Tubular structure having low ionic conductivity

Abstract

The invention relates to a single-layer or multi-layer tubular structure for conveying a coolant, said tube being intended for fuel cell cooling, comprising at least one inner layer (I) comprising at least one thermoplastic polymer selected from the group consisting of polyolefins, thermoplastic vulcanizates (TPV), fluorinated polymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), the coolant has a dielectric conductivity of less than 30 [mu] S / cm as determined after the single-layer or multi-layer tubular structure in contact with the coolant is aged at 80 DEG C for 168 hours.

Description

[0001] The invention relates to a single-layer or multi-layer tubular structure for conveying a coolant, the tube being intended for fuel cell cooling. Prior art

[0002] A fuel cell is an electrochemical energy generator that can convert the chemical energy of a fuel (such as hydrogen) directly into electrical energy. In order to ensure good output and good service life, thermal control of such a fuel cell is important. Heat exchange via a fluid has always been the most efficient and economical system.

[0003] The heat transfer fluid circulates inside the cell. Therefore, in order not to destroy the performance of the fuel cell or even degrade it, the fluid must be dielectric. This fluid must also not contain any chemical elements (oligomers, additives) that could contaminate the cell.

[0004] The tubular structure conveying the coolant of the fuel cell must not change the coolant, in particular its dielectric conductivity. It must also not release oligomers and / or ions into the coolant and must be very resistant to contact with heat transfer fluids.

[0005] Patent US2019 / 0285203A1 describes a tubular structure as a cooling pipe for a motor vehicle, which has five layers and is in particular HDPE / binder / PA6 / binder / HDPE.

[0006] International application WO 2020 / 039356 describes a pipe for a motor vehicle having at least three layers of TPV / PP / TPV (TPV: Thermoplastic Vulcanizate), in particular a motor vehicle temperature control pipe for fluid temperature control and cooling media.

[0007] Application US2007148388A1 describes an engine coolant line comprising at least two layers:

[0008] An outer layer consists of a polyamide composition and an inner layer consists of a polypropylene composition containing at least 50% by weight of polypropylene which is a heterophasic copolymer of propylene and ethylene.

[0009] EP 3670172 A1 describes a multilayer pipe comprising at least one inner layer composed of polypropylene (PP) and at least one outer layer composed of polyphthalamide (PPA).

[0010] However, these tubes disclose neither the use of these tubes for fuel cell cooling, nor aspects of the dielectric conductivity of the coolant transported by these tubes, nor the release of oligomers and / or ions.

[0011] Therefore, there is a need to provide conduits that can be used for fuel cell cooling that are capable of conveying a coolant having dielectric conductivity and that do not release oligomers and / or ions into the coolant.

[0012] The present invention therefore relates to a single-layer or multi-layer tubular structure for conveying a coolant, the tubular structure being intended for fuel cell cooling, comprising at least one inner layer (I) comprising at least one thermoplastic polymer chosen from polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), the coolant having a dielectric conductivity of less than 30 μS / cm, as measured after aging of the single-layer or multi-layer tubular structure in contact with the coolant at 80°C for 168 hours.

[0013] The inventors have surprisingly found that a single-layer or multi-layer tubular structure for transporting a coolant having a dielectric conductivity of less than 30 μS / cm and comprising at least one inner layer (I) comprising at least one thermoplastic polymer as defined above allows cooling of the fuel cell while avoiding the release of oligomers and / or ions into the coolant.

[0014] Throughout this specification, the expression "tubular structure" and the term "tube" or "pipe" have the same meaning and can be used interchangeably.

[0015] The coolant is any heat transfer liquid, in particular a coolant based on water and additives.

[0016] It is based especially on glycol water, in particular on water together with propylene glycol or ethylene glycol.

[0017] The electrical conductivity or dielectric conductivity expressed in microSiemens per centimeter (μS / cm) characterizes the ability of a material or solution to allow the free movement of electric charges and thus allow the passage of electric current. It is measured on the coolant with magnetic stirring and at ambient temperature by means of a calibrated conductivity meter with automatic temperature compensation (HORIBALAQUA-EC220K model, equipped with HORIBA 3552 3G0E0042 probe) after aging the single-layer or multi-layer tubular structure in contact with the coolant for 168 hours at 80°C.

[0018] Regarding the thermoplastic polymer of the inner layer (I)

[0019] It is selected from polyolefins, thermoplastic vulcanizates (TPVs), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA).

[0020] According to the invention, the inner layer (I) consists essentially of polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) or polyphthalamide (PPA). In addition to the thermoplastics, the inner layer (I) may also contain additives or conventional additives.

[0021] Among the additives, mention may especially be made of those chosen from catalysts, antioxidants, heat stabilizers, UV stabilizers, light stabilizers, lubricants, fillers, plasticizers, flame retardants, nucleating agents, dyes, electrical conductors, thermal conductors, impact modifiers or mixtures of these.

[0022] The inner layer suitably consists of at least 90 wt. %, preferably at least 92 wt. %, more preferably at least 95 wt. % and very preferably at least 98 wt. % of a polyolefin, a thermoplastic vulcanizate (TPV), a fluoropolymer, polyphenylene sulfide (PPS) or polyphthalamide (PPA).

