Annular tube structure for transporting fuel to a tank

Description

[0001] The invention relates to a flexible, partly corrugated tubular structure for transporting fuel, in particular petrol or diesel, in particular petrol, in the tank of a motor vehicle.

[0002] The invention relates more particularly to a single-layer or multi-layer tubular structure, located at least partially inside the fuel tank and capable of being at least partially immersed in the vehicle tank.

[0003] Said single-layer or multi-layer tubular structure is therefore intended to be at least partially inside the fuel tank and capable of being at least partially immersed in the vehicle tank.

[0004] Fuels currently used in motor vehicles increasingly include corrosive compounds such as methanol or ethanol.

[0005] Alcoholic compounds and other compounds present in the transported fuels cause the dissolution and diffusion of species, in particular monomers and oligomers from the tube in contact with the gasoline, the tube typically being made of aliphatic materials such as aliphatic polyamides like PA 11 or PA 12.

[0006] Car manufacturers are becoming increasingly demanding about the amount of extractables such as monomers / oligomers dissolved in gasoline, which are more likely to clog injectors.

[0007] According to US patent 5,076,329, a layer of PA 6 as an inner layer makes it possible to at least partially eliminate the problem of excess extractables that would occur with PA 12 as the inner layer of a gasoline transport pipe comprising five layers. The use of a five-layer system makes it possible to obtain a pipe with the impact resistance of PA 12 with a low monomer / oligomer content.

[0008] However, according to WO 94 / 09303, these characteristics cannot be obtained with a pipe comprising less than five layers.

[0009] This document then recommends the use of a partially corrugated two-layer or three-layer pipe comprising, for the two-layer, an outer layer which may be made of PA 11 or PA 12, and an inner layer which is not made of polyamide and chosen from fluorinated compounds such as PVDF. In the context of the three-layer, a bonding layer, in particular made of PVDF, is then introduced between the outer layer and the inner layer.

[0010] However, these pipes have an operating temperature between -40°C and 150°C and are used for vehicle engines.

[0011] EP 1039199 describes partly corrugated pipes for use in the transport of gasoline comprising at least two layers, an outer layer of polyamide and an inner layer of tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV).

[0012] However, this document specifies that the outer layer protects the pipe, for example, from impact caused by a stone when the car is moving and that it is preferable for the resin to have a certain level of resistance to elongation and impact, which implies that the use of this pipe is intended for transporting gasoline after the tank or in the engine.

[0013] US 2011 / 277867 discloses a corrugated tube comprising a layer based on plasticized polyamide 11.

[0014] US 2007 / 075543 discloses a corrugated tube comprising a polyamide 11-based layer.

[0015] WO 2007 / 029424 discloses a corrugated tube comprising a polyamide-based layer, in particular nylon 6 or nylon 66.

[0016] It is therefore necessary for use of the pipe in the vehicle tank to be able to have a pipe which, although able to be immersed at least partially in the vehicle's fuel, has a quantity of extractables which is lower than that of the pipes of the prior art above and satisfies the manufacturers' requirements.

[0017] This was solved by the flexible, partly ringed structure of the invention.

[0018] The present invention therefore relates to a flexible, partly corrugated tubular structure intended to be placed at least partially inside the fuel tank, in particular petrol or diesel, in particular petrol, of a vehicle, said structure being able to be at least partially immersed in said tank and intended for the transport of said fuel in said tank, said tubular structure comprising at least one layer (1) consisting of a composition consisting of a.from 39% to 100% by weight, in particular from 41% to 100% by weight of at least one aliphatic polyamide of formula W / Z in which: W is an aliphatic repeating unit obtained from the polycondensation of at least one C 6 to C 18 lactam, preferably C 7 to C 13, or of at least one C 6 to C 18 aminocarboxylic acid, preferably C 7 to C 13, or is an aliphatic repeating unit XY having an average number of carbon atoms per nitrogen atom noted as from 6 to 18, preferably from 7 to 13, obtained from the polycondensation: of at least one C 6 to C 18 diamine X, said diamine being chosen from a linear or branched aliphatic diamine or a mixture thereof, and of at least one dicarboxylic acid aliphatic Y in C 6 to C 18 , Z is at least one optional polyamide repeating unit, Z being able to be present up to 30% by weight relative to the total weight W / Z, preferably up to 15% by weight relative to the total weight W / Z, b.from 0 to 2% by weight of at least one plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 0% to 37% by weight of at least one additive, the sum a. + b. + c. + d. being equal to 100%, excluding a fuel transport structure from the tank to the vehicle engine.

[0019] In other words, said structure is intended to be placed at least partially inside the fuel tank.

[0020] The inventors have therefore found that a tubular structure comprising a layer comprising a particular composition as defined above makes it possible to significantly reduce the quantity of extractables and in particular the “solubles” and thus to satisfy a car manufacturer’s extractables test.

[0021] The term "flexible" means that the deformation and extension capabilities of the tubular structure allow the formation of relatively small angles allowing the tubular structure to be adapted to a limited space delimited by the fuel tank.

[0022] The expression "situated at least partially inside the tank" means that more than 70%, preferably, more preferably more than 90%, even more preferably more than 95%, and in particular 100% of the total length of the pipe is located in the tank, a part of said pipe being able to exit said tank to adapt to a fuel transport pipe between the tank and the engine by means in particular of a connector.

[0023] There are therefore no other constituents in the said composition than constituents a, b, c and d, the sum of which is equal to 100% by weight.

[0024] Layer (1) is therefore made up only of said composition which itself is made up only of constituents a, b, c and d, the sum of which is equal to 100% by weight.

[0025] Advantageously, 90% to 98% of the total length of the pipe is located in the tank.

[0026] Advantageously, 95% to 98% of the total length of the pipe is located in the tank.

[0027] More specifically, more than 98% of the total pipe length is located in the tank.

[0028] The term "partly corrugated" means that the pipe has a corrugated tubular shape along part of its length. The corrugated portion may form a single portion or several portions of the structure, in which case two corrugated portions are separated by a smooth portion.

[0029] The corrugated part(s) allow(s) to increase the deformation and extension capacity of the tubular structure, particularly in areas of the tank where small angles are necessary.

[0030] Advantageously, the tubular structure is ringed over at least 10% of its length.

[0031] Advantageously, the tubular structure is ringed over a proportion of 10 to more than 90% of its length.

[0032] Advantageously, the tubular structure is ringed over a proportion of 20 to 90% of its length.

[0033] Advantageously, the tubular structure is ringed over a proportion of 30 to more than 90% of its length.

[0034] Advantageously, the tubular structure is ringed over a proportion of 40 to more than 90% of its length.

[0035] Advantageously, the tubular structure is ringed over a proportion of 50 to more than 90% of its length.

[0036] Advantageously, the tubular structure is ringed over a proportion of 60 to more than 90% of its length.

[0037] Advantageously, the tubular structure is ringed over a proportion of 70 to more than 90% of its length.

[0038] Advantageously, the tubular structure is ringed over a proportion of 80 to more than 90% of its length.

[0039] Advantageously, the tubular structure is ringed over a proportion of more than 90% of its length.

[0040] The expression "capable of being at least partially submerged in said tank" means that said structure is either not submerged, regardless of the filling level of the tank, or that at least 30% of the length of said structure is submerged in the fuel.

[0041] It is obvious that this proportion depends on the fuel level in the tank and that the values ​​given correspond to a tank which contains the maximum quantity of fuel it can contain.

[0042] Advantageously, at least 40% of the length of said structure is immersed in the fuel.

[0043] Advantageously, at least 50% of the length of said structure is immersed in the fuel.

[0044] Advantageously, at least 60% of the length of said structure is immersed in the fuel.

[0045] Advantageously, at least 70% of the length of said structure is immersed in the fuel.

[0046] Advantageously, at least 80% of the length of said structure is immersed in the fuel.

[0047] In another embodiment, said structure is located at least partially inside the tank but is not submerged regardless of the filling level of the tank.

[0048] The tubular structure of the invention is intended for transporting fuel in the tank and therefore does not relate to a tubular structure for transporting fuel from the tank to the engine or in the engine of the vehicle, even if it is obvious that the structure of the invention has a small part which is located outside the tank.

[0049] However, this part will be fixed to a connector making it possible to connect the tubular structure of the invention to the tubular structure for transporting fuel from the tank to the engine and cannot therefore be considered as the latter tubular structure for transporting fuel from the tank to the engine.

