Methods for extraction of phthalates contained in PVC plastics and their conversion by alcoholysis and hydrolysis.

Abstract

The present invention relates to a method for obtaining phthalic acid and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, said method comprising: a first series of steps for obtaining a target PVC plastic and at least one easily separable dialkyl phthalate intermediate, in particular by carrying out an alcoholysis reaction; and a second series of steps comprising steps g) and h), in particular for carrying out a hydrolysis reaction of the dialkyl phthalate generated during the first series of steps, which finally makes it possible to recover the phthalic acid in the form of a solid phthalic acid stream.

Description

[Technical Field]

[0001] The present invention relates to the field of recycling of poly(vinyl chloride) (PVC) based plastics, and in particular to a method for extracting and converting phthalates, plasticizers present in the composition of PVC, by a combination of alcoholysis and hydrolysis chemical reactions. More precisely, the present invention relates to a method for recovering phthalic acid (PA) and reusable target PVC plastics from PVC feedstock containing at least one phthalate. [Background technology]

[0002] By definition, plastics are mixtures of a base polymer material and numerous additives, the assembly of which can be molded or finished (generally under elevated temperature and / or pressure) to produce semi-finished products or articles. In commonly accepted practice, plastics are referred to by the name of the polymer from which they are made. Thus, poly(vinyl chloride) (PVC) plastics actually represent the combination of PVC polymer, referred to in the remainder of this specification as "PVC resin," with various additives selected based on the functionality required of the plastic. The additives can be organic molecules or polymers, or inorganic (nano)particles, and are used depending on the properties they impart to the PVC resin: resistance to heat, light, or mechanical stress (stabilizers), flexibility (plasticizers), processability (lubricants), color (dyes / pigments), etc.

[0003] There are several methods for recycling PVC plastics: the "traditional" method with simple mechanical recycling of the plastics, methods that involve modification of their composition, or even chemical transformation of the compounds of which they are made.

[0004] Since the mid-20th century, chemical recycling of PVC plastics has been the subject of numerous studies, directed to dissolving PVC resins with various proportions of additives in a first step, and then recovering the resin in a second step using various chemical methods (precipitation, evaporation, etc.) in the presence of all or part of the soluble additives. For example, Patent Documents 1 to 3 are each directed to recycling various PVC-based articles (flexible or rigid pipes, window frames, cables, etc.), and in particular fiber-reinforced PVC-based articles (tarpaulins, floor coverings, etc.), according to a method involving a first step of dissolving the PVC resin and soluble additives in an organic solvent, followed by a second step of steam precipitation, which allows the recovery of the resin and most of the additives.

[0005] However, it is not always desirable to retain these additives in the PVC that is recovered and recycled in this way. For example, the impact of changing regulations regarding them over time is significant. Therefore, certain plasticizers from the phthalate family, which were particularly widely used to formulate "flexible" PVC about 40 years ago, have been gradually subject to authorization in Europe since the end of 2006 under the REACH regulation, which is aimed at establishing the safety of the production and use of chemicals in European industry, and have ultimately been gradually removed from the list of permitted additives. This applies, in particular, to the following non-exhaustive list of phthalates: dibutyl phthalate (DBP), dioctyl or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentylisopentyl phthalate, dihexyl phthalate, etc.

[0006] These new regulations now prohibit the presence of such compounds in recycled raw materials (RRM). Given the often very long lifespan (decades) of PVC-based articles, PVC-based articles compounded before the end of 2006 and now at the end of their life cannot be recycled via regeneration methods that result in the retention of these prohibited additives, whether said methods are conventional, e.g., mechanical recycling methods, or non-conventional, e.g., the dissolution / precipitation methods exemplified above.

[0007] Furthermore, the phthalate plasticizers currently used in Europe (REACH-compliant phthalates) and in other parts of the world represent high-value-added additives and are not upgraded when they remain in the PVC recycled raw material. The reason for this is that they are expensive products, are present in significant proportions (tens of percent) in the initial PVC formulation, and are not able to directly impart ad-hoc flexibility to the PVC RRM. A significant supply of "fresh" plasticizers is essential for the reusability of recycled PVC materials.

[0008] Extraction of phthalate-type additives from PVC-based articles for removal or upgrading is therefore a major challenge for optimized recyclability of PVC.

[0009] Some methods involving a step of dissolving PVC resin have been adapted to enable this extraction. For example, both Patent Documents 4 and 5 propose a first step of dissolving PVC resin and at least a phthalate-type additive with a first organic solvent, followed by a second step of liquid-liquid extraction of the phthalate from the previously obtained solution through the use of a second organic solvent different from the first organic solvent. Patent Document 6 discloses another possible implementation by dissolving PVC resin and at least a phthalate-type additive through the use of a solvent under supercritical conditions and recovering the phthalate in this same solvent after the "breakdown" of the supercritical conditions.

[0010] The removal or upgrading of phthalate-type additives from PVC plastics may be carried out without going through a preliminary step of dissolving said plastics, in particular through direct extraction of said phthalates from the solid polymer matrix with a suitable organic solvent, as fully indexed in Non-Patent Document 1. The challenge lies in optimizing the extraction conditions (nature of the solvent, contact time, temperature, pressure, etc.) to achieve the best possible yield of extracted phthalates. This methodology for the removal of phthalates from PVC plastics is often used, in particular, to detect and analytically quantify these specific additives in said plastics, although, to the applicant's knowledge, no method for regenerating PVC-based articles involves this technology.

[0011] Although crucial for ensuring efficient recycling of PVC plastics and obtaining reusable recyclable PVC, the extraction of phthalate-type plasticizers is insufficient to ensure the economic viability of a method for recovering PVC-based articles. The main reason often cited is the difficulty in finding an economically viable balance between the costs of the individual operations performed in the recovery process and the resale cost of the resulting product (which corresponds to added value). The product naturally consists of PVC-based recyclable material that does not contain upgradeable phthalates and the extracted phthalates, which themselves have little upgradeability. Specifically, any recovery process involving the extraction of phthalates from PVC-based articles would result in the recovery of a mixture of phthalates, which may contain phthalates that are not "REACH-compliant." Upgrading of the non-REACH-compliant phthalates would naturally be excluded, and the phthalates would have to be treated as designated waste, which would incur additional costs. While advantageous in itself, upgrading of REACH-compliant phthalates is difficult in practice because it involves technically complex and expensive separation / purification processes.

[0012] In the past, several studies focused on contacting phthalate-containing PVC plastics with a highly concentrated aqueous base solution (essentially NaOH) to convert the phthalates and extract the resulting product(s): salts of phthalic acid and, depending on the associated operating conditions, salts of possible decomposition products. This chemical reaction was carried out together with or upstream of the PVC dechlorination process, allowing for the energy recovery by obtaining a non-chlorinated residue that was almost free of phthalates. Carrying out such a radio-frequency or microwave-assisted process upstream of dechlorination has the advantage of recovering upgradeable phthalates, as investigated in the following documents: Patent Document 7; Non-Patent Documents 2 and 3. However, this embodiment has the following major drawbacks: it requires the use of a highly concentrated base, which results in the production of the relevant salts rather than phthalic acid, does not optimize the extraction of phthalates, and does not meet the REACH regulations, applicable since 2006, regarding the recovery of upgradeable compounds as recycled materials. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] European Patent No. 0945481 [Patent Document 2] European Patent No. 1268628 [Patent Document 3] European Patent No. 2276801 [Patent Document 4] European Patent No. 1311599 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-191586 [Patent Document 6] Japanese Patent Application Laid-Open No. 2007-092035 [Patent Document 7] Patent No. 3929352 [Non-patent literature]

[0014] [Non-Patent Document 1] Ugduler et al., "Challenge and opportunities of solvent-based additive extraction methods for plastic recycling", 2020, Waste Management, 104, 148-182 [Non-patent document 2] 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 [Non-patent document 3] SM Shin et al., 2011, "Elution Behavior of Additive Agent from Flexible PVC", 2001, Chawon Rissaikuring, 10, 6, 3 Summary of the Invention [Means for solving the problem]

[0015] (Summary of the Invention) The present invention aims to at least partially overcome the problems of the prior art and is directed in particular to providing a method for the regeneration of PVC-based articles that allows the processing of any type of PVC feedstock containing phthalates and its conversion into two end products that can be upgraded as raw materials: phthalic acid and recyclable PVC plastic that is phthalate-free, in particular free of undesirable phthalates, typically those subject to authorization under the European REACH regulation.

[0016] Phthalic acid is used, inter alia, to produce its derivatives, phthalates, which can be used as raw materials for the production of other chemicals in fields other than plastic compounding, for example, to produce dyes, fragrances, sweeteners, such as saccharin, etc.

[0017] Therefore, in order to achieve at least one of the above mentioned objectives, inter alia, the present invention proposes, according to a first aspect, a method for recovering phthalic acid (PA) and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate in two steps: - a first series of steps: steps a) to d) and optional steps e), f1), f2); obtaining a target PVC plastic and, in particular, at least one dialkyl phthalate intermediate product by carrying out an alcoholysis reaction; the dialkyl phthalate intermediate product can be easily separated, - a second series of steps: steps g) and h); in particular carrying out a hydrolysis reaction of the dialkyl phthalates generated during the first series of steps, which allows the phthalic acid to be recovered in order to finally obtain at least one solid phthalic acid stream.

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

[0019] More specifically, the first series of steps comprises the following steps a) to d), which are also described in French patent application filed under No. 21 / 05.299: a) solid-liquid extraction of PVC feedstock in particulate form; n H 2n+1OH (n is a positive integer less than 4 or greater than 8); producing a liquid phase rich in the phthalate and a solid phase comprising the phthalate-depleted PVC plastic; b) the phthalate of formula C6H4(COOC) in the liquid phase n H 2n+1 ) 2 into dialkyl phthalates by transesterification (alcoholysis) with said alcohol; enriching said liquid phase with said dialkyl phthalates; c) solid-liquid separation between the solid phase and the liquid phase; producing at least one solids stream comprising the phthalate-depleted PVC plastic and recovering the target PVC plastic; d) liquid phase (gas-liquid or liquid-liquid) separation to produce at least a first liquid effluent comprising the dialkyl phthalate and a second liquid effluent comprising the solvent.

[0020] The first series of steps may comprise the following steps e), f1), f2), which are also described in the French patent application filed under No. 21 / 05.299: e) optionally purifying the first liquid effluent comprising said dialkyl phthalate obtained in step d) from the phthalates partially converted and / or not converted in step b), and optionally from soluble impurities, to produce a liquid product consisting essentially of said dialkyl phthalate and a liquid residue comprising said phthalates partially converted and / or not converted in step b) and optionally soluble impurities; f) optional additional step f1) and / or optional additional step f2); the phthalates not converted and / or partially converted in step b) are converted with the alcohol to a compound of formula C6H4(COOC n H 2n+1) 2 by transesterification; and the step f1) is carried out between the steps c) and d) by sending the liquid phase obtained at the completion of all of the steps a), b) and c) to a first additional transesterification reactor to convert the dialkyl phthalate of the formula C6H4(COOC) n H 2n+1 and producing a second liquid stream enriched in the dialkyl phthalate of formula C6H4(COOC), which is sent to step d), and step f2) is carried out after step e) by sending the liquid residue to a second additional transesterification reactor to produce a dialkyl phthalate of formula C6H4(COOC), n H 2n+1 ) producing a third liquid stream enriched in said dialkyl phthalate of step 2, said third liquid stream being sent back to step d).

[0021] The second series of steps of the method according to the invention comprises the following steps g) and h): g) chemical conversion of the phthalates obtained in step d) or in optional step e) by hydrolysis with water to phthalic acid of formula C6H4(COOH)2; generating at least one effluent comprising an aqueous phase enriched in said phthalic acid; h) separating the effluent obtained in step g), resulting in at least one solid stream of phthalic acid (phthalic acid in solid form, for example in the form of a powder, in particular forming flakes or needles).

