Multilayer structure based on polyamide usable as a card

Abstract

The present invention relates to a multilayer structure based on polyamide for use as a card. This 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 constituting the outer layers, intermediate layers, and central layer are made of a composition comprising a polyamide matrix and having a melting point above 150°C, preferably above 160°C, and the binder layers are made of a composition comprising a reactive functional polyolefin. The invention also relates to a method for manufacturing the structure and its use as a data card.

Description

Title of the invention: Multilayer structure based on polyamide usable as a card. Technical field

[0001] The present invention relates to a multilayer structure usable as a card, as well as its manufacturing process. Technical background

[0002] Smart cards provide a structure for securing an electronic identity. They can be used to control access to buildings, networks, and computers. They are also used as national identity cards, thus authenticating their owner. These cards contain data that is either visibly represented by ink or engraving, or invisibly represented by an electronic chip, antenna, magnetic stripe, or other device.

[0003] 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.

[0004] The use of polyamides for manufacturing cards 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. Technical problem to solve

[0005] However, the materials sought must meet specific requirements. Ideally, they should be able to replace PVC in the card manufacturing process without any modification to the process itself. 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 required, 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.

[0006] Thus, a structure essentially based on polyamide was found, the melting temperature of which is much higher than its compression temperature. Therefore, the structure is not altered by this compression step. The adhesion between these layers is ensured by a layer of polyolefin, which melts at a temperature lower than the compression temperature.

[0007] Furthermore, this specific structure has the advantage of being completely recyclable. Brief description of the invention

[0008] The present invention relates to a multilayer structure comprising:

[0009] -an outer layer made 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,

[0010] -a binder layer made up of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or a 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 / lOmn, preferably 0.4 and 20 g / lOmn,

[0011] -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than 8, the composition having 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 having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg of between 0.4 and 30 g / lOmn, preferably 0.4 and 20 g / lOmn,

[0012] -a binder layer made up of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or a 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 / lOmn, preferably 0.4 and 20 g / lOmn,

[0013] -a central layer made of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than 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 / lOmn, preferably 0.4 and 20 g / lOmn,

[0014] -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer having a melting temperature or a 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 / lOmn, preferably 0.4 and 20 g / lOmn,

[0015] -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a ratio C / N greater than 8, the composition having 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 having a Young's modulus measured according to ASTM 1238-2020 at 235°C and 2.16 kg of between 0.4 and 30 g / l·min, preferably 0.4 and 20 g / l·min,

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

[0017] -an outer layer made 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,

[0018] the compositions constituting the outer layers, the intermediate layers and , the central layer having a melting temperature above 150°C, preferably above 160°C.

[0019] The invention also relates to the manufacturing process of the structure as defined above, comprising the following successive steps: l. 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.

[0020] The invention also relates to the use of the structure as a card carrying 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 cabinet, a drawer, a safe, a card to control networks and computers.

[0021] The structure according to the invention has the advantage of being mechanically recyclable. It is unnecessary to sort the polymers. The resulting mixture can be directly recycled either for the same application or for another application.

[0022] Indeed, the composition resulting from the recycling of the structure according to the invention comprises mainly one or more polyamides, a polyolefin compatible with the polyamide, and optionally fillers. In fact, the structure can be melted and then reused to manufacture another object, either by a molding process or by an injection molding process.

[0023] Furthermore, when the structure consists mainly or exclusively of PA 11 as the matrix of the outer, intermediate, and central layers, the structure is predominantly bio-based. Its environmental impact is low compared to raw materials of fossil origin.

[0024] Furthermore, this structure has the advantage of using reactive functional polyolefins as an adhesion layer, rather than glues or thermosetting agents. The latter are either not recyclable or very difficult to recycle.

[0025] Other advantageous features of the structure according to the invention are specified below.

[0026] -In the structure, the matrices of the outer layers can 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.

[0027] -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, as well as mixtures thereof.

[0028] -The matrices of the intermediate layers and the matrix of the central layer may comprise at least one polyamide selected from PAU, PA 12, PA 1010 and PA 1012.

[0029] -The binder layer may comprise a polyolefin bearing carboxylic acid, acid anhydride, or epoxy functions.

[0030] -The binder layer may comprise a polyolefin bearing acid anhydride functions.

[0031] -The outer, intermediate and central layers may include at least one additive selected from flame retardants, antioxidants, UV protective agents, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming auxiliaries, gums, preservatives, antibacterial agents, pigments and mixtures thereof.

[0032] -The intermediate layer(s) can be inked.

