Recycling method

Abstract

Herein a specific method for depolymerizing a polyamide is described. The method comprises the steps of providing a waste stream W0 comprising a polyamide P1, bringing the waste stream W0 into contact with a composition C1 in a reactor R1 to obtain a mixture MI1, and heating the mixture MI1 to obtain a mixture MI2, wherein the reactor R1 is at least partially made of a material MA1, wherein the material MA1 comprises iron and / or nickel.

Description

Recycling MethodDepolymerization reactions fiir polyamides, like polyamide 66, on a laboratory scale are well known to a person skilled in the art. Commonly, polyamide 66 is mixed with additives, like a catalyst or a base, and a solvent and then the mixture is heated. In Example 1 of EP 0 646 106 B1, for example, a method is described, in which on a laboratory scale polyamide 66 is heated to 180°C for 4 hours in the presence of an excess of sodium hydroxide and methanol and water as solvents in a pressure vessel. In the literature, many different materials for reaction vessels for depolymerization are suggested, e.g. PTFE (polytetrafluoroethylene) or glass (e.g. https: / / doi.org / 10.1016 / jjece.2023.109823). The inventors recognized that reactor vessels comprising metal, the risk of leakage or burst of the reaction vessel is significantly improved. However, when repeating and upscaling similar reactions in different kind of common pressure vessels and autoclaves comprising metal, the reaction vessels were corroded within only a few depolymerization reactions to such an extent that they cannot be used any longer due to severe corrosion of the reaction vessel and consequently, there was still a high risk of leakage or burst of the reactor vessel. Thus, it is an object of the present invention to find reaction conditions which lead to: reduced corrosion of the reactor, extended maintenance intervals, and / or, preferably and, reduced risk of leakage or burst of the reaction vessel, enhanced conversion rate of the polyamide.This object is at least partially solved by a method comprising the steps, preferably in this order:I) providing a waste stream WO comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A,II) preferably sorting the waste stream WO to obtain a waste stream W1 , ill) bringing the waste stream WO, preferably the waste stream W1 , into contact with a composition C1 in a reactor R1 to obtain a mixture MI1 , iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2, wherein the reactor R1 is at least partially made, preferably is made, of a material MA1 , wherein the material MA1 comprises iron and / or nickel.Further, this object is at least partially solved by a use of a reactor R1 in a method comprising the steps, preferably in this order:I) providing a waste stream WO comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A,II) preferably sorting the waste stream WO to obtain a waste stream W1 , ill) bringing the waste stream WO, preferably the waste stream W1 , into contact with a composition C1 in the reactor R1 to obtain a mixture MI1 ,iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2, wherein the reactor R1 is at least partially made, preferably is made, of a material MA1 , wherein the material MA1 comprises iron and / or nickel.The inventors recognized, that; especially if the mixture MI1 comprises a polyamide, preferably polyamide 66, a base, preferably an excess of the base with regard to the number of amide bonds of the polyamide, alcohol, preferably methanol, and water; surprisingly the corrosion of the reactor is significantly reduced if the material MA1 of the reactor R1 comprises iron and / or nickel and is further reduced if the material MA1 of the reactor R1 comprises nickel, preferably iron and nickel.In a preferred embodiment, the material MA1 further comprises chromium, molybdenum, copper, tungsten, carbon, silicon, or mixtures thereof. Thus, the corrosion of the reactor is further reduced.In a preferred embodiment, the material MA1 comprises, preferably consists of, an alloy, more preferably an alloy comprising iron and / or nickel, more preferably steel, more preferably stainless steel, more preferably austenitic stainless steel. Thus, the corrosion of the reactor is further reduced. Herein, an austenitic stainless steel is a stainless steel in which the primary crystalline structure is austenite.In a preferred embodiment, the material MA1 comprises, preferably consists of, a metal alloy, preferably an iron and / or nickel based steel, more preferably a steel having an EN-number 1.4541 , 1.4571 , 2.4600, 2.4602, 2.4617; more preferably 2.4600, 2.4602, 2.4617; more preferably 2.4602 or 2.4617. Thus, the corrosion of the reactor is further reduced.In a preferred embodiment, the material MA1 is uncoated; and / or the reactor R1 comprises an inner wall and the inner wall is at least partially, preferably is, uncoated; and / or in the heating step, the material MA1 and the mixture MI1 and / or mixture MI2 are in direct contact.In a preferred embodiment, the reactor R1 is a reactor in which a heating step iv)' has been performed 5 times or more, preferably 50 times or more, more preferably 100 times or more; and / or, preferably and, 10000 times or less, preferably 5000 times or less, more preferably 1000 times or less, preferably wherein in the heating step iv)', a waste stream W0' and a composition CT is heated, preferably to a temperature TT and time tT, more preferably to the temperature T1 and the time t1 as in step iv), preferably wherein the heating step iv)' is a heating step according to step iv), preferably wherein the waste stream W0' is from the same origin and / or has the same ingredients as waste stream W0 or W1 , preferably wherein the waste stream W0' comprises a polyamide PT, preferably wherein the composition CT has the same ingredients, preferably and amounts, as C1 ,preferably wherein temperature T1' is the temperature T1 , preferably wherein the time tT is the time t1 , preferably wherein the polyamide PT is the same polyamide as polyamide P1 , and preferably wherein the polyamide PT is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A; and / or before step i), in the reactor R1 a heating step iv)' is performed 5 times or more, preferably 50 times or more, more preferably 100 times or more; and / or, preferably and, 10000 times or less, more preferably 7500 times or less, preferably 5000 times or less, more preferably 1000 times or less, preferably wherein in the heating step iv)', a waste stream W0' and a composition CT is heated, preferably to a temperature TT and time tT, more preferably to the temperature T1 and the time t1 as in step iv), preferably wherein the heating step iv)' is a heating step according to step iv), preferably wherein the waste stream W0' is from the same origin and / or has the same ingredients as waste stream W0 or W1 , preferably wherein the waste stream W0' comprises a polyamide PT, preferably wherein the composition CT has the same ingredients, preferably and amounts, as C1 , preferably wherein temperature TT is the temperature T1 , preferably wherein the time tT is the time t1 , preferably wherein the polyamide PT is the same polyamide as polyamide P1 , and preferably wherein the polyamide PT is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A. Thus, the risk of leakage or burst of the reaction vessel is reduced and the maintenance intervals are extended.In a preferred embodiment, the reactor R1 is batch reactor or a continuous flow reactor, preferably a batch reactor and / or the reactor R1 has a volume of 1 L or more, preferably 10 L or more, more preferably 50 L or more, more preferably 500 L or more, more preferably 1000 L or more; and / or 100000 L or less, preferably 50000 L or less, more preferably 10000 L or less. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, in the heating step, the temperature T1 is 300 K or more, preferably 310 K or more, more preferably 320 K or more, more preferably 330 K or more, more preferably 340 K or more, more preferably 350 K or more, more preferably 360 K or more, more preferably 370 K or more, more preferably 380 K or more, more preferably 390 K or more, more preferably 400 K or more, more preferably 410 K or more, more preferably 420 K or more, more preferably 430 K or more, more preferably 440 K or more, more preferably 450 K or more, more preferably 460 K or more, more preferably 470 K or more, more preferably 480 K or more, more preferably 490 K or more, more preferably 500 K or more, more preferably 510 K or more. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, in the heating step, the temperature T1 is 550 K (kelvin) or less, preferably 540 K or less, more preferably 530 K or less, more preferably 520 K or less, more preferably 510 K or less, more preferably 500 K or less, more preferably 490 K or less, more preferably 480 K or less, more preferably 470 K or less, more preferably 430K or less, more preferably 420 K or less, more preferably 410 K or less, more preferably 400 K or less, more preferably 390 K or less, more preferably 380 K or less, more preferably 370 K or less, more preferably 360 K or less, more preferably 350 K or less. Thus, the corrosion of the reactor is significantly reduced. Especially, if the temperature T 1 is as described herein and the material MA1 comprises nickel, preferably nickel in a content as described herein, more preferably the material MA1 is as described herein, the corrosion of the reactor is significantly reduced.In a preferred embodiment, in the heating step, the mixture MI 1 is heated to the temperature T1 for 0.1 h or more, preferably 0.2 h or more, more preferably 0.3 h or more, more preferably 0.4 h or more, more preferably 0.5 h or more, more preferably 0.6 h or more, more preferably 0.7 h or more, more preferably 0.8 h or more, more preferably 0.9 h or more, more preferably 1.0 h or more, more preferably 1.3 h or more, more preferably 1.5 h or more, more preferably 1.7 h or more, more preferably 2.0 h or more, more preferably 2.5 h or more, more preferably 3.0 h or more, more preferably 4.0 h or more, more preferably 5.0 h or more, more preferably 6.0 h or more, more preferably 7.0 h or more, more preferably 8.0 h or more, more preferably 9.0 h or more, more preferably 10.0 h or more. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, in the heating step, the mixture MI 1 is heated to the temperature T1 for 50 h or less, preferably 25 h or less, more preferably 10 h or less, more preferably 9 h or less, more preferably 8 h or less, more preferably 7 h or less, more preferably 6 h or less, more preferably 5 h or less, more preferably 4 h or less, more preferably 3 h or less, more preferably 2 h or less, more preferably 1 h or less, more preferably 0.5 h or less. Thus, the corrosion of the reactor is significantly reduced. Especially, if the time is as described herein and the material MA1 comprises nickel, preferably nickel in a content as described herein, more preferably the material MA1 is as described herein, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the composition C1 comprises a base and / or the pH value of the composition C1 is 8 or more, preferably 9 or more, more preferably 10 or more, more preferably 11 or more, more preferably 12 or more, more preferably 13 or more, more preferably 14. Thus, the conversion rate of the polyamide is enhanced. If not stated otherwise, the pH value is preferably determined immediately before the heating step iv).In a preferred embodiment, the composition C1 and / or the mixture MI1 comprises water, preferably wherein a content of the water in the composition C1 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, more preferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or 99 weight-% or less, preferably 90 weight-% or less, more preferably 80 weight-% or less, more preferably 70 weight- % or less, more preferably 60 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 25 weight-% or less, more preferably 20 weight-% or less,more preferably 15 weight- % or less, more preferably 10 weight- % or less, more preferably 5 weight-% or less. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, the composition C1 and / or the mixture MI 1 comprises a base, preferably wherein the base is selected from an inorganic base, more preferably a metal hydroxide, more preferably an alkaline earth metal hydroxide and / or an alkali metal hydroxide, more preferably an alkali metal hydroxide, more preferably NaOH and / or KOH, more preferably NaOH, preferably wherein a content of the base in the composition 01 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, more preferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more; and / or 99 weight-% or less, preferably 90 weight-% or less, more preferably 80 weight-% or less, more preferably 70 weight-% or less, more preferably 60 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 5 weight- % or less. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, the composition C1 and / or the mixture MI1 comprises a solvent S1 , preferably wherein the solvent S1 is selected from a polar solvent, preferably a protic polar solvent, more preferably an alcohol, more preferably methanol, ethanol, diethylene glycol, n-propanol, i-propanol, monoethylene glycol, 1 ,4-butandiol, and mixtures thereof, more preferably methanol, ethanol, and / or i-propanol, more preferably methanol; preferably wherein a content of the solvent in the composition C1 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, more preferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more; and / or 99 weight-% or less, preferably 90 weight-% or less, more preferably 80 weight-% or less, more preferably 70 weight-% or less, more preferably 60 weight-% or less, more preferably 50 weight- % or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 5 weight-% or less. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, the waste stream W0, waste stream W0' and / or waste stream W1 is or is derived from post industrial waste and / or post consumer waste and / or the waste stream W0, waste stream W0' and / or waste stream W1 is or is derived from automotive shredder residue ASR, car, plane, and / or textile, preferably automotive shredder residue, more preferably a polyamide enriched fraction of the automotive shredder residue.In a preferred embodiment, a ratio [weight% / weight-%] of a / the base in weight-% to the waste stream W0, preferably the waste stream W1 , in weight-% in the mixture MI1 is 0.001 or more, preferably 0.01 or more, more preferably 0.1 ormore, more preferably 0.2 or more, more preferably 0.3 or more, more preferably 0.4 or more, more preferably 0.5 or more, more preferably 0.6 or more, more preferably 0.7 or more, more preferably 0.8 or more, more preferably 0.9 or more, more preferably 1 .0 or more. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, a ratio [weight% / weight-%] of the base in weight-% to the waste stream W0, preferably the waste stream W1, in weight-% in the mixture MI1 is 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less, more preferably 2.0 or less, more preferably 1.0 or less, more preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.7 or less, more preferably 0.6 or less, more preferably 0.5 or less, more preferably 0.4 or less, more preferably 0.3 or less, more preferably 0.2 or less, more preferably 0.1 or less. Thus, the corrosion of the reactor is significantly reduced. Especially, if the ratio [weight% / weight-%] of the base in weight-% to the waste stream W0, preferably the waste stream W1 , in weight-% in the mixture MI1 is a described herein and the material MA1 comprises nickel, preferably nickel in a content as described herein, more preferably the material MA1 is as described herein, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the concentration of Cl in the waste stream W0 and / or waste stream W1 is 0.0001 weight- % or more, preferably 0.0005 weight-% or more, more preferably 0.001 weight-% or more, more preferably 0.005 weight-% or more, more preferably 0.01 weight-% or more, more preferably 0.05 weight-% or more, more preferably 0.1 weight-% or more, more preferably 0.5 weight-% or more, more preferably 1 weight-% or more, more preferably 2 weight-% or more, more preferably 3 weight-% or more, more preferably 4 weight-% or more, more preferably 5 weight- % or more; and / or the concentration of Cl in the waste stream W0 and / or waste stream W1 is 5 weight-% or less, preferably 4 weight-% or less, more preferably 3 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.1 weight-% or less, more preferably 0.05 weight-% or less, more preferably 0.01 weight-% or less, more preferably 0.005 weight-% or less, more preferably 0.001 weight-% or less, more preferably 0.0005 weight-% or less, more preferably 0.0001 weight-% or less. Thus, the corrosion of the reactor is significantly reduced. The inventors recognized that especially the combination of chlorine (Cl), a base, preferably Cl, a base and water, is very corrosive. Thus, if the amount of Cl and base, preferably Cl base and water is reduced, the corrosion of the reactor is significantly reduced.In a preferred embodiment, a ratio [weight% / weight-%] of a / the concentration of Cl in the waste stream W1 in weight- % to the a / the concentration of Cl in the waste stream W0 in weight-% is 1 or less, preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.7 or less, more preferably 0.6 or less, more preferably 0.5 or less, more preferably 0.4 or less, more preferably 0.3 or less, more preferably 0.2 or less, more preferably 0.1 or less. Thus, the corrosion of the reactor is significantly reduced.In a preferred embodiment, in the heating step, in the following equation:A*B*C>DD [Kh(weight-%)] is 5, preferably 10, more preferably 50, more preferably 100, more preferably 150, more preferably 200, more preferably 250, more preferably 300, more preferably 350, more preferably 400, more preferably 450, more preferably 500, more preferably 600, more preferably 700, more preferably 800, more preferably 900, more preferably1000, more preferably 1500, more preferably 2000, more preferably 3000, more preferably 4000, more preferably 4500, more preferably 5000, more preferably 5500, more preferably 6000, more preferably 6500, more preferably 7000, more preferably 7500, more preferably 8000, more preferably 8500, more preferably 9000, more preferably 10000, more preferably 15000, more preferably 20000, more preferably 25000, more preferably 30000, more preferably 35000, more preferably 40000, ore preferably 45000, more preferably 50000. wherein A is a temperature T1 in the heating step in [K], wherein B is a time t1 the temperature T1 is applied in [h], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating. Thus, the conversion rate of the polyamide is enhanced. If not stated otherwise, the concentration of a / the base in [weight- %] with regard to the mixture MI1 is preferably determined immediately before the heating step iv).In a preferred embodiment, in the heating step, in the following equation:A*B*C<EE [Kh(weight-%)] is 1*10A10, preferably 1*10A9, more preferably 1*10A8, more preferably 1*10A7, more preferably 1*10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 9.5*10A3, more preferably 9.0*10A3, more preferably 8.5*10A3, more preferably 8.0*10A3, more preferably 7.5*10A3, more preferably 7.0*10A3, more preferably 6.5*10A3, more preferably 6.0*10A3, more preferably 5.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], wherein B is a time t1 the temperature T1 is applied in [h], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating. Thus, the corrosion of the reactor is significantly reduced. Especially, if the parameter E is as described herein and the material MA1 comprises nickel, preferably nickel in a content as described herein, more preferably the material MA1 is as described herein, the corrosion of the reactor is significantly reduced. If not stated otherwise, the concentration of a / the base in [weight- %] with regard to the mixture MI 1 is preferably determined immediately before the heating step iv).In a preferred embodiment, in the heating step, in the following equation:A*C>FF [K(weight-%)] is 5, preferably 10, more preferably 50, more preferably 100, more preferably 150, more preferably 200, more preferably 250, more preferably 300, more preferably 350, more preferably 400, more preferably 450, more preferably 500, more preferably 600, more preferably 700, more preferably 800, more preferably 900, more preferably 1000, more preferably 1500, more preferably 2000, more preferably 3000, more preferably 3250, more preferably 3500, more preferably 3750, more preferably 4000, more preferably 4250, more preferably 5000, more preferably 6000, more preferably 7000, more preferably 8000, more preferably 9000, more preferably 10000, wherein A is a temperature T1 in the heating step in [K], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating.Thus, the conversion rate of the polyamide is enhanced. If not stated otherwise, the concentration of a / the base in [weight- %] with regard to the mixture MI 1 is preferably determined immediately before the heating step iv).In a preferred embodiment, in the heating step, in the following equation:A*C<GG [K(weight-%)] is 1*10A10, preferably 1*10A9, more preferably 1*10A8, more preferably 1*10A7, more preferably 1*10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 5*10A3, more preferably 5.0*10A3, more preferably 4.5*10A3, more preferably 4.2*10A3, more preferably 4.0*10A3, more preferably 3.7*10A3, more preferably 3.5*10A3, more preferably 3.0*10A3, more preferably 2.5*10A3, more preferably 2.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating.Thus, the corrosion of the reactor is significantly reduced. Especially, if the parameter G is as described herein and the material MA1 comprises nickel, preferably nickel in a content as described herein, more preferably the material MA1 is as described herein, the corrosion of the reactor is significantly reduced. If not stated otherwise, the concentration of a / the base in [weight- %] with regard to the mixture MI1 is preferably determined immediately before the heating step iv).In a preferred embodiment, the polyamide P1 is obtainable by polymerizing a diacid and a diamine and / or the polyamide P1 is polyamide of the type AB. Thus, the conversion rate of the polyamide is enhanced, especially of the concentration of the base is enhanced.In a preferred embodiment, the polyamide P1 is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A, preferably a monomer A and a monomer B. Thus, the conversion rate of the polyamide is enhanced.In a preferred embodiment, monomer A is a diacid, preferably a linear and / or unsubstituted aliphatic diacid, more preferably a linear and / or unsubstituted aliphatic diacid comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diacid comprising 5 to 8 carbon atoms, more preferably adipic acid.In a preferred embodiment, monomer B is a diamine, preferably a linear and / or unsubstituted aliphatic diamine, more preferably a linear and / or unsubstituted aliphatic diamine comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diamine comprising 5 to 8 carbon atoms, more preferably hexamethylenediamine.In a preferred embodiment, monomer A is a diamine, preferably a linear and / or unsubstituted aliphatic diamine, more preferably a linear and / or unsubstituted aliphatic diamine comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diamine comprising 5 to 8 carbon atoms, more preferably hexamethylenediamine.In a preferred embodiment, monomer B is a diacid, preferably a linear and / or unsubstituted aliphatic diacid, more preferably a linear and / or unsubstituted aliphatic diacid comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diacid comprising 5 to 8 carbon atoms, more preferably adipic acid.In a preferred embodiment, monomer A is a lactam and / or amino acid, preferably a linear and / or unsubstituted aliphatic lactam and / or amino acid, more preferably a linear and / or unsubstituted aliphatic lactam, more preferably a linear and / or unsubstituted aliphatic lactam comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic lactam comprising 5 to 8 carbon atoms, more preferably caprolactam.In a preferred embodiment, the method comprises the step: sorting the waste stream WO to obtain a waste stream W1 , preferably wherein in the sorting step the content of polyamide P1 , preferably polyamide 66, is increased and / or the content of Cl is reduced.Thus, the conversion rate of the polyamide is enhanced and the corrosion of the reactor is reduced.In a preferred embodiment, the method is a method for depolymerizing a polyamide, preferably polyamide P1 , more preferably polyamide 66.In a preferred embodiment, the method enhances conversion rate of the polyamide P1 , reduces corrosion of the reactor, extends maintenance intervals, and / or, preferably and, reduces risk of leakage or burst of the reaction vessel.In a preferred embodiment, the method comprises the step: separating the mixture MI2 to obtain the monomer A.In a preferred embodiment, the method comprises the step: polymerizing a composition B comprising the monomer A to obtain a polyamide P2, preferably wherein the polyamide P2 is selected from PA6, PA66, PA 6T, PA 6I, and copolymers thereof.In a preferred embodiment, the method comprises the step: converting the composition B comprising the monomer A and / or the polyamide P2 obtainable by or obtained by the method and / or use as described herein or a chemical material obtainable by or obtained by the method and / or use as described herein to obtain a product PRF1.In a preferred embodiment, the product PRF1 is selected from: i) building block or monomer; or ii) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or iii) cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; orvi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acrylate hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate.In a preferred embodiment, the content of the waste stream WO in the product PRF1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or the content of the waste stream W0 in the product PRF1 is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.In a preferred embodiment, the content of iron in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more.In a preferred embodiment, the content of iron in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain iron. Thus, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the content of nickel in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more,more preferably 50 weight-% or more. Thus, the corrosion of the reactor is significantly reduced. The inventors recognised that surprisingly even if a strong base is used, e.g. an alkaline earth metal hydroxide and / or an alkali metal hydroxide, preferably an alkali metal hydroxide, the corrosion of the reactor is significantly reduced, if the content of nickel in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more.In a preferred embodiment, the content of nickel in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain nickel.In a preferred embodiment, the content of chromium in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more. Thus, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the content of chromium in the material MA1 is 90 weight-% or less, preferably 75 weight- % or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain chromium.In a preferred embodiment, the content of molybdenum in the material MA1 is 1 weight-% or more, preferably 3 weight- % or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more. Thus, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the content of molybdenum in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain molybdenum. Especially, if the content of molybdenum is 20 weight-% or more and 40 weight-% or less, the corrosion of the reactor is significantly reduced.In a preferred embodiment, the composition C1 does not comprise ammonia, preferably does not comprise an amine, more preferably does not comprise an organic base.In a preferred embodiment, the polyamide P1 and / or polyamide PT is / are PA 6 and / or PA 66, preferably PA 66; more preferably wherein the polyamide P1 is PA 6 and / or PA 66, preferably PA 66.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

