WO2024110229A1

WO2024110229A1 - Method for recycling and processing used plastics by dissolving in a solvent with staggered solvent addition

Info

Publication number: WO2024110229A1
Application number: PCT/EP2023/081564
Authority: WO
Inventors: Yacine HAROUN; Sina TEBIANIAN; Wilfried Weiss; Stephane GIRARDON; Damien Leinekugel Le Cocq
Original assignee: IFP Energies Nouvelles
Priority date: 2022-11-21
Filing date: 2023-11-13
Publication date: 2024-05-30
Also published as: FR3142191A1

Abstract

The present invention relates to a method for processing a plastics feedstock, the method comprising: a) a dissolution step, implementing: i) a section for bringing the plastics feedstock into contact with at least some of a dissolution solvent, comprising at least one static or dynamic mixer, each mixer being fed with a plastics stream and a fraction of the dissolution solvent so that each mixer has a volume dilution ratio of dissolution solvent of between 3% and 70%, each mixer being run at a temperature of between 100°C and 300°C; then ii) a dissolution section run at a temperature of between 100°C and 300°C and a pressure of between 1.0 and 100.0 MPa absolute; then b) a purification step; then c) a solvent-polymer separation step, in order to obtain at least one fraction of purified thermoplastic polymers.

Description

METHOD FOR RECYCLING AND TREATMENT OF USED PLASTICS BY DISSOLUTION IN A SOLVENT WITH STAGED INTRODUCTION OF THE SOLVENT

TECHNICAL AREA

The present invention relates to a process for treating plastics, in particular used plastics, in order to obtain a flow of purified thermoplastic polymers which can be used for example in the manufacture of new plastic objects. More particularly, the present invention relates to a process for purifying a plastic filler, in particular from plastic waste, comprising thermoplastic polymers in particular polyolefins, for example polyethylene and/or polypropylene, by dissolving the targeted thermoplastics in a solvent then purification of the polymer solution obtained. Said process comprises a staged mixing of the solvent with the plastic filler, to obtain a homogeneous mixture, preferably having a viscosity less than or equal to 50 mPa.s, and very advantageously a coefficient of variation of concentration less than or equal to 10%, of so as to optimize the dissolution of the targeted thermoplastics and the purification of the polymer solution obtained to recover a stream of purified thermoplastics.

PRIOR ART

Plastics from collection and sorting channels can be recycled according to different channels.

So-called mechanical recycling makes it possible to partially reuse certain waste either directly in new objects or by mixing mechanically sorted plastic waste streams with virgin polymer streams. This type of recovery is limited since, even if it makes it possible to obtain a concentrated flow of a particular type of polymer, mechanical sorting does not make it possible to eliminate the impurities which are at least partly trapped in the polymer matrix, such as for example additives, such as fillers (or “fillers” according to Anglo-Saxon terminology), dyes, pigments, and metals.

So-called chemical recycling aims to reform at least partly monomers according to a generally complex sequence of steps. For example, plastic waste can undergo a pyrolysis step and the pyrolysis oil recovered, generally after purification, can be converted at least in part, for example into olefins by steam cracking. These olefins can then be polymerized. This type of sequence can be adapted for poorly sorted loads or refusals from sorting centers but it generally requires significant energy consumption due in particular to high temperature treatments. Another way of recycling plastic waste consists of putting plastics, in particular thermoplastics, into solution, at least in part, with a view to purifying them, by eliminating impurities, for example additives such as fillers or fillers according to the Anglo-Saxon terminology, dyes, pigments, and metals and/or polymers of the filler other than that/those targeted.

Several studies present different methods of processing plastic waste by dissolution and purification. Document US 2017/0021 10 describes a particular method for purifying a polymer filler in particular from plastic waste by dissolving the polymer in a solvent, under particular conditions of temperature and pressure, then contacting the polymer solution obtained with a solid.

Document WO 2018/114047 proposes a method for selectively dissolving a particular polymer of a plastic in a solvent at a dissolution temperature close to the boiling temperature of the solvent. However, the process of document WO 2018/1 14047 does not make it possible to effectively treat and separate impurities other than polymers, for example additives.

Document US 2018/0208736 proposes a treatment process by liquefaction of thermoplastics in a solvent then separation of insolubles and/or gases. The process of document US 2018/0208736 does not make it possible to effectively treat impurities soluble in the solvent.

The present invention aims to improve these processes for treating thermoplastics by dissolution in a solvent. In particular, the present invention seeks to optimize the processes for removing impurities from a plastic filler, by particularly improving the phase of bringing the solvent into contact with the plastic filler to be treated. The present invention thus aims to obtain a homogeneous mixture which advantageously has a sufficiently low viscosity, thus allowing optimal dissolution of the targeted thermoplastics, particularly in terms of dissolution time, stirring power required for mixing in the reactor and cost. Operating. Very advantageously, the elimination of impurities can thus be maximized in order to obtain a flow of purified thermoplastics, in particular a flow of purified polyolefins, which can be reused for example as a polymer base in the manufacture of new plastic objects in particular instead of virgin resin. SUMMARY OF THE INVENTION

The invention relates to a process for treating a plastic filler, comprising: a) a step of dissolving the plastic filler in a dissolution solvent, to obtain at least one crude polymer solution, the dissolution step a) involving work: i) a section for bringing the plastic filler into contact with at least part of the dissolution solvent, comprising at least one static or dynamic mixer, to produce a conditioned filler, each static or dynamic mixer being operated at a temperature comprised between 100°C and 300°C, each static or dynamic mixer being supplied by a plastic flow, comprising the plastic filler, and by a fraction of at least said part of the dissolution solvent, so that each mixer has a rate of volume dilution in dissolving solvent of between 3% and 70%, the rate of volume dilution in dissolving solvent being the ratio between the volume flow rate of the fraction of at least said part of the dissolving solvent which feeds the static or dynamic mixer considered and the sum of the volume flow rates of the fraction of at least said part of the dissolution solvent and the plastic flow which feed the static or dynamic mixer considered; ii) a dissolution section supplied at least by the conditioned charge coming from the contacting section and operated at a dissolution temperature of between 100°C and 300°C and a dissolution pressure of between 1.0 and 100.0 Absolute MPa; then b) a step of purifying the raw polymer solution to obtain a purified polymer solution, said purification step comprising: b1) a sub-step of separating the insolubles; and/or b2) a washing sub-step, by contact with a dense solution; and/or b3) an extraction sub-step, by contact with an extraction solvent; and/or b4) a sub-step of adsorption of impurities by contact with a solid adsorbent; then, c) a solvent-polymer separation step, to obtain at least a fraction of purified thermoplastic polymers.

The advantage of the process of the invention is to provide a process for effective treatment of a plastic load, and in particular plastic waste in particular from collection and sorting sectors, so as to recover thermoplastic polymers, in particular plastic waste. polyolefins, which it contains to be able to recycle them for all types of applications. The method according to the invention makes it possible more particularly to improve the contacting phase of the plastic filler with the dissolving solvent in order to obtain a homogeneous mixture advantageously having a viscosity preferably less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s. Very advantageously, said homogeneous mixture has a coefficient of variation (CoV) of concentration preferably less than or equal to 10%, preferably less than or equal to 5%. Such a mixture has the advantage of thus leading to a sufficiently low effective viscosity in the dissolution reactor, thus participating in the dispersion and homogenization of the plastic filler - dissolution solvent mixture. The dissolution of the thermoplastics that we seek to separate and recover is then optimal, without requiring the provision of excessively high stirring powers and/or while allowing the use of various stirring systems, such as mechanical stirring and/or or agitation by recirculation loop. At the same time, the residence time necessary to effectively dissolve the targeted thermoplastics can also be advantageously reduced, which can result in the use of equipment, for example the dissolution reactor, of optimized size.

The present invention thus makes it possible to effectively pre-mix the plastic filler with the dissolution solvent (or at least part of the dissolution solvent), while respecting the technical constraints imposed by the mixing equipment used, in particular by the system stirring of the dissolution section but also by equipment used in the contacting section, for example static mixers. Generally, static mixers are used to mix fluids whose viscosity ratio between said fluids varies up to 1000 (i.e. < 1000). However, the present invention makes it possible to effectively mix a plastic filler comprising thermoplastics, in particular polyolefins, whose melt viscosity is typically between 300 and 20,000 Pa.s, with a solvent whose viscosity varies between 1 and 0.01 mPa.s, in particular between 0.2 and 0.03 mPa.s, in the temperature range at which the mixing is carried out, i.e. a viscosity ratio between these two fluids in a range of approximately 10 ⁵ -10 ⁹ , which is very high and usually incompatible with the technical constraints of static or dynamic mixers.

The process according to the invention which comprises a dissolution step and in particular an improved bringing into contact of the solvent and the filler thus makes it possible to obtain a flow of purified thermoplastics, advantageously comprising a content of impurities, and in particular of additives, negligible or at least low enough that the stream of purified thermoplastic polymers can be used in any type of plastics formulation in place of virgin resin. For example, the flow of purified thermoplastics and in particular the flow of purified polyolefins, obtained at the end of the process according to the invention, advantageously has an impurity content less than or equal to 5% by weight of impurities, very advantageously less than or equal to 1.0% by weight of impurities, even more preferably a content less than or equal to 0.5% by weight of impurities.

The method according to the invention thus provides a simple diagram corresponding to a sequence of operations, which makes it possible to rid plastic waste of at least part of its impurities, in particular at least part of the additives, and to recover purified thermoplastic polymers, advantageously comprising little or no solvent, so as to be able to recover plastic waste by recycling said purified thermoplastics. Depending on the conditions implemented in the stages of the process, the additives present in the plastic filler can advantageously be soluble or insoluble in the solvent used throughout the process according to the invention, allowing effective purification and separation of the polymers.

The invention also has the advantage of participating in the recycling of plastics and the preservation of fossil resources, by allowing the recovery of plastic waste. It allows, in fact, the purification of plastic waste with a view to obtaining fractions of purified thermoplastic polymers, in particular purified polyolefins, with a reduced content of impurities, in particular decolorized and deodorized thermoplastic fractions, which can be reused to form new plastic objects. The purified thermoplastic fractions obtained can thus be used directly in formulations mixed with additives, for example dyes, pigments, other polymers, instead of or mixed with virgin polymer resins, with a view to obtaining plastic products with usage, aesthetic, mechanical or rheological properties facilitating their reuse and recovery.

