Sports footwear with improved recyclability

Abstract

The invention mainly relates to single-material footwear consisting of: (i) 15% to 65% by weight of thermoplastic polymer chosen from polyamides or copolyamides; (ii) 35% to 85% by weight of PEBA thermoplastic elastomer; and (iii) 0 to 15% by weight of additives. The invention also relates to a method for manufacturing same and also for the recycling thereof, and also to the composition obtainable after recycling and the use thereof for the manufacture of footwear.

Description

[0001] SPORTS SHOES WITH IMPROVED RECYCABILITY

[0002] [Technical field]

[0003] The present patent application relates to shoes with improved recyclability, their manufacturing process as well as their recycling process and the compositions thus obtained as well as their use for the manufacture of shoes.

[0004] [Earlier technique]

[0005] The circular economy helps limit waste production, the depletion of the planet's resources, and environmental impact. Currently, there is a particular focus on producing objects using materials that, after recycling, will have sufficient properties to allow their use in high-performance applications, not just lower-performance applications such as street furniture or roads.

[0006] In the context of sustainable consumption and production patterns, the recyclability of frequently renewed items such as sports equipment and the quality of the resulting recycled products are of particular importance. However, the performance requirements for these items are particularly high.

[0007] Patent EP 3 081 109 B1 proposes, in order to facilitate their recycling, a sports shoe whose upper part (referred to in English as the "upper") and the sole are mainly or entirely made of the same thermoplastic base material. However, it appears that difficulties remain in that the recycling product thus obtained has limits in terms of performance due to the fact that the density of the parts of the shoe differs according to their respective functions.

[0008] Patent application WO 2020 / 201370 A1 proposes a method for recycling such shoes in which the shoe is crushed and then melted. This document, like the previous one, focuses on TPU.

[0009] It is important that the products used are stable enough to be recycled safely. However, when TPU is recycled, the formation of isocyanates, which are hazardous compounds, can occur. Furthermore, the shoes offered do not always allow for the production of recycled compositions with sufficient properties to allow their use as performance polymers.

[0010] [Summary of the invention]

[0011] The invention therefore aims to propose a single-material shoe whose composition is studied so as to allow the obtaining of a composition capable of being used for applications requiring high performance.

[0012] It has been shown that the exclusive combination (without additives) in a single-material shoe of a polyamide fraction and a polyether with amide blocks (PEBA) fraction allows better maintenance of properties during recycling.

[0013] Indeed, the presence of polyamides in the composition provides good resistance to aging and therefore to the life of the object and its recycling process. For its part, the presence of PEBA, which is more flexible, contributes to improving the mechanical resistance of the object throughout its life, before and after recycling.

[0014] Also, according to a first aspect, the invention relates to a single-material shoe consisting of:

[0015] (i) 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides;

[0016] (ii) 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBA; and

[0017] (iii) 0 to 15% by weight of additives.

[0018] According to a preferred embodiment, the shoe consists of:

[0019] (i) 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides;

[0020] (ii) 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBA; and

[0021] (iii) 0 to 15% by weight of additives.

[0022] According to one embodiment, component (i) comprises a polyamide or copolyamide chosen from PA 612, PA 613, PA 912, PA 1010, PA 1012, PA 6, PA 11, PA 12, PA 6 / 11, PA 6 / 12, PA 11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014 alone or as a mixture. According to one embodiment, component (ii) comprises a PEBA selected from those comprising blocks of PA 6 / 11 and derived from PTMG, PA 6 / 12 and derived from PTMG, PA 11 / 12 and derived from PTMG, PA 6 / 11 / 12 and derived from PTMG, PA 6 / 66 / 12 and derived from PTMG, PA 6 / 1010 and derived from PTMG, PA 6 / 1012 and derived from PTMG, PA 6 / 1010 / 1012 and derived from PTMG, PA 6 and derived from PTMG, PA 11 and derived from PTMG, PA 12 and derived from PTMG, PA 6 and derived from PEG, PA 11 and derived from PEG, and PA 12 and derived from PEG.

[0023] According to one embodiment, the polyamides or copolyamides of component (i) have an average ratio of the number of carbon atoms per amide function greater than 6, preferably greater than 8 and in particular 10 or more.

[0024] According to one embodiment, the single-material shoe comprises, as additive, 0 to 10% by weight, preferably 0.1 to 4% by weight of adhesive.

[0025] According to one embodiment, the adhesive comprises or is made of polyurethane.

[0026] According to a second aspect, the invention relates to a method for manufacturing such a single-material shoe, comprising the steps consisting of:

[0027] I. Provide a material comprising one or more polyamides or copolyamides, one or more PEBAs and / or one or more additives suitable for each component of the shoe;

[0028] II. Manufacture the components of the shoe from the respective thermoplastic material; and

[0029] III. Assembling the components of the shoe, using an adhesive if necessary, to form the finished shoe, wherein the materials used are chosen such that the finished shoe comprises 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides; 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives.

[0030] According to one embodiment, the materials used are chosen in such a way that the finished shoe comprises 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives. According to a third aspect, the invention relates to a method for recycling such a single-material shoe, comprising the steps consisting of:

[0031] (a) supply of the used shoe;

[0032] (b) grinding the clean shoe to obtain a ground material;

[0033] (c) heating the ground material until it melts; and

[0034] (d) extrusion of the molten mass into granules.

[0035] According to one embodiment, it further comprises the step of:

[0036] (e) adding new material to the used shoe shredder before or after step (d).

[0037] According to a fourth aspect, the invention relates to a recycled polymer composition capable of being obtained by said recycling process.

[0038] According to a fifth aspect, the invention relates to a composition consisting of:

[0039] (a) 20 to 100% by weight, advantageously from 30 to 99% by weight, even more preferably from 50 to 98% by weight of granulated single-material shoe shredder, consisting of: a. 15 to 65%, in particular 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; b. 35 to 85%, in particular 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and c. 0 to 15% of additives;

[0040] (b) 0 to 80% by weight, preferably 1 to 70% by weight and in particular 2 to 50% by weight of virgin polymer chosen from polyamides, copolyamides and PEBA; and

[0041] (c) 0 to 50% by weight of additives.

