the method of any one of claims 1 to 13, comprising > 0 to less than 10 ppm of bisphenol A and dichlorodiphenylsulfone.

15. The polysulfone (PSU) product of claim 14, further comprising <0.95 wt%, preferably <0.90 wt%, more preferably <0.75 wt%, even more preferably <0.7 wt%, of cyclic dimers, said wt% being based on the total weight of the PSU product.

16. The polysulfone (PSU) product of claim 14 or 15, comprising the presence of TFC membrane impurities, said presence of TFC membrane impurities being detected by ultra-performance liquid chromatography method with mass spectrometry detection (UPLC-MS).

17. The polysulfone (PSU) product of any one of claims 14 to 16, wherein a solution (SP1) containing 5 wt.% of the PSU product dissolved in NMP has :- a color coordinate b* of at most 18, or at most 15, or at most 14;- a chroma C* of at most 18, or at most 15, or at most 14; and / or- a Yellowness Index (YI) of at most 35, or at most 33, or at most 28, wherein the color coordinate b* and chroma C* are measured using CIE color measurement D65-10; and the Yellowness Index is provided according to ATSM E313-20 based on the CIE Color measurement D65-10.

18. The polysulfone (PSU) product of any one of claims 14 to 17, wherein a solution (SP1) containing 5 wt.% of the PSU product dissolved in NMP has :- a color coordinate b* of less than 14, or at most 12, or at most 10, or at most 8, or at most 7, or at most 6, or at most 5, or at most 4, or at most 3, or at most 2;- a chroma C* of less than 14, or at most 12, or at most 10, or at most 8, or at most 7, or at most 6, or at most 5, or at most 4, or at most 3, or at most 2; and / or- a Yellowness Index based on a CIE Color measurement of less than 8, or less than 5, or less than 4, or less than 3.

19. Use of the polysulfone (PSU) product of any one of claims 14 to 18 for making a polymer solution and / or for manufacturing articles such as membranes, coatings, tubings and / or pipings.SSPU 2024 / 042

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