Method for treating used plastics by dissolving the polymer and purifying it by washing

Abstract

Disclosed is a method for processing a 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 comprising contacting the crude polymer solution with an adsorbent 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-poor 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 thermoplastic plastics, such as polyolefins, the method comprising washing a polymer solution with a concentrated solution, such as an aqueous solution, to at least partially remove impurities, especially additives conventionally used in plastic-based materials, such as dyes, pigments, organic and inorganic fillers, so that by separating and excluding the polymers, especially thermoplastic plastics, contained in the feedstock, the plastic feedstock can be upgraded and they can be recovered and reused.

Background Art

[0002] Plastics obtained from the 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 plastic waste stream 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 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, particularly those obtained from plastic waste, to efficiently remove impurities, in particular additives conventionally added to plastic materials, more specifically impurities particularly soluble in organic solvents, thereby upgrading plastic feedstock, particularly plastic waste, by separating, removing, and recovering polymers, particularly thermoplastics, so that they can be used, for example, as polymer bases 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 Initiative] [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: 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); obtaining at least one crude polymer solution; b) A washing step by bringing the crude polymer solution obtained in step a) into contact with a concentrated solvent at a temperature of 100°C to 300°C and a pressure of 1.0 to 20.0 MPa (absolute) and with a mass ratio of 0.05 to 20.0 between the mass flow rate of the concentrated solvent and the mass flow rate of the crude polymer solution supplied to step b); obtaining at least one washed polymer solution and at least one washed effluent; then c) A step of recovering the polymer; a step of 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 containing plastics, in particular plastic waste, especially plastic waste obtained from collection and sorting channels, to recover 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 streams of purified polymers, in particular purified thermoplastics, in particular purified polyolefins, e.g., polyethylene and polypropylene, which are advantageously negligible or contain impurities in such small or at least small amounts that the streams of the purified polymers, in particular purified thermoplastics, can be introduced into any plastic formulation in place of unused polymer resins. For example, the streams of purified polymers, in particular streams of purified thermoplastics, in particular streams of purified polyolefins obtained at the end of the method according to the present invention advantageously contain less than 5% by weight of impurities, and very advantageously less than 1% by weight of impurities.

[0013] The present invention proposes a series of operations that, therefore, allow for the upgrading of plastic waste 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, enabling 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 due to enabling the upgrading of plastic waste. Specifically, it enables the purification of plastic waste for the purpose of obtaining a purified polymer fraction with reduced impurity content, and in particular decolorized and deodorized, which can be reused to form new plastic objects. The obtained purified polymer fraction can 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 so that they can be used in any application, in particular as a substitute for unused polymers. The present invention therefore proposes a purification method by dissolving target polymers, 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, more specifically, at least one step b) of washing the polymer solution, in combination with other intermediate purification steps, from which a purified polymer solution can be obtained and from which the purified polymer can be recovered. [Modes for carrying out the invention]

[0017] (Description of the embodiment) According to the present invention, the expressions "comprised between ... and ..." and "between ... and ..." are equivalent, meaning that both limit values ​​of the interval are included within the range of values ​​stated. If this is not the case, and if both limit values ​​are not included within the range stated, such clarification is 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 individually 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] Specific embodiments of the present invention may be described in the following text. They may be implemented individually or in combination, and there are no restrictions on the combination, as long as it is technically feasible.

[0020] According to the present invention, the pressure is an 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 commonly used in the field of polymers, particularly in the field of polymer formulations. Additives introduced into polymer formulations may be, for example, plasticizers, fillers (organic or inorganic solid compounds used to modify the physical, thermal, mechanical and / or electrical properties of the polymer material or to reduce its cost price), reinforcing agents, dyes, pigments, curing agents, flame retardants, combustion suppressants, stabilizers, antioxidants, UV absorbers, antistatic agents, etc.