[0042] According to a final aspect, the invention aims at the use of said composition resulting from the recycling process for the manufacture of shoes, in particular single-material shoes. [Description of embodiments]

[0043] Definition of terms

[0044] The term "polymer blend" is understood to mean a macroscopically homogeneous polymer composition. The term also includes such compositions composed of immiscible phases dispersed on a micrometric scale.

[0045] The term "copolymer" is understood to mean a polymer resulting from the copolymerization of at least two chemically different types of monomer, called comonomers. A copolymer is therefore formed from at least two repeating units. It can also be formed from three or more repeating units. More specifically, the term "block copolymer" or "block copolymer" is understood to mean copolymers in the above sense, in which at least two distinct monomer blocks are covalently linked. The length of the blocks can be variable. Preferably, the blocks are composed of 1 to 1000, preferably 1 to 100, and in particular 1 to 50 repeating units, respectively. The link between the two monomer blocks may sometimes require an intermediate non-repeating unit called a connecting block.

[0046] The term "monomer" should be taken in the context of polyamides in the sense of "repeating unit". Indeed, the case where a repeating unit of the polyamide is made up of the association of a diacid with a diamine is special. It is considered that it is the association of a diamine and a diacid, that is to say the diamine.diacid couple (in equimolar quantity), which corresponds to the monomer. This is explained by the fact that individually, the diacid or the diamine is only a structural unit, which is not sufficient on its own to polymerize.

[0047] The term "mono-material shoe" is understood to mean a shoe made essentially from polymers of a given family. In the broad definition of the invention, these are thermoplastic polymers chosen from polyamides and their copolymers as well as polyether block amides (PEBA). In principle, a mono-material shoe will not contain other polymers, whether thermosetting polymers or polymers belonging to other families of thermoplastic polymers. On the other hand, it may contain small quantities of agents called additives, either in the formulation of the thermoplastic polymer used for the respective parts of the shoe, or for specific parts of the shoe. As an example, the presence in the mono-material shoe of an adhesive used for its assembly is mentioned.Advantageously, it is a thermoplastic adhesive and in particular an adhesive in the form of polyamide or copolyamide. However, it is also possible to provide a non-thermoplastic adhesive, for example polyurethane, when its presence does not exceed an amount of 10% by weight and preferably 4% by weight relative to the total weight of the shoe.

[0048] The term "inherent viscosity" means the viscosity as measured by the following steps:

[0049] - Taking polymer samples between 0.07 and 0.10 g and preferably 0.15 g maximum,

[0050] - Addition of a sufficient quantity of m-cresol solvent by weighing in order to obtain a concentration (C) of 0.5 g / L,

[0051] - Heating the mixture with stirring on a hot plate, regulated at 100°C ± 5°C, until the polymer is completely dissolved;

[0052] - Cooling the solution to room temperature, preferably for at least 30 minutes;

[0053] - Measurement of the flow time tO of the pure solvent and the flow time t of the solution using a micro-Ubbelohde tube viscometer in a thermostatically controlled bath regulated at 20°C ± 0.05°C,

[0054] - Calculation of viscosity according to the formula 1 / C x Ln (t / tO), where C represents the concentration and Ln the natural logarithm.

[0055] For each sample, three measurements are made on different solutions and then the average is calculated.

[0056] - the term "thermoplastic polymer" means a polymer which has the property of softening when heated sufficiently, and which, upon cooling, becomes hard again.

[0057] The term "semi-crystalline polyamide" is understood to mean a polyamide which has a melting temperature (Tf) in DSC according to the ISO 11357-3:2013 standard, and an enthalpy of crystallization during the cooling step at a rate of 20K / min in DSC measured according to the ISO 11357-3:2013 standard of greater than 20 J / g, preferably greater than 30 J / g.

[0058] The term "enthalpy of fusion" means the heat consumed during the solid / liquid transition of the thermoplastic elastomer, as measured by differential scanning calorimetry, according to ISO 11257-3:1999.

[0059] The nomenclature used to designate the polyamides according to the present invention follows the ISO 1874-1:2010 standard.

[0060] In the following, the hardness is as measured according to ISO 868:2003. The mono-material shoe

[0061] In its broadest definition, the present invention relates in particular to single-material shoes comprising parts which are essentially constituted, that is to say excluding additives, of polymers from the family of polyamides, copolyamides and PEBAs. Apart from these parts, the single-material shoe may comprise in small proportion (less than 12%, preferably less than 10% and even more preferably less than 5% by weight relative to the weight of the finished single-material shoe) functional or decorative elements composed of different materials. Advantageously, the single-material shoe consists essentially of polymers from this family.

[0062] According to one aspect, the invention relates to a single-material shoe consisting of:

[0063] (i) 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides;

[0064] (ii) 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBA; and

[0065] (iii) 0 to 15% by weight of additives.

[0066] Polyamide and copolyamide

[0067] As mentioned above, the single-material shoe according to the invention comprises one or more polyamides or copolyamides.

[0068] In this presentation, the term "copolyamide" refers to polymers resulting from the polymerization of several monomers linked by amide functions. However, this definition excludes copolymers containing polyether blocks such as PEBA.

[0069] According to one embodiment, the polyamide comes from the condensation of one or more monomers of the α,β-aminocarboxylic acid type or one or more monomers of the lactam type (type “Z”).

[0070] Examples of α,α-amino carboxylic acids include alpha-omega amino acids, such as aminocaproic, 7-aminoheptanoic, 11-aminoundecanoic, n-heptyl-11-aminoundecanoic, and 12-aminododecanoic acids.

[0071] Examples of lactams include those having 3 to 12 carbon atoms on the main ring and which may be substituted. Examples include P,p-dimethylpropriolactam, α,α-dimethylpropriolactam, amylolactam, caprolactam, capryllactam, oenantholactam, 2-pyrrolidone and lauryllactam.

[0072] Most often, semi-crystalline polyamides will be used for the manufacture of single-material shoes. Advantageously, these are aliphatic polyamides. Particularly preferred are polyamides whose average number of carbon atoms per amide function is greater than 6, preferably greater than 8 and particularly 10 or more. Advantageously, these are polyamides devoid of cyclic structures, whether aromatic or cycloaliphatic.

