Method for recycling and upcycling polycarbonate-based composite waste

Abstract

A process for recycling composite waste based on polycarbonate comprising the following steps: (a) providing a mass of composite waste (C); (b) dissolving the mass of waste (C) in the presence of 1,3-dioxolane as solvent at a temperature of 50-100°C in an inert atmosphere at a pressure of 20,000-300,000 Pa; (c) separating the mixture from step (b) to recover insoluble fragments (I) and a liquid comprising solvent and polycarbonate; (d) precipitating the polycarbonate (PC) present in the liquid from step (c) in the presence of water in the form of liquid (W) and / or steam (V) and at least one solvent (P) at a temperature of 50-100°C in an inert atmosphere at a pressure of 20,000-100,000 Pa to obtain a gaseous effluent (E) and solid particles of polycarbonate (PC).

Description

Technical Field

[0001] This invention relates to the technical field of physicochemical methods for recycling polycarbonate-based composite waste.

[0002] More specifically, the present invention relates to the field of methods for dissolving polymers from polycarbonate-based composite waste using solvents, on the one hand to enable the upcycling of insoluble fragments, and on the other hand, particularly to enable the upcycling of polycarbonate formulations after reprocessing polycarbonate dissolved in solvents for subsequent reuse. Background Technology

[0003] Polycarbonate, typically with the formula -[CO-O-pPh-C(CH3)2-pPh-O] n (where n is the number of monomers and Ph is a divalent phenyl radical), is a plastic molding polymer known since 1953 and commercially available since 1959. This polymer is typically derived from the polycondensation of bisphenol A with carbonates or phosphogens.

[0004] Polycarbonate is a polymer with excellent properties, particularly mechanical properties (impact resistance and fracture resistance). It offers good transparency, low flammability, and high thermal resistance, allowing it to be used from -100°C to +120°C. Polycarbonate is also a good electrical insulator and is biocompatible.

[0005] Polycarbonate polymers are widely used in the manufacture of a variety of everyday items, including automotive products (rearview mirror bodies, headlights and lamps), electrical and electronic equipment (telephone and computer housings), packaging, and household appliances.

[0006] For these reasons, a large amount of this material is discarded every year. Therefore, recycling processes present a significant ecological and economic challenge. Mechanical recycling of polycarbonate alone is generally straightforward. However, the presence of metal inserts in polycarbonate-based composite waste makes recycling impossible. In fact, when objects intended for recycling contain inserts such as magnetic strips or chips (e.g., French ID cards or French bank cards) or fibers, this prevents the recycling of high-purity components (metals, fibers, polycarbonate) that can be upgraded and reused.

[0007] In fact, careful grinding of these products often results in a mixture of fine particles of a non-uniform composition. Such a mixture is difficult to purify and reuse.

[0008] Document JP 2019104861 A describes a chemical treatment method for recycling carbon fiber reinforced composite waste containing thermoplastic resins (e.g., polycarbonate). The solvent is a mixture of 1,3-dioxolane, tetrahydrofuran (THF), and N-methyl-2-pyrrolidone (NMP), or a mixture of 1,3-dioxolane and tetrahydrofuran (THF). At the end of the process, distillation is performed, and the distillate concentrate is mixed with ethanol to precipitate the polycarbonate. The final solvent containing ethanol cannot be recovered in this method.

[0009] Each of the documents WO 2012 / 158775 A1, CN 105778459 A, and JP 2001270961 relates to the recycling of polycarbonate-based materials. However, none of them mention the use of 1,3-dioxolane.

[0010] To date, polycarbonate is known to dissolve in at least one solvent, such as dichloromethane, trichloromethane, THF (tetrahydrofuran), or N-methyl-3-pyrrolidone (NMP). However, these solvents are toxic and even carcinogenic, mutagenic, and reprotoxic (CMR). Furthermore, there are no commercially available physicochemical (i.e., solvent-based) solutions for recycling polycarbonate-based composite waste.

[0011] Therefore, there is currently no satisfactory solution for the effective recycling of polycarbonate-based composite waste that overcomes the problems of existing technologies.

