EP4214271A1

EP4214271A1 - Polymer foam comprising an ethylene-vinyl acetate (eva) copolymer and/or an ethylene-alkyl (meth)acrylate copolymer and a copolymer comprising polyamide blocks and polyether blocks

Info

Publication number: EP4214271A1
Application number: EP21785953.7A
Authority: EP
Inventors: Blandine Testud; Sébastien QUINEBECHE; Chao-Ting CHANG; Clio COCQUET
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2020-09-15
Filing date: 2021-09-15
Publication date: 2023-07-26
Also published as: FR3114096B1; KR20230068399A; WO2022058678A1; TW202219142A; CN116096794A; FR3114096A1; JP2023541540A; US20230357548A1

Abstract

The invention relates to a polymer foam comprising an ethylene-vinyl acetate (EVA) copolymer and/or an ethylene-alkyl (meth)acrylate copolymer and a copolymer comprising polyamide blocks and polyether blocks (PEBA). The invention also relates to a process for manufacturing such a foam and to the use thereof, in particular in shoes.

Description

DESCRIPTION

TITLE: Polymer foam comprising a copolymer of ethylene-vinyl acetate (EVA) and/or a copolymer of ethylene and alkyl (meth)acrylate and a copolymer with polyamide blocks and with polyether blocks

Field of invention

The present invention relates to a polymer foam comprising a copolymer of ethylene-vinyl acetate (EVA) and/or a copolymer of ethylene and alkyl (meth)acrylate and a copolymer with polyamide blocks and with polyether blocks (PEBA ). The present invention also relates to a method of manufacturing such a foam as well as its use, in particular in shoes.

Technical Background

Various foams based on EVA copolymers are used in particular in the field of sports equipment, such as soles or components of soles, gloves, rackets or golf balls, individual protection elements in particular for the practice of sport (vests, interior parts of helmets, hulls...). Such applications require a set of particular physical properties ensuring an ability to rebound, a low residual deformation in compression and an ability to endure repeated impacts without deforming and to return to the initial shape.

There are many EVA foams, developed with chemical foaming agents for footwear applications. However, these EVA foams have limitations in terms of flexibility, resilience, a relatively restricted temperature range of use, as well as a relatively low stretchability, and imperfect durability. In addition, these foams suffer from a lot of shrinkage, whatever their method of obtaining.

Document WO 2013/192581 describes an EVA foam comprising a polyolefin elastomer and an olefin block copolymer.

Document US2017/0267849 describes a pre-foam composition comprising a partially hydrogenated block thermoplastic elastomer copolymer, a olefin block copolymer and an EVA. The partially hydrogenated block thermoplastic elastomer copolymer is an ABA or AB copolymer where the A block comprises the styrene units and the B block is a random copolymer of ethylene and olefin.

However, it is difficult to have a foam combining the properties of low density and good resilience. Indeed, an improvement in the mechanical properties is generally observed accompanying an increase in the density, or on the contrary, a decrease in density deteriorates the mechanical properties, in particular the resilience.

There is a need to provide polymer foams that are lighter, with reduced shrinkage after forming the foam, and/or having better resilience while maintaining good rigidity.

Summary of the invention

The invention relates firstly to a foam, typically a reticulated foam, comprising:

- a copolymer (a) chosen from an ethylene-vinyl acetate (EVA) copolymer, a copolymer of ethylene and alkyl (meth)acrylate and/or mixtures thereof and,

- a copolymer (b) with polyamide blocks and polyether blocks (PEBA copolymer), said foam having a density less than or equal to 200 kg/m ³ , preferably less than or equal to 180 kg/m ³ , and/or a rebound, according to ISO 8307:2007, greater than or equal to 50%, preferably greater than or equal to 55%.

According to one embodiment, the foam comprises from 30 to 99.9%, typically from 55 to 99.9%, preferably from 60 to 99.9%, more preferably from 70 to 99.9%, by weight of the copolymer (a) relative to the total weight of the foam.

According to one embodiment, the foam comprises from 0.1 to 50%, preferably from 0.1 to 40% by weight of the PEBA copolymer (b) relative to the total weight of the foam. Preferably, the foam comprises from 0.1 to 30%, or from 0.5 to 30%, or from 1 to 25%, or from 1 to 20% by weight of the copolymer (b) PEBA, relative to the total weight foam. According to one embodiment, the foam comprises from 0.1 to 20% by weight of additives, relative to the total weight of the foam.

According to one embodiment, the foam of the present invention may further comprise a polyolefin (c) and/or a thermoplastic elastomeric polymer (d).

According to one embodiment, the foam, typically a reticulated foam, comprises:

- from 30 to 99.9%, typically from 50 to 99.9%, preferably from 60 to 99.9%, more preferably from 70 to 99% by weight of a copolymer (a) chosen from a copolymer of ethylene-vinyl acetate (EVA), a copolymer of ethylene and alkyl (meth)acrylate and/or mixtures thereof and,

- from 0.1 to 40%, preferably from 0.1 to 30% by weight of a copolymer (b) with polyamide blocks and with polyether blocks (PEBA copolymer),

- from 0 to 50% by weight of a polyolefin (c) and/or a thermoplastic elastomer polymer (d); the total being 100% by weight of the foam; said foam having a density less than or equal to 200 kg/m ³ , preferably less than or equal to 180 kg/m ³ , and/or a rebound resilience, according to standard ISO 8307:2007, greater than or equal to 50%, preferably greater than or equal to 55%.

Preferably, the foam comprises from 0.1 to 50%, preferably 0.1 to 40%, or 0.1 to 30%, or 0.1 to 20% by weight, relative to the total weight of the foam, of a polyolefin (c) and/or a thermoplastic elastomeric polymer (d).

The polyolefin (c) can be functionalized or non-functionalized or be a mixture of at least one functionalized and/or of at least one non-functionalized. Preferably the polyolefin (c) is a functionalized polyolefin (c1).

The thermoplastic elastomer polymer (d) can typically be chosen from a copolymer with polyester blocks and polyether blocks, a polyurethane, an olefinic thermoplastic elastomer or an olefinic block copolymer, a styrene diene block copolymer, and/or mixtures thereof.

