EP4259407A1

EP4259407A1 - Method for treating used plastics by dissolving the polymers and purifying them by washing

Info

Publication number: EP4259407A1
Application number: EP21834739.1A
Authority: EP
Inventors: Damien Leinekugel Le Cocq; Wilfried Weiss; Amir Hossein Ahmadi-Motlagh; Yacine HAROUN
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2020-12-14
Filing date: 2021-12-02
Publication date: 2023-10-18
Also published as: MX2023006544A; FR3117395B1; US20240042650A1; IL303664A; FR3117395A1; TW202233743A; AU2021403393A1; JP2023552635A; WO2022128488A1; CN116685630A; KR20230121091A; CA3198556A1

Abstract

The invention relates to a method for treating a plastic feedstock containing polymers, comprising: a) a dissolution step that comprises bringing the plastic feedstock into contact with a dissolving solvent, at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1 and 20.0 MPa abs, in order to dissolve at least part of the polymers of the plastic feedstock and obtain a crude polymer solution; b) a step of washing by placing the crude polymer solution in contact with a dense solution, at a temperature between 100°C and 300°C, a pressure between 1 and 20.0 MPa abs. and at a mass ratio between the dense solution and the crude polymer solution of between 0.05 and 20.0, in order to obtain a washed polymer solution and a washing effluent; and then c) a step of recovering the polymers, in order to obtain a solvent fraction and a fraction of purified polymers.

Description

PROCESS FOR THE TREATMENT OF USED PLASTICS BY DISSOLVING POLYMERS AND PURIFYING BY WASHING

TECHNICAL AREA

The present invention relates to a process for processing used plastics in order to obtain a purified plastic flow which can be recovered, for example, into new plastic objects. More particularly, the present invention relates to a process for treating a plastic filler, in particular from plastic waste, comprising in particular thermoplastics such as for example polyolefins, said process comprising a step of washing a solution of polymers with a solution dense, for example an aqueous solution, in order to at least partly eliminate the impurities, in particular the additives conventionally used in plastic-based materials, for example dyes, pigments, organic and inorganic fillers, so as to to be able to recover the plastic filler, by separating the polymers, in particular the thermoplastics, that said filler contains, in order to be able to recover and reuse them.

PRIOR TECHNIQUE

Plastics from the collection and sorting channels can be recovered through different channels.

So-called mechanical recycling makes it possible to partly 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 mechanical sorting makes it possible to improve the purity of a flow in a given type of polymer, but generally it does not make it possible to sufficiently 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 monomers at least in part according to a sequence of generally complex steps. For example, plastic waste can undergo a pyrolysis step and the recovered pyrolysis oil, 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 suitable for poorly sorted loads or sorting center refusals, but it generally requires significant energy consumption due in particular to high temperature treatments. Another way of recycling plastic waste consists in dissolving, at least in part, the plastics, in particular the thermoplastics, with a view to purifying them by eliminating the polymers of the load other than that/those targeted and/or the impurities. , for example additives such as fillers or fillers according to the Anglo-Saxon terminology, dyes, pigments, and metals.

Several studies thus present different methods of processing plastic waste by dissolution and purification. Document US 2017/002110 describes a specific method for purifying a polymer filler, in particular from plastic waste, by dissolving the polymer in a solvent, under specific temperature and pressure conditions, then contacting the polymer solution obtained with a solid. .

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

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

The present invention aims to overcome these drawbacks and participate in the recycling of plastics, in particular thermoplastics. More particularly, it aims to provide a process for treating a plastic filler, in particular from plastic waste, in order to effectively eliminate at least part of the impurities, in particular the additives conventionally added to plastics, and more particularly the soluble impurities. in particular in organic solvents, so as to be able to recover the plastic filler and more particularly the plastic waste, by separating and recovering the polymers, in particular the thermoplastics, in order to be able to use them for example as a polymer base for new plastic objects.

SUMMARY OF THE INVENTION

The invention relates to a process for treating a plastic filler, comprising: a) a dissolution step comprising bringing the plastic filler into contact with a dissolution solvent, at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 and 20.0 MPa abs., to obtain at least one raw polymer solution b) a washing step by bringing the raw polymer solution from step a) into contact with a dense solution, at a temperature between 100° C. and 300° C., a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude polymer solution which feeds step b) of between 0.05 and 20.0, to obtain at least one washed polymer solution and one effluent washing; then c) a step for recovering the polymers, to obtain at least one solvent fraction and one fraction of purified polymers.

The advantage of the process of the invention is to propose a process for the effective treatment of a load comprising plastics and in particular plastic waste, in particular from collection and sorting channels, so as to recover the polymers, more particularly the thermoplastics, which it contains in order to be able to recycle them for all types of applications. The process according to the invention in fact makes it possible to obtain a flow of purified polymers, more particularly of purified thermoplastics, and in particular of purified polyolefins such as polyethylene and polypropylene, advantageously comprising a negligible impurity content or at least low enough to that said flow of purified polymers, more particularly of purified thermoplastics, can be introduced into any plastic formulation instead of virgin polymer resin. For example, the stream of purified polymers, more particularly the stream of purified thermoplastics and in particular the stream of purified polyolefins, obtained at the end of the process according to the invention advantageously comprises less than 5% by weight of impurities, very advantageously less than 1% weight of impurities.

The process according to the invention thus proposes a sequence of operations which makes it possible to rid the plastic waste of at least some of their impurities, in particular the additives, and to recover purified polymers, so as to be able to recover the plastic waste by recycling of said purified polymers. Advantageously, depending on the conditions implemented in the steps of the process, the compounds present in the plastic filler may be soluble or insoluble in the solvent(s) used throughout the process according to the invention, allowing effective purification polymers.

The invention has the further 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 in order to obtain fractions of purified polymers, with a reduced content of impurities, in particular discolored and deodorized, which can be reused to form new objects. The fractions of purified polymers obtained can thus be used directly in formulations mixed with additives, for example dyes, pigments, other polymers, instead of or in mixing with virgin polymer resins, in order to obtain plastic products with use, aesthetic, mechanical or rheological properties facilitating their reuse and recovery.

The present invention also makes it possible to recover the solvent(s) used to treat the plastic filler of the process and to recycle it(s) after purification in the process, which avoids the excessive consumption of solvent(s). ).

Thus, the present invention aims to purify a plastic filler, in particular plastic waste, to obtain polymers, in particular thermoplastics and more particularly polyolefins such as polyethylene and polypropylene, purified, so as to be able to use them in any application, in particular replacing virgin polymers. The present invention therefore proposes a method of purification by dissolution of the polymers in question, that is to say to separate and purify. More particularly, the present invention aims to provide a method comprising a dissolution step followed by at least one specific purification step, more particularly at least one step b) of washing the polymer solution, optionally supplemented by other steps of intermediate purification, to obtain a purified polymer solution from which the purified polymers can be recovered.

DESCRIPTION OF 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 was not the case and the limit values were not included in the range described, such precision will be provided by the present invention.

Within the meaning of the present invention, the different ranges of parameters 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 may 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 absolute MPa). The terms “upstream” and “downstream” are to be understood according to the general flow of the fluid(s) or stream in question in the process.

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 solid organic or mineral compounds, making it possible to modify the physical, thermal, mechanical and/or polymer materials or to lower their cost price), reinforcing agents, dyes, pigments, hardeners, flame retardants, flame retardants, stabilizers, antioxidants, UV absorbers, antistatic agents, etc.

