Depolymerisation of polyethersulfone, depolymerized mixture recovered therefrom, and 4,4-di-substituted diphenylsulfone products isolated therefrom

Abstract

A method (A) for preparing a mixture comprising 4,4'-substituted diphenylsulfones from a polymeric material comprising at least one PES polymer, comprising (a) contacting the polymeric material with an ammonia source to depolymerize the PES polymer and (b) recovering a depolymerized mixture comprising 4,4'-substituted diphenylsulfones. A method (B) for preparing at least one 4,4'-substituted diphenylsulfone product, comprising the steps (a) and (b) and further at least one isolation step (c). A 4,4'-substituted diphenylsulfone product comprises dapsone and 4-amino-4'-hydroxydiphenylsulfone [A-B compound], or comprises the A-B compound and bisphenol S. When the polymeric material contains PVP, there is no detectable PVP in the 4,4'-substituted diphenylsulfone product.

Description

Depolymerisation of polyethersulfone, depolymerized mixture recovered therefrom, and 4,4’-di-substituted diphenylsulfone products isolated therefrom

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 679364 filed on August 5, 2024, and to European application No. 24217459.7 filed on December 4, 2024, the entire content of these applications being incorporated herein by reference for all purposes.

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a process for depolymerisation of poly ethersulfone (PES) polymer and a diphenyl sulfone product obtained therefrom, said diphenyl sulfone product containing at least one of dapsone, aminohydroxy diphenylsulfone, and bisphenol S.

[0005] BACKGROUND

[0006] The omnipresence of polymers and the importance of environmental policies have led to the increased importance of recycled polymeric materials. Virgin polymer composition replacement is considered to represent a significant way forward to solving 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.

[0007] 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.

[0008] 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 via mechanical means. Compared to chemical 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 which can be re-used as a feedstock for the production of new chemicals and polymers. For most polymers, many chemical recycling methods lead to products other than the constituent monomers, meaning that such recycling methods lack the ability to produce components that are able to be directly repolymerized back to the same polymer.

[0009] 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 or cycled into a higher-value application than the application from which the polymer waste originated. 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. Since polymers reuse in their originally intended application is in general quite limited, an upcycling would be an improvement over incumbent technologies in which polymers are down-cycled for less-demanding and / or lower-value applications thus limiting their end-use.

[0010] 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 dihalogenated diphenylsulfone (the sulfone monomer) along with aromatic diols such as Bisphenol A (BP A), 4,4’- biphenol (BP) or 4,4’ -dihydroxy di phenylsulfone (DHDPS) also known as Bisphenol S.

[0011] The amorphous PAES polymers are successfully used in various applications such as automotive, electronic equipment, medical devices, composites and aerospace. The PAES polymers exhibit a unique property profile particularly useful across these applications that include high temperature resistance, toughness, resistanceto steam sterilization, inherent flame retardancy, transparent, superior chemical resistance, excellent mechanical strength and outstanding dimensional stability ensuring reliability and longevity in products designed for high-performance and critical environments. PAES polymers can also be used as toughening agents in epoxy resin composites. The toughness or the impact properties of such an epoxy composite can be enhanced by increasing the amount of poly sulfones in the matrix.

[0012] In particular, one of the PAES polymers is polyethersulfone (PES), which is a high-performance thermoplastic known for its robustness and exceptional stability across a wide range of temperatures and environments, making it an ideal material for a variety of demanding applications. Products made from PES include components in the aerospace and automotive industries, such as connectors and parts of fuel systems, due to the excellent thermal stability, chemical resistance, and mechanical properties of PES. In the medical field, PES is used for making surgical instruments, medical devices, and membrane filters because of its ability to withstand repeated sterilization processes without degrading. Additionally, its inherent flame retardancy and low smoke emission characteristics make it suitable for electrical and electronic applications, including insulators and circuit boards. The PES polymer is also considered having good biocompatibility - meaning it has a minimal impact on clotting factor for blood when used in hemodialysis membrane applications. As a result, PES finds broad utility in medical devices where steam sterilization is needed, water filtration and membrane separation among other applications including plumbing and aerospace.

[0013] As a consequence of the widespread use of PES, there is an increase in industrial waste and end-of-life products containing PES polymers, and in recent years in lieu of being discarded, there is an increasing interest in recycling such PES-based materials. However, the PES polymer is relatively difficult to decompose due to their excellent chemical resistance and heat resistance.

[0014] A few decomposition methods applicable to chemical recycling of PAES polymers have been studied.

[0015] Low molecular weight PAES polymers (PAES oligomers) can be generated through chemical depolymerization of high molecular weight PAES materials. Since a PAES polymer is a polymer composed of sulfone as well as ether linkages, due to the strong electron withdrawing effect of the sulfone groups, the ether linkages are activated towards nucleophilic attack.

[0016] EP0532893 (Hercules) relates to a process of preparing a reactive reduced molecular weight polyarylene poly ether from a starting polyarylene polyether, in particular a PAES polymer, which includes contacting the starting polyarylenepoly ether with a nucleophilic reagent like hydroxide and amine nucleophiles for a period of time sufficient to reduce the molecular weight of the starting polyarylene poly ether, and then recovering the reactive reduced molecular weight polyarylene poly ether. The most preferred nucleophiles used are alkali metal hydroxides, alkali metal sulfides, alkali metal hydrogen sulfides, ammonia, alkyl amines, hydrazines, and thiol or amino substituted triazoles. Such reactive reduced molecular weight polyarylenes preferably have 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. In Example 19, a poly ethersulfone copolymer Radel® A (“Starting Polymer B”) having a Mw = 56,500 is decomposed into a reduced molecular weight oligomer of a Mw from 4060 to 1340 (see last 3 examples in Table 6) by reaction with ammonia at a temperature of 250 °C and a reactor pressure of 25.5 MPa (3700 psi). While this reference teaches the reduction of the molecular weight of the starting polymer, there is no conversion to monomers and further no isolation of such monomers.

[0017] JP2009173902A (Sumitomo) relates to a decomposition method for decomposing an aromatic ether compound with a basic compound having a >14 acid dissociation constant (pXa) at 25 °C in the presence of a solvent. Among the basic compounds, quaternary ammonium hydroxide, 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.

[0018] These methods, however, lead to oligomeric products with very low yields for phenolic monomers such as Bisphenol S which can be readily repolymerized back to similar PAES polymers. Moreover, due to the low yields in these more valuable phenolic monomers, purification appears quite challenging and cost prohibitive.

[0019] Currently, there is no solution to recycle end-of-life PES-containing membranes or scraps of PES polymers / membranes due to the difficult removal of impurities / additives, including polyvinylpyrrolidone (PVP) which is a hydrophilic viscosity modifier, that embeds themselves into the membranes. The most common purification protocol for PES membranes is to wash with water, bleach (sodium hypochlorite) 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 number of regenerating cycles possible for membranes before the regenerated membranes are deemed unusable. Furthermore, there is no evidencethat sodium hypochlorite can remove all of the PVP from the membrane. It is thus quite challenging to remove PVP from end-of-life PES hemodialysis membranes.

[0020] Regarding circularity, there is also an unmet need to develop ways 1) to effectively generate recycled aromatic sulfone monomers for production of more sustainable PAES polymers, 2) to effectively generate composite hardeners for production of more sustainable composite materials such as to generate high- performance thermosets for use in aerospace applications, or 3) to effectively upcycle end-of-life PES articles (e.g., membranes) and / or scraps of PES polymers into aromatic sulfone materials which can serve as raw materials for high-value applications, such as pharmaceuticals manufacture, and particularly antibiotic production.

[0021] SUMMARY

[0022] The present invention solves the above-mentioned problems by deconstructing a PES-containing material optionally containing additive(s) via depolymerization of the PES polymer into 4,4’-di-substituted diphenylsulfones which are highly desirable monomers and composite hardeners, while at the same time facilitating the removal, from the bulk of the PES polymer, of hard-to-remove additive(s), such as residual PVP, when present in the PES-containing material.

[0023] The present invention thus addresses the recyclability of PES-based materials (such as hemodialysis membranes) where the PES polymer is effectively depolymerized into 4,4’-di-substituted diphenylsulfones with a high yield. The PES polymer reacts with an ammonia source, in the form of liquid or gaseous ammonia or aqueous ammonia, to form a depolymerized mixture comprising 4,4’- di-substituted diphenylsulfones. As would be appreciated by those of ordinary skill in the art, the depolymerized mixture comprises at least two diphenylsulfone compounds selected from the group consisting of 4,4’-diamino-diphenylsulfone, 4-amino-4’-hydroxy-diphenylsulfone, and / or 4,4’-dihydroxydiphenylsulfone. The depolymerized mixture is then subjected to several purification steps in order to isolate a 4,4’-di-substituted diphenylsulfone product of high purity (> 85 wt.% of one or more 4,4’-di-substituted diphenylsulfones). Such a 4,4’-di-substituted diphenylsulfone product can then be recycled to manufacture additional PAES polymer or in other end uses such as hardeners for composites.

[0024] One of the main advantages of the present invention is that the depolymerization process provides a means to facilitate the separation of a water-soluble additive (such as PVP) particularly from PES membranes.

[0025] Another key advantage of the present invention is the depolymerization of end-of- life materials back to di-substituted diphenylsulfone monomers (not oligomers) at high yields. After depolymerization, the additive (e.g., PVP) is washed out due toits water-soluble nature, and this feature is quite helpful during the di-substituted diphenylsulfone purification process.

[0026] Yet another key advantage of the present invention is the separate reclamation of Dapsone, 4-amino-4-hydroxydiphenylsulfone, and bisphenol S from PES polymer that can be reused in a circular fashion to make poly aryl ethersulfones (preferably PES), pharmaceuticals and / or composite materials.

[0027] The invention is set out in the appended set of claims.

[0028] A first aspect of the present invention relates to a method (A) for preparing a depolymerized mixture comprising 4,4 ’-di-substituted diphenylsulfones from a polymeric material defined in any one of Claims 1-13.

[0029] A second aspect of the present invention relates to a method (B) for preparing at least one 4,4’ -di-substituted diphenylsulfone product from a polymeric material comprising at least one poly ethersulfone (PES polymer), defined in any one of Claims 2-12.

[0030] A third aspect of the present invention relates to a depolymerized mixture obtained by the methods of any one of Claims 1 to 12 according to the present invention.

[0031] A fourth aspect of the present invention relates to a 4,4 ’-di-substituted diphenylsulfone product obtained by any of the methods according to the present invention, defined in Claim 14.

[0032] A fifth aspect of the present invention relates to a 4,4 ’-di-substituted diphenylsulfone product selected from product (Pl), product (P2), and / or product (P3), defined in Claim 15.

[0033] A sixth aspect of the present invention relates to the use of the 4,4 ’-di-substituted diphenylsulfone product of Claim 14 or Claim 15, in making composites and / or pharmaceuticals, defined in Claim 15.

[0034] A further aspect of the present invention relates to the use of the 4,4’-di- substituted diphenylsulfone product containing dapsone and / or A-B compound, preferably product (Pl) and / or (P3), as hardeners for making composites.

[0035] Yet a further aspect of the present invention relates to the use of the of the 4,4’-di- substituted diphenylsulfone product containing dapsone and / or A-B compound, preferably product (Pl) and / or (P3), as raw material for making pharmaceuticals, and particularly for antibiotic production.

[0036] Another aspect of the present invention relates to the use of the 4,4’ -di-substituted diphenylsulfone product containing Bisphenol S, such as product (P2), as monomer source for making poly arylethersulfone polymers, preferably PES.

[0037] 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.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 illustrates an embodiment of the reaction scheme for PES depolymerization according to step (a) in the method (A) or (B) of the invention.

[0040] FIG. 2 illustrates a particular embodiment of the method (A) according to the invention.

[0041] FIG. 3 illustrates a particular embodiment of the method (B) according to the invention.

[0042] FIG. 4 represents the HPLC chromatogram of Example 1.

[0043] FIG. 5 represents the HPLC chromatogram of Example 2.

[0044] FIG. 6 represents the HPLC chromatogram of Example 3.

[0045] FIG. 7 represents the GPC trace of Example 3.

[0046] FIG. 8 represents the HPLC chromatogram of Example 4.

[0047] DEFINITIONS

[0048] In the present descriptive specification, some terms are intended to have the following meanings.

[0049] 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 that the 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 embodimentswhere 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 or use, explicitly or implicitly, this being done without departing from the scope of the present description.

[0050] In the present specification, the choice of an element from a group of elements also explicitly describes:

[0051] - the choice of two or the choice of several elements from the group,

[0052] - 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.

[0053] As used herein, the abbreviation “BPS” or “DHDPS” means Bisphenol S; the abbreviation “A-B compound” means 4-amino-4’ -hydroxy-diphenyl sulfone;“Dapsone” means 4,4’ -diamino-diphenyl sulfone; the abbreviation “A-Mx compound” means 4-((4-methoxyphenyl)sulfonyl)aniline; and the abbreviation “A- Ma compound” means 4-((4-aminophenyl)sulfonyl)-N-methylaniline.

[0054] As used herein, the abbreviation “Eq NHS / RPES” means the molar Equivalent of N E relative to 1 mole of the PES recurring unit (RPES) of formula (L).

[0055] 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.

[0056] 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 or -O-Ar-SCh-Ar, where Ar is an unsubstituted benzenic ring.

[0057] The term “recurring unit” designates the smallest unit of a polymer which is repeating in the chain, and which is composed of a condensation of bisphenol S and a dihalodiphenylsulfone. The term “recurring unit” is synonymous to the terms “repeat unit” and “structural unit”.

