Method for the hydrolytic extraction and conversion of phthalates contained in PVC plastics.

Abstract

The present invention relates to a method for obtaining phthalic acid (PA) and recyclable 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 by contacting with an organic extraction solvent, producing a liquid phase containing the phthalate and a first solid phase containing the phthalate-depleted PVC plastic; b) hydrolytically converting the phthalate resulting from step a) to PA; c) solid-liquid separation between the first solid phase and the liquid phase resulting from a) and / or b), producing a solid stream of the phthalate-depleted PVC plastic; d) liquid-solid phase change of the PA from a dissolved state in the aqueous phase to a solid state, producing a mixed stream containing at least one second solid phase enriched in PA; e) solid-liquid separation between the solid PA and the aqueous phase of the mixed stream, producing a solid stream of PA and an aqueous liquid effluent.

Description

[Technical Field]

[0001] The present invention relates to the field of recycling of poly(vinyl chloride) (PVC) based plastics, in particular to a method for the hydrolytic extraction and conversion of phthalates, which are plasticizers present in the composition of PVC. More precisely, the invention relates to a method for the recovery of phthalic acid (PA) and reusable target PVC plastics from PVC feedstocks containing at least one phthalate. [Background technology]

[0002] By definition, a plastic is a mixture of a base polymer material and a number of additives, the assembly of which can be molded or finished (generally at elevated temperatures and / or under pressure) to obtain a semi-finished product or article. In commonly accepted practice, the plastic is referred to by the name of the polymer from which it is made. Thus, poly(vinyl chloride) (PVC) plastic actually corresponds to 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 may 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), coloring (dyes / pigments), etc.

[0003] There are several methods for recycling PVC plastics: the "traditional" method, which involves simple mechanical recycling of the plastics, methods that involve modifying their composition, or even chemical conversion of the compounds from 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 the PVC resin 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 leave these additives in the PVC that is recovered and recycled in this way. For example, changes in regulations regarding them over time are a decisive factor. Thus, while certain plasticizers from the phthalate family were particularly widely used for compounding "flexible" PVC about 40 years ago, since the end of 2006, such plasticizers have gradually become subject to authorization in Europe 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 useful 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 PVC recycled raw materials. 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 unable to directly confer ad hoc flexibility properties to PVC RRM. A significant supply of "fresh" plasticizer 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 as fully indexed in [Publication ID: 1], without proceeding 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. 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 recycled 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 cost of each operation performed in the recovery process and the resale cost of the resulting product (which corresponds to added value). The product consists of naturally upgradeable phthalate-free PVC-based recycled material 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 precluded, and the phthalates would need to be treated as designated waste, which would incur additional costs. Although advantageous in itself, upgrading of REACH-compliant phthalates is difficult in practice because it involves technically complex and expensive separation / purification steps.

[0012] In the past, several studies focused on contacting phthalate-containing PVC plastics with highly concentrated aqueous base solutions (essentially NaOH) to convert the phthalates and extract one or more resulting products: salts of phthalic acid and, depending on the associated operating conditions, salts of possible decomposition products. This chemical reaction is carried out together with or upstream of a PVC dechlorination process, making it possible to obtain a non-chlorinated residue that is almost free of phthalates, thereby enabling its energy recovery. Carrying out such a process with the aid of radio frequency or microwaves upstream of dechlorination has the advantage of recovering upgradeable phthalates, as reported 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 highly concentrated bases, which result in the production of the relevant salts rather than phthalic acid, and the extraction of phthalates is not optimized and does not meet the REACH regulations, which have been in effect since 2006, regarding the recovery of upgradeable compounds as recycled raw 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 phthalates, which are derivatives of phthalic acid, which can be used as raw material for the production of other chemicals in fields other than plastic compounding, for example, to produce dyes, fragrances, sweeteners, such as saccharin, etc.

[0017] The process according to the invention makes it possible in particular to produce phthalic acid powder of good purity from PVC feedstock, typically PVC waste, without stoichiometric consumption of base or acid.

[0018] 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 and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, comprising the following steps: a) a solid-liquid extraction step of the PVC feedstock in particulate form by placing the particles of the PVC feedstock in contact with at least one organic solvent to extract the phthalates; producing a phthalate-rich liquid phase and a first solid phase comprising the phthalate-depleted PVC plastic; b) chemical conversion of the phthalates extracted in step a) by hydrolysis with water to phthalic acid of formula C6H4(COOH)2, resulting in an aqueous phase containing said phthalic acid; c) a solid-liquid extraction step between the first solid phase and the phthalate-rich liquid phase or the aqueous phase containing the phthalic acid; producing at least one solid stream containing the phthalate-depleted PVC plastic and recovering the target PVC plastic; d) converting the phthalic acid from a dissolved state in the aqueous phase to a solid state, thereby producing a mixed stream comprising a phthalic acid-depleted aqueous liquid phase and a phthalic acid-enriched second solid phase; e) solid-liquid separation between the phthalic acid in solid form from step d) and the aqueous liquid phase of said combined stream, resulting in a solid stream of phthalic acid and a liquid effluent containing the residual water from step b).

[0019] One advantage of the present invention lies in the ability of the method to extract and convert a mixture of phthalates initially trapped in the polymer matrix of various articles based on PVC plastics, by means of a solid-liquid extraction process compatible with and combined with a chemical hydrolysis reaction, into a single REACH-compliant and upgradable phthalate product: phthalic acid, 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. Obtaining a single phthalic acid product from a mixture of phthalates further makes it possible to consider the conversion of said phthalic acid into new phthalates, which are still very widely used in many fields, such as plastics processing, in accordance with circular economy principles.

[0020] According to a first variant, steps a) and b) are carried out in the same individual operation, resulting in a stream comprising at least an aqueous phase comprising phthalic acid and a first solid phase comprising PVC plastic depleted in said phthalates.

