Electricity transmission component, in particular for an electric battery

Abstract

The invention relates to an electricity transmission component, wherein the electricity transmission component comprises a metal surface, characterised in that the metal surface is coated over its entire surface: - with an intermediate layer made of inorganic material; and - with a coating layer having a colour different from black made of an electrically insulating composition predominantly comprising at least one polyamide, the number of carbon atoms per nitrogen atom of which is greater than 6.5, and at least one dye, the intermediate layer being positioned between the metal surface of the electricity transmission component and the coating layer; the invention also relates to the method for preparing same.

Description

ELECTRICITY TRANSPORT COMPONENT, IN PARTICULAR FOR ELECTRIC BATTERIES FIELD OF THE INVENTION

[0001] The present invention relates to an electricity transport component, and more particularly to an interconnection bar, colored in particular for an electric battery. TECHNICAL BACKGROUND

[0002] In the field of electric vehicles, connectors called interconnection bars (or bus bars) are used to circulate high-intensity current inside and outside the batteries. These bars must be covered with an insulating coating that is resistant to mechanical stress and aging.

[0003] There are several processes for preparing busbars. The main one is the extrusion of the polymer composition around the central metal strip. Powder coating, dipping, or electrospray coating processes can also be used. These structures are then cut and bent (at room temperature) to the shape required by the vehicle layout.

[0004] For safety reasons, these bars must also have a distinctive color, representative of the current flowing in the bar. It is therefore essential that this color remains stable over time, despite the temperatures to which the bar may be subjected. Indeed, external conditions, proximity to the engine, self-heating during current flow, particularly during battery charging are factors that can affect the color of the coating over time. If the color changes over time, doubt may remain about the voltage of the electric current flowing in the bar, which could cause accidents during servicing or repairs to the engine, for example. It is therefore essential that the color remains stable despite the drastic conditions of its environment. SUBSTITUTION SHEET (RULE 26)

[0005] The technical problem related to the busbar application for batteries consists of forming a thin layer of polymer, whose color does not change over time, while maintaining a high level of flexibility to accommodate the deformation of the busbars. When bending, a material that is too rigid forms cracks on the external face and buckling on the internal face, which is visualized by 'waves' or 'bulges', phenomena which are prohibitive for the application.

[0006] The behavior at the yield point of the material is therefore crucial. Low yield stresses and high yield strain are sought. The strain levels of these coatings remain low, but the material must still have an elongation at break > 50%, preferably greater than 100%, and even more advantageously greater than 200%. Good abrasion resistance is also necessary for this application.

[0007] In addition, depending on the position of these parts within the engine, it may be beneficial for these compositions to be resistant to de-icing salt.

[0008] The coating must also act as an electrical insulator, which is reflected in properties such as breakdown voltage, dielectric strength and comparative tracking index (CTI) > 600V. This insulation must be maintained during accelerated thermal aging of up to 130°C, particularly up to 150°C.

[0009] Finally, the rheological properties of the alloy must be adapted to the extrusion of thin polymer layers of the order of 0.5 mm.

[0010] Furthermore, the prior art does not provide information on the combinations to be made within the formulation to simultaneously achieve flexibility and color stability for the battery busbar application.

[0011] It is known from document US 2021 / 0253854 and document KR101977321 a composition based on polyamide and at least one pigment system. However, it turns out that the disclosed compositions are not mechanically satisfactory. Furthermore, the evolution of the color of these products during aging is not documented. SUMMARY OF THE INVENTION

[0012] The invention relates to an electricity transmission component, wherein the electricity transmission component comprises a metallic surface, characterized in that said metallic surface is coated over its entire surface: - an intermediate layer of inorganic material; and - a coating layer made of an electrically insulating composition comprising mainly at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring material, the intermediate layer being positioned between the metal surface of the electricity transport component and the coating layer.

[0013] Preferably, the coating layer is characterized in that its color is different from a black color.

[0014] According to one embodiment, the electrically insulating composition may have an L* parameter greater than 0, preferably greater than 5, preferably greater than 10, measured in the CIELab system, as defined in the ISO 11664-4: 2008 standard, using a Konica Minolta CM-36dGV spectrophotometer in reflectance mode with a D65 illuminant, an angle of incidence of 10° and an aperture of 8mm and specular component included.

[0015] According to one embodiment, the electrically insulating composition may have a color determined according to the RAL method different from a RAL color of 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017 and 9021.

[0016] Preferably, the intermediate layer of inorganic material is characterized in that the material is other than a metal.

[0017] Preferably, the composition of the coating layer comprises from 60 to 98% by weight of said at least one polyamide.

[0018] Preferably, the composition of the coating layer is characterized in that said at least one polyamide is an aliphatic or cycloaliphatic polyamide, preferably aliphatic.

[0019] Finally, the invention relates to a method for preparing the electricity transmission component as defined above comprising: - a step of coating the entire metal surface of the electricity transport component with an intermediate layer of inorganic material as defined in any one of claims 1, 4 and 5; then - a step of coating the intermediate layer of inorganic material with a coating composition as defined in any one of claims 1 and 6 to 12.

[0020] It was observed that the color of the composition deposited on the component according to the invention remains stable even after aging at high temperature. It was also observed that the composition continues to exhibit certain electrical insulation properties after aging. Furthermore, the composition deposited on the component according to the invention exhibits good mechanical properties: the properties of elongation at break, impact resistance, and the resistance of the polymer layer during bending of the metal bar are very satisfactory. Finally, the electrical component covered with said composition remains easy to strip.

