Processes and systems for the depolymerization of waste plastics

Abstract

To provide a process and system for depolymerizing waste plastics.SOLUTION: There is provided a continuous flow process and system for depolymerizing plastic. A heterogeneous mixture of plastic particles, a solvent, and a catalyst are pumped continuously through a heating zone at a flow rate just high enough to maintain a particle speed great enough to keep the plastic particles in suspension. The temperature of the heterogeneous mixture is raised in the heating zone and maintained in a hold zone to complete depolymerization of the mixture into a homogeneous solution containing a liquefied reaction product. The homogeneous solution is cooled to solidify and precipitate a solid reaction product. The solid reaction product is separated from the solvent to be recycled. The solvent is recirculated to be reused as a constituent of the heterogeneous mixture.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross - reference to related applications This application claims the priority of U.S. Provisional Application No. 62 / 964,948, filed on January 23, 2020, the content of which is incorporated herein by reference.

Background Art

[0002] Background The present invention generally relates to the depolymerization of resins, plastics, or polymers. More particularly, it relates to the depolymerization of waste plastics in a continuous process.

[0003] Conventionally, the depolymerization of plastics has been carried out in large reaction vessels usually equipped with a heating jacket and a stirrer. The depolymerization reaction is confined in the vessel until completion. After depolymerization, the vessel is emptied and refilled. Each batch is heated to promote depolymerization and then cooled to produce a viable feedstock of new polymer. Batch processing typically takes from 20 minutes to 800 minutes. Continuous operation is simulated by sequentially emptying and refilling a group of reaction vessels in a round - robin fashion. The continuous need to fill, heat, cool, empty, and repeat wastes energy and requires additional equipment to appear to flow continuously in a parallel - batch process.

Summary of the Invention

Means for Solving the Problems

[0004] Summary A process embodying the features of the present invention for depolymerizing plastics includes (a) continuously flowing a mixture containing solid plastic particles in a solvent through a line in a heating chamber at a sufficiently large particle velocity to maintain the plastic particles suspended in the solvent and to prevent the plastic particles from agglomerating and clogging the line; and (b) heating the mixture to a reaction temperature by transferring heat through the line in the heating chamber to initiate the depolymerization of the plastic particles in the solvent and to obtain a homogeneous solution containing a liquefied reaction product.

[0005] A system embodying the features of the present invention for the continuous depolymerization of plastics comprises a pump operating at a pump flow rate and a line through which the pump continuously supplies a heterogeneous mixture containing plastic particles in a solvent at particle velocity. A heating zone raises the temperature of the heterogeneous mixture flowing through the line to a reaction temperature of at least 150°C. The conversion of the heterogeneous mixture containing plastic particles into a homogeneous solution containing liquefied reaction products including monomers, dimers, oligomers, and / or reaction by-products is initiated in the heating zone. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a block diagram of a system embodying the features of the present invention for depolymerizing plastics.

[0007] [Figure 2] Figure 2 is a flowchart showing the progress of a certain volume of plastic undergoing the depolymerization process in the system shown in Figure 1. [Modes for carrying out the invention]

[0008] Detailed explanation The system and process for depolymerizing plastics are shown in Figures 1 and 2. This system and process can be used with, but is not limited to, a variety of plastics including PET, modified PET, PET blends, PEN, PBT, PET-G, PLA, PGA, PLGA, PEF, copolyester, polycarbonate, polyamide (nylon), polyurethane, and combinations and blends. Plastics are depolymerized into (but are not limited to) the following: bis(2-hydroxyethyl) terephthalate (BHET), dimethyl terephthalate (DMT), terephthalic acid (TA), bis(2-hydroxyethyl) naphthalate (BHEN), bis(2-hydroxyethyl) furanoate (BHEF), their respective oligomers, acids, half-esters, mixed esters, etc. Furthermore, chemically useful compounds such as dioctyl terephthalate (DOTP), diisobutyl terephthalate (DITP), dibutyl terephthalate (DBTP), bisphenol A (BPA), lactate, bis(2-hydroxyethyl) terephthalamide (BHETA), and other terephthalamides can be listed.

