METHOD FOR PROCESSING USED PLASTIC PARTS TO RECOVER THEIR CONSTITUENTS

Abstract

------ METHOD FOR PROCESSING USED PLASTIC PARTS TO RECOVER THEIR CONSTITUENTS To treat according to the invention a used plastic part comprising an organic filler and an inorganic filler, (A) at least one organic solvent (S1), immiscible with water, a good solvent for plastic and capable of solvating the organic filler and the plastic and releasing the inorganic filler, is added to pieces of the part to be treated; (B) to the mixture obtained, an aqueous solution of an agent complexing the inorganic filler is added, the aqueous solution being capable of transferring by liquid-liquid extraction the inorganic filler from the mixture to the aqueous solution, the inorganic filler then being in a dissolved state in the aqueous solution;(C) to the two immiscible phases obtained, a solvent (S2) immiscible with water, miscible with solvent (S1), a poor solvent for the plastic material and a good solvent for the organic filler, is added to precipitate, following at least one solid phase, the plastic material in dispersed form while leaving the organic filler in the mixture of solvents (S1) and (S2), composing an organic liquid phase, the inorganic filler remaining dissolved in the aqueous solution, composing an aqueous phase; the solid phase of plastic material is recovered by a solid-liquid separation; from each of the organic and aqueous phases obtained, separated by their difference in density, the organic filler and the inorganic filler are respectively isolated.

Description

Title of the invention: METHOD FOR TREATMENT OF USED PLASTIC PARTS TO RECOVER THEIR CONSTITUENTS

[0001] The present invention relates to a process for treating used plastic parts to separate the organic and inorganic components present therein and to recover a regenerated plastic material, which can be used again.

[0002] Plastic parts consist not only of the plastic material itself, but also of fillers (additives) both mineral and organic, which can constitute up to 65% of the total weight of the plastic material.

[0003] Examples include parts made of ABS (Acrylonitrile Butadiene Styrene) thermoplastic material that contain fillers used, for example, for their flame-retardant properties (Sb2O3, tetrabromobisphenol-A, etc.) or to modify the color or intrinsic properties of the thermoplastic material (talc, CaCO3, silica, silicates, etc.). A wide range of fillers is permitted, with more than 400 types identified by the ECHA (European Chemicals Agency). Although many of these fillers do not pose a problem, the ultimate goal of plastic recycling would be to remove these fillers in order to erase all traces of the plastic's previous uses during the recycling process. This would allow the strictest quality criteria and standards for applications using recycled plastics to be met.

[0004] To separate plastics, such as thermoplastics, from their components, current methods generally aim to remove at least some of the fractions to facilitate the processing of the others. It should be noted here that the objective of the invention is not to destroy these components, but rather to fully recover the fillers, whether plastic, inorganic, or organic.

[0005] The main techniques, noted below (1) to (7), allowing this, without altering or by partially altering the fractions, are summarized in Table 1 below: 1. Leaching applies the principles of extractive hydrometallurgy to thermoplastic particles instead of ores. It involves dissolving the fillers present in the plastic, for example, using an acid in aqueous solution. However, this process is hampered by the fact that the plastic contains and isolates the fillers from the acid intended to dissolve them. Depending on the leaching conditions, the plastic may therefore remain intact or be slightly altered. 2. Solvation uses a solvent to induce the mobility of polymer chains without liquefying the plastic material, allowing the extraction of fillers from the polymer matrix via solid-liquid separation, with the plastic material remaining undamaged. 3. Dissolution / precipitation is widely described in the literature and allows, through dissolution, the liquefaction of one or more thermoplastic materials with a specific solvent, followed by the precipitation of one or more polymers from the same family with a suitable non-solvent. This method is often used to separate mixtures of thermoplastic materials.

[0006] (4) and (5) For additives which interfere with pyrolysis or combustion, due to Due to legal standards or risks of equipment degradation, depollution methods are necessary before chemical or thermal recovery (technique 4), such as monomer distillation or chemical treatment with acidic or basic reagents (technique 5).

[0007] (6) After dissolution, the use of a poor solvent is proposed to make precipitate the plastic material and simultaneously extract an inorganic or organic filler with it.