[0022] One advantage of the present invention lies in the ability of the method to convert, by chemical transesterification (alcoholysis), a mixture of phthalates that is initially trapped in the polymer matrix of various articles based on PVC plastic, regardless of the composition of said mixture (i.e. regardless of the nature and origin of the various phthalates), and despite the possible presence of numerous other additives, into a single product, which is DAP, which itself may then be isolated and then chemically converted by a hydrolysis reaction into phthalic acid, which is a precursor product of several REACH-compliant phthalates that are still very widely used in many fields, such as in the field of plastics processing.

[0023] The generation of phthalic acid via a single dialkyl phthalate formed in steps a) to d) and, optionally, step e) and step f1) and / or step f1) also ensures improved purity compared to other conventional methods for producing phthalic acid. Specifically, obtaining only one dialkyl phthalate product from a mixture of phthalates makes its separation easier. This separation makes it possible to isolate this dialkyl phthalate and then perform a hydrolysis reaction on a reaction mass that no longer contains many undesirable compounds present in the PVC or during the extraction process (additives, alcohol from alcoholysis, PVC, degradation products). This ensures the generation of phthalic acid in high purity by hydrolysis while simultaneously limiting the number of separate steps associated with separation / purification operations and, therefore, costs. Furthermore, generating phthalic acid via a hydrolysis reaction can also eliminate the need for stoichiometric amounts of base (NaOH) and acid, as opposed to saponification. The method according to the present invention is therefore fully consistent with circular economy strategies.

[0024] According to a first variant, steps a) and b) are carried out in the same separate operation, resulting in a stream comprising an aqueous phase comprising phthalic acid and a first solid phase comprising PVC plastic depleted in said phthalates.

[0025] According to a second variant, instead of the first variant, steps a) and b) form the object of two separate and distinct operations, step a) producing a stream comprising said liquid phase and said solid phase, which stream is sent to a solid-liquid separation step c) carried out between steps a) and b), step c) producing said stream comprising said phthalate-depleted PVC plastic and a first liquid stream comprising said liquid phase, which first liquid stream is sent to step b). According to one or more embodiments, the hydrolysis in step g) is carried out in the presence of an acid hydrolysis catalyst, which is preferably a homogeneous acid catalyst or a heterogeneous acid catalyst, wherein the homogeneous acid catalyst is selected from the list consisting of inorganic Bronsted acid catalysts, preferably hydrochloric acid, sulfuric acid or phosphoric acid, organic Bronsted acid catalysts, preferably p-toluenesulfonic acid, and Lewis acid catalysts, preferably AlF3, and the heterogeneous acid catalyst is selected from the list consisting of alumina, chlorinated alumina, fluorinated alumina, mesoporous aluminosilicates, zeolites and mixtures thereof with other oxides, (H + ) ion exchange resins, preferably sulfone resins.

[0026] According to one or more embodiments, the hydrolysis in step g) 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, for a period of 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0027] According to one or more embodiments, the hydrolysis in step g) is carried out such that the molar ratio of the amount of water to the amount of the at least one phthalate to be converted extracted in step a) is between 100 and 9000.

[0028] According to one or more embodiments, step h) comprises a phase change of the phthalic acid from a dissolved state in the aqueous phase to a solid state and a solid-liquid separation to produce the solid stream of phthalic acid and at least one aqueous liquid stream.

[0029] According to one or more embodiments, the first liquid effluent in step d) or the liquid product in optional step e) consists essentially of said dialkyl phthalate.

[0030] According to one or more embodiments, the solids stream containing the phthalate-depleted PVC plastic is at least partially recycled to step a).

[0031] According to one or more embodiments, the second liquid effluent from step d) comprising at least said solvent is at least partially recycled to step a) and / or step b).

[0032] According to one or more embodiments, the alcohol is selected from the list consisting of methanol, ethanol, n-propanol, i-propanol, preferably methanol, or from the list consisting of linear or branched nonanol, linear or branched decanol, linear or branched undecanol, linear or branched dodecanol, preferably nonanol or decanol.

[0033] According to one or more embodiments, the solvent also includes an organic co-solvent, preferably a co-solvent of the formula R'COOC n H 2n+1 wherein R' is an alkyl group, preferably containing 1 to 3 carbon atoms, and an ester having the formula: ether; and the organic co-solvent is preferably selected from the group consisting of methyl acetate, methyl propanoate, and cyclopentyl methyl ether, and the organic co-solvent is added to the alcohol in a weight ratio of the organic co-solvent to the alcohol of 0.01 to 4.

[0034] According to one or more embodiments, the organic co-solvent is selected from the group consisting of methyl acetate, methyl propanoate, and cyclopentyl methyl ether.

[0035] According to one or more embodiments, the alcohol is methanol, the dialkyl phthalate is dimethyl phthalate, and the solvent preferably includes methyl propanoate, such that the weight ratio of the methyl propanoate to the alcohol is 0.01 to 4.

[0036] According to one or more embodiments, the chemical conversion carried out by transesterification in step b) and optionally in step f1) and / or step f2) is carried out as follows: the temperature is between room temperature and 200°C, preferably between 40°C and 180°C; the pressure is between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa; the duration is between 1 minute and 10 hours, preferably between 10 minutes and 4 hours; the molar ratio of the amount of alcohol in the solvent to the amount of phthalate to be extracted or converted is between 2 and 250, preferably between 4 and 90; - carried out in the presence of a transesterification catalyst: the catalyst is preferably selected from the list consisting of homogeneous basic or inorganic or organic Brønsted or Lewis acid catalysts, and heterogeneous catalysts formed by alkaline earth metal oxides, or alkali metal and / or alkaline earth metal carbonates or hydrogen carbonates, or alkali metals supported on alumina or zeolites, or zinc oxide and mixtures thereof with other oxides, or ion exchange resins.

[0037] According to one or more embodiments, the at least one phthalate of the PVC feedstock is a phthalate of empirical formula CH(COOR)(COOR), where the ester group is in the ortho position of the benzene ring, and R or R is independently selected from one of the members 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, and R and / or R preferably contain 1 to 20 carbon atoms, or even 1 to 15 carbon atoms.

[0038] According to one or more embodiments, the target PVC plastic is substantially free of said phthalates, preferably containing less than 0.1 wt. % 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-pentylisopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

[0039] According to a second aspect, the present invention relates to a method for recycling PVC-based articles containing at least one phthalate, the method comprising: - conditioning the PVC-based article; which at least includes milling or shredding the PVC-based article; forming a PVC feedstock in particulate form; - Recovery of phthalic acid and reusable target PVC plastic from said PVC feedstock in particulate form according to the first aspect of the invention.

[0040] According to a third aspect, the present invention also relates to a method for producing flexible PVC-based articles comprising phthalates produced from recycled PVC plastic and / or phthalic acid recovered by the method according to the first aspect of the invention.

[0041] Other objects and advantages of the present invention will become apparent on reading the following description of certain exemplary embodiments of the invention, given by way of non-limiting example, which description will be made with reference to the accompanying drawings, which are described below. DETAILED DESCRIPTION OF THE INVENTION

[0042] (List of drawings) FIG. 1 is a diagram illustrating a part (first series of steps) of a method according to an embodiment of the present invention, comprising steps a), b), c) and d).

[0043] FIG. 2 is a diagram of a part (first sequence of steps) of a method according to another embodiment, comprising steps a), b), c) and d), with separation in step d) of DAP, solvent, alcohol-type by-products obtained in step b), and phthalates partially converted and / or not converted in step b), possibly as a mixture with soluble impurities.

[0044] FIG. 3 is a diagram illustrating a part (first series of steps) of the method according to the embodiment illustrated in FIG. 1 or FIG. 2, including steps a), b), c) and d), and illustrating the implementation of other optional steps of transesterification (f1) and recycling of various streams.

[0045] FIG. 4 is a diagram illustrating part of a method (first series of steps) according to another embodiment of the invention, comprising steps a), b), c) and d), further comprising step e) of purification of the first effluent obtained in step d) comprising DAP.

[0046] FIG. 5 illustrates part of the process (first series of steps) according to the embodiment illustrated in FIG. 4 and illustrates implementation of other optional steps of transesterification (f1; f2) and recycling of various streams.

[0047] FIG. 6 is a diagram illustrating part of a method (first series of steps) according to a preferred embodiment of the invention, comprising the implementation of steps a) and b) in the same individual operation (first variant of the method according to the invention), step e) of purification of the first effluent comprising DAP obtained in step d) and an additional step f2) of transesterification of the residue obtained from step e).

[0048] FIG. 7 is a diagram illustrating part of a method (first sequence of steps) according to another embodiment of the invention, comprising steps a), b), c) and d), in which steps a) and b) form the object of two separate and individual operations (second variant of the method according to the invention), and step c) is carried out between steps a) and b).

[0049] FIG. 8 is a diagram illustrating part of a process (first series of steps) as illustrated in FIG. 7 according to a preferred embodiment, comprising a step e) of purification of the first effluent containing DAP obtained in step d) and an additional step f2) of transesterification of the residue obtained from step e).

[0050] FIG. 9 is a diagram illustrating a schematic of part of the method (second series of steps), including steps g) and h), and optionally showing the use of a water-immiscible extraction solvent in separation step h).

[0051] FIG. 10 is a diagram illustrating part of a method (second sequence of steps) according to another embodiment, in which the separation step h) comprises two substeps h1) and h2).

[0052] FIG. 11 is a diagram illustrating part of a method (second sequence of steps) according to another embodiment, in which the separation step h) comprises two substeps h3) and h4).

[0053] FIG. 12 is a diagram illustrating part of a method (second sequence of steps) according to another embodiment, in which the separation step h) comprises three substeps h5), h6) and h2).

[0054] FIG. 13 is a diagram illustrating part of a method (second sequence of steps) according to another embodiment, in which the separation step h) comprises three substeps h7), h8) and h4).

[0055] In the drawings, the same reference numbers refer to identical or equivalent elements.

[0056] (Description of the embodiment) (term) Certain definitions are provided below, although further details regarding the subject matter defined below may be provided later in this specification.

[0057] The term "PVC-based article" is understood to mean an article (generally a consumer article) that comprises, and preferably consists of, at least one PVC plastic.

[0058] The term "poly(vinyl chloride) plastic," also known as PVC plastic or simply PVC, refers to a combination of PVC polymer, also known as PVC resin, with various additives, which are themselves selected based on the functionality desired for the PVC plastic, and which are themselves selected based on the intended use.

[0059] The PVC polymer is derived from the radical polymerization of vinyl chloride (VCM), itself a monomer obtained from chlorine and ethylene. Depending on the embodiment of the polymerization, four families of PVC resins may be used: 1) suspension PVC or S-PVC resins (suspension polymerization of VCM), 2) emulsion PVC or PVC "paste" resins (emulsion polymerization), 3) bulk PVC or M-PVC resins (bulk polymerization), and 4) hyperchlorinated PVC or C-PVC resins obtained by hyperchlorination as a post-treatment on the resins mentioned above.

[0060] The additives contained in the composition of PVC plastics can be organic molecules or macromolecules or inorganic (nano)particles, and are used depending on the properties they impart to the PVC resin: resistance to heat, light or mechanical stress (stabilizers), flexibility (plasticizers), processability (lubricants), color (dyes / pigments).

[0061] The term "phthalate" refers to a group of chemicals formed by dicarboxylic acid esters of phthalic acid. They consist of a benzene ring and two carboxylic acid ester groups placed in the ortho positions on the benzene ring. They have the following formula:

[0062] [ka]

[0063] or by the empirical formula CH(COOR)(COOR), where R and R are independently selected from one of the group consisting of a linear, branched, or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, wherein the alkyl, alkoxyalkyl, aryl, or alkylaryl chain can typically contain 1 to 20 carbon atoms, and can further contain 1 to 15 carbon atoms. For example, R and / or R can be independently selected from ethyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-octyl, n-nonyl, isononyl, n-decyl, isodecyl, methoxyethyl, and benzyl groups.

