Electrical transmission component, in particular for battery

Abstract

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

Description

Technical Field

[0001] This invention relates to an electrical transmission component, and more particularly to a colored busbar, notably for use in batteries. Background Technology

[0002] In the field of electric vehicles, there are connectors known as busbars (interconnects) used to circulate high-intensity currents both inside and outside the battery. These bars must be covered with an insulating coating that is resistant to mechanical stress and aging.

[0003] There are many methods for producing busbars. One major one is to extrude a polymer composition around a central metal strip. Powder coating, dip coating, or electro-spraying methods can also be used. These structures are then cut and bent (at ambient temperature) to achieve the shape required for the vehicle layout.

[0004] For safety reasons, these strips must also have a unique color representing the current flowing through them. Therefore, this color must remain stable over time, regardless of the temperature the strip may be subjected to. Specifically, external conditions, proximity to the engine, self-heating during current flow, and especially during battery charging, are factors that can affect the coating color over time. If the color changes over time, questions may arise regarding the voltage of the current flowing through the strip, potentially leading to accidents, for example, during engine maintenance or repair. Therefore, color stability is essential despite harsh environmental conditions.

[0005] A technical challenge associated with battery busbar applications is forming a thin polymer layer whose color does not change over time, while maintaining a high level of flexibility to accommodate busbar deformation. During bending, excessively rigid material forms cracks on the outer surface and buckles on the inner surface, which is considered "ripples" or "beads," an unacceptable phenomenon for the application.

[0006] Therefore, the behavior of the material below its plastic threshold is crucial. Low stress and high elongation at the threshold are desirable. These coatings maintain low deformation levels, 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] Furthermore, depending on the location of these parts within the engine, these compositions may be advantageous in their resistance to de-icing salt.

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

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

[0010] Furthermore, existing technologies do not provide information on combining these elements in a formulation to simultaneously achieve the flexibility and color stability required for battery busbar applications.

[0011] US 2021 / 0253854 and KR101977321 disclose compositions based on polyamide and at least one pigment system. However, from a mechanical point of view, the disclosed compositions are found to be unsatisfactory. Furthermore, color changes in these products during aging are not documented. Summary of the Invention

[0012] This invention relates to a power transmission component comprising a metal surface, characterized in that the metal surface is coated with:

[0013] - An intermediate layer made of inorganic materials; and

[0014] - A coating made of an electrically insulating composition, said electrically insulating composition comprising primarily at least one polyamide having a carbon number greater than 6.5 per nitrogen atom and at least one dye.

[0015] The intermediate layer is located between the metal surface of the power transmission component and the coating.

[0016] Preferably, the coating is characterized by a color different from black.

[0017] According to one embodiment, the electrical insulating composition may have an L value greater than 0, preferably greater than 5, preferably greater than 10. The parameters, measured in the CIELab system as defined in standard ISO 11664-4:2008, were measured in reflectance mode using a Konica Minolta CM-36dGV spectrophotometer with a D65 light source, an incident angle of 10°, an aperture of 8 mm, and including the specular component.

[0018] According to one embodiment, the electrical insulating composition may have a color determined according to the RAL method, which is different from RAL colors 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017 and 9021.

[0019] Preferably, the intermediate layer is made of an inorganic material, which is different from a metal.

[0020] Preferably, the coating composition comprises 60% to 98% by weight of the at least one polyamide.

[0021] Preferably, the coating composition is characterized in that the at least one polyamide is an aliphatic or alicyclic polyamide, preferably an aliphatic polyamide.

[0022] Finally, the present invention relates to a method for manufacturing a power transmission component as defined above, comprising:

[0023] - The step of coating all metal surfaces of the power transmission component with an intermediate layer of inorganic material as defined in any one of claims 1, 4, and 5; then

[0024] - The step of coating the intermediate layer of the inorganic material with the coating composition as defined in any one of claims 1 to 12.

[0025] It has been observed that the color of the composition deposited on the component according to the invention remains stable even after aging at high temperatures. It has also been observed that the composition continues to possess certain electrical insulating properties after aging. Furthermore, the composition deposited on the component according to the invention exhibits good mechanical properties: the elongation at break, impact strength, and polymer layer properties during metal strip bending are very satisfactory. Finally, the electrical components coated with the composition remain easily peeled off.

[0026] Other advantageous features of the method according to the invention are described in detail below:

[0027] - The component in question is a busbar.

[0028] - The metal surface of the component is made of copper, copper alloy, aluminum, or aluminum alloy.

[0029] - The intermediate layer, made of inorganic materials, is a mica layer, a carbon fiber layer, or a glass fiber layer, preferably a mica layer.

[0030] - The thickness of the intermediate layer made of inorganic material is 0.1 to 2 mm, preferably 0.15 to 1 mm.

[0031] - The polyamide coating has an intrinsic viscosity greater than 1.1 as measured according to standard ISO 307:2007.

[0032] - The polyamide coating has a melting enthalpy greater than 20 J / g, as measured by DSC during the second heating according to standard ISO 11357-3,2013.

[0033] - The polyamide coating has a crystallization temperature strictly below 180°C as measured by DSC during the second heating, according to standard ISO 11357-3,2013.

[0034] - The polyamide used for the coating is selected from PA11, PA12, PA1010, PA1012, PA610, PA612, PA613, PA516, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014, more particularly PA11, PA12, PA1010, or PA1012, even more preferably PA11 or PA12, with PA11 being the most preferred.

[0035] - The dye content ranges from 0.5% to 10% by weight, preferably from 1% to 5% by weight, relative to the total weight of the composition.

[0036] - The polyamide in the coating composition has a difference between its total acidity and total basicity, expressed in absolute value, of less than 70 μeq / g, and a total basicity of less than 60 μeq / g of polyamide.

[0037] -The polyamide in the coating composition has a total acidity of less than 60 μeq / g.

[0038] - In this method, the intermediate layer coating step is performed by extrusion.

