Method for extraction and transformation by hydrolysis of phthalates contained in PVC plastics

Abstract

The present invention relates to a method for obtaining phthalic acid (PA) and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, said method comprising: a) solid‐liquid extraction of the PVC feedstock in contact with an organic extraction solvent, producing a liquid phase comprising said phthalate and a first solid phase comprising PVC plastic depleted in said phthalate; b) transforming said phthalate resulting from a) into PA by hydrolysis; c) solid-liquid separation between the first solid phase and the liquid phase resulting from a) and / or b), producing a solid stream of PVC plastic depleted in said phthalate; d) liquid-solid phase change of the PA, producing a mixed stream comprising at least one second solid phase enriched in PA, e) solid-liquid separation between the solid PA and the aqueous phase of the mixed stream, producing a solid stream of PA and an aqueous liquid effluent.

Description

[0001] PROCESS FOR THE EXTRACTION AND TRANSFORMATION BY HYDROLYSIS OF PHTHALATES CONTAINED IN PVC PLASTICS

[0002] Technical field

[0003] The invention relates to the field of recycling of polyvinyl chloride (PVC) plastics, in particular a process for extracting and transforming phthalates, plasticizers used in the composition of PVC, by hydrolysis. More specifically, the invention relates to a process for recovering phthalic acid (PA) and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate.

[0004] Prior art

[0005] By definition, a plastic is a mixture consisting of a basic polymeric material and numerous additives, the whole being capable of being molded or shaped (generally hot and / or under pressure), in order to produce a semi-finished product or an object. A commonly accepted practice is to name said plastic by the name of the polymer that constitutes it. Thus, poly(vinyl chloride) (PVC) plastic actually corresponds to the association of the PVC polymer, referred to in the remainder of the description as "PVC resin", with various additives chosen according to the functionalities required for said plastic. Said additives can be organic molecules or macromolecules or inorganic (nano)particles and are used according to the properties they confer on the PVC resin: resistance to heat, light or mechanical stress (stabilizers), flexibility (plasticizers), ease of processing (lubricants), coloring (dyes / pigments), etc.

[0006] There are several methods for recycling PVC plastics: so-called conventional methods involving simple mechanical recycling of plastics, methods involving modifications to their composition, or even chemical transformations of the compounds that constitute them.

[0007] Since the middle of the 20th century èmecentury, the recycling of PVC plastic involving chemical action has been the subject of numerous studies aimed, in a first step, at solubilizing the PVC resin with a variable proportion of additives and then, in a second step, at recovering said resin using various chemical processes (precipitation, evaporation, etc.) in the presence of all or part of the soluble additives. For example, patents EP0945481, EP1268628 and EP2276801 aim to recycle respectively various PVC-based objects (flexible or rigid pipes, window frames, cables, etc.) and specifically PVC-based objects reinforced with fibers (tarpaulins, floor coverings, etc.) using a process implementing a first step of dissolving the PVC resin and soluble additives in an organic solvent, followed by a second step of precipitation with water vapor allowing the recovery of the resin and the majority of the additives.

[0008] Maintaining these additives in the PVC thus recovered for recycling is not always desirable, however. For example, the evolution over time of the regulations that concern them has an impact. Thus, certain plasticizers belonging to the phthalate family, notably widely used to formulate so-called "soft" PVC around forty years ago, have gradually been subject to authorization in Europe on the basis of the REACH regulation which, since the end of 2006, aims to secure the manufacture and use of chemical substances in European industry and, finally, gradually excluded from usable additives.This is particularly the case for the following non-exhaustive list of phthalates: dibutyl phthalate (DBP), dioctyl or diethylhexyl phthalate (DOP or DEHP), benzyl and butyl phthalate (BBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl and isopentyl phthalate, dihexyl phthalate, etc. These new regulations now lead to the prohibition of the presence of such compounds in recycled raw materials (RPM). Taking into account the often very long lifespan of PVC-based objects (several decades), PVC-based objects formulated before the end of 2006 and now at the end of their life cannot be recycled using regeneration methods leading to the retention of these prohibited additives, whether said methods are conventional, such as mechanical recycling processes, or not, such as the examples of dissolution / precipitation processes cited above.

[0009] Furthermore, the phthalate plasticizers used today in Europe (so-called REACH-compatible phthalates) and in the rest of the world represent high value-added additives that are not recovered in their current state while they are kept in the recycled PVC raw material. Indeed, they are expensive products, present in significant proportions in the initial PVC formulations (several tens of percent) and do not allow the PVC MPR to be directly given the ad hoc flexibility properties. The addition of "fresh" plasticizers in significant quantities is therefore essential for the reuse of the recycled PVC material.

[0010] The extraction of phthalate-type additives from PVC-based objects for disposal or recovery therefore represents a major challenge for optimized recyclability of PVC.

[0011] Several processes involving a step of dissolving the PVC resin have been adapted to enable this extraction. For example, patents EP1311599 and JP2007191586 both propose a first step of dissolving the PVC resin and at least the phthalate-type additives using a first organic solvent, followed by a second step of liquid-liquid extraction of the phthalates from the solution obtained previously, via the use of a second organic solvent different from the first. Patent JP2007092035 discloses another example of possible implementation with dissolution of the PVC resin and at least the phthalate-type additives via the use of a solvent under supercritical conditions and the recovery of said phthalates in this same solvent after "breaking" of said supercritical conditions.

[0012] The elimination or recovery of phthalate-type additives from PVC plastic can also be implemented without going through a preliminary step of dissolving said plastic, in particular via direct extraction of said phthalates from the solid polymer matrix by a suitable organic solvent, as perfectly listed in the publication by Ügdüler et al., 2020, “Challenge and opportunities of solvent-based additive extraction methods for plastic recycling”, Waste Management, 104, 148-182. The challenge then lies in optimizing the extraction conditions (nature of the solvent, contact time, temperature, pressure, etc.) to achieve the best possible yields of extracted phthalates.Although this methodology for removing phthalates from PVC plastics is frequently used, particularly to analytically detect and quantify these specific additives in said plastics, to our knowledge, no process for regenerating PVC-based objects uses this technique.

[0013] Although critical to ensure efficient recycling of PVC plastics and obtain reusable recycled PVC, the extraction of phthalate-type plasticizers is not sufficient to ensure the economic viability of a process for regenerating PVC-based objects. The main reason frequently put forward is the difficulty in finding an economically viable balance between the cost of the unit operations implemented in the said regeneration process and the resale cost (equivalent to the added value) of the products obtained. The latter are made up of the recycled PVC-based material free of phthalates, which is naturally recoverable, and the said extracted phthalates, which are themselves not very recoverable. Indeed, any regeneration process implementing a step of extracting phthalates from PVC-based objects will lead to the recovery of a mixture of phthalates, the latter possibly including phthalates that are not "REACH compatible".The recovery of said non-REACH compatible phthalates is of course excluded and these will have to be treated as specific waste generating additional costs. The recovery of REACH compatible phthalates, interesting in itself, is in fact delicate because it involves technically complex and costly separation / purification steps.

[0014] In the past, some work has focused on bringing PVC plastics containing phthalates into contact with highly concentrated basic aqueous solutions (essentially NaOH) to transform said phthalates and extract the resulting product(s): a salt of phthalic acid and possible degradation products depending on the associated operating conditions. This chemical reaction was carried out in conjunction with or upstream of a PVC dechlorination step, thus making it possible to obtain a non-chlorinated residue that is largely free of phthalates to enable its energy recovery. Carrying out such a step upstream of dechlorination, and assisted by high frequencies or microwaves, has the advantage of recovering a recoverable phthalic acid salt, as reported in the following documents: patent JP3929352; the publication by F. Osada et al., 2010, “Deplasticization and dechlorination of flexible polyvinyl chloride in NaOH solution by microwave heating”, J. Mater. Cycles Waste Manag., 2010, 12, 245; the publication of SM Shin et al., 2011, “Elution Behavior of Additive Agent from Flexible PVC”, Chawon Rissaikuring, 10, 6, 3. This implementation nevertheless has the following major drawbacks: it requires the use of highly concentrated bases, it leads to the production not of phthalic acid but of its associated salt, and the extraction of phthalates is not optimized and does not comply with the REACH regulations applicable since 2006 for the recovery of a compound that can be used as a recycled raw material.

[0015] Summary of the invention

[0016] The present invention aims to overcome, at least in part, the problems of the prior art, and aims in particular to provide a process for regenerating PVC-based objects allowing the treatment of any type of PVC load containing phthalates and their transformation into two products of interest capable of being recovered as raw materials: phthalic acid and a recyclable PVC plastic free of phthalates, in particular undesirable phthalates, typically those subject to authorization by the European REACH regulation.

