Method for preparing a mixture of diamines or a diamine from plastic wastes containing an ethylene-based (CO)polymer

Abstract

The invention relates to a method (M1) for preparing a mixture of aliphatic diamines (MDA) from a plastic product (P) comprising at least one ethylene-based (co)polymer (POL), wherein the aliphatic diamines are of formula H2N−(CH2)x−NH2 where x is an integer from 6 to 12.

Description

Method for preparing a mixture of diamines or a diamine from plastic wastes containing an ethylene-based (co)polymerThis application claims priority of US provisional application N° 63 / 673,858 filed on 22 July 2024 and European patent application N°24203864.4 filed on 1 October 2024, the content of which being entirely incorporated herein by reference for all purposes. In case of any incoherency between this application and one of the priority applications that would affect the clarity of a term or expression, it should be made reference to this application only.

[0001] The present disclosure relates to a method for preparing a mixture of aliphatic diamines (method M1) or an aliphatic diamine (method M2) from plastic wastes containing an ethylene-based (co)polymer.[Context of the invention]

[0002] Plastic pollution is nowadays a global environmental threat as plastic pollution is now prevalent and ubiquitous. Yet, burning plastic wastes is not an environmentally friendly solution. Plastic pollution calls for new, sustainable and effective ways to recycle plastics and to preserve their material value.

[0003] Today conventional plastics like polyethylene (PE) and polypropylene (PP) represent huge volumes but the plastic wastes based on polyolefins are often placed in landfills or, as a better alternative, energy recycled or mechanically recycled into low value products (see ACS Materials Lett. 2021 , 3, 1660-1676 discloses "Polyolefins and polystyrene as Chemical Resources for a Sustainable Future: Challenges, Advances, and Prospects").[Background art]

[0004] Ind. Eng. Chem. Res. 2017, 56, 14814-14821 (D1) discloses the chemical transformation of polyethylene (LDPE) into diacids with the use of HNO3and microwaves.

[0005] Angew. Chem. int. Ed. 1998, 37, 3306-3308 (D2) also discloses the chemical transformation of HOPE and LDPE into diacids with the use of NO and O2.

[0006] Russ. J. Appl. Chem. 2010, 83, 97-101 (D3) discloses the chemical transformation of polyethylene into diacids.

[0007] Angew. Chem. Int. Ed. 2023, 62, e202301340 (doi.org / 10.1002 / anie.202301340) (D4) discloses a highly selective catalytic oxidative-upcycling of polyethylene to aliphatic dicarboxylic acids.

[0008] Polym. Degrad. Stabil. 2023, 210, 110306 (D5)(https: / / doi.Org / 10.1016 / j.polymdegradstab.2023.110306) discloses the chemical transformation of polyethylene into diacids with the use of HNO3.

[0009] US 10,519,292 (D2*), WO 2019 / 204687 and WO 2021 / 076845 (D6) disclose the chemical transformation of polyethylene into diacids with the use of HNO3.

[0010] ACS Sustainable Chem. Eng. 2019, 7, 11004—11013 (D7) discloses the chemical transformation of polyethylene (HDPE) into diacids with the use of HNO3and microwaves.

[0011] "Oxidative chemical recycling of polyethene" C. R. Acad. Sci., Ser. lie: Chim. 2000, 3, 627-629 (https: / / doi.orq / 10.1016 / S1387- 1609(00)01144-0) (D8) discloses the chemical transformation of LDPE into diacids with the use of NO and O2.

[0012] WO 2023 / 118135 (D9) discloses the chemical transformation of PE into diacids with the use of O2in the presence of a catalyst.

[0013] Science 2022, 378, 207-211 (D10) discloses the chemical transformation of PE into diacids with the use of O2in the presence of at least one catalyst.

[0014] CCS Chem. 2025, Just Published "Photocatalytic Oxidation of Polyethylene to Dicarboxylic Acid over BiOI / BiVO4p-n Heterojunction Under Visible Light" (D11) (htps: / / doi.org / 10.31635 / ccschem.025.2024Q5274) discloses the photooxidation of polyethylene with O2into dicarboxylic acids.

[0015] "Catalytic conversion of mixed polyolefins under mild atmospheric pressure" The Innovation 2024, 5, 100586 (https: / / doi.orq / 10.1016 / j.xinn.2O24.100586) (D11) discloses the oxidation of polyethylene with O2into dicarboxylic acids.

[0016] WO 2021 / 119389 discloses the chemical transformation of polypropylene into nonlinear diacids.

[0017] CN 106220513 (D1*) relates to a process of obtaining crude crystals of azelaic acid by saponification and molecular sieve oxidation of castor oil and utilizing the crude crystals of azelaic acid to obtain azelonitrile by neutralization and two-step dehydration reaction and finally obtaining nonanediamine by hydrogenation. D1 does not disclose the controlled oxidation of a plastic waste as in claim 1 or 2.

[0018] US 3,510,522 (D3*) discloses a process for purifying hexamethylenediamine prepared by hydrogenation of adiponitrile or by the reductive ammonolysis of 1 ,6- hexanediol. D3* does not disclose the controlled oxidation of a plastic waste as in claim 1 or 2.

[0019] Notation * refers to the documents retrieved from the EP search report of EP 24203864.(Technical problem to be solved]

[0020] Geting access to molecules of interest from wastes containing polyethylene is sought after in an effort to move to a sustainable industry.

[0021] Polyamides are high value engineering plastics based on expensive aliphatic diamines such as hexamethylene diamine (e.g. PA 6T / 6I) or 1 ,10-decanediamine. Getting access to these diamines from plastic wastes is therefore sought after to comply with the need for a more and more circular economy. The preparation of polyamides with aliphatic diamines also requires that the diamine exhibits a purity greater than or equal to 99.0% to be used in a polycondensation process for preparing polyamides.

[0022] Geting access to aliphatic diamines of high purity from wastes is therefore sought after.

[0023] The method of the invention aims at solving this technical problem.

[0024] The invention is described in the appended claims.

[0025] The method of the invention is disclosed in one of the claims 1-28.

[0026] The invention relates also to a composition as one of claims 29-36.

[0027] The invention relates also to the use as defined in claim 37.

[0028] More precisions and details about the claimed subject-matters are now provided below.

[0029] wt.% is a percentage by weight and mol% is a percentage by mole.

[0030] When numerical ranges are given herein, unless otherwise expressly indicated, the end-points of the ranges (even in the open-ended ranges such as those comprising "at least", "at most", "lower than", "up to", etc or in ranges comprising “between”) are included. The expression "at least" therefore corresponds to the mathematical symbol > in the context of the present invention. The expression "at most" therefore corresponds to the mathematical symbol < in the context of the present invention. For clarity then, the ranges comprising the expression “between X and Y” are thus equivalent to “from X to Y”. For instance, "x being an integer between 6 and 12" is equivalent to "from 6 to 12".

[0031] The proportions of recurring units in a given polymer are expressed in mol% and given relative to the total amount of recurring units in said polymer.

[0032] In the present application, unless otherwise indicated, any specific embodiment or technical feature relating to one method of the invention is applicable to andinterchangeable with another embodiment or technical feature also relating to said method of the invention and disclosed elsewhere in the application.

[0033] As used herein, the terminology ‘(Cn-Cm)’ in reference to an organic group or a molecule, wherein n and m are integers, respectively, indicates that the group or molecule contains from n carbon atoms to m carbon atoms per group, n and m being included.

[0034] Aik designates a linear alkylene group.

[0035] A linear alkylene group is of formula -(CH2)q- where q is an integer > 1 .

[0036] The following nomenclature is used in the present disclosure:Dlx refers to an aliphatic dicarboxylic acid of formula HOOC-(CH2)x-2-COOH;DAXrefers to an aliphatic diamine of formula H2N-(CH2)x-NH2;DNx refers to an aliphatic dinitrile of formula NC-(CH2)x-2_CN;DEx refers to an aliphatic diester of formula ROOC-(CH2)x-2-COOR where R designates a C1-C20 alkyl group;- as can be seen, with this notation, x thus refers to the number of carbon atoms present in a dicarboxylic acid, the diamine or the dinitrile while for a diester, it refers to the the number of carbon atoms of the carboxylic acid from which the diester is prepared; moreover, the notations '> x' and '< x' mean that the number of carbon atoms in a molecule or in a chemical group is respectively greater than or equal to x and lower than or equal to x. Likewise, the notation 'x-y' means that the number of carbon atoms is from x to y.

[0037] MDI designates a mixture of aliphatic dicarboxylic acids of formula HOOC-Alk-COOH; MDN designates a mixture of aliphatic dinitriles of formula NC-Alk-CN; MDA designates a mixture of aliphatic diamines of formula H2N-Alk-NH2; MDE designates a mixture of aliphatic diesters of formula ROOC-Alk-COOR.

[0038] A separation process is a process that converts a mixture of chemical substances into two or more compositionally-distinct product mixtures.

[0039] Distillation designates the separation of liquids by virtue of their difference in boiling points. Distillation can be a continuous distillation or a batch distillation.[Figures]

[0040] Fig. 1 / 4 represents a block diagram of method (M2) of the invention with the presence of step b). Fig. 1 / 4 illustrates method (M2) where one can obtain one or more purified aliphatic diamines DAXfrom a product P.

[0041] Fig. 2 / 4 represents a block diagram of method (M2) of the invention with the presence of step b). Fig. 2 / 4 illustrates method (M2) where one can obtain one or more purified aliphatic diamines DAXfrom a product P.

[0042] Fig. 3 / 4 represents a block diagram of method (M2) of the invention without step b). Fig. 3 / 4 illustrates method (M2) where one can obtain one or more purified aliphatic diamines DAXfrom a product P.

[0043] Fig. 4 / 4 illustrates a step d) of method (M2) with several separation processes.[Disclosure of the invention]

[0044] As a first aspect, the invention relates to a method (M1) for preparing a mixture of aliphatic diamines (MDA) from a plastic product (P), wherein• an ethylene-based (co)polymer (POL) designates a polymer comprising at least 75.0 mol% of ethylene units, preferably at least 80.0 mol%, preferably at least 90.0 mol%, preferably at least 95.0 mol%, preferably at least 99.0 mol%;• the aliphatic diamines (DAX) are of formula H2N-(CH2)X-NH2(I), where x is an integer from 4 to 12 or from 6 to 12; the method comprising the following steps:• step a): plastic product (P) is subjected to a controlled oxidation of the ethylene-based (co)polymer (POL) effective to obtain a stream (Sa) comprising a mixture of aliphatic dicarboxylic acids (MDI) of formula HOOC-Alk-COOH where Aik designates a linear alkylene group;• optional step b): the stream (Sa) is treated through step b1) and / or step b2) in order to obtain a stream (Sb):- in step b1): the stream (Sa) is treated so as to increase the proportions of aliphatic dicarboxylic acids having a number of carbon atoms greater than or equal to 6 in the mixture of aliphatic diacids;- in step b2): if the reaction mixture used in step a) comprises an oxidizing agent selected in the group consisting of nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3), the stream (Sa) is treated in order to decrease the proportions of the organic acids bearing a nitro group;• step c): the mixture of aliphatic dicarboxylic acids (MDI) present in stream (Sa) or in stream (Sb) is chemically transformed into the mixture of aliphatic diamines (MDA).

