Patent Application
20240227246
The invention relates to the field of the recycling of plastics based on polyvinyl chlorides (PVC), in particular to a process for extracting and transforming phthalates, which are plasticizers included in the composition of PVC, by transesterification. More precisely, the invention relates to a process for recovering a dialkyl phthalate (DAP) and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate.
By definition, a plastic is a mixture consisting of a base polymeric material and numerous additives, the assembly being able to be molded or fashioned (generally at elevated temperature and/or under pressure), so as to obtain a semifinished product or an object. A commonly accepted practice is to name said plastic by the name of the polymer of which it is made. Thus, the plastic polyvinyl chloride (PVC) in fact corresponds to the combination of the polymer PVC, referred to in the rest of the description as “PVC resin”, with various additives chosen as a function of the functionalities required for said plastic. Said additives may be organic molecules or macromolecules or alternatively inorganic (nano)particles and are used as a function of the properties that they afford to the PVC resin: heat resistance, light resistance or resistance to a mechanical stress (stabilizers), flexibility (plasticizers), processability (lubricants), coloring (dyes/pigments), etc.
Several methods for recycling PVC plastics exist: “conventional” methods by simple mechanical recycling of the plastics, methods involving modifications of their composition, or even chemical transformations of the compounds of which they are made.
Since the middle of the 20th century, the recycling of PVC plastic involving a chemical action has been the subject of numerous studies directed, in a first step, toward dissolving the PVC resin with a variable proportion of additives and then, in a second step, toward recovering said resin using various chemical processes (precipitation, evaporation, etc.) in the presence of all or some of the soluble additives. For example, patents EP0945481, EP1268628 and EP2276801 are directed, respectively, toward recycling various PVC-based objects (flexible or rigid pipes, window frames, cables, etc.) and specifically fiber-reinforced PVC-based objects (tarpaulins, floor coverings, etc.) according to a process involving a first step of dissolving the PVC resin and the soluble additives in an organic solvent, followed by a second step of precipitation with water vapor enabling the recovery of the resin and of the majority of the additives.
However, it is not always desirable to keep said additives in the PVC thus recovered to be recycled. For example, the changes over time in the regulations concerning them is a determining factor. Thus, certain plasticizers belonging to the phthalate family, which were notably widely used for formulating “flexible” PVCs about 40 years ago, gradually became subject to authorization in Europe on the basis of the REACH regulation, which, since the end of 2006, is directed toward establishing the safety of the manufacture and use of chemical substances in the European industry and, finally, were gradually excluded from the additives permitted for use. This is notably the case for the following nonexhaustive list of phthalates: dibutyl phthalate (DBP), dioctyl phthalate or diethyl hexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, etc.
These new regulations are now leading toward the banning of the presence of such compounds in recycled raw materials (RRM). Taking into account the often very long service life of PVC-based objects (several decades), PVC-based objects formulated prior to the end of 2006 and now at the end of their service life cannot be recycled via regeneration methods leading to the maintenance of these banned additives, whether said methods are conventional, such as mechanical recycling processes, or not, for instance the dissolution/precipitation process examples mentioned above.
Moreover, the phthalate plasticizers currently used in Europe (REACH-compatible phthalates) and in the rest of the world represent high value-added additives which are not upgraded when they are kept in the PVC recycled raw material. The reason for this is that they are expensive products, present in appreciable proportions in the initial PVC formulations (several tens of percent), and cannot directly give the PVC RRM the ad hoc flexibility properties. Supplying “fresh” plasticizers in appreciable amount is then essential for the reusability of the recycled PVC material.
The extraction of additives of phthalate type from PVC-based objects for removal or upgrading is thus a major challenge for optimized recyclability of PVC.
Several processes involving a step of dissolving the PVC resin have been adapted to enable this extraction. For example, patents EP1311599 and JP2007191586 both propose a first step of dissolving the PVC resin and of at least the phthalate-type additives with a first organic solvent, followed by a second step of liquid-liquid extraction of the phthalates from the solution obtained previously via the use of a second organic solvent different from the first organic solvent. Patent JP2007092035 discloses another possible example of implementation with dissolution of the PVC resin and of at least the phthalate-type additives via the use of a solvent under supercritical conditions and recovery of said phthalates in this same solvent after “rupture” of said supercritical conditions.
The removal or upgrading of phthalate-type additives from a PVC plastic may also be performed without proceeding via a preliminary step of dissolving said plastic, notably via direct extraction of said phthalates from the solid polymer matrix with a suitable organic solvent, as is fully indexed in the publication from 0gdQler et al., 2020, “Challenge and opportunities of solvent-based additive extraction methods for plastic recycling”, Waste Management, 104, 148-182. The challenge then lies in optimizing the extraction conditions (nature of the solvent, contact time, temperature, pressure, etc.) to achieve the best possible yields of extracted phthalates. Although this methodology for the removal of phthalates from PVC plastics is frequently used, notably for detecting and analytically quantifying these specific additives in said plastics, to the Applicant's knowledge, no process for regenerating PVC-based objects involves this technique.
Although critical for ensuring efficient recycling of PVC plastics and for obtaining a reusable recycled PVC, the extraction of phthalate-type plasticizers is insufficient to ensure the economic viability of a process for regenerating PVC-based objects. The main reason frequently put forward is the difficulty in finding an economically viable balance between the cost of the individual operations performed in said regeneration process and the resale cost (equivalent to the added value) of the products obtained. Said products consist of the phthalate-free PVC-based recycled material, which is naturally upgradable, and of said extracted phthalates which are, themselves, sparingly upgradable. Specifically, any regeneration process involving a step of extracting the phthalates from PVC-based objects will lead to the recovery of a mixture of phthalates which may comprise phthalates that are not “REACH-compatible”. The upgrading of said non-REACH-compatible phthalates is, of course, excluded and said phthalates will need to be treated as specific waste giving rise to additional costs. The upgrading of the REACH-compatible phthalates, which is advantageous per se, is in point of fact difficult since it involves technically complex and expensive separation/purification steps.