[0023] The additive corresponds to a part of the impurities of the plastic feedstock to be treated and can be at least partially removed by the treatment method according to the present invention. Other types of impurities may be use-related impurities or plastic materials, such as metal impurities, paper / carton, 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 flow of the target polymer by the method according to the present invention include the additives conventionally used in polymer formulations, the general use-related impurities derived from the life cycle of plastic objects and materials, and / or the impurities derived from the waste collection and sorting circuits. The impurities may be of the metal, organic or mineral type; they may 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 also 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 favorably suspended in the polymer solution, soluble impurities dissolved in the dissolving solvent, and / or possibly 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. b) Washing step by contact with concentrated solution; obtain at least one washing effluent and at least one washed polymer solution. E2) 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. E3) In some cases, a step of adsorption of impurities by contact with an adsorbent solid; obtaining 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 manufacturing defects and / or waste, particularly 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 that, after being molded into shape, are usually mixed with additives for the purpose of constituting various materials and objects (injection molded parts, tubes, films, fibers, cloths, mastic, coatings, etc.). 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, advantageously, be 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 more than 1 mm in size, such as wood, paper, biomass, iron, aluminum, glass, etc., and generally be formed 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 raw 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. Therefore, 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] The dissolution step a) is advantageously supplied by one or more transport devices, comprising at least 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 the supply step a) where appropriate.

[0038] While the plastic feed material is in contact with the dissolving solvent, the dissolving solvent is advantageously in at least partially, preferably completely, liquid form, while the plastic feed material, which contains 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 as 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 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 for the purpose of removing the coarsest particles, in addition to the melt pump; 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, preferably containing one or more hydrocarbons, and more preferably consisting of them, with a boiling point of -50°C to 250°C, preferably -15°C to 150°C, and more preferably 20 to 110°C. Preferably, the dissolution solvent contains one or more hydrocarbons, preferably consisting of them, and more preferably contains one or more alkanes, containing 3 to 12 carbon atoms, preferably 4 to 8 carbon atoms, and more preferably 5 to 7 carbon atoms, for example, isomers of pentane, hexane, 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 130 to 300°C, preferably 180 to 290°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 of 10 to 30°C and atmospheric pressure of 1 bar (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. 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.

[0043] 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).

[0044] 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, 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.

[0045] Much to our advantage, the temperature and pressure conditions of the dissolution achieved in step a) are adjusted so that the mixture (solvent + target polymer) becomes a single-phase mixture.

[0046] 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.

[0047] 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).

[0048] 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 the washing step b) and / or otherwise during one of the optional intermediate purification steps, for example, during the optional step E1) of separation of insoluble substances. 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.

[0049] 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 and / or suspended insoluble impurities or compounds that are similarly dissolved in the dissolving solvent. 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.

[0050] (Optional step E1: Separating and removing insoluble substances) The processing method may optionally include a step E1) of separating and removing insoluble substances by solid-liquid separation, which may be an additional purification step, and advantageously obtains at least one clarified polymer solution and at least one insoluble fraction. When incorporated into the method according to the present invention, the step E1) of separating and removing insoluble substances is located between the dissolution step a) and the polymer recovery step c), upstream or downstream of the washing step b), preferably upstream of the washing step b). The obtained insoluble fraction advantageously contains at least some, preferably all, of the insoluble impurities, particularly suspended in the crude polymer solution obtained from step a).

[0051] 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 as suspensions in the polymer solution, preferably 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.

[0052] 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.

[0053] When incorporated into the present method, step E1) for separating and removing insoluble substances is advantageously carried out at a temperature of 100 to 300°C, preferably 150 to 250°C, and a pressure of 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).

[0054] When incorporated into the present method, step E1) for separating and removing insoluble substances is preferably fed with the 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 the washed polymer solution obtained from washing step b).

[0055] 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, decanter, centrifugal decanter, centrifuge, filter, sand filter, eddy current separator, electrostatic separator, triboelectric separator, preferably a decanter, filter, sand filter and / or electrostatic separator.

[0056] 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.

[0057] 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.

[0058] Clogging of equipment, particularly electrostatic separators or filters, may be performed using a backflush injection solvent. The clogging solvent may be an aqueous solution or an organic solution, preferably an organic solvent of the same properties as that used in dissolution step a) and / or washing step b). According to a particular embodiment, the clogging solvent is of the same properties as the concentrated solution used in washing step b).

[0059] Some insoluble compounds, particularly 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 respect to 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 makes it possible to efficiently remove at least some, preferably all, of the insoluble particles smaller than 1 μm in size. 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, particularly particles smaller than 1 μm in size.

[0060] 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.