[0045] According to an embodiment, method (M1) makes it possible to obtain a mixture of diamines (MDA) that can be further processed in order to separate and isolate one or more of the diamines present in MDA, notably a diamine selected in thegroup consisting of DA6(hexamethylenediamine), DA9(nonanediamine) and DA10 (decanediamine).

[0046] As a second aspect, the invention relates to a method (M2) for preparing at least one aliphatic diamine of formula H2N-(CH2)x-NH2, x being an integer from 6 to 12, from a plastic product (P) comprising at least one ethylene-based (co)polymer (POL), the method comprising the following sequence of steps a), b), c) and d) or steps a), b), c*), d*) and e*):• step a): plastic product (P) is subjected to a controlled oxidation of the ethylene-based (co)polymer (POL) effective to obtain a stream (Sa) comprising a mixture of aliphatic dicarboxylic acids (MDI) of formula HOOC-Alk-COOH where Aik designates a linear alkylene group;• optional step b): the stream (Sa) is treated through step b1) and / or step b2) in order to obtain a stream (Sb):- in step b1): the stream (Sa) is treated so as to increase the proportions of aliphatic dicarboxylic acids having a number of carbon atoms greater than or equal to 6 in the mixture of aliphatic dicarboxylic acids (MDI);- in step b2): if the reaction mixture used in step a) comprises an oxidizing agent selected in the group consisting of nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3), the stream (Sa) is treated in order to decrease the proportions of the organic acids bearing a nitro group; where after step a) or step b), i) steps c) and d) are implemented:• step c): the mixture of aliphatic dicarboxylic acids (MDI) present in stream (Sa) or (Sb) is chemically transformed into a mixture of aliphatic diamines (MDA);• step d): at least one aliphatic diamine of formula H2N-(CH2)x-NH2 is separated and recovered from MDA by at least one separation process; or ii) steps c*), d*) and e*) are implemented:• step c*): the mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is chemically converted into a mixture of aliphatic diesters (MDE) of formula ROOC-Alk-COOR where Aik designates a linear alkylene group and R is a linear or branched C1-C20 alkyl group;• step d*): one or more aliphatic diesters DEXof formula ROOC-(CH2)x- 2-COOR is / are separated from MDE and recovered by at least one separation process;• step e*): diester(s) DEXis / are then chemically converted into the corresponding aliphatic diamine(s) DAXof formula H2N-(CH2)X-NH2, the chemical conversion being notably based on the conversion of a diester into a dinitrile which is converted into the diamine.

[0047] More details about and embodiments relating to both methods are now given below.

[0048] MPA

[0049] MDA is therefore a mixture comprising the diamines (DAX) of formula H2N-(CH2)X-NH2where x is an integer from 4 to 12 or from 6 to 12, the total proportion of said diamines being notably at least 10.0 wt.%, this proportion being relative to the total weight of MDA.

[0050] MDA comprises said diamines and the proportion of each diamine depends on the conditions of the controlled oxidation of step a). As is shown in the Experimental Section, the conditions of the controlled oxidation may be such that is possible to have a high proportion of the dicarboxylic acids having from 4 to 12 or from 6 to 12 carbon atoms. For instance, from milk bottles made of HDPE (example C), it was possible to have a high proportion of C4-C9aliphatic dicarboxylic acids. Examples D and E provide also other conditions for which one obtains a high proportion C4- C12 aliphatic dicarboxylic acids. The later chemical conversion of MDI into the subsequent mixtures such as MDA maintains a high proportion of the C4-Ci2or the C6-Ci2 molecules, notably the diamines (see e.g. claim 12).

[0051] According to an embodiment, MDA comprises the aliphatic diamines (DAX) of formula H2N-(CH2)X-NH2 where x is an integer from 4 to 12 where the total proportion of said diamines is at least 40 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, this proportion being relative to the total proportion of all aliphatic diamines present in MDA.

[0052] According to an embodiment, MDA comprises the aliphatic diamines (DAX) of formula H2N-(CH2)X-NH2 where x is an integer from 6 to 12 where the total proportion of said diamines is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, this proportion being relative to the total proportion of all aliphatic diamines present in MDA.

[0053] Plastic product (P)

[0054] Plastic product (P) comprises at least one ethylene-based (co)polymer (POL).

[0055] An ethylene-based (co)polymer (POL) designates a polymer comprising at least 75.0 mol% of ethylene units, preferably at least 80.0 mol%, preferably at least 90.0mol%, preferably at least 95.0 mol%, preferably at least 99.0 mol%. The richer the proportion of ethylene units in POL, the better the yield of the chemical transformation POL -> aliphatic dicarboxylic acids. Also, the richer the proportion of ethylene units in POL, the better for obtaining a mixture richer in diacids after the oxidation step a).

[0056] The ethylene-based (co)polymer (POL) is preferably a polyolefin.

[0057] The ethylene-based (co)polymer is preferably a polyolefin selected in the group of homopolymers of ethylene and copolymers of ethylene and at least one comonomer selected in the group consisting of C3-C12 alpha-olefins and C3-C12 dienes. Alpha-olefin comonomers are linear or branched. Examples of suitable alpha-olefin comonomers include propylene, 1-butene, 3-methyl-1-butene, 3,3- dimethyl-1 -butene, 1 -pentene, 1 -pentene with one or more methyl, ethyl, or propyl substituents, 1 -hexene, 1 -hexene with one or more methyl, ethyl, or propyl substituents, 1 -heptene, 1 -heptene with one or more methyl, ethyl, or propyl substituents, 1-octene, 1-octene with one or more methyl, ethyl, or propyl substituents, 1-nonene, 1-nonene with one or more methyl, ethyl, or propyl substituents, ethyl, methyl, or dimethyl-substituted 1-decene and 1-dodecene. Butadiene is an example of diene.

[0058] The ethylene-based (co)polymer (POL) is more preferably selected in the group consisting of very low density polyethylene, low density polyethylene (LDPE), linear low density polyethylene, medium density polyethylene, cross-linked polyethylene, high density polyethylene (HDPE), high density cross-linked polyethylene, high molecular weight polyethylene, ultra-low molecular weight polyethylene, ultra-high molecular weight polyethylene and combinations thereof.

[0059] Plastic product (P) usually also comprises at least one polymer additive (Add). The polymer additive (Add) may be selected in the group consisting of fillers, colorants, dyes, pigments, lubricants, plasticizers, flame retardants, nucleating agents, heat stabilizers, UV stabilizers, elastomers, core-shell particles, adhesives, antioxidants and processing aids. The polymer additive (Add) may more particularly be selected in the group consisting of fillers, colorants, dyes, pigments, lubricants, elastomers and heat stabilizers.

[0060] Plastic product (P) to be treated may be in various forms. Indeed, plastic product (P) may for instance be in the form of pellets, powders, films, flakes, molded or extruded or 3D printed parts, tubes, filaments, yarns, textiles, fabrics or under any type of geometry. As an example, plastic product (P) may be in the form of bottles (e.g. milk bottles) of films.

[0061] There is no particular requirement as far as the proportion of ethylene-based (co)polymer (POL) in plastic products (P). Yet, this proportion is advantageously at least 5.0 wt.%, more particularly at least 10.0 wt.%, more particularly at least 15.0 wt.%. This proportion may be 100 wt.% if plastic product (P) consists of ethylenebased (co)polymer (POL). Yet, this situation is rare as the method of the invention is meant to apply to products of our day-to-day life for which polymer additives are usually present in combination with the ethylene-based (co)polymer (POL), notably the polyethylene (PE). The proportion of the ethylene-based (co)polymer (POL) in plastic products (P) is generally less than 99.9 wt.%, more particularly less than 90.0 wt.%.

[0062] Optional pretreatment of plastic product (P)

[0063] Plastic product (P) may be pretreated prior to step a). The pretreatment step may include a mechanical or physical modification of plastic product (P), such as cutting, crushing or grinding.

[0064] Prior to step a), plastic product (P) is advantageously transformed into particles of plastic product (P) with a size lower than 10.0 mm, preferably lower than 5.0 mm, even preferably lower than 3.0 mm. This makes it possible to decrease the reaction time of the oxidation step a).

[0065] Step a)

[0066] In step a), plastic product (P) is subjected to a controlled oxidation of the ethylenebased (co)polymer (POL) effective to obtain a stream (Sa) comprising a mixture of aliphatic diacids (MDI) of formula HOOC-Alk-COOH where Aik designates a linear alkylene group.

[0067] As can be seen in the Experimental Section, Aik is typically a C2-C25 linear alkylene group.

[0068] The controlled oxidation of step a) consists in bringing into contact the ethylenebased (co)polymer (POL) present in plastic product (P) with at least one oxidizing agent. The function of the oxidizing agent is to break down the macromolecules containing the ethylene recurring units and to create carboxylic acid groups. The oxidizing agent is generally selected in the group consisting of oxygen (O2), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3) and combinations thereof. It is advantageously nitric acid.

[0069] The temperature at which the oxidation of step a) is performed is generally at least 100°C.

[0070] The reaction medium (RM) comprising the plastic product (P) and the oxidizing agent in which the controlled oxidation takes place typically comprises water.

[0071] A catalyst is typically present in the reaction medium (RM) comprising the plastic product (P) and the oxidizing agent.

[0072] The controlled oxidation is typically performed in a closed reactor under an autogenous pressure P higher than 1 bar.

[0073] Embodiment (E1)

[0074] According to an embodiment (E1), the oxidizing agent is O2or NO+O2. The temperature at which the oxidation of step a) is performed is generally at least 120°C.

[0075] Conditions disclosed in the above-referenced documents of the background art can be followed for performing step a) under embodiment (E1).

