Polymer foams comprising ethylene-vinyl acetate (EVA) copolymer and / or ethylene-(meth)acrylic acid alkyl ester copolymer and copolymer comprising polyamide blocks and polyether blocks

Abstract

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

Description

Technical Field

[0001] This invention relates to polymer foams comprising ethylene-vinyl acetate (EVA) copolymers and / or copolymers of ethylene and (meth)acrylate alkyl esters, as well as copolymers containing polyamide blocks and polyether blocks (PEBA). The invention also relates to methods for producing such foams, and to uses of said foams, particularly in footwear. Background Technology

[0002] Various foams based on EVA copolymers are primarily used in the field of sports equipment, such as shoe soles or sole components, gloves, rackets or golf balls, personal protective equipment, especially personal protective equipment for practicing sports (jackets, helmet internal components, shells, etc.). This application requires a specific set of physical properties that ensure resilience, low compression set, and the ability to withstand repeated impacts without deformation and to return to its initial shape.

[0003] There are numerous EVA foams developed using chemical foaming agents for footwear applications. However, these EVA foams have limitations in terms of flexibility, resilience, relatively narrow operating temperature range, relatively low stretchability, and unsatisfactory durability. Furthermore, regardless of the method used to obtain these foams, they all suffer from significant shrinkage.

[0004] Document WO 2013 / 192581 describes EVA foam comprising polyolefin elastomers and olefin block copolymers.

[0005] Document US2017 / 0267849 describes a pre-foamed composition comprising a partially hydrogenated thermoplastic elastomer block copolymer, an olefin block copolymer, and EVA. The partially hydrogenated thermoplastic elastomer block copolymer is an ABA or AB copolymer, wherein block A comprises styrene units, and block B is a random copolymer of ethylene and an olefin.

[0006] However, it has been shown that it is difficult to obtain foams that possess both low density and good elasticity. This is because, generally speaking, an improvement in mechanical properties is observed with increasing density, and vice versa; a decrease in density negatively affects mechanical properties, especially resilience.

[0007] There is a need to provide lighter polymer foams that have reduced shrinkage after foam molding and / or better resilience while maintaining good stiffness. Summary of the Invention

[0008] This invention primarily relates to foams, typically cross-linked foams, said foam comprising:

[0009] - Copolymer (a), said copolymer (a) is selected from ethylene-vinyl acetate (EVA) copolymers, copolymers of ethylene and (meth)acrylate alkyl esters, and / or mixtures thereof, and

[0010] - Copolymer (b), said copolymer (b) containing polyamide blocks and polyether blocks (PEBA copolymer),

[0011] The foam has a strength of less than or equal to 200 kg / m³. 3 Preferably less than or equal to 180 kg / m 3 The density, and / or, according to standard ISO 8307:2007, a resilience of 50% or more, preferably 55% or more.

[0012] According to one embodiment, the foam comprises 30% to 99.9% by weight, typically 55% to 99.9% by weight, preferably 60% to 99.9% by weight, more preferably 70% to 99% by weight, of a copolymer (a) relative to the total weight of the foam.

[0013] According to one embodiment, the foam comprises 0.1 wt% to 50 wt%, preferably 0.1 wt% to 40 wt%, of PEBA copolymer (b) relative to the total weight of the foam. Preferably, the foam comprises 0.1 wt% to 30 wt%, or 0.5 wt% to 30 wt%, or 1 wt% to 25 wt%, or 1 wt% to 20 wt%, of PEBA copolymer (b) relative to the total weight of the foam.

[0014] According to one embodiment, the foam contains 0.1% to 20% by weight of additives relative to the total weight of the foam.

[0015] According to one embodiment, the foam of the present invention may additionally comprise a polyolefin (c) and / or a thermoplastic elastomer polymer (d).

[0016] According to one embodiment, the foam, typically a cross-linked foam, comprises:

[0017] -30% by weight to 99.9% by weight, typically 50% by weight to 99.9% by weight, preferably 60% by weight to 99.9% by weight, more preferably 70% by weight to 99% by weight, of copolymer (a) selected from ethylene-vinyl acetate (EVA) copolymers, copolymers of ethylene and (meth)acrylate alkyl esters, and / or mixtures thereof, and

[0018] -0.1% to 40% by weight, preferably 0.1% to 30% by weight, of copolymer (b), said copolymer (b) containing polyamide blocks and polyether blocks (PEBA copolymer),

[0019] -0% by weight to 50% by weight of polyolefins (c) and / or thermoplastic elastomer polymers (d);

[0020] The total amount reaches 100% by weight of the foam;

[0021] The foam has a strength of less than or equal to 200 kg / m³. 3 Preferably less than or equal to 180 kg / m 3 The density, and / or, according to standard ISO 8307:2007, a resilience of 50% or more, preferably 55% or more.

[0022] Preferably, the foam comprises 0.1% to 50% by weight, preferably 0.1% to 40% by weight, or 0.1% to 30% by weight, or 0.1% to 20% by weight of polyolefin (c) and / or thermoplastic elastomer polymer (d) relative to the total weight of the foam.

[0023] The polyolefin (c) may be functionalized or non-functionalized, or a mixture of at least one functionalized and / or at least one non-functionalized component. The polyolefin (c) is preferably a functionalized polyolefin (c1).

[0024] The thermoplastic elastomer polymer (d) is typically selected from copolymers containing polyester and polyether blocks, polyurethanes, olefin thermoplastic elastomers or olefin block copolymers, styrene-diene block copolymers, and / or mixtures thereof.

[0025] The present invention enables the fulfillment of the above-mentioned requirements.

[0026] The present invention provides a foam having improved foamability, low density and one or more of the following advantageous properties: high capacity for recovering elastic energy during low stress loading; low compression set (and thus improved durability); high resilience; and improved elastic properties.

[0027] This is achieved by introducing the PEBA copolymer into a crosslinked foam of ethylene-vinyl acetate (EVA) and / or ethylene and (meth)acrylate alkyl esters.

[0028] The foam proposed in this invention has a low density (i.e., generally less than 200 kg / m³). 3 Preferably less than or equal to 150 kg / m 3 It may be as low as 100kg / m 3 Its application in footwear, especially athletic footwear, is particularly noteworthy due to its high resilience (i.e., greater than 50%, or even greater than 60%).

