OPTIMIZED PLASTICS RECYCLING PROCESS BY POLYMER-SOLVENT DISSOLUTION AND SEPARATION

Abstract

The present invention relates to a process for treating a plastic filler, comprising: a) dissolving the plastic filler in a dissolving solvent, between 100°C and 300°C and between 0.1 and 100.0 MPa absolute, to obtain a crude polymer solution; b) a purification step of the crude polymer solution, to obtain a purified polymer solution; and then c) a solvent-polymer separation step, to obtain a stream of purified thermoplastic polymers, employing one or more gas-liquid separation sections in series, operated at an inlet temperature between 100°C and 300°C and at a pressure lower than the outlet pressure of b), and each producing a gas effluent and a liquid effluent, the liquid effluent from said section or the last gas-liquid separation section constituting said stream of purified thermoplastic polymers. The invention also relates to a device for implementing said process. Figure to be published: 2

Description

Title of the invention: PROCESS FOR RECYCLING PLASTICS BY OPTIMIZED POLYMER-SOLVENT DISSOLUTION AND SEPARATION technical field

[0001] The present invention relates to a process for purifying and recycling plastics, in particular used plastics, in order to obtain a stream of purified thermoplastic polymers that can be used, for example, in the manufacture of new plastic objects. More particularly, the present invention relates to a process for treating a plastic feedstock, particularly 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 using a series of gas-liquid separation sections operated under specific conditions.This process thus makes it possible, after purification of the polymer solution, to separate the dissolving solvent used from the polymer stream in a simple but very efficient manner, and therefore to recover a stream of purified thermoplastics with very low residual solvent content. Previous technique

[0002] Plastics from collection and sorting channels can be recovered through different channels.

[0003] 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.

[0004] So-called chemical recycling aims primarily to eliminate additives and, depending on the processes applied, to more or less chemically modify the macromolecular chains of the polymers considered (for example, recovery of the intact polymer, depolymerization of the latter or non-selective breaking of the chains of various polymers). to obtain mixtures of compounds containing carbon and hydrogen). These various chemical recycling options involve generally complex sequences of steps. For example, plastic waste can undergo a pyrolysis step, and the recovered pyrolysis oil, usually after purification, can be converted, at least in part, for example, into olefins by steam cracking. These olefins can then be polymerized or transformed into monomers before the latter are polymerized. This type of sequence can be adapted for poorly sorted loads or rejects from sorting centers, but it generally requires significant energy consumption, particularly due to the high-temperature treatments.

[0005] Another method for recycling plastic waste involves the deformulation of plastic materials, based on thermoplastics, particularly polyolefins such as (co)polypropylenes and (co)polyethylenes, which appears more environmentally sound. This method of recycling plastic waste consists of dissolving the target polymer in a solvent and removing impurities, such as additives like fillers, colorants, pigments, and metals and / or polymers from the filler other than the target polymer(s), 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.

[0006] Several studies thus present different methods of treating plastic waste by dissolution and purification.

[0007] US patent application 2017 / 002110 describes a particular method for purifying a polymer filler, especially one derived from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, and then contacting the resulting polymer solution with a solid. The method described in US patent application 2017 / 002110 further includes a step of separating the purified polymer from the solvent under temperature and pressure conditions in which the polymer precipitates.

[0008] Document WO 2018 / 114047 proposes a method for the selective dissolution of a particular polymer from a plastic in a solvent at a dissolution temperature close to the boiling point of the solvent. The polymer solution is then centrifuged and the polymer is subsequently separated from the solvent, for example by flash separation.

[0009] Document WO2018 / 118579 describes a method for purifying a polymer feedstock, particularly one derived from plastic waste, by dissolving the polymer in a solvent in a stirred reactor, followed by a sedimentation step. More specifically, WO2018 / 118579 illustrates the purification of a feedstock composed of post-consumer polypropylene by dissolving it in n-butane in a stirred autoclave at 140°C and 900 psig (6.21 MPa), followed by a sedimentation phase after the reactor has stopped. Agitation in the autoclave. The resulting polymer solution is then passed through beds of solids and depressurized to allow at least some of the butane solvent to be separated from the polypropylene.

[0010] The present invention aims to improve these processes for treating thermoplastics by dissolution in a solvent, and in particular the separation of the solvent used from the purified polymer. Specifically, the present invention seeks, in a process for purifying a plastic feedstock comprising thermoplastics by dissolution in a solvent, to optimize the separation of solvents, in particular the dissolution solvent used, from said purified thermoplastics, so as to recover a stream of purified thermoplastics, in particular polyolefins, which is notably decolorized and deodorized, and has a residual solvent content of less than or equal to 5% by weight, preferably in very low solvent levels. The present invention particularly aims to efficiently and simply separate the purified thermoplastics, preferably the purified polyolefins, from the solvent in which they are dissolved. Summary of the invention

[0011] The invention relates to a process for treating a plastic filler comprising thermoplastics, said process comprising:

[0012] a) a step of dissolving the plastic filler in a dissolving 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, to obtain at least one crude polymer solution;

[0013] b) a step of purifying the crude polymer solution, to obtain a purified polymer solution, comprising:

[0014] bl) a substep for separating insolubles; and / or

[0015] b2) a washing substep, by contact with a dense solution; and / or

[0016] b3) an extraction substep, by contact with an extraction solvent; and / or

[0017] b4) a substep of adsorption of impurities by contact with an adsorbent; then

[0018] c) a solvent-polymer separation step of the purified polymer solution, to obtain a stream of purified thermoplastic polymers and at least one stream of solvent,

[0019] said solvent-polymer separation step c) implementing one or more gas-liquid separation sections operating in series,

[0020] said gas-liquid separation section or each of the gas-liquid separation sections being operated at an inlet temperature between 100°C and 300°C and at a pressure lower than the outlet pressure of step b),

[0021] when step c) implements several gas-liquid separation sections, the pressure of the subsequent section being lower than that of the preceding section,

[0022] the purified polymer solution, obtained at the end of step b) of purification, feeding said gas-liquid separation section or the first gas-liquid separation section of the series,

[0023] said gas-liquid separation section or each of the gas-liquid separation sections producing a gas effluent, which corresponds to said at least one solvent stream, and a liquid effluent,

[0024] when step c) implements several gas-liquid separation sections, with the liquid effluent from the earlier section feeding the later section,

[0025] the liquid effluent from said gas-liquid separation section or from the last gas-liquid separation section of the series constituting said purified thermoplastic polymer stream.

[0026] Said at least one solvent stream advantageously comprises the solvent(s) used in the process. In particular, it comprises dissolving solvent and optionally extraction solvent and / or dense solution.

[0027] The advantage of the process according to the invention is to offer a process for recycling, by dissolution, thermoplastics, preferably polyolefins, such as polypropylene, polyethylene, their copolymers, or mixtures thereof, contained in a plastic feed and in particular in plastic waste, for example post-consumer, allowing the recovery of a stream of purified thermoplastics, that is to say freed from at least part of the impurities contained in the plastic feed, and having a very low residual 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.Indeed, the recycling process according to the invention, which is based on the principle of dissolving the thermoplastics in question and purifying the resulting polymer solution, has the advantage, in addition to at least partially eliminating the organic and inorganic impurities contained in the plastic feed, for example additives introduced into the polymer materials by the formulators, of offering a simple and effective scheme for separating the thermoplastics freed from the impurities of the solvent of the polymer solution, in particular the dissolving solvent used.

[0028] Thus, the process according to the invention has the advantage of offering a simple method for recycling thermoplastics, and in particular polyolefins, such as polypropylene, polyethylene, their copolymers, or mixtures thereof, contained in a plastic feedstock, for example, from post-consumer waste, with an optimized solvent-polymer separation step, so as to obtain a purified thermoplastic stream, particularly of polyolefins, notably decolorized and deodorized, with sufficiently low residual impurity and solvent content to that the purified thermoplastics can be used in all types of plastic formulations in place of virgin resin. In particular, the process according to the invention makes it possible to recover a stream of purified thermoplastics, in particular a stream of purified polyolefins, or even polypropylene or polyethylene, 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, relative to the total weight of the stream of purified thermoplastics.

[0029] 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, in effect, the purification of plastic waste to obtain a stream of purified thermoplastic polymers, in particular purified polyolefins, or even purified polypropylene or polyethylene, with reduced impurity content and, in particular, decolorized and deodorized, which can be reused to form new plastic objects. The purified thermoplastics obtained can thus be used directly in formulations mixed with additives, for example, plasticizers, colorants, pigments, fillers, etc., either instead of or in combination with virgin resins, in order to obtain plastic materials with performance, aesthetic, mechanical, or rheological properties that facilitate their reuse and recovery.

[0030] The present invention also relates to a device for processing a plastic feedstock to obtain a stream of purified thermoplastic polymers, said device comprising:

[0031] - means of dissolution for bringing into contact and dissolving at least partially the a plastic filler in a dissolving solvent, and obtain a crude polymer solution

[0032] - purification means for purifying the crude polymer solution and obtaining a purified polymer solution;

[0033] - a solvent-polymer separation device, located downstream of said purification means fication, to separate the purified polymer solution into a stream of purified thermoplastic polymers and at least one solvent effluent,

[0034] characterized in that said solvent-polymer separation device comprises:

[0035] a gas-liquid separation section or several gas-liquid separation sections operating in series, preferably at least two, preferably between two and five, for example three or four, successive gas-liquid separation sections,

[0036] at least one pressure control system in said gas-liquid separation section or in each gas-liquid separation section in the series, so as to adjust the pressure in said gas-liquid separation section or in each gas-liquid separation section in the series to a value lower than the operating pressure at the outlet of the purification means, and when said solvent- The polymer comprises several gas-liquid separation sections, so as to adjust the pressure in the subsequent section to a value lower than that in the preceding section.

[0037] said gas-liquid separation section or each gas-liquid separation section of the series comprising a feed system, a liquid withdrawal system and a gas withdrawal system,

[0038] the supply system of said gas-liquid separation section or of the first gas-liquid separation section of the series being connected to at least one of the purification means and allowing the supply of purified polymer solution to said solvent-polymer separation device,

[0039] where said solvent-polymer separation device comprises several gas-liquid separation sections, the feed system of the later section being connected to the liquid withdrawal system of the earlier section,

[0040] the liquid withdrawal system of said gas-liquid separation section or of the last gas-liquid separation section of the series allowing recovery of said purified thermoplastic polymer stream,

[0041] the gas withdrawal system of said gas-liquid separation section or of each gas-liquid separation section of the series allowing recovery of said at least one solvent effluent, said at least one solvent effluent comprising dissolving solvent. Description of the implementation methods

[0042] In this description, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included in the described range of values. If this is not the case and the limit values ​​are not included in the described range, this clarification will be provided in this description.

[0043] In this description, the expression "greater than..." is understood to mean strictly greater than, and symbolized by the sign ">", and the expression "less than..." is understood to mean strictly less than, and symbolized by the sign "<". When the limit is included, the precision will be provided by the respective expressions "greater than or equal to..." (corresponding to the sign ">") and "less than or equal to" (corresponding to the sign "<").

