Method for treating used plastics by polymer dissolution and adsorption purification

Abstract

Disclosed is a method for processing plastic feedstock, the method comprising: (a) a dissolution step comprising contacting the feedstock with a dissolution solvent at a dissolution temperature of 100°C to 300°C and a dissolution pressure of 1 to 20.0 MPa, the dissolution solvent having a boiling point of -50°C to 250°C, to obtain a crude polymer solution; (b) an adsorption step in which the crude polymer solution is contacted with an absorbent at a temperature of 100 to 300°C and a pressure of 1.0 to 20.0 MPa, to obtain a purified polymer solution; and then (c) a polymer recovery step, to obtain at least a solvent fraction and a purified polymer fraction.

Description

Technical Field

[0001] The present invention relates to a method for treating used plastics to obtain a purified stream of plastics that can be used, for example, as new plastic objects. More specifically, the present invention relates to a method for treating plastic feedstocks, especially those obtained from plastic waste, particularly those containing thermoplastic plastics such as polyolefins, the method including an adsorption step to at least partially remove impurities, especially additives conventionally used in plastic-based materials, such as dyes, pigments, organic and inorganic fillers, and to upgrade the plastic feedstock by separating out the polymers, especially thermoplastic plastics, contained in the feedstock so that they can be recovered and reused.

Background Art

[0002] Plastics obtained from recycling and sorting channels can be upgraded by various channels.

[0003] By "mechanical" recycling, certain waste can be partially reused directly in new objects or by mixing the mechanically sorted stream of plastic waste with the stream of unused polymers. This type of upgrading is limited because mechanical sorting makes it possible to improve the purity of the stream of a given type of polymer, but thereby generally does not make it possible to sufficiently remove impurities that are at least partially trapped in the polymer matrix, such as additives, such as fillers, dyes, pigments and metals.

[0004] "Chemical" recycling generally focuses on modifying monomers at least partially through a complex series of processes. For example, plastic waste may undergo a pyrolysis process, and the recovered pyrolysis oil may, after refining, be converted at least partially to olefins, for example, by steam decomposition. These olefins may then be polymerized. While this type of sequence may be suitable for feedstocks that have undergone little sorting or waste from sorting centers, it generally requires significant energy consumption, especially due to high-temperature processing.

[0005] Another route for recycling plastic waste involves at least partially dissolving plastics, particularly thermoplastics, which aims to purify them by removing polymers and / or impurities from the supply material other than the targeted(s) (one or more), such as additives, fillers, dyes, pigments, and metals.

[0006] Several studies have therefore presented various methods for processing plastic waste by dissolution and purification. Patent Document 1 describes a specific method for purifying polymer feedstock, particularly polymer feedstock obtained from plastic waste, by dissolving the polymer in a solvent under specific temperature and pressure conditions, and then placing the resulting polymer solution in contact with a solid.

[0007] Patent Document 2 proposes a method for dissolving plastics in a solvent at a dissolution temperature close to the solvent's boiling point, in part. However, the method described in Patent Document 2 does not allow for the efficient treatment of impurities other than polymers.

[0008] Patent Document 3 proposes a treatment method in which thermoplastic plastics are liquefied in a solvent, and then insoluble substances and / or gases are separated and removed. However, the method described in Patent Document 3 does not allow for the efficient treatment of impurities that are soluble in the solvent.

[0009] The present invention aims to overcome these drawbacks and contribute to the recycling of plastics, particularly thermoplastics. More specifically, the present invention aims to propose a method for processing plastic feedstock, in particular those obtained from plastic waste, so as to efficiently remove impurities, in particular additives conventionally added to plastic materials, more specifically, at least some of impurities that are particularly soluble in organic solvents, thereby upgrading plastic feedstock, in particular plastic waste, by separating, removing, and recovering polymers, especially thermoplastics, so that they can be used, for example, as a polymer base for new plastic objects. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent Application Publication No. 2017 / 002110 [Patent Document 2] International Publication No. 2018 / 114047 [Patent Document 3] U.S. Patent Application Publication No. 2018 / 0208736 [Overview of the project] [Means for solving the problem]

[0011] (Summary of the invention) The present invention relates to a method for processing plastic supply raw materials, comprising the following steps: a) A dissolution step comprising placing the plastic supply material in contact with a dissolving solvent at a dissolution temperature of 100°C to 300°C and a dissolution pressure of 1.0 to 20.0 MPa (absolute), wherein the dissolving solvent is selected from at least one organic solvent having a boiling point of -50°C to 250°C; to obtain at least one crude polymer solution; b) Adsorption step by contacting the crude polymer solution obtained in step a) with at least one adsorbent at a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute); obtaining at least one purified polymer solution; then c) A step to recover the polymer; obtaining at least one solvent fraction and at least one purified polymer fraction.

[0012] The advantage of the method of the present invention lies in proposing a method for efficiently processing supply materials that include plastics, in particular plastic waste, especially plastic waste obtained from collection and sorting channels, and which includes recovering polymers, in particular thermoplastics, so that they can be recycled into any type of application. The method according to the present invention makes it practically possible to obtain a stream of purified polymers, in particular purified thermoplastics, in particular purified polyolefins, e.g., polyethylene and polypropylene, which, advantageously, contain impurities in a content that is negligible or at least small enough that the stream of purified polymers, in particular purified thermoplastics, can be introduced into any plastic formulation in place of unused polymer resins. For example, the stream of purified polymers, in particular purified thermoplastics, in particular purified polyolefins obtained at the end of the method according to the present invention, advantageously contains less than 5% by weight of impurities, and much more advantageously less than 1% by weight of impurities.

[0013] The present invention thus proposes a series of operations that enable the plastic waste to be upgraded by removing impurities, particularly at least some of the additives, from plastic waste, recovering the purified polymer, and recycling the purified polymer. Advantageously, depending on the conditions used in the steps of the present method, the compounds present in the plastic feedstock may be soluble or insoluble in the solvent(s) used throughout the method according to the present invention, allowing for efficient purification of the polymer.

[0014] The present invention has the further advantage of contributing to plastic recycling and the conservation of fossil resources, which is achieved by enabling the upgrading of plastic waste. Specifically, the present invention enables the purification of plastic waste, which is for the purpose of obtaining a purified polymer fraction with reduced impurity content, and in particular decolorized and deodorized, which may be reused to form new plastic objects. The obtained purified polymer fraction may therefore be used directly in formulations as an additive, for example, as a mixture with dyes, pigments or other polymers, in place of or as a mixture with unused polymer resins, for the purpose of obtaining plastic products with aesthetic, mechanical or rheological processing properties that facilitate their reuse and upgrading.

[0015] The present invention makes it possible to recover the solvent(s) used to process the plastic supply raw materials in this method and recycle them after purification in this method, thereby avoiding excessive consumption of the solvent(s).

[0016] Therefore, the present invention is directed toward purifying plastic supply materials, in particular plastic waste, to obtain polymers, in particular thermoplastics, more specifically polyolefins, such as polyethylene and polypropylene, which are purified and can be used in any application, in particular as a substitute for unused polymers. The present invention therefore proposes a purification method by dissolving the target polymer, that is, by separating and removing them and purifying them. More specifically, the present invention is directed toward proposing a method comprising a dissolution step and a subsequent, at least one specific purification step, adsorption step b), in combination with other intermediate purification steps, to obtain a purified polymer solution from which the purified polymer may be recovered. [Modes for carrying out the invention]

[0017] (Description of Embodiments) According to the present invention, the expressions "comprised between... and..." and "between... and..." are equivalent and mean that the two limit values of the interval are included in the described range of values. If not, and if the two limit values are not included in the described range, such clarification will be provided by the present invention.

[0018] For the purposes of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, may be used alone or in combination. For example, for the purposes of the present invention, a range of suitable pressure values may be combined with a range of more suitable temperature values.

[0019] In the following text, specific embodiments of the present invention may be described. They may be implemented separately or in combination together, and there is no limitation on the combination when the combination is technically feasible.

[0020] According to the present invention, the pressure is absolute pressure and is given in MPa (absolute) (or MPa abs).

[0021] The terms "upstream" and "downstream" should be understood according to the general flow of the fluid (one or more types) or flow (one or more types) under consideration in the present method.

[0022] The term "additive" is a term customarily used in the field of polymers, particularly in the field of polymer formulations. Additives introduced into polymer formulations can be, for example, plasticizers, fillers (organic or inorganic solid compounds used to modify the physical, thermal, mechanical and / or electrical properties of polymer materials or to reduce their cost price), reinforcing agents, dyes, pigments, curing agents, flame retardants, combustion inhibitors, stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, etc.

