A method for recycling waste based on PVC plastics, implementing a device for extracting polymeric compounds in a size-exclusion simulated moving bed

Abstract

The present invention relates to a method for recovering a stream of purified PVC polymer, comprising: a) a dissolution step in which a plastic feedstock is contacted with a dissolution solvent; b) an extraction step by size exclusion in which fixed beds of size-exclusion solids are arranged in series, the crude polymer solution obtained in step a) is fed at injection point F, the eluate is fed at injection point S, the extract is withdrawn at withdrawal point E, and a raffinate comprising the purified polymer solution is withdrawn at withdrawal point R, the injection and withdrawal points shifting by one bed over time with a frequency determined by a predetermined changeover period; and c) a step in which the solvent and the polymer are separated to obtain a stream of purified PVC polymer. The present invention also relates to a device for the treatment of step b) and to a device for treating the recovery method.

Description

[Technical Field]

[0001] The present invention relates to the field of recycling of plastics based on poly(vinyl chloride) (PVC), and in particular to a method for treating a plastic feedstock originating from PVC-based plastic waste in order to obtain at least one purified PVC polymer stream allowing its reuse in the manufacture of new plastic articles. More precisely, the invention relates to a method for treating a plastic feedstock originating in particular from PVC-based plastic waste, comprising dissolving at least one PVC polymer in a solvent, at least one purification step of the polymer solution thus obtained, and separation of the at least one PVC polymer and the at least one solvent, in order to recover at least one purified PVC polymer stream for subsequent upgrading. [Background technology]

[0002] By definition, a plastic is a mixture of a base polymer material and a number of additives, the assembly of which can be molded or finished (generally under high temperature and / or pressure) to produce a semi-finished product or article. In commonly accepted practice, the plastic is referred to by the name of the polymer from which it is made. Thus, the plastic poly(vinyl chloride) (PVC) actually corresponds to the combination of a PVC polymer, sometimes referred to as "PVC resin" in the remainder of this specification, with various additives, selected depending on the functionality required for the plastic. The additives may be organic (macromolecules) or other inorganic (nano)particles, and are used depending on the properties desired for the PVC plastic, i.e., resistance to heat, light or mechanical stress, flexibility, processability, colorability, etc.

[0003] There are several methods for recycling PVC plastics, including "traditional" methods that involve simple mechanical recycling of the plastics, and methods that involve modifying their composition (with optional chemical transformation of the starting components).

[0004] Since the middle of the 20th century, the recycling of PVC plastics using physical methods has been the subject of numerous studies aimed at dissolving the PVC resin with various proportions of additives in a first step, and then recovering the resin in a second step in the presence of all or part of the soluble additives according to various methods (precipitation, evaporation, etc.) For example, reference is made to EP 0945481 and EP 1268628, on the one hand, and EP 2276801, on the other hand, which aim to recycle various PVC-based articles (flexible or rigid pipes, window frames, cables, etc.), in particular fiber-reinforced PVC-based articles (tarpaulins, floor coverings, etc.), according to a method that uses a dissolution step of the PVC resin and soluble additives in an organic solvent, followed by a steam precipitation step that allows the recovery of the PVC resin and most of the additives.

[0005] However, it is not always desirable to retain these additives in the PVC that is recovered and recycled. For example, the impact of changing regulations over time is significant. Thus, although several plasticizers from the phthalate ester family were particularly widely used for compounding "flexible" PVC some 40 years ago, since the end of 2006 they have been gradually authorized in Europe under the REACH regulation, which aims to make the production and use of chemicals safer in European industry. Eventually, they have been gradually removed from the list of permitted additives (Annex XIV and XVII of Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of December 18, 2006). Following the same trend, the use of Cd-based metal stabilizers in PVC plastic compounds, specifically those referred to as "rigid" PVC plastics, was prohibited by amendments to the aforementioned Annex XVII (Regulation 494 / 2011 of May 20, 2011). Similarly, lead-based stabilizers have been subject to restrictions (Annex XV) detailed and adopted by ECHA's Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018. Thus, over the past 20 years, several families of additives have become restricted in their fields of use, and there is a strong risk that this phenomenon will expand in the future.

[0006] These new regulations have now prohibited the presence of many additives in recycled starting materials (RSM), in particular through the establishment of limit thresholds for authorised amounts that are now very restrictive (for example, the amount of phthalates authorised and considered as a mixture must not exceed 1000 ppm of the final composition of the relevant RSM). Considering that PVC-based articles often have a very long lifespan (decades), PVC-based articles compounded before the end of 2006 are now at the end of their lifespan and cannot be recycled by regeneration methods that result in the retention of these prohibited additives, whether said methods are conventional, such as mechanical recycling methods, or non-conventional, such as the example of the dissolution / precipitation method mentioned above.

[0007] Taking into account current and future regulatory constraints on the one hand, and the limitations of fossil resources that underscore the need to move towards a "circular" economy on the other hand, the production of purified polymer resins (i.e., as free as possible from additives) from plastic waste for reuse as RSMs equivalent to virgin resins derived from petroleum is nowadays a major issue in meeting the environmental challenges of the 21st century.

[0008] Numerous methods have been envisioned for extracting various additive families from plastics, including PVC plastics in particular. For example, in a non-exhaustive manner, EP 1311599 and JP 2007191586 both propose a first dissolution step of at least one additive family in PVC resin and phthalate ester-type plasticizers, flame retardants, or lead-based metal stabilizers with a first organic solvent, followed by one or more liquid-liquid extraction steps of at least one additive family from the previously obtained solution using at least one other solvent (organic and / or aqueous) different from the first organic solvent. JP 2007092035 discloses another possible implementation, which involves dissolving PVC resin and at least one phthalate ester-type additive using a mixture of solvents under supercritical conditions, recovering the phthalate esters from this same mixture of solvents after "breaking" the supercritical conditions, and then extracting the lead-based additive from the remaining solid phase containing the PVC resin using at least one liquid surfactant.

[0009] Despite these advances, removing all additives from PVC plastics, and even from mixtures of PVC-based plastics resulting from various formulations (e.g., components of post-consumer waste), still presents scientific and industrial challenges. The dissolution step described above is advantageous for initially removing some of the additives insoluble in the selected solvent(s). On the other hand, additives that are soluble in the solvent(s) are particularly difficult to separate, especially as a result of their highly diverse chemical properties. The first approach involves extracting them based on physicochemical properties such as their polarity, solubility, boiling point, density, etc., but this can lead to an increase in purification steps, given the number of additives present and their diversity. Furthermore, obtaining at least one purified PVC polymer stream is generally not sufficient to ensure the economic viability of a process for the regeneration of PVC-based articles. The main reason for this lack of progress is the difficulty of finding an economically viable balance between the resale cost of the resulting product (corresponding to added value) and the cost of the unit operations performed in the regeneration process, which is true in all cases where many separation steps are envisaged. Finally, processing plastic feedstock from PVC-based plastic waste involves providing a robust and versatile method to take into account the variability of additives present depending on the origin of the waste under consideration (in terms of target use and date of production). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] European Patent No. 0945481 [Patent Document 2] European Patent No. 1268628 [Patent Document 3] European Patent No. 2276801 [Patent Document 4] European Patent No. 1311599 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-191586 [Patent Document 6] Japanese Patent Application Laid-Open No. 2007-092035 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention therefore proposes an alternative approach to address the above-described problem, based on exploiting the size difference, or more precisely the hydrodynamic volume difference, between polymer macromolecules and molecules of impurities, such as molecules of additives.

[0012] As a result, the present invention makes it possible, starting from a polymer solution containing at least one PVC polymer and associated soluble additives dissolved in a dissolution medium, to selectively extract said PVC polymer from the medium, regardless of the nature of said additives.

[0013] Techniques for size-based separation already exist and are commonly used as analytical methods for determining the molecular weight of polymers. This method, called size exclusion chromatography (SEC), operates batchwise and involves implementing a fixed bed containing several levels of porosity. Small molecules explore the bed down to the smallest porosity, resulting in long associated elution times, while large molecules, such as polymers, migrate only through the largest pores, exhibiting short elution times and thus leading to the desired separation. Therefore, the principles of size exclusion chromatography can be applied to the purification of PVC-based plastics, as additives commonly used in the formulation of PVC-based plastics exhibit domain sizes much smaller than the polymer chain size of PVC resins. However, industrial implementation of methods using such principles is problematic, primarily due to the discontinuous nature of batch processes. Furthermore, such methods in batch mode require significant consumption of eluate to ensure efficient separation, which directly impacts the profitability, productivity, and ecological footprint of the process.

[0014] Simulated moving bed (SMB) technology, a concept invented in 1961, allows for the continuous functioning of discontinuous "chromatographic" processes, particularly by adsorption, with increased productivity and limited eluent consumption while ensuring efficient separation. There are numerous industrial references to this technology, particularly in the context of adsorption separations, used in particular for the separation of xylenes by the Eluxyl® or Parex® processes (see the publication Simulated Moving Bed Technology: Principles, Design and Process Applications, A.E. Rodrigues, Elsevier, 2015). The only large-scale application of size-exclusion simulated moving beds (or SMB-SEC, in the case of simulated moving beds with size-exclusion chromatography) is for the separation of n-paraffins from isoparaffins, as outlined in U.S. Pat. No. 2,985,589. Recent publications have mentioned the use of size-exclusion simulated moving bed (SMB-SEC) technology for the fractionation of polyethylene glycols of various molecular weights (M.T. Liang et al., J. Chromatogr. A, 2012, 1229, 107) or for the separation of proteins (E.J. Freydell et al., Chem. Eng. Sc., 2010, 65, 4701). More specifically, U.S. Pat. No. 6,551,512 proposes a method for the separation of proteins from liquid compositions such as milk by size exclusion in a simulated moving bed. Finally, one publication mentions the use of SMB-SEC in a method for the recycling of materials contained in the composition of WEEE (Waste Electrical and Electronic Equipment). WEEE is based on polycarbonate and also contains additives such as poly(styrene-co-acetonitrile) (SAN) and flame retardants. The latter is what the Weeden team is attempting to separate from a ternary solution containing SAN and two flame-retardant compounds, resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate), in an acetone-dichloromethane solvent mixture (GS Weeden et al., Journal of Chromatography A, 2015, 1422, 99).

[0015] The application of SMB-SEC technology as a method for purifying PVC-based plastic waste to obtain a purified PVC polymer stream and enable its reuse as RSM in the manufacture of new plastic articles has not been proposed previously.

