Polyamide composition for coating electrical transmission components

Abstract

The present invention relates to a polyamide composition in powder form, comprising: (a) at least one polyamide, (b) at least one colorant, and (c) calcium carbonate, as well as a method for its preparation. This composition is used for coating an electrical transmission component, and in particular an electric battery busbar. The invention also relates to the use of calcium carbonate to improve the color stability of an electrically insulating, colored polyamide-based coating applied to an electrical transmission component.

Description

Title of the invention: Polyamide composition for coating electrical transmission components. FIELD OF THE INVENTION

[0001] The present invention relates to a polyamide composition in powder form, comprising: (a) at least one polyamide, (b) at least one colorant, and (c) calcium carbonate, as well as a method for its preparation. This composition is used for coating an electrical transmission component, and in particular an electric battery busbar. The invention also relates to the use of calcium carbonate to improve the color stability of an electrically insulating, colored polyamide-based coating applied to an electrical transmission component. TECHNICAL BACKGROUND

[0002] The market for electric and hybrid vehicles has grown significantly in recent years. Increasing the range of these vehicles is a key factor in their development. To achieve this, the architecture of their powertrain must be designed to limit Joule effect losses, which requires the use of high voltages.

[0003] Connectors called busbars are used to carry high-intensity current into and out of the batteries. These busbars are often made of oxygen-free copper (OFHC) and hard-pitch electrolytic copper (ETP) and must be covered with an insulating coating. This coating must be able to maintain its insulating properties during accelerated thermal aging up to 150°C. It must also exhibit a high degree of flexibility to accommodate the deformation of the busbars when they are bent to fit the space provided. A thermoplastic polymer-based coating, such as an epoxy resin and / or a polyamide (FR3118052), is commonly used.

[0004] For safety reasons, these busbars must also have a distinctive color (orange according to ISO 6469-3:2018), representative of the current flowing through the busbar. It is crucial that this color remains stable over time, despite the temperatures to which the busbar may be subjected. Indeed, external conditions, proximity to the motor, and self-heating during current flow, particularly during battery charging, are factors that can affect the coating color over time. If the color changes, doubt may arise regarding the voltage of the electric current flowing through the busbar. This can cause accidents during engine maintenance or repairs, for example. Therefore, it is essential that the color remains stable despite the harsh conditions of its environment.

[0005] To meet this requirement, US2021 / 253854 suggests using a specific pigment mixture that gives the coating a durable orange color. EP3919563, on the other hand, proposes introducing a phosphinic acid derivative into a mixture of polyamide and an aromatic secondary amine, such as melamine cyanurate. In these documents, the insulating coating is formed by an injection molding process.

[0006] Several processes exist for preparing busbars. The main one is the extrusion of the polymer composition around a conductive metal strip, which is implemented in US2021 / 253854 and EP3919563. Coating processes using powder, by dipping or electrospraying, can also be used. These processes are preferred because they adapt to different morphologies of power transmission components without requiring the manufacture of complex and therefore costly molds.

[0007] There therefore remains a need to propose a colored polyamide composition suitable for application as a powder to an electrical transport component, and whose color exhibits good stability over time and under the effect of heat. Summary of the invention

[0008] The invention thus relates to a composition for coating an electrical transmission component, in powder form, comprising:

[0009] (a) at least one polyamide,

[0010] (b) at least one coloring matter,

[0011] (c) calcium carbonate.

[0012] It also relates to a process for preparing this composition, comprising the steps of:

[0013] - mix the polyamide, calcium carbonate and coloring matter,

[0014] - homogenize this mixture by hot extrusion,

[0015] - cool then crush and grind the extrudate to obtain a powder.

[0016] The invention also relates to a method for applying a coating to the metallic surface of an electrical transmission component comprising the following steps:

[0017] - optionally, the application of a mask to the surface,

[0018] - bringing the surface into contact with a composition as defined above, and

[0019] - the melting of the powder.

[0020] The invention further relates to the use of calcium carbonate to improve the color stability of a colored polyamide-based coating, electrically insulating, applied to an electrical transport component.

[0021] It has been observed that the color of the coating obtained from the composition according to the invention remains stable even after aging at high temperature. Furthermore, this coating retains its electrical insulation properties after aging, as well as its mechanical properties (elongation at break, impact resistance, adhesion of the polymer layer when bending the metal bar). This coating also exhibits good chemical resistance, i.e., good resistance to de-icing salt. Finally, the electrical component coated with said composition remains easy to strip. DETAILED DESCRIPTION

[0022] Other features, aspects, objects and advantages of the present invention will become even clearer upon reading the following description.

[0023] It is specified that the expressions "between... and..." and "from... to..." used in this description should be understood as including each of the limits mentioned.

[0024] In addition, unless otherwise indicated, all percentages and proportions are mass percentages and proportions.

