Process for the extraction and transformation by transesterification of phthalates contained in PVC plastics

Abstract

This invention relates to a method for obtaining dialkyl phthalate and reusable target PVC plastic from a PVC raw material containing at least one phthalate, comprising: a) performing solid-liquid extraction on the PVC raw material in particulate form as follows: contacting the particles of the PVC raw material with a solvent to produce a liquid phase rich in the phthalate and a solid phase comprising PVC plastic depleted of the phthalate, the solvent comprising ester, ether, ketal or acetal chemical molecules of the empirical formula (CnH2n+1O)mZ, wherein n<4 or n>8, m is between 1 and 3, and Z (R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR and HCO, and R and R' are alkyl or aryl); b) using the solvent, converting the phthalate in the liquid phase into dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification. c) Perform solid-liquid separation between the solid phase and the liquid phase to produce at least one solid stream comprising PVC plastic that has depleted the phthalate, so as to obtain the target PVC plastic; d) Perform liquid-liquid separation of the liquid phase to produce at least a first liquid effluent comprising the dialkyl phthalate and a second liquid effluent comprising the solvent.

Description

[Technical Field]

[0001] This invention relates to the field of recycling plastics based on polyvinyl chloride (PVC), and more particularly to a conversion method for extracting and transesterifying phthalates, plasticizers included in PVC compositions. More specifically, this invention relates to a method for recovering dialkyl phthalate (DAP) and reusable target PVC plastics from PVC raw materials containing at least one phthalate. [Previous Technology]

[0002] By definition, a plastic is a mixture of a base polymer material and a large number of additives, which can be molded or shaped (usually at high temperatures and / or under pressure) to obtain a semi-finished product or object. It is generally acceptable practice to name the plastic after the polymer in which it is made. Therefore, the plastic polyvinyl chloride (PVC) actually corresponds to the polymer PVC, referred to as "PVC resin" in the remainder of this specification, combined with various additives selected according to the desired function of the plastic. These additives may be organic molecules or macromolecules or alternatively 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 recycling methods for PVC plastics: "conventional" methods of simple mechanical recycling of plastics, methods involving changes in their composition or even chemical transformation of the compounds used to make them.

[0004] Since the mid-20th century, the recycling of PVC plastics involving chemical reactions has become a subject of extensive research. In the first step, PVC resin is dissolved with additives in varying proportions. Then, in the second step, the resin is recovered using various chemical methods (precipitation, evaporation, etc.) in the presence of all or part of the soluble additives. For example, patents EP0945481, EP1268628, and EP2276801 respectively relate to the recycling of various PVC-based objects (flexible or rigid pipes, window frames, cables, etc.) and especially fiber-reinforced PVC-based objects (waterproof fabric, floor coverings, etc.) according to methods involving the following steps: First, PVC resin and soluble additives are dissolved in an organic solvent; then, in the second step, precipitation is carried out using water vapor, thereby enabling the recovery of the resin and most of the additives.

[0005] However, it is not always necessary to retain these additives in PVC recycled for reuse. For example, changes in relevant regulations over time are a determining factor. Thus, certain phthalate plasticizers, which were particularly widely used in formulating "flexible" PVC about 40 years ago, have gradually been approved in Europe under the REACH Regulation (which, since the end of 2006, aims to establish the safety of chemicals manufactured and used in European industry) and have eventually been gradually excluded from the list of permitted additives. This is particularly true of the following non-exhaustive list of phthalates: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), butyl benzoate (BBP), diisobutyl phthalate (DIBP), diamyl phthalate (DPP), diisoamyl phthalate, isoamyl phthalate, dihexyl phthalate, etc.

[0006] These new regulations now prohibit the presence of such compounds in recycled raw materials (RRM). Given that PVC-based items typically have an extremely long service life (decades), PVC-based items formulated before the end of 2006 and now at the end of their service life cannot be recycled by recycling methods, resulting in the continued presence of these prohibited additives, regardless of whether such methods are conventional, such as mechanical recycling methods, for example, the dissolution / precipitation methods mentioned above.

[0007] Furthermore, phthalate plasticizers currently used in Europe (compliant with REACH standards) and other parts of the world represent high-value-added additives, which cannot be purified when retained in recycled PVC raw materials. This is because they are expensive products, present in considerable proportions (tens of percent) in initial PVC formulations, and cannot directly impart the special flexibility properties of PVC RRM. Therefore, supplying a substantial quantity of "fresh" plasticizers is necessary for the reusability of recycled PVC materials.

[0008] The removal or purification of phthalate-type additives extracted from PVC-based objects is therefore a major challenge in optimizing the recyclability of PVC.

[0009] Several methods involving the dissolution of PVC resin have been adapted to achieve this extraction. For example, patents EP1311599 and JP2007191586 both propose a first step of dissolving the PVC resin and at least phthalate-type additives in a first organic solvent, followed by a second step of liquid-liquid extraction using a second organic solvent different from the first organic solvent to extract the phthalates from the previously obtained solution. Patent JP2007092035 discloses another possible example of the embodiment, in which the PVC resin and at least phthalate-type additives are dissolved in a solvent under supercritical conditions and the phthalates are recovered from the same solvent after the supercritical conditions "break down".

[0010] Removal or purification of phthalate-type additives from PVC plastics can also be carried out without a preparatory step of dissolving the plastic, specifically by directly extracting the phthalates from a solid polymer matrix using a suitable organic solvent, as well as clearly indicated in the following publication: Ügdüler et al., 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 (solvent properties, contact time, temperature, pressure, etc.) to achieve the best possible yield of the extracted phthalates. Although this method for removing phthalates from PVC plastics is frequently used, particularly for the detection and quantification of such specific additives in these plastics, to the applicant's knowledge, PVC-based recycling methods do not involve this technology.

[0011] While the extraction of phthalate-type plasticizers is crucial for ensuring the effective recycling of PVC plastics and obtaining reusable recycled PVC, it is insufficient to guarantee the economic viability of PVC-based object recycling methods. A primary reason often cited is the difficulty in finding an economically viable balance between the cost of the individual operations performed in the recycling process and the resale cost (equivalent to added value) of the resulting products. These products consist of naturally reproducible, phthalate-free PVC-based recycled materials and the extracted phthalates, which are difficult to purify on their own. Specifically, any recycling method involving the step of extracting phthalates from PVC-based objects can recover a mixture of phthalates that may contain phthalates that do not "comply with REACH standards." This excludes, of course, the purification of such phthalates that do not comply with REACH standards, which would require disposal as specific waste, incurring additional costs. The purification of phthalates that are inherently advantageous and compliant with REACH standards is, in practice, difficult to carry out due to the technically complex and expensive separation / purification steps involved. [Summary of the Invention]

[0012] The present invention aims to at least partially overcome the problems of the prior art and, in particular, to provide a PVC-based method for recycling objects, which allows the processing of any type of PVC raw material containing phthalates and converting it into two refinable products of interest: specific dialkyl phthalates and recyclable PVC plastic free of phthalates (especially undesirable phthalates), typically those approved under the European REACH regulation. Another object of the present invention is to limit the number of individual steps conventionally associated with phthalate separation / purification operations during the recycling of PVC containing phthalates, thereby potentially limiting the cost of the method.

[0013] Therefore, in order to achieve at least one of the above objectives, the present invention provides, in particular, a method for recovering dialkyl phthalate and reusable target PVC plastic from a PVC raw material containing at least one phthalate, according to the first state sample, comprising the following steps: a) performing solid-liquid extraction on the PVC raw material in particulate form as follows: placing the particles of the PVC raw material in contact with a solvent to produce a liquid phase rich in the phthalate and a solid phase including PVC plastic depleted of the phthalate, the solvent comprising ester, ether, ketal or acetal type chemical molecules of empirical formula (CnH2n+1O)mZ, where n and m are positive integers, wherein n < 4 or n > 8, m is greater than or equal to 1 and less than or equal to 3, and Z is selected from a list of elements consisting of: R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR and HCO, and R and R' are independently selected from straight-chain, branched-chain or cyclic alkyl or aryl groups; b) Using an ester, ether, ketal, or acetal chemical molecule of the experimental formula (CnH2n+1O)mZ, chemically convert the phthalate in the liquid phase into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification, so that the liquid phase is enriched with the dialkyl phthalate; c) Perform solid-liquid separation between the solid phase and the liquid phase to produce at least one solid stream comprising PVC plastic depleted of the phthalate, so as to recover the target PVC plastic; d) Perform liquid-liquid separation of the liquid phase to produce at least a first liquid effluent comprising the dialkyl phthalate and a second liquid effluent comprising at least the solvent.

[0014] One advantage of this invention is that the method can, by means of a chemical transesterification reaction, convert a mixture of phthalates initially trapped in the polymer matrix of various PVC-based articles into a single, REACH-compliant, and purifiable DAP-type phthalate product, regardless of the composition of the mixture (i.e., regardless of the nature and source of the various phthalates) and regardless of any other additives that may be present. The production of a single, specific DAP product from a mixture of phthalates also limits the number of individual steps associated with the separation / purification operation and thus limits costs.

[0015] According to the first variant, steps a) and b) are performed within the same individual operation.

[0016] According to the second variant, which is an alternative to the first variant, steps a) and b) form two different individual operation objects, and step a) generates a stream including liquid and solid phases.

[0017] According to this second variation, step c) can be performed between step a) and step b), including the liquid phase obtained from step a) and the solid phase stream being delivered to solid-liquid separation step c) to produce a stream of PVC plastic including the depleted phthalate and a first liquid stream including the liquid phase, the first liquid stream being delivered to step b).

