Process for treating spent plastics by dissolution of the polymers and purification by adsorption

Abstract

This invention relates to a method for processing plastic raw materials, comprising: a) a dissolution step involving contacting the raw material with a dissolving solvent at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1 MPa abs and 20.0 MPa abs to obtain a crude polymer solution, wherein the boiling point of the dissolving solvent is between -50°C and 250°C; b) an adsorption step involving contacting the crude polymer solution with an adsorbent at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs to obtain a refined polymer solution; and c) a recovery step involving recovering the polymer to obtain at least one solvent fraction and a purified polymer fraction.

Description

Technical Field

[0001] This invention relates to a method for processing waste plastics to obtain purified plastic streams that can be used, for example, as new plastic articles. More specifically, this invention relates to a method for processing plastic raw materials (particularly containing thermoplastic plastics, such as polyolefins), especially those obtained from plastic waste, comprising an adsorption step to at least partially remove impurities, particularly additives conventionally used in plastic-based materials, such as dyes, pigments, organic and inorganic fillers, so that the polymers contained in the raw material, especially the thermoplastic plastics, can be recovered and reused by separating them. Prior Technology

[0002] Plastics obtained from various collection and sorting channels can be upgraded according to different channels.

[0003] Mechanical recycling makes it possible to reuse some waste materials directly in new objects or by mixing mechanically sorted plastic waste streams with virgin polymer streams. This type of upgrade is limited because mechanical sorting makes it possible to improve the purity of a given type of polymer stream, but it usually does not make it possible to adequately remove impurities, such as additives, such as fillers, dyes, pigments, and metals, that are at least partially trapped in the polymer matrix.

[0004] "Chemical" recycling aims to at least partially reconstitute monomers through a series of steps that are typically complex. For example, plastic waste can undergo pyrolysis, and the pyrolysis oil, usually recovered after purification, can be at least partially converted into olefins, for example, by steam cracking. These olefins can then be polymerized. This type of sequence can be applied to feedstocks that undergo minimal sorting or to residues from sorting centers, but it typically requires significant energy consumption due to the high temperatures involved.

[0005] Another approach to recycling plastic waste involves at least partially dissolving the plastic, especially thermoplastics, with the aim of purifying the plastic by removing polymers and / or impurities (such as additives, such as fillers, dyes, pigments and metals) other than one or more target polymers from the raw material.

[0006] Several studies have thus presented various methods for treating plastic waste by dissolution and purification. US 2017 / 002110 describes a specific method for purifying polymer raw materials, particularly those obtained from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, followed by contacting the resulting polymer solution with a solid.

[0007] WO 2018 / 114047, by its very nature, proposes a method for dissolving plastics in a solvent at a dissolution temperature close to the solvent's boiling point. However, the method of WO 2018 / 114047 does not make it possible to effectively treat impurities other than the polymer.

[0008] US 2018 / 0208736 discloses a treatment method that involves liquefying thermoplastics in a solvent and then separating insoluble substances and / or gases. The method in US 2018 / 0208736 does not make it possible to effectively treat impurities soluble in solvents.

[0009] This invention aims to overcome these drawbacks and participate in the recycling of plastics, especially thermoplastics. More specifically, it aims to provide a method for treating plastic raw materials, particularly those obtained from plastic waste, in order to effectively remove at least a portion of impurities, particularly additives conventionally added to plastic materials, and more specifically, impurities soluble in organic solvents, so as to upgrade plastic raw materials and, more specifically, plastic waste, having a system by separating and recovering polymers, especially thermoplastics, so that these thermoplastics can be used, for example, as a polymeric base for new plastic articles. Summary of the Invention

[0010] This invention relates to a method for processing plastic raw materials, comprising: a) A dissolution step, which involves contacting the plastic raw material with a dissolving solvent at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 MPa abs and 20.0 MPa abs to obtain at least one crude polymer solution, wherein the dissolving solvent is selected from at least one organic solvent with a boiling point between -50°C and 250°C; b) An adsorption step, wherein the crude polymer solution obtained from step a) is contacted with at least one adsorbent at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs to obtain at least one refined polymer solution; and subsequently c) Recovery step: The polymers are recovered to obtain at least one solvent fraction and a purified polymer fraction.

[0011] The advantage of the method of the present invention lies in providing a method for effectively processing raw materials containing plastics, especially plastic waste, particularly obtained from collection and sorting channels, in order to recover the contained polymers, more specifically thermoplastics, so that they can be recycled to any type of application. The method according to the invention makes it practically possible to obtain streams of purified polymers, more specifically purified thermoplastics, and particularly purified polyolefins (such as polyethylene and polypropylene), which advantageously contain negligible or at least sufficiently small impurity content for the purified polymer, more specifically purified thermoplastic stream, to replace virgin polymer resins introduced into any plastic formulation. For example, the purified polymer stream, more specifically purified thermoplastic stream, and particularly purified polyolefin stream obtained at the end of the method of the invention advantageously contains less than 5% by weight of impurities, and very advantageously less than 1% by weight of impurities.

[0012] Therefore, the method according to the invention provides a series of operations for releasing at least a portion of the impurities, particularly additives, from the plastic waste and for recovering the purified polymer, so that the plastic waste can be upgraded by recycling the purified polymer. Advantageously, depending on the conditions used in the method steps, compounds present in the plastic raw material may be soluble or insoluble in the solvent used throughout the method according to the invention, allowing for effective purification of the polymer.

[0013] Another advantage of this invention is that it enables the upgrading of plastic waste to participate in plastic recycling and conserves fossil resources. Specifically, it allows for the purification of plastic waste to obtain purified polymer fractions with reduced impurity content, particularly after decolorization and deodorization, which can then be reused to form new plastic articles. The purified polymer fractions obtained can therefore be used directly as a mixture with additives (e.g., dyes, pigments, or other polymers) in formulations to obtain plastic products with aesthetic, mechanical, or rheological properties that promote reuse and upgrading, thus replacing virgin polymer resins or as a mixture with virgin polymer resins.

[0014] This invention also makes it possible to recover the solvent used to process the plastic raw materials in the method and to purify and recycle it in the method, thus avoiding excessive consumption of solvent.

[0015] Therefore, this invention relates to the purification of plastic raw materials, especially plastic waste, to obtain polymers, particularly thermoplastic plastics, and more specifically polyolefins such as polyethylene and polypropylene, which are purified so that they can be used in any application, particularly in replacing virgin polymers. Therefore, this invention proposes a purification method by dissolving the target polymer, that is, separating and purifying it. More specifically, this invention relates to a method comprising a dissolution step, followed by at least one specific purification step, i.e., an adsorption step b), which may be combined with other intermediate purification steps as appropriate, to obtain a purified polymer solution from which the purified polymer can be recovered. Simple Explanation of the Diagram

[0016] Figure 1 illustrates an embodiment of the method of the present invention.

[0017] Figure 2 shows a variation of the implementation of the method according to the present invention as illustrated in Figure 1.

[0018] Figure 3 shows a variation of the implementation of the method according to the present invention as illustrated in Figure 2. Implementation

[0019] According to the present invention, the expressions "including... and..." and "between... and..." are equivalent and mean that the limit value of the interval is included within the described numerical range. If this is not the case and if the limit value is not included within the described range, such clarification will be provided by the present invention.

[0020] For the purposes of this invention, various ranges of parameters for a given step, such as pressure ranges and temperature ranges, can be used individually or in combination. For example, for the purposes of this invention, a preferred pressure range can be combined with a preferred temperature range.

[0021] Specific embodiments of the invention may be described below. Where technically feasible, these embodiments may be implemented separately or in combination without limitation.

[0022] According to the present invention, the pressure is absolute pressure and is given in MPa absolute (or MPa abs).

[0023] The terms "upstream" and "downstream" should be understood to vary depending on the general flow of the fluid or material being described in the method.

[0024] The term "additive" is commonly used in the polymer field, and especially in the field of polymer formulations. Additives introduced into polymer formulations may include, for example, plasticizers, fillers (which are organic or mineral solid compounds used to modify the physical, thermal, mechanical and / or electrical properties of polymer materials or to reduce their cost), reinforcing agents, dyes, pigments, curing agents, flame retardants, combustion retardants, stabilizers, antioxidants, UV absorbers, antistatic agents, etc.

[0025] The additives correspond to a portion of the impurities in the plastic raw material to be treated, and the processing method according to the invention makes it possible to at least partially remove such additives. Other types of impurities may be related impurities or plastic materials, such as metallic impurities, paper / cardboard, biomass, other polymers such as thermosetting or thermoplastic types, etc.