[0061] (Washing process b)) According to the present invention, the processing method comprises step b) washing with a concentrated solution, advantageously obtaining at least one washing effluent and at least one washed polymer solution. The washed polymer solution obtained at the end of step b) advantageously contains the target polymer that the present invention seeks to recover and purify dissolved in the dissolving solvent. In some cases, it still contains residual impurities and / or trace amounts of washing solvent that are particularly soluble in the dissolving solvent.

[0062] Advantageously, the washing step b) is fed a concentrated solution and a polymer solution, preferably 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 optional step b) may, in some cases, be a purified polymer solution obtained from an optional adsorption step E3), which is particularly carried out by adding an adsorbent as a mixture with the polymer solution. Preferably, the washing step b) is fed a concentrated solution and a polymer solution, preferably 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 b), more specifically 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 removed partially or entirely during washing step b) by dissolution or precipitation and / or entrainment in a concentrated solution. Thus, step b) contributes to the processing of the plastic supply material, more specifically to the purification of the polymer solution.

[0063] Washing step b) advantageously includes bringing the crude polymer solution or clarified polymer solution to be fed to step b) 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). In particular, the density of the concentrated solution is 0.85 or higher, preferably 0.9 or higher, and preferredly 1.0 or higher. The concentrated solution may also be polar, or at least more polar than the solvent, and the efficiency of washing the polymer solution is higher, especially for polar impurities.

[0064] The concentrated solution may be an aqueous solution, which preferably contains at least 50% by weight of water, preferably at least 75% by weight of water, more preferably at least 90% by weight of water, and very preferably at least 95% by weight of water. The pH of the aqueous solution may be adjusted using an acid or a base to promote the dissolution of the given compound. The concentrated solution may optionally contain, 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, so that the polymer of the plastic supply material remains insoluble under the temperature and pressure conditions of the optional step b), for example, the organic solvent may optionally be selected from sulfolane or N-methylpyrrolidone (NMP) as a mixture with water. Preferably, the concentrated solution in washing step b) is an aqueous solution, which preferably contains at least 90% by weight of water, very preferably at least 95% by weight of water.

[0065] The temperature at which washing step b) is advantageously carried out is 100 to 300°C, preferably 150 to 250°C, and the pressure at that time 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, washing step b) is carried out at the dissolution temperature and dissolution pressure.

[0066] Advantageously, 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 b) is preferably 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.

[0067] Step b) 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.

[0068] According to a preferred embodiment, the washing step b) 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 cleared 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.

[0069] 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.

[0070] According to another embodiment, the washing step b) is performed 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.

[0071] At the end of washing step b), 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, and possibly purifying 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.

[0072] According to a particular embodiment, if the method according to the present invention includes an optional step E1), the declogging flow (at least partially including insoluble fractions obtained from step E1) which may occur in step E1) is at least partially mixed with the cleaning effluent to remove insoluble impurities removed in steps E1) and b) in a common section.

[0073] (Optional selection process E2) The method according to the present invention may optionally include an extraction step E2) 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 E2) advantageously contains the target polymer that the present invention seeks to recover and purify, dissolved in the dissolving solvent. In some cases, it may still contain residual impurities and / or trace amounts of the extraction solvent, and / or trace amounts of the extraction solvent, if step E2) is performed, which are particularly soluble in the dissolving solvent.

[0074] When incorporated into a method according to the present invention, the extraction step E2) is advantageously located between the washing step b) and the polymer recovery step c). The optional extraction step E2) is advantageously fed a polymer solution, preferably a washed polymer solution obtained from step b) or optionally a purified polymer solution obtained from an adsorption step E3), and an extraction solvent.

[0075] The polymer solution fed to the optional step E2), preferably the washed polymer solution obtained from step b) or the purified polymer solution obtained from the optional step E3), may therefore contain dissolved compounds or dissolved impurities. These dissolved compounds may be partially or completely removed during the extraction step E2) by contacting them with the extraction solvent. Much advantageously, the combination of washing step b) and extraction step E2) allows for improved purification of the polymer solution by utilizing the affinity of the impurities to both the concentrated solvent and, optionally, the polar solvent, and the extraction solvent.