[0033] -The central layer may include a chip, an antenna or a metallic part.

[0034] -The structure may have 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 400 µm, advantageously between 150 and 330 µm, and / or -the central layer has a thickness between 100 and 400 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.

[0035] -The structure has a thickness between 500 pm and 1200 pm, advantageously between 700 pm and 900 pm.

[0036] Other advantageous features of the process according to the invention are specified below.

[0037] -The compression step is carried out at a temperature between 100 and 140°C, preferably between 120 and 135°C.

[0038] -The duration of the compression step is between 2 and 30 minutes, preferably between 10 and 20 minutes.

[0039] -The pressure applied during the compression step is between 1 and 50 bars, preferably between 5 and 30 bars.

[0040] -The process includes an inking step of one or more intermediate layers.

[0041] -The process includes a step of cutting the central layer and a step of depositing an object within the central layer. Detailed description

[0042] Other features, aspects, objects and advantages of the present invention will become even clearer upon reading the following description.

[0043] Unless otherwise stated, all percentages are mass percentages.

[0044] 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.

[0045] It is specified that the expressions "from ... to ..." and "between ... and ..." used in this description should be understood as including each of the limits mentioned.

[0046] Polyamides

[0047] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (Tables 1 and 2), and is well known to those skilled in the art. Thus, PA11 means that it is obtained by polycondensation of 11-amino-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).

[0048] The word "polyamide" covers both homopolyamides and copolyamides.

[0049] The invention is now described in more detail and in a non-limiting manner in the following description.

[0050] 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 designates a diamine and Y designates a diacid. Thus, an amide function is indeed formed by the reaction of an amine function with an acid function.

[0051] By unit, for the purposes of the present invention, means a Z or XY link resulting from the polycondensation of monomers.

[0052] By motif, we mean in the context of the present invention the sequence Z or the sequence X or the sequence Y. In other words, the unit Z consists of a motif Z and the unit XY consists of a motif X and a motif Y.

[0053] By C / N ratio, we mean in the context of the present invention the average number of carbon atoms per nitrogen atom per unit.

[0054] In the case of a PA Z type homopolyamide, where Z designates a motif obtained from an amino acid or a lactam, the number of carbon atoms per nitrogen atom is the number of carbon atoms in the motif. For example, PA 11 obtained by polycondensation of amino-II-undecanoic acid has a C / N ratio of 11.

[0055] In the case of a PA XY type homopolyamide, where X designates a motif obtained from a diamine and Y designates a motif obtained from a diacid, the number of carbon atoms per nitrogen atom is the average of the 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 follows: (6+12) / 2 = 9.

[0056] 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 carried out in molar proportion of the different amide units, i.e., the XaYa and XbYb units. Thus, the coPA 6T / 66 containing 60% of 6T and 40% of 66 is in C6,6: 60%x[(6+8) / 2]+40%x[(6+6) / 2] = 6.6.

[0057] The multilayer structure

[0058] The multilayer structure according to the invention comprises: -an outer layer -a layer of binder -an intermediate layer -a layer of binder -a central layer -a layer of binder -an intermediate layer -a layer of binder -an outer layer.

[0059] The binder layers allow adhesion between adjacent layers. The central layer can accommodate 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.

[0060] The outer layers

[0061] The outer layer consists of a composition comprising a polyamide matrix.

[0062] For the purposes of this invention, the term "matrix" refers to the polyamide that is the major component of the composition, i.e., the polyamide present in the highest concentration in the composition. The polyamide matrix may represent from 40% to 100% by weight of the total composition, preferably from 70% to 90% by weight.

[0063] 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 ASTM-D1003-2011.

[0064] 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.

[0065] The polyamide can be obtained by polycondensation of at least one lactam selected from pyrrolidinone, 2-piperidinone, enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0066] 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 (denoted 10), 11-aminoundecanoic acid (denoted 11), 12-aminododecanoic acid (denoted 12).

[0067] 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.

[0068] The motif (Ca diamine) 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), fundecanediamine (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 para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0069] Advantageously, diamine X is selected from 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0070] Preferably, diamine X is in C12 C10, in particular selected from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0071] The motif (Cb diacid) may be aliphatic, cycloaliphatic or aromatic. The diacid may 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).

[0072] 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.

[0073] 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.

[0074] 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 (Ca diamine) (Cb diacid) motif, with Ca and Cb being as defined above.

[0075] More particularly, the composition mainly comprises PAU, PA12, PA1010, PA 1012, even more preferably PAU or PA12, preferably PA11 and mixtures thereof.