[0023] Additives correspond to a part of the impurities in the plastic feedstock to be processed and can be at least partially removed by the treatment method according to the present invention. Other types of impurities can be use-related impurities or plastic materials, such as metallic impurities, paper / cardboard, biomass, other polymers, such as thermosetting or thermoplastic types, etc.

[0024] Therefore, according to the present invention, the impurities that can be at least partially removed from the stream of the target polymer by the method according to the present invention include the additives conventionally used in polymer formulations, the impurities derived from the life cycle of plastic objects and materials, and / or the impurities derived from the waste collection and sorting circuit. The said impurities can be metallic, organic or inorganic types of impurities; they can be packaging residues, food residues or compostable residues (biomass). These use-related impurities may include glass, wood, cardboard, paper, aluminum, iron, metal, tires, rubber, silicone, rigid polymers, thermosetting polymers, household items, chemical products, cosmetics, used oil and water.

[0025] According to the present invention, the polymer solution is a solution comprising a dissolving solvent and at least a polymer, preferably a target polymer, in particular a target thermoplastic, and especially a target polyolefin, dissolved in the dissolving solvent, wherein the dissolved polymer is initially present in the feed material. The polymer solution may contain soluble and / or insoluble impurities. Depending on the steps of the method according to the present 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 optionally another liquid phase immiscible with the polymer solution.

[0026] The critical temperature and critical pressure of a solvent, particularly a dissolving solvent and / or an extracting solvent, are specific to that solvent and are the temperature and pressure at the solvent's critical point, respectively. As is well known to those skilled in the art, above the critical point, the solvent is in a supercritical form or state, and the operating temperature and pressure conditions are the supercritical conditions for the solvent; it is sometimes called a supercritical fluid.

[0027] The present invention relates to a method for preparing a plastic feedstock, preferably composed of plastic waste, and advantageously comprising a polymer, preferably a thermoplastic, particularly a polyolefin, wherein the method comprises, preferably, the following steps: a) A dissolution step including placing the supply material in contact with a solvent; obtaining at least one crude polymer solution; and then E1) In some cases, a step to separate and remove insoluble substances; to obtain at least one clarified polymer solution and at least one insoluble fraction. E2) In some cases, a washing step by contact with a concentrated solution; to obtain at least one washing effluent and at least one washed polymer solution. E3) In some cases, an extraction step by contact with an extraction solvent; to obtain at least one extracted polymer solution and at least one used solvent. b) Step of adsorption of impurities by contact with an adsorbent solid; obtain at least one purified polymer solution, and finally c) A step to recover the polymer; obtaining at least one solvent fraction and at least one purified polymer fraction.

[0028] (Feed material) The feedstock of the method according to the present invention is known as a plastic feedstock and includes plastic, and the plastic itself more specifically includes polymer. Preferably, the plastic feedstock contains 50% to 100% by weight of plastic, preferably 70% to 100% by weight.

[0029] The plastics contained in the raw materials supplied by the method according to the present invention are generally defective products and / or waste, in particular household waste, construction waste, or electrical and electronic equipment waste. Preferably, the plastic waste originates from collection and sorting channels. Plastics or plastic materials are generally polymers and are usually mixed with additives. This is done for the purpose of forming various materials and objects (injection molded parts, tubes, films, fibers, cloths, mastic, coatings, etc.) after being molded into shape. Additives used in plastics may be organic or inorganic compounds. They include, for example, fillers, dyes, pigments, plasticizers, property modifiers, and combustion retarders.

[0030] The feedstock of the method according to the present invention therefore includes polymers, particularly thermoplastics. The polymers contained in the plastic feedstock may be alkene polymers, diene polymers, vinyl polymers, and / or styrene polymers. Preferably, the polymers contained in the plastic feedstock are polyolefins, such as polyethylene (PE), polypropylene (PP), and / or copolymers of ethylene and propylene. Much preferably, the polymer in the plastic feedstock contains at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight, and very preferably at least 94% by weight of polyolefins relative to the total weight of the feedstock. The method according to the present invention is therefore most specifically directed toward purifying and recovering the polyolefins contained in the feedstock so that they can be reused in various applications.

[0031] The plastic supply material may include a mixture of polymers, particularly a mixture of thermoplastic resins and / or a mixture of thermoplastic resins and other polymers, and impurities, in particular additives that are advantageously used to blend the plastic material with commonly used impurities. Commonly used impurities originate from the lifecycle of the material and the plastic object and / or from the waste collection and sorting circuit. The supply material of the method according to the present invention generally contains less than 50% by weight of impurities, preferably less than 20% by weight of impurities, and preferably less than 10% by weight of impurities.

[0032] The supply material containing plastic may be advantageously pre-treated prior to the Method to remove at least some or all of "coarse" impurities, i.e., impurities in the form of particles 10 mm or larger, preferably 5 mm or larger, and even 1 mm or larger, such as wood, paper, biomass, iron, aluminum, glass, etc., and to form it generally into a segmented solid form to facilitate processing in the Method. This pre-treatment may include a grinding step, a washing step at atmospheric pressure, and / or a drying step. This pre-treatment may be carried out at a different site, for example, a waste collection and sorting center, or at the same site where the processing method according to the present invention is carried out. Preferably, this pre-treatment makes it possible to reduce the impurity content to less than 6% by weight. At the end of the pre-treatment, the supply material is generally stored in a segmented solid form, for example, in the form of ground material or powder, to facilitate handling and transport to the Method.

[0033] (melting step a)) According to the present invention, the method includes a dissolution step a), in which the plastic supply material is placed in contact with a dissolution solvent at a dissolution temperature of 100°C to 300°C and a dissolution pressure of 1.0 to 20.0 MPa (absolute) to obtain a solution of at least one, preferably one, crude polymer. Specifically, this step advantageously enables the dissolution of at least a portion, preferably all, of a polymer, preferably a thermoplastic, most preferably a polyolefin, such as polyethylene and / or polypropylene.

[0034] The term "dissolution" should be understood as any phenomenon that leads to the formation of a solution of at least one polymer, i.e., a liquid containing a polymer dissolved in a solvent, more specifically, a dissolving solvent. Those skilled in the art are well aware of the phenomena involved in polymer dissolution, which include at least the mixing, dispersion, homogenization, and dissociation of polymer chains, particularly thermoplastic chains.

[0035] During and after the dissolution process a), the pressure and temperature conditions make it possible to maintain at least a portion, preferably all, of the dissolution solvent in liquid form, while at least a portion of the soluble fraction of the feed material, particularly the target polymer, preferably the target thermoplastic, preferably the target polyolefin, and impurities, are advantageously at least partially, preferably completely dissolved.

[0036] The process of bringing the dissolving solvent and the plastic feed material into contact to dissolve the polymer of the plastic feed material at least partially, preferably completely, in the dissolving solvent may be carried out in a line and / or apparatus and / or between two apparatuses. Thus, step a) advantageously includes at least one dissolving apparatus, and optionally at least one feed material preparation device, mixing device and / or transport device. These apparatus and / or devices may be, for example, a static mixer, extruder, pump, reactor, parallel or countercurrent column, or a combination of line and apparatus. Devices for transport, particularly for transporting fluids, e.g., gas, liquid or solid, are well known to those skilled in the art. In a non-limiting embodiment, transport devices may include compressors, pumps, extruders, vibrating tubes, endless screws or valves. The apparatus and / or devices may include, or be combined with, a heating system (e.g., an oven, exchanger, tracer, etc.) to achieve the conditions required for dissolution.

[0037] Dissolution step a) is advantageously supplied by one or more transport devices, supplying at least the plastic feed material, particularly in the form of one or more streams of the plastic feed material, and the dissolving solvent, particularly in the form of one or more streams of the dissolving solvent. The streams of the plastic feed material (one or more) may be different from the streams of the dissolving solvent (one or more). Some or all of the plastic feed material may be supplied to step a) as a mixture with some or all of the dissolving solvent, and the remainder of the solvent and / or feed material may be supplied separately to a possible supply step a) where appropriate.

[0038] During contact between the plastic feed material and the dissolving solvent, the dissolving solvent is advantageously in at least partially, preferably completely, liquid form, while the plastic feed material, which includes polymers, particularly thermoplastics, especially polyolefins, may be in solid or liquid form, and may optionally contain solid particles in suspension. The plastic feed material may optionally be injected into the dissolution equipment as a mixture with the dissolving solvent, or in the form of a suspension in the dissolving solvent, and the preparation and injection of the suspension may be continuous or batch.