The present invention makes it possible to meet the need expressed above. It provides a foam having improved foamability, having a low density, and having one or more advantageous properties among: a high capacity to restore elastic energy during stresses under low stress; low residual deformation in compression (and therefore improved durability); high rebound resistance; and improved resilience properties.

This is accomplished through the introduction of the PEBA copolymer into a reticulated foam of ethylene-vinyl acetate (EVA) and/or ethylene and alkyl (meth)acrylate.

The foam provided by the present invention is particularly valuable for the application of shoes, in particular sports shoes, thanks to a low density, namely generally less than 200 kg/m ³ , preferably less than or equal to 150 kg/m ³ , which can reach up to 100 kg/m ³ and a high rebound resilience, namely greater than 50%, or even greater than 60%.

The invention also relates to a method for preparing a foam as described above, comprising:

(i) a step of providing a mixture comprising:

- a copolymer (a),

- a copolymer (b),

- a crosslinking agent, preferably a peroxide,

- a foaming agent, preferably a chemical foaming agent,

- optionally a polyolefin (c), a thermoplastic elastomeric polymer (d), and at least one additive;

(ii) a step of shaping the mixture by injection, compression/molding or extrusion;

(iii) a step of foaming the mixture.

The aforementioned steps can be carried out separately or simultaneously.

According to one embodiment, steps (i)+(ii), (ii)+(iii) or (i)+(ii)+(iii) are performed simultaneously. The steps of the preparation process can be carried out in the same equipment, for example, in a mixer or an extruder.

According to one embodiment, step (i) is carried out by mixing in the molten state:,

- from 30 to 99.9%, typically from 50 to 99.9%, preferably from 60 to 99.9% by weight of the copolymer (a);

- from 0.1 to 50%, typically from 0.1 to 40%, preferably from 0.1 to 30% by weight of the copolymer (b) PEBA;

- from 0 to 50% by weight of the polyolefin (c) and/or of the thermoplastic elastomer polymer (d);

- from 0 to 20%, preferably from 0.1 to 20% by weight of at least one additive;

- from 0.01 to 2% by weight of the crosslinking agent, preferably a peroxide;

- from 0.5 to 10% by weight of the foaming agent, preferably a chemical foaming agent, the total making up 100% by weight of the mixture.

According to another variant, the foaming agent is introduced during and/or after step (ii). The amount of foaming agent introduced into the process is typically 0.5 to 10% by weight relative to the total weight of the mixture.

The invention also relates to a composition or a foam that can be obtained according to the method described above.

The process of the invention makes it possible to prepare a regular, homogeneous polymer foam having the aforementioned advantageous properties.

Typically, the foam obtained at the end of the preparation process described above consists essentially, or even consists, of:

- the (co)polymers constituting a polymer matrix of the foam, and

- the decomposition products and/or the by-products generated from the at least one foaming agent and the at least one crosslinking agent and optionally at least one additive, being dispersed in the polymer matrix.

The invention relates to the use of a foam as described above for the manufacture of an article, preferably a shoe sole.

The invention also relates to an article consisting of or comprising at least one element of a foam as described above. The article may be selected from shoe soles, including sports shoe soles, footballs or balls, gloves, personal protective equipment, rail soles, automotive parts, construction parts and electrical and electronic equipment.

The invention will now be described in more detail.

detailed description

Copolymer (a)

The copolymer (a) according to the invention is a copolymer chosen from an ethylene-vinyl acetate (EVA) copolymer, a copolymer of ethylene and alkyl (meth)acrylate and/or mixtures thereof.

The relative amount of vinyl acetate comonomer incorporated into the EVA copolymer can be from 0.1% by weight up to 40% by weight of the total copolymer, or even more. For example, EVA can have a vinyl acetate content of 2-50% by weight, 5-40%, or 10-30% by weight. EVA can be modified by methods well known to those skilled in the art, including modification with an unsaturated carboxylic acid or its derivatives, such as maleic anhydride or maleic acid.

The copolymer of ethylene and alkyl (meth) acrylate comprises repeating units derived from ethylene and alkyl acrylate, alkyl methacrylate, or combinations thereof, wherein the alkyl moiety contains from 1 to 8 carbon atoms. Examples of alkyl include methyl, ethyl, propyl, butyl or combinations of two or more thereof. The alkyl (meth) acrylate comonomer can be incorporated into the ethylene/alkyl (meth) acrylate copolymer from 0.1% by weight to 45% by weight of the total copolymer or even more. The alkyl group can contain 1 to about 8 carbons. For example, the alkyl (meth)acrylate comonomer may be present in the copolymer at 5-45, 10-35, or 10-28% by weight. Examples of ethylene alky (meth) acrylate copolymer include ethylene/methyl acrylate, ethylene/ethyl acrylate, ethylene/butyl acrylate, or combinations of two or more thereof. A blend of two or more different ethylene-alkyl (meth)acrylate copolymers can be used. Copolymer (a) may have a melt index (MFI) of 0.1 to 60 g/10 minutes, or 0.3 to 30 g/10 minutes. Preferably, copolymer (a) has a low melt index, for example from 0.1 to 20, or from 0.5 to 20, or from 0.5 to 10, or from 0.1 to 5g/10 mins.

In the context of the invention, the melt flow indices (MFI) were measured at a temperature of 190° C. under a load of 2160 grams (units expressed in g/10 minutes) according to the ISO 1133 standard. unless otherwise indicated.

Copolymer (b) with polyamide blocks and polyether blocks (PEBA)

The copolymer (b) of the present invention generally has an instantaneous hardness less than or equal to 72 Shore D, more preferably less than or equal to 68 Shore D or 55 Shore D or 45 Shore D. The hardness measurements can be carried out according to ISO 868:2003.

Three types of polyamide blocks can advantageously be used.

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 6 to 18 carbon atoms, and of a diamine, in particular those having 2 to 20 carbon atoms, preferably those having 5 to 14 carbon atoms.

As examples of dicarboxylic acids, mention may be made of 1,4-cyclohexyldicarboxylic acid, butanedioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic, octadecanedicarboxylic acids and terephthalic and isophthalic acids, but also dimerized fatty acids .