[0058] As used herein, PES dimers, trimers and tetramers have 2, 3, and 4 recurring units (RPES), respectively.

[0059] As used herein, a PES oligomer has at least 5 recurring units (RPES) and preferably has a number average molecular weight Mn of 3000 g / mol or less.

[0060] The contents of recurring units in the PES polymer are given in mol.% relative to the total amount of moles of recurring units in the polymer, unless stated otherwise.

[0061] 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.

[0062] 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.

[0063] 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, batterycomponents, plumbing parts, animal cages, or any used or end-of-life three- dimensional injection-molded, extruded or printed articles or parts thereof.

[0064] The term “post-industrial” polymeric material (or article), also known as “preconsumer” 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 repelletized, 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-dimensional injection-molded, extruded or printed articles or parts thereof.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] DETAILED DESCRIPTION

[0069] The first aspect of the present invention relates to a method for preparing a depolymerized mixture comprising 4,4’-di-substituted diphenylsulfones from a polymeric material comprising least one polyethersulfone (PES polymer), comprising:(a) contacting the polymeric material comprising at least one PES polymer with an ammonia source, under suitable reaction temperature and pressure and for a time sufficient to depolymerize the at least one PESpolymer and to provide a depolymerized mixture comprising 4,4 ’-disubstituted diphenylsulfones of formula (I); and(b) recovering the depolymerized mixture.

[0070] The second aspect of the present invention relates to a method for preparing at least one 4,4’-di-substituted diphenylsulfone product from a polymeric material comprising least one polyethersulfone (PES polymer), comprising:(a) carrying out the depolymerization of the at least one PES polymer to provide the depolymerized mixture comprising 4,4’-di-substituted diphenylsulfones of formula (I), described herein;(b) recovering the depolymerized mixture; and(c) isolating at least one 4,4’-di-substituted diphenylsulfone product from said recovered depolymerized mixture comprising 4,4’-di-substituted diphenylsulfones, by employing at least one technique selected from the group consisting of acid treatments, alkaline treatments, neutralization, washing with water, washing with a volatile organic solvent, liquid-solid extraction with a liquid phase that does not dissolve the 4,4’-di-substituted diphenylsulfone being purified, adsorption, dissolution, solid / liquid separation such as filtration, evaporation and / or distillation, crystallization, chromatographic separation, precipitation, evaporation, drying, and any combination thereof.

[0071] Polymeric material containing the PES polymer

[0072] The polymeric material to be depolymerized in the method (A) or (B) 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.

[0073] The polymeric material to be depolymerized may be in various forms. Indeed the polymeric material may be 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), molded or extruded or 3D printed parts, any other solid 3-D objects, tubes, filaments, membranes, yams, textiles, fabrics or under any type of geometry. 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.

[0074] The polymeric material can comprise at least one material selected from the group consisting of post-consumer polymeric articles, post-industrial polymeric articlesincluding article scraps, off-specification PES 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.

[0075] The polymeric material containing the PES polymer may comprise at least 50 percent by weight (wt.%), based on the total weight of the polymeric material, of the PES 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 PES polymer, based on the total weight of the polymeric material.

[0076] The polymeric material containing the PES 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.

[0077] 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.

[0078] The polymeric material may consist essentially of at least one PES polymer and at least one additive. It is understood that more than one PES polymer may be included in the polymeric material which is subjected to depolymerization.

[0079] 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.

[0080] Optional pretreatment of polymeric material prior to step (a)

[0081] The polymeric material may be pretreated prior to step (a).

[0082] The pretreatment step may include at least one of the following pretreatment steps:i) carrying out a mechanical or physical modification of the polymeric material, preferably transforming into parts of polymeric material such as by cutting, shredding, crushing, and / or grinding with a size lower than 10.0 mm, preferably lower than 5.0 mm, even preferably lower than 3.0 mm; ii) subjecting the polymeric material or parts of polymeric material obtained from step (i) or from step (ii) to a cleaning treatment by contact with a cleaning agent; iii) washing the polymeric material or parts of polymeric material obtained from step (i) or from step (ii) with a volatile solvent such as water and / or a volatile organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C such as acetone, ethanol, chloroform, ethyl acetate; iv) evaporating any volatile solvent such as water and / or organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C; v) sterilization; and / or vi) drying.

[0083] When in step (i), the polymeric material is transformed into small parts of polymeric material, this may permit to decrease the reaction time for the subsequent depolymerization step (a).

[0084] Cleaning in step (ii) before the polymeric material undergoes chemical recycling is preferably carried out for the following reasons: 1 / to ensure the removal of contaminants, biofilms, and / or any adherent substances without damaging the PES polymer in the polymeric material; 2 / to disinfect; and / or 3 / chemically degrade or transform, at least in part, an additive (e.g., PVP) present in the polymeric material.

[0085] The different options for the cleaning step (ii) may include contacting with at least one cleaning agent selected from the group consisting of acids, bases, disinfectants, and oxidizers. When carrying out the cleaning step (ii), the amount of cleaning agent and the time period for cleaning may be selected depending on the nature of the contaminants and the desired outcome of the cleaning treatment in step (ii), and further in a manner that does not negatively impacting the PES polymer in the polymeric material, meaning not chemically modifying or transforming the PES polymer by the cleaning agent.

[0086] When the cleaning step (ii) includes contacting with an acid, the cleaning agent may be an acidic solution selected from a citric acid solution, a dilute hydrochloric acid, or a dilute sulfuric acid. The acid can be used to removemineral deposits, scale, and certain types of biofilms. The acidic solution helps in breaking down these deposits without harming the PES polymeric structure if used in the correct concentration and for a controlled duration to avoid degradation of the PES polymer. The polymeric material or parts thereof should be rinsed after such an acid cleaning in step (ii) to remove any residual acid, which could otherwise degrade the PES polymer over time.

[0087] When the cleaning step (ii) includes contacting with a base, the cleaning agent may be an alkaline solution comprising NaOH. The base can be used to remove organic contaminants, fats, and certain types of biofilms. The use of a base can also help in sanitizing the polymeric material. The concentration of the base and the exposure time should be carefully controlled to prevent the degradation of the PES polymer in the polymeric material. After cleaning, a thorough rinse with deionized water is preferred to neutralize any remaining alkaline residues.

[0088] When the cleaning step (ii) includes contacting with a disinfectant, the cleaning agent may be at least one disinfectant selected from peroxides such as hydrogen peroxide, peracids such as peracetic acid, or sodium hypochlorite. The disinfectant can be used to sanitize the polymeric material by killing bacteria and other microorganisms, and / or to help in breaking down organic contaminants. After cleaning, a thorough rinse with deionized water is preferred to remove any remaining disinfectant residues.

[0089] When the cleaning step (ii) includes contacting with an oxidizer, the cleaning agent may be at least one oxidizer selected from the group consisting of hypochlorite, perchlorate, chlorate, peracids such as peracetic acid, ozone, CIO2, Ch gas dissolved in water, and peroxides such as H2O2. The oxidizer can be used to degrade organic contaminants and disinfect the polymeric material. Oxidizers are particularly useful for breaking down complex organic molecules and biofilms. Proper rinsing after oxidation is necessary to remove any residual oxidizer. In case of use of hypochlorite in step (ii), the oxidizer may include an aqueous solution having at least 1,000 and up to 100,000 ppm, preferably at least 5,000 and up to 10,000 ppm sodium hypochlorite. In case of use of peroxide in step (ii), the oxidizer may include an aqueous solution of hydrogen peroxide.

[0090] It is to be understood that a cleaning agent used in step (ii) may be selected for having several functions. For example, a sodium hypochlorite solution may be used in step (ii) as an oxidizer to degrade organic contaminants and in particular chemically degrade or transform, at least in part, an additive (e.g., PVP) present in the polymeric material, as well as used as a disinfectant to sanitize the polymeric material by killing bacteria and other microorganisms.

[0091] Preferably, the washing step (iii) is carried out in order to remove residues or unused remnant of the cleaning agent used in step ii), namely rinsing after step(ii), and / or to remove loosely bound impurities / contaminants originating from the manufacture and / or use of the polymeric material.

[0092] Preferably, the evaporation step (iv) may use a temperature from 15 °C to 35 °C and / or may be done under vacuum (preferably) or at atmospheric pressure.

[0093] Preferably, the sterilization step (v) may use exposure to ethylene oxide (EtO) gas, irradiation and / or steam sterilization in an autoclave. The selected sterilization technique in step (v) should not negatively impact the PES polymer in the polymeric material, meaning not chemically modifying or transforming the PES polymer. The sterilization step (v) may be carried out on the polymeric material or parts of polymeric material obtained from step (i), prior to or after washing step(iii) and prior to or after cleaning step (ii). The autoclaving technique for sterilization step (v) may be carried out at a temperature of up to 135 °C, preferably up to 121 °C. The irradiation technique for sterilization step (v) is generally gamma irradiation. During autoclaving, the polymeric material or parts of polymeric material obtained from step (i) may be immersed in water.

[0094] Preferably, drying in step (vi) uses a drying temperature which is higher than the boiling point (measured at atmospheric pressure) of any volatile solvent used in step (iii) and preferably which is not higher than 150 °C. The drying step (vi) may be done under vacuum or at atmospheric pressure.

[0095] When the washing step (iii) is carried out, either the evaporating step (iv) and / or the drying step (vi) is preferably carried out to remove the volatile solvent such as water and / or organic solvent having a low boiling point (preferably < 100 °C) such as acetone, ethanol, chloroform, ethyl acetate ....

[0096] The polyethersulfone (PES) polymer

[0097] The polyethersulfone polymer, also referred to as “PES polymer” which is depolymerized in the method (A) or (B) of the present invention comprises a polymeric chain containing at least 80 mol %, at least 85 mol %, at least 90 mol %, at least 95 mol %, or at least 98 mol % of, the mol % being based on the total number of moles of recurring units in the PES polymer, or consists essentially of, recurring units (RPES) of formula (K) or preferably of formula (L).

[0098] The formula (K) is as follows:(K),wherein 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 wherein each i is independently zero or an integer from 1 to 4.

[0099] When at least one i in the formula (K) is 1, then its corresponding R is 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.

[0100] Preferably, both i in the formula (K) are zero, and the recurring unit (RPES) is represented by formula (L):[-Ar-SOi-Ar-O-] (L), in which Ar represents an unsubstituted divalent arylene group.

[0101] The PES polymer has two end groups, each being independently selected from a halide X, an hydroxy group and / or an endcapped 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 endcapped group Re.

[0102] When one end group is a halide X, the other end group is preferably an endcapped group Re, meaning that the PES polymer may be represented by X-PES-Re.

[0103] When one end group is an endcapped group Re, the other end group is preferably a halide X and / or group Re, meaning that the PES polymer may be represented by Re-PES-X and / or Re-PES-Re. In such instance, the PES polymer may have a combination of Re-PES-X and Re-PES-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 PES polymer.

[0104] 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 PES polymer may be represented by HO-PES-X and / or HO-PES-OH. In such instance, the PES polymer may have a combination of HO-PES-X and HO-PES-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 PES polymer.

[0105] The weight average molecular weight Mw of the PES 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.

[0106] The number average molecular weight Mn of the PES polymer from at least 15,000 g / mol to at most 60,000 g / mol, preferably from at least 16,000 g / mol to at most 55,000 g / mol, more preferably from at least 17,000 g / mol to at most 50,000g / mol or from at least 20,000 g / mol to at most 45,000 g / mol, yet more preferably from at least 18,000 g / mol to at most 35,000 g / mol.

[0107] The poly dispersity index of the PES 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.

[0108] The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the PES 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 poly dispersity index (PDI), when reported, is hereby expressed as the ratio of weight average molecular weight (Mw) to the number average molecular weight (Mn).

[0109] The PES polymer may be produced by a variety of methods. The PES polymer is preferably derived by polycondensation from dihydroxy diphenylsulfone (DHDPS), also known as bisphenol S, and dichlorodiphenylsulfone (DCDPS), with potassium carbonate in a polar aprotic solvent (such as sulfolane, dimethylacetamide, N-methyl-2-pyrrolidone, diphenylsulfone).

[0110] The PES polymer is notably commercially available as VERADEL® PES and VIRANTAGE® PES from Solvay Specialty Polymers USA, L.L.C.

[0111] Additive in the polymeric material

[0112] The at least one additive, when present in the polymeric material, may comprise a pore forming agent or hydrophilic viscosity modifier.

[0113] The at least one additive in the polymeric material preferably comprises at least one additive selected from polyvinylpyrrolidones (PVP), polyalkyleneoxides, or any combination thereof.

[0114] 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):in which n in formula (P) is an integer of at least 3.

[0115] The molar mass of PVP may vary from 2,500 g / mol to 3,000,000 g / mol. Preferred PVPs may include PVP kl2 , kl5, kl7, k25, k30, k40, k60 and / or k90, commercially available for example from Fisher Scientific and Sigma-Aldrich.

[0116] 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.%, at most 6 wt.%, at most 5 wt.%, at most 4 wt.%, at most 3 wt.%, or at most 2 wt.% of the one or more PVPs, based on the total weight of the polymeric material.

[0117] As used herein, a poly alkyleneoxide comprises, based on the total number of moles of recurring units in the poly alkyleneoxide, 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 poly alkyleneoxide 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.

[0118] When the additive comprises one or more polyalkyleneoxides, 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 poly alkyleneoxides. 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 polyalkyleneoxides, based on the total weight of the polymeric material.