[0076] Conditions disclosed in D4 and in the supplementary materials of D4 may be followed to convert the ethylene-based (co) polymer (POL) into dicarboxylic acids using O2as an oxidizing agent in the presence of a catalyst. Typically, the oxidation reaction may be performed according to the following conditions: catalyst: Ru / TiO2+ air; temperature between 150 and 200°C; pressure of air > 1 MPa; duration between 5 and 24 hours.

[0077] Conditions disclosed in D2 or in D8 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using NO+O2as an oxidizing agent. The conditions of D8 lead to a MDI comprising essentially succinic, glutaric, adipic and pimelic acids. Example D provides specific conditions according to D8.

[0078] Conditions disclosed in D9 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using O2in the presence of a catalyst.

[0079] Conditions disclosed in D10 and in the supplementary materials of D10 may be followed to convert the ethylene-based (co) polymer (POL) into dicarboxylic acids using O2in the presence of at least one catalyst. Typical conditions are the following: O2and H2under pressure; temperature between 130 and 180°C; catalysts: Co(OAc)2+Mn(OAc)2; N-hydroxyphthalimide. The supplementary materials of D10 disclose the conditions to optimize the proportions of Dl6~i2in the MDI. Example A provides specific conditions according to D10.

[0080] Conditions disclosed in D11 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using O2in the presence of a photocatalyst based on bismuth. Example B provides specific conditions according to D11.

[0081] Conditions disclosed in D12 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using O2in the presence of a catalyst based on Mn and Co. Example C provides specific conditions according to D12.

[0082] Embodiment (E2)

[0083] Conditions disclosed in the above-referenced documents of the background art can be followed for performing step a) under embodiment (E2).

[0084] According to another embodiment, the oxidizing agent is HNO3. The temperature at which the ethylene-based (co)polymer (POL) of plastic product (P) reacts with HNO3is at least 100°C, preferably between 100 and 200°C. The weight ratio HNO3 / ethylene-based (co)polymer (POL) is generally between 1.0 and 30.0. The temperature and duration of the oxidation have an influence on the relative proportions of the dicarboxylic acids as is visible in table 3 of D5. The higher the temperature and the duration of the oxidation, the lower the proportion of Dl>6.

[0085] Conditions disclosed in D1 and D7 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using HNO3. Some conditions of D7 lead to a MDI where the relative proportions of diacids are the following: Dl4(49 wt.%); Dis (39 wt.%) and Die (12 wt.%). Example H provides specific conditions according to D1.

[0086] Other conditions disclosed in the examples of D6 may be followed to convert the ethylene-based (co)polymer (POL) into dicarboxylic acids using HNO3. Typically, the oxidation reaction is performed according to the following conditions: HNO3(e.g. 68 wt.%) + ethylene-based (co)polymer (POL); temperature between 100 and 150°C; weight ratio HNOs / ethylene-based (co)polymer (POL) between 1.5 and 25.0; duration between 1 and 10 hours.

[0087] Examples of MDIs obtained under the conditions disclosed in D6 given below:

[0088] Example E, F and G provide specific conditions according to D6.

[0089] Mixture MDI

[0090] Mixture MDI comprises aliphatic diacids of formula HOOC-Alk-COOH where Aik designates a linear alkylene group.

[0091] At the end of step a) and / or step b), stream (Sa) and the mixture of aliphatic diacids (MDI) typically comprise diacids selected in the group consisting of oxalic acid (Dl2); malonic acid (Dl3); succinic acid (DU); glutaric acid (Dl5); adipic acid (Die); pimelic acid (DI?); suberic acid (Dl8); azelaic acid (Dl9); sebacic acid (DU); undecanedioic acid (Din); dodecanedioic acid (DU) and aliphatic diacids having 13 or more carbon atoms (DI>13).

[0092] According to an embodiment, the conditions of the controlled oxidation are preferably such that in the mixture MDI obtained at the end of step a) or at the end of step b),- the proportion of Dl2is lower than or equal to 12.0 wt.% (< 12.0 wt.%), preferably lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of Dl3is lower than or equal to 12.0 wt.% (< 12.0 wt.%), preferably lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of Dl4is lower than or equal to 20.0 wt.% (< 20.0 wt.%), preferably lower than 15.0 wt.% (< 15.0 wt.%), preferably lower than 5.0 wt.% (< 5.0 wt.%); these proportions being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.

[0093] According to an embodiment, the conditions of the controlled oxidation are preferably such that in the mixture MDI obtained at the end of step a) or at the end of step b),- the proportion of D 112is lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of D113is lower than or equal to 5.0 wt.% (< 5.0 wt.%), preferably lower than 2.0 wt.% (< 2.0 wt.%); and / or- the proportion of each DUi2is greater than or equal to 2.0 wt.% (> 2.0 wt.%), preferably greater than or equal to 1 .0 wt.% (> 1 .0 wt.%); these proportions being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.

[0094] According to an embodiment, the conditions of the controlled oxidation are preferably such that in the mixture MDI obtained at the end of step a) or at the end of step b), the total proportion of Dl6~i2is greater than or equal to 40.0 wt.% (> 40.0wt.%), preferably greater than or equal to 50.0 wt.% (> 50.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.

[0095] According to an embodiment, the conditions of the controlled oxidation are preferably such that in the mixture MDI obtained at the end of step a) or at the end of step b), the total proportion of DI2~13 is greater than or equal to 60.0 wt.% (> 60.0 wt.%), preferably greater than or equal to 70.0 wt.% (> 70.0 wt.%), preferably greater than or equal to 80.0 wt.% (> 80.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.

[0096] According to an embodiment, the conditions of the controlled oxidation are preferably such that in the mixture MDI obtained at the end of step a) or at the end of step b), the total proportion of the aliphatic dicarboxylic acids having > 20 carbon atoms (DI>2O) is lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.

[0097] These proportions can be determined by standard analytical techniques, such as gas or liquid chromatography.

[0098] The conditions disclosed in the Experimental Section may be followed and used for the controlled oxidation of ethylene-based (co)polymer (POL), notably of wastes containing said ethylene-based (co) polymer (POL).

[0099] Optional step b)

[0100] Optional step b) may be performed according to step b1) and / or step b2) and makes it possible to improve the chemical efficiency of steps c) and d) or steps c*) and d*).

[0101] Both steps b1) and b2) are based on at least one separation process conducted by any suitable known methods such as, for example distillation, filtration, extraction, adsorption, crystallization, chromatography and combination of these methods.

[0102] In optional step b1), stream (Sa) is treated so as to increase the proportions of aliphatic dicarboxylic acids having a number of carbon atoms greater than or equal to 6 (Dl>6) in MDI. As it was observed that succinic acid (Dl4) and glutaric acid (Dl5) do not significantly lead to corresponding dinitriles DN4and DN5(see examplel), this step ensures an optimal use of the reactants (such as NHa, H2 and hydrogenation catalyst) that are used in step c).

[0103] As is shown in the Experimental Section, extraction and filtration is a convenient technique to perform this step b1).

[0104] In optional step b2), if the reaction mixture used in step a) comprises an oxidizing agent selected in the group consisting of nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3), the stream (Sa) is treated in order to decrease the proportions of the organic acids bearing a nitro groups. This also ensures an optimal use of the reactants (such as NH3, H2and hydrogenation catalyst) in step c) or c*).

[0105] At the end of optional step b), stream (Sb) is obtained.

[0106] Step c)

[0107] In step c), the mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is chemically converted into a mixture of aliphatic diamines (MDA).

[0108] The mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is typically chemically converted in more than one step into a mixture of aliphatic diamines (MDA).

[0109] The chemical conversion diacids ~~~> diamines is typically based on the following chemical reactions: diacids dinitriles diamines. Those reactions are illustrated below:HOOC-Alk-COOH NHC-Alk-CEN H2N-Alk-NH2They can also be based on the following chemical reactions: diacids diesters dinitriles diamines. Those reactions are illustrated below:HOOC-Alk-COOH ROOC-Alk-COOR N=C-Alk-CHN H2N-Alk-NH2being understood that Aik designates a linear alkylene group and that in those reactions, the number of carbon atoms for each reaction is preserved.

[0110] Other chemical reactions from a diacid into a diamine [diacids diamines] are possible.

[0111] These reactions are now being explained in more details.

[0112] Conversion MDI ---» MDN: several routes of conversion of a dicarboxylic acid into a dinitrile (HOOC-Alk-COOH ~~~> N=C-Alk-C=N) are known to the skilled person and may be followed for the conversion MDI MDN. Many of these routes are based on the diamides as intermediates according to the following schematic chemical reactions: HOOC-Alk-COOH H2N-C(=O)-Alk-C(=O)-NH2N=C-Alk-C=N.

[0113] The reaction converting a dicarboxylic acid (Dlx) into a dinitrile (DNX) is given below: HOOC-(CH2)X.2-COOH NEC-(CH2)X.2-CEN

[0114] The conditions disclosed below may be followed for this conversion:- US 5,202,455: reaction at a temperature higher between 200°C and 350°C of MDI with gaseous NH3in the presence of a catalyst as disclosed in claim 1 ; or- US 2005 / 059836: reaction at a temperature higher around 300°C of MDI with gaseous NH3in the presence of the catalyst TiO2 / SiO2as disclosed in US 2005 / 059836; or- US 2016 / 016153: reaction in a gas— liquid reactor of MDI with gaseous NH3in the presence of a catalyst as disclosed in US 2016 / 016153; or- the MDI is brought into contact with ZnO and p-TsOH*H2O and the mixture is brought into contact with gaseous NH3. The temperature at which the mixture is heated is higher than 200°C, preferably higher than 250°C. The conditions disclosed in the experimental section may more particularly be followed.- the MDI is brought into contact with phosphoric acid and ammonia at a temperature of at least 200°C.

[0115] The conditions provided in the Experimental Section may also be followed.

[0116] Conversion MDN ---» MPA: several routes of conversion of a dinitrile into a diamine (NHC-Alk-C=N H2N-Alk-NH2) are known to the skilled person and may be followed for the conversion MDN MDA.

[0117] The reaction converting a dinitrile (DNX) into a diamine (DAX) is given below: N=C-(CH2)X.2-C=N NH2-(CH2)X-NH2

[0118] The MDN is generally put into contact with hydrogen in the presence of a catalyst, such as a hydrogenation catalyst based on Ni typically Raney® nickel. The conditions disclosed below may more particularly be followed:- US 2011 / 0190541 : MDN is put into contact with a hydrogenation catalyst, ammonia and hydrogen at a temperature between 100°C and 200°C. The hydrogenation catalyst may be a hydrogenation catalyst based on Ni typically Raney® nickel; or- the MDN is brought into contact with a hydrogenation catalyst based on Ni typically Raney® nickel, ammonia, isopropanol and hydrogen. The temperature at which the mixture is heated is higher than 100°C.

