Multi-layer tubular structure for transporting heat transfer fluids - Patents.com

Abstract

The present invention relates to a multi-layer tubular structure (MLT) for transporting a heat transfer fluid, the multi-layer tubular structure comprising: at least one layer (1) comprising a composition (1) that mainly comprises at least one long-chain polyamide (PA) having from 10 to 15 carbon atoms per nitrogen atom and that comprises at least 50% of aliphatic units relative to the total of the units present in said long-chain polyamide; at least one layer (2) located beneath said layer (1), comprising a composition (2) mainly comprising at least one polyamide having from 4 to 9 carbon atoms per nitrogen atom; at least one layer (3) comprising a composition (3) comprising mainly a hydrophobic polymer, in particular polypropylene or polyethylene, a layer (4) comprising a composition (4) comprising PA6, PA66 or a mixture thereof, the composition (4) comprising from 5% to 50% by weight of at least one polyolefin, up to 2% by weight of at least one plasticizer and up to 2% by weight of additives, relative to the total weight of the composition (4); Alternatively, a layer (4) containing any one of the compositions (4') mainly containing at least one C8 to C14 aliphatic polyamide; Including, The layer (4) is in contact with the fluid to be transported, A multi-layer tubular structure, wherein the thickness of said layer (2) occupies at least 70% of the total thickness of the tube.

Description

[Technical field]

[0001] [Technical field] This patent application relates to the application of heat transfer fluids, more particularly hydrocarbon compounds, hydrofluorocarbons, ethers, hydrofluoroethers, CO 2 , N.H. 3 , S.O. 2 and a multi-layer tubular structure (MLT) intended for the transport of refrigerant fluids selected from fluoroolefins, in particular R134, R-1234yf or R-1234ze, more particularly R-1234yf or R-1234ze, and its use for transporting said heat transfer fluids. [Background technology]

[0002] [Prior Art] Tubular structures for transporting heat transfer fluids in the field of automotive air conditioning require two opposing properties: water permeability and high temperature burst (125°C), which must exceed 83 bar.

[0003] Thus, the use of short chain polyamides would be inappropriate for this first property, since long chain polyamides would be able to meet this first property.

[0004] However, these same short chain polyamides allow resistance to high temperature bursting, so this second property does not favor the use of long chain polyamides.

[0005] Furthermore, the EUF-Gas Regulation plans to gradually phase out refrigerant gases with high global warming potential (GWP) from the market: from 100% in 2015, the amount of high GWP hydrofluorocarbon (HFC) refrigerants is required to be reduced by 63% between 2018 and 2020, reaching 21% in 2030.

[0006] From January 2017, new cars sold in Europe will have to be OEM-fitted with air conditioning that runs on R1234yf.

[0007] However, the standard is currently only valid at European level, but may be extended to other geographical zones, such as the United States, in the short term.

[0008] The air conditioning circuit elements, in particular the multi-layer tubular structures, must also meet the following requirements: - Impermeable to the fluids being transported and therefore having barrier properties against these fluids (and more specifically against fluorocarbon refrigerant compounds such as R134, R-1234yf, R-1234ze), as well as barrier properties against water and oxygen. The term "barrier properties" means that the structure is substantially impermeable to the fluids in the air conditioning lines of the vehicle, and therefore substantially no air conditioning line fluids are released into the atmosphere. - Chemical resistance to the transported fluids, compressor oil, water and oxygen to avoid excessive deterioration over time. - have sufficient mechanical strength (especially burst strength) but also sufficient flexibility when both ends of the tube are connected to parts that move relative to each other (especially in automotive air conditioning, where space and under-bonnet mounting constraints require the tube structure to bend) and damp vibrations; - Considering the fact that the transported fluids may be hot and that the environmental temperatures may also be high (especially in automotive air conditioning, where the relevant components may be located close to the engine), it is necessary to consider the following points: 2 It has sufficient heat resistance.

[0009] The current line consists of an aluminum section and a rubber section with a reinforcing braid and a barrier layer.

[0010] It is therefore envisaged that the current lines will be replaced with a thermoplastic pipe solution in order to reduce the weight of the vehicle.

[0011] Thus, WO 2020 / 115420 describes, inter alia, a multi-layer tubular structure of aliphatic polyamide for transporting refrigerant fluids.

[0012] WO 2017 / 103466 describes a multi-layer tubular structure for transporting refrigerant fluids. The mechanical properties are provided by layers made of a mixture of semi-crystalline thermoplastics and continuous fibers.

[0013] WO 2014 / 125219 describes a tubular structure comprising at least one layer of a composition comprising a copolyamide of formula X / 10.T / Y. The proportion of units X is 0.4-0.8 moles per mole of semi-aromatic units 10.Y.

[0014] Hutchinson also sells air conditioning lines constructed from PA6 and PA66 alloys, but these lines face significant problems, particularly being too permeable to water, which causes corrosion in compressors.

[0015] TI Fluid Systems also developed a solution in-house consisting of PA612 and PA11 / 10T layers.

[0016] Evonik offers grades PA610 and PA612 for the production of single layer air conditioning lines.

[0017] The patents EP 2098580, EP 2098365, WO 2014 / 114766 and WO 2017 / 121961 describe thermoplastic tubular structures for transporting gasoline, in particular alcohol gasoline, besides the transport of refrigerant fluids.

[0018] However, none of these technological solutions can meet all of the needs expressed by automakers.

[0019] The present invention therefore relates to a multi-layer tubular structure (MLT) for transporting a heat transfer fluid, said multi-layer tubular structure comprising: at least one layer (1), at least one layer (1) comprising a composition (1) comprising at least one long-chain polyamide (PA) having mainly from 10 to 15 carbon atoms per nitrogen atom and comprising at least 50% of aliphatic units relative to the total of the units present in said long-chain polyamide; - at least one layer (2) located beneath said layer (1), comprising a composition (2) mainly comprising at least one polyamide having from 4 to 9 carbon atoms per nitrogen atom, said polyamide comprising at least 50% of aliphatic units relative to the total of the units present in said polyamide, more particularly said composition (2) comprising at most 12% by weight of polyolefin, relative to the total weight of said composition (2), in particular at most 6% by weight of polyolefin, and at most 2% by weight of at least one plasticizer, relative to the total weight of said composition (2); at least one layer (3) comprising a composition (3) that mainly comprises a hydrophobic polymer, more particularly polypropylene or polyethylene, more particularly said layer (3) being located below said layer (2) or between said layer (1) and said layer (2); - a layer (4) comprising a composition (4) comprising PA6, PA66 or a mixture thereof, said composition (4) comprising from 5% to 50% by weight of at least one polyolefin, more particularly from 10% to 40% by weight of at least one polyolefin, up to 2% by weight of at least one plasticizer and up to 2% by weight of additives, relative to the total weight of said composition (4); Alternatively, a layer (4) containing at least one composition (4') based on a C8 to C14 aliphatic polyamide; Including, The layer (4) is in contact with the fluid to be transported, A multi-layer tubular structure, wherein the thickness of said layer (2) occupies at least 70% of the total thickness of the tube.

[0020] Thus, the inventors have unexpectedly found that the inventive multi-layer tubular structure consisting of at least four layers is able to meet all the needs expressed by the car manufacturers, namely the barrier properties against refrigerant fluids, especially R1234yf, provided by the polyolefin modified PA6 or PA with 8-14 carbon atoms per nitrogen atom, the low water permeability provided by the hydrophobic polymer, while the PA has a water permeability that is too high compared to the requirements of the application, the high temperature burst resistance provided by the short and medium chain PA (4-9 carbon atoms per nitrogen atom) and thus a compromise between weight and mechanical performance, and finally, the long chain PA of the outer layer prevents the ZnCl 2 It has been found that this provides resistance to stress cracking and ensures good resistance to stress cracking.

[0021] According to one embodiment, the multi-layer tubular structure of the present invention has barrier properties against refrigerant fluids, in particular R1234yf, preferably meeting classification C according to the GMW14319 standard.