[0039] Preferably, step a) includes at least one extruder and melting equipment. In this case, the plastic feed material is fed to the extruder, and as a result, at least a portion, preferably all, of the target polymer, in particular the target thermoplastic, in particular polyolefin, contained in the feed material is in a molten form at the outlet of the extruder. The plastic feed material is then injected into the melting equipment in at least a partially molten form. The plastic feed material in at least a partially molten form may be pumped up by a pump specifically for viscous fluids, commonly known as a melt pump or gear pump. The plastic feed material in at least a partially molten form may optionally be filtered at the outlet of the extruder using a filtration device in addition to the melt pump, for the purpose of removing the coarsest particles; generally, the mesh size of this filter is 10 microns to 1 mm, preferably 20 to 200 microns.

[0040] Preferably, step a) includes an extruder into which the dissolving solvent is advantageously injected at several points to promote shearing and therefore to promote tight mixing between the dissolving solvent and the plastic feed material, which contributes to dissolving polymers, in particular thermoplastics, in particular polyolefins.

[0041] The dissolution solvent used in dissolution step a) is preferably an organic solvent or a mixture of solvents (preferably organic). Preferably, the dissolution solvent is selected from organic solvents and preferably contains, preferentially consists of, one or more hydrocarbons, with a boiling point of -50°C to 250°C, preferably 75°C to 250°C, preferably 80 to 220°C, and very preferably 80 to 180°C. Preferably, the dissolution solvent contains, preferentially consists of, one or more hydrocarbons, and very preferably contains one or more alkanes, with 3 to 12 carbon atoms, preferentially 6 to 12 carbon atoms, very preferably 6 to 10 carbon atoms, for example, isomers of cyclohexane and heptane. The dissolving solvent is, much more advantageously, an organic solvent, preferably a hydrocarbon, and preferably the critical temperature of the dissolving solvent is 90 to 400°C, preferably 200 to 390°C, preferably 250 to 350°C, and the critical pressure is 1.5 to 5.0 MPa (absolute), preferably 2.0 to 4.3 MPa (absolute), preferably 2.4 to 4.2 MPa (absolute). According to a particular embodiment, the boiling point of the dissolving solvent is greater than 70°C, preferably 80°C to 220°C, and / or the solvent contains, preferably consists of, an alkane containing at least 7 carbon atoms. According to another preferred embodiment, the boiling point of the dissolving solvent is less than 50°C or greater than 150°C.

[0042] Advantageously, the melting temperature during the melting process is 100°C to 300°C, and the melting pressure is 1.0 to 20.0 MPa (absolute). More specifically, the temperature and pressure progress throughout step a) from ambient conditions, i.e., the temperature of the plastic feed material (10 to 30°C) and atmospheric pressure (0.1 MPa), to melting conditions, more specifically, the melting temperature and melting pressure. In particular, the melting temperature is 100 to 300°C, preferably 150 to 250°C, and the melting pressure is 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and very preferably 2.0 to 10.0 MPa (absolute). Much advantageously, at the end of melting step a), the flow of the melted polymer is at the melting temperature and melting pressure.

[0043] According to a particular embodiment of dissolution step a), the dissolution pressure is 1.5 to 2.4 MPa (absolute), preferably 1.7 to 2.2 MPa (absolute). In this very particular embodiment, water that may be present in the plastic feed material (in the case of wet plastic feed material) may then be vaporized and removed by degassing during dissolution, for example, from vents, particularly those located on the dissolution line and / or equipment, particularly vents located on the extruder. When this particular embodiment of dissolution step a) is performed, the method for processing the plastic feed material according to the present invention does not include the optional step E2) of washing with a concentrated solution, particularly an aqueous solution.

[0044] By limiting the temperature in step a) to 300°C or lower, preferably 250°C or lower, it is possible to prevent or limit the thermal degradation of polymers, especially thermoplastics, and more particularly polyolefins. Preferably, the dissolution temperature is above the melting point of the polymer, especially thermoplastics, and more particularly polyolefins, to promote their dissolution. Preferably, the temperature in dissolution step a) is below the critical temperature of the dissolution solvent to avoid the formation of a supercritical phase that can easily interfere with dissolution during dissolution step a).

[0045] In parallel, the dissolution pressure is higher than the saturated vapor pressure of the solvent at the dissolution temperature, and the solvent is at least partially, preferably completely, in liquid form at the dissolution temperature. Advantageously, the recovery step c) can be carried out under conditions where the dissolution pressure is above the critical pressure of the solvent and at least a portion of the solvent is in a supercritical state, but without requiring a significant increase in the pressure between step a), particularly between the outlet of step a), and step c). If the dissolution pressure in step a) is above the critical pressure of the solvent, the dissolution temperature is below the critical temperature of the solvent, so that the solvent remains at least partially in liquid form.

[0046] Much to our advantage, the temperature and pressure conditions for dissolution achieved in step a) are adjusted so that the mixture (solvent + target polymer) becomes a single-phase mixture.

[0047] Preferably, the weight ratio between the plastic supply material and the dissolving solvent is 0.01 to 5.0, preferably 0.05 to 3.0, and preferably 0.10 to 1.0.

[0048] Advantageously, the dissolution step a) is carried out over a residence time of 1 to 600 minutes, preferably 2 to 300 minutes, and preferably 2 to 180 minutes. The residence time is understood to be the residence time at the dissolution temperature and pressure, i.e., the time spent in step a) of the plastic supply material being dissolved by the solvent at the dissolution temperature and pressure.

[0049] Advantageously, the dissolving solvent used in step a) includes, and preferably consists of, a supply of fresh solvent and / or a stream of recycled solvent obtained from the recovery step c).

[0050] In some cases, the processing method may include an intermediate adsorption step a'). This intermediate adsorption step a') is located during or directly downstream of the dissolution step a) and includes the introduction of an adsorbent solid, preferably, for example, alumina, silica, silica-alumina, activated carbon, or decolorized earth, in the form of segmented particles, into the crude polymer solution obtained at the end of step a) or optionally during the dissolution step a). The adsorbent solid may be removed during one of the optional intermediate purification steps, for example, during the optional step E1) for separation of insoluble substances and / or the optional washing step E2). This optional adsorption step a') makes it possible to optimize the purification of the polymer solution in the presence of the adsorbent solid in segmented form.

[0051] The crude polymer solution obtained at the end of step a) comprises at least the dissolving solvent and the polymer dissolved in the dissolving solvent, particularly the target polymer that the present invention seeks to recover and purify. Generally, the crude polymer solution also contains soluble impurities that are similarly dissolved in the dissolving solvent. It may optionally contain suspended insoluble impurities or compounds. The crude polymer solution obtained at the end of step a) may optionally contain polymers other than the target polymer, for example, in a molten form.

[0052] (Optional step E1: Separating and removing insoluble substances) This processing method may optionally include step E1) of separating and removing insoluble substances by solid-liquid separation, and advantageously obtains at least one clarified polymer solution and at least one insoluble fraction. The insoluble fraction advantageously contains at least some, preferably all, of the insoluble impurities suspended in particular in the crude polymer solution obtained from step a).

[0053] When incorporated into the method according to the present invention, step E1) for separating and removing insoluble substances is located between step a) and step c) and upstream or downstream of step b), preferably upstream of step b). If the optional step E1) for separating and removing insoluble substances is located downstream of step b), then step b) corresponds to an intermediate adsorption step a').

[0054] Step E1), which separates and removes insoluble substances, thus makes it possible to remove at least some, preferably all, of the particles of insoluble compounds in the dissolving solvent under the temperature and pressure conditions of step a). These particles may be present suspended in the crude polymer solution obtained from step a) or the optional step a'). Insoluble impurities removed during the optional step E1), which separates and removes insoluble substances, include, for example, pigments, mineral compounds, packaging residues (glass, wood, corrugated cardboard, paper, aluminum), and insoluble polymers.

[0055] If implemented, this separation step E1) is advantageous in that it can limit operational problems in downstream method processes, particularly clogging and / or corrosion, while simultaneously contributing to the purification of the plastic feed material.

[0056] When incorporated into this method, the temperature at which step E1) for separating and removing insoluble substances is advantageously carried out is 100 to 300°C, preferably 150 to 250°C, and the pressure at which it is advantageous is 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and very preferably 2.0 to 10.0 MPa (absolute). Much more advantageously, the optional step E1) for separating and removing insoluble substances is carried out under the temperature and pressure conditions of dissolution, i.e., under the temperature and pressure conditions at the outlet of step a).

[0057] When incorporated into the present method, step E1) for separating and removing insoluble substances is preferably fed with a crude polymer solution obtained from step a) or from an optional intermediate adsorption step a'). According to another embodiment, the optional step E1) may be fed with a washed polymer solution obtained from an optional washing step E2).

