Tubular structure with low ionic conductivity

Abstract

The present invention relates to a single-layer or multi-layer tubular structure for transporting a cooling liquid, the tube being intended for fuel cell cooling, comprising at least one internal layer (I) comprising at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), the cooling liquid having a dielectric conductivity of less than 30 µS / cm, as determined after ageing the single-layer or multi-layer tubular structure in contact with the cooling liquid for 168 hours at 80°C.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: TUBULAR STRUCTURE WITH LOW IONIC CONDUCTIVITY

[0003] The present invention relates to a single-layer or multi-layer tubular structure for transporting a coolant, said tube being intended for cooling a fuel cell.

[0004] [Prior art]

[0005] A fuel cell is an electrochemical energy generator that can directly convert the chemical energy of a fuel (hydrogen, for example) into electrical energy. Thermal control of this cell is important to ensure good performance and a long service life. The most efficient and economical system remains fluid heat exchange.

[0006] The heat transfer fluid will circulate within the cells. The fluid must therefore be dielectric to avoid disrupting or even damaging the battery's performance. The fluid must also not contain any chemical elements (oligomers, additives) that could pollute the cells.

[0007] The tubular structure that will transport the coolant of the fuel cell must not alter said coolant, in particular its dielectric conductivity. It must also not release oligomers and / or ions into said coolant and it must have very good resistance to contact with the heat transfer fluid.

[0008] Patent US2019 / 0285203A1 describes a five-layer tubular structure and in particular HDPE / binder / PA6 / binder / HDPE as a cooling pipe for a motor vehicle.

[0009] International application WO 2020 / 039356 describes pipes with at least three TPV / PP / TPV layers (TPV: thermoplastic vulcanizate) for a motor vehicle, in particular a thermoregulation pipe for a motor vehicle for thermoregulating and fluid cooling media.

[0010] Application US2007148388A1 describes engine coolant lines containing at least two layers: an outer layer consisting of a polyamide mass and an inner layer consisting of a polypropylene mass, which contains at least 50% by weight of polypropylene, the polypropylene being a multi-phase copolymer of propene and ethene.

[0011] EP 3670172A1 describes a multilayer pipe comprising at least one inner layer made of polypropylene (PP) and at least one outer layer made of polyphthalamide (PPA).

[0012] However, neither the use of these pipes for fuel cell cooling nor the dielectric conductivity aspect of the coolant transported by these pipes nor the release of oligomers and / or ions is disclosed by these pipes.

[0013] There is therefore a need to provide pipes that can be used for fuel cell cooling and that can carry a coolant having a dielectric conductivity that does not release oligomers and / or ions into said coolant.The present invention therefore relates to a single-layer or multi-layer tubular structure for transporting a coolant, said tubular structure being intended for cooling a fuel cell, comprising at least one internal layer (I) comprising at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

[0014] The inventors have therefore unexpectedly found that a single-layer or multi-layer tubular structure for transporting a coolant having a dielectric conductivity of less than 30 pS / cm and comprising at least one internal layer (I) comprising at least one thermoplastic polymer as defined above, allows the cooling of a fuel cell while avoiding the release of oligomers and / or ions into said coolant.

[0015] Throughout the description, the expression "tubular structure", and the terms "tube" or "pipe" have the same meaning and may be used in place of each other.

[0016] Said coolant is any heat transfer liquid, in particular a coolant based on water and additives.

[0017] It is particularly based on glycolated water, in particular based on water with propylene glycol or ethylene glycol.

[0018] The electrical or dielectric conductivity expressed in micro siemens per centimeter (pS / cm) characterizes the ability of a material or solution to allow electrical charges to move freely and therefore allow the passage of an electric current. It is measured on the cooling liquid under magnetic stirring at room temperature after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said cooling liquid using a calibrated conductivity meter with automatic temperature compensation (HORIBA LAQUA-EC220K model equipped with a HORIBA 35523G0E0042 probe).

[0019] Regarding the thermoplastic polymer of the inner layer (I)

[0020] It is selected from a polyolefin, a thermoplastic vulcanizate (TPV), a fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA).