[0064] Phthalates are often used as plasticizers for plastics, especially PVC-type plastics, especially to make them flexible.

[0065] As used herein, the term "dialkyl phthalate" (DAP) refers to a compound having the empirical formula C6H4(COOC n H 2n+1 )2, and refers to the product of the empirical formula C6H4(COOR1)(COOR2) of at least one plasticizer of the phthalate type (especially those of the above empirical formula C6H4(COOR1)(COOR2)) present in the PVC-based article. n H 2n+1 It results from the transesterification of OH (n<4 or n>8) with alcohols. Dimethyl phthalate is a good example of DAP.

[0066] As used herein, the empirical formula C n H 2n+1 The definition of the alcohol OH (n<4 or n>8) is the alcohol of the empirical formula C n H 2n+1 O -(n<4 or n>8) and a cationic counterion, including a metallic one, to compensate for the electronegativity of the conjugate base, which is well known to those skilled in the art. The conjugate base is also known as the "alkoxide" form of the alcohol.

[0067] The term "alcohol-type by-product(s) resulting from the alcoholysis reaction" (AL A ) means one or more by-products of formula ROH or ROH, and the empirical formula C of at least one plasticizer of the phthalate type present in the PVC-based article n H 2n+1 The by-products result from the transesterification of OH (n<4 or n>8) with alcohols. R1 and R2 are defined as R1 and R2 for phthalates. As mentioned above, the definition of the alcohol type of formula R1OH or R2OH is given by the empirical formula R1O - or R2O - and its conjugate base.

[0068] The term "intermediate alkyl phthalate obtained from alcoholysis reaction" (IAP A ) or "partially converted phthalate after alcoholysis" has the empirical formula C6H4(COOR1)(COOC n H 2n+1 ) or C6H4(COOR2)(COOC n H 2n+1 ) by-products of at least one plasticizer of the phthalate type (especially those of the empirical formula C6H4(COOR1)(COOR2) as defined above) present in the PVC-based article; n H 2n+1 It results from an incomplete transesterification of OH (n<4 or n>8) with an alcohol. R1 and R2 are defined as for phthalates.

[0069] As used herein, the term "phthalic acid" (PA), also known as benzene-1,2-dicarboxylic acid or o-phthalic acid, refers to the product of empirical formula CH(COOH) resulting from the hydrolysis reaction between DAP and water (HO).

[0070] The term "alcohol-type by-product(s) obtained from the hydrolysis reaction" (AL H ) is the formula C n H 2n+1 refers to the by-product OH (where n<4 or n>8) resulting from the hydrolysis reaction between DAP and HO described above.

[0071] The term "intermediate alkyl phthalate obtained from hydrolysis reaction" (IAP H ) or "partially converted dialkyl phthalate after alcoholysis" has the empirical formula C6H4(COOH)(COOC n H 2n+1 ) (where n<4 or n>8) by-product resulting from the incomplete hydrolysis reaction between DAP and HO as described above.

[0072] The term "reusable target PVC plastic" means "phthalate-free PVC", i.e. a solid comprising at least PVC resin supplemented with at least one of the additives initially present in the PVC plastic of the PVC feedstock treated according to the present invention, from which the phthalates have been extracted according to the present invention and converted at least into the form of PA. The term "phthalate-free" means in particular that the solid PVC obtained as product of the process according to the invention contains less than 0.1% by weight in total of phthalates which require authorization in Europe by the REACH regulation (Annex XIV of Regulation (EC) No 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), and in particular less than 0.1% by weight of phthalates selected alone or in mixtures from the list consisting of the following phthalates: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentylisopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate.

[0073] As used herein, a compound of empirical formula C, optionally supplemented with at least one organic co-solvent, is n H 2n+1 Alcohols of formula OH (where n<4 or n>8) are also called "solvents."

[0074] In this specification, the solvent optionally used during the separation step h) to produce a solid stream of phthalic acid is specifically referred to as the "separation solvent" and is represented by the empirical formula C, optionally supplemented with at least one organic co-solvent. n H 2n+1 Avoid any confusion with alcohols of OH where n<4 or n>8.

[0075] In this specification, the expression "greater than" is understood as strictly greater than and is represented by the symbol ">", and the expression "less than" is understood as strictly less than and is represented by the symbol '<'.

[0076] As used herein, the subscript "n" in chemical formulae cited is a positive integer (i.e., strictly greater than 0). According to the present invention, n is less than 4 or greater than 8, preferably less than or equal to 20, or even less than or equal to 15.

[0077] As used herein, the term "room temperature" (rt) typically refers to a temperature of 20°C ± 5°C, and the term "atmospheric pressure" refers to a pressure of 0.101325 MPa.

[0078] As used herein, the term "to comprise" is synonymous with (has the same meaning as) "to include" and "to contain" and is inclusive or open-ended and does not exclude other elements not recited. It is understood that the term "comprise" includes the exclusive and closed term "consist."

[0079] As used herein, the expression "between A and B" means that both limits of the interval are included in the range of values ​​stated, unless otherwise specified.

[0080] In the present specification, a stream "consisting essentially" of a compound is understood to mean a stream containing at least 95% by weight, preferably at least 98% by weight, more preferentially at least 99% by weight of said compound.

[0081] Herein, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination, e.g., herein, a range of preferred pressure values ​​can be combined with a more preferred range of temperature values.

[0082] In the following text, specific embodiments of the present invention may be described, which may be implemented separately or in combination together, without limiting the combination, if technically feasible.

[0083] The following description of the method according to the invention refers to the diagrams of FIGS. 1 and 13, which illustrate different embodiments of the method according to the invention.

[0084] According to the present invention, a method for recovering phthalic acid and reusable target PVC plastic from a PVC feedstock containing at least one phthalate may comprise or consist of the following steps: a) solid-liquid extraction of PVC feedstock (1) in particulate form; n H 2n+1 OH (n is a positive integer less than 4 or greater than 8); forming a liquid phase rich in the phthalate and a solid phase comprising the phthalate-depleted PVC plastic; b) Transesterification (alcoholysis) of the liquid phase phthalate of formula C6H4(COOC) n H 2n+1 ) chemical conversion of 2 to a dialkyl phthalate; enriching the liquid phase with said dialkyl phthalate; c) solid-liquid separation between the solid phase and the liquid phase to produce at least one solid stream (6) comprising the phthalate-depleted PVC plastic to recover the target PVC plastic; d) liquid phase (gas-liquid or liquid-liquid) separation to produce at least a first liquid effluent comprising the dialkyl phthalate and a second liquid effluent comprising the solvent; g) chemical conversion of the dialkyl phthalates obtained in step d) into phthalic acid of formula C6H4(COOH)2 by hydrolysis in the presence of water; generating at least one effluent comprising an aqueous phase enriched in said phthalic acid; h) separating the effluent obtained in step g) to produce at least one solid stream (20) of phthalic acid and recovering phthalic acid.

[0085] Steps a) to d) and optionally steps e) and f1) and / or f2) make it possible to obtain at least one intermediate product of dialkyl phthalate (DAP) type (stream (5) or stream (16) in the diagram) and at least one solid stream (6) comprising PVC plastic depleted of said phthalates, in particular by carrying out an alcoholysis reaction, to recover the target PVC plastic.

[0086] Said steps a), b), c), d), e), f1) and f2) are also described in French patent application filed under No. 21 / 05.299.

[0087] Steps g) and h) make it possible to obtain at least one solids stream (20) comprising phthalic acid and to recover the phthalic acid, in particular by carrying out a hydrolysis reaction.

[0088] (Feed material) The process according to the invention is fed with a feedstock (1), known as a "PVC feedstock", which comprises at least one PVC plastic, which necessarily comprises at least one phthalate as described in the present invention.

[0089] The PVC plastic may contain at least 0.1% by weight of phthalates, or even at least 1% by weight of phthalates, or at least 5% by weight of phthalates. Generally, the PVC plastic advantageously contains less than 60% by weight of phthalates, typically less than 40% by weight of phthalates.

[0090] Said PVC feedstock is advantageously a feedstock for recycled PVC of the "production scrap" type, i.e. waste arising from a process for producing PVC polymers during their polymerization, or PVC plastics during compounding / molding of PVC plastics or PVC-based articles during the manufacture of PVC-based articles, or a feedstock for recycled PVC of the "post-consumer waste" type, i.e. waste arising after the use of said PVC-based articles by users.

[0091] In particular, the PVC feedstock to be recycled may be derived from any existing collection and sorting channel or network for production scrap and / or post-consumer waste, especially a collection and sorting channel or network dedicated to plastic waste, which allows for the isolation of at least one PVC plastic-based stream containing at least one phthalate.

[0092] Therefore, the PVC feedstock is typically of the "production scrap" and / or "post-consumer waste" type, which generally comes from the main fields of application in which PVC plastics are used, such as, non-exhaustively, the following: building and construction, packaging, automotive, electrical and electronic equipment, sports, medical equipment. Preferably, the PVC feedstock comes from the building and construction field. More precisely, PVC-based articles are generally used in these fields as various rigid profiles (windows, doors, blinds, roller shutter boxes), pipes and connectors, as well as rigid bottles, plates and films, flexible films and sheets, flexible tubes and profiles, cables, flooring, coated fabrics, etc. Preferably, the PVC-based articles forming the PVC feedstock comprise at least "flexible" PVC, i.e., PVC containing additives of the plasticizer type, preferably of the phthalate type, as is the case, for example, for the following PVC-based articles: flexible films and sheets, flexible tubes and profiles, cables, flooring, coated fabrics, etc.

[0093] Advantageously, the PVC feedstock comprises at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, even more preferably at least 95% by weight of PVC plastic containing at least one phthalate.

[0094] Preferably, the PVC feedstock comprises "flexible" PVC, ie, PVC containing additives of the plasticizer type, preferably of the phthalate type.

[0095] Even more preferably, the PVC feedstock comprises primarily or even exclusively "flexible" PVC, ie PVC containing additives of the plasticizer type, preferably of the phthalate type.

[0096] The PVC feedstock processed in the method for recovering DAP and reusable target PVC plastic according to the present invention is in particulate form. Therefore, whether the PVC feedstock is in the initial form typical of production scrap or post-consumer waste, especially in the latter case, in the initial form of PVC-based articles, it may first undergo a conditioning step that includes at least milling or shredding to form the PVC feedstock in particulate form. Depending on the channels and / or networks that produce these production scraps and / or end-of-life PVC-based articles, the PVC waste may be crushed and / or washed and / or subjected to any other conditioning step as described below to form the PVC feedstock in particulate form suitable for the method according to the present invention. For example, the PVC feedstock may advantageously be in the form of a milled, optionally washed, material whose largest dimension is less than 20 cm, preferably less than 10 cm, preferably less than 1 cm, and even more preferably less than 5 mm. The PVC feedstock may advantageously be in the form of a finely divided solid, i.e. in the form of particles having an average size preferably less than 1 mm, for example between 10 and 800 micrometers (μm), the average size advantageously corresponding to the average diameter of the sphere circumscribed by said particle.

[0097] Therefore, the term "PVC feedstock in particulate form" means particles of PVC plastic having an average size as defined above, typically between 10 μm and 20 cm, for example particles of milled material type having an average size of between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferentially between 1 mm and 1 cm, even more preferentially between 1 mm and 5 mm, or particles derived from micronization (very fine milling resulting in a powder) having an average size of less than 1 mm, preferably between 10 μm and 800 μm.

[0098] Preferably, the PVC feedstock treated in the process according to the invention is in the form of particles of a milled material type, preferably particles having an average size of 1 mm to 5 mm, or particles derived from micronization (very fine milling resulting in a powder) having an average size of less than 1 mm.

