Method for purifying a polymer solution by adsorption on treated bleaching earths

Abstract

The present invention relates to a method for purification by adsorption of a polymer solution to be treated and an organic solvent, comprising a step of adsorption by bringing the polymer solution to be treated into contact with washed bleaching earths at a temperature between 50°C and 250°C, the washed bleaching earths being obtained from a washing process comprising bringing bleaching earths into contact with an acid solution. The present invention also relates to a more comprehensive method for recycling the thermoplastics of a plastics feedstock, comprising: a) a step of dissolving the plastics feedstock in a dissolving solvent to obtain a crude polymer solution; b) a step of purifying the crude polymer solution, comprising an adsorption sub-step b1) implementing the method for purification by adsorption to obtain a purified polymer solution; and c) a step of separating the solvent and polymer.

Description

[0001] METHOD FOR PURIFYING A POLYMERIC SOLUTION BY ADSORPTION ON TREATNED BLEACHING EARTHS

[0002] technical field

[0003] The invention relates to a purification process by adsorption of a polymer solution comprising thermoplastics, preferably polyolefins, advantageously dissolved in an organic solvent, and impurities. More particularly, the invention relates to an optimized process for purifying a polymer solution comprising thermoplastics, preferably polyolefins, by contacting the polymer solution with bleaching earths previously washed with an acidic solution.The said adsorption purification process can advantageously be integrated into a more global plastics recycling process, for example as a purification step of a polymer solution obtained after dissolving a plastic filler, advantageously comprising thermoplastics, preferably polyolefins, in a dissolving solvent, and allowing to obtain a stream of purified thermoplastics which can then be (re)used in all types of plastic formulations in place of virgin resin.

[0004] Previous technique

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

[0006] Mechanical recycling allows for the partial reuse of certain waste materials, either directly in new objects or by mixing mechanically sorted plastic waste streams with streams of virgin polymers. This type of recovery is limited because, even though it yields a plastic stream concentrated in a particular type of polymer, especially thermoplastics, mechanical sorting does not eliminate impurities that are at least partially trapped within the polymer matrix. These impurities include additives such as fillers, colorants, pigments, plasticizers, 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, and so on.Furthermore, mechanical recycling generally only allows for the partial removal of non-intentionally added substances (NIAS) during the plastics' lifecycle, as these substances can sometimes migrate into the polymer matrix and subsequently into the contents if the product is used after mechanical recycling. Chemical recycling primarily aims to remove additives and, depending on the processes used, to chemically modify the macromolecular chains of the polymers in question to varying degrees (for example, recovery of the intact polymer, depolymerization, or non-selective chain breaking of various polymers to obtain mixtures of compounds containing carbon and hydrogen). These 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, into olefins by steam cracking. These olefins can then be polymerized or transformed into monomers before the latter are polymerized.

[0007] Another method for recycling plastic waste involves the deformulation of plastic materials, particularly thermoplastics such as polyolefins, which appears more environmentally sound. This method of plastic waste recycling consists of dissolving the target polymer in a solvent and removing impurities, such as additives like fillers, colorants, pigments, plasticizers, unintentionally added substances, 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.This recycling method can be called physical recycling or solvent-based recycling (or "solvent based recycling" according to the established Anglo-Saxon term).

[0008] Several studies present different methods of treating plastic waste by dissolution and purification.

[0009] The document WO2022 / 128490 describes a process for treating a plastic filler, including a step of adsorbing impurities from a polymer solution including, for example, polyethylene in heptane by adsorption, in particular with activated carbons.

[0010] Document WO2019 / 246017 describes a method for purifying a polymer feedstock, particularly from post-consumer plastic waste, by dissolving the polymer in a solvent, followed by a sedimentation step and then filtration of the polymer solution and optionally a purification step by contact with a solid preferably chosen from among activated carbons, clays, perlites, aluminas, silicas, glass beads, zeolites, etc. The polymer from the purified polymer solution obtained is then separated from the solvent.Finally, document US2017 / 002110 describes more precisely a particular method for purifying a polymer feedstock, in particular from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, then contacting the resulting polymer solution with a solid such as activated carbon, clays, in particular bleaching earths ("fuller's earth"), perlite, alumina, silica, glass beads, sand, etc., and finally separating the purified polymer from the solvent under temperature and pressure conditions in which said polymer precipitates.

[0011] The present invention aims to improve these processes for treating thermoplastics by dissolution. More specifically, the present invention aims to optimize the purification by adsorption of a polymer solution comprising thermoplastics, and in particular polyolefins, so as to obtain a purified polymer solution advantageously free of at least some of the impurities contained in the polymer solution to be treated, while limiting the formation of products resulting from secondary reactions that are often difficult to separate from the targeted thermoplastics. Such an optimized adsorption step can then be integrated into a more comprehensive plastic recycling process, advantageously for thermoplastics, based on the principle of dissolving and purifying the polymer solution.

[0012] Summary of the invention

[0013] The present invention relates to a purification process by adsorption of a polymer solution to be treated comprising thermoplastics and an organic solvent, the process comprising: an adsorption step comprising bringing the polymer solution to be treated into contact with washed bleaching earths obtained at the end of a washing process, the adsorption step being carried out at a temperature between 50°C and 250°C, in which the washing process comprises an acid washing step by contact of bleaching earths with an acid solution.

[0014] The present invention has the advantage of providing a simple yet optimized method for purifying a polymer solution containing thermoplastics, and in particular polyolefins. Indeed, the purification process according to the invention allows for improved purification of the polymer solution since it effectively eliminates impurities, especially soluble ones, and very specifically soluble organic impurities, present in the polymer solution to be treated, while limiting or even preventing degradation reactions of the thermoplastics and / or impurities (for example, mono-, di-, and triglycerides) which generate secondary products that are often difficult to separate from the targeted thermoplastics and dissolved in the solvent of the polymer solution.More particularly, the purification process by adsorption according to the invention, which includes an adsorption step on acid-washed bleaching earths, makes it possible to obtain a polymer solution having a content of impurities, in particular soluble, particularly organic soluble, significantly reduced compared to the content of impurities, in particular soluble, particularly organic soluble, of the polymer solution to be treated.Preferably, the polymer solution obtained at the end of the purification process by adsorption according to the invention has a removal rate (which corresponds to the ratio of the difference between the content of impurities, in particular soluble impurities, of the polymer solution to be treated and the content of impurities, in particular soluble impurities, of the polymer solution obtained at the outlet, relative to the content of impurities, in particular soluble impurities, of the polymer solution to be treated, expressed as a percentage) greater than 15%, preferably greater than 25%, preferably greater than or equal to 30%, preferably greater than or equal to 50%, or even greater than or equal to 60%.

[0015] The adsorption purification process according to the invention allows, along with a significant reduction in the content of impurities, particularly soluble ones, for limiting the degradation of the targeted thermoplastics. The degradation of thermoplastics, especially polymer chains, can be detected, for example, by the melt flow index (MFI) of the thermoplastics, determined according to ASTM D1238 (or ISO 1133). Indeed, a variation in the melt flow index (MFI) is generally indicative of a change in the average molar mass of the tested thermoplastics: an increase in the MFI typically corresponds to a decrease in the average molar mass, while a decrease in the MFI typically corresponds to an increase in the average molar mass.Thus, the adsorption purification process according to the invention makes it possible, in particular, to limit the variations of the melt flow index (or MFI), preferably so as to have a difference between the MFI of the purified thermoplastics and the MFI of the plastic feed to be treated of less than 20 g / 10 min, preferably less than or equal to 17 g / 10 min, or even less than or equal to 15 g / 10 min.

[0016] The present invention also relates to a process for recycling thermoplastics from a plastic filler, comprising: a) a step of dissolving the plastic filler in a dissolving solvent, step a) being carried out at a dissolution temperature between 50°C and 250°C, and at a dissolution pressure between 0.1 MPa and 25 MPa absolute, to obtain at least one crude polymer solution; b) a purification step of the crude polymer solution, comprising at least one substep b1) of adsorption implementing the purification process by adsorption according to the invention, to obtain a purified polymer solution; c) a solvent-polymer separation step, to obtain at least one stream of purified thermoplastics and at least one stream of solvent.

[0017] The advantage of the recycling process according to the invention is to offer a simple process for recycling, by dissolution, thermoplastics, preferably polyolefins, for example (co)polypropylenes and (co)polyethylenes, contained in a plastic feed and in particular in plastic waste, for example from post-consumer and / or post-production, allowing the recovery of a stream of purified thermoplastics, that is to say freed from at least part of the organic and inorganic impurities contained in the plastic feed (in particular freed from at least part of the additives classically introduced in polymer formulations to manufacture plastics, such as colorants, pigments, plasticizers, etc.) and with no or very few secondary products resulting from degradation reactions.

[0018] Most advantageously, the recycling process according to the invention makes it possible to achieve residual levels of impurities, and advantageously also of solvent, sufficiently low so 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, 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, the content of impurities corresponding here to the total content of impurities, that is to say of residual impurities initially present in the plastic feed, such as organic or inorganic formulation additives, and products generated during possible secondary reactions throughout the process.

[0019] The invention also has the advantage of contributing to plastic recycling and the preservation of fossil resources by enabling the recovery of plastic waste. It allows, in effect, the purification of plastic waste to obtain a stream of purified thermoplastic polymers, particularly purified polyolefins, with reduced impurity content and, notably, 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. Description of embodiments

[0020] In this description, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included within the described range. If this is not the case, and the limit values ​​are not included within the described range, this clarification will be provided in this description.

[0021] In this description, the expression "greater than..." is understood as strictly greater than, and symbolized by the sign ">", and the expression "less than..." is understood as strictly less than, and symbolized by the sign "<". When the limit is included, the precision will be provided by the respective expressions "greater than or equal to..." (corresponding to the sign ">") and "less than or equal to" (corresponding to the sign "<").

[0022] 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.

[0023] In the following description, specific embodiments of the invention are described. They can be implemented separately or in combination with each other, without limitation as to the number of combinations where technically feasible.

[0024] According to the present invention, the pressures are absolute pressures and are given indifferently in MPa or in absolute MPa (or MPa abs.).

[0025] The terms "upstream" and "downstream" are to be understood in relation to the general flow of the fluid(s) or flow in question in the process, in particular in relation to the flow of the stream which includes the thermoplastics to be purified.

[0026] In this description, the terms "polymer", "thermoplastic polymer" and "thermoplastic" can be used interchangeably.

[0027] The term "polyolefins" refers to all types of homopolymers and / or copolymers, and their mixtures, having olefins as their unit unit. More specifically, polyolefins can be polyethylene homopolymers, designated by the acronym PE, of any type (for example, high-density, also called HDPE, or low-density, called LDPE), polypropylene homopolymers, designated by the acronym PP, their copolymers, and / or their mixtures.

[0028] 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.

[0029] The additives correspond to at least some of the impurities in the plastic feed to be treated, which the treatment process according to the invention allows to be at least partially eliminated. Other types of impurities present in the plastic feed may be impurities from use or substances not intentionally added, such as metallic impurities, paper / cardboard, biomass, polymers other than the polymer(s) targeted, oils or surfactants from products in contact with the plastic during its life, etc.