[0009] Solid plastic particles of waste polyester material in the form of flakes, fine powders, granules, fine particles, granola, lumps, chunks, and / or powder are mixed with a solvent and catalyst in a mixer 10 to produce a heterogeneous mixture 12. The mixer 10 can perform mixing using a stirrer such as a propeller 13, a stirrer, or other agitator, or by using a recirculated solvent. Alternatively, the mixture can be pre-mixed. Examples of solvents include, but are not limited to, ethylene glycol (EG), diethylene glycol (DEG), glycol ethers, methanol, ethanol, propanol, butanol, 2-ethylhexanol, tetramethylcyclobutanediol (CBDM), cyclohexanedimethanol (CHDM), alcohols, ethanolamine, ionic liquids, polar protic solvents, polar aprotic solvents, and water. Examples of suitable catalysts include, but are not limited to, zinc salts, zinc acetate; zinc chloride; titanium salts; manganese salts; magnesium salts; sodium hydroxide; potassium hydroxide; 1,5,7-triazabicyclo[4.4.0]deca-5-ene (TBD); 1,8-diazabicyclo[5.4.0]undeca-7-ene (DBU); magnesium acetate, 4-dimethylaminopyridine (DMAP); amines; trialkylamines; and combinations of these catalysts. The heterogeneous mixture 12 is transported by a pump 14 through a series of connected lines, such as tubes or pipes. No stirrers, augers, or extruders are required to advance the mixture through the system. The pump 14 operates at a flow rate large enough to move the mixture 12 through the system, at a particle velocity large enough to prevent the particles from agglomerating and clogging the lines, while keeping the particles suspended in the solvent. By operating continuously without stopping, the pump 14 allows the heterogeneous mixture to flow through the system at a stable rate, making the conversion of plastics into liquefied products a function of position within the system rather than a function of time, as in a batch system.

[0010] A preheating heat exchanger (preheater) 16, as needed, is used to preheat the heterogeneous mixture 12. The preheater 16 can heat the heterogeneous mixture 12 by a heat source such as a flame, steam, hot oil, or a circulating heat transfer fluid. Alternatively, a hot, homogeneous solution containing the liquefied product after the depolymerization reaction can be used in the preheater 16 to transfer heat to the heterogeneous mixture and cool itself in the process.

[0011] The preheated heterogeneous mixture 12' flows continuously into the downstream heating chamber 18, through which depolymerization begins. The heating chamber 18 can be realized as a reactor heat exchanger that raises the temperature of the heterogeneous mixture to a reaction temperature of at least 150°C. The heterogeneous mixture is heated in the reaction heat exchanger 18 by a heat source 20. The heat source 20 may directly heat the heterogeneous mixture with, for example, microwave radiation, direct flame, electric heating pipes, induction heating pipes, geothermal energy, Magnon drag thermoelectric, or Ohm. Alternatively, the heat source 20 may indirectly heat the heterogeneous mixture by directly heating a heat transfer fluid outside the heating chamber 18. Examples of suitable transfer fluids include hot oil, thermal fluid, molten salt, and steam. The heated heat transfer fluid is then pumped through a line containing the heterogeneous mixture in the heating chamber 18. Heat is transferred from the heat transfer fluid to the heterogeneous mixture, and depolymerization begins. The heterogeneous mixture flowing through the heating chamber 18 is not directly contacted by the heat transfer fluid.

[0012] The retaining tube 22 after the heating chamber 18 maintains the reaction temperature for at least one minute to complete the conversion of the heterogeneous mixture containing the plastic into a homogeneous solution 24 containing the liquefied product. The retaining tube 22 can be implemented by an insulated spool or coil of pipe or tube, or as a jacketed pipe or container. Alternatively, the retaining tube may be part of the heating chamber rather than a separate component. The reaction is completed within the retaining tube. The resulting homogeneous solution contains the solvent, the spent catalyst, and the depolymerized plastic in the form of the liquefied reaction product, typically including monomers, oligomers, and / or minor by-products from the reaction (e.g., half-esters, half-amides, mixed esters, mixed amides).

[0013] The homogeneous solution 24 is continuously pumped through a preheating heat exchanger 16 as needed to cool itself and preheat the incoming heterogeneous mixture 12. The back pressure regulator 26 maintains a system pressure above the vapor pressure of the solvent at the reaction temperature, for example, 100 psi to 400 psi.

[0014] After flowing through the back pressure regulator 26, the homogeneous solution 24 flows through a chilling heat exchanger (cooling device) 28 as needed, which uses cold water or other cooling heat transfer fluid from the cooled reservoir 30 to remove any excess heat that the preheater 16 did not regenerate. Remove.

