Solvent system for fractionation of a PVC plastic by liquid-liquid extraction

Abstract

The present invention relates to a solvent system specific to fractionation by liquid-liquid extraction, particularly by centrifugal partition chromatography, of a PVC-based feedstock comprising a PVC polymer and at least one additive. The system comprises two non-miscible liquid phases A and B, each comprising an organic solvent or a mixture of organic solvents selected from the same list consisting of ketones, amides, azines, esters, ethers, halogenated solvents, hydrocarbons, sulfur-containing solvents, and dihydrolevoglucosenone. The partition coefficient of the PVC polymer in the solvent system (ratio of the mass concentrations of the PVC polymer dissolved in phase B and in phase A) tends towards zero, and the partition coefficient of the additive in the solvent system (ratio of the mass concentrations of the additive dissolved in phase B and in phase A) is greater than or equal to 0.05.

Description

[0001] SOLVENT SYSTEM FOR THE FRACTIONATION OF PVC PLASTIC BY LIQUID-LIQUID EXTRACTION

[0002] technical field

[0003] The invention relates to the field of separation and / or purification techniques for complex organic materials, particularly poly(vinyl chloride) (PVC)-based plastics, from their production to their recycling. Specifically, the invention relates to the field of liquid-liquid extraction separation and / or purification techniques applied to PVC-based materials, and in particular the development of new solvent systems that meet the specific characteristics of the materials studied and are particularly well-suited to separation by centrifugal partition chromatography (CPC).

[0004] Previous technique

[0005] The ever-increasing production of plastics and the resulting environmental problems are driving the development of a so-called "circular" economy. This aims to simultaneously limit the use of non-renewable fossil resources and the production of non-recoverable waste, meaning waste sent to landfills or, worse, dispersed into the environment. In this context, one of the challenges of material recycling for plastic objects is the ability to characterize them at various stages of their life cycle: after production, after use and collection and sorting, and / or after transformation through processes such as grinding, washing, extrusion, etc., when mechanical recycling methods are used.More recently, numerous studies have focused on developing (physico-)chemical recycling processes that transform plastic-based input materials derived from waste (most often already having undergone mechanical processing) into purified recycled materials such as polymers, monomers, or mixtures of hydrocarbon compounds. Purified recycled material is defined as any material (polymer, monomer, or mixture of hydrocarbon compounds) that meets specific requirements, particularly regarding chemical composition and performance properties, allowing for its eventual reuse in various applications such as food packaging, toys, construction, and building materials. The success of developing these new recycling technologies also depends on the ability of those skilled in the art to assess the efficiency of the transformation process and to determine the quality of the final products obtained.

[0006] The challenges of characterization are significant. Indeed, a plastic is a complex material typically composed of a polymer (often the dominant component) and numerous additives from a wide variety of chemical families. These additives aim to give the final material mechanical, aesthetic, chemical, and other properties corresponding to the desired applications. In short, a plastic is a complex mixture of organic molecules (including organic macromolecules), and even inorganic particles (particularly metal-based), present in highly variable proportions and sizes, ranging from ppm to several tens of percent by weight and from a few nanometers to several millimeters. Its transformation into waste makes it even more complex, as it has been contaminated / polluted by so-called external impurities, which can be residues from other materials (other plastics, metals, glass, glue, etc.).), soiling (food residues, soil, gravel, etc.), etc., or so-called internal impurities, which may be degradation products of the polymer matrix itself, additives or both, which must also be taken into account during its characterization and during the characterization of the intermediate and / or final products resulting from its transformation for recycling (mechanical or (physico-)chemical).

[0007] Analytical techniques used to characterize materials are usually spectroscopic techniques such as infrared (IR), UV-visible or nuclear magnetic resonance (NMR) methods.

[0008] These techniques quickly reach their limits for characterizing plastic materials once formulated, because the polymer contains numerous additives. It is then necessary to add a sample simplification step. When the objective is to characterize the additives, an extraction step (particularly of organic molecules) is most commonly implemented, such as solid / liquid extraction, accelerated solvent extraction (ASE), microwave extraction (MAE), or ultrasonic extraction (UAE). This step allows the additives to be extracted from the polymer matrix and enables access to detailed molecular characterization techniques. When the objective is to characterize both the additives and the polymer matrix, fractionation methods oriented according to a property such as size, polarity, or solubility are used.These methods allow for the generation of several fractions, at least one of which contains the polymer matrix, others containing organic additives and impurities, and still others containing inorganic compounds. Examples include the "dissolution-precipitation" method, which is based on differences in the solubility of compounds, and size-exclusion chromatography, which is based on differences in the size of (macro)molecules in solution.

[0009] Characterization is then carried out for each of the fractions, for example using chromatography methods coupled with high-resolution mass spectrometry detection. For the polymer, it is characterized by its morphology using spectroscopic methods, by its average molar masses and distribution using size exclusion chromatography and its various detectors, by its composition at the molecular level using NMR, IR, RAMAN and UV spectroscopy, by its mechanical properties using rheology, tensile, flexural, shear and hardness measurements, and by its thermal properties using thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis.The present invention aims to provide a method for fractionating a specific plastic, PVC, in order to characterize it at all possible stages of its life cycle, from production to reuse as recycled material after processing, to facilitate the establishment of a more circular PVC economy. Indeed, there is a particular challenge regarding the recycling of PVC plastic, because on the one hand, its polymer of the same name is currently the third most consumed polymer in the world and in Europe, with approximately 43 Mt and 6 Mt of PVC resins used in 2020, respectively, and on the other hand, PVC-based products are mainly used for applications specific to the construction and building sector (windows, flooring, cables, pipes, etc.), and are therefore characterized by long lifespans (up to 100 years) which must be taken into account for recycling.Indeed, given the evolution of European regulations over the past few decades concerning certain PVC additives that were very frequently used in the past (such as low molecular weight phthalates used as plasticizers, which are being progressively banned), there is now a major challenge in improving the recycling of post-consumer waste containing PVC formulated several decades ago. The development of new PVC recycling technologies is therefore logically accompanied by a marked need for effective and comprehensive analytical methods. For this reason, and as mentioned previously, pre-fractionation of the PVC is a crucial step before applying one or more analytical methods.

[0010] Centrifugal partition chromatography (CPC) is a specific liquid / liquid extraction separation technique, as described in the publications of A.P. Foucault (2002), Chapter 4 - Centrifugal partition chromatography: the story of a company (Book), editor(s): A. Berthod, Comprehensive Analytical Chemistry (Elsevier), volume 38, pages 85-113, and A. Berthod, T. Maryutina, B. Spivakov, O. Shpigun, I.A. Sutherland (2009) Countercurrent chromatography in analytical chemistry (IUPAC Technical Report), Pure and Applied Chemistry, volume 81, no. 2, pages 355-387. In the publication by Berthod et al. In 2009, CPC required two immiscible liquid phases, based on at least two immiscible solvents called a "solvent system", one being maintained in the experimental device (usually a column) via the application of a centrifugal force (so-called stationary phase) and the other playing the role of eluent (or mobile phase) flowing from the device.The separation of the constituent elements of a sample in the apparatus, after solubilization (solutes), is based on the difference in their partition coefficients, that is, the difference in the ratios of their chemical activities between the phases. Fractionation by CPC offers recognized advantages: the size of the columns used allows for fractionation on a semi-preparative (or even preparative) scale, meaning that a compound can be isolated in a much larger quantity than when using these columns for analytical purposes (100 or even 1000 times greater), with a level of purity that allows for subsequent experiments, thus yielding concentrated fractions for later characterization.Furthermore, the fractionation occurs without any solid support, thus avoiding irreversible adsorption, as the stationary phase is a liquid. This allows for the recovery of the entire injected solution, unlike simulated moving bed (LMS) or simulated countercurrent (SMB) separation techniques that use columns with adsorbent beds. Finally, the design of custom solvent systems for each application provides access to unique selectivities. Indeed, this step of finding a suitable solvent system is often the limiting factor in the development of new CPC methods, since the system must meet a large number of criteria depending on the number and nature of the compounds to be separated. Thus, the chemical nature of the solvents, as well as their proportions, are critical in the development of an appropriate solvent system.Furthermore, the number of solvents that can be used in a mixture is theoretically infinite for constructing the solvent system, considering the only imposed limitation, which is the two-phase criterion of the final system.

[0011] The CPC separation technique is now mainly used for the purification of natural compounds, for example for the purification of cannabinoids as disclosed in patent US10207199B2 or the purification of proteins as illustrated in international application WO2014137903.

[0012] The inventors focused on the novel application of the CPC separation technique to the fractionation of plastic materials, in particular PVC-based plastic materials, and developed new biphasic solvent systems specific to the liquid-liquid extraction fractionation of PVC plastic, in particular by CPC.

[0013] Objectives and Summary of the Invention

[0014] The present invention aims to enable the fractionation of PVC plastics by liquid-liquid extraction, in particular by CPC, especially for characterization purposes at any stage of their life cycle, but also for the recovery of PVC polymer(s) and additives of interest for their reuse, within the framework of a circular economy.

[0015] Thus, to achieve at least one of the aforementioned objectives, among others, the present invention proposes, according to a first aspect, a two-phase solvent system for the liquid-liquid extraction fractionation of a PVC-based filler comprising one or more PVC polymers and at least one additive and possible impurities, said solvent system comprising two immiscible liquid phases A and B, and being characterized in that:

[0016] - said phase A and said phase B each comprise an organic solvent or a mixture of organic solvents chosen from the same list consisting of ketones, amides, azines, esters, ethers, halogenated solvents, hydrocarbons, sulfide solvents, and dihydrolevoglucosenone;

[0017] - the organic solvent or mixture of organic solvents of said phase A is capable of solubilizing the PVC polymer(s) of the PVC-based filler;

[0018] - said biphasic solvent system is capable of solubilizing said additive; - the partition coefficient of the PVC polymer(s) in said biphasic solvent system, defined as the ratio of the mass concentrations of the PVC polymer(s) dissolved in phase B and in phase A, tends towards zero, and the partition coefficient of said additive in the biphasic solvent system, defined as the ratio of the mass concentrations of said additive dissolved in phase B and in phase A, is greater than or equal to 0.05.