[8005] ; ISSN: 2198-4786; published: February 12, 2024 will be regarded as Reference RF1 , which is incorporated herein by reference in its entirety. Preferably, the product PRF1 is a product as described in Reference RF1 ; paragraphs

[1000] to

[8005] , Preferably, the method / pro- cess described herein is further a method / process for the production of a product, preferably product PRF1 .The converting step to obtain the product PRF1 preferably comprises one or more step(s) as described below and can be performed by conventional methods well known to a person skilled in the art. The converting step preferably comprises one or more step(s) selected from: recycling, preferably depolymerizing, gasifying, pyrolyzing, and / or steam cracking; and / or purifying, preferably crystallizing, (solvent) extracting, distilling, evaporating, hydrotreating, absorbing, adsorbing and / or subjecting to ion exchanger; and / or assembling, preferably foaming, synthesizing, chemical conversion, chemically transforming, polymerizing and / or compounding; and / or forming, preferably foaming, extruding and / or molding; and / or finishing, preferably coating and / or smoothing.In addition, the one or more step(s) are described in detail in Reference RF1; paragraphs

[1000] to

[8005] ,The term "building block”, as used herein, comprises compounds, which are in a gaseous or liquid state under standard conditions of 0°C and 0.1 MPa. Building blocks are typically used in chemical industry to form secondary products, which provide a higher structural complexity and / or higher molecular weight than the building block on which the secondary product is based. The building block is preferably selected from the group consisting of hydrogen, carbon monoxide, carbon dioxide, ethylene oxide, ethylene glycols, syngas comprising a mixture of hydrogen and carbon monoxide, alkanes, alkenes, alkynes and aromatic compounds. The alkanes, alkenes, alkynes and aromatic compounds comprise in particular 1 to 12 carbon atoms, respectively.The term "monomer”, as used herein, comprises molecules, which can react with each other to form polymer chains by polymerization. The monomer is preferably selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid; in particular sodium, potassium and zinc salts; (meth)acrolein and (meth)acrylates. (Meth)acrylates comprising 1 to 22 carbon atoms are preferred, in particular comprising 1 to 8 carbon atoms. The terms (meth)acrylic acid, (meth)acrolein or (meth)acrylate relate to acrylic acid, acrolein or acrylate and also to methacrylic acid, methacrolein or methacrylate, where applicable. Further, the monomer can be selected from hexamethylenediamine (HMD) and adipic acid.The building block can further be an intermediate compound. The term "intermediate compound”, as used herein, comprises organic reagents, which are applied for formation of compounds with higher molecular complexity. The intermediate compound can be selected for example from the group consisting of phosgene, polyisocyanates and propylene oxide. The polyisocyanates are in particular aromatic di- and polyisocyanates, preferably toluene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI).The building block and the monomer and typical converting step(s) to obtain the building block or monomer are described in more detail in paragraphs

[1000] to

[1012] of Reference RF1.The term "polymer A”, as used herein, comprises thermoplastic, e.g., polyamide or thermoplastic polyurethane, thermoset, e.g., polyurethane, elastomer, e.g., polybutadiene, or a copolymer or a mixture thereof and is defined in more detail in paragraphs

[2001] to

[2007] of Reference RF1.The term "polymer composition A”, as used herein, comprises all compositions comprising a polymer as described above and one or more additive(s), e.g. reinforcement, colorant, modifier and / or flame retardant, and is defined in more detail in paragraph

[2008] of Reference RF1.The term "polymer product A”, as used herein, comprises any product comprising the polymer A and / or polymer composition A as described above and is defined in more detail in paragraphs