[0015] After the solution has cooled, it is poured into a precipitation or crystallization tank and cooled until the liquefied product precipitates as a solid reaction product 34. The solvent is then decanted, filtered, centrifuged, or distilled to remove it from the solid reaction product. The solid reaction product may then be filter-pressed for further separation from the remaining solvent. Decantation, filtration, centrifugation, or distillation of the solvent, followed by pressing, to separate the solid reaction product 34 in solution 24 from the solvent 36 is represented in separator 32 in Figure 1.

[0016] The separated solvent 36 is recycled and returned to the mixer 10 for reuse. Solvent washing, purification, or regeneration steps may be required as needed to remove reaction contaminants from the solvent to be supplied to the subsequent heterogeneous mixture 12. Reaction contaminants may include particulate matter, ionic salts, anions, cations, spent catalysts, dyes, adhesives, components from blends, fillers, and / or decomposed solvents. Decontamination 42 may be achieved by passing the separated solvent 36 through a filter and / or over an adsorbent such as activated carbon, ion exchange resin, diatomaceous earth, sand, zeolite, clay, silica, alumina, oxides, sizing exclusion, and / or tangential flow filtration. Decontamination 42 of the solvent 36 may be an in-line or offline process. Decontamination 42 may occur in the separated solvent step 36 or in the homogeneous solution step 24.

[0017] Therefore, the system moves the heterogeneous mixture 12 through four zones: Z1 - the cold entry zone where the mixture is supplied to the system by the pump 14; Z2 - the preheating zone where the mixture is heated in the preheater 16; Z3 - the heating zone where the mixture is heated to its reaction temperature; and Z4 - the holding zone where the mixture is maintained at the reaction temperature to complete the conversion of the heterogeneous mixture into a homogeneous solution 24. The homogeneous solution 24 is moved through a cooling zone Z5 where the homogeneous solution is cooled by the cooler 28 or by heat transfer to the heterogeneous mixture 12 flowing in through the preheater 16. The pump 14 maintains a continuous flow rate through the system, ensuring a particle velocity of the heterogeneous mixture large enough to keep the particles suspended. In this way, plastic particles do not settle in the line and clog the system.

[0018] The sizes of the plastic particles pumped through the system can vary, but are typically between 0.1 μm and 20,000 μm in at least one dimension. To keep the particles suspended, the flow rate of pump 14 is set to ensure a particle velocity of at least 20 cm / s through the system. A particle velocity above 20 cm / s or 30 cm / s provides a safety margin. The pump flow rate is set equal to the product of the desired particle velocity and the cross-sectional area of the line (pipe or tube) through which the mixture is pumped. Lower particle velocities are also possible if a mixer is installed in the line between pump 14 and regulator 26.