[0050] It is obvious that when a plasticizer and / or an impact modifier and / or an additive is or are present, the person skilled in the art will vary the proportions of aliphatic polyamide so that the sum a. + b. + c. + d. is equal to 100%. Regarding layer (1)

[0051] Layer (1) comprises 39% to 100% by weight, in particular 41% to 100% by weight of an aliphatic polyamide of formula W / Z.

[0052] According to the present application, the term "polyamide", also noted PA, refers to: homopolymers (or homopolyamides), copolymers, or copolyamides, based on different amide units, polyamide alloys, provided that polyamide is the majority constituent.

[0053] There is also a category of copolyamides in the broad sense, which although not preferred, is part of the scope of the invention. These are copolyamides comprising not only amide units (which will be in the majority, hence the fact that they are to be considered as copolyamides in the broad sense), but also units of a non-amide nature, for example ether units. The best known examples are PEBA or polyether-block-amide, and their copolyamide-ester-ether, copolyamide-ether, copolyamide ester variants. Among these, we can cite PEBA-12 where the polyamide units are the same as those of PA12, PEBA-612 where the polyamide units are the same as those of PA612.

[0054] The nomenclature used to define polyamides is described in ISO 1874-1:1992 "Plastics -- Polyamide (PA) materials for molding and extrusion -- Part 1: Designation", particularly on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0055] In one embodiment, the tubular structure of the invention consists of at least one layer (1).

[0056] The tubular structure may comprise several identical or different, in particular identical, layers (1).

[0057] In another embodiment, the tubular structure of the invention consists of a single layer (1) but may comprise other layers.

[0058] In yet another embodiment, the structure is single-layer and consists of a single layer (1).

[0059] In the case where the tubular structure is single-layer, said structure is therefore in contact with the essence both by its external surface and by its internal surface. Regarding the W / Z repeating pattern W : aliphatic repeating unit obtained from the polycondensation of at least one aminocarboxylic acid or at least one lactam

[0060] In a first variant of the invention, the aliphatic repeating unit W is obtained from the polycondensation of at least one C 6 -C 18 aminocarboxylic acid, preferably C 7 -C 13.

[0061] Advantageously, said aminocarboxylic acid comprises from 9 to 12 carbon atoms. It can thus be chosen from 9-aminononanoic acid (noted 9), 10-aminodecanoic acid (noted 10), 11-aminoundecanoic acid (noted 11) and 12-aminododecanoic acid (noted 12), advantageously the aminocarboxylic acid is 11-aminoundecanoic acid.

[0062] In a second variant of the invention, the aliphatic repeating unit W is obtained from the polycondensation of at least one C 6 -C 18 lactam, preferably C 7 -C 13.

[0063] Advantageously, the lactam comprises from 9 to 12 carbon atoms. It can thus be chosen from decanolactam (noted 10), undecanolactam (noted 11) and laurolactam or lauryllactam (noted 12), advantageously the lactam is lauryllactam.

[0064] However, it is entirely possible to envisage using, to obtain this same W unit, a mixture of two or more aminocarboxylic acids, a mixture of two or more lactams, but also a mixture of one, two or more aminocarboxylic acids with one, two or more lactams.

[0065] More particularly preferably, the repeating unit W is obtained from a single aminocarboxylic acid or a single lactam.

[0066] In one embodiment, a repeating unit containing at least 20% repeating units obtained from the polycondensation of units derived from a C 12 aminocarboxylic acid or lactam as a starting material is excluded from the definition of W.

[0067] In another embodiment, a repeating unit containing at least 20% of repeating units obtained from the polycondensation of units derived from an aminocarboxylic acid or a C 12 lactam as raw material is excluded from the flexible tubular structure of the invention regardless of the number of layers of said structure.

[0068] In another embodiment, a repeating unit obtained from the polycondensation of a lactam or a C 12 aminocarboxylic acid is excluded from the definition of W.

[0069] In yet another embodiment, a repeating unit obtained from the polycondensation of a lactam or a C 12 aminocarboxylic acid as a raw material is excluded from the flexible tubular structure of the invention regardless of the number of layers of said structure. W : XY aliphatic repeating pattern

[0070] The aliphatic repeating unit XY is a unit obtained from the polycondensation of at least one linear or branched aliphatic diamine X in C 6 -C 18 , preferably in C 7 -C 13 , or a mixture thereof, and at least one aliphatic dicarboxylic acid Y in C 6 -C 18 , preferably in C 7 -C 13 .

[0071] The molar proportions of diamine and dicarboxylic acid are preferably stoichiometric.

[0072] The aliphatic diamine used to obtain this XY repeating unit is an aliphatic diamine which has a linear main chain comprising 6 to 18 carbon atoms.

[0073] This linear main chain may, if necessary, contain one or more methyl and / or ethyl substituent(s); in this latter configuration, we speak of a "branched aliphatic diamine". In the case where the main chain does not contain any substituent, the aliphatic diamine is called a "linear aliphatic diamine".

[0074] Whether or not it contains methyl and / or ethyl substituents on the main chain, the aliphatic diamine used to obtain this XY repeating unit contains from 6 to 18 carbon atoms, in particular from 7 to 13 carbon atoms.

[0075] When this diamine is a linear aliphatic diamine, it corresponds in particular to the formula H2N-(CH2)x-NH2 and can be chosen for example from hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, hexadecanediamine and octadecanediamine. The linear aliphatic diamines which have just been cited can all be bio-resourced within the meaning of standard ASTM D6866.

[0076] When this diamine is a branched aliphatic diamine, it may in particular be 2-methylpentanediamine, 2-methyl-1,8-octanediamine or trimethylene (2,2,4 or 2,4,4) hexanediamine.

[0077] The dicarboxylic acid contains 6 to 18 carbon atoms, especially 7 to 13 carbon atoms.

[0078] The aliphatic dicarboxylic acid may be chosen from linear or branched aliphatic dicarboxylic acids.

[0079] When the dicarboxylic acid is aliphatic and linear, it can be chosen from adipic acid (6), heptanedioic acid (7), octanedioic acid (8), azelaic acid (9), sebacic acid (10), undecanedioic acid (11), dodecanedioic acid (12), brassylic acid (13), tetradecanedioic acid (14), hexadecanedioic acid (16), octadecanedioic acid (18), octadecenedioic acid (18).

[0080] Advantageously, said layer (1) comprises a composition comprising at least 49% by weight of said at least one aliphatic polyamide.

[0081] Advantageously, said layer (1) comprises a composition comprising at least 50% by weight of said at least one aliphatic polyamide.

[0082] Advantageously, said layer (1) comprises a composition comprising at least 60% by weight of said at least one aliphatic polyamide.

[0083] Advantageously, said layer (1) comprises a composition comprising at least 70% by weight of said at least one aliphatic polyamide.

[0084] Advantageously, said layer (1) comprises a composition comprising at least 80% by weight of said at least one aliphatic polyamide. Z : optional repeating pattern

[0085] Z may be any polyamide repeating unit, whether aliphatic, cycloaliphatic, semi-aromatic or aromatic. Z may be present up to 30% by weight relative to the total weight W / Z. Advantageously, Z is present up to 25% by weight. Advantageously, Z is present up to 20% by weight. Advantageously, Z is present up to 15% by weight. Advantageously, Z is present up to 10% by weight. Advantageously, Z is present up to 5% by weight. Advantageously, Z is equal to 0% by weight. Regarding the plasticizer

[0086] The plasticizer is in particular chosen from benzene sulfonamide derivatives, such as n-butyl benzene sulfonamide (BBSA); ethyl toluene sulfonamide or N-cyclohexyl toluene sulfonamide; hydroxybenzoic acid esters, such as ethyl-2-hexyl parahydroxybenzoate and decyl-2-hexyl parahydroxybenzoate; esters or ethers of tetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfuryl alcohol; and esters of citric acid or hydroxymalonic acid, such as oligoethyleneoxy malonate.

[0087] It would not be outside the scope of the invention to use a mixture of plasticizers.

[0088] The particularly preferred plasticizer is n-butyl benzene sulfonamide (BBSA).

[0089] The plasticizer can be introduced into the polyamide during polycondensation or later.

[0090] The plasticizer used in the composition is in a mass proportion of 0 to 2%.

[0091] Beyond 2%, the proportion of plasticizer is too high and the extractables rate is then too high.

