Method for extracting and converting phthalic acid esters contained in PVC plastics by hydrolysis

Abstract

The invention relates to a method for obtaining phthalic acid (PA) and a target PVC plastic that can be reused from a PVC feedstock containing at least one phthalate ester, comprising: a) a solid-liquid extraction of the PVC feedstock in contact with an organic extraction solvent, to produce a liquid phase comprising the phthalate and a first solid phase comprising PVC plastic depleted in the phthalate; b) converting the phthalate from a) to PA by hydrolysis; c) a solid-liquid extraction between the first solid phase and the liquid phase from a) and / or b) to produce a solid stream of PVC plastics depleted in phthalate; d) a liquid-solid phase change of PA produces a mixed stream of at least a second solid phase enriched for PA, e) a solid-liquid separation between the solid PA and the aqueous phase of the mixed stream to produce a solid stream of PA and an aqueous liquid effluent.

Description

Technical Field

[0001] The present invention relates to the field of recycling plastics based on poly(vinyl chloride) (PVC), and more particularly to a method for extracting and converting phthalates, which are plasticizers contained in a PVC composition, by hydrolysis. More precisely, the present invention relates to a method for recovering phthalic acid (PA) and reusable target PVC plastics from a PVC raw material containing at least one phthalate. Prior Art

[0002] By definition, plastics are mixtures composed of a base polymer material and many additives, and the whole can be molded or shaped (usually at elevated temperatures and / or under pressure) to obtain semi-finished products or objects. A commonly accepted practice is to name the plastics after the name of the polymer that constitutes the plastics. Thus, poly(vinyl chloride) (PVC) plastics actually correspond to a combination of a PVC polymer (referred to as "PVC resin" in the remainder of this specification) and various additives selected based on the functions required for the plastics. The additives can be organic molecules or macromolecules or inorganic (nano) particles, and are used according to the properties they provide to the PVC resin: heat resistance, light resistance or mechanical stress resistance (stabilizers), flexibility (plasticizers), processability (lubricants), coloring (dyes / pigments), etc.

[0003] There are several methods for recycling PVC plastics: "conventional" methods by simple mechanical recycling of plastics, and methods involving chemical transformations that change their composition or even the compounds that make them up.

[0004] Since the mid-twentieth century, the recycling of PVC plastics involving chemical action has been the subject of many studies, which involve, in a first step, dissolving a PVC resin containing variable proportions of additives, and then, in a second step, recovering the resin in the presence of all or some soluble additives using various chemical processes (precipitation, evaporation, etc.). For example, patents EP0945481, EP1268628, and EP2276801 respectively relate to recycling various PVC-based objects (flexible or rigid pipes, window frames, cables, etc.), especially fiber-reinforced PVC-based objects (tarpaulins, floor coverings, etc.) according to the following methods, which involve a first step of dissolving the PVC resin and soluble additives in an organic solvent, followed by a second step of steam precipitation in order to be able to recover the resin and most of the additives.

[0005] However, it is not always desirable to retain the additives in the PVC thus recovered for recycling. For example, changes in regulations regarding them over time are a determining factor. Thus, certain plasticizers belonging to the phthalate family, which were particularly widely used about 40 years ago for formulating "flexible" PVC, have gradually become subject to authorization in Europe based on the REACH regulation (which has aimed since the end of 2006 to establish the safety of the manufacture and use of chemical substances in the European industry) and have finally been gradually excluded from the additives allowed for use. This is particularly true of the following non-exhaustive list of phthalates: dibutyl phthalate (DBP), dioctyl phthalate or di(2-ethylhexyl) phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, etc.

[0006] These new regulations now lead to the prohibition of the presence of such compounds in recycled raw materials (RRM). Given the usually very long service life (decades) of PVC-based objects, PVC-based objects formulated before the end of 2006 and now at the end of their service life cannot be recycled by recycling methods that result in the retention of these prohibited additives, whether the method is conventional (such as mechanical recycling processes) or unconventional (for example, the dissolution / precipitation process examples mentioned above).

[0007] In addition, phthalate plasticizers currently used in Europe (REACH-compatible phthalates) and in other parts of the world represent high-value-added additives that are not upgraded when retained in PVC recycled raw materials. The reason is that they are expensive products present in the initial PVC formulation in significant proportions (tens of percent) and do not directly confer special flexibility properties on PVC RRM. Therefore, the supply of a large amount of "fresh" plasticizer is essential for the reusability of recycled PVC materials.

[0008] Therefore, extracting additives of the phthalate type from PVC-based objects in order to remove or upgrade them is a major challenge for optimizing the recyclability of PVC.

[0009] Several methods involving the step of dissolving the PVC resin have been adjusted to achieve this extraction. For example, both Patent EP1311599 and JP2007191586 propose a first step of dissolving the 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 by using a second organic solvent different from the first organic solvent. Patent JP2007092035 discloses another possible embodiment, in which the PVC resin and at least a phthalate-type additive are dissolved by using a solvent under supercritical conditions and the phthalate is recovered in this same solvent after the "destruction" of the supercritical conditions.

[0010] It is also possible to remove or upgrade phthalate-type additives from PVC plastics without a preliminary step of dissolving the plastic, in particular by directly extracting the phthalate from the solid polymer matrix with a suitable organic solvent, as fully indicated in the publication by [authors], 2020, “Challenge and opportunities of solvent-based additive extraction methods for plastic recycling”, Waste Management, 104, 148-182. The challenge thus lies in optimizing the extraction conditions (nature of the solvent, contact time, temperature, pressure, etc.) to achieve the best possible yield of the extracted phthalate. Although this method is often used to remove phthalates from PVC plastics, especially for detecting and analyzing and quantifying these specific additives in the plastic, to the applicant's knowledge, no method for recycling PVC-based objects involves this technology.

[0011] Although crucial for ensuring the efficient recycling of PVC plastics and obtaining reusable recycled PVC, the extraction of phthalate plasticizers is not sufficient to ensure the economic viability of methods for regenerating PVC-based objects. The main reason often put forward is the difficulty in finding an economically viable balance between the cost of the individual operations carried out in the regeneration method and the resale cost of the resulting product (equivalent to added value). The product consists of a naturally upgradable phthalate-free PVC-based recycled material and the extracted phthalates, which are themselves difficult to upgrade. Specifically, any regeneration method involving the step of extracting phthalates from PVC-based objects will result in the recovery of a phthalate mixture that may contain non-"REACH compliant" phthalates. The upgrading of said non-REACH compliant phthalates is of course excluded, and the phthalates need to be treated as specific waste, resulting in additional costs. The upgrading of REACH-compliant phthalates, which are themselves advantageous, is actually difficult because it involves technically complex and expensive separation / purification steps.

[0012] In the past, some studies have focused on contacting PVC plastics containing phthalates with highly concentrated aqueous alkaline solutions (essentially NaOH) to convert the phthalates and extract the resulting products: salts of phthalic acid and possible degradation products depending on the relevant operating conditions. This chemical reaction is carried out either together with or upstream of the PVC dechlorination step, subsequently making it possible to obtain non-chlorinated residues that are mainly free of phthalates in order to be able to carry out energy recovery on them. Carrying out such a step upstream of dechlorination and under high-frequency or microwave assistance has the advantage of recovering upgradable phthalates, as reported in the following documents: patent JP3929352; publication by F. Osada et al., 2010, "Deplasticization and dechlorination of flexible polyvinyl chloride in NaOH solution by microwave heating", J. Mater. Cycles Waste Manag., 2010, 12, 245; publication by S.M. Shin et al., 2011, "Elution Behavior of Additive Agent from Flexible PVC", Chawon Rissaikuring, 10, 6, 3. However, this implementation has the following main drawbacks: it requires the use of highly concentrated alkali, which results in the production of not phthalic acid but its related salts, and the extraction of phthalates is not optimized and does not comply with the REACH regulations regarding the recovery of upgradable compounds as recycled raw materials, which have been applicable since 2006. Summary of the Invention

[0014] The present invention aims to at least partially overcome the problems of the prior art and particularly relates to providing a method for recycling PVC-based objects, which is capable of processing any type of PVC raw material containing phthalates and converting it into two useful products that can be upgraded as raw materials: phthalic acid and recyclable PVC plastics without phthalates, especially undesirable phthalates, usually those that require authorization under the European REACH regulation.