[0119] The at least one additive in the polymeric material comprises, or consists of, at least one polyvinylpyrrolidone (PVP), at least one polyethylene glycol (PEG), or any combination thereof.

[0120] Most preferably, at least one additive in the polymeric material is one or more PVPs.

[0121] Ammonia source

[0122] The ammonia source used during the depolymerization step (a) comprises anhydrous ammonia (NEE) in gaseous and / or liquid form and / or aqueous ammonia. Aqueous ammonia (also known as ‘aqua ammonia’ or ‘ammonium hydroxide solution’) as an ammonia source preferably has a content of from 15 wt.% to 30 wt. % NH3, preferably from 19 wt. % to 30 wt. % NH3, more preferably from 27 wt. % to 30 wt.% NH3. A 28 wt.% aqueous ammonia [CAS No. 1336-21-6] is 15.0 M and has a density of 0.90 g / ml. Anhydrous ammonia [CAS No. 7664-41-7] as anammonia source has a high purity (>99.9 wt.% NH3), a boiling point of -33.4 °C and a freezing point of -77.7 °C.

[0123] Suitable, but not limiting, ammonia sources are 28 wt.% aqueous ammonia from Sigma- Aldrich; EMPARTA® 28-30 wt.% aqueous ammonia by Merck KGaA, Darmstadt, Germany; 19-30 wt.% aqueous ammonia from Airgas Specialty Products (an Air Liquide company); Aqua Ammonia grades 26° Baume (29.4 wt.% and 21° Baume (19.68 wt.%) from Tanner Industries, Inc.; anhydrous ammonia from Airgas Specialty Products (an Air Liquide company), and anhydrous ammonia N36 from Air Liquide (France).

[0124] Without wishing to be bound by such atheory, Applicant believes that the ammonia is used to breakdown the PES polymer by nucleophilic attack via an aromatic substitution reaction (S\ Ar type) into sulfonyl aminated and phenolic monomers. The ammonia may further act to deprotonate phenol monomers (such as bisphenol S). It is believed that during depolymerization of PES polymer, the ammonia (NH3, NH4+) attacks the ether linkages on the polymeric chain (backbone) of the PES polymer, so as to break such linkages, thereby forming a PES fragment with an aromatic amine on one end group and a PES fragment with a phenol end group. Due to the statistical distribution, when either of those fragments (still in polymer or oligomer form) are attacked by ammonia on the other end, then Dapsone, Bisphenol S, or A-B compound may be formed. The phenol end group can make either Bisphenol S or A-B compound, depending on the leaving group. The amine end group can make either Dapsone or A-B compound, depending on the leaving group. As such, it is expected that the molar distribution of the main PES depolymerization products with the ammonia source should be about 50% A-B compound, 25% Bisphenol S and 25% Dapsone. To say another way, the relative molar ratios of A-B : BPS : Dapsone in the PES depolymerization mixture should be close to 2: 1: 1.

[0125] The ammonia source may further include an organic amine which is formed in situ during depolymerization, meaning that it is not added for the depolymerization. Such an organic amine may be formed in situ by way of reaction of the NH3 or NH4+with endcapped end group (Re) of the PES polymer. When the endcapped end group (Re) is an alkoxy group and / or a phenoxy group, preferably a methoxy (-O- CH3) group, the organic amine which may be formed in situ may be an alkylamine and / or a phenylamine, preferably methylamine.

[0126] The ammonia source preferably excludes a quaternary ammonium hydroxide such as tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, hexyltrimethylammonium hydroxide, cetyltrimethylammonium hydroxide, and benzyltrimethylammonium hydroxide.

[0127] The ammonia source more preferably excludes any organic ammonium hydroxide.

[0128] Depolymerization step (a)

[0129] The depolymerization step (a) preferably comprises contacting the polymeric material containing at least one PES polymer with the ammonia source.

[0130] The contacting preferably takes place in a reactor vessel which can operate at a temperature of up to 350 °C and at super-atmospheric pressure, such as up to 17 MPa, or up to 20 MPa, or up to 25 MPa, or up to 30 MPa.

[0131] The reactor vessel may be a well-mixed vessel equipped with a stirring device, such as a turbine or agitator, or may not include an agitator.

[0132] Alternatively, the reactor vessel does not have moving parts, but rather uses a packed bed of polymeric material through which the ammonia source passes therethrough.

[0133] The reactor vessel is preferably equipped with a rupture disk set to a maximum operating pressure.

[0134] The reactor vessel is equipped with gaskets which allow the vessel to be sealed and pressurized. The gaskets should be compatible with ammonia. Suitable gaskets may be selected from graphite gaskets and / or fluoroelastomeric gaskets such as Chemraz® FFKM O-rings.

[0135] All metal components of the reactor vessel such as inside walls and internals (e.g., stirring device, baffles, if any), or even the entire reactor vessel, are preferably constructed of a corrosion-resistant material such as nickel-based alloys. Examples of corrosion-resistant nickel-based alloys are Hastelloy® and Inconel® alloys.

[0136] The polymeric material containing the PES polymer and the ammonia source may be added simultaneously or sequentially to the reactor vessel where the depolymerization step (a) takes place.

[0137] The polymeric material may be loaded first into the reactor vessel, then the reactor vessel may be closed, purged and blanketed with nitrogen gas, pre-heated and pressurized, and then the ammonia source may be loaded to the reactor vessel via a feeding port.

[0138] Preferably, the polymeric material and the ammonia source (especially when in the form of aqueous ammonia) are loaded into the reactor vessel, then the reactor vessel is closed, purged and blanketed with nitrogen gas, pre-heated and pressurized to achieve the desired reaction temperature and pressure, and then these conditions are held for a time sufficient to depolymerize the at least one PES polymer and to provide the depolymerized mixture.

[0139] During step (a), the amount of the ammonia source used in the depolymerization is determined based on the total number of oxygen atoms (the total number ofoxygen equivalents) forming the ether bond of the PES recurring units (RPES). It should be used in the range of at least 50 molar Equivalent of NH3 relative to 1 mole of the PES recurring unit (RPES) of formula (L) [herein “Eq NEE / RPES”], or at least 60 Eq NEE / RPES, or at least 65 Eq NEE / RPES, or at least 70 Eq NEE / RPES, or at least 75 Eq NEE / RPES, and at most 300 Eq NEE / RPES, or at most 275 Eq NEE / RPES, or at most 250 Eq NEE / RPES, or at most 225 Eq NEE / RPES, or at most 200 Eq NEE / RPES, or at most 190 Eq NEE / RPES.

[0140] More preferably, the amount of the ammonia source used in the depolymerization step (a) is in the range of 70 to 250 Eq NEE / RPES, or from 70 to 200 Eq NEE / RPES, or from 75 to 185 Eq NEE / RPES.

[0141] The depolymerization step (a) in the method (A) or (B) of the present invention is carried out at a reaction temperature of from 180 °C to 300 °C.

[0142] Preferably, the reaction temperature suitable for depolymerization in step (a) may be from 180 °C to 290 °C, or from 190 °C to 280 °C, or from 200 °C to 270 °C.

[0143] More preferably, the reaction temperature suitable for step (a) may be from 210 °C to 260 °C.

[0144] Most preferably, the reaction temperature suitable for step (a) may be from 230 °C to 260 °C.

[0145] The method (A) or (B) of the present invention may further comprise, prior to step (a), the step of preheating the ammonia source and the polymeric material loaded in a reactor vessel to reach the desired reaction temperature described above. The heating ramp may be from 3 °C / min to 12 °C / min.

[0146] The depolymerization step (a) in the method (A) or (B) of the present invention is preferably carried out under pressure (meaning above atmospheric pressure).

[0147] The reaction pressure suitable for depolymerization in step (a) may be at least 4 MPa, at least 4.5 MPa, at least 4.6 MPa, at least 4.7 MPa, at least 4.8 MPa, at least 4.9 MPa, at least 5.0 MPa, at least 5.1 MPa, at least 5.2 MPa, at least 5.3 MPa, at least 5.4 MPa, at least 5.5 MPa, at least 5.6 MPa, at least 5.7 MPa, at least 5.8 MPa, at least 5.9 MPa, at least 6.0 MPa, at least 6.5 MPa, or at least 7 MPa, and at most 25 MPa, at most 24.5 MPa, at most 24 MPa, at most 23 MPa, at most 22 MPa, at most 21 MPa, at most 20 MPa, at most 19 MPa, at most 18 MPa, at most 17 MPa, at most 16 MPa, at most 15 MPa, at most 14 MPa, at most 13 MPa, or at most 12.5 MPa.

[0148] In particular, the reaction pressure suitable for depolymerization in step (a) may be from 4 MPa to 25 MPa, preferably from 4 MPa to 24 MPa, more preferably from 4 MPa to 23 MPa, yet more preferably from 4 MPa to 22 MPa, or from 4.5MPa to 21 MPa, or from 4.6 MPa to 20 MPa, still more preferably from 4.7 MPa to 12.5 MPa.

[0149] Preferred range for the reaction pressure for depolymerization in step (a) may be from 4 MPa to 15 MPa, from 4.5 MPa to 15 MPa, from 4.5 MPa to 14 MPa, from 4.6 MPa to 13 MPa, or from 4.7 MPa to 12.5 MPa.

[0150] The method (A) or (B) of the present invention may further comprise, prior to step (a), the step of pressurizing the reactor vessel, into which the ammonia source and polymeric material are loaded, to reach a desired reaction pressure within the ranges described above. The pressurization ramp may be from 50 kPa / min to 150 kPa / min, preferably from 50 kPa / min to 130 kPa / min, more preferably from 50 kPa / min to 120 kPa / min.

[0151] The time period sufficient for depolymerization in step (a) in the method (A) or (B) of the present invention may be at least 3 hours, or at least 4 hours, or at least 5 hours, or at least 6 hours, and / or at most 60 hours, at most 55 hours, or at most 51 hours.

[0152] Since the PES polymer having a polymeric chain comprising at least 80 mol % of the recurring unit (RPES) of the formula (L) described herein is depolymerized in the step (a) of the method (A) or (B) of the present invention, the ammonia source (in the form of NH3 or NH-i ) cleaves the ether bond -O- of the polymeric chain made of the recurring unit (RPES) of the formula (L).

[0153] The depolymerization in step (a) may be carried out in batch mode or continuous mode.

[0154] Absence of hydroxide and alkoxide bases in step (a)

[0155] It is preferred that the depolymerization step (a) does not include the use of a hydroxide or alkoxide base selected from the group consisting of sodium hydroxide (NaOH), cesium hydroxide (CsOH), potassium hydroxide (KOH); tetramethylammonium hydroxide (TMAOH); potassium tert-butoxide, and sodium tert-butoxide is excluded from the depolymerization step (a).

[0156] It is particularly preferred that none of the hydroxide bases selected from the group consisting of sodium hydroxide (NaOH), cesium hydroxide (CsOH), potassium hydroxide (KOH); tetramethylammonium hydroxide (TMAOH) is present during the depolymerization step (a).

[0157] Absence of a carbonate catalyst in step (a)

[0158] The depolymerization step (a) is preferably carried out without a catalyst comprising carbonate and one or more elements in group 1 or group 2 of the periodic table.

[0159] It is preferred that no catalyst comprising carbonate and one or more elements Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, or Ra is present during the depolymerization step (a).

[0160] It is particularly preferred that none of the catalysts disclosed in US2024 / 0228737A1 by MANTE et al., such as those selected from the group consisting of Rb2CO3, Rh(PPh3)3Cl, Rh(OH)3, Rh2(CO3)3, Rh2(COD)2Cl2, 5 percent Rh / CdCO3, 5 percent Rh / ZnCO3, 5 percent Rh / CoCO3, 5 percent Rh / NiCO3is present during the depolymerization step (a).

[0161] Absence of organic solvent in step (a)

[0162] It is preferred that the depolymerization step (a) does not include the use of an organic solvent (e.g., a polar aprotic solvent). Should an organic solvent (e.g., a polar aprotic solvent) be present during depolymerization, its amount is less than 2 parts by weight, preferably less than 1 part by weight, based on 100 parts by weight of the combined polymeric material and ammonia source.

[0163] It is particularly preferred that none of the organic solvents selected from the group consisting of l,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-butylpyrrolidone (NBP), N-ethylpyrrolidone (NEP), N,N'-dimethylacetamide (DMAc), N,N'-dimethylpropyleneurea (DMPU), dimethylformamide (DMF), tetrahydrothiophene-1 -monoxide, and any combination thereof is present during the depolymerization step (a).

[0164] Termination of depolymerization

[0165] To stop the depolymerization reaction, the depolymerized mixture is preferably cooled to reduce the temperature to less than 80 °C, preferably less than 70 °C, or less than 60 °C, or less than 50 °C, or less than 40 °C or less than 30 °C.

[0166] The reactor vessel in which the depolymerization step (a) takes place is preferably depressurized to atmospheric pressure before the depolymerized mixture is recovered from the reactor vessel.

[0167] Therefore, any of the method (A) or (B) according to the invention preferably further comprises: cooling the depolymerized mixture to reduce the temperature to less than 80 °C, preferably less than 70 °C, or less than 60 °C, or less than 50 °C, or less than 40 °C, or less than 30 °C; and depressurizing to atmospheric pressure the reactor vessel in which the depolymerization step (a) takes place.

[0168] Recovery step (b) of the depolymerized mixture

[0169] The depolymerized mixture obtained at the end of the depolymerization step (a), preferably after cooling and depressurizing, and containing 4,4’-di-substituted diphenylsulfones of formula (I) may be in the form of a viscous colored (generally brown-colored) solid or paste, or in the form of a (generally whitish) suspension and a colored (generally brown-colored) solid, or in the form of a colored (generally yellow-colored) suspension.