[0073] Examples of this type of preferred polyamides include PA 6, PA 11 and PA 12, as well as mixtures thereof.

[0074] According to one embodiment, the polyamide comes from the condensation of a dicarboxylic acid with an aliphatic, cycloaliphatic or aromatic diamine (type “XY”, X representing the number of carbon atoms of the diamine and Y representing the number of carbon atoms of the dicarboxylic acid).

[0075] Examples of diamines include aliphatic diamines having 4 to 16 and preferably 6 to 12 carbon atoms, where diamine X can also be aromatic or alicyclic. Examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5 diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophoronediamine (IPD), methyl pentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4 aminocyclohexyl)methane (BMACM), methaxylyenediamine, trimethylhexamethylenediamine.

[0076] Examples of dicarboxylic acids that may be mentioned are acids Y having between 4 and 18 carbon atoms, preferably 9 to 12 carbon atoms. Examples that may be mentioned are butanedioic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, 1,4 cyclohexyldicarboxylic acid, terephthalic acid, the sodium or lithium salt of sulfoisophthalic acid, dimerized fatty acids (in particular those having a dimer content of at least 98% and / or hydrogenated) and 1,2-dodecanedioic acid HOOC-(CH2)IO-COOH.

[0077] Examples of this type of preferred polyamides include PA 516 resulting from the condensation of pentamethylenediamine with hexadecanedioic acid, PA 612 resulting from the condensation of hexamethylenediamine and 1,12-dodecanedioic acid; PA 613 resulting from the condensation of hexamethylenediamine and brassylic acid; PA 912 resulting from the condensation of 1,9-nonanediamine and 1,12-dodecanedioic acid; PA 129 resulting from the condensation of 1,12-dodecamethylenediamine with azelaic acid; PA 1010 resulting from the condensation of 1,10-decanediamine and sebacic acid; and PA 1012 resulting from the condensation of 1,10-decanediamine and 1,12-dodecanedioic acid.

[0078] According to one embodiment, the polyamide is a copolyamide resulting from polycondensation:

[0079] - at least two different monomers chosen from different α,γ-amino carboxylic acids or two different lactams or a lactam and an α,γ-amino carboxylic acid of different carbon numbers; or

[0080] -at least one α,α-amino carboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid, or

[0081] - an aliphatic diamine with an aliphatic dicarboxylic acid and at least one other monomer chosen from aliphatic diamines different from the previous one and aliphatic diacids different from the previous one.

[0082] The notation PA Z / XY, PA Z / Z', PA Z / XY / X'Y', PA Z / Z' / XY, PA Z / Z' / XY / X'Y', etc. refers to copolyamides in which XY, Z, X'Y', Z' etc. represent homopolyamide monomers XY, Z as described above, X'Y' being the same as or different from XY, Z' being the same as or different from Z.

[0083] According to one embodiment, one of the monomers constituting a copolyamide may represent more than 50%, preferably more than 60% by mass of the total mixture of monomers. According to one embodiment, one of the monomers constituting a copolyamide may represent less than 90%, preferably less than 80% by mass of the total mixture of monomers.

[0084] Examples of particularly preferred copolyamides are the blocks PA 6 / 11, PA 6 / 12, PA 11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, as well as mixtures thereof.

[0085] Blends of polyamides may also be used, which may be blends of aliphatic polyamides and semi-aromatic polyamides and blends of aliphatic polyamides and cycloaliphatic polyamides.

[0086] According to one embodiment, the single-material shoe comprises 15 to 65%, in particular 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides. For example, it may comprise 15 to 20%, or 20 to 25%, or 25 to 30%, or 30 to 35%, or 35 to 40%, or 40 to 45%, or 50 to 55%, or 55 to 60%, or 60 to 65% by weight of polyamides and / or copolyamides, relative to the weight of the single-material shoe.

[0087] Polyether block amides (PEBA)

[0088] The single-material shoe of the invention further comprises one or more PEBAs. According to one embodiment, the shoe comprises parts essentially made of PEBA alone or in a mixture with one or more polyamides or copolyamides as described above.

[0089] According to one embodiment, the thermoplastic elastomer is a polyether with amide blocks (PEBA). In these copolymers, the rigid block is a polyamide comprising at least one Z or XY type unit

[0090] • Z being a lactam or an amino acid having 6 to 18 carbon atoms,

[0091] • X being a diamine having 4 to 48 carbon atoms

[0092] • Y being a diacid having 6 to 48 carbon atoms.

[0093] PEBAs result from the polycondensation of polyamide blocks (rigid or hard blocks) with reactive ends with polyether blocks (flexible or soft blocks) with reactive ends, such as, among others, polycondensation:

[0094] 1) polyamide blocks with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chain ends;

[0095] 2) of polyamide blocks with dicarboxylic chain ends with polyetherdiols (aliphatic a,co-dihydroxylated polyoxyalkylene blocks), the products obtained being, in this particular case, polyetheresteramides.

[0096] Polyamide blocks with dicarboxylic chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-limiting dicarboxylic acid. Polyamide blocks with diamine chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-limiting diamine.

[0097] Three types of polyamide blocks can be used advantageously.

[0098] According to a first type, the polyamide blocks come from the condensation of a dicarboxylic acid, in particular those having from 4 to 36 carbon atoms, preferably those having from 4 to 20 carbon atoms, more preferably from 6 to 18 carbon atoms, and an aliphatic or aromatic diamine, in particular those having from 2 to 20 carbon atoms, preferably those having from 6 to 14 carbon atoms.

[0099] Examples of dicarboxylic acids include 1,4-cyclohexyldicarboxylic acid, butanedioic, glutaric, adipic, suberic, azelaic, sebacic, dodecanedioic, brassylic, hexadecanedioic, octadecanedioic, terephthalic and isophthalic acids, as well as dimerized fatty acids.

[0100] Examples of diamines include tetramethylenediamine, hexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, isomers of bis-(4-aminocyclohexyl)-methane (BACM), bis-(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2-2-bis-(3-methyl-4-aminocyclohexyl)-propane (BMACP), paraamino-di-cyclohexyl-methane (PACM), isophoronediamine (IPDA), 2,6-bis-(aminomethyl)-norbornane (BAMN) and piperazine (Pip).