[0099] PVC feedstock may also contain "macroscopic" impurities such as glass, metals, plastics other than PVC (such as PET), wood, paper, cardboard, inorganic elements, etc. Advantageously, the PVC feedstock contains at most 50% by weight of "macroscopic" impurities, preferably at most 30% by weight, preferably at most 10% by weight, even more preferably at most 5% by weight.

[0100] Advantageously, the water content of the PVC feedstock in particulate form is less than or equal to 0.3% by weight, preferably less than or equal to 0.1% by weight.

[0101] The various steps of the method according to the invention leading to phthalic acid and reusable target PVC plastic are detailed in the following paragraphs.

[0102] Optional Step of Preconditioning the PVC Feedstock According to the invention, the method may comprise a step of preconditioning the PVC feedstock (not shown), which comprises at least one step of milling or shredding the PVC feedstock to form the PVC feedstock in solid particulate form as defined above, which can be sent to a solid-liquid extraction step a). This preconditioning step may comprise one or more steps from the following non-exhaustive list: milling by micronization, sorting, advanced sorting, washing, drying, etc. Depending on the nature of the PVC feedstock to be treated, the step or steps involved in the preconditioning step, as well as their possible frequency and sequence, will be chosen by the skilled person, inter alia, to limit the amount of macroscopic impurities and reduce the size of the solid components of which the PVC feedstock is originally composed.

[0103] For example, the preconditioning step makes it possible to provide PVC feedstock in particulate form, for example in the form of a washed, milled material having an average size of less than 5 mm, and which preferably has a macroscopic impurity content of at most 10% by weight, more preferably at most 5% by weight. The preconditioned PVC feedstock can also be in the form of micronized solid particles, i.e. particles having an average size of less than 1 mm, for example between 10 μm and 800 μm.

[0104] The step of preconditioning the PVC feedstock preferably comprises at least one step of drying the PVC feedstock, already in solid particulate form of ad hoc size and macroscopic impurity content, so that the residual water content of said PVC feedstock is 0.3% by weight or less, preferably 0.1% by weight or less.

[0105] (Generation of target PVC and isolated DAP streams) (Step a) Solid-liquid extraction of phthalates) The process according to the invention comprises a step a) of solid-liquid extraction of one or more phthalates from a PVC feedstock (1) in particulate form, which comprises extracting said feedstock from a phthalate or phthalates of the empirical formula C n H 2n+1 and placing it in contact with a solvent (9) comprising an alcohol of OH (n<4 or n>8) to obtain an effluent (2) comprising at least a liquid phase and a solid phase, the liquid phase being enriched in the one or more phthalates and the solid phase comprising PVC plastic depleted in the one or more phthalates.

[0106] The particular choice of n for the solvent alcohol (exclusion: C4, C5, C6, C7 and C8 alcohols) makes it possible during step b) to convert said phthalate by transesterification with said alcohol into at least one DAP as defined below, which is not included among undesired phthalates, such as those requiring authorization according to the REACH regulation discussed above.

[0107] According to one or more embodiments, the alcohol has the empirical formula C n H 2n+1 OH (n<4), for example selected from the list consisting of methanol, ethanol, n-propanol and i-propanol, even more preferably n=1, said alcohol being methanol CH3OH.

[0108] According to one or more embodiments, the alcohol has the empirical formula C n H 2n+1 It is an alcohol with OH (n>8), for example selected from the list consisting of linear or branched nonanol, linear or branched decanol, linear or branched undecanol, linear or branched dodecanol, preferably nonanol or decanol.

[0109] According to one or more embodiments, the alcohol has the empirical formula C n H 2n+1 OH alcohols, where n>8 and n is 20 or less, or even 15 or less.

[0110] According to one or more embodiments, the compound of empirical formula C n H 2n+1 The alcohols of formula OH (n<4 or n>8) are, according to the invention, in the form of their alkoxides, i.e. of the empirical formula C n H 2n+1 O - The alcohol may be used in the form of a conjugate base (n<4 or n>8), and cationic counterions, including metallic ones, that ensure the electronegativity of the conjugate base are well known to those skilled in the art.

[0111] Solvent (9) may also include an organic co-solvent in addition to the alcohol, which aids in the extraction of one or more phthalates from the PVC feedstock (1). In this case, the organic co-solvent may be an ester derived from the alcohol, the ester having the formula R'COOC n H2n+1 wherein n is the same as n of the alcohol from which the ester is derived (n<4 or n>8, e.g., n is 20 or less), R' is an alkyl group (linear, branched or cyclic, preferably linear), for example containing 1 to 3 carbon atoms, e.g., 1 or 2 carbon atoms, or the organic co-solvent may be an ether, for example, non-exhaustively, cyclopentyl methyl ether (CPME), di-n-propyl ether or dioxane, preferably CPME.

[0112] The organic cosolvent is added to the alcohol in such a way that the weight ratio of cosolvent relative to alcohol (cosolvent / solvent) is between 0 and 4, preferably between 0.01 and 4, more preferentially between 0.02 and 0.66, and even more preferably between 0.05 and 0.66.

[0113] Said additional organic co-solvent, preferably when said alcohol is methanol, is advantageously selected from the group consisting of methyl acetate, methyl propanoate and CPME.

[0114] Preferably, step a) of solid-liquid extraction of one or more phthalates from PVC feedstock (1) is carried out by placing said feedstock (1) in particulate form in contact with methanol supplemented with methyl propanoate, preferably in a methyl propanoate to methanol weight ratio of 0 to 4, preferably 0.01 to 4, more preferentially 0.02 to 0.66, even more preferably 0.05 to 0.66. In this case, the DAP produced by the process is dimethyl phthalate (DMP).

[0115] Step a) of the solid-liquid extraction of one or more phthalates from the PVC feedstock (1) is preferably carried out under the following operating conditions: the temperature is between room temperature and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C, even more preferably between 60°C and 145°C; the pressure is between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa; the residence time is between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.

[0116] Preferably, step a) is carried out such that the molar ratio between the amount of alcohol in the solvent (9) and the amount of one or more phthalates to be extracted from the PVC feedstock (1) is between 2 and 250, preferably between 4 and 90, even more preferably between 4 and 30.

[0117] The reactor of step a) of the process according to the invention may advantageously be a stirred reactor, for example a batch or continuous reactor, preferably thoroughly stirred, or a rotary drum reactor, which is agitated by a mechanical stirring system and / or by a recirculation loop and / or by fluidization and / or ultrasonically.

[0118] In accordance with the embodiment, the PVC feedstock (1) in particulate form and the alcohol-containing solvent (9), optionally supplemented with at least one organic co-solvent, are advantageously mixed.

[0119] According to a first option, the mixing may be carried out prior to the introduction of the PVC feedstock and the solvent into the reactor of the solid-liquid extraction step a), in which case the mixture may be formed in a mixer and then introduced into the reactor, the reactor being maintained at the desired pressure and temperature.

[0120] According to a second option, the PVC feedstock (1) in granular form and the alcohol-containing solvent (9), optionally supplemented with at least one organic cosolvent, may be introduced separately into the reactor of step a) of the process according to the invention. The solid PVC feedstock and the solvent are then preferably injected into the reactor via two separate lines, one line allowing the injection of the solvent (9) and the other line allowing the injection of the solid PVC feedstock (1) in granular form. In this case, a mixture of PVC feedstock and solvent is formed directly in the reactor.

[0121] According to the invention, the solid-liquid extraction step a) makes it possible to obtain at least one effluent (2) comprising at least one liquid phase containing at least the extracted phthalates and at least one solid phase containing phthalate-depleted, preferably phthalate-free, PVC plastic.

[0122] (Step b): Chemical conversion of the phthalate by transesterification (alcoholysis) The method according to the invention comprises the step of extracting in step a) one or more phthalates of formula C6H4(COOC n H 2n+1 2) a step b) of chemical conversion of at least one DAP from the one or more phthalates in the liquid phase obtained from step a) with a compound of empirical formula C n H 2n+1 The reaction is preferably carried out in the liquid phase by transesterification (alcoholysis) between an alcohol, OH (n<4 or n>8, preferably n<4, even more preferably n=1, the alcohol being methanol CHOH). In the case where the alcohol is methanol, the transesterification is known as methanolysis.

[0123] The phthalate or phthalates present in the liquid phase at the end of step a) have the formula C6H4(COOC n H 2n+1Step b) of the chemical conversion of 2 to DAP by transesterification is preferably carried out under the following operating conditions: the temperature is between room temperature and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C; the pressure is between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa; the residence time is between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.

[0124] Preferably, step b) is carried out so that the molar ratio of the amount of alcohol in solvent (9) to the amount of phthalates to be converted in the liquid phase containing the one or more phthalates extracted at the end of step a) is between 2 and 250, preferably between 4 and 90, even more preferably between 4 and 30.

[0125] The alcohol used to carry out step b) is the same as that used to carry out step a).

[0126] Preferably, the one or more phthalates extracted in step a) have the formula C6H4(COOC n H 2n+1 Said step b) of chemical conversion of 2 to DAP by transesterification is carried out in the presence of a transesterification catalyst, advantageously introduced into the reaction medium.

[0127] The transesterification catalyst thus used is, for example, selected from the following non-exhaustive list of catalysts well known to the person skilled in the art, preferably from the list consisting of: - homogeneous catalysts, such as basic catalysts (sodium or potassium hydroxide, sodium or potassium methoxide, sodium or potassium carbonate, etc.), inorganic Brønsted acid catalysts (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), organic Brønsted acid catalysts (methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, etc.), Lewis acid catalysts (including, inter alia, boron compounds (BH3, BF3) and aluminum compounds (AlF3, AlCl3)), and organometallic compounds; - Heterogeneous catalysts, such as alkaline earth metal oxides (CaO, BaO, etc.), alkali metal and / or alkaline earth metal carbonates or hydrogen carbonates (CaCO3, etc.), alkali metals supported on alumina or zeolites, zinc oxide and their mixtures with other oxides (e.g. zinc oxide and alumina), ion exchange resins (cationic or anionic), such as sulfonic resins.

[0128] For example, the catalyst used according to the invention is a homogeneous catalyst, in particular a homogeneous catalyst of the basic catalyst type, such as sodium methoxide.

[0129] Preferably, the amount of catalyst introduced is such that the weight ratio of catalyst to the one or more phthalates to be converted is between 0.5% and 10% by weight, preferably between 1% and 8% by weight, even more preferably between 1% and 5% by weight.

[0130] The catalyst, whether homogeneous or heterogeneous, may be recycled and / or removed in the process according to methods well known to those skilled in the art, preferably recycled. It may be isolated in a downstream step of the process or in any other dedicated step, and removed or, preferably, recycled to the transesterification reaction.

[0131] The reactor of step b) of the process according to the invention may advantageously be a stirred reactor, for example a batch or continuous reactor, preferably thoroughly stirred, or a rotary drum reactor, which is agitated by a mechanical stirring system and / or by a recirculation loop and / or by fluidization and / or by ultrasound.

[0132] According to the invention, said step b) of the conversion of phthalates results in the formation of phthalates of formula C6H4(COOC) obtained after transesterification. n H 2n+1 ) at least one liquid phase containing at least 2 DAP, i.e., at least one effluent formed at the end of step a) and comprising a DAP-rich liquid phase in step b) is obtained.

[0133] Steps a) and b) of the method according to the invention may be carried out in the same individual operation or may be the subject of two separate successive individual operations, the individual operation of step a) always being carried out prior to the individual operation of step b).

[0134] In the embodiment depicted in Figures 1 to 5, steps a) and b), although characterized in the form of separate steps (separate "boxes" shown), may be carried out in the same individual operation or may be the subject of two separate, consecutive individual operations. In the first case, effluent (2) is present, for example, in the same reactor used to carry out the two steps a) and b).