[0021] According to the invention, the inner layer (I) consists essentially of polyolefin, thermoplastic vulcanizate (TPV), fluoropolymer, polyphenylene sulfide (PPS) or polyphthalamide (PPA). The inner layer (I) may in particular also comprise additives or conventional additives in addition to said thermoplastic.

[0022] Among the additives, mention may be made in particular of those chosen from a catalyst, an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a filler, a plasticizer, a flame retardant, a nucleating agent, a colorant, an electrically conductive agent, a thermally conductive agent, an impact modifier or a mixture thereof.

[0023] The inner layer suitably consists of at least 90% by weight, preferably at least 92% by weight, more preferably at least 95% by weight and most preferably at least 98% by weight of polyolefin, thermoplastic vulcanizate (TPV), fluoropolymer, polyphenylene sulfide (PPS) or polyphthalamide (PPA).

[0024] Polyolefin

[0025] In one embodiment, the thermoplastic polymer of the inner layer (I) is a polyolefin chosen from functionalized, non-functionalized polyolefins and a mixture of the two.

[0026] For simplicity, the polyolefin has been designated (B) and functionalized polyolefins (B1) and non-functionalized polyolefins (B2) have been described below.

[0027] 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. Examples include:

[0028] - homopolymers and copolymers of polyethylene, in particular LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene) and metallocene polyethylene.

[0029] - homopolymers or copolymers of propylene.

[0030] - ethylene / alpha-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM),

[0031] - 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.

[0032] The functionalized polyolefin (Bl) may be a polymer of alpha olefins having reactive units (the functionalities); such reactive units are acid, anhydride, or epoxy functions. As an example, mention may be made of the preceding polyolefins (B2) 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 by carboxylic acid anhydrides such as maleic anhydride. A functionalized polyolefin is, for example, a PE / EPR blend, the weight ratio of which can vary widely, for example between 40 / 60 and 90 / 10, said blend being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate of, for example, 0.01 to 5% by weight.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:.

[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-olefin copolymers such as ethylene / propylene, EPR (abbreviation of ethylene-propylene-rubber) and ethylene / propylene / diene (EPDM).

[0035] - styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS) block copolymers.

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

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

[0038] - ethylene vinyl acetate (EVA) and alkyl (meth)acrylate copolymers, containing up to 40% by weight of comonomers.

[0039] 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).

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

[0041] 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 ter monomer (the function) 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 above copolymers, (meth)acrylic acid can be salified with Zn or Li.

[0046] The term "alkyl (meth)acrylate" in (B1) or (B2) denotes C1 to C8 alkyl methacrylates and acrylates, and may be chosen from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate. Furthermore, the aforementioned polyolefins (B1) may also be crosslinked by any suitable method 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 therewith or mixtures of at least two functionalized polyolefins capable of reacting with each other.

[0047] The above-mentioned copolymers, (B1) and (B2), can be copolymerized in a random or block manner and have a linear or branched structure.

[0048] The molecular weight, MFI index, and density of these polyolefins can also vary widely, as those skilled in the art will appreciate. MFI, short for Melt Flow Index, is the melt flow index. It is measured according to ASTM 1238.

[0049] 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, high density PE, medium density PE, linear low density PE, low density PE, very low density PE. These polyethylenes are known to those skilled in the art as being produced according to a “radical” process, according to a “Ziegler” type catalysis or, more recently, according to a so-called “metallocene” catalysis.

[0050] Advantageously, the functionalized polyolefins (Bl) 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® (SK functional polymer) or polyolefins grafted with maleic anhydride such as Orevac® (SK functional polymer) as well as terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride and then condensed with polyamides or monoamine oligomers of polyamide may also be mentioned.

[0051] In one embodiment, the polyolefin is non-functionalized.

[0052] Advantageously, the non-functionalized polyolefin is chosen from a polyethylene and a polypropylene, in particular a polyethylene, in particular a high-density polyethylene (HDPE).