[0101] Advantageously, polyamide blocks PA 412, PA 414, PA 418, PA 516, PA 610, PA 612, PA 613, PA 614, PA 618, PA 912, PA 1010, PA 1012, PA 1014, PA 1018 and PA 129 are used. In the PA XY notation, X represents the number of carbon atoms from the diamine residues, and Y represents the number of carbon atoms from the diacid residues, conventionally.

[0102] According to a second type, the polyamide blocks result from the condensation of one or more α,β-aminocarboxylic acids and / or one or more lactams having from 6 to 12 carbon atoms in the presence of a dicarboxylic acid having from 4 to 18 carbon atoms or a diamine. Examples of lactams include caprolactam, oenantholactam and lauryllactam. Examples of α,β-aminocarboxylic acids include aminocaproic, amino-7-heptanoic, amino-10-decanoic, amino-11-undecanoic and amino-12-dodecanoic acids.

[0103] Advantageously, the polyamide blocks of the second type are blocks of PA 10 (polydecanamide), PA 11 (polyundecanamide), PA 12 (polydodecanamide) or PA 6 (polycaprolactam). In the PA X notation, X represents the number of carbon atoms from the amino acid residues.

[0104] According to a third type, the polyamide blocks result from the condensation of at least one α,α-aminocarboxylic acid or lactam with at least one diamine and at least one dicarboxylic acid.

[0105] In this case, the polyamide PA blocks are prepared by polycondensation:

[0106] - linear or aromatic aliphatic diamine(s) having X carbon atoms;

[0107] - of the dicarboxylic acid(s) having Y carbon atoms; and - of the comonomer(s) {Z}, chosen from lactams and α,α-aminocarboxylic acids having Z carbon atoms and equimolar mixtures of at least one diamine having XI carbon atoms and at least one dicarboxylic acid having Y1 carbon atoms, (XI, Yl) being different from (X, Y),

[0108] - said comonomer(s) {Z} being preferably introduced in a weight proportion advantageously ranging up to 50%, preferably up to 20%, even more advantageously up to 10% relative to all of the polyamide precursor monomers;

[0109] - in the presence of a chain limiter chosen from dicarboxylic acids.

[0110] Advantageously, the dicarboxylic acid having Y carbon atoms is used as chain limiter, which is introduced in excess relative to the stoichiometry of the diamine(s).

[0111] According to a variant of this third type, the polyamide blocks result from the condensation of at least two α,β-aminocarboxylic acids or at least two lactams having 6 to 12 carbon atoms or a lactam and an aminocarboxylic acid not having the same number of carbon atoms in the possible presence of a chain limiter.

[0112] Examples of aliphatic α,α-aminocarboxylic acids include aminocaproic, 7-aminoheptanoic, 10-aminodecanoic, 11-aminoundecanoic, and 12-aminododecanoic acids. Examples of lactams include caprolactam, oenantholactam, and lauryllactam. Examples of aliphatic diamines include hexamethylenediamine, dodecamethylenediamine, and trimethylhexamethylenediamine.

[0113] Examples of cycloaliphatic diacids include 1,4-cyclohexyldicarboxylic acid. Examples of aliphatic diacids include butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic acids, and dimerized fatty acids. These dimerized fatty acids preferably have a dimer content of at least 98%; they are preferably hydrogenated; for example, these are the products marketed under the brand name "PRIPOL" by the company "CRODA", or under the brand name EMPOL by the company BASF, or under the brand name Radiacid by the company OLEON, and polyoxyalkylene α, co-diacids. Examples of aromatic diacids include terephthalic (T) and isophthalic (I) acids.

[0114] Examples of cycloaliphatic diamines include the isomers of bis-(4-aminocyclohexyl)methane (BACM), bis-(3-methyl-4-aminocyclohexyl)methane (BMACM) and 2-(2-bis-(3-methyl-4-aminocyclohexyl)propane (BMACP), and paraamino-di-cyclohexylmethane (PACM). Other commonly used diamines include isophoronediamine (IPDA), 2,6-bis-(aminomethyl)norbornane (BAMN), and piperazine.

[0115] Examples of polyamide blocks of the third type include the following:

[0116] - PA 66 / 6, where 66 denotes hexamethylenediamine units condensed with adipic acid and 6 denotes units resulting from the condensation of caprolactam;

[0117] - PA 66 / 610 / 11 / 12, where 66 denotes hexamethylenediamine condensed with adipic acid, 610 denotes hexamethylenediamine condensed with sebacic acid, 11 denotes units resulting from the condensation of aminoundecanoic acid and 12 denotes units resulting from the condensation of lauryllactam.

[0118] The notations PA X / Y, PA X / Y / Z, etc. refer to copolyamides in which X, Y, Z, etc. represent homopolyamide units as described above.

[0119] Advantageously, the polyamide blocks of the copolymer used in the invention comprise polyamide blocks PA 6, PA 10, PA 11, PA 12, PA 54, PA 59, PA 510, PA 512, PA 513, PA 514, PA 516, PA 518, PA 536, PA 64, PA 66, PA 69, PA 610, PA 612, PA 613, PA 614, PA 616, PA 618, PA 636, PA 104, PA 109, PA 1010, PA 1012, PA 1013, PA 1014, PA 1016, PA 1018, PA 1036, PA 10T, PA 124, PA 129, PA 1210, PA 1212, PA 1213, PA 1214, PA 1216, PA 1218, PA 1236, PA 12T, PA 6 / 11, PA 6 / 12, PA 11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12 or mixtures or copolymers thereof; and preferably comprise polyamide blocks PA 6, PA 10, PA 11, PA 12, PA 610, PA 612, PA 1010, PA 1012, PA 11 / 12 or mixtures or copolymers thereof, more preferably polyamide blocks PA 11, PA 12, PA 11 / 12 PA 6, PA 612, or mixtures or copolymers thereof.

[0120] Polyether blocks essentially comprise or consist of alkylene oxide units.

