EP1646679A1 - Method for obtaining a polymer in a solution - Google Patents

Method for obtaining a polymer in a solution

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Publication number
EP1646679A1
EP1646679A1 EP04766212A EP04766212A EP1646679A1 EP 1646679 A1 EP1646679 A1 EP 1646679A1 EP 04766212 A EP04766212 A EP 04766212A EP 04766212 A EP04766212 A EP 04766212A EP 1646679 A1 EP1646679 A1 EP 1646679A1
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EP
European Patent Office
Prior art keywords
solvent
polymer
phase
precipitation
rich
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP04766212A
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German (de)
French (fr)
Inventor
Eric Fassiau
Denis Geets
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Solvay SA
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Solvay SA
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Publication date
Application filed by Solvay SA filed Critical Solvay SA
Publication of EP1646679A1 publication Critical patent/EP1646679A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F6/00—Post-polymerisation treatments
    • C08F6/06—Treatment of polymer solutions
    • C08F6/12—Separation of polymers from solutions
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/06—Recovery or working-up of waste materials of polymers without chemical reactions
    • C08J11/08—Recovery or working-up of waste materials of polymers without chemical reactions using selective solvents for polymer components
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates to a process for recovering a polymer in solution.
  • Polymers are widely used in various forms, mainly in the solid state. However, it often happens that at some point in their existence, they are in solution in a solvent from which they must then be extracted. We are for example confronted with polymer solutions at the end of certain polymerization processes (called “in solution”), during certain recycling processes, during the cleaning of certain installations for the manufacture of objects or paints based on of polymers ...
  • the recovery of these polymers in solution is generally done by precipitation with a non-solvent which can be in liquid or vapor form, or both.
  • patent applications WO 01/23463 and WO 01/70865 in the name of SOLNAY describe a process for recycling a plastic material (PNC or PVDC) by dissolving in a solvent (MEK or methyl ethyl ketone) and by precipitation with a non-solvent (water) both in vapor form (to cause the evaporation of the solvent) and in liquid form (to accelerate the precipitation of the polymer).
  • a solvent MEK or methyl ethyl ketone
  • a non-solvent water
  • This process involves a significant energy cost linked to the quantity of steam used.
  • the Applicant has found that during a gradual addition of non-solvent, this process generally takes place as follows. As the non-solvent is added to the polymer solution to form the precipitation medium, there is first of all a phase separation, i.e.
  • the Applicant has found that the injection of vapor does in fact have a positive influence on the morphology of the polymer particles only during or after the phase inversion and it is therefore unnecessary for the non-solvent to be as a vapor before this stage.
  • the present invention therefore relates to a process for recovering at least one polymer in solution in a solvent by precipitation by means of a non-solvent gradually introduced into the solution to form the precipitation medium, according to which:
  • phase separation in a continuous phase rich in solvent in which the polymer is dissolved and in a dispersed phase consisting of drops rich in non-solvent; and then, to a phase inversion (the continuous phase then becoming the phase rich in non-solvent and the dispersed phase, that rich in solvent containing the dissolved polymer)
  • the non-solvent is initially introduced into the precipitation medium in liquid form only and in a quantity (Q ′) which is not zero but less than the quantity (Q) required to cause the phase inversion, and it is thereafter introduced into the precipitation medium at least partially in the form of vapor.
  • Optimizing the physical form in which the non-solvent is introduced into the solution makes it possible to substantially increase the profitability of the process without deteriorating the quality of the precipitated polymer obtained.
  • the polymer whose recovery is targeted by the process according to the present invention can be of any kind. It may be a thermoplastic resin or an elastomer, but in any case a resin which can be dissolved in a solvent and which therefore is not or only slightly crosslinked.
  • It can be an unused resin (or virgin), which has not undergone any shaping by fusion except for a possible granulation, or a used resin (production waste or recycled resin).
  • It can be an apolar polymer, such as a polyolefin and a in particular, a polymer of Tethylene (PE) or propylene (PP).
  • H can also be a polar polymer such as a halogenated polymer and in particular, a polymer of vinyl chloride (PNC), vinylidene chloride (PVDC), vinylidene fluoride (PVDF) ...; or ENOH (copolymer of ethylene and vinyl alcohol). It can also be a mixture of at least two such polymers of the same or different nature.
  • PNC is intended to denote any homo- or copolymer containing at least 50% by weight of vinyl chloride.
  • the polymer which has been dissolved in the solvent may contain one or more usual additives such as plasticizer (s), stabilizer (s), filler (s), pigment (s) ... Generally called “compound” of type of mixture based on polymer (s) and additive (s).
  • the polymer in the case where the polymer is PNC, it may be “flexible” PVC, ie containing one or more plasticizers generally at a rate of 75% or less, or even 70% or less, or even 65% or less.
  • PVC plasticizers are generally organic esters such as phthalates, adipates, trimellitates ..., phthalates and in particular, DOP (di-octyl-phthalate), being the most used.
  • DOP di-octyl-phthalate
  • the solvent (substance capable of dissolving the polymer) is preferably chosen from liquids having a solubility parameter (for which a definition and experimental values appear in "Properties of Polymers", DW Van Krevelen, Edition of 1990, pp.200- 202, as well as in "Polymer
  • solvent and non-solvent we mean substances as well simple as mixtures of substances.
  • Inorganic liquids are suitable non-solvents, water being generally the preferred non-solvent (in the case of non-water-soluble polymers, of course), taking into account the environmental and economic concerns generally involved in industrial processes.
  • water has the advantage of constituting an azeotrope with certain polar solvents such as MEK, which makes it possible to facilitate the removal of the solvent by azeotropic distillation.
  • the polymer is preferably PVC, the solvent, the MEK and the non-solvent, water.
  • the solutions which can be treated by the process according to the present invention have a polymer concentration such that their viscosity does not disturb the smooth running of the process (it is in particular necessary that the non-solvent can gradually be mixed and / or dispersed in the solution so that the two can interact and that precipitation can actually take place).
  • the process according to the invention makes it possible to work with concentrations of polymer in the solution more high since there is less solvent evaporation.
  • the process according to the invention it is generally possible to work with polymer contents greater than or equal to 100 g per liter of solvent, or even to 250 g / l and sometimes even, to 300 g / l. However, this content generally does not exceed 500 g / l, or even 400 g / l.
  • the presence of at least one dispersing agent during the addition of non-solvent to the solution generally promotes the mixing / dispersion of the non-solvent in the solution and therefore generally allows working with more concentrated solutions of polymer.
  • the term “dispersing agent” is intended to denote a substance which promotes the dispersion of a discrete phase (which may be formed either of liquid droplets or of solid particles) in another continuous phase.
  • This substance generally acts at the interface between the two phases and it prevents agglomeration of the discrete phase (i.e. it promotes obtaining a fine and regular dispersion).
  • non-solvent in liquid form is introduced into the polymer solution in a quantity (Q ′) which is not zero but less than the quantity (Q) necessary to cause the phase inversion .
  • the quantity (Q) which depends in particular on the nature of the solvent and of the non-solvent, on the temperature, on the pressure and in certain cases, on the quantity of dissolved polymer, is easily determined experimentally.
  • the remaining quantity of non-solvent required for the precipitation of the polymer is at least partially introduced in the form of vapor.
  • the fraction of vapor in this flow rate is preponderant.
  • all of the non-solvent introduced into the polymer solution after the quantity Q ′ has been introduced therein is in the form of vapor.
  • the total amount of non-solvent introduced in the form of vapor is preferably sufficient to allow the azeotropic distillation of the solvent. In a particularly preferred manner, this quantity is sufficient to make the medium after precipitation substantially free of solvent.
  • This procedure is particularly advantageous in the case where the non-solvent is water. It is not harmful for the non-solvent introduced into the precipitation medium (whether in liquid or vapor form) possibly to contain a minority concentration (by weight) of solvent; this is interesting insofar as (as will be explained below for the recycling processes in particular), a possible subsequent step in the process can precisely provide such a source of non-solvent, which can thus be reused without particular purification.
  • the non-solvent when water, it is actually meant by “water”, an aqueous medium having a majority weight content (therefore containing more than 50% by weight, even more than 60% and preferably , more than 10% by weight) in water. It is advantageously pure water or water containing a minority amount (by weight) of solvent.
  • the precipitation medium comprises at least one dispersing agent.
  • the precipitation medium comprises two different dispersing agents, one of which has a greater affinity for the non-solvent (dispersing agent 1) and the other has a greater affinity for the solvent (dispersing agent II).
  • the moment of introduction of these dispersing agents is optimized as a function of the course of the precipitation.
  • the dispersing agent having the greater affinity for the non-solvent (dispersing agent I) is mainly added to the precipitation medium before the phase inversion. To do this, it can be present in the solution before introduction of non-solvent, or be introduced via the liquid non-solvent introduced initially. It is also advantageous that the dispersing agent having the highest affinity with respect to the solvent (dispersing agent H) is mainly added to the precipitation medium after the phase inversion. Optimizing the nature and the timing of introduction of the dispersing agents makes it possible to optimize the PSA / average particle diameter ratio and therefore to obtain a compact powder of small particles.
  • the precipitation when the precipitation is finished, there is a suspension of polymer particles in a medium rich in non-solvent.
  • the proportion by weight of solid particles in this suspension can be greater than or equal to 10% without agglomeration of said particles. In particular in the presence of dispersing agents as described above, this proportion can even be greater than or equal to 25%, or even 30%.