[0119] The conditions provided in the Experimental Section may be followed.

[0120] Conversion MDI ---» MDE: the chemical conversion leading to the diesters is based on an esterification reaction:HOOC-Alk-COOH + 2 ROH -» ROOC-Alk-COOR + 2 H2O where R is a linear or branched Ci-C2o alkyl group.

[0121] R is typically selected in the group consisting of methyl, ethyl, n-propyl, / so-propyl, n-butyl, / so-butyl and pentyl.

[0122] The reaction converting a dicarboxylic acid (Dlx) into a diester (DEX) is given below:HOOC-(CH2)X.2-COOH + 2 ROH ROOC-(CH2)X.2-COOR + 2 H2Owhere R is as disclosed herein.

[0123] This reaction of esterification is known as an equilibrated reaction. An acid catalyst is normally used such as sulfuric acid, methanesulfonic acid or an acidic resin such as Amberlyst™. Removal of water to shift the reaction towards the diesters is typically used to improve the yield of conversion into the diesters.

[0124] According to an embodiment, the mixture of aliphatic diesters (MDE) comprises diesters of formula ROOC-(CH2)x-2_COOR where x is an integer from 4 to 12 where the total proportion of said diesters is at least 40.0 wt%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE; and / or comprises the diesters of formula ROOC-(CH2)x-2_COOR where x is an integer from 6 to 12 where the total proportion of said diesters is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE.

[0125] Conversion MDE MDN:

[0126] This conversion is performed in conditions similar to those disclosed above for conversion MDI MDN. A typical reaction involves bringing MDE in contact with ammonia at a temperature higher than 150°C optionally in the presence of a catalyst.

[0127] The reaction converting a diester (DEX) into a dinitrile (DNX) is given below: ROOC-(CH2)X-2-COOR + NH3N=C-(CH2)x-2-C=N

[0128] The conditions provided in the Experimental Section may be followed.

[0129] Therefore, step c) of the method of the invention may be implemented following the two chemical routes below: route 1 : MDI MDN MDA route 2: MDI MDE MDN MDA

[0130] Embodiment (e) of route 2

[0131] According to an embodiment (e) of route 2, the total proportion in MDE of the aliphatic diesters (DEX) that are derived from dicarboxylic acids having >6 carbon atoms is at least 80.0 wt.%, this proportion being relative to the total weight of MDE. This makes it possible to have an efficient use of the reactants such as NH3and hydrogen for the subsequent conversions MDE ~~~> MDN MDA.

[0132] Such MDE enriched in the aliphatic diesters derived from dicarboxylic acids having >6 carbon atoms can be prepared by one or more distillation steps. The conditionsdistillation are adapted to cut off the aliphatic diesters derived from dicarboxylic acids having < 5 carbon atoms.

[0133] At the end of step c), one recovers a mixture of aliphatic diamines (MDA).

[0134] Step d) of method (M2)

[0135] In step d), at least one aliphatic diamine DAXof formula H2N-(CH2)X-NH2is separated from MDA and recovered by at least one separation process.

[0136] The separation process may be selected in the group consisting of distillation, extraction, adsorption, crystallization, chromatography and any combination thereof.

[0137] Step d) of method (M2) may be performed with only one separation process notably from the list of separation processes above or with more than one separation processes notably from the list of separation processes above.

[0138] Fig. 4 / 4 illustrates the case where several separation processes (noted SP) leading to recovery of three distinct diamines DAX, DAyand DAZare performed. These separation processes are performed either in parallel (see separation processes SP2 and SP2*; in SP1 , the mixture of diamines MDA leads to two streams S1 and S1*) or in succession (see separation processes SP2 leading to stream S2 and SP3).

[0139] Step d) conveniently comprises one or more distillation steps. Each distillation step is based on the use of [or performed with] a distillation column. Distillation is a convenient technique for step d2), all the more so that it is observed that the differences between the boiling points of the dinitriles are not as pronounced for the dinitriles as for the diamines.

[0140] One or more of these distillation steps are preferably performed under vacuum, preferably at a pressure below 100 mbar absolute head pressure.

[0141] The operative conditions of the distillation column(s) that can be used (number of theoretical stages, reflux ratio, feed point, pressure) are adapted according to the composition of the stream entering into a column and according to the component(s) to be recovered.

[0142] According to an embodiment, after step d), one recovers at least one aliphatic diamine of formula H2N-(CH2)X-NH2with a purity (p) of at least 99.0 wt.%, preferably at least 99.5 wt.%.

[0143] Step c*), d*) and e*) of method (M2)

[0144] As a variant of method (M2), it is possible to implement after step a) or optional step b), sequence of steps c*), d*) and e*) instead of sequence of steps c) and d).

[0145] Step c*)

[0146] In step c*), the mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is chemically converted into a mixture of aliphatic diesters (MDE). Details and embodiments about the conversion of a diacid into a diester, notably embodiment (e), provided above apply here.

[0147] The esterification reaction is the following:HOOC-Alk-COOH + 2 ROH ROOC-Alk-COOR + 2 H2O where R is a linear or branched Ci-C20alkyl group.

[0148] According to an embodiment, the mixture of aliphatic diesters (MDE) comprises diesters of formula ROOC-(CH2)X.2-COOR where x is an integer from 4 to 12 where the total proportion of said diesters is at least 40.0 wt%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE; and / or comprises the diesters of formula ROOC-(CH2)X.2-COOR where x is an integer from 6 to 12 where the total proportion of said diesters is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE.

[0149] Step d*)

[0150] In step d*), one or more aliphatic diesters DEXof formula ROOC-(CH2)X.2-COOR is / are separated from MDE and recovered by at least one separation process.

[0151] The separation process may be selected in the group consisting of distillation, extraction, adsorption, crystallization, chromatography and any combination thereof.

[0152] Step d*) of method (M2) may be performed with only one separation process notably from the list of separation processes above or with more than one separation processes notably from the list of separation processes above.

[0153] Step d*) conveniently comprises one or more distillation steps. Each distillation step is based on the use of [or performed with] a distillation column. Distillation is a convenient technique for step d*), all the more so that it is observed that the differences between the boiling points of the dinitriles are not as pronounced for the dinitriles as for the diesters. Therefore, the distillation is a convenient technique to purify a diester prior to its being converted into the corresponding diamine.

[0154] The operative conditions of the distillation column(s) that can be used (number of theoretical stages, reflux ratio, feed point, pressure) are adapted according to the composition of the stream entering into a column and according to the component(s) to be recovered.

[0155] R is more particularly methyl or ethyl to have light diesters to be separated by distillation.

[0156] Step e*)

[0157] In step e*), diester DEXis then converted into the corresponding diamine DAX, the chemical conversion being notably based on the conversion of the diester into a dinitrile which is converted into the diamine.

[0158] The chemical conversion can be the following:ROOC-(CH2)X-2-COOR NEC-(CH2)X.2-CEN H2N-(CH2)X-NH2where R designates a C1-C20 alkyl group.

[0159] The route from a diester to a diamine through a dinitrile has already been disclosed above and all details and features disclosed above for the conversion MDE MDA apply here as well.

[0160] After step d) or step e*), diamine DAXmay be purified through one or more distillation steps to obtain the targeted purity (p).

[0161] Diamine of high purity (p)

[0162] The methods of the invention, notably method (M2), make it possible to obtain one or more aliphatic diamines with a high purity (p) suitable to be used in a polycondensation process to prepare a polyamide. For instance, for the preparation of a polyamide, the proportion of monoamines needs to be low.

[0163] According to a preferred embodiment, the total proportion of monoamine(s) in the recovered aliphatic diamine is at most 0.5 wt.%, this proportion being based on the total weight of the aliphatic diamine.

[0164] According to a preferred embodiment, the total proportion of C1-C18 monoamine(s) in the recovered aliphatic diamine is at most 0.5 wt.%, this proportion being based on the total weight of the aliphatic diamine.

[0165] According to an embodiment of the present disclosure, diamine DAXrecovered exhibits a purity (p) of at least 99.0 wt.%, preferably at least 99.5 wt.%, where x is notably any one of the integers present in the range {6—12} and / or diamine DAXrecovered is hexamethylenediamine (x=6), nonanediamine (x=9) or decanediamine (x=10).

[0166] The purity (p) of the diamines and the quantification of the other molecules present can be determined by any suitable analytical technique. A convenient analytical technique for determining the purity (p) is gas chromatography (GC) or liquid chromatography (HPLC).

[0167] As is disclosed above, at the end of step c), one obtains a mixture MDA. After step d) or step d*), one obtains a diamine DAX. The recovered diamine DAXtypicallycontains trace quantities of the other diamines DAx+iand DAx-i where x is any one of the integers present in the range {6-12}.

[0168] Composition (C)

[0169] The recovered diamine DAXis typically part of a composition (C) comprising diamine DAXwhere x is any one of the integers present in the range {6-12} and the diamines DAx+iand DAx~i with the following proportions:- diamine DAX: at least 99.0 wt.%, preferably at least 99.5 wt.%;- each diamine DAx+iand DAx-i: at most 0.5 wt.%, preferably at most 0.1 wt.%; these proportions being based on the total weight of composition (C).

[0170] x is any one of the integers present in the range {6-12}, for example x is 6, 7, 8, 9, 10, 11 or 12.

[0171] For example, if x=6, composition (C) comprises diamine DA6(of formula H2N- (CH2)6-NH2)- diamine DA6: at least 99.0 wt.%, preferably at least 99.5 wt.%;- diamine DA?: at most 0.5 wt.%, preferably at most 0.1 wt.%;- diamine DA5: at most 0.5 wt.%, preferably at most 0.1 wt.%; these proportions being based on the total weight of composition (C).

[0172] As another example, if x=9, composition (C) comprises diamine DAg (of formula H2N-(CH2)9-NH2):- diamine DA9: at least 99.0 wt.%, preferably at least 99.5 wt.%;- diamine DA8: at most 0.5 wt.%, preferably at most 0.1 wt.%;- diamine DAi0: at most 0.5 wt.%, preferably at most 0.1 wt.%; these proportions being based on the total weight of composition (C).

[0173] The proportions in composition (C) are preferably the following:- diamine DAX: at least 99.5 wt.%;- diamine DAx+i: at most 0.1 wt.%;- diamine DAx.i: at most 0.1 wt.%; these proportions being based on the total weight of composition (C).