[0021] Other advantageous characteristics of the method according to the invention are specified below: -the component is an interconnection bar, - the metal surface of the component is made of copper, copper alloy, aluminum or aluminum alloy, - the intermediate layer of inorganic material is a layer of mica, carbon fiber or fiberglass, preferably mica, - the intermediate layer of inorganic material has a thickness of between 0.1 and 2 mm, preferably between 0.15 and 1 mm, - the polyamide(s) of the coating layer have an inherent viscosity measured according to ISO 307:2007 greater than 1.1, - the polyamide(s) of the coating layer have a fusion enthalpy measured by DSC during the second heating according to standard ISO 11357-3, 2013 strictly greater than 20 J / g, - the polyamide(s) of the coating layer have a crystallization temperature measured by DSC during the second heating according to standard ISO 111357-3, 2013 strictly lower than 180°C, - the polyamide of the coating layer is chosen from PA11, PA12, PA1010, PA 1012, PA 610, PA 612, PA 613, PA 516, PA 912, PA 6 / 11, PA 6 / 12, PA 11 / 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 alone or as a mixture, more particularly PA11, PA12, PA1010, PA 1012, even more preferably PA11 or PA12, preferably PA11, - the coloring matter content ranges from 0.5 to 10% by weight, preferably from 1 to 5% by weight relative to the total weight of the composition, - the polyamide(s) in the composition of the coating layer have a difference, expressed as an absolute value, between its total acidity and its total basicity of less than 70 and a basicity of the total polyamide(s) of less than 60 peq / g, - the polyamide(s) in the composition of the coating layer have a total acidity of less than 60 peq / g, -within the process, the coating step of the intermediate layer is carried out by extrusion, -within the process, the step of coating the intermediate layer is carried out by depositing a powder of said coating composition and then melting the powder. DETAILED DESCRIPTION

[0022] Other features, aspects, objects and advantages of the present invention will become even more apparent from the following description.

[0023] 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 meant 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).

[0024] It is further specified that the expressions "between... and..." and "from... to..." used in this description must be understood as including each of the limits mentioned.

[0025] The word "polyamide" covers both homopolyamides and copolyamides.

[0026] The invention is now described in more detail and in a non-limiting manner in the following description. Electricity transmission component

[0027] The subject of the invention is an electricity transport component, preferably an interconnection bar, in which the electricity transport component comprises a metal surface, characterized in that said metal surface is coated over its entire surface: - an intermediate layer of inorganic material; and - a coating layer made of an electrically insulating composition comprising mainly at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring material, the intermediate layer being positioned between the metal surface of the electricity transport component and the coating layer.

[0028] Preferably, the coating layer is characterized in that its color determined by the RAL method is different from a black color. By "black color" is meant a RAL color of 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017 and 9021. The RAL colors of 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017 and 9021 correspond to black colors.

[0029] Preferably, the intermediate layer of inorganic material is characterized in that the material is different from a metal layer.

[0030] The power transmission component is preferably a high-voltage power transmission component. High voltage means voltages between 400 and 1000 V. Preferably, the electricity transmission component is an interconnection bar. In this embodiment, the invention then relates to an interconnection bar comprising: - a metal bar; - an intermediate layer of inorganic material; and - a coating layer made of a composition comprising at least one predominant polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring matter, the intermediate layer being positioned between the metal bar and the coating layer.

[0031] The electricity transmission component can be of any type. It is mainly a high-voltage electricity transmission component. This component can be in the form of a metal cable or comprising metal fibers, for example braided, or thin overlapping metal sheets or metal bars such as those usually used in interconnection bars.

[0032] Preferably, the electricity carrying component is an electrical or electronic component cover, a control device, a connector, a battery cover, an electrical box, an electrical terminal or a cable.

[0033] Preferably, the electricity carrying component comprises a metal surface, preferably copper, copper alloy, aluminum or aluminum alloy, preferably copper or aluminum, preferably copper.

[0034] In one embodiment, the electrical transmission component is an interconnection bar comprising a metal bar, said metal bar preferably being copper, copper alloy, aluminum or aluminum alloy, preferably copper or aluminum, preferably copper. Intermediate layer of inorganic material

[0035] The intermediate layer is a layer of inorganic material. Preferably, this layer completely covers the metal bar.

[0036] The inorganic material of the intermediate layer may be of any type and is in particular chosen from silicates, in particular phyllosilicates, glass, carbon, and more preferably mica, carbon fibers and glass and mixtures thereof. For example, the intermediate layer may be a layer of mica or a layer of glass fibers or even a layer of carbon fibers, preferably a layer of mica or a layer of glass fibers.

[0037] The intermediate layer is preferably in the form of a ribbon of inorganic material, for example a mica ribbon, a carbon fiber ribbon or a glass fiber ribbon, preferably a mica ribbon.

[0038] The layer of inorganic material preferably has a thickness of between 0.1 and 2 mm, preferably between 0.15 and 1 mm, advantageously between 0.2 and 0.5 mm. Thus, preferably, the strip of inorganic material has a thickness of between 0.1 and 2 mm, preferably between 0.15 and 1 mm, advantageously between 0.2 and 0.5 mm.

[0039] For the purposes of the invention, the term "intermediate layer of inorganic material" means an intermediate layer comprising predominantly, i.e. at least 50% by weight, relative to its total weight, of inorganic material as defined above, preferably from 50 to 99% by weight, for example from 75 to 95% by weight.

[0040] The intermediate layer of inorganic material may comprise, in addition to the inorganic material as defined above, a binder resin (or matrix) which may in particular be a thermoplastic polymer resin or a thermosetting polymer resin, preferably a thermosetting polymer resin, such as for example chosen from epoxies, silicones and polyurethanes.

[0041] Particularly advantageously, the layer of inorganic material makes it possible to maintain a stable color over time even at high temperatures while retaining a certain electrical insulation at very high temperatures and mechanical resistance. Coating layer

[0042] The electricity transport component according to the invention, preferably an interconnection bar, comprises a coating layer made of an electrically insulating composition mainly comprising at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring material.

[0043] For the purposes of the present invention, electrically insulating means a material having a dielectric strength greater than 10 kV / mm measured on a 1 mm thick plate on a sample conditioned for 14 days at 25°C at 50% relative humidity according to standard IEC 60243-1:2013.

