Polyamide-based multilayer structure usable as a card

Abstract

The present invention relates to a multilayer structure comprising: - an outer layer; - a binder layer; - an intermediate layer; - a binder layer; - a central layer; - a binder layer; - an intermediate layer; - a binder layer; - an outer layer, the compositions making up the outer layers, the intermediate layers and the central layer consisting of a composition comprising a polyamide matrix and having a melting point higher than 150°C, preferably higher than 160°C, and the binder layers consisting of a composition comprising a reactive functional polyolefin. The invention also relates to a method for manufacturing the structure, and to the use thereof as a card containing data.

Description

[0001] Multilayer structure based on polyamide usable as a card

[0002] technical field

[0003] The present invention relates to a multilayer structure usable as a card, as well as its manufacturing process.

[0004] Technical background

[0005] Smart cards, also known as chip cards, provide a secure framework for electronic identity. They can be used to control access to buildings, networks, and computers. They are also used as national identity cards, authenticating their owners. These cards contain data that is either visibly stored through ink or engraving, or invisibly stored via an electronic chip, antenna, magnetic stripe, or other device.

[0006] Currently, the cards offered are made of PVC. This material is obtained through a relatively toxic synthesis process and has the disadvantage of being difficult to recycle. Therefore, less polluting and recyclable materials are being sought to manufacture these cards.

[0007] The use of polyamides for card manufacturing is known from documents US2021 / 0268823 and US2022 / 0363953. However, the processes described involve a compression step at temperatures exceeding 160°C. These very high temperatures are a limiting factor for card manufacturing.

[0008] Technical problem to solve

[0009] However, the materials sought must meet specific requirements. Ideally, they should be able to replace PVC in the card manufacturing process without any modifications. This process uses a hot compression step to ensure adhesion between the layers. However, the core layers may contain certain heat-sensitive compounds, such as inks or the electronic chip, which require that the temperature not exceed 140°C during this hot compression. Therefore, a multilayer structure is needed, comprising layers that do not melt at temperatures below 140°C and that must adhere to each other during the compression step, which is carried out at a temperature below 140°C.

[0010] Thus, a structure essentially based on polyamide was found, whose melting point is much higher than its compression point. Therefore, the structure is not altered by this compression step. Adhesion between these layers is ensured by a polyolefin layer, which melts at a temperature lower than the compression point.

[0011] Furthermore, this specific structure has the advantage of being completely recyclable.

[0012] Brief description of the invention

[0013] The present invention relates to a multilayer structure comprising:

[0014] -an outer layer consisting of a composition comprising a polyamide matrix, the outer composition having a transmittance rate greater than or equal to 70% in the visible range (400 to 800 nm) on films 600 pm thick, measured according to ASTM-D1003-2011, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0015] -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0016] -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0017] -a central layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0018] -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0019] -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0020] -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min,

[0021] -an outer layer consisting of a composition comprising a polyamide matrix, the outer composition having a transmittance rate greater than or equal to 70% in the visible range (400 to 800 nm) on films 600 pm thick, measured according to ASTM-D1003-2011, the compositions constituting the outer layers, the intermediate layers and the central layer having a melting temperature greater than 150°C, preferably greater than 160°C.

[0022] The invention also relates to the manufacturing process of the structure as defined above, comprising the following successive steps:

[0023] 1. at least one extrusion step of each of the structural components in film form,

[0024] 2. at least one step of stacking the films on top of each other,

[0025] 3. at least one hot compression step at a temperature above the melting or glass transition temperature of the binder layers,

[0026] 4. at least one cooling stage of the structure, possibly under pressure.

[0027] The invention also relates to the use of the structure as a card containing data, such as a card to secure an electronic identity, a bank card, an identity card, a smart card, a card to control access to a space, such as a building, a room, an entrance vestibule, an elevator, a room, such as a storage space like a wardrobe, a drawer, a safe, a card to control networks and computers.

[0028] The structure according to the invention has the advantage of being mechanically recyclable. There is no need to separate the polymers. The resulting mixture can be directly reused either for the same application or for another application.

[0029] Indeed, the composition resulting from the recycling of the structure according to the invention comprises primarily one or more polyamides, a polyolefin compatible with the polyamide, and possibly fillers. The structure can be melted and then reused to manufacture another object, either by molding or injection molding.

[0030] Furthermore, when the structure consists mainly or exclusively of PA 11 as the matrix for the outer, intermediate, and central layers, the structure is largely bio-based. Its environmental impact is low compared to raw materials of fossil origin.

[0031] Furthermore, this structure has the advantage of using reactive functional polyolefins as an adhesive layer, rather than glues or thermosetting agents. However, the latter are either not recyclable or very difficult to recycle.

[0032] Other advantageous features of the structure according to the invention are specified below.

[0033] -In the structure, the matrices of the outer layers may comprise, independently of each other, at least one polyamide selected from PAU, PA12, PA1010, PA 1012, PA 513, PA56, PA510, PA 516, PA 610, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, as well as mixtures thereof. -The matrices of the intermediate layers and the matrix of the central layer comprise 5 to 20% by weight of a reinforcing filler having a form factor between 2 and 9.

[0034] -The matrices of the intermediate layers and the matrix of the central layer may comprise at least one polyamide selected from PAU, PA12, PA1010, PA 1012, PA 513, PA 516, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, MXD10, MXD12, MXD13, PA 11 / 10T and their mixture.

[0035] -The matrices of the intermediate layers and the matrix of the central layer may comprise at least one polyamide selected from PAU, PA12, PA1010 and PA 1012.

[0036] -The binder layer may include a polyolefin bearing carboxylic acid functions, acid anhydrides, or epoxy.

[0037] -The binder layer may include a polyolefin bearing acid anhydride functions.

[0038] -The outer, intermediate and central layers may include at least one additive selected from antioxidants, UV protectants, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming auxiliaries, gums, preservatives, antibacterial agents, pigments and mixtures thereof.

[0039] -The intermediate layer(s) may be inked. -The central layer may include a chip, an antenna, or a metallic component.

[0040] -The structure may have the following layer thicknesses:

[0041] -the outer layers each have a thickness of between 20 and 150 pm, advantageously between 40 and 100 pm, more particularly between 50 and 80 pm, and / or -the intermediate layers each have a thickness of between 100 and 450 pm, advantageously between 150 and 330 pm, and / or

[0042] -the central layer has a thickness between 100 and 450 pm, advantageously between 150 and 330 pm, and / or

[0043] -the binder layers each have a thickness between 2 and 40 µm, advantageously between 5 and 30 µm.

[0044] -The structure has a thickness between 500 pm and 1200 pm, advantageously between 700 pm and 900 pm.

[0045] Other advantageous features of the process according to the invention are specified below. -The compression step is carried out at a temperature between 100 and 140°C, preferably between 120 and 135°C.

[0046] -The duration of the compression stage is between 2 and 30 minutes, preferably between 10 and 20 minutes.

[0047] -The pressure applied during the compression stage is between 1 and 50 bars, preferably between 5 and 30 bars.

[0048] -The process includes an inking step for one or more intermediate layers.

[0049] -The process includes a step of cutting the central layer and a step of depositing an object within the central layer.

[0050] Detailed description

[0051] Other features, aspects, objects and advantages of the present invention will become even clearer upon reading the description that follows.

[0052] Unless otherwise stated, all percentages are mass percentages.

[0053] In this text, the quantities indicated for a given species may apply to that species according to all its definitions (as mentioned in this text), including more restricted definitions.

[0054] It is specified that the expressions "from ... to ..." and "between ... and ..." used in this description should be understood as including each of the mentioned limits.

[0055] Polyamides

[0056] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", specifically on page 3 (Tables 1 and 2), and is well known to those skilled in the art. Thus, PAU signifies that it is obtained by polycondensation of amino-11-undecanoic acid. PA12 is obtained by polycondensation of lauryllactam. PA1010 is obtained by polycondensation of decanediamine (10) and decanedioic acid (10). PA1012 is obtained by polycondensation of decanediamine (10) and dodecanedioic acid (12).

[0057] The word "polyamide" covers both homopolyamides and copolyamides.

[0058] The invention is now described in more detail, without limitation, in the following description. Polyamides are obtained by a polycondensation reaction of monomers, which may be amino acids or lactams, denoted Z, or chains of diacids and diamines, denoted XY, where X represents a diamine and Y a diacid. Thus, an amide group is formed by the reaction of an amine group with an acid group.

[0059] For the purposes of this invention, a unit is understood to be a Z or XY link resulting from the polycondensation of monomers.

[0060] For the purposes of this invention, the term "motif" means the sequence Z, the sequence X, or the sequence Y. In other words, unit Z consists of a motif Z, and unit XY consists of a motif X and a motif Y.

[0061] For the purposes of this invention, the C / N ratio means the average number of carbon atoms per nitrogen atom per unit.