[0018] According to one or more embodiments, the method also includes an additional step f1) by means of the solvent, through a transesterification reaction, to chemically convert the phthalate ester that was not converted and / or partially converted in step b) into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, wherein step f1) is carried out between steps c) and d) by delivering the liquid phase obtained at the end of all steps a), b) and c) to a first additional transesterification reactor to produce a second liquid stream rich in dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, the second liquid stream being delivered to step d).

[0019] According to one or more embodiments, the solvent is supplied and / or at least a portion of the second liquid effluent containing at least the solvent obtained from step d) is recycled to the first additional transesterification reactor.

[0020] According to one or more embodiments, in step d), the first effluent is substantially composed of the dialkyl phthalate.

[0021] According to one or more embodiments, the liquid-liquid separation step d) also produces a third effluent, which includes the ester, ether, ketal or acetal type byproduct obtained during step b) and, if applicable, a fourth effluent, which includes the phthalate ester that was partially converted and / or not converted in step b) and, if applicable, other soluble impurities. The first liquid effluent is substantially composed of the dialkyl phthalate and the second liquid effluent is substantially composed of the solvent.

[0022] According to one or more embodiments, the liquid-liquid separation step d) also produces a third effluent, which includes the ester, ether, ketal or acetal type byproduct obtained during step b), the first liquid effluent comprising the dialkyl phthalate, the partially converted and / or unconverted phthalate esters in step b) and soluble impurities present as appropriate, the second liquid effluent being substantially composed of the solvent, and the method also comprising: e) purifying the first liquid effluent to produce a liquid product substantially composed of the dialkyl phthalate, and a liquid residue comprising the partially converted and / or unconverted phthalate esters in step b) and the soluble impurities present as appropriate.

[0023] According to one or more embodiments, the method also includes an additional step f2) by means of the solvent, through a transesterification reaction, to chemically convert the unconverted and / or partially converted phthalate ester in step b) into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, which is carried out after step e) by delivering the liquid residue to a second additional transesterification reactor to produce a third liquid stream rich in dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, which is returned to step d).

[0024] According to one or more embodiments, the solvent is supplied and / or at least a portion of the second liquid effluent containing at least the solvent obtained from step d) is recycled to a second additional transesterification reactor.

[0025] According to one or more embodiments, the method also includes an additional step f1) of recycling at least a portion of the liquid residue to step b) and / or, by means of the solvent, chemically converting the phthalate that was not converted and / or partially converted in step b) into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by a transesterification reaction, wherein step f1) is carried out between steps c) and d) by delivering the liquid phase obtained at the end of all steps a), b) and c) to a first additional transesterification reactor to produce a second liquid stream rich in dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, the second liquid stream being delivered to step d).

[0026] According to one or more embodiments, a second liquid effluent containing at least the solvent obtained from step d) is at least partially recycled to steps a) and / or b).

[0027] According to one or more embodiments, the solid stream of the phthalate-based PVC plastic is at least partially recycled to step a).

[0028] According to one or more embodiments, the chemical molecule of the solvent is an ester carrying one or more alkoxy groups of the formula (CnH2n+1O) (n<4 or n>8 and m>1 and less than or equal to 3), the ester preferably selected from the list of the following compositions: carboxylic acid esters of formula (CnH2n+1O)COR, carbonates of formula (CnH2n+1O)2CO, orthoesters of formula (CnH2n+1O)3CR, imine esters of formula (CnH2n+1O)CNRR', phosphites of formula (CnH2n+1O)3P, phosphate esters of formula (CnH2n+1O)3PO, sulfites of formula (CnH2n+1O)2SO, sulfate esters of formula (CnH2n+1O)2SO2, and mixtures thereof. The limiting condition is that the esters involved in the mixture contain alkoxy groups CnH2n+1O with the same n value, and more preferably, the chemical molecule of the solvent (9) is a carboxylic acid ester of the formula (CnH2n+1O)COR (n<4 or n>8), preferably selected from the list of the following compositions: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, nonyl acetate (which may be straight-chain or branched chain), decyl acetate (which may be straight-chain or branched chain), methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, nonyl propionate (which may be straight-chain or branched chain) and decyl propionate (which may be straight-chain or branched chain), and preferably methyl acetate or methyl propionate.

[0029] According to one or more embodiments, the chemical molecule of the solvent is an ether of the formula (CnH2n+1O)R (n<4 or n>8), preferably selected from the list of the following compositions: dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dinonyl ether (which may be straight-chain or branched-chain), didecyl ether (which may be straight-chain or branched-chain), and more preferably dimethyl ether or diethyl ether.

[0030] According to one or more embodiments, the chemical molecules of the solvent are ketals or acetals of the formula (CnH2n+1O)2CRR' or (CnH2n+1O)2CRH (n<4 or n>8), preferably selected from the list of the following compositions: diacetal, 2,2-dimethoxypropane, 2,2-dimethoxybutane, diethanolacetal, 2,2-diethoxypropane and 2,2-dipropoxypropane, and more preferably diacetal, 2,2-dimethoxypropane or 2,2-dimethoxybutane.

[0031] According to one or more embodiments, the chemical molecule of the solvent is methyl propionate and the dialkyl phthalate is dimethyl phthalate.

[0032] According to one or more embodiments, the chemical conversion carried out by transesterification reaction in step b) and, if applicable, steps f1) and / or f2) is carried out using a transesterification reaction catalyst, which is preferably selected from the list of the following: inorganic or organic basic or acidic Brønsted homogeneous catalysts, or Lewis acids, and heterogeneous catalysts formed from: alkaline earth metal oxides, or alkali metal and / or alkaline earth metal carbonates or bicarbonates, or alkali metals supported on alumina or zeolite, or zinc oxide and mixtures thereof with other oxides, or ion exchange resins.

[0033] According to one or more embodiments, the at least one phthalate in the PVC raw material is a phthalate of the experimental formula C6H4(COOR1)(COOR2), wherein the ester group is located in the ortho position of the benzene ring, and R1 or R2 is independently selected from one of the elements of the following group of components: straight or branched or cyclic alkyl chain, straight or branched alkoxyalkyl chain or aryl or alkylaryl chain, and R1 and / or R2 preferably contains between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.

[0034] According to one or more embodiments, the target PVC plastic is substantially free of the phthalate and preferably contains less than 0.1% by mass of a total of phthalates selected from the list of the following compositions: dibutyl phthalate, dioctyl phthalate or diethylhexyl phthalate, butyl benzoate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

[0035] According to one or more embodiments, step b) and steps f1) and / or f2) as appropriate are performed at a temperature between room temperature and 200°C, preferably between 40°C and 180°C, at a pressure between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, for a time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours.

[0036] According to one or more embodiments, steps a) and / or b) and, as appropriate, steps f1) and / or f2) are performed such that the molar ratio between the amount of the solvent (9) and the amount of the phthalate to be extracted or converted is between 2 and 250, preferably between 4 and 90.

[0037] According to the second embodiment, the present invention relates to a method for recycling PVC-based articles containing at least one phthalate, comprising: - processing the PVC-based article, including at least grinding or crushing the PVC-based article to form PVC raw material in particulate form; - recovering dialkyl phthalate and reusable target PVC plastic from the PVC raw material in particulate form according to the present invention.

[0038] According to the third embodiment, the present invention relates to a method for manufacturing a flexible PVC-based article comprising recycled PVC plastic and / or dialkyl phthalate, the flexible PVC-based article being obtained by the method according to the present invention for recycling dialkyl phthalate and reusable target PVC plastic.

[0039] Other subject matter and advantages of the invention will become apparent upon reading the description of specific embodiments following the invention, which are given as non-limiting examples and described with reference to the accompanying drawings.

Implementation Method

[0041] Some definitions of terms are given below, but other details regarding objects defined below may be given later in the implementation.

[0042] The term "PVC-based article" means an article that comprises, and preferably is composed of, at least one type of PVC plastic, and is generally a consumer article.

[0043] The term "polyvinyl chloride plastic", also known as PVC plastic or simply PVC, means a combination of PVC polymer (also known as PVC resin) and various additives selected according to the required function of the PVC plastic, which itself is selected according to the intended application.

[0044] This PVC polymer is derived from the free radical polymerization of vinyl chloride (VCM), the vinyl chloride monomer itself being obtained from chlorine and ethylene. Depending on the method of polymerization, four types of PVC resins may be used: 1) suspension PVC or S-PVC resin (suspension polymerization of VCM); 2) emulsion PVC or PVC "paste" resin (emulsion polymerization); 3) block PVC or M-PVC resin (block polymerization); and 4) hyperchlorinated PVC or C-PVC resin, which are obtained by post-treatment of the aforementioned resins by hyperchlorination.

[0045] The additives included in the composition of PVC plastic may be organic molecules or macromolecules or alternatively inorganic (nano) particles and are used according to the properties they provide to the PVC resin: heat resistance, light resistance or mechanical stress resistance (stabilizer), flexibility (plasticizer), processability (lubricant), coloring (dye / pigment), etc.

[0046] The term "phthalate esters" refers to a group of chemical products formed from dicarboxylic acid esters of o-phthalic acid. They consist of a benzene ring and two carboxylic acid ester groups located ortho-to the benzene ring. They can be described by the following formula: [Chemical Formula 1]

[0047] Alternatively, it may be of the empirical formula C6H4(COOR1)(COOR2), wherein R1 and R2 are independently selected from one of the elements of the following group of constituents: straight-chain, branched-chain, or cyclic alkyl chain, straight-chain or branched-chain alkoxyalkyl chain, or aryl or alkylaryl chain. The alkyl, alkoxyalkyl, aryl, or alkylaryl chain may generally comprise between 1 and 20 carbon atoms, or may even comprise between 1 and 15 carbon atoms.

[0048] For example, R1 and / or R2 may be selected from ethyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, isodecyl, methoxyethyl, and benzyl. Phthalate esters are commonly used as plasticizers for plastics, and more specifically as plasticizers for PVC-type plastics, particularly to make them flexible.