[0121] The polyether blocks may in particular be PEG (polyethylene glycol) blocks, i.e., consisting of ethylene oxide units, and / or PPG (propylene glycol) blocks, i.e., consisting of propylene oxide units, and / or PO3G (polytrimethylene glycol) blocks, i.e., consisting of polytrimethylene glycol ether units, and / or PTMG blocks, i.e., consisting of tetramethylene glycol units, also called polytetrahydrofuran. The PEBA copolymers may comprise several types of polyethers in their chain, the copolyethers being able to be block or random. It is also possible to use blocks obtained by oxyethylation of bisphenols, such as, for example, bisphenol A. These latter products are described in particular in document EP 613919.

[0122] Polyether blocks can also be made up of ethoxylated primary amines. Examples of ethoxylated primary amines include products of the formula:

[0123] [Chem. 1] in which m and n are integers between 1 and 20 and x is an integer between 8 and 18. These products are, for example, commercially available under the brand NORAMOX® from the company CECA and under the brand GENAMIN® from the company CLARIANT.

[0124] The polyetherdiol blocks are copolycondensed with polyamide blocks with carboxylic ends. The general method for the two-step preparation of PEBA copolymers having ester bonds between the PA blocks and the PE blocks is known and is described, for example, in FR 2846332. The general method for the preparation of PEBA copolymers having amide bonds between the PA blocks and the PE blocks is known and is described, for example, in EP 1482011. The polyether blocks can also be mixed with polyamide precursors and a diacid chain limiter to prepare polymers with polyamide blocks and polyether blocks having statistically distributed units (one-step process).

[0125] PEBA may comprise amine chain ends, provided that it comprises OH chain ends. PEBAs comprising amine chain ends may result from the polycondensation of polyamide blocks having dicarboxylic chain ends with polyoxyalkylene blocks having diamine chain ends, obtained for example by cyanoethylation and hydrogenation of aliphatic α,α-dihydroxylated polyoxyalkylene blocks called polyetherdiols.

[0126] PEBAs are commercially available. These include products marketed by Arkema under the name PEBAX®, by Evonik under the name Vestamid®, by EMS under the name Grilamid®, and by Sanyo under the name Pelestat®.

[0127] If the block copolymers described above generally comprise at least one polyamide block and at least one polyether block, the PEBAs within the meaning of the present disclosure may also comprise two, three, four (or even more) different blocks chosen from those described in the present description, provided that these blocks comprise at least polyamide and polyether blocks.

[0128] For example, the copolymer may be a segmented block copolymer comprising three different types of blocks (or "triblock"), which results from the condensation of several of the blocks described above. Said triblock may for example be a copolymer comprising a polyamide block, a polyester block and a polyether block or a copolymer comprising a polyamide block and two different polyether blocks, for example a PEG block and a PTMG block. The triblock is preferably a copolyetheresteramide.

[0129] The number-average molar mass of the polyamide blocks in the PEBA copolymer is preferably from 400 to 20,000 g / mol, more preferably from 500 to 10,000 g / mol.

[0130] The number-average molar mass of the polyether blocks is preferably from 100 to 6,000 g / mol, more preferably from 200 to 3,000 g / mol.

[0131] The number-average molar mass is determined by the chain limiter content. It can be calculated according to the relationship:

[0132] Mn — n monomer X Mw repeating unit / n chain limiter + Mw chain limiter

[0133] In this formula, n m monomer represents the number of moles of monomer, chain limiter represents the number of moles of excess diacid limiter, MW mo repeat unit represents the molar mass of the repeat unit, and chain mass M represents the molar mass of the excess diacid.

[0134] The number-average molar mass of polyamide blocks and polyether blocks can be measured prior to copolymerization of the blocks by gel permeation chromatography (GPC).

[0135] Advantageously, the mass ratio of the polyamide blocks to the polyether blocks of the copolymer is from 0.1 to 20, preferably from 0.5 to 18, even more preferably from 0.6 to 15. This mass ratio can be calculated by dividing the number-average molar mass of the polyamide blocks by the number-average molar mass of the polyether blocks. Advantageously, the copolymer with polyamide blocks and polyether blocks has a Shore D hardness of between 10D and 70D, preferably between 25D and 45D.

[0136] Advantageously, the PEBA has an OH function concentration of 0.002 meq / g to 0.2 meq / g, preferably 0.005 meq / g to 0.1 meq / g, more preferably 0.01 meq / g to 0.08 meq / g and / or a COOH function concentration of 0.002 meq / g to 0.2 meq / g, preferably 0.005 meq / g to 0.1 meq / g, more preferably 0.01 meq / g to 0.08 meq / g. The COOH function concentration can be determined by potentiometric analysis and the OH function concentration can be determined by proton NMR. Measurement protocols are detailed in the article “Synthesis and characterization of poly(copolyethers-block-polyamides) - IL Characterization and properties of the multiblock copolymers”, Maréchal et al., Polymer, Volume 41, 2000, 3561-3580.

[0137] Preferably, the polyamide blocks of PEBA are chosen from PA 11, PA 12, PA 10, PA 6, PA 610, PA 612, PA 1010, PA 1012, PA 6 / 11, PA 6 / 12, PA 11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012 and PA 6 / 1010 / 1012, preferably PA 11, PA 12, PA 6, PA 612 and PA 11 / 12. Advantageously, the polyether blocks of PEBA are blocks of polyethylene glycol and / or polytetrahydrofuran.

[0138] According to one embodiment, the PEBA copolymers comprise polyamide blocks as defined above and blocks derived from PTMG, for example: PA 6 / 11 and derived from PTMG, PA 6 / 12 and derived from PTMG, PA 11 / 12 and derived from PTMG, PA 6 / 11 / 12 and derived from PTMG, PA 6 / 66 / 12 and derived from PTMG, PA 6 / 1010 and derived from PTMG, PA 6 / 1012 and derived from PTMG, PA 6 / 1010 / 1012 and derived from PTMG, PA 6 and derived from PTMG, PA 11 and derived from PTMG, PA 12 and derived from PTMG, PA 6 and derived from PEG, PA 11 and derived from PEG, and PA 12 and derived from PEG.

