METHOD FOR PLASTIC PRE-TREATMENT AND SOLVENT-BASED PLASTIC RECYCLING

Abstract

The present invention relates to a method for downsizing, in particular shredding, of plastic material and removing dust from said downsized plastic material. The invention also relates to a method for solvent-based recycling a plastic material with an integrated step of addition of functional solid auxiliaries to the solution comprising the thermoplastic target polymer. The invention also relates to a method for plastic recycling with an integrated extraction step. The invention also relates to a method for removing solvents from suspensions or solutions comprising a dissolved thermoplastic target polymer. The invention also relates to a method for removing additives and/or impurities from a fluidized form comprising a thermoplastic target polymer while being processed in an extruder, wherein the fluidized form comprising a thermoplastic target polymer is subjected to a counter-stream of at least one extractant. It also relates to a plastic waste recycling system for recycling a target polymer.

Claims

1. Method for recycling plastic material comprising at least one target polymer, wherein the method comprises the following dedusting steps: i-1) providing said plastic material, in particular plastic waste; ii-1) downsizing said plastic material; iii-1) classification of the downsized material obtained after step ii-1) by particle size and/or particle weight, in particular by sieving, or contacting of said downsized plastic material with airstream, preferably by means of passing said downsized plastic material through air counter-flow, or a combination thereof; wherein the downsized plastic material obtained after step iii-1) is essentially free of particulate matter, and wherein essentially free of particulate matter means that at least 99 weight% of particles < 300 .Math.m, in particular < 100 .Math.m have been removed from the downsized plastic material.

2. Method according to claim 1 further comprising the following additional steps: iv-1) adding a solvent or a mixture of solvents to the material obtained after step iii-1) to obtain a solution or suspension comprising said target polymer, preferably using a heating system, wherein said target polymer is essentially soluble in said solvent or mixture of solvents.

3. Method according to claim 2 further comprising the following additional steps: v-1) preferably purifying said solution or suspension obtained after step iv-1), in particular by means of mechanical solid-liquid separation; vi-1) optionally, if the solution comprises at least one polymer originating from post-consumer plastic waste, adding a solution cleaning step for decolorization and an additional odor treatment step; vii-1) separating of said target polymer from said solution or suspension; viii-1) preferably degassing and/or extrusion of said target polymer.

4. Method for recycling plastic material comprising at least one thermoplastic target polymer, wherein the method comprises the following steps: i-2) providing a suspension or a solution comprising said thermoplastic target polymer, in particular by adding a solvent or a mixture of solvents to said plastic material, in particular plastic waste or pre-treated plastic waste, preferably using a heating system, wherein said thermoplastic target polymer is essentially soluble in said solvent or said mixture of solvents; ii-2) preferably purifying said solution or suspension, preferably by means of mechanical solid-liquid separation; iii-2) mixing a liquid extractant with said solution or suspension, preferably using a heating system, to produce a multiphasic system, preferably biphasic system, wherein said extractant is a non-solvent for the target polymer, wherein said solvent or said mixture of solvents is essentially immiscible with said extractant, and wherein said extractant and said solvent or said mixture of solvents have essentially different densities; iv-2) separating the fraction comprising the thermoplastic target polymer from the fraction comprising the extractant.

5. Method according to claim 4, wherein the suspension or solution in step i-2) is the suspension or solution obtained by a method comprising: a) providing said plastic material, in particular plastic waste; b) downsizing said plastic material; c) classification of the downsized material obtained after step ii-1) by particle size and/or particle weight, in particular by sieving, or contacting of said downsized plastic material with airstream, preferably by means of passing said downsized plastic material through air counter-flow, or a combination thereof; wherein the downsized plastic material obtained after step iii-1) is essentially free of particulate matter, and wherein essentially free of particulate matter means that at least 99 weight% of particles < 300 .Math.m, in particular < 100 .Math.m have been removed from the downsized plastic material; and d) adding a solvent or a mixture of solvents to the material obtained after step iii-1) to obtain a solution or suspension comprising said target polymer, preferably using a heating system, wherein said target polymer is essentially soluble in said solvent or mixture of solvents.