[0025] Polyamide

[0026] By "polyamide" is meant a polymer comprising at least one polymerization product of one or more monomers selected from: - amino acid or aminocarboxylic acid monomers, and preferably alpha, omega-aminocarboxylic acids; - lactam-type monomers; - the "diamine.diacid" type monomers resulting from the reaction between a an aliphatic diamine and a dicarboxylic acid; and - their mixtures, with monomers having a different number of carbons in the case of mixtures between an amino acid type monomer and a lactam type monomer.

[0027] The term "monomer" in the present description of polyamides should be taken to mean "repeating unit". Indeed, in the case where a repeating unit of the polyamide (PA) is made up of the association of a diacid with a diamine, it is considered that the association of a diamine and a diacid, that is to say the diamine-diacid pair (in equimolar quantity), corresponds to the monomer.

[0028] The polyamide can be a homopolyamide and / or a copolyamide.

[0029] When the polyamide is a homopolyamide, it comprises the polymerization product of a single monomer. When the polyamide is a copolyamide, it comprises the polymerization product of at least two different monomers. Examples of copolyamides formed from the different types of monomers described above include copolyamides resulting from the condensation of at least two alpha,omega-aminocarboxylic acids, or two lactams, or a lactam and an alpha,omega-aminocarboxylic acid. Other examples include copolyamides resulting from the condensation of at least one alpha,omega-aminocarboxylic acid (or a lactam), at least one diamine, and at least one dicarboxylic acid.We can also mention copolyamides resulting from the condensation of an aliphatic diamine with an aliphatic dicarboxylic acid and at least one other monomer chosen from aliphatic diamines different from the previous one and aliphatic diacids different from the previous one.

[0030] 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, PAx designates the polycondensation product of a lactam or an amino acid with x carbon atoms; PAx.y designates the polycondensation product of a diamine with x carbon atoms and a diacid with y carbon atoms. Furthermore, the notations PA X / Y, PA X / Y / Z, etc., refer to copolyamides in which X, Y, Z, etc., represent homopolyamide units as described above.

[0031] Amino acid monomers:

[0032] Examples of alpha,omega-amino acids include those with 4 to 18 carbon atoms, such as aminocaproic, 7-aminoheptanoic, 11-aminoundecanoic, N-heptyl-11-aminoundecanoic and 12-aminododecanoic acids.

[0033] Lactam-type monomers:

[0034] Examples of lactams include those with 3 to 18 carbon atoms on the main ring and which can be substituted. Examples include [3,[3-dimethylpropiolactam, α,α-dimethylpropiolactam, amylolactam, caprolactam (also called lactam 6), capryllactam (also called lactam 8), oenantholactam, and lauryllactam (also called lactam 12).

[0035] Monomers of the "diamine-diacid" type:

[0036] Examples of dicarboxylic acids include those having from 4 to 36 carbon atoms, and preferably from 4 to 18 carbon atoms. Examples include adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid, terephthalic acid, the sodium or lithium salt of sulfisophthalic acid, and other acids. dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% by weight and are preferably hydrogenated), dodecanedioic acid HOOC-(CH2)i0-COOH, and tetradecanedioic acid, preferably, adipic acid, sebacic acid, azelaic acid, suberic acid, butanedioic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% by weight and are preferably hydrogenated), dodecanedioic acid HOOC-(CH2)io-COOH, and tetradecanedioic acid.

[0037] More specifically, fatty acid dimers or dimerized fatty acids refer to the product of the dimerization reaction of fatty acids (generally containing 18 carbon atoms, often a mixture of oleic and / or linoleic acid). Preferably, this is a mixture comprising 0 to 15% by weight of Cl8 monoacids, 60 to 99% by weight of C36 diacids, and 0.2 to 35% by weight of C54 or higher triacids or polyacids.

[0038] As an example of a diamine, one can cite aliphatic diamines having 2 to 36 atoms, preferably 4 to 18 atoms. Examples include hexamethylenediamine, piperazine, aminoethylenepiperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophorone diamine (IPD), methyl pentamethylenediamine (MPMD), bis(aminocyclohexyl)methane (BACM), bis(3-methyl-4-aminocyclohexyl)methane (BMACM), methaxylenediamine, and bis-p-aminocyclohexylmethamine, preferably hexamethylenediamine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, and diamine polyols.

[0039] As “diamines.diacids" include, in particular, those resulting from the condensation of 1,6-hexamethylenediamine with a dicarboxylic acid having 6 to 36 carbon atoms and those resulting from the condensation of 1,10-decamethylenediamine with a diacid having 6 to 36 carbon atoms.

[0040] Examples of "diamine.diacid" type monomers include: 6.6, 6.10, 6.11, 6.12, 6.14, 6.18. Examples of monomers resulting from the condensation of decanediamine with a C6 to C36 diacid include: 10.10, 10.12, 10.14, 10.18. In the numerical notation XY, X represents the number of carbon atoms from the diamine residues, and Y represents the number of carbon atoms from the diacid residues, conventionally.

