PVC PLASTICS-BASED WASTE RECYCLING PROCESS IMPLEMENTING A STERIC EXCLUSION SIMULATED MOVING BED POLYMER CHAIN ​​EXTRACTION DEVICE

Abstract

The present invention relates to a method for recovering a PVC stream, comprising: a) a dissolution step by contacting a plastic feedstock with a dissolving solvent; then b) a size exclusion extraction step, employing fixed beds of a size exclusion solid in series and fed with the polymer solution from a) at an injection point (F) and with an eluent at an injection point (S), and employing the withdrawal of an extract at a withdrawal point (E) and the withdrawal of a raffinate comprising a purified polymer solution at a withdrawal point (R), the injection and withdrawal points being distinct and offset over time by one bed at a predetermined frequency; then c) a polymer-solvent separation step, to obtain a purified PVC stream. The present invention also relates to a device for carrying out step b) and a device for carrying out the recovery process. Figure 1 to be published

Description

Title of the invention: METHOD FOR RECYCLING PVC PLASTICS-BASED WASTE USING A STERIC EXCLUSION SIMULATED MOVING BED POLYMER CHAIN ​​EXTRACTION DEVICE technical field

[0001] The invention relates to the field of recycling plastics based on poly(chloride) vinyl) (PVC), in particular a process for treating a plastic filler derived from PVC-based plastic waste to obtain a stream of at least one purified PVC polymer for reuse in the manufacture of new plastic objects. More specifically, the invention relates to a process for treating a plastic filler, particularly derived from PVC-based plastic waste, comprising dissolving at least one PVC polymer in a solvent, at least one purification step of the polymer solution thus obtained, and separating at least one PVC polymer from at least one solvent to recover a stream of at least one purified PVC polymer for further processing. Previous technique

[0002] By definition, a plastic is a mixture consisting of a base polymer and numerous additives, the whole being capable of being molded or shaped (generally under heat and / or pressure) to produce a semi-finished product or an object. A commonly accepted practice is to refer to the plastic by the name of the polymer from which it is made. Thus, polyvinyl chloride (PVC) plastic, as it is known in English, actually corresponds to the combination of the PVC polymer, sometimes referred to later in the description as "PVC resin," with various additives chosen according to the functionalities required for the plastic. These additives can be organic (macro)molecules or inorganic (nano)particles and are used according to the desired properties of the PVC plastic: resistance to heat, light, or mechanical stress, flexibility, ease of processing, coloring, etc.

[0003] Several methods of recycling PVC plastics exist: so-called conventional methods by simple mechanical recycling of plastics, methods involving modifications of their composition (with possibly chemical transformations of the initial constituents), etc.

[0004] Since the mid-20th century, the recycling of PVC plastic involving a physical process has been the subject of numerous studies aimed, in a first stage, The process involves solubilizing PVC resin with a variable proportion of additives and then, in a second step, recovering the resin using various processes (precipitation, evaporation, etc.) in the presence of all or part of the soluble additives. For example, we cite patents EP0945481 and EP1268628 on the one hand, and EP2276801 on the other, which aim to recycle, respectively, various PVC-based objects (flexible or rigid pipes, window frames, cables, etc.) and, specifically, fiber-reinforced PVC objects (tarpaulins, floor coverings, etc.) using a process that involves dissolving the PVC resin and soluble additives in an organic solvent, followed by a steam precipitation step that allows for the recovery of the PVC resin and the majority of the additives.

[0005] However, retaining these additives in the PVC thus recovered for recycling is not always desirable. For example, the evolution over time of the regulations concerning them has an impact. Thus, certain plasticizers belonging to the phthalate family, widely used in the formulation of so-called "flexible" PVC some forty years ago, have been progressively subjected to authorization in Europe on the basis of the REACH regulation, which, since the end of 2006, has aimed to ensure the safe manufacture and use of chemical substances in European industry and, ultimately, have been progressively excluded from the list of usable additives (Annexes XIV and XVII of Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council of 18 December 2006).Following the same trend, the use of Cd-based metallic stabilizers in PVC plastic formulations, particularly those known as PVC compound (especially so-called "rigid" PVC plastics), was prohibited by an amendment to Annex XVII (Regulation 494 / 2011 of 20 May 2011). Similarly, lead-based stabilizers were subject to restrictions (Annex XV) which were detailed and adopted between December 2017 and March 2018 by the ECHA's Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC). Thus, over the past 20 years, several families of additives have seen their range of use restricted, a phenomenon that is likely to intensify in the coming years.

[0006] These new regulations have led to the prohibition of numerous additives in recycled raw materials (RRMs), notably through the implementation of very stringent limits on authorized quantities (for example, the quantity of phthalates subject to authorization and considered in mixtures must not exceed 1000 ppm of the final composition of the RRM in question). Given the often very long lifespan of PVC-based products (several decades), PVC-based products formulated before the end of 2006 and now at the end of their life cannot be recycled using regeneration methods that would retain these prohibited additives, regardless of the methods used. conventional, such as mechanical recycling processes, or non-conventional, such as the dissolution / precipitation process examples mentioned above.

[0007] In view of, on the one hand, current and future regulatory constraints and, on the other hand, the limitation of fossil resources which highlights the need to move towards a so-called "circular" economy, producing a purified polymeric resin (i.e. free as much as possible from additives) from plastic waste for reuse as an equivalent MPR to a virgin resin from petroleum is today a major challenge to meet the environmental challenges of the 21st century.

[0008] Numerous processes have been considered to enable the extraction of various families of plastic additives, including in particular PVC plastic. For example, and not exhaustively, patents EP1311599 and JP2007191586 both propose a first step of dissolving the PVC resin and at least one family of additives among phthalate-type plasticizers, flame retardants or lead-based metal stabilizers with a first organic solvent, followed by one or more liquid-liquid extraction steps of at least one family of additives from the solution obtained previously via the use of at least one other solvent (organic and / or aqueous) different from the first organic solvent.Patent JP2007092035 discloses another example of a possible implementation involving the dissolution of PVC resin and at least phthalate-type additives via the use of a solvent mixture under supercritical conditions and the recovery of said phthalates in the same solvent mixture after "breaking" said supercritical conditions, followed by a step of extracting lead-based additives from the residual solid phase containing PVC resin via the use of at least one liquid surfactant.

[0009] Despite these advances, removing all additives from a PVC plastic, and even more so from a mixture of PVC-based plastics from various formulations (for example, those constituting post-consumer waste), remains a scientific and industrial challenge today. The dissolution step mentioned earlier is primarily useful for removing some of the additives that are insoluble in the chosen solvent(s). However, additives soluble in the solvent(s) are particularly difficult to separate, notably due to their highly varied chemical nature. One initial approach could be to extract them based on physicochemical properties such as their polarity, solubility, boiling point, density, etc., but this can lead to a multiplication of purification steps given the number and diversity of additives present.Furthermore, obtaining a stream of at least one purified PVC polymer is generally not a sufficient condition to ensure the economic viability of a PVC-based object recycling process. The main reason frequently cited is the difficulty in finding an economically viable balance between the resale cost (equivalent to the value). added) of the products obtained and the cost of the unit operations implemented in said regeneration process, which is all the more true if the separation steps envisaged are numerous. Finally, processing a plastic load from PVC-based plastic waste requires proposing a robust and versatile process to account for the variability of the additives present depending on the origin of the waste considered (in terms of intended use and production date).

[0010] The present invention thus proposes another approach to address the problems explained above, based on exploiting the difference in size, more precisely the hydrodynamic volume, between polymeric macromolecules and impurity molecules such as those of additives.

[0011] The present invention therefore makes it possible, from a polymer solution containing at least one PVC polymer solubilized in a dissolution medium and the associated soluble additives, to selectively extract said PVC polymer from the medium, regardless of the nature of said additives.

[0012] The size separation technique already exists and is commonly used as an analytical method to determine the molecular weight of polymers. This method, called size exclusion chromatography (or SEC), consists of implementing a fixed bed operated discontinuously (called a "batch") and comprising several porosity levels. Small molecules explore this fixed bed down to the lowest porosities, resulting in long elution times, while large molecules, such as polymers, only travel through the largest pores and exhibit short elution times, thus inducing the desired separation.Since the additives commonly used in PVC-based plastic formulations are an order of magnitude smaller than the polymer chains of PVC resin, size exclusion chromatography can be applied to the purification of PVC-based plastics. However, the industrial implementation of a process using this principle is problematic, primarily due to the batch nature of the process. Furthermore, such a batch process would require significant eluent consumption to ensure efficient separation, directly impacting the process's profitability, productivity, and environmental footprint.

[0013] Simulated moving bed (SMB) technology, a concept invented in 1961, allows for the continuous transition of a batch chromatographic process, particularly adsorption chromatography, to a batch process, increasing productivity and reducing the amount of eluent consumed, while ensuring efficient separation. Numerous industrial applications of this technology exist, especially for adsorption separations. used in particular for the separation of xylenes with the ELUXYL® or PAREX® processes (see the book Simulated Moving Bed technology: Principles, Design and Process Applications, AE Rodrigues, Elsevier, 2015). The only large-scale application of a simulated moving bed with size exclusion (or SMB-SEC for "Simulated Moving Bed with Size Exclusion Chromatography" according to the Anglo-Saxon name) concerns the separation of n-paraffins from iso-paraffins, the details of which are specified in US patent 2985589. Recent publications mention the use of simulated size-exclusion moving bed (SMB-SEC) technology for the fractionation of polyethylene glycols of varying molecular weights (MT Liang et al., J. Chromatogr. A, 2012, 1229, 107) or for protein separation (EJ Freydell et al., Chem. Eng. Sc, 2010, 65, 4701).More specifically, US patent 6551512 proposes a method for separating proteins of liquid composition, such as milk, by simulated moving bed size exclusion. Finally, a publication mentions the use of SMB-SEC in a recycling process for materials used in WEEE (waste electrical and electronic equipment). WEEE is polycarbonate-based and also includes poly(styrene-co-acetonitrile) (SAN) and additives such as flame retardants. It is these latter components that Weeden's team is seeking to separate from a ternary solution containing SAN and two flame retardant compounds, resorcinol bis-diphenylphosphate and bisphenol A bis-diphenylphosphate, in a mixture of acetone and dichloromethane solvents (GS Weeden et al., Journal of Chromatography A, 2015, 1422, 99).

[0014] The application of SMB-SEC technology as a method for purifying PVC-based plastic waste to obtain a purified PVC polymer stream enabling its reuse as MPR for the manufacture of new plastic objects has never been proposed.