[0170] The method (A) or (B) of the present invention further includes step (b) for recovering the depolymerized mixture after the depolymerization step (a) is terminated.

[0171] The recovery step (b) may include a solvent wash (bl).

[0172] The solvent wash (bl) comprises washing the depolymerized mixture obtained at the end of the depolymerization step (a) with a volatile solvent and evaporating the resulting washed suspension to dryness to recover the depolymerized mixture.

[0173] This solvent wash (bl) preferably also includes adding some of the volatile solvent into the reactor vessel in order to rinse the reactor vessel interior (such as internal wall surfaces) and internal devices (such as stirrer, baffles) onto which some of the depolymerized mixture may have adhered.

[0174] The volatile solvent preferably has a low boiling point of at most 100 °C and may be selected from water and / or a volatile organic solvent.

[0175] The volatile organic solvent having a low boiling point of at most 100 °C may be further chosen for its ability to dissolve the 4,4’-di-substituted diphenylsulfones in the depolymerized mixture. Suitable but non-limiting examples of volatile organic solvents include acetone, chloroform, ethyl acetate, and / or di chloromethane.

[0176] It is to be understood that the solvent wash (bl) may involve several washing and evaporation cycles. For example, the solvent wash (bl) may comprise: carrying out at least one organic solvent wash (bl’) with a volatile organic solvent (e.g., acetone or dichloromethane) which is suitable to dissolve the 4,4’-di-substituted diphenylsulfones in the depolymerized mixture, optionally evaporating the organic solvent to dryness to obtain an organic solvent-washed solid, followed by: carrying out at least one water wash (bl”) with water,- then evaporating the water to dryness to obtain a final-washed solid, which provides the recovered depolymerized mixture.

[0177] Alternatively or additionally, the recovery step (b) may include a reactive wash (b2).

[0178] The reactive wash (b2) includes contacting the cooled depolymerized mixture as well as the reactor vessel interior (such as internal wall surfaces) and internaldevices (such as stirrer, baffles) onto which some of the depolymerized mixture may have adhered, or a solvent-washed solid obtained from a solvent wash (bl), with an alkaline aqueous solution preferably 1 M to 2 M MOH solution.

[0179] Such reactive wash (b2) may employ stirring the slurry (solid and liquid phases) or solution with the stirring device inside the reactor vessel or another stirring vessel.

[0180] The reactive wash (b2) may take place at a temperature of from 20 to 35 °C, for a time period varying from 15 to 120 minutes, preferably from 30 to 90 minutes.

[0181] The alkaline aqueous solution in reactive wash (b2) is preferably 1 M to 2 M MOH solution, in which M is an alkali metal, preferably K or Na, more preferably Na.

[0182] One of the objectives of the reactive wash (b2) may be to convert the phenolic end groups (-Ar-OH) of the more-desirable 4,4’-di-substituted diphenylsulfones: monohydroxy-diphenylsulfone (A-B compound) and dihydroxy-diphenylsulfone (Bisphenol S) to their respective alkali metal phenolate salt (-Ar-OM) and / or renders these 4,4’-di-substituted diphenylsulfones more water soluble in the alkaline solution, while the 4,4’-diamino-diphenylsulfone (Dapsone) is not water soluble.

[0183] It is also envisioned that the method (A) or (B) of the present invention may include successively one or more solvent washes (bl) and one or more reactive washes (b2) to recover the depolymerized mixture.

[0184] For example, the recovery step (b) may comprise: carrying out at least one organic solvent wash (bl’) with a volatile organic solvent (e.g., acetone or dichloromethane), preferably selected to dissolve the 4,4’-di-substituted diphenylsulfones in the depolymerized mixture, optionally, evaporating the organic solvent to dryness to obtain an organic solvent-washed solid, followed by carrying out at least one reactive wash (b2) with an alkaline solution (preferably an aqueous NaOH solution),- then evaporating to dryness to obtain a final-washed solid, which provides the recovered depolymerized mixture.

[0185] The depolymerized mixture

[0186] The depolymerized mixture obtained at the end of the depolymerization step (a) is recovered as a solid. The recovery (b) preferably includes using at least one solvent wash (step (bl)) and / or using at least one reactive wash (step (b2)).

[0187] The depolymerized mixture comprises 4,4’-di-substituted diphenylsulfones. As used herein, the term “depolymerized mixture” refers to the products (4,4’ -disubstituted diphenylsulfones) and byproducts (dimers, trimers, tetramers andoligomers having 5 or more RPES units) resulting from the depolymerization of the PES polymer.

[0188] Prior to the isolating step (c), the depolymerized mixture comprises the 4,4’-di- substituted diphenylsulfones in an amount of at least 70 wt.%, at least 75 wt.%, or at least 80 wt.%, 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.

[0189] The 4,4’-di-substituted diphenylsulfones in the depolymerized mixture are of general formula (I):RtiAr-SCh-Ar- R2(I), in which Ar represents an unsubstituted divalent arylene group, and each of R1and R2is independently selected from the group consisting of OH, NH2, an endcapped group Re, an aminated endcapped group Reaand a halide X, said endcapped group Re, preferably being selected from an alkoxy group and / or a phenoxy group, more preferably being a methoxy (-O-CH3) group, and said aminated endcapped group Rea, preferably being selected from an alkylamine group and / or a phenylamine group, more preferably being a methylamine group, said halide X, preferably being Cl or F, more preferably being Cl.

[0190] Preferably, the 4,4’-di-substituted diphenylsulfones in the depolymerized mixture include at least:- 4,4’ -diaminodiphenylsulfone [Dapsone],- 4,4’ -dihydroxy diphenylsulfone [bisphenol S], and 4-amino-4’ -hydroxy diphenylsulfone [A-B compound],

[0191] The depolymerized mixture may further comprise at least one of the following: 4-Re-4’-hydroxy-diphenylsulfone,- 4-Re-4’-amino-diphenylsulfone, such as 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound],4- Rea-4’-hydroxy-diphenylsulfone,- 4-Rea-4’-amino-diphenylsulfone such as 4-((4-aminophenyl)sulfonyl)-N- methylaniline [A-Ma compound], and / or 4-X-4’-amino-diphenylsulfone, said endcapped group Re, preferably being selected from an alkoxy group and / or a phenoxy group, more preferably being a methoxy (-O-CH3) group, said aminated endcapped group Rea, preferably being selected from an alkylamine group and / or a phenylamine group, more preferably being a methylamine group, andsaid halide X, preferably being Cl or F, more preferably being Cl.

[0192] The depolymerized mixture may further comprise at least one PES dimer, such as HO-Ar-SO2-Ar-O-Ar-SO2-Ar-OH, HO-Ar-SO2-Ar-O-Ar-SO2-Ar-NH2, NH2-Ar-SO2-Ar-O-Ar-SO2-Ar-NH2, Re-Ar-SO2-Ar-O-Ar-SO2-Ar-NH2, Re-Ar-SO2-Ar-O-Ar-SO2-Ar-OH, Rea-Ar-SO2-Ar-O-Ar-SO2-Ar-NH2, Rea-Ar-SO2-Ar-O-Ar-SO2-Ar-OH, X-Ar-SO2-Ar-O-Ar-SO2-Ar-OH, and / or X-Ar-SO2-Ar-O-Ar-SO2-Ar-NH2, in which :Ar represent an unsubstituted divalent arylene group;Re represents an endcapped group, preferably being selected from an alkoxy group and / or a phenoxy group, more preferably being a methoxy group;Rearepresents an aminated endcapped group, preferably being selected from an alkylamine group and / or a phenylamine group, more preferably being a methylamine group; andX represents Cl or F, preferably Cl.

[0193] As would be appreciated by those of ordinary skill in the art, the 4,4 ’-disubstituted diphenylsulfones correspond to the cleavage of the recurring units (RPES) of formula (L) in the polymeric chain of the PES polymer. In such a manner, the recurring units (RPES) of formula (L) in the PES polymer are cleaved from one another.

[0194] Also, as would be appreciated by those of ordinary skill in the art, when the PES polymer having one hydroxyl end group undergoes the depolymerization reaction, the cleavage during depolymerization of the last recurring unit having a hydroxyl end group may generate the 4-amino-4’-hydroxy-diphenylsulfone, the 4-Re-4’- hydroxy-diphenylsulfone and / or the 4- Rea-4 ’-hydroxy-di phenylsulfone, in which Re is the same as previously described.

[0195] As would be appreciated by those of ordinary skill in the art, when the PES polymer having one encapped group Re in one end group undergoes the depolymerization reaction, the cleavage of the last recurring unit (RPES) of formula (L) having such an encapped group Re may generate the 4-Re-4’ -aminodiphenylsulfone and / or the 4-Re-4’-hydroxy-diphenylsulfone, in which Re is the same as previously described.

[0196] Additionally, when the PES polymer has an alkoxy end group Re of formula -OR’ (in which R’ is an alkyl), the alkoxy end group can react with the ammonia sourceto form free alkyl amine (R’NHs) and a hydroxyl group. The resulting free alkyl amine can participate in the depolymerization of the PES polymer thereby forming alkyl amine end groups in some of the 4,4’-di-substituted diphenylsulfones.

[0197] As an example, when the PES polymer has a methoxy (-OCH3) end group Re, the depolymerization of such a PES may generate 4-methoxy-4’-amino- diphenylsulfone, 4-methoxy-4’-hydroxy-diphenylsulfone, 4-methylamine-4’- amino-diphenylsulfone, and / or 4-methylamine-4’ -hydroxy-diphenylsulfone.

[0198] The identification of the 4,4’-di-substituted diphenylsulfones in the mixture can be done by HPLC-MS, and the content of each 4,4’-di-substituted diphenylsulfone in the mixture can be determined by quantitative UPLC-MS, UPLC-UV or HPLC- UV. Suitable HPLC-UV and UPLC-UV methods for measuring the 4,4’ -disubstituted diphenylsulfones content in the depolymerized mixture and in various 4,4’-di-substituted diphenylsulfone products are described in the examples section.

[0199] As would be appreciated by those of ordinary skill in the art, when the PES polymer having one halide (X) end group undergoes the depolymerization reaction, the cleavage during depolymerization of the last recurring unit (RPES) having such halide end group (X) may generate the 4-X-4-amino-diphenylsulfone, such as 4-chloro-4’-amino-diphenylsulfone and / or the 4-X-4-hydroxy- diphenylsulfone such as 4-chloro-4’ -hydroxy-diphenylsulfone.

[0200] Residual PES polymer, PES dimers, PES trimers, PES tetramers and PES oligomers can be detected by UPLC-MS or GPC analysis.

[0201] The content of the Dapsone in the depolymerized mixture may be at least 10 wt.% up to 30 wt.% based on the total weight of the depolymerized mixture.

[0202] The content of the Bisphenol S in the depolymerized mixture may be at least 10 wt.% up to 30 wt.% based on the total weight of the depolymerized mixture.

[0203] The content of the A-B compound in the depolymerized mixture may be at least 20 wt.% up to 60 wt.% based on the total weight of the depolymerized mixture.

[0204] The content of the A-Mx compound, when present in the depolymerized mixture, may be at least 0.1 wt.% and up to 1 wt.% based on the total weight of the depolymerized mixture.

[0205] The content of the A-Ma compound, when present in the depolymerized mixture, may be at least 0.1 wt.% and up to 1 wt.% based on the total weight of the depolymerized mixture.

[0206] Without wishing to be bound by any particular scientific theory, when the PES polymer having two end groups being an halide X and an alkoxy group Re (resulting from endcapping with an alkyl chloride at the end of polymerization)undergoes the depolymerization reaction, the two recurring units (RPES) of formula (L) at both extremities of the PES polymeric chain are cleaved from the PES chain, and these recurring units at both extremities may generally form the 4- alkoxy -4’-amino-diphenylsulfone such as 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound], the 4-X-4’-amino-diphenylsulfone, such as 4-chloro-4’- aminodiphenylsulfone, the 4-alkoxy -4’ -hydroxy-di phenylsulfone such as 4- methoxy-4’-hydroxy-diphenylsulfone, and / or the 4-X-4’ -hydroxy - diphenylsulfone, such as 4-chloro-4’-hydroxy-diphenylsulfone.

[0207] Additionally, since an alkoxy end group Re can react with ammonia to form free alkyl amine, and the resulting free alkyl amine can participate in the depolymerization of the PES polymer to form alkyl amine end groups, the PES depolymerization can also generate 4-alkylamine-4’-amino-diphenylsulfone and / or 4-alkylamine-4’-hydroxy-diphenylsulfone such as 4-methylamine-4’- amino-diphenylsulfone [A-Ma compound], and / or 4-methylamine-4’ -hydroxy - diphenylsulfone.

[0208] The content of the 4-Re-4’-amino-diphenylsulfone, particularly 4-((4- methoxyphenyl)sulfonyl)aniline [A-Mx compound], when present in the depolymerized mixture, may be in an amount of from 0 wt.% (preferably at least 10 ppm) up to 2 wt.%, preferably up to 1 wt.%, based on the total weight of the depolymerized mixture.

[0209] The content of the 4-Re-4’-hydroxy-diphenylsulfone, particularly 4-methoxy-4’- hydroxy-diphenylsulfone, when present in the depolymerized mixture, may be in an amount of from 0 wt.% (preferably at least 10 ppm) up to 2 wt.%, preferably up to 1 wt.%, based on the total weight of the depolymerized mixture.

