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

Abstract

The present invention relates to a process for processing a plastic filler, comprising: a) a dissolution step, implementing: i) a contacting section for the plastic filler with at least a portion of a dissolving solvent, comprising at least one static or dynamic mixer, each mixer being fed with a plastic stream and a fraction of the dissolving solvent such that each mixer has a volumetric dilution ratio in dissolving solvent of between 3% and 70%, each mixer being operated at a temperature between 100°C and 300°C; then ii) a dissolution section operated at a temperature between 100°C and 300°C and a pressure between 1.0 and 100.0 MPa absolute; then b) a purification step; then c) a solvent-polymer separation step, to obtain at least a fraction of purified thermoplastic polymers. Figure 1 to be published

Description

Title of the invention: METHOD FOR RECYCLING AND TREATMENT OF USED PLASTICS BY DISSOLUTION IN A SOLVENT WITH STAGED INTRODUCTION OF SOLVENT technical field

[0001] The present invention relates to a process for treating plastics, particularly used plastics, to obtain a stream of purified thermoplastic polymers that 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 feedstock, particularly one derived from plastic waste, comprising thermoplastic polymers, especially polyolefins, for example polyethylene and / or polypropylene, by dissolving the thermoplastics in question in a solvent and then purifying the resulting polymer solution. The process comprises a staged mixing of the solvent with the plastic feedstock to obtain a homogeneous mixture, preferably having a viscosity of 50 mPa or less.s, and very advantageously a coefficient of variation of concentration less than or equal to 10%, in order to optimize the dissolution of the targeted thermoplastics and the purification of the polymer solution obtained to recover a stream of purified thermoplastics. Previous technique

[0002] Plastics from collection and sorting channels can be recovered through different channels.

[0003] Mechanical recycling allows for the partial reuse of certain waste materials, either directly in new objects or by mixing mechanically sorted plastic waste streams with streams of virgin polymers. This type of recovery is limited because, even though it allows for a concentrated stream of a particular type of polymer, mechanical sorting does not eliminate impurities that are at least partially trapped in the polymer matrix, such as additives like fillers, colorants, pigments, and metals.

[0004] So-called chemical recycling aims to reform monomers, at least partially, through a generally complex sequence of steps. For example, plastic waste may undergo a pyrolysis step, and the recovered pyrolysis oil, generally after purification, may be converted, at least partially, for example, into olefins by steam cracking. These olefins can then be polymerized. This type of sequence It may be suitable for poorly sorted loads or sorting centre rejects, but it generally requires significant energy consumption due in particular to high-temperature treatments.

[0005] Another way of recycling plastic waste consists of dissolving, at least in part, the plastics, in particular thermoplastics, in order to purify them, by removing impurities, for example additives such as fillers, colorants, pigments, and metals and / or polymers of the filler other than the one(s) concerned.

[0006] Several studies present different methods for treating plastic waste by dissolution and purification. US patent 2017 / 002110 describes a particular method for purifying a polymer filler, notably from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, and then contacting the resulting polymer solution with a solid.

[0007] Document WO 2018 / 114047 proposes a method for the selective dissolution of a particular polymer from a plastic in a solvent at a dissolution temperature close to the boiling point of the solvent. However, the process described in document WO 2018 / 114047 does not allow for the efficient treatment and separation of impurities other than polymers, for example, additives.

[0008] US patent 2018 / 0208736 proposes a process for treating thermoplastics by liquefying them in a solvent and then separating the insolubles and / or gases. The process described in US patent 2018 / 0208736 does not allow for the efficient treatment of impurities soluble in the solvent.

[0009] 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 feedstock, by particularly improving the phase of contact between the solvent and the plastic feedstock to be treated. The present invention thus aims to obtain a homogeneous mixture advantageously exhibiting a sufficiently low viscosity, thereby enabling optimal dissolution of the targeted thermoplastics, particularly in terms of dissolution time, the agitation power required for mixing in the reactor, and operating cost.This process is highly advantageous, as it maximizes the removal of impurities to obtain a stream of purified thermoplastics, in particular a stream of purified polyolefins, which can be reused, for example, as a polymer base in the manufacture of new plastic objects, notably in place of virgin resin. Summary of the invention

[0010] The invention relates to a process for treating a plastic filler, comprising:

[0011] a) a step of dissolving the plastic filler in a dissolving solvent, to obtain at least one crude polymer solution, step a) of dissolution implementing:

[0012] i) a section for contacting the plastic charge with at least a portion of the dissolving solvent, comprising at least one static or dynamic mixer, to produce a conditioned charge, each static or dynamic mixer being operated at a temperature between 100°C and 300°C,

[0013] each static or dynamic mixer being fed by a plastic flow, comprising the plastic charge, and by a fraction of at least said part of the dissolving solvent, so that each mixer has a volumetric dilution rate in dissolving solvent of between 3% and 70%,

[0014] the volumetric dilution rate in dissolving solvent being the ratio between the volumetric 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 volumetric flow rates of the fraction of at least said part of the dissolving solvent and the plastic flow which feed the static or dynamic mixer considered;

[0015] ii) a dissolution section fed at least by the conditioned charge from the contacting section and operated at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 and 100.0 MPa absolute; then

[0016] b) a purification step of the crude polymer solution to obtain a purified polymer solution, said purification step comprising:

[0017] bl) a substep for separating insolubles; and / or

[0018] b2) a washing substep, by contact with a dense solution; and / or

[0019] b3) an extraction substep, by contact with an extraction solvent; and / or

[0020] b4) a substep of adsorption of impurities by contact with a solid adsorbent; Then,

[0021] c) a solvent-polymer separation step, to obtain at least a fraction of purified thermoplastic polymers.

[0022] The advantage of the process of the invention is that it provides an efficient method for treating plastic filler, and in particular plastic waste from collection and sorting channels, in order to recover the thermoplastic polymers, especially polyolefins, it contains so that they can be recycled for all types of applications. The process according to the invention more particularly improves the contact 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, most preferably less than or equal to 5 mPa.s, in a very Preferably, the viscosity should be less than or equal to 1 mPa·s. Advantageously, the homogeneous mixture should have a concentration coefficient of variation (CV) of preferably less than or equal to 10%, and preferably less than or equal to 5%. Such a mixture has the advantage of resulting in a sufficiently low effective viscosity in the dissolution reactor, thus contributing to the dispersion and homogenization of the plastic feedstock-dissolving solvent mixture. The dissolution of the thermoplastics to be separated and recovered is then optimal, without requiring excessively high stirring power and / or while allowing the use of various stirring systems, such as mechanical stirring and / or recirculating loop stirring.In parallel, the residence time required to efficiently dissolve the targeted thermoplastics can also be advantageously reduced, which can be achieved by using equipment, for example the dissolution reactor, of optimized size.

[0023] The present invention thus makes it possible to efficiently premix the plastic filler with the dissolving solvent (or at least a portion of the dissolving solvent), while respecting the technical constraints imposed by the mixing equipment used, in particular by the agitation system of the dissolving 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 varies up to 1000 (i.e., < 1000). However, the present invention makes it possible to efficiently mix a plastic filler comprising thermoplastics, in particular polyolefins, whose molten 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.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 105-109, which is very high and usually incompatible with the technical constraints of static or dynamic mixers.

[0024] The process according to the invention, which includes a dissolution step and, in particular, improved contact between the solvent and the feedstock, thus makes it possible to obtain a stream of purified thermoplastics, advantageously comprising an impurity content, and in particular an additive content, that is negligible or at least sufficiently low so that the stream of purified thermoplastic polymers can be used in any type of plastic formulation in place of virgin resin. For example, 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 has an impurity content of less than or equal to 5% by weight of impurities, very advantageously less than or equal to 1.0% by weight of impurities, and even more preferably a content lower than or equal to 0.5% by weight of impurities.

[0025] The process according to the invention thus proposes a simple scheme corresponding to a sequence of operations, which makes it possible to remove at least some of the impurities from plastic waste, in particular at least some of the additives, and to recover purified thermoplastic polymers, advantageously containing little or no solvent, so as to be able to recover value from the plastic waste by recycling said purified thermoplastics. Depending on the conditions implemented in the steps of the process, the additives present in the plastic feedstock can advantageously be soluble or insoluble in the solvent used throughout the process according to the invention, allowing for efficient purification and separation of the polymers.

[0026] The invention also has the advantage of contributing to plastic recycling and the preservation of fossil resources by enabling the recovery of plastic waste. It allows, in effect, the purification of plastic waste to obtain purified thermoplastic polymer fractions, in particular purified polyolefins, with reduced impurity content, including 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, colorants, pigments, other polymers, either instead of or in combination with virgin polymer resins, in order to obtain plastic products with performance, aesthetic, mechanical, or rheological properties that facilitate their reuse and recovery. Description of the implementation methods

[0027] 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 clarification will be provided by the present invention.

[0028] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred pressure range can be combined with a more preferred temperature range.

