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

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 by contacting it with a solvent comprising at least one alcohol CnH2n+1OH(n8) to produce a liquid phase rich in the phthalate and a solid phase comprising PVC plastic depleted of the phthalate; b) using the alcohol, converting the phthalate in the liquid phase into dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification; c) performing 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, in order to obtain the target PVC plastic; d) performing liquid-liquid separation on 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 polyvinyl chloride (PVC) plastics, and more particularly to a method for extracting and converting phthalates, plasticizers included in PVC compositions, via transesterification. 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. Prior 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 accepted 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 can 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: the "conventional" method of simple mechanical recycling of plastics, and methods involving changes in its composition or even chemical transformation of the compounds used to make it.

[0004] Since the mid-20th century, the recycling of PVC plastics involving chemical reactions has been 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 describe methods for recycling 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 the following steps: The first step involves dissolving PVC resin and soluble additives in an organic solvent, followed by a second step of precipitation with steam, thereby enabling the recovery of the resin and most of the additives.

[0005] However, these additives are not always necessary in PVC recycled for reuse. For example, changes in relevant regulations over time are a determining factor. Thus, certain phthalate plasticizers, which were 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 phased out of the permitted additives. This is particularly true of the following, not 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 the typically long service life (decades) of PVC-based products, those formulated before the end of 2006 and now past their end of life cannot be recycled, allowing these prohibited additives to persist, 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] Removing or purifying phthalate-type additives extracted from PVC-based materials is therefore a major challenge in optimizing PVC recyclability.

[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] The 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 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 these specific additives in such plastics, to the applicant's knowledge, PVC-based recycling methods do not involve this technology.

[0011] While the extraction of phthalate 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 frequently cited primary reason is the difficulty in finding an economically viable balance between the costs of the individual operations performed in such recycling methods and the resale costs (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 extraction of phthalates from PVC-based objects can recover a mixture of phthalates that may contain phthalates that do not conform to REACH standards. This excludes the purification of these non-REACH-compliant phthalates, 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] This invention aims to at least partially overcome the problems of prior art and, in particular, to provide a PVC-based method for recycling objects that allows the processing of any type of phthalate-containing PVC raw material and its conversion into two refinable products of interest: specific dialkyl phthalates and phthalate-free (especially undesirable phthalates) recyclable PVC plastic, typically those approved under the European REACH regulation. Another object of this invention is to limit the number of individual steps conventionally associated with phthalate separation / purification operations during the recycling of phthalate-containing PVC, thereby potentially limiting the cost of the method.

[0013] Therefore, in order to achieve at least one of the above objectives, the present invention specifically provides 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) Solid-liquid extraction of PVC raw material in particle form by contacting it with a solvent comprising at least one alcohol of the formula CnH2n + 1OH (n being a positive integer less than 4 or greater than 8) to produce a liquid phase rich in the phthalate and a solid phase comprising PVC plastic depleted of the phthalate; b) Using the alcohol, 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) Perform solid-liquid separation between the solid phase and the liquid phase to generate at least one solid stream comprising PVC plastic that has depleted the phthalate, in order to recover the target PVC plastic; d) To cause liquid-liquid separation of the liquid phase to produce at least a first liquid effluent comprising dialkyl phthalate and a second liquid effluent comprising solvent.

[0014] One advantage of this invention is that the method can, through chemical transesterification, convert a mixture of initially trapped phthalates in the polymer matrix of various PVC-based plastics into a single, REACH-compliant, and purifiable DAP-type phthalate product, regardless of the composition of the mixture (i.e., the nature and source of the various phthalates) and 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) produces 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 delivery of the liquid phase and the solid phase stream obtained from step a) to solid-liquid separation step c) to produce a stream of PVC plastic that has depleted the phthalate and a first liquid stream comprising 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 alcohol, 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. This 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, which is then 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 liquid 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 alcohol (AL) type byproduct obtained during step b) and, if applicable, a fourth effluent, which includes phthalates that were partially converted and / or not converted in step b) and, if applicable, other soluble impurities, the first liquid effluent consisting substantially of the dialkyl phthalate and the second effluent consisting substantially of the solvent.

[0022] According to one or more embodiments, the liquid-liquid separation step d) also produces a third effluent, which includes the alcohol (Al) type byproduct obtained during step b), the first liquid effluent comprising the dialkyl phthalate, partially converted and / or unconverted phthalates in step b), and soluble impurities as present, the second liquid effluent being substantially composed of the solvent, and the method also includes a step e) of 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 phthalates in step b) and, as present, the soluble impurities as present.