[0210] The content of the 4-Rea-4’-amino-diphenylsulfone, particularly 4-((4- aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound], when present in the depolymerized mixture, may be in an amount of from 0 wt.% (preferably at least 10 ppm) up to 2 wt.%, preferably up to 1 wt.%, based on the total weight of the depolymerized mixture.

[0211] The content of the 4-Rea-4’-hydroxy-diphenylsulfone, particularly 4-methylamine- 4’ -hydroxy-di phenylsulfone, when present in the depolymerized mixture, may be in an amount of from 0 wt.% (preferably at least 10 ppm) up to 2 wt.%, preferably up to 1 wt.%, based on the total weight of the depolymerized mixture.

[0212] The content of the 4-X-4’-amino-diphenylsulfone, particularly 4-chl oro-4’ -aminodiphenylsulfone, 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.

[0213] The content of the 4-X-4’-hydroxy-diphenylsulfone, particularly 4-chloro-4’- hydroxy-diphenylsulfone, 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.

[0214] When one end group of the PES is a methoxy group, the content of 4- methylamine-4’-amino-diphenylsulfone [A-Ma compound] and / or 4- methylamine-4’-hydroxy-diphenylsulfone, 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.

[0215] The content of PES dimers, when present in the depolymerized mixture, may be in an amount of from 0 wt.% (preferably at least 10 ppm or at least 50 ppm or at least 100 ppm) and up to 6 wt.% , up to 5.5 wt.%, 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.

[0216] As would be appreciated by those of ordinary skill in the art, a dimer may be formed by the cleavage of two consecutive recurring units (RPES) of formula (L) from the PES polymer, such as two consecutive recurring units (RPES) at an extremity of the PES polymeric chain, in which case one of the end groups of the dimer corresponds to one end group of the PES polymer, or two consecutive recurring units (RPES) within the PES polymeric chain, in which case both end groups of the dimer correspond to amine groups, alkylamine groups, phenylamine groups, alkoxy groups, phenoxy groups, halogen groups and / or hydroxyl groups, preferably correspond to amine groups, alkylamine groups, alkoxy groups, halogen groups and / or hydroxyl groups, more preferably correspond to amine groups, methylamine groups, methoxy groups, halogen groups and / or hydroxyl groups.

[0217] Prior to the isolation step (c), the depolymerized mixture comprises, based on the total weight of the depolymerized mixture, a total amount of at least 80 wt.%, preferably at least 85 wt.%, or at least 90 wt.%, or at least 92 wt.%, or at least 95 wt.%, of 4,4’-di-substituted diphenylsulfones.

[0218] When at least one PVP is present as additive in the polymeric material, the PVP content in the depolymerized mixture may be, based on the total weight of the depolymerized mixture, from 0 wt.% (or at least 10 ppm or at least 100 ppm) and up to 5 wt.%, preferably up to 4 wt.%, or up to 3 wt.%, or up to 2 wt.%, or up to 1 wt.%, or up to 0.95 wt.%, or up to 0.9 wt.%, or up to 0.8 wt.%, or up to 0.7 wt.% or up to 0.6 wt.%, or up to 0.5 wt.%, or up to 0.4 wt.%, or up to 0.3 wt.%, or up to 0.2 wt.%) of PVP. The detection and quantifying the content of PVP may be done via HPLC-UV. A suitable HPLC-UV method for measuring the PVP content inthe depolymerized mixture and in various 4,4’-di-substituted diphenylsulfone products is described in the examples section.

[0219] When trimers (having 3 RPES units), tetramers (having 4 RPES units), and / or oligomers (having 5 or more RPES units) of PES are present in the depolymerized mixture, the depolymerized mixture may further comprise >0 and up to 5 wt.% of PES trimers, tetramers and oligomers.

[0220] The purity of the depolymerized mixture is defined as the content of 4,4 ’-disubstituted diphenylsulfones in the depolymerized mixture, based on the total weight of the depolymerized mixture. The depolymerized mixture can have a purity in 4,4’-di-substituted diphenylsulfones 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.%.

[0221] A particular embodiment of the method (A) according to the invention is illustrated in FIG. 2, in which in step (a), a polymeric material (10) which comprises least one PES polymer and optionally at least one additive (e.g., PVP), as well as an ammonia source (20), preferably anhydrous ammonia and / or aqueous ammonia, are reacted in a reactor vessel [D] to depolymerize the PES polymer and to form a depolymerized material (30). After cooling and depressurizing in reactor vessel [D], the depolymerized material (30) is recovered by using a solvent wash (bl) via adding a solvent feed (40) to unit [W] and / or a reactive wash (b2) via adding aNaOH aqueous solution feed (50) to unit [W], The solvent wash (bl) and / or reactive wash (b2) is preferably carried out by stirring the slurry of depolymerized material + solvent feed (40) and / or NaOH aqueous solution feed (50). The unit [W] may be the same reactor vessel [D] or a separate vessel. After washing in unit [W], the depolymerized mixture may be subjected to evaporating or drying to remove the solvent and / or water. A final depolymerized material (60) is recovered from unit [W],

[0222] Prior to being subjected to depolymerization in unit [D], a raw polymeric material (5) may be pretreated in at least one unit [PT] to form the polymeric material feed (10) to reactor vessel [D], The pretreatment in unit [PT] may include: i. cutting, shredding, crushing, and / or grinding with a size lower than 10.0 mm, preferably lower than 5.0 mm, even preferably lower than 3.0 mm; ii. cleaning treatment by contact with a cleaning agent, preferably hypochlorite; iii. washing with a volatile solvent such as water and / or a volatile organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C;iv. evaporating any volatile solvent such as water and / or organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C; v. sterilization; and / or vi. drying.

[0223] Any of the embodiments previously described in relation to steps (i) to (vi) is equally applicable for these pretreatment steps in at least one unit [PT] hereinabove.

[0224] In the second aspect of the present invention, in addition to the steps (a) and (b) previously described in relation to the method (A), the method (B) of the present invention further includes an isolation step (c) to obtain at least one 4,4’ -disubstituted diphenylsulfone product.

[0225] Isolation step (c)

[0226] The isolation of at least one 4,4’-di-substituted diphenylsulfone product from the depolymerized mixture may employ at least one technique selected from the group consisting of alkaline treatments; acid treatments; neutralization; washing with water; washing with a volatile organic solvent; liquid-solid extraction with a liquid phase that does not dissolve the 4,4’-di-substituted diphenylsulfones being purified; adsorption; dissolution; solid / liquid separation such as filtration; evaporation and / or distillation; extraction; crystallization; chromatographic separation; precipitation; evaporation; drying; and any combination thereof.

[0227] Preferably, the isolation step (c) includes at least one technique selected from the group consisting of alkaline treatments; acid treatments; washing with water; washing with a volatile organic solvent; solid / liquid separation such as filtration; evaporation and / or distillation; chromatographic separation; precipitation; evaporation; drying; and any combination thereof.

[0228] More preferably, the isolation step (c) includes at least one technique selected from the group consisting of alkaline treatments, acid treatments, solid / liquid separation (such as filtration), precipitation, evaporation, drying, and any combination thereof.

[0229] A particular embodiment of the method (B) according to the invention is illustrated in FIG. 3, in which the depolymerization step (a) and the recovery step (b), as well as the optional pretreatment step, are carried out as explained for FIG.2, and in which the recovered depolymerized material (60) obtained at the end of step (b) is subjected to a series of isolation steps (cl), (c2) and (c3) to obtain three separate 4,4’-di-substituted diphenylsulfone products (Pl), (P2) and (P3) containing primarily Dapsone, Bisphenol S, and A-B compound, respectively.

[0230] In step (cl), the depolymerized mixture (60) at the end of step (b) is subjected to an alkaline treatment [ALK.1] with an alkaline source (100), preferably aNaOH aqueous solution, in a manner effective to render 4-amino-4’- hydroxydiphenylsulfone [A-B compound] and 4,4 ’-dihydroxy diphenylsulfone [bisphenol S] more water-soluble and to precipitate 4,4 ’-diaminodiphenylsulfone [dapsone], and then a dapsone-containing solid (110) is separated in a separation unit [SP.l] from a first aqueous supernatant (120).

[0231] The dapsone-containing solid (110) may be further purified in unit [PUR.1] to obtain the dapsone product (Pl).

[0232] In step (cl), the first aqueous supernatant (120) obtained from step (cl) is subjected to an acidic treatment in unit [“ACID.”] with an aqueous acid solution (130), preferably a HC1 solution, in a manner effective to precipitate 4, d’- dihydroxy diphenylsulfone [bisphenol S] while keeping 4-amino-4’- hydroxy diphenylsulfone [A-B compound] in dissolved form, and a bisphenol S- containing solid (140) is separated in a separation unit [SP. 2] from a second aqueous supernatant (150).

[0233] The bisphenol S-containing solid (140) may be further purified in unit [PUR.l] to obtain the bisphenol S product (P2).

[0234] In step (c3), the second aqueous supernatant (150) obtained from step (c2) exiting unit [SP.2] is subjected to an alkaline treatment [ALK.2] with an alkaline aqueous solution (160), preferably an aqueous NaOH solution, in a manner effective to precipitate 4-amino-4’-hydroxy diphenylsulfone [A-B compound], and an A-B compound-containing solid (170) is separated in the separation unit [SP. 3] from a third aqueous supernatant (180).

[0235] The A-B compound-containing solid (170) may be further purified in unit [PUR. 3] to obtain the Dapsone product (P3).

[0236] The separation units [SP. 1], [SP. 2], [SP. 3] are preferably filtration units.

[0237] The purification in units [PUR. 1], [PUR. 2], [PUR. 3] preferably includes at least one of the following steps: washing with water, washing with a volatile organic solvent, liquid-solid extraction with a liquid phase that does not dissolve the 4,4’-di- substituted diphenylsulfone being purified, adsorption, dissolution, solid / liquid separation such as filtration, evaporation and / or distillation, crystallization,chromatographic separation, precipitation using a shift in solubility by changing the pH in aqueous solution, precipitation using a non-solvent, drying, and any combination thereof.

[0238] While not illustrated, when there is no need to isolate Bisphenol S and A-B compound, step (cl) and step (c3) in FIG.3 may be omitted. In such a case, only a purified product (Pl) containing Dapsone is obtained.

[0239] More preferably, the isolation step (c) includes at least one technique selected from the group consisting of alkaline treatments; acid treatments; solid / liquid separation (such as filtration); precipitation; drying; and any combination thereof.

[0240] Alkaline treatment

[0241] The recovered depolymerized mixture or an aqueous supernatant or filtrate may be subjected to an alkaline treatment. For instance, an alkaline aqueous solution, preferably an aqueous NaOH solution, is mixed with the recovered depolymerized mixture or aqueous supernatant or filtrate. This alkaline treatment converts the 4,4’-di-substituted diphenylsulfone of Formula (I) in which at least one of the R1, R2is an OH group, into phenolate form (such as sodium phenolate salt of bisphenol S and A-B compound when NaOH is used as alkaline agent).

[0242] In such an embodiment, the conversion of the 4,4’-di-substituted diphenylsulfone of Formula (I) having at least one OH end group into phenolate salts renders them more water soluble, while the 4,4’-di-substituted diphenylsulfones of Formula (I) having no OH end group (such as -NH2 and / or Re end groups) remain water insoluble.

[0243] In particular, Dapsone having no OH end group precipitates, while the phenolate salts of A-B compound and bisphenol S remain in solution.

[0244] Acidic treatment

[0245] The alkaline supernatant obtained after an alkaline treatment may be subjected to an acid treatment. For instance, an inorganic acid such as HC1 is mixed with the alkaline supernatant to convert the phenolate salts of 4,4’-di-substituted diphenylsulfone of Formula (I) into protonated form.

[0246] In such an embodiment, the conversion of the 4,4’-di-substituted diphenylsulfones of Formula (I) having at least one OH end group into phenolate salts renders them more water soluble, while the 4,4’-di-substituted diphenylsulfones of Formula (I) having no OH end group and instead having -NH2 and / or Re end groups remain water insoluble.

[0247] Washing

[0248] The description of the washing steps (bl) and (b2) in relation to the recovery step (b) is equally applicable to the washing step with water or with a volatile organic solvent that can be performed for isolation.

[0249] Precipitation

[0250] When one product or byproduct (e.g., dimers, trimmers, oligomers, ... ) resulting from PES depolymerization and containing OH end group is present in dissolved form in an aqueous supernatant or filtrate, its solubility may be modified by changing the pH of the aqueous supernatant or filtrate to cause its precipitation (protonated form phenolate form).

[0251] Alternatively, a non-solvent or poor solvent in which the product or byproduct is not soluble, may be added to the aqueous supernatant or filtrate to cause its precipitation.

[0252] Solid / liquid separation

[0253] When a solid or precipitate is present or is formed in a suspension / slurry, a solid / liquid separation is preferably carried out to remove the solid or precipitate from the liquid phase. The solid / liquid separation preferably includes filtration, but other solid / liquid separation techniques may be employed. The filtering can be performed in a variety of ways, such as vacuum filtering or any form of filtering as desired.

[0254] Drying

[0255] Drying may be carried on a wet solid (such as dapsone product) to recover a dry solid. Drying may be done at a temperature from 80 °C to 120 °C, preferably 90 °C to 110 °C. Drying may be done under vacuum or at atmospheric pressure.

[0256] Optional additional purification step

[0257] While a 4,4’-di-substituted diphenylsulfone product generally has a purity of at least 90 wt.% (preferably at least 92 wt.%, at least 94 wt.%, or at least 95 wt.%), based on the total weight of the 4,4’-di-substituted diphenylsulfone product, in some instances it may be desirable to further increase the purity of the 4,4’-di- substituted diphenyl sulfone product.

