Method for the integrated recycling of composite articles based on a thermoplastic polymer matrix

Abstract

The present invention relates to a method (100) for recycling a first article (10) to be recycled, comprising a composite material based on a fibrous reinforcement and a thermoplastic, preferably (meth)acrylic, polymer matrix, said method for recycling comprising the following steps: - introducing (130) a first article (10) into a system (1) suitable for recycling thermoplastic polymers; - introducing (140) a second article (20) to be recycled, comprising a thermoplastic polymer resin and not comprising any fibrous reinforcement, into a system (1) suitable for recycling thermoplastic polymers; - heating (150) the items to be recycled (10, 20) at a given temperature in said system (1) suitable for recycling thermoplastic polymers in order to depolymerize the thermoplastic, preferably (meth)acrylic, polymer and form the base monomer of said thermoplastic polymer; - recovery (160) of the constituent base monomers of said thermoplastic polymer; The present invention relates to a method comprising the steps of:

Description

Technical Field

[0001] The present invention generally relates to the recycling of articles made of composite materials based on a thermoplastic polymer matrix, and more particularly to a method for recycling articles made of a composite material based on a thermoplastic polymer matrix, especially a (meth)acrylic thermoplastic polymer, and a fibrous reinforcing material. The present invention also relates to a system for recycling articles made of a composite material capable of implementing such a method.

[0002] The present invention is useful in all industrial fields facing the recycling problem of industrial waste such as used products, post-use composite waste having a thermoplastic polymer matrix, especially a (meth)acrylic thermoplastic polymer matrix, or defective products or waste from plastic processing operations.

Background Art

[0003] Composite materials are widely used in various industrial fields, namely transportation (automobile, railway), sports and leisure, health, wind power, ship or aviation. These composite materials (also abbreviated as "composites") are a macro combination of at least two materials that are immiscible with each other. Generally, a composite material is composed of a polymer matrix forming a continuous phase on the one hand and a reinforcing material (or reinforcing agent), which is generally a fibrous reinforcing agent, on the other hand. There are also composite materials composed of a polymer matrix and a mineral filler, such as quartz, marble, silica, aluminum hydroxide, or titanium dioxide. Composite materials optionally include additives. These materials are often further mixed with other components such as metal inserts, wood, or foams to manufacture articles for various industrial purposes. The recycling of composite materials is a major issue in the environment of transitioning to a circular economy for the efficient use of resources and to reduce the environmental impact of products throughout the entire life cycle of composite materials.

[0004] The recycling of articles containing polymer matrix-based composites or polymer composites can be carried out according to several methods. These methods generally involve the thermal degradation of the polymer, i.e., the mechanical and physical properties of the polymer are reduced by increasing the temperature of the polymer, followed by depolymerization of the polymer.

[0005] Pyrolysis is known, which is a thermal process consisting of introducing the article to be treated into a suitable chamber and then heating the chamber so that heat is transferred to the article. The temperature of pyrolysis is generally between 400°C and 1300°C to enable chemical decomposition of the polymer matrix. Pyrolysis of the article results in the formation of gases, oily residues, and solid residues containing the reinforcing agent, inorganic filler, and carbonaceous solid of the composite. The gases obtained after pyrolysis can be used in the manufacture of new polymer articles, and the solid residues obtained after pyrolysis are used, among other things, in the manufacture of other products such as insulating materials. This recycling method generally does not have a very good monomer (e.g., methyl methacrylate) yield. Specifically, it is well known from the literature that composite materials form more residues than pure polymers during pyrolysis and have a low monomer yield.

[0006] Fluidized bed processes are also known where the fluidized bed can be, for example, a bed of silica sand. In this process, the article containing the composite is generally pre-crushed and introduced into a fluidized bed reactor containing the fluidized bed. Fluidization is generally carried out using a gas stream heated to a temperature above 400°C. In this bed, the matrix is rapidly heated and gasified, whereby the reinforcing material is removed from the matrix. Then, a part of the reinforcing material is carried out from the bed in the gas stream to a secondary combustion chamber. Another part is incorporated into a container along with the solids constituting the fluidized bed, where the solids are reheated and after the carbonaceous residues are burned, they are returned to the fluidized bed reactor. Similar to pyrolysis, this method is not designed to optimize the monomer yield.

[0007] In particular, poly(methyl methacrylate) (PMMA) is known for its optical properties and is a well-established thermoplastic polymer. It is sold, for example, under the name Altuglas®, and approximately 300,000 tons of PMMA are produced in Europe every year. Although PMMA can be converted into monomers by thermal depolymerization, the amount of PMMA waste collected for recycling in Europe is only approximately 30,000 tons per year. Also, recycling of PMMA in Europe is mostly based on the current lead process (molten lead bed), and in the lead process, lower-grade PMMA (e.g., in the form of composites or highly filled forms) cannot be reprocessed. This is because a large amount of residue is formed as a result in lower-grade PMMA and the monomer yield is low.

[0008] Known methods for recycling articles containing composite materials are known to involve various heating steps in which monomers are not formed in high yields, especially in the presence of fibrous composites.

[0009] Therefore, from the perspective of energy and the environment, it is desirable to have available recycling methods that can improve the yield of monomer formation during the recycling of fibrous composites based on thermoplastic, e.g., (meth)acrylic-based polymer matrices. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0010] The object of the present invention is to overcome the drawbacks of the prior art. In particular, the present invention aims to propose a simple and efficient solution for depolymerizing the constituent polymers of articles made of composite materials based on fibrous reinforcement materials. MEANS FOR SOLVING THE PROBLEM

[0011] For this purpose, the present invention is a method for recycling a first article to be recycled, comprising a composite material based on a thermoplastic, preferably (meth)acrylic, polymer matrix and a fibrous reinforcement, said recycling method comprising the following steps, namely - introducing the first article to be recycled into a system suitable for recycling the thermoplastic polymer, and - introducing a second article to be recycled, which contains a thermoplastic, preferably (meth)acrylic, polymer resin and no fibrous reinforcement, into a system suitable for recycling the thermoplastic polymer, - depolymerizing the thermoplastic polymer, preferably a (meth)acrylic polymer, and heating each article to be recycled in said system suitable for recycling the thermoplastic polymer to form the base monomer of said thermoplastic polymer at a given temperature, - recovering the constituent base monomer of said thermoplastic polymer characterized in that it comprises the following.

[0012] As will be detailed below and in the examples, such a method makes it possible to improve the production yield of the base monomer.

[0013] According to another optional feature of the method,

[0014] - the method comprises a step of purifying the base monomer recovered in advance. Specifically, considering that the thermoplastic polymers of the first and second articles to be recycled may be different, the method according to the present invention can result in a purification step, for example, various monomers that can be separated during distillation can be generated. Specifically, the first and second articles to be recycled each contain a polymer, preferably a (meth)acrylic polymer, but may contain different comonomers and different additives.

[0015] - The method includes a step of removing solid components generated during the step of heating the first article and the second article to be recycled. Considering the presence of fibrous reinforcing materials and optional fillers, this step can eliminate the recycling system for solid materials that may particularly impair performance in the environment of a continuous recycling system.

[0016] - The thermoplastic polymer matrix of the first article is a poly(methyl methacrylate) matrix. Poly(methyl methacrylate) can depolymerize into methyl methacrylate (MMA) and is particularly suitable for the method according to the present invention.

[0017] - The first article to be recycled and the second article to be recycled are introduced at a mass ratio between 0.1 and 1.5, preferably between 0.1 and 0.5, more preferably between 0.2 and 0.4. As shown in the examples, such a ratio can significantly improve the yield.

[0018] - The first article to be recycled has a mass percentage of fibrous reinforcing material exceeding 30%, preferably exceeding 50%, more preferably exceeding 70%. The higher the mass percentage of the fibrous reinforcing material in the article to be recycled, the lower the yield of base monomer recovery usually is. Nevertheless, under this low-yield condition, the increase expected by the method according to the present invention is large. Therefore, this type of material is very difficult to recycle by the prior art, while the method according to the present invention has significant advantages. In particular, the mass percentage of the fibrous reinforcing material here corresponds to the mass of the fibrous reinforcing material in the first article to be recycled with respect to the total mass of the first article to be recycled.

[0019] - The second article to be recycled is in the form of a syrup at room temperature (e.g., 25°C), and the mass percentage of the corresponding thermoplastic monomer, preferably a (meth)acrylic monomer, exceeds 80%, preferably exceeds 90%, preferably exceeds 95%.

[0020] - In another embodiment, the second article to be recycled has a mass percentage of the corresponding thermoplastic monomer, preferably a (meth)acrylic monomer, of less than 95%, preferably less than 90%, preferably less than 80%, more preferably less than 70%. Specifically, the present invention can function with a cast plate of a substantially pure methacrylic thermoplastic polymer, but according to the present invention, when the second article has a reinforcing material, additive, or filler, it is possible to increase the combined base monomer recovery rate more significantly without substantially reducing the purity.

[0021] - In another embodiment, the second article to be recycled has a mass percentage of the corresponding methyl methacrylate monomer of less than 95%, preferably less than 90%, preferably less than 80%, more preferably less than 70%. As described above, when the second article has a polymer or copolymer not based on methyl methacrylate, according to the present invention, it is possible to increase the combined base monomer recovery rate more significantly. This is particularly advantageous when the thermoplastic polymer matrix of the first article to be recycled is PMMA.