[0053] Thermoplastic vulcanizate

[0054] In another embodiment, the thermoplastic polymer of the inner layer (I) is a thermoplastic vulcanizate (TPV).

[0055] Thermoplastic vulcanizate (TPV) is a mechanical mixture of an olefinic thermoplastic polymer with a polyethylene or polypropylene matrix, in particular a polypropylene matrix, and a vulcanized elastomer such as a vulcanized PP / EPDM (ethylene propylene diene monomer) mixture. The fluoropolymer

[0056] In one embodiment, said thermoplastic polymer of the inner layer (I) is a fluoropolymer.

[0057] Fluoropolymer is a polymer whose repeating unit is a fluorocarbon.

[0058] It can be made up of the following monomers: ethylene (E), propylene (P), vinyl fluoride (VF1), vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoropropylvinylether (PPVE), perfluoromethylvinylether (PMVE) and chlorotrifluoroethylene (CTFE): CFCI=CF2.

[0059] In particular, the fluoropolymer is selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylene (ETFE), a terpolymer of tetrafluoroethylene, ethylene, and hexafluoropropylene (EFEP), a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and mixtures thereof, in particular ethylene tetrafluoroethylene (ETFE).

[0060] Polyphenylene sulfide (PPS)

[0061] In one embodiment, said thermoplastic polymer of the inner layer (I) is a polyphenylene sulfide (PPS).

[0062] Polyphenylene sulfide (PPS) is a thermostable semi-crystalline polymer.

[0063] Polyphthalamide (PPA)

[0064] In one embodiment, said thermoplastic polymer of the inner layer (I) is a polyphthalamide (PPA).

[0065] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0066] Polyphthalamide can be a homopolyamide or a copolyamide.

[0067] When in homopolyamide form, it has the formula XAr or MXDY.

[0068] XAr denotes a unit obtained from the 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.

[0069] The diamine can be linear or branched. Advantageously, it is linear.

[0070] Said 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-undecamethylenediamine, 1,12-dodecamethyldiamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine, octadecenediamine, eicosanediamine, docosanediamine and diamines obtained from fatty acids. Advantageously, said at least one diamine X is C6-C18 and chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine.

[0071] Advantageously, said at least one diamine X in C6 to C12, is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0072] Advantageously, said at least one diamine X in C6 to C12, is in particular chosen from 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

[0073] Advantageously, the diamine X used is C10 to C12, in particular chosen from 1,10-decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine. The aromatic dicarboxylic acid being advantageously chosen from terephthalic acid (denoted T), isophthalic acid (denoted I) and 2,6-naphthalene dicarboxylic acid (denoted N) or mixtures thereof, in particular it is chosen from terephthalic acid (denoted T), isophthalic acid (denoted I) or mixtures thereof. MXDY denotes a unit obtained from the polycondensation of the diamine metaxylylene diamine (MXD) and at least one aliphatic dicarboxylic acid Y.

[0074] Said at least one C6 to C36 dicarboxylic acid Y may be chosen 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.

[0075] The diacid can be linear or branched. Advantageously, it is linear.

[0076] Advantageously, said at least one dicarboxylic acid Y is C6 to C18 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid.

[0077] Advantageously, said at least one dicarboxylic acid Y is C6 to C12 and is chosen from adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid.

[0078] Advantageously, said at least one dicarboxylic acid Y is C10 to C12 and is chosen from sebacic acid, undecanedioic acid, dodecanedioic acid. When said aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y, it can therefore comprise a single diamine or several diamines and a single dicarboxylic acid or several dicarboxylic acids. Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single diamine X with a single dicarboxylic acid Y.

[0079] In particular, polyphthalamide (PPA) is chosen from PA5T, PA6T, PA9T, PA10T, PA11T, PA12T, MXD6, MXD10, MXD12.

[0080] It should be noted that throughout the description, the C9 diamine comprises 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.

[0081] When in copolyamide form, it has the formula:

[0082] 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 the PA1212 / 12T, in particular the PA11 / 10T and the PA11 / 12T.

