A GLYCOLYSIS PROCESS FOR RECYCLING POLYETHYLENE TEREPHTHALATE COMPRISING A STEP FOR SEPARING OTHER POLYMERS

Abstract

The invention relates to a process for preparing BHET by depolymerizing a plastic feed comprising PET and polymers other than PET, comprising: a) depolymerizing the PET, in the presence of a diol, with a weight ratio between the amount of diol and the amount of PET contained in the feed between 0.3 and 8.0, said step a) comprising a reaction phase carried out at a temperature between 150 and 300°C and being carried out in a liquid reaction medium, b) dissolving the polymer other than PET comprising mixing a solvent immiscible with the liquid reaction medium of step a) enabling solubilization of the polymer other than PET, b') separating the immiscible solvent from step b) from the liquid reaction medium, said steps b) and b') being carried out independently during or after step a) of depolymerization, said process producing a purified effluent comprising BHET.

Description

Title of the invention: METHOD FOR RECYCLING POLYETHYLENE TEREPHTHALA BY GLYCOLYSIS COMPRISING A STEP FOR SEPARING OTHER POLYMERS technical field

[0001] The invention relates to a process for preparing bis-(2-hydroxyethyl) terephthalate (BHET) by depolymerizing a plastic feedstock comprising polyethylene terephthalate (PET), said BHET obtained being in particular intended to be (re)polymerized to produce a polyester, more particularly PET (or rPET for "recycled PET" according to Anglo-Saxon terminology), and thus contribute to the recycling of PET-based plastics. More particularly, the invention relates to a process for preparing BHET from a plastic feedstock comprising PET and at least one polymer other than PET, said process comprising a glycolysis step of the PET contained in the plastic feedstock that feeds said process and steps of dissolving and separating the polymer(s) other than PET contained in the reaction medium of the depolymerization step. Previous technique

[0002] Plastic recycling is a major environmental challenge for the coming century. Collection systems, which feed into recycling streams, are structured differently in different countries. They are evolving to maximize the amount of plastic recovered from waste, depending on the nature and quantity of the waste streams and sorting technologies. Several recycling and recovery pathways exist for plastics from collection and sorting systems.

[0003] First of all, there is so-called mechanical recycling: mechanical recycling allows some waste to be reused either directly (after melting and shaping the thermoplastics) in new objects, or by mixing mechanically sorted plastic waste streams with virgin polymer streams.

[0004] Another possible route is the deformulation of plastic materials, in particular those based on thermoplastics: it consists of dissolving the polymer, in particular the thermoplastic in question, in a solvent and removing the additives without modifying the polymer chains by using non-destructive purification methods.

[0005] Chemical recycling, for its part, aims primarily to eliminate additives and, depending on the processes applied, to more or less chemically modify the polymer chains of the plastics in question, by depolymerization of the latter or The production of mixtures of compounds containing carbon and hydrogen is achieved after non-selective chain cleavage of various polymers. These different options involve generally complex sequences of steps.

[0006] Plastics from collection and sorting channels are called recyclable plastics. Recyclable PET can come in particular from the collection of bottles, trays, films, resins and / or fibers composed of polyester (such as textile fibers, tire fibers).

[0007] Recyclable PET can be classified into four main categories:

[0008] - clear PET, consisting mainly of colorless transparent PET (generally at less 60% by weight) and azure transparent PET, which contains no pigments and can be used in mechanical recycling processes,

[0009] - dark or colored PET (green, red, etc.), which can generally contain up to 0.1% by weight of colorants or pigments but remains transparent, or translucent;

[0010] - opaque PET, which contains a significant amount of pigments at levels typically varying between 0.25 and 5.0% by weight to opacify the polymer. Opaque PET is increasingly used, for example, in the manufacture of food containers, such as milk bottles, and in the composition of cosmetic, plant protection product, or dye bottles. Textile fibers can also be considered part of this category of opaque PET;

[0011] - multilayer PET or PET in a mixture with polymers other than PET or a A layer of recycled PET sandwiched between layers of virgin PET (i.e., PET that has not undergone recycling), or an aluminum film, for example. Multilayer PET is used after thermoforming to make packaging such as trays. PET blended with other polymers is used, for example, in the textile industry.

[0012] The chemical recycling of polyester, in particular PET, has been the subject of much work aimed at decomposing polyester recovered as waste into monomers which can again be used as a filler in a polymerization process, as described for example in documents US2004 / 0147624, JP3715812 or FR3053691.

[0013] Document FR3053691 describes, in particular, a process for depolymerizing a polyester filler comprising opaque PET and, specifically, 0.1 to 10 wt% pigments, by glycolysis in the presence of ethylene glycol. A purified BHET effluent, the monomer, is obtained after separation and purification steps: separation of at least some of the ethylene glycol, followed by evaporation of the generated BHET, and finally decolorization of the recovered BHET stream, for example, by adsorption. This process makes it possible to treat polyesters comprising pigments and dyes, in particular azure, colored, and opaque PET.

[0014] However, when other polymers are present in the plastic feed containing PET, fouling and blockages of lines or reactors are often observed in or downstream of the depolymerization stage. These polymers end up in a pasty form in the effluent from the depolymerization reactors, and their accumulation over time causes fouling and damage to equipment (agitators, reactors, pumps, evaporators, pipes, measuring instruments, etc.). This is particularly true for multilayer PET, which, in addition to PET, contains layers of polymers other than PET, such as polyolefins (polyethylene (PE) and polypropylene (PP)), polystyrene (PS), or polyvinyl chloride (PVC). This is also the case when these same polymers from other materials have not been completely separated during the sorting and preparation of the feed to be recycled.

[0015] Processes for separating polymers other than PET in a feed comprising PET intended to be depolymerized by glycolysis are known, as for example described in CN115477786, WO2021 / 211531 or WO2012 / 089809. Thus, document WO2012 / 089809 describes a process for depolymerizing a feed comprising PET and polyolefins comprising a first step of depolymerizing the PET in the presence of a diol (and polyolefins), then a step of separating the polyolefins from the reaction mixture on the basis of density separation, in particular such that the polyolefins are disposed above the alcoholic solvent in the separation vessel, then a cooling step such that the polyolefins which are liquid and / or dissolved in the depolymerization step precipitate at least partially.

[0016] None of the documents mention the addition of a solvent that is not miscible with the reaction phase of PET glycolysis in order to solubilize polymers other than PET in that solvent.

[0017] The present invention seeks to improve prior art processes for preparing BHET by glycolytic depolymerization of a polyester feedstock. More particularly, the present invention seeks to separate unwanted polymers in a depolymerization process of a feedstock comprising PET and other polymers besides PET by dissolving the unwanted polymers in a solvent immiscible with the reaction medium of the depolymerization step, followed by separation of the phase containing the solvent and the dissolved polymer(s) other than PET, so as to obtain an effluent containing BHET at least partially free of the polymer(s) other than PET. This limits fouling and therefore clogging problems in the process lines and equipment. The present invention thus adds a step of injecting an immiscible solvent followed by liquid / liquid extraction and decantation steps in the processes of BHET preparation by glycolysis depolymerization of a polyester filler. Summary of the invention

[0018] The present invention relates to a process for preparing bis-(2-hydroxyethyl) terephthalate BHET by depolymerizing a plastic filler comprising polyethylene terephthalate PET and at least one polymer other than PET, said process comprising:

[0019] a) a step of depolymerizing the PET of the plastic filler, in the presence of a diol, with an amount of diol adjusted so as to have a weight ratio between the amount of diol and the amount of PET contained in the plastic filler between 0.3 and 8.0,

[0020] said depolymerization step comprising a reaction phase carried out at a temperature between 150 and 300°C,

[0021] said depolymerization step being carried out in a liquid reaction medium,

[0022] b) a dissolution step of the polymer(s) other than PET comprising a step of mixing a solvent immiscible with the liquid reaction medium of step a) enabling the solubilization of at least a part of the polymer(s) other than PET,

[0023] b') a step of separating the immiscible solvent introduced in step b) and containing at least a portion of the polymer(s) other than PET solubilized in said immiscible solvent, of the liquid reaction medium,

[0024] said steps b) of dissolution and b') of separation being carried out independently of each other during or after step a) of depolymerization,

[0025] said process producing an effluent comprising BHET.

[0026] The process according to the invention makes it possible to limit fouling and therefore clogging problems in the lines and equipment of the BHET preparation process. The process according to the invention thus makes it possible to reduce the cost and maintenance time of the unit by avoiding or limiting cleaning operations downstream of the dissolution / separation operation. As a result, the continuous operation of the unit is extended.

[0027] The process according to the invention also allows for the acceptance of less purified and therefore less expensive PET feedstocks. Larger quantities of polymers other than PET can be accepted in the feedstock of the process according to the invention.

[0028] The process according to the invention makes it possible to process loads containing multilayer PET.

[0029] The process according to the invention also makes it possible to valorize not only the BHET produced, but also, after recovery, the polymer(s) other than PET.

[0030] According to one variant, the polymer(s) other than PET is / are chosen from a polyolefin, ethylene vinyl alcohol, polystyrene and polyvinyl chloride, alone or in mixture.

[0031] According to one variant, the immiscible solvent is an aprotic and hydrophobic organic solvent chosen from one (or more) hydrocarbon(s) chosen from an alkane, linear, branched or cyclic, an aromatic or a polyaromatic, substituted or unsubstituted, having a boiling point between 25°C and 300°C.

[0032] According to one variant, the immiscible solvent is chosen from at least one linear, branched or cyclic alkane having between 5 and 20 carbon atoms.

[0033] According to one variant, the amount of immiscible solvent added in the mixing step of step b) is between 1% and 50% by weight relative to the weight of the mixture of liquid reaction medium of step a) and immiscible solvent added.

[0034] According to one variant, the mixing temperature of step b) is between 150°C and 300°C.

[0035] According to one variant, the immiscible solvent containing at least part of the polymer(s) other than solubilized PET obtained in step b') is sent to a purification step which allows the polymer(s) other than PET to be extracted on one side and at least part of the immiscible solvent on the other.

[0036] According to one variant, the immiscible solvent obtained after purification is at least partly recycled in the mixing step of step b).