[0015] The present invention aims to overcome the problems of the prior art and to contribute to the recycling of plastics, particularly PVC plastics. More specifically, it aims to provide an efficient, simple, and economically viable process for treating all types of PVC fillers to obtain a purified PVC polymer stream that complies with current regulations and can be reused in the manufacture of new plastic products. The present invention seeks to efficiently separate impurities from used PVC plastics and recover purified PVC resins that can be used in the manufacture of new PVC-based products, using a process with a limited number of unit steps, thereby reducing process costs and improving its environmental performance. Summary of the invention

[0016] Thus, the present invention proposes, according to a first aspect, a method for recovering a stream of at least one purified PVC polymer from a plastic feedstock, comprising:

[0017] a) a dissolution step comprising bringing the plastic filler into contact with a dissolving solvent, to obtain at least one crude polymer solution;

[0018] b') optionally a step of separating the insolubles from the polymer solution crude obtained at the end of step a), to obtain at least one clarified polymer solution;

[0019] b) a size exclusion extraction step of the crude polymer solution obtained at the end of step a) or optionally of the clarified polymer solution obtained at the end of step b'), to obtain a purified polymer solution,

[0020] said steric exclusion extraction step employing at least one train of n fixed beds of a steric exclusion solid, n being an integer greater than or equal to 4, the n fixed beds of the steric exclusion solid being in series,

[0021] said fixed bed train of step b) being fed with crude or clarified polymer solution at at least one injection point F of the polymer solution and with an eluent at at least one injection point S of the eluent,

[0022] said fixed bed train of step b) implementing at least one withdrawal of an extract at at least one withdrawal point E of the extract, and at least one withdrawal of a raffinate at at least one withdrawal point R of the raffinate,

[0023] the injection points of the polymer solution and the eluent and the withdrawal points of the extract and the raffinate being distinct from each other and distributed so as to determine at least three, preferably four, successive main operating zones of the n fixed beds:

[0024] - a zone I for elution of impurities, located between the point of injection of the eluent and the extract point;

[0025] - an elution zone II of at least one PVC polymer, located between the point of extraction of the extract and the point of injection of the polymer solution;

[0026] - an impurity retention zone III, located between the injection point of the polymer solution and the raffinate withdrawal point; and

[0027] - optionally a zone IV located between the raffinate withdrawal point and the point injection of the eluent,

[0028] the injection and withdrawal points being shifted over time from a fixed bed of steric exclusion solid according to a frequency determined by a predetermined permutation period,

[0029] said raffinate being recovered to constitute, at least in part, the polymer solution purified,

[0030] c) a polymer-solvent separation step, to separate the purified polymer solution into a stream of purified PVC polymer and at least a solvent fraction comprising dissolving solvent.

[0031] The advantage of the process of the invention is that it provides an efficient method for treating a feedstock containing PVC-based plastics, particularly plastic waste from collection and sorting channels, in order to recover the PVC resins it contains for recycling into all types of applications. The process according to the invention makes it possible to obtain a purified PVC polymer stream, which is advantageously less colored than the plastic feedstock, or even colorless, and preferably 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, and in particular additives, and a solvent content, in particular dissolving solvent and / or eluent, that is negligible or at least sufficiently low so that the purified PVC polymer stream meets the applicable regulations and can be introduced into any plastic formulation in place of virgin PVC resins. For example, the purified PVC polymer stream obtained has (contents expressed as weight percentages relative to or total weight of the purified PVC polymer stream obtained): .

[0032] - a content of less than 0.1% by weight of phthalates subject to authorization by regulation REACH implementation in Europe (Annex XIV of Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council of 18 December 2006),

[0033] - a content of less than 0.1% by weight of the element lead,

[0034] - a content of less than 0.1% by weight, and preferably less than or equal to 0.01% weight of the element cadmium,

[0035] - more generally a content less than or equal to 10% by weight, preferably in less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight, and even more preferably less than or equal to 0.5% by weight, or even less than or equal to 0.1% by weight, of impurities, and

[0036] - more generally a content less than or equal to 10% by weight, preferably in less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight, and even more preferably less than or equal to 0.1% by weight of solvent.

[0037] The process according to the invention thus proposes a simple scheme corresponding to a minimum sequence of operations, which makes it possible to remove from PVC-based plastic waste at least part of its impurities, in particular at least part of the additives, and to recover at least one purified PVC polymer, so as to be able to recover the value of PVC plastic waste by recycling said purified PVC polymer.

[0038] The invention also has the advantage of contributing to plastic recycling and the preservation of fossil resources by enabling the recovery of plastic waste, particularly PVC-based waste. It allows, in effect, the purification of PVC plastic waste to obtain purified PVC polymer streams with reduced impurity content, which can be reused to form new objects. The purified PVC polymer streams obtained can thus be used directly in formulations mixed with additives, for example, colorants, pigments, or other polymers, either instead of or mixed with virgin PVC resins, in order to obtain plastic products with performance, aesthetic, mechanical, or rheological properties that facilitate their reuse and recovery.

[0039] The present invention also relates, according to a second aspect, to a device for extracting PVC polymer from a polymer solution by size exclusion, said device comprising:

[0040] - n fixed beds of a steric exclusion solid, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 12 and 15, said size-exclusion solid having a volume mean pore diameter preferably between 1 and 500 nm, preferably between 2 and 100 nm, preferably between 2 and 50 nm, preferably between 3 and 30 nm, and preferably being a silica gel, a grafted silica, a carbon molecular sieve, or mixtures thereof,

[0041] the n fixed beds of the steric exclusion solid being distributed in one or more column(s), the n beds being connected in series and preferably in a closed loop,

[0042] - N polymer solution injection systems, N eluent injection systems, N extraction systems for an extract and N extraction systems for a raffinate, N being an integer preferably equal to n, said injection and extraction systems being located between two consecutive beds or possibly upstream of the first bed,

[0043] the injection systems for the polymer solution and the eluent and / or the extraction systems for the extract and the raffinate located at the same position being distinct or identical,

[0044] - each injection and withdrawal system comprising valves adapted for allowing or blocking the flow of polymer solution and / or eluent and / or extract and / or raffinate, preferably by a series of on / off valves controlled by an automatic sequence, or a single rotary valve, such that:

[0045] - to define, at a time t, an injection point of the polymer solution, a point injection point of the eluent, a withdrawal point of the extract and a withdrawal point of the raffinate, said injection and withdrawal points being distinct from each other and determining at least three, preferably four, successive main operating zones of the n fixed beds:

[0046] - a zone I for elution of impurities, comprising between an injection point of the eluent and a point for extracting the extract;

[0047] - an elution zone II of at least one PVC polymer, comprising between the point of extraction of the extract and a point of injection of the polymer solution;

[0048] - an impurity retention zone III, located between the injection point of the polymer solution and a raffinate withdrawal point; and

[0049] - possibly a zone IV between the point of withdrawal of the raffinate and the eluent injection point,

[0050] - and to allow, over time, a shift in the injection and withdrawal points, synchronously or non-synchronously, according to a frequency determined by a predetermined permutation period, of a fixed bed of steric exclusion solid per permutation period.

[0051] The present invention further relates, according to a third aspect, to a device for processing a plastic feedstock to obtain a purified PVC polymer stream, comprising:

[0052] - means for bringing the plastic filler into contact with a dissolving solvent, so as to dissolve at least part of said plastic filler in said dissolving solvent and to obtain a crude polymer solution;

[0053] - possibly suitable solid-liquid separation means for separating insoluble in suspension in the crude polymer solution;

[0054] - at least one size exclusion extraction device according to the invention;

[0055] - means for separating the dissolving solvent and optionally the eluent of a purified PVC polymer stream. List of figures [Fig 1]

[0056] Fig. 1 represents a particular embodiment of the size exclusion extraction step of the present invention, at a given time t of the process, in which said size exclusion extraction step uses 15 fixed beds of size exclusion solid, of the silica gel type, distributed in a single column, said beds being connected to each other in series with respect to each other and in a closed circuit, 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.

[0057] In this particular embodiment and at this time t:

[0058] - the crude polymer solution from step a) of dissolution (not shown in the [Fig. 1]) or possibly the clarified polymer solution from step b') of solid-liquid separation possibly integrated into the process (not shown in [Fig. 1]) is introduced at the injection point F located between bed no. 9 and bed no. 10, these two beds being consecutive,

[0059] - an eluent is introduced at the injection point S located between bed no. 15 and bed no. 1, these two beds being consecutive,

[0060] - an extract, comprising at least some of the impurities present in the solution The polymer that feeds the column is drawn off at the withdrawal point E located between bed no. 6 and bed no. 7, these two beds being consecutive.

[0061] - a raffinate, composed, at least in part, of a purified polymer solution comprising at least one PVC resin present in the polymer solution which feeds the column, is drawn from the drawing point R located between bed no. 13 and bed no. 14, these two beds being consecutive.

[0062] The set of injection and withdrawal points thus defines 4 operating zones:

[0063] - a zone I for elution of impurities, located between the injection of the eluent and the withdrawal from the extract, including 6 beds,

[0064] - an elution zone II of at least one PVC polymer, located between the withdrawal of the extraction and injection of the polymer solution, comprising 3 beds,

[0065] - an impurity retention zone III, located between the injection of the solution polymer and the raffinate extraction, comprising 4 beds, and

[0066] - a zone IV, located between the withdrawal of the raffinate and the injection of the eluent, including 2 beds. [Fig 2]

[0067] Fig. 2 represents another particular embodiment of the size exclusion extraction step of the present invention, at a given time t of the process, in which said size exclusion extraction step comprises 4 fixed beds of size exclusion solid, of the silica gel type, each distributed in a column (i.e. one bed per column), said columns being connected to each other in series with respect to each other and in a closed circuit, a pump located between column No. 4 and column No. 1 allowing column No. 4 and column No. 1 to be connected in series.

[0068] In this particular embodiment and at time t:

[0069] - the polymer solution that feeds the size exclusion extraction step is in introduced at injection point F located between column 2 and column 3,

[0070] - an eluent is introduced at the injection point S located between column 4 and column 1,

[0071] - an extract, comprising at least some of the impurities present in the solution The polymer that feeds the size exclusion extraction step is withdrawn at withdrawal point E located between column 1 and column 2.

[0072] - a raffinate, composed, at least in part, of a purified polymer solution comprising at least one PVC resin present in the polymer solution that feeds the size exclusion extraction step, is withdrawn at the withdrawal point R located between column 3 and column 4. [Fig 3]

[0073] Figure 3 shows the concentration profile obtained in Example 1 for a PVC resin and the didecyl phthalate (DiDP) additive, by simulation along the length of the simulated moving bed, which comprises 15 fixed silica gel beds arranged in a 6 / 3 / 4 / 2 configuration. By convention, the eluent injection is located upstream of bed 1 (and downstream of bed 15). The concentration profile of the PVC resin as a function of the beds is represented by a solid black line, and the concentration profile of the didecyl phthalate (DiDP) additive as a function of the beds is represented by the dashed line. Description of implementation methods Terminology

[0074] Some definitions and / or clarifications are given below, although more details on the objects defined below may be given later in the description.

[0075] A PVC-based object is understood to be an object, generally a consumer product, which comprises, and preferably is made of, at least one PVC plastic.

[0076] Polyvinyl chloride plastic, also called PVC plastic, means the combination of a PVC polymer, also called PVC resin, with various additives chosen according to the functionalities required for the PVC plastic, themselves chosen according to the applications intended.

[0077] PVC polymer is conventionally produced by the radical polymerization of vinyl chloride (VCM), a monomer itself obtained from chlorine and ethylene. The present invention enables the processing of any type of PVC plastic filler and the recycling of any grade of PVC polymer.

[0078] The additives used in the composition of a PVC plastic may be organic molecules or macromolecules, or inorganic (nano)particles, and are used according to the properties they impart to the PVC resin. Generally, and without being exhaustive, the formulation of a PVC plastic involves at least one family of additives described below:

[0079] - stabilizers to limit the degradation of polymer chains by dehydro- Chloridation and / or oxidation under the effect of heat, light, oxygen, and / or mechanical stress. The nature of these stabilizers (metallic compounds (Pb, Sn, Ca, Zn, Cd) or organic compounds) depends on the required properties and therefore the intended applications. We cite here some examples of stabilizers frequently used in the past or currently: lead stearate, dibasic lead stearate, dibasic lead phthalate, zinc stearate, calcium stearate, etc., used alone or in mixtures. Co-stabilizers can also be considered, for example, epoxidized oils,

[0080] - plasticizers to induce flexible behavior and improved resistance The most widely used plasticizers, belonging to the phthalate family, are resistant to shock and cold. These are obtained by reacting phthalic anhydride with alcohols of varying carbon chains and consist of a benzene ring and two carboxylic ester groups positioned ortho to the benzene ring. Dioctyl or diethylhexyl phthalate (DOP or DEHP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP) are examples of phthalates that were widely used in the past and are still used today. Other non-phthalic plasticizers are used today, such as bis(2-ethylhexyl) adipate (DEHA) and cyclohexane-1,2-dicarboxylic acid diisononyl ester (DINCH).