[0076] PA11 has the advantage of being manufactured from plant-based raw materials. 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 over a short period on a human timescale. In particular, this stock must be able to renew itself as quickly as it is consumed.

[0077] The basic raw material of PA11 is castor oil, extracted from the castor bean plant (the common castor bean), from castor seeds. PA11 is obtained by polycondensation of amino-11-undecanoic acid.

[0078] 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%.

[0079] Additives

[0080] 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 auxiliaries, gums, preservatives, antibacterial agents and mixtures thereof.

[0081] Preferably, the composition comprises at least one heat stabilizer, preferably a heat stabilizer comprising at least one metal atom, preferably copper and / or iron. In a preferred embodiment, this metal atom is not in salt form; advantageously, the metal atom is complexed.

[0082] The composition constituting the outer layer may include from 0.5 to 5% by weight of additives relative to the total weight of the composition.

[0083] 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.

[0084] The structure according to the invention comprises two external layers. These may be identical or different.

[0085] 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.

[0086] The outer layers can be inked and / or engraved.

[0087] The intermediate layers

[0088] The intermediate layer consists of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than 8.

[0089] 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 having an MFI measured according to ASTM 1238-2020 at 235°C and 2.16 kg of between 0.4 and 30 g / lOmin, preferably 0.5 to 20 g / lOmin.

[0090] The polyamide present in the matrix of the composition of the intermediate layer 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.

[0091] The polyamide can be obtained by polycondensation of at least one lactam selected from pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0092] The polyamide present in the matrix of the composition of the intermediate layer can also be obtained by polycondensation of at least one amino acid chosen from 9-aminononanoic acid, 10-aminodecanoic acid (denoted 10), amino-11-undecanoic acid (denoted 11), amino-12-dodecanoic acid (denoted 12).

[0093] 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.

[0094] The motif (Ca diamine) 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 (denoted MXD), methylpentamethylene diamine (denoted MPMD), bis(aminomethyl)cyclohexane (denoted BAC), meta-xylylene diamine (MXD, CAS No.: 1477-55-0) and the para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0095] Advantageously, diamine X is selected from 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0096] Most preferably, diamine X is in C12 C10, in particular selected from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0097] 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).

[0098] 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.

[0099] Advantageously, the polyamide present in the matrix of the composition of the intermediate layer is chosen from PAU, PA 12, PA 1010, 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, and their mixture.

[0100] 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 (Ca diamine) (Cb diacid) motif, with Ca and Cb being as defined above.

[0101] More particularly, the composition matrix includes predominantly PAU, PA 12, PA 1010, PA 1012, even more preferably PAU or PA 12, preferably PAU.

[0102] 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%.

[0103] Charges

[0104] The composition constituting the intermediate layer may include one or more fillers. Preferably, the fillers are chosen from among so-called reinforcing fillers. Examples include mineral fillers, such as calcium carbonates, silicas, wollastonites, aluminosilicates, such as kaolin, glass fibers, aramid fibers, glass flakes, glass beads, and talc.

[0105] The composition constituting the intermediate layer may comprise from 2 to 50% by weight of fillers relative to the total weight of the composition, preferably between 5 and 30% by weight.

[0106] Additives

[0107] The composition constituting the intermediate layer may include one or more additives selected from flame retardants, antioxidants, UV protective agents, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming auxiliaries, gums, preservatives, antibacterial agents, pigments and mixtures thereof.

[0108] Preferably, the composition comprises at least one heat stabilizer, preferably a heat stabilizer comprising at least one metal atom, preferably copper and / or iron. In a preferred embodiment, this metal atom is not in salt form; advantageously, the metal atom is complexed.

[0109] The composition constituting the intermediate layer may comprise from 0.4 to 5% by weight of additives relative to the total weight of the composition.

[0110] 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.

[0111] The structure according to the invention comprises at least two intermediate layers. These may be identical or different.

[0112] The intermediate layers preferably have a thickness between 100 and 400 pm, advantageously between 150 and 330 pm.

[0113] Preferably, at least one intermediate layer is inked. Advantageously, both intermediate layers are inked.

[0114] The central layer

[0115] 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 8.

[0116] 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 having an MFI of between 0.4 and 30 g / lOmin, the MFI being measured under the following conditions: 235°C and 2.16 Kg, preferably 0.4 and 20 g / lOmin.

[0117] The polyamide present in the matrix of the composition of the central layer is obtained by polycondensation of at least one motif selected from an alpha,omega-aminocarboxylic acid in C8 to Cl8, 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.