[0029] In the following, particular embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044] 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 in relation 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" can be used interchangeably. The terms "static or dynamic mixer" and "mixer" are used interchangeably and refer to mixing equipment well known to those skilled in the art as static mixers or dynamic mixers. According to the invention, viscosity is defined as a dynamic viscosity, in particular measured at a temperature of 200°C and at a shear rate of 0.1 s1, using a viscometer, preferably using a planar-planar type viscometer for example of type DHR3 from TA Instrument. According to the invention, the coefficient of variation (CoV) of concentration is calculated in dividing the standard deviation of z concentration measurements by the mean concentration, expressed as a percentage: CoV = j with standard deviation on concentration measurements: the average concentration: ^'xi * = 4- n, representing in these mathematical formulas, is the total number of concentration measurements. xi representing the concentration value determined by measurement i; and z being an integer greater than or equal to 2, preferably greater than or equal to 4, and generally less than or equal to 10,000, preferably less than or equal to 1,000, the concentration being determined by any method known to a person 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 commonly used in the field of polymers, and particularly in the field of polymer formulations. Additives introduced into polymer formulations can be, for example, plasticizers, fillers (which are solid organic or mineral compounds that modify the polymer's properties). physical, thermal, mechanical and / or electrical properties of polymer materials or to lower their cost price), reinforcing agents, colorants, pigments, hardeners, flame retardants, combustion retardants, stabilizing agents, antioxidants, UV absorbers, antistatic agents, etc.

[0045] The additives correspond to at least some of the impurities in the plastic feedstock to be treated, which the treatment process according to the invention makes it possible to eliminate at least in part. Other types of impurities may be usage-related impurities, such as, for example, metallic impurities, paper / cardboard, biomass, polymers other than the polymer(s) targeted, etc.

[0046] Thus, according to the invention, the impurities that 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 impurities resulting from the life cycle of plastic materials and objects, and / or from the waste collection and sorting system. These latter impurities may be metallic, organic, or mineral; they may include packaging residues, food residues, or compostable residues (biomass). These impurities may also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, silicones, rigid polymers, thermosetting polymers, household, chemical, or cosmetic products, used oils, and water.

[0047] According to the invention, a polymer solution is a solution comprising the dissolving solvent and at least the thermoplastic polymers referred to, in particular the polyolefins referred to, dissolved (i.e., in particular solvated and dispersed) in said dissolving solvent, the dissolved polymers being initially present in the feedstock. The polymer solution may further comprise soluble impurities (and solubilized in the dissolving solvent) and / or insoluble impurities (and suspended in the polymer solution). Depending on the steps of the process according to the invention, said polymer solution may therefore comprise impurities in the form of insoluble particles which are advantageously suspended in said polymer solution, soluble impurities dissolved in the dissolving solvent, and / or optionally another liquid phase immiscible with said polymer solution.

[0048] It is well known that the boiling point of a compound varies with the operating pressure. However, without further indication, i.e., without an indication of the pressure, the boiling point of the compound in question, in particular of the dissolving solvent, is understood to be the boiling point of said compound, in particular of said dissolving solvent, at atmospheric pressure (in particular equal to 0.1 MPa). Thus, the boiling point that characterizes the dissolving solvent must be understood as the boiling point of said solvent. dissolution at atmospheric pressure (in particular equal to 0.1 MPa).

[0049] The critical temperature and critical pressure of a solvent, particularly a dissolving solvent, are specific to that solvent and depend on the nature of the solvent in question. For a pure substance, the critical temperature and critical pressure of a pure substance are respectively the temperature and pressure of the critical point of said pure substance. As is well known to those skilled in the art, at the critical point and above, the pure substance in question is in supercritical form or in the supercritical state; it can then be called a supercritical fluid.

[0050] 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 preferably comprising:

[0051] a) a step of dissolving the plastic filler in a dissolving solvent, preferably comprising at least one hydrocarbon compound, preferably aliphatic, preferably having a boiling point 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 in a weight ratio between the dissolving 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, to obtain at least one crude polymer solution, the dissolving step a) involving:

[0052] i) a section for contacting the plastic charge with at least a portion of the dissolving solvent, comprising at least one, preferably between one and ten, preferably between two and six, preferably between two and five, static or dynamic mixer(s), advantageously in series, for producing a conditioned charge, each static or dynamic mixer being operated at a temperature between 100°C and 300°C, preferably between 150°C and 250°C, each static or dynamic mixer being fed by a plastic stream, comprising the plastic charge, and by a fraction of at least said portion of the dissolving solvent such that each mixer has a volumetric dilution ratio in dissolving solvent between 3% and 70%, preferably including:

[0053] - between 3% and 50%, preferably between 10% and 35%, and most preferably between 15% and 30%, when the viscosity ratio between the plastic flow and the fraction of at least said part of the dissolving solvent, which feeds the static or dynamic mixer in question, is greater than or equal to 3500, preferably greater than or equal to 3000,

[0054] - between 10% and 70%, preferably between 20% and 65%, very preferably between 30% and 65%, or even between 35% and 65%, when the viscosity ratio between the plastic flow and the fraction of at least said part of the dissolving solvent, which feeds the static or dynamic mixer in question, is less than 3500, preferably less than 3000,

[0055] the volumetric dilution rate in dissolving solvent, for each static or dynamic mixer considered, being the ratio between the volumetric flow rate of the fraction of at least said part of the dissolving solvent that feeds the static or dynamic mixer considered and the sum of the volumetric flow rates of said fraction of at least said part of the dissolving solvent and the plastic flow that feed the static or dynamic mixer considered,

[0056] the contacting section may include a means for melting at least part of the plastic charge, located upstream of the first static or dynamic mixer, the melting means then advantageously being supplied by the plastic charge and possibly also being supplied by a fraction of at least said part of the dissolving solvent, for example between 0.02 and 4.0% wt, or even between 0.1 and 1.0% wt, of the weight of dissolving solvent introduced in step a);

[0057] ii) a dissolution section fed at least by the conditioned charge from the contacting section, and optionally by another portion of the dissolving solvent, and operated at a dissolution temperature between 100°C and 300°C, preferably between 150°C 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 most preferably between 2.0 and 15.0 MPa absolute; then

[0058] b) a purification step of the crude polymer solution, comprising:

[0059] bl) a substep for separating insolubles to obtain at least one clarified polymer solution and one insoluble fraction; and / or

[0060] b2) a washing substep, by contact with a dense solution, allowing to obtain at least one washing effluent and one washed polymer solution; and / or

[0061] b3) an extraction substep, by contact with an extraction solvent, allowing to obtain at least one extracted polymer solution and one used solvent; and / or

[0062] b4) a substep of adsorption of impurities by contact with a solid adsorbent, to obtain at least one refined polymer solution;

[0063] the purification step enabling the obtaining of a purified polymer solution which advantageously corresponds to a clarified or washed or extracted or refined polymer solution; then,

[0064] c) a solvent-polymer separation step, to obtain at least a fraction of purified thermoplastic polymers, more particularly at least a fraction of purified polyolefins.

[0065] The charge

[0066] The process charge according to the invention, called the plastic charge, comprises Plastics which themselves include, more specifically, 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.

[0067] The plastics included in the feedstock of the process according to the invention are generally production scraps and / or post-consumer waste from plastic objects, in particular household plastic waste, construction plastic waste, automotive or any type of transport plastic waste, or waste electrical and electronic equipment. Preferably, the plastic waste comes from collection and sorting channels. Plastics or plastic materials comprise polymers that are mixed with additives to impart specific properties to the materials, with a view to forming, after shaping, various objects (injection-molded parts, tubes, films, fibers, fabrics, sealants, coatings, etc.). The additives used in plastics can be organic or inorganic compounds.These include, for example, fillers, colorants, pigments, plasticizers, property modifiers, combustion retardants, etc.

[0068] The feedstock 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 most preferably at least 90% by weight of thermoplastic polymers. The thermoplastic polymers included in the plastic feedstock may be alkene polymers, diene polymers, vinyl polymers, and / or styrenic polymers. Preferably, the thermoplastic polymers included in the plastic feedstock are polyolefins, such as polyethylene (PE), polypropylene (PP), and / or ethylene-propylene copolymers or mixtures thereof. Preferably, the plastic feedstock comprises at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of polyolefins relative to the total weight of the plastic feedstock.The process according to the invention is thus particularly aimed at purifying and recovering the polyolefins contained in the feedstock so that they can be reused in various applications.

[0069] The plastic feedstock may include polymer blends, in particular blends of thermoplastics and / or blends of thermoplastics and other polymers, additives advantageously used to formulate the plastic material, and generally impurities from the life cycle of plastic materials and articles, and / or from the waste collection and sorting system, all of these compounds being considered impurities. The feedstock of the process according to the invention generally comprises less than 50% by weight of impurities, preferably less than 20% by weight of impurities, and 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.

[0070] The plastic feedstock 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 larger than or equal to 10 mm, preferably larger than or equal to 5 mm, or even larger than or equal to 1 mm, for example, impurities such as wood, paper, biomass, iron, aluminum, glass, etc., and to shape it generally into divided solids so as to facilitate processing in the process. This pretreatment may include a grinding step, an atmospheric pressure washing step, and / or a drying step. This pretreatment may be carried out at a different site, for example, in a waste collection and sorting center, or at the same site where the treatment process according to the invention is implemented.Preferably, this pretreatment reduces the impurity content to less than 20% by weight, preferably less than 15% by weight, and preferably less than 10% by weight, the percentages being given relative to the weight of the plastic feed treated by the process according to the invention. Following the pretreatment, the feed is generally stored in the form of divided solids, for example as chips, flakes, powder, or granules, to facilitate handling and transport to the process.