[0081] - lubricants to control intermolecular friction forces within even of the polymer (internal lubricants such as stearic acid, etc.) or between the polymer and the metal walls of the processing tools (external lubricants such as paraffins, polyethylene waxes, etc.),

[0082] - inert fillers, mostly mineral (CaCO3, black of carbon, kaolin, etc.), which act as diluents or to improve certain mechanical, electrical, thermal, etc. properties,

[0083] - colorants and / or pigments (TiO2, carbon black), the latter being in soluble in the polymer and therefore present as particles dispersed in the PVC plastic,

[0084] - shock-absorbing agents, generally polymers (such as polyacrylates) and co polymers (such as MBS for methacrylate-butadiene-styrene), whose role is to reduce the brittleness of PVC, particularly at low temperatures,

[0085] - other adjuvants: antioxidants, anti-UV agents, biocides, antistatic agents, retardants flame, reinforcements, etc.

[0086] Impurities are understood to mean all elements other than PVC resins constituting a plastic filler, particularly one derived from PVC-based plastic waste that the process according to the invention aims to treat. These impurities correspond, at least in part, to the additives previously mentioned and described. Other types of impurities may be usage-related impurities arising from the life cycle of PVC-based objects and / or from the collection and sorting process, or even from pretreatment operations of PVC-based plastic waste. These usage-related impurities may be metallic, organic, or mineral. They may consist of residues of materials (excluding PVC plastics) constituting PVC-based objects or other objects that have been in contact with PVC-based objects, soiling (food, biomass, soil / rubble, glue, etc.), etc.These everyday impurities can thus, but are not limited to, include glass, wood, cardboard, paper, etc. metal, rubber, silicones, plastics other than PVC (e.g. PET, etc.), mineral elements, etc. Any degradation products of additives formed over time during the life of the PVC-based product are also considered impurities.

[0087] In this description, the expression "purified PVC polymer stream" represents the main and valuable product obtained after processing a plastic feedstock, in particular derived from PVC-based plastic waste, by the process according to the invention. It comprises at least one PVC resin of a given grade, preferably a mixture of PVC resins of the same chemical nature but of varying grades. The term "purified" means in particular that the PVC polymer stream obtained at the end of the process according to the invention comprises negligible or at least very low levels, in all cases compliant with applicable regulations, of impurities (including additives) as described above and of at least one solvent as used according to the process of the invention.Thus, more specifically, the stream of at least one purified PVC polymer has a content (contents expressed as percentages by weight relative to the total weight of the final product, i.e. of the purified PVC polymer stream obtained): .

[0088] - a content of less than 0.1% by weight of phthalates subject to authorization by the rule REACH regulation in Europe (Annex XIV of Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular less than 0.1% by weight of phthalates selected from the list consisting of the following phthalates: dibutyl phthalate (DBP), dioctyl or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), dii-isobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, alone or in mixtures,

[0089] - a content of less than 0.1% by weight of the element lead, in particular said lead content in metallic stabilizer-type additives assessed under the REACH regulation and subject to restrictions (Annex XV) detailed and adopted between December 2017 and March 2018 by the ECHA's Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC),

[0090] - a content of less than 0.1% by weight, and preferably less than 0.01% by weight, of the element cadmium, in particular said cadmium contained in metallic stabilizer type additives prohibited by the REACH regulation according to the amendment of Annex XVII (Regulation 494 / 2011 of 20 May 2011),

[0091] - more generally a content less than or equal to 10% by weight, preferably in less than or equal to 5% by weight, preferably less than 1.0% by weight, even more preferably less than or equal to 0.5% by weight, or even less than or equal to 0.1% by weight, of impurities, and

[0092] - more generally a content less than or equal to 10% by weight, preferably in less than or equal to 5% by weight, preferably less than or equal to 1.0% by weight and even more preferably less than or equal to 0.1% by weight of at least one solvent used in the process according to the invention.

[0093] In this description, the term "polymer solution" refers to a liquid medium comprising a dissolving solvent and at least one dissolved PVC polymer, i.e., solvated and dispersed, in said dissolving solvent, the dissolved PVC polymer being initially present in the plastic feedstock treated by the process according to the invention. The polymer solution may further comprise soluble impurities (dissolving in the dissolving solvent) and / or insoluble impurities (suspended in the polymer solution).Depending on the steps of the process according to the invention implemented, said polymer solution may therefore include impurities in the form of insoluble particles which are advantageously suspended in said polymer solution (in the case of insoluble impurities of nanometric size, we will then speak of colloidal solutions), soluble impurities dissolved in the dissolving solvent and / or possibly another liquid phase immiscible with said polymer solution.

[0094] In this description, the expression "greater than..." is understood to mean strictly greater than, and symbolized by the sign ">", and the expression "less than" means strictly less than, and symbolized by the sign "<". When the limit is included, the clarification will be provided by the respective expressions "greater than or equal to..." (corresponding to the sign ">") and "less than or equal to" (corresponding to the sign "<").

[0095] In this description, ambient temperature (Tamb) is typically understood to mean 20°C ± 5°C, and atmospheric pressure means 0.101325 MPa.

[0096] In this description, the term "include" is synonymous with (means the same as) "comprise", "include", and "contain", and is inclusive or open and does not exclude other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist".

[0097] In this description, the expression "between ... and ..." means that the limit values ​​of the interval are included in the range of values ​​described, unless otherwise specified.

[0098] In this description, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in this description, a preferred pressure range can be combined with a temperature range. Most preferred operating times.

[0099] In the following, particular embodiments of the invention are described. They can be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0100] In the following, the term "step" refers to an operation or group of similar operations performed on a given flow at a certain point in the process. The process is described in its various steps, taken in the order in which the flows or products occur.

[0101] Finally, the terms "upstream" and "downstream" are to be understood in relation to the overall flow of the fluid(s) or stream(s) in question in the process. More specifically, the terms "upstream" and "downstream" are defined in relation to the flow of the stream that includes the PVC resins. For example, the terms "upstream" and "downstream" are defined in the size exclusion step with respect to the polymer solution stream, that is to say, either at the feed of said step b) with crude (or clarified) polymer solution or at the outlet point of the polymer solution extracted during this step b) (i.e., the raffinate withdrawal point).

[0102] The description of the process according to the invention below refers to the diagrams in Figures 1 to 2, illustrating different implementations of the process according to the invention.

[0103] According to the invention, the process for recovering a stream of at least one reusable purified PVC polymer from a plastic feed advantageously derived from PVC-based plastic waste comprises, and may consist of, the following steps:

[0104] a) a dissolution step comprising contacting the plastic filler with at least one dissolving solvent to obtain at least one crude polymer solution; then

[0105] b') an optional step of separating insolubles from the crude polymer solution, allowing for the advantageous obtaining of a clarified polymer solution and preferably an insoluble fraction; then

[0106] b) a size exclusion extraction step of the crude polymer solution obtained at the end of step a) or optionally of the clarified polymer solution obtained at the end of the optional step b'), allowing a purified polymer solution to be obtained,

[0107] said size exclusion extraction step employing at least one train of n fixed beds of a size exclusion solid, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, most preferably between 8 and 21 and preferably between 12 and 15,

[0108] the n fixed beds of the steric exclusion solid being advantageously distributed in one or more column(s), preferably in M ​​column(s), M being an integer between 1 and the total number n of fixed beds of the exclusion solid, the n beds being in series with respect to each other and preferably in a closed loop,

[0109] said at least one fixed bed train of step b) being fed with crude or clarified polymer solution at at least one injection point F of the polymer solution and with an eluent at at least one injection point S of the eluent,

[0110] said at least one fixed bed train of step b) implementing at least one withdrawal of an extract at at least one withdrawal point E of the extract, and at least one withdrawal of a raffinate at at least one withdrawal point R of the raffinate,

[0111] the injection points of the polymer solution and the eluent and the withdrawal points of the extract and the raffinate being distinct from each other, advantageously located between two consecutive beds or possibly upstream of the first bed, and distributed so that they determine at least three, preferably four, successive main operating zones of the n fixed beds:

[0112] - an impurity elution zone I, located between an eluent injection point and a point for extracting the extract;

[0113] - an elution zone II of at least one PVC polymer, located between the point of extraction of the extract and a point of injection of the polymer solution;

[0114] - an impurity retention zone III, located between the injection point of the polymer solution and a raffinate withdrawal point; and

[0115] - optionally, and preferably, a zone IV located between the point of raffinate withdrawal and eluent injection point,

[0116] the injection and withdrawal points being shifted over time from a fixed bed of steric exclusion solid according to a frequency determined by a predetermined permutation period,

[0117] said raffinate being recovered to constitute at least a part, preferably all, of the purified polymer solution; then

[0118] c) a polymer-solvent separation step, to obtain at least a fraction of at least one solvent, comprising in particular dissolving solvent and optionally eluent, and a stream of at least one purified PVC polymer. Charge

[0119] The process according to the invention is fed with a plastic feedstock, in particular PVC-based, and more particularly derived from PVC-based plastic waste. It can also be called "PVC feedstock" and comprises at least one PVC plastic.

[0120] Said plastic filler is advantageously a PVC filler to be recycled of the "production scraps" type, i.e. waste from the production processes of the PVC polymer during its polymerization or of the PVC plastic during its formulation / shaping or of the PVC-based object during its production, or of the "waste" type Post-consumer waste refers to waste generated after the user consumes the PVC-based item. Specifically, the plastic waste to be recycled may originate from any existing collection and sorting channels or networks for production offcuts and / or post-consumer waste that allow for the isolation of a stream containing at least one type of PVC plastic, including collection and sorting channels or networks specifically designed for plastic waste.

[0121] Thus, the plastic filler, which is typically of the "production offcuts" and / or "post-consumer waste" type, generally originates from the major application areas that use PVC plastic, such as, but not limited to, the building and construction, packaging, automotive, electrical and electronic equipment, sports, and medical equipment sectors. Preferably, the PVC filler originates from the building and construction sector. More specifically, PVC-based products are generally used in these sectors as profiles (windows, doors, blinds, roller shutter boxes), pipes and fittings, various rigid products and bottles, rigid sheets and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.

[0122] Advantageously, the plastic filler comprises at least 50% by mass, preferably at least 70% by mass, preferably at least 90% by mass and even more preferably at least 95% by mass of PVC plastic.

[0123] The plastic material processed in the method for recovering a reusable purified PVC polymer stream according to the invention is in the form of particles. Thus, if the PVC material is in an initial form, such as that of production scrap or post-consumer waste, particularly in the latter case, the initial form of PVC-based objects, it may first undergo a conditioning step (as described below) comprising at least one grinding or shredding step to form a PVC material in the form of particles. Depending on the sectors and / or networks from which this production scrap and / or end-of-life PVC-based objects originate, the PVC waste may be ground and / or washed and / or undergo any other conditioning step as described below, in order to form the PVC material in the form of particles adapted to the process according to the invention.For example, the PVC filler may advantageously be in the form of ground material, possibly washed, 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 even more preferably less than or equal to 5 mm. The PVC filler may also advantageously be in the form of micronized solid, that is to say, 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 the spheres circumscribing said particles.

[0124] Thus, the plastic feed which feeds the process according to the invention is advantageously in the form of particles, typically having an average size of between 10 pm and 20 cm, for example ground-type particles having an average size of between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferably between 1 mm and 1 cm, even more preferably between 1 mm and 5 mm, or particles resulting from micronization (very fine grinding to produce a powder) with an average size of less than 1 mm, preferably between 10 pm and 800 pm.