[0039] - In this method, the intermediate layer coating step is performed by depositing powder of the coating composition and then melting the powder. Detailed Implementation

[0040] Other features, aspects, subjects, and advantages of the invention will become clearer from the following description.

[0041] The nomenclature used to define polyamides is described in standard ISO 1874-1:2011 “Plastics—Polyamide (PA) Molding and Extrusion Materials—Part 1: Designation”, notably on page 3 (Tables 1 and 2), and is well known to those skilled in the art. Thus, PA11 is obtained by the polycondensation of 11-aminoundecanoic acid. PA12 is obtained by the polycondensation of lauryl lactam. PA1010 is obtained by the polycondensation of decanediamine (10) and sebacic acid (10). PA1012 is obtained by the polycondensation of decanediamine (10) and dodecanoic acid (12).

[0042] Furthermore, it is stipulated that the expression “between… and…” and the phrase “(from)… to (to)…” used in this specification shall be understood to include each endpoint mentioned.

[0043] The term "polyamide" encompasses both homopolymers and copolymers.

[0044] The invention will now be described in more detail in a non-limiting manner in the following description.

[0045] Power transmission components

[0046] The subject of this invention is a power transmission component, preferably a busbar, wherein the power transmission component comprises a metal surface, characterized in that the metal surface is coated with:

[0047] - An intermediate layer made of inorganic materials; and

[0048] - A coating made of an electrically insulating composition, said electrically insulating composition comprising primarily at least one polyamide having a carbon number greater than 6.5 per nitrogen atom and at least one dye.

[0049] The intermediate layer is located between the metal surface of the power transmission component and the coating.

[0050] Preferably, the coating is characterized in that its color, as determined by the RAL method, is different from black. The term "black" is intended to refer to RAL colors 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017, and 9021. RAL colors 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017, and 9021 correspond to black.

[0051] Preferably, the intermediate layer made of inorganic material is characterized in that the material is different from the metal layer.

[0052] The power transmission components are preferably high-voltage power transmission components. The term "high voltage" refers to a voltage of 400 to 1000 V.

[0053] Preferably, the power transmission component is a busbar. Therefore, in this embodiment, the subject of the invention is a busbar comprising:

[0054] -Metal strip;

[0055] - An intermediate layer made of inorganic materials; and

[0056] - A coating made of a composition comprising at least one primary polyamide having a carbon number greater than 6.5 per nitrogen atom and at least one dye.

[0057] The intermediate layer is located between the metal strip and the coating.

[0058] The power transmission component can be of any type. It is primarily a high-voltage power transmission component. This component can be in the form of a metal cable or contain metal fibers, such as braided ones, or thin metal sheets or metal strips, such as those commonly used in busbars.

[0059] Preferably, the power transmission component is an electrical or electronic component cover, control device, connector, battery relay, electrical housing, electrical terminal, or cable.

[0060] Preferably, the power transmission component includes a metal surface, which is preferably made of copper, a copper alloy, aluminum, or an aluminum alloy, preferably made of copper or aluminum, and most preferably made of copper.

[0061] In one embodiment, the power transmission component is a busbar comprising a metal strip, which is preferably made of copper, a copper alloy, aluminum, or an aluminum alloy, preferably copper or aluminum, and most preferably copper.

[0062] Intermediate layer made of inorganic materials

[0063] The intermediate layer is an inorganic material layer. Preferably, this layer completely covers the metal strip.

[0064] The inorganic material of the intermediate layer can be of any type, and is notably selected from silicates, particularly silicates, glass, carbon, and more preferably mica, carbon fibers, and glass fibers and mixtures thereof. For example, the intermediate layer can be a mica layer, a glass fiber layer, or a carbon fiber layer, preferably a mica layer or a glass fiber layer.

[0065] The intermediate layer is preferably in the form of an inorganic material strip, such as a mica strip, carbon fiber strip, or glass fiber strip, with mica strip being the preferred material.

[0066] The thickness of the inorganic material layer is preferably 0.1 to 2 mm, more preferably 0.15 to 1 mm, and advantageously 0.2 to 0.5 mm. Therefore, preferably, the thickness of the inorganic material strip is between 0.1 and 2 mm, more preferably between 0.15 and 1 mm, and advantageously between 0.2 and 0.5 mm.

[0067] For the purposes of this invention, the term "intermediate layer made of inorganic material" means that the intermediate layer mainly comprises inorganic material as defined above, i.e., at least 50% by weight, preferably 50% to 99% by weight, for example 75% to 95% by weight, relative to its total weight.

[0068] In addition to the inorganic materials defined above, the intermediate layer made of inorganic materials may contain an adhesive resin (or matrix), which may noteably be a thermoplastic polymer resin or a thermosetting polymer resin, preferably a thermosetting polymer resin, such as selected from epoxy resins, silicone and polyurethane.

[0069] In a particularly advantageous way, the inorganic material layer allows for stable color retention over time, even at high temperatures, while maintaining a degree of electrical insulation and mechanical strength at very high temperatures.

[0070] coating

[0071] According to the present invention, the power transmission component, preferably the busbar, comprises a coating made of an electrically insulating composition, the electrically insulating composition comprising primarily at least one polyamide having a carbon number greater than 6.5 per nitrogen atom and at least one dye.

[0072] For the purposes of this invention, the term "electrical insulation" refers to a material with a dielectric strength greater than 10 kV / mm, measured on a 1 mm thick plate for a sample conditioned for 14 days at 25°C and 50% relative humidity, according to standard IEC 60243-1:2013.

[0073] Preferably, the coating thickness is 0.1 mm to 2 mm, particularly 0.2 mm to 1 mm, notably 0.3 mm to 0.8 mm, and more particularly 0.4 mm to 0.6 mm, while maintaining a high level of flexibility to accommodate the strain of the power transmission components. Overly rigid materials can form cracks or "ripples," which is unacceptable for such applications.