[0037] According to one variant, the depolymerization step a) includes a plastic filler conditioning phase, located upstream of the reaction phase, the conditioning phase including a heating phase to melt at least part of said plastic filler and / or a pre-mixing phase to mix said plastic filler possibly at least partly melted with at least part of the diol.

[0038] According to one variant, the process according to the invention includes a step c) of filtering the effluent comprising BHET from steps a), b) and b').

[0039] According to one variant, the process according to the invention comprises at least one other step of purification of the effluent comprising BHET from steps a), b) and b') selected from filtration, precipitation of impurities, ion treatment by contact with at least one ion exchange resin, adsorption, crystallization and / or precipitation of BHET, separation of the diol by gas-liquid separation and evaporation of the BHET, so as to obtain a purified BHET effluent.

[0040] According to one variant, the process according to the invention comprises, after steps a), b) and b'), the following steps:

[0041] c) optionally a filtration step of the effluent comprising BHET from steps a), b) and b');

[0042] d) a diol separation step fed at least by the effluent comprising BHET from steps a), b) and b') or possibly from step c), operated at a temperature between 100 and 250°C, at a pressure lower than that of steps a), b) and b') and producing a diol effluent and a BHET-rich effluent, the diol effluent preferably being at least partly recycled in step a);

[0043] e) a step of separating the BHET-rich effluent from step d) into a heavy impurity effluent and a pre-purified BHET effluent, operated at a temperature less than or equal to 250°C and a pressure less than or equal to 0.001 MPa with a liquid residence time less than or equal to 10 min;

[0044] f) a step of separating said heavy impurity effluent into two fractions: a first fraction which feeds at least in part into step a) and a second fraction which is preferably at least in part discharged from the process;

[0045] g) optionally a decolorization step of the pre-purified BHET effluent, operated at a temperature between 70 and 250°C, and at a pressure between 0.1 and 1.0 MPa in the presence of an adsorbent, and producing a purified BHET effluent;

[0046] h) optionally a crystallization step of the purified BHET effluent, employing at least one solid production section, operated at a temperature between 0 and 100°C and at a pressure between 0.00001 and 1 MPa, followed by a solid-liquid separation section, producing a decolorized and purified BHET effluent.

[0047] According to one variant, the process according to the invention comprises step c) of filtration and / or step g) of decolorization and / or step h) of crystallization.

[0048] According to one variant, the purified BHET effluent feeds a polymerization step to produce PET.

[0049] According to one variant, after step b'), the polymer(s) other than PET, mixed or not with the immiscible solvent, is / are sent into a thermoplastics treatment process by polymer dissolution in order to obtain a purified thermoplastics stream.

[0050] According to one embodiment, after step b'), the polymer(s) other than PET, mixed or not with the immiscible solvent, is / are sent to a pyrolysis process, a cracking process, or an energy recovery unit. LIST OF FIGURES [Fig 1]

[0051] Fig. 1 represents a diagram of the process according to the invention in which the steps b) of dissolution and b') of separation are carried out after the step a) of depolymerization. [Fig 2]

[0052] Figure 2 shows a diagram of the method according to the invention in which the steps b) of dissolution and b') of separation are carried out during step a) of depolymerization between two reaction sections. [Fig 3]

[0053] Figure 3 represents a diagram of the process according to the invention in which step b) of dissolution is carried out during step a) of depolymerization between two reaction sections and step b') of separation is carried out after step a) of depolymerization. [Fig 4]

[0054] Figure 4 shows a diagram of the process according to the invention in which the step b) Dissolution is carried out during step a) of depolymerization in a reaction section and step b') of separation is carried out after step a) of depolymerization.

[0055] According to the invention, polyethylene terephthalate or poly(ethylene terephthalate), also simply called PET, has an elementary repeating formula motif:

[0056] [Chem.l]

[0057] Classically, PET is obtained by polycondensation of terephthalic acid (PTA), or dimethyl terephthalate (DMT), with ethylene glycol.

[0058] In the following text, the expression "per moles of diester in said plastic charge" corresponds to the number of moles of motif -[O-CO-O-(C6H4)-CO-O-CH2-CH2]- in the plastic charge, and which is in particular the diester motif resulting from the reaction of PTA and ethylene glycol.

[0059] In the following description, the term "monomer" or "BHET monomer" or "BHET" refers to bis(2-hydroxyethyl) terephthalate (BHET) of chemical formula HOC2H4-CO2-(C6H4)-CO2-C2H4OH, in which -(C6H4)- represents an aromatic ring, and which is notably the diester motif resulting from the esterification reaction of PTA with ethylene glycol.

[0060] The term "oligomer" typically refers to a small polymer, generally consisting of 2 to 20 repeating units, for example between 2 and 5 repeating units. In the present description, the terms "oligomer", "PET oligomer", "ester oligomer" or "BHET oligomer" are used interchangeably and refer to a terephthalate ester oligomer, comprising between 2 and 20, preferably between 2 and 5, repeating units of formula -[O-CO-(C6H4 )-CO-O-C2H4]-, with -(C6H4)- an aromatic ring.

[0061] In this description, the terms "diol" and "glycol" are used interchangeably and refer to compounds comprising two hydroxyl groups (-OH) and preferably comprising between 2 and 12 carbon atoms, preferably between 2 and 8 carbon atoms. The preferred diol is ethylene glycol, also called monoethylene glycol or MEG.

[0062] The diol stream, used in the depolymerization step of the process of the invention, preferably comprises the diol advantageously defined above. The diol stream preferably comprises at least 95% by weight of diol. Most preferably, the diol stream comprises at least 95% by weight of ethylene glycol.

[0063] In this description, the term "liquid reaction medium" of the depolymerization step means all the constituents present in step a). The liquid reaction medium may include, depending on the progress of the depolymerization, the molten PET to be depolymerized, the diol, the BHET monomer, and possibly BHET oligomers, as well as at least one polymer other than PET and possibly other impurities such as formulation additives like colorants, pigments, plasticizers, polymerization catalysts, etc.

[0064] A solvent immiscible with the reaction medium in step a) of depolymerization is defined as a solvent that is insoluble or very slightly soluble (e.g., < 10 wt.% and generally < 5 wt.%) with the reaction medium. The solvent immiscible with the reaction medium is chosen such that it allows the solubilization of at least a portion of the polymer(s) other than PET while minimizing the extraction of PET, BHET, BHET oligomers, or the diol from the liquid reaction medium. In other words, the immiscible solvent is chosen so that its Hansen parameters lie within the Hansen sphere of the polymer(s) other than PET, and preferably outside the Hansen sphere of PET, BHET, BHET oligomers, and the diol.Hansen's theory allows us to predict the solubility of compounds, and in particular a polymer, in a solvent by determining the Hansen parameters and solubility sphere for the solvent and the compound or polymer in question, respectively, as a function of several parameters, particularly their polar parameters, hydrogen bonding, and dispersion parameters, etc. If a solvent or mixture of solvents has Hansen parameters within the Hansen sphere of the target compound or polymer, then said compound or polymer should be at least partially, and preferably completely, soluble in said solvent.

[0065] The glycolysate phase is understood to mean the liquid phase obtained after the separation step b'), which corresponds to the reaction medium, said reaction medium possibly comprising molten PET, diol, BHET and possibly BHET oligomers, and a minor portion of the polymer(s) other than the unsolubilized PET, and possibly other impurities such as formulation additives like dyes, pigments, plasticizers, polymerization catalysts, etc...

[0066] The terms "upstream" and "downstream" are to be understood in relation to the general flow of the flux in the process.

[0067] According to the present invention, the pressures are absolute pressures and are given in absolute MPa (or MPa abs.) or in absolute mbar (or mbar abs).

[0068] According to the invention, times and durations are expressed in hours (h), minutes (min) and / or seconds (sec).

[0069] In this description, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included in the described range of values. If this were not the case and the limit values ​​were not included in the described range, this clarification will be provided by the present invention.

[0070] 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 range of pressure values ​​can be combined with a preferred range of temperature values.

[0071] In this description, the term "include" is synonymous with (means the same as) "include" and "contain," and is inclusive or open and does not exclude other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist."

[0072] 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. Charge

[0073] The process according to the invention is fed by a plastic charge comprising at least polyethylene terephthalate (PET) and at least one polymer other than PET.

[0074] Said plastic filler is advantageously a recyclable plastic filler, particularly one originating from waste collection and sorting channels. Said plastic filler may originate, for example, from the collection of bottles, trays, films, resins and / or fibers made of polyethylene terephthalate mixed with other polymers other than PET.

[0075] Advantageously, the plastic filler comprises at least 50% by weight, preferably at least 70% by weight, and most preferably at least 90% by weight of polyethylene terephthalate (PET). In particular, the plastic filler comprises at least one PET selected from clear, colored, opaque, dark, multilayer, polyester textile PET and blends thereof. According to a particular embodiment, the plastic filler comprises at less than 10% by weight of multilayer PET, preferably at least 15% by weight of multilayer PET, said multilayer PET being advantageously multilayer PET to be recycled, i.e. from collection and sorting channels.

[0076] The plastic filler also comprises at least one polymer other than PET, in particular at least one polymer selected from polyolefins, such as polyethylene (PE) or polypropylene (PP), ethylene vinyl alcohol (EVOH), ethylene vinyl alcohol copolymers or poly(vinyl alcohol-co-ethylene), polystyrene (PS), polyvinyl chloride (PVC), polyamides (PA), polyurethanes, and mixtures thereof. Preferably, the plastic filler also comprises at least one polymer other than PET, in particular at least one polymer selected from polyolefins, such as polyethylene (PE) or polypropylene (PP), ethylene vinyl alcohol (EVOH), ethylene vinyl alcohol copolymers or poly(vinyl alcohol-co-ethylene), polystyrene (PS), polyvinyl chloride (PVC), and mixtures thereof.

[0077] The plastic filler generally comprises between 0.1% and 10% by weight, advantageously between 0.1% and 5% by weight of each polymer other than PET relative to the weight of the plastic filler.

