Polyamide element for cooling circuits using at least one dielectric fluid

Abstract

The invention relates to the use of at least one element in a cooling circuit using at least one dielectric fluid, in which: the element comprises at least one layer consisting of a composition C, characterized in that: - the composition C comprises from 50 to 99.9% by weight relative to the total weight of the composition of a polyamide matrix having an average C / N ratio greater than or equal to 7 and is free of fibers and reinforcing fillers; - the dielectric fluid is liquid at atmospheric pressure at 23°C and comprises less than 10% by weight of water and glycol ether; and - said layer being intended to be in contact with said dielectric fluid. Figure 1

Description

Title of the invention: Polyamide element for cooling circuits using at least one dielectric fluid Field of the invention

[0001] The present invention relates to polyamide elements for cooling circuits using at least one dielectric fluid, in particular elements or structures for the transport, distribution or storage of said dielectric fluid intended for the cooling, for example direct cooling, of battery cells, in particular hybrid and electric vehicles, or for the cooling of computer servers. Technical background

[0002] Car manufacturers are currently considering the use of direct cooling of traction batteries in hybrid and electric vehicles. It is in fact much more efficient to cool the cells by direct conduction of the fluid with their surface rather than through water-air type exchangers or by conduction through several layers which may include metal in particular.

[0003] The coolants currently used are mixtures of water and glycol. However, these coolants cannot be used for direct cooling. In fact, when in contact with water, there is a very high risk that the cells will self-ignite and that the fire will spread to the entire battery and then to the vehicle.

[0004] Since the battery electrodes cannot be in contact with a conductive liquid, water-based coolants cannot be used for direct cooling. Another major risk is that when the cells come into contact with water, they self-ignite, causing the fire to spread to the entire battery and then to the vehicle.

[0005] It is therefore essential to use cooling fluids that do not contain (or contain very little) water and do not conduct electricity in order to avoid any short circuit in the battery that could cause a fire to start. Direct cooling can be achieved with specific fluids with very low electrical conductivity, called "dielectric fluids". "Dielectric fluids", based on hydrocarbon oils or synthetic esters, are different from the aqueous-based cooling liquids currently used.

[0006] There is therefore a need to provide transport, distribution or storage elements (or structures) suitable for said dielectric fluids. It is necessary to provide elements which have the following property(ies):

[0007] - mechanical resistance and in particular not seeing its constraint or its elongation at break modified by more than 50%, in particular by immersion in the dielectric fluid between -60 and 140°C whether short term (<168 hours) or long term (>10,000 h); - the possibility of being recycled, preferably by a mechanical recycling process; - resistance to fluid pressure, generally between 1 and 6 bars; - resistance to chemical attacks from the internal fluid and various external components, in particular de-icing salts; - thermal resistance; - resistance to hydrolysis; - a low accumulation of electric charge linked to the friction of the dielectric fluid on the internal surface of said element, in particular in the case of a pipe; - low electrical resistivity, volume or surface, typically less than 106 Ohms. Surface electrical resistivity measurements can be carried out according to ASTM D257-14 of 2021; - resistance to the release of soluble or insoluble products which could modify the properties of the dielectric fluid or damage one or other of the components of the direct cooling circuit, - resistance to the release of products that harm the dielectric nature of the fluid, particularly ionic species (anionic or cationic).

[0008] There is a real need to provide such elements which exhibit at least one of these properties throughout the lifetime of the vehicle, in particular between 3000 and 10000 hours, including both the driving phases and also the static load phases of the vehicles on which they are mounted. Summary of the invention

[0009] The present invention relates to the use of at least one element in a cooling circuit using at least one dielectric fluid, in which:

[0010] the element comprises at least one layer consisting of a composition C, characterized in that: - composition C comprises from 50 to 99.9% by weight relative to the total weight of the composition of a polyamide matrix having an average C / N ratio greater than or equal to 7 and is free from reinforcing fibers and fillers; - the dielectric fluid is liquid at atmospheric pressure at 23°C and comprises less than 10% by weight of water and glycol ether; and - said layer being intended to be in contact with said dielectric fluid.

[0011] Preferably, the polyamide matrix has an average C / N ratio greater than or equal to 8, preferably greater than or equal to 9, preferably between 9 and 12.

[0012] Preferably, composition C has an inherent viscosity of between 1 and 1.8, preferably between 1.2 and 1.6, more preferably between 1.3 and 1.6.

[0013] Preferably, the dielectric fluid comprises one or more compounds chosen from mineral oils and mineral oil derivatives, polyalphaolefins, polyalkylene glycols, silicones, esters with a number-average molar mass of between 1000 and 100,000 g / mol, for example polyol ester, POE, partially fluorinated polymers having a number-average molar mass of 1000 and 100,000 g / mol, for example perfluoropolyethers.

[0014] Preferably, the dielectric fluid has a density measured according to the ISO 1675:2022 standard at 23°C of between 0.3 and 1.5, preferably between 0.5 and 1.1, advantageously between 0.7 and 1.05, more preferably between 0.8 and 1.

[0015] Preferably, the dielectric fluid has a kinematic viscosity at 40°C of between 1 and 35 mm2 / s, preferably between 1.5 and 15 mm2 / s, in particular between 2 and 10 mm2 / s and / or a kinematic viscosity at 100°C of between 0.01 and 5 mm2 / s, preferably between 0.1 and 4 mm2 / s, preferably between 0.5 and 3 mm2 / s, more preferably between 0.8 and 2.5 mm2 / s and / or a kinematic viscosity at 25°C of between 5 and 150 mm2 / s, preferably between 10 and 100 mm2 / s, the kinematic viscosity being measured according to the ISO 3104:2020 standard.

[0016] Preferably, composition C further comprises from 0.01 to 1.5%, preferably from 0.05 to 0.5%, more preferably from 0.1 to 0.4%, by weight of a thermal stabilizer relative to the total weight of composition C.

[0017] Preferably, composition C further comprises: - From 10 to 35%, preferably from 15 to 25%, by weight of a flame retardant, preferably a non-halogenated flame retardant, preferably a phosphorus-containing flame retardant; and / or - Beyond 35% by weight, preferably from 2 to 10% by weight of at least one impact modifier; and / or - From 0.5 to 30% by weight of at least one current-conducting filler; and / or - From 0.1 to 10% by weight of at least one additive.

[0018] Preferably, composition C comprises a plasticizer content of less than 10%, preferably less than 6%, preferably less than 5%, preferably less than 3%, preferably less than 1%, by weight, preferably composition C is free of plasticizer, such as BBSA (N-Butyl Benzene Sulfonamide).

[0019] In one embodiment, the element is a pipe for transporting the dielectric fluid.

[0020] In one embodiment, the element is a reservoir for storing the dielectric fluid.

[0021] The invention also relates to a cooling circuit comprising at least one element comprising at least one layer consisting of composition C as described above, in which a dielectric fluid as described above circulates, the layer being in direct contact with said dielectric fluid.

[0022] Preferably, the circuit further comprises at least one housing adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing, said housing being made of a polyamide composition comprising: • from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7; • from 15 to 65% by weight of reinforcing fibers or fillers.

[0023] The present invention also relates to a device for the direct cooling of battery cells by a dielectric fluid as described above, comprising: - a dielectric fluid; - at least one housing (BX) adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing, said housing preferably being made of a polyamide composition comprising: • from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7; • from 15 to 65% by weight of reinforcing fibers or fillers; - upstream of the housing (BX), at least one element as described above in the form of a pipe in which said dielectric fluid circulates towards the housing (BX), - downstream of the housing (BX), at least one element as described above in the form of a pipe in which said dielectric fluid circulates from the housing (BX).