[0019] According to one or more embodiments, the organic solvent(s) for each of phases A and B are chosen from the list consisting of:

[0020] - the following compounds from the ketone family: methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone and cyclohexanone;

[0021] - the following compounds from the amide family: N,N-diethyl formamide, 2-pyrrolidone and N-methyl-2-pyrrolidone;

[0022] - the following compounds from the azine family: pyridine, 4-aminopyridine, 2-aminopyridine, and 4-vinylpyridine;

[0023] - the following compounds from the ester family: methyl acetate, ethyl acetate, methyl propionate, n-butyl propionate, y-butyrolactone and y-valerolactone;

[0024] - the following compounds from the ether family: methoxycyclopentane, diisopropyl ether, tetrahydrofuran and methyl tetrahydrofuran;

[0025] - the following compounds from the family of halogenated solvents, in particular chlorinated: dichloromethane and trichloromethane;

[0026] - the following compounds from the hydrocarbon family: cyclohexane, toluene, isohexane and n-heptane (heptane);

[0027] - the following compound from the family of sulfide solvents: dimethyl sulfoxide;

[0028] - dihydrolevoglucosenone.

[0029] According to one or more embodiments, phase A comprises a mixture of at least two of the following organic solvents:

[0030] - a predominantly sulfurous solvent,

[0031] - a first minor solvent chosen from among the ketones and cyclic esters, preferably chosen from methylethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methylisobutyl ketone, cyclopentanone, y-butyrolactone, and y-valerolactone.

[0032] According to one or more embodiments, phase A comprises a mixture of at least three of the following organic solvents:

[0033] - the major solvent dimethyl sulfoxide, at a content of at least 50% by weight,

[0034] - the first minor solvent chosen from ketones and cyclic esters, preferably from diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, y-butyrolactone and y-valerolactone, and - a second minor solvent chosen from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane.

[0035] According to one or more embodiments, in which phase A comprises a mixture of the following three organic solvents:

[0036] - the major solvent dimethyl sulfoxide, at a content of at least 50% by weight,

[0037] - the first minor solvent diethyl ketone, and

[0038] - the second minor solvent n-heptane, preferably in a content less than or equal to 15% by weight.

[0039] Depending on one or more embodiments, phase A comprises:

[0040] - 50% to 70% by weight of dimethyl sulfoxide, preferably 55% to 65% by weight of dimethyl sulfoxide,

[0041] - 20% to 40% by weight of diethyl ketone, preferably 25% to 35% by weight of diethyl ketone,

[0042] - 5% to 15% by weight of n-heptane, preferably 5% to 10% by weight of n-heptane.

[0043] According to one or more embodiments, in which phase B comprises a mixture of at least two of the following organic solvents:

[0044] - a major solvent chosen from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane,

[0045] - a first minor solvent chosen from among the ketones and cyclic esters, preferably chosen from methylethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methylisobutyl ketone, cyclopentanone, y-butyrolactone, and y-valerolactone.

[0046] According to one or more embodiments, phase B comprises a mixture of at least three of the following organic solvents:

[0047] - the major solvent, with a content of at least 50% by weight, chosen from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane,

[0048] - the first minor solvent chosen from among ketones and cyclic esters, preferably from diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, γ-butyrolactone, and γ-valerolactone, and

[0049] - a second minor solvent chosen from among the sulfide solvents, preferably dimethyl sulfoxide. According to one or more embodiments, phase B comprises a mixture of the following three organic solvents:

[0050] - the major solvent n-heptane, at a content of at least 50% by weight,

[0051] - the first minor solvent diethyl ketone, and

[0052] - the second minor solvent dimethyl sulfoxide, preferably at a content less than or equal to 15% by weight.

[0053] Depending on one or more embodiments, phase B comprises:

[0054] - 50% to 70% by weight of n-heptane, preferably 55% to 65% by weight of n-heptane, - 20% to 40% by weight of diethyl ketone, preferably 25% to 35% by weight of diethyl ketone,

[0055] - 5% to 15% weight of dimethyl sulfoxide, preferably 5% to 10% weight of dimethyl sulfoxide.

[0056] According to one or more embodiments, the two-phase solvent system is capable of solubilizing at least one additive of the PVC-based filler included in the list consisting of:

[0057] - the family of organotins used as stabilizing additives;

[0058] - metallic compounds used as stabilizing additives containing lead or cadmium, preferably lead and cadmium stearates;

[0059] - the family of ortho-phthalates used as plasticizing additives, preferably dioctyl phthalate DOP, bis(2-ethylhexyl) phthalate DEHP, dibutyl phthalate DBP, benzyl butyl phthalate BBP, di-isobutyl phthalate DIBP, di-pentyl phthalate DPP;

[0060] - the family of terephthalates used as plasticizing additives;

[0061] - the family of trimellitates used as plasticizing additives;

[0062] - the family of benzoates used as plasticizers;

[0063] - the family of mono, di and triphosphites and their derivatives used as heat stabilizing additives;

[0064] - the family of phenyl 1,3-diones used as heat-stabilizing additives;

[0065] - the family of organophosphates used as flame retardant additives.

[0066] According to one or more embodiments, the partition coefficient of said additive in the two-phase solvent system is between 0.05 and 5, preferably between 0.5 and 5.

[0067] According to one or more embodiments, the two-phase solvent system does not induce precipitation of the PVC polymer(s).

[0068] According to one or more embodiments, the partition coefficient of the PVC polymer(s) in the two-phase solvent system is less than or equal to 0.01, preferably between 0 and 0.01.

[0069] According to one or more embodiments, the biphasic solvent system is used for the fractionation by centrifugal partition chromatography of a PVC-based feed.

[0070] Other objects and advantages of the invention will become apparent from the following description of particular embodiments of the invention, given by way of illustration and not limitation, the description being made with reference to the attached figures described below.

[0071] List of figures

[0072] Figure 1 is a schematic representation of a CPC device and its operation (based on a diagram published at https: / / rotachrom.com / advanced-chromatography-cpc-modes) that can implement a biphasic solvent system according to the invention. Figure 2 is a diagram representing the elution and extrusion phases during CPC fractionation using a biphasic solvent system according to the invention.

[0073] Description of the implementation methods

[0074] Terminology

[0075] Some definitions and clarifications are given below, although more details on the objects defined below may be given later in the description.

[0076] A PVC-based object is defined as an object, generally a consumer product, which includes, and preferably is made of, at least one PVC plastic.

[0077] Polyvinyl chloride (PVC) plastic, also known as polyvinyl chloride, refers to a combination of PVC polymer with various additives chosen according to the required functionalities of the PVC plastic, which are themselves chosen according to the intended applications. This PVC polymer is typically produced by the free-radical polymerization of vinyl chloride (VCM), a monomer itself obtained from chlorine and ethylene.

[0078] The additives used in the composition of PVC plastic can be organic molecules or macromolecules, as well as inorganic (nano)particles, and are used according to the properties they impart to the PVC polymer. Generally speaking, and without being exhaustive, the formulation of PVC plastic involves at least one of the families of additives described below:

[0079] - Stabilizers to limit the degradation of polymer chains by dehydrochlorination and / or oxidation under the effect of heat, light, oxygen and / or mechanical stress. The nature of these stabilizers, for example metallic compounds (containing Pb, Sn, Ca, Zn, or Cd) or organic compounds, depends on the required properties and therefore the intended applications. Some examples of stabilizers frequently used in the past or currently are the following: lead stearate, dibasic lead stearate, dibasic lead phthalate, zinc stearate, calcium stearate, etc., taken alone or in mixtures, but also organotins (e.g., 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate of 2-ethylhexyl), mono, di and triphosphites and their derivatives (e.g., di(8-methylnonyl) and phenyl phosphite), or phenyl 1,3-diones such as dibenzoylmethane (DBM).Co-stabilizers, understood as improving the performance of primary stabilizers, can also be used, for example epoxidized oils;

[0080] - Plasticizers are used to induce flexibility and improved impact and cold resistance in PVC plastic. The most widely used of these belong to the phthalate family. These are obtained by reacting phthalic anhydride with alcohols of varying carbon chains and consist of a benzene ring and two carboxylic ester groups positioned ortho to the benzene ring. Dioctyl or diethylhexyl phthalate (DOP or DEHP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) are examples of phthalates that were widely used in the past or are still in use today.Other non-phthalic plasticizers are used today such as bis(2-ethylhexyl) adipate (DEHA) or cyclohexane-1,2-dicarboxylic acid diisononyl ester (DINCH), terephthalates such as dibutyl terephthalate or dioctyl terephthalate (DEHT), trimellitates such as trioctyl benzene-1,2,4-tricarboxylate or benzoates;

[0081] - lubricants to control intermolecular friction forces within the polymer itself (internal lubricants such as stearic acid, etc.) or between the polymer and the metal walls of the processing tools (external lubricants such as paraffins, polyethylene waxes, etc.);

[0082] - inert fillers, mostly mineral (calcium carbonate (CaCOs), carbon black, kaolin, glass fibers, etc.), which act as diluents or to improve certain mechanical, electrical, thermal, etc. properties;

[0083] - colorants and / or pigments, such as titanium dioxide (TiOz) or carbon black, the latter being insoluble in the polymer and therefore present as particles dispersed in the PVC plastic,

[0084] - shock-absorbing agents, generally polymers such as polyacrylates and copolymers such as methacrylate-butadiene-styrene (MBS), whose role is to reduce the fragility of PVC, particularly at low temperatures,

[0085] - flame retardants, such as organophosphate compounds like tris(2-ethylhexyl) phosphate, triphenyl phosphate (TPP), tri-o-cresyl phosphate or trixylenyl phosphate,

[0086] - other additives: antioxidants, anti-UV agents, biocides, antistatic agents, reinforcements, etc.