[0017] Phthalic acid is used in particular to manufacture phthalates, which are derivatives of phthalic acid. Phthalic acid can be used as a raw material for the manufacture of other chemicals, in areas other than plastic formulation, for example to manufacture dyes, perfumes, sweeteners such as saccharin, etc.

[0018] The process according to the invention makes it possible in particular to produce a phthalic acid powder of good purity from a PVC load, typically PVC waste, without stoichiometric consumption of base or acid.

[0019] Thus, to achieve at least one of the above-mentioned objectives, among others, the present invention proposes, according to a first aspect, a method for recovering phthalic acid and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, comprising the following steps: a) a solid-liquid extraction of said PVC feedstock in the form of particles by bringing the particles of the PVC feedstock into contact with at least one organic extraction solvent for said phthalate, to produce a liquid phase enriched in said phthalate and a first solid phase comprising PVC plastic depleted in said phthalate; b) a chemical transformation of said phthalate extracted in step a) into phthalic acid of formula C6H4(COOH)2 by hydrolysis using water to produce an aqueous phase comprising said phthalic acid;c) a solid-liquid separation between said first solid phase and said liquid phase enriched in said phthalate or said aqueous phase comprising said phthalic acid to produce at least one solid stream comprising the PVC plastic depleted in said phthalate in order to recover the target PVC plastic; d) a phase change of the phthalic acid from the dissolved state in said aqueous phase to a solid state to produce a mixed stream comprising an aqueous liquid phase depleted in phthalic acid and a second solid phase enriched in phthalic acid; e) a solid-liquid separation between the phthalic acid in the solid state from step d) and the aqueous liquid phase of said mixed stream, to produce a solid stream of phthalic acid and a liquid effluent comprising residual water from step b).;

[0020] An advantage of the present invention lies in the ability of the process, thanks to a compatible solid-liquid extraction step combined with a chemical hydrolysis reaction, to extract and transform a mixture of phthalates initially trapped in polymer matrices of various PVC plastic-based objects, regardless of the composition of said mixture (i.e. regardless of the nature and origin of the different phthalates) and despite the possible presence of many other additives, into a single REACH-compatible and recoverable phthalate product: phthalic acid. Obtaining the single phthalic acid product from the mixture of phthalates also makes it possible to envisage the transformation of said phthalic acid into new and multiple phthalates, still very widely used in many fields such as plastics, according to a circular economy principle.

[0021] According to a first variant, steps a) and b) are implemented within the same unit operation, producing a flow comprising at least the aqueous phase comprising phthalic acid and the first solid phase comprising PVC plastic depleted in said phthalate.

[0022] According to a second alternative variant to the first variant, steps a) and b) are the subject of two separate unit operations, step a) producing a flow comprising the liquid phase enriched in said phthalate and said first solid phase sent to step c) carried out between steps a) and b), step c) producing the flow comprising the PVC plastic depleted in said phthalate and a first liquid flow comprising the liquid phase enriched in said phthalate.

[0023] According to this second variant, the method preferably comprises a step g) of removing at least part of the organic extraction solvent from the first liquid stream prior to step b), to produce a first concentrated liquid stream comprising said phthalate sent to step b).

[0024] According to one or more embodiments, step g) of removing at least part of the organic extraction solvent from the first liquid stream comprises evaporation of the extraction solvent, preferably using a succession of expansion tanks.

[0025] According to one or more embodiments, the organic extraction solvent recovered in step g) is recycled at least in part to step a). According to one or more embodiments, the solid stream comprising the phthalate-depleted PVC plastic separated in step c) is recycled at least in part to step a).

[0026] According to one or more embodiments, the organic extraction solvent is chosen from the list consisting of ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, alcohols with a short, linear or branched aliphatic chain, of empirical formula Cnf iOH with n < 4, n being a non-zero natural integer, and mixtures thereof.

[0027] According to one or more embodiments, the organic extraction solvent is chosen from the list consisting of methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, acetophenone, tetrahydrofuran, cyclohexane, xylenes, toluene, methanol, ethanol, n-propanol, 17-propanol, and mixtures thereof, and preferably is chosen from said alcohols, ketone / alcohol mixtures, hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylenes, methoxycyclopentane, methyl isobutyl ketone, cyclopentanone, acetophenone, and preferably said organic extraction solvent is toluene, methyl ethyl ketone, acetophenone or a methyl ethyl ketone / methanol mixture.

[0028] According to one or more embodiments, the hydrolysis in step b) is carried out in the presence of an acid hydrolysis catalyst, preferably a homogeneous acid catalyst chosen from the list consisting of mineral Brônsted acid catalysts, preferably hydrochloric acid, sulfuric acid, phosphoric acid, organic Brônsted acid catalysts, preferably p-toluenesulfonic acid, and Lewis acid catalysts, preferably AIF3, or a heterogeneous acid catalyst chosen from the list consisting of aluminas, chlorinated aluminas, fluorinated aluminas, mesoporous aluminosilicates, zeolites and their mixtures with other oxides, ion exchange resins (H+), preferably sulfonic resins.

[0029] According to one or more embodiments, the hydrolysis in step b) is carried out at a temperature between room temperature and 150°C, preferably between 40°C and 130°C, at a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, and for a duration of between 1 minute and 10 hours, preferably between 10 minutes and 4 hours.

[0030] According to one or more embodiments, the hydrolysis in step b) is carried out so that the molar ratio between the quantity of water and the quantity of said phthalate extracted in step a) is between 100 and 9000.

[0031] According to one or more embodiments, step d) comprises at least one step of precipitation of the phthalic acid, preferably comprising cooling to a temperature between 10°C and room temperature.

[0032] According to one or more embodiments, said at least one phthalate of said PVC filler is a phthalate of empirical formula CgH^COORiKCOOF ) whose ester groups are in the ortho position of the benzene ring, Ri or R2 being independently chosen from one of the elements of the group consisting of a linear or branched or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, Ri and / or R2 preferably comprising between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.

[0033] According to one or more embodiments, the target PVC plastic is free of said phthalate, and preferably comprises less than 0.1% by mass in total of phthalates selected from the list consisting of dibutyl phthalate, dioctyl or diethylhexyl phthalate, benzyl and butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl and isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

[0034] According to one or more embodiments, the method comprises an additional separation step f) directly upstream of step d) or downstream of step e) to separate at least one aqueous liquid phase from other compounds in liquid or gas phase. When some of said compounds comprise extraction solvent or phthalate extracted in step a) and unconverted and / or partially converted in step b) or water, they are preferably recycled: the extraction solvent can be recycled to step a), and the water and / or phthalate extracted in step a) and unconverted and / or partially converted in step b) can be recycled to step b).

[0035] According to a second aspect, the present invention relates to a method for recycling a PVC-based object containing at least one phthalate comprising:

[0036] - packaging said PVC-based object comprising at least one grinding or shredding of said PVC-based object to form a PVC charge in the form of particles;

[0037] - recovering phthalic acid and a reusable target PVC plastic from said PVC filler in particulate form according to the first aspect of the invention.

[0038] The present invention also relates, according to a third aspect, to a method of manufacturing a flexible PVC-based object comprising a recycled PVC plastic and / or a phthalate manufactured from phthalic acid recovered by the method according to the first aspect of the invention.

[0039] Other objects and advantages of the invention will appear on reading the following description of particular examples of embodiments of the invention, given as non-limiting examples, the description being made with reference to the appended figures described below.

[0040] List of figures

[0041] Figure 1 is a diagram of the process according to one embodiment of the invention comprising steps a), b), c), d) and e), the optional step g) of removing the extraction solvent, and the optional separation step f1), and in which the extraction steps a) and hydrolysis b) are the subject of two separate unit operations with the solid-liquid separation step c) carried out between steps a) and b) (second variant of the process according to the invention). The organic extraction solvent (7) is miscible with water.

[0042] Figure 2 is a diagram of the process according to another embodiment, comprising, as for the embodiment illustrated in Figure 1, separate extraction steps a) and hydrolysis steps b), with an intermediate solid-liquid separation step c), and further comprising the optional step g), and optional separation steps f3) and f2) respectively directly upstream of step d) and downstream of step e). The organic extraction solvent (7) is miscible with water.

