WO2024009042A1

WO2024009042A1 - Tubular structure with low ionic conductivity

Info

Publication number: WO2024009042A1
Application number: PCT/FR2023/051039
Authority: WO
Inventors: Marjorie MARCOURT; Sébastien VAUTIER; Antoine GOUPIL
Original assignee: Arkema France
Priority date: 2022-07-07
Filing date: 2023-07-06
Publication date: 2024-01-11
Also published as: FR3137605A1

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

DESCRIPTION

TITLE OF THE INVENTION: TUBULAR STRUCTURE WITH LOW ION CONDUCTIVITY

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

[Prior art]

The fuel cell is an electrochemical energy generator allowing the direct transformation of the chemical energy of a fuel (hydrogen for example) into electrical energy. Thermal control of this battery is important to guarantee good performance and a good lifespan. The most efficient and economical system remains heat exchange by fluid.

The heat transfer fluid will circulate within the cells. The fluid must therefore be dielectric so as not to disrupt the performance of the battery or even deteriorate it. The fluid must also not contain chemical elements (oligomer, additives) which could pollute the cells.

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

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.

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

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

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).

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

There is therefore the need to provide pipes which can be used for cooling fuel cells capable of transporting a cooling liquid having a dielectric conductivity which does not release oligomers and/or ions into said cooling liquid. The present invention therefore relates to a single-layer or multi-layer tubular structure for transporting a cooling liquid, said tubular structure 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 fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), said coolant having a dielectric conductivity of less than 30 pS/cm, as determined after aging of 168 hours at 80°C of said single-layer or multi-layer tubular structure in contact with said cooling liquid.

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

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

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

It is notably based on glycol water, in particular based on water with propylene glycol or ethylene glycol.

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

Regarding the thermoplastic polymer of the inner layer (I)

It is chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA).

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

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 electrical conductive agent, a thermal conductive agent, an impact modifier or a mixture thereof.

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).

Polyolefin

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

For simplicity, the polyolefin has been designated by (B) and functionalized polyolefins (Bl) and non-functionalized polyolefins (B2) have been described below.

A non-functionalized polyolefin (B2) is conventionally a homopolymer or copolymer of alpha olefins or diolefins, such as for example ethylene, propylene, 1-butene, 1-octene, butadiene. As an example, we can cite:

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

-propylene homopolymers or copolymers.

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

- 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 carboxylic acids saturated such as vinyl acetate (EVA), the proportion of comonomer being able to reach 40% by weight.

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. By way of example, mention may be made of the preceding polyolefins (B2) grafted or co- or ter polymerized with unsaturated epoxides such as glycidyl (meth) acrylate, or with carboxylic acids or the corresponding salts or esters such as (meth)acrylic acid (this can be totally or partially neutralized by metals such as Zn, etc.) or by carboxylic acid anhydrides such as maleic anhydride. A functionalized polyolefin is for example a PE/EPR mixture, the weight ratio of which can vary widely, for example between 40/60 and 90/10, said mixture being co-grafted with an anhydride, in particular maleic anhydride, according to a grafting rate for example of 0.01 to 5% by weight. 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 0.01 to 5% by weight:

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

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

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

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

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

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

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

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

As an example of functionalized polyolefins of the latter type, the following copolymers may be cited, 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:

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

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

- ethylene/vinyl acetate or alkyl (meth)acrylate/(meth)acrylic acid or maleic anhydride or glycidyl methacrylate copolymers.

In the above copolymers, the (meth)acrylic acid can be salified with Zn or Li.

The term "(meth)alkyl acrylate" in (Bl) or (B2) designates C1 to C8 alkyl methacrylates and acrylates, and can be chosen from methyl acrylate, ethyl acrylate , n-butyl acrylate, iso-butyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate. Furthermore, the aforementioned polyolefins (Bl) can also be crosslinked by any appropriate process or agent (diepoxy, diacid, peroxide, etc.); the term functionalized polyolefin also includes mixtures of the aforementioned polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, etc. capable of reacting with these or mixtures of at least two functionalized polyolefins capable of reacting with each other.

The copolymers mentioned above, (Bl) and (B2), can be copolymerized randomly or block-wise and have a linear or branched structure.

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

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 higher alpha olefin type comonomer such as butene, hexene, octene or 4-methyl 1-Pentene. We can cite for example PP, high density PE, medium density PE, linear low density PE, low density PE, very low density PE. These polyethylenes are known by 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 “metlocene” catalysis.

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. As examples of such polymers, mention may be made of ter polymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate such as Lotader® (SK functional polymer) or polyolefins grafted by maleic anhydride such as Orevac® (SK functional polymer) as well as ter polymers of ethylene, alkyl acrylate and (meth)acrylic acid. We can also cite homopolymers or copolymers of polypropylene grafted with a carboxylic acid anhydride then condensed with polyamides or monoamino polyamide oligomers.

In one embodiment, the polyolefin is non-functionalized.

