Process for making phenolic monomer product of high purity from a recycled polyarylethersulfone material

Abstract

A process for producing a phenolic monomer product comprising depolymerizing a recycled polymeric material to obtain a depolymerized mixture comprising phenolic monomers and purifying the depolymerized mixture. The polymeric material comprises at least one PAES polymer and at least one additive, and the PAES polymer preferably comprises a backbone comprising at least one sulfone recurring unit, a first end group being a halide, and a second end-capped group, preferably selected from alkoxy groups and / or phenoxy groups. The additive comprises a polyalkylene oxide and / or a polyvinylpyrrolidone (PVP). A purity of at least 95 wt% of phenolic monomers can be achieved in the product. In particular embodiments in which a recycled hemodialysis membrane comprises a polyethersulfone and PVP, a purity of at least 98 wt% based on the total weight of the phenolic monomer product of 4,4'-sulfonyl phenolic monomers can be achieved after depolymerisation and phenolic monomer purification.

Description

Process for Making Product of High Purity from a Recycled Polyarylethersulfone Material Cross-Reference to Related Applications

[0001] This application claims priority to Indian application No. 202311086676 filed on December 19, 2023, and to European application No. 24162160.6 filed on March 7, 2024, the whole content of these applications being incorporated herein by reference for all purposes. Technical Field

[0002] The present disclosure relates to a process using a source of recycled polyarylethersulfone (PAES) polymer as a reactant for recovering a phenolic monomer product. Background Art

[0003] Products made from or incorporating polymers are a part of almost any workplace or home environment. Generally, the polymers that are used to create these products are formed from virgin polymer materials. That is, the polymers are produced from petroleum and are not made from existing polymer materials. Once the products have outlived their useful lives, they are generally sent to waste disposal or a recycling plant.

[0004] The omnipresence of polymers and the importance of environmental policy have led to the increased importance of recycled polymeric materials. Virgin polymer composition replacement is considered to represent a significant way forward to solve the global polymer waste problem, stop the depletion of limited natural resources, and facilitate a circular economy. Recycling is one of the most significant actions which aims to reduce fossil oil usage, carbon dioxide emissions, the hazards associated with waste disposal, and the high rates of polymer pollution.

[0005] Polymer recycling has a variety of benefits over creating virgin polymer from petroleum. Generally, less energy is required to manufacture an article from recycled polymeric materials derived from post-consumer and post-industrial waste materials and polymer scrap (collectively referred to in this specification as “waste polymeric material”) than from the comparable virgin polymer. Recycling polymeric materials obviates the need for disposing of polymeric materials or polymer products.

[0006] Generally, there are two ways to recycle polymers: physical recovery and chemical recovery. Mechanical recycling, also known as secondary recycling without changing the basic structure of the material, is a process of recovering waste polymer material for re-use in manufacturing polymer products viamechanical means. Compared to recycling, mechanical recycling is more ideal, especially when the polymer to be mechanically recycled is available in large amounts, is free from fillers and impurities / additives, is comprised of only one polymer type, and has not been partially decomposed during its life cycle. However, the availability of clean, filler / additive free, and single polymer-based material for mechanical recyclability is low. Furthermore, most polymers naturally degrade over the course of their life-cycle due to normal thermo- oxidative or UV induced processes resulting in marked decreases in polymer molecular weight. Since molecular weight is correlated to mechanical properties – it is therefore challenging to obtain an end-of-life part possessing the same mechanical properties following mechanical recycling. Chemical recycling is a term used to describe chemical processes that transform high molecular weight polymers into smaller molecules and monomers - usually, liquids or gases - which can be re-used as a feedstock for the production of new petrochemicals and polymers. For most polymers, many chemical recycling methods lead to products other than the constituent monomers, meaning that such recycling method lack the ability to produce components that are able to be directly repolymerized back to the same polymer.

[0007] Given the demand for improved sustainability and circular economy, recycling a polymer back into the same application for which it is intended is highly desired. Such recycling would be viewed as efficient resource utilization where no waste is generated, and the polymer is cycled back into the same application that generated it as waste (after its initial use) in the first place. Such a recycling process would be eco-friendly with high efficiency. This would be an improvement over incumbent technologies in which polymers are recycled for less demanding applications thus limiting their end-use. Polymers reuse in their originally intended application is in general quite limited.

[0008] Poly(aryl ether sulfone) (PAES) polymers are highly thermally stable polymers with excellent toughness and impact strength. PAES is a generic term used to describe any polymer containing at least one sulfone group (-SO2-), at least one ether group (-O-) and at least one arylene group. These resins are generally made by polycondensation reactions typically using dichlorodiphenylsulfone (the sulfone monomer) along with other aromatic diols such as Bisphenol A (BPA), 4,4’-biphenol (BP) or 4,4’-dihydroxydiphenylsulfone (DHDPS) also known as Bisphenol S.

[0009] The amorphous PAES polymers are successfully used in various applications such as automotive, electronic equipment, medical devices, and aerospace because the PAES polymers exhibit a unique property profile that includes high strength,toughness, high temperature resistant to steam in sterilization processes, and are inherently flame retardant and transparent in addition to other attributes. The PAES polymers are also considered having good biocompatibility – meaning they have a minimal impact on clotting factor for blood when used in membrane applications. As a result, they find broad utility in medical devices where steam sterilization is needed, water filtration and hemodialysis membranes among other applications including plumbing and aerospace. For that reason, they are particularly applied in hemodialysis membranes, reverse-osmosis membranes, plumbing parts / forms such as pipes, animal cages, and baby bottles.

[0010] As a consequence of their wide-spread use, there is an increase in industrial waste and end-of-life products containing PAES polymers, and in lieu of being discarded, there is an increasing interest in recent years in recycling such PAES polymeric materials.

[0011] However the PAES polymers are relatively difficult to be decomposed due to their excellent chemical resistance and heat resistance. A few decomposition methods applicable to chemical recycling of PAES polymers have been studied.

[0012] EP0532893 (Hercules) relates to a process of preparing a reactive reduced molecular weight polyarylene polyether from a starting polyarylene polyether, in particular a PAES polymer, which includes contacting the starting polyarylene polyether with a nucleophilic reagent for a period of time sufficient to reduce the molecular weight of the starting polyarylene polyether, and then recovering the reactive reduced molecular weight polyarylene polyether. The most preferred nucleophiles used are alkali metal hydroxides, alkali metal sulfides, alkali metal hydrogensulfides, ammonia, alkylamines, hydrazines, and thiol or amino substituted triazoles. Such reactive reduced molecular weight polyarylenes preferably have tertiary amine reactive end groups. They are intended for use in combination with various other resins including epoxy, bismaleimide, cyanate ester, phenol-formaldehyde, urethane, polyester, vinyl ester, siloxane, cyclopentadiene and higher oligomers, acetylenic, and cyclic polycarbonate resins, or mixtures thereof. For example, a polyethersulfone ‘PES’ (Starting Polymer C) having a Mw of 35,000 is decomposed into a reduced molecular weight PES of a Mw from 5780 to 10,100 (see Ex.3, 8, 11, 12). Such a process does not provide a suitable yield in Bisphenol S. This patent teaches the reduction of the molecular weight of the starting polymer, but not purifying to recover monomer(s).

[0013] JP2009173902A (Sumitomo) relates to a decomposition method for decomposing an aromatic ether compound with a basic compound having a ≥14 acid dissociation constant (pKa) at 25°C in the presence of a solvent. Among the basiccompounds, quaternary alkali metal alkoxide, or alkaline earth metal alkoxide is particularly preferable. Decomposition of a PES polymer (Example 1) though led to a low yield of Bisphenol S.

[0014] However these methods lead to oligomeric products with very low yields for phenolic monomers such as Bisphenol S which can be readily repolymerized back to similar poly(aryl ether sulfone) polymers. Moreover, due to the low yields in these more valuable phenolic monomers, purification appears quite challenging and cost prohibitive.

[0015] Currently, there is no solution to recycle PAES-containing membranes due to the difficult removal of impurities / additives, including PVP, that embed themselves into the membrane. The most common purification protocol for membranes is to wash with water, bleach and other oxidants. The drawback to such a strategy is the incomplete removal of impurities / additives, possible modification of pore structure, and possible destruction of membrane material. Moreover, there is a limited amount of regenerating cycles possible for membranes before they are deemed unusable, and there is a further lack of evidence that sodium hypochlorite can remove all PVP from the membrane. It is thus challenging to remove PVP from end-of-life PAES hemodialysis membranes.

[0016] Regarding circularity, there is also an unmet need to develop ways to source recycled monomers for production of more sustainable polyarylether polymers. Summary of invention

[0017] The present invention solves the above-mentioned problems by deconstructing a PAES-containing material containing additive(s) via depolymerization of the PAES polymer chain to highly desirable recycled phenolic monomers (e.g., bisphenol S, bisphenol A) which, in turn, facilitates the removal of hard-to- remove additive(s), such as residual PVP, from the bulk of the PAES polymer.

[0018] The present invention thus addresses the recyclability of sulfone polymeric materials (such as membranes) where the PAES polymer is effectively depolymerized into phenolic monomers with a high yield in a reaction medium. The PAES polymer, at least partially dissolved in a solvent, reacts with a basic compound in the presence of water in a reaction medium to form a depolymerized mixture. As would be appreciated by those of ordinary skill in the art, the depolymerized mixture comprises at least one phenolic monomer, which generally includes a 4,4’-sulfonyl diphenolic monomer that can be used to manufacture a PAES polymer. In such a manner, the PAES polymer in the reaction medium can be converted into 4.4’-sulfonyl diphenolic monomer and other phenolic monomers with a high conversion. The depolymerized mixture is then subjected to purification in order to generate a phenolic monomer product of high purity (≥process provides a means to facilitate the separation of a water-soluble additive (such as PVP) particularly from PES and PSU membranes. Another key advantage of the present invention is the depolymerization of end-of-life materials back to diphenolic monomers (not oligomers) at high yields. After depolymerization, the additive (e.g., PVP) is washed out due to its water-soluble nature, and this feature is quite helpful during the monomer purification process. Yet another key advantage of the present invention is reclamation of bisphenol S (BPS) from PES or a combination of BPS and bisphenol A (BPA) that can be reused in a circular fashion to make polyarylethersulfones and / or composite materials.

[0020] The invention is set out in the appended set of claims.

[0021] A first aspect of the present invention relates to a process for producing at least one phenolic monomer product.

[0022] A second aspect of the present invention relates to a phenolic monomer product obtained by the process according to the present invention.

[0023] A third aspect of the present invention relates to a phenolic monomer product.

[0024] The various aspects of the invention, as well as the various embodiments of the invention will be more readily understood and appreciated by reference to the detailed description and examples. Detailed Description of the present invention

[0025] Definitions

[0026] In the present descriptive specification, some terms are intended to have the following meanings.

[0027] In the present application: - 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; - 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;- it should be understood elements and / or the characteristics of a composition, 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 composition, product or article, process or use, explicitly or implicitly, this being done without departing from the scope of the present description; - the description of a range of values for a variable, defined by a bottom limit, or 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; - the term "comprising" (or “comprise”) includes "consisting essentially of" (or “consist essentially of”) and also "consisting of" (or “consist of”); and - the term “consisting essentially of” in relation to a composition, compound, product, polymer, solution, process, method, etc. is intended to mean that any 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 composition, compound, product, polymer, solution, process, method, etc. can be included in such an embodiment. For example, when a composition, compound, product, polymer, or solution “consists essentially of” required elements, it is generally understood that any additional element may be present in not more than 1 wt% based on the total weight of the composition, compound, product, polymer, solution, etc. or not more than 1 mol% based on the total number of moles of the composition, compound, product, polymer or solution; - the term “optional” or “optionally” means that the subsequently described component or method step or circumstance may or may not occur, and that the description includes instances where the component or method step or circumstance occurs and instances where it does not; - the use of the singular ‘a’ or ‘one’ herein includes the plural unless specifically stated otherwise; and - it should be understood that the elements, properties, and / or the characteristics of a (co)polymer, product or article, a process, or a use, described in the present specification, may be combined in all possible ways with the other elements, properties and / or characteristics of the (co)polymer, product or article, process oruse, explicitly or implicitly, this done without departing from the scope of the present description.

[0028] In the present specification, the choice of an element from a group of elements also explicitly describes:

[0029] - the choice of two or the choice of several elements from the group,

[0030] - 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.

[0031] The term "solvent" is used herein in its usual meaning that, it indicates a substance capable of dissolving another substance (solute) to form a uniformly dispersed mixture at the molecular level. In the case of a polymeric solute, it is common practice to refer to a solution of the polymer in a solvent when the resulting mixture is transparent, and no phase separation is visible in the system. Phase separation is taken to be the point, often referred to as the "cloud point", at which the solution becomes turbid or cloudy due to the formation of polymer aggregates.

[0032] As used herein, “BPA” means Bisphenol A or 4,4′-isopropylidenediphenol; “BPS” means Bisphenol S or 4,4’-dihydroxydiphenyl sulfone; “DMSO” means dimethylsulfoxide.

[0033] The term “alkoxy” designates a monovalent group containing an oxygen atom covalently attached to at least one alkyl group and is represented by the formula – O-Ra, in which Ra is an alkyl group, preferably a C1-C5 alkyl. In particular, the term “methoxy” is represented by the formula –O-CH3.

[0034] The term “phenoxy” designates a monovalent group containing an oxygen atom covalently attached to at least one phenyl group. Preferably, the “phenoxy” group may be represented by any of the following formulae: -O-Ar ; -O-Ar-C(CH3)2-Ar ; -O-Ar-Ar ; or -O-Ar-SO2-Ar, where Ar may be an unsubstituted or substituted benzenic ring or of a plurality of unsubstituted or substituted benzenic rings fused together by sharing two or more neighboring ring carbon atoms. Non limitative examples of Ar groups are unsubstituted or substituted phenyl, naphthyl, anthryl, phenanthryl, tetracenyl, triphenylyl, pyrenyl, and perylenyl groups. The one or more benzenic rings in Ar may be substituted with an element selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium. More preferably, the “phenoxy” group may be represented by any of the following formulae: -O-Ar ; -O-Ar-C(CH3)2-Ar ; -O-Ar-Ar ; or -O-Ar-SO2- Ar, where Ar represents an unsubstituted benzenic ring.

[0035] The term “recurring unit” designates the smallest unit of a PAES polymer whichis repeating in the chain, and composed of a condensation of a diol compound and a dihalo compound. The term “recurring unit” is synonymous to the terms “repeating unit” and “structural unit”.

[0036] The contents of recurring units in the polymer are given in mol.% relative to the total amount of moles of recurring units in the polymer, unless stated otherwise.

[0037] The term “homopolymer” encompasses a polymer which only has one type of recurring unit. The term “copolymer” encompasses a polymer which may have two or more different types of recurring units.

[0038] The term “phenolic” and its derivatives “diphenolic”, “monophenolic” in relation to a monomer or dimer encompasses a monomer or dimer in a protonated form (phenol) or in a salt form (phenolate).

[0039] The term "membrane" is used herein in its usual meaning, that is to say, it refers to a discrete, generally thin, interface that moderates the permeation of chemical species in contact with it. A membrane generally comprises a polymeric material. Examples of membranes are water purification membranes and hemodialysis membranes.