[0023] Polyolefins

[0024] In one embodiment, the thermoplastic polymer of the inner layer (I) is a polyolefin selected from the group consisting of non-functionalized polyolefins, functionalized polyolefins and mixtures thereof.

[0025] For simplicity, the polyolefin is represented as (B), and the functionalized polyolefin (B1) and the non-functionalized polyolefin (B2) are described below.

[0026] The non-functionalized polyolefin (B2) is conventionally a homopolymer or copolymer of an alpha-olefin or a diene (for example ethylene, propylene, 1-butene, 1-octene or butadiene). By way of example, mention may be made of:

[0027] - polyethylene homopolymers and copolymers, in particular LDPE, HDPE, LLDPE (linear low-density polyethylene), VLDPE (very low-density polyethylene) and metallocene polyethylene,

[0028] - propylene homopolymer or copolymer,

[0029] - ethylene / alpha olefins such as ethylene / propylene, copolymers, EPR (abbreviation for ethylene propylene rubber) and ethylene / propylene / diene (EPDM),

[0030] - copolymers of ethylene and at least one product chosen from salts or esters of unsaturated carboxylic acids, such as alkyl (meth)acrylates (for example methyl acrylate), or vinyl esters of saturated carboxylic acids, such as vinyl acetate (EVA), the proportion of comonomers being up to 40% by weight.

[0031] The functionalized polyolefin (B1) may be a polymer of an alpha olefin having a reactive unit (functional group); such a reactive unit is an acid, anhydride or epoxy functional group. By way of example, the aforementioned polyolefin (B2) grafted or copolymerized or terpolymerized with an unsaturated epoxide such as glycidyl (meth)acrylate, or with a carboxylic acid or a corresponding salt or ester such as (meth)acrylic acid (the latter may be completely or partially neutralized with a metal such as Zn, etc.), or with a carboxylic anhydride such as maleic anhydride. The functionalized polyolefin is, for example, a PE / EPR mixture, the weight ratio of which may vary within a wide range, for example from 40 / 60 to 90 / 10, said mixture being co-grafted with an anhydride (especially maleic anhydride) at a grafting degree of, for example, 0.01% to 5% by weight.

[0032] The functionalized polyolefin (B1) can be selected from the following (co)polymers grafted with maleic anhydride or glycidyl methacrylate, wherein the degree of grafting is, for example, 0.01% to 5% by weight:

[0033] PE, PP, copolymers of ethylene with propylene, butene, hexene or octene, containing, for example, 35 to 80% by weight of ethylene;

[0034] - ethylene / alpha-olefins such as ethylene / propylene, copolymers, EPR (abbreviation for ethylene propylene rubber) and ethylene / propylene / diene (EPDM);

[0035] - styrene / ethylene-butylene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS) and styrene / ethylene-propylene / styrene (SEPS) block copolymers;

[0036] - copolymers of ethylene and vinyl acetate (EVA) containing up to 40% by weight of vinyl acetate;

[0037] - copolymers of ethylene and alkyl (meth)acrylates containing up to 40% by weight of alkyl (meth)acrylates;

[0038] - Copolymers of ethylene with vinyl acetate (EVA) and alkyl (meth)acrylates containing up to 40% by weight of comonomers.

[0039] The functionalized polyolefin (B1) can also be selected from ethylene / propylene copolymers based on propylene, grafted with maleic anhydride and then condensed with monoaminated polyamide (or monoaminated polyamide oligomer) (products described in EP-A-0342066).

[0040] The functionalized polyolefin (B1) may also be a copolymer or terpolymer of at least the following units: (1) ethylene, (2) an alkyl (meth)acrylate or a saturated carboxylic acid vinyl ester, and (3) an anhydride such as maleic anhydride, or (meth)acrylic acid, or an epoxide such as glycidyl (meth)acrylate.

[0041] As examples of functionalized polyolefins of the latter type, mention may be made of the following copolymers, in which ethylene preferably represents at least 60% by weight and in which the termonomer (functional group) represents, for example, from 0.1% to 10% by weight of the copolymer:

[0042] - ethylene / alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers;

[0043] - ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymers;

[0044] - Ethylene / vinyl acetate or alkyl (meth)acrylate / (meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

[0045] In the aforementioned copolymer, (meth)acrylic acid may form a salt with Zn or Li.

[0046] The term "alkyl (meth)acrylate" in (B1) or (B2) refers to C1-C8 alkyl methacrylate and acrylate, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0047] In addition, the polyolefins (B1) mentioned above can also be cross-linked via any suitable method or reagent (diepoxide, diacid, peroxide, etc.); the term "functionalized polyolefin" also includes mixtures of the polyolefins mentioned above and difunctional reagents capable of reacting with these polyolefins (such as diacids, dianhydrides, diepoxides, etc.), or mixtures of at least two functionalized polyolefins that can react with each other.