[0049] In this specification, the term "transesterification reaction" refers to a chemical reaction used to convert the carboxylic acid ester functional group -COOR1 or -COOR2 of at least one phthalic acid ester as defined above into a new carboxylic acid ester functional group COO(CnH2n+1) (n<4 or n>8), regardless of the reagents used.

[0050] In this specification, the term "dialkyl phthalate" (DAP) refers to a product of empirical formula C6H4(COOCnH2n+1)2, which is produced by a plasticizer of at least one phthalate type (specifically, empirical formula C6H4(COOR1)(COOR2) as described above) and any chemical molecule of empirical formula (CnH2n+1O)m2 of ester, ether, ketal or acetal type (also referred to as "reagent" in the remainder of this specification) present in PVC-based articles. The chemical molecule is produced by transesterification between a solvent and a group consisting of n and m, where n and m are positive integers such that n < 4 or n > 8 and m is greater than or equal to 1 and less than or equal to 3, and Z is a group selected from a list of elements consisting of R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR, and HCO, wherein R and R' are independently selected from (straight-chain, branched-chain, or cyclic) alkyl or aryl groups, for example containing between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms. The chemical molecule is described in more detail later in the specification. Dimethyl phthalate is an example of DAP.

[0051] The term "ester, ether, ketal, or acetal type byproduct" (BP) means a byproduct of formula R1OZ or R2OZ produced by transesterification of at least one phthalate-type (specifically, of formula C6H4(COOR1)(COOR2) as described above) plasticizer present in PVC-based articles with a reagent (an ester, ether, ketal, or acetal type chemical molecule of formula (CnH2n+1O)mZ as defined above). The definitions of R1 and R2 are the same as those of phthalate R1 and R2. The definition of Z is the same as that of reagent Z.

[0052] The term "intermediate phthalate" (IAP) means a byproduct of empirical formula C6H4(COOR1)(COOCnH2n+1) or C6H4(COOR2)(COOCnH2n+1), which is produced by an incomplete transesterification reaction between at least one phthalate-type plasticizer (specifically, empirical formula C6H4(COOR1)(COOR2) as described above) and a reagent (an ester, ether, ketal, or acetal chemical molecule of empirical formula (CnH2n+1O)mZ as defined above) present in PVC-based articles. R1 and R2 are defined the same as R1 and R2 for phthalates. Z is defined the same as Z for the reagent.

[0053] The term "reusable target PVC plastic" means "phthalate-free PVC," that is, a solid comprising at least one PVC resin supplemented with at least one additive originally present in the PVC plastic of the PVC raw material processed according to the present invention, wherein the phthalates therein have been extracted and converted into at least one phthalate dialkyl ester form according to the present invention. The term "phthalate-free" specifically means that the solid PVC obtained as a product of the method according to the present invention contains less than 0.1% by weight of phthalates in total, which has been approved in Europe by the REACH Regulation (Annex XIV of Regulation (EC) 1907 / 2006 of the European Parliament and Council of 18 December 2006), specifically, less than 0.1% by weight of phthalates alone or in mixtures, selected from the following phthalates. List of ester compositions: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), butyl benzoate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate.

[0054] 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 "<".

[0055] In this specification, the exponents "n" and "m" in the chemical formulas referenced are positive integers (i.e., strictly greater than zero). According to the invention, n is less than 4 or greater than 8, and preferably less than or equal to 20, or even less than or equal to 15. According to the invention, m is an integer greater than or equal to 1 and less than or equal to 3.

[0056] In this specification, the term "room temperature" (rt) means a temperature of 20°C ± 5°C, and the term "atmospheric pressure" means a pressure of 0.101325 MPa.

[0057] In this specification, the term "comprising" is synonymous with "including" and "containing" (meaning the same thing), and is inclusive or open-ended and does not exclude other unspecified elements. It should be understood that the term "comprising" includes exclusive and closed terms such as "consisting of".

[0058] In this specification, the phrase "between ... and ..." means that the limit value of the interval is included in the range of values ​​described, unless otherwise stated.

[0059] In this specification, various ranges of parameters for a given step can be used individually or in combination, such as pressure ranges and temperature ranges. For example, in this specification, a preferred pressure range can be combined with a preferred temperature range.

[0060] Specific embodiments of the invention may be described herein. Where technically feasible, these embodiments may be implemented separately or in combination without limitation.

[0061] The following description of the method according to the present invention refers to the flowcharts in Figures 1 to 8, which illustrate various embodiments of the method according to the present invention.

[0062] According to the present invention, a method for recovering DAP and reusable target PVC plastic from PVC raw material containing at least one phthalate includes the following steps and may be composed of the following steps: a) performing solid-liquid extraction on the PVC raw material in particle form as follows: placing the particles 1 of the PVC raw material in contact with solvent 9 to produce a liquid phase rich in the phthalate and a solid phase including PVC plastic depleted of the phthalate, the solvent comprising at least one ester, ether, ketal or acetal chemical molecule of empirical formula (CnH2n+1O)mZ, wherein n and m are positive integers, wherein n < 4 or n > 8, m is greater than or equal to 1 and less than or equal to 3, and Z is a group selected from a list of elements consisting of: R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR and HCO, and R and R' are independently selected from straight chain, branched chain or cyclic alkyl or aryl; b) Using an ester, ether, ketal, or acetal chemical molecule of the experimental formula (CnH2n+1O)mZ, the phthalate in the liquid phase is chemically converted to a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification, so that the liquid phase is enriched with the dialkyl phthalate; c) Solid-liquid separation is performed between the solid phase and the liquid phase to produce at least one solid stream 6 comprising PVC plastic depleted of the phthalate, for the purpose of recovering the target PVC plastic; d) Liquid-liquid separation is performed on the liquid phase 4 to produce at least a first liquid effluent (5 or 14) comprising the dialkyl phthalate and at least a second liquid effluent (7 or 12) comprising at least the solvent.

[0063] The raw material is fed into the method according to the invention, referred to as "PVC raw material" 1, which contains at least one PVC plastic, which must contain at least one phthalate as described in the invention.

[0064] The PVC plastic may include at least 0.1% by weight of phthalates, or even at least 1% by weight of phthalates, or an additional at least 5% by weight of phthalates. Generally, PVC plastics advantageously contain less than 60% by weight of phthalates, typically less than 30% by weight of phthalates.

[0065] The PVC raw material is advantageously a "production waste" type of recycled PVC raw material, that is, waste generated during the polymerization of the method used to produce PVC polymer, or waste generated during the formulation / forming of PVC plastic, or waste generated during the production of PVC-based articles, or "post-consumer waste" type waste, that is, waste generated after the user consumes the PVC-based article.

[0066] In detail, the recycled PVC raw material may be derived from any existing collection and sorting channel or network used for production waste and / or post-consumer waste, thereby enabling the separation of the stream based on at least one PVC plastic containing at least one phthalate, particularly for collection and sorting channels or networks specifically designed for plastic waste.

[0067] Therefore, PVC raw materials that are typically of the "production waste" type and / or "post-consumer waste" type generally originate from the main application areas using PVC plastics, such as (in a non-exhaustive manner): the construction and building industry, packaging, motor vehicles, electrical and electronic equipment, sports, medical equipment, etc. Preferably, the PVC raw materials originate from the construction and building industry. More precisely, PVC-based articles are typically used in these fields as various rigid profiles (windows, doors, canopies, roller blind housings), pipes and connectors, and rigid bottles, sheets and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc. Preferably, the PVC-based articles forming the PVC raw materials contain at least one "flexible" PVC, that is, PVC containing plasticizer-type (preferably phthalate-type) additives, such as the following PVC-based articles: flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.

[0068] 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 plastic containing at least one phthalate.

[0069] Preferably, the PVC raw material includes "flexible" PVC, that is, PVC containing plasticizer-type (preferably phthalate-type) additives.

[0070] Even better, the PVC raw material mainly or even only contains "flexible" PVC, that is, PVC containing plasticizer-type (preferably phthalate-type) additives.

[0071] The PVC raw material processed in the method for recycling DAP and reusable target PVC plastic according to the invention is in particulate form. Therefore, if the PVC raw material is in an initial form specifically for use as production waste or post-consumer waste, particularly in the latter case, in the initial form of PVC-based articles, it can first undergo a processing step including at least grinding or crushing to form PVC raw material in particulate form. Depending on the channel and / or network from which such production waste and / or PVC-based articles originate at the end of their service life, the PVC waste can be ground and / or washed and / or subjected to any other processing steps described below to form PVC raw material in particulate form suitable for the method according to the invention. For example, the PVC raw material can advantageously be in a ground and, whereby washed, material form with a maximum size less than 20 cm, preferably less than 10 cm, preferably less than 1 cm, and even more preferably less than 5 mm. PVC raw materials can also advantageously be in the form of micronized solids, i.e., in particle form, with an average size preferably 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 circumcircle of the spheres of these particles.

[0072] Therefore, the term "PVC raw material in particle form" means that the average size of PVC plastic particles, as defined above, is between 10 µm and 20 cm, for example, the average size of abrasive material particles is 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 the average size of particles obtained by micronization (extremely fine grinding to produce powder) is less than 1 mm, preferably between 10 µm and 800 µm.

[0073] Preferably, the PVC raw material processed by the method according to the present invention is in the form of particles of the abrasive material type, with an average particle size preferably between 1 mm and 5 mm, or the average particle size obtained by micronization (extremely fine grinding to produce powder) is less than 1 mm.

[0074] PVC raw materials may also contain "macro" impurities, such as glass, metal, plastics other than PVC (e.g., PET), wood, paper, cardboard, mineral elements, etc. Advantageously, PVC raw materials contain no more than 50% by mass, preferably no more than 30% by mass, preferably no more than 10% by mass, and even more preferably no more than 5% by mass of "macro" impurities.

