Process for depolymerization of polyamide

Abstract

The invention relates to a process for depolymerizing polyamide from a polymeric material comprising the step of contacting, in a solvent, the polymeric material with a Brønsted-Lowry acid in the presence of a Lewis acid catalyst, thereby producing a medium having a liquid phase comprising monomers derived from said polyamide. Abstract Figure: None

Description

Title of the invention: Process for depolymerizing polyamide

[0001] The present invention relates to a process for depolymerizing polyamide. More particularly, the method of the invention relates to the depolymerization of polyamide within a polymeric material. The invention also relates to a compound or compounds generated by the method of the invention.

[0002] Polymers are used in a very large number of fields. This is not only because of their diversity in terms of mechanical, physical and chemical properties, but also because of their relatively low production costs. Polymers are used, for example, in the chemical or pharmaceutical industry, in construction, electronics, aeronautics, automotive and packaging. The textile industry also uses polymers extensively.

[0003] More generally, polymers are the basic constituents of many everyday materials, especially plastics and textiles. A plastic material is essentially made of polymer which, after molding and / or shaping operations, results in an object. Plastics generally have high molecular weights and are usually derived from petrochemicals. Some other plastics can be derived from a natural source. Globally, plastic materials are increasing worldwide [cf. Jambeck, JR et al. Plastic waste inputs from land into the ocean. Science 347, 768-771 (2015)].

[0004] One of the most important synthetic polymers in various industries is polyamide. Polyamides are polymers having regularly repeating amide bonds along a polymer backbone. Such amide bonds may be formed by the condensation of a carboxylic acid and an amine, whereby a nitrogen-carbonyl bond is formed. Depending on the number of monomers linked together, a polymer may have a plurality of structural units having such nitrogen-carbonyl bonds. Monomers used to produce polyamides include diamines, lactams, amino-carboxylic acids and / or dicarboxylic acids.

[0005] The two most commonly used polyamides are so-called polyamide 6.6 and polyamide 6 (also known respectively as nylon 6.6 or nylon 6). Polyamide 6.6 is produced from hexamethylenediamine and adipic acid by polycondensation with water dissociation. Polyamide 6, on the other hand, is produced by ring-opening polymerization of ε-caprolactam with water as the initiator. Due to their strength and toughness, polyamides are often used as construction materials.

[0006] However, polymers and / or plastics have a significant environmental impact.

[0007] Nowadays, there is a growing interest in recycling technologies that allow polymers to be recovered and / or reused. In particular, research is focused on the recovery of monomers used during polymer synthesis, or at least the recovery of oligomers and / or other low molecular weight chemical compounds. Ideally, new polymers can then be synthesized from these recovered monomers and / or oligomers.

[0008] The state of the art discloses various recycling processes for recovering compounds from degraded polymers. Most of the processes concerned are so-called tertiary recycling processes which involve at least a chemical recycling process and heat.

[0009] Chemical recycling processes are generally divided into two categories: those that regenerate starting monomers, and optionally oligomers (mainly hydrolysis) and those that generate other types of molecules with applications in fine chemistry or as fuel (including transesterifications, aminolysis, methanolysis, etc.). Many chemical recycling processes exist in the literature [see DOI: 10.1002 / pol.20230154 or DOI: 10.1016 / j.xcrp.2023.101341, DOI: 10.1039 / dlra08217e.

[0010] As regards the specific recycling of polyamide, the state of the art discloses numerous processes including acid hydrolysis [cf. DOI: 10.1021 / acssuschemeng.0c05706], acid-catalyzed aminolysis [cf. DOI: 10.1039 / D3CC05462D and US5395974], solvolysis [cf. DOI: 10.1007 / sl0924-018-1314-4 & US5668277], alcoholysis [cf. DOI: 10.1007 / sl0163-015-0425-4 & EP1801101], organometallic catalysis [cf. DOI: 10.1002 / ange.202212543], and depolymerization by formaldehyde [cf. WO2023280768].

[0011] However, all state-of-the-art solutions are either implemented under fairly extreme reaction conditions or use highly toxic compounds.

[0012] The high costs and drastic implementation conditions of existing recycling processes (e.g., very high temperatures and pressures) result in both economic and ecological problems. New solutions are needed. In addition, new recycling processes must follow changing legislative provisions worldwide, most of which face environmental challenges.

[0013] Also, the complexity of polymers on the market is a major obstacle to efficient recycling. The majority of these polymers are in fact assemblies (or blends) of polymers, containing more than one polymer, additives, pigments or plasticizers. Separating these different materials is a challenge technological and constitutes a major obstacle to the recycling of polymer materials [see DOI: 10.1021 / acsapm.lc00648]. More specifically, the recycling of mixed polyamide materials has become an important issue in contemporary society and particularly in the textile, automotive and construction industries [see DOI: 10.1098 / rstb.2008.0311 and DOI: 10.1016 / j.cogsc.2023.100763]

[0014] The present invention improves the situation.

[0015] To this end, the invention relates to a process for depolymerizing polyamide from a polymeric material comprising the step of: i. contacting, in a solvent, the polymeric material with a Brpnsted-Lowry acid in the presence of a Lewis acid catalyst, which produces a medium having a liquid phase comprising monomers derived from said polyamide.

[0016] According to a particularly preferred embodiment of the present invention, the polymeric material is made of polyamide and at least one second polymer, and wherein contacting said polymeric material in step i. induces selective depolymerization of the polyamide within the polymeric material, which produces said medium which further comprises a solid phase of said second polymer.

[0017] In this embodiment, the solid phase of the second polymer is preferably made up of at least 90%, preferably 100% of said second polymer.

[0018] According to a preferred embodiment, the polymeric material after step i. is reduced by at least 90%, preferably by 100% of said polyamide.

[0019] According to a preferred embodiment, the medium further comprises oligomers derived from said polyamide, and in which the ratio of said monomers relative to said oligomers varies from 99:1 to 70:30.

[0020] According to a preferred embodiment, the method further comprises the step of: ii. extracting the medium in order to isolate said monomers, and optionally said oligomers, and subsequently evaporating said solvent in order to recover the monomers, and optionally the oligomers.

[0021] According to a preferred embodiment when the process comprises a second polymer, the process of the invention further comprises the step of: iii. filtering the solid phase from said medium, and subsequently washing and drying said solid phase in order to recover the second polymer.

[0022] According to another embodiment, the second polymer is selected from the group consisting of a polyurethane copolymer, a cotton copolymer, a wool copolymer, a polyester copolymer, a silicon copolymer, elastane and a cellulosic material.

[0023] According to a preferred embodiment, the solvent is selected from the group consisting of ethanol, anisole, tetrahydrofuran, preferably 2-methyl-tetrahydrofuran, acetone, water, dioxolane, dioxane, dimethoxyethane, o-dichlorobenzene, dimethyl sulfoxide, methanol, isopropanol, ethylene glycol, acetic acid, trioxane, chloroform and a combination thereof.

[0024] According to a preferred embodiment, the Brpnsted-Lowry acid is selected from the group consisting of a mineral acid and an organic acid,

[0025] wherein the mineral acid is selected from HX, X being selected from Cl, Br, I, H2SO4, H3PO4, nitric acid, sulfuric acid, phosphomolybdic acid, para-toluenesulfonic acid and methylsulfonic acid, and

[0026] in which the organic acid is selected from a compound of formula (I):

[0027] RCOOH (I)

[0028] R being selected from hydrogen, a C1 to C8 alkyl, a perfluoroalkyl group and an aryl group, preferably benzyl or phenyl.

[0029] According to another preferred embodiment, the Brpnsted-Lowry acid is selected from the group consisting of monocarboxylic acid derivatives, dicarboxylic acid derivatives and tricarboxylic acid derivatives, preferably oxalic acid and citric acid.

[0030] According to a preferred embodiment, the Lewis acid is a metal catalyst comprising a metal selected from aluminum, preferably aluminum (III), preferably boron (III), bismuth, preferably bismuth (III), cerium, preferably cerium (III), iron, preferably iron (II) or (III), manganese, copper, preferably copper (II), lanthanum, preferably lanthanum (III), magnesium, preferably magnesium (II), tin, preferably tin (IV), titanium, preferably titanium (IV), zirconium, preferably zirconium (IV), calcium, zinc, preferably zinc (II), and the salts thereof, preferably the chloride salts.