6. Method according to claim 4 further comprising the following steps: v-2) separating said thermoplastic target polymer from the solution obtained after step iv-2); vi-2) preferably degassing and/or extrusion of said thermoplastic target polymer.

7. Method for recycling plastic material comprising at least one thermoplastic target polymer, wherein the method comprises the following steps: i-3) providing a suspension or a solution comprising said thermoplastic target polymer, in particular by adding a solvent or a mixture of solvents to said plastic material, in particular plastic waste or pre-treated plastic waste, preferably using a heating system, wherein said thermoplastic target polymer is essentially soluble in said solvent or said mixture of solvents; ii-3) preferably purifying said solution or suspension, preferably by means of mechanical solid-liquid separation; iii-3) adding a solid additive to said solution or suspension under stirring, in particular using an agitator, preferably using a heating system, wherein said solid additive is essentially insoluble in said solvent or said mixture of solvents.

8. Method according to claim 7, wherein the suspension or solution in step i-3) is the suspension or solution obtained by a method comprising: a) providing said plastic material, in particular plastic waste; b) downsizing said plastic material; c) classification of the downsized material obtained after step ii-1) by particle size and/or particle weight, in particular by sieving, or contacting of said downsized plastic material with airstream, preferably by means of passing said downsized plastic material through air counter-flow, or a combination thereof; wherein the downsized plastic material obtained after step iii-1) is essentially free of particulate matter, and wherein essentially free of particulate matter means that at least 99 weight% of particles < 300 .Math.m, in particular < 100 .Math.m have been removed from the downsized plastic material; and d) adding a solvent or a mixture of solvents to the material obtained after step iii-1) to obtain a solution or suspension comprising said target polymer, preferably using a heating system, wherein said target polymer is essentially soluble in said solvent or mixture of solvents.

9. Method according to claim 7, wherein the suspension or solution in step i-3) is the suspension or solution obtained by a method comprising: a) providing a suspension or a solution comprising said thermoplastic target polymer, in particular by adding a solvent or a mixture of solvents to said plastic material, in particular plastic waste or pre-treated plastic waste, preferably using a heating system, wherein said thermoplastic target polymer is essentially soluble in said solvent or said mixture of solvents; b) preferably purifying said solution or suspension, preferably by means of mechanical solid-liquid separation; c) mixing a liquid extractant with said solution or suspension, preferably using a heating system, to produce a multiphasic system, preferably biphasic system, wherein said extractant is a non-solvent for the target polymer, wherein said solvent or said mixture of solvents is essentially immiscible with said extractant, and wherein said extractant and said solvent or said mixture of solvents have essentially different densities; and d) separating the fraction comprising the thermoplastic target polymer from the fraction comprising the extractant.

10. Method according to claim 7 further comprising the following steps: iv-3) separating said thermoplastic target polymer comprising said additive by flash-evaporation of the mixture obtained in step iii-3); v-3) preferably degassing and/or extrusion of said target polymer.

11. Method for removing a solvent from a fluidized form comprising a thermoplastic target polymer, wherein the method comprises the following steps: i-4) providing said fluidized form; ii-4) preferably purifying said fluidized form, in particular by means of mechanical solid-liquid separation; iii-4) concentrating said fluidized form using a cross-flow filtration unit having a membrane, permeable for the solvent and impermeable for the thermoplastic target polymer.

12. Method according to claim 11, wherein said fluidized form in step i-4) is selected from the group comprising a solution, a suspension, a polymer gel, and polymer melt.

13. Method according to claim 11, wherein said fluidized form in step i-4) is a suspension or solution comprising said target polymer.