  • Introducing non-solvent in liquid form makes it possible to obtain more economically (than with steam) the quantity of non-solvent necessary to obtain a suspension which is sufficiently diluted to avoid the problems of agglomeration of particles. .
  • the polymer particles contained in the suspension are collected by any suitable means: thermal (evaporation of the solvent, possibly by azeotropic distillation: see above), mechanical (filtration, centrifugation ...) or mixed (atomization for example). In the case of polymers sensitive to temperature (such as PVDC for example), mechanical methods will be preferred.
  • the particles collected can then be rinsed, dried, treated by any known means before storage, marketing and / or implementation.
  • the polymer solution to which the present invention applies can be obtained by any appropriate means.
  • the dissolution of the polymer in the solvent is generally carried out under a pressure at least equal to atmospheric pressure, or even at least equal to 1.5 bars.
  • this pressure does not exceed 10 bars, preferably 5 bars.
  • the dissolution temperature is generally at least 75 ° C, or even
  • additives can be added to the solution.
  • additive any organic or inorganic compound not present in the original plastics, or present in an amount less than that desired.
  • inorganic additives mention may be made of inorganic pigments, carbon black, metallic powders, nanoparticles of various kinds ...
  • the process according to the present invention can be integrated into any process involving the recovery of a polymer from a solution.
  • it can be part of a process for recycling articles based on polymer (s).
  • the present invention relates also a process for recycling at least one article based on at least one polymer, according to which a) if necessary, the article is shredded into fragments with an average dimension of 1 cm 50 cm b) bringing the article or the article fragments in contact with a solvent capable of dissolving the polymer c) the polymer is recovered in solution using the method described above.
  • the articles in question can be solids of any shape (sheet, plate, tube, etc.), mono- or multilayer; they can include several polymers (of which then generally only one will be dissolved selectively, although the article can also be used for the manufacture of an alloy) and also, non-polymeric materials (reinforcements, fixings ...) which will then be eliminated before treatment of the solution by the process described above. Note that in the case of articles based on several polymers, it may be advantageous to eliminate the other (or one of the others) polymer (s) before dissolving the polymer which it is desired to recover.
  • the solvent chosen is likely to dissolve several of the polymers of the article, it may be advantageous to first remove the troublesome polymer, for example by means of another solvent, which does not dissolve the polymer to be recovered.
  • another solvent which does not dissolve the polymer to be recovered.
  • one of the polymers is semi-crystalline, its solubility can be reduced by annealing (ie a stay at a temperature and for a period suitable for obtaining maximum crystallization).
  • An example of such polymers are PVC (amorphous polymer) and PVDC (semi-crystalline polymer).
  • an annealing treatment for 1 hour at 70 ° C or 2 days at 40 ° C for example
  • a PVC / PVDC complex makes it possible to make the latter insoluble in MEK at 50 ° C and therefore to selectively dissolve PVC in MEK at 50 ° C (or even at 75 ° C) and to apply the process as described above to the solution obtained.
  • the composition of the solvent can be adapted to selectively dissolve certain polymers of a structure.
  • An important advantage of such a recycling process is that it can operate in a closed loop (either continuously or by batch, but with almost total recirculation of the liquid phase, with the exception of losses, in particular by adsorption on the polymer particles obtained), without generating rejects.
  • the liquid medium obtained after precipitation and separation of the polymer particles and which mainly consists of non-solvent (optionally containing dispersing agents) can optionally be recycled with suitable treatment.
  • This treatment can consist of one or more distillations, flocculations, decantations, washes ... and combinations of these treatments.
  • this treatment includes at least one decantation and in this case, it is advantageous that said decantation takes place or at least partially in the presence of a phase separation agent.
  • a phase separation agent in the case where several decantations take place (in parallel or in series), it is advantageous that at least one of them takes place in the presence of a phase separation agent.
  • phase separation agent is intended to denote a substance which promotes decantation (ie the formation of two phases: one rich in solvent, the other rich in non-solvent) of the condensed vapors. azeotropic distillation. Note however that the Applicant has found that the presence of a phase separation agent in the precipitation medium (as recommended in application WO 01/70865) at the time of the phase inversion and after
  • phase separation agent i.e. contains maximum a few% by weight.
  • said process is a closed loop process in which the solvent and the non-solvent are regenerated at least in part by decantation, and in which a separating agent phases is present at least in part during said decantation but is absent during the precipitation of the polymer.
  • FIG. 1 schematically represents a specific recycling process applied to PVC.
  • PVC in particulate form (1) and a solvent containing mainly MEK (2) are introduced in the dissolution step (D).
  • vapors from azeotropic water / MEK distillation (8) are subjected to a condensation (C) to form an unstable liquid (8 ') which is subjected to a decantation (Dl) at the end of which a water-rich phase (9) and a phase are obtained.
  • C condensation
  • Dl decantation
  • MEK water-rich phase
  • MEK decantation
  • D2 decantation
  • hexane (11) to give a phase rich in water (12) and a phase rich in MEK (13) containing hexane and a little water.
  • the water-rich phase (12) is combined with the water (7) from the separation step (S) and with the water-rich phase (9) from the decantation (Dl) to form the water flow (4) used for precipitation (P).
  • the phase rich in MEK (13) is subjected to a distillation (DST) allowing on the one hand, to regenerate the hexane (11) which is recycled to decantation (D2) and on the other hand, to obtain MEK containing only a few% of water and hexane, and which constitutes the solvent (2) used for dissolution (D).
  • this solvent contains a little hexane is not a problem because although this hexane is found in the precipitation stage (P), it is removed from the medium before the phase inversion (the amount of water liquid Q ′ being less than the quantity of water Q required for the phase inversion, this quantity Q is reached by injection of steam which has the effect of evaporating the hexane, the most volatile compound in the water / MEK / mixture hexane).
  • the phase separation agent is substantially eliminated from the liquid medium resulting from the decantation (D2).
  • the advantage of the alternative era can generalize to any recycling process as described above, provided that it operates in closed loop with at least partial regeneration of the solvent and the non solvent by decantation in the presence of at least partial a phase separating agent, that the phase separating agent has a greater affinity for the solvent than for the non-solvent and that it is substantially removed from the solvent before the polymer is dissolved.
  • substantially eliminated is meant that a maximum of a few% (by weight) of phase separation agent can be left in the solvent and / or the non-solvent.
  • the present invention is also illustrated in a nonlimiting manner by the following examples:
  • Preliminary test determination of the quantity Q Liquid water was gradually added to PVC solutions at various concentrations, temperatures and pressures, and it was observed that the phase inversion took place in each case when the quantity of water was approximately equivalent (by volume) to the amount of MEK used.
  • plasticized PVC PVC of Kw 71 with 25% by weight of 30 wt.
  • DOP dioctyl phthalate
  • S solvent
  • M MEK
  • MWH solvent containing MEK
  • MWH hexane
  • a duration of introduction of the starting liquid of the order of 10 min makes it possible to obtain particles of better quality than a duration of 2 min (example 3 compared to example 2)
  • test 1 a less plasticized PVC was used (PVC of Kw 71 containing 20% by weight of DOP).

Abstract

The invention relates to a method for obtaining at least one polymer in a solution in a solvent by precipitation by means of a non-solvent gradually introduced into the solution in order to form a precipitation medium, wherein a) during the course of the introduction of the non-solvent into the precipitation medium, phase separation initially occurs (into a continuous phase which is rich in solvent wherein the polymer is dissolved and into a dispersed phase consisting of drops which are rich in non-solvent); and subsequently, phase inversion occurs (the continuous phase becomes a phase which is rich in non-solvent and the dispersed phase becomes rich in solvent containing the dissolved polymer; b) the non-solvent is initially introduced into the precipitation medium in an exclusively liquid form whereby the amount thereof (Q') is not zero but lower than the required amount (Q) for phase inversion, and it is subsequently introduced into the precipitation medium in an at least partial manner in the form of vapor.