[0031] According to another embodiment, the Lewis acid is selected from a metal triflate compound and a metal halogen compound, preferably in which said metal is iron, zinc or bismuth.

[0032] According to a preferred embodiment, step i. is carried out at a temperature less than or equal to 110°C, preferably less than or equal to 100°C, less than or equal to 90°C, or less than or equal to 80°C.

[0033] According to a preferred embodiment, the polymeric material is a synthetic material.

[0034] According to one embodiment, the polymeric material comprises additives. The additives can be selected from colorants, mineral fillers, antioxidants and a mixture thereof.

[0035] According to one embodiment, the polymeric material may comprise common impurities.

[0036] According to a preferred embodiment, the second polymer is elastane. More preferably, the elastane is recovered as a fiber or in a knitted form.

[0037] According to one embodiment, the monomers can be selected from adipic acid, adipic acid derivatives, diamine, diamine derivatives, ε-aminocaproic acid.

[0038] According to a preferred embodiment, the contact time in step i. is from 0.1 hour to 72 hours, preferably from 1 hour to 72 hours, more preferably from 12 hours to 72 hours.

[0039] According to a preferred embodiment, the contacting in step i. is carried out with stirring between 100 rpm and 1500 rpm, preferably at 600 rpm.

[0040] According to a preferred embodiment, the pressure in step i is at atmospheric pressure.

[0041] According to another embodiment of the method according to the invention, the polymeric material consists of polyamide.

[0042] Another object of the present invention is a compound generated by the method described above.

[0043] According to one embodiment, the compound is selected from the group consisting of a monomer, an oligomer and a polymer.

[0044] In a particular embodiment, the compound may be elastane or PET cotton. In another embodiment, the compound may be an ε-caprolactam derivative or an HMDA derivative.

[0045] Other characteristics and advantages of the invention will emerge and / or become clear from reading the following description, which includes specific examples given in an illustrative and non-limiting manner, as well as from the drawings in which: Fig.l

[0046] [Fig.l] represents a 1st chemical equation according to an embodiment of the invention; Fig.2

[0047] [Fig.2] represents a 2nd chemical equation according to another embodiment of the invention; Fig.3

[0048] [Fig.3] represents a 3rd chemical equation according to another embodiment of the invention; Fig.4

[0049] [Fig.4] represents a 4th chemical equation according to another embodiment of the invention; Fig.5

[0050] [Fig.5] represents a 5th chemical equation according to another embodiment of the invention; Fig.6

[0051] [Fig.6] represents a 6th chemical equation according to another embodiment of the invention; Fig.7

[0052] [Fig.7] represents a 7th chemical equation according to another embodiment of the invention; Fig.8

[0053] [Fig.8] represents an 8th chemical equation according to another embodiment of the invention; Fig.9

[0054] [Fig.9] represents a 9th chemical equation according to another embodiment of the invention; Fig. 10

[0055] [Fig.10] represents a 10th chemical equation according to another embodiment of the invention; and Fig. ll

[0056] [Fig. 11] represents a 1 Ith chemical equation according to another embodiment of the invention.

[0057] The drawings and description herein contain, for the most part, elements of a defined nature. Therefore, the description and drawings are used not only to better understand the present invention, but also to contribute to the definition thereof, where appropriate.

[0058] In the present description the term "polymeric material" refers to a material comprising at least one polymer. More particularly, according to the invention, a polymeric material is a material comprising at least polyamide. This means that a polymeric material within the meaning of the invention may for example comprise polyamide exclusively or may comprise polyamide in combination with at least one other polymer. Furthermore, a polymeric material within the meaning of the invention may comprise polyamide and two or more other polymers. Furthermore, a polymeric material within the meaning of the invention may comprise polyamide, one or more other polymers and one or more additives and / or colorants. A polymeric material within the meaning of the invention may also comprise polyamide and a cotton fiber and / or yarn and / or a cellulosic material. More generally, a polymeric material within the meaning of the invention may comprise polyamide, one or more other polymers or not, a cotton fiber and / or yarn and / or a cellulosic material or none of the three above, and optionally one or more additives and / or colorants. The term polymeric material thus encompasses a plastic material or a textile material. It also encompasses a material composed of polyamide and polyurethane (with or without additive(s) and / or colorant(s)). It further encompasses a material composed of polyamide and elastane (with or without additive(s) and / or colorant(s)).Other examples include polyamide joined (or blended) with (or coated onto) polyesters, polypropylene, rubber and / or a polyolefin.

[0059] In the present description the term "catalyst" refers to any compound capable of modifying, in particular by increasing, the speed of the chemical reaction in which it participates, and which is regenerated at the end of the reaction. This definition encompasses both conventional catalysts, i.e. compounds which exert their catalytic activity without requiring any modification or conversion, and compounds called precatalysts which are introduced into the reaction medium and converted therein into a catalyst. Consequently, in the present description, no formal distinction is made between catalyst and precatalyst.

[0060] The present invention relates to a process for depolymerizing polyamide from a polymeric material comprising the step of i. contacting, in a solvent, the polymeric material with a Brpnsted-Lowry acid in the presence of a catalyst, which produces a medium having a liquid phase comprising monomers derived from said polyamide.

[0061] The solvent may be present in the range: from 0.01 M to 1 M, preferably from 0.2 to 0.6 M. The Brpnsted-Lowry acid may be present in the range: from 1 to 30 equivalents, preferably from 2 to 12 equivalents. The number of equivalents is calculated with respect to the molecular weight of a repeating unit of the polymers. The Lewis catalyst is present in the range: from 0.01 to 80% by weight, preferably between 1 and 10% by weight.

[0062] The present invention thus relates generally to a process for depolymerizing polyamide. In other words, the invention is designed to depolymerize the polyamide of a polymeric material, whether the polymeric material comprises polyamide or is made of polyamide. The invention can be used for the recycling of plastic and / or textile materials. It can be used in the preparation of aromatic and aliphatic compounds, which in turn can be used as fuels, synthesis intermediates, raw materials in the construction field. More generally, the invention can be used in the petrochemical, electrical, electronic, textile, aeronautical, automotive, pharmaceutical, cosmetic and / or agrochemical industries.

[0063] The bonds targeted and selectively cleaved by the depolymerization process of the invention are the nitrogen-carbonyl bonds of amide functions (-CO-N-). Thus, the CN bonds of functions in which the carbon atom is linked to another carbon atom by a sp or sp2 multiple bond (e.g. C=CO) are not cleaved during the depolymerization process of the invention. For example, aryl ethers found in polyphenols are not cleaved. Urethane-type bonds (O-CO-N) are not cleaved during the reaction. Therefore, elastane will not depolymerize during the process of the invention, i.e., during the main depolymerization reaction of the invention. Single, double and triple CC bonds are also not cleaved by the depolymerization process of the invention. For example, polystyrene (PS) is not depolymerized by the process of the invention.

[0064] Therefore, the invention not only allows the transformation of the polyamide into its monomers and optionally its oligomers, but it also allows the selective depolymerization of the polyamide within materials which include other polymers (often called mixed materials or assembled materials).

[0065] Therefore, in a preferred embodiment of the invention, the polymeric material is made of polyamide and at least one second polymer. In this particular embodiment, contacting said polymeric material in step i. induces a selective depolymerization of the polyamide within the polymeric material, which produces a medium which not only comprises monomers (and optionally oligomers) derived from the polyamide, but also comprises a solid phase of said second polymer.

[0066] Thus, the invention allows the selective recovery of a copolymer from mixed materials resulting from the depolymerization process, such as cellulosic polymers, polyurethane (PU), polyesters, etc. The recovered second polymer (copolymer) can be used in the construction, petrochemical, electrical, electronics, textile, aeronautical, automotive, pharmaceutical, cosmetic and / or agrochemical industries.