[0022] - A system suitable for recycling thermoplastic polymers is selected from the following. · A depolymerization system of an extruder and / or a conveyor, · A rotary drum depolymerization system, and · A system of depolymerization, preferably continuous, on a heating plate.

[0023] - During the heating step, the first and second articles to be recycled are heated to a temperature between 200°C and 1500°C, preferably between 200°C and 600°C, advantageously between 300°C and 600°C.

[0024] - The method also includes moderately heating the thermoplastic polymer, preferably a (meth)acrylic polymer, to at least partially liquefy it. Such moderate heating enables liquefaction but not depolymerization. - During the moderate heating, the thermoplastic polymer, preferably a (meth)acrylic polymer, is heated to a temperature between 200°C and 350°C, preferably between 200°C and 325°C, and advantageously between 225°C and 300°C. The moderate heating may be carried out at a temperature substantially equal to 270°C, such a temperature being sufficient to enable the movement of the liquefied thermoplastic polymer. The moderate heating may be of the second article or of the second article and the first article to be recycled. By carrying out the moderate heating, an improvement in the yield increase may be possible.

[0025] - Recovery of the fibrous reinforcement of the first article to be recycled, said recovery being carried out by at least one of the following methods: centrifugation, draining, spinning, pressing, filtration, screening, and / or cyclone methods. During the heating of the article to be recycled containing the fibrous reinforcement, the polymer matrix is separated from the article to recover the fibrous reinforcement, and then the purity of the monomer recovered can be increased and the fibrous reinforcement can optionally be reused without being degraded.

[0026] For this purpose, the present invention is a method for recycling a first article to be recycled comprising a composite material based on a thermoplastic, preferably (meth)acrylic, polymer matrix and a fibrous reinforcement, said recycling method comprising the following steps, namely · Means for conveying said first article to be recycled, · Means for conveying a second article to be recycled containing a thermoplastic, preferably (meth)acrylic, polymer resin and no fibrous reinforcement, · A reactor suitable for heating the article to be recycled, depolymerizing the thermoplastic polymer, preferably a (meth)acrylic polymer, and forming the base monomer of said thermoplastic polymer relates to a method characterized by including

[0027] Advantageously, although not limited, the recycling system according to the present invention includes a second reactor suitable for moderately heating one of the articles to be recycled, preferably a second article to be recycled, and the second reactor includes an opening arranged to be in fluid communication with the first reactor.

[0028] In a specific embodiment, the recycling system according to the present invention includes means for recovering the constituent base monomers of the thermoplastic polymer.

[0029] In a preferred embodiment, the recycling system according to the present invention includes means for moving the first and second articles to be recycled.

[0030] Other advantages and features of the present invention will become apparent by reading the following description, given by way of illustrative and non-limiting examples, with reference to the accompanying drawings.

Brief Description of the Drawings

[0031]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0032] Aspects of the present invention will be described with reference to the flowcharts and / or block diagrams of methods or systems (or apparatuses) according to embodiments of the present invention. In the drawings, the flowcharts and block diagrams show the configuration, functionality, and operation of possible embodiments of systems and methods according to various embodiments of the present invention. In this regard, each block of the flowchart or block diagram may represent a system, apparatus, or module for performing a given logical operation(s). In certain embodiments, the functions associated with the blocks may be represented in an order different from that shown in the figures. For example, two blocks shown in succession may actually be performed substantially simultaneously, or the blocks may be performed in the reverse order, depending on the functionality involved, in some cases.

[0033] In the following part of this specification, the term "monomer" means a molecule that can be polymerized.

[0034] The term "polymerization" as used relates to the process for converting a monomer or a mixture of monomers into a polymer.

[0035] The term "polymer" means either a copolymer or a homopolymer. A "copolymer" is a polymer in which several different monomer units are gathered together, and a "homopolymer" is a polymer in which the same monomer units are gathered together.

[0036] The term "depolymerization" as used relates to the process for converting a polymer into one or more monomers and / or oligomers and / or polymers having a molecular mass smaller than that of the initial polymer.

[0037] The term "base monomer" means the most dominant monomer unit constituting the polymer. Thus, in PMMA, the base monomer is MMA.

[0038] The term "thermoplastic polymer" or "thermoplastic resin" means a polymer that can be softened or melted under the action of heat in a repetitive manner and can take on a new shape by applying heat and pressure. Examples of thermoplastic resins include, for example, high-density polyethylene (HDPE) used, among other things, in the production of plastic bags or the assembly of automobiles; polyethylene terephthalate (PET) or polyvinyl chloride (PVC) used, among other things, in the production of plastic bottles; polystyrene (PS) used in the fields of packaging and construction; and polymethyl methacrylate (PMMA). Therefore, the use of thermoplastic resins affects a wide variety of fields ranging from packaging to the automotive industry, and the demand for plastics remains high.

[0039] The term "thermoplastic monomer" means a monomer(s) or molecule(s) in the chain of a thermoplastic polymer after polymerization.

[0040] The term "(meth)acrylic thermoplastic polymer" or "(meth)acrylic polymer" means a homopolymer or copolymer based on (meth)acrylic monomers selected from, for example, methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and mixtures thereof. Poly(methyl methacrylate) (PMMA) is a specific example of a (methacrylic) polymer obtained by the polymerization of methyl methacrylate monomer.

[0041] For the purposes of the present invention, the term "PMMA" represents homopolymers and copolymers of methyl methacrylate (MMA), and the weight proportion of MMA in PMMA is preferably at least 70% by weight for MMA copolymers. The term "methyl methacrylate-based copolymer" means a copolymer containing at least one methyl methacrylate monomer. For example, a methyl methacrylate-based copolymer may be a copolymer containing at least 70% by weight, preferably 80% by weight, and advantageously 90% by weight of MMA in PMMA.

[0042] The term "polymer matrix" means a polymer-based solid material that acts as a binder in the context of a composite material. The "matrix" includes polymers and / or oligomers and may also include additives and / or fillers. Thus, "(meth)acrylic polymer matrix" relates to any type of matrix containing acrylic and methacrylic polymers, oligomers, or copolymers. However, it does not deviate from the scope of the present invention if the (meth)acrylic polymer matrix contains up to 49% by weight, preferably less than 40% by weight, of non-acrylic compounds in the form of, for example, monomers, polymers, copolymers, or block copolymers selected from the following group: lactic acid, butadiene, isoprene, styrene, substituted styrenes such as α-methylstyrene or tert-butylstyrene, cyclic siloxanes, vinylnaphthalene, and vinylpyridine.

[0043] For the purposes of the present invention, the term "polymer resin" corresponds to a polymer-based solid material. "Polymer resin" includes polymers and / or oligomers and may also include additives and / or fillers. The polymer resin may be in solid or liquid form (especially in the form of a syrup). Additives and / or fillers can in particular improve specific properties such as impact strength or heat resistance. Thus, "(meth)acrylic polymer resin" relates to any type of resin containing acrylic and methacrylic polymers, oligomers, or copolymers. However, if the (meth)acrylic polymer resin contains up to 49% by weight, preferably less than 40% by weight, of a non-acrylic compound in the form of, for example, a monomer, polymer, copolymer, or block copolymer selected from the following group: namely, methacrylonitrile, lactic acid, butadiene, isoprene, styrene, substituted styrenes such as α-methylstyrene or tert-butylstyrene, cyclic siloxanes, vinylnaphthalene, and vinylpyridine, it does not depart from the scope of the present invention.

[0044] For the purposes of the present invention, the term "syrup" refers to a liquid composition having a dynamic viscosity between 10 mPa·s and 10,000 mPa·s at 25°C. The dynamic viscosity of the syrup is in the range of 10 mPa·s to 10,000 mPa·s, preferably 20 mPa·s to 7,000 mPa·s, and advantageously 20 mPa·s to 5,000 mPa·s. The viscosity of the syrup can be easily measured with a rheometer or viscometer. The dynamic viscosity is measured at 25°C.

[0045] For the purposes of the present invention, the term "composite material" means a multi-component material containing at least two immiscible components, with at least one component being a polymer and the other component being a reinforcing material such as, for example, a fibrous reinforcing material or a filler.

[0046] The term "reinforcing material" generally means a non-depolymerizable or non-gasifiable solid material such as a "fibrous reinforcing material" or a "mineral filler" that remains at the end of recycling.

[0047] The term "fibrous reinforcing material" means an assembly of fibers, unidirectional rovings or continuous filament mats, woven fabrics, felts, or non-woven fabrics, which may be in the form of shreds, webs, braids, strands, or parts. In the context of the present invention, the fibrous reinforcing material preferably corresponds to a reinforcing material containing fibers having a length exceeding 10 mm, more preferably exceeding 20 mm, and even more preferably exceeding 3 cm.

[0048] The term "mineral filler" means all powdered fillers, such as quartz, marble, silica, aluminum hydroxide, or titanium dioxide.

[0049] For the purposes of the present invention, the term "mass ratio" corresponds to the ratio with respect to the weight of the article to be recycled.