[0030] Thus, according to the invention, the impurities that the process according to the invention makes it possible to eliminate, at least in part, include the additives conventionally used in polymer formulations, and in particular thermoplastic formulations, and also potentially impurities from use arising from the life cycle of plastic materials and objects, and / or from the waste collection and sorting system. These latter impurities may be metallic, organic, or mineral; they may consist of packaging residues, food residues, or compostable residues (biomass).These usage impurities may also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, silicones, rigid polymers, thermosetting polymers, thermoplastics of a different nature than the thermoplastics concerned (in particular than the polyolefins concerned), household, chemical or cosmetic products, used oils, water, etc.

[0031] According to the invention, a polymer solution is a solution comprising an organic solvent, in particular the dissolving solvent of step a) of the processing method of the invention, and at least the thermoplastic polymers referred to, in particular the polyolefins referred to, advantageously dissolved in said organic solvent, i.e., advantageously solvated and dispersed in said organic solvent. The polymer solution may further comprise impurities, insoluble (and suspended in the polymer solution) and / or soluble (and solubilized in the organic solvent). Depending on the steps of the process according to the invention, the polymer solution may therefore comprise, in addition to the dissolved thermoplastics referred to, impurities in the form of insoluble particles that are advantageously suspended in said polymer solution, soluble impurities dissolved in the organic solvent, and / or optionally another liquid phase immiscible with said polymer solution.The refined or purified polymer solution comprises a limited content of impurities, in particular soluble and in a very particular organic soluble, in particular a content of impurities in particular soluble and in a very particular organic soluble lower than the content of impurities in particular soluble and in a very particular organic soluble of the polymer solution before treatment by the process according to the invention.Preferably, the refined or purified polymer solution obtained at the end of the adsorption purification process according to the invention has a removal rate (i.e. the ratio of the difference between the content of impurities, particularly soluble impurities at the input and the content of impurities, particularly soluble impurities at the output, relative to the content of impurities, particularly soluble impurities at the input, expressed as a percentage) greater than 25%, preferably greater than 25%, preferably greater than or equal to 30%, preferably greater than or equal to 50%, or even at least 60%.

[0032] Throughout the description, the term "atmospheric pressure" means a pressure equal to 0.1 MPa.

[0033] It is well known that the boiling point of a compound varies with the operating pressure. However, without further specification, particularly without specifying the pressure, the boiling point of the compound in question, especially the dissolving solvent, is understood to be the boiling point of said compound, and in particular of said dissolving solvent, at atmospheric pressure (specifically 0.1 MPa). Thus, the boiling point that characterizes the dissolving solvent should be understood as the boiling point of said dissolving solvent at atmospheric pressure (specifically 0.1 MPa).

[0034] The critical temperature and critical pressure of a solvent, particularly a dissolving solvent, are specific to that solvent and depend on its nature. For a pure substance, the critical temperature and critical pressure are, respectively, the temperature and pressure at the critical point of that pure substance. As is well known to those skilled in the art, at and above the critical point, the pure substance is in a supercritical state; it can then be called a supercritical fluid.

[0035] The invention thus relates to a purification process by adsorption of a polymer solution to be treated (or initial polymer solution) comprising thermoplastics, preferably polyolefins, an organic solvent, and impurities, particularly soluble ones, the process comprising: an adsorption step comprising contacting the polymer solution to be treated with washed bleaching earths, at a temperature between 50°C and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, preferably between 140 and 190°C, and preferably at a pressure between atmospheric pressure (i.e. 0.1 MPa absolute) and 25 MPa absolute, preferably between 0.2 and 20 MPa absolute, preferably between 1.5 and 15 MPa absolute, preferably the adsorption step employing at least one fixed bed comprising the washed bleaching earths and being operated at an hourly volumetric speed (or WH),which corresponds to the ratio between the volumetric flow rate of the polymer solution to be treated that feeds the adsorption step and the volume of the washed bleaching earths in the form of fixed bed(s) for a period of between 0.05 and 10 h-1, preferably between 0.1 and 5.0 h-1, wherein the washed bleaching earths are obtained at the end of a washing process, advantageously implemented prior to the adsorption step, said washing process comprising: an acid washing step by contact of bleaching earths with an acidic solution, preferably the acidic solution being an aqueous solution with an acidic pH, preferably with a pH less than or equal to 5, preferably less than or equal to 4, preferably less than or equal to 2, for example equal to 1, preferably the acidic solution being an aqueous solution comprising an organic or inorganic acid, preferably chosen from hydrochloric acid, sulfuric acid, nitric acid,and organic compounds comprising at least one carboxylic acid functional group and advantageously a linear or branched alkyl chain comprising preferably between 2 and 10 carbon atoms (C2-C10), preferably between 2 and 6 carbon atoms (C2-C6), such as acetic acid, propanoic acid, hexanoic acid, citric acid, tartaric acid, lactic acid, succinic acid, preferably the acid solution is an aqueous solution comprising an inorganic acid, preferably selected from hydrochloric acid, sulfuric acid, nitric acid, most preferably hydrochloric acid, advantageously at a concentration of at least 0.01 mmol / l (i.e. 0.01 mM), preferably at least 0.1 mmol / l (i.e. 0.1 mM), preferably at least 0.01 mol / l (i.e. 0.01 M), and preferably of at most 1 mol / l, for example a concentration of 0.1 mol / l, the acid washing step preferably being carried out at a temperature between 15 and 300°C,preferably between 15 and 250°C, at a pressure greater than or equal to atmospheric pressure and advantageously less than or equal to 25 MPa absolute, preferably less than or equal to 20.0 MPa absolute, preferably less than or equal to 10.0 MPa absolute, and most preferably less than or equal to 5.0 MPa absolute, optionally the washing process further comprising at least one step of rinsing the bleaching earths, preferably with water, downstream of the contact of the bleaching earths with the acid solution (i.e., downstream of the acid washing step), and preferably a drying step, downstream of the acid washing step (i.e., of the contact phase of the bleaching earths with the acid solution) and preferably downstream of the rinsing step of the bleaching earths, the drying step being carried out preferably at a temperature between 80 and 300°C, preferably between 100 and 250°C, for at least 0.1 hours, preferably at minus 0.5 hours,preferably for at least 1 hour and advantageously for no more than 12 hours, preferably for no more than 10 hours, and possibly under gas flow.

[0036] The polymer solution to be treated

[0037] The polymer solution to be treated (or initial polymer solution), which is purified by the purification process according to the invention, comprises thermoplastics, advantageously particular thermoplastics, an organic solvent and impurities, and in particular impurities soluble in the organic solvent.

[0038] Advantageously, the thermoplastics contained in the polymer solution to be treated, advantageously the particular (or targeted) thermoplastics of the polymer solution to be treated, are, at least in part, dissolved in the organic solvent of the polymer solution, that is to say, are advantageously solvated and dispersed in said organic solvent.

[0039] Preferably, the thermoplastics, advantageously specific, of the polymer solution to be treated can be alkene polymers (or olefins, i.e., polyolefins), diene polymers, vinyl polymers, and / or styrenic polymers. In a preferred embodiment of the invention, the thermoplastics, advantageously specific, of the polymer solution to be treated are polyolefins, and in particular polyethylene, polypropylene, their copolymers, and mixtures thereof. Advantageously, in this preferred embodiment, the polyolefins are dissolved in the organic solvent of the polymer solution.

[0040] Preferably, the polymer solution to be treated comprises at least 1% by weight, preferably at least 4% by weight, preferably at least 8% by weight of thermoplastics, advantageously of particular thermoplastics, preferably of polyolefins, relative to the total weight of polymer solution to be treated, and very advantageously up to 85% by weight, in particular up to 75% by weight, more particularly up to 50% by weight or even up to 25% by weight of thermoplastics, advantageously of particular thermoplastics, preferably of polyolefins, relative to the total weight of polymer solution to be treated.

[0041] The initial polymer solution, which is treated by adsorption in the purification process according to the invention, contains impurities. These impurities may be additives commonly used in the formulation of thermoplastic-based plastics or everyday impurities. For example, the impurities in the polymer solution to be treated include plasticizers, colorants, pigments, antioxidants, light-stabilizing agents, antistatic agents, etc. The impurities in the polymer solution to be treated may be soluble or insoluble in the organic solvent of the polymer solution, preferably soluble in the organic solvent of the polymer solution to be treated. In particular, the impurities in the polymer solution to be treated, which are at least partially removed during the adsorption step, are soluble impurities, and especially soluble organic impurities.More specifically, the content of soluble impurities, and particularly soluble organic impurities, in the polymer solution to be treated is such that said soluble impurities represent preferably up to 5% by weight, preferably up to 2% by weight, more particularly up to 1.5% by weight, and preferably at least 0.01% by weight, or even at least 0.05% by weight relative to the weight of the thermoplastics, preferably specific (or targeted) thermoplastics, preferably polyolefins, contained in the polymer solution to be treated. Impurities insoluble in the chosen solvent and conditions, which may be present in the polymer solution to be treated, are preferably removed, at least partially, prior to the adsorption step, in particular by solid-liquid separation.

[0042] Advantageously, the organic solvent for the polymer solution to be treated is preferably chosen so that its Hansen parameters lie within the Hansen sphere of the thermoplastics, advantageously specific to the polymer solution being treated, particularly the polyolefins in question. Hansen's theory allows, in fact, the prediction of the solubility of a polymer, particularly a thermoplastic such as polyolefins (polyethylene and / or polypropylene), in a solvent by determining the Hansen parameters and solubility sphere for the solvent and the polymer, respectively, as a function of several parameters, particularly their polar parameters, hydrogen bonding, dispersion, etc. If a solvent or solvent mixture has Hansen parameters within the Hansen sphere of the target polymer, then the polymer should be at least partially, and preferably completely, soluble in the solvent.Preferably, the organic solvent of the polymer solution to be treated is chosen so that the thermoplastics, advantageously particular, of the polymer solution to be treated, in particular the polyolefins, are at least partly dissolved, i.e. solvated and dispersed, in said organic solvent.

