Method for recycling plastics by dissolution with solvent-polymer separation and solvent reintegration

Abstract

The present invention relates to a method for treating a plastic feedstock, comprising: a) dissolving the plastic feedstock in a dissolution solvent, to obtain a crude polymer solution, b) purifying the crude polymer solution, then c) solvent-polymer separation, comprising a liquid-liquid or supercritical-liquid separation, producing a liquid phase comprising the targeted thermoplastics and a liquid or supercritical solvent phase, then a gas-liquid separation, producing a liquid effluent comprising the targeted thermoplastics, and at least one gaseous effluent, d) a dissolution solvent recycling step, comprising: d1) the recycling, to step a), of at least one fraction of the liquid or supercritical solvent phase; d'1) purification, by tailing, of the liquid or supercritical solvent phase; and / or d2) purification, by topping and / or tailing, of said at least one gaseous effluent. The present invention also relates to a device for implementing said treatment method.

Description

[0001] PLASTICS RECYCLING PROCESS BY DISSOLUTION WITH SOLVENT-POLYMER SEPARATION AND SOLVENT REINTEGRATION

[0002] TECHNICAL FIELD

[0003] The present invention relates to a process for purifying and recycling plastics, particularly used plastics, to obtain a stream of purified thermoplastic polymers that can be used, for example, in the manufacture of new plastic objects. More specifically, the present invention relates to a process for treating a plastic feedstock, particularly one derived from plastic waste, comprising thermoplastics and, in particular, polyolefins, for example, polyethylene and / or polypropylene, by dissolving the thermoplastics in question in a solvent, purifying the resulting polymer solution, and then separating the polymer from the solvent, in particular using liquid-liquid and / or supercritical-liquid separation followed by at least one gas-liquid separation. The process further comprises recycling, after purification, at least a portion of the solvent.The said process thus allows, in addition to the recovery of a stream of purified thermoplastics, the efficient purification of the separated solvent, in particular the dissolving solvent, and therefore the recycling of at least part of the solvent, in particular the dissolving solvent, without accumulation of residual impurities.

[0004] PREVIOUS TECHNIQUE

[0005] Plastics from collection and sorting channels can be recovered through various channels.

[0006] Mechanical recycling allows for the partial reuse of certain waste materials, either directly in new objects or by mixing mechanically sorted plastic waste streams with streams of virgin polymers. This type of recovery is limited because, even though it yields a plastic stream concentrated in a particular type of polymer, mechanical sorting does not eliminate impurities that are at least partially trapped within the polymer matrix, such as additives like fillers, colorants, pigments, and metals. Additives are compounds typically introduced into polymer formulations to give the material, and therefore the final objects, the desired properties, such as high mechanical strength, a specific color, etc.

[0007] Chemical recycling primarily aims to eliminate additives and, depending on the processes used, to chemically modify the macromolecular chains of the polymers in question to varying degrees (for example, recovery of the intact polymer, depolymerization, or non-selective chain breaking of various polymers to obtain mixtures of compounds containing carbon and hydrogen). These different chemical recycling options involve generally complex sequences of steps. For example, plastic waste may undergo a pyrolysis step, and the recovered pyrolysis oil, usually after purification, can be converted, at least in part, into olefins by steam cracking. These olefins can then be polymerized or transformed into monomers before the latter are polymerized.This type of chaining can be adapted for poorly sorted loads or sorting centre rejects, but it generally requires significant energy consumption due in particular to high temperature treatments.

[0008] Another method for recycling plastic waste involves the deformulation of plastic materials, particularly thermoplastics, especially polyolefins such as (co)polypropylene and (co)polyethylene, which appears more environmentally sound. This method of plastic waste recycling consists of dissolving the target polymer in a solvent and removing impurities, such as additives like fillers, colorants, pigments, and metals and / or other polymers from the filler, without altering the macromolecular chains of the target polymer. Preserving the polymer structure reduces the effort required and explains the good performance of this recycling approach, particularly in terms of energy consumption.

[0009] Several studies present different methods of treating plastic waste by dissolution and purification.

[0010] US patent application 2017 / 002110 describes a method for purifying a polymer feedstock, particularly one derived from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, followed by contacting the resulting polymer solution with a solid. The method described in US patent application 2017 / 002110 includes a step of separating the purified polymer from the solvent under temperature and pressure conditions in which the polymer precipitates. However, US patent application 2017 / 002110 does not describe any solvent recycling.

[0011] Document WO 2018 / 118579 describes a method for purifying a polymer feedstock, particularly one derived from plastic waste, by dissolving the polymer in a solvent in a stirred reactor, followed by a sedimentation step. More specifically, WO 2018 / 118579 illustrates the purification of a feedstock composed of post-consumer polypropylene by dissolving it in n-butane in a stirred autoclave at 140°C and 900 psig (6.21 MPa), followed by a sedimentation phase after stirring in the autoclave is stopped. The resulting polymer solution is either passed through solids beds or not, and then depressurized to allow at least some of the butane solvent to be separated from the polypropylene. However, document WO 2018 / 118579 does not describe any solvent recycling.

[0012] Document WO 2018 / 114047 proposes a method for the selective dissolution of a specific polymer from a plastic in a solvent at a dissolution temperature close to the solvent's boiling point. The polymer solution is then centrifuged, and the polymer is subsequently separated from the solvent, for example, by flash separation. WO 2018 / 114047 discloses that the solvent can then be recovered and returned to the dissolution section.

[0013] The present invention aims to improve these processes for recycling used plastics. More particularly, the present invention aims to optimize such processes for recycling thermoplastics, in particular polyolefins, from a plastic filler by dissolution in a solvent, purification of the resulting polymer solution and polymer-solvent separation, in particular by liquid-liquid and / or supercritical-liquid separation followed by at least one gas-liquid separation, so as to limit solvent consumption while avoiding an accumulation of impurities and maintaining the quality of the purified thermoplastic stream obtained at the end of said recycling processes.The present invention seeks in particular to recycle the solvent optimally, and in particular the dissolution solvent, in order to reduce solvent consumption and advantageously costs, without losing in quality of the recovered purified polymers, that is to say by ensuring efficient purification of the targeted thermoplastics.

[0014] SUMMARY OF THE INVENTION

[0015] The invention relates to a process for processing a plastic filler comprising thermoplastics, said process comprising: a) a step of dissolving the plastic filler in a dissolving solvent to obtain a crude polymer solution, step a) being fed by a stream of dissolving solvent which is composed at least partly of a stream of recycled solvent, step a) being carried out at a dissolution temperature between 100°C and 300°C, and at a dissolution pressure between 0.1 and 100.0 MPa absolute; b) a step of purifying the crude polymer solution to obtain a purified polymer solution, the purification step comprising: b1) a substep of separating insolubles; and / or b2) a washing substep.by contact with a dense solution; and / or b3) a substep of impurity extraction by an extraction solvent; and / or b4) a substep of impurity adsorption by contact with at least one adsorbent; c) a solvent-polymer separation step of the purified polymer solution, to obtain a stream of purified thermoplastic polymers, said solvent-polymer separation step c) comprising a liquid-liquid and / or supercritical-liquid separation followed by a gas-liquid separation, the liquid-liquid separation, when carried out, employing a liquid-liquid separation section to produce a liquid phase comprising the thermoplastics in question, and another liquid phase comprising a dissolving solvent and called the liquid solvent phase, the supercritical-liquid separation, when carried out, employing a supercritical-liquid separation section to produce a liquid phase comprising the thermoplastics in question,and a supercritical phase comprising a dissolving solvent and called the supercritical solvent phase, the gas-liquid separation employing a gas-liquid separation section or a series of N gas-liquid separation sections, N being an integer greater than or equal to two, the gas-liquid separation section or sections producing a liquid effluent comprising the thermoplastics of interest, and a gas effluent comprising a dissolving solvent, wherein: where step c) comprises a liquid-liquid separation or a supercritical-liquid separation, the purified polymer solution, obtained at the end of purification step b), feeds the liquid-liquid or supercritical-liquid separation section employed in step c), the liquid phase comprising the thermoplastics of interest, obtained at the end of the liquid-liquid or supercritical-liquid separation section employed in step c),feeds the gas-liquid separation section or the first gas-liquid separation section, where step c) successively comprises a liquid-liquid separation and a supercritical-liquid separation, the purified polymer solution feeds the first liquid-liquid or supercritical-liquid separation section implemented in step c), the liquid phase comprising the targeted thermoplastics, obtained at the end of the first liquid-liquid or supercritical-liquid separation section implemented in step c), feeds the second liquid-liquid or supercritical-liquid separation section implemented in step c), and the liquid phase comprising the targeted thermoplastics, obtained at the end of the second liquid-liquid or supercritical-liquid separation section implemented in step c), feeds the gas-liquid separation section or the first gas-liquid separation section,where the gas-liquid separation of step c) employs a series of N gas-liquid separation sections, the liquid effluent from the preceding gas-liquid separation section feeds the subsequent gas-liquid separation section, the liquid effluent from the gas-liquid separation section or the last gas-liquid separation section constituting said at least one stream of purified thermoplastic polymers; d) a dissolving solvent recycling step, to produce said recycled solvent stream, step d) comprising at least one of the following substeps: d1) the direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section,to compose at least part of the recycled solvent stream; (d) the purification of at least a fraction of the liquid solvent phase and / or the supercritical solvent phase, at least by tailing, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step (a) to compose at least part of the recycled solvent stream; (d) the purification by topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section of step (c) to obtain a purified solvent effluent, then the transfer of at least a portion of the purified solvent effluent to step (a) to compose at least part of the recycled solvent stream; or the purification by tailing of at least a fraction of the gas effluent from the first gas-liquid separation section to obtain a tailed solvent effluent,and / or the purification by tailing of at least a fraction of the gas effluent from the last gas-liquid separation section to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the tailed solvent effluent and / or the tailed solvent effluent to make up at least part of the recycled solvent stream.

[0016] The present invention has the advantage of offering a simple, efficient, and economical process for recycling thermoplastics contained in a plastic feedstock by dissolution, to obtain a stream of high-quality, purified thermoplastics. The process according to the invention proposes a simple sequence of successive operations, in particular dissolution, purification, polymer-solvent separation, and recycling of the dissolving solvent, to treat a plastic feedstock, particularly one composed of plastic waste, for example, post-consumer and / or post-production waste, and to recover a stream of high-quality, purified thermoplastics, in particular purified polyolefins, while limiting solvent losses, particularly of the dissolving solvent, and therefore limiting external solvent inputs, particularly of the dissolving solvent, i.e., limiting the consumption of fresh solvents, particularly fresh dissolving solvent.One advantage of the process according to the invention is therefore to allow, in addition to the recycling of thermoplastics included in a plastic feed, the recovery, at least in part, of the solvent(s) used in the process, in particular the recovery at least in part of the dissolving solvent, and to return at least a fraction of said recovered and purified solvent(s), in particular the recovered and purified dissolving solvent, to at least the dissolving step, while maintaining a low content of impurities in the system.In particular, the process according to the invention makes it possible to recover and recycle the dissolving solvent to the dissolving step, maintaining a low content of light impurities (i.e. compounds having a boiling point lower than that of the solvent, in particular the dissolving solvent) and / or heavy impurities (i.e. compounds having a boiling point higher than that of the solvent, in particular the dissolving solvent), in the system (i.e. in the process, or more precisely in the polymer solution and the solvent(s) involved in the different steps of the process), while limiting the losses of dissolving solvent (for example, while reducing the purging of dissolving solvent).Indeed, a high impurity content in the system, particularly in the dissolving solvent used in the dissolution step, can negatively impact the quality of the purified thermoplastic stream obtained at the end of the process. Therefore, by optimally recycling and purifying at least a portion of the recovered solvent, specifically the dissolving solvent, the process according to the invention reduces the need for fresh solvent, particularly the need for fresh dissolving solvent (i.e., external to the process), and in particular, lowers fresh solvent consumption, especially of the dissolving solvent, compared to prior art plastics recycling processes by dissolution. This is achieved while ensuring efficient purification of the polymer solution and thus a high quality of the purified thermoplastic stream obtained, and advantageously with controlled or even limited energy consumption.By limiting in particular the need for fresh solvent input, the process according to the invention makes it possible both to limit the costs of the process related to raw materials and to limit its carbon impact.

[0017] Furthermore, the process according to the invention makes it possible to obtain, from any plastic feed comprising thermoplastics, preferably polyolefins, such as polypropylene, polyethylene, their copolymers, or mixtures thereof, in particular from a feed composed of plastic waste, for example post-consumer and / or post-production plastic waste, a stream of purified thermoplastics, in particular a stream of purified polyolefins, that is to say freed from at least part of the organic and inorganic impurities contained in the plastic feed, for example additives introduced into the polymer materials by the formulators.More particularly, the process according to the invention makes it possible to obtain a stream of purified thermoplastics, in particular a stream of purified polyolefins, advantageously decolorized and deodorized, which has residual levels of organic and inorganic impurities and solvent sufficiently low so that the purified thermoplastics, in particular the purified polyolefins, can be used in any type of plastic formulation in place of virgin resin.In particular, the process according to the invention makes it possible to recover a stream of purified thermoplastics, in particular a stream of purified polyolefins comprising at most 5% by weight of impurities, very advantageously at most 1.0% by weight of impurities, preferably at most 0.5% by weight of impurities, preferably at most 0.1% by weight of impurities, relative to the total weight of the stream of purified thermoplastics, in particular the stream of purified polyolefins, and having a very low solvent content, in particular less than or equal to 5% by weight, preferably less than or equal to 1.00% by weight, preferably less than or equal to 0.10% by weight, preferably less than or equal to 500 ppm by weight of solvent, relative to the total weight of the stream of purified thermoplastics or the stream of purified polyolefins.

[0018] The invention also has the advantage of contributing to plastic recycling and the preservation of fossil resources by enabling the recovery of plastic waste. It allows for the purification of plastic waste to obtain a stream of purified thermoplastic polymers, particularly purified polyolefins, or even purified polypropylene or polyethylene, with reduced impurity levels and, in particular, decolorized and deodorized, which can be reused to form new plastic objects. The purified thermoplastics obtained, especially the purified polyolefins, can thus be used directly in formulations mixed with additives, such as plasticizers, colorants, pigments, fillers, etc., either instead of or in combination with virgin resins, to obtain plastic materials with performance, aesthetic, mechanical, or rheological properties that facilitate their reuse and recovery.

[0019] The present invention also relates to a device for dissolving a plastic filler to obtain a stream of purified thermoplastic polymers, enabling the process according to the invention to be carried out.

[0020] DESCRIPTION OF IMPLEMENTATION METHODS

[0021] In this description, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included within the described range. If this is not the case, and the limit values ​​are not included within the described range, this clarification will be provided in this description.

[0022] In this description, the expression "greater than..." is understood as strictly greater than, and symbolized by the sign ">", and the expression "less than..." is understood 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..." (corresponding to the sign ">") and "less than or equal to" (corresponding to the sign "<").

[0023] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred pressure range can be combined with a more preferred temperature range.

[0024] In the following description, specific embodiments of the invention are described. They can be implemented separately or in combination with each other, without limitation as to the number of combinations where technically feasible.

[0025] In this description, the term "include" is synonymous with (means the same as) "include" and "contain," is inclusive or open-ended, and does not exclude other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist."

[0026] According to the present invention, the pressures are absolute pressures and are given indifferently in MPa or in absolute MPa (or MPa abs.).

[0027] The terms "upstream" and "downstream" are to be understood in relation to the general flow of the fluid(s) or flow in question in the process, in particular in relation to the flow of the stream which includes the thermoplastics to be purified.

[0028] In this description, the terms "polymer", "thermoplastic polymer" and "thermoplastic" can be used interchangeably.

[0029] The term "polyolefins" refers to any type of homopolymer and / or copolymer having olefins as its unit unit. For example, polyolefins can be polyethylene homopolymers, designated by the acronym PE, of any type (for example, high-density, also called HDPE, or low-density, called LDPE), polypropylene homopolymers, designated by the acronym PP, their copolymers, and / or mixtures thereof.

[0030] The term "additives" is a term classically used in the field of polymers and in particular in the field of polymer formulations. Additives introduced into polymer formulations can be, for example, plasticizers, fillers (which are solid organic or mineral compounds that modify the physical, thermal, mechanical and / or electrical properties of polymer materials or reduce their cost), reinforcing agents, colorants, plasticizers, pigments, hardeners, flame retardants, combustion retardants, stabilizing agents, antioxidants, UV absorbers, antistatic agents, etc.

[0031] The additives correspond to at least some of the impurities in the plastic feedstock to be treated, which the treatment process according to the invention allows to be at least partially removed. Other types of impurities removed during the process according to the invention may be impurities commonly used, such as metallic impurities, paper / cardboard, biomass, polymers other than the polymer(s) targeted, degradation products, etc.

[0032] Thus, according to the invention, the impurities that the process according to the invention makes it possible to eliminate, at least in part, include the additives conventionally used in polymer formulations, and in particular thermoplastic formulations, and also potentially impurities from use arising from the life cycle of plastic materials and objects, and / or from the waste collection and sorting system. These latter impurities may be metallic, organic, or mineral; they may consist of packaging residues, food residues, or compostable residues (biomass).These usage impurities may also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, silicones, rigid polymers, thermosetting polymers, thermoplastics of a different nature than the thermoplastics concerned (in particular than the polyolefins concerned), household, chemical or cosmetic products, used oils, water, etc.

[0033] According to the invention, a polymer solution is a solution comprising the dissolving solvent and at least the thermoplastic polymers referred to, in particular the polyolefins referred to, dissolved in said dissolving solvent, i.e., specifically solvated and dispersed in said dissolving solvent, the dissolved polymers being initially present in the plastic filler. The polymer solution may further comprise insoluble impurities (suspended in the polymer solution) and / or soluble impurities (solubilized in the dissolving solvent).Depending on the steps of the process according to the invention implemented, said polymer solution may therefore include, in addition to the thermoplastics referred to in dissolved form, impurities in the form of insoluble particles which are advantageously suspended in said polymer solution, and / or soluble impurities dissolved in the dissolving solvent, and possibly another liquid phase immiscible with said polymer solution.

[0034] Topping is a separation operation based on the principle of evaporation, preferably by distillation, during which the usable stream is obtained in the residue, and the evaporated stream, or distillate, represents a stream concentrated in impurities.

[0035] It is well known that the boiling point of a compound varies with the operating pressure. However, without further specification, particularly without specifying the pressure, the boiling point of the compound in question, especially the dissolving solvent, is understood to be the boiling point of said compound, and in particular of said dissolving solvent, at atmospheric pressure (specifically 0.1 MPa). Thus, the boiling point that characterizes the dissolving solvent should be understood as the boiling point of said dissolving solvent at atmospheric pressure (specifically 0.1 MPa).

[0036] The critical temperature and critical pressure of a solvent, particularly a dissolving solvent, are specific to that solvent and depend on its nature. For a pure substance, the critical temperature and critical pressure are, respectively, the temperature and pressure at the critical point of that pure substance. As is well known to those skilled in the art, at and above the critical point, the pure substance is in a supercritical state; it can then be called a supercritical fluid.