14. Method according to claim 13, wherein said suspension or solution is the suspension or solution obtained by a method comprising: a) providing said plastic material, in particular plastic waste; b) downsizing said plastic material; c) classification of the downsized material obtained after step ii-1) by particle size and/or particle weight, in particular by sieving, or contacting of said downsized plastic material with airstream, preferably by means of passing said downsized plastic material through air counter-flow, or a combination thereof; wherein the downsized plastic material obtained after step iii-1) is essentially free of particulate matter, and wherein essentially free of particulate matter means that at least 99 weight% of particles < 300 .Math.m, in particular < 100 .Math.m have been removed from the downsized plastic material; and d) adding a solvent or a mixture of solvents to the material obtained after step iii-1) to obtain a solution or suspension comprising said target polymer, preferably using a heating system, wherein said target polymer is essentially soluble in said solvent or mixture of solvents.

15. Method according to claim 13, wherein said suspension or solution is the suspension or solution obtained by a method comprising: a) providing a suspension or a solution comprising said thermoplastic target polymer, in particular by adding a solvent or a mixture of solvents to said plastic material, in particular plastic waste or pre-treated plastic waste, preferably using a heating system, wherein said thermoplastic target polymer is essentially soluble in said solvent or said mixture of solvents; b) preferably purifying said solution or suspension, preferably by means of mechanical solid-liquid separation; c) mixing a liquid extractant with said solution or suspension, preferably using a heating system, to produce a multiphasic system, preferably biphasic system, wherein said extractant is a non-solvent for the target polymer, wherein said solvent or said mixture of solvents is essentially immiscible with said extractant, and wherein said extractant and said solvent or said mixture of solvents have essentially different densities; and d) separating the fraction comprising the thermoplastic target polymer from the fraction comprising the extractant.

16. Method according to claim 11, further comprising the following steps: iv-4) degassing and/or extrusion of said thermoplastic target polymer.

17. Method for removing additives and/or impurities from a fluidized form comprising a thermoplastic target polymer while being processed in an extruder, wherein the fluidized form comprising a thermoplastic target polymer is subjected to a counter-stream of at least one extractant, wherein the method comprises the following steps: i-5) providing said fluidized form; ii-5) delivering said fluidized form to an extruder; wherein said extruder comprises a membrane or sieve, wherein the membrane or sieve is permeable for the extractant, solvent and/or lubricant and impermeable for the thermoplastic target polymer; iii-5) purifying said fluidized form by means of extraction using a counter-stream of at least one extractant and/or a process aid in said extruder, iv-5) degassing and/or extrusion of said thermoplastic target polymer.

18. Method according to claim 17, wherein said fluidized form in step i-5) is selected from the group comprising a solution, a suspension, a polymer gel, and polymer melt.

19. Method according to claim 17, wherein said fluidized form in step i-5) is a suspension or solution comprising said target polymer.

20. Method according to claim 19, wherein said suspension or solution is the suspension or solution obtained by a method comprising: a) providing said plastic material, in particular plastic waste; b) downsizing said plastic material; c) classification of the downsized material obtained after step ii-1) by particle size and/or particle weight, in particular by sieving, or contacting of said downsized plastic material with airstream, preferably by means of passing said downsized plastic material through air counter-flow, or a combination thereof; wherein the downsized plastic material obtained after step iii-1) is essentially free of particulate matter, and wherein essentially free of particulate matter means that at least 99 weight% of particles < 300 .Math.m, in particular < 100 .Math.m have been removed from the downsized plastic material; and d) adding a solvent or a mixture of solvents to the material obtained after step iii-1) to obtain a solution or suspension comprising said target polymer, preferably using a heating system, wherein said target polymer is essentially soluble in said solvent or mixture of solvents.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0832] FIG. 1 schematically shows the stages of the method of pre-treatment and solvent-based recycling of plastic material according to the invention.