[0044] Preferably, the thickness of the coating layer is from 0.1 mm to 2 mm, in particular from 0.2 mm to 1 mm, in particular from 0.3 mm to 0.8 mm, more particularly from 0.4 mm to 0.6 mm, while maintaining a high level of flexibility to accommodate the deformation of the electricity transport component. A material that is too rigid forms cracks or “waves” which are prohibitive for the application. Composition of the coating layer

[0045] The composition forming the coating layer mainly comprises at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring matter.

[0046] For the purposes of the present invention, the term “predominantly” means that the composition comprises at least one polyamide in a content greater than 50% by weight relative to the total weight of the composition. This or these polyamides constitute the matrix of the composition.

[0047] Preferably, the composition of the coating layer comprises between 60 and 98% by weight of at least one polyamide relative to the total weight of the composition, preferably between 70% and 95%.

[0048] Preferably, the composition of the coating layer comprises between 0.5 and 10% by weight, preferably between 1 and 5% by weight of coloring matter.

[0049] Preferably, the composition of the coating layer comprises between 60 and 98% by weight, preferably between 70 and 95% by weight, of polyamide and between 0.5 and 10% by weight, preferably between 1 and 5% by weight of coloring matter.

[0050] In the case of a homopolyamide of the PA-XY type, with X designating a unit obtained from a diamine and Y designating a unit obtained from a diacid, the number of carbon atoms per nitrogen atom is the average of the numbers of carbon atoms present in the unit resulting from the diamine X and in the unit resulting from the diacid Y. Thus PA6.12 is a PA with 9 carbon atoms per nitrogen atom, in other words a C9 PA. PA6.13 is C9.5. In the case of copolyamides, for example of the XaYa / XbYb structure, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is carried out in molar proportion to the different amide units, i.e. the XaYa and XbYb units.

[0051] The majority polyamide present in the composition of the coating layer has a number of carbon atoms per nitrogen atom greater than 6.5, preferably greater than 8.

[0052] For the purposes of the present invention, the term "majority" means that the composition comprises at least one polyamide in a content greater than 50% by weight relative to the total weight of the composition. In other words, the composition may comprise a mixture of polyamides having a number of carbon atoms per nitrogen atom greater than 6.5. This mixture must be majority, that is to say that it must represent at least 50% by weight relative to the total weight of the composition.

[0053] Preferably, the composition comprises between 60 and 98% by weight of at least one polyamide relative to the total weight of the composition, preferably between 70% and 95%.

[0054] In other words, the presence of other polyamides is not excluded. However, it is important that high-carbon polyamides are the majority in the composition.

[0055] The polyamide present in the composition of the coating layer of the component according to the invention is obtained by polycondensation of at least one unit chosen from a C6 to C18 alpha, omega-aminocarboxylic acid, a C5 to C12 lactam and a unit (Ca diamine). (Cb diacid), 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.

[0056] The polyamide can be obtained by polycondensation of at least one lactam chosen from pyrrolidinone, 2-piperidinone, enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and lauryllactam.

[0057] The polyamide 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).

[0058] The polyamide can be obtained by polycondensation of at least one unit corresponding to the formula (Ca diamine). (Cb diacid), 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.

[0059] The unit (Ca diamine) can be aliphatic, cycloaliphatic or aromatic. It 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-xylylenediamine (denoted MXD), methylpentamethylenediamine (denoted MPMD), bis(aminomethyl)cyclohexane (denoted BAC), meta-xylylenediamine (MXD, CAS No.: 1477-55-0) and para-xylylenediamine (PXD, CAS No.: 539-48-0).

[0060] Advantageously, said at least one diamine X in C6 to C12, is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0061] Advantageously, the diamine X used is C10 to C12, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0062] The unit (Cb diacid) can be aliphatic, cycloaliphatic or aromatic. It 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, terephthalic acid (denoted T).

[0063] Advantageously, said unit (Cb 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.

[0064] Advantageously, the polyamide present in the composition according to the invention has an elongation at break > 50%, preferably greater than 100%, even more advantageously greater than 200%. The elongation at break can in particular be measured according to the ISO 527-1 / -2 standard.

[0065] Advantageously, the composition according to the invention comprises less than 25% by weight of polyamide having an elongation at break of less than or equal to 50%, preferably less than 10% by weight, preferably less than 5% by weight, preferably less than 1% by weight, relative to the total weight of said composition. Preferably, the composition according to the invention is free of polyamide having an elongation at break of less than or equal to 50%.

[0066] Advantageously, the polyamide present in the composition of the coating layer of the component according to the invention is aliphatic or cycloaliphatic. Preferably, the polyamide present in the composition of the coating layer of the component according to the invention is aliphatic.

[0067] Advantageously, the polyamide is chosen from PA11, PA12, PA1010, PA 1012, PA 610, PA 612, PA613, PA912, PA 516, 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 alone or as a mixture.

[0068] Preferably, the composition only comprises polyamides having a number of carbon atoms per nitrogen atom greater than 6.5. More particularly, the composition only comprises polyamides having a number of carbon atoms per nitrogen atom greater than 8.

[0069] According to a preferred embodiment, the polyamide is a homopolyamide. This homopolyamide can be obtained by the polycondensation of a lactam, an amino acid or a (Ca diamine) or (Cb diacid) unit, with Ca and Cb being as defined above.

[0070] More particularly, the composition mainly comprises PA11, PA12, PA1010, PA 1012, even more preferably PA11 or PA12, preferably PA11.

[0071] PA11 has the advantage of being made from raw materials of plant origin. Plant materials can be grown in large quantities, depending on demand, across most of the globe and are bio-sourced. A bio-sourced raw material is a natural resource, animal or plant, whose stock can be replenished over a short period on a human scale. In particular, this stock must be able to renew itself as quickly as it is consumed.

