TW202432689A - Process for the recycling of waste based on pvc plastics implementing a device for the extraction of polymer chains in a size-exclusion simulated moving bed - Google Patents

Abstract

The present invention relates to a process for the recovery of a stream of PVC, comprising: a) a stage of dissolution by bringing a plastic feedstock into contact with a dissolution solvent; then (b) a stage of extraction by size exclusion, implementing fixed beds of a size exclusion solid in series and fed with the polymer solution resulting from (a) at an injection point (F) and with an eluent at an injection point (S) and implementing a withdrawal of an extract at a withdrawal point (E) and a withdrawal of a raffinate comprising a purified polymer solution at a withdrawal point (R), the injection and withdrawal points being distinct and shifted over time by one bed according to a predetermined frequency; then (c) a stage of polymer-solvent separation, in order to obtain a stream of purified PVC. The present invention also relates to a device for carrying out stage b) and to a device for carrying out the recovery process.

Description

Method for recycling PVC plastic-based waste using a device for extracting polymer chains in a size exclusion simulated moving bed

The invention relates to the field of recycling of poly(vinyl chloride) (PVC)-based plastics, and in particular to a method for treating plastic raw materials resulting from PVC-based plastic waste in order to obtain at least one purified PVC polymer stream, which can be reused for the manufacture of new plastic objects. More precisely, the invention relates to a method for treating plastic raw materials, in particular plastic raw materials resulting from PVC-based plastic waste, comprising dissolving at least one PVC polymer in a solvent, subjecting the polymer solution thus obtained to at least one purification stage and separating at least one PVC polymer and at least one solvent in order to recover at least one purified PVC polymer stream for subsequent upgrading.

By definition, a plastic is a mixture of a base polymer material and various additives, which can be molded or shaped (generally under heat and/or pressure) to produce a semi-finished product or an object. A generally accepted practice is to name the plastic after the polymer from which it is made. Thus, the plastic poly(vinyl chloride) (PVC) actually corresponds to a combination of a PVC polymer (sometimes indicated as "PVC resin" in the remainder of this specification) and various additives selected according to the desired functionality of the plastic. These additives can be organic (macro) molecules or inorganic (nano) particles and are used according to the properties required of the PVC plastic: heat resistance, light resistance or resistance to mechanical stress, flexibility, processability, colorability and similar properties.

There are several methods of recycling PVC plastics: by the "known" method of simple mechanical recycling of the plastic, by methods involving modification of its composition (optionally chemical transformation of the starting ingredients) and similar methods.

Since the mid-20th century, the recycling of PVC plastics involving physical processes has been the subject of numerous studies whose objectives are, in a first stage, to dissolve the PVC resin with additives in different proportions and then, in a second stage, to recover the resin according to various methods (precipitation, evaporation and similar methods) in the presence of all or some of the soluble additives. By way of example, mention is made of patents EP 0 945 481 and EP 1 268 628 on the one hand, and patent EP 2 276 801 on the other hand, which respectively aim at recycling various PVC-based objects (flexible or rigid pipes, window frames, cables and the like) and in particular fiber-reinforced PVC-based objects (tarpaulins, board coverings and the like), according to a process employing a dissolution phase of the PVC resin and of soluble additives in an organic solvent, followed by a steam precipitation phase, making it possible to recover the PVC resin and a large part of the additives.

However, it is not always necessary to keep these additives in the PVC thus recovered for recycling. For example, changes in the regulations relating to them over time have an impact. Thus, some plasticizers belonging to the phthalate family, which were widely used in particular for the formulation of "flexible" PVC about 40 years ago, were gradually authorized in Europe on the basis of the REACH Regulation, which since the end of 2006 aims to ensure the safety of the manufacture and use of chemicals in European industry, and were eventually gradually excluded from the list of additives allowed for use (Annex XIV and XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006). Following the same trend, the amendment to Annex XVII (Regulation 494/2011 of May 20, 2011) prohibits the use of Cd-based metal stabilizers in PVC plastic formulations, especially "rigid" PVC plastics, known as PVC compounds. Likewise, lead-based stabilizers are restricted (Annex XV), which were detailed and formally adopted by ECHA's Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018. Thus, several series of additives have been restricted in their areas of use over the past 20 years; a phenomenon that is likely to be amplified in the coming years.

These new regulations now prohibit the presence of many additives in recycled starting substances (RSM), in particular by establishing very strict limit values in terms of the authorized amounts (e.g. the amount of phthalates authorized and considered as a mixture must not exceed 1000 ppm of the final composition of the relevant RSM). Taking into account the generally long service life of PVC-based objects (decades), PVC-based objects formulated before the end of 2006 and now at the end of their service life may not be recycled by regeneration methods, resulting in the presence of these banned additives, whether these methods are known, such as mechanical recycling methods, or unknown, as in the example of the dissolution/precipitation method mentioned above.

This highlights the need to move towards a "circular" economy, producing purified polymer resins (i.e. as free of additives as possible) from plastic waste to reuse virgin resins equivalent to petroleum-derived ones as RSM, taking into account current and future regulatory constraints on the one hand and the limitations of fossil resources on the other hand, as a major issue today in responding to the environmental challenges of the 21st century.

Many methods have been devised to make it possible to extract various series of additives from plastics, including in particular PVC plastics. By way of example and not exhaustive, patents EP 1 311 599 and JP2007191586 both propose a first stage of dissolving PVC resin and at least one series of additives from the group consisting of phthalate-type plasticizers, flame retardants or lead-based metal stabilizers with a first organic solvent, followed by one or more stages of liquid-liquid extraction of at least one series of additives from the previously obtained solution using at least one other solvent (organic and/or aqueous) different from the first organic solvent. Patent JP2007092035 discloses another possible embodiment, in which the PVC resin and at least phthalate-type additives are dissolved by using a solvent mixture under supercritical conditions, and the phthalates are recovered from this same solvent mixture after the supercritical conditions are "broken", followed by a stage of extracting the lead-based additives from the residual solid phase containing the PVC resin by using at least one liquid surfactant.

Despite these advances, the removal of all additives from PVC plastics, and even more from PVC-based plastic mixtures resulting from various formulations, such as components of post-consumer waste, still represents a scientific and industrial challenge today. The above-mentioned dissolution stage is firstly advantageous for removing additives that are partially insoluble in the chosen solvent. On the other hand, additives that are soluble in the solvent are particularly difficult to separate, in particular due to their very different chemical properties. A first approach may consist in extracting the additives based on physicochemical properties, such as their polarity, their solubility, their boiling point, their density and the like, but given the great variety of additives present, this may lead to an increase in purification stages. Furthermore, obtaining at least one purified PVC polymer stream is generally not a sufficient condition to ensure the economic viability of a recycling process for PVC-based objects. The main reason often cited is the difficulty in finding an economically viable balance between the resale costs of the products obtained (equivalent to the added value) and the unit operation costs carried out in the recycling process, all the more so if a large number of separation stages are envisaged. Finally, the processing of plastic raw materials from PVC-based plastic wastes requires the provision of a robust and versatile process in order to take into account the variations of the additives present as a result of the waste source under consideration (in terms of target use and date of production).

Therefore, the present invention proposes another method to solve the above-mentioned problem, which is based on utilizing the size difference between polymer macromolecules and impurity molecules (such as additive molecules), more precisely, the hydrodynamic volume difference.

The invention thus makes it possible, starting from a polymer solution containing at least one PVC polymer dissolved in a dissolution medium and associated soluble additives, to selectively extract the PVC polymer from the medium, whatever the nature of the additives.

Techniques for separation by size standards already exist and are commonly used as an analytical method for determining the molecular weight of polymers. This method, called size exclusion chromatography (SEC), involves a fixed bed implemented in batch operation and comprising several porosity levels. Small molecules explore the fixed bed up to the smallest pores and thus have longer associated dissolution times, whereas large molecules (such as polymers) only pass through the largest pores and exhibit short dissolution times, thus inducing the desired separation. Since additives commonly used in PVC-based plastic formulations exhibit domain sizes that are much smaller than the polymer chains of the PVC resin, the principle of size exclusion chromatography can be applied to purify PVC-based plastics. However, the industrial implementation of methods using this principle is problematic, mainly due to the non-continuous nature of the batch process. Furthermore, the batch mode process would require large consumption of solvent to ensure efficient separation, which directly affects the profitability, productivity and ecological footprint of the process.

The Simulated Moving Bed (SMB) technology is a concept invented in 1961 that makes possible the continuous operation of discontinuous "chromatographic" processes, in particular by adsorption, while ensuring efficient separations, increasing productivity and limiting solvent consumption. There are many industrial references to this technology, in particular adsorption separations, which are 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 bed (or SMB-SEC, i.e. simulated moving bed with size exclusion chromatography) involves the separation of n-alkanes and isoalkanes, the outline of which is described in detail in patent US 2 985 589. Recent publications mention the use of size exclusion simulated moving bed (SMB-SEC) technology for the fractionation of polyethylene glycols of different 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, patent US 6 551 512 proposes a method for separating proteins from liquid compositions such as milk by size exclusion in a simulated moving bed. Finally, a publication mentions the use of SMB-SEC in a method for recycling materials included in the WEEE (waste electrical and electronic equipment) component. WEEE is based on polycarbonate and also contains poly(styrene-co-acetonitrile) (SAN) and additives such as flame retardants. Weeden et al. attempted to separate the latter from a ternary solution of SAN and two flame retardant compounds, resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate), in an acetone-dichloromethane solvent mixture (G. S. Weeden et al., Journal of Chromatography A, 2015, 1422, 99).

The application of the SMB-SEC technology as a method for purifying PVC-based plastic wastes in order to obtain a purified PVC polymer stream making it possible to reuse it as RSM for the manufacture of new plastic objects has never been proposed.

One of the objects of the present invention is therefore to overcome the problems of the prior art and to participate in the recycling of plastics, in particular PVC plastics. More specifically, its object is to provide an efficient, simple and economically viable method for treating all types of PVC raw materials in order to obtain a purified PVC polymer stream that complies with current regulations and can be reused for the manufacture of new plastic objects. Specifically, the present invention seeks to effectively separate impurities from waste PVC plastics and to recover purified PVC resins that can be used for the manufacture of new PVC-based objects, by using a method with a limited number of unit stages, thus making it possible to limit the costs of the process and improve its eco-performance qualities.