[0062] In the case of a PA Z homopolyamide, where Z designates a repeating unit obtained from an amino acid or a lactam, the number of carbon atoms per nitrogen atom is the number of carbon atoms in the repeating unit. For example, PA 11 obtained by polycondensation of 11-aminoundecanoic acid has a C / N ratio of 11.

[0063] In the case of a PA XY homopolyamide, where X represents a unit obtained from a diamine and Y represents a unit obtained from a diacid, the number of carbon atoms per nitrogen atom is the average number of carbon atoms present in the XY unit. For example, PA 612, obtained by polycondensation of hexanediamine, a C6 diamine, and dodecanedioic acid, a C12 diacid, has a C / N ratio of 9, calculated as (6+12) / 2 = 9.

[0064] For copolyamides, for example with the structure XaYa / XbYb, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is performed in the molar proportion of the different amide units, that is to say, the XaYa and XbYb units. Thus, the coPA 10T / 106 containing 60% 10T and 40% 106 is in C8.6: 60%x[(10+8) / 2]+40%x[(10+6) / 2] = 8.6.

[0065] The multilayer structure

[0066] The multilayer structure according to the invention comprises:

[0067] -an outer layer

[0068] -a layer of binder

[0069] -an intermediate layer

[0070] -a layer of binder

[0071] -a central layer

[0072] -a layer of binder

[0073] -an intermediate layer

[0074] -a layer of binder

[0075] -an outer layer.

[0076] The binder layers ensure adhesion between adjacent layers. The central layer can house an information-carrying object: a chip, an antenna, or something similar. The intermediate layers can be inked and / or etched. The outer layers can also be inked and / or etched; they can also serve as protective layers for the structure.

[0077] The outer layers

[0078] The outer layer consists of a composition comprising a polyamide matrix. For the purposes of this invention, the term "matrix" means the polyamide that is the major component of the composition, i.e., the polyamide present in the highest concentration. The polyamide matrix may represent from 40% to 100% by weight of the total composition, preferably from 70% to 90% by weight.

[0079] The external composition exhibits a transmittance rate greater than or equal to 70% in the visible range (400 to 800 nm) on films 600 pm thick, measured according to the ASTM-D1003-2011 standard.

[0080] It is obtained by polycondensation of at least one motif chosen from an alpha, omega-aminocarboxylic acid in C6 to C18, a lactam in C5 to C12 and a unit (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0081] Polyamide can be obtained by polycondensation of at least one lactam selected from pyrrolidinone, 2-piperidinone, enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0082] The polyamide present in the composition of the outer layer can also be obtained by polycondensation of at least one amino acid chosen from 9-aminononanoic acid, 10-aminodecanoic acid (noted 10), amino-11-undecanoic acid (noted 11), amino-12-dodecanoic acid (noted 12).

[0083] Polyamide can be obtained by polycondensation of at least one motif corresponding to the formula (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0084] The motif (diamine in Ca) can be aliphatic, cycloaliphatic or aromatic. The diamine can be chosen from butanediamine (a=4), pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7), octanediamine (a=8), nonanediamine (a=9), decanediamine (a=10), undecanediamine (a=11), dodecanediamine (a=12), tridecanediamine (a=13), tetradecanediamine (a=14), hexadecanediamine (a=16), octadecanediamine (a=18), m-xylylene diamine (MXD), methylpentamethylene diamine (MPMD), bis(aminomethyl)cyclohexane (BAC), meta-xylylene diamine (MXD, CAS No. 1477-55-0), and the para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0085] Advantageously, diamine X is chosen from among 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0086] Preferably diamine X is in C12 C10, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0087] The motif (Cb diacid) can be aliphatic, cycloaliphatic or aromatic. The diacid can be chosen from succinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6), heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid (b=12), brassylic acid (b=13), tetradecanedioic acid (b=14), hexadecanedioic acid (b=16), octadecanedioic acid (b=18) and diacids obtained from fatty acids, and terephthalic acid (denoted T). Advantageously, the diacid is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0088] Advantageously, the polyamide present in the composition of the outer layer is chosen from PAU, PA12, PA1010, PA 1012, PA 510, PA 513, PA 516, PA 512, PA 610, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014 and their mixture.

[0089] According to a preferred embodiment, the polyamide present in the composition of the outer layer is a homopolyamide. This homopolyamide can be obtained by the polycondensation of a lactam, an amino acid, or a diamine (Ca) or diacid (Cb) motif, with Ca and Cb being as defined above.

[0090] More specifically, the composition mainly comprises PAU, PA12, PA1010, PA 1012, even more preferably PAU or PA12, preferably PAU and their mixture.

[0091] PAU has the advantage of being made from plant-based raw materials. These plant materials can be cultivated in large quantities, according to demand, across most of the globe, and are bio-based. A bio-based raw material is a natural resource, animal or plant-based, whose stock can be replenished in a short period on a human timescale. In particular, this stock must be able to renew itself as quickly as it is consumed.

[0092] The basic raw material for PAU is castor oil, extracted from the castor bean plant (the common castor bean plant) using castor seeds. PAU is obtained by polycondensation of amino-11-undecanoic acid.

[0093] Preferably, the composition comprises between 70 and 99.5% by weight of at least one polyamide relative to the total weight of the composition, preferably between 85% and 99.5%.

[0094] Additives

[0095] The composition constituting the outer layer may include one or more additives selected from antioxidants, UV protectants, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming aids, gums, preservatives, antibacterial agents, and mixtures thereof. Preferably, the composition includes at least one thermal stabilizer.

[0096] The composition constituting the outer layer may contain from 0.5 to 5% by weight of additives relative to the total weight of the composition.

[0097] According to a preferred embodiment of the invention, the outer layer consists of a polyamide matrix and 0.5 to 5% by weight of additives relative to the total weight of the composition.

[0098] The structure according to the invention comprises two external layers. These may be identical or different.

[0099] The outer layers preferably have a thickness between 20 and 150 pm, advantageously between 40 and 100 pm, more particularly between 50 and 80 pm.

[0100] The outer layers can be inked and / or engraved. The intermediate layers

[0101] The intermediate layer consists of a composition comprising a polyamide matrix consisting mainly of at least one polyamide having a C / N ratio greater than or equal to 8.

[0102] The composition has a Young's modulus measured according to ISO 527-1A 2019 of between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg of between 0.4 and 30 g / 10min, preferably between 0.5 and 20 g / 10min, more preferably between 0.5 and 15 g / 10min, preferably again between 0.5 and 10 g / 10min.

[0103] The polyamide present in the matrix of the intermediate layer composition is obtained by polycondensation of at least one motif chosen from an alpha, omega-aminocarboxylic acid in C8 to C18, a lactam in C8 to C12 and a unit (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0104] Polyamide can be obtained by polycondensation of at least one lactam selected from pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0105] The polyamide present in the matrix of the intermediate layer composition can also be obtained by polycondensation of at least one amino acid chosen from 9-aminononanoic acid, 10-aminodecanoic acid (noted 10), amino-11-undecanoic acid (noted 11), amino-12-dodecanoic acid (noted 12).

[0106] Polyamide can be obtained by polycondensation of at least one motif corresponding to the formula (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0107] The motif (diamine in Ca) can be aliphatic, cycloaliphatic or aromatic. The diamine can be chosen from butanediamine (a=4), pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7), octanediamine (a=8), nonanediamine (a=9), decanediamine (a=10), undecanediamine (a=11), dodecanediamine (a=12), tridecanediamine (a=13), tetradecanediamine (a=14), hexadecanediamine (a=16), octadecanediamine (a=18), m-xylylene diamine (MXD), methylpentamethylene diamine (MPMD), bis(aminomethyl)cyclohexane (BAC), meta-xylylene diamine (MXD, CAS No. 1477-55-0), and the para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0108] Advantageously, diamine X is chosen from among 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0109] Preferably diamine X is in C12 C10, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0110] The motif (Cb diacid) can be aliphatic, cycloaliphatic or aromatic. The diacid can be chosen from succinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6), heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid (b=12), brassylic acid (b=13), tetradecanedioic acid (b=14), hexadecanedioic acid (b=16), octadecanedioic acid (b=18) and diacids obtained from fatty acids, and terephthalic acid (denoted T).

[0111] Advantageously, the diacid is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0112] Advantageously, the polyamide present in the matrix of the composition of the intermediate layer is chosen from PAU, PA12, PA1010, PA 1012, PA 513, PA 516, PA 610, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, MXD10, MXD12, MXD13, PA 11 / 10T and their mixture.

[0113] According to a particular embodiment, the composition according to the invention comprises a mixture of aliphatic polyamide and aromatic polyamide, in which the aliphatic polyamide is the major polyamide.

[0114] According to a particular embodiment, the composition according to the invention comprises a mixture of aliphatic polyamide and aromatic polyamide, in which the aliphatic polyamide is the major polyamide.

[0115] According to a preferred embodiment, the polyamide present in the matrix of the intermediate layer composition is a homopolyamide. This homopolyamide can be obtained by the polycondensation of a lactam, an amino acid, or a diamine (Ca) or diacid (Cb) motif, with Ca and Cb being as defined above.