[0024] The invention also relates to a device for the direct cooling of battery cells by a dielectric fluid comprising: - a dielectric fluid; - optionally at least one tank (RI) as defined below; - at least one box (BX) suitable for receiving battery cells and equipped of an inlet and an outlet allowing the circulation of a dielectric fluid in said housing in direct contact with the battery cells; - upstream of the housings (BX) at least one element (El) for distributing the dielectric fluid coming from the reservoir to the housings (BX), the element (El) comprising an inlet for the dielectric fluid and x outlets connected to the housings (BX), x corresponding to the number of housings (BX), each of the outlets being connected to a housing (BX); - downstream of the boxes (BX) at least one element (E2) for recovering the dielectric fluid coming from the boxes (BX), the element (E2) comprising y inlets for the dielectric fluid and z outlets, y corresponding to the number of boxes (BX) connected to the element (E2) and z corresponding to the number of cooling systems (SI), each of the inlets being connected to a box (BX) and each of the outlets being connected to at least one cooling system (SI); - at least one cooling system (SI), preferably a radiator, as defined below, allowing the cooling of the dielectric fluid coming from the element (E2); - pipes, possibly connected to each other by connectors, as defined below, in which said dielectric fluid circulates between the reservoir (RI), the element (El), the boxes (BX), the element (E2) and the cooling system (SI); - the housings (BX) and the elements (El) and (E2) being made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers; - the dielectric fluid being as defined above.

[0025] Preferably, the inlets of the boxes (BX) are equipped with a nozzle allowing the spraying of the dielectric fluid directly onto the battery cells, preferably the nozzle is made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

[0026] Preferably, the pipes are connected to the inlets and / or outlets of the boxes (BX), of the elements (El) and (E2) directly or using connectors, preferably made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

[0027] The device may be included in a container comprising an inlet and an outlet each equipped with a pipe as defined above, or a plurality of pipes as defined above connected to each other by connectors, in which said dielectric fluid circulates.

[0028] The polyamide composition according to the invention is particularly well suited to the dielectric fluid used in particular for cooling battery cells. Thus, the dielectric fluid will not see its composition modified upon contact with the elements according to the invention comprising the polyamide composition of the invention. Particularly advantageously, after aging for 500 hours at 130°C, the dielectric fluid in contact with the polyamide composition according to the invention does not comprise more than 0.5% by mass, preferably 0.2%, advantageously 0.1% by mass of impurities not initially present. This test is carried out by immersing a 1BA test piece (according to ISO 527) in 100 mL of dielectric fluid according to the invention. The dielectric fluid is preferably Mobil EV therm Elite 701®. These impurities are quantified in two ways: - the dielectric fluid is filtered then the residue is weighed after washing and drying (when the mass no longer varies during drying). - Soluble impurities are quantified by liquid chromatography, in particular HPLC, by comparing the chromatograms before and after aging of the composition in the fluid.

[0029] The impurities according to the invention may be additives, monomers or oligomers, plasticizers or fillers initially included in the polyamide of the composition or impurities having migrated through the composition such as for example other automotive fluids such as lubricants or greases. The impurities are for example phosphorus species and / or BBSA (N-Butyl Benzene Sulfonamide). The pollution of the fluids by the phosphorus species and by the BBSA can be measured indirectly by monitoring the evolution of the contents of elements P and S. These contents can be determined by spectroscopy by plasma torch by inductive coupling according to the standard ASTM D5185.The migration of antioxidants can be assessed qualitatively and quantitatively by fluid analysis in high-performance liquid chromatography coupled with appropriate detection systems for their detection, such as UV photometry, or high-resolution mass spectrometry. The identity of the targeted antioxidants must be confirmed (i) by concordance of retention times between the substances recorded in the sample chromatograms and those recorded in the analysis of standards, (ii) by concordance of mass spectra.

[0030] Preferably, after the aging described above (500 hours at 130°C), the conductivity of the dielectric fluid is less than 10 pS / cm, preferably less than 5 pS / cm, in particular less than 1 pS / cm, advantageously less than 0.1 pS / cm, in particular less than 0.01 pS / cm. The resistivity of the fluid is measured according to the DIN IEC 60247 standard, which makes it possible to calculate the conductivity.

[0031] The water content in the dielectric fluid after aging is determined according to the “Karl Fisher” method following the ISO 760:1978 standard. This aging is carried out by placing the dielectric fluid in contact with a hermetically sealed element according to the invention for 1000 h. The element according to the invention is placed in a controlled atmosphere at 50% relative humidity and at a temperature of 50°C. The thickness of the walls of the element is 2 mm. The water content in the dielectric fluid after this aging is less than 2% by weight, preferably 1% by weight, in particular 0.5% by weight, advantageously 0.1% by weight, in particular 0.05% by weight (the water content of the fluid before aging is less than 50 ppm). Presentation of figures

[0032] [Fig. 1] represents a cooling circuit for battery cells comprising two housings (Bl) and (B2) comprising battery cells. Each of the housings (Bl) and (B2) comprises an inlet and an outlet allowing the flow of dielectric fluid (3). The cooling circuit also comprises two elements (El) and (E2) allowing the distribution of the dielectric fluid in the housings (Bl) and (B2) via the pipes (T). Detailed description

[0033] The invention is now described in more detail and in a non-limiting manner in the following description.

[0034] Unless otherwise indicated, all percentages are mass percentages.

[0035] In this text, the quantities indicated for a given species may apply to this species according to all its definitions (as mentioned in this text), including the more restricted definitions.

[0036] It is further specified that the expressions "between... and..." and "from... to..." used in the present description must be understood as including each of the limits mentioned.

[0037] The term "polyamide matrix" is intended to denote a composition of one or more polyamides. In the context of the present invention, the polyamide matrix represents more than 50% by weight of polyamide relative to the total weight of the composition. In the context of the present invention, all the components included in the polyamide composition according to the invention are dissolved or dispersed in the polyamide matrix.

[0038] The invention relates firstly to the use of at least one element in a cooling circuit using at least one dielectric fluid, in which the element comprises at least one layer consisting of a polyamide C composition, characterized in that: - composition C comprises from 50 to 99.9% by weight relative to the total weight of the composition of a polyamide matrix having an average C / N ratio greater than or equal to 7 and is free from reinforcing fibers; - the dielectric fluid is liquid at atmospheric pressure at 23°C and comprises less than 10% by weight of water and glycol ether; and - said layer being intended to be in contact with said dielectric fluid.

[0039] The element is in particular a structure for the transport, distribution or storage of dielectric fluids, in particular for the distribution or storage of dielectric fluids. Polyamide matrix

[0040] The composition according to the invention preferably comprises from 50 to 99.9%, preferably from 70 to 99%, advantageously from 80 to 98.5%, in particular from 90 to 98% by weight of polyamide matrix relative to the total weight of the composition.

[0041] The polyamide(s) of the polyamide matrix are chosen so that the average C / N ratio of the polyamide mixture of the polyamide matrix is ​​greater than or equal to 7, preferably greater than or equal to 8, preferably greater than or equal to 9, preferably between 9 and 12.

[0042] The composition of the invention comprises less than 20% by weight, preferably less than 10% by weight, for example less than 5% by weight, preferably less than 3% by weight, in particular 0% by weight, relative to the total weight of the composition of one or more polyamides having a C / N ratio of less than 7.

[0043] By average number of carbon atoms per nitrogen atom, we mean the average of the number of carbon atoms per unit, that is to say per chain between two nitrogen atoms. Within a polyamide, the units are linked to each other by amide functions: -CO-NH-. Thus, there are as many nitrogen atoms as there are amide groups (-CO-NH-). In the case of a homopolyamide of type PA-XY, the number of carbon atoms per nitrogen atom is the average of the unit X and the unit Y. Thus PA612 resulting from the polycondensation of hexanediamine and dodecanedioic acid, is a PA with 9 carbon atoms per nitrogen atom, in other words is a C9 PA, according to the following calculation: (6+12) / 2. In the case of copolyamides, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is carried out in molar proportion to the different amide units. Thus, coPA-6.T / 6.6 comprising 60% 6T and 40% 66 is in C6.6: 60%x[(6+8) / 2]+40%x[(6+6) / 2] = 6.6.In the case of a polyamide blend, the number of carbon atoms per nitrogen atom is calculated according to the same principle. The calculation is carried out in molar proportion to the different polyamides. Thus, for a blend of polyamide A and polyamide B comprising 60% A and 40% B, the average C / N ratio is [60% x (C / N ratio of A) + 40% x (C / N ratio of B)] / 2.