[0072] The basic raw material for PA11 is castor oil, extracted from the castor bean plant (Castor oil in English). PA11 is obtained by polycondensation of 11-aminoundecanoic acid. Total acidity and total basicity

[0073] Preferably, the polyamide(s) present in the composition of the coating layer of the component according to the invention have a difference, expressed as an absolute value, between its total acidity and its total basicity strictly less than 70, preferably less than 50, ideally less than 30.

[0074] By difference, expressed as an absolute value, is meant, within the meaning of the present invention, the result of the subtraction of the values ​​of the total acidity of the polyamide(s) and the total basicity of the polyamide(s), without taking into account the sign.

[0075] When the composition contains a blend of polyamides, the acidity and basicity are measured on the blend of polyamides. The difference is therefore expressed for the blend of polyamides.

[0076] Preferably, the polyamide(s) present in the composition of the component according to the invention also have a total basicity strictly less than 60 peq / g, preferably less than 50 peq / g, and ideally less than 40 peq / g.

[0077] Preferably, the polyamide(s) present in the composition of the component according to the invention also have a total acidity strictly less than 60 peq / g, preferably less than 50 peq / g, and ideally less than 40 peq / g.

[0078] Acidity and basicity are measured by potentiometry.

[0079] Acidity is measured using the following method. A sample of polyamide is dissolved in benzyl alcohol. Then, this sample is measured by potentiometry using a 0.02N tetrabutylammonium hydroxide solution.

[0080] Basicity is measured using the following method. A sample of polyamide is dissolved in metacresol. This sample is then assayed potentiometrically using a 0.02N perchloric acid solution.

[0081] According to one embodiment of the invention, the polyamide(s) have a total basicity strictly less than 60 peq / g and a total acidity strictly less than 60 peq / g and a difference, expressed as an absolute value, between its total acidity and its total basicity strictly less than 50, ideally less than 30.

[0082] According to a preferred embodiment, the composition mainly comprises PA11, PA12, PA1010 or PA 1012 and their mixture, this or these polyamides having a total basicity of less than 60 peq / g and a difference, expressed in absolute value, between its total acidity and its total basicity strictly less than 50, ideally less than 30.

[0083] According to a preferred embodiment, the composition mainly comprises PA11 or PA12, having a total basicity of less than 50 peq / g and a total acidity of less than 60 peq / g and a difference, expressed in absolute value, between its total acidity and its total basicity strictly less than 30.

[0084] Preferably, the polyamide(s) present in the composition do not comprise a chain limiter. Inherent viscosity

[0085] Preferably, the polyamide(s) in the composition of the coating layer have an inherent viscosity measured according to ISO 307:2007 greater than 1.1, and preferably greater than 1.2.

[0086] The measurement is carried out at 20°C on a 75 mg sample at a concentration of 0.5% (m / m) in m-cresol.

[0087] When the composition includes a mixture of polyamides, the viscosity is measured on the mixture of polyamides. Enthalpy of fusion

[0088] Preferably, the polyamide(s) in the composition of the coating layer have a fusion enthalpy greater than 20 J / g, preferably greater than 30 J / g and ideally greater than 40 J / g.

[0089] The enthalpy of fusion is measured by DSC (differential scanning calorimetry) according to ISO 11357-3, 2013 (2 nd DSC heating at 20°C / min according to ISO 11357 standard).

[0090] When the composition includes a mixture of polyamides, the enthalpy of fusion is measured on the mixture of polyamides. Crystallization temperature

[0091] Preferably, the polyamide(s) in the composition of the coating layer have a crystallization temperature of less than 180°C, preferably less than 160°C.

[0092] The crystallization temperature is measured by DSC (differential scanning calorimetry) according to ISO 11357-3, 2013 (2 nd DSC heating at 20°C / min according to ISO 11357 standard).

[0093] When the composition comprises a mixture of polyamides, the crystallization temperature is measured on the mixture of polyamides. The coloring matter

[0094] The composition of the coating layer of the component according to the invention comprises at least one coloring material. The coloring material may be a dye or a pigment, in other words, water-soluble dyes or water-insoluble pigments according to the conditions defined below.

[0095] The dye may be of any type known to those skilled in the art. Preferably, the dye according to the invention is selected from the group consisting of azo dyes, anthraquinone dyes, dyes derived from indigo, triarylmethane dyes, chlorine dyes and polymethine dyes.

[0096] The term "pigment" means all pigments that provide color to a polymer composition. Their solubility in water at 25°C and atmospheric pressure (760 mmHg) is less than 0.05% by weight, and preferably less than 0.01%. The pigments that can be used are chosen in particular from organic and / or mineral pigments known in the art, in particular those described in the Kirk-Othmer Encyclopedia of Chemical Technology and in the Ullmann Encyclopedia of Industrial Chemistry.

[0097] Pigments can be of natural or non-natural origin. These pigments can be in the form of powder or pigment paste. They can be coated or uncoated. Pigments can, for example, be chosen from mineral pigments, organic pigments, and their mixtures.

[0098] By mineral pigment is meant any pigment that meets the definition of the Ullmann encyclopedia in the inorganic pigment chapter. Among the mineral pigments useful in the present invention, mention may be made of ochres such as red ochre (clay (in particular kaolinite) and iron hydroxide (hematite for example), brown ochre (clay (in particular kaolinite) and limonite), yellow ochre (clay (in particular kaolinite) and goethite); titanium dioxide, optionally surface-treated; zirconium or cerium oxides; zinc, iron (black, yellow or red), or chromium oxides; manganese violet, ultramarine blue, chromium hydrate and ferric blue; metal powders such as aluminum powder, copper powder.

[0099] We can also cite alkaline earth metal carbonates (such as calcium, magnesium), silicon dioxide, quartz, as well as any other compound used as an inert filler in cosmetic compositions, as long as these compounds bring color or white to the composition under the conditions in which they are used.