DESCRIPTION OF THE EMBODIMENTS

According to the present invention, the expressions “between ... and ...” and “between .... and ...” are equivalent and mean that the limit values of the interval are included in the range of values described . If this is not the case and the limit values are not included in the range described, such precision will be provided by the present invention.

In the sense of the present invention, the different parameter ranges for a given step such as the pressure ranges and the temperature ranges can be used alone or in combination. For example, within the meaning of the present invention, a range of preferred pressure values can be combined with a range of more preferred temperature values. In the following, particular embodiments of the invention can be described. They can be implemented separately or combined with each other, without limitation of combinations when technically feasible.

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

The terms “upstream” and “downstream” are to be understood according to the general flow of the fluid(s) or flow in question in the process.

In this description, the terms "polymer", "thermoplastic polymer" and "thermoplastic" may be used interchangeably in place of one another.

The terms “static or dynamic mixer” and “mixer” are used interchangeably and correspond to mixing equipment well known to those skilled in the art such as static mixer or dynamic mixer.

According to the invention, the viscosity is defined as being a dynamic viscosity, in particular measured at a temperature of 200°C and at a shear rate of 0.1 s ^-1 , using a viscometer, preferably using a plane-plane type viscometer, for example of the DHR3 type from TA Instrument.

According to the invention, the coefficient of variation (CoV) of concentration is calculated by dividing the standard deviation of z concentration measurements by the average concentration, expressed as a percentage:

with I standard deviation on the concentration measurements: a

the average concentration: x =

n representing in these mathematical formulas, the total number of concentration measurements, xi representing the concentration value determined at measurement i; and z being an integer greater than or equal to 2, preferably greater than or equal to 4, and in general less than or equal to 10,000, preferably less than or equal to 1,000, the concentration being determined by any method known to the skilled in the art, for example by visualizing the color of a mixture of fluids of different colors, by measuring the content of a particular compound in samples taken (in particular z samples) and determined for example by liquid chromatography (or HPLC ) or gas chromatography. The lower the coefficient of variation (CoV) of concentration, the better the quality of the mixture, i.e. the more homogeneous the mixture.

The term “additives” is a term conventionally used in the field of polymers and in particular in the field of polymer formulations. The additives introduced into the polymer formulations can be, for example, plasticizers, fillers or “fillers” according to the established Anglo-Saxon terminology (which are organic or mineral solid compounds, making it possible to modify the physical, thermal, mechanical and/or electrical polymer materials or to lower their cost price), reinforcing agents, dyes, pigments, hardeners, flame retardants, combustion retardants, stabilizing agents, antioxidants, UV absorbers, antistatic agents, etc.

The additives correspond to at least part of the impurities of the plastic filler to be treated and which the treatment process according to the invention makes it possible to eliminate at least in part. Other types of impurities may be use impurities, such as for example metal impurities, paper/cardboard, biomass, polymers other than the targeted polymer(s), etc.

Thus according to the invention, the impurities, which the process according to the invention makes it possible to eliminate at least in part, include the additives conventionally used in polymer formulations and generally usage impurities resulting from the life cycle of the materials and objects plastics, and/or from the waste collection and sorting circuit. The latter can be metallic, organic or mineral impurities; it may be packaging residues, food residues or compostable residues (biomass). These use impurities may also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, silicones, rigid polymers, thermosetting polymers, products household, chemical or cosmetic products, used oils, water.

According to the invention, a polymer solution is a solution comprising the dissolution solvent and at least the targeted thermoplastic polymers, in particular the targeted polyolefins, dissolved (that is to say in particular solvated and dispersed). s) in said dissolution solvent, the dissolved polymers being initially present in the feed. The polymer solution may also comprise soluble (and solubilized in the dissolution solvent) and/or insoluble (and suspended in the polymer solution) impurities. Depending on the steps of the process according to the invention undergone, said polymer solution may therefore comprise impurities in the form of insoluble particles which are advantageously suspended in said solution. polymer, soluble impurities dissolved in the dissolution solvent, and/or optionally another liquid phase immiscible with said polymer solution.

It is well known that the boiling temperature of a compound varies with the operating pressure. However, without other indication, that is to say without indication of the pressure, the boiling temperature of the compound considered, in particular of the dissolution solvent, is understood as being the boiling temperature of said compound, in particular of said dissolution solvent, at atmospheric pressure (in particular equal to 0.1 MPa). Thus, the boiling temperature which characterizes the dissolution solvent must be understood as being the boiling temperature of said dissolution solvent at atmospheric pressure (in particular equal to 0.1 MPa).

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

The invention thus relates to a process for treating a plastic filler, preferably composed of plastic waste, and advantageously comprising thermoplastic polymers, more particularly polyolefins, said process comprising, preferably consisting of: a) a step of dissolving the plastic filler in a dissolution solvent, preferably comprising at least one hydrocarbon compound, preferably aliphatic, preferably having a boiling temperature of between -50 and 250°C, preferably between -15 and 150°C, preferably between - 1 and 1 10°C and preferably between 20 and 100°C, preferably according to a weight ratio between the dissolution solvent and the plastic filler, between 0.2 and 100.0, preferably between 0, 3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0, to obtain at least one raw polymer solution, dissolution step a) using: i) a section for bringing the plastic filler into contact with at least part of the dissolution solvent, comprising at least one, preferably between one and ten, preferably between two and six, preferably between two and five, mixer ( s) static or dynamic, advantageously in series, to produce a conditioned load, each static or dynamic mixer being operated at a temperature between 100°C and 300°C, preferably between 150 and 250°C , each static or dynamic mixer being supplied by a plastic flow, including the plastic load, and by a fraction of at least said part of the dissolution solvent so that each mixer has a volume dilution rate of dissolution solvent of between 3% and 70%, preferably comprised:

- between 3% and 50%, preferably between 10% and 35%, and very preferably between 15% and 30%, when the ratio of viscosities between the plastic flow and the fraction of at least said part of the solvent dissolution, which feed the static or dynamic mixer considered, is greater than or equal to 3500, preferably greater than or equal to 3000,

- between 10% and 70%, preferably between 20% and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the fraction d 'at least said part of the dissolution solvent, which feeds the static or dynamic mixer considered, is less than 3500, preferably less than 3000, the volume dilution rate in dissolution solvent, for each static or dynamic mixer considered, being the ratio between the volume flow rate of the fraction of at least said part of the dissolution solvent which feeds the static or dynamic mixer considered and the sum of the volume flow rates of said fraction of at least said part of the dissolution solvent and of the plastic flow which supply the static or dynamic mixer considered, the contacting section may comprise a means for melting at least in part the plastic filler, located upstream of the first static or dynamic mixer, the means for melting then being advantageously supplied by the plastic filler and optionally also being supplied with a fraction of at least said part of the dissolution solvent, for example between 0.02 and 4.0% by weight, or even between 0.1 and 1.0% by weight, of the weight of dissolution solvent introduced in step a); ii) a dissolution section supplied at least by the conditioned charge coming from the contacting section, and possibly by another part of the dissolution solvent, and operated at a dissolution temperature of between 100°C and 300°C, preferably between 150 and 250°C, and a dissolution pressure between 1.0 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute; then b) a step of purification of the raw polymer solution, comprising: b1) a sub-step of separating the insolubles making it possible to obtain at least one clarified polymer solution and an insoluble fraction; and/or b2) a washing sub-step, by contact with a dense solution, making it possible to obtain at least one washing effluent and a washed polymer solution; and/or b3) an extraction sub-step, by contact with an extraction solvent, making it possible to obtain at least one extracted polymer solution and a used solvent; and or b4) a sub-step of adsorption of impurities by contact with a solid adsorbent, to obtain at least one refined polymer solution; the purification step making it possible to obtain a purified polymer solution which advantageously corresponds to a clarified or washed or extracted or refined polymer solution; then, c) a solvent-polymer separation step, to obtain at least one fraction of purified thermoplastic polymers, more particularly at least one fraction of purified polyolefins.

Load

The filler of the process according to the invention, called plastic filler, comprises plastics which themselves comprise more particularly thermoplastic polymers, such as polyolefins. Preferably, the plastic filler comprises between 50 and 100% by weight, preferably between 70% and 100% by weight of plastics.

The plastics included in the load of the process according to the invention are generally production scraps and/or “post-consumer” waste from plastic objects, in particular household plastic waste, plastic waste from construction, automotive plastic waste. or any type of transport or even waste electrical and electronic equipment. Preferably, plastic waste comes from collection and sorting channels. Plastics or plastic materials include polymers which are mixed with additives in order to provide specific properties to the materials, with a view to constituting, after shaping, various objects (injection molded parts, tubes, films, fibers, fabrics). , sealants, coatings, etc.). Additives used in plastics can be organic compounds or inorganic compounds. These include, for example, fillers, dyes, pigments, plasticizers, property modifiers, combustion retardants, etc.

The filler of the process according to the invention comprises in particular thermoplastic polymers, preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 80% by weight and very preferably at least 90% by weight of polymers. thermoplastics. The thermoplastic polymers included in the plastic filler may be alkene polymers, diene polymers, vinyl polymers and/or styrenic polymers. Preferably, the thermoplastic polymers included in the plastic filler are polyolefins, such as polyethylene (PE), polypropylene (PP) and/or copolymers of ethylene and propylene or mixtures thereof. Preferably, the plastic filler comprises at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight, of polyolefins relative to the total weight of the plastic filler. The method according to the invention aims in particular to purify and recover the polyolefins contained in the load to be able to reuse them in different applications.

The plastic filler may comprise mixtures of polymers, in particular mixtures of thermoplastics and/or mixtures of thermoplastics and other polymers, additives advantageously used to formulate the plastic material and generally use impurities resulting from the life cycle of the materials and plastic objects, and/or from the waste collection and sorting circuit, all of these compounds being considered as impurities. The charge for the process according to the invention generally comprises less than 50% by weight of impurities, preferably less than 20% by weight of impurities, preferably less than 10% by weight of impurities. The plastic filler may include, for example, at least 1% by weight of impurities, or even at least 5% by weight of impurities.