The additives correspond to part of the impurities of the plastic filler to be treated and which the treatment method according to the invention makes it possible to eliminate at least in part. Other types of impurities can be impurities from use or plastic materials, such as, for example, metallic impurities, paper/cardboard, biomass, other polymers, for example of the thermosetting or thermoplastic type, etc.

Thus according to the invention, the impurities, which the process according to the invention makes it possible to eliminate at least in part from the flow of polymers targeted, comprise the additives conventionally used in polymer formulations and generally impurities from use resulting from the cycle of life of plastic materials and objects, and/or from the waste collection and sorting circuit. The latter can be impurities of metallic, organic or mineral type; it can be packaging residues, food residues or compostable residues (biomass). These usage impurities can also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, silicones, rigid polymers, thermosetting polymers, 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 polymers, preferably the target polymers, more particularly the target thermoplastics, in particular the target polyolefins, dissolved in said dissolution solvent, the dissolved polymers being initially present in the load. The polymer solution may further comprise soluble and/or insoluble impurities. Depending on the steps of the process according to the invention undergone, said polymer solution may comprise impurities in the form of insoluble particles which are advantageously in suspension in said polymer solution, impurities soluble and dissolved in the dissolution solvent, and/or optionally another liquid phase immiscible with said polymer solution.

The critical temperature and the critical pressure of a solvent, in particular dissolution solvent and/or extraction solvent, are specific to said solvent and are respectively the temperature and the pressure of the critical point of the solvent. As well known to those skilled in the art, at the critical point and beyond, the solvent is in supercritical form or in the supercritical state, the operating conditions of temperature and pressure being supercritical conditions of the solvent; it can then be called supercritical fluid.

The invention relates to a method for purifying a plastic filler, preferably composed of plastic waste, and advantageously comprising polymers, preferably thermoplastics and more particularly polyolefins, said method preferably comprising, consisting of: a) a dissolution step comprising bringing the filler into contact with a solvent to obtain at least one raw polymer solution; then

E1) optionally a step of separating the insolubles to obtain at least one clarified polymer solution and one insoluble fraction; b) a washing step, by contact with a dense solution, to obtain at least one washing effluent and one washed polymer solution;

E2) optionally an extraction step, by contact with an extraction solvent, to obtain at least one extracted polymer solution and one used solvent;

E3) optionally a step of adsorption of the impurities by contact with an adsorbent solid, to obtain at least one refined polymer solution; and finally, c) a stage for recovering the polymers, to obtain at least a solvent fraction and a fraction of purified polymers.

Load

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

The plastics included in the charge of the process according to the invention are generally production scrap and/or waste, in particular household waste, building waste or even waste electrical and electronic equipment. Preferably, plastic waste comes from collection and sorting channels. Plastics or plastic materials are generally polymers which are most often mixed with additives, in order to constitute after shaping various materials and objects (injection molded parts, tubes, films, fibers, fabrics, putties, coatings, etc.). Additives used in plastics can be organic compounds or inorganic compounds. These are, for example, fillers or “fillers”, dyes, pigments, plasticizers, property modifiers, flame retardants, etc.

The feed of the process according to the invention therefore comprises polymers and in particular thermoplastics. The polymers included in the plastic filler can be alkene polymers, diene polymers, vinyl polymers and/or styrenic polymers. Preferably, the polymers included in the plastic filler are polyolefins, such as polyethylene (PE), polypropylene (PP) and/or copolymers of ethylene and propylene. Very preferably, the polymers of the plastic filler comprise at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight and very preferably at least 94% by weight, of polyolefins relative to the total load weight. The method according to the invention is thus particularly aimed at purifying and recovering the polyolefins contained in the charge in order 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, and impurities, in particular the additives advantageously used to formulate the plastic material and generally use impurities resulting from the life cycle of plastic materials and objects, and/or from the waste collection and sorting circuit. 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.

Said filler comprising plastics can advantageously be pretreated upstream of the process so as to remove at least 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 5 mm, or even greater than or equal to 1 mm, for example impurities of the wood, paper, biomass, iron, aluminum, glass, etc. type, and to shape it generally in the form of solids divided in such a way to facilitate processing 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 method according to the invention is implemented. Preferably, this pretreatment makes it possible to reduce the content of impurities to less than 6% by weight. At the end of the pretreatment, the filler is generally stored as divided solids, for example in the form of shredded material or powder, so as to facilitate handling and transport to the process.

Step a) of dissolution

According to the invention, the method comprises a dissolution step a) in which the plastic filler is brought into contact with a dissolution solvent at a dissolution temperature between 100° C. and 300° C. and a dissolution pressure between 1.0 and 20.0 MPa absolute, to obtain at least one, preferably one, raw polymer solution. This step in fact advantageously allows the dissolution of at least some, preferably all, of the polymers, preferably thermoplastics, most particularly polyolefins, such as polyethylene and/or polypropylene.

By dissolution, it is necessary to understand any phenomenon leading to the obtaining of at least one solution of polymers, that is to say a liquid comprising polymers dissolved in a solvent, more particularly in the solvent of dissolution. A person skilled in the art is well aware of the phenomenon(s) involved in the dissolution of polymers and which includes at least a mixing, a dispersion, a homogenization, a disentanglement of the polymer chains and more particularly of the thermoplastic chains.

During and at the end of step a) of dissolution, the pressure and temperature conditions make it possible to maintain the dissolution solvent, at least in part and preferably all of the dissolution solvent, in the liquid state , while the soluble fraction of the filler, in particular the target polymers, preferably the target thermoplastics and preferably the target polyolefins, and at least some of the impurities, is advantageously dissolved at least in part and preferably in full.

The bringing into contact between the dissolution solvent and the plastic filler to dissolve at least partially, preferably completely, the polymers of the plastic filler in the dissolution solvent can be carried out in a line and/or equipment and/or between two devices. Thus, step a) advantageously implements at least one dissolving device, and optionally at least one device for preparing the load, a mixing device and/or a transport device. These equipment and/or devices can be for example a static mixer, an extruder, a pump, a reactor, a co- or counter-current column, or in a combination of lines and equipment. Devices for transporting fluids in particular, such as gases, liquids or solids, are well known to those skilled in the art. In a non-limiting way, the transport devices can comprise a compressor, a pump, an extruder, a vibrating tube, an endless screw, a valve. The equipment and/or devices may also include or be associated with heating systems (eg furnace, exchanger, tracing, etc.) to achieve the conditions necessary for dissolution.

Dissolution step a) is supplied at least with the plastic filler, in particular in the form of one or more streams of plastic filler, and with the dissolution solvent, in particular in the form of one or more streams of dissolution, advantageously by means of one or more transport devices. The plastic filler stream(s) may be separate from the dissolving solvent stream(s). Part or all of the plastic filler can also feed step a) mixed with part or all of the dissolution solvent, the rest of the solvent and/or the filler, if necessary, being able to feed the step a) separately.

When the plastic filler is brought into contact with the dissolution solvent, the dissolution solvent is advantageously at least partly, and preferably entirely, in liquid form, while the plastic filler, which comprises polymers, in particular thermoplastics and in particular polyolefins, can be in solid or liquid form optionally comprising solid particles in suspension. The plastic filler can also optionally be injected into the dissolving equipment, mixed with the dissolving solvent, in the form of a suspension in the dissolving solvent, the preparation and injection of the suspension possibly being continuous or discontinuous.