[0174] According to an embodiment, the total proportion of the aliphatic diamines DAyin composition (C) where y is an integer different from x, x+1 and x-1 , is at most 0.5 wt.%.

[0175] Each diamine DAx+iand DAx-i is typically present in composition (C) at a proportion of at least 0.1 ppm, more particularly at least 0.5 ppm, more particularly at least 1.0 ppm, this proportion being based on the total weight of composition (C).

[0176] For clarity, 1 .0 ppm is equivalent of 1 .0 mg of diamine per kg of composition.

[0177] The total proportion of monoamine(s) in composition (C) of the invention is preferably at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).

[0178] The total proportion of Ci-Cis monoamine(s) in composition (C) of the invention is preferably at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).

[0179] Composition (C) may be used for the preparation of a polyamide comprising in polymerized form a diamine DAX. For instance, the method of the invention makes it possible to obtain a composition (C) comprising 1 ,6-decane diamine as diamine DAx (x=10) which can be used for the preparation of a polyamide such as 10T / BACT where T designates terephthalic acid and BAC designates 1 ,3- Bis(Aminomethyl) cyclohexane.

[0180] Composition (C) can be prepared by the method disclosed herein, notably in the method disclosed in any one of the claims.

[0181] Examples A-H illustrate the chemical conversion of polyethylene into a mixture of dicarboxylic acids. The other examples 1-12 illustrate the preparation of one of more diamines. The conditions of transformation of the mixtures disclosed in examples 1-12 are applicable to mixture of dicarboxylic acids (MDI) obtained in examples A-H.

[0182] Preparation of mixtures of dicarboxylic acids (MDI) from polyethylene

[0183] Example A: illustrates oxidation of PE under embodiment (E1)

[0184] A 316 stainless steel reactor with a 1” Teflon coated stir bar was loaded with 20 ml of glacial acetic acid, followed by the addition of cobalt (II) acetate, manganese (II) acetate, N-hydroxyphthalimide (NHPI) and the polymer substrate. After the addition of all reactants, reactor was pressurized. After reaction, the reactor was placed on ice and cooled to ~20°C, after which it was depressurized and the reaction solution was collected for analysis. Product mixture was filtered through 0.2 pm Nylon and diluted with THF prior to analysis.

[0185] Conditions used: 54 kDa HDPE bead or 99 kDa milk bottle (350 mg, 1250 mM repeating ethylene unit), Co(OAc)2(9.7 wt.%, 9.6 mM), Mn(OAc)2(9.5 wt.%, 9.6 mM), NHPI (22.4 wt.%, 24.0 mM), 8 bar O2 / 72 bar N2, 2.5 hr, 160°C.

[0186] Analysis of MDI was made with an ultra-high pressure liquid chromatography tandem mass spectrometry (UHPLC-MS / MS). HDPE yields a distribution of C4 to C22a,w-dicarboxylic acids.

[0187] Example B: illustrates oxidation of PE under embodiment (E1)

[0188] Preparation of catalyst: the preparation of the photocatalyst included two steps. Firstly, polyvinylpyrrolidone (PVP; 1.0 g), Bi(NO3)3*5H2O (0.8 mmol) were mixed with ethylene glycol (40 mL) (mixture A). 0.8 mmol of NH4VO3was dissolved into 40 mL of deionized water (solution B). Mixture A and solution B were then mixed and stirred for 0.5 h, followed by keeping at 180°C for 10 h. Finally, the solid was filtered out and washed three times with ethanol. The BiVO4nanoparticles obtained were dried in an oven overnight. In the second step, the BiVO4nanoparticles, Bi(NO3)3*5H2O (0.8 mmol), and H2O (400 mL) were mixed under sonication (l / V = 1). Then 20 mL of sodium iodide (Nal) solution (20 mM) was dripped into the above suspension. After stirring for 2 h, the mixture was centrifuged at 10,000 rpm for 10 min at room temperature. The solid obtained was washed 3 times with distilled water and dried at 60°C overnight.

[0189] Oxidation of PE: photocatalytic oxidative depolymerization of PE (LDPE, Mn = 12,000) was performed in a 50 mL stainless-steel reactor equipped with a quartz window. PE (200 mg), photocatalyst BiOI / BiVO4(100 mg) and deionized water (20 mL) were added to the reactor container. Irradiation was performed with a 300 W LED lamp. The autoclave was then sealed and charged with 5 MPa of air. Subsequently, magnetic stirring was initiated at 800 rpm to ensure full contact between the PE and the reactive oxygen species during the reaction. Finally, the PE oxidation reaction was carried out at 150°C and irradiated by a 300 W lightemitting diode (LED) lamp for 6 h.

[0190] The results showed that the carbon yield of saturated dicarboxylic acids was as high as 83.0%, while monocarboxylic acids contributed -10.2% and CO2of~4.3%. Small amounts of byproducts (2.5%) containing unsaturated ketones and C=C groups were also detected. Among all the products, the dicarboxylic acids with a carbon number from C3to C30, with the highest yield being for tetradecanedioic acid (5.1%). Long-chain dicarboxylic acids (C10-C30) comprised 75% of the total products. Monocarboxylic acids ranged from C6to C30, with the majority concentrated in the Ce-C20, and no monocarboxylic acids below C6were detected. The yield of monocarboxylic acids was -10.2% of the total products.

[0191] Example C: illustrates oxidation of PE under embodiment (E1)

[0192] A mixture containing AcOnBu (2 mL) (1.0 equiv per repeating monomer unit), CoCI2*6H20 (3 mol% per repeating monomer unit), MnSO4*H2O (3 mol% per repeating monomer unit) and HBr (48% aqueous solution, 6 mol% per repeating monomer unit) (feeding sequence: CoCI2*6H20, MnSO4*H2O, polyolefin, AcOnBu, HBr) was heated at 120°C under O2balloon in an 18 mL vial.

[0193] Under those conditions, a milk bottle (HOPE) was converted into dicarboxylic acids with a 41% yield, including 75% of C4-C9dicarboxylic acids, alongside the detection of acetic acid and formic acid.

[0194] Example D: illustrates oxidation of PE under embodiment (E1)

[0195] Polyethylene samples (LDPE) were allowed to react with a gas mixture consisting of 6.2 vol% NO, 15.4 vol% O2, and 78.5 vol% N2(total pressure: 640 psi; 1 psi = 0.0689476 bar) at 170 °C for 16 h to be quantitatively degraded to soluble small organic molecule and COx. The soluble products were analyzed by NMR spectroscopy and gas chromatography.1H-NMR (CD3OD) spectra showed the presence of short chain a,ra-diacids: succinic acid (s, 3.2 ppm), glutaric acid (t, 3.0 ppm; p, 2.5 ppm), adipic acid (t, 3.0 ppm; m, 2.3 ppm), and pimelic acid (t, 3.0 ppm; m, 2.25 ppm; p, 2.0 ppm). There were additional low intensity broad peaks at 5.0- 5.75 ppm consistent with the presence of nitro compounds (the CH2NO2group of 6-nitrohexanoic acid appears at 5.1 ppm).

[0196] Moreover, it was discovered that there was a gradual increase in the average length of the diacid (i.e., more pimelic and adipic acids and less succinic acid) when the reaction of LDPE at 170 °C was carried out for 2, 5, 10, and 16 h, respectively. Likewise, lowering the reaction temperature from 170 to 140 °C, resulted in the formation of more pimelic and adipic acids and less succinic acid.

[0197] Example E: illustrates oxidation of PE under embodiment (E2)

[0198] The feedstock for this example was 10 g polyethylene and 100 g of a 70 wt.% aqueous nitric acid. The oxidation reaction was conducted in a vessel for 9 hours at 120°C and atmospheric pressure. The products were dicarboxylic acids (50-65 wt.%) and a separate fraction (35-50 wt.%) containing other components including nitro-substituted dicarboxylic acids. The dicarboxylic acids were separated by distillation of the reaction filtrate followed by evaporation to remove the majority of aqueous nitric acid. The table below provides the ranges of various dicarboxylic acids that were found in that fraction.1 Jic.irbc.xx 1 ic acid Wt %Oxalic acid (C2) 0-10%Maionic acid (C3 ) 0%Succinic acid <C4i 5- lS'VGhiniric acid (Cy< S-2ls"nAdipiv icid (f h i li i-29%Pimelie acid (C7) 10-20%Suberic acid I CX l 9-2n%Azclaic acid (C9) X- 13'%Schack acid l< in) 1-10%Undecanedioic acid (CH) 1 - 8%J Mkxamcdu'ic acid (C l 21 0-5%Iridecaiiediciic acid (C 13 ) 0-4%'leiradcc.inedioic acid I(’14I n-2%?<_ nt.idecatiedioic acid iCl s i 0-0.4%

[0199] Example F: illustrates oxidation of PE under embodiment (E2)

[0200] A 250 mL round bottom flask equipped with a magnetic stir bar was loaded with 10 g polyethylene and 100 g of a 67 wt.% HNOs. The reaction flask was equipped with a glass thermometer, placed onto a temperature-controlled IKA heating plate and attached to a water condenser. The reaction flask was stirred at maximum stir rate (2000 rpm) and heated to a desired reaction temperature. The beginning of the reaction time was marked once the desired temperature has been reached (15—20 min). After reaction time, the heater was turned off, the reaction flask lifted from the heater, and quickly cooled while stirring (15-20 min). The final mixture(aqueous product stream) was filtered through a filter paper on a Hirsch funnel into a 250 mL beaker. Filtrate collected in the 250 mL beaker was evaporated on a hot plate at 75°C to obtain crude dicarboxylic acid product. The crude dicarboxylic acid was subjected to GC analysis (Gas Chromatography) for dicarboxylic acid composition and LC analysis for additional product composition.Dicarboxylic acid Wt %Oxalic .ictd A 2 i 0%Maionic acid (C3 i 0%Succinic acid l( 4) 10-11%Glutaric acid fC5).Adipic acid (('<>! 1 M X%Pimelie acid (C’7) 15-17%Suberic Kid d 'K.i 13-15%A / elaic acid !C9’i l<i-12"».Seh.icie add (( 1% 5-9%Undecanedioic acid (CH) 3-6%Diidccanedioic acid IH 21 1-3%Tr.decatiedioic acid (CI G i i.S- l i"„ rctradecanedioic acid (C14 ) 0-0.2%Petitiidecancdhw acid (<’15 ' 0-0.2%

[0201] Example G: illustrates oxidation of PE under embodiment (E2)

[0202] The feedstock was contaminated plastic film from a material recovery facility. The composition of these films includes LDPE, HDPE, as well as a miscellaneous materials that were not identified. The surface contamination included dirt, debris, food residue and greases. These films were shredded into non-uniform pieces with average size 20 cmx20cm.