As examples of diamines, mention may be made of tetramethylene diamine, 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), para-amino-di-cyclo-hexyl-methane ( PACM), isophoronediamine (IPDA), 2,6-bis-(aminomethyl)-norbornane (BAMN) and piperazine (Pip). Advantageously, polyamide blocks PA 4.12, PA 4.14, PA 4.18, PA 6.10, PA 6.12, PA 6.14, PA 6.18, PA 9.12, PA 10.10, PA 10.12, PA 10.14 and PA 10.18 are used. In the notation PA XY, X represents the number of carbon atoms resulting from the diamine residues, and Y represents the number of carbon atoms resulting from the diacid residues, in a conventional manner.

According to a second type, the polyamide blocks result from the condensation of one or more a,oo-aminocarboxylic acids and/or of one or more lactams having from 6 to 12 carbon atoms in the presence of a dicarboxylic acid having from 4 with 12 carbon atoms or a diamine. Examples of lactams include caprolactam, oenantholactam and lauryllactam. As examples of α,oo-amino carboxylic acid, mention may be made of aminocaproic, amino-7-heptanoic, amino-11-undecanoic and amino-12-dodecanoic acids.

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

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

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

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

- dicarboxylic acid(s) having Y carbon atoms; and

- comonomer(s) {Z}, chosen from lactams and a,oo-aminocarboxylic acids having Z carbon atoms and equimolar mixtures of at least one diamine having X1 carbon atoms and at least one dicarboxylic acid having Y1 carbon atoms, (X1, Y1) being different from (X, Y), said comonomer(s) {Z} being introduced in a proportion by weight advantageously ranging up to 50%, preferably up to 20%, even more advantageously up to 10% relative to all of the polyamide precursor monomers;

- in the presence of a chain limiter chosen from dicarboxylic acids. Advantageously, the dicarboxylic acid having Y carbon atoms is used as chain limiter, which is introduced in excess with respect to the stoichiometry of the diamine or diamines.

According to a variant of this third type, the polyamide blocks result from the condensation of at least two a,oo-aminocarboxylic acids or of at least two lactams having from 6 to 12 carbon atoms or of a lactam and of a aminocarboxylic acid not having the same number of carbon atoms in the optional presence of a chain limiter. As examples of aliphatic α,α-aminocarboxylic acid, mention may be made of aminocaproic, amino-7-heptanoic, amino-11-undecanoic and amino-12-dodecanoic acids. As examples of lactam, mention may be made of caprolactam, oenantholactam and lauryllactam. Examples of aliphatic diamines include hexamethylenediamine, dodecamethylenediamine and trimethylhexamethylenediamine. As examples of cycloaliphatic diacids, mention may be made of 1,4-cyclohexyldicarboxylic acid. As examples of aliphatic diacids, mention may be made of butane-dioic, adipic, azelaic, suberic, sebacic, dodecanedicarboxylic acids, dimerized fatty acids. These dimerized fatty acids preferably have a dimer content of at least 98%; preferably they are hydrogenated; these are, for example, products marketed under the "PRIPOL" brand by the "CRODA" company, or under the EMPOL brand by the BASF company, or under the Radiacid brand by the OLEON company, and polyoxyalkylene a,oo-diacids . As examples of aromatic diacids, mention may be made of terephthalic (T) and isophthalic (I) acids. As examples of cycloaliphatic diamines, mention may be made of 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 para-amino-di-cyclo-hexyl-methane (PACM). Other commonly used diamines can be isophoronediamine (IPDA), 2,6-bis-(aminomethyl)-norbornane (BAMN), and piperazine.

By way of examples of polyamide blocks of the third type, the following may be mentioned:

- PA 6.6/6, where 6.6 denotes hexamethylenediamine units condensed with adipic acid and 6 denotes units resulting from the condensation of caprolactam;

- PA 6.6/6.10/11/12, where 6.6 denotes hexamethylenediamine condensed with adipic acid, 6.10 denotes hexamethylenediamine condensed with adipic acid sebacic acid, 11 designates units resulting from the condensation of aminoundecanoic acid and 12 designates units resulting from the condensation of lauryllactam.

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.

Examples of copolyamides include copolymers of caprolactam and lauryllactam (PA 6/12), copolymers of caprolactam, adipic acid and hexamethylene diamine (PA 6/66), copolymers of caprolactam , lauryl lactam, adipic acid and hexamethylene diamine (PA 6/12/66), copolymers of caprolactam, lauryllactam, amino 11 undecanoic acid, azelaic acid and hexamethylene diamine (PA 6 /69/11/12), copolymers of caprolactam, lauryllactam, 11-amino undecanoic acid, adipic acid and hexamethylene diamine (PA 6/66/11/12), copolymers of lauryllactam, azelaic acid and hexamethylene diamine (PA 69/12), copolymers of 11-amino undecanoic acid, terephthalic acid and decamethylene diamine (PA 11/10T).

Advantageously, the polyamide blocks of the copolymer used in the invention comprise polyamide blocks chosen from PA 6, PA 11, PA 12, PA 5.4, PA 5.9, PA 5.10, PA 5.12, PA 5.13, PA 5.14, PA 5.16, PA 5.18, PA 5.36, PA 6.4, PA 6.9, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 6.18, PA 6.36, PA 10.4, PA 10.9, PA 10.10, PA 10.12, PA 10.13, PA 10.14, PA 10.16, PA 10.18, PA 10.36, PA 10.T, PA 12.4, PA 12.9, PA 12.10, PA 12.12, PA 12.13, PA 12.14, PA 12.16, PA 12.18, PA 12.36, PA 12.T, PA6/12, PA11/12, PA11/10.10 or mixtures or copolymers thereof; and preferably comprise blocks of polyamide PA 6, PA 11, PA 12, PA 6.10, PA 10.10, PA 10.12, PA6/12, PA 11/12 or mixtures or copolymers of these.