[0067] The present invention also relates to the use of aromatic and aliphatic compounds obtained by the process of depolymerization of oxygenated polymer materials according to the invention, in the manufacture of fuels, electronic components, plastic polymers, rubber, medicines, vitamins, cosmetics, perfumes, food products, synthetic threads and fibers, synthetic leathers, glues, pesticides, fertilizers.

[0068] Generally, the present invention can also be used as an analytical tool for determining the content of copolymers assembled with polyamide by selective depolymerization of the polyamide to recover on the one hand the monomers and optionally the oligomers derived from the polyamide and on the other hand the non-depolymerized materials (which are usually other polymers).

[0069] The invention thus drastically improves the situation with regard to the recycling processes disclosed in the state of the art.

[0070] In fact, the main known polyamide recycling processes each have drawbacks, particularly when it comes to assembled polymer materials.

[0071] The process known as acid hydrolysis / acidolysis allows the recycling of several types of polyamide (PA) polymers such as PA 6,6 and PA 10,10. However, this process involves heating a dilute hydrochloric acid solution in water up to 200 °C to allow the depolymerization of the PA. The pressure generated in the reactor is approximately 20 bars. This depolymerization process thus takes place at very high temperatures and pressures. In addition, the reaction requires the use of a microwave reactor, which does not allow, or at least limits, the large-scale scaling up of this process. In other words, this process is limited in terms of industrial application. Furthermore, fibers such as elastane or cotton cannot withstand the drastic reaction conditions. The fibers and cotton are destroyed or degraded during or after the reaction.

[0072] The process known as aminolysis is a reaction of PA 6,6 carried out at 200 °C and 1 bar in the presence of ammonia in ethylene glycol as solvent and a Lewis acid catalyst. The presence of a Lewis acid catalyst promotes the production of the expected products due to the oxophilic nature of the catalyst which in a certain way activates the PA. Here again the depolymerization reaction takes place at very high temperatures. This process does not recover the monomers used in the polyamide industry. It recovers a diamine compound and a diamide compound. Fibers such as elastane or cotton cannot withstand the processing conditions and are destroyed / degraded during or after the reaction. The depolymerization of polyamide plastics using this process requires that the reaction atmosphere be changed, which means evacuating the reaction system and then replacing the atmosphere with ammonia.This action must be repeated, which is invasive in terms of implementation and thus limits its application.

[0073] The process known as solvolysis is another approach to the depolymerization of polyamide. It is also called glycolysis. This process can use ethylene glycol as a solvent while being carried out at elevated temperatures. More particularly, this process is established for the depolymerization of PA 6,6 based on a mixture of ethylene glycol and triethylenetriamine (TETA) at 190 °C in the presence of 2 wt% diammonium hydrogen phosphate as catalyst. The reaction generated substances with molecular weights ranging from 90 to 250 g.mol1 corresponding to PA 6,6 monomers and short oligomers. A process for producing monomers from polyamide 6 is also known from US 5,668,277. In the process, polyamide 6 is dissociated using ammonia, an amine or a mixture thereof as an activating reagent. The reaction takes place at a reaction temperature of between 200 °C and 400 °C and a pressure of about 0.5 atm to 5 atm. The reaction products produced include e-caprolactam and e-caprolactam precursor molecules such as e-aminocaproic acid, which can be used directly for the new synthesis of polyamides. Solvolysis is thus accompanied by rather drastic processing conditions.In particular, extreme pressure conditions are invasive and copolymers such as elastane are degraded in the process.

[0074] The process known as alcoholysis is a process for producing monomers from a polymer comprising a structural unit having a nitrogen-carbonyl bond. The process involves the cleavage of the nitrogen-carbonyl bond in a chemical reaction using an alcohol containing one or more carbon atoms as an activating reagent. The reaction does not require a catalyst, but requires to be carried out at a reaction temperature > 350 °C. The process can be carried out on polyamide 6, from which up to 97% of the ε-caprolactam monomer can be recovered. Apart from the high temperature, the depolymerization reaction also requires high pressures. Fibers such as elastane or cotton cannot withstand the processing conditions and are destroyed / or degraded during or after the reaction.Depolymerization of polyamide plastics using this process requires changing the reaction atmosphere or pressure vessels, which means evacuating the reaction system and then replacing the atmosphere with ammonia. This action must be repeated, which is invasive and limits the application of this process.

[0075] The process known as organometallic depolymerization of polyamide or as Tobin Marks depolymerization of polyamide relates to an organometallic catalysis system for depolymerizing polyamide without reaction solvents. The process uses a lanthanide catalyst and metallocene derivatives (lanthanides and transition metals) under an inert atmosphere to produce the corresponding PA6 monomer, i.e., e-caprolactam. The reaction takes place at temperatures between 220 °C and 240 °C under static vacuum. The catalysts require handling in an inert atmosphere, i.e., a reaction prepared in a glove box under an inert atmosphere. In about 4 hours, the reaction recovers the monomer with yields of about 90%. However, similarly to other Unlike state-of-the-art processes, the depolymerization reaction takes place at high temperatures > 200 °C and is therefore very energy-intensive. Fibers such as elastane or cotton cannot withstand such conditions and are destroyed / degraded during or after the reaction. The catalysts used in the reaction are highly sensitive to oxygen and moisture, and require specific equipment to be properly handled. The reaction is only suitable for carrying out on polyamide PA6 and cannot be applied to PA 6,6 polymers. Depolymerization of polyamide-type plastics with this system requires a vacuum, which requires specific equipment and therefore limits its use.

[0076] The process known as formaldehyde depolymerization involves the use of formaldehyde or para-formaldehyde in the presence of a Lewis acid as a catalyst (Bi(OTf)3) and optionally in the presence of dioxane or chloroform as a solvent. The reaction is carried out in sealed vessels at 165 °C. The depolymerization reaction takes place at moderate to high temperatures (165 °C), but sealed vessels are required. Formaldehyde is a toxic and environmentally harmful compound. Formaldehyde is a known carcinogen and mutagen with acute toxicity. It is also a highly volatile compound (VOC: Volatile Organic Compound). Its volatility, combined with its toxicity / hazard, makes this compound an undesirable by-product on an industrial scale.The monomeric and oligomeric compounds generated during this reaction cannot be directly reused to recreate a polyamide-based polymeric material, as they mainly obtain acetamide derivatives. An additional step is required to obtain industrially exploitable monomers.

[0077] Consequently, the known chemical recycling or tertiary recycling processes have significant implementation drawbacks, and in particular the need to carry out depolymerization reactions at very high temperatures and pressures, and the need to use toxic compounds to catalyze the reactions. In addition, no process aims, or very few processes aim, at the recycling of several types of polymers at the same time (copolymer or assembled polymeric material). None of the processes is satisfactory with regard to the additives present in the materials.

[0078] The recycling industry, and in particular companies dealing with the recycling of plastics and textiles involving chemical recycling, are thus facing a major problem with regard to polyamide materials. More specifically, and to summarize, there are two main problems to be faced when it comes to the recycling of polyamide and / or assembled materials containing polyamides:

[0079] The first problem is the inability to process mixed materials, as they are complex to separate into their respective compounds. Separation generally requires very high technicality. In addition, such separation generates a lot of waste. Therefore, this type of treatment is mostly neglected and the industry focuses almost exclusively on raw materials with a purity > 95%.

[0080] The second problem concerns the high energy costs of recycling processes. Indeed, most known processes are carried out at temperatures above 250 °C, at high pressures and with toxic chemical solvents. As a result, chemical recycling is generally very expensive and limited in relation to the actual environmental benefit of recycling processes.

[0081] No method has been developed in the art that is capable of properly separating an assembled polymeric material to recover one polymer on the one hand, while depolymerizing the second on the other hand in order to obtain the corresponding monomers and optionally oligomers. The invention is capable of doing so. In fact, in an assembled polymeric material comprising polyamide, the invention is capable of depolymerizing said polyamide and recovering any other polymer included in the material. The invention thus provides a method for tertiary recycling of polymeric materials that overcomes the problems of the prior art.