[0008] (7) This technique, a variant of technique 3, involves separation processes solid-liquid on dissolved plastic material (similarly to technique 2) to extract a mineral filler, followed by selective precipitation of the plastic material, leaving one or more problematic additives in solution.

[0009] [Tables 1] Technique: Opening of the plastic material; Extraction of fillers; Fate of the plastic material; Objective 1: Leaching; Recovery of an inorganic filler and a plastic material; 2: Solvation; Solid-liquid separation; Recovery of an organic filler and a plastic material 3. Dissolution, Precipitation, Separation of plastics 4. Depolymerization, Distillation, Monomer Recovery in an organic feedstock 5. Dissolution, Dehalogenation, Precipitation, Recovery of plastic and organic feedstocks 6. Dissolution, Precipitation of inorganic feedstocks by a suitable solvent, Separation of plastic and organic feedstocks 7. Dissolution, Solid-liquid separation of inorganics, Selective precipitation of plastic, Separation of plastic and inorganic and organic feedstocks

[0010] To achieve the aforementioned objective of recycling used plastics, enabling the recovery of reusable plastics for use in industry as raw materials, and the precise extraction of both organic and inorganic fillers for disposal or reuse, the approach proposed according to the present invention offers an alternative to technique 7 described above. It suggests that instead of proceeding by solid-liquid separation to isolate the inorganic fillers (i.e., suspended solid particles), a specific aqueous complexing and extracting solution is added to target a specific inorganic filler suspended in the solvent containing the thermoplastic material and the dissolved organic fillers. This operation can be defined as selective interfacial leaching to dissolve only one type of suspended solid in the phase containing the plastic material.This leaching is associated with a liquid-liquid extraction which allows this targeted and dissolved inorganic load to be transferred out of the liquid phase containing the matter. plastic and organic fillers. The next step, involving a selective precipitation of the plastic material depleted of this inorganic filler, aims at the targeted recovery of organic fillers which then remain in the solvent.

[0011] This thermoplastic recycling technique achieves the intended objective while offering the additional advantages that it is advantageously carried out under ambient temperature and pressure conditions, using solvents and reagents with low environmental impact, that are economical and of low concentration. Furthermore, the process is designed to minimize capital and energy requirements, and also to reuse solvents and aqueous solutions in the form of recycling loops, thus making resource use more efficient.

[0012] The present invention therefore relates to a method for treating a used plastic part comprising at least one organic filler and at least one inorganic filler in order to recover separately: - the regenerated plastic material, depleted in said organic filler(s) and in said inorganic filler(s); - the organic charge(s); and - the inorganic charge(s),

[0013] characterized by the fact that it comprises the following successive steps consisting of: A. Add to the part to be treated, or to pieces thereof, at least one organic solvent (SI), immiscible with water, a good solvent for said plastic material and capable of solvating said organic filler(s) and said plastic material and releasing said inorganic filler(s), to obtain a mixture containing: • in dissolved form, said plastic material and said organic filler(s); and • in solid state in suspension, said inorganic charge(s); B. add to the mixture obtained in step (A) an aqueous solution of at least one complexing agent of said inorganic filler(s), said aqueous solution being capable of transferring by liquid-liquid extraction said inorganic filler(s) of said mixture to said aqueous solution, said inorganic filler(s) then being in a dissolved state in said aqueous solution; C. add to the two immiscible phases thus obtained in step (B) at least one solvent (S2) immiscible with water, miscible with said at least one solvent (S1), a poor solvent for said plastic material and a good solvent for said organic filler(s) to precipitate, according to at least one solid phase, said plastic material in dispersed form while leaving said organic charge(s) in the mixture of said at least one solvent (SI) with said at least one solvent (S2), composing an organic liquid phase, said inorganic charge(s) remaining dissolved in the aqueous solution, composing an aqueous phase;

[0014] recover said solid phase(s) of plastic material by solid-liquid separation; and

[0015] isolate from each of said organic and aqueous phases obtained, separated by their difference in density, respectively said organic charge(s) and said inorganic charge(s).

[0016] Advantageously, the part to be treated is reduced to pieces, in particular with a dimension in its narrowest section less than 1 cm, for example from 50 mm to 0.5 mm, before engaging it in step (A).