[0203] 30 g grams of feedstock was placed into a round bottom flask. 150 mL of a 69 wt.% nitric acid was added to the flask; the plastics were submerged in the liquid solution. The bottom of the flask was heated in a heating mantle; the opening of the flask was connected to a condenser. A stir bar was used to agitate the contents. Once the desired temperature (120°C) was reached, the reaction was timed for 24 hours. Then, the flask was allowed to cool to room temperature while stirring continued.

[0204] Subsequently, filtration via filter paper was performed to separate the oligomeric resin from the liquid solution. The liquid solution was heated to 130°C for 60 minutes to remove the nitric acid. The remaining crystalline solid comprised a mixture of dicarboxylic acids.

[0205] Example H: illustrates oxidation of PE under embodiment (E2)

[0206] A FlexiWave microwave system from Milestone (Sorisole, Italy) with a maximum power of 1900 W was utilized. A 0.5-g portion of LDPE powder ( / Ww~ 35000 g / mol, thickness 70 pm, length 200-300 pm) was placed in a FlexiWave Teflon vial together with 20 mL of aqueous nitric acid solution with the nitric acid (0.50 g / mL). The run times were set to be from 0.5 to 2 h. To reach the desired temperature of 180°C, a 20 min ramp time was needed; thereafter, the temperature was held constant at 180°C and the effect was 1200 W for the duration of the reaction.

[0207] Other examples:

[0208] Materials and methods

[0209] Ammonia was directly fed from a gas cylinder (Air Liquide + ref: NH3-N36+ 1 L + 100%, H2O<100ppm). Nitrogen and hydrogen were directly fed from gas lines.

[0210] Pimelic acid (111-16-0, Sigma-Aldrich, 98%), suberic acid (505-48-6, Sigma- Aldrich, 98%), azelaic acid (123-99-9, Sigma-Aldrich, 98%), sebacic acid (111-20- 6, Sigma-Aldrich, 98%), undecanedioic acid (1852-04-6, Sigma-Aldrich, 97%), dodecanedioic acid (693-23-2, Sigma-Aldrich, 99%), Methanol (67-56-1 , Sigma Aldrich 99.8%), adiponitrile (111-69-3, Sigma-Aldrich, 99%), pimelonitrile (646-20- 8, Sigma-Aldrich, 98%), suberonitrile (629-40-3, Sigma-Aldrich, 98%), sebaconitrile (1871-96-1 , Sigma-Aldrich, 99,2%), zinc oxide (1314-13-2, Sigma- Aldrich, 99,9%) para-toluene sulfonic acid monohydrate, p-TsOH«H2O (6192-52-5, Sigma-Aldrich, >98,5%), isopropanol (67-63-0, Fisher, >99,9%), Raney® Ni andammonium hydroxide 28 wt.% in water (1336-21-6, VWR, 28-32%) were used as received [Raney® Nickel is a registered trademark],

[0211] Nitrilation reactions were carried out in a quartz reactor with a volume of 200 mL, equipped with a mechanical stirrer (IKA Eurostar 60 control with a Rushton turbine), a heating mantle (Elit + type + 73W) and a reflux condenser, the latter connected to an ammonia abatement column. Ammonia was fed from a gas cylinder directly into the molten acid mixture via a gas dispersion tube (diameter, frit pore size, 2 cm above bottom of the reactor) while nitrogen was fed on top of the mixture via one of the necks of the reactor. Gas flows were controlled via individual pressure reducing valves and calibrated flow meters (Bronkhorst EL- FLOW Prestige FG-201CV). The temperature of the reaction was controlled by a thermocouple inserted into the reaction media (2 cm above bottom of the reactor). To follow the progress of the reaction, several aliquots of the reaction mixture were taken by inserting a glass rod.

[0212] Esterification reactions were carried out in a 1-L round bottom flask equipped with a mechanical stirrer. Methanol and water formed during the reaction were distilled off. The crude diesters were subsequently distilled under vacuum on a packed column. In a preferred one, two main fractions were formed, one corresponding to C4-C6 and the major one corresponding to C6-C12.

[0213] Hydrogenation reactions were carried out in a 35-mL autoclave made of Hastelloy C22 (Top Industrie) equipped with a mechanical stirrer (Rushton turbine) and a thermocouple inserted into the reaction media (1 cm above bottom of the reactor). Hydrogen was fed via a mass flow controller.

[0214] The compositions of the reaction mixtures were analyzed by gas chromatography (GC-FID, column HP-5MS Ul Intuvo from Agilent). FID = flame ionisation detector.

[0215] Example 1 : preparation of a mixture of dinitriles from a mixture of dicarboxylic acids (conversion MDI MDN)

[0216] A mixture composed of dicarboxylic acids as indicated in Table 1 was loaded into the nitrilation reactor together with 0.45 g of ZnO and 123 mg of p-TsOH»H2O, and was heated to a temperature of 220°C within 1 h under a nitrogen gas flow (2.5 L / h), and kept at this temperature for another 3 h under a mixed gas flow of nitrogen (5 L / h) and ammonia (10 L / h). During the temperature ramp-up, the acid mixture melted and the stirring speed was gradually increased to 300 rpm. During the ammonia feeding period the stirring speed was adjusted to 600 rpm. Next, the temperature was increased to 280°C within 1 h under a mixed gas flow of nitrogen (2.5 L / h) and ammonia (2.5 L / h) and kept under these conditions and mechanical stirring (600 rpm) for another 3 h. A black viscous mixture was obtained. The yieldsof the dinitriles (and diimides in the case of succinic and glutaric acid) correspond to the different starting acids are reported in Table 1 .Table 1

[0217] As can be seen, the mixture of the dicarboxylic acids (MDI) representative of a mixture obtained from the degradation of polyethylene yields a mixture of dinitriles (MDN). It can be seen that the yields of C4-C6 dinitriles are low.

[0218] Example 2: preparation of a mixture of dinitriles from a mixture of dicarboxylic acids (conversion MDI -> MDN)

[0219] A mixture composed of dicarboxylic acids as indicated in Table 2 was loaded into the nitrilation reactor together with 0.36 g (0.7 wt.%) of ZnO and 84 mg (0.17 wt.%) of p-TsOH«H2O, and heated to a temperature of 190°C within 1 h under a nitrogen gas flow (2.5 L / h), and kept at this temperature for another 3 h under a mixed gas flow of nitrogen (5 L / h) and ammonia (10 L / h). During the temperature ramp-up, the acid mixture melted, and the stirring speed was gradually increased to 300 rpm. During the ammonia feeding period the stirring speed was adjusted to 600 rpm. Next, the temperature was increased to 280°C within 1 h under a mixed gas flow of nitrogen (2.5 L / h) and ammonia (2.5 L / h) and kept under these conditions and mechanical stirring (600 rpm) for another 3 h. The yields of the dinitriles corresponding to the different starting acids are reported in Table 2.Table 2

[0220] Example 3: preparation of a mixture of dinitriles (MDN) from a mixture of dicarboxylic acids (MDI) (conversion MDI MDN)

[0221] A mixture composed of dicarboxylic acids as indicated in Table 3 was loaded into the nitrilation reactor together with 0.5 g (1 wt.%) of phosphoric acid and heated to a temperature of 190°C within 1 h under a nitrogen gas flow (2.5 L / h) , and kept at this temperature for another 3 h under a mixed gas flow of nitrogen (5 L / h) and ammonia (10 L / h). During the temperature ramp-up, the acid mixture melted, and the stirring speed was gradually increased to 300 rpm. During the ammonia feeding period the stirring speed was adjusted to 600 rpm. Next, the temperature was increased to 280°C within 1 h under a mixed gas flow of nitrogen (2.5 L / h) and ammonia (2.5 L / h) and kept under these conditions and mechanical stirring (600 rpm) for another 3 h. The yields of the dinitriles corresponding to the different starting acids are reported in Table 3.Table 3

[0001] Example 4: preparation of a mixture of dinitriles from a mixture of diacids (conversion MDI MDN)

[0002] A mixture composed of diacids as indicated in Table 4 was loaded into the nitrilation reactor together with 0.5 g of phosphoric acid, and was heated to a temperature of 160°C within 30 min under a nitrogen gas flow (2.5 L / h) while increasing steadily the stirring speed as the mixture melted. Then, the stirring speed was increased to 600 rpm and a mixed feed of nitrogen (5 L / h) and ammonia(10 L / h) was introduced via a frit plunged into the reaction medium. The temperature was increased to 180°C and kept for 1 h after which it was increased to 240°C. The feed was kept at 5 L / h for nitrogen and reduced to 5 L / h for ammonia. After another 1 h under these conditions, the feed of nitrogen and ammonia was reduced to 2.5 L / h for each gas and the temperature was increased to 300°C. After 2 h under these conditions the reaction was stopped. Note, that over the course of this last step the ammonia flow dropped to near zero due to a technical issue. The yields of the dinitriles corresponding to the different starting acids are reported in Table 4.Table 4

[0222] Example 5: preparation of a mixture of dinitriles from a mixture of dicarboxylic acids (conversion MDI MDN)

[0223] A mixture composed of dicarboxylic acids as indicated in Table 5 was loaded into the nitrilation reactor together with 0.5 g of phosphoric acid, and was heated to a temperature of 160°C within 30 min under a nitrogen gas flow (2.5 L / h) while increasing steadily the stirring speed as the mixture melted. Then, the stirring speed was increased to 600 rpm and a pure feed of ammonia (10 L / h) was introduced via a frit plunged into the reaction medium. The temperature was increased to 180°C and kept for 2 h after which it was increased to 240°C. The ammonia feed was reduced to 5 L / h. After another 1 h under these conditions, the ammonia feed was reduced to 2.5 L / h and the temperature was increased to 300°C. After 3 h under these conditions the reaction was stopped. The yields of the dinitriles corresponding to the different starting acids are reported in Table 5.Table 5

[0224] Example 6: preparation of a mixture of diamines (MDA) from a mixture of dinitriles (MDN) (conversion MDN MDA)

[0225] A mixture composed of dinitriles as indicated in Table 6 was loaded into the hydrogenation reactor, together with Raney® Ni (0.17 g), aqueous ammonia (8.08 g) and isopropanol (6 ml_). The reactor was closed and purged three times with nitrogen (10 bar), and filled with hydrogen (20 bar). The mixture was brought to a temperature of 110°C and stirred (1400 rpm) for 4 h. The consumption of hydrogen was monitored by measuring the pressure of hydrogen. After cooling down to room temperature, the reaction mixture was filtered (Millipore 0.45 pm hydrophilic) and separated from the solvent in a rotary evaporator. The yields of aliphatic diamines corresponding to the different starting compounds are also reported.Table 6

[0226] Example 7: preparation of a stream (Sb) under step b1)

[0227] A mixture composed of dicarboxylic acids (10.5 g) as indicated in Table 7 was mixed with 15 mL of water and stirred (40 rpm) for 15 min at a temperature of 10°C. The residual solid was filtered off (pore size 3) and mixed again with 15 mL of fresh water and treated as described. After performing this process three times, the solid residue was dried for 30 min at 40°C, affording 4.8 g of a mixture of acids (46% of the initial) with the composition indicated in Table 7. The three filtrates were combined and dried in a rotary evaporator and then for 30 min at 40°C, affording 6.1 g of a mixture of acids with the composition indicated in Table 7. It isimmediately apparent that succinic and glutaric acid were quantitatively washed out from the initial mixture.Table 7

[0228] Example 8: preparation of stream (Sb) under step b1)

[0229] The extraction was carried out as in example 7 but the extraction was instead carried out with 2x22.5 mL of water. The composition of the solid residue and of the filtrate obtained are almost identical to those of Table 7.