[0125] As already mentioned, the PVC filler may also include impurities of use, often "macroscopic," such as glass, wood, cardboard, paper, metal, rubber, silicones, plastics other than PVC (e.g., PET, etc.), mineral elements, etc. Advantageously, the PVC filler comprises at most 50% by mass, preferably at most 30% by mass, preferably at most 10% by mass, and even more preferably at most 5% by mass of "macroscopic" impurities. A possible preliminary conditioning step may, in addition to forming the aforementioned filler into particles, remove all or part of said impurities of use.

[0126] The different steps of the process according to the invention leading to the flow of at least one reusable purified PVC polymer are detailed in the following paragraphs.

[0127] Optional preliminary step of conditioning the PVC load

[0128] According to the invention, the method may include a preliminary conditioning step The processing of the PVC feed (not shown in Figures 1 and 2) includes at least one step of grinding, shredding, or micronizing the PVC feed to form a PVC feed in the form of solid particles as defined above, suitable for sending to step a) of dissolution. This preliminary conditioning step may also include one or more steps mentioned in the following non-exhaustive list: grinding by micronization, sorting, further sorting, washing, drying, etc. Depending on the nature of the PVC feed being processed, the step(s), as well as their frequency and possible sequences, involved in the preliminary conditioning step are chosen by those skilled in the art to limit the amount of impurities and reduce the size of the solid elements initially composing the PVC feed.

[0129] For example, the preliminary conditioning step makes it possible to supply a PVC feedstock in the form of particles, for example washed ground material, with an average size of 5 mm or less, preferably between 1 mm and 5 mm, the content of impurities of use being preferably no more than 10% by mass, and more preferably no more than 5% by mass. This pre-conditioned PVC feedstock may also be in the form of micronized solid particles, i.e., in the form of particle shape having an average size less than 1 mm, for example between 10 pm and 800 pm.

[0130] The preliminary step of conditioning the PVC charge may include a step of drying the PVC charge. Step a) of dissolution

[0131] The process according to the invention comprises a dissolution step a) in which the PVC filler (or plastic filler), advantageously in the form of particles, is contacted with a dissolving solvent to obtain at least one, preferably a single, crude polymer solution. This step advantageously allows the dissolution of at least some, preferably all, of the PVC resins contained in the plastic filler.

[0132] By dissolution, we mean any phenomenon leading to the obtaining of at least one polymer solution, that is to say, a liquid comprising at least the PVC resins dissolved in a solvent, more particularly in the dissolving solvent. Those skilled in the art are well acquainted with the phenomenon(ies) involved in the dissolution of polymers, the phenomenon(ies) comprising at least mixing, homogenization, solvation, disentanglement, and dispersion of the polymer chains, and more particularly here, of the PVC polymer chains.

[0133] The dissolving solvent is chosen, due to its physicochemical properties, for its ability to solvate, disentangle, and disperse the PVC polymer chains. In this regard, those skilled in the art can rely on knowledge of the Hildebrand and / or Hansen solubility parameters of solvents to define, with respect to these same parameters specific to PVC resins, the most suitable solvent or solvent mixture for carrying out step a) of dissolution in the process according to the invention. More particularly, the dissolving solvent is a solvent or a mixture of solvents, especially organic(s), preferably chosen such that its Hansen parameters lie within the Hansen sphere of the targeted PVC polymer.Hansen's theory allows us to predict the solubility of a polymer, particularly a thermoplastic such as PVC, in a solvent, by determining the Hansen parameters and solubility sphere for the solvent and the polymer, respectively, as a function of several parameters, especially their polar, hydrogen bonding, and dispersion parameters. If a solvent or solvent mixture exhibits Hansen parameters within the Hansen sphere of the PVC polymer, then the PVC polymer should be at least partially, and preferably completely, soluble in that solvent. Thus, the dissolving solvent is advantageously an organic solvent or a mixture of organic solvents, preferably chosen from among: ketones (acetone; methyl ethyl ketone or MEK; diethyl ketone or DEK; methyl propyl ketone; 4-heptanone; etc.). 2,4-Dimethyl-3-pentanone; methylisobutyl ketone or MIBK; diisobutyl ketone; methyl- lisoamyl ketone; 4-hydroxy-4-methylpentan-2-one; etc.), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; etc.), amides (N,N-diethyl formamide; N,N-dimethyl acetamide; N,N-dimethyl formamide or DMF; etc.), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; etc.), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; amyl acetate; 2-butoxyethanol acetate; n-butyl propionate; propyl propionate; methyl propionate; allyl acetate; 2-(2-butoxyethoxy)ethyl acetate; propylene glycol methyl ether acetate; propylene glycol ethyl ether acetate; butyl benzoate; benzyl benzoate; ethyl lactate; etc.), cyclic esters (γ-butyrolcatone or GBL; γ-valerolactone or GVL; caprolactone; etc.), ethers (methoxycyclopentane or CPME; propylene glycol phenyl ether; diethylene glycol butyl ether; dipropylene glycol butyl ether; propylene glycol methyl ether; propylene glycol butyl ether; dipropylene glycol methyl ether; ethylene glycol butyl ether; etc.), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane; 2-hydroxymethyloxolane; etc.), chlorinated solvents (dichloromethane; trichloromethane or chloroform; tetrachloromethane; trichloroethylene; etc.), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; etc.), sulfur-containing solvents (dimethyl sulfoxide or DMSO; sulfolane; etc.), nitrogen-containing solvents (1-nitropropane; etc.), the dihydrolevoglucosenone or cyrene, etc.Preferably, the dissolving solvent is chosen from ketones, cyclic ketones, and cyclic esters, such as MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, and GVL, taken alone or in mixtures. Even more preferably, the dissolving solvent is chosen from DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, GBL, and GVL, taken alone or in mixtures.

[0134] Step a) of dissolving the PVC charge is carried out preferably at a dissolution temperature between ambient temperature and 200°C, preferably between 20°C and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and advantageously at a dissolution pressure between atmospheric pressure and 11.0 MPa absolute, preferably between 0.1 and 11.0 MPa absolute, preferably between 0.1 and 5.0 MPa absolute, more preferably between 0.1 and 2.0 MPa absolute. The operating conditions of pressure and temperature are thus chosen so as to maintain the dissolving solvent, at least in part and preferably in full, in a liquid state, while the soluble fraction of the PVC feed, in particular the PVC resins and at least part of the impurities, is advantageously dissolved at least in part and preferably in full.Most advantageously, the temperature and pressure conditions of step a) of dissolution are adjusted so that the mixture (dissolving solvent + PVC resin(s)) is mono-. phasic, insoluble impurities that may possibly be suspended in said mixture.

[0135] Most advantageously, step a) of dissolution is carried out with a residence time of between 1 minute (min) and 10 hours (h), preferably between 10 min and 4 h, more preferably between 10 min and 2 h. Residence time is understood as the residence time at the dissolution temperature and at the dissolution pressure, that is to say the time of implementation of the plastic charge with the dissolving solvent at the dissolution temperature and at the dissolution pressure, in step a).

[0136] Preferably, step a) is fed with said plastic filler and said dissolving solvent, so that the weight quantity of PVC resin(s) present in the plastic filler, relative to the weight of the dissolving solvent, is between 2 and 30% by weight, preferably between 5 and 20% by weight, and even more preferably between 10 and 15% by weight.

[0137] In order to allow contact between the dissolving solvent and the plastic filler, and the dissolution in the dissolving solvent of at least some, preferably all, of the PVC resins contained in the plastic filler, step a) of dissolution may employ various equipment. Thus, step a) may advantageously employ at least one dissolving device, one mixing device, and / or one conveying device. This equipment (or devices) may, for example, be a static mixer, an extruder, a pump, a reactor, or a co-current or counter-current column. Conveying equipment, particularly for fluids such as liquids or solids, is well known to those skilled in the art. By way of non-limitation, conveying equipment may include a compressor, a pump, an extruder, a vibrating tube, a screw conveyor, or a valve.The equipment may also include or be associated with heating systems (e.g., furnace, heat exchanger, tracing, etc.) to achieve the conditions necessary for dissolution. In a very specific way, step a) of dissolution may employ a reactor stirred by a mechanical stirring system and / or by a recirculation loop and / or by fluidization, for example a perfectly stirred batch or continuous reactor, or a rotary drum reactor.

[0138] Step a) of dissolution is fed at least by the plastic filler (or PVC filler) and by the dissolving solvent, in particular in the form of one or more streams of the dissolving solvent, advantageously by means of one or more conveying devices. The PVC filler may be introduced as a stream of solid particles separate from the stream(s) of dissolving solvent. Some or all of the PVC filler may also feed step a) mixed with some or all of the dissolving solvent, in particular as a suspension of solid particles in the liquid solvent, the remainder of the solvent and / or the charge, if applicable, that can supply step a) separately.

[0139] Step a) can be supplied continuously or discontinuously with said plastic charge and / or said dissolving solvent, in mixture or separately.

[0140] Preferably, step a) of dissolution is carried out in a stirred reactor using a mechanical stirring system and / or a recirculation loop and / or fluidization and / or ultrasound, for example, a perfectly stirred batch or continuous reactor, or a rotary drum reactor. Furthermore, the introduction of the PVC feedstock in the form of a solid particle stream, independent of the dissolution solvent stream(s), is preferred.

[0141] Advantageously, the dissolving solvent used in step a) comprises, preferably consists of, fresh solvent (or a fresh solvent top-up) and / or a recycled solvent stream from a later step of the process, in particular from at least part of the recovery step c).

[0142] According to the invention, said step a) of dissolution makes it possible to obtain at least one, preferably a single, polymer solution, referred to herein as crude polymer solution, comprising at least the dissolving solvent and at least the PVC resin(s) dissolved in said solvent. In general, the crude polymer solution also comprises soluble impurities also dissolved in the dissolving solvent and optionally insoluble impurities in suspension.

[0143] Optional step b') of separation of insolubles

[0144] The process according to the invention may optionally include a step b') for separating insolubles from the crude polymer solution, in particular by solid-liquid separation, advantageously located upstream of step b) for size exclusion extraction. Said step b') for separating insolubles advantageously allows, when integrated into the process according to the invention, the separation of an insoluble fraction, which includes at least some, preferably all, of the insoluble impurities, in particular those suspended in the crude polymer solution obtained from step a). The insoluble impurities removed during step b') for separating insolubles are, for example, additives initially present in PVC plastics (pigments, fillers, other polymers, etc.), impurities from use (mineral compounds, glass, wood, paper, metal, other polymers) and / or degradation products, as described above in this description.

[0145] Step b') of separating the insolubles thus makes it possible, when integrated into the process according to the invention, to obtain a clarified polymer solution, which is a polymer solution from which at least some, preferably all, of the insoluble impurities have been removed. Preferably, step b') also makes it possible to obtain an insoluble fraction.

[0146] When implemented, this separation step b') advantageously allows, In addition to removing at least some of the insoluble impurities, the process limits operational problems, particularly clogging and / or erosion, in downstream process steps, while also contributing to the purification of the PVC feedstock. Preferably, the process according to the invention includes a step b') for separating the insolubles.

[0147] Advantageously, the insoluble separation step, when implemented, is located upstream of step b) of size exclusion extraction and typically downstream of step a) of dissolution.

[0148] Step b') of separating the insolubles is advantageously carried out under temperature and pressure conditions close to those of step a). Most advantageously, step b') of separating the insolubles is carried out under the temperature and pressure conditions of step a) of dissolution, as defined above. Thus, most advantageously, step b') is carried out at a temperature between ambient 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.

[0149] When integrated into the process, step b') of separating insolubles is preferably fed with the crude polymer solution from step a).