[0071] Step a) of dissolution

[0072] According to the invention, the process includes a step a) of dissolution in which the plastic filler is brought into contact with a dissolving solvent and the thermoplastics it contains, the separation and purification of which are advantageously aimed at, in particular the polyolefins it contains, are dissolved in the dissolving solvent, to obtain at least one, preferably one, crude polymer solution.The dissolution step (a) then involves i) a contacting section for the plastic filler with some or all of the dissolving solvent, said contacting being advantageously achieved by the staged introduction of the dissolving solvent, and ii) a dissolving section enabling the dissolution of at least some of the plastic filler, preferably at least some of the thermoplastics concerned, preferably all of the thermoplastics concerned, in particular the polyolefins concerned, in the dissolving solvent. The contacting section and the dissolving section may be separate and successive sections, with the contacting section preceding the dissolving section, or they may be joint and simultaneous sections.

[0073] By dissolution, we mean any phenomenon leading to the obtaining of at least one solution of thermoplastic polymers, that is to say a liquid (or fluid) comprising the thermoplastic polymers in question dissolved in the solvent of dis solution. The person skilled in the art is well acquainted with the phenomenon(s) involved in the dissolution of polymers, which includes at least mixing, solvation, dispersion, homogenization, and disentanglement of thermoplastic polymer chains.

[0074] During and at the end of step a) of dissolution, the pressure and temperature conditions allow the dissolving solvent to be maintained, at least in part and preferably in full, in the liquid state or possibly in the supercritical state, while the soluble fraction of the plastic filler, in particular the thermoplastic polymers concerned and especially the polyolefins concerned, and for example at least part of the impurities, is advantageously dissolved, at least in part and preferably in full, in the dissolving solvent.

[0075] The dissolving solvent is an organic solvent or a mixture of organic solvents. Advantageously, the dissolving solvent comprises, preferably consists of, at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic (i.e., saturated), preferably linear or branched. Preferably, the dissolving solvent comprises at least 80% by weight, preferably at least 95% by weight, and 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 as a percentage of the total weight of the dissolving solvent (100% being the maximum).Preferably, the dissolving solvent comprises at least one hydrocarbon compound, preferably aliphatic and in particular paraffinic, having a boiling point (at atmospheric pressure, in particular at 0.1 MPa) 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 dissolving 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 carbon atoms. For example, the dissolving solvent comprises a compound selected from the isomers of butane, pentane, hexane, heptane, and octane.The dissolving solvent may comprise, preferably consisting of, a mixture of isomers of butane, pentane, hexane, heptane and / or octane, and preferably having a content of said mixture in the dissolving 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 dissolving solvent. Most advantageously, a preferred hydrocarbon compound for the dissolving 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. typically between 130 and 300°C, preferably between 180 and 285°C.

[0076] Preferably, step a) of dissolution is fed with the plastic filler and a dissolving solvent, according to a weight ratio between the dissolving solvent and the plastic filler, of between 0.2 and 100.0, preferably between 0.3 and 20.0, more preferably between 1.0 and 10.0, even more preferably between 3.0 and 7.0.

[0077] Advantageously, the dissolving solvent that feeds the 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 into step a), in particular prior to its introduction into the contacting section and possibly into the dissolving section, in order to facilitate the heating of the plastic filler and / or a temperature drop of the material flow in the contacting and possibly dissolving sections of step a).

[0078] Advantageously, the dissolving solvent comprises, preferably consists of, a fresh solvent top-up and / or a recycled solvent stream from a later step of the process, preferably at least partly from step c) of solvent-polymer separation.

[0079] i) the contact section:

[0080] According to the invention, the contact section of the plastic filler with at least a portion of the dissolving solvent comprises at least one static or dynamic mixer, preferably between one and ten, preferably between two and six, most preferably between two and five static or dynamic mixer(s), preferably static. When the contact section comprises several (i.e., at least two) static or dynamic mixers, the static or dynamic mixers are advantageously arranged in series with one another (or successively). Advantageously, each static or dynamic mixer is operated at a temperature preferably between 100°C and 300°C, preferably between 150°C and 250°C.

[0081] Each static or dynamic mixer is fed by a plastic flow, comprising the plastic charge, and by a fraction of at least said portion of the dissolving solvent (i.e., a fraction of the portion, preferably all, of the dissolving solvent that feeds the contacting section i) such that, in each mixer, the volumetric dilution rate of the dissolving solvent is between 3% and 70%. The volumetric dilution rate of the dissolving solvent in a static or dynamic mixer corresponds, according to the invention, to the ratio between the volumetric flow rate of the fraction of dissolving solvent that feeds the static or dynamic mixer in question (more precisely, of the fraction of the portion of the dissolving solvent that feeds the contacting section i) and the sum of the volumetric flow rates of said fraction of dissolving solvent (i.e., the fraction of at least the portion of the dissolving solvent that feeds section i)) and of the plastic flow that feed the static or dynamic mixer in question. The term "plastic flow" corresponds to any flow in the contacting section i) of the dissolution step a), which includes at least the plastic filler and all the fractions of dissolving solvent (i.e., the fractions of at least the portion of the dissolving solvent that feeds section i)) introduced into the contacting section upstream of the static or dynamic mixer in question. In other words, the plastic flow that feeds a static or dynamic mixer corresponds to a flow of material comprising, preferably consisting of, the plastic filler, advantageously at least partially molten, plus all the fractions of dissolving solvent (i.e.Fractions of at least the portion of the dissolving solvent that feeds section i)) are introduced into the static or dynamic mixer(s) located upstream of the static or dynamic mixer in question, and possibly into a means for melting at least part of the plastic filler, possibly located upstream of the first static or dynamic mixer. Thus, the plastic flow feeding contacting section i) corresponds to the plastic filler; the plastic flow exiting contacting section i) corresponds to a conditioned filler flow and includes the plastic filler and at least a portion of the dissolving solvent.The plastic stream feeding the first static or dynamic mixer comprises, in particular, the plastic filler in molten form (or at least partially in molten form) or a premix comprising the plastic filler at least partially in molten form and a fraction of the dissolving solvent: the plastic stream feeding the first static or dynamic mixer is then, in particular, in the form of a viscous fluid. The term "viscous fluid" means that the stream in question is a fluid exhibiting a viscosity, in particular a dynamic viscosity, typically between 0.5 and 20,000 Pa·s, or more particularly between 1.0 and 4,000 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 a planar-planar type viscometer, for example, the TA Instrument DHR3.

[0082] Preferably, the volumetric dilution ratio of the dissolving solvent in each static or dynamic mixer is:

[0083] - between 3% and 50%, preferably between 10% and 35%, and most preferably between 15% and 30%, when the viscosity ratio between the plastic flow and the fraction of dissolving solvent (i.e., the fraction of at least the portion of the dissolving solvent that feeds section i)), which feeds the static or dynamic mixer in question, is greater than or equal to 3500, preferably greater than or equal to 3000,

[0084] - 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 dissolving solvent (i.e. the fraction of at least the part of the dissolving solvent that feeds section i), which feed the static or dynamic mixer in question, is less than 3500, preferably less than 3000.

[0085] Preferably, the dissolving solvent that feeds the dissolution step a) is divided into n partial flows of dissolving solvent, n being an integer equal to m, m+1 or m+2, m being an integer equal to the number of static or dynamic mixers implemented in the contacting section i), each static or dynamic mixer being fed by one of the partial flows of dissolving solvent such that, in each static or dynamic mixer, the volumetric dilution rate in dissolving solvent is between 3% and 70%, and preferably:

[0086] - between 3% and 50%, preferably between 10% and 35%, and most preferably between 15% and 30%, when the viscosity ratio between the plastic flow and the partial flow of dissolving solvent (i.e., the dissolving solvent fraction) feeding the static or dynamic mixer in question is greater than or equal to 3500, preferably greater than or equal to 3000; or

[0087] - 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 (i.e. the fraction of dissolving solvent), which feed the static or dynamic mixer in question, is less than 3500, preferably less than 3000.

[0088] Optionally, a partial flow of dissolving solvent (i.e., a fraction of dissolving solvent) may feed a means for melting at least part of the plastic charge located upstream of the first static or dynamic mixer, and / or a partial flow of dissolving solvent (i.e., a fraction of dissolving solvent) may directly feed the dissolving section ii).

[0089] Each static or dynamic mixer is preferably implemented with a residence time less than or equal to 20 minutes, preferably between 0.01 seconds and 20 minutes, preferably between 0.1 seconds and 10 minutes, preferably between 0.5 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 relative to the sum of the volumetric flow rates of the plastic flow and the fraction of dissolving solvent that feed the static or dynamic mixer considered.

[0090] According to a particular embodiment of the invention, the contacting section (i) may also include a means for melting at least partially the plastic filler, preferably at least partially the thermoplastics referred to, preferably in all the thermoplastics concerned. When the contacting section includes a means for melting at least part of 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 part of the polyester filler is a single- or twin-screw extruder.