Description

Procédé de récupération d'un polymère en solution Method for recovering a polymer in solution
La présente invention concerne un procédé de récupération d'un polymère en solution. Les polymères sont abondamment utilisés sous des formes diverses, principalement à l'état solide. Toutefois, il arrive souvent qu'à un moment donné de leur existence, ils soient en solution dans un solvant dont il faut alors les extraire. On est par exemple confronté à des solutions de polymère à la fin de certains procédés de polymérisation (dits "en solution"), au cours de certains procédés de recyclage, lors du nettoyage de certaines installations de fabrication d'objets ou de peintures à base de polymères... La récupération de ces polymères en solution se fait généralement par précipitation avec un non solvant qui peut être sous forme liquide ou vapeur, voire les deux. Ainsi, les demandes de brevet WO 01/23463 et WO 01/70865 au nom de SOLNAY décrivent un procédé de recyclage d'une matière plastique (PNC ou PVDC) par mise en solution dans un solvant (MEK ou méthyl éthyl cétone) et par précipitation avec un non solvant (eau) à la fois sous forme vapeur (pour provoquer l'évaporation du solvant) et sous forme liquide (pour accélérer la précipitation du polymère). Ce procédé implique un coût énergétique important lié à la quantité de vapeur utilisée. La demanderesse a constaté que lors d'un ajout progressif de non solvant, ce procédé se déroule généralement comme suit. Au fur et à mesure de l'ajout de non solvant à la solution de polymère pour former le milieu de précipitation, on assiste d'abord à une séparation de phases c.à.d. qu'à un moment donné, on passe d'un milieu monophasique constitué d'une phase riche en solvant contenant le polymère dissous et un peu de non solvant, à un milieu biphasique constitué d'une part, d'une phase continue riche en solvant dans laquelle le polymère est dissous et d'autre part, d'une phase dispersée constituée de gouttes riches en non solvant. Ensuite, après ajout d'une quantité donnée de non solvant (déterminée par le diagramme de phases entre solvant et l'eau), on assiste à une inversion de phases, c.àd. que la phase continue (majoritaire) devient alors la phase riche en eau et que la phase dispersée est alors constituée de gouttes de phase riche en solvant contenant le polymère dissous. L'injection de vapeur dans ce milieu permet de substantiellement éliminer le solvant par distillation azéotropique. De manière surprenante, bien que la précipitation du polymère démarre avant l'inversion de phases susmentionnée, la morphologie des particules de polymère obtenues est en fait essentiellement indépendante des étapes antérieures à cette inversion et est par contre principalement dépendante des conditions opératoires pendant et après l'inversion de phases. Or, le fait d'approcher la composition à l'inversion de phases par injection de vapeur provoque inutilement l'évaporation d'une certaine quantité de solvant. En d'autres termes : la demanderesse a trouvé que l'injection de vapeur n'a en fait une influence positive sur la morphologie des particules de polymères que pendant ou après l'inversion de phases et il est donc inutile que le non solvant soit sous forme de vapeur avant ce stade. La présente invention concerne dès lors un procédé de récupération d'au moins un polymère en solution dans un solvant par précipitation au moyen d'un non solvant introduit progressivement dans la solution pour former le milieu de précipitation, selon lequel :The present invention relates to a process for recovering a polymer in solution. Polymers are widely used in various forms, mainly in the solid state. However, it often happens that at some point in their existence, they are in solution in a solvent from which they must then be extracted. We are for example confronted with polymer solutions at the end of certain polymerization processes (called "in solution"), during certain recycling processes, during the cleaning of certain installations for the manufacture of objects or paints based on of polymers ... The recovery of these polymers in solution is generally done by precipitation with a non-solvent which can be in liquid or vapor form, or both. Thus, patent applications WO 01/23463 and WO 01/70865 in the name of SOLNAY describe a process for recycling a plastic material (PNC or PVDC) by dissolving in a solvent (MEK or methyl ethyl ketone) and by precipitation with a non-solvent (water) both in vapor form (to cause the evaporation of the solvent) and in liquid form (to accelerate the precipitation of the polymer). This process involves a significant energy cost linked to the quantity of steam used. The Applicant has found that during a gradual addition of non-solvent, this process generally takes place as follows. As the non-solvent is added to the polymer solution to form the precipitation medium, there is first of all a phase separation, i.e. that at a given moment, one passes from a single-phase medium consisting of a phase rich in solvent containing the dissolved polymer and a little non-solvent, to a two-phase medium consisting on the one hand, of a continuous phase rich in solvent in which the polymer is dissolved and on the other hand, a dispersed phase consisting of drops rich in non-solvent. Then, after adding a given amount of non-solvent (determined by the phase diagram between solvent and water), there is a phase inversion, i.e. that the continuous phase (majority) then becomes the phase rich in water and that the dispersed phase then consists of drops of phase rich in solvent containing the dissolved polymer. The injection of steam into this medium makes it possible to substantially eliminate the solvent by azeotropic distillation. Surprisingly, although the precipitation of the polymer starts before the aforementioned phase inversion, the morphology of the polymer particles obtained is in fact essentially independent of the steps prior to this inversion and is on the other hand mainly dependent on the operating conditions during and after the 'phase inversion. Now, bringing the composition to the phase inversion by injection of vapor unnecessarily causes the evaporation of a certain amount of solvent. In other words: the Applicant has found that the injection of vapor does in fact have a positive influence on the morphology of the polymer particles only during or after the phase inversion and it is therefore unnecessary for the non-solvent to be as a vapor before this stage. The present invention therefore relates to a process for recovering at least one polymer in solution in a solvent by precipitation by means of a non-solvent gradually introduced into the solution to form the precipitation medium, according to which:
- au cours de l'introduction du non solvant dans le milieu de précipitation, on assiste d'abord à une séparation de phases (en une phase continue riche en solvant dans laquelle le polymère est dissous et en une phase dispersée constituée de gouttes riches en non solvant) ; et ensuite, à une inversion de phases (la phase continue devenant alors la phase riche en non solvant et la phase dispersée, celle riche en solvant contenant le polymère dissous)- during the introduction of the non-solvent into the precipitation medium, there is first of all a phase separation (in a continuous phase rich in solvent in which the polymer is dissolved and in a dispersed phase consisting of drops rich in non-solvent); and then, to a phase inversion (the continuous phase then becoming the phase rich in non-solvent and the dispersed phase, that rich in solvent containing the dissolved polymer)
- le non solvant est initialement introduit dans le milieu de précipitation sous forme liquide uniquement et ce en une quantité (Q') non nulle mais inférieure à la quantité (Q) requise pour provoquer l'inversion de phases, et il est par la suite introduit dans le milieu de précipitation au moins partiellement sous forme de vapeur. L'optimisation de la forme physique sous laquelle le non solvant est introduit dans la solution permet d'augmenter sensiblement la rentabilité du procédé sans détériorer la qualité du polymère précipité obtenu. Le polymère dont la récupération est visée par le procédé selon la présente invention peut être de toute nature. Il peut s'agir d'une résine thermoplastique ou d'un élastomère, mais en tout cas d'une résine que l'on peut dissoudre dans un solvant et qui donc, n'est pas ou peu réticulée. Il peut s'agir d'une résine non usagée (ou vierge), qui n'a subi aucune mise en forme par fusion excepté une éventuelle granulation, ou d'une résine usagée (déchets de production ou résine recyclée). Il peut s'agir d'un polymère apolaire, tel qu'une polyoléfine et un particulier, un polymère de Téthylène (PE) ou du propylène (PP). H peut également s'agir d'un polymère polaire tel qu'un polymère halogénée et en particulier, un polymère du chlorure de vinyle (PNC), du chlorure de vinylidène (PVDC), du fluorure de vinylidène (PVDF) ... ; ou d'ENOH (copolymère d'éthylène et d'alcool vinylique). Il peut également s'agir d'un mélange d'au moins deux tels polymères de même nature ou de nature différente. De bons résultats ont été obtenus avec les polymères polaires, halogènes en particulier et tout particulièrement, avec le PVC. Par PNC, on entend désigner tout homo- ou copolymère contenant au moins 50% en poids de chlorure de vinyle. Le polymère qui a été dissous dans le solvant peut contenir un ou plusieurs additifs usuels tels que plastiiïant(s), stabilisant(s), charge(s), pigment(s)... On appelle généralement « compound » de type de mélange à base de polymère(s) et d'additif(s). Un avantage du procédé selon l'invention est qu'il permet de récupérer ces additifs c.à.d. de les co-précipiter avec le polymère. Ainsi par exemple, dans le cas où le polymère est le PNC, il peut s'agir de PVC « souple » c.