[0023] According to one or more embodiments, the method also includes an additional step f2) by means of the alcohol, 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. This step f2) 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 (17) to step b) and / or of chemically converting 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 means of the alcohol via a transesterification reaction. 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, which is 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 PVC plastic containing phthalates is at least partially recycled to step a).

[0028] According to one or more embodiments, the alcohol system is selected from the list of the following components: methanol, ethanol, n-propanol, isopropanol, and preferably methanol, or from the list of the following components: straight-chain or branched nonanol, straight-chain or branched decanol, straight-chain or branched undecylol, straight-chain or branched dodecanol, and preferably nonanol or decylol.

[0029] According to one or more embodiments, the solvent also includes an organic co-solvent, preferably selected from an alcohol-derived ester having the formula R'COOC nH 2n + 1, where n is the same as the n of the alcohol, and R' is preferably an alkyl group containing 1 to 3 carbon atoms; and an ether, wherein the organic co-solvent is added to the alcohol such that the mass ratio of the organic co-solvent to the alcohol is between 0.01 and 4.

[0030] According to one or more embodiments, the organic cosolvent is selected from the group consisting of methyl acetate, methyl propionate and cyclopentyl methyl ether.

[0031] According to one or more embodiments, the alcohol is methanol, the dialkyl phthalate is dimethyl phthalate, and the solvent preferably includes methyl propionate added to the methanol such that the mass ratio of methyl propionate to alcohol is between 0.01 and 4.

[0032] According to one or more embodiments, the chemical transformation carried out by transesterification in step b) and, as appropriate, steps f1) and / or f2) is carried out using a transesterification 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(COOR 1)(COOR 2), wherein the ester group is located ortho to 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, if applicable, steps f1) and / or f2) 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, f1) and / or f2) are performed such that the molar ratio between the amount of alcohol in the solvent 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 object includes at least grinding or crushing the PVC-based object to form PVC raw material in particle form; - Dialkyl phthalate and reusable target PVC plastics are recovered 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 exemplary embodiments of the invention, which are given as non-limiting examples and described below with reference to the accompanying drawings. Simple Explanation of the Diagram

[0040] Figure 1 is a flowchart of a method according to an embodiment of the present invention, which includes steps a), b), c), and d). Figure 2 is a flowchart of a method according to another embodiment including steps a), b), c) and d), wherein in step d), the alcoholic byproducts obtained in step b) in DAP, solvent, and in step b) are separated from the partially converted and / or unconverted phthalates in step b), and, as appropriate, in the form of a mixture with soluble impurities. Figure 3 is a flowchart of a method according to an embodiment illustrated in Figure 1 or Figure 2, including steps a), b), c) and d), and illustrates the implementation of the transesterification reaction (f 1) and other steps for recycling various streams as appropriate. 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) purifying the first effluent containing DAP obtained in step d). Figure 5 is a flowchart of the method according to the embodiment described in Figure 4, and illustrates the implementation of the transesterification reaction (f1; f2) and other steps for recycling various streams as appropriate. Figure 6 is a flowchart of a method according to a preferred embodiment of the present invention, which includes the same individual implementation (a 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 an additional step f2) transesterifying the residue obtained from step e). 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 two distinct individual operations (a second variation of the method according to the present invention) and step c) is performed between steps a) and b). Figure 8 is a flowchart of a method according to a preferred embodiment as illustrated in Figure 7, which includes step e) of obtaining a first effluent containing DAP in purification step d) and an additional step f2 of transesterifying the residue obtained from step e). In the diagram, the same element symbol represents the same or similar element. Implementation

[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 object" means an object that comprises, and preferably is made of, at least one type of PVC plastic, and is generally a consumer object.

[0043] The term "polyvinyl chloride plastic," also known as PVC plastic or simply PVC, refers to a combination of PVC polymer (also known as PVC resin) and various additives selected according to the required function of the PVC plastic, which in turn 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 can 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 plastics 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 the 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, the empirical formula C6H4(COOR 1)(COOR 2) may be used, wherein R1 and R2 are independently selected from one of the elements of the following group of constituents: straight-chain, branched or cyclic alkyl chain, straight-chain or branched alkoxyalkyl chain, or aryl or alkylaryl chain, which typically includes between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms. For example, R1 and / or R2 may be selected from ethyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, isodecyl, methoxyethyl, and benzyl.

[0048] 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 "dialkyl phthalate" (DAP) refers to a product of the empirical formula C6H4(COOCnH2n+1)2, which is produced by transesterification between a plasticizer of at least one phthalate type (specifically, as described above, of the empirical formula C6H4(COOR1)(COOR2)) present in PVC-based articles and an alcohol of the empirical formula CnH2n+1OH (n<4 or n>8). Dimethyl phthalate is an example of DAP.