[0019] In heating zone Z3, the heating chamber 18 raises the temperature to the reaction temperature or higher to initiate the depolymerization reaction, which is completed in holding zone Z4. The length L of the holding tube 22 in holding zone Z4 depends on its cross-sectional area A, the flow rate Q of the pump, and the holding time T required at the reaction temperature to complete the reaction, i.e., L = QT / A. The holding time can range from 5 minutes to 10 minutes, or from 1 minute to 60 minutes. The diameter of the line passing through the zone is from 1 cm to 10 cm, but can be as large as about 100 cm. When using jacketed piping, the diameter of the jacket can range from 1.1 times to 5.0 times the diameter of the inner tube through which the mixture is pumped. The present invention provides, for example, the following items: H (Item 1) A continuous flow process for depolymerizing plastics, wherein the process is as follows: (a) A step of continuously flowing a mixture containing solid plastic particles in a solvent through a line in a heated chamber at a particle rate sufficient to maintain the suspension of the plastic particles in the solvent and prevent the plastic particles from agglomerating and clogging the line, wherein the solid plastic particles consist of modified PET, PET blend, PEN, PBT, PET-G, PLA, PGA, PLGA, PEF, copolyester, polycarbonate, polyamide, polyurethane or any combination thereof, (b) A step of transferring heat through the line in the heating chamber to heat the mixture to the reaction temperature to initiate the depolymerization of the plastic particles in the solvent and to obtain a homogeneous solution containing the liquefied reaction product. A continuous flow process, including a continuous flow process. (Item 2) The continuous flow process according to item 1, wherein the solvent consists of ethylene glycol, diethylene glycol, glycol ether, methanol, ethanol, propanol, butanol, 2-ethylhexanol, tetramethylcyclobutanediol, cyclohexanedimethanol, alcohols, ethanolamine, ionic liquids, polar protic solvents, polar aprotic solvents, water, or a combination thereof. (Item 3) The continuous flow process according to item 1, wherein the liquefied reaction product comprises a monomer, dimer, or oligomer. (Item 4) The continuous flow process described in item 1, wherein the liquefied reaction product comprises (bis(2-hydroxyethyl) terephthalate, dimethyl terephthalate, terephthalic acid, (bis(2-hydroxyethyl) naphthalate, (bis(2-hydroxyethyl) furanoate), their respective oligomers, acids, half esters, mixed esters, dioctyl terephthalate, diisobutyl terephthalate, dibutyl terephthalate, bisphenol A, lactate, bis(2-hydroxyethyl) terephthalamide, other terephthalamides, or any combination thereof. (Item 5) The continuous flow process according to item 1, wherein the reaction temperature is at least 150°C. (Item 6) The continuous flow process according to item 1, further comprising step (b) holding the mixture at the reaction temperature for at least 1 minute. (Item 7) The continuous flow process according to item 1, further comprising step (a) preheating the mixture in a preheating heat exchanger before flowing the mixture into the heating chamber. (Item 8) (c) After the homogeneous solution leaves the heating chamber, the homogeneous solution is flowed through the passage in the preheating heat exchanger, and the homogeneous solution transfers heat to the mixture in the preheating heat exchanger. The continuous flow process described in item 7, further including the following. (Item 9) The continuous flow process according to item 1, further comprising maintaining a system pressure higher than the vapor pressure of the solvent at the reaction temperature in order to prevent the solvent from evaporating. (Item 10) The continuous flow process according to item 1, further comprising step (a) mixing the solid plastic particles and the solvent with a catalyst to form the mixture. (Item 11) The continuous flow process described in item 10, wherein the catalyst comprises a zinc salt, zinc acetate, zinc chloride, titanium salt, titanium(IV) isopropoxide, titanium(IV) n-butoxide, manganese salt, magnesium salt, sodium hydroxide, potassium hydroxide, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1,8-diazabicyclo[5.4.0]undeca-7-ene, magnesium acetate, 4-dimethylaminopyridine, amine, trialkylamine, or any combination thereof. (Item 12) (c) The step of cooling the homogeneous solution to a temperature below 50°C using a cooling heat exchanger. The continuous flow process described in item 1, further including the following. (Item 13) (d) A step of allowing the cooled homogeneous solution to settle at room temperature for a period of about 0.5 to 100 hours to solidify the liquefied reaction product into a solid reaction product. The continuous flow process described in item 12, further including the following. (Item 14) (e) Separating the solid reaction product from the solvent by one or more of the following: decantation, filtration, centrifugation, pressing, and distillation. The continuous flow process described in item 13, further including the following. (Item 15) (f) A step of reusing the solvent separated from the solid reaction product within the process. The continuous flow process described in item 14, which further includes the process described in item 14. (Item 16) (c) A step of separating the solvent from the reaction product; (d) a step of removing contaminants from the solvent by filtration, adsorption, or a combination thereof; and (e) A step of reusing the solvent in the process by mixing solid plastic particles with the solvent to be reused to form the mixture. The continuous flow process described in item 1, further including the following. (Item 17) The continuous flow process described in item 16, wherein the adsorbent consists of activated carbon, ion exchange resin, diatomaceous earth, sand, zeolite, clay, silica, alumina, oxide, or any combination thereof. (Item 18) The continuous flow process according to item 1, wherein the plastic particles have a size between 0.1 μm and 20,000 μm in at least one dimension. (Item 19) The continuous flow process described in item 1, wherein the solid plastic particles are in the form of flakes, fine powder, granules, fine particles, granola, chunks, powder, or any combination thereof. (Item 20) The continuous