[0044] 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.

[0045] In the following description, particular embodiments of the invention are described. They can be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0046] According to the present invention, the pressures are absolute pressures and are given indifferently in MPa or in absolute MPa (or MPa abs.).

[0047] The terms "upstream" and "downstream" are to be understood in terms of the general flow of the fluid(s) or flow in question in the process, in particular in terms of the flow of the stream which includes the thermoplastics to be purified.

[0048] In this description, the terms "polymer", "thermoplastic polymer" and "thermoplastic" may be used interchangeably.

[0049] The term "polyolefins" refers to any type of homopolymer and / or copolymer, and mixtures thereof, having olefins as their unit unit. More specifically, polyolefins may be polyethylene homopolymers, designated by the abbreviation PE, of any range (for example, high density, also called HD PE, or low density, called LDPE), polypropylene homopolymers, designated by the abbreviation PP, their copolymers and / or mixtures thereof.

[0050] 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.

[0051] 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 makes it possible to eliminate at least in part. Other types of impurities eliminated during the process according to the invention may be impurities of use, such as, for example, metallic impurities, paper / cardboard, biomass, polymers other than the polymer(s) targeted, etc.

[0052] 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 possibly 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 be of packaging residues, food residues or compostable residues (biomass). These impurities from use 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.

[0053] 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, that is to say, in particular 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 optionally soluble impurities (solubilized in the dissolving solvent).Depending on the steps of the process according to the invention implemented, said polymer solution may therefore comprise, in addition to the thermoplastics concerned dissolved, impurities in the form of insoluble particles which are advantageously suspended in said polymer solution, possibly soluble impurities dissolved in the dissolving solvent, and / or possibly another liquid phase immiscible with said polymer solution.

[0054] It is well known that the boiling point of a compound varies with the operating pressure. However, without further specification, particularly without specification of the pressure, the boiling point of the compound in question, in particular of the dissolving solvent, is understood to be the boiling point of said compound, in particular of said dissolving solvent, at atmospheric pressure (in particular equal to 0.1 MPa). Thus, the boiling point that characterizes the dissolving solvent must be understood as the boiling point of said dissolving solvent at atmospheric pressure (in particular equal to 0.1 MPa).

[0055] The critical temperature and critical pressure of a solvent, particularly a dissolving solvent, are specific to that solvent and depend on the nature of the solvent in question. For a pure substance, the critical temperature and critical pressure of a pure substance are respectively the temperature and pressure of the critical point of said pure substance. As is well known to those skilled in the art, at the critical point and above, the pure substance in question is in supercritical form or in a supercritical state; it can then be called a supercritical fluid.

[0056] The invention thus relates to a process for treating a plastic filler, comprising thermoplastics, more particularly polyolefins, said process preferably comprising:

[0057] a) a step of dissolving the plastic filler in a dissolving solvent, of preferably comprising at least one hydrocarbon compound, preferably aliphatic and preferably paraffinic, advantageously having a boiling point between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 160°C and preferably between 20 and 120°C, 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, preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0, to obtain at least one crude polymer solution,

[0058] step a) being advantageously carried out at a dissolution temperature 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;

[0059] b) a purification step of the crude polymer solution, comprising:

[0060] bl) a substep for separating insolubles, allowing at least one clarified polymer solution to be obtained; and / or

[0061] b2) a washing substep, by contact with a dense solution, allowing to obtain a washed polymer solution; and / or

[0062] b3) a substep of impurity extraction by an extraction solvent, allowing to obtain at least one extracted polymer solution; and / or

[0063] b4) a substep of adsorption of impurities by contact with an adsorbent, for obtain at least one refined polymer solution;

[0064] the purification step enabling the obtaining of a purified polymer solution which advantageously corresponds to a clarified or washed or extracted or refined polymer solution; then

[0065] c) a solvent-polymer separation step of the purified polymer solution, to obtain at least one stream of purified thermoplastic polymers, more particularly at least one stream of purified polyolefins, and at least one solvent stream,

[0066] said solvent-polymer separation step c) employing one or more gas-liquid separation sections operating in series, preferably solvent-polymer separation step c) employing at least two successive gas-liquid separation sections,

[0067] said gas-liquid separation section or each of the gas-liquid separation sections being operated at an inlet temperature between 100°C and 300°C, preferably between 110°C and 275°C, preferably between 150°C and 250°C, and at a pressure lower than that at the outlet of step b), preferably at a pressure lower than 100.0 MPa absolute, preferably lower than 25.0 MPa absolute, preferably lower than 18.0 MPa absolute, preferably lower than 15.0 MPa absolute,

[0068] where step c) implements several gas-liquid separation sections, the pressure of the subsequent section being lower than that of the preceding section,

[0069] preferably the pressure in the gas-liquid separation section or each of the gas-liquid separation sections being 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, and in particular greater than or equal to 0.0008 MPa,

[0070] said purified polymer solution, obtained at the end of step b) of purification, feeding said gas-liquid separation section or the first gas-liquid separation section of the series,

[0071] said gas-liquid separation section or each of the gas-liquid separation sections producing a gas effluent, which corresponds to said at least one solvent stream and which advantageously comprises at least some dissolving solvent, and a liquid effluent which advantageously comprises the thermoplastics referred to,

[0072] when step c) implements several gas-liquid separation sections, the liquid effluent from the previous section feeding the subsequent section,

[0073] the liquid effluent from said gas-liquid separation section or from the last gas-liquid separation section of the series constituting said purified thermoplastic polymer stream,

[0074] the gas effluent produced can be, in whole or in part, purged and / or purified and / or fractionated and / or recycled to step a) and / or possibly to step b),

[0075] possibly step c) comprising the introduction of at least one additive, in particular an antioxidant agent,

[0076] optionally step c) further implementing an intermediate liquid-liquid or supercritical-liquid separation section, located upstream of the gas-liquid separation section or series of gas-liquid separation sections.

[0077] The charge

[0078] 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.

[0079] 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, in particular household plastic waste, construction plastic waste, automotive or any type of transport plastic waste, or waste electrical and electronic equipment. Preferably, the plastic waste comes from collection and sorting channels. The plastics or materials Plastics are generally compositions (or formulations) comprising polymers mixed with additives to impart specific properties to the materials, with the aim of creating, after shaping, various objects (e.g., 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, flame retardants, etc.

[0080] 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, 100% being advantageously 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, such as polyethylene (PE), polypropylene (PP), and / or ethylene-propylene copolymers or mixtures thereof.Preferably, the plastic filler comprises 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 the 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 a mixture of polypropylene (PP) and polyethylene (PE), in particular at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of a mixture of polypropylene (PP) and polyethylene (PE), relative to the total weight of the plastic filler. The polyethylene may more particularly be high-density polyethylene (HDPE).In this particular embodiment, the 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.

[0081] The plastic filler may comprise mixtures of polymers, in particular thermoplastics other than the thermoplastics referred to, and especially other than the polyolefins referred to, additives advantageously used to formulate the plastic material and possibly impurities from use arising from the life cycle of the materials and plastic objects and / or materials from the waste collection and sorting system, all of these compounds being considered impurities. The feedstock for 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 feedstock may, for example, comprise at least 1% by weight of impurities, or even at least 5% by weight of impurities.

[0082] 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 with a size greater than or equal to 10 mm, preferably greater than or equal to 5 mm, or even greater 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 in the form of divided solids, for example as chips, flakes, powder, or granules, to facilitate handling and transport to the process.

[0083] Step a) of dissolution

[0084] 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 thermoplastics, preferably the polyolefins, present in the plastic filler.

[0085] By dissolution, we mean any phenomenon leading to the obtaining of at least one solution of thermoplastic polymers, that is to say, a liquid (or fluid) comprising the thermoplastic polymers in question dissolved in the dissolving solvent. Those skilled in the art are well acquainted with the phenomena involved in the dissolution of polymers: these phenomena include at least mixing, solvation, dispersion, homogenization, and disentanglement of the thermoplastic polymer chains.

[0086] During and after step a) of dissolution, the pressure and temperature conditions allow the dissolving solvent to be maintained, 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 dissolved, at least partially and preferably entirely, 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.

[0087] The dissolving solvent is an organic solvent or a mixture of organic solvents. Advantageously, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (i.e., saturated), preferably linear, branched, or cyclic, and preferably non-aromatic. Preferably, the dissolving solvent comprises at least 80% by weight, preferably at least 95% by weight, and preferably at least 98% by weight of at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched, or cyclic, and preferably non-aromatic, the percentages being expressed as a percentage of the total weight of the dissolving solvent (100% being the maximum).Preferably, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 160°C and preferably between 50 and 120°C. Preferably, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, has between 3 and 12 carbon atoms, preferably between 4 and 10 carbon atoms, preferably between 5 and 8 carbon atoms, and most preferably has 6, 7 or 8 carbon atoms.For example, said at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, may be selected from isomers of butane, pentane, hexane, heptane, octane, nonane, decane, and mixtures thereof, preferably from isomers of 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 from an isomer or mixture of isomers of . hexane, heptane and / or octane, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0088] Preferably, step a) of dissolution is fed with the plastic filler and said 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, more preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0.

[0089] Advantageously, the dissolving solvent that feeds the dissolution step a) is in liquid or possibly supercritical form. It can 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).

[0090] Advantageously, the dissolving solvent comprises, preferably consists of, fresh solvent (or a fresh solvent top-up) and / or a recycled solvent stream from a later step of the process, preferably at least partly from step c) of solvent-polymer separation.

[0091] 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.

[0092] Limiting the temperature in step a) of dissolution to a temperature less than or equal to 300°C, preferably less than or equal to 250°C, makes it possible to avoid or limit the thermal degradation of the thermoplastics concerned, in particular the polyolefins concerned, but also to limit the energy requirement of the process, thus contributing to limiting the operating costs of the process. Advantageously, the dissolution temperature is greater than or equal to the melting temperature of the thermoplastics. targeted plastics, in particular targeted polyolefins, and very advantageously lower than the evaporation temperature at the dissolution pressure of the dissolving solvent, so as to promote their dissolution and very advantageously reduce the residence time required to efficiently dissolve said thermoplastics in the dissolving solvent. Most preferably, the temperature in dissolution step a) is lower than or equal to the critical temperature of the dissolving solvent, so as to avoid the formation of a supercritical phase during dissolution step a) that could disrupt the dissolution.

[0093] In parallel, the dissolution pressure in step a) of dissolution is greater than the saturated vapor pressure of the dissolving solvent at the dissolution temperature, so that the dissolving solvent is at least partly, 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.

[0094] Most advantageously, the temperature and pressure conditions of dissolution reached 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.

[0095] Advantageously, said dissolution step a) is carried out for a residence time preferably of between 1 and 600 minutes, preferably between 2 and 300 minutes, most preferably between 2 and 180 minutes. Residence time is understood as the residence time at the dissolution temperature and dissolution pressure, that is to say the time during which the plastic filler and the dissolving solvent are at the dissolution temperature and dissolution pressure, in step a).