[0029] The present invention also relates to a method for preparing foam as described above, the method comprising:

[0030] (i) the step of providing a mixture, the mixture comprising:

[0031] -Copolymer(a),

[0032] -Copolymer(b),

[0033] - Crosslinking agent, preferably peroxide

[0034] - Foaming agent, preferably a chemical foaming agent

[0035] -Optionally, a polyolefin (c), a thermoplastic elastomer polymer (d), and at least one additive;

[0036] (ii) The step of shaping the mixture by injection molding, compression / molding or extrusion;

[0037] (iii) The step of foaming the mixture.

[0038] The above steps can be performed individually or simultaneously.

[0039] According to one implementation scheme, steps (i)+(ii), (ii)+(iii) or (i)+(ii)+(iii) are performed simultaneously.

[0040] The steps of the preparation method can be carried out in the same equipment, such as in a mixer or an extruder.

[0041] According to one implementation, step (i) is performed by mixing the following in a molten state:

[0042] -30% to 99.9% by weight, typically 50% to 99.9% by weight, preferably 60% to 99.9% by weight of copolymer (a);

[0043] -0.1% to 50% by weight, typically 0.1% to 40% by weight, preferably 0.1% to 30% by weight of PEBA copolymer (b);

[0044] -0% by weight to 50% by weight of polyolefins (c) and / or thermoplastic elastomer polymers (d);

[0045] -0% to 20% by weight, preferably 0.1% to 20% by weight, at least one additive;

[0046] -0.01% to 2% by weight of a crosslinking agent, preferably a peroxide;

[0047] -0.5% to 10% by weight of foaming agent, preferably chemical foaming agent,

[0048] The total amount reaches 100% by weight of the mixture.

[0049] According to another variation, a foaming agent is introduced during and / or after step (ii). The amount of foaming agent introduced into the method is typically 0.5% to 10% by weight, relative to the total weight of the mixture.

[0050] The present invention also relates to compositions or foams that can be obtained by the methods described above.

[0051] The method of the present invention enables the preparation of regular, uniform polymer foams that possess the aforementioned advantageous properties.

[0052] Typically, the foam obtained at the end of the preparation method described above consists essentially of, or even consists of, the following:

[0053] - The (co)polymer of the polymer matrix that forms the foam, and

[0054] - Decomposition products and / or byproducts generated by at least one foaming agent and at least one crosslinking agent, and optionally at least one additive, are dispersed in the polymer matrix.

[0055] This invention relates to the use of foam, as described above, in the production of articles, preferably shoe soles.

[0056] The present invention also relates to articles comprising or including at least one element of a foam as described above.

[0057] The articles can be selected from shoe soles, especially athletic shoe soles, balls of various sizes, gloves, personal protective equipment, track pads, motor vehicle parts, building parts, and electrical and electronic equipment parts.

[0058] The invention will now be described in more detail. Detailed Implementation

[0059] Copolymer (a)

[0060] The copolymer (a) according to the invention is a copolymer selected from ethylene-vinyl acetate (EVA) copolymers, ethylene and (meth)acrylate alkyl ester copolymers, and / or mixtures thereof.

[0061] The relative amount of vinyl acetate comonomer incorporated into the EVA copolymer can be from 0.1% by weight to up to 40% by weight, or even more, of the total copolymer. For example, the EVA may have a vinyl acetate content of 2% to 50% by weight, 5% to 40% by weight, or 10% to 30% by weight. The EVA can be modified by methods well known to those skilled in the art, including modification with unsaturated carboxylic acids or their derivatives such as maleic anhydride or maleic acid.

[0062] 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 segment contains 1 to 8 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, butyl, or combinations of two or more of these. Alkyl (meth)acrylate comonomers may be incorporated into the ethylene / (meth)acrylate alkyl copolymer in amounts from 0.1% to 45% by weight, or even more, of the total copolymer. The alkyl group may contain 1 to about 8 carbon atoms. For example, alkyl (meth)acrylate comonomers may be present in the copolymer in amounts from 5% to 45% by weight, 10% to 35% by weight, or 10% to 28% by weight. Examples of ethylene-(meth)acrylate copolymers include ethylene / methyl acrylate, ethylene / ethyl acrylate, ethylene / butyl acrylate, or combinations of two or more of these. Mixtures of two or more different ethylene-(meth)acrylate copolymers may be used.

[0063] The copolymer (a) may have a melt flow index (MFI) of 0.1 to 60 g / 10 min or 0.3 to 30 g / 10 min. Preferably, the copolymer (a) has a low melt flow index, for example, 0.1 to 20, or 0.5 to 20, or 0.5 to 10, or 0.1 to 5 g / 10 min.

[0064] In the context of this invention, unless otherwise stated, melt flow index (MFI) (expressed in g / 10 minutes) is measured according to standard ISO 1133 at a temperature of 190°C under a load of 2160 g. Copolymer (b) (PEBA) containing polyamide and polyether blocks.

[0065] The copolymer (b) of the present invention generally has an instantaneous hardness of less than or equal to 72 Shore D, more preferably less than or equal to 68 Shore D, 55 Shore D, or 45 Shore D. Hardness measurement can be performed according to standard ISO 868:2003.

[0066] Three types of polyamide blocks can be used advantageously.

[0067] According to the first type, the polyamide block is derived from the condensation of dicarboxylic acids (especially those containing 4 to 36 carbon atoms, preferably those containing 6 to 18 carbon atoms) and diamines (especially those containing 2 to 20 carbon atoms, preferably those containing 5 to 14 carbon atoms).

[0068] Examples of dicarboxylic acids include 1,4-cyclohexanedicarboxylic acid, succinic acid, adipic acid, azelaic acid, octanoic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, terephthalic acid and isophthalic acid, as well as dimer fatty acids.

[0069] Examples of diamines include tetramethylenediamine, hexamethylenediamine, 1,10-decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, isomers of bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), p-aminodicyclohexylmethane (PACM), isophorone diamine (IPDA), 2,6-bis(aminomethyl)norbornene (BAMN), and piperazine (Pip).

[0070] 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 derived from the diamine residue, and Y represents the number of carbon atoms derived from the diacid residue, which is conventional.

[0071] According to the second type, the polyamide block is formed by 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 12 atoms. Examples of lactams include caprolactam, heptanolactam, and lauryllactam. Examples of α,ω-aminocarboxylic acids include aminohexanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0072] Advantageously, the second type of polyamide block is a PA 11 (polyundecylamide), PA 12 (polydodecylamide), or PA6 (polycaprolactam) block. In the notation PA X, X represents the number of carbon atoms derived from the amino acid residue.