Therefore, according to the first aspect, the present invention proposes a method for recovering at least one purified PVC polymer stream from a plastic raw material, which comprises: a) a dissolution stage, which comprises contacting the plastic raw material with a dissolving solvent to obtain at least one crude polymer solution; b') a stage of separating insoluble substances from the crude polymer solution obtained at the end of stage a) as appropriate, to obtain at least one clarified polymer solution; b) a stage of performing size exclusion extraction on the crude polymer solution obtained at the end of stage a) or, as appropriate, on the clarified polymer solution obtained at the end of stage b') to obtain a purified polymer solution, wherein the size exclusion extraction stage implements at least one series of n size exclusion solid fixed beds, n being an integer greater than or equal to 4, and the n size exclusion solid fixed beds are connected in series, the series of fixed beds of stage b) is fed with a crude polymer solution or a clarified polymer solution as the case may be at at least one polymer solution injection point F and is fed with a solvent at at least one solvent injection point S, wherein the series of fixed beds of stage b) implements at least one extract extraction at at least one extract extraction point E and at least one raffinate extraction at at least one raffinate extraction point R, wherein the polymer solution injection point and the solvent injection point as well as the extract extraction point and the raffinate extraction point are different from each other and are distributed so as to determine at least three, preferably four continuous main operating areas of the n fixed beds: - an impurity dissolution zone I, which is located between the solvent injection point and the extract extraction point; - at least one PVC polymer dissolution zone II, which is located between the extract extraction point and the polymer solution injection point; - an impurity retention zone III, which is located between the polymer solution injection point and the extract extraction point; and - an optional zone IV, which is located between the extract extraction point and the solvent injection point, wherein the injection point and the extraction point move a size exclusion solid fixed bed over time according to a frequency determined by a predetermined replacement cycle, wherein the extract is recovered to constitute at least part of the purified polymer solution, c) Solvent-polymer separation stage, which is used to separate the purified polymer solution into a purified PVC polymer stream and at least one solvent portion containing a dissolved solvent.

The advantage of the method of the invention is that it proposes a method for efficiently treating raw materials containing plastics based on PVC, and in particular plastic waste generated by collecting and sorting channels, in order to recover the PVC resins they contain, thus being able to recycle them in all types of applications. This is because the method according to the invention makes it possible to obtain a purified PVC polymer stream which is very advantageously less colored than the plastic raw material, in fact even colorless, and better deodorized. In particular, the purified PVC polymer stream obtained at the end of the process according to the invention advantageously comprises a content of impurities, in particular a content of additives, and a content of solvents, in particular a content of dissolved and/or dissolving solvents, which is negligible or at least low enough for the purified PVC polymer stream to comply with current regulations and to be able to be introduced into any plastic formulation to replace the original PVC resin. For example, the purified PVC polymer stream obtained exhibits (contents expressed as percentages by weight relative to the total weight of the purified PVC polymer stream obtained): - a phthalate content less than 0.1% by weight, as authorized under the European REACH Regulation (Annex XIV to Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006), - an elemental lead content less than 0.1% by weight, - an elemental cadmium content less than 0.1% by weight, preferably less than or equal to 0.01% by weight, - More generally, the impurity content is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight and more preferably less than or equal to 0.5% by weight, in fact even less than or equal to 0.1% by weight, and - More generally, the solvent content is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight and more preferably less than or equal to 0.1% by weight.

Therefore, the method according to the invention proposes a simple process corresponding to a minimum sequence of operations, which makes it possible to remove at least a portion of impurities, in particular at least a portion of additives, from PVC-based plastic waste and to recover at least one purified PVC polymer, thereby enabling the upgrading of PVC plastic waste by recycling the purified PVC polymer.

Another advantage of the invention is that it participates in the recycling of plastics and the conservation of fossil resources by making the upgrading of plastic waste, in particular plastic waste based on PVC, possible. This is because it makes it possible to purify PVC plastic waste in order to obtain a purified PVC polymer stream with a reduced impurity content, which can be reused to form new objects. The purified PVC polymer stream obtained can therefore be used directly in formulations as a mixture with additives such as dyes, pigments, other polymers, instead of or as a mixture with virgin PVC resin, in order to obtain plastic products with usability, aesthetic, mechanical or rheological properties conducive to their reuse and their upgrading.

According to a second aspect, the present invention also relates to a device for extracting PVC polymer from a polymer solution by size exclusion, the device comprising: - n fixed beds of size exclusion solid, n is an integer greater than or equal to 4, preferably between 4 and 30, preferably between 12 and 15, the size exclusion solid has a volume average pore size preferably between 1 nm and 500 nm, preferably between 2 nm and 100 nm, preferably between 2 nm and 50 nm, preferably between 3 nm and 30 nm, and is preferably silica gel, grafted silica, carbon molecular sieve or a mixture thereof, n fixed beds of size exclusion solid are distributed in one or more columns, the n beds are connected in series and preferably in a closed loop, - N polymer solution injection systems, N solvent injection systems, N extract extraction systems and N raffinate extraction systems, N being an integer preferably equal to n, said injection and extraction systems being located between two consecutive beds or, as the case may be, upstream of the first bed, wherein the polymer solution injection system and solvent injection system and/or extract extraction system and raffinate extraction system located at the same position are different or the same, - each injection and extraction system comprises a valve suitable for allowing or not allowing the polymer solution flow and/or solvent flow and/or extract flow and/or raffinate flow to pass, preferably a series of on-off valves or a single rotary valve controlled by an automatic sequence, so as to: - At time t, the polymer solution injection point, solvent injection point, extract extraction point and raffinate extraction point are defined, which are different from each other and determine at least three, preferably four continuous main operating zones of n fixed beds: - impurity dissolution zone I, which is included between the solvent injection point and the extract extraction point; - at least one PVC polymer dissolution zone II, which is included between the extract extraction point and the polymer solution injection point; - impurity retention zone III, which is included between the polymer solution injection point and the raffinate extraction point; and - zone IV, if present, which is included between the raffinate extraction point and the solvent injection point, - And it makes it possible to move the injection point and the extraction point of a size exclusion solid fixed bed synchronously or asynchronously over time per replacement cycle according to the frequency determined by the predetermined replacement cycle.

According to a third aspect, the present invention also relates to a device for treating a plastic raw material to obtain a purified PVC polymer stream, comprising: - a dissolving component for contacting the plastic raw material with a dissolving solvent so as to dissolve the plastic raw material at least partially in the dissolving solvent to obtain a crude polymer solution; - an optional solid-liquid separation component suitable for separating insoluble substances suspended in the crude polymer solution; - at least one size exclusion extraction device according to the present invention; - a component for separating the dissolving solvent and the optional solvent from the purified PVC polymer stream.

The terms are given certain definitions and/or details below, but more details about the objects defined below may be given later in the description.

The term "PVC-based object" is understood to mean an object, typically a consumer object, comprising and preferably consisting of at least one PVC plastic.

The term "polyvinyl chloride plastic", also known as "PVC plastic", should be understood to mean a combination of PVC polymer (also known as PVC resin) and various additives, wherein the additives are selected according to the desired functions of the PVC plastic, and the PVC plastic itself is selected according to the intended application.

PVC polymers are known to be produced by free radical polymerization of vinyl chloride (VCM), which itself is a monomer obtained from chlorine and ethylene. The present invention makes it possible to process any type of PVC plastic raw material and to recycle any grade of PVC polymer.

The additives involved in the composition of PVC plastics can be organic molecules or macromolecules or inorganic (nano) particles and are used according to the properties they impart to the PVC resin. Generally and non-exhaustively, the formulation of PVC plastics involves at least one series of additives, which are described as follows: - Stabilizers, used to limit the degradation of the polymer chain by dehydrochlorination and/or oxidation under the action of heat, light, oxygen and/or mechanical stress. The nature of these stabilizers (metal (Pb, Sn, Ca, Zn, Cd) compounds or organic compounds) depends on the desired properties and therefore on the target application. Some examples of stabilizers frequently used in the past or currently used are mentioned here: lead stearate, dibasic lead stearate, dibasic lead phthalates, zinc stearate, calcium stearate and their analogs, used alone or as a mixture. Costabilizers may also be considered, such as epoxidized oils, - plasticizers, used to induce flexibility, better impact strength and better cold resistance in PVC plastics, the most widely used component of the phthalate family. The latter are obtained by reaction between phthalic anhydride and alcohols with more or less long carbon chains and consist of a benzene nucleus and two carboxylate groups located adjacent to the benzene nucleus. Dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP) constitute examples of phthalates that were or are very widely used. Other non-phthalic plasticizers are currently used, such as bis(2-ethylhexyl) adipate (DEHA) or di-isononyl cyclohexane-1,2-dicarboxylate (DINCH), - lubricants, which are used to control the intermolecular friction forces, either within the polymer itself (internal lubricants, such as stearic acid and its analogs) or between the polymer and the metal wall of the processing tool (external lubricants, such as wax, polyethylene wax and its analogs), - inert fillers, usually inorganic fillers (CaCO ₃ , carbon black, kaolin and its analogs), which act as diluents or improve certain mechanical properties, electrical properties, thermal properties and the like, - dyes and/or pigments (TiO ₂ , carbon black), which is insoluble in the polymer and therefore exists in the form of particles dispersed in the PVC plastic, - impact modifiers, generally polymers (such as polyacrylates) and copolymers (such as MBS, i.e. methacrylate-butadiene-styrene), whose function is to reduce the brittleness of PVC, especially at low temperatures, - other additives: antioxidants, UV inhibitors, biocides, antistatic agents, flame retardants, reinforcing agents and the like.

The term "impurities" is understood to mean all elements other than the PVC resin constituting the plastic raw material, in particular the plastic raw material resulting from the PVC-based plastic waste treated according to the method proposed in the invention. Such impurities correspond at least in part to the additives mentioned and described above. Other types of impurities may be common impurities resulting from the life cycle of PVC-based objects and/or from collection and sorting circuits, indeed even from pre-treatment operations of PVC-based plastic waste. These common impurities may be of metallic, organic or inorganic type. They may be residues of constituent materials (excluding PVC plastics) of PVC-based objects or other objects in contact with PVC-based objects, stains (food, biomass, soil/gravel, adhesives and the like), and the like. Thus and not exclusively, such common impurities may include glass, wood, cardboard, paper, metal, rubber, silicone, plastics other than PVC (such as PET and the like), inorganic elements and the like. Degradation products of additives that may form over time during the service life of PVC-based products are also considered impurities.

In the present description, the expression "purified PVC polymer stream" means the main and upgradable product obtained by treating a plastic raw material, in particular a plastic raw material resulting from PVC-based plastic waste, according to the method according to the invention. It comprises at least one PVC resin of a given grade, preferably a mixture of PVC resins of chemically identical properties but of different grades. The term "purified" means in particular that the PVC polymer stream obtained at the end of the method according to the invention comprises negligible or at least very low contents of impurities as described above, including additives, and at least one solvent used in the method according to the invention, in all cases in compliance with current regulations. Thus, more specifically, at least one purified PVC polymer stream exhibits the following contents (the contents are expressed as percentages by weight relative to the total weight of the final product, i.e. the purified PVC polymer stream obtained): - a phthalate content of less than 0.1% by weight, as authorized by 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 a phthalate content of less than 0.1% by weight selected from the list consisting of the following phthalates: 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, isoamyl-n-pentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, either alone or as a mixture, - less than 0.1% by weight of elemental lead, in particular if it is contained in metal stabilizer type additives evaluated in the context of REACH and subject to restrictions detailed and formally adopted by ECHA’s Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018 (Annex XV), - less than 0.1% by weight and preferably less than 0.01% by weight of elemental cadmium, in particular if it is contained in metal stabilizer type additives banned under REACH by virtue of the amendment to Annex XVII (Regulation 494/2011 of 20 May 2011), - More generally, the impurity content is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferably less than 1.0% by weight, more preferably less than or equal to 0.5% by weight, in fact even less than or equal to 0.1% by weight, and - More generally, the content of at least one solvent used in the method according to the present invention is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight and more preferably less than or equal to 0.1% by weight.