[0041] The polyamide preferably comprises at least one of the following monomers: 4.6, 5.6, 5.9, 5.10, 5.12, 5.13, 5.14, 5.16, 5.18, 5.36, 6, 6.6, 6.9, 6.10, 6.12, 6.13, 6.14, 6.16, 6.18, 6.36, 9, 10.6, 10.9, 10.10, 10.12, 10.13, 10.14, 10.16, 10.18, 10.36, 11, 12, 12.6, 12.9, 12.10, 12.12, 12.13, 12.14, 12.16, 12.18, 12.36 and their mixtures.

[0042] The polyamide used according to the invention can be a copolymer with polyamide blocks (rigid or hard blocks, with predominantly thermoplastic behavior) and soft blocks (flexible or spongy blocks, with predominantly elastomeric behavior). A "soft block" is defined as a block having a glass transition temperature (Tg) less than or equal to 0°C. The glass transition temperature can be determined by differential scanning calorimetry, according to ISO 11357-2 Plastics - Differential scanning calorimetry (DSC) Part 2.

[0043] The polyamide blocks of the block copolymer can be polyamides (homopolyamides and / or copolyamides) as described above.

[0044] The flexible blocks of the copolymer according to the invention can, in particular, be selected from polyether (PE) blocks, polyester blocks, polysiloxane blocks, such as polydimethylsiloxane (or PDMS) blocks, polyolefin blocks, polycarbonate blocks, and mixtures thereof. Some possible flexible blocks are described, for example, in French patent application FR 2941700 AL

[0045] Preferably, the flexible blocks are chosen from polyether blocks, polyester blocks, and a combination thereof.

[0046] Particularly advantageously, the flexible blocks are polyether blocks. The copolymer according to the invention is then a copolymer of polyamide blocks and polyether blocks (or PEBA).

[0047] PEBAs result from the polycondensation of reactive-end polyamide blocks with reactive-end polyether blocks, such as, among others, polycondensation:

[0048] 1) of polyamide blocks with diamine chain ends with polyoxyalkylene blocks with dicarboxylic chain ends;

[0049] 2) of polyamide blocks with dicarboxylic chain ends with blocks polyoxyalkylenes with diamine chain ends, obtained for example by cyanoethylation and hydrogenation of aliphatic α,co-dihydroxylated polyoxyalkylene blocks called polyetherdiols;

[0050] 3) of polyamide blocks with dicarboxylic chain ends containing polyetherdiols, the products obtained being, in this particular case, polyetheresteramides.

[0051] Polyamide blocks with dicarboxylic acid ends are obtained, for example, from the condensation of polyamide precursors in the presence of a chain-limiting dicarboxylic acid. Polyamide blocks with diamine chain ends are obtained, for example, from the condensation of polyamide precursors in the presence of a chain-limiting diamine.

[0052] The polyether blocks are made up of alkylene oxide motifs.

[0053] The polyether blocks may, in particular, be PEG (polyethylene glycol) blocks and / or PPG (propylene glycol) blocks and / or PO3G (polytrimethylene glycol) blocks and / or PTMG (polytetramethylene glycol) blocks. The copolymers may comprise several types of polyethers in their chain; the copolyethers may be block or statistical.

[0054] Blocks obtained by oxyethylation of bisphenols, such as bisphenol A, can also be used. These latter products are described in particular in document EP 613919.

[0055] Polyether blocks can also be made of ethoxylated primary amines. Examples of ethoxylated primary amines include products with the following formulas:

[0056] [Chem.l] H—(OCHsCHs^—N—(CH2CH2OL—H (CH2)X CH,

[0057] in which m and n are integers between 1 and 20 and x is an integer between 8 and 18. These products are for example available commercially under the brand NORAMOX® of the company CECA and under the brand GENAMIN® of the company CLARIANT.

[0058] Flexible polyether blocks may include polyoxyalkylene blocks with NH2 chain ends, such blocks being obtained by cyanoacetylation of aliphatic α,co-dihydroxylated polyoxyalkylene blocks called polyetherdiols. More specifically, the commercial products Jeffamine or Elastamine may be used (for example, Jeffamine® D400, D2000, ED 2003, XTJ 542, commercial products of Huntsman, also described in documents JP 2004346274, JP 2004352794 and EP 1482011).

[0059] The polyetherdiol blocks are either used as such and copolycondensed with rigid blocks with carboxylic ends, or amined to be transformed into diamine polyethers and condensed with rigid blocks with carboxylic ends.