[0078] Generally, the content of polyolefins or ethylene vinyl alcohol (EVOH) is between 0.1% and 10% by weight, advantageously between 0.1 and 5% by weight relative to the weight of the plastic filler.

[0079] As for the polystyrene (PS) or polyvinyl chloride (PVC) content, it is generally between 0.1% and 5% by weight, advantageously between 0.1% and 3% by weight relative to the weight of the plastic filler.

[0080] The plastic filler may include dyes and pigments.

[0081] Dyes are natural or synthetic substances, soluble particularly in polyester, and used to color the material into which they are introduced. The dyes generally used are of various types and often contain O and N heteroatoms, and conjugated unsaturates, such as quinone, methine, azo groups, or molecules like pyrazolone and quinophthalone. The filler may include between 0.01% and 5% by weight of dyes, in particular between 0.05% and 1% by weight of dyes, preferably between 0.05% and 0.2% by weight of dyes relative to the weight of the plastic filler.

[0082] Pigments are finely divided substances, insoluble in particular in polyester material, used to color and / or opacify the material into which they are introduced. The main pigments used to color and / or opacify polyesters, particularly PET, are metal oxides such as TiO2, CoA12O4, Fe2O3, silicates, polysulfides, and carbon black. Pigments are The particle size is generally between 0.1 and 10 µm, and predominantly between 0.4 and 0.8 µm. The plastic filler can comprise between 0.1% and 10% by weight of pigments, advantageously between 0.1% and 5% by weight relative to the plastic filler.

[0083] In collection and sorting facilities, plastic packaging waste is generally washed and shredded before being used as the plastic feedstock for the process according to the invention. Polyester textile waste can be unstitched (hard points such as buttons and fasteners removed) before being shredded and possibly densified (or shaped) into granules or popcorn so that it can be mechanically introduced into the process according to the invention.

[0084] The plastic filler can therefore be, in whole or in part, in the form of granules or flakes (flakes according to the Anglo-Saxon term), the greatest length of which is less than 10 cm, preferably between 5 and 25 mm, or in the form of a micronized solid, that is to say in the form of particles preferably having a size between 10 microns (10 sqm) and 1 mm.

[0085] According to a particular embodiment, the plastic filler comprises polyester textile waste which can be pre-treated, for example unraveled and shredded, and optionally densified into granules or popcorn.

[0086] The plastic filler may, in addition, include polyester, in particular PET, from production waste from polymerization and / or transformation processes of polyester material.

[0087] The plastic filler may also include "macroscopic" impurities, preferably less than 5% by weight, preferably less than 3% by weight of "macroscopic" impurities, such as glass, metal, wood, cardboard, and mineral elements. This polyester filler may also be, in whole or in part, in the form of fibers, such as textile fibers or tire fibers. The plastic filler may also include elements, for example, metallic elements, used as polymerization catalysts and as stabilizing agents in PET production processes, such as antimony, titanium, and tin. Step a) of depolymerization

[0088] The process according to the invention comprises a step of depolymerizing the PET contained in the plastic filler, in the presence of a diol and preferably in the presence of ethylene glycol, to produce a reaction effluent comprising BHET. More particularly, the process according to the invention comprises a step a) of depolymerizing the PET of the plastic filler, in the presence of a diol, with an amount of diol adjusted so as to have a weight ratio between the amount of diol and the amount of PET contained in the plastic filler between 0.3 and 8.0, said depolymerization step comprising a reaction phase carried out at a temperature between 150 and 300°C, the said depolymerization step being carried out in a liquid reaction medium producing an effluent comprising BHET.

[0089] The reaction implemented in step a) corresponds to a depolymerization reaction of PET by glycolysis.

[0090] Step a) of depolymerization includes a liquid reaction medium. The liquid reaction medium may include, depending on the progress of depolymerization, the molten PET to be depolymerized, the diol, the BHET monomer, and optionally BHET oligomers, as well as at least one polymer other than PET and optionally other impurities such as formulation additives like colorants, pigments, plasticizers, polymerization catalysts, etc.

[0091] Step a) is advantageously supplied with said plastic feed and at least one diol stream, preferably an ethylene glycol stream. The amount of diol introduced in step a), and in particular present in the reaction phase of step a), is adjusted so as to have a weight ratio between the weight quantity of diol, preferably ethylene glycol, present in the liquid reaction phase of step a), relative to the weight quantity of PET contained in plastic feed between 0.3 and 8.0, preferably between 1.0 and 7.0, preferably between 1.5 and 6.0.In other words, the depolymerization step a) is fed by the plastic feedstock and by at least one diol stream, such that the molar ratio between the total amount of moles of diol, preferably ethylene glycol, introduced in step a), and thus present in the liquid reaction phase of step a), relative to the total amount of moles of PET diester motifs contained in the plastic feedstock is respectively between 0.9 and 24.0, preferably between 3.0 and 21.0, preferably between 4.5 and 18.0.

[0092] Advantageously, said reaction phase of step a) of depolymerization may employ one or more reaction sections, preferably at least two reaction sections, preferably between two and four reaction sections, preferably operating in series. Each reaction section advantageously comprises a reactor, more particularly any type of reactor known to those skilled in the art for carrying out a depolymerization or transesterification reaction, and preferably a reactor stirred by a mechanical stirring system and / or by a recirculation loop and / or by fluidization. In each reaction section, the reactor may optionally include a conical bottom for purging impurities.In each reaction section, the reactor may optionally include a top outlet which is located above the glycolysate phase after decantation, configured to collect the immiscible solvent phase containing the polymer(s) other than PET from step b). Preferably, the depolymerization step a) implements at least two reaction sections, preferably between two and four reaction sections, operating in series, the (or the). reaction section(s) from the second reaction section being operated at the same or different temperature, and preferably lower than or equal to the temperature of the first reaction section, preferably lower and preferably lower by 10 to 50°C, or even lower by 20 to 40°C, compared to the temperature of the first reaction section.

[0093] Advantageously, the reaction phase of step a) is carried out at a temperature between 150 and 300°C, preferably between 170 and 290°C, preferably between 180 and 270°C, in particular in the liquid phase.

[0094] The operating pressure of the reaction phase in step a) is advantageously adjusted so as to maintain the reaction medium in the liquid phase. Preferably, the reaction phase in step a) is operated at a pressure of at least 0.1 MPa, preferably at least 0.4 MPa, and preferably less than 5 MPa.

[0095] Preferably, the reaction phase of step a) is carried out with a residence time of between 0.1 and 10 hours, preferably between 0.25 and 8 hours, and preferably between 0.5 and 6 hours. The residence time in the reaction phase of step a) is defined herein as the ratio of the volume of liquid present in the reaction phase, i.e., the total volume of the reaction system, to the volumetric flow rate of the outflow from said reaction phase. Thus, if the reaction phase of step a) uses several reactors, preferably in series, the residence time in the reaction phase is then defined as the ratio of the total volume of liquid present in all the reactors used, particularly in series, to the volumetric flow rate of the outflow from the last reactor in the series.

[0096] A depolymerization catalyst may optionally feed into step a) of depolymerization.

[0097] When a depolymerization catalyst is introduced in step a), said depolymerization catalyst may be homogeneous or heterogeneous and chosen from among the esterification catalysts known to those skilled in the art such as oxide complexes and salts of antimony, tin, titanium, alkoxides of metals of groups (I) and (IV) of the periodic table of elements, organic peroxides, acid-base metal oxides.

[0098] A preferred heterogeneous catalyst advantageously comprises at least 50% by mass relative to the total mass of the catalyst, preferably at least 70% by mass, advantageously at least 80% by mass, most advantageously at least 90% by mass, and even more advantageously at least 95% by mass of a solid solution consisting of at least one spinel of formula ZXA12O(3+X) in which x is between 0 (exclusive limit) and 1, and Z is selected from Co, Fe, Mg, Mn, Ti, Zn, and comprising at most 50% by mass of alumina and oxide of element Z. Said preferred heterogeneous catalyst advantageously contains at most 10% by mass of dopants selected from the silicon, phosphorus and boron taken alone or in mixture. For example, and without limitation, said solid solution may consist of a mixture of ZnAl2O4 spinel and CoA12O4 spinel, or of a mixture of ZnAl 2O4 spinel, MgAl2O4 spinel and FeAl2O4 spinel, or of ZnAl2O4 spinel alone.

[0099] A homogeneous catalyst can be chosen from among the amines, preferably the tertiary mono- and diamines, such as tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), trimethyl-triaza-cyclononane (TACN), triethylamine (TEA), 4-(N,N-dimethylamino)pyridine (DMAP), 1,4-diazabicyclo (2,2,2)octane (DABCO), N-methyl imidazole (NMI), and alkali or alkaline earth hydroxides, such as Mg(OH)2 and NaOH, can be added at step a) of depolymerization.

[0100] A preferred homogeneous catalyst may be chosen from acetates, carbonates, oxides, hydroxides, and their derivatives, of a metal, the metal being an alkali metal, an alkaline earth metal or a transition metal.

[0101] According to one embodiment, the depolymerization step is carried out without adding an external catalyst to the plastic charge.

[0102] The reaction phase of the depolymerization step can be carried out in the presence of a solid adsorbent in granular form, for example as a powder or, in particular, as granules, so as to capture at least some of the impurities, especially dyes, thus relieving any subsequent purification steps. This solid adsorbent is advantageously activated carbon.

[0103] The depolymerization reaction advantageously converts the PET of the plastic filler into at least the bis(2-hydroxyethyl) terephthalate (BHET) monomer and BHET oligomers. The conversion of the PET of the plastic filler in depolymerization step a) is greater than 50%, preferably greater than 70%, and preferably greater than 85%. The molar yield of BHET monomer is greater than 50%, preferably greater than 70%, and preferably greater than 80%. The molar yield of BHET monomer corresponds to the molar flow rate of BHET exiting step a) relative to the molar flow rate of diester (i.e., diester motifs) in the PET of the plastic filler.