[0075] Advantageously, the moisture content of the PVC raw material in particle form is less than or equal to 0.3% by mass and preferably less than or equal to 0.1% by mass.

[0076] The various steps of the method according to the invention for producing DAP and reusable target PVC plastic are detailed in the following paragraphs.

[0077] Preparatory Steps for Processing PVC Raw Materials According to the present invention, the method may include preparatory steps for processing PVC raw materials (not shown in the figures), which include at least one step of grinding or crushing the PVC raw material to form PVC raw material in the form of solid particles as defined above, which may be delivered to the solid-liquid extraction step a). This pretreatment step may also include one or more steps mentioned in the following non-exhaustive list: by micronization grinding, sorting, over-sorting, washing, drying, etc. Depending on the nature of the PVC raw material being processed, the steps involved in the pretreatment step and their possible frequency and sequence are specifically selected by those skilled in the art in order to limit the amount of macroscopic impurities and reduce the size of the solid components initially constituting the PVC raw material.

[0078] For example, the pretreatment step may provide PVC raw material in particle form, such as washed and milled material with an average size of less than 5 mm, wherein the macroscopic impurity content preferably does not exceed 10% by mass and more preferably does not exceed 5% by mass. The pretreated PVC raw material may also be in the form of micronized solid particles, that is, in the form of particles with an average size of less than 1 mm, for example, between 10 µm and 800 µm.

[0079] The pretreatment step of the PVC raw material preferably includes at least one step of drying the PVC raw material into solid particles with a specific size and macroscopic impurity content, such that the residual moisture content of the PVC raw material does not exceed 0.3% by mass and preferably does not exceed 0.1% by mass.

[0080] Step a) Solid-liquid extraction of phthalates According to the method of the present invention, the solid-liquid extraction of phthalates in PVC raw material 1 in particulate form is performed by: contacting the raw material 1 with a solvent 9 to obtain an effluent 2 comprising at least a liquid phase and a solid phase, the solvent comprising, and preferably comprising, esters, ethers, ketals or acetals of the empirical formula (CnH2n+1O)mZ, wherein n < 4 or n > 8, m is greater than or equal to 1 and less than or equal to 3, and Z is a group selected from a list of elements consisting of: R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR and HCO, wherein R and R' are independently selected from (straight-chain, branched-chain or cyclic) alkyl or aryl groups, for example, alkyl or aryl groups containing between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.

[0081] In detail, in the formula (CnH2n+1O)mZ: When m=1, Z is selected from R, COOR, COR, CNRR', HCO; When m=2, Z is selected from CO, SO, SO2; When m=3, Z is selected from PO, P, CR.

[0082] The liquid phase is therefore rich in the phthalate, and the solid phase includes PVC plastic that has depleted the phthalate.

[0083] The specific selection of n for the solvent ester, ether, ketal or acetal type chemical molecule (alkyl chain CnH2n+1, excluding C4, C5, C6, C7 and C8 chains) makes it possible to convert such phthalates into at least one DAP as defined in this specification by means of the ester, ether, ketal or acetal type chemical molecule via a transesterification reaction during step b), which is not a non-desired phthalate such as those phthalates approved under the REACH regulation discussed above.

[0084] According to one or more embodiments, the ester, ether, ketal or acetal type chemical molecule has the empirical formula (CnH2n+1O)mZ, wherein n<4, preferably n=1 or n=2, and even more preferably n=1.

[0085] According to one or more embodiments, the ester, ether, ketal or acetal type chemical molecule has the empirical formula (CnH2n+1O)mZ, wherein n>8 and n< or equal to 20, or even n< or equal to 15.

[0086] Preferably, n is an integer such that n < 4 and more preferably n equals 1 or 2.

[0087] According to one or more embodiments, the chemical molecule is an ester carrying one or more alkoxy groups of the formula (CnH2n+1O)m, wherein n < 4 or n > 8 and m is greater than or equal to 1 and less than or equal to 3.

[0088] The ester is preferably selected from the following list of compositions: carboxylic acid esters of formula (CnH2n+1O)COR, carbonates of formula (CnH2n+1O)2CO, orthoesters of formula (CnH2n+1O3CR, imine esters of formula (CnH2n+1O)CNRR', phosphites of formula (CnH2n+1O)3P, phosphate esters of formula (CnH2n+1O)3PO, sulfites of formula (CnH2n+1O)2SO, and so on. Sulfated esters of (CnH2n+1O)2SO2, formate esters (alkyl formates) of the formula (CnH2n+1O)HCO, such as ethyl formate or methyl formate, and mixtures thereof, provided that the esters involved in the mixture contain alkoxy groups CnH2n+1O with identical n values. This list of esters is not exhaustive. Groups R and R' are independently selected from (straight-chain, branched-chain, or cyclic) alkyl or aryl groups, for example containing between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.

[0089] Preferably, the ester-type chemical molecule is a carboxylic acid ester of the formula (CnH2n+1O)COR (where n such that n<4 or n>8), selected from the list of the following compositions: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, nonyl acetate (straight-chain or branched-chain), decyl acetate (straight-chain or branched-chain), methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, nonyl propionate (straight-chain or branched-chain), and decyl propionate (straight-chain or branched-chain). The ester-type chemical molecule is even more preferably methyl acetate or methyl propionate.

[0090] According to one or more embodiments, the chemical molecule is an ether of the formula (CnH2n+1O)R (n<4 or n>8), preferably selected from the list of the following compositions: dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dinonyl ether (straight-chain or branched-chain), and didecyl ether (straight-chain or branched-chain). Preferably, the chemical molecule is dimethyl ether or diethyl ether. The ether may also be cyclopentylmethyl ether (CPME).

[0091] According to one or more other embodiments, the chemical molecule is a ketal or acetal of the formula (CnH2n+1O)2CRR' or (CnH2n+1O)2CRH, wherein n < 4 or n > 8 and R and R' are independently selected from (straight-chain, branched-chain, or cyclic) alkyl or aryl groups. The ketal or acetal chemical molecule is preferably selected from the list of the following compositions: diacetal, 2,2-dimethoxypropane, 2,2-dimethoxybutane, diethanolacetal, 2,2-diethoxypropane, and 2,2-dipropoxypropane. Preferably, the ketal or acetal type chemical molecule is diacetal, 2,2-dimethoxypropane, or 2,2-dimethoxybutane.

[0092] Preferably, the solid-liquid extraction step a) of the phthalate of PVC raw material 1 is carried out by contacting the raw material 1 in particle form with methyl acetate or methyl propionate (e.g., methyl propionate). In this case, the DAP produced by this method is dimethyl phthalate (DMP).

[0093] The solid-liquid extraction step of phthalate in PVC raw material 1 is preferably carried out under the following operating conditions: temperature between room temperature and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C; 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; residence time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.

[0094] Preferably, step a) is performed such that the molar ratio between the amount of ester, ether, ketal or acetal chemical molecules in solvent 9 and the amount of phthalate to be extracted from PVC raw material 1 is between 2 and 250, more preferably between 4 and 90, and even more preferably between 4 and 30.

[0095] The reactor in step a) of the method according to the invention may advantageously be a reactor type that utilizes a mechanical stirring system and / or a recirculation loop and / or fluidized stirring, such as a discontinuous or continuous fully stirred reactor, or a rotary drum reactor.

[0096] In practice, it is advantageous for the PVC raw material 1 to be mixed with the solvent 9 in particulate form.

[0097] According to the first option, the mixing can be carried out before the feedstock and solvent are introduced into the reactor of the solid-liquid extraction step a). In this case, the mixture can be formed in a mixer and subsequently introduced into the reactor, which is maintained at the desired pressure and temperature.

[0098] According to the second option, the PVC raw material 1 in particulate form and the solvent 9 can be introduced into the reactor of step a) of the method according to the invention. Subsequently, preferably, the solid PVC raw material and solvent are injected into the reactor via two separate pipelines, one allowing the injection of solvent 9 and the other allowing the injection of solid PVC raw material 1 in particulate form. In this case, the mixture of PVC raw material and solvent is formed directly in the reactor.

[0099] According to the present invention, the solid-liquid extraction step a) can obtain at least one effluent 2, which comprises at least a liquid phase containing at least the extracted phthalates and at least a solid phase containing at least the PVC plastic depleted of phthalates (preferably free of phthalates).

[0100] Step b) of the chemical conversion of such phthalates The method according to the invention includes step b) of chemically converting the phthalates extracted in step a) into at least one DAP of the formula C6H4(COOCnH2n+1)2 by transesterification reaction, wherein the transesterification reaction is preferably carried out in a liquid phase, between the phthalate obtained from the liquid phase of step a) and a solvent 9 of the empirical formula (CnH2n+1O)mZ of the ester, ether, ketal or acetal type chemical molecule (as defined above in step a), including all preferred terms of the molecule, as defined in step a) with respect to the solvent 9.

[0101] Step b) of converting the phthalate present in the liquid phase into DAP of formula C6H4(COOCnH2n+1)2 by transesterification at the end of step a) is preferably carried out under the following operating conditions: temperature between room temperature and 200°C, preferably between 40°C and 180°C, more preferably between 60°C and 150°C; 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; residence time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.

[0102] Preferably, step b) is performed such that the molar ratio between the amount of ester, ether, ketal or acetal type chemical molecules in solvent 9 and the amount of phthalate to be converted in the liquid phase containing phthalate extracted at the end of step a) is between 2 and 250, more preferably between 4 and 90, and even more preferably between 4 and 30.

[0103] The solvent used for step b) is the same as the solvent used for step a).

[0104] Preferably, step b) of chemically converting the phthalate extracted in step a) into DAP of formula C6H4(COOCnH2n+1)2 by transesterification reaction is carried out in the presence of a transesterification reaction catalyst, which is advantageously introduced into the reaction medium.