[0026] Therefore, according to the present invention, the method of the present invention enables the removal, at least partially, of impurities from the stream of the target polymer, comprising additives conventionally used in polymer formulations, and typically usage-related impurities obtained from the life cycle of plastic articles and materials and / or from waste collection and sorting recycling. These impurities may be metallic, organic, or mineral-type impurities; they may be packaging residues, food residues, or compostable residues (biomass). These usage-related impurities may also include glass, wood, cardboard, paper, aluminum, iron, metals, tires, rubber, polysiloxane, rigid polymers, thermosetting polymers, household, chemical, or cosmetic products, waste oil, and water.

[0027] According to the invention, the polymer solution is a solution comprising a dissolving solvent and at least one polymer, preferably a target polymer, more specifically a target thermoplastic, particularly a target polyolefin, dissolved in the dissolving solvent, the dissolved polymer initially present in the raw material. The polymer solution may also contain soluble and / or insoluble impurities. Depending on the method steps according to the invention, the polymer solution may contain impurities in the form of insoluble particles advantageously suspended in the polymer solution, soluble impurities dissolved in the dissolving solvent, and / or, as appropriate, another liquid phase immiscible with the polymer solution.

[0028] The critical temperature and critical pressure of a solvent, especially a dissolving solvent and / or an extracting solvent, are inherent to that solvent and are respectively the temperature and pressure of the solvent's critical point. As is well known to those skilled in the art, at and above the critical point, the solvent is in a supercritical form or state, and the temperature and pressure operating conditions are the supercritical conditions of the solvent; it can thus be called a supercritical fluid.

[0029] This invention relates to a method for preparing a plastic raw material, which preferably consists of plastic waste and advantageously contains a polymer, preferably a thermoplastic plastic and more specifically a polyolefin, the method comprising, and preferably comprising, the following: a) A dissolution step, which involves contacting the raw material with a solvent to obtain at least one crude polymer solution; and then... E1) The step of separating the insoluble matter to obtain at least one clear polymer solution and an insoluble fraction, as appropriate; E2) A washing step, selected as appropriate, is used to obtain at least one washing effluent and a washed polymer solution by contact with a concentrated solution; E3) An extraction step, selected as appropriate, which involves contacting an extraction solvent to obtain at least one extracted polymer solution and a waste solvent; b) The step of adsorbing such impurities by contacting them with a solid adsorbent to obtain at least one refined polymer solution; and finally c) Recovery step: The polymers are recovered to obtain at least one solvent fraction and a purified polymer fraction. [raw material]

[0030] The raw material referred to as plastic raw material according to the method of the present invention comprises, more specifically, a plastic comprising a polymer. Preferably, the plastic raw material comprises between 50% and 100% by weight, and more preferably between 70% and 100% by weight, of plastic.

[0031] The plastics included in the raw materials according to the method of the present invention are typically production waste and / or scrap, particularly household waste, construction waste, or electrical and electronic equipment waste. Preferably, the plastic waste is obtained from collection and sorting channels. Plastics or plastic materials are typically polymers mixed with additives for the purpose of forming various materials and objects (injection molded parts, tubes, films, fibers, fabrics, adhesives, coatings, etc.) after molding. The additives used in the plastics can be organic or inorganic compounds. Examples include fillers, dyes, pigments, plasticizers, property modifiers, and flame retardants.

[0032] The raw materials used in the method according to the invention therefore comprise polymers, and more particularly thermoplastic plastics. The polymers included in the plastic raw materials may be olefin polymers, diene polymers, vinyl polymers, and / or styrene polymers. Preferably, the polymers included in the plastic raw materials are polyolefins, such as polyethylene (PE), polypropylene (PP), and / or copolymers of ethylene and propylene. Most preferably, the polymers in the plastic raw materials comprise at least 80% by weight, more preferably at least 85% by weight, more preferably at least 90% by weight, and most preferably at least 94% by weight, of polyolefins relative to the total weight of the raw materials. Therefore, the method according to the invention is most specifically aimed at purifying and recovering the polyolefins contained in the raw materials so that they can be reused in various applications.

[0033] Plastic raw materials may comprise mixtures of polymers, particularly mixtures of thermoplastics and / or mixtures of thermoplastics with other polymers and impurities (particularly additives advantageously used in formulating plastic materials, and typically derived from the life cycle of materials and plastic articles and / or from use-related impurities derived from waste collection and sorting recycling). Raw materials according to the method of the invention typically contain less than 50% by weight of impurities, preferably less than 20% by weight, and more preferably less than 10% by weight of impurities.

[0034] The raw material containing plastics can be advantageously pretreated prior to the method to remove at least all or some of the "coarse" impurities, i.e., impurities in the form of particles larger than or equal to 10 mm, preferably larger than or equal to 5 mm, or even larger than or equal to 1 mm, such as impurities from wood, paper, biomass, iron, aluminum, glass, etc., and to reduce them to some form, typically a powdered solid, to facilitate processing in the method. This pretreatment may include a milling step, a washing step under atmospheric pressure, and / or a drying step. This pretreatment can be performed at different locations, such as at a waste collection and sorting center, or at the same location where the processing method according to the invention is performed. Preferably, this pretreatment makes it possible to reduce the impurity content to less than 6% by weight. At the end of the pretreatment, the raw material is typically stored in the form of a powdered solid, such as in the form of abrasive material or powder, to facilitate handling and transport in the method. [Dissolving Steps] [a)]

[0035] According to the invention, the method includes a dissolution step a), wherein the plastic raw material is contacted with a dissolving solvent at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 MPa absolute and 20.0 MPa absolute to obtain at least one, preferably a, crude polymer solution. Specifically, this step advantageously enables the dissolution of at least a portion, and preferably all, of the polymer, preferably a thermoplastic, most specifically a polyolefin, such as polyethylene and / or polypropylene.

[0036] The term "dissolution" should be understood to mean any phenomenon that results in the formation of at least one polymer solution (i.e., a liquid containing a polymer dissolved in a solvent, or more specifically, a solvent in which it is dissolved). Those skilled in the art fully understand the phenomena involved in polymer dissolution, which at least involve the mixing, dispersion, homogenization, and disentangling of polymer chains, and more specifically, thermoplastic chains.

[0037] During and at the end of dissolution step a), the pressure and temperature conditions make it possible to maintain the dissolving solvent, at least a portion and preferably all of the dissolving solvent, in liquid form, and advantageously at least a portion and preferably all of the soluble portion of the raw material, especially the target polymer, preferably the target thermoplastic and preferably the target polyolefin, and at least a portion of the impurities are dissolved.

[0038] Contacting the dissolving solvent with the plastic raw material to at least partially and preferably completely dissolve the polymer of the plastic raw material in the dissolving solvent can be performed within a line and / or article of the equipment and / or between two articles of the equipment. Therefore, step a) advantageously involves at least one article of the dissolving equipment, and, where appropriate, at least one raw material preparation device, mixing device, and / or conveying device. Such articles of the equipment and / or device can be, for example, static mixers, extruders, pumps, reactors, co-current or convection columns, or combinations of lines and equipment. Devices for conveying, especially fluids (such as gases, liquids, or solids), are well known to those skilled in the art. In a non-limiting manner, the conveying device can include compressors, pumps, extruders, vibrating tubes, infinite torsion machines, or valves. Articles of the equipment and / or device can also include heating systems (e.g., ovens, heat exchangers, insulation, etc.) or combinations thereof to achieve the conditions required for dissolution.

[0039] The dissolving step a) is advantageously fed, at least by means of one or more conveying devices, in particular in the form of one or more plastic raw material streams and in particular in the form of one or more dissolving solvent streams. The plastic raw material stream may be different from the dissolving solvent stream. Part or all of the plastic raw material may also be fed into step a) as a mixture with part or all of the dissolving solvent, solvent and / or the remainder of the raw material, where appropriate, or may be fed into step a) alone.

[0040] During the contact between the plastic raw material and the dissolving solvent, the dissolving solvent is advantageously at least partially and preferably entirely in liquid form, while the plastic raw material, comprising polymers, especially thermoplastics and particularly polyolefins, may be in solid or liquid form, including, where appropriate, solid particles contained in the suspension. Alternatively, the plastic raw material may be injected into the dissolving apparatus as a mixture with the dissolving solvent in the form of a suspension in the dissolving solvent; the preparation and injection of the suspension may be continuous or batch-wise.