The present invention is aimed at overcoming, at least partly, the problems of the prior art and is particularly directed toward providing a process for regenerating PVC-based objects allowing the treatment of any type of PVC feedstock containing phthalates and their transformation into two products of interest that can be upgraded: a specific dialkyl phthalate and a recyclable PVC plastic free of phthalates, notably of undesirable phthalates, typically those that are subject to authorization by the European REACH regulation. Another aim of the present invention is to limit, during the recycling of PVC containing phthalates, the number of individual steps conventionally associated with the phthalate separation/purification operations, thus making it possible to limit the process costs.
Thus, to achieve at least one of the abovementioned objectives, among others, the present invention proposes, according to a first aspect, a process for recovering a dialkyl phthalate and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, including the following steps:
One advantage of the present invention lies in the ability of the process, by means of a chemical transesterification reaction, to transform a mixture of phthalates initially trapped in polymeric matrices of various objects based on PVC plastic, irrespective of the composition of said mixture (i.e. irrespective of the nature and origin of the various phthalates) and despite the possible presence of numerous other additives, into a single REACH-compatible and upgradable phthalate product of DAP type. The production of the single specific DAP product from the mixture of phthalates also makes it possible to limit the number of individual steps associated with the separation/purification operations and thus to limit the costs.
According to a first variant, steps a) and b) are performed within the same individual operation. According to a second variant alternative to the first variant, steps a) and b) form the subject of two distinct individual operations, step a) producing a stream including the liquid phase and the solid phase.
According to this second variant, step c) may be performed between steps a) and b), the stream including the liquid phase and said solid phase obtained from step a) possibly being sent into the solid-liquid separation step c) to produce the stream including the PVC plastic depleted in said phthalate and a first liquid stream including the liquid phase sent into step b).
According to one or more embodiments, the process also comprises an additional step f1) of chemical transformation by transesterification of said phthalate which is unconverted and/or partially converted in step b), into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by means of said alcohol, said step f1) being performed between steps c) and d) by sending said liquid phase obtained on conclusion of all the steps a), b) and c) into a first additional transesterification reactor to produce a second liquid stream enriched in said dialkyl phthalate of formula C6H4(COOCnH2n+1)2, said second liquid stream being sent into step d).
According to one or more embodiments, said solvent is supplied and/or at least a portion of said second liquid effluent comprising at least said solvent obtained from step d) is recycled into the first additional transesterification reactor.
According to one or more embodiments, in step d), said first liquid effluent consists essentially of said dialkyl phthalate.
According to one or more embodiments, the liquid-liquid separation step d) also produces a third effluent including byproducts of alcohol (AL) type obtained during step b) and optionally a fourth effluent including phthalate that is partially converted and/or unconverted in step b) and optionally other soluble impurities, said first liquid effluent consisting essentially of said dialkyl phthalate and said second effluent consisting essentially of said solvent.
According to one or more embodiments, the liquid-liquid separation step d) also produces a third effluent including byproducts of alcohol (AL) type obtained during step b), said first liquid effluent comprising said dialkyl phthalate, phthalate that is partially converted and/or unconverted in step b) and optionally soluble impurities, said second liquid effluent consisting essentially of said solvent, and the process also comprises a step e) of purification of said first liquid effluent to produce a liquid product consisting essentially of said dialkyl phthalate, and a liquid residue comprising said phthalate that is partially converted and/or unconverted in step b) and optionally said soluble impurities.
According to one or more embodiments, the process also comprises an additional step f2) of chemical transformation by transesterification of said phthalate which is unconverted and/or partially converted in step b), into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by means of said alcohol, said step f2) being performed after step e) by sending said liquid residue into a second additional transesterification reactor to produce a third liquid stream enriched in said dialkyl phthalate of formula C6H4(COOCnH2n+1)2, said third liquid stream being returned into step d).
According to one or more embodiments, said solvent is supplied and/or at least a portion of said second liquid effluent comprising at least said solvent obtained from step d) is recycled into the second additional transesterification reactor.
According to one or more embodiments, the process also comprises the recycling of at least a portion of said liquid residue (17) into step b) and/or an additional step f1) of chemical transformation by transesterification of said phthalate which is unconverted and/or partially converted in step b), into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by means of said alcohol, said step f1) being performed between steps c) and d) by sending said liquid phase obtained on conclusion of all the steps a), b) and c) into a first additional transesterification reactor to produce a second liquid stream enriched in said dialkyl phthalate of formula C6H4(COOCnH2n+1)2, said second liquid stream being sent into step d).
According to one or more embodiments, the second liquid effluent comprising at least the solvent obtained from step d) is at least partly recycled into step a) and/or step b).
According to one or more embodiments, the solid stream including the PVC plastic depleted in phthalates is at least partly recycled into step a).
According to one or more embodiments, the alcohol is chosen from the list consisting of methanol, ethanol, n-propanol, i-propanol, and preferably methanol, or from the list consisting of linear or branched nonanol, linear or branched decanol, linear or branched undecanol, linear or branched dodecanol, and preferably nonanol or decanol.
According to one or more embodiments, the solvent also comprises an organic cosolvent, the organic cosolvent preferably being chosen from an ester derived from said alcohol and having the formula R′COOCnH2n+1, n being identical to the n of said alcohol and R′ being an alkyl group preferably comprising between 1 and 3 carbon atoms, and an ether, said organic cosolvent being added to said alcohol so that the mass ratio between said organic cosolvent and said alcohol is between 0.01 and 4.
According to one or more embodiments, the organic cosolvent is chosen from the group consisting of methyl acetate, methyl propanoate and cyclopentyl methyl ether.