[0092] In yet another embodiment, the plasticizer used in the composition is in a mass proportion of 0.1 to 2%.

[0093] The tube being partly corrugated, this geometry of the tubular structure provides a certain flexibility and the said composition of the said layer (1) therefore does not necessarily require the presence of a plasticizer. In an advantageous embodiment, the said composition of the said layer (1) is free of plasticizer.

[0094] Advantageously, the tubular structure is corrugated over a proportion of 10 to more than 90% of its length and said composition of the layer (1) is free of plasticizer. Regarding the shock modifier

[0095] The tubular structure of the invention is located in the tank and therefore, the latter is protected from impacts and does not require particular protection against impacts and therefore the shock modifier is not essential.

[0096] However, to gain flexibility, the presence of shock modifiers can be useful and / or desirable.

[0097] The term "impact modifier" means a polyolefin-based polymer with a flexural modulus of less than 100 MPa measured according to ISO 178:2010 (23°C RH50) and a Tg of less than 0°C (measured according to 11357-2:2013 at the inflection point of the DSC thermogram), in particular a polyolefin.

[0098] The impact modifier can also be a PEBA (polyether-block-amide) type block polymer with a flexural modulus < 200 MPa.

[0099] The polyolefin of the impact modifier may be functionalized or non-functionalized or be a mixture of at least one functionalized and / or at least one non-functionalized. In particular, some or all of the polyolefins carry a function chosen from carboxylic acid, carboxylic anhydride and epoxide functions, and is in particular chosen from an ethylene and propylene copolymer with an elastomeric character (EPR), an ethylene-propylene-diene copolymer with an elastomeric character (EPDM) and an ethylene / alkyl (meth)acrylate copolymer, an ethylene-higher alkene copolymer, in particular an ethylene-octene copolymer, an ethylene-alkyl acrylate-maleic anhydride terpolymer.Advantageously, the impact modifier is chosen from Fusabond ®< N493, Fusabond MF416D, a Lotader ®< , in particular Lotader ®< 4700, Lotader ®< 5500, Lotader ®< 7500 or Lotader ®< 3410, Exellor ®< VA1801 or VA1803, Amplify ®< GR216, Tafmer ®< MH5020, MH5040, MH7020, MH7010, or a mixture of these, in this case they are in a ratio ranging from 0.1 / 99.9 to 99.9 / 0.1, preferably 1 / 2 to 2 / 1 when they are a mixture of two.

[0100] For example, the impact modifier is chosen from the following mixtures: Fusabond ®< N493 / Lotader ®< , in particular Fusabond ®< N493 / Lotader ®< 5500 or Fusabond ®< N493 / Lotader ®< 7500.

[0101] The impact modifier can also be a PEBA (polyether-block-amide).

[0102] The proportion of impact modifier in said composition of said layer (1) is present from 0 to 20%.

[0103] In one embodiment, the impact modifier is present from 3 to 20%.

[0104] In another embodiment, the impact modifier is present from 10 to 18% by weight relative to the total weight of the constituents of the composition of the layer (1).

[0105] In yet another embodiment, the impact modifier is in a weight proportion of 0% relative to the total weight of the constituents of the composition of the layer (1) and is therefore excluded from the composition of said layer (1). Regarding the additive

[0106] The additive(s) d. are selected from carbon black, graphite, graphene, carbon fibers, carbon nanotubes, in particular carbon black and carbon nanotubes, an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent, a colorant, reinforcing fibers, a wax and mixtures thereof.

[0107] Plasticizers and impact modifiers in this application are excluded from the definition of additives.

[0108] Said composition of said layer (1) may comprise at least one additive of 0 to 35% by weight relative to the total weight of the composition.

[0109] Said layer (1) can therefore be conductive or not depending on the presence of carbon black, graphite, graphene, carbon fibers or carbon nanotubes. Advantageously, one of these additives is an antioxidant.

[0110] This antioxidant may be an organic antioxidant or more generally a combination of organic antioxidants, such as a primary phenol-type antioxidant (for example of the type of Irganox ®< 245 or 1098 or 1010 from the company Ciba), a secondary phosphite-type antioxidant, a phenolic or phosphorus-based antioxidant. It is also possible to use amine-type antioxidants such as Naugard ®< 445 from the company Chemtura or polyfunctional antioxidants such as Nylostab ®< S-EED from the company Clariant.

[0111] This antioxidant may also be a mineral antioxidant, such as a copper-based antioxidant. Examples of such mineral antioxidants include copper halides and acetates, particularly CuI / K1. Alternatively, other metals such as silver may be considered, but these are known to be less effective. These copper-based compounds are typically combined with alkali metal halides, particularly potassium.

[0112] The light stabilizer can be a HALS, which stands for Hindered Amine Light Stabilizer (e.g. Tinuvin ®< 770 from Ciba).

[0113] The UV absorber is, for example, Tinuvin ®< 312 from the company Ciba.

[0114] According to a first variant, the additive is carbon black, in particular in a proportion of 5 to 32%, in particular 15 to 28% relative to the total weight of said composition of said layer (I). Said additive which is carbon black may optionally comprise at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes in a proportion of 0 to 5% by weight. The proportion of the additive which is carbon black and optionally of the other additive relative corresponds to d..

[0115] According to a second variant, the additive is carbon nanotubes in a proportion of 0.5 to 10%, in particular 2 to 7%, in particular 4 to 5% by weight relative to the total weight of the composition.

[0116] It would not be outside the scope of the invention if, in these variants, carbon black were partially replaced by carbon nanotubes or vice versa.

[0117] The sum a. + b. + c. + d. by weight represents 100% of the total weight of the composition. Therefore, there can be no other constituents than a., b., c. and d. in the composition.

[0118] It is obvious that whatever the high and low values ​​of the different constituents a., b., c. and d., the total is 100%. In other words, even if the addition of the high value of one of the constituents a., b., c. and d. and the low values ​​of the other constituents may represent more than 100%, it is obvious that the person skilled in the art will vary one or more constituents a., b., c. and d. so that the total of the constituents does not exceed 100% by weight.

[0119] Whether the tubular structure consists of a single layer or comprises other layers, as indicated above, it is located at least partially inside the tank, which means that more than 90% of the total length of the pipe is located in the tank and therefore, said tubular structure is not a structure for transporting fuel between the tank and the engine of a vehicle and this due to the fact that it can be at least partially immersed in the tank, which has the consequence when it is at least partially immersed that both the inner layer of said tubular structure and the outer layer of said tubular structure are in contact with the fuel, and this at least partially for the outer layer.In the embodiment where the structure is single-layer, the single layer (1) is therefore in contact with the fuel both on the internal face and on the external face, at least partially for the latter when it is at least partially immersed.

[0120] The tubular structure of the invention is also not a tubular structure present in the engine.

[0121] The polyamides defined above in their generalities, whether homopolyamides, copolyamides and alloys, can also be distinguished by their number of carbon atoms per nitrogen atom, knowing that there are as many nitrogen atoms as amide groups (-CO-NH-). Tubular structure with an aliphatic polyamide being at least one polyamide noted C obtained from the polycondensation of at least one C 6 lactam has C 18 , or at least one C 6 to C 18 aminocarboxylic acid.

[0122] In one embodiment, the tubular structure defined above is characterized in that said at least one aliphatic polyamide is at least one polyamide denoted C obtained from the polycondensation of at least one C 6 to C 18 lactam, preferably C 7 to C 13, or of at least one C 6 to C 18 aminocarboxylic acid, preferably C 7 to C 13, and having an average number of carbon atoms per nitrogen atom denoted CC of between 9 and 18, advantageously between 10 and 18.

[0123] Throughout the description, the expression "between ... and ... » includes the boundaries and has the same meaning as the expression " understood from ... has ... ".

[0124] It is quite obvious that to obtain an average number of carbon atoms per nitrogen atom denoted CC of between 9 and 18 with a polyamide denoted C obtained from the polycondensation of at least one C7 or C8 lactam, or of at least one C7 or C8 aminocarboxylic acid, said polyamide denoted C must be a copolyamide or a mixture of polyamides whose second unit has an average number of carbon atoms per nitrogen atom denoted CC of greater than 9 depending on the molar proportion of said second unit.

[0125] Advantageously, said aliphatic polyamide is a single polyamide denoted C obtained from the polycondensation of at least one C 6 to C 18 lactam, preferably C 7 to C 13, or of at least one C 6 to C 18 aminocarboxylic acid, preferably C 7 to C 13, and having an average number of carbon atoms per nitrogen atom denoted CC of between 9 and 18, advantageously between 10 and 18.

