WO2022218765A1 - Procédé et appareil pour le recyclage de polyéthylène basse densité (pebd) - Google Patents

Procédé et appareil pour le recyclage de polyéthylène basse densité (pebd) Download PDF

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Publication number
WO2022218765A1
WO2022218765A1 PCT/EP2022/059038 EP2022059038W WO2022218765A1 WO 2022218765 A1 WO2022218765 A1 WO 2022218765A1 EP 2022059038 W EP2022059038 W EP 2022059038W WO 2022218765 A1 WO2022218765 A1 WO 2022218765A1
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ldpe
polymer solution
organic solvent
solvent
nanofiltration
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PCT/EP2022/059038
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German (de)
English (en)
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Michael Kleiber
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Thyssenkrupp Industrial Solutions Ag
Thyssenkrupp Ag
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Publication of WO2022218765A1 publication Critical patent/WO2022218765A1/fr

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    • 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
    • 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
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
    • 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
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/04—Homopolymers or copolymers of ethene
    • C08J2423/06—Polyethene
    • 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
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/10—Homopolymers or copolymers of propene
    • C08J2423/12—Polypropene
    • 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 invention relates to a method for recycling low-density polyethylene (LDPE) by recovering pure LDPE(R) from an impure plastic mixture containing LDPE(U), HDPE (high-density polyethylene) and PP (polypropylene).
  • LDPE low-density polyethylene
  • LDPE is a plastic that is found in many different applications. For example, standard household cling film is made of LDPE. LDPE is also used in various industrial applications. Contamination occurs during the use of LDPE, so that large quantities of contaminated LDPE accumulate as waste. As a rule, this plastic waste is not “single-type", but different plastics such as LDPE, HDPE (high density polyethylene) and PP (polypropylene) are mixed together. Some of the different types of plastic are also processed together.
  • plastic waste particularly waste polyethylene plastic bags, plastic containers and plastic packaging. These represent a large proportion of the amount of plastic waste that is landfilled or incinerated today.
  • LDPE, HDPE and PP belong to the group of substances called polyolefins.
  • Various processes for the recycling of polyolefins are known from the prior art.
  • the German patent application DE 199 05 029 A1 describes a process for separating mixed polyolefins by means of liquid-liquid phase separation.
  • the mixed polyolefins are first dissolved in a solvent.
  • An auxiliary agent is added to the solvent, which causes liquid-liquid separation.
  • the upper phase contains the branched polyolefin LDPE, the solvent, the auxiliary and PP.
  • the lower phase contains the less branched polyolefin HDPE, the solvent and still branched polyolefin (LDPE) and auxiliaries as impurities.
  • LDPE low branched polyolefin
  • auxiliaries as impurities.
  • the process described provides that polymer dissolution is initiated with a toluene solvent and polymer precipitation in granular form is initiated with an isopropanol non-solvent.
  • the slurry from the precipitation is filtered and dried and the recycled LDPE is recovered with a purity of 99.99%.
  • the solvent and non-solvent must be separated by distillation.
  • the process is complex overall and is associated with high costs, inter alia because of the distillation required to separate the solvent and non-solvent.
  • German patent application DE 101 27 875 A1 describes a process for obtaining LDPE from used plastic films, in which, among other things, the process steps “extraction of low-molecular components from the film material” and “precipitation of at least one disruptive polymer from the polymer solution by introducing shear forces into the solution”. This method is therefore very complex and causes considerable costs.
  • the object of the invention is to specify a simple and cost-effective method for recycling LDPE, in particular also large amounts of LDPE.
  • the object of the invention is also to specify a device for carrying out the method.
  • the process according to the invention for recycling low-density polyethylene (LDPE) by recovering pure LDPE(R) from an impure plastic mixture containing LDPE(U), HDPE (high-density polyethylene) and PP (polypropylene) comprises the following process steps:
  • V1) producing a first polymer solution (PL1) in a first process line (I) by selectively dissolving impure LDPE(U) in an organic solvent (L1) at a temperature at which HDPE and PP are not yet dissolved;
  • V3) separating the second polymer solution (PL2) within the second process line (II) in a separation step, which comprises an ultrafiltration process (U) with an ultrafiltration membrane (MU) or a nanofiltration process (N) with a nanofiltration membrane (MN), into a third organic one Solvent (L3) as permeate and a third polymer solution (PL3) as retentate of the ultra (U) or nanofiltration process (N), the third polymer solution (PL3) having a higher concentration of dissolved LDPE than the second polymer solution (PL2);
  • the third polymer solution (PL3) is returned to the first process step (V1) for producing the first polymer solution (PL1), and the first polymer solution (PL1) is recycled into pure LDPE(R) in a separation step comprising a first evaporation process (E1) and a fourth organic solvent (L4) is separated; or
  • the third polymer solution (PL3) is separated in a second evaporation process (E2) comprehensive separation step into pure LDPE(R) and a fifth organic solvent (L5) and the first polymer solution (PL1) in a first evaporation process (E1) comprehensive Separation step in pure LDPE (R) and a fourth organic solvent (L4) is separated.