[0087] Impurities are defined as all elements other than PVC plastics (PVC polymer(s) with additives) as described above. They can be "external" or "internal." External impurities are those resulting from the life cycle of PVC-based products and / or from the collection and sorting process, or even from pre-treatment operations of PVC-based plastic waste. These impurities can be metallic, organic, or mineral. They may include residues of materials (other than PVC plastics) that make up PVC-based products or other objects that have been in contact with PVC-based products, soiling (food, biomass, soil / rubble, glue, etc.), and so on. These impurities from use can thus, and in a non-exhaustive way, include glass, wood, cardboard, paper, metal, rubber, silicones, plastics other than PVC (for example PET, etc.), mineral elements, etc.Any degradation products of PVC polymers and / or additives formed over time during the life of the PVC-based product are also considered impurities and are classified as internal.

[0088] The term "PVC-based filler" in the following text refers to any material containing one or more PVC plastics, potentially obtained at any stage of a PVC plastic's lifecycle, from its production to its mechanical or (physico-)chemical recycling, which requires fractionation within the framework of establishing a circular economy specific to that plastic. Depending on its origin, it may contain one or more PVC polymers, as well as additives derived from one or more PVC plastic formulations. With reference to a CPC experimental process and apparatus, the term "PVC-based sample" is used in this description to designate such a PVC-based filler.

[0089] The term "solvent system" or "biphasic solvent system" refers to the two immiscible liquid phases, comprising at least two organic solvents, necessary for implementing a liquid-liquid extraction separation technique, particularly CPC, and specifically adapted for the fractionation of a PVC-based feedstock. The organic solvents forming the biphasic solvent system are immiscible or partially miscible. Regarding miscibility or partial miscibility: the organic solvents comprising the solvent system are immiscible or partially miscible in such a way as to form two distinct liquid phases separated by an interface (immiscible liquid phases A and B).In CPC separation, one of the liquid phases is maintained in the CPC experimental device via the application of a centrifugal force (stationary phase) and the other plays the role of eluent (or mobile phase) flowing from the device.

[0090] The term "injection solution" refers to the result of one or more preparatory steps of the PVC-based load (e.g., the PVC-based sample) enabling its injection into the liquid-liquid extraction device (e.g., the CPC experimental device).

[0091] Generally speaking, "purity of the product" refers to the quality of the product obtained after fractionation of the PVC-based feedstock (e.g., the PVC-based sample), here the PVC polymer (e.g., solid PVC polymer stream(s)).

[0092] Chromatographic selectivity refers to the ability of a chromatographic process to elute compounds at different times and, consequently, the ability of this process to separate the compounds from each other.

[0093] The term "partition coefficient" refers to the value quantifying the partitioning of a solute between the two immiscible liquid phases A and B of the solvent system, specifically the ratio of the mass concentrations of said solute in phase B (numerator), e.g., the mobile phase in a CPC apparatus, and in phase A (denominator), e.g., the stationary phase in a CPC apparatus. This coefficient governs the elution order of compounds during a CPC process. Preferably, phase A is defined as the stationary phase of the experimental CPC apparatus, and phase B as the mobile phase. In this description, the expression "greater than..." is understood as strictly greater than, and symbolized by the sign ">", and the expression "less than" as strictly less than, and symbolized by the sign ">". When the limit is included, the precision will be provided by the respective expressions "greater than or equal to..."» (and corresponding to the sign « > ”) and « less than or equal to » (corresponding to the sign « < ”).

[0094] In this description, ambient temperature (“Tamb”) is typically 20°C ± 5°C, and atmospheric pressure is 0.101325 MPa.

[0095] According to the present invention, pressures are absolute pressures, and are given in MPa, unless otherwise indicated.

[0096] In this description, the term "include" is synonymous with (means the same as) "comprise," "include," and "contain," and is inclusive or open-ended, not excluding other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist."

[0097] In this description, the expression "between ... and ..." means that the limit values ​​of the interval are included in the range of values ​​described, unless otherwise specified.

[0098] In this description, the various parameter ranges characterizing a given system or device, or relating to a step in a process implementing said device, such as ranges relating to compound concentrations, dimensions (lengths, diameters, etc.), angles, pressure, or temperature ranges, may be used alone or in combination. For example, in this description, a preferred compound concentration range for phase A of the solvent system may be combined with a more preferred compound concentration range for phase B of the solvent system.

[0099] In this description, the various embodiments presented can be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0100] In this description, a step refers to an operation or group of similar operations performed on a given flow at a specific point in the process. The process is described in its various steps, taken in the order in which the flows or products occur.

[0101] The present invention relates to a biphasic solvent system specifically designed for the fractionation, by liquid-liquid extraction, particularly by centrifugal partition chromatography in elution-extrusion mode, of a PVC-based feedstock. This fractionation allows for the recovery of a pure PVC polymer and all additives and impurities for characterization and / or valorization purposes. Before describing the solvent system according to the invention, an experimental CPC setup using said solvent system is described below, as well as a CPC separation method using such a setup, to illustrate the fractionation of a PVC-based sample for characterization. This provides a better understanding of the invention and is in no way limiting.In particular, the solvent system according to the invention can be used by other liquid / liquid extraction type separation processes and devices requiring two immiscible liquid phases, as well as the solvent system according to the invention can be implemented in CPC experimental devices other than those given as examples below.

[0102] CPC experimental setup

[0103] As already mentioned, the CPC separation technique requires the use of a two-phase liquid system made from at least two solvents, called a "solvent system". Specifically, this solvent system is implemented in an experimental setup that can typically use three types of columns: either columns consisting of a hollow cylinder whose wall is hollowed out with radially distributed "partition" or "separation" cells connected to each other by conduits with a cross-section smaller than that of the partition cells, as illustrated in patent FR2802104 or application W02004 / 079363; or columns consisting of stacked discs etched with partition cells connected to each other by conduits with a smaller cross-section, where the seal between the discs is ensured by Teflon® gaskets of the same diameter as the discs, as illustrated in application WOOO / 58722;either columns made up of stacked disks and comprising a network of three-dimensional cells of spherical or ovoid shape, interconnected in series, and communicating with liquid phase circulation channels and distributed around the periphery of at least one disk rotating around a main axis, as illustrated in application W02009 / 066014.

[0104] An example of a CPC 100 device and its operation, which can implement the biphasic solvent system according to the invention, are illustrated in Figure 1. The partition cells 10 are connected to each other and arranged radially around a rotor 20 which drives the entire set of interconnected cells in rotation (arrow 30).

[0105] A constant centrifugal force field, represented by arrow 40 in Figure 1, is generated by the rotation of the experimental setup. This field maintains one of the two liquid phases of the solvent system within the setup, referred to as the stationary phase ("S" in Figure 1). The other liquid phase, referred to as the mobile phase ("M" in Figure 1), flows through it in an "upward" or "downward" direction, as detailed later in the description of the procedure. In the example shown in Figure 1, the mobile phase M flows through the stationary phase S in a downward motion 50 (in the same direction as the centrifugal force 40), due to the lower density ds of the stationary phase compared to the density d M of the mobile phase. The reverse, that is, the circulation of the mobile phase through the stationary phase in an upward direction (opposite to the centrifugal force), is also possible if ds is greater than d M, and corresponds to the preferred case for the implementation of the solvent system according to the invention.

[0106] The mobile phase "percolates" in a sort of "spray" state (whose schematic representation in Figure 1 is in the form of "drops"), through the stationary phase, for example in an ascending mode if the stationary phase is the heavy phase (the denser of the two phases of the biphasic system), or in a descending mode as illustrated in Figure 1 if the stationary phase is the light phase (the less dense of the two phases of the biphasic system).

[0107] The solvent system according to the invention is advantageously implemented in such an experimental CPC device.

[0108] According to the invention, it is thus possible to use a CPC device to separate the compounds of the PVC-based sample comprising one or more PVC polymers and at least one additive and possible impurities, in particular by implementing a single biphasic solvent system comprising two immiscible liquid phases A and B as described, in at least one column comprising a series interconnection of at least one set of partition cells in which the stationary phase is maintained by centrifugal effect and the mobile phase circulates by percolating through said stationary phase, to separate the additive(s) of the PVC-based sample retained in the mobile phase comprising phase B, and produce a purified PVC polymer(s) solution comprising the stationary phase A.

[0109] CPC separation process for a PVC-based sample

[0110] CPC, like high-performance liquid chromatography (HPLC), is based on a chromatographic development method using elution. More precisely, in CPC, the separation of the constituents of a sample after solubilization (solutes or analytes) is based on the difference in their partition coefficients with respect to the two immiscible liquid phases; that is, the difference in the ratios of their chemical activities between the mobile and stationary phases. In other words, the analytes are subject only to the thermodynamic laws of partition equilibria between solvents, which ideally leads to the elution of each analyte according to a Gaussian concentration profile. In practical terms, the higher the partition coefficient for a given solvent system, the more rapidly the corresponding solute is eluted by the mobile phase.Conversely, when the partition coefficient is very low, a solute may not be eluted and may remain in the stationary phase, which is itself held in the apparatus during the separation step by centrifugal force. It can, however, be completely recovered after the elution phase. To do this, the pumping of the mobile phase, which has occurred throughout the elution, is stopped, and the stationary phase is then pumped back into the column. The column contents are then pushed out and recovered along with all the compounds that have a high affinity for the stationary phase. More details on a possible implementation of the process are given later in the description.

[0111] In general, an essential element of CPC separation is the identification of a solvent system specific to the sample to be fractionated, which leads to the development of a separation method specific to each application (JH. Renault et al., 2002, Chapter 3, Solvent systems. Editor(s): A. Berthod. In Comprehensive Analytical Chemistry (Elsevier), vol. 38, pp. 49-83). The solvent system according to the invention is designed so that the partition coefficients of each of the parts to be separated from the PVC-based sample are sufficiently distinct. In particular, the fractionation method implementing a solvent system according to the invention is based on the following strategy:

[0112] - the PVC polymer(s) of the PVC-based sample remain in the stationary phase throughout the separation step, and can be recovered at the end of elution as explained above, for example by pumping the stationary phase once the pumping of the mobile phase has stopped.

[0113] For this purpose, the solvent system according to the invention is designed so that the partition coefficient(s) of the PVC polymer(s) are very low, tending towards 0, this choice being based on the fact that the PVC polymer(s) are specific due to their size and polarity and that it is sought to maximize their separation from other compounds such as additives and possible impurities;

[0114] - The elution of additives and potential impurities in the PVC-based sample is progressive via their transfer into the mobile phase within the experimental setup, thus achieving separation according to the major chemical families of the organic substances involved, using the same solvent system. This solvent system is also designed so that the partition coefficients of the additives and potential impurities allow for such progressive elution into the mobile phase.

