Method for recycling plastics by dissolution with solvent recovery, purification and reintegration

Abstract

The present invention relates to a method for treating a plastic feedstock, comprising: a) a step of dissolving the plastic feedstock in a dissolution solvent comprising a recycled solvent stream, to obtain a crude polymer solution, b) a step of purifying the crude polymer solution, then c) a solvent-polymer separation step to obtain a stream of purified thermoplastics, including a series of gas-liquid separation sections, each producing a liquid effluent, which comprises the targeted thermoplastics, and a gaseous effluent which comprises dissolution solvent, d) a dissolution solvent recycling step, comprising: d1) topping of at least a fraction of the gaseous effluent from the first gas-liquid separation section, and / or d2) tailing of at least a fraction of the gaseous effluent from the last gas-liquid separation section. The present invention also relates to a device for performing said treatment method.

Description

[0001] PLASTICS RECYCLING PROCESS BY DISSOLUTION WITH SOLVENT RECOVERY, PURIFICATION AND 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 a series of gas-liquid separation sections. The process further comprises recycling at least a portion of the solvent after purification.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 also 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 / 1 18579 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 / 1 18579 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 / 1 18579 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, especially polyolefins, by dissolving a plastic filler in a solvent, purifying the resulting polymer solution, and separating the polymer from the solvent, particularly by gas-liquid separation, so as to limit solvent consumption while avoiding the accumulation of impurities and maintaining the quality of the purified thermoplastic stream obtained at the end of said recycling processes. The present invention particularly seeks to optimally recycle the solvent, and in particular the dissolving solvent, so as to reduce solvent consumption and advantageously costs, without compromising the 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 at least one 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, 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 at least one stream of purified thermoplastic polymers, said solvent-polymer separation step c) employing a series of several gas-liquid separation sections, the purified polymer solution, obtained at the end of purification step b), feeding the first gas-liquid separation section, each gas-liquid separation section producing a liquid effluent, which includes the thermoplastics in question, and a gas effluent which includes dissolving solvent, the liquid effluent from the preceding section feeding the subsequent section,and the liquid effluent from the last gas-liquid separation section of the series constituting said purified thermoplastic polymer stream; (d) a dissolving solvent recycling step to produce a recycled solvent stream, step (d) comprising: (d1) a topping of at least a fraction of the gas effluent from the first gas-liquid separation section of step (c), said topping being fed by a fraction or all of the gas effluent from the first gas-liquid separation section of step (c), said topping (d1) producing a topped solvent stream and a light impurities stream, at least a fraction of the topped solvent stream constituting at least part of said recycled solvent stream and / or being sent to the topping (d2), and / or (d2) a topping of at least a fraction of the gas effluent from the last gas-liquid separation section of step (c),said tailing being fed by a fraction or all of the gas effluent from the last gas-liquid separation section of step c), said tailing producing a tailed solvent stream and a heavy impurity stream, at least a fraction of the tailed solvent stream comprising at least part of said recycled solvent stream from the dissolving solvent stream that feeds step a), and / or being sent to the tailing d1).

[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.

[0017] 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, and thus lowers fresh solvent consumption, especially of the dissolving solvent, compared to prior art plastics recycling processes using dissolution. This is achieved while ensuring efficient purification of the polymer solution and therefore 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.

[0018] 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 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.

[0019] 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.

[0020] The present invention also relates to a device for treating a plastic filler by dissolution to obtain a stream of purified thermoplastic polymers, enabling the process according to the invention to be carried out.

[0021] DESCRIPTION OF IMPLEMENTATION METHODS

[0022] 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. In this description, the expression "greater than ..." is understood as strictly greater than, and symbolized by the sign ">", and the expression "less than ..." as strictly less than, and symbolized by the sign ">". When the limit is included, the clarification 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, the polymer solution may therefore comprise, in addition to the dissolved thermoplastics, impurities in the form of insoluble particles advantageously suspended in the polymer solution, and / or soluble impurities dissolved in the dissolving solvent, and optionally another liquid phase immiscible with the polymer solution. Topping corresponds to 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.

[0034] The tailing corresponds to a separation operation based on the principle of evaporation, preferably by distillation, during which the valuable stream is obtained in the evaporated stream, or distillate, and the residue 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 dissolving solvent stream which is composed at least in part of a recycled solvent stream, optionally dried, said dissolving solvent stream which feeds step a) possibly comprising another part of fresh dissolving solvent, step a) advantageously being 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 obtaining 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, advantageously by gas-liquid separation, to obtain at least one stream of purified thermoplastic polymers, more particularly at least one stream of purified polyolefins, said solvent-polymer separation step (c) employing a series of several gas-liquid separation sections, the purified polymer solution, obtained at the end of the purification step (b), feeding the first gas-liquid separation section, each gas-liquid separation section producing a liquid effluent, which advantageously comprises the thermoplastics in question, and a gaseous effluent which comprises the dissolving solvent,the liquid effluent from the preceding section feeding the subsequent section, and the liquid effluent from the last gas-liquid separation section of the series constituting said purified thermoplastic polymer stream; (d) a dissolving solvent recycling step, to produce a 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: (d1) a topping off of at least a fraction of the gas effluent from the first gas-liquid separation section of step (c) and optionally, where step (c) employs at least three gas-liquid separation sections, at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section located between the first and last gas-liquid separation sections, to separate light impurities,said topping (d1) producing a stream of topped solvent and a stream of light impurities, the stream of topped solvent being sent in part or in whole to step (a) to compose at least in part said recycled solvent stream, and / or sent to the topping (d2), and / or (d2) a topping of at least a fraction of the gas effluent from the last gas-liquid separation section of step (c), and optionally, where step (c) employs at least three gas-liquid separation sections, at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section located between the first gas-liquid separation section and the last gas-liquid separation section, to separate heavy impurities, said topping producing a stream of topped solvent and a stream of heavy impurities, said stream of topped solvent being sent in part or in whole to step (a) to compose at least in part said recycled solvent stream,and / or towards the topping step d1); step d) possibly including a solvent-water separation d3) of the recycled solvent stream, located downstream of the topping steps d1) and / or stemming steps d2) and / or another solvent-water separation d3) located upstream of the stemming step.

[0038] Preferably, step d) includes topping d1) and tailing d2).

[0039] The charge

[0040] 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.

[0041] 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.Examples include fillers, colorants, pigments, plasticizers, property modifiers, combustion retardants, etc.

[0042] The feedstock of the process according to the invention (i.e., the plastic feedstock) 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 feedstock, with 100% advantageously being the maximum upper limit. The thermoplastics targeted by the process according to the invention and included in the plastic feedstock 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 feedstock 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.

[0043] 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.

[0044] 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.

[0045] Step a) of dissolution

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Step a) of dissolution is fed by the plastic charge and by a flow of dissolving solvent.

[0050] 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.

[0051] 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 180°C and preferably having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) greater than 70°C, preferably greater than or equal to 75°C, and advantageously less than or equal to 160°C, preferably less than or equal to 130°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).

[0052] 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.

[0053] 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).

[0054] 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. 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 input (i.e., an external supply of dissolving solvent).In particular, said recycled solvent stream, from step d), comprises at least a fraction of the topped solvent stream produced at topping d1) and / or at least a fraction of the tailed solvent stream produced at tailing d2), optionally a fraction of the gas effluent from the first gas-liquid separation section of step c) and / or optionally a fraction of the gas effluent from the last gas-liquid separation section of step c), and optionally part or all of the gas effluent from at least one intermediate gas-liquid separation section located between the first and last gas-liquid separation sections of step c).

[0055] 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.

[0056] 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 maintain 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.

[0057] 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.

[0058] Most advantageously, the temperature and pressure conditions of 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 including insoluble impurities suspended in said mixture.

[0059] Advantageously, said dissolution step a) 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 dissolution pressure, i.e., the time during which the plastic filler and the dissolving solvent are at the dissolution temperature and dissolution pressure, in step a).

[0060] Step a) of dissolution 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.

[0061] 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.

[0062] In order to allow contact between the dissolving solvent and the plastic filler, 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 filler preparation device, a mixing device, and / or a conveying device.The equipment and / or devices used 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. Conveying devices, particularly for fluids such as gases, liquids, or solids, are well known to those skilled in the art. Without limitation, conveying 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., a furnace, a heat exchanger, a heat treatment system) to achieve the conditions necessary for dissolution.