[0043] Preferably, the organic solvent of the polymer solution to be treated comprises, in particular consists of, at least one hydrocarbon and / or oxygenated compound, preferably at least one hydrocarbon compound. Preferably, and in particular when the specific thermoplastics of the polymer solution to be treated are polyolefins, the organic solvent of the polymer solution to be treated comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic or naphthenic (i.e., non-aromatic), and in particular paraffinic (i.e., saturated), preferably linear, branched, or cyclic, preferably non-aromatic.Preferably, the organic solvent of the polymer solution to be treated comprises at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight of at least one hydrocarbon compound, preferably aliphatic or naphthenic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, the percentages being expressed in relation to the total weight of said organic solvent (100% being the maximum).Preferably, the organic solvent of the polymer solution to be treated comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic or naphthenic and in particular paraffinic, having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 180°C and preferably having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) greater than 70°C, preferably greater than or equal to 75°C, and advantageously less than or equal to 160°C, preferably less than or equal to 130°C.Preferably, said at least one hydrocarbon compound, preferably aliphatic or naphthenic 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 or naphthenic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, may be selected from isomers of butane, pentane, hexane, heptane, octane, nonane, decane, and mixtures thereof, preferably from isomers of pentane, hexane, heptane, octane and mixtures thereof.Thus, the organic solvent of the polymer solution to be treated may comprise at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight, of an isomer or mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane, preferably of an isomer or mixture of isomers of pentane, hexane, heptane and / or octane, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0044] Optionally, the adsorption purification process according to the invention includes a step of dissolving a thermoplastic feedstock, comprising thermoplastics, in particular the specific thermoplastics targeted, preferably polyolefins, and impurities, in the organic solvent. This dissolution step is advantageously located upstream of the adsorption step and allows the formation of a crude polymer solution that can be sent directly to the adsorption step or that can optionally undergo intermediate purification steps, such as at least one solid-liquid and / or liquid-liquid separation.In this particular embodiment, the optional dissolution step can be carried out at a temperature between 50°C and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, preferably between 140 and 190°C, and preferably at a pressure between atmospheric pressure (i.e. 0.1 MPa absolute) and 25 MPa absolute (or even between 0.1 and 25.0 MPa absolute), preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute) and most preferably between 1.5 and 15 MPa absolute (or even between 1.5 and 15.0 MPa absolute). The quantities of thermoplastic filler and organic solvent, which feed the optional dissolution step, are preferably adjusted to respect the thermoplastic and impurity contents of the polymer solution to be treated which feeds the adsorption step.For example, the quantities of thermoplastic filler and organic solvent that feed the optional dissolution step are adjusted so as to have a solvent / filler weight ratio between the organic solvent and the thermoplastic filler, of between 0.2 and 100.0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 10.0. According to a particular case of this embodiment of the invention, the thermoplastic filler can correspond to the plastic filler of the treatment process according to the invention described below in this description, the optional dissolution step then corresponding to step a) of dissolution of the treatment process according to the invention and the organic solvent to the dissolving solvent.

[0045] The adsorption step of the adsorption purification process according to the invention comprises contacting the polymer solution to be treated, which includes the organic solvent, thermoplastics advantageously dissolved, at least partially, in said organic solvent, and impurities, with washed bleaching earths, particularly acid-washed earths. The adsorption step, and more generally the adsorption purification process, thus makes it possible to obtain a refined polymer solution, that is to say, one free of at least some of the impurities, particularly soluble impurities, and especially soluble organic impurities, present in the polymer solution to be treated.

[0046] The adsorption step, and more generally the adsorption purification process, has the advantage of enabling optimized purification of the polymer solution being treated. More specifically, it allows for the efficient removal of impurities, particularly soluble ones, and very specifically soluble organic impurities, present in the polymer solution, while limiting, or even preventing, the formation of by-products that can be generated by reactions such as degradation, (trans)esterification, oxidation, cracking, recomposition, etc., of the compounds (impurities, thermoplastics) present in the polymer solution. These by-products are difficult to separate from the target thermoplastics, particularly the targeted polyolefins. For example, the (trans)esterification reactions of mono-, di-, and triglyceride-type impurities present in the polymer solution are limited.

[0047] More specifically, the adsorption step of the adsorption purification process according to the invention makes it possible to obtain a polymer solution having a significantly reduced content of impurities, particularly soluble impurities, and more specifically soluble organic impurities, compared to the content of impurities, particularly soluble impurities, and more specifically soluble organic impurities, of the polymer solution to be treated. Preferably, the polymer solution obtained at the end of the adsorption step has a removal rate greater than 25%, preferably greater than 25%, preferably greater than or equal to 30%, preferably greater than or equal to 50%, or even at least 60%.The removal rate corresponds, here, to the ratio of the difference between the content of impurities, particularly soluble impurities, of the polymer solution to be treated and the content of impurities, particularly soluble impurities, of the polymer solution obtained at the outlet of the adsorption step, relative to the content of impurities, particularly soluble impurities, of the polymer solution to be treated, expressed as a percentage, that is to say:.

[0048] Removal rate = 100 x [(soluble impurity content of the polymer solution to be treated) - (soluble impurity content of the polymer solution obtained)] / (soluble impurity content of the polymer solution to be treated).

[0049] The adsorption step of the purification process according to the invention also allows, along with a significant reduction in the content of impurities, particularly soluble ones, for limiting the degradation of the targeted thermoplastics. This degradation can be detected, for example, by observing changes in the melt flow index (MFI) of the thermoplastics. The melt flow index (MFI) is determined according to ASTM D1238 (or ISO 1133) at a temperature specific to the thermoplastics being tested (in particular, 190°C or 230°C, + / - 0.5°C, for polyethylene or polypropylene, respectively).Thus, the adsorption step of the process according to the invention makes it possible, in particular, to limit the variations of the hot melt index (or MFI) of the targeted thermoplastics, preferably so as to have a difference between the MFI of the purified thermoplastics, obtained at the end of the adsorption step according to the invention and then removal of the solvent, and the MFI of the targeted thermoplastics of the polymer solution to be treated of less than 20 g / 10 min, preferably less than or equal to 17 g / 10 min, or even less than or equal to 15 g / 10 min.Preferably, the adsorption step is carried out at a temperature between 50°C and 250°C, preferably between 110°C and 250°C, preferably between 130°C and 210°C, preferably between 140°C and 190°C, and preferably at a pressure between atmospheric pressure (i.e., 0.1 MPa absolute) and 25 MPa absolute (or even between 0.1 MPa absolute), preferably between 0.2 MPa absolute and 20 MPa absolute (or even between 0.2 MPa absolute), and most preferably between 1.5 MPa absolute and 15 MPa absolute (or even between 1.5 MPa absolute). According to a preferred embodiment in which the thermoplastics concerned (i.e.the specific thermoplastics) of the polymer solution to be treated are polyolefins, the adsorption step is preferably carried out at a temperature between 110 and 250°C, preferably between 130 and 210°C, most preferably between 140 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), most preferably between 1.5 and 15 MPa (or even between 1.5 and 15.0 MPa absolute). According to another preferred embodiment in which the targeted thermoplastic (i.e.The specific thermoplastic of the polymer solution to be treated is polyethylene. The adsorption step is preferably carried out at a temperature between 110 and 250°C, preferably between 120 and 210°C, most preferably between 130 and 210°C, most preferably between 130 and 200°C, and most preferably between 140 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), preferably between 0.5 and 17 MPa absolute (or even between 0.5 and 17.0 MPa absolute), most preferably between 1.0 and 16 MPa (or even between 1.0 and 16.0 MPa absolute), and most preferably between 2.0 and 15 MPa (or even between 2.0 and 15.0 MPa absolute). According to yet another preferred embodiment in which the thermoplastic in question (i.e.The specific thermoplastic of the polymer solution to be treated is polypropylene. The adsorption step is preferably carried out at a temperature between 130 and 250°C, preferably between 130 and 210°C, preferably between 140 and 210°C, most preferably between 150 and 200°C, and most preferably between 160 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), preferably between 0.5 and 15 MPa absolute (or even between 0.5 and 15.0 MPa absolute), most preferably between 1.0 and 12 MPa (or even between 1.0 and 12.0 MPa absolute), and most preferably between 1.5 and 10 MPa (or even between 1.5 and 10.0 MPa absolute).

[0050] Preferably, the adsorption step is carried out at a volumetric hourly rate (or WH) between 0.05 and 10 h' 1 , preferably between 0.1 and 5.0 h' 1The hourly volumetric velocity here corresponds to the ratio between the volumetric flow rate of the polymer solution to be treated, which feeds the adsorption step, and the volume of washed bleaching earths that come into contact with said polymer solution, said bleaching earths preferably being in the form of fixed bed(s). Most preferably, the adsorption step uses at least one fixed bed comprising the washed bleaching earths and is operated at an hourly volumetric velocity (or WH) of between 0.05 and 10 h' 1 , preferably between 0.1 and 5.0 h' 1 .

[0051] Advantageously, the pressure and temperature conditions of the adsorption step allow the organic solvent to remain, at least partially and preferably entirely, in a liquid state, and the targeted thermoplastics, particularly the targeted polyolefins, and possibly (or even generally) at least some of the impurities, dissolved, at least partially and preferably entirely, in the organic solvent. In other words, the temperature and pressure conditions in the adsorption step prevent, or at least limit, the organic solvent from being in gaseous form, thereby optimizing contact with the adsorbent, especially the bleaching earths, and thus optimizing the purification of the polymer solution.

[0052] The adsorption step of the purification process comprises contacting the polymer solution to be treated with washed bleaching earths. According to the invention, the washed bleaching earths are bleaching earths that are washed, prior to the adsorption step, with an acidic solution during a washing process, carried out in situ or ex situ, that is to say:

[0053] - in the same equipment (same unit) as that in which the adsorption step is carried out, or in situ, and preferably in batch or continuous mode, preferably in continuous mode, or

[0054] - in other equipment, i.e. external equipment (external unit), than that in which the adsorption step is carried out, or ex situ, and preferably in discontinuous or continuous mode, in particular in discontinuous mode.

[0055] Advantageously, the washing process includes an acid washing step which involves bringing bleaching earths into contact with an acidic solution. This contact can therefore be called "acid contact" or "acid washing phase".

[0056] Preferably, the initial bleaching earths, which are washed by the acid solution, are clays composed mainly (i.e., comprising at least 50% by weight, preferably at least 75% by weight, preferably at least 90% by weight) of silicates and aluminosilicates. For example, the initial bleaching earths, which are washed by the acid solution, may be chosen from bentonites, montmorillonites, and smectites.

[0057] Preferably, the acid solution is an aqueous solution having an acidic pH, preferably having a pH less than or equal to 5, preferably less than or equal to 4, preferably less than or equal to 2, for example equal to 1. Preferably, the acid solution is an aqueous solution comprising an organic or inorganic acid, preferably selected from hydrochloric acid, sulfuric acid, nitric acid, and organic compounds comprising at least one carboxylic acid function and advantageously a linear or branched alkyl chain comprising preferably between 2 and 10 carbon atoms (C2-C10), preferably between 2 and 6 carbon atoms (C2-C6), such as acetic acid, citric acid, tartaric acid, lactic acid, succinic acid.Preferably, the acid solution is an aqueous solution comprising an inorganic acid, preferably chosen from hydrochloric acid, sulfuric acid, nitric acid, and most preferably hydrochloric acid. Most advantageously, the acid solution is an aqueous solution comprising an organic or inorganic acid, preferably inorganic, at a concentration greater than or equal to 0.01 mmol / L (i.e., 0.01 mM), preferably greater than or equal to 0.1 mmol / L (i.e., 0.1 mM), preferably greater than or equal to 0.01 mol / L (i.e., 0.01 M), and most preferably less than or equal to 1 mol / L. For example, the concentration of inorganic acid in the aqueous acid solution is 0.1 mol / L (0.1 M).