The plastic filler can advantageously be pretreated upstream of the process so as to at least eliminate all or part of the so-called coarse impurities, that is to say impurities in the form of particles of size greater than or equal to 10 mm, preferably greater than or equal to 10 mm. equal to 5 mm, or even greater than or equal to 1 mm, for example impurities such as wood, paper, biomass, iron, aluminum, glass, etc., and to shape it generally in the form of divided solids so as to facilitate the treatment in the process. This pretreatment may include a grinding step, a washing step at atmospheric pressure and/or a drying step. This pretreatment can be carried out on a different site, for example in a waste collection and sorting center, or on the same site where the treatment process according to the invention is implemented. Preferably, this pretreatment makes it possible to reduce the impurity content to less than 20% by weight, preferably less than 15% by weight, preferably less than 10% by weight, the percentages being given relatively to the weight of the filler. plastic treated by the process according to the invention. At the end of pretreatment, the feed is generally stored in the form of divided solids, for example in the form of ground material, flakes or powder, or even granules, so as to facilitate handling and transport to the process.

Step a) dissolution

According to the invention, the process comprises a dissolution step a) in which the plastic filler is brought into contact with a dissolution solvent and the thermoplastics which it contains, and the separation and purification of which are advantageously aimed at, in particular polyolefins. which it contains, are dissolved in the dissolving solvent, to obtain at least one, preferably one, crude polymer solution. Dissolution step a) then implements i) a section for bringing the plastic filler into contact with part or all of the dissolution solvent, said contacting being advantageously carried out by staged introduction of the dissolution solvent, and ii) a dissolution section allowing the dissolution of at least part of the plastic filler, preferably of at least part of the targeted thermoplastics, preferably of all of the targeted thermoplastics, in particular of the targeted polyolefins, in the dissolution solvent. The contacting section and the dissolution section can be distinct and successive sections, the contacting section preceding the dissolution section, or joint and simultaneous sections.

By dissolution, it is necessary to understand any phenomenon leading to obtaining at least one solution of thermoplastic polymers, that is to say a liquid (or fluid) comprising the targeted thermoplastic polymers dissolved in the dissolving solvent. Those skilled in the art are well aware of the phenomenon(s) involved in the dissolution of polymers and which includes at least a mixture, a solvation, a dispersion, a homogenization, a disentanglement of the thermoplastic polymer chains.

During and at the end of the dissolution step a), the pressure and temperature conditions make it possible to maintain the dissolution solvent, at least in part and preferably in totality, in the liquid state or possibly in the liquid state. supercritical state, while the soluble fraction of the plastic filler, in particular the targeted thermoplastic polymers and very particularly the targeted polyolefins, and for example at least part of the impurities, is advantageously dissolved, at least in part and preferably in full , in the dissolving solvent.

The dissolving solvent is an organic solvent or a mixture of organic solvents. Advantageously, the dissolution solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (that is to say saturated), preferably linear or branched. Preferably, the dissolution solvent comprises at least 80% by weight, preferably at least 95% by weight, preferably at least 98% by weight of at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear or branched. , the percentages being expressed relative to the total weight of the dissolving solvent (100% being the maximum). Preferably, the dissolution solvent comprises at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling temperature (at atmospheric pressure, in particular at 0.1 MPa) of between -50 and 250°C, preferably between - 15 and 150°C, preferably between - 1 and 110°C and preferably between 20 and 100°C. Preferably, the dissolution solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear or branched, having between 3 and 12 carbon atoms, preferably between 4 and 8 atoms. of carbon. For example, the dissolution solvent comprises a compound chosen from the isomers of butane, pentane, hexane, heptane and octane. The solvent of dissolution may comprise, preferably consist of, a mixture of isomers of butane, pentane, hexane, heptane and/or octane, and preferably at a content of said mixture in the solvent dissolution greater than or equal to 80% by weight, preferably greater than or equal to 95% by weight, preferably greater than or equal to 98% by weight, relative to the total weight of the dissolution solvent. Very advantageously, a preferred hydrocarbon compound for the dissolution solvent comprises a paraffinic aliphatic compound, having a critical temperature (temperature at the critical point of said pure hydrocarbon compound) preferably between 95 and 350°C, preferably between 130 and 300°C, preferably between 180 and 285°C.

Preferably, the dissolution step a) is supplied with the plastic filler and a dissolution solvent, according to a weight ratio between the dissolution solvent and the plastic filler, of between 0.2 and 100.0, preferably between 0. .3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0.

Advantageously, the dissolution solvent which feeds dissolution step a) is in liquid or possibly supercritical form. It can advantageously be preheated, preferably to a temperature between 100 and 300°C, preferably between 150 and 250°C, prior to its introduction in step a), in particular prior to its introduction into the contacting section and possibly in the dissolution section, in order to facilitate the heating of the plastic filler and/or a drop in temperature of the material flow in the contacting and possibly dissolution sections of step a).

Advantageously, the dissolution solvent comprises, preferably consists of, a make-up of fresh solvent and/or a stream of recycled solvent from a subsequent step of the process, preferably at least in part from step c) of solvent-polymer separation. i) the contact section:

According to the invention, the section for bringing the plastic filler into contact with at least part of the dissolution solvent comprises at least one static or dynamic mixer, preferably between one and ten, preferably between two and six, very preferably between two and five static or dynamic mixer(s), preferably static(s). When the contacting section comprises several (that is to say at least two) static or dynamic mixers, the static or dynamic mixers are advantageously in series with each other (or successive). Advantageously, each static or dynamic mixer is operated at a temperature preferably between 100°C and 300°C, preferably between 150 and 250°C. Each static or dynamic mixer is supplied with a plastic flow, comprising the plastic filler, and with a fraction of at least said part of the dissolution solvent (that is to say a fraction of the part, preferably all, of the dissolving solvent which supplies the contacting section i) so that, in each mixer, the volume dilution rate of dissolving solvent is between 3% and 70%. The volume dilution rate of dissolution solvent in a static or dynamic mixer corresponds, according to the invention, to the ratio between the volume flow rate of the fraction of dissolution solvent which feeds the static or dynamic mixer considered (more precisely of the fraction of the part of the dissolution solvent which supplies the contacting section i) and the sum of the volume flow rates of said fraction of dissolution solvent (ie of the fraction of at least the part of the dissolution solvent which supplies the section i )) and the plastic flow which feeds the static or dynamic mixer considered. The term “plastic flow” corresponds to any flow in section i) of contacting of step a) of dissolution, which includes at least the plastic filler and all of the dissolution solvent fractions (ie fractions d 'at least the part of the dissolution solvent which feeds section i)) introduced into the contacting section upstream of the static or dynamic mixer considered. In other words, the plastic flow, which feeds a static or dynamic mixer, corresponds to a flow of material comprising, preferably consisting of, the plastic filler, advantageously at least partly melted, added to all the fractions of dissolution solvent (ie fractions of at least the part of the dissolution solvent which feeds section i)) introduced into the static or dynamic mixer(s) located upstream of the static or dynamic mixer considered and possibly in a means for melting at least partly the plastic filler possibly located upstream of the first static or dynamic mixer. Thus the plastic flow which supplies the contacting section i) corresponds to the plastic load; the plastic flow leaving the contacting section i) corresponds to a flow of conditioned filler and comprises the plastic filler and at least part of the dissolution solvent. The plastic flow which feeds the first static or dynamic mixer comprises, in particular consists of, the plastic filler which is in molten form (or at least partly in molten form) or a pre-mixture comprising the plastic filler at least partly in molten form. molten form and a fraction of the dissolution solvent: the plastic flow which feeds the first static or dynamic mixer is then in particular in the form of viscous fluid. The expression "viscous fluid" means that the flow considered is a fluid having a viscosity, in particular a dynamic viscosity, typically between 0.5 and 20000 Pa.s, or more particularly between 1.0 and 4000 Pa.s. The viscosity, in particular a dynamic viscosity, is measured at a temperature of 200°C and a shear rate of 0.1 s ^-1 , using a viscometer, preferably using a viscometer of plane-plane type, for example of type DHR3 from TA Instrument. Preferably, the volume dilution rate of dissolution solvent in each static or dynamic mixer is included:

- between 3% and 50%, preferably between 10% and 35%, and very preferably between 15% and 30%, when the ratio of viscosities between the plastic flow and the dissolution solvent fraction (i.e. the fraction at least the part of the dissolution solvent which feeds section i)), which feeds the static or dynamic mixer considered, is greater than or equal to 3500, preferably greater than or equal to 3000,

- between 10% and 70%, preferably between 20% and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the fraction of dissolution solvent (i.e. the fraction of at least the part of the dissolution solvent which feeds section i), which feed the static or dynamic mixer considered, is less than 3500, preferably less than 3000.

Preferably, the dissolution solvent which feeds the dissolution step a) is divided into n partial flows of dissolution solvent, n being an integer equal to m, m+1 or m+2, m being a number integer equal to the number of static or dynamic mixers used in section i) of contacting, each static or dynamic mixer being supplied with one of the partial flows of dissolution solvent so that, in each static or dynamic mixer, the volume dilution rate in dissolution solvent is between 3% and 70%, and preferably:

- between 3% and 50%, preferably between 10 and 35%, and very preferably between 15% and 30%, when the ratio of viscosities between the plastic flow and the partial flow of dissolution solvent (i.e. the fraction dissolution solvent), which feed the static or dynamic mixer considered, is greater than or equal to 3500, preferably greater than or equal to 3000; Or

- between 10% and 70%, preferably between 20 and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the partial flow of dissolution solvent (i.e. the fraction of dissolution solvent), which feed the static or dynamic mixer considered, is less than 3500, preferably less than 3000.

Optionally, a partial flow of dissolution solvent (ie a fraction of dissolution solvent) can supply a means for melting at least in part the plastic filler located upstream of the first static or dynamic mixer, and/or a partial flow of dissolution solvent. dissolution (ie a fraction of dissolution solvent) can directly feed the dissolution section ii). Each static or dynamic mixer is preferably implemented with a residence time less than or equal to 20 minutes, preferably between 0.01 second and 20 minutes, preferably between 0.1 second and 10 minutes, preferably between 0.5 seconds seconds and 5 minutes, the residence time being defined here as the ratio between the volume of liquid (or viscous fluid) in the static or dynamic mixer considered in relation to the sum of the volume flow rates of the plastic flow and the dissolution solvent fraction which feed the static or dynamic mixer considered.

According to a particular embodiment of the invention, the contacting section i) can also comprise a means for melting at least partly the plastic filler, preferably at least partly the targeted thermoplastics, preferably all the thermoplastics targeted. When the contacting section comprises means for melting at least partly the plastic filler, said means is located upstream of the static or dynamic mixer(s), preferably upstream of the first static or dynamic mixer in the series. Preferably, the means for melting at least partly the polyester filler is a single- or twin-screw extruder.