[0060] The general two-step method for preparing PEBA copolymers having ester linkages between PA blocks and PE blocks is known and is described, for example, in document FR 2846332. The general method for preparing PEBA copolymers having amide linkages between PA blocks and PE blocks is known and described, for example, in document EP 1482011. Polyether blocks can also be mixed with polyamide precursors and a diacid chain limiter to prepare polymers with polyamide and polyether blocks having statistically distributed motifs (one-step process).

[0061] Of course, the designation PEBA in the present description of the invention refers as well to PEBAX® marketed by Arkema, Vestamid® marketed by Evonik®, Grilamid® marketed by EMS, Pelestat® type PEBA marketed by Sanyo or any other PEBA from other suppliers.

[0062] The present invention covers copolymers comprising a single polyamide block and a single flexible block, but also copolymers comprising three, four (or even more) different blocks chosen from those described in this description, provided that these blocks include at least one polyamide block and one flexible block.

[0063] For example, the copolymer may be a segmented block copolymer comprising three different types of blocks (or “triblock”), resulting from the condensation of several of the blocks described above. Said triblock may, for example, be a copolymer comprising a polyamide block, a polyester block, and a polyether block, or a copolymer comprising a polyamide block and two different polyether blocks, for example, a PEG block and a PTMG block.

[0064] Advantageously, the polyamide of the powder comprises or is made up of one (or more) homopolyamide(s).

[0065] According to one embodiment, the polyamide is aliphatic and linear.

[0066] According to a preferred embodiment, the polyamide is a semi-polyamide Crystalline. "Semi-crystalline polyamide" refers to a polyamide that exhibits:

[0067] - a crystallization temperature (Te) determined according to ISO standard 11357-3:2013, during the cooling step at a rate of 20°K / min in DSC (differential scanning calorimetry) below 180°C, preferably below 160°C; and

[0068] - and an enthalpy of fusion (AHf) determined according to ISO 11357-3: 2013 during the heating stage at a speed of 20 K / min in DSC, which is greater than 5 J / g, preferably greater than 10 J / g, for example greater than 20 J / g and is generally less than 200 J / g, preferably less than 150 J / g.

[0069] Preferably, the polyamide according to the invention is a semi-crystalline aliphatic and linear polyamide.

[0070] Furthermore, the polyamide may advantageously have an inherent viscosity ranging from 0.5 to 1.5 (g / 100 g), preferably from 0.9 to 1.5 (g / 100 g), more preferably from 1.0 to 1.5 (g / 100 g). The inherent viscosity is measured using an Ubbelhode tube. The measurement is carried out at 20°C on a 75 mg sample at a concentration of 0.5% (w / w) in m-cresol. The inherent viscosity is expressed in (g / 100 g) and is calculated according to the following formula:

[0071] Inherent viscosity = ln(ts / t0) x 1 / C

[0072] with C = m / px 100, where ts is the flow time of the solution, t0 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 ISO 307:2019 except that the measurement temperature is 20°C instead of 25°C.

[0073] Advantageously, the polyamide used in the invention is a polyamide (or comprises polyamide blocks) PA 6, PA 10, PA 11, PA 12, PA 5.4, PA 5.9, PA 5.10, PA 5.12, PA 5.13, PA 5.14, PA 5.16, PA 5.18, PA 5.36, PA 6.4, PA 6.9, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 6.18, PA 6.36, PA 10.4, PA 10.9, PA 10.10, PA 10.12, PA 10.13, PA 10.14, PA 10.16, PA 10.18, PA 10.36, PA 12.4, PA 12.9, PA 12.10, PA 12.12, PA 12.13, PA 12.14, PA 12.16, PA 12.18, PA 12.36, PA 6.6 / 6, PA 6.6 / 6.10 / 11 / 12, PA 10.10 / 11, PA 10.10 / 12, PA 10.10 / 14, PA 10.12 / 11, PA 10.12 / 12, PA 10.12 / 14 or mixtures or copolymers thereof.

[0074] Preferably, the polyamide according to the invention is selected from PA 11, PA 12, PA 6, PA 6.X1, PA 10, PA 10.X2, PA 10.X3 / Y, or combinations thereof. In the list above, Xi is selected from 10, 12, 14, or 18; X2 is selected from 10, 12, or 14; X3 is selected from 10 or 12; and Y is selected from 11, 12, or 14.

[0075] In a particularly preferred manner, the polyamide comprises or is constituted by polyamide 11. PA11 is obtained by polycondensation of amino-11-undecanoic acid, which has the advantage of being manufactured from raw materials of vegetable origin, namely castor oil, extracted from castor seeds.

[0076] Polyamide advantageously represents 60 to 98% by weight, preferably 70 to 95% by weight, relative to the total weight of the composition.

[0077] Coloring agent

[0078] The composition according to the invention comprises at least one coloring agent. "Coloring agent" means a substance capable of imparting a color (which may or may not be white) to the composition according to the invention. The coloring agent is typically in solid form and may be a dye or a pigment. "Dye" means a coloring agent soluble in molten polyamide. "Pigment" means a coloring agent insoluble in molten polyamide.