[0037] The invention thus relates to a process for treating a plastic filler, comprising thermoplastics, more particularly polyolefins, said process comprising, preferably consisting of: a) a step of dissolving the plastic filler in a dissolving solvent, preferably with a weight ratio between the dissolving solvent and the plastic filler of between 0.2 and 100.0, preferably between 0.3 and 20.0, most preferably between 1.0 and 10.0, even more preferably between 3.0 and 10.0, to obtain at least one crude polymer solution, step a) being fed by a stream of dissolving solvent which is composed at least in part of a stream of recycled solvent, optionally dried, said stream of dissolving solvent which feeds step a) possibly comprising for another part a stream of fresh dissolving solvent, step a) being advantageously carried out at a dissolution temperature of between 100°C and 300°C,preferably between 150 and 250°C, and at a dissolution pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute, and most preferably between 2.0 and 15.0 MPa absolute; b) a purification step of the crude polymer solution, comprising at least one of the following substeps: b1) a substep for separating insolubles, yielding at least one clarified polymer solution; and / or b2) a washing substep, by contact with a dense solution, yielding a washed polymer solution; and / or b3) a substep for extracting impurities with an extraction solvent, yielding at least one extracted polymer solution; and / or b4) a substep for adsorbing impurities by contact with at least one adsorbent,to obtain at least one refined polymer solution; the purification step enabling the production of a purified polymer solution which advantageously corresponds to a clarified, washed, extracted, or refined polymer solution; then (c) a solvent-polymer separation step of the purified polymer solution, to at least obtain a stream of purified thermoplastic polymers, in particular a stream of purified polyolefins, said solvent-polymer separation step (c) comprising a liquid-liquid and / or supercritical-liquid separation followed by a gas-liquid separation, the liquid-liquid separation, when carried out, employing a liquid-liquid separation section to produce a liquid phase comprising the thermoplastics in question, and another liquid phase comprising the dissolving solvent, also called the liquid solvent phase, the supercritical-liquid separation, when carried out,employing a supercritical-liquid separation section to produce a liquid phase comprising the thermoplastics in question and a supercritical phase comprising a dissolving solvent, also referred to as the supercritical solvent phase, said gas-liquid separation employing a gas-liquid separation section or a series of N gas-liquid separation sections, N being an integer greater than or equal to two, preferably between two and ten, preferably between two and five, the gas-liquid separation section or each producing a liquid effluent comprising the thermoplastics in question, and a gas effluent comprising a dissolving solvent, wherein: where step c) comprises a liquid-liquid separation or a supercritical-liquid separation, the purified polymer solution obtained at the end of purification step b) feeds the liquid-liquid separation section or the supercritical-liquid separation section,Implementation in step c), the liquid phase comprising the targeted thermoplastics, obtained at the end of the liquid-liquid or supercritical-liquid separation section, feeds the gas-liquid separation section or the first gas-liquid separation section, where step c) successively comprises a liquid-liquid separation and a supercritical-liquid separation (liquid-liquid separation then supercritical-liquid separation, or conversely supercritical-liquid separation then liquid-liquid separation), the purified polymer solution feeds the first separation section, liquid-liquid or supercritical-liquid, the liquid phase comprising the targeted thermoplastics, obtained at the end of the first separation section, liquid-liquid or supercritical-liquid, feeds the second liquid-liquid or supercritical-liquid separation section, and the liquid phase comprising the targeted thermoplastics,obtained at the end of the second separation section, liquid-liquid or supercritical-liquid, feeds the gas-liquid separation section or the first gas-liquid separation section, where the gas-liquid separation of step c) employs a series of N gas-liquid separation sections, the liquid effluent from the preceding gas-liquid separation section feeds the subsequent gas-liquid separation section, the liquid effluent from the gas-liquid separation section or the last gas-liquid separation section constituting said purified thermoplastic polymer stream, in particular the purified polyolefin stream; d) a dissolving solvent recycling step, to produce said recycled solvent stream, optionally dried, which advantageously comprises at least a fraction of the dissolving solvent stream that feeds the dissolving step a), step d) comprising at least one of the following substeps,preferably at least one substep selected from the following substeps d1) and d1): d1) direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section implemented in step c) and / or of a reliquefied solvent phase obtained from at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section implemented in step c), to make up at least part of the recycled solvent stream, said reliquefied solvent phase being obtained in particular after adjusting the temperature and / or pressure downstream of the supercritical-liquid separation section implemented in step c), so that the solvent, in particular the dissolving solvent, of said supercritical solvent phase is entirely in liquid form; and / or d1) purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, by stemming,and possibly topping, of said at least a fraction of the liquid solvent phase and / or of said at least a fraction of the supercritical solvent phase, to obtain a purified solvent phase, then transferring at least a part of the purified solvent phase to step a) to make up at least a part of the recycled solvent stream; and / or d2) the purification by topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then transferring at least a part of the purified solvent effluent to step a) to make up at least a part of the recycled solvent stream; or the purification by topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly of at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s),to separate at least some of the light impurities and obtain a tailed solvent effluent, and / or the tailing purification of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)), to separate at least some of the heavy impurities and obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the tailed solvent effluent and / or the tailed solvent effluent to make up at least part of the recycled solvent stream.

[0038] The charge

[0039] The feedstock of the process according to the invention, referred to as the plastic feedstock, comprises plastics which themselves more particularly comprise thermoplastic polymers, such as polyolefins. Preferably, the plastic feedstock comprises between 50 and 100% by weight, and more preferably between 70% and 100% by weight, of plastics relative to the total weight of the plastic feedstock.

[0040] The plastics included in the feedstock of the process according to the invention are generally production scraps and / or post-consumer waste from plastic objects, including household plastic waste, construction plastic waste, automotive or any type of transport plastic waste, and waste electrical and electronic equipment. Preferably, the plastic waste comes from collection and sorting channels. Plastics or plastic materials are generally compositions (or formulations) comprising polymers mixed with additives to impart specific properties to the materials, with a view to forming, after shaping, various objects (for example, injection-molded parts, tubes, films, fibers, fabrics, sealants, coatings, etc.). The additives used in plastics can be organic or inorganic compounds.These include, for example, fillers, colorants, pigments, plasticizers, property modifiers, flame retardants, etc. The process feed according to the invention (i.e., the plastic feed) comprises, in particular, thermoplastic polymers, preferably at least 50% by weight, preferably at least 70% by weight, most preferably at least 80% by weight, and most preferably at least 90% by weight of thermoplastics, relative to the total weight of the plastic feed, with 100% advantageously being the maximum upper limit. The thermoplastics targeted by the process according to the invention and included in the plastic feed may be alkene (or olefin) polymers, diene polymers, vinyl polymers, and / or styrenic polymers.Preferably, the thermoplastics targeted by the process according to the invention and included in the plastic filler are polyolefins, homopolymers or olefin copolymers, such as polyethylene (PE), polypropylene (PP), and / or ethylene-propylene copolymers, or mixtures thereof. Preferably, the plastic filler comprises at least 50% by weight, preferably at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of polyolefins relative to the total weight of the plastic filler, with 100% advantageously being the maximum upper limit. The process according to the invention is thus particularly aimed at purifying and recovering thermoplastics, especially polyolefins, contained in a plastic filler, particularly one derived from plastic waste, so that they can be reused in various applications.In a particular embodiment, the plastic filler comprises polypropylene (PP), polyethylene (PE), or a mixture of polypropylene (PP) and polyethylene (PE), in particular at least 50% by weight, preferably at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of polypropylene (PP) or polyethylene (PE), or a mixture of polypropylene (PP) and polyethylene (PE), relative to the total weight of the plastic filler. The polyethylene may, in particular, be high-density polyethylene (HDPE). In a very particular embodiment, said mixture comprises, for example, between 5% and 95% by weight of PP and between 5% and 95% by weight of PE, in particular HDPE, or between 50% and 95% by weight of PP and between 5% and 50% by weight of PE, in particular HDPE.

[0041] The plastic filler may comprise polymer blends. It may therefore include, in addition to the thermoplastics covered, thermoplastics other than those covered, and in particular other than the polyolefins covered, additives advantageously used to formulate the plastic material, and possibly impurities resulting from the life cycle of plastic materials and objects and / or from the waste collection and sorting process, degradation products of the compounds contained in the filler materials, etc. Thermoplastics other than those covered, additives, impurities from use, degradation products, etc., are considered, according to the invention, as impurities. The plastic filler of the process according to the invention generally comprises less than 50% by weight of impurities, preferably less than 20% by weight of impurities, and preferably less than 10% by weight of impurities.The plastic filler may include, for example, at least 1% by weight of impurities, or even at least 5% by weight of impurities.

[0042] The plastic feedstock can advantageously be pretreated upstream of the process according to the invention so as to at least eliminate all or part of the so-called coarse impurities, that is to say, impurities in the form of particles larger than or equal to 10 mm, preferably larger than or equal to 5 mm, or even larger than or equal to 1 mm, for example, impurities such as wood, paper, biomass, iron, aluminum, glass, etc., and so as to shape it generally into divided solids to facilitate processing in the process. This pretreatment may include a grinding step, an atmospheric pressure washing step, and / or a drying step. This pretreatment may be carried out at a different site, for example, at a waste collection and sorting center, or at the same site where the treatment process according to the invention is implemented.Preferably, this pretreatment reduces the impurity content to less than 20% by weight, preferably less than 15% by weight, and preferably less than 10% by weight, the percentages being given relative to the weight of the plastic feed treated by the process according to the invention. Following the pretreatment, the feed is generally stored as divided solids, for example as chips, flakes, powder, or granules, to facilitate handling and transport to the processing stage.

[0043] Step a) of dissolution

[0044] According to the invention, the process comprises a dissolution step (a) in which the plastic filler is contacted with a dissolving solvent to obtain at least one, preferably one, crude polymer solution. This step advantageously allows the dissolution of at least some, preferably all, of the targeted thermoplastics, in particular the targeted polyolefins, present in the plastic filler.

[0045] Dissolution refers to any phenomenon that results in at least one solution of thermoplastic polymers, that is, a liquid (or fluid) containing the targeted thermoplastic polymers dissolved in the dissolving solvent. Those skilled in the art are well acquainted with the phenomena involved in polymer dissolution: these phenomena include at least mixing, solvation, dispersion, homogenization, and disentanglement of the thermoplastic polymer chains.

[0046] During and after dissolution step a), the pressure and temperature conditions ensure that the dissolving solvent remains, at least partially and preferably entirely, in a liquid state or possibly in a supercritical state, while the soluble fraction of the plastic filler, in particular the targeted thermoplastic polymers, for example the targeted polyolefins, and possibly (or even generally) at least some of the impurities, is advantageously, at least partially and preferably entirely, dissolved in the dissolving solvent. In other words, the temperature and pressure conditions in step a) prevent, or at least limit, the dissolving solvent from being in gaseous form, thereby optimizing the dissolution of the targeted thermoplastics.

[0047] Step a) of dissolution is fed by the plastic charge and by a flow of dissolving solvent.

[0048] The dissolving solvent is an organic solvent or a mixture of organic solvents, preferably chosen so that its Hansen parameters lie within the Hansen sphere of the target thermoplastics, particularly the target polyolefins. Hansen theory allows us to predict the solubility of a polymer, especially a thermoplastic such as polyolefins (polyethylene and / or polypropylene), in a solvent by determining the Hansen parameters and solubility sphere for the solvent and the polymer, respectively, as a function of several parameters, particularly their polar parameters, hydrogen bonding, and dispersion. If a solvent or solvent mixture has Hansen parameters within the Hansen sphere of the target polymer, then the polymer should be at least partially, and preferably completely, soluble in that solvent.

[0049] Advantageously, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (i.e., saturated), preferably linear, branched or cyclic, and preferably non-aromatic. Preferably, the dissolving solvent comprises at least 80% by weight, preferably at least 95% by weight, and preferably at least 98% by weight of at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, and preferably non-aromatic, the percentages being expressed as a percentage of the total weight of the dissolving solvent (100% being the maximum).Preferably, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 160°C and preferably between 50 and 120°C. Preferably, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, has between 3 and 12 carbon atoms, preferably between 4 and 10 carbon atoms, preferably between 5 and 8 carbon atoms, and most preferably has 6, 7 or 8 carbon atoms.For example, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, may be selected from isomers of butane, pentane, hexane, heptane, octane, nonane, decane, and mixtures thereof, preferably from isomers of pentane, hexane, heptane, octane and mixtures thereof. Thus, the dissolving solvent may comprise at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight, of an isomer or mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane, preferably of an isomer or mixture of isomers of pentane, hexane, heptane and / or octane, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0050] Preferably, step a) of dissolution is fed by the plastic filler and said flow of dissolving solvent, according to a weight ratio between the dissolving solvent and the plastic filler, of between 0.2 and 100.0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 10.0.

[0051] Advantageously, the dissolving solvent that feeds the dissolution step a) is in liquid or possibly supercritical form. It may advantageously be preheated, preferably to a temperature between 100 and 300°C, preferably between 150 and 250°C, prior to its introduction into step a), in particular prior to its introduction into the contacting section and possibly into the dissolving section, in order to facilitate the heating of the plastic charge and / or avoid a temperature drop in the material flow during contacting and dissolving in step a).

[0052] The dissolving solvent stream feeding step a) comprises, preferably consists of, at least in part or entirely of, a recycled solvent stream, optionally dried, advantageously from step d) of the process. The dissolving solvent stream feeding step a) may also include fresh dissolving solvent, in particular a fresh dissolving solvent stream. The dissolving solvent stream feeding step a) is therefore composed at least in part, or even entirely, of a recycled solvent stream, optionally dried, advantageously from the dissolving solvent recycling step d), and possibly of a fresh dissolving solvent supplement (i.e., an external supply of dissolving solvent).

[0053] Most advantageously, the dissolution step is carried out at a temperature, called the dissolution temperature, between 100°C and 300°C, preferably between 150 and 250°C, and preferably at a pressure, called the dissolution pressure, between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and most preferably between 2.0 and 15.0 MPa absolute.The temperature and pressure can change during the dissolution step, from atmospheric conditions or the conditions under which the plastic filler and / or dissolving solvent are introduced into the process, until they reach the dissolution conditions, i.e., the dissolution temperature, in particular between 100 and 300°C, preferably between 150 and 250°C, and the dissolution pressure, in particular between 0.1 and 100.0 MPa, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute, and most preferably between 2.0 and 15.0 MPa absolute. Advantageously, at the end of the dissolution step, the crude polymer solution is at the dissolution temperature and dissolution pressure.

[0054] Limiting the temperature in step a) of dissolution to a temperature of 300°C or lower, preferably 250°C or lower, prevents or limits the thermal degradation of the targeted thermoplastics, particularly the targeted polyolefins, and also reduces the energy requirements of the process, thus contributing to lower operating costs. Advantageously, the dissolution temperature is greater than or equal to the melting point of the targeted thermoplastics, particularly the targeted polyolefins, and very advantageously lower than the evaporation temperature at the dissolution pressure of the dissolving solvent (to keep the dissolving solvent in a non-gaseous state, and particularly in a liquid state), so as to promote their dissolution and very advantageously reduce the residence time required to effectively dissolve said thermoplastics in the dissolving solvent.According to a particular embodiment, the temperature in step a) of dissolution is less than or equal to the critical temperature of the dissolving solvent, so as to avoid the formation of a supercritical phase during step a) of dissolution which could disrupt the dissolution.

[0055] Simultaneously, the dissolution pressure in step a) of dissolution is higher than the saturated vapor pressure of the dissolving solvent at the dissolution temperature, so that the dissolving solvent is at least partially, and preferably entirely, in liquid or possibly supercritical form at the dissolution temperature, thus preventing the dissolving solvent from being partially in gaseous form. Under these operating conditions, particularly regarding temperature and pressure, the dissolution of the targeted thermoplastics, especially the targeted polyolefins, is optimized, particularly in terms of quality and processing time.

[0056] Advantageously, the temperature and pressure conditions for dissolution achieved in step a) of dissolution are adjusted so that the mixture (dissolving solvent + targeted thermoplastics) is single-phase at the end of step a), said mixture possibly containing insoluble impurities suspended in said mixture. Advantageously, said step a) of dissolution is carried out for a residence time preferably between 1 and 600 minutes, preferably between 2 and 300 minutes, preferably between 10 and 180 minutes, preferably between 30 and 150 minutes, and most preferably between 40 and 120 minutes. Residence time is understood as the residence time at the dissolution temperature and pressure, that is, the time during which the plastic feedstock and the dissolving solvent are at the dissolution temperature and pressure, in step a).

[0057] The dissolution step (a) is fed at least by the plastic filler, in particular in the form of one or more plastic filler streams, and by the dissolving solvent, in particular in the form of one or more dissolving solvent streams, advantageously by means of one or more conveying devices. The plastic filler stream(s) may be separate from the dissolving solvent stream(s). Some or all of the plastic filler may also feed step (a) mixed with some or all of the dissolving solvent, with the remainder of the solvent and / or filler, if any, feeding step (a) separately.

[0058] When the plastic filler is brought into contact with the dissolving solvent, the dissolving solvent is advantageously at least partially, and preferably entirely, in liquid form, or possibly supercritical, while the plastic filler, which includes the thermoplastics in question, may be in solid or liquid form, or even in the form of a liquid containing suspended solid particles. The plastic filler may also optionally be injected into the dissolving equipment, mixed with the dissolving solvent, or as a suspension in the dissolving solvent; the preparation and injection of the suspension may be continuous or discontinuous.

[0059] To facilitate contact between the dissolving solvent and the plastic feedstock, and especially to ensure efficient and homogeneous dissolution of the targeted thermoplastics in the dissolving solvent, step a) of dissolution may advantageously employ various types of equipment such as mixing, conveying, and heating devices, for example, a reactor, a pump, a conveying circuit, an agitation system, a furnace, a heat exchanger, a mixer, etc. In particular, step a) advantageously employs at least one piece of dissolving equipment, and possibly at least one feedstock preparation device, a mixing device, and / or a conveying device. The equipment and / or devices employed in step a) may include, for example, static or dynamic mixer(s), an extruder, a pump, a reactor, a co- or counter-current column, and / or conveying devices, advantageously interconnected.Transport devices, particularly for fluids such as gases, liquids, or solids, are well known to those skilled in the art. Without limitation, transport devices may include at least one of the following: a compressor, a pump, an extruder, a vibrating tube, a screw conveyor, or a valve. The equipment and / or devices used in step a) may also include or be combined with heating systems (e.g., furnace, heat exchanger, heat treatment) to achieve the conditions necessary for dissolution.

[0060] Preferably, step a) of dissolution employs at least one means for melting at least part of the plastic feedstock, preferably an extruder, and optionally at least one means for mixing at least part of the dissolving solvent with the plastic feedstock, advantageously at least partially melted, such as one or a series of two to ten mixers (preferably one to ten static mixers), and dissolution equipment, for example at least one continuous stirred tank reactor (CSTR), equipped with at least one mechanical stirring system. In this case, the plastic feedstock feeds the melting means, in particular the extruder, so that, at the outlet of said means, at least part and preferably all of the thermoplastics in question, included in the plastic feedstock, are in a molten state.The plastic feedstock can then be injected into the dissolution equipment, for example, a continuous stirred reactor (CSTR), or possibly into a system comprising a mixer or a series of mixers advantageously followed by a reactor, for example, a continuous stirred reactor (CSTR). The plastic feedstock, at least partially in a molten state, can also be pumped using a pump designed for viscous fluids, often called a melt pump or gear pump. The plastic feedstock, at least partially in a molten state, can also be filtered, at the outlet of said melting equipment, using a filtration device, possibly in addition to the melt pump, to remove the largest particles. Generally, the mesh size of this filter is between 10 µm (micrometers) and 1 mm (millimeters), preferably between 20 and 200 µm.Simultaneously, the dissolving solvent directly feeds the dissolving equipment, the said means for melting, in particular the extruder, and / or the mixer(s).

[0061] Preferably, step a) implements, prior to at least one CSTR-type reactor, an extruder possibly followed by at least one static mixer into which at least a fraction of the dissolving solvent is injected, so as to promote intimate mixing between the dissolving solvent and the plastic filler, which contributes to the dissolution of the targeted thermoplastics.

[0062] Advantageously, the crude polymer solution obtained at the end of dissolution step a) comprises at least the dissolving solvent and the targeted thermoplastics, in particular the targeted polyolefins, dissolved in the dissolving solvent. In general, the crude polymer solution also comprises soluble impurities dissolved in the dissolving solvent and / or insoluble impurities in suspension. The crude polymer solution obtained at the end of dissolution step a) may optionally also include polymers, for example, in a molten state, dissolved or not.