[0073] According to the third type, the polyamide block is formed by the condensation of at least one α,ω-aminocarboxylic acid (or lactam), at least one diamine and at least one dicarboxylic acid.

[0074] In this case, the polyamide PA block is prepared by the following polycondensation:

[0075] - A linear aliphatic or aromatic diamine containing X carbon atoms;

[0076] - A dicarboxylic acid containing Y carbon atoms; and

[0077] - Comonomer {Z}, selected from lactams and α,ω-aminocarboxylic acids 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, where (X1,Y1) is different from (X,Y).

[0078] The comonomer {Z} is introduced in a weight ratio that is advantageously up to 50%, preferably up to 20%, and even more advantageously up to 10% relative to the total amount of the polyamide precursor monomer;

[0079] - In the presence of a chain limiter selected from dicarboxylic acids.

[0080] Advantageously, a dicarboxylic acid containing Y carbon atoms is used as a chain limiting agent, which is introduced in excess relative to the diamine in stoichiometric amounts.

[0081] According to a variant of this third type, the polyamide block is produced by the condensation of at least two α,ω-aminocarboxylic acids or at least two lactams, or one lactam and one aminocarboxylic acid having different numbers of carbon atoms, optionally in the presence of a chain-limiting agent. Examples of aliphatic α,ω-aminocarboxylic acids include aminohexanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Examples of lactams include caprolactam, heptanolactam, and lauryl lactam. Examples of aliphatic diamines include hexamethylenediamine, dodecylmethylenediamine, and trimethylhexamethylenediamine. Examples of alicyclic diacids include 1,4-cyclohexanedicarboxylic acid. Examples of aliphatic diacids include succinic acid, adipic acid, azelaic acid, octanoic acid, sebacic acid, dodecanedicarboxylic acid, and dimer fatty acids. These dimer fatty acids preferably have a dimer content of at least 98%; they are preferably hydrogenated; they are, for example, products sold by Croda under the trademark Pripol, or by BASF under the trademark Empol, or by Oleon under the trademark Radiacid, or polyoxyalkylene α,ω-diacids. Examples of aromatic diacids include terephthalic acid (T) and isophthalic acid (I). Examples of alicyclic diamines include isomers of bis(4-aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), as well as p-aminodicyclohexylmethane (PACM). Other commonly used diamines include isophorone diamine (IPDA), 2,6-bis(aminomethyl)norbornene (BAMN), and piperazine.

[0082] As an example of the third type of polyamide block, the following can be mentioned:

[0083] -PA 6.6 / 6, where 6.6 represents the condensation of hexamethylenediamine unit with adipic acid, and 6 represents the unit generated by the condensation of caprolactam;

[0084] -PA 6.6 / 6.10 / 11 / 12, where 6.6 represents the condensation of hexamethylenediamine with adipic acid, 6.10 represents the condensation of hexamethylenediamine with sebacic acid, 11 represents the unit generated by the condensation of aminoundecanoic acid, and 12 represents the unit generated by the condensation of lauryl lactam.

[0085] Notation such as PA X / Y and PA X / Y / Z involves copolyamides, where X, Y, and Z represent homopolymer units as described above.

[0086] Examples of copolyamides include copolymers of caprolactam and lauryl lactam (PA 6 / 12), copolymers of caprolactam, adipic acid, and hexamethylenediamine (PA 6 / 66), copolymers of caprolactam, lauryl lactam, adipic acid, and hexamethylenediamine (PA 6 / 12 / 66), copolymers of caprolactam, lauryl lactam, 11-aminoundecanoic acid, azelaic acid, and hexamethylenediamine (PA 6 / 69 / 11 / 12), copolymers of caprolactam, lauryl lactam, 11-aminoundecanoic acid, adipic acid, and hexamethylenediamine (PA 6 / 66 / 11 / 12), copolymers of lauryl lactam, azelaic acid, and hexamethylenediamine (PA 69 / 12), and copolymers of 11-aminoundecanoic acid, terephthalic acid, and decamethyldiamine (PA 11 / 10T).

[0087] Advantageously, the polyamide blocks of the copolymers used in this invention comprise polyamide blocks selected from: PA6, PA11, PA12, PA5.4, PA5.9, PA5.10, PA5.12, PA5.13, PA5.14, PA5.16, PA5.18, PA5.36, PA6.4, PA6.9, PA6.10, PA6.12, PA6.13, PA6.14, PA6.16, PA6.18, PA6.36, PA10.4, PA10.9, PA10.10, PA10.12, PA10.13, PA10.14, PA10.16, PA10.18, PA10.36, PA10.16, PA12.4, PA10.16, PA10.18, PA10.18, PA10.19, PA10.10, PA10.10, PA10.12, PA10.13, PA10.14, PA10.16, PA10.18, PA10.19, PA10.10 ... 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, PA 11 / 10.10 or mixtures or copolymers thereof; and preferably containing blocks of polyamide PA 6, PA 11, PA 12, PA 6.10, PA 10.10, PA 10.12, PA 6 / 12, PA 11 / 12 or mixtures or copolymers thereof.

[0088] The polyether blocks of PEBA copolymers are formed from alkylene oxide (alkylene oxide) units. These polyether blocks may be, in particular, PEG (polyethylene glycol) blocks (i.e., blocks formed from ethylene oxide units), and / or PPG (polypropylene glycol) blocks (i.e., blocks formed from propylene oxide units), and / or PO3G (polytrimethylene glycol) blocks (i.e., blocks formed from trimethylene glycol ether units), and / or PTMG (polytetramethylene glycol) blocks (i.e., blocks formed from tetramethylene glycol units) (also known as polytetrahydrofuran). Copolymers may contain various types of polyethers in their chains; the coethers may be block or random.

[0089] Blocks obtained by oxyethylation of bisphenols (e.g., bisphenol A) can also be used. The latter product is specifically described in document EP 613919.

[0090] Polyether blocks can also be formed from ethoxylated primary amines. Examples of ethoxylated primary amines include products of the following formula:

[0091] [Chemical Formula 1]

[0092]

[0093] Where m and n are integers between 1 and 20, and x is an integer between 8 and 18. These products are available, for example, from CECA under the trademark. and from Clariant as a trademark Acquired through commercial purchase.