[0083] It is in particular of formula X / YAr, as described in EP1505099, in particular a semi-aromatic polyamide of formula A / XT in which A is chosen from a unit obtained from an amino acid, a unit obtained from a lactam and a unit corresponding to the formula (Ca diamine). (Cb diacid), with a representing the number of carbon atoms of the diamine and b representing the number of carbon atoms of the diacid, a and b each being between 4 and 36, advantageously between 9 and 18, the unit (Ca diamine) being chosen from linear or branched aliphatic diamines, cycloaliphatic diamines and alkylaromatic diamines and the unit (Cb diacid) being chosen from linear or branched aliphatic diacids, cycloaliphatic diacids and aromatic diacids;

[0084] XT denotes a unit obtained from the polycondensation of a Cx diamine and terephthalic acid, with x representing the number of carbon atoms of the Cx diamine, x being between 6 and 36, advantageously between 9 and 18, in particular a polyamide of formula A / 5T, A / 6T, A / 9T, A / 10T, A / 11T or A / 12T, A being as defined above, in particular a polyamide chosen from a PA 5T / 10T, a PA11 / 10T, a PA MPMDT / 6T, a PA MXDT / 6T, a PA MXDT / 10T, a PA MPMDT / 10T, a PA BACT / 6T, a PA BACT / 10T, a PA 11 / BACT, a PA 11 / 6T / 10T, PA BACT / 10T / 6T, a PA 11 / BACT / 6T, PA 11 / MPMDT / 6T, PA 11 / MPMDT / 10T, PA 11 / BACT / 10T, one PA 11 / MXDT / 6T, one PA 11 / MXDT / 10T, one 11 / 5T / 10T.

[0085] T stands for terephthalic acid, MXD stands for m-xylylenediamine, MPMD stands for methylpentamethylenediamine, and BAC stands for bis(aminomethyl)cyclohexane.

[0086] In particular, said thermoplastic polymer of the inner layer (I) is a polyphthalamide (PPA) selected 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.

[0087] Regarding the structure as such.

[0088] Tubular structure of the invention can be single-layer or multi-layer and it is used for transporting a coolant, and said tube being intended for cooling fuel cells.

[0089] Whether single-layer or multi-layer, it comprises at least one layer (I) which comprises at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

[0090] In one embodiment, it comprises at least one layer (I) which comprises at least one thermoplastic polymer chosen from a non-functionalized polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

[0091] In one embodiment, it comprises at least one layer (I) which comprises at least one thermoplastic polymer chosen from a non-functionalized polyolefin, a thermoplastic vulcanizate (TPV), a fluoropolymer chosen from ETFE, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

[0092] In another embodiment, it comprises at least one layer (I) which comprises at least one thermoplastic polymer chosen from a non-functionalized polyolefin, a thermoplastic vulcanizate (TPV), a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

[0093] In a first variant, said structure is single-layer and layer (I) is therefore in contact with the cooling liquid.

[0094] In a second variant, said structure is multi-layered and layer (I) is therefore the internal layer which is in contact with the coolant.

[0095] In one embodiment of this second variant, said structure is multilayer and it comprises an outer layer (II) comprising at least one thermoplastic polymer, in particular a polyamide. In one embodiment, said structure is multilayer and it comprises an outer layer (II) consisting of at least one thermoplastic polymer, in particular a polyamide.

[0096] Advantageously, said structure is two-layer and is therefore made up from the outside to the inside of the layers (ll) / / (l).

[0097] Advantageously, said internal layer (I) consists of at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA).

[0098] Advantageously, said external layer (II) consists of at least one thermoplastic polymer, in particular a polyamide.

[0099] Advantageously, said inner layer (I) consists of at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA) and said outer layer (II) consists of at least one thermoplastic polymer, in particular a polyamide.

[0100] The outer layer (II) may also include additives or conventional additives in addition to said thermoplastic.