[0079] The colorant can be of any type known to those skilled in the art. Preferably, the colorant according to the invention is selected from the group consisting of azo dyes, anthraquinone dyes, indigo-derived dyes, triarylmethane dyes, chlorine dyes, and polymethine dyes. Carminic acid may be mentioned among the colorants. Other colorants known by the following names may also be mentioned: D&C Red 21 (CI 45380), D&C Orange 5 (CI 45370), D&C Red 27 (CI 45410), D&C Orange 10 (CI 45425), D&C Red 3 (CI 45430), D&C Red 4 (CI 15510), D&C Red 33 (CI 17200), D&C Yellow 5 (CI 19 140), D & C Yellow 6 (CI 15 985), D & C Green (CI 61 570), D & C Yellow 1 O (CI 77 002), D & C Green 3 (CI 42 053), D & C Bine 1 (CI 42 090).

[0080] The pigments that can be used are in particular chosen from among the organic and / or mineral pigments known in the art, in particular those described in Kirk-Othmer's Encyclopedia of Chemical Technology and in Ullmann's Encyclopedia of Industrial Chemistry.

[0081] The pigments may be of natural origin or not. These pigments may be in the form of a powder or pigment paste. They may be coated or uncoated. The pigments may be chosen from mineral pigments, organic pigments, and mixtures thereof.

[0082] Among the mineral pigments useful in the present invention, we can mention ochres such as red ochre (clay, in particular kaolinite, and iron hydroxide, in particular hematite), brown ochre (clay, in particular kaolinite, and limonite), yellow ochre (clay, in particular kaolinite, and goethite); titanium dioxide, possibly surface-treated; zirconium or cerium oxides; zinc, iron (black, yellow or red), or chromium oxides; manganese violet, ultramarine blue, chromium hydrate and ferric blue; metallic powders such as aluminum powder, copper powder and mixtures thereof.

[0083] The organic pigment may in particular be chosen from nitroso, nitro, azo, xanthene, pyrene, quinoline, quinoline, anthraquinone, triphenylmethane, fluorane, phthalocyanine, metal complex type, isoindolinone, isoindoline, quinacridone, perinone, perylene, diketopyrrolopyrrole, indigo, thioindigo, dioxazine, triphenylmethane or quinophthalone.

[0084] In particular, the organic pigments may be selected from carmine, carbon black, aniline black, azo yellow, quinacridone, phthalocyanine blue, the blue pigments coded in the Color Index under references Cl 42090, 69800, 69825, 74100, 74160, the yellow pigments coded in the Color Index under references Cl 11680, 11710, 19140, 20040, 21100, 21108, 47000, 47005, the green pigments coded in the Color Index under references Cl 61565, 61570, 74260, the orange pigments coded in the Color Index under reference CI 11725, 71105, the red pigments coded in the Color Index under the references CI 12085, 12120, 12370, 12420, 12490, 14700, 15525, 15580, 15620, 15630, 15800, 15850, 15865, 15880, 26100, 45380, 45410, 58000, 73360, 73915, 75470.

[0085] Preferably, the composition according to the invention comprises at least one coloring material leading to an orange colour coating.

[0086] By "orange" is meant a color which, in the RAL color system, begins with the number 2 (for example from RAL2000 to RAL2013), in particular RAL2003 and / or which has, in the CIELab color space, the coordinates L*a*b* 66.02 / 41.22 / 52.36. This expression also includes colours that do not deviate significantly from this definition, i.e. having an AE of less than 30 compared to the aforementioned colours, the AE being defined in the ISO 11664-4 standard.

[0087] The colouring material can thus be chosen from: orange organic colourings, such as 12H-phthaloperin-12-one or Solvent Orange 60, D&C Orange 5 (CI 45370), D&C Orange 10 (CI45425); orange mineral pigments, in particular mixtures of metal oxides such as a mixture of titanium dioxide, tin oxide and zinc oxide; orange organic pigments, in particular Pigment Orange 1 (CI 1725) and Vat Orange 7 (CI71105); and mixtures thereof.

[0088] Preferably, the colouring matter is included in a content ranging from 2 to 30% by weight, preferably between 4 and 20% by weight and more preferably between 6 and 15% by weight, relative to the total weight of the composition.

[0089] Calcium carbonate

[0090] The composition according to the invention comprises calcium carbonate, optionally treated hydrophobically (for example with a fatty acid), which ensures the stability of the orange color over time and at high temperatures. It may have an average particle diameter (Dv50) between 1 and 1 µm, for example between 3 and 8 µm.

[0091] An example of usable calcium carbonate according to the invention is the product marketed by OMYA under the trade name Durcal® 5.

[0092] It can represent from 1 to 30% by weight, preferably from 4 to 20% by weight and more preferably from 8 to 15% by weight, relative to the total weight of the composition.