[0150] Advantageously, the optional step b') may implement a section comprising at least one solid-liquid separation device, for example a separator flask, a decanter, a decanter centrifuge, a centrifuge, a filter, a sand filter, a tangential flow filter incorporating a membrane and / or a depth filter possibly with filter aids (for example, diatomaceous earth or sand), an eddy current 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 may be used, with cleaning or unclogging to remove insolubles being carried out using a solvent stream.

[0151] Removing the insoluble fraction may require the use of equipment for transporting and possibly removing solvent that may be impregnated in the separated insoluble fraction. For example, step b') may use a conveyor, a vibrating tube, a screw conveyor, an extruder, or a stripper. Step b') may therefore use equipment for transporting the insoluble fraction and / or for removing the solvent that may be carried along with the separated insoluble fraction. Advantageously, at least some of the solvent that may be carried along with the separated insoluble fraction is recovered and recycled in the process.

[0152] According to a particular embodiment, step b') of insoluble separation uses at least two, and generally fewer than five, solid-liquid separation units in series and / or in parallel. The presence of at least two solid-liquid separation units in series improves the removal of insolubles, while the presence of units in parallel facilitates the maintenance of said units and / or unclogging operations.

[0153] Certain insoluble impurities, particularly certain pigments and mineral fillers, conventionally added during polymer formulation, may be introduced as particles smaller than 1 µm. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. In one embodiment, said insoluble separation step b' advantageously employs an electrostatic separator, which makes it possible to efficiently remove, at least partially, insoluble particles smaller than 1 µm. In another embodiment, the insoluble separation step b' employs a sand filter to remove particles of various sizes, and in particular particles smaller than 1 µm.According to yet another embodiment, step b') of separating insolubles uses a tangential filter employing in particular a membrane and / or a depth filter, possibly in the presence of filtration aids such as diatomaceous earth.

[0154] According to the invention, said optional step b') of insolubles separation allows, when integrated into the process, the obtaining of at least one clarified polymer solution comprising at least the dissolving solvent and at least the PVC resin(s) dissolved in said solvent. Thus, at least some, and preferably all, of the insoluble impurities potentially present in suspension in the crude polymer solution obtained at the end of step a) of the process according to the invention is removed from the polymer solution in step b'). Step b) of size exclusion extraction

[0155] The process according to the invention comprises a size exclusion extraction step (b), which is in particular fed with an eluent and the crude polymer solution from step (a) or optionally with the clarified polymer solution from step (b') of insoluble separation. Advantageously, the size exclusion extraction step (b) makes it possible to obtain at least one purified polymer solution, and preferably a used solvent, in particular one containing impurities.

[0156] The polymer solution that feeds into step b) of size exclusion extraction, in particular the crude polymer solution from step a) or possibly the clarified polymer solution from step b') of insoluble separation, generally includes solubilized impurities, which are advantageously removed at least in part, preferably all, during step b), in particular by contacting it with a size-exclusion solid in the presence of an eluent. Indeed, step b), the size-exclusion extraction step, allows for the separation of the compounds present in the crude or possibly clarified polymer solution, in particular the separation of the dissolved PVC resin(s) and the solubilized impurities, according to their size, particularly at the molecular level (or rather their hydrodynamic volume), by simulated countercurrent chromatography or simulated moving bed chromatography, hereinafter referred to as the "LMS" process or "SMB" for Simulated Mobile Bed according to Anglo-Saxon terminology. Very advantageously, this extraction step of the process according to the invention allows for the selective separation of the PVC resin(s), dissolved in the dissolving solvent, from the solubilized impurities present in the polymer solution that feeds said step b), i.e.the crude or clarified polymer solution. Step b) thus makes it possible to produce a purified polymer solution, said purified polymer solution being a polymer solution freed from at least some, preferably all, of the soluble impurities present in the polymer solution which feeds said step b), i.e. present in the crude or clarified polymer solution.

[0157] Preferably, the eluent that feeds step b) of extraction is a solvent, in particular an organic solvent or a mixture of organic solvents, preferably chosen so that its Hansen parameters are in the Hansen sphere of the target PVC polymer. Preferably, the eluent that feeds step b) of extraction is a solvent, in particular an organic solvent or a mixture of organic solvents chosen from: ketones (acetone; methylethyl ketone or MEK; diethyl ketone or DEK; methylpropyl ketone; 4-heptanone; 2,4-dimethyl-3-pentanone; methylisobutyl ketone or MIBK; diisobutyl ketone; methylisoamyl ketone; 4-hydroxy-4-methylpentan-2-one; etc.), cyclic ketones (cyclopentanone; cyclohexanone; isophorone; etc.), amides (N,N-diethyl formamide; N,N-dimethyl acetamide; N,N-dimethyl formamide or DMF; etc.), cyclic amides (2-pyrrolidone; N-methyl-2-pyrrolidone or NMP; etc.), esters (methyl acetate; ethyl acetate; propyl acetate; butyl acetate; amyl acetate; 2-butoxyethanol acetate; n-butyl propionate; propyl propionate; methyl propionate; allyl acetate; 2-(2-butoxyethoxy)ethyl acetate; propylene glycol methyl ether acetate; propylene glycol ethyl ether acetate; butyl benzoate; benzyl benzoate; ethyl lactate; etc.), cyclic esters (γ-butyrolcatone or GBL; γ-valerolactone or GVL; caprolactone; etc.), ethers (methoxycyclopentane or CPME; propylene glycol phenyl ether; diethylene glycol butyl ether; dipropylene glycol butyl ether; methyl ether of propylene glycol; propylene glycol butyl ether; methyl ether. dipropylene glycol; ethylene glycol butyl ether; etc.), cyclic ethers (tetrahydrofuran or THF; 1,3-dioxolane; 2-hydroxymethyloxolane; etc.), chlorinated solvents (dichloromethane; trichloromethane or chloroform; tetrachloromethane; trichloroethylene; etc.), hydrocarbons (xylene; toluene; limonene; isohexane; cyclohexane; etc.), sulfurized solvents (dimethyl sulfoxide or DMSO; sulfolane; etc.), nitrogenous solvents (1-nitropropane; etc.), dihydrolevoglucosenone or cyrene, etc. Preferably, the eluent is chosen from ketones, cyclic ketones, and cyclic esters, such as MEK, DEK, 4-heptanone, 2,4-dimethyl-3-pentanone, MIBK, cyclopentanone, GBL, and GVL, taken alone or in mixtures.Preferably, the eluent is of the same chemical nature, or even the same solvent, as the dissolving solvent.

[0158] Advantageously, step b) of size exclusion extraction uses at least one train, preferably a single train, of several fixed beds of a size exclusion solid, in operation. Said train(s) is / are advantageously alternated with the crude polymer solution from step a) or optionally the clarified polymer solution from the optional step b'), and with the eluent.When step b) comprises several, in particular between two and four, fixed bed trains of size-exclusion solid, in operation, these fixed bed trains operate in parallel with each other and are each fed by a fraction of the polymer solution that feeds step b), in particular the crude polymer solution from step a) or possibly the clarified polymer solution from the optional step b'), and by a fraction of the eluent that feeds step b), said polymer solution that feeds step b) being then divided into as many partial streams of crude or possibly clarified polymer solution as there are fixed bed trains in operation, and similarly said eluent that feeds step b) being then divided into as many partial streams of eluent as there are fixed bed trains in operation.

[0159] Optionally, the process may also include, in particular in parallel with step b), at least one fixed bed train of steric exclusion solid (as described below), which is (are) not in operation, in particular which is stopped and / or in regeneration and / or backup mode.

[0160] The fixed bed train (or each) of the size-exclusion extraction step (b) comprises n fixed beds of a size-exclusion solid, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, most preferably between 8 and 21, and preferably between 12 and 15. The number of fixed beds must be sufficient to This allows for effective and reasonable separation in order to limit costs, particularly investment costs. The n fixed beds are advantageously arranged in series with each other.

[0161] The n fixed beds of size exclusion solid can operate in a closed loop or in an open loop. Preferably, the n fixed beds of size exclusion solid operate in a closed loop, that is to say that the n fixed beds are connected to each other successively and preferably in a closed loop (the first is connected to the second, the second to the third, etc., and the nth to the first), thus allowing continuous operation of the size exclusion extraction and advantageously a reduction in eluent consumption, since the eluent is advantageously partly regenerated and recycled continuously.

[0162] The n fixed beds of steric exclusion solid are advantageously distributed in one or more columns, preferably in M ​​columns, where M is an integer between 1 and the total number of fixed beds of exclusion solid in the train considered, i.e., M being between 1 and n. Thus, the (or each) fixed bed train of step b) of steric exclusion extraction can implement between 1 and n columns, each comprising one or more fixed beds of steric exclusion solid. For example, the (or each) fixed bed train of step b) can implement one column (or tower), preferably of large capacity (volume), which includes the n fixed beds, or two columns, each of which includes n / 2 fixed beds. These two configurations allow for a significant reduction in investment costs but require unloading the entire column, i.e., the n fixed beds or n / 2 fixed beds, when there is a problem with one of the beds in the column.According to another embodiment, the fixed bed train (or each one) of step b) uses n columns (or towers), preferably each column having a smaller capacity (volume) than in the previous case, each column comprising a fixed bed of steric exclusion solid, thus facilitating maintenance and / or cleaning and / or bypassing, in particular of one bed among the n beds in operation, since in this configuration only one column (which includes a single bed) needs to be unloaded and / or bypassed, and not a set of beds. However, this latter configuration entails higher investment costs.

[0163] Preferably, the size exclusion solid is in the form of solid particles. It may also be called a granular medium. The size exclusion solid is chosen so as to be inert with respect to the polymer solution to be treated, i.e., the dissolving solvent and the PVC resins to be treated, and with respect to the eluent. It is also chosen so as to allow efficient separation of the compounds present, particularly dissolved, in the treated polymer solution, and more specifically efficient separation of impurities solubilized in the dissolving solvent. solution compared to PVC resins, which are also dissolved. The size exclusion solid is advantageously a porous solid (mesoporous and / or macroporous) which can be organic (generally polymeric) and / or inorganic, and preferably having a volume average pore diameter preferably between 1 nm and 500 nm, preferably between 2 nm and 100 nm, most preferably between 2 nm and 50 nm (mesoporous solid), and preferably between 3 nm and 30 nm. Advantageously, the size exclusion solid comprises silica (such as silica gel, also called silica, grafted silica, etc.).), a carbon molecular sieve, a carbon replica, a polymeric molecular sieve (of a chemical nature other than PVC), a porous polymer gel, a preferably dealuminated zeolite (e.g., USY type), a preferably calcined alumina, a metal-organic framework (MOF) material, or mixtures thereof. Preferably, the size exclusion solid comprises, or preferably consists of, a silica gel, a grafted silica, a carbon molecular sieve, or mixtures thereof. Most advantageously, the steric exclusion solid preferably has a pore volume between 0.01 and 3.0 ml / g, preferably between 0.1 and 2.0 ml / g, preferably between 0.3 and 1.2 ml / g.The mean pore diameter and pore volume of the size exclusion solid were determined by mercury porosimetry, specifically measured by mercury intrusion porosimetry according to 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 was 140°, following the recommendations of "Techniques de l'ingénieur, traité analyse et caractérisation", 1950, by J. Charpin and B. Rasneur. To obtain greater accuracy, the given mercury volume value in ml / g corresponds to the total mercury volume in ml / g measured on the sample minus the mercury volume in ml / g measured on the same sample at a pressure of 30 psi (approximately 2 bar).These same parameters, and in particular the volumes and diameters of the solid within the mesoporosity range, can also be measured by nitrogen adsorption / desorption volumetry (also called nitrogen adsorption isotherm), a complementary analytical method to the one mentioned above. This analysis corresponds to the physical adsorption of nitrogen molecules into the material's porosity via a progressive increase in pressure at constant temperature and provides information on textural characteristics. In particular, it allows access to the mesoporous distribution of the steric extrusion solid. Thus, the representative pore distribution of a pore population centered in a range of 2 to 50 nm is determined. terminated by the Barrett-Joyner-Halenda (BJH) model. The nitrogen adsorption-desorption isotherm according to the BJH model is described in the periodical "The Journal of American Society", 73, 373, (1951) written by EP Barrett, LG Joyner and PP Halenda.