[0118] The polyamide can be obtained by polycondensation of at least one lactam selected from pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0119] The polyamide present in the matrix of the composition of the central layer 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), 12-aminododecanoic acid (denoted 12).

[0120] 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.

[0121] The motif (Ca diamine) 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 (denoted MXD), methylpentamethylene diamine (denoted MPMD), bis(aminomethyl)cyclohexane (denoted BAC), meta-xylylene diamine (MXD, CAS No.: 1477-55-0) and the para-xylylene diamine (PXD, CAS No.: 539-48-0).

[0122] Advantageously, diamine X is selected from 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0123] Most preferably, diamine X is in C12 C10, in particular selected from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0124] The motif (Cb diacid) may be aliphatic, cycloaliphatic or aromatic. The diacid may be selected 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).

[0125] Advantageously, the diacid is selected from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0126] Advantageously, the polyamide present in the matrix of the composition of the central layer is chosen from PAU, PA 12, PA 1010, 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, as well as their mixture.

[0127] 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 (Ca diamine) (Cb diacid) motif, with Ca and Cb being as defined above.

[0128] More particularly, the composition matrix includes predominantly PAU, PA 12, PA 1010, PA 1012, even more preferably PAU or PA 12, preferably PAU.

[0129] 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%.

[0130] Charges

[0131] The composition constituting the central layer may include one or more fillers. Preferably, the fillers are chosen from among so-called reinforcing fillers. Examples include mineral fillers, such as calcium carbonates, silicas, wollastonites, aluminosilicates, such as kaolin, fibers (glass, aramid, etc.), glass flakes, glass beads, and talc.

[0132] The composition constituting the central layer may comprise from 2 to 50% by weight of fillers relative to the total weight of the composition, preferably between 5 and 30% by weight.

[0133] Additives

[0134] The composition constituting the central layer may include one or more additives selected from flame retardants, antioxidants, UV protective agents, UV stabilizers, thermal stabilizers, lubricants, flow improvers, flowability improvers, film-forming agents, film-forming auxiliaries, gums, preservatives, antibacterial agents, pigments and mixtures thereof.

[0135] Preferably, the composition comprises at least one heat stabilizer, preferably a heat stabilizer comprising at least one metal atom, preferably copper and / or iron. In a preferred embodiment, this metal atom is not in salt form; advantageously, the metal atom is complexed.

[0136] The composition constituting the central layer may comprise from 0.4 to 5% by weight of additives relative to the total weight of the composition.

[0137] As indicated above, the central layer can be cut out to accommodate an object, such as an antenna, a chip, a metallic object or other.

[0138] The central layer preferably has a thickness between 100 and 400 pm, advantageously between 150 and 330 pm. The thickness of this layer depends on the object to be accommodated.

[0139] The compositions constituting the outer layers, the intermediate layers and the central layer have a melting temperature greater than 140°C.

[0140] The binder layer

[0141] The binder layer consists of a composition comprising a reactive functional polyolefin, that is, a polyolefin that will react with the reactive ends of the polyamide in the adjacent layers to form covalent bonds. The binder layer is non-crosslinked.

[0142] The binder layer has a melting temperature or a glass transition temperature 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.

[0143] Preferably, the binder layer has a melting temperature or a glass transition temperature less than or equal to 110°C.

[0144] Preferably, the binder layer has an MFI index between 0.5 and 30 g / 10 min measured according to ASTM 1238.

[0145] The reactive functional polyolefin can be an alpha-olefin polymer or copolymer having reactive motifs: the functionalities. Such reactive motifs are carboxylic acid, acid anhydride, or epoxy functionalities. The preferred functionalities are acid anhydride functionalities, resulting in better adhesion.

[0146] The 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.

[0147] By way of example, homopolymers or copolymers of alpha olefins or diolefins, such as, for example, ethylene, 1-butene, 1-octene, butadiene, and more particularly: -Ethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low-density polyethylene), VLDPE (very low-density polyethylene) and metallocene polyethylene, -ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), -block copolymers styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS), - ethylene copolymers with at least one product selected from 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 co-monomer up to 40% by weight.

[0148] Examples of unsaturated monomers bearing a reactive motif include: - 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. -unsaturated carboxylic acids and their salts, for example acrylic acid or methacrylic acid and the salts of these same acids. -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.

[0149] The unsaturated monomer bearing a reactive motif is preferably chosen from an unsaturated carboxylic acid anhydride and an unsaturated epoxide.

[0150] With regard to the alpha-olefin monomer, alpha-olefins having 2 to 30 carbon atoms are preferred.