[0050] In this specification, the definition of an alcohol with the empirical formula CnH2n + 1OH (n<4 or n>8) may also include the conjugate base and the relative cation of its empirical formula CnH2n + 1O- (n<4 or n>8), including the relative cation of metallic nature, which, as is well known to those skilled in the art, ensures the electronegativity of the conjugate base. The conjugate base is also known to be in the "alkoxide" form of the alcohol.

[0051] The term "alcohol byproduct" (AL) refers to a byproduct of formula R1OH or R2OH produced by the transesterification reaction between at least one phthalate plasticizer present in PVC-based articles and an alcohol of the empirical formula CnH2n + 1OH (n<4 or n>8). The definitions of R1 and R2 are the same as those for phthalates R1 and R2. As previously mentioned, the definition of this alcohol byproduct of formula R1OH or R2OH may also include its conjugate base of the empirical formula R1O- or R2O-.

[0052] The terms "intermediate phthalate" (IAP) or "partially converted phthalate" refer to byproducts of empirical formula C6H4(COOR 1)(COOC nH 2n + 1) or C6H4(COOR 2)(COOC nH 2n + 1), which are produced by an incomplete transesterification reaction between at least one phthalate-type plasticizer present in PVC-based articles (specifically, empirical formula C6H4(COOR 1)(COOR 2) as described above) and an alcohol of empirical formula C nH 2n + 1OH (n<4 or n>8). The definitions of R1 and R2 are the same as those for phthalate derivatives.

[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 dialkyl phthalate 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, alcohols with the experimental formula CnH2n + 1OH (n<4 or n>8) that contain at least one organic co-solvent are also referred to as "solvents".

[0055] 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 "<".

[0056] In this specification, the exponent "n" in the chemical formulas referenced is a positive integer (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.

[0057] 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.

[0058] In this specification, the term "comprising" is synonymous with "including" and "containing" (meaning the same thing), and is inclusive or open-ended, not excluding other unspecified elements. It should be understood that the term "comprising" includes exclusive and closed terms such as "consisting of".

[0059] In this specification, the phrase "between..." means that the limit of the interval is included within the range of values ​​described, unless otherwise stated.

[0060] 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.

[0061] Specific embodiments of the invention may be described below. Where technically feasible, these embodiments may be implemented separately or in combination without limitation.

[0062] 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.

[0063] According to the present invention, a method for recovering DAP and reusable target PVC plastic from PVC raw materials containing at least one phthalate includes the following steps, and may consist of the following steps: Solid-liquid extraction of the PVC raw material 1 in particle form is performed by contacting the PVC raw material particles with a solvent 9 comprising at least one alcohol of the formula CnH2n + 1OH (n<4 or n>8) to produce a liquid phase rich in the phthalate and a solid phase comprising PVC plastic depleted of the phthalate. b) Using the alcohol, 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) Perform solid-liquid separation between the solid phase and the liquid phase to generate at least one solid stream 6 comprising PVC plastic that has depleted the phthalate, in order to recover the target PVC plastic; d) Perform liquid-liquid separation 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.

[0064] 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.

[0065] 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.

[0066] 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 objects, or "post-consumer waste" type waste, that is, waste generated after the user consumes the PVC-based object.

[0067] In detail, recycled PVC raw materials can be derived from any existing collection and sorting channels or networks used for production waste and / or post-consumer waste, thereby enabling the separation of streams 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.

[0068] Therefore, PVC raw materials typically classified as "production waste" and / or "post-consumer waste" generally originate from the main application areas using PVC plastics, such as (in a non-exhaustive manner): 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 items are commonly 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 items forming the PVC raw materials contain at least one type of "flexible" PVC, i.e., PVC containing plasticizer-type (preferably phthalate-type) additives, such as the following PVC-based items: flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.

[0069] Advantageously, the PVC raw material comprises at least 50% by mass, preferably at least 70% by mass, preferably at least 90% by mass, and even more preferably at least 95% by mass of PVC plastic containing at least one phthalate.

[0070] Preferably, the PVC raw material includes "flexible" PVC, that is, PVC containing plasticizer-type (preferably phthalate-type) additives.

[0071] Even better, the PVC raw material mainly or even only contains "flexible" PVC, that is, PVC containing plasticizer-type (preferably phthalate-type) additives.

[0072] The PVC raw material processed in the method for recycling DAP and reusable target PVC plastics according to the present invention is in particulate form. Therefore, if the PVC raw material is in an initial form specifically for 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 present invention. For example, the PVC raw material can advantageously be in the form of ground and, where appropriate, washed material, 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. The PVC raw material can also advantageously be in a micronized solid form, i.e., in particulate 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 sphere of such particles.