[0012] This invention overcomes the problems of the prior art by proposing a method for recycling polycarbonate-based composite waste, which can recover its high-purity components separately, thus enabling these components to be reused. Summary of the Invention

[0013] This invention relates to a method for recycling polycarbonate-based composite waste, comprising the following steps:

[0014] (a) Providing block-shaped composite waste;

[0015] (b) Dissolve the waste block in the presence of 1,3-dioxolane as a solvent at a temperature of 50°C to 100°C in an inert atmosphere at a pressure of 20,000 Pa to 300,000 Pa.

[0016] (c) Separate the mixture obtained in step (b) to recover the insoluble fragments and the liquid containing the 1,3-dioxolane solvent and the polycarbonate formulation.

[0017] (d) At a temperature of 50°C to 100°C, in an inert atmosphere at a pressure of 20,000 Pa to 100,000 Pa, and in the presence of water in liquid and / or vapor form and at least one solvent, the polycarbonate present in the liquid of step (c) is precipitated to obtain a gaseous effluent and solid polycarbonate particles.

[0018] The recycling method of this invention relates to the physical solvent recovery of polycarbonate-based waste composites using a solvent / antisolvent without chemically degrading the polymer. Unlike JP 2019104861 A, the solvent used, 1,3-dioxolane, is free of CMR (carcinogenic, mutagenic, and reproductive toxic) carcinogens. Water and / or water vapor are used as the antisolvent. At least one other solvent is used in the precipitation step (d).

[0019] Advantageously, the recycling method of the present invention produces recycled polycarbonate having a formulation substantially the same as that in the treated composite waste. Therefore, any additives contained in the polycarbonate are generally retained in the recycled polycarbonate. Thus, the obtained recycled polycarbonate has a certain economic value. Finally, another advantage of the method according to the invention is the possibility of regenerating insoluble matter with a polycarbonate content of almost zero.

[0020] Detailed description

[0021] According to the present invention, “composite waste” refers to a residue (material, substance or product) that cannot be used as is and contains at least two interrelated and difficult-to-separate different components.

[0022] The term "polycarbonate-based" means that the waste contains at least 50% polycarbonate by weight. "Polycarbonate" refers to any homopolymer or copolymer containing 1,3-dioxolane-soluble -[CO-O-pPh-C(CH3)2-pPh-O] units. The term "polycarbonate formulation" refers to polycarbonate and any possible additives (colorants, plasticizers, etc.) known to those skilled in the art. A polycarbonate formulation is soluble in 1,3-dioxolane.

[0023] Therefore, the "polycarbonate-based waste composite" according to the present invention comprises polycarbonate and at least one insoluble substance, such as fiber or metal, typically in the form of a plug-in (electronic chip, etc.). This includes French bank cards and plastic ID cards.

[0024] Step (a) can be carried out using any suitable equipment through a specific operation (typically crushing and / or shredding). Step (a) may also simply involve providing raw materials of suitable size.

[0025] "Block" refers to an object with an average size of 1 cm to 20 cm. The term "fragment" used in this invention refers to a portion derived from these blocks, which has a substantially smaller average size.

[0026] According to the present invention, "A and / or B" means A, or B, or A and B.

[0027] Step (b) is typically carried out in a reactor in the presence of 1,3-dioxolane (an organic solvent with the formula C3H6O2, CAS number 646-06-0) as a solvent. Advantageously, 1,3-dioxolane forms an azeotropic mixture with water, which is capable of dissolving the polycarbonate of the composite waste without dissolving other components (fibers, metals, etc.).

[0028] The 1,3-dioxolane used according to the invention preferably has a purity greater than 90 wt.% (“industrial grade 1,3-dioxolane”) and may contain water and at least one stabilizer (e.g., methanol and / or methylal). For example, it contains up to 7% water by weight, up to 3% methanol by weight, and up to 1% methylal by weight. The solvent used in step (b) comprises, preferably substantially comprises, 1,3-dioxolane, and more preferably consists substantially of such 1,3-dioxolane.