[0091] Advantageously, the means for melting at least part of the plastic filler allows for mixing and melting at least part of the plastic filler, and more particularly for melting at least part, preferably all, of the thermoplastics in question within the plastic filler. Said melting means, preferably said extruder, is therefore advantageously operated at a temperature between 100°C and 300°C, preferably between 150°C and 250°C. The plastic filler thus feeds said potential melting means, for example an extruder, in which it is advantageously heated to a temperature between 100°C and 300°C, preferably between 150°C and 250°C, and in particular to a temperature close to or even slightly above the melting temperature of the thermoplastics in question, for example the polyolefins in question, so as to become in the form of a viscous fluid at the outlet of said melting means.Upon introduction into the melting unit, the plastic filler may already be at a temperature between 100°C and 300°C, preferably between 150°C and 250°C, or at ambient temperature, for example between 10°C and 30°C. It is therefore advantageously heated or maintained at a temperature between 100°C and 300°C, preferably between 150°C and 250°C, within the melting unit, so as to be at least partially melted. Most advantageously, at least 70% by weight of the plastic filler, preferably at least 80% by weight, and preferably at least 90% by weight, of the plastic filler is in the form of a viscous fluid at the outlet of said melting unit, for example, from the extruder. Thus, when integrated into the contacting section, the means for melting at least part of the plastic charge is supplied by the plastic charge, for example in the form of solid particles, and makes it possible to obtain a flow in the form of a viscous fluid, typically with a 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 part of the plastic filler advantageously allows the plastic filler to be brought to a temperature between 100°C and 300°C, preferably between 150 and 250°C, and to 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 melted, and in particular in which the thermoplastics referred to, included in the plastic filler, are at least partly melted, preferably completely melted.

[0092] Feeding the melting means with the plastic charge can advantageously can be carried out by any method known to a person skilled in the art, for example via a feed hopper, and can be inerted in order to limit the introduction of oxygen into the process.

[0093] According to a very particular embodiment of the invention, the contacting section comprises a melting means, preferably an extruder, which is fed by the plastic filler and which can also be fed by a fraction of the dissolving solvent. This can help to reduce the viscosity of the plastic flow exiting said means, thus contributing to the overall homogenization of the plastic filler, at least partially fused with the dissolving solvent, and advantageously limiting the degradation of the thermoplastics in question, particularly the polyolefins in question. Another advantage of this very particular embodiment lies in the fact that this implementation (i.e.introducing a fraction of the dissolving solvent into the melting medium) can improve the efficiency of mixers, in particular the first mixer, and thus allow a reduction in the number of static or dynamic mixers required to achieve a dynamic viscosity of the conditioned charge flow, i.e. of the mixture [plastic charge + dissolving solvent] at the end of the contacting section, less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, most preferably less than or equal to 5 mPa.s, most preferably less than or equal to 1 mPa.s, and most advantageously a coefficient of variation (CoV) of concentration preferably less than or equal to 10%, preferably less than or equal to 5%.When a fraction of the dissolving solvent is introduced into the means to melt at least part of the plastic feed, the quantity of said fraction of dissolving solvent that feeds said means is preferably adjusted so that the weight ratio between the fraction of dissolving solvent that feeds said means and the plastic feed that feeds said means is between 0.001 and 0.20000, preferably between 0.001 and 0.100, preferably between 0.003 and 0.050, most preferably between 0.005 and 0.030. For example, a fraction of the dissolving solvent is introduced into the means to melt at least part of the plastic feed, the quantity of said fraction of dissolving solvent that feeds said means corresponding preferably to between 0.02 and 4.0% by weight, or even between 0.1 and 1.0% by weight, of the total weight of dissolving solvent introduced in step a).

[0094] Preferably, the residence time in the means for melting at least part of the plastic filler, possibly implemented in contacting section i), is advantageously less than or equal to 1 hour, preferably less than or equal to 5 minutes, preferably less than or equal to 2 minutes, and preferably greater than or equal to 0.5 seconds, preferably greater than or equal to 1 second, most preferably greater than or equal to 10 seconds. Said residence time is defined herein as the volume available in said means divided by the volumetric flow rate of the plastic charge.

[0095] The possible means for melting at least part of the plastic charge can advantageously be connected to a vacuum extraction system, so as to remove impurities such as dissolved gases, light organic compounds and / or moisture present in the charge.

[0096] Said possible melting means, preferably an extruder, may also advantageously include at the outlet a filtration system thus enabling the removal of solid particles larger than 20 pm, and preferably smaller than 2 cm, such as sand, wood, or metal particles.For example, the means for melting at least part of the plastic charge, preferably an extruder, is directly connected, at the outlet, to a first filtration system, in particular a filter, adapted to remove solid particles of size typically greater than 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 a gear pump to maintain and / or increase the pressure, followed by a second filtration system adapted to remove solid particles of size typically greater than or equal to 60 pm, preferably greater than or equal to 20 pm.

[0097] At the end of the contacting section i), i.e., at the outlet of the last static mixer, the resulting plastic flow advantageously corresponds to the conditioned feed, which is very advantageously in liquid form, and preferably has 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, most preferably less than or equal to 1 mPa.s. Very advantageously, at the end of the contacting section, the conditioned feed also has a coefficient of variation (CoV) of concentration preferably less than or equal to 10%, preferably less than or equal to 5%.

[0098] The conditioned filler 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 dissolving solvent, preferably in a weight ratio between the dissolving solvent and the plastic filler of between 0.2 and 100.0, preferably between 0.3 and 20.0, most 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 less than or equal to 50 mPa.s, preferably less than or equal to 20 mPa.s, most preferably less than or equal to 5 mPa.s, most preferably less than or equal to 1 mPa.s.

[0099] ii) the dissolution section:

[0100] The conditioned charge from the contacting section feeds the dissolving section in step a) of dissolution. The dissolving section can also be fed with a portion of the dissolving solvent, particularly when the entire quantity of dissolving solvent has not been introduced into the contacting section i) of dissolution. The recovered flow at the outlet of the dissolving section corresponds to a polymer solution, in particular a crude polymer solution.

[0101] Most advantageously, the dissolution section is operated at a dissolution temperature 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 most preferably between 2.0 and 15.0 MPa absolute.The temperature and pressure can evolve within the dissolution section, from the conditions of introduction of the conditioned load from the contacting section and / or the fraction of dissolving solvent possibly introduced into the dissolution section, until reaching the dissolution conditions, i.e., 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 most preferably between 2.0 and 15.0 MPa absolute. Advantageously, at the exit of the dissolution section, the crude polymer solution is at the dissolution temperature and dissolution pressure.

[0102] Limiting the temperature in the dissolution section, and more generally in step a) of dissolution, to a temperature of 300°C or less, preferably 250°C or less, prevents or limits the thermal degradation of thermoplastics, and more particularly polyolefins, and also reduces the energy requirements of the process, thus contributing to lower operating costs. 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 required to effectively dissolve the thermoplastics in question.Preferably, the temperature in the dissolution section and more generally in step a) of dissolution is less than or equal to the critical temperature of the dissolving solvent, so as to avoid the formation of a supercritical phase during step a) of dissolution which could disrupt the dissolution.

[0103] Simultaneously, the dissolution pressure in the dissolution section is greater than the saturated vapor pressure of the dissolving solvent at the dissolution temperature, so that the dissolving solvent is at least partially, and preferably in whole, in liquid or possibly supercritical form, at the dissolution temperature, which allows to optimize the dissolution of the targeted thermoplastics and more particularly polyolefins, especially in terms of quality, of operating time.

[0104] Most advantageously, the temperature and pressure conditions of dissolution reached in section ii) of dissolution are adjusted so that the mixture (dissolving solvent + targeted thermoplastics) is single-phase at the end of step a), said mixture possibly including insoluble impurities suspended in said mixture.

[0105] Advantageously, the dissolution section ii) is carried out for a residence time of between 1 and 600 minutes, preferably between 2 and 300 minutes, and more preferably between 5 and 180 minutes. The residence time is understood, in this case, as the residence time at the dissolution temperature and dissolution pressure, that is to say, the time the plastic filler is carried out with the dissolving solvent at the dissolution temperature and dissolution pressure in the dissolution section.

[0106] Section ii) of dissolution can implement 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 furnace, an exchanger, a mixer, etc.

[0107] According to a particular embodiment, the dissolution section employs a continuously stirred reactor, also called a "Continuous Stirred Tank Reactor" (CSTR) in Anglo-Saxon terminology, or a series of continuously stirred reactors (or CSTR reactors), said series 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 process according to the invention, comprising in particular a contacting section as described above, which makes it possible to obtain a conditioned feedstock having a viscosity preferably less than or equal to 50 mPa·s, preferably less than or equal to 20 mPa·s, most preferably less than or equal to 5 mPa·s, most preferably less than or equal to 1 mPa·s.s, allows the use of reasonable (i.e. limited) mechanical stirring power in the dissolution reactor, thus facilitating the operability of the dissolution section while limiting the costs required for its implementation, and while ensuring optimal homogenization of the mixture and maximum dissolution of the targeted thermoplastics from the plastic feed in the dissolving solvent.