Advantageously, the means for melting at least in part the plastic filler makes it possible to mix and melt at least in part the plastic filler, and more particularly to melt at least in part, preferably in whole, the targeted thermoplastics of the plastic filler. Said means for melting, preferably said extruder, is therefore advantageously used at a temperature of between 100°C and 300°C, preferably between 150 and 250°C. The plastic filler thus feeds said possible means for melting, for example an extruder, in which it is advantageously heated to a temperature between 100°C and 300°C, preferably between 150 and 250°C, and in particular at a temperature close or even slightly higher than the melting temperature of the targeted thermoplastics, for example the targeted polyolefins, so as to become in the form of a viscous fluid, at the outlet of said means for melting. When it is introduced into the means for melting, the plastic filler can already be at a temperature between 100°C and 300°C, preferably between 150 and 250°C, or at an ambient temperature, for example between 10 and 30°C. . It is therefore advantageously heated or maintained at a temperature between 100°C and 300°C, preferably between 150 and 250°C, in the means for melting, so as to be at least partly melted. Very advantageously, at least 70% by weight of the plastic filler, preferably at least 80% by weight, preferably at least 90% by weight, of the plastic filler is in the form of viscous fluid at the outlet of said means for melting, for example extruder. Thus when it is integrated into the contacting section, the means for melting at least partly the plastic filler is supplied by the plastic filler, for example in the form of solid particles, and makes it possible to obtain a flow in the form of viscous fluid, typically of dynamic viscosity between 0.5 and 20000 Pa.s, or more particularly between 1.0 and 3000 Pa.s. The possible means for melting at least in part the plastic filler advantageously makes it possible to bring the plastic filler to a temperature between 100°C and 300°C, preferably between 150 and 250°C, and at a pressure preferably between atmospheric pressure (i.e. 0.1 MPa) and 20 MPa absolute, preferably between 0.15 MPa and 15 MPa absolute, conditions in which said plastic filler is advantageously at least partly molten, and in particular in which the targeted thermoplastics, included in the plastic filler, are at least partly melted, preferably completely melted.

The supply of the means for melting with the plastic filler can advantageously be carried out by any method known to those skilled in the art, for example via a supply hopper, and can be inerted in order to limit the introduction of oxygen into the process.

According to a very particular embodiment of the invention, the contacting section comprises a means for melting, preferably an extruder, which is supplied by the plastic filler and which can also be supplied by a fraction of the dissolution solvent, which can help to reduce the viscosity of the plastic flow at the outlet of said means, thus participating in the overall homogenization of the plastic load at least partly melted with the dissolution solvent, and advantageously making it possible to limit the degradation of the targeted thermoplastics, in particular of the targeted polyolefins. Another advantage of this very particular embodiment lies in the fact that this implementation (ie introduction of a fraction of the dissolution solvent into the means for melting) can make it possible to improve the efficiency of the mixers in particular of the first mixer, and thus allow a reduction in the number of static or dynamic mixers necessary to achieve a dynamic viscosity of the conditioned load flow, that is to say of the mixture [plastic filler + dissolution solvent] at the end of the section contacting, less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s, and very advantageously a concentration coefficient of variation (CoV) preferably less than or equal to 10%, preferably less than or equal to 5%. When a fraction of the dissolution solvent is introduced into the means for melting at least in part the plastic filler, the quantity of said fraction of dissolution solvent which feeds said means is preferably adjusted so that the weight ratio between the fraction of dissolving solvent which feeds said means and the plastic filler which feeds said means is between 0.001 and 0.20000, preferably between 0.001 and 0.100, preferably between 0.003 and 0.050, very preferably between 0.005 and 0.030. For example, a fraction of the dissolution solvent is introduced into the means for melting at least partly the plastic filler, the quantity of said fraction of dissolution solvent which supplies said means corresponding preferably between 0.02 and 4.0% by weight, or even between 0.1 and 1.0% by weight, of the total weight of dissolution solvent introduced in step a).

Preferably, the residence time in the means for melting at least partly the plastic filler, optionally used in the contacting section i), is advantageously less than or equal to 1 hour, preferably less than or equal to 5 min, preferably less than or equal to 2 min, and preferably greater than or equal to 0.5 seconds, preferably greater than or equal to 1 second, very preferably greater than or equal to 10 seconds. Said residence time is defined here as the volume available in said means divided by the volume flow rate of the plastic filler.

The possible means for melting at least partly the plastic filler can advantageously be connected to a vacuum extraction system, so as to eliminate impurities such as dissolved gases, light organic compounds and/or humidity present. in the load.

Said possible means for melting, preferably an extruder, can also advantageously comprise at the outlet a filtration system thus making it possible to eliminate solid particles of size greater than 20 pm, and preferably less than 2 cm, such as sand particles. , wood, metal. For example, the means for melting at least partly the plastic filler, preferably an extruder, is directly connected, at the output, to a first filtration system, in particular a filter, adapted to eliminate solid particles of typically larger size or equal to 1000 pm, preferably greater than or equal to 500 pm, preferably greater than or equal to 400 pm, preferably greater than or equal to 300 pm, followed by a melt pump (or “melt pump” according to the Anglo-Saxon term dedicated) or a gear pump (or gear pump according to the Anglo-Saxon term) making it possible to maintain and/or increase the pressure, followed by a second filtration system adapted to eliminate solid particles of typically greater or equal size at 60 pm, preferably greater than or equal to 20 pm.

At the end of section i) of contacting, that is to say at the outlet of the last static mixer, the plastic flow obtained advantageously corresponds to the conditioned load, which is very advantageously in liquid form, and has preferably a viscosity less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s. Very advantageously, at the end of the contacting section, the conditioned load also has a coefficient of variation (CoV) of concentration preferably less than or equal to 10%, preferably less than or equal to 5%. The conditioned load can then be defined as a homogeneous mixture comprising a polymer solution of thermoplastics, in particular of polyolefins and more particularly of polypropylene and/or polyethylene, in a dissolution solvent, preferably in a weight ratio between the dissolution solvent and the plastic load between 0.2 and 100.0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0, and comprising soluble and/or insoluble impurities, said homogeneous mixture having a viscosity and viscosity less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s. ii) the dissolution section:

The conditioned charge from the contacting section feeds the dissolution section in dissolution step a). The dissolution section can also be supplied with a portion of dissolution solvent, in particular when the entire quantity of dissolution solvent has not been introduced entirely into the contacting section i). The flow recovered at the outlet of the dissolution section corresponds to a polymer solution, in particular to a raw polymer solution.

Very advantageously, the dissolution section is operated at a dissolution temperature of between 100°C and 300°C, preferably between 150 and 250°C, and a dissolution pressure of between 1.0 and 100.0 MPa absolute, of preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. The temperature and pressure can vary in the dissolution section, from the conditions of introduction of the conditioned charge from the contacting section and/or the fraction of dissolution solvent possibly introduced into the dissolution section, up to 'to reach the dissolution conditions, that is to say the dissolution temperature, in particular between 100 and 300°C, preferably between 150 and 250°C, and the dissolution pressure, in particular between 1.0 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. Very advantageously, at the end of the dissolution section, the raw polymer solution is at the dissolution temperature and at the dissolution pressure.

Limiting the temperature in the dissolution section and more generally in dissolution step a) to a temperature less than or equal to 300°C, preferably less than or equal to 250°C, makes it possible to avoid or limit the thermal degradation of thermoplastics and more particularly polyolefins, but also to limit the energy requirement of the process, thus participating in limiting the operating costs of the process. Advantageously, the dissolution temperature is greater than or equal to the melting temperature of the thermoplastics and more particularly polyolefins, so as to promote their dissolution and very advantageously reduce the residence time necessary to effectively dissolve the targeted thermoplastics. Preferably, the temperature in the dissolution section and more generally in dissolution step a) is less than or equal to the critical temperature of the dissolution solvent, so as to avoid the formation of a supercritical phase during the step. a) dissolution likely to disrupt the dissolution.

At the same time, the dissolution pressure in the dissolution section is higher than the saturated vapor pressure of the dissolution solvent, at the dissolution temperature, so that the dissolution solvent is at least partly, and preferably completely , in liquid or possibly supercritical form, at the dissolution temperature, which makes it possible to optimize the dissolution of the targeted thermoplastics and more particularly of polyolefins, in particular in terms of quality and operation time.

Very advantageously, the dissolution temperature and pressure conditions reached in dissolution section ii) are adjusted so that the mixture (dissolution solvent + targeted thermoplastics) is monophasic at the end of step a), said mixture being able to optionally include insoluble impurities suspended in said mixture.

Advantageously, dissolution section ii) is carried out for a residence time of between 1 and 600 minutes, preferably between 2 and 300 minutes, preferably between 5 and 180 minutes. The residence time is understood, in this case, as the residence time at the dissolution temperature and at the dissolution pressure, that is to say the time of implementation of the plastic filler with the dissolution solvent at the dissolution temperature and dissolution pressure, in the dissolution section.

Section ii) of dissolution can use different types of equipment such as mixing, transport, heating devices, and such as for example a reactor, a pump, a transport circuit, an agitation system, a oven, exchanger, mixer, etc.

According to a particular embodiment, the dissolution section uses a continuously stirred reactor, also called "Continuous Stirred Tank Reactor" (CSTR) according to Anglo-Saxon terminology, or a series of continuously stirred reactors (or CSTR reactors). ), said series possibly comprising between two and five CSTR reactors, preferably two or three CSTR reactors, each continuously stirred reactor (CSTR reactor) advantageously comprising a mechanical stirring system. Indeed, the method according to the invention, comprising in particular a contacting section as described above, which makes it possible to obtain a conditioned charge having a viscosity preferably less than or equal to 50 mPa.s, preferably less or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s, allows the use of a reasonable (that is to say limited) mechanical stirring power in the dissolution reactor , thus facilitating the operability of the dissolution section while limiting the costs necessary for its implementation, and while ensuring optimal homogenization of the mixture and maximum dissolution of the targeted thermoplastics of the plastic filler in the dissolution solvent.

The dissolution section can use any reactor stirred by any stirring system. Indeed, obtaining a conditioned load having a viscosity preferably less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, very preferably less than or equal to 5 mPa.s, very preferably less than or equal to 1 mPa.s, and very advantageously a coefficient of variation (CoV) of concentration preferably less than or equal to 10%, preferably less than or equal to 5%, at the end of section i) of implementation contact allows the use of a reasonable (i.e. limited) stirring power in the dissolution reactor, thus facilitating the operability of the dissolution section, which allows the use of any diluting system. agitation, while advantageously allowing a reduction in the mixing time, that is to say the residence time in the dissolution section, and/or the use of a wide range of operating pressures, and in ensuring optimal homogenization of the mixture and therefore maximum dissolution of the targeted thermoplastics from the plastic filler in the dissolution solvent.