[0050] For the purposes of the present invention, the term "mass percentage of equivalent methacrylic monomer" corresponds to the theoretical mass content of the methacrylic monomer with respect to the total weight of the article to be recycled. This percentage is preferably calculated without considering any methacrylic fraction that may be contained in the filler or additive in the mass of the article. The theoretical mass of the methacrylic monomer may correspond to the mass fraction derived from the methacrylic monomer in the polymer or copolymer.

[0051] For the purposes of the present invention, the expression "at least partially liquefying the thermoplastic polymer" means that the thermoplastic polymer contained in the article to be recycled starts to at least partially melt (i.e., significantly exceeds the glass transition temperature T g and / or the melting point T m , but the melting point T m relates only to crystalline or semi-crystalline polymers). Depending on the polymer under consideration, it must be possible for the melted thermoplastic polymer to have a sufficient viscosity for the polymer to be extruded without being completely decomposed by temperature.

[0052] For the purposes of the present invention, the term "substantially equal" means a value that varies by less than 30%, preferably less than 20%, more preferably less than 10% with respect to the comparative value.

[0053] In the following description of the embodiments and the accompanying drawings, the same reference numerals are used to represent the same or similar components.

[0054] Recycling of materials, and even more so of composite materials, requires many parameters to be considered such that the recycling has a carbon footprint and an energy footprint that are more favorable than the energy footprint of the initial production.

[0055] In particular, for the recycling of composite materials having a thermoplastic, preferably (meth)acrylic-based polymer matrix, the technical problem to be solved is to increase the productivity during the depolymerization of the composite material having a (meth)acrylic-based thermoplastic polymer matrix. Specifically, the conventionally provided solution is to increase the depolymerization temperature. However, in the case of a (meth)acrylic-based thermoplastic polymer matrix, an increase in temperature has little effect on the depolymerization rate.

[0056] Surprisingly, the inventor has found that when a composite material is mixed with different grades of thermoplastic polymer matrices, in an advantageous but non-limiting manner, a (meth)acrylic-based matrix, the yield of monomers obtained within a given time is improved. This means that it is higher than the yield obtained by depolymerizing two fractions independently over the same time.

[0057] Thus, the inventor has developed a method for recycling a composite material based on a thermoplastic, preferably (meth)acrylic polymer matrix, with improved monomer yield. As shown in the examples, the increase in yield is more pronounced at a specific mass ratio between the composite and other grades of thermoplastic, preferably (meth)acrylic polymer matrix. A recycling system capable of performing such a method is also proposed.

[0058] According to the present invention, it is possible to achieve a satisfactory production of methyl methacrylate, especially starting from a material based on a (meth)acrylate matrix that is difficult to recycle (i.e., has a low methyl methacrylate production yield).

[0059] Thus, the present invention relates, inter alia, to a method for recycling articles made of composite materials. The article made of a composite material to be recycled, or the first article 10, may in particular be an article made of a composite material based on a thermoplastic polymer matrix, preferably a (meth)acrylic thermoplastic polymer matrix and a fibrous reinforcing material. In particular, it should be noted that the article to be recycled may be a manufactured product or a part of a manufactured product at the end of its life, or waste from the production of such a product. In either case, a preliminary sorting step may be necessary to remove non-depolymerizable waste or any non-depolymerizable product that also contributes to a decrease in energy efficiency.

[0060] An article made of a composite material, or a first article 10 to be recycled, may also contain a polymer other than the thermoplastic polymer matrix of the fiber-reinforced composite material. This may be an adhesive, a foam, a gel coat, or another polymer having properties different from those of the thermoplastic polymer matrix of the composite material. In this case, a separation step 105 may be required either upstream 105a or downstream 105b to remove these other polymers or to reduce the amount of these other polymers. When the separation step 105 is carried out, preferably, the separation step 105 is upstream of the separation step 105b, more preferably, before the grinding step 110.

[0061] As described above, for a fiber-reinforced composite material, the yield of recycled monomers is lower than that of non-composite materials (for example, the yield calculated based on the theoretical content of the base monomer after recovery of condensates and separation of the base monomer), regardless of whether it is on a molar basis or a mass basis. Therefore, the present technology is particularly suitable for such materials. The mass yield of the recovered base monomer relative to the corresponding monomer may be calculated by considering the mass content of the monomer recovered from the condensate and the theoretical mass content of the monomer in the article to be recycled. However, such a calculation assumes that it is possible to calculate the theoretical mass content of the monomer in the recycled article. This has been found to be possible in controlled specific experiments but more difficult when the present invention is used industrially. Therefore, in the examples, the improvement effect of the mass yield is described. This improvement effect is based on the increase in the mass of the base monomer recovered by the method according to the present invention compared to the mass of the base monomer recovered using prior art techniques.

[0062] In the composite material, the thermoplastic polymer matrix is closely bonded to the reinforcing material. The fibrous reinforcing material may often be regarded as a reinforcing means based on glass or carbon fibers. For example, the fibrous reinforcing material may be a woven fabric, a web, a felt, or any other fibrous material. The fibrous reinforcing material is based on, for example, glass fibers, carbon fibers, or basalt fibers, or metal fibers or plant fibers.

[0063] (Meth)acrylic thermoplastic polymers may be, for example, homopolymers or copolymers based on (meth)acrylic monomers selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and mixtures thereof.

[0064] In particular, the composite material of the article to be recycled is based on PMMA and fibrous reinforcing materials.

[0065] The main steps of the recycling method according to the present invention are described in detail in FIG. 1. In particular, the recycling method 100 according to the present invention includes the introduction 130 of a first article 10 to be recycled into a system 1 suitable for recycling thermoplastic polymers, and the introduction 140 of a second article 20 to be recycled, which contains a thermoplastic, preferably (meth)acrylic, polymer resin but no fibrous reinforcing material, into the system 1, heating 150 to a given temperature of the article, and recovery 160 of the constituent base monomers of the thermoplastic, preferably (meth)acrylic, polymer. The second article 20 to be recycled may also contain additives for improving specific properties, such as impact strength and heat resistance. Generally, such additives may interfere with depolymerization.

[0066] The second article to be recycled may also be in the form of a syrup at room temperature, and the mass percentage of a suitable thermoplastic monomer, preferably a (meth)acrylic monomer, may be more than 70%, for example more than 75%, preferably more than 80%, more preferably more than 90%, and even more preferably more than 95%. Specifically, such a syrup can be obtained during the preparation of a plate cast during the prepolymerization of methyl methacrylate or by dissolving PMMA in methyl methacrylate. Preferably, a polymerization inhibitor additive is added to the second article during use of the second article. Such additives may be hydroquinone, hydroquinone monomethyl ether (MEHQ) (4-methoxyphenol), phenothiazine, or topanol (2,4-dimethyl-6-tert-butylphenol). Such a syrup may advantageously consist of a liquid form of Elium® resin, among others.

[0067] Also, as will be detailed below, the method 100 according to the present invention may include each step of separation 105, grinding 110, sorting 120, purification 170 of a pre-recovered base monomer, and removal 180 of solid components generated during the heating step.

[0068] The present invention includes the integrated recycling of two articles having different grades. In particular, the first article is a composite material containing a fibrous reinforcement, while the second article does not contain any fibrous reinforcement.

[0069] Also, as will be detailed below, the present invention can achieve a monomer yield higher than the yield when these materials are recycled separately, especially with the above combination of materials having different grades. Thus, according to the present invention, it becomes possible to achieve an accurate monomer yield, that is, a yield at least higher than the yield of these materials recycled separately from materials that are generally considered to be less recyclable.

[0070] The grading system is a classification specific to industries specialized in the manufacture of materials, particularly composite materials. This system makes it possible to reflect the quality of the material and, in part, its composition. Thus, the grade of a material is influenced, for example, by the following. - The presence or absence of a reinforcing material and the type of reinforcing material used, - The characteristics of the matrix used, i.e., for example, the polymer or possible polymer combinations forming the matrix, with or without crosslinking, and - The presence or absence of additives

[0071] Thus, in the context of the present invention, the first article 10 to be recycled preferably has a first grade, while the second article 20 to be recycled has a second grade different from the first grade.

[0072] In particular, the first article 10 to be recycled contains a fibrous reinforcing material, while the second article 20 to be recycled does not contain any fibrous reinforcing material.

[0073] The first article 10 to be recycled and the second article 20 to be recycled may contain plastic additives, additives for improving heat resistance, additives for improving impact strength, comonomers, such as acrylates or others for blocking / slowing down depolymerization, etc. The first article 10 and the second article 20 may also contain mineral fillers such as alumina, quartz, marble, aluminum hydroxide, and titanium oxide. In particular, a thermoplastic polymer, preferably (meth)acrylic, may contain at least one additive such as a stabilizer, pigment, plasticizer such as phthalate, adhesion promoter, UV absorber, antioxidant, flame retardant, colorant, lubricant, mold release agent, filler, antistatic agent, fungicide, surfactant, and / or crosslinked polymer beads, impact strength additives, etc. In fact, by adding additives, it is generally possible to improve the properties of the thermoplastic composition. For example, fillers improve chemical resistance or heat resistance, plasticizers make it possible to reduce rigidity, stabilizers prevent polymer degradation, antistatic agents prevent dust deposition, lubricants limit wear, and flame retardants provide better fire resistance, etc. Nevertheless, the presence of such additives usually causes a low yield for the recovery of the base monomer in the case of recycling by depolymerization.