[0082] The invention provides a depolymerization process that can be applied to the recycling of polymer materials, especially mixed polymer materials, into high value-added compounds or even monomers. Advantageously, the process of the invention:

[0083] - is environmentally friendly;

[0084] - can be processed under moderate processing conditions (<110°C) and is thus of industrial interest;

[0085] - uses only sustainable and / or bio-sourced solvents;

[0086] - has a very high selectivity with respect to the targeted polymer;

[0087] - leaves the copolymers of assembled polyamide materials intact;

[0088] - avoids the use of polluting, rare and / or expensive metal-based catalysts;

[0089] - is effective, i.e. the polyamide material is converted into compounds chemicals of high purity (at least 90% by mole of the total number of moles of compounds obtained) or at least in compounds which can be easily purified;

[0090] - provides good selectivity with respect to the chemical compounds obtained;

[0091] - allows selective cleavage of certain bonds in the polymer material polyamide;

[0092] - is general purpose and versatile and can be adapted to the type of material polyamide polymer to be depolymerized; and / or

[0093] - is capable of supporting additives present in polymer materials mixed to be depolymerized.

[0094] More particularly, the method of the invention has the advantage of resisting the presence of one or more additive(s) in the polymer materials. No catalyst poisoning problem is observed with the additives commonly used in polymeric materials. As mentioned above, the recycling challenge is not limited to the depolymerization of the polymer present alone in the reaction medium (pure polymer), but also extends to its depolymerization in a commercial material that may contain additives such as dyes, mineral fillers, antioxidants, etc. The presence of these additives in the material may deactivate the catalyst used to carry out the depolymerization, and thus render the reaction inefficient. The invention is not affected by this problem. The process of the invention is therefore of great industrial interest, as it is able to resist additives and / or impurities present in the starting polymeric material, which, for example, may be plastic waste.

[0095] Furthermore, by regulating the processing conditions, the depolymerization of a polymer material comprising a blend of polyamide(s) and / or polyurethane(s) is selective. Regardless of any theory, the difference in reactivity of the nitrogen-carbonyl bonds of an amide function and a urethane function may favor the selective cleavage of one of these functions over the other. In addition, the electronic effect (e.g., inductive effects relating to the polarization of a bond and mesomeric effects due to electron delocalization) and the steric hindrance of the substituents near the nitrogen-carbonyl bond may have an impact on the reactivity of the bond to be cleaved. For example, in the case of a material comprising a PA6 + elastane blend or a material comprising a PA6.6 + cotton blend, the PA6 and PA6.6 are selectively cleaved.Furthermore, within a standard filtration step, the elastane originally blended with PA6 and PA 6,6 can be recovered as a fiber and even in the form of a knitted material in pure form from the reaction described in the patent.

[0096] There is a very high synergistic effect between the Bronsted acid and the Lewis acid catalyst which results in an excellent conversion. The solvent allows a high reaction rate. For example, without ethanol, the reaction rate drops drastically.

[0097] A preferred embodiment of particular interest is when the polymeric material is made of polyamide and at least one second polymer. Contacting the polymeric material in step i. with a Brpnsted-Lowry acid and a Lewis acid catalyst in a solvent induces selective depolymerization of the polyamide within the polymeric material. As a result, the reaction produces a medium which not only comprises a liquid phase comprising monomers and optionally oligomers derived from the polyamide, but also comprises further a solid phase of said second polymer. The solid phase of the second polymer consists of at least 90%, preferably 100% of said second polymer. The solid phase may comprise or consist of polyurethane or elastane for example.

[0098] The process of the invention makes it possible to rid the original polymeric material of the polyamide contained therein. After step i. of bringing the polymeric material into contact with the Brpnsted-Lowry acid and the Lewis acid catalyst in a solvent, the polymeric material is reduced (or devoid) of at least 90%, preferably 100% of said polyamide.

[0099] The polyamide which is depolymerized during the process of the invention is degraded into monomers. Such monomers may be adipic acid, adipic acid derivatives, diamine, diamine derivatives, e-aminocaproic acid or e-caprolactam. The monomers may be recovered in the liquid phase of the reaction medium. Depending on the reaction time and the ingredients used, the liquid phase of the reaction medium may further comprise oligomers derived from the polyamide. Typically, the ratio of said monomers to said oligomers varies from 99:1 to 70:30.

[0100] According to one embodiment of the invention, the aforementioned monomers, and optionally the oligomers, may be recovered from the reaction medium in a step ii. subsequent to contacting the polymeric material with the Brpnsted-Lowry acid and the Lewis acid catalyst in a solvent. For this, the monomers and / or oligomers may be isolated by medium extraction. The monomers and / or oligomers are then recovered by evaporation of the solvent. As an example, the extraction of adipic acid derivatives may be accomplished by basification of water (KOH or NaOH) followed by a second extraction to recover hexamethylenediamine (HMDA). The recovery of monomers may also be accomplished by precipitation of the HMDA salts by adding another organic solvent miscible with water, followed by basification and a second precipitation, thereby recovering the adipic acid derivatives.Purification of monomers can be done by recrystallization, column chromatography or distillation.

[0101] When the polymeric material comprises a second polymer, the method of the invention may further comprise a step of: iii. filtering the medium in order to recover a solid phase. As explained, polymers other than polyamide are not degraded in the liquid phase of the medium. Therefore, other polymers of the polymeric material remain intact or almost intact in a solid form. The second polymer is thus recovered as a solid, and may be washed and dried before being recovered. The washing may be done for example with EtOH and water.

[0102] According to one embodiment, the second polymer may be a polyurethane copolymer, a cotton copolymer, a wool copolymer, a polyester copolymer, elastane, a cellulosic material, silicon copolymers, polyolefin copolymers or cotton PET.

[0103] According to a preferred embodiment of the invention, the polymeric material used in the method of the invention is an assembled material composed of polyamide and polyurethane. Polyurethane is an industrially significant synthetic polymer. Polyurethanes are characterized by regularly repeating urethane groups. As with amide bonds, a portion of these urethane groups is a nitrogen-carbonyl carbon bond, whereby the urethane groups possess an additional oxygen atom unlike amide groups. Polyurethanes are formed during the polyaddition reaction of polyols with polyisocyanates. The reaction of dialcohols (also called diols) with diisocyanates results in linear polyurethanes. The reaction of compounds such as triisocyanate-diisocyanate mixtures with triol-diol mixtures results in crosslinked polyurethanes.Depending on the degree of crosslinking and the isocyanate and alcohol components used, polymers with different properties are produced. Polyurethanes can thus form thermosets, thermoplastics or elastomers. Polyurethanes are most frequently used in the textile industry in the form of elastane. However, they can also be used as adhesives, resins, foams, molding compounds or other. In the textile industry, elastane is very often used to impart elasticity and flexibility to polyamide fibers. Therefore, the textile industry widely uses assembled polymer materials comprising polyamide and elastane. Such an assembled material is used, for example, in underwear.

[0104] The present invention allows the selective recovery of elastane from an assembled material composed of polyamide and elastane. The elastane can be recovered as a solid phase in the reaction medium. The liquid phase of the reaction medium contains monomers (and possibly oligomers) derived from the polyamide initially mixed with the elastane in the polymeric material.

[0105] According to a preferred embodiment, step i. is carried out at a temperature less than or equal to 110°C, preferably less than or equal to 100°C, less than or equal to 90°C, or less than or equal to 80°C. Heating can be carried out using a sand bath or an oil bath. Such a low temperature is a major implementation advantage because the reaction can be carried out in a simple tank. It is therefore not necessary to use one or more specific devices allowing a high temperature and / or an associated high pressure which makes it possible to bring a solvent above its melting point. In addition, the low temperature used in the invention limits costs, particularly given current economic fluctuations in energy prices.

[0106] The contact time in step i. is preferably from 0.1 hour to 72 hours. For example, the contact time could be 24 hours, 36 hours, 48 ​​hours or 60 hours. The contacting in step i. is preferably carried out with stirring at 600 rpm. Stirring can be carried out using a magnetic stirrer. The pressure in step i. is preferably at atmospheric pressure. Thus, no apparatus is necessary to regulate the pressure.

[0107] The Brpnsted-Lowry acid compound used in the invention is preferably chosen from mineral acids and organic acids.