[0022] According to one embodiment, the multilayer tubular structure of the invention advantageously has a zinc chloride resistance corresponding to category 1 (the outer surface of the tube is intact (no cracks) and the burst pressure remains unchanged) according to the protocol described in the examples.

[0023] According to one embodiment, the multi-layer tubular structure of the present invention preferably has a burst stress of 12 MPa or more at 125° C. according to DIN 53758 SAE J3062, as described in the examples.

[0024] According to one embodiment, the multi-layer tubular structure of the present invention preferably has a water permeability of less than 23 g / m2·24 h according to PSA Peugeot Citroën material test method D45.1720, as described in the examples.

[0025] Regarding layer (1) and composition (1): The expression "mainly comprising at least one polyamide" means that the polyamide or polyamides are present in the composition (1) in a proportion by weight of more than 50% relative to the total weight of the composition.

[0026] The term "polyamide" refers to both homopolyamides and copolyamides.

[0027] 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 the person skilled in the art.

[0028] Homopolyamides are obtained from the polycondensation of lactam units, amino acid units or units XY, where X is a diamine and Y is a dicarboxylic acid (or diacid), and have 10 to 15 carbon atoms per nitrogen atom.

[0029] The diamines may be linear or branched aliphatic or cycloaliphatic, preferably linear or branched aliphatic, especially linear aliphatic.

[0030] The dicarboxylic acid may be an aliphatic or cycloaliphatic acid, preferably an aliphatic acid.

[0031] Therefore, the lactams and amino acids used to obtain the homopolyamides must have an average number of carbon atoms (C) per nitrogen atom (N) of 10-15.

[0032] Advantageously, the lactam and amino acid are C11 and C12.

[0033] In the case of homopolyamides resulting from the polycondensation of units XY, the number of atoms per nitrogen atom is calculated by the average of the number of carbon atoms present in the units derived from diamine X and diacid Y.

[0034] Thus, the diamine (X) can be C4 to C36, particularly C6 to C18, more particularly C4 to C12, and the dicarboxylic acid (Y) can be C4 to C36, particularly C6 to C18, more particularly C6 to C12, in that the average number of carbon atoms present in the units derived from the diamine X and the units derived from the diacid Y is 10 to 15.

[0035] Advantageously, the diamine is selected from 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, 1,16-hexadecanediamine and 1,18-octadecanediamine.

[0036] Advantageously, the diamine is chosen from 1,10-decanediamine and 1,12-dodecanediamine.

[0037] Advantageously, the dicarboxylic acid is chosen from sebacic acid and dodecanedioic acid.

[0038] Advantageously, the diamine is chosen from 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from sebacic acid, undecanedioic acid and dodecanedioic acid.

[0039] In the case of copolyamides, the number of carbon atoms per nitrogen atom is calculated according to the same principle as in the case of homopolyamides: the calculation is carried out on a molar proportion basis from the various amide units.

[0040] Thus, the lactams and amino acids used to obtain the copolyamides may have an average number of carbon atoms (C) per nitrogen atom (N) ranging from 6 to 15.

[0041] The diamines X and diacids Y used in the copolyamides may be aromatic diamines and / or diacids, in that the polyamides of composition (1) contain at least 50% aliphatic units relative to the total of the units present in the polyamide.

[0042] In one embodiment, said at least one polyamide of composition (1) comprises at least 60% aliphatic units relative to the total units present in said polyamide.

[0043] In another embodiment, said at least one polyamide of composition (1) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0044] In another embodiment, said at least one polyamide of composition (1) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0045] In another embodiment, said at least one polyamide of composition (1) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0046] In another embodiment, said at least one polyamide of composition (1) comprises 100% aliphatic units relative to the total units present in said polyamide.

[0047] Advantageously, said at least one polyamide of composition (1) consists exclusively of aliphatic units.

[0048] In one embodiment, said composition (1) mainly comprises a single polyamide, said single polyamide therefore being present in the composition in a proportion by weight greater than 50% relative to the total weight of the composition.

[0049] In one embodiment, said polyamide of composition (1) comprises at least 60% aliphatic units relative to the total units present in said polyamide.

[0050] In another embodiment, said polyamide of composition (1) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0051] In another embodiment, said polyamide of composition (1) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0052] In another embodiment, said polyamide of composition (1) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0053] In another embodiment, said polyamide of composition (1) comprises 100% aliphatic units relative to the total of units present in said polyamide, and therefore said polyamide of composition (1) consists exclusively of aliphatic units.

[0054] In one embodiment, said layer (1) is composed of a composition (1) mainly comprising at least one long-chain polyamide having from 10 to 15 carbon atoms per nitrogen atom and containing at least 50% aliphatic units relative to the total units present in said long-chain polyamide.

[0055] In one embodiment, said at least one polyamide of composition (1) comprises at least 60% of aliphatic units relative to the total units present in said polyamide.

[0056] In another embodiment, said at least one polyamide of composition (1) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0057] In another embodiment, said at least one polyamide of composition (1) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0058] In another embodiment, said at least one polyamide of composition (1) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0059] In another embodiment, said at least one polyamide of composition (1) comprises 100% aliphatic units relative to the total of the units present in said polyamide, thus said polyamide consists exclusively of aliphatic units.

[0060] In one embodiment, said layer (1) consists of a composition (1) which mainly comprises a single polyamide and thus said single polyamide is present in the composition in a weight proportion of more than 50% relative to the total weight of the composition.

[0061] In one embodiment, said polyamide of composition (1) comprises at least 60% aliphatic units relative to the total units present in said polyamide.

[0062] In another embodiment, said polyamide of composition (1) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0063] In another embodiment, said polyamide of composition (1) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0064] In another embodiment, said polyamide of composition (1) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0065] In another embodiment, said polyamide of composition (1) comprises 100% aliphatic units relative to the total of units present in said polyamide, and therefore said polyamide of composition (1) consists exclusively of aliphatic units.

[0066] Advantageously, in all the embodiments defined above for composition (1) of layer (1), the lactam is chosen from lauryllactam, the amino acid is chosen from aminoundecanoic acid, the diamine is chosen from 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and tetradecanedioic acid.

[0067] More preferably, the lactam is lauryllactam, the amino acid is aminoundecanoic acid, the diamine is selected from 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is selected from sebacic acid and dodecanedioic acid.

[0068] The composition (1) may contain at least one polyolefin.

[0069] Thus, said composition (1) may comprise, in addition to said at least one polyamide, at least one polyolefin.

[0070] The polyolefin may be functionalized or unfunctionalized, or may be a mixture of at least one functionalized polyolefin and / or at least one functionalized polyolefin. For simplicity, the polyolefin is designated (B) and functionalized polyolefin (B1) and non-functionalized polyolefin (B2) are described below.

[0071] The non-functionalized polyolefin (B2) is typically a homopolymer or copolymer of an alpha-olefin or diolefin, such as ethylene, propylene, 1-butene, 1-octene, butadiene, etc. Examples may include: - polyethylene homopolymers and copolymers, in particular LDPE, HDPE, PE-RT LLDPE (linear low density polyethylene), VLDPE (very low density polyethylene), metallocene polyethylene; - propylene homopolymer or copolymer, - Ethylene / alpha olefins such as ethylene / propylene, EPR (short for ethylene propylene rubber), and ethylene / propylene / diene (EPDM) copolymers; - Styrene / Ethylene Butene / Styrene (SEBS), Styrene / Butadiene / Styrene (SBS), Styrene / Isoprene / Styrene (SIS), Styrene / Ethylene Propylene / Styrene (SEPS) block copolymers, - 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 able to be up to 40% by weight.