Preferably, step a) implements at least one extruder and dissolution equipment. In this case, the plastic load feeds the extruder so that at the outlet of the extruder, at least some and preferably all of the target polymers, in particular the target thermoplastics, more particularly the polyolefins, included in the load found in a molten state. The plastic filler is then injected into the dissolution equipment at least partly in molten form. The plastic filler, at least partly in a molten state, can also be pumped using a dedicated viscous fluid pump often called a melt pump or a gear pump. The plastic filler, at least partly in the molten state, can also be, on leaving the extruder, filtered using a filtration device, possibly in addition to the melt pump, in order to eliminate the larger particles, generally the mesh size of this filter is between 10 microns and 1 mm, preferably between 20 and 200 microns.

Preferably, step a) implements an extruder into which the dissolution solvent is injected, advantageously at several points, so as to promote shearing and therefore intimate mixing between the dissolution solvent and the plastic filler, which contributes to the dissolution of polymers, in particular thermoplastics and more particularly polyolefins.

The dissolution solvent used in step a) of dissolution is advantageously an organic solvent or a mixture of preferably organic solvents. Preferably, the dissolution solvent is chosen from organic solvents, preferably comprising, and preferably consisting of, one (or more) hydrocarbon(s), having a boiling point of between -50°C and 250°C , preferably between -15°C and 150°C, more preferably between 20°C and 110°C. Preferably, the dissolution solvent comprises, preferably consists of, one or more hydrocarbon(s), very preferably one or more alkane(s), having between 3 and 12 carbon atoms, preferentially between 4 and 8 carbon atoms, and very preferably between 5 and 7 carbon atoms, for example the isomers of pentane, hexane and heptane. Preferably, the dissolution solvent, which is very advantageously an organic solvent, preferably a hydrocarbon, has a critical temperature of between 90 and 400° C., preferably between 130 and 300° C. and more preferably between 180 and 290° C. C, and a critical pressure of between 1.5 and 5.0 MPa abs., preferably between 2.0 and 4.3 MPa abs. and preferably between 2.4 and 4.2 MPa abs. According to a particular embodiment, the boiling point of the dissolution solvent is greater than 70° C., preferably between 80° C. and 220° C., and/or the solvent comprises, preferably consists of, an alkane containing at less than 7 carbon atoms. According to another preferred embodiment, the boiling point of the dissolution solvent is below 50°C or above 150°C.

Advantageously, the dissolution is carried out at a dissolution temperature between 100° C. and 300° C. and a dissolution pressure between 1.0 and 20.0 MPa abs. More particularly, the temperature and the pressure evolve throughout step a), from ambient conditions, that is to say a temperature of the plastic filler between 10 and 30° C. and the atmospheric pressure of 1 bar (0.1 MPa), until the dissolution conditions are reached, more particularly the dissolution temperature and the dissolution pressure. In particular, the dissolution temperature is between 100 and 300° C., preferably between 150 and 250° C., and the dissolution pressure, between 1.0 and 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. Very advantageously, at the end of step a) of dissolution, the flow of dissolved polymer is at the dissolution temperature and at the dissolution pressure. Preferably, the weight ratio between the plastic filler and the dissolution solvent is between 0.01 and 5.0, preferably between 0.05 and 3.0, more preferably between 0.10 and 1.0. The fact of limiting the temperature in 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 the polymers, in particular of thermoplastics and more particularly polyolefins. Preferably, the dissolution temperature is greater than or equal to the melting temperature of the polymers, in particular of the thermoplastics and more particularly of the polyolefins, so as to promote their dissolution. Preferably, the temperature in step a) of dissolution is less than or equal to the critical temperature of the dissolution solvent so as to avoid the formation of a supercritical phase during step a) of dissolution likely to disturb the dissolution.

At the same time, the dissolution pressure is greater than the saturation vapor pressure of the dissolution solvent, at the dissolution temperature, so that the dissolution solvent is at least partly, and preferably entirely, in liquid form, at the dissolving temperature. Advantageously, the dissolution pressure is equal to or greater than the critical pressure of the dissolution solvent, so as to be able to carry out in particular step c) of recovery under conditions where at least part of the solvent is in supercritical form without it is necessary to considerably increase the pressure between stage a), in particular between the outlet from stage a) and stage c). In the case where the dissolution pressure in step a) is equal to or greater than the critical pressure of the dissolution solvent, the dissolution temperature is lower than the critical temperature of the dissolution solvent, so as to keep the solvent from at least partly dissolved in liquid form.

Very advantageously, the dissolution temperature and pressure conditions reached in step a) are adjusted so that the mixture (dissolution solvent + target polymers) is single-phase.

Advantageously, said dissolution step a) is implemented for a residence time of between 1 and 600 minutes, preferably between 2 and 300 minutes, preferably between 2 and 180 minutes. The residence time is understood as the residence time at the dissolution temperature and at the dissolution pressure, i.e. the time of implementation of the plastic filler with the dissolution solvent at the dissolution temperature and at the dissolution pressure, in step a).

Advantageously, the dissolution solvent used in step a) comprises, preferably consists of, a make-up of fresh solvent and/or a flow of recycled solvent from step c) of recovery. Optionally, the treatment process may comprise an intermediate adsorption stage a'), located during the dissolution stage a) or directly downstream from the dissolution stage a), and which comprises the introduction of adsorbent solid, preferably of the alumina, silica, silica-alumina, activated carbon or bleaching earth type, in the form of divided particles, in the raw polymer solution obtained at the end of step a) or optionally during step a) of dissolution . The adsorbent solid can then be removed during step b) of washing and/or even during one of the optional intermediate purification steps, for example during an optional step E1) of separation of the insolubles. This optional step a′) of adsorption in the presence of adsorbent solid in divided form makes it possible to optimize the purification of the polymer solution.

The crude polymer solution obtained at the end of step a) of dissolution comprises at least the dissolution solvent, polymers, in particular the targeted polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent. In general, the raw polymer solution also comprises soluble impurities also dissolved in the dissolution solvent and/or insoluble impurities or compounds in suspension. The raw polymer solution obtained at the end of step a) may optionally also comprise polymers, other than the targeted polymers, for example in the molten state. insoluble

The treatment method may optionally also comprise a step E1) of separation of the insolubles by solid-liquid separation, which may be an additional purification step, to advantageously obtain at least one clarified polymer solution and one insoluble fraction. When it is integrated into the process according to the invention, step E1) for separating the insolubles is located between step a) of dissolving and step c) of recovering the polymers, and upstream or downstream of the step b) of washing, preferably upstream of step b) of washing. The insoluble fraction obtained advantageously comprises at least partly, preferably all, insoluble impurities, in particular suspended in the raw polymer solution from step a).

Step E1) for separating the insolubles thus makes it possible to eliminate at least a part, preferably all, of the particles of compounds insoluble in the dissolution solvent under the temperature and pressure conditions of step a), possibly present in suspension in the polymer solution, preferably the raw polymer solution resulting from step a) or from a possible step a′). The insoluble impurities eliminated during the optional step E1) for separating the insolubles are, for example, pigments, compounds minerals, packaging residues (glass, wood, cardboard, paper, aluminum) and insoluble polymers.

When it is implemented, this separation step E1) advantageously makes it possible to limit the operational problems, in particular of the clogging and/or erosion type, of the steps of the process located downstream, while contributing to the purification of the plastic filler .

When it is integrated into the process, step E1) for separating the 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 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. Very advantageously, the optional step E1) for separating the insolubles is implemented under the conditions of dissolution temperature and pressure, that is to say under the conditions of temperature and pressure at the outlet of step a).