[0058] Advantageously, the acid washing step (i.e., contacting the bleaching earths with the acid solution) is carried out at a temperature between 15 and 300°C, preferably between 15 and 250°C. According to a particular embodiment of the invention and in particular of the washing process, the acid washing step is carried out in situ (i.e. in the equipment, for example column, reactor, adsorber, in which the adsorption step is carried out) and is carried out preferably at a temperature between 50 and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C.

[0059] Preferably, the acid washing step is carried out at a pressure greater than or equal to atmospheric pressure (i.e., greater than or equal to 0.1 MPa), and preferably less than or equal to 25 MPa absolute, preferably less than or equal to 20.0 MPa absolute, most preferably less than or equal to 10.0 MPa absolute, and most preferably less than or equal to 5.0 MPa absolute. Preferably, the acid washing step (i.e., the acid contact) is carried out for at least 0.1 hours, preferably at least 0.5 hours, preferably at least 1.0 hour, and advantageously at most 24 hours, preferably at most 12 hours, at most 10 hours.This contact time advantageously corresponds to a residence time which can be defined here as the ratio between the volume of bleaching earths to be treated, for example located in a column or an adsorber, and the volumetric flow rate of the acid solution which passes through said volume of bleaching earths, when the washing process is operated in continuous mode, for example in situ.When the washing process is operated in discontinuous mode, for example ex situ, the contact time described above advantageously corresponds to a contact time which can be defined as the time during which the bleaching earths are in contact with the acid solution, that is to say, it corresponds to a duration from the moment when the bleaching earths to be treated are introduced into the acid solution or the acid solution is introduced onto the bleaching earths to be treated, and until the moment when the bleaching earths and the acid solution are separated (for example by filtration or centrifugation).

[0060] Under these operating conditions and with such an acidic solution, the washed bleaching earths thus obtained allow, when used in the adsorption step of the purification process, under the temperature and pressure conditions of the adsorption step described above, an optimized purification of the polymer solution to be treated, and in particular an effective elimination of soluble impurities and a significant reduction of by-products generated during possible secondary reactions, such as degradation, (trans)esterification, oxidation, cracking, recomposition, etc., of the compounds (thermoplastics and / or impurities) present in the polymer solution to be treated.

[0061] For example, the acid washing step (i.e., the acid contact) of the washing process can be implemented, particularly in batch mode, by introducing bleaching earths into a volume of acid solution, the bleaching earths then preferably representing between 2 and 30% by weight relative to the weight of acid solution, particularly in a reactor, in particular an agitated reactor, a mixer, an impregnator, or any other equipment known to those skilled in the art and adapted to this particular contact, this particular contact preferably being carried out for a time between 0.1 and 10 hours, as detailed above, and being followed by a solid-liquid separation to recover on the one hand the washed bleaching earths and on the other hand an acidic liquid.According to another particular embodiment, the acid washing step (i.e. the acid contact) of the washing process can be implemented, in particular in continuous mode, by permeation of a fixed bed of bleaching earths, in particular by passing a flow of acid solution through a fixed bed of bleaching earths which are for example contained in a column, an adsorber, or a porous tubular support, for example at a volumetric hourly rate (or WH), which corresponds to the ratio between the volumetric flow rate of the acid solution and the volume of bleaching earths washed of between 0.05 and 10 h'. 1 , preferably between 0.1 and 5.0 h -1 Optionally, and regardless of whether the washing process is carried out continuously or discontinuously, the acid solution can at least partially be recycled and reinjected at the inlet of the fixed bed of bleaching earths.

[0062] Optionally, the washing process may also include, downstream of the acid washing step (i.e., contact with acid), at least one rinsing step of the washed bleaching earths, preferably with an aqueous solution. This optional rinsing step may be called water rinsing or water washing.

[0063] Preferably, the washing process includes a drying (or drying step) of the washed, and possibly rinsed, bleaching earths, said drying being located downstream of the acid contact (i.e., the acid washing step) and downstream of the possible water rinsing step. Preferably, the drying of washed bleaching earths is carried out at a temperature between 80 and 300°C, preferably between 100 and 250°C, for at least 0.1 hours, preferably at least 0.5 hours, preferably at least 1.0 hour, and advantageously at most 12 hours, preferably at most 10 hours, and optionally under a gas flow, for example under a flow of air or nitrogen, preferably under a flow of nitrogen, and / or optionally at atmospheric pressure (i.e., 0.1 MPa), under pressure, for example up to a pressure of 25 MPa, in particular up to a pressure of 20 MPa, or under vacuum, for example at a pressure between 0.1 MPa (i.e., between atmospheric pressure) and 10 kPa (i.e.,100 m bar). The drying process may include several drying stages, for example two, three or four drying stages, carried out at different temperatures and / or pressures, in order to optimize water removal.

[0064] The bleaching earths thus washed, and possibly rinsed and preferably dried, can then be used in the adsorption step of the purification process according to the invention.

[0065] The adsorption step of the purification process according to the invention comprises contacting the polymer solution to be treated with washed bleaching earths. Optionally, the adsorption step further comprises contacting the polymer solution to be treated with at least one other adsorbent, other than said washed bleaching earths, preferably one, two, or three, preferably other adsorbent(s), either successively or simultaneously with contacting the washed bleaching earths. Said at least one other adsorbent is advantageously in solid form and may be selected from aluminas, silicas, silica-aluminas, activated carbons, and mixtures thereof, preferably activated carbons.The contact between the polymer solution to be treated and the washed bleaching earths and said at least one other adsorbent may, in particular, be successive: the contact between the polymer solution to be treated and said at least one other adsorbent may then be upstream or downstream of the contact with the washed bleaching earths, or even upstream and downstream. The contact between the polymer solution to be treated and the washed bleaching earths and said at least one other adsorbent may, in particular, be simultaneous: in this particular embodiment, said at least one other adsorbent is advantageously mixed with the washed bleaching earths.

[0066] Preferably, the washed bleaching earths and possibly said at least one other adsorbent are, at the adsorption stage, in the form of fixed bed(s), entrained bed(s) (or slurry(s), i.e. in the form of particles introduced into the flow of polymer solution to be treated and entrained with this flow) or in the form of bubbling bed(s), preferably in the form of fixed bed(s) or entrained bed(s) or even in the form of particles dispersed in the polymer solution to be treated, and preferably in the form of fixed bed(s) or in the form of particles dispersed in the polymer solution to be treated, or even very preferably in the form of fixed bed(s).

[0067] In one particular embodiment, the adsorption step, especially when implemented continuously, uses one or more fixed beds of adsorbent(s). For example, the adsorption step may use one or more, in particular one, two, three, or four, fixed beds of washed and / or treated bleaching earths, and optionally one or more, in particular one, two, three, or four, beds of at least one adsorbent. In another example, the adsorption step may use one or more, in particular one, two, three, or four, fixed beds of a mixture comprising the washed bleaching earths and at least one other adsorbent, and optionally one or more beds of at least one adsorbent.According to this particular embodiment, the fixed bed(s) can be implemented in one or more adsorption columns, preferably one, two, three, or four, containing the washed bleaching earths and / or said other adsorbent(s) when the latter is / are present. The flow of the polymer solution to be treated can, in this / these column(s), be upward or downward through the fixed bed(s).

[0068] According to this particular embodiment, and when the adsorption step uses two adsorption columns, one operating mode can be a so-called "swing" operation, in which one column is in operation while the other is in reserve. When the adsorbent in the in-line column (the washed bleaching earths and / or at least one other adsorbent) is used up, this column is isolated while the reserve column is put into operation.The used adsorbent (washed bleaching earths and / or said at least one other adsorbent) can then be regenerated in situ and / or replaced with fresh adsorbent (washed bleaching earths and / or bleaching earths to be treated and washed in situ according to a washing process as described above, and / or said at least one other adsorbent) so that the column containing it can be put back online once the other column has been isolated.

[0069] Another operating mode for this particular embodiment is to have at least two columns of adsorbent(s) (washed bleaching earths and possibly other adsorbent(s)), operating in series and advantageously staggered with respect to each other. When the adsorbent(s) (washed bleaching earths and possibly other adsorbent(s)) in the leading column is / are depleted, this first column is isolated, and the depleted adsorbent is regenerated in situ or replaced with fresh adsorbent. This column is then placed back in the last position, and so on. This operation is called a permutable mode, or, in English, a "Permutable Reactor System" (PRS), or simply "lead and lag."

[0070] Combining at least two adsorption columns helps to mitigate the potential and rapid poisoning and / or clogging of the bleaching earths and potentially at least one other adsorbent, due to the combined action of impurities, contaminants, and insolubles that may be present in the polymer solution being treated. The presence of at least two adsorption columns facilitates the replacement and / or regeneration of the adsorbent(s), advantageously without interrupting the process, and also helps to control costs and limit adsorbent consumption.

[0071] The purification process according to the invention can be integrated into a more global process for recycling thermoplastics included in a plastic feed, in particular based on the principle of deformulation, and in particular by dissolving at least part of the plastic feed, in particular the thermoplastics concerned, for example polyolefins, then purifying the polymer solution formed, the purification process by adsorption according to the invention corresponding to at least one purification step of the more global recycling process.

[0072] Thus, the invention also relates to a process for recycling thermoplastics, preferably polyolefins, from a plastic filler, comprising: a) a step of dissolving the plastic filler which comprises thermoplastics, in a dissolving solvent, step a) being carried out at a dissolution temperature between 50°C and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, most preferably between 140 and 190°C, and preferably at a dissolution pressure between atmospheric pressure (i.e. 0.1 MPa) and 25 MPa absolute, preferably between 0.2 and 20 MPa absolute, most preferably between 1.5 and 15 MPa absolute, to obtain at least one crude polymer solution;b) a purification step of the crude polymer solution, comprising at least one substep b1) of adsorption implementing the purification process by adsorption described above, to obtain a purified polymer solution, preferably, the purification step b) further comprising at least one other substep implementing any purification method known to the person skilled in the art, for example separation of insolubles, washing by contact with a dense solution such as an aqueous solution and / or extraction by contact with an organic solvent possibly at least partly in supercritical form, preferably the purification step b) further comprising a substep b2) of separation of insolubles, said (or said) other substep(s), for example substep b2), being able to be located upstream or downstream of said substep b1) of adsorption, preferably upstream;(c) a solvent-polymer separation step, to obtain at least one stream of purified thermoplastics and at least one stream of solvent, advantageously at least a fraction of said at least one stream of solvent being recycled to the dissolution step (a) to compose at least a part of the dissolving solvent.

[0073] The plastics feedstock in the recycling process comprises plastics which themselves consist primarily of thermoplastic polymers, such as polyolefins. Preferably, the plastics 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 plastics feedstock.