[0040] The term “post-consumer” polymeric material (or article) refers to a finished good that is used and then recycled; this may provide a source of polymeric material that can be used in the present method. The typical post-consumer polymeric material may include, but is not limited to, packaging, membranes, compounds, automotive components, electronic components, consumer product components such as but not limited to plastic bottles and particularly baby bottles, battery components, plumbing parts, animal cages, or any used or end-of-life three- dimensional injection-molded, extruded or printed articles or parts thereof.

[0041] The term “post-industrial” polymeric material (or article), also known as “pre- consumer” polymeric material (or article), refers to waste generated from manufacturing processes that lead to the creation of the source polymeric material which can be used in the present method. For example, when a polymer is formed into bottles, polymeric scraps may be generated, and they do not end up in the final bottle products. If these polymeric scraps are ground, shredded, or re- pelletized, and used again in making the same article or another article, they will be referred to as “post-industrial” polymeric material. Typical pre-consumer polymeric material may include, but is not limited to, whole articles, parts thereof, or scraps thereof, of packaging, films, fibers, membranes (such as hemodialysis and ultrafiltration membranes), off-specification compounds, or polymeric products including off-specification polyarylethersulfones, automotive components, electronic components, consumer product components such as plastic bottles and particularly baby bottles, battery components, plumbing parts,animal cages, or any three- injection-molded, extruded or printed articles or parts thereof.

[0042] In other words, post-consumer polymeric material (or article or waste) refers to finished goods, while post-industrial polymeric material (or article or waste) refers to waste material generated from a manufacturing process that manufactures polymers or polymeric based articles.

[0043] 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.

[0044] Should the disclosure of any patents, patent applications, and publications that 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.

[0045] Description of preferred embodients

[0046] The first aspect of the present invention relates to a process for recycling a polymeric material comprising at least one polyarylethersulfone and at least one additive to produce a phenolic monomer product, comprising: (a) in a reaction medium containing a polar aprotic solvent, a basic compound, and a polymeric material comprising at least one polyarylethersulfone (“PAES polymer”) and at least one additive, depolymerizing said PAES polymer to obtain a depolymerized mixture comprising phenolic monomers, and (b) purifying the depolymerized mixture to obtain a phenolic monomer product.

[0047] The phenolic monomer product may comprise at least 95 wt% of phenolic monomers based on the total weight of the phenolic monomer product.

[0048] The phenolic monomer product may comprise less than 5 wt% of the at least one additive, said wt% being based on the total weight of the phenolic monomer product, with the proviso that the content of the at least one additive in the phenolic monomer product is less than the content of the at least one additive in the polymeric material before the depolymerizing step.

[0049] Polymeric material containing the PAES polymer

[0050] The polymeric material in the reaction medium in the process of the present invention may be considered a waste, such as end-of-life products, industrial scraps, and / or unsalable (e.g., off-specification, surplus, defects, seconds) products or articles.

[0051] The polymeric material can be in solid forms, such as pellets, fibers, flakes, powder, pieces of shredded or ground articles, coagulated particles, or any other solid 3-D objects, or in form of a solution or slurry in which at least part of the PAES polymer is dissolved before being subjected to the depolymerizing step (a).

[0052] The polymeric material can at least one material selected from the group consisting of post-consumer polymeric articles, post-industrial polymeric articles including article scraps, off-specification PAES polymer products; and any combination thereof, said articles being preferably selected from the group consisting of membranes (such as hemodialysis membranes and ultrafiltration membranes), automotive components, composites, battery components, electronic components, consumer product components such as baby bottles, plumbing parts, animal cages, any parts or scraps thereof, and any combination thereof.

[0053] The polymeric material containing the PAES polymer may comprise at least 50 percent by weight (wt%), based on the total weight of the polymeric material, of the PAES polymer. The polymeric material preferably comprises at least 55 wt%, at least 60 wt%, at least 65 wt%, at least 70 wt%, at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, or at least 98 wt%, of the PAES polymer, based on the total weight of the polymeric material.

[0054] The polymeric material containing the PAES polymer may comprise at most 50 % by weight (wt%), based on the total weight of the polymeric material, of the at least one additive. The polymeric material preferably comprises at most 45 wt%, at most 40 wt%, at most 35 wt%, at most 30 wt%, at most 25 wt%, at most 20 wt%, at most 15 wt%, at most 10 wt%, at most 5 wt%, or at most 2 wt% of the at least one additive, based on the total weight of the polymeric material. The polymeric material preferably comprises at least 0.1 wt%, at least 0.3 wt%, at least 0.5 wt%, at least 0.7 wt%, at least 1 wt%, at least 2 wt%, or at least 3 wt%, of the at least one additive, based on the total weight of the polymeric material.

[0055] In preferred embodiments in which the additive comprises at least one PVP, the at least one PVP in the polymeric material is in an amount of from 0.1 wt% and up to 15 wt%, or from 0.5 wt% and up to 12 wt%, or from 1 wt% and up to 10 wt%, or from 2 wt% and up to 8 wt%, or from 3 wt% and up to 7 wt%, based on the total weight of the polymeric material.

[0056] The polymeric material may consist essentially of at least one PAES polymer and at least one additive. It is understood that more than one PAES polymer may be included in the polymeric material.

[0057] As used herein, the term “consisting essentially of” means that any additional component is present in an amount of at most 1% by weight, based on the total weight of the polymeric material.

[0058] The polyarylethersulfone (PAES) polymer

[0059] The polyethersulfone polymer, hereinafter referred to as “PAES polymer” which is used as a reactant in the process of the present invention comprises a backbone containing at least one recurring unit represented by formula (K) and two endgroups, each being from a halide X, an hydroxyl group and / or an end-capped group Re, with the proviso that when one end group is a halide X, the other end group is an hydroxyl group and / or an end-capped group Re, and when one end group is an end-capped group Re, the other end group is a halide X and / or another end-capped group Re.

[0060] The formula (K) is as follows: (K),from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and wherein each i is independently zero or an integer from1 to 4.

[0061] In alternate embodiments, at least one i in the formula (K) is 1, and its corresponding R is selected from the group consisting of alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, and alkyl phosphonate.

[0062] In preferred embodiments, both i in the formula (K) are zero.

[0063] The PAES polymer may further contain another recurring unit represented by formula (K’), ,- T is a bond or –C(CH3)2-; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4.

[0064] When one end group is a halide other end group is preferably an end- capped group Re, meaning that the PAES polymer may be represented by X- PAES-Re.

[0065] When one end group is an end-capped group Re, the other end group is preferably a same end-capped group Re and / or a halide X, meaning that the PAES polymer may be represented by Re-PAES-X and / or Re-PAES-Re. In such instance, the PAES polymer may have a combination of Re-PAES-X and Re-PAES-Re, in which the content in the X end groups is less than 20 mol% based on the total number of moles of end groups in the PAES polymer.

[0066] When one end group is a hydroxyl group, the other end group is preferably a halide X and / or another hydroxyl group, meaning that the PAES polymer may be represented by HO-PAES-X and / or HO-PAES-OH. In such instance, the PAES polymer may have a combination of HO-PAES-X and HO-PAES-OH, in which the content in the X end groups is less than 45 mol%, preferably less than 40 mol%, based on the total number of moles of OH and X end groups in the PAES polymer.

[0067] The PAES polymer preferably comprises at least 50 percent by mole (mol.%), based on the total number of moles of recurring units of the PAES polymer, of the recurring unit of formula (K).

[0068] The PAES polymer, which is used as a reactant in the process of the present invention, is more preferably a polymer comprising at least 60 mol.%, or at least 65 mol.%, or at least 70 mol.%, or at least 75 mol.%, or at least 80 mol.%, or at least 85 mol.%, or at least 90 mol.%, or at least 95 mol.%, or at least 95 mol.%, based on the total number of moles of recurring units of the PAES polymer, of at least one recurring unit selected from those of formulae (L), (L’), (M), (M’), (N), (N’), (O), (O’), (T), (T’), (U), (U’), (V), (V’), (W), (W’): CH3, ,, , , , ,,, (U’), (V’) and (W’), - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently 0 or an integer from 1 to 4, with the proviso that at least one i is not zero.

[0069] In preferred embodiments for any one of the formulae (L’), (N’), (O’), (Q’), (T’), (U’), (V’) and (W’), at least one i is 1, and its corresponding R is independently preferably selected from the group consisting of alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, and alkyl phosphonate.

[0070] The recurring units selected from those of the formulae (U), (V), (W) may be represented by formulae (U*), (V*), (W*), respectively:.

[0071] having one , , , (N’), (O), (O’), (Q), (Q’), (T), (T’), (U), (U’), (V), (V’), (W), (W’), (U*), (V*), (W*), or may be a copolymer comprising two or more recurring units selected from those of the formulae (L), (L’), (N), (N’), (O), (O’), (Q), (Q’), (T), (T’), (U), (U’), (V), (V’), (W), .

[0072] In, , , , , , (V’) and (W’) as provided above, at least two i are independently selected from integers from 1 to 4, preferably at least two i are 1, and their corresponding R may be independently selected from the group consisting of alkali or alkaline earth metal sulfonates, sulfonic acid (-SO3H), and alkyl sulfonates.

[0073] Alternatively, or in addition, the PAES polymer may be a copolymer comprising at least 60 mol.%, or at least 65 mol.%, or at least 70 mol.%, or at least 75 mol.%, or at least 80 mol.%, or at least 85 mol.%, or at least 90 mol.%, or at least 95 mol.%, or at least 95 mol.%, based on the total number of moles of recurring units in the PAES polymer, or consisting essentially of, - the recurring units of formula (L), - the recurring units of formula (L’), - a combination of the recurring units of formulae (L) and (L’), - the recurring units of formula (N), - the recurring units of formulea (N’), - a combination of the recurring units of formulae (N) and (N’), - the recurring units of formula (O), - the recurring units of formula (O’), - a combination of the recurring units of formulae (O) and (O’), - the recurring units of formula (Q), - the recurring units of formula (Q’), - a combination of the recurring units of formulae (Q) and (Q’), - the recurring units of formula (T), - the recurring units of formula (T’), - a combination of the recurring units of formulae (T) and (T’),- the recurring units of formula , - the recurring units of formula (U’), - a combination of the recurring units of formulae (U) and (U’), - the recurring units of formula (V), - the recurring units of formula (V’), - a combination of the recurring units of formulae (V) and (V’), - the recurring units of formula (W), - the recurring units of formula (W’), or - a combination of the recurring units of formulae (W) and (W’), in which in the recurring units of formulae (L’), (N’), (O’), (Q’), (T’), (U’), (V’), and (W’), at least one i is selected from integers of 1 to 4 (preferably at least one i is 1), and its corresponding R may be independently selected from the group consisting of alkali or alkaline earth metal sulfonates, sulfonic acid (-SO3H), and alkyl sulfonates.

[0074] The PAES polymer preferably comprises at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or at least 95 wt%, based on the total weight of the PAES polymer, of a sulfone polymer selected from the group consisting of: - PPSU, - PSU, - PES, - sulfonated PSU (sPSU), - sulfonated PES (sPES), - sulfonated PPSU (sPPSU), - any polymer derived from a diol monomer selected from isosorbide and / or tetramethyl bisphenol F and a dihalo monomer selected from sulfonated dihalodiphenylsulfone and / or dihalodiphenylsulfone, - any copolymer derived from at least two diols selected from biphenol, bisphenol A, bisphenol S, isosorbide, tetramethyl bisphenol F, and / or hydroquinone and a dihalo monomer selected from sulfonated dihalodiphenylsulfone and / or dihalodiphenylsulfone, - a block polymer in the form A-B or A-B-A, comprising at least one block having one recurring unit selected from those of formulae (L), (L’), (N), (N’), (O), (O’), (Q), (Q’), and at least one block having one recurring unit selected from those of formulae (T), (T’), (U), (U’), (V), (V’), (W), (W’), (U*), (V*), (W*); - a block copolymer in the form A-B or A-B-A, comprising at least one block having one recurring unit selected from those of formulae (L), (L’), (N), (N’), (O),(O’), (Q), (Q’), and at least one oxide or polyvinylpyrrolidone (PVP) block, such as a PEG block, PPG block or a PVP block; and - any combination of two or more thereof.

[0075] As used herein, a polyethersulfone (PES) denotes any polymer comprising at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of recurring units (RPES) of the formula (O): (O),in the PES polymer). PES can be prepared by known methods and is notably available as VERADEL®PES from Solvay Specialty Polymers USA, L.L.C.

[0076] As used herein, a polysulfone (PSU) denotes any polymer comprising at least 50 mol., at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consisting of, recurring units (RPSU) of the formula (L): CH3the. as Udel® PSU from Solvay Specialty Polymers USA, L.L.C.

[0077] As used herein, a polyphenylsulfone (PPSU) denotes any polymer comprising at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consisting of, recurring units (RPPSU) of the formula (Q): ,. available as RADEL®PPSU from Solvay Specialty Polymers USA, L.L.C.

[0078] As used herein, a sulfonated (sPES) denotes any polymer comprising at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of recurring units (RsPES) of the formula (O’): , mol.% of recurring units (RsPES) of recurring units (RPES) of the formulae (O) and recurring units (RsPES) of formula (O’), wherein in the formula (O’), at least one i is 1 and its corresponding R is selected from the group consisting of alkali or alkaline earth metal sulfonates, sulfonic acid (-SO3H), and alkyl sulfonates.

[0079] As used herein, a sulfonated polysulfone (sPSU) denotes any polymer comprising at least 50 mol., at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consisting of, recurring units (RsPSU) of the formula (L’): CH3, mol.% of recurring units (RsPES) of recurring units (RPSU) of the formulae (L) and recurring units (RsPSU) of formula (L’), wherein in the formula (L’), at least one i is 1 and its corresponding R is selected from the group consisting of alkali or alkaline earth metal sulfonates, sulfonic acid (-SO3H), and alkyl sulfonates.

[0080] As used herein, a sulfonated polyphenylsulfone (sPPSU) denotes any polymer comprising at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consisting of, recurring units (RsPPSU) of the formula (Q’):, % of recurring units (RsPES) of recurring units (RPSSU) of the formulae (Q) and recurring units (RsPSSU) of formula (Q’), wherein in the formula (Q’), at least one i is 1 and its corresponding R is selected from the group consisting of alkali or alkaline earth metal sulfonates, sulfonic acid (-SO3H), and alkyl sulfonates.

[0081] The block polymer in the form A-B or A-B-A in the PAES polymer may comprise: - at least one sulfone polymer block having one recurring unit selected from those of PPSU, sPPSU, PSU, sPSU, PES, sPES, and at least one block having recurring units made from tetramethyl bisphenol F and sulfonated or non-sulfonated dihalodiphenylsulfone or from a 1,4:3,6-dianhydrohexitol sugar diol (e.g., isosorbide) and sulfonated or non-sulfonated dihalodiphenylsulfone; or - at least one block polymer having recurring units selected from those of PPSU, sPPSU, PSU, sPSU, PES, sPES, and at least one polyalkylene oxide or polyvinylpyrrolidone (PVP) block, such as a PEG block, a PPG block or a PVP block.

[0082] The PAES polymer more preferably comprises at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, or at least 95 wt%, or consists of, a sulfone polymer selected from the group consisting of PPSU, PSU, PES, sPSU, sPES, sPPSU, and any combination thereof, the wt% being based on the total weight of the PAES polymer.