[0048] The above-mentioned copolymers (B1) and (B2) may be copolymerized in a random or block manner, and may have a linear or branched structure.

[0049] As will be appreciated by those skilled in the art, the molecular weight, MFI index and density of these polyolefins may also vary over a wide range. MFI is the abbreviation for melt flow index. It is measured according to standard ASTM 1238.

[0050] Advantageously, the non-functionalized polyolefin (B2) is selected from polypropylene homopolymers or copolymers, and any ethylene homopolymers, or copolymers of ethylene and higher alpha olefin type comonomers such as butene, hexene, octene, or 4-methyl-1-pentene. For example PP, high-density PE, medium-density PE, linear low-density PE, low-density PE or very low-density PE can be mentioned. These polyethylenes are known to those skilled in the art as produced according to a "free radical" process, according to a "Ziegler" type catalysis, or recently according to a "metallocene" catalysis.

[0051] Advantageously, the functionalized polyolefin (B1) is chosen from any polymer comprising alpha-olefin units and units carrying polar reactive functional groups, such as epoxy, carboxylic acid or carboxylic anhydride functional groups. As examples of such polymers, mention may be made of terpolymers of ethylene, alkyl acrylates and maleic anhydride or glycidyl methacrylate, such as products (SKFunctional Polymer), or polyolefins grafted with maleic anhydride, such as Products (SK Functional Polymer), and terpolymers of ethylene, alkyl acrylates and (meth)acrylic acid. Mention may also be made of polypropylene homopolymers or copolymers grafted with carboxylic anhydrides and then condensed with monoaminated polyamides or monoaminated polyamide oligomers.

[0052] In one embodiment, the polyolefin is non-functionalized.

[0053] Advantageously, the non-functionalized polyolefin is chosen from polyethylene and polypropylene, in particular polyethylene, in particular high density polyethylene (HDPE).

[0054] Thermoplastic Vulcanizate

[0055] In another embodiment, the thermoplastic polymer of the inner layer (I) is a thermoplastic vulcanizate (TPV).

[0056] Thermoplastic vulcanizates (TPVs) are mechanical mixtures of olefinic thermoplastic polymers with a polyethylene or polypropylene matrix, especially with a polypropylene matrix, and vulcanized elastomers, such as vulcanized PP / EPDM (ethylene propylene diene monomer) mixtures.

[0057] Fluoropolymers

[0058] In one embodiment, the thermoplastic polymer of the inner layer (I) is a fluoropolymer.

[0059] Fluoropolymers are polymers having fluorocarbons as repeating units.

[0060] It can be composed of the following monomers: ethylene (E), propylene (P), vinyl fluoride (VF1), vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoropropyl vinyl ether (PPVE), perfluoromethyl vinyl ether (PMVE) and chlorotrifluoroethylene (CTFE): CFCl=CF2.

[0061] In particular, the fluoropolymer is selected from poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene (ETFE), tetrafluoroethylene, a terpolymer of ethylene and hexafluoropropylene (EFEP), a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and mixtures thereof, especially ethylene-tetrafluoroethylene (ETFE).

[0062] Polyphenylene sulfide (PPS)

[0063] In one embodiment, the thermoplastic polymer of the inner layer (I) is polyphenylene sulfide (PPS).

[0064] Polyphenylene sulfide (PPS) is a thermally stable semi-crystalline polymer.

[0065] Polyphthalamide (PPA)

[0066] In one embodiment, the thermoplastic polymer of the inner layer (I) is polyphthalamide (PPA).

[0067] The nomenclature used to define polyamides is described in standard ISO 1874-1:2011, "Plastics—Polyamide (PA) moulding and extrusion materials—Part 1: Designation", in particular page 3 (Tables 1 and 2), and is well known to those skilled in the art.

[0068] The polyphthalamide may be a homopolyamide or a copolyamide.

[0069] When it is in the form of a homopolyamide, it is of the formula XAr or MXDY.

[0070] XAr represents a unit obtained by polycondensation of a diamine X and an aromatic dicarboxylic acid, the diamine X being C6-C36, preferably C6-C18, preferably C6-C12, more preferably C10-C12.

[0071] The diamine may be linear or branched. Advantageously, it is linear.

[0072] The at least one C6-C36 diamine X may in particular be chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undemethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids.

[0073] Advantageously, the at least one diamine X is C6-C18 and is chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undemethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexamethylenediamine and 1,18-octadecamethylenediamine.

[0074] Advantageously, the at least one C6 to C12 diamine X is chosen in particular from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undemethylenediamine and 1,12-dodecamethylenediamine.

[0075] Advantageously, the at least one C6 to C12 diamine X is chosen in particular from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undemethylenediamine and 1,12-dodecamethylenediamine.

[0076] Advantageously, the diamine X used is a C10 to C12 diamine, in particular chosen from 1,10-decamethylenediamine, 1,11-dodecamethylenediamine and 1,12-dodecamethylenediamine.

[0077] The aromatic dicarboxylic acid is advantageously chosen from terephthalic acid (denoted by T), isophthalic acid (denoted by I) and 2,6-naphthalene dicarboxylic acid (denoted by N) or mixtures thereof; in particular, it is chosen from terephthalic acid (denoted by T), isophthalic acid (denoted by I) or mixtures thereof.