[0108] The dissolution section can utilize any reactor stirred by any stirring system. Indeed, obtaining a conditioned feedstock exhibiting a viscosity of 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, most 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 contacting 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 stirring system, while advantageously permitting a reduction in the mixing time, i.e. the residence time in the dissolution section, and / or the use of a wide range of operating pressures, and ensuring optimal homogenization of the mixture and therefore maximum dissolution of the targeted thermoplastics of the plastic feed in the dissolving solvent. .

[0109] Optionally, an adsorbent, advantageously solid, preferably in the form of divided particles, shaped or unshaped, may be introduced into the polymer solution in the 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 removed during the purification step (b), for example, during a substep (b1) for separating insolubles and / or a washing substep (b2). This optional adsorption step (a') in the presence of a solid adsorbent in divided form optimizes the purification of the polymer solution.

[0110] According to a preferred embodiment of the invention, the dissolution step a) involves: i) a section for contacting the plastic charge with at least a portion of a dissolving solvent, having a boiling point 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 employs an extruder, optionally an extruder outlet filtration system, then three, four or five static mixers, operating in series with respect to each other, and the dissolution section ii) employs a continuously stirred reactor by mechanical stirring (i.e. of type CSTR) operated at a temperature between 150 and 250°C and a pressure between 1.5 and 18.0 MPa absolute.The dissolving solvent is divided into n partial flows of dissolving solvent, n being a natural number and the number n of partial flows of dissolving solvent being equal to the number m of static mixers implemented in the contacting section i) (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 with the plastic filler to obtain a plastic stream composed of the plastic filler at least partially melted, in which the targeted thermoplastics, in particular the targeted polyolefins, of the plastic filler are advantageously melted, and optionally a partial stream of dissolving solvent such that the weight ratio between the fraction of dissolving solvent (i.e., the partial stream of dissolving solvent) feeding the extruder and the plastic filler feeding the extruder is between 0.001 and 0.200, preferably between 0.001 and 0.100, preferably between 0.003 and 0.050, most preferably between 0.005 and 0.030, for example, so that the partial stream of dissolving solvent feeding the extruder represents preferably between 0.02 and 4.0% by weight, or even between 0.1 and 1.0% by weight, of the total weight of dissolving solvent introduced in step a).In this preferred embodiment, each of the static mixers is fed by a plastic flow and one of the partial flows of dissolving solvent so that, in each static mixer, the volumetric dilution rate in dissolving solvent is included: .

[0111] - 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 dissolving solvent that feed the static mixer in question is greater than or equal to 3500, preferably greater than or equal to 3000;

[0112] - 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 that feed the static mixer in question is less than 3500, preferably less than 3000.

[0113] Preferably, in this preferred embodiment, the residence time in the extruder, defined as the available volume in said extruder divided by the volumetric flow rate of charge, is between 0.5 seconds and one hour, preferably between 0.5 seconds and 5 minutes, preferably between 1 second and 2 minutes, or between 10 seconds and 2 minutes.

[0114] The dissolution section ii) in particular the CSTR type reactor of this same preferred embodiment is then supplied by the plastic flow from the last static mixer of the contacting section i) and possibly by a partial flow of dissolution solvent.

[0115] The polymer solution, advantageously referred to as the crude solution, obtained at the end of step a) of dissolution comprises at least the dissolving solvent, polymers, in particular the thermoplastic polymers targeted by the present invention, which are to be recovered purified, dissolved in the dissolving solvent. In general, the polymer solution obtained at the end of step a) of dissolution also comprises soluble impurities also dissolved in the dissolving solvent. It may optionally It may also include insoluble impurities in suspension. The polymer solution, advantageously referred to as crude, obtained at the end of step a) may optionally also include polymers other than the polymers referred to, for example in a molten state.

[0116] Step b) of purification of the polymer solution

[0117] The treatment process according to the invention includes a purification step of the crude polymer solution obtained from step a). This purification step b) includes at least one of the substeps b1), b2), b3), b4) described below:

[0118] bl) a substep for separating insolubles,

[0119] b2) a washing substep, by contact with a dense solution,

[0120] b3) an extraction substep, by contact with an extraction solvent,

[0121] b4) a substep of adsorption of impurities by contact with an adsorbent solid.

[0122] Preferably, purification step b) comprises at least one insolubles separation substep bl). Purification step b) preferably comprises several (i.e., at least two) substeps selected from substeps bl), b2), b3), and b4), in series, and preferably at least one insolubles separation substep bl) and, for example, an adsorption substep b4), advantageously in that order. Combining at least two substeps selected from bl), b2), b3), and b4) advantageously allows for 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 dissolving solvent.This purified polymer solution may correspond to a clarified polymer solution from a substep bl) of insoluble separation, a washed polymer solution from a substep b2) of washing, an extracted polymer solution from a substep b3) of extraction or a refined polymer solution from a substep b4) of impurity adsorption.

[0123] Substep bl) of separation of insolubles

[0124] The purification process may include a substep bl) of separating insolubles by solid-liquid separation, advantageously to obtain at least a clarified polymer solution and preferably an insoluble fraction. The insoluble fraction advantageously comprises at least some, preferably all, of the insoluble impurities, in particular those suspended in the crude polymer solution obtained from step a).

[0125] Substep bl) of insoluble separation thus makes it possible to remove at least some, preferably all, of the particles of impurities insoluble in the dissolving solvent, present in suspension in the crude polymer solution obtained from step a). The insoluble impurities removed during substep bl) of insoluble separation are, for example, pigments, mineral compounds, residues packaging (glass, wood, cardboard, paper, aluminum) and insoluble polymers.

[0126] When implemented, this substep bl) of separation allows, in addition to the elimination of at least part of the insoluble impurities, advantageously to limit the operative problems, in particular of the type of clogging and / or erosion, of the downstream process steps, while contributing to the purification of the plastic charge.

[0127] The substep bl) of insoluble separation 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 18.0 MPa absolute, and most preferably between 2.0 and 15.0 MPa absolute. Most advantageously, the substep bl) of insoluble separation is carried out at the temperature and pressure conditions at the outlet of the dissolution step a), that is to say, at the dissolution temperature and dissolution pressure as defined above.

[0128] When integrated into the process, the insolubles separation substep bl) is preferably fed with the crude polymer solution from step a). According to another embodiment, substep bl) can be fed with a washed polymer solution from a washing substep b2).

[0129] Advantageously, substep bl) implements a section comprising at least one solid-liquid separation device, for example selected from a separator flask, a decanter, a decanter centrifuge, a centrifuge, a filter, a sand filter, a tangential flow filter incorporating a membrane and / or a depth filter possibly with filter aids (e.g. 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 may be used, with cleaning or unclogging to remove insolubles being carried out using a solvent stream.

[0130] The removal of the insoluble fraction can be facilitated by equipment that allows the transport and / or removal of any traces of solvent present in the insoluble fraction, for example, a conveyor, a vibrating tube, a screw conveyor, an extruder, or a stripper. Substep 1b) can therefore implement equipment for transporting and / or removing traces of solvent to remove the insoluble fraction. Advantageously, at least some of the solvent recovered during substep 1b) is recycled back into the process.

[0131] According to a particular embodiment, substep bl) of insoluble separation uses at least two, and generally fewer than five, solid-liquid separation equipment in series and / or in parallel. The presence of at least two Solid-liquid separation equipment in series improves the removal of insolubles, while the presence of equipment in parallel allows for the management of the maintenance of said equipment and / or unclogging operations.

[0132] Certain insoluble impurities, particularly certain additives such as pigments and mineral fillers, conventionally added during polymer formulation, may be introduced as particles smaller than 1 µm. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. According to a particular embodiment of substep 1b), said substep 1b) for separating insolubles advantageously employs an electrostatic separator, which makes it possible to efficiently remove, at least partially, insoluble particles smaller than 1 µm. According to another particular embodiment of substep 1b), the substep 1b) for removing insolubles employs a sand filter to remove particles of various sizes, and in particular particles smaller than 1 µm.According to yet another particular embodiment of substep bl), substep bl) of insolubles employs a tangential filter employing in particular a membrane and / or a depth filter, possibly in the presence of filtration aids such as diatomaceous earth.

[0133] Depending on the nature of the feedstock, the polymer solution that feeds substep bl), preferably the crude polymer solution, may optionally also include a second liquid phase, for example, consisting of molten polymers. According to another particular embodiment, substep bl) advantageously employs equipment enabling the separation of this second liquid phase, preferably by means of at least one two-phase or three-phase separator.

[0134] Washing substep b2)

[0135] The treatment process may optionally include a further substep b2) of washing with a dense solution, advantageously to obtain at least one washing effluent and one washed polymer solution. The washed polymer solution obtained at the end of substep b2) advantageously comprises the polymers targeted by the present invention, purified and dissolved in the dissolving solvent. Optionally, the washed polymer solution may also include residual impurities, particularly those soluble in the dissolving solvent, and / or possibly traces of the washing solvent if substep b2) is carried out.

[0136] The washing substep b2) can be integrated upstream or downstream, preferably downstream, of an insolubles separation substep bl) when these two substeps are integrated into the purification step b).