[0104] An internal recirculation loop can advantageously be implemented in step a): a fraction of the reaction medium from the liquid reaction phase is withdrawn, then filtered, and finally reinjected into the reaction phase of step a). Step a) can implement several recirculation loops. For example, when the reaction phase of step a) implements several sections In reaction processes, the reaction phase may utilize several recirculation loops, and each recirculation loop may draw from one reaction section and reinject into the same reaction section or a different reaction section. This (these) internal recirculation loop(s) allows(s) for the removal of solid impurities, particularly "macroscopic" impurities, which may have been introduced with the plastic feedstock.

[0105] Step a) of depolymerization optionally includes a plastic filler conditioning phase, located upstream of the reaction phase. When step a) of the process according to the invention includes a conditioning phase, the latter is advantageously fed by the plastic filler and optionally by at least one diol stream, and allows the production of a conditioned filler stream.

[0106] Said conditioning phase allows in particular for heating and pressurizing said plastic filler to the operating conditions of the reaction phase of the depolymerization step. More particularly, when integrated into step a), the conditioning phase of step a) may include a heating phase to melt at least part of the plastic filler and / or a premixing phase to mix the plastic filler, possibly at least partially melted, with at least part of the diol present in the reaction phase of depolymerization step a).

[0107] Advantageously, during the heating phase of the optional conditioning phase, the plastic filler is progressively heated, preferably to a temperature close to or even slightly above the melting point of the PET contained in said plastic filler, so as to render it at least partially liquid. Advantageously, at least 70% by weight of the PET in the plastic filler, very advantageously at least 80% by weight, preferably at least 90% by weight, preferably at least 95% by weight of the PET in the plastic filler, or even all of the PET in the plastic filler, is melted and in liquid form at the end of the optional conditioning phase of step a).

[0108] During the premixing phase of the conditioning phase, at least a fraction of the total diol present in the reaction phase of step a) is introduced, in particular in the form of one or more diol streams, and mixed with the plastic filler, optionally at least partially molten. In one embodiment, and where step a) includes a conditioning phase with a premixing phase, only a fraction of the total diol present in the reaction phase of step a) is introduced into the premixing phase, and the remaining fraction feeds into the reaction phase. In another embodiment, and where step a) includes a conditioning phase with a premixing phase, all of the total diol present in the reaction phase of step a) is introduced into the premixing phase.

[0109] In a particular embodiment, the immiscible solvent for dissolving the polymer(s) other than PET from step b) can also be introduced, at least in part, into the heating phase and / or into the premixing phase of the conditioning step.

[0110] The conditioning phase of step a) is advantageously carried out at a temperature between 150 and 300°C, preferably between 225 and 275°C, and more preferably between 250 and 290°C. This temperature is kept as low as possible to minimize the thermal degradation of the PET polymer and is advantageously sufficient to melt at least part of the PET in the plastic filler. The conditioning phase can be carried out under an inert atmosphere to limit the introduction of oxygen into the system and the oxidation of the plastic filler. Advantageously, the conditioning phase of step a) is carried out at a pressure preferably between atmospheric pressure (i.e., 0.1 MPa) and 20 MPa, and more preferably between 0.15 MPa and 10 MPa.

[0111] The conditioning phase of step a) may employ any type of equipment known to those skilled in the art for heating and pressurizing a plastic feedstock and / or for mixing said plastic feedstock with a solvent, in particular a diol. For example, the conditioning phase, when integrated into step a), may employ an extruder, in particular a single-screw or twin-screw extruder, solid and liquid feeding systems, and one or more static or dynamic mixers. It may also employ a batch, semi-batch, or continuous PET melting capacity that allows the reaction phase to be fed with a controlled flow rate and temperature.

[0112] When incorporated in step a), a conditioned feedstock, advantageously at least partly in liquid form, is obtained at the end of the conditioning phase and feeds the reaction phase. When step a) does not include a conditioning phase, the reaction phase is directly fed by the plastic feedstock and all of the diol.

[0113] Advantageously, the depolymerization step a) makes it possible to obtain an effluent comprising BHET.

[0114] Step sb) of dissolution and b') of separation of the polymer(s) other than PET

[0115] The process according to the invention comprises a step b) of dissolving the polymer(s) other than PET, comprising a step of mixing an immiscible solvent with the liquid reaction medium of step a) enabling the solubilization of at least a portion of the polymer(s) other than PET, and a step b') of separating the immiscible solvent introduced in step b) and containing at least a portion of the polymer(s) other than PET solubilized in said immiscible solvent, of the liquid reaction medium, said steps b) of dissolution and b') of separation being carried out independently of each other during or after step a) of depolymerization.

[0116] Steps b) and b') of the process make it possible in particular to extract the polymer(s) other than PET from the liquid reaction medium of step a) and thus limit fouling and therefore clogging problems in the lines and equipment of the BHET preparation process.

[0117] The temperature of the mixing step in step b) of dissolution is between 150°C and 300°C, preferably between 170°C and 290°C, and preferably between 180°C and 270°C. The temperature of the mixing step in step b) is specifically chosen such that the BHET oligomers are soluble in the reaction medium and the undesirable polymers are soluble in the solvent.

[0118] When step b) is carried out during step a), in particular by mixing the immiscible solvent with the liquid reaction medium in a reaction section, the temperature of the mixing step of step b) is advantageously identical to the temperature of step a).

[0119] When step b) is carried out after step a), or during step a) between two reaction sections, the temperature of the mixing step of step b) may be the same as or different from the temperature of step a).

[0120] The solvent added in the mixing step of step b) of dissolution is a solvent that is not miscible with the liquid reaction medium of step a). It allows at least part of the polymer(s) other than PET to be solubilized while minimizing the extraction (i.e. solubilization) of PET, BHET, BHET oligomers or diol from the liquid reaction medium.

[0121] Preferably, the immiscible solvent is chosen from an aprotic and hydrophobic organic solvent, preferably comprising, and preferably consisting of, one (or more) hydrocarbon(s) chosen from an alkane, linear, branched or cyclic, an aromatic or a polyaromatic, substituted or unsubstituted, having a boiling point between 25°C and 300°C, preferably between 80°C and 250°C.

[0122] Preferably, the immiscible solvent comprises, preferably consists of, hydrocarbon(s) selected from at least one linear, branched or cyclic alkane, most preferably one linear, branched or cyclic alkane(s) having between 5 and 20 carbon atoms, preferably between 7 and 15 carbon atoms, for example dodecane, heptane, isooctane, xylene or a C5-C7 cut containing isomers of pentane, hexane and heptane.

[0123] The amount of immiscible solvent added in the mixing step of dissolution step b) is generally between 1% and 50% by weight relative to the weight of the mixture of the liquid reaction medium from step a) and the added immiscible solvent, of preference between 2% and 20% by weight, and particularly preferred between 2% and 10% by weight.

[0124] Step b) of dissolution advantageously allows solubilization of at least 70% by weight, preferably at least 90% of the polymer(s) other than PET initially contained in the plastic filler.

[0125] The mixing step of step b) of dissolution can be carried out according to any mixing technique known to those skilled in the art. The mixing can, for example, be carried out in a dedicated dissolution chamber, by static or dynamic mixers (outside the reactors) or within a reaction section (reactor) of step a).

[0126] Step b') of separating the immiscible solvent containing at least a portion of the polymer(s) other than PET from the liquid reaction medium can be carried out using any separation technique known to those skilled in the art, for example in a dedicated separation chamber, for example by decantation, centrifugation, clarification, or liquid-liquid extraction. Preferably, step b') of separation is carried out in a dedicated separation chamber. Preferably, step b') of separation is carried out by decantation.

[0127] Step b') of separation is generally carried out at a temperature that allows the polymer(s) other than PET to remain solubilized in the immiscible solvent, as well as the glycolysate phase, in liquid form. Indeed, it is preferable to avoid precipitation in order to facilitate the separation of the immiscible solvent and the glycolysate phase.

[0128] Said steps b) of dissolution and b') of separation can be carried out independently of each other, during or after step a) of depolymerization, and very advantageously step b') being successive to step b).

[0129] The dissolution step b) can in particular be carried out during the depolymerization step a) during the reaction phase in which BHET is formed by depolymerization of PET in the presence of the diol.

[0130] According to one variant, it can be carried out between two reaction sections (reactors) of step a) by mixing the immiscible solvent with the liquid reaction medium from a reaction section in a chamber dedicated to dissolution.

[0131] According to another embodiment, it can be carried out in one or more reaction sections (reactors) by mixing the immiscible solvent with the reaction medium directly in the reaction section(s). This has the advantage of not requiring the addition of a dedicated dissolution chamber.

[0132] Step b) of dissolution can also be carried out during step a) of depolymerization between the conditioning phase and the reaction phase of step a), i.e. before the PET depolymerization reaction begins. when the reaction medium is liquid (which in this case contains the molten PET and the diol). Indeed, said step b) of dissolution can be carried out as soon as the reaction medium of step a) is liquid, regardless of the progress of the depolymerization reaction.

[0133] The dissolution step b) can also be carried out after the depolymerization step a), in particular directly after the depolymerization step (i.e. after the last reaction section) and before any possible purification steps of the reaction medium described later.

[0134] Step b') of separation, for its part, can in the same way be carried out during step a) of depolymerization during the reaction phase in which BHET is formed by depolymerization of PET in the presence of the diol, but advantageously downstream of step b) of dissolution.

[0135] According to one variant, it can be carried out after step b) of dissolution which has been carried out between two reaction sections (reactors) of step a) in a chamber dedicated to separation which may be identical or different from the chamber dedicated to dissolution.

[0136] According to another variant, it can be carried out after step b) of dissolution which has been carried out in one or more reaction sections (reactors) in a dedicated enclosure (only) for downstream separation, for example a decanter.

[0137] According to yet another embodiment, it can be carried out after step b) of dissolution which has been carried out in one or more reaction sections (reactors) in the reaction section(s) themselves, for example by providing an upper outlet in the reaction section(s) concerned (reactor(s)), the upper outlet being advantageously located in an area of ​​the reaction section(s) concerned situated in the upper part, i.e. in the upper half, of the reaction section(s) concerned. Said upper outlet of the reaction section(s) concerned is located above the glycolysate phase after decantation and is configured to collect the immiscible solvent phase containing the polymer(s) other than PET.