[0094] The polyether block may comprise a polyoxyalkylene block with an NH2 terminus, which can be obtained by cyanoacetylation of an α,ω-dihydroxylated aliphatic polyoxyalkylene block (referred to as a polyether diol). More specifically, commercial products such as Jeffamine or Elastamine (e.g.) can be used. D400, D2000, ED 2003, and XTJ 542 are commercial products from Huntsman and are also described in documents JP 2004346274, JP 2004352794, and EP 1482011.

[0095] The polyether diol block is used in its unmodified form and co-condenses with a polyamide block with a carboxyl end group, or is amination converted into a polyether diamine and condenses with a polyamide block with a carboxyl end group.

[0096] While the PEBA copolymers described above 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 selected from, for example, those described in this specification; polyester blocks, polysiloxane blocks such as polydimethylsiloxane (or PDMS) blocks, polyolefin blocks, polycarbonate blocks, and mixtures thereof. For example, the copolymers according to the invention may be segmented block copolymers (or “triblock” copolymers) comprising three different types of blocks, which are produced by the condensation of a variety of blocks described above. The triblock may, for example, be a copolymer comprising a polyamide block, a polyester block, and a polyether block, or a copolymer comprising a polyamide block and two different polyether blocks (e.g., PEG blocks and PTMG blocks).

[0097] PEBA is produced by the polycondensation of polyamide blocks with reactive ends and polyether blocks with reactive ends, for example, especially the following polycondensation:

[0098] 1) Polyamide blocks with diamine chain ends and polyoxyalkylene blocks with dicarboxyl chain ends;

[0099] 2) Polyamide blocks with dicarboxyl chain ends and polyoxyalkylene blocks with diamine chain ends (e.g., obtained by cyanoethylation and hydrogenation of α,ω-dihydroxylated aliphatic polyoxyalkylene blocks (called polyether glycols));

[0100] 3) Polyamide blocks with dicarboxylic acid chain ends and polyether diols, under this special condition, produce polyether ester amides.

[0101] Polyamide blocks with dicarboxyl groups at the end of their chains originate from, for example, the condensation of polyamide precursors in the presence of chain-restricting dicarboxylic acids. Polyamide blocks with diamine groups at the end of their chains originate from, for example, the condensation of polyamide precursors in the presence of chain-restricting diamines.

[0102] In the context of this invention, particularly preferred PEBA copolymers are copolymers comprising the following blocks: PA 11 and PEG; PA 11 and PTMG; PA 12 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.

[0103] According to one embodiment, the PEBA copolymer is linear.

[0104] According to one embodiment, the number-average molar mass Mn of the polyamide block in the copolymer is preferably 400 to 13000 g / mol, more preferably 500 to 10000 g / mol, even more preferably 600 to 9000 g / mol or between 600 and 6000 g / mol. In the embodiments, the number-average molar mass of the polyamide blocks in the copolymer is 400 to 500 g / mol, or 500 to 1000 g / mol, or 1000 to 1500 g / mol, or 1500 to 2000 g / mol, or 2000 to 2500 g / mol, or 2500 to 3000 g / mol, or 3000 to 3500 g / mol, or 3500 to 4000 g / mol, or 4000 to 5000 g / mol, or 5000 to 6000 g / mol, or 6000 to 7000 g / mol, or 7000 to 8000 g / mol, or 8000 to 9000 g / mol, or 9000 to 10000 g / mol, or 10000 to 11000 g / mol, or 11000 to 12000 g / mol. 000 g / mol, or 12,000 to 13,000 g / mol.

[0105] The number-average molar mass of the polyether block is preferably 100 to 3000 g / mol, more preferably 200 to 2000 g / mol. In embodiments, the number-average molar mass of the polyether block is 100 to 200 g / mol, or 200 to 500 g / mol, or 500 to 800 g / mol, or 800 to 1000 g / mol, or 1000 to 1500 g / mol, or 1500 to 2000 g / mol, 2000 to 2500 g / mol, or 2500 to 3000 g / mol.

[0106] The number-average molar mass is determined by the content of the chain limiting agent. It can be calculated according to the following equation:

[0107] M n =n 单体 x MW 重复单元 / n 限链剂 +MW 限链剂

[0108] In this formula, n 单体 n represents the number of moles of the monomer. 限链剂 The number of moles of excess chain-limiting agent, MW 重复单元 Represents the molar mass of the repeating unit, and MW 限链剂 This represents the molar mass of the excess chain-limiting agent.

[0109] The number-average molar mass of the polyamide and polyether blocks can be measured in tetrahydrofuran (THF) by gel permeation chromatography (GPC) according to standard 16014-1:2012 prior to copolymerization of the blocks.

[0110] The mass ratio of polyamide blocks to polyether blocks in PEBA copolymers is typically 0.1 to 20.

[0111] Preferably, the mass ratio of the polyamide block to the polyether block in the PEBA is 0.3 to 5, more preferably 0.3 to 2.

[0112] Specifically, the mass ratio of the polyamide block to the polyether block in the copolymer may be 0.1 to 0.2, or 0.2 to 0.3, or 0.3 to 0.4, or 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 19 to 20.

[0113] Polyolefins (c)

[0114] The foam may include polyolefins (c) selected from functionalized (c1) and nonfunctionalized (c2) polyolefins and mixtures thereof.

[0115] The polyolefin typically has a flexural modulus of less than 100 MPa (measured according to standard ISO 178) and a Tg of less than 0 °C (measured at the inflection point of the DSC temperature spectrum according to standard 11357-2).

[0116] Nonfunctionalized polyolefins (C2) are typically homopolymers or copolymers of α-olefins or dienes (e.g., ethylene, propylene, 1-butene, 1-octene, or butadiene). For example, it may be mentioned that:

[0117] -Polyethylene homopolymers and copolymers, especially LDPE, HDPE, LLDPE (linear low-density polyethylene), VLDPE (very low-density polyethylene), and metallocene polyethylene.

[0118] -Propylene homopolymer or copolymer

[0119] 1-Ethylene / α-olefin copolymers, such as ethylene / propylene, EPR (an abbreviation for ethylene propylene rubber), and ethylene / propylene / diene (EPDM).

[0120] The functionalized polyolefin (c1) can be a polymer of an α-olefin having reactive units (functionality); these reactive units are acid, anhydride, or epoxy functionalization. For example, the aforementioned polyolefin (c2) can be mentioned, which is grafted or copolymerized or terpolymerized with: unsaturated epoxides, such as glycidyl (meth)acrylate; or carboxylic acids or corresponding salts or esters, such as (meth)acrylic acid (which can be completely or partially neutralized by metals such as Zn); or carboxylic anhydrides such as maleic anhydride. The functionalized polyolefin is, for example, a PE / EPR mixture, the weight ratio of which can vary within a wide range, for example between 40 / 60 and 90 / 10, and depending on the degree of grafting, for example from 0.01% by weight to 5% by weight, said mixture is co-grafted with anhydrides, particularly maleic anhydride.