[0101] Among the additives, mention may be made in particular of those chosen from a catalyst, an antioxidant, a thermal stabilizer, a UV stabilizer, a light stabilizer, a lubricant, a filler, a plasticizer, a flame retardant, a nucleating agent, a colorant, an electrically conductive agent, a thermally conductive agent, an impact modifier or a mixture thereof.

[0102] 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 thermoplastic polymer, in particular a polyamide.

[0103] In one embodiment, said tubular structure releases a quantity of ions into said coolant less than or equal to 700 mg / kg of ions, more particularly less than or equal to 500 mg / kg, in particular less than or equal to 300 mg / kg, in particular less than or equal to 100 mg / kg, the quantity of ions released being determined on a single-layer tube of 8x1 mm2 by inductively coupled plasma mass spectrometry (ICP-MS) or by ion chromatography comprising said coolant.

[0104] Regarding the polyamide of the outer layer (II)

[0105] The polyamide (PA) may be a homopolyamide or a copolyamide or a mixture thereof.

[0106] Advantageously, the polyamide is chosen from semi-crystalline aliphatic polyamides, cycloaliphatic polyamides, and semi-aromatic polyamides (polyphthalamides or PPA).

[0107] In particular, the polyamide of layer (II) is chosen from a semi-crystalline aliphatic polyamide having an average number of carbon atoms per nitrogen atom of C4 to C15 and a semi-aromatic polyamide (PPA). The semi-crystalline aliphatic polyamide of the outer layer (II)

[0108] Semi-crystalline polyamide is understood to mean a material which is generally solid at room temperature and which softens when the temperature increases, in particular after passing its glass transition temperature (Tg), and which can exhibit a clear melting when passing its so-called melting temperature (Tf), and which becomes solid again when the temperature decreases below its crystallization temperature.

[0109] Tg, Te and Tf are determined by differential scanning calorimetry (DSC) according to 11357-2:2013 and 11357-3:2013 respectively.

[0110] The number-average molecular mass Mn of said semi-crystalline polyamide is preferably in a range from 10,000 to 85,000, in particular from 10,000 to 60,000, preferably from 10,000 to 50,000, even more preferably from 12,000 to 50,000. These Mn values ​​may correspond to inherent viscosities greater than or equal to 0.8 as determined in m-cresol according to standard ISO 307:2007 but by changing the solvent (use of m-cresol instead of sulfuric acid and the temperature being 20°C).

[0111] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0112] The term polyamide includes both homopolyamides and copolyamides

[0113] Said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, or from the polycondensation of at least one amino acid, or from the polycondensation of at least one diamine X with at least one dicarboxylic acid Y or from their mixtures.

[0114] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, said at least one lactam may be chosen from a C8 to C18 lactam, preferably a C10 to C18 lactam, more preferably a C10 to C12 lactam. A C8 to C18 lactam is in particular decanolactam, undecanolactam, and lauryllactam.

[0115] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, it can therefore comprise a single lactam or several lactams.

[0116] Advantageously, said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single lactam and said lactam is chosen from lauryllactam and undecanolactam, advantageously lauryllactam.

[0117] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, said at least one amino acid may be chosen from a C8 to C18 amino acid, preferably a C10 to C18 amino acid, more preferably a C10 to C12 amino acid. A C8 to C18 amino acid is in particular 9-aminononanoic acid, 10-aminodecanoic acid, 10-aminoundecanoic acid, 12-aminododecanoic acid and 11-aminoundecanoic acid as well as its derivatives, in particular N-heptyl-11-aminoundecanoic acid.

[0118] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one amino acid, it can therefore comprise a single amino acid or several amino acids.

[0119] Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single amino acid and said amino acid is chosen from 10-aminodecanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid, advantageously 11-aminoundecanoic acid.

[0120] When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine X with 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.

[0121] In one embodiment, the polyamide of layer (II) is selected from a semi-crystalline aliphatic polyamide having an average number of carbon atoms per nitrogen atom of C4 to C15 and a semi-aromatic polyamide (PPA).