[0015] Phthalic acid is particularly used in the manufacture of phthalates, which are derivatives of phthalic acid. Phthalic acid can be used as a raw material for manufacturing other chemicals in fields different from the plastic formulation field, such as for manufacturing dyes, fragrances, sweeteners such as saccharin, etc.

[0016] The method according to the present invention particularly enables the production of phthalic acid powder with good purity from PVC raw materials, usually PVC waste, without the stoichiometric consumption of bases or acids.

[0017] Therefore, in order to achieve at least one of the above objects, the present invention particularly proposes, according to a first aspect, a method for recovering phthalic acid and reusable target PVC plastics from a PVC raw material containing at least one phthalate, which comprises the following steps:

[0018] a) Performing solid-liquid extraction of the PVC raw material in particle form by bringing the particles of the PVC raw material into contact with at least one organic solvent for extracting the phthalate to produce a liquid phase enriched with the phthalate and a first solid phase containing PVC plastics depleted of the phthalate;

[0019] b) Chemically converting the phthalate extracted in step a) into phthalic acid of the formula C6H4(COOH)2 by hydrolysis using water to produce an aqueous phase containing the phthalic acid;

[0020] c) Performing solid-liquid extraction between the first solid phase and the liquid phase enriched with the phthalate or the aqueous phase containing the phthalic acid to produce at least one solid stream containing PVC plastics depleted of the phthalate to recover the target PVC plastics;

[0021] d) Changing the phase of phthalic acid from the dissolved state in the aqueous phase to the solid state to produce a mixed stream containing an aqueous liquid phase depleted of phthalic acid and a second solid phase enriched with phthalic acid;

[0022] e) Solid-liquid separation between the solid phthalic acid from step d) and the aqueous liquid phase of the mixture stream to produce a solid phthalic acid stream and a liquid effluent containing the residual water from step b).

[0023] One advantage of the present invention is that the method can extract and convert the phthalate mixture initially trapped in the polymer matrix of various objects based on PVC plastics into a single REACH-compatible and upgradable phthalate product: phthalic acid, regardless of the composition of the mixture (i.e., regardless of the nature and origin of the various phthalates) and despite the possible presence of many other additives. Moreover, obtaining a single phthalic acid product from the mixture of phthalates makes it possible to consider converting the phthalic acid into novel and diverse phthalates still very widely used in many fields, such as the plastics processing field, according to the principles of the circular economy.

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

[0025] According to a second variant alternative to the first variant, steps a) and b) form the subject of two different single operations. Step a) produces a stream comprising a liquid phase enriched with said phthalates and said first solid phase, which is sent to step c) carried out between steps a) and b). Step c) produces a stream containing PVC plastic depleted of said phthalates and a first liquid stream containing the liquid phase enriched with said phthalates.

[0026] According to this second variant, the method preferably includes a step g) of removing at least a portion of the organic extraction solvent from the first liquid stream before step b) to produce a first concentrated liquid stream containing said phthalates and sent to step b).

[0027] According to one or more embodiments, the step g) of removing at least a portion of the organic extraction solvent from the first liquid stream includes evaporating the extraction solvent, preferably using a series of flash tanks.

[0028] According to one or more embodiments, at least a portion of the organic extraction solvent recovered in step g) is recycled at least in part to step a).

[0029] According to one or more embodiments, at least a portion of the solid stream containing PVC plastic depleted of phthalates separated in step c) is recycled at least in part to step a).

[0030] According to one or more embodiments, the organic extraction solvent is selected from ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, straight-chain or branched short aliphatic chain alcohols having the empirical formula C n H 2n+1 OH where n is a non-zero natural integer, and mixtures thereof.

[0031] According to one or more embodiments, the organic extraction solvent is selected from 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, isopropanol, and mixtures thereof, preferably selected from said alcohols, ketone / alcohol mixtures, hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylene, methoxycyclopentane, methyl isobutyl ketone, cyclopentanone, acetophenone, and preferably, the organic extraction solvent is toluene, methyl ethyl ketone, acetophenone, or a methyl ethyl ketone / methanol mixture.

[0032] 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 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 homogeneous acid catalysts such as AlF3 or heterogeneous acid catalysts selected from alumina, aluminum chloride, aluminum fluoride, mesoporous aluminosilicates, zeolites, and mixtures thereof with other oxides, (H+) ion exchange resins, preferably sulfonic acid resins.

[0033] 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, and at a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, for a time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours.

[0034] 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 the phthalate extracted in step a) is between 100 and 9000.

[0035] According to one or more embodiments, step d) includes at least one step of precipitating phthalic acid, preferably including cooling to a temperature between 10 °C and room temperature.

[0036] According to one or more embodiments, the at least one phthalate of the PVC raw material is a phthalate of the empirical formula C6H4(COOR1)(COOR2), where the ester groups are in the ortho positions of the benzene ring, and R1 or R2 is independently selected from straight-chain, branched, or cyclic alkyl chains, straight-chain or branched alkoxyalkyl chains, or aryl or alkylaryl chains, and R1 and / or R2 preferably contain 1 to 20 carbon atoms, or even 1 to 15 carbon atoms.

[0037] According to one or more embodiments, the target PVC plastic does not contain the phthalate, and preferably contains a total of less than 0.1% by mass of phthalates selected from dibutyl phthalate, dioctyl phthalate or di(2-ethylhexyl) phthalate, benzyl butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

[0038] According to one or more embodiments, the method includes an additional separation step f) directly upstream of step d) or downstream of step e) to separate at least one aqueous liquid phase from other compounds in the liquid or gas phase. When some of the compounds contain the extraction solvent or phthalates extracted in step a) and not converted and / or partially converted in step b) or water, they are preferably recycled: the extraction solvent can be recycled to step a), and water and / or phthalates extracted in step a) and not converted and / or partially converted in step b) can be recycled to step b).

[0039] According to a second aspect, the present invention relates to a method for recycling a PVC-based object containing at least one phthalate, which includes:

[0040] - Conditioning the PVC-based object, which includes at least grinding or shredding the PVC-based object to form a PVC raw material in the form of particles;

[0041] - Recovering phthalic acid and reusable target PVC plastic from the PVC raw material in the form of particles according to the first aspect of the present invention.

[0042] According to a third aspect, the present invention also relates to a method for manufacturing a flexible PVC-based object, the object containing recycled PVC plastic and / or phthalate made from phthalic acid recovered by the method according to the first aspect of the present invention.

[0043] Other subjects and advantages of the present invention will become apparent upon reading the following description of specific embodiments of the present invention given as non-limiting examples, which description is given with reference to the drawings described below.

[0044] List of Drawings

[0045] Figure 1A diagram of a method according to an embodiment of the present invention, which includes steps a), b), c), d) and e), an optional step g) of removing the extraction solvent, and an optional separation step f1), and wherein the extraction step a) and the hydrolysis step b) form the subject matter of two different separate operations, and a solid-liquid separation step c) is carried out between steps a) and b) (second variant of the method according to the present invention). The organic extraction solvent (7) is water-miscible.

[0046] Figure 2 A diagram of a method according to another embodiment, which is similar to Figure 1 the embodiment shown in, including separate extraction step a) and hydrolysis step b), and an intermediate solid-liquid separation step c), and further including an optional step g), and optional separation steps f3) and f2) directly upstream of step d) and downstream of step e) respectively. The organic extraction solvent (7) is water-miscible.

[0047] Figure 3 A diagram of a method according to another preferred embodiment, which is similar to Figure 1 and 2 the embodiment shown in, including separate extraction step a) and hydrolysis step b), and an intermediate solid-liquid separation step c), and further including an optional step g), and an optional separation step f4) directly upstream of step d) and an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is water-immiscible.

[0048] Figure 4 A diagram of a method according to another embodiment of the present invention, which includes steps a), b), c), d) and e), and an optional separation step f1), and wherein the extraction step a) and the hydrolysis step b) are carried out within the same separate operation (first variant of the method according to the present invention). The organic extraction solvent (7) is water-miscible.