[0063] Step b) of purification of the polymer solution

[0064] The purification process according to the invention includes a step of purifying the crude polymer solution from step a). This purification step b) includes at least one of the substeps b1), b2), b3), b4) described below: b1) a substep of separating insolubles, b2) a washing substep, by contact with a dense solution, b3) an extraction substep, by contact with an extraction solvent, b4) a substep of adsorption of impurities by contact with at least one adsorbent.

[0065] The different sub-steps b1), b2), b3) and b4) can be operated continuously, discontinuously (or batch mode) or in fed-batch discontinuous mode.

[0066] Preferably, purification step b) includes at least one substep b1) for separating insolubles. According to a particular embodiment, purification step b) includes several (i.e. at least two) substeps selected from substeps b1), b2), b3) and b4), in series with respect to each other, and preferably at least one substep b1) for separating insolubles and, for example, one substep b4) for adsorption, and most advantageously in the order b1) then b4).The combination of at least two substeps chosen from b1), b2), b3) and b4) advantageously allows optimal purification of the polymer solution, which consequently makes it possible to obtain a stream of purified thermoplastics having very low impurity contents, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight, preferably less than or equal to 0.5% by weight, relative to the total weight of the stream of purified thermoplastics.

[0067] The polymer solution obtained at the end of step b) is a purified polymer solution comprising the targeted thermoplastics, in particular the targeted polyolefins, dissolved in the dissolving solvent. This purified polymer solution may correspond to a clarified polymer solution from a substep b1) separating insolubles, a washed polymer solution from a washing substep b2), an extracted polymer solution from an extraction substep b3, or a refined polymer solution from an impurity adsorption substep b4. Preferably, the temperature and pressure at step b) are adjusted so as to obtain, at the outlet of step b), a polymer solution, i.e., the purified polymer solution, in liquid form.

[0068] Substep b1) of separation of insolubles

[0069] The purification process may include a substep (b1) of separating insolubles, in particular by solid-liquid separation, to advantageously obtain at least one clarified polymer solution (i.e., free from at least some, and preferably all, of the insoluble impurities of the crude polymer solution), and preferably at least one insoluble fraction. This at least one insoluble fraction advantageously comprises at least some, and preferably all, of the insoluble impurities, particularly those suspended in the crude polymer solution obtained in step (a), optionally the dissolving solvent, and optionally soluble impurities.

[0070] Substep b1), the separation of insolubles, thus allows for the removal of at least some, and preferably all, of the insoluble impurities present in suspension in the crude polymer solution from step a). Examples of insoluble impurities removed during substep b1 include pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum), and insoluble polymers. When implemented, this separation substep b1 advantageously allows, in addition to the removal of at least some of the insoluble impurities, the reduction of operational problems, particularly clogging and / or erosion, in process steps downstream of such substep b1), while also contributing to the purification of the plastic feedstock.

[0071] The substep b1) of insoluble separation is advantageously carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, preferably between 160 and 225°C, most preferably between 165 and 210°C, and preferably between 170 and 195°C, and at a pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 18.0 MPa absolute and most preferably between 1.5 and 15.0 MPa absolute. Advantageously, substep b1) of insoluble separation is carried out at the temperature and pressure conditions at the outlet of step a) of dissolution, i.e. at the dissolution temperature and dissolution pressure as defined above, possibly with a reduced pressure, preferably from 0.01 to 10.0 MPa, preferably from 0.1 to 5.0 MPa due to the pressure losses suffered between step a) and substep b1).

[0072] When integrated into the process, substep b1) for separating insolubles is preferably fed with the crude polymer solution from step a) or any other polymer solution from a substep b2), b3), or b4) possibly located upstream of substep b1). In a preferred embodiment, substep b1) is fed with the crude polymer solution from step a). In another embodiment, substep b1) may be fed with a washed polymer solution from a washing substep b2) located upstream of substep b1).

[0073] Advantageously, substep b1) implements any solid-liquid and / or liquid-liquid separation method known to those skilled in the art to separate the insolubles from the polymer solution, the insolubles being solid (such as additives of the type mineral fillers or pigments) or liquid (for example polymers in molten form and of a different nature than that of the thermoplastics concerned), for example a separation step by decantation, filtration, centrifugation, electrostatic separation, etc.

[0074] Preferably, substep b1) comprises at least one, preferably between one and five, preferably between two and five, solid-liquid separation step(s) (or solid-liquid-liquid separation step(s), particularly where the effluent obtained after the dissolution step comprises, in addition to the polymer solution and solid impurities, impurities and / or polymers in liquid form that are poorly or insoluble and of a different nature than the thermoplastics in question). When implemented, substep b1) preferably comprises several, i.e., between two and five, solid-liquid separation (or solid-liquid-liquid separation) steps in series and / or in parallel. The presence of at least two solid-liquid separation steps in series improves the removal of insolubles, while the presence of several solid-liquid separation steps in parallel facilitates equipment maintenance and / or cleaning operations.According to a preferred embodiment, substep b1) of insolubles separation implements a solid-liquid separation step by decantation and / or at least one, preferably between one and four, solid-liquid separation steps by filtration.

[0075] Said at least one solid-liquid separation step preferably employs at least one piece of solid-liquid separation equipment, for example, a separator flask, a decanter, a decanter centrifuge, a filter, a sand filter, a tangential flow filter incorporating a membrane and / or a depth filter, an eddy current separator, an electrostatic separator, a triboelectric separator, and preferably a decanter, a filter, a sand filter, and / or an electrostatic separator. Advantageously, a self-cleaning filter may be used, with cleaning or unclogging to remove insolubles being carried out using a solvent stream. During substep b1), filter aids (for example, diatomaceous earth, perlite, or sand) may optionally be added prior to a decantation step and / or a filtration separation step.Depending on the nature of the plastic filler, the polymer solution feeding substep b1), preferably the raw polymer solution, may also include a second liquid phase, for example, composed of molten polymers, these polymers being of a different nature than the thermoplastics in question. In another particular embodiment, substep b1) advantageously incorporates a solid-liquid-liquid separation section, using equipment for separating two liquid phases and one solid phase, preferably by means of at least one two-phase or three-phase separator.

[0076] The at least one insoluble fraction is preferably removed or treated in such a way as to separate and recover compounds of interest, for example polymers, particularly thermoplastics, and / or any dissolving solvent it may contain. The removal or treatment of the at least one insoluble fraction may be facilitated by equipment enabling the transport and / or separation of any polymer and / or solvent present in the insoluble fraction, for example, a conveyor, a vibrating tube, a screw conveyor, an extruder, or a stripper. Substep b1) may employ transport and / or separation equipment to remove and / or treat the at least one insoluble fraction.Advantageously, substep b1) includes the separation and recovery of at least a portion of the solvent, in particular the dissolving solvent, contained in said at least an insoluble fraction, said at least a portion of the solvent, in particular the dissolving solvent, being able to be recycled in the process, in particular in step a).

[0077] Some insoluble impurities, particularly certain pigments and mineral fillers commonly added during polymer formulation, may be in the form of particles smaller than 1 µm. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. In one particular embodiment, substep b1) of insoluble separation advantageously employs an electrostatic separator, which makes it possible to efficiently remove, at least partially, insoluble particles smaller than 1 µm. In another particular embodiment, substep b1) of insolubles employs a sand filter to remove particles of various sizes, and in particular particles smaller than 1 µm.According to yet another particular embodiment, substep b1) of the insolubles implements a tangential filter including a membrane and / or a depth filter, possibly in the presence of filtration aids such as diatomaceous earth or perlite.

[0078] Substep b2) of washing

[0079] The treatment process may optionally include a substep (b2) of washing with a dense solution, advantageously to obtain a washed polymer solution and preferably at least one washing effluent. The washed polymer solution obtained at the end of substep (b2) advantageously comprises the targeted thermoplastics dissolved in the dissolving solvent. Optionally, the washed polymer solution may also include residual impurities, particularly those soluble in the dissolving solvent, and / or possibly traces of the washing solvent when substep (b2) is carried out.

[0080] The washing substep b2) can be integrated upstream or downstream, preferably downstream, of an insolubles separation substep b1), when these two substeps are integrated into the treatment process according to the invention.

[0081] When integrated into the process, washing substep b2 is fed with a dense solution and the polymer solution from the step or substep directly upstream of b2), in particular the crude polymer solution from step a) or the clarified polymer solution from substep b1). The polymer solution feeding washing substep b2, in particular the crude or possibly clarified polymer solution, may contain insoluble impurities in suspension and / or solubilized impurities. These suspended or solubilized impurities may be partially or completely removed during washing substep b2 by dissolution or precipitation and / or by entrainment in the dense solution. Thus, when implemented, this washing substep b2 contributes to the treatment of the plastic filler and, more specifically, to the purification of the polymer solution.

[0082] Washing substep b2 advantageously comprises contacting the polymer solution that feeds substep b2), in particular the crude or clarified polymer solution, with a dense solution. Advantageously, the dense solution has a higher density than the polymer solution (i.e., the mixture comprising at least the thermoplastics of interest and the dissolving solvent in which the thermoplastics of interest are dissolved), in particular greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to 1.0. The dense solution may be an aqueous solution, preferably comprising at least 50 wt% water, preferably at least 75 wt% water, and most preferably at least 90 wt% water. The pH of the aqueous solution may be adjusted with an acid or a base to promote the dissolution of certain impurities.The dense solution may also optionally be a solution comprising, preferably consisting of, an organic solvent with a density advantageously greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to 1.0, and in which the polymers of the plastic filler remain insoluble under the temperature and pressure conditions of substep b2). Thus, the dense solution may, in particular, comprise an organic solvent, for example, selected from sulfolane or N-methylpyrrolidone (NMP), optionally mixed with water. Most preferably, the dense solution is an aqueous solution comprising preferably at least 50 wt% water, most preferably at least 75 wt% water, most preferably at least 90 wt% water.

[0083] The washing substep b2) is advantageously carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, and most advantageously at a pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 18.0 MPa absolute, and most preferably between 1.5 and 15.0 MPa absolute. Most advantageously, the washing substep b2) is carried out at the dissolution temperature and dissolution pressure, possibly with a reduced pressure, preferably from 0.01 to 10.0 MPa, preferably from 0.1 to 5.0 MPa, due to the pressure losses incurred between step a) and substep b2).

[0084] In substep b2) of washing, when integrated into the process, the mass ratio between the mass flow rate of the dense solution and the mass flow rate of the polymer solution, which feeds substep b2), in particular the crude or clarified polymer solution, is advantageously between 0.05 and 20.0, preferably between 0.10 and 10.0 and preferably between 0.5 and 3.0. The contact between the polymer solution, in particular crude or clarified, and the dense solution can be made at several points of the equipment used, i.e. by several injections of the polymer solution and / or the dense solution at different points along the equipment; it is then the sum of the injected flows that is taken into account in the calculation of the mass ratio.

[0085] Substep b2) may implement one or more washing devices for contacting the polymer solution with the dense solution, and / or one or more separation devices for recovering at least one washing effluent and one washed polymer solution. These devices are well known to those skilled in the art: they include, for example, stirred reactors, static mixers, settling mixers, two-phase or three-phase separator vessels, co-current or counter-current washing columns, tray columns, stirred columns, packed columns, pulsed columns, etc. Each type of device may comprise one or more devices used alone or in combination with devices of another type.

[0086] According to a preferred embodiment, washing substep b2) is carried out in a countercurrent washing column. In this preferred embodiment, the dense solution is advantageously injected into the upper part of the column, preferably the upper half, preferably the upper third, of the column (the upper part of the column meaning the part closest to the column head), and the polymer solution, in particular crude or clarified, is injected into the lower part of the column, preferably the lower half, preferably the lower third, of the column (the lower part of the column meaning the part closest to the column bottom). According to this embodiment, it is possible to recover at least one washed polymer solution, preferably at the top of the column, and one washing effluent, preferably at the bottom of the column.In a very particular way, the flows entering and / or exiting the washing column can be divided and injected at several injection points along the column and / or withdrawn at several withdrawal points along the column.

[0087] According to another embodiment, substep b2) of washing is carried out in a mixer-decanter comprising an agitated mixing zone, to bring the dense solution into contact with the polymer solution in particular crude or clarified, and a decantation zone, allowing the recovery of a washed polymer solution and a washing effluent.

[0088] Following substep b2) of washing, the resulting wash effluent advantageously contains impurities that are solubilized and / or insoluble in the dense solution and carried along in the wash effluent. The wash effluent can be reprocessed in a wash treatment section, firstly to separate, at least partially, the solubilized and / or carried-along impurities and possibly purify the wash effluent to obtain a purified dense solution, and secondly to recycle at least part of the purified dense solution. This optional wash treatment section can utilize one or more well-known solid-liquid separation devices, such as a separator vessel, a settling tank, a decanter, a decanter centrifuge, a centrifuge, or a filter. The wash effluent can also be discharged from the process, for example, to a wastewater treatment plant when the dense solution is aqueous.

[0089] Substep b3) of extraction

[0090] The process according to the invention may include an extraction substep (b3), advantageously involving contacting the polymer solution that feeds substep (b3) with an extraction solvent to obtain at least one extracted polymer solution and, preferably, a used solvent. The extracted polymer solution obtained at the end of substep (b3) advantageously comprises the targeted thermoplastic polymers dissolved in the dissolving solvent. The used solvent comprises extraction solvent and is, in particular, loaded with impurities. Optionally, the extracted polymer solution may also include residual impurities, particularly those soluble in the dissolving solvent, and / or traces of the washing solvent and / or the extraction solvent if substep(s) (b2) and / or (b3) is / are performed.

[0091] When integrated into the treatment process according to the invention, substep b3) of extraction is very advantageously located downstream of a substep b1) of separation of insolubles, and possibly upstream or downstream of a substep b2) of washing and / or a substep b4) of adsorption, when the latter are also integrated into the process.

[0092] Extraction substep b3) is advantageously supplied with an extraction solvent and the polymer solution from the step or substep directly upstream of b3), in particular the crude polymer solution from step a), the clarified polymer solution from substep b1), the washed polymer solution from substep b2), or the refined polymer solution from substep b4). The polymer solution that supplies substep b3), in particular the crude, clarified, washed, or refined polymer solution, may contain impurities, including solubilized impurities, which may be partially or totally removed during extraction substep b3) by contact with an extraction solvent.

[0093] When integrated into the process according to the invention, substep b3) of extraction advantageously implements at least one extraction section, preferably between one and five extraction section(s), most preferably one extraction section.

[0094] Advantageously, the mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution that feeds b3) is between 0.05 and 20.0, preferably between 0.10 and 10.0 and preferably between 0.2 and 5.0. Contact between the polymer solution that feeds substep b3) and the extraction solvent can be made at several points in the extraction section, i.e. by several injections of the polymer solution and / or the extraction solvent at different points along the extraction section; it is then the sum of the injected flows that is taken into account in the calculation of the mass ratio.

[0095] Preferably, the extraction solvent used in substep b3) of extraction comprises an organic solvent or a mixture of organic solvents. Preferably, the extraction solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (i.e., saturated), preferably linear, branched or cyclic, preferably non-aromatic. Preferably, the extraction solvent comprises at least 80% by weight, preferably at least 95% by weight, preferably 98% by weight of at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, the percentages being expressed relative to the total weight of the dissolving solvent (100% being the maximum).Preferably, the extraction solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling point between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 160°C (at atmospheric pressure, in particular at 0.1 MPa). Preferably, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, has between 3 and 12 carbon atoms, preferably between 4 and 10 carbon atoms, preferably between 5 and 8 carbon atoms.For example, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, may be selected from isomers of butane, pentane, hexane, heptane, octane, nonane, decane, and mixtures thereof, preferably from isomers of pentane, hexane, heptane, octane and mixtures thereof. Thus, the extraction solvent may comprise at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight, of an isomer or mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane, in a manner of an isomer or mixture of isomers of pentane, hexane, heptane and / or octane, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0096] Preferably, the extraction solvent used in substep b3) is of the same nature as the dissolution solvent used in step a), possibly in a different physical state (for example, the extraction solvent in the supercritical state compared to the dissolution solvent in the liquid state), so as to facilitate the management of solvents and in particular their purification and recycling, especially to step a) of dissolution and possibly to substep b3) of extraction.Another advantage of using identical dissolution and extraction solvents, in identical or different physical states, in addition to facilitating solvent management (i.e. in particular the recovery, treatment and recycling of solvents involved in the process), more particularly the recycling of the dissolution solvent, is to limit energy consumption and costs in particular generated by the treatment and purification of solvents.

[0097] The extraction section(s) of substep b3) may include one or more extraction devices, allowing contact with the extraction solvent, and / or separation devices enabling the recovery of at least one used solvent, particularly one containing impurities, and an extracted polymer solution. These devices are well known to those skilled in the art: they include, for example, stirred reactors, static mixers, settling mixers, two-phase or three-phase separator vessels, co-current or counter-current washing columns, tray columns, stirred columns, packed columns, pulsed columns, etc. Each type of device may include one or more devices used alone or in combination with devices of another type.

[0098] According to a preferred embodiment of b3), the extraction is carried out in a countercurrent extraction column. In this preferred embodiment, the extraction solvent is advantageously injected into the upper part of the column, preferably the upper half, preferably the upper third, of the column (the upper part of the column meaning the part closest to the column head), and the polymer solution that feeds substep b3) is injected into the lower part of the column, preferably the lower half, preferably the lower third, of the column (the lower part of the column meaning the part closest to the column bottom). According to this embodiment, it is possible to recover at least one extracted polymer solution, preferably at the top of the column, and a used solvent, particularly one containing impurities, preferably at the bottom of the column.The inlet and / or outlet flows of the countercurrent extraction column can be divided into several injection and / or withdrawal points along the column.

[0099] According to another embodiment of b3), the extraction is carried out in a mixer-decanter which advantageously includes an agitated mixing zone to bring the extraction solvent and the polymer solution which feeds b3) into contact, and a decantation zone allowing the recovery of an extracted polymer solution, on the one hand, and a used solvent, on the other.

[0100] Advantageously, substep b3) of extraction is implemented under different temperature and pressure conditions than the temperature and pressure conditions of step a) of dissolution.

[0101] According to a preferred embodiment, substep b3) of extraction, when integrated into the treatment process, employs a liquid / liquid extraction section. Preferably, this liquid / liquid extraction section is operated between 100°C and 300°C, preferably between 150°C and 250°C, and at a pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 18.0 MPa absolute, and most preferably between 1.5 and 15.0 MPa absolute. In all cases, in this embodiment, the temperature and pressure conditions are adjusted so that the extraction solvent is in a liquid state, the dissolving solvent preferably also being in a liquid state.Very advantageously, liquid / liquid extraction, in particular when the extraction solvent is the same as the dissolution solvent, is carried out under temperature and pressure conditions different from the dissolution conditions achieved in step a), in particular at a temperature higher than the dissolution temperature and / or at a pressure lower than the dissolution pressure, so as to place oneself in a two-phase zone of the corresponding polymer-solvent mixing diagram.

[0102] According to another preferred embodiment, substep b3) of extraction implements an extraction section under particular temperature and pressure conditions in which the extraction solvent is advantageously at least partly in supercritical form. Such an extraction may be called supercritical extraction. In this embodiment, the extraction is carried out by contacting the polymer solution that feeds b3) with an extraction solvent that is at least partly, preferably entirely, in the supercritical state (preferably at least 50 wt%, preferably at least 70 wt%, preferably at least 90 wt% of the extraction solvent is in supercritical form).Such a supercritical extraction substep (b3) advantageously allows for efficient purification of the polymer solution, particularly due to the very high affinity of organic impurities, such as certain additives (including some colorants, plasticizers, etc.), for the supercritical phase. The use of a supercritical extraction solvent also creates a significant density difference between the supercritical phase and the liquid polymer solution. This facilitates separation by decantation between the supercritical phase, advantageously laden with impurities, and the liquid phase containing the target thermoplastics, thus contributing to the purification of the polymer solution.