[0058] If incorporated into the present method, step E1) advantageously includes a section comprising at least one solid-liquid separation apparatus, e.g., a separation flask, a decanter, a centrifugal decanter, a centrifuge, a filter, a sand filter, an eddy current separator, an electrostatic separator, a triboelectric separator, preferably a decanter, a filter, a sand filter and / or an electrostatic separator.

[0059] The removal of insoluble fractions may be facilitated by equipment for transporting and / or removing trace amounts of solvent that may be present in the insoluble fractions, such as conveyors, vibrating tubes, endless screws, extruders, or strippers. Step E1) therefore may include equipment for transporting and / or removing trace amounts of solvent to remove the insoluble fractions.

[0060] According to a particular embodiment of the optional step E1), step E1) for separating and removing insoluble substances includes at least two, and generally fewer than five, solid-liquid separation devices in series and / or parallel. The presence of at least two solid-liquid separation devices in series makes it possible to improve the removal of insoluble substances, while the presence of the devices in parallel makes it possible to manage the maintenance and / or declogging of the devices.

[0061] Some insoluble compounds, in particular some pigments and mineral fillers that have been conventionally added during polymer formulations, may be introduced in the form of particles smaller than 1 μm in size. This is the case, for example, with titanium dioxide, calcium carbonate, and carbon black. According to a particular embodiment of the optional step E1), the step E1) for separating and removing insoluble substances advantageously includes an electrostatic separator, which enables efficient removal of at least some, preferably all, of the insoluble particles smaller than 1 μm. According to another particular embodiment of the optional step E1), the step E1) for separating and removing insoluble substances includes a sand filter, which removes particles of different sizes, in particular particles smaller than 1 μm.

[0062] Depending on the properties of the raw materials supplied, the polymer solution, preferably a crude polymer solution, to be fed to step E1) may optionally include a second liquid phase, which is, for example, a molten polymer. According to another specific embodiment of an optional step E1), step E1) advantageously includes equipment for separating and removing this second liquid phase, preferably by at least one three-phase separator.

[0063] (Optional cleaning step E2) The processing method may optionally include step b) washing with a concentrated solution, which is advantageous in obtaining at least one washing effluent and at least one washed polymer solution. The washed polymer solution obtained at the end of the optional step E2) advantageously contains the target polymer that the present invention seeks to recover and purify dissolved in the dissolving solvent. Optionally, it may contain residual impurities particularly soluble in the dissolving solvent and / or, if step E2) is performed, a trace amount of washing solvent.

[0064] When incorporated into the method according to the present invention, the washing step E2) is located upstream or downstream of the adsorption step b) between the dissolution step a) and the polymer recovery step c), preferably upstream of the adsorption step b). If the optional washing step E2) is located downstream of the adsorption step b), the adsorption step b) corresponds to an intermediate adsorption step a'). The washing step E2) may be incorporated upstream or downstream, preferably downstream of the optional step E1) which separates and removes insoluble substances.

[0065] When incorporated into this method, the washing step E2) is fed a concentrated solution and a crude polymer solution obtained from step a) or an optional intermediate adsorption step a'), or otherwise a clarified polymer solution obtained from an optional step E1). The polymer solution fed to the washing step E2), particularly the crude polymer solution or the clarified polymer solution, may contain impurities in the form of suspended insoluble compounds and / or dissolved compounds. These suspended or dissolved compounds may be partially or completely removed during the washing step E2) by dissolution or precipitation and / or entrainment in the concentrated solution. Therefore, when done, this step E2) contributes to the processing of the plastic feedstock, more specifically to the purification of the polymer solution.

[0066] An optional washing step E2) advantageously includes bringing the crude polymer solution or clarified polymer solution to be fed to step E2) into contact with the 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 the solvent in which the target polymer is dissolved), and in particular, the density of the concentrated solution is 0.85 or higher, preferably 0.9 or higher, and more preferably 1.0 or higher. 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 very 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 the given compound. The concentrated solution may optionally contain, and preferably consist of, an organic solvent having a density of advantageously 0.85 or higher, preferably 0.9 or higher, and more preferably 1.0 or higher, wherein the polymer of the plastic supply material remains insoluble under the temperature and pressure conditions of the optional step E2), for example, the organic solvent is selected from sulfolane or N-methylpyrrolidone (NMP), and optionally as a mixture with water. Much 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 very preferably at least 90% by weight of water.

[0067] The temperature at which the optional cleaning step E2) is advantageously carried out is 100 to 300°C, preferably 150 to 250°C, and the pressure at which it is advantageous is 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and very preferably 2.0 to 10.0 MPa (absolute). Much more advantageously, the optional cleaning step E2) is carried out at the dissolution temperature and dissolution pressure.

[0068] In the washing step E2), if it is incorporated into the method, the mass ratio between the mass flow rate of the concentrated solution and the mass flow rate of the crude polymer solution or clarified polymer solution supplied to step E2) is advantageously 0.05 to 20.0, preferably 0.1 to 10.0, and preferably 0.5 to 3.0. The contact arrangement between the crude polymer solution or clarified polymer solution and the concentrated solution may be carried out at several points in the equipment used, i.e., through several injections of the crude polymer solution or clarified polymer solution and / or concentrated solution at different points along the equipment: the total amount of injected flow is taken into consideration in the calculation of the ratio.

[0069] The optional step E2) may be carried out by separation equipment that enables the recovery of at least one type of washing effluent and at least one type of washed polymer solution in one or more washing devices that can be placed in contact with the concentrated solution. This equipment is well known and includes, for example, agitated reactors, static mixers, decant mixers, two-phase or three-phase separation flasks, parallel or counter-flow washing columns, plate columns, agitated columns, packed columns, pulsed columns, etc., and each type of equipment may include one or more devices used alone or in combination with other types of equipment.

[0070] According to a preferred embodiment, an optional washing step E2) is performed in a countercurrent washing column, where, on the one hand, a concentrated solution is injected into preferably half, preferably one-third, of the column closest to the top, and on the other hand, a crude polymer solution or a clarified polymer solution is injected into preferably half, preferably one-third, of the column closest to the bottom. According to this embodiment, it is possible to recover at least one washed polymer solution and at least one washing effluent.

[0071] According to a very specific embodiment, the flow at the inlet and / or outlet of the washing column may be divided and injected at several injection points along the column and / or withdrawn at several withdrawal points along the column.

[0072] According to another embodiment, the washing step E2) is carried out in a mixer-decanter, which includes a stirring and mixing zone for bringing the concentrated solution into contact with the crude polymer solution or clarified polymer solution, and a decantation zone that allows for the recovery of the washed polymer solution and washing effluent.

[0073] At the end of the washing step E2), the resulting washing effluent preferably contains compounds dissolved in the concentrated solvent and / or insoluble compounds entrained in the washing effluent. The washing effluent may be reprocessed in a washing treatment section, on the one hand separating and removing at least partially the dissolved compounds and / or entrained compounds to optionally purify the washing effluent to obtain a purified concentrated solution, and on the other hand recycling at least partially a portion of the purified washing solution. This washing treatment section may include one or more pieces of equipment known for solid-liquid separation, such as separation flasks, decanters, centrifugal decanters, centrifuges, or filters. The washing effluent may be sent outside the method, for example, to a spent water treatment station if the concentrated solution is an aqueous solution.

[0074] (Optional selection process E3) The method according to the present invention may include an extraction step E3) by contacting with an extraction solvent to obtain at least one extracted polymer solution and at least one spent solvent, in particular, containing impurities. The extracted polymer solution obtained at the end of the optional step E3) advantageously contains the target polymer that the present invention seeks to recover and purify, dissolved in the dissolving solvent. In some cases, it may also contain residual impurities that are particularly soluble in the dissolving solvent and / or trace amounts of washing solvent and / or trace amounts of extraction solvent, if steps E2) and / or E3) are performed.

[0075] When incorporated into the method according to the present invention, the extraction step E3) is advantageously located upstream or downstream of the adsorption step b) between the dissolution step a) and the polymer recovery step c).

[0076] An optional extraction step E3) is advantageously fed with an extraction solvent and a polymer solution, particularly a crude polymer solution obtained from step a), a clarified polymer solution obtained from an optional step E1), a washed polymer solution obtained from an optional step E2), or a purified polymer solution obtained from an adsorption step b). Preferably, an optional extraction step E3) is fed with an extraction solvent and a clarified polymer solution obtained from an optional step E1), a washed polymer solution obtained from an optional step E2), or a purified and extracted polymer solution obtained from an adsorption step b). The polymer solution fed to the optional step E3), preferably a clarified polymer solution, a washed polymer solution, or a purified polymer solution, may therefore, in some cases, contain dissolved compounds or dissolved impurities. These dissolved compounds may be partially or completely removed during the extraction step E3) by contact with the extraction solvent. A significant advantage is that the combination of adsorption step b) and extraction step E3) enables improved purification of the polymer solution by utilizing the affinity of impurities to both the adsorbent and the extraction solvent.