[2009] and

[2010] of Reference RF1.The step(s) to obtain the polymer, preferably polymer A, polymer composition, preferably polymer composition A or polymer product, preferably polymer product A is / are described in more detail in paragraph

[2011] of Reference RF1 .The term "industrial use polymer”, as used herein, comprises rheology, polycarboxylate, alkoxylated polyalkylenamine, alkoxylated polyalkylenimine, polyether-based, dye inhibition and soil release cleaning polymers defined in more detail in paragraphs

[3035] to

[3044] of Reference RF1. The term "industrial use surfactant”, as used herein, comprises nonionic, anionic and amphoteric industrial use surfactants defined in more detail in paragraphs

[3008] to

[3034] of Reference RF1. The term "industrial use descaling compound”, as used herein, comprises non-phosphate based builders (NPB) and phosphonates (CoP) described in more detail in paragraphs

[3001] to

[3005] of Reference RF1. The term "industrial use biocide”, as used herein, refers to a chemical compound that kills microorganisms or inhibits their growth or reproduction defined in more detail in paragraphs

[3006] to

[3007] of Reference RF1. The term "industrial use solvent”, as used herein, comprises alkyl amides, alkyl lactamides, alkyl esters, lactate esters, alkyl diester, cyclic alkyl diester, cyclic carbonates, aromatic aldehydes and aromatic esters defined in more detail in paragraphs

[3045] to

[3055] of Reference RF1. The term "industrial use dispersant”, as used herein, comprises anionic and non-ionic industrial use dispersants defined in more detail in paragraphs

[3056] to

[3058] of Reference RF1. The term "composition and / or formulation thereof' with reference to the industrial use polymers, industrial use surfactants, descaling compounds and / or industrial use biocides refers to industrial use compositions and / or institutional use products and / or fabric and home care products and / or personal care products defined in more detail in paragraph

[3059] of Reference RF1. The converting step(s) to obtain the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3060] of Reference RF1. The converting steps to obtain the industrial use composition or formulation of the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3061] of Reference RF1.The term "agrochemical composition”, as used herein, typically relates to a composition comprising an agrochemically active ingredient and at least one agrochemical formulation auxiliary. Examples of agrochemical compositions, active ingredients and auxiliaries are described in more detail in Reference RF1 , paragraph

[4001] ,The agrochemical composition may take the form of any customary formulation. The agrochemical compositions are prepared in a known manner, e.g. described by Mollet and Grubemann, Formulation technology, Wiley VCH, Weinheim, 2001 ; or Knowles, New developments in crop protection product formulation, Agrow Reports DS243, T&F Informa, London, 2005. The converting step(s) to obtain the agrochemically active ingredients and auxiliaries may be conducted in analogy to the production step(s) of their analogues that are based on petrochemicals or other precursors that are not gained by recycling processes. In addition, conversion to compounds mentioned in sections "Polymer” and "Cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or compositions or formulations thereof' may be performed as described in these sections as well as the respective paragraphs in Reference RF1.The term active pharmaceutical ingredients and / or intermediates thereof, as used herein, comprises substances that provide pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body. Intermediates thereof are isolated products that are generated during a multi-step route of synthesis of an active pharmaceutical ingredient. The term pharmaceutical excipients, as used herein, comprises compounds or compound mixtures used in compositions for various pharmaceutical applications, which are not substantially pharmaceutically active on itself. Active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients are defined in more detail in paragraph

[5001] of Reference RF1. The converting step(s) to obtain the active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms animal feed additives, human food additives, dietary supplements, as used herein, comprises Vitamins, Pro- Vitamins and active metabolites thereof including intermediates and precursors, especially Vitamin A, B, E, D, K and esters thereof, like acetate, propionate, palmitate esters or alcohols thereof like retinol or salts thereof and anycombinations thereof; Tetraterpenes, especially isoprenoids like carotenoids and xanthophylls including their intermediates and precursors as well as mixtures and derivates thereof, especially beta carotene, Canthaxanthin, Citranaxan- thin, Astaxanthin, Zeaxanthin, Lutein, Lycopene, Apo-carotenoids, and any combinations thereof; organic acids, especially formic acid, propionic acid and salts thereof, such as sodium, calcium or ammonium salts, and any combinations thereof, such as but not limited to mixtures of formic acid and sodium formiate, propionic acid and ammonium propionate, formic acid and propionic acid, formic acid and sodium formiate and propionic acid, propionic acid and sodium propionate and formic acid and sodium formiate; glycerides of carboxylic acids and short and medium chain fatty acids, conjugated linoleic acids, such as omega-6 fatty acid (C18:2) methyl ester and 1 ,2-propandiol and beverage stabilizers, such as polyvinylpyrrolidone-polymer or polyvinylimidazole / polyvinylpyrrolidone-copolymer. Animal feed additives, human food additives and dietary supplements are defined in more detail in paragraph

[5002] of Reference RF1.The converting step(s) to obtain the animal feed additives, human food additives, dietary supplements may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms aroma chemical and aroma composition as used herein, comprise a volatile organic substance with a molecular weight between 70-250 g / mol comprising a functional group with a carbon skeleton of C5-C16 carbon atoms comprising linear, branched, cyclic, for example with a ring size of C5-C18, bicyclic or tricyclic aliphatic chains and but not necessarily one or more unsaturated structural elements like double bonds, triple bonds, aromatics or heteroaromatics and preferably the one or more additional functional groups are selected from alcohol, ether, ester, ketone, aldehyde, acetal, carboxylic acid, nitrile, thiol, amine. In one aspect, the aroma chemical is a terpene-based aroma chemical, for example selected from monoterpenes and monoterpenoids, sesquiterpenes and sesquiterpenoids, diterpenes, triterpenes or tetraterpenes. Aroma chemicals can be combined with further aroma chemicals to give an aroma composition. Aroma chemicals and aroma compositions are defined in more detail in paragraph

[5003] of Reference RF1.The converting step(s) to obtain the aroma chemical and aroma composition may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The term "aqueous polymer dispersion”, as used herein, comprises aqueous composition(s) comprising dispersed polymer(s) and is defined in more detail in the section

[6001] entitled "aqueous polymer dispersion” of Reference RF1. The dispersed polymer(s) may be selected from acrylic emulsion polymer(s), styrene acrylic emulsion polymer(s), styrene butadiene dispersion(s), aqueous dispersion(s) comprising composite particles, acrylate alkyd hybrid disper- sion(s), polyurethane(s) (including UV-curable polyurethanes) and polyurethane - poly(meth)acrylate hybrid poly- mer(s). The term "emulsion polymer”, as used herein, comprises polymer(s) made by free-radical emulsion polymerization. Aqueous polyurethane dispersion(s) are defined in more detail in the section

[6002] entitled "Polyurethane dispersions” of Reference RF1. UV-curable polyurethane(s) is / are defined in more detail in the section

[6017] of Reference RF1. Polyurethane - poly(meth)acrylate hybrid polymer(s) is / are defined in more detail in the section

[6016] of Reference RF1.The term "polymeric dispersant”, as used herein, comprises preferably polymer(s) comprising polyether side chain, in particular polycarboxylate ether polymer(s) and polycondensation product(s) defined in more detail in paragraph

[6020] entitled "Polymeric dispersant” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polymer dispersion(s) comprising emulsion polymer(s) is / are defined in more detail in the section

[6003] entitled "Emulsion polymerization” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polyurethane dispersion(s) is / are defined in more detail in the section

[6014] entitled "Process for the preparation of aqueous polyurethane dispersions” and section

[6017] entitled "Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” of Reference RF1.Composition(s) and uses of aqueous polymer dispersion(s) and of polymeric dispersant(s) are defined in more detail in the following sections of Reference RF1 : section

[6004] entitled "Uses of aqueous polymer dispersions”, section

[6005] entitled "Binders for architectural and construction coatings” section

[6006] entitled "Binders for paper coating” section

[6007] entitled "Binders for fiber bonding” section

[6008] entitled "Adhesive polymers and adhesive compositions” section

[6015] entitled "Aqueous polyurethane dispersions suitable for use in coating compositions” section

[6016] entitled "Aqueous polyurethane - poly(meth)acrylate hybride polymer dispersions suitable for use in coating compositions” section

[6017] entitled "Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” section

[6018] entitled "Inorganic binder compositions comprising polymeric dispersants and their use”

[6019] 100% curable coating compositionsUV-crosslinkable poly(meth)acrylate(s) and its / their uses are defined in more detail in section

[6009] entitled "UV- crosslinkable poly(meth)acrylates for use in UV-curable solvent-free hotmelt adhesives and their use for making pressure-sensitive self-adhesive articles” of Reference RF1.Polyisocyanate(s), composition(s) comprising them and their uses are defined in more detail in section

[6010] entitled "Polyisocyanates” of Reference RF1.Hyperbranched polyester polyol(s) and its / their uses are defined in more detail in section

[6011] entitled "Organic solvent based hyperbranched polyester polyols suitable for use in coating compositions” of Reference RF1. The converting step(s) to obtain the hyperbranched polyester polyols is / are defined in more detail in the section