[0043] Figure 3 is a diagram of the process according to another preferred embodiment, comprising, as for the embodiments illustrated in Figures 1 and 2, separate extraction steps a) and hydrolysis steps b), with an intermediate solid-liquid separation step c), and further comprising the optional step g), and an optional separation step f4) directly upstream of step d) as well as an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is immiscible with water.

[0044] Figure 4 is a diagram of the process according to another embodiment of the invention comprising steps a), b), c), d) and e), and the optional separation step fl), and in which the extraction steps a) and hydrolysis steps b) are carried out within the same unit operation (first variant of the process according to the invention). The organic extraction solvent (7) is miscible with water.

[0045] Figure 5 is a diagram of the process according to another embodiment, comprising, as for the embodiment illustrated in Figure 4, concomitant extraction steps a) and hydrolysis b), with a solid-liquid separation step c) directly downstream, and further comprising the optional separation steps f3) and f2) respectively directly upstream of step d) and downstream of step e). The organic extraction solvent (7) is miscible with water.

[0046] Figure 6 is a diagram of the process according to another embodiment, comprising, as for the embodiments illustrated in Figures 4 and 5, concomitant extraction steps a) and hydrolysis b), with a solid-liquid separation step c) directly downstream, and further comprising the optional separation step f4) directly upstream of step d) as well as an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is immiscible with water.

[0047] In the figures, the same references designate identical or similar elements.

[0048] Description of the embodiments

[0049] Terminology

[0050] Some definitions are given below, although more details on the objects defined below may be given later in the description.

[0051] A PVC-based object is understood to mean an object, generally a consumer object, which comprises, and preferably is made of, at least one PVC plastic.

[0052] Poly(vinyl chloride) plastic, also known as PVC plastic or simply PVC, is the combination of a PVC polymer, also known as PVC resin, with various additives chosen according to the functionalities required for the PVC plastic, themselves chosen according to the intended applications.

[0053] The said PVC polymer is produced by the radical polymerization of vinyl chloride (VCM), a monomer itself obtained from chlorine and ethylene. Depending on the implementation of the said polymerization, four families of PVC resins can be used: 1) PVC suspension resins or PVC-S (suspension polymerization of VCM), 2) PVC emulsion resins or PVC "pastes" (emulsion polymerization), 3) PVC mass resins or PVC-M (mass polymerization) and 4) superchlorinated PVC resins or PVC-C, obtained by superchlorination in post-treatment of the previous resins.

[0054] Said additives used in the composition of a PVC plastic can be organic molecules or macromolecules or inorganic (nano)particles and are used according to the properties they confer on the PVC resin: resistance to heat, light or mechanical stress (stabilizers), flexibility (plasticizers), ease of processing (lubricants), coloring (dyes / pigments), etc.

[0055] Phthalates are the group of chemicals formed by the carboxylic diesters of phthalic acid. They consist of a benzene ring and two carboxylic ester groups positioned ortho to the benzene ring. They can be described using the following formula: or by the empirical formula CSH4(COORI)(COOR2), where Ri and R2 are independently selected from one of the elements of the group consisting of a linear, branched or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, said alkyl, alkoxyalkyl, aryl or alkylaryl chain typically being able to contain between 1 and 20 carbon atoms, or even to contain between 1 and 15 carbon atoms. For example, Ri and / or R2 can be independently selected from the ethyl, n-butyl, iso-butyl, n-pentyl, iso-pentyl, n-hexyl, n-octyl, n-nonyl, iso-nonyl, n-decyl, iso-decyl, methoxyethyl, benzyl groups. Phthalates are commonly used as plasticizers in plastics, particularly in PVC-type plastics, particularly to make them flexible.

[0056] In the present description, the term "phthalic acid" (PA), also known as benzene-1,2-dicarboxylic acid or o-phthalic acid, designates the product of empirical formula CgPMCOOH resulting from the hydrolysis reaction of at least one phthalate-type plasticizer (and in particular of empirical formula C6H4(COORI)(COOR2), as described above) present in PVC-based objects with water (H2O).

[0057] “Alcohol by-product(s)” (AL) means the by-product(s) of formula RiOH or R2OH resulting from the hydrolysis reaction of at least one phthalate plasticizer present in PVC-based objects with H2O. Ri or R2 are defined identically to Ri and R2 of phthalates.

[0058] The term "alkyl phthalate intermediate" (API) or "partially converted phthalate" means the by-product of the empirical formula C6H4(COOH)(COORI) or C6H4(COOR2)(COOH) resulting from the incomplete hydrolysis reaction of at least one phthalate-type plasticizer (and in particular of the empirical formula CSH4(COORI)(COOR2), as described above) present in PVC-based objects with H2O. Ri or R2 are defined identically to Ri and R2 of phthalates.

[0059] The term "reusable target PVC plastic" means "phthalate-free PVC", i.e. the solid comprising at least the PVC resin added with at least one of the additives initially present in the PVC plastic of the PVC load treated according to the invention, and from which the phthalates have been extracted and transformed according to the invention into phthalic acid in whole or in part.The term "phthalate-free" means in particular that the solid PVC obtained as a product of the process according to the invention contains, in total, less than 0.1% by mass of phthalates subject to authorization by the REACH regulation in Europe (Annex XIV of Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular less than 0.1% by mass of phthalates chosen from the list consisting of the following phthalates: dibutyl phthalate (DBP), dioctyl or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl), alone or in mixture.

[0060] In the present description, the expression "greater than..." is understood as strictly greater, and symbolized by the sign ">", and the expression "less than" as strictly less, and symbolized by the sign "<". In the present description, ambient temperature (Tamb) is understood to mean a temperature typically of 20°C ± 5°C, and atmospheric pressure is understood to mean a pressure of 0.101325 MPa.

[0061] In this description, the term "include" is synonymous with (means the same as) "comprise", "include" and "contain", and is inclusive or open and does not exclude other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist".

[0062] In this description, the expression "between ... and ..." means that the limiting values ​​of the interval are included in the range of values ​​described, unless otherwise specified.

[0063] In the present description, the different parameter ranges for a given step such as pressure ranges and temperature ranges may be used alone or in combination. For example, in the present description, a range of preferred pressure values ​​may be combined with a range of more preferred temperature values.

[0064] In the following, particular embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combinations when technically feasible.

[0065] The description of the method according to the first aspect of the invention below refers to the diagrams of figures 1 to 6, illustrating different implementations of the method according to the invention.

[0066] According to the invention, the method for recovering AP and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, comprises, and may consist of, the following steps: a) a solid-liquid extraction of said PVC feedstock in the form of particles 1 by bringing the particles of the PVC feedstock into contact with at least one organic extraction solvent 7 of said phthalate, to produce a liquid phase enriched in said phthalate and a first solid phase comprising PVC plastic depleted in said phthalate; b) a chemical transformation of said phthalate extracted in step a) into phthalic acid of formula C6H4(COOH)2 by hydrolysis using water 9 to produce an aqueous phase comprising said phthalic acid;c) a solid-liquid separation between said first solid phase and said liquid phase enriched in said phthalate or said aqueous phase comprising said phthalic acid to produce at least one solid stream comprising the PVC plastic depleted in said phthalate 8 in order to recover the target PVC plastic; d) a phase change of the phthalic acid from the dissolved state in the aqueous phase to a solid state to produce a mixed stream comprising an aqueous liquid phase depleted in phthalic acid and a second solid phase enriched in phthalic acid (5, 19, 22); e) a solid-liquid separation between the phthalic acid in the solid state from step d) and the aqueous liquid phase of said mixed stream, to produce at least one solid stream of phthalic acid 6 and a liquid effluent (11, 14, 20) comprising residual water from step b).;

[0067] Charge

[0068] The method according to the invention is supplied with a feedstock called "PVC feedstock" 1 comprising at least one PVC plastic, which necessarily comprises at least one phthalate as described in the present invention. Said PVC plastic may comprise at least 0.1% by mass of phthalates, or even at least 1% by mass of phthalates or even at least 5% by mass of phthalates. In general, PVC plastics advantageously comprise less than 60% by mass of phthalates, typically less than 40% by mass of phthalates.

[0069] Said PVC load is advantageously a PVC load to be recycled of the “production scraps” type, i.e. waste from the production processes of the PVC polymer during its polymerization or of the PVC plastic during its formulation / shaping or of the PVC-based object during its production, or of the “post-consumer waste” type, i.e. waste generated after consumption by the user of said PVC-based object.

[0070] In particular, the PVC load to be recycled can come from any existing collection and sorting channel or network for production scraps and / or post-consumer waste making it possible to isolate a flow based on at least one PVC plastic comprising at least one phthalate, in particular collection and sorting channels or networks specific to plastic waste.