à.d. contenant un ou plusieurs plastifiants généralement à raison de 75% ou moins, voire 70% ou moins, voire même 65% ou moins. Les plastifiants du PVC sont en général des esters organiques tels que les phtalates, adipates, trimellitates..., les phtalates et en particulier, le DOP (di-octyl-phtalate), étant les plus utilisés. Le procédé selon l'invention donne de bons résultas dans le cas des polymères (et en particulier, du PVC) plastifiés. Le solvant (substance capable de dissoudre le polymère) est de préférence choisi parmi les liquides ayant un paramètre de solubilité (dont une définition et des valeurs expérimentales figurent dans "Properties of Polymers", D.W. Van Krevelen, Edition de 1990, pp.200-202, ainsi que dans "Polymer- the non-solvent is initially introduced into the precipitation medium in liquid form only and in a quantity (Q ′) which is not zero but less than the quantity (Q) required to cause the phase inversion, and it is thereafter introduced into the precipitation medium at least partially in the form of vapor. Optimizing the physical form in which the non-solvent is introduced into the solution makes it possible to substantially increase the profitability of the process without deteriorating the quality of the precipitated polymer obtained. The polymer whose recovery is targeted by the process according to the present invention can be of any kind. It may be a thermoplastic resin or an elastomer, but in any case a resin which can be dissolved in a solvent and which therefore is not or only slightly crosslinked. It can be an unused resin (or virgin), which has not undergone any shaping by fusion except for a possible granulation, or a used resin (production waste or recycled resin). It can be an apolar polymer, such as a polyolefin and a in particular, a polymer of Tethylene (PE) or propylene (PP). H can also be a polar polymer such as a halogenated polymer and in particular, a polymer of vinyl chloride (PNC), vinylidene chloride (PVDC), vinylidene fluoride (PVDF) ...; or ENOH (copolymer of ethylene and vinyl alcohol). It can also be a mixture of at least two such polymers of the same or different nature. Good results have been obtained with polar polymers, halogen in particular and very particularly, with PVC. By PNC is intended to denote any homo- or copolymer containing at least 50% by weight of vinyl chloride. The polymer which has been dissolved in the solvent may contain one or more usual additives such as plasticizer (s), stabilizer (s), filler (s), pigment (s) ... Generally called “compound” of type of mixture based on polymer (s) and additive (s). An advantage of the process according to the invention is that it makes it possible to recover these additives, i.e. to co-precipitate them with the polymer. Thus, for example, in the case where the polymer is PNC, it may be “flexible” PVC, ie containing one or more plasticizers generally at a rate of 75% or less, or even 70% or less, or even 65% or less. PVC plasticizers are generally organic esters such as phthalates, adipates, trimellitates ..., phthalates and in particular, DOP (di-octyl-phthalate), being the most used. The process according to the invention gives good results in the case of plasticized polymers (and in particular PVC). The solvent (substance capable of dissolving the polymer) is preferably chosen from liquids having a solubility parameter (for which a definition and experimental values appear in "Properties of Polymers", DW Van Krevelen, Edition of 1990, pp.200- 202, as well as in "Polymer
Handbook", J. Brandrup and E.H. Immergut, Editors, Second Edition, p.IV-337 à IV-359) voisin de celui du polymère à dissoudre et/ou présentant des interactions fortes avec celui-ci (liens hydrogènes par exemple). Le terme « voisin » équivaut généralement à « ne s'écartant pas de plus de 6 unités ». Il s'agit en général d'un solvant organique, de préférence polaire tel que la MEK (méthyl éthyl cétone), qui donne de bons résultats avec de nombreux polymères et en particulier, avec les polymères halogènes tels que le PVC. Quant au non solvant, il est de préférence choisi comme ayant un paramètre de solubilité différent de celui du polymère à dissoudre et ne présentant pas d'interactions fortes avec ceux-ci. Le terme « différent » équivaut généralement à s'écartant de plus de 6 unités. Il est entendu que par solvant et non solvant, on entend aussi bien des substances simples que des mélanges de substances. Les liquides inorganiques sont des non solvants qui conviennent bien, l'eau étant généralement le non solvant préféré (dans le cas des polymères non hydrosolubles bien évidemment) compte tenu des préoccupations environnementales et économiques généralement impliquées dans les procédés industriels. En outre, l'eau présente l'avantage de constituer un azéotrope avec certains solvants polaires tels que la MEK ce qui permet de faciliter l'élimination du solvant par distillation azéotropique. Il résulte de ce qui précède que dans le procédé selon l'invention, le polymère est de préférence le PVC, le solvant, la MEK et le non solvant, l'eau. Les solutions que l'on peut traiter par le procédé selon la présente invention ont une concentration en polymère telle que leur viscosité ne perturbe pas le bon déroulement du procédé (il faut notamment que le non solvant puisse progressivement être mélangé et/ou dispersé dans la solution pour que les deux puissent interagir et que la précipitation puisse effectivement avoir lieu). Par rapport à un procédé ou du non solvant est ajouté depuis le départ sous forme vapeur à la solution (et donc, provoque l'évaporation de solvant), le procédé selon l'invention permet de travailler avec des concentrations en polymère dans la solution plus élevées puisqu'il y a moins d'évaporation de solvant. Ainsi, dans le procédé selon l'invention, on peut généralement travailler avec des teneurs en polymère supérieures ou égales à 100 g par litre de solvant, voire à 250 g/1 et parfois même, à 300 g/1. Toutefois, cette teneur de dépasse généralement pas 500 g/1, voire 400 g/1. A noter que la présence d'au moins un agent dispersant lors de l'ajout de non solvant à la solution favorise généralement le mélange/dispersion du non solvant dans la solution et donc, permet généralement de travailler avec des solutions plus concentrées en polymère. Par « agent dispersant », on entend désigner une substance qui favorise la dispersion d'une phase discrète (qui peut être formée soit de gouttelettes de liquide, soit de particules solides) dans une autre phase, continue. Cette substance agit généralement à l'interface entre les deux phases et elle prévient l'agglomération de la phase discrète (c.à.d. qu'elle favorise l'obtention d'une dispersion fine et régulière). Selon l'invention, une fois le polymère dissous, on introduit dans la solution de polymère, du non solvant sous forme liquide en une quantité (Q') non nulle mais inférieure à la quantité (Q) nécessaire pour provoquer l'inversion de phases. La quantité (Q), qui dépend notamment de la nature du solvant et du non solvant, de la température, de la pression et dans certains cas, de la quantité de polymère dissous, se détermine aisément de manière expérimentale. Il suffît d'introduire progressivement du non solvant sous forme liquide dans la solution jusqu'à observation de l'inversion de phases (aisément identifiable pour l'homme du métier) et de mesurer la quantité de non solvant ajoutée à ce moment là, qui est la quantité Q. De bons résultats ont été obtenus avec une quantité Q' supérieure ou égale à 50% (en volume) de la quantité Q, voire supérieure ou égale à 70%, voire même à 90%. La vitesse d'mtroduction de la quantité Q' de non solvant sous forme liquide a généralement une influence sur le rapport PSA/diamètre moyen des particules de polymère obtenues. De bons résultats ont été obtenus lorsque la durée d'introduction est supérieure ou égale à 10 minutes, voire à plusieurs lo™1 de minutes. Selon l'invention, une fois la quantité Q' introduite dans le milieu de précipitation, la quantité restante de' non solvant requise pour la précipitation du polymère est au moins partiellement introduite sous forme de vapeur. On entend par là qu'au moins une fraction du débit de non solvant ajouté au milieu de précipitation dès ce moment là (et qui est généralement continu) est sous forme de vapeur. Avantageusement, la fraction de vapeur dans ce débit est prépondérante. De manière préférée, tout le non solvant introduit dans la solution de polymère après que la quantité Q' y ait été introduite est sous forme de vapeur. Lorsque le solvant et le non solvant forment un azéotrope, la quantité totale de non solvant introduite sous forme de vapeur est de préférence suffisante pour permettre la distillation azéotropique du solvant. De manière particulièrement préférée, cette quantité est suffisante pour rendre le milieu après précipitation substantiellement exempt de solvant. Cette manière de procéder est particulièrement avantageuse dans le cas où le non solvant est l'eau. Il n'est pas nuisible que le non solvant introduit dans le milieu de précipitation (que ce soit sous forme liquide ou vapeur) contienne éventuellement une concentration minoritaire (en poids) de solvant ; ceci est intéressant dans la mesure où (comme il sera exposé ci-après pour les procédés de recyclage notamment), une éventuelle étape ultérieure du procédé peut précisément fournir une telle source de non solvant, que l'on peut ainsi réutiliser sans épuration particulière. De ce fait, lorsque le non solvant est de l'eau, on entend en fait désigner par « eau », un milieu aqueux ayant une teneur pondérale majoritaire (donc contenant plus de 50% en poids, voire plus de 60% et de préférence, plus de 10% en poids) en eau. Il s'agit avantageusement d'eau pure ou d'eau contenant une quantité minoritaire (en poids) de solvant. Selon une variante de la présente invention, le milieu de précipitation comprend au moins un agent dispersant. Selon une variante avantageuse, le milieu de précipitation comprend deux agents dispersants différents dont l'un a une plus grande affinité pour le non solvant (agent dispersant 1) et l'autre a une plus grande affinité pour le solvant (agent dispersant II). Selon une variante particulièrement avantageuse, le moment d'introduction des ces agents dispersants est optimisé en fonction du déroulement de la précipitation. Ainsi, il est avantageux que l'agent dispersant ayant l'affinité plus grande pour le non solvant (agent dispersant I) soit principalement ajouté au milieu de précipitation avant l'inversion de phases. Pour ce faire, il peut être présent dans la solution avant introduction de non solvant, où être introduit via le non solvant liquide introduit initialement. Il est également avantageux que l'agent dispersant ayant l'affinité la plus élevée vis-à-vis du solvant (agent dispersant H) soit principalement ajouté au milieu de précipitation après l'inversion de phases. Le fait d'optimiser la nature et le moment d'introduction des agents dispersants permet d'optimiser la rapport PSA/diamètre moyen des particules et donc, d'obtenir une poudre compacte de petites particules. Généralement, lorsque la précipitation est teπninée, on est en présence d'une suspension de particules de polymère dans un milieu riche en non solvant. La proportion pondérale de particules solides dans cette suspension peut être supérieure ou égale à 10% sans qu'il y ait agglomération desdites particules. En particulier en présence d'agents dispersants tels que décrits précédemment, cette proportion peut même être supérieure ou égale à 25%, voire à 30%. Le fait d'introduire du non solvant sous forme liquide permet d'obtenir de manière plus économique (qu'avec de la vapeur) la quantité de non solvant nécessaire pour obtenir une suspension qui soit assez diluée pour éviter les problèmes d'agglomération de particules. Les particules de polymère contenues dans la suspension sont recueillies par tout moyen adéquat : thermique (évaporation du solvant, éventuellement