[0126] In another embodiment, said constituent a. of said composition further comprises another polyamide chosen from: at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7; at least one polyamide denoted B having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB of between 7 and 10, advantageously between 7.5 and 9.5; or a mixture thereof, the weighted average mass of the fusion enthalpies of the polyamides being greater than 25J / g (DSC), the average number of carbon atoms per nitrogen atom of the polyamides A, B and C also satisfying the following strict inequality: CA < CB < CC.

[0127] The polyamide denoted A and the polyamide denoted B, said polyamide denoted B having a melting temperature greater than or equal to 180°C, are polyamides obtained either from the polycondensation of at least one lactam, or at least one aminocarboxylic acid and having respectively an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7, and an average number of carbon atoms per nitrogen atom denoted CB of between 7 and 10, advantageously between 7.5 and 9.5, but may also be a PA X'Y' obtained from the polycondensation of a linear or branched aliphatic diamine X', provided that the average number of carbon atoms per nitrogen atom is respected for each of the polyamides A and B.

[0128] Advantageously, the difference between the average numbers of carbon atoms per nitrogen atom (CB -CA ) and / or (CC -CB ) is between 1 and 4, and preferably between 2 and 3.

[0129] The enthalpy of fusion and melting temperature of polyamides are determined according to ISO 11357-3:2013.

[0130] The composition of said layer (1) can therefore comprise a polyamide noted C and a polyamide noted A, or a polyamide noted C and a polyamide noted B, or even a polyamide noted C, a polyamide noted A and a polyamide noted B.

[0131] The mass proportion of the different polyamides in the compositions above is variable, which means that one of the polyamides noted A, B or C is in the majority compared to the sum C + A, C + B or C + A + B.

[0132] In a first variant, said constituent a. of said composition further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7.

[0133] Advantageously, the melting temperature of polyamide A is greater than or equal to 210°C.

[0134] In a second variant, said constituent a. of said composition further comprises at least one polyamide denoted B having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB of between 7 and 10, advantageously between 7.5 and 9.5.

[0135] Advantageously, the melting temperature of polyamide B is less than or equal to 200°C.

[0136] In a third variant, said constituent a. of said composition further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7 and at least one polyamide denoted B having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB of between 7 and 10, advantageously between 7.5 and 9.5.

[0137] Advantageously, the melting temperature of polyamide A is greater than or equal to 210°C and / or the melting temperature of polyamide B is less than or equal to 200°C.

[0138] Advantageously, said composition of the three variants defined above comprises from 34 to 84% by weight of aliphatic polyamide C relative to the total weight of the polyamides present in said composition, preferably between 50 and 80%.

[0139] More advantageously, said composition of the three variants defined above comprises from 60 to 80% by weight of aliphatic polyamide C relative to the total weight of the polyamides present within said composition.

[0140] More advantageously, said composition of the three variants defined above comprises from 70 to 80% by weight of aliphatic polyamide C relative to the total weight of the polyamides present within said composition.

[0141] When said aliphatic polyamide of the tubular structure is at least one polyamide denoted C obtained from the polycondensation of at least one C 6 to C 18 lactam, preferably C 7 to C 13, or of at least one C 6 to C 18 aminocarboxylic acid, preferably C 7 to C 13, then said polyamide C is advantageously chosen from PA11 and PA12, advantageously PA11.

[0142] In the first variant, said polyamide C is advantageously chosen from PA11 and PA12, advantageously PA11 and polyamide A is chosen from PA6, PA46 and PA66.

[0143] In the second variant, said polyamide C is advantageously chosen from PA11 and PA12, advantageously PA11 and polyamide B is chosen from PA610 and PA612.

[0144] In the third variant, said polyamide C is advantageously chosen from PA11 and PA12, advantageously PA11, polyamide B is chosen from PA610, and PA612 and polyamide A is chosen from PA6, PA46 and PA66.

[0145] Advantageously, each of the polyamides A, B, and C has an enthalpy of fusion greater than 25J / g (DSC).

[0146] In one embodiment, said tubular structure is characterized in that W in said aliphatic polyamide of formula W / Z is at least one aliphatic repeating unit XY which is a polyamide denoted B' having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB' of between 7 and 10, advantageously between 7.5 and 9.5 or a polyamide denoted C' having an average number of carbon atoms per nitrogen atom denoted CC' of between 9 and 18, advantageously between 10 and 18.

[0147] In another embodiment, the tubular structure defined above is characterized in that W in said at least one aliphatic polyamide of formula W / Z is an aliphatic repeating unit XY which is a polyamide denoted B' having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB' of between 7 and 10, advantageously between 7.5 and 9.5 or a polyamide denoted C' having an average number of carbon atoms per nitrogen atom denoted CC' of between 9 and 18, advantageously between 10 and 18.

[0148] Repeating units resulting from the polycondensation of lactams and / or aminocarboxylic acids are therefore excluded from polyamides marked B' or C'.

[0149] Advantageously, said aliphatic polyamide is a single polyamide noted B' or a single polyamide noted C'.

[0150] In one embodiment, said constituent a. of said composition consisting of at least one aliphatic polyamide denoted B' or denoted C' further comprises another polyamide chosen from: at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7; at least one polyamide denoted B" having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB" of between 7 and 10, advantageously between 7.5 and 9.5, when said aliphatic polyamide is C', at least one polyamide denoted C" having an average number of carbon atoms per nitrogen atom denoted CC" of between 9 and 18, advantageously between 10 and 18, when said aliphatic polyamide is B'; or a mixture thereof, the weighted average mass of the fusion enthalpies of the polyamides being greater than 25J / g (DSC), the average number of carbon atoms per nitrogen atom of the polyamides A, B', B", C' and C" also satisfying the following strict inequality: CA < CB' or CB" < CC' or CC".

[0151] The polyamide denoted A is a polyamide obtained as described above, the polyamide denoted B" is a polyamide obtained as described above for polyamide B and the polyamide denoted C" is a polyamide obtained as described above for polyamide C, provided that the average number of carbon atoms per nitrogen atom is respected for each of the polyamides A, B" and C".

[0152] Advantageously, the difference between the average numbers of carbon atoms per nitrogen atom (CB' - CA ) and / or (CC' - CB" ) and / or (CC" - CB" ) is between 1 and 4, and preferably between 2 and 3.

[0153] The composition of said layer (1) can therefore comprise: a polyamide marked B' and a polyamide marked A, a polyamide marked B' and a polyamide marked C", a polyamide marked B', a polyamide marked A and a polyamide marked C", a polyamide marked C' and a polyamide marked A, a polyamide marked C' and a polyamide marked B" a polyamide marked C', a polyamide marked A and a polyamide marked B".

[0154] The mass proportion of the different polyamides in the above compositions is variable, which means that one of the polyamides noted A, B' or C" is in the majority compared to the total of polyamides A + B' + C" or that one of the polyamides noted A, B" or C' is in the majority compared to the total of polyamides A + B" + C' present in the composition.

[0155] In a first variant, said at least one aliphatic polyamide denoted B' further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7.

[0156] In a second variant, said at least one aliphatic polyamide denoted B' further comprises at least one polyamide denoted C" having an average number of carbon atoms per nitrogen atom denoted CC" of between 9 and 18, advantageously between 10 and 18.

[0157] In a third variant, said at least one aliphatic polyamide denoted B' further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7 and at least one polyamide denoted C" having an average number of carbon atoms per nitrogen atom denoted CC" of between 9 and 18, advantageously between 10 and 18.

[0158] In a fourth variant, said at least one aliphatic polyamide denoted C' further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7.

[0159] In a fifth variant, said at least one aliphatic polyamide denoted C' further comprises at least one polyamide denoted B" having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB' of between 7 and 10, advantageously between 7.5 and 9.5.

[0160] In a sixth variant, said at least one aliphatic polyamide denoted C' further comprises at least one polyamide denoted A having an average number of carbon atoms per nitrogen atom denoted CA of between 4 and 8.5, advantageously between 4 and 7 and at least one polyamide denoted B" having a melting temperature greater than or equal to 180°C and an average number of carbon atoms per nitrogen atom denoted CB" of between 7 and 10, advantageously between 7.5 and 9.5.