[0017] At step (A), the solvent or each solvent (SI) advantageously has a RED value of less than 1, preferably less than or equal to 0.25, relative to the Hansen sphere of the plastic material.

[0018] For this calculation of the RED value for the solvent or each solvent (SI) - and also for the solvent or each solvent (S2) as will be discussed below - reference should be made to Hansen, CM Hansen Solubility Parameters: A User's Handbook, 2nd ed.; CRC Press: Boca Raton, 2007. Pages 4 to 8, the dataset is available on HSPiP Datasets, Hansen Solubility parameters https: / / www.hansen-solubility.com / HSPiP / datasets.php.

[0019] At step (A), the mass proportion of solvent (SI): plastic material can be from 5:1 to 2:1.

[0020] Step (A) can be conducted at a temperature of 15 to 100°C, in particular at a temperature of 15 to 40°C.

[0021] Step (A) can be conducted at an absolute pressure of at least 105Pa (1 bar).

[0022] In accordance with particular embodiments of the process according to the present invention, in step (B), in the case of several inorganic charges, an aqueous solution containing different complexing agents is used, at a rate of one complexing agent for one inorganic charge considered with a view to a simultaneous dissolution of said charges, or several aqueous solutions are used successively, each containing one complexing agent for one organic charge considered.

[0023] In step (B), an aqueous solution containing at least one additive selected from surfactants, such as the nonionic polyoxyethylene surfactant marketed under the trade name Triton® X-100, and phosphatidylinoline, and phase-transfer catalysts, such as quaternary ammonium salt, may be used. marketed under the trade name Aliquat® 336 and tetrabutylammonium chloride, in concentrations for example of 102 to 104 mol.L 1.

[0024] At step (C), the solvent or each solvent (S2) may have a RED value greater than 1, preferably greater than or equal to 1.25, with respect to the Hansen sphere of the plastic material, and a RED value less than 1, preferably less than or equal to 0.75 with respect to the Hansen sphere of the organic filler.

[0025] Step (B) can be followed by a separation step by filtration of insoluble materials.

[0026] In particular, mention can be made of the process as defined above in which: - the plastic material is a thermoplastic material, such as acrylonitrile-butadiene-styrene or high impact-resistant polystyrene, - the organic filler(s) is or are chosen from brominated flame retardants, such as tetrabromobisphenol-A; - the inorganic filler(s) is / are chosen from flame retardant synergists, such as antimony trioxide; - the solvent(s) (SI) is or are chosen from nitrobenzene, aniline, isoamyl acetate, n-butyl acetate, chloroform, dichloromethane, 2-phenoxyethanol, ethylbenzene, methyl isobutyl ketone and cyclohexanone; - the solvent (S2) is diethyl ether; and - the extraction agent is tartaric acid.

[0027] The process according to the present invention can be carried out in batches, semi-continuously or continuously.

[0028] The following example illustrates the present invention without, however, limiting its scope. It relates to the separation of the brominated flame retardant tetrabromobisphenol-A and the synergist of this retardant, which is antimony oxide Sb2O3, from ABS plastic material obtained from waste electrical and electronic equipment, in order to recover: • a fraction containing antimony; • a fraction recovering the brominated molecules; and • a fraction of ABS plastic material, here in the form of fibers, depleted of its original fillers. Preparatory stage

[0029] Under ambient conditions, ABS plastic sheets from electronic waste consisting of used computer screens were cleaned with MilliQ water and soap. Using wire cutters, the cleaned sheets were cut into 10 mm x 10 mm pieces, each weighing approximately 0.3 g.

[0030] Chemical analyses by X-ray fluorescence demonstrated the presence of 30,500 ppm of Sb2O3 and 90,500 ppm of tetrabromobisphenol-A.

[0031] Step A: Solubilization of the ABS plastic material

[0032] At 25°C and 0.1 MPa absolute (1 bar absolute), approximately 1 g of ABS pieces (three pieces of 0.3 g each on average) were placed in a 20 mL glass tube, which could be closed with a hermetically sealed polypropylene stopper. 10 mL of dichloromethane was added to the tube, which was then closed and shaken on a reciprocating shaker at 200 movements per minute for 3 hours.