[0074] Preferably, the second article 20 to be recycled contains at least 50% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer, more preferably at least 60% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer, even more preferably at least 70% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer.

[0075] Also, the second article 20 to be recycled is advantageously not an article that is normally considered to be easily recyclable. Thus, the second article 20 may preferably contain at least 5% by mass of a filler (such as a mineral filler), more preferably at least 10% by mass of a filler, even more preferably at least 15% by mass of a filler.

[0076] In certain embodiments, the second article 20 to be recycled comprises an acrylic or non-acrylic comonomer between at least 0.5 wt% and 25 wt%, preferably between 1 wt% and 10 wt%.

[0077] Preferably, the second article 20 to be recycled comprises at least 5 wt%, preferably at least 10 wt%, more preferably at least 15 wt% of additives, based on the total weight of the thermoplastic composition, such as a (meth)acrylic composition.

[0078] Preferably, the second article 20 to be recycled comprises at most 50 wt%, preferably less than 40 wt%, more preferably less than 30 wt%, even more preferably less than 25 wt% of additives, based on the total weight of the thermoplastic composition, such as a (meth)acrylic composition. Advantageously, without limitation, the second article 20 to be recycled comprises at most 50 wt%, preferably at most 25% of additives such as an acrylic impact modifier and / or a methacrylate-butadiene-styrene impact modifier and / or an acrylic processing aid. The function of such impact-modifying additives is to improve the impact strength of the thermoplastic material. In certain embodiments, the second article 20 to be recycled comprises at most 30% of a polylactic acid type additive. The polylactic acid type additive is a thermoplastic resin derived from renewable plant resources and is recognized as being compostable. Such a resin may also be accompanied by an impact modifier type additive.

[0079] In particular, the second article 20 to be recycled may comprise a thermoplastic polymer resin that is at least partially crosslinked.

[0080] As shown in FIG. 1, the recycling method 100 according to the present invention may include a preliminary sorting step 120. The sorting step may be a step in which a first article 10 to be recycled, which includes a composite material based on a fibrous reinforcement, is separated and isolated. For example, the first article 10 may be separated and isolated from an article that does not contain any composite material and / or separated and isolated from contaminants such as glass, sand, wood, other polymers, foams, or metals. The sorting step also enables the separation and sorting of plastics by type. For example, it is possible to sort thermoplastic polymers on the one hand and thermosetting polymers on the other hand, and it is also possible to sort various thermoplastic resins from each other. The sorting may also make it possible to remove portions resulting from grinding that are not made of composite material.

[0081] The sorting may be performed by any sorting method suitable for polymer recycling. One possible sorting method may include a decantation system in which waste is introduced into a tank of water and / or brine, or an organic liquid. Eventually, there are heavy components at the bottom of the tank, but the heavy components can be discharged through an air airlock system. The components to be recycled may be extracted from the tank using an endless screw (at the top or bottom depending on the density of the components). The sorting may also include magnetic separation to extract metal particles. The sorting may also include eddy current separation to remove specific metals such as copper and aluminum. It is also possible to combine separation techniques such as sorting by density in a solution, magnetic separation, etc. Spectroscopic techniques such as Raman or infrared may be used in the sorting method to identify the composition of the material. Sorting methods using the triboelectric properties of the material or the thermal adhesion properties of the material may also be used. The sorting may be performed at a sorting center. Advantageously, the sorting step makes it possible to remove components that may damage the various devices used in the implementation of the recycling method 100.

[0082] Also, for example, in order to facilitate the introduction of articles into a reactor suitable for polymer recycling, the articles may be pre-crushed. Thus, in one embodiment, a method 100 for recycling articles includes a step 110 of crushing the articles, which is performed before step 120 of FIG. 1. In this example, it is often coarser than fine crushing, because it facilitates the sorting operation. The crushing step makes it possible to reduce the dimensions of the articles to be recycled (first and / or second), and for example, the crushing step may be performed using any suitable mechanical crusher. Non-contact crushing techniques can also be used. The first and second articles to be recycled are reduced to dimensions such that the crushed material thus obtained can be introduced into an apparatus suitable for recycling according to the present invention. The particles obtained after crushing may have dimensions (for example, radius, diameter, median diameter, length, width, height) such that at least one dimension is between 1 mm and 100 mm, preferably between 3 mm and 50 mm. Preferably, at least one of the dimensions of the second article 20 to be recycled is less than 30 mm. Then, the first and second articles to be recycled may be in the form of chips, granules, or powder. More preferably, the crushing is performed such that at least one of the dimensions of the second article to be recycled is smaller than the maximum dimension of the first article to be recycled. The first and second articles to be recycled may also be in one or more of the above forms in the reactor. Advantageously, the crushing / coarse crushing step 110 may make it possible to facilitate the sorting step. However, generally, it is easier to sort large-sized fragments if the composition of the fragments is uniform. Thus, the crushing operation also serves to produce fragments of uniform composition. For this reason, the crushing operation may be performed before the above sorting operation. The crushing operation can also be selective crushing.

[0083] As shown in FIG. 1, a recycling method 100 according to the present invention includes a step 140 of introducing a first article 10 into a system 1 suitable for recycling a thermoplastic polymer. In particular, the first article 10 may be introduced into a reactor suitable for polymer recycling.

[0084] For example, the first article 10 to be recycled may be introduced into the reactor using an endless screw, a conveyor belt, a hopper, or by a metering module. The flow rate for supplying the first article 10 to be recycled to the reactor may be between 10 kg / h and 2000 kg / h, preferably between 50 kg / h and 500 kg / h, and more preferably between 100 kg / h and 400 kg / h.

[0085] The recycling method 100 according to the present invention also includes a step 120 of introducing a second article 20 to be recycled into a system 1 suitable for recycling thermoplastic polymers.

[0086] The first article 10 and the second article 20 may be introduced into the system continuously or simultaneously, particularly into a depolymerization reactor. Accordingly, the second article 20 to be recycled that does not contain any fibrous reinforcing material may be introduced before the first article 10 to be recycled.

[0087] Alternatively, the first article 10 and the second article 20 may be mixed and then simultaneously introduced into the recycling system 1, particularly into a reactor suitable for polymer recycling. For example, the first article 10 and the second article 20 introduced in the form of granules, chips, needles, small plates, or powder have substantially different particle sizes. Advantageously, the article 10 to be recycled has a larger dimension than the article 20 to be recycled. The method 100 may also include the introduction of some other articles containing thermoplastic polymers, preferably (meth)acrylic thermoplastic polymers.

[0088] Preferably, the first article 10 to be recycled, which comprises a composite material based on a fibrous reinforcing material and a thermoplastic, preferably (meth)acrylic, polymer matrix, and the second article(s) 20, which is / are based on a thermoplastic, preferably (meth)acrylic, polymer resin and does not have a fibrous reinforcing material, are introduced in a mass ratio (second article(s) / first article) between 0.1 and 1.5, preferably between 0.1 and 0.5, and more preferably between 0.2 and 0.4.

[0089] As shown in FIG. 1, the recycling method 100 according to the present invention also includes a step 150 of heating the first article 10 and the second article 20. The heating may be performed, in particular, in a reactor of the system 1 suitable for the recycling of thermoplastic polymers, preferably for the recycling of composite articles containing thermoplastic polymers.

[0090] Preferably, the system 1 suitable for the recycling of thermoplastic polymer resins is selected from the following. - An extruder / conveyor depolymerization system, - A rotary drum depolymerization system, and - A system that depolymerizes on a heating plate, for example, a continuously functioning system.

[0091] The heating is carried out at a temperature that enables the depolymerization of the thermoplastic polymer, preferably a (meth)acrylic polymer, and the formation of the base monomers of the thermoplastic polymers of the first article 10 and the second article 20.

[0092] In particular, the heating of the articles is carried out at a given temperature at which the depolymerization of the thermoplastic polymer and the generation of the base monomers in gaseous form are possible. The heating may be carried out, for example, at a temperature between 200 °C and 1500 °C, preferably between 300 °C and 600 °C, more preferably between 350 °C and 500 °C, and even more preferably between 400 °C and 450 °C. The heating may also be carried out in stages, as a first heating zone at a moderate temperature, followed by a second and final heating zone or second and then multiple heating zones at increasing temperatures. The moderate temperature is preferably between 200 °C and 350 °C, more preferably between 200 °C and 300 °C.

[0093] In a preferred embodiment, the heating of the articles 10, 20 to be recycled is carried out under an inert atmosphere, for example, under reduced pressure, nitrogen, CO2 or argon, or under an atmosphere with substantially low oxygen (for example, oxygen is 0.1% - 10%). Such a low oxygen atmosphere may be obtained, for example, by recycling the combustion gases of the light emissions from the depolymerization unit.