Optionally, an adsorbent, advantageously solid, preferably in the form of divided particles, shaped or not, can be introduced into the polymer solution in dissolution section ii), in particular in the dissolution reactor. In this case, the purification process includes an intermediate adsorption step a’), located during the dissolution step a). The adsorbent is advantageously chosen from aluminas, silicas, silica-aluminas, activated carbons or bleaching earths. The solid adsorbent can then be eliminated during purification step b), for example during a sub-step b1) of separation of insolubles and/or a sub-step b2) of washing. This possible step a') of adsorption in the presence of solid adsorbent in divided form makes it possible to optimize the purification of the polymer solution.

According to a preferred embodiment of the invention, dissolution step a) uses: i) a section for bringing the plastic filler into contact with at least part of a dissolution solvent, having a temperature d boiling between -50 and 250°C, preferably between -15 and 150°C, preferably between 20 and 100°C, and ii) a dissolution section. In this preferred embodiment, the contacting section i) is operated at a temperature between 150 and 250°C and uses an extruder, possibly a filtration system at the extruder outlet, then three, four or five static mixers, operating in series with each other, and dissolution section ii) uses a reactor continuously stirred by mechanical stirring (i.e. CSTR type) operated at a temperature between 150 and 250°C and a pressure between 1.5 and 18.0 MPa absolute. The dissolution solvent is divided into n partial flows of dissolution solvent, n being a natural integer and the number n of partial flows of dissolution solvent being equal to the number m of static mixers used in section i) of implementation in contact (in this embodiment, m being an integer equal to three, four or five) or to a number m+1 or m+2. In this embodiment, the extruder is fed by the plastic filler, to obtain a plastic flow composed of the plastic filler at least partly melted, in which the targeted thermoplastics, in particular the targeted polyolefins, of the plastic filler are advantageously melted, and possibly one of the partial flows of dissolution solvent so that the weight ratio between the fraction of dissolution solvent (ie the partial flow of dissolution solvent) which feeds the extruder and the plastic filler which feeds the extruder is between 0.001 and 0.200, preferably between 0.001 and 0.100, preferably between 0.003 and 0.050, very preferably between 0.005 and 0.030, for example so that the partial flow of dissolution solvent which feeds the extruder preferably represents between 0 .02 and 4.0% by weight, or even between 0.1 and 1.0% by weight, of the total weight of dissolution solvent introduced in step a). In this preferred embodiment, each of the static mixers is supplied with a plastic flow and one of the partial flows of dissolution solvent so that, in each static mixer, the volume dilution rate of dissolution solvent is included:

- between 3% and 50%, preferably between 10 and 35%, and very preferably between 15% and 30%, when the ratio of viscosities between the plastic flow and the partial flow of dissolution solvent which feeds the mixer static considered is greater than or equal to 3500, preferably greater than or equal to 3000;

- between 10% and 70%, preferably between 20 and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the partial flow of dissolving solvent which feeds the static mixer considered is less than 3500, preferably less than 3000.

Preferably, in this preferred embodiment, the residence time in the extruder, defined as the volume available in said extruder divided by the volume flow rate of load, is between 0.5 seconds and one hour, preferably between 0, 5 seconds and 5 minutes, preferably 1 second and 2 minutes, or between 10 seconds and 2 minutes.

The dissolution section ii), in particular the CSTR type reactor, of this same preferred embodiment is then supplied by the plastic flow coming from the last static mixer of section i) of contacting and possibly by a partial flow of dissolution solvent.

The polymer solution, advantageously called raw, obtained at the end of dissolution step a) comprises at least the dissolution solvent, polymers, in particular the targeted thermoplastic polymers that the present invention seeks to recover purified, dissolved in the dissolving solvent. In general, the polymer solution obtained at the end of dissolution step a) also includes soluble impurities also dissolved in the dissolution solvent. It may optionally also include insoluble impurities in suspension. The polymer solution, advantageously called raw, obtained at the end of step a) may optionally also comprise polymers, other than the targeted polymers, for example in the molten state.

Step b) of purification of the polymer solution

The treatment method according to the invention comprises a step of purification of the raw polymer solution resulting from step a). This purification step b) comprises at least one of the sub-steps b1), b2), b3), b4) described below: b1) a sub-step of separating insolubles, b2) a sub-step of washing, by contact with a dense solution, b3) an extraction sub-step, by contact with an extraction solvent, b4) a sub-step of adsorption of impurities by contact with an adsorbent solid.

Preferably, purification step b) comprises at least one substep b1) of separation of insolubles. Purification step b) preferably comprises several (that is to say at least two) sub-steps chosen from sub-steps b1), b2), b3) and b4), in series, and preferred manner at least one sub-step b1) of separation of insolubles and for example a sub-step b4) of adsorption, and very advantageously in this order. The combination of at least two sub-steps chosen from b1), b2), b3) and b4) advantageously allows optimal purification of the polymer solution. The polymer solution obtained at the end of step b) is a purified polymer solution and comprises the targeted thermoplastics dissolved in the dissolution solvent. This purified polymer solution can correspond to a clarified polymer solution resulting from a sub-step b1) of separation of insolubles, a washed polymer solution resulting from a sub-step b2) of washing, an extracted polymer solution resulting from a sub-step -step b3) of extraction or a refined polymer solution resulting from a sub-step b4) of adsorption of impurities.

Sub-step b1) of separation of insolubles The purification process may include a substep b1) of separation of insolubles by solid-liquid separation, to advantageously obtain at least one clarified polymer solution and preferably an insoluble fraction. The insoluble fraction advantageously comprises at least partly, preferably all, insoluble impurities, in particular suspended in the raw polymer solution resulting from step a).

Substep b1) of separation of insolubles thus makes it possible to eliminate at least part, preferably all, of the particles of impurities insoluble in the dissolution solvent, present in suspension in the raw polymer solution resulting from step a ). The insoluble impurities eliminated during substep b1) of separation of insolubles are for example pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum) and insoluble polymers.

When it is implemented, this separation substep b1) allows, in addition to the elimination of at least part of the insoluble impurities, advantageously to limit the operational problems, in particular of the blockage and/or erosion type, of the stages of the process located downstream, while contributing to the purification of the plastic load.

Substep b1) of separation of insolubles is advantageously carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, and at a pressure between 1.0 and 100.0 MPa absolute, of preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. Very advantageously, substep b1) of separation of insolubles is carried out at the temperature and pressure conditions at the outlet of step a) of dissolution, that is to say at the dissolution temperature and pressure dissolution as defined above.

When integrated into the process, substep b1) of separation of insolubles is preferably supplied with the raw polymer solution resulting from step a). According to another embodiment, sub-step b1) can be supplied with a washed polymer solution resulting from a washing sub-step b2).

Advantageously, substep b1) implements a section comprising at least one piece of solid-liquid separation equipment, for example chosen from a separator flask, a decanter, a centrifugal decanter, a centrifuge, a filter, a sand filter, a tangential filter using in particular a membrane and/or a depth filter possibly in the presence of filtration aids (for example diatomaceous earth), 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 can be used, the cleaning or unclogging allowing the elimination of insoluble matter being carried out using a flow of solvent. The evacuation of the insoluble fraction can be facilitated by equipment allowing the transport and/or elimination of traces of solvent possibly present in the insoluble fraction, for example a conveyor, a vibrating tube, an endless screw, an extruder, a striping. Substep b1) can therefore use equipment for transport and/or elimination of traces of solvent to evacuate the insoluble fraction. Advantageously, at least part of the solvent recovered during substep b1) is recycled in the process.

According to a particular embodiment, sub-step b1) of separation of insolubles uses at least two, and generally less than five, solid-liquid separation equipment in series and/or in parallel. The presence of at least two solid-liquid separation equipment in series makes it possible to improve the elimination of insoluble matter while the presence of equipment in parallel makes it possible to manage the maintenance of said equipment and/or unclogging operations.

Certain insoluble impurities, in particular certain additives such as pigments and mineral fillers, conventionally added during the formulation of polymers, can be introduced in the form of particles less than 1 μm in size. This is for example the case of titanium dioxide, calcium carbonate and carbon black. According to a particular embodiment of sub-step b1), said sub-step b1) of separation of insolubles advantageously uses an electrostatic separator, which makes it possible to effectively eliminate, at least in part, the insoluble particles of smaller size at 1 p.m. According to another particular embodiment of sub-step b1), sub-step b1) of insolubles uses a sand filter, to eliminate particles of different sizes and in particular particles of size less than 1 pm. According to yet another particular embodiment of sub-step b1), sub-step b1) of insolubles uses a tangential filter using in particular a membrane and/or a depth filter, possibly in the presence of adjuvants filtration such as diatomaceous earth.

Depending on the nature of the feed, the polymer solution which feeds substep b1), preferably the raw polymer solution, may optionally also comprise a second liquid phase, for example consisting of molten polymers. According to another particular embodiment, substep b1) advantageously uses equipment allowing the separation of this second liquid phase, preferably by means of at least one two-phase or three-phase separator.

Washing sub-step b2)

The treatment process may optionally also comprise a sub-step b2) of washing with a dense solution, to advantageously obtain at least one washing effluent and a washed polymer solution. The washed polymer solution obtained at the end of the sub-step b2) advantageously comprises the targeted polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent. Optionally, the washed polymer solution may also include residual impurities, in particular soluble in the dissolution solvent and/or possibly traces of the washing solvent if substep b2) is carried out.

Washing sub-step b2) can be integrated upstream or downstream, preferably downstream, of a sub-step b1) of separation of insolubles, when these two sub-steps are integrated into step b) of purification.

When it is integrated into the process, the washing sub-step b2) is supplied with a dense solution and with the raw polymer solution from step a) or from a possible intermediate adsorption step a'), or by the clarified polymer solution from b1). The polymer solution which feeds the washing sub-step b2), in particular the crude or clarified polymer solution, may comprise insoluble impurities in suspension and/or solubilized impurities. These suspended or solubilized impurities can, in part or in whole, be eliminated during substep b2) of washing by dissolution or precipitation and/or by entrainment in the dense solution. Thus when it is implemented, this substep b2) contributes to the treatment of the plastic filler and more particularly to the purification of the polymer solution.