[0096] 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, the remainder of the solvent and / or filler, if any, being able to feed step a) separately.

[0097] When the plastic filler is brought into contact with the dissolving solvent, the The dissolving solvent is advantageously at least partly, and preferably entirely, in liquid or possibly supercritical form, while the plastic feedstock, which includes the thermoplastics in question, may be in solid or liquid form and may optionally include suspended solid particles. The plastic feedstock 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.

[0098] In order to allow contact between the dissolving solvent and the plastic feedstock, and especially to ensure efficient and homogeneous dissolution of the thermoplastics in question in the dissolving solvent, step a) of dissolution may advantageously employ various types of equipment such as mixing, conveying, and heating devices, and for example, a reactor, a pump, a conveying circuit, an agitation system, a furnace, a heat exchanger, a mixer, etc. In particular, step a) advantageously employs at least one piece of dissolving equipment, and possibly at least one feedstock preparation device, a mixing device, and / or a conveying device.The equipment and / or devices implemented 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 implemented in step a) may also include or be combined with heating systems (e.g., a furnace, a heat exchanger, a heat treatment system, etc.) to achieve the conditions necessary for dissolution.

[0099] Preferably, step a) of dissolution employs at least one means for melting at least part of the plastic feed, preferably an extruder, optionally at least one means for mixing at least part of the dissolving solvent and the plastic feed, 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 feed supplies the melting means, in particular the extruder, so that, at the outlet of said means, at least part and preferably all of the thermoplastics concerned, included in the plastic feed, are found at The plastic feedstock, at least partially in its molten state, can then be injected into the dissolving 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 its 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 its 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 (millimeter), 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).

[0100] Preferably, step a) implements, prior to at least one CSTR-type reactor, an extruder followed by at least one static mixer into which at least a fraction of the dissolving solvent is injected, so as to promote shearing and intimate mixing between the dissolving solvent and the plastic filler, which contributes to the dissolution of the thermoplastics concerned.

[0101] Most advantageously, the crude polymer solution obtained at the end of step a) of dissolution comprises at least the dissolving solvent and the thermoplastics concerned, in particular the polyolefins concerned, dissolved in the dissolving solvent. In general, the crude polymer solution also comprises soluble impurities also dissolved in the dissolving solvent and / or insoluble impurities in suspension. The crude polymer solution obtained at the end of step a) of dissolution may optionally also comprise polymers, for example in a molten state, dissolved or not.

[0102] Step b) of purification of the polymer solution

[0103] The purification process according to the invention comprises a purification step of the crude polymer solution obtained from step a). This purification step b) comprises at least one of the substeps b1), b2), b3), b4) described below:

[0104] bl) a substep for separating insolubles,

[0105] b2) a washing substep, by contact with a dense solution,

[0106] b3) an extraction substep, by contact with an extraction solvent,

[0107] b4) a substep of adsorption of impurities by contact with an adsorbent.

[0108] The different substeps bl), b2), b3) and b4) can be operated continuously, in discontinuous (or batch mode) or fed-batch discontinuous mode.

[0109] Preferably, the purification step b) comprises at least one substep bl) of separation of insolubles. Preferably, purification step b) comprises several (i.e., at least two) substeps selected from substeps 1b), b2), b3), and b4), in series with respect to each other, and preferably at least one substep 1b) for separating insolubles and, for example, one substep b4) for adsorption, and most advantageously in the order 1b) then b4). The combination of at least two substeps selected from 1b), b2), b3), and b4) advantageously allows 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 wt%, preferably less than or equal to 1.0 wt%, preferably less than or equal to 0.5 wt%, relative to the total weight of the stream of purified thermoplastics.

[0110] 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.

[0111] 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.

[0112] Substep bl) of separation of insolubles

[0113] The purification process may include a substep β) 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, 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, preferably all, of the insoluble impurities, particularly those suspended in the crude polymer solution obtained from step α), optionally the dissolving solvent, and optionally soluble impurities.

[0114] Substep bl) of insolubles separation thus makes it possible to remove at least some, preferably all, of the insoluble impurities present in suspension in the crude polymer solution obtained from step a). The insoluble impurities removed during substep bl) of insolubles separation are, for example, pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum), and insoluble polymers. When implemented, this substep bl) of separation advantageously makes it possible, in addition to removing at least some of the insoluble impurities, to limit operational problems, in particular of the type clogging and / or erosion, of the process steps located downstream of such a substep bl), while contributing to the purification of the plastic charge.

[0115] The substep bl) 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 most 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. Most advantageously, substep bl) of insoluble separation is carried out at the temperature and pressure conditions at the outlet of step a) of dissolution, i.e. at the dissolution temperature and dissolution pressure as defined above, possibly with a reduced pressure, preferably from 0.01 to 10.0 MPa, preferably from 0.1 to 5.0 MPa due to the pressure losses suffered between step a) and substep bl).

[0116] When integrated into the process, the insolubles separation substep bl) 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 bl). According to a preferred embodiment, substep bl) is fed with the crude polymer solution from step a). According to another embodiment, substep bl) may be fed with a washed polymer solution from a washing substep b2) located upstream of substep bl).

[0117] Advantageously, substep bl) implements any solid-liquid separation step known to those skilled in the art to separate insolubles, solid (such as additives of the type mineral fillers or pigments) or liquid (for example polymers in molten form and of a different nature from that of the thermoplastics concerned), for example a separation step by decantation, filtration, centrifugation, electrostatic separation, etc.

[0118] Preferably, substep bl) 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 not at all soluble and of a different nature than the thermoplastics targeted). When implemented, substep bl) preferably comprises several, i.e., between two and five, solid-liquid separation steps (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 allows for better management of the maintenance of equipment and / or unclogging operations. According to a preferred embodiment, substep bl) 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.

[0119] 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, in particular, 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 enabling the removal of insolubles being carried out using a solvent stream. During substep 1b), filter aids (for example, diatomaceous earth or sand) may optionally be added prior to a decantation step and / or a filtration separation step.

[0120] Depending on the nature of the feedstock, the polymer solution that feeds substep bl), preferably the crude polymer solution, may optionally also include a second liquid phase, for example, consisting of molten polymers, these polymers being of a different nature than the thermoplastics targeted. According to another particular embodiment, substep bl) advantageously implements a solid-liquid-liquid separation section, employing equipment enabling the separation of two liquid phases and one solid phase, preferably by means of at least one two-phase or three-phase separator.

[0121] Said 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, in particular thermoplastics, and the dissolving solvent it may contain. The removal or treatment of said at least one insoluble fraction may be facilitated by equipment enabling the transport and / or separation of polymer and / or solvent possibly present in the insoluble fraction, for example a conveyor, a vibrating tube, a screw conveyor, an extruder, or a stripping machine. Substep bl) may employ transport and / or separation equipment to remove and / or treat said at least one insoluble fraction.Advantageously, substep bl) 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).

[0122] Certain insoluble impurities, in particular certain pigments and mineral fillers, Insolubles typically added during polymer formulation can be in the form of particles smaller than 1 µm. Examples include titanium dioxide, calcium carbonate, and carbon black. In one particular embodiment of substep 1b), said substep 1b) for separating insolubles advantageously employs an electrostatic separator, which allows for the efficient removal, at least partially, of insoluble particles smaller than 1 µm. In another particular embodiment of substep 1b), the substep 1b) for separating insolubles employs a sand filter to remove particles of various sizes, particularly particles smaller than 1 µm.According to yet another particular embodiment, substep bl) of the insolubles employs a tangential filter including a membrane and / or a depth filter, possibly in the presence of filtration aids such as diatomaceous earth.

[0123] Washing Substep b2)

[0124] 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, in particular those soluble in the dissolving solvent, and / or possibly traces of the washing solvent when substep b2) is carried out.

[0125] The washing substep b2) can be integrated upstream or downstream, preferably downstream, of an insolubles separation substep bl) when these two substeps are integrated into the treatment process according to the invention.

[0126] When integrated into the process, the washing substep b2) is fed with a dense solution and with the polymer solution from the step or substep directly upstream of b2), in particular with the crude polymer solution from step a) or the clarified polymer solution from a substep bl). The polymer solution that feeds the 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 the washing substep b2) by dissolution or precipitation and / or by entrainment in the dense solution. Thus, when implemented, this substep b2) contributes to the treatment of the plastic filler and, more particularly, to the purification of the polymer solution.

[0127] The washing substep b2) advantageously comprises contacting the polymer solution that feeds substep b2), in particular the polymer solution Crude or clarified, 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, 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 advantageously having a density 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% by weight of water, most preferably at least 75% by weight of water, most preferably at least 90% by weight of water.

[0128] 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).

[0129] 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 b'2), in particular of the crude or clarified polymer solution, is advantageously between 0.05 and 20.0, preferably between 0.1 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.

[0130] Substep b2) may implement one or more washing equipment allowing the polymer solution to be contacted with the dense solution, and / or one or more separation devices allowing the recovery of 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 being able to include one or more devices used alone or in combination with devices of another type.

[0131] According to a preferred embodiment, the washing substep b2) is carried out in a countercurrent washing column. In this preferred embodiment, the dense solution is advantageously injected into the upper part of the column, preferably the upper half, preferably the upper third, of the column (the upper part of the column meaning the part closest to the column head), 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 specific manner, 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.

[0132] 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 recovery of a washed polymer solution and a washing effluent.

[0133] At the end of substep b2) of washing, the resulting wash effluent advantageously comprises impurities solubilized in the dense solvent and / or insoluble 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 wash solution. This possible wash treatment section can employ one or more well-known solid-liquid separation devices, for example, a separator vessel, a decanter, a decanter centrifuge, a centrifuge, or a filter. The wash effluent can also be sent outside the process, for example, to a wastewater treatment plant when the solution dense is an aqueous solution.

[0134] Extraction step b3)

[0135] 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 is advantageously 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.

[0136] When integrated into the treatment process according to the invention, the extraction substep b3) is very advantageously located downstream of an insoluble separation substep bl) and possibly upstream or downstream of a washing substep b2) and / or an adsorption substep b4) when the latter are also integrated into the process.

[0137] The extraction substep b3) is advantageously fed with an extraction solvent and with the polymer solution from the step or substep directly upstream of b3), in particular with 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 feeds substep b3), in particular the crude, clarified, washed or refined polymer solution, may include impurities, in particular solubilized impurities, which may be partially or totally removed during the extraction substep b3) by contacting it with an extraction solvent.

[0138] When integrated into the process according to the invention, substep b3) of extraction advantageously implements at least one extraction section, preferably between one and five extraction section(s), most preferably one extraction section.

[0139] 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 0.1 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.

[0140] Preferably, the extraction solvent used in substep b3) The extraction solvent 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, and preferably between 50 and 120°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, 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 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, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0141] Preferably, the extraction solvent used in substep b3), when integrated into the process according to the invention, is of the same nature as the dissolving solvent used in step a), possibly in a different physical state (for example, the extraction solvent in a supercritical state compared to the dissolving solvent in a liquid state), so as to facilitate solvent management and, in particular, their purification and recycling, especially back to the dissolution step a) and possibly to the extraction substep b3). Another advantage of using identical dissolving and extraction solvents in the same states Whether the physical properties are identical or different, in addition to facilitating solvent management (i.e., in particular the recovery, treatment and recycling of solvents involved in the process), it is to limit energy consumption and costs, in particular those generated by the treatment and purification of solvents.