[0063] Preferably, step a) of dissolution employs at least one means for melting at least part of the plastic filler, preferably an extruder, and optionally at least one means for mixing at least part of the dissolving solvent with the plastic filler, 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 filler 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 filler, 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).

[0064] 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.

[0065] 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.

[0066] Step b) of purification of the polymer solution

[0067] 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.

[0068] The different sub-steps b1), b2), b3) and b4) can be operated continuously, discontinuously (or batch mode) or in fed-batch discontinuous mode.

[0069] Preferably, purification step b) includes at least one substep b1) for separating insolubles. Preferably, 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 for optimal purification of the polymer solution, which consequently makes it possible to obtain a stream of purified thermoplastics with very low impurity contents, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight, and preferably less than or equal to 0.5% by weight, relative to the total weight of the purified thermoplastic stream.

[0070] 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) of insoluble separation, 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.

[0071] Preferably, the temperature and pressure at step b) are adjusted so as to obtain at the output of step b), a polymer solution, i.e. the purified polymer solution, in liquid form.

[0072] Substep b1) of separation of insolubles

[0073] 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.

[0074] Substep b1) of insolubles separation thus makes it possible to remove 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) of insolubles separation are pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum), and insoluble polymers. When implemented, this substep b1) of separation advantageously allows, in addition to the removal of at least some of the insoluble impurities, the limitation of operational problems, particularly clogging and / or erosion, in process steps located downstream of such substep b1), while also contributing to the purification of the plastic feedstock.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 incurred between step a) and substep b1).

[0075] When integrated into the process, substep b1) of insolubles separation 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). According to a preferred embodiment, substep b1) is fed with the crude polymer solution from step a). According to another embodiment, substep b1) may be fed with a washed polymer solution from a washing substep b2) located upstream of substep b1).

[0076] 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 able to be 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.

[0077] 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 insoluble 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.

[0078] 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 centrifugal decanter, a 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.

[0079] 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. According to another specific embodiment, substep b1 advantageously incorporates a solid-liquid-liquid separation section, using equipment that allows the separation of two liquid phases and one solid phase, preferably by means of at least one two-phase or three-phase separator.

[0080] 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).

[0081] 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 uses a tangential filter including a membrane and / or a depth filter, possibly in the presence of filtration aids such as diatomaceous earth or perlite.

[0082] Substep b2) of washing

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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).

[0088] 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.

[0089] Substep b2) may employ one or more washing devices to bring the polymer solution into contact with the dense solution, and / or one or more separation devices to recover 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.

[0090] According to a preferred embodiment, substep b2) of washing 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), on the one hand, 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), on the other hand. 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.

[0091] 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.

[0092] 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 some of 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.

[0093] Extraction Substep b3) The process according to the invention may include an extraction substep b3), advantageously by 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, in particular 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 carried out.

[0094] 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.

[0095] 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.

[0096] When integrated into the process according to the invention, substep b3) of extraction advantageously employs at least one extraction section, preferably between one and five extraction section(s), most preferably one extraction section.

[0097] 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.

[0098] 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).

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] Advantageously, substep b3) of extraction is carried out under different temperature and pressure conditions than the temperature and pressure conditions of step a) of dissolution.

[0104] 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 reached 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.

[0105] 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.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 in relation 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.

[0106] 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.

[0107] 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.

[0108] Substep b4) of adsorption

[0109] 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.

[0110] 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, possibly during substep b1) of insoluble 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 insoluble separation and possibly upstream or downstream of substep b3) of extraction.

[0111] 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.

[0112] 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 .

[0113] 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.Said at least one used adsorbent can then be regenerated in situ and / or replaced with fresh adsorbent so that the column containing it can be put back online once the other column has been isolated.

[0114] 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(s), advantageously without stopping the process, and also allows to control costs and limit the consumption of adsorbent(s).

[0115] Step c) of solvent-polymer separation

[0116] 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).

[0117] 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 mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and 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). Step c) of solvent-polymer separation advantageously includes a gas-liquid separation. Step c) of solvent-polymer separation employs several gas-liquid separation sections, that is, at least two gas-liquid separation sections operating in series.Preferably, step c) solvent-polymer separation employs 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.

[0118] The principle of separation in the gas-liquid separation sections is based on the evaporation, at least in part, of the solvent, in particular the dissolving solvent, present in the polymer solution which feeds each of said sections; and said solvent (or the fraction of said solvent), then in gaseous form, is separated from the polymer solution which is in liquid form.

[0119] Thus, each of the gas-liquid separation sections produces a gaseous effluent, which advantageously comprises solvent, in particular dissolving solvent, in gaseous form, and a liquid effluent, which advantageously comprises the thermoplastics in question, possibly dissolved in a residual fraction of solvent, in particular dissolving solvent. When the liquid effluent comprises a residual fraction of solvent, in particular dissolving solvent, the thermoplastics in question may be dissolved in the residual solvent, and the liquid effluent then corresponds to a polymer solution.Advantageously, the liquid effluent from the last gas-liquid separation section in 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 stream of purified thermoplastic polymers. Preferably, the gaseous effluent produced by each of the gas-liquid separation sections comprises little or no targeted thermoplastics. Preferably, each gaseous effluent produced comprises less than 1% by weight, preferably less than 0.01% by weight of targeted thermoplastics relative to the total weight of the gaseous effluent considered; and in particular, each gaseous effluent produced is free of targeted thermoplastics.

[0120] The purified polymer solution, obtained at the end of purification step b), feeds the first gas-liquid separation section in the series. Then, for the other gas-liquid separation section(s) implemented, the liquid effluent from the preceding section feeds the subsequent section, up to the last section, whose resulting liquid effluent advantageously constitutes the stream of purified thermoplastic polymers. In other words:

[0121] - the purified polymer solution, obtained at the end of step b) of purification, feeds the first gas-liquid separation section of the series, which produces a first gas effluent and a first liquid effluent; - 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;

[0122] - the second liquid effluent obtained at the end of the second gas-liquid separation section feeds the third gas-liquid separation section which produces a third gas effluent and a third liquid effluent;

[0123] - 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,

[0124] - the Nth liquid effluent obtained at the end of the Nth gas-liquid separation section advantageously constitutes the stream of purified thermoplastic polymers.

[0125] Advantageously, the gas effluents produced by the gas-liquid separation sections are recovered and sent to step d) of the dissolution solvent recycling.

[0126] Advantageously, each gas-liquid separation section implemented in step c) is 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, and preferably between 150°C and 250°C. Very advantageously, the temperature is adjusted in 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 in question.

[0127] Advantageously, each gas-liquid separation section implemented in step c) is operated at a pressure lower than the pressure in step b) and preferably lower than the outlet pressure of step b), 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 each of the gas-liquid separation sections, 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, the pressure in the subsequent section is lower than that in the preceding section.In other words, preferably, the pressure in the second gas-liquid separation section is lower than that in the first gas-liquid separation section, the pressure in the third gas-liquid separation section is lower than that in the second gas-liquid separation section, and so on up to the Nth gas-liquid separation section in which the pressure is lower than the pressure in the (N-1)th gas-liquid separation section, the pressure of the first section of the series being lower than the pressure of step b), preferably the outlet pressure of step b).

[0128] The said gas-liquid separation sections 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, said gas-liquid separation sections may employ one or more pieces of equipment selected from: a separator flask, a column, a distilling column, a stripper, equipment including 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.

[0129] Optionally, an entraining agent (or stripping agent) may be introduced in the last (i.e., the Nth) gas-liquid separation section of the series to aid the vaporization of residual solvent present in the polymer solution entering said last section. The addition of an entraining agent thus optimizes solvent-polymer separation in the last gas-liquid separation section. The entraining agent, if introduced in the last (i.e., the Nth) 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.

[0130] Optionally, an inert gas stream, preferably nitrogen, can be introduced into the first gas-liquid separation section to aid vaporization and thus the removal of the solvent, particularly the dissolving solvent, present in the purified polymer solution that feeds step c). The presence of inert gas modifies the phase diagram and can therefore promote solvent evaporation, especially the dissolving solvent, present in the purified polymer solution that feeds step c), thus limiting the operating temperatures in this first section while optimizing solvent evaporation. At the outlet of the gas-liquid separation section, or the first gas-liquid separation section in the series, the inert gas is then advantageously mixed with the gaseous dissolving solvent in the effluent gas.