[0041] Preferably, step a) includes at least one extruder and a melting device. In this case, the plastic raw material is fed into the extruder such that at least a portion, and preferably all, of the target polymer, particularly the target thermoplastic, and more specifically the polyolefin, contained in the raw material is in molten form at the extruder outlet. The plastic raw material is then injected, at least partially in molten form, into the melting device. The plastic raw material, at least partially in molten form, can also be drawn in by means of a pump specifically designed for viscous fluids (commonly referred to as a melt pump or gear pump). For the purpose of removing the coarsest particles, the plastic raw material, at least partially in molten form, may also be filtered at the extruder outlet using a filter device, in addition to the melt pump, as appropriate; typically, the sieve size of this filter is between 10 micrometers and 1 mm, preferably between 20 micrometers and 200 micrometers.

[0042] Preferably, step a) includes an extruder, wherein the dissolving solvent is advantageously injected into the extruder at several points to promote shearing and thus fine mixing between the dissolving solvent and the plastic raw material, which helps to dissolve the polymer, especially thermoplastics and more specifically polyolefins.

[0043] The dissolving solvent used in dissolving step a) is advantageously an organic solvent or, more preferably, a mixture of organic solvents. Preferably, the dissolving solvent is selected from organic solvents, and preferably comprises one or more hydrocarbons with boiling points between -50°C and 250°C, more preferably between 75°C and 250°C, more preferably between 80°C and 220°C, and most preferably between 80°C and 180°C, and preferably composed of such hydrocarbons. Preferably, the dissolving solvent comprises and is preferably composed of one or more hydrocarbons containing between 3 and 12 carbon atoms, more preferably between 6 and 12 carbon atoms, and most preferably between 6 and 10 carbon atoms, and most preferably one or more alkanes, such as cyclohexane and heptane isomers. Preferably, and most advantageously, the critical temperature of the solvent for dissolving the organic solvent (preferably a hydrocarbon) is between 90°C and 400°C, more preferably between 200°C and 390°C, and even more preferably between 250°C and 350°C, and the critical pressure is between 1.5 MPa abs and 5.0 MPa abs, more preferably between 2.0 MPa abs and 4.3 MPa abs, and even more preferably between 2.4 MPa abs and 4.2 MPa abs. According to a particular embodiment, the boiling point of the solvent is greater than 70°C, preferably between 80°C and 220°C, and / or the solvent comprises and is preferably composed of an alkane having at least 7 carbon atoms. According to another preferred embodiment, the boiling point of the solvent is below 50°C or above 150°C.

[0044] Advantageously, dissolution is performed at a dissolution temperature between 100°C and 300°C and a dissolution pressure between 1.0 MPa absolute and 20.0 MPa absolute. More specifically, the temperature and pressure evolve throughout step a) from ambient conditions (i.e., plastic raw material temperature between 10°C and 30°C and atmospheric pressure (0.1 MPa)) until dissolution conditions are met, more specifically, the dissolution temperature and dissolution pressure are met. Specifically, the dissolution temperature is between 100°C and 300°C, preferably between 150°C and 250°C, and the dissolution pressure is between 1.0 MPa abs and 20.0 MPa abs, preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. Most advantageously, at the end of dissolution step a), the flow of dissolved polymer is at the dissolution temperature and dissolution pressure.

[0045] According to a specific embodiment of dissolution step a), the dissolution pressure is between 1.5 MPa abs and 2.4 MPa abs, preferably between 1.7 MPa absolute and 2.2 MPa absolute. In this very specific embodiment, water that may be present in the plastic raw material (in the case of wet plastic raw material) can then be vaporized and removed during dissolution by degassing (e.g., from vents, particularly located in the dissolution line and / or equipment, especially on the extruder). When performing this specific embodiment of dissolution step a), the method for treating plastic raw material according to the invention does not include step E2, which may be used as appropriate, for washing with a concentrated solution, especially an aqueous solution.

[0046] Limiting the temperature in step a) to less than or equal to 300°C, preferably less than or equal to 250°C, makes it possible to prevent or limit the thermal degradation of the polymer, especially thermoplastics and more specifically polyolefins. Preferably, the dissolution temperature is greater than or equal to the melting point of the polymer, especially thermoplastics and more specifically polyolefins, to promote its dissolution. Preferably, the temperature in dissolution step a) is less than or equal to the critical temperature of the dissolving solvent to avoid the formation of a supercritical phase during dissolution step a), which readily disrupts dissolution.

[0047] Simultaneously, the dissolution pressure is greater than the saturated vapor pressure of the dissolving solvent at the dissolution temperature, so that the dissolving solvent is at least partially and preferably entirely in liquid form at the dissolution temperature. Advantageously, the dissolution pressure is greater than or equal to the critical pressure of the dissolving solvent, so that the recovery step c) can be performed, especially under conditions where at least a portion of the solvent is in a supercritical form, without significantly increasing the pressure between steps a), especially between the outlet of step a) and step c). When the dissolution pressure in step a) is greater than or equal to the critical pressure of the dissolving solvent, the dissolution temperature is less than the critical temperature of the dissolving solvent, so as to maintain the dissolving solvent at least partially in liquid form.

[0048] Advantageously, the dissolution temperature and pressure conditions achieved in step a) are adjusted so that the mixture (dissolving solvent + target polymer) is a single-phase mixture.

[0049] Preferably, the weight ratio between the plastic raw material and the solvent is between 0.01 and 5.0, more preferably between 0.05 and 3.0, and more preferably between 0.10 and 1.0.

[0050] Advantageously, the dissolution step a) is performed with a residence time between 1 minute and 600 minutes, preferably between 2 minutes and 300 minutes, and preferably between 2 minutes and 180 minutes. The residence time should be understood as the residence time at the dissolution temperature and at the dissolution pressure, that is, the time during which the plastic raw material and the dissolution solvent are disposed of in step a) at the dissolution temperature and at the dissolution pressure.

[0051] Advantageously, the dissolving solvent used in step a) comprises, and preferably consists of, freshly prepared solvent and / or recycled solvent stream obtained from step c).

[0052] Depending on the circumstances, the treatment method may include an intermediate adsorption step a'), which is located during or directly downstream of the dissolution step a), and includes introducing a powdered adsorbent solid (preferably such as alumina, silica, silica-alumina, activated carbon, or decolorizing clay) into the crude polymer solution obtained at the end of step a) or, depending on the circumstances, during the dissolution step a). The adsorbent solid may then be removed during one of the intermediate purification steps selected as appropriate, such as step E1) for separating insoluble matter and / or washing step E2) selected as appropriate. This selective adsorption step a'), performed in the presence of the powdered adsorbent solid, makes it possible to optimize the purification of the polymer solution.

[0053] The crude polymer solution obtained at the end of dissolution step a) contains at least the dissolving solvent, the purified polymer dissolved in the dissolving solvent, and especially the target polymer that the present invention seeks to recover. Generally, the crude polymer solution also contains soluble impurities dissolved in the dissolving solvent. It may also contain insoluble impurities or compounds in suspension. The crude polymer solution obtained at the end of step a) may also contain polymers other than, for example, the target polymer in molten form. [Steps to be selected depending on the situation for separating insoluble substances] [E1)]

[0054] The processing method may also include step E1), namely, separating the insoluble matter by solid-liquid separation to advantageously obtain at least one clear polymer solution and an insoluble fraction. The insoluble fraction advantageously contains at least some, and preferably all, of the insoluble impurities, particularly in the suspension from the crude polymer solution obtained from step a).

[0055] When incorporated into the method according to the invention, step E1) of separating insoluble matter is located between dissolution step a) and polymer recovery step c), and upstream or downstream of adsorption step b), preferably upstream of adsorption step b). When step E1) of separating insoluble matter, as appropriate, is located downstream of adsorption step b), adsorption step b) corresponds to intermediate adsorption step a').

[0056] Therefore, step E1) of separating insoluble matter makes it possible to remove at least a portion, and preferably all, of the particles of insoluble compounds in the dissolving solvent under the temperature and pressure conditions of step a), such particles being present in the crude polymer solution obtained from step a) or, if applicable, step a'). The insoluble impurities removed during step E1) of separating insoluble matter are, for example, pigments, mineral compounds, packaging residues (glass, wood, cardboard, paper, aluminum), and insoluble polymers.

[0057] When performed, this separation step E1) advantageously makes it possible to limit operational problems in downstream processing steps, especially such as clogging and / or erosion, while promoting the purification of plastic raw materials.

[0058] When incorporated into the method, step E1) of separating the insoluble matter is advantageously performed at a temperature between 100°C and 300°C, preferably between 150°C and 250°C, and at a pressure between 1.0 MPa abs and 20.0 MPa abs, preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. Most advantageously, step E1) of separating the insoluble matter, as appropriate, is performed at the dissolution temperature and pressure conditions, i.e., at the temperature and pressure conditions at the outlet of step a).