flow process according to item 1, wherein the particle velocity through the line is at least 30 cm / s. (Item 21) The continuous flow process according to item 1, wherein in step (b), the mixture is indirectly heated within the line of the heating chamber by pumping a high-temperature heat transfer fluid through the line. (Item 22) A system for the continuous depolymerization of plastics, A pump that operates at a certain flow rate. The pump is a line that continuously supplies a heterogeneous mixture containing solid plastic particles in a solvent at particle velocity, wherein the solid plastic particles consist of modified PET, PET blend, PEN, PBT, PET-G, PLA, PGA, PLGA, PEF, copolyester, polycarbonate, polyamide, polyurethane, or any combination thereof, and A heating zone that raises the temperature of the heterogeneous mixture flowing through the line to a reaction temperature of at least 150°C. A system comprising, where, in the heating zone, the conversion of the heterogeneous mixture containing the solid plastic particles into a homogeneous solution containing liquefied reaction products is initiated. (Item 23) The system according to item 22, wherein a holding tube receives the heated heterogeneous mixture from the heating zone to maintain the reaction temperature for a holding time of at least 1 minute at the flow rate, in order to completely convert the heterogeneous mixture containing the solid plastic particles into the homogeneous solution containing the liquefied reaction product. (Item 24) The system according to item 23, wherein the retaining tube is an insulated pipe or tubing. (Item 25) The length of the retaining tube is long enough to ensure that the conversion of the heterogeneous mixture to the homogeneous solution containing the liquefied reaction product is completed, as described in item 24. (Item 26) The system according to item 25, wherein the holding time in the holding tube is between 1 minute and 60 minutes. (Item 27) The system according to item 25, wherein the holding time in the holding tube is between 5 minutes and 10 minutes. (Item 28) The system according to item 22, further comprising a mixer located upstream of the heating zone for stirring the heterogeneous mixture using a stirrer or a recirculating solvent. (Item 29) The system according to item 22, wherein the heterogeneous mixture comprises the solid plastic particles, the solvent, and the catalyst. (Item 30) The system according to item 22, wherein the solid plastic particles have a size between 0.1 μm and 20,000 μm in at least one dimension. (Item 31) The system according to item 22, wherein the pump maintains the flow rate such that the particle velocity of the solid plastic particles exceeds 30 cm / s. (Item 32) The system according to item 31, wherein the flow rate is set to be equal to the product of the desired particle velocity and the cross-sectional area of ​​the line. (Item 33) The system according to item 22, further comprising a preheating heat exchanger for indirectly preheating the heterogeneous mixture with the homogeneous solution containing the liquefied reaction product, thereby reducing the holding time of the heterogeneous mixture in the heating zone and cooling the homogeneous solution. (Item 34) The system according to item 22, further comprising a reactor heat exchanger within the heating zone for raising the temperature of the heterogeneous mixture to the reaction temperature. (Item 35) The system according to item 34, wherein the heat source is configured to heat a heat transfer fluid that flows past the heterogeneous mixture in the reactor heat exchanger, thereby transferring heat to the heterogeneous mixture. (Item 36) The system according to item 22, further comprising a back pressure regulator downstream of the heating zone for maintaining the system pressure higher than the vapor pressure of the solvent at the reaction temperature. (Item 37) The system according to item 22, further comprising a cooling device including a cooling heat exchanger downstream of the heating zone, wherein the homogeneous solution on one side of the heat exchanger is indirectly cooled by a cold liquid on the other side, and the cooling device lowers the temperature of the homogeneous solution to below 50°C. (Item 38) The system according to item 22, further comprising a separator including a sedimentation tank or a crystallization tank, wherein the liquefied reaction product in the homogeneous solution solidifies and precipitates in the sedimentation tank or crystallization tank. (Item 39) The system according to item 38, wherein the separator separates the solvent from the solid reaction product by one or more of decantation, filtration, centrifugation, pressing, and distillation. (Item 40) The system according to item 38, further comprising a contaminant removal unit downstream of the separator, wherein the contaminant removal unit removes reaction contaminants from the solvent, and the contaminant removal unit includes a filter or adsorbent. (Item 41) The system according to item 40, wherein the filter includes a size exclusion filter or a tangential flow filter. (Item 42) The system according to item 40, wherein the adsorbent consists of activated carbon, ion exchange resin, diatomaceous earth, sand, zeolite, clay, silica, alumina, oxide, or any combination thereof. (Item 43) The system according to item 22, further comprising a preheater located upstream of the heating zone and a retaining tube located behind the heating zone; the preheater, the heating zone, and the retaining tube each include a heat exchanger. (Item 44) The system described in item 43, in which each heat exchanger is a tube-in-shell, tube-s-in-shell, coil-in-shell, tube-in-tube, jacketed piping, plate-and-shell, or plate-and-frame heat exchanger. (Item 45) The system according to item 22, further comprising a preheater located upstream of the heating zone and a retaining tube located behind the heating zone; wherein the preheater, the heating zone, and the retaining tube include a plurality of jacketed pipes having jackets around inner tubes, and the jacketed pipes are connected. (Item 46) The system according to item 45, wherein the inner diameter of the inner pipe in the jacketed piping is between 1 cm and 100 cm, and the diameter of the jacket is between 1.1 and 5.0 times the diameter of the inner pipe.