[0074] Coating composition

[0075] The composition forming the coating mainly comprises at least one polyamide having more than 6.5 carbon atoms per nitrogen atom and at least one dye.

[0076] For the purposes of this invention, the term "major" means that the composition contains at least one polyamide in an amount greater than 50% by weight relative to the total weight of the composition. This or these polyamides constitute the matrix of the composition.

[0077] Preferably, the coating composition contains 60% to 98% by weight, preferably 70% to 95% by weight, of at least one polyamide relative to the total weight of the composition.

[0078] Preferably, the coating composition contains 0.5% to 10% by weight, and more preferably 1% to 5% by weight, of a dye.

[0079] Preferably, the coating composition comprises 60% to 98% by weight, preferably 70% to 95% by weight, of polyamide and 0.5% to 10% by weight, preferably 1% to 5% by weight, of dye.

[0080] In the case of PA-XY type homopolymers, where X represents a unit obtained from a diamine and Y represents a unit obtained from a diacid, the number of carbon atoms per nitrogen atom is the average of the number of carbon atoms present in the units derived from diamine X and the units derived from diacid Y. Therefore, PA6.12 is a PA with 9 carbon atoms per nitrogen atom, in other words, a C9 PA. PA6.13 is a C... 9.5 PA. In the case of copolyamides, for example, having the structure XaYa / XbYb, the number of carbon atoms per nitrogen atom is calculated according to the same principle. For various amide units, i.e., for XaYa and XbYb units, the calculation is performed in molar proportions.

[0081] The main polyamide present in the coating composition has a number of carbon atoms greater than 6.5, preferably greater than 8, per nitrogen atom.

[0082] For the purposes of this invention, the term "major" means that the composition comprises at least one polyamide in an amount 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 carbon number greater than 6.5 per nitrogen atom. This mixture must be major, i.e., it must account for at least 50% by weight relative to the total weight of the composition.

[0083] Preferably, the composition comprises 60% to 98% by weight, preferably 70% to 95% by weight, of at least one polyamide relative to the total weight of the composition.

[0084] In other words, the presence of other polyamides cannot be excluded. However, it is important that polyamides with a high carbon number are the predominant type in the composition.

[0085] The polyamide present in the coating composition of the component according to the invention is obtained by polycondensation of at least one unit selected from C6 to C18 α,ω-aminocarboxylic acid, C5 to C12 lactam and (Ca diamine)-(Cb diacid) unit, wherein a represents the number of carbon atoms of the diamine and b represents the number of carbon atoms of the diacid, and a is between 4 and 36.

[0086] Polyamides can be obtained by polycondensation of at least one lactam selected from pyrrolidone, 2-piperidinone, heptanolactam, 2-azacyclononone, nonanolactam, decanolactam, undecyllactam, and lauryllactam.

[0087] Polyamides can also be obtained by polycondensation of at least one amino acid selected from 9-aminononanoic acid, 10-aminodecanoic acid (represented by 10), 11-aminoundecanoic acid (represented by 11), and 12-aminododecanoic acid (represented by 12).

[0088] Polyamides can be obtained by polycondensation of at least one unit corresponding to the formula (Ca diamine) (Cb diacid), where a represents the number of carbon atoms in the diamine and b represents the number of carbon atoms in the diacid, and a and b are between 4 and 36.

[0089] The (Ca diamine) unit can be aliphatic, alicyclic, or aromatic. It can be selected 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-phenylenediamine (MXD), methylpentamethylenediamine (MPMD), bis(aminomethyl)cyclohexane (BAC), m-phenylenediamine (MXD, CAS No. 1477-55-0), and p-phenylenediamine (PXD, CAS No. 539-48-0).

[0090] Advantageously, the at least one C6 to C12 diamine X is particularly selected from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine and 1,12-dodecimethylenediamine.

[0091] Advantageously, the diamine X used is a C10 to C12 diamine, particularly selected from 1,10-decamethylenediamine, 1,11-undecamethylenediamine and 1,12-dodecimethylenediamine.

[0092] The (Cb diacid) unit can be aliphatic, alicyclic, or aromatic. It can be selected from succinic acid (b=4), glutaric acid (b=5), adipic acid (b=6), pimelic acid (b=7), octanoic acid (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanoic acid (b=11), dodecanoic acid (b=12), tridecanoic acid (b=13), tetradecanoic acid (b=14), hexadecanoic acid (b=16), octadecanoic acid (b=18), and diacids obtained from fatty acids, such as terephthalic acid (denoted as T).

[0093] Advantageously, the (Cb diacid) unit is selected from diacid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid and octadecanoic acid.

[0094] Advantageously, the polyamide present in the composition according to the invention has an elongation at break of >50%, preferably greater than 100%, and even more advantageously greater than 200%. The elongation at break can be notably measured according to standard ISO 527-1 / -2.

[0095] 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, more preferably less than 5% by weight, and more preferably less than 1% by weight, relative to the total weight of the composition. Preferably, the composition according to the invention does not contain any polyamide having an elongation at break of less than or equal to 50%.

[0096] Advantageously, the polyamide present in the composition of the coating of the component according to the invention is aliphatic or alicyclic. Preferably, the polyamide present in the composition of the coating of the component according to the invention is aliphatic.

[0097] Advantageously, the polyamide is selected from PA11, PA12, PA1010, PA1012, PA610, PA612, PA613, PA912, PA516, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014, either alone or as a mixture.

[0098] Preferably, the composition comprises only polyamides having more than 6.5 carbon atoms per nitrogen atom. More particularly, the composition comprises only polyamides having more than 8 carbon atoms per nitrogen atom.

[0099] According to a preferred embodiment, the polyamide is a homopolymer. This homopolymer can be obtained by polycondensation of lactam, amino acid, or (Ca diamine)(Cb diacid) units, wherein Ca and Cb are as defined above.

[0100] More specifically, the composition mainly comprises PA11, PA12, PA1010 or PA1012, or even more preferably PA11 or PA12, with PA11 being the most preferred.