[0049] Figure 5 A diagram of a method according to another embodiment, which is similar to Figure 4 the embodiment shown in, including simultaneous extraction step a) and hydrolysis step b), and a solid-liquid separation step c) directly downstream, and further including optional separation steps f3) and f2) directly upstream of step d) and downstream of step e) respectively. The organic extraction solvent (7) is water-miscible.

[0050] Figure 6 A diagram of a method according to another embodiment, which is similar to Figure 4 and 5The embodiment shown in [description] includes a simultaneous extraction step a) and a hydrolysis step b), as well as a solid-liquid separation step c) directly downstream, and further includes an optional separation step f4) directly upstream of step d) and an optional separation step f5) downstream of step f4). The organic extraction solvent (7) is water-immiscible.

[0051] In the drawings, the same reference numerals denote the same or equivalent elements.

[0052] Description of the Embodiment

[0053] Terms

[0054] Certain definitions are given below, although further details regarding the objects defined below may be given later in the specification.

[0055] The term "PVC-based object" refers to an object that contains at least one PVC plastic and is preferably composed of at least one PVC plastic, typically a consumer product.

[0056] The term "poly(vinyl chloride) plastic", also known as PVC plastic or simply PVC, refers to a combination of a PVC polymer (also known as PVC resin) and various additives selected based on the functions required for the PVC plastic, and the PVC plastic itself is selected based on the intended application.

[0057] The PVC polymer is derived from the radical polymerization of vinyl chloride (VCM), and the vinyl chloride monomer itself is obtained from chlorine and ethylene. Depending on the implementation of the polymerization, four types of PVC resins can be used: 1) suspension PVC or S-PVC resin (suspension polymerization of VCM), 2) emulsion PVC or PVC "paste" resin (emulsion polymerization), 3) bulk PVC or M-PVC resin (bulk polymerization), and 4) superchlorinated PVC or C-PVC resin, which is obtained by post-treatment of the aforementioned resins by superchlorination.

[0058] The additives included in the PVC plastic composition can be organic molecules or macromolecules or inorganic (nano) particles, and are used according to the properties they provide to the PVC resin: heat resistance, light resistance, or mechanical stress resistance (stabilizers), flexibility (plasticizers), processability (lubricants), coloring (dyes / pigments), etc.

[0059] The term "phthalate" refers to a group of chemicals formed by diesters of phthalic acid. They consist of a benzene ring and two carboxylate groups located ortho to each other on the benzene ring. They can be described by the following formula:

[0060] Chemical Formula 1

[0061]

[0062] or is described by the empirical formula C6H4(COOR1)(COOR2), where R1 and R2 are independently selected from straight-chain, branched-chain or cyclic alkyl chains, straight-chain or branched-chain alkoxyalkyl chains or aryl or alkylaryl chains, and said alkyl, alkoxyalkyl, aryl or alkylaryl chains may generally contain from 1 to 20 carbon atoms, or even from 1 to 15 carbon atoms. For example, R1 and / or R2 may be selected from ethyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-octyl, n-nonyl, isononyl, n-decyl, isodecyl, methoxyethyl and benzyl.

[0063] Phthalates are commonly used as plasticizers for plastics, especially for plastics of the PVC type, in particular to make them flexible.

[0064] In this specification, the term "phthalic acid" (PA), also known as benzene-1,2-dicarboxylic acid or o-phthalic acid, denotes the product of empirical formula C6H4(COOH)2 resulting from the hydrolysis reaction of at least one phthalate-type plasticizer present in a PVC-based object (in particular a phthalate of empirical formula C6H4(COOR1)(COOR2) as described above) with water (H2O).

[0065] The term "by-product of alcohol type" (AL) refers to the by-products of formula R1OH or R2OH resulting from the hydrolysis reaction of at least one phthalate-type plasticizer present in a PVC-based object with H2O. The definitions of R1 and R2 are the same as those of R1 and R2 for the phthalate.

[0066] The term "alkyl phthalate intermediate" (IAP) or "partially converted phthalate" refers to the by-products of empirical formula C6H4(COOH)(COOR1) or C6H4(COOR2)(COOH) resulting from the incomplete hydrolysis reaction of at least one phthalate-type plasticizer present in a PVC-based object (in particular a phthalate of empirical formula C6H4(COOR1)(COOR2) as described above) with H2O. The definitions of R1 and R2 are the same as those of R1 and R2 for the phthalate.

[0067] The term "reusable target PVC plastic" refers to "PVC without phthalates", i.e., a solid containing at least PVC resin, supplemented with at least one additive initially present in the PVC plastic of the PVC raw material processed according to the present invention, and from which phthalates have been extracted and completely or partially converted into phthalic acid according to the present invention. The term "without phthalates" particularly means that the solid PVC obtained as a product of the process according to the present invention contains a total of less than 0.1% by weight of phthalates authorized by the European REACH Regulation (Appendix XIV to Regulation (EC) No. 1907 / 2006 of the European Parliament and of the Council of 18 December 2006), in particular less than 0.1% by weight of phthalates selected from the following list of phthalates: dibutyl phthalate (DBP), dioctyl phthalate or di(2-ethylhexyl) phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, either alone or as a mixture.

[0068] In this specification, the term "greater than" is understood to be strictly greater than and is represented by the symbol ">", and the term "less than" is understood to be strictly less than and is represented by the symbol "<".

[0069] In this specification, the term "room temperature" (r.t.) refers to a temperature of typically 20°C ± 5°C, and the term "atmospheric pressure" refers to a pressure of 0.101325 MPa.

[0070] In this specification, the terms "comprising", "including" and "containing" are synonymous (have the same meaning) and are inclusive or open-ended, not excluding other unspecified elements. It is to be understood that the term "comprising" includes the exclusive and closed term "consisting of".

[0071] In this specification, unless otherwise stated, the expression "between... and..." means that the limiting values of the interval are included within the described numerical range.

[0072] In this specification, various parameter ranges for a given step, such as a pressure range and a temperature range, can be used alone or in combination. For example, in this specification, a range of preferred pressure values can be combined with a range of more preferred temperature values.

[0073] Hereinafter, specific embodiments of the present invention may be described. When technically feasible, they can be implemented alone or in combination without limitation to the combination.

[0074] The following description of the method according to the first aspect of the invention refers to Figures 1 to 6 the figures in

[0075] According to the invention, a method for recovering PA and reusable target PVC plastic from a PVC raw material containing at least one phthalate includes the following steps and may consist of the following steps:

[0076] a) Solid-liquid extraction of the PVC raw material 1 in particle form by contacting the particles of the PVC raw material with at least one organic solvent 7 for extracting the phthalate to produce a liquid phase enriched with the phthalate and a first solid phase containing PVC plastic depleted of the phthalate;

[0077] b) Chemically converting the phthalate extracted in step a) into phthalic acid of formula C6H4(COOH)2 by hydrolysis with water 9 to produce an aqueous phase containing the phthalic acid;

[0078] c) Solid-liquid extraction between the first solid phase and the liquid phase enriched with the phthalate or the aqueous phase containing the phthalic acid to produce at least one solid stream 8 of PVC plastic depleted of the phthalate for recovering the target PVC plastic;

[0079] d) Phase change of phthalic acid from the dissolved state in the aqueous phase to the solid state to produce a mixed stream (5, 19, 22) of an aqueous liquid phase depleted of phthalic acid and a second solid phase enriched with phthalic acid;

[0080] e) Solid-liquid separation between the solid phthalic acid from step d) and the aqueous liquid phase of the mixed stream to produce at least a solid stream 6 of phthalic acid and a liquid effluent (11, 14, 20) containing the residual water from step b).

[0081] Raw material

[0082] A raw material called "PVC raw material" 1 containing at least one PVC plastic is fed into the method according to the invention, which must contain at least one phthalate as described in the present invention.