[0094] Similarly, advantageously, the method 100 according to the invention for recycling articles comprises a step 151 of moderately heating the first and / or second article to be recycled. More preferably, the recycling method 100 according to the invention comprises a step 151 of moderately heating the second article to be recycled. This step of moderately heating the article(s) to be recycled may be carried out before the introduction of the article into the reactor and, where appropriate, after comminution. Moderate heating may be carried out using any suitable heating means. In one variant, moderate heating may be initiated in a reactor suitable for polymer depolymerization. The temperature to which the article is preheated may be 50 °C or higher, for example 200 °C. By moderately heating the article(s) to be recycled, part of the polymer may be converted to a molten or liquid state and / or the depolymerization of the polymer matrix may be promoted.

[0095] As a result of the recycling method 100, the polymer matrix may be unstructured and, for example, converted to a mixture in a molten or liquid form. Thus, the heating step 150 may incorporate a step 152 of recovering the fibrous reinforcement. Such a step of recovering the fibrous reinforcement may be carried out during the heating step or at the end of said step. In particular, the step of recovering the fibrous reinforcement may be carried out at the time when the monomers are recovered.

[0096] As shown in FIG. 1, the recycling method 100 according to the invention also comprises a step 160 of recovering the constituent base monomers of a thermoplastic polymer, preferably a (meth)acrylic polymer.

[0097] Advantageously, the method 100 according to the invention may comprise a step of condensing these base monomers from a gaseous state to a liquid state in order to obtain a solution containing the base monomers.

[0098] Preferably, this condensation may be carried out by bringing the monomer in the gaseous state into contact with the monomer in the liquid state. This contacting operation may be carried out, for example, in a shower-type apparatus by spraying the monomer in the liquid state (i.e., cold monomer) into the chamber that collects the monomer in the gaseous state (i.e., hot monomer). In this case, the apparatus may include means for introducing a stabilizer or a polymerization inhibitor.

[0099] Furthermore, the condensation of the gas mixture may be carried out in a fractional mode, resulting in a cleaner fraction containing the base monomer and a less clean fraction containing the monomer and impurities. This fraction containing impurities may also be reintroduced into the reactor to enable better separation of the monomer contained in this fraction.

[0100] The recycling method 100 according to the present invention may also include a step 170 of purifying the pre-recovered base monomer.

[0101] The purification step 170 may include a step of separation using distillation, for example, using a distillation column. This is because impurities may be formed during depolymerization and it is necessary to remove the impurities thereafter.

[0102] The recycling method 100 according to the present invention may also include a step 180 of removing the solid components generated during the step of heating the first article 10 and the second article 20. The separation means for removing the solid components is adapted according to the state of the matrix in the reactor or at the outlet of the reactor, i.e., whether the matrix is converted into a molten state or a liquid state mixture, or a gaseous state mixture. When the reinforcing material is contained in a molten state or a liquid state mixture, the separation means can be any means enabling solid-liquid separation, such as a grid for example. The separation can also be carried out by centrifugation using a centrifuge, or alternatively by decantation, filtration, draining, spinning, pressing, or screening. Preferably, the separation is carried out by filtration, pressing, or decantation in the molten medium. When the matrix is gasified / depolymerized, the gas phase separation means may include, for example, a cyclone or a filter. When using a filter, back pressure is applied periodically to loosen the solids accumulated in the filter. Then, the solid cake is recovered under the filter in a container provided for recovery. Note that during the depolymerization of the matrix, polymer residues may remain in the reinforcing material, and for example, solid phase separation of such solid residues may be carried out by screening (such as separation of glass fiber / carbonaceous powder). By this removal step, advantageously, it becomes possible to treat various types of solid residues formed during the depolymerization reaction, i.e., solid residues entrained in the gas phase, and especially the compressed solid residues seen at the reactor outlet. The solid residues entrained in the gas phase may potentially clog the monomer condensation unit. Therefore, after condensation, these solid residues must be filtered in the gas phase (e.g., via appropriate separation means, i.e., cyclone, filter) or in the liquid phase, whereas the solid residues occurring at the reactor outlet generally remain in the form of a solid mat that can be screened, for example, to separate various solid residues. The hot solid residues must be cooled / can be cooled, for example, by direct contact with water. During this cooling step, the direct contact between the solid and the monomer must be limited to prevent the monomer from directly re-condensing on the solid.

[0103] According to another aspect, the present invention relates to a system 1 for recycling a first article 10 comprising a composite material based on a thermoplastic, preferably (meth)acrylic, polymer matrix and a reinforcing material.

[0104] As schematically shown in FIG. 2, the recycling system 1 according to the present invention comprises means 11 for transporting a first article 10 comprising a composite material based on a thermoplastic, such as a (meth)acrylate-based polymer matrix and a fibrous reinforcing material, and means 21 for transporting a second article 20 to be recycled, comprising a resin of a thermoplastic polymer, preferably a (meth)acrylic polymer. The transport means 11, 21 may be a pipe, endless screw, conveyor belt or hopper, pneumatic transport device, vibrating transport device, or extruder. They may also be connected to a metering device. The recycling system 1 according to the present invention also includes a reactor 50 suitable for heating the articles 10, 20 for the purpose of depolymerizing the thermoplastic polymer, preferably a (meth)acrylic polymer, to form monomers. For example, the heating may be carried out by exposure of the articles to microwaves, pulsed electric fields, or steam, or by contact with a hot surface in an extruder, screw conveyor, rotating drum, etc. The hot surface may be heated by various means, i.e., direct electric heating, heating by a heat transfer fluid (steam, oil, molten salt, etc.).

[0105] The recycling system 1 according to the present invention also includes means 60 for recovering the constituent monomers of the thermoplastic polymer, which is preferably a (meth)acrylic polymer, without limitation.

[0106] Furthermore, the recycling system 1 according to the present invention may also include one or more means for moving the first article 10 and the second article 20 to be recycled, one or more video acquisition means 356, such as an infrared camera, described with respect to FIG. 4, one or more purification means 70, and one or more solid removal means 80.

[0107] The reactor of system 1 according to the present invention may be an extruder or a conveyor, a reactor suitable for pyrolysis, high-temperature pyrolysis, pyrolysis in a molten salt bath, or a fluidized bed reactor, or a reactor suitable for solvolysis, or alternatively a reactor consisting of a hollow plate heated by a heat transfer fluid circulating within the plate. However, reactors have been identified that can further increase the monomer yield, such as extruders, conveyors, extruder conveyors, rotating drums, and / or a set of heating plates.

[0108] A reactor suitable for recycling thermoplastic polymers may also be a pyrolysis reactor, such as a multi-stage pyrolysis reactor or a stirred rotary cylinder reactor. Two configurations are possible, i.e., either the cylinder rotates about its axis or an internal agitation system ensures mixing and heat transfer from the wall to the polymer.

[0109] An extruder conveyor is a reactor that includes one or more endless screws each operated within a barrel and, in particular, enables blending of the components introduced into the barrel. Using an extruder conveyor to perform the recycling method 100 is advantageous from the viewpoints of the environment, security, and safety of the method 100. Specifically, it is not necessary to add a solvent to reduce the viscosity of the molten polymer, and the extruder conveyor enables processing of a high-viscosity molten polymer. The extruder conveyor has the advantage of enabling efficient heat transfer from the barrel to the composite material being processed. The extruder may advantageously be replaced by a screw-conveyor system over all or part of its length. Advantageously, the system may include a combination of a first part conveyor-type device, a subsequent extruder-type device, and a last conveyor-type device configured to transport solids (i.e., reinforcing materials) to the outlet. For example, the conveyor may be of the "auger screw" type or the "endless screw" type.

[0110] Referring to FIG. 3, the recycling system 1 according to the present invention includes an extruder, more particularly a twin-screw extruder 200 including an orifice 201 into which a first article 10 to be recycled, which includes a composite material based on a thermoplastic, preferably a (meth)acrylate polymer matrix and a fibrous reinforcement, may be inserted using, for example, a metering device 210 and conveying means 211. Similarly, a second article 20 to be recycled, which includes a thermoplastic, preferably a (meth)acrylic polymer resin, may be inserted using, for example, a metering device 220 and conveying means 221. The first article 10 and the second article 20 to be recycled may be in the form of a powder or granules. Alternatively, those articles may be introduced into the extruder after undergoing a first heating step.

[0111] Accordingly, the first article 10 and the second article 20 to be recycled may be introduced at a high or low temperature and also heated and / or maintained at a temperature during processing.

[0112] The twin-screw extruder may be, for example, a Clextral® type extruder. The twin-screw extruder typically includes two screws 204 that are parallel and rotate inside a barrel 250. Advantageously, the extruder is of a modular type, i.e., the screws and the barrel 250 are modules assembled in series, and the assembly may be changed. Thus, the barrel 250 here corresponds to a reactor suitable for heating the articles 10, 20 for the purpose of depolymerizing the thermoplastic polymer of the recycling system 1 according to the present invention, as a non-limiting example, a (meth)acrylic polymer. More generally, the reactor 50 of the system according to the present invention may take various forms as long as the gas flow and the temperature can be controlled.

[0113] In the extruder, external heating means 255 for adjusting the temperature of the barrel 250 are advantageously configured to heat the first article 10 and the second article 20 to be recycled and to bring the polymer matrix and the polymer resin into a molten form. The temperature inside the reactor may be between 50°C and 550°C and may be controlled using a temperature sensor (not shown in the figures).