[0131] 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, in particular in the purified polymer solution which feeds step c) or at least one of the liquid effluents produced by the gas-liquid separation sections.In the case where an additive, in particular an antioxidant, is introduced in step c) and since step c) involves several successive gas-liquid separation sections, said additive is preferably introduced downstream of the first gas-liquid separation section in the series, either as a unit or in fractions, more particularly in at least one of the liquid effluents produced by the gas-liquid separation sections in the series (including the first section), and preferably in one of the liquid effluents produced by one of the sections upstream of the last gas-liquid separation section in the series.

[0132] Step d) Recycling of the dissolving solvent

[0133] 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).

[0134] Step d) then includes, preferably consisting of, at least one of the following steps:

[0135] - a topping d1) of at least a fraction, preferably of the whole, of the gas effluent from the first gas-liquid separation section of step c), - a tailing d2) of at least a fraction, preferably of the whole, of the gas effluent from the last gas-liquid separation section of step c).

[0136] Optionally, step d) may also include 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 / or purging 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).

[0137] Thus, according to a first particular embodiment, step d) includes a topping d1) of a fraction or all of the gas effluent from the first gas-liquid separation section of step c), and the tailing d2) of a fraction or all of the gas effluent from the last gas-liquid separation section of step c).

[0138] According to a second particular embodiment, step d) includes purging and / or direct recycling to step a) of at least a fraction, preferably all, of the gas effluent from the first gas-liquid separation section of step c), and tailing d2) of at least a fraction, preferably all, of the gas effluent from the last gas-liquid separation section of step c). If all of the gas effluent from the first gas-liquid separation section of step c) is purged or directly recycled to step a), step d) includes a step d2) of tailing at least a fraction, preferably all, of the gas effluent from the last gas-liquid separation section of step c).

[0139] According to a third particular embodiment, step d) includes a topping d1) of at least a fraction, preferably all, of the gas effluent from the first gas-liquid separation section of step c), and a purging and / or direct recycling to step a) of at least a fraction, preferably all, of the gas effluent from the last gas-liquid separation section of step c). If all of the gas effluent from the last gas-liquid separation section of step c) is purged or directly recycled to step a), step d) includes a step d1) of topping at least a fraction, preferably all, of the gas effluent from the first gas-liquid separation section of step c).

[0140] Optionally, step d) may also include the transfer of a fraction or all, preferably a fraction, of the gas effluent from the first gas-liquid separation section to step b) for use, for example, as an extraction solvent in substep b3) or for cleaning filters implemented in substep b1).

[0141] The topping d1) advantageously corresponds to a purification step of the treated stream, in particular of at least a fraction of the gas effluent from the first gas-liquid separation section of step c), 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 solvent of said treated stream, in particular the dissolving solvent.

[0142] When implemented, the topping step d1) is fed by at least a fraction, preferably all, of the gas effluent from the first gas-liquid separation section of step c). According to a first particular embodiment of this topping step d1), all of the gas effluent from the first gas-liquid separation section of step c) is sent to the topping step d1).According to a second particular embodiment of this topping step d1), a first fraction of the gas effluent from the first gas-liquid separation section of step c) is sent to the topping step d1), a second fraction of the gas effluent from the first gas-liquid separation section of step c) can be recycled directly upstream of step a), and optionally a third fraction of the gas effluent from the first gas-liquid separation section of step c) can be used in step b) for example as an extraction solvent in a substep b3) or to clean filters implemented in a substep b1).According to another particular embodiment of this topping step d1), a first fraction of the gas effluent from the first gas-liquid separation section of step c) is sent to the topping step d1), and a second fraction of the gas effluent from the first gas-liquid separation section of step c) can be purged.

[0143] According to a particular variant, the gas effluent from the first gas-liquid separation section of step c) may be partially condensed, in particular in a partial condenser, prior to the topping step d1), to obtain a partial condenser gas fraction which includes dissolving solvent and advantageously concentrates light impurities, and a partial condenser liquid fraction which includes dissolving solvent and possibly heavy impurities carried along in the gas effluent from the first gas-liquid separation section of step c), said partial condenser gas fraction being, in part or in whole, sent to the topping step d1), purged and / or recycled to step a), and said partial condenser liquid fraction being, in part or in whole, sent to the topping step d2), purged and / or recycled to step a).

[0144] When step c) employs at least three gas-liquid separation sections, the topping step d1) may optionally also be fed by at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section of step c), located between the first and last gas-liquid separation sections. Optionally, a fraction or all of the gas stream(s) from the intermediate gas-liquid separation section(s) of step c) may feed the topping step d1) and / or the tailing step d2) and / or may be recycled directly and / or may be purged.Optionally, the gas stream from at least one intermediate gas-liquid separation section of step c) may be partially condensed, in particular in a partial condenser, prior to the topping step d1), and optionally the tailing step d2), to obtain a partial condenser gaseous 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 being, in part or in whole, sent to the topping step d1), purged and / or recycled to step a), and said partial condenser liquid fraction being, in part or in whole, purged and / or recycled to step a), and / or sent to the tailing step d2).

[0145] Advantageously, the topping step d1) implements a topping section preferably comprising 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 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 topping section employs at least one topping distillation column and optionally one or more partial condenser(s) advantageously located upstream of the topping distillation column.

[0146] The topping step d1) advantageously produces a topped solvent stream, particularly at the bottom of the topping distillation column, and a stream of light impurities, particularly at the top of the topping distillation column.

[0147] The light impurities stream concentrates light impurities, i.e., compounds whose boiling point is lower than that of the dissolving solvent. Advantageously, the light impurities stream has a higher concentration of light impurities than the stream feeding the topping step (d1), i.e., higher than that of at least a fraction of the gas effluent from the first gas-liquid separation section of step (c) and optionally of at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section of step (c). Preferably, the light impurities stream comprises at least 1 wt%, preferably at least 2 wt%, of light impurities relative to the total weight of the light impurities stream. In a very particular way, it can include 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.In general, the light impurities stream also includes 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 impurities stream. The light impurities stream can advantageously be purged, and optionally recovered for purification and valorization. The topped-off solvent stream advantageously includes dissolving solvent, preferably at 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 most 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 topped-off solvent stream.At least part or all of the topped solvent stream is sent, in particular continuously, semi-continuously or discontinuously, to the dissolution step a) and / or to the topping d2), more particularly to the topping feed d2).

[0148] According to a particular embodiment, part of the topped-off solvent stream is sent to step a) and another part of said topped-off solvent stream to the topping d2), for example, in the case where the concentration of heavy impurities in the gas effluent or gas effluents that feed the topping d1) is relatively high. This particular embodiment thus makes it possible to supply step a) with a recycled dissolving solvent stream that has a satisfactory average impurity content while limiting energy consumption, particularly compared to the embodiment in which the entire topped-off solvent stream would be sent to d2), again in the case of a high concentration of heavy impurities in the gas effluent or gas effluents that feed the topping d1).

[0149] The tailing d2) advantageously corresponds to a purification step of the treated stream, in particular of at least a fraction of the gas effluent from the last gas-liquid separation section of step c), 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 solvent of said treated stream, in particular the dissolving solvent.

[0150] When implemented, the tailing step d2) is fed by at least a fraction, preferably all, of the gas effluent from the last gas-liquid separation section of step c). According to a first particular embodiment of this tailing step d2), all of the gas effluent from the last gas-liquid separation section of step c) is sent to the tailing step d2). According to a second particular embodiment of this tailing step d2), a first fraction of the gas effluent from the last gas-liquid separation section of step c) is sent to the tailing step d2), and a second fraction of the gas effluent from the last gas-liquid separation section of step c) can be recycled directly upstream of step a) and / or purged.According to this second particular embodiment of the de-tailing step d2), the gaseous effluent from the last gas-liquid separation section of step c) can be partially condensed, in particular in a partial condenser, prior to the de-tailing step d2), to obtain a partial condenser liquid fraction, which includes dissolving solvent and advantageously concentrates heavy impurities, and a partial condenser gaseous fraction, which includes dissolving solvent and possibly residual light impurities, said partial condenser liquid fraction being, in part or in whole, sent to the de-tailing step d2), purged and / or recycled to step a), and said partial condenser gaseous fraction being, in part or in whole, sent to the topping step d1), purged and / or recycled to step a).