[0076] The optional extraction step E2) advantageously includes at least one extraction section, preferably one to five extraction sections, and most preferably one extraction section. The preferred temperature when the optional extraction step E2) is carried out is 100 to 300°C, preferably 150 to 250°C. The preferred pressure when the optional extraction step E2) is carried out 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). According to a preferred embodiment of the optional extraction step E2), the extraction step E2) is carried out under different temperature and pressure conditions than those of step a).

[0077] 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 E2) 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 the optional step E2) and the extraction solvent may be 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.

[0078] The extraction solvent used in the optional extraction step E2) is advantageously an organic solvent or a mixture of solvents (preferably organic). Preferably, the extraction 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 -15°C to 150°C, and preferably 20 to 110°C. Preferably, the extraction solvent contains, and more preferably consists of, one or more hydrocarbons, and more preferably one or more alkanes, and contains 3 to 12 carbon atoms, preferably 4 to 8 carbon atoms, and more preferably 5 to 7 carbon atoms, for example, isomers of pentane, hexane, 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 130 to 300°C, preferably 180 to 290°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.

[0079] Much preferably, the extraction solvent used in the optional step E2) 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 liquid form), which facilitates the management of the solvents, in particular their purification and recycling, especially their recycling to dissolution step a) and optionally extraction step E2). 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 limiting the energy consumption and costs that particularly arise 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.

[0080] The optional extraction section(s) of step E2) 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, particularly 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.

[0081] According to a preferred embodiment of the optional step E2), 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 E2) 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 E2) 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.

[0082] 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.

[0083] According to another embodiment, the extraction is carried out in a mixer-decanter, which advantageously includes a stirred mixing zone for bringing the extraction solvent into contact with the polymer solution, preferably a washed polymer solution or optionally a 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.

[0084] According to a preferred embodiment of the optional step E2), step E2) 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.

[0085] According to another preferred embodiment of the optional step E2), step E2) 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, extraction is carried out by bringing the polymer solution to be fed to step b), preferably a washed polymer solution or optionally a purified polymer solution, into contact with the extraction solvent under temperature and pressure conditions that enable 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, extraction is carried out by bringing the polymer solution to be fed to step b), preferably a washed polymer solution or a purified polymer solution, into contact with the extraction solvent which is, at least partially, preferably fully supercritical form. Such a supercritical extraction step E2) advantageously allows for the efficient purification of the polymer solution, which is particularly due to the very high affinity of organic impurities, e.g., some additives, in particular certain dyes, plasticizers, etc., to the supercritical phase. The use of an extraction solvent in a supercritical state makes it possible to create a substantial density difference between the supercritical phase and the polymer solution in liquid form, facilitating decantation-based separation between the supercritical and liquid phases, and consequently contributing to the purification of the polymer solution.

[0086] In this particularly preferred embodiment, the optional extraction step E2) uses an extraction solvent having a critical temperature preferably 130-300°C, preferably 180-290°C, and a critical pressure preferably 2.0-4.3 MPa (absolute), preferably 2.4-4.2 MPa (absolute). Much advantageously, in such a supercritical extraction step E2), the extraction solvent is selected from hydrocarbons, preferably containing 4-8 carbon atoms, preferably 5-7 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.

[0087] Advantageously, the temperature during the optional supercritical extraction step E2) 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 the extraction step E2) upstream of the extraction step, so that the extraction solvent is at least partially supercritical in the extraction section.

[0088] In a highly preferred embodiment of the optional extraction step E2), the extraction step E2) 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 decantation during the extraction step and, more specifically, allows for maximizing purification between the liquid phase and the supercritical phase in each extraction phase or plateau.

[0089] Advantageously, at the end of extraction step E2), 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 an optional extraction step E2) 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.

[0090] (Optional adsorption step E3) This processing method may, in some cases, include an optional adsorption step E3), which is located between the dissolution step a) and the polymer recovery step c). Depending on the quality of the starting plastic feed material and the impurities it contains, it may be advantageous to complete the purification of the polymer solution by an optional adsorption step E3), which in fact allows for the acquisition of at least one purified polymer solution.

[0091] When incorporated into a method according to the present invention, the adsorption step E3) is advantageously carried out downstream of the dissolution step a) and upstream of the polymer recovery step c), and upstream or downstream of the washing step b). An optional adsorption step E3) may, in some cases, be carried out upstream or downstream of an optional extraction step b).