[0016] Therefore, the object of the present invention is to overcome the problems of the prior art and to address the recycling of plastics, particularly PVC plastics. More specifically, the object of the present invention is to provide an efficient, simple, and economically viable method for processing any type of PVC feedstock to obtain a purified PVC polymer stream that complies with current regulations and can be reused in the production of new plastic articles. Specifically, the present invention seeks to efficiently separate impurities from waste PVC plastics and recover purified PVC resin that can be used in the production of new PVC-based articles by using a method with a limited number of unit stages, thus limiting the cost of the method and improving its ecological performance qualities. [Means for solving the problem]

[0017] Thus, the present invention provides, according to a first aspect, a process for recovering at least one purified PVC polymer stream from a plastic feedstock, comprising: a) a dissolution step comprising contacting a plastic feedstock with a dissolution solvent to obtain at least one crude polymer solution; b') optionally separating insoluble material from the crude polymer solution obtained at the end of step a) to obtain at least one clarified polymer solution; b) a step of extraction by size exclusion of the crude polymer solution obtained at the end of step a) or optionally of the clarified polymer solution obtained at the end of step b') in order to obtain a purified polymer solution, wherein the size exclusion extraction step implements at least one column of n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, and the n fixed beds of size exclusion solids are in series; The train of fixed beds of step b) is fed with a crude or optionally clarified polymer solution at at least one injection point F for the polymer solution and with an effluent at at least one injection point S for the effluent, The train of fixed beds of step b) implements at least one extraction of the extract at at least one extraction point E of the extract and at least one extraction of the raffinate at at least one extraction point R of the raffinate, The injection points of the polymer solution and the eluate, and the withdrawal points of the extract and the raffinate, are different from one another and are separated into at least three, preferably four, successive main operating zones of n fixed beds: a zone I of elution of impurities, located between the injection point of the eluate and the withdrawal point of the extract; a zone II of elution of at least one PVC polymer, located between the extraction point and the injection point of the polymer solution; a zone III of retention of impurities, located between the injection point of the polymer solution and the withdrawal point of the raffinate; and optionally distributed to define a zone IV located between the withdrawal point of the raffinate and the injection point of the eluate, the injection and withdrawal points are shifted over time through one fixed bed of size exclusion solids according to a frequency determined by a predetermined turnover period; an extraction step in which the raffinate is recovered to at least partially constitute a purified polymer solution; c) a solvent-polymer separation step for separating the purified polymer solution into purified PVC polymer and at least one solvent fraction stream comprising the dissolving solvent; The present invention proposes a method including:

[0018] The advantage of the method of the present invention is that it proposes an efficient method for treating feedstocks containing PVC-based plastics, in particular plastic waste coming from collection and sorting channels, in order to recover the PVC resin they contain so that it can be recycled in any type of application. This is because the method according to the present invention makes it possible to obtain a purified PVC polymer stream which is very advantageously less colored than the plastic feedstock, in fact even colorless, and which is preferably deodorized. In particular, the purified PVC polymer stream obtained at the end of the method according to the present invention advantageously contains negligible or at least sufficiently low impurity contents, in particular additive contents, and solvent contents, in particular dissolution and / or elution solvent contents, so that the purified PVC polymer stream meets current regulations and can be introduced into any formulation of plastics instead of virgin PVC resin. For example, the purified PVC polymer stream obtained exhibits the following (contents expressed as weight percentages relative to the total weight of the purified PVC polymer stream obtained): - Contains less than 0.1% by weight of phthalates subject to authorization under the European REACH regulation (Annex XIV of Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), - a content of elemental lead of less than 0.1% by weight, a content of elemental cadmium of less than 0.1% by weight, preferably equal to or less than 0.01% by weight, more generally a content of impurities less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferentially less than 1.0% by weight, more preferably even less than or equal to 0.5% by weight, indeed even less than or equal to 0.1% by weight, and More generally, a solvent content of less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferentially less than or equal to 1.0% by weight and more preferably even less than or equal to 0.1% by weight.

[0019] The method according to the invention therefore proposes a simple scheme corresponding to a minimum sequence of operations making it possible to remove from PVC-based plastic waste at least some of their impurities, in particular at least some of the additives, and to recover at least one purified PVC polymer, so as to enable upgrading of the PVC plastic waste by recycling said purified PVC polymer.

[0020] The present invention has the additional advantage of contributing to the recycling of plastics and the conservation of fossil resources by enabling the upgrading of plastic waste, particularly PVC-based plastic waste, in order to obtain a purified PVC polymer stream with a reduced content of impurities that can be reused to form new articles. The resulting purified PVC polymer stream can then be used directly in formulations, either in place of or in admixture with virgin PVC resin, or as a mixture with additives, such as dyes, pigments, and other polymers, in order to obtain plastic articles having usable, aesthetic, mechanical, or rheological properties that facilitate their reuse and upgrading.

[0021] The present invention also provides, according to a second aspect, a device for the extraction by size exclusion of PVC polymers from polymer solutions, comprising: - n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, in a preferred manner between 12 and 15, said size exclusion solids preferably having a volume average pore diameter of 1 to 500 nm, preferably between 2 and 100 nm, preferentially between 2 and 50 nm, preferentially between 3 and 30 nm, in a preferred manner being preferably silica gel, grafted silica, carbon molecular sieves or mixtures thereof, n fixed beds of size exclusion solids distributed in one or more columns, the n beds being connected in series, preferably in a closed loop; N injection systems for the polymer solution, N injection systems for the eluate, N withdrawal systems for the extract, and N withdrawal systems for the raffinate, where N is an integer preferably equal to n, said injection and withdrawal systems being located between two successive beds or, optionally, upstream of the first bed, Injection and withdrawal systems for the polymer solution and eluate and / or the extract and raffinate are different or identical, located in one and the same location; Equipped with each injection and withdrawal system is equipped with a valve suitable for allowing or disabling the passage of the polymer solution and / or eluate and / or extract and / or raffinate streams, preferably a series of open / close valves controlled by an automatic sequence, or a single rotary valve, whereby At a time t, an injection point for the polymer solution, an injection point for the eluate, a withdrawal point for the extract and a withdrawal point for the raffinate are defined, said injection points and said withdrawal points being different from one another, and comprising at least three, preferably four, successive main operating zones of n fixed beds: - a zone I of elution of impurities, which is comprised between the injection point of the eluate and the withdrawal point of the extract; a zone II of elution of at least one PVC polymer, which is comprised between the extraction point of the extract and the injection point of the polymer solution; a zone III of retention of impurities contained between the injection point of the polymer solution and the withdrawal point of the raffinate, and - optionally determining a zone IV comprised between the withdrawal point of the raffinate and the injection point of the eluate, - Also relates to a device that allows the shifting of injection and withdrawal points over time, synchronously or asynchronously, with one fixed bed of size exclusion solids per transfer period, according to a frequency determined by the given transfer period.

[0022] The present invention also provides, according to a third aspect, a device for the treatment of a plastic feedstock to obtain a stream of purified PVC polymer, comprising: - dissolving means for contacting the plastic feedstock with the dissolving solvent to at least partially dissolve the plastic feedstock in the dissolving solvent and obtain a crude polymer solution; - optionally solid-liquid separation means suitable for separating insoluble materials in suspension in the crude polymer solution; at least one device for extraction by size exclusion according to the invention, - means for separating the dissolution solvent and optionally an effluent from the purified PVC polymer stream; The present invention relates to a device comprising: [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram illustrating the size exclusion extraction stage at a given time t of a method according to an embodiment of the invention. [Figure 2] FIG. 2 shows a diagram of the stage of extraction by size exclusion at a given time t of a method according to another embodiment of the invention. [Figure 3] FIG. 1 shows the concentration profiles obtained in the context of Example 1 for PVC resin and additive didecyl phthalate (DiDP) by simulation along the entire length of a simulated moving bed comprising 15 fixed beds of silica gel in a 6 / 3 / 4 / 2 configuration. DETAILED DESCRIPTION OF THE INVENTION

[0024] FIG. 1 represents a specific embodiment of the size exclusion extraction step of the present invention at a given time t of the process, said size exclusion extraction step implementing 15 fixed beds of silica gel type size exclusion solid distributed in a single column, said beds being connected together in series with respect to each other, and a pump located between bed No. 15 and bed No. 1 in a closed circuit making it possible to connect bed No. 15 and bed No. 1 in series.

[0025] In this particular embodiment, at this time t: the crude polymer solution resulting from the dissolution stage a) (not shown in FIG. 1) or the clarified polymer solution resulting from the solid-liquid separation stage b') optionally incorporated in the process (not shown in FIG. 1) is introduced at an injection point F located between beds No. 9 and No. 10, these two beds being consecutive, the effluent is introduced at an injection point S located between bed No. 15 and bed No. 1, these two beds being consecutive; an extract containing at least a portion of the impurities present in the polymer solution feeding the column is withdrawn at a withdrawal point E located between bed No. 6 and bed No. 7, these two beds being consecutive; A raffinate, at least partially constituted by the purified polymer solution comprising at least one PVC resin present in the polymer solution feeding the column, is withdrawn at a withdrawal point R located between beds No. 13 and 14, these two beds being consecutive.

[0026] The combined injection and withdrawal points therefore form four operating zones: a zone I for elution of impurities located between the injection of the eluate and the withdrawal of the extract, the zone I comprising six beds; at least one PVC polymer elution zone II located between the extraction of the extract and the injection of the polymer solution, said zone II comprising three beds; - a zone III of retention of impurities located between the injection of the polymer solution and the withdrawal of the raffinate, the zone III comprising four beds; - defining a zone IV located between the withdrawal of the raffinate and the injection of the eluate, the zone IV comprising two beds.

[0027] FIG. 2 represents another particular embodiment of the size exclusion extraction step of the invention at a given time t of the method, said size exclusion extraction step comprising four fixed beds of size exclusion solid of the silica gel type, each distributed in a column (i.e., one bed per column), said columns being connected together in series with respect to each other, and a pump positioned between column no. 4 and column no. 1 in a closed circuit making it possible to connect column no. 4 and column no. 1 in series.

[0028] In this particular embodiment, at time t: the polymer solution feeding the stage of extraction by size exclusion is introduced at injection point F located between columns 2 and 3, - an eluate is introduced at an injection point S located between column 4 and column 1, an extract comprising at least a portion of the impurities present in the polymer solution feeding the size exclusion extraction stage is withdrawn at a withdrawal point E located between columns 1 and 2, A raffinate, at least partially composed of a purified polymer solution comprising at least one PVC resin present in the polymer solution feeding the extraction stage by size exclusion, is withdrawn at a withdrawal point R located between columns 3 and 4.

[0029] 3 represents the concentration profiles obtained in the context of Example 1 for PVC resin and additive didecyl phthalate (DiDP) by simulation along the entire length of a simulated moving bed comprising 15 fixed beds of silica gel in a 6 / 3 / 4 / 2 configuration. By convention, the injection of the eluate is located upstream of bed 1 (and downstream of bed 15). The concentration profile of PVC resin as a function of bed is represented by the solid black line, and the concentration profile of additive didecyl phthalate (DiDP) as a function of bed is represented by the dotted line.

[0030] Certain definitions and / or details are provided below, although further details regarding the subject matter defined below may be provided later in the description.

[0031] The term "PVC-based article" is understood to mean an article (generally a consumer article) that comprises at least one PVC plastic and preferably consists of at least one PVC plastic.

[0032] The term "polyvinyl chloride plastic", also known as "PVC plastic", is understood to mean the combination of PVC polymer, also known as PVC resin, with various additives selected depending on the functionality required for the PVC plastic, which itself is selected depending on the intended use.

[0033] PVC polymer traditionally results from the radical polymerization of vinyl chloride (VCM), itself a monomer derived from chlorine and ethylene. The present invention allows for the processing of any type of PVC plastic feedstock and the recycling of any grade of PVC polymer.

[0034] The additives involved in the composition of PVC plastics may be organic molecules or polymers or other inorganic (nano)particles, and are used depending on the properties they impart to the PVC resin. Generally, and non-exhaustively, the formulation of PVC plastics involves at least one family of additives described below: Stabilizers to limit the degradation of polymer chains by dehydrochlorination and / or oxidation under the influence of heat, light, oxygen, and / or mechanical stress. The nature of these stabilizers (metallic compounds (Pb, Sn, Ca, Zn, Cd) or organic compounds) depends on the required properties and therefore the intended application. Some examples of stabilizers frequently used in the past and present include lead stearate, lead dichloride stearate, lead dichloride phthalate, zinc stearate, and calcium stearate, either alone or in mixtures. Co-stabilizers, such as epoxidized oils, are also considered. These are the most widely used plasticizers that form part of the phthalate family and are used to impart flexibility, improved impact strength, and improved cold resistance to PVC plastics. These are obtained by reacting phthalic anhydride with alcohols with somewhat longer carbon chains and consist of a benzene nucleus and two carboxylic acid ester groups located in the ortho-position to the benzene nucleus. Dioctyl or diethylhexyl phthalate (DOP or DEHP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) constitute examples of phthalates that have been or are currently very widely used. Other non-phthalate plasticizers, such as bis(2-ethylhexyl) adipate (DEHA) or cyclohexane-1,2-dicarboxylic acid diisononyl ester (DINCH), are currently in use. - lubricants to control the intermolecular friction forces, either within the polymer itself (internal lubricants such as stearic acid, etc.) or between the polymer and the metal wall of the processing tool (external lubricants such as paraffin, polyethylene wax, etc.), - inert fillers, mostly inorganic (CaCO3, carbon black, kaolin, etc.), which act as diluents or to improve certain mechanical, electrical, thermal, etc. properties, dyes and / or pigments (TiO2, carbon black), the latter being insoluble in the polymer and therefore present in the form of dispersed particles in the PVC plastic; impact modifiers, generally polymers (such as polyacrylates) and copolymers (such as MBS, in the case of methacrylate-butadiene-styrene), whose role is to reduce the brittleness of PVC, especially at low temperatures; -Other adjuvants: antioxidants, UV inhibitors, biocides, antistatic agents, flame retardants, strengthening agents, etc.