[0044] Preferably, composition C according to the invention has an inherent viscosity of between 1 and 1.8, preferably between 1.2 and 1.6, more preferably between 1.3 and 1.6.

[0045] Preferably, the polyamide matrix according to the invention has an inherent viscosity of between 1 and 1.8, preferably between 1.2 and 1.6, more preferably between 1.3 and 1.6. In the sense of the application, the inherent viscosity of the polyamide matrix is ​​measured after dissolution of the polymer matrix.

[0046] For the purposes of the application, the inherent viscosity is preferably as measured using an "Ubbelohde" tube at 20°C on a 0.5% by weight solution in m-cresol according to ISO 307 of 2019.

[0047] The term polyamide designates both a homopolyamide and a copolyamide.

[0048] The nomenclature used to define polyamides is described in the standard ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", in particular on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0049] The polyamide can be obtained from the polycondensation of lactam units, amino acid units and / or XY units, X denoting a diamine and Y denoting a dicarboxylic acid (or diacid).

[0050] The lactams and amino acids contain from 4 to 12 carbon atoms. Preferably, they are chosen from pyrrolidinone, 2-piperidinone, caprolactam, aminohexanoic acid, pelargolactam, decanolactam, undecanolactam, 10-aminoundecanoic acid, amino-11-undecanoic acid, amino-12-dodecanoic acid, lauryllactam, enantholactam, caprylolactam.

[0051] Advantageously, the lactams and the amino acids are C11 and C12.

[0052] The diamine may be aliphatic, linear or branched, or cycloaliphatic, preferably it is linear or branched aliphatic, in particular linear. The dicarboxylic acid may be aliphatic, cycloaliphatic or aromatic, preferably it is aliphatic or aromatic.

[0053] Concerning the polyamides obtained from the polycondensation of XY units, the diamine (X) can be C4 to C36, in particular C6 to C22, in particular C6 to C18 and the dicarboxylic acid (Y) can be C4 to C36, in particular C6 to C22, in particular C6 to C18.

[0054] Advantageously, the diamine is chosen from butanediamine, pentanediamine, 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, hexadecanediamine, octadecanediamine, octadecenediamine, reicosanediamine, docosanediamine and diamines obtained from fatty acids, 1,3-xylylenediamine (denoted MXD) and 1,4-xylylenediamine (denoted PXD), bis(3,5-dialkyl-4-aminocyclohexyl)-methane, bis(3,5-dialkyl-4-aminocyclohexyl)-ethane, bis(3,5-dialkyl-4-aminocyclohexyl)-propane, bis(3,5-dialkyl-4-aminocyclohexyl)-butane, bis-(3-methyl-4-aminocyclohexyl)-methane or 3'-dimethyl-4,4'-diamino-dicyclohexyl-methane commonly called "BMACM" or "MACM" (and denoted B hereinafter), p-bis(aminocyclohexyl)-methane commonly called "PACM" (and noted P hereinafter), isopropylidenedi(cyclohexylamine) commonly called "PACP", isophorone-diamine (noted IPD hereinafter) and 2,6-bis(amino methyl)norbornane commonly called "BAMN", in particular 1,10-decanediamine.

[0055] A non-exhaustive list of cycloaliphatic diamines is given in the publication "Cycloaliphatic Amines" (Encyclopaedia of Chemical Technology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

[0056] Advantageously, the dicarboxylic acid is chosen from succinic acid, pentanedioic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanoic acid, octadecenoic acid, eicosanedioic acid, docosanedioic acid and fatty acid dimers containing 36 carbons, terephthalic acid (denoted T), isophthalic acid (denoted I), in particular dodecanedioic acid.

[0057] Advantageously, the diamine is chosen from 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,3-bis(aminomethyl)cyclohexane (BAC), 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, in particular 1,10-decanediamine, and the dicarboxylic acid is chosen from sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, terephthalic acid (denoted T), isophthalic acid (denoted I), in particular dodecanedioic acid.

[0058] More advantageously, the lactam is lauryllactam, the amino acid is chosen from 10-aminoundecanoic acid, amino-11-undecanoic acid, amino-12-dodecanoic acid, the diamine is chosen from 2-methyl-1,5-pentanediamine, 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid (denoted T) and isophthalic acid (denoted I).

[0059] According to a very preferred embodiment, the lactam is lauryllactam, the amino acid is chosen from 10-aminoundecanoic acid, amino-11-undecanoic acid, amino-12-dodecanoic acid, the diamine is chosen from butanediamine, 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid (denoted T) and brassylic acid, tetradecanedioic acid. Advantageously, the polyamide present in the composition of the invention is chosen from PA 410, PA412, PA 510, PA 610, PA612, PA 613 PA1010, PA10T, PA10T / 1010, PAU, PA12, PA11 / 10T, PA12 / 10T, PA 1012, PA 1212, PA 1214 PA 618, PA 12T, PA 1010 / 1012, PA BACT / 6T, PA BACT / 10T, PA BACT / 12T, PA MPMDT / 6T, PA MPMDT / 10T, PA MPMDT / 12T, PA MXDT / 6T, PA MXDT / 10T, PA MXDT / 12T, PA11 / BACT / 6T, PA 11 / BACT / 10T, PA 11 / BACT / 12T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / MPMDT / 12T, PA 11 / MXDT / 6T, PA 11 / MXDT / 10T, PA 11 / MXDT / 12T, PA610 / 6T, PA612 / 6T and their mixture. Preferably, the polyamide constituting the matrix of the invention is chosen from PA 12, PA 11, PA 410, PA412, PA 510, PA 610, PA612, PA 613 PA1010, PA 1012, PA9T, PA10T, PA6T / 10T, PA6T / 1010, PA10T / 1010, and PA11 / 10T, PA610 / 6T, PA612 / 6T and their mixture. Preferably, the polyamide constituting the matrix of the invention is chosen from PA12, PA 11, PA 410, PA412, PA 510, PA 610, PA612, PA 613 PA1010, PA 1012, PA610 / 6T, PA612 / 6T. Polyamide composition

[0061] The polyamide C composition according to the invention may further comprise at least one thermal stabilizer.

[0062] If present, the heat stabilizer is used in contents of 0.01 to 1.5%, preferably 0.05 to 0.5%, more preferably 0.1 to 0.4% by weight relative to the total weight of the polyamide composition.

[0063] The thermal stabilizer may be selected from a metal-based stabilizer, an organic stabilizer and a mixture thereof.

[0064] The metal-based stabilizer may consist of one or more constituents selected from iron- or copper-based compounds such as cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous iodide, cupric iodide, cuprous acetate and cupric acetate. Halides and acetates of other metals such as silver may be mentioned. These copper-based compounds are typically combined with alkali metal halides. A well-known example is the mixture of Cul and Kl, where the Cul:Kl ratio is typically between 1:5 and 1:15. An example of such a stabilizer is Polyadd P201® from Ciba. Further details on copper-based stabilizers can be found in the patent US 2,705,227. More recently, complexed metal-based stabilizers have appeared, such as complexed coppers such as Bruggolen H3336®, H3337®, H3373® from the company Brueggemann. The metal-based stabilizers are preferably in non-ionic form, advantageously complexed, this advantageously makes it possible to avoid the release of ions into the dielectric fluid which would lead to an increase in the ionic (electrical) conductivity of said dielectric fluid.