[0103] In this other preferred embodiment, substep b3) employs an extraction solvent comprising at least 80% by weight, preferably at least 95% by weight, preferably 98% by weight of at least one aliphatic paraffinic hydrocarbon (or alkane) compound (100% being the maximum, the percentages being expressed relative to the total weight of the extraction solvent) having a critical temperature preferably between 95 and 350°C, preferably between 130 and 320°C, preferably between 180 and 300°C.Advantageously, the supercritical extraction substep b3) of this other preferred embodiment is carried out at a temperature between 100 and 350°C, preferably between 130°C and 320°C, preferably between 180°C and 280°C, and at a pressure preferably between 2.0 and 100.0 MPa absolute, preferably between 2.0 and 25.0 MPa absolute, preferably between 2.0 and 18.0 MPa absolute, most preferably between 2.7 and 15.0 MPa absolute and most preferably between 3.0 and 7.5 MPa absolute, or even between 3.0 and 5.5 MPa absolute. In all cases, in this embodiment, the temperature and pressure conditions are adjusted, in particular in an adjustment section implemented in sub-step b3) of extraction upstream of the extraction section, so that the extraction solvent is at least partly in the supercritical state in the extraction section.

[0104] In one particular embodiment, substep b3) of extraction employs supercritical extraction, and the extraction solvent is the same as the dissolving solvent, except that the extraction solvent is at least partially in a supercritical state. In this case of supercritical extraction, the dissolving solvent can become at least partially supercritical, advantageously optimizing decantation during the extraction step, particularly at each extraction phase or plateau, between the liquid phase and the supercritical phase, thereby maximizing purification.

[0105] Advantageously, at the end of substep b3) of extraction, the used solvent obtained is particularly laden with impurities, notably soluble impurities. It can be reprocessed in an organic treatment section allowing, on the one hand, the separation of at least some of the impurities and the purification of the solvent to obtain a purified extraction solvent, and on the other hand, the recycling of at least some of the purified extraction solvent back into b3), and / or into the inlet of step a) of dissolution in the case where the dissolution solvent and the extraction solvent are of the same nature. The used solvent can be treated by any method known to those skilled in the art, such as one or more methods including distillation, evaporation, extraction, adsorption, crystallization and precipitation of insolubles, or by purging.

[0106] Substep b4) of adsorption

[0107] The treatment process according to the invention may include an adsorption substep (b4) to obtain a refined polymer solution. The refined polymer solution obtained at the end of substep (b4) advantageously comprises the targeted thermoplastic polymers, in particular the targeted polyolefins, dissolved in the dissolving solvent. When integrated into the process according to the invention, the adsorption substep (b4) is advantageously implemented by contacting the polymer solution feeding it with one or more adsorbents.

[0108] When integrated into the process according to the invention, substep b4) of adsorption is preferably carried out in step b) of purification, upstream of step c) of solvent-polymer separation. However, it may also be carried out during step a) of dissolution, by introducing adsorbent particle(s) mixed with the crude polymer solution, said adsorbent particle(s) being removed during step b) of purification, optionally during substep b1) of insolubles separation or substep b2) of washing. Substep b4) of adsorption may also be carried out during step b) of purification, preferably downstream of substep b1) of insolubles separation and optionally upstream or downstream of substep b3) of extraction.

[0109] Substep b4) of adsorption advantageously employs an adsorption section operated in the presence of at least one adsorbent, preferably solid, and in particular in the form of a fixed bed, a slurry bed (i.e., particles introduced into the stream to be purified and carried along with it), or a bubbling bed, preferably in the form of a fixed or slurry bed, or even in the form of adsorbent particles dispersed in the polymer solution. The adsorbent(s) used in substep b4) is / are preferably alumina, silica, silica-alumina, activated carbon, bleaching earth, or mixtures thereof, preferably in the form of a fixed or slurry bed, with the flow of the streams being able to be upward or downward through said bed.

[0110] Advantageously, when integrated into the process, substep b4) of adsorption is carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, and at a pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 18.0 MPa absolute and most preferably between 1.5 and 15.0 MPa absolute. Advantageously, substep b4) of adsorption is carried out at the dissolution temperature and pressure conditions, i.e. at the dissolution temperature and dissolution pressure reached in step a), possibly with a lower pressure, preferably from 0.01 to 10.0 MPa, preferably from 0.1 to 5.0 MPa due to the pressure losses suffered between step a) and substep b4).Preferably, in substep b4), the hourly volumetric velocity (or WH), which corresponds to the ratio between the volumetric flow rate of the polymer solution that feeds b4) and the volume of adsorbent(s), advantageously in operation in b4), is between 0.05 and 10 h. -1 , preferably between 0.1 and 5.0 h -1 .

[0111] According to a particular embodiment of substep b4), the adsorption section may comprise one or more fixed bed(s) of adsorbent(s), for example in the form of adsorption column(s), preferably at least two adsorption columns, preferably between two and four adsorption columns, containing said adsorbent(s). When the adsorption section comprises two adsorption columns, one operating mode may be a so-called "swing" mode, in which one of the columns is in operation, while the other column is in reserve. When said adsorbent in the in-operation column is depleted, that column is isolated while the reserve column is brought into operation.The said at least one used adsorbent can then be regenerated in situ and / or replaced by said at least one fresh adsorbent so that the column containing it can be put back online once the other column has been isolated.

[0112] Another operating mode for this particular embodiment of b4) is to have at least two adsorbent columns operating in series. When the adsorbent(s) in the leading column is / are depleted, this first column is isolated, and the depleted adsorbent is regenerated in situ or replaced with fresh adsorbent(s). The column is then returned to the last position, and so on. This operation is called a permutable mode, or, in English, a "Permutable Reactor System" (PRS), or "lead and lag" in common English. The combination of at least two adsorption columns helps to mitigate the potential and rapid poisoning and / or clogging of at least one adsorbent due to the combined action of impurities, contaminants, and insoluble materials that may be present in the stream being treated.The presence of at least two adsorption columns facilitates the replacement and / or regeneration of the adsorbent (or adsorbents), advantageously without stopping the process, and also allows to control costs and limit the consumption of adsorbent(s).

[0113] Step c) of solvent-polymer separation

[0114] According to the invention, the process includes a solvent-polymer separation step (c) to obtain at least one stream of purified thermoplastic polymers, more particularly at least one stream of purified polyolefins. This step (c) is downstream of the purification step (b). It is advantageously fed with the purified polymer solution obtained at the end of the purification step (b).

[0115] Step c) of solvent-polymer separation aims to separate, at least in part, preferably predominantly, or even totally, the solvent(s), in particular the dissolving solvent, contained in the purified polymer solution which feeds step c), so as to recover the targeted thermoplastics, freed at least in part, preferably totally, of impurities and the dissolving solvent and possibly other solvent(s) optionally used in particular during step b) of purification (i.e. the extraction solvent and / or the dense solution).By predominantly, we must understand at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, most preferably at least 95% by weight, relative to the weight of the solvent(s) contained in the purified polymer solution that feeds step c), in particular the dissolving solvent and possibly the extraction solvent and / or the dense solution contained in the purified polymer solution that feeds step c).

[0116] Step c) of solvent-polymer separation advantageously comprises two phases (or sub-steps):

[0117] - a liquid-liquid separation or a supercritical-liquid separation, or even a succession of a liquid-liquid separation and a supercritical-liquid separation (in that order or the other order), and

[0118] - a gas-liquid separation, said gas-liquid separation being located downstream of the liquid-liquid separation and / or the supercritical liquid-liquid-liquid separation.

[0119] When incorporated in step (c), the liquid-liquid separation incorporates a liquid-liquid separation section to produce (i) a liquid phase comprising the targeted thermoplastics and generally a dissolving solvent (at a concentration lower than the dissolving solvent concentration of the purified polymer solution), and (ii) another liquid phase comprising dissolving solvent, also referred to as the liquid solvent phase. Preferably, the liquid solvent phase comprises little or no targeted thermoplastics. Preferably, the liquid solvent phase comprises less than 1% by weight, and preferably less than 0.01% by weight, of targeted thermoplastics relative to the total weight of the liquid solvent phase; and in particular, the liquid solvent phase is free of targeted thermoplastics.In the liquid-liquid separation section, the temperature and pressure conditions are advantageously adjusted so as to place the system (i.e. the polymer solution that feeds said liquid-liquid separation section) in a two-phase region of the corresponding polymer-solvent mixing diagram, in which two liquid phases coexist and can demix.In particular, the liquid-liquid separation section is carried out between 100°C and 300°C, preferably between 150°C and 250°C, and at a pressure between 0.1 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 18.0 MPa absolute, and most preferably between 1.5 and 15.0 Pa absolute, under temperature and pressure conditions different from the dissolution conditions achieved in step a), and in particular at a temperature higher than the dissolution temperature and / or at a pressure lower than the dissolution pressure, so as to be placed in a two-phase region of the corresponding polymer-solvent mixing diagram. The two liquid phases thus generated correspond to the liquid phase comprising the targeted thermoplastics and the liquid solvent phase; they can advantageously be separated, for example by decantation and / or centrifugation.

[0120] When incorporated in step (c), the supercritical-liquid separation incorporates a supercritical-liquid separation section to produce (i) a liquid phase comprising the targeted thermoplastics and generally some dissolving solvent (at a concentration lower than the dissolving solvent concentration of the purified polymer solution), and (ii) a supercritical phase comprising dissolving solvent, also referred to as the supercritical solvent phase. Preferably, the supercritical solvent phase comprises little or no targeted thermoplastics. Preferably, the supercritical solvent phase comprises less than 1% by weight, and preferably less than 0.01% by weight, of targeted thermoplastics relative to the total weight of the supercritical solvent phase; and in particular, the supercritical solvent phase is free of targeted thermoplastics.In the supercritical-liquid separation section, the temperature and pressure conditions are advantageously adjusted so that the dissolving solvent, in particular present in the polymer solution which feeds said supercritical-liquid separation section (i.e. in the purified polymer solution), is at least partly in the supercritical state, preferably so that at least 20% by weight, preferably at least 50% by weight, preferably at least 70% by weight of the dissolving solvent of the purified polymer solution is in supercritical form.Preferably, the supercritical-liquid separation section is operated at a temperature between 100 and 350°C, preferably between 130°C and 320°C, preferably between 180°C and 280°C, and at a pressure preferably between 2.0 and 100.0 MPa absolute, preferably between 2.0 and 25.0 MPa absolute, preferably between 2.0 and 18.0 MPa absolute, most preferably between 2.7 and 15.0 MPa absolute and most preferably between 3.0 and 7.5 MPa absolute, or even between 3.0 and 5.5 MPa absolute, and such that the dissolving solvent of the polymer solution that feeds said supercritical-liquid separation section is at least partly in supercritical form. Two phases, a liquid phase and a supercritical phase, are then generated: the liquid phase corresponding to said liquid phase including the targeted thermoplastics, and the supercritical phase corresponding to said supercritical solvent phase including the dissolving solvent.The two phases generated, the liquid phase comprising the targeted thermoplastics and the supercritical solvent phase, can be advantageously separated, for example by decantation and / or centrifugation.

[0121] According to a first preferred embodiment, step c) comprises a liquid-liquid separation followed by a gas-liquid separation. The liquid-liquid separation section implemented in step c) is therefore fed by the purified polymer solution, obtained at the end of purification step b), and the liquid phase comprising the targeted thermoplastics, obtained at the end of the liquid-liquid separation section, feeds the gas-liquid separation (i.e. the gas-liquid separation section or first section).

[0122] According to another preferred embodiment, step c) comprises a supercritical-liquid separation followed by a gas-liquid separation. The supercritical-liquid separation section implemented in step c) is therefore fed by the purified polymer solution, obtained at the end of purification step b), and the liquid phase comprising the targeted thermoplastics, obtained at the end of the supercritical-liquid separation section, feeds the gas-liquid separation (i.e. the gas-liquid separation section or first section).

[0123] According to yet another embodiment, step c) comprises a succession of liquid-liquid separation and supercritical-liquid separation, in this order: liquid-liquid separation followed by supercritical-liquid separation, or in the reverse order: supercritical-liquid separation followed by liquid-liquid separation, followed by gas-liquid separation. In this particular embodiment:

[0124] - the first liquid-liquid or supercritical-liquid separation section implemented in step c), i.e., the first section of the liquid-liquid and supercritical-liquid separation sequence, is fed with the purified polymer solution obtained at the end of purification step b), - the liquid phase comprising the targeted thermoplastics, obtained at the end of said first liquid-liquid or supercritical-liquid separation section, feeds the second liquid-liquid or supercritical-liquid separation section implemented in step c), i.e., the second section of the liquid-liquid and supercritical-liquid separation sequence, and

[0125] - the liquid phase comprising the thermoplastics in question, obtained at the end of said second liquid-liquid or supercritical-liquid separation section, then feeds the gas-liquid separation (i.e. the gas-liquid separation section or first section).

[0126] Advantageously, the liquid solvent phase obtained at the end of the liquid-liquid separation section and / or the supercritical solvent phase obtained at the end of the supercritical-liquid separation section is recovered and sent to step d) of recycling the dissolving solvent.

[0127] Step c) of solvent-polymer separation advantageously includes a gas-liquid separation downstream of the liquid-liquid and / or supercritical-liquid separation. This gas-liquid separation incorporates one or more (i.e., at least two) gas-liquid separation sections, in particular one gas-liquid separation section or a series of N gas-liquid separation sections, where N is an integer greater than or equal to two, preferably between two and ten, and preferably between two and five, for example, two, three, or four. When the gas-liquid separation in step c) incorporates several gas-liquid separation sections, i.e., a series of N gas-liquid separation sections, the gas-liquid separation in step c) may incorporate one or more intermediate gas-liquid separation sections located between the first and last gas-liquid separation sections.Thus, when step c) (or rather the gas-liquid separation of step c)) uses a series of 2 gas-liquid separation sections, there is no intermediate gas-liquid separation section. When step c) uses a series of 3 gas-liquid separation sections, there is one intermediate gas-liquid separation section. When step c) uses a series of 4 gas-liquid separation sections, there are two successive intermediate gas-liquid separation sections; and so on until a series of N gas-liquid separation sections is used, which corresponds to the use of (N-2) successive intermediate sections.

[0128] The separation principle in the gas-liquid separation sections relies on the evaporation, at least in part, of the solvent, in particular the dissolving solvent, present in the polymer solution that feeds the gas-liquid separation section(s). This solvent (or fraction thereof), then in gaseous form, is separated from the polymer solution, which is in liquid form. Thus, the gas-liquid separation section(s) produce a gaseous effluent, which advantageously comprises dissolving solvent in gaseous form, and a liquid effluent, which advantageously comprises the thermoplastics in question, possibly dissolved in a residual fraction of dissolving solvent. Preferably, the gaseous effluent produced by the gas-liquid separation section(s) contains little or no thermoplastics in question.Preferably, the gas effluent produced comprises less than 1% by weight, and preferably less than 0.01% by weight, of the thermoplastics in question relative to the total weight of said gas effluent; in particular, the gas effluent produced is free of the thermoplastics in question. When the liquid effluent includes a residual fraction of dissolving solvent, the thermoplastics in question may be dissolved in the residual dissolving solvent, and the liquid effluent then corresponds to a polymer solution. Most advantageously, the liquid effluent from the last gas-liquid separation section of the series comprises preferably not more than 5% by weight, preferably not more than 1.00% by weight, most preferably not more than 0.10% by weight, or even not more than 500 ppm by weight of solvent, relative to the total weight of said liquid effluent, and advantageously constitutes said purified thermoplastic polymer stream.

[0129] The liquid phase comprising the targeted thermoplastics, obtained at the end of the liquid-liquid separation section or the supercritical-liquid separation section implemented in step c) or obtained at the end of the second liquid-liquid or supercritical-liquid separation section implemented in step c) (i.e. when step c) implements a succession of liquid-liquid and supercritical-liquid separations), feeds the gas-liquid separation section or the first gas-liquid separation section of the series.

[0130] When the gas-liquid separation in step c) employs a series of N gas-liquid separation sections, the liquid effluent from the preceding gas-liquid separation section feeds into the subsequent gas-liquid separation section, up to the last gas-liquid separation section in the series, the resulting liquid effluent of which advantageously constitutes the stream of purified thermoplastic polymers. In other words, when the gas-liquid separation in step c) employs a series of several gas-liquid separation sections:

[0131] - the purified polymer solution, obtained at the end of step b) of purification, feeds the liquid-liquid separation section or the supercritical-liquid separation section, or even the first liquid-liquid or supercritical-liquid separation section of the succession of liquid-liquid and supercritical-liquid separations implemented;

[0132] - the liquid phase comprising the thermoplastics concerned, obtained at the end of the liquid-liquid separation section implemented or the supercritical-liquid separation section implemented, or even obtained at the end of the second liquid-liquid or supercritical-liquid separation section of the succession of liquid-liquid and supercritical-liquid separations implemented, feeds the first gas-liquid separation section of the series, which produces a first gas effluent and a first liquid effluent;

[0133] - the first liquid effluent obtained at the end of the first gas-liquid separation section feeds the second gas-liquid separation section which produces a second gas effluent and a second liquid effluent;

[0134] - and so on up to the Nth section which is fed by the (N-1)th liquid effluent obtained at the end of the (N - 1)th gas-liquid separation section of the series and which produces an Nth gas effluent and an Nth liquid effluent,

[0135] - the Nth liquid effluent obtained at the end of the Nth gas-liquid separation section advantageously constitutes the stream of purified thermoplastic polymers.

[0136] Advantageously, the gas effluent(s) produced by the gas-liquid separation section(s) is / are recovered and sent to step d) of the dissolution solvent recycling.

[0137] Advantageously, the gas-liquid separation section or sections implemented in step c) are operated at an inlet temperature (i.e., at the inlet of each section) between 100°C and 300°C, preferably between 110°C and 275°C, preferably between 150°C and 250°C. Very advantageously, the temperature is adjusted, in the gas-liquid separation section or each of the gas-liquid separation sections, so as to have an operating temperature greater than or equal to the evaporation temperature of the solvent, in particular the dissolving solvent, and advantageously greater than or equal to the melting temperature of the thermoplastics concerned, at the operating pressure of the gas-liquid separation section considered.Advantageously, the gas-liquid separation section(s) implemented in step c) is operated at a pressure lower than the pressure of the liquid-liquid or supercritical liquid separation section, in particular at a pressure lower than 100.0 MPa absolute, preferably lower than 25.0 MPa absolute, preferably lower than 18.0 MPa absolute, and preferably lower than 15.0 MPa absolute. Preferably, in the gas-liquid separation section(s) implemented in step c), the pressure is greater than or equal to 0.000005 MPa absolute, in particular greater than or equal to 0.00001 MPa absolute, in particular greater than or equal to 0.0001 MPa absolute, more particularly greater than or equal to 0.0005 MPa absolute, and particularly greater than or equal to 0.0008 MPa absolute. Preferably, when step c) implements multiple gas-liquid separation sections, the pressure of the later section is lower than that of the earlier section.In other words, preferably, the pressure in the second gas-liquid separation section of the series of several gas-liquid separation sections is less than that in the first gas-liquid separation section of the series, and so on up to the Nth gas-liquid separation section in which the pressure is less than the pressure in the (N-1)th gas-liquid separation section, the pressure of the first section of the series being less than the pressure in the liquid-liquid or supercritical liquid separation section.

[0138] The gas-liquid separation section(s) may implement any type of device known to those skilled in the art for separating gas and liquid, possibly accompanied by means for adjusting temperature and pressure, for example equipment for heating, equipment for adjusting and controlling pressure above atmospheric pressure, equipment for adjusting and controlling pressure below atmospheric pressure (to obtain a vacuum), etc.; mechanical means in particular equipment for moving and bringing the gas and liquid phases into contact.For example, the gas-liquid separation section(s) may implement one or more pieces of equipment chosen from: a separator flask, a column, a distillation column, a stripper, equipment with internals and / or packing facilitating separation between gas and liquid, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating-disc reactor or column, a reactor, a stirred-reactor, an extruder, a kneading reactor, a devolatilizer.