[0071] Thus, the PVC load, which is typically of the “production scrap” type and / or of the “post-consumer waste” type, generally comes from the major application areas using PVC plastic such as, but not limited to, the fields of building and construction, packaging, automotive, electrical and electronic equipment, sports, medical equipment, etc. Preferably, the PVC load comes from the field of building and construction. More specifically, PVC-based objects are generally used in these fields as profiles (windows, doors, blinds, roller shutter boxes), pipes and fittings, various rigid materials and bottles, rigid plates and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.Preferably, the PVC-based objects forming the PVC filler comprise at least so-called flexible PVC, i.e. PVC containing plasticizer-type additives, preferably of the phthalate type, as is the case, for example, for the following PVC-based objects: flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.

[0072] Advantageously, the PVC filler comprises at least 50% by mass, preferably at least 70% by mass, preferably at least 90% by mass and even more preferably at least 95% by mass of PVC plastic comprising at least one phthalate.

[0073] Preferably, the PVC filler comprises so-called soft PVC, i.e. PVC containing plasticizer-type additives, preferably of the phthalate type.

[0074] Even more preferably, the PVC filler comprises mainly, or even exclusively, so-called flexible PVC, i.e. PVC containing plasticizer-type additives, preferably of the phthalate type.

[0075] The PVC feedstock treated in the process for recovering a DAP and a reusable target PVC plastic according to the invention is in the form of particles. Thus, if the PVC feedstock is in an initial form which is that specific to production scraps or post-consumer waste, in particular in the latter case in the initial form of PVC-based objects, it may first undergo a conditioning step comprising at least one grinding or shredding to form a PVC feedstock in the form of particles. Depending on the sectors and / or networks from which these production scraps and / or end-of-life PVC-based objects come, the PVC waste may be ground and / or washed and / or undergo any other conditioning step as described below, in order to form the PVC feedstock in the form of particles suitable for the process according to the invention.For example, the PVC filler may advantageously be in the form of ground material, optionally washed, the largest dimension of which is less than 20 cm, preferably less than 10 cm, more preferably less than 1 cm and even more preferably less than 5 mm. The PVC filler may also advantageously be in the form of a micronized solid, i.e. in the form of particles preferably having an average size of less than 1 mm, for example between 10 micrometers (pm) and 800 micrometers (pm). The average size advantageously corresponds to the average diameter of the spheres circumscribed by said particles.

[0076] Thus, by PVC filler in the form of particles, we mean PVC plastic particles typically having an average size, as defined above, of between 10 pm and 20 cm, for example ground particles having an average size of between 1 mm and 20 cm, preferably of between 1 mm and 10 cm, more preferably of between 1 mm and 1 cm, even more preferably of between 1 mm and 5 mm, or particles resulting from micronization (very fine grinding to produce a powder) of an average size of less than 1 mm, preferably of between 10 pm and 800 pm.

[0077] Preferably, the PVC filler treated in the process according to the invention is in the form of ground particles, preferably particles with an average size of between 1 mm and 5 mm, or particles resulting from micronization (very fine grinding to produce a powder) with an average size of less than 1 mm.

[0078] The PVC filler may also comprise “macroscopic” impurities, such as glass, metal, plastics other than PVC (e.g. PET, etc.), wood, paper, cardboard, mineral elements, etc. Advantageously, the PVC filler comprises at most 50% by mass, preferably at most 30% by mass, more preferably at most 10% by mass and even more preferably at most 5% by mass of “macroscopic” impurities.

[0079] The different stages of the process according to the invention leading to the AP and the reusable target PVC plastic are detailed in the following paragraphs.

[0080] Optional preliminary step of conditioning the PVC load

[0081] According to the invention, the method may comprise a preliminary step of conditioning the PVC feedstock (not shown in the figures) comprising at least one step of grinding or shredding the PVC feedstock to form a PVC feedstock in the form of solid particles as defined above, capable of being sent to step a) of solid-liquid extraction. This preliminary conditioning step may further comprise one or more steps mentioned in the following non-exhaustive list: grinding by micronization, sorting, over-sorting, washing, drying, etc. Depending on the nature of the PVC feedstock being treated, the step or steps, as well as their possible frequencies and sequences, involved in the preliminary conditioning step are in particular chosen by a person skilled in the art so as to limit the quantity of macroscopic impurities and to reduce the size of the solid elements initially making up the PVC feedstock.

[0082] For example, the preliminary conditioning step makes it possible to provide a PVC filler in the form of particles, for example ground, washed, with an average size of less than 5 mm, the content of macroscopic impurities of which is preferably at most 10% by mass, and more preferably at most 5% by mass. Said previously conditioned PVC filler may also be in the form of micronized solid particles, that is to say in the form of particles having an average size of less than 1 mm, for example between 10 μm and 800 μm. Step a) of solid-liquid extraction of phthalates

[0083] The method according to the invention comprises a step a) of solid-liquid extraction of the phthalate(s) from the PVC filler in the form of particles 1 by bringing said filler into contact with an organic extraction solvent 7, in order to obtain an effluent comprising at least one liquid phase and a first solid phase. Said liquid phase is then enriched in said phthalate(s), and the first solid phase comprises PVC plastic depleted in said phthalate(s). The effluent is represented by stream 2 in Figures 1 to 3, where steps a) and b) are carried out separately.

[0084] Said organic extraction solvent 7 is thus chosen because of its physicochemical properties for its ability to penetrate into the polymer matrix while drastically limiting its dissolution, in order to effectively extract the phthalate(s) from the PVC filler in the form of particles. In this, a person skilled in the art can rely on knowledge of the Hildebrand and / or Hansen solubility parameters of the solvents to define, with respect to these same parameters specific to PVC resins and phthalates, the most suitable solvent for carrying out step a) of solid-liquid extraction of the process according to the invention.

[0085] Hansen's theory makes it possible, for example, to estimate the solubility of a polymer, in particular a thermoplastic such as PVC, in a solvent or a mixture of solvents, by determining the Hansen parameters and solubility sphere respectively for the solvent and the polymer. These calculations are based on the estimation of the cohesive forces allowing a compound (here the polymer) to remain in the solid state and which are split into 3 contributions: London interactions, Keesom interactions and hydrogen bonds. If a solvent or a mixture of solvents has Hansen parameters in the Hansen sphere of the PVC polymer, said PVC polymer should be at least partially, preferably entirely, soluble in said solvent. Thus, the person skilled in the art will be able to use these calculations to choose an extraction solvent (i.e.organic solvent / mixture of organic solvents) suitable, which can solubilize the phthalates, while limiting the dissolution of the PVC polymer, which can then be subject to experimental verification (for a given set of operating conditions). Said extraction solvent is also chosen so as to allow the performance of step b) of chemical transformation of said phthalate(s) by hydrolysis, while limiting secondary chemical reactions and making the subsequent separation step(s) necessary for obtaining the AP according to the invention more simple and effective.

[0086] According to one or more embodiments, said extraction solvent is advantageously an organic solvent or a mixture of organic solvents, chosen from:

[0087] - ketones, such as methyl ethyl ketone (MEK), diethyl ketone (DEK), 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone (MIBK), cyclic ketones such as cyclopentanone, cyclohexanone, aromatic ketones such as acetophenone,

[0088] - ethers such as methoxycyclopentane (CPME), cyclic ethers such as tetrahydrofuran (THF), glycol ethers such as 2-Methoxyethanol, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether,

[0089] - cyclic and aromatic hydrocarbons such as cyclohexane, xylenes, toluene,

[0090] - alcohols with a short, linear or branched aliphatic chain, of chemical formula C n H2n+iOH with n < 4, n being a non-zero natural number, such as methanol, ethanol, n-propanol, 17-propanol.

[0091] Preferably, the organic extraction solvent is chosen from the abovementioned alcohols, in particular methanol, ethanol, n-propanol, 17-propanol, the abovementioned ketone / alcohol mixtures, the abovementioned hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylenes, CPME, MEK, MIBK, cyclopentanone, taken alone or as a mixture, and more preferably chosen from the abovementioned alcohols, the abovementioned ketone / alcohol mixtures, the abovementioned hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylenes, acetophenone, MEK, MIBK, cyclopentanone, taken alone or as a mixture.

[0092] The extraction solvent can advantageously be toluene, MEK, acetophenone, or a MEK / methanol mixture.