[0065] The organic stabilizer may be chosen, without this list being restrictive, from: - phenolic antioxidants, for example Irganox 245®, Irganox 1010®, Irganox 1098® from BASF, Irganox MD1024® from BASF, Lowinox 44B25® from SI Group, - phosphorus-based stabilizers, such as phosphites, for example Irgafos 168® from Ciba, - a UV absorber, such as Tinuvin 312® from BASF, - an H ALS, as previously mentioned, - an amine-type stabilizer, such as Naugard 445® from Crompton, or a hindered amine-type stabilizer such as Tinuvin 770® from BASF, - a multifunctional stabilizer such as Nylostab S-EED® from Clariant.

[0066] It is obviously possible to envisage a mixture of two or more of these organic stabilizers.

[0067] Preferably, the thermal stabilizer is non-halogenated and preferably chosen from amine type stabilizers.

[0068] In one embodiment, the stabilizer is a mixture of phenolic antioxidants and phosphites.

[0069] The polyamide composition according to the invention may further comprise (relative to the total weight of the composition): - From 10 to 35%, preferably from 15 to 25%, by weight of a flame retardant (or flame retardant, or flame retardant), preferably a non-halogenated flame retardant, preferably a phosphorus-containing flame retardant; and / or - Beyond 35% by weight, preferably from 2 to 10% by weight of at least one impact modifier; and / or - From 0 to 30%, preferably from 1 to 27%, by weight of at least one current-conducting filler; and / or - From 0.1 to 10%, preferably from 0.2 to 5%, by weight of at least one additive.

[0070] Preferably, the flame retardant is chosen from halogen-free flame retardants, as described in US 2008 / 0274355 and in particular a metal salt chosen from a metal salt of phosphinic acid, a metal salt of diphosphinic acid, a polymer containing at least one metal salt of phosphinic acid, a polymer containing at least one metal salt of diphosphinic acid. The flame retardant may also be chosen from red phosphorus, antimony oxide, zinc oxide, iron oxide, magnesium oxide, metal borates, such as zinc borate, melamine pyrophosphates, melamine cyanurates, anti-drip agents of a silicone or fluorinated nature. The flame retardant may also be a mixture of the aforementioned agents.

[0071] They may also be halogenated flame retardants such as brominated or polybrominated polystyrene, brominated polycarbonate or brominated phenol.

[0072] The flame retardant agent may also be chosen from the metal salt of phosphinic acid of the following formula (I) and the metal salt of diphosphinic acid of the following formula (II):

[0073] with

[0074] RI and R2, independently of one another, denote a linear or branched C1-C6 alkyl group, or an aryl group;

[0075] R3 represents a linear or branched C1-C10 alkylene, C6-C10 arylene, C6-C10 alkylarylene, or C6-C10 arylalkylene group,

[0076] M is an ion of Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, K and / or a protonated amine base

[0077] m denotes an integer from 1 to 4,

[0078] n denotes an integer from 1 to 4,

[0079] x denotes an integer from 1 to 4,

[0080] n and m being chosen so that the salt is neutral, that is to say that it does not carry an electric charge.

[0081] Preferably, M represents a calcium, magnesium, aluminum or zinc ion.

[0082] Preferably, R1 and R2, independently of one another, denote a methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, n-pentyl and / or phenyl group.

[0083] Preferably, R3 represents a methylene, ethylene, n-propylene, iso-propylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene group; phenylene, naphthylene; methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene, tert-butylnaphthylene; phenylmethylene, phenylethylene, phenylpropylene, or phenylbutylene.

[0084] The flame retardant agent may be the product of trade name Exolit OP 1230® sold by Clariant, which is the aluminum salt of diethylphosphinic acid salt (CAS No. 225789-38-8).

[0085] More particularly, the content of flame retardant agent is between 10 and 35% by weight, preferably 15 and 25% by weight, and more particularly between 17 and 23% by weight relative to the total weight of the composition.

[0086] In a preferred embodiment, a synergist agent is also present. The flame retardant synergist agents are in particular as described in

[0087] W02005121234. They can be chosen from nitrogen synergists and phosphorus / nitrogen synergists. The synergist agent can be added at a content of between 3 and 20% by weight relative to the total weight of the composition.

[0088] The polyamide composition according to the invention may comprise at least one impact modifier. Preferably, it may comprise from 1 to 35%, preferably from 1.5 to 20%, more preferably from 2 to 10%, by weight relative to the total weight of the composition of at least one impact modifier.

[0089] The impact modifier is advantageously constituted by a polymer having a flexural modulus of less than 100 MPa measured according to standard ISO 178 at 50% RH and a Tg of less than 0°C measured according to standard 11357-2 of 2013.

[0090] The glass transition temperature Tg of the polyamides is measured using a differential scanning calorimeter (DSC), after a second heating pass, according to the ISO 1 1357-2:2013 standard. The heating and cooling rate is 20°C / min.

[0091] Preferably, the impact modifier consists of one or more polyolefins, some or all of which carry a function chosen from carboxylic acid, carboxylic anhydride and epoxide functions. In particular, the polyolefin may be chosen from an ethylene and propylene copolymer with an elastomeric character (EPR), an ethylene-propylene-diene copolymer with an elastomeric character (EPDM) and an ethylene / alkyl (meth)acrylate copolymer.

[0092] The composition may comprise up to 20% by weight, relative to the total weight of said composition, of a semi-crystalline polyolefin or a mixture of polyolefins, having a flexural modulus, measured according to ISO 178 at 50% RH, greater than 300 MPa, advantageously greater than 800 MPa.

[0093] This impact modifier can be a functionalized polyolefin (Bl).

[0094] According to the invention, functionalized polyolefin (Bl) means the following polymers.

[0095] The functionalized polyolefin (Bl) may be an alpha-olefin polymer having reactive units: the functionalities. Such reactive units are the carboxylic acid, anhydride, or epoxy functions.

[0096] By way of example, polyolefins may be mentioned as homopolymers or copolymers of alpha olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene, and more particularly: - homopolymers and copolymers of ethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene, - homopolymers or copolymers of propylene, - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), - styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers, - copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (for example methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight.

[0097] These polyolefins described above can be grafted, co-polymerized or terpolymerized by reactive units (the functionalities), such as carboxylic acid, anhydride, or epoxy functions.

[0098] More particularly, these polyolefins are grafted or co- or terpolymerized by unsaturated epoxides such as glycidyl (meth)acrylate, or by carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (the latter being able to be neutralized totally or partially by metals such as Zn, etc.) or even by carboxylic acid anhydrides such as maleic anhydride.

[0099] The functionalized polyolefin (Bl) can be chosen from the following (co)polymers, grafted with maleic anhydride or glycidyl methacrylate, in which the grafting rate is for example from 0.01 to 5% by weight: - PE, PP, copolymers of ethylene with propylene, butene, hexene, or octene containing for example 35 to 80% by weight of ethylene; - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), - styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers, - ethylene and vinyl acetate (EVA) copolymers, containing up to 40% by weight of vinyl acetate, - ethylene and alkyl (meth)acrylate copolymers, containing up to 40% by weight of alkyl (meth)acrylate, - ethylene vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0100] A functionalized polyolefin is for example a PE / EPR mixture, the weight ratio of which can vary widely, for example between 40 / 60 and 90 / 10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate for example of 0.01 to 5% by weight.

[0101] The functionalized polyolefin (Bl) can also be chosen from ethylene / propylene copolymers with a majority of propylene grafted with maleic anhydride then condensed with mono-amine polyamide (or a polyamide oligomer) (products described in EP-A-0342066).

[0102] The functionalized polyolefin (Bl) can also be a co- or terpolymer of at least the following units:

[0103] (1) ethylene,

[0104] (2) alkyl (meth)acrylate or vinyl ester of saturated carboxylic acid and

[0105] (3) anhydride such as maleic anhydride or (meth)acrylic acid or epoxy such as Glycidyl (meth)acrylate.