[0100] Preferably, a composition of the invention is free of salts of the metals mentioned above, in particular aluminum salts or copper salts.

[0101] The pigment may be an organic pigment. By "organic pigment" we mean any pigment that meets the definition in the Ullmann Encyclopedia in the organic pigment chapter.

[0102] The organic pigment may in particular be chosen from nitroso, nitro, azo, xanthene, pyrene, quinoline, quinoline, anthraquinone, triphenylmethane, fluorane, phthalocyanine, metal complex type compounds, isoindolinone, isoindoline, quinacridone, perinone, perylene, diketopyrrolopyrrole, indigo, thioindigo, dioxazine, triphenylmethane, quinophthalone.

[0103] In particular, the white or colored organic pigments may be chosen from carmine, carbon black, aniline black, azo yellow, quinacridone, phthalocyanine blue, the blue pigments codified in the Color Index under the references Cl 42090, 69800, 69825, 74100, 74160, the yellow pigments codified in the Color Index under the references Cl 11680, 11710, 19140, 20040, 21100, 21108, 47000, 47005, the green pigments codified in the Color Index under the references Cl 61565, 61570, 74260, the orange pigments codified in the Color Index under the references Cl 11725, 45370, 71105, the red pigments codified in the Color Index under the references Cl 12085, 12120, 12370, 12420, 12490, 14700, 15525, 15580, 15620, 15630, 15800, 15850, 15865, 15880, 26100, 45380, 45410, 58000, 73360, 73915, 75470.

[0104] Advantageously, the pigment is selected from the pigments Cl Pigment Orange 82 [CAS No. 2170864-77-2] and Cl Pigment Yellow 216 [(CAS No. 817181 -98-9]. Pigment Orange 82 may be obtained, for example, under the name Sicopal® Orange K2430 from Sun Chemical, Ludwigshafen, Germany. Pigment Yellow 216 may be obtained, for example, under the name Orange 10P340 from Shepherd, Gent, Belgium.

[0105] Among the colorants, carminic acid may be mentioned. Also mentioned are the colorants known under the following names: D & C Red 21 (Cl 45 380), D & C Orange 5 (Cl 45 370), D & C Red 27 (Cl 45 410), D & C Orange 10 (Cl 45 425), D & C Red 3 (Cl 45 430), D & C Red 4 (Cl 15 510), D & C Red 33 (Cl 17 200), D & C Yellow 5 (Cl 19 140), D & C Yellow 6 (Cl 15 985), D & C Green (Cl 61 570), D & C Yellow 1 O (Cl 77 002), D & C Green 3 (Cl 42 053), D & C Blue 1 (Cl 42 090).

[0106] The coloring matter may be selected from the group consisting of titanium dioxide, carbon black, cobalt oxide, nickel titanate, molybdenum disulfide, aluminum flakes, iron oxide, zinc oxide, organic pigments, such as phthalocyanine and anthraquinone derivatives, and zinc phosphate.

[0107] According to any one of the embodiments, the composition according to the invention comprises less than 1% by weight, in particular less than 0.1% by weight, of carbonaceous filler, relative to the total weight of said composition.

[0108] For the purposes of the invention, the term "carbon filler" means a particulate object containing in its mass only carbon atoms, "apart from impurities", it being understood that there may be other atoms on the surface. A carbon filler may be chosen, without being exhaustive, from carbon blacks, natural and synthetic graphites, carbon fibers, graphenes, fullerenes, acetylene blacks and carbon nanotubes.

[0109] According to any one of the embodiments, the composition according to the invention comprises less than 0.1% by weight of carbon black, relative to its total weight. Preferably, the composition according to the invention is free of carbon black.

[0110] Preferably, the composition according to the invention comprises at least one coloring material leading to a color different from the color black.

[0111] Preferably, the composition according to the invention comprises less than 1% by weight, in particular less than 0.1% by weight, preferably 0% by weight, relative to its total weight, of coloring matter having an L* parameter less than 10, in particular less than 5, in particular less than 1, in particular equal to 0, with the L* parameter being measured in the CIELab system, as defined in the ISO 11664-4: 2008 standard, using a Konica Minolta CM-36dGV spectrophotometer in reflectance mode with a D65 illuminant, an angle of incidence of 10° and an aperture of 8mm and specular component included.

[0112] Preferably, the chosen coloring material(s) lead to a composition having:

[0113] - a parameter L* between 10 and 100, preferably between 20 and 80, advantageously between 40 and 75, in particular between 50 and 70, and / or

[0114] - a parameter a* between 10 and 100, preferably between 20 and 80, advantageously between 35 and 55, and / or

[0115] - a parameter b* between 10 and 100, preferably between 20 and 80, advantageously between 40 and 75, in particular between 50 and 70, with said parameters L*, a* and b* being measured in the CIELab system, as defined in the ISO 11664-4: 2008 standard, using a Konica Minolta CM-36dGV spectrophotometer in reflectance mode with a D65 illuminant, an angle of incidence of 10° and an aperture of 8mm and specular component included.

[0116] Preferably, the composition of the coating layer comprises at least one coloring material leading to an orange color.

[0117] Preferably, the chosen colorant(s) result in a RAL 2003 color composition, i.e. have the following L*a*b* values: L* = 66.0; a* = 41.2 and b* = 52.4.

[0118] Advantageously, the coloring matter is a mixture of at least two pigments. More preferably, the coloring matter comprises titanium dioxide, tin oxide, zinc oxide and their mixture. Even more preferably, the coloring matter comprises titanium dioxide, tin oxide, zinc oxide and at least two additional pigments, preferentially leading to the orange color.

[0119] Preferably, the coloring matter content in the composition is between 0.5 and 10%, advantageously between 1 and 5% by weight relative to the total weight of the composition.

[0120] Preferably, the content of black coloring matter and in particular black pigment, carbon black or other black filler is limited to a maximum of 0.1% by weight.