[0121] The functionalized polyolefin (c1) may be selected from the following (co)polymers grafted with maleic anhydride or glycidyl methacrylate, wherein the grafting degree is, for example, from 0.01% by weight to 5% by weight:

[0122] -PE, PP, copolymers of ethylene with propylene, butene, hexene or octene, said copolymers containing, for example, 35% to 80% by weight of ethylene;

[0123] - Ethylene / α-olefin copolymers, such as ethylene / propylene, EPR (abbreviation for ethylene-propylene rubber) and ethylene / propylene / diene (EPDM);

[0124] - A copolymer of ethylene and vinyl acetate (EVA) containing up to 40% by weight of vinyl acetate;

[0125] - A copolymer of ethylene and alkyl (meth)acrylate, containing up to 40% by weight of alkyl (meth)acrylate;

[0126] - A copolymer of ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate, containing up to 40% by weight of comonomers.

[0127] The functionalized polyolefin (c1) may also be selected from ethylene / propylene copolymers, primarily propylene, grafted with maleic anhydride, and then condensed with a monoamined polyamide (or polyamide oligomer) (the product described in EP-A-0342066).

[0128] The functionalized polyolefin (c1) may also be a copolymer or terpolymer of at least the following units: (1) ethylene, (2) alkyl methacrylate or saturated vinyl carboxylic acid ester, and (3) anhydride such as maleic anhydride, or (meth)acrylic acid, or epoxy group such as glycidyl methacrylate.

[0129] As an example of the latter type of functionalized polyolefin, the following copolymers may be mentioned, wherein ethylene preferably accounts for at least 60% by weight of the copolymer, and wherein the ternary comonomer (functional group) accounts for 0.1% to 10% by weight of the copolymer:

[0130] - Ethylene / (meth)acrylate alkyl ester / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymer;

[0131] - Ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymer;

[0132] - Ethylene / vinyl acetate or (meth)acrylate alkyl ester / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymer.

[0133] In the aforementioned copolymer, the (meth)acrylic acid can form a salt with Zn or Li.

[0134] The term “(meth)acrylate alkyl ester” in (c1) or (c2) means C1 to C8 alkyl methacrylate and C1 to C8 alkyl acrylate, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0135] The copolymers (c1) and (c2) mentioned above can be copolymerized randomly or in block copolymers, and can exhibit linear or branched structures.

[0136] The nonfunctionalized polyolefin (C2) is advantageously selected from polypropylene homopolymers or copolymers, and any ethylene homopolymer, or copolymers of ethylene and higher α-olefin type comonomers (such as butene, hexene, octene, or 4-methyl-1-pentene). For example, PP, high-density PE, medium-density PE, linear low-density PE, low-density PE, or ultra-low-density PE may be mentioned. Those skilled in the art know that these polyethylenes are produced according to a "free radical" process, according to a "Ziegler" type catalyst, or more recently according to a "metallocene" catalyst.

[0137] The functionalized polyolefin (C1) is advantageously selected from any polymer comprising α-olefin units and units with polar reactive functions (e.g., epoxy, carboxylic, or carboxylic anhydride functions). Examples of such polymers include terpolymers of ethylene, alkyl acrylates, and maleic anhydride or glycidyl methacrylate, for example... Products; or polyolefins grafted with maleic anhydride, such as Products; and terpolymers of ethylene, alkyl acrylates, and (meth)acrylic acid. Homopolymers or copolymers of polypropylene, grafted with carboxylic anhydrides, and then condensed with monoamined polyamides or oligomers of polyamides may also be mentioned.

[0138] It has been observed that functionalized polyolefins (c1) can improve the compatibility between copolymers (a) and (b).

[0139] According to one embodiment, the foam comprises 0.1 wt% to 50 wt%, preferably 0.1 wt% to 40 wt%; or 0.1 wt% to 30 wt%, or 0.1 wt% to 20 wt% of the polyolefin(c) as described above, relative to the total weight of the foam.

[0140] Thermoplastic elastomer polymers (d)

[0141] According to one embodiment, the foam comprises 0.1 wt% to 50 wt%, preferably 0.1 wt% to 40 wt%; or 0.1 wt% to 30 wt%, or 0.1 wt% to 20 wt% of a thermoplastic elastomer polymer (d), which, relative to the total weight of the foam, is selected from copolymers containing polyester blocks and polyether blocks, thermoplastic polyurethanes, olefinic thermoplastic elastomers or olefinic block copolymers, styrene-diene block copolymers and / or mixtures thereof.

[0142] Copolymers containing polyester and polyether blocks typically consist of flexible polyether blocks derived from polyether glycols and rigid polyester blocks resulting from the reaction of at least one dicarboxylic acid with at least one chain-extending short-chain glycol unit. The polyester and polyether blocks are linked via ester bonds formed by the reaction of the acid functional group of the dicarboxylic acid with the hydroxyl functional group of the polyether glycol. The sequence of the polyether and the diacid forms the flexible block, while the sequence of ethylene glycol or butanediol with the diacid forms the rigid block of the copolyether ester. The chain-extending short-chain glycol can be selected from neopentyl glycol, cyclohexanediol, and aliphatic glycols of the formula HO(CH2)nOH, where n is an integer ranging from 2 to 10.

[0143] Advantageously, the diacid is an aromatic dicarboxylic acid containing 8 to 14 carbon atoms. Up to 50 mol% of the aromatic dicarboxylic acid may be replaced by at least one other aromatic dicarboxylic acid containing 8 to 14 carbon atoms, and / or up to 20 mol% may be replaced by an aliphatic dicarboxylic acid containing 2 to 14 carbon atoms.

[0144] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, dibenzoic acid, naphthalene dicarboxylic acid, 4,4'-diphenylene dicarboxylic acid, bis(p-carboxyphenyl)methane, ethylene bis(p-benzoic acid), 1,4-tetramethylene bis(p-oxybenzoic acid), ethylene bis(p-oxybenzoic acid), and 1,3-trimethylene bis(p-oxybenzoic acid).