[0078] MXDY represents a unit obtained by polycondensation of meta-xylylenediamine (MXD) and at least one aliphatic dicarboxylic acid Y.

[0079] The at least one C6 to C36 dicarboxylic acid Y may be selected from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and diacids obtained from fatty acids.

[0080] The diacid may be linear or branched. Advantageously, it is linear.

[0081] Advantageously, the at least one dicarboxylic acid Y is a C6 to C18 dicarboxylic acid and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid and octadecanedioic acid.

[0082] Advantageously, said at least one dicarboxylic acid Y is a C6 to C12 dicarboxylic acid and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid and dodecanedioic acid.

[0083] Advantageously, said at least one dicarboxylic acid Y is a C10 to C12 dicarboxylic acid and is chosen from sebacic acid, undecanedioic acid and dodecanedioic acid.

[0084] When the semicrystalline aliphatic polyamide is obtained from the polycondensation of at least one diamine X and at least one dicarboxylic acid Y, it may therefore comprise a single diamine or several diamines and a single dicarboxylic acid or several dicarboxylic acids.

[0085] Advantageously, the semicrystalline aliphatic polyamide is obtained from the polycondensation of a single diamine X with a single dicarboxylic acid Y.

[0086] In particular, the polyphthalamide (PPA) is selected from PA5T, PA6T, PA9T, PA10T, PA11T, PA12T, MXD6, MXD10 and MXD12.

[0087] It should be noted that throughout the present specification, C9 diamine includes a diamine unit containing 60 mol % or more of a 1,9-nonanediamine unit and / or a 2-methyl-1,8-octanediamine unit relative to all C9 diamine units.

[0088] When it is in the form of a copolyamide, it has the formula:

[0089] PA11 / 10T, PA12 / 10T, PA11 / 12T, PA12 / 12T, PA610 / 10T, PA612 / 10T, PA1010 / 10T, PA1012 / 10T, PA1212 / 10T, PA610 / 12T, PA612 / 12T, PA1010 / 12T, PA 1012 / 12T and PA1212 / 12T, especially PA11 / 10T and PA11 / 12T.

[0090] It has in particular a semiaromatic polyamide of formula X / YAr, especially of formula A / XT, as described in EP1505099, in which A is chosen from units obtained from amino acids, units obtained from lactams, and units corresponding to the formula (Ca diamine).(Cb diacid), in which a represents the number of carbon atoms of the diamine and b represents the number of carbon atoms of the diacid, a and b are each from 4 to 36, advantageously from 9 to 18, the (Ca diamine) unit being chosen from linear or branched aliphatic diamines, cycloaliphatic diamines and alkyl aromatic diamines, and the (Cb diacid) unit being chosen from linear or branched aliphatic diacids, cycloaliphatic diacids and aromatic diacids;

[0091] XT represents a unit obtained by the polycondensation of a Cx diamine (wherein x represents the number of carbon atoms of the Cx diamine, x being from 6 to 36, advantageously from 9 to 18) and terephthalic acid, especially a polyamide of the formula: A / 5T, A / 6T, A / 9T, A / 10T, A / 11T or A / 12T (A being as defined above), in particular a polyamide of the formula: PA5T / 10T, PA11 / 10T, PAMPMDT / 6T, PAMXDT / 6T, PA MXDT / 10T, PA MPMDT / 10T, PA BACT / 6T, PABACT / 10T, PA 11 / BACT, PA11 / 6T / 10T, PABACT / 10T / 6T, PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA11 / BACT / 10T, PA11 / MXDT / 6T, PA11 / MXDT / 10T and 11 / 5T / 10T.

[0092] T corresponds to terephthalic acid, MXD corresponds to meta-xylylenediamine, MPMD corresponds to methylpentaalkylenediamine, and BAC corresponds to bis(aminomethyl)cyclohexane.

[0093] In particular, the thermoplastic polymer of the inner layer (I) is a polyphthalamide (PPA) chosen from PA9T, PA6T, PA11 / 10T, PA12 / 10T, PA11 / 12T, PA 12 / 12T, PA610 / 10T, PA612 / 10T, PA1010 / 10T, PA1012 / 10T, PA1212 / 10T, PA610 / 12T, PA612 / 12T, PA1010 / 12T, PA 1012 / 12T and PA1212 / 12T, in particular PA11 / 10T and PA11 / 12T. As for the structure itself.

[0094] The tubular structure of the present invention may be single-layer or multi-layer and is used to transport coolant, and the tube is intended for fuel cell cooling.

[0095] Whether it is a single layer or a multilayer, it comprises at least one layer (I), which layer (I) comprises at least one thermoplastic polymer selected from polyolefins, thermoplastic vulcanizates (TPVs), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the coolant has a dielectric conductivity of less than 30 μS / cm, as measured after the single-layer or multi-layer tubular structure in contact with the coolant is aged at 80°C for 168 hours.