[0139] Optionally, an entraining agent (or stripping agent) may be introduced into the gas-liquid separation section or the last (i.e., the Nth) gas-liquid separation section in the series to aid the vaporization of residual solvent present in the polymer solution entering the inlet of the section. Adding an entraining agent thus optimizes solvent-polymer separation. The entraining agent introduced into the gas-liquid separation section is a compound with a boiling point lower than that of the dissolving solvent (at atmospheric pressure), for example, a compound chosen from water, nitrogen, or hydrogen. Preferably, the amount of entraining agent introduced represents between 10% and 0.1% by weight of the target thermoplastics.

[0140] Optionally, at least one additive may be introduced in step c), and / or possibly upstream of step c). For example, an antioxidant may be introduced in step c), and / or possibly upstream of step c), in order to limit, or even prevent, any degradation of the thermoplastics in question. Those skilled in the art will be able to select this at least one additive, in particular this antioxidant, according to the thermoplastics in question. For example, the antioxidant may be selected from the compounds marketed under the Irganox® and Irgafos® trademarks, and in particular from the following commercial compounds: Irganox® 1010, Irgafos® 168, and Irgafos® 168 oxidized. Those skilled in the art will also be able to adjust the quantity of this at least one additive, in particular this antioxidant, according to the thermoplastics in question and the desired properties.For example, the antioxidant agent may be introduced so as to have a content of said antioxidant agent between 100 and 10,000 ppm by weight, preferably between 500 and 5,000 ppm by weight of antioxidant agent relative to the weight of the thermoplastics concerned, advantageously in the polymer solution which feeds step c), i.e. in the purified polymer solution, or in the liquid phase comprising the thermoplastics concerned, obtained at the end of the liquid-liquid separation section or the supercritical-liquid separation section, or in the (or at least one of the) liquid effluent(s) produced by the gas-liquid separation section(s).

[0141] Step d) Recycling of the dissolving solvent

[0142] According to the invention, the process includes a step d) for recycling the dissolving solvent. Indeed, step d) advantageously allows for the reinjection into step a) of the dissolution process of at least a fraction of the dissolving solvent stream, recovered in step c) and judiciously purified in step d) so as to prevent any accumulation of impurities in the process while maintaining controlled or even optimized energy consumption. Step d) produces a recycled solvent stream, optionally dried, which advantageously constitutes at least a portion of the dissolving solvent stream feeding step a).

[0143] Step d) includes, preferably consisting of, at least one of the following substeps:

[0144] - a substep d1) comprising, preferably consisting of, the direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section implemented in step c) and / or of a reliquefied solvent phase obtained from at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section implemented in step c), to make up at least part of the recycled solvent stream;

[0145] - a substep of 1) comprising, preferably consisting of, the purification of at least a fraction of the liquid solvent phase and / or the supercritical solvent phase, by tailing, and possibly topping, of said at least a fraction of the liquid solvent phase and / or the supercritical solvent phase obtained in step c), to obtain a purified solvent phase, then the transfer of at least a part of the purified solvent phase to step a) to make up at least a part of the recycled solvent stream;

[0146] - a sub-step d2) of purification of at least one gaseous effluent obtained in step c), comprising:

[0147] - where the gas-liquid separation of step c) employs a gas-liquid separation section, the topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, and then the transfer of at least a portion of the purified solvent effluent to step a) to make up at least a portion of the recycled solvent stream; or

[0148] - when the gas-liquid separation of step c) uses several gas-liquid separation sections, a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the intermediate gas-liquid separation section(s)), to separate at least some of the light impurities and obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the intermediate gas-liquid separation section(s)), to separate at least some of the heavy impurities and obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent,to make up at least part of the recycled solvent stream.

[0149] Preferably, step d) includes, preferably consists of:

[0150] - a substep d2) of purification of at least one gas effluent obtained in step c), comprising: a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section of c), to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a) to make up at least a part of the recycled solvent stream;or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section of the series implemented in c) (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate section(s)), to separate at least some of the light impurities and obtain a topped solvent effluent, and / or a topping of at least a fraction of the gas effluent from the last gas-liquid separation section of the series implemented in c) (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate section(s)), to separate at least some of the heavy impurities and obtain a topped solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the topped solvent effluent, to make up at least some of the recycled solvent stream;

[0151] - and possibly: a substep d1) of direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section of step c) and / or of a reliquefied solvent phase obtained from at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section of step c), to make up at least part of the recycled solvent stream, and / or a substep d1) comprising the purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, by stemming, and possibly topping, to obtain a purified solvent phase, then the transfer of at least part of the purified solvent phase to step a) to make up at least part of the recycled solvent stream.

[0152] According to the description, an intermediate gas-liquid separation section corresponds to any gas-liquid separation section implemented in step c) between the first and last gas-liquid separation sections, when step c) (or rather the gas-liquid separation in step c)) implements several gas-liquid separation sections, and in particular at least three gas-liquid separation sections. Thus, when step c) implements a series of two gas-liquid separation sections, there is no intermediate gas-liquid separation section. When step c) implements a series of three gas-liquid separation sections, there is one intermediate gas-liquid separation section.When step c) implements a series of 4 gas-liquid separation sections, there are two successive intermediate gas-liquid separation sections; and so on until the implementation of a series of N gas-liquid separation sections which corresponds to the implementation of (N-2) successive intermediate sections.

[0153] Step d) may also possibly include purging at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of the supercritical solvent phase from the supercritical-liquid separation section.

[0154] When the gas-liquid separation of step c) employs a gas-liquid separation section, step d) may also optionally include purging and / or direct recycling to the dissolution step a) (i.e. without purification, in particular by topping and / or tailing, prior to transfer to the dissolution step a) of at least a fraction of the gas effluent from the gas-liquid separation section.

[0155] Where the gas-liquid separation of step c) employs several gas-liquid separation sections, step d) may also optionally include purging and / or direct recycling to the dissolution step a) (i.e. without purification, in particular by topping and / or tailing, prior to transfer to the dissolution step a) of at least a fraction of the gas effluent from the first gas-liquid separation section, and / or at least a fraction of the gas effluent from the last gas-liquid separation section, and / or, where appropriate, at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s).

[0156] Thus, according to a first particular embodiment, step d) comprises:

[0157] - a substep d1) comprising the direct recycling to step a) of at least a fraction, preferably all of it, of the liquid solvent phase from the liquid-liquid separation section and / or at least a fraction, preferably all of it, of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and

[0158] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0159] According to a second particular embodiment, step d) comprises:

[0160] - a substep of 1) comprising the purification of at least a fraction of the liquid solvent phase and / or the supercritical solvent phase, by stemming, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and

[0161] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0162] According to a third particular embodiment, step d) comprises:

[0163] - a substep of 1) comprising the purification of at least a fraction of the liquid solvent phase and / or the supercritical solvent phase, by stemming and topping, simultaneously or successively, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and

[0164] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0165] According to a fourth particular embodiment, step d) comprises:

[0166] - a substep d1) comprising the direct recycling to step a) of a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and

[0167] - a sub-step of 1) comprising the purification of a fraction of the liquid solvent phase and / or the supercritical solvent phase, by tailing, and possibly topping, to obtain a purified solvent phase, then the transfer of at least part of the purified solvent phase to step a);

[0168] - possibly a purging of a fraction of the liquid solvent phase from the liquid-liquid separation section or of the supercritical solvent phase from the supercritical-liquid separation section, possibly reliquefied; and

[0169] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0170] According to a fifth particular embodiment, step d) comprises:

[0171] - purging of a fraction or all of the liquid solvent phase from the liquid-liquid separation section and / or of the supercritical solvent phase from the supercritical-liquid separation section; and

[0172] - possibly a substep d1) comprising the direct recycling to step a) of a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and

[0173] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0174] According to a sixth particular embodiment, step d) comprises:

[0175] - purging of a fraction or all of the liquid solvent phase from the liquid-liquid separation section and / or of the supercritical solvent phase from the supercritical-liquid separation section; and

[0176] - possibly a substep of 1) comprising the purification of a fraction of the liquid solvent phase and / or the supercritical solvent phase, by stemming and possibly topping, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and

[0177] - a sub-step d2) comprising a topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section, to obtain a purified solvent effluent, then the transfer of at least a part of the purified solvent effluent to step a);or a topping of at least a fraction of the gas effluent from the first gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a topped solvent effluent, and / or a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section (and possibly at least a fraction of the gas effluent from the (or one of the) intermediate gas-liquid separation section(s)) to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or at least a fraction of the tailed solvent effluent.;

[0178] According to a seventh particular embodiment, step c) implements a single gas-liquid separation section and step d) comprises:

[0179] - a substep d1) comprising the direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and / or a substep d1) comprising the purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, by tailing and possibly topping, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and

[0180] - a purge and / or direct recycling to step a) (i.e. without purification, in particular by topping and / or tailing, prior to transfer to step a) of dissolution) of at least a fraction of the gas effluent from the gas-liquid separation section.

[0181] According to a particular eighth embodiment, step c) implements several gas-liquid separation sections and step d) comprises:

[0182] - a substep d1) comprising the direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and / or a substep d1) comprising the purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, by tailing and possibly topping, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and - a purification substep d2) comprising topping at least a fraction of the gas effluent from the first gas-liquid separation section to obtain a topped solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent, and

[0183] - a purge and / or direct recycling to step a) (i.e. without purification, in particular by topping and / or tailing, prior to transfer to step a) of dissolution) of at least a fraction of the gas effluent from the last gas-liquid separation section.

[0184] In this eighth embodiment, the possible gas effluent(s) from the intermediate gas-liquid separation section(s) may be, in whole or in part: purified by topping, the topped solvent then being, at least in part, transferred to step a); purged; and / or recycled directly to step a).

[0185] According to a ninth particular embodiment, step c) implements several gas-liquid separation sections and step d) comprises:

[0186] - a substep d1) comprising the direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from the supercritical solvent phase from the supercritical-liquid separation section; and / or a substep d1) comprising the purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, by tailing and possibly topping, to obtain a purified solvent phase, then the transfer of at least a portion of the purified solvent phase to step a); and

[0187] - purging and / or direct recycling to step a) (i.e., without purification, in particular by topping and / or tailing, prior to transfer to step a) of dissolution) of at least a fraction of the gas effluent from the first gas-liquid separation section; and

[0188] - a sub-step d2) of purification comprising tailing at least a fraction of the gas effluent from the last gas-liquid separation section, then transferring to step a) at least a fraction of the tailed solvent effluent.

[0189] In this ninth embodiment, the possible gas effluent(s) from the intermediate gas-liquid separation section(s) may be, in whole or in part: purified by tailing, the tailed solvent then being, at least in part, transferred to step a); purged; and / or recycled directly to step a).

[0190] When step d) includes a purification substep d) that includes stemming and topping, stemming and topping may be carried out simultaneously (e.g., in the same distillation column) or successively (e.g., in two separate distillation columns). If stemming and topping in d) are carried out successively, the topping in d) may be located upstream or downstream of the stemming in d) (preferably upstream of the stemming in d) ().

[0191] Optionally, step d) may also include a substep d3) of transferring a fraction or all, preferably a fraction, of the liquid or supercritical solvent phase, from the liquid-liquid or supercritical-liquid separation section respectively, to step b), for example to be used as an extraction solvent in a substep b3) or to clean filters implemented in a substep b1).Thus, according to one possible variant, a first fraction of the liquid or supercritical solvent phase from the liquid-liquid or supercritical-liquid separation section respectively is sent to the tailing substep of 1), a second fraction of the liquid or supercritical solvent phase is recycled directly upstream of step a) in a substep d1), a third fraction of the liquid or supercritical solvent phase is used in step b) for example as an extraction solvent in a substep b3) or to clean filters implemented in a substep b1), possibly an additional fraction of the liquid or supercritical solvent phase may be purged.According to another variant, a first fraction of the liquid or supercritical solvent phase from the liquid-liquid or supercritical-liquid separation section respectively is sent to the de-tailing sub-step of 1) or is recycled directly upstream of step a) in a sub-step d1), and a second fraction of the liquid or supercritical solvent phase is used in step b) for example as an extraction solvent in a sub-step b3) or to clean filters implemented in a sub-step b1), optionally an additional fraction of the liquid or supercritical solvent phase may be purged.

[0192] When step c) implements a supercritical-liquid separation section and thus when a supercritical solvent phase is obtained at the end of step c), and when step d) includes a direct recycling substep d1), step d) advantageously includes an adjustment of the temperature and / or pressure, carried out upstream of said substep d1 (and advantageously downstream of the supercritical-liquid separation section of step c), such that the solvent, in particular the dissolving solvent, present in said at least a fraction of the supercritical solvent phase sent to substep d1 (i.e.present in said supercritical solvent phase intended to be recycled directly to step a) without purification), becomes entirely in liquid form before substep d1), that is, before its recycling to a), in other words, so as to obtain the reliquefied solvent phase from at least a fraction of the supercritical solvent phase. This adjustment of temperature and / or pressure can be called the liquefaction adjustment.

[0193] When step c) implements a supercritical-liquid separation section and therefore when a supercritical solvent phase is obtained at the end of step c), and when step d) includes a substep d1) of purification and / or optionally a substep d3) of transfer to step b), step d) preferably includes an adjustment d0) of the temperature and / or pressure, carried out upstream of substep d1) and / or optionally of the optional substep d3) (and advantageously downstream of the supercritical-liquid separation section of step c), so that the solvent, in particular the dissolving solvent, present in said at least a fraction of the supercritical solvent phase sent to substep d1) and / or possibly substep d3), becomes entirely in a non-supercritical state before substep d1) and / or possibly substep d3).In this description, a non-supercritical state means a gaseous state, a liquid state, and / or a gaseous-liquid equilibrium state in which both forms coexist, and advantageously, the absence of a supercritical state. This adjustment of (0) the temperature and / or pressure can be called the non-supercritical adjustment. It allows a non-supercritical solvent phase to be obtained from at least a fraction of the supercritical solvent phase. Preferably, this non-supercritical solvent phase feeds into substep (1) of purification and / or optionally into substep (3) of transfer to step (b), when step (c) implements a supercritical-liquid separation section, instead of the supercritical solvent phase.

[0194] Optionally, when step d) includes a substep d1) of direct recycling of a fraction of the supercritical solvent phase and a substep d1) of purification of a second fraction of the supercritical solvent phase, and / or optionally a substep d3) of transfer to step b), the adjustment d1) of liquefaction and the adjustment d2) of non-supercritical may be separate (i.e. different) or common (i.e. identical), preferably common, i.e. preferably carried out simultaneously and in the same temperature and / or pressure control equipment.

[0195] Optionally, step d) may include at least a partial condensation d’0) of the gas effluent from the gas-liquid separation section of step c) or of the gas effluent from the first gas-liquid separation section of step c) and / or of the gas effluent from the last gas-liquid separation section of step c), in particular in a partial condenser, prior to substep d2) of purification, to obtain a partial condenser gas fraction, which includes dissolving solvent and possibly light impurities, and a partial condenser liquid fraction, which includes dissolving solvent and possibly heavy impurities.Said partial condenser gaseous fraction may advantageously be, in part or in whole, sent to a topping in substep d2) of purification, purged and / or recycled to step a), and said partial condenser liquid fraction may advantageously be, in part or in whole, sent to a topping in substep d2) of purification, purged and / or recycled to step a).

[0196] When step c) implements at least three gas-liquid separation sections downstream of the liquid-liquid separation section and / or the supercritical-liquid separation section, at least a fraction of the gas effluent from the or at least one intermediate gas-liquid separation section of step c) may be sent to substep d2), advantageously to the topping and / or tailing implemented in substep d2), and / or may be recycled directly to a) and / or may be purged.Optionally, the gas effluent from at least one intermediate gas-liquid separation section of step c) may be partially condensed, in particular in a partial condenser, prior to sub-step d2), to obtain a partial condenser gas fraction, which includes dissolving solvent and possibly light impurities, and a partial condenser liquid fraction, which includes dissolving solvent and possibly heavy impurities, said partial condenser gas fraction being, in part or in whole, sent to the topping of sub-step d2), purged and / or recycled to step a), and said partial condenser liquid fraction being, in part or in whole, sent to the topping of sub-step d2), and / or purged and / or recycled to step a).

[0197] In this description, topping advantageously corresponds to a purification of the treated stream, in particular to a purification of at least a fraction of the liquid and / or supercritical solvent phase when topping is carried out in said substep d1), and / or to a purification of the gas effluent from the gas-liquid separation section of step c) or of the gas effluent from the first gas-liquid separation section of step c) and possibly of the intermediate gas-liquid separation section(s) when topping is carried out in said substep d2), to separate and remove light impurities possibly present in the treated stream, i.e. to remove compounds whose boiling point (in particular at atmospheric pressure) is lower than that of the dissolving solvent.

[0198] In this description, tailing advantageously corresponds to a purification of the treated stream, in particular to a purification of at least a fraction of the liquid and / or supercritical solvent phase in substep d1) when implemented, and / or to a purification of the gas effluent from the gas-liquid separation section of step c) or of the gas effluent from the last gas-liquid separation section of step c) and possibly of the intermediate gas-liquid separation section(s) when tailing is implemented in said substep d2), to separate and remove heavy impurities possibly present in the treated stream, i.e. to remove compounds whose boiling point (in particular at atmospheric pressure) is higher than that of the dissolving solvent.

[0199] Advantageously, the purification substep 1) incorporates a tailing section. The tailing section of substep 1) preferably includes at least one gas-liquid separation device, possibly accompanied by means for adjusting temperature and pressure (in particular, temperature and pressure control and adjustment equipment). For example, the tailing section of substep 1) may incorporate one or more pieces of equipment selected from: a partial condenser, a separator flask, a column, a distillation column, a stripper, equipment incorporating internals and / or packing that facilitates gas-liquid separation, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating-disc reactor or column, a reactor, a stirred-film reactor, an extruder, a kneading reactor, or a devolatilizer.Preferably, the stemming section of substep 1) implements at least one stemming distillation column.

[0200] Optionally, substep 1) may also implement a topping section, which preferably includes at least one gas-liquid separation device, possibly accompanied by means for adjusting temperature and pressure (in particular, temperature and pressure control and adjustment equipment). For example, the topping section may implement one or more pieces of equipment selected from: a partial condenser, a separator flask, a column, a distillation column, a stripper, equipment incorporating internals and / or packing that facilitates gas-liquid separation, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating-disc reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, a devolatilizer; and preferably, at least implements a topping distillation column.

[0201] According to a particular embodiment, substep 1) comprises tailing and topping and therefore implements a tailing section and a topping section, which may be identical (i.e., common to each other) or different (i.e., distinct from each other). According to a variant of this particular embodiment, the tailing section of substep 1) and the topping section of substep 1) are identical (or common), i.e., a single purification section (for example, a single distillation column) is implemented in 1) to separate the light and heavy impurities, advantageously recovering the light impurities at the top of the section, the heavy impurities at the bottom of the column, and a purified solvent phase in an intermediate zone. This is the case where the topping and the trimming in d'1) are carried out simultaneously.According to another variant of the particular embodiment in which substep d1) comprises tailing and topping, the tailing section of substep d1) and the topping section of substep d1) are different (or distinct). In this other variant in which tailing and topping are carried out successively, the topping section of d1) may be located upstream or downstream of the tailing section of d1). Thus, said at least a fraction of the liquid solvent phase and / or said at least a fraction of the supercritical solvent phase (advantageously the non-supercritical solvent phase) which feeds substep d1), and which has optionally undergone an adjustment d0) of the temperature and / or pressure (non-supercritical adjustment) prior to d1), feeds:.

[0202] - the topping section of d'1), to separate the light impurities, then the topped stream, in particular recovered at the bottom of the topping section of d'1), feeds the tailing section of d'1), to separate the heavy impurities and thus advantageously recover the purified solvent phase, in particular at the head of the tailing section, or

[0203] - the tailing section of d'1), to separate heavy impurities, then the tailed stream, in particular recovered at the head of the tailing section of d'1), feeds the topping section of d'1), to separate light impurities and thus advantageously recover the purified solvent phase in particular at the bottom of the topping section.