[0116] In a preferred embodiment, the intermediate layer comprises a polyamide matrix consisting mainly of a polyamide, which contains more than 95% of a single monomer. More particularly, the intermediate layer comprises a polyamide matrix consisting mainly of a homopolyamide. Advantageously, the matrix of the intermediate layer composition is made of a homopolyamide.

[0117] Advantageously, the polyamide present in the matrix of the intermediate layer has a glass transition temperature (Tg) greater than 40°C, preferably greater than 50°C, more preferably greater than 60°C, measured by DSC according to ISO 11357-2:2013, measured on a material in the dry state, i.e. containing less than 0.1% moisture, measured according to ISO 11357-1:2009.

[0118] Advantageously, the polyamide present in the matrix of the intermediate layer of the central and / or intermediate layer has a C / N ratio between 10 and 16, preferably between 9 and 14, more preferably between 10 and 12.

[0119] More specifically, the composition matrix mainly comprises PAU, PA12, PA1010, PA 1012, even more preferentially PAU or PA12, preferably PAU.

[0120] Preferably, the composition comprises between 50% and 98% by weight of at least one polyamide relative to the total weight of the composition, preferably between 65% and 95%.

[0121] Charges

[0122] The composition constituting the intermediate layer may include one or more fillers.

[0123] Preferably, the fillers are chosen from calcium carbonate, silicas, quartz, diatomaceous earth, wollastonites, aluminosilicates, such as kaolin, magnesia, slag, slate flour, vermiculite, mica, fibers, preferably ground, preferably ground glass fibers, aramid fibers, glass flakes, glass beads, talc, carbonaceous fillers, such as graphite, expanded graphite, carbon black, nanofillers, metal oxides, such as titanium oxide, most preferably talc and fibers.

[0124] Preferably, the composition constituting the intermediate layer of the structure according to the invention comprises one or more reinforcing fillers having a shape factor between 2 and 9, preferably between 2.5 and 7.

[0125] For the purposes of this invention, "shape factor" means the ratio of the largest dimension, for example the length, to the smallest dimension, for example the thickness, measured on the filler particle. The shape factor defines the shape of the filler within the composition.

[0126] For the purposes of this invention, "reinforcing filler" means a filler which, when present in a content of 10% by weight in a polyamide matrix, relative to the total weight of the assembly {matrix + filler}, increases the Young's modulus (GPa) of this assembly by a factor of at least 30%, preferably at least 50%, measured according to ISO 527-1A 2019, relative to the Young's modulus of the polyamide matrix without filler.

[0127] According to a first preferred embodiment, the reinforcing filler is talc. The talc may be treated or untreated. Preferably, the talc is in lamellar form.

[0128] For example, lamellar talcs are defined by a particle size distribution. The d50 Sedigraph is measured by gravity sedimentation in a liquid according to ISO 13317-3:2001, for example, in a Sedigraph III Plus® instrument. The d50 Laser is measured by laser diffraction according to ISO 13320:2009, for example, on a Malvern Mastersizer 2000® diffractometer.

[0129] The d50 distribution measured by Sedigraph evaluates the smallest particle size. The d50 distribution measured by laser evaluates the largest particle size. Thus, the form factor for these charges is obtained by the ratio of laser d50 to Sedigraph d50.

[0130] Reinforcing fillers can be chosen from talc marketed under the trade name Jetfine® 3CA, lamellar talc marketed under the trade name HAR® W 92, lamellar talc marketed under the trade name HAR® T 84.

[0131] For example, Jetfine 3C talc has Sedigraph d50 values ​​of 1.0 pm and laser d50 values ​​of 3.9 pm, resulting in a form factor of 3.9. Jetfine 3CA talc has a form factor of 3.4. HAR T84 talc has Sedigraph d50 values ​​of 2.2 pm and laser d50 values ​​of 10.5 pm, resulting in a form factor of 4.8.

[0132] The "tapped bulk" density, as defined by ISO 787 / 11 for talcs, is between 0.7 and 1 g / cm³ 3 .

[0133] According to a preferred embodiment, the reinforcing filler of the intermediate layer is talc. The talc may be present in a content of 5 to 20% by weight, preferably 7 to 17% by weight, more preferably 8 to 15% by weight, relative to the total weight of the composition.

[0134] According to a second preferred embodiment, the reinforcing filler is a fiber, preferably ground fibers, most advantageously ground glass fibers. For the purposes of this invention, glass fiber means any glass fiber, in particular as described by Frederick T. Wallenberger, James C. Watson and Hong Li, PPG Industries Inc. (ASM Handbook, Vol. 21: Composites (#06781G), 2001 ASM International).

[0135] Glass fibers typically have a diameter between 5 and 20 pm, preferably the fiber diameter is between 10 and 18 pm.

[0136] Standard glass fibers are generally several millimeters long and, after compounding and extrusion, have average lengths of over 200 µm. Therefore, the shape factor for these fibers is obtained by the ratio of average length to diameter.

[0137] Preferably, the glass fibers of the invention are ground glass fibers, that is to say, glass fibers whose length before compounding and extrusion is less than 100 pm. After compounding and extrusion, these glass fibers therefore have an average length of less than 100 pm.

[0138] Preferably, the glass fibers have an average length in the composition according to the invention, i.e. after grinding and after passing through the extruder, of between 30 and 100 pm, preferably the length of the fibers is between 40 and 80 pm.

[0139] For example, the following commercial glass fibers can be used: Lanxess MF 7904 glass fiber with an average length of 50 µm and an average diameter of 14 µm.

[0140] The composition constituting the intermediate layer may include from 2 to 50% by weight of fillers relative to the total weight of the composition, preferably between 5 and 30% by weight, more preferably between 5 and 20%, and preferably from 7 to 17%.

[0141] According to a preferred embodiment, the reinforcing filler of the intermediate layer is ground glass fiber. The ground glass fibers may be present in a content of 5 to 20% by weight, preferably 7 to 17% by weight, more preferably 8 to 15% by weight, relative to the total weight of the composition.

[0142] Preferably, the composition constituting the intermediate layer may comprise from 5 to 20% by weight of reinforcing fillers having a shape factor between 2 and 9, preferably between 2.5 and 7 relative to the total weight of the composition, preferably between 7 and 17% by weight.

[0143] Preferably, the reinforcing filler of the intermediate layer has a thermal conductivity between 0 and 4 W / mK, preferably between 0 and 3 W / mK, more preferably between 0 and 1 W / mK, measured according to ASTM D5930-17. In other words, the reinforcing filler is thermally insulating.

[0144] Preferably, the reinforcing filler of the intermediate layer has a surface resistivity greater than 1010 Ω, preferably greater than 1011 Ω measured according to IEC 62631-3-2 (2015). In other words, the reinforcing filler is electrically insulating.

[0145] Advantageously, the composition of the intermediate layer comprises 5 to 20% by weight of a reinforcing filler having a shape factor between 2 and 9 and whose largest dimension is less than 100 pm, preferably less than 50 pm.

[0146] Additives

[0147] The composition constituting the intermediate layer may include one or more additives selected from antioxidants, UV protectants, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming aids, gums, preservatives, antibacterial agents, pigments, and mixtures thereof. Preferably, the composition includes at least one thermal stabilizer.

[0148] The composition constituting the intermediate layer may contain from 0.4 to 5% by weight of additives relative to the total weight of the composition.

[0149] According to a preferred embodiment of the invention, the intermediate layer consists of a polyamide matrix, 2 to 50% fillers and 0.4 to 5% by weight of additives relative to the total weight of the composition.

[0150] The structure according to the invention comprises at least two intermediate layers. These may be identical or different.

[0151] The intermediate layers preferably have a thickness between 100 and 450 pm, preferably between 100 and 400 pm, advantageously between 150 and 350 pm, preferably between 150 and 330 pm.

[0152] Preferably, at least one intermediate layer is inked. Advantageously, both intermediate layers are inked.

[0153] According to a preferred embodiment, the intermediate layer consists of a composition comprising a polyamide matrix consisting mainly of a homopolyamide, and on the other hand a reinforcing filler chosen from talc and ground glass fibers.

[0154] In a particularly preferred manner, the intermediate layer consists of a composition comprising a polyamide matrix consisting mainly of a homopolyamide, and on the other hand a reinforcing filler chosen from talc.

[0155] In an alternative embodiment, the intermediate layer consists of a composition comprising a polyamide matrix consisting mainly of a homopolyamide, and on the other hand a reinforcing filler chosen from ground glass fibers.

[0156] The central layer

[0157] Preferably, the central layer consists of a composition comprising 60% to 95% by weight relative to the total weight of the composition of at least one polyamide having a C / N ratio greater than or equal to 8.

