Sports footwear with improved recyclability

Abstract

The present invention mainly relates to a single-material footwear comprising (i) 15 to 65% by weight of a thermoplastic resin polymer selected from polyamide or copolyamide; (ii) 35 to 85% by weight of a PEBA thermoplastic resin elastomer; and (iii) 0 to 15% by weight of an additive. The present invention also relates to a method for manufacturing the same, and a method for recycling the same, and also relates to the composition obtained after recycling and its use for the manufacture of footwear items.

Description

Technical Field

[0001] This patent application relates to footwear items having improved recyclability, methods for manufacturing the same, and methods for recycling the same, and to the resulting compositions and their use in the manufacture of footwear items.

Background Art

[0002] Through a circular economy, it is possible to limit waste generation, depletion of the earth's resources, and environmental impacts. Currently, there is particular interest in manufacturing objects using materials that have sufficient properties to be used not only in low-performance applications such as street furniture or roads after recycling, but also in high-performance applications.

[0003] In the context of sustainable consumption and manufacturing patterns, the recyclability of items that are frequently replaced, such as sports equipment, and the quality of the resulting recycled products are of particular importance. However, these items have particularly high performance requirements.

[0004] Patent EP3081109(B1) proposes sports footwear items in which the upper and sole are mainly or completely made of the same thermoplastic resin-based material in order to facilitate recycling. However, since the densities of the parts of the footwear item vary depending on their respective functions, there still remains the difficulty that the recycled products obtained in this way have limitations in terms of performance.

[0005] Patent application WO2020 / 201370(A1) proposes a method for recycling such footwear items by grinding and melting the items. This document, like the previous one, focuses on TPU.

[0006] It is important that the products used are stable enough to be recycled completely safely. However, when recycling TPU, the formation of isocyanate, a dangerous compound, may be observed.

[0007] Furthermore, the proposed footwear items do not necessarily enable the obtaining of a recycled composition having properties sufficient to allow its use as a performance polymer.

Summary of the Invention

[0008] Therefore, an object of the present invention is to propose a single-material footwear item whose composition has been studied so as to enable the obtaining of a composition that can be used in applications requiring high performance during recycling.

[0009] Currently, in single-material footwear items, the exclusive combination (excluding additives) of a polyamide fraction and a fraction of a polyether containing amide blocks (PEBA) has proven to be able to better maintain properties during recycling.

[0010] In fact, the presence of polyamide in the composition is beneficial, particularly for aging resistance, and thus for the lifespan of the object and its recycling method. In that component, the presence of the more flexible PEBA contributes to the improvement of the mechanical strength of the object over the entire lifespan before and after recycling.

[0011] Therefore, according to a first aspect, one subject of the present invention is (i) one or more thermoplastic resin polymers selected from polyamide and copolyamide, in an amount of 15 to 65% by weight; (ii) one or more thermoplastic resin elastomers selected from PEBA, in an amount of 35 to 85% by weight; (iii) additives in an amount of 0 to 15% by weight, and is a single-material footwear item.

[0012] According to a preferred embodiment, the footwear item is (i) one or more thermoplastic resin polymers selected from 25 to 55% by weight of polyamide or copolyamide; (ii) one or more thermoplastic resin elastomers selected from 45 to 75% by weight of PEBA; (iii) 0 to 15% by weight of additives, and consists of.

[0013] In one embodiment, component (i) includes, alone or as a mixture, a polyamide or copolyamide selected from PA612, PA613, PA912, PA1010, PA1012, PA6, PA11, PA12, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014.

[0014] In one embodiment, component (ii) includes a PEBA selected from those including blocks derived from PA6 / 11 and PTMG, PA6 / 12 and PTMG, PA11 / 12 and PTMG, PA6 / 11 / 12 and PTMG, PA6 / 66 / 12 and PTMG, PA6 / 1010 and PTMG, PA6 / 1012 and PTMG, PA6 / 1010 / 1012 and PTMG, PA6 / 1012 / 12 and PTMG, PA6 and PTMG, PA11 and PTMG, PA12 and PTMG, PA6 and PEG, PA11 and PEG, and PA12 and PEG.

[0015] In one embodiment, the polyamide or copolyamide of component (i) has an average ratio of carbon atoms per amide group of more than 6, preferably more than 8, particularly 10 or more.

[0016] According to one embodiment, a single - material footwear item contains, as an additive, 0 to 10% by weight, preferably 0.1 to 4% by weight, of an adhesive.

[0017] According to one embodiment, the adhesive contains or consists of polyurethane.

[0018] According to a second aspect, the present invention I. providing 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 footwear item; II. manufacturing components of the footwear item from each thermoplastic resin material; III. optionally assembling the components of the footwear item using an adhesive to form a completed footwear item, A method for manufacturing such a single - material footwear item, comprising The materials used are selected such that the completed footwear item comprises 15 to 65% by weight of one or more thermoplastic resin polymers selected from polyamides and copolyamides; 35 to 85% by weight of one or more thermoplastic resin elastomers selected from PEBAs; and 0 to 15% by weight of additives.

[0019] According to one embodiment, the materials used are selected such that the completed footwear item comprises 25 to 55% by weight of one or more thermoplastic resin polymers selected from polyamides and copolyamides; 45 to 75% by weight of one or more thermoplastic resin elastomers selected from PEBAs; and 0 to 15% by weight of additives.

[0020] According to a third aspect, the present invention is a method for recycling a single - material footwear item as follows (a) supplying a used footwear item; (b) Step of crushing a clean footwear item to obtain a crushed material; (c) Step of heating the crushed material until it melts; (d) Step of extruding the melt into pellets, A method for recycling, including the above steps, is targeted.

[0021] According to one embodiment, (e) Step of adding new material to the crushed used footwear item before or after step (d) is further included.

[0022] According to a fourth aspect, the present invention is directed to a recycled polymer composition obtained by the recycling method.

[0023] According to a fifth aspect, the present invention is (a) One or more thermoplastic resin polymers selected from 15 - 65% by weight, particularly 25 - 55% by weight, of polyamide or copolyamide; and (b) One or more thermoplastic resin elastomers selected from 35 - 85% by weight, particularly 45 - 75% by weight, of PEBA; and (c) 0% - 15% of additives, comprising 20 - 100% by weight, preferably 30 - 99% by weight, and even more preferably 50 - 98% by weight of pelletized crushed single - material footwear items; and (b) 0 - 80% by weight, preferably 1 - 70% by weight, particularly 2 - 50% by weight, of virgin polymers selected from polyamide, copolyamide, and PEBA; and (c) 0 - 50% of additives, A composition comprising the above components is targeted.