[0204] Preferably, in this other variant, the topping section of d'1) is advantageously located upstream of the tailing section of d'1).

[0205] Advantageously, the purification substep d2) implements a topping section and / or a tailing section. The topping section of substep d2), when implemented, preferably includes at least one gas-liquid separation device, possibly accompanied by means for adjusting the temperature and pressure (in particular temperature and pressure control and adjustment equipment).For example, the topping section of substep d2) may employ one or more pieces of equipment selected from: a partial condenser, a separator flask, a column, a distillation column, a stripper, equipment incorporating internals and / or packing to facilitate gas-liquid separation, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating disk reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, or a devolatilizer. Preferably, the topping section of substep d2) employs at least one topping distillation column.The tailing section of substep d2), when implemented, preferably includes at least one gas-liquid separation device, possibly accompanied by means for adjusting temperature and pressure (in particular, temperature and pressure control and adjustment equipment). For example, the tailing section of substep d2) may implement one or more pieces of equipment selected from: a partial condenser, a separator flask, a column, a distillation column, a stripper, equipment incorporating internals and / or packing facilitating gas-liquid separation, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating disk reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, a devolatilizer.Preferably, the stemming section of substep d2) implements at least one stemming distillation column.

[0206] According to a particular embodiment, the purification substep d2) includes topping and tailing and therefore implements a topping section and a tailing section, which may be identical or different from each other (i.e., respectively common or distinct from each other).

[0207] According to one variant of this particular embodiment, the topping section of substep d2) and the tailing section of substep d2) are identical (or common), i.e., a single purification section (for example, a single distillation column) is implemented in substep d2) to separate the light and heavy impurities, advantageously recovering the light impurities at the top of the section, the heavy impurities at the bottom of the column, and a purified solvent effluent (i.e., a solvent effluent that has been topped and tailed) in an intermediate zone. This is, for example, the case where tailing and topping in d2) are carried out simultaneously.

[0208] According to another variant of the particular embodiment in which substep d2) includes topping and tailing, the topping section of substep d2) and the tailing section of substep d2) are different (or distinct).

[0209] In this alternative variant, and when step c) uses a single gas-liquid separation section, the tailing and topping are carried out successively, the topping section of d2) being able to be located upstream or downstream of the tailing section of d2). Thus, in this very specific case (i.e., according to this alternative variant in which substep d2) includes topping and tailing, and when step c) uses a single gas-liquid separation section, with tailing and topping being carried out successively), said at least a fraction of the gas effluent from the gas-liquid separation section that feeds substep d2) feeds:

[0210] - the topping section of d2), to separate the light impurities, then the topped flow recovered at the bottom of the topping section of d2) feeds the tailing section of d2), to separate the heavy impurities and thus advantageously recover the purified solvent effluent in particular at the top of the tailing section, or - the tailing section of d2), to separate the heavy impurities, then the tailed flow recovered at the top of the tailing section of d2) feeds the topping section of d2), to separate the light impurities and thus advantageously recover the purified solvent effluent in particular at the bottom of the tailing section.

[0211] Preferably, in this very specific case, the topping section of d2) is advantageously located upstream of the tailing section of d2).

[0212] According to this alternative variant in which substep d2) includes a separate topping section and tailing section, and where step c) implements several gas-liquid separation sections, the topping section and tailing section, implemented in substep d2), can be operated simultaneously and are then fed by very different flows, the topping section being at least fed by at least a fraction of the gas effluent from the first gas-liquid separation section and the tailing section being at least fed by at least a fraction of the gas effluent from the last gas-liquid separation section.

[0213] Optionally, when step d) includes a purification substep d1) and a stemming substep d2, the stemming section of d1) and the stemming section of d2) may be the same or different. Similarly, if substep d1) further includes topping and substep d2) includes topping, the topping section of d1) and the topping section of d2) may be the same or different.

[0214] When d'1) only includes purification by tailing (i.e. no topping), the tailed solvent stream obtained in d'1) corresponds to said purified solvent phase produced in d'1) and which is transferred at least in part to the dissolution step a).

[0215] When d'1) includes a purification by stemming and topping, and the topping being upstream of the stemming, the stream of topped solvent obtained in d'1) is sent at least in part to the stemming section of d'1) and the stream of topped solvent obtained in d'1) corresponds to said purified solvent phase produced in d'1) and which is transferred at least in part to the dissolution step a).

[0216] When d'1) includes a purification by stemming and topping, and the topping being downstream of the stemming, the stream of stemmed solvent obtained in d'1) is sent at least in part to the topping section of d'1) and the stream of topped solvent obtained in d'1) corresponds to said purified solvent phase produced in d'1) and which is transferred at least in part to the dissolution step a).

[0217] When d'1) includes purification by stemming and topping carried out simultaneously (in particular implemented in a common purification section), the purified solvent stream obtained in d'1) corresponds to said purified solvent phase produced in d'1) and which is transferred at least in part to the dissolution step a).

[0218] When step c) implements a single gas-liquid separation section and if d2) is implemented and includes only purification by topping (i.e. no tailing), the topped solvent stream obtained in d2) corresponds to said purified solvent effluent produced in d2) and which is transferred at least in part to step a) of dissolution.

[0219] When step c) implements a single gas-liquid separation section and if d2) is implemented and includes only purification by tailing (i.e. no topping), the tailed solvent stream obtained in d2) corresponds to said purified solvent effluent produced in d2) and which is transferred at least in part to step a) of dissolution.

[0220] When step c) implements a single gas-liquid separation section and if d2) is implemented and includes successive purification by topping and tailing, with topping being upstream of tailing, the flow of topped solvent in obtained d2) is sent at least in part to the tailing section obtained from d2) and the flow of tailed solvent in d2) corresponds to said purified solvent effluent produced in d2) and which is transferred at least in part to the dissolution step a).

[0221] When step c) implements a single gas-liquid separation section and if d2) is implemented and includes successive purification by topping and tailing, with topping being downstream of tailing, the tailed solvent stream obtained in d2) is sent at least in part to the topping section of d2) and the tailed solvent stream obtained in d2) corresponds to said purified solvent effluent produced in d2) and which is transferred at least in part to the dissolution step a).

[0222] When step c) implements a single gas-liquid separation section and if d2) is implemented and includes purification by topping and tailing, simultaneously, the purified solvent stream obtained in d2), advantageously in an intermediate zone of the topping-tailing section, corresponds to said purified solvent effluent produced in d2) and which is transferred at least in part to step a) of dissolution.

[0223] When step c) implements multiple gas-liquid separation sections and if d2) is implemented, d2) includes purification by topping of at least a fraction of the gas effluent from the first gas-liquid separation section and / or tailing of at least a fraction of the gas effluent from the last gas-liquid separation section, the topped solvent stream and / or tailed solvent stream obtained in d2) being transferred at least in part to step a) of dissolution, to make up at least part of the recycled solvent stream.Optionally, when d2) includes a topping of at least a fraction of the gas effluent from the first gas-liquid separation section and a tailing of at least a fraction of the gas effluent from the last gas-liquid separation section, the tailed solvent stream obtained in d2) may at least partially be sent to the tailing section of d2) and then the tailed solvent obtained in d2) is transferred at least partially to the dissolution step a), or the tailed solvent stream obtained in d2) may at least partially be sent to the topping section of d2) and then the tailed solvent obtained in d2) is transferred at least partially to the dissolution step a).

[0224] Advantageously, the purified solvent phase obtained in d1), and / or the purified solvent effluent obtained in d2) or the topped solvent effluent and / or the tailed solvent effluent obtained in d2), which is / are transferred, at least in part, and in particular continuously, semi-continuously or discontinuously, to the dissolution step a), comprises / comprising dissolving solvent, preferably with a content greater than or equal to 60% by weight, preferably greater than or equal to 80% by weight, preferably greater than or equal to 90% by weight and very preferably greater than or equal to 95% by weight, or even greater than or equal to 99% by weight, of dissolving solvent relative to the total weight of the solvent stream considered.

[0225] Advantageously, the recycled solvent stream, which at least partially constitutes the dissolving solvent stream that feeds step a), thus comprises, preferably, depending on substeps d1), d1), d2) carried out in step d) and / or direct recycling of the gas effluent(s) used and / or purging:

[0226] - at least a fraction of the liquid solvent phase from the liquid-liquid separation section of step c) and / or at least a fraction of the reliquefied solvent phase obtained by adjusting the temperature and / or pressure (liquefaction adjustment) of at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section of step c), recycled directly to step a), during substep d1); and / or

[0227] - at least a portion of the purified solvent phase obtained and transferred to step a) during substep 1); and / or

[0228] - at least a portion of the purified solvent effluent obtained during substep d2) and transferred to step a), where step c) employs a single gas-liquid separation section downstream of the liquid-liquid and / or supercritical-liquid separation section; or at least a fraction of the topped and / or tailed solvent effluent obtained during substep d2) and transferred to step a), where step c) employs multiple gas-liquid separation sections downstream of the liquid-liquid and / or supercritical-liquid separation section; and / or

[0229] - at least a fraction of the gas effluent from the gas-liquid separation section of step c) in the case where said step c) implements a single gas-liquid separation section and where at least a fraction of the generated gas effluent is recycled directly to step a); or at least a fraction of the gas effluent from the first gas-liquid separation section of step c) and / or at least a fraction of the gas effluent from the last gas-liquid separation section of step c), and possibly at least a fraction of the gas effluent from the or at least one of the intermediate gas-liquid separation section(s), in the case where said step c) implements several gas-liquid separation sections and where at least a fraction of the gas effluent or gas effluents is recycled directly to step a).

[0230] The light impurity stream(s), when produced, concentrate(s) light impurities, i.e. compounds whose boiling point is lower than that of the dissolving solvent, in particular introduced in step a). Advantageously, the light impurity stream(s) have(s) a light impurity concentration higher than that of the stream feeding substep of 1) and / or d2), i.e. higher than that of said at least a fraction of the liquid or supercritical solvent phase from the liquid-liquid or supercritical-liquid section respectively, or the light impurity concentration of said at least a fraction of the gas effluent from the gas-liquid separation section or the first gas-liquid separation section of step c).Preferably, the light impurity stream(s) comprise(s) at least 1% by weight, preferably at least 2% by weight, of light impurities relative to the total weight of the light impurity stream under consideration. In a very specific case, it(s) may comprise(s) up to 50% by weight, for example up to 30% by weight, of light impurities relative to the total weight of the light impurity stream under consideration. In general, the light impurity stream(s) also comprise(s) dissolving solvent, particularly at least 50% by weight, more particularly at least 70% by weight, or even up to 98% by weight, for example up to 99% by weight, of dissolving solvent relative to the total weight of the light impurity stream under consideration. The stream(s) of light impurities can advantageously be purged, possibly recovered for purification and valorization.

[0231] The heavy impurity stream(s), when produced, concentrate(s) heavy impurities, i.e. compounds whose boiling point is higher than that of the dissolving solvent, in particular introduced in step a). Advantageously, the heavy impurity stream(s) have(s) a concentration of heavy impurities higher than that of the stream feeding substep d 1) and / or d2), i.e. higher than that of said at least a fraction of the liquid or supercritical solvent phase from the liquid-liquid or supercritical-liquid section respectively, or the concentration of heavy impurities of said at least a fraction of the gas effluent from the gas-liquid separation section or the last gas-liquid separation section of step c).Preferably, the heavy impurity stream(s) comprise(s) at least 1% by weight, preferably at least 5% by weight, most preferably at least 10%, and most preferably at least 20% by weight, of heavy impurities relative to the total weight of the heavy impurity stream under consideration. In a very particular case, it(s) may comprise(s) up to 80% by weight of heavy impurities relative to the total weight of the heavy impurity stream under consideration. In general, it(s) also comprise(s) dissolving solvent, particularly at least 20% by weight, more particularly up to 80% by weight, or even up to 90% by weight, for example up to 95% by weight or up to 99% by weight, of dissolving solvent relative to the total weight of the heavy impurity stream under consideration. The heavy impurity stream(s) can advantageously be purged, possibly recovered for purification and valorization.

[0232] Step d) thus makes it possible to supply step a) with a recycled dissolution solvent stream which has satisfactory average levels of light and heavy impurities, i.e. sufficiently low to avoid the accumulation of light and heavy impurities, in a process for treating (or recycling) a plastic feed, such as the process according to the invention, while having reasonable energy consumption.

[0233] If an entraining agent is introduced into the gas-liquid separation section or the last gas-liquid separation section of step c), substep d2) may further include a solvent-entraining agent separation, advantageously located upstream or downstream of the de-tailing (or topping) section.

[0234] Optionally, step d) may also include a solvent-water separation d4) to remove water from the recycled solvent stream. This optional solvent-water separation d4) thus produces a dried recycled solvent stream, which is advantageously sent to a) to compose at least part of the dissolving solvent stream (advantageously instead of the recycled solvent stream), and simultaneously an aqueous stream that is purged or optionally recovered for further processing. This optional solvent-water separation d4) is advantageously located downstream of substeps d1), d1), and / or d2), and obviously upstream of step a), and very advantageously upstream of any mixing with fresh dissolving solvent.This substep d4) of water separation allows the recycled solvent stream, which includes dissolving solvent, to be dried and thus the purification of said stream to be optimized so as to supply step a) with a high-purity dissolving solvent, which helps to limit the degradation of the targeted thermoplastics possibly induced by the presence of water.

[0235] Optionally, step d) may also include one or two additional solvent-water separations d'4) to remove water from the solvent stream feeding the tailing section of d'1) and / or the tailing section of d2), so as to prevent any azeotrope formation with water in the tailing section(s) and thus optimize the tailing purification. More specifically, said additional solvent-water separation(s) d'4) allow(s) the removal of water:

[0236] - of at least a fraction of the liquid and / or supercritical solvent phase, possibly adjusted for temperature and / or pressure, and / or

[0237] - at least a fraction of the gas effluent from the gas-liquid separation section of step c) or the last gas-liquid separation section of step c) and possibly at least a fraction of the gas effluent from at least one of the intermediate gas-liquid separation sections of step c).

[0238] When implemented, said (or said) other solvent-water separation(s) of 4) is / are located at step d) (i.e., downstream of step c) and upstream of substep d1) and / or substep d2). Said (or said) other solvent-water separation(s) of 4) advantageously produces dried solvent effluent(s), which is / are then sent to the de-tailing section of d1) and / or the de-tailing section of d2), in which the formation of azeotropes with water is avoided and therefore in which the separation of heavy impurities (i.e., compounds whose boiling point, particularly at atmospheric pressure, is higher than that of the dissolving solvent) can be efficiently carried out. The said other solvent-water separation(s) of 4) also allow(s) the production of aqueous stream(s) which can be purged, or recovered and treated.

[0239] The said recycled solvent stream, possibly dried, constitutes at least part of the dissolving solvent that feeds step a). The recycled solvent stream, possibly dried, can be mixed with a supply of fresh solvent, i.e., external to the process, to constitute the entire dissolving solvent stream that feeds step a). However, when fresh solvent is added, the quantities of fresh solvent introduced into the process are very reasonable and advantageously much lower than the total quantities of dissolving solvent required to allow good purification and thus the obtaining of a stream of purified, good-quality thermoplastics.

[0240] Thus, the process according to the invention proposes a sequence of simple operations that makes it possible to treat any type of plastic filler, for example, post-consumer plastic waste, by dissolution-purification, and to obtain a stream of purified thermoplastics, in particular a stream of purified polyolefins, of good quality, while limiting the consumption of fresh solvents and in particular the external input of dissolving solvent, and this without inducing the accumulation of impurities and therefore without altering the quality of the purified thermoplastic stream produced. The present invention therefore proposes a simple and efficient process for recycling thermoplastics, in particular polyolefins, for example polypropylene and / or polyethylene, included in any type of post-consumer and / or post-production plastic filler, with reasonable consumption of raw materials and controlled or even limited energy consumption.Furthermore, the recycling process according to the invention, by limiting its need for fresh solvent input, makes it possible, in addition to obtaining a stream of purified thermoplastics of good quality, to limit the costs of the process related to raw materials but also to limit its carbon impact.

[0241] Device

[0242] The present invention also relates to a device for dissolving a plastic filler to obtain a stream of purified thermoplastic polymers, which comprises:

[0243] A) Dissolution means for bringing into contact and dissolving at least part of the plastic filler in a dissolving solvent, and obtaining a crude polymer solution, said dissolution means advantageously being any type of industrial equipment allowing said contact and said dissolution, for example an extruder, static or dynamic mixer(s), and / or one or more continuously stirred reactor(s), also called "Continuous Stirred Tank Reactor" (CSTR) according to Anglo-Saxon terminology, and equipped with suitable stirring system(s);

[0244] B) Purification means, in particular suitable equipment, for purifying the crude polymer solution and obtaining a purified polymer solution, said purification means advantageously being any type of industrial equipment enabling the purification of the crude polymer solution, said purification means being able to include: means, in particular equipment, for solid-liquid (or solid-liquid-liquid) separation, said solid-liquid separation means advantageously being any type of industrial equipment enabling the separation of solids and one or two liquids, such as separation equipment by decantation, filtration, centrifugation and / or static electricity, to obtain a clarified polymer solution; a washing device enabling the crude or clarified polymer solution to be contacted with a dense solution, in particular an aqueous solution, to obtain a washed polymer solution;an extraction device allowing the crude, clarified, or washed polymer solution to be contacted with an organic solvent in liquid form or at least partially in supercritical form, to obtain an extracted polymer solution; and / or an adsorption device allowing the crude, clarified, washed, or extracted polymer solution to be contacted with at least one adsorbent, in particular at least one bed of adsorbent(s) or adsorbent particles in divided form, and allowing the recovery of a refined polymer solution, said clarified, washed, extracted, or refined polymer solution constituting the purified polymer solution;C) a solvent-polymer separation device for separating the purified polymer solution and obtaining at least one stream of purified thermoplastic polymers, said solvent-polymer separation device being advantageously located downstream of said purification means B), said solvent-polymer separation device comprising:;

[0245] C1) a liquid-liquid separation device and / or a supercritical-liquid separation device (i.e., a liquid-liquid separation device, or a supercritical-liquid separation device, or a succession of a liquid-liquid separation device and a supercritical-liquid separation device, in that order or in reverse order), comprising:

[0246] - a feeding system, connected to at least one of the means B) of purification and allowing the supply of purified polymer solution to said solvent-polymer separation device C) and more particularly allowing the supply of purified polymer solution to said liquid-liquid separation device or said supercritical-liquid separation device,

[0247] - a liquid withdrawal system for withdrawing a liquid phase comprising the thermoplastics in question, advantageously said liquid withdrawal system from the liquid-liquid or supercritical-liquid separation device being connected to the feed system of the first gas-liquid separation section of device C2), or optionally to the second liquid-liquid or supercritical-liquid separation device of a succession of a liquid-liquid separation device and a supercritical-liquid separation device, and