[0073] Therefore, the term "PVC raw material in particle form" means that the average size of PVC plastic particles is usually between 10 µm and 20 cm as defined above. 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.

[0074] 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.

[0075] 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.

[0076] Advantageously, the moisture content of the PVC raw material in particulate form is less than or equal to 0.3% by mass and preferably less than or equal to 0.1% by mass.

[0077] The various steps of the method according to the present invention for producing DAP and reusable target PVC plastic are detailed in the following paragraphs.

[0078] [] [deal with] [PVC] [Preparation steps for raw materials, selected as needed] [] According to the present invention, the method may include a preparatory step (not shown in the figures) for processing PVC raw materials, which includes at least one step of grinding or crushing the PVC raw materials to form PVC raw materials 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 materials 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 materials.

[0079] For example, the pretreatment step can provide PVC raw materials in particle form, such as washed and milled materials 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 can 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.

[0080] 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.

[0081] Step a) Solid-liquid extraction of phthalates: The method according to the invention includes a solid-liquid extraction step a), in which phthalates are extracted from PVC raw material 1 in particulate form by contacting it with a solvent 9 comprising an alcohol of the experimental formula CnH2n + 1OH (n<4 or n>8), in order to obtain an effluent 2 comprising at least a liquid phase and a solid phase. The liquid phase is thus rich in the phthalates, and the solid phase comprises PVC plastic depleted of the phthalates.

[0082] The specific selection of n for the alcohol used as a solvent (excluding C4, C5, C6, C7, and C8 alcohols) makes it possible to convert these phthalates into at least one DAP as defined below during step b) by means of the alcohol via a transesterification reaction, which is not a non-desirable phthalate, such as those phthalates approved under the REACH regulation discussed above.

[0083] According to one or more embodiments, the alcohol is an alcohol of the empirical formula CnH2n + 1OH, where n < 4, for example selected from the list of the following compositions: methanol, ethanol, n-propanol and isopropanol, and even more preferably n = 1, in which case the alcohol is methanol CH3OH.

[0084] According to one or more embodiments, the alcohol is an alcohol of the empirical formula CnH2n + 1OH, wherein n>8, for example selected from the list of the following compositions: straight-chain or branched nonanol, straight-chain or branched decol, straight-chain or branched undecylol, straight-chain or branched dodecanol, and preferably nonanol or decylol.

[0085] According to one or more embodiments, the alcohol is an alcohol of the empirical formula CnH2n + 1OH, wherein n>8 and n is less than or equal to 20, or even n is less than or equal to 15.

[0086] According to one or more embodiments, the alcohol of the experimental formula CnH2n + 1OH (n<4 or n>8) can be used in the form of an alkoxide according to the present invention, that is, in the form of the conjugate base, cationic relative ion (including metallic cationic relative ion) of the alcohol of the experimental formula CnH2n + 1O- (n<4 or n>8), which, as is known to those skilled in the art, ensures the electronegativity of the conjugate base.

[0087] Solvent 9 may also include an organic co-solvent added to the alcohol, which facilitates the extraction of phthalates from PVC feedstock 1. In this case, the organic co-solvent may be an ester derived from the alcohol having the formula R'COOC nH 2n + 1, where n is the same as n of the alcohol from which the ester is derived (n < 4 or n > 8, and for example n less than or equal to 20), and R' is (straight-chain, branched-chain, or cyclic, preferably straight-chain) alkyl, for example containing 1 to 3 carbon atoms, such as 1 or 2 carbon atoms, or alternatively, the organic co-solvent may be an ether, such as (in a non-exhaustive manner) cyclopentylmethyl ether (CPME), di-n-propyl ether, or dialkylene, preferably CPME.

[0088] The organic solvent is added to the alcohol such that the mass ratio of the cosolvent to the alcohol (cosolvent / solvent) is between 0 and 4, preferably between 0.01 and 4, more preferably between 0.02 and 0.66, and even more preferably between 0.05 and 0.66.

[0089] When the alcohol is methanol, the additional organic cosolvent is advantageously, preferably, selected from the group consisting of methyl acetate, methyl propionate, and CPME.

[0090] Preferably, the solid-liquid extraction step a) of extracting phthalates from PVC raw material 1 is carried out by contacting the raw material 1 in particulate form with methanol supplemented with methyl propionate, preferably with a mass ratio of methyl propionate to methanol between 0 and 4, more preferably between 0.01 and 4, even more preferably between 0.02 and 0.66, and even more preferably between 0.05 and 0.66. In this case, the DAP produced by this method is dimethyl phthalate (DMP).

[0091] The solid-liquid extraction step of phthalates 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, and even more preferably between 60°C and 145°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, and more preferably between 10 minutes and 2 hours.