[0059] When incorporated into the method, step E1) for separating insoluble matter is preferably fed with a crude polymer solution obtained from step a) or, as appropriate, an intermediate adsorption step a'). According to another embodiment, step E1) may be fed with a washed polymer solution obtained from a washing step E2) as appropriate.

[0060] When incorporated into the method, step E1) advantageously includes a portion comprising at least one article having a solid-liquid separation device, such as a separation flask, decanter, centrifugal decanter, centrifuge, filter, sand filter, eddy current separator, electrostatic separator, triboelectric separator, preferably a decanter, filter, sand filter and / or electrostatic separator.

[0061] The removal of insoluble portions, which may be present in the insoluble portion, can be facilitated by equipment used for conveying and / or removing trace amounts of solvent (e.g., conveyors, vibrating tubes, infinite twisting machines, extruders, or strippers). Step E1) may therefore include equipment for conveying and / or removing trace amounts of solvent to remove the insoluble portion.

[0062] According to one specific embodiment of step E1), which may be selected as appropriate, step E1) for separating insoluble matter includes at least two, and typically fewer than five, articles having solid-liquid separation devices connected in series and / or parallel. The presence of at least two articles with solid-liquid separation devices connected in series makes it possible to improve the removal of insoluble matter, while the presence of devices connected in parallel makes it possible to manage the maintenance of the devices and / or clear blockage operations.

[0063] Conventionally, some insoluble compounds, particularly pigments and mineral fillers, added during polymer formulation can be introduced in the form of particles smaller than 1 µm. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. According to one specific embodiment of step E1), which may be selected as appropriate, step E1) advantageously includes an electrostatic separator, which makes it possible to effectively remove at least some, preferably all, of the insoluble particles smaller than 1 µm. According to another specific embodiment of step E1), which may be selected as appropriate, step E1) includes a sand filter to remove particles of different sizes, particularly particles smaller than 1 µm.

[0064] Depending on the properties of the raw materials, the polymer solution fed into step E1), preferably the crude polymer solution, may also include, for example, a second liquid phase composed of molten polymer. According to another particular embodiment of step E1), whichever is chosen as appropriate, step E1) advantageously includes equipment for separating this second liquid phase, preferably by means of at least one three-phase separator. [Washing steps to be selected as needed] [E2)]

[0065] The processing method may also include, depending on the circumstances, washing with a concentrated solution to advantageously obtain at least one wash effluent and a washed polymer solution (step E2). The washed polymer solution obtained at the end of step E2 (optionally selected) advantageously contains the purified target polymer, dissolved in a dissolving solvent, which the invention seeks to recover. Depending on the circumstances, if step E2 is performed, it may also contain residual impurities, particularly soluble in the dissolving solvent, and / or, depending on the circumstances, trace amounts of the washing solvent.

[0066] When incorporated into the method according to the invention, the washing step E2) is located between the dissolution step a) and the polymer recovery step c), and upstream or downstream of the adsorption step b), preferably upstream of the adsorption step b). When the washing step E2) is selected as appropriate and located downstream of the adsorption step b), the adsorption step b) corresponds to the intermediate adsorption step a'). The washing step E2) may be incorporated upstream or downstream of the step E1) selected as appropriate for separating insoluble matter, preferably downstream.

[0067] When incorporated into the method, washing step E2) is fed with a concentrated solution and a crude polymer solution obtained from step a) or, as appropriate, from an intermediate adsorption step a'), or a clarified polymer solution obtained from step E1), as appropriate. The polymer solution fed into washing step E2), especially the crude or clarified polymer solution, may contain impurities in the form of insoluble compounds in suspension and / or dissolved compounds. These compounds can be partially or completely removed from the suspension or dissolved compounds during washing step E2) by dissolution or precipitation and / or by entrainment in the concentrated solution. Therefore, when performed, step E2) facilitates the treatment of plastic raw materials and, more specifically, the purification of the polymer solution.

[0068] The washing step E2), selected as appropriate, advantageously involves contacting the crude or clarified polymer solution fed into step E2) with a concentrated solution. Advantageously, the concentrated solution has a higher density than the polymer solution (i.e., a mixture containing at least the target polymer and a solvent for dissolving the target polymer), specifically greater than or equal to 0.85, preferably greater than or equal to 0.9, and preferably greater than or equal to 1.0. The concentrated solution may be an aqueous solution, preferably containing at least 50% by weight of water, preferably at least 75% by weight of water, and most preferably at least 90% by weight of water. The pH of the aqueous solution may be adjusted using an acid or base to promote the dissolution of some compounds. The concentrated solution may also be a solution comprising, preferably, the following organic solvents: preferably having a density greater than or equal to 0.85, preferably greater than or equal to 0.9, preferably greater than or equal to 1.0, and wherein the polymer of the plastic raw material remains insoluble therein under the temperature and pressure conditions of step E2) as selected as appropriate, such as an organic solvent selected from cyclobutane or N-methylpyrrolidone (NMP), as a mixture with water as appropriate. Preferably, the concentrated solution is an aqueous solution, preferably containing at least 50% by weight of water, preferably at least 75% by weight of water, and most preferably at least 90% by weight of water.

[0069] The washing step E2), selected as appropriate, is advantageously performed at a temperature between 100°C and 300°C, more preferably between 150°C and 250°C, and at a pressure between 1.0 MPa abs and 20.0 MPa abs, more preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. It is highly advantageous that the washing step E2), selected as appropriate, is performed at a dissolution temperature and dissolution pressure.

[0070] In the washing step E2), when incorporated into the method, the mass ratio between the mass flow rate of the concentrated solution fed into step E2) and the mass flow rate of the crude or clarified polymer solution is advantageously between 0.05 and 20.0, more preferably between 0.1 and 10.0, and even more preferably between 0.5 and 3.0. Contact between the crude or clarified polymer solution and the concentrated solution can be performed at several points in the equipment used, i.e., by repeatedly injecting the crude or clarified polymer solution and / or the concentrated solution at different points along the equipment; this is thus the sum of the injected flow rates taken into account when calculating the ratio.

[0071] Step E2, as appropriate, may be performed in one or more articles of washing equipment that allow contact with the concentrated solution and / or separation equipment, thereby making it possible to recover at least one washing effluent and a washed polymer solution. Such equipment is well-known, such as stirred reactors, static mixers, decanters, two-phase or three-phase separation flasks, co-current or convection washing columns, plate columns, stirred columns, packed columns, pulsed columns, etc., and each type of equipment may include one or more articles of equipment used alone or in combination with another type of equipment.

[0072] According to a preferred embodiment, the washing step E2, selected as appropriate, is performed in a convection washing column, wherein a concentrated solution is preferably injected into the column to the nearest half, preferably one-third, of the column, and a coarse or clarified polymer solution is injected into the column to the nearest half, preferably one-third, of the column. According to this embodiment, it is possible to recover at least one washed polymer solution and a washing effluent.

[0073] According to a specific embodiment, the material flow at the inlet and / or outlet of the washing column can be formed into powder and injected at several injection points along the column, and / or extracted at several extraction points along the column.

[0074] According to another embodiment, the washing step E2) is performed in a mixing decanter containing a stirring mixing zone to contact the concentrated solution with the crude or clarified polymer solution, and is performed in a decanting zone, thereby making it possible to recover the washed polymer solution and the washing effluent.

[0075] At the end of washing step E2), the obtained washing effluent advantageously contains compounds dissolved in the concentrated solvent and / or insoluble compounds entrained in the washing effluent. The washing effluent may be further processed in a washing treatment section to, on the one hand, at least partially separate the dissolved and / or entrained compounds and, where appropriate, purify the washing effluent to obtain a purified concentrated solution, and on the other hand, at least partially recycle a portion of the purified washing solution. This washing treatment section may include one or more items of equipment well known for solid-liquid separation, such as separation flasks, decanters, centrifugal decanters, centrifuges, or filters. The washing effluent may also be sent outside the method, for example, to a wastewater treatment plant if the concentrated solution is an aqueous solution. [Extraction steps to be selected depending on the situation] [E3)]

[0076] The method according to the invention may include step E3) of extraction by contacting an extraction solvent to obtain at least one extracted polymer solution and a waste solvent, particularly containing impurities. The extracted polymer solution obtained at the end of step E3) advantageously contains the purified target polymer dissolved in the dissolving solvent, which the invention seeks to recover. Depending on the circumstances, if steps E2) and / or E3) are performed, it may contain residual impurities, particularly soluble in the dissolving solvent, and / or trace amounts of washing solvent and / or extraction solvent.