[0077] When incorporated into a method according to the present invention, extraction step E3) advantageously includes at least one extraction section, preferably one to five extraction sections, and very preferably one extraction section. The temperature during which the optional extraction step E3) is preferably carried out is 100 to 300°C, preferably 150 to 250°C. The pressure during which the optional extraction step E2) is preferably 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and very preferably 2.0 to 10.0 MPa (absolute). According to a preferred embodiment of the optional extraction step E3), extraction step E3) is carried out under different temperature and pressure conditions than those of step a).

[0078] The mass ratio between the mass flow rate of the extraction solvent and the mass flow rate of the polymer solution to be fed to step E3), preferably a clarified polymer solution, a washed polymer solution, or a purified polymer solution, is advantageously 0.05 to 20.0, preferably 0.1 to 10.0, and preferably 0.2 to 5.0. The contact arrangement between the polymer solution to be fed to step E3), preferably a clarified polymer solution, a washed polymer solution, or a purified polymer solution, and the extraction solvent may occur at several points in the extraction section, i.e., at different points along the extraction solvent via several injections of the polymer solution and / or extraction solvent: the total injected flow is taken into account in the calculation of the ratio.

[0079] The extraction solvent used in extraction step E3) is preferably an organic solvent or a mixture of solvents (preferably organic). Preferably, the solvent is selected from organic solvents, which preferably contain, and more preferably consist of, one or more hydrocarbons, and have a boiling point of -50°C to 250°C, preferably 75°C to 250°C, preferably 80°C to 220°C, and very preferably 80°C to 180°C. Preferably, the extraction solvent contains, and more preferably consists of, one or more hydrocarbons, and very preferably one or more alkanes, and contains 3 to 12 carbon atoms, preferably 6 to 12 carbon atoms, very preferably 6 to 10 carbon atoms, for example, isomers of cyclohexane and heptane. Preferably, the critical temperature of the extraction solvent (which is much more advantageously an organic solvent, preferably a hydrocarbon) is 90 to 400°C, preferably 200 to 390°C, preferably 250 to 350°C, and the critical pressure of the extraction solvent is 1.5 to 5.0 MPa (absolute), preferably 2.0 to 4.3 MPa (absolute), preferably 2.4 to 4.2 MPa (absolute). According to a particular embodiment, the boiling point of the extraction solvent is greater than 70°C, preferably 80°C to 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 less than 50°C or greater than 150°C.

[0080] Much preferably, the extraction solvent used in the optional step E3) is the same solvent as the dissolution solvent used in step a), but in a different physical state (e.g., the extraction solvent is in a supercritical state while the dissolution solvent is in a liquid state), which facilitates the management of the solvents, in particular their purification and recycling, especially their recycling to dissolution step a) and optionally extraction step E3). Another advantage of using the same dissolution and extraction solvents in the same or different physical states is that, in addition to facilitating the technical management of the solvents involved in the method according to the present invention, it has the advantage of particularly limiting the energy consumption and costs that arise in part from the recovery of the solvents, their processing and recycling to at least one of the steps of the method, and the processing and purification of the solvents.

[0081] The extraction section(s) of the optional step E3) may include one or more extraction instruments, which may be arranged in contact with separation equipment for recovering the extraction solvent and / or at least one used solvent, in particular the solvent containing impurities, and the extracted polymer solution. This equipment is well known and may include, for example, a stirred reactor, a static mixer, a decanting mixer, two-phase or three-phase separation flasks, a parallel or counter-current washing column, a plate column, a stirred column, a packed column, a pulsed column, etc., and each type of equipment may include one or more instruments used alone or in combination with other types of equipment.

[0082] According to a preferred embodiment of the optional step E3), the extraction is performed in a countercurrent extraction column, where the extraction solvent is injected on one side and the polymer solution to be fed to step E3) is injected on the other side. According to this embodiment, it is possible to recover at least one extracted polymer solution on one side and the spent solvent, in particular the spent solvent containing impurities, on the other side. Preferably, the polymer solution to be fed to step E3), preferably a clarified, washed, or purified polymer solution, is injected into the half, preferably one-third, of the column closest to the top of the countercurrent extraction column, while the extraction solvent is injected into the half, preferably one-third, of the column closest to the bottom of the countercurrent extraction column.

[0083] The flow at the inlet and / or outlet of the countercurrent extraction column may be divided at several injection and / or extraction points along the column.

[0084] According to another embodiment of the optional step E3), the extraction is carried out in a mixer-decanter, which advantageously includes a stirred mixing zone for contacting the extraction solvent and the polymer solution to be fed to step E3), preferably a clarified, washed, or purified polymer solution, and a decantation zone that allows for the recovery of the extracted polymer solution on the one hand and the spent solvent on the other.

[0085] According to a preferred embodiment of the optional step E3), the extraction step E3) includes a liquid / liquid extraction section. In this embodiment, the extraction solvent is preferably selected from isomers of pentane, hexane, and heptane, preferably from isomers of pentane and hexane, and most preferably from isomers of pentane. Preferably, the temperature when the liquid / liquid extraction section is operated is 100°C to 300°C, preferably 150°C to 250°C, and the pressure is 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and most preferably 2.0 to 10.0 MPa (absolute). 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. Much to the advantage, liquid / liquid extraction is carried out under different temperature and pressure conditions than those achieved in step a), particularly when the extraction solvent is the same as the dissolution solvent, at a temperature higher than the dissolution temperature and / or a pressure lower than the dissolution pressure, thus resulting in a two-phase zone in the corresponding polymer-solvent mixture diagram.

[0086] According to another preferred embodiment of the optional step E3), the extraction step E3) includes a section for extraction under specific temperature and pressure conditions, wherein the extraction solvent is, advantageously, in at least partially supercritical form. Such extraction may be referred to as supercritical extraction. In this embodiment, the extraction is carried out by bringing the polymer solution to be fed to step b), preferably a clarified, washed, or purified polymer solution, into contact with the extraction solvent under temperature and pressure conditions that allow for obtaining a supercritical phase that is, advantageously, overwhelmingly (i.e., preferably at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight) from the extraction solvent. In other words, in this embodiment, the extraction is carried out by bringing the polymer solution to be fed to step b), preferably a clarified, washed, or purified polymer solution, into contact with the extraction solvent which is, at least partially, preferably fully supercritical form. Such a supercritical extraction process (E3) advantageously allows for the efficient purification of the polymer solution, which is particularly due to the very high affinity of organic impurities, such as some additives, especially certain dyes and plasticizers, to the supercritical phase. The use of an extraction solvent in a supercritical state also makes it possible to create a substantial density difference between the supercritical phase and the polymer solution in liquid form, facilitating decantation separation between the supercritical and liquid phases, and consequently contributing to the purification of the polymer solution.

[0087] In this particularly preferred embodiment, the optional extraction step E3) uses an extraction solvent having a critical temperature preferably 200 to 390°C, preferably 250 to 350°C, and a critical pressure preferably 2.0 to 4.3 MPa (absolute), preferably 2.4 to 4.2 MPa (absolute). Much advantageously, in such a supercritical extraction step E3), the extraction solvent is selected from hydrocarbons, preferably containing 4 to 8 carbon atoms, preferably 5 to 7 carbon atoms. The extraction solvent for supercritical extraction may be, for example, a pentane isomer, a hexane isomer, a heptane isomer, or cyclopentane, cyclohexane, or methylcyclopentane.

[0088] Advantageously, the temperature during the optional supercritical extraction step E3) is preferably 150°C to 300°C, preferably 180°C to 280°C, and the pressure is preferably 2.0 to 20.0 MPa (absolute), preferably 2.0 to 15.0 MPa (absolute), and very preferably 3.0 to 10.0 MPa (absolute). In any case, in this embodiment, the temperature and pressure conditions are adjusted, in particular, in a control section included in extraction step E3) upstream of the extraction section, so that the extraction solvent is at least partially supercritical in the extraction section.

[0089] In a highly preferred embodiment of the optional step E3), the extraction step E3) comprises supercritical extraction, wherein the extraction solvent is identical to the dissolving solvent, except that the extraction solvent is at least partially in a supercritical phase. In this highly advantageous case of supercritical extraction, the dissolving solvent may be at least partially in a supercritical form, which favorably optimizes the decantation during the extraction step, and more specifically, makes it possible to maximize purification between the liquid phase and the supercritical phase in each extraction phase or plateau.