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

Thermoplastic vulcanizate

In another embodiment, the thermoplastic polymer of the internal layer (I) is a thermoplastic vulcanizate (TPV).

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

In one embodiment, said thermoplastic polymer of the internal layer (I) is a fluoropolymer.

Fluorinated polymer is a polymer whose repeating unit is a fluorocarbon.

It may consist of the following monomers: ethylene (E), propylene (P), vinyl fluoride (VF1), vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoropropylvinyl ether (PPVE), perfluoromethyl vinyl ether (PMVE) and chlorotrifluoroethylene (CTFE): CFCI=CF2.

In particular, the fluoropolymer is chosen from poly(vinylidene 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, including ethylene tetrafluoroethylene (ETFE).

Polyphenylene sulfide (PPS)

In one embodiment, said thermoplastic polymer of the internal layer (I) is a polyphenylene sulfide (PPS).

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

Polyphthalamide (PPA)

In one embodiment, said thermoplastic polymer of the internal layer (I) is a polyphthalamide (PPA).

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

The polyphthalamide may be a homopolyamide or a copolyamide.

When it is in the form of homopolyamide, it has the formula XAr or MXDY.

XAr designates a unit obtained from the polycondensation of a diamine

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

Said at least one C6-C36 diamine 1,11-undecamethylenediamine, 1,12-dodecamethylediamine, 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 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine, 1,13-tridecamethylenediamine, 1,14-tetradecamethylenediamine, 1,16-hexadecamethylenediamine and 1,18-octadecamethylenediamine.

Advantageously, said at least one diamine decamethylenediamine, 1,11-undecamethylenediamine, 1,12-dodecamethylenediamine.

Advantageously, the diamine The aromatic dicarboxylic acid being advantageously chosen from terephthalic acid (noted T), isophthalic acid (noted I) and 2,6 naphthalene dicarboxylic acid (noted N) or their mixtures, in particular it is chosen from terephthalic acid (noted T), isophthalic acid (noted I) or their mixtures. MXDY designates a unit obtained from the polycondensation of the diamine metaxylylene diamine (MXD) and at least one aliphatic dicarboxylic acid Y.

Said at least one dicarboxylic acid Y in C6 to C36 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.

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

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.

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.

Advantageously, said at least one dicarboxylic acid Y is CIO 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 Advantageously, said aliphatic semi-crystalline polyamide is obtained from the polycondensation of a single diamine X with a single dicarboxylic acid Y.

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

It should be noted that throughout the description, the C9 diamine comprises a diamine unit, containing 60 mole % or more of a 1,9-nonanediamine unit and/or a 2-methyl-1,8-octanediamine unit relative to all diamine units at C9.

When it is in copolyamide form, it has the formula:

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.

It is in particular of formula X/YAr, as described in EP1505099, notably 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 (diamine in Ca). (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 motif (Ca diamine) being chosen from aliphatic, linear or branched diamines, cycloaliphatic diamines and alkylaromatic diamines and the motif (Cb diacid) being chosen from linear or branched aliphatic diacids, cycloaliphatic diacids and aromatic diacids ;

X.T designates 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, 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, a PA 11/MXDT/ 6T, one PA 11/MXDT/10T, one 11/5T/10T.

T is terephthalic acid, MXD is m-xylylene diamine, MPMD is methylpentamethylene diamine, and BAC is bis(aminomethyl)cyclohexane.

In particular, said thermoplastic polymer of the internal 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 the PA1212/12T, in particular the PA11/10T and the PA11/12T.

Regarding the structure as such.

Tubular structure of the invention can be single-layer or multi-layer and it is used for transporting a cooling liquid, and said tube being intended for fuel cell cooling.

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 fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity less than 30 pS/cm, as determined after aging for 168 hours at 80°C of said single-layer or multilayer tubular structure in contact with said coolant.

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, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), and said coolant having a dielectric conductivity less than 30 pS/cm, as determined after aging for 168 hours at 80°C of said single-layer or multilayer tubular structure in contact with said coolant.

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 cooling liquid having a dielectric conductivity less than 30 pS/cm, as determined after aging for 168 hours at 80°C of said monolayer or multilayer tubular structure in contact with said cooling liquid. cooling.

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 cooling liquid having a dielectric conductivity less than 30 pS/cm, as determined after aging for 168 hours at 80°C of said single-layer or multilayer tubular structure in contact with said cooling liquid.

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

In a second variant, said structure is multilayer and layer (I) is therefore the internal layer which is in contact with the cooling liquid.

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

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

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

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

Advantageously, said internal layer (I) consists of at least said one thermoplastic polymer chosen from a polyolefin, a thermoplastic vulcanizate (TPV), a fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA) and said layer external (II) consists of at least said one thermoplastic polymer, in particular a polyamide.

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

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

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 most preferably at least 98%. by weight of thermoplastic polymer, in particular a polyamide.

In one embodiment, said tubular structure releases a quantity of ions into said cooling liquid 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 liquid cooling.