[0083] The PAES polymer may in some instances consist of a blend of PES / PPSU, of PES / PSU, of PSU / PPSU, of PES / PSU / PPSU, of PES / sPES, of PSU / sPSU, or of PPSU / sPPSU.

[0084] The weight average molecular weight Mw of the PAES polymer may be from 30,000 g / mol to 100,000 g / mol, for example from 35,000 g / mol to 90,000 g / mol or from 40,000 g / mol to 85,000 g / mol.

[0085] The number average molecular weight Mn of the PAES polymer may be from 15,000 g / mol to 60,000 g / mol, for example from 17,000 g / mol to 50,000 g / mol or from 20,000 g / mol to 45,000 g / mol.

[0086] The polydispersity index of the PAES polymer may be from 1.8 to 6.0, preferably from 1.9 to 5.0, more preferably from 2.0 to 4.5, yet more preferably from 2.0 to 4.0.

[0087] The weight average molecular (Mw) and the number average molecular weight (Mn) of the PAES polymer may be determined by gel-permeation chromatography (GPC), also known as Size Exclusion Chromatography, using methylene chloride as mobile phase and polystyrene standards for calibration. The polydispersity index (PDI), when reported, is hereby expressed as the ratio of weight average molecular weight (Mw) to the number average molecular weight (Mn).

[0088] The PAES polymer may be produced by a variety of methods. The PAES polymer is preferably derived by polycondensation from at least one aromatic diol monomer and at least one aromatic dihalo monomer.

[0089] For example, U.S. Pat. Nos.4,108,837 and 4,175,175 describe the preparation of polyarylethers and in particular polyarylethersulfones. Several one-step and two- step processes are described in these patents, which patents are incorporated herein by reference in their entireties. In these processes, a double alkali metal salt of a dihydric phenol is reacted with a dihalobenzenoid compound in the presence of a polar aprotic solvent under substantially anhydrous conditions. In a two-step process, the aromatic diol is first converted, in situ, in the presence of the solvent to the alkali metal salt derivative by reaction with an alkali metal or an alkali metal compound. An alkali metal salt is produced as a byproduct of the polymerization.

[0090] Additive in the polymeric material

[0091] The at least one additive in the polymeric material may comprise, or consist of, a pore forming agent.

[0092] The at least one additive comprising a pore forming agent may further comprises a solid filler, a colorant, or any combination thereof.

[0093] The at least one additive in the polymeric material preferably comprises at least one polyvinylpyrrolidone (PVP) and / or at least one polyalkylene oxide. In such instance, the at least one additive in the polymeric material may further comprise at least one solid filler and / or at least one colorant.

[0094] As used herein, a PVP comprises, based on the total number of moles of recurring units in the PVP, at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consists of, recurring units Rpvp of formula (P): (P),in which n in formula (P) is an of at least 3.

[0095] The molar mass of PVP may vary from 2,500 g / mol to 3,000,000 g / mol. Preferred PVPs may include PVP k12 , k15, k17, k25, k30, k40, k60, k85 and / or k90, commercially available for example from Fisher Scientific and Sigma-Aldrich.

[0096] When the additive comprises one or more PVPs, the polymeric material may comprise at most 15% by weight (wt%), based on the total weight of the polymeric material, of the one or more PVPs. The polymeric material preferably comprises at most 12 wt%, at most 10 wt%, at most 9 wt%, at most 8 wt%, at most 7 wt%, or at most 2 wt% of the one or more PVPs, based on the total weight of the polymeric material.

[0097] As used herein, a polyalkylene oxide comprises, based on the total number of moles of recurring units in the polyalkylene oxide, at least 50 mol. %, at least 60 mol.%, at least 70 mol. %, at least 80 mol. %, at least 90 mol. %, at least 95 mol. %, or at least 99 mol. % of, or consists of, recurring units Rpao of formula (P’): -(OCHRCH2)m- (P’), in which m in formula (P’) is an integer of at least 6. A preferred polyalkylene oxide may include a polyethyleneglycol (PEG) consisting of recurring units of formula -(OCH2CH2)m-, preferably of formula weight of at least 200 g / mol; a polypropyleneglycol (PPG) consisting of recurring units of formula -(OCH(CH3)CH2)m-, preferably of formula weight of at least 200 g / mol; or any combination thereof.

[0098] When the additive comprises one or more polyalkylene oxides, the polymeric material may comprise at most 50% by weight (wt%), based on the total weight of the polymeric material, of the one or more polyalkylene oxides. The polymeric material preferably comprises at most 45 wt%, at most 40 wt%, at most 35 wt%, at most 30 wt%, at most 25 wt%, at most 20 wt%, at most 15 wt%, at most 10 wt%, at most 5 wt% or at most 2 wt% of the one or more polyalkylene oxides, based on the total weight of the polymeric material.

[0099] When the additive further comprises a solid filler, the solid filler may be in fibrous form or non-fibrous form such as particulates. For the purpose of the present invention, a fibrous filler is a material having length, width and thickness, wherein the average length is significantly larger than both the width and thickness. Generally, such a fibrous filler has an aspect ratio, defined as the average ratio between the length and the largest of the width and thickness, of at least 5. Preferably, the aspect ratio of the fibers is at least 10, more preferably at least 20, still more preferably at least 50. The fibrous filler may have a round cross-section or a non-circular cross-section (so called “flat fibers”), including oval, elliptical or rectangular. The fibrous filler may be in form of continuous fibers (so called‘long’ fibers) or of chopped milled fibers, whereas chopped fibers are preferred.

[0100] When the additive further comprises a particulate filler, the particulate filler may contain or consist of zinc oxide, zinc sulphide, mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, clay, glass powder, nickel carbonate, iron oxide, quartz powder, magnesium carbonate, fluorocarbon resin, barium sulfate, graphite, carbon powder, carbon nanotubes, glass flakes, glass beads, microbeads and / or hollow glass microspheres, or any combination thereof. The non-fibrous fillers may be in the form of powder or beads, or of flaky particles.

[0101] When the solid filler contains or consists of a glass filler, the glass filler may be glass fibers, glass flakes, glass beads or microbeads and / or hollow glass microspheres. The glass fibers may have a circular cross-section or a non-circular cross-section, sometimes referred to as flat glass fiber.

[0102] When the solid filler contains or consists of a carbon filler, the carbon filler may be carbon fibers, graphite, carbon nanotubes, carbon black, and / or carbon powder.

[0103] When the solid filler contains or consists of a mineral filler, the mineral filler may be talc, mica, kaolin, calcium carbonate, calcium silicate, magnesium carbonate, titanium oxide, zinc oxide, and / or zinc sulfide, or any combination thereof.

[0104] When the solid filler contains or consists of non-polymeric fibers, the non- polymeric fibers may be aluminum fiber, titanium fiber, magnesium fiber, boron carbide fibers, rock wool fiber, steel fiber, wollastonite, or any combination thereof.

[0105] When the additive comprises one or more solid fillers, the polymeric material may comprise at most 50% by weight (wt%), based on the total weight of the polymeric material, of the one or more solid fillers. The polymeric material preferably comprises at most 45 wt%, at most 40 wt%, at most 35 wt%, at most 30 wt%, at most 25 wt%, at most 20 wt%, at most 15 wt%, at most 10 wt%, at most 5 wt% or at most 2 wt% of the one or more solid fillers, based on the total weight of the polymeric material.

[0106] The additive may further comprise a colorant. As used herein, a colorant may be selected from mineral (inorganic) pigments and / or organic dyes.

[0107] Non-limiting examples for suitable organic dyes are as follows: -Monoazo pigments: C. I. Pigment Brown 25; C. I. Pigment Orange 5, 36 and 67; C. I. Pigment Red 3, 48: 2, 48: 3, 48: 4, 52: 2, 63, 112 and 170; C. I. Pigment Yellow 3, 74, 151 and 183;A disazo pigment: C. I. Pigment Red 144, 166, 214 and 242; C. I. Pigment Yellow 83; Anthraquinone pigments: C. I. Pigment Yellow 147 and 177; C. I. Pigment Violet 31; -Benzimidazole pigments: C. I. Pigment Orange 64; Quinacridone pigments: C. I. Pigment oranges 48 and 49; C. I. Pigment Red 122, 202 and 206; C. I. Pigment Violet 19; Quinophthalone pigments: C. I. Pigment Yellow 138; Diketopyrrolopyrrole pigments: C. I. Pigment oranges 71 and 73; C. I. Pigment Red 254, 255, 264 and 270; -Dioxazine pigments: C. I. Pigment violet 23 and 37; -Indanthrone pigments: C. I. Pigment Blue 60; -Isoindoline pigments: C. I. Pigment Yellow 139 and 185; -Isoindoline pigments: C. I. Pigment Orange 61; C. I. Pigment Yellow 109 and 110; -Metal complex pigments: C. I. Pigment yellow 153; -Perinone pigments: C. I. Pigment Orange 43; -Perylene pigments: C. I. Pigment Black 32; C. I. Pigment Red 149, 178 and 179; C. I. Pigment Violet 29; Phthalocyanine pigments: C. I. Pigment Blue 15, 15: 1, 15: 2, 15; 3, 15: 4, 15: 6 and 16; C. I. Pigment Green 7 and 36; -C. I. Pigment Black 1 (aniline black).

[0013] Non-limiting examples inorganic pigments are, for example, the following: -White pigments: Titanium dioxide (CI Pigment White 6), zinc white, colored zinc oxide, zinc sulfite, lithopone; Black pigments: iron oxide black (CI pigment black 11), iron-manganese-black, spinel black (CI pigment black 27); carbon black (CI pigment black 7); -Colored pigments: Chromium oxide, chromium oxide hydrate green, chrome green (CI pigment green 48); cobalt green (CI pigment green 50); ultramarine green; Cobalt blue (CI pigment blue 28 and 36); ultramarine blue; manganese blue; Ultramarine violet, cobalt violet and manganese violet; Iron oxide red (CI Pigment Red 101), cadmium sulfoselenide (CI Pigment Red 108); molybdenum red (CI Pigment Red 104); ultramarine red; Iron oxide tea, mixed brown, spinel and corundum phases (CI Pigment Brown 24, 29 and 31), chrome orange; Iron oxide yellow (CI Pigment Yellow 42); nickel titanium yellow (CI Pigment Yellow 53); I. Chromium titanium yellow; cadmium sulfite and zinc cadmium sulfite (CI Pigment Yellow 37 and 35), chrome green (CI Pigment Yellow 34); bismuth vanadate (CI Pigment Yellow). Yellow 184).

[0014] Examples of inorganic pigments which are usually used as fillers include transparent silicon dioxide, quartz powder, aluminum oxide, aluminum hydroxide, natural mica, natural and precipitated chalk and barium sulfate.

[0108] In some instances, a solid filler may also function as a colorant. Examples of solid fillers that function also as colorant are zine oxide, zinc sulfide, and / or carbon black.

[0109] In some embodiments, the at least one colorant may be selected from titanium dioxide, zinc sulfide, zinc oxide, iron oxide, aluminium-cobalt oxide, bismuth vanadate, carbon black, metal phthalocyanines such as vanadyl phthalocyanine, copper phthalocyanine (e.g., phthalocyanine Pigment Blue 15:3), perylene and perylene derivative Pigment Red 149 or any combination thereof.

[0110] When the additive comprises one or more colorants, the polymeric material may comprise at most 15 wt%, at most 10 wt%, at most 5 wt% or at most 2 wt% of the one or more colorants, based on the total weight of the polymeric material.

[0111] When the additive comprises one or more organic dyes, the polymeric material may comprise at most 5 wt%, at most 4 wt%, at most 3 wt%, at most 2 wt% or at most 1 wt% of the one or more organic dyes, based on the total weight of the polymeric material.

[0112] The at least one additive in the material comprises, or consists of, : - at least one polyvinylpyrrolidone (PVP) and / or at least one polyethylene glycol (PEG), and - optionally at least one second additive selected from the group consisting of: o a solid filler chosen from glass fillers, carbon fillers, and / or mineral fillers, and o a colorant chosen from inorganic pigments and / or organic dyes.

[0113] The at least one additive in the polymeric material is more preferably - a PVP and / or a PEG, and - optionally at least one second additive selected from the group consisting of glass fibers, glass flakes, carbon fibers, carbon powder, talc, mica, zinc sulfide, zinc oxide, carbon black, an organic dye, and any combination thereof.

[0114] The at least one additive in the polymeric material is yet more preferably - a PVP and / or a PEG, and - optionally at least one second additive selected from the group consisting of glass fibers, glass flakes, talc, mica, zinc sulfide, carbon black, an organic dye, and any combination thereof.

[0115] The at least one additive in the polymeric material is even yet more preferably at least one PVP and optionally at least one second additive selected from the group consisting of polyalkylene oxides, such as a polyethylene glycol (PEG) or a polypropylene glycol (PPG), solid fillers selected from glass fillers, carbon fillers, and / or mineral fillers, colorants such as inorganic pigments and / or organic dyes, and any combination of two or more thereof.

[0116] The at least one additive in the polymeric material is most preferably at least one PVP.

[0117] Basic compound

[0118] The basic compound in the reaction medium may contain a base and a counter- cation. The base is preferably selected from hydroxide and / or alkoxide and the counter-cation is preferably selected from quaternary ammonium, an alkali metal cation, and / or an alkaline earth metal cation.

[0119] As used herein, the “counter-cation” in the basic compound is the cation that with the base for example represented by ‘–OH’ or ‘-OR’ group maintains the electric neutrality of the basic compound. For example, when the basic compound is an alkali metal hydroxide ‘MOH’ or an alkali metal alkoxide ‘MOR’, the counter- cation M+would be an alkali metal cation. When M is a counter-cation originating from the basic compoumd, M is preferably a quaternary ammonium, Na, Cs, and / or K.

[0120] The basic compound in the is preferably selected from the group consisting of an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal alkoxide, an alkaline earth metal alkoxide, and any combination thereof.

[0121] Suitable examples of alkali metal hydroxides may be represented by the formula : MOH, in which M+represents the counter-cation in the alkali metal hydroxide. M is an alkali metal such as Li, Na, K, and / or Cs. A preferred alkali metal hydroxide is sodium hydroxide (NaOH), cesium hydroxide (CsOH), and / or potassium hydroxide (KOH). A more preferred alkali metal hydroxide is sodium hydroxide (NaOH) and / or potassium hydroxide (KOH). In such instance, the counter-cation is Na+or K+.

[0122] A suitable quaternary ammonium hydroxide is tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, hexyltrimethylammonium hydroxide, cetyltrimethylammonium hydroxide, and benzyltrimethylammonium hydroxide. A preferred quaternary ammonium hydroxide is tetramethylammoniumm hydroxide (TMAOH) or cetyltrimethylammonium hydroxide. A more preferred quaternary ammonium hydroxide is TMAOH. The quaternary ammonium is the counter-cation in the quaternary ammonium hydroxide.

[0123] Suitable alkali metal and / or alkaline earth metal alkoxides are of formula : MOR, in which M+represents the counter-cation in the alkali metal and / or alkaline earth metal alkoxide. M is an alkali metal and / or alkaline earth metal, such as Li, Na, K, Cs, Mg, and / or Ba. R represents an alkyl group, preferably having from 1 to 10 carbon atoms. A preferred alkali metal and / or alkaline earth metal alkoxide is an alkali metal alkoxide having R being a methyl, ethyl, propyl or butyl group. A more preferred alkali metal alkoxide is potassium tert-butoxide and / or sodium tert- butoxide. K+or Na+represents the counter-cation in these tert-butoxides.