[0151] Examples of alpha-olefins include ethylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-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.

[0152] 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, retylidenenorbornene, vinyl norbornene, dicyclopentadiene, 7-methyl-l,6-octadiene, 4-ethylidiene-8-methyl-l,7-nonadiene, and 5,9-dimethyl-l,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, α-methylstyrene, vinyl chloride, 1,2-difluoroethylene, 1,2-dichloroethylene, tetrafluoroethylene, and 3,3,3-trifluoro-1-propene.

[0153] Ethylene is preferred as the alpha-olefin monomer.

[0154] The alpha-olefin monomer may be associated with a second comonomer not bearing a reactive motif. Examples of a second comonomer not bearing a reactive motif include: -one of the alpha-olefins already mentioned, this one being different from the first alpha-olefin comonomer, -Dienes such as, for example, 1,4-hexadiene, ethylidene norbornene, butadiene; -esters of unsaturated carboxylic acids such as, for example, alkyl acrylates or alkyl methacrylates, grouped under the term 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, and nonacosyl. Methyl, ethyl, and butyl (meth)acrylates are preferred as unsaturated carboxylic acid esters. -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.

[0155] The reactive functional polyolefin may 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, from 0.01 to 5% by weight: -PE, copolymers of ethylene with propylene, butene, hexene, or octene containing, for example, 35 to 80% by weight of ethylene, -ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (short for ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), -block copolymers styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS), -ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate, -ethylene and alkyl (meth)acrylate copolymers, containing up to 40% by weight of alkyl (meth)acrylate, -ethylene and vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0156] The reactive functional 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.

[0157] The reactive functional polyolefin may also be a co- or ter-polymer of at least the following motifs: (1) ethylene, (2) alkyl (meth)acrylate or saturated carboxylic acid vinyl ester and (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as glycidyl (meth)acrylate.

[0158] By way of example of reactive functional polyolefins of this latter type, the following copolymers may be cited, where ethylene preferably represents at least 60% by weight and where the termonomer (the functional group) represents, for example, from 0.1 to 12% by weight of the copolymer: -ethylene / alkyl (meth)acrylate / (meth)acrylic acid copolymers or maleic anhydride or glycidyl methacrylate; -ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers; -ethylene / vinyl acetate copolymers or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate.

[0159] In the preceding copolymers, (meth)acrylic acid may be salified with Zn or Li. The term "alkyl (meth)acrylate" refers to methacrylates and alkyl acrylates in Cl to C8, 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.

[0160] The copolymers mentioned above can be copolymerized statistically or sequentially and have a linear or branched structure.

[0161] 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 polyamide oligomer) (products described in EP-A-0342066).

[0162] Advantageously, the reactive functional polyolefin is selected from any polymer comprising alpha olefin motifs and motifs bearing polar reactive functions such as epoxy, carboxylic acid, or carboxylic acid anhydride functions. 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.

[0163] More specifically, reactive functional polyolefins are: -ethylene, alkyl acrylate and maleic anhydride terpolymers; -ethylene, alkyl acrylate and glycidyl methacrylate terpolymers; -ethylene and propylene copolymers and possibly diene monomer grafted with maleic anhydride; - ethylene and octene copolymers grafted with maleic anhydride; and their mixture.

[0164] 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.

[0165] The composition constituting the binder layer may comprise one or more non-functional reactive polyolefins. The non-functional reactive polyolefins, possibly present in the composition, may be the ungrafted and non-functional reactive polyolefins described above.

[0166] 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.

[0167] Advantageously, the composition constituting the binder layer does not include any polymers other than polyolefins.

[0168] The structure according to the invention comprises at least four binder layers. These may be identical or different.

[0169] According to a preferred embodiment, the multilayer structure according to the invention consists of: -an outer layer -a layer of binder -an intermediate layer -a layer of binder -a central layer -a layer of binder -an intermediate layer -a layer of binder -an outer layer. The binder layers preferably have a thickness between 2 and 40 pm, advantageously between 5 and 30 pm.

[0170] Preferably, the structure according to the invention has a thickness between 500 pm and 1200 pm, advantageously between 700 pm and 900 pm.

[0171] The manufacturing process

[0172] 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: 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 step of the structure, possibly under pressure.

[0173] The process includes a first step of extruding each of the compositions in film form. Each layer can be extruded independently. It is also possible to co-extrude at least two layers together.

[0174] 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 temperature. 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 so-called CAST process) or calendered through a passage 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.

[0175] 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.