[0035] The term "impurities" is understood to mean all elements other than the PVC resin that constitute the plastic feedstock, especially those resulting from PVC-based plastic waste that the method according to the invention proposes to treat. These impurities correspond at least in part to the additives mentioned above. Other types of impurities may actually be ordinary impurities resulting from the life cycle of PVC-based articles, even from pretreatment operations on PVC-based plastic waste, and / or from collection and sorting circuits. These ordinary impurities may be metallic, organic, or inorganic. They may be residues of the constituent materials of the PVC-based articles (excluding PVC plastic), or residues of other articles that have been in contact with the PVC-based articles, dirt (food, biomass, soil / waste, adhesives, etc.), etc. These ordinary impurities may therefore non-exhaustively include glass, wood, cardboard, paper, metal, rubber, silicone, plastics other than PVC (e.g., PET, etc.), inorganic elements, etc. Possible decomposition products of additives formed over time during the life of the PVC-based product are also considered impurities.

[0036] In this document, the expression "purified PVC polymer stream" denotes the main upgradable product obtained after the treatment of a plastic feedstock, in particular resulting from PVC-based plastic waste, by the method according to the invention. It comprises at least one PVC resin of a given grade, preferably a mixture of PVC resins of the same chemical nature but of different grades. The term "purified" in particular means that the PVC polymer stream obtained at the end of the method according to the invention contains, in all cases, in accordance with current regulations, a negligible or at least very low content of impurities (including additives) as mentioned above and of at least one solvent as used according to the method of the invention. Thus, more specifically, the at least one purified PVC polymer stream has a certain content (expressed as a percentage by weight relative to the total weight of the final product, i.e. the purified PVC polymer stream obtained): - less than 0.1% by weight of phthalates subject to authorization under the European REACH Regulation (Annex XIV of Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular less than 0.1% by weight of phthalates selected from the list consisting of the following phthalates, alone or in mixtures: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, isopentyl n-pentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, -elemental lead contained in additives of the metal stabilizer type that have been assessed in the context of the REACH Regulation and are subject to the restrictions (Annex XV) detailed and adopted by the ECHA Risk Assessment Committee (RAC) and the Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018, in particular a content of said lead of less than 0.1% by weight; the element cadmium contained in additives of the metal stabilizer type prohibited by the REACH Regulation, as amended by Annex XVII (Regulation 494 / 2011 of 20 May 2011), in particular a content of less than 0.1% by weight, preferably less than 0.01% by weight, of said cadmium, more generally a content of impurities less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferentially less than 1.0% by weight, more preferably even less than or equal to 0.5% by weight, indeed even less than or equal to 0.1% by weight, and more generally denotes a content of at least one solvent used in the process according to the invention of less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferentially less than or equal to 1.0% by weight and more preferably even less than or equal to 0.1% by weight.

[0037] In this specification, the expression "polymer solution" refers to a liquid medium comprising a dissolution solvent and at least one PVC polymer dissolved, i.e. solvated and dispersed, in said dissolution solvent, the dissolved PVC polymer being initially present in the plastic feedstock treated by the method according to the invention. The polymer solution may further comprise soluble impurities (dissolved in the dissolution solvent) and / or insoluble impurities (suspended in the polymer solution). Thus, depending on the stage of the method according to the invention carried out, said polymer solution may advantageously comprise impurities in the form of insoluble particles suspended in said polymer solution (in the case of insoluble impurities of nanometer size, a colloidal solution as referred to later), soluble impurities dissolved in the dissolution solvent, and / or optionally another liquid phase immiscible with said polymer solution.

[0038] In this specification, the expression "greater than" is understood to mean strictly greater than and is represented by the symbol ">", and the expression "less than" is understood to mean strictly less than and is represented by the symbol <. If a limitation is involved, this information is provided by the respective expressions "greater than or equal to" (and corresponding to the symbol ≧") and "less than or equal to" (corresponding to the symbol ≦").

[0039] In this specification, the term "room temperature" (rt) is understood to mean a temperature of typically 20°C ± 5°C, and the term "atmospheric pressure" is understood to mean a pressure of 0.101325 MPa.

[0040] As used herein, the term "to comprise" is synonymous with (has the same meaning as) "to include" and "to contain" and is inclusive or open-ended and does not exclude other elements not recited. The term "to comprise" is understood to include the exclusive and closed term "to consist."

[0041] As used herein, the phrase "between" means that the limits of the interval are included within the stated range of values, unless otherwise specified.

[0042] Herein, various ranges of parameters for a given stage, such as pressure ranges and temperature ranges, may be used alone or in combination, for example, here a range of preferred pressure values ​​may be combined with a range of more preferred temperature values.

[0043] Subsequently, specific embodiments of the present invention will be described, which may be carried out separately or in combination with one another, without limiting the combination, if technically feasible.

[0044] Subsequently, the term "stage" is used to denote an operation or group of similar operations performed on a given stream at a particular point in the process. The process is described in terms of its various stages, which are performed in the order of the stream or product flow.

[0045] Finally, the terms "upstream" and "downstream" should be understood according to the general flow of the fluid(s) or stream(s) considered in the method. More specifically, the terms "upstream" and "downstream" are defined according to the flow of the stream containing the PVC resin. For example, the terms "upstream" and "downstream" are defined in the size exclusion step either with respect to the polymer solution stream, i.e., the feeding of the crude (or clarified) polymer solution to the above step b), or with respect to the exit point of the polymer solution extracted during this step b) (i.e., the withdrawal point of the raffinate).

[0046] In the following description of the method according to the invention, reference is made to the diagrams of Figures 1 and 2 which illustrate different embodiments of the method according to the invention.

[0047] According to the present invention, the method for the recovery of at least one reusable purified PVC polymer stream from a plastic feedstock advantageously originating from PVC-based plastic waste comprises the following steps: a) a dissolution step comprising contacting a plastic feedstock with at least one dissolution solvent to obtain at least one crude polymer solution, then b') an optional step of separating insoluble materials from the crude polymer solution, which advantageously makes it possible to obtain a clarified polymer solution, preferably an insoluble fraction, then (b) a step of extraction by size exclusion of the crude polymer solution obtained at the end of step a) or, optionally, of the clarified polymer solution obtained at the end of optional step b'), making it possible to obtain a purified polymer solution, said stage of extraction by size exclusion implements at least one train of n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferentially between 8 and 24, very preferentially between 8 and 21, and in a preferred manner between 12 and 15; Advantageously, the n fixed beds of size exclusion solids are distributed in one or more columns, preferably M columns, where M is an integer between 1 and the total number n of fixed beds of exclusion solids, the n beds being in series with one another, preferably in a closed loop; The at least one fixed bed of step b) is fed with a crude or clarified polymer solution at at least one injection point F for the polymer solution and with an effluent at at least one injection point S for the effluent, The at least one row of fixed beds of step b) implements at least one withdrawal of the extract at at least one withdrawal point E of the extract and at least one withdrawal of the raffinate at at least one withdrawal point R of the raffinate, The injection points of the polymer solution and the eluate, and the withdrawal points of the extract and the raffinate, are distinct from one another and are advantageously located between two successive beds or, optionally, upstream of the first bed, and are arranged in at least three, preferably four, successive main operating zones of n fixed beds: a zone I of elution of impurities, located between the injection point of the eluate and the withdrawal point of the extract; a zone II of elution of at least one PVC polymer, located between the extraction point and the injection point of the polymer solution; a zone III of retention of impurities, located between the injection point of the polymer solution and the withdrawal point of the raffinate; and optionally and preferably distributed to define a zone IV located between the withdrawal point of the raffinate and the injection point of the eluate, the injection and withdrawal points are shifted over time through one fixed bed of size exclusion solids according to a frequency determined by a predetermined turnover period; The raffinate is recovered to constitute at least a portion, preferably all, of the purified polymer solution, followed by an extraction step. c) It may comprise or consist of a step of polymer-solvent separation of the purified polymer solution to obtain at least one fraction of at least one solvent, in particular comprising the dissolution solvent and optionally an eluate, and at least one stream of purified PVC polymer.

[0048] feedstock The method according to the invention is fed with a plastic feedstock, which is in particular PVC-based, more particularly originating from PVC-based plastic waste, sometimes referred to as "PVC feedstock", and which comprises at least one PVC plastic.

[0049] Said plastic feedstock is advantageously a recycled PVC feedstock of the "production scrap" type, i.e. waste arising from a process for producing a PVC polymer during its polymerization, or from a process for producing a PVC plastic during its compounding / formulation, or from a process for producing a PVC-based article during its production, or of the "post-consumer waste" type, i.e. waste generated after consumption of said PVC-based article by a user. In particular, the recycled plastic feedstock may come from any existing network or collection and sorting channel for production scrap and / or post-consumer waste, in particular a network or collection and sorting channel specific for plastic waste, which makes it possible to segregate at least one PVC plastic-based stream.

[0050] Thus, the plastic feedstock, which is typically of the "production scrap" and / or "post-consumer waste" type, generally comes from the main application fields using PVC plastics, such as the non-exhaustive list below: building and construction, packaging, automotive, electrical and electronic equipment, sports, medical equipment, etc. Preferably, the PVC feedstock comes from the building and construction field. More precisely, PVC-based articles are widely used in these fields as profiles (for windows, doors, blinds, roller shutters), pipes and fittings, various rigid and bottle products, rigid plates and films, flexible films and sheets, flexible tubes and profiles, cables, flooring, coated fabrics, etc.

[0051] Advantageously, the plastic feedstock comprises at least 50% by weight, preferably at least 70% by weight, in a preferred manner at least 90% by weight, more preferably even at least 95% by weight of PVC plastic.

[0052] The plastic feedstock processed in the method for recovering a stream of reusable purified PVC polymer according to the present invention is in the form of particles. Therefore, when the PVC feedstock is in the initial form typical of production scrap or post-consumer waste, especially in the latter case, in the initial form of PVC-based articles, the PVC feedstock can be previously subjected to a conditioning step (as described below) that includes at least crushing or shredding to form a PVC feedstock in the form of particles. Depending on the channels and / or networks that give rise to these production scraps and / or end-of-life PVC-based articles, the PVC waste can be crushed and / or washed, as described below, and / or subjected to any other conditioning step, in order to form a PVC feedstock in the form of particles suitable for the method according to the present invention. For example, the PVC feedstock can advantageously be in the form of a crushed, optionally washed material, the largest dimension of which is 20 cm or less, preferably 10 cm or less, in a preferred manner 1 cm or less, and even more preferably 5 mm or less. The PVC feedstock may also advantageously be in the form of a finely divided solid, i.e., in the form of particles having an average size preferably less than 1 mm, for example between 10 and 800 micrometers (μm), the average size advantageously corresponding to the average diameter of the sphere circumscribed by said particles.

[0053] The plastic feedstock fed to the process according to the invention is therefore advantageously in the form of particles typically having an average size of between 10 μm and 20 cm, for example particles of the ground material type having an average size of between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferentially between 1 mm and 1 cm, even more preferentially between 1 mm and 5 mm, or particles resulting from micronization (very fine grinding to produce a powder) having an average size of less than 1 mm, preferably between 10 μm and 800 μm.

[0054] As already mentioned, the PVC feedstock may also contain conventional impurities, often "macroscopic" impurities, such as glass, wood, cardboard, paper, metal, rubber, silicone, plastics other than PVC (e.g., PET, etc.), inorganic elements, etc. Advantageously, the PVC feedstock contains at most 50% by weight, preferably at most 30% by weight, in a preferred manner at most 10% by weight, and even more preferably at most 5% by weight of "macroscopic" impurities. An optional preconditioning step, in addition to introducing the above-mentioned feedstock in particulate form, can make it possible to remove all or part of the above-mentioned conventional impurities.