[0106] As examples of functionalized polyolefins of the latter type, the following copolymers may be mentioned, where ethylene preferably represents at least 60% by weight and where the termonomer (the function) represents, for example, from 0.1 to 12% by weight of the copolymer: - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers; - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers; - ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0107] In the above copolymers, the (meth)acrylic acid may be salified with Zn or Li. The term "alkyl (meth)acrylate" in (Bl) denotes C1 to C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0108] Furthermore, the aforementioned polyolefins (B 1) can also be crosslinked by any suitable process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, etc. capable of reacting with them or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0109] The above-mentioned copolymers (Bl) can be copolymerized in a random or block manner and have a linear or branched structure.

[0110] The molecular weight, the MFI index, the density of these polyolefins can also vary to a large extent, which a person skilled in the art will appreciate. The MFI index, abbreviation of Melt Flow Index, is the melt flow index. It is measured according to the ASTM 1238 standard.

[0111] Advantageously, the functionalized polyolefins (B 1) are chosen from any polymer comprising alpha olefinic units and units carrying polar reactive functions such as epoxy, carboxylic acid or carboxylic acid anhydride functions. Examples of such polymers include terpolymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate such as Lotader® from the company SK Geocentric or polyolefins grafted with maleic anhydride such as Orevac® from the company SK Geocentric as well as terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Mention may also be made of homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride then condensed with polyamides or mono-amino oligomers of polyamide, as described in application EP 0 342 066.

[0112] More particularly, the functionalized polyolefins (Bl) are: - terpolymers of ethylene, alkyl acrylate and maleic anhydride; - terpolymers of ethylene, alkyl acrylate and methacrylate glycidyl; - polypropylene and polyethylenes grafted with maleic anhydride; - copolymers of ethylene and propylene and possibly of diene monomer grafted with maleic anhydride; - copolymers of ethylene and octene grafted with maleic anhydride;

[0113] and their mixture.

[0114] The functionalized polyolefin (Bl) is present in a content of between 0 and 20% by weight, preferably between 1 and 10% by weight relative to the total weight of the composition.

[0115] The composition according to the invention may comprise at least one non-functionalized polyolefin (B2).

[0116] A non-functionalized polyolefin (B2) is typically a homopolymer or copolymer of alpha olefins or diolefins, such as, for example, ethylene, propylene, butene-1, octene-1, butadiene. By way of example, mention may be made of: - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene, - homopolymers or copolymers of propylene, - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM), - styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers, - copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (for example methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight

[0117] and their mixture.

[0118] The above-mentioned copolymers (B2) can be copolymerized in a random or block manner and have a linear or branched structure.

[0119] Advantageously, the non-functionalized polyolefins (B2) are chosen from homopolymers or copolymers of polypropylene and any homopolymer of ethylene or copolymer of ethylene and a comonomer of higher alpha olefin type such as butene, hexene, octene or 4-methyl-1-pentene. Examples that may be mentioned are PP (PolyPropylene), high density polyethylenes, medium density polyethylenes, linear low density polyethylenes, low density polyethylenes, very low density polyethylenes. These polyethylenes are known to those skilled in the art. as being produced according to a root process, according to a “Ziegler” type catalysis or, more recently, according to a so-called metallocene catalysis. Also preferred are copolymers of ethylene and vinyl acetate (EVA), such as those marketed under the trade name EVATANE® by the Applicant.

[0120] When the composition according to the invention comprises one or more non-functionalized polyolefins, the MFI of (A) and the MFIs of (B1) and (B2) can be chosen from a wide range, however, it is recommended to facilitate the dispersion of (B1) and (B2) that the viscosities of (B1) and (B2) are close.

[0121] The non-functionalized polyolefin is present in a content of between 0 and 20% by weight, preferably between 1 and 10% by weight relative to the total weight of the composition.

[0122] Advantageously, the impact modifier may also be a copolymer formed from polyamide blocks and polyether blocks, the polyamide blocks and the polyether blocks being linked by an ester function. These products are described in document FR 2 273 021 and sold under the trade name PEBAX® by the company ARKEMA.

[0123] Polyamide block copolymers (abbreviated below as PA) and polyether block copolymers (abbreviated below as PE) result from the copolycondensation of polyamide blocks with reactive ends with polyether blocks with reactive ends. For example, it is possible to react: - polyether diol, and a polyamide dicarboxylic acid, - polyether diamine and a polyamide dicarboxylic acid, - polyether diol and a polyamide diamine.

[0124] The polyamide blocks with dicarboxylic chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-regulating dicarboxylic acid. The polyamide blocks with diamine chain ends originate, for example, from the condensation of polyamide precursors in the presence of a chain-regulating diamine. Thus, the bond between the blocks is either an ester bond or an amide bond. The polymers with PA blocks and PE blocks may comprise a single PA block and a single PE block.

[0125] They can also comprise several PA blocks identical in terms of the structure of the monomer(s) constituting the polyamide and identical PE randomly distributed. Said polymers can be prepared by simultaneous reaction of the PE blocks and the precursors of the PA blocks. A polymer is then obtained having PE blocks and PA blocks of very variable length depending on the moment at which the chain regulator intervenes during the formation of the PA block, but also the different reagents having reacted randomly which are randomly distributed (statistically) along the polymer chain.

[0126] The impact modifier is preferably a polar functional polyolefin.

[0127] In the context of the present invention, the term “polar functional polyolefin” means a functional polyolefin as defined above comprising polar monomers such as vinyl acetates, acrylic or methacrylic acids, acrylates, methacrylates and glycidyl methacrylate or a

[0128] PEBA, preferably the impact modifier is a PEBA.

[0129] Preferably, composition C comprises less than 15% by weight of apolar functional polyolefin, preferably less than 10% by weight, in particular less than 5% by weight, preferably composition C does not comprise apolar functional polyolefin.

[0130] Preferably, the impact modifier of the invention is a functional polyolefin, preferably a polyolefin (Bl) as described above, comprising at least one heteroatom, preferably at least one nitrogen atom or one oxygen atom.

[0131] Preferably, the impact modifier of the invention is a functional polyolefin chosen from copolymers of ethylene with at least one product chosen from salts or esters of unsaturated carboxylic acids such as alkyl (meth)acrylate (for example methyl acrylate), or vinyl esters of saturated carboxylic acids such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight.

[0132] The polyamide composition according to the invention may also comprise from 0 to 10% by weight of additives relative to the total weight of the composition, preferably from 0.1 to 10%.

[0133] Preferably, the additives present in the polyamide composition of the invention are chosen from lubricants, organic or inorganic pigments, anti-UV agents, antistatic agents, mineral fillers, such as, for example, talc, silica, calcium carbonate, titanium dioxide, zinc oxide and organic fillers.

[0134] Preferably, the composition according to the invention comprises a plasticizer content of less than 10%, preferably less than 6%, preferably less than 5%, preferably less than 3%, more preferably less than 1%, by weight relative to the total weight of composition C, preferably the composition according to the invention is free of plasticizer, such as BBSA (BenzylButylSulfonAmide).

[0135] The polyamide composition according to the invention may comprise from 0 to 30%, preferably from 1 to 27%, more preferably from 2 to 25%, by weight relative to the total weight of composition C, of ​​at least one current-conducting filler relative to the total weight of the composition.

[0136] The conductive filler may be chosen from carbon blacks, graphites, graphenes, carbon nanotubes, and metallic fillers such as metallic fibers or metallic powders. These metallic fillers advantageously comprise iron or copper.

[0137] Preferably, when the current-conducting filler is carbon black or graphite, it is comprised in a content of 15 to 30%, preferably 18 to 27%, by weight relative to the total weight of composition C. When the current-conducting filler is a filler other than carbon black and graphite, for example graphene, carbon nanotubes, it is comprised in a content of 0.5 to 6%, preferably 1 to 5%, by weight relative to the total weight of composition C.