[6012] entitled "Preparation of organic solvent based hyperbranched polyester polyols” of Reference RF1. Coating composition(s) comprising hyperbranched polyester polyol(s), polyisocyanate(s) and additive(s) and substrate(s) coated therewith aredefined in more detail in section

[6013] entitled "Organic solvent based two component coating compositions comprising hyperbranched polyester polyols and polyisocyanates” of Reference RF1.Unsaturated polyester polyol(s), solvent-based coating composition(s) comprising said unsaturated polyester polyol(s) and substrate(s) for coating with said coating composition(s) are defined in more detail in section

[6018] entitled "Organic solvent based coating composition comprising unsaturated polyester polyols” of Reference RF1. 100% curable coating composition(s) is / are defined in more detail in section

[6019] of Reference RF1.Polymeric dispersant(s) for inorganic binder compositions is / are defined in more detail in section

[6020] of Reference RF1 . The inorganic binder composition(s) comprising the polymeric dispersants and their use are defined in more detail in section

[6021] of Reference RF1. The converting step(s) to obtain the polymeric dispersant(s) are defined in more detail in section

[6020] of Reference RF1. The term "inorganic binder composition” comprising the polymeric disper- sant(s), as used herein, comprises preferably in particular hydraulically setting compositions and compositions comprising calcium sulfate and is defined in more detail in section

[6021] of Reference RF1 entitled "Inorganic binder compositions comprising the polymeric dispersant and their use”. Specific building material formulation(s) comprising polymeric dispersant(s) or building product(s) produced by a building material formulation comprising a polymeric dispersant are disclosed in more detail in section

[6021] of Reference RF1.The term "cosmetic surfactant”, as used herein, comprises non-ionic, anionic, cationic and amphoteric surfactants and is defined in more detail in paragraph

[7002] of Reference RF1. The term "emollient”, as used herein, refers to a chemical compound used for protecting, moisturizing, and / or lubricating the skin and is defined in more detail in paragraph

[7003] of Reference RF1. The term "wax”, as used herein, comprises pearlizers and opacifiers and is defined in more detail in paragraph

[7004] of Reference RF1. The term "cosmetic polymer”, as used herein, comprises any polymer that can be used as an ingredient in a cosmetic formulation and is defined in more detail in paragraph

[7005] of Reference RF1. The term "UV filter”, as used herein, refers to a chemical compound that blocks or absorbs ultraviolet light and is defined in more detail in paragraph

[7006] of Reference RF1. The term "further cosmetic ingredient”, as used herein, comprises any ingredient suitable for making a cosmetic formulation. Several sources disclose cosmetically acceptable ingredients. E. g. the database Cosing on the internet pages of the European Commission discloses cosmetic ingredients and the International Cosmetic Ingredient Dictionary and Handbook, edited by the Personal Care Products Council (PCPC), discloses cosmetic ingredients. The term "composition and / or formulation thereof' with reference to the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter and / or further cosmetic ingredient refers to personal care and / or cosmetic compositions or formulations defined in more detail in paragraph

[7007] of Reference RF1. The converting step(s) to obtain the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter or further cosmetic ingredient is / are defined in more detail in paragraph

[7008] of Reference RF1.The terms "polymer B”, "polymer composition B”, "coating composition”, "other functional composition”, "foil”, "molded body”, "coating” and "coated substrate” are well known to the person skilled in the art and are defined in more detail from paragraph