Washing sub-step b2) advantageously comprises bringing the polymer solution, crude or clarified, which feeds sub-step b2) into contact with a dense solution. Advantageously, the dense solution has a higher density than the polymer solution (that is to say the mixture comprising at least the targeted thermoplastics and the dissolution solvent in which the targeted thermoplastics are dissolved), in particular greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to 1.0. The dense solution may be an aqueous solution, which preferably comprises at least 50% by weight of water, preferably at least 75% by weight of water, very preferably at least 90% by weight of water. The pH of the aqueous solution can be adjusted using an acid or a base so as to promote the dissolution of certain impurities. The dense solution may also optionally be a solution comprising, preferably consisting of, an organic solvent with a density advantageously greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to 1.0, and in which the polymers of the plastic filler remain insoluble under the temperature and pressure conditions of substep b2), for example an organic solvent chosen from sulfolane or N-methylpyrrolidone (NMP), optionally mixed with water. Very preferably, the dense solution is an aqueous solution which preferably comprises at least 50% by weight of water, preferably at least 75% by weight of water, very preferably at least 90% by weight of water.

Washing substep b2) is advantageously carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, and at a pressure between 1.0 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 15.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. Very advantageously, washing substep b2) is carried out at the dissolution temperature and the dissolution pressure.

In substep b2) of washing, when it is integrated into the process, the mass ratio between the mass flow rate of the dense solution and the mass flow rate of the polymer solution, raw or clarified, which feeds substep b2) is advantageously between 0.05 and 20.0, preferably between 0.1 and 10.0 and preferably between 0.5 and 3.0. The bringing into contact between the polymer solution, raw or clarified, and the dense solution can be carried out at several points of the equipment(s) used, that is to say by several injections of the polymer solution. raw or clarified and/or the dense solution at different points along the equipment(s), it is then the sum of the injected flows which is taken into account in the calculation of the ratio.

Substep b2) can be carried out in one or more washing equipment allowing contact with the dense solution and/or with separation equipment making it possible to recover at least one washing effluent and a washed polymer solution. This equipment is well known, for example stirred reactors, static mixers, decanter mixers, two-phase or three-phase separator flasks, co- or counter-current washing columns, plate columns, stirred columns, packed columns, pulsed columns, etc., each type of equipment which may include one or more pieces of equipment used alone or in combination with equipment of another type.

According to a preferred embodiment, the washing sub-step b2) is carried out in a counter-current washing column in which the dense solution is injected, preferably into half, preferably a third, of the column. closer to the column head, on the one hand and the crude or clarified polymer solution is injected, preferably into half, preferably a third, of the column closest to the column bottom, on the other hand. According to this embodiment, it is possible to recover at least one washed polymer solution and a washing effluent.

According to a very particular mode, the flows entering and/or leaving the washing column can be divided and injected into several injection points along the column and/or drawn off at several withdrawal points along the column. According to another embodiment, washing sub-step b2) is carried out in a mixer-settler comprising an agitated mixing zone, to bring the dense solution and the raw or clarified polymer solution into contact, and a decantation zone, making it possible to recover a washed polymer solution and a washing effluent.

At the end of washing sub-step b2), the washing effluent obtained advantageously comprises impurities solubilized in the dense solvent and/or insoluble and entrained in the washing effluent. The washing effluent can be reprocessed in a washing treatment section, on the one hand to separate at least in part the solubilized and/or entrained impurities and possibly purify the washing effluent, to obtain a purified dense solution, and on the other hand to recycle at least part of the purified washing solution. This washing treatment section can use one or more well-known solid-liquid separation equipment(s), for example a separator flask, a decanter, a centrifugal decanter, a centrifuge, a filter. The washing effluent can also be sent outside the process, for example to a wastewater treatment plant when the dense solution is an aqueous solution.

Extraction step b3)

Step b) of the process according to the invention may comprise a sub-step b3) of extraction by bringing into contact with an extraction solvent, to obtain at least one extracted polymer solution and a used solvent in particular loaded with impurities . The extracted polymer solution obtained at the end of substep b3) advantageously comprises the targeted thermoplastic polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent. Optionally, the extracted polymer solution may also include residual impurities in particular soluble in the dissolution solvent and/or traces of the washing solvent and/or the extraction solvent if the substep(s) b2) and /or b3) is(are) carried out.

When integrated into the process according to the invention, substep b3) of extraction is advantageously located between step a) of dissolution and step c) of solvent-polymer separation, and possibly upstream or downstream. downstream of an adsorption sub-step b4) if the latter is also integrated into step b), and preferably downstream of a sub-step b1) of separation of insolubles.

The extraction substep b3) is advantageously supplied with an extraction solvent and with the polymer solution, in particular the raw polymer solution resulting from step a), the clarified polymer solution resulting from substep b1) , the washed polymer solution from sub-step b2) or the refined polymer solution from an adsorption sub-step b4). Preferably, the extraction substep b3) is supplied with an extraction solvent and by the clarified polymer solution from sub-step b1) or the washed polymer solution from sub-step b2), or even possibly by a refined polymer solution from an adsorption sub-step b4). The polymer solution which feeds substep b3), preferably the clarified polymer solution, the washed polymer solution or the refined polymer solution, can therefore also include solubilized impurities. These solubilized impurities can be partially or entirely eliminated during substep b3) of extraction by contact with an extraction solvent. Very advantageously, the combination of an extraction sub-step b3) with a sub-step b1) of separation of insolubles and optionally an adsorption sub-step b4) allows improved purification of the polymer solution, optionally using both the affinity of the impurities for the adsorbent and for the extraction solvent.

When integrated into the method according to the invention, the extraction substep b3) advantageously implements at least one extraction section, preferably between one and five extraction section(s), in a very preferred an extraction section.

The mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution which feeds b3), preferably the clarified polymer solution, the washed polymer solution or the refined polymer solution, is advantageously between 0.05 and 20.0, preferably between 0.1 and 10.0 and more preferably between 0.2 and 5.0. The bringing into contact between the polymer solution which feeds substep b3), preferably the clarified polymer solution, the washed polymer solution or the refined polymer solution, and the extraction solvent can be carried out at several points of section d extraction, that is to say by several injections of the polymer solution and/or the extraction solvent at different points along the extraction section, it is then the sum of the injected flows which is taken into account taken into account when calculating the ratio.

The extraction solvent used in extraction substep b3) advantageously comprises an organic solvent or a mixture of organic solvents. Preferably, the extraction solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (that is to say saturated), preferably linear or branched. Preferably, the extraction solvent comprises at least 80% by weight, preferably at least 95% by weight, preferably 98% by weight of at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, preferably linear or branched, the percentages being expressed relative to the total weight of the dissolving solvent (100% being the maximum). Preferably, the extraction solvent comprises at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling temperature of between -50 and 250°C, preferably between -15 and 150°C, preferably between - 1 and 110°C and so preferred between 20 and 100°C (at atmospheric pressure, in particular at 0.1 MPa). Preferably, the extraction solvent comprises, preferably consists of, at least one aliphatic hydrocarbon compound, in particular paraffinic, preferably linear or branched, having between 3 and 12 carbon atoms, preferably between 4 and 8 carbon atoms. For example, the extraction solvent comprises a compound chosen from the isomers of butane, pentane, hexane, heptane and octane. The extraction solvent may comprise, preferably consist of, a mixture of isomers of butane, pentane, hexane, heptane and/or octane, and preferably at a content of said mixture of isomers in the extraction solvent greater than or equal to 80% by weight, preferably greater than or equal to 95% by weight, preferably greater than or equal to 98% by weight, relative to the total weight of the extraction solvent. Preferably, the extraction solvent comprises a paraffinic aliphatic compound, having a critical temperature (temperature at the critical point of said pure hydrocarbon compound) preferably between 95 and 350°C, preferably between 130 and 300°C, preferably between 180 and 285°C.

Very preferably, the extraction solvent used in b3) is the same solvent as the dissolution solvent used in step a), possibly in a different physical state (for example the extraction solvent with supercritical state relative to the dissolution solvent in the liquid state), so as to facilitate the management of the solvents and in particular their purification and their recycling in particular towards the dissolution step a) and possibly towards the sub-step b3) d 'extraction. Another advantage of using identical dissolution and extraction solvents, in identical or different physical states, is, in addition to facilitating the management of the solvents involved in the process according to the invention, in particular the recovery of the solvents, their treatment and their recycling towards at least one of the stages of the process, to limit energy consumption and costs in particular generated by the treatment and purification of solvents.

The extraction section(s) of b3) may include extraction equipment(s), allowing contact with the extraction solvent and/or with separation equipment making it possible to recover at least one used solvent, in particular loaded with impurities, and an extracted polymer solution. This equipment is well known, such as for example stirred reactors, static mixers, decanter mixers, two-phase or three-phase separator flasks, co- or counter-current washing columns, plate columns, stirred columns, packed columns, pulsed columns, etc., each type of equipment may include one or more equipment used alone or in combination with equipment of another type.

According to a preferred embodiment of b3), the extraction is carried out in a counter-current extraction column where the extraction solvent is injected on the one hand and the solution polymer which feeds sub-step b3) is injected on the other hand. According to this embodiment, it is possible to recover at least one extracted polymer solution, on the one hand, and a used solvent in particular loaded with impurities, on the other hand. Preferably, the polymer solution which feeds b3), preferably the clarified, washed or refined polymer solution, is injected into half, preferably a third, of the column closest to the head of the extraction column at countercurrent while the extraction solvent is injected into half, preferably a third, of the column closest to the bottom of the countercurrent extraction column.

The flows entering and/or leaving the counter-current extraction column can be divided into several injection and/or withdrawal points along the column.

According to another embodiment of b3), the extraction is carried out in a mixer-decanter which advantageously comprises an agitated mixing zone to bring the extraction solvent into contact with the polymer solution which feeds b3), preferably the solution clarified, washed or refined polymer, and a decantation zone making it possible to recover an extracted polymer solution on the one hand and a used solvent on the other hand.

Advantageously, extraction substep b3) is carried out under temperature and pressure conditions different from the temperature and pressure conditions of dissolution step a).