[0124] The basic compound is more preferably selected from the group consisting of sodium hydroxide (NaOH), cesium hydroxide (CsOH), potassium hydroxide (KOH); tetramethylammonium hydroxide (TMAOH); potassium tert-butoxide, sodium tert-butoxide; and any combination thereof.

[0125] The basic compound is most preferably NaOH.

[0126] Without wishing to be bound by such a theory, Applicant believes that the basic compound is used in the reaction medium in the presence of water to breakdown the PAES polymer by nucleophilic attack of the hydroxide or alkoxide nucleophile via an aromatic substitution reaction (SNAr type) into sulfonyl phenolic monomers and optionally other phenolic monomer(s). The basic compound further acts todeprotonate phenol monomers as bisphenol S) to form salts of phenolic monomers (such as sodium or potassium salt of bisphenol S).

[0127] The amount of the basic compound used in the depolymerisation is determined based on the total number of oxygen atoms (the total number of oxygen equivalents) forming the ether bond of the PAES recurring units. The amount of the basic compound should be used in the range of from 1 to 10 equivalents, preferably in the range of from 2 to 8 equivalents, more preferably in the range of from 2 to 7 equivalents, even more preferably of in the range from 2 to 6 equivalents, most preferably in the range of from 2 to 5 equivalents, relative to the total number of oxygen equivalents (oxygen atoms forming the ether bond of the PAES recurring units).

[0128] For illustration purposes, in instances when the PAES may be a PES polymer which consists of recurring units (RPES) of formula (O) which has a formula weight of 464 g / mol and 2 oxygen atoms forming an ether bond per recurring unit (RPES), 1 oxygen equivalent for 1 g of PES polymer to be depolymerized would thus correspond to 4.1 mmol oxygen atoms, the calculation being shown below: 1 Eq O = 1 g PES / 464 g RPES / mol RPES* 2 mol O / g RPES =4.1 mmol O. In such instance, an amount of 2 equivalents for the basic compound would mean using 8.2 mmol of the basic compound in the depolymerization.

[0129] Alternatively, in instances when the PAES may be a PSU polymer which consists of recurring units (RPSU) of formula (L) which has a formula weight of 442 g / mol and 2 oxygen atoms forming an ether bond per recurring unit (RPSU), 1 oxygen equivalent for 1 g PSU to be depolymerized would thus correspond to 4.1 mmol oxygen atoms: 1 Eq O = 1 g PSU / 442 g RPSU / mol RPSU * 2 mol O / g RPSU = 4.525 mmol O. In such instance, an amount of 2 equivalents for the basic compound would mean using 9.05 mmol of the basic compound in the depolymerization.

[0130] Polar aprotic solvent

[0131] As used herein, the polar aprotic solvent used in the depolymerisation method of the present invention may be referred to as “depolymerisation solvent”. The depolymerisation solvent may be any solvent that can dissolve or disperse, preferably dissolve, the PAES polymer appropriately. However selecting a solvent that can dissolve the basic compound used in the depolymerisation is more preferable. Furthermore, when after the depolymerisation reaction, the depolymerized mixture is subjected to separation and purification to recover the phenolic monomer product, it may be preferable that the depolymerisation solvent has a low boiling point because separation and purification may become easier if an evaporation or distillation technique is used.

[0132] The polar aprotic solvent may from the group consisting of 1,3- dimethyl-2-imidazolidinone (DMI), dimethylsulfoxide (DMSO), dimethylsulfone (DMSO2), diphenylsulfone, diethylsulfoxide, diethylsulfone, diisopropylsulfone, tetrahydrothiophene-1, 1-dioxide (commonly called tetramethylene sulfone or also called ‘sulfolane’), N-alkyl-2-pyrrolidone like N-Methyl-2-pyrrolidone (NMP), N- butylpyrrolidinone (NBP), N-ethylpyrrolidone (NEP), N,N′-dimethylacetamide (DMAc), N,N′-dimethylpropyleneurea (DMPU), dimethylformamide (DMF), tetrahydrothiophene-1-monoxide, and any combination thereof.

[0133] As shown in the examples, the use of DMSO as the polar aprotic solvent in the reaction medium for the depolymerisation is particularly advantageous to obtain a good yield of sulfonyl phenolic monomers, in particular of a yield of Bisphenol S > 80 mol%.

[0134] The amount of the polar aprotic solvent used in the reaction medium may be optimized as appropriate depending on the type of PAES polymer and / or the basic compound used in the depolymerisation.

[0135] When the PAES polymer is dissolved in the polar aprotic solvent, it is preferable to determine the amount of the solvent used so that the PAES polymer can be completely dissolved in the range of 1 wt% to 10 wt%, said wt% being based on the total weight of PAES polymer and polar aprotic solvent. It is particularly preferable to determine the amount of the polar aprotic solvent used so that the PAES polymer can be dissolved in the range of 1 to 9 wt%, or in the range of 2 to 8 wt%, or in the range of 3 to 7 wt%, said wt% being based on the total weight of PAES polymer and polar aprotic solvent.

[0136] In some embodiments, the polar aprotic solvent may be used in an amount of from 8 to 100 parts by weight (pbw), preferably from 9 to 99 pbw, or from 10 to 99 pbw, or from 10 to 49 pbw, or from 11 to 49 parts, or from 12 to 49 pbw, or from 13 to 33 pbw, or from 15 to 24 pbw, relative to 1 part by weight (pbw) of the PAES polymer.

[0137] The Depolymerization

[0138] The depolymerizing preferably comprises mixing a polar aprotic solvent, water, the polymeric material and a basic compound in a reactor vessel to form the reaction medium.

[0139] The various components of the reaction medium (that is to say, the polymeric material containing the additive and the PAES polymer, water, the basic compound, the polar aprotic solvent, and any other optional components) may be added simultaneously or sequentially to a reactor vessel where the depolymerization step takes place.

[0140] Preferably the polymeric first into the reactor vessel with the polar aprotic solvent in order to dissolve the PAES polymer, and then basic compound is added either alone or in combination of another portion of polar aprotic solvent. The water may be added to the reactor vessel after or preferably during the PAES polymer dissolution, and / or may be added to the reactor vessel at the same time as when the basic compound is loaded.

[0141] In some embodiments, the polymeric material may be added to the reactor vessel in solid form, such as pellets, fibers, powder, flakes, pieces of shredded articles, ground articles, coagulated or precipitated solids (e.g., coagulated polymer beads, particles, or prills), any other solid 3-D objects, or any mixture thereof. The pellets for example may be in any shape, such as cylindrical, spherical, or ovoid. In particular, when the polymeric material may comprise a post-industrial waste from a polyarylethersulfone manufacturing plant, such waste may be obtained after a coagulation step (in coagulated form) and subsequently not dried before being recycled and used as a reactant in the current process. The shape and size of the polymeric material are not critical so long as the PAES polymer can dissolve, at least in part, preferably completely, in the preferred polar aprotic solvent.

[0142] In some embodiments, the PAES polymer in a polymeric material which is in solid form may be “pre-dissolved” in the reactor vessel with some or all of the preferred polar aprotic solvent. In such instances, the pre-dissolution may be carried out with only the polymeric material and the preferred polar aprotic solvent, and then a mixture of the basic compound, the preferred polar aprotic solvent, and water is then added to that PAES solution to form the reaction medium. In other instances, water may be added during the PAES pre-dissolution into the preferred polar aprotic solvent before adding the basic compound to finally form the reaction medium.

[0143] It may be necessary to provide heat during PAES pre-dissolution in order to facilitate the dissolution of PAES polymer. The PAES dissolution may be favored at a temperature of at least ambient temperature but should not exceed the boiling point the preferred polar aprotic solvent, preferably from 50oC to 150oC or from 70oC to 130oC. Or preferably the reaction medium can be heated to a temperature of at least 100℃, or at least 110℃, or at least 120℃ and at most 180℃ or at most 170℃, or at most 160℃, or at most 150℃. Further, the heating of the reaction medium can occur for a duration of at least 5 hours and at most 24 hours (e.g., from 6 hours to 24 hours, from 7 hours to 24 hours, from 8 hours to 24 hours, from 9 hours to 24 hours, from 10 hours to 24 hours, from 11 hours to 24 hours, or from 12 hours to 24 hours).

[0144] In alternate embodiments, the material may be added to the reactor vessel in form of a solution or slurry in which at least some of the PAES polymer is “pre-dissolved” ex-situ, that is to say, not in the reactor vessel, before being added to the reactor vessel. In such instances, the polymeric material may be mixed with a polar aprotic solvent. It may be necessary to heat the mixture of the PAES polymer and solvent in order to facilitate the dissolution of PAES polymer into the solvent. The dissolution may be favored at a temperature of at least ambient temperature but should not exceed the boiling point of the solvent, preferably from 50oC to 150oC or from 70oC to 130oC. Such pre-dissolution would take place in a vessel separate from the reactor vessel (e.g., a feed tank). In instances when the resulting pre-dissolved PAES polymer is in the form of a slurry containing solids such as insoluble fillers originating from the polymeric material, the solids may be removed (e.g., the slurry is filtered) to recover a PAES polymer solution. The PAES polymer solution is then added to the reactor vessel. The polar aprotic solvent into which the PAES polymer may be pre-dissolved is preferably the same polar aprotic solvent used in the reaction medium. Such polar aprotic solvent is particularly selected for its ability to completely dissolve the PAES polymer when it is mixed ex-situ with PAES polymer. While the following polar aprotic solvents such as N-alkyl-2-pyrrolidone (e.g., N-methyl-2- pyrrolidone (NMP), N-butyl-2-pyrrolidinone (NBP), N-ethyl-2-pyrrolidinone (NEP)), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone (DMI), tetramethylene sulfone (sulfolane), N,N′-dimethylacetamide (DMAc) or any mixture thereof may be suitable for pre-dissolving the PAES polymer before addition to the reactor vessel, the polar aprotic solvent used for pre-dissolution of PAES polymer is preferably DMSO as described above. Water may be also added during PAES pre-dissolution whether it may be done in situ (meaning inside the reactor vessel) or ex situ (in a separate vessel different than the reactor vessel).

[0145] The various additional steps for preparing the reaction medium may be carried out as follows:

[0146] - the polymeric material is loaded into the reactor vessel with the solvent to dissolve the PAES polymer into the solvent, preferably by heating at a temperature of from ambient temperature to less than the boiling point of the solvent, preferably from 50oC to 150oC or from 70oC to 130oC, or preferably the reaction medium can be heated to a temperature of at least 100℃, or at least 110℃, or at least 120℃ and at most 180℃ or at most 170℃, or at most 160℃, or at most 150℃; and - the basic compound and water are added, simultaneously or in succession, to the reactor vessel after the PAES polymer is dissolved. Further, the heating of thereaction medium can occur for a of at least 5 hours and at most 24 hours (e.g., 6 hours to 24 hours, 7 hours to 24 hours, 8 hours to 24 hours, 9 hours to 24 hours, 10 hours to 24 hours, 11 hours to 24 hours, or 12 hours to 24 hours).

[0147] In alternate embodiments, the various additional steps for preparing the reaction medium may be carried out as follows: - the polymeric material is premixed ex-situ (i.e., in a feed tank separate from the reactor vessel) with a solvent to dissolve the PAES polymer, said solvent being the same or different than the polar aprotic solvent used for depolymerisation, preferably by heating at a temperature of from ambient temperature to less than the boiling point of the solvent, preferably from 50oC to 150oC or from 70oC to 130oC, preferably the reaction medium can be heated to a temperature of at least 100℃, or at least 110℃, or at least 120℃ and at most 180℃ or at most 170℃, or at most 160℃, or at most 150℃; and optionally after dissolution, filtered to remove solids; and - then the basic compound, water, the polar aprotic solvent and this premixture containing the pre-dissolved PAES polymer are added, simultaneously or successively, to the reactor vessel. Further, the heating of the reaction medium can occur for a duration of at least 5 hours and at most 24 hours (e.g., 6 hours to 24 hours, 7 hours to 24 hours, 8 hours to 24 hours, 9 hours to 24 hours, 10 hours to 24 hours, 11 hours to 24 hours, or 12 hours to 24 hours).

[0148] The depolymerization reaction

[0149] During the depolymerisation reaction in the process of the present invention, the basic compound and the PAES polymer may be present in the reaction medium in a molar ratio of basic compound to oxygen atoms forming ether bonds in the PAES polymer of at least 2:1, and at most 8:1, preferably at most 7:1, or at most 6:1, or at most 5:1, or at most 4.5:1.

[0150] The depolymerisation step in the process of the present invention is preferably carried out at a reaction temperature of at least 80℃, or at least 100℃, or at least 110℃, or at least 120℃ and / or at most 180℃, or at most 170℃, or at most 160℃, or at most 150℃.

[0151] The process of the present invention may further comprise the step of heating the reaction medium to reach the reaction temperature described above.

[0152] The depolymerisation step in the process of the present invention may be carried out under pressure or under reduced pressure, and the pressure in the depolymerisation may be determined depending on the type of polar aprotic solvent to be used and the depolymerisation temperature. For practicality however, atmospheric pressure (about 100-102 kPa) is preferable during depolymerisation.

[0153] During the depolymerisation process of the present invention, the polar aprotic solvent and water may be present in the reaction medium in a volumetric ratio of the polar aprotic solvent to water of at least 10:1, preferably at least 15:1, or at least 20:1, and at most 150:1, preferably at most 140:1, or at most 130:1, or at most 120:1, or at most 110:1, or at most 100:1, or at most 80:1, or at most 60:1, or at most 50:1.

[0154] The depolymerisation in the process of the present invention is preferably carried out in the reaction medium for a time period of at least 3 hours, or at least 4 hours, or at least 5 hours and / or at most 24 hours, at most 22 hours, at most 20 hours.

[0155] When the PAES polymer having a backbone comprising at least one recurring unit of the formula (K) or comprising at least one recurring unit selected from those of the formulae (L), (L’), (M), (M’), (N), (N’), (O), (O’), (T), (T’), (U), (U’), (V), (V’), (W), (W’) described above, is depolymerized in the process of the present invention, the basic compound cleaves the ether bond –O– of the recurring unit(s).

[0156] A depolymerized material is thus obtained by the depolymerisation step in the process according to the invention to obtain a depolymerized mixture comprising phenolic monomers thus forms a depolymerized material.

[0157] The depolymerized mixture

[0158] The depolymerized mixture comprises phenolic monomers in a liquid phase. As used herein, the term “depolymerized mixture” refers to the products and byproducts resulting from the depolymerization reaction of the PAES polymer in the polar aprotic solvent, remaining additive and remaining water (if any).

[0159] Prior to purifying, the depolymerized mixture comprises the phenolic monomers in an amount of at least 75 wt%, at least 80 wt%, and preferably at least 85 wt%, or at least 90 wt%, or at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 98 wt%, or at least 99 wt%, or at least 99.5 wt%, based on the total weight of the depolymerized mixture without solvent.

[0160] The phenolic monomers in the depolymerized mixture may comprise : - a 4,4’-sulfonyl diphenolic monomer of formula (I), - at least one monophenolic mononer selected from a 4,4’-sulfonyl monophenolic monomer of formula (Ia) comprising the end-capped group Re, and / or a 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) comprising the halide X, and - optionally a phenolic dimer of formula (IIIa).