[0083] The PVC plastic may include at least 0.1% by weight of phthalate, or even at least 1% by weight of phthalate or at least 5% by weight of phthalate. Generally, the PVC plastic advantageously contains less than 60% by weight of phthalate, usually less than 40% by weight of phthalate.

[0084] The PVC raw material is advantageously a PVC raw material to be recycled of the "production waste" type, i.e., waste from the PVC polymer production process during its polymerization, or from PVC plastics during their formulation / molding, or from PVC-based objects during their production, or a PVC raw material to be recycled of the "post-consumer waste" type, i.e., waste generated after the PVC-based object has been used by the user.

[0085] In particular, the PVC raw material to be recycled can come from any existing collection and sorting channels or networks for production waste and / or post-consumer waste (which are capable of separating a stream of PVC plastics containing at least one phthalate), in particular collection and sorting channels or networks dedicated to plastic waste.

[0086] Thus, the PVC raw material, which is generally of the "production waste" type and / or "post-consumer waste" type, generally comes from the main application fields using PVC plastics, such as but not limited to the following fields: construction, packaging, motor vehicles, electrical and electronic equipment, sports, medical equipment, etc. Preferably, the PVC raw material comes from the construction field. More precisely, the PVC-based objects are generally used in these fields as various rigid profiles (windows, doors, shutters, roller shutter boxes), pipes and fittings, as well as rigid bottles, plates and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc. Preferably, the PVC-based objects forming the PVC raw material contain at least "flexible" PVC, i.e., PVC containing additives of the plasticizer type, preferably of the phthalate type, as is the case for example with the following PVC-based objects: flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.

[0087] Advantageously, the PVC raw material contains at least 50% by mass, preferably at least 70% by mass, preferably at least 90% by mass, and even more preferably at least 95% by mass of PVC plastics containing at least one phthalate.

[0088] Preferably, the PVC raw material contains "flexible" PVC, i.e., PVC containing additives of the plasticizer type, preferably of the phthalate type.

[0089] More preferably, the PVC raw material mainly or even completely contains "flexible" PVC, i.e., PVC containing additives of the plasticizer type, preferably of the phthalate type.

[0090] In the process for recycling DAP and the target PVC plastic that can be reused according to the present invention, the PVC raw material to be processed is in the form of particles. Therefore, if the PVC raw material is in its initial form characteristic of production waste or post-consumer waste, especially in the case of post-consumer waste, the initial form of an object based on PVC, it can first undergo a conditioning step, which includes at least grinding or shredding to form a PVC raw material in the form of particles. Depending on the channels and / or networks from which these production wastes and / or end-of-life PVC-based objects come, the PVC waste can be ground and / or washed and / or can undergo any other conditioning steps as described below to form a PVC raw material in the form of particles suitable for the process according to the present invention. For example, the PVC raw material can advantageously be in the form of ground and optionally washed material, with a maximum size of less than 20 cm, preferably less than 10 cm, preferably less than 1 cm, and even more preferably less than 5 mm. The PVC raw material can also advantageously be in the form of micronized solids, i.e., preferably particles with an average size of less than 1 mm, for example, between 10 micrometers (μm) and 800 micrometers (μm). The average size advantageously corresponds to the average diameter of the sphere circumscribing the particles.

[0091] Therefore, the term "PVC raw material in the form of particles" refers to particles of PVC plastic generally having an average size as defined above between 10 μm and 20 cm, for example, abrasive material-type particles with an average size between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferably between 1 mm and 1 cm, and even more preferably between 1 mm and 5 mm, or particles generated by micronization (very fine grinding to produce powder) with an average size of less than 1 mm, preferably between 10 μm and 800 μm.

[0092] Preferably, the PVC raw material processed in the process according to the present invention is in the form of abrasive material-type particles, preferably particles with an average size between 1 mm and 5 mm, or particles generated by micronization (very fine grinding to produce powder) with an average size of less than 1 mm.

[0093] The PVC raw material can also contain "macroscopic" impurities such as glass, metal, plastics other than PVC (such as PET, etc.), wood, paper, cardboard, mineral elements, etc. Advantageously, the PVC raw material contains at most 50% by weight, preferably at most 30% by weight, preferably at most 10% by weight, and even more preferably at most 5% by weight of "macroscopic" impurities.

[0094] The various steps of the process according to the present invention for obtaining PA and the target PVC plastic that can be reused are described in detail in the following paragraphs.

[0095] Optional preliminary step of conditioning the PVC raw material

[0096] According to the present invention, the method may include a preliminary step of conditioning the PVC raw material (not shown in the figures), which includes at least one step of grinding or shredding the PVC raw material to form a PVC raw material in the form of solid particles as defined above that can be fed into the solid-liquid extraction step a). Such a pre-conditioning step may also include one or more steps mentioned in the following non-exhaustive list: grinding by micronization, sorting, over-sorting, washing, drying, etc. Depending on the nature of the PVC raw material being processed, the person skilled in the art will in particular select the one or more steps involved in the pre-conditioning step and their possible frequency and sequence in order to limit the amount of macroscopic impurities and reduce the size of the solid components initially constituting the PVC raw material.

[0097] For example, the pre-conditioning step makes it possible to provide a PVC raw material in the form of particles, such as a washed and ground material with an average size of less than 5 mm, the content of macroscopic impurities of which is preferably at most 10% by weight, more preferably at least 5% by weight. The pre-conditioned PVC raw material may also be in the form of micronized solid particles, i.e., in the form of particles with an average size of less than 1 mm, for example between 10 μm and 800 μm.

[0098] Solid-liquid extraction step a) of phthalates

[0099] The method according to the present invention includes a step a) of solid-liquid extraction of phthalates from a PVC raw material 1 in the form of particles by bringing said raw material into contact with an organic extraction solvent 7 in order to obtain an effluent comprising at least a liquid phase and a first solid phase. The liquid phase is thus enriched with said phthalates, and the first solid phase contains PVC plastic depleted of said phthalates. This effluent is represented by the stream 2 in Figures 1 to 3 where steps a) and b) are carried out separately.

[0100] The organic extraction solvent 7 is thus selected because of its physicochemical properties, since it is capable of penetrating into the polymer matrix while significantly limiting its dissolution in order to effectively extract phthalates from the PVC raw material in the form of particles. To this end, the person skilled in the art can rely on knowledge of the Hildebrand and / or Hansen solubility parameters of the solvent in order to define the most appropriate solvent for carrying out the solid-liquid extraction step a) of the method according to the present invention relative to these same parameters specific to the PVC resin and phthalates.

[0101] Due to the determination of the Hansen solubility parameters and spheres of the solvent and the polymer separately, the Hansen theory enables, for example, the estimation of the solubility of a polymer, in particular a thermoplastic such as PVC, in a solvent or a solvent mixture. These calculations are based on the estimation of the cohesive forces that keep a compound (here the polymer) in the solid state, and said cohesive forces are divided into 3 contributions: London interactions, Keesom interactions, and hydrogen bonds. If the solvent or solvent mixture has Hansen parameters within the Hansen sphere of the PVC polymer, then the PVC polymer should be at least partially, preferably completely soluble in the solvent. Thus, a person skilled in the art knows how to use these calculations to select an appropriate extraction solvent (i.e., a mixture of organic solvents / organic solvents) that can dissolve phthalates while limiting the dissolution of the PVC polymer, which can subsequently be the subject of experimental verification (under a given set of operating conditions).

[0102] The extraction solvent is also selected so as to be able to carry out step b) of the chemical conversion of the phthalate by hydrolysis, while limiting secondary chemical reactions and at the same time making the subsequent separation steps necessary for obtaining AP according to the invention simpler and more efficient.

[0103] According to one or more embodiments, the extraction solvent is advantageously an organic solvent or a mixture of organic solvents selected from the following:

[0104] - 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,

[0105] - ethers, such as cyclopentyl methyl ether (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,

[0106] - cyclic and aromatic hydrocarbons, such as cyclohexane, xylene, and toluene,

[0107] - alcohols with a straight or branched short aliphatic chain having the empirical formula C n H 2n+1 OH where n is a non - zero natural integer, such as methanol, ethanol, n - propanol, and isopropanol.