[0055] The various steps of the method according to the invention leading to at least one reusable purified PVC polymer stream are described in detail in the following sections.

[0056] Optional step of preconditioning PVC feedstock According to the invention, the method may comprise a stage of preconditioning of the PVC feedstock, which comprises at least one stage of grinding or crushing or micronizing the PVC feedstock (not shown in Figures 1 and 2) to form a PVC feedstock in the form of solid particles as defined above, which can be passed to the dissolution stage a). This preconditioning stage may additionally comprise one or more of the stages mentioned in the following non-exhaustive list: grinding by micronization, sorting, oversorting, washing, drying, etc. Depending on the nature of the PVC feedstock to be treated, the stage or stages involved in the preconditioning stage, as well as their possible frequency and sequence, will be specifically chosen by those skilled in the art in order to limit the amount of usual impurities and reduce the size of the solid components constituting the initial PVC feedstock.

[0057] For example, the preconditioning step makes it possible to provide a PVC feedstock in the form of particles of washed, e.g. ground material, having an average size of less than 5 mm, preferably between 1 mm and 5 mm, the content of normal impurities of which is preferably at most 10% by weight, more preferably at most 5% by weight. The preconditioned PVC feedstock may be in the form of micronized solid particles, i.e. particles having an average size of less than 1 mm, e.g. between 10 μm and 800 μm.

[0058] The step of preconditioning the PVC feedstock may include the step of drying the PVC feedstock.

[0059] Dissolution step a) The process according to the invention comprises a dissolution step a) in which the PVC feedstock (or plastic feedstock), advantageously in the form of particles, is brought into contact with a dissolution solvent to obtain at least one, preferably only one, crude polymer solution, which step advantageously allows at least part, preferably all, of the PVC resin contained in the plastic feedstock to be dissolved.

[0060] The term "dissolution" should be understood to mean any phenomenon that results in obtaining at least one polymer solution, i.e. a liquid comprising at least a PVC resin dissolved in a solvent, more specifically a dissolution solvent. The skilled person is well aware of the phenomenon / phenomena involved in the dissolution of a polymer, which phenomenon / phenomena include at least the mixing, homogenization, solvation, disentanglement and dispersion of the polymer chains, more specifically in this case the PVC polymer chains.

[0061] The dissolution solvent is selected for its ability to solvate, disentangle, and disperse PVC polymer chains as a result of its physicochemical properties. In this regard, those skilled in the art can rely on knowledge of the Hildebrand and / or Hansen solubility parameters of the solvent to define the most suitable solvent or solvent mixture for carrying out the dissolution step a) of the method according to the present invention in terms of these same parameters specific to PVC resin. More specifically, the dissolution solvent is preferably a solvent or solvent mixture, particularly an organic solvent(s), selected so that its Hansen parameter falls within the Hansen sphere of the target PVC polymer. Hansen theory makes it possible to predict the solubility of polymers, particularly thermoplastic resins such as PVC, in a solvent by determining the Hansen solubility parameters and spheres for the solvent and polymer, respectively, as a function of several parameters, particularly their polarity, hydrogen bonding, and dispersion parameters. If a solvent or solvent mixture exhibits a Hansen parameter within the Hansen sphere of the PVC polymer, the PVC polymer should be at least partially, preferably completely, soluble in the solvent.The dissolution medium is therefore advantageously an organic solvent or a mixture of organic solvents, preferably ketones (acetone; methyl ethyl ketone or MEK; diethyl ketone or DEK; methyl propyl ketone; 4-heptanone; 2,4-dimethyl-3-pentanone; methyl isobutyl ketone or MIBK; diisobutyl ketone; methyl isoamyl ketone; 4-hydroxy-4-methylpentan-2-one; etc.), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; etc.), amides (N,N-diethylformamide, etc.), amides (N,N-dimethylacetamide; N,N-dimethylformamide or DMF; etc.), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; etc.), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; amyl acetate; 2-butoxyethyl acetate; n-butyl propionate; propyl propionate; methyl propionate; allyl acetate; 2-(2-butoxyethoxy)ethyl acetate; propylene glycol methyl ether acetate; propylene glycol ethyl ether acetate; butyl benzoate; benzyl benzoate; ethyl lactate; etc.), cyclic esters (γ-butyrolactone or GBL; γ-valerolactone or GVL; caprolactone; etc.), ethers (methoxycyclopentane or CPME; propylene glycol phenyl ether; diethylene glycol butyl ether; dipropylene glycol butyl ether; propylene glycol methyl ether; propylene glycol butyl ether; dipropylene glycol methyl ether; ethylene glycol butyl ether; etc.), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane; 2-hydroxymethyloxolane; etc.), chlorinated solvents (dichloromethane; trichloromethane or chloroform; tetrachloromethane; trichloroethylene; etc.), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; etc.), sulfur-based solvents (dimethyl sulfoxide or DMSO; sulfolane; etc.), nitrogen-based solvents (1-nitropropane; etc.), dihydrolevoglucosenone or silane, etc.Preferably, the dissolution solvent is selected from ketones, cyclic ketones and cyclic esters, such as MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, GVL, taken alone or in mixtures. Even more preferably, the dissolution solvent is selected from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, taken alone or in mixtures.

[0062] The dissolution of the PVC feedstock in step a) is preferably carried out at a dissolution temperature between room temperature and 200°C, preferably between 20°C and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and advantageously at a dissolution pressure between atmospheric pressure and 11.0 MPa absolute, preferably between 0.1 and 11.0 MPa absolute, preferably between 0.1 and 5.0 MPa absolute, more preferably between 0.1 and 2.0 MPa absolute. The pressure and temperature operating conditions are therefore selected to keep the dissolution solvent at least partially, preferably completely, in a liquid state, while the soluble fraction of the PVC feedstock, in particular the PVC resin and at least a portion of the impurities, are advantageously at least partially, preferably completely, dissolved. Highly advantageously, the temperature and pressure conditions of the dissolution step a) are adjusted so that the dissolution solvent + PVC resin(s) mixture is a single-phase mixture, with insoluble impurities optionally being able to be suspended in said mixture.

[0063] Very advantageously, the dissolution step a) is carried out with a residence time of between 1 minute (min) and 10 hours (h), preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours. Residence time is understood to be the residence time at the dissolution temperature and dissolution pressure, i.e. the treatment time of the plastic feedstock with the dissolution solvent at the dissolution temperature and dissolution pressure in step a).

[0064] Preferably, in step a) the plastic feedstock and the dissolving solvent are fed such that the weight of PVC resin(s) present in the plastic feedstock relative to the weight of the dissolving solvent is between 2% and 30% by weight, preferably between 5% and 20% by weight, even more preferably between 10% and 15% by weight.

[0065] The dissolving step a) may include various equipment to allow the dissolving solvent to contact the plastic feedstock and dissolve at least a portion, preferably all, of the PVC resin contained in the plastic feedstock in the dissolving solvent. Thus, step a) may advantageously include at least one dissolving device, one mixing device, and / or one transport device. These devices (or devices) may be, for example, static mixers, extruders, pumps, reactors, cocurrent or countercurrent columns. Transport devices, especially those for transporting fluids such as liquids or solids, are well known to those skilled in the art. Without limitation, the transport devices may include compressors, pumps, extruders, vibrating pipes, endless screws, or valves. The equipment may also include or be combined with a heating system (e.g., furnace, exchanger, heating cable, etc.) to achieve the conditions required for dissolution. More specifically, the dissolving step a) may include a reactor agitated by a mechanical stirring system and / or a recirculation loop and / or fluidization, such as a batch or continuous fully stirred reactor, or a rotary drum reactor.

[0066] Dissolution stage a) is fed with at least the plastic feedstock (or PVC feedstock) and the dissolution solvent, in particular in the form of one or more dissolution solvent streams, advantageously by one or more transport device(s). The PVC feedstock may also be introduced in the form of a stream of solid particles different from the dissolution solvent stream(s). Part or all of the PVC feedstock may be fed to stage a) in a mixture with part or all of the dissolution solvent, in particular in the form of a suspension of solid particles in a liquid solvent, and the remainder of the solvent and / or the feedstock can, if desired, be fed separately to stage (a).

[0067] In step a), the plastic feedstock and / or the melt may be fed as a mixture or separately, continuously or batchwise.

[0068] Preferably, the dissolution step a) can be carried out in a reactor of the type agitated by a mechanical stirring system and / or a recirculation loop and / or fluidization, and / or by ultrasound, for example in a batch or continuous fully stirred reactor, or in a rotating drum reactor.Furthermore, it is preferred to introduce the PVC feedstock in the form of a stream of solid particles, independently of the stream(s) of dissolution solvent.

[0069] Advantageously, the dissolution solvent used in step a) comprises, preferably consists of, fresh solvent (or a contribution of fresh solvent) and / or a stream of recycled solvent originating from a subsequent step of the method, in particular originating at least partly from recovery step c).

[0070] According to the invention, said dissolution step a) makes it possible to obtain at least one, preferably only one, polymer solution, referred to herein as crude polymer solution, comprising at least a dissolution solvent and at least PVC resin(s) dissolved in said dissolution solvent. Generally, the crude polymer solution also comprises soluble impurities also dissolved in the dissolution solvent and optionally insoluble impurities in suspension.

[0071] Optional step b') of separating insoluble material The method according to the invention may optionally include a step b') of separating insoluble materials from the crude polymer solution, in particular by solid-liquid separation, advantageously located upstream of the step b) of extraction by size exclusion. Thus, when incorporated into the method according to the invention, the step b') of separating insoluble materials makes it possible to obtain a clarified polymer solution, which is a polymer solution from which at least some, preferably all, insoluble impurities have been removed. The above-mentioned step b') of separating insoluble materials also advantageously makes it possible, when incorporated into the method according to the invention, to separate an insoluble fraction, in particular comprising some, preferably all, of the insoluble impurities in suspension in the crude polymer solution resulting from step a). The insoluble impurities removed during the step b') of separating insoluble materials are, for example, additives (pigments, fillers, other polymers, etc.), common impurities (inorganic compounds, glass, wood, paper, metals, other polymers) and / or decomposition products initially present in the PVC plastic, as described herein above. Preferably, step b') also makes it possible to obtain a clarified polymer solution and an insoluble fraction.

[0072] If carried out, this separation step b') advantageously makes it possible, in addition to removing at least a portion of the insoluble impurities, to limit operational problems in the downstream process steps, in particular clogging and / or erosion type, while contributing to the purification of the PVC feedstock. Preferably, the process according to the invention comprises a step b') of separation of insoluble material.

[0073] Advantageously, the step of separation of insoluble material, if carried out, is located upstream of the step b) of extraction by size exclusion and typically downstream of the lysis step a).

[0074] Step b') of separating the insoluble material is advantageously carried out under temperature and pressure conditions close to those of step a). Very advantageously, step b') of separating the insoluble material is carried out under the temperature and pressure conditions of dissolution step a), as defined above. Very advantageously, step b') is therefore carried out at a temperature between room temperature and 200°C, preferably between 20°C and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and advantageously at a pressure between atmospheric pressure and 11.0 MPa absolute, preferably between 0.1 and 11.0 MPa absolute, preferably between 0.1 and 5.0 MPa absolute, more preferably between 0.1 and 2.0 MPa absolute.

[0075] If incorporated into the process, step b') of the separation of insoluble material is preferably fed by the crude polymer solution resulting from step a).

[0076] Advantageously, optional step b') may implement at least one solid-liquid separation device, such as a knockout drum, a decanter, a centrifugal decanter, a centrifuge, a filter, a sand filter, in particular a tangential filter implementing a membrane and / or a depth filter, an eddy current separator, an electrostatic separator, a triboelectric separator, optionally in the presence of a filter aid (for example diatomaceous earth or sand), preferably a section comprising a decanter, a filter, a sand filter and / or an electrostatic separator. Advantageously, self-cleaning filters may be used, in which cleaning or declogging to remove insoluble materials is carried out in particular using a solvent stream.