[0021] According to a second variant, instead of the first variant, steps a) and b) form the object of two distinct and separate operations, step a) producing a stream comprising a liquid phase enriched in said phthalates, and said first solid phase being sent to step c), which is carried out between steps a) and b), which produces a stream comprising PVC plastic depleted in said phthalates and a first liquid stream comprising said liquid phase enriched in phthalates.

[0022] According to this second variant, the process preferably comprises a step g) for removing at least a portion of the organic extraction solvent from said first liquid stream before step b), resulting in a first concentrated liquid stream comprising said phthalates, which first concentrated liquid stream is sent to step b).

[0023] According to one or more embodiments, step g) of removing at least a portion of the organic extractant from the first liquid stream comprises evaporation of the extractant, preferably using a series of flash drums.

[0024] According to one or more embodiments, the organic extraction solvent recovered in step g) is at least partially recycled to step a).

[0025] According to one or more embodiments, the solids stream comprising the phthalate-depleted PVC plastic separated in step c) is at least partially recycled to step a).

[0026] According to one or more embodiments, the organic extraction solvent may be selected from the group consisting of ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, and hydroxybenzoates of empirical formula C. n H 2n+1 The alcohol is selected from the list consisting of alcohols having a straight or branched short aliphatic chain of OH (n<4, n being a non-zero natural integer) and mixtures thereof.

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

[0028] According to one or more embodiments, the hydrolysis in step b) is carried out in the presence of an acid hydrolysis catalyst, which is preferably a homogeneous or 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 sulfonic resins.

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

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

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

[0032] 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.

[0033] According to one or more embodiments, the target PVC plastic is free of said phthalates and preferably contains less than 0.1% by weight 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.

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

[0035] According to a second aspect, the present invention relates to a method for recycling 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.

[0036] According to a third aspect, the present invention also relates to a method for producing flexible PVC-based articles comprising recycled PVC plastic and / or phthalates produced from phthalic acid recovered by the method according to the first aspect of the invention.

[0037] Other objects and advantages of the present invention will become apparent on reading the following description of particular examples of 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

[0038] (List of drawings) 1 is a diagram of a process according to one embodiment of the invention, comprising steps a), b), c), d) and e), an optional step g) of removing the extraction solvent, and an optional separation step f1), wherein extraction step a) and hydrolysis step b) form the object of two distinct and separate operations, and solid-liquid separation step c) is carried out between steps a) and b) (second variant of the process according to the invention). The organic extraction solvent (7) is water-miscible.

[0039] Figure 2 is a diagram of a process according to another embodiment, which, like the embodiment illustrated in Figure 1, comprises separate steps of extraction a) and hydrolysis b), with an intermediate solid-liquid separation step c), and further comprises optional step g), and optional separation steps f3) and f2), immediately upstream of step d) and downstream of step e), respectively. The organic extraction solvent (7) is water-miscible.

[0040] Figure 3 is a diagram of a process according to another preferred embodiment, which, like the embodiment illustrated in Figures 1 and 2, comprises separate steps of extraction a) and hydrolysis b), with an intermediate solid-liquid separation step c), and further comprises an optional step g), an optional separation step f4) immediately upstream of step d), and an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is immiscible with water.

[0041] 4 is a diagram of a process according to another embodiment of the invention, comprising steps a), b), c), d) and e) and an optional separation step f1), in which extraction step a) and hydrolysis step b) are carried out in the same separate operation (first variant of the process according to the invention). The organic extraction solvent (7) is water-miscible.

[0042] Figure 5 is a diagram of a process according to another embodiment, which, like the embodiment illustrated in Figure 4, comprises simultaneous steps of extraction a) and hydrolysis b), with a solid-liquid separation step c) immediately downstream, and further includes optional separation steps f3) and f2) immediately upstream of step d) and downstream of step e), respectively. The organic extraction solvent (7) is water-miscible.

[0043] Figure 6 is a diagram of a process according to another embodiment, which, like the embodiment illustrated in Figures 4 and 5, comprises simultaneous steps of extraction a) and hydrolysis b), with an immediately downstream solid-liquid separation step c), and further comprises an optional separation step f4) immediately upstream of step d), and also an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is immiscible with water.

[0044] In the drawings, the same reference numbers refer to identical or equivalent elements.

[0045] (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.

[0046] The term "PVC-based article" means an article (typically a consumer article) that comprises, and preferably consists of, at least one PVC plastic.

[0047] 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.

[0048] 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.

[0049] 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).

[0050] 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:

[0051] [ka]

[0052] 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.

[0053] Phthalates are often used as plasticizers for plastics, especially PVC-type plastics, especially to make them flexible.

[0054] As used herein, the term "phthalic acid" (PA), also known under the name benzene-1,2-dicarboxylic acid or o-phthalic acid, refers to a product of empirical formula CH(COOH) resulting from the hydrolysis reaction of at least one phthalate-type plasticizer present in a PVC-based article (in particular, empirical formula CH(COOR)(COOR) as defined above) with water (HO).

[0055] The term "one or more by-products of alcohol type" (AL A) means one or more by-products of formula ROH or ROH resulting from the hydrolysis reaction with HO of at least one phthalate-type plasticizer present in the PVC-based article, where R and R are defined as R and R of the phthalate.

[0056] The term "intermediate alkyl phthalate" (IAP) or "partially converted phthalate" means a by-product of empirical formula C6H4(COOH)(COOR1) or C6H4(COOR2)(COOH) resulting from the incomplete hydrolysis reaction with HO of at least one phthalate-type plasticizer (especially one with empirical formula C6H4(COOR1)(COOR2) as described above) present in a PVC-based article. R1 and R2 are defined as R1 and R2 of the phthalate.

[0057] 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 are extracted and converted fully or partially to phthalic acid according to the present invention. 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.

[0058] In this specification, the term "greater than" is understood as strictly greater than and is represented by the symbol ">", and the term "less than" is understood as strictly less than and is represented by the symbol "<".

[0059] 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.

[0060] As used herein, the term "comprise" is synonymous with (has the same meaning as) "include" and "contain" and is inclusive or open-ended and does not exclude other elements not expressly stated. It is understood that the term "to comprise" includes the exclusive and closed term "to consist."