[0092] Preferably, step a) is performed such that the molar ratio between the amount of alcohol 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.

[0093] The reactor in step a) of the method according to the invention can 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.

[0094] In practice, it is advantageous to mix PVC raw material 1 in particulate form with solvent 9, which may be supplemented with at least one organic co-solvent, including alcohol, as appropriate.

[0095] 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.

[0096] According to the second option, PVC raw material 1 in particulate form and solvent 9 comprising alcohol (with at least one organic co-solvent added if applicable) 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.

[0097] 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).

[0098] Step b) of the chemical conversion of phthalates according to the method of the present invention includes step b): chemically converting the phthalates extracted in step a) into at least one DAP of the formula C6H4(COOCnH2n+1)2 by transesterification, preferably in the liquid phase, between the phthalate obtained from the liquid phase of step a) and an alcohol of the empirical formula CnH2n+1OH (n<4 or n>8, preferably n<4, even more preferably n=1), wherein the alcohol is therefore methanol CH3OH. In the case that the alcohol is methanol, the transesterification reaction is called a methanol decomposition reaction.

[0099] Step b) of chemically converting the phthalate present in the liquid phase to 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, and even more preferably between 60°C and 145°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; and residence time between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, and more preferably between 10 minutes and 2 hours.

[0100] Preferably, step b) is performed such that at the end of step a), the molar ratio between the amount of alcohol in solvent 9 and the amount of phthalate to be converted in the liquid phase containing the extracted phthalates is between 2 and 250, more preferably between 4 and 90, and even more preferably between 4 and 30.

[0101] The alcohol used in step b) is the same as the alcohol used in step a).

[0102] Preferably, step b), which involves chemically converting the phthalate extracted in step a) into DAP of formula C6H4(COOCnH2n+1)2 via transesterification, is carried out in the presence of a transesterification catalyst, which is advantageously introduced into the reaction medium.

[0103] The catalyst used for the transesterification reaction is selected from, for example, a non-exhaustive list of catalysts, which are well known to those skilled in the art, and preferably from a 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.

[0104] 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.

[0105] Preferably, the amount of catalyst introduced is such that the mass ratio of the catalyst to the phthalate to be converted is between 0.5% by mass and 10% by mass, more preferably between 1% by mass and 8% by mass, and even more preferably between 1% by mass and 5% by mass.

[0106] Whether homogeneous or heterogeneous, the catalyst can be recycled and / or removed during the process according to methods known to those skilled in the art, and preferably recycled. It can be separated, removed, or preferably recycled for transesterification in downstream steps of the process, such as in step c), step d), and / or step e), or in any other dedicated step.

[0107] The reactor in step b) of the method according to the invention can 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.

[0108] According to the present invention, step b) of the phthalate conversion 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., the liquid phase formed at the end of step a) and rich in DAP in step b).

[0109] 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 therefore always performed before the individual operation of step b).

[0110] In the embodiments presented in Figures 1 to 5, steps a) and b) are characterized as separate "blocks," but can be performed in the same individual operation or can be two distinct and consecutive individual operations. In the first case, effluent 2 is present in, for example, the same reactor used for performing steps a) and b).

[0111] In the embodiment presented in Figure 6 (which is one of the preferred embodiments according to the present invention), steps a) and b) are the same individual operations, which are characterized by using a single "box" (a+b).

[0112] In the embodiments shown in Figures 7 and 8, the embodiment in Figure 8 is one of the preferred embodiments according to the present invention, where steps a) and b) form two distinct and consecutive individual operations, corresponding to the flowchart of step c) between steps a) and b), as described below.

[0113] Step c) Solid-liquid separation: The method according to the invention includes a solid-liquid separation step c), in which the liquid phase contains phthalates extracted in step a) and / or DAP of formula C6H4(COOCnH2n+1)2 obtained after transesterification reaction in step b), and in the other hand, the solid phase contains PVC plastic that is depleted of phthalates (preferably free of phthalates).

[0114] The physical separation of the liquid and solid phases can be carried out using 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.

[0115] This solid-liquid separation step c) 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.

[0116] The production of reusable target PVC as defined in this 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.

[0117] The possibility of recycling solids flow is illustrated in Figures 2 through 8.

[0118] 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.

[0119] 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 when 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.).

[0120] For example, according to this second variation of the method shown in Figures 7 and 8, step c) is performed between steps a) and b). According to the invention, steps a) and c) 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.

[0121] In another example, step c) can be performed by centrifuging a liquid phase containing at least extracted phthalates and / or DAP with a 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.