[0230] Example 9: distillation of MPA

[0231] Through simulation with ASPEN PLUS, it was determined that a batch column with 50 theoretical stages operating at 10 mbar absolute head pressure could be used for a MDA having the following composition: 500 g of diamines mixture containing 160 g of DA?, 150 g, DAa, 100 g of DAg, 60 g of DA10, 30 g of DA12. With a reflux ratio of 20, it is possible to isolate successively each of the individual diamines with very high purity >99.9 wt.% at temperatures between 75°C and 160°C.

[0232] Increasing the number of theoretical stages and the reflux ratio is adapted to complex mixtures of diamines (MDA) or of diesters (MDE).

[0233] Example 10: preparation of a mixture of diesters from a mixture of diacids

[0234] 150 g of crude diacids (purity determined by potentiometry close to 98.5%) are dissolved in 600 g of methanol. This solution is subsequently placed in a round bottom flask comprising 100 g of sulfonic resin (sold by Rohm & Haas under the name AmberLyst™ 36DRY) washed beforehand with methanol. The combined mixture is brought to reflux for 6 h. The acid functional groups are titrated by potentiometry with sodium hydroxide, showing that the degree of conversion of the acids reaches 95%. After cooling, the resins are separated by filtration and washed 3 times with 150 mL of methanol. The various methanol phases are combined andmethanol and water formed during the esterification are separated by distillation The crude diesters are subsequently distilled at 105°C under 20 mbar on a packed column. A yield of diesters close to 92% is obtained with a purity determined by chromatographic analysis, of greater than 99%.

[0235] Example 11 : preparation of a mixture of dinitriles from a mixture of diesters through gas phase process

[0236] 20 g of Y-AI2O3are introduced in the fixed bed reactor (20-40 mesh). The reactor + catalyst is heated @ 360°C under 100 mL / min nitrogen for 1 h to activate the catalyst. After the catalyst activation is complete, A mixture composed of diesters as indicated in Table 8 (MDE) and ammonia gas are continuously fed to the reactor (ammonia gas flow 22 mL / min, molar ratio of ammonia gas to MDE was 4:1). The reaction mixture was separated by gas— liquid and stored in a tank. After the reaction was complete, the reaction mixture in the storage tank was washed by adding 2 times the mass of dichloromethane in two parts and the organic phase (methanol + dichloromethane) was evaporated to dryness to give the product MDN in a molar yield close to 90%.Table 8nd: not determined

[0237] Example 12: preparation of dinitriles by liquid phase nitrilation of diesters

[0238] 100 g of MDE is introduced in a kettle reactor with 1 g of zinc oxide. The reactor is heated @ 160°C. Ammonia is introduced when temperature is reaching 160°C @ a rate of 1 mol / h. The introduction is lasting at least the time necessary to get an acid index below 0.1 mg KOH / g. Continuous removal of methanol took place during this step. The temperature is then increased till 270°C as in a conventional process starting form diacids. Continuous removal of water is done during the reaction. The reaction is halted after 6 hours. The global yield in MDN is close to90 mol% and is not significantly different between the nitrile whatever the chain length between C7 and C12.