[0145] Examples of diols include ethylene glycol, 1,3-trimethylenediol, 1,4-tetramethylenediol, 1,6-hexamethylenediol, 1,3-propanediol, 1,8-octamethylenediol, 1,10-decamethylenediol, and 1,4-cyclohexyldimethylethanol. Copolymers containing polyester and polyether blocks are, for example, copolymers containing polyether units derived from polyether diols such as polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylenediol (PO3G), or polytetramethyldiol (PTMG), dicarboxylic acid units such as terephthalic acid, and diols (ethylene glycol) or 1,4-butanediol units. Such copolyether esters are described in patents EP 402 883 and EP 405 227. These polyethers are thermoplastic elastomers. They may contain plasticizers.

[0146] Thermoplastic polyurethanes are linear or microbranched polymers composed of rigid blocks and flexible elastomer-type blocks. They are prepared by reacting flexible elastomer-type polyethers or polyesters with hydroxyl-terminated groups with diisocyanates such as methylene diisocyanate or toluene diisocyanate. These polymers can be chain-extended using glycols, diamines, diacids, or amino alcohols. The reaction product of isocyanates and alcohols is polyurethane, and these blocks are relatively rigid with high melting points. These high-melting-point rigid blocks are the reason for the thermoplasticity of polyurethanes.

[0147] Alkene thermoplastic elastomers comprise 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, norbornene, or combinations of two or more of these. The alkene elastomers can be functionalized by grafting with anhydrides such as maleic anhydride.

[0148] Styrene-diene block copolymers comprise repeating units derived from polystyrene and polydiene units. The polydiene units are derived from polybutadiene, polyisoprene units, or copolymers of both. These copolymers can be hydrogenated to produce saturated rubber backbone segments commonly known as styrene / butadiene / styrene (SBS) or styrene / isoprene / styrene (SIS) thermoplastic elastomers, or styrene / ethylene-butene / styrene (SEBS) or styrene / ethylene-propylene / styrene (SEPS) block copolymers. They can also be functionalized by grafting with anhydrides such as maleic anhydride.

[0149] additive

[0150] The foam may contain 0.1% to 20% by weight, preferably 0.1% to 15% by weight, or 0.1% to 12% by weight, or 0.1% to 10% by weight of additives relative to the total weight of the foam.

[0151] Additives are typically used in foams as conventional additives that help improve the properties of the foam and / or the foaming process.

[0152] Typically, the additives may be pigments (TiO2 and other compatible colored pigments), dyes, adhesion promoters (for improving the adhesion of expanded foam to other materials), organic or inorganic fillers (e.g., calcium carbonate, barium sulfate, and / or silicon oxides), reinforcing agents, plasticizers, nucleating agents (in pure or concentrated form, such as CaCO3, ZnO, SiO2, or combinations of two or more of them), rubber (for improving rubber elasticity, such as natural rubber, SBR, polybutadiene, and / or ethylene-propylene terpolymers), stabilizers, antioxidants, UV absorbers, flame retardants, carbon black, carbon nanotubes, release agents, impact modifiers, and additives for improving processability (processing aids), such as stearic acid. The antioxidants may include phenolic antioxidants.

[0153] method

[0154] Foam can be produced through a number of processes, such as compression molding, injection molding, or a combination of extrusion and molding.

[0155] Methods for preparing cross-linked foams as defined above generally include:

[0156] (i) the step of providing a mixture, the mixture comprising:

[0157] -Copolymer(a),

[0158] -At least one copolymer (b),

[0159] - Crosslinking agent, preferably peroxide

[0160] - Foaming agent, preferably a chemical foaming agent

[0161] -Optionally, a polyolefin (c), a thermoplastic elastomer polymer (d), and at least one additive;

[0162] (ii) The step of shaping the mixture by injection molding, compression / molding or extrusion;

[0163] (iii) The step of foaming the mixture.

[0164] According to one implementation, step (i) is performed by mixing the following in a molten state:

[0165] -30% by weight to 99.9% by weight copolymer (a);

[0166] -0.1% to 50% by weight, preferably 0.1% to 40% by weight, of PEBA copolymer (b);

[0167] -0% by weight to 50% by weight of polyolefins (c) and / or thermoplastic elastomer polymers (d);

[0168] -0% to 20% by weight, preferably 0.1% to 20% by weight, at least one additive;

[0169] -0.01% to 2% by weight of a crosslinking agent, preferably a peroxide;

[0170] -0.5% to 10% by weight of foaming agent, preferably chemical foaming agent,

[0171] The total amount reaches 100% by weight of the mixture.

[0172] A homogeneous molten mixture is obtained at the end of the mixing step.

[0173] According to one embodiment, 0.01% to 2% by weight, preferably 0.05% to 2% by weight, or 0.05% to 1.8% by weight of a crosslinking agent is introduced into the mixture.

[0174] Generally, the crosslinking agent is selected from reagents capable of crosslinking EVA and / or ethylene and (meth)acrylate alkyl esters, and may contain one or more organic peroxides, such as those selected from dialkyl peroxides, peroxy esters, peroxydicarbonates (salts), peroxyketals, diacylperacids, or combinations of two or more of these. Examples of peroxides include dicumyl peroxide, bis(3,3,5-trimethylhexanoyl) peroxide, tert-butyl peroxyneopentate (salt), tert-butyl peroxyneopentate (salt), di(sec-butyl) peroxydicarbonate (salt), tert-pentyl peroxyneopentate (salt), 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl-cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,3-bis(tert-butylperylperoxyisopropyl)benzene, or combinations of two or more of these. These peroxides and other peroxides may be traded under various names. (Sold by Arkema)

[0175] The foaming agent (also known as a blowing agent) can be a chemical or physical reagent. It is preferably a chemical reagent, such as azodicarbonamide, dinitrospentamethylenetetramine, p-toluenesulfonyl hydrazine, p,p'-oxobis(benzenesulfonyl hydrazine), or a combination of two or more of these, or a mixture based on citric acid and sodium bicarbonate (NaHCO3) (e.g., from Clariant). (Series of products). It can also be a physical agent, such as dinitrogen or carbon dioxide, or hydrocarbons, chlorofluorocarbons, hydrochlorocarbons, hydrofluorocarbons, or hydrochlorofluorocarbons (saturated or unsaturated). For example, butane or pentane can be used. To accommodate the expansion decomposition temperature and foaming process, the foaming agent can be a (physical and / or chemical) foaming agent, or a mixture of foaming agent and activator.