[0114] Depolymerization may result in a product in the form of a gas that is extracted from the extruder for processing. The solid residue is removed, in part, via suitable means 202. In particular, the reactor can operate under negative pressure or under a gas flow in order to convey the monomers formed, via collection means, to a condensation unit. The gas produced may be led via pipe 208 to a recovery device 260 for condensation. The condensate obtained in chamber 209 for collection purposes may then be collected.

[0115] In order to enable the recovery of the gas resulting from the implementation of the recycling method 100, a system 200.1 suitable for recycling may include one or more purification devices. For example, the system may include a purification device (not shown in the figures) corresponding to a system for separation by distillation, for example a distillation column. The distillation column enables the separation of compounds according to their boiling points.

[0116] Another type of system advantageous for the recycling of a first article 10 comprising a composite material based on a fibrous reinforcement and a thermoplastic, preferably (meth)acrylic, polymer matrix includes a device consisting of hollow plates heated by a heat transfer fluid circuit (steam under pressure, oil, molten salt). During the process of its treatment, the article progresses on a temperature-rising plate in a first stage. The solid residue passes through the reactor by passing over a plate at a lower temperature where heat exchange from the residue to the heat transfer fluid occurs. The heat transfer fluid thus heated then serves to preheat the article at the reactor inlet.

[0117] Therefore, in particular, referring to the schematic diagram of FIG. 4, the recycling system 300 according to the present invention includes an enclosure 350 provided with heating plates 351 and 352. The system particularly includes two tanks 312 and 322 for storing the first article 10 and the second article 20 to be recycled, respectively. These tanks are connected to the enclosure 350 via transfer pipes 311 and 321, and these tanks enable the articles to be recycled, which have preferably been crushed / coarsely crushed / peeled to an appropriate particle size in advance, to be introduced into the tanks. As shown in FIG. 4, the system includes one or more heating supports 352 (such as heating plates) configured to receive the second article 20 to be recycled and raise the temperature of the thermoplastic polymer. After the thermoplastic polymer begins to melt under the influence of the temperature, it falls onto the second heating support 351. Alternatively, according to a configuration not shown, in the recycling system according to the present invention, the first article 10 to be recycled is arranged to fall onto the second article 20 to be recycled, and the second article to be recycled is preheated moderately.

[0118] Further, the system may include means 355 (e.g., actuated by a piston, blade, or claw) for moving the second article 20 arranged to push it towards the second heating support 351. As shown, the second heating support 351 (such as a heating plate) is arranged to receive the first article 10 to be recycled and bring the first article 10 into contact with the second article 20 to be recycled which is at least partially molten. Also, the second heating support 351 is configured such that the polymer matrix can depolymerize under the influence of temperature. Inside the enclosure 350, the first article 10 and the second article 20 to be recycled are heated, and the polymer matrix and resin are depolymerized at a temperature regulated using the heating supports 351, 352. The system is configured at this time to maintain a temperature high enough to depolymerize the thermoplastic polymer, preferably a (meth)acrylic polymer. The temperature inside the enclosure may be between 50°C and 550°C and may be controlled using a temperature sensor not shown in FIG. 4. The system is arranged at this time to push the mixture of the first article 10 and the second article 20 to be recycled towards a third heating support (or a multi-stage cascade) or towards separating means 381 such as a screen or grid for separating the solid residues according to their diameter. Such separating means may be used, for example, to separate the fiber residues 15 from other fillers that may be contained in the second article 20 to be recycled. Also, the separating means 381 may be connected to means 382 for moving (e.g., a piston, a motor) to improve and / or accelerate the separation. The solid residues may then be removed via suitable means 302.

[0119] In the reactor, in the case of an article to be recycled made of a meta (acrylic-based) thermoplastic polymer, the polymer, preferably a meta (acrylic-based) polymer, is depolymerized under the action of heat, resulting in, among other things, methyl methacrylate monomer in gaseous form. The generated gas 358 may be led to a cooling system 360 via a pipe 359 for condensation. Then, the condensate obtained in a chamber for collection purposes may be collected. The enclosure and the chamber are preferably under negative pressure or under gas flow in order to convey the formed monomer to the condensation unit. The condensation unit can, more particularly, condense the base monomer mixture in a gaseous state. In particular, as shown above with respect to FIG. 3, the reactor can operate under negative pressure or under gas flow via collection means to convey the formed monomer to the condensation unit. In particular, the generated gas may be led to a recovery device 360 via a pipe 359 for condensation. Then, the condensate obtained in a chamber 309 for collection purposes may be collected. The recycling-appropriate system 300 may include one or more purification devices so that the gas generated by the implementation of the recycling method 100 can be recovered. For example, the system may include a purification device (not shown in the figure) corresponding to a system for separation by distillation, for example a distillation column. By means of the distillation column, separation of the compounds according to the boiling points of the compounds is possible.

[0120] Also, the gas generated in the reactor may be conveyed to a gas / solid separator such as a cyclone. Such a separator may be inside or outside the reactor. Also, there may be a plurality of serial separators, internal and external, for the purpose of recovering the reinforcing material particles. Thus, the solid particles entrained in the gas phase are filtered / separated either in the gas phase before the condenser or in the liquid phase after the condenser.

[0121] In a third embodiment, a system suitable for recycling a first article 10 comprising a fibrous reinforcing material and a composite material based on a (meth)acrylic thermoplastic polymer matrix includes a mixer-conveyor type apparatus, such as a paddle dryer mixer-conveyor. This apparatus includes a reactor in which an impeller / rotating paddle is installed. Thus, the impeller enables mixing and homogenization of a mixture of the first article to be recycled and a second article. The mixer-conveyor has the advantage of being able to process large amounts of solid waste / residue. It also enables good heat transfer between the wall and the waste. Such an apparatus may be used at a low temperature to dry the solid, but in the context of the present invention, it is possible to induce depolymerization by raising the temperature.

[0122] A fourth embodiment of a recycling system 400 according to the present invention is shown in FIG. 5. Such a system may include a rotating drum type apparatus in which the entire reactor rotates about a longitudinal axis. Alternatively, the drum may be fixed and have a rotating impeller / blade (paddle drying type).

[0123] The rotating drum type apparatus preferably includes a reactor 450 including an orifice 403, through which a first article 10 to be recycled, which is a composite material based on a thermoplastic, preferably (meth)acrylic, polymer matrix and a fibrous reinforcing material, may be inserted using, for example, a metering device 410 and conveying means 411. Similarly, a second article 20 to be recycled, which includes a thermoplastic, preferably (meth)acrylic, polymer resin, may be inserted using, for example, a metering device 420 and conveying means 421. As described above, the reactor of the system according to the present invention may take various forms as long as it can control the gas flow and temperature. Thus, the reactor of the system according to the present invention may be suitable for a rotating drum type apparatus.

[0124] The first article 10 and the second article 20 to be recycled may be in the form of powder or granules, or may be crushed. In this embodiment, the orifice 403 is arranged to receive the first article 10 to be recycled via the conveying means 411 of the weighing device 410 and the second article 20 to be recycled via the conveying means 421 of the weighing device 420.

[0125] Regarding the production of base monomers from the thermoplastic polymers obtained from the articles 10, 20 to be recycled, in order to improve the yield, the system 1 according to the invention may include a second reactor 480 suitable for moderately heating one of the articles 10, 20 to be recycled. Advantageously, but not limited to, such a reactor 480 may correspond to a single-screw extruder or a twin-screw extruder 200 as described with respect to FIG. 3 and includes one or two screws 404 rotating inside the second reactor 480.

[0126] In this embodiment, the reactor 480 includes an orifice 401 through which the first article 10 and the second article 20 to be recycled may be inserted, for example, via the aforementioned weighing device and conveying means. Preferably, the second article 20 to be recycled is introduced through the orifice 401 of the reactor 480 and is moderately heated while passing through the reactor.

[0127] Similar to the heating means of the twin-screw extruder 200, the external heating means 455 is configured to adjust the temperature of the reactor 450 and, advantageously, to heat the second article 20 to be recycled to bring the polymer resin into a molten form without inducing depolymerization. The temperature inside the reactor may be between 200°C and 350°C and may also be controlled using a temperature sensor not shown in the figure.

[0128] Such moderate heating advantageously enables all or part of the polymer resin of the article 20 to be recycled to be liquefied, so that the article is conveyed to the reactor 450 in the form of a viscous mixture via an orifice 402 arranged to enable fluid communication between the reactors 450 and 480. Thus, the article 10 to be recycled is preferentially added immediately after the article 20 to be recycled is introduced into the reactor 450 by mechanical or pneumatic transport.

[0129] Further, the reactor 450 may include a motor source (not shown) for rotationally driving the reactor 450 around a fixed axis 451 in the case of a rotary drum or around a rotating axis 451 in the case of a paddle dryer type mixer conveyor reactor 450. Such an axis 451 may advantageously include one or more means 452 for moving, fixed along said axis, or one or more mixing components. Such means for moving may advantageously take the form of blades or impellers having any geometric shape suitable for mixing the articles 10, 20 to be recycled. Thus, the means 452 for moving can mix and homogenize the mixture of the first article 10 and the second article 20 to be recycled.