[0072] The functionalized polyolefins (B1) can be polymers of alpha-olefins having reactive units (functional groups), such as acid, anhydride or epoxy functional groups. By way of example, mention may be made of the aforementioned polyolefins (B2) grafted or copolymerized or terpolymerized with unsaturated epoxides, such as glycidyl (meth)acrylate, or with carboxylic acids or their salts or esters, such as (meth)acrylic acid, the latter of which can be fully or partially neutralized with metals, such as Zn, or with carboxylic anhydrides, such as maleic anhydride. The functionalized polyolefins are, for example, PE / EPR mixtures, the weight ratio of which varies, for example, between 40 / 60 and 90 / 10, said mixtures being cografted with anhydrides, in particular maleic anhydride, for example with a grafting degree of 0.01-5% by weight.

[0073] The functionalized polyolefin (B1) can be chosen from the following (co)polymers grafted with maleic anhydride or with glycidyl methacrylate, the degree of grafting being, for example, between 0.01% and 5% by weight: - PE, PP, copolymers of ethylene with propylene, butene, hexene or octene (for example with an ethylene content of 35% to 80% by weight). - Ethylene / alpha olefins such as ethylene / propylene, EPR (short for ethylene propylene rubber), and ethylene / propylene / diene (EPDM) copolymers; - Styrene / Ethylene Butene / Styrene (SEBS), Styrene / Butadiene / Styrene (SBS), Styrene / Isoprene / Styrene (SIS), Styrene / Ethylene Propylene / Styrene (SEPS) block copolymers, - Ethylene and vinyl acetate copolymer (EVA) (containing up to 40% vinyl acetate by weight), - copolymers of ethylene and alkyl (meth)acrylates (containing up to 40% by weight of alkyl (meth)acrylates); - Copolymer of ethylene, vinyl acetate (EVA) and alkyl (meth)acrylate with up to 40% by weight of comonomer.

[0074] The functionalized polyolefin (B1) can also be selected from ethylene / propylene copolymers based on propylene, grafted with maleic anhydride and then condensed with a monoaminated polyamide (or polyamide oligomer) (products described in EP-A-0 342 066).

[0075] The functionalized polyolefin (B1) may 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 epoxy such as glycidyl (meth)acrylate.

[0076] Examples of the latter type of functionalized polyolefins include the following copolymers, in which ethylene preferably accounts for at least 60% by weight and the termonomer (functional group) accounts for, for example, 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.

[0077] In the aforementioned copolymers, the (meth)acrylic acid may be salified with Zn or Li.

[0078] The term "alkyl (meth)acrylate" in (B1) or (B2) means C1 to C8 alkyl methacrylates and acrylates, and may be selected from methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

[0079] Furthermore, the above polyolefins (B1) may be crosslinked via any suitable process or agent (diepoxy, diacid, peroxide, etc.) The term "functionalized polyolefin" also includes mixtures of the above polyolefins with difunctional agents such as diacids, dianhydrides, diepoxy, etc. that can react with these polyolefins, or mixtures of at least two functionalized polyolefins that can react together.

[0080] The above copolymers (B1) and (B2) can be copolymerized randomly or in a block form, and may have a linear or branched structure.

[0081] The molecular weight, MFI index and density of these polyolefins may also vary within wide limits recognized by those skilled in the art. MFI is the abbreviation for Melt Flow Index. It is measured according to standard ASTM 1238.

[0082] The non-functionalized polyolefin (B2) is advantageously chosen from polypropylene homopolymers or copolymers and any ethylene homopolymer or copolymer of ethylene with a comonomer of higher alpha-olefin type 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. These polyethylenes are known to the skilled artisan to be produced by the "radical" process, by "Ziegler" type catalysts or, more recently, by "metallocene" catalysts.

[0083] Advantageously, the functionalized polyolefin (B1) is selected from any polymer that contains alpha-olefin units and units with polar reactive functional groups, such as epoxy, carboxylic acid or carboxylic anhydride functional groups. Examples of such polymers include terpolymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate (e.g., Lotader® (SK Functional Polymers) products), or polyolefins grafted with maleic anhydride by the applicant (e.g., Orevac® (SK Functional Polymers) products), and terpolymers of ethylene, alkyl acrylate and (meth)acrylic acid. Also included are polypropylene homopolymers or copolymers grafted with carboxylic anhydrides and then condensed with polyamides or monoamino oligomers of polyamides.

[0084] Advantageously, the polyolefin is an impact modifier, which preferably consists of a polymer with a flexural modulus of less than 100 MPa, measured according to standard ISO 178:2010, measured at 23°C at a relative humidity: RH 50%, and a Tg of less than 0°C (measured according to standard 11357-2:2013 at the inflection point of the DSC thermogram).

[0085] Advantageously, said composition (1) comprises up to 40% by weight of at least one polyolefin.

[0086] Advantageously, said composition (1) comprises at least 3% by weight of at least one polyolefin, more particularly at least 6% by weight of at least one polyolefin, more particularly between 6% and 20% by weight, in particular between 10% and 12% by weight, relative to the total weight of said composition (1).

[0087] The composition (1) may contain at least one plasticizer.

[0088] Thus, said composition (1) may comprise, in addition to said at least one polyamide, at least one plasticizer.

[0089] Exemplary plasticizers are selected from benzenesulfonamide derivatives, such as n-butylbenzenesulfonamide (BBSA), ethyltoluenesulfonamide, or N-cyclohexyltoluenesulfonamide, hydroxybenzoic acid esters, such as 2-ethylhexyl parahydroxybenzoate, 2-decylhexyl parahydroxybenzoate, esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol, and esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxymalonate.

[0090] It would not be outside the scope of the invention to use a mixture of plasticizers.

[0091] Advantageously, said composition (1) comprises up to 8% by weight of at least one plasticizer relative to the weight of said composition (1).

[0092] In another embodiment, the composition (1) does not contain a plasticizer.

[0093] The composition (1) may contain an additive.

[0094] The additives optionally used in the composition of the invention are conventional additives used in polyamides and are well known to those skilled in the art and are described in particular in EP 2 098 580.

[0095] For example, they include antistatic fillers selected from carbon black, graphite, carbon fibers, carbon nanotubes, more particularly carbon black and carbon nanotubes, antioxidants, heat stabilizers, UV absorbers, light stabilizers, lubricants, inorganic fillers, flame retardants, nucleating agents and dyes, reinforcing fibers, waxes, and mixtures thereof.

[0096] By way of example, the stabilizer may be a UV stabilizer, an organic stabilizer, or more generally a combination of organic stabilizers, such as phenolic type antioxidants (for example, types Irganox® 245 or 1098 or 1010 from Ciba-BASF), or phosphorous type antioxidants (for example, Irgafos® 126 or Irgafos® 168 from Ciba-BASF), and optionally other stabilizers, such as HALS, which stands for hindered amine light stabilizers (for example, Tinuvin® 770 from Ciba-BASF), UV inhibitors (for example, Tinuvin® 312 from Ciba), or phosphorus-based stabilizers. It is also possible to use amine type antioxidants, such as Naugard® 445 from Crompton, or multifunctional stabilizers, such as Nylostab® S-EED from Clariant.

[0097] The stabilizer may be a mineral stabilizer, such as a copper-based stabilizer. Examples of such mineral stabilizers include copper halides and copper acetate. Other metals, such as silver, may then be considered, but these are known to be less effective. These copper-based compounds are usually combined with halides of alkali metals, especially potassium.

[0098] In one embodiment, the composition (1) comprises, by weight: - 60% to 100% of at least one C10 to C15 long chain polyamide as defined above, - 0-30% of at least one polyolefin, - 0-8% of at least one plasticizer, - 0-2% of at least one additive, The total is 100% by weight.

[0099] In another embodiment, said composition (1) comprises, by weight: - 60% to 97% of at least one C10 to C15 long chain polyamide as defined above, - 3 to 30% of at least one polyolefin, - 0-8% of at least one plasticizer, - 0-2% of at least one additive, The total is 100% by weight.