[0101] PA11 has the advantage of being made from plant-derived raw materials. Plant materials can be grown in large quantities in most parts of the world as needed and are bio-based. Bio-based raw materials are natural animal or plant resources whose reserves can be reconstructed in a short time on a human timescale. Of particular importance is that these reserves can be regenerated as quickly as they are consumed.

[0102] The basic raw material for PA11 is castor oil, which is extracted from the seeds of a plant of the same name (castor oil plant). PA11 is obtained through the condensation polymerization of 11-aminoundecanoic acid.

[0103] Total acidity and total alkalinity

[0104] Preferably, the difference (expressed in absolute value) between the total acidity and the total basicity of the polyamide present in the coating composition of the component according to the invention is strictly less than 70, preferably less than 50, and ideally less than 30.

[0105] For the purposes of this invention, the term difference is expressed in absolute value and should be understood as the result of subtracting the total basicity value of the polyamide from the total acidity value of the polyamide, regardless of the sign.

[0106] When the composition includes a mixture of polyamides, the acidity and alkalinity of the polyamide mixture are measured. Therefore, the difference is expressed as a percentage of the polyamide mixture.

[0107] Preferably, the polyamide present in the composition of the component according to the invention also has a total alkalinity of strictly less than 60 μeq / g, preferably less than 50 μeq / g, and ideally less than 40 μeq / g.

[0108] Preferably, the polyamide present in the composition of the component according to the invention also has a total acidity of strictly less than 60 μeq / g, preferably less than 50 μeq / g, and ideally less than 40 μeq / g.

[0109] Acidity and alkalinity are measured by potentiometric method.

[0110] Acidity was measured using the following method: The polyamide sample was dissolved in benzyl alcohol. The sample was then analyzed by potentiometry using a 0.02 N tetrabutylammonium hydroxide solution.

[0111] Alkalinity was measured using the following method: The polyamide sample was dissolved in m-cresol. The sample was then analyzed using a potentiometry method with 0.02 N perchloric acid solution.

[0112] According to one embodiment of the invention, the polyamide has a total basicity strictly less than 60 μeq / g and a total acidity strictly less than 60 μeq / g, and a difference in absolute value between its total acidity and its total basicity strictly less than 50, ideally less than 30.

[0113] According to a preferred embodiment, the composition mainly comprises PA11, PA12, PA1010 or PA1012 and mixtures thereof, wherein the polyamide or these polyamides have a total basicity of less than 60 μeq / g and a difference in absolute value between their total acidity and total basicity that is strictly less than 50 and ideally less than 30.

[0114] According to a preferred embodiment, the composition mainly comprises PA11 or PA12, having a total basicity of less than 50 μeq / g and a total acidity of less than 60 μeq / g, and a difference in absolute value between its total acidity and its total basicity that is strictly less than 30.

[0115] Preferably, the polyamide present in the composition does not contain chain restrictors.

[0116] Intrinsic viscosity

[0117] Preferably, the polyamide in the coating composition has an intrinsic viscosity greater than 1.1, and more preferably greater than 1.2, as measured according to standard ISO 307:2007.

[0118] A 75 mg sample containing 0.5% (m / m) m-cresol was measured at 20°C.

[0119] When the composition includes a mixture of polyamides, the viscosity of the polyamide mixture is measured.

[0120] enthalpy of melting

[0121] Preferably, the polyamide in the coating composition has a melting enthalpy greater than 20 J / g, preferably greater than 30 J / g, and ideally greater than 40 J / g.

[0122] The enthalpy of fusion was measured by DSC (differential scanning calorimetry) according to standard ISO 11357-3, 2013 (a second DSC heating was performed at 20°C / min according to standard ISO 11357).

[0123] When the composition includes a mixture of polyamides, the enthalpy of melting of the polyamide mixture is measured.

[0124] Crystallization temperature

[0125] Preferably, the polyamide in the coating composition has a crystallization temperature below 180°C, and preferably below 160°C.

[0126] Crystallization temperature was measured by DSC (differential scanning calorimetry) according to standard ISO 11357-3, 2013 (second DSC heating was performed at 20°C / min according to standard ISO 11357).

[0127] When the composition includes a mixture of polyamides, the crystallization temperature of the polyamide mixture is measured.

[0128] dye

[0129] The composition of the coating of the component according to the invention comprises at least one dye. The dye may be a dyeing agent or a pigment, in other words, a water-soluble dyeing agent or a water-insoluble pigment, depending on the conditions defined below.

[0130] The dye can be any type known to those skilled in the art. Preferably, the dye according to the invention is selected from azo dyes, anthraquinone dyes, indigo dyes, triarylmethane dyes, chloro dyes, and polymethystine dyes.

[0131] The term "pigment" refers to any pigment that imparts color to a polymer composition. They have a solubility in water of less than 0.05% by weight, preferably less than 0.01%, at 25°C and atmospheric pressure (760 mmHg). Pigments that can be used are notably selected from organic and / or inorganic pigments known in the art, particularly those described in Kirk-Othmer's Encyclopedia of Chemical Technology and Ullmann's Encyclopedia of Industrial Chemistry.

[0132] Pigments can be of natural or non-natural origin. They can be in the form of pigment powders or pastes. They can be coated or uncoated. Pigments can be selected from, for example, inorganic pigments, organic pigments, and mixtures thereof.

[0133] The term "inorganic pigment" refers to any pigment that meets the definition in the chapter on inorganic pigments in the Ullmann Encyclopedia. Among the inorganic pigments that can be used in this invention, references may be made to ochre, such as red ochre (clay (especially kaolinite) and iron hydroxide (e.g., hematite)), brown ochre (clay (especially kaolinite) and goethite), yellow ochre (clay (especially kaolinite) and goethite); titanium dioxide, optionally surface-treated; zirconium oxide or cerium oxide; zinc oxide, iron oxide (black, yellow, or red) or chromium oxide; manganese violet, ultramarine, chromium hydrate, and iron blue; and metal powders, such as aluminum or copper powder.