[8000] to

[8005] of Reference RF1.Methods and DefinitionsIf not stated otherwise, normal conditions are used and / or applied, e.g., room temperature, preferably 25°C, and 1 bar, preferably 1013.25 mbar. If not stated otherwise, the temperature is preferably measured directly in the mixture Ml 1.The pH value is preferably measured by Mettler-Toledo F20-Meter FiveEasy.To determine the content of chlorine (Cl) in the sample, e.g. the waste stream WO or W1, preferably, the following method is used:The content of Cl is an average of 10 representative samples of 3 kg taken by a person skilled in the art from the solid sample.Before analysis all solid samples are homogenized, e.g., by shredding or mixing, preferably to a particle size of about 3 mm or less. The content of chlorine (Cl) is determined according to DIN EN 15408:2011-05. The detection limit is 5.00E-03. A value below 5.00E-03 is set to 0.In summary, embodiments and preferred embodiments are the following embodiments. The scope of protection is defined by the claims. The combination of two or more embodiments, e.g. 3, 4 or 8 embodiments is further preferred. Definitions and general statements herein preferably also apply for the following embodiments and preferred embodiments. In addition, if not stated otherwise, definitions and general statements herein referring the method also apply for the use, and vice versa. Preferably, the steps described in the embodiments below are conducted, if present in the claims, in the order of the embodiments below.1 . Method comprising the steps, preferably in this order:I) providing a waste stream W0 comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A,II) preferably sorting the waste stream W0 to obtain a waste stream W1 , ill) bringing the waste stream W0, preferably the waste stream W1 , into contact with a composition C1 in a reactor R1 to obtain a mixture MI1 , iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2.2. Use of a reactor R1 in a method comprising the steps, preferably in this order:I) providing a waste stream W0 comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A,ii) preferably sorting the waste stream WO to obtain a waste stream W1 , iii) bringing the waste stream WO, preferably the waste stream W1 , into contact with a composition C1 in the reactor R1 to obtain a mixture MI1 , iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2.3. Method or use according to any one of the preceding embodiments, wherein the reactor R1 is at least partially made, preferably is made, of a material MA1 .4. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises iron.5. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises nickel.6. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises chromium.7. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises molybdenum.8. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises copper.9. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises tungsten.10. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises carbon.11 . Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises silicon.12. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises, preferably consists of, an alloy, more preferably an alloy comprising iron and / or nickel, more preferably steel, more preferably stainless steel, more preferably austenitic stainless steel.13. Method or use according to any one of the preceding embodiments, wherein the material MA1 comprises, preferably consists of, a metal alloy, preferably an iron and / or nickel based steel, more preferably a steel having an EN-number 1.4541 , 1.4571 , 2.4600, 2.4602, 2.4617; more preferably 2.4600, 2.4602, 2.4617; more preferably 2.4602 or 2.4617.Method or use according to any one of the preceding embodiments, wherein the material MA1 is uncoated. Method or use according to any one of the preceding embodiments, wherein the reactor R1 comprises an inner wall and the inner wall is at least partially, preferably is, uncoated. Method or use according to any one of the preceding embodiments, wherein in the heating step, the material MA1 and the mixture MI1 and / or mixture MI2 are in direct contact. Method or use according to any one of the preceding embodiments, wherein the reactor R1 is a reactor in which a heating step iv)' has been performed 5 times or more, preferably 50 times or more, more preferably 100 times or more; and / or, preferably and, 10000 times or less, preferably 5000 times or less, more preferably 1000 times or less, preferably wherein in the heating step iv)', a waste stream W0' and a composition CT is heated, preferably to a temperature TT and time tT, more preferably to the temperature T1 and the time t1 as in step iv), preferably wherein the heating step iv)' is a heating step according to step iv), preferably wherein the waste stream W0' is from the same origin and / or has the same ingredients as waste stream W0 or W1 , preferably wherein the waste stream W0' comprises a polyamide PT, preferably wherein the composition CT has the same ingredients, preferably and amounts, as C1 , preferably wherein temperature TT is the temperature T1 , preferably wherein the time tT is the time t1 , preferably wherein the polyamide PT is the same polyamide as polyamide P1 , and preferably wherein the polyamide PT is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A. Method or use according to any one of the preceding embodiments, wherein before step I), in the reactor R1 a heating step iv)' is performed 5 times or more, preferably 50 times or more, more preferably 100 times or more; and / or, preferably and, 10000 times or less, more preferably 7500 times or less, preferably 5000 times or less, more preferably 1000 times or less, preferably wherein in the heating step iv)', a waste stream W0' and a composition CT is heated, preferably to a temperature TT and time tT, more preferably to the temperature T1 and the time t1 as in step iv), preferably wherein the heating step iv)' is a heating step according to step iv), preferably wherein the waste stream W0' is from the same origin and / or has the same ingredients as waste stream W0 or W1 , preferably wherein the waste stream W0' comprises a polyamide PT, preferably wherein the composition CT has the same ingredients, preferably and amounts, as C1 , preferably wherein temperature TT is the temperature T1 , preferably wherein the time tT is the time t1 ,preferably wherein the polyamide P1 ' is the same polyamide as polyamide P1 , and preferably wherein the polyamide P1' is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A.19. Method or use according to any one of the preceding embodiments, wherein the reactor R1 is batch reactor or a continuous flow reactor, preferably a batch reactor.20. Method or use according to any one of the preceding embodiments, wherein the reactor R1 has a volume of 1 L or more, preferably 10 L or more, more preferably 50 L or more, more preferably 500 L or more, more preferably 1000 L or more; and / or 100000 L or less, preferably 50000 L or less, more preferably 10000 L or less.21 . Method or use according to any one of the preceding embodiments, wherein, in the heating step, the temperature T1 is 300 K or more, preferably 310 K or more, more preferably 320 K or more, more preferably 330 K or more, more preferably 340 K or more, more preferably 350 K or more, more preferably 360 K or more, more preferably 370 K or more, more preferably 380 K or more, more preferably 390 K or more, more preferably 400 K or more, more preferably 410 K or more, more preferably 420 K or more, more preferably 430 K or more, more preferably 440 K or more, more preferably 450 K or more, more preferably 460 K or more, more preferably 470 K or more, more preferably 480 K or more, more preferably 490 K or more, more preferably 500 K or more, more preferably 510 K or more.22. Method or use according to any one of the preceding embodiments, wherein in the heating step, the temperature T 1 is 550 K (kelvin) or less, preferably 540 K or less, more preferably 530 K or less, more preferably 520 K or less, more preferably 510 K or less, more preferably 500 K or less, more preferably 490 K or less, more preferably 480 K or less, more preferably 470 K or less, more preferably 430 K or less, more preferably 420 K or less, more preferably 410 K or less, more preferably 400 K or less, more preferably 390 K or less, more preferably 380 K or less, more preferably 370 K or less, more preferably 360 K or less, more preferably 350 K or less.23. Method or use according to any one of the preceding embodiments, wherein, in the heating step, the mixture Ml 1 is heated to the temperature T1 for 0.1 h or more, preferably 0.2 h or more, more preferably 0.3 h or more, more preferably 0.4 h or more, more preferably 0.5 h or more, more preferably 0.6 h or more, more preferably 0.7 h or more, more preferably 0.8 h or more, more preferably 0.9 h or more, more preferably 1.0 h or more, more preferably 1.3 h or more, more preferably 1.5 h or more, more preferably 1.7 h or more, more preferably 2.0 h or more, more preferably 2.5 h or more, more preferably 3.0 h or more, more preferably 4.0 h or more, more preferably 5.0 h or more, more preferably 6.0 h or more, more preferably 7.0 h or more, more preferably 8.0 h or more, more preferably 9.0 h or more, more preferably 10.0 h or more.24. Method or use according to any one of the preceding embodiments, wherein, in the heating step, the mixture MI 1 is heated to the temperature T1 for 50 h or less, preferably 25 h or less, more preferably 10 h or less, more preferably 9 h or less, more preferably 8 h or less, more preferably 7 h or less, more preferably 6 h or less, morepreferably 5 h or less, more preferably 4 h or less, more preferably 3 h or less, more preferably 2 h or less, more preferably 1 h or less, more preferably 0.5 h or less. Method or use according to any one of the preceding embodiments, wherein the composition C1 comprises a base and / or wherein the pH value of the composition C1 is 8 or more, preferably 9 or more, more preferably 10 or more, more preferably 11 or more, more preferably 12 or more, more preferably 13 or more, more preferably 14. Method or use according to any one of the preceding embodiments, wherein the composition C1 and / or the mixture MI 1 comprises water. Method or use according to any one of the preceding embodiments, wherein a content of the water in the composition C1 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, more preferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight- % or more. Method or use according to any one of the preceding embodiments, wherein a content of the water in the composition C1 and / or the mixture MI 1 is 99 weight-% or less, preferably 90 weight-% or less, more preferably80 weight-% or less, more preferably 70 weight-% or less, more preferably 60 weight-% or less, more preferably50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably25 weight-% or less, more preferably 20 weight-% or less, more preferably 15 weight-% or less, more preferably10 weight-% or less, more preferably 5 weight-% or less. Method or use according to any one of the preceding embodiments, wherein the composition C1 and / or the mixture MI 1 comprises a base, preferably wherein the base is selected from an inorganic base, more preferably a metal hydroxide, more preferably an alkaline earth metal hydroxide and / or an alkali metal hydroxide, more preferably an alkali metal hydroxide, more preferably NaOH and / or KOH, more preferably NaOH. Method or use according to any one of the preceding embodiments, wherein a content of the base in the composition C1 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, morepreferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more. Method or use according to any one of the preceding embodiments, wherein a content of the base in the composition C1 and / or the mixture MI 1 is 99 weight-% or less, preferably 90 weight-% or less, more preferably 80 weight-% or less, more preferably 70 weight-% or less, more preferably 60 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 5 weight-% or less. Method or use according to any one of the preceding embodiments, wherein the composition C1 and / or the mixture MI1 comprises a solvent S1 , preferably wherein the solvent S1 is selected from a polar solvent, preferably a protic polar solvent, more preferably an alcohol, more preferably methanol, ethanol, diethylene glycol, n- propanol, i-propanol, monoethylene glycol, 1 ,4-butandiol, and mixtures thereof, more preferably methanol, ethanol, and / or i-propanol, more preferably methanol. Method or use according to any one of the preceding embodiments, wherein a content of the solvent in the composition C1 and / or the mixture MI1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 10 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 35 weight-% or more, more preferably 40 weight-% or more, more preferably 45 weight-% or more, more preferably 50 weight-% or more, more preferably 60 weight-% or more, more preferably 70 weight-% or more, more preferably 80 weight-% or more. Method or use according to any one of the preceding embodiments, wherein a content of the solvent in the composition C1 and / or the mixture MI 1 is 99 weight-% or less, preferably 90 weight-% or less, more preferably 80 weight-% or less, more preferably 70 weight-% or less, more preferably 60 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 5 weight-% or less. Method or use according to any one of the preceding embodiments, the waste stream W0, waste stream W0' and / or waste stream W1 is or is derived from post industrial waste and / or post consumer waste. Method or use according to any one of the preceding embodiments, the waste stream W0, waste stream W0' and / or waste stream W1 is or is derived from automotive shredder residue ASR, car, plane, and / or textile, preferably automotive shredder residue, more preferably a polyamide enriched fraction of the automotive shredder residue.Method or use according to any one of the preceding embodiments, wherein a ratio [wei g ht% / weig ht-%] of a / the base in weight-% to the waste stream WO, preferably the waste stream W1, in weight-% in the mixture MI1 is 0.001 or more, preferably 0.01 or more, more preferably 0.1 or more, more preferably 0.2 or more, more preferably 0.3 or more, more preferably 0.4 or more, more preferably 0.5 or more, more preferably 0.6 or more, more preferably 0.7 or more, more preferably 0.8 or more, more preferably 0.9 or more, more preferably 1.0 or more. Method or use according to any one of the preceding embodiments, wherein a ratio [weight% / weight-%] of the base in weight-% to the waste stream W0, preferably the waste stream W1 , in weight-% in the mixture MI1 is 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less, more preferably 2.0 or less, more preferably 1.0 or less, more preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.7 or less, more preferably 0.6 or less, more preferably 0.5 or less, more preferably 0.4 or less, more preferably 0.3 or less, more preferably 