Claims

1. A continuous flow process for depolymerizing plastics, wherein the process is as follows: (a) Providing a continuous loop flow line including (i) a cold entry zone, (ii) a preheating zone, (iii) a heating zone, (iv) a holding zone, and (v) a cooling zone; (b) A step of continuously flowing a heterogeneous mixture comprising plastic particles, a catalyst, and a solvent through the cold entry zone, the preheating zone, and then the heating zone of the line, wherein the heterogeneous mixture flows at a rate sufficient to maintain the suspension of the plastic particles in the solvent through the cold entry, preheating, and heating zones to prevent the plastic particles from agglomerating and clogging the line, wherein the plastic particles consist of polyethylene terephthalate, modified polyethylene terephthalate, polyethylene terephthalate blend, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate glycol, polylactic acid, polyglycolic acid, poly-D,L-lactic acid-glycolic acid copolymer, polyethylene 2,5-francicarboxylate, copolyester, polyamide, or any combination thereof, and the solvent consists of ethylene glycol, diethylene glycol, glycol ether, 2-ethylhexanol, tetramethylcyclobutanediol, cyclohexanedimethanol, alcohols, ethanolamine, ionic liquids, polar protic solvents, polar aprotic solvents, or any combination thereof; (c) A step of transferring heat through the line in the heating zone to heat the heterogeneous mixture to a reaction temperature of at least 150°C to initiate the depolymerization of the plastic particles in the solvent and to obtain a homogeneous solution containing the liquefied reaction product; (d) the step of holding the mixture in the holding zone at the reaction temperature for at least one minute; and (e) The homogeneous solution flows through the cooling zone, and steps are taken to cool the homogeneous solution. P A continuous flow process, including a continuous flow process.

2. The continuous flow process according to claim 1, wherein the liquefied reaction product comprises a monomer, a dimer, or an oligomer.

3. The continuous flow process according to claim 1, wherein the liquefied reaction product comprises (bis(2-hydroxyethyl) terephthalate, dimethyl terephthalate, terephthalic acid, (bis(2-hydroxyethyl) naphthalate, (bis(2-hydroxyethyl) furanoate), their respective oligomers, acids, half-esters, mixed esters, dioctyl terephthalate, diisobutyl terephthalate, dibutyl terephthalate, bisphenol A, lactate, bis(2-hydroxyethyl) terephthalamide, other terephthalamides, or any combination thereof.

4. The continuous flow process according to claim 1, further comprising maintaining a system pressure higher than the vapor pressure of the solvent at the reaction temperature in order to prevent the solvent from evaporating.

5. The continuous flow process according to claim 1, wherein the catalyst comprises a zinc salt, zinc acetate, zinc chloride, titanium salt, titanium(IV) isopropoxide, titanium(IV) n-butoxide, manganese salt, magnesium salt, sodium hydroxide, potassium hydroxide, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1,8-diazabicyclo[5.4.0]undeca-7-ene, magnesium acetate, 4-dimethylaminopyridine, amine, trialkylamine, or any combination thereof.

6. (e) The step of cooling the homogeneous solution to a temperature below 50°C using a cooling heat exchanger; (f) Allowing the cooled homogeneous solution to settle at room temperature for a period of about 0.5 to 100 hours to solidify the liquefied reaction product into a solid reaction product; (g) the step of separating the solid reaction product from the solvent by one or more of decantation, filtration, centrifugation, pressing, and distillation; and (h) A step of reusing the solvent separated from the solid reaction product within the process. The continuous flow process according to claim 1, further comprising:

7. (e) A step of separating the solvent from the reaction product; (f) the step of removing contaminants from the solvent by filtration or adsorption; and (g) A step of reusing the solvent in the process by mixing solid plastic particles with the solvent to be reused to form the mixture. The continuous flow process according to claim 1, further comprising:

8. The continuous flow process according to claim 1, wherein the plastic particles have a size between 0.1 μm and 20,000 μm in at least one dimension.

9. The continuous flow according to claim 1, wherein the plastic particles are maintained at a speed of 20 cm / s. - Process.