[0161] Advantageously, the melting temperature of polyamide A is greater than or equal to 210°C and / or the melting temperature of polyamide C" is less than or equal to 200°C and / or the temperature of polyamide B" is greater than or equal to 180°C.

[0162] Advantageously, said composition of three of the six variants defined above comprises from 34 to 84% by weight of aliphatic polyamide B' relative to the total weight of the polyamides present in said composition, preferably between 50 and 80%.

[0163] More advantageously, said composition of three of the six variants defined above comprises from 60 to 80% by weight of aliphatic polyamide B' relative to the total weight of the polyamides present within said composition.

[0164] More advantageously, said composition of three of the six variants defined above comprises from 70 to 80% by weight of aliphatic polyamide B' relative to the total weight of the polyamides present within said composition.

[0165] Advantageously, said composition of three of the six variants defined above comprises from 34 to 84% by weight of aliphatic polyamide C' relative to the total weight of the polyamides present in said composition, preferably between 50 and 80%.

[0166] More advantageously, said composition of three of the six variants defined above comprises from 60 to 80% by weight of aliphatic polyamide C' relative to the total weight of the polyamides present within said composition.

[0167] More advantageously, said composition of three of the six variants defined above comprises from 70 to 80% by weight of aliphatic polyamide C' relative to the total weight of the polyamides present within said composition.

[0168] When said at least one aliphatic polyamide of the tubular structure is an aliphatic repeating unit which is a polyamide denoted B', then said polyamide B' is advantageously chosen from PA610 and PA612, advantageously PA610.

[0169] When said at least one aliphatic polyamide of the tubular structure is an aliphatic repeating unit which is a polyamide denoted C', then said polyamide C' is advantageously chosen from PA1012, PA618 and PA1010.

[0170] In the first variant, said polyamide B' is advantageously chosen from PA610 and PA612, advantageously PA610 and polyamide A is chosen from PA6, PA46 and PA66.

[0171] In the second variant, said polyamide B' is advantageously chosen from PA610 and PA612, advantageously PA610 and polyamide C" is chosen from PA11, PA12, PA1012, PA618 and PA1010.

[0172] In the third variant, said polyamide B' is advantageously chosen from PA610 and PA612, advantageously PA610 and polyamide A is chosen from PA6, PA46 and PA66 and polyamide C" is chosen from PA11, PA12, PA1012, PA618 and PA1010.

[0173] In the fourth variant, said polyamide C' is chosen from PA1012, PA618 and PA1010, and polyamide A is chosen from PA6, PA46 and PA66.

[0174] In the fifth variant, said polyamide C' is chosen from PA1012, PA618 and PA1010, and polyamide B" is advantageously chosen from PA610 and PA612, advantageously PA610.

[0175] In the sixth variant, said polyamide C' is chosen from PA1012, PA618 and PA1010, polyamide A is chosen from PA6, PA46 and PA66, and polyamide B" is advantageously chosen from PA610 and PA612, advantageously PA610.

[0176] Advantageously, each of the polyamides A, B', B", C' and C" has a fusion enthalpy greater than 25J / g (DSC).

[0177] Advantageously, when the structure consists of a single layer which is the layer (1), the composition of said layer (1) is free of additive chosen from carbon black, graphite, graphene, carbon fibers and carbon nanotubes.

[0178] In this embodiment, the tubular structure is therefore non-conductive and devoid of any other layer.

[0179] All the characteristics of the different constituents a., b., c. and d. defined above are valid for this particular embodiment with the exception of the additives chosen from carbon black, graphite, graphene, carbon fibers and carbon nanotubes.

[0180] Advantageously, when the tubular structure is single-layer, the thickness of said layer (1) is at least 600µm.

[0181] Advantageously, said single-layer tubular structure free of additive chosen from carbon black, graphite, graphene, carbon fibers and carbon nanotubes is also free of plasticizer. Tubular structure in which the additive is at least carbon black

[0182] In one embodiment, said tubular structure, defined above, comprises an additive in the layer (1) which is at least carbon black.

[0183] Other additives may be present in said layer (1) but they are then not conductive.

[0184] Said tubular structure can be single-layer or multi-layer.

[0185] Advantageously, it is multi-layered.

[0186] In a first variant, said tubular structure defined above is characterized in that said composition of said layer (1) comprises: a. from 39% to 95% by weight, in particular from 41% to 85% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 0% to 20% by weight of at least one impact modifier, d. from 5% to 32%, in particular from 15 to 28% by weight of an additive which is carbon black, and from 0 to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

[0187] Additives, plasticizers, impact modifiers are as defined above.

[0188] In one embodiment, said tubular structure defined above is characterized in that said composition of said layer (1) consists of: a. from 39% to 95% by weight, in particular from 41% to 85% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 0% to 20% by weight of at least one impact modifier, d. from 5% to 32%, in particular from 15 to 28% by weight of an additive which is carbon black, and from 0 to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100% of the total weight of the composition.

[0189] In a second variant, said tubular structure defined above is characterized in that said composition of said layer (1) comprises: a. from 39% to 85% by weight, in particular from 41% to 75% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 5% to 32%, in particular from 15 to 28% by weight of an additive which is carbon black and from 0 to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

[0190] In one embodiment, said tubular structure defined above is characterized in that said composition of said layer (1) consists of: a. from 39% to 85% by weight, in particular from 41% to 75% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 5% to 32%, in particular from 15 to 28% by weight of an additive which is carbon black and from 0 to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100% of the total weight of the composition. Tubular structure in which the additive is at least carbon nanotubes

[0191] In one embodiment, said tubular structure, defined above, comprises an additive in the layer (1) which is at least carbon nanotubes.

[0192] Other additives may be present in said layer (1) but they are then not conductive.

[0193] Said tubular structure can be single-layer or multi-layer.

[0194] In a first variant, said tubular structure defined above is characterized in that said composition of said layer (1) comprises: a. from 70% to 99.5% by weight, in particular from 80% to 98% by weight, in particular from 80% to 96% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, and from 0 to 19%, preferably from 0 to 22%, in particular from 0 to 24% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

[0195] In one embodiment, said tubular structure defined above is characterized in that said composition of said layer (1) consists of: a. from 70% to 99.5% by weight, in particular from 80% to 98% by weight, in particular from 80% to 96% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, and from 0 to 19%, preferably from 0 to 22%, in particular from 0 to 24% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100% of the total weight of the composition.

[0196] In a second variant, said tubular structure defined above is characterized in that said composition of said layer (1) comprises a. from 70% to 89.5% by weight, in particular from 80% to 88% by weight, in particular from 80% to 86% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, and from 0 to 19%, preferably from 0 to 22%, in particular from 0 to 24% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

[0197] In one embodiment, said tubular structure defined above is characterized in that said composition of said layer (1) consists of: a. from 70% to 89.5% by weight, in particular from 80% to 88% by weight, in particular from 80% to 86% by weight of at least one aliphatic polyamide, b. from 0% to 2% of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, and from 0 to 19%, preferably from 0 to 22%, in particular from 0 to 24% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibers and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100% of the total weight of the composition.

[0198] Advantageously, the layer (1) of one of the tubular structures defined above is free of plasticizer. Tubular structure comprising at least one layer (1) and at least one layer (2)

[0199] In another embodiment, the tubular structure defined above is characterized in that it comprises at least one second layer (2) which may be conductive or not, in particular conductive, said layer (1) being located above or below said layer (2).

[0200] The expression "above" means outside the tubular structure, said layer (1) therefore being the outer layer and said layer (2) being the inner layer.

[0201] The expression "below" means inside the tubular structure, said layer (1) therefore being the inner layer and said layer (2) being the outer layer.

[0202] The tubular structure then corresponds to a multi-layer structure (MLT).

[0203] Advantageously, said layer (1) is located above said layer (2).

[0204] Advantageously, the thickness of the layer (1) in the MLT structure is from approximately 600 µm to approximately 950 µm.

[0205] Advantageously, the thickness of said layer (2) in the MLT structure represents less than 25% of the total thickness of the MLT.

[0206] Advantageously, when said second layer (2) is conductive, its thickness is between 50 and 200 µm.

[0207] Advantageously, said tubular structure comprising at least one second layer (2), is characterized in that said second layer (2) comprises at least one aliphatic polyamide or fluorinated materials such as PVDF or functionalized fluorinated materials such as functionalized ethylene and tetrafluoroethylene copolymer (ETFE), functionalized ethylene, tetrafluoroethylene and hexafluoropropylene copolymer (EFEP), a tetrafluoroethylene-perfluoro(alkylvinylether)-chlorotrifluoroethylene (CPT) copolymer.