[0134] Also mentioned are carbonates of alkaline earth metals (such as calcium or magnesium), silica, quartz, and any other compounds used as inert fillers in cosmetic compositions, provided that these compounds provide color or whiteness to the composition under the conditions in which they are used.

[0135] Preferably, the compositions of the present invention do not contain any salts of the aforementioned metals, particularly aluminum or copper salts.

[0136] Pigments can be organic pigments. The term "organic pigment" refers to any pigment that meets the definition in the "Pigments, Organic" section of the Ullmann Encyclopedia.

[0137] Organic pigments can be notably selected from nitroso compounds, nitro compounds, azo compounds, xanthracene compounds, pyrene compounds, quinoline compounds, anthraquinone compounds, triphenylmethane compounds, fluorane compounds, phthalocyanine compounds, metal complex compounds, isoindolineone compounds, isoindoline compounds, quinacridone compounds, perylene compounds, perylene compounds, diketopyrrolopyrrole compounds, indigo compounds, thioindigo compounds, dioxazine compounds, triphenylmethane compounds, and quinoline phthalocyanine compounds.

[0138] Specifically, white or colored organic pigments may be selected from carmine, carbon black, aniline black, azo yellow, quinacridone, phthalocyanine, blue pigments coded in the Color Index with index numbers CI 42090, 69800, 69825, 74100, 74160, blue pigments coded in the Color Index with index numbers CI 11680, 11710, 19140, 20040, 21100, 21108, 47000, 47005, yellow pigments coded in the Color Index with index numbers CI 61565, 61570, 74260, orange pigments coded in the Color Index with index numbers CI 11725, 45370, 71105, and others. The red pigments in the Index are coded with index numbers CI12085, 12120, 12370, 12420, 12490, 14700, 15525, 15580, 15620, 15630, 15800, 15850, 15865, 15880, 26100, 45380, 45410, 58000, 73360, 73915 and 75470.

[0139] Advantageously, the pigments are selected from CI Pigment Orange 82 [CAS No. 2170864-77-2] and CI Pigment Yellow [CAS No. 817181-98-9]. Pigment Orange 82 can be obtained, for example, under the name Sicopal® Pigment Orange K2430 from Sun Chemical, Ludwigshafen, Germany. Pigment Yellow 216 can be obtained, for example, under the name Orange 10P340 from Shepherd, Gent, Belgium.

[0140] Carmine acid may be mentioned in the dyeing agents. Dyes known by the following names may also be mentioned: D&C Red 21 (CI 45 380), D&C Orange 5 (CI 45 370), D&C Red 27 (CI 45 410), D&C Orange 10 (CI 45 425), D&C Red 3 (CI 45 430), D&C Red 4 (CI 15 510), D&C Red 33 (CI 17 200), D&C Yellow 5 (CI 19 140), D&C Yellow 6 (CI 15 985), D&C Green 5 (CI 61 570), D&C Yellow 10 (CI 77 002), D&C Green 3 (CI 42 053), and D&C Blue 1 (CI 42 090).

[0141] The dyes can be selected from 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.

[0142] According to any embodiment, the composition according to the invention contains less than 1% by weight, notably less than 0.1% by weight, of carbon-based filler relative to the total weight of the composition.

[0143] For the purposes of this invention, the term "carbon-based filler" refers to particulate matter containing only carbon atoms in its mass, "other than impurities," meaning that other atoms may be present on the surface. Carbon-based fillers may be selected from, but are not limited to, carbon black, natural and synthetic graphite, carbon fibers, graphene, fullerene, acetylene black, and carbon nanotubes.

[0144] According to any embodiment, the composition according to the invention contains less than 0.1% by weight of carbon black relative to its total weight. Preferably, the composition according to the invention contains no carbon black.

[0145] Preferably, the composition according to the invention comprises at least one dye that produces a color other than black.

[0146] Preferably, the composition according to the invention comprises less than 1% by weight, noteworthyly less than 0.1% by weight, and preferably 0% by weight of L having a content of less than 10, particularly less than 5, particularly less than 1, and noteworthyly equal to 0, relative to its total weight. The parameters of the dye, where L The parameters were measured in reflectance mode using a Konica Minolta CM-36dGV spectrophotometer in the CIELab system as defined in standard ISO 11664-4:2008, with a D65 light source, an incident angle of 10°, and an aperture of 8 mm, and including the specular component.

[0147] Preferably, the selected dye causes the composition to have:

[0148] - L between 10 and 100, preferably between 20 and 80, advantageously between 40 and 75, and noteworthyly between 50 and 70 Parameters, and / or

[0149] - a between 10 and 100, preferably between 20 and 80, advantageously between 35 and 55 Parameters, and / or

[0150] - Between 10 and 100, preferably between 20 and 80, advantageously between 40 and 75, and noteworthyly between 50 and 70. parameter,

[0151] Wherein L a and b The parameters were measured in reflection mode using a Konica Minolta CM-36dGV spectrophotometer in the CIELab system as defined in standard ISO 11664-4:2008, with a D65 light source, an incident angle of 10°, an aperture of 8 mm, and including the specular component.

[0152] Preferably, the coating composition includes at least one dye that causes orange color.

[0153] Preferably, the selected dyes result in RAL 2003 color compositions, i.e., they have the following L a b Value: L =66.0; a =41.2 and b =52.4.

[0154] Advantageously, the dye is a mixture of at least two pigments. More preferably, the dye comprises titanium dioxide, tin oxide, zinc oxide, and mixtures thereof. Even more preferably, the dye comprises titanium dioxide, tin oxide, zinc oxide, and at least two other pigments, preferably producing an orange color.

[0155] Preferably, the dye content in the composition is from 0.5% to 10% by weight, advantageously from 1% to 5% by weight, relative to the total weight of the composition.

[0156] Preferably, the content of black dye, notably black pigment, carbon black or other black filler is limited to a maximum of 0.1% by weight.