[0024] According to the last aspect, the present invention is directed to the use of the composition obtained from the recycling method for the manufacture of footwear items, particularly single - material footwear items.

Embodiments for Carrying Out the Invention

[0025] Definition of Terms The term "polymer blend" is intended to represent a macroscopically homogeneous polymer composition. This term also encompasses such compositions consisting of immiscible phases dispersed on the micrometer scale.

[0026] The term "copolymer" is understood to represent a polymer obtained from the copolymerization of at least two chemically different monomers called comonomers. Thus, a copolymer is formed from at least two repeating units. It may also be formed from three or more repeating units. More specifically, the terms "continuous copolymer" or "block copolymer" are understood to represent copolymers in the above-mentioned sense in which at least two different monomer blocks are covalently bonded. The length of the blocks may be variable. Preferably, the blocks are each composed of 1 to 1,000, preferably 1 to 100, and particularly 1 to 50 repeating units. The bond between two monomer blocks may require an intermediate non-repeating unit known as a junction block.

[0027] In the context of polyamides, the term "monomer" should be interpreted in the sense of "repeating unit". In fact, the case where the repeating unit of a polyamide consists of a combination of a diacid and a diamine is a special case. It is considered that what corresponds to the monomer is the combination of a diamine and a diacid, that is, the pair (equimolar amounts) of a diamine and a diacid. The basis is that a diacid or a diamine is merely a structural unit individually and cannot be polymerized alone.

[0028] The term "single material footwear item" is understood to mean a footwear item essentially manufactured from a given family of polymers. In the broad definition of the present invention, these are thermoplastic resin polymers selected from polyamides and their copolymers, as well as polyethers containing amide blocks (PEBA). In principle, a single material footwear item does not include other polymers, whether they are thermosetting polymers or polymers belonging to other families of thermoplastic resin polymers. On the other hand, the formulations of thermoplastic resin polymers used for each part of the item, or for any particular part of the item, may contain small amounts of agents called additives. Examples cited include the presence of adhesives used for the purpose of assembling a single material footwear item. Advantageously, this is a thermoplastic resin adhesive, particularly an adhesive in the form of a polyamide or copolyamide. Nevertheless, when its presence does not exceed an amount of 10% by weight, preferably 4% by weight, based on the total weight of the footwear item, a non-thermoplastic resin adhesive, such as a polyurethane adhesive, can also be provided.

[0029] The term "intrinsic viscosity" is as follows: - a step of taking a sample of the polymer of 0.07 to 0.10 g, preferably at most 0.15 g; - a step of adding a sufficient amount of m-cresol solvent by weighing to obtain a concentration (C) of 0.5 g / L; - a step of heating the mixture with stirring on a hot plate adjusted to 100 °C ± 5 °C until the polymer is completely dissolved; - a step of cooling the solution to room temperature, preferably for at least 30 minutes; - a step of measuring the flow time t0 of the pure solvent and the flow time t of the solution using a micro-Ubbelohde tube viscometer in a bath controlled by a thermostat adjusted to 20 °C ± 0.05 °C; - a step of calculating the viscosity according to the formula 1 / C × Ln(t / t0) [wherein C represents the concentration and Ln represents the natural logarithm]; It is understood to represent the viscosity measured in accordance with.

[0030] For each sample, three measurements are taken with different solutions and the average is calculated.

[0031] The term "thermoplastic resin polymer" is understood to represent a polymer that softens when heated sufficiently and hardens again when cooled.

[0032] The term "semicrystalline polyamide" is understood to represent a polyamide having a melting point (Tm) in DSC according to ISO11357-3:2013 standard, and an enthalpy of crystallization during the cooling process at a rate of 20 K / min in DSC measured according to the ISO11357-3 standard of 2013 and exceeding 20 J / g, preferably exceeding 30 J / g.

[0033] The term "enthalpy of fusion" is understood to represent the heat consumed during the solid / liquid transition of a thermoplastic resin elastomer measured by differential scanning calorimetry according to the ISO11257-3:1999 standard.

[0034] The nomenclature used to represent the polyamide according to the present invention follows the ISO1874-1:2010 standard.

[0035] Hereinafter, the hardness is measured according to the ISO868:2003 standard.

[0036] Single-material footwear item In its broadest definition, the present invention relates in particular to single-material footwear items comprising parts consisting essentially of polyamides, copolyamides, and polymers of the PEBA family, i.e., parts that are free of additives. Apart from these parts, the single-material footwear item can contain a minor proportion of functional or decorative elements made of different materials (less than 12% by weight, preferably less than 10% by weight, more preferably less than 5% by weight relative to the weight of the finished single-material footwear item). Advantageously, the single-material footwear item consists essentially of polymers derived from this family.

[0037] According to one aspect, the present invention is directed to (i) one or more thermoplastic resin polymers selected from polyamides and copolyamides, in an amount of 15 to 65% by weight; (ii) one or more thermoplastic resin elastomers selected from PEBA, in an amount of 35 to 85% by weight; (iii) additives, in an amount of 0 to 15% by weight, and relates to single-material footwear items consisting of these components.

[0038] Polyamides and copolyamides As described above, the single-material footwear items according to the present invention contain one or more polyamides or copolyamides.

[0039] In the context of this description, the term "copolyamide" is understood to represent a polymer derived from the polymerization of a plurality of monomers linked by amide groups. However, copolymers containing polyether blocks such as PEBA are excluded from this definition.

[0040] According to one embodiment, the polyamide results from the condensation of one or more monomers of the α,ω-aminocarboxylic acid type or one or more monomers of the lactam type ("Z" type).

[0041] Examples of α,ω - aminocarboxylic acids include α,ω - amino acids such as aminocaproic acid, 7 - aminoheptanoic acid, 11 - aminoundecanoic acid, n - heptyl - 11 - aminoundecanoic acid, and 12 - aminododecanoic acid.