[0100] In another embodiment, said composition (1) comprises, by weight: - 70% to 94% of at least one C10 to C15 long chain polyamide as defined above, - 6 to 20% of at least one polyolefin, - 0-8% of at least one plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0101] Advantageously, said composition (1) does not contain a plasticizer and comprises the following components by weight: - 50% to 100% of at least one C10 to C15 long chain polyamide as defined above, - 0-40% of at least one polyolefin, - 0-8% plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0102] More advantageously, said composition (1) comprises the following components by weight: - 60% to 97% of at least one C10 to C15 long chain polyamide as defined above, - 3 to 30% of at least one polyolefin, - 0-8% plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0103] More advantageously, said composition (1) comprises the following components by weight: - 70% to 94% of at least one C10 to C15 long chain polyamide as defined above, - 6 to 20% of at least one polyolefin, - 0-8% plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0104] More specifically, said composition (1) comprises, by weight: - 50% to 90% of at least one C10 to C15 long chain polyamide as defined above, - 6 to 12% of at least one polyolefin, - 0-8% plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0105] The present invention also encompasses various embodiments in which the term "comprising" in composition (1) is replaced with the term "consisting of."

[0106] It is clear that the various compositions (1) with or without at least one polyolefin and / or at least one plasticizer and / or at least one additive refer to all the above embodiments.

[0107] In one embodiment, the at least one polyamide of layer (1) of the tubular structure defined above is selected from PA11, PA12, PA1010, PA1012, PA1210 and PA1212.

[0108] Layer (1) of the tubular structure defined above may be the outermost layer.

[0109] Advantageously, said layer (1) of the tubular structure defined above is the outermost layer of said structure.

[0110] Advantageously, said structure (1) comprises a single layer (1).

[0111] Regarding layer (2) and composition (2): The expression "mainly comprising at least one polyamide" is as defined above for layer (1).

[0112] The term "polyamide" refers equally to both homopolyamides and copolyamides.

[0113] Homopolyamides result from the polycondensation of lactam units, amino acid units or units XY, where X is a diamine and Y is a dicarboxylic acid (or diacid), and have 4 to 9 carbon atoms per nitrogen atom.

[0114] The diamines may be linear or branched aliphatic or cycloaliphatic, preferably linear or branched aliphatic, especially linear aliphatic.

[0115] The dicarboxylic acid may be an aliphatic or cycloaliphatic acid, preferably an aliphatic acid.

[0116] Therefore, the lactams and amino acids used to obtain the homopolyamides must have an average number of carbon atoms (C) per nitrogen atom (N) between 4 and 9.

[0117] Advantageously, the lactam and the amino acid are C12.

[0118] In the case of homopolyamides resulting from the polycondensation of units XY, the number of atoms per nitrogen atom is calculated by the average of the number of carbon atoms present in the units derived from diamine X and diacid Y.

[0119] Thus, the diamine (X) can be C4 to C14, particularly C4 to C12, more particularly C4 to C10, and the dicarboxylic acid (Y) can be C4 to C14, particularly C4 to C12, more particularly C4 to C10, in that the average number of carbon atoms present in the units derived from the diamine X and the units derived from the diacid Y is 4 to 9.

[0120] Advantageously, the diamine is selected from butanediamine, pentanediamine, 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, in particular 1,6-hexamethylenediamine.

[0121] Advantageously, the dicarboxylic acid is chosen from succinic acid, pentanedioic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, in particular sebacic acid and dodecanedioic acid.

[0122] Advantageously, the diamine is butanediamine, pentanediamine, 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, The dicarboxylic acids are selected from succinic acid, pentanedioic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and tetradecanediacids, in particular sebacic acid and dodecanedioic acid.

[0123] The diamines X and diacids Y used in the copolyamides may be aromatic diamines and / or diacids, in that the polyamides of composition (2) contain at least 50% aliphatic units relative to the total of the units present in the polyamide.

[0124] In one embodiment, said at least one polyamide of composition (2) comprises at least 60% of aliphatic units relative to the total units present in said polyamide.

[0125] In another embodiment, said at least one polyamide of composition (2) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0126] In another embodiment, said at least one polyamide of composition (2) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0127] In another embodiment, said at least one polyamide of composition (2) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0128] In another embodiment, said at least one polyamide of composition (2) comprises 100% aliphatic units relative to the total of the units present in said polyamide, thus the at least one polyamide consists exclusively of aliphatic units.

[0129] In one embodiment, said composition (2) mainly comprises a single polyamide, said single polyamide therefore being present in the composition in a proportion by weight greater than 50% relative to the total weight of the composition.

[0130] In one embodiment, the polyamide of the composition (2) comprises at least 60% aliphatic units relative to the total units present in the polyamide.

[0131] In another embodiment, the polyamide of the composition (2) comprises at least 70% aliphatic units relative to the total units present in the polyamide.

[0132] In another embodiment, the polyamide of the composition (2) comprises at least 80% aliphatic units relative to the total units present in the polyamide.

[0133] In another embodiment, the polyamide of composition (2) comprises at least 90% aliphatic units relative to the total units present in the polyamide.

[0134] In another embodiment, the polyamide of composition (2) comprises 100% aliphatic units relative to the total units present in the polyamide, and therefore the polyamide of composition (2) consists exclusively of aliphatic units.

[0135] In one embodiment, said layer (2) consists of a composition (1) mainly comprising at least one long-chain polyamide having from 4 to 9 carbon atoms per 2 nitrogen atoms and containing at least 50% aliphatic units relative to the total number of units present in said long-chain polyamide.

[0136] In one embodiment, said at least one polyamide of said composition (2) comprises at least 60% of aliphatic units relative to the total units present in said polyamide.

[0137] In another embodiment, said at least one polyamide of said composition (2) comprises at least 70% aliphatic units relative to the total units present in said polyamide.

[0138] In another embodiment, said at least one polyamide of said composition (2) comprises at least 80% aliphatic units relative to the total units present in said polyamide.

[0139] In another embodiment, said at least one polyamide of said composition (2) comprises at least 90% aliphatic units relative to the total units present in said polyamide.

[0140] In another embodiment, the at least one polyamide of composition (2) comprises 100% aliphatic units relative to the total of the units present in the polyamide, and therefore the polyamide of composition (2) consists exclusively of aliphatic units.

[0141] In one embodiment, said layer (2) consists of a composition (2) which mainly comprises a single polyamide, said single polyamide therefore being present in the composition in a weight proportion of more than 50% relative to the total weight of the composition.

[0142] In one embodiment, the polyamide of the composition (2) comprises at least 60% aliphatic units relative to the total units present in the polyamide.

[0143] In another embodiment, the polyamide of the composition (2) comprises at least 70% aliphatic units relative to the total units present in the polyamide.

[0144] In another embodiment, the polyamide of the composition (2) comprises at least 80% aliphatic units relative to the total units present in the polyamide.

[0145] In another embodiment, the polyamide of composition (2) comprises at least 90% aliphatic units relative to the total units present in the polyamide.

[0146] In another embodiment, the polyamide of composition (2) comprises 100% aliphatic units relative to the total units present in the polyamide, and therefore the polyamide consists exclusively of aliphatic units.

[0147] Advantageously, in all the embodiments defined above for composition (2) of layer (2), the lactam is caprolactam, the amino acid is aminohexanoic acid, the diamine is selected from 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine and 1,10-decanediamine, and the dicarboxylic acid is selected from adipic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and tetradecanedioic acid.

[0148] More preferably, the lactam is caprolactam, the amino acid is aminohexanoic acid, the diamine is selected from 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,10-decanediamine and 1,12-dodecanediamine, and the dicarboxylic acid is selected from adipic acid, sebacic acid and dodecanedioic acid.

[0149] In one embodiment, the lactam is caprolactam, the amino acid is aminohexanoic acid, the diamine is selected from 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,10-decanediamine, and 1,12-dodecanediamine, and the dicarboxylic acid is selected from adipic acid, sebacic acid, and dodecanedioic acid.

[0150] Advantageously, said polyamide of said composition (2) comprises at least 60% of aliphatic units relative to the total of the units present in said polyamide.