[0138] In one embodiment, the polyamide composition according to the invention comprises less than 10% by weight, preferably less than 5% by weight, preferably less than 2% by weight, preferably less than 1% by weight, of carbon black and / or black dye, preferably does not comprise carbon black and / or black dye.

[0139] Preferably, the polyamide composition according to the invention comprises less than 5% by weight, preferably less than 2% by weight, preferably less than 1% by weight, of crosslinked material, preferably the polyamide composition according to the invention does not comprise crosslinked material. Thus and particularly advantageously, the composition C according to the invention is preferably completely heat-meltable, this advantageously allows easy recycling of the composition.

[0140] The following compositions C according to the invention are preferred (the percentages are given by weight relative to the total weight of composition C):

[0141] Cl) comprising or consisting of: - 44 to 88.9% by weight of polyamide matrix having an average C / N ratio greater than or equal to 9 - 1 to 30% by weight of impact modifier - 10 to 35% by weight of flame retardant - 0.1 to 1% by weight of additives

[0142] C2) comprising or consisting of: - 79 to 99.9% by weight of polyamide matrix having an average C / N ratio greater than or equal to 9 - 0 to 20% by weight of impact modifier - 0.1 to 1% by weight of additives

[0143] C3) comprising or consisting of: - 49 to 98.9% by weight of polyamide matrix having an average C / N ratio greater than or equal to 9 - 1 to 30% by weight of current-carrying filler - 0 to 20% by weight of impact modifier - 0.1 to 1% by weight of additives. Dielectric fluid

[0144] The dielectric fluid according to the invention preferably comprises one or more compounds chosen from mineral oils and mineral oil derivatives, polyalphaolefins, polyalkylene glycols, silicones, esters with a number-average molar mass of between 1000 and 100,000 g / mol, preferably between 10,000 and 100,000 g / mol, preferably between 20,000 and 100,000 g / mol, preferably between 50,000 and 100,000 g / mol, for example polyol ester, POE, partially fluorinated polymers having a number-average molar mass of 1000 and 100,000 g / mol, preferably between 10,000 and 100,000 g / mol, preferably between 20,000 and 100,000 g / mol, preferably between 50,000 and 100,000 g / mol, for example perfluoropolyethers.

[0145] Preferably, the dielectric fluid according to the invention comprises less than 5% by weight of halogenated compound, preferably does not comprise any halogenated compound. In the context of the present invention, the term halogenated compound means a compound comprising at least one halogen atom.

[0146] Preferably, the dielectric fluid according to the invention comprises one or more compounds chosen from mineral oils and mineral oil derivatives, polyalphaolefins, polyalkylene glycols, silicones, esters with a number-average molar mass of between 1000 and 100,000 g / mol, preferably between 10,000 and 100,000 g / mol, preferably between 20,000 and 100,000 g / mol, preferably between 50,000 and 100,000 g / mol, for example polyol ester, POE.

[0147] Preferably, the mineral oils and mineral oil derivatives have a number-average molar mass of between 1000 and 100,000 g / mol, preferably between 20,000 and 100,000 g / mol, more preferably between 50,000 and 100,000 g / mol.

[0148] Preferably, the dielectric fluid according to the invention has a density at 23°C of between 0.3 and 1.5, preferably between 0.5 and 1.1, advantageously between 0.7 and 1.05, more preferably between 0.8 and 1. The density measurement is carried out according to standard ISO 1675:2022 at 23°C.

[0149] Preferably, the dielectric fluid according to the invention has a kinematic viscosity at 40°C of between 1 and 35 mm2 / s, preferably between 1.5 and 15 mm2 / s, in particular between 2 and 10 mm2 / s and / or a kinematic viscosity at 100°C of between 0.01 and 5 mm2 / s, preferably between 0.1 and 4 mm2 / s, preferably between 0.5 and 3 mm2 / s, more preferably between 0.8 and 2.5 mm2 / s and / or a kinematic viscosity at 25°C of between 5 and 150 mm2 / s, preferably between 10 and 100 mm2 / s. The kinematic viscosity is measured according to the ISO 3104:2020 standard.

[0150] Preferably, the dielectric fluid according to the invention: - comprises one or more compounds chosen from mineral oils and mineral oil derivatives, polyalphaolefins, polyalkylene glycols, silicones, esters, for example polyol ester, POE, polymers partially fluorinated low molecular weights, for example perfluoropolyethers; - a density less than 1.5, preferably less than 1; - a kinematic viscosity at 40°C between 1 and 35 mm2 / s, of preferably between 1.5 and 15 mm2 / s, in particular between 2 and 10 mm2 / s and / or a kinematic viscosity at 100°C of between 0.01 and 5 mm2 / s, preferably between 0.1 and 4 mm2 / s, preferably between 0.5 and 3 mm2 / s, more preferably between 0.8 and 2.5 mm2 / s and / or a kinematic viscosity at 25°C of between 5 and 150 mm2 / s, preferably between 10 and 100 mm2 / s.

[0151] Mineral oils are preferably mixtures obtained from the distillation of fossil fuels such as petroleum, coal, etc. Mineral oils are composed of hydrocarbons and mainly C15 to C40 alkanes.

[0152] Preferably, the dielectric fluid is free of halogen, water and glycol ether.

[0153] Among the particular dielectric fluids, we can cite the oils ExxonMobil Mobil EV ThermElite 701® (mixture of alkylnaphthenic hydrocarbon bases, PAO & esters), M&I Mivolt DF7® (mixture of polyol esters), Engineered FLuids Ampcool AC-110® (mixture of hydrocarbon bases and esters) and Shell Diala S4 ZX-I® (mixtures of hydrocarbon bases), but also the oils Croda Xenitron 3221® (mixtures of esters), Total EnergiesEco Friendly® (mixtures of hydrocarbon bases of biomass origin) and Total Energies Cell Shield® (mixtures of synthetic oils).

[0154] The dielectric fluid according to the invention has, before contact with the elements to be cooled, for example the battery cells, a temperature below 40°C, preferably below 30°C, for example between -10 and 30°C. The dielectric fluid according to the invention has, after contact with the elements to be cooled, for example the battery cells, a temperature between 40 and 110°C, preferably between 40 and 90°C, preferably between 40 and 65°C, advantageously between 40 and 60°C, preferably between 40 and 50°C. Elements according to the invention

[0155] The elements according to the invention are for example elements or structures for the transport, distribution or storage of said dielectric fluids, preferably for the distribution or storage of said dielectric fluids.

[0156] In one embodiment, the element (or structure) according to the invention is a pipe, preferably for the transport or distribution of the dielectric fluid. Preferably, the pipes according to the invention have an internal diameter greater than or equal to 10 mm, for example between 13 and 16 mm. The pipes can be smooth pipes or corrugated pipes, preferably corrugated pipes.

[0157] In another embodiment, the element (or structure) according to the invention is a reservoir for storing the dielectric fluid.

[0158] The elements according to the invention may comprise one or more layers, at least one of which is made up of composition C. Preferably, the elements according to the invention are made up of a layer made up of composition C according to the invention. Even more preferably, the elements according to the invention are made up of composition C according to the invention.

[0159] The single-layer structures are produced by extrusion. A “Maillefer” industrial extrusion line is used.