[0042] Examples of lactams include those having 3 to 12 carbon atoms, which may be substituted, on the main ring. For example, β,β - dimethylpropiolactam, α,α - dimethylpropiolactam, amylolactam, caprolactam, capryllactam, oenanthlactam, 2 - pyrrolidone, and lauryllactam can be mentioned.

[0043] Semicrystalline polyamides are most preferably used in the manufacture of single - material footwear items. Advantageously, these are aliphatic polyamides. Particularly preferred are polyamides in which the average number of carbon atoms per amide group is more than 6, preferably more than 8, and most particularly 10 or more. Advantageously, these are polyamides lacking a cyclic structure, whether aromatic or alicyclic.

[0044] Examples of this type of preferred polyamide include PA6, PA11, and PA12, as well as mixtures thereof.

[0045] According to one embodiment, the polyamide results from the condensation of a dicarboxylic acid with an aliphatic diamine, an alicyclic diamine, or an aromatic diamine [“XY” type, where X represents the number of carbon atoms of the diamine and Y represents the number of carbon atoms of the dicarboxylic acid].

[0046] Examples of the diamine include aliphatic diamines having 4 to 16 carbon atoms, preferably 6 to 12 carbon atoms, and the 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, polyol diamines, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), meta-xylylenediamine, and trimethylhexamethylenediamine.

[0047] Examples of the dicarboxylic acid include acid Y having 4 to 18 carbon atoms, preferably 9 to 12 carbon atoms. For example, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, sodium salt or lithium salt of sulfoisophthalic acid, dimerized fatty acids (especially those having a dimer content of at least 98% and / or hydrogenated), and 1,2-dodecanedioic acid HOOC-(CH2) 10 -COOH can be mentioned.

[0048] Examples of this type of preferred polyamide include PA516 obtained by condensation of pentamethylenediamine and hexadecanedioic acid, PA612 obtained by condensation of hexamethylenediamine and 1,12-dodecanedioic acid; PA613 obtained by condensation of hexamethylenediamine and brassilic acid; PA912 obtained by condensation of 1,9-nonanediamine and 1,12-dodecanedioic acid; PA129 obtained by condensation of 1,12-dodecamethylenediamine and azelaic acid; PA1010 obtained by condensation of 1,10-decanediamine and sebacic acid; and PA1012 obtained by condensation of 1,10-decanediamine and 1,12-dodecanedioic acid.

[0049] According to one embodiment, the polyamide is as follows: - Polycondensation of at least two different monomers selected from different α,ω-aminocarboxylic acids, or two different lactams, or one lactam and one α,ω-aminocarboxylic acid having different numbers of carbons; or - Polycondensation of at least one α,ω-aminocarboxylic acid (or lactam), at least one diamine, and at least one dicarboxylic acid; or - Polycondensation of an aliphatic diamine with at least one other monomer selected from an aliphatic dicarboxylic acid and an aliphatic diamine other than those described above and an aliphatic diacid other than those described above is a copolyamide obtained from the polycondensation.

[0050] Designations such as PA Z / XY, PA Z / Z’, PA Z / XY / X’Y’, PA Z / Z’ / XY, PA Z / Z’ / XY / X’Y’ etc. relate to copolyamides where XY, Z, X’Y’, Z’ etc. represent the above XY or Z homopolyamide monomers, X’Y’ is the same as or different from XY, and Z’ is the same as or different from Z.

[0051] According to one embodiment, one of the monomers constituting the copolyamide can represent more than 50% by mass, preferably more than 60% by mass, of the total monomer mixture. According to one embodiment, one of the monomers constituting the copolyamide can represent less than 90% by mass, preferably less than 80% by mass, of the total monomer mixture.

[0052] Examples of particularly preferred copolyamides are block PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014, and further mixtures thereof.

[0053] Mixtures of polyamides can also be used, which can be mixtures of aliphatic polyamides and semi-aromatic polyamides, and mixtures of aliphatic polyamides and cycloaliphatic polyamides.

[0054] According to one embodiment, a single-material footwear item comprises 15 to 65% by weight, in particular 25 to 55% by weight, of one or more thermoplastic resin polymers selected from polyamides and copolyamides. For example, with respect to the weight of the single-material footwear item, it can contain 15 to 20% by weight, or 20 to 25% by weight, or 25 to 30% by weight, or 30 to 35% by weight, or 35 to 40% by weight, or 40 to 45% by weight, or 50 to 55% by weight, or 55 to 60% by weight, or 60 to 65% by weight of polyamide and / or copolyamide.

[0055] Polyether (PEBA) containing amide blocks The single-material footwear item of the present invention further comprises one or more PEBA. According to one embodiment, the footwear item comprises a component consisting essentially of only PEBA, or a component mixed with one or more polyamides or copolyamides as described above.

[0056] According to one embodiment, the thermoplastic resin elastomer is a polyether (PEBA) having amide blocks. In these copolymers, the rigid block is a polyamide containing at least one Z-type unit or XY-type unit. - Z is a lactam or amino acid having 6 to 18 carbon atoms. - X is a diamine having 4 to 48 carbon atoms. - Y is a diacid having 6 to 48 carbon atoms.

[0057] PEBA is obtained from the polycondensation of a polyamide block (rigid or hard block) having reactive ends and a polyether block (flexible or soft block) having reactive ends, in particular from the following polycondensation. 1) Polycondensation of a polyamide block having a diamine chain end and a polyoxyalkylene block having a dicarboxyl chain end; 2) Polycondensation of a polyamide block having a dicarboxyl chain end and a polyether diol (α,ω-dihydroxylated aliphatic polyoxyalkylene block). In this case, the resulting product is a polyether ester amide.

[0058] The polyamide block having a dicarboxyl chain end results, for example, from the condensation of a polyamide precursor in the presence of a chain-limiting dicarboxylic acid. The polyamide block having a diamine chain end results, for example, from the condensation of a polyamide precursor in the presence of a chain-limiting diamine.

[0059] Three types of polyamide blocks can be advantageously used.

[0060] According to the first type, the polyamide block results from the condensation of a dicarboxylic acid, especially one containing 4 to 36 carbon atoms, preferably one containing 4 to 20 carbon atoms, more preferably one containing 6 to 18 carbon atoms, and an aliphatic or aromatic diamine, especially one containing 2 to 20 carbon atoms, preferably one containing 6 to 14 carbon atoms.