[0108] The mineral acids may be selected from HX, X being selected from Cl, Br, I, H2SO4, H3PO4, nitric acid, sulfuric acid, phosphomolybdic acid, para-toluenesulfonic acid, methylsulfonic acid.

[0109] The organic acids may be selected from a compound of formula (I):

[0110] RCOOH(I)

[0111] R being selected from hydrogen, a C1 to C8 alkyl, such as methyl, ethyl, propyl, butyl, etc., a perfluoroalkyl group and an aryl group, preferably benzyl or phenyl.

[0112] The acid may be selected from mono-, di- or tricarboxylic acid derivatives. The acid may be selected from oxalic acid, citric acid, etc.

[0113] The Lewis acid may be a metal catalyst. Preferably, the metal catalyst may comprise a metal from the following group: aluminum, bismuth, cerium, iron, manganese, copper, lanthanum, magnesium, tin, titanium, zirconium, calcium, niobium or zinc. The metals may preferably be used in the form of oxides. The metals may preferably be used in the form of their chloride salts. The use of other salts is also possible. Preferred oxidation states of the aforementioned metal catalysts are aluminum (III), boron (III), bismuth (III), cerium (III), iron (III) and iron (II), copper (II), lanthanum (III), magnesium (II), tin (IV), titanium (IV), zirconium (IV) or zinc (II).

[0114] According to one embodiment of the invention, a metal triflate compound or a halogenated metal compound, preferably iron, zinc or bismuth, can be used as a metal catalyst. The triflate compounds can be used as Lewis acids in the reaction carried out in the invention. The advantage of these salt compounds is the high stability of the triflate anion. Even when dissolved in water, the triflate anion does not react further, unlike many other conventional Lewis acids. Therefore, the reaction can be substantially controlled and / or undesirable side reactions can be avoided.

[0115] With respect to the metal halogen compound, preferred embodiments relate to iron halogen, zinc halogen, aluminum halogen, cerium(III) halogen, scandium halogen, neodymium halogen, samarium halogen, yttrium halogen, lanthanum halogen or gadolinium halogen.

[0116] With respect to the metal triflate salts, preferred embodiments relate to bismuth triflate, zinc triflate, aluminum triflate, cerium(III) triflate, scandium triflate, neodymium triflate, samarium triflate, yttrium triflate, lanthanum triflate or gadolinium triflate.

[0117] According to one embodiment, the method according to the invention is carried out in the presence of an additive and / or a ligand for the catalyst. Such additives may be a nitrogen-containing compound such as triethanolamine, triethylamine, TBD, DBU, pyridine, DMAP, 2-aminopyridyne.

[0118] According to one embodiment, the process according to the invention is carried out in the presence of an additive and / or a ligand for the catalyst. Such additives may be a phosphine derivative of the following formula:

[0119] PRiR2R3

[0120] The aromatic groups Rh R2 and R3 of the phosphine ligand PRiR2R3 are preferably selected from the group consisting of phenyl, o-tolyl, m-tolyl, p-tolyl, 3,5-dimethylphenyl, 4-n-butylphenyl, 4-methoxyphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2-isopropoxyphenyl, 4-methoxy-3,5-dimethyl phenyl, 3,5-di-tert-butyl-4-methoxyphenyl, 4-chlorophenyl, 3,5-Bis(trifluoromethyl)phenyl, benzyl, naphthyl, dinaphthyl, pyridyl, bisphenyl, furyl and thienyl.

[0121] The hydrocarbyl groups RB R2 and R3 of the phosphine ligand PRiR2R3 contain 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, more preferably 3 and 10 between the carbon atoms. Preferably, the hydrocarbyl groups Rb R2 and R3 of the phosphine ligand PRiR2R3 complexed with nickel are selected from the group consisting of the following groups: methyl, ethyl, propyl, isopropyl, N-butyl, tertiary butyl, pentyl, cyclopentyl, hexyl, cyclohexyl, octyl, 2-ethylhexyl, benzyl and adamantyl.

[0122] The invention preferably uses a so-called "green" solvent which is non-toxic and environmentally neutral. According to one embodiment, the solvent used in the invention is selected from the group consisting of ethanol, anisole, tetrahydrofuran, preferably 2-methyl-tetrahydrofuran, acetone, ethyl acetate, water, dioxolane, dioxane, dimethoxyethane, o-dichlorobenzene, dimethyl sulfoxide, methanol, isopropanol, ethylene glycol, acetic acid, trioxane, chloroform and a combination thereof. ci. The solvent system can be used in the reaction of the invention as a combination of the above-mentioned solvents with a ratio between two solvents varying from 0 / 100 exclusive to 100 / 0 exclusive (ratio expressed by volume).

[0123] In sum, a major advantage of the invention lies in the moderate implementation conditions of the invention (low temperature, atmospheric pressure, non-toxic materials, etc.). In particular, the solvent, which is the main chemical product of the reaction in terms of mass and quantity, can be a mixture of green solvent(s) with water. The solvent can be recycled by vacuum distillation and therefore consumption is limited. These moderate conditions make it possible in particular to preserve the original state and / or properties of the non-depolymerized material when the invention is carried out on an assembled material comprising at least one polymer that is combined with the polyamide. The polyamide that is ultimately depolymerized from the assembled material leaves behind the non-target material (i.e., the non-target polymer) in its original state or near-original state.For example, the elastic properties of elastane or the strength of cotton fibers are not degraded by the process of the invention. The invention is pioneering with regard to the recovery of elastane materials.

[0124] GENERAL EXPERIMENTAL PROTOCOL ACCORDING TO THE INVENTION OF REDUCTION OF POLYMERIC MATERIAL BASED ON POLYAMIDE.

[0125] 1. In air, the polymeric material is placed in a round-bottomed flask equipped with a magnetic stirrer and reflux condenser, followed by the addition of solvents and Brpnsted-Lowry acid. Alternatively, the round-bottom flask can be replaced with a 30 ml reaction tube. Both embodiments are suitable for the reaction.

[0126] 2. The catalyst is added to the reaction medium. The catalyst generally varies from 1 to 0.001 molar equivalents calculated relative to the molar number of the polymeric material initially added.

[0127] 3. Optionally, a catalyst ligand and / or additives may be added as the last ingredient in the reaction medium.

[0128] 4. The reaction flask (or tube) is stoppered with a septa and heated within a sand or oil bath preheated to the desired temperature. The invention allows the reaction to be carried out at relatively low temperatures ranging from about 20°C to 110°C. The reaction is stirred at the set temperature for a desired time, generally ranging from about 12 h to 72 h. The reaction is monitored by proton NMR.

[0129] In the case where the polymeric material is made of polyamide, the polymeric material solubilizes during the reaction. The solubilized polyamide is thus contained in a liquid phase. The solubilized polyamide is ideally made of monomers only, but can be made of a mixture of monomers and oligomers.

[0130] In the case where the polymeric material is made of polyamide and at least one other polymer, the polymeric material partially solubilizes during the reaction. The polyamide is depolymerized (into monomers, and optionally into oligomers) while the other polymer(s) remain(s) in the solid phase. The other polymer(s) is / are not soluble at the end of the reaction and can / can be recovered by filtration.

[0131] 4. When the reaction is complete (after 0.1 h to 72 h, more particularly after 12 h to 72 h), the reaction mixture is cooled to room temperature and filtered to recover the solid phase (also called copolymer), i.e. the polymeric material from which the polyamide fraction was extracted. The solid phase is washed with hot ethanol and water to recover the desired copolymer.

[0132] 5. With regard to the solubilized polyamide (i.e. PA 6,6, PA 10,10, etc.): The organic solvent from the filtrate is evaporated. The solution is then extracted with ethyl acetate several times. The organic phases are combined and the solvent is evaporated to recover monomers of the original polyamide, or optionally a mixture of monomers and oligomers of the original polyamide (e.g. a mixture of dicarboxylic acid derivatives).

[0133] 6. The aqueous phase (e.g. diamine) is evaporated to provide a solid (with the presence of the dye). The solid is then recrystallized from a mixture of water / EtOH / acetone. An off-white / grey precipitate was obtained and removed by filtration. (If the precipitate is still colored by the dye, the recrystallization can be repeated to obtain the pure compounds).

