A method for separating polyamide from a waste stream primarily composed of a mixture of polymeric matter

Abstract

This document summarizes the claims for selective depolymerization of polyamides, either pure or in mixtures, for instance textiles, blends, composites, multilayers or complex mixed polymers comprising but not limited to polyamides, polyesters, polycarbonate, cotton, polyurethanes, polyolefins and spandex. The present methods are a solution for the chemical recycling of polyamides either via dissolution (extractive approach) or depolymerization (deconstructive approach), in a way that is no seen in literature. The ways to perform this can be summarized in two approaches: a completely alcoholic medium: ALCHYD+ (Alcoholic acidic hydrolysis) and WALCHYD+ (Aqueous-Alcoholic acidic hydrolysis). With ALCHYD+, selective dissolution and / or depolymerization of polyamides can be performed, whilst with WALCHYD+, one-pot selective depolymerization of polyamides can be performed.

Description

[0001] A METHOD FOR SEPARATING POLYAMIDE FROM A WASTE STREAM PRIMARILY COMPOSED OF A MIXTURE OF POLYMERIC MATTER

[0002] Background and Summary

[0003] BACKGROUND OF THE INVENTION

[0004] A. Field of the Invention

[0005] The present invention relates generally to a method of depolymerization of polyamides and, more particularly to a system and method for efficient targeted depolymerization of polyamides in a mixed waste stream or it concerns selective solubilization of polyamides out of a mixed waste stream at room temperature and depolymerization of polyamides at mild temperatures. The method allows highly selective solubilization of polyamides out of a mixed waste stream at room temperature in and anhydrous alcohol acidified with inorganic acid for separation from other polymeric materials (WALCHYD+). And also it concerns a method of depolymerization of polyamides at mild temperatures. This method is called, standing for alcoholic acidic depolymerization and WALCHYD+ standing for alcoholic acidic depolymerization in presence of water.

[0006] In particular the present invention relates to a method for obtaining a refined polyamide polymer from a heterogeneous mixture of polymer material with polyamide polymer, the method comprising the steps, in order: a) submersing or suspending the heterogeneous mixture in a sealed vessel at ambient temperature or in the absence of heating and during a range of time from 1 to 24 h in an anhydrous alcohol acidified with inorganic acid to dissolve the polyamide polymer and b) thereof separation of the alcoholic polyamide extract from solids and c) precipitating the dissolved polyamide polymer using a non-solvent to obtain a polyamide polymer precipitate and d) separating the polyamide polymer precipitate from the supernatant And a specific aspect the present invention relates to a method for obtaining depolymerized polyamide from feedstock of a heterogeneous mixture of polymers, the method comprising the steps, in order: a) submersing or suspending the heterogeneous material mixture in an aqueous-alcoholic liquid that is acidified with an inorganic acid and heating this mixture at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C during a range of time from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, while excluding ambient gases or preventing ingress of atmospheric gases, to depolymerize polyamide and b) separating the depolymerized polyamide extract from the remaining solids.

[0007] An integration of these surprising finding is a method, whereby a) i) the heterogeneous mixture of polymers is firstly submersed or suspended in an anhydrous alcohol acidified with inorganic acid at ambient temperature or in the absence of heating and while excluding ambient gases or preventing ingress of atmospheric gases during a range of time from 1 to 24 h to dissolve the polyamide polymer and ii) consequently forming this heterogeneous mixture of polymers in acidified alcoholic liquid into a heterogeneous mixture of polymers in inorganic acid acidified aqueous-alcoholic liquid and heating this mixture at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C during a range of time from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, while excluding ambient gases or preventing ingress of atmospheric gases, to depolymerize polyamide and b) separating the depolymerized polyamide extract from the remaining solids.

[0008] Furthermore the present invention relates generally to a method for dissolution and depolymerization of polyamides and, more particularly to a method for selective and fast depolymerization of polyamides, for instance depolymerization within a time frame from 20 and up to 60 min, of polymer structures such as but not limited to Polyamide 6 (PA6) and polyamide 6,6 (PA66) with micrometric (for instance 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter ) or millimetric dimension (for instance 1 to 10 mm Feret Diameter (FD) or 1 to 10 mm Equivalent Circular Diameter).

[0009] The method of present invention is also particularly suitable for selectively dissolution of polyamides out of mixtures of different natural and synthetic polymer structures such as, but not limited to polyesters, polyolefins, polyurethanes, polyether-polyurea copolymer (spandex or elastane), and cotton of any dimension, within a time frame from 1 and up to 360 min.

[0010] B. Description of the Related Art

[0011] Nylon solubility has been reported to occur at room temperature in HFIP (1,1,1,3,3,3-hexafluoroisopropanol) [United States Patent 3691092], Methanol:CaCl2 3:1 at 80 °C [Nakajima & Tanaami (Polymer Journal, 1973) for nylon-6], formic acid at room temperature [RSC Adv., 2016, 6, 6823-6831 | 6823] and alcoholic solutions (methanol, ethanol and isopropanol) of metal halides (LiCI, MgCl2, ZnCl2 and CaCl2) at room temperature, nevertheless, none of the solubilizing media has been reported to efficiently depolymerize nylon at milder conditions than reported in literature.

[0012] All of the reported depolymerization methods for nylons are related to single streams of one type of nylon (pure polyamide) and do not focus on the importance of mixed streams. This is of extreme importance in textiles, where polyamides are inseparably mixed with other textiles, namely polyesters, polyether-polyurea copolymer (spandex or elastane) and cotton.

[0013] Advantageous effects of the invention is that its method to depolymerize nylons is more energy efficient than similar approaches and uses readily available substances already applied at industrial scale (common alcohols, inorganic acids and alkalis). For instance with present invention an optimized condition for depolymerisation of nylon

[0014] 6 fibers concerns only depolymerisation at 120 °C for a period of only 30 min.

[0015] Yet another advantageous effect of the present invention is that the method allows highly selective, for instance, solubilization of 99 % of polyamides out of a mixed waste stream at room temperature and depolymerization of polyamides at mild temperatures (<150°C).

[0016] Moreover, waste recycling is a large, global market with billions of tonnes of waste processed annually. Despite the increase in recycling activity year on year, there are still many complex waste streams which are difficult or impossible to recycle in an environmentally friendly manner.

[0017] There is therefore a need for an improved process for recycling complex waste streams with minimal environmental impact and in particular there is a need in the art for a method that serves to selectively dissolve nylons out of a mixture of polymers and or textiles, for instance a mixture composed of but not limited to polyamides, polyesters, polycarbonate, polyolefins, polyurethanes, polyether-polyurea copolymer (spandex or elastane) and cotton, and subsequently depolymerize the said nylons at mild temperatures and short times without adding any additional solvent other than water.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention solves the problems of the related art by providing a feasible, fast and low energy demanding way of 1) selectively dissolving nylons from a mixed polymer / textile waste 2) depolymerize nylons in less than 3 h at temperatures ranging from 110 to 140 °C, preferably at 120 °C in 1 h.

[0020] In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to chemical recycling of polyamides / nylons. In one aspect of the invention, ALCHYD+ selectively dissolve polyamides out of a mixture of polymers and or textiles, for instance a mixture composed of but not limited to polyamides, polyesters, polycarbonate, polyolefins, polyurethanes, polyether-polyurea copolymer (spandex or elastane) and cotton.

[0021] Another aspect of the invention is the depolymerization of polyamide / nylon into monomers, dimers and trimers, when the aforementioned polymer solution is heated up to temperatures from 120 to 140 °C in presence of water in a time frame from 1 to 3 h.

[0022] In still another aspect of the invention, selective depolymerization of polyamides can be achieved when a mixed stream of polymer containing polyamides, polyolefins, polycarbonates and polyesters treated with WALCHYD+ temperatures from 120 to 140 °C in presence of water in a time frame from 1 to 3 h, yielding monomers, dimers and trimers, while leaving the other polymers untouched.

[0023] According to one embodiment the invention concern a method of obtaining a refined polyamide polymer from a heterogeneous mixture of polymer material comprising polyamide polymer, the method comprising in the following order the steps: a) submersing or suspending the heterogeneous mixture in a sealed vessel at ambient temperature or in the absence of heating and during a range of time from 1 to 24 h in an anhydrous alcohol acidified with inorganic acid to dissolve the polyamide polymer and b) separating the dissolved polyamide polymer from solids and c) precipitating the dissolved polyamide polymer using a non-solvent to obtain a polyamide polymer precipitate, and d) separating the polyamide polymer precipitate from the supernatant.

[0024] This embodiment of the invention advantageously comprises the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing. In another aspect, the method of present invention provides, that in step c) the non-solvent is added to alcoholic polyamide extract to achieve a ratio from 2 to 50 % non- solvent by volume of alcoholic polyamide extract and preferably 15 to 25% non-solvent by volume of alcoholic polyamide extract.

[0025] In another aspect, the method of present invention provides, that the non-solvent is water.

[0026] In another aspect, the method of present invention provides, that the sealed vessel is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases.

[0027] In another aspect, the method of present invention provides, that the sealed vessel is a pressure-resistant vessel sealed to maintain internal pressure.

[0028] In another aspect, the method of present invention provides, that the alcoholic polyamide extract is separated from the solids by centrifugation or filtration.

[0029] In another aspect, the method of present invention provides, that the polyamide polymer precipitate is separated from the supernatant by centrifugation.