When it is integrated into the process, said step E1) of separation of the insolubles is preferably supplied with the raw polymer solution resulting from step a) or resulting from a possible step a′) of intermediate adsorption. According to another embodiment, the optional step E1) can be supplied with a washed polymer solution resulting from the washing step b).

When it is integrated into the process, step E1) advantageously implements a section comprising at least one piece of solid-liquid separation equipment, for example a separator flask, a decanter, a centrifugal decanter, a centrifuge, a filter, a sand filter, an eddy current separator, an electrostatic separator, a triboelectric separator, preferably a decanter, a filter, a sand filter and/or an electrostatic separator.

The evacuation of the insoluble fraction can be facilitated by equipment allowing the transport and/or the elimination of the traces of solvent possibly present in the insoluble fraction, for example a conveyor, a vibrating tube, an endless screw, an extruder, a stripping. Step E1) can therefore implement transport equipment and/or the elimination of traces of solvent to evacuate the insoluble fraction.

According to a particular embodiment of the optional step E1), the step E1) for separating the insolubles implements 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 while the presence of equipment in parallel makes it possible to manage the maintenance of said equipment and/or unclogging operations.

The unclogging of equipment, in particular filters or electrostatic separators, can be carried out by means of a solvent injected against the current (backflush according to the Anglo-Saxon terminology). The unclogging solvent can be an aqueous or organic solution, preferably an organic solvent of the same nature as that used in step a) dissolution and/or b) washing. According to a particular embodiment, the unclogging solvent is identical in nature to the dense solution used in step b) of washing.

Certain insoluble compounds, in particular certain pigments and mineral fillers, conventionally added during the formulation of the polymers, can be introduced in the form of particles with a size of less than 1 μm. This is for example the case of titanium dioxide, calcium carbonate and carbon black. According to a particular embodiment of the optional step E1), said step E1) of separation of the insolubles advantageously implements an electrostatic separator, which makes it possible to effectively eliminate at least partly, preferably completely, the insoluble particles less than 1 µm in size. According to another particular embodiment of optional step E1), step E1) of separation of insolubles implements a sand filter, to eliminate particles of different sizes and in particular particles of size less than 1 μm.

Depending on the nature of the filler, the polymer solution which feeds step E1), preferably the crude polymer solution, may optionally also comprise a second liquid phase, for example consisting of molten polymers. According to another particular embodiment of optional step E1), step E1) advantageously implements equipment allowing the separation of this second liquid phase, preferably by means of at least one three-phase separator.

According to the invention, the treatment method comprises a step b) of washing with a dense solution, to advantageously obtain at least one washing effluent and one washed polymer solution. The washed polymer solution obtained at the end of step b) advantageously comprises the targeted polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent. Optionally, it may also comprise residual impurities, in particular soluble in the dissolution solvent and/or traces of the washing solvent.

Advantageously, step b) of washing is supplied with a dense solution and the polymer solution, preferably the raw polymer solution resulting from step a) or resulting from a optional step a′) of intermediate adsorption, or alternatively by the clarified polymer solution resulting from step E1) optional. The polymer solution that feeds optional step b) can also optionally be a refined polymer solution resulting from an optional adsorption step E3) in particular implemented by adding the adsorbent mixed with the polymer solution. Preferably, step b) of washing is supplied with a dense solution and the polymer solution, preferably the raw polymer solution resulting from step a) or resulting from a possible step a′) of intermediate adsorption, or alternatively with the clarified polymer solution resulting from optional step E1). The polymer solution which feeds step b) of washing, more particularly the raw polymer solution or the clarified polymer solution, can comprise impurities in the form of insoluble compounds in suspension and/or solubilized compounds. These compounds in suspension or solubilized can, in part or in whole, be eliminated during step b) of washing by dissolution or precipitation and/or by entrainment in the dense solution. Thus step b) contributes to the treatment of the plastic filler and more particularly to the purification of the polymer solution.

Washing step b) advantageously comprises bringing the raw or clarified polymer solution which feeds step b) 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 target polymers and the dissolution solvent in which the target polymers are dissolved). In particular, the density of the dense solution is 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 can also advantageously be polar or at least more polar than the dissolution solvent, so as to increase the efficiency of the purification of the polymer solution in particular towards polar impurities.

The dense solution can be an aqueous solution, which preferably comprises at least 50% by weight of water, preferentially at least 75% by weight of water, more preferably at least 90% by weight of water, very preferably at least 95% water weight. The pH of the aqueous solution can be adjusted using an acid or a base so as to promote the dissolution of certain compounds. The dense solution can also 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 optional step b), for example an organic solvent chosen from sulfolane or N-methylpyrrolidone (NMP), optionally mixed with water. Preferably, the dense solution of washing step b) is an aqueous solution, comprising preferably at least 90% by weight of water, very preferably at least 95% by weight of water.

Washing step b) 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 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. Very advantageously, step b) of washing is implemented at the dissolution temperature and the dissolution pressure.

Advantageously, the mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude or clarified polymer solution which feeds step b) is preferably 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 raw or clarified polymer solution 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 raw polymer solution or clarified and/or of the dense solution at different points along the equipment(s), it is then the sum of the flows injected which is taken into account in the calculation of the ratio.

Step b) can be implemented 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 one washed polymer solution. These pieces of equipment are well known, for example stirred reactors, static mixers, settler mixers, two-phase or three-phase separator drums, co or counter-current washing columns, tray column, stirred column, packed column, pulsed column, etc., each type equipment which may include one or more equipment used alone or in combination with equipment of another type.

According to a preferred embodiment, washing step b) is carried out in a countercurrent washing column into which the dense solution is injected, preferably into half, preferably one third, of the column furthest close to the column head, on the one hand, and the crude or clarified polymer solution is injected, preferably into half, preferably one 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 one washing effluent.

According to a very particular mode, the flows entering and/or leaving the washing column can be divided and injected at several injection points along the column and/or withdrawn at several withdrawal points along the column. According to another embodiment, step b) of washing is implemented in a mixer-settler comprising an agitated mixing zone, to bring the dense solution and the crude or clarified polymer solution into contact, and a settling zone , making it possible to recover a washed polymer solution and a washing effluent.

At the end of washing step b), the washing effluent obtained advantageously comprises compounds dissolved 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 compounds and optionally to 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 implement one or more well-known solid-liquid separation equipment(s), for example a separating 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.

According to a particular embodiment and in the case where the method according to the invention comprises the optional step E1), the unclogging flow possibly generated in step E1) and which comprises at least in part the insoluble fraction resulting from the step E1), is at least partly mixed with the washing effluent, so as to eliminate the insoluble impurities eliminated in steps E1) and b) in a common section.

The method according to the invention may optionally further comprise a step E2) of extraction by bringing it 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 optional step E2) advantageously comprises the targeted polymers that the present invention seeks to recover purified, dissolved in the dissolution solvent. Optionally, it may also include residual impurities, in particular soluble in the dissolution solvent and/or traces of the washing solvent and/or traces of extraction solvent if step E2) is carried out.