[0122] Step d) of liquid-liquid separation: The method according to the invention includes a liquid-liquid separation step d) for DAP of liquid-phase extract formula C6H4(COOCnH2n+1)2 obtained at the end of at least steps a), b) and c).

[0123] 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.

[0124] Liquid-liquid separation step d) can be performed using methods familiar to those skilled in the art, such as (in a non-exhaustive manner) distillation, decantation, evaporation, liquid-liquid extraction, etc., either alone or in combination. The operating conditions (temperature, pressure, etc.) for this step are determined based on the selected separation method.

[0125] 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 Figure 1 (or as an option in Figure 3)) consists of the residual liquid phase after DAP extraction, which contains at least the solvent (i.e., an alcohol supplemented with a co-solvent, if applicable), alcoholic (AL) byproducts, intermediate alkyl phthalates (IAP), and possibly unconverted phthalates 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 entirely, to step b) of the method according to the invention.

[0126] In this case (such case), depending particularly on the selected liquid-liquid separation method (e.g., using side-extraction distillation or liquid-liquid extraction), it is possible not only to separate the solvent from the liquid phase, but also to separate AL and, very 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 AL 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, especially 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.

[0127] 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 potentially soluble impurities, 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 effluent 12 preferably composed substantially of the solvent, and a third effluent 10 comprising AL, preferably 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 AL from the solvent becomes significantly possible. In the case where the second effluent 12 is substantially composed of the solvent thus recovered, the second effluent 12 may then be advantageously returned part or all, preferably all, 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.

[0128] DAP purification step e) (as appropriate): The method according to the invention may include the following step e, which may be 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).

[0129] When step e) is performed, the solvent is advantageously separated during step d). Furthermore, the IAP extracted at the end of step a) of the method according to the invention, and, if applicable, the unconverted phthalates present at the end of step b), may be separated during step d) of the method according to the invention, or alternatively, during the purification step e).

[0130] Therefore, a first effluent 14 containing DAP, partially converted and / or unconverted phthalates from step b), and possibly soluble impurities can be delivered to this purification step e) to form a liquid product 16 consisting essentially of the DAP and a liquid residue 17 containing partially converted and / or unconverted phthalates and possibly soluble impurities from step b).

[0131] The recovered liquid residue 17 can then be advantageously returned to step b) of the method according to the invention, particularly to the first and second variations of the method according to the invention, so as to continue the chemical reaction and produce DAP, as illustrated in FIG4 or FIG5.

[0132] Purification step e) can advantageously be carried out by methods familiar 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.

[0133] 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 conversion of IAP and / or the extracted phthalates that may not have been converted at the end of step b).

[0134] Therefore, the method may also include an additional step f1), as shown in Figure 3 or Figure 5, which chemically converts the unconverted phthalate ester from step b) and / or at least one IAP produced in step b) into DAP of the formula C6H4(COOCnH2n+1)2 by means of a solvent including an alcohol and a 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 produce 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).

[0135] The method may also include an additional step f2), which uses a solvent including an alcohol to chemically convert the unconverted phthalate from step b) and / or at least one IAP generated in step b) or, as appropriate, step f1) into a DAP of the formula C6H4(COOCnH2n+1)2 after step e), by delivering the liquid residue 17 obtained from step e) to a second additional transesterification reactor to produce a third liquid stream 15 rich in the DAP, which is returned to step d).

[0136] Additional steps f1) and / or f2) of the chemical transformation of the transesterification reaction may be carried out in either the first variation (solid-liquid separation step c) after steps a) and b) or the second variation (solid-liquid separation step c) between steps a) and b).

[0137] Preferably, the method according to the invention includes only one additional step of chemical transformation by transesterification reaction, and more preferably step f2).

[0138] 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.

[0139] 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).

[0140] 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). The stream is 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).

[0141] Depending on the order of steps f1) and / or f2), it may be necessary to additionally supply a solvent containing an alcohol of the experimental formula CnH2n + 1OH (n<4 or n>8), supplemented with at least one organic co-solvent. This additional supply of solvent 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.

[0142] When purification step e) is performed, at least a portion of the liquid residue 17 produced in step e) can be recycled to step f 1), as illustrated in Figure 5, so that the chemical reaction can continue to produce DAP.

[0143] Figures 6 and 8 illustrate preferred embodiments of the first variant (solid-liquid separation step c) of the method according to the present invention (performed after steps a) and b) and the second variant (solid-liquid separation step c) (performed between steps a) and b), respectively.

[0144] As shown in Figure 6, 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 step e) purifying the first effluent 14 containing DAP obtained in step d); and, advantageously, an additional step f2) subjecting the residue 17 obtained in step e) to a transesterification reaction.