[0096] In one embodiment, it comprises at least one layer (I) comprising at least one thermoplastic polymer selected from non-functionalized polyolefins, thermoplastic vulcanizates (TPVs), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the coolant has a dielectric conductivity of less than 30 μS / cm, as measured after aging the single-layer or multi-layer tubular structure in contact with the coolant at 80°C for 168 hours.

[0097] In one embodiment, it comprises at least one layer (I) comprising at least one thermoplastic polymer selected from non-functionalized polyolefins, thermoplastic vulcanizates (TPVs), fluoropolymers selected from ETFE, polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the coolant has a dielectric conductivity of less than 30 μS / cm, as measured after aging the single-layer or multi-layer tubular structure in contact with the coolant at 80°C for 168 hours.

[0098] In another embodiment, it comprises at least one layer (I) comprising at least one thermoplastic polymer selected from non-functionalized polyolefins, thermoplastic vulcanizates (TPVs), polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the coolant has a dielectric conductivity of less than 30 μS / cm, as measured after aging the single-layer or multi-layer tubular structure in contact with the coolant at 80°C for 168 hours.

[0099] In a first variant, the structure is a single layer and therefore layer (I) is in contact with the coolant.

[0100] In a second variant, the structure is multilayered and layer (I) is therefore the inner layer in contact with the coolant.

[0101] In one embodiment of this second variant, the structure is multilayer and it comprises an outer layer (II) comprising at least one thermoplastic polymer, in particular a polyamide.

[0102] In one embodiment, the structure is multilayer and comprises an outer layer (II) consisting of at least one thermoplastic polymer, in particular a polyamide.

[0103] Advantageously, the structure is two-layered and therefore consists, from the outside to the inside, of layers (II) / / (I).

[0104] Advantageously, said inner layer (I) consists of said at least one thermoplastic polymer chosen from polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA).

[0105] Advantageously, said outer layer (II) consists of said at least one thermoplastic polymer, in particular a polyamide.

[0106] Advantageously, the inner layer (I) consists of at least one thermoplastic polymer chosen from polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the outer layer (II) consists of at least one thermoplastic polymer, in particular polyamide.

[0107] Besides the thermoplastics mentioned, the outer layer (II) may also comprise, in particular, additives or customary additives.

[0108] Among the additives, mention may especially be made of agents chosen from catalysts, antioxidants, heat stabilizers, UV stabilizers, light stabilizers, lubricants, fillers, plasticizers, flame retardants, nucleating agents, dyes, electrical conductors, thermal conductors, impact modifiers or mixtures of these.

[0109] The outer layer (II) suitably consists of at least 90% by weight, preferably at least 92% by weight, more preferably at least 95% by weight and very preferably at least 98% by weight of a thermoplastic polymer, in particular a polyamide.

[0110] In one embodiment, the amount of ions released by the tubular structure into the coolant is less than or equal to 700 mg / kg ions, more particularly less than or equal to 500 mg / kg ions, particularly less than or equal to 300 mg / kg ions, and especially less than or equal to 100 mg / kg ions, and the amount of ions released is measured by inductively coupled plasma mass spectrometry (ICP-MS) or by ion chromatography in an 8×1 mm2 container containing the coolant. 2 Determination on a monolayer tube.

[0111] About the polyamide of the outer layer (II)

[0112] The polyamide (PA) can be a homopolyamide or a copolyamide or a mixture of these.

[0113] Advantageously, the polyamide is chosen from semicrystalline aliphatic polyamides, cycloaliphatic polyamides, and semiaromatic polyamides (polyphthalamide or PPA).

[0114] In particular, the polyamide of layer (II) is chosen from semicrystalline aliphatic polyamides having an average number of carbon atoms per nitrogen atom of from C4 to C15, and semiaromatic polyamides (PPA).

[0115] Semi-crystalline aliphatic polyamide of outer layer (II)

[0116] “Semicrystalline polyamide” is understood to mean a material which is generally solid at ambient temperature and softens during temperature increase, in particular after exceeding its glass transition temperature (Tg), and can melt sharply when exceeding its so-called melting temperature (Tm) and becomes solid again when the temperature drops below its crystallization temperature.

[0117] Tg, Tc and Tm were determined by differential scanning calorimetry (DSC) according to standards 11357-2:2013 and 11357-3:2013, respectively.

[0118] The number average molecular mass Mn of the semicrystalline polyamide is preferably within a range extending from 10 000 to 85 000, in particular from 10 000 to 60 000, preferentially from 10 000 to 50 000, even more preferentially from 12 000 to 50 000. These Mn values ​​may correspond to an intrinsic viscosity greater than or equal to 0.8, as measured in m-cresol according to standard ISO 307:2007 but with a change of solvent (m-cresol is used instead of sulfuric acid and the temperature is 20° C.).

[0119] The nomenclature used to define polyamides is described in standard ISO 1874-1:2011, "Plastics—Polyamide (PA) moulding and extrusion materials—Part 1: Designation", in particular page 3 (Tables 1 and 2), and is well known to those skilled in the art.

[0120] The term polyamide covers both homopolyamides and copolyamides.