[0105] The catalyst used in this transesterification reaction is selected from, for example, a non-exhaustive list of catalysts known to those skilled in the art, and preferably from the list of the following compositions: - Homogeneous catalysts, such as basic catalysts (sodium hydroxide or potassium hydroxide, sodium methoxide or potassium carbonate, sodium carbonate or potassium carbonate, etc.), Brønsted inorganic acid catalysts (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), Brønsted organic acid catalysts (methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, etc.), Lewis acid catalysts, particularly including boron compounds (BH3, BF3) and aluminum compounds (AlF3, AlCl3), and organometallic compounds; - Heterogeneous catalysts, such as alkaline earth metal oxides (CaO, BaO, etc.), alkali metal and / or alkaline earth metal carbonates or bicarbonates (CaCO3, etc.), alkali metals supported on alumina or zeolites, zinc oxides and mixtures thereof with other oxides (e.g., zinc oxide and alumina), ion exchange resins (cationic or anionic), such as sulfonic acid resins, etc.

[0106] For example, the catalyst used according to the present invention is a homogeneous catalyst, particularly a basic catalyst type homogeneous catalyst, such as sodium methoxide.

[0107] When the chemical molecule is an ester as defined in step a) above, the ester of the detailed formula (CnH2n+1O)COR (where n makes n<4 or n>8) is preferably selected from the list of the following compositions: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, nonyl acetate (straight-chain or branched-chain), decyl acetate (straight-chain or branched-chain), methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, nonyl propionate (straight-chain or branched-chain), decyl propionate (straight-chain or branched-chain), for example methyl acetate or ethyl acetate. The preferred catalyst is a homogeneous catalyst, especially a basic homogeneous catalyst, such as sodium methoxide.

[0108] When the chemical molecule is an ether as defined in step a) above, the ether of the formula (CnH2n+1O)R (n<4 or n>8) is preferably selected from the list of the following compositions: dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dinonyl ether (straight or branched), didecyl ether (straight or branched) and cyclopentylmethyl ether, such as dimethyl ether or diethyl ether. The preferred catalyst is a homogeneous catalyst, especially an acid catalyst, usually a Brønsted organic acid catalyst, such as methanesulfonic acid, trifluoromethanesulfonic acid or trifluoroacetic acid.

[0109] When the chemical molecule is a ketal or acetal as defined in step a) above, specifically (CnH2n+1O)2CRR' or (CnH2n+1O)2CRH (n<4 or n>8, and R and R' are independently selected from (straight-chain, branched-chain or cyclic) alkyl or aryl), the ketal or acetal chemical molecule is preferably selected from the list of the following compositions: diacetal, 2,2-dimethoxypropane, 2,2-dimethoxybutane, diethanolacetal, 2,2-diethoxypropane and 2,2-dipropoxypropane, for example diacetal, the preferred catalyst is a homogeneous catalyst, especially an acid catalyst, usually a Brønsted organic acid catalyst, such as methanesulfonic acid, trifluoromethanesulfonic acid or trifluoroacetic acid.

[0110] Preferably, the amount of catalyst introduced is such that the mass ratio between the catalyst and the phthalate to be converted is between 0.5% by mass and 15% by mass, more preferably between 1% by mass and 10% by mass, and even more preferably between 1% by mass and 8% by mass.

[0111] The catalyst, whether homogeneous or heterogeneous, may be recycled and / or removed in the process according to methods known to those skilled in the art, and preferably recycled. It may be separated, removed or preferably recycled for transesterification reaction in downstream steps of the process, such as in step c), step d) and / or step e), or in any other dedicated step.

[0112] The reactor in step b) of the method according to the invention may advantageously be a reactor type that utilizes a mechanical stirring system and / or a recirculation loop and / or fluidization, such as a discontinuous or continuous fully stirred reactor, or a rotary drum reactor.

[0113] According to the present invention, step b) of converting phthalates makes it possible to obtain at least one effluent containing at least one liquid phase containing at least one DAP of the formula C6H4(COOCnH2n+1)2 obtained after the transesterification reaction, i.e., a liquid phase formed at the end of step a) and rich in DAP in step b).

[0114] According to the method of the present invention, steps a) and b) can be performed in the same individual operation or can be two different and consecutive individual operations, and the individual operation of step a) is always performed before the individual operation of step b).

[0115] In the embodiments presented in Figures 1 to 5, steps a) and b) are characterized as separate "blocks," but may be performed in the same individual operation or may be two distinct and consecutive individual operations. In the first case, the effluent 2 is present, for example, in the same reactor used for performing steps a) and b).

[0116] In the embodiment presented in FIG6 (which is one of the preferred embodiments according to the present invention), steps a) and b) are the same individual operation objects, which are characterized by using a single "box" (a+b).

[0117] In the embodiments shown in FIG7 and FIG8, the embodiment of FIG8 is one of the preferred embodiments of the present invention, steps a) and b) form two different and consecutive individual operations, which correspond to the flowchart of step c) between steps a) and b), as described below.

[0118] Step c) Solid-liquid separation The method according to the invention includes step c) of solid-liquid separation between a liquid phase and a solid phase, wherein, on one hand, the liquid phase contains the phthalates extracted in step a) and / or the DAP of formula C6H4(COOCnH2n+1)2 obtained after the transesterification reaction in step b), and on the other hand, the solid phase contains PVC plastic that is depleted of phthalates (preferably free of phthalates).

[0119] The physical separation of the liquid and solid phases can be carried out according to techniques known to those skilled in the art, such as (in a non-exhaustive manner) filtration, centrifugation, electrostatic precipitation or decantation, which may be used alone or in combination in any order.

[0120] This step c) of solid-liquid separation thus makes it possible to generate at least one solid stream (6) comprising the phthalate-depleted PVC plastic extracted in step a) in order to recycle the reusable target PVC plastic.

[0121] The production of reusable target PVC as defined in the present invention may require returning all or part of the solid stream (6) obtained in step c) to step a), if necessary, through multiple cycles, in order to produce the target PVC plastic.

[0122] This possibility of recycling solid flow is shown in Figures 2 to 8.

[0123] According to a first variation of the method of the present invention, the solid-liquid separation step c) is performed after steps a) and b). This first variation is illustrated in Figures 1 to 6. In this case, the liquid effluent 3 obtained from step b) is delivered to the solid-liquid separation step c), which causes the liquid phase containing at least the DAP obtained after the transesterification reaction in step b) to separate from the solid phase containing the depleted phthalate PVC plastic. It is advantageous for this first variation of the method of the present invention that steps a) and b) are performed together in the same individual operation. This particular embodiment reduces the number of individual operations required to perform the method of the present invention, and thus reduces the number of equipment items, the amount of solvent used, the energy involved, etc., and thus reduces costs. A preferred example of an embodiment according to this variation is illustrated in Figure 6.

[0124] According to a second variation of the method of the present invention, the solid-liquid separation step c) is performed after step a) and before step b). This second variation is specifically illustrated in Figures 7 and 8. In this case, the liquid effluent 2 obtained from step a) is delivered to the solid-liquid separation step c), thereby causing the separation of the liquid phase containing the extracted phthalates from the solid phase containing the PVC depleted of phthalates. Thus, for this second variation, steps a) and b) become two separate individual operations. Step c) thereby produces a solid stream 6 comprising the PVC plastic depleted of phthalates and a first liquid stream 18 containing the phthalates extracted in step a) and then delivered to step b) to convert the phthalates by transesterification. This second variation is particularly suitable where the PVC raw material to be treated would result in the formation of a solid phase during step a), which is detrimental to the transesterification chemical reaction (in terms of chemical or rheological properties, etc.).

[0125] For example, according to an embodiment of this second variation of the method shown in Figures 7 and 8, step c) is performed between steps a) and b), and steps a) and c) according to the invention can be performed continuously in the same discontinuous reactor having means for filtering liquid effluent 2, thereby allowing several cycles of self-solid phase extraction of phthalates, and means for at least extracting solid phase 6, thereby allowing the final recovery of the target PVC plastic.

[0126] In another example, step c) may be performed by centrifuging the liquid phase containing at least the extracted phthalates and / or DAP with the liquid effluent 2 or 3 obtained from the solid phase of step a), such that the solid 6 is separated, and advantageously, all or part of the solid is returned to step a), preferably pre-placed in a suspension, for example by means of supplying solvent 9 (not shown), until a reusable target PVC plastic is produced.

[0127] Liquid-liquid separation step d) The method according to the invention includes a liquid-liquid separation step d) for DAP of liquid-phase extractive C6H4(COOCnH2n+1)2 obtained at the end of at least steps a), b) and c).

[0128] The liquid stream (4, 13) containing the liquid phase is advantageously fed into this liquid-liquid separation step d), thereby making it possible to produce a first liquid effluent (stream 5 or 14 according to the diagram) containing at least DAP and a second liquid effluent (stream 7 or 12 according to the diagram) containing at least the solvent.

[0129] Liquid-liquid separation step d) can be performed according to methods familiar to those skilled in this technique, such as (in a non-detailed manner) distillation, decantation, evaporation, liquid-liquid extraction, etc., performed alone or in combination. The operating conditions (temperature, pressure, etc.) for this step are determined according to the selected separation method.

[0130] According to one or more embodiments, the first effluent 5 is substantially composed of the DAP. In this case (such cases), the second liquid effluent 7 (e.g., shown in FIG. 1 (or as an option in FIG. 3)) consists of the residual liquid phase after the extraction of the DAP, which contains at least a solvent, ester, ether, ketal or acetal type byproduct (BP), intermediate alkyl phthalate (IAP), and possibly unconverted phthalate esters extracted at the end of step a) of the method according to the invention. The second liquid effluent 7 may be returned wholly or partially, preferably wholly, to step b) of the method according to the invention.