[0033] The solvent dissolved the ABS and tetrabromophenol-A, while the solid Sb2O3 was released from the plastic material and suspended in the liquid.

[0034] Step B: Liquid-liquid extraction of the inorganic feedstock Sb 2 O 3

[0035] At room temperature and ambient pressure, 10 mL of an aqueous solution of 0.1M tartaric acid was added to the tube as a complexing agent, to leach the solid antimony oxide Sb2O3 and to carry out a liquid-liquid extraction from the dichloromethane solvent to the aqueous solution.

[0036] For this purpose, the tube was hermetically sealed and placed on the shaker at the same frequency for 96 hours.

[0037] During this process, Sb2O3 is transferred into the aqueous phase, forming a complex by the following reaction:

[0038] Sb2O3(s) + 2C4H6O6(aq) -> Sb2(C4H2O6)22 (aq) + H2O + 2H+(aq)

[0039] The result of this step is the coexistence of two immiscible phases, namely: • one containing dichloromethane, ABS, and dissolved tetrabromobisphenol-A; and • the other, the aqueous solution with the antimony complex.

[0040] Step C: Insolubilization of the ABS plastic material

[0041] The mixture obtained in step B was transferred to 30 mL of diethyl ether as a non-solvent, resulting in the formation of three phases, namely: • an organic phase consisting of solvents and including tetrabromobisphenol-A; • an aqueous phase comprising the antimony tartrate complex; and • a fraction of ABS plastic material in solid form at the interface between the two liquid phases.

[0042] The non-solvent diethyl ether also serves as an extraction solvent for brominated molecules.

[0043] It was previously refrigerated at 4°C for 12 hours to aggregate the ABS plastic particles into fine fibers, which facilitates their recovery by liquid filtration.

[0044] The fraction of solid plastic material obtained was cleaned with 10 mL of clean non-solvent diethyl ether, and it was dried in an oven above the boiling point of solvents for 24 hours to remove residual solvents.

[0045] The two liquid phases were then separated by density difference. Antimony tartrate and tetrabromobisphenol A were recovered from their respective phases by evaporation / precipitation prior to analysis.

[0046] Table 2 below reports the characteristics of the different compounds: ABS, antimony compound and brominated compound before and after treatment by the process according to the invention.

[0047] [Tables2] Analytical Method SEC* XRF** Retention Time (min) Mn (g / mol) MW (g / mol) Polydispersity Sb (ppm) Br (ppm) Plastic before extraction 16.874 159897 281616 1.76 30500 90500 Plastic after extraction 16.883 155494 285773 1.83 <500 1980 Variation (abs) 0.009 4409 4157 0.07 30000 89320 Extraction yield (%) 98.4% 97.8%

[0048] * The molecular masses and molecular mass distributions have been determined using size exclusion chromatography. The SEC system comprises a Waters 1515 isocratic high-performance liquid chromatography pump, two Styragel HR 5E columns, and a refractive index detector. The eluent used is DMF containing 0.01 mol / L LiBr, with a flow rate of 1.0 mL / min. The separation column and the refractive index detector are maintained at 60°C and 40°C, respectively. The calibration samples are commercial monodisperse polystyrenes.

[0049] ** The solid samples were analyzed by fluorescence spectrometry of X-rays using the Malvem Epsilon 1 analyzer, using an X-ray tube X with a silver anode capable of a maximum voltage of 50 kV and a current of 1 mA. The antimony (Sb) concentration is determined from the characteristic peaks at 26.359 keV (Ka) and 3.604 keV (La), while the bromine (Br) concentration is based on the peaks at 11.922 keV (Ka) and 13.29 keV (K[3]. Calibration uses reference samples prepared from ABS Resinex, pure antimony trioxide, and tetrabromobisphenol-A.

[0050] This example therefore demonstrates the ability of the process according to the invention to separately recover the different organic (Br) and inorganic (Sb) fillers and produce a new ABS plastic material which is depleted of its initial fillers down to the adequate minimum content and which is reusable in the plastics industry.