[0030] In another aspect, the method of present invention provides, that the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N- butyl alcohol and N-propyl alcohol.

[0031] In another aspect, the method of present invention provides, that the anhydrous alcohol that is acidified by an inorganic acid containing methanol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight.

[0032] In another aspect, the method of present invention provides, that the anhydrous alcohol that is acidified containing inorganic acid is in an amount of 1% to 10% by weight and preferably in an amount 2,5% to 7,5% by weight.

[0033] In another aspect, the method of present invention provides, that the anhydrous alcohol is acidified by sulfuric acid. In another aspect, the method of present invention provides, that said ambient temperature is a temperature from 20°C to 25°C.

[0034] In another aspect, the method of present invention provides, that at least the polyamide material is in the form of particulates, pellets or fibers.

[0035] In another aspect, the method of present invention provides, that in step a) said polyamide material are at millimetre dimension of 1 to 10 mm Feret Diameter (FD) or 1 to 10 mm Equivalent Circular Diameter.

[0036] In another aspect, the method of present invention provides, that said polyamide material are of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

[0037] In another aspect, the method of present invention provides, that the heterogeneous mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

[0038] In another aspect, the method of present invention provides, that the heterogeneous mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, Polyvinyl chloride (PVC), polyurethanes, polyetherpolyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate (PBT) and Polyethylene terephthalate (PET).

[0039] In another aspect, the method of present invention provides, that the polyamide material is of the group consisting of polyamide 6 (Nylon 6), polyamide 11 (Nylon 11), polyamide 12 (Nylon 12), polyamide 66 (Nylon 66), polyamide 610 (Nylon 610), polyamide 66 / 610 (Nylon 66 / 610), polyamide 6 / 12 (Nylon 6 / 12), polyamide 666 (Nylon 666 or 6 / 66), polyamide 6 / 69 (Nylon 6 / 69), Nylon 1010, Nylon 1012, polyarylamide, polyaramides (Kevlar®), polyphthalamide and polyamidoamine.

[0040] In another aspect, the method of present invention provides, that the polyamide in the feedstock is cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide-containing materials or textiles. In another aspect, the method of present invention provides, that the polyamide and other materials in the feedstock are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide-containing materials or textiles.

[0041] In another aspect, the method of present invention provides, further drying the polyamide polymer precipitate or optionally further comprising washing and drying the polyamide polymer precipitate.

[0042] The present invention provides method of obtaining a refined polyamide polymer from a heterogeneous mixture of polymer material comprising polyamide polymer, the method comprising in the following order the steps: a) submersing or suspending the heterogeneous mixture in a sealed vessel at ambient temperature or in the absence of heating and during a range of time from 1 to 24 h in an anhydrous alcohol acidified with inorganic acid to dissolve the polyamide polymer and b) separating the dissolved polyamide polymer from solids and c) precipitating the dissolved polyamide polymer using a non-solvent to obtain a polyamide polymer precipitate, and d) separating the polyamide polymer precipitate from the supernatant.

[0043] In an aspect, the method of present invention provides, that the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing.

[0044] In another aspect, the method of present invention provides, that in step c) the non-solvent is added to alcoholic polyamide extract to achieve a ratio from 2 to 50 % non- solvent by volume of alcoholic polyamide extract and preferably 15 to 25% non-solvent by volume of alcoholic polyamide extract.

[0045] In yet another aspect, the method of present invention provides, that the nonsolvent is water.

[0046] In yet another aspect, the method of present invention provides, that the sealed vessel is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases. In yet another aspect, the method of present invention provides, that the sealed vessel is a pressure-resistant vessel sealed to maintain internal pressure.

[0047] In yet another aspect, the method of present invention provides, that the alcoholic polyamide extract is separated from the solids by centrifugation or filtration.

[0048] In yet another aspect, the method of present invention provides, that the polyamide polymer precipitate is separated from the supernatant by centrifugation.

[0049] In yet another aspect, the method of present invention provides, that the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N- butyl alcohol and N-propyl alcohol.

[0050] In yet another aspect, the method of present invention provides, that the anhydrous alcohol that is acidified by an inorganic acid containing methanol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight.

[0051] In yet another aspect, the method of present invention provides, that the anhydrous alcohol that is acidified containing inorganic acid is in an amount of 1% to 10% by weight and preferably in an amount 2,5% to 7,5% by weight.

[0052] In yet another aspect, the method of present invention provides, that the anhydrous alcohol is acidified by sulfuric acid.

[0053] In yet another aspect, the method of present invention provides, that said ambient temperature is a temperature from 20°C to 25°C.

[0054] In yet another aspect, the method of present invention provides, that at least the polyamide material is in the form of particulates, pellets or fibers.

[0055] In yet another aspect, the method of present invention provides, that in step a) said polyamide material are at millimetre dimension of 1 to 10 mm Feret Diameter (FD) or 1 to 10 mm Equivalent Circular Diameter. In yet another aspect, the method of present invention provides, that said polyamide material are of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

[0056] In yet another aspect, the method of present invention provides, that the heterogeneous mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

[0057] In yet another aspect, the method of present invention provides, that the heterogeneous mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, Polyvinyl chloride (PVC), polyurethanes, polyetherpolyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate (PBT) and Polyethylene terephthalate (PET).

[0058] In yet another aspect, the method of present invention provides, that polyamide material is of the group consisting of polyamide 6 (Nylon 6), polyamide 11 (Nylon 11), polyamide 12 (Nylon 12), polyamide 66 (Nylon 66), polyamide 610 (Nylon 610), polyamide 66 / 610 (Nylon 66 / 610), polyamide 6 / 12 (Nylon 6 / 12), polyamide 666 (Nylon 666 or 6 / 66), polyamide 6 / 69 (Nylon 6 / 69), Nylon 1010, Nylon 1012, polyarylamide, polyaramides (Kevlar®), polyphthalamide and polyamidoamine.

[0059] In yet another aspect, the method of present invention provides, that the polyamide in the feedstock is cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide-containing materials or textiles.

[0060] In yet another aspect, the method of present invention provides, that the polyamide and other materials in the feedstock are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide-containing materials or textiles.

[0061] In yet another aspect, the method of present invention provides, drying the polyamide polymer precipitate or optionally further comprising washing and drying the polyamide polymer precipitate.

[0062] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

[0063] Some embodiments of the invention are set forth in claim format directly below:

[0064] 1. A method of obtaining depolymerized polyamide from a feedstock of a heterogeneous mixture of polymers, the method comprising the steps of, in the following order: a) submersing or suspending the heterogeneous mixture of polymers in an aqueous-alcoholic liquid that is acidified with an inorganic acid, and heating this liquid and the mixture of polymers therein, at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C, during a time period from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, to depolymerize polyamide while excluding ambient gases or preventing ingress of atmospheric gases, and b) separating the depolymerized polyamide from the remaining solids

[0065] 2. The method according to statement 1, whereby step a) comprises i) firstly submersing or suspending the heterogeneous mixture of polymers is in an anhydrous alcohol acidified with inorganic acid at ambient temperature or in the absence of heating and while excluding ambient gases or preventing ingress of atmospheric gases during a timeperiod from 1 to 24 h to dissolve the polyamide polymer and ii) consequently forming this heterogeneous mixture of polymers in acidified alcoholic liquid into a heterogeneous mixture of polymers in inorganic acid acidified aqueous-alcoholic liquid and heating the liquid and polymers at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C during a range of time from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, while excluding ambient gases or preventing ingress of atmospheric gases, to depolymerize polyamide.

[0066] 3. The method according to any one of the statements 1 to 2, whereby the remaining solids are non-polyamide polymers.

[0067] 4. The method according to any one of the statements 1 to 2, whereby the remaining solids are non-polyamide polymers and other non-polymer contaminants.

[0068] 5. The method according to any one of the statements 1 to 4, whereby the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing.

[0069] 6. The method according to any one of the statements 1 to 5, whereby step a) is carried out in a sealed vessel that is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases.

[0070] 7. The method according to any one of the statements 1 to 6, whereby step a) is carried out in a sealed vessel on in a pressure-resistant vessel sealed to maintain internal pressure.

[0071] 8. The method according to any one of the statements 1 to 7, whereby the polyamide extract is separated from the solids by centrifugation or filtration. The method according to any one of the statements 1 to 9, whereby the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N-butyl alcohol and N-propyl alcohol. The method according to any one of the statements 2 to 10, whereby the anhydrous alcohol that is acidified by an inorganic acid containing alcohol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight. The method according to any one of the statements 2 to 10, whereby the anhydrous alcohol is acidified by an inorganic acid in an amount of 1 % - to 10 % by volume of the liquid and preferably in an amount 2,5 % to 7,5 % by volume of the liquid and most preferably in an amount 4 % to 5 % by volume of the liquid. The method according to any one of the statements 1 to 11, whereby the aqueous-alcoholic mixture the volumetric percentage of acid with respect to alcohol is 0,5 to 10% of the liquid, preferably 0,8 to 8% of the liquid and yet more preferably 1 to 5% of the liquid and yet more preferably in an amount 2,5% to 7,5% of the liquid. The method according to any one of the statements 1 to 12, whereby the aqueous-alcoholic liquid contains an amount of water in a range of 2% to 50% by weight of the liquid, preferably in a range of 10 to 30% by weight of the total liquid. 14. The method according to any one of the statements 1 to 13, whereby the anhydrous alcohol or the aqueous-alcoholic mixture is acidified by sulfuric acid.