[0131] In this case (such case), depending particularly on the selected liquid-liquid separation method (e.g., by side-extraction distillation or liquid-liquid extraction), it is also possible not only to separate the solvent from the liquid phase, but also to separate BP and, extremely advantageously, to separate IAP, wherein, if present, the unconverted phthalates extracted in step a). Such separation is illustrated, for example, in Figure 2 or Figure 7 (and as an alternative to the product stream 7 in Figure 3), where it can be found that, in addition to the first effluent 5, which is essentially composed of the DAP, and the second effluent 12, which is essentially composed of the solvent, step d) also produces a third effluent 10 and a fourth effluent 11, the third effluent comprising the BP obtained during the transesterification reaction in step b), and the fourth effluent comprising partially converted phthalates (IAP) and / or unconverted phthalates from step b) and possibly other soluble impurities. The fourth effluent 11 can then be advantageously returned to step b) of the method according to the invention, particularly the first and second variations of the method according to the invention, in order to continue the chemical reaction, thereby producing DAP and thus improving the yield of this product.

[0132] According to one or more alternative embodiments, as shown in Figures 4 to 6 and Figure 8, the first liquid effluent 14 comprising DAP also contains other compounds, such as partially converted phthalates (IAP) and / or unconverted phthalates and / or soluble impurities (e.g., IAP) in step b). As described later, according to this or such embodiments, a step of purifying the DAP in the first effluent is required. According to this or such embodiments, the liquid-liquid separation step d) thus advantageously produces the first liquid effluent 14 of impure DAP, a second liquid effluent 12 preferably composed substantially of the solvent, and a third effluent 10 comprising BP obtained during the transesterification reaction in step b). Depending on the selected liquid-liquid separation method, such as side-extraction distillation or liquid-liquid extraction, the separation of BP from the solvent becomes significantly possible. In cases where the second liquid effluent 12 is substantially composed of the solvent thus recovered, it is advantageous to then return part or all, preferably all, of the second liquid effluent 12 to steps a) and / or b) of the method according to the invention, and particularly to the first and second method variations according to the invention.

[0133] DAP purification step e) (as appropriate) The method according to the invention may include the following step e) selected as appropriate: purifying the first effluent 14 containing DAP obtained from the liquid-liquid separation step d) to improve its quality and thus ultimately improve its purification. The embodiments shown in Figures 4, 5, 6 and 8 illustrate implementation of this purification step e).

[0134] When performing step e), the solvent is advantageously separated during the implementation of step d). Furthermore, the IAP extracted at the end of step a) of the method according to the invention and the phthalates present thereas that are not converted at the end of step b) may be separated during step d) of the method according to the invention, or alternatively separated during the implementation of the purification step e).

[0135] Therefore, a first effluent 14 containing DAP, phthalates partially converted and / or unconverted in step b), and possibly soluble impurities can be delivered to this purification step e) to form a liquid product 16 consisting substantially of the DAP and a liquid residue 17 containing phthalates partially converted and / or unconverted in step b) and possibly soluble impurities.

[0136] The liquid residue 17 recovered therefrom can then be advantageously returned to step b) of the method according to the invention, particularly the first and second variations of the method according to the invention, so as to continue the chemical reaction to produce DAP, as illustrated in FIG4 or FIG5.

[0137] Purification step e) can advantageously be carried out by methods well known to those skilled in the art, such as precipitation, crystallization, or adsorption, followed by filtration or centrifugation, as appropriate. Purification step e) may include the parallel or sequential execution of several of these methods. For example (and not exhaustively), purification step e) may include precipitation and filtration followed by adsorption, or alternatively adsorption and filtration followed by precipitation, or alternatively crystallization and filtration. The operating conditions (temperature, pressure, etc.) of this step e) are determined according to the purification method selected.

[0138] Additional chemical conversion steps f1) and / or f2) (as applicable) via transesterification reaction In order to facilitate the generation of DAP according to the present invention, it is possible to perform additional chemical conversion steps independently of step b) which chemically converts the phthalates extracted in step a), thereby allowing the IAP and / or the extracted phthalates that may not have been converted at the end of step b) to be converted.

[0139] Therefore, the method may also include an additional step f1), as shown in FIG3 or FIG5, which uses a solvent to chemically convert the unconverted phthalate ester from step b) and / or at least one IAP generated in step b) into DAP of the formula C6H4(COOCnH2n+1)2 by transesterification reaction. In these embodiments, step f1) is performed between steps c) and d) and advantageously after step b) as follows: the liquid phase 4 obtained advantageously after all steps a), b) and c) is delivered to a first additional transesterification reactor to generate a second liquid stream 13 rich in DAP, which is delivered to step d). According to this embodiment, step c) is preferably performed at the end of step b).

[0140] The method may also include an additional step f2), which uses a solvent to chemically convert the unconverted phthalate ester from step b) and / or at least one IAP generated in step b) or, if appropriate, in optional step f1) into DAP of formula C6H4(COOCnH2n+1)2 by transesterification reaction. Step f2) is carried out after step e) by delivering liquid residue 17 to a second additional transesterification reactor to generate a third liquid stream 15 rich in the DAP, which is returned to step d).

[0141] Additional steps f1) and / or f2) of the chemical transformation of the transesterification reaction may be carried out in the first variant (solid-liquid separation step c) after steps a) and b) or in the second variant (solid-liquid separation step c) between steps a) and b).

[0142] Preferably, the method according to the invention includes only one additional step of chemical transformation by transesterification reaction, and more preferably step f2).

[0143] The implementation of steps f1) and / or f2) is as described with respect to step b) of the method according to the invention. In particular, the ranges related to the operating conditions of steps b) and f1) and / or f2) are similar, and those skilled in the art select these ranges based on the chemical properties of the streams processed at the inlet of steps f1) and / or f2) in order to promote DAP generation.

[0144] The same applies to the preferred use of the transesterification catalyst 8, as described in step b). The transesterification catalyst in steps f1) and / or f2) may be the same as or different from the transesterification catalyst used in step b).

[0145] The stream delivered to step f1) and / or step f2) (stream 4 or liquid residue 17) is a liquid phase containing one or more phthalates and possibly soluble impurities that were extracted in step a) and may have been partially converted (IAP) and / or unconverted in step b), and which were then separated during liquid-liquid separation step d) of the method according to the invention or during purification step e) of the method according to the invention (if such step is advantageous to perform).

[0146] Depending on the sequence of steps f1) and / or f2), additional solvent supply may be required. This additional solvent supply may come from supplying "fresh" solvent 9 or from recycling the solvent stream 12, which may be separated at the end of step d) of the method according to the invention. This additional supply, carried out in step f1), in the first additional transesterification reactor and / or in step f2), in the second additional transesterification reactor, by supplying fresh solvent 9 and / or by recycling the second effluent 12 composed of that solvent, is illustrated in Figures 3, 5, 6, and 8.

[0147] When purification step e) is performed, at least a portion of the liquid residue 17 produced in step e) can be recycled to step f1), as illustrated in FIG5, so that the chemical reaction can continue to occur and produce DAP.

[0148] Figures 6 and 8 show preferred embodiments of the first variant (solid-liquid separation step c) of the method according to the present invention after steps a) and b) and the second variant (solid-liquid separation step c) between steps a) and b).

[0149] As shown in FIG6, according to a preferred embodiment of a first variant of the present invention, the method includes: performing steps a) and b) in the same individual operation; a solid-liquid separation step c) after steps a) and b); a liquid-liquid separation step d); a purification step e) of the first effluent 14 containing DAP obtained in step d); and an additional step f2, advantageously, subjecting the residue 17 obtained in step e) to a transesterification reaction.

[0150] According to this embodiment, as schematically illustrated in FIG6, pretreated PVC raw material 1 in particulate form is introduced into a reactor in which steps a) and b) are combined, namely solid-liquid extraction and chemical conversion by transesterification reaction (preferably in the presence of catalyst 8), respectively. In addition to this method, a fresh solvent stream 9 is also fed into the reactor, which comprises at least, and preferably, ester, ether, ketal or acetal type chemical molecules of empirical formula (CnH2n+1O)mZ as defined above, such as methyl acetate or methyl propionate, preferably methyl propionate, and at least a portion of the solvent stream 12 separated in liquid-liquid separation step d) is added as appropriate. The reaction effluent 3, containing a liquid phase containing at least DAP (preferably DMP) and a solid phase containing depleted phthalate (preferably phthalate-free) PVC plastic, is fed to a solid-liquid separation step c), for example, by centrifugation, to produce a solid stream 6 containing the extracted phthalate-depleted PVC plastic for the recovery of the reusable target PVC plastic, and a liquid stream 4 containing at least DAP (preferably DMP) and at least solvent. Solid stream 6 can be partially recycled to step a). The liquid stream 4 obtained from step c), containing DAP, solvent, possibly unconverted or partially converted phthalate (IAP), and possible byproducts (BP), is fed to a liquid-liquid separation step d), thereby separating not only the solvent stream 12 but also, preferably, the BP stream 10, and ultimately separating a liquid effluent 14 containing DAP (preferably DMP), possibly partially converted and / or unconverted phthalate, and possibly soluble impurities. The liquid effluent 14 is delivered to purification step e) to obtain purified DAP, preferably DMP. Since the residue 17 obtained from this purification step e) may still contain unconverted or partially converted (IAP) phthalates, an additional transesterification chemical conversion step f2) is preferably performed. Therefore, the residue 17 is advantageously delivered to a second transesterification reactor containing a suitable transesterification catalyst to transesterify the unconverted or partially converted (IAP) phthalates using solvent 9. The solvent may be a fresh supply or may be derived from stream 12, which is at least partially recycled to this step f2). This step f2) produces a DAP-rich, preferably DMP-rich liquid stream 15, which is returned to the liquid-liquid separation step d).