[0161] The formula (I) for the 4,4’-sulfonyl diphenolic monomer is(I);in - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer from 1 to 4; - M is a counter-cation originating from the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs.

[0162] As would be appreciated by those of ordinary skill in the art, the 4,4’-sulfonyl diphenolic monomer of formula (I) corresponds to the cleavage of the recurring units of formula (K) in the backbone (main chain) of the PAES polymer. In such a manner, the recurring units of formula (K) in the PAES polymer are cleaved from one another to form 4,4’-sulfonyl diphenolic monomer, which is a salt of bisphenol S obtained with the counter-cation M of the basic compound.

[0163] Also, as would be appreciated by those of ordinary skill in the art, when the PAES polymer having one hydroxyl end group undergoes the depolymerization reaction, the cleavage during polymerization of the last recurring unit having the hydroxyl end group also generates the 4,4’-sulfonyl diphenolic monomer of formula (I).

[0164] The formula (Ia) for the 4,4’-sulfonyl monophenolic monomer is (Ia), in- each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer from 1 to 4;- M is a counter-cation the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs; and - Reis an end-capped group, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group.

[0165] As would be appreciated by those of ordinary skill in the art, when the PAES polymer having one encapped group Re in one end group undergoes the depolymerization reaction, the cleavage of the last recurring unit of formula (K) having such an encapped group Re generates the 4,4’-sulfonyl monophenolic monomer of formula (Ia).

[0166] The content of the monomer of formula (Ia) in the depolymerized mixture may be at least 10 ppm up to 2 wt% (e.g., at least 10 ppm up to 1 wt%, or at least 100 ppm up to 2 wt%), based on the total weight of the depolymerized mixture without solvent.

[0167] The formula (IIa) for the 4,4’-sulfonyl monohalo monophenolic monomer is (IIa), in which- each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer from 1 to 4; - M is a counter-cation originating from the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs; and - X is a halide, preferably being Cl or F.

[0168] As would be appreciated by those of ordinary skill in the art, when the PAES polymer having one halide (X) end group undergoes the depolymerization reaction, the cleavage during polymerization of the last recurring unit of formula (K) having such halide group generates the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa).

[0169] Without wishing to be bound by any particular scientific theory, when the PAES polymer having two end groups being the encapped group Reand the halide X undergoes the depolymerization reaction, the two recurring units of formula (K) atboth extremities of the PAES are cleaved from the PAES backbone, and these recurring units at both extremities generally form the monomers of formula (Ia) and formula (IIa).

[0170] The content of the monohalo monophenolic monomer of formula (IIa), when present in the depolymerized mixture, may be in an amount of from 0 wt% (preferably at least 10 ppm) up to 2 wt%, based on the total weight of the depolymerized mixture without solvent.

[0171] The formula (IIIa) for the sulfonyl phenolic dimer is : (IIIa),- each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; and - each of R2’, R2” is independently selected from an end-capped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group, in which M is a counter- cation originating from the basic compound used in the depolymerization step, preferably being selected from a quaternary ammonium, Na, K, and / or Cs, with the proviso that at least one of R2’ and R2” in the formula (IIIb) is an -OM group and / or a halide X.

[0172] The content of the phenolic dimer of formula (IIIa), when present in the depolymerized mixture, may be in an amount of from 0 wt% (preferably at least 10 ppm or at least 100 ppm) and up to 5 wt%, up to 4.5 wt% , up to 4 wt%, up to 3 wt%, or up to 2 wt%, based on the total weight of the depolymerized mixture without solvent.

[0173] As would be appreciated by those of ordinary skill in the art, the dimer of formula (IIIa) may be formed by the cleavage of two consecutive recurring units of formula (K) from the PAES polymer, such as two consecutive recurring units at an extremity of the PAES backbone, in which case one of the groups R2’, R2” of the dimer of formula (IIIa) corresponds to one end group of the PAES polymer,or two consecutive recurring the PAES backbone, in which case both end groups of the dimer of formula (IIIa) correspond to –OM groups.

[0174] In some embodiments, when the PAES polymer backbone further comprises recurring units of the formula (K’), the PAES polymer backbone preferably comprises more than 95 mol% and up to 100 mol% of recurring units of the formulae (K) and (K’).

[0175] In such instances, the phenolic monomers in the depolymerized mixture may further comprise 4,4’-diphenolic monomer of formula (I’): (I’),- T is a bond or –C(CH3)2-; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4.

[0176] The phenolic monomers in the depolymerized mixture may further comprise a monophenolic monomer of formula (Ib): (Ib),- T is a bond or –C(CH3)2-; - M is a counter-cation originating from the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs; - Reis an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and- each i is independently zero of 1 to 4.

[0177] T is a bond in formula (Ib) when the PAES polymer comprises a PPSU recurring unit of the formula (Q) and / or sPPSU recurring unit of the formula (Q’) at an extremity of the polymeric chain comprising the encapped group Re.

[0178] T is –C(CH3)2- in formula (Ib) when the PAES polymer comprises PSU recurring units of the formula (L) and / or sPSU recurring units of the formula (L’) at an extremity of the polymeric chain comprising the encapped group Re.

[0179] The encapped group Re in formula (Ib) is preferably a methoxy group.

[0180] The phenolic monomers in the depolymerized mixture may further comprise a monochloro monophenolic monomer of formula (IIb): (IIb),- T is a bond or –C(CH3)2-; - M is a counter-cation originating from the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs; - X is a halide, preferably being Cl or F; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4.

[0181] T is a bond in formula (IIb) when the PAES polymer comprises a PPSU recurring unit of the formula (Q) and / or sPPSU recurring unit of the formula (Q’) at an extremity of the polymeric chain comprising the halide end group.

[0182] T is –C(CH3)2- in formula (IIb) when the PAES polymer comprises PSU recurring units of the formula (L) and / or sPSU recurring units of the formula (L’) at an extremity of the polymeric chain comprising the halide end group.

[0183] X in formula (IIb) is preferably chloride or fluoride.

[0184] The phenolic monomers in the depolymerized mixture may further comprise a phenolic dimer of formula (IIIb) :, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group, in which M is a counter- cation originating from the basic compound used in the depolymerization step, preferably being selected from a quaternary ammonium, Na, K, and / or Cs, or M is H when the formula (IIIb) is in protonated form, with the proviso that at least one of R2’ and R2” in the formula (IIIb) is an -OM group and / or a halide X; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4.

[0185] T is a bond in formula (IIIb) when the PAES polymer comprises a PPSU recurring unit of the formula (Q) and / or sPPSU recurring unit of the formula (Q’).

[0186] T is –C(CH3)2- in formula (IIIb) when the PAES polymer comprises PSU recurring units of the formula (L) and / or sPSU recurring units of the formula (L’).

[0187] Depending on the composition of the PAES polymer (recurring units and end groups) that undergoes the depolymerization reaction, it would be appreciated that the presence and content of the monomer of formula (Ia), of the monomer of formula (IIa), and of the dimer of formula (IIIa) may vary in the depolymerized mixture.

[0188] For example, if the PAES polymer is a PES polymer, then the cleavage of the PES recurring units of formula (O) from the polymer backbone by nucleophilic attack forms a majority of the aforementioned 4,4’-sulfonyl diphenolic monomer of formula (I) in which all i are 0 (meaning a salt of bisphenol S).

[0189] When the PAES polymer is a PSU polymer, then the cleavage of the PSU recurring units of formula (L) from the polymer backbone by nucleophilic attack forms a majority of the aforementioned 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-isopropylidenebisphenolic monomer of formula (I’) in which all i are 0 and T=C(CH3)2, meaning a combination of salts of both bisphenol S and bisphenol A.

[0190] If the PAES polymer is a PPSU then the cleavage of the PPSU recurring units of formula (Q) from the polymer backbone by nucleophilic attack forms a majority of the aforementioned 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) in which all i are 0 and T is a bond, meaning a combination of salts of both bisphenol S and 4,4’-biphenol.

[0191] Prior to purifying, the depolymerized mixture comprises the phenolic monomers in an amount of at least 80 wt%, and preferably at least 85 wt%, or at least 90 wt%, or at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 98 wt%, or at least 99 wt%, or at least 99.5 wt%, based on the total weight of the depolymerized mixture without solvent.

[0192] The depolymerized mixture may futher comprise >0 (e.g., at least 10 ppm or at least 100 ppm) and up to 15 wt%, preferably up to 14 wt%, or up to 13 wt%, or up to 12 wt%, or up to 11 wt%, or up to 10 wt%, or up to 9 wt%, or up to 8 wt%, or up to 7 wt% or up to 6 wt%, or up to 5 wt%, or up to 4 wt%, or up to 3 wt%, or up to 2 wt%) of the at least one additive, said wt% being based on the total weight of the depolymerized mixture without solvent. The additive can be any of the additives described herein in relation to the polymeric material. Notably, the additive may preferably comprise or be at least one PEG, at least one PVP, at least one solid filler, at least one colorant, or any combination thereof.

[0193] In some embodiments, the depolymerized mixure may further comprise >0 and up to 5 wt% of an oligomer of the PAES polymer. As used herein, an oligomer is a PAES polymer having a Mn of at most 1500 g / mol. The Mn of the oligomer may be measured by a1H-NMR technique such as the one described in the examples section, a GPC technique for example using methylene chloride as mobile phase and polystyrene standards for calibration, a matrix-assisted laser desorption / ionization technique with mass spectrometry (MALDI MS), the GPC or MALDI MS technique being preferred.

[0194] The purity of the depolymerized mixture is defined as the content of phenolic monomers in the depolymerized mixture, based on the total weight of the depolymerized mixture without solvent. The depolymerized mixture can have a purity in phenolic monomers of at least 80 wt%, and preferably at least 85 wt%, or at least 90 wt%, or at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 98 wt%, or at least 99 wt%, or at least 99.5 wt%.

[0195] Termination of depolymerisation

[0196] To stop the depolymerisation reaction, the now-formed depolymerized mixture is preferably cooled to reduce the temperature to less than 80oC, preferably less than 60oC, or less than 50oC, or less than 40oC, or less than 30oC or less than 20oC, or less than 10oC.

[0197] Optional acid treatment

[0198] In preferred embodiments, after the depolymerisation reaction is completed in the reactor vessel, the cooled depolymerized mixture may be subjected to an acid treatment. For instance, the depolymerized material can be acidified with an acid (preferably a mineral acid such as HCl). As would be appreciated by those of skill in the art, this acid treatment results in lowering the pH to less than 5, and preferably less than 4, or less than 3, or less than 2, or less than 1.5, or preferably at about 1. This acid treatment also converts the monomers in phenolate form (such as salt of bisphenol S of formula (I) in which for example, M is Na or K) present in the depolymerized mixture to form in the acidified depolymerized mixture, the respective protonated form of these monomer(s) such as bisphenol S of formula (I) in which M is replaced by H.

[0199] In such an embodiment, any of the phenolic monomers such as of formulae (I), (I’), (Ia), (Ib), (IIa), (IIb), phenolic dimers (if present) such as of formulae (IIIa), (IIIb) and any PAES oligomers (if present) are converted to their respective protonated form in the acidified depolymerized mixture, meaning that the ‘M’ in the –OM groups are replaced by H.

[0200] Precipitation

[0201] In particular embodiments, the depolymerized mixture (acidified or not) is then subjected to precipitation using a non-solvent or poor solvent (such as water) in which the PAES polymeric / oligomeric / dimeric materials are not soluble, but in which the phenolic monomers have a much greater solubility. Such precipitation thus results in forming a precipitate containing mostly PAES oligomeric / dimeric materials as well any unreacted PAES polymer along with some or all of the additive and in forming a liquid supernate containing the desired phenolic monomers such as the biphenolic monomer of formula (I) or its protonated form, preferably bisphenol S.

[0202] Solid / liquid separation

[0203] After precipitation, a solid / liquid separation is preferably carried out to remove the precipitate. The solid / liquid separation preferably includes filtration, but other solid / liquid separation techniques may be employed.

[0204] The filtering can be performed in a variety of ways, such as vacuum filtering or any form of filtering as desired. As it would be appreciated by those of ordinary skill in the art, a portion of the resulting depolymerized material will be in a solid form (precipitate) while another portion of the depolymerized material will be in solution (supernate). The supernate thus should contain the liquid components used in the reaction medium and used in precipitation (non-solvent / poor solvent), such as water and polar aprotic solvent and Bisphenol S, which is preferably offormula (A’), in soluble form. solid / liquid separation includes filtration, the precipitate is recovered as the filtered solid and the supernate is recovered as the filtrate.

[0205] Optional drying of precipitate

[0206] This precipitate (e.g., filtered solid) may be dried at a temperature from 80 to 120 °C, preferably 90 to 110°C, preferably at 100°C. This dried precipitate (e.g., filtered solid) may be referred as the solid byproduct. This solid byproduct which can be analysed by1H-NMR spectroscopy generally contains PAES oligomers (containing more than 2 ether bonds and generally having a Mn of at least 500 and less than 1500 g / mol ) or dimers such as those of formulae (IIIa) and / or (IIIb) described above.

[0207] Recovery of phenolic monomer product from the liquid supernate

[0208] The liquid supernate (e.g., filtrate) generally comprises the majority of the formed phenolic monomers dissolved in the water / polar aprotic solvent mixture or in water / polar aprotic solvent / non-solvent mixture in instances when the non- solvent used in precipitation is not water.

[0209] This liquid supernate (e.g., filtrate) may be extracted with ethyl acetate (EtAc), and the liquid / liquid extraction is preferably repeated several times (such as 3 times).

[0210] The organic (EtAc) phase resulting from such extraction may be then dried over a chemical dessicant such as NaSO4, filtered and the remaining solvent is evaporated to dryness under reduced pressure such as in a rotary evaporation system (40 °C, 180 mbar). The recovered solid obtained from extraction of the liquid supernate (e.g., filtrate) provides the phenolic monomer product.

[0211] The obtained phenolic monomer product generally has a purity of at least 95 wt%(preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of phenolic monomers (based on the total weight of the phenolic monomer product).

[0212] In preferred embodiments, the obtained phenolic monomer product has a purity of at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of Bisphenol S or of its phenolate Na or K salt (based on the total weight of the phenolic monomer product).

[0213] Optional additional purification step

[0214] While the phenolic monomer product generally has a purity of at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%), based on the total weight of the phenolic monomer product, of phenolic monomers, in some instances it may be desirable to further increase the purity of the phenolic monomer product.

[0215] The phenolic monomer product be further purified by recrystallization in a chlorobenzene / ethyl acetate mixture. This is particularly advantageous when the phenolic monomer product contains the preferred phenolic monomers: - the monomers of formula (I) and of formula (Ia) (in phenolate or protonated form); or - the combination of the monomer of formula (I), monomer of formula (I’) in which T=C(CH3)2 (in phenolate or protonated form), monomers of formulae (Ia) and (Ib) in which T=C(CH3)2 (in phenolate or protonated form), or - the combination of the monomer of formula (I), monomer of formula (I’) in which T is a bond (in phenolate or protonated form), monomers of formulae (Ia) and (Ib) in which T is a bond (in phenolate or protonated form).

[0216] The phenolic monomer product is dissolved in a boiling mixture of ethyl acetate:chlorobenzene (generally 4 / 1 vol / vol). The ethyl acetate is removed by evaporation until the phenolic monomers precipitate out of solution. A highly- purified phenolic monomer product is then collected using hot filtration.