[0072] 15. The method according to any one of the statements 1 to 14, whereby the ambient temperature is a temperature from 20°C to 25°C.

[0073] 16. The method according to any one of the statements 1 to 15, whereby at least the polyamide in the feedstock mixture is in the form of particulates, pellets or fibers.

[0074] 17. The method according to any one of the statements 1 to 16, whereby in step a) said polyamide in the feedstock mixture are at millimetre dimension of 1 to 10 mm feret diameter or 1 to 10 mm equivalent circular diameter.

[0075] 18. The method according to any one of the statements 1 to 15, whereby said polyamide in the feedstock mixture is of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

[0076] 19. The method according to any one of the statements 1 to 18, whereby the feedstock mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

[0077] 20. The method according to any one of the statements 1 to 19, whereby the feedstock mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, poly vinyl chloride, polyurethanes, polyetherpolyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate and polyethylene terephthalate. The method according to any one of the statements 1 to 20, whereby the polyamide in the feedstock mixture is of the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 66 / 610, polyamide 6 / 12, polyamide 666, polyamide 6 / 69, nylon 1010, nylon 1012, polyarylamide, polyaramides polyphthalamide and polyamidoamine. The method according to any one of the statements 1 to 21, whereby the polyamide in the feedstock mixture are cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide- containing materials or textiles. The method according to any one of the statements 1 to 22, whereby the polyamide and other materials in the feedstock mixture are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide-containing materials or textiles. The method according to any one of the statements 1 to 23, whereby the depolymerized polyamide is in the form of monomers, dimers, trimers and dissolved oligomers. 25. The method according to statement 25 , further concentrating the refined monomers, dimers, and trimers from depolymerized polyamide by vacuum concentrating.

[0078] 26. The method according to any one of the statements 1 to 25, whereby the depolymerized polyamide is further fractioned by cooling the concentrated aqueous / alcohol solution to 40-80% (vol) alcohol slowly to a temperature between 4°C to -20°C for crystallization of trimer, dimers and / or monomer components and subsequently separating the trimer, dimers and / or monomer components by filtration.

[0079] 27. The method according to statement 26, further refining monomers, dimers, and trimers by solid-phase extraction or resin adsorption, for instance with cation-exchange resins to retain amines and / or anion-exchange resins to retain polyamine derived monomers acids and is eluted with dilute HCI or NaOH, or salt gradients to fractionate components based on charge or polarity.

[0080] Yet some embodiments of the invention are set forth in claim format directly below:

[0081] 1. A method of obtaining a refined polyamide polymer from a heterogeneous mixture of polymer material comprising polyamide polymer, the method comprising in the following order the steps: e) submersing or suspending the heterogeneous mixture in a sealed vessel at ambient temperature or in the absence of heating and during a range of time from 1 to 24 h in an anhydrous alcohol acidified with inorganic acid to dissolve the polyamide polymer and f) separating the dissolved polyamide polymer from solids and g) precipitating the dissolved polyamide polymer using a non-solvent to obtain a polyamide polymer precipitate, and h) separating the polyamide polymer precipitate from the supernatant. 2. The method according to statement 1, whereby the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing.

[0082] 3. The method according to any one of the statements 1 to 2, whereby in step c) the non-solvent is added to alcoholic polyamide extract to achieve a ratio from 2 to 50 % non- solvent by volume of alcoholic polyamide extract and preferably 15 to 25% non-solvent by volume of alcoholic polyamide extract.

[0083] 4. The method according to any one of the statements 1 to 3, whereby the non-solvent is water.

[0084] 5. The method according to any one of the statements 1 to 4, whereby the sealed vessel is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases.

[0085] 6. The method according to any one of the statements 1 to 5, whereby the sealed vessel is a pressure-resistant vessel sealed to maintain internal pressure.

[0086] 7. The method according to any one of the statements 1 to 6, whereby the alcoholic polyamide extract is separated from the solids by centrifugation or filtration.

[0087] 8. The method according to any one of the statements 1 to 7, whereby the polyamide polymer precipitate is separated from the supernatant by centrifugation.

[0088] 9. The method according to any one of the statements 1 to 8, whereby the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N-butyl alcohol and N-propyl alcohol.

[0089] 10. The method according to any one of the statements 1 to 9, whereby the anhydrous alcohol that is acidified by an inorganic acid containing methanol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight.

[0090] 11. The method according to any one of the statements 1 to 9, whereby the anhydrous alcohol that is acidified containing inorganic acid is in an amount of 1% to 10% by weight and preferably in an amount 2,5% to 7,5% by weight.

[0091] 12. The method according to any one of the statements 1 to 11, whereby the anhydrous alcohol is acidified by sulfuric acid.

[0092] 13. The method according to any one of the statements 1 to 12, whereby said ambient temperature is a temperature from 20°C to 25°C.

[0093] 14. The method according to any one of the statements 1 to 13, whereby at least the polyamide material is in the form of particulates, pellets or fibers.

[0094] 15. The method according to any one of the statements 1 to 14, whereby in step a) said polyamide material are at millimetre dimension of 1 to 10 mm Feret Diameter (FD) or 1 to 10 mm Equivalent Circular Diameter.

[0095] 16. The method according to any one of the statements 1 to 15, whereby said polyamide material are of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

[0096] 17. The method according to any one of the statements 1 to 16, whereby the heterogeneous mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

[0097] 18. The method according to any one of the statements 1 to 17, whereby the heterogeneous mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, Polyvinyl chloride (PVC), polyurethanes, polyether-polyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate (PBT) and Polyethylene terephthalate (PET).

[0098] 19. The method according to any one of the statements 1 to 18, whereby the polyamide material is of the group consisting of polyamide 6 (Nylon 6), polyamide 11 (Nylon 11), polyamide 12 (Nylon 12), polyamide 66 (Nylon 66), polyamide 610 (Nylon 610), polyamide 66 / 610 (Nylon 66 / 610), polyamide 6 / 12 (Nylon 6 / 12), polyamide 666 (Nylon 666 or 6 / 66), polyamide 6 / 69 (Nylon 6 / 69), Nylon 1010, Nylon 1012, polyarylamide, polyaramides (Kevlar®), polyphthalamide and polyamidoamine.

[0099] 20. The method according to any one of the statements 1 to 19, whereby the polyamide in the feedstock is cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide-containing materials or textiles.

[0100] 21. The method according to any one of the statements 1 to 20, whereby the polyamide and other materials in the feedstock are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide- containing materials or textiles.

[0101] 22. The method according to any one of the statements 1 to 23, further comprising drying the polyamide polymer precipitate or optionally further comprising washing and drying the polyamide polymer precipitate.

[0102] Detailed Description

[0103] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0104] Definitions

[0105] Herein, "room temperature" means as generally considered to be around 20 to 25 degrees Celsius (68 to 77 degrees Fahrenheit). Herein, "continuous" means herein herein concerning the stirring process that there is no interruption in the process or at least in 50%, preferably 80% and most preferably more than 90% of the process time.

[0106] Herein "polyamide" means all the polymers belonging to such a chemical category such as: polyamide 6 (Nylon 6), polyamide 11 (Nylon 11), polyamide 12 (Nylon 12), polyamide 66 (Nylon 66), polyamide 610 (Nylon 610), polyamide 66 / 610 (Nylon 66 / 610), polyamide 6 / 12 (Nylon 6 / 12), polyamide 666 (Nylon 666 or 6 / 66), polyamide 6 / 69 (Nylon 6 / 69), Nylon 1010, Nylon 1012, polyarylamide, polyaramides (Kevlar®), polyphthalamide, polyamidoamines, etc. Possible products used as starting material are containers for packaging, food trays, films, belts, tubing, ropes, nets, pads, pipes, textiles of all type such as shoes, clothing, garments, Jackets, etc.

[0107] The term 'nylon' as used herein refers to synthetic polyamides, including but not limited to nylon-6, nylon-6, 6, and copolymers thereof

[0108] Herein, Feret Diameter (FD) means the maximum diameter of a circle inscribed within the particle's perimeter. It is measured along a perpendicular line passing through the particle's centroid.

[0109] Herein, Equivalent Circular Diameter means the diameter of a circle that has the same area as the particle cross section.

[0110] Polyamide 6 (PA6) and polyamide 6,6 (PA66) are both synthetic polymers belonging to the family of polyamides, also known as nylons. Polyamide 6 is synthesized from caprolactam, a monomer with six carbon atoms. Polyamide 6,6 is synthesized from hexamethylenediamine and adipic acid, both of which have six carbon atoms. It is a more crystalline polymer than PA6, with a melting point of around 265°C (510°F). Herein, fully alcoholic medium (ALCHYD+) means anhydrous alcohol acidified with inorganic acid. Such ALCHYD+ mediums may include, as alcohol, methyl alcohol (MeOH), ethanol (EtOH), isopropyl alcohol (IPA) and / or n-butyl alcohol (n-BuOH) and, as inorganic acid, and acid of the group consisting of hydrochloric acid (HCI), sulfuric acid (H2SO4), phosphoric acid (H3PO4), nitric aAcid (HNO3), hydrofluoric acid (HF) and boric acid (H3BO3).

[0111] These are just a few examples, and there are many other inorganic acids with varying properties and applications. Inorganic acids play a crucial role in various industries and scientific research. It's important to handle them with care due to their corrosive nature.