[0115] PVC-based filler

[0116] The solvent system according to the invention is suitable for the liquid-liquid extraction fractionation of a PVC-based feedstock, in particular for the CPC fractionation of a PVC-based sample.

[0117] The PVC-based filler, already described in general terms above, comprises one or more PVC polymers and at least one additive, as well as possible impurities. The additives and impurities have also already been described in general terms above.

[0118] The PVC-based filler can typically comprise between 30% and 99.9% by weight, preferably between 30% and 95% by weight and even more preferably between 35% and 80% by weight, of PVC polymer(s).

[0119] The PVC-based filler can typically comprise between 0.1 and 70% by weight, preferably between 5 and 70% by weight and, even more preferably, between 20 and 65% by weight of additives.

[0120] The additive(s) contained in the PVC-based filler may be included in the following list:

[0121] - stabilizing or co-stabilizing additives, of the metallic compound type (containing Pb, Sn, etc.)

[0122] Ca, Zn, or Cd) or organic, chosen for example from metallic stearates of zinc (e.g., zinc stearate), calcium (e.g., calcium stearate), lead (e.g., lead stearate, dibasic lead stearate) or cadmium (e.g., cadmium stearate), dibasic lead phthalate, epoxidized oils, organotins (e.g., 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate of 2-ethylhexyl), mono, di and triphosphites and their derivatives (e.g., di(8-methylnonyl) and phenyl phosphite), phenyl 1,3-diones (e.g., dibenzoylmethane (DBM)), etc.;

[0123] - plasticizing additives chosen, for example, from the phthalate family, such as dioctyl or bis(2-diethylhexyl) phthalate (DOP or DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), di-n-octyl phthalate (DNOP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl phthalate, isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, or from other non-phthalic compounds such as bis(2-ethylhexyl) adipate (DEHA) or diisononyl ester of acid cyclohexane-l,2-dicarboxylic (DINCH), terephthalates such as dibutyl terephthalate or dioctyl terephthalate (DEHT), trimellitates such as trioctyl benzene-l,2,4-tricarboxylate or benzoates;

[0124] - lubricant additives chosen for example from stearic acid, paraffins and polyethylene waxes;

[0125] - inert additives or colourings chosen for example from calcium carbonate (CaCO3), carbon black, kaolin, glass fibres, titanium dioxide (TiO2);

[0126] - anti-shock polymer or copolymer additives chosen for example from polyacrylates and methacrylate-butadiene-styrene;

[0127] - flame retardant additives chosen for example from organophosphates such as tris(2-ethylhexyl) phosphate, triphenyl phosphate (TPP), tri-o-cresyl phosphate or trixylenyl phosphate.

[0128] Preferably, the PVC-based filler includes additives that may be additives closely monitored by ECHA (ECHA, Investigation Report on PVC and PVC additives, version no. 1, 22 / 11 / 2023) and / or subject to REACH regulations, in particular selected from the group consisting of:

[0129] - the organotin family, used as stabilizers, such as 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate of 2-ethylhexyl (DOTE), etc.;

[0130] - metallic compounds used as stabilizers such as those based on lead and cadmium subject to REACH restrictions, such as lead and cadmium stearates, etc.;

[0131] - the family of ortho-phthalates, used as plasticizers, some of which are subject to regulations, such as dioctyl phthalate (DOP), bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), di-isobutyl phthalate (DIBP), dipentyl phthalate (DPP), etc.;

[0132] - the terephthalate family, used as plasticizers, such as dibutyl terephthalate, etc.; - the trimellitate family, used as plasticizers, such as trioctyl benzene-1,2,4-tricarboxylate, etc.;

[0133] - the benzoate family, used as plasticizers;

[0134] - the family of mono, di and triphosphites and their derivatives, used as heat stabilizers, such as di(8-methylnonyl) and phenyl phosphite, etc.;

[0135] - the phenyl 1,3-dione family, used as heat stabilizers, such as dibenzoylmethane (DBM), etc.;

[0136] - the family of organophosphates used as flame retardants, such as tris(2-ethylhexyl) phosphate, etc.

[0137] Any impurities present are products resulting from cross-contamination or degradation of additives.

[0138] PVC-based filler is usually in solid form (under normal temperature and pressure conditions), particularly in the form of solid particles.

[0139] The PVC-based filler may originate from production scraps or "installation scraps," i.e., waste generated during the installation or placement of the plastic-based article in its environment of use (e.g., flooring installation by tradespeople), or from post-consumer waste, and may have undergone a conditioning step that may include at least one grinding or shredding process to form a PVC-based filler in particle form. Any other conditioning step, including a washing step, may have been carried out to provide the PVC-based filler.

[0140] For example, the PVC-based filler can advantageously be in the form of shredded material, possibly washed, the largest dimension of which is less than or equal to 20 cm, preferably less than or equal to 10 cm, preferably less than or equal to 1 cm and even more preferably less than or equal to 5 mm.

[0141] The PVC-based filler can also advantageously be in the form of a micronized solid, that is, in the form of particles preferably having an average size of less than 1 mm, for example, between 10 micrometers (µm) and 800 micrometers (µm). The average size advantageously corresponds to the average diameter of the spheres circumscribing said particles.

[0142] Thus, the PVC-based feedstock to be fractionated according to the liquid-liquid extraction separation process, particularly CPC, implementing the solvent system according to the invention, is advantageously in the form of particles, typically having an average size of between 10 µm and 20 cm, for example, ground-type particles having an average size of between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferably between 1 mm and 1 cm, even more preferably between 1 mm and 5 mm, or particles resulting from micronization (very fine grinding to produce a powder) with an average size of less than 1 mm, preferably between

[0143] 10 pm and 800 pm.

[0144] For use in the CPC separation process employing the solvent system according to the invention, the PVC-based sample generally undergoes a preparation step so that it can be injected as a solution into the CPC device. This PVC-based sample preparation step is detailed later in the description of the implementation of the CPC separation process.

[0145] Solvent system

[0146] As already mentioned, the biphasic solvent system according to the invention is specific to the liquid-liquid extraction fractionation of a PVC-based feed comprising one or more PVC polymers and at least one additive, and possible impurities.

[0147] The solvent system according to the invention comprises, and preferably consists of, two immiscible liquid phases A and B, and is characterized in particular in that:

[0148] - phase A and phase B each comprise an organic solvent or a mixture of organic solvents chosen from the same list consisting of ketones, amides, azines, esters, ethers, halogenated solvents (preferably chlorinated, brominated, fluorinated), hydrocarbons, sulfide solvents, and dihydrolevoglucosenone;

[0149] - the organic solvent or mixture of organic solvents of said phase A is capable of solubilizing the PVC polymer(s) of the PVC-based filler;

[0150] - the two-phase solvent system is capable of solubilizing said additive;

[0151] - the partition coefficient of the PVC polymer(s) in the two-phase solvent system (defined as the ratio of the mass concentrations of the PVC polymer(s) dissolved in phase B and in phase A) tends towards zero, and the partition coefficient of said additive in the two-phase solvent system is greater than or equal to 0.05.

[0152] The solvent system constituting the two-phase system is composed of a phase A based on at least one organic solvent (i.e., an organic solvent or mixture of organic solvents) capable of solubilizing at least 90% by weight of the PVC polymer(s) in the PVC-based filler, preferably at least 95% by weight, even more preferably at least 98% by weight, and even more preferably at least 99% of the PVC polymer(s) in the PVC-based filler, and a phase B, immiscible with A, based on at least one organic solvent (i.e., an organic solvent or mixture of organic solvents) exhibiting little affinity for solubilization with said PVC polymer(s). Thus, the partition coefficient of the PVC polymer(s) in the solvent system according to the invention tends towards zero.By tending towards zero, we mean in this context having a value approaching zero and in all cases at least less than or equal to 0.01, and preferably between 0 and 0.01. By dissolution of the PVC polymer(s), we must understand any phenomenon leading to the obtaining of at least one polymer solution, that is to say a liquid constituting phase A comprising at least the PVC polymers dissolved in said at least one solvent of phase A. Those skilled in the art are well acquainted with the phenomena classically involved in the dissolution of polymers, which include at least mixing, homogenization, solvation, disentanglement and dispersion of the polymer chains and more particularly here of the PVC polymer chains.

[0153] Thus, at least one solvent for phase A is chosen, based on its physicochemical properties, for its ability to solvate, disentangle, and disperse the PVC polymer chains. In this regard, a person skilled in the art can rely on knowledge of the Hildebrand and / or Hansen solubility parameters of solvents to define, with respect to these same parameters specific to PVC polymers, the most suitable solvent for inclusion in the composition of phase A. More specifically, phase A comprises a solvent or a mixture of solvents, particularly organic(s), preferably chosen so that its Hansen parameters lie within the Hansen sphere of the targeted PVC polymer(s).Hansen's theory allows us to predict the solubility of a polymer, particularly a thermoplastic such as PVC, in a solvent. This is achieved by determining the Hansen parameters and solubility sphere for the solvent and the polymer, respectively, as a function of several parameters, especially their polar, hydrogen bonding, and dispersion parameters. If a solvent or solvent mixture exhibits Hansen parameters within the Hansen sphere of the PVC polymer, then the PVC polymer should be at least partially, and preferably completely, soluble in that solvent or solvent mixture.

[0154] By equivalent reasoning, phase A includes at least one solvent chosen to be a good dissolving solvent for at least one additive and any impurities.

[0155] According to an equivalent but opposite line of reasoning, phase B includes at least one solvent chosen to be a less good dissolving solvent for the PVC polymer(s) compared to phase A, in addition to being non-miscible or partially miscible with the latter.