[0151] As shown in FIG8, according to another preferred embodiment of the present invention, according to a second variant, the method includes performing steps a) and b) in two different individual operations, wherein step c) is performed between steps a) and b), followed by step d), and also includes step e) purifying the first effluent 14 containing DAP obtained from step d), and an additional step f2) transesterifying the residue 17 obtained from step e).

[0152] According to this embodiment, as schematically illustrated in FIG8, a pre-treated PVC raw material 1 in particulate form is introduced into a reactor to perform step a) of solid-liquid extraction of phthalates from the PVC raw material. In addition to this method, a fresh solvent stream 9 is fed into the reactor, which at least comprises, and preferably comprises, ester, ether, ketal, or acetal type chemical molecules, such as methyl acetate or methyl propionate, preferably methyl propionate, and, if appropriate, a solvent stream 12 separated in a subsequent liquid-liquid separation step d). The effluent 2 produced in step a) comprises at least a liquid phase containing at least the phthalates extracted from the raw material 1 and at least a solid phase containing PVC plastic depleted of phthalates, preferably free of the extracted phthalates. Effluent 2 is fed to solid-liquid separation step c), for example, by centrifugation, to produce a solid stream 6 comprising the PVC plastic depleted of phthalates, in order to recover the reusable target PVC plastic and a liquid stream 18 containing at least the phthalates extracted in step a) and at least solvent. Liquid stream 18 is then fed to a reactor for transesterification, preferably in the presence of catalyst 8, to chemically convert the extracted phthalates in step b). Alternatively, a fresh solvent stream 9 containing the same ester, ether, ketal, or acetal type chemical molecules, such as methyl acetate or methyl propionate, preferably methyl propionate, may be fed into the transesterification reactor, and, where appropriate, at least a portion of the solvent stream 12 separated in liquid-liquid separation step d). The reaction effluent 4, containing at least DAP (preferably DMP), solvent, possibly unconverted or partially converted (IAP) phthalates, and possible byproducts (BP), is delivered to the liquid-liquid separation step d), thereby separating not only the solvent stream 12 but also the BP stream 10, and ultimately separating a liquid effluent 14 containing DAP (preferably DMP), possibly partially converted (IAP) and / or unconverted phthalates, and possibly soluble impurities. Liquid effluent 14 is preferably delivered to the purification step e) to obtain purified DAP 16, preferably DMP. Since the residue 17 obtained from this purification step e) may still contain unconverted or partially converted (IAP) phthalates, an additional transesterification chemical conversion step f2 is preferably performed. The residue 17 is advantageously delivered to a second transesterification reactor, preferably containing a catalyst suitable for the transesterification reaction, to transesterify the unconverted or partially converted (IAP) phthalate using a solvent 9 containing an ester, ether, ketal, or acetal type chemical molecule of the empirical formula (CnH2n+1O)mZ as defined above. The solvent may be supplied fresh or may be derived from stream 12, which is at least partially recycled to this step f2). This step f2) produces a liquid stream 15 rich in DAP, preferably rich in DMP, which is returned to the liquid-liquid separation step d).

[0153] The present invention also relates to a method for recycling PVC-based articles containing at least one phthalate, the recycling method comprising: - processing the PVC-based articles comprising at least grinding or crushing the PVC-based articles to form PVC raw material in particulate form; - recovering DAP and reusable target PVC plastic from the PVC raw material in particulate form according to the method detailed above regarding the recycling of DAP and reusable target PVC plastic.

[0154] The steps for processing PVC-based objects may include the various steps detailed above for the pretreatment of PVC raw materials prior to introduction in step a).

[0155] The present invention also relates to a method for manufacturing a flexible PVC-based article comprising recycled PVC plastic and / or DAP, wherein the recycled PVC plastic and / or DAP are obtained by means of the method for recycling DAP and reusable target PVC plastic detailed above.

[0156] Such manufacturing methods typically include the steps of recycling DAP and reusable target PVC plastic as detailed above, followed by the steps of mixing the reusable target PVC plastic with additives or mixing the recycled DAP with PVC resin, and then forming the mixture.

[0157] Example 1 This example 1 illustrates the present invention without limiting its scope, and specifically illustrates the extraction of phthalates contained in PVC plastic and the conversion of phthalates into dimethyl phthalate by transesterification using the carboxylic acid ester chemical methyl propionate in the presence of a catalyst.

[0158] 18.2 g of PVC plastic raw material (obtained from a PVC-based "medical catheter" type object) in extrusion form with an average size of 2 mm and containing 4.4 g of didecyl phthalate (DIDP) was introduced into the reactor and stirred using a paddle-type mechanical stirring system. Then, 17.35 g of methyl propionate was added, resulting in a methyl propionate / DIDP molar ratio of 20. Next, 0.17 g of catalyst (NaOMe) was added to the mixture, bringing the NaOMe / DIDP mass percentage to 4%.

[0159] The reactor was sealed, purged with nitrogen, and then heated to 100°C at a pressure of approximately 1.2 MPa. Under these conditions, it was maintained for 4 hours with stirring at 1000 rpm. The reactor was then cooled.

[0160] After 4 hours, solid and liquid were obtained and analyzed.

[0161] Analysis by gas chromatography combined with gas-phase flame ionization detection (GC-FID) showed that, due to partial conversion of DIDP, the gas phase contained 0.13 g of dimethyl phthalate (DMP) obtained from the conversion of DIDP and 0.07 g of methyl decyl phthalate. Identification was achieved by comparing the residence times of analytical grade standards, and quantification was performed by determining the reaction coefficients obtained from the analysis of these same standards.

[0162] The obtained solids were pre-separated by preparative size exclusion chromatography (SEC) equipped with dual optical detection (UV / visible) and refractive index (RI). The collected dissolved fractions were analyzed by high performance liquid chromatography (HPLC) equipped with quantitative UV-visible optical detection. The results indicated the presence of DIDP in the target PVC plastic at a concentration of less than 1000 ppm, which complies with the currently implemented European regulations.

[0163] These results demonstrate the acquisition of phthalate-free PVC according to the present invention, with 10% DIDP conversion. This conversion rate considers the total conversion of DIDP to DMP and its partial conversion. Unconverted DIDP is in the liquid phase. In this example, the extraction and conversion of DIDP are carried out in the same step.

[0164] Example 2 This Example 2 illustrates the present invention without limiting its scope, and specifically illustrates the extraction of phthalates contained in PVC plastic and the conversion of phthalates into dimethyl phthalate by transesterification using the carboxylic acid ester chemical methyl acetate in the presence of a catalyst.

[0165] 13.23 g of PVC plastic raw material (obtained from a PVC-based "medical catheter" type object) containing 3.2 g of didecyl phthalate (DIDP) in extrusion form with an average size of 2 mm was introduced into the reactor and stirred using a paddle-type mechanical stirring system. Then, 10.61 g of methyl acetate was added, resulting in a methyl acetate / DIDP molar ratio of 20. Next, 0.12 g of catalyst (NaOMe) was added to the mixture, bringing the NaOMe / DIDP mass percentage to 4%.

[0166] The reactor was sealed, purged with nitrogen, and then heated to 100°C with an autogenous pressure of approximately 1.2 MPa. Under these conditions, the reactor was maintained at 1000 rpm for 4 hours with stirring. The reactor was then cooled.

[0167] After 4 hours, solid and liquid were obtained and analyzed.

[0168] Analysis by gas chromatography combined with gas-phase flame ionization detection (GC-FID) showed that, due to partial conversion of DIDP, the gas phase contained 0.07 g of dimethyl phthalate (DMP) obtained from the conversion of DIDP and 0.17 g of methyl decyl phthalate. Identification was achieved by comparing the residence times of analytical grade standards, and quantification was performed by determining the reaction coefficients obtained from the analysis of these same standards.

[0169] The obtained solids were pre-separated by preparative size exclusion chromatography (SEC) equipped with dual optical detection (UV / visible light) and refractive index (RI). The collected dissolved components were analyzed by high performance liquid chromatography (HPLC) equipped with quantitative UV-visible light optical detection. The results indicated the presence of DIDP in the target PVC plastic at a concentration of less than 1000 ppm, which complies with the currently implemented European regulations.

[0170] These results demonstrate the phthalate-free PVC obtained according to the present invention, with a 9% DIDP conversion. This conversion rate considers the total conversion of DIDP to DMP and its partial conversion. Unconverted DIDP is in the liquid phase. In this example, the extraction and conversion of DIDP are carried out in the same step. [Simplified Explanation of the Diagram]

[0040] [Figure 1] Figure 1 is a flowchart of a method according to one embodiment of the present invention, which includes steps a), b), c), and d). [Figure 2] Figure 2 is a flowchart of a method according to another embodiment, including steps a), b), c), and d), wherein in step d), separation is performed between DAP, solvent, alcohol, ether, ketal, or acetal type byproduct obtained in step b), and, if applicable, partially converted and / or unconverted phthalates mixed with soluble impurities. [Figure 3] Figure 3 is a flowchart of a method according to an embodiment illustrated in Figure 1 or Figure 2, which includes steps a), b), c), and d), and illustrates an implementation of the transesterification reaction (f1) and other steps selected as appropriate for recycling various streams. [Figure 4] Figure 4 is a flowchart of a method according to another embodiment of the present invention, which includes steps a), b), c), and d), and step e) for purifying the first effluent containing DAP obtained in step d). [Figure 5] Figure 5 is a flowchart of the method according to the embodiment illustrated in Figure 4, and illustrates the implementation of transesterification reactions (f1; f2) and other steps for recycling various streams as appropriate. [Figure 6] Figure 6 is a flowchart of a method according to a preferred embodiment of the present invention, which includes the implementation of the same individual (first variant of the method according to the present invention) in steps a) and b), step e) purifying the first effluent containing DAP obtained in step d), and the additional step f2) transesterifying the residue obtained from step e). [Figure 7] Figure 7 is a flowchart of a method according to another embodiment of the present invention, which includes steps a), b), c) and d), wherein steps a) and b) form the object of two different individual operations (second variant of the method according to the present invention), and wherein step c) is performed between steps a) and b). [Figure 8] Figure 8 is a flowchart of a method according to a preferred embodiment as illustrated in Figure 7, which includes step e) of purifying the first effluent containing DAP obtained in step d) and an additional step f2) of transesterifying the residue obtained from step e). In the figure, the same element symbols represent the same or similar elements.