[0176] For the purposes of this invention, film means layers with a thickness between 30 and 350 pm, preferably between 40 and 335 pm, and more particularly between 50 and 320 pm.

[0177] The so-called binder layers have a thickness of between 2 and 50 pm, preferably between 4 and 30 pm.

[0178] By stacking in the sense of the present invention, we mean an assembly of films, by superimposing them one on top of the other.

[0179] As indicated above, each layer has a specific thickness depending on its function within the structure.

[0180] The films are then assembled one on top of the other. In other words, they are stacked on top of each other.

[0181] The films thus assembled are compressed.

[0182] The compression step consists of applying hot pressure to the structure so as to cause the binder layers to melt without causing the other layers to melt. 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.

[0183] The process according to the invention has the advantage of linking the different films together during the compression stage of the structure and of achieving the final thickness of the desired structure.

[0184] The temperature during the compression step is preferably between 100 and 140°C, more preferably between 120 and 135°C.

[0185] The duration of the compression step is preferably between 2 and 30 minutes, preferably between 10 and 20 minutes. The duration must be sufficient to allow the bonding layers to melt.

[0186] The pressure applied during the compression step is preferably between 1 and 50 bars, preferably between 5 and 30 bars.

[0187] According to one embodiment, the process according to the invention comprises a single compression step.

[0188] According to another embodiment, the process according to the invention comprises - a first step of assembling the central layer and the intermediate layers, - a first compression step enabling adhesion of the central and intermediate layers, - a second stage of assembling the structure thus formed with the external layers, and - a second compression stage allowing the structure thus formed to adhere to the external layers.

[0189] The compressed structure is then cooled. It is possible to maintain the pressure during cooling. The pressure can be that of the compression stage or a lower pressure.

[0190] Depending on the size of the desired 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 for example Films measuring 0.5 m wide by 1 m long are produced, 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.

[0191] The method according to the invention may include additional steps.

[0192] These structures are preferably cards, such as bank cards, identity cards, cards enabling any kind of identification, cards having 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.

[0193] Thus, the method according to the invention may include one or more additional steps to provide the structure with this information or objects.

[0194] Additional inking step

[0195] It is possible to ink at least one external surface of at least one layer of the structure, such as the central layer, the intermediate layers or the external layers.

[0196] Indeed, it is known that identity cards, for example, contain inscriptions made with very specific inks allowing the authenticity of the card to be attested.

[0197] Preferably, the method according to the invention includes an inking step on the outer face 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 particularly, this step is performed before the sheet assembly step.

[0198] When the intermediate layer is inked, the outer layer has a role of protecting these inscriptions arranged on the outer face of the intermediate layer.

[0199] The method 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 optionally after the cooling step.

[0200] Additional engraving step

[0201] 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 optionally after the cooling step.

[0202] Additional step of cutting the middle layer

[0203] 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, then a step of depositing The object is placed in the cavity formed during the film assembly stage. According to this embodiment, the intermediate layers form the cavity in which the object is placed.

[0204] Consequently, 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.

[0205] Use

[0206] 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.

[0207] The invention will be explained in more detail in the examples that follow. EXAMPLES Example 1 1. Preparation of compositions

[0208] 1. Composition of the inner and outer layers

[0209] The composition was prepared from the compounds listed in Table 1 below. The composition was prepared by extrusion on 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.

[0210] [Tab 1] 1 PA11(1) 52.3 PA11(2) 34.1 Platamid (3 '12 Stabilizer (4 '1.6 Tf (°C) 189 Transmittance (%) 80 MYoung (GPa) 1.4 MFI (g / lOmin) 1

[0211] Table 1

[0212] (1)PA11 is a PA 11 KNO whose inherent viscosity is between 1.3 and 1.5

[0213] ®PA11 is a PA 11 BESHVO with an inherent viscosity between 1.35 and 1.52

[0214] (3) Platamid is a Platamid reference HX2507 sold by ARKEMA.

[0215] (4) The stabilizer is a mixture of ADK Stab AO 40; ADK stab 2112 and Palmarol EXP 242 marketed under the trade name ADK Stab CB 132 CB sold by ADEKA polymer additive Europe.

[0216] The properties of the composition are measured according to the following protocols:

[0217] Measurement of 1 at melting temperature 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. The following program was followed for all measurements presented in this report: Equilibrium at -40°C Initial heating from -40°C to 270°C at 20°C / min Cooling from 270°C to -40°C at 20°C / min Second heating from -40°C to 270°C at 20°C / min In order to disregard the thermal history of the material, the value at the second heating is recorded.