[0029] As is known to those skilled in the art, step (b) is preferably carried out under stirring, and those skilled in the art can determine the mixing conditions, typically the type and speed of the stirrer. This stirring also improves the contact between the 1,3-dioxolane solvent and the waste complex.

[0030] Those skilled in the art can determine the conditions of step (b), such as the duration and the ratio of waste to 1,3-dioxolane solvent. Typically, the duration is between 30 min and 180 min, preferably between 60 min and 120 min; and the ratio of waste to 1,3-dioxolane solvent is 1% to 20% by mass (or in amount based on the mass of each liter of 1,3-dioxolane solvent), preferably 5% to 15% by mass. Generally, the amount of 1,3-dioxolane solvent is chosen such that the increase in viscosity due to polycarbonate dissolution is compatible with the smooth progress of the process, particularly during the separation process in step (c).

[0031] Here, the use of the terms "between X and Y" or "from X to Y" refers to an inclusion constraint.

[0032] The term "inert atmosphere" refers to an atmosphere in which no reaction occurs during the process under discussion. As is known to those skilled in the art, an inert atmosphere is typically an oxygen-free air atmosphere, and more preferably a neutral gas atmosphere (e.g., typically nitrogen).

[0033] At the end of step (b), a mixture comprising a liquid and insoluble fragments in the liquid phase is obtained, the liquid being essentially composed of the solvent 1,3-dioxolane, in which polycarbonate (in the form of a polycarbonate formulation) is dissolved.

[0034] Step (c) involves separating the mixture from step (b) into two components: an insoluble fragment on one hand and a liquid containing 1,3-dioxolane solvent and polycarbonate on the other. Preferably, step (c) is a filtration step, for example using at least one sieve or cloth with openings from 0.01 mm to 10 mm. Step (c) may include several filtration sub-steps, typically progressively finer filtrations, usually in one or more reactors.

[0035] Step (c) may also recover at least one component from composite waste (e.g., antennas or tags). Typically, this component was originally present in the block from step (a) and is not usually upgraded and recycled in this way.

[0036] According to one embodiment, steps (b) and (c) are performed simultaneously, i.e., within a common time period. Preferably, steps (b) and (c) are performed substantially simultaneously. This typically corresponds to the case where steps (b) and (c) are carried out in the same reactor, followed by dissolution and separation, and preferably simultaneous filtration.

[0037] According to another preferred embodiment, steps (b) and (c) are sequential, meaning they do not share a common time period: steps (b) and (c) are performed one after the other. In this case, steps (b) and (c) are typically performed in at least two different spaces.

[0038] Preferably, the insoluble fragments from step (c) are washed with 1,3-dioxolane, followed by evaporation and / or distillation to remove all trace amounts of 1,3-dioxolane. This is typically carried out in the same reactor used in step (c). Preferably, this step is a steam cleaning step (commonly referred to as "stripping" by those skilled in the art). As is known to those skilled in the art, this step is typically carried out using steam at a temperature of 90°C to 110°C. This allows for better recovery and therefore better recycling, particularly internal recycling, of 1,3-dioxolane (e.g., a possible condensation step (g) of the effluent gas, followed by recovery of 1,3-dioxolane for steps (b) and / or (d)). Importantly, this makes it possible to obtain purer insoluble fragments for subsequent reuse.

[0039] In step (d), steam and / or water are injected to cause the polycarbonate to precipitate as solid particles, while the gaseous effluent is discharged, typically into the reactor.

[0040] Step (d) can also be advantageously used to evaporate and remove the water-1,3-dioxolane azeotropic mixture in gaseous form. The azeotropic mixture can then be collected and condensed. The unevaporated liquid is essentially water and solid polycarbonate particles, preferably water and solid polycarbonate particles. Collection of the polycarbonate particles becomes possible when almost all of the 1,3-dioxolane has been removed.

[0041] The solvent in step (d) is advantageously an alkane selected from the group consisting of isohexane, hexane, heptane, octane, and pentane. Isohexane is preferred as the solvent in step (d).