[0138] The separation step b') can also be carried out after the dissolution step b) which was carried out during the depolymerization step a) between the conditioning phase and the reaction phase of step a).

[0139] The separation step b') can also be carried out after the dissolution step b) which was carried out after the depolymerization step a), in particular directly after the depolymerization step (i.e. after the last reaction section) and before any possible purification steps of the reaction medium described later.

[0140] According to a preferred embodiment, step b) of dissolution is carried out during step a) of depolymerization in one or more reaction sections (reactors) in by mixing the immiscible solvent with the reaction medium directly in the reaction section(s), preferably by mixing the immiscible solvent with the reaction medium directly in the first reaction section. This has the advantage of preventing fouling of the equipment by the polymer(s) other than PET contained in the plastic feed, starting from the first reactor. The separation step b', on the other hand, is preferably carried out either between two reaction sections (reactors) of step a), preferably between the last two reaction sections (reactors) of step a), or after the depolymerization step a), in particular directly after the depolymerization step (i.e., after the last reaction section), preferably in a dedicated separation chamber.

[0141] Said steps b) of dissolution and b') of separation thus make it possible to obtain a liquid phase which comprises the immiscible solvent containing at least a part of the polymer(s) other than PET, at least partially solubilized in said immiscible solvent, and another liquid phase (glycolysate phase) which corresponds to the reaction medium, said reaction medium being able to comprise melted PET, diol, BHET and possibly BHET oligomers, and a minor part of the polymer(s) other than PET not solubilized, and possibly other impurities such as formulation additives like colorants, pigments, plasticizers, polymerization catalysts, etc.

[0142] Valorization of the immiscible solvent phase containing at least a portion of the polymer(s) other than PET

[0143] The immiscible solvent containing at least a part of the polymer(s) other than PET, at least partially solubilized in said immiscible solvent, can be recovered in various ways.

[0144] According to one variant, the immiscible solvent containing at least part of the polymer(s) other than PET obtained at the end of step b') can be sent to a purification step which allows the polymer(s) other than PET to be extracted on one side and at least part of the immiscible solvent on the other side.

[0145] This purification step can be carried out by any technique known to those skilled in the art, for example by evaporation, extraction, or precipitation. Preferably, it is carried out by evaporation of the solvent.

[0146] The immiscible solvent thus recovered can be recycled at least in part in step b) of dissolution.

[0147] According to one embodiment, the polymer(s) other than PET, mixed or not with the immiscible solvent, may be sent to a thermoplastics processing method, for example a polymer dissolution process based on the principle of deformulation, in order to obtain a flow of Purified thermoplastics can be used, for example, in formulations to manufacture new plastic objects. This is the case when the polymer, other than PET, is a polyolefin, polyvinyl chloride (PVC), polystyrene (PS), or ethylene vinyl alcohol (EVOH). Such processes are described, for example, in documents WO2022 / 128487, WO2022 / 128488, WO2022 / 128490, or WO2017003798. These processes generally include a first step of dissolving a thermoplastic polymer without altering the polymer chain (equivalent to step b) of the process according to the invention), followed by at least one purification step, for example, by extraction or adsorption, allowing the recovery of polymer chains free of impurities such as additives or pigments.

[0148] According to another variant, the polymer(s) other than PET, mixed or not with the immiscible solvent, can be sent to a pyrolysis process, a cracking process or an energy recovery unit.

[0149] Effluent purification steps including BHET

[0150] The effluent comprising BHET from steps a), b) and b') can be subjected to purification steps in order to recover purified BHET which can be reused in polymerization to remanufacture PET.

[0151] Optionally, the process according to the invention may include further effluent purification steps comprising BHET located downstream of step a) depolymerization and steps b) dissolution and b') separation.

[0152] These steps allow the removal of at least some of the compounds other than the targeted BHET present in the effluent, such as diol, in particular ethylene glycol, solid impurities (macroscopic impurities, pigments, inorganic fillers, etc.), dyes, polymerization and / or depolymerization catalysts, oligomers, not fully converted, possibly unconverted PET polymer or polymer(s) other than PET not dissolved in step b), etc.

[0153] In particular, said optional purification steps may include one or more steps selected from:

[0154] - at least one filtration, for example by means of one or more filter(s) in series or not, with a mesh size that can be between 1 and 1000 pm, preferably between 1 and 500 pm, for example between 1 and 250 pm;

[0155] - a precipitation of impurities (such as pigments or dyes), for example by cooling the possibly filtered effluent, then by filtering the cooled effluent in particular by passing through a filter of size for example between 1 and 50 pm, and preferably between 1 and 10 pm;

[0156] - an adsorption, by contact with at least one adsorbent, for example chosen from activated carbons, aluminas and clays;

[0157] - an ionic treatment by contact with at least one ion exchange resin, in in particular with at least one cation exchange resin and / or with at least one anion exchange resin;

[0158] - a crystallization and / or precipitation of BHET, for example by cooling and / or contact with a solvent (e.g., water), advantageously followed by solid-liquid separation, for example by filtration;

[0159] - a separation of the diol, in particular by gas-liquid separation, or even a succession of gas-liquid separation, the recovered liquid phase including BHET, the gas phase including diol.

[0160] - an evaporation of BHET, to produce a BHET-rich stream and a BHET-rich stream heavy impurities.

[0161] A person skilled in the art will be able to choose the most appropriate purification method(s) for these optional purification steps. For example, they may choose from the purification steps disclosed in documents US2004 / 0147624, JP3715812, and / or KR20230069611 and KR20230127720.

[0162] The process according to the invention can, in particular, advantageously be integrated into a process as described in FR3053691. Thus, the process according to the invention can comprise, in addition to steps a) and b) and b'), the following steps:

[0163] c) optionally a filtration step of the effluent comprising BHET from steps a), b) and b');

[0164] d) a diol separation step fed at least by the effluent comprising BHET from steps a), b) and b') or possibly from step c), operated at a temperature between 100 and 250°C, at a pressure lower than that of steps a), b) and b') and producing a diol effluent and a BHET-rich effluent, the diol effluent preferably being at least partly recycled in step a);

[0165] e) a step of separating the BHET-rich effluent from step d) into a heavy impurity effluent and a pre-purified BHET effluent, operated at a temperature less than or equal to 250°C and a pressure less than or equal to 0.001 MPa with a liquid residence time less than or equal to 10 min;

[0166] f) a step of separating said heavy impurity effluent into two fractions: a first fraction which feeds at least in part into step a) and a second fraction which is preferably at least in part discharged from the process;

[0167] g) optionally a decolorization step of the pre-purified BHET effluent, operated at a temperature between 70 and 250°C, and at a pressure between 0.1 and 1.0 MPa in the presence of an adsorbent, and producing a purified BHET effluent;

[0168] h) optionally a crystallization step of the purified BHET effluent, incorporating at least one solid production section, operated at a temperature between 0 and 100°C and at a pressure between 0.00001 and 1.00 MPa, followed by a solid-liquid separation section, producing a coloured and purified BHET effluent.

[0169] The various optional steps will be detailed later. Step c) Filtration (optional)

[0170] The process according to the invention may include, after steps a), b) and b'), and preferably directly after steps a), b) and b'), a step c) of filtering the effluent comprising BHET from steps a), b) and b').

[0171] This filtration step can in particular be carried out when there remains undissolved polymer(s) other than PET in the effluent containing BHET.

[0172] The filtration step can be carried out using any technique known to a person skilled in the art.

[0173] The filtration step is generally carried out at a temperature between 100 and 250°C. Step d) of diol separation

[0174] The process according to the invention may include a diol separation step d) fed at least by the effluent comprising BHET from steps a), b) and b'), or possibly from step c), operated at a temperature between 100 and 250°C, at a pressure lower than that of steps a), b) and b') and producing a diol effluent and a BHET-rich effluent, the diol effluent preferably being at least partly recycled in step a).

[0175] The main function of step d) is to recover all or part of the unreacted diol.

[0176] Step d) is carried out at a lower pressure than steps a), b) and b') of in order to vaporize a fraction of the effluent containing BHET into a gaseous effluent and a liquid effluent. Said liquid effluent constitutes the liquid BHET-rich effluent. The gaseous effluent, consisting of more than 50% by weight of diol, preferably more than 70% by weight, preferably more than 90% by weight, constitutes a diol effluent. The term "BHET-rich" here means that the stream considered contains BHET at a higher concentration than the BHET concentration of the stream feeding step d).

[0177] Step d) is advantageously implemented in a gas-liquid separation section or a series of gas-liquid separation sections, advantageously from 1 to 5 successive gas-liquid separation sections, most advantageously from 3 to 5 successive gas-liquid separation sections. Each of the gas-liquid separation sections produces a liquid effluent and a gas effluent. The liquid effluent from the preceding section feeds the subsequent section. All the gas effluents are recovered to constitute the diol effluent. The liquid effluent from the last gas-liquid separation section constitutes the BHET-rich effluent.

[0178] Advantageously, one, or even at least two, gas-liquid separation sections can be implemented in a falling film evaporator or a scraped film evaporator or a short-path distillation.

[0179] Step d) is carried out such that the temperature of the liquid effluents is maintained above the value below which the BHET monomer and polyester oligomers precipitate, and below a high value, dependent on the diol / monomer molar ratio, above which the monomer re-polymerizes significantly. The temperature in step d) is between 100 and 250°C, preferably between 110 and 220°C, and preferably between 120 and 210°C. The operation, consisting of a series of gas-liquid separations, advantageously a series of 2 to 5, preferably 3 to 5 successive separations, is particularly advantageous because it allows the temperature of the liquid effluent to be adjusted in each separation to meet the aforementioned constraints.

[0180] A re-polymerization inhibitor can advantageously be mixed with the liquid monomer-rich effluent before feeding said step d).

[0181] The pressure in step d) is lower than that in steps a), b) and b') and is advantageously adjusted to allow the diol to evaporate at a temperature while minimizing re-polymerization and allowing optimal energy integration. It is preferably between 0.00001 and 0.2 MPa, preferably between 0.00004 and 0.15 MPa, and most preferably between 0.00004 and 0.1 MPa.