[0151] More preferably, the polyamide of composition (2) comprises at least 60% aliphatic units relative to the total units present in the polyamide, and the long-chain polyamide of composition (1) comprises at least 60% aliphatic units relative to the total units present in the long-chain polyamide.

[0152] Advantageously, said composition (2) does not comprise polyamides other than aliphatic polyamides.

[0153] More advantageously, said polyamide of said composition (2) consists of aliphatic units.

[0154] In one embodiment, the polyamide of the composition (2) comprises aliphatic units and the long chain polyamide of the composition (1) comprises aliphatic units.

[0155] Advantageously, said composition (2) and said composition (1) do not contain polyamides other than aliphatic polyamides.

[0156] Said composition (2) may comprise at least one plasticizer in a proportion by weight of up to 2% relative to the total weight of the composition.

[0157] The plasticizer is as defined for composition (1).

[0158] The composition (2) may contain at least one additive.

[0159] In one embodiment, the additive is present in a weight percentage of up to 2% relative to the total weight of the composition.

[0160] The additives are as defined for composition (1).

[0161] In one embodiment, said composition (2) comprises, by weight: - 84% to 100%, in particular 90% to 100%, of at least one C4 to C9 polyamide as defined above, - 0-12%, in particular 0-6%, of at least one polyolefin, - 0-2% of at least one plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0162] In another embodiment, said composition (2) does not comprise a polyolefin and comprises, by weight: - 96% to 100% of at least one C4 to C9 polyamide as defined above, - 0-2% of at least one plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0163] Advantageously, said composition (2) does not contain a plasticizer and said composition (2) comprises the following components by weight: - 86% to 100%, in particular 92% to 100% by weight, of at least one C4 to C9 polyamide as defined above, - 0-12%, in particular 0-6%, of at least one polyolefin, - 0-2% of at least one additive. The total is 100% by weight.

[0164] It is clear that the various compositions (1), with or without at least two polyolefins and / or at least one plasticizer and / or at least one additive, refer to all the embodiments mentioned above for composition (2).

[0165] In one embodiment, the at least one polyamide of layer (2) of the tubular structure defined above is selected from PA6, PA66, PA6 / 66, PA610, PA410, PA412 and PA612.

[0166] Regarding layer (3) and composition (3) The layer (3) comprises a composition (3) that mainly comprises a hydrophobic polymer, more particularly polypropylene or polyethylene, and more particularly, the layer (3) is disposed below the layer (2) or between the layer (1) and the layer (2).

[0167] This means that composition (3) comprises, relative to its total weight, at least 50% by weight of a hydrophobic polymer, and more particularly of polypropylene or polyethylene.

[0168] According to one embodiment, composition (3) may comprise, relative to its total weight, at least 60% by weight, such as at least 70% by weight, for example at least 80% by weight, or even 100% by weight, of a hydrophobic polymer, more particularly polypropylene or polyethylene.

[0169] According to one embodiment, layer (3) mainly comprises composition (3), i.e. it comprises more than 50% by weight of composition (3) relative to its total weight.

[0170] According to one embodiment, layer (3) may comprise at least 60% by weight, such as at least 70% by weight, such as at least 80% by weight, or even 100% by weight of composition (3).

[0171] The expression "hydrophobic polymer" means a water barrier or partial barrier polymer. It can be a non-polar polymer or a filled polymer through which the diffusion of water is slowed down (for example a polyamide such as graphene-filled PA11).

[0172] More specifically, a polymer is considered to be hydrophobic within the meaning of the present invention if, according to the Hansen Solubility Parameters (HANSEN SOLUBILITY PARAMETERS - A User's Handbook - second edition - Charles M.), the solubility constant for polar interactions (δp) is less than or equal to 5 MPa 1 / 2 and the solubility constant for hydrogen bonds (δh) is less than or equal to 5 MPa 1 / 2.

[0173] The hydrophobic polymer may be non-functionalized as described above in (B2) or functionalized as described above in B1.

[0174] In one embodiment, the hydrophobic polymer is selected from polypropylene and polyethylene.

[0175] Polypropylene has a solubility coefficient for polar interactions (δp) of less than 5 MPa 1 / 2 and, according to the Hansen solubility parameters defined above, a solubility coefficient for hydrogen bonds (δh) of less than 5 MPa 1 / 2. Polypropylene is therefore a truly hydrophobic polymer within the meaning of the present invention.

[0176] Polyethylene has a solubility coefficient for polar interactions (δp) of less than 5 MPa 1 / 2 and, according to the Hansen solubility parameters defined above, a solubility coefficient for hydrogen bonds (δh) of less than 5 MPa 1 / 2. Polyethylene is therefore a truly hydrophobic polymer within the meaning of the present invention.

[0177] Ethylene vinyl alcohol (or EVOH) is not considered a hydrophobic polymer within the meaning of the present invention.

[0178] The solubility coefficient for polar interactions (δp) of ethylene vinyl alcohol is greater than 5 MPa 1 / 2 (between 10 and 15), and the solubility coefficient for hydrogen bonds (δh) is greater than 5 MPa 1 / 2 (between 10 and 15) based on the Hansen solubility parameters defined above.

[0179] In another embodiment, said polypropylene or said polyethylene is crosslinked.

[0180] Advantageously, the hydrophobic polymer of layer (3) is chosen from grafted polypropylene, preferably grafted with maleic anhydride, and grafted high density polyethylene (HDPE), preferably grafted with maleic anhydride.

[0181] In one embodiment, the MFI of the polypropylene or polyethylene is 0.5 to 10 g / 10 min.

[0182] MFI stands for Melt Flow Index, which is an index of fluidity in the molten state. It is measured at 230°C and 2.16 kg in accordance with the standard ASTM 1238.

[0183] Regarding layer (4) and composition (4) The layer (4) is on the inside and in contact with the fluid to be transported.

[0184] Layer (4) comprises a composition (4) comprising PA6, PA66 or a mixture thereof, at least one polyolefin, more particularly a functionalized polyolefin, preferably comprising from 5% to 50% by weight of at least one polyolefin, at most 2% by weight of at least one plasticizer and at most 2% by weight of additives relative to the total weight of the composition, or a composition (4') based on at least one polyamide having 8 to 14 carbon atoms per nitrogen atom and comprising at least 20% by weight, preferably at least 25% by weight, of at least one polyolefin relative to the total weight of said composition (4').

[0185] In one embodiment, the composition (4) comprises: - 50 to 95% by weight of PA6, PA66 or mixtures thereof, - 5 to 50% by weight, preferably 10 to 40% by weight, of at least one polyolefin, in particular a functionalized polyolefin, - 0 to 2% by weight of at least one plasticizer, - 0-2% by weight of at least one additive.

[0186] In another embodiment, the composition (4) comprises: - 60-90% PA6, PA66 or mixtures thereof, - 10 to 40% by weight of at least one polyolefin, in particular a functionalized polyolefin, - 0 to 2% by weight of at least one plasticizer, - 0-2% by weight of at least one additive.

[0187] In a variant of these two embodiments, said composition (4) consists of the elements defined above for these two embodiments.

[0188] The plasticizers and additives of composition (4) are the same as those defined for composition (1).

[0189] The term "polyamide" in composition (4') likewise denotes both homopolyamides and copolyamides.

[0190] Homopolyamides are obtained from the polycondensation of lactam units, amino acid units or units XY, where X is a diamine and Y is a dicarboxylic acid (or diacid), and have 8 to 14 carbon atoms per nitrogen atom.

[0191] The diamines may be linear or branched aliphatic or cycloaliphatic, preferably linear or branched aliphatic, especially linear aliphatic.

[0192] The dicarboxylic acid may be an aliphatic or cycloaliphatic acid, preferably an aliphatic acid.

[0193] Therefore, the lactams and amino acids used to obtain the homopolyamides must have an average number of carbon atoms (C) per nitrogen atom (N) between 8 and 14.

[0194] Advantageously, the lactam and amino acid are C11 and C12.