[0042] The solvent ratio in step (d) is preferably 5 wt.% to 25 wt.% based on the total weight of the solvent (1,3-dioxolane, water and solvent).

[0043] Step (d) may also involve the use of a supplemental solvent, which is contained in the solvent of step (d). In this case, the solvent from step (d) may refer to the “main” solvent. The supplemental solvent advantageously acts as a dispersant. The term “dispersant” refers to any molecule that restricts the aggregation of grains during precipitation. The supplemental solvent is typically selected from alcohols, esters, oxopentabenzenes, ethers, and ketones with boiling points between 1,3-dioxolane and water. Preferably, the supplemental solvent is selected from the group consisting of isopropanol, propyl acetate, 2-methyl-1,3-dioxolane, and dimethoxyethane. Preferably, the supplemental solvent is isopropanol.

[0044] The proportion of the supplemental solvent is preferably 1 wt.% to 10 wt.% relative to the total weight of the solvent (1,3-dioxolane, water and / or vapor and other solvents including the solvent and the supplemental solvent).

[0045] As is known to those skilled in the art, step (d) is preferably carried out under stirring, and those skilled in the art can determine the mixing conditions, typically the type and speed of the stirrer. Advantageously, such stirring improves the volume distribution of the vapor and allows for the granulation of polycarbonate. Although referred to only as "polycarbonate granules" below, the composition of the polycarbonate granules essentially corresponds to the original polycarbonate formulation.

[0046] In step (d), the components of the solvent mixture (i.e., 1,3-dioxolane, water, and the solvent from step (d)) facilitate the separation between the aqueous and organic phases of the condensed outflow gas.

[0047] Those skilled in the art can determine the conditions of step (d), such as the duration, the proportion of 1,3-dioxolane in the solvent mixture, and the proportion of water and / or water vapor in the solvent mixture. Typically, the duration is between 30 min and 240 min, preferably between 60 min and 180 min. Typically, the proportion of 1,3-dioxolane in the solvent mixture is selected to be between 60% m. and 100% m., preferably between 70% m. and 90% m., and the proportion of water and / or water vapor in the solvent mixture is selected to be between 50% m. and 150% m., preferably between 80% m. and 120% m., to promote the evaporation of the azeotropic mixture.

[0048] If necessary, 1,3-dioxolane may also be added to step (d).

[0049] According to a preferred embodiment, a supplementary step (e) is performed after step (d) to steam clean (“stripping”) the polycarbonate granules obtained in step (d) that are typically present in a mixture primarily containing water. This is typically carried out in the same reactor used in step (d). As known to those skilled in the art, step (e), which removes the remaining solvent mixture typically adsorbed onto the polycarbonate granules, is typically carried out using steam at a temperature of 90°C to 110°C. This allows for better recovery and therefore better recycling, particularly internal recycling of 1,3-dioxolane (e.g., a possible condensation step (g) of the effluent gas, followed by recovery of the 1,3-dioxolane used in step (b), and then step (d)). Importantly, this makes it possible to obtain purer polycarbonate granules for subsequent reuse.

[0050] Optionally, the method further includes a supplementary step (f) for drying the polycarbonate granules obtained in step (e). This drying can be carried out in a conventional manner known to those skilled in the art, for example in a fluidized bed dryer.

[0051] According to one embodiment, a condensation step (g) for the gaseous effluent from step (d) is performed after step (d), thereby producing an aqueous liquid effluent and an organic liquid effluent. Step (g) is performed after step (d) and is independent of steps (e) and / or (f).

[0052] Preferably, the aqueous liquid effluent from step (g) is subjected to step (d) with water in liquid and / or vapor form (preferably liquid).

[0053] Preferably, the organic liquid effluent from step (g) is subjected to step (b) with 1,3-dioxolane, and optionally step (d) with 1,3-dioxolane if necessary.

[0054] According to one implementation, step (g) more typically processes any gaseous stripping effluent.