[0112] Herein, aqueous-alcoholic mixtures (WALCHYD+) means water containing alcoholic acidic Hydrolysis depolymerization solution-mediums that contain both water and alcohols. Such WALCHYD+ mediums may include, as alcohol, methyl alcohol (MeOH), ethanol (EtOH), isopropyl alcohol (IPA or isopropanol) and / or n-butyl alcohol (n- BuOH) and, as inorganic acid, and acid of the group consisting of hydrochloric acid (HCI), sulfuric acid (H2SO4), phosphoric acid (H3PO4), nitric aAcid (HNO3), hydrofluoric acid (HF) and boric acid (H3BO3).

[0113] Herein, spandex means a polyether-polyurea copolymer. The polyuria can be derived from the reaction of a diol and a diisocyanate. Two classes of spandex are defined by the doils one of diols is the oligomer produced from tetrahydrofuran (i.e. polytetrahydrofuran) and another class of diols, the so-called ester diols, are oligomers derived from condensation of adipic acid and glycol. The polyether-polyurea copolymer can be in the form of fibers, by the skilled person recognized by its exceptional elasticity. There are many brands for such product such as spandex include Lycra (made by The Lycra Company, previously a division of DuPont Textiles and Interiors), Elaspan (The Lycra Company), Acepora (Taekwang Group), Creora (Hyosung), INVIYA (Indorama Corporation), ROICA and Dorlastan (Asahi Kasei), Linel (Fillattice), and ESPA (Toyobo).

[0114] To "heat" or "heating" in the context of the invention means to the transfer of thermal energy for instance into the reactor or the reaction medium for instance to obtain the desired temperature range. Such heating can be direct heating. For instance by electric heaters. Electric heating elements (such as resistance heaters) can be placed inside or around the reactor to provide direct heat. Or such heating can be indirect heating as is done with jacketed reactors. For instance when the reactor is surrounded by a jacket through which a heating medium (like steam, hot water, or oil) circulates to transfer heat indirectly or when coils inside the reactor carry a heating medium, providing an internal heat source or when heat exchangers external to the reactor are used to heat the reactant stream before it enters the reactor. Heating can be carried out by circulating heating medium such as steam or thermal oil. Of the electrical methods induction heating of the reactor walls or contents directly through electromagnetic induction, microwave heating with microwaves directly to heat the reactants if they are microwave absorbent, infrared heating providing radiant heat directly to the reactor surface or contents. There are also combined methods, the so called hybrid systems that are a combination of the above methods. In case of nonheating a method, process or the reaction is generally carried at room temperature.

[0115] Herein, "Convection heating" refers to the process of transferring thermal energy to the reaction mixture through the movement of a heated fluid surrounding the reaction vessel or by coils or tubes are placed inside the reactor through which the heating fluid is circulated. By forced convection heat transfer is enhanced by actively circulating the heating fluid using pumps or fans, which provides more uniform and faster heating.

[0116] Both d4Methanol and d2Sulfuric acid are isotopically labelled versions of common chemicals, where "d" refers to deuterium, a heavier isotope of hydrogen. In essence, both d4Methanol and d2Sulfuric acid are isotopically modified versions of their original counterparts, specifically designed for NMR spectroscopy. d4Methanol, also known as Methanol-d4 or CD3OD, concerns a regular methanol (CH3OH) which has three hydrogen atoms wherein all four hydrogens are replaced with deuterium (CD3OD). This is generally used for Nuclear Magnetic Resonance (NMR) spectroscopy. Because deuterium has a different magnetic spin than hydrogen, d4Methanol acts as a solvent that doesn't interfere with the NMR signals of the sample being studied. d2Sulfuric Acid, also known as Sulfuric Acid-d2, is a regular sulfuric acid (H2SO4), which has two acidic hydrogens, whereby hese two hydrogens are replaced with deuterium (D2SO4). Similar to d4Methanol, d2Sulfuric acid finds use in NMR spectroscopy. As the deuterium atoms don't contribute to the NMR signal of the target molecule, allowing for clearer analysis.

[0117] The following detailed description of the invention refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents thereof.

[0118] In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to the use of an alcoholic medium, for instance methanol or ethanol medium with an inorganic acid, for instance sulfuric acid, as selective depolymerization agent without any further addition of organic solvents, under microwave action (heating) or any other heating method, to achieve fast depolymerization at temperatures under 140 °C and low reaction times, for instance within 30 min, for almost 100%, for instance 98 - 99,9 %, depolymerization of polyamide structures of any suitable shape and morphology such as flakes, fibres, powder, sheet, pellet, spheres, pearls, dendrites, discs or any other three- dimensional shape with a micrometric or millimetric dimension, singly or in combination if these are millinized structures, microsized structures, structures having a thickness up to 5 mm or structures having a maximum dimension of not more than 10 mm.

[0119] In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is broadly drawn to the use of an alcoholic medium, for instance methanol or ethanol medium with an inorganic acid, for instance sulfuric acid, as selective solubilization medium at room temperature and low reaction times, for instance within 3 h, for instance 2 h, for almost 100%, for instance 98 - 99,9 %, solubilization of polyamide structures of any suitable shape and morphology such as flakes, fibres, powder, sheet, pellet, spheres, pearls, dendrites, discs or any other three-dimensional shape with a micrometric or millimetric dimension, singly or in combination if these are millinized structures, microsized structures, structures having a thickness up to 10 mm or structures having a maximum dimension of not more than 20 mm.

[0120] A medium used in an aspect of present invention is, ALCHYD+. The abbreviation ALCHYD+ stands for Alcoholic Acidic Hydrolysis depolymerization solution. Whenever ALCHYD+ is mentioned in this application, it refers specifically to an alcohol + an inorganic acid (e.g. methanol + sulfuric acid) and the percentage is the volumetric percentage of the inorganic acid (e.g. sulphuric acid) with respect to the alcohol (e.g. methanol) and for instance ALCHYD+5% stands for an alcoholic acidic hydrolysis depolymerization solution with 5% inorganic acid.

[0121] Whenever ALCHYD+ is mentioned in the understanding examples, it refers specifically to methanol + sulfuric acid and the percentage is the volumetric percentage of sulphuric acid with respect to the methanol. Other substances in the examples will be specifically mentioned to differentiate from the methanolic solution, however, they are also covered by this patent. With this invention, the problem of selective dissolution and depolymerization of nylons out of mixed streams of polymers is solved with fairly available reagents and mild temperatures compared to the state of the art in polyamides depolymerization. The following examples (the examples a, b, c, d, e, f, g, h, I, j, k, i) illustrate the depolymerization experiments performed and the results confirm selective depolymerization and solubilization of nylon out of a mixture.

[0122] EXAMPLES:

[0123] Example 1. A magnetic stir bar (2x6 mm), 0.5 g of Polyamide 6 pellets and 10 ml Methanol were poured in a high-pressure vial and tight sealed using a rubber septum embedded in an aluminium cap. Through the rubber septum, 0.5 ml of concentrated sulfuric acid were injected under stirring using a syringe while keeping the system closed (forming the solution we call ALCHYD+). The addition of acid caused a temporary increase of temperature and after complete transfer, the mixture was left under stirring at room temperature (around 20 °C). The size of pellets gradually diminished and after 2 h, a completely transparent solution was obtained. Polyamide 6 was fully dissolved at room temperature and was stored for 4 h at room temperature without stirring. The solution remained clear transparent and stable. The polymer was precipitated by addition of water (non-solvent), which caused the formation of a white powder that was filtered off and washed with water. The FTIR in FIG 01 (comparing starting material consisting of polyamide 6 pellets) corroborates that there is no significant structural changes). In FIG 02 the DSC of the precipitated Polyamide is showed and compared with the DSC of Polyamide6 pellets. Melting point of the melting events differ less than 0.5%, which demonstrates that there is not a significant change of structure, as Fig 1 indicated. In FIG 03 the SEC chromatograms of Polyamide 6 compared to the precipitated polymer shows that there is a slight molar mass loss after the procedure, however, it might be due to the long storage time. Optimization of dissolution time and temperature during dissolution is critical to avoid that molar mass loss.

[0124] Example 2. A magnetic stir bar (2x6 mm), 0.5 g of Polyamide 6 pellets, 10 ml Methanol and 5 ml water were poured in a high-pressure vial and tight sealed using a rubber septum embedded in an aluminium cap. Through the rubber septum, 0.5 ml of concentrated sulfuric acid were injected under stirring using a syringe while keeping the system closed (forming the solution we call WALCHYD+). The mixture was heated up to 140 °C for 20 min using Microwaves heating. After reaction period, a homogeneous transparent solution was obtained. The solution was neutralized and additional water added, which produced an aqueous transparent solution. The absence of precipitate demonstrated the depolymerization of Polyamide 6 into oligomers of small size. The reaction produces elevated pressures due to the in-situ formation of dimethylether, a byproduct that can be captured and used in an industrial process.

[0125] Example 3. A magnetic stir bar (2x6 mm), 0.5 g of Polyamide 6,6 pellets, 10 ml Methanol and 5 ml water were poured in a high-pressure vial and tight sealed using a rubber septum embedded in an aluminium cap. Through the rubber septum, 0.5 ml of concentrated sulfuric acid were injected under stirring using a syringe while keeping the system closed (forming the solution we call WALCHYD+). The mixture was heated up to 140 °C for 20 min using Microwaves heating. After reaction period, a homogeneous transparent solution was obtained. The solution was neutralized and additional water added, which produced an aqueous transparent solution, demonstrating thus the depolymerization of Polyamide 6,6. The reaction produces elevated pressures due to the in-situ formation of dimethylether, a byproduct that can be captured and used in an industrial process.