[0218] Measurement of 1 a transmittance 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:

[0219] - Accessory: Integration sphere (transmission including diffusion)

[0220] - Spectral range 800-200 nm

[0221] - Speed: 60 nm / min

[0222] - 1 nm bandwidth

[0223] - Scale: Transmittance Measurement of Young's modulus

[0224] The modulus of the composition is measured according to ISO 527-1A 2019 on an injected specimen or on a specimen cut from the multilayer structure according to the following measurement protocol:

[0225] Dynamometer: Instron

[0226] Test pieces: ISO 527-1A

[0227] Test speed: 1 mm / min (modulus), then 50 mm / min (cont. and ail. to break)

[0228] Jaw: Pneumatic

[0229] Distance between jaws: 115 mm

[0230] Extensometer: mechanical (L0=75mm)

[0231] Force cell: 10 kN

[0232] Temperature: 23°C

[0233] Storage: 15 days at 23°C at 50% relative humidity. MFI Measurement

[0234] MFI is measured according to ASTM 1238-2020 at 235°C and 2.16 kg. 1. Composition of binder layers

[0235] Orevac, Lotryl and Lotader functionalized polyolefins are sold by SK Functional Polymer.

[0236] The functionalized polyolefins useful in the structures according to the invention are:

[0237] Orevac 18342 N is a maleic anhydride-grafted high-density polyethylene (HDPE) sold by SK Functional Polymer. It has a MFI of 3.5 g / lOmin and a melting point of 125°C.

[0238] Lotader 3410 is a terpolymer of ethylene, methyl acrylate and maleic anhydride. It has a MFI of 5 g / lOmin and a melting point of 89°C.

[0239] Lotader 4513T is a terpolymer of ethylene, methyl acrylate and maleic anhydride sold by SK Functional Polymer. It has an MFI of 8 g / lOmin and a melting point of 96°C.

[0240] Orevac OE850 is a maleic anhydride-grafted LDPE. It has an MFI of 7.5 g / 10min and a melting point of 104°C.

[0241] MFI is measured according to ASTM 1238-2020 at 190°C and 2.16 kg.

[0242] The comparative polyolefins are:

[0243] Orevac 18722 and Orevac 18732 are maleic anhydride modified polypropylenes. They have a MFI of 7 and 8 g / l min respectively at 230°C under 2.16 kg and a melting point of 143 and 134°C respectively.

[0244] Lotryl 18MA02 is a copolymer of ethylene and methyl acrylate (EMA). This polyolefin is not functionalized. It has a melting point of 2 g / lOmin at 190°C under 2.16 kg and a melting point of 83°C. 1. Preparation of the structures#

[0245] A three-layer structure is prepared in such a way as 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.

[0246] The three-layer structure: Composition 1 / binder / Composition 1 is prepared by compressing a film of composition 1 coated with binder, i.e. a two-layer structure: Composition 1 / binder, onto a second film of composition 1.

[0247] The binder films have a thickness of between 25 and 50 µm. The films of composition 1 have a thickness of 200 µm.

[0248] 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.

[0249] The three-layer structures described in Table 2 were prepared. The Tf column indicates the melting temperature of the binder layer. The MFI column indicates the MFI of the binder layer as well as the measurement conditions.

[0250] [Tab 2] Outer layer Binder layer Inner layer Tf (°C) of binder Cl 1 Orevac 18722 1 143 C2 1 Orevac 18732 1 134 C3 1 Lotryl 18MA02 1 83 II 1 Lotader 3410 1 89 12 1 Orevac 18342N 1 125 13 1 Lotader 4513T 1 96 14 1 Orevac OE850 1 104

[0251] Table 2 1. Evaluation of structures

[0252] The adhesive performance is measured according to the method described below:

[0253] Measurement of adhesive performance The adhesion between the layers is measured according to the ISO 10373-1-2020 standard.

[0254] An adhesion greater than 5 N / cm is acceptable for this application. 1. Results#

[0255] The results of the structures are shown in Table 3 below:

[0256] [Tab 3] Adhesion (N / cm) Cl 0 C2 0 C3 0 II 10.5 12 20.5 13 19 14 11.3

[0257] Table 3 1. Conclusions#

[0258] The results show that the level of adhesion is satisfactory when the binder is a functionalized polyolefin, i.e., one that includes a reactive function, and when the polyolefin has a melting point of 130°C or less. Example 2 1. Preparation of compositions

[0259] 1. Layer composition

[0260] Composition 1 described above in Example 1 is used in the structures described below. 1. Composition of the binder layer

[0261] Orevac 18342N is as described in Example 1. 1. Preparation of the structures#

[0262] The three-layer structure composition 1 / binder / composition 1 according to the invention is prepared according to two different processes: Process 1#:

[0263] The three-layer structure: composition 1 / binder / composition 1 is prepared by compression of a film of composition 1 coated with binder, i.e. a two-layer structure: composition 1 / binder on a second film of composition 1.