[0217] The highly-purified phenolic monomer product generally has a purity of at least 99.0 wt% (based on the total weight of the phenolic monomer product) of phenolic monomers.

[0218] In preferred embodiments, the phenolic monomer product which is further purified has a purity of at least 99.0 wt%, preferably at least 99.3 wt%, or more preferably at least 99.5 wt% (based on the total weight of the phenolic monomer product) for Bisphenol S represented by formula (I) in which M is replaced by H.

[0219] Phenolic monomer product

[0220] After purifying, the process which comprises depolymerisation of a PAES polymer into a depolymerized mixture and purification of the depolymerized mixture generates a phenolic monomer product according to the invention.

[0221] Particularly the present invention also relates to a phenolic monomer product obtained by the process.

[0222] After the purification step, the phenolic monomer product preferably comprises at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of phenolic monomers (based on the total weight of the phenolic monomer product).

[0223] After the purification step, the content of the at least one additive in the phenolic monomer product is less than the content of the at least one additive in the polymeric material before depolymerisation.

[0224] The content of the at least one additive in the phenolic monomer product after purification is preferably 80% less, 90% less, 95% less, 96% less, 97% less, 98% less, 99% less, 99.3% less, or 99.5% less than the content of the same additive inthe polymeric material before said % being calculated as [1- Af / A0] / 100 in which Afis the additive content in the phenolic monomer product and A0is the content of the same additive in the polymeric material.

[0225] For example, when the additive in the polymeric material is 5 wt% (= 50000 ppm) PVP, a PVP content of 1000 ppm or 150 ppm in the phenolic monomer product is 98% less or 99.7% less than its content in the polymeric material.

[0226] In preferred emboidments, the phenolic monomer product comprises from 0 ppm to 2 wt% of the at least one additive, based on the total weight of the phenolic monomer product.

[0227] The phenolic monomer product preferably comprises less than 2 wt% of at least one additive. This additive is preferably selected from the group consisting of PEG, PPG, PVP, a solid filler, a colorant, and any combination of two or more thereof.

[0228] The purity of the phenolic monomer product can be confirmed by1H-NMR spectroscopy and / or HPLC-MS analysis. Detection of PVP additive for example can be done using HPLC-UV. The analytical methods based on1H-NMR, HPLC- MS, and HPLC-UV provided in the Examples section are suitable for determining purity of the phenolic monomer product.

[0229] In some embodiments when the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of formula (K), the phenolic monomer product comprises: ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of the 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form, preferably of Bisphenol S; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or of the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive; said ppm and wt% being based on the total weight of the phenolic monomer product, wherein the formulae (K), (I), (Ia), (IIa) are previously described, in which - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; - each i is independently zero or an integer of 1 to 4;- M is a quaternary ammonium, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (Ia), (IIa) are in protonated form; - Reis an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X is a halide, preferably being Cl or F.

[0230] The phenolic monomer product may further comprise:  ^ up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form, said wt% being based on the total weight of the phenolic monomer product, wherein the formula (IIIa) is previously described, in which - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer from 1 to 4; - each of R2’, R2” is independently selected from an end-capped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group, in which M is selected from a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formula (IIIa) is in protonated form, with the proviso that at least one of R2’ and R2” in the formula (IIIa) is an -OM group and / or a halide X.

[0231] In some embodiments when the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of the formula (K) and formula (K’) in which T is C(CH3)2, said mol% being based on the total number of moles of recurring units in the PAES polymer, the phenolic monomer product comprises: ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) in which T is C(CH3)2or a combination of their respective protonated form, preferably of a combination of bisphenol S and bisphenol A; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; ^ from 10 ppm up to 2 wt% of the 4,4’-biphenolic monomer of formula (I’), the monophenolic monomer of formula (Ib), the monochloro monophenolicmonomer of formula (IIb), their respective protonated form, in which T in formulae (I’), (Ib), (IIb) is C(CH3)2; ^ optionally from 0 ppm up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form and / or the phenolic dimer of formula (IIIb) in which T is C(CH3)2, and / or their respective protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product, wherein the formulae (K), (K’), (I), (Ia), (IIa), (Ib), (IIb), (IIIa), (IIIb) are previously described, and in which - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; - T is a bond or –C(CH3)2-; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb), (IIIa), (IIIb) are in protonated form; - Re is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X is a halide, preferably being Cl or F.

[0232] In some embodiments when the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of the formula (K) and formula (K’) in which T is a bond, said mol% being based on the total number of moles of recurring units in the PAES polymer, the phenolic monomer product comprises: ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) in which T is a bond, or a combination of their respective protonated form, preferably of a combination of bisphenol S and 4,4’-biphenol; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; ^ from 10 ppm up to 2 wt% of the 4,4’-biphenolic monomer of formula (I’), the monophenolic monomer of formula (Ib), the monochloromonophenolic monomer (IIb), and / or their respective protonated form, in which T in formulae (I’), (Ib), (IIb) is a bond; ^ optionally from 0 ppm up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form and / or the phenolic dimer of formula (IIIb) in which T is a bond, and / or their respective protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product, wherein the formulae (K), (K’), (I), (Ia), (IIa), (Ib), (IIb), (IIIa), (IIIb) are previously described, and in which - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; - T is a bond or –C(CH3)2-; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb), (IIIa), (IIIb) are in protonated form; - Re is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X is a halide, preferably being Cl or F.

[0233] In preferred embodiments, Re in monomers of formulae (Ia) and (Ib) is a methoxy group.

[0234] In preferred embodiments, X in monomers of formulae (IIa) and (IIb) is Cl and / or F, preferably Cl.

[0235] M in the phenolic monomersof any of the formulae (I), (Ia), (IIa), (I’), (Ib), (IIb) and dimers of formulae (IIIa) and (IIIb) is preferably Na, K, or tetramethylammonium (TMA), or in their respective protonated form, M is H.

[0236] In preferred embodiments, the R2’, R2” in dimers of formulae (IIIa) and (IIIb) are Cl and –OM group; two –OM groups; or Cl and a methoxy group.

[0237] In a first particular embodiment, the phenolic monomer product comprises: - at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form, preferably Bisphenol S,- from 10 ppm up to 2 wt% of sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or a 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form, preferably of the protonated form of the 4,4’-sulfonyl monophenolic monomer of formula (Ia); and - from 0 to 2 wt% of at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product; wherein the formulae (I), (Ia), (IIa) are previously described, in which - each R in formulae (I), (Ia), (IIa) is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i in formulae (I), (Ia), (IIa) is independently zero or an integer of 1 to 4; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (Ia), (IIa) are in protonated form; - Rein formulae (Ia) is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X in formulae (IIa) is a halide, preferably being Cl or F.

[0238] In a second particular embodiment, the phenolic monomer product according to the invention comprises at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of phenolic monomers comprising : ^ 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form, ^ the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form, and ^ optionally the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa), the phenolic dimer of formula (IIIa), the 4,4’-isopropylidenebisphenolic monomer and / or 4,4’-biphenolic monomer of formula (I’), the monophenolic monomer of formula (Ib), the monochloro monophenolic monomer of formula (IIb), the phenolic dimer of formula (IIIb), and / or their respective protonated form; and ^ from 0 wt% to 2 wt% of the at least one additive; said wt% being based on the total weight of the phenolic monomer product, wherein the formulae (I), (Ia), (IIa), (Ib), (IIb), (IIIa), (IIIb) are previously described, in which- each R is independently the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; - T is a bond or –C(CH3)2-; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb) are in protonated form; - Re is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; - X is a halide, preferably being Cl or F; and - each of R2’, R2” is independently selected from an endcapped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group, in which M is selected from a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (IIIa), (IIIb) are in protonated form, with the proviso that at least one of R2’ and R2” in the formulae (IIIa) and (IIIb) is an -OM group and / or a halide X.

[0239] In a third particular embodiment, a phenolic monomer product comprises - at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) or of a combination of their respective protonated form, in which T is C(CH3)2 or a bond, preferably of a combination of bisphenol S and bisphenol A or of a combination of bisphenol S and 4,4’-biphenol; - from 10 ppm up to 2 wt% of a 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or a 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form, preferably of the protonated form of the 4,4’-sulfonyl monophenolic monomer of formula (Ia); - from 10 ppm up to 2 wt% of a monophenolic monomer of formula (Ib) or its protonated form, a monochloro monophenolic monomer of formula (IIb) or its protonated form, in which T is the same as in formula (I’), preferably of the protonated form of the monophenolic monomer of formula (Ib); and - from 0 ppm to 2 wt% of the at least one additive;said ppm and wt% being based total weight of the phenolic monomer product, wherein the formulae (I), (I’), (Ia), (IIa), (Ib), (IIb) are previously described, in which - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; - T is a bond or –C(CH3)2-; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb) are in protonated form; - Reis an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X is a halide, preferably being Cl or F.

[0240] In a fourth particular embodiment, when the PAES comprises or consists essentially of a PES polymer having the encapped group Re as one endgroup, the phenolic monomer product according to the invention may comprise at least 95 wt% based on the total weight of the phenolic monomer product (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of phenolic monomers comprising : the 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form in which M is H (e.g., bisphenol S or sulfonated bisphenol S), the at least one 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form in which M is H, and optionally the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form in which M is H.

[0241] In a fifth particularly preferred embodiment of the present invention, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of bisphenol S, ^ from 100 ppm up to 2 wt% of at least one 4,4’-sulfonyl monophenol monomer of the formula (Ia) in its protonated form, in which Reis a methoxy group and M is H; and ^ optionally, up to 5 wt% or less of at least one 4,4’-sulfonyl monohalo phenol monomer of the formula (IIa) in its protonated form, in which M is replaced by H,said ppm and wt% being the total weight of the phenolic monomer product.

[0242] In a sixth particularly embodiment, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of 4,4’-sulfonyl diphenolic monomer of the formula (I); ^ from 100 ppm up to 2 wt% of at least one 4,4’-sulfonyl monophenolic monomer of formula (Ia), in which Re is a methoxy group; and ^ optionally, up to 5 wt% of at least one 4,4’-sulfonyl monohalo phenolic monomer of formula (IIa); said ppm and wt% being based on the total weight of the phenolic monomer product, in which M in the formulae (I), (Ia) and (IIa) is the same and preferably selected from Na or K.

[0243] In a seventh particularly embodiment, when the PAES comprises or consists essentially of a PSU polymer having the encapped group Re as one end group and the halide X as the other end group, the phenolic monomer product according to the invention may comprise : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of the 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form in which M is H (e.g., bisphenol S or sulfonated bisphenol S); and ^ from 100 ppm up to 5 wt% of - the 4,4’-isopropylidenebisphenolic monomer of formula (I’) in which T is C(CH3)2 or its protonated form in which M is H (e.g., bisphenol A or sulfonated bisphenol A), - the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form in which M is H, - the at least one monochloro monophenolic monomer of formula (Ib) or its protonated form in which T is C(CH3)2and M is H, - the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form in which M is H, and / or - the 4,4’ monohalo monophenolic monomer of formula (IIb) or its protonated form in which T is C(CH3)2and M is H.

[0244] In an eighth particular embodiment, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of bisphenol S and bisphenol A;^ from 100 ppm up to 2 the monophenolic monomers of formula (Ia) and of formula (Ib) in their respective protonated form, in which Re in formulae (Ia) and (Ib) is a methoxy group, M in formulae (Ia) and (Ib) is replaced by H, and T in formula (Ib) is C(CH3)2; and ^ optionally, up to 5 wt% of the monohalo phenolic monomers of formula (IIa) and of formula (IIb) in their respective protonated form, in which M in formulae (IIa) and (IIb) is replaced by H, and T in formula (IIb) is C(CH3)2, said ppm and wt% being based on the total weight of the phenolic monomer product.

[0245] In a ninth particular embodiment, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of 4,4’-sulfonyl diphenolic monomer of the formula (I) and 4,4’-isopropylidenebisphenolic monomer of the formula (I’) in which T is C(CH3)2; ^ from 100 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) and the monophenolic monomer of formula (Ib), in which Re is a methoxy group; and ^ optionally, up to 5 wt% of at least one 4,4’-sulfonyl monohalo phenolic monomer of formula (IIa) and the monochloro monophenolic monomer of formula (IIb), in which X is Cl and / or F, said ppm and wt% being based on the total weight of the phenolic monomer product. In such an instance, M in the formulae (I), (I’), (Ia), (Ib), (IIa) and (IIb) is preferably the same and selected from Na or K.

[0246] In a tenth particular embodiment, when the PAES comprises or consists essentially of a PPSU polymer having the encapped group Re as one end group and the halide X as the other end group, the phenolic monomer product according to the invention may comprise : - at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of the 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form in which M is replaced by H (e.g., bisphenol S or sulfonated bisphenol S) and the 4,4’-biphenolic monomer of formula (I’) in which T is a bond or its protonated form in which M is H (e.g., 4,4’-biphenol or sulfonated 4,4’-biphenol), ^ from 100 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) and the monophenolic monomer of formula (Ib), in which Re is a methoxy group;^ from 100 ppm up to 2 the at least one monochloro monophenolic monomer of formula (Ib) or its protonated form in which M is replaced by H, and the monohalo monophenolic monomer of formula (IIb) or its protonated form in which M is H, said ppm and wt% being based on the total weight of the phenolic monomer product.

[0247] In an eleventh particular embodiment of the present invention, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of bisphenol S and 4,4’- bisphenol; ^ from 100 ppm up to 2 wt% of the monophenolic monomers of formula (Ia) and of formula (Ib) in their respective protonated form, in which Re in formula (Ia) is a methoxy group, M in formulae (Ia) and (Ib) is replaced by a hydrogen atom, and T in formula (Ib) is a bond; and ^ optionally, up to 5 wt% of monohalo phenolic monomers of formula (IIa) and of formula (IIb) in their respective protonated form, in which M in formulae (IIa) and (IIb) is replaced by H, X is Cl and / or F and T in formula (IIb) is a bond, said ppm and wt% being based on the total weight of the phenolic monomer product.

[0248] In a twelfth particular embodiment, the phenolic monomer product comprises : ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of 4,4’-sulfonyl diphenolic monomer of the formula (I) and 4,4’-biphenolic monomer of the formula (I’) in which T is a bond; ^ from 100 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) and the monophenolic monomer of formula (Ib), in which Re is a methoxy group and T in formula (Ib) is a bond; and ^ optionally, up to 5 wt% of at least one 4,4’-sulfonyl monohalo phenolic monomer of formula (IIa) and the monochloro monophenolic monomer of formula (IIb), in which X is Cl and / or F and T in formula (IIb) is a bond, said ppm and wt% being based on the total weight of the phenolic monomer product. In such an instance, M in the formulae (I), (I’), (Ia), (Ib), (IIa) and (IIb) is preferably the same and selected from Na and / or K.

[0249] In more preferred embodiments, monomer product is substantially free (meaning less than 100 ppm based on the total weight of the phenolic monomer product) of the at least one additive being a PVP.

[0250] When present, the content of the at least one additive in the phenolic monomer product may be from 10 ppm up to 2 wt%, or from 100 ppm to 2 wt%, or from 100 ppm to less than 2 wt%, or from 100 ppm to 1 wt%, or from 100 ppm to 500 ppm, or from 100 ppm to 200 ppm, said ppm and wt% being based on the total weight of the phenolic monomer product.