[0077] When incorporated into the method according to the invention, the extraction step E3) is advantageously located between the dissolution step a) and the polymer recovery step c), and upstream or downstream of the adsorption step b).

[0078] The extraction step E3), selected as appropriate, is advantageously fed with an extraction solvent and a polymer solution, particularly the crude polymer solution obtained from step a), the clarified polymer solution obtained from step E1, the washed polymer solution obtained from step E2, or the purified polymer solution obtained from the self-adsorption step b). Preferably, the extraction step E3 is fed with an extraction solvent and the clarified polymer solution obtained from step E1, the washed polymer solution obtained from step E2, or the purified extraction polymer solution obtained from the self-adsorption step b). The polymer solution, preferably the clarified polymer solution, the washed polymer solution, or the purified polymer solution fed into step E3 may therefore contain dissolved compounds or dissolved impurities, depending on the circumstances. These dissolved compounds may be partially or completely removed during the extraction step E3 by contact with the extraction solvent. Advantageously, the combination of adsorption step b) and extraction step E3) allows for improved purification of the polymer solution by utilizing the affinity of impurities for the adsorbent and extraction solvent.

[0079] When incorporated into the method according to the invention, extraction step E3) advantageously involves at least one extraction section, preferably between one and five extraction sections, and most preferably one extraction section. Extraction step E3) selected as appropriate is preferably performed at a temperature between 100°C and 300°C, preferably between 150°C and 250°C. Extraction step E3) selected as appropriate is preferably performed at a pressure between 1.0 MPa abs and 20.0 MPa abs, preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. According to one preferred embodiment of extraction step E3) selected as appropriate, extraction step E3) is performed at temperature and pressure conditions different from those of step a).

[0080] The mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution (preferably a clarified polymer solution, a washed polymer solution, or a refined polymer solution) fed into step E3) is advantageously between 0.05 and 20.0, more preferably between 0.1 and 10.0, and even more preferably between 0.2 and 5.0. Contact between the polymer solution (preferably a clarified polymer solution, a washed polymer solution, or a refined polymer solution) fed into step E3) and the extraction solvent can be performed at several points in the extraction section, i.e., by repeatedly injecting the polymer solution and / or the extraction solvent at different points along the extraction section; this is thus the sum of the injected flow rates taken into account when calculating the ratio.

[0081] The extraction solvent used in extraction step E3) is advantageously an organic solvent or, more preferably, a mixture of organic solvents. Preferably, the solvent is selected from organic solvents, and preferably comprises one or more hydrocarbons with boiling points between -50°C and 250°C, more preferably between 75°C and 250°C, more preferably between 80°C and 220°C, and most preferably between 80°C and 180°C. Preferably, the extraction solvent comprises, and more preferably comprises, one or more hydrocarbons containing between 3 and 12 carbon atoms, more preferably between 6 and 12 carbon atoms, and most preferably between 6 and 10 carbon atoms, preferably one or more alkanes, such as cyclohexane and heptane isomers. Preferably, and most advantageously, the critical temperature of the extraction solvent (preferably a hydrocarbon) is between 90°C and 400°C, more preferably between 200°C and 390°C, and even more preferably between 250°C and 350°C, and the critical pressure of the extraction solvent is between 1.5 MPa abs and 5.0 MPa abs, more preferably between 2.0 MPa abs and 4.3 MPa abs, and even more preferably between 2.4 MPa abs and 4.2 MPa abs. According to a particular embodiment, the boiling point of the extraction solvent is greater than 70°C, preferably between 80°C and 220°C, and / or the solvent contains at least 7 carbon atoms. According to another preferred embodiment, the boiling point of the extraction solvent is lower than 50°C or higher than 150°C.

[0082] Ideally, the extraction solvent used in step E3) is selected as the same solvent as the dissolving solvent used in step a), but in a different physical state (e.g., supercritical relative to the liquid dissolving solvent), to facilitate solvent management, and particularly to facilitate its purification and, especially, its recycling to dissolution step a) and, if applicable, to extraction step E3). In addition to facilitating the management of the solvents involved in the method according to the invention, another advantage of using the same dissolving and extraction solvents in the same or different physical states is, in particular, the recovery, treatment, and recycling of the solvents to at least one of the steps of the method, and the limitation of energy consumption and costs, especially by means of solvent treatment and purification.

[0083] The extraction section of step E3, as appropriate, may include one or more extraction devices that allow contact with the extraction solvent and / or with separation equipment used to recover at least one waste solvent (especially containing impurities) and the extracted polymer solution. This equipment is well-known, such as stirred reactors, static mixers, decanters, two-phase or three-phase separation flasks, co-current or convection washing columns, plate columns, stirred columns, packed columns, pulsed columns, etc. Each type of equipment may include one or more items used alone or in combination with another type of equipment.

[0084] According to one preferred embodiment of step E3), whichever is chosen as appropriate, the extraction is performed in a convection extraction column, wherein the extraction solvent is injected on one side and the polymer solution fed into step E3) is injected on the other. According to this embodiment, it is possible to recover at least one extracted polymer solution on one side and waste solvent, particularly that containing impurities, on the other. Preferably, the polymer solution fed into step E3), preferably a clarified, washed, or purified polymer solution, is injected into the half, preferably one-third, closest to the top of the convection extraction column, while the extraction solvent is injected into the half, preferably one-third, closest to the bottom of the convection extraction column.

[0085] The material flow at the inlet and / or outlet of the convection extraction column can be powdered at several injection and / or extraction points along the column.

[0086] According to another embodiment of step E3), which may be selected as appropriate, the extraction is performed in a mixer-decanter, which advantageously includes a stirring mixing zone for contacting the extraction solvent with the polymer solution fed into step E3), preferably a clarified, washed or purified polymer solution, and a decanting zone that makes it possible to recover the extracted polymer solution on the one hand and the waste solvent on the other.

[0087] According to one preferred embodiment of step E3) selected as appropriate, the extraction step E3) involves a liquid / liquid extraction section. In this embodiment, the extraction solvent is preferably selected from pentane, hexane, and heptane isomers, more preferably from pentane and hexane isomers, and most preferably from pentane isomers. Preferably, the liquid / liquid extraction section is operated at a temperature between 100°C and 300°C, more preferably between 150°C and 250°C, and at a pressure between 1.0 MPa abs and 20.0 MPa abs, more preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. In any case, in this embodiment, the temperature and pressure conditions are adjusted so that the extraction solvent is in liquid form, and the dissolving solvent itself is also preferably in liquid form. Advantageously, especially when the extraction solvent and the dissolution solvent are the same, liquid / liquid extraction is performed at temperature and pressure conditions different from the dissolution conditions achieved in step a), especially at temperatures above the dissolution temperature and / or at pressures below the dissolution pressure, thus placing it in the biphase region of the corresponding polymer-solvent mixture diagram.

[0088] According to another preferred embodiment of step E3), which may be selected as appropriate, the extraction step E3) includes a portion for extraction under specific temperature and pressure conditions, wherein the extraction solvent is advantageously at least partially in a supercritical form. Such extraction can be referred to as supercritical extraction. In this embodiment, extraction is performed by placing the polymer solution, preferably clarified, washed, or purified, into contact with the extraction solvent at temperature and pressure conditions that make it possible to obtain a supercritical phase consisting primarily of the extraction solvent (i.e., preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight). In other words, in this embodiment, extraction is performed by contacting the polymer solution, preferably clarified, washed, or purified, with an extraction solvent that is at least partially, preferably entirely, in a supercritical form. Such a supercritical extraction step E3) advantageously allows for efficient purification of the polymer solution, particularly due to the extremely high affinity of organic impurities (e.g., some additives, particularly some dyes, plasticizers, etc.) for the supercritical phase. Using an extraction solvent in supercritical form also makes it possible to create a substantial density difference between the supercritical phase and the polymer solution in liquid form, which promotes separation by decantation between the supercritical and liquid phases, and thus helps to purify the polymer solution.

[0089] In this particularly preferred embodiment, the extraction step E3) selected as appropriate uses an extraction solvent with a critical temperature preferably between 200°C and 390°C and more preferably between 250°C and 350°C, and a critical pressure preferably between 2.0 MPa abs and 4.3 MPa abs and more preferably between 2.4 MPa abs and 4.2 MPa abs. Advantageously, in such supercritical extraction steps E3), the extraction solvent is selected from hydrocarbons preferably containing between 4 and 8 carbon atoms, and more preferably between 5 and 7 carbon atoms. The extraction solvent used for supercritical extraction can be, for example, a pentane isomer, a hexane isomer, a heptane isomer, or cyclopentane, cyclohexane, or methylcyclopentane.