[0176] According to one embodiment, when using a chemical foaming agent, an additional 0.1% to 10% by weight, or preferably 0.1% to 5% by weight, of a foaming agent activator is introduced into the mixture. The activator may be one or more metal oxides, metal salts, or organometallic complexes, or combinations of two or more of these. Examples include ZnO, zinc stearate, MgO, or combinations of two or more of these.

[0177] The compounds can be mixed in any manner known to those skilled in the art, such as using a Banbury mixer, a high-intensity mixer, a roller mixer, an open mill, or an extruder.

[0178] Time, temperature, and shear rate can be adjusted to ensure optimal dispersion without premature crosslinking or foaming. High mixing temperatures can lead to premature crosslinking and foaming due to the decomposition of crosslinking agents (e.g., peroxides) and foaming agents. When these compounds are 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 to 130°C, they form a homogeneous mixture. The upper limit of the temperature range for satisfactory operation may depend on the initial decomposition temperatures of the crosslinking agents and foaming agents used.

[0179] The (co)polymer can be mixed in the molten state before being mixed with other compounds. For example, the polymer can be mixed in the molten state in an extruder at temperatures up to about 250°C to achieve good potential mixing. The resulting mixture can then be mixed with the other compounds described above.

[0180] After mixing, the mixture can be shaped by injection molding, compression in a mold, or extrusion.

[0181] The mixture can be shaped into sheets, pellets, or granules, with appropriate dimensions for foaming. Roller mixers are frequently used to produce sheets. Extruders can be used to shape the composition into pellets or granules.

[0182] The foaming step can be performed in a compression mold at a temperature and time that allows for the decomposition of the crosslinking agent and the foaming agent. The foaming step can be performed during injection of the composition into the mold and / or by opening the mold. Those skilled in the art can readily adjust the temperature and time applied during the foaming step to optimize the foaming of EVA and / or ethylene and (meth)acrylate alkyl esters. Alternatively, the foaming step can be performed directly upon exiting the extrusion. The resulting foam can also be shaped into finished product dimensions by any means known in the art, such as thermoforming and compression molding.

[0183] It has been observed that PEBA copolymers do not contribute to the crosslinking of foams under these conditions, but surprisingly, their presence does not hinder the formation of foams crosslinked with EVA and / or ethylene and (meth)acrylate alkyl esters, and further provides particularly meaningful (interesting) properties to the foams as described above.

[0184] Foam and its uses

[0185] The foam according to the invention preferably has a content of less than or equal to 200 kg / m³. 3 A preferred strength is 180 kg / m³ or less. 3 Its density. For example, it can have a density of 25 to 200 kg / m³. 3 Furthermore, a preferred weight is 50 to 180 kg / m³. 3 or 50 to 160 kg / m3 The density can be controlled by adjusting the parameters of the production process.

[0186] Preferably, according to standard ISO 8307:2007, the foam has a resilience of 50% or more, preferably 55% or more. Generally, the resilience of the foam of the present invention is less than 80%, or less than 75%, or less than 70%.

[0187] Preferably, according to standard ISO 7214:2012, the foam has a compression set of less than or equal to 60% after 30 minutes, preferably less than or equal to 55%, or less than or equal to 50%.

[0188] Preferably, the foam also exhibits excellent properties in terms of fatigue strength and damping.

[0189] The foam of this invention has improved resilience while still maintaining appropriate stiffness and lightness, good dimensional stability and good abrasion resistance, which makes it particularly suitable for use in footwear.

[0190] Furthermore, the foam of this invention provides better adhesion to other components, facilitating complex assembly. This is because EVA foam is a substrate with low polarity and weak adhesion to other components of the shoe, thus complicating the assembly process. This is particularly important in the context of shoes (which are often multi-layered).

[0191] The foam according to the invention can be used to prepare sports articles, such as sports shoe soles, ski boots, midsoles, insoles or functional sole components, in the form of inserts in various parts of the sole (e.g., heels or arches), or upper parts of the shoe, in the form of reinforcements or inserts in the upper structure of the shoe, or in the form of protection.

[0192] It can also be used to manufacture balls, sports gloves (such as football gloves), golf ball parts, rackets, and protective components (jackets, helmet internal parts, shells, etc.). Typically, these products are manufactured by injection molding, or by injection molding followed by compression molding.

[0193] The foam according to the invention possesses advantageous shock resistance, vibration resistance, and noise reduction properties, combined with tactile properties suitable for use in equipment goods. Therefore, it can also be used in the production of rail mats, or various components in the automotive, transportation, electrical and electronic equipment, construction, or manufacturing industries. The invention will be further explained in a non-limiting manner with the aid of the following examples.

[0194] Example

[0195] Examples were conducted using the mixtures described in Table 1.

[0196] The EVA copolymer used is a product sold by SK Functional Polymer. 28-05 is an EVA copolymer with a vinyl acetate content of 28% by weight and a melt flow index of 5 g / 10 min.

[0197] The copolymers of Example 1 and Comparative Examples 2 and 3 comprise PA 6 / 12 blocks with a number-average molar mass of 1000 g / mol and PTMG blocks with a number-average molar mass of 1000 g / mmol. The mass ratio of polyamide blocks to polyether blocks is equal to 1.

[0198] The compound was mixed in a mixer at 100°C for 10 minutes to form a melt. The mixture was then shaped (in sheet form) at 95°C using a roller mixer. The resulting sheet was then foamed by compression / molding at 160°C for 20 minutes in a Darragon press.

[0199] The mechanical tests performed on the foam are as follows:

[0200] - Density measurement (kg / m³) 3 According to standard ISO 845;

[0201] - Hardness (Asker C),

[0202] - Shrinkage (%) after 1 hour at 70°C

[0203] - Ball rebound resilience (%): According to standard ISO 8307 (a 16.8g steel ball with a diameter of 16mm is dropped from a height of 500mm onto a foam sample; the rebound resilience corresponds to the percentage of energy returned to the ball, or the percentage of the initial height reached by the ball upon rebound), and

[0204] -Compression set (comp.set%): This measurement is performed by compressing a sample to a given degree of deformation and holding it for a given time, then releasing the stress and recording the residual deformation after a recovery time; the measurement is adapted from standard ISO 7214, where the deformation is 50%, the holding time is 6 hours, and the temperature is 50°C.

[0205] [Table 1]

[0206]

[0207] PHR = Parts / Hundreds of parts resin (The unit of measurement used in the formulation is expressed as parts by mass of the component / hundreds of polymer matrix).