[0077] The removal of the insoluble fraction may require the use of equipment that allows transport and, optionally, removal of solvent that may be impregnated in the separated insoluble fraction. For example, step b') may implement a conveyor, a vibrating tube, an endless screw, an extruder or a stripper. Thus, step b') may implement a transport device to discharge the insoluble fraction and / or to remove solvent that may be entrained in the separated insoluble fraction. Advantageously, at least a portion of the solvent that may be entrained in the separated insoluble fraction is recovered and reused in the method.

[0078] According to a particular embodiment, stage b') of separation of insoluble material implements at least two, generally less than five, solid-liquid separation devices in series and / or parallel. The presence of at least two solid-liquid separation devices in series makes it possible to improve the removal of insoluble material, while the presence of parallel devices makes it possible to manage the maintenance and / or unclogging operations of said devices.

[0079] Certain insoluble impurities, particularly certain pigments and inorganic fillers, that are conventionally added during polymer compounding can be introduced in the form of particles less than 1 μm in size. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. According to one embodiment, the insoluble material separation step b') advantageously employs an electrostatic separator, which allows for at least partial efficient removal of insoluble particles less than 1 μm in size. According to another embodiment, the insoluble material separation step b') employs a sand filter to remove particles of different sizes, particularly particles less than 1 μm in size. According to yet another embodiment, the insoluble material separation step b') employs a tangential filter, particularly a membrane and / or depth filter, optionally in the presence of a filter aid such as diatomaceous earth.

[0080] According to the invention, said optional separation step b') of insoluble materials, when incorporated into the process, makes it possible to obtain at least one clarified polymer solution comprising at least a dissolution solvent and at least PVC resin(s) dissolved in said solvent. Thus, at least part, and preferably all, of the insoluble impurities that may be present in suspension in the crude polymer solution obtained at the end of step a) of the process according to the invention are removed from the polymer solution in step b').

[0081] Size exclusion extraction step (b) The process according to the invention comprises a step b) of extraction by size exclusion, which is fed in particular by the eluate and crude polymer solution resulting from step a) or, optionally, by the clarified polymer solution resulting from step b') of separation of insoluble materials. Advantageously, step b) of extraction by size exclusion makes it possible to obtain at least one purified polymer solution and, preferably, in particular, waste solvent full of impurities.

[0082] The polymer solution fed to stage b) of extraction by size exclusion, in particular the crude polymer solution resulting from stage a) or the optionally clarified polymer solution resulting from stage b') of separation of insoluble materials, generally comprises dissolved impurities, which are advantageously at least partially, preferably completely, removed during stage b), in particular by contacting the crude or optionally clarified polymer solution with a size exclusion solid in the presence of an eluent, since stage b) of extraction by size exclusion allows the separation of the compounds present in the crude or optionally clarified polymer solution, in particular the dissolved PVC resin(s) and solubilized impurities, according to their size, in particular on the molecular scale (or rather their hydrodynamic volume), by simulated countercurrent chromatography or simulated moving bed chromatography, denoted below by the method term SMB. Very advantageously, this extraction stage of the method according to the invention makes it possible to selectively separate the PVC resin(s) dissolved in the dissolution solvent from the solubilized impurities present in the polymer solution fed to step b) above (i.e. the crude or optionally clarified polymer solution). Step b) therefore makes it possible to produce a purified polymer solution from which at least some, preferably all, of the soluble impurities present in the polymer solution fed to step b), i.e. the crude or optionally clarified polymer solution, have been removed.

[0083] Preferably, the eluate fed to extraction step b) is a solvent, in particular an organic solvent or a mixture of organic solvents, preferably selected such that its Hansen parameters lie within the Hansen sphere of the targeted PVC polymer.Preferably, the eluate fed to the extraction step b) is a solvent, in particular an organic solvent or a mixture of organic solvents, such as ketones (acetone; methyl ethyl ketone or MEK; diethyl ketone or DEK; methyl propyl ketone; 4-heptanone; 2,4-dimethyl-3-pentanone; methyl isobutyl ketone or MIBK; diisobutyl ketone; methyl isoamyl ketone; 4-hydroxy-4-methylpentan-2-one; etc.), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; etc.), amides (N,N-diethyl Formamide; N,N-dimethylacetamide; N,N-dimethylformamide or DMF; etc.), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; etc.), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; amyl acetate; 2-butoxyethyl acetate; n-butyl propionate; propyl propionate; methyl propionate; allyl acetate; 2-(2-butoxyethoxy)ethyl acetate; propylene glycol methyl ether acetate; propylene glycol ethyl ether acetate butyl benzoate; benzyl benzoate; ethyl lactate; etc.), cyclic esters (γ-butyrolactone or GBL; γ-valerolactone or GVL; caprolactone; etc.), ethers (methoxycyclopentane or CPME; propylene glycol phenyl ether; diethylene glycol butyl ether; dipropylene glycol butyl ether; propylene glycol methyl ether; propylene glycol butyl ether; dipropylene glycol methyl ether; ethylene glycol butyl ether; etc.), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane; 2-hydroxymethyloxolane; etc.), chlorinated solvents (dichloromethane; trichloromethane or chloroform; tetrachloromethane; trichloroethylene; etc.), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; etc.), sulfur-based solvents (dimethyl sulfoxide or DMSO; sulfolane; etc.), nitrogen-based solvents (1-nitropropane; etc.), dihydrolevoglucosenone or silane, etc.Preferably, the eluent is selected from ketones, cyclic ketones and cyclic esters, such as MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, GVL, taken alone or in a mixture. Preferentially, the eluent is selected from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, taken alone or in a mixture. Very preferably, the eluent is of the same chemical nature as the dissolution solvent, indeed even the same solvent.

[0084] Advantageously, stage b) of extraction by size exclusion implements, in operation, at least one train, preferably a single train, of several fixed beds of size exclusion solids. Said train(s) are advantageously fed by the crude polymer solution resulting from stage a) or, optionally, the clarified polymer solution resulting from optional stage b'), and by the eluate. If stage b) comprises several, in particular 2 to 4, trains of fixed beds of size exclusion solids, in operation, these trains of fixed beds operate in parallel with one another and are each fed by a fraction of the polymer solution feeding stage b), in particular the crude polymer solution resulting from stage a), or, optionally, the clarified polymer solution resulting from optional stage b'), and by a fraction of the eluate feeding stage b). In this case, the polymer solution fed to step b) is then divided into as many partial streams of crude or optionally clarified polymer solution as there are rows of fixed beds in operation, and similarly, the effluent fed to step b) is then divided into as many partial streams of effluent as there are rows of fixed beds in operation.

[0085] Optionally, the method may also comprise, in particular in parallel with step b), at least one train of fixed beds of size exclusion solids (as described below) that is not in operation, in particular in shutdown and / or regeneration and / or backup mode.

[0086] The (or each) train of fixed beds advantageously in operation in step b) of extraction by size exclusion comprises n fixed beds of size-exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferentially between 8 and 24, very preferentially between 8 and 21, and in a preferred manner between 12 and 15. The number of fixed beds must be sufficient to allow efficient separation and reasonable to limit costs, especially capital costs. The n fixed beds are in series with one another.

[0087] The n fixed beds of size exclusion solids can be operated in a closed loop or in an open circuit. Preferably, the n fixed beds of size exclusion solids are operated in a closed loop, i.e., the n fixed beds are connected to each other in series, preferably in a closed loop (the first is connected to the second, the second to the third, etc., and the nth is connected to the first), thus allowing continuous operation of the extraction by size exclusion and advantageously reducing consumption of eluate, since the eluate is then partially continuously regenerated and reused.

[0088] In one (or each) fixed bed column, n fixed beds of size exclusion solids are advantageously distributed over one or more columns, preferably M columns, where M is an integer between 1 and the total number of fixed beds of exclusion solids in the column under consideration, i.e., M is between 1 and n. Thus, the fixed bed column (or each column) of stage b) of extraction by size exclusion may contain 1 to n columns, each containing one or more fixed beds of size exclusion solids. For example, the fixed bed column (or each column) of stage b) may contain a single column (or tower), preferably of large capacity (volume), containing n fixed beds, or two columns, each containing n / 2 fixed beds. These two configurations allow to significantly limit capital costs, but if there is a problem with one of the beds of a column, it is necessary to remove the entire column, i.e., n or n / 2 fixed beds. According to another embodiment, the (or each) train of fixed beds of step b) implements n columns (or towers), preferably each of which has a smaller capacity (volume) than in the previous case, each of which contains a fixed bed of size exclusion solids, thus facilitating the maintenance and / or cleaning and / or bypass of one in particular of the n beds during operation, since in this configuration only one column (containing only one bed) has to be removed and / or bypassed, rather than an assembly of beds. However, the latter configuration incurs higher capital costs.

[0089] Preferably, the size-exclusion solid is provided in the form of solid particles. Size-exclusion solids are sometimes called granular media. The size-exclusion solid is selected so as to be inert to the polymer solution to be treated, i.e., the dissolving solvent and the PVC resin to be treated, as well as to the eluate. The size-exclusion solid is also selected so as to enable efficient separation of the compounds present in the treated polymer solution, particularly the dissolved compounds, more particularly the impurities solubilized in the dissolving solvent with respect to the PVC resin itself, which is also dissolved therein. The size-exclusion solid may advantageously be organic (generally polymeric) and / or inorganic, and is preferably a porous (mesoporous and / or macroporous) solid, preferably having a volume-average pore size of 1 nm to 500 nm, preferentially 2 nm to 100 nm, very preferentially 2 nm to 50 nm (mesoporous solids), and in a preferred manner, 3 nm to 30 nm. Advantageously, the size exclusion solid comprises silica (e.g., silica gel, also called silica, and / or grafted silica), carbon molecular sieves, carbon replicas, polymeric molecular sieves (chemically different from PVC), porous polymer gels, preferably dealuminated zeolites (e.g., USY type), preferably calcined alumina, MOF (metal organic framework) type materials or mixtures thereof. Preferably, the size exclusion solid comprises, preferably consists of, silica gel (or silica), grafted silica, carbon molecular sieves or mixtures thereof. Very advantageously, the size exclusion solid exhibits a pore volume of preferably 0.01 to 3.0 ml / g, preferably 0.1 to 2.0 ml / g, preferentially 0.3 to 1.2 ml / g. The average pore size and pore volume of the size-excluded solids are determined by mercury porosimetry, more specifically measured by mercury intrusion porosimetry at a maximum pressure of 4000 bar, using a surface tension of 484 dynes / cm and a contact angle of 140°, according to standard ASTM D4284-83.Following the recommendation on page 1050 of the publication "Techniques de l'ingenieur, trait analyze et characterization" [Engineering Techniques, Analysis and Characterization Treatise] by J. Charpin and B. Rasneur, the wetting angle was taken equal to 140°. For better accuracy, a given value of mercury volume (ml / g) corresponds to the total mercury volume (ml / g) measured on the sample minus the mercury volume (ml / g) measured on the same sample at a pressure equivalent to 30 psi (approximately 2 bar). These same parameters, especially the volume and diameter of solids in the mesoporous range, can also be measured by nitrogen adsorption / desorption volumetrics (also known as nitrogen adsorption isotherms), a complementary analytical method to the one mentioned above. This analysis corresponds to the physical adsorption of nitrogen molecules in the porosity of a material through a gradual increase in pressure at a constant temperature, providing information on textural properties. In particular, it allows access to the mesoporous distribution of size-excluded solids. Therefore, the pore distribution, which represents a population of pores centered in the 2-50 nm range, is determined by the Barrett-Joyner-Halenda (BJH) model. The nitrogen adsorption / desorption isotherm according to the BJH model is described in the journal "The Journal of the American Chemical Society, 73, 373 (1951)" by E.P. Barrett, L.G. Joyner, and P.P. Halenda.