[0195] In the case of homopolyamides resulting from the polycondensation of units XY, the number of atoms per nitrogen atom is calculated by the average of the number of carbon atoms present in the units derived from diamine X and diacid Y.

[0196] Thus, the diamine (X) can be C4 to C36, particularly C6 to C18, more particularly C4 to C12, and the dicarboxylic acid (Y) can be C4 to C36, particularly C6 to C18, more particularly C6 to C12, in that the average number of carbon atoms present in the units derived from the diamine X and the units derived from the diacid Y is 10 to 15.

[0197] Advantageously, the diamine is selected from 2-methyl-1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,12-dodecanediamine, 1,13-tridecanediamine, 1,14-tetradecanediamine, 1,16-hexadecanediamine and 1,18-octadecanediamine.

[0198] Advantageously, the diamine is chosen from 1,10-decanediamine and 1,12-dodecanediamine.

[0199] Advantageously, the dicarboxylic acid is chosen from sebacic acid and dodecanedioic acid.

[0200] Advantageously, the diamine is chosen from 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from sebacic acid, undecanedioic acid and dodecanedioic acid.

[0201] In the case of copolyamides, the number of carbon atoms per nitrogen atom is calculated according to the same principle as in the case of homopolyamides: the calculation is carried out on a molar proportion basis from the various amide units.

[0202] Thus, the lactams and amino acids used to obtain the copolyamides may have an average number of carbon atoms (C) per nitrogen atom (N) of between 6 and 15.

[0203] The diamines X and diacids Y used in the copolyamide may be aromatic diamines and / or diacids, in that the polyamide of composition (4') contains at least 50% aliphatic units relative to the total of the units present in the polyamide.

[0204] In one embodiment, said at least one polyamide of composition (4') comprises at least 60% of aliphatic units relative to the total of the units present in said polyamide.

[0205] In another embodiment, said at least one polyamide of composition (4') comprises at least 70% of aliphatic units relative to the total of the units present in said polyamide.

[0206] In another embodiment, said at least one polyamide of composition (4') comprises at least 80% aliphatic units relative to the total of the units present in said polyamide.

[0207] In another embodiment, said at least one polyamide of composition (4') comprises at least 90% aliphatic units relative to the total of the units present in said polyamide.

[0208] In another embodiment, said at least one polyamide of composition (4') comprises 100% aliphatic units relative to the total of the units present in said polyamide, and therefore said at least one polyamide of composition (4') consists exclusively of aliphatic units.

[0209] In one embodiment, said composition (4') comprises mainly a single polyamide, said single polyamide therefore being present in the composition in a proportion by weight greater than 50% relative to the total weight of the composition.

[0210] In one embodiment, said polyamide of composition (4') comprises at least 60% of aliphatic units relative to the total of the units present in said polyamide.

[0211] In another embodiment, said polyamide of composition (4') comprises at least 70% aliphatic units relative to the total of the units present in said polyamide.

[0212] In another embodiment, said polyamide of composition (4') comprises at least 80% aliphatic units relative to the total of the units present in said polyamide.

[0213] In another embodiment, said polyamide of composition (4') comprises at least 90% aliphatic units relative to the total of the units present in said polyamide.

[0214] In another embodiment, said polyamide of composition (4') comprises 100% aliphatic units relative to the total of the units present in said polyamide, and therefore said polyamide of composition (4') consists exclusively of aliphatic units.

[0215] In one embodiment, said layer (4) consists of a composition (4') mainly comprising at least one long-chain polyamide having 8 to 14 carbon atoms per 4 nitrogen atoms and containing at least 50% aliphatic units relative to the total number of units present in said long-chain polyamide.

[0216] In one embodiment, said at least one polyamide of composition (4') comprises at least 60% of aliphatic units relative to the total of the units present in said polyamide.

[0217] In another embodiment, said at least one polyamide of composition (4') comprises at least 70% of aliphatic units relative to the total of the units present in said polyamide.

[0218] In another embodiment, said at least one polyamide of composition (4') comprises at least 80% aliphatic units relative to the total of the units present in said polyamide.

[0219] In another embodiment, said at least one polyamide of composition (4') comprises at least 90% aliphatic units relative to the total of the units present in said polyamide.

[0220] In another embodiment, said at least one polyamide of composition (4') comprises 100% aliphatic units relative to the total of the units present in said polyamide, said polyamide therefore consists exclusively of aliphatic units.

[0221] In one embodiment, said layer (4) consists of a composition (4) which mainly comprises a single polyamide, said single polyamide therefore being present in the composition in a weight proportion of more than 50% relative to the total weight of the composition.

[0222] In one embodiment, said polyamide of composition (4') comprises at least 60% of aliphatic units relative to the total of the units present in said polyamide.

[0223] In another embodiment, said polyamide of composition (4') comprises at least 70% aliphatic units relative to the total of the units present in said polyamide.

[0224] In another embodiment, said polyamide of composition (4') comprises at least 80% aliphatic units relative to the total of the units present in said polyamide.

[0225] In another embodiment, said polyamide of composition (4') comprises at least 90% aliphatic units relative to the total of the units present in said polyamide.

[0226] In another embodiment, the polyamide of composition (4') comprises 100% aliphatic units relative to the total of the units present in the polyamide, and therefore the polyamide of composition (1) consists exclusively of aliphatic units.

[0227] Advantageously, in all the embodiments defined above for composition (4') of layer (4), the lactam is chosen from lauryllactam, the amino acid is chosen from aminoundecanoic acid, the diamine is chosen from 1,8-octanediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,10-decanediamine, 1,11-undecanediamine, 2-butyl-2-ethyl-1,5-pentanediamine and 1,12-dodecanediamine and the dicarboxylic acid is chosen from suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and tetradecanedioic acid.

[0228] More preferably, the lactam is lauryllactam, the amino acid is aminoundecanoic acid, the diamine is selected from 1,10-decanediamine and 1,12-dodecanediamine and the dicarboxylic acid is selected from sebacic acid and dodecanedioic acid.

[0229] The composition (4') of the layer (4) comprises at least 20% by weight, preferably at least 25% by weight, of at least one polyolefin.

[0230] The polyolefin is as defined for composition (1).

[0231] Said composition (4') may contain at least one plasticizer and / or at least one additive.

[0232] The plasticizers and additives are as defined above.

[0233] In one embodiment, said composition (4') comprises by weight: - 54% to 80%, in particular 54% to 75%, of at least one C8 to C14 polyamide as defined above, - 20 to 40%, preferably 25 to 40%, of at least one polyolefin, - 0-4% of at least one plasticizer, - 0-2% of at least one additive. The total is 100% by weight.

[0234] The plasticizers and additives of composition (4) are the same as those defined for composition (1).

[0235] Tubular structure: The tubular structure can include at least one layer (1), at least one layer (2), at least one layer (3), and an inner layer (4).

[0236] The present invention also relates to a multi-layer tubular structure (MLT) for transporting a heat transfer fluid, said multi-layer tubular structure comprising: at least one layer 1 comprising a composition 1 mainly comprising at least one long-chain polyamide (PA) having from 10 to 15 carbon atoms per nitrogen atom and comprising at least 50% of aliphatic units relative to the total of the units present in said long-chain polyamide; at least one layer 2 located beneath said layer 1, said layer 2 comprising a composition 2 based on at least one polyamide having from 4 to 9 carbon atoms per nitrogen atom, said polyamide comprising at least 50% of aliphatic units relative to the total of the units present in said polyamide, more particularly said composition 2 comprising at most 12% by weight of polyolefin, relative to the total weight of said composition 2, in particular at most 6% by weight of polyolefin, and at most 2% by weight of at least one plasticizer, relative to the total weight of said composition 2; at least one layer 3 comprising a composition 3 mainly comprising a hydrophobic polymer, more particularly polypropylene or polyethylene, more particularly said layer 3 being located below said layer 2 or between said layer 1 and said layer 2, a layer 4, the composition 4 comprising PA6, PA66 or a mixture thereof, said composition 4 comprising from 5% to 50% by weight of at least one polyolefin, more particularly from 10% to 40% by weight of at least one polyolefin, up to 2% by weight of at least one plasticizer and up to 2% by weight of additives, relative to the total weight of said composition 4, Alternatively, a layer 4 comprising at least one composition 4' based on a C8 to C14 aliphatic polyamide, The layer 4 is in contact with the fluid to be transported, and layer 5 is present between layers 3 and 4, the layer 5 comprising composition 2, and the thickness of layers 2 and 5 occupies at least 70% of the total thickness of the tube.