[0074] The plastics included in the plastic feed of the recycling process according to the invention are generally production by-products and / or post-consumer waste from plastic objects, including household plastic waste, construction plastic waste, automotive or any type of transport plastic waste, and waste electrical and electronic equipment. Preferably, the plastic waste comes from collection and sorting channels. Plastics or plastic materials are generally compositions (or formulations) comprising polymers mixed with additives to impart specific properties to the materials, in order to form, after shaping, various objects (for example, injection-molded parts, tubes, films, fibers, fabrics, sealants, coatings, etc.). The additives used in plastics can be organic or inorganic compounds.Examples include fillers, colorants, pigments, plasticizers, property modifiers, combustion retardants, antioxidants, light-stabilizing agents, antistatic agents, etc.

[0075] The plastic feedstock comprises, in particular, thermoplastic polymers, preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight, and most preferably at least 90% by weight of thermoplastics, relative to the total weight of the plastic feedstock, with 100% advantageously being the maximum upper limit. The thermoplastics targeted by the process according to the invention and included in the plastic feedstock may be alkene (or olefin) polymers, diene polymers, vinyl polymers, and / or styrenic polymers. Most preferably, the thermoplastics targeted by the recycling process according to the invention and included in the plastic feedstock are polyolefins, homopolymers, or olefin copolymers, such as polyethylene (PE), polypropylene (PP), and / or ethylene-propylene copolymers, or mixtures thereof.Preferably, the plastic filler comprises at least 50% by weight, preferably at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of polyolefins relative to the total weight of the plastic filler, with 100% advantageously being the maximum upper limit. The recycling process according to the invention is thus particularly aimed at purifying and recovering thermoplastics, especially polyolefins, contained in a plastic filler, particularly one derived from plastic waste, so that they can be reused in various applications.In a particular embodiment, the plastic filler comprises polypropylene (PP), polyethylene (PE), or a mixture of polypropylene (PP) and polyethylene (PE), in particular at least 50% by weight, preferably at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of polypropylene (PP) or polyethylene (PE), or a mixture of polypropylene (PP) and polyethylene (PE), relative to the total weight of the plastic filler. The polyethylene may, in particular, be high-density polyethylene (HDPE). In a very particular embodiment, said mixture comprises, for example, between 5% and 95% by weight of PP and between 5% and 95% by weight of PE, in particular HDPE, or between 50% and 95% by weight of PP and between 5% and 50% by weight of PE, in particular HDPE.

[0076] The plastic filler may comprise polymer blends. It may therefore include, in addition to the thermoplastics covered, thermoplastics other than those covered, and in particular other than the polyolefins covered, additives advantageously used to formulate the plastic material, and possibly impurities resulting from the life cycle of the plastic materials and articles and / or from the waste collection and sorting system, degradation products of the compounds contained in the filler materials, etc. Thermoplastics other than those covered, additives, impurities from use, degradation products, etc., are considered, according to the invention, as impurities. The plastic filler generally comprises less than 50% by weight of impurities, preferably less than 20% by weight of impurities, and preferably less than 10% by weight of impurities.The plastic filler may include, for example, at least 1% by weight of impurities, or even at least 5% by weight of impurities.

[0077] The plastic material can advantageously be pretreated upstream of the recycling process according to the invention, so as to at least eliminate all or part of the so-called coarse impurities, that is to say, impurities in the form of particles larger than or equal to 10 mm, preferably larger than or equal to 5 mm, or even larger than or equal to 1 mm, for example, impurities such as wood, paper, biomass, iron, aluminum, glass, etc., and so as to shape it generally into divided solids to facilitate processing in the process. This pretreatment may include a grinding step, an atmospheric pressure washing step, and / or a drying step. This pretreatment may be carried out at a different site, for example, at a waste collection and sorting center, or at the same site where the recycling 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, these percentages being relative to the weight of the plastic feed. Following pretreatment, the plastic feed is generally stored as divided solids, for example as chips, flakes, powder, or granules, to facilitate handling and transport.

[0078] Step a) of dissolution

[0079] The recycling process according to the invention 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, and preferably all, of the targeted thermoplastics, particularly the targeted polyolefins, present in the plastic filler.

[0080] Dissolution refers to any phenomenon leading to the production of at least one thermoplastic polymer solution, that is, a liquid (or fluid) containing the targeted thermoplastics dissolved in the dissolving solvent. Those skilled in the art are well acquainted with the phenomena involved in the dissolution of thermoplastic polymers: these phenomena include at least mixing, solvation, dispersion, homogenization, and disentanglement of the thermoplastic polymer chains.

[0081] During and after dissolution step a), the pressure and temperature conditions ensure that the dissolving solvent remains, at least partially and preferably entirely, in a liquid state or possibly in a supercritical state, while the soluble fraction of the plastic filler, in particular the targeted thermoplastic polymers, for example the targeted polyolefins, and possibly (or even generally) at least some of the impurities, is advantageously, at least partially and preferably entirely, dissolved in the dissolving solvent. In other words, the temperature and pressure conditions in step a) prevent, or at least limit, the dissolving solvent from being in gaseous form, thereby optimizing the dissolution of the targeted thermoplastics.

[0082] Step a) of dissolution is fed by the plastic filler and a flow of dissolving solvent. The dissolving solvent is an organic solvent or a mixture of organic solvents, and preferably chosen so that its Hansen parameters lie within the Hansen sphere of the targeted thermoplastics, in particular the targeted polyolefins.

[0083] Advantageously, the dissolving solvent corresponds to the organic solvent of the polymer solution to be treated in the adsorption purification process described above. Thus, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon and / or oxygenated compound, preferably at least one hydrocarbon compound. Preferably, and particularly when the thermoplastics in question are polyolefins, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic or naphthenic (i.e., non-aromatic), 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, preferably at least 98% by weight of at least one hydrocarbon compound, preferably aliphatic or naphthenic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, the percentages being expressed in relation to 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 or naphthenic and in particular paraffinic, having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) between -50 and 250°C, preferably between -15 and 200°C, preferably between 15 and 180°C and preferably having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) above 70°C, preferably above or equal to 75°C, and advantageously below or equal to 160°C, preferably below or equal to 130°C.Preferably, said at least one hydrocarbon compound, preferably aliphatic or naphthenic 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 or naphthenic and in particular paraffinic, preferably linear, branched or cyclic, preferably non-aromatic, may be selected from isomers of butane, pentane, hexane, heptane, octane, nonane, decane, and mixtures thereof, preferably from isomers of pentane, hexane, heptane, octane and mixtures thereof.Thus, the dissolving solvent may comprise at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight, of an isomer or mixture of isomers of butane, pentane, hexane, heptane, octane, nonane and / or decane, preferably of an isomer or mixture of isomers of pentane, hexane, heptane and / or octane, the percentages being expressed in relation to the total weight of the dissolving solvent (100% being the maximum).

[0084] Preferably, step a) of dissolution is fed by the plastic filler and the flow of dissolving solvent, according to a weight ratio between the dissolving solvent and the plastic filler, of between 0.2 and 100.0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 10.0.

[0085] Advantageously, the dissolving solvent that feeds into step a) of dissolution is in liquid form or possibly supercritical. It may advantageously be preheated, preferably to a temperature between 50 and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, prior to its introduction into step a), in particular prior to its contact with the plastic filler, in order to facilitate the heating of the plastic filler and / or avoid a drop in the temperature of the material stream during contact and dissolution in step a).

[0086] The dissolving solvent stream feeding step a) comprises, preferably consists of, at least in part or entirely of, a recycled solvent stream, advantageously from step c). The dissolving solvent stream feeding step a) may also include fresh dissolving solvent. The dissolving solvent stream feeding step a) is therefore composed at least in part, or even entirely, of a recycled solvent stream, advantageously from step c), and possibly of a fresh dissolving solvent input (i.e., an external supply of dissolving solvent).

[0087] Most advantageously, the dissolution step is carried out at a temperature, called the dissolution temperature, between 50°C and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, most preferably between 140 and 190°C, and preferably at a pressure, called the dissolution pressure, between 0.1 and 25 MPa absolute (in particular 0.1 and 25.0 MPa absolute), preferably between 0.2 and 20 MPa absolute (in particular 0.2 and 20.0 MPa absolute), and most preferably between 1.5 and 15 MPa absolute (in particular 1.5 and 15.0 MPa absolute).The temperature and pressure may change during the dissolution stage, from atmospheric conditions or the conditions of introduction of the plastic charge and / or the dissolving solvent into the recycling process, until reaching the dissolution conditions, i.e. the dissolution temperature, in particular between 50 and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, very preferably between 140 and 190°C, and the dissolution pressure, in particular between 0.1 and 25 MPa (or even 0.1 and 25.0 MPa absolute), preferably between 0.2 and 20 MPa absolute (or even 0.2 and 20.0 MPa absolute), and very preferably between 1.5 and 15 MPa absolute (or even 1.5 and 15.0 MPa absolute). Most advantageously, at the end of step a) of dissolution, the crude polymer solution is at the dissolution temperature and at the dissolution pressure.

[0088] Limiting the temperature in step a) of dissolution, to a temperature less than or equal to 250°C, or even less than or equal to 210°C or less than or equal to 190°C, makes it possible to avoid or limit the thermal degradation of the targeted thermoplastics, in particular the targeted polyolefins, 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 point of the thermoplastics in question, particularly the polyolefins in question, and very advantageously lower than the evaporation temperature at the dissolution pressure of the dissolving solvent (to keep the dissolving solvent in a non-gaseous state, and particularly in a liquid state), so as to promote their dissolution and very advantageously reduce the residence time required to efficiently dissolve said thermoplastics in the dissolving solvent. According to a particular embodiment, the temperature in dissolution step a) is less 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.

[0089] Simultaneously, the dissolution pressure in step a) of dissolution is higher than the saturated vapor pressure of the dissolving solvent at the dissolution temperature, so that the dissolving solvent is at least partially, and preferably entirely, in liquid or possibly supercritical form at the dissolution temperature, thus preventing the dissolving solvent from being partially in gaseous form. Under these operating conditions, particularly regarding temperature and pressure, the dissolution of the targeted thermoplastics, especially the targeted polyolefins, is optimized, particularly in terms of quality and processing time.

[0090] Most advantageously, the temperature and pressure conditions of dissolution achieved in step a) of dissolution are adjusted so that the mixture (dissolving solvent + targeted thermoplastics) is single-phase at the end of step a), said mixture possibly including insoluble impurities suspended in said mixture.

[0091] According to a preferred embodiment in which the thermoplastics targeted for recycling are polyolefins, the dissolution step is preferably carried out at a temperature between 110 and 250°C, preferably between 130 and 210°C, most preferably between 140 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), most preferably between 1.5 and 15 MPa (or even between 1.5 and 15.0 MPa absolute).According to another preferred embodiment in which the thermoplastic in question is polyethylene, the dissolution step is preferably carried out at a temperature between 110 and 250°C, preferably between 120 and 210°C, preferably between 130 and 210°C, most preferably between 130 and 200°C, and most preferably between 140 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), preferably between 0.5 and 17 MPa absolute (or even between 0.5 and 17.0 MPa absolute), most preferably between 1.0 and 16 MPa (or even between 1.0 and 16.0 MPa absolute), and most preferably between 2.0 and 15 MPa (or even between 2.0 and 15.0 MPa absolute). absolute MPa).According to yet another preferred embodiment in which the thermoplastic is polypropylene, the dissolution step is preferably carried out at a temperature between 130 and 250°C, preferably between 130 and 210°C, preferably between 140 and 210°C, most preferably between 150 and 200°C, and most preferably between 160 and 190°C, and advantageously at a pressure preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), preferably between 0.5 and 15 MPa absolute (or even between 0.5 and 15.0 MPa absolute), most preferably between 1.0 and 12 MPa (or even between 1.0 and 12.0 MPa absolute), and most preferably between 1.5 and 10 MPa (or even between 1.5 and 10.0 MPa absolute).