[0061] Examples of dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, butanedioic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, brassilic acid, hexadecanedioic acid and octadecanedioic acid, terephthalic acid and isophthalic acid, and dimerized fatty acids.

[0062] Examples of diamines include tetramethylenediamine, hexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), and isomers of 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), para-aminodicyclohexylmethane (PACM), isophoronediamine (IPDA), 2,6-bis(aminomethyl)norbornane (BAMN), and piperazine (Pip).

[0063] Advantageously, polyamide blocks PA412, PA414, PA418, PA516, PA610, PA612, PA613, PA614, PA618, PA912, PA1010, PA1012, PA1014, PA1018, and PA129 are used. In the PA XY notation, conventionally, X represents the number of carbon atoms resulting from the diamine residue, and Y represents the number of carbon atoms resulting from the diacid residue.

[0064] According to the second type, the polyamide block results from the condensation of one or more α,ω-aminocarboxylic acids and / or one or more lactams containing 6 to 12 carbon atoms in the presence of a dicarboxylic acid or diamine containing 4 to 18 carbon atoms. Examples of lactams include caprolactam, enantholactam, and lauryllactam. Examples of α,ω-aminocarboxylic acids include aminocaproic acid, 7-aminoheptanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0065] Advantageously, the second type of polyamide block is a PA10 (polydecaneamide), PA11 (polyundecaneamide), PA12 (polydodecaneamide), or PA6 (polycaprolactam) block. In the notation PA X, X represents the number of carbon atoms derived from the amino acid residue.

[0066] According to the third type, the polyamide block is obtained from the condensation of at least one α,ω-aminocarboxylic acid or lactam with at least one diamine and at least one dicarboxylic acid.

[0067] In this case, the polyamide PA block is as follows: - Polycondensation of a linear aliphatic or aromatic diamine containing X carbon atoms; - Polycondensation of a dicarboxylic acid containing Y carbon atoms; and - Polycondensation of a comonomer {Z} selected from a lactam and an aminocarboxylic acid containing Z carbon atoms, and an equimolar mixture of at least one diamine containing X1 carbon atoms and at least one dicarboxylic acid containing Y1 carbon atoms [(X1, Y1) is different from (X, Y)]; - Said comonomer or comonomer {Z} is preferably introduced in a weight ratio ranging from advantageously up to 50%, preferably up to 20%, even more advantageously up to 10% with respect to the total amount of polyamide precursor monomers; - In the presence of a chain limiter selected from dicarboxylic acids prepared by polycondensation of.

[0068] Advantageously, a dicarboxylic acid containing Y carbon atoms is used as the chain limiting substance, which is introduced in excess with respect to the stoichiometry of the diamine.

[0069] According to one variant of this third type, the polyamide block is obtained from the condensation of at least two α,ω-aminocarboxylic acids, or at least two lactams containing 6 to 12 carbon atoms, or one lactam and one aminocarboxylic acid having a different number of carbon atoms, in the presence of any chain limiting substance.

[0070] Examples of aliphatic α,ω-aminocarboxylic acids include aminocaproic acid, 7-aminoheptanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Examples of lactams include caprolactam, oenantholactam, and lauryllactam. Examples of aliphatic diamines include hexamethylenediamine, dodecamethylenediamine, and trimethylhexamethylenediamine.

[0071] Examples of alicyclic diacids include 1,4-cyclohexanedicarboxylic acid. Examples of aliphatic diacids include succinic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, and dimerized fatty acids. These dimerized fatty acids preferably have a dimer content of at least 98%; are preferably hydrogenated; for example, products sold under the brand name Pripol by Croda, Empol by BASF, or Radiacid by Oleon, and polyoxyalkylene α,ω-diacids. Examples of aromatic diacids include terephthalic acid (T) and isophthalic acid (I).

[0072] Examples of alicyclic diamines include bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), and isomers of 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), and para-aminodicyclohexylmethane (PACM). Other commonly used diamines can be isophoronediamine (IPDA), 2,6-bis(aminomethyl)norbornane (BAMN), and piperazine.

[0073] Examples of the third type of polyamide block can include the following. - PA66 / 6 [where 66 represents the unit obtained from the condensation of adipic acid and hexamethylenediamine, and 6 represents the unit obtained from the condensation of caprolactam] - PA66 / 610 / 11 / 12 [where 66 represents hexamethylenediamine condensed with adipic acid, 610 represents hexamethylenediamine condensed with sebacic acid, 11 represents a unit obtained from the condensation of aminoundecanoic acid, and 12 represents a unit obtained from the condensation of lauryllactam]

[0074] The notations such as PA X / Y, PA X / Y / Z, etc. relate to copolyamides in which X, Y, Z, etc. represent the above-mentioned homopolyamide units.

[0075] Advantageously, the polyamide blocks of the copolymer used in the present invention include polyamide blocks PA6, PA10, PA11, PA12, PA54, PA59, PA510, PA512, PA513, PA514, PA516, PA518, PA536, PA64, PA66, PA69, PA610, PA612, PA613, PA614, PA616, PA618, PA636, PA104, PA109, PA1010, PA1012, PA1013, PA1014, PA1016, PA1018, PA1036, PA10T, PA124, PA129, PA1210, PA1212, PA1213, PA1214, PA1216, PA1218, PA1236, PA12T, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, or PA6 / 1012 / 12, or mixtures or copolymers thereof; preferably include polyamide blocks PA6, PA10, PA11, PA12, PA610, PA612, PA1010, PA1012, or PA11 / 12, or mixtures or copolymers thereof, more preferably include polyamide blocks PA11, PA12, PA11 / 12 PA6, or PA612, or mixtures or copolymers thereof.

[0076] The polyether block essentially contains alkylene oxide units or consists of alkylene oxide units.

[0077] The polyether block can in particular be a PEG (polyethylene glycol) block, i.e. a block consisting of ethylene oxide units, and / or a PPG (propylene glycol) block, i.e. a block consisting of propylene oxide units, and / or a PO3G (polytetramethylene glycol) block, i.e. a block consisting of polytetramethylene glycol ether units, and / or a PTMG block, i.e. a block consisting of tetramethylene glycol (also called polytetrahydrofuran) units. The PEBA copolymer can contain several types of polyethers in its chain, and the copolyether can be in block or statistical form.