[0145] 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 fed into the reactor, which contains at least one alcohol of the experimental formula CnH2n + 1OH (where n<4 or n>8), preferably methanol, supplemented with a co-solvent selected as appropriate, preferably methyl propionate, and at least a portion of the solvent stream 12 separated in liquid-liquid separation step d), if 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 delivered 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 possibly AL, is delivered to a liquid-liquid separation step d), thereby separating not only the solvent stream 12 but also, preferably, the AL stream 10, and ultimately separating a liquid effluent 14 containing DAP (preferably DMP) and possibly partially converted and / or unconverted phthalates 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, it is preferable to perform an additional transesterification chemical conversion step f 2). Therefore, the residue 17 is advantageously delivered to a second transesterification reactor containing a suitable transesterification catalyst to carry out the transesterification of unconverted or partially converted (IAP) phthalates using an alcohol comprising the experimental formula CnH2n + 1OH (n<4 or n>8), supplemented with a co-solvent (preferably methyl propionate) as appropriate. The solvent may be a supply of fresh solvent or may be derived from stream 12, which is at least partially recycled to this step f 2). This step f 2) produces a liquid stream 15 rich in DAP, preferably rich in DMP, which is returned to the liquid-liquid separation step d).

[0146] As shown in Figure 8, 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).

[0147] According to this embodiment, as schematically illustrated in FIG8, a pre-treated PVC raw material 1 in particulate form is introduced into the reactor for solid-liquid extraction of phthalates from the PVC raw material in step a). In addition to this method, a fresh solvent stream 9 is fed into the reactor, comprising at least one alcohol of the experimental formula CnH2n + 1OH (n being an integer of n < 4 or n > 8), preferably methanol, and supplemented with a co-solvent, 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 depleted phthalates, preferably free of the extracted phthalates, of PVC plastic. 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 a solvent. The 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 alcohol, preferably methanol, supplemented with a co-solvent, preferably methyl propionate, and, if applicable, at least a portion of the solvent stream 12 separated in liquid-liquid separation step d) may be fed into the transesterification reactor. The reaction effluent 4, containing at least DAP (preferably DMP), solvent, and unconverted or partially converted (IAP) phthalates, is delivered to the liquid-liquid separation step d), thereby separating not only the solvent stream 12 but also the AL 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 f 2 is preferably performed. The residue 17 is advantageously delivered to a second transesterification reactor, preferably containing a suitable catalyst for the transesterification reaction, to transesterify the unconverted or partially converted (IAP) phthalate using an alcohol comprising the experimental formula CnH2n + 1OH (where n < 4 or n > 8), supplemented with a co-solvent (preferably methyl propionate) as selected, to an appropriate solvent. The solvent may be a supply of fresh solvent 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).

[0148] This invention also relates to a method for recycling PVC-based articles containing at least one phthalate, the recycling method comprising: - Processing PVC-based objects involves at least grinding or crushing PVC-based objects to form PVC raw materials in particle form; -Based on the method detailed above regarding the recycling of DAP and reusable target PVC plastics, the PVC raw material is recycled from particulate form to produce DAP and reusable target PVC plastics.

[0149] The steps for processing PVC-based objects may include the various steps detailed above regarding the pretreatment of PVC raw materials prior to introduction in step a).

[0150] 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.

[0151] Such manufacturing methods typically include the steps of recycling DAP from PVC raw materials 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.

[0152] Examples This example illustrates the 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 methanol decomposition in the presence of a catalyst.

[0153] 18.2 g of PVC plastic raw material (obtained from PVC-based "medical catheter" type items), containing 4.4 g of didecyl phthalate (DIDP) in the form of an extrusion with an average size of 2 mm, was introduced into the reactor and stirred using a paddle-type mechanical stirring system. Subsequently, 26.5 g of methanol and 17.7 g of methyl propionate (organic co-solvent) were added, with a methyl propionate / methanol mass ratio of 0.66 and a methanol / DIDP molar ratio of 84. Then, 0.17 g of catalyst (NaOMe) was added to the mixture, resulting in a NaOMe / DIDP mass percentage of 4%.

[0154] 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.

[0155] Four hours later, solid and liquid samples were obtained and analyzed.

[0156] Analysis by gas chromatography combined with gas-phase flame ionization detection (GC-FID) revealed that, due to partial conversion of DIDP, the gas phase contained 1.89 g of dimethyl phthalate (DMP) and 0.05 g of methyl decyl phthalate obtained from the conversion of DIDP. The liquid phase also contained 3.11 g of decanol (C10H22O) obtained from the methanol decomposition reaction of DIDP. 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.

[0157] The obtained solids were pre-separated using preparative size exclusion chromatography (SEC) equipped with dual optical detection (UV / visible) and refractive index (RI). The collected dissolved components 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.