[0157] Preferably, black dye is excluded.

[0158] Preferably, the color of the composition is characterized in that its color, as measured by the RAL method, is different from RAL colors 2100, 6015, 7021, 8022, 9004, 9005, 9011, 9017, or 9021.

[0159] Preferably, the coating composition comprises 60% to 98% by weight, preferably 70% to 95% by weight, of polyamide and 0.5% to 10% by weight, preferably 1% to 5% by weight, of dye.

[0160] additive

[0161] Preferably, the composition according to the invention comprises at least one additive selected from flame retardants, UV protectants, UV stabilizers, heat stabilizers, lubricants, flow improvers, pourability improvers, film-forming agents, fillers, film-forming aids, colloids, preservatives, antibacterial agents, and mixtures thereof. Preferably, the composition according to the invention does not contain any metal-based additives to avoid any harmful interactions between the metal surface to be coated and these additives that may be present in the composition according to the invention.

[0162] antioxidants

[0163] Preferably, the coating composition contains at least one antioxidant.

[0164] For example, stabilizers can be organic stabilizers or, more generally, combinations of organic stabilizers, such as phenolic antioxidants (e.g., Irganox® 245, 1098, or 1010 from Ciba-BASF), or phosphite-type antioxidants (e.g., Irgafos® 126 or Irgafos® 168 from Ciba-BASF), and even optional other stabilizers, such as HALS, which refers to hindered amine light stabilizers (e.g., Tinuvin® 770 from Ciba-BASF), UV stabilizers (e.g., Tinuvin® 312 from Ciba-BASF), or phosphorus-based stabilizers. Amine-type antioxidants, such as Naugard® 445 from Crompton, or multifunctional stabilizers, such as Nylostab® S-EED from Clariant, can also be used.

[0165] According to a preferred embodiment, the power transmission component includes a metal surface, characterized in that the metal surface is coated with:

[0166] - An intermediate layer made of inorganic materials; and

[0167] - A coating made from a composition comprising primarily at least one polyamide having more than 8 carbon atoms per nitrogen atom and at least one dye.

[0168] The intermediate layer is located between the metal surface of the power transmission component and the coating.

[0169] The metal surface is made of copper.

[0170] According to an even more preferred embodiment, the power transmission component includes a metal surface, characterized in that the metal surface is coated with:

[0171] - An intermediate layer made of inorganic materials; and

[0172] - A coating made from a composition comprising

[0173] - Primarily at least one polyamide, the polyamide having:

[0174] - The difference between its total acidity and its total alkalinity, expressed as an absolute value, less than 70, and

[0175] - Total alkalinity less than 60 μeq / g, and

[0176] The composition mainly comprises at least one polyamide having more than 6.5 carbon atoms per nitrogen atom and at least one dye.

[0177] The intermediate layer is located between the metal surface of the power transmission component and the coating.

[0178] The metal surface is made of copper.

[0179] Applications of power transmission components

[0180] In one embodiment, the power transmission component, preferably the busbar, is located inside and / or outside the battery, particularly a vehicle battery, especially a motor vehicle battery. For example, it may be immersed in coolant.

[0181] Method for manufacturing power transmission components

[0182] According to another aspect, the present invention relates to a method for manufacturing a power transmission component, preferably a busbar, notably for a battery busbar, the method comprising:

[0183] - The step of coating all metal surfaces of the power transmission components with an intermediate layer of inorganic material as defined above; then

[0184] - The step of coating an intermediate layer of an inorganic material with a coating composition as defined above.

[0185] According to another aspect, the present invention relates to a method for preparing a busbar, notably a method for a busbar used in a battery, the method comprising:

[0186] - The step of coating all metal surfaces of the busbar with an intermediate layer of inorganic material as defined above; then

[0187] - The step of coating an intermediate layer of an inorganic material with a coating composition as defined above.

[0188] Preferably, the step of covering the intermediate layer of the inorganic material with the coating composition as defined above can be performed by extruding the composition or by depositing powder of the coating composition and then melting the powder.

[0189] Preferably, the preparation method includes an extrusion step but does not include a powder coating step.

[0190] It is possible that the metal surface of the power transmission component (preferably a metal strip) undergoes a pretreatment step before being covered with an intermediate layer of inorganic material. This method may include, for example, a degreasing step on the metal surface and / or a flame treatment step and / or a preheating step.

[0191] All the features defined above are valid for this method.

[0192] Other objects and advantages of the invention will become apparent from the following embodiments, which are given without any implied limitations.

[0193] Example

[0194] Preparation of coating composition

[0195] The coating composition according to the present invention is prepared using the following compounds.

[0196] The polyamide named PA11 was prepared according to the following method: 43.00 kg of 11-aminoundecanoic acid, 30 g of phosphoric acid, and 6.0 kg of deionized water were loaded into an autoclave and heated to 250°C while maintaining autogenous pressure for 30 minutes. Once the monomers melted, the mixture was stirred at 40 rpm throughout the synthesis. Gradual expansion was applied for 2 hours, decreasing to 1 bar, and the temperature was raised to 255°C. The system was then flushed with nitrogen at a flow rate of 100 L / h for 30 minutes while maintaining the temperature at 255°C. Finally, stirring was stopped, and the molten material was extruded at a pressure of 6 bar. The rods were cooled in a water bath and then granulated.

[0197] Polyamide PA12 was prepared according to the following method. 25.00 kg of laurolactam and 2.20 kg of deionized water were charged into an autoclave and heated at 290°C for 5 hours at a pressure of 32 bar. Once the monomers melted, the mixture was stirred at 40 rpm throughout the synthesis. Gradual expansion was applied for 8 hours, decreasing to 8 bar while maintaining the temperature at 290°C. Then, expansion was increased to 0.2 bar over one hour while gradually decreasing the temperature to 265°C. The system was then flushed with nitrogen at a flow rate of 100 L / h for 15 minutes while maintaining the temperature at 265°C. Finally, a vacuum was applied to reach a pressure of 0.3 bar for 15 minutes. Finally, stirring was stopped and the molten material was extruded at a pressure of 10 bar. The rods were cooled in a water bath and then granulated.