According to one or more embodiments, the alcohol is methanol, the dialkyl phthalate is dimethyl phthalate, and the solvent preferably comprises methyl propanoate added to the methanol so that the mass ratio between the methyl propanoate and the alcohol is between 0.01 and 4.
According to one or more embodiments, the chemical transformation performed by transesterification in step b), and optionally in step f1) and/or f2), is performed using a transesterification catalyst preferably chosen from the list consisting of mineral or organic basic or acidic Brønsted homogeneous catalysts, or Lewis acids, and heterogeneous catalysts formed by alkaline-earth metal oxides, or alkali metal and/or alkaline-earth metal carbonates or hydrogen carbonates, or alkali metals supported on aluminas or zeolites, or zinc oxides and mixtures thereof with other oxides, or ion-exchange resins.
According to one or more embodiments, said at least one phthalate of said PVC feedstock is a phthalate of empirical formula C6H4(COOR1)(COOR2) in which the ester groups are in the ortho position of the benzene nucleus, R1 or R2 being chosen independently from one of the elements of the group consisting of a linear or branched or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, R1 and/or R2 preferably comprising between 1 and 20 carbon atoms, or even between 1 and 15 carbon atoms.
According to one or more embodiments, the target PVC plastic is substantially free of said phthalate, and preferably comprises less than 0.1% by mass in total of phthalates chosen from the list consisting of dibutyl phthalate, dioctyl phthalate or diethylhexyl phthalate, benzyl butyl phthalate, dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, and mixtures thereof.
According to one or more embodiments, step b), and optionally steps f1) and/or f2), are performed at a temperature of between room temperature and 200° C., preferably between 40° C. and 180° C., at a pressure of between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, and for a time of between 1 minute and 10 hours, preferably between 10 minutes and 4 hours.
According to one or more embodiments, step a) and/or step b), and optionally steps f1) and/or f2), are performed such that the mole ratio between the amount of alcohol of the solvent and the amount of said phthalate to be extracted or to be transformed is between 2 and 250, preferably between 4 and 90.
According to a second aspect, the present invention relates to a process for recycling a PVC-based object containing at least one phthalate, including:
According to a third aspect, the present invention relates to a process for manufacturing a flexible PVC-based object including a recycled PVC plastic and/or a dialkyl phthalate which are obtained via the process for recovering a dialkyl phthalate and a reusable target PVC plastic according to the invention.
Other subjects and advantages of the invention will become apparent on reading the description which follows of particular exemplary embodiments of the invention, which are given as non-limiting examples, the description being made with reference to the appended figures described below.
In the figures, the same references denote identical or analogous elements.
Certain definitions are given below, although further details regarding the objects defined hereinbelow may be given later in the description.
The term “PVC-based object” means an object, generally a consumer object, which comprises, and preferably consists of, at least one PVC plastic.
The term “polyvinyl chloride plastic”, also known as PVC plastic or simply PVC, means the combination of a PVC polymer, also known as PVC resin, with various additives chosen as a function of the functionalities required for the PVC plastic, which are themselves chosen as a function of the intended applications.
Said PVC polymer is derived from the radical polymerization of vinyl chloride (VCM), which monomer is itself obtained from chlorine and ethylene. Depending on the implementation of said polymerization, four families of PVC resins may be used: 1) suspension PVC or S-PVC resins (suspension polymerization of VCM), 2) emulsion PVC or PVC “paste” resins (emulsion polymerization), 3) mass PVC or M-PVC resins (mass polymerization) and 4) superchlorinated PVC or C-PVC resins, obtained by superchlorination as a post-treatment on the preceding resins.
Said additives included in the composition of a PVC plastic may be organic molecules or macromolecules or alternatively inorganic (nano)particles and are used as a function of the properties that they afford to the PVC resin: heat resistance, light resistance or resistance to a mechanical stress (stabilizers), flexibility (plasticizers), processability (lubricants), coloring (dyes/pigments), etc.
The term “phthalates” means the group of chemical products formed by dicarboxylic esters of o-phthalic acid. They are composed of a benzene nucleus and of two carboxylic ester groups placed in the ortho position on the benzene nucleus. They may be described by means of the following formula:
or alternatively by the empirical formula C6H4(COOR1)(COOR2), in which R1 and R2 are independently chosen from one of the elements of the group consisting of a linear, branched or cyclic alkyl chain, a linear or branched alkoxyalkyl chain, or an aryl or alkylaryl chain, said alkyl, alkoxyalkyl, aryl or alkylaryl chain typically possibly including between 1 and 20 carbon atoms, or even including between 1 and 15 carbon atoms. For example, R1 and/or R2 may be chosen from ethyl, n-butyl, isobutyl, n-pentyl, iso-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, isodecyl, methoxyethyl and benzyl groups.
Phthalates are commonly used as plasticizers for plastics and in particular as plasticizers for plastics of PVC type, notably to make them flexible.
In the present description, the term “dialkyl phthalate” (DAP) denotes the product of empirical formula C6H4(COOCnH2n+1)2 resulting from the transesterification reaction between at least one plasticizer of phthalate type (and in particular of empirical formula C6H4(COOR1)(COOR2), as described above) present in PVC-based objects with an alcohol of empirical formula CnH2n+1OH, n<4 or n>8. Dimethyl phthalate is an example of DAP.
In the present description, the definition of said alcohol of empirical formula CnH2n+1OH, n<4 or n>8 may also comprise its conjugate base of empirical formula CnH2n+1O−, with n<4 or n>8, the cationic counterion, including that of metallic nature, which ensures the electronegativity of said conjugate base being well known to those skilled in the art. Said conjugate base is also known as the “alkoxide” form of said alcohol.