[0158] These results demonstrate the phthalate-free PVC obtained according to the present invention, with 99.9% DIDP conversion. In this example, the extraction and conversion of DIDP are carried out in the same step.

[0159] 1: PVC raw materials 2: Liquid effluent 3: Liquid effluent 4: Liquid Flow 5: First liquid effluent 6: Solid Flow 7: Second liquid effluent 8: Transesterification catalyst 9: Fresh solvent 10: Third-party outflow 11: Fourth outflow 12: Second liquid effluent / solvent flow 13: Second Liquid Flow 14: First liquid effluent 15: Third Liquid Flow 16: Liquid products 17: Liquid Residue 18: First Liquid Flow a: Steps b: Steps c: Steps d: Steps e: Steps f 1: Steps f 2: Steps

Claims

1. A method for recovering dialkyl phthalate and reusable target PVC plastic from PVC raw materials containing at least one phthalate, comprising the following steps: a) Solid-liquid extraction of the PVC raw material (1) in particle form by contacting it with a solvent (9) comprising at least one alcohol of the formula CnH2n+1OH, wherein n is a positive integer less than 4 or greater than 8, to produce a liquid phase rich in the phthalates and a solid phase comprising PVC plastic depleted of the phthalates; b) Using the alcohol, the phthalates in the liquid phase are chemically converted into dialkyl phthalate of the formula C6H4(COOCnH2n+1)2 by transesterification, so that the liquid phase is rich in 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 phthalates, for the purpose of recovering the target PVC plastic; d) Perform liquid-liquid separation on the liquid phase to produce a first liquid effluent (5, 14) comprising at least the dialkyl phthalate and a second liquid effluent (7, 12) comprising at least the solvent.

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 the PVC plastic containing the depleted 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 alcohol, through a transesterification reaction, to chemically convert the phthalate esters that were not converted and / or partially converted in step b) into dialkyl phthalates 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 (13) rich in dialkyl phthalates 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 liquid 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 the alcohol byproduct obtained during step b); and, if present, a fourth effluent (11) comprising the 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 ester 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 alcohol-type byproduct obtained during step b). The first liquid effluent (14) contains the dialkyl phthalate, partially converted and / or unconverted phthalates from 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 partially converted and / or unconverted phthalates from 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 alcohol, through a transesterification reaction, to chemically convert the unconverted and / or partially converted phthalate esters in step b) into dialkyl phthalates of the formula C6H4(COOCnH2n+1)2, 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 phthalates 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 of chemically converting the phthalate esters that were not converted and / or partially converted in step b) into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by means of the alcohol via 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 (13) rich in dialkyl phthalate of formula C6H4(COOCnH2n+1)2, wherein the second liquid stream (13) is 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 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 alcohol is selected from the list of the following components: methanol, ethanol, n-propanol, isopropanol, or selected from the list of the following components: straight-chain or branched nonanol, straight-chain or branched decanol, straight-chain or branched undecylol, straight-chain or branched dodecanol.

16. The method of claim 15, wherein the alcohol is methanol, nonanol, or decanol.

17. The method of any one of claims 1 to 6 and 9 to 12, wherein the solvent also comprises an organic co-solvent.

18. The method of claim 17, wherein the solvent also comprises an organic co-solvent selected from an alcohol-derived ester having the formula R'COOCnH2n+1, where R' is an alkyl group containing 1 to 3 carbon atoms; and an ether, wherein the organic co-solvent is added to the alcohol such that the mass ratio of the organic co-solvent to the alcohol is between 0.01 and 4.

19. The method of claim 17, wherein the organic cosolvent is selected from the group consisting of methyl acetate, methyl propionate and cyclopentyl methyl ether.

20. The method of any one of claims 1 to 6 and 9 to 12, wherein the alcohol is methanol and the dialkyl phthalate is dimethyl phthalate.

21. The method of claim 20, wherein the solvent comprises methyl propionate such that the mass ratio of the methyl propionate to the alcohol is between 0.01 and 4.

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

23. The method of claim 22, wherein the transesterification 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.

24. 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 ortho to 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, and R1 and / or R2 comprising 1 to 20 carbon atoms.

25. 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.

26. The method of claim 25, 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.

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

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

29. 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 28, recovering dialkyl phthalate and reusable target PVC plastic from the PVC raw material in particle form.

30. A method for manufacturing a flexible PVC-based article comprising the method of any one of claims 1 to 28 to obtain recycled PVC plastic and / or dialkyl phthalate, wherein the recycled PVC plastic and / or the dialkyl phthalate is contained in the flexible PVC-based article.

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