Concerning the polyamide of the outer layer (II)

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

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

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)

The term semi-crystalline polyamide means a material that is generally solid at room temperature, and which softens upon an increase in temperature, in particular after passing its glass transition temperature (Tg), and which may present a clear melting upon passage. of its so-called melting temperature (Tf), and which becomes solid again when the temperature drops below its crystallization temperature.

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

The number average molecular mass Mn of said semi-crystalline polyamide is preferably in a range going 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 can correspond at 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 in place of sulfuric acid and the temperature being 20°C).

The term polyamide includes both homopolyamides and copolyamides.

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 at least one dicarboxylic acid Y or mixtures thereof.

When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one lactam, said at least one lactam can be chosen from a C8 to C18 lactam, preferably CIO to C18, more preferably CIO at C12. A C8 to C18 lactam includes decanolactam, undecanolactam, and lauryllactam.

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.

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.

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 can be chosen from a C8 to C18 amino acid, preferably CIO to C18, more preferably CIO at C12. 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 the acid N-heptyl-ll-aminoundecanoic.

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.

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.

When said at least one aliphatic semi-crystalline polyamide is obtained from the polycondensation of at least one diamine as defined above.

In one embodiment, 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) .

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 CIO to 15.

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.

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

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

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

In another 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 and a binder layer (III) located between said inner layer (I ) and said outer layer (II).

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

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

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.

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

In yet another embodiment of this second variant and its embodiments, 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 at least 5% of the total thickness of said structure.

Regarding the binder layer

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

It is implicit that the layers (II) and (binder) or (I) and (binder) adhere to each other. The binder layer is intended to be inserted between two layers which do not or have difficulty adhering to each other.

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

It is quite 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 has adhesion between the different layers.

For example, we can imagine a structure of the type (from the outside to the inside):

(I l)//binder//PA//binder//(l).

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

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

All characteristics defined for the structure are valid for its use.

EXAMPLES

The invention will now be described in more detail using the following examples which are not limiting.

The following structures were prepared by extrusion:

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

The screws used are single extrusion screws with screw profiles suitable for polyamides. In addition to the 5 extruders and the multilayer extrusion head, the extrusion line includes:

- 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 which compose it, as well as the dimensions of the tube and the line speed;

- a vacuum tank with an adjustable depression level. Water circulates in this tank, generally maintained at 20°C, into 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 the water is maintained at around 20°C, allowing the tube to be cooled along the route from the head to the draw bench;

- a diameter measurer;

- a drawing bench.

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

In the case of structures with a number of layers less than 5, several extruders are then fed with the same material.

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 produce the internal layer, in contact with the fluid.

Before the tests, in order to ensure the best tube properties and good extrusion quality, we check that the extruded materials have a residual humidity level before extrusion of less than 0.08%. Otherwise, an additional step of drying the material is carried out before the tests, generally in a vacuum dryer, for 1 night at 80°C.

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

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

In general, the temperatures of the extruders and the tools (head and connector) must be adjusted so as to be sufficiently higher than the melting temperature of the compositions considered, so that they remain in the molten state, thus avoiding that they solidify and block the machine.

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

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

PAU = Rilsan BESN P123 Black TL (Arkema)

Fluorinated polymer: ETFE EP7000 (Daikin Chemicals)

PA9T: Genestar N1001D (Kuraray)

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

Binder2: Orevac® 18729 (SK functional polymers)

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

TPV: Santoprene (R° 101-87 (Exxonmobil)

[Table 1]

NT: not tested

Table 2 shows the tests used and the classification of the results.

[Table 2]

Claims

1. Single-layer or multi-layer tubular structure for transporting a cooling liquid, said 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 vulcanizate thermoplastic (TPV), a fluoropolymer, a polyphenylene sulfide (PPS) and a polyphthalamide (PPA), said coolant having a dielectric conductivity 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 cooling liquid.

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

3. Single-layer or multi-layer tubular structure for transporting a cooling liquid 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 of these. this.

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 fluoropolymer, 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, in particular poly(vinylidene fluoride) ( PVDF). Multilayer tubular structure according to one of claims 1 to 3, characterized in that said thermoplastic polymer of the internal 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, particularly the PA11/10T and the PA11/12T. Multilayer tubular structure according to one of claims 3 to 8, characterized in that the polyamide of the layer (II) is chosen from a semi-crystalline aliphatic polyamide having an average number of carbon atoms per C4 nitrogen atom at 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 from CIO 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, the PA1210, the PA1212, PA1214, PA1218, the PAU and the PA12, in particular the PA612, the PA614, PA618, the PA1010, PA1012, PA1014, PA1018, the PA1210, the PA1212, PA1214, PA1218, the PAU and the PA12 , including PA614, PA618, PA1010, PA1012, PA1014, PA1018, PA1210, PA1212, 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% 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 less than lg/m ² , after aging of 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 fuel cell cooling.