[0122] In particular, the polyamide of layer (II) is a semi-crystalline aliphatic polyamide which has an average number of carbon atoms per nitrogen atom from C8 to C15, in particular from C9 to C15, in particular from C10 to 15.

[0123] In particular, the semi-crystalline aliphatic polyamide of layer (II) is chosen from PA610, PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12, in particular PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12, in particular PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12.

[0124] Advantageously, the semi-crystalline aliphatic polyamide of layer (II) is chosen from PAU and PA12.

[0125] The semi-aromatic polyamide of the outer layer (II)

[0126] It is as defined for the PPA of the inner layer (I).

[0127] In another embodiment of this second variant, said structure is multi-layer and it comprises an external layer (II) comprising at least one thermoplastic polymer, in particular a polyamide and a binder layer (III) located between said internal layer (I) and said external layer (II).

[0128] Advantageously, said structure is three-layer and is therefore made up from the outside to the inside of the layers (I l) / / binder / / (l).

[0129] Advantageously, said inner layer (I) consists of at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA). Advantageously, said outer layer (II) consists of at least one thermoplastic polymer, in particular a polyamide.

[0130] Advantageously, said inner layer (I) consists of at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA) and said outer layer (II) consists of at least one thermoplastic polymer, in particular a polyamide.

[0131] In one embodiment of this second variant and its embodiments, the internal layer (I) has a thickness representing from 5% to 95% of the total thickness of said structure.

[0132] In another embodiment of this second variant and its embodiments, the external layer (II) has a thickness of at least 5% of the total thickness of said structure.

[0133] In yet another embodiment of this second variant and its embodiments, the inner layer (I) has a thickness of 5 to 95% of the total thickness of said structure and the outer layer (II) has a thickness of at least 5% of the total thickness of said structure.

[0134] Regarding the binder layer

[0135] Said binder layer may comprise a binder as described, in particular in patents EP 1452307 and EP1162061, EP 1216826 and EP0428833.

[0136] It is implied that layers (II) and (binder) or (I) and (binder) adhere to each other. The binder layer is intended to be inserted between two layers that do not adhere or adhere with difficulty to each other.

[0137] The binder may be, for example, but not limited to, a composition based on 50% copolyamide 6 / 12 (70 / 30 ratio by mass) of Mn 16000, and 50% copolyamide 6 / 12 (30 / 70 ratio by mass) of Mn 16000, a composition based on PP (polypropylene) grafted with maleic anhydride, known as Admer® QF551A from Mitsui, a composition based on PA610 (of Mn 30000, and as defined elsewhere) and 36% PA6 (of Mn 28000) and 1.2% organic stabilizers (consisting of 0.8% phenol Lowinox® 44B25 from Great Lakes, 0.2% phosphite Irgafos® 168 from BASF, 0.2% of anti-UV Tinuvin® 312 from BASF), a composition based on PA612 (of Mn 29000, and as defined elsewhere) and 36% of PA6 (of Mn 28000, and as defined elsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenol Lowinox® 44B25 from Great Lakes, 0.2% of phosphite Irgafos® 168 from BASF, 0.2% of anti-UV Tinuvin® 312 from BASF), a composition based on PA610 (of Mn 30000, and as defined elsewhere) and 36% of PA12 (of Mn 35000, and as defined elsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenol Lowinox® 44B25 from Great Lakes, 0.2% of phosphite Irgafos® 168 from BASF, 0.2% of anti-UV Tinuvin® 312 from BASF), a composition based on 40% PA6 (of Mn 28000, and as defined elsewhere), 40% of PA12 (of Mn 35000, and as defined elsewhere) and 20% of functionalized EPR Exxelor® VA1801 (Exxon company) and 1.2% organic stabilizers (consisting of 0.8% Lowinox® 44B25 phenol from Great Lakes company, 0.2% Irgafos® 168 phosphite from BASF company, 0.2% Tinuvin® 312 UV stabilizer from BASF company) or a composition based on 40% PA6.10 (of Mn 30000, and as defined elsewhere), 40% of PA6 (of Mn 28000, and as defined elsewhere) and 20% of ethylene / ethyl acrylate / anhydride type impact modifier in a mass ratio of 68.5 / 30 / 1.5 (MFI 6 at 190°C under 2.16 kg), and 1.2% of organic stabilizers (consisting of 0.8% of Lowinox® 44B25 phenol from Great Lakes, 0.2% of Irgafos® 168 phosphite from BASF, 0.2% of Tinuvin® 312 UV stabilizer from BASF).