[0134] Alternatively, steps 5. and 6. above may be:

[0135] 5bis. With regard to the solubilized polyamide (i.e. PA6, PA6.6, etc.): Acetone is added to the crude reaction mixture until a gray / white solid precipitate is obtained. It should be noted that the precipitate can be colored with the dye from the starting material. The precipitate is removed by filtration and dried in an oven (60 °C) until the mass of the solid no longer changes.

[0136] 6bis. In the case of PA6.6, PA10.10, etc.: The volatile compounds of the filtrate are evaporated under reduced pressure (or removed by distillation). The remaining aqueous phase is extracted several times. The organic phases are combined and the solvent is evaporated in order to recover monomers of the original polyamide, or optionally a mixture of monomers and oligomers of the original polyamide (e.g. a mixture of dicarboxylic acid derivatives).

[0137] Examples of the present invention are presented below. For example, examples of depolymerization of synthetic or bio-based polymer materials in the presence of various other polymers are provided. Some of the catalysts tested are for example FeCl3, FeCl2, AlCl3, ZnCl2, CaCl2, Fe(OTf)3, Zn(OTf)2, La(OTf)3, Bi(OTf)3, Y(OTf)3, Sc(OTf)3, etc. The Brpnsted-Lowry acids preferably used are HCl, H2SO4, CH3CO2H, HCO2H, CF3CO2H, CF3SO3H 4-CH3-C6H4-SO3H. Suitable polar organic solvents include dioxolane, tetrahydrofuran, 2-methyl-tetrahydrofuran, dioxane, dimethoxyethane, o-dichlorobenzene, dimethyl sulfoxide, methanol, ethanol, isopropanol, acetone, ethyl acetate, ethylene glycol, acetic acid, trioxane or chloroform, preferably methanol, ethanol or 2-methyl-THF. The polymer materials used are composed of PA6 and / or PA6.6 blended with PET, elastane, cotton and wool. The polyamides used are textile waste received by lingerie and clothing brands as well as textile manufacturers.

[0138] The depolymerization of the polyamide according to the invention generates monomers. Oligomers can be generated in addition. In order to determine the ratio of monomers to oligomers, the conversion can be defined as the rate of hydrolysis of the polyamide that is being studied. The conversion, therefore, reflects the number of bonds between the monomers that have been broken within the given depolymerization. The conversion is determined by means of an NMR analysis of the crude reaction mixture. In fact, it is possible to evaluate the ratio between the polyamide (PA) remaining in solution and the products which are mainly hexamethylenediamine (HMDA) derivatives and adipic acid (AA) derivatives. This methodology for determining the conversion is known from Pahovnic and Zagar [cf. DOI: 10.1021 / acssuschemeng.0c05706].

[0139] Taking into account the known signal in the NMR spectra of each constituent of the reaction mixture, it is possible to determine the conversion with the following formula:

[0140] [Math.l] L Conversion = 1 - 7—-p— 1PA±lRMDA

[0141] Where IPA is the integration of the PA peak at 3.0 ppm and IHmda is the integration of the HMDA peaks at 2.75 ppm.

[0142] In the case where there is some remaining solid (i.e. unreacted polyamide) that cannot be accounted for in the raw NMR analysis, the solid remaining in the reaction is removed from the reaction by filtering, dried until the mass no longer changes and then weighed. The mass of the remaining solid is used to establish a fixed conversion. Said fixed conversion is then multiplied by the conversion from the raw NMR analysis to provide the final conversion of the reaction.

[0143] In the case of a blended material in which polyamide is assembled with another polymer, the conversion calculation requires taking into account the polymer that is not depolymerized during the depolymerization reaction. More particularly, the second polymer (or non-depolymerized polymer) is dried until the mass is stabilized. It is then weighed. The second polymer is preferably characterized by FTIR or NMR (if possible) to evaluate the purity and the content of polyamide remaining in the polymers in the case where the depolymerization reaction is not complete (i.e., less than 100% of the PA is converted into monomers and optionally into oligomers). In this case, the weight of the second polymer that is not affected by the polymerization reaction is deducted from the original mass of the starting blended material of the reaction to accurately evaluate the conversion.

[0144] Since the depolymerization process of the invention focuses on efficiency, i.e., the conversion rate of the reaction, the yield is not of particular interest. However, the yield can be determined by the molar amount of the products compared to the molar amount of a monomer in the polyamide starting material. Yields are generally determined only for isolated products. This means that yields are calculated when the reaction is completed and the products are purified and isolated by suitable purification techniques (distillation, recrystallization, extraction, column chromatography, etc.).

[0145] The examples described herein do not limit the scope of the claimed invention. In the examples, the most commonly used polymers (for example: PA6 and PA6.6) are given. The amount of Brpnsted-Lowry acid required to carry out the depolymerization reaction according to the invention is substantially dependent on the type of polymeric material used. It should be noted that, by approximation, and in order to calculate the molar yield of the depolymerization reactions, the starting product can be considered to be exclusively formed of the polymer studied.

[0146] The yield of chemical compounds having an average molar mass of less than 600 g / mol obtained by the process of the invention depends on the starting polymer material. In addition, the yield depends on the processing conditions applied as explained above, and in particular depends on the reaction time. The yield is generally good (from 68 to 98 mol% relative to the total number of moles of monomer units present in the polymer(s) of the starting product.

[0147] As mentioned above, by approximation, and in order to efficiently calculate the molar yield of the depolymerization process, the starting polymer material is considered to be made up of or exclusively formed from the polymer studied. EXAMPLES

[0148] Example 1: Reaction on boxer shorts based on black polyamide (purity > 98%) in EtOH.

[0149] [Fig.l] represents the chemical equation.

[0150] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, black PA6,6 from underwear (elastane < 2%) is added followed by 8 ml of EtOH. Then, 1 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by the catalysts (4 wt% FeCl3). The tube is capped with a septum and placed in a sand bath heated to 80 °C. The reaction medium is stirred for 14 h at 600 rpm. The reaction resulted in a conversion to the corresponding monomers of 34%.

[0151] This is the first time that such a reaction occurs at 75 °C with such a high level of conversion rate in 14 h. Therefore, additional reactions with different concentrations and reaction times were carried out. One of them proved to be very productive, as in the presence of ZnCl2 as catalyst under reflux for 48 h, the NMR conversion was determined to be 76%. No more textiles were observable in the reaction mixture (nor any solids, see below Example 2).

[0152] Example 2: Reaction on boxer based on black polyamide (purity > 98%) in EtOH with ZnCl2 catalyst.

[0153] [Fig.2] represents the chemical equation.

[0154] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, black PA6,6 from underwear (elastane < 2%) is added followed by 8 ml of an EtOH / water mixture. Then, 1 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by the catalysts (4 wt% ZnCl2). The tube is capped with a septum and placed in a sand bath heated to 80 °C. The reaction medium is stirred for 48 h at 600 rpm. The reaction resulted in complete conversion of the starting material and resulted in the corresponding monomers with a conversion of 76% and 24% oligomers.

[0155] Example 3: Reaction on black polyamide-based textile (76% PA, 24% elastane) in EtOH / H2O with FeCl3 catalyst and recovery of elastane.

[0156] [Fig.3] represents the chemical equation.

[0157] Following the experimental procedure described above, in a 250 ml round-bottomed flask equipped with a magnetic stirrer, 5 g of black PA6,6 from a textile in one piece (elastane about 24%) is added followed by 40 ml of a solvent mixture of EtOH / H2O (1 / 1: v / v). Then, 10 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by a catalyst (4 wt% FeCl3). The flask is placed in a sand bath heated to 80 °C. The reaction medium is stirred for 72 h at 600 rpm. After this time, the reaction is filtered. A lightly colored knitted fiber is recovered. The textile is elastic and recovered at 24 wt% of the starting materials, e.g. 1.202 g.

[0158] The reaction resulted in complete conversion of the starting material into polyamide and resulted in the corresponding monomers with a conversion rate of 81%.

[0159] Example 4: Reaction on textile based on purple polyamide (94% PA, 6% elastane) in EtOH / H2O with FeCl3 catalyst and recovery of elastane.