[0078] Blocks obtained by oxyethylation of bisphenols, such as bisphenol A, can also be used. The latter products are described in particular in EP613919.

[0079] The polyether block can also consist of ethoxylated primary amines. Examples of ethoxylated primary amines can include products of the following formula. TIFF2025520315000001.tif25170m and n are integers from 1 to 20, and x is an integer from 8 to 18. These products are commercially available, for example, under the brand name Noramox® from CECA and under the brand name Genamin® from Clariant.

[0080] The polyether diol block is co-polycondensed with the carboxy-terminated polyamide block. General methods for the two-step preparation of PEBA copolymers containing an ester bond between the PA block and the PE block are known and are described, for example, in FR2846332. General methods for the preparation of PEBA copolymers having an amide bond between the PA block and the PE block are known and are described, for example, in EP1482011. The polyether block can also be mixed with a polyamide precursor and a chain-limiting diacid to prepare a polymer containing a polyamide block and a polyether block having randomly distributed units (one-step method).

[0081] PEBA can contain amine chain ends, provided that it contains OH chain ends. PEBA containing amine chain ends can be obtained from the polycondensation of a polyamide block having dicarboxyl chain ends and a polyoxyalkylene block having diamine chain ends, and can be obtained, for example, by the cyanoethylation and hydrogenation of an α,ω-dihydroxylated aliphatic polyoxyalkylene block known as a polyether diol.

[0082] PEBA is commercially available. In particular, products sold under the names Pebax® by Arkema, Vestamid® by Evonik, Grilamid® by EMS, and Pelestat® by Sanyo can be mentioned.

[0083] The above block copolymers generally contain at least one polyamide block and at least one polyether block, but PEBA in the sense of this specification can also contain two, three, four (or more) different blocks selected from those described herein, as long as these blocks contain at least a polyamide block and a polyether block.

[0084] For example, the copolymer can be a segmented block copolymer comprising three different types of blocks (or a "triblock" copolymer), which can be obtained from the condensation of some of the above blocks. The triblock can be, for example, 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, such as a PEG block and a PTMG block. The triblock is preferably a copolyetheresteramide.

[0085] The number average molar mass of the polyamide block in the PEBA copolymer is preferably 400 to 20,000 g / mol, more preferably 500 to 10,000 g / mol.

[0086] The number average molar mass of the polyether block is preferably 100 to 6,000 g / mol, more preferably 200 to 3,000 g / mol.

[0087] The number average molar mass is set by the content of the chain limiting substance. It can be calculated according to the following formula. M n =n モノマー ×MW 繰り返し単位 / n 鎖制限剤 +MW 鎖制限剤

[0088] In this formula, n モノマー represents the number of moles of the monomer, n 鎖制限物質 represents the number of moles of the excess diacid limiting substance, MW 繰り返し単位 represents the molar mass of the repeating unit, MW 鎖制限物質 represents the molar mass of the excess diacid.

[0089] The number average molar masses of the polyamide block and the polyether block can be measured by gel permeation chromatography (GPC) before the copolymerization of the blocks.

[0090] Advantageously, the mass ratio of the polyamide block to the polyether block of the copolymer is from 0.1 to 20, preferably from 0.5 to 18, and even more preferably from 0.6 to 15. This mass ratio can be calculated by dividing the number-average molar mass of the polyamide block by the number-average molar mass of the polyether block. Advantageously, the polyamide block-polyether block copolymer has a Shore D hardness of 10D to 70D, preferably 25D to 45D.

[0091] Advantageously, the PEBA has an OH group concentration of from 0.002 meq / g to 0.2 meq / g, preferably from 0.005 meq / g to 0.1 meq / g, more preferably from 0.01 meq / g to 0.08 meq / g, and / or a COOH group concentration of from 0.002 meq / g to 0.2 meq / g, preferably from 0.005 meq / g to 0.1 meq / g, more preferably from 0.01 meq / g to 0.08 meq / g.

[0092] The COOH group concentration can be determined by potentiometric analysis, and the OH group concentration can be determined by proton NMR. The measurement protocol is described in detail in the paper "Synthesis and characterization of poly(copolyethers-block-polyamides) - II. Characterization and properties of multiblock copolymers", Marechal et al., Polymer, Vol. 41, 2000, pages 3561 - 3580.

[0093] Preferably, the polyamide block of the PEBA is selected from PA11, PA12, PA10, PA6, PA610, PA612, PA1010, PA1012, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, and PA6 / 1010 / 1012, and preferably selected from PA11, PA12, PA6, PA612, and PA11 / 12. Advantageously, the polyether block of the PEBA is a polyethylene glycol and / or polytetrahydrofuran block.

[0094] According to one embodiment, the PEBA copolymer comprises a polyamide block as defined above and a block derived from PTMG, for example, derived from PA6 / 11 and PTMG, derived from PA6 / 12 and PTMG, derived from PA11 / 12 and PTMG, derived from PA6 / 11 / 12 and PTMG, derived from PA6 / 66 / 12 and PTMG, derived from PA6 / 1010 and PTMG, derived from PA6 / 1012 and PTMG, derived from PA6 / 1010 / 1012 and PTMG, derived from PA6 / 1012 / 12 and PTMG, derived from PA6 and PTMG, derived from PA11 and PTMG, derived from PA12 and PTMG, derived from PA6 and PEG, derived from PA11 and PEG, and derived from PA12 and PEG.

[0095] Particularly preferred PEBA copolymers in the context of the present invention are copolymers comprising blocks from PA10 and PEG; PA10 and PTMG; PA11 and PEG; PA11 and PTMG; PA12 and PEG; PA12 and PTMG; PA610 and PEG; PA610 and PTMG; PA6 and PEG; PA6 and PTMG; PA612 and PEG; PA612 and PTMG.

[0096] Advantageously, the PEBA can be a recycled PEBA and / or a partially or fully bio-based PEBA.

[0097] According to one embodiment, the weight ratio of the polyether block in the copolymer is at least 50% based on the total weight of the copolymer. Preferably, the mass ratio of the polyether block is 45 - 85% based on the total weight of the copolymer, more preferably 50 - 80%, particularly 60 - 70% based on the total weight of the copolymer.

[0098] The mass ratio of the blocks in the copolymer can be determined from the number average molar mass of the blocks, 1 and can be determined by 1H NMR.