[0258] The 4,4’-di-substituted diphenylsulfone product may be further purified by recrystallization in a chlorobenzene / ethyl acetate mixture. This is particularly advantageous when the 4,4’-di-substituted diphenylsulfone product is one of the more preferred 4,4’-di-substituted diphenylsulfones:- Dapsone;- A-B compound;- Bisphenol S.

[0259] The preferred 4,4’-di-substituted diphenylsulfone product is dissolved in a boiling mixture of ethyl acetate: chlorobenzene (generally using a 4 / 1 vol / vol ratio). Theethyl acetate is removed by evaporation until the preferred 4,4’-di-substituted diphenylsulfone precipitate out of solution. A highly-purified preferred 4,4’-di- substituted diphenylsulfone product is then collected using hot filtration.

[0260] The highly -purified preferred 4,4’-di-substituted diphenylsulfone product generally has a purity of at least 99.0 wt.% (based on the total weight of the product) of such 4,4’-di-substituted diphenylsulfone.

[0261] In more preferred embodiments, the highly-purified 4,4’-di-substituted diphenylsulfone product has a purity of at least 99.1 wt.%, preferably at least 99.3 wt.%, or more preferably at least 99.5 wt.% (based on the total weight of the product) of such 4,4’-di-substituted diphenylsulfone.

[0262] 4,4’-di-substituted diphenylsulfone product

[0263] The method (B) which comprises (a) depolymerization of a PES polymer into a depolymerized mixture, (b) recovery of the depolymerized mixture and (c) isolation generates at least one 4,4’-di-substituted diphenylsulfone product according to the invention.

[0264] The present invention thus further relates to a 4,4’ -substituted diphenylsulfone product obtained by the method (B), comprising:4,4 ’-diaminodiphenylsulfone [dapsone], 4-amino-4’-hydroxydiphenylsulfone [A-B compound], optionally 4,4’ -dihydroxy diphenylsulfone [bisphenol S], 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4- methoxyphenyl)sulfonyl)aniline [A-Mx compound] ; or comprising:4,4’-dihydroxydiphenylsulfone [bisphenol S], 4-amino-4’-hydroxydiphenylsulfone [A-B compound], optionally 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound], and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound],

[0265] Particularly, the present invention thus relates to a 4,4’-di-substituted diphenylsulfone product selected from the group consisting of:

[0266] a product (Pl) comprising:> 70 wt.%, preferably >75 wt.%, more preferably >80 wt.% or >85 wt.% or >90 wt.% of 4,4’ -diaminodiphenylsulfone [Dapsone],> 0 wt.%, preferably >0.2 wt.%, more preferably >0.5 wt.%, still more preferably >0.7 wt.% or >1.0 wt.% or >2.0 wt.%, of 4-amino-4’- hydroxy diphenylsulfone [A-B compound], and from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound];wherein the wt.% is based on the total weight of the product (Pl); and / or

[0267] a product (P2) comprising:> 70 wt.% of 4,4’-dihydroxydiphenylsulfone [bisphenol S]> 0 wt.%, preferably > 0.1 wt.% and up to 30 wt.%, more preferably > 0.5 wt.% and up to 25 wt.%, of 4-amino-4’-hydroxydiphenylsulfone [A-B compound], and from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, of 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound]; wherein the wt.% is based on the total weight of the product (P2); and / or

[0268] a product (P3) comprising:> 70 wt.%, preferably >75 wt.%, more preferably >80 wt.% or >85 wt.% of 4- amino-4’ -hydroxy diphenyl sulfone [A-B compound],> 0 wt.% and up to 10 wt.%, preferably > 0.5 wt.% and up to 9 wt.%, of 4, d’- dihydroxy diphenylsulfone [bisphenol S], from 0 and up to 10 wt.%, preferably > 0.05 wt.% and up to 9 wt.%, more preferably > 0.1 wt.% and up to 8 wt.%, of 4,4’ -diaminodiphenylsulfone [Dapsone], and from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, of 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound]; wherein the wt.% is based on the total weight of the product (P3).

[0269] After the isolation step (c), the content of the at least one additive in the 4,4’ -disubstituted diphenylsulfone product, in particular in the product (Pl), product (P2) and / or product (P3), is less than the content of the at least one additive in the polymeric material before depolymerisation.

[0270] Preferably, when the additive in the polymeric material is PVP (generally in an amount of about 1 to 8 wt.% PVP), the content of PVP after isolation (c) 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 PVP content in the polymeric material before depolymerisation, said % being calculated as [1-Af / AQ] / 100 in which Af is the additive content in the 4,4’-di-substituted diphenylsulfone product and Ao is the content of the same additive in the polymeric material.

[0271] For example, when the additive is PVP and its content is about 1 to 8 wt.% PVP in the polymeric material, there is no detectable amount of PVP (generally less than 100 ppm) in the 4,4’-di-substituted diphenylsulfone product, in particular in the product (Pl), product (P2) and / or product (P3).

[0272] The purity of 4,4’-di-substituted diphenylsulfone product, in particular of the product (Pl), product (P2) and / or product (P3), can be confirmed by 'H-NMR spectroscopy and / or UPLC-MS analysis. Detection of PVP additive can be done using a particularly suitable HPLC-UV method described in the Examples.

[0273] The analytical methods based on 'H-NMR. UPLC-MS, and HPLC-UV provided in the Examples section are suitable for determining purity of the various 4,4’ -di- substituted-diphenylsulfone products according to the invention.

[0274] Use of the 4,4’-di-substituted diphenylsulfone product

[0275] The 4,4’-di-substituted diphenylsulfone product according to the present invention can be used in at least one of the following, but not limited to, applications: composites, adhesives, electronics, coatings, fibers, films, moldings, extrusions, polyethersulfone manufacture, and / or pharmaceuticals manufacture, such as antibiotic manufacture. The 4,4’-di-substituted diphenyl sulfone products according to the present invention provide sources of raw materials which are substantially 100% carbon sustainable.

[0276] In particular, the 4,4’-di-substituted diphenylsulfone product according to the present invention which contains dapsone and / or A-B compound can be used as composite hardeners for production of more sustainable composite materials such as to generate high-performance thermosets for use in aerospace applications, or can serve as raw materials for making pharmaceuticals, in particular for making antibiotics.

[0277] The 4,4’-di-substituted diphenylsulfone product according to the present invention which contains dapsone and / or A-B compound may be used as composite hardener in composite resin formulations in combination with high-strength filaments or fibers such as carbon (graphite), glass, silicon carbide and other ceramic fibers, alumina, titania, boron, aromatic polyamide or other organic reinforcing fibers, in the preparation of composites.

[0278] In particular, the 4,4’-di-substituted diphenylsulfone product according to the present invention which contains dapsone and / or A-B compound may be used as composite hardener in combination with a resin such as epoxy, bismaleimide, cyanide ester, phenol-formaldehyde, urethane, polyester, vinyl ester, siloxane, cyclopentadiene and higher oligomers, acetylenic, cyclic polycarbonate resins, or mixtures thereof.

[0279] Thus, another aspect of the present invention provides the use of the 4,4 ’-disubstituted diphenylsulfone product which contains dapsone and / or A-B compound as a hardener for preparing a composite (or a part thereof). The resin matrix of the composite may include an epoxy resin, a polyurethane resin or an unsaturated polyester resin.

[0280] The present invention thus also relates to a method for preparing a composite (or a part thereof) which comprises using the 4,4’-di-substituted diphenylsulfone product according to the invention which contains dapsone and / or A-B compound as a hardener in a resin matrix.

[0281] The resin matrix preferably comprises the 4,4’-di-substituted diphenylsulfone product which contains dapsone (such as product (Pl)) and / or which contains A-B compound (such as product (P3)) and an additional component which can, for example, be at least one epoxy component and / or a curing agent (for example polyalkylenepolyamines, such as ethylene diamine (EDA), diethylene triamine (DETA), triethylene tetramine (TETA), tetraethylene pentamine (TEPA), and polyethylene polyamines (PEPA)).

[0282] The term “epoxy component” means a compound that contains more than one epoxy group, preferably two epoxy groups, per molecule. These epoxy compounds may be either saturated or unsaturated and aliphatic, cycloaliphatic, aromatic or heterocyclic and may also have hydroxyl groups. They are preferably glycidyl ethers which derive from polyhydric phenols, especially bisphenols or aminophenols and novolacs.

[0283] In another aspect of the present invention, the 4,4’-di-substituted diphenylsulfone product according to the present invention which contains dapsone and / or A-B compound, can be used as raw material for the production of sustainable pharmaceuticals, such as antibiotic compositions.

[0284] The present invention thus also relates to a method for preparing a sustainable pharmaceutical which comprises using the 4,4’-di-substituted diphenylsulfone product according to the invention which contains dapsone and / or A-B compound as a raw material for making a pharmaceutical composition, in particular an antibiotic composition.

[0285] Yet another aspect of the present invention provides the use of the 4,4’ -disubstituted diphenylsulfone product which contains Bisphenol S (such as product (P2)) as a raw material (monomer) for preparing a polyethersulfone by polycondensation of Bisphenol S and dihalodiphenyl sulfone, in a polar aprotic solvent such as sulfolane, DMAc, NMP, DMI, diphenylsulfone, in the presence of a carbonate salt (preferably potassium carbonate). Such a use makes sustainable PES polymers, thereby effectively recycling end-of-life PES membranes or scraps of PES polymers into new PES polymers.

[0286] The present invention thus also relates to a method for preparing a sustainable PES (co)polymer which comprises using the 4,4’-di-substituted diphenylsulfone product which contains Bisphenol S (such as product (P2)) as a raw material (monomer), in a reaction medium comprising at least one dihalogenated diphenylsulfone, optionally another diol, and a carbonate salt (preferably potassium carbonate) and a polar aprotic solvent.

[0287] EXAMPLES

[0288] 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.

[0289] Raw Materials:

[0290] In the following examples, hemodialysis fibers containing polyethersulfone (PES) and polyvinylpyrrolidone (PVP) (generally 3-6 wt.% PVP in the fibers) were used.

[0291] Veradel® (PES) 3000 MP powder was from Solvay Specialty Polymers USA (member of the Syensqo group).

[0292] Aqueous 28% ammonium hydroxide (NH4OH), sodium hydroxide (NaOH), and HC1 were purchased from Sigma-Aldrich.

[0293] Ammonia N36 was purchased from Air Liquide.

[0294] Analytical Methods

[0295] 1H-NMR spectroscopy:

[0296] Samples were dissolved in deuterated dimethyl sulfoxide (DMSO). All samples were run on a Bruker 400 MHz NMR, with a DI set to 1 seconds and 64 scans. Data was processed using Topspin / NMR notebook software.

[0297] HPLC- UVfor PVP detection:

[0298] Size exclusion chromatography 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 pm 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 min1at a column temperature of 60 °C and an injection volume of 20 pL. The PVP was detected and quantified utilizing the wavelength of 200 nm. The limit of detection, on a sample basis, for PVP was 100 ppm.

[0299] UPLC-MS (Method 1):

[0300] Reversed-phase chromatography was employed, utilizing a Waters Acquity UPLC with a photodiode array detector (PDA) for UV purity and a Synapt G2 HDMS mass spectrometer for analyte identification. A Waters Acquity UPLC BEH C18 (2.1 mm x 100 mm x 1.7 pm) column was used as the stationary phase and a mobile phase gradient starting with 95% A and 5% B (A = 0.1% formic acid in water, B = 0.1% formic acid in acetonitrile) was employed and held for 1 minute. The gradient was increased to 100% B over 13 minutes, held at 100% B for 2 minutes, followed by return to the starting mobile phase ratio by 16.5 minutes. The column was reequilibrated at the starting mobile phase ratio for 3.5 minutes prior to the nextsample analysis for a total sample analysis time of 20 minutes. The flow rate was set to 0.350 mL min the column temperature was maintained at 40 °C and the injection volume was set to 2 pL. The PDA was set to acquire data in the 190-500 nm wavelength region and UV purity determined using the total wavelength absorbance chromatogram. All mass spectra were acquired in both positive and negative electrospray ionization modes, with a scan range of m / z 50-1200.

[0301] HPLC-UV (Method 2):

[0302] Reversed-phase chromatography was employed, utilizing an Agilent HPLC 1260 with a photodiode array detector (PDA) for UV purity. A XBridge BEH Cl 8 (3.0 mm x 100 mm x 2.5 pm) column was used as the stationary phase and a mobile phase gradient starting with 95% A and 5% B (A = 0.05 % v / v H3PO4 85% in water, B = acetonitrile) was employed and held for 1 minute. The gradient was increased to 95% B over 15.9 minutes, held at 95% B for 7.7 minutes, followed by return to the starting mobile phase ratio by 0.4 minutes. The column was re-equilibrated at the starting mobile phase ratio for 4.0 minutes prior to the next sample analysis. The flow rate was set to 1.200 mL min1, the column temperature was maintained at 40 °C and the injection volume was set to 2 pL. The PDA was set to acquire data in the 190-400 nm wavelength region and UV purity determined using 210 nm wavelength detection. The quantification of monomers content in wt% (Dapsone, BPS and A-B compound) in the depolymerization mixture was achieved through calibration curve obtained with analytical standards. For A-B compound, an average response factor was calculated with those of Dapsone and BPS.