[0126] Example 4. Demonstration of Selective depolymerization: PET pellets were submitted to depolymerization under the same conditions related in b and c at 140 °C for 20 min. No significant difference was observed in the vial. The reaction mixture was conserved at room temperature for 4 weeks inside the vial to verify if there is significant reaction, as occurs with alcoholic alkali when in contact with PET. After the period at room temperature, no visible changes were observed, except for the deposition of a very small amount of solid on the surface of PET pellets. From the 0.5060 g of initially fed PET, 0.5080 were recovered, which could mean there is surface reaction (probably esterification) that could explain the presence of the solid on the surface, however, the amount of solid is not significant and it can be claimed that selective depolymerization of Polyamide is possible when in presence of PET pellets under the conditions here related.

[0127] Example 5. The percentage of sulfuric acid was varied to estimate the molar mass variation induced by it. For this purpose, approximately 0.5 g of Polyamide were loaded into high-pressure vials along with 10 ml methanol and a stir-bar, then 1, 2, 3 4 and 5%v / vH2SO4 was added via syringe. Mixtures were heated for 5 min at 140 °C. Transparent homogeneous mixtures were obtained and they were stored at -20 °C for 12 h to induce precipitation of solubilized polymer.

[0128] ALCHYD+5% 0.5021 g - > Transparent homogeneous

[0129] ALCHYD+4% 0.5041 g - > 23% solid precipitated

[0130] ALCHYD+3% 0.5013 g - > 56% solid precipitated

[0131] ALCHYD+2% 0.5045 g - > 70% solid precipitated

[0132] ALCHYD+1% 0.5023 g - > 78% solid precipitated

[0133] The amount of solid precipitated indicates the degree of depolymerization. The DSC in FIG 04. suggests that precipitate solid underwent mass loss, reflected in the reduction of melting point, compared to the melting point of pristine Polyamide.

[0134] Example 6. The ALCHYD+ systems can be modified into ALCHYDEt+ (Ethanolic medium) and ALCHYDiP+ (isopropanolic medium). One advantage of the reactions with isopropanol and ethanol is the production of isopropyl ether and diethylether as subproducts, which can be easily recovered (unlike dimethyl ether). Approximately 0.5 g of Polyamide6 were fed to a high pressure vials along with 10 ml of solvent (either ethanol or isopropanol). The vials were sealed and 0.5 ml of sulfuric acid (0.5 %v / v) were added via syringe. Vials reacted for 0.5 h at 140 °C under microwaves and at the end of the period, near full depolymerization was observed in the vial with ethanol while the isopropanol one showed some unreacted polymer. This indicates that for depolymerization, increasing the size of the alcohol requires as well an increase on the reaction time. Solubilization of Polyamide was not observed at room temperature with neither ethanol nor isopropanol, being an exclusive feature of the methanolic medium. Example 7. Around 5 ml of deuterated methanol (d4-methanol) were poured in a 5 ml high pressure vial along with 0.25 g Polyamide 6 and a stir bar. The vial was tight sealed and deuterated sulfuric acid (d2SO4) was added dropwise via syringe. The mixture was left under stirring at room temperature for 2 h, after which, a transparent homogeneous mixture (Polyamide 6 dissolved in deuterated ALCHYD) was obtained. FIG 05 displays the proton NMR spectrum of the solution formed, corresponding in the peaks’ chemical shift and peaks’ ratio to polyamide 6.

[0135] Example 8. In a typical experiment, 0.5 g of Polyamide 6 pellets are fed into a high- pressure vial along with 5 ml water and 5 ml methanol. Further, 0.5 ml sulfuric acid are added via syringe (forming thus the claimed solution WALCHYD+5%) and the mixture is left to react at 140 °C for 30 min, yielding aminocaproic acid and dimethyl sulfate, which can be further separated via selective dissolution with common solvents such as diethyl ether and alcohols. In this reaction, the water induces an equilibrium that avoids the formation of dialkylether, which is an improvement with respect to the ALCHYD+ system. The H1NMR spectrum of the solid obtained is shown in FIG 06 and compared to the spectrum of pure Aminocaproic acid.

[0136] Example 9. In a typical experiment, 0.5 g of Polyamide 6,6 pellets are fed into a high- pressure vial along with 5 ml water and 5 ml methanol. Further, 0.5 ml sulfuric acid are added via syringe (forming thus the claimed solution WALCHYD+5%) and the mixture reacted at 140 C for 60 min, yielding hexamethylenediamine and adipic acid along with dimethyl sulfate, which can be further separated via selective dissolution with common solvents such as diethyl ether and alcohols. In this reaction, the water induces an equilibrium that avoids the formation of dialkylether, which is an improvement with respect to the ALCHYD+ system.

[0137] Example 10. A mixture of PET (0.332 g) , PC (0.325 g) and PA6 (0.335 g) pellets were left in contact with 10 ml ALCHYD+5% solution during 2 weeks under stirring to verify at what extent the ALCHYD+ affects polycarbonate and PET. After the 2 weeks period, the remaining pellets were filtered off and washed with methanol (10 ml). At this point, the filtered PA6 in solution was submitted to the same treatment and isolation procedure related in a. The filtered pellets were washed with water (10 ml) and methanol (10 ml) and left dry in an oven at 70 °C. The unreacted pellets did not suffer any change, with mass loss around ± 0.05%. This demonstrates the potential for physical recycling of Polyamide in mixed stream waste containing PET, PC and Polyamides.

[0138] Example 11. To assess the effect of ALCHYD+ solution in cotton, 0.1 g of cotton fibers and 0.5 g of Polyamide 6 pellets were poured in a closed vial along with 15 ml of methanol and 1 stir bar. Further, 7.5 ml sulfuric acid were added dropewise and the mixture was left at R.T under stirring for 24 h. After 2.5 h the pellets were not visible any longer, however, the mixture was left under stirring until 24h, afterwhich, the cotton was removed via filtration and washed with ethanol (10 ml), water (10 ml) and ethanol (10 ml). After drying, a 0.495 g of cotton were collected, which represents a 1% mass loss, which is explained on the defibrillation of the tissue more than any degradation nor depolymerization. The WAXS patterns of cotton before and after the ALCHYD+ treatment (FIG 07) confirms that ALCHYD+ does not induce significant changes on crystal structure of cotton, therefore, cotton based textiles can be submitted to ALCHYD+ selective dissolution and depolymerization.

[0139] Example 12. In a typical experiment of selective solubilization of a polyamide-elastane textile, 0.502 g of a polyamide-elastane textile (labelled as 10% elastane) was poured in a closed vial along with 15 ml of ALCHYD+ solution. The mixture was left under stirring for 4 h at R.T, after which, a suspension was observed along with some remaining fibers. The filtered liquid was neutralized with aqueous KOH, solid precipitated, filtered off and washed with water and dried at 70 °C overnight. Around 0.5 g of solid was collected (the solid was identified as Polyamide6 as shown in FTIR displayed in Fig 08). The remaining fibers were washed with methanol (10 ml) and water (10 ml). The remaing fibers were identified as elastane using FTIR (Fig 08). Example 13. In a typical one-pot selective depolymerization of polyamide in a polyamide-elastane textile, 0.507 g of a polyamide-elastane textile (labelled as 10% elastane) was poured in a closed vial along with 15 ml of ALCHYD+ solution. The mixture was reacted for 1 h at 120 °C with magnetic stirring (600 rpm). A yellowish liquid was obtained along with a solid that agglomerated in the bottom of the vessel (see Inset image in FIG 06). The mixture was filtered off, the solid washed with water (10 ml) and methanol (10 ml) and dried at 70 °C. The FTIR of the solid in FIG 06 confirms that most of the peaks match with the expected peaks of elastane and match the result showed in (k). On the other hand, the liquid was filtered off and neutralized, followed by filtration of some impurities precipitated and the remaining liquid was worked up as described in (a), and the product showed the same characteristic peaks of the product (aminocaproic acid) observed in Fig 06.

[0140] Example 14. A mixture of commercial fabrics described in Table 1 was poured into a 500 ml round-botton flask and 300 ml methanol were added (enough to cover all the fabrics) along with a stir bar. The flask was sealed with a septum and 5%v / vsulfuric acid (15 ml) was added dropwise. The mixture was left under stirring for 2 h, after which, the mixture was filtered off, obtaining a brownish solution of Polyamide in the filtrate and the undissolved textiles in the residue. The residue was washed with methanol and the methanolic filtrate was kept apart. The residue was further washed with water and ethanol using 1 min ultrasound each time to release the Polyamide precipitate in the interstices of the fabrics. The residue was dried under vacuum at 50 °C. The output masses shown in Table 1 demonstrates a high recovery of the polyamide that was in the brown textile as a physically unseparable mixture. At the same time, the other components do not present significant mass losses, meaning they are not being attacked / dissolved by the ALCHYD solution. This is confirmed by FTIR showed in FIG 09, where the FTIR spectra of the fabrics before and after the ALCHYD treatment is displayed, demonstrating a complete match of spectra. The brown fabrics that were initially input and that contained the aimed polyamide were converted to elastane fabrics and polyamide powder. Based on the labelled content of the brown fabrics, it was reached a 91.1% extraction of elastane and 95% extraction of polyamide. The identity of polyamide and spandex is confirmed via FTIR of the extracted polymers compared to reference polymers (Fig 10).