[0121] Preferably, black coloring materials are excluded.

[0122] Preferably, the color of the composition is characterized in that its color measured by the RAL method is different from a RAL color of 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017 or 9021.

[0123] Preferably, the composition of the coating layer comprises between 60 and 98% by weight, preferably between 70 and 95% by weight, of polyamide and between 0.5 and 10% by weight, preferably between 1 and 5% by weight of coloring matter. Additives

[0124] Preferably, the composition according to the invention comprises at least one additive chosen from flame retardants, UV protective agents, UV stabilizers, heat stabilizers, lubricants, fluidity improving agents, flowability improving agents, film-forming agents, fillers, film-forming auxiliaries, gums, preservatives, antibacterial agents and mixtures thereof. Preferably, the composition according to the invention does not comprise metal-based additives, so as to avoid any harmful interaction between the metal surface to be covered and these additives potentially present within the composition according to the invention. Antioxidants

[0125] Preferably, the composition of the coating layer comprises at least one antioxidant

[0126] For example, the stabilizer may be an organic stabilizer or more generally a combination of organic stabilizers, such as a phenol-type antioxidant (for example of the type of irganox® 245 or 1098 or 1010 from the company Ciba-BASF), a phosphite-type antioxidant (for example irgafos® 126 or Irgafos® 168 from the company Ciba-BASF) and possibly other stabilizers such as a HALS, which stands for Hindered Amine Light Stabilizer or hindered amine light stabilizer (for example Tinuvin® 770 from the company Ciba-BASF), a UV stabilizer (for example Tinuvin® 312 from the company Ciba), a phosphorus-based stabilizer. It is also possible to use amine-type antioxidants such as Naugard® 445 from Crompton or polyfunctional stabilizers such as Nylostab® S-EED from Clariant.

[0127] According to a preferred embodiment, the electricity transport component comprises a metal surface, characterized in that said metal surface is coated over its entire surface: - an intermediate layer of inorganic material; and - a coating layer made of a composition comprising predominantly at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 8 and at least one coloring matter, the intermediate layer being positioned between the metal surface of the electricity transport component and the coating layer, the metal surface being made of copper.

[0128] According to an even more preferred embodiment, the electricity transport component comprises a metal surface, characterized in that said metal surface is coated over its entire surface: - an intermediate layer of inorganic material; and - a coating layer in a composition comprising - predominantly at least one polyamide, the polyamide(s) having: - a difference, expressed in absolute value, between its total acidity and its total basicity less than 70 and - a total basicity of less than 60 peq / g, and the composition comprising mainly at least one polyamide having a number of carbon atoms per nitrogen atom greater than 6.5 and at least one coloring material, the intermediate layer being positioned between the metal surface of the electricity transport component and the coating layer, the metal surface being copper. Use of the electricity transmission component

[0129] In one embodiment, said electricity transport component, preferably said interconnection bar, is located inside and / or outside electric batteries, in particular vehicle electric batteries, in particular motor vehicle batteries. It may be, for example, immersed in a coolant. Process for preparing the electricity transmission component

[0130] According to yet another aspect, the present invention relates to a method for preparing an electricity transport component, preferably an interconnection bar, in particular for an electric battery, comprising: - a step of coating the entire metal surface of the electricity transport component with an intermediate layer of inorganic material as defined above; then - a step of coating the intermediate layer of inorganic material with a coating composition as defined above.

[0131] According to yet another aspect, the present invention relates to a method for preparing an interconnection bar, in particular an electric battery, comprising: - a step of coating the entire metal surface of the interconnecting bar with an intermediate layer of inorganic material as defined above; then - a step of coating the intermediate layer of inorganic material with a coating composition as defined above.

[0132] Preferably, the step of covering the intermediate layer of inorganic material with a coating composition as defined above can be carried out by extrusion of the composition or by depositing a powder of said coating composition and then melting the powder.

[0133] Preferably, the preparation method comprises an extrusion step and does not comprise a powder coating step.

[0134] It is possible for the metal surface of the electricity transport component, preferably the metal bar, to undergo a pre-treatment step before being covered by the intermediate layer of inorganic material. The method may comprise, for example, a step of degreasing the metal surface and / or a singeing step and / or a pre-heating step.

[0135] All the characteristics defined above are valid for the process.

[0136] Other aims and advantages of the present invention will appear on reading the following examples given without any limitation being implied. EXAMPLES ] Preparation of coating compositions

[0137] Coating compositions according to the invention were prepared using the following compounds.

[0138] The polyamide denoted PA11 is prepared according to the following process. 43.00 kg of 11-amino-undecanoic acid, 30 g of phosphoric acid and 6.0 kg of deionized water are loaded into an autoclave and heated to 250°C while maintaining autogenous pressure for 30 min. As soon as the monomer melts, the medium is stirred at 40 rpm for the entire duration of the synthesis. A progressive expansion is applied for 2 hours up to 1 bar while raising the temperature to 255°C. A nitrogen sweep at a flow rate of 100 L / h is then applied for 30 minutes while maintaining the temperature at 255°C. Finally, stirring is stopped and the melt extruded under a pressure of 6 bars. The rod is cooled in a water bath, then granulated.

[0139] Polyamide PA12 is prepared according to the following process. 25.00 kg of laurolactam and 2.20 kg of deionized water are loaded into an autoclave and heated to 290°C under a pressure of 32 bar for 5 hours. As soon as the monomer melts, the medium is stirred at 40 rpm for the entire duration of the synthesis. A progressive pressure reduction is applied for 8 hours up to 8 bar while maintaining the temperature at 290°C. Then a pressure reduction over one hour down to 0.2 bar is applied by gradually lowering the temperature to 265°C. A nitrogen flush at a flow rate of 100 L / h is then applied for 15 minutes while maintaining the temperature at 265°C. Finally, a vacuum is applied to bring the pressure to 0.3 bar for 15 minutes. Finally, stirring is stopped and the melt extruded under a pressure of 10 bar. The rush is cooled in a water bath, then granulated.