The term “byproduct(s) of alcohol type” (AL) means the byproduct(s) of formula R1OH or R2OH resulting from the transesterification reaction between at least one plasticizer of phthalate type present in PVC-based objects with the alcohol of empirical formula CnH2n+1OH, n<4 or n>8. R1 and R2 are defined identically to R1 and R2 of the phthalates. As previously, the definition of said byproduct of alcohol type of formula R1OH or R2OH may also comprise its conjugate base of empirical formula R1O− or R2O−.
The term “intermediate alkyl phthalate” (IAP) or “partially converted phthalate” means the byproduct of empirical formula C6H4(COOR1)(COOCnH2n+1) or C6H4(COOR2)(COOCnH2n+1) resulting from the incomplete transesterification reaction between at least one plasticizer of phthalate type (and in particular of empirical formula C6H4(COOR1)(COOR2) as described above) present in PVC-based objects with an alcohol of empirical formula CnH2n+1OH, n<4 or n>8. R1 and R2 are defined identically to R1 and R2 of the phthalates.
The term “reusable target PVC plastic” means a “phthalate-free PVC”, i.e. the solid comprising at least one PVC resin supplemented with at least one of the additives initially present in the PVC plastic of the PVC feedstock treated according to the invention, and from which the phthalates have been extracted and transformed in the form of at least one dialkyl phthalate according to the invention. The term “phthalate-free” in particular means that the solid PVC obtained as product of the process according to the invention contains, in total, less than 0.1% by weight of phthalates subject to authorization by the REACH regulation in Europe (appendix XIV of the regulation (EC) Number 1907/2006 of the European Parliament and of the Council of 18 Dec. 2006), in particular less than 0.1% by weight of phthalates, chosen from the list consisting of the following phthalates: dibutyl phthalate (DBP), dioctyl phthalate or diethylhexyl phthalate (DOP or DEHP), benzyl butyl phthalate (BBP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), dipentyl phthalate (DPP), diisopentyl phthalate, n-pentyl isopentyl phthalate, dihexyl phthalate, bis(2-methoxyethyl) phthalate, alone or as a mixture.
In the present description, the alcohol of empirical formula CnH2n+1OH, with n<4 or n>8, optionally supplemented with at least one organic cosolvent, is also referred to as “solvent”.
In the present description, the term “greater than . . . ” is understood as strictly greater than, and is symbolized by the sign “>”, and the term “less than . . . ” is understood as strictly less than, and is symbolized by the sign “<”.
In the present description, the index “n” in the cited chemical formulae 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.
In the present description, the term “room temperature” (r.t.) means a temperature typically of 20° C. 5° C., and the term “atmospheric pressure” means a pressure of 0.101325 MPa.
In the present description, the term “comprise” is synonymous with (means the same as) “include” and “contain”, and is inclusive or open-ended and does not exclude other elements which are not specified. It is understood that the term “comprise” includes the exclusive and closed term “consist”.
In the present description, the expression “between . . . and . . . ” means that the limit values of the interval are included in the described range of values, unless otherwise mentioned.
In the present description, the various ranges of parameters for a given step, such as the pressure ranges and the temperature ranges, may be used alone or in combination. For example, in the present description, a range of preferred pressure values can be combined with a range of more preferred temperature values.
In the text hereinbelow, particular embodiments of the invention may be described. They may be implemented separately or combined together without limitation of combinations when this is technically feasible.
The below description of the process according to the invention refers to the schemes in
In accordance with the invention, the process for recovering a DAP and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate includes, and may consist of, the following steps:
The process according to the invention is fed with a feedstock known as “PVC feedstock” 1 comprising at least one PVC plastic, which necessarily comprises at least one phthalate as described in the present invention.
Said PVC plastic may include at least 0.1% by mass of phthalates, or even at least 1% by mass of phthalates or else at least 5% by mass of phthalates. In general, the PVC plastics advantageously comprise less than 60% by weight of phthalates, typically less than 30% by weight of phthalates.
Said PVC feedstock is advantageously a feedstock of PVC to be recycled of the “production scraps” type, i.e. waste resulting from the processes for producing the PVC polymer during its polymerization or from the PVC plastic during its formulation/forming or of the PVC-based object during its production, or of the “post-consumption waste” type, i.e. waste generated after consumption by the user of said PVC-based object.
In particular, the PVC feedstock to be recycled may be derived from any existing collection and sorting channels or networks for production scraps and/or post-consumption waste making it possible to isolate a stream based on at least one PVC plastic comprising at least one phthalate, notably the collection and sorting channels or networks specific to plastic waste.
Thus, the PVC feedstock, which is typically of “production scraps” type and/or of “post-consumption waste” type, generally comes from the main fields of application which use PVC plastic, such as, in a nonexhaustive manner, the building and construction sectors, packaging, motor vehicles, electrical and electronic equipment, sports, medical equipment, etc. Preferably, the PVC feedstock comes from the building and construction sector. More precisely, the PVC-based objects are generally used in these fields as various rigid profiles (windows, doors, awnings, roller blind casings), pipes and connections, and rigid bottles, plates and films, flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc. Preferably, the PVC-based objects forming the PVC feedstock comprise at least one “flexible” PVC, i.e. PVC containing additives of plasticizer type, preferably of phthalate type, as is the case, for example, for the following PVC-based objects: flexible films and sheets, flexible tubes and profiles, cables, floor coverings, coated fabrics, etc.
Advantageously, the PVC feedstock 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 comprising at least one phthalate.
Preferably, the PVC feedstock comprises “flexible” PVC, i.e. PVC containing additives of plasticizer type, preferably of phthalate type.
Even more preferably, the PVC feedstock predominantly or even exclusively comprises “flexible” PVC, i.e. PVC containing additives of plasticizer type, preferably of phthalate type.