In the present description, the expression "polymer solution" refers to a liquid medium comprising a dissolving solvent and at least one PVC polymer dissolved (i.e. dissolved and dispersed) in the dissolving solvent, the dissolved PVC polymer being initially present in the plastic raw material treated by the method according to the invention. The polymer solution may additionally comprise soluble impurities (which are dissolved in the dissolving solvent) and/or insoluble impurities (which are suspended in the polymer solution). Depending on the stage of the method according to the invention carried out, the polymer solution may thus comprise impurities in the form of insoluble particles, which are advantageously suspended in the polymer solution (in the case of nano-sized insoluble impurities, this will then be referred to as a colloidal solution); soluble impurities dissolved in the dissolving solvent and/or in another liquid phase which is present, if appropriate, and which is immiscible with the polymer solution.

In this specification, the expression "greater than ..." is understood to be strictly greater than and is indicated by the symbol ">", and the expression "less than" is understood to be strictly less than and is indicated by the symbol "<". When limit values are included, this information is provided by the corresponding expressions "greater than or equal to ..." (and corresponds to the symbol "≥") and "less than or equal to" (corresponds to the symbol "≤").

In this specification, the term "room temperature" (r.t.) should be understood to mean a temperature of usually 20°C ± 5°C, and the term "atmospheric pressure" should be understood to mean a pressure of 0.101325 MPa.

In this specification, the term "comprising" is synonymous with "including" and "containing" (having the same meaning), and is inclusive or open and does not exclude other elements not mentioned. It should be understood that the term "comprising" includes the exclusive and closed term "consisting of..."

In this specification, unless otherwise specified, the expression "between..." means that the limit values of the interval are included in the described value range.

In this specification, various parameter ranges (such as pressure ranges and temperature ranges) for a given stage can be used alone or in combination. For example, in this specification, a preferred pressure value range can be combined with a more preferred temperature value range.

Subsequently, specific embodiments of the present invention are described, which can be implemented separately or in combination, and the combination method is not limited if it is technically feasible.

Subsequently, the term "phase" is used to denote an operation or set of similar operations performed on a given stream at a certain point in the process. The process is described in phases in the order in which the streams or products flow.

Finally, the terms "upstream" and "downstream" are to be understood as depending on the overall flow of the fluid or stream in question in the process. More specifically, the terms "upstream" and "downstream" are defined as depending on the flow of the stream comprising the PVC resin. For example, the terms "upstream" and "downstream" are defined in the size exclusion stage relative to the polymer solution flow, i.e. relative to the outlet point of the crude (or clarified) polymer solution fed into stage b) or the polymer solution withdrawn during this stage b) (i.e. the raffinate extraction point).

The following description of the method according to the present invention refers to the diagrams of Figures 1 and 2, which illustrate different implementations of the method according to the present invention.

According to the invention, a method for recovering at least one reusable purified PVC polymer stream from a plastic raw material advantageously produced from PVC-based plastic waste comprises and can consist of the following stages: a) a dissolution stage, which comprises contacting the plastic raw material with at least one dissolving solvent to obtain at least one crude polymer solution; then b') an optional stage of separating insoluble substances from the crude polymer solution, making it possible to advantageously obtain a clear polymer solution and preferably an insoluble fraction; then (b) a stage of size exclusion extraction of the crude polymer solution obtained at the end of stage a) or, if applicable, of the clarified polymer solution obtained at the end of stage b'), whereby a purified polymer solution is obtained, wherein the size exclusion extraction stage is carried out using at least one series of n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, very preferably between 8 and 21 and preferably between 12 and 15, Advantageously, n size exclusion solid fixed beds are distributed in one or more columns, preferably in M columns, M being an integer between 1 and the total number of size exclusion solid fixed beds n, the n beds are connected in series relative to each other and are preferably in a closed loop, the at least one series of fixed beds in stage b) is fed with a crude polymer solution or a clarified polymer solution at at least one polymer solution injection point F and is fed with a solvent at at least one solvent injection point S, wherein the at least one series of fixed beds in stage b) performs at least one extract extraction at at least one extract extraction point E, and performs at least one extract extraction at at least one extract extraction point R, The polymer solution injection point and the solvent injection point as well as the extract extraction point and the raffinate extraction point are different from each other, advantageously located between two continuous beds or upstream of the first bed as appropriate, and are distributed so as to determine at least three, preferably four, continuous main operating zones of each fixed bed: - impurity dissolution zone I, which is located between the solvent injection point and the extract extraction point; - at least one PVC polymer dissolution zone II, which is located between the extract extraction point and the polymer solution injection point; - impurity retention zone III, which is located between the polymer solution injection point and the raffinate extraction point; and - optionally and preferably, zone IV, which is located between the raffinate extraction point and the solvent injection point, wherein the injection and extraction points are moved over time in a fixed bed of size exclusion solids at a frequency determined by a predetermined replacement cycle, wherein the raffinate is recovered to constitute at least part, preferably all, of the purified polymer solution; and subsequently (c) a polymer-solvent separation stage of the purified polymer solution to obtain at least a portion of at least one solvent, which in particular comprises a dissolving solvent and, if appropriate, a solvent, and at least one purified PVC polymer stream.

The raw material is fed with plastic raw materials, in particular plastic raw materials based on PVC, and more specifically plastic raw materials produced from PVC-based plastic waste. It can also be called "PVC raw materials" and contains at least one PVC plastic.

The plastic raw material is advantageously a PVC raw material to be recycled, of the "production waste" type, i.e. waste resulting from the manufacturing process of PVC polymers during their polymerization or of PVC plastics during their formulation/formation or of PVC-based objects during their production, or of the "post-consumer waste" type, i.e. waste resulting after the user has consumed the PVC-based object. In particular, the plastic raw material to be recycled can come from any existing network or collection and sorting channel for production waste and/or post-consumer waste, making it possible to separate a stream based on at least one PVC plastic, in particular a network or collection and sorting channel dedicated to plastic waste.

Thus, plastic raw materials, usually of the "production waste" type and/or "post-consumer waste" type, generally come from the main application areas in which PVC plastics are used, such as and not exclusively from the following areas: building and construction, packaging, motor vehicles, electrical and electronic equipment, sports, medical equipment and the like. Preferably, the PVC raw materials come from the building and construction sector. More precisely, PVC-based objects are generally used in these sectors as profiles (windows, doors, shutters, roller shutter casings), pipes and fittings, various rigid and bottles, rigid panels and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics and the like.

Advantageously, the plastic raw material comprises at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight and more preferably at least 95% by weight of PVC plastic.

The plastic raw material treated in the method for recycling a reusable purified PVC polymer stream according to the invention is in the form of particles. Thus, if the PVC raw material is in an initial form characteristic of production waste or post-consumer waste, in particular in the latter case of PVC-based objects, it can previously undergo a treatment phase (as described below) which at least comprises grinding or comminution to form the PVC raw material in the form of particles. Depending on the channel and/or network from which these production wastes and/or end-of-life PVC-based objects come, the PVC waste can be ground and/or washed and/or undergo any other treatment phase as described below to form the PVC raw material in the form of particles suitable for the method according to the invention. For example, the PVC raw material may advantageously be in the form of a ground and, if appropriate, washed material, the largest dimension of which is less than or equal to 20 cm, preferably less than or equal to 10 cm, preferably less than or equal to 1 cm and more preferably less than or equal to 5 mm. The PVC raw material may also advantageously be in the form of a micronized solid, i.e. in the form of particles, preferably having an average size of less than 1 mm, for example between 10 micrometers (µm) and 800 micrometers (µm). The average size advantageously corresponds to the average diameter of a sphere circumscribing the particles.

Thus, the plastic raw material fed to the process according to the invention is advantageously in the form of particles, generally having an average size between 10 μm and 20 cm, for example particles of abrasive material having an average size between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferably between 1 mm and 1 cm, more preferably 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.

As already mentioned, the PVC raw material may also contain common impurities, usually "macro" impurities, such as glass, wood, cardboard, paper, metal, rubber, silicone, plastics other than PVC (such as PET and its analogs), inorganic elements and the like. Advantageously, the PVC raw material contains up to 50% by weight, preferably up to 30% by weight, preferably up to 10% by weight and more preferably up to 5% by weight of "macro" impurities. In addition to making the above raw materials into particle form, the optional pretreatment stage makes it possible to remove all or some of these common impurities.

The various stages of the method according to the invention for producing at least one reusable purified PVC polymer stream are described in detail in the following sections.

Optional pretreatment stage of the PVC raw material According to the invention, the process may comprise a pretreatment stage of the PVC raw material (not shown in FIGS. 1 and 2 ), which comprises at least one stage of grinding or comminuting or micronizing the PVC raw material to form the PVC raw material in the form of solid particles as defined above, so as to be able to be sent to the dissolution stage a). This pretreatment stage may additionally comprise one or more of the stages mentioned in the following non-exhaustive list: grinding by micronization, sorting, over-sorting, washing, drying and the like. Depending on the nature of the PVC raw material treated, the one or more stages involved in the pretreatment stage and their possible frequency and sequence are specifically chosen by those skilled in the art in order to limit the amount of common impurities and to reduce the size of the solid components that initially constitute the PVC raw material.

For example, the pretreatment stage makes it possible to provide a PVC raw material in the form of particles, for example a washed ground material, whose average size is less than or equal to 5 mm, preferably between 1 mm and 5 mm, whose content of common impurities is preferably at most 10% by weight and more preferably at most 5% by weight. The pretreated PVC raw material can also be in the form of micronized solid particles, that is to say in the form of particles with an average size of less than 1 mm, for example between 10 μm and 800 μm.

The pretreatment stage of the PVC raw materials may include a drying stage of the PVC raw materials.

Dissolution phase a ) The method according to the invention comprises a dissolution phase a), in which the PVC raw material (or plastic raw material), advantageously in the form of particles, is contacted with a dissolving solvent to obtain at least one, preferably only one, crude polymer solution. This phase advantageously makes it possible to dissolve at least a portion, preferably all, of the PVC resin contained in the plastic raw material.

The term "dissolution" is understood to mean any phenomenon leading to obtaining at least one polymer solution, i.e. a liquid comprising at least PVC resin dissolved in a solvent, more specifically in a dissolving solvent. A person skilled in the art is fully aware of the one or more phenomena involved in polymer dissolution, which one or more phenomena include at least mixing, homogenization, dissolution, entanglement and dispersion of polymer chains, and more specifically in this case PVC polymer chains.