[0160] [Fig.4] represents the chemical equation.

[0161] Following the experimental procedure described above, in a 250 ml round-bottomed flask equipped with a magnetic stirrer, 5 g of purple PA6,6 from a single-piece textile (elastane content about 6%) is added followed by 40 ml of a solvent mixture of EtOH / H2O (1 / 1: v / v). Then, 10 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by the catalysts (4 wt. % FeCl3). The flask is placed in a sand bath heated to 90 °C. The reaction medium is stirred for 72 h at 600 rpm. After this time, the reaction is filtered. A slightly pink colored knitted fiber is recovered. The textile is elastic and has been recovered at 6 wt. % of the starting materials, e.g. 0.302 g. The textile is pure elastane according to FTIR spectroscopy.

[0162] The reaction resulted in complete conversion of the starting material to polyamide and resulted in the corresponding monomers with a conversion of 67%.

[0163] Example 5: Reaction on textile based on white PA6 (84% PA, 16% elastane) in EtOH / H2O with FeCl3 catalyst and recovery of elastane.

[0164] [Fig.5] represents the chemical equation.

[0165] Following the experimental procedure described above, in a 25 ml round-bottomed flask equipped with a magnetic stirrer, 0.5 g of single-piece white PA6 tights (elastane content approximately 16%) is added followed by 8 ml of a solvent mixture EtOH / H2O (1 / 1: v / v). Then, 1 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by the catalyst (4 wt% FeCl3). The flask is placed in a sand bath heated to 100 °C. The reaction medium is stirred for 12 h at 600 rpm. After this time, the reaction is filtered. One fiber is recovered.

[0166] The textile is elastic and has been recovered at 16% by weight of the starting materials, e.g. 0.099 g. The textile is pure elastane according to FTIR spectroscopy.

[0167] The reaction resulted in complete conversion of the starting material to polyamide and resulted in the corresponding monomers with a conversion of 49%.

[0168] Example 6: Comparison of the acid used in the reaction.

[0169] [Fig.6] represents the chemical equation.

[0170] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 0.5 g of one-piece black PA6,6 underwear (elastane content < 2%) is added followed by 8 ml of a solvent mixture of EtOH / H2O (1 / 1: v / v). Then, 12 equivalents of selected acid are added to the reaction mixture followed by the catalyst (4% by weight of FeCl3). The flask is placed in a sand bath heated to 100 °C. The reaction medium is stirred for 12 h at 600 rpm. After this time, the reaction is filtered.

[0171] The results for the acids tested are reported in Table 1 below:

[0172] [Tableauxl] Acid Polyamide Conversion Monomer / Oligomer Ratio HCl 100% 99 / 1 H2SO4 100% 99 / 1 Acetic Acid >5% ND No Acid >5% ND pTsOH 100% 96 / 4 Orthophosphoric Acid 100% 54 / 46 Phosphomolybdic Acid 100% ND Table 1: Acids tested

[0173] Example 7: Effect of the catalyst on PA6,6.

[0174] [Fig.7] represents the chemical equation.

[0175] In a 30 ml tube equipped with a magnetic stirrer, a black PA6,6 boxer shorts mixed with elastane from underwear is added followed by 8 ml of an EtOH / Water mixture (1 / 1: v / v). Then, 1 ml of HCl in water (37%, 12 M) is added to the reaction mixture followed by the selected catalyst (10% by weight). The tube is capped with a septum and placed in a sand bath heated to 90 °C. The reaction medium is stirred for 48 h at 600 rpm. After this time, the reaction is filtered.

[0176] The results for the catalysts tested are reported in Table 2 below:

[0177] [Tables2] Catalyst Conversion of P A6,6. Conversion to monomers Remaining textile A1C13 100% 74% 94 mg (elastane) ZnCl2 100% 87% 86 mg (elastane) Cu(OAc)2 [INCOMPLETE REACTION] ND >49% 205 mg (elastane / PA) La(OTf)3 100% 87% None Fe(OTf)3 100% 94% None Y(OTf)3 100% 61% None Table 2: Catalysts tested

[0178] Example 8: Effect of additives within the system on PA6,6.

[0179] [Fig.8] represents the chemical equation.

[0180] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 0.5 g of one-piece black PA6,6 underwear (elastane content < 2%) is added followed by 8 ml of a solvent mixture EtOH / H2O (1 / 1: v / v). Then, 1 ml of HCl (37%) is added to the reaction mixture followed by the catalysts (4 wt% FeCl3). Then, the respective additive (2.0 equivalents compared to the catalyst loading) is added to the reaction mixture. The flask is placed in a sand bath heated to 100 °C. The reaction medium is stirred for 16 h at 600 rpm. After this time, the reaction is filtered.

[0181] The results concerning the additives tested are reported in Table 3 below:

[0182] [Tables3] Additive Polyamide Conversion Monomer / Oligomer Ratio Triethanolamine 100% 71 / 29 TBD 100% 85 / 15 PPh3 100% ND 2-Cyanopyridine 100% 63 / 37 DBU 100% 65 / 35 DMAP 100% 77 / 23 Table 3: Additives tested

[0183] Example 9: Effect of the solvent within the system on PA6,6.

[0184] [Fig.9] represents the chemical equation.

[0185] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 0.5 g of one-piece black PA6,6 underwear (elastane content < 2%) is added followed by 8 ml of solvent. Then, 1 ml of HCl (37%) is added to the reaction mixture followed by the catalysts (4% by weight of FeCl3). Then, the additives are added to the reaction mixture. The flask is placed in a sand bath heated to 100 °C. The reaction medium is stirred for 16 h at 600 rpm. After this time, the reaction is filtered.

[0186] The results for the solvents tested are reported in Table 4 below:

[0187] [Tables4] Solvent Conversion of polyamide Monomer / oligomer ratio EtOH / H2O: 1 / 0 > 10% ND EtOH / H2O: 6 / 2 23% 60 / 40 EtOH / H2O: 4 / 4 100% 72 / 28 EtOH / H2O: 2 / 6 100% 58 / 42 EtOH / H2O: 0 / 8 100% 34 / 66 Me-THF 100% ND DMSO 76% ND Acetone 100% NDa EtOH / H2O / Acetone: 4 / 4 / 1 100% 84 / 16 H2O / Acetone: 4 / 4 100% 91 / 9 AcOET 100% NDa Table 4: Solvents tested. “1 h instead of 16 h.

[0188] Example 10: Determination of the elastane content in a polyamide-based blended material from an underwear.

[0189] The determination of the elastane content within a polyamide boxer short was carried out in two reactions, the first for the body part of the boxer short and the second on the rubber part of the boxer short.

[0190] 1st reaction: Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 5 g of black PA6.6 boxer body in one piece are added, followed by 40 ml of a mixture of EtOH / H2O (1 / 1: v / v). Then, 10 ml of HCl (37%) is added to the reaction mixture followed by the catalyst (4% by weight of FeCl3). The flask is placed in a sand bath heated to 100 °C. The reaction medium is stirred for 72 h at 600 rpm. After this time, the reaction is filtered. 101 mg of elastane was recovered.

[0191] The body of the boxer contains 2% elastane and 98% polyamide.

[0192] 2nd reaction: Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 0.5 g of black PA6,6 boxer rubber in one piece is added, followed by 8 ml of a mixture of EtOH / H2O (1 / 1: v / v). Then, 1 ml of HCl (37%) is added to the reaction mixture followed by the catalyst (4% by weight of FeCl3). The flask is placed in a sand bath heating to 100 °C. The reaction medium is stirred for 72 h at 600 rpm. After this time, the reaction is filtered. 86 mg of elastane was recovered as a knitted textile composed solely of elastane.

[0193] The rubber part of the boxer shorts contains 17% elastane and 83% polyamide.

[0194] Example 11: Recovery of cotton fiber from a material based on mixed polyamide.

[0195] [Fig. 10] represents the chemical equation.