The PVC feedstock treated in the process for recovering a DAP and a reusable target PVC plastic according to the invention is in the form of particles. Thus, if the PVC feedstock is in an initial form which is that specific to production scraps or post-consumption waste, notably, in the latter case, in the initial form of PVC-based objects, it may first undergo a conditioning step comprising at least milling or shredding to form a PVC feedstock in the form of particles. Depending on the channels and/or networks from which these production scraps and/or PVC-based objects at the end of their service life are derived, the PVC waste may be milled and/or washed and/or may undergo any other conditioning step as described hereinbelow, so as to form the PVC feedstock in the form of particles that are suitable for the process according to the invention. For example, the PVC feedstock may advantageously be in the form of milled and optionally washed material, the largest dimension of which is less than 20 cm, preferably less than 10 cm, preferably less than 1 cm and even more preferably less than 5 mm. The PVC feedstock may also advantageously be in micronized solid form, i.e. in the form of particles preferably having a mean size of less than 1 mm, for example between 10 micrometers (μm) and 800 micrometers (μm). The mean size advantageously corresponds to the mean diameter of the spheres in which said particles are circumscribed.
Thus, the term “PVC feedstock in the form of particles” means particles of PVC plastic typically having a mean size, as defined previously, of between 10 μm and 20 cm, for example particles of milled material type with a mean size of between 1 mm and 20 cm, preferably between 1 mm and 10 cm, more preferentially between 1 mm and 1 cm, even more preferentially between 1 mm and 5 mm, or particles derived from micronization (very fine milling to produce a powder) with a mean size of less than 1 mm, preferably between 10 μm and 800 μm.
Preferably, the PVC feedstock treated in the process according to the invention is in the form of particles of milled material type, preferably particles with a mean size of between 1 mm and 5 mm, or particles derived from micronization (very fine milling to produce a powder) with a mean size of less than 1 mm.
The PVC feedstock may also comprise “macroscopic” impurities, such as glass, metal, plastics other than PVC (for example PET, etc.), wood, paper, cardboard, mineral elements, etc. Advantageously, the PVC feedstock comprises not more than 50% by mass, preferably not more than 30% by mass, preferably not more than 10% by mass and even more preferably not more than 5% by mass of “macroscopic” impurities.
Advantageously, the PVC feedstock in the form of particles has a water content of less than or equal to 0.3% by mass and preferably less than or equal to 0.1% by mass.
The various steps of the process according to the invention leading to the DAP and to the reusable target PVC plastic are detailed in the paragraphs that follow.
According to the invention, the process may comprise a preliminary step of conditioning the PVC feedstock (not shown in the figures) including at least one step of milling or shredding the PVC feedstock to form a PVC feedstock in the form of solid particles as defined above, which can be sent into the solid-liquid extraction step a). This preconditioning step may also comprise one or more steps mentioned in the following nonexhaustive list: milling by micronization, sorting, oversorting, washing, drying, etc. Depending on the nature of the PVC feedstock treated, the step or steps, and their possible frequencies and sequences, involved in the preconditioning step are notably chosen by a person skilled in the art so as to limit the amount of macroscopic impurities and to reduce the size of the solid elements of which the PVC feedstock is initially composed.
For example, the preconditioning step makes it possible to provide a PVC feedstock in the form of particles, for example washed milled material with a mean size of less than 5 mm, the macroscopic impurity content of which is preferably not more than 10% by mass and more preferably not more than 5% by mass. Said preconditioned PVC feedstock may also be in the form of micronized solid particles, i.e. in the form of particles with a mean size of less than 1 mm, for example between 10 μm and 800 μm.
The step of preconditioning of the PVC feedstock preferably comprises at least one step of drying the PVC feedstock which is already in the form of solid particles of ad hoc size and macroscopic impurity content, such that said PVC feedstock has a residual water content of not more than 0.3% by mass and preferably not more than 0.1% by mass.
The process according to the invention comprises a step a) of solid-liquid extraction of the phthalate(s) from the PVC feedstock in the form of particles 1 by placing said feedstock 1 in contact with a solvent 9 including an alcohol of empirical formula CnH2n+1OH, n<4 or n>8, so as to obtain an effluent 2 comprising at least a liquid phase and a solid phase. Said liquid phase is then enriched in said phthalate(s), and the solid phase includes PVC plastic depleted in said phthalate(s).
The specific choice of n for the alcohol of the solvent (exclusion of C4, C5, C6, C7 and C8 alcohols) makes it possible, during step b), to transform, by transesterification by means of said alcohol, said phthalates into at least one DAP as defined hereinbelow, which is not among the undesirable phthalates such as those that are subject to authorization by the REACH regulation discussed hereinabove.
According to one or more embodiments, said alcohol is an alcohol of empirical formula CnH2n+1OH with n<4, for example chosen from the list consisting of methanol, ethanol, n-propanol and i-propanol, and even more preferably n=1, said alcohol then being methanol CH3OH.
According to one or more embodiments, said alcohol is an alcohol of empirical formula CnH2n+1OH with n>8, for example chosen from the list consisting of linear or branched nonanol, linear or branched decanol, linear or branched undecanol, linear or branched dodecanol, and preferably nonanol or decanol.
According to one or more embodiments, said alcohol is an alcohol of empirical formula CnH2n+1OH with n>8 and n less than or equal to 20, or even n less than or equal to 15.
According to one or more embodiments, said alcohol of empirical formula CnH2n+1OH, n<4 or n>8 may be used according to the invention in its alkoxide form, i.e. in the form of the conjugate base of said alcohol of empirical formula CnH2n+1O−, with n<4 or n>8, the cationic counterion, including that of metallic nature, which ensures the electronegativity of said conjugate base being well known to those skilled in the art.