[0160] This line includes a single-screw extrusion extruder equipped with a screw with a screw profile adapted to polyamides. In addition, the extrusion line includes:

[0161] a die-punch assembly, located at the end of the extrusion head; the internal diameter of the die and the external diameter of the punch are chosen according to the structure to be produced and the materials which compose it, as well as the dimensions of the tube and the line speed; a vacuum tank with an adjustable depression level. In this tank circulates water maintained at 20°C in general, a gauge is inserted in the front of this tank allowing the element to be shaped in its final dimensions. The diameter of the gauge is adapted to the dimensions of the element, in particular the tube, to be produced, typically from 13.1 to 15 mm for a tube with an external diameter of 13 mm and a thickness of 1.5 mm;

[0162] a cooling tank in which water is maintained at around 20°C, allowing the element to be cooled along the path from the head to the drawing bench; a diameter gauge; a drawing bench. Before the tests, in order to ensure the best properties for the element and good extrusion quality, it is checked that the extruded materials have a residual moisture content before extrusion of less than 0.08%. Otherwise, an additional step of drying the material is carried out before the tests, generally in a vacuum dryer, for 1 night at 80°C.

[0163] The elements according to the invention can be used in cooling circuits in the automotive field, in particular in battery cell cooling circuits, in cooling circuits for energy storage systems, in cooling circuits for computer servers. Preferably, the elements according to the invention are used in cooling circuits in the automotive field, in particular in battery cell cooling circuits. Cooling circuit and device

[0164] The present application also relates to a cooling circuit using a dielectric fluid comprising at least one element according to the invention, in which a dielectric fluid as defined above circulates, the layer being in direct contact with said dielectric fluid.

[0165] Said cooling circuit according to the invention may also comprise at least one housing adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing, said housing preferably being made of a polyamide composition comprising: • from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7; • from 15 to 65% by weight of reinforcing fibers or fillers.

[0166] The present application relates to a device for the direct cooling of battery cells by a dielectric fluid according to the invention comprising: - A dielectric fluid; - At least one housing (BX) adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing in direct contact with the battery cells; - Upstream of the housing (BX), at least one pipe according to the invention in which said dielectric fluid circulates towards the housing (BX), - Downstream of the housing (BX), at least one pipe according to the invention in which said dielectric fluid circulates from the housing (BX),

[0167] the housing (BX) preferably being made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers;

[0168] the dielectric fluid being as defined according to the invention.

[0169] Preferably, the fluid entering the housing (BX) is a cold fluid and the fluid leaving the housing (BX) is a hot fluid. The pipes can be connected to the inlet and / or outlet of the housing (BX) directly or using a connector, the connector preferably being made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers. In one embodiment, the inlet of the housing (BX) is equipped with a nozzle, connected to the pipe, allowing the cells to be sprayed with the dielectric fluid. Preferably, the nozzle is made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

[0170] In one embodiment, the device may comprise a reservoir of dielectric fluid, said reservoir preferably being according to the invention and being connected to the other elements of the device by the pipes according to the invention directly or using connectors as defined above.

[0171] In one embodiment, the hot fluid from the housing (BX) is transported to a cooling system. In one embodiment, the cold fluid entering the housing (BX) comes from a reservoir, preferably a reservoir according to the invention. In this embodiment, upstream, the pipe connects the reservoir to the housing (BX) either directly or via connectors as defined above.

[0172] In one embodiment, the device comprises a plurality of pipes connected to each other using connectors. The connectors are preferably made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

[0173] In the context of the present invention, the term “cold dielectric fluid” means a dielectric fluid whose temperature is less than 40°C, preferably less than 30°C, for example between -10 and 30°C, and the term “hot dielectric fluid” means a dielectric fluid whose temperature is greater than 40°C, preferably between 40 and 110°C, preferably between 40 and 90°C, preferably between 40 and 65°C, advantageously between 40 and 60°C, preferably between 40 and 50°C.

[0174] The present application also relates to a device for the direct cooling of battery cells by a dielectric fluid comprising: - A dielectric fluid; - Optionally at least one element according to the invention in the form of a reservoir (RI); - At least one housing (BX) adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing in direct contact with the battery cells; - Upstream of the at least one box (BX) at least one element (El) for distributing the dielectric fluid coming from the reservoir to the boxes (BX), the element (El) comprising an inlet for the dielectric fluid and x outlets connected to the boxes (BX), x corresponding to the number of boxes (BX), each of the outlets being connected to a box (BX); - Downstream of the boxes (BX) at least one element (E2) for recovering the dielectric fluid coming from the boxes (BX), the element (E2) comprising y inlets for the dielectric fluid and z outlets, y corresponding to the number of boxes (BX) connected to the element (E2) and z corresponding to the number of cooling systems (SI), each of the inlets being connected to a box (BX) and each of the outputs being connected to at least one cooling system (SI); - At least one cooling system (SI), preferably a radiator, allowing the cooling of the dielectric fluid coming from the element (E2); - elements, in particular in the form of a pipe, according to the invention in which said dielectric fluid circulates between the reservoir (RI), the element (El), the housings (BX), the element (E2) and the cooling system (SI); - the housings (BX) and the elements (El) and (E2) being made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers; - The dielectric fluid being as defined according to the invention.

[0175] Preferably z equals 1.

[0176] The housings (BX) are preferably housings adapted to receive battery cells and the dielectric fluid.

[0177] The elements (El) and (E2) are preferably valves or valves or connectors. Preferably, the pipes according to the invention are made up of several pipes according to the invention connected to each other by connectors. Preferably, the pipes are connected to the inlets and / or outlets of the boxes (BX) and elements (El) and (E2) directly or using a connector.

[0178] In one embodiment, the inputs of the boxes (BX) are equipped with a nozzle allowing the spraying of the dielectric fluid directly onto the battery cells.

[0179] The connectors and / or nozzles are preferably made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

[0180] In one embodiment, the device according to the invention is included in a container comprising an inlet and an outlet each equipped with a pipe according to the invention, or a plurality of pipes according to the invention connected to each other by connectors preferably made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers, and allowing the circulation of said dielectric fluid.

[0181] In the context of the present invention, connector is understood to mean an interface part allowing the connection between two pipes, the connection between a pipe and a housing, the connection between a pipe and any other element of the device or circuit according to the invention. Preferably, the connectors according to the invention are injected parts, advantageously comprising a polyamide and reinforcing fibers.

[0182] The device or circuit of the invention may comprise at least one housing, preferably at least 2 housings, preferably at least 6 housings, preferably at least 10 housings, preferably at least 16 housings, for example from 1 to 50 housings, preferably from 1 to 26 housings, preferably from 1 to 16 housings. Preferably, the number of housings is an even number.

[0183] The present application also relates to the use of a composition for the transport, storage or distribution of a dielectric fluid, in which the composition is implemented in the form of a layer in an element or structure for the transport, storage or distribution of dielectric fluid, said layer being in contact with the dielectric fluid and in which: - the composition comprises from 50 to 99.9% by weight relative to the total weight of the composition of a polyamide matrix having an average C / N ratio greater than 7 and is free from reinforcing fibers and fillers; - the dielectric fluid is liquid at atmospheric pressure at 23°C and comprises less than 10% by weight of water and glycol ether.

[0184] The composition and the dielectric fluid being as defined above.

[0185] The invention will be explained in more detail in the following examples. Examples

[0186] Unless otherwise stated, the percentages are expressed by weight relative to the total weight of the composition.

[0187] The evolution of the properties of different elements according to the invention before and after soaking in the Mobil EV therm Elite 701® fluid from the company EXXON MOBIL after 168 hours at a temperature of 130°C was measured.

[0188] Tensile tests on 1BA dumbbells with a thickness of 2 mm were carried out at 23 °C according to ISO 527 in order to quantify the differences in properties before and after aging. The evolution of the stress and elongation at break for different comparative compositions and according to the invention are represented below.