[0208] The parameter "Foaming property" in Table 1 indicates the ability of the composition to repeatedly form quality foam. It is determined according to the following standards:

[0209] o: The foam expands well in three spatial directions, and its size is maintained after cooling, exhibiting a fine and uniform cell structure.

[0210] x: The foam expands weakly (or not at all), the size of the foam is lost due to collapse after cooling, and / or the cell structure is rough and uneven.

[0211] [Table 2]

[0212]

[0213]

[0214] Crosslinked EVA foam containing 20% ​​by weight PEBA in a polymer matrix (Example 1) formed uniformly and stably. Test results were repeatable (three foams were produced in three tests). Evaluation of the foam's mechanical properties revealed a 50% increase in resilience compared to 53% for the previous foam, and a decrease in density (210 vs. 192 kg / m³). 3 The hardness or compression set did not deteriorate, and shrinkage decreased after annealing at 70°C for 1 hour. In contrast, Table 1 shows that under similar conditions, it is impossible to obtain quality foam from PEBA alone (Comparative Example 2), nor is it possible to obtain quality foam from a composition containing more than 40% by weight of PEBA in a polymer matrix (Comparative Example 3).

Claims

1. A cross-linked foam, said cross-linked foam comprising: -30% by weight to 80% by weight of copolymer (a), said copolymer (a) being selected from ethylene-vinyl acetate (EVA) copolymers, copolymers of ethylene and (meth)acrylate alkyl esters, and / or mixtures thereof. -1% by weight to 30% by weight of copolymer (b), said copolymer (b) containing polyamide blocks and polyether blocks, -0% by weight to 40% by weight of polyolefins (c) and / or thermoplastic elastomer polymers (d); -0% to 20% by weight of at least one additive; The total amount reaches 100% by weight of the foam; The foam has a strength of less than or equal to 200 kg / m³. 3 The density, and / or, according to standard ISO 8307:2007, a resilience of 50% or greater. The polyolefin (c) and thermoplastic elastomer polymer (d) are different from copolymers (a) and / or copolymers (b).

2. The foam of claim 1, wherein the crosslinked foam comprises 50% to 80% by weight of copolymer (a).

3. The foam according to claim 1, wherein the foam has a density of less than or equal to 190 kg / m³. 3 The density.

4. The foam according to claim 1, wherein the foam has a resilience of 55% or more according to standard ISO 8307:2007.

5. The foam according to claim 1, wherein the copolymer (b) is a PEBA copolymer.

6. The foam according to claim 1, wherein the mass ratio of the polyamide block to the polyether block of the copolymer (b) is 0.3 to 5.

7. The foam according to claim 6, wherein the mass ratio of the polyamide block to the polyether block of the copolymer (b) is 0.3 to 2.

8. The foam according to any one of claims 1 to 7, wherein the foam contains 0.1% to 20% by weight of at least one additive relative to the total weight of the foam.

9. The foam according to any one of claims 1 to 7, wherein the polyolefin (c) is a functionalized polyolefin (c1).

10. The foam of claim 9, wherein the foam comprises 0.1% to 40% by weight of the polyolefin(c) relative to the total weight of the foam.

11. The foam of claim 10, wherein the foam comprises 0.1% to 30% by weight of the polyolefin(c) relative to the total weight of the foam.

12. The foam of claim 11, wherein the foam comprises 0.1% to 20% by weight of the polyolefin(c) relative to the total weight of the foam.

13. The foam according to any one of claims 1 to 7, wherein the thermoplastic elastomer polymer (d) is selected from copolymers containing polyester blocks and polyether blocks, thermoplastic polyurethanes, olefinic thermoplastic elastomers or olefinic block copolymers, styrene-diene block copolymers, and / or mixtures thereof.

14. The foam according to any one of claims 1 to 7, wherein the polyamide block of said copolymer (b) comprises a polyamide block selected from the group consisting of: 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 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, PA 11 / 10.10, or mixtures or copolymers thereof.

15. The foam according to any one of claims 1 to 7, wherein the polyether block of the copolymer (b) is selected from PEG blocks, and / or PPG blocks, and / or PO3G (polytrimethylene glycol) blocks, and / or PTMG blocks.

16. The foam according to any one of claims 1 to 7, wherein the number-average molecular weight Mn of the polyamide block is between 400 and 13,000 g / mol, and the number-average molecular weight Mn of the polyether block is between 100 and 3,000 g / mol.

17. The foam of claim 16, wherein the number-average molecular weight Mn of the polyamide block is between 500 and 10000 g / mol.

18. The foam of claim 17, wherein the number-average molecular weight Mn of the polyamide block is between 600 and 9000 g / mol.

19. The foam of claim 18, wherein the number-average molecular weight Mn of the polyamide block is between 600 and 6000 g / mol.

20. The foam of claim 16, wherein the number-average molecular weight Mn of the polyether block is between 200 and 2000 g / mol.

21. A method for preparing foam according to any one of claims 1 to 20, the method comprising: (i) the step of providing a mixture, the mixture comprising: -30% by weight to 80% by weight copolymer (a), -1% by weight to 30% by weight copolymer (b), -0.01% by weight to 2% by weight of crosslinking agent; -0.5% to 10% by weight of foaming agent, -0 to 40% by weight of polyolefin (c) and / or thermoplastic elastomer polymer (d), and 0% to 20% by weight of at least one additive, The total amount reaches 100% by weight of the mixture; (ii) The step of shaping the mixture by injection molding, compression / molding or extrusion; (iii) The step of foaming the mixture. The polyolefin (c) and thermoplastic elastomer polymer (d) are different from copolymers (a) and / or copolymers (b).

22. The method of claim 21, wherein the method includes the step of providing the mixture by mixing in a molten state.

23. The method of claim 21, wherein the mixture comprises 50% to 80% by weight of copolymer (a).

24. The method of claim 21, wherein the crosslinking agent is a peroxide.

25. The method according to claim 21, wherein the foaming agent is a chemical foaming agent.

26. The method of claim 21, wherein the mixture comprises 0.1% to 20% by weight of at least one additive.

27. Foam obtained by the method according to any one of claims 21 to 26.

28. An article comprising at least one element composed of a foam according to any one of claims 1 to 20 or 27.

29. The article of claim 28, wherein the article is selected from shoe soles, large or small balls, gloves, personal protective equipment, track pads, motor vehicle parts, building parts, and electrical and electronic equipment parts.

30. The article of claim 29, wherein the sole is selected from athletic shoe soles.

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