[0164] The size-exclusion solid particles preferably have a volume-equivalent mean diameter (preferably determined by laser granulometry, i.e., by laser diffraction using a particle size analyzer) of between 20 and 5000 pm, preferably between 50 and 1500 pm, preferably between 100 and 800 pm, and even more preferably between 300 and 600 pm. Advantageously, the solid particles are substantially spherical.

[0165] According to the invention, the fixed bed train (or each fixed bed train) of the size exclusion extraction step b) is fed with crude or clarified polymer solution at at least one injection point F of the polymer solution and with at least one eluent at one injection point S of the eluent. Preferably, the operating fixed bed train considered is fed with crude or clarified polymer solution at one injection point F of the polymer solution and with an eluent at one injection point S of the eluent.

[0166] Preferably, the eluent and the polymer solution feed the (or each) fixed bed train of the size-exclusion extraction step at a ratio of the volumetric flow rates of the eluent to the polymer solution of 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, such a ratio being also referred to as the solvent ratio. Such a solvent ratio, i.e., such a setting of the volumetric flow rates of the crude or clarified polymer solution and of the eluent, for the (or each) train, contributes to the efficiency of the size-exclusion separation of the PVC resins from the impurities present in the polymer solution that feeds the extraction step b).

[0167] When the fixed bed train includes several injection points Fi of the polymer solution, for example two injection points Fl and F2 of the polymer solution, the flow of the crude or clarified polymer solution that feeds said considered fixed bed train of the extraction step is divided into as many partial flows of polymer solution to feed said fixed bed train at said injection points Fi, said partial flows of polymer solution having equal or different flow rates between them.

[0168] When the fixed bed train includes several eluent injection points Si, for example two injection points SI and S2, the total eluent flow that feeds said fixed bed train is divided into as many partial eluent flows to feed said fixed bed train at said injection points Si, said partial eluent flows having equal or different flow rates.

[0169] The (or each) fixed bed train of step b) of size exclusion extraction implements at least one withdrawal of an extract at at least one withdrawal point E of the extract, and at least one withdrawal of a raffinate at at least one withdrawal point R of the raffinate. Preferably, the (or each) fixed bed train of step b) of size exclusion extraction implements a withdrawal of an extract at a withdrawal point E of the extract, and a withdrawal of a raffinate at a withdrawal point R of the raffinate.

[0170] The injection points F of the polymer solution and S of the eluent, and the withdrawal points E of the extract and R of the raffinate, are distinct from one another. They are advantageously located between two consecutive beds, or possibly upstream of the first bed, particularly in the case of an open circuit (in the case of a closed loop of n fixed beds, the nth bed being connected to the first bed, these two beds are considered consecutive). However, in one embodiment, particularly according to a Varicol® process (described below), they may be located, on average over an operating cycle, in the middle of a fixed bed or within a fixed bed. The injection points of the polymer solution and the eluent, and the withdrawal points of the extract and the raffinate, are distributed relative to one another so as to define at least three, preferably four, successive main operating zones of the n fixed beds:

[0171] - a zone I for elution of impurities, located between the injection point S of the eluent and the extraction point E of the extract;

[0172] - an elution zone II of at least one PVC polymer, comprising between the point of extraction point E of the extract and injection point F of the polymer solution;

[0173] - an impurity retention zone III, comprising the injection point F of the polymer solution and the raffinate withdrawal point R; and

[0174] - optionally, and preferably, a zone IV comprising between the point of withdrawal R of the raffinate and the injection point S of the eluent.

[0175] When there are multiple injection points F) of the polymer solution and / or Si of the eluent and / or multiple withdrawal points of the extract and / or raffinate, zones I, II, III, and IV begin at the first injection and / or withdrawal point of the stream under consideration (eluent, polymer solution, extract, or raffinate), the term "first" being defined here as the upstream point of all the injection and / or withdrawal points of said stream under consideration. When there are multiple injection points Fi of the polymer solution and / or Si of the eluent and / or multiple withdrawal points of the extract and / or raffinate, secondary operating zones may also be defined, in particular within zones I, II, III, and IV, which are the primary operating zones.

[0176] When the n fixed beds of the train considered in step b) operate in open circuit, the eluent is introduced at the eluent injection point(s) S, the crude or possibly clarified polymer solution is introduced at the polymer solution injection point(s) F, the extract is withdrawn at the extract withdrawal point(s) E, and everything else is withdrawn at the raffinate withdrawal point(s) R. The injection and withdrawal points thus define three main successive operating zones: zones I, II, and III. In this embodiment, a significant quantity of eluent relative to the polymer solution is generally required to maximize separation. For example, this open-circuit operating mode requires a volumetric flow rate ratio of eluent to polymer solution between 2.0 and 50.0, preferably between 5.0 and 20.0, or even between 5.0 and 10.0.

[0177] When the n fixed beds of the considered train in step b) operate in a closed loop, the eluent is introduced at the eluent injection point(s) S, the crude or possibly clarified polymer solution is introduced at the polymer solution injection point(s) F, an extract is withdrawn at the extract withdrawal point(s) E, a raffinate is withdrawn at the raffinate withdrawal point(s) R, and at least a portion of the introduced eluent advantageously remains circulating in the closed loop of the n beds (this is referred to as eluent recycling). In this embodiment, the injection and withdrawal points then define four main successive operating zones, zones I, II, III, and IV, with zone IV being designated as the eluent regeneration and recycling zone. In this particular embodiment, the eluent supply requirements (i.e.The quantities of eluent introduced in S) are very advantageously less important than in the case of an open-circuit operating mode to ensure efficient separation. For example, this closed-loop operating mode requires a volumetric flow rate ratio of the eluent to the polymer solution between 0.1 and 10, preferably between 0.2 and 5.0, or even between 0.8 and 2.0.

[0178] Advantageously, in the case of a closed loop of n fixed beds, the n steric exclusion solid beds are distributed in zones I to IV, preferably according to a so-called a / b / c / d type configuration, the distribution of the steric exclusion solid beds in zones I to IV with respect to the total number n of steric exclusion solid beds being such that:

[0179] - a is the number of steric exclusion solid beds in zone I,

[0180] - b, the number of steric exclusion solid beds in zone II,

[0181] - c, the number of steric exclusion solid beds in zone III, and

[0182] - d, the number of steric exclusion solid beds in zone IV,

[0183] and in which:

[0184] - a = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30),

[0185] - b = (n * 0.15) * (1 ± 0.40, preferably 1 ± 0.30),

[0186] - c = (n * 0.25) * (1 ± 0.40, preferably 1 ± 0.30), and

[0187] - d = (n * 0.30) * (1 ± 0.40, preferably 1 ± 0.30).

[0188] It is obvious to a 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, the total number of fixed beds in the operating fixed bed train under consideration. Thus, a 6 / 3 / 4 / 2 configuration means that there are 15 fixed beds of steric exclusion solid distributed as follows: 6 fixed beds in zone I, 3 fixed beds in zone II, 4 fixed beds in zone III, and 2 beds in zone IV.

[0189] Most advantageously, the filling density of each of the n fixed beds of steric exclusion solid, expressed as mass of steric exclusion solid per unit bed volume (i.e. per kg of solid per m3 of bed) can vary between 100 and 1500 kg / m3, preferably between 300 and 1000 kg / m3, preferably between 400 and 800 kg / m3.

[0190] According to the invention, the injection points F and S and the withdrawal points E and R are shifted over time in a bed of steric exclusion solid at a frequency determined by a predetermined permutation period. A permutation period can be defined as the time between two successive displacements (or shifts) of the injection and withdrawal points in a fixed bed. The periodic displacement (or shift) of the injection points F and S and the withdrawal points E and R can be performed synchronously or asynchronously, the latter case (asynchronous) being known as VARICOL®.The periodic movement of the injection and withdrawal points along the n fixed beds makes it possible in particular to define an operating cycle and also advantageously a cycle time which corresponds to the time required for the injection and withdrawal points to return to their initial position, i.e. to the number of beds n multiplied by the permutation period.

[0191] When the n fixed beds of exclusion solid operate in a closed loop, an operating cycle advantageously comprises as many permutation periods as there are beds of steric exclusion solid present in the closed separation loop. For example, an operating cycle of a train comprising 12 fixed beds of steric exclusion solid includes 12 permutation periods.

[0192] Thus, in the preferred embodiment in which the n fixed beds of exclusion solid of the considered train operate in a closed loop, the switching period is preferably adjusted to define a cycle time, which corresponds to the time required for the injection and withdrawal points to return to their initial position, ranging from 1 minute to 600 minutes, preferably from 5 minutes to 200 minutes, and most preferably from 10 minutes to 90 minutes. Such a cycle time contributes to the efficiency of the size exclusion separation of PVC resins and impurities present in the polymer solution that feeds the extraction step b).

[0193] In the case of the embodiment in which the n fixed beds operate in open circuit (i.e. that everything is drawn off with the extract and the raffinate), the cycle time can also be between 1 minute and 600 minutes, preferably between 5 minutes and 200 minutes, preferably between 10 minutes and 90 minutes.

[0194] The movement of the injection points F and S and of the withdrawal points E and R can be done by the installation of a series of on / off valves, controlled by an automatic sequence, or even by a single rotary valve.

[0195] In general, the liquid flow in the fixed beds is advantageously from bed i to bed i+1, where i is an integer between 1 and n, the total number of fixed beds, i.e., from upstream to downstream. This flow may be called downward liquid flow, even if the presence of pump(s) is / are necessary (particularly between the nth bed and the first bed in the case of closed-loop operation where the n beds are in a column). At the time of the switchover (or relocation of the injection and withdrawal points), the supply and withdrawal points are moved one bed, located downstream of the previous bed, thus creating / simulating a countercurrent liquid flow, possibly called an upward flow. A cutoff flow rate can then be defined when the two countercurrent liquid flows are equal, i.e., when the downward liquid flow rate equals the upward liquid flow rate.This stopping flow rate can be calculated by dividing the intergranular volume of the size exclusion solid in the beds by the permutation period, the intergranular volume of the size exclusion solid in the beds being a function of the filling density of the fixed beds of size exclusion solid and the density of the size exclusion solid particles. More specifically, the intergranular volume (V(intergranular)) of the size exclusion solid can be calculated by the following formula: .

[0196] V(intergranuiar) = V(iits)x(l - d (filling) / d(grain)) + Vmort

[0197] with:

[0198] Intergranular) ■ The intergranular volume of the steric exclusion solid in the beds (in m3);

[0199] V(iits): the geometric volume of the beds (in m3);

[0200] : the filling density of the steric exclusion solid in the beds (in kg / m3), corresponding to the actual filling density of the steric exclusion solid, i.e. the mass of said solid per unit volume of the bed. As a first approximation, it can be assimilated to the compacted filling density which consists of the mass of solid that occupies a given volume after compaction by vibration of said solid, according to a principle derived from standards D4164 and D4180 applied to the case of catalysts;

[0201] d(grain) ■ the grain density of the steric exclusion solid, typically measured by mercury porosimetry (in kg / m3);

[0202] Vmort: the volume (in m3) of the equipment without steric exclusion solid but through which the fluid concerned flows, in particular the polymer solution (for example the volume of the upstream, downstream lines, etc.).