The polyether blocks of the PEBA copolymer consist of alkylene oxide units. The polyether blocks may in particular be PEG (polyethylene glycol) blocks, i.e. consisting of ethylene oxide units, and/or PPG (polypropylene glycol) blocks, i.e. consisting of propylene oxide units, and/ or PO3G (polytrimethylene glycol) blocks, i.e. consisting of trimethylene ether glycol units, and/or PTMG (polytetramethylene glycol) blocks, i.e. consisting of tetramethylene glycol units glycol also called polytetrahydrofuran. The copolymers can comprise in their chain several types of polyethers, the copolyethers possibly being 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.

The polyether blocks can also consist of ethoxylated primary amines. By way of example of ethoxylated primary amines, mention may be made of the products of formula:

[Chem in which m and n are integers between 1 and 20 and x 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 CLARIFYING.

The polyether blocks can comprise polyoxyalkylene blocks with ends of NH2 chains, such blocks being able to be obtained by cyanoacetylation of polyoxyalkylene a,oo-dihydroxylated aliphatic blocks called polyetherdiols. More particularly, the commercial products Jeffamine or Elastamine can be used (for example Jeffamine® D400, D2000, ED 2003, XTJ 542, commercial products from the company Huntsman, also described in the documents JP 2004346274, JP 2004352794 and EP 1482011).

The polyetherdiol blocks are either used as such and copolycondensed with polyamide blocks with carboxyl ic ends, or aminated to be transformed into polyether diamines and condensed with polyamide blocks with carboxyl ic ends.

If the above PEBA copolymers comprise at least one polyamide block and at least one polyether block as described above, the present invention also covers copolymers comprising three, four (or even more) different blocks chosen from those described in the present description, for example; polyester blocks, polysiloxane blocks, such as polydimethylsiloxane (or PDMS) blocks, polyolefin blocks, polycarbonate blocks, and mixtures thereof. For example, the copolymer according to the invention can 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 can 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.

PEBAs result from the polycondensation of polyamide blocks with reactive ends with polyether blocks with reactive ends, such as, among others, the polycondensation:

1) polyamide blocks with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chain ends;

2) polyamide blocks at the ends of dicarboxylic chains with polyoxyalkylene blocks at the ends of diamine chains, obtained for example by cyanoethylation and hydrogenation of aliphatic polyoxyalkylene a,oo-dihydroxylated blocks called polyetherdiols;

3) polyamide blocks with dicarboxylic chain ends with polyetherdiols, the products obtained being, in this particular case, polyetheresteramides.

The polyamide blocks with dicarboxylic chain ends come, for example, from the condensation of polyamide precursors in the presence of a chain-limiting dicarboxylic acid. The polyamide blocks with diamine chain ends come, for example, from the condensation of polyamide precursors in the presence of a chain-limiting diamine.

Particularly preferred PEBA copolymers in the context of the invention are copolymers comprising blocks: PA 11 and PEG; PA 11 and PTMG; PA12 and PEG; PA 12 and PTMG; PA 6.10 and PEG; PA 6.10 and PTMG; PA 6 and PEG; PA 6 and PTMG, PA 6/12 and PTMG, PA 6/12 and PEG, PA11/12 and PTMG, PA 11/12 and PEG.

According to one embodiment, the PEBA copolymer is linear. According to one embodiment, the number-average molar mass Mn of the polyamide blocks in the copolymer is preferably from 400 to 13,000 g/mol, more preferably from 500 to 10,000 g/mol, even more preferably from 600 to 9,000 g/mol. mol or between 600 and 6000 g/mol. In some embodiments, the number-average molar mass of the polyamide blocks in the copolymer is from 400 to 500 g/mol, or from 500 to 1000 g/mol, or from 1000 to 1500 g/mol, or from 1500 to 2000 g/mol, or from 2000 to 2500 g/mol, or from 2500 to 3000 g/mol, or from 3000 to 3500 g/mol, or from 3500 to 4000 g/mol, or from 4000 to 5000 g/mol, or from 5000 to 6000 g/mol, or from 6000 to 7000 g/mol, or from 7000 to 8000 g/mol, or from 8000 to 9000 g/mol, or from 9000 to 10000 g/mol, or from 10000 to 11000 g /mol, or from 11000 to 12000 g/mol, or from 12000 to 13000 g/mol.

The number-average molar mass of the polyether blocks is preferably from 100 to 3000 g/mol, preferably from 200 to 2000 g/mol. In some embodiments, the number average molar mass of the polyether blocks is from 100 to 200 g/mol, or from 200 to 500 g/mol, or from 500 to 800 g/mol, or from 800 to 1000 g/mol , or from 1000 to 1500 g/mol, or from 1500 to 2000 g/mol, or from 2000 to 2500 g/mol, or from 2500 to 3000 g/mol.

The number-average molar mass is fixed by the content of chain limiter. It can be calculated according to the relationship:

Mn ⁼ Hmonomer X Mwrepetition pattern / Hstring limiter + Mwistring mimic

In this formula, nmonomer represents the number of moles of monomer, nchain-limiter represents the number of moles of excess chain limiter, MWrepeating unit represents the molar mass of the repeating unit, and MWichain-limiter represents the molar mass of the limiter excess chain.

The number-average molar mass of the polyamide blocks and of the polyether blocks can be measured before the copolymerization of the blocks by gel permeation chromatography (GPC) according to standard ISO 16014-1:2012, in tetrahydrofuran (THF).

The mass ratio of the polyamide blocks relative to the polyether blocks of the PEBA copolymer is typically from 0.1 to 20.

Preferably, the mass ratio of the polyamide blocks relative to the polyether blocks of the PEBA is 0.3 to 5, more preferentially from 0.3 to 2. In particular, the mass ratio of the polyamide blocks relative to the polyether blocks of the copolymer can be from 0.1 to 0.2, or from 0.2 to 0.3, or from 0.3 to 0.4, or from 0 .4 to 0.5, or 0.5 to 0.6, or 0.6 to 0.7, or 0.7 to 0.8, or 0.8 to 0.9, or 0 .9 to 1, or 1 to 1.5, or 1.5 to 2, or 2 to 2.5, or 2.5 to 3, or 3 to 3.5, or 3.5 to 4, or 4 to 4.5, or 4.5 to 5, or 5 to 5.5, or 5.5 to 6, or 6 to 6.5, or 6.5 to 7 , or 7 to 7.5, or 7.5 to 8, or 8 to 8.5, or 8.5 to 9, or 9 to 9.5, or 9.5 to 10, or 10 to 11, or 11 to 12, or 12 to 13, or 13 to 14, or 14 to 15, or 15 to 16, or 16 to 17, or 17 to 18, or 18 to 19, or from 19 to 20.