[0189] The 1BA type dumbbells were made by injection molding for tensile testing. The following parameters were used: ENGEL VICTORY 500, 160T hydraulic press - Injection temperature (feed / nozzle): 230C / 250C - Mold temperature: 40°C - Holding time: 20s - Material holding pressure: 622 bars - Cooling time: 15 s

[0190] The following products were tested: - EU: Element consisting of a layer of a composition comprising 70% by weight of polyamide 11 and 30% by weight of polar-type functional polyolefins (Lotader 4700® marketed by SK Geocentric) - EI2: Element consisting of a layer of a composition comprising 80% by weight of polyamide 12 and 20% by weight of polar-type functional polyolefins (Lotader 4700® marketed by SK Geocentric) - EC1: Element consisting of a layer of a composition comprising 55% by weight of polyamide 6, 10% by weight of polar functional polyolefins (Lotader AX8900® marketed by SK Geocentric) and 35% of apolar functional polyolefins (Orevac IM 800® marketed by SK Geocentric) - EC2: Element made of a layer of a polypropylene composition (Hostalen® PPH1886) - EC3: Element consisting of a layer of a TPV composition (Santoprene® 101.87)

[0191] [Tables 1] Loss of stress at break after 168h at 130°C in the dielectric fluid Loss of elongation at break after 168h at 130°C in the dielectric fluid El 1 <5% <5% El 2 <5% <5% EC1 9% 17% EC2 50% 75% EC3 35% 70%

Claims

Claims

1. Use of at least one element in a cooling circuit using at least one dielectric fluid, wherein: the element comprises at least one layer consisting of a composition C, characterized in that: - composition C comprises from 50 to 99.9% by weight relative to the total weight of the composition of a polyamide matrix having an average C / N ratio greater than or equal to 7 and is free of fibers and reinforcing fillers; - the dielectric fluid is liquid at atmospheric pressure at 23°C and comprises less than 10% by weight of water and glycol ether; and - said layer being intended to be in contact with said dielectric fluid.

2. Use according to claim 1 in which the polyamide matrix has an average C / N ratio greater than or equal to 8, preferably greater than or equal to 9, preferably between 9 and 12.

3. Use according to claim 1 or 2, in which composition C has an inherent viscosity of between 1 and 1.8, preferably between 1.2 and 1.6, more preferably between 1.3 and

4. 1,u. Use according to any one of the preceding claims, in which the dielectric fluid comprises one or more compounds chosen from mineral oils and mineral oil derivatives, polyalphaolefins, polyalkylene glycols, silicones, esters with a number-average molar mass of between 1000 and 100,000 g / mol, for example polyol ester, POE, partially fluorinated polymers having a number-average molar mass of 1000 and 100,000 g / mol, for example perfluoropoly ethers.

5. Use according to any one of the preceding claims, in which the dielectric fluid has a density measured according to ISO 1675:2022 at 23°C of between 0.3 and 1.5, preferably between 0.5 and 1.1, advantageously between 0.7 and 1.05, more preferably between 0.8 and 1.

6. Use according to any one of the preceding claims, wherein the dielectric fluid has a kinematic viscosity at 40°C of between 1 and 35 mm2 / s, preferably between 1.5 and 15 mm2 / s, in particular between 2 and 10 mm2 / s and / or a kinematic viscosity at 100°C of between 0.01 and 5 mm2 / s, preferably between 0.1 and 4 mm2 / s, preferably between 0.5 and 3 mm2 / s, more preferably between 0.8 and 2.5 mm2 / s and / or a kinematic viscosity at 25°C of between 5 and 150 mm2 / s, preferably between 10 and 100 mm2 / s, the kinematic viscosity being measured according to ISO 3104:2020.

7. Use according to any one of the preceding claims, wherein composition C further comprises from 0.01 to 1.5%, preferably from 0.05 to 0.5%, more preferably from 0.1 to 0.4%, by weight of a heat stabilizer relative to the total weight of composition C.

8. Use according to any one of the preceding claims, wherein composition C further comprises: - From 10 to 35%, preferably from 15 to 25%, by weight of a flame retardant, preferably a non-halogenated flame retardant, preferably a phosphorus-containing flame retardant; and / or - From 35% by weight, preferably from 2 to 10% by weight of at least one impact modifier; and / or - From 0.5 to 30% by weight of at least one current-conducting filler; and / or - From 0.1 to 10% by weight of at least one additive.

9. Use according to any one of the preceding claims, wherein composition C comprises a plasticizer content of less than 10%, preferably less than 6%, preferably less than 5%, preferably less than 3%, preferably less than 1%, by weight, preferably composition C is free of plasticizer, such as BBSA (N-Butyl Benzene Sulfonamide).

10. Use according to any one of claims 1 to 9, wherein the element is a pipe for transporting the dielectric fluid.

11. Use according to any one of claims 1 to 9, wherein the element is a reservoir for storing the dielectric fluid.

12. Cooling circuit comprising at least one element comprising at least one layer made of composition C as described according to any one of claims 1 to 3 and 7 to 9, in which a dielectric fluid as described according to any one of claims 1 and 4 to 6 circulates, the layer being in direct contact with said dielectric fluid.

13. Cooling circuit according to claim 12 further comprising at least one housing adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing, said housing being made of a polyamide composition comprising: • from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7; • from 15 to 65% by weight of reinforcing fibers or fillers.

14. Device for the direct cooling of battery cells by a dielectric fluid as described according to any one of claims 1 and 4 to 6, comprising: - a dielectric fluid; - At least one housing (BX) adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of said dielectric fluid in said housing, said housing preferably being made of a polyamide composition comprising: • from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7; • from 15 to 65% by weight of reinforcing fibers or fillers;- Upstream of the housing (BX), at least one element as described in any one of claims 1 to 3 and 7 to 9 in the form of a pipe in which said dielectric fluid circulates towards the housing (BX), - Downstream of the housing (BX), at least one element as described in any one of claims 1 to 3 and 7 to 9;

15. in the form of a pipe in which said dielectric fluid circulates from the housing (BX). Device for the direct cooling of battery cells by a dielectric fluid comprising: - A dielectric fluid; - Optionally at least one reservoir (RI) as defined in claim 11; - At least one housing (BX) adapted to receive battery cells and provided with an inlet and an outlet allowing the circulation of a dielectric fluid in said housing in direct contact with the battery cells; - Upstream of the boxes (BX) at least one element (El) for distributing the dielectric fluid coming from the reservoir to the boxes (BX), the element (El) comprising an inlet for the dielectric fluid and x outlets connected to the boxes (BX), x corresponding to the number of boxes (BX), each of the outlets being connected to a box (BX); - Downstream of the boxes (BX) at least one element (E2) for recovering the dielectric fluid coming from the boxes (BX), the element (E2) comprising y inlets for the dielectric fluid and z outlets, y corresponding to the number of boxes (BX) connected to the element (E2) and z corresponding to the number of cooling systems (SI), each of the inlets being connected to a box (BX) and each of the outlets being connected to at least one cooling system (SI); - At least one cooling system (SI), preferably a radiator, allowing the cooling of the dielectric fluid coming from the element (E2); - pipes, possibly connected to each other by connectors, as defined in claim 10 in which said dielectric fluid circulates between the reservoir (RI), the element (El), the boxes (BX), the element (E2) and the cooling system (SI); - the housings (BX) and the elements (El) and (E2) being made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers; - The dielectric fluid being as defined according to any one of claims 1, 4 to 6.

16. Device according to claim 15, in which the inlets of the boxes (BX) are equipped with a nozzle allowing the spraying of the dielectric fluid directly onto the battery cells, preferably the nozzle is made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

17. Device according to any one of claims 14 to 16, in which the pipes are connected to the inlets and / or outlets of the housings (BX), of the elements (El) and (E2) directly or using connectors, preferably made of a polyamide composition comprising from 35 to 85% by weight of a polyamide matrix preferably having an average C / N ratio greater than or equal to 7 and from 15 to 65% by weight of reinforcing fibers or fillers.

18. Device according to any one of claims 14 to 17 included in a container comprising an inlet and an outlet each equipped with a pipe as defined in claim 10, or a plurality of pipes as defined in claim 10 connected together by connectors, in which said dielectric fluid circulates.

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