[0135] The embodiment depicted in FIG. 6 is one of the preferred embodiments of the present invention, in which steps a) and b) are the subject of the same individual operation, which in this case is characterized by the use of a single (a+b) step (a single (a+b) "box" as shown).

[0136] In the embodiment represented in Figures 7 and 8 (the embodiment of Figure 8 being one of the preferred embodiments of the present invention), steps a) and b) form the object of two separate and consecutive individual operations, and step c) corresponds to a scheme carried out between steps a) and b), as will be explained below.

[0137] (Step c): Solid-liquid separation to obtain a solid stream containing phthalate-depleted PVC plastic) The process according to the invention comprises, on the one hand, the extraction of one or more phthalates of formula C6H4(COOC) obtained after the transesterification in step a) and / or n H 2n+1 ) a step c) of solid-liquid separation between a liquid phase containing 2 DAP and, on the other hand, a solid phase containing phthalate-depleted, preferably phthalate-free, PVC plastic.

[0138] The physical separation of the liquid and solid phases may advantageously be carried out according to techniques known to those skilled in the art, such as, non-exhaustively, filtration, centrifugation, electrostatic precipitation or sedimentation, said techniques being used alone or in combination in any order.

[0139] This step c) of solid-liquid separation thus makes it possible to generate at least one solid stream (6) comprising PVC plastic depleted of one or more phthalates extracted in step a), recovering said reusable target PVC plastic.

[0140] The production of a reusable target PVC as defined according to the present invention may require returning all or part of the solids stream (6) obtained in step c) to step a) for the number of cycles required to produce said target PVC plastic.

[0141] This possibility of recycling the solids stream is illustrated in Figures 2-8.

[0142] According to a first variant of the process according to the invention, the solid-liquid separation step c) is carried out after steps a) and b) have been carried out. This first variant is illustrated in FIGS. 1 to 6. In this case, the liquid effluent (3) obtained from step b) is sent to solid-liquid separation step c). This leads to a separation between a liquid phase containing at least the DAP obtained after the transesterification reaction in step b) and a solid phase containing the PVC plastic depleted in one or more phthalates. Advantageously, in this first variant of the process according to the invention, steps a) and b) are carried out together in the same individual operation; this particular embodiment leads to a reduction in the number of individual operations required to carry out the process according to the invention, thus limiting the number of equipment, the amount of solvent used, the energy used, etc., and therefore reducing costs. A preferred example of this embodiment is illustrated in FIG. 6.

[0143] According to a second variant of the process according to the invention, a solid-liquid separation step c) is carried out after carrying out step a) and before carrying out step b). This second variant is illustrated in particular in Figures 7 and 8. In this case, the liquid effluent (2) obtained from step a) is sent to a solid-liquid separation step c), which results in the separation of a liquid phase containing the extracted phthalates from a solid phase containing PVC depleted in one or more phthalates. Consequently, in this second variant, steps a) and b) form the object of two separate and distinct operations. Step c) therefore gives rise to a solid stream (6) comprising PVC plastic depleted in one or more phthalates, and a first liquid stream (18), which contains the one or more phthalates extracted in step a) and is then sent to step b) for the conversion of said one or more phthalates by transesterification. This second variant is particularly suitable in cases where the PVC feedstock to be treated would lead to the formation of a solid phase during step a) that is unfavorable (in terms of chemical or rheological properties, etc.) for carrying out the transesterification chemistry.

[0144] For example, according to an embodiment according to this second variant of the method shown in Figures 7 and 8, step c) is carried out between steps a) and b), and steps a) and c) according to the invention may be carried out successively in the same batch reactor, which comprises a device for filtering the liquid effluent (2) to allow the extraction of phthalates from the solid phase over several cycles, and a device for withdrawing at least the solid phase (6) to allow the final recovery of the target PVC plastic.

[0145] In another example, step c) may be carried out by centrifugation of the liquid effluent (2) or (3), comprising a liquid phase containing at least the extracted phthalates and / or DAP, and the solid phase obtained from step a), leading to the separation of said solids (6), advantageously all or part of which are returned to step a), preferably pre-suspended for example with a replenishing solvent (9) (not shown), until a reusable target PVC plastic is obtained.

[0146] (Separation step d): Obtaining a first liquid effluent containing dialkyl phthalate) The process according to the invention comprises the step of extracting from the liquid phase obtained at the end of carrying out at least steps a), b) and c) a compound of formula C6H4(COOC n H 2n+1 ) 2) includes a gas-liquid or liquid-liquid separation step d) to extract the DAP.

[0147] The liquid stream ((4), (13)) containing said liquid phase is advantageously fed to this separation step d), thereby making it possible to produce at least a first liquid effluent (stream (5) or (14) according to the figures) containing DAP and a second liquid effluent (stream (7) or (12) according to the figures) containing at least said solvent. The second effluent is in liquid form, and even if the separation is a gas-liquid separation, the gas phase can be condensed to form the second liquid effluent.

[0148] The separation step d) may be carried out according to methods well known to those skilled in the art, such as, but not limited to, distillation, sedimentation, evaporation, liquid-liquid extraction, etc., carried out alone or in combination. The operating conditions (temperature, pressure, etc.) of this step depend on the separation method chosen.

[0149] According to one or more embodiments, the first effluent (5) consists essentially of said DAP. In this case (these cases), the second liquid effluent (7), for example depicted in FIG. 1 (or optionally in FIG. 3), consists of the liquid phase remaining after extraction of the DAP, which is the solvent, i.e. alcohol, optionally supplemented with co-solvents, alcohol-type by-products (AL A ), intermediate alkyl phthalate (IAP A ) and the optionally unconverted phthalate or phthalates extracted at the end of step a) of the process according to the invention. The second liquid effluent (7) can be recycled completely or partially, preferably completely, to step b) of the process according to the invention.

[0150] In this case (or cases), depending inter alia on the separation method chosen, e.g., distillation with a side stream, a series of distillation columns or liquid-liquid extraction, not only the solvent but also the AL A and very advantageously IAP A It is also possible to separate the AL obtained during the transesterification in step b) from the liquid phase, optionally together with the phthalates extracted and not converted in step a). Such a separation is illustrated, for example, in Figure 2 or Figure 7 (and in Figure 3 as an alternative to the production of stream (7)), in which step d) produces a first effluent (5) consisting essentially of the DAP and a second effluent (12) consisting essentially of the solvent, as well as the AL obtained during the transesterification in step b). A and a third effluent (10) containing the partially converted (IAP) A It may be appreciated that a fourth effluent (11) is produced comprising the phthalate(s) and / or one or more unconverted phthalates, and possibly other soluble impurities. The fourth effluent (11) may advantageously be returned to step b) of the process according to the invention, in particular according to the first and second variants of the process according to the invention, to continue the chemical reaction leading to DAP and thus improve the yield of this product.

[0151] According to one or more alternative embodiments, as shown in Figures 4-6 and 8, the first liquid effluent (14) containing DAP can be partially converted into other compounds, such as IAP, in step b). A ) and / or one or more unconverted phthalates and possibly also soluble impurities. As will be explained later, according to this or these embodiments, a step of purification of the DAP of the first effluent is necessary. According to this or these embodiments, separation step d) therefore advantageously separates said first liquid effluent (14) of impure DAP, a second effluent (12) preferably consisting essentially of said solvent, and preferably the AL obtained during the transesterification in step b). A A third effluent (10) is produced, which contains, in particular, AL A and isolation of the solvent is possible, inter alia, depending on the chosen separation method, for example distillation with a side stream, a series of distillation columns or liquid-liquid extraction. In the case where the second effluent (12) essentially consists of the solvent thus recovered, the second effluent (12) can advantageously be partially or completely, preferably completely, recycled to step a) and / or step b) of the process according to the invention, in particular the first and second variants of the process according to the invention.

[0152] (Step e): Purification of DAP (optional) The process according to the invention may comprise an optional step e) of purification of the first effluent (14) containing DAP obtained from the separation step d) in order to improve its quality and therefore ultimately its upgrading. The embodiments shown in Figures 4, 5, 6 and 8 illustrate the implementation of such a purification step e).

[0153] When carrying out said step e), the solvent is advantageously isolated during the implementation of step d). Aand, optionally, the one or more phthalates extracted at the end of step a) of the process according to the invention and which have not been converted at the end of step b) may be isolated during step d) of the process according to the invention or may be isolated during said purification step e).

[0154] It is therefore possible to send the first effluent (14) comprising DAP, one or more phthalates partially and / or not converted in step b), and optionally soluble impurities, to this purification step e) to form a liquid product (16) consisting essentially of said DAP and a liquid residue (17) comprising one or more phthalates partially and / or not converted in step b), and optionally soluble impurities.

[0155] The liquid residue (17) thus recovered can advantageously be returned to step b) of the process according to the invention, in particular according to the first and second variants of the process according to the invention, to continue the chemical reaction leading to DAP, as illustrated in FIG. 4 or FIG. 5.

[0156] Purification step e) may advantageously be carried out by methods well known to those skilled in the art, such as precipitation, crystallization or adsorption, optionally followed by filtration or centrifugation. Purification step e) may involve the implementation of several of these methods in parallel or sequentially. For example, and without being exhaustive, purification step e) may involve a precipitation and filtration step followed by an adsorption step, or an adsorption and filtration step optionally followed by a precipitation step, or a crystallization and filtration step. The operating conditions (temperature, pressure, etc.) of this step e) are determined depending on the purification method chosen.

[0157] (Optional additional steps f1) and / or f2) of chemical transformation of phthalates by transesterification) In order to promote the production of DAP according to the present invention, the IAP can be produced independently of step b) of chemical transformation of one or more phthalates extracted in step a). A and / or at the end of step b), it is possible to carry out an additional chemical conversion step which allows the conversion of one or more extracted phthalates which may not have been converted.

[0158] The method therefore comprises the step of converting one or more phthalates not converted in step b) and / or at least one IAP produced in step b) as shown in FIG. 3 or FIG. A Formula: C6H4(COOC n H 2n+1 )2 to DAP by transesterification using a solvent containing an alcohol. In these embodiments, step f1) is carried out between steps c) and d), advantageously after step b), by sending the liquid phase (4), advantageously obtained at the end of all steps a), b) and c), to a first additional transesterification reactor to produce a second liquid stream (13) enriched in DAP, which is sent to step d). According to this embodiment, step c) is preferably carried out at the end of step b).

[0159] This method comprises the step of converting one or more phthalates not converted in step b) and / or at least one IAP produced in step b) or possibly in the optional step f1). A Formula: C6H4(COOC n H 2n+1 )2) may comprise an additional step f2) of chemical conversion by transesterification with a solvent comprising an alcohol to DAP, which step f2) is carried out after step e) by sending the liquid residue (17) obtained from step e) to a second additional reactor, to produce a third liquid stream (15) enriched in DAP, which third liquid stream (15) is sent back to step d).

[0160] The implementation of the additional step f1) and / or the additional step f2) of chemical transformation by transesterification may be carried out according to the first variant of the process according to the invention (solid-liquid separation step c) is carried out after steps a) and b)) or according to the second variant (solid-liquid separation step c) is carried out between steps a) and b)).

[0161] Preferably, the process according to the invention comprises only one additional step of chemical transformation by transesterification, preferably only step f2).

[0162] The implementation of steps f1) and / or f2) is as described for step b) of the process according to the invention. In particular, the ranges relating to the operating conditions of steps b) and f1) and / or f2) are similar, said ranges being chosen by the skilled person to promote the production of DAP at the inlet of said steps f1) and / or f2) depending on the chemical nature of the stream to be treated.

[0163] This also applies to the preferred use of a transesterification catalyst (8) as described in step b). The transesterification catalyst in step f1) and / or step f2) may be the same as or different from that used in step b).