Polyolefin (c)

The foam may comprise a polyolefin (c) chosen from functionalized (c1) and non-functionalized (c2) polyolefins and mixtures thereof.

The polyolefin can typically have a flexural modulus of less than 100 MPa measured according to the ISO 178 standard and a Tg of less than 0°C (measured according to the 1 1357-2 standard at the inflection point of the DSC thermogram).

A non-functionalized polyolefin (c2) is conventionally a homopolymer or copolymer of alpha-olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene. By way of example, we can cite:

- Polyethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low density polyethylene, or linear low density polyethylene), VLDPE (very low density polyethylene, or very low density polyethylene) and metallocene polyethylene.

- Propylene homopolymers or copolymers.

- ethylene/alpha-olefin copolymers such as ethylene/propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene/propylene/diene (EPDM).

The functionalized polyolefin (c1) can be a polymer of alpha-olefins having reactive units (the functionalities); such reactive units are acid, anhydride or epoxy functions. By way of example, mention may be made of the preceding polyolefins (c2) grafted or co- or ter polymerized by unsaturated epoxides such as glycidyl (meth) acrylate, or by carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (which can be totally or partially neutralized by metals such as Zn, etc.) or else by carboxylic acid anhydrides such as maleic anhydride. A functionalized polyolefin is, for example, a PE/EPR mixture, the weight ratio of which can vary widely, for example between 40/60 and 90/10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a degree of grafting for example of 0.01 to 5% by weight.

The functionalized polyolefin (c1) can be chosen from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the degree of grafting is for example from 0.01 to 5% by weight:

- PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing for example from 35 to 80% by weight of ethylene;

- ethylene/alpha-olefin copolymers such as ethylene/propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene/propylene/diene (EPDM);

- ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate;

- copolymers of ethylene and (meth)alkyl acrylate, containing up to 40% by weight of (meth)alkyl acrylate;

- ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

The functionalized polyolefin (c1) can also be chosen from ethylene/propylene copolymers with a majority of propylene grafted with maleic anhydride then condensed with monoamino polyamide (or a polyamide oligomer) (products described in EP-A-0342066) .

The functionalized polyolefin (c1) can also be a co- or ter polymer of at least the following units: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

By way of example of functionalized polyolefins of this latter type, mention may be made of the following copolymers, in which the ethylene preferably represents at least 60% by weight and in which the ter monomer (the function) represents, for example, from 0.1 to 10% by weight of the copolymer:

- ethylene/(meth)acrylate/(meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers;

- ethylene/vinyl acetate/maleic anhydride copolymers or glycidyl methacrylate;

- ethylene/vinyl acetate or alkyl (meth)acrylate/(meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

In the above copolymers, the (meth)acrylic acid can be salified with Zn or Li.

The term "alkyl (meth)acrylate" in (c1) or (c2) denotes C1 to C8 alkyl methacrylates and acrylates, and can be chosen from methyl acrylate, ethyl acrylate , n-butyl acrylate, isobutyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

The copolymers mentioned above, (c1) and (c2), can be randomly or block copolymerized and have a linear or branched structure.

Advantageously, the non-functionalized polyolefins (c2) are chosen from polypropylene homopolymers or copolymers and any homopolymer of ethylene or copolymer of ethylene and a comonomer of higher alpha olefinic type such as butene, hexene, octene or 4-methyl 1 - Pentene. Mention may be made, for example, of PP, high-density PE, medium-density PE, linear low-density PE, low-density PE, very low-density PE. These polyethylenes are known to those skilled in the art as being produced according to a “radical” process, according to a “Ziegler” type catalysis or, more recently, according to a so-called “metallocene” catalysis.

Advantageously, the functionalized polyolefins (c1) are chosen from any polymer comprising alpha-olefin units and units carrying polar reactive functions such as epoxy, carboxylic acid or carboxylic acid anhydride functions. Examples of such polymers include ter-polymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate such as Lotader® or polyolefins grafted with maleic anhydride such as Orevac® as well as terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Mention may also be made of polypropylene homopolymers or copolymers grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamino polyamide oligomers.

It has been observed that the functionalized polyolefin (c1) can improve the compatibility between the copolymer (a) and the copolymer (b). According to one embodiment, the foam comprises from 0.1 to 50%, preferably 0.1 to 40%; or 0.1 to 30%, or 0.1 to 20% by weight, to the total weight of the foam, of a polyolefin (c) as described above.

Thermoplastic elastomer polymer (d)

According to one embodiment, the foam comprises from 0.1 to 50%, preferably 0.1 to 40%; or 0.1 to 30%, or 0.1 to 20% by weight, to the total weight of the foam, of a thermoplastic elastomeric polymer (d) chosen from a copolymer with polyester blocks and polyether blocks, a thermoplastic polyurethane, a olefinic thermoplastic elastomer or olefinic block copolymer, styrene diene block copolymer, and/or mixtures thereof.

The copolymer with polyester blocks and polyether blocks are typically made up of flexible polyether blocks derived from polyetherdiols and of rigid polyester blocks which result from the reaction of at least one dicarboxylic acid with at least one chain-extending short diol unit. The polyester blocks and the polyether blocks are linked by ester bonds resulting from the reaction of the acid functions of the dicarboxylic acid with the hydroxyl functions of the polyetherdiol. The sequence of polyethers and diacids forms the flexible blocks while the sequence of glycol or butane diol with the diacids forms the rigid blocks of the copolyetherester. The chain-extending short diol can be chosen from the group consisting of neopentylglycol, cyclohexanedimethanol and aliphatic glycols of formula HO(CH2)nOH in which n is an integer ranging from 2 to 10.