[0198] The tested polyamides have the characteristics shown in Table 1 below:

[0199]

[0200] Table 1

[0201] Measurement of total alkalinity

[0202] Alkalinity was measured as follows: 1 g of polyamide was dissolved in 80 ml of hot m-cresol. The sample was then cooled. Next, the alkalinity was determined by potentiometry using a Metrohm titrator (888 or 716) with a combined pH electrode and an acetic acid solution containing 0.02 N perchloric acid. A graph of potential as a function of volume shows the jump with equivalent volume, from which the total alkalinity can be calculated using the following formula:

[0203]

[0204] Where Viq represents the equivalent volume obtained by potentiometric titration, and [HClO4] represents the concentration of the perchloric acid solution, i.e., 0.02 N.

[0205] m represents the mass of the sample, i.e., 1g.

[0206] Measurement of total acidity

[0207] Acidity was measured as follows: 1 g of polyamide was dissolved in 80 ml of hot benzyl alcohol. The sample was then cooled. Next, the acidity was determined by potentiometry using a Metrohm titrator (888 or 716) with a combined pH electrode and a 0.02 N tetrabutylammonium hydroxide solution. The graph of potential as a function of volume shows the abrupt change with equivalent volume, from which the total acidity can be calculated using the following formula:

[0208]

[0209] in

[0210] Veq represents the equivalent volume obtained by potentiometric titration.

[0211] [TBAOH] indicates the concentration of the tetrabutylammonium hydroxide solution, i.e., 0.02N.

[0212] m represents the mass of the sample, i.e., 1g.

[0213] Calculation of the difference between total acidity and total alkalinity

[0214] The difference between the total acidity and total alkalinity is obtained by subtracting the values ​​of total acidity and total alkalinity, and is taken as the absolute value, i.e., the sign is not considered.

[0215] For example, for PA11:

[0216]

[0217] Measurement of intrinsic viscosity

[0218] A 75 mg sample containing 0.5% (m / m) m-cresol was measured at 20°C. The intrinsic viscosity was calculated using the following formula:

[0219] Intrinsic viscosity = ln(t) s / t0)x 1 / C, where C=m / px 100,

[0220] in:

[0221] t s t0 is the flow time of the solution, m is the flow time of the solvent, and p is the mass of the sample whose viscosity is to be measured.

[0222] Apart from the fact that the measured temperature is 20°C instead of 25°C, the measurement corresponds to the standard ISO 307:2007.

[0223] Measurement of enthalpy of melting

[0224] The enthalpy of fusion was determined by DSC during the second heating according to standard ISO 11357-3:2013.

[0225] Measurement of crystallization temperature

[0226] Crystallization temperature was determined by differential scanning calorimetry (DSC) according to standard ISO 11357-3:2013 during cooling at a rate of 20°C / min.

[0227] The tested composition also includes the following compounds:

[0228] A phenolic primary antioxidant sold by BASF under the trade name Irganox® 245 (CAS No. 36443-68-2).

[0229] A minor phosphite antioxidant sold by BASF under the trade name Irgafos® 168 (CAS No. 31570-04-4).

[0230] Pigment blends sold by Avient under the trade name 338160 ORA LLDPE AO Smartbatch, comprising 28% pigment.

[0231] The following compositions were prepared by mixing various molten starting materials in a co-rotating twin-screw extruder with a diameter of 26 mm. The products were extruded at a flow rate of 16 kg / h, a temperature of 250°C, and a screw speed of 250 rpm. Upon exiting the machine, the products were cooled in a water bath and then granulated. Finally, these products were vacuum dried at 80°C for 8 hours. The formulations of the compositions are shown in Table 2 below, where the contents are expressed as a weight percentage relative to the total weight of the compositions:

[0232]

[0233] Table 2

[0234] Sample preparation

[0235] These compositions were used to injection mold plates (60 × 60 × 1 mm) and ISO 527-1A dumbbells at a temperature of 260°C.

[0236] Measurement of mechanical properties

[0237] Tensile mechanical properties were measured on dry samples according to standard ISO 527-1:2012. The machine used was an Instron 5966 with a crosshead speed of 50 mm / min.

[0238] De-icing salt resistance was measured on a 1 mm thick plate according to EN 16811-1:2016.

[0239] The results are listed in Table 3 below:

[0240]

[0241] Table 3

[0242] Measurement of optical and electrical properties:

[0243] Dielectric strength was measured at 25°C on a 1 mm thick plate according to IEC 60243-1:2013.

[0244] The colorimetric properties of the samples were measured in reflectance mode using a Konica Minolta CM-36dGV spectrophotometer in the CIELab system, as defined in standard ISO 11664-4:2008, with a D65 light source, an incident angle of 10°, an aperture of 8 mm, and including the specular component.

[0245] In the L a b In the system, L Indicates brightness, a Indicates the green / red axis, b Indicates the blue / yellow axis. L The higher the value, the lighter the color or the lower the intensity. Conversely, L... The lower the value, the darker or more intense the color. The higher the value, the redder the hue. The higher the value, the more yellow the hue.

[0246] The results are presented in Table 4 below:

[0247]

[0248] Table 4

[0249] After aging at 150°C for 240 hours in a ventilated oven, the dielectric strength of each of compositions A and B remains greater than 10 kV / mm.

[0250] Preparation of coated metal strips

[0251] A plate with dimensions of 60 × 60 × 1 mm is prepared by injection molding at 260°C from each of compositions A and B.

[0252] Use the following intermediate layer:

[0253] Intermediate layer 1: Woven glass fiber membrane sold by Yuniu Fiberglass Roving under the name YN-FW-001

[0254] Intermediate layer 2: Mica film sold by Final Advanced Materials under the name MC-5000HT, consisting of approximately 90% phlogopite and 10% silicone binder resin.