[0156] Furthermore, the nature and proportion of the solvents used in phases A and B are determined in such a way as to never induce precipitation, even partial, of the PVC polymer(s). In this regard, it should be noted that the precipitation of a PVC polymer is defined as the transition of macromolecules from a liquid to a solid state. The completely disentangled chains of the polymer regroup and form a solid. It is possible to verify the absence of precipitation by transparency, provided that no other insoluble molecules in the system interfere with the assessment. For example, if inorganic molecules insoluble in the solvent system are present in the plastic waste and initial solubilization has been carried out, the polymer solubilization will not be visible to the naked eye, and a mass balance can be used to confirm that all of the PVC polymer has been solubilized.Furthermore, the nature and proportion of the solvents constituting phases A and B are chosen so as to solubilize, at least partially, the additives and potential impurities of the PVC-based filler according to the invention, such that these are distributed between phases A and B, regardless of the specific distribution. Following the same principle as explained above, the solubilization of the additives and potential impurities is understood to mean the dispersion of said additives and potential impurities in the chosen solvents. As above, those skilled in the art can also refer to the Hildebrand and / or Hansen solubility parameters to estimate, based on the composition of the PVC-based filler, the distribution of the additives and associated potential impurities.

[0157] The partition coefficient of the additive(s) (and any impurities) in the solvent system, defined as the ratio of the mass concentrations of the additive(s) (and any impurities) dissolved in phase B and in phase A, is greater than or equal to 0.05. Preferably, the partition coefficient of the additive(s) in the solvent system is between 0.05 and 5, preferably between 0.5 and 5.

[0158] Preferably, the two-phase solvent system according to the invention (i.e., the composition formed by the solvents of phases A and B of said system) is capable of solubilizing at least one additive of the PVC-based filler included in the list consisting of:

[0159] - stabilizing additives chosen for example from metallic stearates of zinc (e.g. zinc stearate), calcium (e.g. calcium stearate), lead (e.g. lead stearate, dibasic lead stearate) or cadmium (e.g. cadmium stearate), epoxidized oils, organotins such as 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate of 2-ethylhexyl, mono, di and triphosphites as well as their derivatives, such as di(8-methylnonyl) and phenyl phosphite, or phenyl 1,3-diones such as dibenzoylmethane (DBM);

[0160] - plasticizing additives chosen, for example, from among phthalates such as dioctyl or bis(2-diethylhexyl) phthalate (DOP or DEHP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), di-n-octyl phthalate (DNOP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl phthalate, isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, or from among other non-phthalic compounds such as bis(2-ethylhexyl) adipate (DEHA) or diisononyl ester of acid cyclohexane-l,2-dicarboxylic (DINCH), terephthalates such as dibutyl terephthalate or dioctyl terephthalate (DEHT), trimellitates such as trioctyl benzene-l,2,4-tricarboxylate or benzoates;

[0161] - lubricant additives chosen for example from paraffins and polyethylene waxes;

[0162] - anti-shock polymer or copolymer additives chosen from polyacrylates and methacrylate-butadiene-styrene; - flame retardant additives chosen for example from organophosphates such as tris(2-ethylhexyl) phosphate, triphenyl phosphate (TPP), tri-o-cresyl phosphate or trixylenyl phosphate.

[0163] Preferably, the two-phase solvent system is capable of solubilizing PVC-based filler additives that are heavily monitored by ECHA (ECHA, Investigation Report on PVC and PVC additives, version no. 1, 22 / 11 / 2023) and / or subject to REACH regulations, in particular additives selected from the group consisting of:

[0164] - the organotin family, used as stabilizers, such as 10-ethyl-4,4-dioctyl-7-oxo-8-oxa-3,5-dithia-4-stannatetradecanoate of 2-ethylhexyl (DOTE), etc.;

[0165] - metallic compounds used as stabilizers such as those based on lead and cadmium subject to REACH restrictions, such as lead and cadmium stearates, etc.;

[0166] - the family of ortho-phthalates, used as plasticizers, some of which are subject to regulations, such as dioctyl phthalate (DOP), bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), di-isobutyl phthalate (DIBP), dipentyl phthalate (DPP), etc.;

[0167] - the terephthalate family, used as plasticizers, such as dibutyl terephthalate, etc.;

[0168] - the trimellitate family, used as plasticizers, such as trioctyl benzene-1,2,4-tricarboxylate, etc.;

[0169] - the benzoate family, used as plasticizers;

[0170] - the family of mono, di and triphosphites and their derivatives, used as heat stabilizers, such as di(8-methylnonyl) and phenyl phosphite, etc.;

[0171] - the phenyl 1,3-dione family, used as heat stabilizers, such as dibenzoylmethane (DBM), etc.;

[0172] - the family of organophosphates used as flame retardants, such as tris(2-ethylhexyl) phosphate, etc.

[0173] The list of specific molecules cited is not exhaustive and other examples of molecules for each family cited above are listed in the ECHA report mentioned above.

[0174] The two-phase solvent system according to the invention may also be capable of solubilizing one or more impurities in the PVC-based filler.

[0175] The partition coefficient of said impurity(ies) in the solvent system (ratio of mass concentrations of said impurity(ies) dissolved in phase B and in phase A) is preferably between 0.05 and 5, preferably between 0.5 and 5.

[0176] Furthermore, the immiscible phases A and B of the solvent system according to the invention have, by definition, different densities, such that one is "above" the other when these two phases are placed in a fixed container. The "above" phase, having the lower density, is called the "light phase." Conversely, the "below" phase, having the higher density, is called the "heavy phase." Depending on the chemical compositions chosen for phases A and B of the solvent system, phases A and B can act as the light and heavy phases, respectively, and vice versa.

[0177] Phase A comprises, and preferably consists of, an organic solvent or a mixture of organic solvents selected from the list consisting of:

[0178] - ketones, such as methyl ethyl ketone (MEK), diethyl ketone (DEK), 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone (MIBK), including cyclic ketones such as cyclopentanone or cyclohexanone;

[0179] - amides, such as N,N-diethyl formamide, including cyclic amides, such as 2-pyrrolidone or N-methyl-2-pyrrolidone;

[0180] - azines, such as pyridine, 4-aminopyridine, 2-aminopyridine, or 4-vinylpyridine;

[0181] - esters, such as methyl acetate, ethyl acetate, methyl propionate, n-butyl propionate, including cyclic esters such as y-butyrolactone (gamma-butyrolactone or GBL) or y-valerolactone (gamma-valerolactone or GVL);

[0182] - ethers, such as methoxycyclopentane (CPME) or diisopropyl ether, including cyclic ethers such as tetrahydrofuran (THF) or methyl tetrahydrofuran (MeTHF);

[0183] - halogenated solvents (chlorinated, brominated, fluorinated), in particular chlorinated solvents, such as dichloromethane or trichloromethane;

[0184] - hydrocarbons, such as xylene, cyclohexane, toluene, isohexane or n-heptane (heptane), and preferably cyclohexane, toluene, isohexane or n-heptane;

[0185] - sulfide solvents such as dimethyl sulfoxide (DMSO);

[0186] - dihydrolevoglucosenone (cyrene).

[0187] Preferably, phase A comprises, and may consist of, a mixture of at least two organic solvents: a major solvent, by weight (i.e. at least 50% by weight, relative to the total weight of said phase A), which is a sulfide solvent such as DMSO, and a minor solvent (i.e. less than 50% by weight, relative to the total weight of said phase A) which is selected from ketones, including cyclic ketones, and cyclic esters, preferably selected from MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, and GVL. In the case where phase A comprises (or is made up of) a mixture of two organic solvents, the content of the major solvent is advantageously strictly greater than 50% by weight, relative to the total weight of said phase A, and the content of the minor solvent is advantageously strictly less than 50% by weight, relative to the total weight of said phase A.Preferably, phase A comprises, and may consist of, a mixture of at least three organic solvents:

[0188] - the major solvent, by weight (i.e. at least 50% by weight relative to the total weight of said phase A), which is DMSO,

[0189] - a first minor solvent chosen from among the cyclic ketones and esters, preferably from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, and

[0190] - a second minor solvent chosen from among hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane, more preferably from cyclohexane, isohexane and n-heptane.

[0191] Even more preferably, phase A comprises, and can be made up of, a mixture of three organic solvents:

[0192] - the major solvent, by weight (i.e. at least 50% by weight relative to the total weight of phase A), which is DMSO,

[0193] - the first minor solvent, which is DEK, preferably in a concentration chosen according to the other two solvents (DMSO and heptane), and

[0194] - a second minor solvent which is heptane, preferably in a content less than or equal to 15% by weight (relative to the total weight of phase A).

[0195] In one or more embodiments, phase A comprises, and preferably consists of:

[0196] - 50% to 70% weight of DMSO (relative to the total weight of phase A), preferably 55% to 65% weight of DMSO,

[0197] - 20% to 40% DEK weight (relative to the total weight of phase A), preferably 25% to 35% DEK weight,

[0198] - 5% to 15% weight of heptane (relative to the total weight of phase A), preferably 5% to 10% weight of heptane.

[0199] According to the invention, phase B comprises an organic solvent or a mixture of organic solvents chosen from the same list as that given for phase A.

[0200] Thus, phase B comprises, and preferably consists of, an organic solvent or a mixture of organic solvents chosen from the same list consisting of:

[0201] - ketones, such as methyl ethyl ketone (MEK), diethyl ketone (DEK), 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone (MIBK), including cyclic ketones such as cyclopentanone or cyclohexanone;

[0202] - amides, such as N,N-diethyl formamide, including cyclic amides, such as 2-pyrrolidone or N-methyl-2-pyrrolidone;

[0203] - azines, such as pyridine, 4-aminopyridine, 2-aminopyridine, or 4-vinylpyridine; - esters, such as methyl acetate, ethyl acetate, methyl propionate, n-butyl propionate, including cyclic esters such as γ-butyrolactone (GBL) or γ-valerolactone (GVL);

[0204] - ethers, such as methoxycyclopentane (CPME) or diisopropyl ether, including cyclic ethers such as tetrahydrofuran (THF) or methyl tetrahydrofuran (MeTHF);

[0205] - halogenated solvents (chlorinated, brominated, fluorinated), in particular chlorinated solvents, such as dichloromethane or trichloromethane;

[0206] - hydrocarbons, such as cycohexane, toluene, isohexane or n-heptane;

[0207] - sulfide solvents such as dimethyl sulfoxide (DMSO);

[0208] - dihydrolevoglucosenone (cyrene).