The solvent 9 may also comprise an organic cosolvent, added to said alcohol, which aids the extraction of the phthalate(s) from the PVC feedstock 1. In this case, said organic cosolvent may be an ester derived from said alcohol, said ester having the formula R′COOCnH2n+1, n being identical to the 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′ being a (linear, branched or cyclic, preferably linear) alkyl group, for example comprising between 1 and 3 carbon atoms, for example 1 or 2 carbon atoms, or alternatively said organic cosolvent may be an ether such as, in a nonexhaustive manner, cyclopentyl methyl ether (CPME), di-n-propyl ether or dioxane, preferably CPME.
Said organic cosolvent is added to said alcohol so that the mass ratio of the cosolvent relative to the alcohol (cosolvent/solvent) is between 0 and 4, preferably between 0.01 and 4, more preferentially between 0.02 and 0.66 and even more preferably between 0.05 and 0.66.
Said additional organic cosolvent is advantageously chosen, preferably when said alcohol is methanol, from the group consisting of methyl acetate, methyl propanoate and CPME.
Preferably, step a) of solid-liquid extraction of the phthalate(s) from the PVC feedstock 1 is performed by placing said feedstock 1, in the form of particles, in contact with methanol supplemented with methyl propanoate, preferably such that the mass ratio between the methyl propanoate and the methanol is between 0 and 4, preferably between 0.01 and 4, more preferentially between 0.02 and 0.66 and even more preferably between 0.05 and 0.66. In this case, the DAP produced by the process is dimethyl phthalate (DMP).
Step a) of solid-liquid extraction of the phthalate(s) of the PVC feedstock 1 is preferably performed under the following operating conditions: a temperature of 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., a pressure of between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa, a residence time of between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.
Preferably, step a) is performed so that the mole ratio between the amount of alcohol of the solvent 9 and the amount of the phthalate(s) to be extracted from the PVC feedstock 1 is between 2 and 250, preferably between 4 and 90 and even more preferably between 4 and 30.
The reactor of step a) of the process according to the invention may advantageously be a reactor of the type stirred with a mechanical stirring system and/or with a recirculation loop and/or with fluidization, for example a perfectly stirred reactor of discontinuous or continuous type, or a reactor of rotating drum type.
As regards the implementation, the PVC feedstock in the form of particles 1 and the solvent 9 including the alcohol, optionally supplemented with at least one organic cosolvent, are advantageously mixed.
According to a first option, said mixing may be performed prior to the introduction of the feedstock and the solvent into the reactor of the solid-liquid extraction step a). In this case, said mixture may be formed in a mixer and may then be introduced into the reactor, said reactor being maintained at a desired pressure and temperature.
According to a second option, the PVC feedstock in the form of particles 1 and the solvent 9 including the alcohol, optionally supplemented with at least one organic cosolvent, may be introduced separately into the reactor of step a) of the process according to the invention. Said solid PVC feedstock and the solvent are then preferably injected into the reactor via two separate lines, one allowing the injection of the solvent 9 and the other the solid PVC feedstock in the form of particles 1. In this case, the mixture of the PVC feedstock and of the solvent forms directly in said reactor.
In accordance with the invention, said solid-liquid extraction step a) makes it possible to obtain at least one effluent 2 comprising at least a liquid phase containing at least the extracted phthalates and at least a solid phase containing the PVC plastic depleted in phthalates, preferably free of phthalates.
The process according to the invention comprises a step b) of chemical transformation of the phthalate(s) extracted in step a) into at least one DAP of formula C6H4(COOCnH2n+1)2 by transesterification reaction, preferably in liquid phase, between said phthalate(s) of the liquid phase obtained from step a) and the alcohol of empirical formula CnH2n+1OH, with n<4 or n>8, preferably with n<4, even more preferably with n=1, said alcohol then being methanol CH3OH. In the case where said alcohol is methanol, said transesterification reaction is then known as a methanolysis reaction.
Step b) of chemical transformation of the phthalate(s) present in the liquid phase on conclusion of step a) into a DAP of formula C6H4(COOCnH2n+1)2 by transesterification reaction is preferably performed under the following operating conditions: a temperature of 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., a pressure of between atmospheric pressure and 11.0 MPa, preferably between atmospheric pressure and 5.0 MPa, more preferably between atmospheric pressure and 2.0 MPa, a residence time of between 1 minute and 10 hours, preferably between 10 minutes and 4 hours, more preferably between 10 minutes and 2 hours.
Preferably, step b) is performed so that the mole ratio between the amount of the alcohol of the solvent 9 and the amount of the phthalates to be transformed of the liquid phase containing the phthalate(s) extracted on conclusion of step a) is between 2 and 250, preferably between 4 and 90 and even more preferably between 4 and 30.
The alcohol used for performing step b) is the same as that used for performing step a). Preferably, said step b) of chemical transformation of the phthalate(s) extracted in step a) into a DAP of formula C6H4(COOCnH2n+1)2 by transesterification reaction is performed in the presence of a transesterification catalyst, advantageously introduced into the reaction medium.
The transesterification catalyst thus used is chosen, for example, from the catalysts of the following nonexhaustive list, which is well known to those skilled in the art, and preferably from the list consisting of:
For example, the catalyst used according to the invention is a homogeneous catalyst, notably a homogeneous catalyst of basic catalyst type such as sodium methoxide.
Preferably, the amount of catalyst introduced is such that the mass ratio between the catalyst and the phthalate(s) to be transformed is between 0.5% and 10% by mass, preferably between 1% and 8% by mass and even more preferably between 1% and 5% by mass.
Whether it is homogeneous or heterogeneous, the catalyst may be recycled and/or removed in the process according to methods that are well known to those skilled in the art, and is preferably recycled. It may be isolated, to be removed or preferably recycled for the transesterification reaction, in the downstream steps of the process, for example in step c), in step d) and/or in step e), or in any other dedicated step.