[0151] When step c) employs at least three gas-liquid separation sections, the tailing step d2) may optionally also be fed by at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section of step c), located between the first and last gas-liquid separation sections. Optionally, a fraction or all of the gas stream(s) from the intermediate gas-liquid separation section(s) of step c) may feed the tailing step d2) and / or the topping step d1) and / or may be recycled directly and / or may be purged.

[0152] Optionally, the gas stream from at least one intermediate gas-liquid separation section of step c) may be partially condensed, in particular in a partial condenser, prior to the de-tailing step d2), and optionally the topping step d1), to obtain a partial condenser gaseous 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 being, in part or in whole, purged and / or recycled to step a) and / or sent to the topping step d1), and said partial condenser liquid fraction being, in part or in whole, sent to the de-tailing step d2), purged and / or recycled to step a).

[0153] Advantageously, the de-tailing step d2) implements a de-tailing section preferably comprising 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 de-tailing 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 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 de-tailing section employs at least one de-tailing distillation column and possibly one or more partial condenser(s) advantageously located upstream of the de-tailing distillation column.

[0154] The de-tailing step d2) advantageously produces a tailed solvent stream, particularly at the top of the de-tailing distillation column, and a heavy impurity stream, particularly at the bottom of the de-tailing distillation column.

[0155] The heavy impurities stream concentrates heavy impurities, that is, compounds whose boiling point is higher than that of the dissolving solvent. Advantageously, the heavy impurities stream has a higher concentration of heavy impurities than the stream feeding the tailing step (d2), that is, higher than that of at least a fraction of the gas effluent from the last gas-liquid separation section of step (c) and possibly of at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section of step (c). Preferably, the heavy impurities stream comprises at least 1% by weight, preferably at least 5% by weight, most preferably at least 10%, and preferably at least 20% by weight, of heavy impurities relative to the total weight of the heavy impurities stream.In a very specific way, it can comprise up to 80% by weight of heavy impurities relative to the total weight of the heavy impurity stream. Generally, it also includes a dissolving solvent, specifically 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. The heavy impurity stream can advantageously be purged, possibly recovered for purification and valorization.

[0156] The tailed solvent stream advantageously comprises 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 most 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 tailed solvent stream. At least part or all of the tailed solvent stream is sent, in particular continuously, semi-continuously, or discontinuously, to the dissolving step (a) and / or to the tailing (d1), more particularly to the tailing feed (d1).According to a particular embodiment, part of the tailed solvent stream is sent to step a) and another part of said tailed solvent stream to the topping d1), for example, in the case where the concentration of light impurities in the gas effluent or gas effluents feeding the topping d2) is relatively high. This particular embodiment thus makes it possible to supply step a) with a recycled dissolving solvent stream that has a satisfactory average content of light and heavy impurities, while limiting energy consumption, particularly compared to the embodiment in which the entire tailed solvent stream would be sent to d1), again in the case of a high concentration of light impurities in the gas effluent or gas effluents feeding the topping d1).

[0157] Advantageously, part or all of the tailed solvent stream sent to step a) can be mixed with part or all of the tailed solvent stream sent to step a), the mixing being carried out prior to the entry of step a) (i.e. upstream of the dissolution step a), said mixture advantageously comprising at least part of the recycled solvent stream which itself comprises at least part of the dissolution solvent stream which feeds step a).

[0158] Optionally, when step c) implements at least three gas-liquid separation sections, step d) may also include direct recycling, i.e., direct transfer to the dissolution step a), of at least a fraction of the gas effluent(s) produced by the intermediate gas-liquid separation section(s) located between the first and last gas-liquid separation sections of step c). Thus, according to a particular embodiment, a fraction of the gas effluent(s) produced by the intermediate gas-liquid separation section(s) of step c) may be sent to the topping section d1), a second fraction to the tailing section d2), and a third fraction may be recycled directly to step a) without being purified by either topping or tailing.According to another embodiment, all or at least one of the gas effluent(s) produced by the intermediate gas-liquid separation section(s) of step c) can be recycled directly, i.e. sent directly, to step a), without being purified by topping or tailing.

[0159] According to a preferred embodiment of the invention, step d) comprises, preferably consists of, tailing d2) at least a fraction, or all, of the gas effluent from the last gas-liquid separation section of step c) and optionally at least a fraction of the gas effluent(s) from the intermediate gas-liquid separation section(s) of step c). According to this embodiment, the gas effluent from the first gas-liquid separation section of step c) is then purged and / or sent directly to step a) and / or sent to purification step b) for use as an extraction solvent or for cleaning purification equipment, for example, for cleaning filters.Preferably, the gas effluent from the first gas-liquid separation section of step c) is sent directly to step a) and / or possibly sent, at least in part, to step b) for purification, for example to clean filters, continuously or discontinuously.

[0160] According to a second preferred embodiment of the invention, step d) comprises, preferably consists of, a topping d1 ) of at least a fraction, or all, of the gas effluent from the first gas-liquid separation section of step c) and a tailing d2) of at least a fraction, or all, of the gas effluent from the last gas-liquid separation section of step c), optionally the gas effluent(s) from the intermediate gas-liquid separation section(s) of step c) being at least partly sent to the topping d1 ) and / or the tailing d2).According to a particular case of this embodiment, a fraction of the gas effluent from the first gas-liquid separation section of step c) feeds the topping d1) and a second fraction of the gas effluent from the first gas-liquid separation section can be recycled directly to step a), optionally a third fraction can be sent to the purification step b), for example to a sub-step b3), continuously or discontinuously.

[0161] According to this second embodiment, the topping section and the tailing section are either separate or combined (i.e., distinct or common). For example, topping is performed in a first distillation column, and tailing is performed in a second distillation column that is separate from the first. In another example, both topping and tailing are performed in a single distillation column, which therefore produces a stream of light impurities at the top of the column, a stream of heavy impurities at the bottom of the column, and a stream of purified solvent—that is, topped and tailed—in an intermediate zone of the column located between the top and the bottom of the column. Preferably, the topping section and the pollarding section are common, i.e. a single section implements both topping and pollarding, in order to limit energy consumption and therefore the costs associated with this consumption.

[0162] According to another particular embodiment of the invention, step d) preferably comprises a removal d1) of at least a fraction, or all, of the gas effluent from the first gas-liquid separation section of step c) and optionally of the gas effluent(s) from the intermediate gas-liquid separation section(s) of step c). According to this embodiment, the gas effluent from the last gas-liquid separation section of step c) is then purged and / or sent directly to step a). When an entraining agent is introduced into the last gas-liquid separation section of step c), step d) may further comprise a solvent-entraining agent separation, advantageously located:

[0163] - upstream of tailing d2) and preferably upstream of any possible splitting of the gas effluent from the last gas-liquid separation section of c) into at least two partial streams, for example before said gas effluent is divided into a fraction sent to d2) and a fraction recycled directly to a) or purged; or

[0164] - downstream of tailing d2) and upstream or downstream, preferably upstream, of any possible mixing of the tailed solvent stream with the tailed solvent and / or with at least a fraction of one (or more) gas effluent(s) from step c) and directly recycled to step a).

[0165] When an inert gas stream is introduced into the first gas-liquid separation section of step c), step d) may further include a condensation-separation during which the gas effluent from the first section of c) is partially condensed and an inert gas stream is separated from a solvent effluent which is then sent at least partly to the topping d1), the inert gas stream being able to be recycled to the first gas-liquid separation section of step c) and constitute said inert gas stream.

[0166] Advantageously, the fraction or all of the topped solvent stream transferred to step a) and / or the fraction or all of the tailed solvent stream transferred to step a) constitute(s) at least a part of said recycled solvent stream. Optionally, when step c) implements at least three gas-liquid separation sections of step c), the recycled solvent stream may also include a fraction or all of a gas effluent from at least one intermediate section of step c) located between the first and last gas-liquid separation sections of c), and advantageously recycled directly without being treated by topping d1) and / or tailing d2).Furthermore, in the case where a fraction of the gas effluent from the first gas-liquid separation section of step c) and / or a fraction of the gas effluent from the last gas-liquid separation section of step c) is / are recycled directly to step a), without undergoing topping and / or tailing, the recycled solvent stream may then include, in addition, a fraction of the gas effluent from the first section of c) and / or a fraction of the gas effluent from the last section of c).