par distillation azéotropique : voir ci-dessus), mécanique (filtration, centrifugation...) ou mixte (atomisation par exemple). Dans le cas des polymères sensibles à la température (tel que le PVDC par exemple), on préférera les méthodes mécaniques. Les particules recueillies peuvent alors être rincées, séchées, traitées par tout moyen connu avant stockage, commercialisation et/ou mise en oeuvre. La solution de polymère à laquelle s'applique la présente invention peut être obtenue par tout moyen approprié. Toutefois, la dissolution du polymère dans le solvant s'effectue généralement sous une pression au moins égale à la pression atmosphérique, voire au moins égale à 1.5 bars. Avantageusement, cette pression n'excède pas 10 bars, de préférence 5 bars. La température de dissolution est généralement d'au moins 75°C, voireHandbook ", J. Brandrup and EH Immergut, Editors, Second Edition, p.IV-337 to IV-359) close to that of the polymer to be dissolved and / or exhibiting strong interactions with it (hydrogen bonds for example). The term “neighbor” is generally equivalent to “not deviating by more than 6 units.” It is generally an organic solvent, preferably polar, such as MEK (methyl ethyl ketone), which gives good results with many polymers and in particular with halogenated polymers such as PVC As for the non-solvent, it is preferably chosen as having a solubility parameter different from that of the polymer to be dissolved and having no strong interactions with The term "different" is generally equivalent to deviating by more than 6 units. It is understood that by solvent and non-solvent, we mean substances as well simple as mixtures of substances. Inorganic liquids are suitable non-solvents, water being generally the preferred non-solvent (in the case of non-water-soluble polymers, of course), taking into account the environmental and economic concerns generally involved in industrial processes. In addition, water has the advantage of constituting an azeotrope with certain polar solvents such as MEK, which makes it possible to facilitate the removal of the solvent by azeotropic distillation. It follows from the above that in the process according to the invention, the polymer is preferably PVC, the solvent, the MEK and the non-solvent, water. The solutions which can be treated by the process according to the present invention have a polymer concentration such that their viscosity does not disturb the smooth running of the process (it is in particular necessary that the non-solvent can gradually be mixed and / or dispersed in the solution so that the two can interact and that precipitation can actually take place). Compared to a process where non-solvent is added from the start in vapor form to the solution (and therefore causes solvent evaporation), the process according to the invention makes it possible to work with concentrations of polymer in the solution more high since there is less solvent evaporation. Thus, in the process according to the invention, it is generally possible to work with polymer contents greater than or equal to 100 g per liter of solvent, or even to 250 g / l and sometimes even, to 300 g / l. However, this content generally does not exceed 500 g / l, or even 400 g / l. Note that the presence of at least one dispersing agent during the addition of non-solvent to the solution generally promotes the mixing / dispersion of the non-solvent in the solution and therefore generally allows working with more concentrated solutions of polymer. The term “dispersing agent” is intended to denote a substance which promotes the dispersion of a discrete phase (which may be formed either of liquid droplets or of solid particles) in another continuous phase. This substance generally acts at the interface between the two phases and it prevents agglomeration of the discrete phase (i.e. it promotes obtaining a fine and regular dispersion). According to the invention, once the polymer has dissolved, non-solvent in liquid form is introduced into the polymer solution in a quantity (Q ′) which is not zero but less than the quantity (Q) necessary to cause the phase inversion . The quantity (Q), which depends in particular on the nature of the solvent and of the non-solvent, on the temperature, on the pressure and in certain cases, on the quantity of dissolved polymer, is easily determined experimentally. It suffices to introduce gradually non-solvent in liquid form in the solution until the phase inversion is observed (easily identifiable for those skilled in the art) and measure the amount of non-solvent added at this time, which is the quantity Q. Good results have been obtained with a quantity Q ′ greater than or equal to 50% (by volume) of the quantity Q, or even greater than or equal to 70%, or even even 90%. The rate of introduction of the quantity Q ′ of non-solvent in liquid form generally has an influence on the PSA / average diameter ratio of the polymer particles obtained. Good results have been obtained when the duration of introduction is greater than or equal to 10 minutes, or even several lo ™ 1 of minutes. According to the invention, once the quantity Q ′ introduced into the precipitation medium, the remaining quantity of non-solvent required for the precipitation of the polymer is at least partially introduced in the form of vapor. By this is meant that at least a fraction of the flow rate of non-solvent added to the precipitation medium at that time (and which is generally continuous) is in the form of vapor. Advantageously, the fraction of vapor in this flow rate is preponderant. Preferably, all of the non-solvent introduced into the polymer solution after the quantity Q ′ has been introduced therein is in the form of vapor. When the solvent and the non-solvent form an azeotrope, the total amount of non-solvent introduced in the form of vapor is preferably sufficient to allow the azeotropic distillation of the solvent. In a particularly preferred manner, this quantity is sufficient to make the medium after precipitation substantially free of solvent. This procedure is particularly advantageous in the case where the non-solvent is water. It is not harmful for the non-solvent introduced into the precipitation medium (whether in liquid or vapor form) possibly to contain a minority concentration (by weight) of solvent; this is interesting insofar as (as will be explained below for the recycling processes in particular), a possible subsequent step in the process can precisely provide such a source of non-solvent, which can thus be reused without particular purification. Therefore, when the non-solvent is water, it is actually meant by "water", an aqueous medium having a majority weight content (therefore containing more than 50% by weight, even more than 60% and preferably , more than 10% by weight) in water. It is advantageously pure water or water containing a minority amount (by weight) of solvent. According to a variant of the present invention, the precipitation medium comprises at least one dispersing agent. According to an advantageous variant, the precipitation medium comprises two different dispersing agents, one of which has a greater affinity for the non-solvent (dispersing agent 1) and the other has a greater affinity for the solvent (dispersing agent II). According to a particularly advantageous variant, the moment of introduction of these dispersing agents is optimized as a function of the course of the precipitation. Thus, it is advantageous that the dispersing agent having the greater affinity for the non-solvent (dispersing agent I) is mainly added to the precipitation medium before the phase inversion. To do this, it can be present in the solution before introduction of non-solvent, or be introduced via the liquid non-solvent introduced initially. It is also advantageous that the dispersing agent having the highest affinity with respect to the solvent (dispersing agent H) is mainly added to the precipitation medium after the phase inversion. Optimizing the nature and the timing of introduction of the dispersing agents makes it possible to optimize the PSA / average particle diameter ratio and therefore to obtain a compact powder of small particles. Generally, when the precipitation is finished, there is a suspension of polymer particles in a medium rich in non-solvent. The proportion by weight of solid particles in this suspension can be greater than or equal to 10% without agglomeration of said particles. In particular in the presence of dispersing agents as described above, this proportion can even be greater than or equal to 25%, or even 30%. Introducing non-solvent in liquid form makes it possible to obtain more economically (than with steam) the quantity of non-solvent necessary to obtain a suspension which is sufficiently diluted to avoid the problems of agglomeration of particles. . The polymer particles contained in the suspension are collected by any suitable means: thermal (evaporation of the solvent, possibly by azeotropic distillation: see above), mechanical (filtration, centrifugation ...) or mixed (atomization for example). In the case of polymers sensitive to temperature (such as PVDC for example), mechanical methods will be preferred. The particles collected can then be rinsed, dried, treated by any known means before storage, marketing and / or implementation. The polymer solution to which the present invention applies can be obtained by any appropriate means. However, the dissolution of the polymer in the solvent is generally carried out under a pressure at least equal to atmospheric pressure, or even at least equal to 1.5 bars. Advantageously, this pressure does not exceed 10 bars, preferably 5 bars. The dissolution temperature is generally at least 75 ° C, or even