Advantageously, the diacids are aromatic dicarboxylic acids having from 8 to 14 carbon atoms. Up to 50 mole % of the aromatic dicarboxylic acid may be replaced by at least one other aromatic dicarboxylic acid having 8 to 14 carbon atoms, and/or up to 20 mole % may be replaced by an aliphatic acid dicarboxylic having from 2 to 14 carbon atoms.

By way of example of aromatic dicarboxylic acids, mention may be made of terephthalic, isophthalic, bibenzoic, naphthalene dicarboxylic acid, 4,4'-diphenylenedicarboxylic acid, bis(p-carboxyphenyl) methane acid, ethylene bis p-benzoic acid, 1-4 tetramethylene bis(p-oxybenzoic acid), ethylene bis(p-oxybenzoic acid), 1,3-trimethylene bis(p-oxybenzoic) acid.

Examples of glycols include ethylene glycol, 1,3-trimethylene glycol, 1,4-tetramethylene glycol, 1,6-hexamethylene glycol, 1,3 propylene glycol, 1,8 octamethylene glycol, 1,10-decamethylene glycol and 1,4-cyclohexylene dimethanol. The copolymers with polyester blocks and polyether blocks are, for example, copolymers having polyether units derived from polyetherdiols such as polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (PO3G) or polytetramethylene glycol (PTMG). ), dicarboxylic acid units such as terephthalic acid and glycol (ethane diol) or butane diol units, 1-4. Such copolyetheresters are described in patents EP 402 883 and EP 405 227. These polyetheresters are thermoplastic elastomers. They may contain plasticizers.

Thermoplastic polyurethanes are linear or slightly branched polymers made up of hard blocks and soft elastomeric blocks. They can be produced by reacting soft hydroxy-terminated elastomeric polyethers or polyesters with diisocyanates such as methylene diisocyanate or toluene diisocyanate. These polymers can be chain extended with glycols, diamines, diacids or amino alcohols. The reaction products of isocyanates and alcohols are urethanes and these blocks are relatively hard and high melting. These high melting point hard blocks are responsible for the thermoplastic nature of polyurethanes.

The olefinic thermoplastic elastomer comprising repeating units of ethylene and higher primary olefins such as propylene, hexene, octene or combinations of two or more of these and optionally 1,4-hexadiene, ethylidene norbornene, norbornadiene or combinations of two or more thereof. The olefinic elastomer can be functionalized by grafting with an acid anhydride such as maleic anhydride.

The styrene diene block copolymer includes repeating units derived from polystyrene units and polydiene units. Polydiene units are derived from polybutadiene, polyisoprene units or copolymers of these two. The copolymer can be hydrogenated to produce a saturated rubbery backbone segment commonly referred to as thermoplastic elastomers styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS) or styrene/ethylene-butene/styrene (SEBS), styrene/ethylene-propylene/styrene (SEPS) block copolymers. They can also be functionalized by grafting with an acid anhydride such as maleic anhydride.

Additives

The foam may comprise from 0.1 to 20%, preferably from 0.1 to 15%, or from 0.1 to 12%, or from 0.1 to 10% by weight, relative to the total weight of the foam , additives.

Additives are typically common additives used in foams, which help to improve the properties of the foams and/or the foaming process.

Typically, the additives can be a pigment (TiC and other compatible colored pigments), colorant, adhesion promoter (to improve the adhesion of expanded foam to other materials), organic or inorganic fillers (for example, calcium carbonate, barium sulphate and/or silicon oxide), a reinforcing agent, plasticizers, a nucleating agent (in pure form or in concentrated form, for example, CaCOs, ZnO, SiO2, or combinations of two or more thereof, rubber (to improve rubbery elasticity, such as natural rubber, SBR, polybutadiene and/or ethylene propylene terpolymer), stabilizers, antioxidants, UV absorbers, flame retardants , carbon black, carbon nanotubes, a mold release agent, impact resistant agents, and additives for improving processability (“processing aids”, for example, stearic acid). Antioxidants can include phenolic antioxidants.

Process

Foam can be produced by a number of processes, such as compression molding, injection molding, or hybrids of extrusion and molding.

The process for preparing a reticulated foam as defined above generally comprises:

(i) a step of providing a mixture comprising: - a copolymer (a),

- at least one copolymer (b),

- a crosslinking agent, preferably a peroxide,

- a foaming agent, preferably a chemical foaming agent,

(iii) a step of foaming the mixture.

According to one embodiment, step (i) is carried out by mixing in the molten state:

- from 30 to 99.9% by weight of the copolymer (a);

- from 0.1 to 50%, preferably from 0.1 to 40% by weight of the PEBA copolymer (b);

- from 0 to 20%, preferably from 0.1 to 20% by weight of at least one additive;

- 0.01 to 2% by weight of the crosslinking agent, preferably a peroxide;

A homogeneous molten mixture is obtained at the end of the mixing step.

According to one embodiment, 0.01 to 2%, preferably 0.05 to 2%, or 0.05 to 1.8% by weight of a crosslinking agent are introduced into the mixture.

Generally, the crosslinking agent is chosen from an agent allowing the crosslinking of EVA and/or ethylene and alkyl (meth)acrylate, which may comprise one or more organic peroxides, for example chosen from dialkyl peroxides , peroxyesters, peroxydicarbonates, peroxyketals, diacyl peracids, or combinations of two or more thereof. Examples of peroxides include dicumyl peroxide, di(3,3,5-trimethyl hexanoyl) peroxide, t-butyl peroxypivalate, t-butyl peroxyneodecanoate, di(sec-butyl) peroxydicarbonate, t-amyl peroxyneodecanoate, 1,1-di-t-butyl-peroxy-3,3,5-trimethylcyclohexane, t-butyl-cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl - peroxy) hexane, 1,3-bis (tert-butyl-peryl-peroxy -isopropyl) benzene, or combinations of two or more of them. These peroxides and others are available under the Luperox® brand marketed by Arkema.