[0142] The extraction section(s) of substep b3) may include one or more extraction equipment(s) for contacting the extraction solvent, and / or separation equipment for recovering at least one used solvent, particularly one containing impurities, and an extracted polymer solution. This equipment is well known to those skilled in the art: 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 equipment may include one or more pieces of equipment used alone or in combination with equipment of another type.

[0143] 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), on the one hand, 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), on the other hand. 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.

[0144] 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 recovery of an extracted polymer solution on the one hand and a used solvent on the other.

[0145] Advantageously, substep b'3) of extraction is carried out under temperature and pressure conditions different from the temperature and pressure conditions of step a) of dissolution.

[0146] According to a preferred embodiment, substep b3) of extraction, when integrated into the treatment process, implements a liquid extraction section / liquid. Preferably, said 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.Advantageously, liquid / liquid extraction, particularly when the extraction solvent is the same as the dissolution solvent, is carried out under temperature and pressure conditions different from the dissolution conditions achieved in step a), in particular at a temperature higher than the dissolution temperature and / or at a pressure lower than the dissolution pressure, so as to place oneself in a two-phase region of the corresponding polymer-solvent mixing diagram.

[0147] 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% by weight, preferably at least 70% by weight, most preferably at least 90% by weight 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, which facilitates separation by decantation between the supercritical phase, advantageously loaded with impurities, and the liquid phase containing the target thermoplastics, thus contributing to the purification of the polymer solution.

[0148] 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.

[0149] 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 substep 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.

[0150] In a particular embodiment, substep b3) of extraction employs supercritical extraction, and the extraction solvent is the same as that of 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 in supercritical form, 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.

[0151] Advantageously, at the end of substep b3) of extraction, the used solvent obtained is particularly laden with 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 to the input of b3), and / or to the input 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.

[0152] Substep b4) of adsorption

[0153] 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 carried out by contacting the polymer solution feeding it with one or more adsorbents.

[0154] When integrated into the process according to the invention, substep b4) of adsorption is preferably implemented downstream of step b) decantation and upstream of step c) solvent-polymer separation. However, it can be implemented during step a) dissolution, by introducing adsorbent particles mixed with the crude polymer solution, said adsorbent particles being removed during step b) purification, possibly during substep b1) separation of insolubles or substep b2) washing. Substep b4) adsorption can also be implemented during step b) purification, preferably downstream of substep b1) separation of insolubles and possibly upstream or downstream of substep b3) extraction.

[0155] 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, the flow of the stream being able to be upward or downward through said bed.

[0156] Advantageously, when integrated into the process, the adsorption substep b4) 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, advantageously operating in b4), is between 0.05 and 10 h1, preferably between 0.1 and 5.0 h1.

[0157] According to a particular embodiment of substep b4), the adsorption section may comprise one or more fixed bed(s) of adsorbent, for example in the form of adsorption column(s), preferably at least two adsorption columns, preferably between two and four adsorption columns, containing said (or said) Adsorbent(s). When the adsorption section comprises two adsorption columns, one operating mode is known as "swing," in which one column is in operation while the other is in reserve. When the adsorbent in the in-operation column is depleted, that column is isolated while the reserve column is brought online. The depleted adsorbent can then be regenerated in situ and / or replaced with fresh adsorbent so that the column containing it can be brought online again once the other column has been isolated.

[0158] Another operating mode of this particular embodiment of b4) is to have at least two adsorbent columns operating in series. When the adsorbent in the leading column is depleted, this first column is isolated, and the depleted adsorbent is regenerated in situ or replaced with fresh adsorbent. 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 the established English term. The combination of at least two adsorption columns makes it possible to overcome the potential and rapid poisoning and / or clogging of the adsorbent due to the combined action of impurities, contaminants, and insolubles 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, advantageously without stopping the process, and also allows for cost control and limiting adsorbent consumption.

[0159] Step c) of solvent-polymer separation

[0160] According to the invention, the process comprises 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, and preferably at least one stream of solvent. 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).

[0161] Step c) of solvent-polymer separation aims to separate, at least partially, preferably predominantly, or even completely, the solvent(s), in particular the dissolving solvent, contained in the purified polymer solution that feeds step c), so as to recover the targeted thermoplastics, freed at least partially, preferably completely, of impurities and the dissolving solvent, and preferably also of any other solvent(s) possibly used, particularly during step b) of the process (i.e., the extraction solvent and / or the dense solution). By predominantly, it should be understood as at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight. highly preferred 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).

[0162] Thus, step c) of solvent-polymer separation employs one or more gas-liquid separation sections operating in series. The expression "multiple gas-liquid separation sections" means, according to this description, at least two, and preferably between two and ten, preferably between two and five, for example three or four, gas-liquid separation sections. Preferably, step c) of solvent-polymer separation employs at least two, preferably between two and ten, most preferably between two and five, for example three or four, successive gas-liquid separation sections.In other words, step c) of solvent-polymer separation preferably implements N gas-liquid separation sections, N being an integer greater than or equal to two, preferably between two and ten, preferably between two and five, N being for example three or four.

[0163] The principle of separation in said gas-liquid separation section or in the gas-liquid separation sections of the series is based on the evaporation, at least in part, of the solvent, in particular the dissolving solvent, present in the polymer solution which feeds said section or 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.

[0164] Thus, the gas-liquid separation section or 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 the residual dissolving solvent. When the liquid effluent comprises residual solvent, in particular residual dissolving solvent, the thermoplastics in question are dissolved in the residual solvent, and the liquid effluent therefore corresponds to a polymer solution.Most advantageously, the liquid effluent from said gas-liquid separation section or 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 purified thermoplastic polymer stream.

[0165] The purified polymer solution, obtained at the end of purification step b), feeds said gas-liquid separation section or the first gas-liquid separation section in the series. When step c) uses several se In gas-liquid separation, the liquid effluent from the earlier section feeds the later section. In other words, when step c) implements N successive gas-liquid separation sections, with N an integer greater than or equal to two, preferably between two and ten, preferably between two and five, for example N being three or four:

[0166] 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;

[0167] the first liquid effluent obtained at the end of the first gas-liquid separation section feeds the second gas-liquid separation section of the series which produces a second gas effluent and a second liquid effluent;

[0168] the second liquid effluent obtained at the end of the second gas-liquid separation section feeds the third gas-liquid separation section of the series which produces a third gas effluent and a third liquid effluent;

[0169] 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,

[0170] The Nth liquid effluent obtained at the end of the Nth gas-liquid separation section advantageously constitutes the purified thermoplastic polymer stream.

[0171] The gas effluent produced by said gas-liquid separation section or the gas effluents produced by the gas-liquid separation sections of the series is / are recovered and may be, in whole or in part, purged and / or purified and / or fractionated and / or recycled, directly or after purification, to step a) and / or possibly to step b). For example, the gas effluent produced by said gas-liquid separation section or the gas effluents produced by the gas-liquid separation sections of the series may be completely purged; or partially purged and partially recycled directly to step a); or completely recycled directly to step a) with a total purge at regular intervals and for a fixed period; or at least partially purified and then recycled to step a).According to another embodiment, at least a portion of the gas effluent produced by said gas-liquid separation section or the gas effluents produced by the gas-liquid separation sections of the series may be recovered and sent to purification step b) and used as a cleaning solvent for at least one piece of purification equipment, for example to clean filters.

[0172] Said gas-liquid separation section or each of the gas-liquid separation sections, implemented in step c), is operated at an inlet temperature (i.e., at the inlet of said section or each section) between 100°C and 300°C, preferably between 110 and 275°C, preferably between 150 and 250°C, and at an in- lower than the pressure of step b) and preferably lower than the outlet pressure of step b), in particular a pressure less than 100.0 MPa absolute, preferably less than 25.0 MPa absolute, preferably less than 18.0 MPa absolute, preferably less than 15.0 MPa absolute. Preferably, in the gas-liquid separation section or 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.Advantageously, the temperature is adjusted, in the gas-liquid separation section or 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 considered.

[0173] When step c) implements several gas-liquid separation sections, the pressure of the subsequent section is lower than that of the preceding section. In other words, when step c) implements N successive gas-liquid separation sections, N being an integer greater than or equal to two, preferably between two and ten, preferably between two and five, for example N being chosen from three and four, the pressure of the second section in the series is lower than that of the first section in the series, the pressure of the third section in the series is lower than that of the second section in the series, and so on up to the Nth section in which the pressure is lower than the pressure of the (Nl)th section in the series, the pressure of the first section in the series being lower than the pressure of step b), preferably the outlet pressure of step b). In particular,the first gas-liquid separation section can be operated at an inlet temperature between 100 and 300°C, preferably between 110 and 275°C, and at a pressure less than 100.0 MPa absolute, preferably less than 25.0 MPa absolute, preferably less than 15.0 MPa absolute, and advantageously greater than or equal to 0.0008 MPa absolute; while the Nth section can be operated at an inlet temperature between 100 and 300°C, preferably between 110 and 275°C, and at a pressure between 0.000005 and 1.00 MPa absolute (i.e., between 0.05 mbar and 10.0 bar), preferably between 0.00001 and 1.00 MPa absolute (i.e., between 0.1 mbar and 10.0 bar), preferably between 0.0001 and 1.00 MPa absolute (i.e., between 1 mbar and 10.0 bar), preferably between 0.0005 and 0.10 MPa absolute (i.e., between 5 mbar and 1.0 bar), most preferably between 0.0005 and 0.0020 MPa absolute (that is, between 5 mbar and 20 mbar) and most preferably between 0,0008 and 0.0010 MPa absolute (i.e., between 8 mbar and 10 mbar). In this particular case, the , pressure in each intermediate section, located between the first and the Nth section, if applicable, i.e. when it is / are implemented, is adjusted in a decreasing manner and is between the pressure of the first section and the pressure of the last section.

[0174] According to a very particular embodiment, the thermoplastic in question is polypropylene and the dissolving solvent is an isomer or a mixture of isomers of hexane, heptane and / or octane. In this particular embodiment, step a) of dissolution is carried out at a dissolution temperature between 150 and 250°C, preferably between 160 and 225°C, preferably between 170 and 200°C, and at a dissolution pressure between 1.0 and 25.0 MPa absolute, preferably between 1.0 and 12.0 MPa absolute, preferably between 1.5 and 6.0 MPa absolute, preferably between 2.0 and 5.0 MPa absolute. According to this particular embodiment, step b) is carried out in the same temperature and pressure ranges and makes it possible to obtain a purified polymer solution comprising the targeted polypropylene and which is sent to step c) of solvent-polymer separation.In this embodiment, step c) implements, for example, four successive gas-liquid separation sections, in which: .