[0140] The polyamides tested have the characteristics indicated in Table 1 below: Table 1 Measurement of total basicity

[0141] Basicity is measured using the following method. 1 g of polyamide is dissolved in 80 mL of hot metacresol. The sample is then cooled. Then, it is measured by potentiometry using a Metrohm titrator (888 or 716) with a combined pH electrode, with a 0.02N perchloric acid solution in acetic acid. The potential versus volume curve gives a jump with an equivalent volume from which the total basicity is calculated using the following formula: Veq X [HC104] Total basicity (meq / g) = - m in which Veq denotes the equivalent volume obtained using potentiometric dosing, [HCIO4] denotes the concentration of the perchloric acid solution, i.e. 0.02 N, m denotes the mass of the sample, i.e. 1 g. Total acidity measurement

[0142] Acidity is measured using the following method. 1 g of polyamide is dissolved in 80 mL of hot benzyl alcohol. The sample is then cooled. Then, it is determined by potentiometry using a Metrohm titrator (888 or 716) with a combined pH electrode, with a 0.02N tetrabutylammonium hydroxide solution. The potential versus volume curve gives a jump with an equivalent volume from which the total acidity is calculated using the following formula: Veq X [TBAOH] Total acidity (meq / g) = - m in which Veq denotes the equivalent volume obtained using potentiometric dosing, [TBAOH] denotes the concentration of tetrabutylammonium hydroxide solution, i.e. 0.02 N, m denotes the mass of the sample, i.e. 1 g. Tl Calculation of the difference between total acidity and basicity

[0143] The difference is obtained by calculating the subtraction of the values ​​between the total acidity and the total basicity, in absolute value, that is to say without taking into account the sign.

[0144] For example, for PA 11: = |57 - 48| = 9 Measurement of inherent viscosity

[0145] The measurement is carried out at 20°C on a 75 mg sample at a concentration of 0.5% (m / m) in m-cresol. The inherent viscosity is calculated according to the following formula: Inherent viscosity = ln(t s / to) x 1 / C, with C = m / px 100, in which t sis the flow time of the solution, to is the flow time of the solvent, m is the mass of the sample whose viscosity is determined and p is the mass of the solvent. This measurement corresponds to the ISO 307:2007 standard except that the measurement temperature is 20°C instead of 25°C. Measurement of the enthalpy of fusion

[0146] The enthalpy of fusion is determined according to ISO 11357-3:2013 by DSC during the second heating. Measurement of crystallization temperature

[0147] The crystallization temperature is determined according to ISO 11357-3:2013 by differential scanning calorimetry (DSC) during cooling at a rate of 20°C / min.

[0148] The tested compositions also include the following compounds:

[0149] A phenolic-type primary antioxidant sold under the trade name Irganox 245® by BASF (CAS No.: 36443-68-2).

[0150] A phosphite-type secondary antioxidant sold under the trade name Irgafos 168® by BASF (CAS No.: 31570-04-4).

[0151] A mixture of pigments sold under the trade name 338160 ORA LLDPE AO Smartbatch by Avient containing 28% pigments.

[0152] The following compositions are prepared by melt mixing the various raw materials in a 26 mm diameter co-rotating twin-screw extruder. The products are extruded at a flow rate of 16 kg / h, at a temperature of 250°C and with a screw speed of 250 rpm. At the machine outlet, the products are cooled by passing through a water tank and then granulated. These products are finally vacuum dried for 8 hours at 80°C. The formulations of the compositions are shown in Table 2 below; the contents in the table are indicated as a percentage by weight relative to the total weight of the composition. Table 2 Sample preparation

[0153] From these compositions, plates (60x60x1 mm) and ISO 527-1 A dumbbells are injected at a temperature of 260°C. Measurement of mechanical properties

[0154] The tensile mechanical properties are measured according to ISO 527-1:2012 on dry samples. The machine used is an Instron 5966 with a crosshead speed of 50 mm / min.

[0155] Resistance to de-icing salts is measured according to EN 16811-1:2016 on a 1 mm thick plate.

[0156] The results are presented in Table 3 below: Table 3 Measurement of optical and electrical properties:

[0157] Dielectric strength is measured according to IEC 60243-1:2013 on a 1 mm thick plate at 25°C.

[0158] The colorimetric properties of the samples are measured in the CIELab system, as defined in ISO 11664-4:2008, using a Konica Minolta CM-36dGV spectrophotometer in reflectance mode with a D65 illuminant, an incidence angle of 10° and an aperture of 8mm and specular component included.

[0159] In this L* a* b* system, L* represents brightness, a* indicates the green / red color axis and b* the blue / yellow color axis. The higher the value of L*, the lighter or less intense the color. Conversely, The lower the value of L*, the darker or more intense the color. The higher the value of a*, the redder the shade, and the higher the value of b*, the more yellow the shade. The results are presented in Table 4 below: Table 4

[0160] The dielectric strength of each of compositions A and B after aging at 150°C for 240 hours in a ventilated oven remains greater than 10kV / mm. Preparation of coated metal bars

[0161] From each of the compositions A and B, plates of dimensions 60x60x1 mm are prepared by injection at 260°C.

[0162] The following intermediate layers are used:

[0163] Intermediate layer 1: Woven fiberglass film marketed as YN-FW-001 by Yuniu fiberglass roving

[0164] Intermediate layer 2: Mica film marketed as MC-5000HT by Final Advanced materials, composed of approximately 90% phlogopite mica and 10% silicone binder resin.

[0165] Representative structures of the invention are prepared by superimposing the following layers: Composition A or B / intermediate layer 1 or 2 / copper / intermediate layer 1 or 2 / composition A or B.