[0061] As used herein, the expression "of between A and B" means that both limits of the interval are included in the range of values ​​stated, unless otherwise specified.

[0062] 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.

[0063] In the remainder of this text, specific embodiments of the present invention may be described, which may be implemented separately or in combination with each other, without limitation of combination, if technically feasible.

[0064] The following description of the method according to the first aspect of the invention refers to the diagrams in Figures 1 to 6 which illustrate various embodiments of the method according to the invention.

[0065] According to the present invention, a method for recovering PA and reusable target PVC plastic from a PVC feedstock containing at least one phthalate comprises and may consist of the following steps: a) a solid-liquid extraction step of the PVC feedstock (1) in particulate form by placing the particles of PVC feedstock in contact with at least one organic solvent (7) for extracting the phthalates; resulting in a liquid phase rich in the phthalates and a first solid phase containing the phthalate-depleted PVC plastic; b) chemical conversion of the phthalates extracted in step a) by hydrolysis with water (9) to phthalic acid of formula C6H4(COOH)2, resulting in an aqueous phase containing said phthalic acid; c) a solid-liquid extraction step between the first solid phase and the phthalate-rich liquid phase or the aqueous phase containing the phthalic acid, resulting in at least one solid stream (8) containing the phthalate-depleted PVC plastic and recovering the target PVC plastic; d) A phase change process of phthalic acid from a dissolved state in an aqueous phase to a solid state, resulting in a mixed stream containing a phthalic acid-depleted aqueous liquid phase and a phthalic acid-enriched second solid phase ((5), (19), (22)); e) a solid-liquid separation step between the phthalic acid in solid form from step d) and the aqueous liquid phase of said combined stream, resulting in a solid stream (6) of at least phthalic acid and a liquid effluent ((11), (14), (20)) containing the residual water from step b).

[0066] (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.

[0067] 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.

[0068] Said PVC feedstock is advantageously a feedstock for recycled PVC of the "production scrap" type, i.e. waste arising during polymerization from a process for producing PVC polymers 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.

[0069] 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.

[0070] 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, etc. 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.

[0071] Advantageously, the PVC feedstock comprises at least 50%, preferably at least 70%, preferably at least 90%, even more preferably at least 95% by weight of PVC plastic comprising at least one phthalate.

[0072] Preferably, the PVC feedstock comprises "flexible" PVC, ie, PVC containing additives of the plasticizer type, preferably of the phthalate type.

[0073] 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.

[0074] 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 an 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 milled and / or washed and / or may undergo 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The various steps of the method according to the invention leading to PA and reusable target PVC plastics are detailed in the following paragraphs.

[0079] Optional Preliminary Step of Conditioning the PVC Feedstock According to the invention, the process may comprise a preliminary step of conditioning the PVC feedstock (not shown), which comprises at least one step of milling or shredding the PVC feedstock to form a PVC feedstock in solid particulate form as defined above, which can be sent to the 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 initially composed.

[0080] 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 may 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.

[0081] (Step a) Solid-liquid extraction of phthalates) The process according to the invention comprises step a) of solid-liquid extraction of one or more phthalates from a PVC feedstock (1) in particulate form, by placing said feedstock in contact with an organic extraction solvent (7), so as to obtain an effluent comprising at least a liquid phase and a first solid phase, said liquid phase being enriched in said one or more phthalates and said first solid phase comprising PVC plastic depleted in said one or more phthalates. The effluent is represented in Figures 1 to 3 by stream (2), and steps a) and b) are carried out separately.

[0082] The organic extraction solvent (7) is therefore chosen for its physicochemical properties regarding its ability to penetrate the polymer matrix while significantly limiting its dissolution, effectively extracting one or more phthalates from the PVC feedstock in particulate form. To this end, the skilled person may rely on knowledge of the Hildebrand and / or Hansen solubility parameters of the solvent, which, relative to these same parameters specific for the PVC resin and the phthalates, define the most suitable solvent for carrying out the solid-liquid extraction step a) of the method according to the invention.

[0083] Hansen's theory makes it possible to estimate the solubility of a polymer, particularly a thermoplastic, such as PVC, in a solvent or solvent mixture by determining the Hansen solubility parameter and sphere of the solvent and polymer, respectively. These calculations are based on the estimation of the cohesive force that allows a compound (here, a polymer) to remain in a solid state. This cohesive force is divided into three contributions: London interactions, chisome interactions, and hydrogen bonds. If a solvent or solvent mixture has a Hansen parameter within the Hansen sphere of a PVC polymer, the PVC polymer should be at least partially, preferably completely, soluble in the solvent. Therefore, those skilled in the art know how to use these calculations to select an appropriate extraction solvent (i.e., an organic solvent / organic solvent mixture) that can dissolve phthalates while limiting the dissolution of the PVC polymer, which can then be subject to experimental verification (for a given set of operating conditions).

[0084] The extraction solvent is also chosen so as to allow step b) of chemical conversion by hydrolysis of the phthalate(s) to be carried out, while limiting secondary chemical reactions and making the subsequent separation step(s) necessary to obtain the PA according to the invention simpler and more effective.

[0085] According to one or more embodiments, the extraction solvent is advantageously an organic solvent or a mixture of organic solvents chosen from: ketones, such as methyl ethyl ketone (MEK), diethyl ketone (DEK), 4-heptanone, 2,4-dimethyl-3-pentanone, methyl isobutyl ketone (MIBK), cyclic ketones, such as cyclopentanone and cyclohexanone, and aromatic ketones, such as acetophenone; ethers, such as methoxycyclopentane (CPME), cyclic ethers, such as tetrahydrofuran (THF), glycol ethers, such as 2-methoxyethanol, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether and diethylene glycol monoethyl ether, cyclic and aromatic hydrocarbons, such as cyclohexane, xylene and toluene; - Empirical Formula C n H 2n+1 Alcohols with straight or branched short aliphatic chains of OH (n<4, n being a non-zero natural integer), such as methanol, ethanol, n-propanol and i-propanol.