  • E2 second evaporation process
  • E1 comprehensive Separation step in pure LDPE
  • L4 fourth organic solvent
  • the impure LDPE is dissolved in the organic solvent for economic reasons, among other things, but an undissolved residual amount of LDPE and an undissolved residual amount of HDPE and PP remain. Pure LDPE can be recovered from the first polymer solution PL1 by evaporating the solvent.
  • the contaminated LDPE(U) dissolves at a temperature at which HDPE and PP do not yet dissolve, the contaminated LDPE(U) is “selectively” dissolved in the organic solvent.
  • the first polymer solution (PL1) contains only dissolved LDPE and no dissolved HDPE or PP. Therefore, pure LDPE(R) can subsequently be recovered from the first polymer solution (PL1).
  • the undissolved residual amount of LDPE is dissolved in a second method step V2) in a second organic solvent L2.
  • the undissolved residual amount of LDPE from the first process step V1) is small compared to the amount of LDPE that is fed to the first process step V1).
  • a comparatively large amount of organic solvent L2 is used in order to completely dissolve this small residual amount of LDPE in method step V2) in the organic solvent L2.
  • This second polymer solution PL2 has a significantly lower concentration of dissolved LDPE than the first polymer solution PL1.
  • the method according to the invention therefore proposes as the third method step V3) the separation of the second polymer solution PL2 within the second process line (II) in a separation step which comprises an ultrafiltration method U with an ultrafiltration membrane MU or a nanofiltration method N with a nanofiltration membrane MN.
  • This separation step separates the second polymer solution PL2 into a third organic solvent L3 as permeate and a third polymer solution PL3 as retentate of the ultrafiltration or nanofiltration process.
  • the third polymer solution PL3 has a higher concentration of dissolved LDPE than the second polymer solution PL2.
  • the dissolved LDPE can be recovered from the third polymer solution PL3 enriched in this way in a much more energy-efficient and cost-effective manner than from the “thin” polymer solution PL2.
  • the method according to the invention proposes two alternatives for the further treatment of the third polymer solution PL3.
  • the third polymer solution PL3 is returned to the first method step V1) for the production of the first polymer solution PL1.
  • the third polymer solution PL3 can be mixed, for example, with the finished first polymer solution PL1 produced in the first method step V1). Or the third polymer solution PL3 is fed back into the process for producing the first polymer solution PL1, so that the mixing takes place before the first polymer solution PL1 has been produced.
  • the first polymer solution PL1 is then separated into pure LDPE(R) and a fourth organic solvent L4 in a separation step comprising a first evaporation process E1.
  • the evaporation process E1 works in relation to the yield of purified LDPE much more energy-efficiently and cost-effectively than an evaporation process for the "thin" second polymer solution PL2 would work.
  • the third polymer solution PL3 is separated into pure LDPE(R) and a fifth organic solvent L5 in a separation step comprising a second evaporation method E2, and the first polymer solution (PL1) in one a separation step comprising a first evaporation process (E1) into pure LDPE(R) and a fourth organic solvent (L4).
  • an additional evaporation method is therefore provided in the second alternative.
  • there are no contaminations caused by precipitating agents or other auxiliaries as is the case with the processes known from the prior art. Therefore, no additional separation steps are required to remove such auxiliaries.
  • the process is therefore simple and inexpensive. It can be used for the recovery of pure LDPE on a large technical or industrial scale.
  • the first evaporation method E1 in method step V4) and the second evaporation method E2 in method step V5) are each two-stage methods in which in a first stage so much solvent is evaporated that a still flowable mixture of Solvent and LDPE are formed, and in which, in a second stage, this mixture is introduced into a heatable extruder, in which the remaining solvent is evaporated under vacuum and from which the pure LDPE(R) is drawn off. In this way, the efficiency of the process is increased.