When it is integrated into the process according to the invention, step E2) of extraction is advantageously located between step b) of washing and step c) of recovery of the polymers. The optional extraction step E2) is advantageously supplied with the polymer solution, preferably the washed polymer solution resulting from step b) or optionally a refined polymer solution resulting from an optional adsorption step E3), and a extraction solvent. The polymer solution that feeds optional step E2), preferably the washed polymer solution from step b) or a refined polymer solution from an optional step E3), can therefore optionally comprise solubilized compounds or solubilized impurities. These solubilized compounds can be partially or totally eliminated during step E2) of extraction by bringing into contact with an extraction solvent. Very advantageously, the combination of a step b) of washing with a step E2) of extraction allows an improved purification of the polymer solution, by using both the affinity of the impurities for the dense and possibly polar solvent and for the extraction solvent.

The optional extraction step E2) advantageously implements at least one extraction section, preferably between one and five extraction section(s), very preferably one extraction section. The optional extraction step E2) is preferably carried out at a temperature between 100 and 300°C, preferably between 150 and 250°C. The optional extraction step E2) is preferably implemented at a pressure between 1.0 and 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. According to a preferred embodiment of the optional step E2), the extraction step E2) is implemented under temperature and pressure conditions different from the temperature and pressure conditions of step a).

The mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution which feeds step E2) is advantageously between 0.05 and 20.0, preferably between 0.1 and 10.0 and preferably between 0.2 and 5.0. The contacting between the polymer solution which feeds the optional step E2) and the extraction solvent can be carried out at several points of the extraction section, that is to say by several injections of the polymer solution and /or of the extraction solvent at different points along the extraction section, it is then the sum of the flows injected which is taken into account in the calculation of the ratio.

The extraction solvent used in the optional extraction step E2) is advantageously an organic solvent or a mixture of preferably organic solvents. Preferably, the extraction solvent is chosen from organic solvents, preferably comprising, and preferably consisting of, one (or more) hydrocarbon(s), having a boiling point of between -50°C and 250°C , preferably between -15°C and 150°C, more preferably between 20°C and 110°C. Preferably, the extraction solvent comprises, preferably consists of, one or more hydrocarbon(s), very preferably one or more alkane(s), having between 3 and 12 carbon atoms, preferentially between 4 and 8 carbon atoms and very preferably between 5 and 7 carbon atoms, for example the isomers of pentane, hexane and heptane. Preferably, the critical temperature of the solvent extraction, which is very advantageously an organic solvent, preferably a hydrocarbon, is between 90 and 400°C, preferably between 130 and 300°C and more preferably between 180 and 290°C, and the critical pressure of the extraction solvent is between 1.5 and 5.0 MPa abs., preferably between 2.0 and 4.3 MPa abs. and preferably between 2.4 and 4.2 MPa abs. According to a particular embodiment, the boiling point of the extraction solvent is greater than 70° C., preferably between 80° C. and 220° C., and/or the solvent contains at least 7 carbon atoms. According to another preferred embodiment, the boiling point of the extraction solvent is below 50°C or above 150°C.

Very preferably, the extraction solvent used in optional step E2) is the same solvent as the dissolution solvent used in step a), possibly in a different physical state (for example the solvent extraction in the supercritical state with respect 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 step a) of dissolution and possibly towards the step E2) of extraction. Another advantage of using identical dissolution and extraction solvents, in identical or different physical states, is, in addition to facilitating the technical management of the solvents involved in the process according to the invention, in particular the recovery solvents, their treatment and their recycling to at least one of the stages of the process, and to limit the energy consumption and the costs in particular generated by the treatment and purification of the solvents.

The optional extraction section(s) of step E2) can comprise one or more 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 one extracted polymer solution. This equipment is well known, such as, for example, stirred reactors, static mixers, settling mixers, two-phase or three-phase separator drums, co or counter-current washing columns, tray column, stirred column, packed column, pulsed column, 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 the optional step E2), the extraction is carried out in a countercurrent extraction column where the extraction solvent is injected on the one hand and the polymer solution which feeds the step E2) 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 step E2) is injected into the half, preferably the third, of the column closest to the head of the countercurrent extraction column while the extraction solvent is injected into the half, preferably the third, of the column closest to the bottom of the countercurrent extraction column.

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

According to another embodiment, the extraction is carried out in a mixer-settler which advantageously comprises an agitated mixing zone to bring the extraction solvent and the polymer solution into contact, preferably the washed polymer solution or optionally the polymer solution refined, and a settling zone for recovering an extracted polymer solution on the one hand and a used solvent on the other.

According to a preferred embodiment of the optional step E2), step E2) implements a liquid/liquid extraction section. In this embodiment, the extraction solvent is preferably chosen from the isomers of pentane, hexane and heptane, preferably from the isomers of pentane and hexane and very preferably from pentane isomers. 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 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. 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 also preferably 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 above the dissolution temperature and/or at a pressure below 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 optional step E2), step E2) implements an extraction section under particular temperature and pressure conditions in which the extraction solvent is advantageously at least partly under supercritical form. Such extraction can be called supercritical extraction. In this embodiment, the extraction is carried out by bringing the polymer solution, preferably the washed polymer solution or optionally the refined polymer solution, into contact with an extraction solvent, advantageously under temperature and pressure conditions which make it possible to obtain a supercritical phase composed mainly (that is to say preferably at least 50% by weight, preferably at least 70% by weight, so 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 washed or refined polymer solution, into contact with an extraction solvent which is at least partly, preferably entirely in the supercritical state. Such a step E2) of supercritical extraction advantageously allows effective purification of the polymer solution, in particular due to the very strong affinity of the organic impurities, such as for example certain of the 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 difference in density 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 particularly preferred embodiment, the optional extraction step E2) uses an extraction solvent having a critical temperature preferably between 130 and 300°C and preferably between 180 and 290°C, and a critical pressure preferably between 2.0 and 4.3 MPa abs. and preferably between 2.4 and 4.2 MPa abs. Very advantageously, in such a step E2) of supercritical extraction, the extraction solvent is chosen from hydrocarbons preferably having between 4 and 8 carbon atoms, preferably between 5 and 7 carbon atoms. The extraction solvent of the supercritical extraction can for example be an isomer of pentane, an isomer of hexane, an isomer of heptane, or else cyclopentane, cyclohexane or methylcyclopentane.

Advantageously, the optional step E2) of supercritical extraction is implemented 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 to 20.0 MPa abs., preferably between 2.0 and 15.0 MPa abs. and very preferably between 3.0 and 10.0 MPa abs. In all cases, in this embodiment, the temperature and pressure conditions are adjusted, in particular in an adjustment section implemented in step E2) of extraction upstream of the extraction section, so that the extraction solvent is at least partly in the supercritical state in the extraction section.

In a very preferred embodiment of the optional step E2), the extraction step E2) implements a supercritical extraction and the extraction solvent is the same as the dissolution solvent, except for the fact that the solvent extraction 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 settling during the extraction step, more particularly at each phase or plateau extraction, between the liquid phase and the supercritical phase, which thus makes it possible to maximize purification.

Advantageously, at the end of step E2) of extraction, 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 a part of the impurities and purify the solvent to obtain a purified extraction solvent, and on the other hand to recycle at least a part of the solvent. extraction purified at the input of the optional extraction step E2), and/or at the input of the 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 from distillation, evaporation, extraction, adsorption, crystallization and precipitation of the insolubles, or by purging.

The treatment process may optionally also comprise an optional adsorption step E3), located between step a) of dissolution and step c) of recovery of the polymers. Depending on the quality of the starting plastic filler and the impurities it contains, it may in fact be advantageous to complete the purification of the polymer solution with an optional adsorption step E3) making it possible to obtain at least one polymer solution refined.