[0086] Preferably, the organic extraction solvent is chosen from the abovementioned alcohols, in particular methanol, ethanol, n-propanol, i-propanol, the abovementioned ketone / alcohol mixtures, the abovementioned hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylene, CPME, MEK, MIBK and cyclopentanone, used alone or in mixtures, and more preferentially from the abovementioned alcohols, the abovementioned ketone / alcohol mixtures, the abovementioned hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylene, acetophenone, MEK, MIBK and cyclopentanone, used alone or in mixtures.

[0087] The extraction solvent may advantageously be toluene, MEK, acetophenone, or a MEK / methanol mixture.

[0088] 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, and even more preferentially 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 5 minutes and 4 hours, more preferably between 5 minutes and 2 hours, and even more preferably between 10 minutes and 30 minutes.

[0089] Preferably, step a) is carried out such that the molar ratio of the amount of solvent (7) to the amount of one or more phthalates to be extracted from the PVC feedstock (1) is between 2 and 250, preferably between 4 and 100, even more preferably between 4 and 30.

[0090] The reactor used in step a) of the process according to the invention may advantageously be a stirred reactor, for example a batch or continuous reactor, preferably fully 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.

[0091] Regarding the embodiment, the PVC feedstock (1) in particulate form and the organic extraction solvent (7) are advantageously mixed.

[0092] According to a first option, the mixing may be carried out prior to the introduction of the PVC feedstock and the extraction 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.

[0093] According to a second option, the PVC feedstock (1) in granular form and the solvent (7) 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 extraction solvent (7) 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.

[0094] According to the invention, the solid-liquid extraction step a) makes it possible to obtain at least one effluent comprising at least a liquid phase containing at least the extracted phthalates and at least a second solid phase containing phthalate-depleted, preferably phthalate-free, PVC plastic.

[0095] Under the operating conditions of this process, the extracted phthalate(s) are advantageously in liquid form.

[0096] (Step b): Chemical conversion of the phthalate by hydrolysis) The process according to the invention comprises a step b) of chemical conversion of the phthalate(s) extracted in step a) by hydrolysis reaction, preferably in liquid phase, between said phthalate(s) extracted in step a) and water (HO), to give at least phthalic acid of formula CH(COOH).

[0097] Step b) of hydrolysis of the phthalate(s) present to form phthalic acid 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.

[0098] Water (9) is therefore introduced into this step b) of the process to carry out the hydrolysis reaction of one or more phthalates to form phthalic acid.

[0099] Preferably, step b) is carried out so that the molar ratio of the amount of water (9) to the amount of phthalates to be converted in the liquid phase containing one or more phthalates extracted at the end of step a) is between 100 and 9000, preferably between 150 and 1800, even more preferably between 200 and 850.

[0100] Preferably, said hydrolysis step b) is carried out in the presence of a hydrolysis catalyst (10), which is advantageously introduced into the reaction medium.

[0101] The hydrolysis catalyst (10) thus used is advantageously an acid catalyst, for example 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 Bronsted acid catalysts (e.g., hydrochloric acid, sulfuric acid, phosphoric acid, etc.), organic Bronsted acid catalysts (e.g., methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, p-toluenesulfonic acid, etc.), and Lewis acid catalysts (e.g., AlF3); Heterogeneous catalysts, such as alumina, chlorinated or fluorinated alumina, mesoporous aluminosilicates, zeolites and mixtures thereof with other oxides, (H+) ion exchange resins, such as sulfonic resins.

[0102] For example, the catalyst used according to the invention is a homogeneous catalyst, in particular a homogeneous catalyst of the organic Bronsted acid catalyst type, such as p-toluenesulfonic acid.

[0103] Preferably, the amount of catalyst introduced is such that the weight ratio of catalyst to the phthalate(s) to be converted is between 0.02% and 10% by weight, preferably between 1% and 8% by weight, even more preferably between 1% and 5% by weight.

[0104] The catalyst, whether homogeneous or heterogeneous, may be recycled and / or removed in the process by methods well known to those skilled in the art, and is preferably recycled. It may be isolated in a downstream step of the process or in any other dedicated step, and is removed or, preferably, recycled to the hydrolysis reaction.

[0105] The reactor used in step b) may advantageously be an agitated reactor, such as a batch or continuous reactor, preferably a fully stirred one or a rotary drum reactor, agitated by a mechanical agitation system and / or by a recirculation loop and / or by fluidization and / or by ultrasound.

[0106] According to the invention, said step b) of converting phthalates makes it possible to obtain an effluent (stream (4) in Figures 1 to 3 or stream (24) in Figures 4 to 6) comprising at least one aqueous phase containing at least phthalic acid obtained after the hydrolysis reaction of the phthalates extracted in step a) that were initially contained in the liquid phase formed in step a).

[0107] Steps a) and b) of the process according to the invention may be carried out in the same individual operation upstream of the solid-liquid separation step c) of the process according to the invention, as shown in Figures 3 to 6, or they form the subject of two different individual operations separated by at least said step c), the individual operation of step a) always being carried out before the individual operation of step b), as shown in Figures 1 to 3 and set out in more detail below.

[0108] (Step c): Solid-liquid separation) The process according to the invention comprises a step c) of solid-liquid separation between, on the one hand, a first solid phase containing phthalate-depleted, preferably phthalate-free, PVC plastic, and, on the other hand, a liquid phase containing one or more phthalates extracted in step a) (aqueous phase containing the phthalic acid obtained in step b)), according to the first and second process variants described in detail below and depending on the position of step c) relative to steps a) and b).

[0109] 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, the use of, for example, hydrocyclones, electrostatic precipitation or sedimentation, said techniques being used alone or in combination in any order.

[0110] This step c) of solid-liquid separation thus makes it possible to generate at least one solid stream (8) comprising PVC plastic depleted of one or more phthalates extracted in step a), recovering said reusable target PVC plastic.