[0093] Step a) of solid-liquid extraction of the phthalate(s) from the PVC filler 1 is preferably carried out according to the following operating conditions: a temperature between room temperature and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, and even more preferably between 60°C and 145°C, a pressure between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa, a residence time between 1 min and 10 h, preferably between 5 min and 4 h, more preferably between 5 min and 2 h and even more preferably between 10 min and 30 min.

[0094] Preferably, step a) is carried out so that the molar ratio between the quantity of solvent 7 and the quantity of the phthalate(s) to be extracted from the PVC charge 1 is between 2 and 250, preferably between 4 and 100, and even more preferably between 4 and 30.

[0095] The reactor used in step a) of the process according to the invention may advantageously be a reactor of the type stirred by a mechanical stirring system and / or by recirculation loop and / or by fluidization, and / or by ultrasound, for example a discontinuous (also called "batch") or continuous type reactor, preferably perfectly stirred, or a rotating drum type reactor.

[0096] In terms of implementation, the PVC filler in the form of particles 1 and the organic extraction solvent 7 are advantageously mixed.

[0097] According to a first option, said mixture can be carried out prior to the introduction of the PVC feedstock and the extraction solvent into the reactor of step a) of solid-liquid extraction. In this case, said mixture can be formed in a mixer and can then be introduced into the reactor, the latter being maintained at a desired pressure and temperature.

[0098] According to a second option, the PVC feedstock in the form of particles 1 and the solvent 7 can be introduced separately into the reactor of step a) of the process according to the invention. Said solid PVC feedstock and the solvent are then preferably injected into the reactor by two separate lines, one for injecting the extraction solvent 7, and the other the solid PVC feedstock in the form of particles 1. In this case, the mixture of the PVC feedstock and the solvent is formed directly in said reactor.

[0099] According to the invention, said solid-liquid extraction step a) makes it possible to obtain at least one effluent comprising at least one liquid phase containing at least the extracted phthalates and at least one first solid phase containing the PVC plastic depleted in phthalates, preferably free of phthalates.

[0100] Under the operating conditions of this step, the extracted phthalate(s) are advantageously in a liquid form.

[0101] Step b) of chemical transformation of said phthalates by hydrolysis

[0102] The process according to the invention comprises a step b) of chemical transformation of the phthalate(s) extracted in step a) into at least phthalic acid of formula CgH^COOH by hydrolysis reaction, preferably in the liquid phase, between said phthalate(s) extracted in step a) and water (H2O).Step b) of hydrolysis of the phthalate(s) present to form phthalic acid is preferably carried out under the following operating conditions: a temperature between room temperature and 150°C, preferably between room temperature and 145°C, more preferably between 40°C and 130°C, and more preferably between 60°C and 110°C, a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, more preferably between atmospheric pressure and 0.5 MPa, a residence time between 1 min and 10 h, preferably between 10 min and 4 h, more preferably between 10 min and 2 h and even more preferably between 10 min and 1 h.

[0103] Water 9 is therefore introduced at this step b) of the process, to carry out the hydrolysis reactions of the phthalate(s) in order to form phthalic acid.

[0104] Preferably, step b) is carried out so that the molar ratio between the quantity of water 9 and the quantity of phthalates to be transformed from the liquid phase containing the phthalate(s) extracted at the end of step a) is between 100 and 9000, preferably between 150 and 1800 and even more preferably between 200 and 850.

[0105] Preferably, said hydrolysis step b) is carried out in the presence of a hydrolysis catalyst 10, advantageously introduced into the reaction medium.

[0106] The hydrolysis catalyst 10 thus used is advantageously an acid catalyst, for example chosen from the acid catalysts of the following non-exhaustive list, well known to those skilled in the art, and preferably from the list consisting of:

[0107] - homogeneous catalysts such as mineral Brônsted acid catalysts (e.g. hydrochloric, sulfuric, phosphoric acids, etc.), organic Brônsted acid catalysts (e.g. methanesulfonic, trifluoromethanesulfonic, trifluoroacetic, p-toluenesulfonic acids, etc.), and Lewis acid catalysts (e.g. AIF3);

[0108] - acid heterogeneous catalysts such as aluminas, chlorinated or fluorinated aluminas, mesoporous aluminosilicates, zeolites and their mixtures with other oxides, ion exchange resins (H + ), such as sulfonic resins, etc.

[0109] For example, the catalyst used according to the invention is a homogeneous catalyst, in particular a homogeneous catalyst of the organic Brônsted acid catalyst type such as p-toluenesulfonic acid.

[0110] Preferably, the quantity of catalyst introduced is such that the mass ratio between the catalyst and the phthalate(s) to be transformed is between 0.02% and 10% by mass, preferably between 0.5% and 8% by mass and even more preferably between 1% and 5% by mass.

[0111] The catalyst, whether homogeneous or heterogeneous, can be recycled and / or eliminated in the process according to methods well known to those skilled in the art, and is preferably recycled. It can be isolated, to be eliminated or preferably recycled for the hydrolysis reaction, in the downstream steps of the process or during any other dedicated step.

[0112] The reactor used in step b) may advantageously be a reactor of the type stirred by a mechanical stirring system and / or by recirculation loop and / or by fluidization, and / or by ultrasound, for example a reactor of the discontinuous or continuous type, preferably perfectly stirred, or a reactor of the rotating drum type.

[0113] In accordance with the invention, said step b) of transformation of the phthalates makes it possible to obtain an effluent (stream 4 in figures 1 to 3 or stream 24 in figures 4 to 6) comprising at least one aqueous phase containing at least the phthalic acid obtained after hydrolysis reaction of the phthalates extracted in step a), initially contained in the liquid phase formed in step a).

[0114] Steps a) and b) of the process according to the invention can be implemented within the same unit operation upstream of step c) of solid-liquid separation of the process according to the invention, as shown in Figures 3 to 6, or else be the subject of two separate unit operations separated by at least said step c), the unit operation of step a) then always being carried out prior to the unit operation of step b), as shown in Figures 1 to 3, and explained in more detail below.

[0115] Step c) solid-liquid separation

[0116] The method according to the invention comprises a step c) of solid-liquid separation between, on the one hand, the first solid phase containing the PVC plastic depleted in phthalates, preferably free of phthalates, and on the other hand, the liquid phase containing the phthalate(s) extracted in step a) or the aqueous phase comprising the phthalic acid obtained in step b), according to the first and second variants of the method described in detail below, and depending on the position of step c) relative to steps a) and b).

[0117] The physical separation of the liquid and solid phases can advantageously be implemented according to techniques known to those skilled in the art such as, but not limited to, filtration, centrifugation, for example the use of hydrocyclones, electrostatic precipitation, or decantation, said techniques being used alone or in combination, in any order.

[0118] This step c) of solid-liquid separation therefore makes it possible to produce at least one solid stream 8 comprising the PVC plastic depleted in the phthalate(s) extracted in step a), in order to recover said reusable target PVC plastic.

[0119] Obtaining the reusable target PVC as defined according to the invention may require returning all or part of the solid stream 8 obtained in step c) to step a), according to as many cycles as necessary in order to produce said target PVC plastic.

[0120] This possibility of recycling the solid flow is shown in Figures 1 to 6.

[0121] For example, step c) can be carried out by centrifugation of the liquid effluent 2 comprising the liquid phase from step a) containing at least the extracted phthalates and the first solid phase, leading to the separation of said solid 8, and advantageously to the return of all or part of said solid to step a), preferably previously suspended, for example by means of an addition of extraction solvent 7 (not shown in the figures), until the reusable target PVC plastic is produced.