[0164] The stream (stream (4) or liquid residue (17)) sent to step f1) and / or step f2) contains one or more phthalates extracted in step a) and optionally one or more phthalates partially converted in step b) (IAP A ) and / or the unconverted phthalate(s) and possibly soluble impurities, which are then isolated either during separation step d) of the process according to the invention or during purification step e), if this step is advantageously carried out.

[0165] Depending on the order of steps considered to involve step f1) and / or step f2), the empirical formula C n H2n+1 It may be necessary to use an additional supply of solvent containing an alcohol of formula OH (where n<4 or n>8), optionally supplemented with at least one organic cosolvent, which can be obtained by making up "fresh" solvent (9) or else by recycling said solvent stream (12), optionally isolated at the end of step d) of the process according to the invention. This additional supply by making up with fresh solvent (9) and / or recycling the second effluent (12) consisting of said solvent in the first additional transesterification reactor used in step f1) and / or the second additional transesterification reactor used in step f2) is illustrated in Figures 3, 5, 6 and 8.

[0166] If a purification step e) is carried out, at least a portion of the liquid residue (17) produced in step e) may be recycled to step f1), as illustrated in FIG. 5, to continue the chemical reaction leading to DAP.

[0167] 6 and 8 represent preferred embodiments, respectively according to the first variant (solid-liquid separation step c)) after carrying out steps a) and b) of the method according to the invention and according to the second variant (solid-liquid separation step c)) between steps a) and b).

[0168] As can be seen in FIG. 6, according to a preferred embodiment of the invention according to the first variant, the process comprises the implementation in one and the same separate operation of steps a) and b), a solid-liquid separation step c) after steps a) and b), a separation step d), a step e) of purification of the first effluent (14) comprising the DAP obtained in step d) and advantageously an additional step f2) of transesterification of the residue (17) obtained from step e).

[0169] According to this embodiment, as illustrated diagrammatically in Figure 6, PVC feedstock (1) in particulate form, optionally preconditioned, is introduced into a reactor to carry out steps a) and b), respectively, combined with solid-liquid separation and chemical conversion by transesterification, preferably in the presence of a catalyst (8). The reactor is also fed with a stream of fresh solvent (9) external to the process, which is represented by the empirical formula C n H 2n+1 The reaction effluent (3) contains at least one alcohol of formula (OH) (where n<4 or n>8), preferably methanol, supplemented with an optional co-solvent, preferably methyl propanoate, and optionally at least a portion of the solvent stream (12) isolated in separation step d). The reaction effluent (3) containing a liquid phase at least containing DAP, preferably DMP, and a solid phase containing phthalate-depleted, preferably phthalate-free, PVC plastic is sent to a solid-liquid separation step c), for example by centrifugation, to produce a solid stream (6) containing the PVC plastic depleted in one or more phthalates extracted to recover the reusable target PVC plastic, and a liquid stream (4) containing at least DAP, preferably DMP, and at least the solvent. The solid stream (6) may be partially recycled to step a). The DAP, solvent, and optionally unconverted or partially converted one or more phthalates (IAP) are then separated. A ), and possibly AL A The liquid stream (4) obtained from step c) containing AL is sent to a separation step d), which on the one hand makes it possible to isolate the solvent as stream (12) but also preferably isolates AL Aas stream (10) and finally a liquid effluent (14) containing DAP, preferably DMP, and optionally one or more partially converted and / or unconverted phthalates and optionally soluble impurities. The liquid effluent (14) is sent to a purification step e) to obtain purified DAP, preferably DMP. The residue (17) obtained from this purification step e) contains unconverted or partially converted phthalates (IAP). A Since the residue (17) may still contain esters of the empirical formula C, an additional transesterification chemical conversion step f2) is preferably carried out. The residue (17) is therefore advantageously sent to a second transesterification reactor, which contains a suitable transesterification catalyst and is n H 2n+1 A solvent (9) containing an alcohol of formula (OH) where n<4 or n>8 is used to react unconverted or partially converted (IAP A ) carries out the transesterification of one or more phthalates. The solvent may be a make-up of fresh solvent or may originate from a stream (12) that is at least partially recycled to this step f2). This step f2) produces a liquid stream (15) enriched in said DAP, preferably DMP, which is sent back to the separation step d).

[0170] According to another preferred embodiment of the invention, as shown in FIG. 8, according to a second variant, the process comprises the implementation of steps a) and b) in two distinct and separate operations, step c) being carried out between steps a) and b) and followed by step d), and also comprising a step e) of purification of the first effluent (14) comprising DAP obtained in step d), and an additional step f2) of transesterification of the residue (17) obtained from step e).

[0171] According to this embodiment, as illustrated diagrammatically in Figure 8, PVC feedstock (1) in particulate form, optionally preconditioned, is introduced into a reactor to carry out step a) of solid-liquid extraction of one or more phthalates from said PVC feedstock. The reactor is fed with a stream of fresh solvent (9) external to the process, which is represented by the empirical formula C n H 2n+1 The feedstock (1) comprises at least one alcohol, preferably methanol, of the formula (OH) (n is an integer < 4 or > 8), supplemented with an optional co-solvent, preferably methyl propanoate, and optionally with a solvent stream (12) isolated in a subsequent separation step (d). The effluent (2) obtained in step (a) comprises at least one liquid phase containing at least one phthalate or phthalates extracted from the feedstock (1) and at least one solid phase containing the extracted phthalate-depleted, preferably phthalate-free, PVC plastic. The effluent (2) is sent to a solid-liquid separation step (c), for example by centrifugation, to produce a solid stream (6) containing the PVC plastic depleted of one or more phthalates, a liquid stream (18) containing at least one phthalate or phthalates extracted in step (a), and at least solvent, so as to recover the reusable target PVC plastic. The liquid stream (18) is then sent to a reactor to carry out step b) of chemical conversion of the extracted phthalate(s) by transesterification, preferably in the presence of a catalyst (8). The transesterification reactor may be fed with a stream of fresh solvent (9) external to the process, which stream comprises the same alcohol, preferably methanol, supplemented with an optional co-solvent, preferably methyl propanoate, and optionally supplemented with at least a portion of the solvent stream (12) isolated in separation step d). The DAP, preferably DMP, solvent and unconverted or partially converted phthalate(s) (IAP) are then mixed together to form a mixture of DAP, preferably DMP, solvent and unconverted or partially converted phthalate(s). AThe reaction effluent (4), which contains a liquid phase comprising at least AL, is sent to a separation step d), which makes it possible on the one hand to isolate the solvent as stream (12) and also to separate the AL A as a stream (10), and finally, DAP, preferably DMP, and optionally partially converted (IAP A It is also possible to isolate a liquid effluent (14) containing unconverted (IAP) and / or one or more phthalates and possibly soluble impurities. The liquid effluent (14) is preferably sent to a purification step e) to obtain purified DAP (16), preferably DMP. The residue (17) obtained from this purification step e) contains unconverted or partially converted (IAP). A ) may still contain one or more phthalates, so an additional transesterification chemical conversion step f2) is preferably carried out. The residue (17) is advantageously sent to a second transesterification reactor, which contains a suitable transesterification catalyst and is reacted with a phthalate of the empirical formula C n H 2n+1 A solvent (9) containing an alcohol of formula (OH) where n<4 or n>8 is used to react unconverted or partially converted (IAP) methyl methyl propanoate with an optional co-solvent, preferably methyl propanoate. A ) carries out the transesterification of one or more phthalates. The solvent may be a make-up of fresh solvent or may originate from a stream (12) that is at least partially recycled to this step f2). This step f2) produces a liquid stream (15) enriched in said DAP, preferably DMP, which is sent back to the separation step d).

[0172] (Production of solid phthalic acid) Steps g) and h) can be performed at the conclusion of various embodiments and variants of the method of the present invention for carrying out the above-described steps a) to d) and possibly related optional steps.

[0173] For example, the embodiment illustrated in FIG. 3 is an example of carrying out steps a) to d) and optional step f1) resulting in a stream (5) consisting essentially of DAP; this embodiment can thus be combined with FIG. 9, which illustrates a general implementation of steps g) and h), to obtain at least one solids stream containing phthalic acid.

[0174] According to an essential aspect of the present invention, phthalic acid is produced from the DAP produced upon completion of steps a) to d), and optionally e) and f1) and / or f2), which is isolated according to steps g) and h) detailed below, to facilitate the production of phthalic acid having good purity.

[0175] (Step g): Chemical transformation by hydrolysis of the DAP obtained at the end of steps a) to d) The process according to the invention comprises a step g) of chemical transformation of the dialkyl phthalate obtained in step d) (stream (5)) or in optional step e) (stream (16)) by hydrolysis reaction between said DAP and water (HO), preferably in the liquid phase, to give at least phthalic acid of formula CH(COOH).

[0176] The DAP hydrolysis step g) is preferably carried out under the following operating conditions: the temperature is between room temperature and 150°C, preferably between room temperature and 145°C, more preferentially between 40°C and 130°C, more preferably between 60°C and 110°C; the pressure is between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, more preferably between atmospheric pressure and 0.5 MPa; the residence time is between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours, even more preferably between 10 minutes and 1 hour.

[0177] Preferably, step g) is carried out so that the molar ratio of the amount of water (21) to the amount of DAP to be converted is between 100 and 9000, preferably between 150 and 1800, even more preferably between 200 and 850.

[0178] Preferably, said DAP hydrolysis step g) is carried out in the presence of a hydrolysis catalyst (22), advantageously introduced into the reaction medium.

[0179] The hydrolysis catalyst (22) thus used is advantageously an acid catalyst, for example one selected from the following non-exhaustive list of acid catalysts well known to those skilled in the art, preferably from the list consisting of: - homogeneous catalysts, such as inorganic Brønsted acid catalysts (e.g. hydrochloric acid, sulfuric acid, phosphoric acid, etc.), organic Brønsted acid catalysts (methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, paratoluenesulfonic acid, etc.), and especially Lewis acid catalysts (e.g. AlF3); Heterogeneous acid catalysts, such as alumina, chlorinated or fluorinated alumina, mesoporous aluminosilicates, zeolites and their mixtures with other oxides, (H + ) Ion exchange resins, such as sulfone resins.

[0180] For example, the catalyst used according to the invention is a homogeneous catalyst, especially a homogeneous catalyst of the organic Bronsted acid catalyst type, such as p-toluenesulfonic acid.

[0181] Preferably, the amount of catalyst introduced is such that the weight ratio of catalyst to DAP is between 0.02% and 10% by weight, preferably between 0.5% and 8% by weight, even more preferably between 1% and 5% by weight.

[0182] The catalyst, whether homogeneous or heterogeneous, can be recycled and / or removed in the process according to methods well known to those skilled in the art, and is preferably recycled: it may be isolated and removed in a downstream step of the process or in any other dedicated step, or preferably recycled to the hydrolysis reaction.

[0183] The reactor used in step g) may advantageously be a stirred reactor, agitated by a mechanical stirring system and / or by a recirculation loop and / or by fluidization and / or ultrasonically, such as a batch or continuous reactor, preferably thoroughly stirred, or a rotary drum reactor.

[0184] According to the invention, the DAP hydrolysis step g) makes it possible to obtain at least one effluent (19). The effluent (19) comprises at least one aqueous phase containing at least the phthalic acid of formula CH(COOH) obtained after the hydrolysis reaction of DAP. The DAP is initially contained in streams (5) and (16), which are formed at the end of steps d) and e), respectively, and sent to step g).

[0185] (Step (h): Separating at least one solid effluent containing phthalic acid) The process according to the invention also comprises a step h) comprising at least one solid-liquid separation, which is carried out on at least the effluent (19) resulting from step g) to produce at least one solid stream (20) containing phthalic acid for the purpose of recovering PA, and at least three other liquid streams (23), (24) and (25), which contain at least the residual water from hydrolysis step g), at least DAP and / or IAP resulting from the partial hydrolysis of said DAP. H , as well as at least AL H (by-products resulting from the partial or complete hydrolysis of DAP) respectively and separately.

