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).

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

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• 2003
  • 2003-07-15 FR FR0308691A patent/FR2857670B1/fr not_active Expired - Fee Related
• 2004
  • 2004-07-14 WO PCT/EP2004/051482 patent/WO2005014705A1/fr active Application Filing
  • 2004-07-14 CN CNB2004800204855A patent/CN100443531C/zh not_active Expired - Fee Related
  • 2004-07-14 US US10/564,700 patent/US7846986B2/en not_active Expired - Fee Related
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