The dissolving solvent is selected according to its physicochemical properties, its ability to dissolve, disentangle and disperse the PVC polymer chains. In this regard, the person skilled in the art can rely on the knowledge of the Hildebrand and/or Hansen solubility parameters of the solvent, relative to these same parameters specific to the PVC resin, to define the solvent or solvent mixture that is most suitable for carrying out the dissolving phase a) of the method according to the invention. More specifically, the dissolving solvent is a solvent or solvent mixture, in particular an organic solvent, preferably selected so that its Hansen parameters are within the Hansen sphere of the target PVC polymer. The Hansen theory makes it possible to predict the solubility of polymers, especially thermoplastics such as PVC, in solvents by determining the Hansen solubility parameters and the Hansen spheres of the solvents and polymers, respectively, as a function of several parameters, especially their polarity, hydrogen bonding and dispersion parameters. If a solvent or a solvent mixture exhibits Hansen parameters in the Hansen spheres of a PVC polymer, the PVC polymer should be at least partially, preferably completely, soluble in the solvent. Therefore, the dissolving solvent is advantageously an organic solvent or a mixture of organic solvents, which is preferably selected from 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; and the like), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; and the like), amides (N,N-diisobutyl ketone; cyclopentanone; isophorone; and the like), Ethylformamide; N,N-dimethylacetamide; N,N-dimethylformamide or DMF; and its analogs), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; and its analogs), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; pentyl 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; and its analogs), cyclic esters (γ-butyrolactone or GBL; γ-valerolactone or GVL; caprolactone; and its analogs), 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; and its analogs), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane ; 2-hydroxymethyloxolane; and its analogs), chlorinated solvents (dichloromethane; chloroform or chloroform; tetrachloromethane; trichloroethylene; and its analogs), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; and its analogs), sulfur-based solvents (dimethyl sulfoxide or DMSO; cyclobutane sulfone; and its analogs), nitrogen-containing solvents (1-nitropropane; and its analogs), dihydro-L-glucose ketone or dihydro-L-glucose glycoside (cyrene) and its analogs. Preferably, the dissolving 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, used alone or as a mixture. More preferably, the dissolving solvent is selected from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, used alone or as a mixture.

The dissolution stage a) of the PVC raw material 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 pressure, preferably between 0.1 and 11.0 MPa absolute pressure, preferably between 0.1 and 5.0 MPa absolute pressure, more preferably between 0.1 and 2.0 MPa absolute pressure. Therefore, the pressure and temperature operating conditions are selected so that the dissolving solvent remains at least partially and preferably completely in liquid form, while the soluble part of the PVC raw material, in particular the PVC resin and at least a part of the impurities are advantageously at least partially and preferably completely dissolved. Very advantageously, the temperature and pressure conditions of the dissolving stage a) are adjusted so that the dissolving solvent + PVC resin mixture is a single-phase mixture, in which insoluble impurities may be suspended as appropriate.

Very advantageously, the dissolution phase a) is carried out with a residence time between 1 minute (min) and 10 hours (h), preferably between 10 min and 4 h, more preferably between 10 min and 2 h. In phase a), the residence time is understood to be the residence time at the dissolution temperature and dissolution pressure, i.e. the time during which the plastic raw material is processed with the dissolution solvent at the dissolution temperature and dissolution pressure.

Preferably, the plastic raw material and the dissolving solvent are fed in stage a) so that the weight of the PVC resin present in the plastic raw material is between 2 wt % and 30 wt %, preferably between 5 wt % and 20 wt %, and more preferably between 10 wt % and 15 wt % relative to the weight of the dissolving solvent.

In order to allow the dissolving solvent and the plastic raw material to contact and to allow at least a portion, preferably all, of the PVC resin contained in the plastic raw material to be dissolved in the dissolving solvent, the dissolving stage a) can be implemented with different equipment. Therefore, stage a) can advantageously implement at least one dissolving device, one mixing device and/or one transport device. Such equipment (or devices) can be, for example, a static mixer, an extruder, a pump, a reactor, a co-current or countercurrent column. Transport equipment, in particular transport equipment for transporting fluids (such as liquids or solids), is well known to those skilled in the art. Without limitation, the transport equipment can include a compressor, a pump, an extruder, a vibrating tube, an infinite torsion machine or a valve. The apparatus may also comprise or be combined with a heating system (e.g. an oven, an exchanger, heating cables and the like) in order to achieve the conditions required for dissolution. Very particularly, the dissolution phase a) may be carried out in a reactor with a mechanical stirring system and/or a recirculation circuit and/or a fluidized stirring reactor, such as a batch or continuous type completely stirred reactor, or a drum type reactor.

The dissolving phase a) is fed with at least the plastic raw material (or PVC raw material) and the dissolving solvent, in particular in the form of one or more dissolving solvent streams, advantageously fed by one or more transport devices. The PVC raw material can be introduced in the form of a solid particle stream different from the dissolving solvent stream. Part or all of the PVC raw material can also be fed to phase a) as a mixture with part or all of the dissolving solvent, in particular in the form of a suspension of solid particles in a liquid solvent. If appropriate, the remaining solvent and/or raw material can be fed separately to phase (a).

In stage a), the plastic raw material and/or the dissolving solvent may be fed continuously or in batches in the form of a mixture or separately.

Preferably, the dissolution stage a) can be carried out in a reactor of the type with a mechanical stirring system and/or a recirculation circuit and/or fluidization and/or ultrasonic stirring, such as a batch or continuous complete stirring reactor, or a drum reactor. In addition, the PVC raw material is preferably introduced in the form of a solid particle flow independent of the dissolving solvent flow.

Advantageously, the dissolution solvent used in stage a) comprises, preferably consists of, fresh solvent (or a portion of fresh solvent) and/or a recycled solvent stream resulting from a subsequent stage of the process, in particular at least partly from a recovery stage c).

According to the invention, the dissolution phase a) makes it possible to obtain at least one, preferably only one, polymer solution, referred to herein as a crude polymer solution, which comprises at least a dissolution solvent and at least a PVC resin dissolved in the dissolution solvent. In general, the crude polymer solution also comprises soluble impurities also dissolved in the dissolution solvent and, if appropriate, suspended insoluble impurities.

Optionally present stage b ' ) of separation of insoluble substances The process according to the invention may optionally comprise a stage b') of separation of insoluble substances from the crude polymer solution, in particular by solid-liquid separation, advantageously upstream of the size exclusion extraction stage b). Thus, when incorporated into the process according to the invention, stage b') of separation of insoluble substances makes it possible to obtain a clarified polymer solution, which is a polymer solution from which at least a portion, preferably all, of the insoluble impurities have been removed. When incorporated into the method according to the invention, the phase b') of separating the insoluble substances also makes it possible to advantageously separate the insoluble fraction, which comprises at least a part and preferably all of the insoluble impurities, in particular suspended insoluble impurities, in the crude polymer solution resulting from phase a). The insoluble impurities removed during phase b') of separating the insoluble substances are, for example, additives (pigments, fillers, other polymers and the like), common impurities (inorganic compounds, glass, wood, paper, metals, other polymers) and/or degradation products originally present in the PVC plastic, as described above in this specification. Preferably, phase b') also makes it possible to obtain a clear polymer solution and an insoluble fraction.

When this separation phase b') is carried out, in addition to removing at least a portion of the insoluble impurities, it is advantageously possible to limit operating problems in the process phases located downstream, in particular of the clogging and/or corrosion type, while promoting the purification of the PVC raw material. Preferably, the process according to the invention comprises a phase b') of separating the insoluble substances.

Advantageously, when the stage for separation of insoluble matter is performed, it is located upstream of the size exclusion extraction stage b) and usually downstream of the solubilization stage a).

Phase b') of separation of insoluble substances is advantageously carried out under temperature and pressure conditions close to those of phase a). Very advantageously, phase b') of separation of insoluble substances is carried out under temperature and pressure conditions of the dissolution phase a) defined above. Therefore, very advantageously, phase 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 and 11.0 MPa absolute, preferably between 0.1 and 5.0 MPa absolute, more preferably between 0.1 and 2.0 MPa absolute.

When incorporated into the process, stage b') for separation of insoluble matter is preferably fed with the crude polymer solution resulting from stage a).

Advantageously, the phase b') present, if applicable, can be implemented as a section comprising at least one solid-liquid separation device, such as a liquid-gas separator, a decanter, a centrifuge, a filter, a sand filter, a tangential filter (especially a membrane filter and/or a depth filter, optionally in the presence of a filter aid such as diatomaceous earth or sand), a vortex separator, an electrostatic separator, a triboelectric separator, preferably a decanter, a filter, a sand filter and/or an electrostatic separator. Advantageously, a self-cleaning filter can be used, in particular cleaning or declogging with a solvent stream, to remove insoluble substances.

The removal of the insoluble fraction may require the use of equipment capable of transporting and, if appropriate, removing solvents that may have been impregnated into the separated insoluble fraction. For example, stage b') may implement a conveyor, a vibrating tube, an infinite torsion machine, an extruder or a stripper. Thus, stage b') may implement a transport device in order to discharge the insoluble fraction and/or remove solvents that may be entrained by the separated insoluble fraction. Advantageously, at least a portion of the solvent that may be entrained by the separated insoluble fraction is recovered and recycled into the process.

According to a particular embodiment, the phase b') of separating the insoluble matter is implemented with at least two and generally less than five solid-liquid separation devices connected in series and/or in parallel. The presence of at least two solid-liquid separation devices connected in series makes it possible to improve the removal of insoluble matter, while the presence of parallel devices makes it possible to manage the maintenance and/or declogging operations of the device.

Certain insoluble impurities, in particular certain pigments and inorganic fillers, which are known to be added during polymer formulation, can be introduced in the form of particles with a size of less than 1 μm. This is the case, for example, with titanium dioxide, calcium carbonate and carbon black. According to one embodiment, the stage b') of separating the insoluble substances advantageously implements an electrostatic separator, which makes it possible to effectively remove at least part of the insoluble particles with a size of less than 1 μm. According to another embodiment, the stage b') of separating the insoluble substances implements a sand filter to remove particles of different sizes and in particular particles with a size of less than 1 μm. According to a further embodiment, stage b') of separating the insoluble substances is carried out using a tangential filter, in particular a membrane filter and/or a depth filter, optionally in the presence of a filter aid such as diatomaceous earth.

According to the invention, when incorporated into the process, the optionally present stage b') of separating the insoluble substances makes it possible to obtain at least one clear polymer solution, which comprises at least the dissolving solvent and at least the PVC resin dissolved in the solvent. Thus, at least a part and preferably all of the insoluble impurities which may be present in suspension in the crude polymer solution obtained at the end of stage a) of the process according to the invention are removed from the polymer solution in stage b').

Size Exclusion Extraction Stage ( b ) The process according to the invention comprises a size exclusion extraction stage b), which in particular feeds the solvent and the crude polymer solution resulting from stage a) or, as the case may be, the clarified polymer solution obtained from stage b') of separation of insoluble substances. Advantageously, the size exclusion extraction stage b) makes it possible to obtain at least one purified polymer solution and preferably waste solvent, in particular waste solvent loaded with impurities.