[0092] The optional adsorption step E3) described above 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, a conjugated bed (or slurry, i.e., particles introduced into and accompanied by the flow to be purified) or a boiling bed. The adsorption section is advantageously operated in the presence of at least one adsorbent, preferably alumina, silica, silica-alumina, activated carbon, or decolorized earth type adsorbent, preferably in the form of a fixed bed or conjugated bed, with the circulation of the flow optionally rising or falling. If the method according to the present invention includes an optional adsorption step E3) upstream of the washing step b), the adsorption section is preferably operated in the presence of an adsorbent in the form of a conjugated bed (i.e., in the form of segmented particles introduced into a polymer solution). If the method according to the present invention includes an adsorption step E3) downstream of the washing step b), the adsorption section is much more preferably operated in the presence of an adsorbent in the form of a fixed bed.

[0093] The temperature at which the optional adsorption step E3) is advantageously carried out is 100 to 300°C, preferably 150 to 250°C, and the pressure at that time 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, step E3) 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 E3), the hourly space velocity (HSV) corresponds to the ratio between the volumetric flow rate of the polymer solution supplied to step E3) 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.

[0094] According to a particular embodiment of the optional step E3), 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 is then 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.

[0095] Another mode of functioning of this particular embodiment of process E3) involves having one or more fixed beds of adsorbent and having at least two columns functioning 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 potential 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 replace and / or regenerate the adsorbent without interrupting the process, and also makes it possible to control costs and limit the consumption of the adsorbent.

[0096] A significant advantage is that the combination of washing step b) and the optional adsorption step E3) enables improved purification of the polymer solution by utilizing the affinity of residual impurities to both the concentrated solvent and the adsorbent solid.

[0097] The adsorption section of an optional step E3) may, according to another embodiment, consist of adding adsorbent particles to a polymer solution, particularly a crude polymer solution, the particles of which may be separated from the polymer solution via a step of removing adsorbent particles located downstream of the adsorption section, for example, during washing step b) if the optional step E3) is located upstream of step b). Such implementation of the optional adsorption step E3) advantageously corresponds to an optional intermediate adsorption step a') by performing solid / liquid separation following the introduction of adsorbent particles, as described herein.

[0098] (Process c for polymer recovery) According to the present invention, the method includes step c) recovering the polymer, thereby obtaining at least one solvent fraction and at least one purified polymer fraction.

[0099] 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 or purified polymer solution.

[0100] The polymer recovery step c) is therefore directed, firstly, towards separating and removing at least partially, preferably overwhelmingly, the solvent(s), particularly the dissolving solvent and possibly the washing solvent, or even the extraction solvent, contained in the polymer solution fed to step c), i.e., the washed polymer solution or optionally the extracted polymer solution or the purified polymer solution, and at least partially, preferably overwhelmingly preferentially completely, the polymer free from the dissolving solvent and other solvent(s), 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), particularly the dissolving solvent and possibly the washing solvent, contained in the 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, difference in density, especially decantation or centrifugation.

[0101] 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.

[0102] The polymer recovery step c) is also directed towards recovering, at least partially, preferably overwhelmingly and preferentially, the solvent(s), particularly the dissolving solvent and optionally the washing solvent, and also the extraction solvent, contained in the washed polymer solution or optionally the extracted or purified polymer solution fed to step c), in order 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 / or the washing step b) and / or the extraction step E2). 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), which are contained in the washed polymer solution or optionally the extracted or purified polymer solution fed to step c).

[0103] The polymer recovery step c) advantageously includes at least one solvent recovery section, where the temperature therein is 0 to 350°C, preferably 5 to 300°C, preferably 10 to 250°C, and the pressure therein 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).

[0104] Advantageously, polymer recovery step c) includes at least one solvent recovery section, each comprising equipment operated at different temperatures and pressures for the purpose of obtaining, preferably, 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 washing step b), and optionally in extraction step E2), step c) may include several solvent recovery sections, for example, two, three, or four solvent recovery sections, to recover the various solvents, in particular the dissolution solvent, washing solvent, and optionally the extraction solvent, separately, sequentially, and / or continuously.

[0105] 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.