The foaming agent (also called blowing agent) can be a chemical or physical agent. Preferably, it is a chemical agent such as for example azodicarbonamide, dinitroso-pentamethylene-tetramine, p-toluene sulfonyl hydrazide, p, p'-oxy-bis (benzenesulfonyl hydrazide), or combinations two or more of them, or mixtures based on citric acid and sodium hydrogen carbonate (NaHCOs) (such as the product from the Hydrocerol® range from Clariant). It can also be a physical agent, such as for example dinitrogen or carbon dioxide, or a hydrocarbon, chlorofluorocarbon, hydrochlorocarbon, hydrofluorocarbon or hydrochlorofluorocarbon (saturated or unsaturated). For example butane or pentane can be used. To adapt the expansion-decomposition temperature and the foaming processes, a foaming agent can be a mixture of foaming agents (physical and/or chemical) or of foaming agents and an activator.

According to one embodiment, when a chemical foaming agent is used, 0.1 to 10%, or preferably 0.1 to 5% by weight, of an activator of the foaming agent is also introduced into the mixed. An activator can be one or more metal oxides, metal salts or organometallic complexes, or combinations of two or more of them. Examples include ZnO, Zn stearate, MgO or combinations of two or more of these.

The compounds can be mixed by any means known to those skilled in the art, such as with a Banbury mixer, intensive mixers, a roller mixer, a cylinder mixer, or an extruder.

Time, temperature and shear rate can be regulated to ensure optimum dispersion without premature crosslinking or foaming. High mixing temperature can cause premature crosslinking and foaming by decomposition of crosslinking agents, eg peroxides and foaming agents. The compounds can form a homogeneous mixture when mixed at temperatures of about 60°C to about 200°C, or 80°C to 180°C, or 70°C to 150°C, or 80°C. C to 130°C. The upper temperature limit for proper operation may depend on the initial decomposition temperatures of crosslinking agents and foaming agents used.

The (co)polymers can be melt mixed before being mixed with other compounds. For example, the polymers can be melt blended in an extruder at a temperature up to about 250°C to allow for good blending potential. The resulting mixture can then be mixed with the other compounds described above.

After mixing, shaping can be done by injection, compression in a mold or extrusion.

The mixture can be formed into sheets, pellets or granules of the appropriate dimensions for foaming. Roller mixers are often used to make sheets. An extruder can be used to shape the composition into pellets or pellets

The foaming step can be performed in a compression mold at a temperature and time to complete the decomposition of the crosslinking agents and foaming agents. The foaming step can be carried out during its injection into the mould, and/or by opening the mould. The temperature and time applied during the foaming step can easily be regulated by those skilled in the art to optimize the foaming of EVA and/or ethylene and alkyl (meth)acrylate. Alternatively, the foaming step can be performed directly at the outlet of an extrusion. The resulting foam can further be shaped to finished product size by any means known in the art such as thermoforming and compression molding.

It has been observed that the PEBA copolymer does not contribute to the crosslinking of the foam under these conditions but that, unexpectedly, its presence does not prevent the formation of the crosslinked foam of the EVA and/or of ethylene and of alkyl (meth)acrylate and further contributes particularly advantageous properties to the foam as indicated above.

Foam and its use

The foam according to the invention preferably has a density less than or equal to 200 kg/m ³ , particularly preferably less than or equal to 180 kg/m ³ . It may for example have a density of 25 to 200 kg/m ³ , and more particularly preferably from 50 to 180 kg/m ³ , from 50 to 160 kg/m ³ . Density control can be achieved by adapting the parameters of the manufacturing process.

Preferably, this foam has a rebound resilience, according to standard ISO 8307:2007, greater than or equal to 50%, preferably greater than or equal to 55%. Generally, the resilience of the foam of the invention is less than 80%, or 75%, or 70%.

Preferably, this foam has a permanent deformation in compression after 30 minutes, according to standard ISO 7214:2012, less than or equal to 60%, preferably less than or equal to 55%, or even less than or equal to 50%.

Preferably, this foam also has excellent fatigue resistance and damping properties.

The foam of the present invention exhibits improved resilience while maintaining appropriate stiffness and lightness, good dimensional stability and good abrasion resistance, which is particularly suitable for application in footwear.

Furthermore, the foam of the present invention provides better adhesion to other elements to facilitate complex assembly. Indeed, EVA foams are low polar substrates, weakly adhesive on the other elements of the shoe making the assembly steps complex. This is particularly interesting in the context of a shoe that often comes in the form of multilayers.

The foam according to the invention can be used to manufacture sports articles, such as soles of sports shoes, ski boots, intermediate soles, insoles, or even functional components of soles, in the form of inserts in different parts of the sole (heel or arch for example), or even components of shoe uppers in the form of reinforcements or inserts in the structure of the shoe upper, in the form of protections. It can also be used to manufacture balls, sports gloves (for example football gloves), golf ball components, rackets, protective elements (vests, interior elements of helmets, hulls, etc.). ). Typically, these articles can be made by injection molding or by injection molding followed by compression molding.

The foam according to the invention has interesting anti-shock, anti-vibration and anti-noise properties, combined with haptic properties suitable for capital goods. It can therefore also be used for the manufacture of rail shoes, or various parts in the automotive industry, in transport, in electrical and electronic equipment, in construction or in the manufacturing industry.

The invention will be further explained in a non-limiting manner using the Examples which follow.

EXAMPLES

The examples were carried out with the mixtures described in Table 1.

The EVA copolymer used is a product marketed by SK functional polymer: Evatane® 28-05, an EVA copolymer with a vinyl acetate content of 28% by weight and a melt index of 5 g / 10 minutes.

The copolymer of Example 1 and of Comparative Examples 2 and 3 comprises blocks of PA 6/12 with a number-average molar mass of 1000 g/mol and blocks of PTMG with a number-average molar mass of 1000 g/mol. The mass ratio of the polyamide blocks relative to the polyether blocks equals 1.

The compounds were mixed at 100°C for 10 minutes in a blender to form a melt. The mixtures were then shaped (in sheet form) at 95°C using a roller mixer. The resulting sheets were then foamed by compression/press molding (Darragon) for 20 minutes at 160°C.