[0138] It is obvious that the multilayer tubular structure of the invention could comprise other layers, provided that layer (I) is always the internal layer and that layer (II) is always the external layer and that there is adhesion between the different layers.

[0139] For example, we can imagine a structure of the type (from the exterior to the interior):

[0140] (I l) / / binder / / PA / / binder / / (l).

[0141] Whatever the tubular structure described above, said tubular structure has a quantity of soluble and insoluble extractables released into said cooling liquid of less than 1 g / m 2 , after aging for 1200 hours at 80°C of said multilayer tubular structure in contact with said cooling liquid.

[0142] According to another aspect, the present invention relates to a tubular structure as defined above, for cooling a fuel cell.

[0143] All the characteristics defined for the structure are valid for its use.

[0144] EXAMPLES

[0145] The invention will now be described in more detail with the aid of the following examples which are not limiting.

[0146] The following structures were prepared by extrusion:

[0147] Multilayer tubes are produced by coextrusion. A McNeil industrial multilayer extrusion line is used, equipped with 5 extruders, connected to a multilayer extrusion head with spiral mandrels.

[0148] The screws used are single-screw extrusions with screw profiles adapted to polyamides. In addition to the 5 extruders and the multi-layer extrusion head, the extrusion line includes:

[0149] - a die-punch assembly, located at the end of the coextrusion 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 it is made of, as well as the dimensions of the tube and the line speed;

[0150] - a vacuum tank with an adjustable depression level. In this tank circulates water maintained at 20°C in general, in which a gauge is immersed to conform the tube to its final dimensions. The diameter of the gauge is adapted to the dimensions of the tube to be produced, typically from 8.5 to 10 mm for a tube with an external diameter of 8 mm and a thickness of 1 mm; - a succession of cooling tanks in which water is maintained at around 20°C, allowing the tube to be cooled along the route from the head to the drawing bench;

[0151] - a diameter gauge;

[0152] - a draw bench.

[0153] The 5 extruder configuration is used to produce tubes ranging from 2 layers to 5 layers.

[0154] In the case of structures with fewer than 5 layers, several extruders are then fed with the same material.

[0155] In the case of structures with 6 layers, an additional extruder is connected and a spiral mandrel is added to the existing head, in order to create the internal layer, in contact with the fluid.

[0156] Before testing, in order to ensure the best tube properties 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 testing, generally in a vacuum dryer, for 1 night at 80°C.

[0157] The tubes, which meet the characteristics described in this patent application, were taken after stabilization of the extrusion parameters, the target tube dimensions no longer changing over time. The diameter is controlled by a laser diameter meter installed at the end of the line. Generally, the line speed is typically 20m / min. It generally varies between 5 and 100m / min.

[0158] The screw speed of extruders depends on the layer thickness and screw diameter as is known to those skilled in the art.

[0159] Generally speaking, the temperatures of the extruders and tools (head and connector) must be set so as to be sufficiently higher than the melting temperature of the compositions in question, so that they remain in the molten state, thus preventing them from solidifying and blocking the machine.

[0160] The tubular structures were tested on different parameters (Table 1).

[0161] The amount of soluble and insoluble extractables after 1200 h at 80°C, electrical conductivity, total extractable ion amount, coolant resistance as well as shock and burst at 110°C were evaluated.