[0099] Preferably, the polyether block amide (PEBA) is a linear (non-crosslinked) copolymer.

[0100] According to one embodiment, a single-material footwear item comprises from 35% to 85% by weight, particularly from 45% to 75% by weight, of one or more thermoplastic resin polymers selected from PEBA. For example, relative to the weight of the single-material footwear item, it can comprise from 35% to 40% by weight, or from 40% to 45% by weight, or from 45% to 50% by weight, or from 50% to 55% by weight, or from 55% to 60% by weight, or from 60% to 65% by weight, or from 70% to 75% by weight, or from 75% to 80% by weight, or from 80% to 85% by weight of PEBA.

[0101] Additives In addition to achieving desirable properties, and for aesthetic purposes as well, a single-material footwear item can also include specific additives in some or all of its parts.

[0102] An additive is, in the broadest sense, a compound that does not meet the definitions of components (i) and (ii), that is, it is neither a polyamide nor a copolyamide nor a PEBA.

[0103] Among the additives, in particular, flame retardants, fire retardants, UV inhibitors, antioxidants, abrasion resistant agents, light stabilizers, impact modifiers, antistatic agents, fluorescent brighteners, nucleating agents, plasticizers, adhesion promoters, adhesives, lubricants, foaming agents, and pigments can be mentioned.

[0104] Fillers and reinforcing agents can also be present as additives. In particular, fiber reinforcing agents such as short or continuous glass fibers or carbon fibers, and optionally those coated with resin, or alternatively plant fibers or mineral fibers can be mentioned. As variants, for example, non-fiber reinforcing agents such as solid glass beads, as well as lightweight reinforcing agents such as hollow glass beads or encapsulated foaming agents can also be envisaged.

[0105] More generally, there may be a need to provide the footwear item with a limited amount of polymers other than polyamide, copolyamide, or PEBA.

[0106] Thus, the parts of the footwear item are usually assembled using an adhesive. Preferably, this is an adhesive that is polyamide or copolyamide, or alternatively PEBA. Advantageously, it can be copolyamide. Alternatively, the adhesive used can also be selected especially from polyurethanes.

[0107] Thus, in one embodiment, a single-material footwear item can include additives in the form of polymers that are not polyamide, copolyamide, or PEBA. Preferably, such an adhesive, if present, is present in a low content of, for example, 0.01 wt% to 10 wt%, advantageously 0.1 wt% to 5 wt%, very particularly 1 wt% to 2.5 wt% based on the weight of the footwear item.

[0108] Overall, the single-material footwear item includes additives in an amount of 0 to 15 wt%, for example 0 to 2.5 wt%, or 2.5 to 5 wt%, or 5 to 7.5 wt%, or 7.5 to 10 wt%, or 10 to 12.5 wt%, or 12.5 to 15 wt% based on the weight of the single-material footwear item.

[0109] Depending on the design used for the single-material footwear item, the item includes parts that include one or more polyamides or copolyamides as a single polymer and others that include one or more PEBAs as a single polymer.

[0110] Alternatively, the single-material footwear item can include some or all of the parts made from a polyamide or copolyamide alloy combined with PEBA.

[0111] Finally, a single-material footwear item can include components that comprise a single polymer family and other components made of an alloy of polyamide and / or copolyamide combined with PEBA.

[0112] Method for manufacturing a single-material footwear item The single-material footwear item of the present invention can be manufactured by any method known in the art.

[0113] In particular, according to another aspect, the present invention I. providing 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 footwear item; II. manufacturing components of the footwear item from each thermoplastic resin material; III. assembling the components of the footwear item, optionally using an adhesive, to form a completed footwear item, A method for manufacturing a single-material footwear item of the present invention, comprising wherein the materials used are selected such that the completed footwear item comprises one or more thermoplastic resin polymers selected from polyamide and copolyamide in an amount of 15 to 65% by weight; one or more thermoplastic resin elastomers selected from PEBA in an amount of 35 to 85% by weight; and additives in an amount of 0 to 15% by weight.

[0114] According to one embodiment, the materials used are selected such that the completed footwear item comprises one or more thermoplastic resin polymers selected from polyamide and copolyamide in an amount of 25 to 55% by weight; one or more thermoplastic resin elastomers selected from PEBA in an amount of 45 to 75% by weight; and additives in an amount of 0 to 15% by weight.

[0115] Thus, materials based on polyamide, copolyamide, or PEBA are exclusively selected for each component of the footwear item, in particular for those forming the upper and those forming the sole. Depending on the stress on each component, a material consisting only of polyamide or copolyamide, only of PEBA, or alternatively a mixture of these polymers, excluding additives, is selected.

[0116] According to one embodiment, a single - material footwear item according to the present invention can be designed with an upper mainly made of polyamide, a cord made of polyamide, and a sole mainly made of PEBA.

[0117] Thus, for example, a single - material footwear item according to the present invention can include an upper containing a woven part made of polyamide, a cord made of polyamide, and a midsole and an outsole both made of PEBA, as shown in Table 1 below. [Table 1] TIFF2025520315000002.tif63170

[0118] The properties of the components of the single - material footwear item can be optimized by selecting specific grades of polyamide, copolyamide, or PEBA respectively. Furthermore, alloys of these polymers can also be used. Since the weight of each component can also be adjusted, the single - material footwear item has a ratio of polyamide / copolyamide to PEBA as claimed. A single - material footwear item designed in this way may be able to obtain a recycled composition with good properties.

[0119] Method for recycling a single - material footwear item The single-material footwear item of the present invention has the advantage of being easily recyclable due to the fact that it consists essentially of a thermoplastic resin material. Furthermore, the footwear item of the present invention does not pose a risk of isocyanate formation like TPU-based footwear items, so it can also be recycled completely safely.

[0120] Accordingly, in another aspect, the present invention is a method for recycling a single-material footwear item according to the present invention, comprising: (a) supplying a used footwear item; (b) grinding the clean footwear item to obtain a ground material; (c) heating the ground material until it melts; (d) extruding the melt into pellets, and is directed to a method for recycling.

[0121] It is also possible to provide a washing step before or after step (b) to remove dirt.

[0122] The ground footwear material obtained at the end of step (b) is usually in the form of shredded material. The shapes and sizes vary, but most often contain particles about a few millimeters in size.