[0203] The stopping flow rate, which is a volumetric flow rate, allows the calculation of dimensionless parameters, particularly those relating to zones II and IV, in particular the ratio between the flow rate The volumetric flow rate in zone II and the cutoff flow rate, and the ratio between the volumetric flow rate in zone IV and the cutoff flow rate. Preferably, the ratio of the volumetric flow rate of zone IV divided by the cutoff flow rate is less than or equal to 2, preferably between 0.5 and 1.5 and even more preferably between 0.8 and 1.0; preferably the ratio of the volumetric flow rate of zone II divided by the cutoff flow rate is between 0.5 and 3.0, preferably between 0.9 and 1.5 and preferably between 1.0 and 1.25. Thus, the cutoff flow rate helps to adjust the settings of extraction step b) and therefore the efficiency of the separation.

[0204] Furthermore, and very advantageously, the surface velocity in the fixed beds of an operating zone, which corresponds to the volumetric flow rate in the zone considered divided by the cross-section of said zone (i.e., of the column in which the beds of said zone are located), can be adjusted so that this surface velocity is between 0.01 and 10.0 cm / s and preferably between 0.05 and 2.5 cm / s. Adjusting the surface velocity in the fixed beds advantageously allows, in particular, the control of the attrition of the size-exclusion solid particles and thus the adjustment of the operation of the fixed bed train in the extraction stage in such a way as to avoid high pressure losses (especially encountered at high velocities) and / or dispersion problems (especially encountered at low velocities).

[0205] Preferably, the size exclusion extraction step of step b) is carried out at a temperature between ambient temperature and 200°C, preferably between 20°C and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and advantageously at a pressure between atmospheric pressure and 11.0 MPa absolute, preferably between 0.1 MPa and 11.0 MPa absolute, preferably between 0.1 MPa and 5.0 MPa absolute, more preferably between 0.1 MPa and 2.0 MPa absolute. Under these operating conditions, the PVC resins remain dissolved in the dissolving solvent and optionally in the eluent, the latter (i.e., the dissolving solvent and the eluent) being at least partially in liquid form. Preferably, the temperature and pressure conditions of step b) are the same as those of step a) of dissolution.

[0206] Step b) of size exclusion extraction thus recovers at least one extract which includes at least some, preferably all, of the impurities present in the polymer solution that feeds said step b), and at least one raffinate which includes a polymer solution freed at least some, preferably all, of impurities. Said raffinate recovered at the end of the size exclusion extraction step constitutes at least some, preferably all, of the purified polymer solution. This purified polymer solution is then preferably sent, at least some, preferably all, to step c) of polymer-solvent separation. However, if necessary, it can be sent to other steps Possible purification steps are taken to optimize the purification of the targeted PVC resins, if necessary. This size exclusion extraction step allows for the efficient and continuous separation of impurities, particularly soluble ones, from the crude or clarified polymer solution, which includes the PVC resin(s) dissolved in the solvent.

[0207] Size exclusion chromatography, particularly in the case of a closed-loop fixed-bed system, allows for the efficient separation of impurities from PVC polymers in a continuous manner. This reduces the labor required for this step while also facilitating its operation. It also offers high productivity, especially compared to batch size exclusion chromatography, while providing relatively low eluent consumption. Step c) Polymer-solvent separation

[0208] According to the invention, the process includes a step c) of polymer-solvent separation, to obtain at least one stream of at least one purified PVC polymer and at least one fraction of at least one solvent comprising the dissolving solvent.

[0209] Step c) of polymer-solvent separation advantageously implements at least one solvent recovery section and preferably between one and five solvent recovery section(s).

[0210] Advantageously, step c) is fed with the purified polymer solution obtained at the end of step b) or possibly a final purified polymer solution from an additional purification step located downstream of step b) of size exclusion extraction.

[0211] Step c) of polymer-solvent separation is thus aimed first at separating at least partially, preferably predominantly, the dissolving solvent and possibly the eluent from the PVC polymer(s) contained in the polymer solution that feeds step c), more particularly the purified polymer solution or possibly a final purified polymer solution from a further purification step, so as to recover at least one PVC polymer, freed at least partially, preferably predominantly and preferably totally, from the dissolving solvent, and possibly the eluent, still present in the polymer solution that feeds step c). By predominantly, it is understood 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, most preferably at least 99% by weight, or even at least 99.9% by weight, of the solvent(s) (i.e.of the dissolving solvent and possibly of the eluent) contained in the purified polymer solution, relative to the weight of the solvent(s) contained in the purified polymer solution which feeds step c), in particular of the dissolving solvent and possibly the eluent. content(s) in said purified polymer solution. Any solvent / polymer separation method known to those skilled in the art may be implemented, in particular any method allowing a phase change of the polymer(s) and / or solvent(s). The solvent(s) may be separated, for example, by precipitation or crystallization of the polymers, evaporation of the solvents, devolatilization by flash, atomization (high-pressure nozzle, rotary atomizer, bi-fluid nozzle, ultrasonic atomizer), stripping, demixing, extrusion, density difference, and in particular decantation or centrifugation, etc.

[0212] The stream of at least one purified PVC polymer thus obtained may correspond to a concentrated polymer solution or to at least one purified PVC resin in solid form. Preferably, step c) of polymer-solvent separation further comprises a conditioning section for conditioning at least one purified PVC resin in solid form, and more particularly in the form of powder, beads, or granules.

[0213] Step c) of polymer-solvent separation also aims to recover at least partially, preferably predominantly, and preferably entirely, the solvent(s) contained in the purified polymer solution that feeds step c). Step c) of polymer-solvent separation also aims optionally to purify and recycle the recovered solvent fraction, particularly upstream of step a) of dissolution. By predominantly, it should be understood as at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight, and even more preferably at least 95% by weight relative to the weight of the solvent(s) contained in the purified polymer solution that feeds step c).

[0214] Advantageously, step c) of polymer-solvent separation implements at least one solvent recovery section, the latter preferably comprising equipment operated at different temperatures and different pressures, in order to obtain at least one solvent fraction and one purified polymer fraction.

[0215] Thus, the process according to the invention makes it possible to efficiently and continuously recover PVC polymers from a plastic feedstock, with high productivity and a limited number of operations. Very advantageously, the process according to the invention makes it possible to obtain a PVC polymer stream having 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 even more preferably strictly greater than 99.9% (by weight of PVC polymer relative to the total weight of the recovered purified stream), from any type of PVC-based plastic feedstock.Another advantage of the process according to the invention also lies in the fact that an efficient separation of impurities, in particular additives, present in the plastic charge, is possible, while allowing reasonable consumption of solvents, in particular of dissolving solvent and eluent, and lower energy consumption than that ne. necessary for more conventional, so-called thermal separations, such as crystallization. The process according to the invention thus makes it possible to obtain a purified PVC polymer stream, less colored than the plastic feed to be treated, or even colorless, and very advantageously deodorized. More particularly, the process according to the invention makes it possible to obtain a purified PVC polymer stream free of at least some, preferably all, of the impurities, such as additives, present in the plastic feed, and free, at least some or even all, of solvent, in particular the dissolving solvent and the eluent.

[0216] Thus, the process according to the invention advantageously makes it possible to obtain a purified PVC polymer stream comprising a solvent content, in particular a dissolving solvent or eluent content, of 10% by weight or less, preferably 5% by weight or less, preferably 1.0% by weight or less, and even more preferably 0.1% by weight or less, and very advantageously an impurity content of 10% by weight or less, preferably 5% by weight or less, and preferably 1.0% by weight or less, even more preferably 0.5% by weight or less, or even 0.1% by weight or less, the percentages being given relative to the total weight of the purified PVC polymer stream. In particular, the purified PVC polymer stream obtained very advantageously has the following contents:

[0217] - less than 0.1% by weight of phthalates subject to regulatory authorization REACH in Europe (Annex XIV of Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular strictly less than 0.1% by weight of phthalates selected from the list consisting of the following phthalates: dibutyl phthalate (DBP), dioctyl or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), dii-isobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, alone or in mixtures,

[0218] - less than 0.1% by weight of the element lead, in particular said lead contained in metallic stabilizer additives assessed under the REACH regulation and subject to detailed restrictions (Annex XV) adopted between December 2017 and March 2018 by the ECHA's Risk Assessment Committee (RAC) and Socio-Economic Analysis Committee (SEAC),

[0219] - less than 0.1% by weight, and preferably less than 0.01% by weight, of the element cadmium, in particular said cadmium contained in metallic stabilizer type additives prohibited by the REACH regulation according to the amendment of Annex XVII (Regulation 494 / 2011 of 20 May 2011). Size exclusion extraction device

[0220] The present invention also relates to a size exclusion extraction device adapted for separating PVC polymers from impurities contained in a polymer solution. Said device comprises:

[0221] - n fixed beds of a steric exclusion solid, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 8 and 24, most preferably between 8 and 21 and preferably between 12 and 15, said size-exclusion solid having a volume mean pore diameter 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 a silica gel, a grafted silica, a carbon molecular sieve, or mixtures thereof,

[0222] the n fixed beds of the steric exclusion solid being distributed in one or more column(s), preferably in M ​​column(s), M being an integer between 1 and the total number n of fixed beds of the exclusion solid, the n beds being connected in series and preferably in a closed loop,

[0223] - N injection systems, preferably distinct from each other, for the polymer solution, N injection systems, preferably distinct from each other, for an eluent, N withdrawal systems, preferably distinct from each other, for an extract and N withdrawal systems, preferably distinct from each other, for a refiner, N being an integer preferably equal to n, said injection and withdrawal systems being located between two consecutive beds or possibly upstream of the first bed,

[0224] the injection systems for the polymer solution and the eluent and / or the withdrawal systems for the extract and the raffinate located in the same position, i.e. between the same two consecutive beds or possibly upstream of the first bed, being distinct or identical (by identical, it must be understood that a valve system can allow either the introduction of the polymer solution or that of the eluent, or the withdrawal of one or the other flow, i.e. of the extract or the raffinate),

[0225] - each injection and withdrawal system comprising at least one suitable valve to allow or prevent the passage of a flow of polymer solution and / or eluent and / or extract and / or raffinate, preferably i) a series of on / off valves controlled by an automatic sequence, or ii) a single rotary valve, so as:

[0226] - to define, at a time t, an injection point of the polymer solution, a point injection point of the eluent, a withdrawal point of the extract and a withdrawal point of the raffinate, said injection and withdrawal points being distinct from each other and determining at least three, preferably four, successive main operating zones of the n fixed beds:

[0227] - a zone I for elution of impurities, comprising between an injection point of the eluent and a point for extracting the extract;

[0228] - an elution zone II of at least one PVC polymer, comprising between the point of extraction of the extract and a point of injection of the polymer solution;

[0229] - an impurity retention zone III, comprising between the injection point of the polymer solution and a raffinate withdrawal point; and

[0230] - possibly a zone IV between the raffinate withdrawal point and the eluent injection point;

[0231] - and to allow, over time, a shift in the injection and withdrawal points, synchronously or non-synchronously, according to a frequency determined by a predetermined permutation period, of a fixed bed of steric exclusion solid per permutation period. Plastic filler processing device

[0232] Such a size-exclusion extraction device can be integrated into a more comprehensive device for processing a plastic feedstock to obtain a purified PVC polymer stream, which includes:

[0233] - means for bringing the plastic filler into contact with a dissolving solvent so as to dissolve at least part of said plastic filler in said dissolving solvent and to obtain a crude polymer solution;

[0234] - possibly suitable solid-liquid separation means for separating insoluble in suspension in the crude polymer solution;

[0235] - at least one size exclusion extraction device according to the invention and as described above, advantageously connected to said means for contacting and dissolving or possibly to at least one of said solid-liquid separation means;

[0236] - means for separating the dissolving solvent and possibly the eluent of a purified PVC polymer stream, advantageously connected to at least one size exclusion extraction device.