[0090] Advantageously, the supercritical extraction step E3, selected as appropriate, is performed at a temperature preferably between 150°C and 300°C, preferably between 180°C and 280°C, and at a pressure preferably between 2.0 MPa abs and 20.0 MPa abs, preferably between 2.0 MPa abs and 15.0 MPa abs, and most preferably between 3.0 MPa abs and 10.0 MPa abs. In any case, in this embodiment, the temperature and pressure conditions are adjusted, particularly in the adjustment section upstream of the extraction section included in the extraction step E3), such that the extraction solvent is at least partially in a supercritical form in the extraction section.

[0091] In one of the preferred embodiments of step E3), which is selected as appropriate, the extraction step E3) involves supercritical extraction, except that the extraction solvent is at least partially in the supercritical phase, and the extraction solvent is the same as the dissolving solvent. In this highly advantageous case of supercritical extraction, the dissolving solvent can become at least partially in a supercritical form, advantageously optimizing the decanting between the liquid phase and the supercritical phase during the extraction step, more specifically at each extraction stage or stationary stage, thereby making it possible to maximize purification.

[0092] Advantageously, at the end of extraction step E3), the resulting waste solvent contains particularly impurities. These impurities can be further processed in the organic treatment section, making it possible, on the one hand, to at least partially separate the impurities and purify the solvent to obtain purified extraction solvent, and on the other hand, to recycle at least a portion of the purified extraction solvent to the inlet of extraction step E3), and / or to the inlet of dissolution step a), provided the dissolving solvent is the same as the extraction solvent. The waste solvent can be treated by any method known to those skilled in the art, such as one or more of distillation, evaporation, extraction, adsorption, crystallization, and precipitation of insoluble matter, or by rinsing. [Adsorption Step] [b)]

[0093] The processing method according to the invention includes an adsorption step b) to obtain at least one purified polymer solution. The purified polymer solution obtained at the end of step b) advantageously contains the target polymer, purified and dissolved in a solvent, which the invention seeks to recover.

[0094] The adsorption step b) is advantageously performed downstream of the dissolution step a) and upstream of the polymer recovery step c). The adsorption step b) is preferably performed upstream or downstream of an additional purification step. For example, it may be performed upstream of steps E1) and / or E2), and particularly corresponding to an intermediate adsorption step a'), if applicable. It may also be performed, for example, upstream or downstream of an extraction step E3), if applicable. Thus, the adsorption step b) is performed by contacting the polymer solution fed into step b), particularly a crude polymer solution obtained from step a), a clarified polymer solution obtained from step E1), a washed polymer solution obtained from step E2), or an extracted polymer solution obtained from step E3), with one or more adsorbents.

[0095] The adsorption step b) advantageously includes an adsorption section operating in the presence of at least one adsorbent, preferably a solid, and particularly in the form of a fixed bed, an entrained bed (or slurry, i.e., introduced into the stream in the form of particles to be purified and entrained in the stream), or a fluidized bed, preferably a fixed bed or an entrained bed. The adsorbent used in step b) is preferably alumina, silica, silica-alumina, activated carbon, decolorizing clay, or a mixture thereof, preferably activated carbon, decolorizing clay, or a mixture thereof, preferably in the form of a fixed bed or an entrained bed, and the circulation of the stream may be upward or downward.

[0096] Advantageously, the adsorption step b) is performed at a temperature between 100°C and 300°C, preferably between 150°C and 250°C, and at a pressure between 1.0 MPa abs and 20.0 MPa abs, preferably between 1.5 MPa abs and 15.0 MPa abs, and most preferably between 2.0 MPa abs and 10.0 MPa abs. Most advantageously, the adsorption step b) is performed at the dissolution temperature and pressure conditions, i.e., at the dissolution temperature and pressure achieved in step a). Preferably, in step b), the space velocity (or HSV) corresponding to the ratio between the volumetric flow rate of the polymer solution fed into step b) and the volume of the adsorbent is between 0.05 and 10 h⁻¹, preferably between 0.1 and 5.0 h⁻¹.

[0097] According to a specific embodiment of step b), the adsorption section may comprise one or more fixed beds of adsorbent, for example, in the form of adsorption columns containing the adsorbent, preferably at least two adsorption columns, preferably between two and four adsorption columns. When the adsorption section comprises two adsorption columns, one operating mode may be, according to the technical terminology, a "swing" operator, where one column is online, i.e., in use, while the other column is in reserve. When the adsorbent in the online column is depleted, this column is isolated, leaving the reserve column online, i.e., in use. The depleted adsorbent can then be regenerated in situ and / or replaced with fresh adsorbent, so that the column containing the adsorbent can be online again once the other column is isolated.

[0098] Another functional mode of this particular embodiment, including step b) which involves one or more fixed beds of adsorbent, is to have at least two columns operating in series. When the adsorbent in the first column is depleted, this first column is isolated, and the depleted adsorbent is regenerated in situ or replaced with fresh adsorbent. The last column is then brought back online, and so on. This mode of operation is referred to as a switchable mode or a switchable reactor system PRS, or, according to the specific terminology, "lead and lag." The combination of at least two adsorption columns makes it possible to address the potential for rapid adsorbent poisoning and / or clogging (attributable to the combined effects of impurities, contaminants, and insoluble substances that may be present in the feed stream). The reason for this is that the presence of at least two adsorption columns facilitates adsorbent replacement and / or regeneration, advantageously without requiring the method to be stopped, and also makes it possible to control costs and limit adsorbent consumption.

[0099] According to a specific embodiment of the adsorption step b) in the fixed bed of adsorbent, step b) is preferably performed downstream of step E1) and / or washing step E2) (optionally selected for the separation of insoluble matter) and upstream or downstream of extraction step E3) (optionally selected for the extraction). Advantageously, the combination of step E1) and / or washing step E2) for the separation of insoluble matter with extraction step E3) and adsorption step b) allows for improved purification of the polymer solution by utilizing the affinity of residual impurities for the adsorbed solid, as well as the extraction solvent and, if applicable, concentrated solution.

[0100] According to another embodiment, the adsorption portion of step b) involves adding adsorbent particles to the polymer solution, particularly a crude polymer solution, which may be separated from the polymer solution by removing the adsorbent particles located downstream of the adsorption portion. Removal of the adsorbent particles may then advantageously correspond to step E1) or washing step E2) for separating insoluble matter. Such implementation of adsorption step b) advantageously corresponds to the intermediate adsorption step a' (selected as appropriate) previously described in the description of the invention, by introducing adsorbent particles followed by solid / liquid separation. [Steps for recycling polymers] [c)]

[0101] According to the present invention, the method includes step c) recovering the polymer to obtain at least one solvent fraction and a purified polymer fraction.

[0102] Polymer recovery step c) advantageously includes at least one solvent recovery section, preferably between one and five solvent recovery sections. Polymer recovery step c) feeds in a purified polymer melt solution or, as appropriate, an extracted polymer solution.

[0103] Polymer recovery step c) therefore first at least partially, preferably primarily, separates the solvent contained in the polymer solution fed into step c), especially the dissolving solvent, i.e., the purified polymer solution or, if applicable, the extracted polymer solution, so as to at least partially, preferably primarily, and preferably entirely recover the polymer, which is free from the dissolving solvent and other solvents, such as the extraction solvent, that may still be present in the polymer solution fed into step c). The term "primarily" should be understood to mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and most preferably at least 95% by weight of the solvent contained in the polymer solution fed into step c), especially the dissolving solvent and, if applicable, the extraction solvent, or, if applicable, the extracted polymer solution fed into step c). Any method known to those skilled in the art for separating solvent from polymers can be performed, particularly any method that enables phase change of the polymer or solvent. The solvent can be separated, for example, by evaporation, stripping, backmixing, density difference, and especially decantation or centrifugation.

[0104] The obtained purified polymer fraction may correspond to a concentrated polymer solution or a solid purified polymer. Preferably, polymer recovery step c) also includes a conditioning step for conditioning the polymer in solid form, and more specifically, in solid particulate form.

[0105] Polymer recovery step c) is also intended to at least partially, preferably substantially and preferably completely recover the solvent contained in the purified polymer solution or, as appropriate, the extracted polymer solution fed into step c), and in particular the dissolving solvent and, as appropriate, the extraction solvent. Polymer recovery step c) is also intended, as appropriate, to purify and recycle, particularly upstream of dissolving step a) and, as appropriate, upstream of extraction step E3). The term "substantially" should be understood to mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and most preferably at least 95% by weight of the solvent contained in the purified polymer solution or, as appropriate, the extracted polymer solution fed into step c).