[0092] Advantageously, said dissolution step a) is carried out for a residence time preferably between 1 and 600 minutes, preferably between 2 and 300 minutes, preferably between 10 and 180 minutes, preferably between 30 and 150 minutes, and most preferably between 40 and 120 minutes. Residence time is understood here as the residence time at the dissolution temperature and dissolution pressure, i.e., the time during which the plastic filler and the dissolving solvent are at the dissolution temperature and dissolution pressure, in step a).

[0093] The dissolution step (a) is fed at least by the plastic filler, in particular in the form of one or more plastic filler streams, and by the dissolving solvent, in particular in the form of one or more dissolving solvent streams, advantageously by means of one or more conveying devices. The plastic filler stream(s) may be separate from the dissolving solvent stream(s). Some or all of the plastic filler may also feed step (a) mixed with some or all of the dissolving solvent, with the remainder of the solvent and / or filler, if any, feeding step (a) separately.

[0094] When the plastic filler is brought into contact with the dissolving solvent, the dissolving solvent is advantageously at least partially, and preferably entirely, in liquid form, or possibly supercritical, while the plastic filler, which includes the thermoplastics in question, may be in solid or liquid form, or even in the form of a liquid containing suspended solid particles. The plastic filler may also optionally be injected into the dissolving equipment, mixed with the dissolving solvent, or as a suspension in the dissolving solvent; the preparation and injection of the suspension may be continuous or discontinuous.

[0095] In order to allow contact between the dissolving solvent and the plastic filler and to enable efficient and homogeneous dissolution of the targeted thermoplastics in the dissolving solvent, step a) of dissolution may advantageously employ various types of equipment such as mixing, conveying, and heating devices, for example, a reactor, a pump, a conveying circuit, an agitation system, a furnace, a heat exchanger, a mixer, etc. In particular, step a) advantageously employs at least one piece of dissolving equipment, and possibly at least one device for preparing the plastic filler, a mixing device, and / or a conveying device.The equipment and / or devices used in step a) may include, for example, static or dynamic mixer(s), an extruder, a pump, a reactor, a co- or counter-current column, and / or conveying devices, advantageously interconnected. Conveying devices, particularly for fluids such as gases, liquids, or solids, are well known to those skilled in the art. Without limitation, conveying devices may include at least one of the following: a compressor, a pump, an extruder, a vibrating tube, a screw conveyor, or a valve. The equipment and / or devices used in step a) may also include or be combined with heating systems (e.g., a furnace, a heat exchanger, a heat treatment system, etc.) to achieve the conditions necessary for dissolution.

[0096] Preferably, step a) of dissolution employs at least one means for melting at least part of the plastic feed, preferably an extruder, and optionally at least one means for mixing at least part of the dissolving solvent with 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 at least one, preferably one, dissolving 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 melting means, at least part, and preferably all, of the thermoplastics in question, included in the plastic feed, are in a molten state.The plastic feedstock can then be injected into the dissolution equipment, for example, a continuous stirred reactor (CSTR), or possibly into a system comprising a mixer or a series of mixers advantageously followed by a reactor, for example, a continuous stirred reactor (CSTR). The plastic feedstock, at least partially in a molten state, can also be pumped using a pump designed for viscous fluids, often called a melt pump or gear pump. The plastic feedstock, at least partially in a molten state, can also be filtered, at the outlet of said melting equipment, using a filtration device, possibly in addition to the melt pump, to remove the largest particles. Generally, the mesh size of this filter is between 10 µm (micrometers) and 1 mm (millimeters), preferably between 20 and 200 µm.Simultaneously, the dissolving solvent directly feeds the dissolving equipment, the said means for melting, in particular the extruder, and / or the mixer(s).

[0097] Preferably, step a) implements, prior to at least one CSTR-type reactor, an extruder possibly followed by at least one static mixer into which at least a fraction of the dissolving solvent is injected, so as to promote intimate mixing between the dissolving solvent and the plastic filler, which contributes to the dissolution of the targeted thermoplastics.

[0098] Advantageously, the crude polymer solution obtained at the end of dissolution step a) comprises at least the dissolving solvent and the targeted thermoplastics, in particular the targeted polyolefins, dissolved at least partially 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) may optionally also comprise polymers, for example, in a molten state, dissolved or not.

[0099] Step b) of purification of the polymer solution

[0100] The recycling process according to the invention includes a step b) of purifying the crude polymer solution obtained from step a) to obtain a purified polymer solution. According to the invention, step b) of purifying the crude polymer solution includes a substep b1) of adsorption which implements the purification process by adsorption described above. Step b) of purification may also include at least one other purification substep implementing any purification method known to those skilled in the art. For example, step b) of purification may include separation of insolubles, washing by contact with a dense solution such as an aqueous solution, and / or extraction by contact with an organic solvent, possibly at least partially in supercritical form.Preferably, step b) of purification includes, in addition to substep b1) of adsorption which implements the purification process by adsorption described above, a substep b2) of separation of insolubles.

[0101] The adsorption substep b1, which implements the purification process by adsorption described above, and the said possible at least other purification substep, preferably said insoluble separation substep b2, if integrated into the purification step b, may be operated continuously, discontinuously (or batch mode) or in fed-batch mode.

[0102] Preferably, purification step b) comprises at least adsorption substep b1) and at least one other purification substep, preferably at least insolubles separation substep b2). This other purification substep(s), preferably insolubles separation substep b2, may be carried out upstream or downstream of b1. Preferably, purification step b) comprises at least one adsorption substep b1) and at least one insolubles separation substep b2, most advantageously in the order b2) then b1).Combining substep b1) with at least one other purification substep, preferably a substep b2) for separating insolubles, advantageously allows optimal purification of the crude polymer solution, which consequently makes it possible to obtain a stream of purified thermoplastics with very low impurity contents, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight, preferably less than or equal to 0.5% by weight, relative to the total weight of the purified thermoplastics stream obtained at the outlet of the recycling process.

[0103] The polymer solution obtained at the end of step b) is a purified polymer solution comprising the targeted thermoplastics, in particular the targeted polyolefins, at least partially dissolved in the dissolving solvent. The purified polymer solution obtained may correspond to a refined polymer solution from substep b1) of adsorption implementing the purification process by adsorption described above, or possibly to a clarified polymer solution from substep b2) of insoluble separation, if step b) includes a substep b2) downstream of b1).

[0104] Preferably, the temperature and pressure at step b) are adjusted during substep b1) of adsorption and possibly during substep b2), so as to obtain at the output of step b), a polymer solution, i.e. the purified polymer solution, in liquid form.

[0105] Substep b2) of separation of insolubles

[0106] The recycling process may include, in addition to substep b1) of adsorption which implements the purification process by adsorption described earlier in this description, a substep b2) of separation of insolubles, in particular by solid-liquid separation and / or by liquid-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 (solid or liquid). The insoluble fraction may also optionally include a dissolving solvent and optionally soluble impurities.

[0107] Substep b2) of insolubles separation thus makes it possible to remove at least some, and preferably all, of the insoluble impurities present in the crude polymer solution from step a). Examples of insoluble impurities removed during substep b2) of insolubles separation are pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum), and insoluble polymers. When implemented, this substep b2) of insolubles separation advantageously allows, in addition to the removal of at least some of the insoluble impurities, the limitation of operational problems, particularly clogging and / or erosion, in process steps downstream of such substep b2), while also contributing to the purification of the plastic feedstock.

[0108] Substep b2) of insoluble separation is advantageously carried out at a temperature between 50 and 250°C, preferably between 110 and 250°C, preferably between 130 and 210°C, preferably between 140 and 190°C, and preferably at a pressure between 0.1 and 25 MPa absolute (or even between 0.1 and 25.0 MPa absolute), preferably between 0.2 and 20 MPa absolute (or even between 0.2 and 20.0 MPa absolute), and most preferably between 1.5 and 15 MPa absolute (or even between 1.5 and 15.0 MPa absolute). Optionally, substep b2) of insoluble separation can be carried out at the pressure conditions at the outlet of step a) of dissolution, i.e. at the dissolution pressure as defined above. possibly lowered preferably from 0.01 to 10.0 MPa, preferably from 0.1 to 5.0 MPa due to pressure losses incurred between step a) and substep b2).

[0109] When integrated into the process, substep b2) of insoluble separation is preferably located upstream of substep b1) of adsorption. Thus, when integrated into the process, substep b2) of insoluble separation is preferably fed by the crude polymer solution from step a).

[0110] Advantageously, substep b2) employs any solid-liquid and / or liquid-liquid separation method known to those skilled in the art to separate the insolubles from the polymer solution. The insolubles may be solid (such as additives like mineral fillers or pigments) or liquid and / or in gel form (e.g., polymers in molten form and / or as physical gels and / or solvent-swollen cross-linked networks of a different nature than the thermoplastics in question). For example, substep b2) employs separation by decantation, filtration, centrifugation, electrostatic separation, etc.Preferably, substep b2) comprises at least one, preferably between one and five, preferably between two and five, solid-liquid separation(s) and / or liquid-liquid separation(s) and / or solid-liquid-liquid separation(s), particularly where the effluent obtained at the end of 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. When implemented, substep b2) may preferably comprise several, i.e., between two and five, solid-liquid and / or liquid-liquid separation(s) (or solid-liquid-liquid separation(s)) in series and / or in parallel.The presence of at least two solid-liquid and / or liquid-liquid separations in series improves the removal of insolubles, while the presence of several solid-liquid and / or liquid-liquid separations in parallel facilitates equipment maintenance and / or unclogging / cleaning operations. In a preferred embodiment, substep b2) of insoluble separation implements a separation by decantation and / or at least one, preferably between one and four, separation(s) by filtration.

[0111] Said at least one solid-liquid and / or liquid-liquid separation preferably employs at least one piece of solid-liquid or liquid-liquid separation equipment, for example, a separator flask, a decanter, a decanter with inserts, a lamella decanter, a centrifugal decanter, a centrifuge, a hydrocyclone, a filter, a sand filter, a tangential flow filter incorporating a membrane and / or a depth filter, a self-cleaning filter, a scraped filter, an eddy current separator, an electrostatic separator, a triboelectric separator, and preferably a decanter, a filter, a sand filter, an electrostatic separator, and / or a two-phase or three-phase separator. Advantageously, a self-cleaning filter may be used, with cleaning or unclogging to remove insolubles being carried out using a solvent stream.During substep b2), filter aids (e.g. diatomaceous earth, perlite or sand) may optionally be added prior to separation by settling and / or separation by filtration.