[0122] According to a first variant of the method according to the invention, step c) of solid-liquid separation occurs after the performance of step a) and before the performance of step b). This first variant is illustrated in particular in Figures 1 to 3. In this case, the liquid effluent 2 from step a) is sent to step c) of solid-liquid separation which leads to the separation of the liquid phase containing the extracted phthalates from the first solid phase containing the PVC depleted in phthalate(s). Step c) therefore produces the solid stream 8 comprising the PVC plastic depleted in phthalate(s), and a first liquid stream 3 which contains the phthalate(s) extracted in step a) and which is then sent to step b) for the transformation of said phthalate(s) by hydrolysis or to the optional step g) described below in the present invention allowing the total or partial elimination of the extraction solvent before sending the phthalates to be transformed to step b).This first variant is particularly suitable for the case where the PVC feedstock to be treated would lead to the formation, during step a), of a solid phase not favorable to carrying out the chemical hydrolysis reaction (in terms of chemical or rheological properties, etc.). A preferred example of implementation according to this variant is illustrated in Figure 3. According to a second variant of the method according to the invention, step c) of solid-liquid separation occurs after carrying out steps a) and b) implemented within the same unit operation. This second variant is illustrated in particular in Figures 4 to 6. In this case, the liquid stream 24, resulting from the concomitant steps a) and b), is sent to step c) of solid-liquid separation, which leads to the separation between at least the aqueous phase containing at least the AP obtained after the hydrolysis reaction in step b), and the first solid phase containing the PVC plastic depleted in phthalate(s).The liquid phase (aqueous and organic) and the first solid phase containing the PVC plastic depleted in phthalate(s) are separated at the end of this step c). The concomitant (joint) implementation within the same unit operation of steps a) and b) leads to a reduction in the number of unit operations necessary for carrying out the method according to the invention and therefore to a limitation of the number of equipment, the energy used, etc., and therefore to a reduction in costs. A preferred example according to this variant is illustrated in Figure 5, the simultaneous implementation of steps a) and b) being represented by the use of a single step (a+b) (a single “box” (a+b) represented). In this case, the presence of water 9 during the extraction phase can advantageously modify the extraction properties of the solvent 7 that it would have had if used alone.For example, the combination of extraction solvent 7 and water 9 can make it possible to use an extraction solvent 7 initially suitable for the extraction of phthalates but having too great a power to solubilize the PVC resin, and which is thus counterbalanced by the presence of water, the mixture ultimately having less power to solubilize the PVC resin.

[0123] Furthermore, for this second variant, a temperature greater than or equal to room temperature and less than or equal to 150°C, preferably less than or equal to 145°C, and more preferably less than or equal to 100°C, is preferred in order to avoid any degradation of the PVC resin, for example by dechlorination reaction.

[0124] At the end of all steps a) b) and c), the AP is mainly in liquid form in an aqueous phase contained in the liquid effluent 4. Said liquid effluent 4 may contain one or more liquid phases, for example a single liquid phase (single-phase liquid) or two liquid phases (two-phase liquid), in particular depending on the nature of the extraction solvent (for example miscible or not with water) and / or the operating conditions chosen.

[0125] Step d) liquid-solid phase change of phthalic acid

[0126] The method according to the invention comprises a step d) of phase change of the AP from the dissolved state in the aqueous phase obtained at the end of all steps a), b) and c) (liquid effluent 4) to a solid state allowing its recovery at a subsequent step e) of solid-liquid separation. This liquid-solid phase change can advantageously be implemented by means of one or more crystallization or precipitation operation(s) according to techniques known to those skilled in the art such as, and in a non-exhaustive manner, cold wall crystallization, the use of a precipitating agent, batch distillation, etc., said techniques being used alone or in combination, in any order.

[0127] This liquid-solid phase change step d) therefore makes it possible to produce at least one mixed stream comprising an aqueous liquid phase depleted in phthalic acid and a second solid phase enriched in phthalic acid. This is stream 5 in Figures 1 and 4, stream 19 in Figures 2 and 5, and stream 22 in Figures 3 and 6. In the embodiment shown in Figure 3, which is one of the preferred embodiments according to the invention, the aqueous liquid effluent enriched in AP 21 is for example cooled to a temperature between 10°C and ambient temperature, for example a temperature of 15°C, via the implementation of cold wall crystallization so as to cause precipitation of the AP to obtain the mixed stream 22 comprising AP in the solid state.

[0128] Step e) of solid-liquid separation for the recovery of AP

[0129] The method according to the invention comprises a step e) of solid-liquid separation carried out on the mixed stream (5, 19 and 22 depending on the embodiments) resulting from step d), comprising a second solid phase enriched in phthalic acid (phthalic acid in the solid state), to produce at least one solid stream comprising AP 6 in order to recover the AP and a liquid effluent (11, 14 or 20 depending on the embodiments) comprising residual water resulting from the hydrolysis step b).

[0130] Residual water may still contain dissolved phthalic acid in low concentration.

[0131] Solid flux AP 6 is in powder form.

[0132] The physical solid-liquid separation of the mixed flow from step d) can advantageously be implemented according to techniques known to those skilled in the art such as, but not limited to, filtration, centrifugation, for example the use of hydrocyclones, electrostatic precipitation or decantation, said techniques being used alone or in combination, in any order.

[0133] In the embodiment shown in Figure 3, which is one of the preferred embodiments according to the invention, the mixed effluent 22 is for example treated by centrifugation so as to obtain the solid stream comprising the AP 6 and an aqueous stream 14, preferably returned in whole or in part to step b) of the process according to the invention.

[0134] According to one or more embodiments (not shown in the figures), steps d) and e) are implemented within the same unit operation.

[0135] Phthalic anhydride can be produced by sending the solid stream of AP 6 to a dehydration step, where phthalic anhydride can be the starting compound used to synthesize PVC phthalates. Dehydration of AP to form phthalic anhydride is known, and such a dehydration step can be carried out as described, for example, in US3720692.

[0136] Step g) removal of the extraction solvent before step c) (optional)

[0137] According to the first variant of the process of the invention, the process according to the invention preferably comprises a step g) allowing the elimination of at least a portion of the extraction solvent 7, and at best of all of said solvent, used during step a). This step g) is carried out downstream of the solid-liquid separation step c) and upstream of step b) of the process according to the invention, as illustrated for example in Figures 1 to 3). The elimination, at most total, of the extraction solvent allows the obtaining of a liquid effluent 12 at least concentrated in the phthalate(s) extracted in step a) and at best free of the extraction solvent. This liquid stream concentrated in said phthalate 12 is sent to step b).This step g), while allowing the continued operation of a liquid effluent of rheology compatible with the various embodiments according to the invention, promotes the hydrolysis reaction involved in step b) by a favorable shift in the thermodynamic equilibrium of said reaction in the direction of the formation of the AP. In addition, the extraction solvent thus eliminated can be recovered and returned at least to step a) of the process according to the invention. Preferably, only a portion of the extraction solvent is eliminated in this step.

[0138] The removal of part or all of the extraction solvent 7 is advantageously carried out by evaporation according to techniques known to those skilled in the art such as distillation, evaporation, liquid-liquid separation, etc., said techniques being used alone or in combination, in any order. Step g) may thus comprise a gas-liquid separation, preferably the evaporation of the solvent, for example using a succession of expansion tanks.

[0139] When the extraction solvent comprises at least one short, linear or branched aliphatic chain alcohol of empirical formula Cnh n+iOH with n < 4, said extraction solvent is preferably removed.

[0140] In the embodiment shown in Figure 3, which is one of the preferred embodiments according to the invention, the liquid stream 3 containing the phthalate(s) extracted in step a) and resulting from step c) is treated by evaporation during the optional step g) so as to obtain the liquid stream 12 concentrated in said phthalate(s), itself sent to step b). The extraction solvent is typically a solvent immiscible with water, for example toluene, and is not completely eliminated during step g), which makes it possible in the downstream steps of the process to benefit from this immiscible character for the separation of the components of the stream 12, and in particular of the phthalic acid from the other compounds. The extraction solvent thus recovered is preferably recycled, at least in part, in the form of the stream 13, in step a).

[0141] Separation step(s) f) (optional)

[0142] Depending on the choice of extraction solvent and the various embodiments of the process according to the invention, with in particular integration of the optional step g) described above, a liquid effluent 4 enriched in at least the AP is obtained at the end of step b) of said process. This liquid effluent 4 comprises an aqueous phase comprising the AP. The chemical nature and the quantity of the other constituents of said stream are variable depending on the embodiments chosen and can have an impact on the nature of the medium, typically the liquid effluent 4 can be single-phase or two-phase. The process according to the invention can thus comprise one or more optional liquid-liquid and / or liquid-gas separation steps located upstream and / or downstream of steps d) and e) of the process according to the invention for:

[0143] - promote the implementation of steps d) and e), and therefore the obtaining of at least one solid flow comprising AP 6 in order to recover the AP, and / or

[0144] - recover and return to the process the residual water from hydrolysis step b) (stream 14) and the extraction solvent (stream 15), and / or

[0145] - recover and return to the process the possibly unconverted and / or partially converted phthalate(s) resulting from hydrolysis step b), and / or

[0146] - recover alcohols, by-products of the chemical hydrolysis reaction, which can be recovered or burned to produce part of the energy required for the process according to the invention.