[0106] The polymer recovery step c) advantageously includes at least one solvent recovery section at a temperature between 0°C and 350°C, preferably between 5°C and 300°C, and preferably between 10°C and 250°C, and at a pressure between 0.1 MPa abs and 20.0 MPa abs, preferably between 0.1 MPa abs and 15.0 MPa abs, and most preferably between 0.1 MPa abs and 10.0 MPa abs.

[0107] Advantageously, for the purpose of obtaining at least one solvent fraction and a purified polymer fraction, polymer recovery step c) includes at least one solvent recovery section, each solvent recovery section preferably contained in equipment operating at different temperatures and pressures. When several different solvents are used in the processing method according to the invention, particularly in dissolution step a) and, if appropriate, extraction step E3), step c) may include several solvent recovery sections, such as two, three, or four solvent recovery sections, to recover the various solvents individually, sequentially, and / or continuously, particularly the dissolution solvent and, if appropriate, the extraction solvent.

[0108] According to a specific embodiment of the present invention, the method of the present invention comprises, advantageously, continuous or simultaneous: - Solvent recovery section (c1), during which the polymer solution is preferably heated to a temperature above the polymer melting point to obtain the solvent portion and the purified polymer portion. - Adjustment section c2), during which the purified polymer fraction separated from the solvent is advantageously cooled to a temperature below the polymer melting point to obtain a fraction comprising the polymer in solid form.

[0109] According to a preferred embodiment of the invention, step c) includes recovering the solvent from step c) under temperature and pressure conditions adjusted to be in supercritical conditions (i.e., above the critical point) (especially above the critical point of the dissolving solvent) of the solvent to be separated, thereby advantageously making it possible to easily separate and recover at least a portion of the solvent. In this embodiment, the solvent recovery portion particularly includes a fluid system consisting of a supercritical phase mainly containing the solvent, especially the dissolving solvent, and a liquid phase containing the polymer. The term "mainly" herein means at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and most preferably at least 95% by weight relative to the weight of the feed stream under consideration (i.e., the supercritical phase feed stream). The separation can thus be referred to as supercritical separation of one or more solvents. Supercritical separation of solvents makes it possible to effectively separate the solvent, especially the dissolving solvent, on the one hand, and to effectively separate the polymer or, as appropriate, a concentrated polymer solution on the other hand, which is advantageously permitted by the significant density difference between the two phases. Furthermore, compared to the simple vaporization of solvents, supercritical separation of solvents can significantly reduce energy and environmental costs because there is no latent heat of vaporization during the transition to the supercritical state.

[0110] According to a specific embodiment of the present invention, at least a portion of the purified polymer fraction obtained at the end of step c) can be recycled to the dissolution step a) to undergo another processing cycle in order to improve the polymer purification efficiency.

[0111] Advantageously, the solvent portion recovered at the end of step c) can be treated in the organic treatment section located at the end of step c) to purify it and obtain a purified solvent, especially a purified dissolving solvent, so that it can be advantageously recycled to the dissolving step a) and / or, if appropriate, to the extraction step E3) selected as appropriate. This organic treatment section at the end of step c) can be performed using any method known to those skilled in the art, such as one or more of distillation, evaporation, liquid-liquid extraction, adsorption, crystallization, and precipitation of insoluble matter, or by rinsing.

[0112] Therefore, the method according to the invention makes it possible to obtain purified streams of polymers, particularly thermoplastics and more specifically polyolefins, from plastic waste, which can be used in any application, for example, to replace the same polymer in its virgin form. The purified stream of polymer obtained by the method according to the invention, i.e., the purified polymer portion, therefore has a sufficiently low impurity content to be usable in any application.

[0113] According to a preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E1): Separate the insoluble matter fed in with the crude polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step b): Adsorption is performed by contacting the clarified polymer solution with the adsorbent, preferably in a fixed bed, to obtain at least one purified polymer solution; and - Step c): Recovering polymer from self-purified polymer solution, preferably including supercritical solvent separation to obtain solvent fraction and purified polymer fraction.

[0114] According to another preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E1): Separate the insoluble matter fed in with the crude polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step b): Adsorption is performed by contacting the clarified polymer solution with the adsorbent, preferably in a fixed bed, to obtain at least one refined polymer solution; - Step E3): Extract the refined polymer solution with an extraction solvent, preferably including supercritical extraction, to obtain at least one extracted polymer solution and a waste solvent; and - Step c): Recovering the polymer from the extracted polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain a solvent fraction and a purified polymer fraction; The dissolving solvent and the extraction solvent are preferably the same.

[0115] According to a preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E1): Separate the insoluble matter fed in with the crude polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step E3): Extract the clarified polymer solution with an extraction solvent, preferably including supercritical extraction, to obtain at least one extracted polymer solution and a waste solvent; - Step b): Adsorption is performed by contacting the extracted polymer solution with an adsorbent, preferably in a fixed bed, to obtain at least one purified polymer solution; and - Step c): Recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain a solvent fraction and a purified polymer fraction; The dissolving solvent and the extraction solvent are preferably the same.

[0116] According to another preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E1): Separate the insoluble matter fed in with the crude polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step E2): Washing the clarified polymer solution by contacting it with a concentrated solution to obtain at least one wash effluent and a washed polymer solution; - Step E3): Extract the washed polymer solution with an extraction solvent, preferably including supercritical extraction, to obtain at least one extracted polymer solution and a waste solvent; - Step b): Adsorption is performed by contacting the extracted polymer solution with an adsorbent, preferably in a fixed bed, to obtain at least one purified polymer solution; and - Step c): Recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain a solvent fraction and a purified polymer fraction; The dissolving solvent and the extraction solvent are preferably the same.

[0117] According to another preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E1): Separate the insoluble matter fed in with the crude polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step E2): Washing the clarified polymer solution by contacting it with a concentrated solution to obtain at least one wash effluent and a washed polymer solution; - Step b): Adsorption is performed by contacting the washed polymer solution with the adsorbent, preferably in a fixed bed, to obtain at least one purified polymer solution; - Step E3): Extract the refined polymer solution with an extraction solvent, preferably including supercritical extraction, to obtain at least one extracted polymer solution and a waste solvent; and - Step c): Recovering the polymer from the extracted polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain a solvent fraction and a purified polymer fraction; The dissolving solvent and the extraction solvent are preferably the same.

[0118] According to another preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E2): Washing the crude polymer solution by contacting it with a concentrated solution to obtain at least one wash effluent and a washed polymer solution; - Step b): Adsorption is performed by contacting the washed polymer solution with the adsorbent, preferably in a fixed bed, to obtain at least one purified polymer solution; and - Step c): Recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain the solvent portion and the purified polymer portion.

[0119] According to another preferred embodiment of the present invention, a method for processing plastic raw materials comprises, and preferably consists of, the following: - Step a): Dissolve in a solvent having a preferred boiling point between 75°C and 220°C to obtain at least one crude polymer solution; - Step E2): Washing the crude polymer solution by contacting it with a concentrated solution to obtain at least one wash effluent and a washed polymer solution; - Step E1): Separate the insoluble matter fed in with the washed polymer solution to obtain at least one clear polymer solution and an insoluble fraction; - Step b): Adsorption is performed by contacting the clarified polymer solution with the adsorbent, preferably in a fixed bed, to obtain at least one refined polymer solution; - Step E3): Extract the refined polymer solution with an extraction solvent, preferably including supercritical extraction, to obtain at least one extracted polymer solution and a waste solvent; and - Step c): Recovering the polymer from the extracted polymer solution obtained in step b), preferably including supercritical solvent separation, to obtain a solvent fraction and a purified polymer fraction; The dissolving solvent and the extraction solvent are preferably the same.

[0120] The following examples and figures illustrate the present invention, especially specific embodiments thereof, but do not limit its scope. List of diagrams

[0121] The information regarding the elements mentioned in Figures 1 to 3 enables a better understanding of the invention, but the invention is not limited to the specific embodiments illustrated in Figures 1 to 3. The various embodiments presented can be used alone or in combination with each other without limitation.

[0122] Figure 1 illustrates an embodiment of the method of the present invention, which includes: - Step a): Dissolve the plastic raw material 1 containing the polymer in the solvent 2 to obtain a crude polymer solution 3; - Step b): Adsorption is carried out by contacting the crude polymer solution 3 with the adsorbent to obtain the refined polymer solution 12; - Step c): Recover the polymer from the purified polymer solution 12 obtained in step b) to obtain solvent portion 13 and purified polymer portion 14.