[0141] Example 15. A mixture of fabrics and carpets described in Table 2 was poured into a 500 ml round-bottom flask and 200 ml methanol were added (enough to cover all the fabrics and carpets) along with a stir bar. The flask was sealed with a septum and 5%v / vsulfuric acid (10 ml) was added dropwise. The mixture was left under stirring for 2 h, after which, the mixture was filtered off, obtaining a transparent solution of Polyamide in the filtrate and the undissolved textiles and carpets in the residue. The residue was washed with methanol and the methanolic filtrate was kept apart. The residue was further washed with water and ethanol using 1 min ultrasound each time to release the Polyamide precipitate in the interstices of the fabrics. The residue was dried under vacuum at 50 °C. The output masses shown in Table 2 demonstrates a high recovery of the polyamide that was in the white textile as a physically unseparable mixture. At the same time, the PVC based carpets do not present significant mass losses, meaning they are not being attacked / dissolved by the ALCHYD solution. This is confirmed by FTIR showed in FIG 11, where the FTIR spectra of the carpets before and after the ALCHYD treatment is displayed, demonstrating a complete match of spectra with only some Polyamide impurities that could have adsorbed on the surface but do not represent a serious issue and can be removed by further washing. The identity of polyamide as polyamide 6 is demonstrated in FIG 12, where the spectrum of the reclaimed polymer is compared to the spectra of Polyamide 6 and 66.

[0142] Example 16. Selective dissolution of Polyamide6 out of a complex mixture and further depolymerization

[0143] A mixture of fabrics, carpets and polyolefin as described in Table 3 was poured into a 20 ml high pressure vial and 10 ml methanol were added (enough to cover all the fabrics and carpets) along with a stir bar. The flask was tight sealed 5%v / vsulfuric acid (0.5 ml) was added in less than 1 min through a syringe. The vial was kept submerged in a cold ice bath to better control the temperature changes. After 1 h, additional 2.5%v / vsulfuric acid (0.25 ml) and left under stirring outside the cold bath at room temperature. The mixture was left under stirring for 2.5 h in total, after which, the residue was further washed with water and ethanol using 1 min ultrasound each time to release the Polyamide precipitate in the interstices of the fabrics. The residue was dried under vacuum at 50 °C. Most of the solution (some of it was kept to compare molar mass) was removed and transferred to another high pressure vial containing 5 ml water. This mixture was let reacting at 130 °C and 4h. The reaction mixture was neutralized with KOH in methanol 1.25 M until pH higher than 9. This caused the precipitation of potassium sulfate, which was removed via filtration. The filtrate was rotary evaporated and a soft solid (pale yellow) was obtained.

[0144] The mass losses in Table 3 demonstrate little to no affection on the PVC commercial samples, which demonstrated that this type of samples are compatible for an ALCHYD selective dissolution. In FIG 13, the FTIR spectra of the different materials are compared before and after ALCHYD process, showing that the process is highly selective towards Polyamide6 while leaving untouched materials as varied as PVC, polyolefins, cotton, spandex and polyesters. Even after a selective dissolution out of a complex mixture like that, the identity of Polyamide 6 is preserved in the precipitated polymer as shown in FIG 14. The DSC of the reclaimed Polyamide 6 in FIG 15 confirms that fact; for the melting point of the reclaimed polymer matches 100% with the one of the starting material, therefore, the primary structure of the polymer was mainly unaffected. Although, the result of SEC in FIG 16 shows that there is a small molar mass loss. Nevertheless, this likely reduction of molar mass does not represent a big obstacle for implementation of physicochemical recycling of Polyamides.

[0145] The FTIR in FIG 17 shows the differences among Polyamide 6 that was recovered from the complex mixture and its depolymerization product. Those differences add up to the macroscopical evidence and lead into thinking that an oligomer was obtained. The GPC in FIG 18 demonstrates the depolymerization, going from 31 kDa to 0.6 kDa. The oligomers obtained need to be further investigated to find their best applicability, since they are mixed with monomer, therefore, optimization of reaction conditions might lead to obtaining only monomer (aminocaproic acid).

[0146] Example 17. Depolymerization of Polyamide 6,6 1.00 g Polyamide 6,6 was poured into a 20 ml high pressure vial and 10 ml methanol and 5 ml water were added along with a stir bar. The flask was tight sealed and 5%v / vsulfuric acid (0.5 ml) was added in less than 1 min through a syringe. The contents of the vial were left to react at 130 °C for 2 h using microwaves heating. At the end of the reaction period, a transparent yellowish solution was obtained and KOH in Methanol was added until pH switched to basic. The precipitated potassium sulfate was removed via filtration and the filtrate was submitted to rotary evaporation at 200 mbar and 50 °C. It was further dried under high vacuum at 60 °C. A white solid was obtained. In FIG 19, the FTIR of the solid is displayed and compared to the starting material (Polyamide 6,6). There is a clear modification that leads to believe in the complete transformation of the polymer into monomers and oligomers. The DSC in FIG 20 confirms this, due to the presence of endothermic transitions at relatively low temperatures. These transitions might correspond to adipic acid and hexamethylene diamine or their oligomers. Further study will reveal what conditions are necessary for separation of these compounds.

[0147] Example 18. Depolymerization of Polyamide 12

[0148] 1.00 g Polyamide 12 was poured into a 20 ml high pressure vial and 10 ml methanol and 5 ml water were added along with a stir bar. The flask was tight sealed and 5%v / vsulfuric acid (0.5 ml) was added in less than 1 min through a syringe. The contents of the vial were left to react at 130 °C for 2 h using microwaves heating. At the end of the reaction period, a transparent yellowish solution was obtained and KOH in Methanol was added until pH switched to basic. The precipitated potassium sulfate was removed via filtration and the filtrate was submitted to rotary evaporation at 200 mbar and 50 °C. It was further dried under high vacuum at 60 °C. A white solid was obtained. In FIG 21, the FTIR of the solid is displayed and compared to the starting material (Polyamide 12). There is a clear modification that leads to believe in the complete transformation of the polymer into monomers and oligomers. The DSC in FIG 22 confirms this, due to the presence of endothermic transitions at relatively low temperatures (melting point of Polyamide 12 is around 180 °C). These transitions might correspond to oligomers of different sizes. Further study will reveal what conditions are necessary for separation of these compounds. It will be apparent to those skilled in the art that various modifications and variations can be made in polyamide starting material, composition of mixtures containing polyamide, reaction conditions and heating method of the present invention and in construction of the system and method without departing from the scope or spirit of the invention. Examples of such modifications have been previously provided.

[0149] Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.

[0150] It is intended that the specification and examples be considered as exemplary only.

[0151] Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are part of the description and are a further description and are in addition to the preferred embodiments of the present invention.

[0152] Each of the claims set out a particular embodiment of the invention.

[0153] Tables to this application

[0154] Table 1. Input and output mass of each component submitted to ALCHYD selective dissolution of polyamide.

[0155] „ . output mass Mass loss

[0156] Textile input mass (g)

[0157] Brown fabrics composed of 5.00 0 100.0

[0158] Elastanel9% and Polyamide81%

[0159] White fabrics composed of 5.00 4.81 3.8

[0160] Cotton 95% and Elastane 5%

[0161] Multicoloured fabrics composed of Cotton 50% and Polyester 50 5.00 4.76 4.8

[0162] % Pure Elastane fabrics 0.00 0.82 xx

[0163] Pure Polyamide 0.00 3.9 xx

[0164] Table 2. Input and output mass of each component submitted to ALCHYD selective dissolution of polyamide.

[0165] Textile / sample input mass (g)

[0166] PVC-glass fiber-Polyester carpet (white pigmented with Calcium 5.00 4.88 2.4 carbonate)

[0167] PVC-glass fiber-Polyester carpet

[0168] (black pigmented with charcoal)

[0169] High tenacity PET reinforced ,AA

[0170] PVC multilayer tarpaulin (blue)

[0171] Polyamide75% Elastane25% 100 0 white fabric

[0172] Pure Polyamide 0.00 3.9 xx

[0173] Pure Elastane 0.00 0.92 xx Table 3. Input and output mass of each component submitted to ALCHYD selective dissolution of polyamide.

[0174] Textile / sample input mass (g) output mass (g) Mass loss (%)

[0175] PVC-glass fiber-Polyester carpet (black pigmented 1.040 1.050 0.0 with charcoal)

[0176] Polypropylene flakes 0.251 0.251 0.0

[0177] Elastane film 0.135 0.133 1.5 Polycarbonate pellets 0.261 0.261 0.7

[0178] Polyethylene terephthalate

[0179] 0.249 0.248 0.7 pellets

[0180] Cotton 95% -Elastane 5%

[0181] 0.296 0.304 0 fabrics

[0182] Polyamide 6 pellets 1.002 0.000 100

[0183] Precipitated polyamide 6 0.000 0.950 XXX

[0184] Drawing Description

[0185] BRIEF DESCRIPTION OF THE DRAWINGS

[0186] The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

[0187] FIG 01. provides Fourier Transform Infrared (FTIR) spectra of the Polyamide 6 precipitated from the ALCHYD+ solution and Polyamide 6 pellets.