0.2 or less, more preferably 0.1 or less. Method or use according to any one of the preceding embodiments, wherein the concentration of Cl in the waste stream W0 and / or waste stream W1 is 0.0001 weight-% or more, preferably 0.0005 weight-% or more, more preferably 0.001 weight-% or more, more preferably 0.005 weight-% or more, more preferably 0.01 weight-% or more, more preferably 0.05 weight-% or more, more preferably 0.1 weight-% or more, more preferably 0.5 weight-% or more, more preferably 1 weight-% or more, more preferably 2 weight-% or more, more preferably 3 weight-% or more, more preferably 4 weight-% or more, more preferably 5 weight-% or more. Method or use according to any one of the preceding embodiments, wherein the concentration of Cl in the waste stream W0 and / or waste stream W1 is 5 weight-% or less, preferably 4 weight-% or less, more preferably 3 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.1 weight-% or less, more preferably 0.05 weight-% or less, more preferably 0.01 weight-% or less, more preferably 0.005 weight-% or less, more preferably 0.001 weight-% or less, more preferably 0.0005 weight-% or less, more preferably 0.0001 weight-% or less. Method or use according to any one of the preceding embodiments, wherein a ratio [weight% / weight-%] of a / the concentration of Cl in the waste stream W1 in weight-% to the a / the concentration of Cl in the waste stream W0 in weight-% is 1 or less, preferably 0.9 or less, more preferably 0.8 or less, more preferably 0.7 or less, more preferably 0.6 or less, more preferably 0.5 or less, more preferably 0.4 or less, more preferably 0.3 or less, more preferably 0.2 or less, more preferably 0.1 or less. Method or use according to any one of the preceding embodiments, wherein, in the heating step, in the following equation:A*B*C>DD [Kh(weight-%)] is 5, preferably 10, more preferably 50, more preferably 100, more preferably 150, more preferably 200, more preferably 250, more preferably 300, more preferably 350, more preferably 400, morepreferably 450, more preferably 500, more preferably 600, more preferably 700, more preferably 800, more preferably 900, more preferably 1000, more preferably 1500, more preferably 2000, more preferably 3000, more preferably 4000, more preferably 4500, more preferably 5000, more preferably 5500, more preferably 6000, more preferably 6500, more preferably 7000, more preferably 7500, more preferably 8000, more preferably 8500, more preferably 9000, more preferably 10000, more preferably 15000, more preferably 20000, more preferably 25000, more preferably 30000, more preferably 35000, more preferably 40000, ore preferably 45000, more preferably 50000. wherein A is a temperature T1 in the heating step in [K], wherein B is a time t1 the temperature T1 is applied in [h], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating. Method or use according to any one of the preceding embodiments, wherein, in the heating step, in the following equation:A*B*C<EE [Kh(weight-%)] is 1 *10A10, preferably 1 *10A9, more preferably 1 *10A8, more preferably 1 *10A7, more preferably 1*10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 9.5*10A3, more preferably 9.0*10A3, more preferably 8.5*10A3, more preferably 8.0*10A3, more preferably 7.5*10A3, more preferably 7.0*10A3, more preferably 6.5*10A3, more preferably 6.0*10A3, more preferably 5.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], wherein B is a time t1 the temperature T1 is applied in [h], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating. Method or use according to any one of the preceding embodiments, wherein, in the heating step, in the following equation:A*C>FF [K(weight-%)] is 5, preferably 10, more preferably 50, more preferably 100, more preferably 150, more preferably 200, more preferably 250, more preferably 300, more preferably 350, more preferably 400, more preferably 450, more preferably 500, more preferably 600, more preferably 700, more preferably 800, more preferably 900, more preferably 1000, more preferably 1500, more preferably 2000, more preferably 3000, more preferably 3250, more preferably 3500, more preferably 3750, more preferably 4000, more preferably 4250, more preferably 5000, more preferably 6000, more preferably 7000, more preferably 8000, more preferably 9000, more preferably 10000, wherein A is a temperature T1 in the heating step in [K], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating. Method or use according to any one of the preceding embodiments, wherein, in the heating step, in the following equation:A*C<GG [K(weight-%)] is 1 *10A10, preferably 1 *10A9, more preferably 1*10A8, more preferably 1 *10A7, more preferably 1 *10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 5*10A3, more preferably 5.0*10A3, more preferably 4.5*10A3, more preferably 4.2*10A3, more preferably 4.0*10A3, more preferably 3.7*10A3, more preferably 3.5*10A3, more preferably 3.0*10A3, more preferably 2.5*10A3, more preferably 2.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating.46. Method or use according to any one of the preceding embodiments, wherein the polyamide P1 is obtainable by polymerizing a diacid and a diamine.47. Method or use according to any one of the preceding embodiments, wherein the polyamide P1 is polyamide of the type AB.48. Method or use according to any one of the preceding embodiments, wherein the polyamide P1 is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A, preferably a monomer A and a monomer B.49. Method or use according to any one of the preceding embodiments, wherein monomer A is a diacid, preferably a linear and / or unsubstituted aliphatic diacid, more preferably a linear and / or unsubstituted aliphatic diacid comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diacid comprising 5 to 8 carbon atoms, more preferably adipic acid.50. Method or use according to any one of the preceding embodiments, wherein monomer B is a diamine, preferably a linear and / or unsubstituted aliphatic diamine, more preferably a linear and / or unsubstituted aliphatic diamine comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diamine comprising 5 to 8 carbon atoms, more preferably hexamethylenediamine.51 . Method or use according to any one of the preceding embodiments, wherein monomer A is a diamine, preferably a linear and / or unsubstituted aliphatic diamine, more preferably a linear and / or unsubstituted aliphatic diamine comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diamine comprising 5 to 8 carbon atoms, more preferably hexamethylenediamine.52. Method or use according to any one of the preceding embodiments, wherein monomer B is a diacid, preferably a linear and / or unsubstituted aliphatic diacid, more preferably a linear and / or unsubstituted aliphatic diacid comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic diacid comprising 5 to 8 carbon atoms, more preferably adipic acid.53. Method or use according to any one of the preceding embodiments, wherein monomer A is a lactam and / or amino acid, preferably a linear and / or unsubstituted aliphatic lactam and / or amino acid, more preferably a linear and / or unsubstituted aliphatic lactam, more preferably a linear and / or unsubstituted aliphatic lactam comprising 4 to 12 carbon atoms, more preferably a linear and / or unsubstituted aliphatic lactam comprising 5 to 8 carbon atoms, more preferably caprolactam.54. Method or use according to any one of the preceding embodiments, comprising the step: sorting the waste stream WO to obtain a waste stream W1.55. Method or use according to any one of the preceding embodiments, wherein in the sorting step the content of polyamide P1 , preferably polyamide 66, is increased.56. Method or use according to any one of the preceding embodiments, wherein in the sorting step the content of Cl is reduced.57. Method or use according to any one of the preceding embodiments, wherein the method is a method for depolymerizing a polyamide, preferably polyamide P1 , more preferably polyamide 66.58. Method or use according to any one of the preceding embodiments, wherein the method enhances conversion rate of the polyamide P1, reduces corrosion of the reactor, extends maintenance intervals, and / or, preferably and, reduces risk of leakage or burst of the reaction vessel.59. Method or use according to any one of the preceding embodiments, comprising the step: separating the mixture MI2 to obtain the monomer A.60. Method or use according to any one of the preceding embodiments, comprising the step: polymerizing a composition B comprising the monomer A to obtain a polyamide P2, preferably wherein the polyamide P2 is selected from PA6, PA66, PA 6T, PA 6I, and copolymers thereof.61 . Method, preferably according to any one of the preceding embodiments, comprising the step: converting the composition B comprising the monomer A and / or the polyamide P2 obtainable by or obtained by the method and / or use according to any one of the preceding embodiments or a chemical material obtainable by or obtained by the method and / or use according to any one of the preceding embodiments to obtain a product PRF1 .62. Method or use according to any one of the preceding embodiments, wherein the product PRF1 is selected from:I) building block or monomer; orii) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or ill) cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; or vi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acrylate hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate. Method or use according to any one of the preceding embodiments, wherein the content of the waste stream WO in the product PRF1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight- % or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of the waste stream W0 in the product PRF1 is 100 weight-% or less, preferably 95 weight- % or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight- % or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard. Method or use according to any one of the preceding embodiments, wherein the content of iron in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more. Method or use according to any one of the preceding embodiments, wherein the content of iron in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, morepreferably 20 weight-% or less, more preferably 10 weight- % or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain iron.66. Method or use according to any one of the preceding embodiments, wherein the content of nickel in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight-% or more.67. Method or use according to any one of the preceding embodiments, wherein the content of nickel in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain nickel.68. Method or use according to any one of the preceding embodiments, wherein the content of chromium in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight- % or more.69. Method or use according to any one of the preceding embodiments, wherein the content of chromium in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain chromium.70. Method or use according to any one of the preceding embodiments, wherein the content of molybdenum in the material MA1 is 1 weight-% or more, preferably 3 weight-% or more, more preferably 5 weight-% or more, more preferably 7 weight-% or more, more preferably 10 weight-% or more, more preferably 12 weight-% or more, more preferably 15 weight-% or more, more preferably 20 weight-% or more, more preferably 25 weight-% ormore, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 50 weight- % or more.71 . Method or use according to any one of the preceding embodiments, wherein the content of molybdenum in the material MA1 is 90 weight-% or less, preferably 75 weight-% or less, more preferably 65 weight-% or less, more preferably 50 weight-% or less, more preferably 40 weight-% or less, more preferably 30 weight-% or less, more preferably 20 weight-% or less, more preferably 10 weight-% or less, more preferably 8 weight-% or less, more preferably 6 weight-% or less, more preferably 4 weight-% or less, more preferably 2 weight-% or less, more preferably 1 weight-% or less, more preferably 0.5 weight-% or less, more preferably 0.2 weight-% or less, more preferably 0.1 weight-% or less, more preferably wherein the material MA1 does not contain molybdenum.72. Method or use according to any one of the preceding embodiments, wherein the composition C1 does not comprise ammonia, preferably does not comprise an amine, more preferably does not comprise an organic base.73. Method or use according to any one of the preceding embodiments, wherein the polyamide P1 and / or polyamide P1' is / are PA 6 and / or PA 66, preferably PA 66; more preferably wherein the polyamide P1 is PA 6 and / or PA 66, preferably PA 66.ExamplesInventive example 1 :A mixture of 9.9 g of NaOH, 60 ml water and 28 g polyamide 66 was transferred to an autoclave (steel EN-number 2.4602) and heated to 160°C for 2 hours. After cooling to room temperature, a small amount of granulate was still present, indicating that the PA66 was not completely depolymerized. Thus, no yield could be determined. No corrosion of the reaction vessel was observed.Inventive example 2:A mixture of 12.87 g of NaOH, 130.03 ml water and 36.4 g polyamide 66 was transferred to an autoclave (steel EN- number 2.4602) and heated to 160°C for 8 hours. After cooling to room temperature, a small amount of granulate was still present, indicating that the polyamide 66 was not completely depolymerized. Thus, no yield could be determined. No corrosion of the reaction vessel was observed.Inventive examples 3 to 5:A mixture of 12.87 g NaOH, 19.5 ml of water, 36.4 ml methanol and 36.4 g polyamide 66 was transferred to an autoclave (steel EN-number 2.4602) and heated to 160°C for 2, 4 and 8 hours, respectively. After cooling to room temperature, a white suspension was obtained, which was filtered off. No corrosion of the reaction vessels was observed.The yield was determined as follows: After filtration and washing, a filter cake comprising sodium adipate and a filtrate comprising hexamethylenediamine HMD were obtained. The solvent of the filtrate was distilled of with a rotary evaporator to obtain hexamethylenediamine. The filter cake comprising the sodium adipate was dissolved in water and acidified with sulphuric acid to obtain adipic acid AA.The contents of each component, reaction conditions and yields are summarized in Table 1.T able 1 : contents of each component, reaction conditions and yieldsExample PA66 H2O NaOH MeOH T t yield HMD yield AA A*B*C A*C# g g g g °C h % % K*h*% K*%1 28 60 9.9 0 160 2 - - 8757 43792 36.4 130.0 12.9 0 160 8 - - 24864 31083 36.4 19.5 12.9 110.5 160 2 84 72 6217 31094 36.4 19.5 12.9 110.5 160 4 >99 71 12434 31095 36.4 19.5 12.9 110.5 160 8 >99 78 24868 3109No reference example was performed due to the high risk of leakage or burst of the reaction vessel.Many modifications and other embodiments of the invention set forth herein will come to mind to the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