[0123] Figure 2 is a variation of the method according to the present invention shown in Figure 1, which includes: - Step a): Dissolve the plastic raw material 1 containing the polymer in the solvent 2 to obtain a crude polymer solution 3; - Step E1): Separate the insoluble matter fed in with the crude polymer solution 3 to obtain a clear polymer solution 5 and an insoluble portion 4; - Step E2): Wash the clarified polymer solution 5 by contacting it with the concentrated solution 6 to obtain the wash effluent 7 and the washed polymer solution 8; - Step E3): Extract the washed polymer solution 8 with extraction solvent 9 to obtain the extracted polymer solution 11 and waste solvent 10; - Step b): Adsorption is carried out by contacting the extracted polymer solution 11 with the adsorbent to obtain a purified polymer solution 12; - Step c): Recover the polymer from the purified polymer solution 12 obtained in step E3) to obtain solvent portion 13 and purified polymer portion 14.

[0124] Figure 3 shows a variation of the implementation of the method according to the present invention illustrated in Figure 2. In the embodiment shown in Figure 3, the method includes an intermediate step a') between step a) and step E1). For the purpose of obtaining an adsorbent included in the suspension and feeding it into the polymer solution 21 of separation step E1), the crude polymer solution 3 is contacted with the adsorbent in powdered solid form. The adsorbent previously introduced in step a') is then separated and removed in the insoluble portion 4.

[0125] Figures 1 through 3 only show the main steps using the primary material flow to allow for a better understanding of the invention. It should be understood that even without these illustrations, all the equipment required for operation (containers, pumps, exchangers, furnaces, tubing, etc.) is present. [Example] [Example] [1] [(] [According to the present invention] [)]

[0126] 125 ml of n-heptane and 23 g of polyethylene-based plastic raw material in the form of a blue abrasive material smaller than 5 mm in size were introduced into a 500 ml autoclave equipped with a stirrer. 30 g of activated carbon (Chemviron CPG-LF 12x40) was placed in a basket above the liquid level.

[0127] The autoclave was then sealed and heated at 160°C with stirring at a rate of 2°C per minute and 500 rpm. Once the temperature of 160°C was reached, it was maintained at an autogenous pressure of 2.0 MPa abs for 3 hours with stirring. After 3 hours, all the polyethylene was dissolved in n-heptane. During this stage, the resulting crude polymer solution did not come into contact with the basket containing activated carbon, as the basket was positioned above the liquid. The crude polymer solution was observed to be blue through the autoclave's inspection port.

[0128] The basket containing activated carbon was then immersed in the liquid, bringing the crude polymer solution into contact with the activated carbon. The temperature was maintained at 160°C, the pressure at 2.0 MPa abs, and the mixture was stirred at 500 rpm. These temperature, pressure, and stirring conditions were then maintained for 2 hours, after which stirring was stopped.

[0129] The purified polymer solution, as observed through the inspection port of the autoclave, showed a significant decolorization compared to the crude polymer solution, demonstrating the effectiveness of activated carbon as an adsorbent in decolorizing the n-heptane-based polymer solution.

[0130] Take 15 ml of the purified polymer solution and place it in a crystallization dish. Then place the crystallization dish in an oven at 180°C and atmospheric pressure, and rinse it with nitrogen for 6 hours.

[0131] Next, a white solid with a very light blue tint was obtained from the crystallization disk. [Example] [2 () [Not based on the present invention] [)]

[0132] 125 ml of n-heptane and 23 g of blue, ground polyethylene raw material in the form of 5 mm diameter abrasive beads were introduced into a 500 ml autoclave equipped with a stirrer.

[0133] The autoclave was then sealed and heated at 160°C with stirring at a rate of 2°C per minute and 500 rpm. Once the temperature of 160°C was reached, the temperature was maintained at an autogenous pressure of 2.0 MPa abs for 3 hours with stirring. After 3 hours, all the polyethylene was dissolved in n-heptane. The crude polymer solution observed through the autoclave's inspection port was blue.

[0134] Then maintain these temperature (160°C), pressure (2.0 abs), and stirring (500 rpm) conditions for 2 hours, after which stirring is stopped.

[0135] The polymer solution observed through the inspection port of the autoclave remained blue, the same as the crude polymer solution previously observed.

[0136] Take 15 ml of polymer solution and place it in a crystallization dish. Then place the crystallization dish in an oven at 180°C and atmospheric pressure, and rinse with nitrogen for 6 hours.

[0137] A blue solid was obtained, the color of which was similar to that of the milled polyethylene material used as the starting material.

[0138] 1: Plastic raw materials 2: Dissolving solvent 3: Crude polymer solution 4: Insoluble portion 5: Clarified polymer solution 6: Concentrated solution 7: Washing effluent 8: Washed polymer solution 9: Extraction solvent 10: Waste solvent 11: Extracted polymer solution 12: Refined polymer solution 13: Solvent section 14: Purified polymer fraction 21: Polymer solution

Claims

1. A method for processing a plastic raw material comprising polyolefin, comprising: a) a dissolution step involving contacting the plastic raw material with a dissolving solvent at a dissolution temperature between 150°C and 250°C and a dissolution pressure between 1.5 MPa abs and 15.0 MPa abs to obtain at least one crude polymer solution, the dissolving solvent being selected from at least one organic solvent having a boiling point between 80°C and 180°C and containing one or more hydrocarbons having between 6 and 10 carbon atoms; b) an adsorption step involving contacting the crude polymer solution obtained from step a) with at least one adsorbent at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs to obtain at least one refined polymer solution; and then c) a recovery step involving recovering the polymer to obtain at least one solvent fraction and a purified polyolefin fraction.

2. The method of claim 1, wherein the critical temperature of the dissolving solvent is between 250°C and 350°C, and the critical pressure is between 2.0 MPa abs and 4.3 MPa abs.

3. The method of claim 1, wherein the dissolution pressure in step a) is between 2.0 MPa abs and 10.0 MPa abs.

4. The method of claim 1, wherein the dissolution pressure in step a) is between 1.5 MPa abs and 2.4 MPa abs.

5. The method of claim 1, wherein the dissolution pressure in step a) is between 1.7 MPa abs and 2.2 MPa abs.

6. The method of claim 1, wherein the adsorption step b) is performed at the dissolution temperature and the dissolution pressure of step a).

7. The method of claim 1, wherein the adsorption step b) is performed in the presence of at least one adsorbent, which is in the form of a fixed bed, an entrained bed or a fluidized bed.

8. The method of claim 1, wherein the adsorbent is alumina, silica, silica-alumina, activated carbon, decolorizing clay, or a mixture thereof.

9. The method of claim 1, wherein the adsorbent is activated carbon, decolorizing clay, or a mixture thereof.

10. The method of claim 1, wherein the polymer recovery step c) includes a solvent recovery portion at a temperature between 10°C and 250°C and a pressure between 0.1 MPa abs and 10.0 MPa abs.

11. The method of claim 1, wherein the polymer recovery step c) includes at least one solvent recovery section under temperature and pressure conditions adjusted to be under supercritical conditions of the dissolved solvent.

12. The method of claim 1, comprising step E1) of separating insoluble matter by solid-liquid separation at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs, the step being located between the dissolution step a) and the polymer recovery step c), and upstream or downstream of the adsorption step b).

13. The method of claim 12, wherein step E1) of separating the insoluble matter includes an electrostatic separator and / or a filter and / or a sand filter.

14. The method of claim 1, comprising step E2) of washing with a concentrated solution at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs, the step being located between the dissolution step a) and the polymer recovery step c), and upstream or downstream of the adsorption step b), wherein the concentrated solution is an aqueous solution.

15. The method of claim 1, comprising step E3) of extraction by contacting an extraction solvent at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs to obtain at least one extracted polymer solution and a waste solvent, wherein the extraction solvent is an organic solvent having a critical temperature between 90°C and 400°C and a critical pressure between 1.5 MPa abs and 5.0 MPa abs.

16. The method of claim 1, comprising: a) a dissolution step involving contacting the plastic raw material with a dissolving solvent at a dissolution temperature between 150°C and 250°C and a dissolution pressure between 1.5 MPa abs and 15.0 MPa abs to obtain at least one crude polymer solution; E1) a step of separating insoluble matter by solid-liquid separation at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs, wherein step E1) is fed with the crude polymer solution obtained from step a) to obtain at least one clarified polymer solution and an insoluble fraction; b) an adsorption step involving contacting the clarified polymer solution with at least one adsorbent at a temperature between 100°C and 300°C and a pressure between 1.0 MPa abs and 20.0 MPa abs to obtain at least one refined polymer solution; and then c) a polymer recovery step to obtain at least one solvent fraction and a purified polyolefin fraction.

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