[0833] FIG. 2 shows separation of the fraction comprising the target polymer from the fraction comprising the extractant in a settler 203. The mixture is transferred from a mixer 201 to a settler 203 in the form of emulsion 202. The heavy phase comprising the target polymer 205 and light phase liquids 204 are separated by gravity. At the end of the settler two individual weirs are located to separately collect the fraction comprising the target polymer and the fraction comprising the extractant.

[0834] FIG. 3 shows separation of the fraction comprising the target polymer from the fraction comprising the extractant in a mixer-settler 301. The heavy phase comprising the target polymer 303 and light phase liquids 302 are separated by gravity. At the end of the settler two individual weirs are located to separately collect the fraction comprising the target polymer and the fraction comprising the extractant.

[0835] FIG. 4 shows separation of the fraction comprising the target polymer from the fraction comprising the extractant in a carrousel extractor. The carousel extractor consists of a rotating sectioned cylinder 401 and rotary feeder 407. The solution comprising target polymer 402 is admitted through an inlet 403 into a chamber 410 and an extractant 404 is admitted into a chamber at one or several locations. The material is transported continuously and the extractant flows through the chambers. The extractant passes through the material in the chamber removing impurities from the material and then runs off through the bottom wall 405 underneath the rotor into a collecting chamber from where it is removed. The fraction comprising the target polymer 408 runs off through the outlet 406 into a collecting chamber 409.

[0836] FIG. 5 shows an air classifier in detail.

[0837] FIG. 6 shows an extruder with an integrated membrane, which can be used for removing additives and/or impurities from a fluidized form comprising a thermoplastic target polymer. The vacuum pump is used to establish a reduced pressure in Segment 4. Granulates comprising the thermoplastic target polymer or a solution or a suspension comprising the thermoplastic target polymer is transferred to the extruder via the dosing funnel. Extrusion is started and the thermoplastic target polymer is melted within Segment 1. When the melt reaches Segment 2, solvent pump 2 is switched on to transfer an extractant or a mixture of an extractant and a solvent to the extruder. The melt and the extractant are mixed in Segment 3. The 3-way melt valve is opened to the position which enables transporting the mixture to melt pump 1. Melt pump 1 is switched on to transfer the mixture into Segment 2. Solvent pump 1 is switched on to transport the extract via the membrane out of the extruder. The valve of the vacuum system is opened to enable degassing the melt in Segment 4. The 3-way-melt valve is switched to the position which enables transporting the melt to melt pump 2. Melt pump 2 is switched on to transport the melt to the pelletizing unit.

[0838] FIG. 7 shows a plastic waste recycling plant 500 comprising several stations. The plastic waste recycling plant is only a possible implementation for the method. Also plastic production plants for producing polymers by polymerization may use the described method for solvent-based recycling a plastic material comprising at least one target polymer with an integrated extraction step. A shredding device 508 for plastic waste 509 is comprised in a first station 501. Said plastic waste may be transported by a first conveyor belt 510 into the shredding device 508 and by a second conveyor belt 512 shredded plastic wastes 511 may be transported out of the shredding device 508. An air classifier 513 is comprised in a second station 502. The shredded plastic waste 511 is transported into the air classifier 513. Preferably in some embodiments the plastic waste recycling plant 500 comprises a third station 503 for washing the air-classified plastic waste 514. Said third station 503 may comprise a container 515 with a washing liquid 516 such as water, wherein air-classified plastic waste 514 is purified. The purified shredded plastic waste 517 may be transported, e.g. by another conveyor belt 518, to a forth station 504 comprising a vessel 519, wherein the vessel 519 comprises an agitator 520 and/or a heating system 521, e.g. as part of the vessel 519. In some embodiments the air-classified plastic waste 514 is directly transported from the second station 502 to the forth station 504. The forth station preferably contains a solvent 522, wherein the target polymer is dissolved in said solvent thus forming a solution or a suspension 523. A fifth station 505 may comprise a centrifuge 524 for solid-liquid separation. A sixth station 506 comprises a filtration or evaporation unit 525. In some embodiments a seventh station 507 that comprises a plastic extruder 526 for the production of polymer pellets 527. As discussed above the plastic waste recycling plant has a transfer system that transfers materials from each station to the next in the above listed order. Often said transfer system is a combination of conveyor belts and fluid pipes depending on the consistency of the transported material. In some embodiments the solvent from the sixth station 506 is recycled for providing a suspension for reuse using a recycling system 528.