When it is integrated into the process according to the invention, step E3) of adsorption is implemented downstream of step a) of dissolution and upstream of step c) of recovery of the polymers, and advantageously upstream or downstream of step b) of washing. The optional adsorption step E3) can optionally be implemented upstream or downstream of an optional extraction step E2).

Said optional adsorption step E3) advantageously implements 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, that is 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 an ebullated bed. The adsorption section is advantageously operated in the presence of at least one adsorbent, preferably of the alumina, silica, silica-alumina, activated carbon or bleaching earth type, preferably in the form of a fixed bed or an entrained bed, the circulation of flow can be ascending or descending. When the method according to the invention comprises an optional step E3) of adsorption upstream of step b) of washing, the adsorption section is preferably operated in the presence of the adsorbent in the form of an entrained bed (c′ i.e. in the form of divided particles introduced into the polymer solution). When the process according to the invention comprises a step E3) of adsorption downstream of step b) of washing, the section adsorption is very preferably carried out in the presence of the adsorbent in the form of a fixed bed.

Said optional adsorption step E3) 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 20.0 MPa abs., preferably between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs. Very advantageously, step E3) is implemented under the conditions of dissolution temperature and pressure, that is to say at the dissolution temperature and the dissolution pressure reached in step a). Preferably, in step E3), the hourly volume velocity (or WH), which corresponds to the ratio between the volume flow rate of the polymer solution which feeds step E3) and the volume of adsorbent is between 0.05 and 10 h ⁻¹ , preferably between 0.1 and 5.0 h ⁻¹ .

According to a particular embodiment of optional step E3), the adsorption section can 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. When the adsorption section comprises two adsorption columns, an operating mode can be an operation called "swing", according to the accepted Anglo-Saxon term, in which one of the columns is in line, i.e. i.e. in operation, while the other column is in reserve. When the adsorbent of the online column is spent, 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 with fresh adsorbent so that the column containing it can be brought back online once the other column has been isolated.

Another mode of operation of this particular embodiment of step E3), comprising one or more fixed bed(s) of adsorbent, is to have at least two columns operating in series. When the adsorbent of the column placed at the head is spent, this first column is isolated and the spent adsorbent is either regenerated in situ or replaced by fresh adsorbent. The column is then brought back in line in the 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 Anglo-Saxon term. The association of at least two adsorption columns makes it possible to compensate for poisoning and/or possible and possibly rapid clogging of the adsorbent under the joint action of impurities, contaminants and insolubles possibly present in the flow. 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 the consumption of adsorbent. Very advantageously, the combination of a step b) of washing with an optional step E3) of adsorption allows an improved purification of the polymer solution, by using both the affinity of the residual impurities for the dense solvent and also for the adsorbent solid.

The adsorption section of step E3) optional may, according to another embodiment, consist of adding particles of adsorbent to the polymer solution, in particular the crude polymer solution, said particles being able to be separated from the solution polymer via a step for eliminating adsorbent particles located downstream of said adsorption section, for example during step b) of washing in the case where the optional step E3) is located upstream of the step b). Such implementation of the optional step E3) of adsorption, by introduction of the adsorbent particles then solid/liquid separation, advantageously corresponds to the possible step a′) of intermediate adsorption, described further on in this description. .

According to the invention, the method comprises a step c) of recovering the polymers, to obtain at least a solvent fraction and a fraction of purified polymers.

Step c) for recovering the polymers advantageously implements at least one solvent recovery section, preferably between one and five solvent recovery section(s). Step c) for recovering the polymers is supplied with the washed polymer solution, or optionally an extracted or refined polymer solution.

Step c) for recovering the polymers thus aims firstly to separate at least in part, preferably mainly, the solvent(s), and in particular the dissolution solvent and possibly the washing solvent, or even also of the extraction solvent, contained in the polymer solution which feeds step c), that is to say the washed polymer solution or optionally the extracted polymer solution or the refined polymer solution, so as to recover the polymers, freed at least in part, preferably mostly and preferably completely, of the dissolution solvent and of the other solvent(s) used in the process possibly still present in the polymer solution which feeds step c). By predominantly, 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%, relative to the weight of the solvent(s) contained in the polymer solution which feeds stage c), in particular the dissolution solvent and optionally the washing solvent contained in the polymer solution which feeds stage c). Any method for separating the solvent from the polymers known to those skilled in the art can be implemented, in particular all the methods allowing a phase change of the polymers or of the solvent(s). The solvent(s) can be separated, for example, by evaporation, stripping, demixing, difference in density and in particular decantation or centrifugation, etc.

The fraction of purified polymers obtained can correspond to a concentrated polymer solution or to solid purified polymers. Preferably step c) for recovering the polymers also comprises a conditioning section for conditioning the polymers, in solid form and more particularly in the form of solid granules.

Step c) for recovering the polymers also aims to recover at least in part, preferably mainly and preferably in full, the solvent(s) contained in the washed polymer solution or optionally the extracted polymer solution or refined which feeds step c), and in particular the dissolution solvent and optionally the washing solvent, or even also the extraction solvent. Stage c) for recovering the polymers also aims optionally to purify and recycle the recovered solvent fraction, in particular upstream of stage a) of dissolution and/or upstream of stages b) of washing and/or E2) of extraction. By predominantly, 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%, relative to the weight of the solvent(s) contained in the washed polymer solution or optionally the extracted or refined polymer solution which feeds step c).

Said step c) for recovering the polymers advantageously implements at least one solvent recovery section at a temperature between 0 and 350°C, preferably between 5 and 300°C and preferably between 10 and 250°C, and at a pressure between 0.1 and 20.0 MPa abs., preferably between 0.1 and 15.0 MPa abs. and very preferably between 0.1 and 10.0 MPa abs.

Advantageously, step c) for recovering the polymers implements at least one solvent recovery section, each preferably comprising equipment operated at different temperatures and different pressures, with a view to obtaining at least one solvent fraction and one fraction of purified polymers. In the case where several different solvents have been used in the treatment process according to the invention, in particular in steps a) of dissolution and b) of washing, optionally a step E2) of extraction, step c ) can implement several solvent recovery sections, for example two, three or four solvent recovery sections, so as to recover separately, sequentially and/or successively the various solvents, in particular the dissolution solvent, the washing solvent and optionally the extraction solvent.

According to a particular embodiment of the invention, the method of the present invention implements, advantageously successively or simultaneously:

- a solvent recovery section c1) during which the polymer solution is preferably heated to a temperature above the melting point of the polymers, to obtain a solvent fraction and a fraction of purified polymers,

- a conditioning section c2) during which the fraction of purified polymers, advantageously separated from the solvent(s), is cooled, advantageously to a temperature below the melting point of the polymers, to obtain a fraction comprising polymers with the solid state.

According to a preferred embodiment of the invention, step c) implements a solvent recovery section from step c) under temperature and pressure conditions adjusted so as to be placed under supercritical conditions, that is to say beyond the critical point of the solvent(s) to be separated, in particular beyond the critical point of the dissolution solvent, advantageously making it possible to easily separate and recover at least part of the solvent , in particular of the dissolution solvent. In this embodiment, said solvent recovery section implements in particular a fluid system which consists of a supercritical phase mainly comprising solvent, in particular dissolution, and a liquid phase comprising the polymers. The term “predominantly” here means at least 50% by weight, 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 flux in question, c ie the supercritical phase. The separation can then be called supercritical separation of the solvent(s). The supercritical separation of the solvent(s) makes it possible to effectively separate on the one hand the solvent(s) and in particular the dissolution solvent and on the other hand the polymers or possibly or a concentrated polymer solution, the supercritical separation being advantageously permitted by the significant difference in density between the two phases. In addition, the supercritical separation of the solvent(s) advantageously makes it possible to present a significantly reduced energy and environmental cost compared to a simple vaporization of the solvent, since during the transition to the supercritical state, there is no latent heat of vaporization.