[0093] Additives

[0094] Preferably, the composition according to the invention comprises at least one additive selected from antioxidants, UV absorbers, UV stabilizers, thermal stabilizers, lubricants, flow improvers, anti-cratering or spreading agents (such as polyacrylates possibly modified with silicone and / or supported on silica), film-forming agents, fillers, film-forming auxiliaries and mixtures thereof.

[0095] In particular, the composition according to the invention comprises at least one antioxidant, in particular a phenol (for example Irganox® 245 or 1098 or 1010 from BASF), a phosphite (for example Irgafos® 126 or Irgafos® 168 from BASF) or an aromatic amine (for example Tinuvin® 770 from BASF or Naugard® 445 from Crompton), preferably a phosphite.

[0096] The antioxidant may represent from 0.1 to 3% by weight and preferably from 0.5 to 2% by weight, relative to the total weight of the composition.

[0097] Process

[0098] The composition according to the invention can be prepared by dry mixing its various constituents in one step (the constituents being all added to the mixture simultaneously) or in several stages (a premix of certain components being carried out first before the addition of other components). The mixture thus obtained is homogenized by hot extrusion, then crushed and ground after cooling. In one embodiment of the invention, the polyamide mixed with the other components may consist of a prepolymer, that is to say, a polyamide having reactive functions capable of polymerizing. A polycondensation step may then be carried out after the grinding step.

[0099] Preferably, the median volume diameter Dv50 of the powder particles of the composition according to the invention ranges from 10 to 300 pm, more preferably from 30 to 150 pm, even more preferably from 60 to 120 pm.

[0100] The Dv50 corresponds to the particle size at the 50th percentile (by volume) of the cumulative particle size distribution. It can be determined according to ISO 9276 - parts 1 to 6.

[0101] It can be used to coat an electrical transmission component, preferably an electric battery busbar, to form an electrically insulating coating. By "electrically insulating coating" is meant that the coating has a dielectric strength greater than 10 kV / mm measured on a 1 mm thick plate, the measurement being carried out on a sample conditioned for 14 days at 25°C at 50% relative humidity according to IEC 60243-1:2013.

[0102] 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 metallic cable or comprise metallic fibers, for example braided, or thin superimposed metallic sheets or busbars.

[0103] This electrical transmission component has a metallic surface that may comprise or be made of copper, a copper alloy, aluminum, or an aluminum alloy. Optionally, this surface may be treated, i.e., it may have undergone surface treatment to improve its performance, particularly its corrosion resistance and / or electrical conductivity. This may be a chemical treatment, such as tinning, silver plating, nickel plating, phosphating, or chromating. Alternatively, it may be a mechanical or thermal treatment, in particular degreasing, sandblasting, flaming, and / or preheating.

[0104] According to the invention, the application of a coating to the metallic surface of the power transmission component can be carried out directly on the metallic surface, without the need for a primer. The method implemented according to the invention comprises the following steps:

[0105] - optionally, the application of a mask to the surface, when only a part of this must be covered,

[0106] - bringing the surface into contact with a composition as defined previously, and

[0107] - the melting of the powder.

[0108] Contact between the surface and the composition can be achieved in various ways, including fluidized bed immersion, electrostatic spraying or hot powder coating.

[0109] An electrostatic projection process can be used, comprising the steps of:

[0110] - electrically charging the powder;

[0111] - spraying of the electrically charged powder onto the surface;

[0112] - heating the powder-coated surface to a temperature above the melting temperature of polyamide, preferably at least 30°C higher than the melting temperature of polyamide.

[0113] Electrostatic spray coating consists of depositing electrostatically charged powder particles onto a surface, particularly at room temperature. The powder can be electrostatically charged as it passes through the nozzle of a spraying device. The resulting charged powder composition can then be sprayed onto the object, which includes the surface to be coated and is connected to a zero potential. The coated object can then be placed in an oven at a temperature that allows the coating to melt.

[0114] The equipment for projecting (or spraying) the powder can be of any type. Preferably, the nozzle is held at a high potential of between ten and one hundred kilovolts, with negative or positive polarity. Preferably, the equipment for projecting the powder is an electrostatic gun that charges the powder by corona discharge and / or triboelectricity.

[0115] Preferably, the powder flow rate in the projection equipment is from 10 to 200 g / min, and more preferably from 50 to 120 g / min.

[0116] Preferably, the electrostatic application temperature of the powder is from 15 to 25°C.

[0117] Preferably, the residence time of the surface in the oven is 3 to 15 minutes.

[0118] Advantageously, the surface heating temperature can range from 180 to 300°C, preferably 200 to 250°C.

[0119] The surface can then be cooled, for example, to room temperature.

[0120] If a mask has been used, it can be removed.