[0090] Advantageously, at the end of extraction step E3), the used solvent obtained contains impurities in particular. It may be reprocessed in an organic processing section, which on the one hand separates and removes impurities and purifies the solvent to obtain a purified extraction solvent, and on the other hand, allows at least a portion of the purified extraction solvent to be recycled to the inlet of extraction step E3) and / or to the inlet of dissolution step a) if the dissolution solvent and the extraction solvent are the same. The used solvent may be processed according to any method known to those skilled in the art, for example, by one or more methods from distillation, evaporation, extraction, adsorption, crystallization and precipitation of insoluble substances or by purging.

[0091] (Adsorption step b)) The processing method according to the present invention comprises an adsorption step b), which yields at least one purified polymer solution. The purified polymer solution obtained at the end of step b) preferably contains the target polymer that the present invention seeks to recover and purify, dissolved in a dissolving solvent.

[0092] The adsorption step b) is advantageously carried out downstream of the dissolution step a) and upstream of the polymer recovery step c). The adsorption step b) is preferably carried out upstream or downstream of an additional purification step. For example, it may be carried out upstream of an optional step E1) and / or E2), and may particularly correspond to an optional intermediate adsorption step a'). It may be carried out upstream or downstream of an optional step E3), for example. Thus, the adsorption step b) is carried out by bringing the polymer solution to be fed to step b), in particular the crude polymer solution obtained from step a), the clarified polymer solution obtained from an optional step E1), or the washed polymer solution obtained from an optional step E2), or the extracted polymer solution obtained from another optional step E3), into contact with one or more adsorbents.

[0093] The adsorption step b) advantageously includes an adsorption section and is operated in the presence of at least one adsorbent (preferably a solid), in particular in the form of a fixed bed, an entrained bed (or a slurry, i.e., a form of particles introduced into and accompanied by the flow to be purified) or a boiling bed, preferably in the form of a fixed bed or an entrained bed. The adsorbent (one or more) used in step b) is preferably alumina, silica, silica-alumina, activated carbon, decolorized earth, or a mixture thereof, preferably in the form of a fixed bed or an entrained bed, and the circulation of the flow may be upward or downward.

[0094] Advantageously, the temperature during the adsorption step b) is 100 to 300°C, preferably 150 to 250°C, and the pressure is 1.0 to 20.0 MPa (absolute), preferably 1.5 to 15.0 MPa (absolute), and very preferably 2.0 to 10.0 MPa (absolute). Much more advantageously, the adsorption step b) is carried out under the conditions of dissolution temperature and pressure, i.e., the dissolution temperature and pressure achieved in step a). Preferably, in step b), the hourly space velocity (HSV) corresponds to the ratio between the volumetric flow rate of the polymer solution supplied to step b) and the volume of the adsorbent, and is 0.05 to 10 h -1 Prioritizing 0.1 to 5.0 hours -1 That is the case.

[0095] According to a particular embodiment of step b), the adsorption section may include one or more fixed beds of adsorbent, for example, in the form of adsorption columns, preferably at least two adsorption columns, preferably two to four adsorption columns, containing the adsorbent. If the adsorption section includes two adsorption columns, one mode of operation may be called a “swing” operation according to technical terms, where one column is online, i.e., in service, while the other column is in reserve. When the adsorbent in the online column is depleted, this column is isolated, while the in-reserve column is made online, i.e., in service. The used adsorbent may then be regenerated in situ and / or replaced with fresh adsorbent, and the column containing it may be made online again once the other column has been isolated.

[0096] Another mode of functionalization of this particular embodiment of step b) involves one or more fixed beds of adsorbent and having at least two columns operating in series. When the adsorbent in the leading column is depleted, this first column is isolated, and the used adsorbent is either regenerated in-situ or replaced with fresh adsorbent. The column is then brought back online at the rearmost position, and this is repeated. This mode of operation is known as the variable-arrange mode, or according to PRS for permutable reactor system, or other technical terms, "lead and lag." The combination of at least two adsorption columns makes it possible to overcome possible and potentially rapid poisoning and / or clogging of the adsorbent due to the binding action of impurities, contaminants, and insoluble substances that may be present in the flow to be processed. The reason for this is that the presence of at least two adsorption columns makes it advantageous to facilitate the replacement and / or regeneration of adsorbent without stopping the process, and also makes it possible to control costs and limit adsorbent consumption.

[0097] According to this particular embodiment of step b) of adsorption of the adsorbent on a fixed bed, step b) is preferably carried out downstream of the optional step E1) and / or optional washing step E2) of separation of insoluble substances, and upstream or downstream of the optional extraction step E3). Advantageously, the combination of the steps E1) and / or washing step E2) and extraction step E3) of separation of insoluble substances with step b) enables improved purification of the polymer solution by utilizing the affinity of residual impurities to both the adsorbent solid and the extraction solvent, and optionally to the concentrated solution.

[0098] The adsorption section of step b) may, according to another embodiment, consist of adding adsorbent particles to a polymer solution, particularly a crude polymer solution, the particles may be separated from the polymer solution via a step of removing the adsorbent particles located downstream of the adsorption section. The removal of the adsorbent particles may, advantageously, correspond to a step E1) or a washing step E2) for separating and removing insoluble substances. Such implementation of adsorption step b) may, advantageously, correspond to an optional intermediate adsorption step a') described herein by performing solid / liquid separation following the introduction of adsorbent particles.

[0099] (Step c) for recovering polymers) According to the present invention, the method includes step c) of recovering the polymer, thereby obtaining at least one solvent fraction and at least one purified polymer fraction.

[0100] The polymer recovery step c) advantageously includes at least one solvent recovery section, preferably 1 to 5 solvent recovery sections. The polymer recovery step c) is fed the washed polymer solution or optionally the extracted polymer solution.

[0101] The polymer recovery step c) is therefore directed, firstly, towards separating and removing the solvent(s), in particular the dissolving solvent, contained in the polymer solution fed to step c), i.e., the purified polymer solution or optionally the extracted polymer solution, at least partially, preferably overwhelmingly, and at least partially, preferably overwhelmingly, and most preferably completely, the dissolving solvent and any other solvent(s), such as the extraction solvent, used in this method, that may still be present in the polymer solution fed to step c). The term “overwhelmingly” should be understood to mean at least 50% by weight, preferredly at least 70% by weight, preferably at least 90% by weight, and very preferably at least 95% by weight, relative to the weight of the solvent(s), in particular the dissolving solvent and optionally the extraction solvent contained in the purified polymer solution or optionally the extracted polymer solution fed to step c). Any method known to those skilled in the art for separating a solvent from a polymer may be employed, in particular any method that allows for a phase change of the polymer or solvent(s). The solvent(s) may be separated and removed, for example by evaporation, stripping, demixing, density difference, decantation or centrifugation, etc.

[0102] The resulting purified polymer fraction may correspond to a concentrated polymer solution or a solid purified polymer. Preferably, polymer recovery step c) also includes a conditioning section for conditioning the polymer in a solid form, more specifically in the form of solid granules.

[0103] The polymer recovery step c) is also directed towards recovering at least partially, preferably overwhelmingly and preferentially whole, the solvent(s), in particular the dissolving solvent and optionally the extraction solvent, contained in the purified polymer solution or optionally the extracted polymer solution fed to step c). The polymer recovery step c) is also optionally directed towards purifying and recovering the recovered solvent fraction, in particular, upstream of the dissolution step a) and optionally upstream of the extraction step E3). The term “overwhelmingly” should be understood to mean at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and very preferably at least 95% by weight, relative to the weight of the solvent(s), contained in the purified polymer solution or optionally the extracted polymer solution fed to step c).

[0104] The polymer recovery step c) advantageously includes at least one solvent recovery section where the temperature is 0 to 350°C, preferably 5 to 300°C, preferably 10 to 250°C, and the pressure is 0.1 to 20.0 MPa (absolute), preferably 0.1 to 15.0 MPa (absolute), and very preferably 0.1 to 10.0 MPa (absolute).

[0105] Advantageously, polymer recovery step c) includes at least one solvent recovery section, each preferably comprising equipment operated at different temperatures and pressures, for the purpose of obtaining at least one solvent fraction and at least one purified polymer fraction. In cases where several different solvents are used in the processing method according to the present invention, particularly in dissolution step a) and optionally in extraction step E3), step c) may include several solvent recovery sections, for example, two, three, or four solvent recovery sections, to recover various solvents, in particular dissolution solvents and optionally extraction solvents, separately, sequentially, and / or continuously.