[0130] Suitable means for moving are selected according to the nature and dimensions of the articles 10, 20 to be recycled in the form of powders or granules.

[0131] Finally, the reactor 450 may advantageously include external heating means 455 configured to heat the articles 10, 20 to be recycled and to melt the polymer matrix of the article 10 to be recycled and the polymer resin of the article 20 to be recycled. As described above with respect to FIG. 2, the heating may also be staged as a first heating zone at a moderate temperature, followed by a second and final heating zone or a second and then multiple heating zones at increasing temperatures.

[0132] Similar to the system 1 described with respect to FIG. 3, depolymerization may result in a gaseous product being extracted from the apparatus for processing. In particular, the reactor 450 can operate under negative pressure or under a gas flow in order to convey the monomers formed, via collecting means, to a condensation unit. The gas produced may be led via pipe 408 to a recovery device 460 for condensation. The condensate obtained in chamber 409 for collection purposes may then be collected.

[0133] The system shown with respect to FIG. 5 may also include a purification device (not shown in the figures) which may correspond to the system for separation by distillation described in connection with FIG. 3, for example a distillation column.

[0134] Thus, when the articles 10, 20 to be recycled are introduced and brought into contact in the reactor 450, these articles have their polymer matrix and polymer resin depolymerized respectively. Specifically, the reactor 450 also includes heating means 455, which are preferably configured to induce a settable temperature between 200° C. and 1500° C. and are suitable for inducing the depolymerization of the articles 10 and 20 to be recycled. The heating may also be staged.

[0135] In addition to enabling the articles 10, 20 to be recycled to be homogenized, the means 452 for moving facilitates their depolymerization in the reactor 450 by promoting the contact of the articles 10, 20.

[0136] In contrast to known rotary drum systems, the system may advantageously be used in the absence of a solid which serves to promote heat transfer, which is particularly suitable for the recycling of composite articles.

[0137] Those skilled in the art will understand that the conveying means used is specific to each embodiment of the recycling system according to the present invention, and is thus particularly suitable for the use of paddle dryer type mixer conveyors, rotary drums, or twin screw extruders. Similarly, it is assumed that each embodiment of the system according to the present invention can include recovery means 405 suitable for residues or solids derived from the depolymerized articles to be recycled.

[0138] The present invention is further illustrated by the following examples. However, these examples should in no way be construed as limiting the scope of the present invention.

Examples

[0139] A] Preparation of composite materials containing fibrous reinforcements to be recycled By dissolving PMMA pearls composed of a copolymer of methyl methacrylate and acrylate, two composite compositions are prepared. Preferably, the acrylate is selected from methyl acrylate, butyl acrylate, and ethyl acrylate.

[0140] This type of product is commercially available, for example, from Altuglas under the Altuglas® BS series. Altuglas® PMMA or acrylic glass has the unique feature that it can be depolymerized into methyl methacrylate and can thus be reintroduced into the process for manufacturing new resins, and is thus a typical material corresponding to the recycling and circularity mechanism.

[0141] Prepare composite compositions from recycled polymers. For example, use injection-molded PMMA parts such as automotive tail lights, or transparent plates used in thin TVs or computer monitors. After washing, drying, and pulverizing the respective parts, they are dissolved in methyl methacrylate.

[0142] The preparation of various composite materials C1, C2, C3 to be recycled as shown in the present invention is described below.

[0143] Example 1: Composite Material 1 (C1) In this example, PMMA pearls composed of a copolymer of methyl acrylate and methyl methacrylate (MMA) are obtained. 100 g of pearls with an average particle size of 0.150 to 0.200 mm, a density of 0.7 g / ml, and a Tg (glass transition temperature) of 107°C are dissolved in 900 g of methyl methacrylate stabilized with 100 mg / kg of hydroquinone monoethyl ether (HQME).

[0144] 10 g of benzoyl peroxide is added to the dissolved mixture.

[0145] For the preparation of the test composite material, a glass fiber woven fabric of 600 g / m 2 is used. The PMMA / MMA solution is manually impregnated into the woven fabric. The solution is spread on a mold using a brush or roller, and then a layer of the first woven fabric is applied. Then, a new layer of the solution is applied and spread with a roller, which also serves to remove air bubbles. This operation is repeated until 10 layers of the glass fiber woven fabric overlap. An absorbent tissue is finally placed at a predetermined position to facilitate peeling from the mold. The whole is placed in a plastic bag and placed under an incomplete vacuum (500 mbar, i.e., under negative pressure). Then, the whole is heated at 80°C for 4 hours and then left to cool to room temperature.

[0146] Example 2: Composite Material 2 (C2) Example 1 is repeated, but 200 g of pearls with a Tg of 110°C, an average particle size of 0.150 mm to 0.200 mm, and a density of 0.7 g / ml are used, and this is dissolved in 800 g of methyl methacrylate. 10 g of benzoyl peroxide is added to the mixture. The other operations are the same as in Example 1.

[0147] Example 3: Composite Material 3 (C3) In this example, 100 kg of PMMA plates obtained by decomposing flat screens of TVs and computers are used. Therefore, this product is the product of production from several PMMA manufacturers, and the product has been produced over several years and is of various origins, mainly Asian considering the nature of the decomposed products. The selected plates are relatively clean so as not to interfere with the tests, and their edges are cut off to remove any traces of contamination by adhesives, metals, and other polymers. The plates are crushed into fragments with dimensions of about 1 centimeter, then washed and dried. Then, the said product is dissolved in 900 kg of methyl methacrylate. When the dissolution is complete, the solution is filtered to remove foreign substances and any polymers that are not completely dissolved. Then, 10 kg of benzoyl peroxide is added. A composite material is produced as in Example 1 so as to consume all of the prepared solution.

[0148] The composite materials C1, C2, and C3 are crushed to a maximum dimension of 2 cm.

[0149] B] Composition of the depolymerization test 1) Experimental test apparatus The experimental reactor is a batch reactor with a working volume of 4.5 liters, having a 1.2-liter cast iron pot, with a removable grid attached and heated electrically from the outside. The vapor generated during pyrolysis is condensed using cold traps attached in series. The first three traps are made of stainless steel and are maintained at 5°C, 0°C, and -78°C respectively. The last trap is made of Pyrex and is maintained at -78°C. The non-condensable gas is led outside. When the reactor is filled, the reactor is purged under reduced pressure and / or under nitrogen to remove molecular oxygen from the enclosure. The test is carried out under a reduced pressure of about 2.5 kPa.

[0150] 2) Pilot test apparatus A pilot test is conducted in a cylindrical reactor with a length of 3 m and a diameter of 0.6 m. This reactor is externally heated to avoid any condensation within the facility. Heating for the depolymerization reaction is carried out by a hot plate to which a heat transfer fluid is supplied. The product to be depolymerized is introduced onto the hot plate and flowed through the facility. The assembly includes a supply system, a condensation unit, a system for discharging solid residues, and a vacuum pump. In continuous mode, the system can deliver 50 kg / h. Considering the available amount of the composite material, the test was carried out in the first stage in "batch" mode. In this mode, the systems for residue supply and removal are not used, and the bed of the product to be depolymerized is introduced into a rectangular container on the heating plate.

[0151] The container is filled with the product to be depolymerized, weighed, and introduced into the reactor. The condenser functions by spraying the pyrolysis gas and is initially filled with water. The condensate circulates through the facility to maintain a continuous flow within the condenser. When starting the facility, the air inside the reactor and the peripheral equipment is evacuated using a vacuum pump. Then, the reactor is heated to the desired temperature.

[0152] Pyrolysis is carried out in the pilot reactor at a pressure of 380 °C, -425 °C, and 2.1 kPa. The generated gas is rapidly cooled in two spray column-type condensers in series. In the first condenser, the vapor is cooled using a portion of the liquid condensed at the bottom and cooled with water. During the test, the excess liquid accumulated in the condenser is automatically discharged into a container attached to each condenser. The gas exiting the first condenser enters the second condenser, where it contacts the condensate again at the bottom of the condenser and is cooled with water. The water condensed in this second condenser is separated by decantation of the recovered product.

[0153] When stopping the pyrolysis, the heating is stopped, and the pressure is increased to atmospheric pressure by adding nitrogen to prevent any oxidation during solid cooling.

[0154] After the reaction, the mass of the residual solid and the mass of the collected liquid are measured to determine the material balance.

[0155] 3) Sampling procedure Decant and separate the aqueous and organic phases collected in the laboratory condenser or pilot condenser and store them in plastic containers. Collect representative samples after homogenization. Store the samples under low-temperature conditions and protect them from light before analysis.

[0156] C] Depolymerization test - Laboratory test Example 4 Charge 200 g of Altuglas® HT121 resin pellets with a density of 1.19 into the depolymerization reactor. This product is available from Altuglas.

[0157] Example 5 Repeat Example 4 using 200 g of Altuglas® HFI10 resin with a density of 1.15. This product is available from Altuglas.