[0112] The at least one insoluble fraction, advantageously obtained at the end of step b2), is preferably removed or treated in such a way as to separate and recover compounds of interest, for example polymers, in particular thermoplastics, and / or the dissolving solvent it may contain. The removal or treatment of the at least one insoluble fraction may be facilitated by equipment enabling the transport and / or separation of 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 b2) may thus employ transport and / or separation equipment to remove and / or treat the at least one insoluble fraction.Advantageously, substep b2) includes the separation and recovery of at least a portion of the dissolving solvent contained in said at least an insoluble fraction, said at least a portion of the recovered dissolving solvent being able to be recycled in the recycling process, in particular in step a).

[0113] According to the invention, the recycling process includes a solvent-polymer separation step (c) to obtain at least one stream of purified thermoplastics, more particularly at least one stream of purified polyolefins. Step (c) is located downstream of the purification step (b). It is advantageously fed by the purified polymer solution obtained at the end of the purification step (b).

[0114] Step c) of solvent-polymer separation aims to separate, at least in part, preferably predominantly, or even entirely, the solvent(s), in particular the dissolving solvent, contained in the purified polymer solution which feeds step c), so as to recover the targeted thermoplastics, at least partially free of impurities and the dissolving solvent and possibly other solvent(s) optionally used in particular during step b) of purification (i.e. the extraction solvent and / or the dense solution).By predominantly, we must understand at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, most preferably at least 95% by weight, relative to the weight of the solvent(s) contained in the purified polymer solution which feeds step c), in particular the dissolving solvent and possibly the extraction solvent and / or the dense solution contained in the purified polymer solution.

[0115] Preferably, solvent-polymer separation step c) advantageously includes a gas-liquid separation. Optionally, solvent-polymer separation step c) may further include a liquid-liquid or supercritical-liquid separation to separate the solvent(s), in particular the dissolving solvent, then in liquid or supercritical form, from a liquid phase comprising the thermoplastics in question.

[0116] Preferably, step c) of solvent-polymer separation employs several gas-liquid separation sections, i.e., at least two gas-liquid separation sections, operating in series, to achieve said gas-liquid separation. Preferably, step c) of solvent-polymer separation employs N gas-liquid separation sections, operating in series, where N is an integer between two and ten, preferably between two and five, for example, three or four. The separation principle in the gas-liquid separation sections is based on the evaporation, at least in part, of the solvent, in particular the dissolving solvent, present in the polymer solution that feeds each of the gas-liquid separation sections; and the evaporated solvent (or the fraction of solvent that evaporates), then in gaseous form, is separated from the polymer solution, which is in liquid form.

[0117] The gas-liquid separation section(s) 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, optionally dissolved in a residual fraction of solvent, in particular dissolving solvent. Most advantageously, the liquid effluent from the gas-liquid separation section or 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, in particular dissolving solvent, relative to the total weight of said liquid effluent, and advantageously constitutes said stream of purified thermoplastic polymers.Advantageously, the purified polymer solution obtained at the end of purification step b) feeds the gas-liquid separation section or the first gas-liquid separation section in the series. When step c) uses several gas-liquid separation sections, for the other (or other) gas-liquid separation section(s) implemented after the first section in the series, the liquid effluent from the preceding section feeds the subsequent section, up to the last section, the resulting liquid effluent of which advantageously constitutes the stream of purified thermoplastic polymers. In other words, when step c) uses several sections:

[0118] - 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;

[0119] - the first liquid effluent obtained at the end of the first gas-liquid separation section feeds the second gas-liquid separation section which produces a second gas effluent and a second liquid effluent;

[0120] - the second liquid effluent obtained at the end of the second gas-liquid separation section feeds the third gas-liquid separation section which produces a third gas effluent and a third liquid effluent;

[0121] - 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,

[0122] - the Nth liquid effluent obtained at the end of the Nth gas-liquid separation section advantageously constitutes the stream of purified thermoplastic polymers.

[0123] Preferably, the gaseous effluent produced by the gas-liquid separation section(s) contains little or no covered thermoplastics. Preferably, each gaseous effluent produced contains less than 1% by weight, preferably less than 0.01% by weight, of covered thermoplastics relative to the total weight of the gaseous effluent considered; and in particular, each gaseous effluent produced is free of covered thermoplastics. Preferably, the gaseous effluent(s) produced by the gas-liquid separation section(s) is / are recovered and at least partially recycled to step a) of dissolution. It may be purified, in part or in full, before being recycled to step a).

[0124] Advantageously, the gas-liquid separation section (or sections) implemented in step c) is operated at an inlet temperature (i.e., at the inlet of each section) between 100°C and 300°C, preferably between 110°C and 275°C, and preferably between 150°C and 250°C. Most advantageously, the temperature is adjusted in each of the gas-liquid separation sections so as to have an operating temperature greater than or equal to the evaporation temperature of the solvent, in particular the dissolving solvent, and advantageously greater than or equal to the melting temperature of the thermoplastics concerned, at the operating pressure of the gas-liquid separation section in question.

[0125] Advantageously, the gas-liquid separation section (or sections) implemented in step c) is operated at a pressure lower than the pressure in step b) and preferably lower than the outlet pressure of step b), in particular at a pressure lower than 25.0 MPa absolute, preferably lower than 20.0 MPa absolute, and preferably lower than 15.0 MPa absolute. Preferably, in the gas-liquid separation section (or sections), the pressure is greater than or equal to 0.000005 MPa absolute, in particular greater than or equal to 0.00001 MPa absolute, in particular greater than or equal to 0.0001 MPa absolute, more particularly greater than or equal to 0.0005 MPa absolute, and particularly greater than or equal to 0.0008 MPa absolute. Preferably, when step c) implements multiple sections, the pressure of the later section is less than that of the earlier section.In other words, preferably, the pressure in the second gas-liquid separation section is less than the pressure in the first gas-liquid separation section, the pressure in the third gas-liquid separation section is less than the pressure in the second gas-liquid separation section, and so on up to the Nth gas-liquid separation section in which the pressure is less than the pressure in the (N-1)th gas-liquid separation section, the pressure of the first section of the series being less than the pressure of step b), preferably the outlet pressure of step b).

[0126] The gas-liquid separation section(s) of step c) may implement any type of device known to those skilled in the art for separating gas and liquid, possibly accompanied by means for adjusting temperature and pressure, for example equipment for heating, equipment for adjusting and controlling pressure above atmospheric pressure, equipment for adjusting and controlling pressure below atmospheric pressure (to obtain a vacuum), etc.; mechanical means, in particular equipment for moving and bringing the gas and liquid phases into contact.For example, said gas-liquid separation sections may employ one or more pieces of equipment selected from: a separator flask, a column, a distilling column, a stripper, equipment including internals and / or packing facilitating separation between gas and liquid, an evaporator, a thin-film evaporator, a scraped-film evaporator, a falling-film evaporator, a paddle evaporator, a rotating-disc reactor or column, a reactor, a stirred-reactor, an extruder, a kneading reactor, a devolatilizer.

[0127] Optionally, an entraining agent (or stripping agent) can be introduced in the last gas-liquid separation section of the series to aid the vaporization of residual solvent present in the polymer solution entering that section. Adding an entraining agent thus optimizes solvent-polymer separation in the final gas-liquid separation section. The entraining agent is advantageously a compound with a boiling point lower than that of the dissolving solvent (at atmospheric pressure), for example, a compound chosen from water, nitrogen, or hydrogen. Preferably, the amount of entraining agent represents between 10% and 0.1% by weight of the target thermoplastics.

[0128] Optionally, an inert gas stream, preferably nitrogen, can be introduced into the first gas-liquid separation section to aid vaporization and thus the removal of the solvent, particularly the dissolving solvent, present in the purified polymer solution that feeds step c). The presence of inert gas modifies the phase diagram and can therefore promote solvent evaporation, especially the dissolving solvent, present in the purified polymer solution that feeds step c), thus limiting the operating temperatures in this first section while optimizing solvent evaporation. At the outlet of the gas-liquid separation section, or the first gas-liquid separation section in the series, the inert gas is then advantageously mixed with the gaseous dissolving solvent in the effluent gas.

[0129] Optionally, at least one additive may be introduced in step c), and / or possibly upstream of step c), and advantageously downstream of step b). For example, an antioxidant may be introduced in step c), and / or possibly upstream of step c), and advantageously downstream of step b), so as to limit, or even prevent, any degradation of the thermoplastics in question. Those skilled in the art will be able to select this at least one additive, in particular this antioxidant, according to the thermoplastics in question. For example, the antioxidant may be chosen from among the compounds marketed under the Irganox® and Irgafos® trademarks, and in particular from among the following commercial compounds: Irganox® 1010, Irgafos® 168, and Irgafos® 168 oxidized. A person skilled in the art will also know how to adjust the quantity of said at least one additive, in particular said antioxidant, to be introduced according to the thermoplastics concerned and the desired properties.For example, the antioxidant agent may be introduced so as to have a content of said antioxidant agent between 100 and 10,000 ppm by weight, preferably between 500 and 5,000 ppm by weight of antioxidant agent relative to the weight of the thermoplastics concerned, advantageously in the polymer solution, in particular in the purified polymer solution which feeds step c) or at least one of the liquid effluents produced by the gas-liquid separation sections.In the case where an additive, in particular an antioxidant, is introduced in step c) and where step c) employs several successive gas-liquid separation sections, said additive is preferably introduced downstream of the first gas-liquid separation section in the series, either as a unit or in fractions, more particularly in at least one of the liquid effluents produced by the gas-liquid separation sections in the series (including the first section), and preferably in one of the liquid effluents produced by one of the sections upstream of the last gas-liquid separation section in the series.

[0130] Thus, the recycling process according to the invention makes it possible to treat a plastic feed, including the targeted thermoplastics, in particular the targeted polyolefins, in order to obtain purified thermoplastics which can be used in any type of plastic formulation in place of virgin resin.More particularly, the process according to the invention makes it possible to recover from a plastic feed, for example from post-consumer and / or post-production waste, a stream of purified thermoplastics, in particular a stream of purified polyolefins, comprising at most 5% by weight of impurities, very advantageously at most 1.0% by weight of impurities, preferably at most 0.5% by weight of impurities, relative to the total weight of the purified thermoplastics stream, the impurity content corresponding to the total content of impurities, i.e. residual impurities initially present in the plastic feed and by-products generated during possible secondary reactions throughout the process.

[0131] The examples and figures that follow illustrate the invention, in particular particular embodiments of the invention, without limiting its scope.