Claims

ClaimsClaim 1. Method (M1) for preparing a mixture of aliphatic diamines (MDA) from a plastic product (P) comprising at least ethylene-based (co)polymer (POL), wherein• an ethylene-based (co)polymer (POL) designates a polymer comprising at least 75.0 mol% of ethylene units, preferably at least 80.0 mol%, more preferably at least 90.0 mol%, even more preferably at least 95.0 mol%, even more preferably at least 99.0 mol%;• the aliphatic diamines (DAX) are of formula H2N-(CH2)X-NH2(I), where x is an integer from 4 to 12 or from 6 to 12; the method comprising the following steps:• step a): plastic product (P) is subjected to a controlled oxidation of the ethylene-based (co)polymer (POL) effective to obtain a stream (Sa) comprising a mixture of aliphatic diacids (MDI) of formula HOOC-Alk-COOH where Aik designates a linear alkylene group, Aik being notably a C2-C25linear alkylene group;• optional step b): the stream (Sa) is treated through step b1) and / or step b2) in order to obtain a stream (Sb):- in step b1): the stream (Sa) is treated so as to increase the proportions of aliphatic diacids having a number of carbon atoms greater than or equal to 6 in the mixture of aliphatic dicarboxylic acids (MDI);- in step b2): if the reaction mixture used in step a) comprises an oxidizing agent selected in the group consisting of nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3), the stream (Sa) is treated in order to decrease the proportions of the organic acids bearing a nitro groups;• step c): the mixture of aliphatic diacids (MDI) present in stream (Sa) or in stream (Sb) is chemically transformed into a mixture of aliphatic diamines (MDA).Claim 2. Method (M1) according to claim 1 , where the mixture of aliphatic diamines (MDA) is further processed in order to separate and isolate, notably by one or more distillation steps, one or more of the diamines (DAX) present in MDA, notably a diamine selected in the group consisting of DAe (hexamethylenediamine), DAg (nonanediamine) and DA10 (decanediamine).Claim 3. Method (M2), notably according to claim 2, for preparing at least one aliphatic diamine (DAX) of formula H2N-(CH2)X-NH2from a plastic product (P) comprising at least ethylene-based (co)polymer (POL), wherein:• x is an integer from 6 to 12;• an ethylene-based (co)polymer (POL) designates a polymer comprising at least 75.0 mol% of ethylene units, preferably at least 80.0 mol%, more preferably at least 90.0 mol%, even more preferably at least 95.0 mol%, even more preferably at least 99.0 mol%; the method comprising the following sequence of steps a), b), c) and d) or a), b), c*), d*) and e*):• step a): plastic product (P) is subjected to a controlled oxidation of the ethylene-based (co)polymer (POL) effective to obtain a stream (Sa) comprising a mixture of aliphatic diacids (MDI) of formula HOOC-Alk-COOH where Aik designates a linear alkylene group, Aik being notably a C2-C25linear alkylene group;• optional step b): the stream (Sa) is treated through step b1) and / or step b2) in order to obtain a stream (Sb):- in step b1): the stream (Sa) is treated so as to increase the proportions of aliphatic diacids having a number of carbon atoms greater than or equal to 6 in the mixture of aliphatic diacids (MDI);- in step b2): if the reaction mixture used in step a) comprises an oxidizing agent selected in the group consisting of nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNOa), the stream (Sa) is treated in order to decrease the proportions of the organic acids bearing a nitro groups; where after step a) or step b): i) steps c) and d) are implemented:• step c): the mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is chemically transformed into a mixture of aliphatic diamines (MDA);• step d): the aliphatic diamine(s) (DAX) of formula H2N-(CH2)X-NH2is / are recovered and separated from MDA by at least one separation process, notably selected in the group consisting of distillation, extraction, adsorption, crystallization, chromatography and any combination thereof; or steps c*), d*) and e*) are implemented:• step c*): the mixture of aliphatic diacids (MDI) present in stream (Sa) or (Sb) is chemically converted into a mixture of aliphatic diesters (MDE) offormula ROOC-Alk-COOR where Aik designates a linear alkylene group and R is a linear or branched C1-C20 alkyl group, R being preferably methyl or ethyl;• step d*): one or more aliphatic diesters DEXof formula ROOC-(CH2)X- 2-COOR is / are separated from MDE and recovered by at least one separation process, being notably selected in the group consisting of distillation, extraction, adsorption, crystallization, chromatography and any combination thereof;• step e*): diester(s) DEXis / are then converted into the corresponding aliphatic diamine(s) DAXof formula H2N-(CH2)X-NH2, the chemical conversion being notably based on the conversion of a diester into a dinitrile which is converted into the diamine.Claim 4. Method according to any one of the preceding claims, wherein the ethylene-based (co)polymer (POL) is a polyolefin selected in the group of homopolymers of ethylene and copolymers of ethylene and at least one comonomer selected in the group consisting of C3- C12 alpha-olefins and C3-C12 dienes.Claim 5. Method according to any one of the preceding claims, wherein the controlled oxidation of step a) consists in bringing the ethylene-based (co)polymer (POL) present in plastic product (P) into contact with at least one oxidizing agent, notably selected in the group consisting of oxygen (O2), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), nitric acid (HNO3) and combinations thereof, the oxidizing agent preferably being O2 or NO+O2 or HNO3.Claim 6. Method according to any one of the preceding claims, wherein the mixture MDI obtained at the end of step a) and / or step b) comprises diacids selected in the group consisting of oxalic acid (Dl2); malonic acid (Dl3); succinic acid (Dl4); glutaric acid (Dl5); adipic acid (Die) ; pimelic acid (DI?); suberic acid (Dis); azelaic acid (Dig); sebacic acid (DI10); undecanedioic acid (Din); dodecanedioic acid (DI12) and aliphatic diacids having 13 or more carbon atoms (DI>13).Claim 7. Method according to any one of the preceding claims, wherein in the mixture MDI obtained at the end of step a) or at the end of step b),- the proportion of oxalic acid (DI2) is lower than or equal to 12.0 wt.% (< 12.0 wt.%), preferably lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of malonic acid (Dl3) is lower than or equal to 12.0 wt.% (< 12.0 wt.%), preferably lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of succinic acid (DU) is lower than or equal to 20.0 wt.% (< 20.0 wt.%), preferably lower than 15.0 wt.% (< 15.0 wt.%), preferably lower than 5.0 wt.% (< 5.0 wt.%); these proportions being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.Claim 8. Method according to any one of the preceding claims, wherein in the mixture MDI obtained at the end of step a) or at the end of step b),- the proportion of dodecanedioic acid (DI12) is lower than or equal to 10.0 wt.% (< 10.0 wt.%), preferably lower than 5.0 wt.% (< 5.0 wt.%); and / or- the proportion of tridecanedioic acid (DI13) is lower than or equal to 5.0 wt.% (< 5.0 wt.%), preferably lower than 2.0 wt.% (< 2.0 wt.%); and / or- the proportion of each of the aliphatic dicarboxylic acids having from 6 to 12 carbon atoms (DI6-12) is greater than or equal to 2.0 wt.% (> 2.0 wt.%), preferably greater than or equal to 1 .0 wt.% (> 1 .0 wt.%); these proportions being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.Claim 9. Method according to any one of the preceding claims, wherein in the mixture MDI obtained at the end of step a) or at the end of step b),- the total proportion of the aliphatic dicarboxylic acids having from 6 to 12 carbon atoms (DI6-12) is greater than or equal to 40.0 wt.% (> 40.0 wt.%), preferably greater than or equal to 50.0 wt.% (> 50.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI; and / or- the total proportion of the aliphatic dicarboxylic acids having from 2 to 13 carbon atoms (Dl2~i3) is greater than or equal to 60.0 wt.% (> 60.0 wt.%), preferably greater than or equal to 70.0 wt.% (> 70.0 wt.%), more preferably greater than or equal to 80.0 wt.% (> 80.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDIClaim 10. Method according to any one of the preceding claims, wherein in the mixture MDI obtained at the end of step a) or at the end of step b), the total proportion of the aliphatic dicarboxylic acids having > 20 carbon atoms (Dl>2o) is lower than or equal to 10.0 wt.% (<10.0 wt.%), preferably lower than or equal to 5.0 wt.% (< 5.0 wt.%), this proportion being given in wt.% relative to the total proportions of all aliphatic dicarboxylic acids in MDI.Claim 11 . Method according to any one of the preceding claims, wherein in the mixture MDI obtained at the end of step a) or at the end of step b), the total proportion of the aliphatic dicarboxylic acids having > 20 carbon atoms (DI>20) is lower than or equal to 5.0 wt.%.Claim 12. Method according to any one of the preceding claims, wherein:• the mixture MDA obtained i) with method (M1) or ii) in step c) of method (M2): comprises diamines of formula H2N-(CH2)X-NH2where x is an integer from 4 to 12 where the total proportion of said diamines is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, this proportion being relative to the total proportion of all aliphatic diamines present in MDA; and / or comprises the diamines of formula H2N-(CH2)X-NH2where x is an integer from 6 to 12 where the total proportion of said diamines is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, this proportion being relative to the total proportion of all aliphatic diamines present in MDA.Claim 13. Method according to any one of the preceding claims, wherein:• the mixture of aliphatic diesters (MDE) obtained with i) method (M1) if step c) involves the conversion of (MDI) into a mixture of aliphatic diesters (MDE) or ii) in step c*) of method (M2): comprises diesters of formula ROOC-(CH2)X.2-COOR where x is an integer from 4 to 12 where the total proportion of said diesters is at least 40.0 wt%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, even more preferably at least 80.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE; and / or comprises the diesters of formula ROOC-(CH2)X.2-COOR where x is an integer from 6 to 12 where the total proportion of said diesters is at least 40.0 wt.%, preferably at least 50.0 wt.%, more preferably at least 60.0 wt.%, even more preferably at least 70.0 wt.%, this proportion being relative to the total proportion of all aliphatic diesters present in MDE.Claim 14. Method according to any one of the preceding claims, wherein the chemical conversion of step c) is based on the following chemical reactions:HOOC-Alk-COOH N=C-Alk-C=N H2N-Alk-NH2or on the following ones:HOOC-Alk-COOH -> ROOC-Alk-COOR NnC-Alk-C=N -> H2N-Alk-NH2where Aik designates a linear alkylene group and R is a Ci-C20alkyl group, notably ethyl or methyl.Claim 15. Method according to any one of the preceding claims, wherein the chemical conversion of step c) is based:- on the conversion of the mixture of aliphatic dicarboxylic acids (MDI) into a mixture of aliphatic dinitriles (MDN) which is converted in MDA; or- on the conversion of the mixture of aliphatic dicarboxylic acids (MDI) into a mixture of aliphatic diesters (MDE) which is converted in a mixture of aliphatic dinitriles (MDN) which is converted in MDA.Claim 16. Method according to any one of the preceding claims, wherein step c) or step c*) involves the conversion of a mixture of aliphatic diacids (MDI) into a mixture of aliphatic diesters (MDE) and the total proportion in MDE of the aliphatic diesters (DEX) that are derived from dicarboxylic acids having >6 carbon atoms is at least 80.0 wt.%, this proportion being relative to the total weight of MDE.Claim 17. Method according to claim 3 or any one of claims 3-16 in combination with claim 3, wherein step d) or step d*) comprises one or more distillation steps, a distillation step being based on the use of a distillation column.Claim 18. Method according to claim 3 or any one of claims 3-17 in combination with claim 3, wherein: in step d), the aliphatic diamine(s) (DAX) of formula H2N-(CH2)X-NH2is / are recovered by one or more distillation steps; or in step d*), the aliphatic diester(s) (DEX) of formula ROOC-(CH2)X.2-COOR is / are recovered by one or more distillation steps; each distillation step being based on the use of a distillation column.Claim 19. Method according to any one claims 2-18, wherein after step d) or step e*), diamine DAXis further purified through one or more distillation steps.Claim 20. Method according to any one claims 2-19, wherein the recovered aliphatic diamine DAXexhibits a purity (p) of at least 99.0 wt.%, preferably at least 99.5 wt.%, x being notably any one of the integers present in the range {6-12}, purity (p) being notably determined by gas chromatography (GC) or high pressure liquid chromatography (HPLC).Claim 21. Method according to any one of claims 2-20, wherein the total proportion of monoamine(s) in the recovered aliphatic diamine (DAX) is at most 0.5 wt.%, this proportion being based on the total weight of the aliphatic diamine.Claim 22. Method according to any one of claims 2-21 , wherein recovered aliphatic diamine (DAX) is hexamethylenediamine (x=6), nonanediamine (x=9) or decanediamine (x=10).Claim 23. Method according to any one of claims 2-22, wherein recovered aliphatic diamine DAXis part of a composition (C) comprising diamine DAXof formula NH2-(CH2)X-NH2and the diamines DAx+iand DAx~i having respective formulae NH2-(CH2)X+I-NH2and NH2-(CH2)X.I- NH2with the following proportions:- diamine DAX: at least 99.0 wt.%, preferably at least 99.5 wt.%;- each diamine DAx+iand DAx~i : at most 0.5 wt.%, preferably at most 0.1 wt.%; these proportions being based on the total weight of composition (C); or the following ones:- diamine DAX: at least 99.5 wt.%;- diamine DAx+i: at most 0.1 wt.%;- diamine DAx.i : at most 0.1 wt.%; these proportions being based on the total weight of composition (C); x being notably an integer from 6 to 12.Claim 24. Method according to claim 23, wherein in composition (C), the total proportion of the aliphatic diamines DAyof formula NH2-(CH2)y-NH2where y is an integer in the range {0- 12} and y is different from x, x+1 and x-1 , is at most 0.5 wt.%.Claim 25. Method according to claim 23 or claim 24, wherein each diamine DAx+iand DAx-i is present in composition (C) at a proportion of at least 0.1 ppm, more particularly at least 0.5 ppm, more particularly at least 1 .0 ppm, this proportion being based on the total weight of composition (C).Claim 26. Method according to any one of claims 23-25, wherein the total proportion of monoamine(s) in composition (C) of the invention is at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).Claim 27. Method according to any one of claims 23-26, wherein the total proportion of Ci- Cis monoamine(s) in composition (C) of the invention is at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).Claim 28. Method according to any one of the preceding claims, wherein the total proportion of the aliphatic diamines (DAX) present in MDA is at least 10.0 wt%, this proportion being relative to the total weight of MDA.Claim 29. Composition (C), notably prepared by a method of any one of claims 2-28, comprising aliphatic diamine (DAX) of formula NH2-(CH2)X-NH2and the aliphatic diamines (DAx+i) and (DAx~i) of respective formulae NH2-(CH2)X+I-NH2and NH2-(CH2)X.I-NH2with the following proportions:- diamine DAX: at least 99.0 wt.%, preferably at least 99.5 wt.%;- each diamine DAx+iand DAx-i: at most 0.5 wt.%, preferably at most 0.1 wt.%; these proportions being based on the total weight of composition (C); where x is an integer from 6 to 12, x being notably 6, 9 or 10.Claim 30. Composition (C) according to claim 29, wherein the proportion of DAXis at least 99.5 wt.%.Claim 31. Composition (C) according to any one of claims 29-30, wherein the total proportion of monoamine(s) in composition (C) is at most 0.5 wt.%, this proportion being based on the total weight of the aliphatic diamines.Claim 32. Composition (C) according to any one of claims 29-31 , wherein aliphatic diamine DAXis hexamethylenediamine (x=6), nonanediamine (x=9) or decanediamine (x=10).Claim 33. Composition (C) according to claim 29-32, wherein the total proportion of the aliphatic diamines DAyof formula H2N-(CH2)y-NH2in composition (C) where y is an integer in the range {6-12} and y is different from x, x+1 and x-1 , is at most 0.5 wt.%.Claim 34. Composition (C) according to any one of claims 29-33, wherein each diamine DAx+iof formula H2N-(CH2)X+I-NH2and DAx-i of formula H2N-(CH2)X.I-NH2present incomposition (C) has a proportion of at least 0.1 ppm, more particularly at least 0.5 ppm, more particularly at least 1.0 ppm, this proportion being based on the total weight of composition (C). Claim 35. Composition (C) according to any one of claims 29-34, wherein the total proportion of monoamine(s) in composition (C) is at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).Claim 36. Composition (C) according to any one of claims 29-35, wherein the total proportion of C1-C18 monoamine(s) in composition (C) is at most 0.5 wt.%, preferably at most 0.25 wt.%, this proportion being based on the total weight of composition (C).Claim 37. Use of the composition (C) according to any one of claims 29-36 for the preparation of a polyamide comprising in polymerized form the diamine DAX.

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