The polymer solution fed to the size exclusion extraction stage b), in particular the crude polymer solution resulting from stage a) or, as the case may be, the clarified polymer solution resulting from stage b') of separation of insoluble matter, generally comprises dissolved impurities, which are advantageously at least partially and preferably completely removed during stage b), in particular by contacting the crude polymer solution or, as the case may be, the clarified polymer solution with a size exclusion solid in the presence of a solvent. This is because the size exclusion extraction stage b) makes it possible to separate the compounds present in the crude polymer solution or, as the case may be, the clarified polymer solution, in particular the dissolved PVC resin and dissolved impurities, according to size, in particular size on the molecular scale (or actually hydrodynamic volume), by means of simulated countercurrent chromatography or simulated moving bed chromatography, denoted hereinafter by the process term SMB. Very advantageously, this extraction stage of the process according to the invention makes it possible to selectively separate the PVC resin dissolved in the dissolving solvent from the dissolved impurities present in the polymer solution fed to stage b), i.e. the crude polymer solution or, as the case may be, the clarified polymer solution. Stage b) thus makes it possible to produce a purified polymer solution, that is, a polymer solution which is free from at least a portion, preferably all, of the soluble impurities present in the polymer solution fed to stage b), i.e. in the crude polymer solution or, as the case may be, the clarified polymer solution.

Preferably, the solvent fed to the extraction stage b) is a solvent, in particular an organic solvent or a mixture of organic solvents, preferably selected so that its Hansen parameters are within the Hansen sphere of the target PVC polymer. Preferably, the solvent fed to the extraction stage b) is a solvent, in particular an organic solvent or a mixture of organic solvents, selected from: 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; and analogs thereof), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; and analogs thereof) , amides (N,N-diethylformamide; N,N-dimethylacetamide; N,N-dimethylformamide or DMF; and analogs thereof), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; and analogs thereof), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; pentyl 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; and its analogs), cyclic esters (γ-butyrolactone or GBL; γ-valerolactone or GVL; caprolactone; and its analogs), 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; and its analogs), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane; 2-hydroxymethyloxolane; and its analogs), chlorinated solvents (dichloromethane; chloroform or chloroform; tetrachloromethane; trichloroethylene; and its analogs), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; and its analogs), sulfur-based solvents (dimethyl sulfoxide or DMSO; cyclobutane sulfone; and its analogs), nitrogen-containing solvents (1-nitropropane; and its analogs), dihydro-L-glucoside or dihydro-L-glucoside and its analogs. Preferably, the 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, used alone or as a mixture. Preferably, the solvent is selected from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL and GVL, used alone or as a mixture. Very preferably, the solvent has the same chemical properties as the dissolving solvent, and is in fact even the same solvent.

Advantageously, the size exclusion extraction stage b) is implemented in operation with at least one, preferably a single, train of several fixed beds of size exclusion solids. The train(s) are advantageously fed with the crude polymer solution resulting from stage a) or, as the case may be, the clarified polymer solution resulting from stage b'), if present, and with the solvent. When stage b) comprises several, in particular two to four, trains of fixed beds of size exclusion solids, in operation, the fixed beds of these trains are operated in parallel with one another and are each fed with a portion of the polymer solution fed to stage b), in particular the crude polymer solution resulting from stage a) or, as the case may be, the clarified polymer solution resulting from stage b'), if present, and a portion of the solvent fed to stage b). In this case, the polymer solution fed into stage b) is subsequently divided into as many partial streams of crude polymer solution or, if applicable, clarified polymer solution as there are operating fixed bed trains, and similarly, the solvent fed into stage b) is subsequently divided into as many partial streams of solvent as there are operating fixed bed trains.

Optionally, the process may also comprise, in particular in parallel with stage b), at least one train of fixed beds of size exclusion solids (as described below) which are not in operation, in particular in rest and/or regeneration and/or standby mode.

Advantageously, in operation, the (or each) series of fixed beds of the size exclusion extraction stage b) comprises n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, very preferably between 8 and 21 and preferably between 12 and 15. The number of fixed beds must be sufficient to enable an efficient separation and reasonable in order to limit costs, in particular investment costs. The n fixed beds are connected in series relative to each other.

The n size exclusion solid fixed beds can be operated in a closed loop or in an open loop. Preferably, the n size exclusion solid fixed beds are operated in a closed loop, i.e. the n fixed beds are connected to each other in sequence and preferably in a closed loop (the first to the second, the second to the third, and so on, and the nth to the first), thus making continuous operation of the size exclusion extraction possible and advantageously reducing the consumption of the solvent, since the solvent is then partially continuously regenerated and recycled.

In one (or each) series of fixed beds, the n size exclusion solid fixed beds are advantageously distributed in one or more columns, preferably in M columns, M being an integer from 1 to the total number of the size exclusion solid fixed beds considered in the series, i.e. M being between 1 and n. Thus, the (or each) series of fixed beds of stage b) of the size exclusion extraction can implement 1 to n columns, each of which comprises one or more size exclusion solid fixed beds. For example, the (or each) series of fixed beds of stage b) can implement a single column (or tower), preferably of large capacity (volume), comprising n fixed beds; or two columns, each of which comprises n/2 fixed beds. These two configurations make it possible to limit investment costs significantly, but when there is a problem with one of the beds in the column, it is necessary to unload the entire column, that is to say n fixed beds or n/2 fixed beds. According to another embodiment, the (or each) series of fixed beds of stage b) implements n columns (or towers), preferably each column having a smaller capacity (volume) than in the previous case, each column comprising a size exclusion solid fixed bed, thereby facilitating maintenance and/or cleaning and/or bypassing, in particular of one of the n beds in operation, since in this configuration only one column (which comprises only one bed) has to be unloaded and/or bypassed, and not the assembly of beds. However, the latter configuration results in higher investment costs.

Preferably, the size exclusion solid is provided in the form of solid particles. It can also be referred to as a particulate medium. The size exclusion solid is selected to be inert with respect to the polymer solution to be treated (i.e. the dissolving solvent and the PVC resin to be treated) and with respect to the solvent. It is also selected to make it possible to efficiently separate the compounds present in the treated polymer solution, in particular dissolved, and more specifically, to efficiently separate the impurities dissolved in the dissolving solvent with respect to the PVC resin which is also dissolved itself. The size exclusion solid is advantageously a porous (mesoporous and/or macroporous) solid, which may be organic (generally polymeric) and/or inorganic and preferably has a volume average pore size preferably between 1 nm and 500 nm, preferably between 2 nm and 100 nm, very preferably between 2 nm and 50 nm (mesoporous solids) and preferably between 3 nm and 30 nm. Advantageously, the size exclusion solid comprises silica (such as silica gel, also known as silica and/or grafted silica and the like), a carbon molecular sieve, a carbon replica, a polymer molecular sieve (chemically different from PVC), a porous polymer gel, preferably a dealuminated zeolite (e.g. USY type), preferably calcined alumina, a MOF (metal organic framework) type material or a mixture thereof. Preferably, the size exclusion solid comprises, preferably consists of silica gel (or silica), grafted silica, a carbon molecular sieve or a mixture thereof. Very advantageously, the size exclusion solid preferably has a pore volume of 0.01 to 3.0 ml/g, preferably 0.1 to 2.0 ml/g, preferably 0.3 to 1.2 ml/g. The average pore diameter and pore volume of the size-excluded solids are determined by mercury intrusion porosimetry and more specifically by mercury intrusion porosimetry according to standard ASTM D4284-83 at a maximum pressure of 4000 bar, using a surface tension of 484 dyne/cm and a contact angle of 140°. The wetting angle taken is equal to 140°, as recommended in the publication "Techniques de l'ingénieur, traité analyse et caractérisation" [Engineering Techniques, Analysis and Characterization Treatise], p. 1050, by J. Charpin and B. Rasneur. To achieve higher precision, the given value for the mercury volume (ml/g) is equivalent to the total mercury volume (ml/g) measured on the sample minus the mercury volume (ml/g) measured on the same sample corresponding to a pressure of 30 psi (approximately 2 bar). These same parameters, and in particular the volume and diameter of the solid in the mesopore range, can also be measured by nitrogen adsorption/desorption volumetry (also known as nitrogen adsorption isotherm), an analytical method complementary to the above. This analysis amounts to the physical adsorption of nitrogen molecules in the pores of the material by gradually increasing pressure at constant temperature and provides information on the textural characteristics. In particular, it makes it possible to obtain the mesopore distribution in size-excluded solids. Thus, the Barrett-Joyner-Halenda (BJH) model determines a pore distribution representing a pore population centered in the range of 2 to 50 nm. Nitrogen adsorption-desorption isotherms according to the BJH model are described in the journal "The Journal of the American Chemical Society", 73, 373 (1951), edited by E. P. Barrett, L. G. Joyner and P. P. Halenda.

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

According to the invention, the (or each) series of fixed beds of the size exclusion extraction stage b) is fed with a crude polymer solution or, if applicable, a clarified polymer solution at at least one polymer solution injection point F and with at least one solvent at a solvent injection point S. Preferably, the series of fixed beds in the operation under consideration is fed with a crude polymer solution or, if applicable, a clarified polymer solution at a polymer solution injection point F and with a solvent at a solvent injection point S.

Preferably, the solvent and polymer solution are fed to the (or each) train of fixed beds of the size exclusion extraction stage according to a ratio of the volumetric flow rate of the solvent to the volumetric flow rate of the polymer solution between 0.1 and 50.0, preferably between 0.2 and 10.0, preferably between 0.5 and 5.0, preferably between 0.8 and 2.0. This ratio may also be referred to as the solvent level. Such adjustment of the solvent level, i.e. the volume flow rate of the crude polymer solution or, as the case may be, the clarified polymer solution and of the solvent for the (or each) train under consideration, contributes to the efficiency of the size exclusion separation of the PVC resin and impurities present in the polymer solution fed to the extraction stage b).

When the series of fixed beds comprises several polymer solution injection points Fi, for example two polymer solution injection points F1 and F2, the crude polymer solution or clarified polymer solution flow of the series of fixed beds under consideration for feeding into the extraction stage is divided into a plurality of partial polymer solution flows to be fed into the series of fixed beds at the injection points Fi, and the partial polymer solution flows exhibit flow rates which are the same as or different from each other.

When the series of fixed beds comprises several solvent injection points Si, for example two injection points S1 and S2, the total solvent flow fed into the series of fixed beds under consideration is divided into a plurality of partial solvent flows (i.e., into i partial solvent flows, i being an integer equal to the number of solvent injection points Si) so as to be fed into the series of fixed beds at said injection points Si, said partial solvent flows exhibiting flow rates which are the same as or different from each other.

The (or each) series of fixed beds in the size exclusion extraction stage b) implements at least one extract extraction at at least one extract extraction point E, and implements at least one raffinate extraction at at least one raffinate extraction point R. Preferably, the (or each) series of fixed beds in the size exclusion extraction stage b) implements extract extraction at the extract extraction point E, and implements raffinate extraction at the raffinate extraction point R.