[0111] The production of a reusable target PVC as defined according to the present invention may require returning all or part of the solids stream (8) obtained in step c) to step a) for the number of cycles required to produce said target PVC plastic.

[0112] This possibility of recycling the solids stream is illustrated in Figures 1-6.

[0113] For example, step c) may be carried out by centrifugation of the liquid effluent (2) comprising the liquid phase from step a) containing at least the extracted phthalates and the first solid phase, resulting in the separation of said solids (8), advantageously leading to the total or partial return of said solids to step a), preferably previously placed in suspension, for example by feeding an extraction solvent (7) (not shown) until reusable target PVC plastic is produced.

[0114] According to a first 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 first variant is illustrated in Figures 1 to 3. In this case, the liquid effluent (2) from step a) is sent to a solid-liquid separation step c). The solid-liquid separation step c) results in the separation of a liquid phase containing the extracted phthalates from a first solid phase containing the PVC plastic depleted in one or more phthalates. Step c) thus gives rise to a solids stream (8) comprising the PVC plastic depleted in one or more phthalates and a first liquid stream (3). The first liquid stream (3) contains the phthalate(s) extracted in step a) and is then sent to step b) for conversion by hydrolysis of said phthalate(s), or to an optional step g) described below in the present invention, which allows complete or partial removal of the extraction solvent before sending the phthalates to be converted in step b). This first variant is particularly suitable in cases where the PVC feedstock to be treated during step a) results in the formation of a solid phase that is unfavorable for carrying out the chemical hydrolysis reaction (in terms of chemical or rheological properties, etc.). A preferred example of an embodiment according to this variant is shown in Figure 3.

[0115] According to a second variant of the process according to the invention, the solid-liquid separation step c) is carried out after steps a) and b) are carried out in the same individual operation. This second variant is particularly illustrated in FIGS. 4 to 6. In this case, the liquid effluent (24) from the simultaneous steps a) and b) is sent to a solid-liquid separation step c), which results in the separation of at least an aqueous phase containing at least the PA obtained after the hydrolysis reaction in step b) from a first solid phase containing the PVC plastic depleted in one or more phthalates. The (aqueous and organic) liquid phase and the first solid phase containing the PVC plastic depleted in one or more phthalates are separated at the end of this step c). The simultaneous (joint) implementation of steps a) and b) in the same individual operation results in 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 energy used, etc., and therefore reducing costs. A suitable example of this variant is illustrated in Figure 5, where the simultaneous implementation of steps a) and b) is shown by the use of a single step (a+b) (a single "box" (a+b)). In this case, the presence of water (9) in the extraction phase may advantageously modify the extraction properties of solvent (7) that would have been present if it had been used alone. For example, the combination of extraction solvent (7) with water (9) may allow the use of an extraction solvent (7) that is initially suitable for the extraction of phthalates but has too high a solubilizing power for PVC resin; therefore, compensated for by the presence of water, the mixture ultimately has a lower solubilizing power for PVC resin.

[0116] Furthermore, for the second variant, temperatures above room temperature and below 150°C, preferably below 145°C and more preferentially below 100°C, are preferred in order to prevent any degradation of the PVC resin, for example due to dechlorination reactions.

[0117] At the end of all steps a), b) and c), the PA is in predominantly liquid form in the aqueous phase contained in liquid effluent (4), which may contain one or more liquid phases, for example a single liquid phase (single-phase liquid) or two liquid phases (two-phase liquid), depending inter alia on the nature of the extraction solvent (e.g., water-miscible or water-immiscible) and / or the selected operating conditions.

[0118] (Step d) Liquid-Solid Phase Change of Phthalic Acid) The process according to the invention comprises a step d) of phase change of the PA from the dissolved state in the aqueous phase (liquid effluent (4)) obtained at the end of all of steps a), b) and c) to the solid state, allowing it to be recovered in a subsequent solid-liquid separation step e). This liquid-solid phase change may advantageously be carried out by one or more crystallization or precipitation operations according to techniques known to those skilled in the art, such as, non-exhaustively, cold-wall crystallization, the use of precipitants, batch distillation, etc., said techniques being used alone or in combination in any order.

[0119] This step d) of liquid-solid phase change therefore makes it possible to generate at least one mixed stream comprising an aqueous liquid phase depleted in phthalic acid and a second solid phase enriched in phthalic acid: stream (5) in Figures 1 and 4, stream (19) in Figures 2 and 5, and stream (22) in Figures 3 and 6.

[0120] The embodiment illustrated in FIG. 3 is one of the preferred embodiments according to the present invention, in which the PA-enriched aqueous liquid effluent (21) is cooled, for example, via the use of cold-wall crystallization, to a temperature between 10° C. and room temperature, for example, 15° C., causing precipitation of the PA to obtain a mixed stream (22) containing the PA in a solid state.

[0121] (Step e) Solid-liquid separation for recovery of PA) The process according to the invention comprises a step e) of solid-liquid separation carried out on the combined stream (5, 19 and 22 depending on the embodiment) from step d) containing a second solid phase enriched in phthalic acid (phthalic acid in the solid state), to give at least a solid stream containing PA (6), and recovering the PA and a liquid effluent (11, 14 or 20 depending on the embodiment) containing the residual water from hydrolysis step b).

[0122] Residual water may still contain low levels of dissolved phthalates.

[0123] The PA in the solid stream (6) is in the form of a powder.

[0124] The solid-liquid physical separation of the mixed stream from step d) may advantageously be carried out according to techniques known to the person skilled in the art, such as, non-exhaustively, filtration, centrifugation, for example using a hydrocyclone, electrostatic precipitation or decantation, said techniques being used alone or in combination in any order.

[0125] The embodiment shown in FIG. 3 is one of the preferred embodiments according to the present invention, in which the mixed effluent (22) is treated, for example by centrifugation, to obtain a solids stream comprising PA (6) and an aqueous stream (14), which is preferably returned, in whole or in part, to step b) of the method according to the present invention.

[0126] According to one or more embodiments (not represented in the drawings), steps d) and e) are performed in the same individual operation.