According to a particular embodiment of the invention, at least part of the fraction of purified polymers obtained at the end of step c) can be recycled to step a) of dissolution, to again undergo a cycle of treatment so as to increase the efficiency of purification of the polymers.

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, by in particular a purified dissolution solvent, in order to be able to advantageously recycle it to step a) of dissolution and/or optionally to step b) of washing and/or the optional step E2) of extraction. Said optional 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 from distillation, evaporation, liquid-liquid extraction, adsorption, crystallization and precipitation of insolubles, or by purging.

The process according to the invention thus makes it possible to obtain a purified stream of polymers, in particular of thermoplastics and more particularly of polyolefins, from plastic waste, which can be used in any application, for example as a replacement for the same polymers at the blank state. The purified flow of polymers, that is to say the fraction of purified polymers, obtained by the process according to the invention thus has a sufficiently low content of impurities to be able to be used in any application.

According to a preferred embodiment of the invention, the process for treating the plastic filler comprises, preferably consists of:

- a step a) of dissolution in a dissolution solvent, to obtain at least one raw polymer solution;

- a step b) of washing the raw polymer solution by contact with a dense solution, to obtain at least one washing effluent and one washed polymer solution;

- a step E2) of extracting the polymer solution washed with an extraction solvent, preferably implementing supercritical extraction, to obtain at least one extracted polymer solution and one used solvent; and

- a step c) for recovering the polymers from the extracted polymer solution, preferably implementing a supercritical separation of the solvent(s), in particular a supercritical separation of the dissolution solvent, to obtain a solvent fraction and a fraction of purified polymers, the dissolution solvent and the extraction solvent preferably being identical.

According to another preferred embodiment of the invention, the process for treating the plastic filler comprises, preferably consists of: - a step a) of dissolution in a dissolution solvent, to obtain at least one raw polymer solution;

- a step E1) for separating the insolubles, supplied with the raw polymer solution, to obtain at least one clarified polymer solution and one insoluble fraction;

- a step b) of washing the clarified polymer solution by contact with a dense solution, to obtain at least one washing effluent and one washed polymer solution;

- a step c) for recovering the polymers from the extracted polymer solution, preferably implementing a supercritical separation of the solvent(s), to obtain a solvent fraction and a fraction of purified polymers; the dissolution solvent and the extraction solvent preferably being identical.

According to an alternative preferred embodiment of the invention, the process for treating the plastic filler comprises, preferably consists of:

- a step E1) for separating the insolubles, supplied with the washed polymer solution, to obtain at least one clarified polymer solution and an insoluble fraction;

- a step E2) of extracting the clarified polymer solution with an extraction solvent, preferably implementing supercritical extraction, to obtain at least one extracted polymer solution and one used solvent; and

According to another particular embodiment of the invention, the process for treating the plastic filler comprises, preferably consists of:

- a step E1) for separating the insolubles, supplied with the raw polymer solution, to obtain at least one clarified polymer solution and one insoluble fraction; - a step b) of washing the clarified polymer solution by contact with a dense solution, to obtain at least one washing effluent and one washed polymer solution;

- a step E2) of extracting the polymer solution washed with an extraction solvent, preferably implementing supercritical extraction, to obtain at least one extracted polymer solution and one used solvent;

- a step E3) of adsorption by bringing the extracted polymer solution into contact with an adsorbent, preferably in a fixed bed, to obtain at least one refined polymer solution; and

- a stage c) of recovery of the polymers from the refined polymer solution resulting from E3), preferably implementing a supercritical separation of the solvent(s), to obtain a solvent fraction and a fraction of purified polymers; the dissolution solvent and the extraction solvent preferably being identical.

- a step E2) of extracting the clarified polymer solution with an extraction solvent, preferably implementing supercritical extraction, to obtain at least one extracted polymer solution and one used solvent;

The following examples and figures illustrate the invention, in particular particular embodiments of the invention, without limiting its scope. LIST OF FIGURES

The mention of the elements referenced in Figures 1 to 3 allows a better understanding of the invention, without it being limited to the particular embodiments illustrated in Figures 1 to 3. The different embodiments presented can be used alone or in combination with each other, without limitation of combination.

Figure 1 shows the diagram of an embodiment of the method of the present invention, comprising:

- a step a) of dissolving the plastic filler 1 comprising polymers in a dissolution solvent 2, to obtain a crude polymer solution 3;

- a washing step b) of the crude polymer solution 3 with a dense solution, preferably an aqueous solution 6, to obtain a washed polymer solution 8 and a washing effluent 7;

- a step c) of recovering the polymers from the washed polymer solution 8 resulting from step b), to obtain a solvent fraction 13 and a fraction of purified polymers 14.

Figure 2 shows a variant of the implementation of the method according to the invention shown in Figure 1, comprising:

- a step E1) for separating the insolubles, supplied with the crude polymer solution 3, to obtain a clarified polymer solution 5 and an insoluble fraction 4;

- a step b) of washing the clarified polymer solution 5 by contact with a dense solution 6, to obtain a washing effluent 7 and a washed polymer solution 8;

- an extraction step E2) of the washed polymer solution 8 with an extraction solvent 9, to obtain an extracted polymer solution 11 and a used solvent 10;

- a step E3) of adsorption by bringing the extracted polymer solution 11 into contact with an adsorbent, to obtain a refined polymer solution 12;

- a step c) of recovering the polymers from the refined polymer solution 12 resulting from step E3), to obtain a solvent fraction 13 and a purified polymer fraction 14.

Figure 3 shows a variant of the implementation of the method according to the invention shown in Figure 2. In the embodiment shown in Figure 3, the method comprises a step a′) intermediate between step a) and step E1). The crude polymer solution 3 is brought into contact with an adsorbent in the form of divided solids in order to obtain a polymer solution 21 comprising the adsorbent in suspension and feeding the separation step E1). The adsorbent, introduced beforehand in step a′), is then separated and eliminated in the insoluble fraction 4.

Only the main steps, with the main flows, are represented in Figures 1 to 3, in order to allow a better understanding of the invention. It is understood that all the equipment necessary for operation is present (balloons, pumps, exchangers, ovens, columns, etc.), even if not shown.

EXAMPLES

Example 1 (in accordance with the invention)

250 ml of n-pentane and 23 g of a plastic filler in the form of beads 5 mm in diameter, pink-violet in color and based on polypropylene, are introduced into a 500 ml autoclave fitted with a stirrer.

The autoclave is then hermetically sealed and heated to 180°C at a rate of 2°C per minute, stirring at 500 rotations per minute (rpm). Once the temperature of 180°C has been reached, the temperature and stirring are maintained for 3 hours, at an autogenous pressure of 26 bar (i.e. 2.6 MPa). After 3 hours, all the polypropylene is dissolved in the n-pentane. A highly colored liquid phase, the raw polymer solution, is obtained.

Then 125 mL of water are added to the system, maintaining the temperature at 180°C, the pressure at 2.6 MPa and the stirring at 500 rpm. Then, these conditions of temperature, pressure and agitation are maintained for 5 minutes, before stopping the agitation. After stopping the agitation, the system then settles. After 5 minutes at rest, the fluid system inside the autoclave settles to form two phases at the end of the washing step. The upper phase, containing the polymer and corresponding to a washed polymer solution, is less colored than the mixture before the washing step.