[0106] According to a particular embodiment of the present invention, the method of the present invention preferably includes the following, either sequentially or simultaneously: - Solvent recovery section c1); The polymer solution is preferably heated to a temperature above the melting point of the polymer to obtain a solvent fraction and a purified polymer fraction. - Conditioning section c2); The purified polymer fraction (preferably separated from one or more solvents) is cooled to a temperature favorably below the melting point of the polymer to obtain a fraction containing the polymer in solid form.

[0107] According to a preferred embodiment of the present invention, step c) includes a section for recovering the solvent of step c) under temperature and pressure conditions adjusted to be supercritical, i.e., above the critical point of the solvent(s) to be separated and excluded, in particular above the critical point of the dissolving solvent, which is advantageously possible to easily separate, exclude and recover at least a portion of the solvent, in particular the dissolving solvent. In this embodiment, the solvent recovery section particularly includes a fluid system comprising a supercritical phase overwhelmingly containing the solvent, in particular the dissolving solvent, and a liquid phase containing the polymer. The term “overwhelmingly” here means at least 50% by weight, preferably at least 70% by weight, preferably at least 90% by weight, and very preferably at least 95% by weight, relative to the weight of the flow under consideration, i.e., the supercritical phase. The separation is sometimes referred to as supercritical separation of the solvent(s). Supercritical separation of a solvent(s) allows for the efficient separation of a solvent(s), particularly a dissolving solvent, on the one hand, and a polymer or, in some cases, a concentrated polymer solution, where supercritical separation is advantageously permissible due to a significant difference in density between the two phases. Furthermore, supercritical separation of a solvent(s) offers the advantage of significantly reduced energy and environmental costs compared to simple vaporization of the solvent, because there is no latent heat of vaporization during the transition to the supercritical state.

[0108] According to a particular embodiment of the present invention, at least a portion of the purified polymer fraction obtained at the end of step c) may be recycled to the dissolution step a) and undergo another processing cycle to improve the polymer purification efficiency.

[0109] Much to our advantage, the solvent fraction recovered at the end of step c) may be processed in an organic processing section located at the end of step c) to purify it and obtain a purified solvent, in particular a purified dissolution solvent, which can be advantageously recycled to dissolution step a) and / or optionally an extraction step E3). The optional organic processing section at the end of step c) may use any method known to those skilled in the art, such as one or more methods from distillation, evaporation, liquid-liquid extraction, adsorption, crystallization and precipitation of insoluble substances, or by purging.

[0110] The method according to the present invention makes it possible to obtain a purified stream of polymer, particularly thermoplastics, and more specifically polyolefins, from plastic waste, which can be used in any application, for example, as a substitute for the same polymer in unused form. The impurity content of the purified stream of polymer obtained through the method according to the present invention, i.e., the purified polymer fraction, is therefore low enough to be used in any application.

[0111] According to a preferred embodiment of the present invention, a method for processing plastic supply raw materials comprises, preferably, the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E1: Feeding a crude polymer solution and separating and removing insoluble substances; obtaining at least one clarified polymer solution and at least one insoluble fraction; - Step b) Obtaining at least one purified polymer solution by placing the clarified polymer solution in contact with an adsorbent, preferably on a fixed bed; and - Step c) of recovering the polymer from the purified polymer solution, preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction.

[0112] According to another preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E1 involves feeding a crude polymer solution and separating and removing insoluble substances; this yields at least one clarified polymer solution and at least one insoluble fraction; - Step b) Obtain at least one purified polymer solution by placing the clarified polymer solution in contact with an adsorbent, preferably on a fixed bed; - Step E3) of extracting the purified polymer solution with an extraction solvent, preferably including supercritical extraction; to obtain at least one extracted polymer solution and at least one used solvent; and - Step c) of recovering the polymer from the extracted polymer solution, preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, preferably consists of, the dissolving solvent and the extraction solvent, and preferably they are the same.

[0113] According to another preferred alternative embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E1 involves feeding a crude polymer solution and separating and removing insoluble substances; this yields at least one clarified polymer solution and at least one insoluble fraction; - Step E3) of extracting the clarified polymer solution with an extraction solvent, preferably step E3) including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; - Step b) Obtaining at least one purified polymer solution by placing the extracted polymer solution in contact with an adsorbent, preferably on a fixed bed; and - Step c) is a step of recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, preferably consists of, the dissolving solvent and the extraction solvent, and preferably they are the same.

[0114] According to another preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E1 involves feeding a crude polymer solution and separating and removing insoluble substances; this yields at least one clarified polymer solution and at least one insoluble fraction; - Step E2: Washing the clarified polymer solution by contact with a concentrated solution; obtaining at least one washing effluent and at least one washed polymer solution; - Step E3) of extracting the washed polymer solution with an extraction solvent, preferably step E3) including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; - Step b) Obtaining at least one purified polymer solution by placing the extracted polymer solution in contact with an adsorbent, preferably on a fixed bed; and - Step c) is a step of recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, preferably consists of, the dissolving solvent and the extraction solvent, and preferably they are the same.

[0115] According to another preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E1 involves feeding a crude polymer solution and separating and removing insoluble substances; this yields at least one clarified polymer solution and at least one insoluble fraction; - Step E2: Washing the clarified polymer solution by contact with a concentrated solution; obtaining at least one washing effluent and at least one washed polymer solution; - Step b) Obtain at least one purified polymer solution by placing the washed polymer solution in contact with an adsorbent, preferably on a fixed bed; - Step E3) of extraction of the purified polymer solution with an extraction solvent, preferably step E3) including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; and - Step c) is a step of recovering the polymer from the extracted polymer solution obtained in step b), preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, preferably consists of, the dissolving solvent and the extraction solvent, and preferably they are the same.

[0116] According to another preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E2: Washing the crude polymer solution by contact with a concentrated solution; obtaining at least one type of washing effluent and at least one type of washed polymer solution; - Step b) Obtaining at least one purified polymer solution by placing the washed polymer solution in contact with an adsorbent, preferably on a fixed bed; and - Step c) is a step of recovering the polymer from the purified polymer solution obtained in step b), preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, and preferably consists of, these elements.

[0117] According to another preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) dissolution in a dissolving solvent, wherein the dissolving solvent preferably has a boiling point of 75 to 220°C; to obtain at least one crude polymer solution; - Step E2: Washing the crude polymer solution by contact with a concentrated solution; obtaining at least one type of washing effluent and at least one type of washed polymer solution; - Step E1 involves feeding the washed polymer solution and separating and removing insoluble substances; obtaining at least one clarified polymer solution and at least one insoluble fraction; - Step b) Obtain at least one purified polymer solution by placing the clarified polymer solution in contact with an adsorbent, preferably on a fixed bed; - Step E3) of extraction of the purified polymer solution with an extraction solvent, preferably including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; and - Step c) is a step of recovering the polymer from the extracted polymer solution obtained in step b), preferably including supercritical separation of one or more solvents); to obtain a solvent fraction and a purified polymer fraction; It includes, preferably consists of, the dissolving solvent and the extraction solvent, and preferably they are the same.

[0118] The following examples and figures illustrate the present invention, and in particular specific embodiments thereof, but do not limit the scope of the present invention.

[0119] (List of drawings) The information relating to the elements referenced in Figures 1-3 is intended to enable a better understanding of the present invention and does not limit the invention to the specific embodiments shown in Figures 1-3. The various embodiments presented may be used individually or in combination with each other, and there are no restrictions on such combinations.

[0120] Figure 1 shows a scheme of one embodiment of the method of the present invention, which includes the following steps: - Step a of dissolving the plastic supply material (1): The plastic supply material (1) contains the polymer in the dissolving solvent (2) to obtain a crude polymer solution (3); - Step b) involves placing the crude polymer solution (3) in contact with the adsorbent to perform adsorption; a purified polymer solution (12) is obtained; - Step c); recover the polymer from the purified polymer solution (12) obtained in step b); obtain a solvent fraction (13) and a purified polymer fraction (14).

[0121] Figure 2 shows a variation of the method according to the present invention shown in Figure 1, and includes the following steps: - Step a of dissolving the plastic supply material (1): The plastic supply material (1) contains the polymer in the dissolving solvent (2) to obtain a crude polymer solution (3); - Step E1: Feed the crude polymer solution (3) and separate and remove the insoluble substance; obtain the clarified polymer solution (5) and the insoluble fraction (4); - Step E2 involves washing the clarified polymer solution (5) by contact with a concentrated solution (6); obtaining the washing effluent (7) and the washed polymer solution (8); - Step E3: Extraction of the washed polymer solution (8) with the extraction solvent (9); obtain the extracted polymer solution (11) and the used solvent (10); - Step b) involves placing the extracted polymer solution (11) in contact with the adsorbent to perform adsorption; a purified polymer solution (12) is obtained; - Step c); recover the polymer from the purified polymer solution (12) obtained in step b); obtain a solvent fraction (13) and a purified polymer fraction (14).