[0208] All the technical characteristics detailed above for layer (1) of the tubular structure are valid for this embodiment in which at least one layer (1) and at least one layer (2) are present.

[0209] Said at least one second layer (2) is conductive or not, which means that it can contain additives chosen from carbon black, graphite, graphene, carbon fibers and carbon nanotubes and said layer (1) is conductive or not.

[0210] In a first variant, said at least one second layer (2) is free of plasticizer.

[0211] In a second variant, said at least one second layer (2) is conductive and comprises from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, or from 5% to 24%, in particular from 15 to 24% by weight of an additive which is carbon black, relative to the total weight of the composition of said layer (2).

[0212] In a third variant, said at least one second layer (2) is conductive and comprises from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, or from 5% to 24%, in particular from 15 to 24% by weight of an additive which is carbon black, relative to the total weight of the composition of said layer (2) and is free of plasticizer.

[0213] In a fourth variant, said at least one second layer (2) is conductive and comprises from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, or from 5% to 24%, in particular from 15 to 24% by weight of an additive which is carbon black, relative to the total weight of the composition of said layer (2) and said layer (1) is non-conductive.

[0214] In a fifth variant, said at least one second layer (2) is conductive and comprises from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, or from 5% to 24%, in particular from 15 to 24% by weight of an additive which is carbon black, relative to the total weight of the composition of said layer (2), said layer (2) being free of plasticizer and said layer (1) is non-conductive.

[0215] In a sixth variant, said at least one second layer (2) is conductive and comprises from 0.5 to 10%, preferably from 2% to 7%, in particular from 4 to 5% by weight of an additive which is carbon nanotubes, or from 5% to 24%, in particular from 15 to 24% by weight of an additive which is carbon black, relative to the total weight of the composition of said layer (2), said layer (2) being free of plasticizer and said layer (1) is non-conductive and said layer (1) is free of plasticizer.

[0216] In another embodiment, the tubular structure defined above is characterized in that it comprises two conductive or non-conductive layers (2), in particular conductive, said layer (1) being located between the two said layers (2).

[0217] The term "barrier layer" means a layer that is very little permeable to fuels, particularly alcoholic gasolines, and which therefore allows very little fuel, particularly alcoholic gasolines, to pass into the atmosphere.

[0218] In particular, the term "barrier layer" means that the proportion of fuel, in particular alcoholic gasoline, which passes into the atmosphere is less than 20 g.mm / m 2< .day as determined with a CE 10 fuel at 60°C.

[0219] Fuel permeability measurements, particularly for gasoline, are determined at 60°C using a gravimetric method with CE10: isooctane / toluene / ethanol = 45 / 45 / 10 vol.% and CE85: isooctane / toluene / ethanol = 7.5 / 7.5 / 85 vol.% on plates made of a polymer material. The instantaneous permeability is zero during the induction period, then it gradually increases to an equilibrium value which corresponds to the steady-state permeability value. This value obtained in steady-state is considered to be the permeability of the material.

[0220] This barrier property is essential for pipes in contact with the atmosphere.

[0221] In the case of the tubular structures of the invention, the latter being immersed in the fuel, a barrier layer is not necessary. Consequently, advantageously,

[0222] In a variant, the tubular structure defined above comprising at least a second layer (2) is devoid of a barrier layer and the tubular structure is then made only of aliphatic polyamides.

[0223] Said aliphatic polyamide of layer (2) is as defined above and may comprise the same additives, impact modifier, plasticizer as the polyamide of layer (1) and this in ranges of proportions identical to those of layer (1).

[0224] Said fluorinated material may comprise additives similar to those of the polyamide of the layer (1) and in ranges of proportions identical to those of the layer (1). Advantageously, said second layer (2) comprises a composition comprising at least one aliphatic polyamide, as defined for said layer (1).

[0225] In another embodiment, the tubular structure defined above and comprising at least a second layer (2) also comprises a third layer (2'), identical to or different from the second layer (2).

[0226] Advantageously, said layer (2') comprises a composition comprising a polyamide as defined for said layer (2).

[0227] Advantageously, said layers (2) and (2') are conductive and the layer (1) is non-conductive. Advantageously, when the tubular structure comprises at least one layer (1) and at least one layer (2), the thickness of said layer (1) is 60% to 95% of the total thickness of the tube.

[0228] According to another aspect, the present invention relates to the use of a tubular structure as defined above, for the transport of fuels in the tank, in particular the transport of gasoline in the tank.

[0229] All the characteristics defined above for the tubular structure are valid for this use.

[0230] According to another aspect, the present invention relates to the use of a tubular structure as defined above, to satisfy an extractables test, said test consisting in particular of filling said multilayer tubular structure MLT with alcoholic essence type FAM-B and heating the assembly to 60°C for 96 hours, then emptying it by filtering it into a beaker, then allowing the filtrate from the beaker to evaporate at room temperature to finally weigh this residue, the proportion of which must be less than or equal to approximately 10g / m 2< of internal tube surface, preferably less than or equal to approximately 6g / m 2< .

[0231] According to another aspect, the present disclosure relates to a method of measuring extractables from a tubular structure, as defined above, comprising the following steps: 1) filling said tubular structure with FAM-B type alcoholic gasoline, 2) heating said tubular structure immersed in said gasoline, the whole at 60°C for 96 hours, 3) emptying with simultaneous filtration into a beaker, 4) evaporation of the filtrate from the beaker at room temperature 5) weighing of the residue after evaporation, the proportion of which must be less than or equal to approximately 6 g / m2 of internal tube surface, EXAMPLES

[0232] The invention will now be described in more detail with the aid of the following examples which are not limiting.

[0233] 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.

[0234] The screws used are single-screw extrusions with screw profiles adapted to polyamides. In addition to the 5 extruders and the multi-layer extrusion head, the extrusion line includes: a die-punch assembly, located at the end of the coextrusion head; the inside diameter of the die and the outside diameter of the punch are chosen according to the structure to be produced and the materials that compose it, as well as the dimensions of the tube and the line speed; a vacuum tank with an adjustable depression level. In this tank circulates water maintained at 20°C in general, in which a gauge is immersed to conform the tube to its final dimensions. The diameter of the gauge is adapted to the dimensions of the tube to be produced, typically from 8.5 to 10 mm for a tube with an outside diameter of 8 mm and a thickness of 1 mm; a succession of cooling tanks in which water is maintained at around 20°C, allowing the tube to be cooled along the route from the head to the drawing bench; a diameter gauge; a drawing bench.

[0235] The 5-extruder configuration is used to produce tubes ranging from 2 layers to 5 layers. For structures with fewer than 5 layers, multiple extruders are fed with the same material.

[0236] In the case of structures with 6 layers, an additional extruder is connected and a spiral mandrel is added to the existing head, in order to create the internal layer, in contact with the fluid.

[0237] Before testing, in order to ensure the best tube properties and good extrusion quality, it is checked that the extruded materials have a residual moisture content before extrusion of less than 0.08%. Otherwise, an additional step of drying the material is carried out before testing, generally in a vacuum dryer, for 1 night at 80°C.

[0238] The tubes, which meet the characteristics described in this patent application, were taken after stabilization of the extrusion parameters, the targeted tube dimensions no longer changing over time. The diameter is controlled by a laser diameter meter installed at the end of the line.

[0239] Generally, the line speed is typically 20m / min. It generally varies from 5 to 100m / min.

[0240] 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. Generally, 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 in question, so that they remain in the molten state, thus preventing them from solidifying and blocking the machine.

[0241] The tubular structures were tested on different parameters (Table I).

[0242] All layer thicknesses are expressed in µm.