[0255] The structure representing the present invention is prepared by covering the following layers:

[0256] Composition A or B / Intermediate Layer 1 or 2 / Copper / Intermediate Layer 1 or 2 / Composition A or B.

[0257] The assembly, surrounded by a frame of the same thickness as the overall assembly, was compressed in a press at 220°C. Without applying pressure, the pressure plate was placed in contact with the overlay for 90 seconds. Next, a pressure of 50 bar was applied for 60 seconds. Finally, the assembly was cooled for 2 minutes while maintaining a pressure of 30 bar. A comparative example was prepared similarly without an intermediate layer. The structures are shown in Table 5 below:

[0258]

[0259] Table 5

[0260] Structural assessment

[0261] Evaluation of color change

[0262] The multi-layer structure was aged in a ventilated oven at 150°C for 240 h.

[0263] ΔE was measured on a copper plate coated with the aging composition and on a copper plate coated with the composition and an intermediate layer (also aged).

[0264] Before and after this aging, the colorimetric properties of the samples were measured in reflectance mode using a Konica Minolta CM-36dGV spectrophotometer in the CIELab system, as defined in standard ISO 11664-4:2008, with a D65 light source, an incident angle of 10°, an aperture of 8 mm, and including the specular component.

[0265] In the L a b In the system, L Indicates brightness, a Indicates the green / red axis, b Indicates the blue / yellow axis. L The higher the value, the lighter the color or the lower the intensity. Conversely, L... The lower the value, the darker or more intense the color. The higher the value, the redder the hue. The higher the value, the more yellow the hue.

[0266] Therefore, color aging corresponds to the color change between an unaged board (i.e., at t=0) and a board aged at 150°C for t=240h. This change is measured by ΔE according to the following equation:

[0267]

[0268] In this equation, L a and b This represents the value measured on the aging plate at t=240h, and L0 a0 and b0 This indicates the value measured on an unaged plate. A higher ΔE value indicates a greater color change during aging, suggesting instability of the composition.

[0269] The results are given in Table 6 below:

[0270]

[0271] Table 6

[0272] Evaluation of high temperature resistance:

[0273] The structures shown were placed in an oven at 500°C for 5 minutes. The dielectric strength of these samples was measured according to IEC 60243-1:2013.

[0274] The results of the evaluation test are given in Table 7 below.

[0275]

[0276] Table 7

[0277] Examples show that the structure according to the invention has good mechanical properties and exhibits color stability over time, while maintaining a certain degree of electrical insulation after exposure to 500°C (and the burning of the polyamide layer) (see dielectric strength results). Thus, advantageously, the inorganic material layer remains insulating after exposure to 500°C without ensuring a good level of dielectric strength (>10 kV / mm).

[0278] As previously stated, after aging at 150°C for 240 hours in a ventilated oven, the dielectric strength of each of compositions A and B remains greater than 10 kV / mm.

Claims

1. A power transmission component, wherein, The power transmission component includes a metal surface, characterized in that the metal surface is coated with: - An intermediate layer made of inorganic materials; and - A coating having a color different from black, which is made of an electrically insulating composition comprising primarily at least one polyamide having a carbon number greater than 6.5 per nitrogen atom and at least one dye. The intermediate layer is located between the metal surface of the power transmission component and the coating.

2. The composition according to claim 1, characterized in that, The intermediate layer, made of inorganic materials, is different from metal.

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

4. The composition according to claims 1 to 3, characterized in that, The at least one polyamide is an aliphatic or alicyclic polyamide.

5. The power transmission component according to any one of the preceding claims, wherein the power transmission component is a busbar.

6. The power transmission component according to any one of the preceding claims, wherein, The metal surface is made of copper, copper alloy, aluminum, or aluminum alloy.

7. The power transmission component according to any one of the preceding claims, wherein, The intermediate layer, made of inorganic materials, is a mica layer, a carbon fiber layer, or a glass fiber layer, preferably a mica layer.

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

9. The power transmission component according to any one of the preceding claims, characterized in that, The dye 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. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide coating has an intrinsic viscosity greater than 1.1 as measured according to standard ISO 307:2007.

11. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide coating has a melting enthalpy greater than 20 J / g, as measured by DSC during the second heating according to standard ISO 11357-3,2013.

12. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide coating has a crystallization temperature of less than 180°C as measured by DSC during the second heating according to standard ISO 11357-3,2013.

13. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide used in the coating is selected from PA11, PA12, PA1010, PA1012, PA610, PA612, PA613, PA516, PA912, PA6 / 11, PA6 / 12, PA11 / 12, PA6 / 11 / 12, PA6 / 66 / 12, PA6 / 1010, PA6 / 1012, PA6 / 1010 / 1012, PA6 / 1012 / 12, PA6 / 66 / 11 / 12, and PA6 / 1010 / 1012 / 1014, more particularly PA11, PA12, PA1010, or PA1012, even more preferably PA11 or PA12, and most preferably PA11.

14. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide in the coating composition has a difference between its total acidity and total basicity, expressed in absolute value, of less than 70 μeq / g, and a total basicity of the polyamide of less than 60 μeq / g, wherein the total acidity and total basicity are measured by potentiometry.

15. The power transmission component according to any one of the preceding claims, characterized in that, The polyamide composition of the coating has a total acidity of less than 60 μeq / g, as measured by potentiometry.

16. A method for manufacturing a power transmission component according to any one of claims 1 to 15, comprising: - The step of coating all metal surfaces of the power transmission component with an intermediate layer of inorganic material as defined in any one of claims 1, 7, and 8; then - The step of coating the intermediate layer of the inorganic material with the coating composition as defined in any one of claims 1 to 15.

17. The method according to claim 16, characterized in that, The process of coating the intermediate layer is performed by extrusion.

18. The method according to claim 16, characterized in that, The step of coating the intermediate layer is performed by depositing powder of the coating composition and then melting the powder.

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