[0137] When integrated into the process, the washing substep b2) is supplied with a dense solution and with the crude polymer solution from step a) or from a possible intermediate adsorption step a'), or with the polymer solution The clarified polymer solution from step b1) feeds into washing substep b2), particularly the crude or clarified polymer solution, and may contain insoluble impurities in suspension and / or solubilized impurities. These suspended or solubilized impurities may be partially or completely removed during washing substep b2 by dissolution or precipitation and / or by entrainment in the dense solution. Thus, when implemented, this substep b2) contributes to the treatment of the plastic filler and, more specifically, to the purification of the polymer solution.

[0138] Substep b2) of washing advantageously comprises contacting the crude or clarified polymer solution that feeds substep b2) with a dense solution. Advantageously, the dense solution has a higher density than the polymer solution (i.e., the mixture comprising at least the thermoplastics of interest and the dissolving solvent in which the thermoplastics of interest 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, preferably comprising at least 50 wt% water, preferably at least 75 wt% water, and most preferably at least 90 wt% water. The pH of the aqueous solution may be adjusted with an acid or a base to promote the dissolution of certain impurities.The dense solution may also optionally be a solution comprising, preferably consisting of, an organic solvent advantageously having a density 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 selected from sulfolane or N-methylpyrrolidone (NMP), optionally mixed with water. Most preferably, the dense solution is an aqueous solution comprising preferably at least 50% by weight of water, most preferably at least 75% by weight of water, most preferably at least 90% by weight of water.

[0139] The 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 most preferably between 2.0 and 15.0 MPa absolute. Most advantageously, the washing substep b2) is carried out at the dissolution temperature and dissolution pressure.

[0140] In substep b2) of washing, when integrated into the process, the mass ratio between the mass flow rate of the dense solution and the mass flow rate of the crude or clarified polymer solution that 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 contact between the crude or clarified polymer solution clarified, and the dense solution can be made at several points of the equipment used, i.e. by several injections of the crude or clarified polymer solution and / or the dense solution at different points along the equipment, it is then the sum of the injected flows that is taken into account in the calculation of the ratio.

[0141] Substep b2) can be carried out in one or more washing equipment allowing contact with the dense solution and / or with separation equipment allowing the recovery of at least one washing effluent and one washed polymer solution. This equipment is well known, for example stirred reactors, static mixers, settling mixers, two-phase or three-phase separator vessels, co-current or counter-current washing columns, tray columns, stirred columns, packed columns, pulsed columns, etc., each type of equipment being able to comprise one or more pieces of equipment used alone or in combination with equipment of another type.

[0142] According to a preferred embodiment, substep b2) of washing is carried out in a countercurrent washing column in which the dense solution is injected, preferably into the half, preferably one-third, of the column closest to the column head, on the one hand, and the crude or clarified polymer solution is injected, preferably into the 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.

[0143] According to a very particular mode, the flows into and / or out of the washing column can be divided and injected into several injection points along the column and / or withdrawn into several withdrawal points along the column.

[0144] According to another embodiment, substep b2) of washing is carried out in a mixer-decanter comprising an agitated mixing zone, to bring the dense solution into contact with the crude or clarified polymer solution, and a decantation zone, allowing recovery of a washed polymer solution and a washing effluent.

[0145] At the end of substep b2) of washing, the resulting wash effluent advantageously comprises impurities solubilized in the dense solvent and / or insoluble and carried along in the wash effluent. The wash effluent can be reprocessed in a wash treatment section, firstly to separate at least some of the solubilized and / or carried-along impurities and possibly purify the wash effluent to obtain a purified dense solution, and secondly to recycle at least some of the purified wash solution. This wash treatment section can employ one or more well-known solid-liquid separation devices, for example, a separator vessel, a decanter, a decanter centrifuge, a centrifuge, or a filter. The wash effluent can also be discharged from the process, for example in a wastewater treatment plant when the dense solution is an aqueous solution.

[0146] Extraction step b3)

[0147] Step b) of the process according to the invention may include a substep b3) of extraction by contacting the polymer with an extraction solvent, to obtain at least one extracted polymer solution and a used solvent, particularly one containing impurities. The extracted polymer solution obtained at the end of substep b3) advantageously comprises the thermoplastic polymers targeted by the present invention, purified and dissolved in the dissolving solvent. Optionally, the extracted polymer solution may also include residual impurities, particularly those soluble in the dissolving solvent, and / or traces of the washing solvent and / or the extraction solvent if substep(s) b2) and / or b3) is / are carried out.

[0148] 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 of a substep b4) of adsorption if the latter is also integrated into step b), and preferably downstream of a substep bl) of separation of insolubles.

[0149] The extraction substep b3) is advantageously fed with an extraction solvent and the polymer solution, in particular the crude polymer solution from step a), the clarified polymer solution from substep b1), the washed polymer solution from substep b2), or the refined polymer solution from an adsorption substep b4). Preferably, the extraction substep b3) is fed with an extraction solvent and the clarified polymer solution from substep b1), or the washed polymer solution from substep b2), or possibly a refined polymer solution from an adsorption substep b4. The polymer solution feeding substep b3), preferably the clarified polymer solution, the washed polymer solution, or the refined polymer solution, may therefore also include solubilized impurities.These solubilized impurities can be partially or completely removed during substep b3) of extraction by contacting them with an extraction solvent. Very advantageously, combining a substep b3) of extraction with a substep bl) of insolubles separation and possibly a substep b4) of adsorption allows for improved purification of the polymer solution, possibly utilizing both the affinity of the impurities for the adsorbent and for the extraction solvent.

[0150] When integrated into the process according to the invention, substep b3) of extraction advantageously implements at least one extraction section, preferably between one and five extraction section(s), most preferably one extraction section.

[0151] The mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution that 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 preferably between 0.2 and 5.0. The contacting of the polymer solution that 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 in the extraction section, i.e. 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 fluxes that is taken into account in the calculation of the ratio.

[0152] The extraction solvent used in substep b3) of extraction 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 (i.e., 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 as a percentage of 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 point between -50 and 250°C, preferably between -15 and 150°C, preferably between -1 and 110°C, and preferably 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 selected from the isomers of butane, pentane, hexane, heptane, and octane.The extraction solvent may preferably comprise a mixture of isomers of butane, pentane, hexane, heptane, and / or octane, and preferably have 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, and 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, and preferably between 180 and 285°C.

[0153] Most preferably, the solvent extraction implemented in b3) is the same The solvent used in step a) may be in a different physical state than the dissolving solvent used in step a), possibly in a different physical state (for example, the extraction solvent in a supercritical state compared to the dissolving solvent in a liquid state), in order to facilitate solvent management, particularly their purification and recycling, especially back to step a) of dissolution and possibly to substep b3) of extraction. Another advantage of using identical dissolving and extraction solvents, in identical or different physical states, is that, in addition to facilitating the management of the solvents involved in the process according to the invention, particularly solvent recovery, treatment, and recycling back to at least one of the process steps, it also limits energy consumption and costs, particularly those generated by solvent treatment and purification.

[0154] The extraction section(s) of b3) may include one or more extraction devices, allowing contact with the extraction solvent and / or with separation devices enabling the recovery of at least one used solvent, particularly one containing impurities, and an extracted polymer solution. These devices are well known, such as stirred reactors, static mixers, settling mixers, two-phase or three-phase separator vessels, co-current or counter-current washing columns, tray columns, stirred columns, packed columns, pulsed columns, etc. Each type of device may include one or more devices used alone or in combination with devices of another type.

[0155] According to a preferred embodiment of b3), the extraction is carried out in a countercurrent extraction column where the extraction solvent is injected on one side and the polymer solution that feeds substep b3) is injected on the other. According to this embodiment, it is possible to recover at least one extracted polymer solution, on the one hand, and a used solvent, particularly one containing impurities, on the other. Preferably, the polymer solution that feeds b3), preferably the clarified, washed, or refined polymer solution, is injected into half, preferably one-third, of the column closest to the top of the countercurrent extraction column, while the extraction solvent is injected into half, preferably one-third, of the column closest to the bottom of the countercurrent extraction column.

[0156] The inlet and / or outlet flows of the countercurrent extraction column can be divided into several injection and / or withdrawal points along the column.

[0157] According to another embodiment of b3), the extraction is carried out in a mixer-decanter which advantageously includes an agitated mixing zone to bring the extraction solvent and the polymer solution which feeds b3), preferably the clarified, washed or refined polymer solution, into contact, and a decantation zone allowing recovery of an extracted polymer solution on the one hand and a used solvent on the other.

[0158] Advantageously, substep b3) of extraction is carried out under different temperature and pressure conditions than the temperature and pressure conditions of step a) of dissolution.

[0159] According to a preferred embodiment of b3), substep b3) of extraction employs 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, preferably between 1.0 and 25.0 MPa absolute, preferably between 1.5 and 18.0 MPa absolute, and most 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 a liquid state, the dissolving solvent preferably also being in a liquid state.Advantageously, liquid / liquid extraction, particularly when the extraction solvent is the same as the dissolution solvent, is carried out under temperature and pressure conditions different from the dissolution conditions achieved 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 place oneself in a two-phase region of the corresponding polymer-solvent mixing diagram.