[0055] Therefore, step (g) is preferably performed on the effluent gas from the stripping step of insoluble fragments in step (c). Similarly, step (g) is preferably performed on the effluent gas from step (e), in which step (e) strips the polycarbonate granules from step (c).

[0056] All these internal recycling steps advantageously make the process more self-sufficient and thus make its use more eco-responsible. Attached Figure Description

[0057] The embodiments of the present invention and the advantages therefrom will become apparent from the following description of the embodiments and with the support of the accompanying drawings, wherein:

[0058] [Fig.1] Figure 1 This is a schematic diagram illustrating the working principle of the method of the present invention.

[0059] It is generally accepted that Figure 1 The dimensions and proportions of the components shown may be exaggerated relative to reality, and are given only for the purpose of understanding the invention. Detailed Implementation

[0060] like Figure 1 As illustrated, apparatus 1 is used to implement the method according to the invention.

[0061] Apparatus 1 includes a reactor 2 in which a composite waste block C to be processed by the method is placed. Block C may be provided as such, or it may be ground (not shown). In the latter case, block C is fed into reactor 2 via pipe 10 (step (a)). In reactor 2, block C is dissolved in the presence of a solvent mixture P, which mainly comprises 1,3-dioxolane and is supplied via pipe 20.

[0062] exist Figure 1 In this process, steps (b) and (c) are performed simultaneously in the same reactor 2 and space 4. Component 3 represents the separation occurring in reactor 2, which includes primary filtration. Line 12 transfers the liquid effluent from reactor 2 to space 4, which is equipped with component 5, representing the separation occurring in space 4. Space 4 corresponds to an auxiliary filtration system. Line 16 transfers the filtered liquid effluent from space 4 to reactor 6. Components of the composite waste, such as inserts or metal parts A, can also be discharged from space 4 via line 23.

[0063] A new solvent mixture P can be added to reactor 2 as an optional step for rinsing insoluble fragments.

[0064] Furthermore, either after or without this optional step, the insoluble fragments I are preferentially stripped using steam V from line 14. Then, preferably, the gaseous effluent E from reactor 2 is supplied through line 15 to a dedicated space 7 and condensed therein. After the insoluble fragments I are free of all trace solvents, they are discharged through line 13. Figure 1 As shown, this stripping can be carried out in reactor 2, but it can also be carried out in space 4 (not shown).

[0065] In reactor 6, polycarbonate PC present in the liquid effluent is precipitated. For this purpose, if necessary, line 21 provides an additional solvent mixture P from space 7, and line 22 provides an aqueous phase primarily containing water W. In step (d), vapor V is also provided via line 17 to initiate the precipitation of polycarbonate in granular form, preferably followed by a stripping step (e). The gaseous effluent E from reactor 6 is fed into space 7 via line 19 and condenses in space 7, thereby producing a liquid organic phase P and a liquid aqueous phase W. After the polycarbonate granules are free of all trace solvent, they are discharged via line 18. The effluent gas E, after condensation in space 7, can be used in a closed loop for the organic phase P via lines 20 and 21 and for the aqueous phase W via line 22.

[0066] Because of the high purity of polycarbonate granules (PC) and insoluble fragments (I, for example, which may be metals), they can be advantageously upgraded and modified.

[0067] Example

[0068] Example 1

[0069] Polycarbonate ID cards were selectively dissolved and precipitated in the presence of 1,3-dioxolane. The ID cards were pulverized into medium-sized pieces of several square centimeters, then provided in 10g increments and mixed with 200g of 1,3-dioxolane. The mixture was stirred at 60°C for 2 hours. A hot filtration process was then performed, yielding three distinct phases: a metallic phase (copper fibers and electronic chips), a polycarbonate solution phase, and a coating phase (varnish).

[0070] This small-scale experiment demonstrates the feasibility and effectiveness of the method described in this invention.

[0071] Example 2

[0072] As in Example 1, a larger-scale selective dissolution-precipitation of polycarbonate ID cards was carried out in the presence of 1,3-dioxolane.