According to a preferred embodiment of b3), the extraction substep b3) implements a liquid/liquid extraction section. Preferably, the liquid/liquid extraction section is operated between 100°C and 300°C, preferably between 150°C and 250°C, and at a pressure between 1.0 and 100.0 MPa absolute, of preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. In all cases, in this embodiment, the temperature and pressure conditions are adjusted so that the extraction solvent is in the liquid state, the dissolution solvent preferably also being in the liquid state. Very advantageously, the liquid/liquid extraction, in particular when the extraction solvent is the same as the dissolution solvent, is carried out under temperature and pressure conditions different from the dissolution conditions reached in step a). , in particular at a temperature higher than the dissolution temperature and/or at a pressure lower than the dissolution pressure, so as to thus be placed in a two-phase zone of the corresponding polymer-solvent mixture diagram.

According to another preferred embodiment of b3), the extraction substep b3) implements an extraction section under particular temperature and pressure conditions in which the extraction solvent is advantageously at least partly under shape supercritical. Such extraction may be called supercritical extraction. In this embodiment, the extraction is carried out by bringing the polymer solution, preferably the clarified, washed or refined polymer solution, into contact with an extraction solvent, advantageously under temperature and pressure conditions which allow the obtaining a supercritical phase composed mainly (that is to say preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight) of the extraction solvent. In other words, in this embodiment, the extraction is carried out by bringing the polymer solution, preferably the clarified, washed or refined polymer solution, into contact with an extraction solvent which is at least partly, preferably in full, in the supercritical state. Such a substep b3) of supercritical extraction advantageously allows effective purification of the polymer solution, in particular due to the very strong affinity of organic impurities, such as for example certain additives, in particular certain dyes, plasticizers, etc., for the supercritical phase. The use of an extraction solvent in the supercritical state also makes it possible to create a significant density difference between the supercritical phase and the polymer solution in liquid form, which facilitates separation by decantation between the supercritical phase and the phase liquid, and therefore which contributes to the purification of the polymer solution.

In this other preferred embodiment, substep b3) uses an extraction solvent comprising at least 80% by weight, preferably at least 95% by weight, preferably 98% by weight of at least one paraffinic hydrocarbon compound. aliphatic (or alkane) (100% being the maximum, the percentages being expressed relative to the total weight of the extraction solvent) having a critical temperature preferably between 95 and 350°C, preferably between 130 and 300°C, of preferably between 180 and 285°C.

Advantageously, substep b3) of supercritical extraction of this other particular embodiment is carried out at a temperature preferably between 150°C and 300°C, preferably between 180°C and 280°C, and at a pressure preferably between 2.0 and 100.0 MPa absolute, preferably between 2.0 and 25.0 MPa absolute, preferably between 2.0 and 18.0 MPa absolute and very preferably between 3, 0 and 15.0 MPa absolute. Very preferably, the operating pressure of such a sub-step b3) of supercritical extraction is between 2.7 MPa and 7.5 MPa absolute, preferably between 3.0 MPa and 5.5 MPa absolute. In all cases, in this embodiment, the temperature and pressure conditions are adjusted, in particular in an adjustment section implemented in sub-step b3) of extraction upstream of the extraction section, of so that the extraction solvent is at least partly in the supercritical state in the extraction section.

In a very preferred embodiment of b3), the extraction substep b3) implements a supercritical extraction and the extraction solvent is the same as the dissolution solvent, apart from the fact that the extraction solvent is at least partly in the supercritical phase. In this very advantageous case of supercritical extraction, the dissolution solvent can become at least partly in supercritical form, advantageously optimizing the decantation during the extraction step, more particularly at each phase or extraction plate, between the liquid phase and the supercritical phase, which thus makes it possible to maximize purification.

Advantageously at the end of extraction substep b3), the used solvent obtained is in particular loaded with impurities. It can be reprocessed in an organic treatment section making it possible on the one hand to separate at least part of the impurities and purify the solvent to obtain a purified extraction solvent, and on the other hand to recycle at least part of the solvent. purified extraction at the inlet of extraction b3), and/or at the inlet of dissolution step a) in the case where the dissolution solvent and the extraction solvent are identical. The used solvent can be treated according to any method known to those skilled in the art, such as for example one or more methods including distillation, evaporation, extraction, adsorption, crystallization and precipitation of insolubles, or by purging.

Adsorption sub-step b4)

Step b) of the treatment process according to the invention may comprise an adsorption sub-step b4), to obtain at least one refined polymer solution. The refined polymer solution obtained at the end of substep b4) advantageously comprises the targeted thermoplastic polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent.

When integrated into the process according to the invention, substep b4) of adsorption is advantageously carried out downstream of step a) of dissolution and upstream of step c) of solvent-polymer separation . It can be implemented upstream of a sub-step b1) of separation of insolubles and/or b2) of washing and correspond in particular to the possible step a') of intermediate adsorption. Preferably, it is implemented downstream of a sub-step b1) of separation of insolubles and possibly of a sub-step b2) of washing itself preferably downstream of sub-step b1). It can also be implemented, for example, upstream or downstream of an extraction sub-step b3). Thus, when it is integrated into the process according to the invention, substep b4) of adsorption is implemented by bringing the polymer solution which feeds it into contact with one or more adsorbent(s).

Adsorption substep b4) advantageously uses an adsorption section operated in the presence of at least one adsorbent, preferably solid, and in particular in the form of a fixed bed, an entrained bed (or slurry, i.e. that is to say in the form of particles introduced into the flow to be purified and entrained with this flow) or in the form of a bubbling bed, preferably in the form of a fixed bed or a driven bed. The adsorbent(s) used in sub-step b) is(are) preferably an alumina, a silica, a silica-alumina, an activated carbon, a bleaching earth, or their mixtures, so as to preferred activated carbon, bleaching earth or mixtures thereof, preferably in the form of a fixed bed or entrained bed, the circulation of the flows being able to be ascending or descending.

Advantageously, when integrated into the process, adsorption substep b4) is carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C, and at a pressure between 1.0 and 100.0 MPa absolute, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and very preferably between 2.0 and 15.0 MPa absolute. Very advantageously, adsorption substep b4) is carried out at the dissolution temperature and pressure conditions, that is to say at the dissolution temperature and the dissolution pressure reached in step a). . Preferably, in the possible substep b4), the hourly volume velocity (or WH), which corresponds to the ratio between the volume flow rate of the polymer solution which feeds b4) and the volume of adsorbent, advantageously in operation in b4 ), is between 0.05 and 10 h ^-1 , preferably between 0.1 and 5.0 h ^-1 .

According to a particular embodiment of sub-step b4), the adsorption section may comprise one or more fixed bed(s) of adsorbent, for example in the form of adsorption column(s), preferably at least two adsorption columns, preferably between two and four adsorption columns, containing said adsorbent(s). When the adsorption section comprises two adsorption columns, an operating mode can be an operation called "swing", according to the established Anglo-Saxon term, in which one of the columns is in line, i.e. -say in operation, while the other column is in reserve. When the adsorbent in the online column is used up, this column is isolated while the reserve column is put online, that is to say in operation. The spent adsorbent can then be regenerated in situ and/or replaced by fresh adsorbent so that the column containing it can be put back online once the other column has been isolated.

Another mode of operation of this particular embodiment of b4) is to have at least two columns operating in series. When the adsorbent in the column placed at the top is worn out, this first column is isolated and the spent adsorbent is regenerated in situ or replaced by fresh adsorbent. The column is then put back online in last position and so on. This operation is called permutable mode, or according to the English term “PRS” for Permutable Reactor System or even “lead and lag” according to the established Anglo-Saxon term. The combination of at least two adsorption columns makes it possible to overcome possible poisoning and/or possible rapid clogging of the adsorbent under the joint action of impurities, contaminants and insoluble matter possibly present in the flow. has to treat. The presence of at least two adsorption columns in fact facilitates the replacement and/or regeneration of the adsorbent, advantageously without stopping the process, and also makes it possible to control costs and limit adsorbent consumption.

According to this particular embodiment of sub-step b4) of adsorption in a fixed bed of adsorbent, sub-step b4) is preferably implemented downstream of a sub-step b1) of separation of insolubles and /or a washing sub-step b2), and upstream or downstream of an extraction sub-step b3). Advantageously, the combination of a sub-step b1) of separation of insolubles, and/or a sub-step b2) of washing, and of a sub-step b3) of extraction with a sub-step b4) adsorption allows improved purification of the polymer solution, using both the affinity of the residual impurities for the adsorbent solid and also for the extraction solvent and possibly a dense solution.

The adsorption section of b4) can, according to another embodiment, consist of adding adsorbent particles to the polymer solution, in particular the raw polymer solution, said particles being able to be separated from the polymer solution via a step for eliminating adsorbent particles located downstream of said adsorption section. The elimination of the adsorbent particles can then advantageously correspond to a step b1) of separation of insolubles or to step b2) of washing. Such implementation of adsorption sub-step b4), by introduction of adsorbent particles then solid/liquid separation, advantageously corresponds to the possible intermediate adsorption step a'), described further in this description. .

Step c) of solvent-polymer separation

According to the invention, the process comprises a step c) of solvent-polymer separation, to obtain at least one fraction of purified thermoplastic polymers, more particularly at least one fraction of purified polyolefins, and preferably at least one fraction of solvent.

Step c) of solvent-polymer separation aims to separate, at least in part, preferably mainly, or even entirely, the solvent(s), in particular the dissolution solvent, contained in the solution. purified polymer which feeds step c), so as to recover the thermoplastics freed at least in part, preferably completely, of impurities and of the dissolution solvent, and possibly of the other solvent(s) used in the process ( ie the extraction solvent and/or the dense solution). By majority, it is necessary to understand at least 50% by weight, preferably at least preferably at least 70% by weight, preferably at least 90% by weight, very preferably at least 95% by weight, relative to the weight of the (or ) solvent(s) contained in the purified polymer solution which feeds step c), in particular the dissolution solvent and possibly the solvent extraction and/or the dense solution contained in the purified polymer solution which feeds step c). Any solvent-polymer separation method known to those skilled in the art can be used, in particular all methods allowing a phase change of the polymers or solvent(s). The solvent(s) can be separated, for example, by evaporation, stripping, demixing, difference in density and in particular decantation or centrifugation, etc. Step c) can implement several separation operations in series. For example, step c) may comprise a solvent-polymer separation by demixing at least part of the solvent(s) in supercritical form, the solvent(s) being in supercritical form after adjustment of the temperature and/or pressure conditions in step c), preferably adjustment of the pressure and the temperature being maintained between 100 and 300°C, preferably between 150 and 250°C, so as to be in the conditions supercritical of at least one of the compounds of the solvent(s), followed by at least one separation of the residual solvent by evaporation in particular under pressure conditions lower than the pressure used for the transition to the supercritical state of the solvent, in particular at a pressure between 4 and 0.000005 MPa (i.e. 5 Pa), preferably between 3 and 0.000005 MPa (i.e. 5 Pa), the temperature being able to be maintained between 100 and 300°C, preferably between 150 and 250°C.