[0108] Preferably, the organic extraction solvent is selected from the above-mentioned alcohols alone or as a mixture, especially methanol, ethanol, n-propanol, isopropanol, the above-mentioned ketone / alcohol mixture, the above-mentioned hydrocarbon / alcohol mixture, cyclohexane, toluene, xylene, CPME, MEK, MIBK and cyclopentanone, more preferably selected from the above-mentioned alcohols alone or as a mixture, the above-mentioned ketone / alcohol mixture, the above-mentioned hydrocarbon / alcohol mixture, cyclohexane, toluene, xylene, acetophenone, MEK, MIBK and cyclopentanone.

[0109] The extraction solvent can advantageously be toluene, MEK, acetophenone or a MEK / methanol mixture.

[0110] Step a) of solid-liquid extraction of phthalates from the PVC raw material 1 is preferably carried out under the following operating conditions: at a temperature between room temperature and 200 °C, preferably between 40 °C and 180 °C, more preferably between 60 °C and 150 °C, still more preferably between 60 °C and 145 °C, at a pressure between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa, and at a residence time between 1 minute and 10 hours, preferably between 5 minutes and 4 hours, more preferably between 5 minutes and 2 hours, still more preferably between 10 minutes and 30 minutes.

[0111] Preferably, step a) is carried out such that the molar ratio of the amount of the solvent 7 to the amount of phthalates to be extracted from the PVC raw material 1 is between 2 and 250, preferably between 4 and 100, still more preferably between 4 and 30.

[0112] The reactor used in step a) of the process according to the invention can advantageously be a stirred reactor by means of a mechanical stirring system and / or by means of a recirculation loop and / or by fluidization and / or by ultrasonic stirring, for example preferably a fully stirred batch or continuous reactor, or a drum reactor.

[0113] Regarding the implementation, the PVC raw material 1 in particle form and the organic extraction solvent 7 are advantageously mixed.

[0114] According to the first option, the mixing can be carried out before introducing the PVC raw material and the extraction solvent into the reactor of the solid-liquid extraction step a). In this case, the mixture can be formed in a mixer and then introduced into the reactor, which is maintained at the required pressure and temperature.

[0115] According to the second option, the PVC raw material 1 in particulate form and the solvent 7 can be introduced separately into the reactor in step a) of the process according to the invention. The solid PVC raw material and the solvent are then preferably injected into the reactor via two separate pipelines, one pipeline being capable of injecting the extraction solvent 7 and the other pipeline being capable of injecting the solid PVC raw material 1 in particulate form. In this case, the mixture of the PVC raw material and the solvent is directly formed in the reactor.

[0116] 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 first solid phase containing a PVC plastic depleted in phthalates, preferably free of phthalates.

[0117] Under the operating conditions of this step, the extracted phthalates are advantageously in liquid form.

[0118] Step b) of the chemical conversion of the phthalates by hydrolysis

[0119] The process according to the invention comprises a step b) of chemically converting the phthalates extracted in step a) by a hydrolysis reaction between the phthalates extracted in step a) and water (H2O), preferably in the liquid phase, to obtain at least phthalic acid of formula C6H4(COOH)2.

[0120] The step b) of hydrolyzing the phthalates present to form phthalic acid is preferably carried out under the following operating conditions: at a temperature between room temperature and 150 °C, preferably between room temperature and 145 °C, more preferably between 40 °C and 130 °C, more preferably between 60 °C and 110 °C, at a pressure between atmospheric pressure and 5.0 MPa, preferably between atmospheric pressure and 2.0 MPa, more preferably between atmospheric pressure and 0.5 MPa, and at a residence time 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.

[0121] Water 9 is thus introduced into this step b) of the process to carry out the hydrolysis reaction of the phthalates to form phthalic acid.

[0122] Preferably, step b) is carried out such that the molar ratio of the amount of water 9 to the amount of phthalates to be converted in the liquid phase containing 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.

[0123] Preferably, the hydrolysis step b) is carried out in the presence of a hydrolysis catalyst 10 advantageously introduced into the reaction medium.

[0124] The hydrolysis catalyst 10 used thereby is advantageously an acid catalyst, for example, an acid catalyst selected from the following non-exhaustive list known to those skilled in the art, preferably selected from the following list:

[0125] - Homogeneous catalysts, such as inorganic Bronsted acid catalysts (e.g., hydrochloric acid, sulfuric acid, phosphoric acid, etc.), organic Bronsted acid catalysts (methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, p-toluenesulfonic acid, etc.), and Lewis acid catalysts (e.g., AlF3);

[0126] - 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 sulfonic acid resins, etc.

[0127] For example, the catalyst used according to the present invention is a homogeneous catalyst, especially a homogeneous catalyst of the organic Bronsted acid catalyst type, such as p-toluenesulfonic acid.

[0128] Preferably, the amount of the catalyst introduced is such that the weight ratio of the catalyst to the phthalate to be converted is between 0.02 wt% and 10 wt%, preferably between 1 wt% and 8 wt%, and more preferably between 1 wt% and 5 wt%.

[0129] Regardless of whether it is homogeneous or heterogeneous, the catalyst can be recycled and / or removed in this method according to methods known to those skilled in the art, and is preferably recycled. It can be separated in a downstream step of this method or in any other dedicated step to be removed or preferably recycled for the hydrolysis reaction.

[0130] The reactor used in step b) can advantageously be a stirred reactor by a mechanical stirring system and / or by a recycle loop and / or by fluidization and / or by ultrasonic stirring, for example, preferably a fully stirred batch or continuous reactor, or a drum reactor.

[0131] According to the present invention, the step b) of converting the phthalate enables the obtaining of an effluent ( Figures 1 to 3 the stream 4 in Figures 4 to 6 or the stream 24 in

[0132] which contains at least one aqueous phase, and the aqueous phase contains at least phthalic acid obtained after the hydrolysis reaction of the phthalate extracted in step a) initially contained in the liquid phase formed in step a). Figures 3 to 6 The steps a) and b) of the method according to the present invention can be carried out in the same single operation upstream of the solid-liquid separation step c) of the method according to the present invention as shown in Figures 1 to 3As shown in and as explained in more detail below constitutes the subject of two different individual operations separated by at least said step c), the individual operation of step a) is then always carried out before the individual operation of step b).

[0133] Solid-liquid separation step c)

[0134] According to the first and second variants of the process described in detail below, and according to the position of step c) relative to steps a) and b), the process according to the invention comprises a solid-liquid separation step c) between, on the one hand, a first solid phase containing phthalate-poor, preferably phthalate-free PVC plastic and, on the other hand, a phthalate-containing liquid phase extracted in step a) or a phthalic acid-containing aqueous phase obtained in step b).

[0135] The physical separation of liquid and solid phases may advantageously be carried out according to techniques known to those skilled in the art, such as, but not limited to, filtration, centrifugation (eg using a hydrocyclone), electrostatic precipitation or decantation, alone or in combination in any order.

[0136] This solid-liquid separation step c) thus makes it possible to produce at least one solid stream 8 comprising the phthalate-depleted PVC plastic extracted in step a) in order to recover the reusable target PVC plastic.

[0137] The production of a reusable target PVC as defined according to the invention may require that all or part of the solid stream 8 obtained in step c) is sent back to step a) in a number of cycles, depending on the need for the production of said target PVC plastic.

[0138] This possibility of solids stream recirculation is shown in Figures 1 to 6 middle.

[0139] For example, step c) can be carried out by centrifuging the liquid effluent 2 comprising a liquid phase from step a) containing at least the extracted phthalates and a first solid phase, so as to cause separation of said solid 8, and advantageously returning all or part of said solid to step a), preferably pre-suspended, for example by supplying an extraction solvent 9 (not shown in the figure), until a reusable target PVC plastic is produced.