[0248] - another liquid withdrawal system from the liquid-liquid separation device for withdrawing a liquid solvent phase, and / or a supercritical withdrawal system from the supercritical-liquid separation device for withdrawing a supercritical solvent phase, said liquid solvent phase and / or said supercritical liquid solvent phase comprising dissolving solvent and no or little of the thermoplastics concerned, and preferably less than 1% by weight, preferably less than 0.01% by weight of the thermoplastics concerned relative to the total weight of said liquid or supercritical solvent phase, the other liquid withdrawal system from the liquid-liquid separation device and / or the supercritical withdrawal system from the supercritical-liquid separation device being advantageously connected to the dissolving solvent recycling device D),C2) a gas-liquid separation device comprising a gas-liquid separation section or a series of N gas-liquid separation sections operating in series, N being an integer greater than or equal to two, preferably between two and ten, preferably between two and five, for example two, three or four, said gas-liquid separation device C2) being located downstream of the liquid-liquid and / or supercritical-liquid separation device, the gas-liquid separation section or sections in the series comprising a feed system, a liquid withdrawal system for withdrawing a liquid effluent which includes the thermoplastics concerned, and a gas withdrawal system for withdrawing a gaseous effluent which includes dissolving solvent,the feed system of the gas-liquid separation section or of the first gas-liquid separation section being connected to the liquid withdrawal system of the liquid-liquid or supercritical-liquid separation device, or possibly to the second liquid-liquid or supercritical-liquid separation device of a succession of a liquid-liquid separation device and a supercritical-liquid separation device, and allowing the feeding of liquid phase including the thermoplastics referred to in said gas-liquid separation device C2), where the device C2) comprises several gas-liquid separation sections, the feed system of each subsequent gas-liquid separation section, in particular subsequent to the first gas-liquid separation section, being connected to the liquid withdrawal system of its preceding gas-liquid separation section (i.e. the section directly preceding the section being fed,for example the feeding system of section 2 is connected to the liquid withdrawal system of section 1, etc., and the feeding system of section N is connected to the liquid withdrawal system of section (N-1)), the liquid withdrawal system of the gas-liquid separation section or of the last section (or Nth section or section N) of gas-liquid separation allowing the recovery of said purified thermoplastic polymer stream, the gas withdrawal system of the or each gas-liquid separation section being advantageously connected to the device D) for recycling the dissolving solvent,

[0249] D) a device for recycling the dissolving solvent, characterized in that said device for recycling the dissolving solvent comprises at least one of the following devices, preferably at least one of the following devices D1) and D'1):

[0250] D1) a direct recycling device to the dissolution means A) of at least a fraction of the liquid and / or supercritical solvent phase, comprising: a liquid and / or supercritical feed system (or inlet point) connected, directly or indirectly, to the other liquid withdrawal system of the liquid-liquid separation device C1) or to the supercritical withdrawal system of the supercritical-liquid separation device C1), an outlet system connected, directly or indirectly, to the dissolution means A) of the dissolution, optionally a liquefaction adjustment system DO) in particular where device C1) includes a supercritical-liquid separation device, for adjusting the temperature and / or pressure and advantageously obtaining a solvent phase entirely in liquid form from at least a fraction of the supercritical solvent phase, said optional liquefaction adjustment system being, on the one hand,directly connected to the supercritical-liquid feed system of D1) (and more specifically, connected to the supercritical withdrawal system of the supercritical-liquid separation device of device C1), and connected, on the other hand, to the output system of D1); and / or,

[0251] D'1) a first purification device, for purifying at least a fraction of the liquid and / or supercritical solvent phase and thus obtaining a purified solvent phase, said first purification device comprising:

[0252] - a first de-tailing section for separating heavy impurities (i.e., compounds whose boiling point is higher than that of the distillation solvent) from at least a fraction of the liquid and / or supercritical solvent phase of device C1), the first de-tailing section comprising a feeding system, a withdrawal system for a heavy impurity stream and a withdrawal system for a de-tailed solvent phase, the feeding system of said first de-tailing section being connected, directly or indirectly, to said other liquid withdrawal system of device C1) for liquid-liquid separation or to said supercritical withdrawal system of device C1) for supercritical-liquid separation, the withdrawal system for a de-tailed solvent phase from the first de-tailing section being connected, directly or indirectly, to the means A) for dissolution and / or possibly to the feeding system of a first de-tailing section,

[0253] - possibly a first topping section to separate light impurities (i.e., compounds whose boiling point is lower than that of the distillation solvent) from at least a fraction of the liquid and / or supercritical solvent phase of device C1), the first topping section comprising a feed system, a light impurity stream withdrawal system and a topped solvent phase withdrawal system, the feed system of said possible first topping section being connected, directly or indirectly, to said other liquid withdrawal system of liquid-liquid separation device C1), or to said supercritical withdrawal system of supercritical-liquid separation device C1), or to the topped solvent phase withdrawal system of the first topping section, the topped solvent phase withdrawal system of the possible first topping section being connected, directly or indirectly,to the means A) of dissolution and / or possibly to the feeding system of the first de-tailing section, the fraction of the tailed solvent phase or of the possible topped solvent phase advantageously composing the purified solvent phase obtained at the end of said first device D'1) of purification,

[0254] - possibly a non-supercritical adjustment system D'O) in particular when device C1) is a supercritical-liquid separation device, to adjust the temperature and / or pressure and advantageously obtain a solvent phase entirely in the non-supercritical state, in particular obtain a solvent phase entirely in the liquid and / or gaseous state, said possible non-supercritical adjustment system being directly connected, on the one hand, to the supply system of D'1) (and therefore, more particularly, to the supercritical withdrawal system of the supercritical-liquid separation device of device C1), and connected, on the other hand, to the first tailing section or possibly to the first topping section;

[0255] D2) a second purification device to purify at least a fraction of the gas effluent from the gas-liquid separation section of device C2), or at least a fraction of the first gas-liquid separation section of device C2), and / or at least a fraction of the last gas-liquid separation section of device C2), comprising:

[0256] - a second topping section for at least a fraction of the gas effluent withdrawn from the gas-liquid separation section of device C2) or from the first gas-liquid separation section of device C2), to separate light impurities (i.e. compounds whose boiling point is lower than that of the distillation solvent), the second topping section comprising a feed system, a light impurity withdrawal system and a withdrawal system for a topped solvent stream, the feed system of said second topping section being connected, directly or indirectly, to the gas withdrawal system of the gas-liquid separation section of device C2) or at least to the gas withdrawal system of the first gas-liquid separation section of device C2),said solvent withdrawal system from the second topping section being connected directly or indirectly to the dissolution means A) and / or possibly to the feed system of the topping section, and / or,

[0257] - a second de-tailing section for at least a fraction of the gas effluent withdrawn from the gas-liquid separation section of device C2) or from the last gas-liquid separation section of device C2), to separate heavy impurities (i.e. compounds whose boiling point is higher than that of the distillation solvent), the second de-tailing section comprising a feed system, a withdrawal system for a heavy impurity stream and a withdrawal system for a de-tailed solvent stream, the feed system of said second de-tailing section being connected, directly or indirectly, to the gas withdrawal system of the gas-liquid separation section of device C2) or at least to the gas withdrawal system of the last gas-liquid separation section of device C2),said system for drawing off a tailed solvent stream from the second tailing section being connected directly or indirectly to the means A) for dissolution and / or possibly to the feeding system of the second topping section,

[0258] - possibly, when the device C2) comprises at least three gas-liquid separation sections, a transport system connecting the gas withdrawal system of the intermediate gas-liquid separation section(s), located between the first and last gas-liquid separation section of the device C), to the feed system of the second topping section and / or to the feed system of the second tailing section, and / or directly or indirectly to the dissolution means A), and

[0259] - possibly a transfer section which connects the gas withdrawal system from the gas-liquid separation section of device C2) or which connects the gas withdrawal system from the first and / or last gas-liquid separation section of device C2), to the means A) of dissolution, and which therefore makes it advantageous to send to the means A) of dissolution a fraction or all of the gas effluent from the gas-liquid separation section or from the first and / or last gas-liquid separation section of device C2) of solvent-polymer separation.

[0260] Optionally, the dissolving solvent recycling device D) includes a device D3) for transferring a fraction or all, preferably a fraction, of the liquid or supercritical solvent phase to at least one of the purification means B) for use, for example, to use said at least a fraction of the liquid or supercritical solvent phase as an extraction solvent or to clean filters implemented as means of the solid-liquid (or solid-liquid-liquid) separation device, said optional transfer device being connected, on the one hand, directly or indirectly, to said other liquid withdrawal system of the liquid-liquid separation section or to said supercritical withdrawal system of the supercritical-liquid separation device C1), and connected, on the other hand, to the feed system of D'1).

[0261] Optionally, the dissolving solvent recycling device D) may also include a purging system for at least a fraction of the liquid and / or supercritical solvent phase, and / or a purging system for at least a fraction of the gas effluent from the gas-liquid separation section of device C2), or at least a fraction of at least one gas effluent from the succession of gas-liquid separation sections of device C2).

[0262] When the possible first topping section is integrated into the first purification device D'1), the first tailing section and the first topping section may be common or separate.

[0263] When the possible first topping section is integrated into the first purification device D'1) and distinct from the first tailing section, the possible first topping section is located upstream or downstream of the first tailing section.In a variant of this particular embodiment, in which the possible first topping section is located downstream of the first tailing section, the feed system of the first tailing section is connected to said other liquid withdrawal system of the liquid-liquid separation device C1) or to said supercritical withdrawal system of the supercritical-liquid separation device C1) and the tailing-out solvent phase withdrawal system of the first tailing section is then connected to the feed system of the possible first topping section whose tailing-out solvent phase withdrawal system is connected to the dissolution means A), the tailing-out solvent phase then constituting said purified solvent phase.In another variant of the same particular embodiment, in which the possible first topping section is located upstream of the first tailing section, the feed system of the possible first topping section is connected to said other liquid withdrawal system of the liquid-liquid separation device C1) or to said supercritical withdrawal system of the supercritical-liquid separation device C1), the withdrawal system of a tailed solvent phase from the possible first topping section is connected to the feed system of the first tailing section, and the withdrawal system of a tailed solvent phase from the first tailing section is connected to the dissolution means A), the tailed solvent phase then constituting said purified solvent phase.When the possible first topping section is integrated into the first purification device D'1) and is common to the first tailing section, the feeding system of the first topping and tailing section is connected to said other liquid withdrawal system of the liquid-liquid separation device C1) or said supercritical withdrawal system of the supercritical-liquid separation device C1), includes a light impurity withdrawal system, a heavy impurity withdrawal system and a purified solvent phase (topped and tailed) withdrawal system, said purified solvent phase withdrawal system being connected to the dissolution means A).

[0264] Optionally, when integrated into the dissolving solvent recycling device D), the optional device D3) for transferring a fraction or all of the liquid or supercritical solvent phase to at least one of the purification means B) includes a non-supercritical adjustment system, in particular when the device C1) is a supercritical-liquid separation device, to adjust the temperature and / or pressure and advantageously obtain a solvent phase entirely in the non-supercritical state, in particular in the liquid and / or gaseous state, said optional non-supercritical adjustment system being located upstream of said at least one of the purification means B).

[0265] Advantageously, the first and second topping and tailing sections may, for example, incorporate one or more pieces of equipment selected from: a partial condenser, a separator flask, a column, a distillation column, a stripper, equipment incorporating internals and / or packing to facilitate gas-liquid separation, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating disk reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, or a devolatilizer. Preferably, the first and second topping sections may each, either separately or jointly, incorporate at least one topping distillation column and optionally one or more partial condensers, advantageously located upstream of the topping distillation column.Preferably, the first and second stemming sections can each employ, separately or possibly jointly, a stemming distillation column and possibly one or more partial condenser(s) advantageously located upstream of the stemming distillation column.

[0266] Advantageously, the device D) for recycling the dissolving solvent makes it possible to obtain at its outlet a recycled solvent stream which includes:

[0267] - at least a fraction of the liquid solvent phase and / or the supercritical solvent phase, preferably after use of a DO liquefaction adjustment system to obtain a completely liquid solvent phase, and / or - at least a fraction of the purified solvent phase, and / or

[0268] -at least a fraction of a topped-off solvent stream, and / or

[0269] - at least a fraction of a dequeued solvent stream, and / or

[0270] - at least a fraction of the gas effluent withdrawn from the gas-liquid separation section of device C2) or at least a fraction of the gas effluent withdrawn from the first gas-liquid separation section of device C2) and / or the last gas-liquid separation section of device C2), and possibly from at least one intermediate gas-liquid separation section of device C2).

[0271] Optionally, the solvent recycling device D) may further include a solvent-water separation system to remove water from the recycled solvent stream. When integrated into the treatment device, this optional solvent-water separation system is advantageously located downstream of devices D1), D'1), D2), and the optional device D3). This optional solvent-water separation system includes, at its outlet, a withdrawal of dried recycled solvent stream and a withdrawal of an aqueous stream, the withdrawal of dried recycled solvent stream being connected to the dissolution means A).

[0272] Optionally, the dissolving solvent recycling device D) may also include at least one other solvent-water separation system to remove water from the stream feeding the first tailing section of device D'1) and / or the second tailing section of device D2). This optional at least one other solvent-water separation system is advantageously located upstream of said first tailing section of device D'1) and / or the second tailing section of device D2).

[0273] Advantageously, the liquid-liquid or supercritical-liquid separation device C1) comprises, on the one hand, any equipment enabling the temperature and / or pressure to be adjusted to obtain two phases, liquid-liquid or supercritical-liquid, from the purified polymer solution and, on the other hand, any equipment enabling the separation of the two liquid-liquid or supercritical-liquid phases, for example by decantation and / or centrifugation. For example, the liquid-liquid or supercritical-liquid separation device C1) may employ one or more pieces of equipment selected from: gravity columns containing tray or packed internals, stirred columns, pulsed columns, and one or more mixer-decanters.

[0274] The gas-liquid separation section(s) of device C2) may implement any type of device known to those skilled in the art for separating gas and liquid, possibly accompanied by means for adjusting temperature and pressure, for example equipment for heating, equipment for adjusting and controlling pressure above atmospheric pressure, equipment for adjusting and controlling pressure below atmospheric pressure (to obtain a vacuum), etc.; mechanical means in particular equipment for moving and contacting the gas and liquid phases.For example, the gas-liquid separation section(s) may implement one or more pieces of equipment chosen from: a separator flask, a column, a distillation column, a stripper, equipment with internals and / or packing facilitating separation between gas and liquid, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating-disc reactor or column, a reactor, a stirred-reactor, an extruder, a kneading reactor, a devolatilizer.

[0275] The treatment device according to the invention may also include a liquid supply device E) for introducing fresh dissolving solvent. This device E) is located upstream of the dissolving means A) and may be connected, directly or indirectly, to said dissolving means A). In a particular embodiment, the device E) preferably comprises a liquid supply system connected via connecting lines to the dissolving means A) and optionally at least one pump for circulating the fresh solvent from said liquid supply system to the dissolving means A) via said connecting lines. This liquid supply system includes any equipment known to those skilled in the art for storing fresh dissolving solvent, particularly at least temporarily (i.e.in particular buffer storage), adjusting the required amount of fresh dissolving solvent and / or optionally adjusting the pressure and temperature of the fresh dissolving solvent. According to another particular embodiment, device E) comprises, in addition to a liquid supply system connected via connecting lines to the dissolving means A) and optionally at least one pump, mixing equipment in which the fresh dissolving solvent is mixed with the recycled solvent stream, optionally dried, from the recycling device D). In this other particular embodiment, the mixing equipment is connected, at the supply end, to the liquid supply system and the recycling device D) and, at the outlet, to the dissolving means A) via connecting lines.

[0276] Advantageously, the treatment device according to the invention also includes transport equipment between said means, devices and systems, for example connecting lines, pumps, etc.

[0277] Such a treatment device makes it very advantageous to recycle all types of plastic feed including thermoplastics, in particular polyolefins, and to recover a stream of purified thermoplastics, in particular a stream of purified polyolefins, of good quality, while having limited consumption of fresh dissolution solvent, controlled energy consumption and a reasonable operating cost.

[0278] The examples and figures that follow illustrate the invention, in particular particular embodiments of the invention, without limiting its scope.

[0279] LIST OF FIGURES

[0280] Figure 1 represents a particular embodiment of the process according to the invention. It illustrates in particular the process described in Example 2.

[0281] In this embodiment, a plastic filler 1, comprising thermoplastics, preferably polyolefins, is dissolved in a dissolving solvent during step a) of dissolution. This step a) of dissolution is fed with the plastic filler 1 and a stream 3 of dissolving solvent composed partly of a stream 2 of fresh dissolving solvent and partly of a stream 13 of recycled solvent. A crude polymer solution 4 is obtained at the outlet of step a) of dissolution.

[0282] The crude polymer solution 4 feeds into a purification step b) which allows the separation of impurities 6 and yields a purified polymer solution 5 which is sent to a solvent-polymer separation step c).

[0283] In this particular embodiment, step c) implements a supercritical-liquid separation section (c1) and two gas-liquid separation sections (c2) and (c3), which operate in series.

[0284] The purified polymer solution 5, obtained at the end of purification step b), feeds the supercritical-liquid separation section (c1). The supercritical-liquid separation section (c1) produces a liquid phase 11 comprising the target thermoplastics, and a supercritical solvent phase sc1 comprising the dissolving solvent. The liquid phase 11 feeds the first gas-liquid separation section (c2), and the supercritical solvent phase sc1 feeds a dissolving solvent recycling step d). The first gas-liquid separation section (c2) produces a liquid effluent, I2, comprising the target thermoplastics and feeding the second gas-liquid separation section (c3), and a gas effluent, g2, comprising the dissolving solvent and feeding the dissolving solvent recycling step d).An additive 8, in particular an antioxidant, is introduced, for example, into the liquid effluent I2 produced by the first gas-liquid separation section c2, before being fed into the second section (c3). The second gas-liquid separation section (c3) produces a liquid effluent, I3, which includes the targeted thermoplastics, and a gas effluent, g3, which includes dissolving solvent and feeds into the dissolving solvent recycling step d). The liquid effluent I3 produced by section (c3) constitutes a stream 7 of purified thermoplastic polymers that can then be used in any type of application.

[0285] In this particular embodiment, step d) includes:

[0286] - a substep of adjusting (due) the temperature and / or pressure of the supercritical solvent phase sc1, obtained at the end of the supercritical-liquid separation section (c1), said adjustment (due) allowing to obtain a reliquefied solvent phase rl1 which is then divided into a fraction rl 1 a and another fraction rl 1 b such that the fraction rl 1 a represents 46% weight of the total weight of the reliquefied solvent phase rl1 and the fraction rl1 b represents 54% weight of the total weight of the reliquefied solvent phase rl1;

[0287] - a substep d1) of direct recycling of the fraction rl 1 a of the reliquefied solvent phase to step a), to compose part of the recycled solvent stream 13;

[0288] - a substep of 1) for purifying the fraction rl1 b of the reliquefied solvent phase, by tailing, said substep of 1) implementing a tailing section (d'1) to produce a tailed solvent phase 9, which corresponds to a purified solvent phase and which is transferred to step a) to compose part of the recycled solvent stream 13, and a heavy impurity stream 10 which is purged;

[0289] - direct recycling to step a) of the gas effluent g2 of the gas-liquid separation section (c2) (flow 11), to make up part of the recycled solvent flow 13;

[0290] - direct recycling to step a) of the gas effluent g3 from the gas-liquid separation section (c3) (flow 12), to make up part of the recycled solvent flow 13.

[0291] In the specific embodiment shown in Figure 1, the recycled solvent stream 13 is therefore composed of:

[0292] - the rl1a fraction of the reliquefied solvent phase;

[0293] - the tailed solvent phase 9;

[0294] - the flux l 1, which corresponds to the gas effluent g2 sent directly to a); and

[0295] - the flow 12, which corresponds to the gas effluent g2 sent directly to a).

[0296] EXAMPLES

[0297] In the examples below, the analyses performed on the load and the products obtained are as follows:

[0298] - The ash content, which indicates the level of inorganic impurities, is determined by thermogravimetric analysis (TGA). The ash content is determined using a Perkin Elmer TGA 8000 instrument, according to ISO 11358-1 (2014). A 10-20 mg sample of material is placed on a platinum plate. The temperature is equilibrated at 50°C for 10 minutes, then increased at a heating rate of 20°C / min up to 950°C under a nitrogen flow. The ash content corresponds to the weight determined at 850°C relative to the weight of the initial sample, expressed as a percentage by weight (% by weight).

[0299] - The color parameters are expressed in the CIE L*a*b* reference system (defined by the International Commission on Illumination (CIE)), determined by colorimetry (according to ISO 11664-4), with:

[0300] - a parameter L* of clarity (or luminance), such that the closer L* is to 100, the clearer or more transparent the analyzed solid is; conversely, the closer L* is to 0, the more opaque the analyzed solid is;

[0301] - a parameter a* (corresponding to a green-red axis), which measures the color ranging from green (negative values) to red (positive values); a target value of a* is a value approaching 0;

[0302] - a parameter b* (corresponding to a blue-yellow axis), which measures the color ranging from blue (negative values) to yellow (positive values); a target value of b* is a value approaching 0.