10. A system for the continuous depolymerization of plastics, A pump that operates at a certain flow rate; The pump continuously supplies a heterogeneous mixture comprising solid plastic particles, a catalyst, and a solvent at the flow rate of a line comprising (i) a cold entry zone, (ii) a preheating heat exchanger, (iii) a heating zone, and (iv) a retaining tube, wherein the flow rate is sufficient to ensure a particle velocity that maintains the suspension of the plastic particles in the solvent within the cold entry zone, the preheating heat exchanger, and the heating zone, and the solid plastic particles are polyethylene terephthalate, modified polyethylene terephthalate, polyethylene terephthalate blend, polyethylene naphthalate, polybutylene terephthalate, polyethylene terephthalate glycol, polylactic acid, polyglycolic acid, poly-D,L-lactic acid-glycolic acid copolymer, polyethylene A line comprising 2,5-flange carboxylate, copolyester, polycarbonate, polyamide, or any combination thereof, wherein the solvent comprises ethylene glycol, diethylene glycol, glycol ether, 2-ethylhexanol, tetramethylcyclobutanediol, cyclohexanedimethanol, alcohols, ethanolamine, ionic liquid, polar protic solvent, polar aprotic solvent, or any combination thereof; A heating zone that raises the temperature of the heterogeneous mixture flowing through the line to a reaction temperature of at least 150°C, wherein the conversion of the heterogeneous mixture containing the solid plastic particles into a homogeneous solution containing liquefied reaction products is initiated in the heating zone; To complete the conversion of the heterogeneous mixture containing the solid plastic particles into the homogeneous solution containing the liquefied reaction product, the holding tube receives the heated heterogeneous mixture from the heating zone to maintain the reaction temperature within the holding tube at the flow rate for a holding time of at least one minute; and A preheating heat exchanger for preheating the heterogeneous mixture located upstream of the heating zone, wherein the preheating heat exchanger indirectly preheats the heterogeneous mixture with the homogeneous solution containing the liquefied reaction product and cools the homogeneous solution. A system that includes this.

11. The system according to claim 10, further comprising a mixer located upstream of the heating zone for stirring the heterogeneous mixture using a stirrer or a recirculating solvent.

12. The system according to claim 11, wherein the retaining tube is an insulated pipe or tubing having a length sufficient to ensure that the conversion of the heterogeneous mixture to the homogeneous solution containing the liquefied reaction product is completed.

13. The system according to claim 12, wherein the holding time in the holding tube is between 1 minute and 60 minutes.

14. The system according to claim 10, further comprising a reactor heat exchanger within the heating zone for raising the temperature of the heterogeneous mixture to the reaction temperature, wherein the heat source is configured to heat a heat transfer fluid flowing past the heterogeneous mixture in the reactor heat exchanger to transfer heat to the heterogeneous mixture.

15. The system according to claim 10, further comprising a contaminant removal unit containing a filter or adsorbent downstream of the heating zone, wherein the contaminant removal unit is configured to remove reactive contaminants from the solvent.

16. The system according to claim 10, further comprising a cooling device including a cooling heat exchanger downstream of the heating zone, wherein the homogeneous solution on one side of the heat exchanger is indirectly cooled by a cold liquid on the other side, and the cooling device lowers the temperature of the homogeneous solution to less than 50°C.

17. The system according to claim 10, further comprising a separator including a sedimentation tank or a crystallization tank, wherein the liquefied reaction product in the homogeneous solution solidifies into a solid reaction product and precipitates in the sedimentation tank or crystallization tank.

18. The system according to claim 10, wherein the heating zone includes a heat exchanger, and the heat exchanger and the preheating heat exchanger in the heating zone are, respectively, a tube-in-shell, tube-s-in-shell, coil-in-shell, tube-in-tube, jacketed piping, plate-and-shell, plate-and-shell, or plate-and-frame heat exchanger.

19. The system according to claim 10, wherein the heating zone and the preheating heat exchanger each include a plurality of jacketed pipes of various lengths having a jacket around an inner tube, and the jacketed pipes are connected.

20. The system according to claim 19, wherein the inner diameter of the inner pipe in the jacketed piping is between 1 cm and 100 cm, and the diameter of the jacket is between 1.1 and 5.0 times the diameter of the inner pipe.

21. The system according to claim 10, wherein the particle velocity is 20 cm / s.

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