[0303] GPC analysis:

[0304] Samples (40 mg) were dissolved in 30 g of solvent (0.01 M LiBr in NMP), stirred for 4 hours at ambient temperature, and filtrated over a 0.45 pm PTFA filter. Gel Permeation Chromatography (GPC) was performed on an Agilent 1260 instrument equipped with two mixed C 180 / 181 A columns. The flow rate of the mobile phase (0.01 M LiBr in NMP) was set to 0.7 mL / min while the oven temperature was set to 45 °C. The sample volume was 100 pL. A RI (refractive index) detector was used.

[0305] Reaction Scheme:

[0306] The PES depolymerization tests were conducted in Examples 1 and 2 with aqueous ammonia in the Reactor 1, in Examples 3 and 4 with anhydrous ammonia in the Reactor 7, and in Examples 5 and 6 with anhydrous ammonia in the Reactor 2 according to the scheme shown in FIG. 1.

[0307] Reactors:

[0308] Reactor 1: Small-scale experiments (starting with ca. 1 g PES polymer) were carried out in a Top Industrie 35-mL autoclave vessel made of Hastelloy equippedwith a Rushton turbine, a rupture disc set at 17 MPa (2466 psi), and a manometer. CHEMRaz® FFKM gaskets compatible with ammonia were used to seal the reactor vessel.

[0309] Reactor 2: For larger-scale depolymerization tests (10-20 g), a Series 4600 Pressure Vessel System from Parr Instrument Company was used. All metal components of the 1-L Parr vessel and head were made of Hastelloy. The Parr vessel had a maximum working pressure of 20 MPa (2901 psi) at 350 °C, and graphite gaskets were used to prevent chemical degradation.

[0310] Example 1: PES depolymerization in aqueous ammonia (ammonium hydroxide)

[0311] Procedure: 1 g of PES powder (4.31 mmol) was loaded into the 35-mL autoclave reactor vessel (Reactor / . followed by 20 g of aqueous ammonia (28 wt.% NH3, 329 mmol, 76 Eq NHS / RPES). Then the reactor vessel was purged and loaded with 1.1 MPa (160 psi) of nitrogen. The temperature was increased to 210 °C within 15 minutes under mechanical stirring (300 rpm) and kept at this temperature for 51 hours. A pressure of 4.8 MPa (697 psi) was measured under these conditions. After depressurizing the reactor vessel to atmospheric pressure, the reactor was opened to recover a yellowish suspension (depolymerized mixture) which, after evaporation to dryness in a rotary evaporator, provided 1.07 g of a brown, powdery solid. Since1H NMR analysis (in DMSO) of this powdery solid showed a complex mixture, the powdery solid was dissolved in 30 mL of acetone and evaporated to dryness. Then 30 mL of water were added and the resulting suspension was evaporated again, leading to 0.82 g of a brownish solid (depolymerized mixture).

[0312] According to HPLC-UV (Method 2) analysis (FIG. 4), the solid depolymerized mixture contained Dapsone (23.0 wt.%, 189 mg, 0.76 mmol), A-B compound (47.0 wt.%, 385 mg, 1.54 mmol), and BPS (26.7 wt.%, 219 mg, 0.88 mmol), corresponding to non-isolated yields of 70, 72, and 81%, respectively, of the assumed 25, 50, and 25% theoretical yields of these monomers. UPLC and1H NMR analysis also showed the presence of PES dimers and trimers; however no residual PES polymer was detected.

[0313] Counter-Example 2: PES depolymerization in aqueous ammonia

[0314] Procedure: 1 g of PES powder (4.31 mmol) was loaded into the 35-mL autoclave reactor vessel (Reactor 7), followed by 20 g of aqueous ammonia (28 wt.% NH3, 329 mmol, 76 Eq NHS / RPES). Then the reactor vessel was purged and loaded with 1.1 MPa (160 psi) of nitrogen. The temperature was increased to 160 °C within 15 minutes under mechanical stirring (300 rpm) and kept at this temperature for 48 hours. A pressure of 3.2 MPa (464 psi) was measured under these conditions. After depressurizing, the reactor was opened to recover a white suspension and a greyish solid. After washing twice with 5 mL of water, the combined suspensionwas evaporated to dryness in a rotary evaporator, affording 0.63 g of a brown, powdery solid. UPLC-MS (FIG. 5) andJH NMR analysis showed that the solid consisted of unreacted PES polymer, PES oligomers, and only traces of 4,4’ -disubstituted diphenylsulfones (Dapsone, A-B compound, and BPS).

[0315] Example 3: PES depolymerization in pure ammonia

[0316] Procedure: About 20 mL of ammonia (799 mmol, 185 Eq NFE / RPES) were condensed into a 60 mL ACE tube (pressure-proof to 1.14 MPa =150 psig) equipped with a septum and transfer needle, and cooled with a dry ice / acetone mixture to -78 °C. The liquid ammonia was rapidly transferred into a 35 mL autoclave reactor vessel (Reactor 7) pre-cooled for 2 minutes at -78 °C with a dry ice / acetone mixture. Then, 1 g of PES powder (4.31 mmol) was carefully added and the reactor vessel was quickly closed. The reactor vessel was allowed to warm to room temperature under mechanical stirring (200 rpm) at which point a pressure of 0.9 MPa (130 psi) was read. The reactor vessel was then heated to 150 °C within 45 minutes, at which point a pressure of 12 MPa (1740 psi) was reached. The reactor vessel was kept at this temperature (150 °C) for 24 hours, and to stop the reaction, the reactor vessel was then allowed to cool down to room temperature. The reactor vessel was then depressurized into a wash bottle loaded with aqueous HC1 to neutralize the excess ammonia. Then the reactor vessel was opened, and a brown, caramel-like substance was recovered. The reactor vessel and the mechanical stirrer were washed twice with 20 mL of dichloromethane and twice with 20 mL of acetone. The resulting solution was combined with the brown solid, and evaporated to dryness with the help of a rotary evaporator, for 1.21 g of a brown solid to be recovered and that could be easily ground to a powder.

[0317] GPC analysis (FIG. 7) showed that the solid mainly consisted of PES oligomers, some 4,4’-di-substituted diphenylsulfones, but no residual PES polymer was present. According to HPLC-UV (Method 2) analysis (FIG. 6), the solid contained Dapsone (2.6 wt.%, 32 mg, 0.13 mmol), A-B compound (9.5 wt.%, 116 mg, 0.47 mmol), and BPS (5.0 wt.%, 65 mg, 0.26 mmol), corresponding to non-isolated yields of 12%, 22%, and 24%, respectively, of the assumed 25, 50, and 25% theoretical yields of these three 4,4’-di-substituted diphenylsulfones.

[0318] Example 4: PES depolymerization in pure ammonia

[0319] Procedure: Anhydrous ammonia (ca. 10 mL, 399 mmol, 93 Eq NEL / RPES) was condensed into a 60 mL ACE tube (pressure-proof to 1.14 MPa =150 psig) equipped with a septum and transfer needle, and cooled with a dry ice / acetone mixture to -78 °C. The liquid ammonia was rapidly transferred into the 35-mL autoclave reactor vessel (Reactor 7) pre-cooled for 2 minutes at -78 °C with a dry ice / acetone mixture. Then, 1 g of PES powder (4.31 mmol) was carefully addedto the reactor vessel, and the reactor vessel was quickly closed. The reactor vessel was allowed to warm to room temperature under mechanical stirring (200 rpm) at which point a reactor pressure of 0.9 MPa (131 psi) was read. The reactor vessel was then heated to 160 °C within 45 minutes, at which point a pressure of 12.2 MPa (1769 psi) was reached. After 9 hours, the reaction was stopped by allowing the reactor vessel to cool down to room temperature. The reactor vessel was then depressurized into a wash bottle loaded with aqueous HC1 to neutralize the excess ammonia. Then the reactor vessel was opened, and a brown, caramel-like substance was recovered. The reactor vessel and the mechanical stirrer were washed three times with 30 mL of acetone. The resulting solution was combined with the brown solid and evaporated to dryness with the help of a rotary evaporator, upon 1.05 g of a brown solid was recovered which could be easily ground to a powder. UPLC-MS andJH NMR analysis showed that the solid mainly consisted of some 4,4’-di- substituted diphenylsulfones, unreacted PES polymer, PES dimers, PES trimers, PES tetramers, containing 2, 3, or 4 recurring units (RPES), respectively, and PES oligomers (containing 5 or more recurring units (RPES)).

[0320] According to HPLC-UV (Method 2) analysis (FIG. 8), the solid contained Dapsone (1.1 wt.%, 12 mg, 0.05 mmol), A-B compound (4.8 wt.%, 50 mg, 0.20 mmol), and BPS (2.3 wt.%, 24 mg, 0.09 mmol), corresponding to non-isolated yields of 4%, 9%, and 9%, respectively, of the assumed 25, 50, and 25% theoretical yields of these monomers.

[0321] Example 5: Depolymerization of Polyethersulfone to Isolate Dapsone

[0322] In the 1-L Hastelloy reactor vessel from Parr (Reactor 2) was charged with 20 g (86.113 mmol) of PES polymer. In a hood, 400 g of 28% ammonium hydroxide (6.575 mol of aqueous ammonia, 76 Eq NHS / RPES). was added to the reactor vessel. After the reactor vessel is sealed, the entire reactor vessel was purged with nitrogen for 10 minutes. The N2 was then turned off and the system is fully sealed (N2 pressure: 69 kPa = 10 psi). The reaction vessel was then heated to 240 °C and maintained at that reaction temperature for 48 hours (gradual temp, ramp = 5 °C / min.) with a final pressure around 9.65-10.34 MPa (1400-1500 psi). Afterward, the reactor vessel was cooled down to room temperature.

[0323] Next, a solution of 2 M NaOH (200 g) was added to the reaction mixture and stirred at 30 °C for 1 hour.

[0324] The reaction slurry was then filtered to obtain a solid and an alkaline filtrate, and the resulting solid was washed with 1 L of water.

[0325] The leftover solid (which contained primarily Dapsone) was dissolved in a minimal amount of acetone, and then the acetone was removed under reduced pressure, meaning evaporated under subatmospheric pressure, to isolate dapsone.

[0326] The alkaline filtrate was acidified with 2 M HC1 until a pH of 2 was reached and then was stirred at 50 °C for 1 hour, and a precipitate was formed.

[0327] The precipitate (which contained primarily BPS and A-B compound) was then filtered to obtain a BPS-containing solid and an acidic filtrate and washed with 1 L of water, then dried at 120 °C for 12 hours.

[0328] The acidic filtrate was then neutralized with 2 M NaOH until at pH of 7 was reached and a final precipitate is formed. The final precipitate (which contained primarily A-B compound) was filtered and washed with water. The washed A-B compoundcontaining solid was then dried at 120 °C for 12 hours.

[0329] Dapsone was isolated at a 75% yield assuming a 25% theoretical yield after depolymerization.

[0330] The purity of the isolated dapsone product (measured by UPLC-UV Method 1) was 94.6% dapsone with 3.22% 4-((4-aminophenyl)sulfonyl)phenol (A-B compound), 0.78% 4-((4-aminophenyl)sulfonyl)-N-methylaniline (A-Ma compound), and 0.30% bisphenol S (BPS) as the main impurities, the % values representing the peak area percentages in the chromatogram obtained by the UPLC-UV Method 1.

[0331] BPS was isolated with an overall yield of 65% assuming a 25% theoretical yield after depolymerization.

[0332] The purity of the isolated BPS product measured by UPLC-UV (Method 1) was 74.3% BPS with 24.5% 4-((4-aminophenyl)sulfonyl)phenol (A-B compound), 0.15% 4-((4-aminophenyl)sulfonyl)-N-methylaniline (A-Mx compound), and 0.40% dimers as the main impurities, the % values representing the peak area percentages in the chromatogram obtained by the UPLC-UV Method 1.

[0333] The A-B compound was isolated in a 73% yield assuming a 50% theoretical yield.

[0334] The purity of the isolated AB monomer product measured by UPLC-UV (Method 1) was 85.5% 4-((4-aminophenyl)sulfonyl)phenol (A-B compound) with 8.2% BPS, 5.69% Dapsone, and 0.48% 4-((4-aminophenyl)sulfonyl)-N-methylaniline (A-Ma compound) as the most significant impurities, the % values representing the peak area percentages in the chromatogram obtained by the UPLC-UV Method 1.

[0335] Example 6:

[0336] In a 1-L Hastelloy reactor vessel (Reactor 2) was charged with 10 g (40.903 mmol) of hemodialysis fiber comprising PVP. In a hood, 250 g of 28 wt.% ammonium hydroxide (4. 110 mol of ammonia, 100 Eq NHS / RPES) was added to the Parr vessel. After the reactor vessel was sealed, the reactor vessel was purged with nitrogen for 10 minutes. The N2 was then turned off and the entire reactor vessel was fully sealed (N2 pressure: 69 kPa = 10 psi). The reactor vessel was then heated to 250 °C and maintained at that reaction temperature for 48 hours (gradual temperature ramp =5°C / min.) with a final pressure around 8963 kPa (1300 psi). Afterward, the reactor vessel was cooled to room temperature.

[0337] Next, a solution of 2 M NaOH (150 g) was added to the reaction slurry and stirred at 30 °C for 1 hour. The reaction slurry was then filtered to obtain a solid and an alkaline filtrate, and the obtained solid was washed with 1 L of water.

[0338] The leftover solid (containing mostly dapsone) was dissolved in ethyl acetate and then washed with water twice. The ethyl acetate was removed under reduced pressure, meaning evaporated under subatmospheric pressure, to isolate dapsone.

[0339] The alkaline filtrate was then acidified with 2 M HC1 until a pH of 5 was observed, and then was stirred at 50 °C for 1 hour, and a precipitate is formed.