[0121] The at least one semicrystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam, or of at least one amino acid, or of at least one diamine X and at least one dicarboxylic acid Y, or a mixture thereof.

[0122] When the at least one semicrystalline aliphatic polyamide is obtained by polycondensation of at least one lactam, the at least one lactam may be selected from C8 to C18, preferably C10 to C18, more preferably C10 to C12 lactams. C8 to C18 lactams are especially decanolactam, undecanolactam, and lauryllactam.

[0123] When the at least one semicrystalline aliphatic polyamide is obtained from the polycondensation of at least one lactam, it may therefore comprise a single lactam or several lactams.

[0124] Advantageously, said at least one semicrystalline aliphatic polyamide is obtained by polycondensation of a single lactam, and said lactam is chosen from lauryllactam and undecyllactam, advantageously lauryllactam.

[0125] When the at least one semicrystalline aliphatic polyamide is obtained by polycondensation of at least one amino acid, the at least one amino acid may be chosen from C8 to C18, preferentially C10 to C18, more preferentially C10 to C12 amino acids.

[0126] C8 to C18 amino acids are especially 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid, and derivatives thereof, especially N-heptyl-11-aminoundecanoic acid.

[0127] When the at least one semicrystalline aliphatic polyamide is obtained from the polycondensation of at least one amino acid, it may therefore comprise a single amino acid or several amino acids.

[0128] Advantageously, the semicrystalline aliphatic polyamide is obtained by polycondensation of a single amino acid, and the amino acid is chosen from 10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, advantageously 11-aminoundecanoic acid.

[0129] When the at least one semicrystalline aliphatic polyamide is obtained from the polycondensation of at least one diamine X and at least one aliphatic dicarboxylic acid Y, the diamine X may be as defined above and the aliphatic diacid Y may be as defined above.

[0130] In one embodiment, the polyamide of layer (II) is selected from semicrystalline aliphatic polyamides having an average number of carbon atoms per nitrogen atom of C4 to C15, and semiaromatic polyamides (PPA).

[0131] In particular, the polyamide of layer (II) is a semicrystalline aliphatic polyamide having an average number of carbon atoms per nitrogen atom of C8 to C15, in particular C9 to C15, especially C10 to 15.

[0132] In particular, the semicrystalline aliphatic polyamide of layer (II) is selected from PA610, PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, in particular PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, especially PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12.

[0133] Advantageously, the semicrystalline aliphatic polyamide of layer (II) is chosen from PA11 and PA12.

[0134] Semi-aromatic polyamide of outer layer (II)

[0135] It is as defined for the PPA of the inner layer (I).

[0136] In another embodiment of this second variant, the structure is multilayer and comprises an outer layer (II) comprising at least one thermoplastic polymer, in particular a polyamide, and a binder layer (III) located between the inner layer (I) and the outer layer (II).

[0137] Advantageously, the structure is three-layered and therefore consists, from the outside to the inside, of layer (II) / / binder / / (I).

[0138] Advantageously, said inner layer (I) consists of said at least one thermoplastic polymer chosen from polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA).

[0139] Advantageously, said outer layer (II) consists of said at least one thermoplastic polymer, in particular a polyamide.

[0140] Advantageously, the inner layer (I) consists of at least one thermoplastic polymer chosen from polyolefins, thermoplastic vulcanizates (TPV), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), and the outer layer (II) consists of at least one thermoplastic polymer, in particular polyamide.

[0141] In one embodiment of this second variant and its embodiments, the thickness of the inner layer (I) represents 5% to 95% of the total thickness of the structure.

[0142] In another embodiment of this second variant and embodiments thereof, the thickness of the outer layer (II) is at least 5% of the total thickness of the structure.

[0143] In yet another embodiment of this second variant and embodiments thereof, the thickness of the inner layer (I) is from 5% to 95% of the total thickness of the structure and the thickness of the outer layer (II) is at least 5% of the total thickness of the structure.

[0144] About the adhesive layer

[0145] The adhesive layer may comprise an adhesive as described in particular in patents EP 1452307 and EP 1162061, EP 1216826 and EP0428833.

[0146] It is implied that layers (II) and (binder) or (I) and (binder) adhere to each other. A binder layer is intended to be between two layers that do not adhere to each other or do not adhere to each other.