[0122] Figure 3 shows a variation of the method according to the present invention shown in Figure 2. In the embodiment shown in Figure 3, the method includes an intermediate step a') between step a) and step E1). A crude polymer solution (3) is placed in contact with an adsorbent in the form of divided solids. This is for the purpose of obtaining a polymer solution (21) containing the adsorbent in suspension and feeding it to the separation step E1). The adsorbent introduced in step a') is separated and removed into an insoluble substance fraction (4).

[0123] Figures 1-3 show only the main processes along with the main flow to enable a better understanding of the present invention. Even if not shown, it is clear that all the equipment necessary for functionality (containers, pumps, exchangers, furnaces, columns, etc.) is present.

[0124] (Examples) (Example 1 (Conforms to the present invention)) 125 mL of n-heptane and 23 g of plastic feed material are introduced into a 500 mL autoclave equipped with a stirrer. The plastic feed material is in the form of blue-colored crushed material with a size of less than 5 mm, and is polyethylene-based. 30 g of activated carbon (Chemviron CPG-LF 12×40) is placed above the liquid level in the basket.

[0125] The autoclave is then sealed and heated to 160°C at a rate of 2°C per minute, while stirring at 500 revolutions per minute (rpm). Once the temperature reaches 160°C, the temperature and stirring are maintained at a spontaneous pressure of 2.0 MPa (absolute) for 3 hours. After 3 hours, all the polyethylene is dissolved in n-heptane. At this stage, the resulting crude polymer solution is not in contact with the basket containing activated carbon, as the basket is located above the liquid. The crude polymer solution is observed through the autoclave's viewing window and is blue in color.

[0126] The basket containing the activated carbon is then immersed in the liquid to bring the crude polymer solution into contact with the activated carbon. The temperature is maintained at 160°C, the pressure at 2.0 MPa (absolute), and the stirring is maintained at 500 rpm. These temperature, pressure, and stirring conditions are then maintained for 2 hours, after which the stirring is stopped.

[0127] The purified polymer solution was observed through the autoclave's viewing window and was significantly decolorized compared to the crude polymer solution, demonstrating the effectiveness of activated carbon used as an adsorbent for decolorizing the n-heptane-based polymer solution.

[0128] 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, flashing with nitrogen for 6 hours.

[0129] A very slightly bluish-white solid is then obtained in a crystal dish.

[0130] (Example 2 (not conforming to the present invention)) 125 mL of n-heptane and 23 g of plastic feed material are introduced into a 500 mL autoclave equipped with a stirrer. The plastic feed material is in the form of blue-colored crushed material with a size of less than 5 mm, and is polyethylene-based.

[0131] The autoclave is then sealed and heated to 160°C at a rate of 2°C per minute, while stirring at 500 revolutions per minute (rpm). Once the temperature reaches 160°C, the temperature and stirring are maintained at a spontaneous pressure of 2.0 MPa (absolute) for 3 hours. After 3 hours, all the polyethylene is dissolved in n-heptane. The crude polymer solution is observed through the autoclave's viewing window and is blue.

[0132] Maintain these conditions—temperature (160°C), pressure (2.0 MPa (absolute)), and stirring (500 rpm)—for 2 hours, after which stop stirring.

[0133] The polymer solution, observed through the autoclave's viewing window, remains blue and is identical to the crude polymer solution observed earlier.

[0134] Take 15 mL of the polymer solution and place it in a crystallization dish. Then, place the crystallization dish in an oven at 180°C and atmospheric pressure, flashing with nitrogen for 6 hours.

[0135] A blue solid is obtained. This is similar in color to the crushed polyethylene material used as the starting feed material. [Brief explanation of the drawing]

[0136] [Figure 1] This shows a scheme of one embodiment of the method of the present invention. [Figure 2] This is a variation of the method according to the present invention, as shown in Figure 1. [Figure 3] Figure 2 shows a variation of the method according to the present invention.

Claims

1. A method for processing a plastic supply material containing a polyolefin, comprising the following steps: a) A dissolution step comprising placing a plastic supply material in contact with a dissolution solvent at a dissolution temperature of 150°C to 250°C and a dissolution pressure of 1.5 to 15.0 MPa (absolute), wherein the dissolution solvent is selected from at least one organic solvent containing one or more alkanes having a boiling point of 75°C to 250°C and containing 6 to 10 carbon atoms; to obtain at least one crude polymer solution; b) Adsorption step by contacting the crude polymer solution obtained in step a) with at least one adsorbent at a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute); obtaining at least one purified polymer solution; then c) A step to recover the polymer; obtaining at least one solvent fraction and at least one purified polyolefin fraction.

2. The method according to claim 1, wherein the dissolving solvent is selected from organic solvents having a boiling point of 80°C to 220°C.

3. The method according to claim 2, wherein the dissolving solvent is selected from organic solvents having a boiling point of 80°C to 180°C.

4. The method according to any one of claims 1 to 3, wherein the critical temperature of the dissolving solvent is 200 to 390°C and the critical pressure is 2.0 to 4.3 MPa (absolute).

5. The method according to any one of claims 1 to 4, wherein the dissolution pressure in step a) is 2.0 to 10.0 MPa (absolute).

6. The method according to any one of claims 1 to 4, wherein the dissolution pressure in step a) is 1.5 to 2.4 MPa (absolute).

7. The method according to claim 6, wherein the dissolution pressure in step a) is 1.7 to 2.2 MPa (absolute).

8. The method according to any one of claims 1 to 7, wherein the adsorption step b) is performed at the dissolution temperature and dissolution pressure of step a).

9. The method according to any one of claims 1 to 8, wherein the adsorption step b) is carried out in the presence of at least one adsorbent, the adsorbent being in the form of a fixed bed, an accompanying bed, or a boiling bed.

10. The method according to any one of claims 1 to 9, wherein the adsorbent is alumina, silica, silica-alumina, activated carbon, decolorized earth, or a mixture thereof.

11. The method according to claim 10, wherein the adsorbent is activated carbon, decolorized earth, or a mixture thereof.

12. The method according to any one of claims 1 to 11, wherein the polymer recovery step c) includes a solvent recovery section in which the temperature is 10 to 250°C and the pressure is 0.1 to 15.0 MPa (absolute).

13. The method according to any one of claims 1 to 12, wherein the polymer recovery step c) includes at least one solvent recovery section, wherein the temperature and pressure are adjusted to bring the dissolving solvent under supercritical conditions.

14. The method according to any one of claims 1 to 13, comprising step E1) separating and removing insoluble substances by solid-liquid separation at a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute), wherein the step is located upstream or downstream of the adsorption step b) between the dissolution step a) and the polymer recovery step c).

15. The method according to claim 14, wherein step E1) for separating and removing insoluble substances comprises an electrostatic separator and / or a filter and / or a sand filter.

16. The method according to any one of claims 1 to 15, comprising step E2) washing with a high-density solvent at a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute), wherein the step is located upstream or downstream of the adsorption step b) between the dissolution step a) and the polymer recovery step c), and the high-density solvent is an aqueous solution.

17. The method according to any one of claims 1 to 16, comprising step E3) extraction by contacting an extraction solvent with a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute), wherein the extraction solvent is an organic solvent, the critical temperature of the organic solvent is 90 to 400°C, and the critical pressure is 1.5 to 5.0 MPa (absolute), and obtaining at least one extracted polymer solution and at least one spent catalyst medium.

18. A method according to any one of claims 1 to 17, comprising the following steps: a) A dissolution step comprising placing the plastic supply material in contact with a dissolving solvent at a dissolution temperature of 150°C to 250°C and a dissolution pressure of 1.5 to 15.0 MPa (absolute); obtaining at least one crude polymer solution; E1) A step E1) in which insoluble substances are separated and removed by solid-liquid separation at a temperature of 100 to 300°C and a pressure of 1.0 to 20.0 MPa (absolute), wherein the crude polymer solution obtained from step a) is fed E1); at least one clarified polymer solution and at least one insoluble fraction are obtained; b) Adsorption step by contacting the clarified polymer solution with at least one adsorbent at a temperature of 100 to 300°C and a pressure of 1.0 to 20.0 MPa (absolute); obtaining at least one purified polymer solution; then c) Polymer recovery step: obtain at least one solvent fraction and at least one purified polyolefin fraction.

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