[0167] Optionally, step d) may also include a solvent-water separation d3) to separate (and thus remove) water from the recycled solvent stream. This optional solvent-water separation d3) produces a dried recycled solvent stream, which is advantageously sent to a) to compose at least part of the dissolving solvent stream, and simultaneously an aqueous stream that is purged and possibly recovered for further processing. This optional solvent-water separation d3) is advantageously located downstream of the topping steps d1) and / or tailing steps d2), and obviously upstream of step a). This water separation step dries the recycled solvent stream, which contains dissolving solvent, and thus optimizes the purification of said stream to supply step a) with a high-purity dissolving solvent, thereby limiting the degradation of the targeted thermoplastics that could be induced by the presence of water.

[0168] Optionally, step d) may also include another solvent-water separation of 3) to separate (and thus remove) water from the solvent stream feeding the tailing step, so as to avoid any azeotrope formation with water in the tailing section and thus optimize tailing. More specifically, said other solvent-water separation of 3) makes it possible to remove water from at least a fraction of the gas effluent from the last gas-liquid separation section of step c) (when said fraction is sent to the tailing) and possibly at least a fraction of the gas effluent from at least one of the intermediate gas-liquid separation sections of step c). When implemented, said other solvent-water separation of 3) is located at step d) (i.e. downstream of step c) and upstream of the stemming step d2), when the latter is also implemented.The aforementioned solvent-water separation of 3) advantageously produces a dried solvent effluent, which is then sent to the dehulling section where the formation of azeotropes with water is prevented, and thus where 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 aforementioned solvent-water separation of 3) also produces an aqueous stream containing water, which can be purged or recovered and treated.

[0169] The said recycled solvent stream, possibly dried, constitutes at least part of the dissolving solvent that feeds step a). The recycled solvent stream 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 supplied, 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.

[0170] Thus, the process according to the invention proposes a sequence of simple operations that allows for the treatment of all types of plastic fillers, for example, post-consumer plastic waste, by dissolution-purification, thereby obtaining a stream of purified thermoplastics, in particular a stream of purified polyolefins, of good quality, while limiting the consumption of fresh solvents and especially external inputs 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 all types of plastic fillers, 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.

[0171] Device

[0172] The present invention also relates to a device for dissolving a plastic filler to obtain a stream of purified thermoplastic polymers, which comprises:

[0173] 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 being advantageously 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);

[0174] B) purification means 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: solid-liquid (or solid-liquid-liquid) separation means, 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;

[0175] (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: a succession 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 three or four, each gas-liquid separation section in the series comprising a feed system, a liquid withdrawal system for withdrawing a liquid effluent which includes the thermoplastics in question, and a gas withdrawal system for withdrawing a gaseous effluent which includes dissolving solvent.the feed system of the first gas-liquid separation section being connected to at least one of the purification means and allowing the supply of purified polymer solution to said solvent-polymer separation device C), the feed system of each subsequent gas-liquid separation section being connected to the liquid withdrawal system of its previous gas-liquid separation section (i.e., the section directly preceding the fed section, for example the feed system of section 2 is connected to the liquid withdrawal system of section 1, etc., and the feed system of section N is connected to the liquid withdrawal system of section (N-1)), the liquid withdrawal system of the last (or Nth section or section N) gas-liquid separation section allowing the recovery of said purified thermoplastic polymer stream,the gas withdrawal system of each gas-liquid separation section being advantageously connected to the device D) for recycling the dissolving solvent,

[0176] D) a dissolving solvent recycling device, characterized in that said dissolving solvent recycling device comprises: - a topping section for at least a fraction of the gaseous effluent withdrawn from the first gas-liquid separation section of device C), for separating light impurities (i.e. compounds whose boiling point is lower than that of the distillation solvent), the topping section comprising a feed system, a light impurity withdrawal system and a topped solvent flow withdrawal system, the feed system of said topping section being connected, directly or indirectly, at least to the gaseous withdrawal system of the first gas-liquid separation section of solvent-polymer separation device C),said solvent flow withdrawal system being connected directly or indirectly to the dissolution means and / or possibly to the feed system of the de-tailing section, and / or,

[0177] - a de-tailing section for at least a fraction of the gaseous effluent withdrawn from the last gas-liquid separation section of device C), to separate heavy impurities (i.e. compounds whose boiling point is higher than that of the distillation solvent), the 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 de-tailing section being connected, directly or indirectly, at least to the gaseous withdrawal system of the last gas-liquid separation section of solvent-polymer separation device C), said withdrawal system for a de-tailed solvent stream being connected directly or indirectly to the dissolution means and / or possibly to the feed system of the de-tailing section,

[0178] - possibly, when the solvent-polymer separation device C) comprises at least three gas-liquid separation sections, a transport section connecting the gas withdrawal system of the intermediate gas-liquid separation section(s), located between the first and last gas-liquid separation section of device C), to the feed system of the topping section and / or to the feed system of the tailing section, and / or directly or indirectly to the dissolution means A), and

[0179] - possibly a first transfer section which connects the gas withdrawal system of the first gas-liquid separation section of the solvent-polymer separation device C) to the dissolution means A), and which therefore allows a fraction or all of the gas effluent from the first gas-liquid separation section of the solvent-polymer separation device C) to be sent to the dissolution means A), and / or

[0180] - possibly a second transfer section which connects the gas withdrawal system of the last gas-liquid separation section of the solvent-polymer separation device C) to the dissolution means A), and which therefore allows to send to the dissolution means A) a fraction or all of the gas effluent from the last gas-liquid separation section of the solvent-polymer separation device C).

[0181] Optionally, the dissolving solvent recycling device D) may also include a system for purging at least a fraction of at least one gas effluent from the succession of gas-liquid separation sections of device C).

[0182] Preferably, the dissolving solvent recycling device D) includes a topping section and a tailing section. In this preferred embodiment, the topping and tailing sections may or may not be separate (i.e., distinct from each other or shared). When the solvent-polymer separation device includes at least three gas-liquid separation sections, device D) further includes a transport section.

[0183] Advantageously, the de-tailing section includes at least one gas-liquid separation device, optionally accompanied by devices for adjusting temperature and pressure, to allow purification by de-tailing, that is, the separation of compounds whose boiling point is lower than that of the distillation solvent.The topping and tailing sections may, for example, implement one or more pieces of equipment chosen from: a partial condenser, a separator flask, a column, a distilling column, a stripper, equipment including 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.Preferably, the topping section employs at least one topping distillation column and possibly one or more partial condenser(s) advantageously located upstream of the topping distillation column; the tailing section employs at least one tailing distillation column and possibly one or more partial condenser(s) advantageously located upstream of the tailing distillation column.

[0184] Advantageously, the dissolving solvent recycling device D) makes it possible to obtain at its outlet a recycled solvent stream which includes at least a fraction of the topped solvent and / or at least a fraction of the tailed solvent, and possibly at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section of device C) and located between the first and last gas-liquid separation sections, possibly a fraction of the gas effluent from the first gas-liquid separation section of device C) and / or a fraction of the gas effluent from the last gas-liquid separation section of device C).

[0185] Optionally, the dissolving solvent recycling device (D) may further include a solvent-water separation section to remove water from the recycled solvent stream. When integrated into the treatment device, this optional solvent-water separation section is advantageously located downstream of the topping and / or stemming sections and, where applicable, the transport section, or advantageously located downstream of the stemming section.The said possible solvent-water separation section includes a supply, preferably connected to the withdrawal system of a tipped solvent stream from the tipping section, to the withdrawal system of a tailed solvent stream from the tailing section, to the gas withdrawal system of the intermediate gas-liquid separation section(s) of device C) when it is / are present, possibly to the gas withdrawal system of the first gas-liquid separation section of device C), possibly to the gas withdrawal system of the last gas-liquid separation section of device C), or a combination of at least two of these withdrawal systems or all of these withdrawal systems.The said possible solvent-water separation section includes at the outlet a withdrawal of dried recycled solvent stream and a withdrawal of an aqueous stream, said withdrawal of dried recycled solvent stream being connected with the means A) of dissolution.

[0186] Optionally, the dissolving solvent recycling device D) may also include another solvent-water separation section to remove water from the stream feeding the tailing section. This optional additional solvent-water separation section is advantageously located upstream of the tailing section. It is advantageously connected at least to the gas withdrawal system of the last gas-liquid separation section of device C) and optionally to the gas withdrawal system(s) of at least one intermediate gas-liquid separation section of device C).The gas-liquid separation sections of device C) can 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, gas-liquid separation sections may employ one or more pieces of equipment selected from: a separator flask, a column, a distilling 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.