[0839] FIG. 8 shows a plastic waste recycling plant 600 comprising several stations. The plastic waste recycling plant is only a possible implementation for the method. Also plastic production plants for producing polymers by polymerization may use the described method for solvent-based recycling a plastic material comprising at least one target polymer with an integrated extraction step. Preferably a shredding device 608 for plastic waste 609 is comprised in a first station 601. Said plastic waste may be transported by a first conveyor belt 610 into the shredding device 608 and by a second conveyor belt 612 shredded plastic wastes 611 may be transported out of the shredding device 608. Preferably in some embodiments the plastic waste recycling plant 600 comprises a second station 602 for washing the shredded plastic waste 611. Said second station 602 may comprise a container 613 with a washing liquid 614 such as water, wherein shredded plastic waste 611 is purified. The purified shredded plastic waste 611 may be transported, e.g. by another conveyor belt 624, to a third station 603 comprising a vessel 618, wherein the vessel 618 comprises an agitator 617 and/or a heating system 615, e.g. as part of the vessel 618. In some embodiments the shredded plastic waste 611 is directly transported from the first station 601 to the third station 603. The third station preferably contains a solvent 616, wherein the target polymer is dissolved in said solvent thus forming a solution or a suspension 619. A fourth station 604 may comprise a centrifuge 620 for solid-liquid separation. A fifth station 505 comprises a mixer-settler unit or a carousel extractor 621. A sixth station 606 comprises a filtration or evaporation unit 622. In some embodiments a seventh station 607 that comprises a plastic extruder 623 for the production of polymer pellets 625. As discussed above the plastic waste recycling plant has a transfer system that transfers materials from each station to the next in the above listed order. Often said transfer system is a combination of conveyor belts and fluid pipes depending on the consistency of the transported material. In some embodiments the solvent from the sixth station 606 is recycled for providing a suspension for reuse using a recycling system 626.

[0840] FIG. 9 shows a plastic waste recycling plant 700 comprising several stations. The plastic waste recycling plant is only a possible implementation for the method. Also plastic production plants for producing polymers by polymerization may use the described method for solvent-based recycling a plastic material comprising at least one target polymer with an integrated extraction step. Preferably a shredding device 708 for plastic waste 709 is comprised in a first station 701. Said plastic waste may be transported by a first conveyor belt 710 into the shredding device 708 and by a second conveyor belt 712 shredded plastic wastes 711 may be transported out of the shredding device 708. Preferably in some embodiments the plastic waste recycling plant 700 comprises a second station 702 for washing the shredded plastic waste 711. Said second station 702 may comprise a container 713 with a washing liquid 714 such as water, wherein shredded plastic waste 711 is purified. The purified shredded plastic waste 711 may be transported, e.g. by another conveyor belt 724, to a third station 703 comprising a vessel 718, wherein the vessel 718 comprises an agitator 717 and/or a heating system 715, e.g. as part of the vessel 718. In some embodiments the shredded plastic waste 711 is directly transported from the first station 701 to the third station 703. The third station preferably contains a solvent 716, wherein the target polymer is dissolved in said solvent thus forming a solution or a suspension 719. A fourth station 704 may comprise a centrifuge 720 for solid-liquid separation. A fifth station 705 comprises a flash evaporation unit 721. In some embodiments a sixth station 706 that comprises a plastic extruder 722 for the production of polymer pellets 723. As discussed above the plastic waste recycling plant has a transfer system that transfers materials from each station to the next in the above listed order. Often said transfer system is a combination of conveyor belts and fluid pipes depending on the consistency of the transported material.