The polymer solution injection point F and the solvent injection point S as well as the extract extraction point E and the raffinate extraction point R are different from each other. They are advantageously located between two consecutive beds or, as the case may be, upstream of the first bed, in particular in the case of an open loop (in the case of a closed loop of n fixed beds, since the nth bed is connected to the first bed, these two beds are considered to be continuous). However, in the case of one embodiment in particular according to the Varicol® process (described below), they can be located in the middle of the fixed bed or in the fixed bed on average during the operating cycle. The polymer solution injection points and the solvent injection points as well as the extract and raffinate extraction points are distributed relative to each other so that they determine at least three, preferably four, continuous main operating zones of the n fixed beds: - impurities dissolution zone I, contained between the solvent injection point S and the extract extraction point E; - at least one PVC polymer dissolution zone II, contained between the extract extraction point E and the polymer solution injection point F; - impurities retention zone III, contained between the polymer solution injection point F and the raffinate extraction point R; and - optionally and preferably, zone IV, contained between the raffinate extraction point R and the solvent injection point S.

When there are several polymer solution injection points Fi and/or several solvent injection points Si and/or several extract extraction points and/or several raffinate extraction points, zones I, II, III and IV start at the first injection point and/or extraction point of the stream under consideration (solvent, polymer solution, extract or raffinate), the term "first" being defined herein as the point most upstream of all injection points and/or extraction points of the stream under consideration. When there are several polymer solution injection points Fi and/or several solvent injection points Si and/or several extract extraction points and/or several raffinate extraction points, secondary operating zones may also be defined, in particular within zones I, II, III and IV as primary operating zones.

When the series of n fixed beds considered in phase b) is operated in an open loop, the solvent is introduced at the solvent injection point S, the crude polymer solution or, if applicable, the clarified polymer solution is introduced at the polymer solution injection point F, the extract is extracted at the extract withdrawal point E, and any residue is extracted at the raffinate withdrawal point R. The injection points and the withdrawal points thus define three consecutive main operating zones, namely zones I, II, III. In this embodiment, a large amount of solvent is generally required relative to the polymer solution in order to be able to maximize the separation. By way of example, this operating mode in an open loop requires a volume flow rate ratio of solvent to polymer solution of 2.0 to 50.0, preferably 5.0 to 20.0, in practice even 5.0 to 10.0.

When the series of n fixed beds considered in phase b) is operated in a closed circuit, the solvent is introduced at the solvent injection point S, the crude polymer solution or, if applicable, the clarified polymer solution is introduced at the polymer solution injection point F, the extract is extracted at the extract extraction point E, the raffinate is extracted at the raffinate extraction point R, and at least a portion of the solvent introduced is advantageously kept in circulation in the closed circuit of the n beds (the expression used is subsequently recycling of the solvent). In this embodiment, the injection points and extraction points then define four consecutive main operating zones, namely zones I, II, III and IV, zone IV possibly being referred to as the solvent regeneration and recycling zone. In this particular embodiment, the solvent supply requirement (i.e. the amount of solvent introduced at S) is very advantageously smaller than in the case of an open loop mode of operation to ensure efficient separation. For example, this mode of operation in a closed loop requires a volume flow rate ratio of solvent to polymer solution of 0.1 to 10, preferably 0.2 to 5.0, in fact even 0.8 to 2.0.

Advantageously, in the case of a closed circuit of n fixed beds, n size-exclusion solid beds are distributed in zones I to IV, preferably according to a configuration known as type a/b/c/d, the size-exclusion solid beds being distributed in zones I to IV in such a manner that, relative to the total number n of size-exclusion solid beds: - a is the number of size-exclusion solid beds in zone I, - b is the number of size-exclusion solid beds in zone II, - c is the number of size-exclusion solid beds in zone III, and - d is the number of size-exclusion solid beds in zone IV, and wherein: - 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 obvious to the person 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, i.e. the total number of fixed beds in the fixed bed train under consideration for operation. Thus, a 6/3/4/2 configuration means that there are 15 fixed beds of size exclusion solid, 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.

Very advantageously, the bulk density of each of the n fixed beds of size-excluded solid, expressed as the weight of size-excluded solid per unit volume of bed (i.e. kg solid/ ^m3 bed), may vary between 100 and 1500 kg/ ^m3 , preferably between 300 and 1000 kg/ ^m3 , preferably between 400 and 800 kg/ ^m3 .

According to the invention, injection points F and S and extraction points E and R move a size exclusion solid bed over time according to a frequency determined by a predetermined replacement cycle. The replacement cycle can be defined as the time period between two consecutive displacements (or movements) of the injection points and extraction points of a fixed bed. The periodic displacement (or movement) of the injection points F and S and extraction points E and R can be carried out synchronously or asynchronously, the latter case (asynchronous) possibly being known under the name of Varicol®. The periodic displacement of the injection points and extraction points all along the n fixed beds makes it particularly possible to define the operating cycle and also advantageously to define a cycle time corresponding to the time period required for the injection points and extraction points to return to their initial position (i.e. corresponding to the number of beds n multiplied by the replacement cycle).

When n size exclusion solid fixed beds are operated in a closed loop, the operating cycle therefore advantageously comprises as many replacement cycles as there are size exclusion solid beds present in the closed separation loop. For example, an operating cycle comprising a train of 12 size exclusion solid fixed beds comprises 12 replacement cycles.

Therefore, in the preferred embodiment considered in which the train of n exclusion solid fixed beds is operated in a closed loop, the replacement period is preferably adjusted so as to define a circulation time, corresponding to the period of time required for the injection point and the extraction point to return to their initial position, between 1 minute and 600 minutes, preferably between 5 minutes and 200 minutes, preferably between 10 minutes and 90 minutes. The circulation time contributes to the efficiency of the separation by size exclusion of the PVC resin and impurities present in the polymer solution fed to the extraction stage b).

In the case of an embodiment in which n fixed beds are operated in an open loop (i.e. all material is withdrawn together with the extract and the raffinate), the cycle time may also be between 1 minute and 600 minutes, preferably between 5 minutes and 200 minutes, more preferably between 10 minutes and 90 minutes.

The displacement of the injection points F and S and the extraction points E and R can be achieved by installing a series of on-off valves controlled by an automatic sequence or alternatively by installing a single rotary valve.

In general, the liquid flow in a fixed bed is preferably from bed i to bed i+1, i being an integer between 1 and n (the total number of fixed beds), i.e. from upstream to downstream, which may be referred to as downward liquid flow, even if the presence of a pump is required (particularly between the nth bed and the first bed in the case of operation in a closed loop, where n beds are in a column). In case of displacement (or displacement of injection and extraction points), the injection and extraction points are shifted by one bed and placed downstream of the previous bed, thereby generating/simulating a countercurrent liquid flow, which may be referred to as upward liquid flow, as the case may be. 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, a stop flow rate may be defined. The stop flow rate can be calculated by dividing the interparticle volume of the size exclusion solid in the bed by the replacement period, where the interparticle volume of the size exclusion solid in the bed varies with the bulk density of the fixed bed of the size exclusion solid and the density of the size exclusion solid particles. More specifically, the interparticle volume of the size-excluded solid (V _{( interparticle )} ) can be calculated by the following formula: V _{( interparticle )} = V _{( bed )} x (1 - d _{( bulk )} /d _{( particle )} ) + _Vdeath where: V _{( interparticle )} : interparticle volume of the size-excluded solid in the bed ( ^m3 ); V _{( bed )} : geometric volume of the bed ( ^m3 ); d _{( bulk )} : bulk density of the size-excluded solid in the bed (kg/ ^m3 ), which corresponds to the true bulk density of the size-excluded solid, i.e. the weight of the size-excluded solid per unit bed volume. As a first method, it can be compared to the tapped bulk density, which consists of the weight of the solid occupying a given volume after compacting the solid by vibration, according to the principle derived from standards D4164 and D4180 applicable to the case of catalysts; d _{( particles )} : particle density of the size-excluded solid, usually measured by mercury porosimetry (kg/m ³ ); V _dead : volume (m ³ ) of the equipment through which the associated fluid, in particular the polymer solution, flows without the size-excluded solid (e.g. the volume of upstream pipelines, downstream pipelines and the like).

The stop flow rate is a volumetric flow rate, making it possible to calculate dimensionless parameters, in particular dimensionless parameters relating to zones II and IV, in particular the ratio of the volumetric flow rate to the stop flow rate in zone II and the ratio of the volumetric flow rate to the stop flow rate in zone IV. Preferably, the ratio of the volumetric flow rate in zone IV divided by the stop flow rate is less than or equal to 2, preferably between 0.5 and 1.5 and more preferably between 0.8 and 1.0. Preferably, the ratio of the volumetric flow rate in zone II divided by the stop flow rate is between 0.5 and 3.0, preferably between 0.9 and 1.5 and more preferably between 1.0 and 1.25. The stop flow rate thus makes it possible to facilitate the adjustment of the extraction phase b) and thus improve the separation efficiency.

Moreover, very advantageously, the superficial velocity in the fixed bed of the operating zone, which corresponds to the volume flow rate in the zone under consideration divided by the cross section of the zone (that is to say the column in which the bed of the zone under consideration is located), can be adjusted so that this superficial velocity is between 0.01 and 10.0 cm/s and preferably between 0.05 and 2.5 cm/s. The adjustment of the superficial velocity in the fixed bed advantageously makes it possible in particular to control the attrition of the size-excluded solid particles and thus to adjust the operation of the fixed bed train of the extraction phase in order to avoid large pressure drops (in particular encountered at high speeds) and/or dispersion problems (in particular encountered at low speeds).

Preferably, the size exclusion extraction stage of stage 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 pressure, preferably between 0.1 and 11.0 MPa absolute pressure, preferably between 0.1 and 5.0 MPa absolute pressure, more preferably between 0.1 and 2.0 MPa absolute pressure. Under these operating conditions, the PVC resin dissolves in the dissolving solvent and, if appropriate, in the solvent, the latter (i.e. the dissolving solvent and the solvent) being at least partially in liquid form for their part. Preferably, the temperature and pressure conditions of phase b) are the same as those of the dissolving phase a).

Thus, the size-exclusion extraction stage b) makes it possible to recover at least one extract which at least partially, preferably completely, comprises the impurities present in the polymer solution fed to stage b), and at least one raffinate which comprises a polymer solution which is at least partially, preferably completely, free of impurities. The raffinate recovered at the end of the size-exclusion extraction stage constitutes at least partially, preferably completely, a purified polymer solution. This purified polymer solution is then preferably sent at least partially, preferably completely, to a polymer-solvent separation stage c). However, if necessary, it can be sent to other, optionally present, purification stages in order to optimize the purification of the target PVC resin as desired. This size exclusion extraction stage thus makes it possible to efficiently and continuously separate impurities, in particular soluble impurities, from a crude polymer solution or, as the case may be, a clear polymer solution comprising a PVC resin dissolved in a dissolving solvent.

Size exclusion extraction, especially in the case of a fixed bed closed loop, makes it possible to effectively separate impurities from PVC polymers according to a continuous mode, which makes it possible to limit the labor required to operate this stage, while making it easier to operate. It also achieves high productivity, especially compared to size exclusion chromatography operation in batch mode, while providing relatively low solvent consumption.

Polymer - Solvent Separation Phase c ) According to the invention, the process comprises a polymer-solvent separation phase c) of the purified polymer solution in order to obtain at least one stream of at least one purified PVC polymer and at least a portion of at least one solvent comprising a dissolving solvent.