[0127] The solid stream of PA (6) can be subjected 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.

[0128] (Step g) (Optional): Removal of extraction solvent before step c) According to a first variant of the process of the present invention, the process preferably comprises a step g) that allows the removal of at least a portion of, and possibly all, the extraction solvent (7) used during step a). This step g) is carried out downstream of the solid-liquid separation step c) and upstream of step b) of the process of the present invention, as illustrated, for example, in Figures 1 to 3. Maximum complete removal of the extraction solvent allows the one or more phthalates extracted in step a) to be concentrated to a minimum, resulting in a liquid effluent (12) that is as free as possible from the extraction solvent. This liquid stream enriched in phthalates (12) is sent to step b). This step g) promotes the hydrolysis reaction involved in step b) by appropriately shifting the thermodynamic equilibrium of said reaction toward the formation of PA, while still allowing a liquid effluent having a rheology compatible with the various embodiments of the present invention to be obtained. Furthermore, the extraction solvent thus removed can be recovered and returned at least to step a) of the process of the present invention.

[0129] Preferably, only a portion of the extraction solvent is removed in this step.

[0130] The removal of part or all of the extraction solvent (7) is advantageously carried out by evaporation, using techniques known to those skilled in the art, such as distillation, evaporation, liquid-liquid separation, etc., said techniques being used alone or in any combination in any order. Step g) may therefore comprise a gas-liquid separation, preferably evaporation of the solvent, using, for example, a series of flash drums.

[0131] The extraction solvent is n H 2n+1 If it contains at least one alcohol with a linear or branched short aliphatic chain with OH (n<4), the extraction solvent is preferably removed.

[0132] 3 is one of the preferred embodiments according to the present invention, in which the liquid stream (3) containing one or more phthalates extracted in step a) and obtained from step c) is treated by evaporation in optional step g) to obtain a liquid stream (12) enriched in said one or more phthalates, which is itself sent to step b). The extraction solvent is typically a water-immiscible solvent, such as toluene, and is not completely removed during step g), allowing downstream steps of the process to benefit from this immiscibility for the separation of the components of stream (12), in particular phthalic acid, from other compounds. The extraction solvent thus recovered is preferably at least partially recycled to step a) in the form of stream (13).

[0133] ((Optional) One or More Separation Steps f)) Depending on the choice of extraction solvent and the various embodiments of the method according to the invention, in particular by the integration of the above-mentioned optional step g), a liquid effluent (4) enriched in at least PA is obtained at the end of step b) of the method. This liquid effluent (4) comprises an aqueous phase containing PA. The chemical nature of the stream and the amount of other constituents may vary depending on the embodiment chosen and may have an influence on the nature of the medium; typically, liquid effluent (4) may be monophasic or biphasic. The method according to the invention may therefore comprise one or more optional steps of liquid-liquid and / or liquid-gas separation, located upstream and / or downstream of steps d) and e) of the method according to the invention, which perform the following: - carrying out steps d) and e), thus preferentially producing at least one solids stream containing PA (6), and recovering the PA, and / or - recovering the residual water (stream (14)) and the extraction solvent (stream (15)) obtained from the hydrolysis step b) and returning them to the process, and / or - recovering the possibly unconverted and / or partially converted phthalates resulting from hydrolysis step b) and returning them to the process, and / or - Recovering the alcohol by-product of the chemical hydrolysis reaction; this may be upgraded or combusted to generate part of the energy required for the process according to the invention.

[0134] The optional separation step f) may be carried out according to methods well known to those skilled in the art, such as, but not limited to, distillation, decantation, evaporation, liquid-liquid extraction, etc., carried out alone or in combination. The operating conditions (temperature, pressure, etc.) of this or these steps depend on the chosen separation method.

[0135] In particular, one or more separation steps f) (see steps f1) to f4) below) are carried out immediately upstream of step d) or downstream of step e) to separate at least one aqueous liquid phase (i.e., containing water) from other compounds in the liquid or gas phase.

[0136] The extraction solvent, or a portion of said compounds, including the phthalates extracted in step a) and unconverted and / or partially converted in step b), or water, may advantageously be recycled to step a) or step b), respectively.

[0137] In Figures 1 to 6, the various separation steps f1), f2), f3), f4) and f5) are depicted and are explained in more detail below.

[0138] Steps f1) and f2) are performed immediately downstream of step e). Steps f3) and f4) are performed immediately upstream of step d). Step f5) is a separation step immediately downstream of separation step f4).

[0139] According to one or more embodiments of the present invention, the solvent and the operating conditions of the inventive process are chosen so that the solvent and water (9) form one and the same liquid phase in the effluent (4) containing at least PA and, optionally, other components: extracted in step a) and unconverted phthalates, IAP and AL, provided that it is not completely removed from stream (3) via step g), if this step is carried out.

[0140] According to this or these embodiments represented in FIGS. 1 and 4, the stream obtained at the end of step e) comprises a solids stream containing PA (6) and a liquid effluent (11) containing residual water (from step b)), said liquid effluent (11) being in the form of a single liquid phase.

[0141] The choice of a water-miscible solvent, such as MEK or a MEK / methanol mixture, may make it possible to obtain a single liquid phase for the effluents (4) and (11) resulting from steps b) and e) of the process, respectively.

[0142] The single-phase liquid phase (11) comprises water (in particular the residual water from step b), the extraction solvent, and optionally the phthalates extracted in step a) and not converted, IAP and AL. Starting from the single-phase liquid effluent (11), it is possible to separate, during step f1), preferably immediately downstream of step e), according to separation methods well known to those skilled in the art, for example distillation with a side stream or liquid-liquid extraction, not only the extraction solvent (stream (15)) and the residual water (stream (14)), but also the AL (stream (17)) and, very advantageously, the IAP (stream (16)) extracted in step a) and possibly containing the phthalates not converted.