[0147] The binder may be, for example, but not limited to, a composition based on 50% of a copolyamide 6 / 12 of Mn 16 000 (70 / 30 mass ratio) and 50% of a copolyamide 6 / 12 of Mn 16 000 (30 / 70 mass ratio), a PP (polypropylene) grafted with maleic anhydride (referred to as QF551A, from Mitsui), based on PA610 (Mn 30 000, and as defined elsewhere) and 36% of PA6 (Mn 28 000) and 1.2% of an organic stabilizer (composed of 0.8% of phenol ( 44B25, obtained from Great Lakes), 0.2% phosphite ( 168, available from BASF) and 0.2% of UV stabilizer ( 312 from BASF)) based on PA612 (Mn 29 000 and as defined elsewhere) and 36% of PA6 (Mn 28 000 and as defined elsewhere) and 1.2% of an organic stabilizer (composed of 0.8% of phenol ( 44B25, obtained from Great Lakes), 0.2% phosphite ( 168, available from BASF) and 0.2% of UV stabilizer ( 312 from BASF)), based on PA610 (Mn 30 000, and as defined elsewhere) and 36% of PA12 (Mn 35 000, and as defined elsewhere) and 1.2% of an organic stabilizer (composed of 0.8% of phenol ( 44B25, obtained from Great Lakes), 0.2% phosphite ( 168, available from BASF) and 0.2% of UV stabilizer ( 312, available from BASF)) composition, based on 40% PA6 (Mn 28 000, and as defined elsewhere), 40% PA12 (Mn 35 000, and as defined elsewhere) and 20% functionalized EPR VA1801 (Exxon) and 1.2% organic stabilizer (composed of 0.8% phenol ( 44B25, obtained from Great Lakes), 0.2% phosphite ( 168, available from BASF) and 0.2% of UV stabilizer ( 312, from BASF)), or a composition based on 40% PA6.10 (Mn 30 000, and as defined elsewhere), 40% PA6 (Mn 28 000, and as defined elsewhere) and 20% of an ethylene / ethyl acrylate / anhydride type impact modifier (MFI 6 at 190°C and 2.16 kg) in a mass ratio of 68.5 / 30 / 1.5 and 1.2% of an organic stabilizer (composed of 0.8% phenol ( 44B25, obtained from Great Lakes), 0.2% phosphite ( 168, available from BASF) and 0.2% of UV stabilizer ( 312 obtained from BASF) composition.

[0148] It is obvious that the multilayer tubular structure of the present invention may comprise further layers, provided that layer (I) is always the inner layer and layer (II) is always the outer layer, and that there is adhesion between the layers.

[0149] For example, the following type of structure is conceivable (from outside to inside): (II) / / Binder / / PA / / Binder / / (I).

[0150] Regardless of the above tubular structure, after the multilayer tubular structure in contact with the coolant is aged at 80° C. for 1200 hours, the tubular structure has a particle size of less than 1 g / m 2 The amount of soluble and insoluble extractables released into the coolant.

[0151] According to another aspect, the invention relates to a tubular structure as defined above for use in fuel cell cooling.

[0152] All features defined for this structure are valid for its use. Example

[0153] The invention will now be described in more detail with the aid of the following non-limiting examples.

[0154] The following structures were prepared by extrusion:

[0155] The multilayer tubes were produced by coextrusion. A McNeil Industrial multilayer extrusion line was used, which was equipped with five extruders connected to a multilayer extruder head with a spiral mandrel.

[0156] The screw used is a single extrusion screw with a screw profile suitable for polyamide. In addition to the five extruders and the multilayer extrusion head, the extrusion line also includes:

[0157] - a die-punch assembly at the end of the coextrusion head; the inner diameter of the die and the outer diameter of the punch are selected according to the structure to be produced and the material constituting the structure, as well as the size of the tube and the line speed;

[0158] - a vacuum tank with adjustable vacuum. Water, usually maintained at 20°C, circulates in this tank, in which a gauge is immersed for conforming the tube to its final dimensions. The diameter of the gauge is adapted to the dimensions of the tube to be produced, usually 8.5 to 10 mm for a tube with an external diameter of 8 mm and a thickness of 1 mm;

[0159] - a series of cooling tanks (with water maintained at about 20°C) for cooling the tube along the way from the die to the drawing machine;

[0160] - caliper;

[0161] -Drawing machines.

[0162] A five-extruder configuration is used to produce tubes ranging from two to five layers. In the case of structures with fewer than five layers, several extruders are fed with the same material.

[0163] In the case of a structure comprising six layers, in order to produce the inner layer in contact with the fluid, an additional extruder is connected and a spiral mandrel is added to the existing die head.

[0164] Before testing, to ensure optimal properties and good extrusion quality of the tubes, it was verified that the extruded material had a residual moisture content of less than 0.08% before extrusion. If this was not the case, an additional step of drying the material before testing was performed - typically overnight at 80°C in a vacuum desiccator.

[0165] After the extrusion parameters have stabilized (the target dimensions of the tube no longer vary over time), a tube is taken out that meets the characteristics described in this patent application. The diameter is monitored by a laser caliper installed at the end of the line.

[0166] Generally speaking, the line speed is usually 20 m / min. It usually varies between 5 and 100 m / min.

[0167] As known to those skilled in the art, the screw speed of the extruder depends on the thickness of the layer and the diameter of the screw.

[0168] Generally speaking, the temperature of the extruder and tooling (die and connectors) should be set so as to be sufficiently above the melt temperature of the compositions in question so that they remain molten, thereby preventing them from solidifying and blocking the machine.

[0169] The tubular structures were tested with respect to various parameters (Table 1).

[0170] The amount of soluble and insoluble extractables after 1200 hours at 80°C, electrical conductivity, total amount of extractable ions, coolant resistance, and impact and burst at 110°C were evaluated.