[0264] The assembly step can be illustrated as follows:

[0265] composition 1 / binder + composition 1 —> composition 1 / binder / composition 1

[0266] The binder layer is applied directly onto the layer of composition 1.

[0267] The binder film has a thickness of 15 µm. The films of composition 1 have a thickness between 250 and 300 pm.

[0268] The 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. Method 2#:

[0269] The three-layer structure: composition 1 / binder / composition 1 is prepared by compression of bilayer structures composition 1 / binder.

[0270] The assembly step can be illustrated as follows:

[0271] composition 1 / binder + binder / composition 1 —> composition 1 / binder / composition 1

[0272] The binder layers are applied one on top of the other.

[0273] The binder films have a thickness of 15 µm. The films of composition 1 have a thickness of 250 and 300 µm.

[0274] The compression is carried out at 135°C, for 15 minutes under a pressure of 15 bar. The final thickness is between 255 and 310 µm. 1. Evaluation of structures

[0275] The measurement of adhesive performance is measured according to the method described above in point 3 of example 1. 1. Results#

[0276] The results of the structures are shown in Table 4 below:

[0277] [Tab 4] Adhesion (N / cm) Process 1 70 Process 2 30

[0278] Table 4 1. Conclusions#

[0279] 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

1. Demands 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 / lOmn, preferably 0.4 and 20 g / lOmn, -an intermediate layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than 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 / lOmn, preferably 0.4 and 20 g / lOmn, -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 / lOmn, preferably 0.4 and 20 g / lOmn, -a central layer consisting of a composition comprising a polyamide matrix comprising predominantly at least one polyamide having a C / N ratio greater than 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 / lOmn, preferably 0.4 and 20 g / lOmn, -a binder layer consisting of a composition comprising a reactive functional polyolefin, the binder layer exhibiting a melting point or glass transition temperature of 130°C or less and a melting point (MFI) measured according to ASTM 1238-2020 at 190°C and 2.16 kg of material between 0.4 and 30 g / l·min, preferably 0.4 and 20 g / l·min; an intermediate layer consisting of a composition comprising a polyamide matrix predominantly composed of at least one polyamide having a C / N ratio greater than 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 a melting point (MFI) measured according to ASTM 1238-2020 at 235°C and 2.16 kg of material between 0.4 and 30 g / l·min, preferably 0.4 and 20 g / l·min; and 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 with a concentration between 0.4 and 30 g / lOmn, preferably 0.4 and 20 g / lOmn, - 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 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, and their mixtures.

4. Structure according to claim 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, PA 12, PA1O1 and PA 1012.

5. 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.

6. Structure according to claim 5, characterized in that the composition constituting the binder layer comprises a polyolefin bearing acid anhydride functions.

7. 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 flame retardants, 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.

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

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

10. A 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 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 400 pm, advantageously between 150 and 330 pm, and / or - the central layer has a thickness of between 100 and 400 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.

11. 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.

12. A method for manufacturing the structure as defined in any one of claims 1 to 11, comprising the following successive steps:

1. at least one extrusion step of each of the compositions of the structure in the form of films, 2. at least one step of stacking the films one on top of the 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 step of the structure, optionally under pressure.

13. A method according to claim 12, characterized in that the compression step is carried out at a temperature between 100 and 140°C, preferably between 120 and 135°C.

14. A method according to claim 12 or 13, characterized in that the duration of the compression step is between 2 and 30 minutes, preferably between 10 and 20 minutes.

15. A method according to any one of claims 12 to 14, characterized in that the pressure applied during the compression step is between 1 and 50 bars, preferably between 5 and 30 bars.

16. A method according to any one of claims 12 to 15, characterized in that it comprises an inking step of one or more intermediate layers.

17. A method according to any one of claims 12 to 16, characterized in that it comprises a step of cutting the central layer and a step of depositing an object within the central layer.

18. Use of the structure as defined in any one of claims 1 to 11 as a data-carrying card, such as a card for securing an electronic identity, a bank card, an identity card, a smart card, a card for controlling access to a space, such as a building, a room, an airlock entrance, an elevator, a room, such as a storage space like a wardrobe, a drawer, a safe, a card to control networks and computers.