[0209] Preferably, phase B comprises, and may consist of, a mixture of at least two organic solvents: a major solvent, by weight (i.e. at least 50% by weight) selected from hydrocarbons, preferably selected from xylene, cyclohexane, isohexane and n-heptane, and more preferably selected from cyclohexane, isohexane and n-heptane, and a minor solvent (i.e. less than 50% by weight relative to the total weight of phase B) selected from ketones, including cyclic ketones, and cyclic esters, preferably selected from MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, and GVL.In the case where phase B comprises (or is made up of) a mixture of two organic solvents, the content of the major solvent is advantageously strictly greater than 50% by weight, relative to the total weight of said phase B, and the content of the minor solvent is advantageously strictly less than 50% by weight, relative to the total weight of said phase B.

[0210] Preferably, phase B comprises, and may consist of, a mixture of at least three organic solvents:

[0211] - the major solvent, by weight (i.e. at least 50% by weight relative to the total weight of said phase B) chosen from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane, and more preferably from cyclohexane, isohexane and n-heptane,

[0212] - a first minor solvent selected from ketones, including cyclic ketones, and cyclic esters, preferably from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, and

[0213] - a second minor solvent chosen from among the sulfide solvents such as DMSO.

[0214] Even more preferably, phase B comprises, and can be constituted by, a mixture of three organic solvents:

[0215] - the major solvent, by weight (i.e. at least 50% by weight relative to the total weight of said phase B), which is heptane,

[0216] - the first minor solvent, which is DEK, preferably in a content chosen according to the other two (that of heptane and that of DMSO), and - the second minor solvent, which is DMSO, preferably at a content less than or equal to 15% by weight (relative to the total weight of said phase B).

[0217] In one or more embodiments, phase B comprises, and preferably consists of:

[0218] - 50% to 70% heptane by weight (relative to the total weight of phase B), preferably 55% to 65% heptane by weight,

[0219] - 20% to 40% DEK weight (relative to the total weight of phase B), preferably 25% to 35% DEK weight,

[0220] - 5% to 15% weight of DMSO (relative to the total weight of phase B), preferably 5% to 10% weight of DMSO.

[0221] The compositions of phases A and B of the solvent system according to the invention given above, in particular the preferred mixture compositions of at least two or three solvents for each phase described above, are advantageously combined together.

[0222] For example, according to one or more embodiments, the solvent system comprises:

[0223] - phase A comprising a mixture of three organic solvents, of which a major solvent is DMSO, preferably in a content of between 50% and 70% by weight (relative to the total weight of said phase A), a first minor solvent is DEK, preferably in a content chosen according to the other two (that of DMSO and that of heptane), and more preferably in a content of between 20% and 40% by weight (relative to the total weight of said phase A), and a second minor solvent is heptane, preferably in a content of between 5% and 15% by weight (relative to the total weight of said phase A), and

[0224] - phase B comprising a mixture of three organic solvents, of which a major solvent is heptane, preferably in a content of between 50% and 70% by weight (relative to the total weight of said phase B), a first minor solvent which is DEK, preferably in a content chosen according to the other two (that of heptane and that of DMSO), and more preferably in a content of between 20% and 40% by weight (relative to the total weight of said phase B), and a second minor solvent which is DMSO, preferably in a content of between 5% and 15% by weight (relative to the total weight of said phase B).

[0225] According to the invention, phase A, which has the greatest affinity for the PVC polymer(s), is defined as the stationary phase of the experimental CPC device, with phase B logically being the mobile phase.

[0226] Implementation of the CPC separation process of a PVC-based sample

[0227] According to the invention, the solvent system is specific to the liquid-liquid extraction fractionation of a PVC-based feedstock, and in particular to the CPC fractionation of a PVC-based sample, said sample comprising one or more PVC polymers, at least one additive and possible impurities.

[0228] According to the invention, the solvent system can thus be used to separate the PVC polymer(s) from all the additives and potential impurities in the sample, the latter typically being dependent on the origin of said sample, according to a CPC separation process comprising, and possibly consisting of, the following steps: a) preferably a step of preparing the PVC-based sample allowing its injection into the CPC separation column in the form of a liquid injection solution, b) a CPC fractionation step of the PVC-based sample, contained in whole or in part in the injection solution obtained at the end of step a), implementing the solvent system according to the invention, and leading to the separation of the PVC polymer(s) and all the additives and potential impurities, preferably by major chemical families of the organic substances involved.

[0229] Step a) Preparation of the PVC-based sample

[0230] Before the CPC fractionation step, the PVC-based sample is advantageously prepared to be in a form compatible with its injection into the CPC system at the top of the column, i.e. in a solubilized form compatible with at least one of the two phases A and B of the solvent system according to the invention and described above.

[0231] As is typical before a CPC separation step, the sample to be fractionated is preferably solubilized in a solution with a composition equivalent to the phase in which it exhibits the highest solubility, for obvious productivity reasons. This preferred approach also has the advantage of limiting destabilization of the biphasic solvent system. Indeed, destabilization of the biphasic system can occur if the sample is solubilized directly into one of the phases within the CPC device, due to the influence of the sample's chemical nature on the equilibrium of the biphasic system. Thus, prior solubilization of the sample before its injection into the CPC device can lead to a better injection profile and therefore better retention of the stationary phase in the experimental setup during step b), and consequently, better CPC separation (L. Marchai et al.)., 2003, Rational improvement of centrifugal partition chromatographic settings for the production of 5-n-alkylresorcinols from wheat bran lipid extract. I. Flooding conditions-optimizing the injection step, Journal of Chromatography A, vol. 1005, n° 1-2, pp. 51-62).

[0232] Thus, the PVC-based sample is preferably initially solubilized in a solution of equivalent composition to phase A of the solvent system, said phase A being the stationary phase in the CPC device. Preferably, the solubilization of the PVC sample in step a) is carried out at a temperature between Tamb and 140°C, preferably between Tamb and 80°C, and even more preferably between Tamb and 50°C, for a time t between 2h and 24h, preferably between 2h and 10h, and even more preferably between 4h and 8h. The pressure is preferably atmospheric pressure.

[0233] Step a) of preparing the PVC-based sample may also include one or more operations to remove insoluble compounds after solubilization of the PVC-based sample, for example by centrifugation, filtration, decantation, etc. Such a step to remove insoluble compounds is particularly required when the solubilization process results in a suspension due to the presence of additives and / or impurities that are insoluble under the operating conditions applied.

[0234] The result of the dissolution, or even the dissolution / elimination of insolubles, leads to obtaining a solution called "injection solution" containing between 1% and 30% by weight of PVC polymer(s) (relative to the total weight of the injection solution), preferably between 2% and 20% by weight and even more preferably between 3% and 15% by weight, the remaining constituent elements of the injection solution (in addition to the solvent(s) of phase A) being the additive(s) and any impurities solubilized under the conditions as defined above.

[0235] Step b) Fractionation by CPC of the PVC-based sample; bl) Equilibration phase

[0236] As mentioned previously, the experimental CPC setup is a chromatography column corresponding to a succession of cavities, preferably parallelepiped or cylindrical, connected to each other by channels.

[0237] Initially, the column is empty. Each CPC separation therefore begins by completely filling the column by pumping the stationary phase, generally using a low rotational speed to generate centrifugal force, in order to first obtain a centrifugal partition chromatography column filled with stationary phase (phase A of the solvent system as described above). This filling step requires a high flow rate. This flow rate is determined by a person skilled in the art based on the geometry and size of the column. A non-limiting example of a stationary phase flow rate for filling the column is between 500 and 600 ml / min.

[0238] Once the column is filled, the working rotation is applied. Similar to the flow rate, the working rotation depends on the geometry and size of the column. Generally, the operator will benefit from generating the highest possible rotation of the experimental setup, as this will improve the mass transfer of the solutes (and therefore their separation) by increasing the exchange surface area between the mobile and stationary phases. The upper limit depends on the apparatus's tolerance to pressure drop. For example, a rotation between 50 rpm and 3000 rpm is applied once the column is filled with the stationary phase. The mobile phase is then introduced by pumping into the column, which has been previously filled with the stationary phase.The presence of this new phase displaces a volume of stationary phase in each partition cell, a volume that depends on the solvent system, rotation, and flow rate, until hydrodynamic equilibrium is reached. This equilibrium is characterized by the ratio of the stationary phase volume to the total column volume, denoted Sf and called retention. In practice, when the mobile phase is pumped, the stationary phase exits the column until equilibrium is reached, detected by the appearance (exit) of the mobile phase. At this equilibrium state, for each volume of mobile phase pumped, the same volume of mobile phase exits the column. A CPC chromatographic system is therefore partly characterized by the stationary phase retention rate in the column. Typically, separations are possible with retention rates between 40% and 85%.The flow rate required for the introduction of the mobile phase must be controlled by a person skilled in the art to avoid disturbing the hydrodynamic equilibrium. This flow rate is advantageously the same as that applied during the elution step following this equilibration step. For example, the flow rate during the introduction of the mobile phase in this equilibration step is between 5 ml / min and 600 ml / min. b2) Elution phase.

[0239] During the elution phase, the mobile phase passes through the stationary phase. This is the phase during which the separation of the PVC polymer-based sample compounds takes place, in particular the separation of the PVC polymer(s).

[0240] An injection solution, as defined and advantageously obtained in step a), is introduced into the column of the CPC device filled with the solvent system according to the invention. Specifically, the injection solution is injected either via an injection loop, which is a component of the CPC device that stores the solution and injects it by pushing the solution forward at the beginning of elution, or via a pump, being pushed by the mobile phase (i.e., phase B of the solvent system according to the invention) at the time of the introduction of said phase B into the device during elution. The injection solution is therefore the first to enter the CPC system, followed by the (mobile) phase B.

[0241] After the injection of the injection solution, containing all or part of the PVC-based sample, into the CPC device, the sample undergoes fractionation through the separation of the various compounds of interest between the stationary and mobile phases along the column cells. This fractionation is carried out for a sufficient time to purify the PVC polymer(s), that is, to elute all additives and potential impurities present in the injection solution.