100°C ; elle n'excède généralement pas 125°C, voire 110°C. Lors de cette dissolution, il peut s'avérer avantageux de travailler sous atmosphère inerte, par exemple sous azote, pour éviter tout risque d'explosion et de dégradation du solvant et/ou du non solvant. Après ou durant la dissolution du polymère, mais avant la précipitation, on peut ajouter à la solution, un ou plusieurs additifs. Par "additif selon cette variante de l'invention, on entend désigner tout composé organique ou inorganique non présent dans les matières plastiques d'origine, ou présent dans une quantité inférieure à celle désirée. A titre d'additifs inorganiques, on peut citer les pigments inorganiques, le noir de carbone, les poudres métalliques, les nanoparticules de natures diverses... A titre d'additifs organiques, on peut citer les pigments organiques, les stabilisants, les oligomères, plastifiants... Le procédé selon la présente invention peut être intégré à tout procédé impliquant la récupération d'un polymère à partir d'une solution. En particulier, il peut faire partie d'un procédé de recyclage d'articles à base de polymère(s). Ainsi, la présente invention concerne également un procédé de recyclage d'au moins un article à base d'au moins un polymère, selon lequel a) si nécessaire, on déchiquette l'article en des fragments d'une dimension moyenne de 1 cm à 50 cm b) on met l'article ou les fragments d'article en contact avec un solvant capable de dissoudre le polymère c) on récupère le polymère en solution en utilisant le procédé décrit ci-dessus. Les articles dont il est question peuvent être des solides de toute forme (feuille, plaque, tube...), mono- ou multicouche ; ils peuvent inclure plusieurs polymères (dont alors généralement un seul sera dissous sélectivement, bien que l'article puisse également servir à la fabrication d'un alliage) et également, des matières non polymériques (renforts, fixations...) qui seront alors éliminées avant traitement de la solution par le procédé décrit ci avant. A noter que dans le cas des articles à base de plusieurs polymères, il peut s'avérer intéressant d'éliminer l'autre (ou un des autres) polymère(s) avant mise en solution du polymère que l'on désire récupérer. Ainsi par exemple, si le solvant choisi est susceptible de dissoudre plusieurs des polymères de l'article, il peut s'avérer intéressant de d'abord éliminer le polymère gênant, par exemple au moyen d'un autre solvant, qui ne dissout pas le polymère à récupérer. A noter que lorsqu'un des polymères est semi cristallin, sa solubilité peut être diminuée par recuit (c.à.d. un séjour à une température et pendant une durée adaptée pour obtenir une cristallisation maximale). Un exemple de tels polymères sont le PVC (polymère amorphe) et le PVDC (polymère semi cristallin). Ainsi par exemple, un traitement de recuit (durant lh à 70°C ou 2 jours à 40°C par exemple) sur un complexe PVC/PVDC permet de rendre ce dernier insoluble dans la MEK à 50°C et donc, de dissoudre sélectivement le PVC dans la MEK à 50°C (voire même à 75°C) et d'appliquer le procédé tel que décrit ci-dessus à la solution obtenue. A noter également que la composition du solvant peut être adaptée pour dissoudre sélectivement certains polymères d'une structure. Dans le procédé de recyclage décrit ci-dessus, les conditions de solubihsation (pression, température, agitation...) du polymère et de séparation éventuelle des éléments non polymériques ou à base d'un polymère gênant avant précipitation (par filtration, mise en solution préalable...), seront optimisées par tout moyen connu de l'homme du métier. Un enseignement utile à cet effet figure dans les demandes EP 945481, WO 01/23463 et WO 01/70865 au nom de SOL VA Y, et est incorporé par référence dans la présente demande. Un tel procédé de recyclage a été appliqué avec succès à des articles comprenant du PVC. Un avantage important d'un tel procédé de recyclage est qu'il peut fonctionner en boucle fermée (soit en continu, soit par batch, mais avec recirculation quasi-totale de la phase liquide, à l'exception des pertes notamment par adsorption sur les particules de polymère obtenues), sans générer de rejets. En effet, le milieu liquide obtenu après précipitation et séparation des particules de polymère et qui est principalement constitué de non solvant (contenant éventuellement des agents dispersants) peut être recyclé éventuellement moyennant un traitement adéquat. Ce traitement peut consister en une ou plusieurs distillations, floculations, décantations, lavages... et en des combinaisons de ces traitements. De même, lorsque le solvant a été éliminé du milieu de précipitation par distillation azéotropique avec le non solvant, les vapeurs résultant de cette distillation peuvent être condensées et constituer une phase liquide qui peut être traitée comme décrit ci avant. De préférence, ce traitement inclut au moins une décantation et dans ce cas, il est avantageux que ladite décantation se déroule ou moins partiellement en présence d'un agent de séparation de phases. Ainsi, dans le cas ou plusieurs décantations ont lieu (en parallèle ou en série), il est avantageux qu'au moins l'une d'entre elles ait lieu en présence d'un agent de séparation de phases. Par « agent de séparation de phases », on entend désigner une substance qui favorise la décantation (c.à.d. la formation de deux phases : l'une riche en solvant, l'autre riche en non solvant) des vapeurs condensées de la distillation azéotrope. A noter cependant que la demanderesse a constaté que la présence d'un agent de séparation de phases dans le milieu de précipitation (comme recommandé dans la demande WO 01/70865) au moment de l'inversion de phases et après100 ° C; it generally does not exceed 125 ° C, or even 110 ° C. During this dissolution, it may prove advantageous to work under an inert atmosphere, for example under nitrogen, to avoid any risk of explosion and degradation of the solvent and / or the non-solvent. After or during the dissolution of the polymer, but before precipitation, one or more additives can be added to the solution. By "additive according to this variant of the invention, is meant any organic or inorganic compound not present in the original plastics, or present in an amount less than that desired. As inorganic additives, mention may be made of inorganic pigments, carbon black, metallic powders, nanoparticles of various kinds ... As organic additives, mention may be made of organic pigments, stabilizers, oligomers, plasticizers ... The process according to the present invention can be integrated into any process involving the recovery of a polymer from a solution. In particular, it can be part of a process for recycling articles based on polymer (s). Thus, the present invention relates also a process for recycling at least one article based on at least one polymer, according to which a) if necessary, the article is shredded into fragments with an average dimension of 1 cm 50 cm b) bringing the article or the article fragments in contact with a solvent capable of dissolving the polymer c) the polymer is recovered in solution using the method described above. The articles in question can be solids of any shape (sheet, plate, tube, etc.), mono- or multilayer; they can include several polymers (of which then generally only one will be dissolved selectively, although the article can also be used for the manufacture of an alloy) and also, non-polymeric materials (reinforcements, fixings ...) which will then be eliminated before treatment of the solution by the process described above. Note that in the case of articles based on several polymers, it may be advantageous to eliminate the other (or one of the others) polymer (s) before dissolving the polymer which it is desired to recover. So for example, if the solvent chosen is likely to dissolve several of the polymers of the article, it may be advantageous to first remove the troublesome polymer, for example by means of another solvent, which does not dissolve the polymer to be recovered. It should be noted that when one of the polymers is semi-crystalline, its solubility can be reduced by annealing (ie a stay at a temperature and for a period suitable for obtaining maximum crystallization). An example of such polymers are PVC (amorphous polymer) and PVDC (semi-crystalline polymer). Thus for example, an annealing treatment (for 1 hour at 70 ° C or 2 days at 40 ° C for example) on a PVC / PVDC complex makes it possible to make the latter insoluble in MEK at 50 ° C and therefore to selectively dissolve PVC in MEK at 50 ° C (or even at 75 ° C) and to apply the process as described above to the solution obtained. Note also that the composition of the solvent can be adapted to selectively dissolve certain polymers of a structure. In the recycling process described above, the conditions for solubilization (pressure, temperature, stirring, etc.) of the polymer and possible separation of non-polymeric elements or those based on a troublesome polymer before precipitation (by filtration, prior solution ...), will be optimized by any means known to those skilled in the art. A teaching useful for this purpose appears in the applications EP 945481, WO 01/23463 and WO 01/70865 in the name of SOL VA Y, and is incorporated by reference in the present application. Such a recycling process has been successfully applied to articles comprising PVC. An important advantage of such a recycling process is that it can operate in a closed loop (either continuously or by batch, but with almost total recirculation of the liquid phase, with the exception of losses, in particular by adsorption on the polymer particles obtained), without generating rejects. Indeed, the liquid medium obtained after precipitation and separation of the polymer particles and which mainly consists of non-solvent (optionally containing dispersing agents) can optionally be recycled with suitable treatment. This treatment can consist of one or more distillations, flocculations, decantations, washes ... and combinations of these treatments. Likewise, when the solvent has been removed from the precipitation medium by azeotropic distillation with the non-solvent, the vapors resulting from this distillation can be condensed and constitute a liquid phase which can be treated as described above. Preferably, this treatment includes at least one decantation and in this case, it is advantageous that said decantation takes place or at least partially in the presence of a phase separation agent. Thus, in the case where several decantations take place (in parallel or in series), it is advantageous that at least one of them takes place in the presence of a phase separation agent. The term “phase separation agent” is intended to denote a substance which promotes decantation (ie the formation of two phases: one rich in solvent, the other rich in non-solvent) of the condensed vapors. azeotropic distillation. Note however that the Applicant has found that the presence of a phase separation agent in the precipitation medium (as recommended in application WO 01/70865) at the time of the phase inversion and after