Claims

1. A method for recovering dialkyl phthalate and reusable target PVC plastic from a PVC raw material containing at least one phthalate, comprising the following steps: a) performing solid-liquid extraction on the PVC raw material (1) in particulate form as follows: placing the particles of the PVC raw material in contact with a solvent (9) to produce a liquid phase rich in the phthalate and a solid phase comprising PVC plastic depleted of the phthalate, the solvent comprising at least one ester, ether, ketal or acetal chemical molecule of the empirical formula (CnH2n+1O)mZ, wherein n and m are positive integers, n < 4 or n > 8, m is greater than or equal to 1 and less than or equal to 3, and Z is a group selected from a list of elements consisting of: R, COOR, CO, CR, CNRR', PO, P, SO, SO2, COR and HCO, and R and R' are independently selected from straight-chain, branched-chain or cyclic alkyl or aryl groups; b) Using the ester, ether, ketal, or acetal type chemical molecule of experimental formula (CnH2n+1O)mZ, the phthalate in the liquid phase is chemically converted into a dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by transesterification, so that the liquid phase is enriched with the dialkyl phthalate; c) Solid-liquid separation is performed between the solid phase and the liquid phase to produce at least one solid stream (6) of the PVC plastic including the depleted phthalate, so as to recover the target PVC plastic; d) Liquid-liquid separation is performed on the liquid phase to produce a first liquid effluent (5, 14) including at least the dialkyl phthalate and a second liquid effluent (7, 12) including at least the solvent.

2. As in the method of request item 1, steps a) and b) are performed within the same individual operation.

3. The method of claim 1, wherein steps a) and b) form two different individual operation objects, and step a) generates a stream comprising the liquid phase and the solid phase (2).

4. The method of claim 3, wherein step c) is performed between step a) and step b), the stream (2) comprising the liquid phase and the solid phase obtained from step a) is delivered to the solid-liquid separation step c) to produce a stream (6) comprising PVC plastic depleted of the phthalate and a first liquid stream (18) comprising the liquid phase, the first liquid stream being delivered to step b).

5. The method of claim 1 also includes an additional step f1) by means of the solvent (9) to chemically convert the phthalate ester that was not converted and / or partially converted in step b) into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification reaction, wherein step f1) is carried out between steps c) and d) by delivering the liquid phase obtained at the end of all steps a), b) and c) to a first additional transesterification reactor to produce a second liquid stream (13) rich in dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, the second liquid stream (13) being delivered to step d).

6. The method of claim 5, wherein the solvent (9) is supplied and / or at least a portion of the second liquid effluent (7, 12) containing at least the solvent obtained from step d) is recycled to the first additional transesterification reactor.

7. The method of any one of claims 1 to 4, wherein in step d), the first effluent (5) is substantially composed of the dialkyl phthalate.

8. The method of any one of claims 1 to 4, wherein the liquid-liquid separation step d) also produces a third effluent (10) comprising ester, ether, ketal or acetal byproducts obtained during step b); and, if present, a fourth effluent (11) comprising partially converted and / or unconverted phthalate esters from step b) and, if present, other soluble impurities, wherein the first liquid effluent (5) is substantially composed of the dialkyl phthalate and the second liquid effluent (12) is substantially composed of the solvent.

9. As in request item 1, where: The liquid-liquid separation step d) also produces a third effluent (10), which includes the ester, ether, ketal or acetal type byproducts obtained during step b). The first liquid effluent (14) contains the dialkyl phthalate, the partially converted and / or unconverted phthalate esters in step b), and soluble impurities as present. The second liquid effluent (12) is substantially composed of the solvent. The method also includes: e) purifying the first liquid effluent (14) to produce a liquid product (16) substantially composed of the dialkyl phthalate and a liquid residue (17) containing the partially converted and / or unconverted phthalate esters in step b) and, as present, the soluble impurities as present.

10. The method of claim 9 also includes an additional step f2) by means of the solvent (9) to chemically convert the phthalate ester that was not converted and / or partially converted in step b) into a dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification reaction, wherein step f2) is carried out after step e) by delivering the liquid residue (17) to a second additional transesterification reactor to produce a third liquid stream (15) rich in dialkyl phthalate of the formula C6H4(COOCnH2n+1)2, the third liquid stream (15) being returned to step d).

11. The method of claim 10, wherein the solvent (9) is supplied and / or at least a portion of the second liquid effluent (12) containing at least the solvent obtained from step d) is recycled to the second additional transesterification reactor.

12. The method of claim 9 also includes an additional step f1) of recycling at least a portion of the liquid residue (17) to step b) and / or, by means of the solvent (9), chemically converting the phthalate that was not converted and / or partially converted in step b) into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by transesterification, wherein step f1) is carried out between steps c) and d) by delivering the liquid phase obtained at the end of all steps a), b) and c) to a first additional transesterification reactor to produce a second liquid stream (13) rich in dialkyl phthalate of formula C6H4(COOCnH2n+1)2, the second liquid stream (13) being delivered to step d).

13. The method of any one of claims 1 to 6 and 9 to 12, wherein the second liquid effluent (7, 12) of the solvent (9) obtained from step d) is at least partially recycled to step a) and / or step b).

14. The method of any of claims 1 to 6 and 9 to 12, comprising at least partially recycling the solid stream (6) of the phthalate-containing PVC plastic to step a).

15. The method of any one of claims 1 to 6 and 9 to 12, wherein the chemical molecule of the solvent (9) is an ester carrying one or more alkoxy groups of the formula (CnH2n+1O)m, wherein n < 4 or n > 8 and m is greater than or equal to 1 and less than or equal to 3, subject to the limitation that the esters involved in the mixture contain alkoxy groups CnH2n+1O with exactly the same n value.

16. The method of claim 15, wherein the chemical molecule of the solvent (9) is selected from methyl acetate and methyl propionate.

17. The method of any one of claims 1 to 6 and 9 to 12, wherein the chemical molecule of the solvent (9) is an ether of the formula (CnH2n+1O)R, wherein n < 4 or n > 8.

18. The method of any one of claims 1 to 6 and 9 to 12, wherein the chemical molecule of the solvent (9) is a ketal or acetal of formula (CnH2n+1O)2CRR' or (CnH2n+1O)2CRH, wherein n < 4 or n > 8.

19. The method of claim 18, wherein the chemical molecule of the solvent (9) is selected from the list of the following: diacetal, 2,2-dimethoxypropane, 2,2-dimethoxybutane, diethanolacetal, 2,2-diethoxypropane and 2,2-dipropoxypropane.

20. The method of any one of claims 1 to 6 and 9 to 12, wherein the chemical molecule of the solvent (9) is methyl propionate and the dialkyl phthalate is dimethyl phthalate.

21. The method of any of claims 1 to 6 and 9 to 12, wherein the chemical conversion carried out by transesterification in step b) and, as appropriate, steps f1) and / or f2) is carried out in the presence of a catalyst.

22. The method of claim 21, wherein the catalyst is selected from the list of the following: inorganic or organic basic or acidic Brønsted homogeneous catalysts, or Lewis acids, and heterogeneous catalysts formed from: alkaline earth metal oxides, or alkali metal and / or alkaline earth metal carbonates or bicarbonates, or alkali metals supported on alumina or zeolite, or zinc oxide and mixtures thereof with other oxides, or ion exchange resins.

23. The method of any one of claims 1 to 6 and 9 to 12, wherein the at least one phthalate in the PVC raw material is a phthalate of the empirical formula C6H4(COOR1)(COOR2), wherein the ester group is located in the ortho position of the benzene ring, and R1 or R2 is independently selected from one of the elements of the group consisting of: a straight or branched or cyclic alkyl chain, a straight or branched alkoxyalkyl chain, or an aryl or alkylaryl chain.

24. The method of any one of claims 1 to 6 and 9 to 12, wherein the target PVC plastic is substantially free of the phthalate.

25. The method of claim 24, wherein the target PVC plastic comprises a total of less than 0.1% by mass of phthalates selected from the list of the following compositions: dibutyl phthalate, dioctyl phthalate or diethylhexyl phthalate, butyl benzoate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl phthalate isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.

26. The method of any of claims 1 to 6 and 9 to 12, wherein step b) and, if applicable, steps f1) and / or f2) are performed at a temperature between room temperature and 200°C, and at a pressure between atmospheric pressure and 11.0 MPa for a time between 1 minute and 10 hours.

27. The method of any one of claims 1 to 6 and 9 to 12, wherein step a) and / or step b) and, whereby, step f1) and / or f2) are performed such that the molar ratio between the amount of the solvent (9) and the amount of the phthalate to be extracted or converted is between 2 and 250.

28. A method for recycling PVC-based articles containing at least one phthalate, comprising: Processing the PVC-based article includes at least grinding or crushing the PVC-based article to form PVC raw material in particle form; and, as claimed in any of claims 1 to 27, recovering dialkyl phthalate and reusable target PVC plastic from the PVC raw material in particle form.

29. A method for manufacturing a flexible PVC-based article comprising recycled PVC plastic and / or dialkyl phthalate, wherein the recycled PVC plastic and / or dialkyl phthalate is obtained by any one of claims 1 to 27.

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