[0090] The particles of the size-excluded solid preferably have a volume-average equivalent diameter (preferably determined by laser particle size analysis, i.e. laser diffraction using a particle size analyzer) of 20 to 5000 μm, preferably 50 to 1500 μm, preferentially 100 to 800 μm, even more preferably 300 to 600 μm. Advantageously, the solid particles are substantially spherical.

[0091] According to the invention, the (or each) train of fixed beds of stage b) of extraction by size exclusion is fed with a crude or optionally clarified polymer solution at at least one injection point F for the polymer solution and with at least one eluate at an injection point S for the eluate. Preferably, the operating fixed bed train under consideration is fed with a crude or optionally clarified polymer solution at an injection point F for the polymer solution and with the eluate at an injection point S for the eluate.

[0092] Preferably, the eluate and the polymer solution are fed to the (each) fixed-bed column of the stage of extraction by size exclusion in accordance with a ratio of the volumetric flow rate of the eluate to the volumetric flow rate of the polymer solution of 0.1 to 50.0, preferably 0.2 to 10.0, preferably 0.5 to 5.0, preferentially 0.8 to 2.0, such ratio also being referred to as the solvent level. Such solvent level, i.e., such adjustment of the volumetric flow rates of the crude or optionally clarified polymer solution and the eluate for the (each) column under consideration, contributes to the efficiency of the separation by size exclusion of the PVC resin and impurities present in the polymer solution fed to extraction stage b).

[0093] If the train of fixed beds comprises several injection points Fi of polymer solution, for example two injection points F1 and F2 of polymer solution, the stream of crude or clarified polymer solution feeding the train of fixed beds considered in the extraction stage is divided into partial streams of polymer solution for feeding the train of fixed beds at the injection points Fi, the partial streams of polymer solution exhibiting the same or different flow rates from one another.

[0094] If a train of fixed beds comprises several injection points Si for eluate, for example two injection points S1 and S2, the total stream of eluate feeding the train of fixed beds considered above is divided into partial streams of eluate (i.e., into i partial streams of eluate, where i is an integer equal to the number of injection points Si for eluate) for feeding the train of fixed beds at the injection points Si, said partial streams of eluate exhibiting the same or different flow rates from one another.

[0095] The (or each) train of fixed beds of stage b) of extraction by size exclusion implements at least one withdrawal of the extract at at least one withdrawal point E for the extract and at least one withdrawal of the raffinate at at least one withdrawal point R for the raffinate. Preferably, the (or each) train of fixed beds of stage b) of extraction by size exclusion implements a withdrawal of the extract at the extraction point E for the extract and a withdrawal of the raffinate at the raffinate withdrawal point R.

[0096] The injection points F of the polymer solution and S of the eluate, as well as the withdrawal points E of the extract and R of the raffinate, are different from one another. They are advantageously located between two successive beds, especially in the case of an open circuit, or optionally upstream of the first bed (in the case of a closed loop of n fixed beds, these two beds are considered to be successive, since the nth bed is connected to the first bed). However, they may also be located in the middle of the fixed bed or in the fixed bed, on average over the operating cycle, especially in the case of an embodiment according to the Varicol® process (described below). The injection points of the polymer solution and the eluate and the withdrawal points of the extract and the raffinate are such that they are located in at least three, preferably four, successive main operating zones of the n fixed beds: a zone I of elution of impurities, comprised between the injection point S of the eluate and the withdrawal point E of the extract; a zone II of elution of at least one PVC polymer, which is comprised between the extraction point E of the extract and the injection point F of the polymer solution, a zone III of retention of impurities, comprised between the injection point F of the polymer solution and the withdrawal point R of the raffinate, and Optionally, a zone IV preferably included between the withdrawal point R of the raffinate and the injection point S of the eluate. are distributed relative to one another to determine

[0097] If there are several injection points Fi of the polymer solution and / or several injection points Si of the eluate and / or several withdrawal points of the extract and / or raffinate, zones I, II, III and IV start with the first injection and / or withdrawal point of the stream under consideration (eluate, polymer solution, extract or raffinate), the term "first" being defined here as being the furthest upstream of all injection and / or withdrawal points of said streams under consideration. If there are several injection points Fi of the polymer solution and / or several injection points Si of the eluate and / or several withdrawal points of the extract and / or raffinate, secondary operating zones may also be defined, in particular inside the main operating zones, zones I, II, III and IV.

[0098] When the n fixed beds of the considered train of step b) are operated in an open circuit, the eluate is introduced at the eluate injection point(s) S, the crude or optionally clarified polymer solution is introduced at the polymer solution injection point(s) F, the extract is withdrawn at the extract withdrawal point(s) E, and the remainder is withdrawn at the raffinate withdrawal point(s) R. The injection and withdrawal points thus define three successive main operating zones: Zones I, II, and III. In this embodiment, a large amount of eluate relative to the polymer solution is generally required to maximize the separation. For example, this mode of operation in an open circuit requires a volumetric flow ratio of eluate to polymer solution of 2.0 to 50.0, preferably 5.0 to 20.0, and in practice even 5.0 to 10.0.

[0099] When the n fixed beds of the train under consideration in step b) are operated in a closed loop, the eluate is introduced at eluate injection point(s) S, the crude or optionally clarified polymer solution is introduced at polymer solution injection point(s) F, the extract is withdrawn at extract withdrawal point(s) E, and the raffinate is withdrawn at raffinate withdrawal point(s) R, with at least a portion of the introduced eluate advantageously remaining circulating within the closed loop of the n beds (the expression used is then eluate recycle). In this embodiment, the injection and withdrawal points then define four successive main operating zones: zones I, II, III, and IV, with zone IV being referred to as the zone for eluate regeneration and recycle. In this particular embodiment, the eluate supply requirement (i.e., the amount of eluate introduced at S) is advantageously much smaller than in the case of an open-circuit operating mode, ensuring efficient separation. For example, this mode of operation in closed loop requires a ratio of volumetric flow rate of eluate to polymer solution of 0.1 to 10, preferably 0.2 to 5.0, and in practice even 0.8 to 2.0.

[0100] Advantageously, in the case of a closed loop of n fixed beds, the n beds of size-exclusion solids are distributed in zones I to IV according to a configuration preferably referred to as being of the a / b / c / d type, the distribution of the beds of size-exclusion solids in zones I to IV relative to the total number n of beds of size-exclusion solids being: - a is the number of beds of size-excluded solids in zone I, - b is the number of beds of size-excluded solids in zone II, - c is the number of beds of size-excluded solids in zone III, - d is the number of beds of size-excluded solids in zone IV, where: - a = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30), -b=(n*0.15)*(1±0.40, preferably 1±0.30), -c=(n*0.25)*(1±0.40, preferably 1±0.30), and -d = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30) It is as if.

[0101] It will be clear to those skilled in the art that the sum of the number of fixed beds in zones I, II, III and IV (i.e., a+b+c+d) is advantageously equal to n, the total number of fixed beds in the train of fixed beds considered in operation. Thus, a 6 / 3 / 4 / 2 configuration means that there are 15 fixed beds of size-excluded solids divided into 6 fixed beds in zone I, 3 fixed beds in zone II, 4 fixed beds in zone III, and 2 beds in zone IV.

[0102] Very advantageously, the size exclusion is determined by the weight of size-excluded solids per unit volume of bed (i.e., per m of bed) 3 The packing density of each of the n fixed beds of size-excluded solids, expressed in kg of solids per m, is between 100 and 1500 kg / m 3 , preferably 300 to 1000 kg / m 3 , preferentially 400-800 kg / m 3 It can change.

[0103] According to the invention, the injection points F and S and the withdrawal points E and R are shifted over time by one bed of size-exclusion solids according to a frequency determined by a predetermined transfer period. A transfer period can be defined as the period between two successive displacements (or shifts) of the injection and withdrawal points by one fixed bed. The periodic displacements (or shifts) of the injection points F and S and the withdrawal points E and R can be carried out synchronously or asynchronously, the latter case (asynchronous) being known under the name Varicol®. The periodic displacement of the injection and withdrawal points along the entire n number of fixed beds makes it possible in particular to define an operating cycle and also advantageously a cycle time corresponding to the period required for the injection and withdrawal points to return to their initial positions, i.e., a cycle time corresponding to the number n of beds multiplied by the transfer period.

[0104] When n fixed beds of exclusion solids are operated in a closed loop, the operating cycle therefore advantageously includes as many changeover periods as there are beds of size exclusion solids in the closed separation loop, for example, the operating cycle of a train containing 12 fixed beds of size exclusion solids includes 12 changeover periods.

[0105] Thus, in a preferred embodiment in which the n fixed beds of rejected solids of the train under consideration operate in a closed loop, the transfer periods are preferably adjusted to define cycle times corresponding to the time required for the injection and withdrawal points to return to their initial positions, between 1 and 600 minutes, preferably between 5 and 200 minutes, and in a preferred manner between 10 and 90 minutes. Such cycle times contribute to the efficiency of the separation by size exclusion of the PVC resin and impurities present in the polymer solution feeding the extraction stage b).

[0106] In the case of an embodiment in which the n fixed beds operate in an open circuit (i.e., all are withdrawn together with the extract and raffinate), the cycle time may also be from 1 minute to 600 minutes, preferably from 5 minutes to 200 minutes, and in a preferred manner from 10 minutes to 90 minutes.

[0107] The displacement of the injection points F and S and the withdrawal points E and R may be carried out by the installation of a series of open / close valves controlled by an automatic sequence, or equally by the installation of a single rotary valve.

[0108] In general, the liquid in the fixed beds advantageously flows from bed i to bed i+1, where i is an integer between 1 and n, the total number of fixed beds, i.e., from upstream to downstream. This flow may be referred to as downward liquid flow, even if a pump(s) is required (especially between the nth bed and the first bed in closed-loop operation, where n beds are in a column). At the time of reassignment (or displacement of the injection and withdrawal points), the feed and withdrawal points are displaced by a bed located downstream of the preceding bed, thus creating / simulating a countercurrent liquid flow, optionally referred to as upward liquid flow. A stop flow rate can then be defined when the two countercurrent liquid flow rates are equal, i.e., when the downward liquid flow rate is equal to the upward liquid flow rate. This stop flow rate can be calculated by dividing the interparticle volume of the size-excluded solids in the bed by the reassignment period, and the interparticle volume of the size-excluded solids in the bed is a function of the packing density of the fixed bed of size-excluded solids and the particle density of the size-excluded solids. More specifically, the intergranular volume of the size-excluded solid (V( 粒間 )) can be calculated by the following formula:

[0109] V (粒間) =V (床) ×(1-d (充填) / d (粒) )+V dead where: V (粒間) : Intergranular volume of size-excluded solids in the bed (m 3 ), V (床) : Geometric volume of floor (m 3 ), d (充填) : the true packed density of the size-excluded solids, i.e. the packed density of the size-excluded solids in the bed (kg / m), corresponding to the weight of said size-excluded solids per unit volume of the bed 3 As a first approach, it can be analogized to the tapped density, which consists of the weight of a solid that occupies a given volume after tapping said solid by vibration, according to principles derived from standards D4164 and D4180, which apply in the case of catalysts.

[0110] d(粒) : Particle density (kg / m) of size-excluded solids, typically measured by mercury porosimetry 3 ), V dead : The volume (m) of the device through which no size-excluded solids flow but which is subject to associated fluids, especially polymer solutions. 3 ) (e.g., volume of the line upstream, downstream, etc.).

[0111] The stop flow rate, which is a volumetric flow rate, makes it possible to calculate dimensionless parameters, particularly for zones II and IV, such as the ratio of the volumetric flow rate of zone II to the stop flow rate and the ratio of the volumetric flow rate of zone IV to the stop flow rate. Preferably, the ratio of the volumetric flow rate of zone IV divided by the stop flow rate is less than or equal to 2, preferentially 0.5 to 1.5, and more preferably still 0.8 to 1.0. Preferably, the ratio of the volumetric flow rate of zone II divided by the stop flow rate is 0.5 to 3.0, preferentially 0.9 to 1.5, and preferably 1.0 to 1.25. The stop flow rate thus makes it possible to adjust the extraction step b) and thus the efficiency of the separation.