[0143] According to the first and second variants of the process according to the invention, the stream (15) containing the extraction solvent and the stream (14) containing water can advantageously be recycled to steps a) and b) of the process according to the invention, respectively. Likewise, the stream (16) containing the IAP extracted in step a) and possibly containing unconverted phthalates can advantageously be recycled to step b) to continue the chemical reaction leading to the PA and thus improve the yield of PA.

[0144] According to one variant (not shown), the extraction solvent can be completely extracted from stream (3) in step g), and step b) can be carried out by those skilled in the art so that an effluent leaving said step b) is formed in the same liquid phase containing at least the residual water and PA, and potentially the phthalates, IAP and AL extracted in step a) and not converted. The downstream steps are identical to steps d), e) and f1) described above in connection with FIG. 1, except for the fact that the extraction solvent is no longer present downstream of step g) and therefore there is no production of stream (15) in step f1).

[0145] According to one or more embodiments of the present invention, provided that when step g) is carried out, the extraction solvent is not completely removed from stream (3) during step g), said solvent and the operating conditions of the inventive process are chosen such that said solvent and water (9) form a first liquid phase of effluent (4) containing at least the PA, and that a second liquid phase immiscible with the first liquid phase is also formed, containing at least the phthalates extracted in step a) and not converted.

[0146] According to this or these embodiments represented in FIGS. 2 and 5, in step f3), preferably immediately upstream of step d), it is possible to separate at least the two preceding immiscible phases to obtain at least one stream (18) comprising a first liquid phase containing water and solvent and also containing PA, and a stream (16) comprising a second liquid phase, which is an organic phase immiscible with the first liquid phase, containing at least IAP and the phthalates extracted in step a) and not converted.

[0147] The choice of a water-miscible solvent, such as MEK or a MEK / methanol mixture, is compatible with obtaining two immiscible liquid phases in the effluent (4).

[0148] Stream (16) is advantageously returned to step b) of the process according to the invention to continue the chemical reaction leading to PA, thus improving the yield of PA. The stream obtained at the end of step e) comprises a solids stream containing PA (6) and a liquid effluent (20) containing residual water (from step b), said liquid effluent (20) being in the form of a single liquid phase comprising water and the extraction solvent. Starting from said single-phase liquid effluent (20), it is possible to separate the extraction solvent (stream (15)) and water (stream (14)) in step f2), preferably immediately downstream of step e), by separation methods well known to those skilled in the art, for example by distillation, and these can advantageously be reused in steps a) and b), respectively, as described above in connection with FIGS. 1 and 4. According to this or these embodiments, depending on their chemical nature, the ALs may be present either in stream (16) resulting from separation step f3) and / or in stream (20) resulting from step e) and may therefore be removed from the process in the form of stream (17) before recycling the various streams (14), (15) and (16).

[0149] According to one variant (not shown), the extraction solvent may be completely extracted from stream (3) in step g), and step b) may be carried out by those skilled in the art in such a way that the effluent leaving said step b) comprises at least a first liquid phase containing at least the PA and a second liquid phase immiscible with the first liquid phase extracted in step a) and containing the unconverted phthalates and AL. The downstream steps are identical to steps d), e), f2) and f3) described in connection with FIG. 2, except for the fact that the extraction solvent is no longer present downstream of step g) and therefore there is no production of stream (15) in step f2).

[0150] According to one or more embodiments of the present invention, provided that step g) is not completely removed from stream (3) when it is performed, the solvent and the operating conditions of the inventive process are selected such that the solvent and water (9) form two immiscible liquid phases in effluent (4). The first of these liquid phases is an aqueous phase containing at least PA; it comprises the residual water and PA from step b) and is immiscible with the extraction solvent. The second of these liquid phases is an organic phase containing the extraction solvent and contains at least the phthalates, IAP and AL extracted in step a) and not converted.

[0151] According to this or these embodiments represented in Figures 3 and 6, in step f4), preferably immediately downstream of step d), it is possible to at least separate the two preceding immiscible phases to obtain at least one stream (21) comprising an aqueous liquid phase containing the PA and at least one stream (23) comprising an organic phase containing the extraction solvent.

[0152] The choice of a water-immiscible extraction solvent, e.g., toluene, may allow for the production of the first aqueous liquid phase, which is immiscible with the organic liquid phase containing the extraction solvent that forms effluent (4).

[0153] The implementation of steps d) and e) starting from stream (21) results in the production of at least a solids stream containing PA (6) and at least an aqueous stream (14), the latter preferably being returned completely or partially to step b).

[0154] Starting from the organic liquid stream (23), it is possible to separate, in step f5), according to separation methods known to those skilled in the art, known liquid-liquid and / or liquid-gas separation methods, such as distillation, decantation, evaporation, liquid-liquid extraction, carried out alone or in combination, not only the extraction solvent (stream (15)), but also the AL (stream (17)) and, very advantageously, the IAP (stream (16)) extracted in step a) and possibly containing unconverted phthalates. Stream (16) can advantageously be returned to step b) to continue the chemical reaction leading to PA and thus improve the yield of PA. Likewise, stream (15) can advantageously be returned to step a).

[0155] (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 PA and reusable target PVC plastic from said PVC feedstock in particulate form; carried out by the method of the first aspect of the invention as detailed above.

[0156] The process 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).

[0157] From the perspective of a circular economy, it is advantageous to use the phthalic acid obtained by the described recovery method to recover 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, which can be more easily manufactured, meet current standards for phthalates, and contain only REACH-compliant phthalates, by being manufactured from raw materials that respect or are adapted to respect said standards, 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.

[0158] (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.

[0159] 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.

[0160] (Example) This example illustrates the present invention without limiting its scope, and in particular illustrates the extraction of phthalates contained in PVC plastic and the conversion of the phthalates to phthalic acid in the presence of a catalyst and water.

[0161] 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). 53.19 g of water and 35.11 g of acetophenone (organic extraction solvent) are then added, resulting in an acetophenone / water weight ratio of 0.66, an acetophenone / DIDP weight ratio of 29.7, and a water / DIDP molar ratio of 300. 0.13 g of catalyst is then added to the mixture, resulting in an APTS / DIDP weight ratio of 3%. The catalyst is p-toluenesulfonic acid (APTS).