[0242] The time required to purify the PVC polymer(s) preferably corresponds to a duration of approximately 10 to 30 column volumes (the time corresponding to the passage of x times the volume of a column for the mobile phase). The flow rate at which fractionation occurs during the elution phase is determined by a person skilled in the art to avoid disturbing the two-phase equilibrium within the CPC column without loss of stationary phase.

[0243] Depending on the density of the stationary phase, the mobile phase can flow through it in an upward or downward direction. More specifically, if the stationary phase is denser (heavier phase), the pumping of the lighter mobile phase occurs in an upward direction (opposite to the centrifugal force), thus promoting the retention of the stationary phase within the device. Conversely, if the stationary phase is less dense (lighter phase), the pumping of the heavier mobile phase occurs in a downward direction (in the direction of the centrifugal force), also to promote the retention of the stationary phase within the device.

[0244] Preferably, the solvent system according to the invention is such that phase A, which is the stationary phase, is also the heavy phase, which favors an operation of the CPC device according to an upward circulation mode of the mobile phase.

[0245] During the elution phase, the recovered effluent, consisting of the mobile phase (i.e. phase B) containing the separated compounds having a greater affinity for the mobile phase, is advantageously collected, typically by means of an automatic fraction collector.

[0246] It is possible to collect the effluent in the form of different liquid fractions over time, in cases where the aim is to separate the additives (and any impurities) by major chemical families, made possible by the progressive elution of said additives (and any impurities) in the mobile phase according to their partition coefficient in the solvent system. b3) Extrusion phase

[0247] During the extrusion phase, the mobile and stationary phases are pushed out of the cells of the CPC device column.

[0248] After elution of all additives and other potential impurities present in the injection solution, the stationary phase containing the PVC polymer(s) is recovered during this extrusion phase, advantageously by pumping the stationary phase into the device. Typically, to perform the extrusion, the contents of the column are expelled by a fresh introduction of stationary phase, for example, at a flow rate similar to that used during the equilibration phase.

[0249] The extrusion effluent is advantageously recovered in the automatic fraction collector.

[0250] The duration of the extrusion step typically depends on the flow rate and column volume.

[0251] The extrusion effluent comprises a "purified PVC polymer(s) solution" which includes the PVC polymer(s) (at least 99%, or even all of the polymer initially injected), the solvent(s) of phase A and less than 1% by weight, preferably 0.1% by weight, or even 0.01% by weight of additives and any impurities (relative to the total weight of the sum of the PVC polymer(s) and the additives and any residual impurities).

[0252] The extrusion effluent therefore contains the purified polymer solution(s), as well as the mobile phase, since the entire liquid content of the column is recovered during the extrusion phase. The mobile phase of the extrusion effluent consists primarily of phase B, as all additives and any impurities were removed from the CPC device along with the mobile phase during the elution phase.

[0253] Figure 2 illustrates, in a schematic diagram, the elution (b2) and extrusion (b3) phases during CPC fractionation using a biphasic solvent system according to the invention. The x-axis represents time T, a function of the retention volume in the cells, and the y-axis represents a signal S, the response of a detector identifying a compound from the PVC-based sample in solution injected into the CPC device. A family of additives Ad1 and a family of additives Ad2 are eluted during the elution (b2) phase and recovered with the mobile phase flowing out of the CPC device over time.

[0254] We can see that it is therefore possible, depending on the time of collection of the mobile phase during phase b2), to retrieve the Adl and Ad2 families separately or together.

[0255] The polymer P, retained in the stationary phase, is recovered during the extrusion phase b3), after the additive families Adl and Ad2 have been recovered during the preceding elution phase b2).

[0256] Preferably, step b) of CPC fractionation is carried out at ambient temperature Tamb (typically 20°C ± 5°C, eg 25°C), and at atmospheric pressure.

[0257] Optional step c) of separating phases A and B of the extrusion effluent

[0258] Phases A and B present in the extrusion effluent can be separated by gravity due to their difference in density, for example, in a separatory funnel. This step yields a single-phase solution of phase A containing the PVC polymer fraction(s), also referred to here as the purified single-phase PVC polymer(s) solution, and a single-phase solution of phase B. Such a step may be required to facilitate the recovery of the PVC polymer(s) in solid form from the single-phase solution of phase A in a subsequent step, for example, depending on the nature of the solvent that could be used to precipitate the PVC polymer(s) by contacting said solvent.

[0259] Preferably, step c) is carried out at ambient temperature Tamb (typically 20°C ± 5°C, eg 25°C), and at atmospheric pressure.

[0260] Optional step d) recovery of the PVC polymer(s) in solid form

[0261] The PVC polymer(s), purified by CPC, can be recovered in solid form in a further step. The effluent recovered during the extrusion step is a two-phase system (phase A / phase B) and is sent to step c) to separate the remaining phase B from phase A containing the PVC polymer fraction by sedimentation.

[0262] Following step c), the denser, single-phase solution of phase A, now recovered and free of phase B, can then be brought into contact in step d) with a precipitation solvent such as methanol. This solvent precipitates the PVC polymer(s) due to its very low affinity for these macromolecules. The solid is then collected on the filter by a liquid filtration step.

[0263] However, any other method of recovering polymers in solid form known to those skilled in the art may be implemented, including any methods allowing a phase change of the polymer(s) and / or solvent(s).

[0264] The CPC separation process implementing the solvent system according to the invention allows access to very high chromatographic selectivities compared to other chromatographic methods applied to plastics and to purities exceeding 99%, preferably 99.9%.

[0265] Furthermore, the CPC separation process implementing the solvent system according to the invention can allow the recovery of additives and any impurities separated by major chemical families.

[0266] Characterization of compounds separated from the PVC-based sample

[0267] The PVC polymer(s), and any additives and impurities, separated by CPC can advantageously be characterized using known analytical methods.

[0268] Thus, an analysis step can be performed on the purified PVC polymer(s) solution obtained at the end of step b), or on the single-phase A solution obtained in step c), or on the solid PVC polymer(s) obtained from said solution at the end of step d), and preferably on the solid PVC polymer(s), preferably by Fourier transform infrared spectroscopy (FTIR) and / or nuclear magnetic resonance (NMR). These methods, well known to those skilled in the art, allow for molecular characterization of the polymer.

[0269] Regarding the thermal properties of the PVC polymer, thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses can be carried out, which are also techniques known to those skilled in the art.

[0270] Preferably, additives and any impurities collected as one or more liquid fractions can be analyzed during this analytical step for characterization using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) for additive identification. This method allows for the determination of a potential structure for each molecule present in the liquid fractions. Examples

[0271] These examples illustrate the invention without limiting its scope, and in particular illustrate the separation by CPC and the characterization of PVC-based samples from different origins, allowing the recovery of purified PVC polymer solutions.

[0272] Example 1 - CPC fractionation of virgin PVC plastic

[0273] 1. Nature of the PVC-based sample

[0274] The PVC-based sample is virgin PVC plastic in the form of 2-3 mm granules, the composition of which, by weight percentages, is as follows:

[0275] - 55.31% PVC resin (polymer) with a K-value of 75 (K-value expressing the average molecular weight of PVC resin), corresponding to a molar mass MW=120,000 g / mol,

[0276] - 24.34% diisodecyl phthalate (DIDP),

[0277] - 3.32% epoxidized soybean oil,

[0278] - 0.11% polyethylene wax AC 629,

[0279] - 16.59% calcium carbonate,

[0280] - 0.11% zinc stearate,

[0281] - 0.17% calcium stearate,

[0282] - 0.06% blue pigment.

[0283] 2. Preparation of the PVC-based sample for obtaining the injection solution

[0284] 300 mg of the PVC-based sample are solubilized in an initial solution with the same composition as the stationary phase, i.e., phase A of the exemplified solvent system. This initial solution is composed (like phase A), by weight percentages, of 61.4% dimethyl sulfoxide, 30.9% diethyl ketone, and 7.7% heptane. The mixture is placed in an oven for 5 hours at 70°C. The resulting suspension is then centrifuged for 10 minutes at 5300 rpm to remove insoluble components (in this case, calcium carbonate, zinc stearate, calcium stearate, and the blue pigment). An injection solution, suitable for introduction into the CPC device, is obtained after centrifugation.

[0285] 3. Fractionation of the PVC-based sample in the form of an injection solution a. Apparatus

[0286] The instrument used is an Armen Instrument SCPC100 Centrifugal Partition Chromatograph coupled to Spot Prep II (Gilson Purification, USA), which includes the column, pumps, and collector. The column used is 131 mL. b. Biphasic solvent system

[0287] The solvent system used is a combination of two immiscible phases, A and B. Phase A (stationary phase) is composed of 61.4% dimethyl sulfoxide, 30.9% diethyl ketone, and 7.7% heptane (weight percentages relative to the total weight of phase A), and phase B (mobile phase) is composed of 62% heptane, 30.3% diethyl ketone, and 7.8% dimethyl sulfoxide (weight percentages relative to the total weight of phase B). c. Implementation of the separation

[0288] The splitting in the column is implemented in an ascending manner.

[0289] The column is filled with stationary phase (phase A) and rotated at 500 rpm in upward mode at a flow rate of 30 ml / min, then the rotation is set at 2000 rpm. Mobile phase (phase B) is introduced at 7 ml / min to equilibrate the chromatographic system, with a stationary phase retention of 50% and a pressure drop of 0.53 MPa. No leakage is observed.

[0290] The injection solution is then introduced into the column via a 5 mL injection loop, subsequently pushed by the mobile phase at 7 mL / min in upward flow mode. Elution is continued for 2 hours. Following elution, extrusion is performed with a fresh introduction of the stationary phase at 30 mL / min for 10 minutes. The effluent is fractionated using an automatic fraction collector.

[0291] The additives are analyzed by liquid chromatography coupled to high-resolution mass spectrometry LC-HRMS: Agilent 1290 coupled to timsTOF (TIMS for Trapped Ion Mobility Spectrometry, which is the spectrometry of the mobility of trapped ions, and TOF for Time of flight, which is the time of flight, corresponding to a type of analyzer in mass spectrometry), Bruker Daltonics, Germany using an Apollo II source, Bruker Daltonics, Germany.