[0132] List of figures

[0133] Fig 1

[0134] Figure 1 illustrates a particular embodiment of the thermoplastic recycling process according to the invention. According to this particular embodiment of the invention, the thermoplastic recycling process, for example polyolefins, of a plastic feedstock 1 comprises a dissolution step (a) and a purification step (b) including an adsorption substep (b1) which implements an adsorption purification process according to the invention, i.e., which includes an adsorption step on acid-washed bleaching earths obtained after a washing process. More specifically, the plastic feedstock 1 is sent to a dissolution step (a) which is also supplied with a flow (2) of dissolving solvent, to obtain a crude polymer solution (3). The crude polymer solution (3) is sent to a purification step (b) including an adsorption substep (b1) on acid-washed bleaching earths.A purified polymer solution 4 is obtained at the end of step b) of purification; it feeds into a step c) of solvent-polymer separation, to obtain a stream 6 of purified thermoplastics and at least one stream of solvent 7.

[0135] Fig 2

[0136] Figure 2 illustrates another particular embodiment of the thermoplastic recycling process according to the invention. According to this other particular embodiment of the invention, the thermoplastic recycling process, for example polyolefins, of a plastic feedstock 1 comprises a dissolution step (a) and a purification step (b) including a substep (b2) of insoluble separation followed by an adsorption substep (b1) which implements an adsorption purification process according to the invention, i.e., which includes an adsorption step on acid-washed bleaching earths obtained after a washing process. More particularly, the plastic feedstock 1 is sent to a dissolution step (a) which is also supplied with a flow (2) of dissolving solvent, to obtain a crude polymer solution (3).The crude polymer solution 3 is sent to a purification step b) comprising a substep b2) for separating insolubles, which separates a stream 5 containing at least some of the impurities, particularly insoluble ones, present in the crude polymer solution 3, and a clarified polymer solution 3', which is sent to an adsorption substep b1) on acid-washed bleaching earths. A purified polymer solution 4 is obtained at the end of the purification step b); it feeds a solvent-polymer separation step c) to obtain a stream 6 of purified thermoplastics and solvent streams 7. In this particular embodiment of the invention, step c) comprises two gas-liquid separation sections (c1, c2), each producing a gas stream (g1, g2) comprising the dissolving solvent and a liquid stream (g1, g2) comprising the targeted thermoplastics, for example, the targeted polyolefins.The liquid effluent 11 from the first gas-liquid separation section c1 feeds the second gas-liquid separation section c2; the liquid effluent I2 from the second (and last) gas-liquid separation section c2 corresponds to the purified thermoplastics stream 6. Optionally, an additive 8, for example an antioxidant, may be introduced during step c), for example downstream of the first gas-liquid separation section c1 and upstream of the last gas-liquid separation section c2. Examples.

[0137] Example 1

[0138] In this Example 1, the same polymer solution with 10% by weight of a polypropylene filler (approximately 98% by weight of PP and 2% by weight of soluble organic impurities) is treated by adsorption on different adsorbents: bleaching earths washed or unwashed.

[0139] Washing stage of the bleaching earths, acid wash

[0140] Bleaching earths (Tonsil® 630GL from Clariant) are contacted with a 0.1 M aqueous hydrochloric acid solution (pH 1) at 80°C for 5 hours. The washed bleaching earths are then collected, rinsed with water, and dried at 100°C for 10 hours. The washed and dried bleaching earths are then introduced into a test column as a fixed bed.

[0141] Washing stage of the bleaching earths, basic washing

[0142] Bleaching earths (Tonsil® 630GL from Clariant), the same initial bleaching earths as those washed with acid, are washed with a basic solution instead of the acidic solution described above. The same washing protocol as that described above for acid washing is used, except that the washing solution is in this case a 0.1 M aqueous solution of sodium hydroxide (NaOH).

[0143] Dissolution stage

[0144] A polymer solution to be treated is prepared by dissolving in heptane a filler comprising polypropylene and soluble organic impurities, such that said filler represents 10% by weight of the resulting polymer solution. The dissolution is carried out at 200°C and a pressure of 2.0 MPa.

[0145] Adsorption stage

[0146] The polymer solution is then contacted, at a specific temperature (200°C or 180°C) and 2.0 MPa, with an adsorbent which can be: bleaching earths (TONSIL® 630GL from Clariant) as supplied, said bleaching earths previously washed with acid, or said bleaching earths previously washed with sodium hydroxide. The tested adsorbent is in the form of a fixed bed in a column. The contact is carried out continuously at a volumetric rate WH of approximately 0.4 h⁻¹. 1 Retrieving the PP

[0147] After adsorption, the purified polymer solutions are recovered, placed in an oven at 90°C for approximately 12 hours under nitrogen flow, and the recovered solid is then ground into particles (approximately 2 mm in diameter) before being tested, in particular before being melted in the MFI test or extracted for HPLC-MS analysis.

[0148] Analyses

[0149] The melt flow index (MFI) of the solid feedstock (before dissolution) (initial MFI) and the MFI of the propylene recovered after adsorption and solvent removal (final MFI) are determined according to ASTM D1238 (or ISO 1133), at a temperature of 230°C + / - 0.5°C, for each adsorption test (i.e., for each adsorbent). The final MFI and the initial MFI are compared, for each test, to obtain the change in MFI: final MFI - initial MFI.

[0150] In parallel, the polypropylene filler and the polypropylene recovered after adsorption and solvent removal, for each test, are also tested by HPLC-MS, after extraction in a 95 / 5 volume / volume isopropanol / cyclohexane solvent. The extract thus obtained is analyzed by HPLC-MS. The sum of the areas under the curve of the chromatogram obtained for the polypropylene recovered after adsorption is determined for each test and is compared to the sum of the areas under the curve obtained for the polypropylene filler, in order to calculate the reduction rate for each test (100 x [(sum of the areas of the filler) - (sum of the areas of the obtained PP)] / (sum of the areas of the filler)).

[0151] The operating conditions of each test (adsorbent, temperature, pressure and WH of the adsorption step) as well as the results of MFI variation and the abatement rates determined for each PP obtained are presented in Table 1.

[0152] Table 1

[0153] According to Table 1, it appears that the highest removal rates (64% and 70%) are obtained for tests B and D respectively, according to the invention, the adsorption step of which was carried out on bleaching earths washed with acid (HCl 0.1 M), which means that the purification (i.e. the removal of impurities soluble in heptane) is optimal in the presence of bleaching earths washed with acid, compared to unwashed bleaching earths (43% removal) or washed with soda (15% removal).

[0154] Furthermore, it also appears from Table 1 that the degradation of the polypropylene (PP) in question is limited when adsorption is carried out on acid-washed bleaching earths, since the MFI only increases by 15 g / 10min for the PP obtained after adsorption on acid-washed bleaching earths at 200°C, or by 10 g / min for adsorption at 180°C, compared to the MFI of the PP obtained after adsorption at 200°C on unwashed or soda-washed bleaching earths (MFI increase of 20 g / 10min).

Claims

DEMANDS 1. A purification process by adsorption of a polymer solution to be treated comprising thermoplastics and an organic solvent, the process comprising: an adsorption step comprising bringing the polymer solution to be treated into contact with washed bleaching earths obtained at the end of a washing process, the adsorption step being carried out at a temperature between 50°C and 250°C, in which the washing process comprises an acid washing step by contact of bleaching earths with an acid solution.

2. A process according to claim 1, wherein the thermoplastics included in the polymer solution to be treated are polyolefins and the organic solvent comprises at least one hydrocarbon compound preferably having between 3 and 12 carbon atoms and most preferably between 4 and 10 carbon atoms.

3. A process according to claim 1 or 2, wherein the adsorption step is carried out at a temperature between 110 and 250°C, preferably between 130 and 210°C, preferably between 140 and 190°C.

4. A method according to any one of the preceding claims, wherein the adsorption step is carried out at a pressure between 0.1 MPa absolute and 25 MPa absolute, preferably between 0.2 and 20 MPa absolute, preferably between 1.5 and 15 MPa absolute.

5. A method according to any one of the preceding claims, wherein the adsorption step employs at least one fixed bed comprising the washed bleaching earths and is operated at an hourly volumetric rate of between 0.05 and 10 h' 1 , preferably between 0.1 and 5.0 h' 1 .

6. A method according to any one of the preceding claims, wherein the acid solution of the acid washing step is an aqueous solution with an acidic pH, preferably with a pH less than or equal to 5, preferably less than or equal to 4, preferably less than or equal to 2, for example equal to 1.

7. A process according to any one of the preceding claims, wherein the acid solution of the acid washing step is an aqueous solution comprising an organic or inorganic acid, preferably selected from hydrochloric acid, sulfuric acid, nitric acid, and organic compounds comprising at least one carboxylic acid function and advantageously a linear or branched alkyl chain comprising preferably between 2 and 10 carbon atoms (C2-C10), preferably between 2 and 6 carbon atoms (C2-C6), such as acetic acid, citric acid, tartaric acid, lactic acid, succinic acid, said organic or inorganic acid being at a concentration preferably of at least 0.01 mmol / l, preferably at least 0.1 mmol / l, preferably at least 0.01 mol / l, for example a concentration of 0.1 mol / l.

8. A process according to any one of the preceding claims, wherein the acid washing step is carried out at a temperature between 15 and 300°C, preferably between 15 and 250°C, at a pressure greater than or equal to 0.1 MPa and preferably less than or equal to 25 MPa absolute.

9. A method according to any one of the preceding claims, wherein the washing process comprises at least one rinsing step, preferably with water, downstream of the acid washing step, and preferably a drying step, downstream of the acid washing step and preferably downstream of the rinsing step, the drying step being carried out preferably at a temperature between 80 and 300°C, for at least 0.1 hours, optionally under a gas flow.

10. A process for recycling thermoplastics contained in a plastic feed, comprising: a) a step of dissolving the plastic feed in a dissolving solvent, step a) being carried out at a dissolution temperature between 50°C and 250°C, and at a dissolution pressure between 0.1 MPa and 25 MPa absolute, to obtain at least one crude polymer solution; b) a purification step of the crude polymer solution, comprising at least one substep b1) of adsorption implementing the purification process by adsorption according to any one of claims 1 to 9, to obtain a purified polymer solution; c) a solvent-polymer separation step, to obtain at least one stream of purified thermoplastics and at least one stream of solvent.

11. A process according to claim 10, wherein the thermoplastics included in the plastic filler are polyolefins and the dissolving solvent comprises at least one hydrocarbon compound preferably having between 3 and 12 carbon atoms and most preferably between 4 and 10 carbon atoms.

12. A method according to claim 10 or 11, wherein the dissolution step a) is carried out at a dissolution temperature between 110 and 250°C, preferably between 130 and 210°C, most preferably between 140 and 190°C.

13. A method according to any one of claims 10 to 12, wherein the dissolution step a) is carried out at a dissolution pressure between 0.2 and 20 MPa absolute, preferably between 1.5 and 15 MPa absolute.

14. A method according to any one of claims 10 to 13, wherein the purification step b) comprises a substep b2) of insolubles separation, preferably located upstream of said substep b1) of adsorption.

15. A process according to any one of claims 10 to 14, wherein at least a fraction of said at least one solvent stream obtained in step c) is recycled to the dissolution step a) to compose at least a part of the dissolving solvent.

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