[0187] Advantageously, the solvent-polymer separation device (C) further includes at least one pressure control system in each gas-liquid separation section of the series, so as to adjust the pressure in each gas-liquid separation section to a value lower than the outlet pressure of the purification means, and so as to adjust the pressure in the subsequent section to a value lower than that of the preceding section. Optionally, the solvent-polymer separation device (C) may also include at least one temperature control system, in particular for the inlet temperature, of each gas-liquid separation section.

[0188] 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, the device E) comprises, in addition to a liquid supply system connected via connecting lines to the dissolving means A), connecting lines 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.

[0189] Advantageously, the treatment device according to the invention also includes transport equipment between said means, devices and systems, for example connecting lines, pumps, etc.

[0190] 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.

[0191] The examples and figures that follow illustrate the invention, in particular particular embodiments of the invention, without limiting its scope.

[0192] LIST OF FIGURES

[0193] Figure 1

[0194] Figure 1 represents a particular embodiment of the process according to the invention. It illustrates the process described in Example 2, in which step d) comprises topping and tailing carried out in two separate sections, the topping section (d1) for topping and the tailing section (d2) for tailing.

[0195] 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 by 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 15 of recycled solvent. A crude polymer solution 4 is obtained at the outlet of step a) of dissolution.

[0196] 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).

[0197] In this particular embodiment, step c) implements four gas-liquid separation sections (c1), (c2), (c3), (c4), which operate in series. Each gas-liquid separation section (c1), (c2), (c3), (c4) produces a liquid effluent, respectively I1, I2, I3, I4, which includes the targeted thermoplastics, and a gas effluent, respectively g1, g2, g3, g4, which includes the dissolving solvent. The purified polymer solution 5 feeds the first gas-liquid separation section (c1), while each of the subsequent sections (c2), (c3), (c4) is fed by the liquid effluent produced by the preceding section; that is, section (c2) by the liquid effluent I1 produced by (c1), section (c3) by the liquid effluent I2 produced by (c2), and section (c4) by the liquid effluent I3 produced by (c3). The liquid effluent I4 produced by section (c4) constitutes a stream 7 of purified thermoplastic polymers which can then be used in any type of application.An additive 16, in particular an antioxidant, is introduced for example into the liquid effluent I3 produced by the third gas-liquid separation section c3.

[0198] The gas effluents g1, g2, g3, g4 produced are then sent to a step d) for recycling the dissolving solvent. In this particular embodiment, step d) includes topping and tailing carried out in separate topping (d1) and tailing (d2) sections.

[0199] More specifically, the gas effluent g1 produced by the first gas-liquid separation section (c1) is divided into two partial streams g1a and g1b, for example, into two equal streams (i.e., a 50 / 50 weight distribution of streams g1a and g1b). The partial stream g1a is sent to the topping section (d1) to produce a stream 9 of topped solvent, which is recycled to step a) to form part of the recycled solvent stream 15, and a stream 8 of light impurities, which is purged. The partial stream g1b is recycled directly to step a) (stream g1c) to form another part of the recycled solvent stream 15 and / or possibly sent, at least in part, to the purification step b) (stream g1d), either continuously or discontinuously, for example, to clean filters used in step b).In the specific embodiment of Figure 1, the gas effluent g2 produced by the second gas-liquid separation section (c2) is mixed with a partial stream g3b to form stream 10, which is recycled directly to step a) and thus constitutes part of the recycled solvent stream 15. The gas effluent g3 produced by the third gas-liquid separation section (c3) is divided into two equal partial streams g3a and g3b (i.e., with a 50 / 50 weight distribution of streams g3a and g3b). The partial stream g3b, as described above, is mixed with the gas effluent g2 to form stream 10, which is recycled to step a). The partial stream g3a is then sent to the tailing section (d2).The gas effluent g4 produced by the last gas-liquid separation section (c4) is sent to a solvent-water separation stage (d'3) to produce a dried solvent effluent 11 and an aqueous stream 12 containing water, which is purged. This dried solvent effluent 11 is then mixed with the partial stream g3a and sent to the tailing section (d2). The tailing section (d2) produces a stream 13 of heavy impurities, which is purged, and a stream 14 of tailed solvent, which is recycled to stage a) to form part of the recycled solvent stream 15.

[0200] In the case of the embodiment shown in Figure 1, the recycled solvent stream 15 is therefore composed of:

[0201] - the 9 stream of tipped solvent;

[0202] - the 14 stream of dequeued solvent;

[0203] - the partial flow g1 c which is a fraction of the gas effluent g1 from the first gas-liquid separation section (c1) and which is sent directly to a); and

[0204] - the stream 10 comprising the entire gas effluent g2 and a fraction g3b of the gas effluent g3, which are sent directly to a).

[0205] Figure 2

[0206] Figure 2 represents another particular embodiment of the process according to the invention. It illustrates the process described in Example 3 and whose step d) includes topping and tailing carried out in a common section (d1 ) / (d2).

[0207] In the embodiment shown in Figure 2, the steps a) dissolution, b) purification and c) solvent-polymer separation are identical to those of the process illustrated in Figure 1.

[0208] Thus, in the embodiment of Figure 2, 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 by 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 15 of recycled solvent. A crude polymer solution 4 is obtained at the outlet of step a) of dissolution.

[0209] 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).

[0210] In this particular embodiment, step c) implements 4 gas-liquid separation sections (c1), (c2), (c3), (c4), which operate in series.

[0211] Each gas-liquid separation section (c1), (c2), (c3), (c4) produces a liquid effluent, respectively I1, I2, I3, I4, which includes the targeted thermoplastics, and a gas effluent, respectively g1, g2, g3, g4, which includes the dissolving solvent. The purified polymer solution 5 feeds the first gas-liquid separation section (c1), while each of the subsequent sections (c2), (c3), (c4) is fed by the liquid effluent produced by the preceding section; that is, section (c2) by the liquid effluent I1 produced by (c1), section (c3) by the liquid effluent I2 produced by (c2), and section (c4) by the liquid effluent I3 produced by (c3). The liquid effluent I4 produced by section (c4) constitutes a stream 7 of purified thermoplastic polymers, which can then be used in any type of application.An additive 16, in particular an antioxidant, is introduced for example into the liquid effluent I3 produced by the third gas-liquid separation section c3.

[0212] The gas effluents g1, g2, g3, g4 produced are then sent to a step d) for recycling the dissolving solvent. In this particular embodiment, step d) includes topping and tailing carried out in a common topping (d1) and tailing (d2) section ((d1) / (d2)).

[0213] More specifically, the gas effluent g1 produced by the first gas-liquid separation section (c1) is divided into two partial streams g1a and g1b, for example, into two equal streams (i.e., a 50 / 50 weight distribution of streams g1a and g1b). The partial stream g1b is recycled directly to step a) (stream g1c) to constitute part of the recycled solvent stream 15 and / or possibly sent, at least in part, to the purification step b) (stream g1d), either continuously or discontinuously, for example, to clean filters used in step b). The partial stream g1a is sent to the common topping / tailing section (d1) / (d2). Prior to the common topping-tailing section (d1 ) / (d2 ), the partial flow g1 a is mixed with a flow 11 and a partial flow g3a to form the flow 14 which feeds said common topping-tailing section (d1 ) / (d2 ).The gas effluent g3 produced by the third gas-liquid separation section (c3) is indeed divided into two partial streams, g3a and g3b, which are equal in weight (i.e., with a 50 / 50 weight distribution between streams g3a and g3b). Partial stream g3a, as described above, is mixed with stream 11 and partial stream g1a before being sent to the common topping / tailing section (d1) / (d2). Partial stream g3b is mixed with the gas effluent g2 produced by the second gas-liquid separation section (c2) to form stream 10, which is recycled directly to step a) and constitutes part of the recycled solvent stream 15. The gas effluent g4 produced by the last gas-liquid separation section (c4) is sent to a solvent-water separation stage (d'3) to produce said stream 11 which corresponds to a dried solvent effluent, and an aqueous stream 12 which includes water and is purged.The stream 11 is sent to the common topping-tailing section (d1 ) / (d2). Said common topping-tailing section (d1 ) / (d2) produces a stream 9 of purified solvent (i.e. topped and tailed), which is recycled to step a) to constitute part of the recycled solvent stream 15, a stream 8 of light impurities and a stream 13 of light impurities which are both purged.