[0140] According to a first variant of the process of the invention, the solid-liquid separation step c) is carried out after carrying out step a) and before carrying out step b). This first variant is shown in Figures 1 to 3In this case, the liquid effluent 2 from step a) is fed to a solid-liquid separation step c), which results in the separation of a liquid phase containing the extracted phthalate from a first solid phase containing PVC depleted in phthalate. Step c) thus produces a solid stream 8 comprising PVC plastic depleted in phthalate, and a first liquid stream 3 containing the phthalate extracted in step a), and then the first liquid stream 3 is sent to step b) to convert the phthalate by hydrolysis, or to an optional step g) below of the present invention, which is capable of completely or partially removing the extraction solvent before sending the phthalate to be converted in step b). This first variant is particularly suitable in cases where the PVC raw material to be treated leads to the formation of a solid phase during step a) that is disadvantageous for carrying out the chemical hydrolysis reaction (in terms of chemical properties or rheological properties, etc.). A preferred example of the implementation according to this variant is shown in Figure 3 In.

[0141] According to a second variant of the method of the present invention, the solid-liquid separation step c) is carried out after steps a) and b) are carried out in the same single operation. This second variant is particularly shown in Figures 4 to 6 In. In this case, the liquid effluent 24 from the simultaneous steps a) and b) is fed to the solid-liquid separation step c), which results in the separation between an aqueous phase containing at least PA obtained after the hydrolysis reaction in step b) and a first solid phase containing PVC plastic depleted in phthalate. At the end of this step c), the (aqueous and organic) liquid phases and the first solid phase containing PVC plastic depleted in phthalate are separated. The simultaneous (combined) implementation of steps a) and b) in the same single operation reduces the number of single operations required for carrying out the method according to the present invention, and thus limits the number of equipment items, the energy used, etc., and thus reduces costs. A preferred example according to this variant is shown in Figure 5 In, the simultaneous implementation of steps a) and b) is depicted by using a single step (a + b) (showing a single "box" (a + b)). In this case, the presence of water 9 during the extraction phase can advantageously modify the extraction properties that the extraction solvent 7 has when used alone. For example, the combination of the extraction solvent 7 and water 9 enables the use of an extraction solvent 7 that is initially suitable for extracting phthalates but has too high a dissolving power for the PVC resin, which is thus balanced by the presence of water, and the mixture finally has a lower dissolving power for the PVC resin.

[0142] Furthermore, for the second variant, a temperature above or equal to room temperature and below or equal to 150 °C, preferably below or equal to 145 °C, more preferably below or equal to 100 °C is preferred to prevent any degradation of the PVC resin, for example by dechlorination reactions.

[0143] At the end of all steps a), b) and c), the PA is mainly in liquid form in the aqueous phase contained in the liquid effluent 4. The liquid effluent 4 may contain one or more liquid phases, such as a single liquid phase (single-phase liquid) or two liquid phases (two-phase liquid), in particular depending on the nature of the extraction solvent (e.g., miscible or immiscible with water) and / or depending on the selected operating conditions.

[0144] Liquid-solid phase transition step d) of phthalic acid

[0145] The method according to the invention comprises step d): the PA changes from the dissolved state in the aqueous phase (liquid effluent 4) obtained at the end of all steps a), b) and c) to the solid state so that it can be recovered in the subsequent solid-liquid separation step e). This liquid-solid phase transition can advantageously be carried out by means of one or more crystallization or precipitation operations according to techniques known to those skilled in the art, such as but not limited to cold-wall crystallization, use of a precipitant, batch distillation, etc., which techniques are used alone or in any order of combination.

[0146] This liquid-solid phase transition step d) thus makes it possible to produce at least one mixed stream, which contains an aqueous liquid phase poor in phthalic acid and a second solid phase rich in phthalic acid. This is Figure 1 and 4 the stream 5 in Figure 2 and 5 the stream 19 in Figure 3 and 6 the stream 22 in.

[0147] In Figure 3 the embodiment shown in, which is one of the preferred embodiments according to the invention, by using cold-wall crystallization, the aqueous liquid effluent 21 rich in PA is cooled, for example, to a temperature between 10 °C and room temperature, for example a temperature of 15 °C, to cause precipitation of PA to obtain a mixed stream 22 containing solid PA.

[0148] Solid-liquid separation step e) for recovering PA

[0149] The method according to the invention comprises a solid-liquid separation step e) of the mixed stream (5, 19 and 22, depending on the embodiment) from step d) containing a second solid phase (solid phthalic acid) rich in phthalic acid, to produce at least a solid stream 6 containing PA for recovering PA, and a liquid effluent (11, 14 or 20, depending on the embodiment) containing the residual water from the hydrolysis step b).

[0150] This residual water may still contain phthalic acid dissolved at a low concentration.

[0151] The PA in the solid stream 6 is in powder form.

[0152] The solid-liquid physical separation of the mixture stream from step d) can advantageously be carried out according to techniques known to those skilled in the art, such as but not limited to filtration, centrifugation (e.g., using a hydrocyclone), electrostatic precipitation, or decantation, which are used alone or in any order in combination.

[0153] In Figure 3 the embodiment shown, which is one of the preferred embodiments of the present invention, the mixed effluent 22 is treated, for example, by centrifugation to obtain a solid stream 6 containing PA and an aqueous stream 14, and the aqueous stream 14 is preferably sent back in whole or in part to step b) of the process according to the present invention.

[0154] According to one or more embodiments (not shown in the figures), steps d) and e) are carried out within the same single operation.

[0155] Phthalic anhydride can be produced by sending the solid stream 6 of PA to a dehydration step, and phthalic anhydride can be the starting compound for phthalate esters used in the synthesis of PVC. The dehydration of PA to form phthalic anhydride is known, and such a dehydration step can be carried out as described, for example, in patent US3720692.

[0156] Step g) of removing the extraction solvent before (optionally) step c)

[0157] According to a first variant of the process according to the present invention, the process according to the present invention preferably includes step g), which makes it possible to remove at least a part of the extraction solvent 7 used in step a), and preferably all of said solvent. As shown, for example, in Figures 1 to 3 this step g) is carried out downstream of the solid-liquid separation step c) and upstream of step b) of the process according to the present invention. Removing (up to completely removing) the extraction solvent makes it possible to obtain a liquid effluent 12 which is at least concentrated in the phthalate esters extracted in step a) and preferably free of the extraction solvent. This liquid stream 12, which concentrates the phthalate esters, is sent to step b). This step g) promotes the hydrolysis reaction involved in step b) by a suitable displacement of the thermodynamic equilibrium of the reaction towards the formation of PA while being able to continue to obtain a liquid effluent with a rheology compatible with the various embodiments according to the present invention. In addition, the extraction solvent thus removed can be recovered and sent back at least to step a) of the process according to the present invention.

[0158] Preferably, only a part of the extraction solvent is removed in this step.

[0159] Removal of some or all of the extraction solvent 7 advantageously takes place by evaporation according to techniques known to those skilled in the art, such as distillation, evaporation, liquid-liquid separation, etc., which are used alone or in any order in combination. Step g) can thus include gas-liquid separation, preferably solvent evaporation, for example using a series of flash tanks.

[0160] When the extraction solvent comprises at least one alcohol having a straight or branched short aliphatic chain with an empirical formula C n H 2n+1 OH, it is preferred to remove the extraction solvent.

[0161] In the embodiment shown in Figure 3 , which is one of the preferred embodiments of the present invention, during the optional step g), the liquid stream 3 containing the phthalate extracted in step a) and coming from step c) is treated by evaporation to obtain a liquid stream 12 in which the phthalate is concentrated, which is itself sent to step b). The extraction solvent is generally a water-immiscible solvent, such as toluene, and is not completely removed during step g), which makes it possible to benefit from this immiscible property in the downstream steps of the process to separate the components of stream 12, in particular phthalic acid, from other compounds. The extraction solvent thus recovered is preferably recycled at least in part to step a) in the form of stream 13.