[0147] The optional separation step(s) f) may be carried out according to methods well known to those skilled in the art such as, but not limited to, distillation, decantation, evaporation, liquid-liquid extraction, etc., carried out alone or in combination. The operating conditions of this or these steps (temperature, pressure, etc.) are determined according to the separation method chosen. In particular, one or more separation steps f) (see steps fl) to f4) described below) are carried out directly upstream of step d) or downstream of step e) to separate at least one aqueous liquid phase (i.e. which contains water) from other compounds in the liquid or gas phase.

[0148] Some of said compounds which comprise extraction solvent, or phthalate extracted in step a) and not converted and / or partially converted in step b), or water, can advantageously be recycled respectively to step a) or to step b).

[0149] In Figures 1 to 6, different separation steps f1), f2), f3), f4) and f5) are shown, and described in more detail below.

[0150] Steps fl) and f2) are carried out directly downstream of step e). Steps f3) and f4) are carried out directly upstream of step d). Step f5) is a separation step directly downstream of separation step f4).

[0151] According to one or more embodiments of the invention, and provided that the extraction solvent has not been completely eliminated from the stream 3 via step g) when it is implemented, said solvent and the operating conditions of the process of the invention are chosen so that said solvent and the water 9 form a single liquid phase of the effluent 4 containing at least the AP, the possible other components: phthalates extracted in step a) and not converted, API, and AL.

[0152] According to this or these embodiments, represented in figures 1 and 4, the flows obtained at the end of step e) comprise the solid flow comprising the AP 6 and a liquid effluent 11 comprising residual water (from step b)), said liquid effluent 11 being in the form of a single-phase liquid phase.

[0153] The choice of a solvent miscible with water, such as MEK or a MEK / methanol mixture, can make it possible to obtain a single-phase liquid phase for effluents 4 and 11 from steps b) and e) of the process respectively.

[0154] Said single-phase liquid effluent 11 comprises water (in particular residual water from step b)), extraction solvent, and optionally the phthalates extracted in step a) and not converted, the APIs and the LAs. From said single-phase liquid effluent 11, it is then possible, according to separation methods well known to those skilled in the art, for example distillation with lateral withdrawal or liquid-liquid extraction, to separate, during a step fl), preferably directly downstream of step e), not only the extraction solvent (stream 15) and the residual water (effluent 14), but also the LAs (stream 17) and very advantageously the APIs with optionally the phthalates extracted in step a) and not converted (stream 16).

[0155] According to the first and second variants of the process according to the invention, the stream 15 comprising extraction solvent and the stream 14 comprising water can then be advantageously returned respectively to step a) and to step b) of the process according to the invention. Similarly, the stream 16 comprising the APIs with possibly the phthalates extracted in step a) and not converted is advantageously returned to step b), so as to continue the chemical reactions leading to the AP and thus improve the AP yield.

[0156] According to a variant (not shown), the extraction solvent can be extracted in its entirety from the stream 3 in step g), and step b) can be implemented by a person skilled in the art so that the effluent leaving said step b) forms a single liquid phase containing at least residual water and the AP, and optionally the phthalates extracted in step a) and not converted, the APIs, and the ALs. The steps implemented downstream are identical to steps d), e) and fl) described above in relation to FIG. 1, except that the extraction solvent is no longer present downstream of step g), and therefore there is no production of a stream 15 in step fl).According to one or more embodiments of the invention, and provided that the extraction solvent has not been completely removed from the stream 3 during step g) when it is implemented, said solvent and the operating conditions of the process of the invention are chosen so that said solvent and the water 9 form a first liquid phase of the effluent 4 containing at least the AP, a second liquid phase immiscible with the first also being formed and comprising at least the phthalates extracted in step a) and not converted.

[0157] According to this or these embodiments, represented in figures 2 and 5, it is possible to separate in a step f3), preferably directly upstream of step d), at least the two preceding immiscible phases so as to obtain at least one stream 18 comprising the first liquid phase containing the water and the solvent as well as the AP, and a stream 16 comprising the second liquid phase immiscible with the first, which is an organic phase, containing at least the APIs and the phthalates extracted in step a) and not converted.

[0158] The choice of a water-miscible solvent, such as MEK or a MEK / methanol mixture, is compatible with obtaining two immiscible liquid phases in effluent 4.

[0159] Stream 16 is advantageously returned to step b) of the process according to the invention, so as to continue the chemical reactions leading to the AP and thus improve the AP yield. The streams obtained at the end of step e) then comprise the solid stream comprising the AP 6 and a liquid effluent 20 comprising residual water (from step b)), said liquid effluent 20 being in the form of a single-phase liquid phase comprising water and extraction solvent. From said single-phase liquid effluent 20, it is then possible, according to separation methods well known to those skilled in the art, for example distillation), to separate in a step f2), preferably directly downstream of step e), the extraction solvent (stream 15) and the water (stream 14), which can advantageously be reused respectively in step a) and in step b) as described above in relation to FIGS. 1 and 4.According to this or these embodiments, and depending on their chemical nature, the ALs can be present indifferently in the stream 16 resulting from the separation step f3) and / or the stream 20 resulting from step e), and be eliminated accordingly in the form of a stream 17 leaving the process, before recycling the various streams 14, 15 and 16.

[0160] According to a variant (not shown), the extraction solvent can be extracted in its entirety from the stream 3 in step g), and step b) can be implemented by a person skilled in the art so that the effluent leaving said step b) comprises at least a first liquid phase containing at least the AP and a second liquid phase immiscible with the first containing the phthalates extracted in step a) and not converted and the ALs. The steps implemented downstream are identical to steps d), e), f2) and f3) described in relation to FIG. 2, except that the extraction solvent is no longer present downstream of step g), and therefore there is no production of a stream 15 in step f2).

[0161] According to one or more embodiments of the invention, and provided that the extraction solvent has not been completely removed from the stream 3 in step g) when it is implemented, said solvent and the operating conditions of the process of the invention are chosen so that said solvent and the water 9 form two immiscible liquid phases of the effluent 4. The first of these liquid phases is an aqueous phase containing at least the AP; it comprises the residual water from step b) and the AP, and is immiscible with the extraction solvent. The second of these liquid phases is an organic phase comprising the extraction solvent, and containing at least the phthalates extracted in step a) and not converted, the APIs and the ALs.

[0162] According to this or these embodiments, represented in figures 3 and 6, it is possible to separate in a step f4), preferably directly downstream of step d), at least the two preceding immiscible phases so as to obtain at least one stream 21 comprising the aqueous liquid phase containing the AP and at least one stream 23 comprising the organic phase containing the extraction solvent.

[0163] The choice of an extraction solvent immiscible with water, such as toluene, can make it possible to obtain said first aqueous liquid phase immiscible with the organic liquid phase comprising the extraction solvent forming the effluent 4.

[0164] The implementation of steps d) and e) from the stream 21 leads to the obtaining of at least the solid stream comprising the AP 6 and at least the aqueous stream 14, preferably returned in whole or in part to step b).

[0165] From the organic liquid stream 23, it is possible, according to separation methods well known to those skilled in the art, for example well-known liquid-liquid or liquid-gas separation methods such as distillation, decantation, evaporation, liquid-liquid extraction, etc., carried out alone or in combination, to separate during a step f5) not only the extraction solvent (stream 15), but also the LAs (stream 17) and very advantageously the APIs with possibly the phthalates extracted in step a) and not converted (stream 16). Stream 16 can advantageously be returned to step b), so as to continue the chemical reactions leading to the AP and thus improve the AP yield. Similarly, stream 15 can advantageously be returned to step a).

[0166] Recycling process

[0167] The present invention also relates to a method for recycling a PVC-based object containing at least one phthalate, said recycling method comprising:

[0168] - packaging the PVC-based object comprising at least one grinding or shredding of the PVC-based object to form a PVC charge in the form of particles;

[0169] - recovering the AP and a reusable target PVC plastic from said PVC filler in particulate form according to the method according to the first aspect of the invention described above in detail.

[0170] The stage of conditioning the PVC-based object may include the various stages detailed above for the preliminary conditioning of the PVC load before its introduction in stage a).

[0171] It is advantageous, from a circular economy perspective, to use the phthalic acid obtained by the recovery process described to obtain again phthalates suitable for the formulation of soft PVC plastics and / or to use the target PVC plastic produced by the recovery process according to the invention to manufacture a new object based on soft PVC. Such an object can then be manufactured more easily so as to meet the standards in force with regard to phthalates, and include only REACH compatible phthalates, by being manufactured from raw materials meeting or adapted to meet said standards, i.e. the recovered target PVC plastic free of non-REACH compatible phthalates, and the AP allowing the production of REACH compatible phthalates.