[0841] FIG. 10 shows a plastic waste recycling plant 800 comprising several stations. The plastic waste recycling plant is only a possible implementation for the method. Also plastic production plants for producing polymers by polymerization may use the described method for solvent-based recycling a plastic material comprising at least one target polymer with an integrated extraction step. Preferably a shredding device 808 for plastic waste 809 is comprised in a first station 801. Said plastic waste may be transported by a first conveyor belt 810 into the shredding device 808 and by a second conveyor belt 812 shredded plastic wastes 811 may be transported out of the shredding device 808. Preferably in some embodiments the plastic waste recycling plant 800 comprises a second station 802 for washing the shredded plastic waste 811. Said second station 802 may comprise a container 813 with a washing liquid 814 such as water, wherein shredded plastic waste 811 is purified. The purified shredded plastic waste 811 may be transported, e.g. by another conveyor belt 824, to a third station 803 comprising a vessel 818, wherein the vessel 818 comprises an agitator 817 and/or a heating system 815, e.g. as part of the vessel 818. In some embodiments the shredded plastic waste 811 is directly transported from the first station 101 to the third station 803. The third station preferably contains a solvent 816, wherein the target polymer is dissolved in said solvent thus forming a solution or a suspension 819. A fourth station 804 may comprise a centrifuge 820 for solid-liquid separation. A fifth station 805 comprises a cross-flow filtration unit 822 having a membrane 823. There may also be a pre-treatment unit 821, which often also is a cross-flow filtration unit, however with a larger pore size. In some embodiments a sixth station 806 that comprises a plastic extruder 825 for the production of polymer pellets 826. As discussed above the plastic waste recycling plant has a transfer system that transfers materials from each station to the next in the above listed order. Often said transfer system is a combination of conveyor belts and fluid pipes depending on the consistency of the transported material. In some embodiments the solvent from the fifth station 805 is recycled for providing a suspension for reuse using a recycling system 827.

[0842] FIG. 11 shows a plastic waste recycling plant 900 comprising several stations. The plastic waste recycling plant is only a possible implementation for the method. Also plastic production plants for producing polymers by polymerization may use the described method for solvent-based recycling a plastic material comprising at least one target polymer with an integrated extraction step. Preferably a shredding device 908 for plastic waste 909 is comprised in a first station 901. Said plastic waste may be transported by a first conveyor belt 910 into the shredding device 908 and by a second conveyor belt 912 shredded plastic wastes 911 may be transported out of the shredding device 908. Preferably in some embodiments the plastic waste recycling plant 900 comprises a second station 902 for washing the shredded plastic waste 911. Said second station 902 may comprise a container 913 with a washing liquid 914 such as water, wherein shredded plastic waste 911 is purified. The purified shredded plastic waste 911 may be transported, e.g. by another conveyor belt 924, to a third station 903 comprising a vessel 918, wherein the vessel 918 comprises an agitator 917 and/or a heating system 915, e.g. as part of the vessel 918. In some embodiments the shredded plastic waste 911 is directly transported from the first station 901 to the third station 903. The third station preferably contains a solvent 916, wherein the target polymer is dissolved in said solvent thus forming a solution or a suspension 919. A fourth station 904 may comprise a centrifuge 920 for solid-liquid separation. A fifth station 905 comprises a filtration or evaporation unit 921. In some embodiments a sixth station 906 that comprises a plastic extruder with an integrated membrane 922 for the production of polymer pellets 923. As discussed above the plastic waste recycling plant has a transfer system that transfers materials from each station to the next in the above listed order. Often said transfer system is a combination of conveyor belts and fluid pipes depending on the consistency of the transported material. In some embodiments the solvent from the fifth station 905 is recycled for providing a suspension for reuse using a recycling system 925.

[0843] The features of the invention disclosed in the above description, the claims and the drawing can be essential, both individually and in any combination, to implement the invention in its various embodiments.