(c.à.d. durant les étapes conditionnant la morphologie des particules de polymère) avait généralement un effet néfaste sur ladite morphologie. Aussi, dans le cas d'un procédé en boucle fermée utilisant un agent de séparation de phases, il est avantageux que la solution de polymère à précipiter soit substantiellement exempte d'agent de séparation de phases (c.à.d. en contienne maximum quelques % en poids). Toutefois, la présence de cet agent de séparation de phases lors des traitements de décantation susmentionnés est favorable. Par conséquent, selon une variante particulièrement avantageuse du procédé de recyclage tel que décrit ci avant, ledit procédé est un procédé en boucle fermée où le solvant et le non solvant sont régénérés au moins en partie par décantation, et dans lequel un agent de séparation de phases est présent au moins en partie lors de ladite décantation mais est absent durant la précipitation du polymère. Pour ce faire, il est substantiellement éliminé du milieu liquide (solvant principalement) avant la précipitation du polymère et il est rajouté au(x) milieu(x) liquide(s) issus de la précipitation avant ou pendant leur décantation. L'élimination de l'agent de séparation de phases peut se faire par tout moyen connu à cet effet ; une distillation donne de bons résultats lorsque le point d'ébullition de cet agent est sensiblement différent de celui du solvant et du non solvant. Une telle variante est illustrée de manière non limitative par la figure 1 qui représente de manière schématique, un procédé spécifique de recyclage appliqué au PVC. Dans ce procédé, du PVC sous forme particulaire (1) et un solvant contenant principalement de la MEK (2) sont introduits à l'étape de dissolution (D). Il en résulte une solution de PVC (3) qui est introduite à l'étape de précipitation (P) conjointement avec un non solvant contenant principalement de l'eau (4). Celui-ci est introduit à l'étape de précipitation (P) d'abord sous forme liquide uniquement (4') et ensuite, moyennant une vaporisation (V), sous forme de vapeur (4"). Le flux (4') est calculé pour injecter à la précipitation (P), une quantité d'eau Q'inférieure à la quantité Q requise pour provoquer l'inversion de phases. Quant au flux (4"), il est calculé pour permettre la précipitation totale du PVC et l'élimination complète de la MEK du milieu de précipitation par distillation azéotropique. A l'issue de l'étape de précipitation (P), on est en présence :(ie during the stages conditioning the morphology of the polymer particles) generally had a detrimental effect on said morphology. Also, in the case of a closed loop process using a phase separation agent, it is advantageous that the polymer solution to be precipitated is substantially free of phase separation agent (i.e. contains maximum a few% by weight). However, the presence of this phase separation agent during the above-mentioned settling treatments is favorable. Consequently, according to a particularly advantageous variant of the recycling process as described above, said process is a closed loop process in which the solvent and the non-solvent are regenerated at least in part by decantation, and in which a separating agent phases is present at least in part during said decantation but is absent during the precipitation of the polymer. To do this, it is substantially eliminated from the liquid medium (mainly solvent) before the precipitation of the polymer and it is added to the liquid medium (s) resulting from the precipitation before or during their decantation. The elimination of the phase separation agent can be done by any means known for this purpose; distillation gives good results when the boiling point of this agent is significantly different from that of the solvent and of the non-solvent. Such a variant is illustrated in a nonlimiting manner by FIG. 1 which schematically represents a specific recycling process applied to PVC. In this process, PVC in particulate form (1) and a solvent containing mainly MEK (2) are introduced in the dissolution step (D). This results in a PVC solution (3) which is introduced in the precipitation step (P) together with a non-solvent mainly containing water (4). This is introduced in the precipitation stage (P) first in the form liquid only (4 ') and then, by means of vaporization (V), in the form of vapor (4 "). The flow (4') is calculated to inject at the precipitation (P), a quantity of water Q 'lower at the quantity Q required to cause the phase inversion. As for the flow (4 "), it is calculated to allow the total precipitation of the PVC and the complete elimination of the MEK from the precipitation medium by azeotropic distillation. At the end of the precipitation step (P), we are in the presence of:
- d'une part, d'une suspension de PVC dans de l'eau (5) que l'on soumet à une séparation solide/liquide (S) pour obtenir des particules de PVC (6) et de l'eau (7)- firstly, a suspension of PVC in water (5) which is subjected to a solid / liquid separation (S) to obtain PVC particles (6) and water (7 )
- d'autre part, de vapeurs issues de la distillation azéotropique eau/MEK (8). Ces vapeurs (8) sont soumises à une condensation (C) pour former un liquide instable (8') qui est soumis à une décantation (Dl) à l'issue de laquelle on obtient une phase riche en eau (9) et une phase riche en MEK (10). Cette dernière est à son tour soumise à une décantation (D2) en présence d'hexane (11) pour donner une phase riche en eau (12) et une phase riche en MEK (13) contenant de l'hexane et un peu d'eau.- on the other hand, vapors from azeotropic water / MEK distillation (8). These vapors (8) are subjected to a condensation (C) to form an unstable liquid (8 ') which is subjected to a decantation (Dl) at the end of which a water-rich phase (9) and a phase are obtained. rich in MEK (10). The latter is in turn subjected to decantation (D2) in the presence of hexane (11) to give a phase rich in water (12) and a phase rich in MEK (13) containing hexane and a little water.
La phase riche en eau (12) est combinée avec l'eau (7) issue de l'étape de séparation (S) et avec la phase riche eau (9) issue de la décantation (Dl) pour former le flux d'eau (4) utilisé à la précipitation (P). La phase riche en MEK (13) est soumise à une distillation (DST) permettant d'une part, de régénérer l'hexane (11) qui est recyclé à la décantation (D2) et d'autre part, d'obtenir de la MEK ne contenant plus que quelques % d'eau et d'hexane, et qui constitue le solvant (2) utilisé à la dissolution (D). Le fait que ce solvant contienne un peu d'hexane n'est pas gênant car bien que cet hexane se retrouve à l'étape de précipitation (P), il est éliminé du milieu avant l'inversion de phases (la quantité d'eau liquide Q' étant inférieure à la quantité d'eau Q requise pour l'inversion de phases, cette quantité Q est atteinte par injection de vapeur qui a pour effet d'évaporer l'hexane, composé le plus volatil du mélange eau/MEK/hexane). Dans le procédé selon la figure 1, l'agent de séparation de phases est substantiellement éliminé du milieu liquide issu de la décantation (D2). Cette manière de procéder permet, moyennant l'utilisation d'un tampon de solvant (c.à.d. d'un « double » de solvant qui est en traitement (décantation/distillation) pendant qu'un cycle de fabrication a lieu et qui est utilisé durant le cycle suivant, pendant que le solvant usagé du cycle précédent est traité à son tour), de ne pas rallonger la durée des cycles de fabrication (ou batches). Alternativement, l'agent de séparation de phases peut être éliminé entre l'étape de dissolution (D) et l'étape de précipitation (P). Cette alternative est toutefois moins avantageuse car : - le fait de distiller la solution de polymère peut avoir une influence sur la morphologie des particules de polymère qui seront obtenues - le temps de cycle (durée d'un batch) est rallongé puisque l'utilisation d'un tampon de solvant n'est pas possible. L'avantage de la lère alternative peut se, généraliser à tout procédé de recyclage tel que décrit précédemment, pour peu qu'il fonctionne en boucle fermée avec régénération au moins partielle du solvant et du non solvant par décantation en présence au moins partielle d'un agent de séparation de phases, que l'agent de séparation de phases ait une affinité plus grande pour le solvant que pour le non solvant et qu'il soit substantiellement éliminé du solvant avant la dissolution du polymère. Par « substantiellement éliminé », on entend que maximum quelques % (en poids) d'agent de séparation de phases peuvent être laissés dans le solvant et/ou le non solvant. La présente invention est également illustrée de manière non limitative par les exemples suivants :The water-rich phase (12) is combined with the water (7) from the separation step (S) and with the water-rich phase (9) from the decantation (Dl) to form the water flow (4) used for precipitation (P). The phase rich in MEK (13) is subjected to a distillation (DST) allowing on the one hand, to regenerate the hexane (11) which is recycled to decantation (D2) and on the other hand, to obtain MEK containing only a few% of water and hexane, and which constitutes the solvent (2) used for dissolution (D). The fact that this solvent contains a little hexane is not a problem because although this hexane is found in the precipitation stage (P), it is removed from the medium before the phase inversion (the amount of water liquid Q ′ being less than the quantity of water Q required for the phase inversion, this quantity Q is reached by injection of steam which has the effect of evaporating the hexane, the most volatile compound in the water / MEK / mixture hexane). In the process according to FIG. 1, the phase separation agent is substantially eliminated from the liquid medium resulting from the decantation (D2). This way of proceeding allows, by means of the use of a solvent buffer (ie a "double" of solvent which is in treatment (decantation / distillation) while a manufacturing cycle takes place and which is used during the next cycle, while the solvent used from the previous cycle is being treated in turn), not to extend the duration of the manufacturing cycles (or batches). Alternatively, the agent phase separation can be eliminated between the dissolution step (D) and the precipitation step (P). This alternative is however less advantageous because: - the fact of distilling the polymer solution can have an influence on the morphology of the polymer particles which will be obtained - the cycle time (duration of a batch) is lengthened since the use of 'A solvent pad is not possible. The advantage of the alternative era can generalize to any recycling process as described above, provided that it operates in closed loop with at least partial regeneration of the solvent and the non solvent by decantation in the presence of at least partial a phase separating agent, that the phase separating agent has a greater affinity for the solvent than for the non-solvent and that it is substantially removed from the solvent before the polymer is dissolved. By "substantially eliminated" is meant that a maximum of a few% (by weight) of phase separation agent can be left in the solvent and / or the non-solvent. The present invention is also illustrated in a nonlimiting manner by the following examples:
Essai préliminaire : détermination de la quantité Q On a progressivement ajouté de l'eau liquide à des solutions de PVC à des concentrations, températures et pressions diverses, et on a observé que l'inversion de phases avait dans chaque cas lieu lorsque la quantité d'eau était environ équivalente (en volume) à la quantité de MEK utilisée.Preliminary test: determination of the quantity Q Liquid water was gradually added to PVC solutions at various concentrations, temperatures and pressures, and it was observed that the phase inversion took place in each case when the quantity of water was approximately equivalent (by volume) to the amount of MEK used.