[0237] Said device for processing a PVC charge to obtain a purified PVC polymer stream also advantageously includes means for transporting said means and devices.

[0238] Such a device makes it very advantageous to recover PVC polymers with high purity from a PVC-based plastic feed which may include a multitude of impurities.

[0239] The following example and figures illustrate the invention, in particular particular embodiments of the invention, without limiting its scope. EXAMPLES Example 1

[0240] This example is the result of numerical simulations carried out on the basis of experiments carried out in the laboratory.

[0241] The charge to be treated is composed of a Poly(Vinyl Chloride) or PVC resin (55% by weight) with a molar mass MW=120,000 g / mol, and a di-decyl phthalate (DiDP) additive (45% by weight), the percentages being given in weight relative to the total weight of the charge.

[0242] The filler is first dissolved in diethylketone (DEK) at 100°C, at atmospheric pressure, to form a homogeneous crude polymer solution comprising 80% by weight of DEK and 20% by weight of filler (polymer and additive).

[0243] The crude polymer solution obtained is introduced into a simulated moving bed comprising 15 fixed beds of a silica gel solid. These fixed beds are arranged in a 6 / 3 / 4 / 2 configuration (see [Fig. 1]). The eluent is diethyl ketone (DEK).

[0244] Silica gel has the following properties:

[0245] - ball diameter = 500 pm;

[0246] - pore diameter = 6-10 nm;

[0247] - porous volume = 0.50 ml / g of solid;

[0248] - filling density = 530 kg of solids / m3 lit.

[0249] Each bed is modeled by a 1D fixed-bed piston model with axial dispersion and a Fick model for intragranular transfer. Since the radius of gyration of PVC is estimated at 39 nm, the polymer is considered to be present only in the extragranular phase. The additives and the solvent have a radius of gyration of less than 1 nm and can therefore diffuse into the intragranular porosity. The medium in the beds is considered isothermal (100 °C) and the density of the polymer solution is considered constant (800 kg / m³).

[0250] The extraction is adjusted with the following settings:

[0251] - cycle time = 15 min, i.e. a permutation period of 60 seconds;

[0252] - volumetric flow rate of eluent relative to the volumetric flow rate of polymer solution S / F = 1.32;

[0253] - Zone IV flow rate / stop flow rate = 0.97;

[0254] - Zone II flow rate / stop flow rate = 1.05;

[0255] - maximum surface velocity = 1.43 cm / s.

[0256] The concentration profiles obtained for PVC and the additive by simulation are illustrated in [Fig. 3], which shows the concentration profile of PVC (solid line) and that of DiDP (dashed line). By convention, the eluent is injected just upstream of bed 1. The concentrations throughout the bed are given as weight percentages of the tracked compound, i.e., PVC or the additive, relative to the weight of DEK.

[0257] According to [Fig.3], it appears that the PVC, which does not explore the intra-granular porosity, is carried towards the raffinate and drawn off between beds 13 and 14. The DiDP additive being smaller, it diffuses into the intra-granular porosity and is carried towards the extract with a draw-off between beds 6 and 7.

[0258] Extraction performed in a simulated moving bed yields the following performance:

[0259] - purity of separated PVC = 99.93% by weight (which corresponds to the weight, or weight flow rate, of PVC in the raffinate relative to the total weight, or total weight flow, of the PVC and additive in the raffinate, excluding DEK solvent);

[0260] - efficiency of separated PVC = 99.95% (which corresponds to the weight flow rate of PVC extracted from the raffinate divided by the weight flow of PVC extracted in the whole extracted + raffinate);

[0261] - productivity = 149 kg of PVC extracted from the raffinate / h / m3 of bed.

[0262] The raffinate exiting the simulated moving bed of size exclusion extraction can then to be recovered and sent to a polymer-solvent separation section, in particular a DEK solvent evaporation section.

Claims

Demands

1. A method for recovering a stream of at least one purified PVC polymer from a plastic feedstock, comprising: a) a dissolution step comprising bringing the plastic filler into contact with a dissolving solvent, to obtain at least one crude polymer solution, the dissolving solvent being a solvent chosen such that its Hansen parameters are in the Hansen sphere of the targeted PVC polymer; b') optionally a step of separating insolubles from the crude polymer solution obtained at the end of step a), to obtain at least one clarified polymer solution; (b) a size exclusion extraction step of the crude polymer solution obtained at the end of step (a) or optionally of the clarified polymer solution obtained at the end of step (b'), to obtain a purified polymer solution, said size exclusion extraction step employing at least one train of n fixed beds of a size exclusion solid, n being an integer greater than or equal to 4, the n fixed beds of the size exclusion solid being in series, said size exclusion solid comprising silica, a carbon molecular sieve, a carbon replica, a polymeric molecular sieve of a chemical nature other than PVC, a porous polymer gel, a zeolite, alumina, a metal-organic framework (MOF) material, or mixtures thereof,said fixed bed train of step b) being fed with crude or clarified polymer solution at at least one injection point F of the polymer solution and with an eluent at at least one injection point S of the eluent, said eluent being a solvent chosen such that its Hansen parameters lie within the Hansen sphere of the targeted PVC polymer, said fixed bed train of step b) implementing at least one withdrawal of an extract at at least one withdrawal point E of the extract, and at least one withdrawal of a raffinate at at least one withdrawal point R of the raffinate, the injection points of the polymer solution and the eluent and the withdrawal points of the extract and the raffinate being distinct from one another and distributed so as to define at least three, preferably four, successive principal operating zones of the n fixed beds: - a zone I for elution of impurities, located between the injection point of, the eluent and the extract withdrawal point; - a zone II for elution of at least one PVC polymer, located between the extract withdrawal point and the polymer solution injection point; - a zone III for impurity retention, located between the polymer solution injection point and the raffinate withdrawal point; and - optionally a zone IV located between the raffinate withdrawal point and the eluent injection point, the injection and withdrawal points being shifted over time by a fixed bed of size exclusion solid according to a frequency determined by a predetermined permutation period, said raffinate being recovered to constitute, at least in part, the purified polymer solution, c) a polymer-solvent separation step, to separate the purified polymer solution into a stream of purified PVC polymer and at least a solvent fraction comprising dissolving solvent.

2. A process according to claim 1, wherein the dissolving solvent is an organic solvent selected from ketones, amides, esters, ethers, chlorinated solvents, sulfurous solvents, nitrogenous solvents, hydrocarbons, and mixtures thereof, preferably from methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, N,N-diethyl formamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, γ-butyrolcatone, γ-valerolactone, methoxycyclopentane, tetrahydrofuran, dichloromethane, dhnetyl sulfoxide, xylene, isohexane, dihydrolevoglucosenone, or cyrene, and mixtures thereof, most preferably among diethylketone, 4-heptanone, 2,4-dimethyl-3-pentanone, y-butyrolcatone, y-valerolactone, and mixtures thereof.

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

4. A method according to any one of the preceding claims, wherein the size exclusion extraction step b) employs at least one train of n fixed beds of a size exclusion solid, n being an integer between 4 and 30, and preferably between 12 and 15.

5. A method according to any one of the preceding claims, wherein the size-exclusion solid is a porous solid having a diameter average pore size in volume between 1 and 500 nm, preferably between 2 and 100 nm, preferably between 2 nm and 50 nm, preferably between 3 and 30 nm.

6. A method according to any one of the preceding claims, wherein the size-exclusion solid comprises a silica gel, a grafted silica, a carbon molecular sieve, or mixtures thereof.

7. A method according to any one of the preceding claims, wherein the eluent and the polymer solution feed into step b) in a ratio of the volumetric flow rates of the eluent relative to the polymer solution of 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.

8. A method according to any one of the preceding claims, wherein the injection points of the polymer solution and the eluent and the withdrawal points of the extract and the raffinate are located between two consecutive beds or possibly upstream of the first bed.

9. A method according to any one of the preceding claims, wherein the n beds of size-exclusion solid operate in a closed loop and are distributed in four main operating zones, zones I to IV, in a so-called a / b / c / d configuration, the distribution of the size-exclusion solid beds in zones I to IV relative to the total number n of size-exclusion solid beds being preferably such that: - a, the number of size-exclusion solid beds in zone I, - b, the number of size-exclusion solid beds in zone II, - c, the number of size-exclusion solid beds in zone III, and - d, 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).

10. A method according to any one of the preceding claims, wherein the n beds are in a closed loop and the switching period is preferably adjusted so as to define a cycle time, which corresponds to the time required for the injection and withdrawal points to return to their initial position, of between 1 and 600 minutes, preferably between 5 and 200 minutes, preferably between 10 and 90 minutes.

11. A method according to any one of the preceding claims, wherein the step a) is operated at a dissolution temperature between 20 and 200°C, preferably between 40 and 180°C, preferably between 60 and 150°C, and a dissolution 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.

12. A method according to any one of the preceding claims, wherein the weight quantity of PVC polymer in the plastic feed that feeds step a) is between 2 and 30% by weight, preferably between 5 and 20% by weight, preferably between 10 and 15% by weight, relative to the weight of the dissolving solvent.

13. A method according to any one of the preceding claims, wherein step b) is carried out at a temperature between 20 and 200°C, preferably between 40 and 180°C, preferably between 60 and 150°C, and 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.

14. A device for processing a plastic filler to obtain a purified PVC polymer stream, comprising: - means for contacting the plastic filler and a dissolving solvent, so as to dissolve at least part of said plastic filler in said dissolving solvent and to obtain a crude polymer solution; - solid-liquid separation means suitable for separating insolubles suspended in the crude polymer solution; - at least one size-exclusion extraction device, connected to at least one of said solid-liquid separation means; - means for separating the dissolving solvent and optionally the eluent from a purified PVC polymer stream, said means for separating the dissolving solvent being connected to said at least one size-exclusion extraction device;in which said at least one size exclusion extraction device comprises: - n fixed beds of a size exclusion solid, n being an integer greater than or equal to 4, preferably between 4 and 30, preferably between 12 and 15, said size exclusion solid having a volume mean pore diameter preferably between 1 and 500 nm, preferably between 2 and 100 nm, preferably between 2 and 50 nm, preferably between 3 and 30 nm, and preferably being a silica gel, a grafted silica, a molecular sieve; to coal, or mixtures thereof, the n fixed beds of the steric exclusion solid being distributed in one or more column(s), the n beds being connected in series and preferably in a closed loop, - N polymer solution injection systems, N eluent injection systems, N extract withdrawal systems and N raffinate withdrawal systems, N being an integer preferably equal to n, said injection and withdrawal systems being located between two consecutive beds or possibly upstream of the first bed, the polymer solution and eluent injection systems and / or the extract and raffinate withdrawal systems located at the same position being distinct or identical, - each injection and withdrawal system comprising valves adapted to allow or prevent the passage of a flow of polymer solution and / or eluent and / or extract and / or raffinate, preferably a series of on / off valves controlled by an automatic sequence, or a single rotary valve, such that: - to define, at a given time t, an injection point for the polymer solution, an injection point for the eluent, a withdrawal point for the extract and a withdrawal point for the raffinate, said injection and withdrawal points being distinct from each other and determining at least three, preferably four, successive main operating zones of the n fixed beds: - a zone I for elution of impurities, located between an injection point of the eluent and a withdrawal point of the extract; - a zone II of elution of at least one PVC polymer, located between the point of withdrawal of the extract and a point of injection of the polymer solution; - a zone III for impurity retention, located between the point of injection of the polymer solution and a point of withdrawal of the raffinate; and - possibly a zone IV located between the point of withdrawal of the raffinate and the point of injection of the eluent, - and to allow, over time, a shift in the injection and withdrawal points, synchronously or non-synchronously, according to a frequency determined by a predetermined permutation period, of a fixed bed of steric exclusion solid per permutation period.

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