[0251] The phenolic dimer of formula (IIIa) or (IIIb) can also be removed from the phenolic monomer product, being present in an amount from >0 (e.g., at least 10 ppm or at least 100 ppm) and up to 2 wt%, or up to 1 wt%, or preferably up to 500 ppm or up to 200 ppm, said ppm and wt% being based on the total weight of the phenolic monomer product. Examples

[0252] The invention will be now described in more detail with reference to the following examples whose purpose is merely illustrative and not limitative of the scope of the invention.

[0253] Raw Materials

[0254] In the following examples, hemodialysis fibers containing polyethersulfone (PES) and polyvinylpyrrolidone (PVP) (generally 3-6 wt% PVP in the fibers) were used.

[0255] Sodium hydroxide (NaOH), potassium hydroxide (KOH), dimethylsulfoxide (DMSO), HCl, NaCl, sodium sulfate (Na2SO4) were available from Sigma-Aldrich.

[0256] Analytical Methods

[0257] 1H-NMR spectroscopy: Samples were dissolved in deuterated dimethyl sulfoxide (DMSO). All samples were run on a Bruker 400 MHz NMR, with a D1 set to 1 seconds and 64 scans. Data was processed using Topspin / NMR notebook software.

[0258] HPLC-MS: An Agilent HPLC-PDA-MS (800 bar) was used to determine the BPS purity. A gradient method was used where the sample was dissolved in acetonitrile at a concentration of 0.5 mg / mL. The mobile phase was a gradient of acetonitrile / 0.1% acetic acid. The column used was a Sunfire C18 Column. The PDA detection wavelength was at 273 nm, and the mass detection was performed using an ESI / APCI mix in negative mode. Purity was based on peak area integration.In the following tests, different basic compounds, different solvents, different reaction temperatures and times, different alkali contents (in term of Equivalence with respect to PES molar amount), and different DMSO / water volumetric ratios were investigated.

[0259] HPLC-UV: Size exclusion was performed, utilizing an Agilent 1100 series HPLC with a photodiode array (PDA) detector, for PVP detection and quantification. A PL Aquagel-OH 60 (8 µm x 300 mm x 7.5 mm) column was used as the stationary phase and an isocratic mobile phase consisting of 50 / 50 water / acetonitrile was implemented, with a total analysis time of 25 minutes. The flow rate was set to 1 mL min-1 at a column temperature of 60 °C and an injection volume of 20 µL. The PVP was detected and quantified utilizing the wavelength of 200 nm. The limit of detection, on a sample basis, for PVP is 100 ppm.

[0260] Example 1

[0261] Procedure 1

[0262] Depolymerisation: In a three-neck, 500 mL round bottom flask fitted with a reflux condenser and temperature sensor, 5 g of hemodiaylsis fiber, 50 mL of DMSO, and a stir bar were added. The PES in the hemodiaylsis fiber had chloride and methoxy end groups. The reaction mixture was heated in an oil bath to 90 °C and stirred for 20 minutes. Subsequently, 2.5 mL of water was added to the solution in portions. Once the PES was completely dissolved, 4.09 g (5 molar equiv.) of sodium hydroxide pellets were added. After about 2 hours, the reaction mixture became homogeneous and yellow coloured. The reaction mixture was heated to 125 °C for 24 hours under nitrogen atmosphere. Afterward, the reaction mixture was cooled to room temperature (often solidification of the whole reaction mass was observed).

[0263] Neutralisation by acidification: Then, HCl (2 M) was added to the solution until a pH of 1–2 was observed while maintaining 10–22 °C temperature. The mixture was stirred for 15 minutes. A sample was taken to check the crude reaction mixture profile.

[0264] Precipitation: Afterward, the reaction mixture was poured into 125 mL of deionized water and stirred for 30 minutes. At this step it was generally observed that a bisphenol S dimer, undissolved PVP, and optionally other dimers / oligomers precipitated.

[0265] Filtration: The acidified aqueous mixture was then filtered through Whatman No. 1 paper under vacuum to recover an impure product filtrate (which is aqueous) and a solid. The solid contained at least some bisphenol S dimer and precipitated PVP. The impure product filtrate contained bisphenol S, some sulfonyl monophenolic monomers, some remnant PVP, and some remnant of DMSO.

[0266] Liquid / liquid Extraction: The impure product filtrate was extracted three times with 70 mL of ethyl acetate (EtAc) to generate an aqueous phase and an organic (EtAc) phase, in which the organic phase contained the desired bisphenol S and some sulfonyl monophenolic monomers and some remnant of water, and the aqueous phase contained some PVP and DMSO dissolved in water.

[0267] EtAc removal: The organic phase was then washed with NaCl brine (although this wash is optional in the procedure), and water was removed by contact with solid sodium sulfate (Na2SO4). The solid sodium sulfate was then removed from the organic (EtAc) phase by filtration, and the ethyl acetate in the resulting organic filtrate was removed under reduced pressure to yield a solid.

[0268] Drying and monomer recovery: The isolated solid was dried under high vacuum for 8 hours to yield a monomer product 1 (MP1). The MP1 was an off-white solid.

[0269] Overall yield in Bisphenol S from PES (number of moles of BPS relative to the number of moles of PES in the reaction medium) = 80 mol%

[0270] Analysis of the monomer product 1 (MP1):

[0271] Purity in Bisphenol S measured by HPLC-MS was 97.9 wt% in MP1. Analytically calculated for C12H10O4S: C (57.59%), H (4.03%), N (0.00), S (12.81%); Found: C (56.74%), H (4.10%), N (0.01%), S (13.48%).

[0272] HPLC-MS also detected 1.05 wt% of monomethoxy bisphenol S, 0.54 wt% of Bisphenol S dimer and 0.02 wt% of monochloro bisphenol S.

[0273] No PVP was detected using the HPLC-UV method down to 100 ppm.

[0274] Example 2

[0275] Procedure 2

[0276] The depolymerisation was carried out in the same manner as in Procedure 1 for Example 1, except that the reaction mixture was heated to 100 °C for 24 hours under nitrogen atmosphere. The subsequent steps (Neutralisation by acidification, Precipitation, Filtration, Liquid / liquid Extraction, EtAc removal, Drying and monomer recovery) were carried out as described in the Procedure 1 for Example 1 to obtain a monomer product 2 (MP2).

[0277] Overall yield in Bisphenol S from PES (number of moles of BPS relative to the number of moles of PES in the reaction medium) = 63 mol%

[0278] Analysis of the monomer product 2 (MP2):

[0279] Purity in Bisphenol S measured by HPLC-MS was 97.9 wt% in MP2. Analytically calculated for C12H10O4S: C (57.59%), H (4.03%), N (0.00), S (12.81%); Found: C (56.75%), H (4.19%), N (0.00%), S (13.48%). HPLC-MS also detected 1.52 wt% monomethoxy Bisphenol S, 0.30 wt% of Bisphenol S dimer and 0.16 wt% monochloro Bisphenol S in MP2.

[0280] PVP was detected using the LC-UV method at 154 ppm.

[0281] Example 3

[0282] Procedure 3

[0283] The same procedure was performed acoording to Procedure 1 for Example 1 to obtain a monomer product 3 (MP3), except that KOH replaced NaOH as the basic coumpound during depolymerisation.

[0284] Overall yield in Bisphenol S (number of moles of BPS relative to the number of moles of PES in the reaction medium) = 89 mol%.

[0285] Analysis of the monomer product 3 (MP3):

[0286] Purity in Bisphenol S (BPS) in MP3 was 98.5 wt% measured by HPLC-MS. Analytically calculated for C12H10O4S: C (57.59%), H (4.03%), N (5.76), S (12.81%); Found: C (56.8%), H (4.2%), N (0.0%), S (13.4%). HPLC-MS also detected 1.05 wt% monomethoxy Bisphenol S, 0.01 wt% Bisphenol S dimer and 0.12 wt% monochloro Bisphenol S.

[0287] Example 4

[0288] The monomer product 3 (MP3) obtained in Example 3 was further purified to increase the BPS content by recrystallization in a chlorobenzene / ethyl acetate mixture. The monomer product 3 containing 98.5 wt% BPS was dissolved in a boiling 4:1 mixture of ethyl acetate:chlorobenzene. The ethyl acetate was removed until the BPS precipitated out of solution. A highly-purified BPS product (MP4) was collected using hot filtration.

[0289] Analysis of the highly-purified BPS product (MP4)

[0290] Purity of BPS determined by HPLC-MS was 99.7 wt% in MP4.

[0291] HPLC-MS also detected 0.13 wt% monomethoxy Bisphenol S, 0.01 wt% of bisphenol S dimer and 0.03 wt% of monochloro bisphenol S in MP4.

[0292] In Table 1 is summarized the yield in Bisphenol S from Examples 1-4 and purity of the phenolic monomer products (MP1, MP2, MP3, MP4), as well as certain depolymerisation conditions in Procedures 1-3 (polymerization temp., basic compound).

[0293] Table 1 Example 1 Example 2 Example 3 Example 4 Basic compound NaOH NaOH KOH - Depolym. Temp.,oC 125 100 125 - Yield of BPS, mol% 80 63 89 - monomer product, wt% MP1 MP2 MP3 MP4 BPS 97.9 97.9 98.5 99.7 Monomethoxy BPS 1.05 1.52 1.05 0.13 Monochloro BPS 0.02 0.16 0.12 0.03 BPS dimer 0.54 0.30 0.01 0.01 PVP, ppm <100 154

[0294] In Table 1, the “BPS” represents Bisphenol S represented by formula (I) in which M is replaced by H and in which i=0 for all R. The “monomethoxy BPS” represents the monomer of formula (Ia) in which M is replaced by H; Re is a methoxy and i=0 for all R. The “monochloro BPS” represents the monomer of formula (IIa) in which M is replaced by H; X is Cl and i=0 for all R.

[0295] While preferred embodiments invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of systems and methods are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the preferred embodiments of the present invention.

[0296] What is claimed is:

Claims

1. A process for recycling a polymeric material comprising at least one polyarylethersulfone and at least one additive to produce a phenolic monomer product, comprising: ^ in a reaction medium containing a polar aprotic solvent, a basic compound, and a polymeric material comprising at least one polyarylethersulfone (“PAES polymer”) and at least one additive, depolymerizing said PAES polymer at a reaction temperature of at least 80℃, or at least 100℃, or at least 110℃, or at least 120℃ and at most 180℃, or at most 170℃, or at most 160℃, or at most 150℃ to obtain a depolymerized mixture comprising phenolic monomers, said PAES polymer comprising a backbone containing at least one recurring unit represented by formula (K) and two end groups, each being independently selected from a halide X, an hydroxy group and / or an end-capped group Re, with the proviso that when one end group is a halide X, the other end group is an hydroxy group and / or an end-capped group Re, and when one end group is an end-capped group Re, the other end group is a halide X and / or another end-capped group Re; said additive comprising at least one polyvinylpyrrolidone (PVP), at least one polyalkylene oxide (PAO), or any combination thereof; said basic compound in the reaction medium containing a base and a counter- cation, said base being selected from hydroxide and / or alkoxide, and said counter-cation of the basic compound being selected from quaternary ammonium, an alkali metal cation, and / or an alkaline earth metal cation; the amount of the basic compound used in the depolymerization being in the range from 2 to 8 equivalents, preferably from 2 to 7 equivalents, more preferably from 2 to 6 equivalents, still more preferably from 2 to 5 equivalents, said equivalent being relative to the total number of oxygen atoms (the total number of oxygen equivalents) forming the ether bonds in the PAES polymer; and ^ purifying the depolymerized mixture to obtain a phenolic monomer product; wherein, after purifying, ^ the phenolic monomer product comprises at least 95 wt% of phenolic monomers and from 0 to 5 wt% of the at least one additive, said wt% being based on the total weight of the phenolic monomer product, with the proviso that the content of the at least one additive in the phenolic monomer product is less than the content of the at least one additive in the polymeric material before the depolymerizing step; wherein the phenolic monomers in the phenolic monomer product comprise:^ a 4,4’-sulfonyl diphenolic of formula (I) or its protonated form, preferably bisphenol S; ^ at least one monophenolic monomer selected from a 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or a 4,4’- sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; and ^ optionally, at least one 4,4’-sulfonyl dimer of formula (IIIa) or its protonated form; wherein the formula (K) of the PAES recurring unit is as follows: ,- in the formula (K), each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - in the formula (K), each i is independently zero or an integer of 1 to 4; and wherein the formulae (I), (Ia), (IIa), (IIIa) are represented as follows: ;; - in formulae (I), (Ia), (IIa), M is a counter-cation originating from the basic compound used in the depolymerization step, M being preferably a quaternary ammonium, Na, K, and / or Cs, or M is H in the protonated form of the formulae (I), (Ia), (IIa); - in formula (Ia), Reis an end-capped group, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; and - in formula (IIa), X is a halide, preferably being Cl or F; - in formulae (I), (Ia), (IIa), (IIIa), each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; - in formulae (I), (Ia), (IIa), (IIIa), each i is independently zero or an integer of 1 to 4; and - in formula (IIIa), each of R2’, R2” is independently selected from an end-capped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group in which M is a counter- cation originating from the basic compound used in the depolymerization step, preferably selected from a quaternary ammonium, Na, K, and / or Cs, more preferably selected from Na and / or K, or M is H when the formula (IIIa) is in protonated form, with the proviso that at least one of R2’ and R2” in the formula (IIIa) is an -OM group and / or a halide X.

2. The process of Claim 1, wherein the PAES polymer further contains another recurring unit represented by formula (K’), ,- T is a bond or –C(CH3)2-; - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkalineearth metal sulfonate, sulfonic acid (- , alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4.

3. The process of Claim 2, wherein the phenolic monomers in the phenolic monomer product further comprise : ^ a 4,4’-biphenolic monomer of formula (I’) or its protonated form; ^ at least one monophenolic monomer selected from a monophenolic monomer of formula (Ib) or its protonated form and / or a monochloro monophenolic monomer of formula (IIb) or its protonated form; and ^ optionally a phenolic dimer of formula (IIIb) or its protonated form, wherein the formulae (I’), (Ib), (IIb), (IIIb) are represented as follows: (IIIb),- in formulae (I’), (Ib), (IIb), (IIIb), each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; - in formulae (I’), (Ib), (IIb), (IIIb), each i is independently zero or an integer of 1 to 4;- T in the formulae (I’), (Ib), (IIb), (IIIb) or –C(CH3)2-, and is the same T present in the formula (K’); - in the formulae (I’), (Ib), (IIb), M is a counter-cation originating from the basic compound used in the depolymerization step, preferably a quaternary ammonium, Na, K, and / or Cs, more preferably Na and / or K, or M is H in the protonated form of the formulae (I’), (Ib), (IIb); - in formula (Ib), Re is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; - in formula (IIb), X is a halide, preferably being Cl or F; and - in formula (IIIb), each of R2’, R2” is independently selected from an end-capped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group in which M is a counter-cation originating from the basic compound used in the depolymerization step, preferably being selected from a quaternary ammonium, Na, K, and / or Cs, more preferably Na and / or K, or M is H when the formula (IIIb) is in protonated form, with the proviso that at least one of R2’ and R2” in the formula (IIIb) is an -OM group and / or a halide X.