[0160] According to another preferred embodiment of b3), the extraction substep b3) implements an extraction section under specific temperature and pressure conditions in which the extraction solvent is advantageously at least partly in supercritical form. Such an extraction may be called supercritical extraction. In this embodiment, the extraction is carried out by contacting the polymer solution, preferably the clarified, washed, or refined polymer solution, with an extraction solvent, advantageously under temperature and pressure conditions that allow the formation of a supercritical phase composed predominantly (i.e., preferably at least 50 wt., preferably at least 70 wt., most preferably at least 90 wt.) of the extraction solvent.In other words, in this embodiment, extraction is carried out by contacting the polymer solution, preferably the clarified, washed, or refined polymer solution, with an extraction solvent that is at least partly, and preferably entirely, in the supercritical state. Such a supercritical extraction substep (b3) advantageously allows for efficient purification of the polymer solution, particularly due to the very high affinity of organic impurities, such as certain additives, including some colorants, plasticizers, etc., for the supercritical phase. The use of a supercritical extraction solvent also creates a significant density difference between the supercritical phase and the liquid polymer solution, which facilitates separation by decantation. supercritical phase and liquid phase, and consequently this contributes to the purification of the polymer solution.

[0161] In this other preferred embodiment, substep b3) employs an extraction solvent comprising at least 80% by weight, preferably at least 95% by weight, preferably 98% by weight of at least one aliphatic paraffinic hydrocarbon (or alkane) compound (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, preferably between 180 and 285°C.

[0162] Advantageously, the supercritical extraction substep b3) 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 most preferably between 3.0 and 15.0 MPa absolute. Most preferably, the operating pressure of such a supercritical extraction substep b3) 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 substep b3) of extraction upstream of the extraction section, so that the extraction solvent is at least partly in the supercritical state in the extraction section.

[0163] In a highly preferred embodiment of b3), the extraction substep b3) employs supercritical extraction, and the extraction solvent is the same as the dissolving solvent, except that the extraction solvent is at least partially in the supercritical phase. In this highly advantageous case of supercritical extraction, the dissolving solvent can become at least partially in supercritical form, advantageously optimizing decantation during the extraction step, particularly at each extraction phase or plateau, between the liquid phase and the supercritical phase, thereby maximizing purification.

[0164] Advantageously, at the end of substep b3) of extraction, the used solvent obtained is particularly laden with impurities. It can be reprocessed in an organic treatment section allowing, on the one hand, the separation of at least some of the impurities and the purification of the solvent to obtain a purified extraction solvent, and on the other hand, the recycling of at least some of the purified extraction solvent to the input of b3) of extraction, and / or to the input of step a) of dissolution 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 sulphation and precipitation of insolubles, or by purging.

[0165] Substep b4) of adsorption

[0166] Step b) of the treatment process according to the invention may include a substep b4) of adsorption, to obtain at least one refined polymer solution. The refined polymer solution obtained at the end of substep b4) advantageously comprises the thermoplastic polymers targeted by the present invention, purified and dissolved in the dissolving solvent.

[0167] When integrated into the process according to the invention, substep b4) of adsorption is advantageously implemented downstream of step a) of dissolution and upstream of step c) of solvent-polymer separation. It can be implemented upstream of a substep b1) of insoluble separation and / or b2) of washing and correspond in particular to the possible intermediate adsorption step a'). Preferably, it is implemented downstream of a substep b1) of insoluble separation and possibly of a substep b2) of washing itself, preferably downstream of substep b1). It can also be implemented, for example, upstream or downstream of a substep b3) of extraction. Thus, when 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).

[0168] Substep b4) of adsorption advantageously employs an adsorption section operated in the presence of at least one adsorbent, preferably solid, and in particular in the form of a fixed bed, a slurry bed (i.e., particles introduced into the stream to be purified and carried along with it), or a bubbling bed, preferably in the form of a fixed or slurry bed. The adsorbent(s) used in substep b) is / are preferably alumina, silica, silica-alumina, activated carbon, bleaching earth, or mixtures thereof, preferably in the form of a fixed or slurry bed, with the flow of the stream being either upward or downward.

[0169] Advantageously, when integrated into the process, the 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 most preferably between 2.0 and 15.0 MPa absolute. Most advantageously, the adsorption substep b4) is carried out at the dissolution temperature and pressure conditions, i.e., at the dissolution temperature and pressure reached in step a). Preferably, in the possible substep b4), the hourly volumetric velocity (or WH), which corresponds to the ratio between the volumetric flow rate of the polymer solution feeding b4) and the volume of adsorbent, advantageously in operation in b4), is between 0.05 and 10 h1, preferably between 0.1 and 5.0 h1.

[0170] According to a particular embodiment of substep 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, one operating mode may be a so-called "swing" mode, in which one of the columns is in operation, while the other column is in reserve. When the adsorbent in the in-operation column is depleted, that column is isolated while the reserve column is brought into operation.The used adsorbent can then be regenerated in situ and / or replaced with fresh adsorbent so that the column containing it can be put back online once the other column has been isolated.

[0171] Another operating mode of this particular embodiment of b4) is to have at least two columns operating in series. When the adsorbent in the leading column is depleted, this first column is isolated, and the depleted adsorbent is regenerated in situ or replaced with fresh adsorbent. The column is then returned to the last position, and so on. This operation is called a permutable mode, or, in English, a "Permutable Reactor System" (PRS), or "lead and lag" in the established English term. The combination of at least two adsorption columns makes it possible to overcome the potential and potentially rapid poisoning and / or clogging of the adsorbent due to the combined action of impurities, contaminants, and insolubles that may be present in the stream being treated.The presence of at least two adsorption columns facilitates the replacement and / or regeneration of the adsorbent, advantageously without stopping the process, and also allows for cost control and limiting adsorbent consumption.

[0172] According to this particular embodiment of substep b4) of fixed-bed adsorption of the adsorbent, substep b4) is preferably carried out downstream of a substep bl) of insoluble separation and / or a substep b2) of washing, and upstream or downstream of a substep b3) of extraction. Advantageously, the combination of a substep bl) of insoluble separation, and / or a substep b2) of washing, and a substep b3) of extraction with a substep b4) of adsorption allows for 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.

[0173] The adsorption section of b4) may, according to another embodiment, consist of The addition of adsorbent particles to the polymer solution, particularly the crude polymer solution, is possible. These particles can be separated from the polymer solution via an adsorbent particle removal step located downstream of the adsorption section. The removal of adsorbent particles can then advantageously correspond to a step bl) for separating insolubles or to step b2) for washing. Such an implementation of substep b4) of adsorption, by introducing the adsorbent particles followed by solid / liquid separation, advantageously corresponds to the possible intermediate adsorption step a') described later in this document.

[0174] Step c) of solvent-polymer separation

[0175] According to the invention, the process includes a step c) of solvent-polymer separation, to obtain at least a fraction of purified thermoplastic polymers, more particularly at least a fraction of purified polyolefins, and preferably at least a fraction of solvent.

[0176] Step c) of solvent-polymer separation aims to separate, at least in part, preferably predominantly, or even totally, the solvent(s), in particular the dissolving solvent, contained in the purified polymer solution which feeds step c), so as to recover the thermoplastics freed at least in part, preferably totally, of impurities and of the dissolving solvent, and possibly of the other solvent(s) used in the process (i.e. the extraction solvent and / or the dense solution).By predominantly, we mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and most preferably at least 95% by weight, relative to the weight of the solvent(s) contained in the purified polymer solution used in step c), in particular the dissolving solvent and possibly the extraction solvent and / or the dense solution contained in the purified polymer solution used in step c). Any solvent-polymer separation method known to those skilled in the art may be used, including any method that induces a phase change in the polymers or solvent(s). The solvent(s) may be separated, for example, by evaporation, stripping, demixing, density difference, and in particular decantation or centrifugation, etc. Step c) may involve several separation operations in series.For example, step c) may include a solvent-polymer separation by demixing of at least a portion 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 supercritical conditions 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 transitioning the solvent to a supercritical state, 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.

[0177] The fraction of purified thermoplastic polymers obtained at the end of step c) may correspond to a concentrated polymer solution or to purified thermoplastic polymers in liquid (i.e., the molten state) or solid form. Step c) of solvent-polymer separation may optionally include a conditioning section for conditioning the recovered thermoplastics in solid form, and more particularly in the form of solid granules. In this optional conditioning section, the recovered purified thermoplastic polymers are cooled, advantageously to a temperature below the melting point of the polymers, to obtain a fraction containing polymers in the solid state.

[0178] Step c) of solvent-polymer separation also aims to recover at least partially, preferably predominantly, and preferably entirely, the solvent(s) contained in the purified polymer solution that feeds step c), and in particular the dissolving solvent and possibly the extraction solvent and / or the dense solution. By predominantly, we mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and most preferably at least 95% by weight, relative to the weight of the solvent(s) contained in the purified polymer solution that feeds step c). Thus, step c) advantageously allows us to obtain at least a fraction of the solvent.Step c) of solvent-polymer separation also aims possibly to purify the recovered solvent fraction and to recycle it in particular upstream of step a) of dissolution and possibly upstream of sub-step b2) and / or sub-step b3).