Claims

Demands

1. - Method for treating a used plastic part comprising at least one organic load and at least one inorganic load for separate recovery: - the regenerated plastic material, depleted in said organic filler(s) and in said inorganic filler(s); - the organic charge(s); and - the inorganic charge(s), characterized by the fact that it comprises the following successive steps consisting of: A. Add to the part to be treated, or to pieces thereof, at least one organic solvent (SI), immiscible with water, a good solvent for said plastic material and capable of solvating said organic filler(s) and said plastic material and of releasing said inorganic filler(s), to obtain a mixture containing: • in dissolved form, said plastic material and said organic filler(s); and • in solid state in suspension, said inorganic charge(s); B. add to the mixture obtained in step (A) an aqueous solution of at least one complexing agent of said inorganic filler(s), said aqueous solution being capable of transferring by liquid-liquid extraction said inorganic filler(s) of said mixture to said aqueous solution, said inorganic filler(s) then being in a dissolved state in said aqueous solution; C. Add to the combination of the two immiscible phases thus obtained in step (B) at least one solvent (S2) immiscible with water, miscible with said at least one solvent (S1), a poor solvent for said plastic material and a good solvent for said organic filler(s) to precipitate, according to at least one solid phase, said plastic material in dispersed form while leaving said organic filler(s) in the mixture of said plastic material and S2 in the mixture. minus one solvent (SI) with said at least one solvent (S2), composing an organic liquid phase, said or said inorganic fillers remaining dissolved in the aqueous solution, composing an aqueous phase; recover said or said solid phases of plastic material by a solid-liquid separation; and isolate from each of said organic and aqueous phases obtained, separated by their difference in density, respectively said or said organic fillers and said or said inorganic fillers.

2. - Method according to claim 1, characterized in that the part to be treated is reduced into pieces, in particular of a dimension in its narrowest section less than 1 cm, for example from 50 mm to 0.5 mm, before engaging it in step (A).

3. - A process according to any one of claims 1 and 2, characterized in that at step (A), the solvent or each solvent (SI) has a RED value of less than 1, preferably less than or equal to 0.25, relative to the Hansen sphere of the plastic material.

4. - A process according to any one of claims 1 to 3, characterized in that at step (A), the mass proportion of solvent (SI): plastic material is from 5:1 to 2:

1.

5. - A method according to any one of claims 1 to 4, characterized in that step (A) is conducted at a temperature of 15 to 100°C.

6. - Method according to claim 5, characterized in that step A is carried out at a temperature of 15 to 40°C.

7. - A method according to any one of claims 1 to 6, characterized in that step (A) is carried out at an absolute pressure of at least 105Pa (1 bar).

8. - A method according to any one of claims 1 to 7, characterized in that in step (B), in the case of several inorganic feeds, an aqueous solution containing different complexing agents is used, at a ratio of one complexing agent for one inorganic feed considered in order to simultaneously dissolve said feeds, or several aqueous solutions are used successively, each containing one complexing agent for one organic feed considered.

9. - A method according to any one of claims 1 to 8, characterized in that in step (B), an aqueous solution containing at least an additive chosen from among surfactants and phase transfer catalysts.

10. - A process according to any one of claims 1 to 9, characterized in that at step (C), the solvent or each solvent (S2) has a RED value greater than 1, preferably greater than or equal to 1.25, with respect to the Hansen sphere of the plastic material, and a RED value less than 1, preferably less than or equal to 0.75 with respect to the Hansen sphere of the organic filler.

11. - A method according to any one of claims 1 to 10, characterized in that step (B) is followed by a separation step by filtration of insoluble materials.

12. - A process according to any one of claims 1 to 11, characterized in that: - the plastic material is a thermoplastic material, such as acrylonitrile-butadiene-styrene or high-impact polystyrene; - the organic filler(s) is / are selected from brominated flame retardants, such as tetrabromobisphenol A; - the inorganic filler(s) is / are selected from synergists of brominated flame retardants, such as antimony trioxide; - the solvent(s) (S1) is / are selected from nitrobenzene, aniline, isoamyl acetate, n-butyl acetate, chloroform, dichloromethane, 2-phenoxyethanol, ethylbenzene, methyl isobutyl ketone, and cyclohexanone; - the solvent (S2) is diethyl ether; - the extraction agent is tartaric acid.

13. - A process according to any one of claims 1 to 12, characterized in that it is carried out in batches, semi-continuously or continuously.