[0106] 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 solution of a polymer, or possibly a concentrated polymer, on the other hand. Supercritical separation is advantageously permitted by significant differences 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.

[0107] 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.

[0108] 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 dissolving solvent, which can be advantageously recycled to dissolution step a) and / or optionally washing step b) and / or an optional extraction step E2). The optional organic processing section at the end of step c) may use any method known to those skilled in the art, for example, one or more methods from distillation, evaporation, liquid-liquid extraction, adsorption, crystallization and precipitation of insoluble substances, or by purging.

[0109] 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.

[0110] According to a preferred embodiment of the present invention, a method for processing plastic supply material comprises the following steps: - Step a) Dissolution in a dissolving solvent; obtain a solution of at least one crude polymer; - Step b) Washing the crude polymer solution by contact with a concentrated solution; obtain at least one type of washing effluent and at least one type of washed polymer solution; - Step E2) of extracting the washed 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, particularly supercritical separation of the dissolving solvent); 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.

[0111] 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; obtain a solution of at least one crude polymer; - 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) Washing the clarified polymer solution by contact with a concentrated solution; obtain at least one type of washing effluent and at least one type of washed polymer solution; - Step E2) of extracting the washed polymer solution with an extraction solvent, preferably step E2) including supercritical extraction); obtaining 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.

[0112] According to a 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; obtain a solution of at least one crude polymer; - Step b) Washing the crude polymer solution by contact with a concentrated solution; obtain 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 E2) of extracting the clarified polymer solution with an extraction solvent, preferably step E2) 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 specific embodiment of the present invention, a method for processing plastic supply raw materials comprises the following steps: - Step a) Dissolution in a dissolving solvent; obtain a solution of at least one crude polymer; - 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) Washing the clarified polymer solution by contact with a concentrated solution; obtain at least one type of washing effluent and at least one type of washed polymer solution; - Step E2) of extracting the washed polymer solution with an extraction solvent, preferably step E2) including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; - Step E3 of adsorption by placing the extracted polymer solution in contact with an adsorbent, preferably on a fixed bed); obtain at least one purified polymer solution; and - Step c) recovers the polymer from the purified polymer solution obtained from step E3), 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 specific embodiment of the present invention, a method for processing plastic supply raw materials comprises the following steps: - Step a) Dissolution in a dissolving solvent; obtain a solution of at least one crude polymer; - Step b) Washing the crude polymer solution by contact with a concentrated solution; obtain 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 E2) of extracting the washed polymer solution with an extraction solvent, preferably step E2) including supercritical extraction); to obtain at least one extracted polymer solution and at least one used solvent; - Step E3 of adsorption by placing the extracted polymer solution in contact with an adsorbent, preferably on a fixed bed); obtain at least one purified polymer solution; and - Step c) is a step of recovering the polymer from the purified polymer solution obtained from step E3), 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] 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.

[0116] (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.

[0117] Figure 1 shows a scheme of one embodiment of the method of the present invention, and includes the following: - 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) to wash the crude polymer solution (3) with a concentrated solution (6), preferably an aqueous solution (6); to obtain the washed polymer solution (8) and the washing runoff (7); - Step c) recovers the polymer from the washed polymer solution (8) obtained in step b), obtaining a solvent fraction (13) and a purified polymer fraction (14).

[0118] 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 b) involves washing the clarified polymer solution (5) by contact with the concentrated solution (6); to obtain the washing effluent (7) and the washed polymer solution (8); - Step E2: Extraction of the washed polymer solution (8) with the extraction solvent (9); obtain the extracted polymer solution (11) and the used solvent (10); - Step E3: Adsorption by placing the extracted polymer solution (11) in contact with the adsorbent; to obtain the purified polymer solution (12); - Step c) recovers the polymer from the purified polymer solution (12) obtained in step E3); a solvent fraction (13) and a purified polymer fraction (14) are obtained.

[0119] 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).

[0120] 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.

[0121] (Examples) (Example 1 (Conforms to the present invention)) 250 mL of n-pentane 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 5 mm diameter pink-purple colored beads and is polypropylene based.