[0196] Following the experimental procedure described above, in a 30 ml tube equipped with a magnetic stirrer, 5 g of black PA6,6 containing single-piece cotton strand / yarn stitching (elastane content < 2%) is added followed by 8 ml of a solvent mixture. Then, 10 ml of HCl (37%) is added to the reaction mixture followed by the catalyst (4 wt% FeCl3). The flask is placed in a sand bath heating to 100 °C. The reaction medium is stirred for 72 h at 600 rpm. The cotton strand was recovered intact and the conversion of PA6,6 to monomers was determined to be 87%.

[0197] Example 12: Depolymerization of an entire bra.

[0198] [Fig. 11] represents the chemical equation.

[0199] Following the experimental procedure described above, in a 500 ml round bottom flask equipped with a magnetic stirrer and a reflux condenser, 20 g of a purple bra containing PET strand / yarn seams, spandex, rubber, metal parts, polypropylene in one piece is added followed by 200 ml of a solvent mixture. Then, 40 ml of HCl (37%) is added to the reaction mixture followed by the catalyst (4 wt% ZnCl2). The flask is placed in a sand bath heating to 100 °C. The reaction medium is stirred for 72 h at 600 rpm. The PET strand, spandex, rubber, metal parts, polypropylene were recovered intact and the conversion of PA6,6 to monomers was determined to be 100%. The conclusion of the reaction and precipitation Following monomer extractions resulted in the recovery of 10.2 g of pure e-aminocaproic acid derivatives.

[0200] By carrying out the process of the invention, the nature of the final product obtained by depolymerization could change. More particularly, the nature of the final product depends directly on the nature of the starting material used in the process of the invention. Furthermore, the final product can take various forms or aspects depending on the solvent, Brpnsted-Lowry acid and catalyst selected, as well as depending on the reaction time (reaction duration).

[0201] In the context of the present invention, selectivity relates to the nature of the products formed as well as the nature of the bonds cleaved.

[0202] The invention described above provides a method for depolymerizing polyamide in blended (or assembled) materials by selectively depolymerizing said polyamide. The selective depolymerization is accomplished by selectively cleaving nitrogen-carbonyl bonds of amide functions (-CO-N-) in the presence of different copolymers such as polyurethanes, cotton, wool, polyesters. According to a preferred embodiment of the invention, one step consists of bringing the assembled polyamide polymeric material into contact with a Brpnsted-Lowry acid and a Lewis acid catalyst in a solvent (i.e., an environmentally acceptable solvent). The reaction of the invention only requires a temperature of less than or equal to 110°C. The conditions for implementing the invention do not require any specific apparatus for managing pressure.Furthermore, the conversion rate of the polymer of the present invention into the corresponding monomers, and optionally into oligomers, is very high (> 90%). The depolymerization of polyamide at such a low temperature, i.e., less than or equal to 110 °C, is a pioneering achievement in the field of the invention. The moderate processing conditions appear to be related to the combined use of a Bronsted acid, a Lewis acid catalyst and a well-defined solvent system. The present invention describes for the first time depolymerization reactions of polyamide-based materials (textiles, plastics, etc.) at a temperature below 110 °C, without pressure and in green, biologically derived and non-harmful solvents.The recovery of a synthetic (elastane) and natural (cotton) polymer (copolymer or assembled) in its original form (knitted for example) from an assembled material containing polyamide through a depolymerization reaction of the polyamide of textiles and plastics has never been reported. The present invention has described for the first time the recovery of elastane in its original form from the depolymerization reaction of polyamide-based materials assembled with elastane, polyurethane, cotton, wool, a cellulosic material. More generally, the combination of Brpnsted-Lowry acid and . Lewis acid has never been reported for the depolymerization reaction of polyamide materials. In other words, the invention describes the first use of a combination of Brpnsted-Lowry acid and Lewis acid catalysts for the selective depolymerization of polyamide-based materials. Furthermore, the use of a combination of bio-based and non-harmful green solvents such as ethanol, anisole, MeTHF, acetone, ethyl acetate and water for the depolymerization of polyamide-based materials at low temperature has never been reported to date. The invention described the first use of a green solvent system that allows the depolymerization reaction of polyamide to proceed at low temperature.

[0203] With respect to a very preferable embodiment of the invention, the polymeric material is made of at least a first polymer and a second polymer. It is an assembled polymeric material. It is in solid form, such as a textile (e.g., underwear). In this embodiment, the invention can be defined as a:

[0204] A method of depolymerizing a polymeric material made of at least a first polymer and a second polymer, said method comprising the steps of:

[0205] a. contacting, in a solvent, said polymeric material with a Brpnsted-Lowry acid in the presence of a Lewis acid catalyst, in order to selectively depolymerize said first polymer within the polymeric material, thereby obtaining monomers and optionally oligomers, of the first depolymerized polymer originating from the polymeric material; and

[0206] b. collecting the polymeric material, wherein said polymeric material is reduced by at least 90%, preferably 100% of the original content of said first polymer in the polymeric material and wherein said first polymer is polyamide.

[0207] The monomers, and optionally the oligomers, obtained by step a. above are derived from the polyamide contained in the assembled polymeric material. The monomers, and optionally the oligomers, can be recovered in the liquid phase of the reaction medium.

[0208] The final material (i.e., the polymeric material after step a.) generally consists of at least 90% of the second polymer. The polymeric material can be recovered as a solid phase from the reaction medium. The polymeric material is freed or devoid of polyamide after step a. above of the depolymerization process.

[0209] Of course, the present invention can also be applied to materials which are composed of a non-polymeric material, such as a metal, and a polymeric material such as polyamide. For example, metals which are coated with polyamide can undergo the process of the invention and thus it is possible to recover on one side the degraded polyamide (monomers and optionally oligomers), and on the other side the intact metal which has been stripped of its polyamide coating. Another example would be metals which are coated with a polymeric material composed of an assembly of polyamide and at least one other polymer (such as elastane or other). If applied to the method of the invention, it would be possible to recover the stripped metal, the degraded polyamide (monomers and optionally oligomers), and another intact polymer (such as elastane or other).

Claims

Claims

1. A process for depolymerizing polyamide from a polymeric material comprising the step of: i. contacting, in a solvent, the polymeric material with a Brpnsted-Lowry acid in the presence of a Lewis acid catalyst, thereby producing a medium having a liquid phase comprising monomers derived from said polyamide.

2. A method according to claim 1, wherein the polymeric material is made of polyamide and at least one second polymer, and wherein contacting said polymeric material in step i. induces selective depolymerization of the polyamide within the polymeric material, which produces said medium which further comprises a solid phase of said second polymer.

3. Method according to claim 2, in which the solid phase of the second polymer consists of at least 90%, preferably 100% of said second polymer.

4. Method according to one of the preceding claims, in which the polymeric material after step i. is reduced by at least 90%, preferably by 100% of said polyamide.

5. A method according to any preceding claim, wherein said medium further comprises oligomers derived from said polyamide, and wherein the ratio of said monomers to said oligomers ranges from 99:1 to 70:

30.

6. A method according to any preceding claim, further comprising the step of: ii. extracting the medium in order to isolate said monomers, and optionally said oligomers, and subsequently evaporating said solvent in order to recover the monomers, and optionally the oligomers.

7. A method according to any one of claims 2 to 6, further comprising the step of: iii. filtering the solid phase from said medium, and subsequently washing and drying said solid phase to recover the second polymer.

8. A method according to one of the preceding claims, wherein said second polymer is selected from the group consisting of a polyurethane copolymer, a cotton copolymer, a

9.

10.

11.

12.

13.

14. copolymer of wool, a polyester copolymer, a silicon copolymer, elastane and a cellulosic material. Method according to one of the preceding claims, in which step i. is carried out at a temperature less than or equal to 110°C, preferably less than or equal to 100°C, less than or equal to 90°C, or less than or equal to 80°C. Method according to preceding claims 2 to 9, in which the second polymer is elastane. The method of claim 10, wherein said elastane is recovered as a fiber or in a knitted form. Method according to one of the preceding claims, in which the pressure in step i is at atmospheric pressure. The method of claim 1, wherein the polymeric material is polyamide. A compound generated by the method of any preceding claim, wherein said compound is selected from the group consisting of a monomer, monomer derivatives, an oligomer, a polymer, elastane, PET cotton, an e-caprolactam derivative, or an HMD A derivative.