[0121] Alternatively, the coating can be applied by fluidized bed dip. Thus, the step of contacting the surface with the powder can include the following steps: - heating the surface to a temperature above the melting point of polyamide; - soaking the surface in a fluidized bed containing the powder.

[0122] The surface to be coated is preheated to a temperature that allows the powder according to the invention to melt. The surface is then immersed in a fluidized bed containing the powder according to the invention. The powder melts upon contact with the surface and forms a coating on it. The coated surface is then preferably cooled, for example, in ambient air. If present, the mask can then be removed.

[0123] Preferably, the surface heating temperature ranges from 180 to 450°C, more preferably from 250 to 350°C.

[0124] Preferably, the surface heating is carried out at a temperature 30 to 120°C above the melting temperature of polyamide.

[0125] Preferably, the immersion time of the surface in the fluidized bed ranges from 1 to 10 seconds, more preferably from 3 to 7 seconds. The immersion of the surface in the fluidized bed may take place once or several times (each immersion preferably having a duration of 1 to 10 s, more preferably from 3 to 7 s).

[0126] In other embodiments, the coating is applied by hot powder coating. The step of bringing the surface into contact with the powder then includes the steps of: - heating the surface to a temperature above the melting point of the polyamide; - spraying the powder onto the surface.

[0127] The surface heating temperature can be as described above in relation to the fluidized bed dip coating.

[0128] The surface can then be cooled, for example, to room temperature. When a mask has been used, it can be removed. The sprayed powder may or may not be electrostatically charged.

[0129] These processes yield an electricity transport component comprising a film-like coating with a thickness of 50 to 800 pm, preferably 100 to 600 pm, more preferably 200 to 500 pm.

[0130] This coating exhibits color stability following thermal aging at 150°C for 150 hours, or even for 240 hours, expressed as an AE < 10, or even less than 5, or even less than 2, for a 1 mm thick plate made of the composition. This color stability following thermal aging at 150°C for 150 hours, or even for 240 hours, is expressed as an AE less than 10, or even less than 5, or even less than 2, for a composition in the form of a 1 mm thick plate covering a copper substrate.

[0131] In addition, it offers the following advantages:

[0132] - a yield stress < 60 MPa, preferably < 50 MPa, and / or

[0133] - a yield elongation > 3%, advantageously > 4% measured according to ISO standard 527-1 / 2:2012. Good resistance to voltage tests

[0134] The invention will be better understood in the light of the following non-limiting examples. EXAMPLES

[0135] Example 1: Manufacture of colored polyamide compositions

[0136] A pigmented powder composition based on polyamide was manufactured according to the following process.

[0137] First, a low-viscosity polyamide 11, referred to hereafter as the "prepolymer," was synthesized from 1.2 kg of amino-11-undecanoic acid in the presence of 0.5 kg of water, 3.6 g of antioxidant, and 6 g of phosphoric acid. The mixture was heated to a temperature of 190°C in 2 hours with stirring, starting as soon as the temperature reached 160°C or the pressure exceeded 8.5 bar. During the synthesis, the water initially saturated with amino-11-undecanoic acid was removed by evaporation at constant pressure (P = 10 bar). After removing 510 g of water, the molten prepolymer was extruded using a twin-screw extruder. The mixture is then cooled using two steel rollers with circulating cold water to solidify, cool and crush into flakes.

[0138] The prepolymer thus obtained is mixed in a suitable container with a formulation of additives: pigment, anti-crater agent (acrylic polymer supported on silica) and possibly CaCO3 (in different quantities) in the proportions indicated in Table 1 below.

[0139] This mixture is introduced into a twin-screw extruder to be melted and thoroughly mixed, then extruded. The mixture is then cooled using two steel rollers with circulating cold water to solidify and cool, then crushed into flakes.

[0140] The pigmented and additive prepolymer recovered in the form of flakes is then ground.

[0141] in a hammer mill equipped with an internal selector until a powder is obtained having a median volume diameter Dv50, as measured according to ISO 9276 - parts 1 to 6, of IlOqm.

[0142] The ground powder is then subjected to solid phase polycondensation in a dryer at 140-152°C under vacuum in order to increase the viscosity of the polyamide up to 1.05 (g / lOOg) *.

[0143] [Tables 1] Comparative Powder Powder 1 (invention) Powder 2 (invention) PAU 88.97 79.97 84.47 Antioxidant 0.35 0.35 0.35 H3PO4 0.65 0.65 0.65 CaCO3 0.00 9.00 4.50 Orange pigment 9.31 9.31 9.31 Anti-crater agent 0.72 0.72 0.72 Example 2: Colorimetric Evaluation

[0144] The powders prepared in Example 1 were used in a fluidized bed dipping coating process.

[0145] To do this, each powder composition is applied to steel or aluminum plates measuring 100x50x3mm. The application conditions include heating the plates for 10 min at 330°C, followed by immersion for 4 seconds in a fluidized bed, and then air cooling.