[0158] Apply a temperature ramp to the reactor so that the nominal temperature of 400 °C is reached in 30 minutes. After 1 hour, stop heating and return the temperature to room temperature. After stopping heating, leave the aggregate under a nitrogen stream at atmospheric pressure for 2 hours. The trap can be removed when the temperature has returned below 50 °C, and the mass of the condensate may be weighed.

[0159] Collect the polymer decomposition products for analysis. Determine the mass balance. Determine the mass of the residual polymer. Weigh the condensate trapped in the trap. The difference in mass is due to the loss of light products by cracking (methane, light hydrocarbons, CO, CO2, etc.), also known as non-condensable gases.

[0160] The condensate is analyzed, inter alia, by gas chromatography.

[0161] Examples 6 and 7 Repeat the foregoing examples with 300 g of granules.

[0162] Examples 8 and 9 For Examples 1 and 2, C1 and C2, use 200 g of the composite material each, crush it to obtain fragments with a maximum dimension of less than 2 cm. Put the crushed composite material into the depolymerization furnace and apply the same protocol as in the previous examples.

[0163] Examples 10 and 11 Repeat the previous examples using 300 g of the composite material.

[0164] Examples 12 to 19 Prepare a mechanically mixed material of the composite material and resin particles. Put the mixture into a plastic bag and homogenize it by shaking until no visual non-uniformity can be identified. Then repeat the depolymerization protocol.

[0165] Good linearity of the decomposition products is observed for the same samples at 200 g and 300 g. Therefore, within this range, the device is not limited with respect to heat and mass transfer. [Table 1]

[0166] In this way, by the integrated recycling of the first article to be recycled (C1, C2) containing the fibrous reinforcing material and the second article to be recycled containing a thermoplastic, preferably a (meth)acrylic polymer resin, it becomes possible to significantly increase the production yield of the base monomer.

[0167] Thus, for the resin granule / composite material mixture, it is observed that the mass of the depolymerization product (condensate) is higher than the simple addition of the masses obtained from the pure substances. Furthermore, the amount of recovered MMA is observed to be higher than the simple addition of the masses of MMA obtained from the pure substances for the experiments conducted under the same time limit. Therefore, when a mixture of the composite material and injection molding grade or extrusion grade PMMA is prepared, the productivity is higher and the quality of the recovered product is excellent. Thus, in fact, compared with the mass of the base monomer recovered using the prior art method, the mass of the base monomer recovered using the method according to the present invention is increased.

[0168] C] Depolymerization Test - Pilot Test Pilot Examples 20 to 23 Charge about 20 kg of the pulverized composite material, or about 20 kg of PMMA granules of the VM100 type available from Altuglas, or a mechanically mixed product of these two into a metal container. [Table 2]

[0169] Also in the pilot test, a significant increase in the base monomer production yield can be observed.

[0170] Thus, the present invention proposes a simple and efficient solution for increasing the overall base monomer production yield during the recycling of composite articles, especially in the case of a first article containing a fibrous reinforcing material and having a low monomer production yield. The method according to the present invention enables the recycling of articles containing composite materials, and the composite materials are more environmentally friendly because their carbon footprint is reduced.

Claims

1. A method (100) for recycling a first article (10) to be recycled, comprising a composite material based on a fibrous reinforcing material and a thermoplastic, preferably (meth)acrylic, polymer matrix, the recycling method comprising the following steps: - Introduction (130) of the first article (10) into a system (1) suitable for recycling thermoplastic polymers, - Introduction (140) of a second article (20) to be recycled, which contains a thermoplastic, preferably (meth)acrylic, polymer resin and does not contain any fibrous reinforcing material, into a system (1) suitable for recycling thermoplastic polymers, - Heating (150) the article (10, 20) to be recycled in the said system (1) suitable for recycling thermoplastic polymers to depolymerize the thermoplastic polymer, preferably (meth)acrylic polymer, to form the base monomer of the said thermoplastic polymer, - Recovery (160) of the constituent base monomer of the said thermoplastic polymer characterized in that it comprises. Method (100).

2. The recycling method (100) according to claim 1, characterized in that it comprises a step (170) of purifying the pre-recovered base monomer.

3. The recycling method (100) according to claim 1 or 2, characterized in that it comprises a step (180) of removing the solid components generated during the step of heating the first article and the second article (10, 20) to be recycled.

4. The recycling method (100) according to any one of claims 1 to 3, characterized in that the thermoplastic polymer matrix of the first article (10) is a poly(methyl methacrylate) matrix.

5. The recycling method (100) according to any one of claims 1 to 4, characterized in that the first article (10) to be recycled and the second article (20) to be recycled are introduced in a mass ratio between 0.1 and 1.5, preferably between 0.1 and 0.5, more preferably between 0.2 and 0.

4.

6. The recycling method (100) according to any one of claims 1 to 5, characterized in that the first article (10) to be recycled has a mass percentage of fibrous reinforcing material of more than 30%, preferably more than 50%, more preferably more than 70%.

7. The recycling method (100) according to any one of claims 1 to 6, characterized in that the second article (20) is in the form of a syrup at room temperature and has a mass percentage of equivalent thermoplastic monomers, preferably (meth)acrylic monomers, of more than 80%, preferably more than 90%, preferably more than 95%.

8. The recycling method (100) according to any one of claims 1 to 6, characterized in that the second article (20) to be recycled has a mass percentage of equivalent thermoplastic monomers, preferably (meth)acrylic monomers, of less than 95%, preferably less than 90%.

9. The recycling method (100) according to any one of claims 1 to 6, characterized in that the second article to be recycled has a mass percentage of equivalent methyl methacrylate monomers of less than 95%, preferably less than 90%.

10. A system (1) suitable for recycling thermoplastic polymer resins, - a depolymerization system of an extruder and / or a conveyor, - a rotary drum depolymerization system, and - a system for depolymerization on a heating plate The recycling method (100) according to any one of claims 1 to 9, characterized in that it is selected from.

11. The recycling method (100) according to any one of claims 1 to 10, characterized in that the first article and the second article (10, 20) to be recycled are heated to a temperature between 200 °C and 1500 °C, preferably between 300 °C and 600 °C, during the heating step.

12. The recycling method (100) according to any one of claims 1 to 11, characterized in that it also includes moderately heating (151) to at least partially liquefy a thermoplastic polymer, preferably a (meth)acrylic polymer.

13. The method includes the recovery (152) of the fibrous reinforcement of the first article (10) to be recycled, and the recovery is carried out by at least one of the following methods: centrifugation, draining, spinning, pressing, filtration, screening, and / or cyclone method. The recycling method (100) according to any one of claims 1 to 12, characterized in that it is carried out.

14. The recycling method (100) according to any one of claims 1 to 13, characterized in that it includes a preliminary sorting step (120).

15. The recycling method (100) according to any one of claims 1 to 14, characterized by including a pulverization step (110).

16. The recycling method (100) according to any one of claims 1 to 15, characterized in that the second article (20) to be recycled contains at least 50% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer, more preferably at least 60% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer, still more preferably at least 70% by mass of a thermoplastic polymer, such as a (meth)acrylic polymer.

17. A system (1) for recycling a first article (10) to be recycled, which is based on a fibrous reinforcing material and a thermoplastic, preferably (meth)acrylic, polymer matrix, wherein the system (1) comprises: - means (11) for conveying the first article (10) to be recycled; - means (21) for conveying a second article (20) to be recycled, which contains a thermoplastic, preferably (meth)acrylic, polymer resin and does not contain any fibrous reinforcing material; - a reactor (50) suitable for heating the article (10, 20) to be recycled, depolymerizing the thermoplastic polymer, preferably (meth)acrylic polymer, and forming the base monomer of the thermoplastic polymer; means (60) for recovering the constituent base monomer of the thermoplastic polymer and including a second reactor (480) suitable for moderately heating one of the articles (10, 20) to be recycled, the second reactor (480) including an opening (402) arranged to be in fluid communication with the first reactor (450); The system (1), characterized in that the reactor (50) is an extruder or a conveyor.

18. A system (1) for recycling a first article (10) to be recycled, which is based on a fibrous reinforcing material and a thermoplastic, preferably (meth)acrylic, polymer matrix, wherein the system (1) comprises: - means (11) for conveying the first article (10) to be recycled; - means (21) for conveying a second article (20) to be recycled, which contains a thermoplastic, preferably (meth)acrylic, polymer resin and does not contain any fibrous reinforcing material; - Heating an article (10, 20) to be recycled to depolymerize a thermoplastic polymer, preferably a (meth)acrylic polymer, and a reactor (50) suitable for forming the base monomer of the thermoplastic polymer, means (60) for recovering the constituent base monomer of the thermoplastic polymer and including a second reactor (480) suitable for moderate heating of one of the articles (10, 20) to be recycled, the second reactor (480) including an opening (402) arranged to be in fluid communication with a first reactor (450), A system (1), characterized in that the reactor (50) is a pyrolysis reactor. **Claim 19**: A system (1) according to claim 17 or 18, comprising a second reactor (480) suitable for moderate heating of a second article (20) to be recycled, the second reactor (480) including an opening (402) arranged to be in fluid communication with a first reactor (450). **Claim 20** A system (1) according to any one of claims 17 to 19, characterized in that it includes means (404, 452) for moving the first and second articles to be recycled.

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