Exemple de référence RI et exemples 2 à 4 (conformes à l'invention)Example of RI reference and examples 2 to 4 (in accordance with the invention)
Dans chacun de ces essais, on a dissous (en 1 heure, à 75°C, sous pression atmosphérique et avec un agitateur hélicoïdal tournant à 250 tours/min) 333 g de PVC plastifié (PVC de Kw 71 avec 25% en poids de DOP (dioctyl phtalate)) dans une quantité donnée de solvant (S) qui est soit de la MEK (M) pure, soit un solvant contenant de la MEK, de l'eau et de l'hexane (MWH) en des quantités fonction de la concentrations visée (voir tableau ci-dessous). On a ensuite porté ces solutions à 50-55°C, réduit la pression à 600 mbar et introduit de l'eau liquide en une quantité (Q'< Q) et avec une durée d'introduction (t) données. On a ensuite procédé à l'injection de vapeur à un débit de 3.6 kg/h en une quantité (Q") au moins suffisante pour provoquer la précipitation totale du PVC. Le solvant a été récupéré par condensation pour réutilisation. Le compound de PVC recueilli était en suspension dans de l'eau. Il a été filtré sur un filtre métallique de 125 μm et a ensuite été séché en étuve sous vide (0.2 bara) à 80°C pendant 5 heures. La poudre de compound de PVC précipité a alors été tamisée sur un tamis de 1 mm avant utilisation et on a ensuite mesuré leur PSA et leur diamètre moyen et calculé le rapport PSA/diamètre moyen, qui constitue un indice de la qualité des particules de PVC obtenues.In each of these tests, 333 g of plasticized PVC (PVC of Kw 71 with 25% by weight of 30 wt.) Were dissolved (in 1 hour, at 75 ° C., at atmospheric pressure and with a helical agitator rotating at 250 rpm). DOP (dioctyl phthalate)) in a given quantity of solvent (S) which is either pure MEK (M) or a solvent containing MEK, water and hexane (MWH) in functional quantities of the target concentration (see table below). These solutions were then brought to 50-55 ° C, reduced the pressure to 600 mbar and introduced liquid water in a quantity (Q '<Q) and with a given introduction time (t). Steam was then injected at a flow rate of 3.6 kg / h in an amount (Q ") at least sufficient to cause total precipitation of the PVC. The solvent was recovered by condensation for reuse. The PVC compound collected was suspended in water. It was filtered on a 125 μm metal filter and was then dried in a vacuum oven (0.2 bara) at 80 ° C for 5 hours. The precipitated PVC compound powder was then sieved through a 1 mm sieve before use and their PSA and their average diameter were then measured and the PSA / average diameter ratio calculated, which constitutes an index of the quality of the PVC particles. obtained.
Le détail de ces essais ainsi que les résultats obtenus figurent dans le tableau 1. On constate que : - malgré l'injection d'une quantité de vapeur nettement moindre que dans l'exemple de référence RI, les exemples conformes à l'invention permettent d'obtenir des particules de qualité voisine, voire supérieureThe details of these tests as well as the results obtained are shown in Table 1. It can be seen that: - despite the injection of a much smaller quantity of vapor than in the reference example RI, the examples according to the invention allow obtain particles of similar quality, or even higher
- une durée d'introduction du liquide de départ de l'ordre de 10 min permet d'obtenir des particules de meilleure qualité qu'une durée de 2 min (exemple 3 par rapport à l'exemple 2)a duration of introduction of the starting liquid of the order of 10 min makes it possible to obtain particles of better quality than a duration of 2 min (example 3 compared to example 2)
Exemples 5 à 8 (conformes à l'invention)Examples 5 to 8 (in accordance with the invention)
On a procédé comme dans les exemples 1 à 4 mais à plus grande échelle et en variant les quantités de PVC dissous pour obtenir les concentrations pondérales qui figurent dans le tableau 1 , où figure également le détail des essais et les résultats obtenus.The procedure was as in Examples 1 to 4 but on a larger scale and by varying the quantities of dissolved PVC to obtain the weight concentrations which appear in Table 1, which also shows the details of the tests and the results obtained.
Dans l'essai 1, un PVC moins plastifié a été utilisé (PVC de Kw 71 contenant 20% en poids de DOP).In test 1, a less plasticized PVC was used (PVC of Kw 71 containing 20% by weight of DOP).
On constate que : - l'augmentation de la concentration en plastifiant a un effet néfaste sur la qualité des particules de PVC obtenues (exemple 6 par rapport à l'exemple 7)It can be seen that: the increase in the concentration of plasticizer has a detrimental effect on the quality of the PVC particles obtained (example 6 compared with example 7)
- la présence d'hexane au moment de l'inversion de phase a également un effet néfaste sur la qualité des particules de PVC obtenues (exemple 8 par rapport à l'exemple 5). - The presence of hexane at the time of phase inversion also has a detrimental effect on the quality of the PVC particles obtained (Example 8 compared to Example 5).

Claims

R E V END I CAT I ON S R E V END I CAT I ON S
1 - Procédé de récupération d'au moins un polymère en solution dans un solvant par précipitation au moyen d'un non solvant introduit progressivement dans la solution pour former le milieu de précipitation, selon lequel :1 - Process for recovering at least one polymer in solution in a solvent by precipitation using a non-solvent gradually introduced into the solution to form the precipitation medium, according to which:
- au cours de l'introduction du non solvant dans le milieu de précipitation, on assiste d'abord à une séparation de phases (en une phase continue riche en solvant dans laquelle le polymère est dissous et en une phase dispersée constituée de gouttes riches en non solvant) ; et ensuite, à une inversion de phases (la phase continue devenant alors la phase riche en non solvant et la phase dispersée, celle riche en solvant contenant le polymère dissous)- during the introduction of the non-solvent into the precipitation medium, there is first of all a phase separation (in a continuous phase rich in solvent in which the polymer is dissolved and in a dispersed phase consisting of drops rich in non-solvent); and then, to a phase inversion (the continuous phase then becoming the phase rich in non-solvent and the dispersed phase, that rich in solvent containing the dissolved polymer)
- le non solvant est initialement introduit dans le milieu de précipitation sous forme liquide uniquement et ce en une quantité (Q') non nulle mais inférieure à la quantité (Q) requise pour provoquer l'inversion de phases, et il est par la suite introduit dans le milieu de précipitation au moins partiellement sous forme de vapeur.- the non-solvent is initially introduced into the precipitation medium in liquid form only and in a quantity (Q ′) which is not zero but less than the quantity (Q) required to cause the phase inversion, and it is thereafter introduced into the precipitation medium at least partially in the form of vapor.
2 - Procédé selon la revendication 1, caractérisé en ce que le polymère est le PVC, le solvant est la MEK (méthyl éthyl cétone) et le non solvant est l'eau.2 - Process according to claim 1, characterized in that the polymer is PVC, the solvent is MEK (methyl ethyl ketone) and the non-solvent is water.
3 - Procédé selon l'une quelconques des revendications précédentes, caractérisé en ce que la quantité Q'est supérieure ou égale à 50% (en volume) de la quantité Q.3 - Method according to any one of the preceding claims, characterized in that the quantity Q is greater than or equal to 50% (by volume) of the quantity Q.
4 - Procédé selon l'une quelconques des revendications précédentes, caractérisé en ce que la durée d'introduction de la quantité Q' dans le milieu de précipitation est supérieure ou égale à 10 minutes.4 - Method according to any one of the preceding claims, characterized in that the duration of introduction of the quantity Q 'in the precipitation medium is greater than or equal to 10 minutes.
5 - Procédé selon l'une quelconques des revendications précédentes, caractérisé en ce que tout le non solvant introduit dans le milieu de précipitation après que la quantité Q' y ait été introduite est sous forme de vapeur.5 - Method according to any one of the preceding claims, characterized in that all the non-solvent introduced into the precipitation medium after the quantity Q 'has been introduced therein is in the form of vapor.
6 - Procédé selon l'une quelconque des revendications précédentes, caractérisé en ce que le solvant et le non solvant forment un azéotrope et en ce la quantité totale de non solvant introduite sous forme de vapeur est suffisante pour permettre la distillation azéotropique du solvant. 7 - Procédé selon la revendication précédente, caractérisé en ce que le milieu de précipitation comprend deux agents dispersants différents dont l'un a une plus grande affinité pour le non solvant (agent dispersant I) et l'autre a une plus grande affinité pour le solvant (agent dispersant II). 8 - Procédé de recyclage d'au moins un article à base d'au moins un polymère, selon lequel6 - Method according to any one of the preceding claims, characterized in that the solvent and the non-solvent form an azeotrope and in that the total amount of non-solvent introduced in the form of vapor is sufficient to allow azeotropic distillation of the solvent. 7 - Method according to the preceding claim, characterized in that the precipitation medium comprises two different dispersing agents, one of which has a greater affinity for the non-solvent (dispersing agent I) and the other has a greater affinity for the solvent (dispersing agent II). 8 - Process for recycling at least one article based on at least one polymer, according to which
a) si nécessaire, on déchiquette l'article en des fragments d'une dimension moyenne de 1 cm à 50 cma) if necessary, the article is shredded into fragments with an average size of 1 cm to 50 cm
b) on met l'article ou les fragments d'article en contact avec un solvant capable de dissoudre le polymèreb) the article or the article fragments are brought into contact with a solvent capable of dissolving the polymer
c) on récupère le polymère en solution en utilisant un procédé selon l'une quelconque des revendications précédentes.c) the polymer is recovered in solution using a method according to any one of the preceding claims.
9 - Procédé de recyclage selon la revendication précédente, caractérisé en ce ledit procédé est un procédé en boucle fermée où le solvant et le non solvant sont régénérés au moins en partie par décantation, et en ce qu'un agent de séparation de phases est présent au moins en partie lors de ladite décantation mais est substantiellement absent durant la précipitation du polymère.9 - recycling process according to the preceding claim, characterized in that said process is a closed loop process where the solvent and the non-solvent are regenerated at least in part by decantation, and in that a phase separation agent is present at least partly during said decantation but is substantially absent during the precipitation of the polymer.
10 - Procédé selon la revendication précédente, caractérisé en ce que l'agent de séparation de phases a une affinité plus grande pour le solvant que pour le non solvant et qu'il est substantiellement éliminé du solvant régénéré avant la dissolution du polymère. 10 - Process according to the preceding claim, characterized in that the phase separation agent has a greater affinity for the solvent than for the non-solvent and that it is substantially removed from the regenerated solvent before the polymer is dissolved.
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FR2857670B1 (en) 2006-02-03
WO2005014705A1 (en) 2005-02-17
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