[0158] The composition has a Young's modulus measured according to ISO 527-1A 2019 of between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and an MFI of between 0.4 and 30 g / 10min, the MFI being measured under the following conditions: 235°C and 2.16 Kg, preferably 0.4 and 20 g / 10min, more preferably between 0.5 and 15 g / 10min, preferably again between 0.5 and 10 g / 10min.

[0159] The polyamide present in the matrix of the central layer composition is obtained by polycondensation of at least one motif chosen from an alpha, omega-aminocarboxylic acid in C8 to C18, a lactam in C8 to C12 and a unit (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0160] Polyamide can be obtained by polycondensation of at least one lactam selected from pelargolactam, decanolactam, undecanolactam, and lauryllactam. The polyamide present in the matrix of the central layer composition can also be obtained by polycondensation of at least one amino acid selected from 9-aminononanoic acid, 10-aminodecanoic acid (denoted 10), 11-aminoundecanoic acid (denoted 11), and 12-aminododecanoic acid (denoted 12).

[0161] Polyamide can be obtained by polycondensation of at least one motif corresponding to the formula (diamine in Ca). (diacid in Cb), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b being between 4 and 36.

[0162] The motif (diamine in Ca) can be aliphatic, cycloaliphatic or aromatic. The diamine can be chosen from butanediamine (a=4), pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7), octanediamine (a=8), nonanediamine (a=9), decanediamine (a=10), undecanediamine (a=11), dodecanediamine (a=12), tridecanediamine (a=13), tetradecanediamine (a=14), hexadecanediamine (a=16), octadecanediamine (a=18), m-xylylene diamine (MXD), methylpentamethylene diamine (MPMD), bis(aminomethyl)cyclohexane (BAC), meta-xylylene diamine (MXD, CAS No. 1477-55-0), and the para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0163] Advantageously, diamine X is chosen from among 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0164] Preferably diamine X is in C12 C10, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0165] The motif (Cb diacid) can be aliphatic, cycloaliphatic or aromatic. The diacid can be chosen from succinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6), heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid (b=12), brassylic acid (b=13), tetradecanedioic acid (b=14), hexadecanedioic acid (b=16), octadecanedioic acid (b=18) and diacids obtained from fatty acids, and terephthalic acid (denoted T).

[0166] Advantageously, the diacid is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0167] Advantageously, the polyamide present in the matrix of the composition of the central layer is chosen from PAU, PA12, PA1010, PA 1012, PA 513, PA 516, PA 610, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, MXD10, MXD12, MXD13, PA 11 / 10T and their mixture.

[0168] In one embodiment, the polyamide matrix of the central layer comprises at least two polyamides. The matrix may, for example, comprise a mixture of a major aliphatic polyamide and a semi-aromatic polyamide.

[0169] According to a preferred embodiment, the polyamide present in the matrix of the central layer composition is a homopolyamide. This homopolyamide can be obtained by the polycondensation of a lactam, an amino acid, or a diamine (Ca) or diacid (Cb) motif, with Ca and Cb being as defined above.

[0170] In a preferred embodiment, the central layer comprises a polyamide matrix consisting mainly of a polyamide, which contains more than 95% of a single monomer. More particularly, the intermediate layer comprises a polyamide matrix consisting mainly of a homopolyamide. Advantageously, the matrix of the intermediate layer composition consists of a homopolyamide.

[0171] Advantageously, the polyamide present in the composition of the matrix of the central layer has a glass transition temperature (Tg) greater than 40°C, preferably greater than 50°C, more preferably greater than 60°C, measured by DSC according to ISO 11357-2:2013, measured on a material in the dry state, i.e. containing less than 0.1% moisture, measured according to ISO 11357-1:2009.

[0172] Advantageously, the polyamide present in the composition of the matrix of the central layer has a C / N ratio between 10 and 16, preferably between 10 and 14, more preferably between 10 and 12.

[0173] More specifically, the composition matrix mainly comprises PAU, PA12, PA1010, PA 1012, even more preferentially PAU or PA12, preferably PAU.

[0174] Preferably, the composition comprises between 45% and 98% by weight of at least one polyamide relative to the total weight of the composition, preferably between 65% and 95%.

[0175] Charges

[0176] The composition constituting the central layer may include one or more fillers. Preferably, the fillers are chosen from calcium carbonate, silicas, quartz, diatomaceous earth, wollastonites, aluminosilicates, such as kaolin, magnesia, slag, slate flour, vermiculite, mica, fibers, preferably ground, preferably ground glass fibers, aramid fibers, glass flakes, glass beads, talc, carbonaceous fillers, such as graphite, expanded graphite, carbon black, nanofillers, metal oxides, such as titanium oxide, most preferably talc and fibers.

[0177] Preferably, the composition constituting the central layer of the structure according to the invention comprises one or more reinforcing fillers having a shape factor between 2 and 9, preferably between 2.5 and 7.

[0178] For the purposes of this invention, "shape factor" means the ratio of the largest dimension, for example, length, to the smallest dimension, for example, thickness, measured on the filler particle. The shape factor defines the shape of the filler within the composition

[0179] For the purposes of this invention, "reinforcing filler" means a filler which, when present in a content of 10% by weight in a polyamide matrix, relative to the total weight of the assembly {matrix + filler}, increases the Young's modulus (GPa) of this assembly by a factor of at least 30%, preferably at least 50%, measured according to ISO 527-1A 2019, relative to the Young's modulus of the polyamide matrix without filler.

[0180] According to a first preferred embodiment, the reinforcing filler is talc. The talc may be treated or untreated. Preferably, the talc is lamellar in form. For example, lamellar talcs are defined by a particle size distribution. The d50 Sedigraph is measured by gravity sedimentation in a liquid according to ISO 13317-3:2001, for example, in a Sedigraph III Plus® instrument. The d50 Laser is measured by laser diffraction according to ISO 13320:2009, for example, on a Malvern Mastersizer 2000® diffractometer.

[0181] The d50 distribution measured by Sedigraph evaluates the smallest particle size. The d50 distribution measured by laser evaluates the largest particle size. Thus, the form factor for these charges is obtained by the ratio of laser d50 to Sedigraph d50.

[0182] Reinforcing fillers can be chosen from talc marketed under the trade name Jetfine® 3CA, lamellar talc marketed under the trade name HAR® W 92, lamellar talc marketed under the trade name HAR® T 84.

[0183] For example, Jetfine 3C talc has Sedigraph d50 values ​​of 1.0 pm and laser d50 values ​​of 3.9 pm, resulting in a form factor of 3.9. Jetfine 3CA talc has a form factor of 3.4. HAR T84 talc has Sedigraph d50 values ​​of 2.2 pm and laser d50 values ​​of 10.5 pm, resulting in a form factor of 4.8.

[0184] The "tapped bulk" density, as defined by ISO 787 / 11 for talcs, is between 0.7 and 1 g / cm³ 3 .

[0185] According to a preferred embodiment, the reinforcing filler of the central layer is talc. The talc may be present in a content of 5 to 20% by weight, preferably 7 to 17% by weight, more preferably 8 to 15% by weight, relative to the total weight of the composition. According to a second preferred embodiment, the reinforcing filler is a fiber, preferably ground fibers, most advantageously ground glass fibers.

[0186] For the purposes of this invention, glass fiber means any glass fiber, including as described by Frederick T. Wallenberger, James C. Watson and Hong Li, PPG Industries Inc. (ASM Handbook, Vol. 21: Composites (#06781G), 2001 ASM International).

[0187] Glass fibers typically have a diameter between 5 and 20 pm, preferably the fiber diameter is between 10 and 18 pm.

[0188] Standard glass fibers are generally several millimeters long and, after compounding and extrusion, have average lengths of over 200 µm. Therefore, the shape factor for these fibers is obtained by the ratio of average length to diameter.

[0189] Preferably, the glass fibers of the invention are ground glass fibers, that is to say, glass fibers whose length before compounding and extrusion is less than 100 pm. After compounding and extrusion, these glass fibers therefore have an average length of less than 100 pm.

[0190] Preferably, the glass fibers have an average length in the composition according to the invention, i.e. after grinding and after passing through the extruder, of between 30 and 100 pm, preferably the length of the fibers is between 40 and 80 pm.

[0191] For example, the following commercial glass fibers may be used: Lanxess MF 7904 glass fiber with an average length of 50 µm and an average diameter of 14 µm. The composition constituting the core layer may contain from 2 to 50% by weight of fillers relative to the total weight of the composition, preferably from 5 to 30% by weight, more preferably from 5 to 20%, and preferably from 7 to 17%. In a preferred embodiment, the reinforcing filler of the core layer is ground glass fiber. The ground glass fibers may be present in a content of 5 to 20% by weight, preferably from 7 to 17% by weight, more preferably from 8 to 15% by weight, relative to the total weight of the composition.

[0192] Preferably, the composition constituting the central layer may comprise from 5 to 20% by weight of reinforcing fillers having a shape factor between 2 and 9, preferably between 2.5 and 7 relative to the total weight of the composition, preferably between 7 and 17% by weight.