[0182] The separating section(s) are advantageously agitated by any method known to a person skilled in the art.

[0183] The diol effluent may contain other compounds such as dyes, acetaldehyde, dioxane, dioxolane, light alcohols, water, diamine monomers, urethane, diols including diethylene glycol or cyclomethane diol. At least a fraction of the diol effluent is preferably recycled, in liquid form (i.e., after condensation), to step a) in the reaction phase and / or to the conditioning phase, and optionally to step g) of decolorization, possibly mixed with an external diol input to the process according to the invention.

[0184] All or part of said diol effluent may be treated in a purification step prior to its recycling, in liquid form (i.e. after condensation), to step a) and / or its use in a mixture in step g). This purification step may include, but is not limited to, adsorption on solid (e.g. on activated carbon) to remove dyes and one or more distillations to separate impurities such as diethylene glycol, water and other alcohols.

[0185] The BHET-rich effluent obtained in step d) is generally sent to the separation step e). Step e) of monomer separation

[0186] The process according to the invention may include a step e) of separating the BHET-rich effluent from step d) into a heavy impurity effluent and a pre-purified BHET effluent, operated at a temperature less than or equal to 250°C and a pressure less than or equal to 0.001 MPa with a liquid residence time less than or equal to 10 min.

[0187] Said step e) is advantageously carried out at a temperature less than or equal to 250°C, preferably less than or equal to 230°C, and most preferably less than or equal to 220°C, and preferably greater than or equal to 110°C, and at a pressure less than or equal to 0.001 MPa, preferably less than or equal to 0.0005 MPa, preferably greater than or equal to 0.000001 MPa, with a liquid residence time less than or equal to 10 min, preferably less than or equal to 5 min, preferably less than or equal to 3 min, and preferably greater than or equal to 0.1 second. The liquid residence time is defined as the ratio of the liquid volume in step e) to the volumetric flow rate of the liquid flowing out of step e).

[0188] This separation step e) aims to separate all or part of the BHET monomer, which is vaporized, from the oligomers, not fully converted, possibly from the unconverted PET polymer, and also from impurities, such as pigments, traces of polymers other than PET possibly still present, polymerization catalysts and possibly depolymerization catalysts, while minimizing the loss of monomers by re-polymerization.

[0189] The pre-purified BHET effluent comprises at least 50% by weight of BHET monomer, preferably at least 70% by weight of BHET monomer, preferably at least 80% by weight of BHET monomer, preferably at least 90% by weight of BHET monomer, relative to the total weight of said effluent.

[0190] Preferably, the heavy impurities stream comprises heavy compounds, in particular fully unconverted PET oligomers, unconverted PET polymer, impurities, in particular heavy impurities such as pigments, any non-PET polymer(s) still present, polymerization catalysts, and optionally depolymerization catalysts. Preferably, the heavy impurities stream may comprise at least 15% by weight of heavy compounds, in particular at least 25% by weight of heavy compounds, or even at least 40% by weight of heavy compounds, relative to the total weight of said heavy impurities stream. The heavy impurities stream may also comprise unseparated BHET monomer.

[0191] Due to the possible presence of polymerization catalysts in the polyester feed, the separation must be carried out with very short liquid residence times and at a temperature not exceeding 250°C, in order to limit any risk of monomer repolymerization during this step. Separation by simple atmospheric distillation is therefore not feasible.

[0192] Step e) of separation is advantageously carried out by evaporation, in a falling film or scraped film evaporation system, or by short-path falling film or scraped film distillation. A very low operating pressure is required to be able to carry out step e) at a temperature below 250°C, preferably below 230°C, while still allowing vaporization of the monomer.

[0193] A polymerization inhibitor can advantageously be mixed with the BHET-rich effluent before feeding said step e).

[0194] A fluxing agent can also advantageously be mixed with the BHET-rich effluent before feeding said step e), so as to facilitate the removal of heavy impurities, particularly pigments, from the bottom of the evaporation or short-path distillation system. This fluxing agent must have a boiling point much higher than that of BHET under the operating conditions of step e). It could be, for example, polyethylene glycol or PET oligomers. The fluxing agent could also be the immiscible solvent used to extract the polymer(s) other than PET if it has a boiling point much higher than that of BHET and is slightly soluble in the glycolysate phase.

[0195] Said heavy impurity effluent includes in particular pigments, oligomers and unseparated monomer. Said heavy impurity effluent obtained in step e) is generally sent to separation step f).

[0196] Step f) of separating the effluent from heavy impurities

[0197] The process according to the invention may include a step f) of separating said heavy impurity effluent from step e) so as to produce two fractions: a first fraction which feeds at least in part into step a) and a second fraction which is preferably at least in part discharged from the process.

[0198] The heavy impurity effluent obtained at the end of step e) comprises BHET monomer, oligomers and heavy impurities, including pigments, unconverted polyester polymer, possibly other polymers and polymerization catalysts.

[0199] Preferably, the first fraction comprises at least 50% by weight, preferably at least 70%, preferably at least 80% by weight, or even at least 90% by weight of the heavy impurities effluent obtained at the end of step e).

[0200] According to a first embodiment, step f) of separating said heavy impurities effluent consists of a simple division into two fractions, the two fractions having the same chemical composition.

[0201] According to a second embodiment, step f) of separating said heavy impurities effluent comprising the monomer, oligomers and heavy impurities is carried out so as to obtain a first fraction enriched in monomer and oligomers and a second fraction enriched in heavy impurities, that is to say that the first fraction enriched in oligomers has a content of monomer and oligomers strictly greater than the content of monomer and oligomers of said heavy impurities effluent from step e) and that the second fraction has a content of heavy impurities strictly greater than the content of heavy impurities of said heavy impurities effluent. For example, the first fraction enriched in monomers and oligomers has a content of at least 10% by weight, preferably at least 50% by weight, preferably 100% by weight of monomers and oligomers greater than the content of monomers and oligomers of said effluent in heavy impurities from step e).For example, the second fraction enriched in heavy impurities has a content at least 10% by weight, preferably at least 50% by weight, preferably 100% by weight, greater than the heavy impurity content of said heavy impurity effluent from step e). In the second embodiment, the separation of said heavy impurity effluent can be carried out by filtration, decantation, ethylene glycol extraction, centrifugation, etc. For example, said heavy impurity effluent from step e) may advantageously undergo at least one separation step, for example by filtration, so as to reduce the quantity of pigments and / or other solid impurities in the first fraction and recover a second fraction enriched in pigments and / or other solid impurities.

[0202] Preferably, the entire first fraction obtained in step f) is recycled in the depolymerization step a).

[0203] To facilitate separation, the heavy impurity effluent can be mixed with a diol effluent, for example with a portion of the diol effluent from step d), an external diol addition to the process according to the invention, or mixtures thereof.

[0204] Before being recycled to step a), the first fraction can advantageously be mixed with a diol effluent, for example, with a portion of the diol effluent from step d), an external diol supplement to the process according to the invention, or mixtures thereof. This mixing can be carried out in a static or dynamic mixer. Mixing the first fraction with a diol effluent facilitates the recycling of ester oligomers, in particular BHET oligomers, since the mixing helps to fluidize the first fraction, which potentially concentrates solid particles such as pigments and traces of polymers other than PET. present in the treated polyester charge and contributing to increasing the viscosity and fouling power of said residues, and therefore simplifying the operability of their transport, and on the other hand reducing the viscosity of said first fraction and thus promoting its mixing with the polyester charge at the depolymerization stage.

[0205] According to one embodiment, the entire second solid-enriched fraction can advantageously be purged from the process, for example by being sent to an incineration system.

[0206] Alternatively, according to a second embodiment, a portion of the second solids-enriched fraction can be recycled in step a) of depolymerization by injecting it into the reaction section or sections downstream of the first reaction section, the remaining portion of the second fraction being purged from the process, for example, by being sent to an incineration system. In this second embodiment, the portion of the second fraction that is purged can represent at least 50% by weight, or even at least 70%, preferably at least 80% of the second fraction. Optional step g) of decolorization

[0207] Advantageously, the process according to the invention may include a step of decolorizing the pre-purified BHET effluent from step e), operated at a temperature between 70 and 250°C, preferably between 80 and 180°C, and preferably between 90 and 120°C, and at a pressure between 0.05 and 1.0 MPa, preferably between 0.05 and 0.8 MPa, and preferably between 0.1 and 0.5 MPa in the presence of at least one adsorbent and producing a purified BHET effluent.

[0208] Said adsorbent may be any adsorbent known to a person skilled in the art capable of capturing dyes, such as activated carbon, clays, advantageously activated carbon.

[0209] The pre-purified BHET effluent can advantageously be mixed with a solvent. The pre-purified BHET effluent can be contacted with the solvent prior to contacting the adsorbent. The solvent introduced may be, for example, a fraction of the diol effluent from step d), possibly previously treated in a purification step, or, for example, with an external diol supplement to the process according to the invention, or, for example, with water. Optional step h) of crystallization

[0210] The purified BHET effluent obtained in the optional step g) may optionally be introduced into a crystallization step h). When implemented, the crystallization step h) advantageously incorporates at least one solid production section and at least one solid-liquid separation section. The crystallization step h), allows obtaining a purified, decolorized monomer diester effluent and discharges a used solvent effluent.

[0211] Advantageously, the crystallization step h) incorporates one or more crystallization or precipitation operations and one or more solid-liquid separation operations. In one particular embodiment, the crystallization step h) incorporates a solid production section as described below, followed by a solid-liquid separation section as detailed below. In another particular embodiment, the crystallization step h) incorporates several solid production sections, preferably between two and five, as described below, each solid production section being followed by a solid-liquid separation section as detailed below.

[0212] The solid production section of step h) is advantageously fed with the purified BHET effluent from the optional step g). Optionally, the solid production section may also be fed with a crystallization solvent, which is the same as or different from the solvent used in the optional step g). The crystallization solvent is advantageously selected from water, monoalcohols, diols, ethers, aldehydes, esters, hydrocarbons, and mixtures of at least two of these compounds belonging to the same chemical family or to different chemical families. Preferably, said crystallization solvent is selected from water, a monoalcohol having between 1 and 12 carbon atoms, such as methanol or ethanol, or a diol having between 1 and 12 carbon atoms, such as ethylene glycol.Preferably, the crystallization solvent is water, a diol having between 1 and 12 carbon atoms, preferably ethylene glycol, or mixtures thereof.