[0179] 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 dissolving solvent, so that it can advantageously be recycled to the dissolution step a), and / or possibly to the washing substep b2) or the extraction substep b3). This possible organic treatment section at the end of step c) can employ any method known to those skilled in the art, such as one or more methods including distillation, evaporation, liquid-liquid extraction, adsorption, crystallization and precipitation of insolubles, or purging.

[0180] Thus, the process according to the invention makes it possible to obtain a purified stream of thermoplastic polymers, and more particularly of polyolefins, from plastic waste, which can be used in any application, for example as a replacement for the same polymers in their virgin state. The purified polymer stream, that is to say the The purified thermoplastic polymer fraction obtained by the process according to the invention thus has a sufficiently low impurity content to be usable in any application. Preferably, the purified thermoplastic polymer stream, and in particular the purified polyolefin stream obtained at the end of the process according to the invention (i.e., the purified thermoplastic polymer fraction), advantageously has an impurity content of less than or equal to 5% by weight of impurities, very advantageously less than or equal to 1.0% by weight of impurities, or even less than or equal to 0.5% by weight of impurities.Most advantageously, the purified thermoplastic polymer stream obtained at the end of the process (i.e. the purified thermoplastic polymer fraction) has a residual solvent content (in particular, a dissolving solvent) of 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 less than or equal to 500 ppm by weight of residual solvent, relative to the total weight of the thermoplastic polymer stream.

[0181] The following examples and figures illustrate the invention, in particular particular embodiments of the invention, without limiting its scope. LIST OF FIGURES [Fig 1]

[0182] Figure 1 shows a diagram of one embodiment of the process of the present invention, comprising:

[0183] - a step a) of dissolving the plastic filler 1 in a dissolving solvent 19, to obtain a crude polymer solution 12, step a) implementing:

[0184] - a section ai) for contacting the plastic filler 1 with a solvent of dis solution 19 for obtaining a conditioned charge 11, said section ai) employing an extruder (A) to obtain a plastic charge 1* at least partially molten, and five static exchangers M1, M2, M3, M4, M5, each exchanger being supplied by a partial flow of dissolving solvent 2, 4, 6, 8, 10, from the total flow of dissolving solvent 19, and by a plastic flow 1*, 3, 5, 7, 9,

[0185] - a dissolution section a-ii) employing in particular a stirred reactor continuous CSTR type, to obtain a crude polymer solution 12,

[0186] - a purification step b) preferably comprising a separation of the in soluble followed in particular by an adsorption substep, to obtain a purified polymer solution 13 and an insoluble fraction 14,

[0187] - a step c) of solvent-polymer separation, to obtain a thermo fraction purified plastics 15, and more particularly a fraction of purified polyolefins, and a solvent stream 16.

[0188] The solvent stream 16 is advantageously purified, for example in a distillation section d), to recover a purified dissolving solvent stream 17 which is mixed with a fresh solvent stream 18 to constitute the dissolving solvent 19, the latter being divided into five partial streams 2, 4, 6, 8, 10, of dissolving solvent to feed the static mixers M1, M2, M3, M4, M5 of section ai). EXAMPLES Example 1 (according to the invention)

[0189] In this example, only section i) of contacting a purification process corresponding to the embodiment shown schematically in [Fig. 1] is tested, and in which section i) of contacting the dissolution step a) comprises:

[0190] - an extruder A, which includes a feed hopper through which The extruder is fed with plastic material from the collection and sorting stream; followed by

[0191] - five static mixers M1, M2, M3, M4, M5, in series.

[0192] The plastic filler comprises: 95% by weight of polypropylene; 5% by weight of polyethylene and impurities, in particular additives such as pigments, dyes, fillers, etc.

[0193] The contacting section is implemented at a temperature of 200°C and at a pressure of 2.5 MPa (25 bars).

[0194] The plastic feed rate introduced into extruder A is 50 kg / h. The feed 1* is melted at least in part at the outlet of extruder A; more particularly, the polyolefins, and therefore at least the polypropylene, that said feed contains, are in melted form at the outlet of the extruder.

[0195] The dissolving 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 rate of n-heptane 19, which feeds the dissolving step a), is 250 kg / h.

[0196] Each static mixer M1, M2, M3, M4, M5, is fed with a partial stream of n-heptane, respectively 2, 4, 6, 8, 10, and a plastic stream, respectively 1*, 3, 5, 7, 9, which includes at least molten polypropylene. The coefficient of variation of the target concentration at the outlet of each static mixer is 5% (or 0.05).

[0197] Table 1 shows both the quantities of dissolving solvent introduced into each static mixer and the evolution of the viscosity of the inlet / outlet flows of each static mixer under the operating temperature and pressure conditions. Table 1 also gives the viscosity ratio between the plastic flow and the n-heptane flow entering each static mixer, as well as the volumetric dilution rate of n-heptane in each mixer.

[0198] [Tables] Flux X Nature of the flow Flow rate (kg / h) at the mixer inlet Dilution rate of n-heptane (%vol) Weight ratio of cumulative n-heptane / load (kg / kg) Viscosity of the flow considered (mPa.s) Viscosity ratio 1* Plastic load 50.0 - - 3,000,000 21,428 57 1 2 n-heptane 13.75 - - 0.14 3 Plastic flow 63.75 30% (Ml) 0.28 19,703.0 140,736 4 n-heptane 20.00 - - 0.14 5 Plastic flow 83.75 30% (M2) 0.68 548.0 3,914 6 n-heptane 28.75 - - 0.14 7 Plastic flow 112.50 30% (M3) 1.25 44.7 321 8 n-heptane 70.00 - - 0.14 9 Plastic flux 182.50 42% (M4) 2.65 3.8 58 10 n-heptane 117.50 - - 0.14 11 Plastic flux 300.00 42% (M5) 5.00 0.95 -

[0199] At the end of the contacting section ai) of step a), which uses an extruder followed by five static mixers fed with partial streams of n-heptane, the viscosity of the conditioned feed stream is less than 1 mPa·s (0.95 mPa·s), while respecting the technical constraints imposed by the static mixers with respect to the viscosities of the streams involved. Such a viscosity facilitates subsequent homogenization of the mixture in a CSTR-type dissolution reactor in the dissolution section, said dissolution reactor being of the CSTR type.

Claims

Demands

1. A process for treating a plastic filler, comprising: a) a step of dissolving the plastic filler in a dissolving solvent, to obtain at least one crude polymer solution, step a) of dissolution implementing: (i) a section for contacting the plastic charge with at least a portion of the dissolving solvent, comprising at least one static or dynamic mixer, to produce a conditioned charge, each static or dynamic mixer being operated at a temperature between 100°C and 300°C, each static or dynamic mixer being fed by a plastic stream, comprising the plastic charge, and by a fraction of at least said portion of the dissolving solvent such that each mixer has a volumetric dilution ratio in dissolving solvent of between 3% and 70%,the volumetric dilution rate in the dissolving solvent being the ratio between the volumetric flow rate of the fraction of at least said part of the dissolving solvent that feeds the static or dynamic mixer in question and the sum of the volumetric flow rates of the fraction of at least said part of the dissolving solvent and the plastic flow that feed the static or dynamic mixer in question; ii) a dissolution section fed at least by the conditioned charge from the contacting section and operated at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 and 100.0 MPa absolute; then b) a purification step of the crude polymer solution to obtain a purified polymer solution, said purification step comprising: bl) a substep of separating insolubles; and / or b2) a washing substep, by contact with a dense solution; and / or b3) an extraction substep, by contact with an extraction solvent; and / or b4) a substep 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. A method according to claim 1, wherein 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. A method according to claim 1 or 2, wherein each mixer has a volumetric dilution ratio in dissolving solvent of: - between 3% and 50%, preferably between 10% and 35%, and most preferably between 15% and 30%, when the ratio of viscosities between the plastic flow and the fraction of at least said part of the dissolving solvent, 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%, most preferably between 30% and 65%, or even between 35% and 65%, when the ratio of viscosities between the plastic flow and the fraction of at least said part of the dissolving solvent, which feeds the static or dynamic mixer considered, is less than 3500, preferably less than 3000.

4. A method according to any one of the preceding claims, wherein the contacting section comprises a means for melting at least part of the plastic filler, located upstream of the first static or dynamic mixer, said melting means preferably being an extruder.

5. A process according to any one of the preceding claims, wherein the dissolving solvent comprises at least one aliphatic paraffinic hydrocarbon compound having a boiling point between -50 and 250°C, preferably between -15 and 150°C, preferably between -1 and 110°C and preferably between 20 and 100°C.

6. A method according to any one of the preceding claims, wherein the dissolving solvent and the plastic filler feed step a) in a weight ratio between the dissolving 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. A method according to any one of the preceding claims, wherein each static or dynamic mixer is operated at a temperature between 150 and 250°C.

8. A method according to any one of the preceding claims, wherein the dissolution section is operated at a dis- temperature solution between 150 and 250°C.

9. A method according to any one of the preceding claims, wherein 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 most preferably between 2.0 and 15.0 MPa absolute.

10. A method according to any one of the preceding claims, wherein the purification step b) comprises a substep bl) of insolubles preferably followed by at least one adsorption substep.

11. A method according to any one of the preceding claims, wherein the plastic filler comprises thermoplastic polymers, more particularly polyolefins.

Images