[0193] Preferably, the reinforcing filler of the central layer has a thermal conductivity between 0 and 4 W / mK, preferably between 0 and 3 W / mK, more preferably between 0 and 1 W / mK, measured according to ASTM D5930-17. In other words, the reinforcing filler is thermally insulating.

[0194] Preferably, the reinforcing filler of the central layer has a surface resistivity greater than 1010 Ω, preferably greater than 1011 Ω measured according to IEC 62631-3-2 (2015). In other words, the reinforcing filler is electrically insulating.

[0195] Advantageously, the composition of the central layer comprises 5 to 20% by weight of a reinforcing filler having a shape factor between 2 and 9 and whose largest dimension is less than 100 pm, preferably less than 50 pm.

[0196] Additives

[0197] The composition constituting the core layer may include one or more additives selected from among antioxidants, UV protectants, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming aids, gums, preservatives, antibacterial agents, pigments, and mixtures thereof. Preferably, the composition includes at least one thermal stabilizer.

[0198] The composition constituting the central layer may contain from 0.4 to 5% by weight of additives relative to the total weight of the composition.

[0199] As noted above, the middle layer can be cut out to accommodate an object, such as an antenna, a chip, a metallic object, or something else.

[0200] The central layer preferably has a thickness between 100 and 450 µm, preferably between 100 and 400 µm, advantageously between 150 and 350 µm, and preferably between 150 and 330 µm. The thickness of this layer depends on the object to be accommodated.

[0201] The compositions constituting the outer layers, the intermediate layers and the central layer have a melting point above 140°C. Preferably, the intermediate layers and the central layer are identical.

[0202] According to a first embodiment of the structure according to the invention, the central layer and the intermediate layers comprise talc as a filler.

[0203] According to a second embodiment of the structure according to the invention, the central layer and the intermediate layers comprise ground glass fibers as filler. According to a preferred embodiment, the central layer consists of a composition comprising a polyamide matrix mainly composed of homopolyamide, and, on the other hand, a reinforcing filler selected from talc and ground glass fibers.

[0204] In a particularly preferred manner, the central layer consists of a composition comprising a polyamide matrix consisting mainly of a homopolyamide, and on the other hand a reinforcing filler chosen from talc.

[0205] In an alternative embodiment, the central layer consists of a composition comprising a polyamide matrix consisting mainly of a homopolyamide, and on the other hand a reinforcing filler chosen from ground glass fibers.

[0206] The binder layer

[0207] The binder layer consists of a composition including a reactive functional polyolefin, that is, a polyolefin that will react with the reactive ends of the polyamide in adjacent layers to form covalent bonds. The binder layer is non-crosslinked.

[0208] The binder layer has a melting temperature or glass transition temperature of less than or equal to 130°C and an MFI, abbreviation for Melt Flow Index, measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min.

[0209] Preferably, the binder layer has a melting temperature or glass transition temperature less than or equal to 110°C.

[0210] Preferably, the binder layer has an MFI index between 0.5 and 30 g / 10 min measured according to ASTM 1238.

[0211] Reactive functional polyolefin can be an alpha-olefin polymer or copolymer with reactive motifs: the functionalities. Such reactive motifs are carboxylic acid, acid anhydride, or epoxy groups. Acid anhydride groups are preferred for their superior adhesion properties.

[0212] Reactive functional polyolefin can be obtained by grafting an unsaturated monomer bearing a reactive motif onto a polyolefin or by copolymerizing an unsaturated monomer bearing a reactive motif with at least one alpha olefin.

[0213] As an example, homopolymers or copolymers of alpha olefins or diolefins can be cited as polyolefins, such as, for example, ethylene, 1-butene, 1-octene, butadiene, and more specifically:

[0214] -Ethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low-density polyethylene), VLDPE (very low-density polyethylene) and metallocene polyethylene,

[0215] -ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM),

[0216] -block copolymers styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS),

[0217] - Copolymers of ethylene with at least one product selected from among the salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (e.g., methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being up to 40% by weight. Examples of unsaturated monomers bearing a reactive motif include:

[0218] - Unsaturated epoxides. These include, for example, aliphatic glycidyl esters and ethers such as allylglycidyl ether, vinylglycidyl ether, glycidyl maleate and itaconate, and glycidyl acrylate and methacrylate. They also include, for example, alicyclic glycidyl esters and ethers such as 2-cyclohexene-1-glycidyl ether, cyclohexene-4,5-diglycidylcarboxylate, cyclohexene-4-glycidyl carboxylate, 5-norbornene-2-methyl-2-glycidyl carboxylate, and endocis-bicyclo(2,2,l)-5-heptene-2,3-diglycidyl dicarboxylate. Glycidyl methacrylate is preferred as the unsaturated epoxide.

[0219] -unsaturated carboxylic acids and their salts, for example acrylic acid or methacrylic acid and the salts of these same acids.

[0220] -Carboxylic acid anhydrides. These can be chosen, for example, from maleic, itaconic, citraconic, allylsuccinic, and cyclohex-4-ene-1,2-dicarboxylic anhydrides. Maleic anhydride is preferred as the carboxylic acid anhydride.

[0221] The unsaturated monomer bearing a reactive motif is preferably chosen from an unsaturated carboxylic acid anhydride and an unsaturated epoxide.

[0222] With regard to the alpha-olefin monomer, alpha-olefins with 2 to 30 carbon atoms are preferred.

[0223] As an alpha-olefin, mention may be made of ethylene, 1-butene, 1-pentene, 3-methyl-l-butene, 1-hexene, 4-methyl-l-pentene, 3-methyl-l-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene, 1-hexacocene, 1-octacocene, and 1-triacontene.

[0224] We can also mention cyclo-olefins having from 3 to 30 carbon atoms, preferably from 3 to 20 carbon atoms, such as cyclopentane, cycloheptene, norbornene, 5-methyl-2-norbomene, tetracyclododecene, and 2-methyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene; di and polyolefins, such as butadiene, isoprene, 4-methyl-1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, 1,3-hexadiene, 1,3-octadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, ethylidenenorbomene, vinyl norbornene, dicyclopentadiene, 7-methyl-1,6-octadiene, 4-ethylidiene-8-methyl-1,7-nonadiene, and 5,9-dimethyl-1,4,8-decatriene;aromatic vinyl compounds such as mono- or poly alkylstyrenes (including styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, dimethylstyrene, o-ethylstyrene, m-ethylstyrene and p-ethylstyrene), and derivatives comprising functional groups such as methoxystyrene, ethoxystyrene, vinyl benzoic acid, vinyl methyl benzoate, vinyl benzyl acetate, hydroxystyrene, o-chlorostyrene, p-chlorostyrene, di-vinyl benzene, 3-phenylpropene, 4-phenylpropene, alpha-methylstyrene, vinyl chloride, 1,2-difluoroethylene, 1,2-dichloroethylene, tetrafluoroethylene, and 3,3,3-trifluoro-l-propene.;

[0225] Ethylene is preferred as the alpha-olefin monomer.

[0226] The alpha-olefin monomer can be associated with a second comonomer that does not carry a reactive motif. Examples of a second comonomer without a reactive motif include: - one of the alpha-olefins already mentioned, provided it is different from the first alpha-olefin comonomer; - dienes such as 1,4-hexadiene, ethylidene norbornene, and butadiene; - esters of unsaturated carboxylic acids such as alkyl acrylates or alkyl methacrylates, collectively known as alkyl (meth)acrylates. The alkyl chains of these (meth)acrylates can have up to 30 carbon atoms. Examples of alkyl chains include methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, hencosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl.Methyl, ethyl and butyl (meth)acrylates are preferred as unsaturated carboxylic acid esters.

[0227] -Vinyl esters of carboxylic acids. Examples of vinyl esters of carboxylic acids include vinyl acetate, vinyl versatate, vinyl propionate, vinyl butyrate, and vinyl maleate. Vinyl acetate is preferred as the vinyl ester of carboxylic acids.

[0228] The reactive functional polyolefin can be selected from the following (co)polymers (or any mixture of the following (co)polymers), grafted with maleic anhydride or glycidyl methacrylate, in which the grafting ratio is, for example, 0.01 to 5% by weight:

[0229] -PE, copolymers of ethylene with propylene, butene, hexene, or octene containing, for example, 35 to 80% by weight of ethylene,

[0230] -ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM),

[0231] -block copolymers styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS),

[0232] -ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate,

[0233] -ethylene and alkyl (meth)acrylate copolymers, containing up to 40% by weight of alkyl (meth)acrylate,

[0234] -ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0235] The functional reactive polyolefin can be, 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 grafting rate, for example, of 0.01 to 5% by weight.

[0236] Reactive functional polyolefin can also be a co- or ter-polymer of at least the following motifs:

[0237] (1) ethylene,

[0238] (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and

[0239] (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0240] As an example of reactive functional polyolefins of this latter type, we can cite the following copolymers, where ethylene preferably represents at least 60% by weight and where the termonomer (the function) represents for example from 0.1 to 12% by weight of the copolymer: -ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers;

[0241] -ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers;

[0242] -ethylene / vinyl acetate copolymers or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate.