[0213] Preferably, when steps g) of decolorization and h) of crystallization are implemented and crystallization solvent is introduced in step h), the quantity of crystallization solvent introduced into the solid production section is adjusted so that the purified BHET effluent that feeds step g) represents between 1 and 75% by weight, preferably between 5 and 45% by weight, preferably between 10 and 35% by weight, of the total weight of the mixture in said solid production section (i.e. the mixture comprising the purified monomer effluent, the solvent introduced in step g) and the crystallization solvent introduced in step h)).

[0214] Prior to its introduction into the solid production section, all or part of the crystallization solvent may be heated, preferably to the temperature at which the adsorption section is operated, or cooled and in particular brought to a temperature preferably between 0 and 120°C, preferably between 5 and 100°C, and preferably between 10 and 90°C.

[0215] Advantageously, the solid production section of the optional step h) is operated at a temperature (i.e., such that the effluent temperature from said solid production section is) between 0 and 100°C, preferably between 5 and 80°C, and preferably between 10 and 70°C. More specifically, in the solid production section, the purified monomer effluent pretreated by adsorption, possibly mixed with the crystallization solvent, is cooled from the temperature at which the adsorption section is operated, i.e. from a temperature between 70 and 180°C, preferably between 80°C and 150°C, preferably between 90 and 120°C, to a temperature between 0 and 100°C, preferably between 5 and 80°C, and preferably between 10 and 70°C.

[0216] Cooling can be implemented according to any method known to those skilled in the art. For example, in particular in batch mode, the temperature cooling can be carried out without regulation of the temperature decrease (i.e. without an imposed temperature ramp; thus only the initial and final temperatures are controlled) or according to at least a decreasing temperature ramp, in particular according to a decreasing temperature ramp between 5 and 30°C / hour and more particularly between 8 and 15°C / hour, or even according to the two modes which follow each other successively, i.e. without control for one part of the cooling and according to a decreasing temperature ramp, for another part of the cooling.According to another example, the cooling can simply be due to the introduction of the stream to be cooled, i.e. the BHET effluent pretreated by adsorption from the adsorption step g) or the mixture comprising the monomer effluent pretreated by adsorption and the crystallization solvent, into a vessel, the volume of which is advantageously adapted to the flow rate of the stream to be cooled, maintained at a temperature between 0 and 100°C, preferably between 5 and 80°C, and preferably between 10 and 70°C.

[0217] The solid production section is advantageously operated at a pressure between 0.00001 and 1 MPa, preferably between 0.0001 and 0.50 MPa, and preferably between 0.001 and 0.20 MPa. According to a particular embodiment of the invention, the solid production section is operated under vacuum, preferably at a pressure between 0.0001 and 0.10 MPa, preferably between 0.001 and 0.01 MPa. According to another particular embodiment, the solid production section is advantageously operated in a double-jacketed reactor, at a pressure between 0.01 and 1 MPa, preferably between 0.05 and 0.20 MPa, preferably at atmospheric pressure, i.e., at 0.10 MPa.

[0218] Advantageously, the solid production section is designed to solidify, that is, to crystallize or precipitate, at least partially the BHET monomer present in the purified BHET effluent pretreated by adsorption and obtained from step g). Thus, the solid production section preferably comprises a phase of Precipitation or crystallization is carried out using any precipitation or crystallization technique known to those skilled in the art. Preferably, the solid production section is a crystallization section, for example, by cooling or concentration, implemented in any equipment known to those skilled in the art, such as, for example, as defined in the journal Techniques de L'ingénieur, "Industrial Crystallization - Practical Aspects," ref. J2788 VI, followed by liquid-solid separation. Crystallization can be carried out, in particular, by direct cooling or by heat exchange (indirect), by evaporative cooling of the solvent under vacuum (adiabatic), or by isothermal evaporative cooling (with heating).

[0219] According to a preferred embodiment, water as a crystallization solvent is mixed with the purified BHET effluent from step g) and the solid production section in step h) is operated under conditions such that the temperature of the effluent from said solid production section is between 5 and 50°C, preferably between 10 and 40°C.

[0220] According to another preferred embodiment, the crystallization solvent introduced and mixed with the purified BHET effluent from step g) is ethylene glycol and the solid production section is operated under conditions such that the temperature of the effluent from said solid production section is between 5 and 50°C, preferably between 10 and 40°C.

[0221] Advantageously said solid production section, preferably by crystallization, comprises one or more crystallization operation(s), operating in series or in parallel, carried out in batch or continuously, preferably continuously.

[0222] The solid production section yields a heterogeneous effluent, comprising a solid BHET phase and a liquid phase. The heterogeneous effluent is advantageously sent to the solid-liquid separation section.

[0223] In the solid-liquid separation section of optional step h), the BHET monomer, advantageously in solid form, particularly as crystals, is separated from the liquid phase comprising all or part of the solvent introduced in step g) and the crystallization solvent optionally introduced in the solid production section. The solid-liquid separation section advantageously employs any solid-liquid separation method known to those skilled in the art, in particular at least one filtration, decantation, and / or centrifugation system. The solid BHET thus separated constitutes the purified, colorless BHET effluent, and the liquid phase constitutes the used solvent effluent.

[0224] According to a particular embodiment, the purified, decolorized BHET effluent, recovered at the end of the optional step h) in solid form preferably by filtration or centrifugation, may further advantageously undergo all or some of the following operations, carried out once or several times without predefined chronological order: rinsing with a solvent, identical or different from the solvent supplying step g) or possibly the solid production section of step h); further filtration or centrifugation; removal of residual solvent by any method known to those skilled in the art, for example by evaporative drying; shaping, for example into powder or granules; and storage of the solid.

[0225] According to another embodiment, the purified, decolorized BHET effluent is recovered, preferably by filtration or centrifugation, in the solid-liquid separation section and then sent directly (i.e. without a solid storage phase) to a polymerization step known to those skilled in the art, optionally, prior to the polymerization reaction, a rinse with water or a diol effluent, for example an ethylene glycol effluent, preferably a rinse with water, of the solid purified, decolorized BHET effluent, and then heating of the rinsed solid to be melted.

[0226] According to another embodiment, the purified, decolorized BHET effluent is recovered, preferably by filtration or centrifugation, in the solid-liquid separation section and then the monomer is dried by one of the means known to those skilled in the art before being stored or conveyed to a polymerization step known to those skilled in the art.

[0227] According to another embodiment, the purified, decolorized BHET effluent is recovered, preferably by filtration or centrifugation, in the solid-liquid separation section, and then the monomer is shaped after possibly having been dried by one of the means known to those skilled in the art (granulation, pelletization) before being stored or conveyed to a polymerization step known to those skilled in the art.

[0228] The purified, decolorized BHET effluent from the optional step h) can advantageously feed a polymerization step known to those skilled in the art to produce PET that is indistinguishable from virgin PET. The purified, decolorized BHET effluent can advantageously be mixed with ethylene glycol, terephthalic acid, or dimethyl terephthalate, depending on the polymerization step selected, prior to the polymerization reaction. Feeding the purified, decolorized BHET effluent into a polymerization step reduces the required flow rate of dimethyl terephthalate or terephthalic acid by an equivalent amount.

[0229] The figures illustrate diagrams of the process according to the invention without limiting its scope.

[0230] Figure [1] represents in particular a diagram of the process according to the invention in which the steps b) of dissolution and b') of separation are carried out after the step a) of depolymerization.

[0231] In the embodiment described with reference to [Fig. 1], the process implements a step (a) of depolymerizing the filler (1) comprising PET and at least one polymer other than PET, in the presence of diol (2) and (11). The depolymerization step (a) may include a conditioning phase (n) to condition the feed (1) and obtain a free-flowing feed. The conditioned feed stream is introduced into the reaction phase of the depolymerization step (a), which employs several reaction sections, for example: a first reaction section (A) and a second reaction section (B), or even other reaction sections. In [Fig. 1], only reaction sections (A), (B), and (N) are shown. Without departing from the scope of the invention, there may be other reaction sections between reaction section (B) and reaction section (N). The mixture passes successively through reaction section (A), then through reaction section (B), possibly through a reaction section not shown, and then through reaction section (N).Each of the reaction sections can be supplied with fresh diol (2) or with diol (11) from step (d).

[0232] The effluent (3) obtained at the end of the depolymerization step (a) is introduced into the dissolution step (b), which comprises a mixing step of a solvent (4) immiscible with the liquid reaction medium (3) of step (a) to solubilize at least a portion of the polymer(s) other than PET, followed by a separation step (b') of the immiscible solvent containing at least a portion of the solubilized polymer(s) other than PET (5) from the liquid reaction medium. The dissolution step (b) is thus carried out in a dedicated dissolution chamber. The separation step (b') is carried out in a dedicated separation chamber, which may or may not be identical to the dissolution chamber.

[0233] The immiscible solvent containing at least part of the solubilized non-PET polymer(s) (5) from step (b') can be introduced into a purification step (M) allowing the extraction on one side of the non-PET polymer(s) (6) and on the other side of at least part of the immiscible solvent (7) which is advantageously recycled, in whole or in part, in step (b). According to another variant, the immiscible solvent containing at least part of the non-PET solubilised polymer(s) obtained at the end of step (b') and / or the non-PET polymer(s) (6) obtained after the purification step (M) can be sent into a process dedicated to the treatment of thermoplastics by polymer dissolution in order to obtain a purified thermoplastic stream (not shown).

[0234] The process according to the invention may also include the following steps:

[0235] The effluent (8) comprising BHET (glycolysate phase) obtained after steps (a), (b) and (b') is introduced, preferably directly, into the optional filtration step (c) which retains by filtration any polymer other than undissolved PET (9) in the immiscible solvent. The effluent (10) from step (c) is introduced into a diol separation step (d) which recovers a diol effluent (11). and an effluent rich in BHET (12). The diol effluent (11) is preferably at least partly recycled in step a).