[0139] Particularly preferred PEBA copolymers in the context of the invention are copolymers comprising blocks: PA 10 and PEG; PA 10 and PTMG; PA 11 and PEG; PA 11 and PTMG; PA 12 and PEG; PA 12 and PTMG; PA 610 and PEG; PA 610 and PTMG; PA 6 and PEG; PA 6 and PTMG; PA 612 and PEG; PA 612 and PTMG.

[0140] Advantageously, the PEBA can be a recycled PEBA and / or a partially or completely bio-sourced PEBA.

[0141] According to one embodiment, the mass proportion of polyether blocks in the copolymer is at least 50% relative to the total weight of the copolymer. Preferably, the mass proportion of polyether blocks is from 45 to 85% relative to the total weight of the copolymer, and more preferably from 50 to 80%, and in particular from 60 to 70% relative to the total weight of the copolymer.

[0142] The mass proportions of blocks in the copolymer can be determined from the number-average molar masses of the blocks, which can be determined by 1 H NMR.

[0143] Preferably, the polyether block amide (PEBA) is a linear (non-crosslinked) copolymer.

[0144] According to one embodiment, the single-material shoe comprises 35 to 85%, in particular 45 to 75% by weight of one or more thermoplastic polymers chosen from PEBAs. For example, it may comprise 35 to 40%, or 40 to 45%, or 45 to 50%, or 50 to 55%, or 55 to 60%, or 60 to 65%, or 70 to 75%, or 75 to 80%, or 80 to 85% by weight of PEBA, relative to the weight of the single-material shoe.

[0145] Additives

[0146] In order to achieve the desired properties but also for aesthetic purposes, the mono-material shoe may also include certain additives, in some or all of the parts.

[0147] In their broadest definition, additives are compounds that do not fall within the definition of components (i) and (ii), i.e. they are neither a polyamide or copolyamide, nor a PEBA.

[0148] Among the additives, we can mention in particular fire-resistant agents, flame retardants, anti-UV agents, antioxidants, anti-abrasion agents, light stabilizers, impact modifiers, antistatic agents, optical brighteners, nucleating agents, plasticizers, adhesion promoters, adhesives, lubricants, foaming agents and pigments.

[0149] Fillers and reinforcements can also be present as additives. These include, in particular, fibrous reinforcements such as glass fibers or carbon fibers, short or continuous, and possibly coated with resin, or plant fibers or mineral fibers. Alternatively, non-fibrous reinforcements, such as solid glass beads, can be considered, but also lightweight reinforcements such as hollow glass beads or encapsulated foaming agents.

[0150] More generally, it may be necessary to provide limited quantities of polymers other than polyamides, copolyamides or PEBA in the shoe.

[0151] Thus, the parts of the shoe are generally assembled using an adhesive. Preferably, this is an adhesive that is a polyamide or copolyamide or even a PEBA. Advantageously, it can be a copolyamide. Alternatively, the adhesive used can also be chosen in particular from polyurethanes.

[0152] In one embodiment, the mono-material shoe may therefore comprise an additive in the form of a polymer which is not a polyamide, copolyamide or PEBA. Preferably, such an adhesive, if present, is present in a low content, for example from 0.01% to 10%, advantageously from 0.1% to 5% by weight and most particularly from 1 to 2.5% by weight relative to the weight of the shoe. Overall, the mono-material shoe comprises 0 to 15% of additives, for example 0 to 2.5%, or 2.5 to 5%, or 5 to 7.5%, or 7.5% to 10%, or 10 to 12.5%, or 12.5 to 15% by weight of additives relative to the weight of the mono-material shoe.

[0153] Depending on the design chosen for the single-material shoe, the shoe includes parts comprising one or more polyamides or copolyamides as the sole polymer and others comprising one or more PEBAs as the sole polymer.

[0154] Alternatively, the mono-material shoe may also have some or all of the parts made from a polyamide or copolyamide alloy in combination with PEBA.

[0155] Finally, it is possible that the mono-material shoe includes parts made from a single family of polymer and other parts made with an alloy of polyamide and / or copolyamide in association with PEBA.

[0156] Manufacturing process of single-material shoes

[0157] The single-material shoe of the invention may be manufactured by any of the methods known in the art.

[0158] In particular, according to another aspect, the invention relates to a method of manufacturing a single-material shoe according to the invention comprising the steps consisting of:

[0159] I. Provide a material comprising one or more polyamides or copolyamides, one or more PEBAs and / or one or more additives suitable for each component of the shoe;

[0160] II. Manufacture the components of the shoe from the respective thermoplastic material; and

[0161] III. Assembling the components of the shoe, using an adhesive if necessary, to form the finished shoe, wherein the materials used are chosen such that the finished shoe comprises 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides; 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives.

[0162] According to one embodiment, the materials used are chosen in such a way that the finished shoe comprises 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives.

[0163] Therefore, we will choose exclusively materials based on polyamide, copolyamide or PEBA for each part of the shoe, in particular those forming the upper part and those forming the sole. Depending on the constraints of each part, we will choose a material made, without additives, of polyamide or copolyamide alone, PEBA alone or a mixture of these polymers.

[0164] According to one embodiment, a single-material shoe according to the invention may be designed with an upper part composed mainly of polyamide, laces composed of polyamide, and a sole composed mainly of PEBA.

[0165] Thus, for example, a single-material shoe according to the invention may comprise an upper part comprising a polyamide textile part, polyamide laces, a midsole and an outer sole both made of PEBA, as indicated in Table 1 below.

[0166] [Table 1]

[0167] The properties of the parts of the mono-material shoe can be optimized respectively by opting for certain specific grades of polyamide, copolyamide or PEBA. Furthermore, it is possible to use alloys between these polymers. It will then also be possible to modulate the weight of the respective parts so that the mono-material shoe has the ratio between polyamide / copolyamide and PEBA as claimed. The mono-material shoe thus designed will allow the obtaining of a recycled composition with good properties. Recycling process for mono-material shoes

[0168] Due to the fact that it is essentially made of thermoplastic materials, the mono-material shoe of the invention has the advantage of being easily recycled. Furthermore, the shoes of the invention can also be recycled safely, because they do not risk forming isocyanates like shoes made from TPU.