  • a large part of the solvent can be evaporated in the first stage of the two-stage evaporation process, and in the second stage only a small part of the solvent has to be evaporated under vacuum, at the same time the pure LDPE(R) is compressed in the extruder and used as further Mass can be extruded.
  • an organic solvent L6 is fed to the retentate of the ultrafiltration or nanofiltration method, the quantity of solvent L6 fed in being such that no deposits of undissolved LDPE are deposited on the surface of the ultrafiltration membrane on the retentate side MU or nanofiltration membrane MN occurs.
  • the concentration of the dissolved LDPE in the third polymer solution PL3 is adjusted by the supplied solvent L6 in such a way that undissolved LDPE is not deposited on the membrane and thus the porosity of the membrane is not blocked or clogged.
  • the LDPE concentration at which undissolved LDPE is deposited on the membrane depends on the type of organic solvent on the one hand and on the operating temperature and the operating pressure at which process step V3) is carried out on the other. It therefore makes sense to determine these values in experiments as part of the concrete design of the method according to the invention.
  • the second polymer solution PL2 is forced through the ultrafiltration membrane MU or nanofiltration membrane MN at pressures of 8 bar to 40 bar. This is a reasonable pressure range for the operation of commercially available membranes.
  • the first polymer solution PL1 is subjected to an ultrafiltration step or nanofiltration step to increase the LDPE concentration in the solution before it is fed to the first evaporation method E1. As a result, the first polymer solution PL1 is concentrated and less solvent has to be evaporated in the evaporation process E1 in order to recover the pure LDPE.
  • the ultrafiltration step or nanofiltration step can be carried out in a separate device.
  • the membrane used in method step V3) is a nanofiltration membrane (M) which allows molecules with a molecular weight of up to 1000 g/mol to pass as permeate and molecules with a molecular weight of more than 1000 g/mol retains as retentate.
  • M nanofiltration membrane
  • the person skilled in the art also says that it has a value for the molecular weight cutoff of 1000 g/mol. With such a membrane, the larger LDPE molecules can be retained well on the retentate side of the membrane, so that the second polymer solution PL2 is concentrated.
  • the device according to the invention for recycling low density polyethylene (LDPE) by obtaining pure LDPE(R) from impure LDPE(U) comprises a first device for dissolving impure LDPE(U) in an organic solvent L1 to produce a first polymer solution PL1 , wherein the first device has a device for discharging impure LDPE(U) which has not dissolved in the solvent L1 in the first device, a second device which the discharged from the first device LDPE(U) and a second organic Solvent L2 can be supplied in order to dissolve the LDPE(U) in the second organic solvent L2 to produce a second polymer solution PL2, a first thermal separation device E1 with an evaporation device for separating the first polymer solution PL1 into pure LDPE(R) and a fourth organic Solvent L4, an ultrafiltration system U with an ultrafiltration membrane MU or a nanofiltration system N m with a nanofiltration membrane MN to separate the second Polymer solution PL2 in a third solvent L
  • Concentrating the second polymer solution PL2 in the ultrafiltration system U or nanofiltration system N enables the polymer solution with an increased LDPE concentration to be returned to the first device for producing the first polymer solution PL1, as provided for in the first alternative of the independent device claim, without dilution occurring the first polymer solution PL1 and thus to an increased energy requirement for the evaporation of the solvent in the first thermal separation device E1.
  • the recycling process can, for example, be carried out in such a way that the concentrated polymer solution which leaves the ultrafiltration system U or the nanofiltration system N has the same or almost the same LDPE concentration as the polymer solution PL1 which leaves the first device.
  • the two polymer solutions PL1 and PL2 can be mixed with one another in the first device or downstream of the first device.
  • the polymer solution produced by this mixing is then fed to the first thermal separator E1 to evaporate the solvent and recover the pure LDPE. Due to the increased LDPE concentration, a comparatively small amount of energy is required in the first thermal separating device E1 in order to evaporate the solvent.
  • the device can therefore work in an energy-efficient and economical manner.
  • a second thermal separating device E2 instead of returning the polymer solution concentrated in the ultrafiltration system U or nanofiltration system N to the first device, a second thermal separating device E2 is provided.
  • the concentrated polymer solution is fed to this second thermal separation device E2 in order to evaporate the solvent from the concentrated polymer solution and to recover the pure LDPE.
  • recycling and mixing of the concentrated polymer solution with the first polymer solution is saved, but a second thermal separating device E2 is required.