Claims1 . Method comprising the steps: i) providing a waste stream WO comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A, ii) preferably sorting the waste stream WO to obtain a waste stream W1 , ill) bringing the waste stream WO, preferably the waste stream W1, into contact with a composition C1 in a reactor R1 to obtain a mixture MI1, iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2; wherein the reactor R1 is at least partially made of a material MA1, wherein the material MA1 comprises iron and / or nickel.

2. Method according to claim 1, wherein the material MA1 comprises nickel, preferably wherein the content of nickel in the material MA1 is 15 weight- % or more, preferably 40 weight-% or more.

3. Method according to claim 1 or 2, wherein the material MA1 comprises, preferably consists of, a metal alloy, preferably an iron and / or nickel based steel, more preferably a steel having an EN-number 1.4541, 1.4571, 2.4600, 2.4602, 2.4617; more preferably 2.4600, 2.4602, 2.4617; more preferably 2.4602 or 2.4617.

4. Method according to any one of the preceding claims, wherein the reactor R1 is a reactor in which a heating step iv)' has been performed 5 times or more, preferably 50 times or more, more preferably 100 times or more; and / or, preferably and, 10000 times or less, preferably 5000 times or less, more preferably 1000 times or less, preferably wherein in the heating step iv)', a waste stream W0' and a composition CT is heated, preferably to a temperature TT and time tT, more preferably to the temperature T1 and the time t1 as in step iv), preferably wherein the heating step iv)' is a heating step according to step iv), preferably wherein the waste stream W0' is from the same origin and / or has the same ingredients as waste stream W0 or W1, preferably wherein the waste stream W0' comprises a polyamide PT, preferably wherein the composition CT has the same ingredients, preferably and amounts, as C1, preferably wherein temperature TT is the temperature T1, preferably wherein the time tT is the time t1, preferably wherein the polyamide PT is the same polyamide as polyamide P1 , and preferably wherein the polyamide PT is obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A.

5. Method according to any one of the preceding claims, wherein the reactor R1 has a volume of 1 L or more, preferably 10 L or more, more preferably 50 L or more, more preferably 500 L or more, more preferably 1000 L or more; and / or 100000 L or less, preferably 50000 L or less, more preferably 10000 L or less.

6. Method according to any one of the preceding claims, wherein in the heating step, the temperature T 1 is 370 K or more and more preferably 490 K or less, preferably 400 K or more and 470 or less, more preferably 440 K or more and 469 K or less; and / or wherein, in the heating step, the mixture MI1 is heated to the temperature T1 for 0.1 h or more and 50 h or less, preferably 0.5 h or more and 10 h or less, more preferably 1 .0 h or more and 5 h or less.

7. Method according to any one of the preceding claims, wherein the composition C1 comprises a base and / or wherein the pH value of the composition C1 is 8 or more, preferably 9 or more, more preferably 10 or more, more preferably 11 or more, more preferably 12 or more, more preferably 13 or more, more preferably 14.

8. Method according to any one of the preceding claims, wherein the composition C1 and / or the mixture MI1 comprises water, preferably wherein a content of the water in the composition C1 and / or the mixture MI1 is 1 weight-% or more and 40 weight-% or less, preferably 10 weight-% or more and 30 weight-% or less, more preferably 15 weight-% or more and 25 weight-% or less.

9. Method according to any one of the preceding claims, wherein the composition C1 and / or the mixture MI1 comprises a base, preferably wherein the base is selected from an inorganic base, more preferably a metal hydroxide, more preferably an alkaline earth metal hydroxide and / or an alkali metal hydroxide, more preferably an alkali metal hydroxide, more preferably NaOH and / or KOH, more preferably NaOH; and / or wherein the composition C1 and / or the mixture MI 1 comprises a solvent S1 , preferably wherein the solvent S1 is selected from a polar solvent, preferably a protic polar solvent, more preferably an alcohol, more preferably methanol, ethanol, diethylene glycol, n-propanol, i-propanol, monoethylene glycol, 1 ,4-butandiol, and mixtures thereof, more preferably methanol, ethanol, and / or i-propanol, more preferably methanol.

10. Method according to any one of the preceding claims, wherein a ratio [weight% / weight-%] of a / the base in weight-% to the waste stream W0, preferably the waste stream W1, in weight-% in the mixture MI 1 is 0.001 or more and 5.0 or less, preferably 0.1 or more and 1.0 or less, more preferably 0.2 or more and 0.7 or less, more preferably 0.3 or more and 0.6 or less.11 . Method according to any one of the preceding claims, wherein, in the heating step, in the following equation: A*C<GG [K(weight-%)] is 1 *10A10, preferably 1 *10A9, more preferably 1*10A8, more preferably 1 *10A7, more preferably 1 *10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 5*10A3, more preferably 5.0*10A3, more preferably 4.5*10A3, more preferably 4.2*10A3, more preferably 4.0*10A3, morepreferably 3.7*10A3, more preferably 3.5*10A3, more preferably 3.0*10A3, more preferably 2.5*10A3, more preferably 2.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating.

12. Method according to any one of the preceding claims, wherein, in the heating step, in the following equation: A*B*C<EE [Kh(weight-%)] is 1 *10A10, preferably 1 *10A9, more preferably 1 *10A8, more preferably 1 *10A7, more preferably 1*10A6, more preferably 1*10A5, more preferably 5*10A4, more preferably 1*10A4, more preferably 9.5*10A3, more preferably 9.0*10A3, more preferably 8.5*10A3, more preferably 8.0*10A3, more preferably 7.5*10A3, more preferably 7.0*10A3, more preferably 6.5*10A3, more preferably 6.0*10A3, more preferably 5.0*10A3, more preferably 1*10A3, more preferably 5*10A2, more preferably 1*10A2, wherein A is a temperature T1 in the heating step in [K], wherein B is a time t1 the temperature T1 is applied in [h], and wherein C is a concentration of a / the base in [weight- %] with regard to the mixture MI 1 before heating.

13. Method according to any one of the preceding claims, comprising the step(s): polymerizing a composition B comprising the monomer A to obtain a polyamide P2, preferably wherein the polyamide P2 is selected from PA6, PA66, PA 6T, PA 6I, and copolymers thereof; and / or converting the composition B comprising the monomer A and / or the polyamide P2 obtainable by or obtained by the method according to any one of the preceding claims or a chemical material obtainable by or obtained by the method according to any one of the preceding claims to obtain a product PRF1 .

14. Method according to claim 13, wherein the content of the waste stream W0 in the product PRF1 is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight- % or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of the waste stream W0 in the product PRF1 is 100 weight-% or less, preferably 95 weight- % or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight- % or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.

15. Use of a reactor R1 in a method comprising the steps, preferably in this order: i) providing a waste stream W0 comprising a polyamide P1 obtainable or obtained by polymerizing a composition A1 comprising, preferably consisting of, a monomer A,ii) preferably sorting the waste stream WO to obtain a waste stream W1 , iii) bringing the waste stream WO, preferably the waste stream W1, into contact with a composition C1 in the reactor R1 to obtain a mixture MI1, iv) heating the mixture MI1 to obtain a mixture MI2, v) preferably separating the mixture MI2 to obtain the monomer A, and vi) preferably polymerizing a composition B comprising the monomer A to obtain a polyamide P2; wherein the reactor R1 is at least partially made of a material MA1, wherein the material MA1 comprises iron and / or nickel.