[0166] This assembly, surrounded by a frame of the same thickness as the total assembly, is compressed in a press at 220°C. The plates of the press are brought into contact with the superimposed layers for 90s without applying pressure. Then, a pressure of 50 bars is applied for 60s. Finally, the assembly is cooled for 2 min while maintaining a pressure of 30 bar. The comparative examples are prepared in the same way without an intermediate layer. The structures are shown in Table 5 below: Table 5 Evaluation of structures Evaluation of color variation

[0167] The multi-layer structures are aged at 150°C for 240 hours in a ventilated oven.

[0168] The AE measurement is carried out on the copper plates covered with the aged composition and on the copper plates covered with the composition and the intermediate layer, also aged.

[0169] Before and after this aging, the colorimetric data of the samples are measured in the CIELab system, as defined in ISO 11664-4: 2008, using a Konica Minolta CM-36dGV spectrophotometer in reflectance mode with a D65 illuminant, an incidence angle of 10° and an aperture of 8mm and specular component included.

[0170] In this L* a* b* system, L* represents brightness, a* indicates the green / red color axis and b* the blue / yellow color axis. The higher the value of L*, the lighter or less intense the color. Conversely, the lower the value of L*, the darker or more intense the color. The higher the value of a*, the redder the shade, and the higher the value of b*, the yellower the shade. The color aging therefore corresponds to the color variation between the unaged plate, i.e. at t = 0 and the plate aged at 150°C at t = 240h. This variation is measured by the AE according to the following equation:

[0171] In this equation, L*, a* and b* represent the values ​​measured on the aged plate, at t = 240h and Lo*, ao* and bo* represent the values ​​measured on the unaged plates. The higher the value of AE, the more the color has evolved during aging, illustrating the instability of the composition.

[0172] The results are given in Table 6 below: High temperature resistance evaluation:

[0173] The exemplified structures are placed in an oven at 500°C for 5 minutes. On these samples, a dielectric strength measurement is carried out according to IEC 60243-1:2013.

[0174] The results of the evaluation tests are given in Table 7 below:

[0175] The examples show that the structures according to the invention have good mechanical properties and exhibit color stability over time while retaining a certain electrical insulating character (see the dielectric strength results) after exposure to 500°C (and burning of the polyamide layer). Thus, advantageously, the layer of inorganic material remains insulating without guaranteeing a good level of dielectric strength (> 10kV / mm) after exposure to 500°C.

[0176] As previously indicated, the dielectric strength of each of compositions A and B after aging at 150°C for 240 hours in a ventilated oven remains greater than 10kV / mm.

Claims

Claims

1. [An electricity transport component, wherein the electricity transport component comprises a metal surface, characterized in that said metal surface is coated over its entire surface: - an intermediate layer of inorganic material; and - a coating layer having a color other than black in an electrically insulating composition comprising mainly at least one polyamide whose number of carbon atoms per nitrogen atom is greater than 6.5 and at least one coloring material, the intermediate layer being positioned between the metal surface of the electricity transport component and the coating layer.

2. Composition according to claim 1, characterized in that the intermediate layer of inorganic material is other than a metal.

3. Composition according to claim 1 or 2, characterized in that the composition comprises from 60 to 98% by weight of said at least one polyamide.

4. Composition according to claim 1 to 3, characterized in that said at least one polyamide is an aliphatic or cycloaliphatic polyamide.

5. An electricity transmission component according to any preceding claim, being an interconnection bar.

6. An electricity transmission component according to any preceding claim, wherein the metal surface is copper, copper alloy, aluminum or aluminum alloy.

7. An electricity transmission component according to any preceding claim, wherein the intermediate layer of inorganic material is a layer of mica, carbon fiber or glass fiber, preferably mica.

8. An electricity transport component according to any one of the preceding claims, wherein the intermediate layer of inorganic material has a thickness of between 0.1 and 2 mm, preferably between 0.15 and 1 mm.

9. An electricity transport component according to any one of the preceding claims, characterized in that the coloring matter content ranges from 0.5 to 10% by weight, preferably from 1 to 5% by weight relative to the total weight of the composition.

10. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide(s) of the coating layer have an inherent viscosity measured according to standard ISO 307:2007 greater than 1.

1.

11. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide(s) of the coating layer have an enthalpy of fusion measured by DSC during the second heating according to standard ISO 11357-3, 2013 strictly greater than 20 J / g.

12. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide(s) of the coating layer have a crystallization temperature measured by DSC during the second heating according to standard ISO 111357-3, 2013 strictly less than 180°C.

13. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide of the coating layer is chosen from PA11, PA12, PA1010, PA 1012, PA 610, PA 612, PA 613, PA 516, PA 912, PA 6 / 11, PA 6 / 12, PA 11 / 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 alone or as a mixture, more particularly PA11, PA12, PA1010, PA 1012, or PA1014 alone or as a mixture. more preferably PA11 or PA12, preferably PA11.

14. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide(s) of the composition of the coating layer have a difference, expressed as an absolute value, between its total acidity and its total basicity of less than 70 and a basicity of the total polyamide(s) of less than 60 peq / g, the total acidity and the total basicity being measured by potentiometry.

15. Electricity transport component according to any one of the preceding claims, characterized in that the polyamide(s) of the composition of the coating layer have a total acidity measured by potentiometry of less than 60 peq / g.

16. A method of preparing an electricity transmission component according to any one of claims 1 to 15 comprising: - a step of coating the entire metal surface of the electricity transport component with an intermediate layer of inorganic material as defined in any one of claims 1, 7 and 8; then - a step of coating the intermediate layer of inorganic material with a coating composition as defined in any one of claims 1 and 9 to 15.

17. Method according to claim 16, characterized in that the step of coating the intermediate layer is carried out by extrusion.

18. A method according to claim 16, characterized in that the step of coating the intermediate layer is carried out by depositing a powder of said coating composition and then melting the powder.

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