  • the first thermal separating device E1 and the second thermal separating device E2 are constructed in two stages, with a first stage of the separating device (E1 or E2) comprising an evaporation device with which so much solvent can be evaporated that a still flowable mixture of solvent and LDPE is formed, and a second stage of the separation device (E1 or E2) comprises a heatable extruder into which this mixture can be introduced and in which the remaining solvent can be evaporated under vacuum and from which the pure LDPE (R) is subtracted.
  • the efficiency of the recycling process is increased by the two-stage structure of the first and (if present) the second thermal separation device.
  • a large part of the solvent can be evaporated in the first stage of each thermal separator E1 or E2, and in the second stage of each thermal separator E1 or E2 only a small part of the solvent has to be evaporated under vacuum, with the pure LDPE(R) can be compacted in the extruder and extruded as a further usable mass.
  • the ultrafiltration membrane MU divides the ultrafiltration system U or the nanofiltration membrane MN divides the nanofiltration system N into a retentate side R and a permeate side P, with a sixth organic solvent L6 being able to be fed to the retentate side R, and with a control device being provided is, with which the quantity of the supplied sixth organic solvent L6 depending on the concentration of the LDPE in the polymer solution on the retentate side R can be regulated.
  • the ultrafiltration system U or nanofiltration system N has a pressure control device with which a higher operating pressure can be set on the retentate side R than on the permeate side P. This pressure difference forces the polymer solution PL2 to be concentrated through the membrane.
  • a pressure difference between the retentate side (R) and the permeate side (P) can be set in the range from 8 bar to 40 bar via the pressure control device.
  • the filtration system works efficiently in this pressure range.
  • a nanofiltration system N is provided for separating the second polymer solution PL2, which has a nanofiltration membrane MN which has a so-called molecular weight cutoff value of approximately 1000 g/mol. This achieves good separation of the dissolved LDPE molecules from the second polymer solution PL2.
  • the nanofiltration system can be operated stably and efficiently with a nanofiltration system that has a molecular weight cutoff value of around 1000 g/mol.
  • an ultrafiltration system U or a nanofiltration system N is provided, with which the first polymer solution PL1 is subjected to an ultrafiltration step or nanofiltration step to increase the LDPE concentration in the solution before it is fed to the first thermal separation device E1.
  • the result of this is that less solvent has to be evaporated in the first thermal separation device E1 in order to recover the pure LDPE from the solution. The amount of energy required in the first thermal separator is reduced accordingly.
  • FIG. 1 schematically shows a process flow diagram of the process according to the invention.
  • the process flow diagram according to FIG. 1 shows two process lines I and II, which are optically separated from one another in FIG. 1 by the dashed dividing line T.
  • Process line I comprises a first device 1 for producing a first polymer solution PL1 and a first thermal separating device E1.
  • the first method step V1) takes place in the first device 1 .
  • the organic solvent is evaporated from the supplied polymer solution in order to recover pure LDPE(R) from the polymer solution.
  • the evaporated solvent is withdrawn from the first thermal separation device E1 as solvent L4.
  • the pure LDPE(R) recovered by evaporating the solvent is drawn off from the first thermal separating device E1.
  • Process line II comprises a second device 2, in which contaminated LDPE(U), which has not gone into solution in the first device 1, is brought into contact with a second organic solvent L2 (process step V2)).
  • the contaminated LDPE(U) goes into solution and the second polymer solution PL2 is formed.
  • the second polymer solution PL2 is then a filtration step in an ultrafiltration system U with fed to an ultrafiltration membrane MU or in a nanofiltration system N with a nanofiltration membrane MN.
  • the second polymer solution PL2 is separated into a concentrated third polymer solution PL3 and the third solvent L3.
  • the method according to the invention provides two alternatives for the further use of the third polymer solution PL3.
  • the third polymer solution PL3 is returned to the first method step V1) or to the first device 1.
  • the third polymer solution PL3 is mixed with the polymer solution that is produced in method step V1) by dissolving the contaminated LDPE(U) in the first organic solvent L1. In this way, the first polymer solution PL1 is formed. This is then fed to the first thermal separator E1.
  • process step V5 the concentrated third polymer solution PL3 produced in process step V3) is fed to a second thermal separating device E2.
  • the organic solvent is evaporated in this second thermal separating device E2, so that pure LDPE(R) is recovered and the fifth solvent L5 is obtained.
  • a first device 1 is supplied with a contaminated polyolefin mixture, which comprises contaminated LDPE(U), HDPE and PP, and a first organic solvent L1.
  • the polyolefin mixture is brought into contact with the first organic solvent L1 at a temperature at which the LDPE dissolves but the HDPE and the PP do not yet dissolve.