[0175] - the first section is preferably operated at an inlet temperature between 165 and 275°C, preferably between 170 and 275°C, and at a pressure between 0.5 and 4.0 MPa, preferably between 0.5 and 2.0 MPa absolute, preferably between 0.5 and 1.0 MPa absolute,

[0176] - the fourth section is preferably operated at an inlet temperature between 165 and 275°C, preferably between 170 and 275°C, and at a pressure between 0.000005 and 0.0050 MPa absolute (i.e., between 0.05 and 50 mbar), preferably between 0.00001 and 0.0050 MPa absolute (i.e., between 0.1 and 50 mbar), preferably between 0.0001 and 0.0050 MPa absolute (i.e., between 1 and 50 mbar), most preferably between 0.0005 and 0.0020 MPa absolute (i.e., between 5 and 20 mbar), most preferably between 0.0008 and 0.0010 MPa absolute (i.e., between 8 and 10 mbar), or at a pressure between 0.000005 and 1.0 MPa absolute (i.e., between 0.05 mbar and 10 bar) in the presence of an agent of stripping introduced at the level of the fourth gas-liquid separation section;

[0177] - the second and third gas-liquid separation sections (i.e. the sections of se Intermediate gas-liquid separations are carried out at an inlet temperature between 165 and 275°C, preferably between 170 and 275°C, and at a pressure lower than that of the first gas-liquid separation section and higher than that of the fourth gas-liquid separation section, and more specifically: for the second gas-liquid separation section, at a pressure lower than the pressure of the first gas-liquid separation section and higher than that of the third gas-liquid separation section; and for the third gas-liquid separation section, at a pressure in lower than the pressure of the second gas-liquid separation section and higher than that of the fourth gas-liquid separation section.

[0178] According to another particular embodiment, the thermoplastic in question is polyethylene and the dissolving solvent is preferably an isomer or a mixture of isomers of butane, pentane, hexane, heptane and / or octane. In this particular embodiment, step a) of dissolution is carried out at a dissolution temperature between 120 and 300°C, preferably between 130 and 275°C, preferably between 150 and 250°C, and at a dissolution pressure between 1.0 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute, preferably between 2.0 and 15.0 MPa absolute. Step b) is carried out in the same temperature and pressure ranges and allows a purified polymer solution to be obtained, including the targeted polyethylene, which is sent to step c) of solvent-polymer separation.In this other particular embodiment, step c) can implement, for example, four successive gas-liquid separation sections, in which: .

[0179] - the first section is preferably operated at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure greater than or equal to 0.1 MPa absolute and less than the outlet pressure of step b), the temperature and pressure being advantageously adjusted so as to evaporate some of the dissolving solvent, present in the purified polymer solution which feeds the first section;

[0180] - the fourth section is preferably operated at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure between 0.000005 and 0.0500 MPa absolute (i.e. between 0.05 and 500 mbar), preferably between 0.00001 and 0.0100 MPa absolute (i.e. between 0.1 and 100 mbar), preferably between 0.0001 and 0.0050 MPa absolute (i.e. between 1 and 50 mbar);

[0181] - the second and third gas-liquid separation sections (i.e. the sections of se Intermediate gas-liquid separations) are carried out at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure lower than that of the first gas-liquid separation section and higher than that of the fourth gas-liquid separation section, and more particularly: for the second gas-liquid separation section, at a pressure lower than the pressure of the first gas-liquid separation section and higher than that of the third gas-liquid separation section; and for the third gas-liquid separation section, at a pressure lower than the pressure of the second gas-liquid separation section and higher than that of the fourth gas-liquid separation section.

[0182] Said gas-liquid separation section or 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 means for heating, means for adjusting and controlling pressure above atmospheric pressure, means for adjusting and controlling pressure below atmospheric pressure (to obtain a vacuum), etc.; mechanical means for setting the gas and liquid phases in motion and in contact.For example, said gas-liquid separation section or gas-liquid separation sections may implement one or more pieces of equipment selected from: a separator flask, a column, a distillation column, a stripper, equipment comprising 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 disk reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, a devolatilizer. According to a very particular embodiment, said gas-liquid separation section or gas-liquid separation sections may implement a gas-liquid separator comprising: .

[0183] - an enclosure comprising a cylindrical upper part and a lower part cylindrical extending into a base with a decreasing cross-section, said lower part advantageously comprising a liquid retention zone at the bottom of the enclosure

[0184] - an inlet pipe, for supplying said separator with a gas / liquid flow, said inlet conduit opening at one end into the lower part of said enclosure and said end being advantageously angled (i.e. the internal end being advantageously angled),

[0185] - an outlet pipe located at the bottom of said enclosure, for evacuating a flow of liquid separated from said gas-liquid separator,

[0186] - a gas-liquid separation system which can be:

[0187] - a cyclone with a cylindrical-conical body, internal to said enclosure, and comprising

[0188] a tangential inlet tube for supplying said cyclone with a gas / liquid mixture, said tube being located in the upper part of said enclosure,

[0189] an outlet tube for discharging a separate gas stream, said outlet tube located at the top of said cylindrical-conical body, said outlet tube opening outside the enclosure of the gas-liquid separator, and

[0190] an opening at the base of said cylindro-conical body, said opening being connected to a return leg for a liquid flow, said return leg opening into said liquid guard zone at the bottom of the enclosure of said gas-liquid separator; and / or

[0191] - a gas-liquid separation device equipped with a helical spiral located in the upper part of said enclosure, said gas-liquid separation device being capped with an upper dome which includes at its upper end a gas discharge duct and at its lower end a vertical duct concentric to intake conduit allowing the return of the separated liquid to the liquid holding zone at the bottom of the enclosure of said gas-liquid separator;

[0192] - possibly means for injecting an entraining agent and / or a flow of inert gas.

[0193] According to this particular embodiment, the lower part of the enclosure, and more specifically the liquid retention zone at the bottom of the enclosure, can be equipped with an agitator. Also according to this particular embodiment, a pump, in particular a pump capable of driving viscous fluids, also called a melt pump, can be implemented at the external end (of said gas-liquid separator) of said outlet line located at the bottom of the enclosure.

[0194] An entraining agent (or stripping agent) may optionally be introduced into the gas-liquid separation section or the last (i.e., the Nth) gas-liquid separation section in the series, to aid the vaporization of the residual solvent present in the polymer solution entering said last section. The addition of an entraining agent thus optimizes the solvent-polymer separation in the last gas-liquid separation section. It makes it possible to achieve very low residual solvent contents in the purified thermoplastic stream, in particular less than or equal to 5 wt%, preferably less than or equal to 1.00 wt%, preferably less than or equal to 0.10 wt%, preferably less than or equal to 500 ppm wt% of solvent relative to the total weight of the purified thermoplastic stream, without the need to achieve a high vacuum in the last section, i.e.without reaching a pressure between 0.000005 and 1.00 MPa absolute, in particular between 0.00001 and 1.00 MPa absolute, especially between 0.0001 and 1.00 MPa absolute, more particularly between 0.0005 and 0.0020 MPa absolute, or even, very specifically, between 0.0008 and 0.0010 MPa absolute. Any entraining agent introduced is a compound lighter than the dissolving solvent, i.e., a compound with a boiling point lower than that of the dissolving solvent (at atmospheric pressure), for example, water, nitrogen, or hydrogen. Preferably, the amount of any entraining agent introduced represents between 10% and 0.1% by weight of entraining agent relative to the thermoplastics of interest.

[0195] Optionally, an inert gas stream, preferably a nitrogen stream, may be introduced into the gas-liquid separation section or the first gas-liquid separation section in the series to aid vaporization and thus the removal of the solvent, in particular the dissolving solvent, present in the purified polymer solution that feeds step c). The presence of an inert gas modifies the phase diagram. The presence of the inert gas, in particular nitrogen, can therefore promote the evaporation of the solvent, in particular the dissolving solvent, present in the purified polymer solution that feeds step c), and thus limit the temperature Operating temperatures in said section or first section, while optimizing solvent evaporation. At the outlet of the gas-liquid separation section or the first gas-liquid separation section of the series, the inert gas is then advantageously mixed with the gaseous dissolving solvent in the effluent gas. The presence of the inert gas, particularly nitrogen, can also modify the phase diagram such that the solvent, especially the dissolving solvent, present in the purified polymer solution, is at least partially in a supercritical state. In this situation, the fraction of the solvent, particularly the dissolving solvent, that is in supercritical form can be separated from the polymer solution by density difference, for example by decantation, notably in a settling tank.The presence of inert gas, particularly nitrogen, can also alter the phase equilibrium of the purified polymer solution, which may demix and become biphasic, with a first liquid phase comprising the thermoplastics and a second liquid phase composed primarily of solvent, particularly the dissolving solvent. In the case of an inert gas flow, particularly a nitrogen flow, said inert gas flow is introduced in such a quantity that the weight ratio between the inert gas flow rate and the purified polymer solution flow rate is between 0.000001 and 1.00, preferably between 0.0001 and 0.50.

[0196] Optionally, solvent-polymer separation step c) may include an intermediate separation upstream of the successive gas-liquid separation(s). Thus, step c) may implement an intermediate separation section located upstream of the successive gas-liquid separation section(s). This intermediate separation may be a liquid-liquid separation, which advantageously employs a liquid-liquid intermediate separation section, or a supercritical-liquid separation, which advantageously employs a supercritical-liquid intermediate separation section. The optional liquid-liquid or supercritical-liquid intermediate separation section is advantageously supplied with the purified polymer solution from step b), and optionally with a stream of inert gas, in particular a stream of nitrogen.It enables the production of a liquid phase comprising the targeted thermoplastics, in particular dissolved in the residual dissolving solvent, and a second liquid phase or a supercritical phase comprising the dissolving solvent, respectively in the liquid state or at least partially supercritical, and which is advantageously low in targeted thermoplastics, preferably containing less than 5% by weight, preferably less than 1.00% by weight, preferably less than 0.10% by weight, or even less than 500 ppm by weight of targeted thermoplastics relative to the total weight of said second liquid phase or supercritical phase, or even free of targeted thermoplastics. The said possible inert gas flow can indeed assist in the demixing of the purified polymer solution to form a bi-liquid system. phasic, or help at least some of the dissolving solvent to transition to the supercritical state.

[0197] When an intermediate liquid-liquid separation is integrated in step c), said intermediate liquid-liquid separation advantageously comprises (i) an adjustment of the temperature and / or pressure so as to obtain the demixing of the purified polymer solution, and then (ii) a separation by density difference, in particular by decantation, of a first liquid phase, which comprises the thermoplastics in particular dissolved in the residual dissolving solvent, and of a second liquid phase, which is poor in thermoplastics in particular, i.e. which comprises less than 5% by weight, preferably less than 1.00% by weight, preferably less than 0.10% by weight, or even less than 500 ppm by weight of thermoplastics in relation to the total weight of said second liquid phase.Thus, when step c) includes an intermediate liquid-liquid separation, the temperature and / or pressure are adjusted in the intermediate liquid-liquid separation section to form a two-phase system from the purified polymer solution, possibly in the presence of an inert gas flow. Preferably, the temperature in the intermediate liquid-liquid separation section is adjusted to a value below the critical temperature of the dissolving solvent (but above the melting temperature of the thermoplastics being treated).Preferably, the pressure in the intermediate liquid-liquid separation section is adjusted to a value less than or equal to the bubble point pressure of the dissolving solvent at the operating temperature, preferably adjusted to a value between a pressure less than 1.0 MPa below the bubble point pressure or equal to said bubble point pressure of the dissolving solvent at the operating temperature.