[0171] PA11=Rilsan BESN P123 Black TL(Arkema)

[0172] Fluoropolymer: ETFE EP7000 (Daikin Chemicals)

[0173] PA9T: Genestar N1001D (Kuraray)

[0174] Binder 1: 18342N(SK Functional Polymers)

[0175] Binder 2: 18729(SK Functional Polymers)

[0176] 4261AIM (LyondellBasell)

[0177] PP 4935 (Sabic)

[0178] TPV: 101-87 (Exxonmobil)

[0179] [Table 1]

[0180]

[0181]

[0182] NT: Not tested

[0183] Table 2 shows the tests used and the classification of the results.

[0184] [Table 2]

[0185]

[0186]

Claims

1. A single-layer or multi-layer tubular structure for conveying a coolant, the tube being intended for fuel cell cooling, the single-layer or multi-layer tubular structure comprising at least one inner layer (I), the inner layer (I) comprising at least one thermoplastic polymer selected from polyolefins, thermoplastic vulcanizates (TPVs), fluoropolymers, polyphenylene sulfide (PPS) and polyphthalamide (PPA), the coolant having a dielectric conductivity of less than 30 μS / cm, as measured after aging the single-layer or multi-layer tubular structure in contact with the coolant at 80°C for 168 hours.

2. The single-layer or multi-layer tubular structure for transporting coolant according to claim 1, characterized in that It is a single layer.

3. The single-layer or multi-layer tubular structure for transporting coolant according to claim 1, characterized in that It is multilayer and it comprises an outer layer (II) comprising at least one thermoplastic polymer, in particular a polyamide.

4. The single-layer or multi-layer tubular structure according to claim 1, characterized in that The thermoplastic polymer of the inner layer (I) is a polyolefin selected from non-functionalized polyolefins, functionalized polyolefins and mixtures of these.

5. The single-layer or multi-layer tubular structure according to claim 1, characterized in that The polyolefin of the inner layer (I) is a non-functionalized polyolefin.

6. The single-layer or multi-layer tubular structure according to claim 5, characterized in that The non-functionalized polyolefin is selected from polyethylene and polypropylene, especially polyethylene, especially high density polyethylene.

7. The multilayer tubular structure according to claim 1, characterized in that The thermoplastic polymer of the inner layer (I) is a fluoropolymer, in particular selected from poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene-tetrafluoroethylene, tetrafluoroethylene, a terpolymer of ethylene and hexafluoropropylene (EFEP), a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and mixtures thereof, especially poly(vinylidene fluoride) (PVDF).

8. The multilayer tubular structure according to claim 1, characterized in that The thermoplastic polymer of the inner layer (I) is a polyphthalamide (PPA), in particular selected from PA9T, PA6T, PA11 / 10T, PA12 / 10T, PA11 / 12T, PA12 / 12T, PA610 / 10T, PA612 / 10T, PA1010 / 10T, PA1012 / 10T, PA1212 / 10T, PA610 / 12T, PA612 / 12T, PA1010 / 12T, PA 1012 / 12T and PA1212 / 12T, in particular PA11 / 10T and PA11 / 12T.

9. Multilayer tubular structure according to one of claims 3 to 8, characterized in that The polyamide of layer (II) is selected from semicrystalline aliphatic polyamides having an average number of carbon atoms per nitrogen atom of C4 to C15, and semiaromatic polyamides (PPA).

10. The multilayer tubular structure according to claim 9, characterized in that The polyamide of the layer (II) is a semicrystalline aliphatic polyamide having an average number of carbon atoms per nitrogen atom of C8 to C15, in particular C9 to C15, especially C10 to 15.

11. The multilayer tubular structure according to claim 10, characterized in that The semi-crystalline aliphatic polyamide is selected from PA610, PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, in particular PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12, especially PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA11 and PA12.

12. The multilayer tubular structure according to claim 10 or 11, characterized in that The semi-crystalline aliphatic polyamide is selected from PA11 and PA12.

13. Multilayer tubular structure according to one of claims 3 to 12, characterized in that The thickness of the inner layer (I) accounts for 5% to 95% of the total thickness of the structure.

14. Multilayer tubular structure according to one of claims 3 to 12, characterized in that The thickness of the outer layer (II) is at least 5% of the total thickness of the structure.

15. The multilayer tubular structure according to any one of claims 13 and 14, characterized in that The thickness of the inner layer (I) is from 5% to 95% of the total thickness of the structure, and the thickness of the outer layer (II) is at least 5% of the total thickness of the structure.

16. Multilayer tubular structure according to one of claims 3 to 15, characterized in that The tubular structure comprises an adhesive layer (III) located between the inner layer (I) and the outer layer (II).

17. Single-layer or multi-layer tubular structure according to one of claims 1 to 16, characterized in that After the multilayer tubular structure in contact with the coolant is aged at 80° C. for 1200 hours, the tubular structure has a relative humidity of less than 1 g / m 2 The amount of soluble and insoluble extractables released into the coolant.

18. Use of a tubular structure according to one of claims 1 to 17 for cooling fuel cells.

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