  • the contaminated LDPE(U) goes into solution (“selective dissolving of the LDPE”).
  • the first polymer solution PL1 is formed.
  • step V2 the undissolved LDPE(U) withdrawn from the first device 1 is brought into contact with the second organic solvent L2. In doing so, A relatively large amount of second solvent L2 is added in relation to the amount of impure LDPE(U), resulting in a relatively highly diluted second polymer solution PL2 with a low LDPE concentration.
  • This second polymer solution PL2 is now concentrated in process step V3) by a filtration step.
  • the filtration step is designed either as an ultrafiltration step U (using an ultrafiltration membrane MU) or as a nanofiltration step N (using a nanofiltration membrane MN).
  • the membrane divides the filtration system into a retentate side R and a permeate side P. With regard to its pore size, the membrane is selected so that it has a molecular weight cutoff value of approx. 1000 g/mol.
  • the relatively large LDPE molecules are retained well on the retentate side R, while the solvent and any other smaller polymer molecules still contained in the second polymer solution PL2 (such as HDPE or PP ) pass through the membrane and reach the permeate side P.
  • the LDPE concentration on the retentate side R increases, i.e. the polymer solution 2 is concentrated in terms of the LDPE concentration.
  • the driving force for the filtration is achieved by a pressure difference between the retentate side R and the permeate side P, i.e. the pressure on the retentate side R is set significantly higher than on the permeate side P.
  • a pressure difference in the range of 7 to 40 bar has proven to be favorable .
  • the pressure on the permeate side P can be the ambient pressure of about 1 bar, and on the retentate side R an overpressure in the range from 8 bar to 40 bar is set. At these operating pressures, the ultra- or nanofiltration process works stably and efficiently.
  • the invention provides that the filtration system on the retentate side R has a sixth organic Solvent L6 is supplied, the supplied amount of solvent L6 being such that there are no deposits of undissolved LDPE on the retentate-side surface of the ultrafiltration membrane MU or the nanofiltration membrane MN.
  • a control device is provided according to the invention, with which the quantity of the supplied sixth organic solvent L6 can be controlled depending on the instantaneous concentration of the LDPE in the polymer solution on the retentate side R. In this way it can be safely avoided that the critical LDPE concentration on the retentate side R is exceeded. The formation of undesired, undissolved LDPE deposits on the membrane surface on the rented material side R can thus be reliably prevented.
  • process step V3) the third solvent L3 is drawn off on the permeate side P.
  • the concentrated third polymer solution PL3 is drawn off and used further within the scope of the recycling process according to the invention.
  • the third polymer solution PL3 is returned to method step V1) (method step V4)).
  • the third polymer solution PL3 can be added to the polymer solution produced in the first device 1 in the area of the outlet of the first device 1 .
  • the first polymer solution PL1 is then produced, which is then fed to the first thermal separating device E1 (method steps V4) and V5)).
  • the organic solvent is evaporated in the first thermal separating device E1 and drawn off as the fourth solvent L4.
  • the pure LDPE remaining after evaporation of the solvent is also drawn off and can be put to further use.
  • This first method alternative with method step V4) is shown in FIG. 1 by the dashed arrow.
  • the concentrated third polymer solution PL3 is not recirculated but fed to a second thermal separating device E2 (method step V5)).
  • this second thermal separating device E2 the organic solvent is evaporated from the third polymer solution and drawn off as the fifth solvent L5.
  • the pure LDPE that remains after the solvent has evaporated is also drawn off and can be put to further use.
  • This second method alternative with method step V5) is shown in FIG. 1 by the dot-dash arrow.
  • the organic solvents L1, L2, L3, L4, L5 and L6 are preferably formed by a single organic solvent, ie they are preferably not different organic solvents.
  • the method according to the invention can be carried out either as a continuous process or as a batch process. If it is designed as a continuous process, the polymer solutions PL1, PL2 and PL3 and the solvents L1, L2, L3, L4, L5 and L6 are continuous mass flows.
  • the first device 1 can be designed as a stirred tank.
  • the second device 2 can be designed as a stirred tank.
  • the first thermal separating device E1 can include a heatable stirred tank or a forced circulation evaporator and also have an extruder. In the heated stirred tank or the forced circulation evaporator, so much solvent is evaporated that a mixture of solvent and LDPE that is still flowable is produced. This mixture is fed into a heatable extruder, in which the remaining solvent is evaporated under vacuum. The pure LDPE(R) is withdrawn from the extruder.