[0162] PAU = Rilsan BESN P123 Black TL (Arkema)

[0163] Fluorinated polymer: ETFE EP7000 (Daikin Chemicals)

[0164] PA9T: Genestar N1001D (Kuraray)

[0165] Binder 1: Orevac® 18342N (SK functional polymers)

[0166] Binder2: Orevac® 18729 (SK functional polymers)

[0167] HDPE = Lupolen®4261 AIM (LyondelIBasell) PP = SABIC®PP 4935 (Sabie)

[0168] TPV: Santoprene (R° 101-87 (Exxonmobil)

[0169] [Table 1]

[0170] NT: not tested

[0171] Table 2 shows the tests used and the classification of the results.

[0172] [Table 2]

Claims

CLAIMS 1. Single-layer or multi-layer tubular structure for transporting a coolant, said tube being intended for cooling a fuel cell, comprising at least one internal layer (I) comprising at least one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluorinated polymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), said coolant having a dielectric conductivity of less than 30 pS / cm, as determined after aging for 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said coolant.

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

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

4. Single-layer or multi-layer tubular structure according to one of claims 1 to 3, characterized in that said thermoplastic polymer of the internal layer (I) is a polyolefin chosen from non-functionalized polyolefins, functionalized polyolefins and a mixture thereof.

5. Single-layer or multi-layer tubular structure according to one of claims 1 to 4, characterized in that said polyolefin of the internal layer (I) is a non-functionalized polyolefin.

6. Single-layer or multi-layer tubular structure according to claim 5, characterized in that said non-functionalized polyolefin is chosen from a polyethylene and a polypropylene, in particular a polyethylene, in particular a high-density polyethylene.

7. Multilayer tubular structure according to one of claims 1 to 3, characterized in that said thermoplastic polymer of the internal layer (I) is a fluorinated polymer, in particular chosen from poly(vinylidene fluoride) (PVDF), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), ethylene tetrafluoroethylene, a terpolymer of tetrafluoroethylene, ethylene, and hexafluoropropylene (EFEP), a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and mixtures thereof, including polyvinylidene fluoride (PVDF). Multilayer tubular structure according to one of claims 1 to 3, characterized in that said thermoplastic polymer of the inner layer (I) is a polyphthalamide (PPA), in particular 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.Multilayer tubular structure according to one of claims 3 to 8, characterized in that the polyamide of layer (II) is chosen from a semi-crystalline aliphatic polyamide having an average number of carbon atoms per nitrogen atom of C4 to C15 and a semi-aromatic polyamide (PPA). Multilayer tubular structure according to claim 9, characterized in that the polyamide of layer (II) is a semi-crystalline aliphatic polyamide which has an average number of carbon atoms per nitrogen atom of C8 to C15, in particular of C9 to C15, in particular of C10 to 15.Multilayer tubular structure according to claim 10, characterized in that the semi-crystalline aliphatic polyamide is chosen from PA610, PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12, in particular PA612, PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12, in particular PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PAU and PA12, in particular PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, PA1214, PA1218, PA1214, PA1218, PAU and PA12. Multilayer tubular structure according to claim 10 or 11, characterized in that the semi-crystalline aliphatic polyamide is chosen from PAU and PA12. Multilayer tubular structure according to one of claims 3 to 12, characterized in that the internal layer (I) has a thickness representing from 5% to 95% of the total thickness of said structure.

14. Multilayer tubular structure according to one of claims 3 to 12, characterized in that the external layer (II) has a thickness of at least 5% of the total thickness of said structure.

15. Multilayer tubular structure according to one of claims 13 or 14, characterized in that the internal layer (I) has a thickness of 5 to 95% of the total thickness of said structure and the external layer (II) has a thickness of at least 5% of the total thickness of said structure.

16. Multilayer tubular structure according to one of claims 3 to 15, characterized in that said tubular structure comprises a binder layer (III) located between said internal layer (I) and said external layer (II).

17. Single-layer or multi-layer tubular structure according to one of claims 1 to 16, characterized in that said tubular structure has a quantity of soluble and insoluble extractables released into said cooling liquid of less than 1 g / m 2 , after aging for 1200 hours at 80°C of said multilayer tubular structure in contact with said cooling liquid.

18. Use of a tubular structure as defined in one of claims 1 to 17, for cooling a fuel cell.

Images