[0122] The autoclave is then sealed and heated to 180°C at a rate of 2°C per minute while stirring at 500 revolutions per minute (rpm). Once the temperature reaches 180°C, the temperature and stirring are maintained at a spontaneous pressure of 26 bar (or 2.6 MPa) for 3 hours. After 3 hours, all the polypropylene is dissolved in n-pentane. At the end of the dissolution process, a crude polymer solution is obtained, which is a highly colored liquid phase.

[0123] 125 mL of water is then added to the system while maintaining stirring at a temperature of 180°C, a pressure of 2.6 MPa, and 500 rpm. These temperature, pressure, and stirring conditions are then maintained for 5 minutes, after which stirring is stopped. After stopping stirring, the system is separated by sedimentation. After standing for 5 minutes, the fluid system in the autoclave separates by sedimentation, forming two phases at the end of the washing process. The upper phase, which contains polymers and corresponds to the washed polymer solution, is lighter in color than the mixture before the washing process.

[0124] Take 15 mL of the washed polymer solution and place it in a crystallization dish. Then, place the crystallization dish in an oven at 180°C and atmospheric pressure for 6 hours, while flashing with nitrogen.

[0125] A slightly pinkish-white solid is then obtained in a crystallization dish.

[0126] (Example 2 (not conforming to the present invention)) 250 mL of n-pentane 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 5 mm diameter pink-purple colored beads and is polypropylene based.

[0127] The autoclave is then sealed and heated to 180°C at a rate of 2°C per minute while stirring at 500 revolutions per minute (rpm). Once the temperature reaches 180°C, the temperature and stirring are maintained at a spontaneous pressure of 2.6 MPa for 3 hours. After 3 hours, all the polypropylene is dissolved in n-pentane. A crude polymer solution, which is a highly colored liquid phase, is obtained.

[0128] Take 15 mL of the crude 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 pink-purple colored solid is obtained in this way in a crystallization dish. The color of the obtained solid is close to the color of the beads from the initial supply material. [Brief explanation of the drawing]

[0130] [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 plastic supply raw materials, comprising the following steps: a) A dissolution step comprising bringing a plastic supply material into contact with a dissolving solvent selected from organic solvents containing hydrocarbons and having a boiling point of -50°C to 250°C, at a dissolution temperature of 150°C to 250°C and a dissolution pressure of 1.0 to 20.0 MPa (absolute); obtaining at least one crude polymer solution; b) A washing step in which the crude polymer solution obtained in step a) is brought into contact with a high-density solvent having a density of 0.85 or more at a temperature of 150°C to 250°C, a pressure of 1.0 to 20.0 MPa (absolute), and a mass ratio of 0.05 to 20.0 between the mass flow rate of the high-density solvent and the mass flow rate of the crude polymer solution supplied to step b); at least one washed polymer solution and at least one washed effluent are obtained; then c) Step of recovering the polymer; obtain at least one solvent fraction and at least one purified polymer fraction.

2. The method according to claim 1, wherein the boiling point of the organic solvent is -15°C to 150°C, or 20°C to 110°C.

3. The method according to claim 1 or 2, wherein the critical temperature of the dissolving solvent is 90 to 400°C, or 130 to 300°C, or 180 to 290°C, and the critical pressure is 1.5 to 5.0 MPa (absolute), or 2.0 to 4.3 MPa (absolute), or 2.4 to 4.2 MPa (absolute).

4. The method according to any one of claims 1 to 3, wherein the dissolution pressure is 1.5 to 15.0 MPa (absolute) or 2.0 to 10.0 MPa (absolute).

5. The method according to any one of claims 1 to 4, wherein the density of the high-density solvent used in step b) is 0.9 or greater, or 1.0 or greater.

6. The method according to any one of claims 1 to 5, wherein the high-density solvent used in step b) is an aqueous solution comprising at least 50% by weight of water, or at least 75% by weight of water, or at least 90% by weight of water, or at least 95% by weight of water.

7. The method according to any one of claims 1 to 6, wherein the washing step b) is performed at the dissolution temperature and dissolution pressure.

8. The method according to any one of claims 1 to 7, wherein the polymer recovery step c) includes a solvent recovery section where the temperature therein is 0 to 350°C, or 5 to 300°C, or 10 to 250°C, and the pressure therein is 0.1 to 20.0 MPa (absolute), or 0.1 to 15.0 MPa (absolute), or 0.1 to 10.0 MPa (absolute).