[0237] In one embodiment, the thickness of said layer (2) is more particularly at most 90% of the total thickness of the tube, in particular at most 80% of the total thickness of the tube.

[0238] In one embodiment, the multi-layer tubular structure defined above is characterized in that layer (2) is free of plasticizers.

[0239] In another embodiment, the multi-layer tubular structure as defined above is characterized in that layer (2) and layer (1) are free of plasticizers.

[0240] In yet another embodiment, the multi-layer tubular structure as defined above is characterized in that all layers present in the structure are free of plasticizers.

[0241] In one embodiment, said structure comprises a layer (5) between said layer (3) and said layer (4), said layer (5) comprising composition (2), and the thickness of said layers (2) and (5) represents at least 80% of the total thickness of the tube.

[0242] Layer (2) and layer (5) may be the same or different.

[0243] In one embodiment, the multi-layer tubular structure defined above is characterized in that layer (1) is the outermost layer of the multi-layer tubular structure.

[0244] According to a first variant, the tubular structure is characterized in that it is made up of four layers (1) / / (2) / / (3) / / (4) or (1) / / (3) / / (2) / / (4).

[0245] According to a second variant, the tubular structure is characterized in that it is composed of five layers (1) / / (2) / / (3) / / (5) / / (4) or (1) / / (3) / / (2) / / (5) / / (4).

[0246] In one embodiment, the multi-layer tubular structure as defined above is adapted for use in a thermal transfer fluid comprising a hydrocarbon compound, a hydrofluorocarbon, an ether, a hydrofluoroether, CO 2 , N.H. 3 , S.O. 2 and fluoroolefins.

[0247] In one embodiment, the heat transfer fluid is CO 2, fluoropropene, fluoropropane and fluoroethane, preferably 1,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene, 1,2,3,3,3-pentafluoropropene, 1,1,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, 2,3,3-trifluoropropene, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, difluoromethane, 1,1-difluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1-trifluoropropane, 1,1,1,3,3,3-hexafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, trifluoroiodomethane and mixtures thereof.

[0248] In one embodiment, the heat transfer fluid is a refrigerant fluid selected from 1,3,3,3-tetrafluoropropene (1234ze) and 2,3,3,3-tetrafluoropropene (1234yf), more particularly, 1,3,3,3-tetrafluoropropene (1234ze) and 2,3,3,3-tetrafluoropropene (1234yf).

[0249] Advantageously, the refrigerant fluid is preferably selected from mineral oils, silicone oils, naturally occurring paraffins, naphthenes, synthetic paraffins, alkylbenzenes, polyalphaolefins, polyalkylene glycols, polyol esters and / or polyvinyl ethers, and the lubricant contains a lubricant more particularly preferably selected from polyalkylene glycols or polyol esters.

[0250] According to another aspect, the present invention relates to a method for the preparation of heat transfer fluids, more particularly hydrocarbon compounds, hydrofluorocarbons, ethers, hydrofluoroethers, CO 2 , N.H. 3 , S.O. 2and fluoroolefins, in particular R134, R-1234yf or R-1234ze, more particularly R-1234yf or R-1234ze.

[0251] According to yet another aspect, the invention relates to the use of a multi-layer tubular structure as defined above, for satisfying a test for extractables, said test in particular comprising filling said multi-layer tubular structure MLT with foran, heating the assembly at 60° C. for 96 hours, then emptying it by filtering it into a beaker, then evaporating the filtrate in the beaker at room temperature, and finally weighing this residue, the proportion of which is about 6 g / m 2 of the internal surface area of ​​the tube. 2 The residue on the filter after filtration must be less than 1 g / m 2 Less than 0.5 g / m 2 The present invention relates to a method for using the present invention, comprising the steps of:

[0252] In other words, the invention relates to the use of a multi-layer tubular structure as defined above to reduce the proportion of soluble and insoluble compounds released by the tubular structure as defined above after the multi-layer tubular structure MLT as defined above has been contacted with Foran. The proportion of compounds released is determined by an extractables test, which in particular consists of filling the multi-layer tubular structure MLT as defined above with Foran, heating the assembly at 60° C. for 96 hours, then filtering it and emptying it into a beaker, then evaporating the filtrate in the beaker at room temperature and finally weighing this residue, the proportion being approximately 6 g / m 2 of the inner tube surface area. 2 The residue rate on the filter after filtration must be less than 1 g / m 2 Less than 0.5 g / m 2 The following is the result.

[0253] This tubular structure therefore allows a reduction in the proportion of soluble and insoluble compounds after contact with the forane compared to prior art structures.

[0254] Working Example The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0255] The following structures were prepared by extrusion: The multi-layer tubes are produced by co-extrusion. A McNeil industrial multi-layer extrusion line with five extruders connected to a multi-layer extrusion head with a spiral mandrel is used.

[0256] The screw used is a single extrusion screw with a screw profile suitable for polyamides. In addition to the five extruders and the multi-layer extrusion head, the extrusion line includes: a die punch assembly disposed at the end of the coextrusion head, the inner diameter of the die and the outer diameter of the punch being selected according to the structure and material of construction to be produced, the dimensions of the tube, and the line speed; A vacuum tank with adjustable vacuum level. Water, usually kept at 20°C, circulates in it, and the gauges are immersed in it to allow the tube to be shaped to its final dimensions. The gauge diameter is adjusted to suit the dimensions of the tube to be produced, and is usually 8.8 to 11 mm for a tube with an internal diameter of 6 mm and a thickness of 1.3 mm. a series of cooling tanks in which water is maintained at approximately 20°C, capable of cooling the tube along its path from the head to the drawing stand; A diameter measuring instrument; Pull-out stand.

[0257] A configuration with five extruders is used to produce tubes with two to five layers. For structures with fewer than five layers, multiple extruders are fed with the same material.

[0258] For a six-layer construction, an additional extruder is connected and a spiral mandrel is added to the existing head to produce the inner layer that comes into contact with the fluid.

[0259] Prior to testing, it is verified that the extrusion material prior to extrusion has a residual moisture content of less than 0.08% to ensure the best properties of the tube and good quality of the extrusion. If the opposite is true, an additional step is performed prior to testing, usually drying the material overnight at 80°C in a vacuum dryer.

[0260] Tubes corresponding to the characteristics described in this patent application are removed after the extrusion parameters have stabilized and the dimensions of the tubes in question no longer change over time. The diameter is monitored by a laser diameter gauge installed at the end of the line.

[0261] The line speed is usually 20 m / min. It usually varies in the range of 5 to 100 m / min.

[0262] The extruder screw speed depends on the layer thickness and the screw diameter, as known to those skilled in the art.

[0263] In general, the temperature of the extruder and tooling (head and couplings) must be adjusted to be sufficiently higher than the melting point of the composition in question so that it remains in a molten state and prevents it from solidifying and clogging the machinery.