[0198] When an intermediate supercritical-liquid separation is incorporated in step c), said intermediate supercritical-liquid separation preferably comprises (i) an adjustment of the temperature and / or pressure in the intermediate supercritical-liquid separation section, possibly in the presence of an inert gas flow, so that the dissolving solvent is at least partially in the supercritical state, and then (ii) a separation by density difference, in particular by decantation, of a liquid phase comprising the thermoplastics in particular dissolved in the residual dissolving solvent, and of a supercritical phase comprising the dissolving solvent in the supercritical state.The possible intermediate supercritical-liquid separation can in particular be integrated into step c) when the dissolving solvent is sufficiently light, in particular when the dissolving solvent has a boiling point (at atmospheric pressure, in particular at 0.1 MPa) between -50 and 100°C, preferably between -50 and 70°C, preferably between -45 and 50°C.

[0199] The liquid phase comprising the targeted thermoplastics obtained at the end of the possible intermediate liquid-liquid or supercritical-liquid separation section feeds the gas-liquid separation section or the first gas-liquid separation section, advantageously instead of the purified solution.

[0200] For example, the thermoplastic in question is polyethylene and the dissolving solvent is preferably an isomer or a mixture of isomers of butane, pentane, hexane, heptane and / or octane. In this particular case, step a) of dissolution is carried out at a dissolution temperature between 120 and 300°C, preferably between 130 and 275°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, preferably between 2.0 and 15.0 MPa absolute. Step b) is carried out in the same temperature and pressure ranges and allows a purified polymer solution to be obtained, including the targeted polyethylene, which is sent to step c) of solvent-polymer separation.In this particular case, step c) may implement at least one intermediate liquid-liquid or supercritical-liquid separation section and two or three successive gas-liquid separation section(s), for example in the following manner: .

[0201] - the intermediate liquid-liquid or supercritical-liquid separation section, of preferably supercritical-liquid, is operated at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure greater than or equal to between 3.0 and 10.0 MPa absolute, preferably between 3.0 and 100.0 MPa absolute, the temperature and pressure being advantageously adjusted so as to obtain a two-phase liquid-liquid system or so as to have at least a portion of the dissolving solvent, present in the purified polymer solution which feeds the first section, in the supercritical state; said intermediate liquid-liquid or supercritical-liquid separation section thus produces a liquid effluent which includes polyethylene and which is sent to the first gas-liquid separation section, and another liquid effluent or a supercritical effluent, preferably a supercritical effluent, which includes dissolving solvent;

[0202] - the first gas-liquid separation section is operated at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure greater than or equal to 0.1 MPa absolute and less than the outlet pressure of the intermediate liquid-liquid or supercritical-liquid separation section;

[0203] - the last gas-liquid separation section is operated at an inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure between 0.000005 and 0.0500 MPa absolute (i.e., between 0.05 and 500 mbar), preferably between 0.00001 and 0.0100 MPa absolute (i.e., between 0.1 and 100 mbar), preferably between 0.0001 and 0.0050 MPa absolute (i.e., between 1 and 50 mbar);

[0204] - the possible intermediate gas-liquid separation section is operated at a temperature inlet temperature between 130 and 300°C, preferably between 150 and 275°C, and at a pressure lower than that of the first gas-liquid separation section and higher than that of the last gas-liquid separation section.

[0205] Optionally, at least one additive may be introduced in step c), and / or possibly upstream of step c), in particular upstream of step a) dissolution, in step a) dissolution, or in step b), and more particularly in a substep bl) of insoluble separation. For example, an antioxidant may be introduced in step c), and / or possibly upstream of step c), for example upstream of step a) dissolution, in step a) dissolution, or in step b), and more particularly in a substep bl) of insoluble separation, so as to limit, or even prevent, any degradation of the thermoplastics concerned. A person skilled in the art will be able to select said at least one additive, in particular said antioxidant, according to the thermoplastics concerned.For example, the antioxidant can be chosen from compounds marketed under the Irganox® and Irgafos® brands, and in particular from the following commercial compounds: Irganox® 1010, Irgafos® 168, and Irgafos® 168 oxidized. A person skilled in the art will also be able to adjust the quantity of at least one additive, in particular the antioxidant, to be introduced, according to the thermoplastics being treated and the desired properties. For example, the antioxidant can be introduced in such a way as to adjust the content of said antioxidant to between 100 and 10,000 ppm by weight, preferably between 500 and 5,000 ppm by weight of antioxidant relative to the weight of the thermoplastics being treated.In the case where an additive, in particular an antioxidant, is introduced in step c), and where step c) employs a single gas-liquid separation section, said additive, in particular antioxidant, is preferably introduced upstream of said gas-liquid separation section, more particularly in the purified polymer solution from b) or possibly in the liquid phase from the intermediate liquid-liquid or supercritical-liquid separation section optionally employed upstream of said gas-liquid separation section.Where an additive, in particular an antioxidant, is introduced in step c), and where step c) employs several successive gas-liquid separation sections, said additive, in particular the antioxidant, is preferably introduced downstream of the first gas-liquid separation section in the series, either as a single unit or in fractions, more particularly into at least one of the liquid effluents produced by the gas-liquid separation sections in the series (including the first section), and preferably into one of the liquid effluents produced by one of the sections upstream of the last gas-liquid separation section in the series. Where an additive, in particular an antioxidant, . is introduced in step c), and where step c) implements an intermediate liquid-liquid or supercritical-liquid separation section and one or more successive gas-liquid separation section(s), and said additive, in particular antioxidant agent, is preferably introduced downstream of said intermediate section, in a unitary or fractional manner, more particularly in the liquid phase from said intermediate section and / or in the liquid effluent produced by the gas-liquid separation section or in at least one of the liquid effluents produced by the gas-liquid separation sections of the series (including the first section), and preferably in the liquid phase from said intermediate section and / or in the liquid effluent produced by the gas-liquid separation section or in one of the liquid effluents produced by one of the sections upstream of the last gas-liquid separation section of the series.

[0206] Thus, the process according to the invention makes it possible to obtain a stream of purified thermoplastics, and more particularly of purified polyolefins, having a very low residual solvent content (in particular, a dissolving solvent), and 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, or even a content less than or equal to 500 ppm by weight, relative to the total weight of the purified thermoplastic stream. More particularly, the purified thermoplastic stream, and more particularly of purified polyolefins, obtained at the end of the process according to the invention has a volatile organic compound (VOC) content 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, or even a content less than or equal to 500 ppm by weight, relative to the total weight of the purified thermoplastic stream.The VOC content provides a good indication of the solvent content and, in particular, the residual solvent content in the purified thermoplastic stream obtained.

[0207] Preferably, the volatile organic compound (VOC) content is determined by gas chromatography with headspace extraction (or HS for headspace according to the Anglo-Saxon term) coupled with mass spectrometry (MS) or with a flame ionization detector (FID), preferably coupled with mass spectrometry (MS).

[0208] The purified thermoplastic polymer stream obtained at the end of the process according to the invention also very advantageously has an impurity content of less than or equal to 5% by weight of impurities, preferably less than or equal to 1.0% by weight of impurities, and preferably less than or equal to 0.5% by weight of impurities relative to the total weight of the purified thermoplastic stream. The purified thermoplastic polymer stream obtained at the end of the process according to the invention can then be used in any application, for example, as a replacement for the same polymers in their virgin state.

[0209] Device

[0210] The present invention also relates to a device for processing a plastic feedstock to obtain a stream of purified thermoplastic polymers, which comprises:

[0211] A) Dissolution means for bringing into contact and dissolving at least part of the plastic filler in a dissolving solvent, and obtaining a crude polymer solution, said dissolution means advantageously being any type of industrial equipment allowing said contact and said dissolution, for example an extruder, static or dynamic mixer(s), and / or one or more continuously stirred reactor(s), also called "Continuous Stirred Tank Reactor" (CSTR) according to Anglo-Saxon terminology, and equipped with suitable stirring system(s);

[0212] 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 for purifying the crude polymer solution, said purification means possibly comprising:

[0213] 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;

[0214] a washing device allowing the crude or clarified polymer solution to be brought into contact with a dense solution, in particular an aqueous solution, to obtain a washed polymer solution;

[0215] 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 a supercritical state, to obtain an extracted polymer solution; and / or

[0216] 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 or adsorbent particles in divided form, and allowing the recovery of a refined polymer solution,

[0217] said clarified, washed, extracted or refined polymer solution constituting the purified polymer solution;

[0218] C) a solvent-polymer separation device, located downstream of said purification means, for separating the purified polymer solution into a stream of purified thermoplastic polymers and at least one solvent effluent advantageously comprising a dissolving solvent,

[0219] characterized in that said solvent-polymer separation device comprises:

[0220] a gas-liquid separation section or several gas-liquid separation sections operating in series, preferably at least two, preferably between two and ten, most preferably between two and five, for example three or four, successive gas-liquid separation sections,

[0221] at least one pressure control system in said gas-liquid separation section or in each gas-liquid separation section in the series, so as to adjust the pressure in said gas-liquid separation section or each gas-liquid separation section in the series to a value lower than the outlet pressure of the purification means, and where said solvent-polymer separation device comprises several gas-liquid separation sections, so as to adjust the pressure in the subsequent section to a value lower than that of the preceding section,

[0222] possibly at least one temperature control system, in particular for the inlet temperature, of said gas-liquid separation section or of each gas-liquid separation section in the series,

[0223] said gas-liquid separation section or each gas-liquid separation section of the series comprising a feed system, a liquid withdrawal system and a gas withdrawal system,

[0224] the supply system of said gas-liquid separation section or of the first gas-liquid separation section of the series being connected to at least one of the purification means and allowing the supply of purified polymer solution to said solvent-polymer separation device,

[0225] where said solvent-polymer separation device comprises several gas-liquid separation sections, the feed system of the later section being connected to the liquid withdrawal system of the earlier section,

[0226] the liquid withdrawal system from said gas-liquid separation section or from the last gas-liquid separation section in the series allowing recovery of said purified thermoplastic polymer stream,

[0227] the gas withdrawal system of said gas-liquid separation section or of each gas-liquid separation section in the series allowing the recovery of said at least one solvent effluent which includes dissolving solvent, and the gas withdrawal system of said section or of each gas-liquid separation section being optionally able to be connected directly or indirectly to devices for condensing, for purifying, for fractionating and / or for recycling one or more solvent effluents to said dissolving means and / or optionally to said purification means.