[0243] In the preceding copolymers, (meth)acrylic acid may be salified with Zn or Li. The term "alkyl (meth)acrylate" refers to methyl acrylates and alkyl acrylates in the Cl to C8 groups, and may be selected 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 may be copolymerized statistically or sequentially and may exhibit a linear or branched structure.

[0244] The reactive functional polyolefin can also be selected from ethylene / propylene copolymers major in propylene grafted with maleic anhydride and then condensed with mono-amino polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0245] Advantageously, the reactive functional polyolefin is selected from all polymers comprising alpha olefin motifs and motifs bearing polar reactive functions such as epoxy, carboxylic acid, or carboxylic acid anhydride groups. Examples of such polymers include terpolymers of ethylene, alkyl acrylate, and maleic anhydride or glycidyl methacrylate, such as Lotader® from SK Geocentric, or polyolefins grafted with maleic anhydride, such as Orevac® from SK Geocentric. Also included are homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or mono-amino oligomers of polyamide, as described in EP 0 342 066.

[0246] More specifically, reactive functional polyolefins are:

[0247] -ethylene, alkyl acrylate and maleic anhydride terpolymers;

[0248] -ethylene, alkyl acrylate and glycidyl methacrylate terpolymers;

[0249] -ethylene and propylene copolymers and possibly diene monomer grafted with maleic anhydride;

[0250] - ethylene and octene copolymers grafted with maleic anhydride; and their mixture.

[0251] Preferably, the composition constituting the binder layer comprises from 15% to 100% by weight relative to the total weight of the reactive functional polyolefin composition.

[0252] The composition constituting the binder layer may include one or more non-functional reactive polyolefins. The non-functional reactive polyolefins that may be present in the composition could be the ungrafted, non-functional reactive polyolefins described above.

[0253] Preferably, the composition constituting the binder layer comprises predominantly, preferably exclusively, one or more reactive functional polyolefins and one or more reactive non-functional polyolefins.

[0254] Advantageously, the composition constituting the binder layer does not include any polymers other than polyolefins.

[0255] The structure according to the invention comprises at least four layers of binder. These may be identical or different.

[0256] According to a preferred embodiment, the multilayer structure of the invention consists of: -an outer layer -a binder layer -an intermediate layer -a binder layer -a central layer -a binder layer -an intermediate layer -a binder layer -an outer layer. The binder layers preferably have a thickness of between 2 and 40 µm, advantageously between 5 and 30 µm.

[0257] Preferably, the structure according to the invention has a thickness between 500 pm and 1200 pm, advantageously between 700 pm and 900 pm.

[0258] Preferably, the intermediate layers and the central layer comprise an identical polyamide matrix, advantageously the matrix comprises predominantly a homopolyamide.

[0259] Preferably, the intermediate layers and the central layer have an identical composition.

[0260] The manufacturing process

[0261] The invention also relates to the method of manufacturing the structure according to the invention. The method according to the invention comprises the following steps:

[0262] 1. at least one extrusion step of each of the structural components in film form,

[0263] 2. at least one step of stacking the films on top of each other,

[0264] 3. at least one hot compression step at a temperature above the melting or glass transition temperature of the binder layers,

[0265] 4. at least one cooling stage of the structure, possibly under pressure.

[0266] The process includes a first step of extruding each of the compositions as a film. Each layer can be extruded independently. It is also possible to co-extrude at least two layers together.

[0267] Polymer film extrusion can be carried out by melting polymer granules through a heated Archimedes screw. The transformation temperature must be strictly higher than the polymer's melting point. This extrudate (molten polymer) then passes through a flat die and is drawn in air and then cooled by contact with a thermostatically controlled roller (the CAST process) or calendered by passing between two thermostatically controlled rollers (the calendering process). According to one embodiment of the invention, it is possible to co-extrude a bilayer structure comprising a polyamide layer and a binder layer.

[0268] According to another embodiment of the invention, it is possible to co-extrude a three-layer structure comprising a binder layer, a layer comprising polyamide and a binder layer.

[0269] For the purposes of this invention, film means layers with a thickness between 30 and 450 pm, preferably between 40 and 350 pm, and preferably between 40 and 335 pm and more particularly between 50 and 320 pm.

[0270] The so-called binder layers have a thickness of between 2 and 50 pm, preferably between 4 and 30 pm.

[0271] Stacking, as used in the present invention, means assembling the films by layering them one on top of the other.

[0272] As mentioned above, each layer has a specific thickness depending on its function within the structure.

[0273] The films are then assembled on top of each other. In other words, they are stacked on top of one another. The assembled films are then compressed.

[0274] The compression step involves applying hot pressure to the structure to melt the binder layers without melting the other layers. The melting of the binder allows the films to adhere to each other. The temperature during compression must be higher than the melting or glass transition temperature of the binder layer and lower than the melting temperature of the other layers.

[0275] The process according to the invention has the advantage of linking the different films together during the compression stage of the structure and achieving the final thickness of the desired structure.

[0276] The temperature during the compression stage is preferably between 100 and 140°C, even more preferably between 120 and 135°C.

[0277] The compression step should preferably last between 2 and 30 minutes, and ideally between 10 and 20 minutes. This duration must be sufficient to allow the layers to adhere to each other.

[0278] The pressure applied during the compression stage is preferably between 1 and 50 bars, preferably between 5 and 30 bars.

[0279] According to one embodiment, the process according to the invention comprises a single compression step.

[0280] According to another embodiment, the method according to the invention comprises

[0281] - a first step of assembling the central layer and the intermediate layers,

[0282] - a first compression stage allowing adhesion of the central and intermediate layers,

[0283] - a second stage of assembling the structure thus formed with the external layers, and

[0284] - a second compression stage allowing the structure thus formed to adhere to the external layers.

[0285] The compressed structure is then cooled. It is possible to maintain the pressure during cooling. The pressure can be the same as that of the compression stage or a lower pressure.

[0286] Depending on the desired size of the final object, the resulting structure can be cut. In other words, the manufacturing process for the structure according to the invention can utilize large films, such as films 0.5 m wide by 1 m long, with the size of the press often being the limiting factor in these industrial processes. Once this large structure is compressed, a cutting step allows it to achieve the desired shape and therefore the final size.

[0287] The method according to the invention may include additional steps.

[0288] These structures are preferably cards, such as bank cards, identity cards, cards allowing any kind of identification, cards with key functions, in other words cards containing data, whether visibly by inking or engraving or invisibly, via an electronic chip, an antenna, a magnetic stripe or any other device.

[0289] Thus, the process according to the invention may include one or more additional steps for providing this information or these objects to the structure. Additional anchoring step

[0290] It is possible to ink at least one external surface of at least one layer of the structure, such as the central layer, intermediate layers or external layers.

[0291] Indeed, it is known that identity cards, for example, contain inscriptions made with very specific inks to attest to the authenticity of the card.

[0292] Preferably, the process according to the invention includes an inking step on the outer surface of the intermediate layer. Since the structure comprises two intermediate layers, this step can be performed twice, that is, on each of the intermediate layers of the structure. More specifically, this step is performed before the film assembly step.

[0293] When the intermediate layer is inked, the outer layer has a role of protecting these inscriptions placed on the outer face of the intermediate layer.

[0294] The process according to the invention may also include an inking step of one or both of the external surfaces of the structure after the compression step, and / or possibly after the cooling step.

[0295] Additional engraving step

[0296] The process according to the invention may also include a step of engraving one or both of the external surfaces of the structure, after the compression step, and / or possibly after the cooling step.

[0297] Additional step of cutting the middle layer

[0298] When the structure according to the invention accommodates an object, such as an antenna, an electronic chip, a metallic device, or any other device, the method may include a step of cutting the central layer, followed by a step of depositing the object into the cavity formed during the film assembly step. According to this embodiment, the intermediate layers form the cavity in which the object is placed.

[0299] Therefore, the process according to the invention may include one or more film assembly steps depending on the specificity and treatment of each: inking and / or engraving.

[0300] Use

[0301] The invention also relates to the use of the structure as defined above as a card containing information, such as a card to secure an electronic identity, a bank card, an identity card, a smart card, a card to control access to a space, such as a building, a room, an entrance vestibule, an elevator, a room, such as a storage space like a wardrobe, a drawer, a safe, a card to control networks and computers.

[0302] The invention will be explained in more detail in the examples that follow.

[0303] EXAMPLES

[0304] Example 1 l. Preparation of compositions

[0305] The following compositions were prepared for the purpose of manufacturing the structures described below. 1.1. Compositions of the outer layers

[0306] The compositions were prepared from the compounds listed in Table 1 below.