[0303] The L*a*b* values ​​are determined using a standard Konica / Minolta Colorimeter CM-3700A instrument, on solid samples of approximately 20 g of cryogenically ground material. They represent a first indicator of the purity of the polyolefin-based product.

[0304] Example 1 (not in accordance with the invention)

[0305] Step a) of dissolution:

[0306] A feedstock derived from plastic waste and containing 96% polypropylene (PP) by weight is fed in flake form into an extruder heated to 190°C. At the extruder outlet, the feedstock is at least partially molten and is mixed with a stream of n-pentane, used as a dissolving solvent and preheated to 190°C, at a solvent-to-feedstock weight ratio of 4:1. The n-pentane stream used in step a) is entirely fresh n-pentane. The mixture of solvent and feedstock is introduced into a stirred reactor at 190°C and maintained at 190°C and 9.0 MPa absolute for a residence time of 1 hour. A crude polymer solution is then obtained.

[0307] Step b) of purification:

[0308] The crude polymer solution, continuously collected from the stirred reactor, is filtered through a 10 µm mesh filter and then through a 1 µm mesh filter. The filtered polymer solution is then sent to an adsorption column containing an activated carbon bed and operated at 190°C and 9 MPa absolute (i.e., at an adsorption column outlet pressure of approximately 9 MPa). The purified polymer solution, collected from the adsorption column outlet, is then subjected to a solvent-polymer separation step.

[0309] Step b) of purification allows the removal of impurities 6.

[0310] Step c) of solvent-polymer separation:

[0311] The purified polymer solution, recovered from the adsorption column, is then subjected to a solvent-polymer separation step (c) which employs a supercritical-liquid separation section (c1) and two gas-liquid separation sections (c2, c3), these sections being successive. The supercritical-liquid separation section (c1) and the gas-liquid separation sections (c2, c3) are operated under the following temperature (the temperatures given below being the inlet temperatures for each section) and pressure conditions (the pressures being absolute pressures in each section): Stage d: T = 210°C, P = 4.3 MPa, Stage c2: T = 180°C, P = 4.8 MPa.

[0312] Stage c3: T = 190°C, P = 0.0052 MPa (or 5.2 kPa, i.e. 52 mbar).

[0313] The purified polymer solution, recovered from the adsorption column outlet, feeds the supercritical-liquid separation section c1. The liquid phase 11 produced by the supercritical-liquid separation section c1 feeds the first gas-liquid separation section c2. The liquid effluent I2 produced by the first gas-liquid separation section c2 is mixed with an antioxidant, Irgafos® 168, to represent 600 ppm by weight of antioxidant relative to the weight of polypropylene in the liquid effluent I2. This mixture then feeds the second gas-liquid separation section c3. From the outlet of the second gas-liquid separation section c3, a liquid effluent I3 is recovered and placed under atmospheric conditions, i.e., at a temperature of approximately 20°C and a pressure of approximately 0.1 MPa.

[0314] A polypropylene A compound is then obtained. It is analyzed according to the methods described above. The results are presented in Table 1.

[0315] The supercritical-liquid separation section c1 also produces a supercritical solvent phase, and the gas-liquid separation sections c2 and c3 produce gas effluents. The supercritical solvent phase and the gas effluents produced by the supercritical-liquid separation section c1 and the gas-liquid separation sections c2 and c3, respectively, are purged.

[0316] Example 2 (according to the invention)

[0317] A batch of plastic waste containing 96% polypropylene (PP) by weight, identical to that processed in Example 1, is treated in Example 2. The steps a) dissolution, b) purification, and c) solvent-polymer separation are carried out in the process of Example 2 in the same manner as in the process described in Example 1, except for the source of the n-pentane stream that feeds step a) dissolution. The process of Example 2 also includes a step d) for recycling the dissolution solvent. The process of Example 2 is illustrated in Figure 1.

[0318] In Example 2, a polypropylene B is obtained at the end of the process, and more specifically from step c) of polymer-solvent separation. It is analyzed according to the methods described above. The results are presented in Table 1.

[0319] In the process of Example 2, the supercritical solvent phase sc1 produced by the supercritical-liquid separation section c1 and the gas effluents g2, g3, produced respectively by the supercritical-liquid separation section c1 and the gas-liquid separation section c2, c3, are recovered and treated in a dissolving solvent recycling step d), as illustrated in Figure 1.

[0320] The supercritical solvent phase sc1, obtained at the end of the supercritical-liquid separation section (c1), undergoes temperature and / or pressure adjustment (d) to obtain a reliquefied solvent phase rl1, which is divided into two fractions: a fraction rl1a representing 46% by weight of the total reliquefied solvent phase rl1; and another fraction rl1b representing 54% by weight of the total reliquefied solvent phase rl1. The rl1a fraction is sent directly to the dissolution step a) to form part of the recycled solvent stream 13. The rl1b fraction is sent to a decantation section (d'1) which uses a distillation column operating at 3.0 MPa and a temperature between 189 and 191°C.The tailing section produces a tailed solvent phase 9, which corresponds to a purified solvent phase and is transferred to the dissolution step a) to make up part of the recycled solvent stream 13, and a heavy impurity stream 10 which is purged.

[0321] The gas effluents g2, g3, produced respectively by the gas-liquid separation sections c2, c3, are recycled directly to step a) (thus constituting respectively the streams 11 and 12), to compose a part of the recycled solvent stream 13.

[0322] The recycled solvent stream 13, obtained at the end of step d), corresponds to 99.7% by weight of the dissolving solvent stream 3 which feeds the dissolving step a), and the fresh solvent stream 2 corresponds to 0.3% by weight of the dissolving solvent stream 3 which feeds the step a).

[0323] Table 1 below compares the quality parameters (ash content and colorimetry) of the polypropylenes obtained from the processes in Examples 1 and 2 with respect to the feedstock. Table 1

[0324] The process in Example 2, which conforms to the invention, consumes only 0.3% by weight of fresh solvent compared to the total quantity of dissolving solvent required to supply step a), with 99.7% by weight of the dissolving solvent being recycled solvent. In Example 1, which does not conform, all the dissolving solvent used in step a) is fresh solvent. However, this difference in the origin of the dissolving solvent does not appear to have any impact on the quality of the product obtained. Indeed, the polypropylenes A and B obtained from the processes of Examples 1 and 2 respectively, are purified polypropylenes, and exhibiting purities close to each other (ash content < 1000 ppm by weight; colorimetric parameter L greater than 90, or even greater than or equal to 95; colorimetric parameter a approaching 0, i.e. between -1.2 and -1.4; colorimetric parameter b between 4.0 and 4.2).

Claims

DEMANDS 1. A process for treating a plastic filler comprising thermoplastics, comprising: a) a step of dissolving the plastic filler in a dissolving solvent to obtain a crude polymer solution, step a) being fed by a dissolving solvent stream that is composed at least partly of a recycled solvent stream, step a) being carried out at a dissolution temperature between 100°C and 300°C, and at a dissolution pressure between 0.1 and 100.0 MPa absolute; b) a step of purifying the crude polymer solution to obtain a purified polymer solution, the purification step comprising: b1) a substep of separating insolubles; and / or b2) a washing substep.by contact with a dense solution; and / or b3) a substep of impurity extraction by an extraction solvent; and / or b4) a substep of impurity adsorption by contact with at least one adsorbent; c) a solvent-polymer separation step of the purified polymer solution, to obtain a stream of purified thermoplastic polymers, said solvent-polymer separation step c) comprising a liquid-liquid and / or supercritical-liquid separation followed by a gas-liquid separation, the liquid-liquid separation, when carried out, employing a liquid-liquid separation section to produce a liquid phase comprising the thermoplastics in question, and another liquid phase comprising a dissolving solvent and called the liquid solvent phase, the supercritical-liquid separation, when carried out, employing a supercritical-liquid separation section to produce a liquid phase comprising the thermoplastics in question,and a supercritical phase comprising a dissolving solvent and referred to as the supercritical solvent phase, the gas-liquid separation employing a gas-liquid separation section or a series of N gas-liquid separation sections, N being an integer greater than or equal to two, the gas-liquid separation section or sections producing a liquid effluent comprising the thermoplastics of interest, and a gas effluent comprising a dissolving solvent, wherein: where step c) comprises a liquid-liquid separation or a supercritical-liquid separation, the purified polymer solution obtained at the end of purification step b) feeds, the liquid-liquid or supercritical-liquid separation section implemented in step c), the liquid phase comprising the targeted thermoplastics, obtained at the end of the liquid-liquid or supercritical-liquid separation section implemented in step c), feeds the gas-liquid separation section or the first gas-liquid separation section, where step c) successively comprises a liquid-liquid separation and a supercritical-liquid separation, the purified polymer solution feeds the first liquid-liquid or supercritical-liquid separation section implemented in step c), the liquid phase comprising the targeted thermoplastics, obtained at the end of the first liquid-liquid or supercritical-liquid separation section implemented in step c), feeds the second the liquid-liquid or supercritical-liquid separation section implemented in step c), and the liquid phase comprising the targeted thermoplastics,obtained at the end of the second liquid-liquid or supercritical-liquid separation section implemented in step c), feeds the gas-liquid separation section or the first gas-liquid separation section, where the gas-liquid separation of step c) implements a series of N gas-liquid separation sections, the liquid effluent from the earlier gas-liquid separation section feeds the later gas-liquid separation section, the liquid effluent from the gas-liquid separation section or the last gas-liquid separation section constituting said at least one stream of purified thermoplastic polymers; d) a step of recycling the dissolving solvent, to produce said recycled solvent stream,step d) comprising at least one of the following substeps: d1) direct recycling to step a) of at least a fraction of the liquid solvent phase from the liquid-liquid separation section and / or of a reliquefied solvent phase obtained from at least a fraction of the supercritical solvent phase from the supercritical-liquid separation section, to make up at least part of the recycled solvent stream; d1) purification of at least a fraction of the liquid solvent phase and / or of the supercritical solvent phase, at least by tailing, to obtain a purified solvent phase, then transfer of at least a portion of the purified solvent phase to step a) to make up at least part of the recycled solvent stream; d2) purification by topping and / or tailing of at least a fraction of the gas effluent from the gas-liquid separation section of step c) to obtain a purified solvent effluent,then the transfer of at least a portion of the purified solvent effluent to step a) to make up at least a portion of the recycled solvent stream; or, the purification by topping of at least a fraction of the gas effluent from the first gas-liquid separation section to obtain a topped solvent effluent, and / or the purification by tailing of at least a fraction of the gas effluent from the last gas-liquid separation section to obtain a tailed solvent effluent, then the transfer to step a) of at least a fraction of the topped solvent effluent and / or the tailed solvent effluent to make up at least part of the recycled solvent stream.

2. A method according to claim 1, wherein the plastic filler and the flow of dissolving solvent feed the step a) in a weight ratio of the dissolving solvent to the plastic filler of between 0.2 and 100.0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 10.

0.

3. A process according to claim 1 or 2, wherein the plastic filler comprises polyolefins and step c) enables the production of a stream of purified polyolefins.

4. A process according to any one of the preceding claims, wherein the dissolving solvent comprises at least one hydrocarbon compound, said dissolving solvent having a boiling point between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 160°C and preferably between 50 and 120°C.

5. A method according to any one of the preceding claims, wherein the dissolving solvent comprises an isomer or a mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane, and preferably, an isomer or a mixture of isomers of pentane, hexane, heptane and / or octane.

6. A method according to any one of the preceding claims, wherein the dissolving solvent stream that feeds step a) is composed at least partly of said recycled solvent stream and optionally partly of a fresh dissolving solvent stream.

7. A method according to any one of the preceding claims, wherein step c) implements N gas-liquid separation sections, operating in series, N being an integer between two and ten, preferably between two and five, for example three or four.

8. A method according to any one of the preceding claims, wherein step d) comprises at least one substep selected from d1) and d'1).

9. A method according to any one of the preceding claims, wherein, where step d) comprises substep d1) and step c) implements a supercritical-liquid separation section to produce a supercritical solvent phase, step d) comprises a adjustment due) of the temperature and / or pressure, upstream of said substep d1), so as to obtain the reliquefied solvent phase from at least a fraction of the supercritical solvent phase.

10. A method according to any one of the preceding claims, wherein substep 1) comprises tailing and topping at least a fraction of the liquid solvent phase or supercritical solvent phase, tailing and topping being carried out simultaneously or successively.

11. A method according to any one of the preceding claims, wherein, where step d) includes substep 1) and step c) implements a supercritical-liquid separation section to produce a supercritical solvent phase, step d) includes an adjustment of 0) of the temperature and / or pressure, upstream of said substep 1), so as to obtain a non-supercritical solvent phase from at least a fraction of the supercritical solvent phase.

12. A method according to any one of the preceding claims, wherein step d) comprises purging at least a fraction of the liquid solvent phase from the liquid-liquid separation section or of the supercritical solvent phase from the supercritical-liquid separation section.

13. A method according to any one of the preceding claims, wherein step d) comprises purging and / or direct recycling to step a) of dissolving at least a fraction of the gas effluent from the gas-liquid separation section, or purging and / or direct recycling to step a) of dissolving at least a fraction of the gas effluent from the first gas-liquid separation section, and / or at least a fraction of the gas effluent from the last gas-liquid separation section.

14. A process according to any one of the preceding claims, wherein step d) comprises a solvent-water separation d4), located downstream of substeps d1), d1) and / or d2), and upstream of step a), for producing a stream of dried recycled solvent, said stream of dried recycled solvent comprising at least part of the dissolving solvent stream which feeds step a).

15. Device for dissolving a plastic feedstock to obtain a stream of purified thermoplastic polymers, said processing device comprising: A) Dissolution means for bringing the plastic filler into contact and dissolving at least partially in a dissolving solvent, and obtaining a crude polymer solution; B) purification means to purify the crude polymer solution and obtain a purified polymer solution; C) a solvent-polymer separation device for the purified polymer solution, to obtain at least one stream of purified thermoplastic polymers, said solvent-polymer separation device comprising: C1) a liquid-liquid separation device and / or a supercritical-liquid separation device, comprising: - a feeding system, connected to at least one of the means B) of purification and allowing the supply of purified polymer solution to said solvent-polymer separation device C) and more particularly to said liquid-liquid or supercritical-liquid separation device, - a liquid withdrawal system for withdrawing a liquid phase comprising the thermoplastics referred to, advantageously said liquid withdrawal system from the liquid-liquid or supercritical-liquid separation device being connected to the feed system of the first gas-liquid separation section of device C2), or to the second liquid-liquid or supercritical-liquid separation device of a succession of a liquid-liquid separation device and a supercritical-liquid separation device, and - another liquid withdrawal system from the liquid-liquid separation device to withdraw a liquid solvent phase, and / or a supercritical withdrawal system from the supercritical-liquid separation device to withdraw a supercritical solvent phase, the other liquid withdrawal system from the liquid-liquid separation device and / or the supercritical withdrawal system from the supercritical-liquid separation device being advantageously connected to the dissolving solvent recycling device D), C2) a gas-liquid separation device comprising a gas-liquid separation section or a series of N gas-liquid separation sections operating in series, N being an integer greater than or equal to two, said gas-liquid separation device C2) being located downstream of the liquid-liquid and / or supercritical-liquid separation device, the gas-liquid separation section or sections in the series comprising a feed system, a liquid withdrawal system for withdrawing a liquid effluent that includes the thermoplastics concerned, and a gas withdrawal system for withdrawing a gaseous effluent that includes dissolving solvent, the feed system of the gas-liquid separation section or of the first gas-liquid separation section being connected to the liquid withdrawal system of the device liquid-liquid or supercritical-liquid separation, or to the second liquid-liquid or supercritical-liquid separation device in a succession of a liquid-liquid separation device and a supercritical-liquid separation device, and allowing the feeding of liquid phase comprising thermoplastics to said gas-liquid separation device C2), where the device C2) comprises several gas-liquid separation sections, the feeding system of each subsequent gas-liquid separation section being connected to the liquid withdrawal system of its preceding gas-liquid separation section, the liquid withdrawal system of the gas-liquid separation section or of the last gas-liquid separation section allowing the recovery of said purified thermoplastic polymer stream, D) a device for recycling the dissolving solvent, characterized in that said device D) comprises at least one of the following devices: D1) a direct recycling device to the means A) for dissolving, of at least a fraction of the liquid and / or supercritical solvent phase, comprising: a liquid or supercritical feed system connected, directly or indirectly, to the other liquid withdrawal system of the liquid-liquid separation device C1) or to the supercritical withdrawal system of the supercritical-liquid separation device C1), an outlet system connected, directly or indirectly, to the means A) for dissolving, optionally a liquefaction adjustment system DO) for adjusting the temperature and / or pressure so as to obtain a solvent phase entirely in liquid form from at least a fraction of the supercritical solvent phase, said optional liquefaction adjustment system being connected to the supercritical withdrawal system of the supercritical-liquid separation device of device C1), and to the outlet system of D1); D'1) a first purification device for purifying at least a fraction of the liquid and / or supercritical solvent phase and obtaining a purified solvent phase, said first purification device D'1) comprising: - a first de-tailing section for separating heavy impurities from at least a fraction of the liquid and / or supercritical solvent phase of device C1), the first de-tailing section comprising a feeding system, a withdrawal system for a heavy impurity stream and a withdrawal system for a de-tailed solvent phase, the feeding system of said first de-tailing section being connected to said other liquid withdrawal system of device C1) for liquid-liquid separation or to said supercritical withdrawal system of device C1) for supercritical-liquid separation, the system for withdrawing a tailed solvent phase from the first tailing section being connected directly or indirectly to the means A) of dissolution and / or possibly to the feeding system of a first topping section, - possibly a first topping section to separate light impurities from at least a fraction of the liquid and / or supercritical solvent phase of device C1), the first topping section comprising a feeding system, a system for withdrawing a stream of light impurities and a system for withdrawing a topped solvent phase, the feeding system of said possible first topping section being connected to said other liquid withdrawal system of device C1) for liquid-liquid separation or to said supercritical withdrawal system of device C1) for supercritical-liquid separation, or to the withdrawal system for a topped solvent phase of the first topping section, the withdrawal system for a topped solvent phase of the possible first topping section being connected, directly or indirectly, to the means A) for dissolution and / or possibly to the feeding system of the first topping section,the fraction of the tailed solvent phase or of the possible tailed solvent phase comprising the purified solvent phase obtained at the end of said first purification device D'1), D2) a second purification device for purifying at least a fraction of the gas effluent from the gas-liquid separation section of device C2), or at least a fraction of the first gas-liquid separation section and / or at least a fraction of the last gas-liquid separation section of device C2), comprising: - a second topping section for separating light impurities, comprising a feeding system, a system for withdrawing a light impurity stream and a system for withdrawing a topped-off solvent stream, the feeding system of said second topping section being connected to the gaseous withdrawal system of the gas-liquid separation section of device C2) or at least to the gaseous withdrawal system of the first gas-liquid separation section of device C2), the system for withdrawing a topped-off solvent stream from the second topping section being connected directly or indirectly to the dissolution means A) and / or possibly to the feeding system of the topping section, and / or - a second de-tailing section for separating heavy impurities, comprising a feeding system, a system for withdrawing a stream of heavy impurities and a system for withdrawing a stream of tailed solvent, the feeding system of said second de-tailing section being connected to the gas withdrawal system of the gas-liquid separation section of device C2) or at least to the gas withdrawal system of the last gas-liquid separation section of device C2), said system for withdrawing a stream of tailed solvent from the second de-tailing section being connected directly or indirectly to the means A) of dissolution and / or possibly to the feeding system of the second de-tailing section, - possibly a transfer section which connects the gas withdrawal system from the gas-liquid separation section of device C2) or which connects the gas withdrawal system from the first and / or last gas-liquid separation section of device C2), to the means A) of dissolution.

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