[0186] The phthalic acid in solid form is separated in this step h) to produce a solid stream of phthalic acid (20), which can be shaped in step h) according to various embodiments detailed below in relation to Figures 10-13.

[0187] The present invention does not exclude that a portion of the phthalic acid in solid form is produced in step g).

[0188] To facilitate the implementation of step h), at least a DAP and / or an IAP H A water-immiscible organic solvent (26), also called "separation solvent", having a physicochemical affinity with the phthalic acid may be used to facilitate obtaining a solids stream (20) containing phthalic acid. The water-immiscible separation solvent is advantageously selected from the list consisting of ketones, such as 2,4-dimethyl-3-pentanone, ethers, such as methoxycyclopentane (CPME), hydrocarbons, especially cyclic and aromatic hydrocarbons, such as toluene, xylene, and isohexane, used alone or in mixtures. Preferably, the separation solvent is selected from 2,4-dimethyl-3-pentanone, CPME, toluene, and xylene. When such a separation solvent is used, it is advantageously separated according to methods well known to those skilled in the art and is preferably returned to step h) (stream (27)).

[0189] Preferably, step h) is carried out without adding additional separation solvent.

[0190] Steps g) and h) of the method according to the invention are represented in general FIG.

[0191] The solid-liquid physical separation of the effluent (19) from step g) can advantageously be carried out according to techniques known to those skilled in the art, such as, non-exhaustively, filtration, centrifugation, the use of precipitants, electrostatic precipitation or sedimentation, said techniques being used alone or in any combination in any order. In particular, depending on the solvent used in steps a) to d) of the process according to the invention, the DAP (empirical formula CH(COOC)) thus formed can be separated. n H 2n+1 Depending on the chemical nature of (2), where n<4 or n>8, several separation steps can be carefully selected and arranged to generate the above streams (20), (23), (24), and (25) as well as possible.

[0192] Various embodiments of step h) are described below in connection with FIGS.

[0193] A first example of the embodiment of step h) is shown in FIG. 10, in which the DAP sent to step g) has the formula C6H4(COOC n H 2n+1 )2, where n<4, i.e., n=1, 2 or 3.

[0194] According to this configuration, the effluent (19) may contain a single liquid phase or two immiscible liquid phases, and in particular, the effluent (19) contains a single liquid phase (single-phase liquid) when n is 2 or less.

[0195] The effluent (19) is sent to a first step h1) which combines a liquid-solid phase change of the phthalic acid with a first solid-liquid separation of the medium thus obtained, to obtain at least one solid stream (20) containing phthalic acid (phthalic acid in solid state).

[0196] This liquid-solid phase change consists of the phase change of phthalic acid from a dissolved state in the aqueous phase of the effluent (19) obtained at the end of step g) to a solid state that allows its subsequent recovery during the first solid-liquid separation of step h1). The liquid-solid phase change of phthalic acid can advantageously be carried out by one or more crystallization or precipitation operations using techniques known to those skilled in the art, such as, but not limited to, cold-wall crystallization, the use of precipitants, batch distillation, etc., said techniques being used alone or in any combination, in any order. For example, the phase change of phthalic acid from the dissolved state to the solid state can be obtained by cooling, for example by the use of cold-wall crystallization, to a temperature between 10°C and room temperature, for example 15°C, causing said precipitation of phthalic acid to form a solid phthalic acid phase. Following the formation of phthalic acid in the solid state, gas-liquid or liquid-liquid separation is carried out according to techniques well known to those skilled in the art, such as distillation, sedimentation, evaporation, liquid-liquid extraction, etc., performed alone or in combination, to obtain DAP and / or IAP. Hand at least an organic liquid stream (24) containing at least water and Al. H and an aqueous liquid stream (28) containing at least 1,2,4-trimethyl-2,5-dichloro ... H The at least two liquid streams (23) and (25) containing the AL can be sent to a second separation step h2) to recover the liquid streams (23) and (25), which step h2) can be a liquid-liquid or gas-liquid separation and can involve, for example, a distillative separation, optionally followed by a more complete separation, for example, a membrane separation. The streams (23) and (25) can then advantageously be returned to steps g) and b) of the process according to the invention, respectively, to these steps containing water or a solvent (AL). H For the specific case of product (e.g., n = 1), AL H The product is methanol), thus optimizing the reactant / solvent feed of the process.

[0197] In the specific case of n=1, AL H Since the product is methanol, it can also be extracted directly in step g), for example by gas-liquid separation, for example by reactive distillation, upgrading the formation of phthalic acid by chemical shifting of the thermodynamic equilibrium of the hydrolysis reaction. The embodiments of steps h1) and h2) remain unchanged in this case.

[0198] A second example of the embodiment of step h) is shown in FIG. 11, in which the DAP fed to step g) of the method according to the invention has the formula C6H4(COOC n H 2n+1 ) 2, where n>8. In this configuration, the effluent (19) is composed of at least two immiscible liquid phases: an aqueous liquid phase containing phthalic acid and an IAP H and / or DAP and / or AL HThe effluent (19) is sent to a first step h3), which combines the liquid-solid phase change of phthalic acid with the solid-liquid separation of the medium thus obtained to obtain at least one solid stream (20) containing phthalic acid (in the solid state), DAP, IAP. H and AL H and at least one aqueous liquid stream (23) containing at least water. The liquid-solid phase change of phthalic acid and the separation of the streams thus obtained can advantageously be carried out according to the same technique as that described above in relation to Figure 10 for step h1). Stream (29) can then be sent to a second separation step h4), which makes it possible to recover at least two liquid organic streams (24) and (25), stream (24) being the first to be separated from DAP and / or IAP. H and stream (25) contains AL H For example, the technique implemented for the separation of the liquid streams in steps h3) and h4) is liquid-liquid extraction. As in one or more embodiments described in connection with Figure 10, the various streams (23), (24) and (25) may advantageously be returned to certain steps further upstream in the process. For example, the stream (23) containing residual water and the DAP and IAP may be recycled. H The stream (24) containing AL can be recycled to step g), in particular to provide water and / or to continue the chemical reaction leading to phthalic acid, respectively, thus improving its yield, and H The stream (25) containing the AL produced in step g) can be recycled to step b), in particular by supplying the solvent to this step b) (said solvent being the AL produced in step g). H (if it contains ), thus optimizing the supply of solvent to the process.

[0199] A third example of the embodiment of step h) is shown in FIG. 12, in which the DAP sent to step g) has the formula C6H4(COOC n H 2n+1) 2, where n=3. According to this configuration, the effluent (19) contains at least two immiscible liquid phases: DAP and / or IAP. H and an organic liquid phase containing at least phthalic acid, AL H and at least one aqueous liquid phase containing at least water. The effluent (19) is sent to a first separation step h5) to separate the organic liquid phase from the aqueous liquid phase, producing two separate streams (24) and (30) containing an organic phase and an aqueous phase, respectively. H The stream (24) comprising the organic phase containing phthalic acid can then advantageously be sent back to step g) to continue the chemical reaction leading to phthalic acid, thus improving the yield of this product. H and residual water, is sent to step h6), which combines a liquid-solid phase change of phthalic acid with solid-liquid separation, as already explained in relation to Figure 10 for part of step h1) (concerning the change of state of phthalic acid from dissolved to solid state and solid-liquid separation), to produce at least one solid stream of phthalic acid (20) and at least one aqueous liquid stream (28). Said streams are sent to step h2), as explained in relation to Figure 10, to produce two streams (23) and (25), which can be recycled as already explained in relation to Figure 10.

[0200] A fourth example of the embodiment of step h) is shown in FIG. 13, in which the DAP sent to step g) has the formula C6H4(COOC n H 2n+1 ) 2, where n>8. According to this configuration, the effluent (19) is composed of at least two immiscible liquid phases: DAP, IAP H and AL Hand at least one aqueous liquid phase containing at least phthalic acid and residual water. The effluent (19) is sent to a first separation step h7) to separate the organic liquid phase from the aqueous liquid phase, producing two separate streams (29) and (31) containing an organic phase and an aqueous phase, respectively. The aqueous liquid stream (31) containing at least phthalic acid and residual water is sent to step h8), which combines the liquid-solid phase change of phthalic acid and solid-liquid separation, as well as the separations already described for part of step h1) in connection with FIG. 10 (the part relating to the change of the state of phthalic acid from the dissolved state to the solid state and solid-liquid separation), to produce at least one solid stream (20) of phthalic acid and at least one aqueous liquid stream (23) containing residual water. As mentioned above, the aqueous liquid stream (23) produced in step h8) can advantageously be returned to a further upstream step of the process, for example step g). The stream (29) resulting from step h7) is sent to step h4) as described above in connection with FIG. 11 to produce two streams (24) and (25), which can be recycled in the same way as already described in connection with FIG. 11.

[0201] The solid stream of PA (20) can be sent to a dehydration process to produce phthalic anhydride, which can be the starting compound used to synthesize the phthalates of PVC. The dehydration of PA to form phthalic anhydride is known, and such a dehydration process can be carried out, for example, as described in patent US3720692.

[0202] (Recycling method) The present invention also relates to a method for recycling PVC-based articles containing at least one phthalate, said recycling method comprising: - conditioning the PVC-based article; including at least milling or shredding the PVC-based article; forming a PVC feedstock in particulate form; - recovery of phthalic acid and reusable target PVC plastic from said PVC feedstock in particulate form by the method of the first aspect of the invention as detailed above.

[0203] The step of conditioning the PVC-based article may include the various steps detailed above with respect to preconditioning the PVC feedstock before it is introduced into step a).

[0204] From the perspective of a circular economy, it is advantageous to use the phthalic acid obtained by the described recovery method to re-obtain phthalates suitable for compounding flexible PVC plastics, and / or to use the target PVC plastic resulting from the recovery method according to the invention to manufacture new flexible PVC-based articles. Such articles can then be manufactured from raw materials that respect or are adapted to respect current standards for phthalates, i.e., from recovered target PVC plastic that does not contain non-REACH compliant phthalates, and from PA that allows the production of REACH compliant phthalates, so that they meet current standards for phthalates and can be more easily manufactured to contain only REACH compliant phthalates.

[0205] (Manufacturing method) The present invention also relates to a method for producing flexible PVC-based articles comprising phthalates made from recycled PVC plastic and / or phthalic acid recovered by the method according to the first aspect of the invention.

[0206] The present invention also relates to a method for producing flexible PVC-based articles comprising recycled PVC plastic obtained via the method for recovering phthalic acid and reusable target PVC plastic according to the first aspect of the invention detailed above.

[0207] Such manufacturing methods typically involve recovering phthalic acid and reusable target PVC plastic from a PVC feedstock, as detailed above, followed by blending the reusable target PVC plastic with additives and then forming the blend.

[0208] (Example) This example illustrates the present invention without limiting its scope, and in particular illustrates the extraction of phthalates contained in PVC plastic, the conversion of phthalates to dimethyl phthalate (DMP) by methanolysis in the presence of a catalyst, and the conversion of DMP to phthalic acid in the presence of a catalyst and water.

[0209] 18.2 g of PVC plastic feedstock (obtained from "medical tubing" type PVC-based products) is introduced into a reactor stirred by a paddle-type mechanical stirring system. The PVC plastic feedstock is in the form of extrudates with an average size of 2 mm and contains 4.4 g of didecyl phthalate (DIDP). 26.5 g of methanol and 17.7 g of methyl propanoate (organic cosolvent) are then added. Here, the mass ratio of methyl propanoate / methanol is 0.66, and the molar ratio of methanol / DIDP is 84. 0.17 g of catalyst (NaOMe) is then added to the mixture so that the mass percentage of NaOMe / DIDP is 4%.