The reactor of step b) of the process according to the invention may advantageously be a reactor of the type stirred with a mechanical stirring system and/or with a recirculation loop and/or with fluidization, for example a perfectly stirred reactor of discontinuous or continuous type, or a reactor of rotating drum type.
In accordance with the invention, said step b) of transformation of the phthalates makes it possible to obtain at least one effluent comprising at least one liquid phase containing at least the DAP of formula C6H4(COOCnH2n+1)2 obtained after transesterification reaction, i.e. the liquid phase formed on conclusion of step a) and enriched in DAP in step b).
Steps a) and b) of the process according to the invention may be performed in the same individual operation or may be the subject of two distinct and consecutive individual operations, the individual operation of step a) then always being performed prior to the individual operation of step b).
In the embodiments presented in
In the embodiment presented in
In the embodiments represented in
The process according to the invention comprises a step c) of solid-liquid separation between, on the one hand, the liquid phase containing the phthalate(s) extracted in step a) and/or the DAP of formula C6H4(COOCnH2n+1)2 obtained after transesterification reaction in step b), and, on the other hand, the solid phase containing the PVC plastic depleted in phthalates, preferably free of phthalates.
The physical separation of the liquid phase and of the solid phase may advantageously be performed according to the techniques known to those skilled in the art, such as, in a nonexhaustive manner, filtration, centrifugation, electrostatic precipitation or decantation, said techniques being used alone or in combination, in any order.
This step c) of solid-liquid separation thus makes it possible to produce at least one solid stream (6) including the PVC plastic depleted in the phthalate(s) extracted in step a), so as to recover said reusable target PVC plastic.
The production of the reusable target PVC as defined according to the invention may necessitate returning all or a portion of the solid stream (6) obtained in step c) into step a), in as many cycles as necessary so as to produce said target PVC plastic.
This possibility of recycling the solid stream is shown in
According to a first variant of the process according to the invention, said solid-liquid separation step c) takes place after performing steps a) and b). This first variant is illustrated in
According to a second variant of the process according to the invention, the solid-liquid separation step c) takes place after performing step a) and before performing b). This second variant is illustrated in particular in
For example, according to embodiments in accordance with this second variant of the process as shown in
For another example, step c) may take place by centrifugation of the liquid effluent 2 or 3 comprising the liquid phase containing at least the extracted phthalates and/or the DAP and of the solid phase obtained from step a), leading to the separation of said solid 6, and advantageously to the return of all or a portion of said solid into step a), preferably placed in suspension beforehand, for example by means of supplying solvent 9 (not shown in the figures), until the reusable target PVC plastic is produced.
The process according to the invention comprises a liquid-liquid separation step d) for extracting the DAP of formula C6H4(COOCnH2n+1)2 from the liquid phase obtained on conclusion of the implementation of at least steps a), b) and c).
A liquid stream (4, 13) containing said liquid phase advantageously feeds this liquid-liquid separation step d), which thus makes it possible to produce at least a first liquid effluent including the DAP (stream 5 or 14 according to the figures) and a second liquid effluent comprising at least said solvent (stream 7 or 12 according to the figures).
The liquid-liquid separation step d) may be performed according to methods that are well known to those skilled in the art, such as, in a nonexhaustive manner, distillation, decantation, evaporation, liquid-liquid extraction, etc., performed alone or in combination. The operating conditions of this step (temperature, pressure, etc.) are determined as a function of the chosen separation method.
According to one or more embodiments, the first effluent 5 consists essentially of said DAP. In this case (these cases), the second liquid effluent 7, represented, for example, in
It is also possible in this case (these cases), notably depending on the chosen liquid-liquid separation methods, for example distillation with side withdrawal or liquid-liquid extraction, to separate from the liquid phase not only the solvent, but also the ALs and very advantageously the IAPs optionally with the unconverted phthalates extracted in step a). Such a separation is illustrated, for example, in
According to one or more alternative embodiments, as shown in
The process according to the invention may comprise an optional step e) of purification of the first effluent 14 comprising the DAP obtained from the liquid-liquid separation step d), to improve its quality and thus, ultimately, its upgrading. The embodiments shown in
In the case of performing said step e), the solvent was advantageously isolated during the implementation of step d). Moreover, the IAPs and optionally the phthalate(s) extracted on conclusion of step a) of the process according to the invention that are not converted on conclusion of step b) may have been isolated during step d) of the process according to the invention, or alternatively may be isolated during the implementation of said purification step e).
Thus, it is possible to send the first effluent 14, comprising the DAP, phthalate(s) which are partially converted and/or unconverted in step b) and possibly soluble impurities, into this purification step e) to form a liquid product 16 consisting essentially of said DAP, and a liquid residue 17 comprising the phthalate(s) which are partially converted and/or unconverted in step b) and possibly the soluble impurities.
The liquid residue 17 thus recovered may then be advantageously returned into step b) of the process according to the invention, notably according to the first and second variants of the process according to the invention, so as to continue the chemical reactions leading to the DAP, as illustrated in
The purification step e) may advantageously be performed via methods that are well known to those skilled in the art, such as precipitation, crystallization or adsorption, optionally followed by filtration or centrifugation. The purification step e) may comprise the implementation of several of these methods in parallel or in series. For example, and without being exhaustive, the purification step e) may comprise a precipitation and filtration step, followed by an adsorption step, or alternatively may comprise an adsorption and filtration step, optionally followed by a precipitation step, or may alternatively comprise a crystallization and filtration step. The operating conditions of this step e) (temperature, pressure, etc.) are determined as a function of the chosen purification method.
Additional Step(s) f1) and/or f2) of Chemical Transformation by Transesterification (Optional)
In order to promote the production of the DAP according to the invention, it is possible to perform, independently of step b) of chemical transformation of the phthalate(s) extracted in step a), an additional chemical transformation step allowing the transformation of the IAPs and/or of the extracted phthalate(s) which are possibly not converted on conclusion of step b).