[0340] The precipitate (which contained primarily BPS and A-B compound) was then filtered and washed with copious amounts of water, then dried at 120 °C for 12 hours.

[0341] Dapsone was isolated at a 67% yield assuming a 25% theoretical yield after depolymerization and 5% PVP in the hemofiber.

[0342] The purity of the isolated dapsone measured by UPLC- UV (Method 1) was 88.1 wt.% Dapsone with 1.88% 4-((4-aminophenyl)sulfonyl)phenol (A-B compound), 2.0% 4-((4-aminophenyl)sulfonyl)-N-methylaniline (A-Ma compound), and 6% of various PES dimers as the main impurities, the % values representing the peak area percentages in the chromatogram obtained by the UPLC-UV (Method 1).

[0343] The BPS and A-B compound were isolated with an overall combined yield of 74% assuming a 75% theoretical yield (25%+50%) after depolymerization.

[0344] The isolated BPS+A-B acidic product had the following product composition via UPLC-UV (Method 1):- 54.7% 4-((4-aminophenyl)sulfonyl)phenol (A-B compound),- 24.5% BPS,- 13.9% Dapsone,- 5.0% PES dimers, and- 0.5% 4-((4-aminophenyl)sulfonyl)-N-methylaniline (A-Ma compound), the % values representing the peak area percentages in the chromatogram obtained by the UPLC-UV Method 1.

[0345] No PVP was detected in the isolated Dapsone product or the isolated BPS+A-B product.

[0346] While preferred embodiments of this 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.

[0347] What is claimed is:

Claims

CLAIMS1. A method [“method A”] for preparing a mixture comprising 4,4’-di-substituted diphenylsulfones from a polymeric material comprising least one polyethersulfone (PES polymer), wherein: said PES polymer designates a polymer comprising a polymeric chain terminated by two end groups, said PES polymeric chain comprising, based on the total amount of recurring units in the PES polymer, at least 80 mol %, at least 85 mol %, at least 90 mol %, at least 95 mol %, at least 98 mol %, or at least 99 mol %, of recurring units (RPES) represented by formula (L):[-Ar-SCh-Ar-O-] (L), in which Ar represents an unsubstituted divalent arylene group, each end group of the PES polymer is independently selected from a halide X, an hydroxy group and / or an endcapped 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 endcapped group Re; said 4,4’-di-substituted diphenylsulfones are of general formula (I): i -Ar-SOz-Ar-R2(I), in which Ar represents an unsubstituted divalent arylene group, and each of R1, R2is independently selected from the group consisting of OH, NH2, an endcapped group Re, an aminated endcapped group Rea, and a halide X, said endcapped Re group being selected from an alkoxy group and / or a phenoxy group, preferably a methoxy group, said aminated endcapped group Reabeing selected from an alkylamine group and / or a phenylamine group, preferably a methylamine group, and said halide X being Cl or F, said process comprising:(c) contacting the polymeric material comprising at least one PES polymer with an ammonia source at a reaction temperature of from 180 °C to 300 °C and at a reaction pressure of from 4 MPa to 25 MPa for a time period sufficient to depolymerize the at least one PES polymer and to provide a depolymerized mixture comprising 4,4’-di-substituted diphenylsulfones of the formula (I), wherein the ammonia source comprises anhydrous ammonia in liquid or gaseous form and / or in the form of an ammonium hydroxide solution; and(d) recovering the depolymerized mixture.

2. A method [“method B”] for preparing at least one 4,4’-di-substituted diphenylsulfone product from a polymeric material comprising least one polyethersulfone (PES polymer), wherein: said PES polymer designates a polymer comprising a polymeric chain terminated by two end groups, said PES polymeric chain comprising, based on the total amount of recurring units in the PES polymer, at least 80 mol %, at least 85 mol %, at least 90 mol %, at least 95 mol %, at least 98 mol %, or at least 99 mol %, of recurring units (RPES) represented by formula (L):[-Ar-SCh-Ar-O-] (L), in which Ar represents an unsubstituted divalent arylene group, each end group of the PES polymer is independently selected from a halide X, a hydroxy group and / or an endcapped group Re, with the proviso that when one end group is a halide X, the other end group is a hydroxy group and / or an endcapped group Re; said 4,4’-di-substituted diphenylsulfones are of general formula (I): R^Ar-SCh-Ar-R2(I), in which Ar represents an unsubstituted divalent arylene group, and each of R1, R2is independently selected from the group consisting of OH, NH2, an endcapped group Re , and a halide X, said endcapped Re group being selected from an alkoxy group and / or a phenoxy group, preferably a methoxy group, and said halide X being Cl or F, said method comprising:(a) contacting the polymeric material comprising at least one PES polymer with an ammonia source at a reaction temperature of from 180 °C to 300 °C and at a reaction pressure of from 4 MPa to 25 MPa for a time period sufficient to depolymerize the at least one PES polymer and to provide the depolymerized mixture comprising 4,4’-di-substituted diphenylsulfones of formula (I), wherein the ammonia source comprises anhydrous ammonia in liquid or gaseous form and / or in the form of an ammonium hydroxide solution,(b) recovering the depolymerized mixture; and(c) isolating at least one 4,4’-di-substituted diphenylsulfone product from said depolymerized mixture, by employing at least one technique selected from the group consisting of acid treatment, alkaline treatment, neutralization, washing,dissolution, solid / liquid separation such as filtration, evaporation and / or distillation, extraction, precipitation, and any combination thereof.

3. The process of Claim 1 or 2, wherein the polymeric material comprises at least one waste material selected from the group consisting of post-consumer and postindustrial polymeric articles, polymeric scraps, off-specification PES polymer products; and any combination thereof, preferably selected from the group consisting of membranes, fibers, films, automotive components, electronic components, consumer product components such as baby bottles, composites, battery components, plumbing parts, animal cages, and any combinations thereof, more preferably selected from the group consisting of hemodialysis membranes, fibers, films, and any combinations thereof.

4. The process of any one of Claims 1 to 3, wherein prior to step a), the polymeric material is pretreated using at least one of the following pretreatment steps: i. carrying out a mechanical or physical modification of the polymeric material, preferably transforming into parts of polymeric material such as by cutting, shredding, crushing, and / or grinding with a size lower than 10.0 mm, preferably lower than 5.0 mm, even preferably lower than 3.0 mm; ii. subjecting the polymeric material or parts of polymeric material obtained from step (i) to a cleaning treatment by contact with a cleaning agent; iii. washing the polymeric material or parts of polymeric material obtained from step (i) or from step (ii) with a volatile solvent such as water and / or a volatile organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C; iv. evaporating any volatile solvent such as water and / or organic solvent having a low boiling point (measured at atmospheric pressure) of at most 100 °C; v. sterilization; and / or vi. drying.

5. The process of any one of Claims 1 to 4, wherein prior to step a), the numberaverage molecular weight (Mn) of the PES polymer is from at least 15,000 g / mol to at most 60,000 g / mol, preferably from at least 16,000 g / mol to at most 55,000 g / mol, more preferably from at least 17,000 g / mol to at most 50,000 g / mol or from at least 20,000 g / mol to at most 45,000 g / mol, yet more preferably from at least18,000 g / mol to at most 35,000 g / mol, said Mn being measured by Gel Permeation Chromatography using methylene chloride as mobile phase and polystyrene standards for calibration.

6. The process of any one of Claims 1 to 5, wherein the polymeric material further comprises at least one polyvinylpyrrolidone (PVP), and wherein the depolymerized mixture comprising the 4,4’-di-substituted diphenylsulfones has no detectable PVP content.

7. The process of Claim 2 or any one of Claims 3 to 6 in combination with Claim 2, wherein the polymeric material further comprises at least one polyvinylpyrrolidone (PVP), and wherein the 4,4’-di-substituted diphenylsulfone product has no detectable PVP content after isolation.

8. The process of any one of Claims 1 to 7, wherein during step (a), the content of the ammonia source is from 70 to 250 molar Equivalent of NH3 [ Eq NHS / RPES ] relative to 1 molar Equivalent of the PES recurring unit (RPES) of formula (L) [ Eq NEE / RPES ], preferably from 70 to 200 Eq NEE / RPES, more preferably from 75 to 185 Eq NEE / RPES.

9. The process of any one of Claims 1 to 8, wherein during step a), the reaction temperature is from 180 °C to 290 °C, preferably from 190 °C to 280 °C, more preferably from 200 °C to 270 °C, yet more preferably from 210 °C to 260 °C, and the reaction pressure is from 4 MPa to 24 MPa, preferably from 4 MPa to 23 MPa, more preferably from 4 MPa to 22 MPa, or from 4.5 MPa to 21 MPa, or from 4.6 MPa to 20 MPa, still more preferably from 4.7 MPa to 12.5 MPa.

10. The process of any one of Claims 1 to 9, wherein step (b) comprises at least one of these steps:(bl) solvent washing with water and / or an organic solvent having a boiling point of at most 100 °C, and evaporating to dryness; and / or(b2) reactive washing with an alkaline aqueous solution to dissolve the depolymerized mixture and convert the phenolic end groups to phenolate end groups, and evaporating to dryness.

11. The process of Claim 2 or any one of Claims 3 to 10 in combination with Claim 2, wherein step (c) comprises these steps:(cl) subjecting the depolymerized mixture to an alkaline treatment with an alkaline aqueous solution in a manner effective to render 4-amino-4’- hydroxy diphenylsulfone [A-B compound] and 4,4’ -dihydroxy diphenylsulfone [bisphenol S] more water-soluble and to precipitate 4,4 ’-diaminodiphenylsulfone [Dapsone], and separating a dapsone-containing solid from a first aqueous supernatant;(c2) subjecting the first aqueous supernatant from step (cl) to an acidic treatment with a strong inorganic acid solution in a manner effective to precipitate 4,4’- dihydroxy diphenyl sulfone [bisphenol S] while keeping 4-amino-4’- hydroxy diphenylsulfone [A-B compound] in dissolved form, and separating a bisphenol S-containing solid from a second aqueous supernatant; and(c3) subjecting the second aqueous supernatant from step (c2) to an alkaline treatment with an alkaline aqueous solution in a manner effective to precipitate 4- amino-4’ -hydroxy diphenylsulfone [A-B compound], and separating an A-B compound-containing solid from a third aqueous supernatant.

12. The process of any one of Claims 1 to 11, wherein the depolymerized mixture comprises:- 4,4’ -diaminodiphenylsulfone [dapsone],- 4-amino-4’ -hydroxy diphenylsulfone [A-B compound],- 4,4’ -dihydroxy diphenylsulfone [bisphenol S], and optionally, 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound],13. A depolymerized mixture obtained by the method of any one of Claims 1 to 12, comprising:4,4’ -diaminodiphenylsulfone [dapsone],4-amino-4’ -hydroxy diphenylsulfone [A-B compound],4,4’ -dihydroxy diphenylsulfone [bisphenol S], and optionally 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound],14. A 4,4’-di-substituted diphenylsulfone product obtained by the method of Claim 2 or any one of Claims 3 to 13 in combination with Claim 2, comprising:4,4 ’ -diaminodiphenylsulfone [dapsone] ,4-amino-4’ -hydroxy diphenylsulfone [A-B compound],optionally 4,4’ -dihydroxy diphenylsulfone [bisphenol S] and / or optionally 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound] ; or4,4 ’-dihydroxy diphenylsulfone [bisphenol S],4-amino-4’ -hydroxy diphenylsulfone [A-B compound], and optionally 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound] .

15. A 4,4’-di-substituted diphenylsulfone product, being selected from the group consisting of:- a product (Pl) comprising:> 70 wt.%, preferably >75 wt.%, more preferably >80 wt.% or >85 wt.% or >90 wt.% of 4,4’ -diaminodiphenylsulfone [Dapsone],> 0 wt.%, preferably >0.2 wt.%, more preferably >0.5 wt.%, still more preferably >0.7 wt.% or >1.0 wt.% or >2.0 wt.%, of 4-amino-4’-hydroxydiphenylsulfone [A-B compound]; from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, of 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound]; wherein the wt.% is based on the total weight of the product (Pl);- a product (P2) comprising:> 70 wt.% of 4,4’ -dihydroxy diphenylsulfone [bisphenol S],> 0 wt.%, preferably > 0.1 wt.% and up to 30 wt.%, more preferably > 0.5 wt.% and up to 25 wt.%, of 4-amino-4’ -hydroxy diphenylsulfone [A-B compound], and from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, of 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound] ; wherein the wt.% is based on the total weight of the product (P2); and / or- a product (P3) comprising:> 70 wt.%, preferably >75 wt.%, more preferably >80 wt.% or >85 wt.% of 4-amino- 4’ -hydroxy diphenylsulfone [A-B compound],> 0 wt.% and up to 10 wt.%, preferably > 0.5 wt.% and up to 9 wt.%, of 4, d’- dihydroxy diphenyl sulfone [bisphenol S]; from 0 and up to 10 wt.%, preferably > 0.05 wt.% and up to 9 wt.%, more preferably > 0.1 wt.% and up to 8 wt.%, of 4,4’ -diaminodiphenylsulfone [Dapsone], and from 0 to 1 wt.%, preferably > 0.05 wt.% to 0.9 wt.%, more preferably > 0.1 wt.% to 0.8 wt.%, of 4-((4-aminophenyl)sulfonyl)-N-methylaniline [A-Ma compound] and / or 4-((4-methoxyphenyl)sulfonyl)aniline [A-Mx compound]; wherein the wt.% is based on the total weight of the product (P3).

Images