[0243] The amount of extractables, bursting properties and flexibility were determined. Examples and counterexamples Extractables (3) Burst (1) Flexibility (2) Counterexample c1: PA12-TL >50 + +++++ single layer 1000µm thick Counterexample c2: PA11-TL >40 ++ ++++++ single layer 1000µm thick Counterexample c3: PA610-TL >40 ++++ ++++ single layer 1000µm thick Counterexample c4: PA612-TL >40 +++ ++++ single layer 1000µm thick Counterexample c5 (multilayer): PA12-TL / / PA612-TL / / PA12-TL >40 +++ +++++ thicknesses: 100 / / 800 / 100µm Example 1: PA11-NoPlast <4 ++ +++ single layer 1000µm thick Example 2: PA610-NoPlast <4 ++++ ++ single layer 1000µm thick Example 3: PA612-NoPlast <4 +++ ++ single layer 1000µm thick Example 4: PA612-NoPlast-B <4 ++++ + single layer 1000µm thick Example 5 (multilayer): PA12-NoPlast / / PA612-NoPlast <5 +++ ++ thicknesses: 100 / / 900µm Example 6 (multilayer): PA12-NoPlast / / PA612-NoPlast / / PA12-NoPlast <5 +++ +++ thicknesses: 100 / / 800 / / 100µm Example 7 (multilayer): PA11-NoPlast / / PA612-NoPlast / / PA11-NoPlast <4 +++ +++ thicknesses: 100 / / 800 / / 100µm Example 8 (multilayer): PA11-NoPlast / / PA610-NoPlast / / PA11-NoPlast <4 ++++ +++ thicknesses: 100 / / 800 / / 100µm Example 9 (multilayer): PA11-NoPlast / / PA610-NoPlast / / PA11cond -NoPlast <4 ++++ ++ thicknesses: 100 / / 800 / / 100µm Example 10 (multilayer): EFEPc / / PA610-NoPlast / / EFEPc <2 ++++ ++ thicknesses: 100 / / 800 / / 100µm Example 11 (multilayer): EFEPc / / PA11-NoPlast / / EFEPc <2 ++ ++ thicknesses: 100 / / 800 / / 100µm Example 12 (multi-layer): PA12-NoPlast / / Binder-NoPlast / / PA6-NoPlast <5 ++++ ++ thicknesses: 100 / / 100 / / 800µm Example 13 (multilayer): PA12-NoPlast / / Binder-NoPlast / / PA6-NoPlast / / Binder-NoPlast / / PA12-NoPlast <5 +++ +++ thicknesses: 100 / / 100 / / 600 / / 100 / / 100µm Example 14 (multi-layer): <6 ++++ +++ PA11-TL / / PA610-NoPlast thicknesses: 100 / / 900µm Example 15: PA11-P <9 ++ +++++ single layer 1000µm thick (1) Burst is the bursting (according to DIN 53758) after at least 96 hours with FAM-B bio-essence inside, so we are looking for a value high enough to withstand the pressure. The higher the number of "+", the better the bursting. (2) Flexibility and flexural modulus (according to ISO 178) on the tube in the conditioned state at 23°C in RH50. The lower the modulus, the higher the flexibility, which is favorable for tube assembly. The higher the number of "+", the more favorable the flexibility. (3) Extractables. This test consists of a tube filled with FAM-B type alcoholic essence at 60°C, for 96 hours, then emptied and filtered into a beaker which is then left to evaporate and the residue is weighed, the latter preferably being less than or equal to 6g / m2 (of internal tube surface). FAM B alcoholic gasoline is described in DIN 51604-1:1982, DIN 51604-2:1984 and DIN 51604-3:1984.Briefly, FAM A alcoholic gasoline is first prepared with a mixture of 50% toluene, 30% isooctane, 15% di-isobutylene and 5% ethanol, then FAM B. Compositions

[0244] PA12-TL: designates a composition based on polyamide 12, containing 6% plasticizer and 6% EPR1, and 1.2% organic stabilizers. The melting temperature of this composition is 175°C. PA11-TL designates a composition based on polyamide 11, containing 5% plasticizer, 6% impact modifier such as ethylene / ethyl acrylate / anhydride in a mass ratio of 68.5 / 30 / 1.5 (MFI 6 at 190°C under 2.16 kg), and 1.2% organic stabilizers. The melting temperature of this composition is 185°C.PA12-NoPlast = PA12-TL without the plasticizer (the latter is replaced by PA12) PA11-NoPlast = PA11-TL without the plasticizer (the latter is replaced by PA11) PA610-TL = PA610 + 12% impact modifier EPR1 + organic stabilizer + 10% plasticizer PA610-NoPlast = PA610-TL without the plasticizer (the latter is replaced by PA610) PA612-TL = PA612 + 12% impact modifier EPR1 + organic stabilizer + 9% plasticizer PA612-NoPlast = PA612-TL without the plasticizer (the latter is replaced by PA612) PA612-NoPlast-B = PA612-TL without the plasticizer or EPR1 (these are replaced by PA612) PA11cond-noplast = PA11 of Mn 15000 + 9%EPR1 + 26% carbon black type Ensaco 250G PA6-NoPlast = PA6 + 12% impact modifier EPR1 + organic stabilizer Binder-NoPlast = Composition based on 48.8% PA612 (as defined elsewhere), 30% PA6 (as defined elsewhere), and 20% impact modifier type EPR1, and 1.2% organic stabilizers.EFEPc = Functionalized and conductive EFEP type Neoflon RP5000AS from Daikin PA11-P = designates a composition based on polyamide 11, containing 1% plasticizer, 6% 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% organic stabilizers. The melting temperature of this composition is 188°C. Constituents of the compositions :

[0245] PA12: Polyamide 12 of Mn (number molecular weight) 35000. The melting temperature is 178°C, its enthalpy of fusion is 54kJ / m2 PA11: Polyamide 11 of Mn (number molecular weight) 29000. The melting temperature is 190°C, its enthalpy of fusion is 56kJ / m2 PA610: Polyamide 6.10 of Mn (number molecular weight) 30000. The melting temperature is 223°C, its enthalpy of fusion is 61kJ / m2 PA612: Polyamide 6.12 of Mn (number molecular weight) 29000. The melting temperature is 218°C, its enthalpy of fusion is 67kJ / m2 PA6: Polyamide 6 of Mn (number molecular weight) 28000. The melting temperature is 220°C, its enthalpy of fusion is 68kJ / m2 EPR1: Designates an EPR functionalized by a reactive anhydride group (at 0.5-1% by mass), of MFI 9 (at 230°C, under) 10kg, of the Exxellor ®< VA1801 type from the Exxon company. Organic stabilizer = 1.2% of organic stabilizers consisting of 0.8% phenol (Lowinox ®< 44B25 from Great Lakes), 0.2% phosphite (Irgafos ®< 168 from Ciba, 0.2% anti-UV (Tinuvin ®< 312 from Ciba). Plasticizer = BBSA (benzyl butyl sulfonamide).

Claims

1. Flexible, partially corrugated tubular structure intended to be placed at least partially inside the fuel tank, in particular petrol or diesel tank, in particular petrol tank, of a vehicle, it being possible for said structure to be at least partially immersed in said tank and intended to transport said fuel in said tank, said tubular structure comprising at least one layer (1) consisting of a composition consisting of: a. from 39% to 100% by weight, in particular from 41% to 100% by weight, of at least one aliphatic polyamide of formula W / Z, in which: W is an aliphatic repeating unit obtained from the polycondensation of at least one C6 to C18, preferentially C7 to C13, lactam, or at least one C6 to C18, preferentially C7 to C13, aminocarboxylic acid, or is an aliphatic repeating unit XY having a mean number of carbon atoms per nitrogen atom denoted of from 6 to 18, preferentially from 7 to 13, obtained from the polycondensation: - of at least one C6 to C18 diamine X, said diamine being selected from a linear or branched aliphatic diamine or a mixture thereof, and - of at least one aliphatic C6 to C18 dicarboxylic acid Y, Z is at least one optional polyamide repeating unit, where Z may be present up to 30% by weight relative to the total weight W / Z, preferentially up to 15% by weight relative to the total weight W / Z, b. from 0% to 2% by weight of at least one plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 0% to 37% by weight of at least one additive, the sum a. + b. + c. + d. being equal to 100%, excluding a structure for transporting fuel going from the tank to the engine of the vehicle.

2. Tubular structure according to Claim 1, characterized in that said at least one aliphatic polyamide is at least one polyamide, denoted C, obtained from the polycondensation of at least one C6 to C18, preferentially C7 to C13, lactam, or at least one C6 to C18, preferentially C7 to C13, aminocarboxylic acid, and having a mean number of carbon atoms per nitrogen atom, denoted CC, of between 9 and 18, advantageously between 10 and 18.