[0236] The BHET-rich effluent (12) is then introduced into the separation step (e) to obtain a pre-purified BHET effluent (13) and to remove a heavy impurity effluent (14), containing oligomers and heavy impurities, which is sent to the separation step (f).

[0237] At the separation step (f), the heavy impurities effluent (14) is separated into two fractions: a first fraction (15) constituting the recycled oligomer effluent which feeds the step (a) and a second fraction (16) which is discharged from the process according to the invention, in other words which is purged.

[0238] The pre-purified BHET effluent (13) obtained at the end of step e) can be sent to a decolorizing step (g) by adsorption, then to a crystallization step (h) to recover a decolorized purified BHET effluent (17).

[0239] The diol effluent (11) obtained in step (d) is advantageously recycled, in whole or in part, to step (a) in one or more of the reaction sections (A), (B) and (N) or a possible additional reaction section between section (B) and (N). In addition, a fraction of the diol effluent (11) obtained in step (d) may be recycled to one or more of the following steps: to step (g), to step (h), to step (f) (not shown).

[0240] Figure 2 represents a diagram of the process according to the invention in which the steps b) of dissolution and b') of separation are carried out during the step a) of depolymerization between two reaction sections.

[0241] The references used in [Fig.2] are identical to the references used in [Fig.1] and represent and designate the same elements.

[0242] Figure 3 shows a schematic representation of the process according to the invention, wherein step b) of dissolution is carried out during step a) of depolymerization between two reaction sections, and step b') of separation is carried out after step a) of depolymerization. The reference numerals used in Figure 3 are identical to those used in Figure 1 and represent and designate the same elements. In this case, the solvent (4) is introduced between two reaction sections (in Figure 3, after reaction section (B)) in a chamber dedicated to dissolution. The separation step (b') is carried out after step a) of depolymerization in a chamber dedicated to separation. At least a portion of the solvent (7) is advantageously recycled in step (b), after an optional purification step (M).At least part of the solvent (7) can also be recycled into one or more of the reaction sections (A), (B) and (N) or a possible additional reaction section between section (B) and (N) (not shown).

[0243] Figure 4 represents a diagram of the process according to the invention in which step b) of dissolution is carried out during step a) of depolymerization in a reaction section and step b') of separation is carried out after step a) of depolymerization.

[0244] The references used in [Fig.4] are identical to the references used in [Fig.1] and represent and designate the same elements.

[0245] In this case, the solvent (4) is directly introduced into said reaction section (in [Fig. 4], reaction section (B)). The separation step (b') is carried out after the depolymerization step (a) in a dedicated separation chamber. At least a portion of the solvent (7) is advantageously recycled in step (b), after an optional purification step (M). At least a portion of the solvent (7) can also be recycled into one or more of the reaction sections (A), (B), and (N), or a possible additional reaction section between sections (B) and (N) (not shown).

[0246] The following example illustrates the invention without limiting its scope. EXAMPLE

[0247] The plastic feedstock that feeds the process is a polyester feedstock from packaging collection and sorting channels, comprising PET and 2.3% by weight of polypropylene.

[0248] 4 kg / h of polyester filler sequins are brought to a temperature of 250°C The mixture was then injected with 11.5 kg / h of ethylene glycol (MEG) into a first stirred reactor maintained at 250°C, and then successively into a second and third stirred reactor maintained at 220°C. The reactors were maintained at a pressure of 0.4 MPa. The residence time, defined as the ratio of the liquid volume in the reactor to the sum of the liquid volumetric flow rates entering the reactor, was set at 20 min in the first reactor and 2.1 h in the second and third reactors.At the outlet of the third reactor, the reaction effluent consists of 67.7% by weight of diol composed predominantly of ethylene glycol (MEG) (predominantly meaning here: comprising 95% by weight or more of MEG), 25.8% by weight of diester monomer composed predominantly of bis-(2-hydroxyethyl) terephthalate (BHET) (predominantly meaning here: comprising 95% by weight or more of BHET), and 6.1% by weight of heavy compounds containing, among other things, BHET dimers and / or oligomers as well as polypropylene.

[0249] During depolymerization, the polypropylene forms a ball that moves within the reaction chamber. At the end of depolymerization, this ball settles in a few tens of seconds. After the chamber has cooled and been emptied, the polypropylene forms a solid mass adhered to the stirring shaft.

[0250] This same test is reproduced according to the method of the invention: 12% by weight of n-dodecane as an immiscible solvent relative to the weight of the mixture of liquid reaction medium and immiscible solvent was added to solubilize the polypropylene in solution. Two liquid phases are observed during mixing, which separate within a few seconds when stirring is stopped. After cooling the container for draining, the mixed phase of polypropylene + n-dodecane was recovered as a free-flowing liquid phase.

[0251] This solvent phase containing polypropylene is therefore less adherent to the surfaces of the process (does not form a sticky solid ball but a fluid liquid phase) and more easily separable (decantation into a liquid phase in a few seconds).

Claims

Demands

1. A process for preparing bis-(2-hydroxyethyl) terephthalate BHET by depolymerizing a plastic filler comprising polyethylene terephthalate (PET) and at least one polymer other than PET, said process comprising: a) a step of depolymerizing the PET of the plastic filler, in the presence of a diol, with an amount of diol adjusted to have a weight ratio between the amount of diol and the amount of PET contained in the plastic filler between 0.3 and 8.0, said depolymerization step comprising a reaction phase carried out at a temperature between 150 and 300°C, said depolymerization step being carried out in a liquid reaction medium, b) a step of dissolving the polymer(s) other than PET comprising a step of mixing an immiscible solvent with the liquid reaction medium of step a) enabling the solubilization of at least a portion of the polymer(s) other than PET,b') a step of separating the immiscible solvent introduced in step b) and containing at least a portion of the polymer(s) other than PET solubilized in said immiscible solvent, from the liquid reaction medium, said steps b) of dissolution and b') of separation being carried out independently of each other during or after step a) of depolymerization, said process producing an effluent comprising BHET.

2. A method according to claim 1, wherein the polymer(s) other than PET is / are selected from polyolefin, ethylene vinyl alcohol, polystyrene and polyvinyl chloride, alone or in mixture.

3. A process according to any one of the preceding claims, wherein the immiscible solvent is an aprotic and hydrophobic organic solvent selected from one (or more) hydrocarbon(s) selected from a linear, branched or cyclic alkane, an aromatic or a polyaromatic, substituted or unsubstituted, having a boiling point between 25 °C and 300 °C.

4. A method according to any one of the preceding claims, wherein the immiscible solvent is selected from at least one linear, branched or cyclic alkane having between 5 and 20 carbon atoms.

5. A process according to any one of the preceding claims, wherein the amount of immiscible solvent added in the mixing step of step b) is between 1% and 50% by weight relative to the weight of the liquid reaction medium mixture of step a) and the added immiscible solvent.

6. A method according to any one of the preceding claims, wherein the mixing temperature of step b) is between 150°C and 300°C.

7. A process according to any one of the preceding claims, wherein the immiscible solvent containing at least a portion of the non-PET solubilized polymer(s) obtained in step b') is sent to a purification step which allows the non-PET polymer(s) to be extracted on one side and at least a portion of the immiscible solvent on the other.

8. A process according to claim 7, wherein the immiscible solvent obtained after purification is at least partly recycled in the mixing step of step b).

9. A process according to any one of the preceding claims, wherein the depolymerization step a) comprises a plastic filler conditioning phase, located upstream of the reaction phase, the conditioning phase comprising a heating phase to melt at least part of said plastic filler and / or a premixing phase to mix said plastic filler, possibly at least partially melted, with at least part of the diol.

10. A process according to any one of the preceding claims comprising a step c) of filtering the effluent comprising BHET from steps a), b) and b').

11. A process according to any one of the preceding claims comprising at least one further step of effluent purification comprising BHET from steps a), b) and b') selected from filtration, precipitation of impurities, ion treatment by contact with at least one ion-exchange resin, adsorption, crystallization and / or precipitation of BHET, and diol separation

12.

13.

14.

15. by gas-liquid separation and evaporation of BHET, in order to obtain a purified BHET effluent. A method according to any one of claims 1 to 9 comprising, after steps a), b) and b'), the following steps: c) optionally a filtration step of the effluent comprising BHET from steps a), b) and b'); d) a diol separation step fed at least by the effluent comprising BHET from steps a), b) and b') or possibly from step c), operated at a temperature between 100 and 250°C, at a pressure lower than that of steps a), b) and b') and producing a diol effluent and a BHET-rich effluent, the diol effluent preferably being at least partly recycled in step a); e) a separation step of the BHET-rich effluent from step d) into a heavy impurities effluent and a pre-purified BHET effluent, operated at a temperature less than or equal to 250°C and a pressure less than or equal to 0.001 MPa with a liquid residence time less than or equal to 10 min; f) a step of separating said heavy impurity effluent into two fractions: a first fraction which feeds at least in part into step a) and a second fraction which is preferably at least in part discharged from the process; (g) optionally a decolorization step of the pre-purified BHET effluent, operated at a temperature between 70 and 250°C, and at a pressure between 0.1 and 1.0 MPa in the presence of an adsorbent, and producing a purified BHET effluent; (h) Optionally, a crystallization step of the purified BHET effluent, comprising at least one solid production section, operated at a temperature between 0 and 100°C and at a pressure between 0.00001 and 1 MPa, followed by a solid-liquid separation section, producing a decolorized and purified BHET effluent. A process according to claim 12 comprising the filtration step (c) and / or the decolorization step (g) and / or the crystallization step (h). A process according to any one of claims 11 to 13, wherein the purified BHET effluent feeds a polymerization step for the production of PET. A process according to any one of the preceding claims, wherein after step b'), the polymer(s) other than PET, mixed or not with the immiscible solvent, is / are sent into a process

16. thermoplastic processing by dissolving polymers to obtain a purified thermoplastic stream. A process according to any one of the preceding claims, wherein after step b'), the polymer(s) other than PET, mixed or not with the immiscible solvent, is / are sent to a pyrolysis process, a cracking process or an energy recovery unit.

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