[0264] Tubular structures using the following polymers: P1: PA6 + 35 wt% Orevac® IM 800 (maleic anhydride modified HDPE (SK Functional Polymers)) P2: PA11 Rilsan® BESN Black TL P024 (Arkema) P3: PA612 + 20 wt% Orevac® IM 800 (maleic anhydride modified HDPE (SK functionalized polymer)) P4: PP-g-MAH (maleic anhydride grafted polypropylene) Admer QB509E (Mitsui) P5: HDPE-g-MAH (maleic anhydride grafted high density polyethylene), obtained by blending 93 wt% of XRT70 PERT Type II (total energy) and 7 wt% of Orevac OE25 (SK functionalized polymer). P6: EVOH Eval 171B (Kuraray) P7: PA6 + 10 wt% Orevac® IM 800 (maleic anhydride modified HDPE (SK Functional Polymers)) Various parameters were tested, as shown in Table 1. [Table 1] TIFF2025509213000001.tif140170

[0265] CE1~7: Counterexample A counter example would be a wall that is too permeable to water, i.e. a flow rate of 23 g / m 2 24h or longer, or the burst stress is too low, i.e. the stress is less than 12MPa, or it does not block the flow of R1234yf, i.e. classification A or B, or it has low contact resistance with zinc chloride, i.e. classification 2 or 3.

[0266] EI1 to EI4: Examples according to the present invention Only the four-layer structure according to the invention has a burst pressure of more than 12 MPa, barrier properties against air conditioning fluids (R1234yf) (Class C), resistance to zinc chloride (Class 1), and a strength of 23 g / m 2 · A good trade-off was shown for the four evaluated criteria, such as water permeability at flow rates below 24 h, whereas the counterexample did not provide a good combination of performance for the four evaluated criteria.

[0267] Details of the studies used are shown in Table 2. [Table 2] TIFF2025509213000002.tif233170

Claims

1. 1. A multi-layer tubular structure (MLT) for transporting a heat transfer fluid, the multi-layer tubular structure comprising: at least one layer (1) comprising a composition (1) predominantly comprising at least one long-chain polyamide (PA) having from 10 to 15 carbon atoms per nitrogen atom and comprising at least 50% of aliphatic units relative to the total of the units present in said long-chain polyamide; at least one layer (2) located beneath said layer (1), mainly comprising a composition (2) comprising at least one polyamide having 4 to 9 carbon atoms per nitrogen atom, said polyamide comprising at least 50% of aliphatic units relative to the sum of the units present in said polyamide, more particularly said composition (2) comprising at most 12% by weight of polyolefin, relative to the total weight of said composition (2), in particular at most 6% by weight of polyolefin, and at most 2% by weight of at least one plasticizer, relative to the total weight of said composition (2); at least one layer (3) mainly comprising a composition (3) comprising a hydrophobic polymer, more particularly polypropylene or polyethylene, and more particularly located below said layer (2) or between said layer (1) and said layer (2); a layer (4) comprising a composition (4) comprising PA6, PA66 or a mixture thereof, comprising from 5% to 50% by weight of at least one polyolefin, more particularly a functionalized polyolefin, preferably from 10% to 40% by weight of at least one polyolefin, up to 2% by weight of at least one plasticizer and up to 2% by weight of additives, relative to the total weight of said composition (4); Alternatively, a layer (4) comprising any of the compositions (4') mainly comprising at least one C8 to C14 aliphatic polyamide; Including, said layer (4) being in contact with said fluid to be transported; and the thickness of said layer (2) occupies at least 70% of the total thickness of the tube.

2. 2. A multi-layer tubular structure according to claim 1, characterized in that between said layers (3) and (4) there is a layer (5), said layer (5) comprising the composition (2), and the thickness of said layers (2) and (5) occupies at least 80% of the total thickness of the tube.

3. A multi-layer tubular structure according to claim 1 or 2, characterized in that said layer (1) is the outermost layer of said multi-layer tubular structure.

4. 4. A multilayer tubular structure according to claim 1, characterized in that the composition (1) comprises up to 40% by weight of at least one polyolefin.

5. 5. A multilayer tubular structure according to any one of claims 1 to 4, characterized in that the composition (1) comprises at least 3% by weight of at least one polyolefin, more particularly at least 6% by weight of at least one polyolefin, in particular between 10% and 12% by weight of at least one polyolefin, relative to the total weight of the composition (1).

6. 6. The multilayer tubular structure according to any one of claims 1 to 5, wherein the composition (1) comprises up to 8% by weight of at least one plasticizer relative to the weight of the composition (1), more particularly, the layer (1) is free of plasticizers.

7. The heat transfer fluid is a hydrocarbon compound, a hydrofluorocarbon, an ether, a hydrofluoroether, CO ２ , N.H. ３ , S.O. ２ 7. The multilayer tubular structure according to claim 1, wherein the refrigerant fluid is selected from the group consisting of fluoroolefins and fluoroolefins.

8. The heat transfer fluid is CO ２ , fluoropropene, fluoropropane and fluoroethane, preferably 1,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene, 1,2,3,3,3-pentafluoropropene, 1,1,3,3-tetrafluoropropene, 3,3,3-trifluoropropene, 2,3,3-trifluoropropene, 1,1,1,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethane, pentafluoroethane, 8. The multi-layer tubular structure according to claim 7, characterized in that the refrigerant fluid is selected from the group consisting of fluoroethane, difluoromethane, 1,1-difluoroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1-trifluoropropane, 1,1,1,3,3,3-hexafluoropropane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, trifluoroiodomethane and mixtures containing them.

9. 9. A multilayer tubular structure according to claim 7 or 8, characterized in that the heat transfer fluid is a refrigerant fluid selected from 1,3,3,3-tetrafluoropropene (1234ze) and 2,3,3,3-tetrafluoropropene (1234yf), more particularly, the heat transfer fluid is 2,3,3,3-tetrafluoropropene (1234yf).

10. 10. The multilayer tubular structure according to any one of claims 7 to 9, characterized in that the refrigerant fluid contains a lubricant, preferably selected from mineral oil, silicone oil, naturally occurring paraffins, naphthenes, synthetic paraffins, alkylbenzenes, polyalphaolefins, polyalkylene glycols, polyol esters and / or polyvinyl ethers, more preferably the lubricant is a polyalkylene glycol or a polyol ester.

11. 11. The multilayer tubular structure according to any one of claims 1 to 10, characterized in that the at least one polyamide of layer (1) is selected from PA11, PA12, PA1010, PA1210 and PA1212.

12. 12. A multilayer tubular structure according to any one of claims 1 to 11, characterized in that the at least one polyamide of layer (2) is selected from PA6, PA66, PA6 / 66, PA610, PA410, PA412 and PA612.

13. 13. A multilayer tubular structure according to any one of claims 1 to 12, characterized in that the at least one hydrophobic polymer of layer (3) is selected from grafted polypropylene, preferably grafted with maleic anhydride, and grafted high density polyethylene (HDPE), preferably grafted with maleic anhydride.

14. 14. A multi-layer tubular structure according to any one of claims 1 to 13, characterized in that it consists of four layers (1) / / (2) / / (3) / / (4) or (1) / / (3) / / (2) / / (4).

15. 14. A multi-layer tubular structure according to any one of claims 1 to 13, characterized in that it consists of five layers (1) / / (2) / / (3) / (5) / / (4) or (1) / / (3) / / (2) / (5) / / (4).

16. Heat transfer fluids in the field of automotive air conditioning, more specifically hydrocarbon compounds, hydrofluorocarbons, ethers, hydrofluoroethers, CO ２ , N.H. ３ , S.O. ２ 16. Use of the multilayer cyclic structure according to any one of claims 1 to 15 for transporting refrigerant fluids selected from the group consisting of fluoroolefins, in particular R134, R-1234yf or R-1234ze, more particularly R-1234yf or R-1234ze.

17. Use of a multi-layer tubular structure according to any one of claims 1 to 15 for satisfying a test for extractables, said test in particular comprising filling said multi-layer tubular structure MLT with foran, heating the assembly at 60°C for 96 hours, then emptying it by filtering it into a beaker, then evaporating the filtrate in the beaker at room temperature and finally weighing this residue, the proportion of said residue being less than about 6 g / m2 of the inner tube surface area. ２ The residue rate on the filter after filtration must be less than 1 g / m ２ Less than 0.5 g / m ２ The use of, including, measuring, which is as follows.

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