[0146] The thickness of the coatings obtained from Comparative Powders, 1 and 2 (respectively Comparative Coatings, 1 and 2) is on the order of 350pm.

[0147] The color of the coatings on the plates was then measured on an Insitec spectrophotometer from Malvern using their L*, a*, b* coordinates. The evolution of the color of the samples after aging for 150 h at 240°C is expressed by their AE, calculated according to ISO 18314. The higher the AE value, the more the color has changed during aging, illustrating the instability of the composition.

[0148] The results of the AE values ​​are presented in Table 2 below:

[0149] [Tables2] Substrate Comparative Coating Coating 1 (invention) Coating 2 (invention) Steel 4.8 1.9 — Aluminum 7.0 5.9 4.7

[0150] As can be seen from this table, the addition of calcium carbonate improves the color stability of the polyamide-based coating, regardless of the metallic substrate used.

[0151] Example 3: Mechanical and dielectric properties

[0152] The tensile properties of coatings identical to those of Example 2, but applied to a silicone substrate, in order to obtain free films, were evaluated according to ISO 527-3.

[0153] The results of this test are summarized in Table 3 below.

[0154] [Tables3] Comparative Coating Coating 1 Coating 2 Elongation at break (%) 203 (Standard deviation = 25) 190 (Standard deviation = 23) 186 (Standard deviation = 24)

[0155] The dielectric strength of Comparative coatings 1 and 2, applied to steel bars, in accordance with ISO 19642-2:2019 "Road vehicles - Automotive cables - Part 2", was also evaluated before and after thermal aging of 3000 hours at 125°C: all three coatings met the tensile tests defined in this standard.

[0156] This test demonstrates that the flexibility of the coating obtained according to the invention and its insulating properties are equivalent to those of the comparative coating. The presence of calcium carbonate therefore does not negatively affect these properties.

Claims

Demands

1. Composition for coating an electrical transmission component, in powder form comprising: (a) at least one polyamide, (b) at least one colouring material, (c) calcium carbonate.

2. Composition according to claim 1, characterized in that said at least one polyamide is selected from: PA 11, PA 12, PA 6, PA 6.Xb, PA 10, PA 1O.X2, PA 1O.X3 / Y or combinations thereof, where Xi is selected from 10, 12, 14 or 18, X2 is selected from 10, 12 or 14 and X3 is selected from 10 or 12, preferably Y is selected from 11, 12 or 14, more preferably the polyamide comprises or is constituted by polyamide 11.

3. Composition according to claim 1 or 2, characterized in that the polyamide represents from 60 to 98% by weight, preferably from 70 to 95% by weight, relative to the total weight of the composition.

4. Composition according to any one of the preceding claims, characterized in that the colouring material is selected from: orange organic colorants, such as 12H-phthaloperin-12-one or Solvent Orange 60, D&C Orange 5 (CI 45370), D&C Orange 10 (CI45425); orange mineral pigments, in particular mixtures of metal oxides such as a mixture of titanium dioxide, tin oxide and zinc oxide; orange organic pigments, in particular Pigment Orange 1 (CI 1725) and Vat Orange 7 (CI71105); and mixtures thereof.

5. Composition according to any one of the preceding claims, characterized in that the colouring matter is included in a content of 2 to 30% by weight, preferably between 4 and 20% by weight and more preferably between 6 and 15% by weight, relative to the total weight of the composition.

6. Composition according to any one of the preceding claims, characterized in that it further comprises at least one antioxidant.

7. A composition according to any one of the preceding claims, characterized in that calcium carbonate represents from 1 to 30% by weight, preferably from 4 to 20% by weight and more preferably 8 to 15% by weight, relative to the total weight of the composition.

8. A method for preparing the composition according to any one of claims 1 to 7, comprising the steps of: - mixing the polyamide, calcium carbonate and colouring matter, - homogenizing this mixture by hot extrusion, - cooling then crushing and grinding the extrudate to obtain a powder.

9. A method for applying a coating to the metallic surface of an electrical transport component comprising the following steps: - optionally, the application of a mask to the surface, - bringing the surface into contact with a composition as defined in any one of claims 1 to 7, and - melting the powder.

10. Method according to claim 9, characterized in that the metallic surface is made of copper, copper alloy, aluminum or aluminum alloy.

11. A method according to claim 9 or 10, characterized in that the coating is a film having a thickness of 50 to 800 pm, preferably 100 to 600 pm, more preferably 200 to 500 pm.

12. A method according to any one of claims 9 to 11, characterized in that the coating is applied by electrostatic spraying, fluidized bed dipping or hot powder coating, preferably by electrostatic spraying.

13. Use of calcium carbonate to improve the colour stability of a coloured, electrically insulating polyamide-based coating applied to an electrically transporting component.