[0169] Also, according to another aspect, the invention relates to a method for recycling the single-material shoe according to the invention comprising the steps consisting of:

[0170] (a) supply of the used shoe;

[0171] (b) grinding the clean shoe to obtain a ground material;

[0172] (c) heating the ground material until it melts; and

[0173] (d) extrusion of the molten mass into granules.

[0174] A cleaning step can also be provided before or after step (b) to remove any dirt.

[0175] The shoe shredder obtained from step (b) is generally in the form of shredded material. It comprises particles of varying shape and size, but most often of the order of several millimeters in size.

[0176] Depending on the intended application for the recycling product, it may be advantageous to add one or more virgin materials to the crushed shoe obtained from the used shoe. Also, according to one embodiment, the recycling method further comprises the step of:

[0177] (e) adding new material to the used shoe shredder before or after step (d).

[0178] The new material may in particular be one or more thermoplastic polymers chosen from polyamides and copolyamides. Alternatively or in combination, it may also be one or more thermoplastic elastomers chosen from PEBA.

[0179] It is also possible to add specific additives, including stabilizers, especially chain extenders to compensate for the aging of the material during its manufacture and prior use. Recycled polymer composition

[0180] The mono-material shoes of the invention can be recycled to produce materials with excellent properties. In particular, these materials have low density, good elastic recovery, suitable tensile modulus, and stable inherent viscosity, which makes them suitable for demanding applications and multiple recycling cycles.

[0181] Although the resulting recycled material has advantageous mechanical properties, the fact remains that the recycled polymer is modified compared to the virgin polymer. In particular, thermal and generally oxidative stresses during the manufacture of the shoe, its use and subsequent recycling affect some of its reactive functions.

[0182] The ground material and the resulting composition are unique in that the polymers present are derived from used shoes. During their use, the shoes were exposed to air and light, as well as to the perspiration of the people who wore them and the products of their degradation by microorganisms.

[0183] Also another aspect of the invention relates to a recycled polymer composition capable of being obtained by the process according to the invention.

[0184] This composition may in particular consist of:

[0185] (a) 20 to 100% by weight, advantageously from 30 to 99% by weight, even more preferably from 50 to 98% by weight of granulated single-material shoe shredder, consisting of: a. 15 to 65%, in particular 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; b. 35 to 85%, in particular 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and c. 0 to 15% of additives;

[0186] (b) 0 to 80% by weight, preferably 1 to 70% by weight and in particular 2 to 50% by weight of virgin polymer chosen from polyamides, copolyamides and PEBA, preferably from polyamides; and

[0187] (c) 0 to 50%, preferably 5 to 40%, more preferably 10 to 30%, and in particular 15 to 25% by weight of additives. Preferably, the virgin polymers are chosen from the preferred polyamides and copolyamides and PEBA described above in the context of the single-material shoe.

[0188] The possible additives of component (c) may be chosen in particular from the list of agents and compounds mentioned above concerning the additives present in the single-material shoe. Advantageously, these additives include fillers and reinforcements as mentioned above.

[0189] Use

[0190] Due to these advantageous properties, the composition resulting from the recycling of the monomaterial shoe of the invention can be recycled for various uses, and in particular for performance applications.

[0191] According to one embodiment, this composition resulting from recycling can be used to remanufacture shoe parts, in particular single-material shoes, in particular sports shoes. This variant is particularly interesting because it represents closed-loop recycling.

[0192] The invention will be explained in more detail in the following examples.

[0193] [Examples]

[0194] Unless otherwise stated, the percentages are expressed below by weight relative to the total weight of the composition.

[0195] The following materials were used:

[0196] Polyamide 11: Rilsan® FMNO, polyamide 11 homopolymer with an inherent viscosity in solution of 1.05, marketed by Arkema.

[0197] PEBA 1: Pebax® RNew 40R53 SPO1, marketed by Arkema, with a hardness of 90 Shore A, as measured after 3s according to the ISO 868:2003 standard.

[0198] PEBA 2: Pebax® 2533 SD02, marketed by Arkema, with a hardness of 75

[0199] Shore A, as measured after 3s according to ISO 868:2003.

[0200] PEBA 3: Pebax® RNew 72R53 SP01, marketed by Arkema, with a hardness of 72 Shore D, as measured after 3s according to ISO 868:2003. TPU 1: Elastollan® 1180A, marketed by BASF, with a hardness of 80

[0201] Shore A, as measured after 3s according to ISO 868:2003.

[0202] TPU 2: Elastollan® 1164D, marketed by BASF, with a hardness of 64

[0203] Shore D, as measured after 3s according to ISO 868:2003.

[0204] Antioxidant 1: Irganox® 245 marketed by BASF.

[0205] Antioxidant 2: Irgafos® 168 marketed by BASF.

[0206] [Example El 1 to EI2]

[0207] Different formulations of polyamide and PEBA, with the composition indicated in Table 2 below, are prepared by compounding in a co-rotating twin-screw extruder at a temperature of 230°C in order to evaluate their behavior after aging and recycling.

[0208] At the extruder outlet, the molten polymer is solidified by passing it through a water bath at 25°C and then cut into granules. These are then dried for 8 hours at 80°C in a vacuum oven to achieve a residual moisture content of < 0.1%.

[0209] The products are then implemented by injection at 250°C in the form of plates measuring 100x100x2mm. These samples are subjected to 1000h UV aging in a QSun Xenon chamber to simulate their first life.

[0210] These aged samples are shredded in a knife mill model RS2402 from the supplier Getecha. This ground material is then re-melted and homogenized in a co-rotating twin-screw extruder at 230°C. The molten polymer is frozen by passing it through a water bath at 25°C and then cut into recycled product granules which are then dried for 8 hours under vacuum to achieve a humidity level of less than 0.1%.

[0211] The recycled product granules are finally injected at 250°C to form the test pieces necessary for characterization: ISO 527 IA dumbbells (traction), bars measuring 80x10x4 mm (Charpy impact) and plates measuring 100x100x2 mm. 3 Before measurement, the test pieces are conditioned for 15 days in a controlled atmosphere at 23°C and 50% relative humidity.

[0212] The manufactured specimens are then used to evaluate the mechanical properties of the formulations after recycling as follows. A. Tensile modulus and elongation at break

[0213] Tensile modulus and elongation at break are measured on a Zwick dynamometer at 23°C and 50% relative humidity according to ISO 527-1-2019.