[0228] Said gas-liquid separation section or gas-liquid separation sections may implement any type of device, in particular any type of industrial equipment known to those skilled in the art for separating gas and liquid, possibly accompanied by devices for adjusting the temperature, by particular the inlet temperature, and the pressure, for example equipment for heating, equipment for adjusting and controlling the pressure above atmospheric pressure, equipment for adjusting and controlling the pressure below atmospheric pressure (to obtain a vacuum), etc.; equipment for moving and contacting the gas and liquid phases.For example, said gas-liquid separation section or gas-liquid separation sections may implement one or more pieces of equipment selected from: a separator flask, a column, a distillation column, a stripper, equipment comprising 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 disk reactor or column, a reactor, a stirred reactor, an extruder, a kneading reactor, a devolatilizer. According to a very particular embodiment, said gas-liquid separation section or gas-liquid separation sections may implement a gas-liquid separator comprising: .

[0229] - an enclosure comprising a cylindrical upper part and a lower part cylindrical extending into a base with a decreasing cross-section, said lower part advantageously comprising a liquid retention zone at the bottom of the enclosure

[0230] - an inlet pipe, for supplying said separator with a gas / liquid flow, said inlet conduit opening at one end into the lower part of said enclosure and said end being advantageously angled (i.e. the internal end being advantageously angled),

[0231] - an outlet pipe located at the bottom of said enclosure, for evacuating a flow of liquid separated from said gas-liquid separator,

[0232] - a gas-liquid separation system which can be:

[0233] - a cyclone with a cylindrical-conical body, internal to said enclosure, and comprising

[0234] a tangential inlet tube for supplying said cyclone with a gas / liquid mixture, said tube being located in the upper part of said enclosure,

[0235] an outlet tube for discharging a separate gas flow, said outlet tube located at the top of said cylindrical-conical body, said outlet tube opening outside the enclosure of the gas-liquid separator, and

[0236] an opening at the base of said cylindrical-conical body, said opening being connected to a return leg for a liquid flow, said return leg opening into said liquid guard zone at the bottom of the enclosure of said gas-liquid separator; and / or

[0237] - a gas-liquid separation device equipped with a helical spiral located in the upper part of said enclosure, said gas-liquid separation device being capped with an upper dome which includes at its upper end a gas discharge duct and at its lower end a vertical duct concentric to intake conduit allowing the return of the separated liquid to the liquid holding zone at the bottom of the enclosure of said gas-liquid separator;

[0238] - possibly means for injecting an entraining agent and / or a flow of inert gas.

[0239] According to this particular embodiment, the lower part of the enclosure, and more specifically the liquid retention zone at the bottom of the enclosure, can be equipped with an agitator. Also according to this particular embodiment, a pump, in particular a pump capable of driving viscous fluids, also called a melt pump, can be implemented at the external end (of said gas-liquid separator) of said outlet line located at the bottom of the enclosure.

[0240] According to a preferred embodiment, said purification means B) comprise at least solid-liquid separation means advantageously followed by an adsorption device. In this particular embodiment, said solid-liquid separation means comprise in particular at least one decanter optionally followed by at least one other solid-liquid separation means, for example at least one filter.

[0241] Optionally, the solvent-polymer separation device C) may include an intermediate liquid-liquid or supercritical-liquid separation section upstream of said gas-liquid separation section or of the first gas-liquid separation section in the series. In this particular embodiment, said liquid-liquid or supercritical-liquid separation section is connected to at least one of the purification means, and the feed system of said gas-liquid separation section or of the first gas-liquid separation section in the series is connected to said liquid-liquid or supercritical-liquid separation section, and not to at least one of the purification means.The optional intermediate supercritical-liquid separation section preferably includes at least temperature and pressure control systems, density difference separation devices, for example decantation equipment, of two liquid phases of different densities or of a liquid phase and a supercritical phase, and withdrawal systems of a liquid phase comprising the thermoplastics concerned and withdrawal systems of another liquid phase and a supercritical phase, composed essentially of solvent and in particular of dissolving solvent.

[0242] Optionally, the gas-liquid separation section or the first intermediate gas-liquid separation section and / or the possible intermediate liquid-liquid or supercritical-liquid separation section, may include a system for introducing an inert gas stream.

[0243] The treatment device according to the invention may optionally include, in addition, at least one additive introduction system, for example, for an anti- oxidant. In particular, said at least one additive introduction system is included in the solvent-polymer separation device, and preferably is located upstream of said gas-liquid separation section or upstream of the last gas-liquid separation section in the series. Preferably, when said solvent-polymer separation device includes said at least one additive introduction system and several gas-liquid separation sections, said at least one additive introduction system is located downstream of the first gas-liquid separation section.

[0244] Said device for processing a plastic load also advantageously includes transport equipment between said means, devices and systems.

[0245] 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, having a very low residual solvent content (in particular dissolving solvent).

[0246] The following examples and figures illustrate the invention, in particular particular embodiments of the invention, without limiting its scope. LIST OF FIGURES [Fig 1]

[0247] Figure 1 represents a particular embodiment of the process according to the invention. The particular embodiment of Figure 1 corresponds to the process described in Example 1. [Fig 2]

[0248] Figure 2 represents a preferred embodiment of the method according to the invention. The embodiment of Figure 2 corresponds to the method described in Example 2. [Fig 3]

[0249] Figure 3 represents a particular embodiment of the process according to the invention. The embodiment of Figure 3 corresponds to the process described in Example 3. EXAMPLES

[0250] In the examples below, the analyses carried out on the charge and the products obtained are as follows:

[0251] - the volatile organic compound (VOC) content, which gives an indication of the solvent content, in particular residual solvent in the stream of targeted thermoplastics, is determined by gas chromatography with headspace extraction (or HS for headspace according to the Anglo-Saxon term) coupled with mass spectrometry;

[0252] - the ash content, which gives an indication of the level of inorganic impurities, is determined by thermogravimetric analysis (TGA). The ash content is determined by thermogravimetric analysis (TGA) 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).

[0253] - the color parameters are expressed in the CIE L*a*b* reference system (defined by the International Commission on Illumination (CIE)), determined by colorimetry (according to ISO 11664-4), with:

[0254] - a brightness (or luminance) parameter L*, such that the closer L* is to 100, the more the The analyzed solid is clear or transparent; conversely, the closer L* is to 0, the more opaque the analyzed solid is;

[0255] - a parameter a* (corresponding to a green-red axis), which measures the color going from green (negative values) to red (positive values); a target value of a* is a value approaching 0;

[0256] - a parameter b* (corresponding to a blue-yellow axis), which measures the color going from blue (negative values) to yellow (positive values); a target value of b* is a value approaching 0.

[0257] 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. Example 1 (according to the invention)

[0258] The process of Example 1 is illustrated schematically in [Fig. 1].

[0259] Step a) of dissolution:

[0260] A feedstock 1 derived from plastic waste and containing 95% polypropylene (PP) by weight is introduced 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 n-heptane 2, used as a dissolving solvent and preheated to 200°C, in a solvent / feedstock weight ratio of 4:1. The mixture comprising the solvent and the 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 3 is then obtained.

[0261] Purification step b):

[0262] The crude polymer solution 3, 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 The decanter is 1 hour, the residence time corresponding to the ratio between the useful volume of the decanter (i.e. the volume of material in the decanter which is a function of the filling rate of the decanter) and the volumetric flow rate of crude polymer solution 3 feeding the decanter.

[0263] Impurities settle at the bottom of the decanter, forming a "cake" which is purged discontinuously (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.

[0264] 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 the adsorption column of 2.0 MPa).

[0265] The adsorbed polymer solution 4, recovered at the outlet of the adsorption column, is then subjected to a solvent-polymer separation step.

[0266] Step c) of solvent-polymer separation:

[0267] The solvent-polymer separation step employs a gas-liquid separation section cl. An antioxidant 7, Irgafos® 168, is introduced into the adsorbed polymer solution 4, so as to represent 600 ppm by weight of antioxidant relative to the weight of polypropylene included in the adsorbed polymer solution 4. The mixture then feeds the gas-liquid separation section cl, which is operated at an inlet temperature of 180°C and an absolute pressure of 0.14 MPa.

[0268] At the outlet of gas-liquid separation section cl, a gas effluent gl and a liquid effluent 11 are recovered. The gas effluent gl can then be, in whole or in part, purged and / or recycled. The liquid effluent 11 is placed under atmospheric conditions, i.e. at a temperature of approximately 20°C and a pressure of approximately 0.1 MPa.

[0269] A solid A (flux 6) is obtained. It is analyzed according to the methods described above. The results are presented in Table 1.

[0270] [Tables 1] Solid Charge A VOC Content _(D 5% by weight Ash Content 1.1% by weight < 1000ppm by weight Colorimetry: 57.5 92.8 Cielab - L 14.7 0.2 Cielab - a 10.8 4.6 Cielab - b

[0271] (1): The VOC content of the charge was not measured.

[0272] Solid A is composed of polypropylene, purified since it has a level of The ash content was reduced (<1000 ppm by weight) (and despite the introduction of an antioxidant in step c) compared to that of the feed (1.1% by weight), and the Cielab colorimetry parameters were also improved compared to those of the feed. Furthermore, solid A showed a satisfactory VOC content, and therefore a satisfactory residual solvent content (5% by weight of volatile organic compounds, VOCs, relative to the weight of solid A). Example 2 (according to the invention)

[0273] The process detailed in Example 2 is schematically illustrated in [Fig. 2].

[0274] A feedstock 1 identical to that of Example 1, i.e., derived from plastic waste and containing 95% by weight of polypropylene (PP), is processed in Example 2. The process of Example 2 comprises the same dissolution (a) and purification (b) steps as those described in Example 1.

[0275] Step c) of solvent-polymer separation:

[0276] The adsorbed polymer solution 4, recovered at the outlet of the adsorption column, is then subjected to a solvent-polymer separation step c) which employs four successive gas-liquid separation sections (or stages) c1, c2, c3, c4. Gas-liquid separation sections (or stages) 1 to 4 (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):

[0277] Stage cl: T = 180°C, P = 0.79 MPa,

[0278] Stage c2: T = 180°C, P = 0.61 MPa,

[0279] Stage c3: T = 180°C, P = 0.14 MPa,

[0280] Stage c4: T = 250°C, P = 0.0014 MPa (i.e. 14 mbar).

[0281] The adsorbed polymer solution 4, recovered at the outlet of the adsorption column, The first gas-liquid separation section c1 is fed. The liquid effluent 11 produced by the first gas-liquid separation section c1 feeds the second section c2. The liquid effluent 12 produced by the second gas-liquid separation section c2 feeds the third section c3. An antioxidant 7, Irgafos® 168, is introduced into the liquid effluent 13 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 13, and the mixture then feeds the fourth gas-liquid separation section c4. At the outlet of the fourth gas-liquid separation section c4, a liquid effluent 14 is collected and placed under atmospheric conditions, i.e., at a temperature of approximately 20°C and a pressure of approximately 0.1 MPa.

[0282] A solid B (flux 6) is then obtained. It is analyzed according to the methods described above. The results are presented in Table 2.

[0283] Each section cl, c2, c3, c4 of the gas-liquid separation also produces an effluent gas, respectively the gl, g2, g3 and g4 flows. The produced gas effluents gl, g2, g3 and g4 are recovered and can then be, in whole or in part, purged and / or recycled.