15 mL of the washed polymer solution are taken and poured into a crystallizer. The crystallizer is then placed in an oven at 180°C and atmospheric pressure, under nitrogen flushing for 6 hours.

A slightly pink whitish solid is then obtained in the crystallizer. Example 2 (not according to the invention)

250 mL of n-pentane and 23 g of a plastic filler in the form of beads 5 mm in diameter, pink-violet in color and based on polypropylene are introduced into a 500 ml autoclave fitted with a stirrer. The autoclave is then hermetically sealed and heated to 180°C at a rate of 2°C per minute, stirring at 500 rotations per minute (rpm). Once the temperature of 180°C has been reached, the temperature and stirring are maintained for 3 hours, at an autogenous pressure of 2.6 MPa. After 3 hours, all the polypropylene is dissolved in the n-pentane. A highly colored liquid phase, the raw polymer solution, is obtained. 15 mL of the crude polymer solution are taken and poured into a crystallizer. The crystallizer is then placed in an oven at 180°C and atmospheric pressure, under nitrogen flushing for 6 hours.

A pink-violet colored solid is then obtained in the crystallizer. The solid obtained has a color close to that of the balls of the initial charge.

Claims

1. Process for treating a plastic filler, comprising: a) a dissolution step comprising bringing the plastic filler into contact with a dissolution solvent, at a dissolution temperature between 100°C and 300°C and a pressure dissolution between 1.0 and 20.0 MPa abs., to obtain at least one raw polymer solution; b) a washing step by bringing the raw polymer solution from step a) into contact with a dense solution, at a temperature between 100° C. and 300° C., a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude polymer solution which feeds step b) of between 0.05 and 20.0, to obtain at least one washed polymer solution and one effluent washing; then c) a step for recovering the polymers, to obtain at least one solvent fraction and one fraction of purified polymers.

2. Method according to claim 1, in which the dissolution solvent is chosen from organic solvents having a boiling point of between -50°C and 250°C, preferably between -15°C and 150°C, of preferably between 20°C and 110°C.

3. Method according to claim 1 or 2, in which the dissolution solvent has a critical temperature of between 90 and 400°C, preferably between 130 and 300°C and preferably between 180 and 290°C, and a pressure critical between 1.5 and 5.0 MPa abs., preferably between 2.0 and 4.3 MPa abs. and preferably between 2.4 and 4.2 MPa abs.

4. Method according to one of the preceding claims, in which the dissolution temperature in step a) is between 150 and 250° C. and the dissolution pressure is between 1.5 and 15.0 MPa abs. and very preferably between 2.0 and 10.0 MPa abs.

5. Method according to one of the preceding claims, in which the dense solution implemented in step b) has a density greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to at 1.0.

6. Method according to one of the preceding claims, in which the dense solution implemented in step b) is an aqueous solution, which preferably comprises at least 50% by weight of water, preferably at least 75% weight of water, preferably at least 90% weight of water, very preferably at least 95% weight of water.

7. Method according to one of the preceding claims, in which step b) of washing is carried out at the dissolution temperature and the dissolution pressure.

8. Method according to one of the preceding claims, in which step step c) for recovering the polymers implements a solvent recovery section at a temperature between 0 and 350° C., preferably between 5 and 300° C. and preferably between 10 and 250°C, and at a pressure between 0.1 and 20.0 MPa abs., preferably between 0.1 and 15.0 MPa abs. and very preferably between 0.1 and 10.0 MPa abs.

9. Method according to one of the preceding claims, in which step step c) for recovering the polymers implements at least one solvent recovery section under temperature and pressure conditions adjusted so as to be placed in supercritical conditions of the dissolution solvent.

10. Method according to one of the preceding claims, comprising a step E2) of extraction by bringing the washed polymer solution into contact with an extraction solvent, at a temperature between 100° C. and 300° C., a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the washed polymer solution is between 0.05 and 20.0, wherein the extraction solvent is preferably an organic solvent which exhibits a critical temperature between 90 and 400°C, preferably between 130 and 300°C and preferably between 180 and 290°C, and a critical pressure between 1.5 and 5.0 MPa abs., preferably between 2 .0 and 4.3 MPa abs. and preferably between 2.4 and 4.2 MPa abs., to obtain at least one extracted polymer solution and one waste solvent.

11. Process according to claim 10, in which the extraction solvent is the same as the dissolution solvent and is at least partly, preferably entirely, in the supercritical state.

12. Method according to one of the preceding claims, comprising a step E1) of separating the insolubles by solid-liquid separation, at a temperature between 100° C. and 300° C., a pressure between 1.0 and 20.0 MPa abs ., said step E1) being located between step a) of dissolving and step c) of recovering the polymers, and upstream or downstream of step b) of washing, preferably upstream of step b) of washing, and in which step E1) of separation of the insolubles preferably implements an electrostatic separator and/or a filter and/or a sand filter.

13. Method according to one of the preceding claims, comprising a step E3) of adsorption located between step a) of dissolution and step c) of recovery of the polymers and implementing an adsorption section operated in the presence of at least one adsorbent, at a temperature between 100 and 300° C. and a pressure between 1.0 and 20.0 MPa abs.

14. Method according to one of the preceding claims, comprising: a) a dissolution step comprising bringing the plastic filler into contact with a dissolution solvent, at a dissolution temperature between 100°C and 300°C and at a dissolution pressure between 1.0 and 20.0 MPa abs., to obtain at least one raw polymer solution; b) a washing step by bringing the raw polymer solution from step a) into contact with a dense solution, at a temperature between 100° C. and 300° C., at a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude polymer solution of between 0.05 and 20.0, said dense solution preferably being an aqueous solution, to obtain at least one washed polymer solution and a washing effluent;

E2) an extraction step by bringing the washed polymer solution from step b) into contact with an extraction solvent, at a temperature between 100° C. and 300° C., at a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the washed polymer solution of between 0.05 and 20.0, to obtain at least one extracted polymer solution and one used solvent; then c) a step for recovering the polymers, to obtain at least a solvent fraction and a fraction of purified polymers, said step for recovering the polymers preferably implementing at least one solvent recovery section under temperature and pressure adjusted so as to be placed under supercritical conditions of the dissolution solvent.

15. Method according to one of the preceding claims, comprising: a) a dissolution step comprising bringing the plastic filler into contact with a dissolution solvent, at a dissolution temperature between 100°C and 300°C and at a dissolution pressure between 1.0 and 20.0 MPa abs., to obtain at least one raw polymer solution; b) a washing step by bringing the raw polymer solution from step a) into contact with a dense solution, at a temperature between 100° C. and 300° C., at a pressure between 1.0 and 20.0 MPa abs. and at a mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude polymer solution of between 0.05 and 20.0, said dense solution preferably being an aqueous solution, to obtain at least one washed polymer solution and a washing effluent; E3) an adsorption step supplied with the washed polymer solution from step b) and implementing an adsorption section operated in the presence of at least one adsorbent, at a temperature between 100°C and 300°C and a pressure between 1.0 and 20.0 MPa abs., to obtain at least one refined polymer solution; then c) a step for recovering the polymers, to obtain at least a solvent fraction and a fraction of purified polymers, said step for recovering the polymers preferably implementing at least one solvent recovery section under temperature and pressure adjusted so as to be placed under supercritical conditions of the dissolution solvent.