3. Tubular structure according to Claim 2, characterized in that said constituent a. of said composition further comprises another polyamide selected from: - at least one polyamide, denoted A, having a mean number of carbon atoms per nitrogen atom, denoted CA, of between 4 and 8.5, advantageously between 4 and 7; - at least one polyamide, denoted B, having a melting point of greater than or equal to 180°C and a mean number of carbon atoms per nitrogen atom, denoted CB, of between 7 and 10, advantageously between 7.5 and 9.5; or a mixture thereof, the weighted mean by mass of the enthalpies of fusion of the polyamides being greater than 25 J / g (DSC), the mean number of carbon atoms per nitrogen atom of the polyamides A, B and C additionally corresponding to the following strict inequation: CA < CB < CC.

4. Tubular structure according to Claim 2 or 3, characterized in that the composition comprises from 34% to 84% by weight of aliphatic polyamide C relative to the total weight of the polyamides present within said composition, preferably between 50% and 80%.

5. Tubular structure according to either of Claims 3 and 4, characterized in that polyamide A is selected from PA 6, PA 46 and PA 66, polyamide B is selected from PA 610 and PA 612, preferably PA 610, and polyamide C is selected from PA 11 and PA 12.

6. Tubular structure according to Claim 1, characterized in that W in said at least one aliphatic polyamide of formula W / Z is an aliphatic repeating unit XY which is a polyamide, denoted B', having a melting point of greater than or equal to 180°C and a mean number of carbon atoms per nitrogen atom, denoted CB', of between 7 and 10, advantageously between 7.5 and 9.5, or a polyamide, denoted C', having a mean number of carbon atoms per nitrogen atom, denoted CC', of between 9 and 18, advantageously between 10 and 18.

7. Tubular structure according to Claim 6, characterized in that said constituent a. of said composition consisting of at least one aliphatic polyamide denoted B' or denoted C' additionally comprises another polyamide selected from: - at least one polyamide, denoted A, having a mean number of carbon atoms per nitrogen atom, denoted CA, of between 4 and 8.5, advantageously between 4 and 7; - at least one polyamide, denoted B", having a melting point of greater than or equal to 180°C and a mean number of carbon atoms per nitrogen atom, denoted CB", of between 7 and 10, advantageously between 7.5 and 9.5, when said aliphatic polyamide is C', - at least one polyamide, denoted C", having a mean number of carbon atoms per nitrogen atom, denoted CC", of between 9 and 18, advantageously between 10 and 18, when said aliphatic polyamide is B'; or a mixture thereof, the weighted mean by mass of the enthalpies of fusion of the polyamides being greater than 25 J / g (DSC), the mean number of carbon atoms per nitrogen atom of the polyamides A, B', B", C' and C" additionally corresponding to the following strict inequation: CA < CB' or CB" < CC' or CC".

8. Tubular structure according to Claim 6 or 7, characterized in that the composition comprises from 34% to 84% by weight of aliphatic polyamide B' or aliphatic polyamide C' relative to the total weight of the polyamides present within said composition, preferably between 50% and 80%.

9. Tubular structure according to either of Claims 7 and 8, characterized in that polyamide A is selected from PA 6, PA 46 and PA 66, polyamide B' is selected from PA 610 and PA 612, preferably PA 610, and polyamide C" is selected from PA 11, PA 12, PA 1012, PA 618 and PA 1010, or the polyamide polyamide A is selected from PA 6, PA 46 and PA 66, polyamide B" is selected from PA 610 and PA 612, preferably PA 610, and polyamide C' is selected from PA 1012, PA 618 and PA 1010.

10. Tubular structure according to one of Claims 1 to 9, characterized in that the additives d. are selected from carbon black, graphite, graphene, carbon fibres, carbon nanotubes, in particular carbon black and carbon nanotubes, an antioxidant, a heat stabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganic filler, a flame retardant, a nucleating agent, a colorant, reinforcing fibres, a wax, and mixtures thereof.

11. Tubular structure according to Claim 10, characterized in that said additive is at least carbon black.

12. Tubular structure according to Claim 11, characterized in that said composition of said layer (1) comprises: a. from 39% to 95% by weight, in particular from 41% to 85% by weight, of at least one aliphatic polyamide, b. from 0% to 2% by weight of a plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 5% to 32%, in particular from 15% to 28%, by weight of an additive which is carbon black, and from 0% to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibres and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

13. Tubular structure according to Claim 11 or 12, characterized in that said composition of said layer (1) comprises: a. from 39% to 85% by weight, in particular from 41% to 75% by weight, of at least one aliphatic polyamide, b. from 0% to 2% by weight of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 5% to 32%, in particular from 15% to 28%, by weight of an additive which is carbon black, and from 0% to 5% by weight of at least one additive other than carbon black, graphite, graphene, carbon fibres and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

14. Tubular structure according to Claim 10, characterized in that said additive is at least carbon nanotubes.

15. Tubular structure according to Claim 14, characterized in that said composition of said layer (1) comprises: a. from 70% to 99.5% by weight, particularly from 80% to 98% by weight, in particular from 80% to 96% by weight, of at least one aliphatic polyamide, b. from 0% to 2% by weight of a plasticizer, c. from 0% to 20% of at least one impact modifier, d. from 0.5% to 10%, preferentially from 2% to 7%, in particular from 4% to 5%, by weight of an additive which is carbon nanotubes, and from 0% to 19%, preferentially from 0% to 22%, in particular from 0% to 24%, by weight of at least one additive other than carbon black, graphite, graphene, carbon fibres and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

16. Tubular structure according to Claim 14 or 15, characterized in that said composition of said layer (1) comprises a. from 70% to 89.5% by weight, particularly from 80% to 88% by weight, in particular from 80% to 86% by weight, of at least one aliphatic polyamide, b. from 0% to 2% by weight of a plasticizer, c. from 10% to 18% of at least one impact modifier, d. from 0.5% to 10%, preferentially from 2% to 7%, in particular from 4% to 5%, by weight of an additive which is carbon nanotubes, and from 0% to 19%, preferentially from 0% to 22%, in particular from 0% to 24%, by weight of at least one additive other than carbon black, graphite, graphene, carbon fibres and carbon nanotubes, the sum a. + b. + c. + d. being equal to 100%.

17. Tubular structure according to one of Claims 1 to 16, characterized in that the layer (1) is devoid of plasticizer.

18. Tubular structure according to one of Claims 1 to 17, characterized in that said structure is corrugated over at least 10% of its length.

19. Tubular structure according to one of Claims 1 to 18, characterized in that at least 90% of the length of said structure is inside the tank.

20. Tubular structure according to one of Claims 1 to 19, characterized in that at least 30% of the length of said structure is immersed in the fuel, preferentially at least 80%.

21. Tubular structure according to one of Claims 1 to 12 and 17 to 20, characterized in that it consists of a single layer and is devoid of additives selected from carbon black, graphite, graphene, carbon fibres and carbon nanotubes.

22. Tubular structure according to Claim 21, characterized in that the thickness of said layer (1) is at least 600 µm.

23. Tubular structure according to one of Claims 1 to 20 and 22, characterized in that it comprises at least one second layer (2) which may or may not be conductive, and in particular is conductive, said layer (1) being situated on the outside or on the inside of said layer (2).

24. Tubular structure according to Claim 23, characterized in that said layer (1) is situated on the outside of said layer (2).

25. Tubular structure according to either of Claims 23 and 24, characterized in that said second layer (2) comprises at least one aliphatic polyamide or fluorinated materials such as PVDF or functionalized fluorinated materials such as functionalized ethylene-tetrafluoroethylene (ETFE) copolymer, functionalized ethylene-tetrafluoroethylene-hexafluoropropylene (EFEP) copolymer, a tetrafluoroethylene-perfluoro(alkyl vinyl ether)-chlorotrifluoroethylene (CPT) copolymer.

26. Tubular structure according to either of Claims 23 and 24, characterized in that said structure is devoid of a barrier layer, said second layer (2) comprising at least one aliphatic polyamide.

27. Use of a tubular structure as defined in one of Claims 1 to 26, for the transport of fuels in the tank, in particular the transport of petrol in the tank.

28. Use of a tubular structure as defined in one of Claims 1 to 26, for complying with an extractables test, said test consisting especially in filling said multilayer tubular structure MLT with alcohol-blended petrol of FAM B type and in heating everything at 60°C for 96 hours, then in emptying it by filtering it into a beaker, then in leaving the filtrate of the beaker to evaporate at ambient temperature, in order to finally weigh this residue, the proportion of which must be less than or equal to 10 g / m2 of tube inner surface area, preferably less than or equal to approximately 6 g / m2.