[0188] FIG 02. provides Differential Scanning Calorimetry of the Polyamide 6 precipitated from the ALCHYD+ solution and Polyamide 6 pellets.

[0189] FIG 03. provides Gel Permeation Chromatography (GPC) of Polyamide 6 pellets compared to the physically recycled Polyamide 6. The chromatograms are overlayed and show the signal from the Multi-angle Light scattering detector. The analysis was performed in a Waters HFIP GPC system containing four detectors. The analyses were performed three times for each sample and displayed are the average values ± 1 standard deviation. Presented are also the Dispersity (D) which are calculated as the ratio of Mw and Mn. FIG 04. provides the Differential Scanning Calorimetry of the precipitated solids at low temperature. The difference in melting point shows that a molar mass reduction is likely in these and it is reflected in the decrease of melting temperature compared to pure Polyamide 6. The higher the content of acid in the ALCHYD+ solution, the higher the degree of depolymerization.

[0190] FIG 05. provides H'NMR spectrum of solubilized pellets registered in deuterated methanol.

[0191] FIG 06. provides a H'NMR of: commercial aminocaproic acid (left) and Depolymerization product of Nylon 6 reaction with WALCHYD+ solution for 30 min at 140 C (Right).

[0192] FIG 07. provides a wide Angle X-Rays Scattering (WAXS) diffractograms of pure cotton (dashed line) and cotton after treating with ALCHYD+ solution for 24 h.

[0193] FIG 08. shows a comparison of FTIR of the Spandex and the polyamide components of a commercial garment containing 90% polyamide and 10% spandex after selective dissolution of polyamide with ALCHYD+ and selective reaction of the polyamide with WALCHYD+.

[0194] FIG 09. provides FTIR analyses of: a. Coloured polycotton fabric (50% polyester, 50% cotton) before and after selective dissolution of Polyamide out of a mixture containing Coloured polycotton fabric ((50% polyester, 50% cotton), Cotton-Elastane fabric (95% cotton, 5% elastane) and a brown fabric (Polyamide83%, Elastanel7%). b. Cotton- Elastane fabric (95% cotton, 5% elastane) fabric before and after selective dissolution of Polyamide out of a mixture containing Coloured polycotton fabric ((50% polyester, 50% cotton), Cotton-spandex fabric (95% cotton, 5% spandex) and a brown fabric (Polyamide83%, Elastane 17%).

[0195] FIG 10. provides a. Comparison of Polyamide 6, 66 and the polyamide recovered after selective dissolution of a mixture containing Coloured polycotton fabric ((50% polyester, 50% cotton), Cotton-spandex fabric (95% cotton, 5% spandex) and a brown fabric (Polyamide83%, Elastanel7%). b. FTIR spectra of reference Elastane compared to Elastane tissue obtained from a brown fabric (Polyamide83%, Elastane 17%) after selective dissolution of Polyamide out of a mixture containing Coloured polycotton fabric ((50% polyester, 50% cotton), Cotton-spandex fabric (95% cotton, 5% spandex) and a brown fabric (Polyamide83%, Elastane 17%).

[0196] FIG 11. provides a FTIR spectra of: a. Polyester layer of a PVC-Glassfiber-Polyester white carpet before and after selective dissolution of Polyamide out of a mixture containing PVC- Glass fibers-Polyester black carpet, PVC-Glass fibers-Polyester white carpet, multilayer PVC-PET tarpaulin (blue) and Polyamide-spandex fabric, b. Tarpaulin surface before and after selective dissolution of Polyamide out of a mixture containing PVC- Glass fibers-Polyester black carpet, PVC-Glass fibers-Polyester white carpet, multilayer PVC-PET tarpaulin (blue) and Polyamide-spandex fabric, c. Polyester layer of a PVC-Glassfiber-Polyester black carpet before and after selective dissolution of Polyamide out of a mixture containing PVC- Glass fibers-Polyester black carpet, PVC-Glass fibers-Polyester white carpet, multilayer PVC-PET tarpaulin (blue) and Polyamide-spandex fabric, d. PVC layer of a PVC-Glassfiber-Polyester black carpet before and after selective dissolution of Polyamide out of a mixture containing PVC- Glass fibers-Polyester black carpet, PVC-Glass fibers-Polyester white carpet, multilayer PVC-PET tarpaulin (blue) and Polyamide-spandex fabric

[0197] FIG 12. provides FTIR of Reclaimed Polyamide after the ALCHYD+ selective dissolution out of a mixture containing P VC-poly ester, Polycotton50, Cotton95%Elastane5% fabric and Polyamide81%Elastanel9% fabric.

[0198] FIG 13. provides FTIR spectra of: a. PVC layer of a PVC-Glassfiber-Polyester carpet before and after selective dissolution of Polyamide 6 out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton- Elastane fabrics, PVC- Glass fibers-Polyester carpet and Polyamide 6 pellets, b. Polyester layer of a PVC-Glassfiber-Polyester carpet before and after selective dissolution of Polyamide 6 out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers- Polyester carpet and Polyamide 6 pellets, c. Polypropylene pellets before and after selective dissolution of Polyamide 6 out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers-Polyester carpet and Polyamide 6 pellets, d. Elastane film before and after selective dissolution of Polyamide 6 out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers-Polyester carpet and Polyamide 6 pellets.

[0199] FIG 14. provides Fourier Transform Infrared Spectroscopy (FTIR) analysis of Polyamide 6 pellets compared to the physically recycled Polyamide 6, selectively dissolved out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers- Polyester carpet and Polyamide 6 pellets.

[0200] FIG 15. provides Differential Scanning Calorimetry (DSC) analysis of Polyamide 6 pellets compared to the physically recycled Polyamide 6, selectively dissolved out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers-Polyester carpet and Polyamide 6 pellets.

[0201] FIG 16. provides Gel Permeation Chromatography (GPC) of Polyamide 6 pellets compared to the physically recycled Polyamide 6, selectively dissolved out of a mixture containing Elastane film, Polypropylene flakes, Polycarbonate pellets, PET pellets, Cotton-Elastane fabrics, PVC- Glass fibers-Polyester carpet and Polyamide 6 pellets. The chromatogram is overlayed and shows the signal from the Multi-angle Light scattering detector. The analysis was performed in a Waters HFIP GPC system containing four detectors. The analyses were performed three times for each sample and displayed are the average values ± 1 standard deviation. Presented are also the Dispersity (D) which are calculated as the ratio of Mw and Mn. FIG 17. provides Fourier Transform Infrared Spectroscopy (FTIR) analysis of polyamide 6 compared to the depolymerization product (white solid) obtained after depolymerization reaction of Polyamide 6 with the WALCHYD+ reaction system.

[0202] FIG 18. provides Gel Permeation Chromatography (GPC) of Polyamide 6 compared to its depolymerization product obtained after reaction with the WALCHYD+ process during 2 h at 130 °C. The chromatogram is overlay ed and shows the signal from the Multi -angle Light scattering detector. The analysis was performed in a Waters HFIP GPC system containing four detectors.

[0203] FIG 19. provides Fourier Transform Infrared Spectroscopy (FTIR) analysis of polyamide 6,6 compared to the depolymerization product (white solid) obtained after depolymerization reaction of Polyamide 6,6 with the WALCHYD+ reaction system.

[0204] FIG 20. provides Differential Scanning Calorimetry (DSC) analysis of the depolymerization product (white solid) obtained after depolymerization reaction of Polyamide 6,6 with the WALCHYD+ reaction system.

[0205] FIG 21. provides Fourier Transform Infrared Spectroscopy (FTIR) analysis of polyamide 12 compared to the depolymerization product (white solid) obtained after depolymerization reaction of Polyamide 12 with the WALCHYD+ reaction system.

[0206] FIG 22. provides Differential Scanning Calorimetry (DSC) analysis of the depolymerization product (white solid) obtained after depolymerization reaction of Polyamide 12 with the WALCHYD+ reaction system.

Claims

A METHOD FOR SEPARATING POLYAMIDE FROM A WASTE STREAM PRIMARILY COMPOSED OF A MIXTURE OF POLYMERIC MATTERClaimsWhat is claimed is:

1. A method of obtaining depolymerized polyamide from a feedstock of a heterogeneous mixture of polymers, the method comprising the steps of, in the following order: a) submersing or suspending the heterogeneous mixture of polymers in an aqueous-alcoholic liquid that is acidified with an inorganic acid, and heating this liquid and the mixture of polymers therein, at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C, during a time period from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, to depolymerize polyamide while excluding ambient gases or preventing ingress of atmospheric gases, and b) separating the depolymerized polyamide from the remaining solids2. The method according to claim 1, whereby step a) comprises i) firstly submersing or suspending the heterogeneous mixture of polymers is in an anhydrous alcohol acidified with inorganic acid at ambient temperature or in the absence of heating and while excluding ambient gases or preventing ingress of atmospheric gases during a timeperiod from 1 to 24 h to dissolve the polyamide polymer and ii) consequently forming this heterogeneous mixture of polymers in acidified alcoholic liquid into a heterogeneous mixture of polymers in inorganic acid acidified aqueous-alcoholic liquid and heating the liquid and polymers at temperatures ranging from 80 to 180 °C , preferably from 100°C to 160°C, yet more preferably from 120°C to 150 °C during a range oftime from 15 min to 6 h, preferably from 15 min to 2h, yet more preferably from 15 min to lh, while excluding ambient gases or preventing ingress of atmospheric gases, to depolymerize polyamide.