[0307] These compositions were prepared by extrusion using a ZSK26 twin-screw co-rotating extruder (screw diameter 26 mm). The throughput was 30 kg / h at a screw speed of 300 rpm. The extruder temperature was regulated at 260°C. All components were introduced into the main hopper located on the first barrel of the extruder.

[0308] Table 1

[0309] (1) PA11 B is a PA 11 KNO with an inherent viscosity of 1.4, and a glass transition temperature between 40 and 60°C.

[0310] (2)PA11 A is a PA 11 BESHVO with an inherent viscosity of 1.45, and a glass transition temperature between 40 and 60°C.

[0311] (3) Platamid is a Platamid reference HX2507 sold by ARKEMA.

[0312] (4) The stabilizer is a mixture of ADK Stab AO 40; ADK stab 2112 and Palmarole EXP 242 marketed under the trade name ADK Stab CB 132 CB sold by ADEKA polymer additive Europe.

[0313] The properties of the compositions are measured according to the following protocols:

[0314] Measurement of melting point

[0315] Enthalpy of fusion was measured by DSC using a TA Instruments Q2000DSC instrument according to ISO 11357. Thermograms were processed using TA Universal Analysis software. DSCs were performed under nitrogen with a 6-8 mg sample.

[0316] The following program was followed for all the measures presented in this report:

[0317] Equilibrium at -40°C

[0318] Initial heating from -40°C to 270°C at 20°C / min

[0319] Cooling from 270°C to -40°C at 20°C / min

[0320] Second heating from -40°C to 270°C at 20°C / min

[0321] In order to disregard the thermal history of the material, the value at the second heating is recorded.

[0322] Transmittance measurement

[0323] Transmittance is measured according to the ASTDM D1003-2011 standard, on 0.6 mm thick samples by UV-Vis spectrometry on the Cary 300 spectrometer under the following conditions:

[0324] - Accessory: Integration sphere (transmission including diffusion)

[0325] - Spectral range 800-200 nm

[0326] - Speed: 60 nm / min

[0327] - 1 nm bandwidth

[0328] - Scale: Transmittance Measurement of the MFI

[0329] The MFI of these outer layers is measured according to ASTM 1238-2020 at 235°C and 2.16 kg.

[0330] 1.2. Composition of the intermediate and central layers

[0331] The compositions were prepared from the compounds listed in Table 2 below. These compositions were prepared by extrusion using a ZSK26 twin-screw co-rotating extruder (screw diameter 26 mm). The throughput was 30 kg / h at a screw speed of 300 rpm. The extruder temperature was regulated at 250°C.

[0332] The polyamides and stabilizer are introduced into the main hopper located on the first barrel of the extruder. The fiberglass and talc are introduced via a lateral feeder on barrel 5.

[0333] Table 2

[0334] (!) BESHVO, whose inherent viscosity is 1.45, and whose glass transition temperature is between 40 and 60°C.

[0335] (2) PAH B is a PA 11 KNO, whose inherent viscosity is 1.4, and whose glass transition temperature is between 40 and 60°C.

[0336] (3) PA MXD10 is an XMFO polyamide sold by ARKEMA.

[0337] (4) The glass fibers are marketed under the trade name Lanxess7928 and sold by Lanxess. These fibers are then ground to an average size of 400 µm. The aspect ratio is 36.

[0338] (5) The talc is marketed under the trade name HAR W92 and sold by Imerys. The form factor is 4.8.

[0339] (6)The stabilizer is a mixture of ADK Stab AO 40; ADK stab 2112 and Palmarole EXP 242 marketed under the trade name ADK Stab CB 132 CB sold by ADEKA polymer additive Europe.

[0340] The melting temperature and MFI measurements of these intermediate and outer central layers are measured according to the methods described above in point 1.1.

[0341] Measurement of Young's modulus

[0342] The modulus of the composition is measured according to ISO 527-1A 2019 on an injection-molded test specimen according to the following measurement protocol:

[0343] Dynamometer: Instron

[0344] Specimens: ISO 527-1A Test speed: 1 mm / min (modulus), then 50 mm / min (continuous and axial to break)

[0345] Jaw: Pneumatic

[0346] Distance between jaws: 115 mm

[0347] Extensometer: mechanical (L0=75mm)

[0348] Force cell: 10 kN

[0349] Temperature: 23°C

[0350] Storage: 15 days at 23°C at 50% relative humidity.

[0351] 1.3. Composition of binder layers

[0352] The binder compositions used in the structures below are commercial products.

[0353] Orevac 18342 N is a maleic anhydride-grafted high-density polyethylene (HDPE) sold by SK Functional Polymer. It has a melting point of 3.5 g / 10 min and a melting point of 125 °C. The product is designated by O in Table 2 below.

[0354] Lotader 4513T is a terpolymer of ethylene, methyl acrylate, and maleic anhydride sold by SK Functional Polymer. It has a melting point of 8 g / 10 min and a melting point of 96 °C. The product is designated by L in Table 2 below.

[0355] MFI Measurement

[0356] MFI is measured according to ASTM 1238-2020 at 190°C, 2.16 kg for binder layers.

[0357] The melting temperature of the binder layer is measured according to the method described above in point 1.1.

[0358] Generally, MFI and Tf values ​​are provided by the manufacturers. These values ​​are available in the product's TDS (Total Data Sheet).

[0359] 2. Preparation of the structures

[0360] The structures are prepared according to the following protocol:

[0361] 1. The layers are extruded as a film. The extruded layers are produced using a Collin brand cast extrusion line. The line consists of three extruders with diameters of 25, 30, and 45 mm. The processing temperature is set at 240°C for all polymers.

[0362] 2. The films are stacked on top of each other.

[0363] 3. The stacked films are compressed at 135°C for a period of 20 minutes under a pressure of 15 bars.

[0364] 4. The consolidated structure is then cooled to a temperature of 23°C for 20 minutes at a pressure of 15 bar.

[0365] The consolidated structures are then removed from the press and are ready for use.

[0366] The structures have a thickness of 840 µm before compression and 800 µm after compression. The intermediate and inner layers each have a thickness of 220 µm. The outer layers each have a thickness of 60 µm. The binder layers each have a thickness of 15 µm. The following structures, described in Table 3, were prepared from the compositions described in Tables 5 and 6 above and from the binders described above:

[0367] Table 3

[0368] *structure produced by extrusion calendering

[0369] 3. Evaluation of structures

[0370] The following physicochemical properties are evaluated on the structures described in Table 4:

[0371] Measurement of adhesive performance

[0372] The adhesion between the layers is measured according to the ISO 10373-1-2020 standard.

[0373] Adhesion is measured on the films: Outer Layer / Binder / Intermediate Layer and Middle Layer / Binder / Intermediate Layer. The lower of these two measurements is retained.

[0374] An adhesion greater than 5 N / cm is acceptable for this application.

[0375] Measurement of the traction modulus

[0376] The tensile modulus is measured according to ISO 178:2019 on a sample cut from the structure and then conditioned for 15 days at 23°C and 50% relative humidity. The tensile strength measurement is performed on test specimens conforming to ISO 5271-A:2019.

[0377] A tensile modulus for the structure greater than 1 GPa is acceptable for this application.

[0378] 4. Results

[0379] The results of the properties evaluated on the structures are shown in Table 4 below:

[0380] Table 4. The following table 5 shows the composition of the structure once melted for recycling. The composition includes all the components of all the layers of the structure. The component contents of this composition are calculated by taking into account the component contents in each layer and the thickness of each layer. The thickness factor of each layer is converted into a percentage relative to the total thickness of the structure.

[0381] Table 5

[0382] 5. Conclusions

[0383] The results show that the structures according to the invention are satisfactory in terms of interlayer adhesion and rigidity. Furthermore, their chemical compositions make them fully recyclable.

[0384] Example 2 l. Preparation of compositions

[0385] 1.1. Composition of the inner and outer layers

[0386] The composition used is composition 2 from example 1 described above.

[0387] 1.2. Composition of binder layers

[0388] Orevac, Lotryl, and Lotader functionalized polyolefins are sold by SK Functional Polymer. The functionalized polyolefins useful in the structures according to the invention are:

[0389] Orevac 18342 N is a maleic anhydride-grafted high-density polyethylene (HDPE) sold by SK Functional Polymer. It has a melting point of 3.5 g / 10 min and a melting point of 125°C.

[0390] Lotader 3410 is a terpolymer of ethylene, methyl acrylate, and maleic anhydride. It has a melting point of 5 g / 10 min and a melting point of 89°C.

[0391] Lotader 4513T is a terpolymer of ethylene, methyl acrylate, and maleic anhydride sold by SK Functional Polymer. It has a melting point of 8 g / 10 min and a melting point of 96°C.

[0392] Orevac OE850 is a maleic anhydride-grafted LDPE. It has a melting point of 7.5 g / 10 min and a melting point of 104°C. The melting point is measured according to ASTM 1238-2020 at 190°C and 2.16 kg.