[0214] In the case of the embodiment of Figure 2, the recycled solvent stream 15 is therefore composed of: - the purified solvent stream 9;

[0215] - the partial flow g1 c which is a fraction of the gas effluent g1 from the first gas-liquid separation section (c1) and which is sent directly to a); and

[0216] - the stream 10 comprising the entire gas effluent g2 and a fraction g3b of the gas effluent g3, which are sent directly to a).

[0217] EXAMPLES

[0218] In the examples below, the analyses performed on the load and the products obtained are as follows:

[0219] - 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).

[0220] - 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 1164-4), with:

[0221] - 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;

[0222] - 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;

[0223] - 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.

[0224] 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.

[0225] Example 1 (not in accordance with the invention)

[0226] Step a) Dissolution: A feedstock derived from plastic waste and containing 96.5% polypropylene (PP) by weight is fed in flake form into an extruder heated to 200°C. At the extruder outlet, the feedstock is at least partially molten and is mixed with a stream of n-heptane, used as a dissolving solvent and preheated to 200°C, at a solvent-to-feedstock weight ratio of 4:1. The n-heptane stream used in step a) is entirely fresh n-heptane. The mixture of solvent and feedstock is introduced into a stirred reactor at 190°C and maintained at 190°C and 2.0 MPa absolute for a residence time of 1 hour. A crude polymer solution is then obtained.

[0227] Step b) of purification:

[0228] The crude polymer solution, which is continuously recovered from the stirred reactor, is injected into a decanter operated at 190°C and 2.0 MPa. The residence time in the decanter is 1 hour, the residence time corresponding to the ratio between the effective volume of the decanter (i.e., the volume of material in the decanter, which is a function of the decanter's filling rate) and the volumetric flow rate of crude polymer solution feeding the decanter.

[0229] Impurities settle at the bottom of the decanter, forming a "cake" which is purged intermittently (flow 5). At the outlet of the decanter, the recovered polymer solution is filtered through a 10 µm mesh opening filter and then through a 1 µm mesh opening filter.

[0230] The filtered polymer solution is then sent into an adsorption column containing a bed of activated carbon, and operated at 190°C and 2.0 MPa absolute (i.e. at an outlet pressure of 2.0 MPa from the adsorption column).

[0231] The purified polymer solution, recovered at the outlet of the adsorption column, is then subjected to a solvent-polymer separation step.

[0232] Step c) of solvent-polymer separation:

[0233] The purified polymer solution, recovered from the adsorption column outlet, is then subjected to a solvent-polymer separation step (c) which employs four successive gas-liquid separation sections (or stages) c1, c2, c3, c4. The gas-liquid separation sections (or stages) (i.e., c1, c2, c3, c4) 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):

[0234] Stage d: T = 180°C, P = 0.79 MPa,

[0235] Stage c2: T = 180°C, P = 0.61 MPa,

[0236] Stage c3: T = 180°C, P = 0.14 MPa,

[0237] Stage c4: T = 250°C, P = 0.0014 MPa (i.e., 14 mbar). The purified polymer solution, recovered from the adsorption column outlet, feeds the first gas-liquid separation section c1. The liquid effluent I1 produced by the first gas-liquid separation section c1 feeds the second section c2. The liquid effluent I2 produced by the second gas-liquid separation section c2 feeds the third section c3. An antioxidant, Irgafos® 168, is introduced into the liquid effluent I3 produced by the third gas-liquid separation section c3, so as to represent 600 ppm by weight of antioxidant relative to the weight of polypropylene in the liquid effluent I3. The liquid effluent I3 produced by the second gas-liquid separation section c3, mixed with the antioxidant, then feeds the fourth gas-liquid separation section c4.At the outlet of the fourth gas-liquid separation section c4, a liquid effluent I4 is recovered and placed under atmospheric conditions, i.e. at a temperature of about 20°C and a pressure of about 0.1 MPa.

[0238] A polypropylene A is then obtained. It is analyzed according to the methods described above. The results are presented in Table 1.

[0239] Each section c1, c2, c3, c4 of gas-liquid separation also produces a gas effluent, respectively the flows g1, g2, g3 and g4.

[0240] The gas effluents g1, g2, g3 and g4 produced by the gas-liquid separation sections of step c), respectively sections c1, c2, c3, c4, are purged.

[0241] Example 2 (according to the invention)

[0242] A batch of plastic waste containing 96.5% 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-heptane stream that feeds step a) dissolution. In fact, 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.

[0243] In Example 2, a polypropylene B is obtained at the end of the process. It is analyzed according to the methods described above. The results are presented in Table 1.

[0244] In the process of Example 2, the gas effluents g1, g2, g3, and g4 produced by the gas-liquid separation sections of step c), respectively sections c1, c2, c3, and c4, are recovered and treated in a dissolving solvent recycling step d), as illustrated in Figure 1. Step d) comprises a topping step d1) with a topping distillation column and a tailing step d2) with a tailing distillation column, the topping and tailing distillation columns being separate from each other. More specifically, the gas effluent g1 produced by the first gas-liquid separation section (c1) is divided into two equal partial streams g1a and g1b (i.e., a 50 / 50 weight distribution of the g1a and g1b streams).The partial stream g1a is sent to the topping distillation column (d1) to produce a stream 9 of topped solvent, which is recycled to step a) to form part of the recycled solvent stream 15, and a stream 8 of light impurities, which is purged. The partial stream g1b is recycled directly to step a) (stream g1c) to form another part of the recycled solvent stream 15. The gas effluent g2 produced by the second gas-liquid separation section (c2) is mixed with a partial stream g3b to form stream 10, which is recycled directly to step a) and forms part of the recycled solvent stream 15. The gas effluent g3 produced by the third gas-liquid separation section (c3) is divided into two equal partial streams, g3a and g3b (i.e., with a 50 / 50 weight distribution of streams g3a and g3b). The partial stream g3b is mixed with the gas effluent g2, to form stream 10 which is recycled to step a).The partial stream g3a is sent to the tailing section (d2). The gas effluent g4 produced by the last gas-liquid separation section (c4) is sent to a solvent-water separation stage (d'3) to produce a dried solvent effluent 11 and an aqueous stream 12 containing water, which is purged. This dried solvent effluent 11 is then mixed with the partial stream g3a and sent to the tailing distillation column (d2). The tailing distillation column (d2) produces a stream 13 of heavy impurities, which is purged, and a stream 14 of tailed solvent, which is recycled to stage a) to form part of the recycled solvent stream 15.

[0245] The recycled solvent stream 15, obtained at the end of step d), corresponds to 99.8% by weight of the dissolving solvent stream 3 which feeds the dissolving step a), and the fresh solvent stream 2 corresponds to 0.2% by weight of the dissolving solvent stream 3 which feeds the step a).

[0246] Example 3 (according to the invention)

[0247] A plastic waste load containing 96.5% polypropylene (PP) by weight, identical to that processed by the process in Example 1 or the process in Example 2, is processed in Example 3. The steps a) dissolution, b) purification, and c) solvent-polymer separation are carried out in the process of Example 3 in the same manner as in the process described in Example 1, except for the source of the n-heptane stream that feeds the dissolution step a). The process in Example 3 also includes a step d) for recycling the dissolution solvent. The process in Example 3 is illustrated in Figure 2.

[0248] In Example 3, a polypropylene C is obtained at the end of the process. It is analyzed according to the methods described above. The results are presented in Table 1.

[0249] In the process of Example 3, the gas effluents g1, g2, g3 and g4 produced by the gas-liquid separation sections of step c), respectively sections c1, c2, c3, c4, are recovered and treated in a step d) of dissolving solvent recycling, as illustrated in Figure 2: step d) includes a topping step d1) and a tailing step d2) the topping and tailing being carried out in the same distillation column (d1) / (d2).