[0162] The reactor is sealed, purged with nitrogen, then heated to 100° C. at an autogenous pressure of the order of 1.2 MPa and maintained under these conditions for 4 hours with stirring at 1000 rpm.

[0163] After 4 hours, a solid and a liquid are obtained, which are separated hot at 65°C, which allows obtaining, on the one hand, a PVC solid with a very low phthalate content, and, on the other hand, a liquid. This liquid is then cooled to 10°C, leading to the precipitation of a second solid, mainly consisting of phthalic acid. The resulting suspension is filtered. The remaining liquid (filtrate) is then left for three times again under the same conditions as before. At the end of each reaction step, a precipitation step identical to that specified above allows the extraction of a solid phase mainly consisting of phthalic acid, increasing the final phthalic acid yield. At the end of this protocol, the secondary solid fractions are combined and analyzed.

[0164] Analysis of the secondary solid phase by gas chromatography with flame ionization detection (GC-FID) shows that it contains 1.47 g of phthalic acid resulting from the conversion of DIDP and 0.30 g of monomethyl phthalate (2-(isodeoxycarbonyl)benzoic acid) resulting from the partial hydrolysis of DIDP. The liquid contains, in part, isodecanol (C ) resulting from the hydrolysis of DIDP. 10 H 220) 2.96 g. Identification was made possible by comparison of retention times with pure analytical standards, and quantification was carried out by determination of response factors derived from the analysis of these standards.

[0165] The resulting solid was pre-fractionated by preparative size-exclusion chromatography (SEC) with dual optical detection (UV / visible) and refractive index measurement (RI). The collected fractions were analyzed by high-performance liquid chromatography (HPLC) with quantitative UV-visible optical detection. The results showed that DIDP was present in the target PVC plastic at a content of less than 1000 ppm, which meets current European regulations.

[0166] 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 process. [Brief explanation of the drawings]

[0167] [Figure 1] FIG. 1 is a diagram of a method according to one embodiment of the present invention. [Figure 2] FIG. 10 is a diagram of a method according to another embodiment. [Figure 3] FIG. 1 is a diagram of a method according to another preferred embodiment. [Figure 4] FIG. 4 is a diagram of a method according to another embodiment of the present invention. [Figure 5] FIG. 10 is a diagram of a method according to another embodiment. [Figure 6] FIG. 10 is a diagram 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) a solid-liquid extraction step of the PVC feedstock (1) in particulate form by placing the PVC feedstock particles in contact with at least one organic solvent (7) for extracting the phthalates, resulting in a phthalate-rich liquid phase and a first solid phase containing the phthalate-depleted PVC plastic; b) the phthalate of formula C extracted in step a) ６ H ４ (COOH) ２ by hydrolysis with water to form an aqueous phase containing said phthalic acid; c) a solid-liquid extraction step between the first solid phase and the phthalate-rich liquid phase or the aqueous phase containing the phthalic acid, producing at least one solid stream (8) containing the phthalate-depleted PVC plastic and recovering the target PVC plastic; d) phase change of the phthalic acid from a dissolved state in the aqueous phase to a solid state, resulting in a combined stream ((5), (19), (22)) containing a phthalic acid-depleted aqueous liquid phase and a phthalic acid-enriched second solid phase; e) a solid-liquid separation step between the phthalic acid in solid form from step d) and the aqueous liquid phase of the combined stream, resulting in a solid stream of phthalic acid (6) and a liquid effluent ((11), (14), (20)) containing the residual water from step b).

2. 10. The method of claim 1, wherein steps a) and b) are performed in the same separate operation to produce a stream (24) comprising at least the aqueous phase comprising the phthalic acid and the first solid phase.

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 phthalate-rich liquid phase and the first solid phase, which stream (2) is sent to step c), which is carried out between steps a) and b), and step c) producing the stream (8) comprising the phthalate-depleted PVC plastic and a first liquid stream (3) comprising the phthalate-rich liquid phase.

4. 4. The method of claim 3, further comprising a step g) for removing at least a portion of the organic extractant from said first liquid stream (3) before step b), resulting in a first concentrated liquid stream comprising said phthalates, said first concentrated liquid stream being sent to step b).

5. 5. The method of claim 4, wherein the organic extraction solvent recovered in step g) is at least partially recycled to step a).

6. 6. The method according to any one of claims 1 to 5, wherein the solids stream (8) comprising the phthalate-depleted PVC plastic separated in step c) is at least partially recycled to step a).

7. The organic extractant (7) may be selected from the group consisting of ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, empirical formula C ｎ H ２ｎ＋１ 7. The method according to claim 1, wherein the alcohol is selected from the list consisting of alcohols with a linear or branched short aliphatic chain of OH, n<4, n being a non-zero natural integer, and mixtures thereof.

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

9. The hydrolysis in step b) is carried out in the presence of an acid hydrolysis catalyst, which is preferably a homogeneous acid catalyst or a heterogeneous acid catalyst, and the homogeneous acid catalyst is selected from 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 AlF ３ 9. The process according to any one of claims 1 to 8, wherein 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 sulfonic resins.

10. 10. The method according to any one of claims 1 to 9, wherein the hydrolysis in step b) is carried out at a temperature between room temperature and 150°C, preferably between 40°C and 130°C, at a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, for a period of 1 minute to 10 hours, preferably 10 minutes to 4 hours.

11. 11. The method according to any one of claims 1 to 10, wherein the hydrolysis in step b) is carried out such that the molar ratio of the amount of water to the amount of phthalate extracted in step a) is between 100 and 9000.

12. 12. The method according to any one of claims 1 to 11, wherein step d) comprises at least one step of precipitating the phthalic acid, preferably comprising cooling to a temperature between 10°C and room temperature.

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 free of said phthalates and preferably contains less than 0.1 wt. % in total of phthalates selected from the list consisting of dibutyl phthalate, dioctyl or diethylhexyl phthalate, benzyl butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-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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