[0393] The comparative polyolefins are:

[0394] Orevac 18722 and Orevac 18732 are maleic anhydride modified polypropylenes. They have a melting point of 7 and 8 g / 10min respectively at 230°C under 2.16 kg and a melting point of 143 and 134°C respectively.

[0395] Lotryl 18MA02 is a copolymer of ethylene and methyl acrylate (EMA). This polyolefin is not functionalized. It has a melting point of 2 g / 10 min at 190°C under 2.16 kg and a melting point of 83°C.

[0396] 2. Preparation of the structures

[0397] A three-layer structure is prepared to test the adhesion between the layers. This series of tests illustrates the behavior of the layers within a multilayer structure according to the invention, i.e., a structure comprising at least 9 layers.

[0398] The three-layer structure: Composition 2 / binder / Composition 2 is prepared by compressing a film of composition 2 coated with binder, i.e. a two-layer structure: Composition 2 / binder, on a second film of composition 2.

[0399] The binder films have a thickness between 25 and 50 µm. The films of composition 1 have a thickness of 200 µm.

[0400] The compression is carried out at 135°C for 50 seconds under a pressure of 9.8 bar. The final thickness obtained is between 215 and 250 µm depending on the compressibility of the layers.

[0401] The three-layer structures described in Table 6 were prepared. The Tf column indicates the melting temperature of the binder layer. The MFI column indicates the MFI of the binder layer along with the measurement conditions.

[0402] 3. Evaluation of structures

[0403] Adhesive performance is measured according to the method described below:

[0404] Measurement of adhesive performance

[0405] The adhesion between the layers is measured according to the ISO 10373-1-2020 standard.

[0406] An adhesion greater than 5 N / cm is acceptable for this application.

[0407] 4. Results The results of the structures are shown in Table 7 below:

[0408] Table 7

[0409] 5. Conclusions

[0410] The results show that the level of adhesion is satisfactory when the binder is a functionalized polyolefin, i.e. one which has a reactive function and when the polyolefin has a melting temperature less than or equal to 130°C.

[0411] Example 3

[0412] 1. Preparation of compositions

[0413] 1.1. Layer Composition

[0414] Composition 2 described above in example 1 is used in the structures described below.

[0415] 1.2. Composition of the binder layer

[0416] Orevac 18342N is as described in example 2.

[0417] 2. Preparation of the structures

[0418] The three-layer structure composition 2 / binder / composition 2 according to the invention is prepared according to two different processes:

[0419] Method 1:

[0420] The three-layer structure: composition 2 / binder / composition 2 is prepared by compressing a film of composition 2 coated with binder, i.e. a two-layer structure: composition 2 / binder on a second film of composition 2.

[0421] The assembly step can be illustrated as follows: composition 2 / binder + composition 2 -> composition 2 / binder / composition 2

[0422] The binder layer is applied directly onto the layer of composition 2.

[0423] The binder film has a thickness of 15 µm. The films of composition 2 have a thickness between 250 and 300 µm. Compression is carried out at 135°C for 15 minutes under a pressure of 15 bar. The final thickness obtained varies between 255 µm and 310 µm.

[0424] Method 2:

[0425] The three-layer structure: composition 2 / binder / composition 2 is prepared by compression of two-layer structures composition 2 / binder.

[0426] The assembly step can be illustrated as follows: composition 2 / binder + binder / composition 2 -> composition 2 / binder / composition 2

[0427] The binder layers are applied one on top of the other.

[0428] The binder films have a thickness of 15 µm. The films of composition 2 have a thickness of 250 and 300 µm.

[0429] The compression is carried out at 135°C for 15 minutes under a pressure of 15 bars. The final thickness is between 255 and 310 µm.

[0430] 3. Evaluation of structures

[0431] The measurement of adhesive performance is measured according to the method described above in point 3 of example 2.

[0432] 4. Results

[0433] The results of the structures are shown in Table 8 below:

[0434] Table 8

[0435] 5. Conclusions

[0436] The results show that the level of adhesion is satisfactory for both structures. The results show that both processes provide a very good level of adhesion, with a preference for process 1.

Claims

Demands 1. Multilayer structure comprising: -an outer layer consisting of a composition comprising a polyamide matrix, the outer composition having a transmittance rate greater than or equal to 70% in the visible range (400 to 800 nm) on films 600 pm thick, measured according to ASTM-D1003-2011, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -a central layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than or equal to 8, the composition having a Young's modulus measured according to ISO 527-1A 2019 between 1.8 and 4 GPa, preferably between 2 and 3.5 GPa, and having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or glass transition temperature less than or equal to 130°C and an MFI measured according to ASTM 1238-2020 at 190°C and 2.16 kg between 0.4 and 30 g / 10min, preferably 0.4 and 20 g / 10min, -an outer layer consisting of a composition comprising a polyamide matrix, the outer composition having a transmittance rate greater than or equal to 70% in the visible range (400 to 800 nm) on films 600 pm thick, measured according to ASTM-D1003-2011, the compositions constituting the outer layers, the intermediate layers and the central layer having a melting temperature greater than 150°C, preferably greater than 160°C.

2. Structure according to claim 1, characterized in that the matrices of the outer layers comprise, independently of each other, at least one polyamide selected from PAU, PA12, PA1010, PA 1012, PA 513, PA56, PA510, PA 516, PA 610, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, as well as mixtures thereof.

3. Structure according to claim 1 or 2, characterized in that the matrices of the intermediate layers and the matrix of the central layer comprise from 5 to 20% by weight of a reinforcing filler having a form factor between 2 and 9.

4. Structure according to any one of claims 1 to 3, characterized in that the matrices of the intermediate layers and the matrix of the central layer comprise at least one polyamide selected from PAU, PA12, PA1010, PA 1012, PA 513, PA 516, PA 612, PA613, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA 6 / 11 / 12, PA 6 / 66 / 12, PA 6 / 1010, PA 6 / 1012, PA 6 / 1010 / 1012, PA 6 / 1012 / 12, PA 6 / 66 / 11 / 12, PA 6 / 1010 / 1012 / 1014, MXD10, MXD12, MXD13, PA11 / 10T and mixtures thereof.

5. Structure according to claim 4, characterized in that the matrices of the intermediate layers and the matrix of the central layer comprise at least one polyamide selected from PAU, PA12, PA1010 and PA 1012.

6. Structure according to any one of the preceding claims, characterized in that the composition constituting the binder layer comprises a polyolefin bearing carboxylic acid, acid anhydride, or epoxy functions.

7. Structure according to claim 6, characterized in that the composition constituting the binder layer comprises a polyolefin bearing acid anhydride functions.

8. Structure according to any one of the preceding claims, characterized in that the outer, intermediate and central layers comprise at least one additive selected from antioxidants, UV protectants, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming auxiliaries, gums, preservatives, antibacterial agents, pigments and mixtures thereof.

9. Structure according to any one of the preceding claims, characterized in that the intermediate layer(s) are inked.

10. Structure according to any one of the preceding claims, characterized in that the central layer comprises a chip, an antenna or a metallic part.

11. Structure according to any one of the preceding claims, characterized in that it has the following layer thicknesses: -the outer layers each have a thickness between 20 and 150 pm, advantageously between 40 and 100 pm, more particularly between 50 and 80 pm, and / or -the intermediate layers each have a thickness between 100 and 450 pm, advantageously between 150 and 330 pm, and / or -the central layer has a thickness between 100 and 450 pm, advantageously between 150 and 330 pm, and / or -the binder layers each have a thickness between 2 and 40 µm, advantageously between 5 and 30 µm.

12. Structure according to any one of the preceding claims, characterized in that it has a thickness between 500 pm and 1200 pm, advantageously between 700 pm and 900 pm.

13. A method for manufacturing the structure as defined in any one of claims 1 to 12, comprising the following successive steps:

1. at least one extrusion step of each of the structural components in film form, 2. at least one step of stacking the films on top of each other, 3. at least one hot compression step at a temperature above the melting or glass transition temperature of the binder layers, 4. at least one cooling stage of the structure, possibly under pressure.

14. Method according to claim 13, characterized in that the compression step is carried out at a temperature between 100 and 140°C, preferably between 120 and 135°C.

15. Method according to claim 13 or 14, characterized in that the duration of the compression step is between 2 and 30 minutes, preferably between 10 and 20 minutes.

16. A method according to any one of claims 13 to 15, characterized in that the pressure applied during the compression step is between 1 and 50 bars, preferably between 5 and 30 bars.

17. A method according to any one of claims 13 to 16, characterized in that it comprises an inking step of one or more intermediate layers.

18. A method according to any one of claims 13 to 17, characterized in that it comprises a step of cutting the central layer and a step of depositing an object within the central layer.

19. Use of the structure as defined in any one of claims 1 to 12 as a card containing data, such as a card to secure an electronic identity, a bank card, an identity card, a smart card, a card to control access to a space, such as a building, a room, an entry vestibule, an elevator, a premises, such as a storage space like a wardrobe, a drawer, a safe, a card to control networks and computers.

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