[0250] More specifically, the gas effluent g1 produced by the first gas-liquid separation section (c1) is divided into two equal partial streams, g1a and g1b (i.e., a 50 / 50 weight distribution of streams g1a and g1b). The partial stream g1b is recycled directly to step a) (stream g1c) to form part of the recycled solvent stream 15. The partial stream g1a is sent to the topping-tailing distillation column (d1) / (d2). Prior to the common topping-tailing distillation column (d1) / (d2), the partial stream g1a is mixed with a stream 11 and a partial stream g3a to form the stream 14 that feeds said topping-tailing distillation column (d1) / (d2). The gas effluent g3 produced by the third gas-liquid separation section (c3) is divided into two equal partial streams g3a and g3b (i.e. with a weight distribution of the streams g3a and g3b of 50 / 50).The partial stream g3a is mixed with stream 11 and partial stream g1a before being sent to the topping-tailing distillation column (d1) / (d2). The partial stream g3b is mixed with the gas effluent g2 produced by the second gas-liquid separation section (c2) to form stream 10, which is recycled directly to step a) and constitutes part of the recycled solvent stream 15. The gas effluent g4 produced by the last gas-liquid separation section (c4) is sent to a solvent-water separation step (d'3) to produce stream 11, which corresponds to a dried solvent effluent, and an aqueous stream 12, which includes water and is purged. Stream 11 is sent to the topping-tailing distillation column (d1) / (d2). The topping-tailing distillation column (d1) / (d2) produces a stream 9 of purified solvent (i.e.(headed and tailed), which is recycled to step a) to constitute part of stream 15 of recycled solvent, a stream 8 of light impurities and a stream 13 of light impurities which are both purged.

[0251] The recycled solvent stream 15, obtained at the end of step d), corresponds to 99.8% by weight of the dissolving solvent stream 3 which feeds the dissolving step a), and the fresh solvent stream 2 corresponds to 0.2% by weight of the dissolving solvent stream 3 which feeds the step a).

[0252] Table 1 below compares the quality parameters (ash content and colorimetry) of the polypropylenes obtained from the processes in Examples 1, 2, and 3 with respect to the feedstock. Table 1 also compares the energy consumption for the topping and tailing steps of the processes in Examples 2 and 3, relative to each other, with the energy consumption of the topping and tailing distillation columns in Example 2 being taken as the reference consumption. Table 1

[0253] The processes in Examples 2 and 3, which conform to the invention, consume only 0.2% by weight of fresh solvent compared to the total quantity of dissolving solvent required to supply step a), with 99.8% 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, B and C obtained from the processes of Examples 1, 2 and 3 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 93; colorimetric parameter a approaching 0, i.e. between -0.3 and 0.6; colorimetric parameter b between 3.6 and 3.2).

[0254] Furthermore, it appears that the topping-tailing distillation column (d1 ) / (d2) of Example 3 has a significant energy consumption gain (-70%, i.e. 100-30) compared to the two topping and tailing distillation columns (d1 ) and (d2) of Example 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 at least one 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, comprising: b1) a substep of separating insolubles; and / or b2) a substep of washing by contact with a dense solution; and / or b3) a substep of extracting impurities by an extraction solvent; and / or b4) a substep of adsorbing impurities by contact with at least one adsorbent;(c) a solvent-polymer separation step of the purified polymer solution, to obtain at least one stream of purified thermoplastic polymers, said solvent-polymer separation step (c) employing a series of several gas-liquid separation sections, the purified polymer solution, obtained at the end of purification step (b), feeding the first gas-liquid separation section, each gas-liquid separation section producing a liquid effluent, which includes the thermoplastics in question, and a gas effluent which includes dissolving solvent, the liquid effluent from the earlier section feeding the later section, and the liquid effluent from the last gas-liquid separation section of the series constituting said stream of purified thermoplastic polymers;d) a step of recycling the dissolving solvent, to produce a recycled solvent stream, step d) comprising: d1 ) a topping of at least a fraction of the gas effluent from the first gas-liquid separation section of step c), said topping being fed by a fraction or all of the gas effluent from the first gas-liquid separation section of step c), said topping d1 ) producing a topped solvent stream and a light impurities stream,; at least a fraction of the decapped solvent stream constituting at least part of said recycled solvent stream and / or being sent to decapping d2), and / or d2) decapping of at least a fraction of the gas effluent from the last gas-liquid separation section of step c), said decapping being fed by a fraction or all of the gas effluent from the last gas-liquid separation section of step c), said decapping producing a decapped solvent stream and a heavy impurities stream, at least a fraction of the decapped solvent stream comprising at least part of said recycled solvent stream of the dissolving solvent stream that feeds step a), and / or being sent to decapping d1).

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

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 180°C; preferably the dissolving solvent comprises an isomer or a mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane.

5. A method according to any one of the preceding claims, wherein step c) employs 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.

6. A method according to any one of the preceding claims, wherein step d) comprises topping d1) and tailing d2).

7. Method according to the preceding claim, wherein the topping d1) employs a topping section and the tailing d2) employs a tailing section, said topping section and said tailing section being distinct from each other or not.

8. A method according to any one of the preceding claims, wherein, when step c) employs at least three gas-liquid separation sections, the topping d1) is fed by at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section located between the first gas-liquid separation section and the last gas-liquid separation section.

9. A method according to any one of the preceding claims, wherein, where step c) employs at least three gas-liquid separation sections, tailing d2) is fed by at least a fraction of the gas effluent from at least one intermediate gas-liquid separation section located between the first gas-liquid separation section and the last gas-liquid separation section.

10. A method according to any one of the preceding claims, wherein step d) comprises a solvent-water separation d3) of the recycled solvent stream, said solvent-water separation d3) being located downstream of the topping steps d1) and / or stemming steps d2), to separate water from the dissolving solvent included in the recycled solvent stream and to produce a dried recycled solvent stream and an aqueous stream, said dried recycled solvent stream comprising at least a part of the dissolving solvent stream that feeds step a), and / or another solvent-water separation d3) located upstream of the stemming step, to separate water from the dissolving solvent included in at least a fraction of the gas effluent produced by the last gas-liquid separation section of step c).

11. A process according to any one of the preceding claims, wherein the purification step b) comprises a substep b1) of insoluble separation, advantageously followed by a substep b4) of adsorption, said substep of insoluble separation comprising a decantation step.

12. A method according to any one of the preceding claims, wherein the plastic filler comprises polyolefins.

13. 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: a succession of N gas-liquid separation sections operating in series, N being an integer greater than or equal to two, each gas-liquid separation section 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 first gas-liquid separation section being connected to at least one of the purification means and enabling the supply of purified polymer solution to said solvent-polymer separation device (c),the feed 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 last gas-liquid separation allowing the recovery of said purified thermoplastic polymer stream, D) a device for recycling the dissolving solvent, characterized in that said device for recycling the dissolving solvent comprises: - a topping section for at least a fraction of the gaseous effluent withdrawn from the first gas-liquid separation section of device C), for separating light impurities, the topping section comprising a feed system, a light impurity withdrawal system and a stripped solvent flow withdrawal system, the feed system of said topping section being connected at least to the gaseous withdrawal system of the first gas-liquid separation section of solvent-polymer separation device C), said stripped solvent flow withdrawal system being connected directly or indirectly to the dissolution means A) and / or possibly to the feed system of the topping section, and / or - a tailing section for at least a fraction of the gas effluent withdrawn from the last gas-liquid separation section of device C), to separate heavy impurities, the tailing section comprising a feeding system, a system for withdrawing a stream of heavy impurities and a system for withdrawing a stream of tailed solvent, the feed system of said tailing section being connected at least to the gas withdrawal system of the last gas-liquid separation section of the solvent-polymer separation device C), said withdrawal system of a tailed solvent stream being connected directly or not to the dissolution means A) and / or possibly to the feed system of the tailing section. - possibly a first transfer section which connects the gas withdrawal system of the first gas-liquid separation section of the solvent-polymer separation device C) to the dissolution means A), and which therefore allows a fraction or all of the gas effluent from the last gas-liquid separation section of the solvent-polymer separation device C) to be sent to the dissolution means A), and / or - possibly a second transfer section which connects the gas withdrawal system of the last gas-liquid separation section of the solvent-polymer separation device C) to the dissolution means A), and which therefore allows to send to the dissolution means A) a fraction or all of the gas effluent from the last gas-liquid separation section of the solvent-polymer separation device C).

14. Device according to claim 13, comprising a section for transporting intermediate gaseous effluents, where the solvent-polymer separation device C) comprises at least three gas-liquid separation sections, said transport section connecting the gas withdrawal system of the intermediate gas-liquid separation section(s), located between the first and last gas-liquid separation section of device C), to the feed system of the topping section and / or feed system of the tailing section, and / or to the dissolution means A).

15. Device according to claim 13 or 14, comprising a topping section, a tailing section, the topping section and the tailing section being distinct from each other or not.

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