[0214] B. Impact resistance

[0215] The energy dissipated (resilience) during a Charpy impact with notch is measured at a temperature of - 30°C according to the ISO 179 / :1993 leA standard.

[0216] C. Tear resistance

[0217] Tear resistance is measured on an angular specimen with a notch, die-cut from a 100x100x2mm plate. The test is carried out on a Zwick dynamometer at 23°C, 50% relative humidity and a speed of 500 mm / min, according to ISO 34-1-2010.

[0218] D. Compounds produced during the recycling process

[0219] The presence of isocyanate functions (toxic) is detected by FTIR infrared spectrometry in ATR mode on diamond crystal by verifying the appearance of the specific absorption band at 2270 cm' 1 This measurement is carried out on the recycled product granules one hour after their extrusion.

[0220] [Examples of comparison EC A to EC E]

[0221] Formulations comprising polyamide and PEBA in different proportions and based on TPU are prepared as indicated in examples Eli and EI2 above and the same procedure is followed to age them and then to make test pieces which are evaluated in the same way.

[0222] The composition of the formulations and the evaluation results are summarized in Table 2 below.

[0223] [Table 2] Compositions of the mixtures studied and recycling properties

[0224] The results show that examples E1 1 and E1 2, representative of shoes according to the invention, still exhibit good properties after recycling, which makes them interesting as a starting material for the manufacture of performance articles such as sports shoes. The combination of polyamide and PEBA in the specific ratio of the invention in fact makes it possible to obtain excellent mechanical properties, both in terms of modulus and resistance to tearing and Charpy impact with notch.

[0225] Conversely, comparative examples EC A, EC C, EC D and EC F demonstrate that compositions that do not meet the criteria of the invention exhibit poor properties after recycling and therefore cannot be considered for demanding applications. Indeed, when the shoe contains too much PEBA, the tensile modulus becomes insufficient, and the tear and impact resistance drop, as illustrated by examples EC A, EC C and EC D. When the shoe contains too much polyamide, the mixture has a very high tensile modulus, incompatible with reuse for the manufacture of shoes, as illustrated by comparative example EC B. Finally, the recycling of TPU, beyond the low performance obtained, results in the formation of isocyanates, which makes the use of this material for recyclable articles delicate from an HSE point of view. [List of cited documents]

[0226] EP 3 081 109 B1

[0227] WO 2020 / 201370 Al

Claims

CLAIMS Single-material shoe made of: (i) 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides; (ii) 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBA; and (iii) 0 to 15% by weight of additives. Shoe according to claim 1, consisting of: (i) 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; (ii) 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBA; and (iii) 0 to 15% by weight of additives. Mono-material shoe according to claim 1 or 2, wherein component (i) comprises a polyamide or copolyamide selected from PA 612, PA 613, PA 912, PA 1010, PA 1012, PA 6, PA 11, PA 12, PA 6 / 11, PA 6 / 12, PA 11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014 alone or as a mixture. Single-material shoe according to one of claims 1 to 3, wherein component (ii) comprises a PEBA chosen from comprising blocks of PA 6 / 11 and derived from PTMG, PA 6 / 12 and derived from PTMG, PA 11 / 12 and derived from PTMG, PA 6 / 11 / 12 and derived from PTMG, PA 6 / 66 / 12 and derived from PTMG, PA 6 / 1010 and derived from PTMG, PA 6 / 1012 and derived from PTMG, PA 6 / 1010 / 1012 and derived from PTMG, PA 6 and derived from PTMG, PA 11 and derived from PTMG, PA 12 and derived from PTMG, PA 6 and derived from PEG, PA 11 and derived from PEG, and PA 12 and derived from PEG.Single-material shoe according to one of claims 1 to 4, in which the polyamides or copolyamides of component (i) have an average ratio of the number of atoms of. carbon per amide function greater than 6, preferably greater than 8 and in particular 10 or more.

6. Single-material shoe according to one of claims 1 to 5, comprising, as additive 0 to 10% by weight, preferably 0.1 to 4% by weight of adhesive.

7. A single-material shoe according to claim 6, wherein the adhesive comprises or consists of polyurethane.

8. Method for manufacturing a single-material shoe according to one of claims 1 to 7, comprising the steps consisting of: I. Provide a material comprising one or more polyamides or copolyamides, one or more PEBAs and / or one or more additives suitable for each component of the shoe; II. Manufacture the components of the shoe from the respective thermoplastic material; and III. Assembling the components of the shoe, using an adhesive if necessary, to form the finished shoe, wherein the materials used are chosen such that the finished shoe comprises 15 to 65% by weight of one or more thermoplastic polymers chosen from polyamides and copolyamides; 35 to 85% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives.

9. Manufacturing method according to claim 8, wherein the materials used are chosen in such a way that the finished shoe comprises 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and 0 to 15% by weight of additives 10. Method for recycling the single-material shoe according to one of claims 1 to 7, comprising the steps consisting of: (a) supply of the used shoe; (b) crushing the clean shoe to obtain a ground material; (c) heating the ground material until it melts; and (d) extrusion of the molten mass into granules.

11. The recycling method of claim 10, further comprising the step of: (e) adding new material to the used shoe shredder before or after step (d).

12. Recycled polymer composition obtainable by the process according to claims 9 to 11.

13. Composition consisting of: (a) 20 to 100% by weight, advantageously from 30 to 99% by weight, even more preferably from 50 to 98% by weight of granulated single-material shoe shredder, consisting of: a. 15 to 65%, in particular 25 to 55% by weight of one or more thermoplastic polymers chosen from polyamides or copolyamides; b. 35 to 85%, in particular 45 to 75% by weight of one or more thermoplastic elastomers chosen from PEBAs; and c. 0 to 15% of additives; (b) 0 to 80% by weight, preferably 1 to 70% by weight and in particular 2 to 50% by weight of virgin polymer chosen from polyamides, copolyamides and PEBA; and (c) 0 to 50% by weight of additives.

14. Use of the composition according to claim 12 or 13 for the manufacture of shoes.

15. Use according to claim 14, wherein the shoes are single-material shoes.

Images