[0123] Depending on the intended use of the recycled product, it may be advantageous to add one or more virgin materials to the ground footwear item obtained from the used footwear item. Accordingly, according to one embodiment, the recycling method further comprises: (e) adding a new material to the ground used footwear item before or after step (d) and further includes.

[0124] This new material can in particular be one or more thermoplastic resin polymers selected from polyamides and copolyamides. Alternatively, or in combination, it can also be one or more thermoplastic resin elastomers selected from PEBA.

[0125] It is also possible to add specific additives, in particular stabilizers, especially chain extenders, which makes it possible to compensate for the aging of the material during manufacture and before use.

[0126] Recycled polymer composition The single-material footwear items of the present invention can be recycled to produce materials with excellent properties. In particular, these materials have low density, good elastic recovery, appropriate tensile modulus, and stable intrinsic viscosity, which makes them suitable for demanding applications and use over multiple recycling cycles.

[0127] The resulting recycled materials have advantageous mechanical properties, but the fact remains that the recycled polymers are modified compared to virgin polymers. In particular, the heat and generally oxidative stress during the manufacture, use, and subsequent recycling of footwear items affects part of their reaction functions.

[0128] The ground materials and the compositions obtained therefrom are characterized in that the polymers present are derived from used footwear items. Footwear items are exposed during use to the products of degradation by air and light, as well as the sweat and microorganisms of the person wearing them.

[0129] According to another aspect, the present invention relates to a recycled polymer composition obtained by the method according to the present invention.

[0130] This composition in particular comprises (a) one or more thermoplastic resin polymers selected from polyamides and copolyamides, from 15 to 65% by weight, in particular from 25 to 55% by weight; b. 35 to 85% by weight, particularly 45 to 75% by weight, of one or more thermoplastic elastomers selected from PEBA; c. 0% to 15% of additives; comprising 20 to 100% by weight, preferably 30 to 99% by weight, even more preferably 50 to 98% by weight of a pelletized and ground single - material footwear item; (b) 0 to 80% by weight, preferably 1 to 70% by weight, particularly 2 to 50% by weight of virgin polymers selected from polyamides, copolyamides, and PEBA, preferably from polyamides; (c) 0 to 50% by weight, preferably 5 to 40% by weight, more preferably 10 to 30% by weight, particularly 15 to 25% by weight of additives; which may consist of.

[0131] Preferably, the virgin polymer is selected from the preferred polyamides, copolyamides, and PEBA described above in the context of a single - material footwear item.

[0132] Any additives of component (c) can be specifically selected from the list of agents and compounds described above in relation to the additives present in the single - material footwear item. Advantageously, these additives include fillers and reinforcing agents as described above.

[0133] Use Due to these advantageous properties, the composition obtained from the recycling of the single - material footwear item of the present invention can be recycled for various uses, particularly performance applications.

[0134] According to one embodiment, this composition obtained from recycling can be used to remanufacture footwear parts, particularly those of single - material footwear items, especially sports footwear items. This variant is particularly advantageous as it represents a closed - loop recycling.

[0135] The present invention will be described in more detail in the following examples.

Example

[0136] Unless otherwise specified, percentages are by weight based on the total weight of the composition hereinafter.

[0137] The following materials were used. Polyamide 11: Rilsan (registered trademark) FMNO, a polyamide 11 homopolymer with an inherent viscosity of 1.05 in solution, sold by Arkema. PEBA1: Pebax (registered trademark) RNew 40R53 SP01, sold by Arkema, with a Shore A hardness of 90 measured after 3 seconds according to ISO standard 868:2003. PEBA2: Pebax (registered trademark) 2533 SD02, sold by Arkema, with a Shore A hardness of 75 measured after 3 seconds according to ISO standard 868:2003. PEBA3: Pebax (registered trademark) RNew 72R53 SP01, sold by Arkema, with a Shore D hardness of 72 measured after 3 seconds according to ISO standard 868:2003. TPU1: Elastollan (registered trademark) 1180A, sold by BASF, with a Shore A hardness of 80 measured after 3 seconds according to ISO standard 868:2003. TPU2: Elastollan (registered trademark) 1164D, sold by BASF, with a Shore D hardness of 64 measured after 3 seconds according to ISO standard 868:2003. Antioxidant 1: Irganox (registered trademark) 245 sold by BASF. Antioxidant 2: Irgafos (registered trademark) 168 sold by BASF.

[0138] (Examples EI 1 - EI2) To evaluate the behavior after aging and recycling, various blends of polyamide and PEBA (the compositions are shown in Table 2 below) are prepared by compounding at a temperature of 230°C in a co - rotating twin - screw extruder.

[0139] After emerging from the extruder, the molten polymer is solidified by passing through a water bath at 25°C and chopped into pellets. Next, it is dried at 80°C for 8 hours in an oven under reduced pressure to reach a residual moisture content of <0.1%.

[0140] Next, the product is injection molded at 250°C in the form of plates having dimensions of 100×100×2 mm for use. These samples are subjected to 1,000 hours of UV aging in a xenon QSun enclosure to simulate the first life.

[0141] These aged samples are shredded with a model RS2402 cutter mill from supplier Getecha. This shredded material is remelted and homogenized at 230°C in a co-rotating twin-screw extruder. The molten polymer is solidified by passing through a water bath at 25°C, chopped into pellets of the recycled product, and then dried under reduced pressure for 8 hours to reach a humidity of less than 0.1%.

[0142] The pellets of the recycled product are finally injected at 250°C to form test specimens required for: ISO 527 1A dumbbells (tensile), bars (Charpy impact) with dimensions 80×10×4 mm, and plates with dimensions 100×100×2 mm 3 Before measurement, the test specimens are conditioned for 15 days in a controlled atmosphere at 23°C and 50% relative humidity.

[0143] Subsequently, the manufactured test specimens are used to evaluate the mechanical properties of the formulation after recycling as follows.

[0144] A. Modulus of elasticity and elongation at break under tensile load The tensile modulus of elasticity and elongation at break are measured with a Zwick dynamometer at 23°C and 50% relative humidity according to ISO standard 527-1-2019.

[0145] B. Impact resistance The energy (elastic) dissipated during Charpy impact using a notch is measured at a temperature of -30°C in accordance with ISO standard 179 / :1993 1eA.