[0162] (Optional) separation step f)

[0163] Depending on the choice of extraction solvent and the various embodiments of the process according to the invention, in particular the integration with the above-mentioned optional step g), at least a liquid effluent 4 enriched in PA is obtained at the end of step b) of the process. This liquid effluent 4 contains an aqueous phase containing PA. The chemical nature and amount of the other components of the stream vary according to the embodiment chosen and may have an impact on the properties of the medium. Generally, the liquid effluent 4 can be single-phase or two-phase. The process according to the invention can thus include one or more optional liquid-liquid and / or liquid-gas separation steps upstream and / or downstream of steps d) and e) of the process according to the invention in order to:

[0164] - Facilitate the implementation of steps d) and e) and thus produce at least one solid stream 6 containing PA for the recovery of PA, and / or

[0165] - Recover the residual water (stream 14) and the extraction solvent (stream 15) from the hydrolysis step b) and send them back to the process, and / or

[0166] - Recover the possibly unreacted and / or partially reacted phthalate from the hydrolysis step b) and send it back to the process, and / or

[0167] - The recovered alcohol, which is a by-product of the hydrolysis chemical reaction, can be upgraded or combusted to generate part of the energy required by the method according to the present invention.

[0168] The optional separation step f) can 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 are determined according to the separation method selected.

[0169] In particular, one or more separation steps f) (see: steps f1) to f4) described below) are carried out directly upstream of step d) or downstream of step e) to separate at least one aqueous liquid phase (i.e., which contains water) from other compounds in the liquid or gas phase.

[0170] Some of the said compounds containing the extraction solvent, or phthalates extracted in step a) and not converted and / or partially converted in step b), or water, can be advantageously recycled to step a) or step b) respectively.

[0171] In Figures 1 to 6 are shown various separation steps f1), f2), f3), f4) and f5), and are described in more detail below.

[0172] Steps f1) and f2) are carried out directly downstream of step e). Steps f3) and f4) are carried out directly upstream of step d). Step f5) is a separation step directly downstream of separation step f4).

[0173] According to one or more embodiments of the present invention, and provided that the extraction solvent has not been completely removed from stream 3 via step g) when step g) is carried out, the solvent and the operating conditions of the method of the present invention are selected such that the solvent and water 9 form the same liquid phase of effluent 4, which contains at least AP, optionally other components: phthalates extracted in step a) and not converted, IAP and AL.

[0174] According to Figure 1 and 4 in this or these embodiments shown, the stream obtained at the end of step e) contains a solid stream 6 containing PA and a liquid effluent 11 containing residual water (from step b)), and the liquid effluent 11 is in the form of a single-phase liquid phase.

[0175] The selection of a water-miscible solvent, such as MEK or a MEK / methanol mixture, can enable the obtaining of single-phase liquid phases of effluents 4 and 11 respectively from steps b) and e) of the method.

[0176] The single-phase liquid phase 11 contains water (especially residual water from step b), an extraction solvent, and optionally phthalates, IAP, and AL that were extracted in step a) and not converted. Starting from the single-phase liquid effluent 11, then, according to separation methods known to those skilled in the art, such as distillation with a side draw stream or liquid-liquid extraction, in the process of step f1), preferably directly downstream of step e), not only the extraction solvent (stream 15) and the residual water (effluent 14) can be separated, but also AL (stream 17) can be separated, and very advantageously IAP (stream 16) that may contain phthalates extracted in step a) and not converted can be separated.

[0177] According to the first and second variants of the method according to the invention, the stream 15 containing the extraction solvent and the stream 14 containing water can then advantageously be returned to step a) and step b) of the method according to the invention, respectively. Similarly, the stream 16 containing IAP and possibly phthalates extracted in step a) and not converted is advantageously returned to step b) to continue the chemical reaction for producing PA and thereby improve the yield of PA.

[0178] According to a 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 the effluent leaving step b) forms the same liquid phase, which contains at least residual water and PA, and possibly phthalates, IAP, and AL that were extracted in step a) and not converted. Except for the fact that there is no longer an extraction solvent downstream of step g) and thus no stream 15 is produced in step f1), the steps carried out downstream are the same as steps d), e), and f1) described above. Figure 1 The steps d), e), and f1) described above.

[0179] According to one or more embodiments of the invention, and provided that the extraction solvent has not been completely removed from stream 3 during the process of step g) when step g) is carried out, the solvent and the operating conditions of the method of the invention are selected so that the solvent and water 9 form a first liquid phase of the effluent 4 containing at least AP, and also form a second liquid phase that is immiscible with the first liquid phase and contains at least phthalates extracted in step a) and not converted.

[0180] According to Figure 2 and 5 In this or these embodiments shown in, in step f3), preferably directly upstream of step d), at least two of the aforementioned immiscible phases can be separated to obtain at least one stream 18 and stream 16, the stream 18 containing the first liquid phase containing water, solvent, and PA, and the stream 16 containing the second liquid phase immiscible with the first liquid phase, which is an organic phase containing at least IAP and phthalates extracted in step a) and not converted.

[0181] 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.

[0182] The stream 16 is advantageously sent back to step b) of the process according to the invention to continue the chemical reaction for producing PA and thereby improve the yield of PA. The stream obtained at the end of step e) then comprises a solid stream 6 containing PA and a liquid effluent 20 containing residual water (from step b)), said liquid effluent 20 being in the form of a single-phase liquid phase comprising water and the extraction solvent. Starting from said single-phase liquid effluent 20, the extraction solvent (stream 15) and water (effluent 14) can then be separated, for example by distillation, in step f2) preferably directly downstream of step e), according to separation methods known to those skilled in the art, and can be advantageously reused respectively for steps a) and b) as described above Figure 1 and 4 described. According to this or these embodiments, and depending on their chemical nature, AL can be present in stream 16 from separation step f3) and / or in stream 20 from step e), and is thus removed from the process in the form of stream 17 before recycling the various streams 14, 15 and 16.

[0183] According to a 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 the effluent leaving said step b) comprises at least a first liquid phase containing at least PA and a second liquid phase immiscible with the first liquid phase containing the phthalate and AL extracted and not converted in step a). Except for the fact that there is no longer an extraction solvent downstream of step g) and thus no stream 15 is produced in step f2), the steps carried out downstream are the same as steps d), e), f2) and f3) described above Figure 2 described.

[0184] According to one or more embodiments of the invention, and provided that the extraction solvent has not been completely removed from stream 3 in step g) when step g) is carried out, the solvent and the operating conditions of the process according to the invention are chosen so that the solvent and water 9 form two immiscible liquid phases of the effluent 4. The first of these liquid phases is an aqueous phase containing at least PA; it contains 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 containing at least the phthalate, IAP and AL extracted and not converted in step a).

[0185] According to Figure 3 and 6The one or more embodiments shown in may, in step f4), preferably directly downstream of step d), separate at least two of the aforementioned immiscible phases to obtain at least one stream 21 and at least one stream 23, the stream 21 containing the aqueous liquid phase containing PA and the stream 23 containing the organic phase containing the extraction solvent.

[0186] The selection of a water-immiscible extraction solvent, such as toluene, can enable the production of the first aqueous liquid phase immiscible with the organic liquid phase containing the extraction solvent to form the effluent 4.

[0187] Carrying out steps d) and e) starting from stream 21 results in at least the production of a solid stream 6 containing PA and at least an aqueous stream 14, which is preferably sent back completely or partially to step b).

[0188] Starting from the organic liquid stream 23, during step f5), not only the extraction solvent (stream 15) but also the AL (stream 17) can be separated, and very advantageously the IAP (stream 16) that may have phthalates extracted and not converted in step a) can be separated, according to separation methods known to those skilled in the art, such as known liquid-liquid and / or liquid-gas separation methods, such as distillation, decantation, evaporation, liquid-liquid extraction, etc., carried out alone or in combination. The stream 16 can advantageously be sent back to step b) to continue the chemical reaction for producing PA and thereby improve the yield of PA. Similarly, the stream 15 can advantageously be sent back to step a).

[0189] Recycling method

[0190] The present invention also relates to a method for recycling a PVC-based object containing at least one phthalate, the recycling method comprising:

[0191] - Conditioning the PVC-based object, which includes at least grinding or chopping the PVC-based object to form a PVC raw material in the form of particles;

[0192] - Recovering PA and the reusable target PVC plastic from the PVC raw material in the form of particles according to the method of the first aspect of the present invention described in detail above.

[0193] The step of conditioning the PVC-based object may include the various steps of pre-conditioning the PVC raw material before introducing it into step a) detailed above.