The process may thus also comprise an additional step f1), as shown in
The process may also comprise an additional step f2) of chemical transformation by transesterification of the unconverted phthalate(s) in step b) and/or of at least one IAP produced in step b) or optionally in the optional step f1), into DAP of formula C6H4(COOCnH2n+1)2 using the solvent including the alcohol, step f2) being performed after step e) by sending the liquid residue 17 obtained from step e) into a second additional transesterification reactor to produce a third liquid stream 15 enriched in said DAP, said third liquid stream 15 being returned into step d).
The implementation of the additional step f1) and/or of the additional step f2) of chemical transformation by transesterification may be performed according to the first variant (solid-liquid separation step c) performed after steps a) and b)) or the second variant (solid-liquid separation step c) between steps a) and b)) of the process according to the invention.
Preferably, the process according to the invention comprises only one additional step of chemical transformation by transesterification, and preferably step f2).
The implementation of step f1) and/or of step f2) is as described for step b) of the process according to the invention. In particular, the ranges associated with the operating conditions of steps b) and f1) and/or f2) are similar, and said ranges are chosen by a person skilled in the art so as to promote the production of the DAP as a function of the chemical nature of the stream to be treated at the inlet of said step f1) and/or step f2).
This is likewise the case for the preferred use of a transesterification catalyst 8, as described in step b). The transesterification catalyst in step(s) f1) and/or f2) may be identical to or different from the one used in step b).
Said stream sent into step f1) and/or step f2) (stream 4 or liquid residue 17) is a liquid phase comprising one or more phthalates extracted in step a) and which are possibly partially converted (IAP) and/or unconverted in step b), and possibly soluble impurities, which are then isolated either during the implementation of the liquid-liquid separation step d) of the process according to the invention, or during the implementation of the purification step e) of the process according to the invention if said step is advantageously performed.
Depending on the sequence of steps considered involving step f1) and/or step f2), it may be necessary to use an additional supply of solvent comprising the alcohol of empirical formula CnH2n+1OH with n<4 or n>8, optionally supplemented with at least one organic cosolvent, this additional supply of solvent possibly resulting from a supply of “fresh” solvent 9 or else from recycling of the stream 12 of said solvent optionally isolated on conclusion of step d) of the process according to the invention. This additional supply in the first additional transesterification reactor performed in step f1) and/or in the second additional transesterification reactor performed in step f2), by supplying fresh solvent 9, and/or by recycling the second effluent 12 consisting of said solvent, is illustrated in
When the purification step e) is performed, at least a portion of said liquid residue 17 produced in step e) may be recycled into step f1), as illustrated in
As may be seen in
According to this embodiment, as illustrated schematically in
As shown in
According to this embodiment, as illustrated schematically in
The present invention also relates to a process for recycling a PVC-based object containing at least one phthalate, said recycling process including:
The step of conditioning of the PVC-based object may include the various steps detailed above for the preconditioning of the PVC feedstock before it is introduced into step a).
The present invention also relates to a process for manufacturing a flexible PVC-based object including a recycled PVC plastic and/or a DAP which are obtained via the process for recovering a DAP and a reusable target PVC plastic described above in detail.
Such a manufacturing process typically comprises a step of recovering a DAP and a reusable target PVC plastic from a PVC feedstock, as detailed above, followed by a step of mixing said reusable target PVC plastic with additives or a step of mixing said recovered DAP with a PVC resin, and then a step of forming said mixture.
This example illustrates the invention without limiting the scope thereof, and notably illustrates the extraction of a phthalate contained in a PVC plastic and the conversion of the phthalate into dimethyl phthalate in the presence of a catalyst, by methanolysis. 18.2 g of a PVC plastic feedstock (obtained from PVC-based objects of “medical tubing” type), in the form of extrudates with a mean size of 2 mm, containing 4.4 g of didecyl phthalate (DIDP), are introduced into a reactor stirred with a mechanical stirring system, of paddle type. 26.5 g of methanol and 17.7 g of methyl propanoate (organic cosolvent) are then added, the methyl propanoate/methanol mass ratio being 0.66 and the methanol/DIDP mole ratio being 84. 0.17 g of catalyst (NaOMe) are then added to the preceding mixture so that the NaOMe/DIDP mass percentage is 4%.
The reactor is hermetically closed, purged with nitrogen and then heated to 100° C. with an autogenous pressure of the order of 1.2 MPa and maintained under these conditions for 4 hours with stirring of 1000 rpm. The reactor is then cooled.
After 4 hours, a solid and a liquid are obtained, and are analyzed.
The analyses by gas chromatography with flame ionization detection (GC-FID) of the liquid phase show that it contains 1.89 g of dimethyl phthalate (DMP) obtained from the conversion of the DIDP and 0.05 g of decyl methyl phthalate due to a partial conversion of the DIDP. The liquid also contains 3.11 g of decanol (C10H22O) obtained from the DIDP methanolysis reaction. Identification was made possible by comparison of the retention times of pure analytical standards and quantification was performed by determination of the response coefficients derived from the analysis of these same standards.
The solid obtained was prefractionated by preparative size exclusion chromatography SEC equipped with double optical detection (UV/visible) and refractometry (RI). The fractions obtained from the collection were analyzed by high-performance liquid chromatography (HPLC) equipped with optical detection of quantitative UV-visible type The results indicate the presence of DIDP in the target PVC plastic in a content of less than 1000 ppm, which complies with the European regulations in force.
These results show that a phthalate-free PVC in accordance with the invention is obtained, and that the DIDP was 99.9% converted. In this example, the extraction of the DIDP and its conversion are performed in the same step.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2105299 | May 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/062081 | 5/5/2022 | WO |