[0284] [Tables2] Solid Charge B VOC Content _(D 500 ppm by weight Ash Content 1.1% by weight < 1000 ppm by weight Colorimetry: 57.5 92.9 Cielab - L 14.7 -0.3 Cielab - a 10.8 4.6 Cielab - b

[0285] (1): The VOC content of the charge was not measured.

[0286] Solid B is composed of purified polypropylene, exhibiting a reduced ash content (< 1000 ppm wt.) (despite the introduction of an antioxidant in step c) compared to that of the filler (1.1 wt.), and Cielab colorimetric parameters that are also improved compared to those of the filler. Furthermore, solid B shows a very low VOC content, and therefore a very low residual solvent content (200 ppm wt. of volatile organic compounds relative to the weight of solid B). Example 3 (according to the invention)

[0287] The process of Example 3 is schematically illustrated in [Fig.3].

[0288] Step a) of dissolution:

[0289] A feedstock 1 derived from plastic waste and containing 95% polypropylene (PP) by weight is introduced 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 n-pentane 2, used as a dissolving solvent and preheated to 190°C, in a solvent / feedstock weight ratio of 4:1. The mixture comprising the solvent and the feedstock is introduced into a stirred reactor at 190°C and maintained at 190°C and 10.0 MPa absolute for a residence time of 1 hour. A crude polymer solution 3 is then obtained.

[0290] Purification step b):

[0291] The crude polymer solution 3, which is continuously recovered from the stirred reactor, is injected into a decanter operated at 190°C and 9.9 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 filling rate of the decanter) and the volumetric flow rate of crude polymer solution 3 feeding the decanter.

[0292] Impurities settle at the bottom of the decanter, forming a "cake" which is purged discontinuously (flow 5). At the outlet of the decanter, the recovered polymer solution is filtered through a 10 pm mesh opening filter and then through a 1 pm mesh opening filter.

[0293] The filtered polymer solution is then sent into an adsorption column containing a bed of activated carbon, and operated at 190°C and 9.7 MPa absolute (i.e. at an outlet pressure of the adsorption column of 9.7 MPa).

[0294] The adsorbed polymer solution 4, recovered at the outlet of the adsorption column, is then subjected to a solvent-polymer separation step.

[0295] Step c) of solvent-polymer separation:

[0296] The solvent-polymer separation step employs a supercritical solvent decantation section cl. An antioxidant 7, Irgafos® 168, is introduced into the adsorbed polymer solution 4, so as to represent 600 ppm by weight of antioxidant relative to the weight of polypropylene in the adsorbed polymer solution 4. The mixture then feeds the supercritical solvent decantation section cl, which is operated at an inlet temperature of 209°C and an absolute pressure of 4.1 MPa.

[0297] At the outlet of gas-liquid separation section cl, a supercritical salt effluent and a liquid effluent 11 are recovered. The supercritical salt effluent can then be, in whole or in part, purged and / or recycled. The liquid effluent 11 is then subjected to a gas-liquid separation section (or stage) c2 at 180°C and 1 MPa. The resulting gas effluent gl is recovered and can then be, in whole or in part, purged and / or recycled.

[0298] At the outlet of the gas-liquid separation section c2, a liquid effluent 12 is recovered and placed under atmospheric conditions, i.e. at a temperature of about 20°C and a pressure of about 0.1 MPa.

[0299] A solid C (flux 6) is then obtained. It is analyzed according to the methods described above. The results are presented in Table 3.

[0300] [Tables3] Solid Charge C VOC Content _(D 200 ppm by weight Ash Content 1.1% by weight < 1000 ppm by weight Colorimetry: 57.5 92.7 Cielab - L 14.7 0.1 Cielab - a 10.8 4.5 Cielab - b

[0301] (1): The VOC content of the charge was not measured.

[0302] Solid C is composed of polypropylene, purified since it has a level of Reduced ash content (<1000 ppm wt.) (despite the introduction of antioxidant in step c) compared to the feed (1.1 wt.), and Cielab colorimetry parameters are also improved compared to those of the feed. Solid C shows a very low VOC content, and therefore a very low residual solvent content (200 ppm wt. of volatile organic compounds relative to the weight of solid C).

Claims

Claims

1. A method of treating a plastic filler (1) comprising thermoplastics, said method comprising: a) a step of dissolving the plastic filler in a dissolving solvent (2), step a) being carried out at a dissolving temperature of between 100°C and 300°C and at a dissolving pressure of between 0.1 and 100.0 MPa absolute, to obtain at least one crude polymer solution (3); b) a step of purifying the crude polymer solution, to obtain a purified polymer solution (4), comprising: bl) a sub-step of separating the insolubles; and / or b2) a washing sub-step, by contact with a dense solution; and / or b3) an extraction sub-step, by contact with an extraction solvent; and / or b4) a sub-step of adsorption of impurities by contact with an adsorbent; then c) a step of solvent-polymer separation of the purified polymer solution, to obtain a stream of purified thermoplastic polymers (6) and at least one stream of solvent, said solvent-polymer separation step c) implementing a gas-liquid separation section (cl) or several gas-liquid separation sections (cl, c2, c3, c4) operating in series, said gas-liquid separation section (cl) or each of the gas-liquid separation sections (cl, c2, c3, c4) being operated at an inlet temperature of between 100°C and 300°C, and at a pressure lower than the outlet pressure of step b), when step c) implements several gas-liquid separation sections (cl, c2, c3, c4), the pressure of the later section being lower than that of the earlier section, the purified polymer solution, obtained at the end of the purification step b), feeding said gas-liquid separation section (cl) or the first gas-liquid separation section (cl) of the series, said gas-liquid separation section (cl) or each of the gas-liquid separation sections (cl, c2, c3, c4) producing a gas effluent (gl, g2, g3, g4),which corresponds to said at least one solvent flow, and a liquid effluent (11,12,13,14), when step c) implements several gas-separation sections, liquid (cl, c2, c3, c4), the liquid effluent from the previous section feeding the subsequent section, the liquid effluent from said gas-liquid separation section (cl) or from the last gas-liquid separation section of the series (c4) constituting said flow of purified thermoplastic polymers (6).

2. Method according to claim 1, in which the dissolving solvent (2) and the plastic filler (1) feed step a) according to a weight ratio of the dissolving solvent relative to the plastic filler, between 0.2 and 100.0, preferably between 0.3 and 20.0, more preferably between 1.0 and 10.0, even more preferably between 3.0 and 7 O

3. / ,v. Method according to claim 1 or 2, in which the dissolving solvent comprises at least one hydrocarbon compound, said dissolving solvent having a boiling point of between -50 and 250°C, preferably between - 15 and 200°C, preferentially between 15 and 160°C and more preferably between 50 and 120°C.

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

5. A method according to any one of the preceding claims, wherein the pressure in the gas-liquid separation section (cl) or each of the gas-liquid separation sections (cl, c2, c3, c4) 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, and more particularly greater than or equal to 0.0008 MPa.

6. Method according to any one of the preceding claims, in which said step c) of solvent-polymer separation implements several successive gas-liquid separation sections, preferably at least two, preferably between two and ten, very preferably between two and five, for example three or four successive gas-liquid separation sections.

7. A method according to claim 6, wherein the first gas-liquid separation section is operated at an inlet temperature of between 100 and 300°C, preferably between 110 and 275°C, and at a pressure of less than 100.0 MPa absolute, preferably less than 25.0 MPa. absolute, preferably less than 15.0 MPa absolute, and advantageously greater than or equal to 0.0008 MPa absolute; the last section is operated at an inlet temperature of between 100 and 300°C, preferably between 110 and 275°C, and at a pressure of between 0.000005 and 1.00 MPa absolute, preferably between 0.00001 and 1.00 MPa absolute, preferably between 0.0001 and 1.00 MPa absolute, very preferably between 0.0005 and 0.10 MPa absolute, very preferably between 0.0005 and 0.0020 MPa absolute; and the pressure in each intermediate section is adjusted decreasingly between the pressure of the first section and the pressure of the last section.

8. Method according to any one of the preceding claims, in which the or each gas effluent produced is, in whole or in part, purged and / or purified and / or fractionated and / or recycled to step a) and / or optionally step b).

9. A method according to any preceding claim, wherein step c) comprises an intermediate liquid-liquid or supercritical-liquid separation section, located upstream of the gas-liquid separation section or series of gas-liquid separation sections, to obtain a liquid phase, which comprises the target thermoplastics, and a second liquid phase or a supercritical phase which comprises dissolving solvent, and wherein the liquid phase, which comprises the target thermoplastics, feeds the gas-liquid separation section or the first gas-liquid separation section, instead of the purified polymer solution.

10. A method according to any one of the preceding claims, wherein step c) comprises the introduction of at least one additive, in particular an antioxidant agent.

11. Method according to any one of the preceding claims, in which step b) of purification comprises a sub-step b1) of separation of the insolubles, advantageously followed by a sub-step b4) of adsorption.

12. A method according to any preceding claim, wherein the plastic filler comprises polyolefins.

13. Device for treating a plastic filler to obtain a flow of purified thermoplastic polymers, said device comprising: - dissolution means for bringing into contact and dissolving at least in part the plastic filler in a dissolution solvent, and obtain a crude polymer solution; - purification means for purifying the crude polymer solution and obtaining a purified polymer solution; - a solvent-polymer separation device, located downstream of said purification means, for separating the purified polymer solution into a stream of purified thermoplastic polymers and at least one solvent effluent, characterized in that said solvent-polymer separation device comprises: a gas-liquid separation section or several gas-liquid separation sections operating in series, preferably at least two, preferably between two and five, for example three or four, successive gas-liquid separation sections, at least one pressure control system in said gas-liquid separation section or in each gas-liquid separation section of the series, so as to adjust the pressure in said gas-liquid separation section or in each gas-liquid separation section of the series to a value lower than the operating pressure at the outlet of the purification means, and when said solvent-polymer separation device comprises several gas-liquid separation sections, so as to adjust the pressure in the later section to a value lower than that in the earlier section, said gas-liquid separation section or each gas-liquid separation section of the series comprising a feed system, a liquid withdrawal system and a gas withdrawal system, the feed system of said gas-liquid separation section or of the first gas-liquid separation section of the series being connected to at least one of the purification means and allowing the supply of purified polymer solution to said solvent-polymer separation device, when said solvent-polymer separation device comprises several gas-liquid separation sections, the feed system of the later section being connected to the liquid withdrawal system of the earlier section, the liquid withdrawal system of said gas-liquid separation section or of the last gas-liquid separation section of the series making it possible to recover said flow of purified thermoplastic polymers, the gas withdrawal system of said gas-liquid separation section or of each gas-liquid separation section of the series making it possible to recover said at least one solvent effluent, said at least one solvent effluent comprising dissolution solvent.

14. Device according to claim 13, comprising an intermediate liquid-liquid or supercritical-liquid separation section, upstream of said gas-liquid separation section or of the first gas-liquid separation section of the series.

15. Device according to claim 13 or 14, comprising at least one additive introduction system.

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