  • the second thermal separating device E2 can include a heatable stirred tank or a forced circulation evaporator and also have an extruder. In the heated stirred tank or the forced circulation evaporator, so much solvent is evaporated that a mixture of solvent and LDPE that is still flowable is produced. This mixture is fed into a heatable extruder, in which the remaining solvent is evaporated under vacuum. The pure LDPE(R) is extruded from the extruder.

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  • Life Sciences & Earth Sciences (AREA)
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  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

La présente invention concerne un procédé de recyclage de polyéthylène basse densité (PEBD) par récupération de PEBD(R) pur à partir de PEBD(U) impur, comprenant les étapes de procédé suivantes : V1) la production d'une première solution de polymère (PL1) par dissolution de PEBD(U) impur dans un solvant organique (L1) ,dans une première ligne de procédé (I) ; V2) la production d'une deuxième solution de polymère (PL2) par dissolution de PEBD(U) impur, qui n'a pas été dissous dans le solvant organique (L1) à l'étape V1), dans un solvant organique (L2), dans une seconde ligne de procédé (II) ; V3) la séparation de la deuxième solution de polymère (PL2) au sein de la seconde ligne de procédé (II) dans une étape de séparation comprenant un procédé d'ultrafiltration (U) avec une membrane d'ultrafiltration (MU) ou un procédé de nanofiltration (N) avec une membrane de nanofiltration (MN) dans un troisième solvant organique (L3) en tant que perméat et une troisième solution de polymère (PL3) en tant que rétentat provenant de l'ultrafiltration (U) ou de la nanofiltration (N), la troisième solution de polymère (PL3) ayant une concentration en PEBD dissous plus élevée que la deuxième solution de polymère (PL2), soit V4) la troisième solution de polymère (PL3) étant recyclée dans la première étape de procédé (V1) pour la production de la première solution de polymère (PL1) et la première solution de polymère (PL1) étant séparée dans une étape de séparation comprenant un premier procédé d'évaporation (E1) en PEBD(R) pur et un quatrième solvant organique (L4) ; soit V5) la troisième solution de polymère (PL3) étant séparée dans une étape de séparation comprenant un second procédé d'évaporation (E2) en PEBD(R) pur et un cinquième solvant organique (L5) et la première solution de polymère (PL1) étant séparée dans une étape de séparation comprenant un premier procédé d'évaporation (E1) en PEBD(R) pur et un quatrième solvant organique (L4).
PCT/EP2022/059038 2021-04-14 2022-04-05 Procédé et appareil pour le recyclage de polyéthylène basse densité (pebd) WO2022218765A1 (fr)

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DE102021203708.9A DE102021203708B3 (de) 2021-04-14 2021-04-14 Verfahren und Vorrichtung für das Recycling von Low Density Polyethylene (LDPE)
DE102021203708.9 2021-04-14

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WO2022218765A1 true WO2022218765A1 (fr) 2022-10-20

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19905029A1 (de) 1999-01-29 2000-11-16 Bgb Ges Tu Berlin Verfahren zur Trennung vermischter Polyolefine
CA2376488A1 (fr) * 1999-06-16 2000-12-21 Wolfgang Lindner Procede de separation de matieres plastiques polyolefiniques melangees
DE10127875A1 (de) 2001-06-08 2003-01-30 Der Gruene Punkt Duales Syst Verfahren zur Gewinnung von LDPE aus gebrauchten Kunststofffolien
WO2022029318A1 (fr) * 2020-08-07 2022-02-10 Apk Ag Procédé de prétraitement de matière plastique et de recyclage à base de solvant de matière plastique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19905029A1 (de) 1999-01-29 2000-11-16 Bgb Ges Tu Berlin Verfahren zur Trennung vermischter Polyolefine
CA2376488A1 (fr) * 1999-06-16 2000-12-21 Wolfgang Lindner Procede de separation de matieres plastiques polyolefiniques melangees
DE10127875A1 (de) 2001-06-08 2003-01-30 Der Gruene Punkt Duales Syst Verfahren zur Gewinnung von LDPE aus gebrauchten Kunststofffolien
WO2022029318A1 (fr) * 2020-08-07 2022-02-10 Apk Ag Procédé de prétraitement de matière plastique et de recyclage à base de solvant de matière plastique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PENSIRI NAVIROJJAMES TREACYCONRAD URFFER: "Chemical Recycling of Plastics by Dissolution", 20 May 2019, UNIVERSITY OF PENNSYLVANIA

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