The polymer-solvent separation stage c) is advantageously implemented with at least one solvent recovery section and preferably with one to five solvent recovery sections.

Advantageously, stage c) is fed with the purified polymer solution obtained at the end of stage b) or, if appropriate, with the final purified polymer solution resulting from an additional purification stage located downstream of the size exclusion extraction stage b).

Therefore, the polymer-solvent separation stage c) is primarily intended to separate at least partially, preferably mainly, the dissolved solvent and, if applicable, the solvent present, from the PVC polymer contained in the polymer solution fed to stage c), more particularly the purified polymer solution or, if applicable, the final purified polymer solution resulting from an additional purification stage, in order to recover at least one PVC polymer which is at least partially, preferably mainly and preferably completely free from the dissolved solvent and, if applicable, the solvent present, still present in the polymer solution fed to stage c). The term "predominantly" is understood to mean that at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, more preferably at least 95% by weight, very preferably at least 99% by weight, in fact even at least 99.9% by weight of the solvent (i.e. the dissolving solvent and, if applicable, the dissolving solvent) contained in the purified polymer solution fed into phase c) is removed. Any solvent/polymer separation method known to the person skilled in the art, in particular any method which makes possible a phase change of the polymer and/or the solvent, can be used. The solvent can be separated, for example, by precipitation or crystallization of the polymer, evaporation of the solvent, flash devolatiles, atomization (high-pressure jet, rotary atomizer, two-fluid nozzle, ultrasonic atomizer), stripping, phase separation, extrusion, density differences and in particular by sedimentation or centrifugal separation and the like.

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

The polymer-solvent separation stage c) is also intended to at least partially, preferably predominantly and preferably completely recover the solvent contained in the purified polymer solution fed to stage c), in particular the dissolving solvent and, if applicable, the solvent present. The polymer-solvent separation stage c) is also intended to purify and recycle part of the recovered solvent, in particular upstream of the dissolution stage a). The term "predominantly" is understood to mean at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight and more preferably at least 95% by weight, relative to the weight of the solvent contained in the purified polymer solution fed to stage c).

Advantageously, the polymer-solvent separation stage c) is implemented with at least one solvent recovery section, the latter preferably comprising equipment operating at different temperatures and different pressures, in order to obtain at least one solvent fraction and one purified polymer fraction.

The process according to the invention thus makes it possible to efficiently and continuously recover PVC polymers from plastic raw materials with high productivity and limited number of operations. Very advantageously, the process according to the invention makes it possible, starting from any type of PVC-based plastic raw material, to obtain a PVC polymer stream exhibiting a high purity, preferably greater than or equal to 90%, preferably greater than or equal to 95%, preferably greater than or equal to 99% and more strictly greater than 99.9% (weight of PVC polymer relative to the total weight of the purified recycling stream). Another advantage of the process according to the invention is also the fact that the impurities present in the plastic raw material, in particular additives, can be separated with high efficiency, while the solvent, in particular the dissolving solvent and the solvent can be consumed with reasonable energy consumption, which is lower than that required for the more familiar "thermal" separation such as crystallization. The process according to the invention thus makes it possible to obtain a purified PVC polymer stream which is less colored than the plastic raw material to be treated, in fact even colorless, and very advantageously deodorized. More specifically, the process according to the invention makes it possible to obtain a purified PVC polymer stream which is free from at least a part, preferably all, of the impurities present in the plastic raw materials, such as additives, and which is at least partially, practically or even completely, free of solvents, in particular dissolving solvents and solvents.

Thus, the method according to the invention advantageously makes it possible to obtain a purified PVC polymer stream comprising a content of solvent (in particular dissolving solvent or solvant) less than or equal to 10% by weight, preferably less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight and better still less than or equal to 0.1% by weight, and a content of impurities very advantageously less than or equal to 10% by weight, preferably less than or equal to 5% by weight and better still less than or equal to 1.0% by weight, better still less than or equal to 0.5% by weight and in fact even less than or equal to 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 exhibits the following contents: - Phthalates content less than 0.1% by weight, which is authorized 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 phthalates selected from the list consisting of the following phthalates, the content of which is strictly less than 0.1% by weight: 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, isoamyl-n-pentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, either alone or as a mixture, - less than 0.1% by weight of elemental lead, in particular if it is contained in metal stabilizer type additives evaluated in the context of REACH and subject to restrictions detailed and formally adopted by ECHA’s Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC) between December 2017 and March 2018 (Annex XV), - less than 0.1% by weight and preferably less than 0.01% by weight of elemental cadmium, in particular if it is contained in metal stabilizer type additives banned under REACH by virtue of the amendment to Annex XVII (Regulation 494/2011 of 20 May 2011).

Size exclusion extraction device The present invention also relates to a size exclusion extraction device suitable for separating PVC polymers from impurities contained in a polymer solution. The device comprises: - n fixed beds of size exclusion solids, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, very preferably between 8 and 21 and preferably between 12 and 15, the size exclusion solids having a volume average pore size preferably between 1 nm and 500 nm, preferably between 2 nm and 100 nm, preferably between 2 nm and 50 nm, preferably between 3 nm and 30 nm, and preferably being silica gel, grafted silica, carbon molecular sieve or a mixture thereof, n fixed beds of size exclusion solids are distributed in one or more columns, preferably in M columns, M being an integer between 1 and the total number n of fixed beds of size exclusion solids, the n beds being connected in series and preferably in a closed loop, - N polymer solution injection systems (preferably different from each other), N solvent injection systems (preferably different from each other), N extract extraction systems (preferably different from each other) and N raffinate extraction systems (preferably different from each other), N being an integer preferably equal to n, the injection and extraction systems being located between two consecutive beds or, as the case may be, upstream of the first bed, wherein the polymer solution injection system and the solvent injection system and/or the extract extraction system and the raffinate extraction system, which are located at the same location, i.e. between two substantially continuous beds or, as the case may be, upstream of the first bed, are different or identical (the term "identical" is understood to mean that the valve system can introduce the polymer solution or the solvent, or extract one or the other stream, i.e. the extract or the raffinate), - each injection and extraction system comprises at least one valve suitable for allowing or not allowing the polymer solution stream and/or the solvent stream and/or the extract stream and/or the raffinate stream to pass, preferably i) a series of on-off valves controlled by an automatic sequence or ii) a single rotary valve, so as to: - At time t, the polymer solution injection point, solvent injection point, extract extraction point and raffinate extraction point are defined, which are different from each other and determine at least three, preferably four continuous main operating zones of the n fixed beds: - impurity dissolution zone I, which is included between the solvent injection point and the extract extraction point; - at least one PVC polymer dissolution zone II, which is included between the extract extraction point and the polymer solution injection point; - impurity retention zone III, which is included between the polymer solution injection point and the raffinate extraction point; and - zone IV, if present, which is included between the raffinate extraction point and the solvent injection point; - And it makes it possible to move the injection point and the extraction point of a size exclusion solid fixed bed synchronously or asynchronously over time per replacement cycle according to the frequency determined by the predetermined replacement cycle.

Plastic raw material processing device The size exclusion extraction device can be incorporated into a more inclusive plastic raw material processing device to obtain a purified PVC polymer stream, the device comprising: - a dissolving member for contacting the plastic raw material with a dissolving solvent so as to at least partially dissolve the plastic raw material in the dissolving solvent, the dissolving member being any type of equipment for contacting the plastic raw material with a dissolving solvent and dissolving it in the dissolving solvent to obtain a crude polymer solution; - a solid-liquid separation member, in particular any type of solid-liquid separation equipment, suitable for separating insoluble substances suspended in the crude polymer solution; - at least one size exclusion extraction device according to the invention and as described above, which is advantageously connected to the dissolving means for contacting and dissolving or, as the case may be, to at least one of the solid-liquid separation means; - means for separating the dissolving solvent and, as the case may be, a solvent present from a purified PVC polymer flow, in particular any type of apparatus for separating the dissolving solvent and, as the case may be, a solvent present from a purified PVC polymer flow, which is advantageously connected to the at least one size exclusion extraction device.

The device for processing PVC raw materials to obtain a purified PVC polymer stream also advantageously comprises means for transport between said means and the device.

The device very advantageously makes it possible to recover high-purity PVC polymers from PVC-based plastic raw materials which may contain various impurities.

The following examples and figures illustrate the present invention, particularly specific embodiments of the present invention, but do not limit the scope thereof.

Examples Example 1 This example is the result of digital simulation based on experiments conducted in the laboratory.

The raw material to be treated consisted of poly(vinyl chloride) or PVC resin (55 wt %) with a molar mass MW = 120 000 g/mol and didecyl phthalate (DiDP) additive (45 wt %), the weight percentages being given relative to the total weight of the raw material.

The raw materials were first dissolved in diethyl ketone (DEK) at 100° C. under atmospheric pressure to form a homogeneous crude polymer solution containing 80 wt % DEK and 20 wt % raw materials (polymer and additives).

The obtained crude polymer solution was introduced into a simulated moving bed, which contained 15 fixed beds of solids composed of silica gel. The fixed beds were arranged in a 6/3/4/2 configuration (see Figure 1). The solvent was diethyl ketone (DEK).

Silica gel exhibits the following properties: - bead diameter = 500 µm; - pore size = 6 - 10 nm; - pore volume = 0.50 ml/g solid; - bulk density = 530 kg solid/m ³ bed.

Each bed was modeled by a 1D piston fixed bed model with axial dispersion and the Fick model for intraparticle transport. Since the gyration radius of PVC was estimated to be 39 nm, the polymer was considered to be present only in the extraparticle phase. The gyration radius of additives and solvents was less than 1 nm and could therefore diffuse into the intraparticle pores. The medium in the bed was considered to be isothermal (100 °C) and the density of the polymer solution was considered to be constant (800 kg/m ³ ).

The extraction was adjusted with the following settings: - Cycle time = 15 min, i.e. a displacement period of 60 s; - Relationship between the volume flow rate of solvent and the volume 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 superficial velocity = 1.43 cm/s.

The concentration profiles of PVC and additives obtained by simulation are plotted in Figure 3, which shows the concentration profiles of PVC (solid line) and DiDP (dashed line). As is customary, solvent injection is performed only upstream of bed 1. The concentrations along the entire length of the bed are given as the weight percentage of the compound being tracked (i.e., PVC or additive) relative to the weight of DEK.

It is obvious from Figure 3 that the PVC that did not explore the pores within the particles was entrained into the raffinate and extracted between beds 13 and 14. Since the additive DiDP was smaller, it could diffuse into the pores within the particles and was entrained into the extract and extracted between beds 6 and 7.

Carrying out the extraction step in a simulated moving bed makes it possible to obtain the following performance qualities: - purity of the separated PVC = 99.93% by weight (which corresponds to the weight of PVC or the weight flow rate in the raffinate relative to the total weight or the total weight flow rate of the combination of PVC and additives excluding the solvent DEK in the raffinate); - yield of the separated PVC = 99.95% (which corresponds to the weight flow rate of PVC extracted in the raffinate divided by the weight flow rate of PVC extracted in the extract + raffinate combination); - productivity = 149 kg of PVC extracted in the raffinate/h/ ^{m3 of} bed.