[0146] C. Tear resistance Tear resistance is measured on a rectangular test piece with a notch cut out with a punch from a 100×100×2 mm plate. The test is carried out on a Zwick dynamometer at 23°C, 50% relative humidity, and a speed of 500 mm / min in accordance with ISO standard 34-1-2010.

[0147] D. Compounds manufactured by a recycling method The presence of isocyanate groups (toxic) is detected by checking for the appearance of a specific absorption band at 2270 cm -1 in the ATR mode of infrared FTIR spectroscopy in diamond crystals. This measurement is carried out on the pellets of the recycled product 1 hour after extrusion.

[0148] (Comparative examples EC A to EC E) Formulations based on TPU containing polyamide and PEBA in different ratios are prepared as shown in the above Examples EI1 and EI2, aged in the same procedure to produce test pieces therefrom, and evaluated in the same way.

[0149] The composition of the formulations and the evaluation results are compared in Table 2 below. [Table 2] Composition and recyclability of the tested mixtures TIFF2025520315000003.tif149170

[0150] The results demonstrate that Examples EI 1 and EI 2, which are representative of the footwear items according to the present invention, still exhibit good properties after recycling, and are particularly advantageous as starting materials for the manufacture of performance articles such as sports footwear items. The combination according to the invention of polyamide and PEBA in specific ratios makes it possible to obtain excellent mechanical properties both in terms of modulus of elasticity and in terms of tear resistance and notched Charpy impact resistance.

[0151] Conversely, Comparative Examples EC A, EC C, EC D, and EC F demonstrate that compositions that do not meet the criteria of the present invention exhibit weak properties after recycling and thus cannot be envisioned for demanding applications. In fact, as shown in Examples EC A, EC C, and EC D, when a footwear item contains too much PEBA, the tensile modulus becomes insufficient and the tear and impact resistances decrease. As shown in Comparative Example EC B, when a footwear item contains too much polyamide, the mixture has a very high tensile modulus and is not suitable for the reuse in the manufacture of footwear items. Finally, in the recycling of TPU, not only is the resulting performance low, but isocyanates are generated, making it difficult to use this material in recyclable articles from an HSE perspective.

[0152] (List of cited documents) European Patent No. 3081109 (B1) International Publication No. 2020 / 201370 (A1)

Claims

1. (i) 15 to 65% by weight of one or more thermoplastic resin polymers selected from polyamides and copolyamides; (ii) 35 to 85% by weight of one or more thermoplastic resin elastomers selected from PEBA; (iii) 0 to 15% by weight of additives, consisting of a single material footwear item.

2. (i) 25 to 55% by weight of one or more thermoplastic resin polymers selected from polyamide or copolyamide; (ii) 45 to 75% by weight of one or more thermoplastic resin elastomers selected from PEBA; (iii) 0 to 15% by weight of additives, consisting of the footwear item according to Claim 1.

3. The single material footwear item according to Claim 1 or 2, wherein component (i) comprises, alone or as a mixture, a polyamide or copolyamide selected from PA612, PA613, PA912, PA1010, PA1012, PA6, PA11, PA12, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014.

4. The single material footwear item according to any one of Claims 1 to 3, wherein component (ii) comprises a PEBA selected from those containing blocks derived from PA6 / 11 and PTMG, PA6 / 12 and PTMG, PA11 / 12 and PTMG, PA6 / 11 / 12 and PTMG, PA6 / 66 / 12 and PTMG, PA6 / 1010 and PTMG, PA6 / 1012 and PTMG, PA6 / 1010 / 1012 and PTMG, PA6 / 1012 / 12 and PTMG, PA6 and PTMG, PA11 and PTMG, PA12 and PTMG, PA6 and PEG, PA11 and PEG, and PA12 and PEG.

5. The single material footwear item according to any one of Claims 1 to 4, wherein the polyamide or copolyamide of component (i) has an average ratio of carbon atoms per amide group of more than 6, preferably more than 8, particularly 10 or more.

6. A single-material footwear item according to any one of claims 1 to 5, comprising 0 to 10% by weight, preferably 0.1 to 4% by weight, of an adhesive as an additive.

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

8. I. Providing 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 footwear item; II. Manufacturing components of the footwear item from each thermoplastic resin material; III. Optionally assembling the components of the footwear item using an adhesive to form a completed footwear item, A method for manufacturing a single-material footwear item according to any one of claims 1 to 7, comprising The materials used are selected such that the completed footwear item comprises 15 to 65% by weight of one or more thermoplastic resin polymers selected from polyamides and copolyamides; 35 to 85% by weight of one or more thermoplastic resin elastomers selected from PEBAs; and 0 to 15% by weight of additives. A method for manufacturing.

9. The method according to claim 8, wherein the materials used are selected such that the completed footwear item comprises 25 to 55% by weight of one or more thermoplastic resin polymers selected from polyamide or copolyamide; 45 to 75% by weight of one or more thermoplastic resin elastomers selected from PEBAs; and 0 to 15% by weight of additives.

10. A method for recycling a single-material footwear item according to any one of claims 1 to 7, comprising (a) Supplying a used footwear item; (b) Grinding the clean footwear item to obtain a ground material; (c) Heating the ground material until it melts; (d) Extruding the melt into pellets, A method for recycling, comprising

11. (e) Adding new material to the ground used footwear item before or after step (d) The recycling method according to claim 10, further comprising

12. A recycled polymer composition obtained by the method according to any one of claims 9 to 11.

13. (a) a. 15 to 65% by weight, in particular 25 to 55% by weight, of one or more thermoplastic resin polymers selected from polyamides or copolyamides; b. 35 to 85% by weight, in particular 45 to 75% by weight, of one or more thermoplastic resin elastomers selected from PEBA; c. 0% to 15% of additives, comprising 20 to 100% by weight, preferably 30 to 99% by weight, even more preferably 50 to 98% by weight of a pelletized and ground single-material footwear item; (b)0 to 80% by weight, preferably 1 to 70% by weight, in particular 2 to 50% by weight, of virgin polymers selected from polyamides, copolyamides, and PEBA; (c)0 to 50% by weight of additives, a composition comprising.

14. Use of the composition according to claim 12 or 13 for the manufacture of a footwear item.

15. Use according to claim 14, wherein the footwear item is a single-material footwear item.

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