[0112] Furthermore, very advantageously, the superficial velocity in the fixed bed of said operating zone, which corresponds to the volumetric flow rate in the zone under consideration divided by the cross section of the operating zone (i.e. of the column in which the bed of said zone under consideration is located), can be adjusted so that this superficial velocity is between 0.01 and 10.0 cm / s, preferentially between 0.05 and 2.5 cm / s. Adjusting the superficial velocity in the fixed bed advantageously makes it possible to adjust the operation of the column of fixed beds of the extraction stage in order to control the attrition of the particles, in particular of the size-excluded solids, and thus to avoid large pressure drops (encountered in particular at high velocities) and / or dispersion problems (encountered in particular at low velocities).

[0113] Preferably, the size exclusion extraction step of step b) is carried out at a temperature between room temperature and 200°C, preferably between 20°C and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and advantageously at a pressure between atmospheric pressure and 11.0 MPa absolute, preferably between 0.1 MPa absolute and 11.0 MPa absolute, preferably between 0.1 MPa absolute and 5.0 MPa absolute, more preferably between 0.1 MPa absolute and 2.0 MPa absolute. Under these operating conditions, the PVC resin is dissolved in the dissolution solvent and optionally in the elution liquid, the latter (i.e., the dissolution solvent and the elution liquid) being at least partly in liquid form. Preferably, the temperature and pressure conditions of step b) are the same as those of the dissolution step a).

[0114] Stage b) of extraction by size exclusion thus makes it possible to recover at least one extract containing at least partially, preferably completely, the impurities present in the polymer solution fed to said stage b), and at least one raffinate comprising a polymer solution from which the impurities have been at least partially, preferably completely removed. The raffinate recovered at the end of the stage of extraction by size exclusion constitutes at least partially, preferably completely, a purified polymer solution. This purified polymer solution is then preferably at least partially, preferably completely, sent to stage c) of polymer-solvent separation. However, if necessary, the purified polymer solution may be sent to other optional purification stages in order to optimize, if necessary, the purification of the target PVC resin. This stage of extraction by size exclusion therefore makes it possible to efficiently and continuously separate impurities, in particular soluble impurities, from a crude or optionally clarified polymer solution comprising PVC resin(s) dissolved in a dissolution solvent.

[0115] Extraction by size exclusion, especially in the case of a fixed-bed closed loop, allows for the efficient separation of impurities from the PVC polymer in a continuous mode, which makes it possible to limit the effort required to operate the stage while facilitating operation. It also allows for a high productivity, especially compared to size exclusion chromatography operation in batch mode, while providing a relatively low consumption of eluent.

[0116] Polymer-solvent separation step c) According to the invention, the method comprises a step c) of polymer-solvent separation of the purified polymer solution to obtain at least one stream of at least one purified PVC polymer and at least one fraction of at least one solvent comprising the dissolution solvent.

[0117] Stage c) of polymer-solvent separation advantageously implements at least one solvent recovery section, preferably between 1 and 5 solvent recovery sections.

[0118] Advantageously, step c) is fed by the purified polymer solution obtained at the end of step b) or by the final purified polymer solution resulting from an additional purification step, optionally located downstream of step b) of extraction by size exclusion.

[0119] Thus, stage c) of polymer-solvent separation has the main purpose of separating the dissolving solvent and optionally the eluate at least partially, preferably for the most part, from the polymer solution fed to stage c), more particularly the PVC polymer(s) contained in the purified polymer solution or, optionally, the final purified polymer solution resulting from an additional purification stage, in order to recover at least one PVC polymer from which the dissolving solvent and optionally the eluate still present in the polymer solution fed to stage c) have been at least partially, preferably for the most part, and preferentially completely removed. The term "for the most part" is to be understood to mean the removal of at least 50% by weight, preferentially at least 70% by weight, in a preferred manner at least 90% by weight, more preferably at least 95% by weight, very preferentially at least 99% by weight, indeed even at least 99.9% by weight, of the solvent(s) contained in the purified polymer solution (i.e. the dissolving solvent and optionally the eluate) relative to the weight of the solvent(s) contained in the purified polymer solution fed to stage c), in particular the dissolving solvent and optionally the eluate contained in said purified polymer solution. Any method of solvent(s) / polymer(s) separation known to those skilled in the art can be carried out, in particular any method that allows a phase change of the polymer(s) and / or solvent(s). The solvent(s) can be separated, for example, by precipitation or crystallization of the polymer, evaporation of the solvent, flash devolatilization, atomization (high pressure jet, rotary atomizer, two-fluid nozzle, ultrasonic atomizer), stripping, phase separation, extrusion, separation by density difference, in particular by sedimentation or centrifugation, etc.

[0120] The stream of at least one purified PVC polymer thus obtained may correspond to a concentrated polymer solution or to at least one purified PVC resin in solid form. Preferably, stage c) of the polymer-solvent separation additionally comprises a conditioning section for conditioning the at least one purified PVC resin in solid form, more particularly in the form of a powder, beads or granules.

[0121] Stage c) of polymer-solvent separation also aims at at least partially, preferably for the most part, and preferentially completely, recovering the solvent(s) contained in the purified polymer solution fed to stage c), in particular the dissolution solvent and optionally the eluate. Stage c) of polymer-solvent separation also aims, optionally, to purify and recycle the recovered solvent fraction, in particular upstream of dissolution stage a). The term "for the most part" should be understood to mean at least 50% by weight, preferentially at least 70% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight, relative to the weight of the solvent(s) contained in the purified polymer solution fed to stage c).

[0122] Advantageously, stage c) of polymer-solvent separation implements at least one solvent recovery section, the latter preferably comprising equipment operated at different temperatures and different pressures with the aim of obtaining at least one solvent fraction and one purified polymer fraction.

[0123] The process according to the invention thus allows for the efficient and continuous recovery of PVC polymer from plastic feedstocks with high productivity and a limited number of operations. Very advantageously, the process according to the invention makes it possible, starting from any type of PVC-based plastic feedstock, to obtain a PVC polymer stream exhibiting a high purity, preferably greater than 90%, preferably greater than 95%, preferentially greater than 99%, and more preferably still strictly greater than 99.9% (weight of PVC polymer relative to the total weight of the purified stream recovered). Another advantage of the process according to the invention also lies in the fact that it allows for the efficient separation of impurities, in particular additives, present in the plastic feedstock, while allowing for a reasonable consumption of solvents, in particular dissolving solvents and eluates, and for energy consumption that is lower than that required for more conventional "thermal" separations, such as crystallization. The process according to the invention therefore makes it possible to obtain a purified PVC polymer stream that is less colored than the plastic feedstock being treated, practically even colorless, and that is very advantageously deodorized. More specifically, the process according to the invention makes it possible to obtain a purified PVC polymer stream from which at least some, preferably all, of the impurities, such as additives, present in the plastic feedstock have been removed, and from which solvents, in particular dissolution solvents and eluates, have been at least partially, indeed even completely, removed.

[0124] The process according to the invention therefore advantageously makes it possible to obtain a purified PVC polymer stream having a content of solvents, in particular dissolving solvents or eluates, of not more than 10% by weight, preferably not more than 5% by weight, preferentially not more than 1.0% by weight and even more preferably not more than 0.1% by weight, and a content of impurities very advantageously not more than 10% by weight, preferably not more than 5% by weight, preferentially not more than 1.0% by weight and even more preferably not more than 0.5% by weight and indeed not more than 0.1% by weight, the percentages being given relative to the total weight of the purified PVC polymer stream. In particular, the purified PVC polymer stream obtained very advantageously has the following contents: - less than 0.1% by weight of phthalates subject to authorisation under the European REACH Regulation (Annex XIV of Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular less than 0.1% by weight of phthalates selected from the list consisting of the following phthalates, alone or in mixtures: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, isopentyl n-pentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, -elemental lead contained in additives of the metal stabilizer type that have been assessed in the context of the REACH Regulation and are subject to the restrictions (Annex XV) detailed and adopted by the ECHA Risk Assessment Committee (RAC) and the Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018, in particular a content of said lead of less than 0.1% by weight; - the element cadmium contained in additives of the metal stabilizer type prohibited by the REACH Regulation as amended by Annex XVII (Regulation 494 / 2011 of 20 May 2011), in particular a content of less than 0.1% by weight, preferably less than 0.01% by weight, of said cadmium.

[0125] Device for extraction by size exclusion The invention also relates to a device for extraction by size exclusion suitable for separating PVC polymer from impurities contained in the polymer solution, the device comprising: - n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferentially between 8 and 24, very preferentially between 8 and 21, and in a preferred manner between 12 and 15, said size exclusion solids preferably having a volume average pore diameter between 1 nm and 500 nm, preferably between 2 nm and 100 nm, preferentially between 2 nm and 50 nm, preferentially between 3 nm and 30 nm, and in a preferred manner being silica gel, grafted silica, carbon molecular sieves or mixtures thereof, n fixed beds of size exclusion solids distributed in one or more columns, preferably M columns, where M is an integer between 1 and the total number n of fixed beds of exclusion solids, and the n beds are connected in series, preferably in a closed loop; N injection systems, preferably different from one another, for the polymer solution, N injection systems, preferably different from one another, for the eluate, N withdrawal systems, preferably different from one another, for the extract, and N withdrawal systems, preferably different from one another, for the raffinate, where N is an integer preferably equal to n, said injection and withdrawal systems being located between two successive beds or optionally upstream of the first bed, the injection and withdrawal systems of the polymer solution and eluate, and / or the extract and raffinate, located in one and the same position, i.e. between the two actual successive beds or optionally upstream of the first bed, being different or identical (the term "identical" should be understood to mean that the system of valves may allow either the introduction of the polymer solution or the eluate, or the withdrawal of one or the other stream, i.e. the extract or the raffinate), and Equipped with each injection and withdrawal system comprises at least one valve suitable for allowing or disabling the passage of the polymer solution and / or eluate and / or extract and / or raffinate streams, preferably i) a series of open / close valves controlled by an automatic sequence, or ii) a single rotary valve, whereby At a time t, an injection point for the polymer solution, an injection point for the eluate, a withdrawal point for the extract and a withdrawal point for the raffinate are defined, said injection points and withdrawal points being different from one another, and comprising at least three, preferably four, consecutive main operating zones of n fixed beds: - a zone I of elution of impurities, which is comprised between the injection point of the eluate and the withdrawal point of the extract; a zone II of elution of at least one PVC polymer, which is comprised between the extraction point of the extract and the injection point of the polymer solution; a zone III of retention of impurities contained between the injection point of the polymer solution and the withdrawal point of the raffinate, and - optionally determining a zone IV comprised between the withdrawal point of the raffinate and the injection point of the eluate; It also allows for the shifting of injection and withdrawal points over time, synchronously or asynchronously, with one fixed bed of size-excluded solids per transfer period, according to a frequency determined by the given transfer period.

[0126] Device for processing plastic feedstock Such a device for extraction by size exclusion can be incorporated into a more comprehensive device for the processing of plastic feedstocks to obtain a stream of purified PVC polymer, which device: - dissolving means for contacting a plastic feedstock with a dissolving solvent to at least partially dissolve said plastic feedstock in said dissolving solvent, said dissolving means being any type of equipment for contacting a plastic feedstock with a dissolving solvent to dissolve it in the dissolving solvent and obtaining a crude polymer solution; - optionally solid-liquid separation means, in particular any type of equipment for solid-liquid separation, optionally suitable for separating insoluble materials in suspension in the crude polymer solution, at least one device for extraction by size exclusion according to the invention and, as described above, advantageously connected to said dissolution means for contacting and dissolving or optionally to at least one of said solid-liquid separation means, - means for separating the dissolution solvent and optionally the eluate from the stream of purified PVC polymer, in particular any type of equipment for separating the dissolution solvent and optionally the eluate from the stream of optionally purified PVC polymer, advantageously connected to at least one device for extraction by size exclusion as described above, Equipped with.