[0194] From the perspective of circular economy, it is advantageous to use the phthalic acid obtained by the said recycling method to obtain again phthalates suitable for formulating flexible PVC plastics and / or to use the target PVC plastics produced by the recycling method according to the invention to manufacture new flexible PVC-based objects. Such objects can then be more easily manufactured to meet the current standards regarding phthalates and only include REACH-compatible phthalates - made from raw materials that comply or are suitable for complying with said standards, namely the recycled target PVC plastics free of non-REACH-compatible phthalates and PA capable of producing REACH-compatible phthalates.

[0195] Manufacturing method

[0196] The invention also relates to a method for manufacturing flexible PVC-based objects, said objects comprising recycled PVC plastics and / or phthalates made from phthalic acid recovered by the method according to the first aspect of the invention.

[0197] Such a manufacturing method generally comprises the steps of recovering phthalic acid and reusable target PVC plastics from PVC raw materials as detailed above, subsequently mixing said reusable target PVC plastics with additives, and then shaping the mixture. Examples

[0198] This example illustrates the invention without limiting its scope, in particular illustrates the extraction of phthalates contained in PVC plastics and the conversion of phthalates into phthalic acid in the presence of a catalyst and water.

[0199] 18.2 g of PVC plastic raw material in the form of an extrudate with an average size of 2 mm containing 4.4 g of diisodecyl phthalate (DIDP) (obtained from a PVC-based object of the "medical tubing" type) was introduced into a reactor stirred with a paddle-type mechanical stirring system. Then 53.19 g of water and 35.11 g of acetophenone (organic extraction solvent) were added, with an acetophenone / water weight ratio of 0.66, an acetophenone / DIDP weight ratio of 29.7, and a water / DIDP molar ratio of 300. Then 0.13 g of catalyst (which is p-toluenesulfonic acid) (APTS) was added to the above mixture to make the APTS / DIDP weight ratio 3%.

[0200] The reactor was hermetically sealed, purged with nitrogen, then heated to 100 °C under an autogenous pressure of about 1.2 MPa and held under these conditions with stirring at 1000 rpm for 4 hours.

[0201] After 4 hours, a solid and a liquid are obtained, which are separated while hot at 65 °C, which makes it possible to obtain 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, which results in the precipitation of a second solid consisting mainly of phthalic acid. The resulting suspension is filtered. The remaining liquid (filtrate) is then subjected to the same conditions three times as described above. At the end of each reaction step, the same precipitation step as defined above makes it possible to extract the solid phase consisting mainly of phthalic acid in order to increase the final phthalic acid yield. At the end of this procedure, the secondary solid fractions are collected together and analyzed.

[0202] 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 obtained from the conversion of DIDP and 0.30 g of monomethyl phthalate (2-(isodecyloxycarbonyl)benzoic acid) resulting from partial hydrolysis of DIDP. The liquid itself contains 2.96 g of isodecanol (C 10 H 22 O) resulting from the hydrolysis reaction of DIDP. Identification is achieved by comparing the retention times of pure analytical standards and quantification is carried out by determining the response coefficients derived from the analysis of these same standards.

[0203] The resulting solid is pre-fractionated by preparative size exclusion chromatography SEC equipped with dual optical detection (UV / visible light) and refractometry (RI). The fractions collected are analyzed by high performance liquid chromatography (HPLC) equipped with quantitative UV-visible light type optical detection. The results show that DIDP is present in the target PVC plastic at a content of less than 1000 ppm, which complies with current European regulations.

[0204] These results show that a phthalate-free PVC according to the invention has been obtained and that the conversion rate of DIDP is 99.9%. In this example, the extraction of DIDP and its conversion are carried out in the same step.

Claims

1. A method for recovering phthalic acid and reusable target PVC plastic from a PVC raw material containing at least one phthalate, comprising the following steps: a) performing solid-liquid extraction of the PVC raw material (1) in particle form by contacting the particles of the PVC raw material with at least one organic solvent (7) for extracting the phthalate to produce a liquid phase enriched with the phthalate and a first solid phase containing PVC plastic depleted of the phthalate; b) chemically converting the phthalate extracted in step a) into phthalic acid of the formula C6H4(COOH)2 by hydrolysis using water to produce an aqueous phase containing the phthalic acid; c) performing solid-liquid extraction between the first solid phase and the liquid phase enriched with the phthalate or the aqueous phase containing the phthalic acid to produce at least one solid stream (8) containing PVC plastic depleted of the phthalate to recover the target PVC plastic; d) the phthalic acid changing from a dissolved state in the aqueous phase to a solid state to produce a mixed stream (5, 19, 22) containing an aqueous liquid phase depleted of phthalic acid and a second solid phase enriched with phthalic acid; e) performing solid-liquid separation between the solid phthalic acid from step d) and the aqueous liquid phase of the mixed stream to produce a solid stream (6) of phthalic acid and a liquid effluent (11, 14, 20) containing residual water from step b).

2. The method according to claim 1, wherein steps a) and b) are carried out in the same single operation to produce a stream (24) comprising at least the aqueous phase containing the phthalic acid and the first solid phase.

3. The method according to claim 1, wherein steps a) and b) form the subject matter of two different single operations, step a) producing a stream (2) containing the liquid phase enriched with the phthalate and the first solid phase, which is sent to step c) carried out between steps a) and b), and step c) producing the stream (8) containing PVC plastic depleted of the phthalate and a first liquid stream (3) containing the liquid phase enriched with the phthalate.

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

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

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

7. The method according to any one of the preceding claims, wherein the organic extraction solvent (7) is selected from ketones, ethers, glycol ethers, cyclic and aromatic hydrocarbons, straight-chain or branched short aliphatic-chain alcohols having the empirical formula C n H 2n+1 OH where n is a non-zero natural integer, and mixtures thereof.

8. The method according to claim 7, wherein the organic extraction solvent (7) is selected from 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, isopropanol and mixtures thereof, preferably selected from the alcohols, ketone / alcohol mixtures, hydrocarbon / alcohol mixtures, cyclohexane, toluene, xylene, methoxycyclopentane, methyl isobutyl ketone, cyclopentanone, acetophenone, and preferably, the organic extraction solvent (7) is toluene, methyl ethyl ketone, acetophenone or a methyl ethyl ketone / methanol mixture.

9. The method according to any one of the preceding claims, wherein the hydrolysis in step b) is carried out in the presence of an acid hydrolysis catalyst, and the acid hydrolysis catalyst is preferably selected from inorganic Brønsted acid catalysts, preferably hydrochloric acid, sulfuric acid or phosphoric acid, organic Brønsted acid catalysts, preferably p-toluenesulfonic acid, and Lewis acid catalysts, preferably homogeneous acid catalysts such as AlF3 or heterogeneous acid catalysts selected from alumina, aluminum chloride, aluminum fluoride, mesoporous aluminosilicates, zeolites and mixtures thereof with other oxides, (H+) ion exchange resins, preferably sulfonic acid resins.

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

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

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

13. The method according to any one of the preceding claims, wherein the at least one phthalate ester of the PVC raw material is a phthalate ester of the empirical formula C6H4(COOR1)(COOR2), wherein the ester groups are in the ortho position of the benzene ring, and R1 or R2 is independently selected from straight-chain, branched-chain or cyclic alkyl chains, straight-chain or branched-chain alkoxyalkyl chains or aryl or alkylaryl chains, and R1 and / or R2 preferably contain 1 to 20 carbon atoms, or even 1 to 15 carbon atoms.

14. The method according to any one of the preceding claims, wherein the target PVC plastic does not contain the phthalate ester, and preferably contains a total of less than 0.1% by weight of phthalate esters selected from dibutyl phthalate, dioctyl phthalate or di(2-ethylhexyl) phthalate, benzyl butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate and mixtures thereof.

15. A method for recycling a PVC-based object containing at least one phthalate, comprising: - Conditioning the PVC-based object, which includes at least grinding or shredding the PVC-based object to form a PVC raw material in the form of particles; - Recovering phthalic acid and reusable target PVC plastic from the PVC raw material in the form of particles according to any one of claims 1 to 14.

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