The fraction of purified thermoplastic polymers obtained at the end of step c) can correspond to a concentrated polymer solution or to purified liquid (i.e. the molten state) or solid thermoplastic polymers. Solvent-polymer separation step c) may optionally also comprise a conditioning section for conditioning the recovered thermoplastics, in solid form and more particularly in the form of solid granules. In this possible conditioning section, the purified thermoplastic polymers recovered are cooled, advantageously to a temperature below the melting temperature of the polymers, to obtain a fraction comprising polymers in the solid state.

Step c) of solvent-polymer separation also aims to recover at least in part, preferably mainly and preferably in totality, the solvent(s) contained in the purified polymer solution which feeds step c ), and in particular the dissolution solvent and optionally the extraction solvent and/or the dense solution. By majority, it is necessary to understand at least 50% by weight, preferably at least preferably at least 70% by weight, preferably at least 90% by weight, very preferably at least 95% by weight, relative to the weight of the (or ) solvent(s) contained in the purified polymer solution which feeds step c). Thus, step c) advantageously makes it possible to obtain at least one solvent fraction. Step c) of solvent-polymer separation also possibly aims to purify the recovered solvent fraction and recycle it in particular upstream of dissolution step a) and possibly upstream of sub-step b2) and/or sub-step b3).

Very advantageously, the solvent fraction recovered at the end of step c) can be treated in an organic treatment section located at the end of step c), so as to purify it and obtain a purified solvent, in particular a purified dissolution solvent, to be able to advantageously recycle it towards the dissolution step a) and/or possibly towards the washing sub-step b2) or the extraction sub-step b3). Said possible organic treatment section at the end of step c) can implement any method known to those skilled in the art, such as for example one or more methods among distillation, evaporation, liquid-liquid extraction, adsorption, crystallization and precipitation of insolubles, or by purging.

Thus, the process according to the invention makes it possible to obtain a purified stream of thermoplastic polymers and more particularly polyolefins, from plastic waste, which can be used in any application, for example to replace the same polymers in the virgin state. The purified stream of polymers, that is to say the fraction of purified thermoplastic polymers, obtained by the process according to the invention thus has a sufficiently low impurity content to be able to be used in any application. Preferably, the flow of purified thermoplastic polymers and in particular the flow of purified polyolefins obtained at the end of the process according to the invention (that is to say the fraction of purified thermoplastic polymers) advantageously has a lower content of impurities or equal to 5% by weight of impurities, very advantageously impurities less than or equal to 1.0% by weight of impurities, or even a content less than or equal to 0.5% by weight of impurities. Very advantageously, the stream of purified thermoplastic polymers obtained at the end of the process (that is to say the fraction of purified thermoplastic polymers) has a residual solvent content (in particular dissolution solvent) less than or equal to 5 % by weight of residual solvent, preferably less than or equal to 1.0% by weight of residual solvent, preferably less than or equal to 0.1% by weight of residual solvent, or even a content less than or equal to 500 ppm by weight of residual solvent , relative to the total weight of the flow of thermoplastic polymers.

The examples and figures which follow illustrate the invention, in particular particular embodiments of the invention, without limiting its scope.

LIST OF FIGURES

Figure 1 represents the diagram of an embodiment of the method of the present invention, comprising: - a step a) of dissolving the plastic filler 1 in a dissolution solvent 19, to obtain a raw polymer solution 12, step a) implementing:

- a section a-i) for bringing the plastic filler 1 into contact with a dissolving solvent 19 to obtain a conditioned filler 11, said section a-i) using an extruder (A) to obtain a plastic filler 1 * at least in part melted, and five static exchangers M1, M2, M3, M4, M5, each exchanger being supplied with a partial flow of dissolution solvent 2, 4, 6, 8, 10, resulting from the total flow of dissolution solvent 19, and by a plastic flow 1 *, 3, 5, 7, 9,

- a dissolution section a-ii), using in particular a continuously stirred reactor of the CSTR type, to obtain a raw polymer solution 12,

- a purification step b), preferably comprising a separation of the insolubles followed in particular by an adsorption sub-step, to obtain a purified polymer solution 13 and an insoluble fraction 14,

- a step c) of solvent-polymer separation, to obtain a fraction of purified thermoplastics 15, and more particularly a fraction of purified polyolefins, and a flow of solvent 16.

The solvent stream 16 is advantageously purified, for example in a distillation section d), to recover a stream of purified dissolution solvent 17 which is mixed with a stream of fresh solvent 18 to constitute the dissolution solvent 19, the latter being divided into five partial flows 2, 4, 6, 8, 10, of dissolution solvent to supply the static mixers M1, M2, M3, M4, M5 of section a-i).

EXAMPLES

Example 1 (in accordance with the invention)

In this example, only section i) of bringing into contact with a purification process corresponding to the embodiment shown schematically in Figure 1 and in which section i) of bringing into contact with step a) of dissolution comprises :

- an extruder A, which includes a feed hopper through which the extruder is supplied with plastic filler from the collection and sorting sector; followed by

- five static mixers M1, M2, M3, M4, M5, in series.

The plastic filler includes: 95% by weight of polypropylene; 5% by weight of polyethylene and impurities, in particular additives such as pigments, dyes, fillers, etc.

The contacting section is operated at a temperature of 200°C and a pressure of 2.5 MPa (25 bars). The flow rate of plastic feed introduced into extruder A is 50 kg/h. Charge 1* is melted at least in part at the outlet of extruder A; more particularly, the polyolefins, and therefore at least the polypropylene, which said filler contains, are in molten form at the exit of the extruder.

The dissolution solvent used is n-heptane and a mixture 19 of a stream 17 of purified and recycled n-heptane with a stream of fresh n-heptane 18. The total flow of n-heptane 19, which feeds the step a) dissolution, is 250 kg/h.

Each static mixer M1, M2, M3, M4, M5, is supplied with a partial flow of n-heptane, respectively 2, 4, 6, 8, 10, and a plastic flow, respectively 1 *, 3, 5, 7, 9, which comprises at least molten polypropylene. The target concentration variation coefficient at the outlet of each static mixer is 5% (or 0.05).

Table 1 presents both the quantities of dissolution solvent introduced into each static mixer and the evolution of the viscosity of the inlet/outlet flows of each static mixer under the operating conditions of temperature and pressure. Table 1 also gives the ratio of viscosities between the plastic flow and the flow of n-heptane which enter each static mixer as well as the volume dilution rate of n-heptane in each mixer.

Table 1

At the end of the contacting section ai) of step a) using an extruder followed by five static mixers supplied with partial flows of n-heptane, the viscosity of the conditioned feed flow is less than 1 mPa .s (0.95 mPa.s), this while respecting the technical constraints imposed by static mixers relative to the viscosities of the flows involved. Such viscosity then makes it possible to facilitate the homogenization of the mixture in a dissolution reactor of the CSTR type in the dissolution section, said dissolution reactor being of the CSTR type.

Claims

1. Process for treating a plastic filler, comprising: a) a step of dissolving the plastic filler in a dissolution solvent, to obtain at least one raw polymer solution, the dissolution step a) implementing: i) a section for bringing the plastic filler into contact with at least part of the dissolution solvent, comprising at least one static or dynamic mixer, to produce a conditioned filler, each static or dynamic mixer being operated at a temperature between 100°C and 300°C, each static or dynamic mixer being supplied by a plastic flow, comprising the plastic filler, and by a fraction of at least said part of the dissolution solvent so that each mixer presents a volume dilution rate of dissolution solvent between 3% and 70%, the volume dilution rate in dissolution solvent being the ratio between the volume flow rate of the fraction of at least said part of the dissolution solvent which feeds the static or dynamic mixer considered and the sum of the flow rates volume of the fraction of at least said part of the dissolution solvent and the plastic flow which feed the static or dynamic mixer considered; ii) a dissolution section supplied at least by the conditioned charge coming from the contacting section and operated at a dissolution temperature of between 100°C and 300°C and a dissolution pressure of between 1.0 and 100.0 Absolute MPa; then b) a step of purifying the raw polymer solution to obtain a purified polymer solution, said purification step comprising: b1) a sub-step of separating the insolubles; and/or b2) a washing sub-step, by contact with a dense solution; and/or b3) an extraction sub-step, by contact with an extraction solvent; and/or b4) a sub-step of adsorption of impurities by contact with a solid adsorbent; then, c) a solvent-polymer separation step, to obtain at least a fraction of purified thermoplastic polymers.

2. Method according to claim 1, in which the contacting section comprises between one and ten, preferably between two and six, preferably between two and five, static or dynamic mixer(s), preferably in series.

3. Method according to claim 1 or 2, in which each mixer has a volume dilution rate of dissolution solvent comprised:

- between 10% and 70%, preferably between 20% and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the fraction d 'at least said part of the dissolution solvent, which feeds the static or dynamic mixer considered, is less than 3500, preferably less than 3000.

4. Method according to any one of the preceding claims, in which the contacting section comprises means for melting at least partly the plastic filler, located upstream of the first static or dynamic mixer, said means for melting preferably being an extruder.

5. Method according to any one of the preceding claims, in which the dissolution solvent comprises at least one paraffinic aliphatic hydrocarbon compound having a boiling temperature of between -50 and 250°C, preferably between - 15 and 150°C , preferably between - 1 and 1 10°C and preferably between 20 and 100°C.

6. Method according to any one of the preceding claims, in which the dissolution solvent and the plastic filler feed step a) according to a weight ratio between the dissolution solvent and the plastic filler, of between 0.2 and 100, 0, preferably between 0.3 and 20.0, preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0.

7. Method according to any one of the preceding claims, in which each static or dynamic mixer is operated at a temperature between 150 and 250°C.

8. Method according to any one of the preceding claims, in which the dissolution section is operated at a dissolution temperature of between 150 and 250°C.

9. Method according to any one of the preceding claims, in which the dissolution section is operated at a dissolution pressure between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute and in a manner very preferred between 2.0 and 15.0 MPa absolute.

10. Method according to any one of the preceding claims, in which purification step b) comprises a sub-step b1) of separation of insolubles preferably followed by at least one adsorption sub-step.

11. Method according to any one of the preceding claims, in which the plastic filler comprises thermoplastic polymers, more particularly polyolefins.