The mechanical tests carried out on the foams are as follows:

- density measurement (kg/m ³ ), according to the ISO 845 standard;

- hardness (Asker C),

- shrinkage (%) after 1 hour at 70°C, - resilience by bouncing of a ball (%): according to the ISO 8307 standard (a steel ball weighing 16.8 g and 16 mm in diameter is dropped from a height of 500 mm on a sample of foam, the resilience rebound then corresponds to the percentage of energy returned to the ball, or percentage of the initial height reached by the ball on rebound) and

- Residual compression deformation (DRC, %): a measurement is carried out consisting in compressing a sample at a deformation rate and for a given time, then releasing the stress, and noting residual deformation after a recovery time; the measurement is adapted from the ISO 7214 standard, with a deformation of 50%, a holding time of 6 h, a temperature of 50°C.

[Table 1] PHR = parts per hundred of resin, known as parts per hundred of resin (unit of measurement used in formulation designating the number of parts of a constituent per hundred parts of polymer matrix by mass). The so-called "Foamability" parameter shown in Table 1 designates the ability of the composition to form a quality foam in a repeatable manner. It is determined according to the following criteria: o: good expansion of the foam in the 3 directions of space, dimensions of the foam retained after cooling, fine and homogeneous cellular structure, x: low expansion of the foam (even zero), foam dimensions lost after cooling by collapse and/or coarse and heterogeneous cell structure.

[Table 2]

The reticulated EVA foam comprising 20% by weight of PEBA (Example 1) in the polymer matrix was formed in a homogeneous and stable manner. Test results are repeatable (3 shaped foams out of 3 trials). The evaluation of the mechanical performance of the foams reveals an increase in resilience 50 vs. 53%, a reduction in density (210 vs. 192 kg/m ³ ) without deterioration of hardness and DRC, as well as a decrease in shrinkage after annealing for 1 hour at 70°C. Conversely, Table 1 shows that under similar conditions it was not possible to obtain quality foams from PEBA alone (Comparative Example 2) or from a composition comprising more than 40% by weight of PEBA in the polymer matrix (Comparative Example 2).

Claims

27 CLAIMS

1 . Reticulated foam including:

- from 30 to 99.9%, typically from 50 to 99.9% by weight of a copolymer (a) chosen from an ethylene-vinyl acetate (EVA) copolymer, a copolymer of ethylene and alkyl (meth)acrylate and/or mixtures thereof,

- from 0 to 50% by weight of a polyolefin (c) and/or a thermoplastic elastomer polymer (d); the total being 100% by weight of the foam; said foam having a density less than or equal to 200 kg/m ³ , preferably less than or equal to 190 kg/m ³ , and/or a rebound resilience, according to standard ISO 8307:2007, greater than or equal to 50%, preferably greater than or equal to 55%.

2. Foam according to claim 1, in which the mass ratio of the polyamide blocks relative to the polyether blocks of the copolymer (b) is 0.3 to 5, even more preferably from 0.3 to 2.

3. Foam according to one of the preceding claims, comprising from 0.1 to 20% by weight of additives, relative to the total weight of the foam.

4. Foam according to one of the preceding claims, in which the polyolefin (c) is a functionalized polyolefin (c1).

5. Foam according to claim 4, comprising from 0.1 to 50%, preferably 0.1 to 40%, or 0.1 to 30%, or 0.1 to 20% by weight, to the total weight of the foam , polyolefin (c).

6. Foam according to one of the preceding claims, in which the thermoplastic elastomeric polymer (d) is chosen from a copolymer with polyester blocks and polyether blocks, a thermoplastic polyurethane, an olefinic thermoplastic elastomer or an olefinic block copolymer, a block copolymer styrene diene, and/or mixtures thereof.

7. Foam according to one of the preceding claims, wherein the polyamide blocks of the copolymer (b) comprise polyamide blocks chosen from PA 6, PA 11, PA 12, PA 5.4, PA 5.9, PA 5.10, PA 5.12, PA 5.13 , PA 5.14, PA 5.16, PA 5.18, PA 5.36, PA 6.4, PA 6.9, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 6.18, PA 6.36, PA 10.4, PA 10.9, PA 10.10, PA 10.12, PA 10.13, PA 10.14, PA 10.16, PA 10.18, PA 10.36, PA 10.T, PA 12.4, PA 12.9, PA 12.10, PA 12.12, PA 12.13, PA 12.14, PA 12.16, PA 12.18, PA 12.36, PA 12.T, PA 6/12, PA 11/12, PA11/10.10, or mixtures or copolymers thereof.

8. Foam according to one of the preceding claims, in which the polyether blocks of the copolymer (b) are chosen from PEG blocks, and/or PPG blocks, and/or PO3G (polytrimethylene glycol) blocks and/or PTMG blocks. .

9. Foam according to one of the preceding claims, in which the number-average molecular weight Mn of the polyamide blocks is between 400 and 13,000 g/mol, or preferably between 500 and 10,000 g/mol, or between 600 and 9 000 g/mol, or between 600 and 6000 g/mol and the number-average molecular weight Mn of the polyether blocks is between 100 and 3000 g/mol, or preferably between 200 and 2000 g/mol.

10. Process for preparing a foam according to one of the preceding claims, comprising:

(i) a step of providing a mixture, preferably by melt-mixing, comprising:

- from 30 to 99.9%, preferably from 50 to 99.9% by weight of a copolymer (a).

- from 0.1 to 40%, preferably from 0.1 to 30% by weight of a copolymer (b),

- from 0.01 to 2% by weight of a crosslinking agent, preferably a peroxide,

- from 0.5 to 10% by weight of a foaming agent, preferably a chemical foaming agent,

- from 0 to 50% by weight of a polyolefin (c) and/or a thermoplastic elastomer polymer (d), and from 0 to 20%, preferably from 0.1 to 20% by weight of at least one additive , the total being 100% by weight of the mixture;

(iii) a step of foaming the mixture.

11. Foam obtainable by the method of claim 10.

12. Article, comprising at least one element consisting of a foam according to one of claims 1 to 9, or 11.

13. Article according to claim 12, is chosen from shoe soles, in particular the soles of sports shoes, footballs or balls, gloves, personal protective equipment, rail pads, automotive parts, construction parts and electrical and electronic equipment parts.