3. The method according to any one of the claims 1 to 2, whereby the remaining solids are non-polyamide polymers.

4. The method according to any one of the claims 1 to 2, whereby the remaining solids are non-polyamide polymers and other non-polymer contaminants.

5. The method according to any one of the claims 1 to 4, whereby the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing.

6. The method according to any one of the claims 1 to 5, whereby step a) is carried out in a sealed vessel that is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases.

7. The method according to any one of the claims 1 to 6, whereby step a) is carried out in a sealed vessel on in a pressure-resistant vessel sealed to maintain internal pressure.

8. The method according to any one of the claims 1 to 7, whereby the polyamide extract is separated from the solids by centrifugation or filtration.

9. The method according to any one of the claims 1 to 9, whereby the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N-butyl alcohol and N-propyl alcohol.

10. The method according to any one of the claims 2 to 10, whereby the anhydrous alcohol that is acidified by an inorganic acid containing alcohol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight.

11. The method according to any one of the claims 2 to 10, whereby the anhydrous alcohol is acidified by an inorganic acid in an amount of 1 % - to 10 % by volume of the liquid and preferably in an amount 2,5 % to 7,5 % by volume of the liquid and most preferably in an amount 4 % to 5 % by volume of the liquid.

12. The method according to any one of the claims 1 to 11, whereby the aqueous-alcoholic mixture the volumetric percentage of acid with respect to alcohol is 0,5 to 10% of the liquid, preferably 0,8 to 8% of the liquid and yet more preferably 1 to 5% of the liquid and yet more preferably in an amount 2,5% to 7,5% of the liquid.

13. The method according to any one of the claims 1 to 12, whereby the aqueous-alcoholic liquid contains an amount of water in a range of 2% to 50% by weight of the liquid, preferably in a range of 10 to 30% by weight of the total liquid.

14. The method according to any one of the claims 1 to 13, whereby the anhydrous alcohol or the aqueous-alcoholic mixture is acidified by sulfuric acid.

15. The method according to any one of the claims 1 to 14, whereby the ambient temperature is a temperature from 20°C to 25°C.

16. The method according to any one of the claims 1 to 15, whereby at least the polyamide in the feedstock mixture is in the form of particulates, pellets or fibers.

17. The method according to any one of the claims 1 to 16, whereby in step a) said polyamide in the feedstock mixture are at millimetre dimension of 1 to 10 mm feret diameter or 1 to 10 mm equivalent circular diameter.

18. The method according to any one of the claims 1 to 15, whereby said polyamide in the feedstock mixture is of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

19. The method according to any one of the claims 1 to 18, whereby the feedstock mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

20. The method according to any one of the claims 1 to 19, whereby the feedstock mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, poly vinyl chloride, polyurethanes, polyetherpolyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate and polyethylene terephthalate.

21. The method according to any one of the claims 1 to 20, whereby the polyamide in the feedstock mixture is of the group consisting of polyamide 6, polyamide 11, polyamide 12, polyamide 66, polyamide 610, polyamide 66 / 610, polyamide 6 / 12, polyamide 666, polyamide 6 / 69, nylon 1010, nylon 1012, polyarylamide, polyaramides polyphthalamide and polyamidoamine.

22. The method according to any one of the claims 1 to 21, whereby the polyamide in the feedstock mixture are cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide- containing materials or textiles.

23. The method according to any one of the claims 1 to 22, whereby the polyamide and other materials in the feedstock mixture are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide-containing materials or textiles.

24. The method according to any one of the claims 1 to 23, whereby the depolymerized polyamide is in the form of monomers, dimers, trimers and dissolved oligomers.

25. The method according to claim 25 , further concentrating the refined monomers, dimers, and trimers from depolymerized polyamide by vacuum concentrating.

26. The method according to any one of the claims 1 to 25, whereby the depolymerized polyamide is further fractioned by cooling the concentrated aqueous / alcohol solution to 40-80% (vol) alcohol slowly to a temperature between 4°C to -20°C for crystallization of trimer, dimers and / or monomer components and subsequently separating the trimer, dimers and / or monomer components by filtration.

27. The method according to claim 26, further refining monomers, dimers, and trimers by solid-phase extraction or resin adsorption, for instance with cation-exchange resins to retain amines and / or anion-exchange resins to retain polyamine derived monomers acids and is eluted with dilute HCI orNaOH, or salt gradients to fractionate components based on charge or polarity.

28. A method of obtaining a refined polyamide polymer from a heterogeneous mixture of polymer material comprising polyamide polymer, the method comprising in the following order the steps: i) submersing or suspending the heterogeneous mixture in a sealed vessel at ambient temperature or in the absence of heating and during a range of time from 1 to 24 h in an anhydrous alcohol acidified with inorganic acid to dissolve the polyamide polymer and j) separating the dissolved polyamide polymer from solids and k) precipitating the dissolved polyamide polymer using a non-solvent to obtain a polyamide polymer precipitate, and l) separating the polyamide polymer precipitate from the supernatant.

29. The method according to claim 28, whereby the submersing or suspending the heterogeneous mixture is under continuous stirring or mixing.

30. The method according to any one of the claims 28 to 29, whereby in step c) the non-solvent is added to alcoholic polyamide extract to achieve a ratio from 2 to 50 % non- solvent by volume of alcoholic polyamide extract and preferably 15 to 25% non-solvent by volume of alcoholic polyamide extract.

31. The method according to any one of the claims 28 to 30, whereby the nonsolvent is water.

32. The method according to any one of the claims 28 to 31, whereby the sealed vessel is hermetically sealed for exclusion of all ambient gases or is configured to prevent ingress of atmospheric gases.

33. The method according to any one of the claims 28 to 32, whereby the sealed vessel is a pressure-resistant vessel sealed to maintain internal pressure.

34. The method according to any one of the claims 28 to 33, whereby the alcoholic polyamide extract is separated from the solids by centrifugation or filtration.

35. The method according to any one of the claims 28 to 34, whereby the polyamide polymer precipitate is separated from the supernatant by centrifugation.

36. The method according to any one of the claims 28 to 35, whereby the alcohol is selected from the group consisting of methyl alcohol, ethanol, isopropyl alcohol, N-butyl alcohol and N-propyl alcohol.

37. The method according to any one of the claims 28 to 36, whereby the anhydrous alcohol that is acidified by an inorganic acid containing methanol is in an amount of at least 90% by weight and containing water in an amount of maximum 1% by weight, preferably in an amount of maximum 0,5% by weight.

38. The method according to any one of the claims 28 to 37, whereby the anhydrous alcohol that is acidified containing inorganic acid is in an amount of 1% to 10% by weight and preferably in an amount 2,5% to 7,5% by weight.

39. The method according to any one of the claims 28 to 38, whereby the anhydrous alcohol is acidified by sulfuric acid.

40. The method according to any one of the claims 28 to 39, whereby said ambient temperature is a temperature from 20°C to 25°C.

41. The method according to any one of the claims 28 to 40, whereby at least the polyamide material is in the form of particulates, pellets or fibers.

42. The method according to any one of the claims 1 to 41, whereby in step a) said polyamide material are at millimetre dimension of 1 to 10 mm Feret Diameter (FD) or 1 to 10 mm Equivalent Circular Diameter.

43. The method according to any one of the claims 28 to 42, whereby said polyamide material are of a micrometric dimension, of 1 to 100 pm Feret Diameter (FD) or 1 to 100 pm Equivalent Circular Diameter).

44. The method according to any one of the claims 28 to 43, whereby the heterogeneous mixture is composed of polyamide comprised in a blend, tissue, cotton or copolymer.

45. The method according to any one of the claims 28 to 44, whereby the heterogeneous mixture is composed of polyamide in multilayer component comprising a polymer of the group consisting of polyethylene polyolefins, polypropylene polyolefins, Polyvinyl chloride (PVC), polyurethanes, polyether-polyurea copolymer (spandex or elastane), polycarbonate, polyester, polybutylene terephthalate (PBT) and Polyethylene terephthalate (PET).

46. The method according to any one of the claims 28 to 45, whereby the polyamide material is of the group consisting of polyamide 6 (Nylon 6), polyamide 11 (Nylon 11), polyamide 12 (Nylon 12), polyamide 66 (Nylon 66), polyamide 610 (Nylon 610), polyamide 66 / 610 (Nylon 66 / 610), polyamide 6 / 12 (Nylon 6 / 12), polyamide 666 (Nylon 666 or 6 / 66), polyamide 6 / 69 (Nylon 6 / 69), Nylon 1010, Nylon 1012, polyarylamide, polyaramides (Kevlar®), polyphthalamide and polyamidoamine.

47. The method according to any one of the claims 28 to 46, whereby the polyamide in the feedstock is cut, shredded, ground, or otherwise micronized to millimeter-scale dimensions from larger polyamide-containing materials or textiles.

48. The method according to any one of the claims 28 to 47, whereby the polyamide and other materials in the feedstock are cut, shredded, ground, or otherwise millimetrized of micronized particles from larger polyamide- containing materials or textiles.

49. The method according to any one of the claims 28 to 49, further comprising drying the polyamide polymer precipitate or optionally further comprising washing and drying the polyamide polymer precipitate.