4. The process of any one of Claims 1 to 3, wherein, prior to purifying, the depolymerized mixture comprises the phenolic monomers in an amount of at least 75 wt%, at least 80 wt%, and preferably at least 85 wt%, or at least 90 wt%, or at least 92 wt%, or at least 95 wt%, or at least 97 wt%, or at least 98 wt%, or at least 99 wt%, or at least 99.5 wt%, based on the total weight of the depolymerized mixture without solvent.

5. The process of any one of Claims 1 to 4, wherein ^ the monophenolic monomer of formula (Ia) or its protonated form, when present in the phenolic monomer product, is in an amount of at least 10 ppm up to 2 wt%; and / or ^ the monohalo monophenolic monomer of formula (IIa) or its protonated form, when present in the phenolic monomer product, is in an amount of at least 10 ppm up to 2 wt%; and / or ^ the phenolic dimer of formula (IIIa) or its protonated form, when present in the phenolic monomer product, is in an amount of at least 10 ppm up to 5 wt%; and / or ^ the at least one additive, when present in the phenolic monomer product, is in an amount of at least 10 ppm up to 2 wt%, said ppm and wt% being based on the total weight of the phenolic monomer product.

6. The process of any one of Claims 1 said end-capped group Re is selected from phenoxy groups, alkoxy groups, or combination thereof, preferably is an alkoxy group, more preferably is a methoxy group.

7. The process of any one of Claims 1 to 6, wherein one end group of the PAES polymer is a halide X, and the other end group of the PAES polymer is an end-capped group Re.

8. The process of any one of Claims 1 to 7, wherein the depolymerizing step comprises mixing the polar aprotic solvent, water, the polymeric material and the basic compound in a reactor vessel to form the reaction medium.

9. The process of any one of Claims 1 to 8, wherein the polar aprotic solvent in the reaction medium is selected from the group consisting of N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N-butylpyrrolidinone (NBP), tetramethylene sulfone (sulfolane), dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone (DMI), N,N dimethylacetamide (DMAc), diphenyl sulfone (DPS), and any combination thereof.

10. The process of any one of Claims 1 to 9, wherein the basic compound in the reaction medium is an alkali metal hydroxide, a quaternary ammonium hydroxide, an alkali metal alkoxide and / or an alkaline earth metal alkoxide, preferably an alkali metal hydroxide selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), and / or cesium hydroxide (CsOH), more preferably sodium hydroxide (NaOH) and / or potassium hydroxide (KOH).

11. The process of any one of Claims 1 to 10, wherein the depolymerizing step further comprises the step of heating the reaction medium to reach a reaction temperature of at least 100℃, or at least 110℃, or at least 120℃ and / or at most 180℃, or at most 170℃, or at most 160℃, or at most 150℃.

12. The process of any one of Claims 1 to 11, wherein the reaction medium comprises water, and wherein the polar aprotic solvent and water are present in the reaction medium in a volumetric ratio of polar aprotic solvent to water of at least 10:1, preferably at least 15:1, or at least 20:1, and at most 150:1, and / or at most 140:1, or at most 130:1, or at most 120:1, or at most 110:1, or at most 100:

1.

13. The process of any one of Claims 1 to 12, wherein the PAES polymer in the polymeric material is selected from the group consisting of: PPSU;PSU; PES; sulfonated PSU; sulfonated PES; sulfonated PPSU; any polymer derived from a diol monomer selected from isosorbide and / or tetramethyl bisphenol F and a dihalo monomer selected from sulfonated dihalodiphenylsulfone and / or dihalodiphenylsulfone; any copolymer derived from at least two diols selected from biphenol, bisphenol A, bisphenol S, isosorbide, tetramethyl bisphenol F, and / or hydroquinone and a dihalo monomer selected from sulfonated dihalodiphenylsulfone and / or dihalodiphenylsulfone; a block polymer in the form A-B or A-B-A, comprising at least one sulfone polymer block having one recurring unit selected from those of PPSU, sPPSU, PSU, sPSU, PES, sPES, and at least one block having one recurring unit made from tetramethyl bisphenol F and sulfonated or non-sulfonated dihalodiphenylsulfone or from a 1,4:3,6-dianhydrohexitol sugar diol and sulfonated or non-sulfonated dihalodiphenylsulfone; and a block copolymer in the form A-B or A-B-A, comprising at least one block polymer having one recurring unit selected from those of PPSU, sPPSU, PSU, sPSU, PES, sPES, and at least one polyalkylene oxide or polyvinylpyrrolidone (PVP) block, such as a PEG block, PPG block or a PVP block; and any combination thereof.

14. The process of any one of Claims 1 to 13, wherein the polymeric material is in solid form, such as pellets, fibers, flakes, powder, pieces of shredded or ground articles, coagulated particles, or any other solid 3-D objects, or in form of a solution or slurry in which at least part of the PAES polymer is dissolved before being subjected to the depolymerizing step.

15. The process of any one of Claims 1 to 14, wherein the polymeric material comprises at least one material selected from the group consisting of post-consumer and post- industrial polymeric articles, polymeric scraps, off-specification PAES polymer products; and any combination thereof, said polymeric articles preferably being selected from the group consisting of membranes, automotive components, electronic components, consumer product components such as baby bottles, composites, battery components, plumbing parts, animal cages, and any combinations thereof.

16. The process of any one of Claims 1 the at least one additive in the polymeric material is selected from the group consisting of : ^ at least one PVP, ^ at least one PEG, ^ at least one PPG, and ^ any combination thereof; preferably selected from the group consisting of: ^ at least one PVP, ^ at least one PEG, and   ^ any combination thereof; more preferably selected from the group consisting of: ^ at least one PVP.

17. The process of any one of Claims 1 to 16, further comprising subjecting the depolymerized mixture to an acid treatment before the purifying step.

18. The process of any of Claims 1 to 17, wherein the purifying step comprises - mixing the depolymerized mixture in a non-solvent to form a precipitate which optionally contains at least one solid additive, and a liquid phase which contains at least a portion of the phenolic monomer product and optionally at least one soluble additive; - separating, preferably by filtration, said liquid phase from the precipitate; and - drying said liquid phase to recover a phenolic monomer product in solid form.

19. The process of Claim 18, wherein, when the phenolic monomer product contains at least one water-soluble additive, the purifying step further comprises: - mixing the phenolic monomer product in solid form with ethyl acetate (“EtAc”) to generate a mixture; - performing a liquid-liquid extraction, preferably counter-currently, with water on said mixture to form a water phase rich in the at least one water-soluble additive and an EtAc phase rich in the phenolic monomer product and containing some remnant water; - adding a solid dessicant agent, such as sodium sulfate, to the EtAc phase to remove at least a portion of the remnant water; and - evaporating the ethyl acetate to recover a purified phenolic monomer product.

20. The process of any one of Claims 1 wherein the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of formula (K), and wherein the phenolic monomer product comprises: ^ at least 95 wt% of the 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form, preferably of Bisphenol S; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or of the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; ^ optionally from 0 ppm up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive; said ppm and wt% being based on the total weight of the phenolic monomer product.

21. The process of any one of Claims 2 to 20, wherein the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of the formula (K) and formula (K’) in which T is C(CH3)2, said mol% being based on the total number of moles of recurring units in the PAES polymer, and wherein the phenolic monomer product comprises: ^ at least 95 wt% of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) in which T is C(CH3)2 or a combination of their respective protonated form, preferably of a combination of bisphenol S and bisphenol A; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; ^ from 10 ppm up to 2 wt% of the 4,4’-biphenolic monomer of formula (I’), the monophenolic monomer of formula (Ib), the monochloro monophenolic monomer of formula (IIb), and / or their respective protonated form, in which T in formulae (I’), (Ib), (IIb) is C(CH3)2; ^ optionally from 0 ppm up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form and / or the phenolic dimer of formula (IIIb) in which T is C(CH3)2, and / or their respective protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product.

22. The process of any one of Claims 2 to 21, wherein the PAES polymer comprises more than 95 mol% and up to 100 mol% of recurring units of the formula (K) and formula (K’)in which T is a bond, said mol% being the total number of moles of recurring units in the PAES polymer, and wherein the phenolic monomer product comprises: ^ at least 95 wt% of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) in which T is a bond, or a combination of their respective protonated form, preferably of a combination of bisphenol S and 4,4’-biphenol; ^ from 10 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or the 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form; ^ from 10 ppm up to 2 wt% of the 4,4’-biphenolic monomer of formula (I’), the monophenolic monomer of formula (Ib), the monochloro monophenolic monomer of formula (IIb), and / or their respective protonated form, in which T in formulae (I’), (Ib), (IIb) is a bond; ^ optionally from 0 ppm up to 5 wt% of the phenolic dimer of formula (IIIa) or its protonated form and / or the phenolic dimer of formula (IIIb) in which T is a bond, and / or their respective protonated form; and ^ from 0 ppm to 2 wt% of the at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product.

23. The phenolic monomer product obtained by the process of any one of Claims 1 to 22.

24. A phenolic monomer product, comprising ^ at least 95 wt% of a 4,4’-sulfonyl diphenolic monomer of formula (I) or its protonated form, preferably Bisphenol S, ^ from 10 ppm up to 2 wt% of at least one sulfonyl monophenolic monomer selected from a 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or a 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form, preferably of the protonated form of the 4,4’-sulfonyl monophenolic monomer of formula (Ia); and ^ from 0 to 2 wt% of at least one additive, said ppm and wt% being based on the total weight of the phenolic monomer product; or ^ at least 95 wt% of a combination of 4,4’-sulfonyl diphenolic monomer of formula (I) and 4,4’-biphenolic monomer of formula (I’) or of a combination of their respective protonated form, in which T is C(CH3)2or a bond, preferably of a combination of bisphenol S and bisphenol A or of a combination of bisphenol S and 4,4’-biphenol;^ from 10 ppm up to 2 wt% of at least monophenolic monomer selected from a 4,4’-sulfonyl monophenolic monomer of formula (Ia) or its protonated form and / or a 4,4’-sulfonyl monohalo monophenolic monomer of formula (IIa) or its protonated form, preferably of the protonated form of the 4,4’-sulfonyl monophenolic monomer of formula (Ia); ^ from 10 ppm up to 2 wt% of at least one monophenolic monomer selected from a monophenolic monomer of formula (Ib) or its protonated form, a monochloro monophenolic monomer of formula (IIb) or its protonated form, in which T is the same as in formula (I’), preferably of the protonated form of the monophenolic monomer of formula (Ib); and ^ from 0 ppm to 2 wt% of the at least one additive; said ppm and wt% being based on the total weight of the phenolic monomer product, wherein the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb) are represented as follows: ; ;(IIb);  in - each R is independently selected from the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer of 1 to 4; - T is a bond or –C(CH3)2-; - M is a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (I), (I’), (Ia), (Ib), (IIa), (IIb) are in protonated form; - Re is an end-capped group, preferably selected from an alkoxy group and / or phenoxy group, more preferably a methoxy group; and - X is a halide, preferably being Cl or F.

25. The phenolic monomer product of Claim 24, comprising: - less than 2 wt% of at least one additive selected from the group consisting of PEG, PPG, PVP, and any combination of two or more thereof.

26. The phenolic monomer product of Claim 24 or 25, further comprising: - up to 5 wt% of a phenolic dimer of formula (IIIa) or its protonated form and / or a phenolic dimer of formula (IIIb) or its protonated form, preferably of the phenolic dimer of formula (IIIa) in protonated form, said wt% being based on the total weight of the phenolic monomer product, wherein the formulae (IIIa), (IIIb) are represented as follows: ,- each R is independently the group consisting of halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali or alkaline earth metal sulfonate, sulfonic acid (-SO3H), alkyl sulfonate, alkali or alkaline earth metal phosphonate, alkyl phosphonate, amine, and quaternary ammonium; and - each i is independently zero or an integer from 1 to 4; - T is a bond or –C(CH3)2-; - each of R2’, R2” is independently selected from an end-capped group Re, preferably selected from an alkoxy group and / or a phenoxy group, more preferably a methoxy group; a halide X, preferably selected from chloride and / or fluoride, more preferably chloride; and / or an -OM group, in which M is selected from a quaternary ammonium, Na, K, and / or Cs, preferably Na and / or K, or M is H when the formulae (IIIa), (IIIb) are in protonated form, with the proviso that at least one of R2’ and R2” in the formulae (IIIa) and (IIIb) is an - OM group and / or a halide X.

27. The phenolic monomer product of any one of Claims 24 to 26, comprising ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of bisphenol S, ^ from 10 ppm up to 2 wt% of at least one sulfonyl monophenol monomer selected from the 4,4’-sulfonyl monophenol monomer of the formula (Ia) in its protonated form, in which M is H; and / or the 4,4’-sulfonyl monohalo phenol monomer of the formula (IIa) in its protonated form, in which M is hydrogen, preferably of the 4,4’-sulfonyl monophenol monomer of the formula (Ia) in its protonated form, in which Re is a methoxy group and M is H; said ppm and wt% being based on the total weight of the phenolic monomer product.

28. The phenolic monomer product of any one of Claims 24 to 26 comprising ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of the 4,4’-sulfonyl diphenolic monomer of the formula (I); and ^ from 10 ppm up to 2 wt% of at least one sulfonyl monophenol monomer selected from the 4,4’-sulfonyl monophenol monomer of the formula (Ia) and / or the 4,4’-sulfonyl monohalo phenol monomer of the formula (IIa), preferably of the 4,4’-sulfonyl monophenol monomer of the formula (Ia) in which Re is a methoxy group;^ said ppm and wt% being the total weight of the phenolic monomer product, in which M in the formulae (I), (Ia) and (IIa) is the same and selected from Na and / or K.

29. The phenolic monomer product of any one of Claims 24 to 26, comprising ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of bisphenol S and bisphenol A; ^ from 100 ppm up to 2 wt% of the monophenolic monomers of formula (Ia) and of formula (Ib) in their respective protonated form, in which M in formulae (Ia) and (Ib) is a hydrogen atom, and T in formula (Ib) is C(CH3)2, preferably in which Re in formulae (Ia) and (Ib) is a methoxy group, and ^ optionally, up to 5 wt% of monohalo phenolic monomers of formula (IIa) and of formula (IIb) in their respective protonated form, in which M in formulae (IIa) and (IIb) is a hydrogen atom, and T in formula (IIb) is C(CH3)2,preferably in which X in formulae (Ia) and (Ib) is Cl; said ppm and wt% being based on the total weight of the phenolic monomer product.

30. The phenolic monomer product of any one of Claims 24 to 26, comprising ^ at least 95 wt% (preferably at least 96 wt%, at least 97 wt%, or at least 98 wt%, or at least 99.5 wt%) of a combination of bisphenol S and 4,4’-biphenol; ^ from 100 ppm up to 2 wt% of the 4,4’-sulfonyl monophenolic monomers of formula (Ia) and of formula (Ib) in their respective protonated form, in which M is H, and T in formula (Ib) is a bond, preferably in which Re in formula (Ia) is a methoxy group and X in formula (Ib) is Cl; and ^ optionally, up to 5 wt% of the monohalo phenolic monomers of formula (IIa) and of formula (IIb) in their respective protonated form, in which M in formulae (IIa) and (IIb) is H, and T in formula (IIb) is a bond, preferably in which X in formulae (IIa) and (IIb) is Cl; said ppm and wt% being based on the total weight of the phenolic monomer product.