[0172] Manufacturing process

[0173] The present invention also relates to a method of manufacturing a flexible PVC-based object comprising a recycled PVC plastic and / or a phthalate manufactured from phthalic acid recovered by the method according to the first aspect of the invention.

[0174] Such a manufacturing process typically comprises a step of recovering phthalic acid and a reusable target PVC plastic from a PVC feedstock, as detailed above, then a step of mixing said reusable target PVC plastic with additives, then a step of shaping said mixture. Example

[0175] This example illustrates the invention without limiting its scope, and illustrates in particular the extraction of a phthalate contained in a PVC plastic and the conversion of the phthalate into phthalic acid in the presence of a catalyst and water.

[0176] 18.2 g of a PVC plastic filler (from PVC-based objects of the "medical tube" type), in the form of extrudates of average size of 2 mm, containing 4.4 g of di-decyl phthalate (DIDP), are introduced into a reactor stirred by a mechanical stirring system, of the paddle type. 53.19 g of water and 35.11 g of acetophenone (organic extraction solvent) are then added, the acetophenone / water mass ratio being 0.66, the acetophenone / DIDP molar ratio being 29.7 and the water / DIDP molar ratio being 300. 0.13 g of catalyst which is p-toluene sulfonic acid (PTSA) are then added to the previous mixture so that the PTSA / DIDP mass ratio is 3%.

[0177] The reactor is sealed, purged with nitrogen and then heated to 100°C with an autogenous pressure of around 1.2 MPa and maintained under these conditions for 4 hours with stirring at 1000 rpm.

[0178] After 4 hours, a solid and a liquid are obtained which are separated while hot at 65°C, which makes it possible to obtain a PVC solid with a very low phthalate content on the one hand and a liquid on the other hand. This liquid is then cooled to 10°C, which leads to the precipitation of a second solid mainly consisting of phthalic acid. The suspension obtained is filtered. The remaining liquid (filtrate) is then left to react three times again under the same conditions as previously described. At the end of each reactive step, a precipitation step, identical to that specified above, makes it possible to extract a solid phase mainly consisting of phthalic acid, increasing the yield of final phthalic acid. At the end of this protocol, the secondary solid fractions are combined and analyzed.

[0179] Gas chromatography with flame ionization detection (GC-FID) analyses of the secondary solid phase show that it contains 1.47 g of phthalic acid resulting from the conversion of DIDP and 0.30 g of monomethyl phthalate (2-(isodecoxycarbonyl)benzoic acid) resulting from a partial hydrolysis of DIDP. The liquid phase contains 2.96 g of isodecanol (C10H22O) resulting from the hydrolysis reaction of DIDP. Identification was made possible by comparing the retention times of pure analytical standards and quantification was carried out from the determination of the response coefficients resulting from the analysis of these same standards.

[0180] The solid obtained was prefractionated by preparative SEC size exclusion chromatography equipped with dual optical detection (UV / Visible) and refractometry (RI). The fractions from the collection were analyzed by high performance liquid chromatography (HPLC) equipped with quantitative UV-Visible optical detection. The results indicate the presence of DIDP in the target PVC plastic at a content lower than 1000 ppm, which is in compliance with current European regulations.

[0181] These results show that phthalate-free PVC is obtained in accordance with the invention, and that DIDP has been converted to 99.9%. In this example, the extraction of DIDP and its conversion are carried out in the same step.

Claims

Claims 1. A method for recovering phthalic acid and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, comprising the following steps: a) a solid-liquid extraction of said PVC feedstock in the form of particles (1) by bringing said particles of the PVC feedstock into contact with at least one organic extraction solvent (7) of said phthalate, to produce a liquid phase enriched in said phthalate and a first solid phase comprising PVC plastic depleted in said phthalate; b) a chemical transformation of said phthalate extracted in step a) into phthalic acid of formula CgH^COOH by hydrolysis using water to produce an aqueous phase comprising said phthalic acid;c) a solid-liquid separation between said first solid phase and said liquid phase enriched in said phthalate or said aqueous phase comprising said phthalic acid to produce at least one solid stream comprising the PVC plastic depleted in said phthalate (8) in order to recover said target PVC plastic; d) a phase change of the phthalic acid from the dissolved state in said aqueous phase to a solid state to produce a mixed stream comprising an aqueous liquid phase depleted in phthalic acid and a second solid phase enriched in phthalic acid (5, 19, 22); e) a solid-liquid separation between the phthalic acid in the solid state from step d) and the aqueous liquid phase of said mixed stream to produce a solid stream of phthalic acid (6) and a liquid effluent (11, 14, 20) comprising residual water from step b).; 2. Method according to claim 1, in which steps a) and b) are implemented within the same unit operation producing a stream (24) comprising at least said aqueous phase comprising said phthalic acid and said first solid phase.

3. Method according to claim 1, in which steps a) and b) are the subject of two separate unit operations, step a) producing a flow (2) comprising said liquid phase enriched in said phthalate and said first solid phase sent to step c) carried out between steps a) and b), step c) producing said flow comprising the PVC plastic depleted in said phthalate (8) and a first liquid flow (3) comprising said liquid phase enriched in said phthalate.

4. Method according to claim 3, comprising a step g) of removing at least part of the organic extraction solvent from said first liquid stream (3) prior to step b), to produce a first concentrated liquid stream comprising said phthalate sent to step b).

5. Process according to claim 4, in which the organic extraction solvent recovered in step g) is recycled at least in part to step a).

6. Method according to any one of the preceding claims, wherein said solid stream comprising the phthalate-depleted PVC plastic (8) separated in step c) is recycled at least in part to step a).

7. Method according to any one of the preceding claims, in which said organic extraction solvent (7) is chosen from the list consisting of ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, alcohols with a short, linear or branched aliphatic chain, of empirical formula Cnh n+iOH with n < 4, n being a non-zero natural integer, and mixtures thereof.

8. The method of claim 7, wherein said organic extraction solvent (7) is selected from the list consisting of methyl ethyl ketone, diethyl ketone, 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, acetophenone, tetrahydrofuran, cyclohexane, xylenes, toluene, methanol, ethanol, n-propanol, 17-propanol, and mixtures thereof, and preferably is selected from said alcohols, ketone / alcohol mixtures, hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylenes, methoxycyclopentane, methyl isobutyl ketone, cyclopentanone, acetophenone, and preferably said organic extraction solvent (7) is toluene, methyl ethyl ketone, acetophenone or a methyl ethyl ketone / methanol mixture.

9. Process according to any one of the preceding claims, in which the hydrolysis in step b) is carried out in the presence of an acid hydrolysis catalyst, preferably an acid homogeneous catalyst chosen from the list consisting of inorganic Brônsted acid catalysts, preferably hydrochloric acid, sulfuric acid, phosphoric acid, organic Brônsted acid catalysts, preferably p-toluenesulfonic acid, and Lewis acid catalysts, preferably AIF3, or an acid heterogeneous catalyst chosen from the list consisting of aluminas, chlorinated aluminas, fluorinated aluminas, mesoporous aluminosilicates, zeolites and their mixtures with other oxides, ion exchange resins (H+), preferably sulfonic resins.

10. Process according to any one of the preceding claims, wherein the hydrolysis in step b) is carried out at a temperature between room temperature and 150°C, preferably between 40°C and 130°C, at a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, and for a time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours.

11. Process according to any one of the preceding claims, in which the hydrolysis in step b) is carried out so that the molar ratio between the quantity of water and the quantity of said phthalate extracted in step a) is between 100 and 9000.

12. Method according to any one of the preceding claims, in which step d) comprises at least one step of precipitation of the phthalic acid, preferably comprising cooling to a temperature between 10°C and room temperature.

13. Method according to any one of the preceding claims, in which said at least one phthalate of said PVC filler is a phthalate of empirical formula CSH4(COORI)(COOR2) whose ester groups are in the ortho position of the benzene ring, Ri or R2 being independently chosen from one of the elements of the group consisting of a linear or branched or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, Ri and / or R2 preferably comprising between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.

14. A method according to any one of the preceding claims, wherein said target PVC plastic is free of said phthalate, and preferably comprises less than 0.1% by weight in total of phthalates selected from the list consisting of dibutyl phthalate, dioctyl or diethylhexyl phthalate, benzyl butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

15. Process for recycling a PVC-based object containing at least one phthalate comprising: - packaging said PVC-based object comprising at least one grinding or shredding of said PVC-based object to form a PVC charge in the form of particles; - recovering phthalic acid and a reusable target PVC plastic from said particulate PVC feedstock according to any one of claims 1 to 14.

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