[0073] To this end, 500g of pulverized ID card fragments were mixed with 3kg of 1,3-dioxolane and stirred at 60°C for 45 minutes. After filtration, three phases were produced: a polycarbonate solution phase, a coating phase (varnish), and a metallic phase (copper fibers and electronic chips).

[0074] The metal was flushed with 1,3-dioxolane, then stripped with steam and dried.

[0075] The obtained polycarbonate solution (3.4 kg) was injected into a reactor stirred at 700 rpm, where the temperature was increased from an initial 20°C to 100°C after 2 hours and 15 minutes, in two stages, adjusting at 60°C and then at 100°C. After 45 minutes, steam was added at a rate of 1.5 kg per hour.

[0076] The precipitate began to settle at 40 minutes and continued until 2 hours. Isohexane (the main solvent; hydrophobic agent) and isopropanol (an additional solvent; dispersant) were added from the outset at ratios of 15 wt.% and 4 wt.% respectively, based on the total weight of the solvents (1,3-dioxolane, water, isohexane, and isopropanol). This caused the polycarbonate to precipitate as a powder.

[0077] The solid-liquid mixture was then filtered and dried. The recovered final polycarbonate powder had the highest purity.

[0078] This larger-scale experiment makes it possible to demonstrate the feasibility and effectiveness of the method described in this invention.

Claims

1. A method for recycling polycarbonate-based composite waste, comprising the following steps: (a) Providing the composite waste in block form; (b) Dissolve the waste block at a temperature of 50°C to 100°C in the presence of 1,3-dioxolane as a solvent in an inert atmosphere at a pressure of 20,000 Pa to 300,000 Pa; (c) Separate the mixture from step (b) to recover the insoluble fragments and the liquid containing the solvent and polycarbonate; (d) At a temperature of 50°C to 100°C, in an inert atmosphere at a pressure of 20,000 Pa to 100,000 Pa, in the presence of water in liquid and / or vapor form and at least one solvent, the polycarbonate present in the liquid of step (c) is precipitated to obtain a gaseous effluent and solid particles of the polycarbonate.

2. The method of claim 1, wherein, Separation step (c) is the filtration step.

3. The method of claim 1 or 2, wherein, Step (c) includes several filtering sub-steps.

4. The method according to claim 1, wherein, Step (c) also recovers at least one component from the composite waste.

5. The method according to claim 1, wherein, Steps (b) and (c) are sequential.

6. The method according to claim 1, wherein, The insoluble fragments from step (c) are washed with solvent, followed by evaporation and / or distillation to remove all trace amounts of 1,3-dioxolane.

7. The method according to claim 1, wherein, The solvent in step (d) is an alkane selected from the group consisting of isohexane, hexane, heptane, octane and pentane.

8. The method according to claim 7, wherein, The solvent in step (d) further includes additional solvents selected from the group consisting of isopropanol, propyl acetate, 2-methyl-1,3-dioxolane and dimethoxyethane.

9. The method according to claim 1, wherein, An additional step (e) is performed after step (d), which is to steam clean the polycarbonate granules obtained in step (d).

10. The method of claim 9, further comprising a supplementary step (f) for drying the polycarbonate granules produced in step (e).

11. The method according to claim 1, wherein, Step (g) is performed after step (d), which is to condense the gaseous effluent from step (d) to produce an aqueous liquid effluent and an organic liquid effluent.

12. The method according to claim 11, wherein, The aqueous liquid effluent from step (g) is then subjected to step (d) with water in liquid and / or vapor form.

13. The method according to claim 11 or 12, wherein, The organic liquid effluent from step (g) is subjected to step (b) with 1,3-dioxolane.

14. The method according to claim 11 or 12, wherein, The organic liquid effluent from step (g) is subjected to step (b) and step (d) with 1,3-dioxolane.

15. The method according to claim 11, wherein, Step (g) is performed on the gaseous effluent from the steam cleaning step of the insoluble fragments from step (c).

16. The method according to claim 11, wherein, Step (g) is performed on the gaseous effluent from step (e), where step (e) is steam cleaning of the polycarbonate granules from step (c).

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