[0127] Said device for treating a PVC feedstock to obtain a stream of purified PVC polymer also advantageously comprises transport means between said means and the device.

[0128] Such a device highly advantageously allows for the recovery of PVC polymer in high purity from PVC-based plastic feedstocks that may contain numerous impurities.

[0129] The following examples and figures illustrate the invention and in particular certain embodiments of the invention without limiting its scope.

[0130] Example Example 1 This example is the result of a digital simulation based on experiments carried out in the laboratory.

[0131] The feedstock to be treated consisted of poly(vinyl chloride) or PVC resin (55 wt%) with molar mass MW = 120000 g / mol and didecyl phthalate (DiDP) additive (45 wt%), percentages given by weight relative to the total weight of the feedstock.

[0132] The feedstock is first dissolved in diethyl ketone (DEK) at 100° C. and atmospheric pressure to form a homogeneous crude polymer solution containing 80 wt % DEK and 20 wt % feedstock (polymer and additives).

[0133] The crude polymer solution obtained is introduced into a simulated moving bed system containing 15 fixed beds of silica gel, distributed according to a 6 / 3 / 4 / 2 configuration (see Figure 1). The eluent is diethyl ketone (DEK).

[0134] Silica gel exhibits the following properties:

[0135] -Bead diameter = 500 μm -Pore size=6~10nm -Pore volume = 0.50 ml / g of solid - Packing density = solids 530kg / bed m 3 Each bed is modeled by a 1D fixed piston bed model with axial dispersion and a Fick model for intragranular migration. The radius of gyration for PVC is estimated to be 39 nm, so the polymer is considered to reside exclusively in the extragranular phase. Additives and solvents have radii of gyration less than 1 nm and can therefore diffuse into the intragranular porosity. The medium within the bed is considered isothermal (100 °C) and the density of the polymer solution is constant (800 kg / m 3 ) is thought to be the case.

[0136] The extraction is adjusted using the following settings:

[0137] - Cycle time = 15 minutes, i.e. 60 seconds changeover period -Volumetric flow rate of eluate to volumetric flow rate of polymer solution S / F = 1.32 -Zone IV flow rate / stop flow rate = 0.97 -Zone II flow rate / stop flow rate = 1.05 -Maximum sky speed=1.43cm / s The concentration profiles obtained for PVC and additives by simulation are shown in Figure 3, which shows the concentration profile of PVC (solid line) and that of DiDP (dotted line). By convention, the injection of eluate occurs just upstream of bed 1. The concentrations along the entire length of the bed are given as the weight percent of the following compound, i.e., PVC or additive, relative to the weight of DEK.

[0138] From Figure 3 it is clear that the PVC, which does not explore the intragranular porosity, is entrained towards the raffinate and drawn off between beds 13 and 14. The additive DiDP, being smaller, diffuses into the intragranular porosity and is entrained towards the extract by drawing off between beds 6 and 7.

[0139] The extraction carried out in a simulated moving bed makes it possible to obtain the following performance qualities: - purity of separated PVC = 99.93 wt.% (this corresponds to the weight or weight flow rate of PVC in the raffinate relative to the total weight or total weight flow rate of the combination of PVC and additives in the raffinate, excluding the solvent DEK); - Yield of separated PVC = 99.95% (this corresponds to the weight flow rate of PVC withdrawn in the raffinate divided by the weight flow rate of PVC withdrawn in the extract + raffinate combination); Productivity = 149 kg / h / bed m of PVC extracted in the raffinate 3 .

[0140] The raffinate at the outlet of the simulated moving bed for extraction by size exclusion can then be recovered and sent to a polymer-solvent separation section, in particular to a section for evaporation of the solvent DEK.

Claims

1. 1. A process for recovering at least one purified PVC polymer stream from a plastic feedstock, comprising: a) a dissolution step comprising contacting said plastic feedstock with a dissolution solvent to obtain at least one crude polymer solution; b') optionally separating insoluble materials from said crude polymer solution obtained at the end of step a) to obtain at least one clarified polymer solution; b) a step of extraction by size exclusion of said crude polymer solution obtained at the end of step a) or optionally of said clarified polymer solution obtained at the end of step b') in order to obtain a purified polymer solution, the size exclusion extraction step implements at least one train of n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, and the n fixed beds of size exclusion solids being in series; The train of fixed beds of step b) is fed with a crude or optionally clarified polymer solution at at least one injection point F of the polymer solution and with the effluent at at least one injection point S of the effluent, The train of fixed beds of step b) implements at least one withdrawal of the extract at at least one withdrawal point E of the extract and at least one withdrawal of the raffinate at at least one withdrawal point R of the raffinate, The injection points of the polymer solution and the eluate, and the withdrawal points of the extract and the raffinate are different from each other and are located in at least three, preferably four, successive main operating zones of the n fixed beds: a zone I of elution of the impurities, located between the injection point of the eluate and the withdrawal point of the extract; - at least one zone II of elution of PVC polymer located between the withdrawal point of the extract and the injection point of the polymer solution; a zone III of retention of the impurities located between the injection point of the polymer solution and the withdrawal point of the raffinate, and optionally distributed to define a zone IV located between the withdrawal point of the raffinate and the injection point of the eluate, the injection point and the withdrawal point are shifted over time by one fixed bed of size exclusion solids according to a frequency determined by a predetermined turnover period; an extraction step in which the raffinate is recovered to at least partially constitute the purified polymer solution; c) a solvent-polymer separation step for separating the purified polymer solution into purified PVC polymer and at least one solvent fraction stream comprising dissolving solvent; A method comprising:

2. 2. The method according to claim 1, wherein the dissolution solvent is an organic solvent selected from ketones, amides, esters, ethers, chlorinated solvents, sulfur-based solvents, nitrogen-based solvents, hydrocarbons and mixtures thereof, preferably methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, N,N-diethylformamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, methoxycyclopentane, tetrahydrofuran, dichloromethane, dimethyl sulfoxide, xylene, isohexane, dihydrolevoglucosenone or silane and mixtures thereof, very preferably diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, γ-butyrolactone, γ-valerolactone and mixtures thereof.

3. The method according to claim 1 or 2, wherein the eluent is an organic solvent of the same chemical nature as the dissolution solvent.

4. 4. The method according to claim 1, wherein step b) of extraction by size exclusion implements at least one train of n fixed beds of size exclusion solids, n being an integer between 4 and 30, preferably between 12 and 15.

5. 5. The method according to any one of claims 1 to 4, wherein the size-excluded solid is a porous solid having a volume-average pore diameter of from 1 nm to 500 nm, preferably from 2 nm to 100 nm, preferentially from 2 nm to 50 nm, preferentially from 3 nm to 30 nm.

6. The method of any one of claims 1 to 5, wherein the size exclusion solid comprises silica gel, grafted silica, carbon molecular sieve, or a mixture thereof.

7. 7. The method according to any one of claims 1 to 6, wherein the eluate and the polymer solution are fed in step b) according to a ratio of the volumetric flow rate of the eluate to the volumetric flow rate of the polymer solution of between 0.1 and 50.0, preferably between 0.2 and 10.0, preferably between 0.5 and 5.0, preferentially between 0.8 and 2.

0.

8. 8. The process according to claim 1, wherein the injection points of the polymer solution and the eluate and the withdrawal points of the extract and the raffinate are located between two successive beds or, optionally, upstream of the first bed.

9. The n beds of size-exclusion solids operate in a closed loop and are distributed among four main operating zones, zones I to IV, according to a configuration referred to as being of the a / b / c / d type, and the distribution of the beds of size-exclusion solids in zones I to IV relative to the total number n of beds of size-exclusion solids is preferably: - a is the number of beds of size-excluded solids in zone I, - b is the number of beds of size-excluded solids in zone II, -c is the number of beds of size-excluded solids in zone III; - d is the number of beds of size-excluded solids in zone IV; where: - a = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30), -b = (n * 0.15) * (1 ± 0.40, preferably 1 ± 0.30), -c=(n*0.25)*(1±0.40, preferably 1±0.30), and -d = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30) The method according to any one of claims 1 to 8, wherein

10. 10. The method according to any one of claims 1 to 9, wherein the n beds are in a closed loop and the transfer periods are preferably adjusted to define a cycle time corresponding to the time required for the injection and withdrawal points to return to their initial positions, between 1 minute and 600 minutes, preferably between 5 minutes and 200 minutes, in a preferred manner between 10 minutes and 90 minutes.

11. 11. The method according to any one of claims 1 to 10, wherein step a) is carried out at a dissolution temperature of from 20°C to 200°C, preferably from 40°C to 180°C, preferentially from 60°C to 150°C, and at a dissolution pressure of from 0.1 to 11.0 MPa absolute, preferably from 0.1 to 5.0 MPa absolute, preferentially from 0.1 to 2.0 MPa absolute.

12. 12. The method according to any one of the preceding claims, wherein the weight of PVC polymer of the plastic feedstock fed in step a) represents from 2% to 30% by weight, preferably from 5% to 20% by weight, in a preferred manner from 10% to 15% by weight, relative to the weight of the dissolution solvent.

13. 13. The method according to any one of claims 1 to 12, wherein step b) is carried out at a temperature between 20°C and 200°C, preferably between 40°C and 180°C, preferentially between 60°C and 150°C, and at a pressure between 0.1 and 11.0 MPa absolute, preferably between 0.1 and 5.0 MPa absolute, preferentially between 0.1 and 2.0 MPa absolute.

14. 1. A device for the extraction by size exclusion of PVC polymers from polymer solutions, comprising: - n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, in a preferred manner between 12 and 15, said size exclusion solids preferably having a volume average pore diameter of between 1 and 500 nm, preferably between 2 and 100 nm, preferentially between 2 and 50 nm, preferentially between 3 and 30 nm, in a preferred manner preferably being silica gel, grafted silica, carbon molecular sieves or mixtures thereof, n fixed beds of size exclusion solids distributed in one or more columns, the n beds being connected in series, preferably in a closed loop; N injection systems for the polymer solution, N injection systems for the eluate, N withdrawal systems for the extract and N withdrawal systems for the raffinate, N being an integer preferably equal to n, said injection systems and said withdrawal systems being located between two successive beds or, optionally, upstream of said first bed, an injection system and a withdrawal system for the polymer solution and the eluate, and / or the withdrawal system for the extract and the raffinate, located in one and the same position, being different or the same; Equipped with each injection and withdrawal system is equipped with a valve suitable for allowing or disabling the passage of the polymer solution and / or eluate and / or extract and / or raffinate streams, preferably a series of open / close valves controlled by an automatic sequence, or a single rotary valve, whereby At a time t, an injection point for the polymer solution, an injection point for the eluate, a withdrawal point for the extract and a withdrawal point for the raffinate are defined, said injection points and said withdrawal points being different from one another, and at least three, preferably four, consecutive main operating zones of said n fixed beds: a zone I of elution of said impurities, comprised between the injection point of said eluate and the withdrawal point of said extract; a zone II of elution of at least one PVC polymer, comprised between the withdrawal point of the extract and the injection point of the polymer solution; a zone III of retention of said impurities contained between the injection point of said polymer solution and the withdrawal point of said raffinate, and - optionally determining a zone IV comprised between the withdrawal point of the raffinate and the injection point of the eluate, - a device that also allows the shifting of said injection and withdrawal points over time, synchronously or asynchronously, according to a frequency determined by the given transfer periods, by one fixed bed of size exclusion solids per transfer period.

15. 1. A device for the processing of a plastic feedstock to obtain a stream of purified PVC polymer, comprising: - dissolving means for contacting said plastic feedstock with said dissolving solvent to at least partially dissolve said plastic feedstock in said dissolving solvent and obtain a crude polymer solution; - optionally solid-liquid separation means suitable for separating insoluble materials in suspension in said crude polymer solution; - at least one device for extraction by size exclusion according to claim 14, - means for separating said dissolution solvent and optionally said eluate from a stream of purified PVC polymer; A device comprising:

Images