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

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15: bed E: extract extraction point F: polymer solution injection point R: extract extraction point S: solvent injection point

FIG. 1 shows a specific embodiment of the size exclusion extraction stage of the present invention at a given time t of the method, wherein the size exclusion extraction stage implements 15 fixed beds of size exclusion solids of the silica type distributed in a single column, the beds being connected in series with each other and in a closed loop, and a pump located between bed No. 15 and bed No. 1 making it possible to connect bed No. 15 and bed No. 1 in series. In this particular embodiment and at this moment t: - the crude polymer solution resulting from the dissolution stage a) (not shown in FIG. 1 ) or the optionally present clarified polymer solution resulting from the optionally solid-liquid separation stage b') incorporated in the process (not shown in FIG. 1 ) is introduced at an injection point F between beds 9 and 10, these two beds being continuous, - the solvent is introduced at an injection point S between beds 15 and 1, these two beds being continuous, - an extract is extracted at an extraction point E between beds 6 and 7, which extract comprises at least a portion of the impurities present in the polymer solution fed to the column, these two beds being continuous, - A raffinate is extracted at an extraction point R located between beds 13 and 14, which consists at least in part of a purified polymer solution comprising at least one PVC resin present in the polymer solution fed into the column, these two beds being continuous. Thus, the combined injection and extraction points define 4 operating zones: - impurity dissolution zone I, located between solvent injection and extract extraction, comprising 6 beds, - at least one PVC polymer dissolution zone II, located between extract extraction and polymer solution injection, comprising 3 beds, - impurity retention zone III, located between polymer solution injection and raffinate extraction, comprising 4 beds, and - zone IV, located between raffinate extraction and solvent injection, comprising 2 beds. FIG. 2 shows another specific embodiment of the size exclusion extraction stage of the present invention at a given time t of the method, wherein the size exclusion extraction stage comprises 4 fixed beds of size exclusion solid of the silica gel type, each of which is distributed in a column (i.e. one bed per column), the columns being connected in series with respect to each other and in a closed loop, and a pump located between column No. 4 and column No. 1 making it possible to connect column No. 4 and column No. 1 in series. In this particular embodiment and at time t: - a polymer solution is introduced at injection point F between columns 2 and 3, which feeds the size exclusion extraction stage, - a solvent is introduced at injection point S between columns 4 and 1, - an extract is extracted at extraction point E between columns 1 and 2, which contains at least a portion of the impurities present in the polymer solution fed to the size exclusion extraction stage, - a raffinate is extracted at extraction point R between columns 3 and 4, which consists at least in part of a purified polymer solution containing at least one PVC resin present in the polymer solution fed to the size exclusion extraction stage. Figure 3 shows the concentration distribution of PVC resin and additive didecyl phthalate (DiDP) obtained by simulation along the entire length of a simulated moving bed comprising 15 fixed beds of silicone according to a 6/3/4/2 configuration in the context of Example 1. Solvent injection is conventionally located upstream of bed 1 (and downstream of bed 15). The bed-dependent concentration distribution of PVC resin is represented by the solid black line, and the bed-dependent concentration distribution of additive didecyl phthalate (DiDP) is represented by the dashed line.

1,2,3,4,5,6,7,8,9,10,11,12,13,14,15: Bed

E: Extraction point

F: Polymer solution injection point

R: Residue extraction point

S: Solvent injection point

Claims (15)

A method for recovering at least one purified PVC polymer stream from a plastic raw material, comprising: a) a dissolution phase, which comprises contacting the plastic raw material with a dissolution solvent to obtain at least one crude polymer solution; b') a phase of separating insoluble substances from the crude polymer solution obtained at the end of phase a), if applicable, to obtain at least one clarified polymer solution; b) a phase of performing size exclusion extraction on the crude polymer solution obtained at the end of phase a) or, if applicable, on the clarified polymer solution obtained at the end of phase b'), if applicable, to obtain a purified polymer solution, The size exclusion extraction stage implements at least one series of n size exclusion solid fixed beds, n is an integer greater than or equal to 4, and the n size exclusion solid fixed beds are connected in series. The series of fixed beds in stage b) is fed with a crude polymer solution or a clarified polymer solution as the case may be at at least one polymer solution injection point F and is fed with a solvent at at least one solvent injection point S. The series of fixed beds in stage b) implements at least one extract extraction at at least one extract extraction point E and at least one raffinate extraction at at least one raffinate extraction point R. The polymer solution injection points and solvent injection points as well as the extract extraction points and raffinate extraction points are different from each other and are distributed so as to determine at least three, preferably four continuous main operating zones of the n fixed beds: Impurity dissolution zone I, which is located between the solvent injection point and the extract extraction point; At least one PVC polymer dissolution zone II, which is located between the extract extraction point and the polymer solution injection point; Impurity retention zone III, which is located between the polymer solution injection point and the raffinate extraction point; and Zone IV, if present, which is located between the raffinate extraction point and the solvent injection point, wherein the injection points and extraction points move a fixed bed of size exclusion solids over time at a frequency determined by a predetermined replacement cycle, wherein the raffinate is recovered to constitute at least part of the purified polymer solution; c) a solvent-polymer separation stage for separating the purified polymer solution into a purified PVC polymer stream and at least one solvent portion comprising a dissolved solvent. The method of claim 1, wherein the dissolving solvent is an organic solvent selected from ketones, amides, esters, ethers, chlorinated solvents, sulfur-based solvents, nitrogen-containing solvents, hydrocarbons and mixtures thereof, preferably selected from 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, dihydro-levorotatory glucosone or dihydro-levorotatory glucoside (cyrene) and mixtures thereof, preferably selected from diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, γ-butyrolactone, γ-valerolactone and mixtures thereof. The method of claim 1 or 2, wherein the solvent is an organic solvent having the same chemical properties as the dissolving solvent. The method of any of the preceding claims, wherein the size exclusion extraction stage b) is carried out using at least one series of n fixed beds of size exclusion solids, n being an integer between 4 and 30 and preferably between 12 and 15. The method of any of the preceding claims, wherein the size exclusion solid is a porous solid having a volume average pore size between 1 nm and 500 nm, preferably between 2 nm and 100 nm, preferably between 2 nm and 50 nm, preferably between 3 nm and 30 nm. The method of any of the preceding claims, wherein the size exclusion solid comprises silica, grafted silica, carbon molecular sieves, or mixtures thereof. A method as in any of the preceding claims, wherein the solvent and the polymer solution are fed into phase b) according to a ratio of the volume flow rate of the solvent to the volume flow rate of the polymer solution between 0.1 and 50.0, preferably between 0.2 and 10.0, preferably between 0.5 and 5.0, preferably between 0.8 and 2.0. A method as claimed in any of the preceding claims, wherein the polymer solution injection points and the solvent injection points as well as the extract extraction points and the raffinate extraction points are located between two consecutive beds or, as the case may be, upstream of the first bed. A method as claimed in any of the preceding claims, wherein the n size exclusion solid beds are operated in a closed loop and are distributed in four main operating zones, namely zones I to IV, according to a configuration referred to as type a/b/c/d, and the distribution of the size exclusion solid beds in zones I to IV is preferably such that, relative to the total number n of size exclusion solid beds, the following is true: a is the number of size exclusion solid beds in zone I, b is the number of size exclusion solid beds in zone II, c is the number of size exclusion solid beds in zone III, and d is the number of size exclusion solid beds in zone IV, and wherein: 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). A method as in any of the preceding claims, wherein the n beds are in a closed loop and the replacement period is preferably adjusted so as to define a cycle time corresponding to the time period required for the injection and extraction points to return to their initial positions, which is between 1 minute and 600 minutes, preferably between 5 minutes and 200 minutes, and preferably between 10 minutes and 90 minutes. The method of any of the preceding claims, wherein stage a) is carried out at a dissolution temperature between 20°C and 200°C, preferably between 40°C and 180°C, preferably between 60°C and 150°C and at a dissolution pressure between 0.1 and 11.0 MPa absolute pressure, preferably between 0.1 and 5.0 MPa absolute pressure, preferably between 0.1 and 2.0 MPa absolute pressure. A method as claimed in any of the preceding claims, wherein the amount of PVC polymer in the plastic raw material fed into stage a) is 2% to 30% by weight, preferably 5% to 20% by weight, preferably 10% to 15% by weight, relative to the weight of the dissolving solvent. A method as claimed in any of the preceding claims, wherein stage b) is carried out at a temperature between 20°C and 200°C, preferably between 40°C and 180°C, preferably 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, preferably between 0.1 and 2.0 MPa absolute. A device for extracting PVC polymer from a polymer solution by size exclusion, the device comprising: n size exclusion solid fixed beds, n is an integer greater than or equal to 4, preferably between 4 and 30, preferably between 12 and 15, the size exclusion solid has a volume average pore size preferably between 1 nm and 500 nm, preferably between 2 nm and 100 nm, preferably between 2 nm and 50 nm, preferably between 3 nm and 30 nm, and is preferably silica gel, grafted silica, carbon molecular sieve or a mixture thereof, the n size exclusion solid fixed beds are distributed in one or more columns, the n beds are connected in series and preferably in a closed loop, N polymer solution injection systems, N solvent injection systems, N extract extraction systems and N raffinate extraction systems, N being an integer preferably equal to n, said injection and extraction systems being located between two consecutive beds or, as the case may be, upstream of the first bed, wherein said polymer solution injection systems and solvent injection systems and/or extract extraction systems and raffinate extraction systems located at the same position are different or the same, each injection and extraction system comprises a valve suitable for allowing or not allowing the polymer solution flow and/or solvent flow and/or extract flow and/or raffinate flow to pass through, preferably a series of on-off valves or a single rotary valve controlled by an automatic sequence, so as to: At time t, the polymer solution injection point, solvent injection point, extract extraction point and raffinate extraction point are defined, and the injection points and extraction points are different from each other and determine at least three, preferably four continuous main operating areas of the n fixed beds: Impurity dissolution zone I, which is included between the solvent injection point and the extract extraction point; At least one PVC polymer dissolution zone II, which is included between the extract extraction point and the polymer solution injection point; Impurity retention zone III, which is included between the polymer solution injection point and the raffinate extraction point; and Zone IV, which is included between the raffinate extraction point and the solvent injection point, And it makes it possible to move the injection points and extraction points by a fixed bed of size exclusion solids over time, synchronously or asynchronously with each replacement cycle, according to a frequency determined by a predetermined replacement cycle. A device for treating a plastic raw material to obtain a purified PVC polymer stream, comprising: a dissolving component for contacting the plastic raw material with a dissolving solvent so as to at least partially dissolve the plastic raw material in the dissolving solvent to obtain a crude polymer solution; an optional solid-liquid separation component suitable for separating insoluble substances suspended in the crude polymer solution; at least one size exclusion extraction device as claimed in claim 14; a component for separating the dissolving solvent and the optional solvent from the purified PVC polymer stream.