9. The method according to any one of claims 1 to 8, wherein step c) polymer recovery step includes at least one solvent recovery section under temperature and pressure conditions adjusted to bring the dissolving solvent under supercritical conditions.

10. The method according to any one of claims 1 to 9, comprising step E2) extraction, in which the washed polymer solution is brought into contact with an extraction solvent at a temperature of 100°C to 300°C, a pressure of 1.0 to 20.0 MPa (absolute), and a mass ratio of 0.05 to 20.0 between the mass flow rate of the extraction solvent and the mass flow rate of the washed polymer solution, to obtain at least one extracted polymer solution and at least one used solvent.

11. The method according to claim 10, wherein the extraction solvent is an organic solvent, its critical temperature is 90 to 400°C, or 130 to 300°C, or 180 to 290°C, and its critical pressure is 1.5 to 5.0 MPa (absolute), or 2.0 to 4.3 MPa (absolute), or 2.4 to 4.2 MPa (absolute).

12. The method according to claim 10, wherein the extraction solvent is the same as the dissolution solvent and is at least partially or completely in a supercritical state.

13. The method according to any one of claims 1 to 12, 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 step E1) is located between the dissolution step a) and the polymer recovery step c), and upstream or downstream of the washing step b).

14. The method according to claim 13, wherein step E1) for separating and removing insoluble substances includes an electrostatic separator and / or a filter and / or a sand filter.

15. The method according to any one of claims 1 to 14, comprising an adsorption step E3), the step E3) being located between a dissolution step a) and a polymer recovery step c), and comprising an adsorption section operated in the presence of at least one adsorbent, wherein the temperature during the operation is 100 to 300°C and the pressure is 1.0 to 20.0 MPa (absolute).

16. A method according to any one of claims 1 to 15, comprising the following steps: a) A dissolution step in which the plastic supply material is brought into contact with a dissolving solvent selected from organic solvents containing hydrocarbons and having a boiling point of -50°C to 250°C, at a dissolution temperature of 150°C to 250°C and a dissolution pressure of 1.0 to 20.0 MPa (absolute); at least one crude polymer solution is obtained; b) A washing step by bringing the crude polymer solution obtained in step a) into contact with a high-density solvent at a temperature of 150°C to 250°C, a pressure of 1.0 to 20.0 MPa (absolute), and a mass ratio of 0.05 to 20.0 between the mass flow rate of the high-density solvent and the mass flow rate of the crude polymer solution; obtaining at least one washed polymer solution and at least one washed effluent; E2) Extraction step by contacting the washed polymer solution obtained from step b) with an extraction solvent at a temperature of 100°C to 300°C, a pressure of 1.0 to 20.0 MPa (absolute), and a mass ratio of the mass flow rate of the extraction solvent to the mass flow rate of the washed polymer solution of 0.05 to 20.0; obtaining at least one extracted polymer solution and at least one used solvent; then c) Polymer recovery step: obtain at least one solvent fraction and at least one purified polymer fraction.

17. A method according to any one of claims 1 to 16, comprising the following steps: a) A dissolution step in which the plastic supply material is brought into contact with a dissolving solvent selected from organic solvents containing hydrocarbons and having a boiling point of -50°C to 250°C, at a dissolution temperature of 150°C to 250°C and a dissolution pressure of 1.0 to 20.0 MPa (absolute); at least one crude polymer solution is obtained; b) A washing step by bringing the crude polymer solution obtained in step a) into contact with a high-density solvent at a temperature of 150°C to 250°C, a pressure of 1.0 to 20.0 MPa (absolute), and a mass ratio of 0.05 to 20.0 between the mass flow rate of the high-density solvent and the mass flow rate of the crude polymer solution; obtaining at least one washed polymer solution and at least one washed effluent; E3) An adsorption step comprising feeding the washed polymer solution obtained from step b) and operating an adsorption section in the presence of 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) Polymer recovery step: obtain at least one solvent fraction and at least one purified polymer fraction.

18. The method according to claim 16 or 17, wherein the high-density solvent is an aqueous solution.

19. The method according to claim 16 or 17, wherein the polymer recovery step comprises at least one solvent recovery section under temperature and pressure conditions adjusted to be under supercritical conditions for the dissolving solvent.

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