[0292] The additives found in the extrusion fractions are:

[0293] The plasticizer di-isodecyl phthalate (DIDP) type,

[0294] The co-stabilizer epoxidized soybean oil,

[0295] Polyethylene wax lubricant.

[0296] The purified PVC polymer is analyzed by FTIR on a Nicolet™ iS50 FTIR Spectrometer (ThermoFisher Scientific) and by NMR analysis 1 H and 13C. The polymer is recovered in 100% pure form. The polymer is found to be pure, without the presence of any other species, by NMR and FTIR analysis.

[0297] Example 2 - CPC fractionation of waste PVC plastic from cables

[0298] 1. Nature of the PVC-based sample

[0299] The PVC-based sample is a PVC plastic corresponding to waste whose composition is unknown except for a PVC polymer concentration of 50%. 2. Preparation of the PVC-based sample for obtaining the injection solution

[0300] 300 mg of the PVC-based sample are solubilized in an initial solution with the same composition as the stationary phase, i.e., phase A of the exemplified solvent system. This initial solution is composed (like phase A), by weight percentages, of 61.4% dimethyl sulfoxide, 30.9% diethyl ketone, and 7.7% heptane. The mixture is placed in an oven for 5 hours at 70°C. The PVC polymer is completely dissolved. The resulting suspension is then centrifuged for 10 minutes at 5300 rpm to remove insoluble matter. An injection solution, suitable for introduction into the CPC device, is obtained after centrifugation.

[0301] 3. Fractionation of the PVC-based sample in the form of an injection solution a. Apparatus

[0302] The instrument used is an SCPC100 Centrifugal Partition Chromatograph coupled to Spot Prep II from Armen Instrument, France (Gilson Purification, USA), which includes the column, pumps, and collector. The column used is 131 mL. b. Biphasic solvent system

[0303] The solvent system used is a combination of two immiscible phases, A and B. Phase A (stationary phase) is composed of 61.4% dimethyl sulfoxide, 30.9% diethyl ketone, and 7.7% heptane (weight percentages relative to the total weight of phase A), and phase B (mobile phase) is composed of 62% heptane, 30.3% diethyl ketone, and 7.8% dimethyl sulfoxide (weight percentages relative to the total weight of phase B). c. Implementation of the separation

[0304] The splitting in the column is implemented in an ascending manner.

[0305] The column is filled with stationary phase (phase A) and rotated at 500 rpm in upward mode at a flow rate of 30 ml / min, then the rotation is set at 2000 rpm. Mobile phase (phase B) is introduced at 7 ml / min to equilibrate the chromatographic system, with a stationary phase retention of 50% and a pressure drop of 0.53 MPa. No leakage is observed.

[0306] The injection solution is then introduced into the column via a 5 mL injection loop, subsequently pushed by the mobile phase at 7 mL / min in upward flow mode. Elution is continued for 2 hours. Following elution, extrusion is performed with a fresh introduction of the stationary phase at 30 mL / min for 10 minutes. The effluent is fractionated using an automatic fraction collector.

[0307] The additives are analyzed by liquid chromatography coupled to high-resolution mass spectrometry LC-HRMS: Agilent 1290 coupled to timsTOF (TIMS for Trapped Ion Mobility Spectrometry, which is the spectrometry of the mobility of trapped ions, and TOF for Time of flight, which is the time of flight, corresponding to a type of analyzer in mass spectrometry), Bruker Daltonics, Germany using an Apollo II source, Bruker Daltonics, Germany.

[0308] 500 compounds were identified, and some known additives were noted, such as phthalate-type plasticizers (DEHP, DIDP, DINP, DBP), organophosphate flame retardants (TPP, tri-ocresyl, etc.), co-stabilizers such as epoxidized soybean oil, and UV absorbers like benzophenones. Among these compounds, degradations of additives were also identified.

[0309] The purified PVC polymer is analyzed by FTIR on a Nicolet™ iS50 FTIR Spectrometer (ThermoFisher Scientific) and by NMR analysis 1 H and 13 C. The polymer is recovered in 100% pure form. The polymer is found to be pure, without the presence of any other species, as confirmed by NMR and FTIR analysis. The additional peaks observed with NMR analysis are degradations of the polymer chains.

Claims

35 Demands 1. A two-phase solvent system for the liquid-liquid extraction fractionation of a PVC-based feed comprising one or more PVC polymers and at least one additive and any impurities, said solvent system comprising two immiscible liquid phases A and B, and being characterized in that: said phase A and said phase B each comprise an organic solvent or a mixture of organic solvents selected from the same list consisting of ketones, amides, azines, esters, ethers, halogenated solvents, hydrocarbons, sulfide solvents, and dihydrolevoglucosenone; the organic solvent or mixture of organic solvents of said phase A is capable of solubilizing the PVC polymer(s) of the PVC-based feed; said two-phase solvent system is capable of solubilizing said additive;the partition coefficient of the PVC polymer(s) in said biphasic solvent system, defined as the ratio of the mass concentrations of the PVC polymer(s) dissolved in phase B and in phase A, tends towards zero, and the partition coefficient of said additive in the biphasic solvent system, defined as the ratio of the mass concentrations of said additive dissolved in phase B and in phase A, is greater than or equal to 0.

05.

2. A two-phase solvent system according to claim 1, wherein the organic solvent(s) for each of phases A and B are selected from the list consisting of: the following compounds from the ketone family: methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone and cyclohexanone; the following compounds from the amide family: N,N-diethyl formamide, 2-pyrrolidone and N-methyl-2-pyrrolidone; - the following compounds from the azine family: pyridine, 4-aminopyridine, 2-aminopyridine, and 4-vinylpyridine; the following compounds from the ester family: methyl acetate, ethyl acetate, methyl propionate, n-butyl propionate, γ-butyrolactone and γ-valerolactone; the following compounds from the ether family: methoxycyclopentane, diisopropyl ether, tetrahydrofuran and methyl tetrahydrofuran;the following compounds from the family of chlorinated solvents: dichloromethane and trichloromethane; 36 the following compounds from the hydrocarbon family: xylene, cyclohexane, toluene, isohexane and n-heptane; the following compound from the sulfide solvent family: dimethyl sulfoxide; dihydrolevoglucosenone.

3. Biphasic solvent system according to claim 1 or 2, wherein phase A comprises a mixture of at least two of the following organic solvents: a major sulfur solvent, a first minor solvent selected from ketones and cyclic esters, preferably selected from methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, γ-butyrolactone, and γ-valerolactone.

4. Biphasic solvent system according to claim 3, wherein phase A comprises a mixture of at least three of the following organic solvents: the major solvent dimethyl sulfoxide, at a content of at least 50% by weight, the first minor solvent selected from ketones and cyclic esters, preferably from diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, γ-butyrolactone and γ-valerolactone, and a second minor solvent selected from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane.

5. Biphasic solvent system according to claim 4, wherein phase A comprises a mixture of the following three organic solvents: the major solvent dimethyl sulfoxide, in a content of at least 50% by weight, the first minor solvent diethyl ketone, and the second minor solvent n-heptane, preferably in a content less than or equal to 15% by weight.

6. A two-phase solvent system according to claim 5, wherein phase A comprises: 50% to 70% by weight of dimethyl sulfoxide, preferably 55% to 65% by weight of dimethyl sulfoxide, 20% to 40% by weight of diethyl ketone, preferably 25% to 35% by weight of diethyl ketone, and 5% to 15% wt of n-heptane, preferably 5% to 10% wt of n-heptane.

7. Biphasic solvent system according to any one of the preceding claims, wherein phase B comprises a mixture of at least two of the following organic solvents: a major solvent, selected from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane, n first minor solvent selected from ketones and cyclic esters, preferably selected from methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, y-butyrolactone, and y-valerolactone.

8. Biphasic solvent system according to claim 7, wherein phase B comprises a mixture of at least three of the following organic solvents: the major solvent, at a content of at least 50% by weight, selected from hydrocarbons, preferably from xylene, cyclohexane, isohexane and n-heptane, the first minor solvent selected from ketones and cyclic esters, preferably from diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, γ-butyrolactone, and γ-valerolactone, and a second minor solvent selected from sulfide solvents, preferably dimethyl sulfoxide.

9. Biphasic solvent system according to claim 8, wherein phase B comprises a mixture of the following three organic solvents: the major solvent n-heptane, at a content of at least 50% by weight, the first minor solvent diethyl ketone, and the second minor solvent dimethyl sulfoxide, preferably at a content less than or equal to 15% by weight.

10. A two-phase solvent system according to claim 9, wherein phase B comprises: 50% to 70% by weight of n-heptane, preferably 55% to 65% by weight of n-heptane, 20% to 40% by weight of diethyl ketone, preferably 25% to 35% by weight of diethyl ketone, and 5% to 15% by weight of dimethyl sulfoxide, preferably 5% to 10% by weight of dimethyl sulfoxide.

11. Biphasic solvent system according to any one of the preceding claims, capable of solubilizing at least one additive of the PVC-based filler included in the list consisting of: the family of organotins used as stabilizing additives; Metallic compounds used as stabilizing additives containing lead or cadmium, preferably lead and cadmium stearates; the orthophthalate family used as plasticizing additives, preferably dioctyl phthalate DOP, bis(2-ethylhexyl) phthalate DEHP, dibutyl phthalate DBP, benzyl butyl phthalate BBP, diisobutyl phthalate DIBP, dipentyl phthalate DPP; the terephthalate family used as plasticizing additives; the trimellitate family used as plasticizing additives; the benzoate family used as plasticizers; the mono-, di-, and triphosphite family and their derivatives used as heat-stabilizing additives; the 1,3-phenyl dione family used as heat-stabilizing additives; the family of organophosphates used as flame retardant additives.

12. Biphasic solvent system according to any one of the preceding claims, wherein the partition coefficient of said additive in the biphasic solvent system is between 0.05 and 5, preferably between 0.5 and 5.

13. Biphasic solvent system according to any one of the preceding claims, wherein the partition coefficient of the PVC polymer(s) in the biphasic solvent system is less than or equal to 0.01, preferably between 0 and 0.

01.

14. Biphasic solvent system according to any one of the preceding claims, for the fractionation by centrifugal partition chromatography of a PVC-based feed.

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