[0210] The reactor is sealed, purged with nitrogen, and then heated to 100° C. at an autogenous pressure of about 1.2 MPa and maintained under these conditions for 4 hours with stirring at 1000 rpm. The reactor is then cooled.

[0211] After 4 hours, a solid and a liquid are obtained and analyzed.

[0212] Analysis of the liquid phase by gas chromatography with flame ionization detection (GC-FID) shows that it contains 1.89 g of dimethyl phthalate (DMP) obtained from the conversion of DIDP and 0.05 g of decylmethyl phthalate from the partial conversion of DIDP. This liquid is also purified by the elution of 3.11 g of decanol (C) obtained from the DIDP methanolysis reaction. 10 H 22 Identification was made possible by comparison of retention times with pure analytical standards, and quantification was achieved by determination of response factors derived from the analysis of those same standards.

[0213] The resulting solid was pre-fractionated by preparative size-exclusion chromatography (SEC) with dual optical (UV / visible) and refractometric (RI) detection. The collected fractions were analyzed by high-performance liquid chromatography (HPLC) with quantitative UV-visible optical detection. The results indicated that DIDP was present in the target PVC plastic at a content of less than 1000 ppm, which meets current European regulations.

[0214] These results show that phthalate-free PVC according to the invention is obtained and that the DIDP is converted to 99.9%. In this example, the extraction of DIDP and its conversion are carried out in the same step.

[0215] At the end of this methanol decomposition, 1.89 g of DMP is reintroduced into the reactor, which is stirred by a paddle-type mechanical stirring system. 52.56 g of water is then added (water / DMP molar ratio 300). 0.06 g of catalyst is then added to the mixture so that the PTSA / DMP weight ratio is 3%. The catalyst is p-toluenesulfonic acid (PTSA).

[0216] The reactor is sealed, purged with nitrogen, and then heated to 100°C at an autogenous pressure of about 1.2 MPa and maintained under these conditions for 4 hours with stirring at 1000 rpm. The reactor is then cooled to 65°C.

[0217] After 4 hours, the reaction medium is cooled to 10°C, which leads to the precipitation of a solid consisting mainly of phthalic acid. The solid obtained is filtered. The remaining liquid (filtrate) is then left to stand again three times under the same conditions as before. At the end of each reaction step, a low-temperature reprecipitation step makes it possible to extract the solid phase consisting mainly of phthalic acid. At the end of this protocol, the secondary solid fractions are combined and analyzed.

[0218] Analysis of the solid phase by gas chromatography with flame ionization detection (GC-FID) shows that it contains 1.45 g of phthalic acid (PA) resulting from the conversion of DMP and 0.18 g of monomethyl phthalate (2-(methoxycarbonyl)benzoic acid) resulting from the partial hydrolysis of DMP. The liquid also contains, for its part, 0.59 g of methanol (CHO) resulting from the DMP hydrolysis reaction. Comparison of the retention times with pure analytical standards allowed identification, and quantification was carried out by determining the response factors derived from the analysis of these same standards.

[0219] These results therefore also show that the DMP was converted by 99.9%. [Brief explanation of the drawings]

[0220] [Figure 1] 1 illustrates a portion (first series of steps) of a method according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram of a part (first series of steps) of a method according to another embodiment. [Figure 3] 1 illustrates a portion (first series of steps) of a method according to the embodiment illustrated in FIG. 1 or FIG. 2. [Figure 4] 1 illustrates a portion (first series of steps) of a method according to another embodiment of the present invention. [Figure 5] 5 illustrates a portion (first series of steps) of a method according to the embodiment illustrated in FIG. 4. [Figure 6] 1 illustrates a portion (first series of steps) of a method according to a preferred embodiment of the present invention. [Figure 7]1 illustrates a portion (first series of steps) of a method according to another embodiment of the present invention. [Figure 8] 8 illustrates a portion (first series of steps) of a method as illustrated in FIG. 7 according to a preferred embodiment. [Figure 9] A part of the method (second series of steps) is shown diagrammatically. [Figure 10] 1 illustrates a portion (second series of steps) of a method according to another embodiment. [Figure 11] 1 illustrates a portion (second series of steps) of a method according to another embodiment. [Figure 12] 1 illustrates a portion (second series of steps) of a method according to another embodiment. [Figure 13] 1 illustrates a portion (second series of steps) of a method according to another embodiment.

Claims

1. 1. A method for recovering phthalic acid and reusable target PVC plastic from a PVC feedstock containing at least one phthalate, the method comprising the steps of: a) solid-liquid extraction of the PVC feedstock (1) in particulate form; ｎ H ２ｎ＋１ and placing the phthalate-enriched PVC plastic in contact with a solvent (9) comprising at least one alcohol of the formula (III) OH, where n is a positive integer less than 4 or greater than 8; to produce a liquid phase enriched in the phthalate and a solid phase comprising the phthalate-depleted PVC plastic; b) the phthalate of formula C in the liquid phase ６ H ４ (COOC ｎ H ２ｎ＋１ ) ２ to a dialkyl phthalate by transesterification with said alcohol; enriching said liquid phase in said dialkyl phthalate; c) solid-liquid separation between the solid phase and the liquid phase to produce at least one solids stream (6) comprising the phthalate-depleted PVC plastic and recover the target PVC plastic; d) separating the liquid phases to produce a first liquid effluent ((5), (14)) comprising at least the dialkyl phthalate and a second liquid effluent ((7), (12)) comprising at least the solvent; e) optionally purifying the first liquid effluent (14) containing the dialkyl phthalate obtained in step d) from the phthalates partially and / or not converted in step b) and optionally from soluble impurities, to produce a liquid product (16) consisting essentially of the dialkyl phthalate and a liquid residue (17) containing the phthalates partially and / or not converted in step b) and optionally from soluble impurities; f) the unconverted and / or partially converted phthalates of formula C in step b) ６ H ４ (COOC ｎ H ２ｎ＋１ ) ２ an optional additional step f of chemical conversion by transesterification with said alcohol to dialkyl phthalate of １ ) and / or optional additional step f ２ ); the step f １ Between steps c) and d), the liquid phase obtained at the end of all of steps a), b) and c) is sent to a first additional transesterification reactor, ６ H ４ (COOC ｎ H ２ｎ＋１ ) ２ and sending said second liquid stream (13) to step d), and said step f ２ ) after step e), the liquid residue (17) is sent to a second additional transesterification reactor to produce a product of formula C ６ H ４ (COOC ｎ H ２ｎ＋１ ) ２ and returning said third liquid stream (15) to step d); g) the phthalate of formula C obtained in step d) or in optional step e) ６ H ４ (COOH) ２ to phthalic acid by hydrolysis with water; producing an effluent (19) comprising an aqueous phase containing phthalic acid; h) Separating the phthalic acid converted into solid form from step g) to produce at least one solid phthalic acid stream (20).

2. 10. The method of claim 1, wherein steps a) and b) are performed in the same separate operation.

3. 2. The method of claim 1, wherein steps a) and b) form the object of two separate and distinct operations, step a) producing a stream (2) comprising the liquid phase and the solid phase, which is sent to a solid-liquid separation step c), which is carried out between steps a) and b), and step c) producing the stream (6) comprising the phthalate-depleted PVC plastic and a first liquid stream (18) comprising the liquid phase, which first liquid stream (18) is sent to step b).

4. The hydrolysis in step g) is carried out in the presence of an acid hydrolysis catalyst, a homogeneous acid catalyst, or a heterogeneous acid catalyst, the homogeneous acid catalyst being preferably an inorganic Brønsted acid catalyst, preferably hydrochloric acid, sulfuric acid, or phosphoric acid, an organic Brønsted acid catalyst, preferably p-toluenesulfonic acid, and a Lewis acid catalyst, preferably AlF ３ and the heterogeneous acid catalyst is selected from the list consisting of alumina, chlorinated alumina, fluorinated alumina, mesoporous aluminosilicates, zeolites, and mixtures thereof with other oxides, (H ＋ 4. The method according to claim 1, wherein the cation exchange resin is selected from the list consisting of: 1) an ion exchange resin, preferably a sulfonic resin.

5. 5. The process according to any one of claims 1 to 4, wherein the hydrolysis in step g) 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, for a period of 1 minute to 10 hours, preferably 10 minutes to 4 hours.

6. 6. The method according to claim 1, wherein the hydrolysis in step g) is carried out in such a way that the molar ratio of the amount of water to the amount of the at least one phthalate to be converted extracted in step a) is between 100 and 9000.

7. 7. The method of any one of claims 1 to 6, wherein step h) comprises a phase change of phthalic acid from a dissolved state in the aqueous phase to a solid state and solid-liquid separation to produce the solid stream (20) of phthalic acid and at least one aqueous liquid stream ((23), (28)).

8. 8. The process according to any one of claims 1 to 7, wherein the first liquid effluent (5) in step d) or the liquid product (16) in optional step e) consists essentially of the dialkyl phthalate.

9. 9. The method according to any one of claims 1 to 8, wherein the solids stream (6) comprising the phthalate-depleted PVC plastic separated in step c) is at least partially recycled to step a).

10. 10. The method according to any one of claims 1 to 9, wherein the alcohol is selected from the list consisting of methanol, ethanol, n-propanol, i-propanol, preferably methanol, or from the list consisting of linear or branched nonanol, linear or branched decanol, linear or branched undecanol, and linear or branched dodecanol, preferably nonanol or decanol.

11. The solvent also includes an organic co-solvent, preferably an organic co-solvent of the formula R'COOC ｎ H ２ｎ＋１ 11. The method of any one of claims 1 to 10, wherein the organic co-solvent is selected from the group consisting of esters having the formula: (R' is an alkyl group, preferably containing 1 to 3 carbon atoms), and ethers, and the organic co-solvent is preferably selected from the group consisting of methyl acetate, methyl propanoate and cyclopentyl methyl ether, and the organic co-solvent is added to the alcohol in a weight ratio of the organic co-solvent to the alcohol of from 0.01 to 4.

12. Step b) and optionally step f １ ) and / or step f ２ 12. The method according to claim 1, wherein the chemical transformation carried out by transesterification in the temperature is between room temperature and 200°C, preferably between 40°C and 180°C; the pressure is between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa; the duration is between 1 minute and 10 hours, preferably between 10 minutes and 4 hours; the molar ratio of the amount of alcohol in solvent (9) to the amount of phthalate to be extracted or converted is between 2 and 250, preferably between 4 and 90; and - carried out in the presence of a transesterification catalyst, preferably chosen from the list consisting of homogeneous basic or inorganic or organic Brønsted or Lewis acid catalysts, and heterogeneous catalysts formed by alkaline earth metal oxides, or alkali metal and / or alkaline earth metal carbonates or hydrogen carbonates, or alkali metals supported on alumina or zeolites, or zinc oxide and mixtures thereof with other oxides, or ion exchange resins.

13. The at least one phthalate of the PVC feedstock has the empirical formula C ６ H ４ (COOR １ ) (COOR ２ ) phthalate, where the ester group is in the ortho position of the benzene ring, and R １ or R ２ is independently selected from one of the members of the group consisting of a linear, branched, or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain; R １ and / or R ２ The method according to any one of claims 1 to 12, wherein preferably contains 1 to 20 carbon atoms, or even 1 to 15 carbon atoms.

14. 14. The method of any one of claims 1 to 13, wherein the target PVC plastic is substantially free of said phthalates, preferably containing less than 0.1 wt. % 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-pentylisopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

15. 1. A method for recycling PVC-based articles containing at least one phthalate, the method comprising: conditioning the PVC-based article; comprising at least milling or shredding the PVC-based article; forming a PVC feedstock in particulate form; - Recovery of phthalic acid and reusable target PVC plastic from said PVC feedstock in particulate form according to any one of claims 1 to 14.

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